Interaction of streptomycin and streptomycylamine derivatives with negatively charged lipid layers. Correlation between binding, conformation of complexes and inhibition of lysosomal phospholipase activities.

Aminoglycoside antibiotics induce a lysosomal phospholipidosis in kidney proximal tubules after conventional therapy in animals and man. We have previously demonstrated that these drugs bind to negatively charged phospholipid bilayers at acid pH and inhibit the activity of lysosomal acid phospholipases in vitro and in vivo. A combined biochemical and conformational study [Brasseur et al., Biochem. Pharmac. 33, 629 (1984)] showed major and consistent differences between 6 aminoglycosides in current clinical use with respect to the stability of the complexes they form with phosphatidylinositol, their inhibitory potency towards the activity of lysosomal phospholipases and their current toxicity ranking (e.g. gentamicin greater than amikacin greater than streptomycin). In the present study we have extended this approach to experimental derivatives of streptomycin. The derivatives examined were: dihydrostreptomycin, dideguanyldihydrostreptomycin, streptomycylamine, dideguanylstreptomycylamine, N-butyl- and N-benzyl-dideguanylstreptomycylamine. These compounds were examined for (i) their binding to negatively charged liposomes, measured by gel permeation on Sepharose 4B; (ii) their interactions with phosphatidylinositol assessed by semi-empirical conformational analysis and (iii) their inhibitory effect on the activities of lysosomal phospholipases towards phosphatidylcholine present in negatively charged liposomes. Streptomycin and gentamicin were also used as reference compounds with low and high affinity (and inhibitory potency), respectively. Our observations can be summarized as follows: (i) the replacement of the aldehyde in the streptose ring by a methylamino group strikingly changes the conformation of the molecule, allowing a better interaction with phosphatidylinositol. Thus, streptomycylamine binds much more tightly to phospholipid bilayers and shows a higher inhibitory potency towards phospholipase activity, as compared to streptomycin. The conformational analysis shows, however, that this effect is only partially due to the additional cationic charge carried by streptomycylamine. Other modifications of the streptomycin molecule, such as the replacement of the guanidinium groups by aminogroups or the addition of hydrophobic moieties (butyl or benzyl groups) to the streptose do not markedly further strengthen the interactions of the molecule with phosphatidylinositol. (ii) Even though some derivatives (e.g. dideguanylstreptomycylamine) bind as tightly to phospholipids as gentamicin, they remain much less inhibitory towards lysosomal phospholipases.(ABSTRACT TRUNCATED AT 400 WORDS)