GRP75 Involves in Retinal Ganglion Cell Apoptosis After Rat Optic Nerve Crush

Preserving mitochondrial function by inhibiting GRP75 ameliorates neuron injury under ischemic stroke

Ischemic stroke is a life-threatening disease, which is closely related to neuron damage during ischemia. Mitochondrial dysfunction is essentially involved in the pathophysiological process of ischemic stroke. Mitochondrial calcium overload contributes to the development of mitochondrial dysfunction. However, the underlying mechanisms of mitochondrial calcium overload are far from being fully revealed. In the present study, middle cerebral artery obstruction (MCAO) was performed in vivo and oxygen and glucose deprivation (OGD) in vitro. The results indicated that both MCAO and OGD induced significant mitochondrial dysfunction in vivo and in vitro. The mitochondria became fragmented under hypoxia conditions, accompanied with upregulation of the heat shock protein 75 kDa glucose-regulated protein (GRP75). Inhibition of GRP75 was able to effectively ameliorate mitochondrial calcium overload and preserve mitochondrial function, which may provide evidence for further translational studies of ischemic diseases.

The role and therapeutic potential of heat shock proteins in haemorrhagic stroke

Heat shock proteins (HSPs) are induced after haemorrhagic stroke, which includes subarachnoid haemorrhage (SAH) and intracerebral haemorrhage (ICH). Most of these proteins function as neuroprotective molecules to protect cerebral neurons from haemorrhagic stroke and as markers to indicate cellular stress or damage. The most widely studied HSPs in SAH are HSP70, haeme oxygenase-1 (HO-1), HSP20 and HSP27. The subsequent pathophysiological changes following SAH can be divided into two stages: early brain injury and delayed cerebral ischaemia, both of which determine the outcome for patients. Because the mechanisms of HSPs in SAH are being revealed and experimental models in animals are continually maturing, new agents targeting HSPs with limited side effects have been suggested to provide therapeutic potential. For instance, some pharmaceutical agents can block neuronal apoptosis signals or dilate cerebral vessels by modulating HSPs. HO-1 and HSP70 are also critical topics for ICH research, which can be attributed to their involvement in pathophysiological mechanisms and therapeutic potential. However, the process of HO-1 metabolism can be toxic owing to iron overload and the activation of succedent pathways, for example, the Fenton reaction and oxidative damage; the overall effect of HO-1 in SAH and ICH tends to be protective and harmful, respectively, given the different pathophysiological changes in these two types of haemorrhagic stroke. In the present study, we focus on the current understanding of the role and therapeutic potential of HSPs involved in haemorrhagic stroke. Therefore, HSPs may be potential therapeutic targets, and new agents targeting HSPs are warranted.

Wogonin prevents TLR4-NF-κB-medicated neuro-inflammation and improves retinal ganglion cells survival in retina after optic nerve crush

Chronic neuro-inflammation is involved in the death of retinal ganglion cells (RGCs) in glaucoma. The aim of this study is to determine whether wogonin can suppress inflammatory responses and rescue RGCs death after optic nerve crush (ONC), an ideal animal model of glaucoma. Wogonin was administered intraperitoneally 10 min after establishment of ONC model. In this study, wogonin treatment reduced RGCs loss and inhibited RGCs apoptosis demonstrated by the increased Brn3a labeling RGCs at day 14 and the decreased cleaved caspase-3 expression at day 7 after ONC, respectively. In ONC model, number of GFAP-positive glial cells and iba1-positive microglial cells were increased, combined of the elevated level of pro-inflammatory cytokines released in retina at day 7. However, most of these responses were inhibited after wogonin treatment. The level of TLR4 expression, NF-κB-P65 nucleus location and NF-κB-P65 phosphorylation were increased in retina at day 1 after ONC, which was significantly reduced after wogonin treatment. These results demonstrated that wogonin protected RGCs survival and suppressed neuro-inflammation in retina after ONC by inhibiting TLR4-NF-κB pathways. We conclude that wogonin could be a possible strategy for the treatment of glaucoma.

Overexpression of GRP75 inhibits inflammation in a rat model of intracerebral hemorrhage

Glucose‑regulated protein 75 (GRP75) is a member of the heat shock protein 70 family and previous studies have demonstrated that GRP75 is involved in diseases of the central nervous system. However, the biological function of GRP75 in intracerebral hemorrhage (ICH) remains to be clarified. Thus, the aim of the present study was to evaluate the effects of GRP75 in a rat model of ICH. Western blotting was used to detect the protein expression of GRP75, active caspase‑3, Bax, Bcl‑2, p‑Akt and Akt in brain tissues following ICH. The levels of tumor necrosis factor‑α (TNF‑α) and interleukin (IL)‑1β were evaluated using ELISA assay. Expression of GRP75 mRNA and protein was demonstrated to be reduced in the brain tissues of rats with ICH compared with sham‑operated rats. In addition, overexpression of GRP75 in brain tissues with ICH significantly inhibited the production of the inflammatory cytokines TNF‑α and IL-1β and increased Bcl‑2/decreased Bax levels compared with ICH alone. Furthermore, overexpression of GRP75 in brain tissues with ICH resulted in significantly increased phosphorylation of Akt compared with ICH alone. Therefore, the present study demonstrated, for the first time to the best of our knowledge, significantly reduced GRP75 expression in brain tissues following ICH, and that overexpression of GRP75 inhibits inflammation and potentially inhibits neuronal apoptosis in a rat model of ICH. GRP75 may, therefore, represent a promising target in the treatment of ICH.