Inhibition of Sphingosine Kinase 2 Results in PARK2-Mediated Mitophagy and Induces Apoptosis in Multiple Myeloma

ROS-DRP1-mediated excessive mitochondrial fission and autophagic flux inhibition contribute to heat stress-induced apoptosis in goat Sertoli cells

BACKGROUND

Heat stress (HS) poses a significant threat to male goat reproduction. Sertoli cells (SCs) provide both structural and nutritional support necessary for germ cells. HS induces physiological and biochemical changes in SCs. Nevertheless, the molecular mechanisms involved are still not fully understood. Melatonin is a classic antioxidant that can alleviate HS-induced male reproductive damage. However, the underlying molecular mechanisms by which melatonin mitigates damage to goat testicular SCs remain unclear and require further investigation.

RESULTS

In this study, an in vivo heat stress model was established in goats. The results showed that HS exposure led to testicular injury, abnormal spermatogenesis and apoptosis of SCs. To elucidate the mechanism of HS-induced SC apoptosis, primary SCs were isolated and cultured from goat testes, then exposed to HS. HS exposure increased the production of reactive oxygen species (ROS), decreased adenosine triphosphate (ATP) synthesis, and reduced mitochondrial membrane potential in SCs. Additionally, HS increased the expression of mitochondrial fission proteins 1 (FIS1) and dynamin-related protein 1 (DRP1) while decreasing the expression of mitochondrial fusion proteins Mitofusin 1 (MFN1), Mitofusin 2 (MFN2), and optic atrophy 1 (OPA1). This resulted in excessive mitochondrial fission and mitochondria-dependent apoptosis. Mdivi-1 (DRP1 inhibitor) reduces mitochondria-dependent apoptosis by inhibiting excessive mitochondrial fission. Mitochondrial fission is closely related to mitophagy. HS activated upstream mitophagy but inhibited autophagic flux, disrupting mitophagy and exacerbating mitochondria-dependent apoptosis. Finally, the classical antioxidant melatonin was shown to reduce mitochondria-dependent apoptosis in SCs exposed to HS by decreasing ROS levels, restoring mitochondrial homeostasis, and normalizing mitophagy.

CONCLUSIONS

In summary, these findings indicated that the mechanism of HS-induced mitochondria-dependent apoptosis in SCs is mediated by hyperactivation of the ROS-DRP1-mitochondrial fission axis and inhibition of mitochondrial autophagy. Melatonin inhibited HS-induced mitochondria-dependent apoptosis in SCs by restoring mitochondrial homeostasis. This study enhances the understanding of the mechanisms through which heat stress triggers apoptosis and provides a vision for the development of drugs against HS by targeting mitochondria in goats.

Astaxanthin Inhibits H2O2-Induced Excessive Mitophagy and Apoptosis in SH-SY5Y Cells by Regulation of Akt/mTOR Activation

Oxidative stress, which damages cellular components and causes mitochondrial dysfunction, occurs in a variety of human diseases, including neurological disorders. The clearance of damaged mitochondria via mitophagy maintains the normal function of mitochondria and facilitates cell survival. Astaxanthin is an antioxidant known to have neuroprotective effects, but the underlying mechanisms remain unclear. This study demonstrated that astaxanthin inhibited H2O2-induced apoptosis in SH-SY5Y cells by ameliorating mitochondrial damage and enhancing cell survival. H2O2 treatment significantly reduced the levels of activated Akt and mTOR and induced mitophagy, while pretreatment with astaxanthin prevented H2O2-induced inhibition of Akt and mTOR and attenuated H2O2-induced mitophagy. Moreover, the inhibition of Akt attenuated the protective effect of astaxanthin against H2O2-induced cytotoxicity. Taken together, astaxanthin might inhibit H2O2-induced apoptosis by protecting mitochondrial function and reducing mitophagy. The results also indicate that the Akt/mTOR signaling pathway was critical for the protection of astaxanthin against H2O2-induced cytotoxicity. The results from the present study suggest that astaxanthin can reduce neuronal oxidative injury and may have the potential to be used for preventing neurotoxicity associated with neurodegenerative diseases.

Natural Products and Small Molecules Targeting Cellular Ceramide Metabolism to Enhance Apoptosis in Cancer Cells

Molecular targeting strategies have been used for years in order to control cancer progression and are often based on targeting various enzymes involved in metabolic pathways. Keeping this in mind, it is essential to determine the role of each enzyme in a particular metabolic pathway. In this review, we provide in-depth information on various enzymes such as ceramidase, sphingosine kinase, sphingomyelin synthase, dihydroceramide desaturase, and ceramide synthase which are associated with various types of cancers. We also discuss the physicochemical properties of well-studied inhibitors with natural product origins and their related structures in terms of these enzymes. Targeting ceramide metabolism exhibited promising mono- and combination therapies at preclinical stages in preventing cancer progression and cemented the significance of sphingolipid metabolism in cancer treatments. Targeting ceramide-metabolizing enzymes will help medicinal chemists design potent and selective small molecules for treating cancer progression at various levels.