ALA protects against ERS-mediated apoptosis in a cochlear cell model with low citrate synthase expression

The Chemoprotective Potentials of Alpha-lipoic Acid against Cisplatin-induced Ototoxicity: A Systematic Review

PURPOSE

Ototoxicity is one of the major adverse effects of cisplatin therapy which restrict its clinical application. Alpha-lipoic acid administration may mitigate cisplatin-induced ototoxicity. In the present study, we reviewed the protective potentials of alpha-lipoic acid against the cisplatin-mediated ototoxic adverse effects.

METHODS

Based on the PRISMA guideline, we performed a systematic search for the identification of all relevant studies in various electronic databases up to June 2022. According to the inclusion and exclusion criteria, the obtained articles (n=59) were screened and 13 eligible articles were finally included in the present study.

RESULTS

The findings of in-vitro experiments showed that cisplatin treatment significantly reduced the auditory cell viability in comparison with the control group; nevertheless, the alpha-lipoic acid co-administration protected the cells against the reduction of cell viability induced by cisplatin treatment. Moreover, the in-vivo results of the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) tests revealed a decrease in DPOAE and an increase in ABR threshold of cisplatin-injected animals; however, it was shown that alpha-lipoic acid co-treatment had an opposite pattern on the evaluated parameters. Other findings demonstrated that cisplatin treatment could significantly induce the biochemical and histopathological alterations in inner ear cells/tissue; in contrast, alpha-lipoic acid co-treatment ameliorated the cisplatin-mediated biochemical and histological changes.

CONCLUSION

The findings of audiometry, biochemical parameters, and histological evaluation showed that alpha-lipoic acid co-administration alleviates the cisplatin-induced ototoxicity. The protective role of alpha-lipoic acid against the cisplatin-induced ototoxicity can be due to different mechanisms of anti-oxidant, anti-apoptotic, anti-inflammatory activities, and regulation of cell cycle progression.

The Effects of Prolonged Basic Amino Acid Exposures on Mitochondrial Enzyme Gene Expressions, Metabolic Profiling and Insulin Secretions and Syntheses in Rat INS-1 β-Cells

In order to investigate the chronic effects of basic amino acids (BAA) on β-cell metabolism and insulin secretion, INS-1 β-cells were randomly assigned to cultures in standard medium (Con), standard medium plus 10 mM L-Arginine (Arg), standard medium plus 10 mM L-Histidine (His) or standard medium plus 10 mM L-Lysine (Lys) for 24 h. Results showed that insulin secretion was decreased by the Arg treatment but was increased by the His treatment relative to the Con group (p < 0.05). Higher BAA concentrations reduced the high glucose-stimulated insulin secretions (p < 0.001), but only Lys treatment increased the intracellular insulin content than that in the Con group (p < 0.05). Compared with Arg and Lys, the His treatment increased the mitochondrial key enzyme gene expressions including Cs, mt-Atp6, mt-Nd4l and Ogdh, and caused a greater change in the metabolites profiling (p < 0.05). The most significant pathways affected by Arg, His and Lys were arginine and proline metabolism, aminoacyl-tRNA biosynthesis and pyrimidine metabolism, respectively. Regression analysis screened 7 genes and 9 metabolites associated with insulin releases during BAA stimulations (p < 0.05). Together, different BAAs exerted dissimilar effects on β-cell metabolism and insulin outputs.

Effect of downregulated citrate synthase on oxidative phosphorylation signaling pathway in HEI-OC1 cells

Background

Citrate Synthase (Cs) gene mutation (locus ahL4) has been found to play an important role in progressive hearing loss of A/J mice. HEI-OC1 cells have been widely used as an in vitro system to study cellular and molecular mechanisms related to hearing lose. We previously reported the increased apoptosis and the accumulation of reactive oxygen species in shRNACs-1429 cells, a Cs low-expressed cell model from HEI-OCI. The details of the mechanism of ROS production and apoptosis mediated by the abnormal expression of Cs needed to research furtherly.

Methods

iTRAQ proteomics was utilized to detect the differentially expressed proteins (DEPs) caused by low expression of Cs. The GO and KEGG pathways analysis were performed for annotation of the differentially expressed proteins. Protein–protein interaction network was constructed by STRING online database. Immunoblotting was utilized to confirm the protein levels of the the differentially expressed proteins.

Results

The differentially expressed proteins were significantly enriched in various signaling pathways mainly related to mitochondrial dysfunction diseases including Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, et al. Most noteworthy, the oxidative phosphorylation pathway was most significantly suppressed in the shRNACs-1429 cells,, in which a total of 10 differentially expressed proteins were enriched and were all downregulated by the abnormal expression of Cs. The downregulations of Ndufb5, Ndufv1 and Uqcrb were confirmed by immunoblotting. Meanwhile, the ATP levels of shRNACs-1429 cells were also reduced.

Conclusions

These results suggest that low level expression of Cs induces the inhibition of oxidative phosphorylation pathway, which is responsible for the high level production of reactive oxygen species and low level of ATP, leading to the apoptosis of cochlear cells. This study may provide new theories for understanding and therapy of progressive hearing loss.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12953-022-00196-0.

Role of gene regulation and inter species interaction as a key factor in gut microbiota adaptation

Gut microbiota is a class of microbial flora present in various eukaryotic multicellular complex animals such as human beings. Their community's growth and survival are greatly influenced by various factors such as host-pathogen, pathogen-environment and genetic regulation. Modern technologies like metagenomics have particularly extended our capacity to uncover the microbial treasures in challenging conditions like communities surviving at high altitude. Molecular characterizations by newly developed sequencing tools have shown that this complex interaction greatly influences microbial adaptation to the environment. Literature shows that gut microbiota alters the genetic expression and switches to an alternative pathway under the influence of unfavorable conditions. The remarkable adaptability of microbial genetic regulatory networks enables them to survive and expand in tough and energy-limited conditions. Variable prevalence of species in various regions has strengthened this initial evidence. In view of the interconnection of the world in the form of a global village, this phenomenon must be explored more clearly. In this regard, recently there has been significant addition of knowledge to the field of microbial adaptation. This review summarizes and shed some light on mechanisms of microbial adaptation via gene regulation and species interaction in gut microbiota.

H55 N variation in citrate synthase leads to decrement in the enzyme activity and transport rate to mitochondria in HEI-OC1 cells

A/J mouse is a typical animal model of age-related deafness. Previous studies have shown that the mice suffer from progressive hearing loss and degeneration of cochlear cells, and a variation of H55 N in citrate synthase (CS) causes about 40% the hearing loss. CS is a key enzyme in the tricarboxylic acid cycle, which is transported from cytoplasm to mitochondria after synthesis, sorted by the mitochondrial targeting sequence (MTS). To explore the mechanism of CS (H55 N) variation in affecting its function, HEI-OC1 cells were infected with lentivirus particles to express CS-Flag or CS(H55 N)-Flag. The results showed that H55 N variation in CS, as purified by co-immunoprecipitation, decreased the enzyme activity by about 50%. Confocal microscope co-localization indicated that the CS (H55 N) variation led to a decrement in its mitochondrial content. Western blot also showed the amount of CS(H55 N)-Flag was more than that of CS(WT)-Flag in the cytosol. The results suggest H55 N variation in CS lead to decrement of its enzyme activity and targeting transport to mitochondria. We therefore conclude that decrement in CS activity and mitochondrial delivery contributes to the degeneration of cochlear cells and thus the hearing loss in A/J mice.