bims-mitinf 2019-01-20 papers

Issue of 2019‒01‒20
three papers selected by
Prafull Kumar Singh
University of Freiburg Medical Center

Cells. 2019 Jan 17. pii: E65. [Epub ahead of print]8(1):

Oxidative Insults and Mitochondrial DNA Mutation Promote Enhanced Autophagy and Mitophagy Compromising Cell Viability in Pluripotent Cell Model of Mitochondrial Disease.

Dar-Shong Lin, Yu-Wen Huang, Che-Sheng Ho, Pi-Lien Hung, Mei-Hsin Hsu, Tuan-Jen Wang, Tsu-Yen Wu, Tsung-Han Lee, Zo-Darr Huang, Po-Chun Chang, Ming-Fu Chiang.

Dysfunction of mitochondria causes defects in oxidative phosphorylation system (OXPHOS) and increased production of reactive oxygen species (ROS) triggering the activation of the cell death pathway that underlies the pathogenesis of aging and various diseases. The process of autophagy to degrade damaged cytoplasmic components as well as dysfunctional mitochondria is essential for ensuring cell survival. We analyzed the role of autophagy inpatient-specific induced pluripotent stem (iPS) cells generated from fibroblasts of patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) with well-characterized mitochondrial DNA mutations and distinct OXPHOS defects. MELAS iPS cells recapitulated the pathogenesis of MELAS syndrome, and showed an increase of autophagy in comparison with its isogenic normal counterpart, whereas mitophagy is very scarce at the basal condition. Our results indicated that the existence of pathogenic mtDNA alone in mitochondrial disease was not sufficient to elicit the degradation of dysfunctional mitochondria. Nonetheless, oxidative insults induced bulk macroautophagy with the accumulation of autophagosomes and autolysosomes upon marked elevation of ROS, overload of intracellular calcium, and robust depolarization of mitochondrial membrane potential, while mitochondria respiratory function was impaired and widespread mitophagy compromised cell viability. Collectively, our studies provide insights into the dysfunction of autophagy and activation of mitophagy contributing to the pathological mechanism of mitochondrial disease.

Keywords: MELAS; autophagy; iPS cells; mitochondrial diseases; mitophagy

DOI: https://doi.org/10.3390/cells8010065

Cells. 2019 Jan 16. pii: E61. [Epub ahead of print]8(1):

Autophagy in Chronic Kidney Diseases.

Tien-An Lin, Victor Chien-Chia Wu, Chao-Yung Wang.

Autophagy is a cellular recycling process involving self-degradation and reconstruction of damaged organelles and proteins. Current evidence suggests that autophagy is critical in kidney physiology and homeostasis. In clinical studies, autophagy activations and inhibitions are linked to acute kidney injuries, chronic kidney diseases, diabetic nephropathies, and polycystic kidney diseases. Oxidative stress, inflammation, and mitochondrial dysfunction, which are implicated as important mechanisms underlying many kidney diseases, modulate the autophagy activation and inhibition and lead to cellular recycling dysfunction. Abnormal autophagy function can induce loss of podocytes, damage proximal tubular cells, and glomerulosclerosis. After acute kidney injuries, activated autophagy protects tubular cells from apoptosis and enhances cellular regeneration. Patients with chronic kidney diseases have impaired autophagy that cannot be reversed by hemodialysis. Multiple nephrotoxic medications also alter the autophagy signaling, by which the mechanistic insights of the drugs are revealed, thus providing the unique opportunity to manage the nephrotoxicity of these drugs. In this review, we summarize the current concepts of autophagy and its molecular aspects in different kidney cells pathophysiology. We also discuss the current evidence of autophagy in acute kidney injury, chronic kidney disease, toxic effects of drugs, and aging kidneys. In addition, we examine therapeutic possibilities targeting the autophagy system in kidney diseases.

Keywords: autophagy; inflammation; kidney diseases; mitochondria; oxidative stress

DOI: https://doi.org/10.3390/cells8010061

Free Radic Biol Med. 2019 Jan 09. pii: S0891-5849(18)31748-9. [Epub ahead of print]

Roles of TRPA1 and TRPV1 in Cigarette Smoke -induced Airway Epithelial Cell Injury Model.

Muyun Wang, Yanbei Zhang, Mengmeng Xu, Hai Zhang, Yuqing Chen, Kian Fan Chung, Ian M Adcock, Feng Li.

Transient receptor potential protein (TRP) ion channels TRPA1 and TRPV1 may be important in mediating airway tissue injury and inflammation. This study was designed to clarify the role of TRPA1 and TRPV1 channels in cigarette smoke extract (CSE)-induced damage to bronchial and alveolar epithelial cells. Alveolar epithelial (A549) cells and bronchial epithelial (Beas-2B) cells were treated with CSE in the presence and absence of a TRPA1 inhibitor (100μM, A967079), a TRPV1 inhibitor (100μM, AMG9810) or both. DCFH-DA and MitoSOX Red probes were used to assay intracellular and mitochondrial oxidative stress, respectively. The mRNA levels of inflammatory mediators (IL-1β, IL-8, IL-18, IL-33) and antioxidants (HO-1, NQO1, MnSOD, Catalase) and the protein expression levels of mitochondrial and inflammasome factors (MFN2, OPA1, DRP1, MFF, NLRP3,Caspase-1) were detected by Western Blot. The results were validated in TRPA1 shRNA and TRPV1 shRNA cells. In both cell types, 10% CSE increased intracellular and mitochondrial oxidative stress, induced Ca2+ influx, increased inflammatory gene expression, reduced antioxidant gene expression and inhibited the activities of mitochondrial respiratory chain (MRC) complexes. 10% CSE increased the expression of mitochondrial fission proteins (MFF and DRP1), Caspase-1 and NLRP3 protein expression and decreased that of mitochondrial fusion proteins (MFN2 and OPA1). Both inhibitors and gene-knockout of TRPA1 and TRPV1 reduced oxidative stress, blocked Ca2+ influx, and inhibited inflammatory and increased antioxidant gene expression. They also prevented the changes in mitochondrial fission and fusion proteins and in MRC complexes activities induced by CSE. Both TRPA1 and TRPV1 mediate CSE-induced damage of airway and alveolar epithelial cells via modulation of oxidative stress, inflammation and mitochondrial damage and their inhibition should be considered as potential therapy for COPD.

Keywords: COPD; TRPA1; TRPV1; airway epithelial cell injury; cigarette smoke; mitochondria damage; oxidative stress

DOI: https://doi.org/10.1016/j.freeradbiomed.2019.01.004