IN-VIVO INTERFERENCE OF PAROMOMYCIN WITH MITOCHONDRIAL ACTIVITY OF LEISHMANIA

Paromomycin is an aminocyclitol aminoglycoside antibiotic used for the treatment of leishmaniasis. In view of the central role of mitochondr ia in cellular energetics and metabolism, its effect on in vivo mitoch ondrial activities of leishmania donovani promastigotes-the parasite f lagellate form-was investigated. The approach used flow cytometry, amp erometric measure of O-2 consumption, and, as a global estimate of mit ochondrial dehydrogenases, thiazolyl blue reduction (MTT test); some i n vitro controls were also made. When added to promastigote cultures f or 24-72 h at 150-200 mu M (= LC50), paromomycin doubled the generatio n time, inhibited respiration, and lowered its associated electric pot ential difference across mitochondrial membranes, as measured by rhoda mine 123 fluorescence. The chemical analogue neomycin was ineffective. Furthermore, the in vivo mitochondrial dehydrogenase activities were lower, seemingly because of the shortage of respiratory substrates. In deed, succinate addition to paromomycin-treated cultures partly restor ed mitochondrial membrane potential. However, no immediate effect of p aromomycin on respiration was observed, neither inhibition of redox ch ain nor increase of membrane permeability (uncoupling). It is proposed that paromomycin acts at a metabolic level upstream of the respirator y chain itself This would have the observed delayed consequence becaus e the cell energy supply would progressively decline since it depends upon the proton gradient-viz., membrane potential-generated by respira tion. In conclusion, paromomycin is an antibiotic affecting the cell's energetic metabolism the respiratory dysfunction it induces may be a crucial aspect of its action against Leishmania and possibly other cel ls. (C) 1997 Academic Press.