Autophagy promotes T-cell survival through degradation of proteins of the cell death machinery

No energy, no autophagy-Mechanisms and therapeutic implications of autophagic response energy requirements

Autophagy is a lysosome-mediated self-degradation process of central importance for cellular quality control. It also provides macromolecule building blocks and substrates for energy metabolism during nutrient or energy deficiency, which are the main stimuli for autophagy induction. However, like most biological processes, autophagy itself requires ATP, and there is an energy threshold for its initiation and execution. We here present the first comprehensive review of this often-overlooked aspect of autophagy research. The studies in which ATP deficiency suppressed autophagy in vitro and in vivo were classified according to the energy pathway involved (oxidative phosphorylation or glycolysis). A mechanistic insight was provided by pinpointing the critical ATP-consuming autophagic events, including transcription/translation/interaction of autophagy-related molecules, autophagosome formation/elongation, autophagosome fusion with the lysosome, and lysosome acidification. The significance of energy-dependent fine-tuning of autophagic response for preserving the cell homeostasis, and potential implications for the therapy of cancer, autoimmunity, metabolic disorders, and neurodegeneration are discussed.

The roles of arginases and arginine in immunity

Arginase activity and arginine metabolism in immune cells have important consequences for health and disease. Their dysregulation is commonly observed in cancer, autoimmune disorders and infectious diseases. Following the initial description of a role for arginase in the dysfunction of T cells mounting an antitumour response, numerous studies have broadened our understanding of the regulation and expression of arginases and their integration with other metabolic pathways. Here, we highlight the differences in arginase compartmentalization and storage between humans and rodents that should be taken into consideration when assessing the effects of arginase activity. We detail the roles of arginases, arginine and its metabolites in immune cells and their effects in the context of cancer, autoimmunity and infectious disease. Finally, we explore potential therapeutic strategies targeting arginases and arginine.

From defense to dysfunction: Autophagy's dual role in disease pathophysiology

Autophagy is a fundamental pillar of cellular resilience, indispensable for maintaining cellular health and vitality. It coordinates the meticulous breakdown of cytoplasmic macromolecules as a guardian of cell metabolism, genomic integrity, and survival. In the complex play of biological warfare, autophagy emerges as a firm defender, bravely confronting various pathogenic, infectious, and cancerous adversaries. Nevertheless, its role transcends mere defense, wielding both protective and harmful effects in the complex landscape of disease pathogenesis. From the onslaught of infectious outbreaks to the devious progression of chronic lifestyle disorders, autophagy emerges as a central protagonist, convolutedly shaping the trajectory of cellular health and disease progression. In this article, we embark on a journey into the complicated web of molecular and immunological mechanisms that govern autophagy's profound influence over disease. Our focus sharpens on dissecting the impact of various autophagy-associated proteins on the kaleidoscope of immune responses, spanning the spectrum from infectious outbreaks to chronic lifestyle ailments. Through this voyage of discovery, we unveil the vast potential of autophagy as a therapeutic linchpin, offering tantalizing prospects for targeted interventions and innovative treatment modalities that promise to transform the landscape of disease management.

Research progress of T cell autophagy in autoimmune diseases

T cells, as a major lymphocyte population involved in the adaptive immune response, play an important immunomodulatory role in the early stages of autoimmune diseases. Autophagy is a cellular catabolism mediated by lysosomes. Autophagy maintains cell homeostasis by recycling degraded cytoplasmic components and damaged organelles. Autophagy has a protective effect on cells and plays an important role in regulating T cell development, activation, proliferation and differentiation. Autophagy mediates the participation of T cells in the acquired immune response and plays a key role in antigen processing as well as in the maintenance of T cell homeostasis. In autoimmune diseases, dysregulated autophagy of T cells largely influences the pathological changes. Therefore, it is of great significance to study how T cells play a role in the immune mechanism of autoimmune diseases through autophagy pathway to guide the clinical treatment of diseases.

Interactions Between Extracellular Vesicles and Autophagy in Neuroimmune Disorders

Neuroimmune disorders, such as multiple sclerosis, neuromyelitis optica spectrum disorder, myasthenia gravis, and Guillain-Barré syndrome, are characterized by the dysfunction of both the immune system and the nervous system. Increasing evidence suggests that extracellular vesicles and autophagy are closely associated with the pathogenesis of these disorders. In this review, we summarize the current understanding of the interactions between extracellular vesicles and autophagy in neuroimmune disorders and discuss their potential diagnostic and therapeutic applications. Here we highlight the need for further research to fully understand the mechanisms underlying these disorders, and to develop new diagnostic and therapeutic strategies.

Effect of daylong exposure to indoor overheating on autophagy and the cellular stress response in older adults

To protect vulnerable populations during heat waves, public health agencies recommend maintaining indoor air temperature below ∼24-28 °C. While we recently demonstrated that maintaining indoor temperatures ≤26 °C mitigates the development of hyperthermia and cardiovascular strain in older adults, the cellular consequences of prolonged indoor heat stress are poorly understood. We therefore evaluated the cellular stress response in 16 adults (six females) aged 66-78 years during 8 h rest in ambient conditions simulating homes maintained at 22 °C (control) and 26 °C (indoor temperature upper limit proposed by health agencies), as well as non-air-conditioned domiciles during hot weather and heat waves (31 and 36 °C, respectively; all 45% relative humidity). Western blot analysis was used to assess changes in proteins associated with the cellular stress response (autophagy, apoptosis, acute inflammation, and heat shock proteins) in peripheral blood mononuclear cells harvested prior to and following exposure. Following 8 h exposure, no cellular stress response-related proteins differed significantly between the 26 and 22 °C conditions (all, P ≥ 0.056). By contrast, autophagy-related proteins were elevated following exposure to 31 °C (p62: 1.5-fold; P = 0.003) and 36 °C (LC3-II, LC3-II/I, p62; all ≥2.0-fold; P ≤ 0.002) compared to 22 °C. These responses were accompanied by elevations in apoptotic signaling in the 31 and 36 °C conditions (cleaved-caspase-3: 1.8-fold and 3.7-fold, respectively; P ≤ 0.002). Furthermore, HSP90 was significantly reduced in the 36 °C compared to 22 °C condition (0.7-fold; P = 0.014). Our findings show that older adults experience considerable cellular stress during prolonged exposure to elevated ambient temperatures and support recommendations to maintain indoor temperatures ≤26 °C to prevent physiological strain in heat-vulnerable persons.

Autophagy differentially regulates tissue tolerance of distinct target organs in graft-versus-host disease models

Tissue-intrinsic mechanisms that regulate severity of systemic pathogenic immune-mediated diseases, such as acute graft-versus-host disease (GVHD), remain poorly understood. Following allogeneic hematopoietic stem cell transplantation, autophagy, a cellular stress protective response, is induced in host nonhematopoietic cells. To systematically address the role of autophagy in various host nonhematopoietic tissues, both specific classical target organs of acute GVHD (intestines, liver, and skin) and organs conventionally not known to be targets of GVHD (kidneys and heart), we generated mice with organ-specific knockout of autophagy related 5 (ATG5) to specifically and exclusively inhibit autophagy in the specific organs. When compared with wild-type recipients, animals that lacked ATG5 in the gastrointestinal tract or liver showed significantly greater tissue injury and mortality, while autophagy deficiency in the skin, kidneys, or heart did not affect mortality. Treatment with the systemic autophagy inducer sirolimus only partially mitigated GVHD mortality in intestine-specific autophagy-deficient hosts. Deficiency of autophagy increased MHC class I on the target intestinal epithelial cells, resulting in greater susceptibility to damage by alloreactive T cells. Thus, autophagy is a critical cell-intrinsic protective response that promotes tissue tolerance and regulates GVHD severity.

The intensity-dependent effects of exercise and superimposing environmental heat stress on autophagy in peripheral blood mononuclear cells from older men

Autophagy is a vital cellular process, essential to maintaining cellular function during acute physiological stressors including exercise and heat stress. We previously showed that autophagy occurs during exercise in an intensity-dependent manner in peripheral blood mononuclear cells (PBMCs) from young men, with elevated responses in the heat. However, given autophagy declines with age, it is unclear whether a similar pattern of response occurs in older adults. Therefore, we evaluated autophagy and the cellular stress response [i.e., apoptosis, inflammation, and the heat shock response (HSR)] in PBMCs from 10 healthy older men [mean (SD): aged 70 yr (5)] in response to 30 min of semirecumbent cycling at low, moderate, and vigorous intensities [40, 55, and 70% maximal oxygen consumption (V̇o2max), respectively] in a temperate (25°C) environment, with an additional vigorous-intensity bout (70% of V̇o2max) performed in a hot environment (40°C). Responses were evaluated before and after exercise, as well as throughout a 6-h seated recovery period performed in the same environmental conditions as the respective exercise bout. Proteins were assessed via Western blot. Although we observed elevations in mean body temperature with each increase in exercise intensity, autophagy was only stimulated during vigorous-intensity exercise, where we observed elevations in LC3-II (P < 0.05). However, when the same exercise was performed in the heat, the LC3-II response was attenuated, which was accompanied by significant p62 accumulation (P < 0.05). Altogether, our findings demonstrate that older adults exhibit autophagic impairments when the same vigorous-intensity exercise is performed in hot environments, potentially underlying heat-induced cellular vulnerability in older men.NEW & NOTEWORTHY We demonstrate that autophagic stimulation occurs in response to short-duration (30-min) vigorous-intensity exercise in peripheral blood mononuclear cells from older adults; however, no changes in autophagy occur during low- or moderate-intensity exercise. Moreover, older adults exhibit autophagic impairments when the same vigorous-intensity exercise is performed in hot ambient conditions. When paired with an attenuated heat shock response, as well as elevated apoptotic responses, older men may exhibit greater cellular vulnerability to exertional heat stress.

Insights into Autophagic Machinery and Lysosomal Function in Cells Involved in the Psoriatic Immune-Mediated Inflammatory Cascade

Impaired autophagy, due to the dysfunction of lysosomal organelles, contributes to maladaptive responses by pathways central to the immune system. Deciphering the immune-inflammatory ecosystem is essential, but remains a major challenge in terms of understanding the mechanisms responsible for autoimmune diseases. Accumulating evidence implicates a role that is played by a dysfunctional autophagy-lysosomal pathway (ALP) and an immune niche in psoriasis (Ps), one of the most common chronic skin diseases, characterized by the co-existence of autoimmune and autoinflammatory responses. The dysregulated autophagy associated with the defective lysosomal system is only one aspect of Ps pathogenesis. It probably cannot fully explain the pathomechanism involved in Ps, but it is likely important and should be seriously considered in Ps research. This review provides a recent update on discoveries in the field. Also, it sheds light on how the dysregulation of intracellular pathways, coming from modulated autophagy and endolysosomal trafficking, characteristic of key players of the disease, i.e., skin-resident cells, as well as circulating immune cells, may be responsible for immune impairment and the development of Ps.

Exploiting autophagy balance in T and NK cells as a new strategy to implement adoptive cell therapies

Autophagy is an essential cellular homeostasis pathway initiated by multiple stimuli ranging from nutrient deprivation to viral infection, playing a key role in human health and disease. At present, a growing number of evidence suggests a role of autophagy as a primitive innate immune form of defense for eukaryotic cells, interacting with components of innate immune signaling pathways and regulating thymic selection, antigen presentation, cytokine production and T/NK cell homeostasis. In cancer, autophagy is intimately involved in the immunological control of tumor progression and response to therapy. However, very little is known about the role and impact of autophagy in T and NK cells, the main players in the active fight against infections and tumors. Important questions are emerging: what role does autophagy play on T/NK cells? Could its modulation lead to any advantages? Could specific targeting of autophagy on tumor cells (blocking) and T/NK cells (activation) be a new intervention strategy? In this review, we debate preclinical studies that have identified autophagy as a key regulator of immune responses by modulating the functions of different immune cells and discuss the redundancy or diversity among the subpopulations of both T and NK cells in physiologic context and in cancer.

Beclin1 is essential for the pancreas development

Beclin1 (Becn1) is a multifunctional protein involved in autophagy regulation, membrane trafficking, and tumor suppression. In this study, we examined the roles of Becn1 in the pancreas development by generating mice with conditional deletion of Becn1 in the pancreas using pancreatic transcriptional factor 1a (Ptf1a)-Cre mice (Becn1f/f; Ptf1aCre/+). Surprisingly, loss of Becn1 in the pancreas resulted in severe pancreatic developmental defects, leading to insufficient exocrine and endocrine pancreatic function. Approximately half of Becn1f/f; Ptf1aCre/+ mice died immediately after birth. However, duodenum and neural tissue development were almost normal, indicating that pancreatic insufficiency was the cause of death. These findings demonstrated a novel role for Becn1 in pancreas morphogenesis, differentiation, and growth, and suggested that loss of this factor leaded to pancreatic agenesis at birth.

Reactive nitrogen species as therapeutic targets for autophagy/mitophagy modulation to relieve neurodegeneration in multiple sclerosis: Potential application for drug discovery

Multiple sclerosis (MS) is a neuroinflammatory disease with limited therapeutic effects, eventually developing into handicap. Seeking novel therapeutic strategies for MS is timely important. Active autophagy/mitophagy could mediate neurodegeneration, while its roles in MS remain controversial. To elucidate the exact roles of autophagy/mitophagy and reveal its in-depth regulatory mechanisms, we conduct a systematic literature study and analyze the factors that might be responsible for divergent results obtained. The dynamic change levels of autophagy/mitophagy appear to be a determining factor for final neuron fate during MS pathology. Excessive neuronal autophagy/mitophagy contributes to neurodegeneration after disease onset at the active MS phase. Reactive nitrogen species (RNS) serve as key regulators for redox-related modifications and participate in autophagy/mitophagy modulation in MS. Nitric oxide (•NO) and peroxynitrite (ONOO-), two representative RNS, could nitrate or nitrosate Drp1/parkin/PINK1 pathway, activating excessive mitophagy and aggravating neuronal injury. Targeting RNS-mediated excessive autophagy/mitophagy could be a promising strategy for developing novel anti-MS drugs. In this review, we highlight the important roles of RNS-mediated autophagy/mitophagy in neuronal injury and review the potential therapeutic compounds with the bioactivities of inhibiting RNS-mediated autophagy/mitophagy activation and attenuating MS progression. Overall, we conclude that reactive nitrogen species could be promising therapeutic targets to regulate autophagy/mitophagy for multiple sclerosis treatment.

Proteostasis in T cell aging

Aging leads to a decline in immune cell function, which leaves the organism vulnerable to infections and age-related multimorbidities. One major player of the adaptive immune response are T cells, and recent studies argue for a major role of disturbed proteostasis contributing to reduced function of these cells upon aging. Proteostasis refers to the state of a healthy, balanced proteome in the cell and is influenced by synthesis (translation), maintenance and quality control of proteins, as well as degradation of damaged or unwanted proteins by the proteasome, autophagy, lysosome and cytoplasmic enzymes. This review focuses on molecular processes impacting on proteostasis in T cells, and specifically functional or quantitative changes of each of these upon aging. Importantly, we describe the biological consequences of compromised proteostasis in T cells, which range from impaired T cell activation and function to enhancement of inflamm-aging by aged T cells. Finally, approaches to improve proteostasis and thus rejuvenate aged T cells through pharmacological or physical interventions are discussed.

The interaction between autophagy, Helicobacter pylori, and gut microbiota in gastric carcinogenesis

Chronic infection with Helicobacter pylori is the primary risk factor for the development of gastric cancer. Hindering our ability to comprehend the precise role of autophagy during H. pylori infection is the complexity of context-dependent autophagy signaling pathways. Recent and ongoing progress in understanding H. pylori virulence allows new frontiers of research for the crosstalk between autophagy and H. pylori. Novel approaches toward discovering autophagy signaling networks have further revealed their critical influence on the structure of gut microbiota and the metabolome. Here we intend to present a holistic view of the perplexing role of autophagy in H. pylori pathogenesis and carcinogenesis. We also discuss the intermediate role of autophagy in H. pylori-mediated modification of gut inflammatory responses and microbiota structure.

Physiological responses to 9 hours of heat exposure in young and older adults. Part II: Autophagy and the acute cellular stress response

With rising global temperatures, heat-related mortality is increasing, particularly among older adults. Although this is often attributed to declines in thermoregulatory function, little is known regarding the effect of age on the cellular processes associated with mitigating heat-induced cytotoxicity. We compared key components of the cellular stress response in 19 young (19-31 yr; 10 female) and 37 older adults (61-78 yr; 10 female) during 9 h of heat exposure (40°C, 9% relative humidity). Mean body temperature (Tbody) was calculated from core and skin temperatures. Changes in proteins associated with autophagy, apoptotic signaling, acute inflammation, and the heat shock response were assessed via Western blot in peripheral blood mononuclear cells harvested before and after exposure. Tbody increased by 1.5 (SD 0.3)°C and 1.7 (0.3)°C in the young and older adults, respectively. We observed similar elevations in autophagy-related proteins (LC3-II and LC3-II/I) in young and older adults (both P ≥ 0.121). However, the older adults displayed signs of autophagic dysfunction, evidenced by a 3.7-fold [95% CI: 2.4, 5.6] greater elevation in the selective autophagy receptor p62 (P < 0.001). This was paired with elevations in apoptotic responses, with a 1.7-fold [1.3, 2.3] increase in cleaved caspase-3 in the older relative to young adults (P < 0.001). Older adults also exhibited diminished heat shock protein 90 responses (0.7-fold [0.5, 0.9] vs. young, P = 0.011) and, at any given level of thermal strain (Tbody area under the curve), elevated tumor necrosis factor-α (1.5-fold [1.0, 2.5] vs. young, P = 0.008). Attenuated autophagic responses may underlie greater vulnerability to heat-induced cellular injury in older adults.NEW & NOTEWORTHY We demonstrate for the first time that peripheral blood mononuclear cells from older adults exhibit signs of autophagic impairments during daylong (9 h) heat exposure relative to their younger counterparts. This was paired with greater apoptotic signaling and inflammatory responses, and an inability to stimulate components of the heat shock response. Thus, autophagic dysregulation during prolonged heat exposure may contribute to age-related heat vulnerability during hot weather and heat waves.

Endoplasmic reticulum stress in T cell-mediated diseases

T cells synthesize a large number of proteins during their development, activation, and differentiation. The build-up of misfolded and unfolded proteins in the endoplasmic reticulum, however, causes endoplasmic reticulum (ER) stress. Thus, T cells can maintain ER homeostasis via endoplasmic reticulum-associated degradation, unfolded protein response, and autophagy. In T cell-mediated diseases, such as rheumatoid arthritis, systemic lupus erythematosus, Sjogren's syndrome, type 1 diabetes and vitiligo, ER stress caused by changes in the internal microenvironment can cause disease progression by affecting T cell homeostasis. This review discusses ER stress in T cell formation, activation, differentiation, and T cell-mediated illnesses, and may offer new perspectives on the involvement of T cells in autoimmune disorders and cancer.

Crosstalk between autophagy and metabolic regulation of (CAR) T cells: therapeutic implications

Despite chimeric antigen receptor (CAR) T cell therapy's extraordinary success in subsets of B-cell lymphoma and leukemia, various barriers restrict its application in solid tumors. This has prompted investigating new approaches for producing CAR T cells with superior therapeutic potential. Emerging insights into the barriers to CAR T cell clinical success indicate that autophagy shapes the immune response via reprogramming cellular metabolism and vice versa. Autophagy, a self-cannibalization process that includes destroying and recycling intracellular components in the lysosome, influences T cell biology, including development, survival, memory formation, and cellular metabolism. In this review, we will emphasize the critical role of autophagy in regulating and rewiring metabolic circuits in CAR T cells, as well as how the metabolic status of CAR T cells and the tumor microenvironment (TME) alter autophagy regulation in CAR T cells to restore functional competence in CAR Ts traversing solid TMEs.

Modulation of the immunity and inflammation by autophagy

Autophagy, a highly conserved cellular self-degradation pathway, has emerged with novel roles in the realms of immunity and inflammation. Genome-wide association studies have unveiled a correlation between genetic variations in autophagy-related genes and heightened susceptibility to autoimmune and inflammatory diseases. Subsequently, substantial progress has been made in unraveling the intricate involvement of autophagy in immunity and inflammation through functional studies. The autophagy pathway plays a crucial role in both innate and adaptive immunity, encompassing various key functions such as pathogen clearance, antigen processing and presentation, cytokine production, and lymphocyte differentiation and survival. Recent research has identified novel approaches in which the autophagy pathway and its associated proteins modulate the immune response, including noncanonical autophagy. This review provides an overview of the latest advancements in understanding the regulation of immunity and inflammation through autophagy. It summarizes the genetic associations between variants in autophagy-related genes and a range of autoimmune and inflammatory diseases, while also examining studies utilizing transgenic animal models to uncover the in vivo functions of autophagy. Furthermore, the review delves into the mechanisms by which autophagy dysregulation contributes to the development of three common autoimmune and inflammatory diseases and highlights the potential for autophagy-targeted therapies.

Deficiency of Pink1 promotes the differentiation of Th1 cells

Previous studies have found that Pink1 is crucial for T cell activation and the function of Treg cells. However, the effect of Pink1 on inflammatory Th1 cells is largely unknown. In the process of Th1 differentiation from human naïve T cells, we found a reduction of Pink1 and Parkin. We then focused our attention on the Pink1 KO mice. Although there was no difference in the baseline of the T cell subset of Pink1 KO mice, Th1 differentiation from Pink1 KO naïve T cells in vitro showed a significant increase. Subsequently, we transferred naïve CD4⁺ T cells into Rag2 KO mice to establish a T-cell colitis mouse model and found that CD4⁺ T cells in mesentery lymph nodes of mice receiving Pink1 KO cells increased significantly, especially Th1 cells. Intestinal IHC staining also showed that the transcription factor T-bet of Th1 increased. Treatment of CD4⁺ T cells from lupus-like mice with mitophagy agonist urolithin A, a reduction of Th1 cells was observed, suggesting the clinical value of using mitophagy agonists to suppress Th1-dominated disease in the future.

Immunomodulatory effects of umbilical mesenchymal stem cell-derived exosomes on CD4+ T cells in patients with primary Sjögren's syndrome

BACKGROUND

Primary Sjögren's syndrome (pSS) is an autoimmune disease that leads to the destruction of exocrine glands and multisystem lesions. Abnormal proliferation, apoptosis, and differentiation of CD4⁺ T cells are key factors in the pathogenesis of pSS. Autophagy is one of the important mechanisms to maintain immune homeostasis and function of CD4⁺ T cells. Human umbilical cord mesenchymal stem cell-derived exosomes (UCMSC-Exos) may simulate the immunoregulation of MSCs while avoiding the risks of MSCs treatment. However, whether UCMSC-Exos can regulate the functions of CD4⁺ T cells in pSS, and whether the effects via the autophagy pathway remains unclear.

METHODS

The study analyzed retrospectively the peripheral blood lymphocyte subsets in pSS patients, and explored the relationship between lymphocyte subsets and disease activity. Next, peripheral blood CD4⁺ T cells were sorted using immunomagnetic beads. The proliferation, apoptosis, differentiation, and inflammatory factors of CD4⁺ T cells were determined using flow cytometry. Autophagosomes of CD4⁺ T cells were detected using transmission electron microscopy, autophagy-related proteins and genes were detected using western blotting or RT-qPCR.

RESULTS

The study demonstrated that the peripheral blood CD4⁺ T cells decreased in pSS patients, and negatively correlated with disease activity. UCMSC-Exos inhibited excessive proliferation and apoptosis of CD4⁺ T cells in pSS patients, blocked them in the G0/G1 phase, inhibited them from entering the S phase, reduced the Th17 cell ratio, elevated the Treg ratio, inhibited IFN-γ, TNF-α, IL-6, IL-17A, and IL-17F secretion, and promoted IL-10 and TGF-β secretion. UCMSC-Exos reduced the elevated autophagy levels in the peripheral blood CD4⁺ T cells of patients with pSS. Furthermore, UCMSC-Exos regulated CD4⁺ T cell proliferation and early apoptosis, inhibited Th17 cell differentiation, promoted Treg cell differentiation, and restored the Th17/Treg balance in pSS patients through the autophagy pathway.

CONCLUSIONS

The study indicated that UCMSC-Exos exerts an immunomodulatory effect on the CD4⁺ T cells, and maybe as a new treatment for pSS.

Autophagy pathways in autoimmune diseases

Autophagy comprises a growing range of cellular pathways, which occupy central roles in response to energy deprivation, organelle turnover and proteostasis. Over the years, autophagy has been increasingly linked to governing several aspects of immunity, including host defence against various pathogens, unconventional secretion of cytokines and antigen presentation. While canonical autophagy-mediated antigen processing in thymic epithelial cells supports the generation of a self-tolerant CD4+ T cell repertoire, mounting evidence suggests that deregulated autophagy pathways contribute to or sustain autoimmune responses. In animal models of multiple sclerosis (MS), non-canonical autophagy pathways such as microtubule-associated protein 1 A/1 B-light chain 3 (LC3)-associated phagocytosis can contribute to major histocompatibility complex (MHC) class II presentation of autoantigen, thereby amplifying autoreactive CD4+ T cell responses. In systemic lupus erythematosus (SLE), increased type 1 interferon production is linked to excessive autophagy in plasmacytoid dendritic cells (DCs). In rheumatoid arthritis (RA), autophagy proteins contribute to pathological citrullination of autoantigen. Immunotherapies effective in autoimmune diseases modulate autophagy functions, and strategies harnessing autophagy pathways to restrain autoimmune responses have been developed. This review illustrates recent insights in how autophagy, distinct autophagy pathways and autophagy protein functions intersect with the evolution and progression of autoimmune diseases, focusing on MS, SLE and RA.

A single-cell atlas reveals shared and distinct immune responses and metabolic profiles in SARS-CoV-2 and HIV-1 infections

Introduction: Within the inflammatory immune response to viral infection, the distribution and cell type-specific profiles of immune cell populations and the immune-mediated viral clearance pathways vary according to the specific virus. Uncovering the immunological similarities and differences between viral infections is critical to understanding disease progression and developing effective vaccines and therapies. Insight into COVID-19 disease progression has been bolstered by the integration of single-cell (sc)RNA-seq data from COVID-19 patients with data from related viruses to compare immune responses. Expanding this concept, we propose that a high-resolution, systematic comparison between immune cells from SARS-CoV-2 infection and an inflammatory infectious disease with a different pathophysiology will provide a more comprehensive picture of the viral clearance pathways that underscore immunological and clinical differences between infections. Methods: Using a novel consensus single-cell annotation method, we integrate previously published scRNA-seq data from 111,566 single PBMCs from 7 COVID-19, 10 HIV-1+, and 3 healthy patients into a unified cellular atlas. We compare in detail the phenotypic features and regulatory pathways in the major immune cell clusters. Results: While immune cells in both COVID-19 and HIV-1+ cohorts show shared inflammation and disrupted mitochondrial function, COVID-19 patients exhibit stronger humoral immunity, broader IFN-I signaling, elevated Rho GTPase and mTOR pathway activity, and downregulated mitophagy. Discussion: Our results indicate that differential IFN-I signaling regulates the distinct immune responses in the two diseases, revealing insight into fundamental disease biology and potential therapeutic candidates.

Autophagy of naïve CD4+ T cells in aging - the role of body adiposity and physical fitness

Life expectancy has increased exponentially in the last century accompanied by disability, poor quality of life, and all-cause mortality in older age due to the high prevalence of obesity and physical inactivity in older people. Biologically, the aging process reduces the cell's metabolic and functional efficiency, and disrupts the cell's anabolic and catabolic homeostasis, predisposing older people to many dysfunctional conditions such as cardiovascular disease, neurodegenerative disorders, cancer, and diabetes. In the immune system, aging also alters cells' metabolic and functional efficiency, a process known as 'immunosenescence', where cells become more broadly inflammatory and their functionality is altered. Notably, autophagy, the conserved and important cellular process that maintains the cell's efficiency and functional homeostasis may protect the immune system from age-associated dysfunctional changes by regulating cell death in activated CD4+ T cells. This regulatory process increases the delivery of the dysfunctional cytoplasmic material to lysosomal degradation while increasing cytokine production, proliferation, and differentiation of CD4+ T cell-mediated immune responses. Poor proliferation and diminished responsiveness to cytokines appear to be ubiquitous features of aged T cells and may explain the delayed peak in T cell expansion and cytotoxic activity commonly observed in the 'immunosenescence' phenotype in the elderly. On the other hand, physical exercise stimulates the expression of crucial nutrient sensors and inhibits the mechanistic target of the rapamycin (mTOR) signaling cascade which increases autophagic activity in cells. Therefore, in this perspective review, we will first contextualize the overall view of the autophagy process and then, we will discuss how body adiposity and physical fitness may counteract autophagy in naïve CD4+ T cells in aging.

New insights into autophagy in inflammatory subtypes of asthma

Asthma is a heterogeneous airway disease characterized by airway inflammation and hyperresponsiveness. Autophagy is a self-degrading process that helps maintain cellular homeostasis. Dysregulation of autophagy is involved in the pathogenesis of many diseases. In the context of asthma, autophagy has been shown to be associated with inflammation, airway remodeling, and responsiveness to drug therapy. In-depth characterization of the role of autophagy in asthma can enhance the understanding of the pathogenesis, and provide a theoretical basis for the development of new biomarkers and targeted therapy for asthma. In this article, we focus on the relationship of autophagy and asthma, and discuss its implications for asthma pathogenesis and treatment.

CD8+ T cell metabolic changes in breast cancer

Immunometabolism has advanced our understanding of how the cellular environment and nutrient availability regulates immune cell fate. Not only are metabolic pathways closely tied to cell signaling and differentiation, but can induce different subsets of immune cells to adopt unique metabolic programs, influencing disease progression. Dysregulation of immune cell metabolism plays an essential role in the progression of several diseases including breast cancer (BC). Metabolic reprogramming plays a critical role in regulating T cell functions. CD8⁺ T cells are an essential cell type within the tumor microenvironment (TME). To induce antitumor responses, CD8⁺ T cells need to adapt their metabolism to fulfill their energy requirement for effective function. However, different markers and immunologic techniques have made identifying specific CD8⁺ T cells subtypes in BC a challenge to the field. This review discusses the immunometabolic processes of CD8⁺ T cell in the TME in the context of BC and highlights the role of CD8⁺ T cell metabolic changes in tumor progression.

Aberrant tolerogenic functions and proinflammatory skew of dendritic cells in STAT1 gain-of-function patients may contribute to autoimmunity and fungal susceptibility

STAT1 gain-of-function (GOF) mutations underlie an inborn error of immunity hallmarked by chronic mucocutaneous candidiasis (CMC). Beyond the fungal susceptibility, attributed to Th17 failure, over half of the reported patients suffer from autoimmune manifestations, mechanism of which has not been explained yet. We hypothesized that the STAT1 mutations would affect dendritic cells' (DCs) properties and alter their inflammatory and tolerogenic functions. To test the hypothesis, we generated monocyte-derived DCs (moDCs) and tolerogenic DCs (tDCs). Functional and signaling studies, co-culture experiments and RNA sequencing demonstrated that STAT1 GOF DCs were profoundly altered in their phenotype and functions, characterized by loss of tolerogenic functions, proinflammatory skew and decreased capacity to induce Th17. Cytokine signaling, autophagy and metabolic processes were identified as the most prominently altered cellular processes. The results suggest that DCs are directly involved in STAT1 GOF-associated immune pathology, possibly contributing to both autoimmune manifestations and the failure of antifungal defense.

Interactions of Autophagy and the Immune System in Health and Diseases

Autophagy is a highly conserved process that utilizes lysosomes to selectively degrade a variety of intracellular cargo, thus providing quality control over cellular components and maintaining cellular regulatory functions. Autophagy is triggered by multiple stimuli ranging from nutrient starvation to microbial infection. Autophagy extensively shapes and modulates the inflammatory response, the concerted action of immune cells, and secreted mediators aimed to eradicate a microbial infection or to heal sterile tissue damage. Here, we first review how autophagy affects innate immune signaling, cell-autonomous immune defense, and adaptive immunity. Then, we discuss the role of non-canonical autophagy in microbial infections and inflammation. Finally, we review how crosstalk between autophagy and inflammation influences infectious, metabolic, and autoimmune disorders.

The role of polyamine metabolism in remodeling immune responses and blocking therapy within the tumor immune microenvironment

The study of metabolism provides important information for understanding the biological basis of cancer cells and the defects of cancer treatment. Disorders of polyamine metabolism is a common metabolic change in cancer. With the deepening of understanding of polyamine metabolism, including molecular functions and changes in cancer, polyamine metabolism as a new anti-cancer strategy has become the focus of attention. There are many kinds of polyamine biosynthesis inhibitors and transport inhibitors, but not many drugs have been put into clinical application. Recent evidence shows that polyamine metabolism plays essential roles in remodeling the tumor immune microenvironment (TIME), particularly treatment of DFMO, an inhibitor of ODC, alters the immune cell population in the tumor microenvironment. Tumor immunosuppression is a major problem in cancer treatment. More and more studies have shown that the immunosuppressive effect of polyamines can help cancer cells to evade immune surveillance and promote tumor development and progression. Therefore, targeting polyamine metabolic pathways is expected to become a new avenue for immunotherapy for cancer.

Autophagy: A Versatile Player in the Progression of Colorectal Cancer and Drug Resistance

Colorectal cancer (CRC) is among the topmost malignancies for both genders. Despite the high incidence rate and advances in diagnostic tools, treatment in many cases is still ineffective. Most cancerous lesions in CRC begin as benign, followed by the development of invasive forms and metastases. The development of CRC has been linked to defects in autophagy, which plays both a pro-and anti-tumor role and is mainly context-dependent. Autophagy suppression could enhance apoptosis via p53 activation, or autophagy also promotes tumor progression by maintaining tumor growth and increasing resistance to chemotherapy. Autophagy promotes the invasion and metastasis of CRC cells via increased epithelial-mesenchymal transition (EMT). Moreover, dysbiosis of gut microbiota upregulated autophagy and metastasis markers. Autophagy responses may also modulate the tumor microenvironment (TME) via regulating the differentiation process of several innate immune cells. Treatments that promote tumor cell death by stimulating or inhibiting autophagy could be beneficial if used as an adjunct treatment, but the precise role of various autophagy-modulating drugs in CRC patients is needed to be explored. In this article, we present an overview of the autophagy process and its role in the pathogenesis and therapeutic resistance of CRC. Also, we focused on the current understanding of the role of the EMT and TME, including its relation to gut microbiota and immune cells, in autophagic manipulation of CRC. We believe that there is a potential link between autophagy, TME, EMT, and drug resistance, suggesting that further studies are needed to explore this aspect.

Induction of autophagy-dependent ferroptosis to eliminate drug-tolerant human retinoblastoma cells

Carboplatin is the most used first-line drug for the treatment of human retinoblastoma (RB), a rare form of cancer in infancy and childhood. However, the clinical application of carboplatin is restricted due to the emergence of acquired multi-drug resistance (MDR) after long-term treatment. Here, we report a new strategy to eliminate MDR RB cells by inducing autophagy-dependent ferroptosis. Compared with parent cells, carboplatin-resistant human RB cells have higher autophagy activity, which drives the formation of MDR to other chemotherapeutic drugs (e.g., etoposide and vincristine). In addition to confirming the traditional strategy of inhibiting autophagy to overcome MDR, we also establish an approach of inducing selective ferritinophagy to eliminate drug-resistant cells. We evaluate the effectiveness and safety of 4-octyl itaconate, a cell-permeable derivative of the metabolite itaconate, in inducing ferritinophagy-dependent ferroptosis in the treatment of MDR RB cells in vitro and in xenograft mouse models. These findings may provide essential clues for initiating clinical trials that target autophagy-dependent ferroptosis to kill drug-tolerant persistent cells during RB therapy.

Mechanisms and Therapeutic Strategies of Viral Myocarditis Targeting Autophagy

Viral myocarditis is caused by infection with viruses or bacteria, including coxsackievirus B3 (CVB3), and is characterized by acute or chronic inflammatory responses in the heart. The mortality associated with severe viral myocarditis is considerable. In some patients, viral myocarditis may develop into dilated cardiomyopathy or heart failure. Autophagy is involved in a wide range of physiological processes, including viral infection and replication. In the present review, we focus on the responses of cardiac tissues, cardiomyocytes, and cardiac fibroblasts to CVB3 infection. Subsequently, the effects of altered autophagy on the development of viral myocarditis are discussed. Finally, this review also examined and assessed the use of several popular autophagy modulating drugs, such as metformin, resveratrol, rapamycin, wortmannin, and 3-methyladenine, as alternative treatment strategies for viral myocarditis.

The Role of Autophagy in the Function of CD4+ T Cells and the Development of Chronic Inflammatory Diseases

Uncontrolled acute inflammation progresses to persistent inflammation that leads to various chronic inflammatory diseases, including asthma, Crohn’s disease, rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus. CD4⁺ T cells are key immune cells that determine the development of these chronic inflammatory diseases. CD4⁺ T cells orchestrate adaptive immune responses by producing cytokines and effector molecules. These functional roles of T cells vary depending on the surrounding inflammatory or anatomical environment. Autophagy is an important process that can regulate the function of CD4⁺ T cells. By lysosomal degradation of cytoplasmic materials, autophagy mediates CD4⁺ T cell-mediated immune responses, including cytokine production, proliferation, and differentiation. Furthermore, through canonical processes involving autophagy machinery, autophagy also contributes to the development of chronic inflammatory diseases. Therefore, a targeted intervention of autophagy processes could be used to treat chronic inflammatory diseases. This review focuses on the role of autophagy via CD4⁺ T cells in the pathogenesis and treatment of such diseases. In particular, we explore the underlying mechanisms of autophagy in the regulation of CD4⁺ T cell metabolism, survival, development, proliferation, differentiation, and aging. Furthermore, we suggest that autophagy-mediated modulation of CD4⁺ T cells is a promising therapeutic target for treating chronic inflammatory diseases.

Rewiring mitochondrial metabolism to counteract exhaustion of CAR-T cells

Short persistence and early exhaustion of T cells are major limits to the efficacy and broad application of immunotherapy. Exhausted T and chimeric antigen receptor (CAR)-T cells upregulate expression of genes associated with terminated T cell differentiation, aerobic glycolysis and apoptosis. Among cell exhaustion characteristics, impaired mitochondrial function and dynamics are considered hallmarks. Here, we review the mitochondrial characteristics of exhausted T cells and particularly discuss different aspects of mitochondrial metabolism and plasticity. Furthermore, we propose a novel strategy of rewiring mitochondrial metabolism to emancipate T cells from exhaustion and of targeting mitochondrial plasticity to boost CAR-T cell therapy efficacy.

Senescent CD4+CD28- T Lymphocytes as a Potential Driver of Th17/Treg Imbalance and Alveolar Bone Resorption during Periodontitis

Senescent cells express a senescence-associated secretory phenotype (SASP) with a pro-inflammatory bias, which contributes to the chronicity of inflammation. During chronic inflammatory diseases, infiltrating CD4⁺ T lymphocytes can undergo cellular senescence and arrest the surface expression of CD28, have a response biased towards T-helper type-17 (Th17) of immunity, and show a remarkable ability to induce osteoclastogenesis. As a cellular counterpart, T regulatory lymphocytes (Tregs) can also undergo cellular senescence, and CD28⁻ Tregs are able to express an SASP secretome, thus severely altering their immunosuppressive capacities. During periodontitis, the persistent microbial challenge and chronic inflammation favor the induction of cellular senescence. Therefore, senescence of Th17 and Treg lymphocytes could contribute to Th17/Treg imbalance and favor the tooth-supporting alveolar bone loss characteristic of the disease. In the present review, we describe the concept of cellular senescence; particularly, the one produced during chronic inflammation and persistent microbial antigen challenge. In addition, we detail the different markers used to identify senescent cells, proposing those specific to senescent T lymphocytes that can be used for periodontal research purposes. Finally, we discuss the existing literature that allows us to suggest the potential pathogenic role of senescent CD4⁺CD28⁻ T lymphocytes in periodontitis.

Autophagy modulation in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis (MS), a white matter demyelinating disease of the central nervous system (CNS), is characterized by neuroinflammatory and neurodegenerative. Experimental autoimmune encephalomyelitis (EAE) is a commonly used animal model for investigating pathogenic mechanisms of MS, representing the destruction of the blood-brain barrier (BBB), the activation of T cells, and the infiltration of myeloid cells. An increasing number of studies have documented that autophagy plays a critical role in the pathogenesis of both MS and EAE. Autophagy maintains CNS homeostasis by degrading the damaged organelles and abnormal proteins. Furthermore, autophagy is involved in inflammatory responses by regulating the activation of immune cells and the secretion of inflammatory factors. However, the specific mechanisms of autophagy involved in MS and EAE are not completely understood. In this review, we will summarize the complex mechanisms of autophagy in MS and EAE, providing potential therapeutic approaches for the management of MS.

A single-cell atlas reveals shared and distinct immune responses and metabolism during SARS-CoV-2 and HIV-1 infections

SARS-CoV-2 and HIV-1 are RNA viruses that have killed millions of people worldwide. Understanding the similarities and differences between these two infections is critical for understanding disease progression and for developing effective vaccines and therapies, particularly for 38 million HIV-1 ⁺ individuals who are vulnerable to SARS-CoV-2 co-infection. Here, we utilized single-cell transcriptomics to perform a systematic comparison of 94,442 PBMCs from 7 COVID-19 and 9 HIV-1 ⁺ patients in an integrated immune atlas, in which 27 different cell types were identified using an accurate consensus single-cell annotation method. While immune cells in both cohorts show shared inflammation and disrupted mitochondrial function, COVID-19 patients exhibit stronger humoral immunity, broader IFN-I signaling, elevated Rho GTPase and mTOR pathway activities, and downregulated mitophagy. Our results elucidate transcriptional signatures associated with COVID-19 and HIV-1 that may reveal insights into fundamental disease biology and potential therapeutic targets to treat these viral infections.

HIGHLIGHTS

COVID-19 and HIV-1 ⁺ patients show disease-specific inflammatory immune signatures COVID-19 patients show more productive humoral responses than HIV-1 ⁺ patients SARS-CoV-2 elicits more enriched IFN-I signaling relative to HIV-IDivergent, impaired metabolic programs distinguish SARS-CoV-2 and HIV-1 infections.

Over Fifty Years of Life, Death, and Cannibalism: A Historical Recollection of Apoptosis and Autophagy

Research in biomedical sciences has changed dramatically over the past fifty years. There is no doubt that the discovery of apoptosis and autophagy as two highly synchronized and regulated mechanisms in cellular homeostasis are among the most important discoveries in these decades. Along with the advancement in molecular biology, identifying the genetic players in apoptosis and autophagy has shed light on our understanding of their function in physiological and pathological conditions. In this review, we first describe the history of key discoveries in apoptosis with a molecular insight and continue with apoptosis pathways and their regulation. We touch upon the role of apoptosis in human health and its malfunction in several diseases. We discuss the path to the morphological and molecular discovery of autophagy. Moreover, we dive deep into the precise regulation of autophagy and recent findings from basic research to clinical applications of autophagy modulation in human health and illnesses and the available therapies for many diseases caused by impaired autophagy. We conclude with the exciting crosstalk between apoptosis and autophagy, from the early discoveries to recent findings.

MicroRNA-590-3p inhibits T helper 17 cells and ameliorates inflammation in lupus mice

T helper 17 (Th17) cells have a pathogenic effect in many autoimmune diseases. Inhibition of Th17 cells can alleviate the inflammatory damage in autoimmune diseases. Our previous study found that microRNA-590-3p (miR-590-3p) was involved in the differentiation of Th17 cells in systemic lupus erythematosus (SLE). Here, we demonstrated that an increase in Th17 cells was correlated with low expression of miR-590-3p in patients with SLE and in lupus mice. Upregulation of miR-590-3p reduced the differentiation and promoted apoptosis of Th17 cells. Subsequent experiments demonstrated that miR-590-3p promoted apoptosis in Th17 cells by inhibiting autophagy. Autophagy-related 7 (Atg7) was the direct target of miR-590-3p that blocked the autophagy pathway. Finally, treatment of MRL/lpr mice with miR-590-3p agomir ameliorated lupus nephritis and skin lesions. Our work revealed that miR-590-3p inhibited Th17 cells by suppressing autophagy and that increased miR-590-3p expression was able to ameliorate the clinical symptoms of lupus. Therefore, miR-590-3p may be a promising therapeutic target for SLE and other Th17 cell-dependent autoimmune diseases.

Therapeutic Targeting of Immune Cell Autophagy in Multiple Sclerosis: Russian Roulette or Silver Bullet?

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) in which the immune system damages the protective insulation surrounding nerve fibers that project from neurons. The pathological hallmark of MS is multiple areas of myelin loss accompanied by inflammation within the CNS, resulting in loss of cognitive function that ultimately leads to paralysis. Recent studies in MS have focused on autophagy, a cellular self-eating process, as a potential target for MS treatment. Here, we review the contribution of immune cell autophagy to the pathogenesis of experimental autoimmune encephalomyelitis (EAE), the prototypic animal model of MS. A better understanding of the role of autophagy in different immune cells to EAE might inform the development of novel therapeutic approaches in MS and other autoimmune and inflammatory diseases.

HBV-Specific CD8+ T-Cell Tolerance in the Liver

Hepatitis B virus (HBV) remains a leading cause of liver-related morbidity and mortality through chronic hepatitis that may progress to liver cirrhosis and cancer. The central role played by HBV-specific CD8+ T cells in the clearance of acute HBV infection, and HBV-related liver injury is now well established. Vigorous, multifunctional CD8+ T cell responses are usually induced in most adult-onset HBV infections, while chronic hepatitis B (CHB) is characterized by quantitatively and qualitatively weak HBV-specific CD8+ T cell responses. The molecular basis of this dichotomy is poorly understood. Genomic analysis of dysfunctional HBV-specific CD8+ T cells in CHB patients and various mouse models suggest that multifaceted mechanisms including negative signaling and metabolic abnormalities cooperatively establish CD8+ T cell dysfunction. Immunoregulatory cell populations in the liver, including liver resident dendritic cells (DCs), hepatic stellate cells (HSCs), myeloid-derived suppressor cells (MDSCs), may contribute to intrahepatic CD8+ T cell dysfunction through the production of soluble mediators, such as arginase, indoleamine 2,3-dioxygenase (IDO) and suppressive cytokines and the expression of co-inhibitory molecules. A series of recent studies with mouse models of HBV infection suggest that genetic and epigenetic changes in dysfunctional CD8+ T cells are the manifestation of prolonged antigenic stimulation, as well as the absence of co-stimulatory or cytokine signaling. These new findings may provide potential new targets for immunotherapy aiming at invigorating HBV-specific CD8+ T cells, which hopefully cures CHB.

The role of miRNAs in the regulation of autophagy in autoimmune diseases

Autoimmune diseases (AD), which are classified as chronic injuries, are caused by a specific auto-reactive reaction. The etiology of most ADs is not well understood. Meanwhile, Autophagy is a protective response defining as a catabolic method by lysosomes tending to maintain homeostasis acts by recycling and discrediting cell compartments. Autophagy plays a crucial role in controlling immune homeostasis by eliminating intracellular pathogens and presenting antigens to immune cognition. MicroRNAs are commonly known as endogenous non-coding small RNAs, which span 18-25 nt and take part in the gene expression at the post-transcriptional level regulation. miRNAs play important roles in different processes like, cell differentiation, duplicating, and apoptosis. Moreover, miRNAs are the critical molecules for the regular function of the immune system by modulating immune tolerance mechanisms and autoimmunity. Recent findings support the role of dysregulated miRNAs in the pathogenesis of ADs and in the regulation of autophagy. In this review, we will focus on the role of the miRNAs in the regulation of autophagy and then will explain the role of dysregulated miRNAs in the initiation of the ADs by modulating autophagy.

Regulation of eosinophil functions by autophagy

Eosinophils are granule-containing leukocytes which develop in the bone marrow. For many years, eosinophils have been recognized as cytotoxic effector cells, but recent studies suggest that they perform additional immunomodulatory and homeostatic functions. Autophagy is a conserved intracellular process which preserves cellular homeostasis. Autophagy defects have been linked to the pathogenesis of many human disorders. Evidence for abnormal regulation of autophagy, including decreased or increased expression of autophagy-related (ATG) proteins, has been reported in several eosinophilic inflammatory disorders, such as Crohn's disease, bronchial asthma, eosinophilic esophagitis, and chronic rhinosinusitis. Despite the increasing extent of research using preclinical models of immune cell-specific autophagy deficiency, the physiological relevance of autophagic pathway in eosinophils has remained unknown until recently. Owing to the increasing evidence that eosinophils play a role in keeping organismal homeostasis, the regulation of eosinophil functions is of considerable interest. Here, we discuss the most recent advances on the role of autophagy in eosinophils, placing particular emphasis on insights obtained in mouse models of infections and malignant diseases in which autophagy has genetically dismantled in the eosinophil lineage. These studies pointed to the possibility that autophagy-deficient eosinophils exaggerate inflammation. Therefore, the pharmacological modulation of the autophagic pathway in these cells could be used for therapeutic interventions.

CD4+ T-cell differentiation and function: Unifying glycolysis, fatty acid oxidation, polyamines NAD mitochondria

The progression through different steps of T-cell development, activation, and effector function is tightly bound to specific cellular metabolic processes. Previous studies established that T-effector cells have a metabolic bias toward aerobic glycolysis, whereas naive and regulatory T cells mainly rely on oxidative phosphorylation. More recently, the field of immunometabolism has drifted away from the notion that mitochondrial metabolism holds little importance in T-cell activation and function. Of note, T cells possess metabolic promiscuity, which allows them to adapt their nutritional requirements according to the tissue environment. Altogether, the integration of these metabolic pathways culminates in the generation of not only energy but also intermediates, which can regulate epigenetic programs, leading to changes in T-cell fate. In this review, we discuss the recent literature on how glycolysis, amino acid catabolism, and fatty acid oxidation work together with the tricarboxylic acid cycle in the mitochondrion. We also emphasize the importance of the electron transport chain for T-cell immunity. We also discuss novel findings highlighting the role of key enzymes, accessory pathways, and posttranslational protein modifications that distinctively regulate T-cell function and might represent prominent candidates for therapeutic purposes.

Autophagy in T-cell differentiation, survival and memory

Over the past decade, autophagy has emerged as a critical regulatory mechanism of the immune system through critically controlling various aspects of T cell biology and determining the fate of different T cell subsets. Autophagy maintains T cell development and survival by regulating the degradation of organelles and apoptotic proteins. The autophagic process also impacts the formation of memory T cells. Alteration of autophagy in T cells may lead to a variety of pathological conditions such as inflammation, autoimmune diseases and cancer. In this review, we discuss how autophagy impacts T cell differentiation, survival and memory, and its implication in immunotherapy for various diseases.

Emerging role of autophagy in anti-tumor immunity: Implications for the modulation of immunotherapy resistance

Immunotherapies such as CAR-T cell transfer and antibody-targeted therapy have produced promising clinical outcomes in patients with advanced and metastatic cancer that are resistant to conventional therapies. However, with increasing use of cancer immunotherapy in clinical treatment, multiple therapy-resistance mechanisms have gradually emerged. The tumor microenvironment (TME), an integral component of cancer, can significantly influence the therapeutic response. Thus, it is worth exploring the potential of TME in modulating therapy resistance, in the hope to devise novel strategies to reinforcing anti-cancer treatments such as immunotherapy. As a crucial recycling process in the complex TME, the role of autophagy in tumor immunity has been increasingly appreciated. Firstly, autophagy in tumor cells can affect their immune response through modulating MHC-I-antigen complexes, thus modulating immunogenic tumor cell death, changing functions of immune cells via secretory autophagy, reducing the NK- and CTL-mediated cell lysis and degradation of immune checkpoint proteins. Secondly, autophagy is critical for the differentiation, maturation and survival of immune cells in the TME and can significantly affect the immune function of these cells, thereby regulating the anti-tumor immune response. Thirdly, alteration of autophagic activity in stromal cells, especially in fibroblasts, can reconstruct the three-dimensional stromal environment and metabolic reprogramming in the TME. A number of studies have demonstrated that optimal induction or inhibition of autophagy may lead to effective therapeutic regimens when combined with immunotherapy. This review discusses the important roles of autophagy in tumor cells, immune cells and stromal cells in the context of tumor immunity, and the potential of combining the autophagy-based therapy with immunotherapy as novel therapeutic approaches against cancer.

The Intraflagellar Transport Protein IFT20 Recruits ATG16L1 to Early Endosomes to Promote Autophagosome Formation in T Cells

Lymphocyte homeostasis, activation and differentiation crucially rely on basal autophagy. The fine-tuning of this process depends on autophagy-related (ATG) proteins and their interaction with the trafficking machinery that orchestrates the membrane rearrangements leading to autophagosome biogenesis. The underlying mechanisms are as yet not fully understood. The intraflagellar transport (IFT) system, known for its role in cargo transport along the axonemal microtubules of the primary cilium, has emerged as a regulator of autophagy in ciliated cells. Growing evidence indicates that ciliogenesis proteins participate in cilia-independent processes, including autophagy, in the non-ciliated T cell. Here we investigate the mechanism by which IFT20, an integral component of the IFT system, regulates basal T cell autophagy. We show that IFT20 interacts with the core autophagy protein ATG16L1 and that its CC domain is essential for its pro-autophagic activity. We demonstrate that IFT20 is required for the association of ATG16L1 with the Golgi complex and early endosomes, both of which have been identified as membrane sources for phagophore elongation. This involves the ability of IFT20 to interact with proteins that are resident at these subcellular localizations, namely the golgin GMAP210 at the Golgi apparatus and Rab5 at early endosomes. GMAP210 depletion, while leading to a dispersion of ATG16L1 from the Golgi, did not affect basal autophagy. Conversely, IFT20 was found to recruit ATG16L1 to early endosomes tagged for autophagosome formation by the BECLIN 1/VPS34/Rab5 complex, which resulted in the local accumulation of LC3. Hence IFT20 participates in autophagosome biogenesis under basal conditions by regulating the localization of ATG16L1 at early endosomes to promote autophagosome biogenesis. These data identify IFT20 as a new regulator of an early step of basal autophagy in T cells.

Autophagy and heat: a potential role for heat therapy to improve autophagic function in health and disease

Autophagy is a crucial cell survival mechanism that involves the degradation and recycling of old or damaged organelles and proteins to maintain cellular homeostasis. Impairments in autophagy are central to the pathogenesis of many conditions including metabolic and neurodegenerative disorders, cardiovascular and pulmonary diseases, diabetes, and aging. Although various pharmacological agents may be able to stimulate autophagic function, to our knowledge, few interventions exist that have been deemed safe and effective in humans. An emerging body of evidence suggests that targeting the autophagic pathway via passive heating (heat therapy) may stimulate autophagic function. Therefore, the primary focus of the present review is to analyze the mechanisms in which passive heating induces autophagy as defined by in vitro and in vivo (animal and human) models. Our secondary focus is to examine the implications of utilizing passive heating to restore dysfunctional autophagy in chronic disease and aging. Finally, we discuss potential therapeutic strategies to implement passive heating to stimulate autophagic function in humans.

Mitophagy and the Brain

Stress mechanisms have long been associated with neuronal loss and neurodegenerative diseases. The origin of cell stress and neuronal loss likely stems from multiple pathways. These include (but are not limited to) bioenergetic failure, neuroinflammation, and loss of proteostasis. Cells have adapted compensatory mechanisms to overcome stress and circumvent death. One mechanism is mitophagy. Mitophagy is a form of macroautophagy, were mitochondria and their contents are ubiquitinated, engulfed, and removed through lysosome degradation. Recent studies have implicated mitophagy dysregulation in several neurodegenerative diseases and clinical trials are underway which target mitophagy pathways. Here we review mitophagy pathways, the role of mitophagy in neurodegeneration, potential therapeutics, and the need for further study.

Arf1 and Arf6 Synergistically Maintain Survival of T Cells during Activation

ADP-ribosylation factor (Arf) family consisting of six family members, Arf1-Arf6, belongs to Ras superfamily and orchestrates vesicle trafficking under the control of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins. It is well established that brefeldin A, a potent inhibitor of ArfGEFs, blocks cytokine secretion from activated T cells, suggesting that the Arf pathway plays important roles in T cell functions. In this study, because Arf1 and Arf6 are the best-characterized members among Arf family, we established T lineage-specific Arf1-deficient, Arf6-deficient, and Arf1/6 double-deficient mice to understand physiological roles of the Arf pathway in the immune system. Contrary to our expectation, Arf deficiency had little or no impact on cytokine secretion from the activated T cells. In contrast, the lack of both Arf1 and Arf6, but neither Arf1 nor Arf6 deficiency alone, rendered naive T cells susceptible to apoptosis upon TCR stimulation because of imbalanced expression of Bcl-2 family members. We further demonstrate that Arf1/6 deficiency in T cells alleviates autoimmune diseases like colitis and experimental autoimmune encephalomyelitis, whereas Ab response under Th2-polarizing conditions is seemingly normal. Our findings reveal an unexpected role for the Arf pathway in the survival of T cells during TCR-induced activation and its potential as a therapeutic target in the autoimmune diseases.

Autophagy in the Regulation of Tissue Differentiation and Homeostasis

Autophagy is a constitutive pathway that allows the lysosomal degradation of damaged components. This conserved process is essential for metabolic plasticity and tissue homeostasis and is crucial for mammalian post-mitotic cells. Autophagy also controls stem cell fate and defective autophagy is involved in many pathophysiological processes. In this review, we focus on established and recent breakthroughs aimed at elucidating the impact of autophagy in differentiation and homeostasis maintenance of endothelium, muscle, immune system, and brain providing a suitable framework of the emerging results and highlighting the pivotal role of autophagic response in tissue functions, stem cell dynamics and differentiation rates.