Reactive Oxygen Species from Mitochondria Induce Cyclooxygenase-2 Gene Expression in Human Mesangial Cells

Abstract

Hyperglycemia increases the production of reactive oxygen species (ROS) from the mitochondrial electron transport chain in bovine endothelial cells. Because several studies have postulated a role for prostaglandins (PGs) in the glomerular hyperfiltration seen in early diabetes, we evaluated the effect of mitochondrial ROS on expression of the inducible isoform of cyclooxygenase (COX-2) in cultured human mesangial cells (HMCs). We first confirmed that incubation of HMC with 30 mmol/l glucose significantly increased COX-2 mRNA but not COX-1 mRNA, compared with 5.6 mmol/l glucose. Similarly, incubation of HMCs with 30 mmol/l glucose significantly increased mitochondrial membrane potential, intracellular ROS production, COX-2 protein expression, and PGE2 synthesis, and these events were completely suppressed by thenoyltrifluoroacetone or carbonyl cyanide m-chlorophenylhydrazone, inhibitors of mitochondrial metabolism, or by overexpression of uncoupling protein-1 or manganese superoxide dismutase. Furthermore, increased expression of COX-2 mRNA and protein was confirmed in glomeruli of streptozotocin-induced diabetic mice. In addition, hyperglycemia induced activation of the COX-2 gene promoter, which was completely abrogated by mutation of two nuclear factor κB (NF-κB) binding sites in the promoter region. Our results suggest that hyperglycemia increases mitochondrial ROS production, resulting in NF-κB activation, COX-2 mRNA induction, COX-2 protein production, and PGE2 synthesis. This chain of events might contribute to the pathogenesis of diabetic nephropathy.

Diabetic Nephropathy Is Associated with Oxidative Stress and Decreased Renal Nitric Oxide Production

“…Observations highlight the relevance of mitochondrial oxidative stress in diabetic vascular complications. [22][23][24][25] Our data from ZSF 1 rats clearly demonstrated increased mitochondrial oxidative stress in the kidney as reflected by increased urinary 8-OHdG excretion and by the increased renal presence of 8-OHdG by immunohistochemistry. It is likely that atherosclerosis and hyperglycemia may cause elevation of 8-OHdG; however, the magnitude of changes BASIC RESEARCH www.jasn.org (almost eight-fold rise) seen in our study cannot be accounted for by either of those conditions, implicating renal disease as an important contributor to oxidative stress and consequent elevation of 8-OHdG.…”

2,2′,4,4′-Tetrachlorobiphenyl upregulates cyclooxygenase-2 in HL-60 cells via p38 mitogen-activated protein kinase and NF-κB

“…ROS, such as superoxide anion, contribute to changes in COX-2 gene regulation induced by a number of different stimuli in a variety of cell systems. In human mesangial cells exposed to high glucose, in human monocytes undergoing differentiation, and in human fibroblasts subjected to cyclic stretch stimuli, increased COX-2 expression was dependent on generation of ROS (Amma et al 2005;Barbieri et al 2003;Kiritoshi et al 2003). These changes occurred through activation of p38 MAP kinase and a variety of transcription factors including NF-κB (Amma et al 2005;Kim et al 2005;Singer et al 2003).…”

HBx targeting to mitochondria and ROS generation are necessary but insufficient for HBV-induced cyclooxygenase-2 expression

“…COX-2 expression can be induced by various cellular signals such as NF-κB, ROS, and p38 kinase in different cellular systems [22,23]. To determine whether the HBV replicon could induce mitochondrial redox changes, we transfected Huh7 cells with the HBV replicon and evaluated ROS levels using DCF-DA that became highly fluorescent upon oxidation by intracellular ROS [7].…”