Fingolimod Alleviates Inflammation after Cerebral Ischemia via HMGB1/TLR4/NF-κB Signaling Pathway

Background: Clinically, ischemic reperfusion injury is the main cause of stroke injury. This study aimed to assess the effectiveness of fingolimod in suppressing inflammation caused by ischemic brain injury and explore its pharmacological mechanisms. Methods: In total, 75 male Sprague-Dawley rats were randomly and equally assigned to five distinct groups: sham, middle cerebral artery occlusion/reperfusion (MCAO/R) surgery, fingolimod low-dose (F-L), fingolimod medium-dose (F-M), and fingolimod high-dose (F-H). Neurobehavioral tests, 2,3,5-triphenyltetrazolium chloride staining, and the brain tissue drying-wet method were conducted to evaluate neurological impairment, cerebral infarction size, and brain water content. Enzyme-linked immunosorbent assay was employed to quantify pro-inflammatory cytokines interleukin (IL)-1 beta , IL-6, and tumor necrosis factor-alpha (TNF- alpha ) protein levels. Western blotting and immunohistochemical staining were performed to assess high mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), and nuclear factor kappa-B p65 (NF- kappa Bp65) levels. Results: Rats in the F-L, F-M, and F-H groups exhibited lower Longa scores, reduced infarction volumes, and decreased brain edema than those in the MCAO/R group. Additionally, the F-L, F-M, and F-H groups exhibited lower serum levels of IL-1 beta , IL-6, and TNF- alpha than those of the MCAO/R group. Additionally, F-L, F-M, and F-H treatments resulted in decreased HMGB1, TLR4, and NF- kappa Bp65 protein expression levels in the hippocampus of MCAO/R rats. Conclusions: Fingolimod was found to reduce ischemic brain injury in a dose-dependent manner. Moreover, it was also found to alleviate inflammation following ischemic brain injury via the HMGB1/TLR4/NF- kappa B signaling pathway.