Association Between Heat Stress Protein 70 Induction and Decreased Pulmonary Fibrosis in an Animal Model of Acute Lung Injury

The hyperthermia-induced activation of the stress protein response allows cells to withstand metabolic insults that would otherwise be lethal. This phenomenon is referred to as thermotolerance. Heat shock protein 70 (HSP70) has been shown to play an important role in this hyperthermia-related cell protection. HSP70 confers protection against cellular and tissue injury. Our objective was to determine the effect of heat stress on the histopathology of pulmonary fibrosis caused by the administration of lipopolysaccharide (LPS) in Wistar rats. The rats were randomly divided into three groups. In the control group, rats were heated to 42°C for 15 min. In the LPS group, rats were given LPS in 0.9% NaCl solution (10 mg/kg body weight). In the WH (whole-body hyperthermia) +LPS group, rats were heated to 42°C for 15 min, and 48 h later they were injected with LPS dissolved in a 0.9% NaCl solution (10 mg/kg body weight). We investigated lung histopathology and performed a Northern blot analysis daily. Hyperthermia was shown to reduce tissue injury caused by the administration of LPS. Pulmonary tissue HSP70 mRNA was found to be elevated at 3 h after heating. HSP70 protein levels in the serum increased after whole-body hyperthermia. However, neither the expression of HSP47 mRNA nor the expression of type I or type III collagen mRNA was induced by the administration of LPS after whole-body hyperthermia. These data indicate that thermal pretreatment is associated with the induction of HSP70 protein synthesis, which subsequently attenuates tissue damage in experimental lung fibrosis.