Retigeric acid B-induced mitophagy by oxidative stress attenuates cell death against prostate cancer cells in vitro

Aim:

Retigeric acid B (RAB), a pentacyclic triterpenic acid from Lobaria kurokawae Yoshim, has been found to induce apoptosis in prostate cancer cells. The aim of this study was to investigate the roles of mitochondrial damage-caused mitophagy in RAB-induced prostate cancer cell death in vitro.

Methods:

Human prostate cancer PC3 and LNCaP cells were tested. Cell viability was analyzed with MTT assay. Cell apoptosis, ROS level and mitochondrial transmembrane potential (mtΔψ) were measured with flow cytometry. Autophagy- and apoptosis-related proteins were studied using Western blotting. GFP-LC3B puncta, mitochondrial swelling and mitophagy were examined morphologically. Quantitative RT-PCR was used to measure LC3B mRNA level, and siRNA was used to knock down LC3BII.

Results:

In both PC3 and LNCaP cells, RAB (15 μmol/L) increased ROS accumulation and decreased mtΔψ in a time-dependent manner. Furthermore, RAB induced mitochondrial swelling and mitophagy, significantly increased LC3B expression and conversion of LC3BI to LC3BII, and the elimination of mitochondria by LC3BII-containing autophagolysosomes. In addition, RAB suppressed the PI3K/Akt/mTOR pathway activation. Pretreatment of PC3 cells with autophagy inhibitor 3-MA (5 mmol/L) or the lysosomal protease inhibitor CQ (10 μmol/L) significantly increased RAB-induced apoptosis. Similar results were obtained in RAB-treated PC3 cells with LC3B knocked down.

Conclusion:

RAB induces mitochondrial damage and mitophagy that attenuates RAB-induced prostate cancer cell death. Thus, suppression of mitophagy might be a potential strategy for improving the chemotherapeutic effects of RAB.     

Melatonin and verteporfin synergistically suppress the growth and stemness of head and neck squamous cell carcinoma through the regulation of mitochondrial dynamics

The prevalence of head and neck squamous cell carcinoma (HNSCC) has continued to rise for decades. However, drug resistance to chemotherapeutics and relapse, mediated by cancer stem cells (CSCs), remains a significant impediment in clinical oncology to achieve successful treatment. Therefore, we focused on analyzing CSCs in HNSCC and demonstrated the effect of melatonin (Mel) and verteporfin (VP) on SCC-25 cells. HNSCC CSCs were enriched in the reactive oxygen species-low state and in sphere-forming cultures. Combination treatment with Mel and VP decreased HNSCC viability and increased apoptosis without causing significant damage to normal cells. Sphere-forming ability and stem cell population were reduced by co-treatment with Mel and VP, while mitochondrial ROS level was increased by the treatment. Furthermore, the expression of mitophagy markers, parkin and PINK1, was significantly decreased in the co-treated cells. Mel and VP induced mitochondrial depolarization and inhibited mitochondrial function. Parkin/TOM20 was localized near the nucleus and formed clusters of mitochondria in the cells after treatment. Moreover, Mel and VP downregulated the expression of markers involved in epithelial-mesenchymal transition and metastasis. The migration capacity of cells was significantly decreased by co-treatment with Mel and VP, accompanied by the down-regulation of MMP-2 and MMP-9 expression. Taken together, these results indicate that co-treatment with Mel and VP induces mitochondrial dysfunction, resulting in the apoptosis of CSCs. Mel and VP could thus be further investigated as potential therapies for HNSCC through their action on CSCs.     

Doxorubicin alters the mitochondrial dynamics machinery and mitophagy in the liver of treated animals

Doxorubicin (Dox) is an effective chemotherapeutic agent, but known to cause cardiac and hepatic toxicity. Mechanisms of toxicity have not been clearly identified, but shown to involve oxidative stress and mitochondrial dysfunction. However, antioxidant supplementation has only shown modest protection from Dox‐induced toxicity in clinical trials. Therefore, further research is required to discern alternative mechanisms that may also play an important role in Dox‐induced toxicity. Thus, we aimed to investigate the role of mitochondrial fusion and fission in Dox‐induced hepatic toxicity, which has not yet been investigated. Six‐week‐old male F344 rats were injected IP with 20 mg/kg of Dox or saline. Once administered, both groups of animals were fasted with no food or water until sacrifice 24 h later. Dox decreased content of primary regulators of mitochondrial fusion (OPA1, MFN1, and MFN2) with no effect on regulators of fission (DRP1 and FIS1), thus shifting the balance favoring mitochondrial fission. Moreover, it was determined that mitochondrial fission was likely not coupled to cell proliferation or cytochrome c release leading to the activation of mitochondrial‐mediated apoptotic signaling. Rather, mitochondrial fission may be coupled to mitophagy and may be an adaptive response to protect against Dox‐induced hepatic toxicity. This is the first study to report the role of altered mitochondrial dynamics and mitophagy machinery in Dox‐induced hepatic injury.     

Precision Neurology for Parkinson’s Disease: Coupling Miro1-Based Diagnosis With Drug Discovery

Parkinson’s disease (PD) is a debilitating movement disorder, significantly afflicting the aging population. Efforts to develop an effective treatment have been challenged by the lack of understanding of the pathological mechanisms underlying neurodegeneration. We have shown that Miro1, an outer mitochondrial membrane protein, situates at the intersection of the complex genetic and functional network of PD. Removing Miro1 from the surface of damaged mitochondria is a prerequisite for mitochondrial clearance via mitophagy. Parkinson’s proteins PINK1, Parkin, and LRRK2 are the molecular helpers to remove Miro1 from dysfunctional mitochondria destined for mitophagy. We have found a delay in clearing Miro1 and initiating mitophagy in postmortem brains and induced pluripotent stem cell–derived neurons from PD patients harboring mutations in LRRK2, PINK1, or Parkin, or from sporadic PD patients with no known mutations. In addition, we have shown that reducing Miro1 by both genetic and pharmacological approaches can correct this Miro1 phenotype and rescue Parkinson’s-relevant phenotypes in human neurons and fly PD models. These results suggest that the Miro1 defect may be a common denominator for PD, and compounds that reduce Miro1 promise a new class of drugs to battle PD. We propose to couple this Miro1 phenotype with Miro1-based drug discovery in future therapeutic studies, which could significantly improve the success of clinical trials. © 2020 International Parkinson and Movement Disorder Society     

Deregulated mitochondrial quality control,the heel of Achilles in elucidating the role of autophagy in SARM1-mediated axon degeneration

Autophagic dysfunction in neurodegenerative diseases is being extensively studied, yet the exact mechanism of macroautophagy/autophagy in axon degeneration is still elusive. A recent study by Kim et al. links autophagic stress to the sterile α and toll/interleukin 1 receptor motif containing protein 1 (SARM1)-dependent core axonal degeneration program, providing a new insight into the role of autophagy in axon degeneration. In the classical Wallerian axon degeneration model of axotomy, disruption of axonal transport destroys the coordinated activity of pro-survival and pro-degenerative factors in the axoplasm and activates the NADase activity of SARM1, thus triggering the axonal self-destruction program. However, the mechanism for SARM1 activation in the chronic neurodegenerative disorders is more complex. Mitochondrial defects and oxidative stress contribute to the activation of SARM1, while mitophagy can inhibit mitochondrial dysfunction and promote the clearance of SARM1 on mitochondria, thus protecting against neuronal degeneration. Therefore, in-depth elucidation of the underlying mechanisms of mitophagy during axonal degeneration can help develop promising strategies for the prevention and treatment of various neurodegenerative disorders.     

Role and mechanisms of autophagy in acetaminophen‐induced liver injury

Acetaminophen (APAP) overdose is the most frequent cause of acute liver failure in the USA and many other countries. Although the metabolism and pathogenesis of APAP has been extensively investigated for decades, the mechanisms by which APAP induces liver injury are incompletely known, which hampers the development of effective therapeutic approaches to tackle this important clinical problem. Autophagy is a highly conserved intracellular degradation pathway, which aims at recycling cellular components and damaged organelles in response to adverse environmental conditions and stresses as a survival mechanism. There is accumulating evidence indicating that autophagy is activated in response to APAP overdose in specific liver zone areas, and pharmacological activation of autophagy protects against APAP‐induced liver injury. Increasing evidence also suggests that hepatic autophagy is impaired in nonalcoholic fatty livers (NAFLD), and NAFLD patients are more susceptible to APAP‐induced liver injury. Here, we summarized the current progress on the role and mechanisms of autophagy in protecting against APAP‐induced liver injury.     

线粒体自噬在眼科相关疾病中的研究进展

线粒体自噬是一种选择性自噬,是指细胞通过自噬的机制选择性地清除线粒体的过程。线粒体自噬在清除功能失调的线粒体、降低线粒体数量及维持细胞稳态中起着重要的作用。它的分子机制涉及PINK1/Parkin、BNIP3、NIX和FUNDC1等多种蛋白。线粒体发生功能障碍或损坏都可能造成严重的后果,甚至导致细胞死亡。研究发现线粒体自噬紊乱与多种眼科疾病的发生有关,如白内障、青光眼、年龄相关性黄斑变性(age-related macular degenration, AMD)、糖尿病视网膜病变(diabetic retinopathy, DR)等。本文就线粒体自噬的发生机制和它在眼科相关疾病中的研究进行综述。     

Mitochondrial dysfunction in neurodegenerative diseases and the potential countermeasure

Mitochondria not only supply the energy for cell function, but also take part in cell signaling. This review describes the dysfunctions of mitochondria in aging and neurodegenerative diseases, and the signaling pathways leading to mitochondrial biogenesis (including PGC‐1 family proteins, SIRT1, AMPK) and mitophagy (parkin‐Pink1 pathway). Understanding the regulation of these mitochondrial pathways may be beneficial in finding pharmacological approaches or lifestyle changes (caloric restrict or exercise) to modulate mitochondrial biogenesis and/or to activate mitophagy for the removal of damaged mitochondria, thus reducing the onset and/or severity of neurodegenerative diseases.