This study aimed to detect indicators related to oxidative stress and inflammation in patients with early-onset ischaemic stroke. The results showed significantly higher levels of MDA, IL-6, TNF-α, and lower expression of SOD in the ischaemic stroke group compared to the control group, indicating the involvement of oxidative stress and inflammation in the early pathological progression of ischaemic stroke. These findings are consistent with previous studies[24] that have also reported similar associations between oxidative stress, inflammation, and ischaemic stroke progression[25].
Ischaemic stroke is a complex pathophysiological process involving various factors that contribute to its occurrence and progression. In the core infarct zone, rapid cellular death leads to neuronal dysfunction and loss of electrical activity and metabolism. In contrast, oxidative stress and inflammation in the peripheral ischaemic penumbra trigger cellular and molecular cascades that lead to neuronal degeneration and death[26, 27]. This study found a downward trend in BMAL1 and SIRT1 expression along with increased activation of oxidative stress (MDA) and inflammatory factors (IL-6, TNF-α) in patients with early-onset ischemic stroke. As a core biological clock protein, BMAL1 plays a crucial role in regulating the circadian rhythm[19, 28, 29], and previous studies have demonstrated that its transcriptional activation is regulated by acetylation/deacetylation, the circadian vibration of Per2 and BMAL1 luciferase is weakened, and transcription of BMAL1 ceases after SIRT1 deacetylation[30]. The present study found significantly lower levels of BMAL1 in the ischaemic stroke group than that in the control group, and the corresponding low expression of SIRT1 was consistent with BMAL1 oscillation, indicating that SIRT1 regulates BMAL1 and participates in the early occurrence of ischaemic stroke. Earlier studies suggested that the incidence of stroke is highest at night[31], while more recent research found peak incidence at 06:00–12:00[32] and bimodal pattern with peaks at 6:00–12:00 and 18:00–20:00[33]. Approximately 24% of cerebrovascular events occur within the first hour after waking[34], and the transition from sleep to wakefulness might be an independent risk factor for stroke in the morning or after a nap[35]. This study also analyzed BMAL1 and SIRT1 levels across four different time subgroups (00:00–05:59, 06:00–11:59, 12:00–17:59, and 18:00–23:59) and found that the expression levels were lowest in patients with ischaemic stroke onset from subgroup 2 (6:00–11:59), while subgroup 3 (12:00–17:59) showed a higher trend of BMAL1 and SIRT1 levels. This suggested that the decreased expression of SIRT1-BMAL1 may be associated with a higher incidence of ischaemic cerebral infarction in the morning but not significantly associated with a higher incidence in the afternoon. Additionally, this study found that SIRT1-BMAL1 exhibited time-dependent synchronization with initial systolic blood pressure and MPO. MPO is expressed in infiltrating neutrophils, activated microglia, neurons, and astrocytes in ischemic brain tissue and catalyzes the reaction of chloride ions to produce HOCl, contributing to oxidative stress-induced modification of lipoproteins[36], induction of endothelial dysfunction[37], and increased plaque vulnerability[38]. Our study found MPO to be moderately positively correlated with MDA and to exhibit a circadian rhythm inversely consistent with that of SIRT1-BMAL1, suggesting that the SIRT1-BMAL1 pathway might play a certain role in the early occurrence of ischaemic stroke.
In the pathogenesis of acute myocardial infarction, BMAL1 boosts antioxidant activity by enhancing the redox state of HSPB1[39]. However, the impact of BMAL1 on oxidative stress and inflammation in the progression of ischaemic stroke remains unclear. We examined the expression levels of the antioxidant stress kinase SOD and TNF-α at different onset times of ischaemic stroke and found that their expression levels were consistent with those of SIRT1-BMAL1. Correlation analysis revealed a moderate positive correlation between BMAL1 and SIRT1 and oxidative stress factor SOD, but a negative correlation with IL-6, TNF-ɑ, and MDA. Therefore, we suggest that the SIRT1-BMAL1 pathway may involve the antioxidant response of SOD and have a negative regulatory effect on the oxidative stress factor MDA and inflammatory factors IL-6 and TNF-ɑ.
Dyslipidaemia is an independent risk factor for AIS, as demonstrated by previous studies. BMAL1 knockout in mice has been shown to cause hyperlipidemia and increase atherosclerosis[40], likely due to BMAL1’s regulation of key lipolysis enzymes such as ATGL, LPL, and HSL[41]. However, this study did not observe significant circadian rhythm changes in TGs, TC, LDL, HDL, immediate systolic blood pressure and diastolic blood pressure, blood glucose and HCY. The unstable biological indicators during early-stage acute cerebral infarction may be due to the small he sample size of the subgroup.
In addition, the severity of ischaemic stroke at onset also showed rhythmic changes. However, unlike SIRT1-BMAL1, patients with onset at 00:00–05:59 had the highest NIHSS score while those with onset between 12:00–17:59 had the lowest. Shokri et al.[42] analyzed 1450 acute ischaemic stroke patients and found that patients with morning onset had the highest NIHSS score while the lowest was observed during the period from 18:01 to 24:00. This phenomenon is likely associated with delays in seeking medical attention. Our study found that patients with onset at night had the highest NIHSS score but further analysis of related factors is needed through follow-up experiments.
This study focused on the expression of SIRT1-BMAL1 and risk factors during different onset times of ischemic stroke and revealed that SIRT1-BMAL1 may contribute to the early onset of ischemic stroke by regulating oxidative stress.