Thrombin Induces Cerebral Vasospasm Effect via Proteinase-Activated Receptor-1 (PAR-1)/Tumor Necrosis Factor-α (TNF-α) Inflammatory Pathways in Subarachnoid Hemorrhage Rat Model

Abstract

To study thrombin (TM) damage effect and detailed quantitative relation on cerebral vessels function, and to explore inflammatory mechanism of TM on cerebral vasospasm (CVS) in vivo. Wild type SD rats were randomly assigned into different groups for further experiments. Subarachnoid hemorrhage (SAH) rat model was established with double injections of the autogenous blood into the cisterna magna. TM injection was performed during the first injection of the autogenous blood. Primary groups were control group, SAH group TM group and TM+SAH group. In addition, TM+SAH group contains several groups with different injection doses or TM intervention duration. HE staining was performed to detect injury of cerebral basilar artery. Histopathologic examination was performed to detect intra-lumen area of cerebral basilar artery. Each specimen was to be detected the expressive level of Proteinase-activated Receptor-1 (PAR-1) and Tumor necrosis factor-α (TNF-α) by immunohistochemistry. The mean optical density (MOD) values of PAR-1 and TNF-α were used as the semiquantitative indicators to conduct statistical analysis. Compared with the control group, the rat basilar artery intra-lumen area of TM group and TM+SAH group were significantly smaller (P < 0.05), while MOD value of PAR-1 and TNF-α of basilar artery were higher (P < 0.05). With equal dose of TM, the basilar artery intra-lumen area of TM+SAH group are larger than SAH group (P < 0.05), suggesting TM exacerbated SAH injury. Among TM+SAM sub-groups, with the TM concentration increased, the basilar artery intra-lumen area became smaller, and the MOD value of PAR-1 and TNF-α of basilar artery gradually increased, suggesting CVS effect of TM was dose-dependent. Meanwhile, CVS effect of TM was also time-dependent, verified by comparisons of sub-groups with different TM intervention duration (P < 0.05). Thrombin induces CVS effect to aggravate SAH injury via PAR-1/TNF-α inflammatory pathways. Such pathological role of TM was both dose-dependent and time-dependent.