Selective and non-selective cox inhibitors up-regulate heat shock protein-70 expression and protect human monocytes and macrophages from the cytotoxic effect of hydrogen peroxide

Abstract

Heat shock protein 70 (HSP-70) is a molecular chaperone that protects cells against stress stimuli. The expression of HSP-70 is normally up regulated in response to stress. However, in patients with severe sepsis, HSP-70 expression is suppressed. We hypothesized that inhibitors of cyclooxygenase (COX) could up regulate the expression of HSP-70 in human macrophages and monocytes, which in turn will improve the resistance of these cells to stress. Human monocytes and macrophages were untreated or treated with aspirin, ibuprofen or NS-398, a selective COX-2 inhibitor, for 1.5 to 24 hrs. A parallel group was exposed to a 30-min heat shock at 42°C. Western blotting and real-time polymerase chain reaction quantified, respectively, time dependent changes in HSP-70 protein expression and mRNA production. To evaluate whether elevated HSP-70 expression protects the cells from stress, cell viability was determined after exposure of cells to cytotoxic concentrations of hydrogen peroxide. Changes in cell viability were monitored using propidium iodide and fluorescent microscopy. Treatment of the monocytes or macrophage cultures with either aspirin, ibuprofen or NS-398 caused a statistically significant increase (p < 0.05; n = 4) of about 2.5 fold in HSP-70 mRNA expression that peaked at 1.5 hrs. Heat shock caused a 25-fold increase in HSP-70 mRNA expression at 1.5 hrs. The COX inhibitors also triggered a statistically significant increase (p < 0.05; n = 8) of about 2-fold in HSP-70 expression within 1.5 hrs of treatment, while the heat shock triggered a 3–5 fold increase in both cell populations. The protein levels remained elevated for 24 hrs in all treated groups. Significantly, pretreatment of the cells with either the COX inhibitors or the heat shock protected the cells from the cytotoxic effect of hydrogen peroxide. These findings suggest that both selective and non-selective COX inhibitors may be as effective as a febrile response in augmenting the body’s resistance to stress.