Recombinant bactericidal/permeability-increasing protein attenuates the systemic inflammatory response syndrome in lower limb ischemia-reperfusion injury

Objectives: Hind limb ischemia-reperfusion (I/R) injury increases gut perme ability, and resultant endotoxemia is associated with an amplified systemic inflammatory response syndrome leading to multiple organ dysfunction syndr ome. We studied the potential role of recombinant bactericidal/permeability -increasing protein (rBPI(21)), a novel antiendotoxin therapy, in modulatin g endotoxin-enhanced systemic inflammatory response syndrome in hind limb I /R injury. Methods: In this prospective, randomized, controlled, experimental animal s tudy, 48 male Wistar rats, weighing 300 to 350 g, were randomized to a cont rol group (sham) and five groups undergoing 3 hours bilateral hind limb isc hemia with 2 hours reperfusion (I/R) (n = 8 per group). The control and unt reated I/R groups received thaumatin, a control-protein preparation, at 2 m g/kg. Treatment groups were administered rBPI(21) intravenously at 1, 2, or 4 mg/kg body weight at the beginning of reperfusion; an additional group w as administered rBPI(21) intravenously at 2 mg/kg after 1 hour of reperfusi on. Plasma interleukin-6 concentration was estimated by bioassay as a measu re of systemic inflammation. Plasma endotoxin concentration was determined by use of an amebocyte lysate chromogenic assay. Cross-reactive immunoglobu lin G and M antibodies to the highly conserved inner core region of endotox in were measured by use of an enzyme-linked immunosorbent assay. The lung t issue wet-to-dry weight ratio and myeloperoxidase concentration were used a s markers of edema and neutrophil sequestration, respectively. Results: I/R provoked highly significant elevation in plasma interleukin-6 concentrations (1351.20 pg/mL [860.16 - 1886.40 pg/mL]) compared with contr ols (125.32 pg/mL [87.76-157.52 pg/mL; P < .0001]), but treatment with rBPI (21) 2 mg/kg at onset of reperfusion (715.89 pg/mL [573.36-847.76 pg/mL]) s ignificantly decreased interleukin-6 response compared with the nontreatmen t group (P < .016). I/R increased plasma endotoxin concentrations significa ntly (21.52 pg/mL [6.20-48.23 pg/mL]), compared with control animals (0.90 pg/mL [0.00-2.30 pg/mL; P < .0001]), and treatment with rBPI(21) 4 mg/kg at reperfusion significantly decreased endotoxemia (1.30 pg/mL [1.20-2.20 pg/ mL]), compared with the untreated group (P < .001). The lung tissue myelope roxidase level was significantly increased in the untreated I/R group (208. 18% [128.79%-221.81%]), compared with in controls (62.00% [40.45%-80.92%; P < .0001]), and attenuated in those treated with rBPI(21) 2 mg/kg (129.54% [90.49%-145.78%; P < .05]). Data represent median and interquartile range, comparisons made with the nonparametric Mann-Whitney U test. Conclusions: These findings show that hind limb ischemia-reperfusion injury is associated with endotoxemia, elevations in plasma interleukin-6, and pu lmonary leukosequestration. Treatment with rBPI(21) after ischemia reduces endotoxemia, the interleukin-6 response, and attenuates pulmonary leukosequ estration in response to hind limb reperfusion injury.