ABSTRACT
BACKGROUND: Sepsis is the tenth leading cause of death in the U.S. and creates a $16.7 billion burden on the healthcare system every year. Sepsis is characterized by a severe uncontrolled inflammatory response to the infection. Various cells and mediators are activated, and the result is a complex interaction between the inflammation and coagulation cascades leading to capillary leakage and end-organ ischemia. Current therapeutic strategies, such as recombinant human activated protein C, focus on this interplay. However, this drug's precise mechanism of action is not well understood. The aim of this study was to assess cytokine production, tissue damage, and apoptosis in a rat model of sepsis in response to various doses of this drug. METHODS: Sprague-Dawley rats were divided into eight groups, including negative control, sham, sepsis only, and five treatment groups. The sepsis and treatment groups were given Escherichia coli. Each of the treatment groups received a different dose of recombinant activated protein C to complete 30-min or 270-min infusion times from the onset of sepsis. Serum and tissue samples were collected. Interleukin (IL)-6 concentrations were measured, and serum malondialdehyde (MDA) concentrations were determined to assess generalized tissue damage. Apoptosis in the lung was evaluated using a semi-quantitative ligation-mediated polymerase chain reaction assay. RESULTS: The physiologic effects of recombinant activated protein C are dose dependent and determined by the duration of infusion. Higher doses of the drug were associated with less inflammation, apoptosis, and generalized tissue damage. Sepsis increased the mean concentration of MDA (2.1 vs. 10.9 pmol/mg of protein) and IL-6 (0 vs. 10,763 pg/mL) compared with sham-treated animals, as well as the magnitude of apoptosis in lung (2,037 vs. 8,709 pixels) (all p < 0.05). Infusion of recombinant activated protein C attenuated these responses in a dose-response manner. Interleukin-6 and MDA concentrations were increased by lower-dose therapy, but attenuated significantly by the higher-dose infusion at 5 mg/kg/h. Apoptosis was attenuated by both the lower and the higher dose, but more so with the higher dose. CONCLUSIONS: These data can assist in establishing an optimal dose and infusion time of this drug for extrapolation to therapy of human beings. The goal now is to elucidate these findings further so that the maximum benefit of the drug may be achieved with the least possible harmful effects.
