Mitophagy in ototoxicity

A comprehensive review of the impact of natural products in preventing drug-induced ototoxicity

Ototoxicity, the property of certain drugs to cause hearing loss, is a significant concern in medical treatments, particularly with the use of chemotherapeutic agents like cisplatin and aminoglycosides. These drugs can lead to permanent sensorineural hearing loss (SNHL), affecting a substantial proportion of patients. Existing strategies to alleviate these side effects are limited, prompting interest in natural products as potential protective agents. Natural products are being investigated for their ability to counteract these mechanisms through anti-inflammatory and antioxidant properties. The review seeks to highlight the potential of these natural products as complementary therapies to conventional ototoxic medications, emphasizing their protective roles, which are involved in cochlear cellular damage and programmed cell death. Further research is essential to establish standardized protocols for their use and to ensure their integration into clinical practice as effective therapeutic options.

Natural small molecules regulating the mitophagy pathway counteract the pathogenesis of diabetes and chronic complications

Diabetes mellitus (DM) is a chronic metabolic disorder marked by sustained hyperglycemia. These disturbances contribute to extensive damage across various tissues and organs, giving rise to severe complications such as vision loss, kidney failure, amputations, and higher morbidity and mortality rates. Furthermore, DM imposes a substantial economic and emotional burden on patients, families, and healthcare systems. Mitophagy, a selective process that targets the clearance of damaged or dysfunctional mitochondria, is pivotal for sustaining cellular homeostasis through mitochondrial turnover and recycling. Emerging evidence indicates that dysfunctional mitophagy acts as a key pathogenic driver in the pathogenesis of DM and its associated complications. Natural small molecules are particularly attractive in this regard, offering advantages such as low toxicity, favorable pharmacokinetic profiles, excellent biocompatibility, and a broad range of biochemical activities. This review systematically evaluates the mechanistic roles of natural small molecules-including ginsenosides, resveratrol, and berberine-in enhancing mitophagy and restoring mitochondrial homeostasis via activation of core signaling pathways (e.g., PINK1/Parkin, BNIP3/NIX, and FUNDC1). These pathways collectively ameliorate pathological hallmarks of DM, such as oxidative stress, chronic inflammation, and insulin resistance. Furthermore, the integration of nanotechnology with these compounds optimizes their bioavailability and tissue-specific targeting, thereby establishing a transformative therapeutic platform for DM management. Current evidence demonstrates that mitophagy modulation by natural small molecules not only offers novel therapeutic strategies for DM and its chronic complications but also advances the mechanistic foundation for future drug development targeting metabolic disorders.

VDAC1 Inhibition Protects Against Noise-Induced Hearing Loss via the PINK1/Parkin Pathway

AIMS

This study examined the effect of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an anion channel blocker of voltage-dependent anion channel 1 (VDAC1), on noise-induced hearing loss (NIHL) and its underlying mechanisms.

METHODS

Cochlear explants and House Ear Institute-Organ of Corti 1 (HEI-OC1) cells were used to assess the effect of DIDS in vitro. Auditory brainstem responses were used to assess auditory functions in mice. Immunofluorescence staining of myosin 7a and CTBP2 were used to examine hair cells and synaptic ribbons. The accumulation of reactive oxygen species (ROS) was measured by 4-HNE staining. The gene expression changes of cochlea were analyzed using RNA sequencing.

RESULTS

DIDS reduced the levels of ROS in cochlear explants and attenuated cell death caused by hydrogen peroxide in both cochlear explants and HEI-OC1 cells. In C57BL/6 mice, DIDS reduced ROS generation and tumor necrosis factor-α induced by noise exposure, thereby protecting outer hair cells and inner hair cell synaptic ribbons from noise-induced damage through a mechanism involving the PINK1/Parkin signaling pathway. The preventive effect of DIDS in cochlear explants was eliminated by mitophagy inhibition.

CONCLUSION

VDAC1 inhibition enhances mitophagy in cochlear hair cells, playing a critical role in defending against oxidative stress and inflammation. Downregulation of VDAC1 may thus be considered a therapeutic strategy for preventing cochlear hair cell damage and reducing NIHL.

Ototoxic Effect of Nicotinamide Riboside

We studied the function of the auditory system in Wistar rats after repeated intravenous administration of nicotinamide riboside (NR). The functional activity of the receptor and retrocochlear parts of the auditory system were assessed by recording short-latency auditory evoked potentials (SLAEPs) and distortion-product otoacoustic emissions (DPOAEs) at baseline, immediately after NR administration, and 1 and 2 months later. Repeated intravenous NR administration (cumulative dose of 2700 mg/kg) to Wistar rats has a detrimental impact on the structures within the cochlear section of the auditory system.

Calcium supplementation attenuates fluoride-induced bone injury via PINK1/Parkin-mediated mitophagy and mitochondrial apoptosis in mice

Excessive consumption of fluoride can cause skeletal fluorosis. Mitophagy has been identified as a novel target for bone disorders. Meanwhile, calcium supplementation has shown great potential for mitigating fluoride-related bone damage. Hence, this study aimed to elucidate the association between mitophagy and skeletal fluorosis and the precise mechanisms through which calcium alleviates these injuries. A 100 mg/L sodium fluoride (NaF) exposure model in Parkin knockout (Parkin-/-) mice and a 100 mg/L NaF exposure mouse model with 1% calcium carbonate (CaCO3) intervention were established in the current study. Fluoride exposure caused the impairment of mitochondria and activation of PTEN-induced putative kinase1 (PINK1)/E3 ubiquitin ligase Park2 (Parkin)-mediated mitophagy and mitochondrial apoptosis in the bones, which were restored after blocking Parkin. Additionally, the intervention model showed fluoride-exposed mice exhibited abnormal bone trabecula and mechanical properties. Still, these bone injuries could be effectively attenuated by adding 1% calcium to their diet, which reversed fluoride-activated mitophagy and apoptosis. To summarize, fluoride can activate bone mitophagy through the PINK1/Parkin pathway and mitochondrial apoptosis. Parkin-/- and 1% calcium provide protection against fluoride-induced bone damage. Notably, this study provides theoretical bases for the prevention and therapy of animal and human health and safety caused by environmental fluoride contamination.

The role of mitophagy in metabolic diseases and its exercise intervention

Mitochondria are energy factories that sustain life activities in the body, and their dysfunction can cause various metabolic diseases that threaten human health. Mitophagy, an essential intracellular mitochondrial quality control mechanism, can maintain cellular and metabolic homeostasis by removing damaged mitochondria and participating in developing metabolic diseases. Research has confirmed that exercise can regulate mitophagy levels, thereby exerting protective metabolic effects in metabolic diseases. This article reviews the role of mitophagy in metabolic diseases, the effects of exercise on mitophagy, and the potential mechanisms of exercise-regulated mitophagy intervention in metabolic diseases, providing new insights for future basic and clinical research on exercise interventions to prevent and treat metabolic diseases.

The Relevance of Autophagy within Inner Ear in Baseline Conditions and Tinnitus-Related Syndromes

Tinnitus is the perception of noise in the absence of acoustic stimulation (phantom noise). In most patients suffering from chronic peripheral tinnitus, an alteration of outer hair cells (OHC) starting from the stereocilia (SC) occurs. This is common following ototoxic drugs, sound-induced ototoxicity, and acoustic degeneration. In all these conditions, altered coupling between the tectorial membrane (TM) and OHC SC is described. The present review analyzes the complex interactions involving OHC and TM. These need to be clarified to understand which mechanisms may underlie the onset of tinnitus and why the neuropathology of chronic degenerative tinnitus is similar, independent of early triggers. In fact, the fine neuropathology of tinnitus features altered mechanisms of mechanic-electrical transduction (MET) at the level of OHC SC. The appropriate coupling between OHC SC and TM strongly depends on autophagy. The involvement of autophagy may encompass degenerative and genetic tinnitus, as well as ototoxic drugs and acoustic trauma. Defective autophagy explains mitochondrial alterations and altered protein handling within OHC and TM. This is relevant for developing novel treatments that stimulate autophagy without carrying the burden of severe side effects. Specific phytochemicals, such as curcumin and berberin, acting as autophagy activators, may mitigate the neuropathology of tinnitus.