Mitochondrial dysfunction and endoplasmic reticulum (ER) stress occur in ischemic stroke. The disruption of these two organelles can directly lead to cell death through various signaling pathways. Thus, investigation of the associated molecular mechanisms in cerebral ischemia is a prerequisite for stroke treatment. Pleckstrin homology-like domain family A member 1 (PHLDA1) is a multifunctional protein that can modulate mitochondrial function and ER stress in cardiomyocyte and cancer cells. This work studied the role of PHLDA1 in cerebral ischemic/reperfusion (I/R) injury and explored the underlying mechanisms associated with mitochondrial functions and ER stress. Middle cerebral artery occlusion/reperfusion (MCAO/R)-treated mice and oxygen-glucose deprivation/reoxygenation (OGD/R)-stimulated neurons were used as I/R models in vivo and in vitro, respectively. PHLDA1 was upregulated in ischemic penumbra of MCAO/R-induced mice and OGD/R-exposed neurons. In vitro , PHLDA1 knockdown protected neurons from OGD/R-induced apoptosis. In vivo , PHLDA1 silencing facilitated functional recovery and reduced cerebral infarct volume. Mechanistically, PHLDA1 knockdown promoted PPARγ nuclear translocation, which may mediate the effects on reversion of mitochondrial functions and alleviation of ER stress. In summary, PHLDA1 knockdown alleviates neuronal ischemic injuries in mice. PPARγ activation and mitochondrial dysfunction and endoplasmic reticulum stress attenuation are involved in the underlying mechanisms.
Cerebral ischemia/reperfusion injury is the main cause of neurological deficit following stroke. Pleckstrin homology-like domain, family A, member 1 (PHLDA1) is increasingly recognized as a critical determinant in immunological regulation and cell apoptosis, but its role in neuroinflammation during cerebral ischemia/reperfusion injury remains to be elucidated. In this study, middle cerebral artery occlusion/reperfusion (MCAO/R) in C57BL/6 mice and oxygen-glucose deprivation/reoxygenation (OGD/R) in BV-2 cells were used as models in vivo and in vitro , respectively. MACO/R mice and OGD/R cells were treated with scramble or PHLDA1 small interfering RNAs (siRNAs) to achieve the goal of PHLDA1 knockdown. The results showed that the expression of PHLDA1 was significantly increased in MCAO/R mice and OGD/R cells compared to their normal controls, respectively. Mice treated with PHLDA1 siRNA exhibited a lower degree of infarct volume and brain water content compared to the NC siRNA-treated mice. Notably, PHLDA1 knockdown switched the M1 pro-inflammatory phenotype to the M2 anti-inflammatory phenotype by decreasing the expression of M1 markers (i.e., CD16, TNF-α, IL-6 and IFN-γ, and iNOS) and elevating the expression of M2 markers (i.e., CD206, IL-4, IL-10, and Arg-1). Moreover, PHLDA1 knockdown suppressed the NLRP3 inflammasome activation by reducing NLRP3, ASC, cleaved caspase 1 and cleaved IL-1β expression. In summary, these results suggest that PHLDA1 blockade effectively alleviates the ischemia/reperfusion-induced cerebral injury by switching microglial M1/M2 polarization and inhibiting NLRP3 inflammasome activation. Targeting PHLDA1 could be considered as a novel strategy in the treatment against post-ischemic brain injury.
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