Chronic exposure to high glucose impairs bradykinin-stimulated nitric oxide production by interfering with the phospholipase-C-implicated signalling pathway in endothelial cells: evidence for the involvement of protein kinase C

Abstract

Aims/hypothesis. Overwhelming evidence indicates that endothelial cell dysfunction in diabetes is characterised by diminished endothelium-dependent relaxation, but the matter of the underlying molecular mechanism remains unclear. As nitric oxide (NO) production from the endothelium is the major player in endothelium-mediated vascular relaxation, we investigated the effects of high glucose on NO production, and the possible alterations of signalling pathways implicated in this scenario. Methods. NO production and intracellular Ca 2+ levels ([Ca 2+ ] i ) were assessed using the fluorescent probes 4,5-diaminofluorescein diacetate and fura-2 respectively. Results. Exposure of cultured bovine aortic endothelial cells to high glucose for 5 or 10 days significantly reduced NO production induced by bradykinin (but not by Ca 2+ ionophore) in a time-and dose-dependent manner. This was probably due to an attenuation in bradykinin-induced elevations of [Ca 2+ ] i under these conditions, since a close correlation between [Ca 2+ ] i increases and NO generation was observed in intact bovine aortic endothelial cells. Both bradykinin-promoted intracellular Ca 2+ mobilisation and extracellular Ca 2+ entry were affected. Moreover, bradykinin-induced formation of Ins(1,4,5)P 3 , a phospholipase C product leading to increases in [Ca 2+ ] i , was also inhibited following high glucose culture. This abnormality was not attributable to a decrease in inositol phospholipids, but possibly to a reduction in the number of bradykinin receptors. The alterations in NO production, the increases in [Ca 2+ ] i , and the bradykinin receptor number due to high glucose could be largely reversed by protein kinase C inhibitors and D-α-tocopherol (antioxidant). Conclusions/interpretation. Chronic exposure to high glucose reduces NO generation in endothelial cells, probably by impairing phospholipase-C-mediated Ca 2+ signalling due to excess protein kinase C activation. This defect in NO release may contribute to the diminished endothelium-dependent relaxation and thus to the development of cardiovascular diseases in diabetes.

Insulin treatment attenuates diabetes-increased atherosclerotic intimal lesions and matrix metalloproteinase 9 expression in apolipoprotein E-deficient mice

“…Thus, MMP9 expression is associated with endothelial dysfunction. Given that chronic exposure to high glucose reduces NO generation in endothelial cells, probably by impairing phospholipase-C-mediated Ca 2C signaling due to excess protein kinase C activation (Tang & Li 2004), it is obvious that diabetes downregulates MMP9 expression via endothelial dysfunction and subsequent reduction in NO production from endothelial cells.…”

Receptor-mediated activation of nitric oxide synthesis by arginine in endothelial cells

“…Signaling via G proteins leads to a variety of cellular responses, including activation of phospholipase C, yielding second messengers, diacylglycerol and IP 3 . Activation of several receptor systems that lead to endothelial NO synthesis has been shown to involve G protein-coupled signaling via phospholipase C activation (44)(45)(46). A similar pathway may be responsible for L-arginine-mediated NO signaling.…”

LncRNA NONRATT021972 siRNA attenuates P2X7 receptor expression and inflammatory cytokine production induced by combined high glucose and free fatty acids in PC12 cells

“…However, there is no effective therapy for inflammation or for DNP. LncRNAs, typically defined as transcripts longer than 200 nucleotides, are recently regarded as a potential therapeutic target for inflammatory relevant diseases, including diabetes and DNP [26][27][28][29][30][31][32][33][34][35][36][37][38]. However, the functional question of massive lncRNAs in DNP has not been characterized [26,27,30].…”