engleski

Lipopolysaccharide-induced acute inflammation exerts anti-apoptotic effect on Fas- mediated liver injury through Stat3 dependent pathway

Introduction: The exact effects of acute inflammation on the liver apoptotic processes are still not well elucidated. We explored the nature of inflammation- apoptosis crosstalk in liver and to evaluate underlying mechanisms. Methods: Male C57BL/6 mice were treated with ruxolitinib, selective JAK1/2 inhibitor, or vehicle followed by intraperitoneal injection of LPS (0.025 µg/g) 2 hours after. Liver samples were collected after 90 minutes for determination of phosphorylated Stat3 (pStat3) and Stat3 expressions by western blot. The gene expression of proinflammatory cytokines and apoptosis-related factors were analyzed (qPCR). To explore the possible involvement of JAK/Stat3 pathway in the anti-apoptotic effect of the inflammation, mice were treated with ruxolitinib or vehicle, followed by LPS and anti-Fas (JO2) activating antibody (0.25 μg/g, intravenously) 2 hours after LPS. Samples were collected 6 hours after anti-Fas application. Results: LPS treatment induced the phosphorylation of Stat3 in hepatocytes. Immunoblots revealed an increase in pStat3 expression in liver samples after LPS treatment, while immunohistochemical analysis showed an increase in pStat3 positive hepatocytes when compared to saline treated mice. Ruxolitinib pretreatment successfully inhibited the LPS-induced Stat3 phosphorilation. Densitometry showed lower pStat3/Stat3 ratio in ruxolitinib/LPS treated mice in comparison with vehicle/LPS group (p=0.008). Finally, in-vivo experiments showed that ruxolitinib pretreatment abrogates the anti-apoptotic effect of LPS. Ruxolitinib/LPS/anti-Fas treated mice had significantly higher levels of ALT when compared with vehicle/LPS/anti-Fas treated group. Finally, ruxolitinib pretreatment augmented the LPS-induced gene expression of proinflammatory cytokines (TNF- alpha, IL-1 and IL-6), and significantly reduced the expression of Bcl-xL in comparison with LPS treated mice (p=0.02). Conclusion: Acute inflammation induced by LPS protects mice from Fas-mediated liver injury. Stat3 could be one of the crucial mediators involved in this protective effect, as ruxolitinib-induced inhibition of JAK signaling significantly reversed the anti-apoptotic feature of LPS.

lipopolysaccharide ; Fas ; apoptosis ; Stat3 ; ruxolitinib

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