Tigrin, a venom-derived cysteine-rich secretory protein from Rhabdophis tigrinus, triggers interleukin-8 release from endothelial cells.

Tigrin, a protein isolated from Rhabdophis tigrinus venom, is homologous to snake venom cysteine-rich secretory proteins (CRISPs); however, its biological function remains poorly understood. This study aimed to investigate whether tigrin induces pro-inflammatory cytokine production in human endothelial and monocytic cells. Tigrin was purified from the crude R. tigrinus venom and identified using SDS-PAGE. Human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes were stimulated with either crude venom or purified tigrin. mRNA expression levels of IL-1β, IL-6, IL-8, and TNF-α were analyzed by quantitative polymerase chain reaction, and protein secretion of IL-6, IL-8, von Willebrand factor (VWF), and P-selectin was measured by ELISA. Crude venom increased IL-8 mRNA and protein expression in both cell types, with a markedly stronger effect in HUVECs than in monocytes. The purified tigrin preparation induced IL-8 secretion from HUVECs in a dose-dependent manner; however, it did not stimulate IL-6, VWF, or P-selectin secretion. Tigrin activated the p44/42 mitogen-activated protein kinase pathway, and inhibition of this pathway suppressed IL-8 production. These findings suggest selective IL-8 release, possibly via Weibel-Palade bodies. This study suggests that the tigrin-enriched fraction induces selective IL-8 secretion in endothelial cells. Tigrin may enhance local inflammation and synergize with the procoagulant effects of R. tigrinus venom. These findings provide new insights into the snake venom CRISP biology and venom-induced inflammatory responses.