Neuroprotective effects of prostaglandin A1 in rat models of permanent focal cerebral ischemia are associated with nuclear factor‐κB inhibition and peroxisome proliferator‐activated receptor‐γ up‐regulation

Abstract

We have previously reported that prostaglandin A(1) (PGA(1)) reduces infarct size in rodent models of focal ischemia. This study seeks to elucidate the possible molecular mechanisms underlying PGA(1)'s neuroprotective effects against ischemic injury. Rats were subjected to permanent middle cerebral artery occlusion (pMCAO) by intraluminal suture blockade. PGA(1) was injected intracerebroventricularly (icv) immediately after ischemic onset. Western blot analysis was employed to determine alterations in IkappaBalpha, pIKKalpha, and peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Immunohistochemistry was used to confirm the nuclear translocation of nuclear factor-kappaB (NF-kappaB) p65 and the expression of PPAR-gamma. RT-PCR was used to detect levels of c-Myc mRNA. The contribution of PPAR-gamma to PGA(1)'s neuroprotection was evaluated by pretreatment with the PPAR-gamma irreversible antagonist GW9662. A brief increase in pIKKalpha levels and rapid reduction in IkappaBalpha were observed after ischemia. PGA(1) blocked ischemia-induced increases in pIKKalpha levels and reversed the decline in IkappaBalpha levels. Ischemia-induced nuclear translocation of NF-kappaB p65 was attenuated by PGA(1). PGA(1) also repressed the ischemia-induced increase in expression of NF-kappaB target gene c-Myc mRNA. Immunohistochemistry demonstrated an increase in PPAR-gamma immunoreactivity in the nucleus of striatal cells at 3 hr after pMCAO. Western blot analysis revealed that the expression of PPAR-gamma protein significantly increased at 12 hr and peaked at 24 hr. PGA(1) enhanced the ischemia-triggered induction of PPAR-gamma protein. Pretreatment with the irreversible PPAR-gamma antagonist GW9662 attenuated PGA(1)'s neuroprotection against ischemia. These findings suggest that PGA(1)-mediated neuroprotective effect against ischemia appears to be associated with blocking NF-kappaB activation and likely with up-regulating PPAR-gamma expression.