107 - Hypothiocyanous Acid (HOSCN) Re-Directs Macrophage Glycolytic Flux Through the Pentose Phosphate Pathway - An Adaption to Oxidative Stress in Inflammation?

Abstract

A host of chronic inflammatory diseases are accelerated by the formation of hypochlorous acid (HOCl) by myeloperoxidase (MPO), which is released by activated neutrophils. HOCl is a powerful oxidant that causes extensive tissue damage and cell death. In the presence of thiocyanate (SCN – ), the production of HOCl by MPO is decreased in favour of the formation of a milder oxidant, hypothiocyanous acid (HOSCN). Unlike HOCl, HOSCN reacts selectively with thiols to result in reversible modifications that can be repaired, which has led to the hypothesis that SCN – may reduce the extent of MPO-induced damage during inflammation. In this study, we examined the cellular targets and consequences of the reaction of HOSCN with macrophages, a key inflammatory cell type. We show that exposure of macrophages to HOSCN results in the reversible modification of multiple proteins associated with glycolysis and metabolism. This leads to decreased glycolysis, glycolytic reserve, and glycolytic capacity, which is associated with the reduced formation of ATP, NADH and lactate, the end-product of glycolysis. HOSCN did not influence glucose uptake in the macrophages, but was associated with reduced respiration, consistent with a decrease in the pyruvate pool available for mitochondrial oxidative phosphorylation. However, HOSCN treatment also led to an increase in the activity of glucose 6-phosphate dehydrogenase and elevated levels of NADPH, suggesting re-routing of the glycolytic flux through the pentose phosphate pathway. This glycolytic switch was not observed on exposure of macrophages to HOCl. These results suggest that HOSCN may induce an adaptive response in the macrophages, whereby the increased NADPH could increase the capacity of the cellular enzymatic antioxidant systems to deal with an oxidative insult. This provides new insight into potential pathways by which SCN – could modulate the reactivity of MPO-derived oxidants, which may have implications for the treatment of inflammatory diseases.