Neuroprotector Effect Of Strength Training In An Neuroinflammation Animal Model


 Background: The preventive role of muscular strength in the diminishing of a neuroinflammation is yet unknown. In this study, the role of the prophylactic muscular strength exercise was investigated, whether it would diminish cognitive alterations and modify the antioxidant intracellular scenery in an animal neuroinflammation model of the CA1 region of the hippocampus. Methods: The animals received muscular strength training for eight weeks, three times a week. Subsequently, the stereotaxic surgery, with intra-hippocampal infusion of either saline solution or l ipopolysaccharide (LPS) was performed. Next, behavioral tests were performed: objects and social recognition. At last, the animals were euthanized and the collect of the hippocampus and the prefrontal cortex were performed and, later, the dosage of the antioxidant activity was performed. Results: The results showed that the muscular strength exercises was capable of showing a beneficial prophylactic effect in the oxidative stress caused by an acute neuroinflammation. There was diminishing of the reduced glutathione concentration (GSH) and increase of the activity of the catalase enzyme (CAT) in the group (SE + LPS), regarding the control groups. In the prefrontal cortex, there was only an increase of the CAT activity in the group (SE + LPS), regarding the groups (CT) and (SE + SAL). As for the cognitive alterations there were found in the (SE + LPS) group, diminishing the mnemonic hazard of the discriminative and social memories, when compared to the control groups. Conclusion: We concluded, therefore, that the induction of a local inflammatory process in the hippocampus leads to mnemonic deficits in behavioral activities and increase of the GSH concentration, and that the muscular strength exercise performed prophylactically presents a protective effect capable of minimizing such mnemonic deficits and increasing the antioxidant defenses in mice that suffered a local neuroinflammatory process in the hippocampus.

INTRODUCTION 95 aiming at eliminating the aggressive stimulation and reparing the tissue damage 114 [1,7]. 115 It is known that the neuroinflammatory process is a needed mechanism 116 and important in the brain homeostasis [3]. However, when outside 117 (environmental) harmful persistent stimulation and/or internal stimulation are 118 recognized by the microglia [8], a system of positive retro-feeding is sustained, 119 6 over-elevating the production of pro-inflammatory factors, which promote cell 120 death and atrophy of local neural synapses, inducing symptoms such as cognitive 121 decline, movement alterations and memory loss [4]. 122 The constant activation of the microglia, the increase of the oxidative 123 stress, the reduction of the neurotrophic support, the alteration of the metabolism 124 of neurotransmitters and the rupture of the brain-blood barrier are described in 125 the literature as associated mechanisms to pathologies and neuropsychiatric 126 disorders, including Alzheimer's disease [6,9], Parkinson disease and 127 depression [5]. 128 It is foreseen that neuroinflammatory/neurodegenerative diseases will be the   capacity for 5 animals, covered with shaving, which was switched every two days. 163 They received water and food at ease. The maximum concern was deliberated 164 with the purpose of minimizing the suffering of the animals and reducing the 165 number of animals to be used in the research. All the experiments were according 166 8 to the rules of the CEUA/UNIPAMPA and of the "Principles of laboratory animal 167 care" (NIH publication N° 85-23, revised in 1996), under the report #046/2017. 168 For the experiments, the animals were divided into six groups, having ten 169 animals per group. The groups were divided into control groups: group naive,  The animals were submitted to eight weeks of training, three times a week.   immediately before losing the adherence the maximum tension was recorded.

216
Three tests were performed and as result, a mean value was obtained [18].  Object recognition memory test 234 To evaluate the discriminative memory, the object recognition test was 235 performed. From the first to the fourth day of the experiment of such task, 236 considering the habituation period, the animal was put in the left superior corners 237 of the device, a 50 cm × 50 cm × 50 cm box, made of compensated, acrylic 238 transparent polyvinyl chloride, and then left it there for 5 minutes, without a single 239 object inside the box, so that the animal could get used to the environment.

240
During the training session, one day after the last day of the habituation day, 241 the animal was once again put in the box with two equal objects, A and B, located  Social recognition memory test 253 The task of evaluating the social memory is an adaptation of the social 254 interaction test proposed by [21]. The task was performed in 3 days. First, the 255 animals were placed in a habituation field (the same size and characteristics 256 described in the previously described task of object recognition) with two small 257 cages during 20 minutes for free exploration. In the following day, the training 258 was performed with the inclusion of a juvenile mouse in one of cages for 1 h of 259 free exploration, being, at the same period, one cage left empty. After 24 h, the 260 test was performed when the same mouse of the training (which means, the 261 mouse that became familiar) and a new mouse were put for exploration for 5 min.

262
The time spent exploring the new mouse and the familiar mouse was registered.

263
The exploration of the animal was defined as smelling or touching the cages with 264 the nose and/or front legs [19].    After all the behavioral tasks, the animals were euthanized, and then the 291 collect of the hippocampus, prefrontal cortex and heart mass was performed. For 292 the heat mass collect, the open chest procedure was performed and blood was 293 drawn by cardiac puncture, followed by the removal of the heart. After such 294 removal, the heart was washed with saline solution (0.9%) to remove the excess 295 of blood and, immediately the heart mass was weighed using an analytic scale.

296
The index of cardiac hypertrophy was calculated through the reason between 297 heart mass (mg) and body mass (g).    Quantification of the GSH and LOOH levels 328 As described by [26,27], 50 µl of the homogenate was added to 40 µL of 329 12,5% of thrichloroacetic. Next, the material was centrifuged at 1.4 G / 15 min.       The mice were submitted to eight weeks of strength exercise training 408 protocol. As followed, they received intra-CA1 dorsal bilateral infusion of either        The animals had their level of anxiety analyzed in the elevated plus maze.

519
The results of the performance in such task for all groups are shown in Figure 6.       The mice were submitted to eight weeks of training in the strength exercise 582 protocol. As followed, they received the intra-CA1 dorsal bilateral infusion of 583 saline (SAL) or LPS (40 µg/side). The groups NAIVE and control (CT) were not 584 submitted to the intra-CA1 infusion procedure. After being euthanized, the heart 585 of the animals was removed and then weighted. The heart mass was corrected 586 by the body mass. For such correction, the following formula was used: (Total 587 weight of the heart/body weight) x 100. Two-way ANOVA, followed by Newman-588 Keuls multiple comparison test, a P < 0.05 when compared to the group NAIVE. 589 bb P < 0.01 when compared to the group SAL not exercised. c P < 0.05 when 590 compared to the group LPS not exercised.

591
The prophylactic intervention of muscular strength exercise was able to 592 induce a physiological hypertrophy, compensatory/adaptation, needed to 593 30 maintain a cardiac performance in increased condition of circulatory overload 594 during the animals' training. It is known that the intensive and long-lasting 595 physical training induces cardiovascular adaptations, including a cardiac 596 hypertrophy, which allows the heart an exceptional physical performance. We 597 noticed, in this study, a statistical difference in the heart mass of the animals 598 which trained, when compared to the ones that did not train, which shows that 599 the heart of the trained animals became adapted to the muscular strength            control groups, as well as regarding the group that had also induced local 770 neuroinfammation, but which did not suffer the previous protocol of strength 771 exercise. In the prefrontal cortex, it was verified that the muscular strength 772 exercise reduced the activity of the enzyme CAT in such brain region, compared 773 with the mice that were not exercised, except for the reduction in the activity of 774 CAT in the exercised group.

775
In the object recognition test, we discovered that the prophylactic strength  In conclusion, the present study reinforces evidences that the muscular    The datasets used and/or analysed during the current study are available from 965 the corresponding author on reasonable request.