Upregulation of HSP60 expression in the postnatal rat cochlea and rats with drug-induced hearing loss

Machine learning model identifies genetic predictors of cisplatin-induced ototoxicity in CERS6 and TLR4

BACKGROUND

Cisplatin-induced ototoxicity remains a significant concern in pediatric cancer treatment due to its permanent impact on quality of life. Previously, genetic association analyses have been performed to detect genetic variants associated with this adverse reaction.

METHODS

In this study, a combination of interpretable neural networks and Generative Adversarial Networks (GANs) was employed to identify genetic markers associated with cisplatin-induced ototoxicity. The applied method, BRI-Net, incorporates biological domain knowledge to define the network structure and employs adversarial training to learn an unbiased representation of the data, which is robust to known confounders. Leveraging genomic data from a cohort of 362 cisplatin-treated pediatric cancer patients recruited by the CPNDS (Canadian Pharmacogenomics Network for Drug Safety), this model revealed two statistically significant single nucleotide polymorphisms to be associated with cisplatin-induced ototoxicity.

RESULTS

Two markers within the CERS6 (rs13022792, p-value: 3 × 10-4) and TLR4 (rs10759932, p-value: 7 × 10-4) genes were associated with this cisplatin-induced adverse reaction. CERS6, a ceramide synthase, contributes to elevated ceramide levels, a known initiator of apoptotic signals in mouse models of inner ear hair cells. TLR4, a pattern-recognition protein, initiates inflammation in response to cisplatin, and reduced TLR4 expression has been shown in murine hair cells to confer protection from ototoxicity.

CONCLUSION

Overall, these findings provide a foundation for understanding the genetic landscape of cisplatin-induced ototoxicity, with implications for improving patient care and treatment outcomes.

Protective effect of ginsenoside Rd on military aviation noise-induced cochlear hair cell damage in guinea pigs

Noise pollution has become one of the important social hazards that endanger the auditory system of residents, causing noise-induced hearing loss (NIHL). Oxidative stress has a significant role in the pathogenesis of NIHL, in which the silent information regulator 1(SIRT1)/proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling pathway is closely engaged. Ginsenoside Rd (GSRd), a main monomer extract from ginseng plants, has been confirmed to suppress oxidative stress. Therefore, the hypothesis that GSRd may attenuate noise-induced cochlear hair cell loss seemed promising. Forty-eight male guinea pigs were randomly divided into four groups: control, noise exposure, GSRd treatment (30 mg/kg Rd for 10d + noise), and experimental control (30 mg/kg glycerol + noise). The experimental groups received military helicopter noise exposure at 115 dB (A) for 4 h daily for five consecutive days. Hair cell damage was evaluated by using inner ear basilar membrane preparation and scanning electron microscopy. Terminal dUTP nick end labeling (TUNEL) and immunofluorescence staining were conducted. Changes in the SIRT1/PGC-1α signaling pathway and other apoptosis-related markers in the cochleae, as well as oxidative stress parameters, were used as readouts. Loss of outer hair cells, more disordered cilia, prominent apoptosis, and elevated free radical levels were observed in the experimental groups. GSRd treatment markedly mitigated hearing threshold shifts, ameliorated outer hair cell loss and lodging or loss of cilia, and improved apoptosis through decreasing Bcl-2 associated X protein (Bax) expression and increasing Bcl-2 expression. In addition, GSRd alleviated the noise-induced cochlear redox injury by upregulating superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels, decreasing malondialdehyde (MDA) levels, and enhancing the activity of SIRT1 and PGC-1α messenger ribonucleic acid (mRNA) and protein expression. In conclusion, GSRd can improve structural and oxidative damage to the cochleae caused by noise. The underlying mechanisms may be associated with the SIRT1/PGC-1α signaling pathway.

Gap Junction-Mediated Intercellular Communication of cAMP Prevents CDDP-Induced Ototoxicity via cAMP/PKA/CREB Pathway

In the cochlea, non-sensory supporting cells are directly connected to adjacent supporting cells via gap junctions that allow the exchange of small molecules. We have previously shown that the pharmacological regulation of gap junctions alleviates cisplatin (CDDP)-induced ototoxicity in animal models. In this study, we aimed to identify specific small molecules that pass through gap junctions in the process of CDDP-induced auditory cell death and suggest new mechanisms to prevent hearing loss. We found that the cyclic adenosine monophosphate (cAMP) inducer forskolin (FSK) significantly attenuated CDDP-induced auditory cell death in vitro and ex vivo. The activation of cAMP/PKA/CREB signaling was observed in organ of Corti primary cells treated with FSK, especially in supporting cells. Co-treatment with gap junction enhancers such as all-trans retinoic acid (ATRA) and quinoline showed potentiating effects with FSK on cell survival via activation of cAMP/PKA/CREB. In vivo, the combination of FSK and ATRA was more effective for preventing ototoxicity compared to either single treatment. Our study provides the new insight that gap junction-mediated intercellular communication of cAMP may prevent CDDP-induced ototoxicity.

CREG1 improves the capacity of the skeletal muscle response to exercise endurance via modulation of mitophagy

CREG1 (cellular repressor of E1A-stimulated genes 1) is involved in tissue homeostasis and influences macroautophagy/autophagy to protect cardiovascular function. However, the physiological and pathological role of CREG1 in the skeletal muscle is not clear. Here, we established a skeletal muscle-specific creg1 knockout mouse model (creg1;Ckm-Cre) by crossing the Creg1-floxed mice (Creg1^fl/fl) with a transgenic line expressing Cre recombinase under the muscle-specific Ckm (creatine kinase, muscle) promoter. In creg1;Ckm-Cre mice, the exercise time to exhaustion and running distance were significantly reduced compared to Creg1^fl/fl mice at the age of 9 months. In addition, the administration of recombinant (re)CREG1 protein improved the motor function of 9-month-old creg1;Ckm-Cre mice. Moreover, electron microscopy images of 9-month-old creg1;Ckm-Cre mice showed that the mitochondrial quality and quantity were abnormal and associated with increased levels of PINK1 (PTEN induced putative kinase 1) and PRKN/PARKIN (parkin RBR E3 ubiquitin protein ligase) but reduced levels of the mitochondrial proteins PTGS2/COX2, COX4I1/COX4, and TOMM20. These results suggested that CREG1 deficiency accelerated the induction of mitophagy in the skeletal muscle. Mechanistically, gain-and loss-of-function mutations of Creg1 altered mitochondrial morphology and function, impairing mitophagy in C2C12 cells. Furthermore, HSPD1/HSP60 (heat shock protein 1) (401-573 aa) interacted with CREG1 (130-220 aa) to antagonize the degradation of CREG1 and was involved in the regulation of mitophagy. This was the first time to demonstrate that CREG1 localized to the mitochondria and played an important role in mitophagy modulation that determined skeletal muscle wasting during the growth process or disease conditions.Abbreviations: CCCP: carbonyl cyanide m-chlorophenylhydrazone; CKM: creatine kinase, muscle; COX4I1/COX4: cytochrome c oxidase subunit 4I1; CREG1: cellular repressor of E1A-stimulated genes 1; DMEM: dulbecco's modified eagle medium; DNM1L/DRP1: dynamin 1-like; FCCP: carbonyl cyanide p-trifluoro-methoxy phenyl-hydrazone; HSPD1/HSP60: heat shock protein 1 (chaperonin); IP: immunoprecipitation; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MFF: mitochondrial fission factor; MFN2: mitofusin 2; MYH1/MHC-I: myosin, heavy polypeptide 1, skeletal muscle, adult; OCR: oxygen consumption rate; OPA1: OPA1, mitochondrial dynamin like GTPase; PINK1: PTEN induced putative kinase 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PRKN/PARKIN: parkin RBR E3 ubiquitin protein ligase; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; RFP: red fluorescent protein; RT-qPCR: real-time quantitative PCR; SQSTM1/p62: sequestosome 1; TFAM: transcription factor A, mitochondrial; TOMM20: translocase of outer mitochondrial membrane 20; VDAC: voltage-dependent anion channel.

Fetal bovine serum inhibits neomycin-induced apoptosis of hair cell-like HEI-OC-1 cells by maintaining mitochondrial function

Aging and exposure to noise or ototoxic drugs are major causes of hair cell death leading to human hearing loss, and many agents have been developed to protect hair cells from apoptosis. Fetal bovine serum (FBS) is a fundamental ingredient in the culture medium of hair cell-like House Ear Institute Organ of Corti 1 (HEI-OC-1) cells, but there have been no reports about the function of FBS in HEI-OC-1 cell apoptosis. In this study, we found that FBS deprivation alone significantly increased HEI-OC-1 cell apoptosis in the absence of neomycin exposure and that the presence of FBS significantly inhibited HEI-OC-1 cell apoptosis after neomycin exposure compared to FBS-deprived cells. Further, we found that the protective effect of FBS was dose dependent and more effective than the growth factors B27, N2, EGF, bFGF, IGF-1, and heparan sulfate. We also found that FBS deprivation significantly disrupted the expression level of mitochondrial proteins, increased pro-apoptotic gene expression, decreased the mitochondrial membrane potential, and increased reactive oxygen species accumulation in HEI-OC-1 cells after neomycin exposure. These findings indicate that FBS is involved in maintaining the level of mitochondrial proteins, maintaining the balance of oxidant gene expression, and preventing the accumulation of ROS, and thus FBS maintains normal mitochondrial function and inhibits apoptosis in HEI-OC-1 cells after neomycin exposure.