Effect of chemically modified tetracycline on transforming growth factor-β1 and caspase-3 activation in liver of septic rats*

Abstract

We have previously demonstrated that hepatic matrixmetalloproteinase (MMP)-9 and gelatinase activity increased significantly after sepsis, and pretreatment with chemically modified tetracycline (CMT-3) inhibited these expressions and improved survivability. It has been established that MMP-9 release from hepatic nonparenchymal cells activates transforming growth factor (TGF)-beta1, which in turn catalyzes the conversion of procaspase-8 into active caspase-8. Caspase-8 activates caspase-3, which in turn degrades fibronectin and focal adhesion kinase and leads to disruption of hepatic architecture and integrity. We have been interested in investigating the role of posttreatment with CMT-3 on hepatic MMP-9, TGF-beta1, and caspase-3 activity following sepsis. Laboratory experiment. University laboratory. Male Sprague-Dawley rats. In this study, sepsis was induced in rats by cecal ligation and puncture (CLP), and 2 hrs later, half of the rats received CMT-3 (25 mg/kg), whereas the other half received vehicle by gavage. Twenty-four and 48 hrs after sepsis induction, blood and liver samples were collected. Plasma glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) levels were determined by enzymatic method, and the activation states of hepatic MMP-9, MMP-2, tissue inhibitor of metalloproteinase (TIMP)-1, TGF-beta1, and caspase-3 were determined by Western immunoblotting. Plasma GOT, GPT, and hepatic MMP-9 activity increased 2.5-fold, and TFG-beta1 and caspase-3 activity increased 1.5- to 2-fold at 24 hrs and 48 hrs post-CLP; CMT-3 treatment blocked these increases. Furthermore, CMT-3 treatment also led to increased TIMP-1 level, an in vivo inhibitor of MMP-9. MMP-2 level was unaffected by CLP. The 24-hr and 48-hr mortality rates for CLP rats were 29% and 50%, whereas posttreatment with CMT-3 resulted in 0% mortality. Our results are consistent with an MMP-9-induced caspase-3 activation in response to CLP. CMT-3 posttreatment increased TIMP-1 level and thereby inhibited MMP-9, which in turn decreased TGF-beta1 and caspase-3 signaling pathways and improved survivability in septic rats.