Pathophysiology of the vascular wall: the role of nitric oxide in renal disease

Amphotericin B severely affects expression and activity of the endothelial constitutive nitric oxide synthase involving altered mRNA stability

The therapeutic use of the antifungal drug amphotericin B (AmB) is limited due to severe side effects like glomerular vasoconstriction and risk of renal failure during AmB administration. As nitric oxide (NO) has substantial functions in renal autoregulation, we have determined the effects of AmB on endothelial constitutive NO synthase (ecNOS) expression and activity in human and rat endothelial cell cultures. AmB used at concentrations of 0.6 to 1.25 microg ml(-1) led to increases in ecNOS mRNA and protein expression as well as NO production. This was the result of an increased ecNOS mRNA half-life. In contrast, incubation of cells with higher albeit subtoxic concentrations of AmB (2.5 - 5.0 microg ml(-1)) resulted in a decrease or respectively in completely abolished ecNOS mRNA and protein expression with a strongly reduced or inhibited ecNOS activity, due to a decrease of ecNOS mRNA half-life. None of the AmB concentrations affected promoter activity as found with a reporter gene construct stably transfected into ECV304 cells. Thus, our experiments show a concentration-dependent biphasic effect of AmB on expression and activity of ecNOS, an effect best explained by AmB influencing ecNOS mRNA stability. In view of the known renal accumulation of this drug the results reported here could help to elucidate its renal toxicity.

Why is the pathology of falciparum worse than that of vivax malaria?

Here, Ian Clark and Bill Cowden summarize new evidence suggesting that nitric oxide (NO) generated by inducible NO synthase (iNOS) provides a functional link between the previously competing approaches to malarial disease pathogenesis: ischaemic hypoxia and NO. When combined with the newly recognized roles of iNOS in renal and pulmonary function and glucose metabolism, synergy between inflammatory cytokines and hypoxia in iNOS induction provides a framework to help explain, at a molecular level, the differences in the pathology seen in falciparum and vivax malaria. Thus sequestration, through localized hypoxia, might contribute to pathology by enhancing cytokine-induced iNOS. Generalized hypoxia might have the same effect.