Beneficial effects of diminished production of hydrogen sulfide or carbon monoxide on hypertension and renal injury induced by nitric oxide withdrawal
ABSTRACT Background and PurposeWhether nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) back-up for each other when one or more are depleted is unclear. Inhibiting NO synthase (NOS) causes hypertension and kidney injury. Both global depletion of H2S by cystathionine γ-lyase (CSE) gene deletion and low levels of exogenous H2S causes hypertension. Inhibiting CO-producing enzyme heme oxygenase-1 (HO-1) makes rodents hypersensitive to hypertensive stimuli. We hypothesize that combined inhibition of NOS and HO-1 aggravate hypertension and renal injury, but how combined inhibition of NOS and CSE affect hypertension and renal injury was uncertain. Experimental ApproachRats (n=6/group) were treated with inhibitors of NOS (L-nitroarginine; LNNA), CSE (DL-propargylglycine; PAG), or HO-1 (Tin protoporphyrin; SnPP) singly for one or four weeks or in combinations for four weeks. Key ResultsLNNA always reduced NO, and decreased H2S and increased CO after four weeks. PAG abolished H2S, always enhanced CO, and reduced NO but not when used in combined inhibition. SnPP always increased NO, and enhanced H2S and inhibited CO after one week. LNNA, but not PAG and SnPP, rapidly developed hypertension followed by renal dysfunction. LNNA-induced hypertension was ameliorated and renal dysfunction was prevented by all additional treatments. Renal HO-1 expression was increased with LNNA in injured tubules and was increased in all tubules by all other treatments. Conclusions and ImplicationsThe amelioration of LNNA-induced hypertension and renal injury by additional inhibition of H2S and/or CO producing enzymes appeared to be associated with secondary increases in renal CO or NO production.