The phosphokinase activity of IRE1ɑ prevents the oxidative stress injury through miR‐25/Nox4 pathway after ICH.

Background: Endoplasmic reticulum (ER) stress and oxidative stress are the major pathologies encountered after intracerebral hemorrhage (ICH). Inositol‐requiring enzyme‐1 alpha (IRE1α) is the most evolutionarily conserved ER stress sensor, which plays a role in monitoring and responding to the accumulation of unfolded/misfolded proteins in the ER lumen. Recent studies have shown that ER stress is profoundly related to oxidative stress in physiological or pathological conditions. The purpose of this study was to investigate the role of IRE1α in oxidative stress and the potential mechanism. Methods: A mouse model of ICH was established by autologous blood injection. The IRE1α phosphokinase inhibitor KIRA6 was administrated intranasally at 1 h after ICH, antagomiR‐25 and agomiR‐25 were injected intraventricularly at 24 h before ICH. Western blot analysis, RT‐qPCR, immunofluorescence staining, hematoma volume, neurobehavioral tests, dihydroethidium (DHE) staining, H2O2 content, brain water content, body weight, Hematoxylin and Eosin (HE) staining, Nissl staining, Morris Water Maze (MWM) and Elevated Plus Maze (EPM) were performed. Results: Endogenous phosphorylated IRE1α (p‐IRE1α), miR‐25‐3p, and Nox4 were increased in the ICH model. Administration of KIRA6 downregulated miR‐25‐3p expression, upregulated Nox4 expression, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, reduced body weight, aggravated spatial learning and memory deficits, and increased anxiety levels. Then antagomiR‐25 further upregulated the expression of Nox4, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, whereas agomiR‐25 reversed the effects promoted by KIRA6. Conclusion: The IRE1α phosphokinase activity is involved in the oxidative stress response through miR‐25/Nox4 pathway in the mouse ICH brain. [ABSTRACT FROM AUTHOR]