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

Objectives: 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)-β1, 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 post-treatment with CMT-3 on hepatic MMP-9, TGF-β1, and caspase-3 activity following sepsis. Design: Laboratory experiment. Setting: University laboratory. Subjects: Male Sprague-Dawley rats. Interventions: 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. Measurements and Main Results: 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-β1, and caspase-3 were determined by Western immunoblotting. Plasma GOT, GPT, and hepatic MMP-9 activity increased 2.5-fold, and TFG-β1 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 post-treatment with CMT-3 resulted in 0% mortality. Conclusions: Our results are consistent with an MMP-9-induced caspase-3 activation in response to CLP. CMT-3 post-treatment increased TIMP-1 level and thereby inhibited MMP-9, which in turn decreased TGF-β1 and caspase-3 signaling pathways and improved survivability in septic rats.