Hormone-dependent enhancement in binding of oto- and nephrotoxic aminoglycoside antibiotics

Daidzein normalized gentamicin-induced nephrotoxicity and associated pro-inflammatory cytokines in MDCK and zebrafish: Possible mechanism of nephroprotection

This study investigates the therapeutic activity of daidzein, an isoflavone that occurs naturally in plants and herbs, against gentamicin-induced nephrotoxicity in Madin-Darby canine kidney (MDCK) cells in-vitro and zebrafish model in-vivo. The in-vitro studies revealed that daidzein protected MDCK cells from gentamicin-induced inflammation by suppressing oxidative stress and apoptosis. The zebrafish were divided into groups and injected with gentamicin (140 mg/mL) to induce nephrotoxic conditions. After injection, renal dysfunction, nitric oxide production, antioxidant consumption, exaggerated apoptosis, and inflammation were all observed in the zebrafish model. We also observed that during kidney inflammation in zebrafish, pro-inflammatory cytokines such as cyclooxygenase (COX-2), tumor necrosis factor (TNF-α), and interleukin-1β (IL-1β) are upregulated. Furthermore, daidzein treatment after gentamicin injection showed a strong protective anti-inflammatory effect. Daidzein activity was associated with an increase in antioxidant biomarkers such as superoxide dismutase (SOD) and glutathione reductase (GSH), whereas lipid peroxidation (LPO) and nitric oxide (NO) production were decreased in a dose-dependent factor. Moreover, histopathological alteration caused by gentamicin in zebrafish kidneys was normalized due to daidzein treatment. Daidzein also downregulated the pro-inflammatory cytokines gene expression in gentamicin-induced kidney inflammation in zebrafish. These results revealed that daidzein could potentially prevent nephrotoxic conditions through pro-inflammatory cytokines inhibition and its antioxidant property.

Distribution of gentamicin in the guinea pig inner ear after local or systemic application

Uptake and retention of gentamicin by cells in the guinea pig inner ear after a single peritoneal injection or local application on the round window were investigated using immunocytochemistry to localize the drug. The cells that accumulated the drug under the two conditions were the same, but staining for the drug was more intense and was often accompanied by widespread cochlear degeneration following local application. Soon after drug administration by either route, there was diffuse staining for the drug throughout all tissue within the labyrinth, including bone. At later times when distinct cell staining became evident, virtually all cell types were found to be positive, with several cell types staining more darkly for the drug than hair cells, indicating that hair cells were not the most avid in accumulating gentamicin. The infracuticular portion of auditory and vestibular hair cells as well as type III fibrocytes of the spiral ligament were positively stained in almost all cases and these sites were found to be positive for as long as six months post administration. In animals with loss of the organ of Corti, there was unusually intense staining for gentamicin in root cells of the spiral ligament, in marginal cells of the stria vascularis, and in cells of the spiral limbus. Dark staining of surviving cells in cases with overt tissue destruction suggests that variability in the extent of damage caused by the drug was determined more by the degree of its local uptake than by differences in animals' capacities to metabolize the drug systemically. The present results show that gentamicin may damage or destroy all cochlear cells following a single round window application. The findings broaden the scope of our knowledge of cochlear gentamicin uptake and damage and have implications for treatment of patients with vestibular disorders by infusion of aminoglycosides into the middle ear, as well as implications for prospects of rehabilitating patients that have been deafened by aminoglycosides.