The anti-inflammatory effect of curcumin in an experimental model of sepsis is mediated by up-regulation of peroxisome proliferator-activated receptor-γ

OBJECTIVE: Although phytochemical curcumin has been shown to possess anti-inflammatory properties, it remains unknown whether this agent has any beneficial effects in sepsis. The purpose of this study was to demonstrate whether curcumin protects septic animals and, if so, whether activation of peroxisome proliferator-activated receptor (PPAR)-γ, an anti-inflammatory nuclear receptor, plays any role. DESIGN: Prospective, controlled, and randomized animal study. SETTING: A research institute laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: A bolus injection of 0.2 μmol of curcumin was given intravenously to male adult rats, followed by continuous infusion of curcumin (0.24 μmol/day) for 3 days via a primed 2-mL mini-pump. The rats were then subjected to sepsis by cecal ligation and puncture (CLP). MEASUREMENTS AND MAIN RESULTS: Serum levels of liver enzymes (alanine aminotransferase and aspartate aminotransferase), lactate, albumin, and tumor necrosis factor (TNF)-α were measured at 20 hrs after CLP (i.e., late stage of sepsis). In addition, a 10-day survival curve was conducted following CLP and cecal excision with or without curcumin treatment. Furthermore, macrophages cell line RAW 264.7 cells were treated with curcumin followed by stimulation with endotoxin. TNF-α and PPAR-γ expression were then measured. The results indicate that intravenous administration of curcumin before the onset of sepsis attenuated tissue injury, reduced mortality, and decreased the expression of TNF-α in septic animals. Similar results were also found when curcumin was administered after the onset of sepsis. Moreover, the down-regulated PPAR-γ in the liver at 20 hrs after CLP was significantly improved by curcumin treatment. Concurrent administration of curcumin and GW9662, a specific PPAR-γ antagonist, completely abolished the beneficial effects of curcumin under such conditions. In cultured RAW 264.7 cells, curcumin inhibited endotoxin-induced increases in TNF-α expression and markedly up-regulated PPAR-γ expression without affecting cell viability. Curcumin also prevented morphologic alterations in macrophages induced by endotoxin. CONCLUSIONS: The protective effect of curcumin makes it or its analogues strong candidates as a novel therapy for sepsis. The beneficial effect of curcumin appears to be mediated by up-regulation of nuclear receptor PPAR-γ.