Senescence marker protein 30 confers neuroprotection in oxygen-glucose deprivation/reoxygenation-injured neurons through modulation of Keap1/Nrf2 signaling: Role of SMP30 in OGD/R-induced neuronal injury

SMP30 alleviates cerebral ischemia/reperfusion-induced neuronal injury by inhibiting HDAC4/PSD-95 to preserve mitochondrial function

Ischemic stroke is a major cause of global death and permanent disability. Major consequences of ischemic stroke include neuronal mitochondrial dysfunction. We investigated the effects of senescence marker protein 30 (SMP30) on mitochondria-mediated apoptosis and histone deacetylase 4 (HDAC4)/postsynaptic density-95 (PSD-95) signaling in stroke models in vivo and in vitro. Rats with middle cerebral artery occlusion/reperfusion (MCAO/R) were used to simulate cerebral ischemia/reperfusion (I/R) injury. SMP30 was downregulated in the brain tissues of rats after I/R induction. SMP30 overexpression decreased MCAO/R-induced infarct volumes and improved neurologic function and histopathological changes. Increasing SMP30 expression suppressed neuronal apoptosis and reduced mitochondrial dysfunction. SMP30 overexpression in SH-SY5Y and PC12 cells treated with oxygen-glucose deprivation/reoxygenation (OGD/R) decreased HDAC4 and PSD-95 expression; PSD-95 could bind to HDAC4. Furthermore, HDAC4 upregulation abolished the effects of SMP30 overexpression on OGD/R-induced apoptosis and mitochondrial dysfunction in SH-SY5Y cells. Together, these findings indicate that SMP30 alleviates cerebral I/R-induced neuronal injury by inhibiting HDAC4/PSD-95 to preserve mitochondrial function. These interactions might provide new treatment methods for patients with ischemic stroke.

Targeting Nrf2 in ischemia-reperfusion alleviation: From signaling networks to therapeutic targeting

The nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of redox balance and it responds to various cell stresses that oxidative stress is the most well-known one. The Nrf2 should undergo nuclear translocation to exert its protective impacts and decrease ROS production. On the other hand, ischemic/reperfusion (I/R) injury is a pathological event resulting from low blood flow to an organ and followed by reperfusion. The I/R induces cell injury and organ dysfunction. The present review focuses on Nrf2 function in alleviation of I/R injury. Stimulating of Nrf2 signaling ameliorates I/R injury in various organs including lung, liver, brain, testis and heart. The Nrf2 enhances activity of antioxidant enzymes to reduce ROS production and prevent oxidative stress-mediated cell death. Besides, Nrf2 reduces inflammation via decreasing levels of pro-inflammatory factors including IL-6, IL-1β and TNF-α. Nrf2 signaling is beneficial in preventing apoptosis and increasing cell viability. Nrf2 induces autophagy to prevent apoptosis during I/R injury. Furthermore, it can interact with other molecular pathways including PI3K/Akt, NF-κB, miRNAs, lncRNAs and GSK-3β among others, to ameliorate I/R injury. The therapeutic agents, most of them are phytochemicals such as resveratrol, berberine and curcumin, induce Nrf2 signaling in I/R injury alleviation.

Senescence marker protein 30 (SMP30) protects against high glucose-induced apoptosis, oxidative stress and inflammatory response in retinal ganglion cells by enhancing Nrf2 activation via regulation of Akt/GSK-3β pathway

Senescence marker protein 30 (SMP30) is an aging-related protein that participates in the regulation of tissue damage under various pathological conditions. However, the role of SMP30 in mediating high glucose (HG)-induced injury of retinal ganglion cells (RGCs) has not been fully determined. We found that SMP30 expression declined during HG stimulation in RGCs. Cellular functional studies showed that the up-regulation of SMP30 dramatically prohibited HG-evoked apoptosis, oxidative stress and inflammatory response in RGCs. Mechanism research reported that SMP30 overexpression led to the enhancement of nuclear factor erythroid 2-related factor (Nrf2) activation in HG-stimulated RGCs. Moreover, SMP30 overexpression enhanced the phosphorylation of Akt and glucogen synthase kinase-3β (GSK-3β), and the suppression of Akt markedly abolished SMP30-mediated Nrf2 activation in HG-stimulated RGCs. Additionally, the suppression of Nrf2 substantially reversed SMP30-overexpression-induced anti-HG injury effects in RGCs. Overall, these findings suggest that SMP30 protects against HG injury of RGCs by potentiating Nrf2 through regulation of the Akt/GSK-3β pathway. Our work underscores that SMP30/Akt/GSK-3β/Nrf2 may exert a vital role in mediating the injury of RGCs during diabetic retinopathy.