Long Term Recovery from Ischemic Stroke
Title:
Normobaric intermittent hypoxic training regulates microglia phenotype and enhances phagocytic activity
Abstract:
The microglia are the resident immune cells in the central nerve system. In the various pathological conditions, prolonged activated microglia could deteriorate brain damage. The regulation of the microglia polarization should be considered in developing an intervention for ischemic stroke patients. Normobaric intermittent hypoxic training protects the brain from intensive ischemic stresses. This study examined the role of intermittent hypoxic training in the regulation of microglia polarization that occurs in the in vitro model of oxygen–glucose deprivation (OGD)–reoxygenation. EOC20 were assigned to the following groups; (1) Normoxia, (2) oxygen–glucose deprivation–reoxygenation, (3) intermittent hypoxic training, (4) oxygen–glucose deprivation–reoxygenation + intermittent hypoxic training; 24 h after the intermittent hypoxic training, microglia were harvested to perform the following experiments; cell viability (Calcein AM and LDH activity assay), quantification of proteins (Western blot), cytokine (ELISA), and reactive oxygen species (ROS) (H2DCFDA assays), phagocytic activity by using latex beads coated with FITC, and cell phenotype (immunocytochemistry and flow cytometric analysis, and immunoblot CD206 (M2)). One-way ANOVA with Tukey’s post hoc test was used for the statistical analysis. Oxygen–glucose deprivation/reoxygenation decreases cell viability to 50% of normoxia. Intermittent hypoxic training protects the microglia from oxygen–glucose deprivation/reoxygenation stress. Intermittent hypoxic training regulates the polarization of the microglial phenotype toward anti-inflammatory type M2 (vs. oxygen–glucose deprivation and reoxygenation). Intermittent hypoxic training increases phagocytic activity (about 12 folds) vs. normoxia. ROS in the oxygen–glucose deprivation/reoxygenation group is increased, but intermittent hypoxic training lowers the ROS generation by oxygen–glucose deprivation/reoxygenation. The protein content of the toll-like receptor (TLR2) was significantly elevated in the oxygen–glucose deprivation and reoxygenation group, and intermittent hypoxic training lowered to normoxia level. Anti-inflammatory cytokines, such as IL-10 and IL-4, were significantly increased in the intermittent hypoxic training groups. Due to the effect of intermittent hypoxic training on the microglia phenotype, intermittent hypoxic training could be considered as an effective intervention in the treatment or rehabilitation program for the ischemic stroke victims.
Conclusion:
In summary, the results of this study support that IHT induces the M2 microglia phenotype in the in vitro OGD–reoxygenation stress model. This finding could be beneficial in the long-term recovery of patients who suffered from ischemic stroke. Possibly, IHT protects the microglia from the ischemic stroke and subsequent reperfusion so that more microglia gets involved in the early healing procedure. Importantly, 24 h after the ischemic stroke occurs, IHT also increases the anti-inflammatory phenotype of microglia. This regulatory function of IHT in the induction of M2 microglia will dampen the CNS injury that is attributed to the prolonged inflammatory responses observed in the ischemic stroke patients. The IHT-induced M2 microglia maintains the phagocytic activity of activated microglia and mitigates ROS generation. Therefore, IHT can be considered as an efficient intervention that could be adapted in the current rehabilitation programs.
Full study can be found HERE