Life and Death Decisions-The Many Faces of Autophagy in Cell Survival and Cell Death

The Many Faces of Autophagy: Balancing Survival and Cell Death

Autophagy and apoptosis are two fundamental biological mechanisms that may cooperate or be antagonistic, and both are involved in deciding the fate of cells in physiological or pathological conditions [...].

ONC206 targeting ClpP induces mitochondrial dysfunction and protective autophagy in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common form of liver cancer, accounting for approximately 90 % of all cases. ONC201, a member of the imipridone drug family, has shown promising therapeutic potential and a good safety profile in both malignant pediatric central nervous system tumors (diffuse midline glioma [DMG]) and hematologic malignancies. ONC206 is a more potent analog of ONC201. However, the ONC206 potential and mechanism of action in HCC remain to be elucidated. We found that ONC206 hindered HCC growth by suppressing cell proliferation and inducing apoptosis. Moreover, ONC206 induced cytoprotective autophagy, and blocking autophagy enhanced the proapoptotic effect of ONC206. Additionally, ONC206 induced mitochondrial swelling, reduced the mitochondrial membrane potential (MMP), and led to the accumulation of mitochondrial ROS in HCC cells, ultimately resulting in mitochondrial dysfunction. The HCC patient samples exhibited notably elevated levels of caseinolytic protease proteolytic subunit (ClpP), which serves as a mediator of ONC206-induced mitochondrial dysfunction and the activation of protective autophagy. knockdown of ClpP reversed the cytotoxic effects of ONC206 on HCC cells. In summary, our results provide the first insight into the mechanism by which ONC206 exerts its anti-HCC effects and induces protective autophagy in HCC cells through ClpP.

Anticancer Activity of Delta-Tocotrienol in Human Hepatocarcinoma: Involvement of Autophagy Induction

(1) Hepatocellular carcinoma (HCC) is the predominant form of primary liver cancer. Surgical resection, tumor ablation, and liver transplantation are curative treatments indicated for early-stage HCC. The management of intermediate and advanced stages of pathology is based on the use of systemic therapies which often show important side effects. Vitamin E-derivative tocotrienols (TTs) play antitumoral properties in different tumors. Here, we analyzed the activity of delta-TT (δ-TT) on HCC human cell lines. (2) We analyzed the ability of δ-TT to trigger apoptosis, to induce oxidative stress, autophagy, and mitophagy in HepG2 cell line. We evaluated the correlation between the activation of autophagy with the ability of δ-TT to induce cell death. (3) The data obtained demonstrate that δ-TT exerts an antiproliferative and proapoptotic effect in HCC cells. Furthermore, δ-TT induces the release of mitochondrial ROS and causes a structural and functional alteration of the mitochondria compatible with a fission process. Finally, δ-TT triggers selective autophagy process removing dysfunctional mitochondria. Inhibition of autophagy reversed the cytotoxic action of δ-TT. (4) Our results demonstrate that δ-TT through the activation of autophagy could represent a potential new approach in the treatment of advanced HCC.

The Multifaceted Interactions of Dictyostelium Atg1 with Mitochondrial Function, Endocytosis, Growth, and Development

Autophagy is a degradative recycling process central to the maintenance of homeostasis in all eukaryotes. By ensuring the degradation of damaged mitochondria, it plays a key role in maintaining mitochondrial health and function. Of the highly conserved autophagy proteins, autophagy-related protein 1 (Atg1) is essential to the process. The involvement of these proteins in intracellular signalling pathways, including those involving mitochondrial function, are still being elucidated. Here the role of Atg1 was investigated in the simple model organism Dictyostelium discoideum using an atg1 null mutant and mutants overexpressing or antisense-inhibiting atg1. When evaluated against the well-characterised outcomes of mitochondrial dysfunction in this model, altered atg1 expression resulted in an unconventional set of phenotypic outcomes in growth, endocytosis, multicellular development, and mitochondrial homeostasis. The findings here show that Atg1 is involved in a tightly regulated signal transduction pathway coordinating energy-consuming processes such as cell growth and multicellular development, along with nutrient status and energy production. Furthermore, Atg1's effects on energy homeostasis indicate a peripheral ancillary role in the mitochondrial signalling network, with effects on energy balance rather than direct effects on electron transport chain function. Further research is required to tease out these complex networks. Nevertheless, this study adds further evidence to the theory that autophagy and mitochondrial signalling are not opposing but rather linked, yet strictly controlled, homeostatic mechanisms.

Biosensors; a novel concept in real-time detection of autophagy

Autophagy is an early-stage response with self-degradation properties against several insulting conditions. To date, the critical role of autophagy has been well-documented in physiological and pathological conditions. This process involves various signaling and functional biomolecules, which are involved in different steps of the autophagic response. During recent decades, a range of biochemical analyses, chemical assays, and varied imaging techniques have been used for monitoring this pathway. Due to the complexity and dynamic aspects of autophagy, the application of the conventional methodology for following autophagic progression is frequently associated with a mistake in discrimination between a complete and incomplete autophagic response. Biosensors provide a de novo platform for precise and accurate analysis of target molecules in different biological settings. It has been suggested that these devices are applicable for real-time monitoring and highly sensitive detection of autophagy effectors. In this review article, we focus on cutting-edge biosensing technologies associated with autophagy detection.

Endoplasmic reticulum stress and quality control in relation to cisplatin resistance in tumor cells

The endoplasmic reticulum (ER) is a crucial organelle that orchestrates key cellular functions like protein folding and lipid biosynthesis. However, it is highly sensitive to disturbances that lead to ER stress. In response, the unfolded protein response (UPR) activates to restore ER homeostasis, primarily through three sensors: IRE1, ATF6, and PERK. ERAD and autophagy are crucial in mitigating ER stress, yet their dysregulation can lead to the accumulation of misfolded proteins. Cisplatin, a commonly used chemotherapy drug, induces ER stress in tumor cells, activating complex signaling pathways. Resistance to cisplatin stems from reduced drug accumulation, activation of DNA repair, and anti-apoptotic mechanisms. Notably, cisplatin-induced ER stress can dualistically affect tumor cells, promoting either survival or apoptosis, depending on the context. ERAD is crucial for degrading misfolded proteins, whereas autophagy can protect cells from apoptosis or enhance ER stress-induced apoptosis. The complex interaction between ER stress, cisplatin resistance, ERAD, and autophagy opens new avenues for cancer treatment. Understanding these processes could lead to innovative strategies that overcome chemoresistance, potentially improving outcomes of cisplatin-based cancer treatments. This comprehensive review provides a multifaceted perspective on the complex mechanisms of ER stress, cisplatin resistance, and their implications in cancer therapy.

Computational Design of Novel Cyclic Peptides Endowed with Autophagy-Inhibiting Activity on Cancer Cell Lines

(1) Autophagy plays a significant role in development and cell proliferation. This process is mainly accomplished by the LC3 protein, which, after maturation, builds the nascent autophagosomes. The inhibition of LC3 maturation results in the interference of autophagy activation. (2) In this study, starting from the structure of a known LC3B binder (LIR2-RavZ peptide), we identified new LC3B ligands by applying an in silico drug design strategy. The most promising peptides were synthesized, biophysically assayed, and biologically evaluated to ascertain their potential antiproliferative activity on five humans cell lines. (3) A cyclic peptide (named Pep6), endowed with high conformational stability (due to the presence of a disulfide bridge), displayed a Kd value on LC3B in the nanomolar range. Assays accomplished on PC3, MCF-7, and A549 cancer cell lines proved that Pep6 exhibited cytotoxic effects comparable to those of the peptide LIR2-RavZ, a reference LC3B ligand. Furthermore, it was ineffective on both normal prostatic epithelium PNT2 and autophagy-defective prostate cancer DU145 cells. (4) Pep6 can be considered a new autophagy inhibitor that can be employed as a pharmacological tool or even as a template for the rational design of new small molecules endowed with autophagy inhibitory activity.

Unveiling the mechanisms and challenges of cancer drug resistance

Cancer treatment faces many hurdles and resistance is one among them. Anti-cancer treatment strategies are evolving due to innate and acquired resistance capacity, governed by genetic, epigenetic, proteomic, metabolic, or microenvironmental cues that ultimately enable selected cancer cells to survive and progress under unfavorable conditions. Although the mechanism of drug resistance is being widely studied to generate new target-based drugs with better potency than existing ones. However, due to the broader flexibility in acquired drug resistance, advanced therapeutic options with better efficacy need to be explored. Combination therapy is an alternative with a better success rate though the risk of amplified side effects is commonplace. Moreover, recent groundbreaking precision immune therapy is one of the ways to overcome drug resistance and has revolutionized anticancer therapy to a greater extent with the only limitation of being individual-specific and needs further attention. This review will focus on the challenges and strategies opted by cancer cells to withstand the current therapies at the molecular level and also highlights the emerging therapeutic options -like immunological, and stem cell-based options that may prove to have better potential to challenge the existing problem of therapy resistance. Video Abstract.

Enhanced Sensitivity of A549 Cells to Doxorubicin with WS2 and WSe2 Nanosheets via the Induction of Autophagy

The excellent physicochemical properties of two-dimensional transition-metal dichalcogenides (2D TMDCs) such as WS2 and WSe2 provide potential benefits for biomedical applications, such as drug delivery, photothermal therapy, and bioimaging. WS2 and WSe2 have recently been used as chemosensitizers; however, the detailed molecular basis underlying WS2- and WSe2-induced sensitization remains elusive. Our recent findings showed that 2D TMDCs with different thicknesses and different element compositions induced autophagy in normal human bronchial epithelial cells and mouse alveolar macrophages at sublethal concentrations. Here, we explored the mechanism by which WS2 and WSe2 act as sensitizers to increase lung cancer cell susceptibility to chemotherapeutic agents. The results showed that WS2 and WSe2 enhanced autophagy flux in A549 lung cancer cells at sublethal concentrations without causing significant cell death. Through the autophagy-specific RT2 Profiler PCR Array, we identified the genes significantly affected by WS2 and WSe2 treatment. Furthermore, the key genes that play central roles in regulating autophagy were identified by constructing a molecular interaction network. A mechanism investigation uncovered that WS2 and WSe2 activated autophagy-related signaling pathways by interacting with different cell surface proteins or cytoplasmic proteins. By utilizing this mechanism, the efficacy of the chemotherapeutic agent doxorubicin was enhanced by WS2 and WSe2 pre-treatment in A549 lung cancer cells. This study revealed a feature of WS2 and WSe2 in cancer therapy, in which they eliminate the resistance of A549 lung cancer cells against doxorubicin, at least partially, by inducing autophagy.

Determination of Autophagy in Human Cervicovaginal Smears by Cytological and İmmunocytochemical Methods

Background

Autophagy is a catabolic process whereby organelles and long-lived proteins are recycled through lysosomes to maintain cellular homeostasis. This process is being widely studied using culture techniques and animal models; however, cervicovaginal smears have not been used to detect autophagy.

Aims

Our study aims to detect and evaluate autophagy in normal, malignant, infectious, and atypical cells in cervicovaginal smears by using cytological and immunocytochemical methods.

Materials and Methods

Papanicolaou-stained 200 cervicovaginal smears were examined and 55 of 200 (27.5%) smears containing negative for intraepithelial lesion or malignancy (NILM) with identifiable infections and/or reactive/reparative changes (INF); briefly, NILM-INF (n = 31, 56.4%), atypical (n = 4, 7.3%), and malignant cells (n = 20, 36.3%) were evaluated as a study group. One hundred forty-five of 200 (72.5%) normal smears were accepted as the NILM without any identifiable infections (control group). The autophagy marker protein Microtubule-associated protein 1 light chain 3 A (MAP1LC3A) was used for immunocytochemical examination.

Results

The staining intensity of the MAP1LC3A protein and autophagy positivity were lower in the malignant cells; however, they were higher in the NILM-INF and atypical cells. A statistically significant correlation between the malignant and normal cells was obtained for the autophagy positivity (P = 0.012). In view of the staining intensity of MAP1LC3A protein by the H-score method, a significant correlation was found between the NILM-INF and the normal cells (P = 0.015).

Conclusions

Autophagy was detected in various cervicovaginal smears for the first time in this study. Our findings indicate that an autophagy process is essential in infectious cells as well as in the transformation of atypical cells into malignant cells in carcinogenesis.

The Beneficial and Adverse Effects of Autophagic Response to Caloric Restriction and Fasting

Each cell is equipped with a conserved housekeeping mechanism, known as autophagy, to recycle exhausted materials and dispose of injured organelles via lysosomal degradation. Autophagy is an early-stage cellular response to stress stimuli in both physiological and pathological situations. It is thought that the promotion of autophagy flux prevents host cells from subsequent injuries by removing damaged organelles and misfolded proteins. As a correlate, the modulation of autophagy is suggested as a therapeutic approach in diverse pathological conditions. Accumulated evidence suggests that intermittent fasting or calorie restriction can lead to the induction of adaptive autophagy and increase longevity of eukaryotic cells. However, prolonged calorie restriction with excessive autophagy response is harmful and can stimulate a type II autophagic cell death. Despite the existence of a close relationship between calorie deprivation and autophagic response in different cell types, the precise molecular mechanisms associated with this phenomenon remain unclear. Here, we aimed to highlight the possible effects of prolonged and short-term calorie restriction on autophagic response and cell homeostasis.

Autophagy deficiency protects against ocular hypertension and neurodegeneration in experimental and spontanous glaucoma mouse models

Glaucoma is a group of diseases that leads to chronic degeneration of retinal ganglion cell (RGC) axons and progressive loss of RGCs, resulting in vision loss. While aging and elevated intraocular pressure (IOP) have been identified as the main contributing factors to glaucoma, the molecular mechanisms and signaling pathways triggering RGC death and axonal degeneration are not fully understood. Previous studies in our laboratory found that overactivation of autophagy in DBA/2J::GFP-LC3 mice led to RGC death and optic nerve degeneration with glaucomatous IOP elevation. We found similar findings in aging GFP-LC3 mice subjected to chronic IOP elevation. Here, we further investigated the impact of autophagy deficiency on autophagy-deficient DBA/2J-Atg4bko and DBA/2J-Atg4b+/- mice, generated in our laboratory via CRISPR/Cas9 technology; as well as in Atg4bko mice subjected to the experimental TGFβ2 chronic ocular hypertensive model. Our data shows that, in contrast to DBA/2J and DBA/2J-Atg4b+/- littermates, DBA/2J-Atg4bko mice do not develop glaucomatous IOP elevation. Atg4b deficiency also protected against glaucomatous IOP elevation in the experimental TGFβ2 chronic ocular hypertensive model. Atg4 deletion did not compromise RGC or optic nerve survival in Atg4bko mice. Moreover, our results indicate a protective role of autophagy deficiency against RGC death and ON atrophy in the hypertensive DBA/2J-Atg4b+/- mice. Together, our data suggests a pathogenic role of autophagy activation in ocular hypertension and glaucoma.

The Role of mTORC1 Pathway and Autophagy in Resistance to Platinum-Based Chemotherapeutics

Cisplatin (cis-diamminedichloroplatinum I) is a platinum-based drug, the mainstay of anticancer treatment for numerous solid tumors. Since its approval by the FDA in 1978, the drug has continued to be used for the treatment of half of epithelial cancers. However, resistance to cisplatin represents a major obstacle during anticancer therapy. Here, we review recent findings on how the mTORC1 pathway and autophagy can influence cisplatin sensitivity and resistance and how these data can be applicable for the development of new therapeutic strategies.

The MAP Kinase PvMK1 Regulates Hyphal Development, Autophagy, and Pathogenesis in the Bayberry Twig Blight Fungus Pestalotiopsis versicolor

Bayberry twig blight caused by the ascomycete fungus Pestalotiopsis versicolor is a devastating disease threatening worldwide bayberry production. However, the molecular basis underlying the pathogenesis of P. versicolor is largely unknown. Here, we identified and functionally characterized the MAP kinase PvMk1 in P. versicolor through genetic and cellular biochemical approaches. Our analysis reveals a central role of PvMk1 in regulating P. versicolor virulence on bayberry. We demonstrate that PvMk1 is involved in hyphal development, conidiation, melanin biosynthesis, and cell wall stress responses. Notably, PvMk1 regulates P. versicolor autophagy and is essential for hyphal growth under nitrogen-depleting conditions. These findings suggest the multifaceted role of PvMk1 in regulating P. versicolor development and virulence. More remarkably, this evidence of virulence-involved cellular processes regulated by PvMk1 has paved a fundamental way for further understanding the impact of P. versicolor pathogenesis on bayberry.

The STAT3-Regulated Autophagy Pathway in Glioblastoma

Glioblastoma (GBM) is the most common primary brain malignancy in adults with a dismal prognosis. Despite advances in genomic analysis and surgical technique and the development of targeted therapeutics, most treatment options are ineffective and mainly palliative. Autophagy is a form of cellular self-digestion with the goal of recycling intracellular components to maintain cell metabolism. Here, we describe some recent findings that suggest GBM tumors are more sensitive to the excessive overactivation of autophagy leading to autophagy-dependent cell death. GBM cancer stem cells (GSCs) are a subset of the GBM tumor population that play critical roles in tumor formation and progression, metastasis, and relapse, and they are inherently resistant to most therapeutic strategies. Evidence suggests that GSCs are able to adapt to a tumor microenvironment of hypoxia, acidosis, and lack of nutrients. These findings have suggested that autophagy may promote and maintain the stem-like state of GSCs as well as their resistance to cancer treatment. However, autophagy is a double-edged sword and may have anti-tumor properties under certain conditions. The role of the STAT3 transcription factor in autophagy is also described. These findings provide the basis for future research aimed at targeting the autophagy-dependent pathway to overcome the inherent therapeutic resistance of GBM in general and to specifically target the highly therapy-resistant GSC population through autophagy regulation.

Autophagy in Inflammatory Response against SARS-CoV-2

The coronavirus disease pandemic, which profoundly reshaped the world in 2019 (COVID-19), and is currently ongoing, has affected over 200 countries, caused over 500 million cumulative cases, and claimed the lives of over 6.4 million people worldwide as of August 2022. The causative agent is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Depicting this virus' life cycle and pathogenic mechanisms, as well as the cellular host factors and pathways involved during infection, has great relevance for the development of therapeutic strategies. Autophagy is a catabolic process that sequesters damaged cell organelles, proteins, and external invading microbes, and delivers them to the lysosomes for degradation. Autophagy would be involved in the entry, endo, and release, as well as the transcription and translation, of the viral particles in the host cell. Secretory autophagy would also be involved in developing the thrombotic immune-inflammatory syndrome seen in a significant number of COVID-19 patients that can lead to severe illness and even death. This review aims to review the main aspects that characterize the complex and not yet fully elucidated relationship between SARS-CoV-2 infection and autophagy. It briefly describes the key concepts regarding autophagy and mentions its pro- and antiviral roles, while also noting the reciprocal effect of viral infection in autophagic pathways and their clinical aspects.

Enhanced Levels of Peroxisome-Derived H2O2 Do Not Induce Pexophagy but Impair Autophagic Flux in HEK-293 and HeLa Cells

Peroxisomes are functionally specialized organelles that harbor multiple hydrogen peroxide (H2O2)-producing and -degrading enzymes. Given that this oxidant functions as a major redox signaling agent, peroxisomes have the intrinsic ability to mediate and modulate H2O2-driven processes, including autophagy. However, it remains unclear whether changes in peroxisomal H2O2 (po-H2O2) emission impact the autophagic process and to which extent peroxisomes with a disturbed H2O2 metabolism are selectively eliminated through a process called “pexophagy”. To address these issues, we generated and validated HEK-293 and HeLa pexophagy reporter cell lines in which the production of po-H2O2 can be modulated. We demonstrate that (i) po-H2O2 can oxidatively modify multiple selective autophagy receptors and core autophagy proteins, (ii) neither modest nor robust levels of po-H2O2 emission act as a prime determinant of pexophagy, and (iii) high levels of po-H2O2 impair autophagic flux by oxidative inhibition of enzymes involved in LC3II formation. Unexpectedly, our analyses also revealed that the autophagy receptor optineurin can be recruited to peroxisomes, thereby triggering pexophagy. In summary, these findings lend support to the idea that, during cellular and organismal aging, peroxisomes with enhanced H2O2 release can escape pexophagy and downregulate autophagic activity, thereby perpetuating the accumulation of damaged and toxic cellular debris.

Role of SIRT3 in Microgravity Response: A New Player in Muscle Tissue Recovery

Life on Earth has evolved in the presence of a gravity constraint. Any change in the value of such a constraint has important physiological effects. Gravity reduction (microgravity) alters the performance of muscle, bone and, immune systems among others. Therefore, countermeasures to limit such deleterious effects of microgravity are needed considering future Lunar and Martian missions. Our study aims to demonstrate that the activation of mitochondrial Sirtuin 3 (SIRT3) can be exploited to reduce muscle damage and to maintain muscle differentiation following microgravity exposure. To this effect, we used a RCCS machine to simulate microgravity on ground on a muscle and cardiac cell line. During microgravity, cells were treated with a newly synthesized SIRT3 activator, called MC2791 and vitality, differentiation, ROS and, autophagy/mitophagy were measured. Our results indicate that SIRT3 activation reduces microgravity-induced cell death while maintaining the expression of muscle cell differentiation markers. In conclusion, our study demonstrates that SIRT3 activation could represent a targeted molecular strategy to reduce muscle tissue damage caused by microgravity.

Autophagy Requirements for Eye Lens Differentiation and Transparency

Recent evidence points to autophagy as an essential cellular requirement for achieving the mature structure, homeostasis, and transparency of the lens. Collective evidence from multiple laboratories using chick, mouse, primate, and human model systems provides evidence that classic autophagy structures, ranging from double-membrane autophagosomes to single-membrane autolysosomes, are found throughout the lens in both undifferentiated lens epithelial cells and maturing lens fiber cells. Recently, key autophagy signaling pathways have been identified to initiate critical steps in the lens differentiation program, including the elimination of organelles to form the core lens organelle-free zone. Other recent studies using ex vivo lens culture demonstrate that the low oxygen environment of the lens drives HIF1a-induced autophagy via upregulation of essential mitophagy components to direct the specific elimination of the mitochondria, endoplasmic reticulum, and Golgi apparatus during lens fiber cell differentiation. Pioneering studies on the structural requirements for the elimination of nuclei during lens differentiation reveal the presence of an entirely novel structure associated with degrading lens nuclei termed the nuclear excisosome. Considerable evidence also indicates that autophagy is a requirement for lens homeostasis, differentiation, and transparency, since the mutation of key autophagy proteins results in human cataract formation.

The Emerging Role of Autophagy as a Target of Environmental Pollutants: An Update on Mechanisms

Autophagy is an evolutionarily conserved cellular system crucial for cellular homeostasis that protects cells from a broad range of internal and extracellular stresses. Autophagy decreases metabolic load and toxicity by removing damaged cellular components. Environmental contaminants, particularly industrial substances, can influence autophagic flux by enhancing it as a protective response, preventing it, or converting its protective function into a pro-cell death mechanism. Environmental toxic materials are also notorious for their tendency to bioaccumulate and induce pathophysiological vulnerability. Many environmental pollutants have been found to influence stress which increases autophagy. Increasing autophagy was recently shown to improve stress resistance and reduce genetic damage. Moreover, suppressing autophagy or depleting its resources either increases or decreases toxicity, depending on the circumstances. The essential process of selective autophagy is utilized by mammalian cells in order to eliminate particulate matter, nanoparticles, toxic metals, and smoke exposure without inflicting damage on cytosolic components. Moreover, cigarette smoke and aging are the chief causes of chronic obstructive pulmonary disease (COPD)-emphysema; however, the disease's molecular mechanism is poorly known. Therefore, understanding the impacts of environmental exposure via autophagy offers new approaches for risk assessment, protection, and preventative actions which will counter the harmful effects of environmental contaminants on human and animal health.

Vacuolar Processing Enzymes in Plant Programmed Cell Death and Autophagy

Vacuolar processing enzymes (VPEs) are plant cysteine proteases that are subjected to autoactivation in an acidic pH. It is presumed that VPEs, by activating other vacuolar hydrolases, are in control of tonoplast rupture during programmed cell death (PCD). Involvement of VPEs has been indicated in various types of plant PCD related to development, senescence, and environmental stress responses. Another pathway induced during such processes is autophagy, which leads to the degradation of cellular components and metabolite salvage, and it is presumed that VPEs may be involved in the degradation of autophagic bodies during plant autophagy. As both PCD and autophagy occur under similar conditions, research on the relationship between them is needed, and VPEs, as key vacuolar proteases, seem to be an important factor to consider. They may even constitute a potential point of crosstalk between cell death and autophagy in plant cells. This review describes new insights into the role of VPEs in plant PCD, with an emphasis on evidence and hypotheses on the interconnections between autophagy and cell death, and indicates several new research opportunities.

The Yin and Yang dualistic features of autophagy in thermal burn wound healing

Burn healing should be regarded as a dynamic process consisting of two main, interrelated phases: (a) the inflammatory phase when neutrophils and monocytes infiltrate the injury site, through localized vasodilation and fluid extravasation, and (b) the proliferative-remodeling phase, which represents a key event in wound healing. In the skin, both canonical autophagy (induced by starvation, oxidative stress, and environmental aggressions) and non-canonical or selective autophagy have evolved to play a discrete, but, essential, “housekeeping” role, for homeostasis, immune tolerance, and survival. Experimental data supporting the pro-survival roles of autophagy, highlighting its Yang, luminous and positive feature of this complex but insufficient explored molecular pathway, have been reported. Autophagic cell death describes an “excessive” degradation of important cellular components that are necessary for normal cell function. This deadly molecular mechanism brings to light the darker, concealed, Yin feature of autophagy. Autophagy seems to perform dual, conflicting roles in the angiogenesis context, revealing once again, its Yin–Yang features. Autophagy with its Yin–Yang features remains the shadow player, able to decide quietly whether the cell survives or dies.