ABSTRACT
Some Pseudomonas aeruginosa strains are cyanogenic, and cyanide may contribute to the bacterium's virulence. Using human isolates of P. aeruginosa, we have shown that Drosophila melanogaster suspended above cyanogenic strains become motionless and develop bradycardia and that flies injected with cyanogenic bacterial strains die more rapidly than those injected with noncyanogenic strains. Flies exposed to cyanogenic strains had high cyanide and low adenosine triphosphate (ATP) concentrations in body extracts, and treatment with a cyanide antidote equalized survival of flies injected with cyanogenic and noncyanogenic strains. P. aeruginosa PAO1 strain with a mutation in the hydrogen cyanide synthase gene cluster was much less toxic to flies than the parental cyanogenic strain or 2 knock-in strains. Transgenic flies overexpressing rhodanese, which detoxifies cyanide by converting it to thiocyanate, were resistant to cyanide and the increased virulence of cyanogenic strains. We conclude that D. melanogaster is a good model for studying cyanide produced by P. aeruginosa.
Subject(s)
Cyanides/isolation & purification , Cyanides/toxicity , Drosophila melanogaster/drug effects , Pseudomonas aeruginosa/isolation & purification , Adenosine Triphosphate/metabolism , Adenosine Triphosphate/pharmacology , Animals , Drosophila melanogaster/classification , Heart Rate/drug effects , Humans , Nitrates/pharmacology , Nitrites/pharmacology , Pseudomonas aeruginosa/physiology , Thiocyanates/isolation & purification , Thiocyanates/metabolism , Thiocyanates/pharmacologyABSTRACT
Sodium nitroprusside is used to treat hypertensive emergencies and acute heart failure. It acts by releasing nitric oxide (NO), a highly potent vasodilator, but unfortunately, for each NO molecule released, five cyanide ions are released. Thus, nitroprusside therapy is limited by cyanide toxicity. Therefore, a cyanide scavenger could be beneficial when administering nitroprusside. Hydroxocobalamin, which has a relatively high binding affinity for cyanide, has been shown to reduce cyanide levels in nitroprusside-treated patients. Cobinamide, the penultimate precursor in hydroxocobalamin biosynthesis, has a much greater affinity for cyanide than cobalamin, and binds two cyanide ions. We now show that cobinamide is highly effective in neutralizing cyanide ions released by nitroprusside in cultured mammalian cells, Drosophila melanogaster, and mice. Cobinamide also binds NO, but at molar concentrations 2.5-5 times that of nitroprusside, it did not decrease NO concentrations or the physiological effectiveness of nitroprusside. We conclude that cobinamide could be a valuable adjunct to nitroprusside therapy.
Subject(s)
Antihypertensive Agents/pharmacokinetics , Cobamides/pharmacology , Cyanides/metabolism , Nitric Oxide/metabolism , Nitroprusside/pharmacokinetics , Adenosine Triphosphate/metabolism , Animals , Antihypertensive Agents/pharmacology , Cells, Cultured , Drosophila melanogaster , Heart Rate/drug effects , Male , Malpighian Tubules/drug effects , Malpighian Tubules/metabolism , Mice , Mice, Inbred C57BL , Mitochondria/drug effects , Mitochondria/metabolism , Myocytes, Smooth Muscle/drug effects , Myocytes, Smooth Muscle/metabolism , Nitrates/metabolism , Nitrites/metabolism , Nitroprusside/pharmacology , Oxygen Consumption/drug effects , Pulmonary Artery/cytology , Rats , Thiocyanates/blood , Thiocyanates/urine , Vitamin B 12ABSTRACT
Septic shock has an extremely high mortality rate, with approximately 200,000 people dying from sepsis annually in the U.S. The high mortality results in part from severe hypotension secondary to high serum NO concentrations. Reducing NO levels should be beneficial in sepsis, but NOS inhibitors have had a checkered history in animal models, and one such agent increased mortality in a clinical trial. An alternative approach to reduce NO levels in sepsis is to use an NO scavenger, which should leave sufficient free NO for normal physiological functions. Using a well-established model of bacterial sepsis in Drosophila melanogaster, we found that cobinamide, a B(12) analog and an effective NO scavenger in vitro, dramatically improved fly survival. Cobinamide augmented the effect of an antibiotic and was beneficial even in immune-deficient flies. Cobinamide's mechanism of action appeared to be from reducing NO levels and improving cardiac function.
