Functional and physical interaction between Bcl-X(L) and a BH3-like domain in Beclin-1

Eucalyptol relieves the toxicity of diisobutyl phthalate in Ctenopharyngodon idellus kidney cells through Keap1/Nrf2/HO-1 pathway: Apoptosis-autophagy crosstalk and immunoregulation

Diisobutyl phthalate (DiBP), one of the commonly used plasticizers in industry, is an endocrine disruptor and environmental contaminant that can persist in water and threaten the health of aquatic creatures. Eucalyptol (Euc), a monoterpenoid extracted from plants, has been proved to have anti-inflammatory, antioxidant, and detoxification properties. However, the protective mechanism of Euc against cell injury caused by DiBP exposure and the involvement of apoptosis, autophagy, and immunity remains unknown. In the current investigation, 27.8 μg/mL DiBP or/and 20 μM Euc has been applied to Ctenopharyngodon idellus kidney (CIK) cells for 24 h. The findings showed that exposure to DiBP raised intracellular ROS levels, inducing oxidative stress, and enhanced the rate of apoptosis as well as the expression of the apoptotic markers Bax, Caspase3, Caspase9, and Cytc while decreasing the expression of Bcl-2. Furthermore, DiBP inhibited IL-2, IFN-γ, Hepcidin-1, and β-defensin expression and elevated TNF-α, and IL-1β levels, causing immune dysfunction. DiBP and Euc co-treatment significantly activated the Keap1/Nrf2/HO-1 pathway, restored antioxidant enzyme activity, and elevated autophagy pathway-associated genes ATG5, Beclin1, and LC3B decreased p62 expression, enhanced cell autophagy, reduced apoptosis, and improved immunity. In conclusion, Euc promotes autophagy, alleviates DiBP-induced apoptosis, and improves immunological dysfunction in CIK cells by regulating the Keap1/Nrf2/HO-1 pathway. These results demonstrated the threat of DiBP exposure to fish while providing a theoretical foundation for using Euc in aquaculture.

Regulation of the apoptosis/autophagy switch by propionic acid in ventromedial hypothalamus of rats with type 2 diabetes mellitus

Background

Hypothalamic dysregulation may cause abnormal glucose metabolism and type 2 diabetes mellitus (T2DM). The balance between autophagy and apoptosis is important for maintaining cellular/tissue homeostasis and may be disrupted in T2DM.

Objectives

Since propionic acid (PA) exerts neuroprotective effects, the aim was to investigate its effects on apoptosis/autophagy switch in the ventromedial hypothalamus (VMH) of T2DM rats.

Materials and methods

Male Wistar rats were divided: 1) control; 2) T2DM; groups that received (14 days, orally): 3) metformin (60 mg/kg); 4) sodium salt of PA (60 mg/kg); 5) PA + metformin. Western blotting (Bax, Bcl-xl, LC3, Beclin-1, caspase-3), RT-PCR (Bax, Bcl-xl, LC3, Beclin-1), transmission electron microscopy and immunohistochemical staining (Bax, Bcl-xl) were performed on the VMH samples.

Results

T2DM-induced apoptosis and mitoptosis, enlarged endoplasmic reticulum (ER) tubules/cisterns were observed in VMH, and accompanied by an imbalance of pro- and anti-apoptotic factors: elevation of pro-apoptotic markers Bax and caspase-3, decrease in autophagy protein LC3 and anti-apoptotic Bcl-xl. Metformin and PA administration partially improved VMH ultrastructural changes by reducing mitochondrial swelling and diminishing the number of apoptotic neurons. Metformin inhibited neuronal apoptosis, however, caused reactive astrogliosis and accumulation of lipofuscin granules. Elevated number of autophagosomes was associated with the LC3, Beclin-1 and Bcl-xl increase and decrease in Bax and caspase-3 vs. T2DM. PA switched cell fate from apoptosis to autophagy by elevating LC3 and Beclin-1 levels, increasing Bcl-xl content that altogether may represent adaptive response to T2DM-induced apoptosis. PA + metformin administration lowered relative area of ER membranes/cisterns vs. control, T2DM and metformin, and was optimal considering ratio between the pro-apoptotic, anti-apoptotic and autophagy markers.

Conclusion

T2DM was associated with apoptosis activation leading to impairments in VMH. PA in combination with metformin may be effective against diabetes-induced cell death by switching apoptosis to autophagy in VMH.

SHP-1/STAT3-Signaling-Axis-Regulated Coupling between BECN1 and SLC7A11 Contributes to Sorafenib-Induced Ferroptosis in Hepatocellular Carcinoma

Ferroptosis is a type of iron-dependent cell death pertaining to an excess of lipid peroxidation. It has been suggested that sorafenib—an anti-angiogenic medication for hepatocellular carcinoma (HCC)—induces ferroptosis, but the underlying mechanism for this remains largely unknown. We employed siRNA-mediated gene silencing to investigate the role of Src homology region 2 domain-containing phosphatase-1 (SHP-1), following sorafenib treatment, in cystine/glutamate-antiporter-system-Xc⁻-regulated cystine uptake. Co-immunoprecipitation was also performed to examine the interactions between MCL1, beclin 1 (BECN1), and solute carrier family 7 member 11 (SLC7A11), which functions as the catalytic subunit of system Xc⁻. The results of this study showed that sorafenib enhanced the activity of SHP-1, dephosphorylated STAT3, downregulated the expression of MCL1 and, consequently, reduced the association between MCL1 and BECN1. In contrast, increased binding between BECN1 and SLC7A11 was observed following sorafenib treatment. The elevated interaction between BECN1 and SLC7A11 inhibited the activity of system Xc⁻, whereas BECN1 silencing restored cystine intake and protected cells from ferroptosis. Notably, ectopic expression of MCL1 uncoupled BECN1 from SLC7A11 and rescued cell viability by attenuating lipid peroxidation. The results revealed that ferroptosis could be induced in HCC via SHP-1/STAT3-mediated downregulation of MCL1 and subsequent inhibition of SLC7A11 by increased BECN1 binding.

The Roles of Mitophagy and Autophagy in Ineffective Erythropoiesis in β-Thalassemia

β-Thalassemia is one of the most common genetically inherited disorders worldwide, and it is characterized by defective β-globin chain synthesis leading to reduced or absent β-globin chains. The excess α-globin chains are the key factor leading to the death of differentiating erythroblasts in a process termed ineffective erythropoiesis, leading to anemia and associated complications in patients. The mechanism of ineffective erythropoiesis in β-thalassemia is complex and not fully understood. Autophagy is primarily known as a cell recycling mechanism in which old or dysfunctional proteins and organelles are digested to allow recycling of constituent elements. In late stage, erythropoiesis autophagy is involved in the removal of mitochondria as part of terminal differentiation. Several studies have shown that autophagy is increased in earlier erythropoiesis in β-thalassemia erythroblasts, as compared to normal erythroblasts. This review summarizes what is known about the role of autophagy in β-thalassemia erythropoiesis and shows that modulation of autophagy and its interplay with apoptosis may provide a new therapeutic route in the treatment of β-thalassemia. Literature was searched and relevant articles were collected from databases, including PubMed, Scopus, Prospero, Clinicaltrials.gov, Google Scholar, and the Google search engine. Search terms included: β-thalassemia, ineffective erythropoiesis, autophagy, novel treatment, and drugs during the initial search. Relevant titles and abstracts were screened to choose relevant articles. Further, selected full-text articles were retrieved, and then, relevant cross-references were scanned to collect further information for the present review.

Correlation of Ferroptosis and Other Types of Cell Death in Neurodegenerative Diseases

Ferroptosis is defined as an iron-dependent, non-apoptotic cell death pathway, with specific morphological phenotypes and biochemical changes. There is a growing realization that ferroptosis has significant implications for several neurodegenerative diseases. Even though ferroptosis is different from other forms of programmed death such as apoptosis and autophagic death, they involve a number of common protein molecules. This review focuses on current research on ferroptosis and summarizes the cross-talk among ferroptosis, apoptosis, and autophagy that are implicated in neurodegenerative diseases. We hope that this information provides new ideas for understanding the mechanisms and searching for potential therapeutic approaches and prevention of neurodegenerative diseases.

NIX Mediates Mitophagy in Spinal Cord Injury in Rats by Interacting with LC3

Excessive mitophagy plays a role in neuronal death in spinal cord injury (SCI), its molecular regulation remains largely unknown. The present study aims to determine the role of NIX, a member of a unique subfamily of death-inducing mitochondrial proteins, in the regulation of mitophagy in SCI. Here we show that NIX is highly upregulated in SCI and hypoxia, and localized to mitochondria. The mitochondria-bound NIX interacts with autophagosome-localized LC3 (Microtubule-associated protein 1 light chain 3) to form a mitochondria-NIX-LC3-autophagosome complex, resulting in excessive mitophagy in SCI. Downregulation of NIX by RNA interference restores the function of mitochondria in spinal cord neurons under hypoxia. Importantly, inhibition of NIX improves recovery of locomotor function in rats after SCI. The present study demonstrates that NIX interacts with LC3 to activate excessive mitophagy in SCI. Inhibition of NIX is therefore likely a neuroprotective strategy.

The cross-talk of autophagy and apoptosis in breast carcinoma: implications for novel therapies?

Breast cancer is still the most common cancer in women worldwide. Resistance to drugs and recurrence of the disease are two leading causes of failure in treatment. For a more efficient treatment of patients, the development of novel therapeutic regimes is needed. Recent studies indicate that modulation of autophagy in concert with apoptosis induction may provide a promising novel strategy in breast cancer treatment. Apoptosis and autophagy are two tightly regulated distinct cellular processes. To maintain tissue homeostasis abnormal cells are disposed largely by means of apoptosis. Autophagy, however, contributes to tissue homeostasis and cell fitness by scavenging of damaged organelles, lipids, proteins, and DNA. Defects in autophagy promote tumorigenesis, whereas upon tumor formation rapidly proliferating cancer cells may rely on autophagy to survive. Given that evasion of apoptosis is one of the characteristic hallmarks of cancer cells, inhibiting autophagy and promoting apoptosis can negatively influence cancer cell survival and increase cell death. Hence, combination of antiautophagic agents with the enhancement of apoptosis may restore apoptosis and provide a therapeutic advantage against breast cancer. In this review, we discuss the cross-talk of autophagy and apoptosis and the diverse facets of autophagy in breast cancer cells leading to novel models for more effective therapeutic strategies.

Bcl-xL is required for the protective effects of low-dose berberine against doxorubicin-induced cardiotoxicity through blocking apoptosis and activating mitophagy-mediated ROS elimination

BACKGROUND

Doxorubicin (DOX)-induced cardiotoxicity is related to abnormal autophagy and apoptosis in the heart. Berberine (BBR) is a well-known natural compound with potential cardioprotective and autophagic modulatory properties.

HYPOTHESIS

We hypothesized that BBR ameliorates DOX-induced cardiotoxicity by balancing cardiomyocyte autophagy and apoptosis.

STUDY DESIGN/METHODS

DOX was used to generate in vivo and in vitro cardiotoxic models. Larval and adult zebrafish and human AC16 cells were used to study (i) the effects of BBR on autophagy and apoptosis upon DOX challenge and (ii) the underlying mechanisms.

RESULTS

BBR protected AC16 cells and zebrafish hearts from DOX-induced cytotoxicity and apoptosis. Bcl-xL knockdown in AC16 cells and zebrafish demonstrated that Bcl-xL is required for BBR's anti-apoptotic activity. DOX treatment promoted Beclin1 binding to Bcl-xL, disrupted mitophagy, and increased ROS accumulation in AC16 cells. In AC16 cells and zebrafish hearts, pretreatment with BBR enhanced mitophagy via dissociation of the Bcl-xL-Beclin1 complex and decreased ROS accumulation. Inhibition of autophagy attenuated this effect of BBR. Intriguingly, BBR increased Bcl-xL binding to Bnip3, sequestration, and mitophagy, indicating that Bcl-xL may play a beneficial role in BBR-induced mitophagy. Additionally, BBR significantly ameliorated DOX-induced cardiac dysfunction in zebrafish, whereas Bcl-xL knockdown abolished this effect. Notably, we discovered that BBR exerts biphasic dose-response effects in response to DOX; the cardioprotective properties were observed upon treatment with low-dose BBR (≤ 1 μM in cells, ≤ 10 μM in zebrafish), but not with relatively high-dose BBR.

CONCLUSION

These findings indicate that the protective effects of low-dose BBR against DOX-induced cardiotoxicity are mediated by Bcl-xL.

Protective Role of miR-34c in Hypoxia by Activating Autophagy through BCL2 Repression

Hypoxia leads to significant cellular stress that has diverse pathological consequences such as cardiovascular diseases and cancers. MicroRNAs (miRNAs) are one of regulators of the adaptive pathway in hypoxia. We identified a hypoxia-induced miRNA, miR-34c, that was significantly upregulated in hypoxic human umbilical cord vein endothelial cells (HUVECs) and in murine blood vessels on day 3 of hindlimb ischemia (HLI). miR-34c directly inhibited BCL2 expression, acting as a toggle switch between apoptosis and autophagy in vitro and in vivo. BCL2 repression by miR-34c activated autophagy, which was evaluated by the expression of LC3-II. Overexpression of miR-34c inhibited apoptosis in HUVEC as well as in a murine model of HLI, and increased cell viability in HUVEC. Importantly, the number of viable cells in the blood vessels following HLI was increased by miR-34c overexpression. Collectively, our findings show that miR-34c plays a protective role in hypoxia, suggesting a novel therapeutic target for hypoxic and ischemic diseases in the blood vessels.

Beth Levine’s Legacy: From the Discovery of BECN1 to Therapies. A Mentees’ Perspective

With great sadness, the scientific community received the news of the loss of Beth Levine on 15 June 2020. Dr. Levine was a pioneer in the autophagy field and work in her lab led not only to a better understanding of the molecular mechanisms regulating the pathway, but also its implications in multiple physiological and pathological conditions, including its role in development, host defense, tumorigenesis, aging or metabolism. This review does not aim to provide a comprehensive view of autophagy, but rather an outline of some of the discoveries made by the group of Beth Levine, from the perspective of some of her own mentees, hoping to honor her legacy in science.

Protective effects of dexmedetomidine in vital organ injury: crucial roles of autophagy

Vital organ injury is one of the leading causes of global deaths. Accumulating studies have demonstrated that dexmedetomidine (DEX) has an outstanding protective effect on multiple organs for its antiinflammatory and antiapoptotic properties, while the underlying molecular mechanism is not clearly understood. Autophagy, an adaptive catabolic process, has been found to play a crucial role in the organ-protective effects of DEX. Herein, we present a first attempt to summarize all the evidence on the proposed roles of autophagy in the action of DEX protecting against vital organ injuries via a comprehensive review. We found that most of the relevant studies (17/24, 71%) demonstrated that the modulation of autophagy was inhibited under the treatment of DEX on vital organ injuries (e.g. brain, heart, kidney, and lung), but several studies suggested that the level of autophagy was dramatically increased after administration of DEX. Albeit not fully elucidated, the underlying mechanisms governing the roles of autophagy involve the antiapoptotic properties, inhibiting inflammatory response, removing damaged mitochondria, and reducing oxidative stress, which might be facilitated by the interaction with multiple associated genes (i.e., hypoxia inducible factor-1α, p62, caspase-3, heat shock 70 kDa protein, and microRNAs) and signaling cascades (i.e., mammalian target of rapamycin, nuclear factor-kappa B, and c-Jun N-terminal kinases pathway). The authors conclude that DEX hints at a promising strategy in the management of vital organ injuries, while autophagy is crucially involved in the protective effect of DEX.

Advances in indole-containing alkaloids as potential anticancer agents by regulating autophagy

Cancer is a leading cause of death worldwide, and cancer development is often associated with disturbances in the autophagy process. Autophagy is a catabolic process involved in many physiological processes, crucial for cell growth and survival. It is an intracellular lysosomal/vacuolar degradation system. In this system, inner cytoplasmic cell membrane is degraded by lysosomal hydrolases, and the products are released back into the cytoplasm. Indole alkaloids are natural products extensively found in nature and have been proven to possess various pharmacological activities. In recent years, pharmacological studies have demonstrated another potential of indole alkaloids, autophagy regulation. The regulation may contribute to the efficacy of indole alkaloids in preventing and treating cancer. This review summarizes the current understanding of indole alkaloids' effect on tumor cells and autophagy. Then, we focus on mechanisms by which indole alkaloids can target the autophagy process associated with cancer, including the PI3K/Akt/mTOR signaling pathway, MAPK signaling pathway, ROS signaling pathway, Beclin-1, and so on. Literature has been surveyed primarily from 2009 to Nov. 2021, and some semisynthetic or fully synthetic indole derivatives are also discussed.

Adenosine A2a Receptor Regulates Autophagy Flux and Apoptosis to Alleviate Ischemia-Reperfusion Injury via the cAMP/PKA Signaling Pathway

Exploring effective methods to lessen myocardial ischemia-reperfusion injury still has positive significance. The adenosine A2a receptor (A2aR) has played a crucial part in cardiac ischemia-reperfusion injury. Previous studies revealed that the adenosine A2a receptor regulated autophagy, but the specific mechanism in myocardial ischemia-reperfusion injury was still unclear. We established an ischemia-reperfusion model (30 min of ischemia and 2 h of reperfusion) in vivo and a model with oxygen-glucose deprivation for 6 h and reoxygenation for 18 h (OGDR) in vitro. The ischemia-reperfusion injury resulted in prolonged QTc interval, left ventricular systolic dysfunction, and myocardial infarction. In vitro model, we found that the OGDR-induced autophagosomes and apoptosis caused myocardial cell death, as evidenced by a significant increase in the generation of lactate dehydrogenase and creatine kinase-MB. Furthermore, overactivated autophagy with rapamycin showed an anti-apoptotic effect. The interaction between autophagy and apoptosis in myocardial ischemia-reperfusion injury was complex and variable. We discovered that the activation of adenosine A2a receptor could promote the expression of Bcl-2 to inhibit the levels of Beclin-1 and LC3II. The number of autophagosomes exceeded that of autolysosomes under OGDR, but the result reversed after A2aR activation. Activated A2aR with its agonist CGS21680 before reperfusion saved cellular survival through anti-apoptosis and anti-autophagy effect, thus improving ventricular contraction disorders, and visibly reducing myocardial infarction size. The myocardial protection of adenosine A2a receptor after ischemia may involve the cAMP-PKA signaling pathway and the interaction of Bcl-2-Beclin-1.

Mcl-1 Differentially Regulates Autophagy in Response to Changes in Energy Status and Mitochondrial Damage

Myeloid cell leukemia-1 (Mcl-1) is a unique antiapoptotic Bcl-2 member that is critical for mitochondrial homeostasis. Recent studies have demonstrated that Mcl-1′s functions extend beyond its traditional role in preventing apoptotic cell death. Specifically, data suggest that Mcl-1 plays a regulatory role in autophagy, an essential degradation pathway involved in recycling and eliminating dysfunctional organelles. Here, we investigated whether Mcl-1 regulates autophagy in the heart. We found that cardiac-specific overexpression of Mcl-1 had little effect on baseline autophagic activity but strongly suppressed starvation-induced autophagy. In contrast, Mcl-1 did not inhibit activation of autophagy during myocardial infarction or mitochondrial depolarization. Instead, overexpression of Mcl-1 increased the clearance of depolarized mitochondria by mitophagy independent of Parkin. The increase in mitophagy was partially mediated via Mcl-1′s LC3-interacting regions and mutation of these sites significantly reduced Mcl-1-mediated mitochondrial clearance. We also found that Mcl-1 interacted with the mitophagy receptor Bnip3 and that the interaction was increased in response to mitochondrial stress. Overall, these findings suggest that Mcl-1 suppresses nonselective autophagy during nutrient limiting conditions, whereas it enhances selective autophagy of dysfunctional mitochondria by functioning as a mitophagy receptor.

All-Trans-Retinoic Acid Combined With Valproic Acid Can Promote Differentiation in Myeloid Leukemia Cells by an Autophagy Dependent Mechanism

Acute myeloid leukemia (AML) is an aggressive blood cancer with an overall survival of 30%. One form of AML, acute promyelocytic leukemia (APL) has become more than 90% curable with differentiation therapy, consisting of all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO). Application of differentiation therapy to other AML subtypes would be a major treatment advance. Recent studies have indicated that autophagy plays a key role in the differentiation of ATRA-responsive APL cells. In this study, we have investigated whether differentiation could be enhanced in ATRA resistant cells by promoting autophagy induction with valproic acid (VPA). ATRA sensitive (NB4) and resistant leukemia cells (NB4R and THP-1) were co-treated with ATRA and valproic acid, followed by assessment of autophagy and differentiation. The combination of VPA and ATRA induced autophagic flux and promoted differentiation in ATRA-sensitive and -resistant cell lines. shRNA knockdown of ATG7 and TFEB autophagy regulators impaired both autophagy and differentiation, demonstrating the importance of autophagy in the combination treatment. These data suggest that ATRA combined with valproic acid can promote differentiation in myeloid leukemia cells by mechanism involving autophagy.

Effects and Mechanism of Ganoderma lucidum Polysaccharides in the Treatment of Diabetic Nephropathy in Streptozotocin-Induced Diabetic Rats

Ganoderma lucidum polysaccharides (GLP) have renal protection effect but there was no study on the diabetic nephropathy. This study was designed to investigate its effect and mechanism using a diabetic rat model induced by streptozotocin (50 mg/kg, i.p.). The diabetic rats were treated with GLP (300 mg/kg/day) for 10 weeks. The blood glucose, glycated hemoglobin, body weight, and the levels of blood creatinine, urea nitrogen, and urine protein were assessed. And renal pathologies were assessed by the tissue sections stained with hematoxylin-eosin, Masson's trichome, and periodic acid-Schiff. The expression of phosphorylated phosphoinositide 3 kinase (p-PI3K), phosphorylated protein kinase B (p-Akt), and phosphorylated mammalian target of rapamycin (p-mTOR), the autophagy proteins beclin-1, LC3-II, LC3-I, and P62; the apoptosis-related proteins caspase-3 and caspase-9; and the inflammation markers IL-6, IL-1β, and TNF-ɑ were assessed. Results showed that GLP alleviated the impairment of renal function by reducing urinary protein excretion and the blood creatinine level and ameliorated diabetic nephropathy. The expression of p-PI3K, p-Akt, and p-mTOR in the diabetic kidney were significantly reduced in the GLP treatment group compared to the without treatment group. GLP treatment activated the autophagy indicators of beclin-1 and the ratio of LC3-II/LC3-I but reduced p62 and also inhibited the expression of caspase-3, caspase-9 and IL-6, IL-1β, and TNF-ɑ. In conclusion, the effect of GLP amelioration diabetic nephropathy may be via the PI3k/Akt/mTOR signaling pathway by inhibition of the apoptosis and inflammation and activation of the autophagy process.

The regulation of neuronal autophagy and cell survival by MCL1 in Alzheimer's disease

Maintaining neuronal integrity and functions requires precise mechanisms controlling organelle and protein quality. Alzheimer's disease (AD) is characterized by functional defects in the clearance and recycling of intracellular components. As such, neuronal homeostasis involves autophagy, mitophagy, and apoptosis. Compromised activity in these cellular processes may cause pathological phenotypes of AD. Dysfunction of mitochondria is one of the hallmarks of AD. Mitophagy is a critical mitochondria quality control system, and the impaired mitophagy is observed in AD. Myeloid cell leukemia 1 (MCL1), a member of the pro-survival B-cell lymphoma protein 2 (BCL2) family, is a mitochondria-targeted protein that contributes to maintaining mitochondrial integrity. Mcl1 knockout mice display peri-implantation lethality. The studies on conditional Mcl1 knockout mice demonstrate that MCL1 plays a central role in neurogenesis and neuronal survival during brain development. Accumulating evidence reveals the critical role of MCL1 as a regulator of neuronal autophagy, mitophagy, and survival. In this review, we discuss the emerging neuroprotective function of MCL1 and how dysregulation of MCL1 signaling is involved in the pathogenesis of AD. As the pro-survival BCL2 family of proteins are promising targets of pharmacological intervention with BH3 mimetic drugs, we also discuss the promise of MCL1-targeting therapy in AD.

Role of Mitochondrial Stress Response in Cancer Progression

Mitochondria are subcellular organelles that are a hub for key biological processes, such as bioenergetic, biosynthetic, and signaling functions. Mitochondria are implicated in all oncogenic processes, from malignant transformation to metastasis and resistance to chemotherapeutics. The harsh tumor environment constantly exposes cancer cells to cytotoxic stressors, such as nutrient starvation, low oxygen, and oxidative stress. Excessive or prolonged exposure to these stressors can cause irreversible mitochondrial damage, leading to cell death. To survive hostile microenvironments that perturb mitochondrial function, cancer cells activate a stress response to maintain mitochondrial protein and genome integrity. This adaptive mechanism, which is closely linked to mitochondrial function, enables rapid adjustment and survival in harsh environmental conditions encountered during tumor dissemination, thereby promoting cancer progression. In this review, we describe how the mitochondria stress response contributes to the acquisition of typical malignant traits and highlight the potential of targeting the mitochondrial stress response as an anti-cancer therapeutic strategy.

Human Respiratory Syncytial Virus NS2 Protein Induces Autophagy by Modulating Beclin1 Protein Stabilization and ISGylation

Paramyxoviruses such as respiratory syncytial virus (RSV) are the leading cause of pneumonia in infants, the elderly, and immunocompromised individuals. Understanding host-virus interactions is essential for the development of effective interventions. RSV induces autophagy to modulate the immune response. The viral factors and mechanisms underlying RSV-induced autophagy are unknown. Here, we identify the RSV nonstructural protein NS2 as the virus component mediating RSV-induced autophagy. We show that NS2 interacts and stabilizes the proautophagy mediator Beclin1 by preventing its degradation by the proteasome. NS2 further impairs interferon-stimulated gene 15 (ISG15)-mediated Beclin1 ISGylation and generates a pool of "hypo-ISGylated" active Beclin1 to engage in functional autophagy. Studies with NS2-deficient RSV revealed that NS2 contributes to RSV-mediated autophagy during infection. The present study is the first report to show direct activation of autophagy by a paramyxovirus nonstructural protein. We also report a new viral mechanism for autophagy induction wherein the viral protein NS2 promotes hypo-ISGylation of Beclin1 to ensure availability of active Beclin1 to engage in the autophagy process. IMPORTANCE Understanding host-virus interactions is essential for the development of effective interventions against respiratory syncytial virus (RSV), a paramyxovirus that is a leading cause of viral pneumonia in infants. RSV induces autophagy following infection, although the viral factors involved in this mechanism are unknown. Here, we identify the RSV nonstructural protein 2 (NS2) as the virus component involved in autophagy induction. NS2 promotes autophagy by interaction with and stabilization of the proautophagy mediator Beclin1 and by impairing its ISGylation to overcome autophagy inhibition. To the best of our knowledge, this is the first report of a viral protein regulating the autophagy pathway by modulating ISGylation of autophagy mediators. Our studies highlight a direct role of a paramyxovirus nonstructural protein in activating autophagy by interacting with the autophagy mediator Beclin1. NS2-mediated regulation of the autophagy and ISGylation processes is a novel function of viral nonstructural proteins to control the host response against RSV.

Macamide B Pretreatment Attenuates Neonatal Hypoxic-Ischemic Brain Damage of Mice Induced Apoptosis and Regulates Autophagy via the PI3K/AKT Signaling Pathway

Lepidium meyenii (maca) is an annual or biennial herb from South America that is a member of the genus Lepidium L. in the family Cruciferae. This herb possesses antioxidant and antiapoptotic activities, enhances autophagy functions, prevents cell death, and protects neurons from ischemic damage. Macamide B, an effective active ingredient of maca, exerts a neuroprotective effect on neonatal hypoxic-ischemic brain damage (HIBD), but the mechanism underlying its neuroprotective effect is not yet known. The purpose of this study was to explore the effect of macamide B on HIBD-induced autophagy and apoptosis and its potential neuroprotective mechanism. The modified Rice-Vannucci method was used to induce HIBD in 7-day-old (P7) macamide B- and vehicle-pretreated pups. TTC staining was performed to evaluate the cerebral infarct volume in pups, the brain water content was measured to evaluate the neurological function of pups, neurobehavioural testing was conducted to assess functional recovery after HIBD, TUNEL and FJC staining was performed to detect cellular autophagy and apoptosis, and Western blot analysis was used to detect the levels of proteins in the pro-survival phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) signaling pathway and autophagy and apoptosis-related proteins. Macamide B pretreatment significantly decreases brain damage and improves the recovery of neural function after HIBD. At the same time, macamide B pretreatment activates the PI3K/AKT signaling pathway after HIBD, enhances autophagy, and reduces hypoxic-ischemic (HI)-induced apoptosis. In addition, 3-methyladenine (3-MA), an inhibitor of the PI3K/AKT signaling pathway, significantly inhibits the increase in autophagy levels, aggravates HI-induced apoptosis, and reverses the neuroprotective effect of macamide B on HIBD. Our data indicate that a macamide B pretreatment might regulate autophagy through the PI3K/AKT signaling pathway, thereby reducing HIBD-induced apoptosis and exerting neuroprotective effects on neonatal HIBD. Macamide B may become a new drug for the prevention and treatment of HIBD.

Identification of Small Molecules Inhibiting Cardiomyocyte Necrosis and Apoptosis by Autophagy Induction and Metabolism Reprogramming

Improvement of anticancer treatments is associated with increased survival of cancer patients at risk of cardiac disease. Therefore, there is an urgent need for new therapeutic molecules capable of preventing acute and long-term cardiotoxicity. Here, using commercial and home-made chemolibraries, we performed a robust phenotypic high-throughput screening in rat cardiomyoblast cell line H9c2, searching for small molecules capable of inhibiting cell death. A screen of 1600 compounds identified six molecules effective in preventing necrosis and apoptosis induced by H₂O₂ and camptothecin in H9c2 cells and in rat neonatal ventricular myocytes. In cells treated with these molecules, we systematically evaluated the expression of BCL-2 family members, autophagy progression, mitochondrial network structure, regulation of mitochondrial fusion/fission, reactive oxygen species, and ATP production. We found that these compounds affect autophagy induction to prevent cardiac cell death and can be promising cardioprotective drugs during chemotherapy.

The complex interplay between autophagy and cell death pathways

Autophagy is a universal cellular homeostatic process, required for the clearance of dysfunctional macromolecules or organelles. This self-digestion mechanism modulates cell survival, either directly by targeting cell death players, or indirectly by maintaining cellular balance and bioenergetics. Nevertheless, under acute or accumulated stress, autophagy can also contribute to promote different modes of cell death, either through highly regulated signalling events, or in a more uncontrolled inflammatory manner. Conversely, apoptotic or necroptotic factors have also been implicated in the regulation of autophagy, while specific factors regulate both processes. Here, we survey both earlier and recent findings, highlighting the intricate interaction of autophagic and cell death pathways. We, Furthermore, discuss paradigms, where this cross-talk is disrupted, in the context of disease.

Polyphyllin D induces apoptosis and protective autophagy in breast cancer cells through JNK1-Bcl-2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Polyphyllin D (PD), an active component from rhizome of Paris polyphylla Sm, root and rhizome, shows a strong anti-cancer activity in several cancers. However, whether autophagy is involved in PD-induced cell death in breast cancer cells and its molecular mechanism has not yet been elucidated.

AIM OF THE STUDY

To explore the anti-tumor effects of PD in breast cancer and the underlying mechanisms.

MATERIALS AND METHODS

PD was isolated from P. polyphylla Sm and confirmed by HPLC and NMR. The role of PD in cell viability, apoptosis, autophagy in breast cancer cells were determined.

RESULTS

PD shows significant anti-tumor activity by inhibit cell proliferation and induce caspase-dependent apoptosis in breast cancer cells. Moreover, PD treatment could induce autophagy by activation of JNK1/Bcl-2 pathway. Importantly, blocking of autophagy by using autophagy inhibitor 3-methyladenine (3-MA) dramatically increase PD-induced apoptosis as evidence by the increased percentage of apoptotic cell death. The anti-tumor effects of PD also investigated in vivo. The results showed that the combinatory treatment of PD with autophagy inhibitor significantly promote PD-induced apoptosis.

CONCLUSION

PD could induce caspase-dependent apoptosis and cyto-protectvie autophagy by activation of JNK1/Bcl-2 pathway in breast cancer cells. Combination with an autophagy inhibitor significantly enhance cytotoxic effect of PD and this combination may be a promising candidate for breast cancer therapy.

Scalp Acupuncture Attenuates Brain Damage After Intracerebral Hemorrhage Through Enhanced Mitophagy and Reduced Apoptosis in Rats

To study the effect of scalp acupuncture (SA) on the mitophagy signaling pathway in the caudate nucleus of Sprague-Dawley rats following intracerebral hemorrhage (ICH). An ICH model was established by injecting autologous arterial blood into the caudate nucleus in 200 male Sprague-Dawley rats, which were divided into five groups: sham, ICH, 3-methyladenine group (3-MA, 30 mg/kg), SA, and SA+3-MA. Animals were analyzed at 6 and 24 h as well as at 3 and 7 days. Composite neurological scale score was significantly higher in the SA group than in the ICH group. Transmission electron microscopy showed less structural damage and more autophagic vacuoles within brain in the SA group than in the ICH group. SA group showed higher levels of Beclin1, Parkin, PINK1, NIX protein, and a lower level of Caspase-9 in brain tissue. These animals consequently showed less neural cell apoptosis. Compared with the SA group, however, the neural function score and levels of mitophagy protein in the SA+3-MA group were decreased, neural cell apoptosis was increased with more severe structural damage, which suggested that 3-MA may antagonize the protective effect of SA on brain in rats with ICH. SA may mitigate the neurologic impairment after ICH by enhancing mitophagy and reducing apoptosis.

Mechanistic Insight on Autophagy Modulated Molecular Pathways in Cerebral Ischemic Injury: From Preclinical to Clinical Perspective

Cerebral ischemia is one of the most devastating brain injuries and a primary cause of acquired and persistent disability worldwide. Despite ongoing therapeutic interventions at both the experimental and clinical levels, options for stroke-related brain injury are still limited. Several evidence suggests that autophagy is triggered in response to cerebral ischemia, therefore targeting autophagy-related signaling pathways can provide a new direction for the therapeutic implications in the ischemic injury. Autophagy is a highly conserved lysosomal-dependent pathway that degrades and recycles damaged or non-essential cellular components to maintain neuronal homeostasis. But, whether autophagy activation promotes cell survival against ischemic injury or, on the contrary, causes neuronal death is still under debate. We performed an extensive literature search from PubMed, Bentham and Elsevier for various aspects related to molecular mechanisms and pathobiology involved in autophagy and several pre-clinical studies justifiable further in the clinical trials. Autophagy modulates various downstream molecular cascades, i.e., mTOR, NF-κB, HIF-1, PPAR-γ, MAPK, UPR, and ROS pathways in cerebral ischemic injury. In this review, the various approaches and their implementation in the translational research in ischemic injury into practices has been covered. It will assist researchers in finding a way to cross the unbridgeable chasm between the pre-clinical and clinical studies.

A Balance Between Autophagy and Other Cell Death Modalities in Cancer

Autophagy is an intracellular self-digestive process involved in catabolic degradation of damaged proteins, and organelles, and the elimination of cellular pathogens. Initially, autophagy was considered as a prosurvival mechanism, but the following insights shed light on its prodeath function. Nowadays, autophagy is established as a crucial player in the development of various diseases through interaction with other molecular pathways within a cell. Additionally, disturbance in autophagy is one of the main pathological alterations that lead to resistance of cancer cells to treatment. These autophagy-related pathologies gave rise to the development of new therapeutic drugs. Here, we summarize the current knowledge on the autophagic role in disease pathogenesis, particularly in cancer, and the interplay between autophagy and other cell death modalities in order to combat cancer.

Cellular Senescence and Regulated Cell Death of Tubular Epithelial Cells in Diabetic Kidney Disease

Cellular senescence is frequently evident at etiologic sites of chronic diseases and involves essentially irreversible arrest of cell proliferation, increased protein production, resistance to apoptosis, and altered metabolic activity. Regulated cell death plays a vital role in shaping fully functional organs during the developmental process, coordinating adaptive or non-adaptive responses, and coping with long-term harmful intracellular or extracellular homeostasis disturbances. In recent years, the concept of 'diabetic tubulopathy' has emerged. tubular epithelial cells are particularly susceptible to the derangements of diabetic state because of the virtue of the high energy requirements and reliance on aerobic metabolism render. Hyperglycemia, oxidative stress, persistent chronic inflammation, glucose toxicity, advanced glycation end-products (AGEs) accumulation, lipid metabolism disorders, and lipotoxicity contribute to the cellular senescence and different patterns of regulated cell death (apoptosis, autophagic cell death, necroptosis, pyroptosis, and ferroptosis) in tubular epithelial cells. We now explore the 'tubulocentric' view of diabetic kidney disease(DKD). And we summarize recent discoveries regarding the development and regulatory mechanisms of cellular senescence, apoptosis, autophagic cell death, necroptosis, pyroptosis, and ferroptosis in the pathogenesis of DKD. These findings provide new perspectives on the mechanisms of DKD and are useful for designing novel therapeutic approaches for the treatment of DKD.

Molecular Mechanisms and Regulation of Mammalian Mitophagy

Mitochondria in the cell are the center for energy production, essential biomolecule synthesis, and cell fate determination. Moreover, the mitochondrial functional versatility enables cells to adapt to the changes in cellular environment and various stresses. In the process of discharging its cellular duties, mitochondria face multiple types of challenges, such as oxidative stress, protein-related challenges (import, folding, and degradation) and mitochondrial DNA damage. They mitigate all these challenges with robust quality control mechanisms which include antioxidant defenses, proteostasis systems (chaperones and proteases) and mitochondrial biogenesis. Failure of these quality control mechanisms leaves mitochondria as terminally damaged, which then have to be promptly cleared from the cells before they become a threat to cell survival. Such damaged mitochondria are degraded by a selective form of autophagy called mitophagy. Rigorous research in the field has identified multiple types of mitophagy processes based on targeting signals on damaged or superfluous mitochondria. In this review, we provide an in-depth overview of mammalian mitophagy and its importance in human health and diseases. We also attempted to highlight the future area of investigation in the field of mitophagy.

BNIP3L/NIX-mediated mitophagy: molecular mechanisms and implications for human disease

Mitophagy is a highly conserved cellular process that maintains the mitochondrial quantity by eliminating dysfunctional or superfluous mitochondria through autophagy machinery. The mitochondrial outer membrane protein BNIP3L/Nix serves as a mitophagy receptor by recognizing autophagosomes. BNIP3L is initially known to clear the mitochondria during the development of reticulocytes. Recent studies indicated it also engages in a variety of physiological and pathological processes. In this review, we provide an overview of how BNIP3L induces mitophagy and discuss the biological functions of BNIP3L and its regulation at the molecular level. We further discuss current evidence indicating the involvement of BNIP3L-mediated mitophagy in human disease, particularly in cancer and neurological disorders.

The Cross Talk Between p53 and mTOR Pathways in Response to Physiological and Genotoxic Stresses

The tumor suppressor p53 is activated upon multiple cellular stresses, including DNA damage, oncogene activation, ribosomal stress, and hypoxia, to induce cell cycle arrest, apoptosis, and senescence. Mammalian target of rapamycin (mTOR), an evolutionarily conserved serine/threonine protein kinase, serves as a central regulator of cell growth, proliferation, and survival by coordinating nutrients, energy, growth factors, and oxygen levels. p53 dysfunction and mTOR pathway hyperactivation are hallmarks of human cancer. The balance between response to stresses or commitment to cell proliferation and survival is governed by various regulatory loops between the p53 and mTOR pathways. In this review, we first briefly introduce the tumor suppressor p53 and then describe the upstream regulators and downstream effectors of the mTOR pathway. Next, we discuss the role of p53 in regulating the mTOR pathway through its transcriptional and non-transcriptional effects. We further describe the complicated role of the mTOR pathway in modulating p53 activity. Finally, we discuss the current knowledge and future perspectives on the coordinated regulation of the p53 and mTOR pathways.

Autophagy in Alzheimer's disease pathogenesis: Therapeutic potential and future perspectives

Alzheimer's disease (AD) is a complex neurodegenerative disease in the elderly and the most common cause of human dementia. AD is characterized by accumulation of abnormal protein aggregates including amyloid plaques (composed of beta-amyloid (Aβ) peptides) and neurofibrillary tangles (formed by hyper-phosphorylated tau protein). Synaptic plasticity, neuroinflammation, calcium signaling etc. also show dysfunction in AD patients. Autophagy is an evolutionarily conserved lysosome-dependent cellular event in eukaryotes. It is closely linked to modulation of protein metabolism, through which damaged organelles and mis-folded proteins are degraded and then recycled to maintain protein homeostasis. Accumulating evidence has shown that impaired autophagy also contributes to AD pathogenesis. In the present review, we highlight the role of autophagy, including bulk and selective autophagy, in regulating metabolic circuits in AD pathogenesis. We also discuss the potential and future perspectives of autophagy-inducing strategies in AD therapeutics.

Hepatitis B virus X Protein Promotes Liver Cancer Progression through Autophagy Induction in Response to TLR4 Stimulation

Hepatitis B virus X (HBx) protein has been reported as a key protein regulating the pathogenesis of HBV-induced hepatocellular carcinoma (HCC). Recent evidence has shown that HBx is implicated in the activation of autophagy in hepatic cells. Nevertheless, the precise molecular and cellular mechanism by which HBx induces autophagy is still controversial. Herein, we investigated the molecular and cellular mechanism by which HBx is involved in the TRAF6-BECN1-Bcl-2 signaling for the regulation of autophagy in response to TLR4 stimulation, therefore influencing the HCC progression. HBx interacts with BECN1 (Beclin 1) and inhibits the association of the BECN1-Bcl-2 complex, which is known to prevent the assembly of the pre-autophagosomal structure. Furthermore, HBx enhances the interaction between VPS34 and TRAF6-BECN1 complex, increases the ubiquitination of BECN1, and subsequently enhances autophagy induction in response to LPS stimulation. To verify the functional role of HBx in liver cancer progression, we utilized different HCC cell lines, HepG2, SK-Hep-1, and SNU-761. HBx-expressing HepG2 cells exhibited enhanced cell migration, invasion, and cell mobility in response to LPS stimulation compared to those of control HepG2 cells. These results were consistently observed in HBx-expressed SK-Hep-1 and HBx-expressed SNU-761 cells. Taken together, our findings suggest that HBx positively regulates the induction of autophagy through the inhibition of the BECN1-Bcl-2 complex and enhancement of the TRAF6-BECN1-VPS34 complex, leading to enhance liver cancer migration and invasion.

Regulation of mitochondrial cargo-selective autophagy by posttranslational modifications

Mitochondria are important organelles in eukaryotes. Turnover and quality control of mitochondria are regulated at the transcriptional and posttranslational level by several cellular mechanisms. Removal of defective mitochondrial proteins is mediated by mitochondria resident proteases or by proteasomal degradation of individual proteins. Clearance of bulk mitochondria occurs via a selective form of autophagy termed mitophagy. In yeast and some developing metazoan cells (e.g., oocytes and reticulocytes), mitochondria are largely removed by ubiquitin-independent mechanisms. In such cases, the regulation of mitophagy is mediated via phosphorylation of mitochondria-anchored autophagy receptors. On the other hand, ubiquitin-dependent recruitment of cytosolic autophagy receptors occurs in situations of cellular stress or disease, where dysfunctional mitochondria would cause oxidative damage. In mammalian cells, a well-studied ubiquitin-dependent mitophagy pathway induced by mitochondrial depolarization is regulated by the mitochondrial protein kinase PINK1, which upon activation recruits the ubiquitin ligase parkin. Here, we review mechanisms of mitophagy with an emphasis on posttranslational modifications that regulate various mitophagy pathways. We describe the autophagy components involved with particular emphasis on posttranslational modifications. We detail the phosphorylations mediated by PINK1 and parkin-mediated ubiquitylations of mitochondrial proteins that can be modulated by deubiquitylating enzymes. We also discuss the role of accessory factors regulating mitochondrial fission/fusion and the interplay with pro- and antiapoptotic Bcl-2 family members. Comprehensive knowledge of the processes of mitophagy is essential for the understanding of vital mitochondrial turnover in health and disease.

Sanguinarine impairs lysosomal function and induces ROS-dependent mitophagy and apoptosis in human hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common tumor types globally. Despite the progress made in surgical procedures and therapeutic options, HCC remains a considerable cause of cancer-related mortality. In this study, we investigated the antitumor effects of sanguinarine (Sang) on HCC and its potential mechanisms. Our findings showed that Sang impairs the acidic environment of lysosomes by inhibiting cathepsin D maturation. In addition, Sang inhibited the formation of autolysosomes in RFP-GFP-LC3 transfected cells, subsequently suppressing late mitophagy. Sang also induced reactive oxygen species (ROS)-dependent autophagy and apoptosis in HCC cells, which was significantly attenuated following treatment with a ROS scavenger. Further investigation using autophagy inhibitors revealed that sanguinarine-induced mitochondrial dysfunction and mitophagy led to mitochondrial apoptosis in HCC cells. Immunohistochemical staining of sanguinarine-treated xenograft samples revealed that it initiated and blocked autophagy. In summary, our findings suggest that in HCC cells, Sang impairs lysosomal function and induces ROS-dependent mitophagy and apoptosis.

Marek's disease virus prolongs survival of primary chicken B-cells by inducing a senescence-like phenotype

Marek’s disease virus (MDV) is an alphaherpesvirus that causes immunosuppression and deadly lymphoma in chickens. Lymphoid organs play a central role in MDV infection in animals. B-cells in the bursa of Fabricius facilitate high levels of MDV replication and contribute to dissemination at early stages of infection. Several studies investigated host responses in bursal tissue of MDV-infected chickens; however, the cellular responses specifically in bursal B-cells has never been investigated. We took advantage of our recently established in vitro infection system to decipher the cellular responses of bursal B-cells to infection with a very virulent MDV strain. Here, we demonstrate that MDV infection extends the survival of bursal B-cells in culture. Microarray analyses revealed that most cytokine/cytokine-receptor-, cell cycle- and apoptosis-associated genes are significantly down-regulated in these cells. Further functional assays validated these strong effects of MDV infections on cell cycle progression and thus, B-cell proliferation. In addition, we confirmed that MDV infections protect B-cells from apoptosis and trigger an accumulation of the autophagy marker Lc3-II. Taken together, our data indicate that MDV-infected bursal B-cells show hallmarks of a senescence-like phenotype, leading to a prolonged B-cell survival. This study provides an in-depth analysis of bursal B-cell responses to MDV infection and important insights into how the virus extends the survival of these cells.

Upon MDV entry via the respiratory tract, B-cells are among the first cells to be infected in the lung and allow an efficient amplification of the virus. B-cells ensure the transmission of the virus to activated T-cells in which it replicates and ultimately transforms CD4-positive T-cells. Although playing a pivotal role in the MDV life cycle, the response of B-cells to MDV is currently not fully understood. Here, by using an in vitro infection model of primary bursal B-cells, we show that MDV infection leads to a prolonged B-cell survival resulting from decreased cell proliferation, protection from apoptosis and activation of autophagy. Our study provides new insights into the B-cell response to MDV infection, demonstrating that MDV triggers a senescence-like phenotype in B-cells that could potentiate their role in MDV pathogenesis.

Emerging role of BAD and DAD1 as potential targets and biomarkers in cancer

As key regulators of apoptosis, BAD and defender against apoptotic cell death 1 (DAD1) are associated with cancer initiation and progression. Multiple studies have demonstrated that BAD and DAD1 serve critical roles in several types of cancer and perform various functions, such as participating in cellular apoptosis, invasion and chemosensitivity, as well as their role in diagnostic/prognostic judgement, etc. Investigating the detailed mechanisms of the cancerous effects of the two proteins will contribute to enriching the options for targeted therapy, and may improve clinical treatment of cancer. The present review summarizes research advances regarding the associations of BAD and DAD1 with cancer, and a hypothesis on the feasible relationship and interaction mechanism between the two proteins is proposed. Furthermore, the present review highlights the potential of the two proteins as therapeutic targets and valuable diagnostic and prognostic biomarkers.

B Cell Lymphoma 2: A Potential Therapeutic Target for Cancer Therapy

Defects in the apoptosis mechanism stimulate cancer cell growth and survival. B cell lymphoma 2 (Bcl-2) is an anti-apoptotic molecule that plays a central role in apoptosis. Bcl-2 is the founding constituent of the Bcl-2 protein family of apoptosis controllers, the primary apoptosis regulators linked with cancer. Bcl-2 has been identified as being over-expressed in several cancers. Bcl-2 is induced by protein kinases and several signaling molecules which stimulate cancer development. Identifying the important function played by Bcl-2 in cancer progression and development, and treatment made it a target related to therapy for multiple cancers. Among the various strategies that have been proposed to block Bcl-2, BH3-mimetics have appeared as a novel group of compounds thanks to their favorable effects on many cancers within several clinical settings. Because of the fundamental function of Bcl-2 in the regulation of apoptosis, the Bcl-2 protein is a potent target for the development of novel anti-tumor treatments. Bcl-2 inhibitors have been used against several cancers and provide a pre-clinical platform for testing novel therapeutic drugs. Clinical trials of multiple investigational agents targeting Bcl-2 are ongoing. This review discusses the role of Bcl-2 in cancer development; it could be exploited as a potential target for developing novel therapeutic strategies to combat various types of cancers. We further highlight the therapeutic activity of Bcl-2 inhibitors and their implications for the therapeutic management of cancer.

BH3 Mimetics in Hematologic Malignancies

Hematologic malignancies (HM) comprise diverse cancers of lymphoid and myeloid origin, including lymphomas (approx. 40%), chronic lymphocytic leukemia (CLL, approx. 15%), multiple myeloma (MM, approx. 15%), acute myeloid leukemia (AML, approx. 10%), and many other diseases. Despite considerable improvement in treatment options and survival parameters in the new millennium, many patients with HM still develop chemotherapy-refractory diseases and require re-treatment. Because frontline therapies for the majority of HM (except for CLL) are still largely based on classical cytostatics, the relapses are often associated with defects in DNA damage response (DDR) pathways and anti-apoptotic blocks exemplified, respectively, by mutations or deletion of the TP53 tumor suppressor, and overexpression of anti-apoptotic proteins of the B-cell lymphoma 2 (BCL2) family. BCL2 homology 3 (BH3) mimetics represent a novel class of pro-apoptotic anti-cancer agents with a unique mode of action—direct targeting of mitochondria independently of TP53 gene aberrations. Consequently, BH3 mimetics can effectively eliminate even non-dividing malignant cells with adverse molecular cytogenetic alterations. Venetoclax, the nanomolar inhibitor of BCL2 anti-apoptotic protein has been approved for the therapy of CLL and AML. Numerous venetoclax-based combinatorial treatment regimens, next-generation BCL2 inhibitors, and myeloid cell leukemia 1 (MCL1) protein inhibitors, which are another class of BH3 mimetics with promising preclinical results, are currently being tested in several clinical trials in patients with diverse HM. These pivotal trials will soon answer critical questions and concerns about these innovative agents regarding not only their anti-tumor efficacy but also potential side effects, recommended dosages, and the optimal length of therapy as well as identification of reliable biomarkers of sensitivity or resistance. Effective harnessing of the full therapeutic potential of BH3 mimetics is a critical mission as it may directly translate into better management of the aggressive forms of HM and could lead to significantly improved survival parameters and quality of life in patients with urgent medical needs.

Ceramide Regulates Anti-Tumor Mechanisms of Erianin in Androgen-Sensitive and Castration-Resistant Prostate Cancers

Prostate cancer is the second most prevalent malignancy worldwide. In the early stages, the development of prostate cancer is dependent on androgens. Over time with androgen deprivation therapy, 20% of prostate cancers progress to a castration-resistant form. Novel treatments for prostate cancers are still urgently needed. Erianin is a plant-derived bibenzyl compound. We report herein that erianin exhibits anti-tumor effects in androgen-sensitive and castration-resistant prostate cancer cells through different mechanisms. Erianin induces endoplasmic reticulum stress-associated apoptosis in androgen-sensitive prostate cancer cells. It also triggers pro-survival autophagic responses, as inhibition of autophagy predisposes to apoptosis. In contrast, erianin fails to induce apoptosis in castration-resistant prostate cancer cells. Instead, it results in cell cycle arrest at the M phase. Mechanistically, C16 ceramide dictates differential responses of androgen-sensitive and castration-resistant prostate cancer cells to erianin. Erianin elevates C16 ceramide level in androgen-sensitive but not castration-resistant prostate cancer cells. Overexpression of ceramide synthase 5 that specifically produces C16 ceramide enables erianin to induce apoptosis in castration-resistant prostate cancer cells. Our study provides both experimental evidence and mechanistic data showing that erianin is a potential treatment option for prostate cancers.

The multiple mechanisms of MCL1 in the regulation of cell fate

MCL1 (myeloid cell leukemia-1) is a widely recognized pro-survival member of the Bcl-2 (B-cell lymphoma protein 2) family and a promising target for cancer therapy. While the role MCL1 plays in apoptosis is well defined, its participation in emerging non-apoptotic signaling pathways is only beginning to be appreciated. Here, we synthesize studies characterizing MCL1s influence on cell proliferation, DNA damage response, autophagy, calcium handling, and mitochondrial quality control to highlight the broader scope that MCL1 plays in cellular homeostasis regulation. Throughout this review, we discuss which pathways are likely to be impacted by emerging MCL1 inhibitors, as well as highlight non-cancerous disease states that could deploy Bcl-2 homology 3 (BH3)-mimetics in the future.

In this review Widden and Placzek synthesize studies characterizing the influence that myeloid cell leukemia-1 (MCL1) has on cell proliferation, DNA damage response, autophagy, calcium handling, and mitochondrial quality control to highlight the broader scope that it plays in cellular homeostasis regulation. They discuss which pathways are likely to be impacted by emerging MCL1 inhibitors, as well as highlight non-cancerous disease states that could deploy BH3-mimetics in the future.

Phytochemicals: Targeting Mitophagy to Treat Metabolic Disorders

Metabolic disorders include metabolic syndrome, obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease and cardiovascular diseases. Due to unhealthy lifestyles such as high-calorie diet, sedentary and physical inactivity, the prevalence of metabolic disorders poses a huge challenge to global human health, which is the leading cause of global human death. Mitochondrion is the major site of adenosine triphosphate synthesis, fatty acid β-oxidation and ROS production. Accumulating evidence suggests that mitochondrial dysfunction-related oxidative stress and inflammation is involved in the development of metabolic disorders. Mitophagy, a catabolic process, selectively degrades damaged or superfluous mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial function. It is considered to be one of the major mechanisms responsible for mitochondrial quality control. Growing evidence shows that mitophagy can prevent and treat metabolic disorders through suppressing mitochondrial dysfunction-induced oxidative stress and inflammation. In the past decade, in order to expand the range of pharmaceutical options, more and more phytochemicals have been proven to have therapeutic effects on metabolic disorders. Many of these phytochemicals have been proved to activate mitophagy to ameliorate metabolic disorders. Given the ongoing epidemic of metabolic disorders, it is of great significance to explore the contribution and underlying mechanisms of mitophagy in metabolic disorders, and to understand the effects and molecular mechanisms of phytochemicals on the treatment of metabolic disorders. Here, we investigate the mechanism of mitochondrial dysfunction in metabolic disorders and discuss the potential of targeting mitophagy with phytochemicals for the treatment of metabolic disorders, with a view to providing a direction for finding phytochemicals that target mitophagy to prevent or treat metabolic disorders.

The Mechanism and Effect of Autophagy, Apoptosis, and Pyroptosis on the Progression of Silicosis

Silicosis remains one of the most severe pulmonary fibrotic diseases worldwide, caused by chronic exposure to silica dust. In this review, we have proposed that programmed cell death (PCD), including autophagy, apoptosis, and pyroptosis, is closely associated with silicosis progression. Furthermore, some autophagy, apoptosis, or pyroptosis-related signaling pathways or regulatory proteins have also been summarized to contribute greatly to the formation and development of silicosis. In addition, silicosis pathogenesis depends on the crosstalk among these three ways of PCD to a certain extent. In summary, more profound research on these mechanisms and effects may be expected to become promising targets for intervention or therapeutic methods of silicosis in the future.

Characterization of the effects of heat stress on autophagy induction in the pig oocyte

BACKGROUND

Heat stress (HS) occurs when body heat accumulation exceeds heat dissipation and is associated with swine seasonal infertility. HS contributes to compromised oocyte integrity and reduced embryo development. Autophagy is a potential mechanism for the oocyte to mitigate the detrimental effects of HS by recycling damaged cellular components.

METHODS

To characterize the effect of HS on autophagy in oocyte maturation, we utilized an in vitro maturation (IVM) system where oocytes underwent thermal neutral (TN) conditions throughout the entire maturation period (TN/TN), HS conditions during the first half of IVM (HS/TN), or HS conditions during the second half of IVM (TN/HS).

RESULTS

To determine the effect of HS on autophagy induction within the oocyte, we compared the relative abundance and localization of autophagy-related proteins. Heat stress treatment affected the abundance of two well described markers of autophagy induction: autophagy related gene 12 (ATG12) in complex with ATG5 and the cleaved form of microtubule-associated protein 1 light chain 3 beta (LC3B-II). The HS/TN IVM treatment increased the abundance of the ATG12-ATG5 complex and exacerbated the loss of LC3B-II in oocytes. The B-cell lymphoma 2 like 1 protein (BCL2L1) can inhibit autophagy or apoptosis through its interaction with either beclin1 (BECN1) or BCL2 associated X, apoptosis regulator (BAX), respectively. We detected colocalization of BCL2L1 with BAX but not BCL2L1 with BECN1, suggesting that apoptosis is inhibited under the HS/TN treatment but not autophagy. Interestingly, low doses of the autophagy inducer, rapamycin, increased oocyte maturation.

CONCLUSIONS

Our results here suggest that HS increases autophagy induction in the oocyte during IVM, and that artificial induction of autophagy increases the maturation rate of oocytes during IVM. These data support autophagy as a potential mechanism activated in the oocyte during HS to recycle damaged cellular components and maintain developmental competence.

PKD2/polycystin-2 induces autophagy by forming a complex with BECN1

Macroautophagy/autophagy is an intracellular process involved in the breakdown of macromolecules and organelles. Recent studies have shown that PKD2/PC2/TRPP2 (polycystin 2, transient receptor potential cation channel), a nonselective cation channel permeable to Ca2+ that belongs to the family of transient receptor potential channels, is required for autophagy in multiple cell types by a mechanism that remains unclear. Here, we report that PKD2 forms a protein complex with BECN1 (beclin 1), a key protein required for the formation of autophagic vacuoles, by acting as a scaffold that interacts with several co-modulators via its coiled-coil domain (CCD). Our data identified a physical and functional interaction between PKD2 and BECN1, which depends on one out of two CCD domains (CC1), located in the carboxy-terminal tail of PKD2. In addition, depletion of intracellular Ca2+ with BAPTA-AM not only blunted starvation-induced autophagy but also disrupted the PKD2-BECN1 complex. Consistently, PKD2 overexpression triggered autophagy by increasing its interaction with BECN1, while overexpression of PKD2D509V, a Ca2+ channel activity-deficient mutant, did not induce autophagy and manifested diminished interaction with BECN1. Our findings show that the PKD2-BECN1 complex is required for the induction of autophagy, and its formation depends on the presence of the CC1 domain of PKD2 and on intracellular Ca2+ mobilization by PKD2. These results provide new insights regarding the molecular mechanisms by which PKD2 controls autophagy.Abbreviations: ADPKD: autosomal dominant polycystic kidney disease; ATG: autophagy-related; ATG14/ATG14L: autophagy related 14; Baf A1: bafilomycin A1; BCL2/Bcl-2: BCL2 apoptosis regulator; BCL2L1/BCL-XL: BCL2 like 1; BECN1: beclin 1; CCD: coiled-coil domain; EBSS: Earle's balanced salt solution; ER: endoplasmic reticulum; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; GOLGA2/GM130: golgin A2; GST: glutathione s-transferase; LAMP1: lysosomal associated membrane protein 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTORC1: mechanistic target of rapamycin kinase complex 1; NBR1: NBR1 autophagy cargo receptor; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PKD2/PC2: polycystin 2, transient receptor potential cation channel; RTN4/NOGO: reticulon 4; RUBCN/RUBICON: rubicon autophagy regulator; SQSTM1/p62: sequestosome 1; UVRAG: UV radiation resistance associated; WIPI2: WD repeat domain, phosphoinositide interacting 2.

Pyoluteorin Induces Apoptosis and Autophagy in NSCLC Cells

Pyoluteorin is a natural occurring antibiotic and its anti-tumor activity has rarely been reported. This study aims to investigate the anti-tumor effects of pyoluteorin on human non-small cell lung cancer (NSCLC) cells. The cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was determined through caspase3 activity assay and immunoblotting. Autophagy was measured by transmission electron microscope (TEM) and immunostaining. The autophagy-related proteins were detected through immunoblotting. We found that pyoluteorin showed significant anti-tumor effects on human NSCLC cell lines H1299 (IC₅₀ = 1.57 µM) and H2030 (IC₅₀ = 1.94 µM). Moreover, pyoluteorin could induce apoptosis and autophagy as evidence by the upregulation of caspase3 activity, the accumulation of LC3 and expression of apoptosis or autophagy related proteins. In addition, pyoluteorin induced autophagy through c-Jun N-terminal kinase/B-cell lymphoma-2 (JNK/Bcl-2) signal pathway. Blocking JNK/Bcl-2 pathway significantly attenuated pyoluteorin-induced autophagy. Moreover, inhibition of autophagy by 3-methyladenine (3-MA) or Beclin1 knockout greatly promoted pyoluteorin-induced apoptosis and cell death. Our results showed that pyoluteorin could induce both apoptosis and autophagy in human NSCLC cells. Combination of pyoluteorin with autophagy inhibitior significantly promoted pyoluteorin-induced apoptosis and may be a potential anticancer strategy in the NSCLC therapy.

Apoptosis, Autophagy, Necrosis and Their Multi Galore Crosstalk in Neurodegeneration

The progression of neurodegenerative disorders is mainly characterized by immense neuron loss and death of glial cells. The mechanisms which are active and regulate neuronal cell death are namely necrosis, necroptosis, autophagy and apoptosis. These death paradigms are governed by a set of molecular determinants that are pivotal in their performance and also exhibit remarkable overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the switching of death paradigms in various neurodegenerative diseases. In this review, we discuss various molecules and the concurrent crosstalk mediated by them. According to our present knowledge and research in neurodegeneration, molecules like Atg1, Beclin1, LC3, p53, TRB3, RIPK1 play switching roles toggling from one death mechanism to another. In addition, the review also focuses on the exorbitant number of newer molecules with the potential to cross communicate between death pathways and create a complex cell death scenario. This review highlights recent studies on the inter-dependent regulation of cell death paradigms in neurodegeneration, mediated by cross-communication between pathways. This will help in identifying potential targets for therapeutic intervention in neurodegenerative diseases.

GEFT Inhibits Autophagy and Apoptosis in Rhabdomyosarcoma via Activation of the Rac1/Cdc42-mTOR Signaling Pathway

Autophagy and apoptosis are dynamic processes that determine the fate of cells, and regulating these processes can treat cancer. GEFT is highly expressed in rhabdomyosarcoma (RMS), which accelerates the tumorigenicity and metastasis of RMS by activating Rac1/Cdc42 signaling, but the regulatory mechanisms of autophagy and apoptosis are unclear. In our study, we found that the RMS tissues had high Rac1, Cdc42, mTOR, and Bcl-2 expression levels and low Beclin1, LC3, and Bax expression levels compared with the normal striated muscle tissues (P < 0.05). In addition, multivariate analysis has proven that Rac1 is an independent prognostic factor (P < 0.05), and the high expression level of the Beclin1 protein was closely associated with the tumor diameter of the RMS patients (P = 0.044), whereas the high expression level of the LC3 protein was associated with the clinical stage of the RMS patients (P = 0.027). Furthermore, GEFT overexpression could inhibit autophagy and apoptosis in RMS. A Rac1/Cdc42 inhibitor was added, and the inhibition of autophagy and apoptosis decreased. Rac1 and Cdc42 could regulate mTOR to inhibit autophagy and apoptosis in RMS. Overall, these studies demonstrated that the GEFT–Rac1/Cdc42–mTOR pathway can inhibit autophagy and apoptosis in RMS and provide evidence for innovative treatments.