Curcumin Inhibits TLR2/4-NF-κB Signaling Pathway and Attenuates Brain Damage in Permanent Focal Cerebral Ischemia in Rats

Abstract

Toll-like receptors 2 and 4 (TLR2/4) and the downstream nuclear factor-kappa B (NF-κB) signaling pathway, which mediate the inflammatory reaction in cerebral ischemia, were demonstrated to be involved in the extension of cerebral infarction and the aggravation of ischemic brain damage. Reports showed that curcumin provides neuroprotection against ischemic brain damage. In this study, we investigated whether curcumin inhibits the activation of TLR2/4-NF-κB signaling pathway in rats of permanent focal cerebral ischemia. Adult male Sprague-Dawley rats underwent permanent middle cerebral artery occlusion (pMCAO). Curcumin was administered by intraperitoneal injection twice at 2 and 12 h after the onset of ischemia. Neurological deficit scores, cerebral infarct size, morphological characteristic, and cerebral water content were measured after 24 h of pMCAO. The enzymatic activity of myeloperoxidase (MPO) was assessed after 24 h of pMCAO. Expression of TLR2 and TLR4 in ischemic brain was determined by western blot. Expression of NF-κB p65 in ischemic brain was detected by immunohistochemistry and western blot. The release of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in blood was examined by ELISA. Curcumin significantly reduced neurological deficit scores, cerebral infarct size, neuronal damage, cerebral water content, and MPO activity. It also inhibited the expression of TLR2/4 and decreased the expression and activity of NF-κB p65 in rat brain. In addition, curcumin attenuated the release of TNF-α and IL-1β in blood. Our results suggest that curcumin reduces inflammatory reaction and brain damage in a rat model of permanent focal cerebral ischemia. The neuroprotective effect and anti-inflammatory property of curcumin in cerebral ischemia might be associated with the inhibition of TLR2/4-NF-κB signaling pathway.