Autophagy impairment as a key feature for acetaminophen-induced ototoxicity.

Macroautophagy/autophagy is a highly conserved self-digestion pathway that plays an important role in cytoprotection under stress conditions. Autophagy is involved in hepatotoxicity induced by acetaminophen (APAP) in experimental animals and in humans. APAP also causes ototoxicity. However, the role of autophagy in APAP-induced auditory hair cell damage is unclear. In the present study, we investigated autophagy mechanisms during APAP-induced cell death in a mouse auditory cell line (HEI-OC1) and mouse cochlear explant culture. We found that the expression of LC3-II protein and autophagic structures was increased in APAP-treated HEI-OC1 cells; however, the degradation of SQSTM1/p62 protein, the yellow puncta of mRFP-GFP-LC3 fluorescence, and the activity of lysosomal enzymes decreased in APAP-treated HEI-OC1 cells. The degradation of p62 protein and the expression of lysosomal enzymes also decreased in APAP-treated mouse cochlear explants. These data indicate that APAP treatment compromises autophagic degradation and causes lysosomal dysfunction. We suggest that lysosomal dysfunction may be directly responsible for APAP-induced autophagy impairment. Treatment with antioxidant N-acetylcysteine (NAC) partially alleviated APAP-induced autophagy impairment and apoptotic cell death, suggesting the involvement of oxidative stress in APAP-induced autophagy impairment. Inhibition of autophagy by knocking down of Atg5 and Atg7 aggravated APAP-induced ER and oxidative stress and increased apoptotic cell death. This study provides a better understanding of the mechanism responsible for APAP ototoxicity, which is important for future exploration of treatment strategies for the prevention of hearing loss caused by ototoxic medications.

Biomechanical Analysis of Angular Motion in Association with Bilateral Semicircular Canal Function.

The aim of this study was to characterize cupular deformation by calculating the degree of cupular expansion and cupular deflection using a finite element model of bilateral human semicircular canals (SCCs). The results showed that cupular deflection responses were consistent with Ewald's II law, whereas each pair of bilateral cupulae simultaneously expanded or compressed to the same degree. In addition, both the degree of cupular expansion and cupular deflection can be expressed as the solution of forced oscillation during head sinusoidal rotation, and the amplitude of cupular expansion was approximately two times greater than that of cupular deflection. Regarding the amplitude frequency and phase frequency characteristics, the amplitude ratios among the horizontal SCC, the anterior SCC, and the posterior SCC cupular expansion was constant at 1:0.82:1.62, and the phase differences among them were constant at 0 or 180° at the frequencies of 0.5-6 Hz. However, both the amplitude ratio and the phase differences of the cupular deflection increased nonlinearly with the increase of frequency and tended to be constant at the frequency band between 2 and 6 Hz. The results indicate that the responses of cupular expansion might only be related to the mass and rigidity of three cupulae and the endolymph, but the responses of cupular deflection are related to the mass, rigidity, or damping of them, and these physical properties would be affected by vestibular dysfunction. Therefore, both the degree of cupular expansion and cupular deflection should be considered important mechanical variables for induced neural signals as these variables provide a better understanding of the SCCs system's role in the vestibulo-ocular reflex during the clinical rotating chair test and the vestibular autorotation test. Such a numerical model can be further built to provide a useful theoretical approach for exploring the biomechanical nature underlying vestibular dysfunction.

[Inducement effect of synthetic indiosides from Solanum indicum L.on apoptosis of human hepatocarcinoma cell line Bel-7402 and its mechanism].

BACKGROUND & OBJECTIVE: Solanum indicum L., an anti-inflammatory and wound-healing herb in traditional Chinese medicine, is enriched of unique dioscins, that is, indiosides. Our previous studies revealed that several synthetic indiosides from Solanum indicum L. have potent anticancer effects. This study was to investigate the anticancer mechanism of synthetic indiosides I from Solanum indicum L. METHODS: Human hepatocarcinoma Bel-7402 cells were treated with different concentrations of indiosides. The inhibitory rate of cell proliferation and 50% inhibitory concentration (IC50) of indiosides were detected by the acid phosphatase assay (APA). Cell morphology was observed under optical microscope with crystal violet staining. The expression of apoptosis-related proteins was detected by Western blot. RESULTS: Indiosides significantly inhibited proliferation of Bel-7402 cells: when treated with indioside I for 72 h, the IC50 value was 4.2 microg/ml, cell density was decreased, and bubbles were observed in cytoplasm. Western blot showed that the cytoplasmic level of cytochrome c was increased significantly, Caspase-3 was activated, and poly (ADR-ribose) polymerase (PARP) was cleavaged after indioside I treatment. CONCLUSION: Indiosides have dose-dependent inhibitory effect on proliferation of Bel-7402 cells, and can induce cell apoptosis through mitochondria-dependent pathway.