Reduced TRMU expression increases the sensitivity of hair-cell-like HEI-OC-1 cells to neomycin damage in vitro

Abstract

Aminoglycosides are ototoxic to the cochlear hair cells, and mitochondrial dysfunction is one of the major mechanisms behind ototoxic drug-induced hair cell death. TRMU (tRNA 5-methylaminomethyl-2-thiouridylate methyltransferase) is a mitochondrial protein that participates in mitochondrial tRNA modifications, but the role of TRMU in aminoglycoside-induced ototoxicity remains to be elucidated. In this study, we took advantage of the HEI-OC-1 cell line to investigate the role of TRMU in aminoglycoside-induced cell death. We found that TRMU is expressed in both hair cells and HEI-OC-1 cells, and its expression is significantly decreased after 24 h neomycin treatment. We then downregulated TRMU expression with siRNA and found that cell death and apoptosis were significantly increased after neomycin injury. Furthermore, when we down-regulated TRMU expression, we observed significantly increased mitochondrial dysfunction and increased levels of reactive oxygen species (ROS) after neomycin injury, suggesting that TRMU regulates mitochondrial function and ROS levels. Lastly, the antioxidant N-acetylcysteine rescued the mitochondrial dysfunction and cell apoptosis that was induced by TRMU downregulation, suggesting that ROS accumulation contributed to the increased aminoglycosides sensitivity of HEI-OC-1 cells after TRMU downregulation. This study provides evidence that TRMU might be a new therapeutic target for the prevention of aminoglycoside-induced hair cell death.

c-Myb knockdown increases the neomycin-induced damage to hair-cell-like HEI-OC1 cells in vitro

“…6a,c). Previous studies have reported that cleaved caspase-3 and TUNEL can be used as markers of apoptosis in aminoglycoside-induced HC death303233343536. To confirm our findings, we performed active caspase-3 and TUNEL staining to detect the apoptotic HEI-OC1 cells.…”

“…HEI-OC1 cells, a HC-like cell line, express several molecular markers of cochlear HCs, including calbindin, calmodulin, math1, myosin7a, and prestin28293031, and they are commonly used to study the protection of HCs. We used Myosin 7a as the HC marker, and immunostaining showed that all HEI-OC1 cells could be double labeled by Myosin 7a and c-Myb, demonstrating that c-Myb is expressed in HEI-OC1 cells (Fig.…”

STK33 alleviates gentamicin‐induced ototoxicity in cochlear hair cells and House Ear Institute‐Organ of Corti 1 cells

“…It is reported that ROS is involved in aminoglycoside‐induced HC damage . The intracellular ROS level was increased after gentamicin treatment by DCFH‐DA staining compared with the untreated control in primary culture of cochlear HCs, but NAC inhibited the intracellular ROS level after gentamicin damage (Figure A).…”

“…Hearing loss is regarded as a very common sensory disorder in humans all over the world, which seriously affects the quality of human life. In most cases, hearing loss is mainly attributable to hair cell (HC) damage caused by ototoxic drugs, of which aminoglycoside antibiotics, including kanamycin, amikacin, neomycin and gentamicin, are such a typical kind of drugs, with the potential to elicit toxic reactions to structures of the inner ear . Although those drugs are widely used to treat gram‐negative bacterial infections, the ototoxic side effects have a great limitation in clinical use.…”

“…In most cases, hearing loss is mainly attributable to hair cell (HC) damage caused by ototoxic drugs, of which aminoglycoside antibiotics, including kanamycin, amikacin, neomycin and gentamicin, are such a typical kind of drugs, with the potential to elicit toxic reactions to structures of the inner ear. 1,2 Although those drugs are widely used to treat gram-negative bacterial infections, the ototoxic side effects have a great limitation in clinical use. Therefore, it is indispensable to better understand the underlying mechanism of aminoglycosides-induced ototoxicity, which may, in turn, conduce to developing more effective therapies.…”