The novel Janus kinase inhibitor ruxolitinib confers protection against carbon tetrachloride-induced hepatotoxicity via multiple mechanisms.

Therapeutic targeting of the JAK/STAT pathway, the principal signaling mechanism for numerous cytokines, might be an effective approach for limiting inflammation in different organs, including the liver. Therefore, we investigated whether targeting this pathway by the novel JAK inhibitor ruxolitinib could mitigate hepatic damage provoked by carbon tetrachloride (CCl4). Male mice received ruxolitinib treatments (75 and 150 mg/kg, oral) 2 h prior to intoxication with CCl4 (10 ml/kg of 0.3% v/v CCl4 solution in olive oil, intraperitoneal) for 24 h. Our results showed that ruxolitinib treatments dose-dependently alleviated CCl4-induced hepatic injury and necroinflammation, as indicated by biochemical markers of injury and histopathology. We unraveled also the mechanisms involved in these hepatoprotective effects. These comprise (i) reducing infiltration of neutrophils and macrophages, as demonstrated by reducing myeloperoxidase activity and F4/80 positive macrophages; (ii) abating apoptosis of hepatocytes, as denoted by decreasing hepatocytes positive for Bax protein; (iii) inhibiting elevation of TNF-α, IL-1β and IL-10; (iv) inhibiting NF-κB activation and translocation to the nucleus, as visualized immunohistochemically; (v) attenuating activation of the IL-23/IL-17 pathway via targeting IL-17, but not IL-23; (vi) antagonizing hepatic oxidative stress by increasing the antioxidant levels (reduced glutathione, glutathione-S-transferase and superoxide dismutase) and decreasing products of lipid peroxidation (malondialdehyde and 4-hydroxynonenal) and total nitrate/nitrite; and (vii) more interestingly, modulating hepatocyte regeneration according to the extent of damage, as quantified by PCNA-immunohistochemistry. In conclusion, our study sheds light on the therapeutic usefulness and the potential underlying mechanisms of the novel JAK inhibitor ruxolitinib in hepatic inflammatory disorders.