INDUCTION OF HEAT-SHOCK-PROTEIN-70 BY ZINC-BIS-(DL-HYDROGENASPARTATE)REDUCES CYTOKINE LIBERATION, APOPTOSIS, AND MORTALITY-RATE IN A RAT MODEL OF LD100 ENDOTOXEMIA

A prospective, randomized model of LD100/24 h endotoxemia was performe d in male Wistar rats (n = 26; 250-300 g). The animals were divided in to four groups: Group I (n = 5; saline treatment only), Group II (n = 5; Zn2+ treatment only), Group III (n = 8; saline pretreatment, lipopo lysaccharide (LPS) treatment), and Group IV (n = 8; Zn2+ pretreatment, LPS treatment). Zn2+ pretreatment was carried out by intraperitoneal injection of 50 mg/kg zinc-bis-(DL-hydrogenaspartate) (10 mg/kg Zn2+). LD100/24 h endotoxemia was induced by intraperitoneal administration of 20 mg/kg LPS of the Escherichia coil strain WO111:B4. Tumor necrosi s factor alpha, interleukin-1 beta, and interleukin-6 were detected by enzyme-linked immunosorbent assay (ELISA). HSP70 expression in the lu ngs, the liver, and the kidneys was determined by immunohistochemistry , Western blotting, and an HSP70 ELISA. Apoptosis was also detected by an in situ apoptosis detection kit (TUNEL) and a cell death detection ELISA, respectively. This rat model of endotoxemia proves the close r elationship between HSP70 expression, cytokine liberation, and develop ment of apoptosis. The data demonstrate that: 1) Zn2+ is a potent indu cer of HSP70 expression; 2) the application of Zn2+ leads to slightly increased cytokine plasma levels; and 3) the manipulation of the heat shock response by Zn2+ significantly increases the survival rate after LD100 endotoxemia. Enhanced survival rate in animals pretreated with Zn2+ may be explained by increased tissue levels of HSP70, a subsequen t significantly decreased liberation of the proinflammatory cytokines after LPS challenge, and a significantly decreased rate of apoptosis.