Neuroprotectin D1 attenuates brain damage induced by transient middle cerebral artery occlusion in rats through TRPC6/CREB pathways.

Neuroprotectin D1 (NPD1) may serve an endogenous neuroprotective role in brain ischemic injury, yet the underlying mechanism involved is poorly understood. In the present study, we aimed to investigate whether intracerebroventricular (ICV) injection of NPD1 is neuroprotective against transient focal cerebral ischemia. We also sought to verify the neuroprotective mechanisms of NPD1. Rats subjected to 2 h ischemia followed by reperfusion were treated with NPD1 at 2 h after reperfusion. PD98059 was administered 20 min prior to surgery. Western blot analysis was performed to detect the protein levels of calpain-specific aII-spectrin breakdown products of 145 kDa (SBDP145), transient receptor potential canonical (subtype) 6 (TRPC6) and phosphorylation of cAMP/Ca2+-response element binding protein (p-CREB) at 12, 24 and 48 h after reperfusion. The immunoreactivity of p-CREB and TRPC6 was measured by quantum dot‑based immunofluorescence analysis. Infarct volume and neurological scoring were evaluated at 48 h after reperfusion. NPD1, when applied at 2 h after reperfusion, significantly reduced infarct volumes and increased neurological scores at 48 h after reperfusion, accompanied by elevated TRPC6 and p-CREB activity, and decreased SBDP145 activity. When mitogen‑activated protein kinase kinase (MEK) activity was specifically inhibited, the neuroprotective effect of NPD1 was attenuated and correlated with decreased CREB activity. Our results clearly showed that ICV injection of NPD1 at 2 h after reperfusion improves the neurological status of middle cerebral artery occlusion (MCAO) rats through the inhibition of calpain‑mediated TRPC6 proteolysis and the subsequent activation of CREB via the Ras/MEK/ERK pathway.