Inhibition of matrix metalloproteinase on hepatic transforming growth factor beta1 and caspase-3 activation in hemorrhage.

Objectives: Hemorrhage initiates an inflammatory response that induces the systemic release of cytokines and sequestration of polymorphonuclear neutrophils. Sequestered polymorphonuclear neutrophils release proteases, including matrix metalloproteinases (MMPs) that degrade elements of the extracellular matrix, contributing to the morbidity and mortality seen from hemorrhage. Activation of MMPs may be associated with changes in transforming growth factor beta1 (TGF-beta1) and caspase-3 signaling pathways. In this study, the authors examined hemorrhage-induced changes in the expression of rat hepatic MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-l), TGF-beta1, and caspase-3 activities in the presence and absence of the MMP inhibitor hydroxamate.

Methods: Hemorrhagic shock was induced in fasted, anesthetized, and cannulated rats by rapid phlebotomy to a mean arterial pressure level of 40 mm Hg, maintained for 90 minutes by withdrawal and infusion of blood, followed by a resuscitation period of lactated Ringer's infusion. Rats received either hydroxamate (25 mg/kg) or vehicle by gavage before hemorrhage. Twenty-four hours after resuscitation, plasma and liver samples were collected. Liver MMP-9, TGF-beta1, and caspase-3 levels were quantified by Western immunoblotting. Plasma glutamic oxaloacetic transaminase (GOT) and plasma glutamic pyruvic transaminase (GPT) were determined enzymatically.

Results: Plasma GOT, plasma GPT, and liver MMP-9, TGF-beta1, and caspase-3 levels were all significantly elevated at 24 hours postresuscitation when compared with the control values. Hepatic TIMP-1, an in vivo inhibitor of MMP-9, was unaltered at 24 hours. Hydroxamate treatment reduced GOT, GPT, MMP-9, TGF-beta1, and caspase-3 levels at 24 hours. The mortality of hemorrhaged untreated rats was 29% after 24 hours, and pretreatment with hydroxamate reduced mortality to 0%.

Conclusions: These results indicate the beneficial effects of MMP inhibitor in preventing an increase in GOT, GPT, MMP-9, TGF-beta1, and caspase-3 activity with the potential for improvement of hepatic injury due to hemorrhage.