Thymoquinone Protects Against Cigarette Smoke Extract‐induced Vascular Dysfunction Through Inhibition of the RhoA/Rho‐Kinase Signaling Pathway

Abstract

BackgroundThere is an ever‐growing focus on the role of natural products in modulating reactive oxygen species (ROS) and RhoA/Rho kinase‐mediated vascular disease. Thymoquinone (TQ), a constituent of the volatile oil derived from Nigella sativa seeds, possesses promising antioxidant and vasodilating properties via its effect on multiple signaling pathways; however, the effect of TQ on the RhoA/Rho‐Kinase pathway remains to be investigated. The aims of the present study were to examine whether TQ protects against CSE‐induced vascular dysfunction and to identify the underlying mechanisms of TQ on CSE‐induced ED in isolated rat aorta.MethodsCigarette smoke extract (CSE)‐exposed rat aortic rings were mounted in a wire myograph and subjected to contraction and relaxation. Quantitative assessment of RhoA activation was determined using G‐LISA RhoA activation assay kit where phosphorylation of myosin light chain‐20, myosin phosphatase‐targeting subunit 1 and protein kinase CPI‐17were determined by western blot analysis in the hole tissue protein extracts.The GSH content of aortic tissues was calculated using HPLC.ResultsTQ protected against CSE‐induced impairment of acetylcholine‐induced endothelium‐dependent relaxation, and decreased CSE‐induced ROS generation and glutathione depletion. Preincubation of aortic rings for 20 min with TQ attenuated the CSE‐enhanced phenylephrine‐induced vascular tension in endothelium‐denuded rings. TQ‐pretreated rings showed a decrease in CSE‐induced RhoA activation and phosphorylation of myosin light chain‐20, myosin phosphatase‐targeting subunit 1 and protein kinase CPI‐17.ConclusionsThese data indicate that TQ inhibited ROS generation‐induced RhoA/Rho kinase pathway activation, protecting against CSE‐induced vascular dysfunction. This study provides mechanistic insight for understanding the molecular basis and efficacy of TQ on vascular disease management.