Resveratrol downregulates the TLR 4 signaling pathway to reduce brain damage in a rat model of focal cerebral ischemia

Previous studies have demonstrated that inflammation and disruption of the blood-brain barrier (BBB) are important pathological processes during focal cerebral ischemia. Therefore, the present study evaluated the neuroprotective effects of resveratrol against brain damage, inflammation and BBB disruption in rats with focal cerebral ischemia and assessed the potential underlying molecular mechanisms. Sprague‐Dawley rats underwent cerebral ischemia/reperfusion (IR) and then received intraperitoneal resveratrol (10 and 100 mg/kg) 2 h following the onset of ischemia. Following 24 h of ischemia, neurological deficit scores, cerebral infarctions, morphological characteristics, cerebral water content, myeloperoxidase (MPO) activity and Evans blue extravasation were assessed. Additionally, the protein expression levels of Toll‐like receptor 4 (TLR4) and nuclear factor (NF)-κB p65 were detected using western blot analyses, the mRNA expression levels of cyclooxygenase‐2 (COX‐2) and matrix metalloproteinase‐9 (MMP‐9) were examined by reverse‐transcription polymerase chain reaction, and tumor necrosis factor (TNF)-α and interleukin (IL)-1β blood levels were determined by ELISA. Resveratrol significantly reduced neurological deficit scores, cerebral infarct sizes, neuronal injury, MPO activity and EB content. Cerebral ischemia increased the expression levels of TLR4, NF-κB p65, COX‐2, MMP‐9, TNF‐α and IL-1β, but all of these factors were reduced by resveratrol. In conclusion, the present data suggest that resveratrol reduces inflammation, BBB disruption and brain damage in rats following focal cerebral ischemia. Additionally, the neuroprotective effects of resveratrol against cerebral ischemia may be associated with downregulation of the TLR4 pathway. Introduction Brain injuries caused by transient or permanent focal cerebral ischemia develop according to a series of pathological mechanisms that include free radical release, blood-brain barrier (BBB) disruption, microglial activation, inflammation and neuronal apoptosis (1). Additionally, post‐ischemic inflammation mediates the pathological processes associated with ischemic brain injury (2) Toll-like receptors (TLRs) serve a central role in innate immunity and are implicated in a range of inflammatory diseases (3). Several studies have demonstrated that TLR4 expression is elevated following cerebral ischemia (4) and that the degree of ischemic brain injury and neuroinflammation is significantly lower in TLR4‐deficient mice compared with wild‐type mice (5). Furthermore, nuclear factor (NF)-κB, which is a key downstream factor of the TLR4 signaling pathway, is activated following cerebral ischemia, to promote inflammatory reactions and produce inflammatory molecules that further aggravate ischemic brain injury (5-7). TLR4 signaling is a promising therapeutic target for the treatment of ischemic stroke (8) because the downregulation of TLR4 expression inhibits NF‐κB and reduces the expression of inflammatory molecules; this ultimately leads to the attenuation of ischemic brain injury. Resveratrol is a polyphenol that is abundantly expressed in a wide variety of plant species and has been reported to possess cardioprotective (9), anticancer (10), anti-inflammatory (11) and neuroprotective properties (12). Although a study demonstrated that resveratrol reduces ischemia-induced brain damage due to its anti‐oxidative properties (13), its potential underlying molecular mechanisms remain unknown. Therefore, the present study investigated whether resveratrol downregulates activity in the TLR4 signaling pathway in a rat model of cerebral ischemia. Materials and methods Induction of ischemia‐reperfusion. A total of 140 adult Sprague‐Dawley rats weighing 250‐300 g were obtained from the Shanghai Laboratory Animal Center (Shanghai, China). All animal experiments were approved by the Institutional Animal Care and Use Committee of Hubei University of Medicine (Shiyan, China). Rats were housed in a colony room under controlled temperature (22 ̊C), a humidity of 40‐70% and Resveratrol downregulates the TLR4 signaling pathway to reduce brain damage in a rat model of focal cerebral ischemia JUN‐RONG LEI1,2, XIAN-KUN TU2, YANG WANG1, DE‐WEN TU2 and SONG‐SHENG SHI2 1Department of Neurosurgery, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei 442000; 2Department of Neurosurgery, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China Received June 23, 2018; Accepted November 23, 2018 DOI: 10.3892/etm.2019. 7324 Correspondence to: Dr Xian-Kun Tu, Department of Neurosurgery, Fujian Medical University Union Hospital, 29 Xinquan Road, Fuzhou, Fujian 350001, P.R. China E-mail: unionnstu@hotmail.com