Disorders in the gut and liver are involved in depression contagion between isosexual post-stroke depression mice and the healthy cohabitors

ClC-3-depedent polarization of microglia protects against cerebral ischemic injury in mice

Polarization of microglia has attracted great attention in ischemic stroke. Emerging evidence suggests that chloride channel 3 (ClC-3) is involved in inflammatory responses and stroke. However, the link between ClC-3 and polarization of microglia in ischemic stroke remains unclear. Herein, we found both cerebral ischemia and oxygen-glucose deprivation (OGD) induced a significant upregulation of ClC-3 in microglia. While knockdown of ClC-3 markedly increased nuclear factor kappa B (NF-κB) and CD86, and decreased CD206 in BV-2 cells under OGD conditions, facilitating them to shift into a M1-like phenotype. Furthermore, ClC-3 knockout significantly aggravated infarct volume and neurological deficits, accompanied by increased activated microglia in the peri-infarct area 1 day after cerebral ischemia. By contrast, ClC-3 overexpression obviously suppressed nuclear translocation of NF-κB, decreased OGD-induced elevated mRNA levels of TNF-α, IL-1β and IL-10, and enhanced M2-like markers (Arg1, CD206, and TREM2) in microglia, leading to alleviated infarct volume and neurological deficits. While ClC-3 overexpression could not reverse a transformation from M1-like phenotype to M2-like polarization in presence of lipopolysaccharide (LPS) and interferon gamma (IFNγ) treatment for 24 h. Collectively, our findings indicate that ClC-3-dependent polarization of microglia is critically important for protecting against cerebral ischemia injury, suggesting ClC-3 is a promising therapeutic target for ischemic stroke.

Adjusting the composition of gut microbiota prevents the development of post-stroke depression by regulating the gut-brain axis in mice

Disturbances in gut microbiota contribute to an imbalanced gut-brain axis, which is critical for post-stroke depression (PSD), while the underlying mechanisms remain unclear. The objective of this study was to examine the effects of modifying gut microbiota through antibiotic treatment (ABX) and fecal microbiota transplantation (FMT) on the progression of PSD. The PSD model was established by occluding the middle cerebral artery (MCAO), followed by a four-week isolated housing and restraint stress initiated three days after MCAO. For ABX, the PSD mice received antibiotic water for four weeks. While another group of PSD mice underwent FMT or fluoxetine (FLX) for four weeks. At day 35 post-MCAO, behavioral tests were conducted. Results indicated ABX and FMT significantly altered the composition of intestinal flora caused by PSD, all the treatments markedly attenuated anxiety- and depressive-like behaviors and inflammation in the gut and brain. ABX obviously alleviated PSD-induced disorder of intestinal barrier, decreased mRNA levels of TNF-α, IL-1β and IL-6, and decreased CD4+ cells in the colon. While FMT significantly decreased CD8+ cells and increased the goblet cells in colon. Furthermore, both ABX and FMT could reduce activated microglia and pro-inflammatory cytokines in the brain, alleviate decreased Nissl's bodies in the hippocampus, and reverse the decreases in 5-HT, Glu and DA in the striatum caused by PSD. Unlike ABX, FMT was similar to FLX. These findings suggest homeostasis of gut microbiota is indispensable for the development of PSD; adjusting the gut microbiota significantly improves PSD with enhanced functions of gut-brain axis.

Contagion of depression: a double-edged sword

Depression is a significant mental health issue with extensive economic implications, and recent studies suggest it may be transmitted between individuals. However, the mechanisms of this contagion remain unclear, and the social buffering effect has been understudied. This research employs three rodent models, including stress crossover, cohabitation-induced, and non-contact induced depression contagion models, to explore these mechanisms. Here, we report that that naive mice cohabiting with depressed mice showed increased corticosterone levels and depressive behaviors, unlike those with stressed mice, who did not exhibit these changes and even mitigated desperation in stressed mice. Non-contact cohabitation did not produce significant behavioral differences, but exposure to bedding from depressed mice reduced sucrose preference in naive mice. This study introduces reliable models of depression contagion, suggesting it operates independently of stress transmission. The interplay between depression contagion and social buffering may vary in different contexts. These findings provide new insights into the mechanisms of depression contagion and potential strategies for preventing depressive disorders.

Gut microbiota is necessary for pair-housing to protect against post-stroke depression in mice

The goal of this study is to investigate the role of microbiota-gut-brain axis involved in the protective effect of pair-housing on post-stroke depression (PSD). PSD model was induced by occluding the middle cerebral artery (MCAO) plus restraint stress for four weeks. At three days after MCAO, the mice were restrained 2 h per day. For pair-housing (PH), each mouse was pair housed with a healthy isosexual cohabitor for four weeks. While in the other PH group, their drinking water was replaced with antibiotic water. On day 35 to day 40, anxiety- and depression-like behaviors (sucrose consumption, open field test, forced swim test, and tail-suspension test) were conducted. Results showed pair-housed mice had better performance on anxiety- and depression-like behaviors than the PSD mice, and the richness and diversity of intestinal flora were also improved. However, drinking antibiotic water reversed the effects of pair-housing. Furthermore, pair-housing had an obvious improvement in gut barrier disorder and inflammation caused by PSD. Particularly, they showed significant decreases in CD8 lymphocytes and mRNA levels of pro-inflammatory cytokines (TNF-a, IL-1β and IL-6), while IL-10 mRNA was upregulated. In addition, pair-housing significantly reduced activated microglia and increased Nissl's body in the hippocampus of PSD mice. However, all these improvements were worse in the pair-housed mice administrated with antibiotic water. We conclude that pair-housing significantly improves PSD in association with enhanced functions of microbiota-gut-brain axis, and homeostasis of gut microbiota is indispensable for the protective effect of pair-housing on PSD.

The oxytocin receptor is essential for the protective effect of pair housing on post-stroke depression in mice

The beneficial effect of social interaction in mitigating the incidence of post-stroke depression (PSD) and ameliorating depressive symptoms has been consistently demonstrated through preclinical and clinical studies. However, the underlying relationship with oxytocin requires further investigation. In light of this, the present study aimed to explore the protective effect of pair housing on the development of PSD and the potential relationship with oxytocin receptors. The PSD model was induced by middle cerebral artery occlusion (MCAO) for 50 min, followed by 4-week isolated housing and restrained stress. Subsequently, each mouse in the pair-housing group (PH) was pair-housed with an isosexual healthy partner. Another group was continuously administrated fluoxetine (10 mg/Kg, i.p, once a day) for 3 weeks. To elucidate the potential role of oxytocin, we subjected pair-housed PSD mice to treatment with an oxytocin receptor (OXTR) antagonist (L368,889) (5 mg/Kg, i.p, once a day) for 3 weeks. At 31 to 32 days after MCAO, anxiety- and depressive-like behaviors were assessed using sucrose consumption, forced swim test, and tail-suspension test. The results showed that pair housing significantly improved post-stroke depression to an extent comparable to that of fluoxetine treatment. Furthermore, pair housing significantly decreased corticosterone in serum, increasing OXT mRNA expression in the hypothalamus. Treatment with L368,889 essentially reversed the effect of pair housing, with no discernible sex differences apart from changes in body weight. Pair housing increased hippocampal serotonin (5-HT), but treatment with L368,889 had no significant impact. Additionally, pair housing effectively reduced the number of reactive astrocytes and increased Nissl's body in the cortex and hippocampal CA3 regions. Correspondingly, treatment with L368,889 significantly reversed the changes in the Nissl's body and reactive astrocytes. Moreover, pair housing downregulated mRNA levels of TNF-α, IL-1β, and IL-6 in the cortex caused by PSD, which was also reversed by treatment with L368,889. In conclusion, pair housing protects against the development of PSD depending on OXT and OXTR in the brain, with no significant divergence based on sex. These findings provide valuable insights into the potential of social interaction and oxytocin as therapeutic targets for PSD. Further research into the underlying mechanisms of these effects may contribute to the development of novel treatments for PSD.

Research progress on post-stroke depression

Stroke is a highly prevalent and widely detrimental cardiovascular disease, frequently resulting in impairments of both motor function and neural psychological capabilities, such as post-stroke depression (PSD). PSD is the most prevalent neuropsychological disorder among stroke patients, characterized by persistent emotional lowness and diminished interest as its primary features. This article summarizes the mechanism research, animal models and related treatments of PSD. Further improvements are needed in the screening of research subjects and the construction of animal models in the study of PSD. At the same time, in the study of the mechanism of PSD, we need to consider the interaction between multiple systems. The treatment of PSD requires more careful consideration. This can help us to find something new in the study of the mechanism of complex PSD, which provides a new direction for us to develop new treatment delivery.

The role of IL-23/IL-17 axis in ischemic stroke from the perspective of gut-brain axis

Bidirectional communication between central nervous system (CNS) and intestine is mediated by nerve, endocrine, immune and other pathways in gut-brain axis. Many diseases of CNS disturb the homeostasis of intestine and gut microbiota. Similarly, the dysbiosis of intestinal and gut microbiota also promotes the progression and deterioration of CNS diseases. IL-23/IL-17 axis is an important inflammatory axis which is widely involved in CNS diseases such as experimental autoimmune encephalomyelitis (EAE), multiple sclerosis (MS), and ischemic stroke (IS). Attributing to the long anatomically distances between ischemic brain and gut, previous studies on IL-23/IL-17 axis in IS are rarely focused on intestinal tissues. However, recent studies have found that IL-17⁺T cells in CNS mainly originate from intestine. The activation and migration of IL-17⁺T cells to CNS is likely to be affected by the altered intestinal homeostasis. These studies promoted the attention of IL-23/IL-17 axis and gut-brain axis. IS is difficult to treat because of its extremely complex pathological mechanism. This review mainly discusses the relationship between IL-23/IL-17 axis and IS from the perspective of gut-brain axis. By analyzing the immune pathways in gut-brain axis, the activation of IL-23/IL-17 axis, the roles of IL-23/IL-17 axis in gut, CNS and other systems after stoke, this review is expected to provide new enlightenments for the treatment strategies of IS.