Membrane vesicle delivery of a streptococcal M protein disrupts the blood-brain barrier by inducing autophagic endothelial cell death.

M family proteins are critical virulence determinants of Streptococci. Streptococcus equi subsp. zooepidemicus (SEZ) are Group C streptococci that cause meningitis in animals and humans. SzM, the M protein of SEZ, has been linked to SEZ brain invasion. Here, we demonstrate that SzM is important in SEZ disruption of the blood-brain barrier (BBB). SEZ release SzM-bound membrane vesicles (MVs), and endocytosis of these vesicles by human brain endothelial microvascular cells (hBMECs) results in SzM-dependent cytotoxicity. Furthermore, administration of SzM-bound MVs disrupted the murine BBB. A CRISPR screen revealed that SzM cytotoxicity in hBMECs depends on PTEN-related activation of autophagic cell death. Pharmacologic inhibition of PTEN activity prevented SEZ disruption of the murine BBB and delayed mortality. Our data show that MV delivery of SzM to host cells plays a key role in SEZ pathogenicity and suggests that MV delivery of streptococcal M family proteins is likely a common streptococcal virulence mechanism.

Autophagy Promotes Cell Death Induced by Hydrogen Peroxide in Physcomitrium patens.

The autophagy-defective mutants (atg5 and atg7) of Physcomitrium patens exhibit strong desiccation tolerance. Here, we examined the effects of H2O2 on wild-type (WT) and autophagy-defective mutants of P. patens, considering that desiccation induces reactive oxygen species (ROS). We found that atg mutants can survive a 30-min treatment with 100 mM H2O2, whereas WT cannot, implying that autophagy promotes cell death induced by H2O2. Concomitant with cell death, vacuole collapse occurred. Intracellular H2O2 levels in both WT and atg5 increased immediately after H2O2 treatment and subsequently reached plateaus, which were higher in WT than in atg5. The ROS scavenger N-acetylcysteine lowered the plateau levels in WT and blocked cell death, suggesting that higher H2O2 plateau caused cell death. The uncoupler of electron transport chain (ETC) carbonyl cyanide m-chlorophenylhydrazone also lowered the H2O2 plateaus, showing that ROS produced in the ETC in mitochondria and/or chloroplasts elevated the H2O2 plateau. The autophagy inhibitor 3-methyladenine lowered the H2O2 plateau and the cell death rate in WT, suggesting that autophagy occurring after H2O2 treatment is involved in the production of ROS. Conversely, the addition of bovine serum albumin, which is endocytosed and supplies amino acids instead of autophagy, elevated the H2O2 plateau in atg5 cells, suggesting that amino acids produced through autophagy promote H2O2 generation. These results clearly show that autophagy causes cell death under certain stress conditions. We propose that autophagy-derived amino acids are catabolized using ETCs in mitochondria and/or chloroplasts and produce H2O2, which in turn promotes the cell death accompanying vacuole collapse.

Piperine induces autophagy of colon cancer cells: Dual modulation of AKT/mTOR signaling pathway and ROS production.

BACKGROUND: Colorectal cancer (CRC) is a prevalent malignancy and poses a significant clinical challenge. Piperine, an alkaloid molecule extracted from Piper nigrum and Piper longum, has emerged as a promising anticancer agent. However, the molecular mechanisms of piperine' antitumor effects in CRC need to be further elucidated. METHODS: Human colorectal cancer cells were treated with piperine in vitro. CCK-8 and clone formation assays were adopted to detect cell viability. The accumulation of autophagosomes was assessed by Western blotting and immunofluorescence. Apoptosis and reactive oxygen species (ROS) levels were analyzed by flow. In vivo, a xenograft tumor mouse model was constructed using CT26 cells. RESULTS: Piperine inhibited CRC cell viability and suppressed tumor weight and volume in a mouse model. Additionally, piperine treatment induced the accumulation of autophagosomes in CRC cells. This effect was attributed to the inhibition of the AKT/mTOR pathway and the accumulation of ROS. activation of AKT or clearance of ROS attenuated piperine-mediated tumor suppression. CONCLUSION: This study shows that piperine induces autophagy-dependent cell death in CRC cells by increasing ROS production and inhibiting Akt/mTOR signaling.

Mechanisms of Alveolar Type 2 Epithelial Cell Death During Acute Lung Injury.

Diffuse alveolar epithelial cell (AEC) death occurs extensively during acute lung injury (ALI). Due to the limited proliferative capacity of alveolar type 1 epithelial (AT1) cells, the differentiation and regenerative capacity of alveolar type 2 epithelial (AT2) cells are required to restore the barrier function of AECs. However, during lung injury, AT1 cells are particularly susceptible to injury, and ATII cells die in the presence of severe or certain types of injury. This disruption ultimately results in a hindrance to the ability of AT2 cells to proliferate and differentiate into AT1 cells in time to repair the extensively damaged AECs. Therefore, understanding the mechanism of injury death of AT2 cells may be beneficial to reverse the above situation. This article reviews the main death modes of AT2 cells, including apoptosis, necrosis, necroptosis, pyroptosis, autophagic cell death, and ferroptosis. It compares the various forms of death, showing that various cell injury death modes have unique action mechanisms and partially overlapping pathways. Studying the mechanism of AT2 cell death is helpful in screening and analyzing the target pathway of AEC barrier function recovery. It opens up new ideas and strategies for preventing and treating ALI.

Combination of betulinic acid and EGFR-TKIs exerts synergistic anti-tumor effects against wild-type EGFR NSCLC by inducing autophagy-related cell death via EGFR signaling pathway.

BACKGROUND: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of lung cancer patients with mutated EGFR. However, the efficacy of EGFR-TKIs in wild-type EGFR tumors has been shown to be marginal. Methods that can sensitize EGFR-TKIs to EGFR wild-type NSCLC remain rare. Hence, we determined whether combination treatment can maximize the therapeutic efficacy of EGFR-TKIs. METHODS: We established a focused drug screening system to investigate candidates for overcoming the intrinsic resistance of wild-type EGFR NSCLC to EGFR-TKIs. Molecular docking assays and western blotting were used to identify the binding mode and blocking effect of the candidate compounds. Proliferation assays, analyses of drug interactions, colony formation assays, flow cytometry and nude mice xenograft models were used to determine the effects and investigate the molecular mechanism of the combination treatment. RESULTS: Betulinic acid (BA) is effective at targeting EGFR and synergizes with EGFR-TKIs (gefitinib and osimertinib) preferentially against wild-type EGFR. BA showed inhibitory activity due to its interaction with the ATP-binding pocket of EGFR and dramatically enhanced the suppressive effects of EGFR-TKIs by blocking EGFR and modulating the EGFR-ATK-mTOR axis. Mechanistic studies revealed that the combination strategy activated EGFR-induced autophagic cell death and that the EGFR-AKT-mTOR signaling pathway was essential for completing autophagy and cell cycle arrest. Activation of the mTOR pathway or blockade of autophagy by specific chemical agents markedly attenuated the effect of cell cycle arrest. In vivo administration of the combination treatment caused marked tumor regression in the A549 xenografts. CONCLUSIONS: BA is a potential wild-type EGFR inhibitor that plays a critical role in sensitizing EGFR-TKI activity. BA combined with an EGFR-TKI effectively suppressed the proliferation and survival of intrinsically resistant lung cancer cells via the inhibition of EGFR as well as the induction of autophagy-related cell death, indicating that BA combined with an EGFR-TKI may be a potential therapeutic strategy for overcoming the primary resistance of wild-type EGFR-positive lung cancers.

The misregulation of mitochondria-associated genes caused by GAGA-factor lack promotes autophagic germ cell death in Drosophila testes.

The Drosophila GAGA-factor encoded by the Trithorax-like (Trl) gene is DNA-binding protein with unusually wide range of applications in diverse cell contexts. In Drosophila spermatogenesis, reduced GAGA expression caused by Trl mutations induces mass autophagy leading to germ cell death. In this work, we investigated the contribution of mitochondrial abnormalities to autophagic germ cell death in Trl gene mutants. Using a cytological approach, in combination with an analysis of high-throughput RNA sequencing (RNA-seq) data, we demonstrated that the GAGA deficiency led to considerable defects in mitochondrial ultrastructure, by causing misregulation of GAGA target genes encoding essential components of mitochondrial molecular machinery. Mitochondrial anomalies induced excessive production of reactive oxygen species and their release into the cytoplasm, thereby provoking oxidative stress. Changes in transcription levels of some GAGA-independent genes in the Trl mutants indicated that testis cells experience ATP deficiency and metabolic aberrations, that may trigger extensive autophagy progressing to cell death.

Spatiotemporal roles of AMPK in PARP-1- and autophagy-dependent retinal pigment epithelial cell death caused by UVA.

BACKGROUND: Although stimulating autophagy caused by UV has been widely demonstrated in skin cells to exert cell protection, it remains unknown the cellular events in UVA-treated retinal pigment epithelial (RPE) cells. METHODS: Human ARPE-19 cells were used to measure cell viability, mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP), mitochondrial mass and lysosomal mass by flow cytometry. Mitochondrial oxygen consumption rate (OCR) was recorded using Seahorse XF flux analyzer. Confocal microscopic images were performed to indicate the mitochondrial dynamics, LC3 level, and AMPK translocation after UVA irradiation. RESULTS: We confirmed mitochondrial ROS production and DNA damage are two major features caused by UVA. We found the cell death is prevented by autophagy inhibitor 3-methyladenine and gene silencing of ATG5, and UVA induces ROS-dependent LC3II expression, LC3 punctate and TFEB expression, suggesting the autophagic death in the UVA-stressed RPE cells. Although PARP-1 inhibitor olaparib increases DNA damage, ROS production, and cell death, it also blocks AMPK activation caused by UVA. Interestingly we found a dramatic nuclear export of AMPK upon UVA irradiation which is blocked by N-acetylcysteine and olaparib. In addition, UVA exposure gradually decreases lysosomal mass and inhibits cathepsin B activity at late phase due to lysosomal dysfunction. Nevertheless, cathepsin B inhibitor, CA-074Me, reverses the death extent, suggesting the contribution of cathepsin B in the death pathway. When examining the role of EGFR in cellular events caused by UVA, we found that UVA can rapidly transactivate EGFR, and treatment with EGFR TKIs (gefitinib and afatinib) enhances the cell death accompanied by the increased LC3II formation, ROS production, loss of MMP and mass of mitochondria and lysosomes. Although AMPK activation by ROS-PARP-1 mediates autophagic cell death, we surprisingly found that pretreatment of cells with AMPK activators (A769662 and metformin) reverses cell death. Concomitantly, both agents block UVA-induced mitochondrial ROS production, autophagic flux, and mitochondrial fission without changing the inhibition of cathepsin B. CONCLUSION: UVA exposure rapidly induces ROS-PARP-1-AMPK-autophagic flux and late lysosomal dysfunction. Pre-inducing AMPK activation can prevent cellular events caused by UVA and provide a new protective strategy in photo-oxidative stress and photo-retinopathy.

Pomiferin targets SERCA, mTOR, and P-gp to induce autophagic cell death in apoptosis-resistant cancer cells, and reverses the MDR phenotype in cisplatin-resistant tumors in vivo.

Drug resistance in cancer has been classified as innate resistance or acquired resistance, which were characterized by apoptotic defects and ABC transporters overexpression respectively. Therefore, to preclude or reverse these resistance mechanisms could be a promising strategy to improve chemotherapeutic outcomes. In this study, a natural product from Osage Orange, pomiferin, was identified as a novel autophagy activator that circumvents innate resistance by triggering autophagic cell death via SERCA inhibition and activation of the CaMKKß-AMPK-mTOR signaling cascade. In addition, pomiferin also directly inhibited the P-gp (MDR1/ABCB1) efflux and reversed acquired resistance by potentiating the accumulation and efficacy of the chemotherapeutic agent, cisplatin. In vivo study demonstrated that pomiferin triggered calcium-mediated tumor suppression and exhibited an anti-metastatic effect in the LLC-1 lung cancer-bearing mouse model. Moreover, as an adjuvant, pomiferin potentiated the anti-tumor effect of the chemotherapeutic agent, cisplatin, in RM-1 drug-resistant prostate cancer-bearing mouse model by specially attenuating ABCB1-mediated drug efflux, but not ABCC5, thereby promoting the accumulation of cisplatin in tumors. Collectively, pomiferin may serve as a novel effective agent for circumventing drug resistance in clinical applications.

Hernandezine induces autophagic cell death in human pancreatic cancer cells via activation of the ROS/AMPK signaling pathway.

Hernandezine (Her) is a bisbenzylisoquinoline alkaloid extracted from the traditional Chinese herbal medicine Thalictrum glandulosissimum. Evidence shows that Her is a natural agonist of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and induces apoptosis and autophagy in tumor cells. In this study, we investigated the role of autophagy in Her-induced cell death in human pancreatic cancer cell lines. We showed that Her dose-dependently suppressed cell proliferation, promoted autophagy and induced autophagic death in pancreatic ductal adenocarcinoma (PDAC) cell lines Capan-1 and SW1990. The IC50 values of Her in inhibition of Capan-1 and SW1990 cells were 47.7 µM and 40.1 µM, respectively. Immunoblotting showed that Her (1-40 µM) promoted the conversion of LC3-I to LC3-II, and Her exerted concentration-dependent and time-dependent effects on autophagy activation in PDAC cells. In transmission electron microscopy and fluorescence image analysis, we found that autophagic vacuoles were significantly increased in Her-treated cells. Knockdown of ATG5, a key gene in the autophagy pathway, alleviated the activation of autophagy by Her. These results demonstrated that Her induced autophagy in PDAC cells. Intensely activated autophagy could promote cell death. The autophagy inhibitors, BafA1 and HCQ significantly inhibited Her-induced cell death, implying that Her induced autophagic cell death in PDAC cells. Moreover, we showed that Her activated autophagy by increasing the phosphorylation of AMPK and decreasing the phosphorylation of mTOR/p70S6K. Knockdown of AMPKα relieves the autophagic cell death induced by Her. Furthermore, Her concentration-dependently enhanced reactive oxygen species (ROS) generation in PDAC cells. Antioxidants could reduce the phosphorylation of AMPK and suppress autophagic cell death induced by Her. Our study provides evidence for the development of Her as a therapeutic agent for the treatment of pancreatic cancer.

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.

Polystyrene microplastic particles induce autophagic cell death in BEAS-2B human bronchial epithelial cells.

The detection of high levels of microplastics in indoor and outdoor air has increased concerns regarding its toxic effects on the respiratory system. They are not easily degradable and can be deposited deep in the lungs. Although several studies have reported inhalation toxicities of microplastics, they are still controversial due to a lack of evidence. Herein, we evaluated the inhalation toxicities of three differently charged polystyrene microplastics (PS-MPs), the most abundant microplastics in the air. Cytotoxicity and ROS generation were evaluated using WST-1 and DCF-DA assays, respectively. To evaluate the toxic effects on the lung, inflammatory responses were analyzed after repeated exposure to the PS-MPs through intratracheal instillation. To explore the mechanism of toxicity, autophagy and ER stress-associated proteins were analyzed. Only the positively charged PS-MPs (NH2 -PS-MPs) showed cytotoxicity and increased ROS generation in BEAS-2B cells. Similarly, only NH2 -PS-MPs significantly increased the expression and secretion of the pro-inflammatory cytokine IL-ß in the animal experiments. The expression of ER stress proteins indicated that NH2 -PS-MPs increased ER stress via PERK-EIF2α and ATF4-CHOP pathways. Moreover, accumulation of NH2 -PS-MPs in lysosomes and deformity of the nucleus were observed in BEAS-2B cells with autophagy induction. Taken together, our results demonstrated that NH2 -PS-MPs induced autophagic cell death in bronchial epithelial cells, leading to inflammatory responses in the lungs. These results suggest that repeated inhalation of microplastics can result in inflammatory responses in the lung through cellular damage of lung epithelial cells, and that inhalation microplastics should be monitored to reduce inhalation health risks.

Distinct Signaling Pathways for Autophagy-Driven Cell Death and Survival in Adult Hippocampal Neural Stem Cells.

Autophagy is a cellular catabolic process that degrades and recycles cellular materials. Autophagy is considered to be beneficial to the cell and organism by preventing the accumulation of toxic protein aggregates, removing damaged organelles, and providing bioenergetic substrates that are necessary for survival. However, autophagy can also cause cell death depending on cellular contexts. Yet, little is known about the signaling pathways that differentially regulate the opposite outcomes of autophagy. We have previously reported that insulin withdrawal (IW) or corticosterone (CORT) induces autophagic cell death (ACD) in adult hippocampal neural stem (HCN) cells. On the other hand, metabolic stresses caused by 2-deoxy-D-glucose (2DG) and glucose-low (GL) induce autophagy without death in HCN cells. Rather, we found that 2DG-induced autophagy was cytoprotective. By comparing IW and CORT conditions with 2DG treatment, we revealed that ERK and JNK are involved with 2DG-induced protective autophagy, whereas GSK-3ß regulates death-inducing autophagy. These data suggest that cell death and survival-promoting autophagy undergo differential regulation with distinct signaling pathways in HCN cells.

Mechanisms of cancer cell death induction by paclitaxel: an updated review.

Chemoresistance of cancer cells is a major problem in treating cancer. Knowledge of how cancer cells may die or resist cancer drugs is critical to providing certain strategies to overcome tumour resistance to treatment. Paclitaxel is known as a chemotherapy drug that can suppress the proliferation of cancer cells by inducing cell cycle arrest and induction of mitotic catastrophe. However, today, it is well known that paclitaxel can induce multiple kinds of cell death in cancers. Besides the induction of mitotic catastrophe that occurs during mitosis, paclitaxel has been shown to induce the expression of several pro-apoptosis mediators. It also can modulate the activity of anti-apoptosis mediators. However, certain cell-killing mechanisms such as senescence and autophagy can increase resistance to paclitaxel. This review focuses on the mechanisms of cell death, including apoptosis, mitotic catastrophe, senescence, autophagic cell death, pyroptosis, etc., following paclitaxel treatment. In addition, mechanisms of resistance to cell death due to exposure to paclitaxel and the use of combinations to overcome drug resistance will be discussed.

F-box protein FBXO41 plays vital role in arsenic trioxide-mediated autophagic death of cancer cells.

Arsenic trioxide (ATO), a potent anti-neoplastic drug, is known to prevent cancer cell growth through induction of autophagic cell death. However, importance of cellular factors in ATO-mediated autophagic cell death is poorly understood. In this study, using biochemical and immunofluorescence techniques, we show that F-box protein FBXO41 plays a critical role in anti-proliferative activity of ATO. Our study reveals the importance of FBXO41 in induction of autophagic death of cancer cells by ATO. Further, we show that the autophagic cell death induced by FBXO41 is distinct and independent of apoptosis and necrosis, showing that FBXO41 may play vital role in inducing autophagic death of apoptosis resistant cancer cells. Overall, our study elucidates the importance of FBXO41 in ATO induced autophagic cell death to prevent cancer progression, which could be explored to develop promising cancer therapeutic strategy.

Targeting regulated cell death in aortic aneurysm and dissection therapy.

Regulated cell death (RCD) is a basic biological phenomenon associated with cell and tissue homeostasis. Recent studies have enriched our understanding of RCD, and many novel cell death types, such as ferroptosis and pyroptosis, have been discovered and defined. Aortic aneurysm and dissection (AAD) is a life-threatening condition, but the pathogenesis remains largely unclear. A series of studies have indicated that the death of smooth muscle cells, endothelial cells and inflammatory cells participates in the development of AAD and that corresponding interventions could alleviate disease progression. Many treatments against cell death have been used to impede the process of AAD in vitro and in vivo, which provides strategies to protect against this condition. In this review, we focus on various types of regulated cell death and provide a framework of their roles in AAD, and the information contributes to further exploration of the molecular mechanisms of AAD.

Overexpression of TRIM32 promotes pancreatic ß-cell autophagic cell death through Akt/mTOR pathway under high glucose conditions.

Type 2 diabetes mellitus (T2DM) is a growing worldwide epidemic and is characterized by progressive pancreatic ß-cell dysfunction and insulin resistance. Tripartite motif protein 32 (TRIM32) belongs to the TRIM family protein and has been shown to be involve in insulin resistance in skeletal muscle and the liver. However, the effect of TRIM32 on pancreatic ß-cell dysfunction and its mechanism remains unknown. In the current study, we found that serum TRIM32 concentrations of T2DM in patients were significantly elevated compared to those in healthy controls, which indicated that TRIM32 might be used as a diagnostic biomarker in T2DM patients. In INS-1 cells, exposure to high glucose (HG) conditions caused a significant elevation in TRIM32 expression and TRIM32 was located in the nucleus. Overexpression of TRIM32 in INS-1 cells exacerbated the effects of HG-induced autophagy and impaired insulin secretion. In contrast, the silencing of TRIM32 produced the opposite effect. Furthermore, TRIM32 overexpression decreased the phosphorylation levels of Akt and mTOR under HG conditions. However, the activation of Akt/mTOR by MHY1485 reversed the effects of TRIM32 on HG-treated INS-1 cells. Collectively, the present results suggested that TRIM32 participates in the development of T2DM by modulating autophagic cell death and insulin secretion, which might occur through the Akt/mTOR pathway. Thus, TRIM32 might be a promising target in T2DM therapy.

ACT001 inhibits pituitary tumor growth by inducing autophagic cell death via MEK4/MAPK pathway.

ACT001, derived from traditional herbal medicine, is a novel compound with effective anticancer activity in clinical trials. However, little is known regarding its role in pituitary adenomas. Here, we demonstrated that ACT001 suppressed cell proliferation and induced cell death of pituitary tumor cells in vitro and in vivo. ACT001 was also effective in suppressing the growth of different subtypes of human pituitary adenomas. The cytotoxic mechanism ACT001 employed was mainly related to autophagic cell death (ACD), indicated by autophagosome formation and LC3-II accumulation. In addition, ACT001-mediated inhibitory effect decreased when either ATG7 was downregulated or cells were cotreated with autophagy inhibitor 3-methyladenine (3-MA). RNA-seq analysis showed that mitogen-activated protein kinase (MAPK) pathway was a putative target of ACT001. Specifically, ACT001 treatment promoted the phosphorylation of JNK and P38 by binding to mitogen-activated protein kinase kinase 4 (MEK4). Our study indicated that ACT001-induced ACD of pituitary tumor cells via activating JNK and P38 phosphorylation by binding with MEK4, and it might be a novel and effective anticancer drug for pituitary adenomas.

The lysosome as an imperative regulator of autophagy and cell death.

Lysosomes are single membrane-bound organelles containing acid hydrolases responsible for the degradation of cellular cargo and maintenance of cellular homeostasis. Lysosomes could originate from pre-existing endolysosomes or autolysosomes, acting as a critical juncture between autophagy and endocytosis. Stress that triggers lysosomal membrane permeabilization can be altered by ESCRT complexes; however, irreparable damage to the membrane results in the induction of a selective lysosomal degradation pathway, specifically lysophagy. Lysosomes play an indispensable role in different types of autophagy, including microautophagy, macroautophagy, and chaperone-mediated autophagy, and various cell death pathways such as lysosomal cell death, apoptotic cell death, and autophagic cell death. In this review, we discuss lysosomal reformation, maintenance, and degradation pathways following the involvement of the lysosome in autophagy and cell death, which are related to several pathophysiological conditions observed in humans.

Apoptosis, autophagic cell death, and necroptosis: different types of programmed cell death in bovine corpus luteum regression.

In mammals, the corpus luteum (CL) is a transient organ that secretes progesterone (P4). In the absence of pregnancy, the CL undergoes regression (luteolysis), which is a crucial preparation step for the next estrous cycle. Luteolysis, initiated by uterine prostaglandin F2α (PGF) in cattle, is usually divided into two phases, namely functional luteolysis characterized by a decline in P4 concentration and structural luteolysis characterized by the elimination of luteal tissues from the ovary. Programmed cell death (PCD) of luteal cells, including luteal steroidogenic cells (LSCs) and luteal endothelial cells (LECs), plays a crucial role in structural luteolysis. The main types of PCD are caspase-dependent apoptosis (type 1), autophagic cell death (ACD) via the autophagy-related gene (ATG) family (type 2), and receptor-interacting protein kinase (RIPK)-dependent programmed necrosis (necroptosis, type 3). However, these PCD signaling pathways are not completely independent and interact with each other. Over the past several decades, most studies on luteolysis have focused on apoptosis as the principal mode of bovine luteal cell death. Recently, ATG family members were reported to be expressed in bovine CL, and their levels increased during luteolysis. Furthermore, the expression of RIPKs, which are crucial mediators of necroptosis, is reported to increase in bovine CL during luteolysis and is upregulated by pro-inflammatory cytokines in bovine LSCs and LECs. Therefore, apoptosis, ACD, and necroptosis may contribute to bovine CL regression. In this article, we present the recent findings regarding the mechanisms of the three main types of PCD and the contribution of these mechanisms to luteolysis.

ATG7-dependent and independent autophagy determine the type of treatment in lung cancer.

Based on the role of ATG7 in the initiation of autophagy, autophagy can be divided into ATG7-dependent selective autophagy and ATG7-independent alternative autophagy. However, the detailed roles of two different types of autophagy in antitumor therapy have not been fully elucidated so far. Here, we for the first time demonstrated an investigational inducer, w09, could induce both selective autophagy and alternative autophagy in NSCLC, but the phenotypes of these two kinds of autophagy are different：(1) w09-induced selective autophagy mainly promoted cell apoptosis, while w09-triggered alternative autophagy markedly induced autophagic cell death in NSCLC；(2) w09-induced ATG7 dependent autophagy mainly promoted the accumulation of SQSTM1/p62, while w09-triggered ATG7 independent autophagy markedly accelerated the degradation of SQSTM1/p62. These above results were further confirmed by knockout ATG7 gene in A549 cells or restoration of ATG7 function in H1650 cells. Deletion of ATG7 gene markedly attenuated the effect of w09-induced autophagy or apoptosis on A549 cells, while restoration of functional ATG7 markedly enhanced the effect of w09-induced autophagy and apoptosis on H1650 cells. Mechanistically, we further revealed that w09 induced two different types of autophagy through inhibiting PI3K/AKT/mTOR signaling pathway. Notably, compared with A549WT xenograft model, the in vivo antitumor effect of w09 or Taxel on the ATG7-deficient A549 xenograft model was significantly attenuated. Therefore, a special attention must be paid to distinguish which kinds of autophagy have been induced by autophagy inducers with antitumor agents by targeting PI3K/AKT/mTOR signaling pathway.