Gentamicin triggers fatty acid oxidation-dependent mitochondrial ROS, driving greater nephrotoxicity than apramycin...

Apramycin has emerged as a promising antibacterial drug candidate that has demonstrated great preclinical efficacy and safety profile. In comparative studies, apramycin was found to be significantly less nephrotoxic than gentamicin; however, the underlying mechanisms have not been clarified. In the present study, we investigated whether different aminoglycoside antibiotics share the same toxicity mechanisms and whether cotreatment with the antioxidant N-acetyl-cysteine (NAC) can ensure even safer apramycin use. In addition, we investigated whether cilastatin decreases apramycin content in the kidneys and thus mitigates adverse effects. We found that NAC in combination with apramycin was not beneficial; a similar or even greater increase in nephrotoxicity markers was observed with this combination in rats and mice. Furthermore, we found that only gentamicin and, to a lesser extent, arbekacin and kanamycin induced a prominent increase in the mitochondrial fatty acid oxidation (FAO)-dependent production of H₂O₂. Apramycin, paromomycin, neomycin, dibekacin, geneticin, amikacin, tobramycin, and plazomicin stimulated neither FAO nor H₂O₂ production in kidney mitochondria. We also found that gentamicin C1, which is one of the congeners in clinically used gentamicin, did not increase mitochondrial FAO or related H₂O₂ production. In rats, treatment with cilastatin combined with apramycin partially prevented glomerular but not tubular kidney damage induced by a high dose of apramycin. In the same animals, we found that cilastatin did not affect apramycin content in the kidneys. In conclusion, gentamicin differs from other aminoglycoside antibiotics by coupling fatty-acid oxidation to mitochondrial reactive oxygen species (ROS) generation. Gentamicin congener C1, apramycin, and 10 other tested aminoglycosides do not stimulate mitochondrial ROS production, and the use of antioxidants to protect the kidneys against these aminoglycosides is not a reasonable strategy. Cilastatin protects against aminoglycoside-induced glomerular damage independent of the inhibition of aminoglycoside transport into kidney cells.