Isoliquiritigenin attenuates neuroinflammation after subarachnoid hemorrhage through inhibition of NF-B-mediated NLRP3 inflammasome activation

Neuroinflammation contributes to neurological dysfunction in the patients who suffer from subarachnoid hemorrhage (SAH). Isoliquiritigenin (ISL) is a bioactive component extracted from Genus Glycyrrhiza. This work is to investigate whether ISL ameliorates neuroinflammation after SAH. In this study, intravascular perforation of male Sprague-Dawley rats was used to establish a SAH model. ISL was administered by intraperitoneal injection 6 h after SAH in rats. The mortality, SAH grade, neurological score, brain water content, and blood-brain barrier (BBB) permeability were examined at 24 h after the treatment. Expressions of tumor necrosis factor-alpha, interleukin-6, Iba-1, and MPO were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Besides, the expression levels of NF-kappa B p65 and NLRP3, ASC, caspase-1, IL-1 beta, and IL-18 were analyzed by western blot. The experimental data suggested that ISL treatment could ameliorate neurological impairment, attenuate brain edema, and ameliorate BBB injury after SAH in rats. ISL treatment repressed the expression of proinflammatory cytokines TNF-alpha and IL-6, and meanwhile inhibited the expression of Iba-1 and MPO. ISL also repressed NF-kappa B p65 expression as well as the transport from the cytoplasm to the nucleus. In addition, ISL significantly suppressed the expression levels of NLR family pyrin domain containing 3 (NLRP3), ASC, caspase-1, IL-1 beta, and IL-18. These findings suggest that ISL inactivates NLRP3 pathway by inhibiting NF-kappa B p65 translocation, thereby repressing the neuroinflammation after SAH, and it is a potential drug for the treatment of SAH.