C-JUN NH2-TERMINAL KINASE MEDIATES THE HEPATIC STRESS RESPONSE AFTER RAT HEMORRHAGE/RESUSCITATION

Abstract

Inhibition of c-JUN NH2-terminal kinase (JNK), a mitogen activated protein kinase (MAPK), with a novel, specific, cell-penetrating, protease resistant peptide inhibitor (D-JNKI-1) reduced hepatic damage and serum Il-6 levels after hemorrhage/resuscitation (H/R) in rats, as we reported previously. Here, we elucidate mechanisms that provide this protection. Methods: Male Sprague-Dawley rats received D-JNKI-1 (11 mg/kg i.p.) or vehicle. 30 min later, rats were hemorrhaged to a blood pressure of 30-35 mmHg for 60 mins and resuscitated (60% of the shed blood and 2× the shed blood volume as Ringers Lactate). 2 h after resuscitation, liver tissue was harvested and polymorphnuclear leukocytes (PMN) were identified by chloroacetate esterase staining and counted in a blinded fashion. Immunohistochemistry for 4-hydroxy-2-nonenal (4-HNE) as a marker for oxidative stress and Western blotting for phosphorylated c-JUN was performed. A P < 0.05 was considered significant (ANOVA). Results: Hepatic PMN infiltration significantly increased after H/R in the vehicle treated group but was largely diminished after D-JNKI-1 pretreatment. 4-HNE staining revealed a strong hepatic oxidative stress after H/R that was attenuated in the D-JNKI-1 treated group. H/R induced phosphorylation of c-JUN and inhibition of JNK blocked this effect. Conclusion: Inhibition of JNK reduces hepatic injury, leukocyte infiltration, oxidative stress and c-JUN phosphorylation after H/R. These results highlight the importance of JNK after H/R, but understanding of its position within the complex signalling network of MAPKs after resuscitated blood loss remains subject to further study.