Pro-survival Function Of Autophagy Research Articles

The dysregulated autophagy in osteoarthritis: Revisiting molecular profile

The risk factors of osteoarthritis (OA) are different and obesity, lifestyle, inflammation, cell death mechanisms and diabetes mellitus are among them. The changes in the biological mechanisms are considered as main regulators of OA pathogenesis. The dysregulation of autophagy is observed in different human diseases. During the pathogenesis of OA, the autophagy levels (induction or inhibition) change. The supportive and pro-survival function of autophagy can retard the progression of OA. The protective autophagy prevents the cartilage degeneration. Moreover, autophagy demonstrates interactions with cell death mechanisms and through inhibition of apoptosis and necroptosis, it improves OA. The non-coding RNA molecules can regulate autophagy and through direct and indirect control of autophagy, they dually delay/increase OA pathogenesis. The mitochondrial integrity can be regulated by autophagy to alleviate OA. Furthermore, therapeutic compounds, especially phytochemicals, stimulate protective autophagy in chondrocytes to prevent cell death. The protective autophagy has ability of reducing inflammation and oxidative damage, as two key players in the pathogenesis of OA.

The dual role of poly(ADP-ribose) polymerase-1 in modulating parthanatos and autophagy under oxidative stress in rat cochlear marginal cells of the stria vascularis

Oxidative stress is reported to regulate several apoptotic and necrotic cell death pathways in auditory tissues. Poly(ADP-ribose) polymerase-1 (PARP-1) can be activated under oxidative stress, which is the hallmark of parthanatos. Autophagy, which serves either a pro-survival or pro-death function, can also be stimulated by oxidative stress, but the role of autophagy and its relationship with parthanatos underlying this activation in the inner ear remains unknown. In this study, we established an oxidative stress model in vitro by glucose oxidase/glucose (GO/G), which could continuously generate low concentrations of H2O2 to mimic continuous exposure to H2O2 in physiological conditions, for investigation of oxidative stress-induced cell death mechanisms and the regulatory role of PARP-1 in this process. We observed that GO/G induced stria marginal cells (MCs) death via upregulation of PARP-1 expression, accumulation of polyADP-ribose (PAR) polymers, decline of mitochondrial membrane potential (MMP) and nuclear translocation of apoptosis-inducing factor (AIF), which all are biochemical features of parthanatos. PARP-1 knockdown rescued GO/G-induced MCs death, as well as abrogated downstream molecular events of PARP-1 activation. In addition, we demonstrated that GO/G stimulated autophagy and PARP-1 knockdown suppressed GO/G-induced autophagy in MCs. Interestingly, autophagy suppression by 3-Methyladenine (3-MA) accelerated GO/G-induced parthanatos, indicating a pro-survival function of autophagy in GO/G-induced MCs death. Taken together, these data suggested that PARP-1 played dual roles by modulating parthanatos and autophagy in oxidative stress-induced MCs death, which may be considered as a promising therapeutic target for ameliorating oxidative stress-related hearing disorders.

A new function for miRNAs as regulators of autophagy.

Autophagy is a self-digestive process regulated by an intricate network of factors able either to ensure the prosurvival function of autophagy or to convert it in a death pathway. Recently, the involvement of miRNAs in the regulation of autophagy networks has been reported. This review will summarize the main features of these small noncoding endogenous RNAs, focusing on their relevance in cancer and finally addressing their impact on autophagy.

Abstract 2838: The role of cyclin D1-associated kinase activity in the regulation of autophagy and senescence in gastric cancer cells

Abstract Introduction: Cyclin D1 regulates cell cycle progression through its ability to bind and activate cyclin-dependent kinases 4 and 6 (CDK4/6). Recent work carried out in mammary epithelial cells (MECs) propagated in vitro has revealed that the functional status of cyclin D1 modulates a balance between senescence and autophagy, two processes commonly disrupted in human cancers. Thus, in contrast to the commonly held assumption that autophagy is an effector process of senescence, inhibition of autophagy was accompanied by an induction or exacerbation of senescence in MECs deficient in cyclin D1-associated kinase activity, a reflection of the pro-survival function of autophagy in these cells. Materials and methods: In the present study, we set out to confirm these findings in gastric cancer cell lines (AGS, MKN-45 and KATO III) that may differ in their ability to induce senescence. To this end, we first treated AGS (cyclin D1+; pRB+; p53+) cells with Palbociclib (a specific inhibitor of cyclin D-CDK4/6 complexes), Spautin-1 (a specific inhibitor of autophagy), or a combination of these drugs, and assessed the effect of the treatment on the ability of these cells to proliferate or undergo senescence. Results and discussion: Unlike what was previously reported, our results suggest that autophagy is not required for the implementation of the senescent phenotype in AGS cells treated with Palbociclib. Nonetheless, senescent cells in which autophagy was disrupted were larger and often displayed multiple nuclei, suggesting the existence of different senescence programs depending on autophagy function. Citation Format: Leandro Vargas, Sindy Bravo, Claudio Valenzuela, Nelson E. Brown. The role of cyclin D1-associated kinase activity in the regulation of autophagy and senescence in gastric cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2838.

AT-101 simultaneously triggers apoptosis and a cytoprotective type of autophagy irrespective of expression levels and the subcellular localization of Bcl-xL and Bcl-2 in MCF7 cells

The effects of autophagy on cell death are highly contextual and either beneficial or deleterious. One prime example for this dual function of autophagy is evidenced by the cell responses to the BH3 mimetic AT-101 that is known to induce either apoptotic or autophagy-dependent cell death in different settings. Based on previous reports, we hypothesized that the expression levels of pro-survival Bcl-2 family members may be key determinants for the respective death mode induced by AT-101. Here we investigated the role of autophagy in the response of MCF7 breast cancer cells to AT-101. AT-101 treatment induced a prominent conversion of LC3-I to LC3-II and apoptotic cell death characterized by the appearance of Annexin-positive/PI-negative early apoptotic cells and PARP cleavage. Inhibition of the autophagy pathway, either through application of 3-MA or by lentiviral knockdown of ATG5, strongly potentiated cell death, indicating a pro-survival function of autophagy. Overexpression of wild type Bcl-xL significantly diminished the net amount of AT-101-induced cell death, but failed to alter the death-enhancing effects of the ATG5 knockdown. This was also observed with the organelle-specific variants Bcl-xL-ActA and Bcl-2-ActA (mitochondrial) as well as Bcl-xL-cb5 and Bcl-2-cb5 (ER) which all reduced AT-101-induced cell death, but did not affect the death-enhancing effects of 3-MA. Collectively, our data indicate that in apoptosis-proficient MCF7 cells, AT-101 triggers Bcl-2- and Bcl-xL-dependent apoptosis and a cytoprotective autophagy response that is independent of the expression and subcellular localization of Bcl-xL and Bcl-2.

Autophagy in aging, disease and death: the true identity of a cell death impostor

Although strictly speaking, the term autophagy merely means ‘self-eating’, many presume that this cellular self-eating is inevitably a form of cellular self-destruction. Indeed, within the cell death research field, autophagy has also long been defined as a form of non-apoptotic, or type II, programmed cell death. However, as revealed in this issue of Cell Death and Differentiation, which contains nine review papers on the topic of Autophagy in Aging, Disease and Death1–9 and one article outlining the recommendations of the Nomenclature Committee on Cell Death 2009,10 a consensus is emerging that autophagy is largely a cell death impostor which, in reality, functions primarily to promote cellular and organismal health.