Phoenixin 14 inhibits ischemia/reperfusion-induced cytotoxicity in microglia

The process of ischemia/reperfusion (IR) in ischemic stroke often leads to significant cell death and permanent neuronal damage. Safe and effective treatments are urgently needed to mitigate the damage caused by IR injury. The naturally occurring pleiotropic peptide phoenixin 14 (PNX-14) has recently come to light as a potential treatment for IR injury. In the present study, we examined the effects of PNX-14 on several key processes involved in ischemic injury, such as pro-inflammatory cytokine expression, oxidative stress, and the related cascade mediated through the toll-like receptor 4 (TLR4) pathway, using BV2 microglia exposed to oxygen-glucose deprivation and reoxygenation (OGD/R). Our results demonstrate an acute ability of PNX-14 to regulate the expression levels of proinflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). PNX-14 also prevented oxidative stress by reducing the generation of reactive oxygen species (ROS) and increasing the level of the antioxidant glutathione (GSH). Importantly, PNX-14 inhibited high-mobility group box 1 (HMGB1)/TLR4/myeloid differentiation primary response 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway, by inhibiting the activation of TLR4 and preventing the nuclear translocation of p65 protein. We further confirmed the cerebroprotective effects of PNX-14 in an MCAO rat model, which resulted in reduced infarct volume and decreased microglia activation. Together, the results of this study implicate a possible protective role of PNX-14 against various aspects of IR injury in vitro.