Light treatment ameliorates sub-chronic MK-801-induced cognitive deficits in mice through up-regulating BDNF/p-CREB/p-ERK signaling pathway

doi:10.21203/rs.3.rs-2716465/v1

Download PDF

Research Article

Light treatment ameliorates sub-chronic MK-801-induced cognitive deficits in mice through up-regulating BDNF/p-CREB/p-ERK signaling pathway

https://doi.org/10.21203/rs.3.rs-2716465/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Cognitive impairment associated with schizophrenia (CIAS) is regarded as a core symptom of the illness, and there is still no effective treatment. Light plays an important role in regulation of cognitive functions. However, whether light treatment (LT) can improve CIAS remains unknown. The current study investigated the efficacy of LT on CIAS and explored the underlying molecular mechanisms in a CIAS model. The CIAS and control group were sub-chronically injected with MK-801 and saline respectively, and the LT/CIAS group were CIAS mice exposed to LT (3,000 Lux, 2 hr/day, 3 weeks). Results showed that the performance of LT/CIAS mice significantly improved in the novel object recognition test, novel location recognition test and Morris water maze compared with the CIAS group. And the behavioral improvement effects of LT could last over 4 weeks after LT was terminated. Golgi-cox staining revealed that the dendritic spine density and morphological complexity of hippocampal CA1 pyramidal neurons were increased after 3 weeks LT. Further research found that higher expression of brain-derived neurotrophic factor (BDNF), accompanied by elevated cAMP response element-binding phosphorylation (p-CREB) level in the hippocampus of LT/CIAS group compared to the CIAS group. Moreover, LT elevated phosphorylated extracellular signal-regulated kinase (p-ERK) level in the hippocampus of LT/CIAS group compared to the CIAS group. Taken together, long term LT ameliorated sub-chronic MK-801-induced cognitive deficits in mice, and the altered dendritic spines density and morphology of CA1 pyramidal neurons were rescued in LT/CIAS mice group, which might associate with up-regulating BDNF/p-CREB/p-ERK signaling pathway in LT/CIAS mice.

light treatment

cognition impairments

MK-801

dendritic spines

BDNF/p-CREB/p-ERK

Cognitive impairment associated with schizophrenia (CIAS) is widely regarded as a core symptom of the illness[1], which is reported present prior to the initiation of antipsychotic treatment[2]. Extensive evidences have displayed that CIAS is one of the most robust determinants of the poor functional outcome that characterizes this disorder and the focus on the CIAS have increased dramatically [3]. However, existing antipsychotic medications cannot meaningfully impact the cognitive impairment that is frequently found in schizophrenia, thought they are generally efficacious treatments for positive symptoms [4,5]. Therefore, more and more researchers try to improve cognition impairments through various intervention approaches, which is considering as a critically important treatment target for schizophrenia.

Light can modulate a range of powerful biological effects beyond image vision, including regulation of cognitive and emotional functions [6-9]. It has been documented that there are seasonal fluctuations in human cognitive brain function [10]. Daytime brighter light exposure has been reported to improve cognitive performance in healthy participants [11-14], as well as to attenuate cognitive deterioration in early-stage dementia [15-17]. Additionally, bright light interventions have been demonstrated to enhance learned fear memory and spatial memory [18-21] in adult mouse. On the other hand, insufficient light intensity or disturbed light patterns could lead to impaired learning and memory [22] and mood disorders [7,23,24].

Thus, much attention has been given to the mechanisms through which bright light modulates cognitive functions in recent years. Brain-derived neurotrophic factor (BDNF) is known to have a variety of effects in the nervous system. Besides cortex, it is widely expressed in the hippocampus, and is involved in learning and memory though regulating neuronal structure and function [25], and synaptic plasticity in the adult brain [26,27]. It has been found that the cognition promoting effects of LT associated with up-regulated BDNF levels. These effects have been documented in humans [28,29] , as well as in laboratory animals [30-32].

It is worth noting that reduced hippocampal BDNF levels are thought to be closely associated with cognitive dysfunction in schizophrenia. And a large number of clinical studies have demonstrated that low levels of BDNF are associated with cognitive impairment in patients with schizophrenia [33-35]. Neurodevelopmental animal models of schizophrenia have revealed that altered synaptic efficiency and connectivity accompany with a decline in BDNF concentration[36,37], which consistent with clinical findings[38]. Pharmacological animal models of schizophrenia have demonstrated that reduced BDNF mRNA concentrations are associated with psychotic symptoms[39-41]. These previous findings suggested a possibility of the potential for LT to improve cognitive dysfunctions associated with schizophrenia.

Taken together, although the beneficial effects of LT on cognition have been well documented, the effect of LT on CIAS has not been evaluated. In the present study, we investigated the effect of LT on cognitive deficits of CIAS model and explored the underlying molecular mechanism. N-methyl-D-aspartate receptor (NMDAR) dysfunction model of schizophrenia was widely adopted in identification of novel treatments for cognitive impairments in schizophrenia[42-45]. The effects of LT on CIAS were firstly investigated by novel object recognition (NOR), novel location recognition (NLR), Y-maze, and Morris water maze (MWM) experiments. Then, the underlying mechanisms of the promoting effects of LT were further explored and the hippocampal dendritic spine density and morphology were detected by Golgi-cox staining. Moreover, the alterations of critical molecules that play dominant roles in synaptic plasticity, including BDNF, cAMP response element-binding phosphorylation(p-CREB) and phosphorylated extracellular signal-regulated kinase(p-ERK) were also detected.

Animal model

C57BL/6J male mice were purchased from the Hangzhou Ziyuan, Inc. of China, and housed under a standard environment (22 ± 1℃, 50 ± 10% humidity) in a 12h light/dark cycle from 8 a.m. to 8 p.m. (~ 200 lux white ambient illumination) with food and water provided ad libitum. Mice (3 weeks old) were randomly divided into three groups: CIAS, LT/CIAS, and control group. The CIAS and LT/CIAS groups were administered with MK-801(Abcam, England, 0.5mg/kg in saline, i.p.) twice a day for 7 consecutive days, and rested for another 7 days without injections. The dose of MK-801 was chosen based on previous study[46]. The control group was received the same procedure except for the injection of saline. To evaluate the effect of LT on memory performance, the animals in LT/CIAS group were kept on bright light exposure (Cool LED lights, 3,000 lux white ambient illumination from 2 p.m. to 4 p.m.) for 3 consecutive weeks in a custom-designed light cabinet. The light intensity was determined by averaging the measurements from the top and four sides of the cabinet. The protocol was adapt from the previous reports [19].

Behavioral Tests

Behavioral tests were performed during the light phase (9 a.m. to 5 p.m.). All mice were allowed to habituate to a testing environment and a single experimenter for at least 3 days prior to each behavioral testing. The experimenter observed animal behaviors via a video monitor and kept quiet during the whole test. All behavioral data were recorded with an infrared camera placed above the box and analyzed with ANY-maze software (Stoelting, United Kingdom). After each test, cleaned the device with a paper towel soaked in 75% ethanol and dried thoroughly with paper towel.

Open Field Test

The spontaneous locomotor activity and anxiety level were examined by the open field test (OFT). Each mouse was gently placed into the center of the bottom of a white box (40 cm long, 40 cm wide and 40 cm high) and allowed to explore freely for 30 min. The first 10 min was used as time for the mice to acclimatize to the device, and the second 20 min was used to assess the amount of movement of mice. The total distance explored and the averaged velocity of movements during the last 20 min were considered to be indexes of spontaneous locomotor activity. The bottom of box was marked with a central area (20 cm × 20 cm cm) by offline sorting in the ANY-maze software (Stoelting, United Kingdom). The distance traveled in the central area, and the number of central entries (with all four paws placed into the central area) were considered to be indexes of anxiety level.

Novel Object Location And Novel Object Recognition Test

The ability of learning and memory in mice were tested with novel location recognition (NLR) and novel object recognition (NOR) tests as previously described. Briefly, for NLR test, the mice were habituated to a white Plexiglas box (25 cm long, 25 cm wide and 25 cm high) for 10 min per day for 3 consecutive days. Firstly, mice were allowed to explore two identical objects (placed in 2 corners of the arena 4 cm from the wall) for 10 min. Then, the mice were returned to the home cage. After an hour, the test of memory of the location was started. One of the objects was moved to the diagonal position of the box and the mice were allowed to explore again in the box for 5 min. Object exploration time was calculated when the mice sniffed or approached an object within 2 cm of the object. The NLR recognition index, reflecting the capacity for location memory, was defined as the percentage of time that the mice spent exploring the novel location in 5 min. For the NOR test, one of the familiar objects in the NLR test was replaced with a novel object that had the same material but a different shape, and the locations of these objects were unchanged. Also, the acclimating and exploration phases were the same as the NLR. The NOR recognition index, reflecting the capacity for object memory, was defined as the percentage of time that the mice spent exploring the novel object in 5 min. The used objects had been screened in advance, and the mice had no obvious preference for them.

Y-maze Test

The short-term spatial working memory of mouse was assessed by spontaneous alternations in Y-maze tests. The Y-maze consisted of three white, opaque plastic arms (40 cm long, 10 cm wide and 15 cm high) in which the angle between each of the two adjacent arms is 120◦. Each mouse was gently placed at the center of Y-maze and permitted free exploration for 8 min. An arm entry was considered when the mice's four paws were within the arm area. The total arm entries and sequences of each arm were recorded. The percentage of spontaneous alternation was defined as the proportion of arm choices that differed from the last two choices. The total arm entries and the percentage of spontaneous alternations represented exploratory activity and spatial working memory of the mice, respectively.

Morris Water Maze Test

The spatial learning and memory ability of mice was evaluated with the hidden platform version of the Morris water maze (MWM). The device consisted of a circular pool (120 cm diameter and 70 cm depth) filled with water (25–26℃), and the pool was equally divided into 4 quadrants with distinct visual cues fixed onto the pool wall. Titanium dioxide was added to make the water white and opaque to prevent the mice from seeing the hided platform (12 cm diameter, submerged about 1 cm beneath the water surface) located in a constant position (in one of the quadrants and 20 cm from the wall).

All mice were allowed to habituate to the pool one day prior to the start of training. In the following 4 days, the mice were trained to find the hidden platform in a fixed quadrant. Mice received four trials a day and the trials were separated by a one-hour interval. For each trial, the mice were gently placed into the pool, facing the wall of the pool. Mice were allowed to explore freely for a maximum of 90 s per trial, and were allowed to stay on the platform for 10 s after finding it. Mice that did not find the platform in 90 s were guided to the platform with a wooden stick, and allowed to remain there for 10 s. After each training session, the mice were dried with paper towels and placed in their home cages. Latency to platform and swimming speed were recorded for offline analysis. On the fifth day, the platform was removed and the mice were allowed to free swim for 90 s in the pool. The path length and the time spent in the target quadrant were recorded to assess spatial memory.

Forced Swimming Test

The potential depressive-like behavior in mice was explored by forced swimming test (FST). Briefly, mice were placed individually in a clear plastic cylinder (25 cm height and 10 cm diameter) filled with 10 cm high 24 ± 2°C fresh water for 6 min, and the duration of immobility during the last 4 min of a 6-minute trial was recorded. The immobile was defined as floating motionless or making only those movements necessary to keep its head above the water by a trained observer.

Golgi-cox Staining And Analysis

The morphology of neurons was revealed with the Golgi-cox staining (FD Rapid Golgi Stain kit). Briefly, mice were anesthetized with pentobarbital (50 mg/kg, i.p.) and the brain was removed and quickly transferred to a Golgi solution (mixture of solution A and B with equal volume) for 2 weeks. The brains were then transferred to Solution C for three days. The tissues were kept at room temperature (RT) and kept away from light. Coronal slices (100 µm thickness) containing the hippocampus were cut by a vibratome (Leica VT1200S, Leica Microsystems, Germany). All slices were decolorized with ethanol and bleached with xylene. The dendritic length and the number of intersections at concentric circles (10 µm apart) were analyzed by Sholl, and the number of dendritic spines per 10 µm was calculated using ImageJ software (version 1.52a, National Institutes of Health).

Western Blot Analysis

Western blot analysis

The mice were deeply anesthetized with pentobarbital (50 mg/kg, i.p.). Briefly, the hippocampus tissues were directly lysed in sodium dodecyl sulfate sample buffer and incubated at 95℃ for 5 min before being loaded onto a 10% sodium dodecyl sulfate-polyacrylamide gel. The protein concentration was determined before being loaded onto gel and then 40 µg protein per sample was loaded onto each track. Proteins were separated by electrophoresis and then transferred to a nitrocellulose membrane (BioRad, Hercules, California, USA). The membrane was blocked in 5% milk-TBST and probed with P-p44/42 MAPK (T202/Y204, P-Erk1/2) antibody (9101S, CST., USA), (1:1000), p44/42 MAPK (Erk1/2) antibody (4695S, CST., USA), (1:1000), p-CREB(Ser133) antibody (9198S, CST., USA), (1:1000),CREB antibody (ab32515, abcam., USA), (1:1000), BDNF antibody (ab6201, abcam., USA),(1:1000) at 4°C overnight and then reacted with the Alexa Fluor 800 conjugated antibody (1:5000) for 60 min. Detection and quantification of specific bands were performed using a fluorescence scanner (Odyssey Infrared Imaging System, LI-COR Biotechnology, Lincoln, NE, USA). All samples were analyzed at least in triplicate. β-actin (AC026, Abclonal, China) served as an internal protein control (1:5000).

Statistical analysis

Statistical analyses were performed with GraphPad Prism 7.0. For NOR, NLR, OFT data, Y-maze and FST, One-way ANOVA and unpaired t-test was used to compare pairs of means. For MWM behavioral data, two-way ANOVA followed by Turkey’s post hoc test was used to analyze the reach the platform. The potential relationship between locomotors activity and cognitive performance was analyzed by the Pearson’s correlation analysis. The number of dendritic intersections was analyzed by two-way repeated-measures ANOVA by Turkey’s post hoc test. Data were presented as mean ± SEM. p < 0.05 was considered as threshold of statistical significance for all results.

Light treatment increased the recognition index of novel objects and locations in CIAS mice

To evaluate the effect of LT on the memory performance in CIAS mice, a CIAS model was firstly established. As shown in Fig. 1A, mice were intraperitoneally injected with either saline or MK-801 twice a day for 7 consecutive days and then rested for another 7 days without injections. Particularly, the LT /CIAS group underwent 3 weeks of LT. Finally, the capability of learning and memory of all mice were evaluated by a series of behavioral experiments. As expected, the recognition index of novel locations (Fig. 1B, F (2, 41) = 7.167, p = 0.0150) and objects (Fig. 1C, F (2, 47) = 6.456, p = 0.0086) in CIAS group were significantly decreased compared to that of control group. Notably, the novel location index (Fig. 1B, p = 0.0021) and the novel object recognition index (Fig. 1C, p = 0.0033) were significantly improved in LT/CIAS mice compared to the CIAS group, while the spontaneous alternations of the mice in three groups showed no difference in Y-maze (Fig. 1D, F (2, 47) = 2.057, p = 0.1392). Further, we tested the novel object and novel location recognition index again 4 weeks after LT was terminated. The performance of LT/CIAS group was still better than that of CIAS group in NOR (Fig. 1F, p = 0.0002) and NLR (Fig. 1E, p = 0.0497) test. These results confirmed the beneficial efficacy of LT on cognitive behavioral performance in CIAS mice, and the promoting effects of LT (3,000 lux, 2 h/day, 3 weeks) could last over at least 1 month.

Light Treatment Promoted Spatial Memory In Cias Mice

To investigate the effects of LT on spatial memory in CIAS mice, Morris water maze (MWM) was conducted to assess spatial memory of three groups. Mice were trained to find a hidden platform for four days (four trials per day), and tested their spatial memory of the location of the hidden platform on the fifth day in which the platform had been removed. We found that the latency of LT/CIAS mice were shorter than that of control (Fig. 2D, F (2, 24) = 4.127, p = 0.0347) and CIAS (Fig. 2D, p = 0.0305) mice on the second day, and the latency of LT/CIAS (Fig. 2D, p = 0.0408) and control (Fig. 2D, p = 0.0263) group were shorter than that of CIAS group on the third day. Additionally, the control (Fig. 2E, F (2, 22) = 8.904, p = 0.0011) and LT/CIAS (Fig. 2E, p = 0.0377) group spent more time in the target quadrant than the CIAS group on the fifth day. The total path length (Fig. 2F, F (2, 26) = 0.6078, p = 0.5521) and the average speed (Fig. 2G, F (2, 27) = 0.09944, p = 0.9057) were not significantly different among the three groups.

The altered cognitive performance after light treatment could not due to locomotion activity in the mice

The spontaneous locomotor activity and anxiety level of the mice were examined using the open field test. Both the total distance explored (Fig. 3A, F (2, 26) = 2.503, p = 0.1013) and the averaged velocity of movements (Fig. 3B, F (2, 26) = 2.484, p = 0.1030) were similar among the three groups. There were no significant alteration in the distance traveled in the central area (Fig. 3C, F (2, 26) = 0.7018, p = 0.5048), the number of central entries (Fig. 3D, F (2, 25) = 0.1882, p = 0.8296), and the immobility time in forced swimming test (Fig. 3E, p = 0.1538) among the three groups. To further probe the effects of locomotor activities on the altered cognitive behavioral performance, we next analyzed the correlation between the total distance of OFT and performance in NOR (Fig. 2F), NLR (Fig. 2G) or MWM (Fig. 2H) tests. The results showed that there was no significant correlation between the mobility and the cognitive performance in LT/CIAS (Fig. 2F, R² = 0.002618, p = 0.8884; Fig. 2G, R² = 0.02852, p = 0.641; Fig. 2H, R² = 0.01723, p = 0.7364), CIAS (Fig. 2F, R² = 0.01807, p = 0.7302; Fig. 2G, R² = 0.02784, p = 0.6679; Fig. 2H, R² = 0.02521, p = 0.7072) and control (Fig. 2F, R² = 0.04314, p = 0.5648; Fig. 2G, R² = 0.0157, p = 0.7301; Fig. 2H, R² = 0.3896, p = 0.0981) groups.

Reduced morphological complexity and dendritic spines density of CA1 pyramidal neurons in CIAS mice were partially rescued with light treatment

Neuronal morphology was central to brain development and plasticity and closely associated with abnormal hippocampus function, cognitive deficits associated with schizophrenia and numerous diseases. Then, Golgi-cox staining was conducted to detect potential alterations in CA1 neuronal morphology of three group mice. As shown in Fig. 4, LT has a significant effect on the primary dendrite morphology and dendrite spine density of CA1 neurons (Fig. 4A and 4B). Particularly, the CA1 pyramidal neurons of CIAS mice exhibited markedly decreased spines density compared with the control group (Fig. 4C, F (2, 24) = 18.19, p < 0.0001), which was noticeably rescued by LT (F (2, 24) = 18.19, p = 0.0439). Additionally, the number of intersections, indicating the level of complexity of CA1 pyramidal neurons (Fig. 4D, two-way repeated-measures ANOVA followed by Tukey’s post-hoc test: factor of different group: F (19, 300) = 221.2, p < 0.0001, factor of distance from soma: F (2, 300) = 20.71, p < 0.0001, interaction of two factors: F (38, 300) = 1.664) were significantly different among three groups.

Light Treatment Led To Increased Bdnf Expression And Enhanced Bdnf/p-creb/p-erk Signaling

Previous studies had revealed that BDNF played key roles in neuronal processes such as neurite elongation, spine head enlargement, neurite branch and spine neck elongation [47], which closely related with synaptic plasticity, learning and memory. Therefore, we examined the expression level of BDNF in hippocampal tissue from three groups of mice by Western blot analyses. As shown in the Fig. 5B, the expression of BDNF in hippocampal of mice was found to be significantly decreased (F (2, 6) = 78.25, p < 0.0001) in the CIAS group compared to that in the control group. In addition, the BDNF expression level was significantly increased (F (2, 6) = 78.25, p < 0.0001) in the LT/CIAS group compared to that in the CIAS group, while there was still significant difference in BDNF expression level between LT/CIAS group and control group (F (2, 6) = 78.25, p < 0.0001).

It was well-known that BDNF was a target gene of the transcription factor CREB [48], which played an important role in the formation of long-term memory. To determine whether the altered expression of BDNF was relevant to the p-CREB level in mice in the CIAS and LT/CIAS groups, the levels of p-CREB and CREB in the hippocampus of mice in the three groups were examined. The results showed that p-CREB/CREB from the hippocampus of mice was significantly decreased (Fig. 5C, F (2, 6) = 12.21, p = 0.0204) in the CIAS group compared with the control group. Additionally, p-CREB/CREB was significantly increased (Fig. 5C, p = 0.0086) in the LT/CIAS group compared to the CIAS group. Thus, we suggested that LT could lead to increased phosphorylation of CREB, which may up-regulate the BDNF expression level in the hippocampus of mice.

The ERK pathways were reported to activate CREB and involved in the capability of learning and memory [49]. Hence, we examined the p-ERK/ERK level in the hippocampus of mice in the three groups. Results revealed that the p-ERK/ERK level was increased in the hippocampus of mice in the LT/CIAS group compared with the CIAS and control group (Fig. 5F). These findings indicated that LT facilitated the phosphorylation of ERK and CREB, which resulted in the up-regulation of BDNF signaling, further supporting an important beneficial effect of LT in the regulation of cognitive behaviors in CIAS mice.

This is the first study to investigate the effects of long-term bright light treatment on the cognitive impairment associated with schizophrenia in a mouse model. Results showed significant and long-lasting promoting effects of LT in CIAS mice induced by sub-chronic MK-801injection. Further studies revealed that significant alteration in the dendritic spine density and morphological complexity of CA1 pyramid neurons and the BDNF/p-CREB/p-ERK pathway of hippocampus in CIAS and LT/CIAS mice. These results indicated that the LT ameliorated cognitive deficits in CIAS mice might through up-regulating BDNF/p-CREB/p-ERK signaling pathway.

Cognitive impairment associated with schizophrenia (CIAS) seriously affects patients' social function and quality of life[50]. Thus, developing more effective therapeutic interventions is essential. The NMDAR hypofunction animal models of schizophrenia have been identified their potential utility for therapeutic applications[42]. The cognitive impairments caused by sub-chronic administration of NMDAR noncompetitive antagonist dizocilpine (MK-801) in the current study are significantly robust. In CIAS mice, the cognitive performance such as NLR, NOR and MWM, were declined compared to the saline control mice after 1 week withdraw of MK-801 administration. These results were consistent with previous findings [43, 51]. Additionally, the promoting effects of LT on cognitive deficits in CIAS mice were significant and these beneficial effects of LT could last over 4 weeks after LT was terminated. We found that the cognitive performance of mice in LT/CIAS group such as NLR, NOR and MWM, were getting better compared with the CIAS mice after 3 weeks LT. Further, the NLR and NOR recognition indices of mice in LT/CIAS group still higher than CIAS group 4 weeks after LT was completed. In addition, there was no difference in total distance and velocity across groups and there was no correlation between total distance and cognitive performance. Therefore, group differences were unlikely to be attributed to motivation ability. The effect of light on mood function were excluded by OFT and FST. According to the anxiety and depressive behavior results, the alterations in cognitive performance after 3 weeks of bright light exposure were not relevant to the level of anxiety or depressive. These findings firstly report the enhancing effects of long-term bright LT on a CIAS mouse model.

Dendritic spines are the main sites for receiving and processing synaptic information [52]and the retraction or generation of dendritic spines may be the underlying morphological neural mechanism of learning and memory[53–55]. Additionally, reductions in dendritic spine density of pyramidal neurons in schizophrenia model were found existed along with cognitive impairments[56, 57]. Thus, the morphology of pyramidal neurons in hippocampal CA1 was investigated by Golgi-cox staining. As expected, the pyramidal neurons in hippocampal CA1 of CIAS mice had fewer dendrites, lower spinal density compared to the saline control mice. Notably, we found an enhancement in dendritic complexity and increased dendritic spine density of CA1 pyramidal neurons in LT/CIAS mice compared to the CIAS group. These results suggested that the pyramidal neurons of CA1 in LT/CIAS mice have higher signaling efficiency with other neurons than in CIAS mice, which may be partly responsible for the improved cognitive function in LT/CIAS mice.

Then, we make further exploration of the molecular mechanism that underlies the effects of LT on CIAS mice. It is well known that BDNF is one of the most widely distributed growth factors in the central nervous system, it is essential for the growth and development of the whole brain. Accumulating evidence from both clinical and preclinical studies suggest that the BDNF plays a crucial role in regulating synaptogenesis, synaptic plasticity and memory formation [58] [59, 60]. Hippocampus-specific deletion of BDNF in adult mice have been found displayed impaired spatial memory and extinction of aversive memories [61, 60]. Particularly, BDNF are widely involved in the pathogenesis and treatment of schizophrenia [33, 62–64].

In this study, whether LT would increase the BDNF expression levels were investigated. Consistently, we found that the hippocampal BDNF expression levels of CIAS mice were decreased compared to the control group. Also, up-regulated protein expression levels of BDNF were found in the hippocampus of LT/CIAS mice, suggesting that the BDNF pathway may play critical roles in the cognitive improvement caused by LT.

CREB is a transcription factor that binds to the promoter regions of many genes and is closely related to memory and synaptic plasticity[65]. BDNF can be regulated by phosphorylated CREB [66]. It has been reported that the expression level of CREB is significantly decreased in the brain of patients with schizophrenia after death [67]. Cognitive impairment in schizophrenia is closely related to BDNF/p-CREB/p-ERK signaling pathway. Low CREB levels have been reported to result in reduced phosphorylation of BDNF, which affects the memory function [68, 69]. Therefore, to understand why bright light causes the upregulation of BDNF, p-CREB/CREB and p-ERK/ERK levels in hippocampal were further examined. In our results, p-CREB/p-ERK was decreased in the hippocampus of animals in CIAS mice compared to the control mice. Additionally, p-CREB/p-ERK was increased in the hippocampus of animals in LT/CIAS mice compared to the CIAS mice. Based on these findings, we hypothesize that elevated p-CREB/p-ERK levels might lead to up-regulation of BDNF, and consequently activated of BDNF/p-CREB/p-ERK signaling pathway. And our results confirmed that LT improves cognitive function in CIAS mice by up-regulating the BDNF/p-CREB/p-ERK pathway. However, increasing CREB expression is believed to up-regulate BDNF signaling pathway, improve learning and memory, and reduce pathological damage of hippocampal neurons, so as to improve cognitive deficits and synaptic dysfunction in schizophrenia model mice [68, 69].

There are some limitations to our study. First, the effects of LT on other CIAS models have not been explored. Second, further studies are needed to determine the effects of LT on the electrophysiological properties of neurons in hippocampus of CIAS model and the related neuronal circuit mechanism. The present study is the first to apply LT in CIAS model, which might provide a starting point for developing promising therapies against cognitive impairments in schizophrenia.

In conclusion, long term LT ameliorated sub-chronic MK-801-induced cognitive deficits in mice, and partially rescued the morphology of CA1 pyramidal neurons, which might associate with up-regulating BDNF/p-CREB/p-ERK signaling pathway in LT/CIAS mice.

Acknowledgements: Thanks to the Laboratory Animal Center of Ningbo University for the technical support. Thanks for the technical support by the Core Facilities, Ningbo University School of Medicine. Author contributions: All authors contributed to the study conception and design. Keke Cui and Lizhi Zhang performed the behavioral test and analyzed the data. Keke Cui and Yudong Ying performed the Golgi staining experiment. Yiying Zhou and Yan Xue performed the western blot analysis. The first draft of the manuscript was written by Zhengchun Wang, Keke Cui, Qinwen Wang, Jiajie Gu, Xiaoqin Zhang, Wenhua Zhou and Haowei Shen. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding: This work was supported by the Natural Science Foundation of Zhejiang Province (LY21C090001 and LGF21C010001), National Natural Science Foundation of China (31800874), Ningbo Science and Technology Plan Project (2022S027), and K. C. Wong Magna Fund in Ningbo University.

Data Availability: The authors will provide the data under a reasonable request.

Ethics approval: All experiments were conducted in line with the National Institutes of Health Guide for the Care and Use of Laboratory Animal, which were approved by the Animal Care and Use Committees of Ningbo University.

Consent to participate: Not applicable.

Consent for publication: All authors read and approved the final manuscript.

Declaration of interest: The authors have no relevant financial or non-financial interests to disclose.

Keefe RS, Eesley CE, Poe MP (2005) Defining a cognitive function decrement in schizophrenia. Biol Psychiatry 57 (6):688-691. doi:10.1016/j.biopsych.2005.01.003
Saykin AJ, Shtasel DL, Gur RE, Kester DB, Mozley LH, Stafiniak P, Gur RC (1994) Neuropsychological deficits in neuroleptic naive patients with first-episode schizophrenia. Arch Gen Psychiatry 51 (2):124-131. doi:10.1001/archpsyc.1994.03950020048005
Bowie CR, Harvey PD (2006) Cognitive deficits and functional outcome in schizophrenia. Neuropsychiatr Dis Treat 2 (4):531-536. doi:10.2147/nedt.2006.2.4.531
Désaméricq G, Schurhoff F, Meary A, Szöke A, Macquin-Mavier I, Bachoud-Lévi AC, Maison P (2014) Long-term neurocognitive effects of antipsychotics in schizophrenia: a network meta-analysis. Eur J Clin Pharmacol 70 (2):127-134. doi:10.1007/s00228-013-1600-y
Woodward ND, Purdon SE, Meltzer HY, Zald DH (2005) A meta-analysis of neuropsychological change to clozapine, olanzapine, quetiapine, and risperidone in schizophrenia. Int J Neuropsychopharmacol 8 (3):457-472. doi:10.1017/s146114570500516x
Vandewalle G, Schwartz S, Grandjean D, Wuillaume C, Balteau E, Degueldre C, Schabus M, Phillips C, Luxen A, Dijk D, Maquet P (2010) Spectral quality of light modulates emotional brain responses in humans. Proceedings of the National Academy of Sciences of the United States of America 107 (45):19549-19554. doi:10.1073/pnas.1010180107
LeGates T, Altimus C, Wang H, Lee H, Yang S, Zhao H, Kirkwood A, Weber E, Hattar S (2012) Aberrant light directly impairs mood and learning through melanopsin-expressing neurons. Nature 491 (7425):594-598. doi:10.1038/nature11673
Bedrosian TA, Nelson RJ (2017) Timing of light exposure affects mood and brain circuits. Transl Psychiatry 7 (1):e1017. doi:10.1038/tp.2016.262
Zhu H, Wang N, Yao L, Chen Q, Zhang R, Qian J, Hou Y, Guo W, Fan S, Liu S, Zhao Q, Du F, Zuo X, Guo Y, Xu Y, Li J, Xue T, Zhong K, Song X, Huang G, Xiong W (2018) Moderate UV Exposure Enhances Learning and Memory by Promoting a Novel Glutamate Biosynthetic Pathway in the Brain. Cell 173 (7):1716-1727.e1717. doi:10.1016/j.cell.2018.04.014
Meyer C, Muto V, Jaspar M, Kussé C, Lambot E, Chellappa SL, Degueldre C, Balteau E, Luxen A, Middleton B, Archer SN, Collette F, Dijk DJ, Phillips C, Maquet P, Vandewalle G (2016) Seasonality in human cognitive brain responses. Proc Natl Acad Sci U S A 113 (11):3066-3071. doi:10.1073/pnas.1518129113
Kretschmer V, Schmidt KH, Griefahn B (2013) Bright-light effects on cognitive performance in elderly persons working simulated night shifts: psychological well-being as a mediator? Int Arch Occup Environ Health 86 (8):901-914. doi:10.1007/s00420-012-0826-9
Okamoto Y, Nakagawa S (2015) Effects of daytime light exposure on cognitive brain activity as measured by the ERP P300. Physiol Behav 138:313-318. doi:10.1016/j.physbeh.2014.10.013
Barkmann C, Wessolowski N, Schulte-Markwort M (2012) Applicability and efficacy of variable light in schools. Physiol Behav 105 (3):621-627. doi:10.1016/j.physbeh.2011.09.020
Baron RA, Rea MS, Daniels SG (1992) Effects of indoor lighting (illuminance and spectral distribution) on the performance of cognitive tasks and interpersonal behaviors: The potential mediating role of positive affect. Motivation and Emotion 16:1-33
Yamadera H, Ito T, Suzuki H, Asayama K, Ito R, Endo S (2000) Effects of bright light on cognitive and sleep-wake (circadian) rhythm disturbances in Alzheimer-type dementia. Psychiatry Clin Neurosci 54 (3):352-353. doi:10.1046/j.1440-1819.2000.00711.x
Riemersma-van der Lek RF, Swaab DF, Twisk J, Hol EM, Hoogendijk WJ, Van Someren EJ (2008) Effect of bright light and melatonin on cognitive and noncognitive function in elderly residents of group care facilities: a randomized controlled trial. Jama 299 (22):2642-2655. doi:10.1001/jama.299.22.2642
Forbes D, Culum I, Lischka AR, Morgan DG, Peacock S, Forbes J, Forbes S (2009) Light therapy for managing cognitive, sleep, functional, behavioural, or psychiatric disturbances in dementia. Cochrane Database Syst Rev (4):Cd003946. doi:10.1002/14651858.CD003946.pub3
Warthen DM, Wiltgen BJ, Provencio I (2011) Light enhances learned fear. Proc Natl Acad Sci U S A 108 (33):13788-13793. doi:10.1073/pnas.1103214108
Huang X, Huang P, Huang L, Hu Z, Liu X, Shen J, Xi Y, Yang Y, Fu Y, Tao Q, Lin S, Xu A, Xu F, Xue T, So K, Li H, Ren C (2021) A visual circuit related to the nucleus reuniens for the spatial-memory-promoting effects of light treatment. Neuron 109 (2):347-362.e347. doi:10.1016/j.neuron.2020.10.023
Huiberts LM, Smolders KC, de Kort YA (2015) Shining light on memory: Effects of bright light on working memory performance. Behav Brain Res 294:234-245. doi:10.1016/j.bbr.2015.07.045
Soler JE, Robison AJ, Núñez AA, Yan L (2018) Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat (Arvicanthis niloticus). Hippocampus 28 (3):189-200. doi:10.1002/hipo.22822
Hu J, Shi Y, Zhang J, Huang X, Wang Q, Zhao H, Shen J, Chen Z, Song W, Zheng P, Zhan S, Sun Y, Cai P, An K, Ouyang C, Zhao B, Zhou Q, Xu L, Xiong W, Zhang Z, Meng J, Chen J, Ma Y, Zhao H, Zhang M, Qu K, Hu J, Luo M, Xu F, Chen X, Xiong Y, Bao J, Xue T (2022) Melanopsin retinal ganglion cells mediate light-promoted brain development. Cell 185 (17):3124-3137.e3115. doi:10.1016/j.cell.2022.07.009
Fernandez D, Fogerson P, Lazzerini Ospri L, Thomsen M, Layne R, Severin D, Zhan J, Singer J, Kirkwood A, Zhao H, Berson D, Hattar S (2018) Light affects mood and learning through distinct retina-brain pathways. Cell 175 (1):71-84.e18. doi:10.1016/j.cell.2018.08.004
An K, Zhao H, Miao Y, Xu Q, Li Y, Ma Y, Shi Y, Shen J, Meng J, Yao Y, Zhang Z, Chen J, Bao J, Zhang M, Xue T (2020) A circadian rhythm-gated subcortical pathway for nighttime-light-induced depressive-like behaviors in mice. Nature neuroscience 23 (7):869-880. doi:10.1038/s41593-020-0640-8
Huang EJ, Reichardt LF (2001) Neurotrophins: roles in neuronal development and function. Annu Rev Neurosci 24:677-736. doi:10.1146/annurev.neuro.24.1.677
Bekinschtein P, Cammarota M, Igaz LM, Bevilaqua LR, Izquierdo I, Medina JH (2007) Persistence of long-term memory storage requires a late protein synthesis- and BDNF- dependent phase in the hippocampus. Neuron 53 (2):261-277. doi:10.1016/j.neuron.2006.11.025
Bekinschtein P, Cammarota M, Katche C, Slipczuk L, Rossato JI, Goldin A, Izquierdo I, Medina JH (2008) BDNF is essential to promote persistence of long-term memory storage. Proc Natl Acad Sci U S A 105 (7):2711-2716. doi:10.1073/pnas.0711863105
Bright-light therapy in the treatment of mood disorders.
Tirassa P, Iannitelli A, Sornelli F, Cirulli F, Mazza M, Calza A, Alleva E, Branchi I, Aloe L, Bersani G, Pacitti F (2012) Daily serum and salivary BDNF levels correlate with morning-evening personality type in women and are affected by light therapy. Riv Psichiatr 47 (6):527-534. doi:10.1708/1178.13059
Heo JC, Park JA, Kim DK, Lee JH (2019) Photobiomodulation (660 nm) therapy reduces oxidative stress and induces BDNF expression in the hippocampus. Sci Rep 9 (1):10114. doi:10.1038/s41598-019-46490-4
Xuan W, Agrawal T, Huang L, Gupta GK, Hamblin MR (2015) Low-level laser therapy for traumatic brain injury in mice increases brain derived neurotrophic factor (BDNF) and synaptogenesis. J Biophotonics 8 (6):502-511. doi:10.1002/jbio.201400069
Shang M, Zhang J, Shen M, Sun Z, Gao P, Li J, Xing J, Guo G (2021) Bright light exposure induces dynamic changes of spatial memory in nocturnal rodents. Brain Res Bull 174:389-399. doi:10.1016/j.brainresbull.2021.06.019
Zhang XY, Liang J, Chen DC, Xiu MH, Yang FD, Kosten TA, Kosten TR (2012) Low BDNF is associated with cognitive impairment in chronic patients with schizophrenia. Psychopharmacology (Berl) 222 (2):277-284. doi:10.1007/s00213-012-2643-y
Chukaew P, Bunmak N, Auampradit N, Siripaiboonkij A, Saengsawang W, Ratta-Apha W (2022) Correlation of BDNF, VEGF, TNF-α, and S100B with cognitive impairments in chronic, medicated schizophrenia patients. Neuropsychopharmacol Rep 42 (3):281-287. doi:10.1002/npr2.12261
Singh S, Khushu S, Kumar P, Goyal S, Bhatia T, Deshpande SN (2018) Evidence for regional hippocampal damage in patients with schizophrenia. Neuroradiology 60 (2):199-205. doi:10.1007/s00234-017-1954-4
Favalli G, Li J, Belmonte-de-Abreu P, Wong AH, Daskalakis ZJ (2012) The role of BDNF in the pathophysiology and treatment of schizophrenia. J Psychiatr Res 46 (1):1-11. doi:10.1016/j.jpsychires.2011.09.022
Lipska BK, Lerman DN, Khaing ZZ, Weinberger DR (2003) The neonatal ventral hippocampal lesion model of schizophrenia: effects on dopamine and GABA mRNA markers in the rat midbrain. Eur J Neurosci 18 (11):3097-3104. doi:10.1111/j.1460-9568.2003.03047.x
Green MJ, Matheson SL, Shepherd A, Weickert CS, Carr VJ (2011) Brain-derived neurotrophic factor levels in schizophrenia: a systematic review with meta-analysis. Mol Psychiatry 16 (9):960-972. doi:10.1038/mp.2010.88
Snigdha S, Neill JC, McLean SL, Shemar GK, Cruise L, Shahid M, Henry B (2011) Phencyclidine (PCP)-induced disruption in cognitive performance is gender-specific and associated with a reduction in brain-derived neurotrophic factor (BDNF) in specific regions of the female rat brain. J Mol Neurosci 43 (3):337-345. doi:10.1007/s12031-010-9447-5
Ashe PC, Chlan-Fourney J, Juorio AV, Li XM (2002) Brain-derived neurotrophic factor (BDNF) mRNA in rats with neonatal ibotenic acid lesions of the ventral hippocampus. Brain Res 956 (1):126-135. doi:10.1016/s0006-8993(02)03176-1
Mattson MP (2008) Glutamate and neurotrophic factors in neuronal plasticity and disease. Ann N Y Acad Sci 1144:97-112. doi:10.1196/annals.1418.005
Cui K, Yu Z, Xu L, Jiang W, Wang L, Wang X, Zou D, Gu J, Gao F, Zhang X, Wang Z (2022) Behavioral features and disorganization of oscillatory activity in C57BL/6J mice after acute low dose MK-801 administration. Front Neurosci 16:1001869. doi:10.3389/fnins.2022.1001869
Kim HR, Rajagopal L, Meltzer HY, Martina M (2021) Depolarizing GABA(A) current in the prefrontal cortex is linked with cognitive impairment in a mouse model relevant for schizophrenia. Sci Adv 7 (14). doi:10.1126/sciadv.aba5032
Meltzer HY, Rajagopal L, Huang M, Oyamada Y, Kwon S, Horiguchi M (2013) Translating the N-methyl-D-aspartate receptor antagonist model of schizophrenia to treatments for cognitive impairment in schizophrenia. Int J Neuropsychopharmacol 16 (10):2181-2194. doi:10.1017/s1461145713000928
Cadinu D, Grayson B, Podda G, Harte MK, Doostdar N, Neill JC (2018) NMDA receptor antagonist rodent models for cognition in schizophrenia and identification of novel drug treatments, an update. Neuropharmacology 142:41-62. doi:10.1016/j.neuropharm.2017.11.045
Zhou D, Lv D, Wang Z, Zhang Y, Chen Z, Wang C (2018) GLYX-13 Ameliorates Schizophrenia-Like Phenotype Induced by MK-801 in Mice: Role of Hippocampal NR2B and DISC1. Front Mol Neurosci 11:121. doi:10.3389/fnmol.2018.00121
Ji Y, Lu Y, Yang F, Shen W, Tang TT, Feng L, Duan S, Lu B (2010) Acute and gradual increases in BDNF concentration elicit distinct signaling and functions in neurons. Nat Neurosci 13 (3):302-309. doi:10.1038/nn.2505
Finkbeiner S, Tavazoie SF, Maloratsky A, Jacobs KM, Harris KM, Greenberg ME (1997) CREB: a major mediator of neuronal neurotrophin responses. Neuron 19 (5):1031-1047. doi:10.1016/s0896-6273(00)80395-5
Albert-Gascó H, Ros-Bernal F, Castillo-Gómez E, Olucha-Bordonau FE (2020) MAP/ERK Signaling in Developing Cognitive and Emotional Function and Its Effect on Pathological and Neurodegenerative Processes. Int J Mol Sci 21 (12). doi:10.3390/ijms21124471
McCutcheon RA, Keefe RSE, McGuire PK (2023) Cognitive impairment in schizophrenia: aetiology, pathophysiology, and treatment. Mol Psychiatry. doi:10.1038/s41380-023-01949-9
Li JT, Su YA, Guo CM, Feng Y, Yang Y, Huang RH, Si TM (2011) Persisting cognitive deficits induced by low-dose, subchronic treatment with MK-801 in adolescent rats. Eur J Pharmacol 652 (1-3):65-72. doi:10.1016/j.ejphar.2010.10.074
Sala C, Segal M (2014) Dendritic spines: the locus of structural and functional plasticity. Physiol Rev 94 (1):141-188. doi:10.1152/physrev.00012.2013
Kasai H, Matsuzaki M, Noguchi J, Yasumatsu N, Nakahara H (2003) Structure-stability-function relationships of dendritic spines. Trends Neurosci 26 (7):360-368. doi:10.1016/s0166-2236(03)00162-0
Segal M (2017) Dendritic spines: Morphological building blocks of memory. Neurobiol Learn Mem 138:3-9. doi:10.1016/j.nlm.2016.06.007
de Bartolomeis A, Latte G, Tomasetti C, Iasevoli F (2014) Glutamatergic postsynaptic density protein dysfunctions in synaptic plasticity and dendritic spines morphology: relevance to schizophrenia and other behavioral disorders pathophysiology, and implications for novel therapeutic approaches. Mol Neurobiol 49 (1):484-511. doi:10.1007/s12035-013-8534-3
Kasahara Y, Arime Y, Hall FS, Uhl GR, Sora I (2015) Region-specific dendritic spine loss of pyramidal neurons in dopamine transporter knockout mice. Curr Mol Med 15 (3):237-244. doi:10.2174/1566524015666150330143613
Hajszan T, Leranth C, Roth RH (2006) Subchronic phencyclidine treatment decreases the number of dendritic spine synapses in the rat prefrontal cortex. Biol Psychiatry 60 (6):639-644. doi:10.1016/j.biopsych.2006.03.015
Bekinschtein P, Cammarota M, Izquierdo I, Medina JH (2008) BDNF and memory formation and storage. Neuroscientist 14 (2):147-156. doi:10.1177/1073858407305850
Zagrebelsky M, Tacke C, Korte M (2020) BDNF signaling during the lifetime of dendritic spines. Cell Tissue Res 382 (1):185-199. doi:10.1007/s00441-020-03226-5
Chen YS, Zhang SM, Tan W, Zhu Q, Yue CX, Xiang P, Li JQ, Wei Z, Zeng Y (2023) Early 7,8-Dihydroxyflavone Administration Ameliorates Synaptic and Behavioral Deficits in the Young FXS Animal Model by Acting on BDNF-TrkB Pathway. Mol Neurobiol. doi:10.1007/s12035-023-03226-w
Heldt SA, Stanek L, Chhatwal JP, Ressler KJ (2007) Hippocampus-specific deletion of BDNF in adult mice impairs spatial memory and extinction of aversive memories. Mol Psychiatry 12 (7):656-670. doi:10.1038/sj.mp.4001957
Rao J, Chiappelli J, Kochunov P, Regenold WT, Rapoport SI, Hong LE (2015) Is schizophrenia a neurodegenerative disease? Evidence from age-related decline of brain-derived neurotrophic factor in the brains of schizophrenia patients and matched nonpsychiatric controls. Neurodegener Dis 15 (1):38-44. doi:10.1159/000369214
Peng S, Li W, Lv L, Zhang Z, Zhan X (2018) BDNF as a biomarker in diagnosis and evaluation of treatment for schizophrenia and depression. Discov Med 26 (143):127-136
Fiore M, Korf J, Antonelli A, Talamini L, Aloe L (2002) Long-lasting effects of prenatal MAM treatment on water maze performance in rats: associations with altered brain development and neurotrophin levels. Neurotoxicol Teratol 24 (2):179-191. doi:10.1016/s0892-0362(01)00214-8
Benito E, Barco A (2010) CREB's control of intrinsic and synaptic plasticity: implications for CREB-dependent memory models. Trends Neurosci 33 (5):230-240. doi:10.1016/j.tins.2010.02.001
Landeira BS, Santana T, Araújo JAM, Tabet EI, Tannous BA, Schroeder T, Costa MR (2018) Activity-Independent Effects of CREB on Neuronal Survival and Differentiation during Mouse Cerebral Cortex Development. Cereb Cortex 28 (2):538-548. doi:10.1093/cercor/bhw387
Ren X, Rizavi HS, Khan MA, Bhaumik R, Dwivedi Y, Pandey GN (2014) Alteration of cyclic-AMP response element binding protein in the postmortem brain of subjects with bipolar disorder and schizophrenia. J Affect Disord 152-154:326-333. doi:10.1016/j.jad.2013.09.033
Guo C, Liu Y, Fang MS, Li Y, Li W, Mahaman YAR, Zeng K, Xia Y, Ke D, Liu R, Wang JZ, Shen H, Shu X, Wang X (2020) ω-3PUFAs Improve Cognitive Impairments Through Ser133 Phosphorylation of CREB Upregulating BDNF/TrkB Signal in Schizophrenia. Neurotherapeutics 17 (3):1271-1286. doi:10.1007/s13311-020-00859-w
Fang MS, Li X, Qian H, Zeng K, Ye M, Zhou YJ, Li H, Wang XC, Li Y (2017) ω-3PUFAs prevent MK-801-induced cognitive impairment in schizophrenic rats via the CREB/BDNF/TrkB pathway. J Huazhong Univ Sci Technolog Med Sci 37 (4):491-495. doi:10.1007/s11596-017-1762-4

Download PDF

Reviewers agreed at journal
04 Jun, 2023
Reviewers invited by journal
18 May, 2023
Editor invited by journal
18 Apr, 2023
Editor assigned by journal
23 Mar, 2023
First submitted to journal
22 Mar, 2023

You are reading this latest preprint version

Light treatment ameliorates sub-chronic MK-801-induced cognitive deficits in mice through up-regulating BDNF/p-CREB/p-ERK signaling pathway

Status:

Version 1

Abstract

Figures

Introduction

Materials And Methods

Animal model

Behavioral Tests

Open Field Test

Novel Object Location And Novel Object Recognition Test

Y-maze Test

Morris Water Maze Test

Forced Swimming Test

Golgi-cox Staining And Analysis

Western Blot Analysis

Statistical analysis

Result

Light treatment increased the recognition index of novel objects and locations in CIAS mice

Light Treatment Promoted Spatial Memory In Cias Mice

Light Treatment Led To Increased Bdnf Expression And Enhanced Bdnf/p-creb/p-erk Signaling

Discussion

Declarations

References

Status:

Version 1