Downregulation of nitrovasodilator‐induced cyclic GMP accumulation in cells exposed to endotoxin or interleukin‐1β

Abstract

Induction of nitric oxide synthase (iNOS) results in overproduction of nitric oxide (NO), which may be a principal cause of the massive vasodilatation and hypotension observed in septic shock. Since NO‐induced vasorelaxation is mediated via the soluble isoform of guanylate cyclase (sGC), the regulation of sGC activity during shock is of obvious importance, but yet poorly understood. The aim of the present study was to investigate the activation of sGC by sodium nitroprusside (SNP) before and after exposure of rat aortic smooth muscle cells to endotoxin (LPS) or interleukin‐1β (IL‐1β). Exposure of rat aortic smooth muscle cells to SNP (10 μm) elicited up to 200 fold increases in cyclic GMP. This effect was attenuated by 30–70% in IL‐1β‐ or LPS‐pretreated cells, in a pretreatment time‐and IL‐1β‐ or LPS‐concentration‐dependent manner. When, however, cells were exposed to IL‐1β or LPS and then stimulated with the particulate guanylate cyclase activator, atriopeptin II, no reduction in cyclic GMP accumulation was observed. Pretreatment of rats with LPS (5 mg kg−1, i.v.) for 6 h led to a decrease in aortic ring SNP‐induced cyclic GMP accumulation. The IL‐1β‐induced reduction in SNP‐stimulated cyclic GMP accumulation in cultured cells was dependent on NO production, as arginine depletion abolished the downregulation of cyclic GMP accumulation in response to SNP. Reverse‐transcriptase‐polymerase chain reaction analysis revealed that the ratio of steady state mRNA for the α1 subunit of sGC to glyceraldehyde phosphate dehydrogenase was decreased in LPS‐ or IL‐1β‐treated cells, as compared to vehicle‐treated cells. Protein levels of the α1 sGC subunit remained unaltered upon exposure to LPS or IL‐1β, suggesting that the early decreased cyclic GMP accumulation in IL‐1β‐ or LPS‐pretreated cells was probably due to reduced sGC activation. Thus, the observed decreased responsiveness of sGC to NO stimulation following cytokine or LPS challenge may represent an important homeostatic mechanism to offset the extensive vasodilatation seen in sepsis.

Downregulation of vascular soluble guanylate cyclase induced by high salt intake in spontaneously hypertensive rats

“…Similar data have been reported for the aorta of SHR (Auch-Schwelk et al, 1989) and the forearm vasculature of patients with essential hypertension (Garcia et al, 1995). Furthermore, it is possible that sGC expression may be inhibited by overproduction of NO, namely the presence of a negative autoregulatory mechanism (Scott & Nakayama, 1998;Filippov et al, 1997;Papapetropoulos et al, 1996). This might be plausible in the case of salt-loaded SHR, because NO synthesis increases with a high salt diet as described above.…”

Nitrovasodilators inhibit platelet-derived growth factor-induced proliferation and migration of activated human hepatic stellate cells

“…42 At the cellular level, prolonged pretreatment with mediators such as interleukin 1␤ and lipopolysaccharide causes a marked inhibition of sodium nitroprusside-induced activation of sGC. 62 In addition, an endogenous inhibitor of sGC has been identified and partially purified from bovine lung. 63 Because the lack of detectable expression of the heterodimeric form ␣1␤1 of sGC is common to HSC lines isolated from normal liver tissue obtained from different individuals and activated by culture on plastic, it is tempting to speculate that this represents a general feature related to the process of HSC activation in which several structural and functional changes occur, including the establishment of autocrine loops for growth factors, cytokines, and other soluble mediators.…”

Guanylyl Cyclase Activation Reverses Resistive Breathing–Induced Lung Injury and Inflammation

“…Treatment of cultured cells with inflammatory stimuli attenuates the sGC mRNA stability or protein expression (17)(18)(19)(20). Increased inflammation and TNF-α, IL-6 or IL-1β upregulation was documented in the BALF of mice after RB.…”