Upregulation of inducible NO synthase by exogenous adenosine in vascular smooth muscle cells activated by inflammatory stimuli in experimental diabetes

Abstract

BackgroundAdenosine has been shown to induce nitric oxide (NO) production via inducible NO synthase (iNOS) activation in vascular smooth muscle cells (VSMCs). Although this is interpreted as a beneficial vasodilating pathway in vaso-occlusive disorders, iNOS is also involved in diabetic vascular dysfunction. Because the turnover of and the potential to modulate iNOS by adenosine in experimental diabetes have not been explored, we hypothesized that both the adenosine system and control of iNOS function are impaired in VSMCs from streptozotocin-diabetic rats.MethodsMale Sprague–Dawley rats were injected with streptozotocin once to induce diabetes. Aortic VSMCs from diabetic and nondiabetic rats were isolated, cultured and exposed to lipopolysaccharide (LPS) plus a cytokine mix for 24 h in the presence or absence of (1) exogenous adenosine and related compounds, and/or (2) pharmacological agents affecting adenosine turnover. iNOS functional expression was determined by immunoblotting and NO metabolite assays. Concentrations of adenosine, related compounds and metabolites thereof were assayed by HPLC. Vasomotor responses to adenosine were determined in endothelium-deprived aortic rings.ResultsTreatment with adenosine-degrading enzymes or receptor antagonists increased iNOS formation in activated VSMCs from nondiabetic and diabetic rats. Following treatment with the adenosine transport inhibitor NBTI, iNOS levels increased in nondiabetic but decreased in diabetic VSMCs. The amount of secreted NO metabolites was uncoupled from iNOS levels in diabetic VSMCs. Addition of high concentrations of adenosine and its precursors or analogues enhanced iNOS formation solely in diabetic VSMCs. Exogenous adenosine and AMP were completely removed from the culture medium and converted into metabolites. A tendency towards elevated inosine generation was observed in diabetic VSMCs, which were also less sensitive to CD73 inhibition, but inosine supplementation did not affect iNOS levels. Pharmacological inhibition of NOS abolished adenosine-induced vasorelaxation in aortic tissues from diabetic but not nondiabetic animals.ConclusionsEndogenous adenosine prevented cytokine- and LPS-induced iNOS activation in VSMCs. By contrast, supplementation with adenosine and its precursors or analogues enhanced iNOS levels in diabetic VSMCs. This effect was associated with alterations in exogenous adenosine turnover. Thus, overactivation of the adenosine system may foster iNOS-mediated diabetic vascular dysfunction.

H2S attenuates acute lung inflammation induced by administration of lipopolysaccharide in adult male rats

“…Previous researchers documented that LPS activates the excess production of NO via upregulation of iNOS as detected in the present study and by others Zhang et al 2016;Wei et al 2017). Another study reported that the iNOS gene is a highly inducible gene and its transcription is readily upregulated by inflammatory cytokines (Nassi et al 2016). Excess cytokines production might be caused by the LPS ability to stimulate mitogen activated protein kinase (MAPK) (Peng et al 2016) and NF-κB (Jang et al 2017) pathways.…”

Advanced glycation end-products decreases expression of endothelial nitric oxide synthase through oxidative stress in human coronary artery endothelial cells

“…Inflammatory also play an important role in the development of vascular damage associated to hyperglycemia [ 31 , 32 ]. During inflammation, inducible nitric oxide synthase activation generates an overabundance of NO in the circulation and induced the cardiovascular dysfunction.…”

Identification and quantification of protein nitration sites in human coronary artery smooth muscle cells in the absence and presence of peroxynitrous acid/peroxynitrite

“…Activated macrophages are a significant source [ [4] , [5] , [6] ] but other cells also generate •NO, albeit at lower levels, via the constitutive enzymes eNOS and nNOS, and can therefore contribute to the flux of ONOOH formed in vivo . The presence of NOS isoforms in vascular smooth muscle cells is controversial [ [55] , [56] , [57] , [58] , [59] ]. Whilst there are considerable data consistent with iNOS expression on exposure of these cells to injury or cytokines this isoform, and also the endothelial isoform (eNOS), do not appear to be endogenously expressed in vascular smooth muscle cells [ 58 , 59 ].…”