Atg5 but not Atg7 in dendritic cells enhances IL-2 and IFN-γ production by Toxoplasma gondii-reactive CD4+ T cells

Autophagy mediated immune response regulation and drug resistance in cancer

Autophagy is a critical regulator of cellular homeostasis. The proteins involved in autophagy orchestrate the functions to strike the balance between cell survival and cell death in context-specific situations like aging, infections, inflammation and most importantly carcinogenesis. One of the major dead-locks in cancer treatment is the development of resistance to the available drugs (multi-drug resistance) as well as immune-suppressions in patients. Different studies over time have shown that autophagy is being involved in chemotherapy by working hand in hand with apoptosis or drug resistance through proliferative signals. Resistance to various drugs, such as, Cisplatin, Vincristine, Tamoxifen (TAM) occurs by epigenetic modifications, changed expression levels of microRNAs (miRNAs/miRs), and long non-coding RNAs (lncRNAs), which are regulated by the aberrant autophagy levels in lung, and breast cancers. More interestingly in the tumour microenvironment the immune suppressor cells also bring in autophagy in different pathway regulations either helping or opposing the whole carcinogenesis process. Macrophages, T cells, B cells, dendritic cells (DCs), neutrophils, and fibroblasts show involvement of autophagy in their differentiation and development in the tumor microenvironment (TME). Here, this extensive review for the first time tries to bring under a single canopy, several recent examples of autophagy-mediated immune regulations and autophagy-mediated epigenetically regulated drug resistance in different types of cancers.

Inflammasomes and autophagy in cancer: unlocking targeted therapies

This study clarifies the interaction between autophagy and inflammasome within the cancer framework. The inflammasome generates pro-inflammatory cytokines to direct the immune response to pathogens and cellular stressors. Autophagy maintains cellular homeostasis and can either promote or inhibit cancer. These pathways interact to affect tumorigenesis, immune responses, and therapy. Autophagy controls inflammasome activity by affecting cancer pathogenesis and tumor microenvironment inflammation, highlighting novel cancer therapeutic approaches. Recent studies indicate that modulating autophagy and inflammasome pathways can boost anti-cancer immunity, reduce drug-resistance, and improve therapeutic efficacy. Recent studies indicate modulating inflammasome and autophagy pathways can augment anti-cancer immunity, mitigate therapy resistance, and improve treatment efficacy. Cancer research relies on understanding the inflammasome-autophagy relationship to develop targeted therapies that enhance anti-tumor efficacy and reduce inflammatory symptoms. Customized therapies may improve outcomes based on autophagy gene variations and inflammasome polymorphisms. This study investigates autophagy pathways and the inflammasome in tumor immunopathogenesis, cytokine function, and cancer therapeutic strategies, highlighting their significance in cancer biology and treatment.

The role of autophagy in cancer: from molecular mechanism to therapeutic window

Autophagy is a cellular degradation process that plays a crucial role in maintaining metabolic homeostasis under conditions of stress or nutrient deprivation. This process involves sequestering, breaking down, and recycling intracellular components such as proteins, organelles, and cytoplasmic materials. Autophagy also serves as a mechanism for eliminating pathogens and engulfing apoptotic cells. In the absence of stress, baseline autophagy activity is essential for degrading damaged cellular components and recycling nutrients to maintain cellular vitality. The relationship between autophagy and cancer is well-established; however, the biphasic nature of autophagy, acting as either a tumor growth inhibitor or promoter, has raised concerns regarding the regulation of tumorigenesis without inadvertently activating harmful aspects of autophagy. Consequently, elucidating the mechanisms by which autophagy contributes to cancer pathogenesis and the factors determining its pro- or anti-tumor effects is vital for devising effective therapeutic strategies. Furthermore, precision medicine approaches that tailor interventions to individual patients may enhance the efficacy of autophagy-related cancer treatments. To this end, interventions aimed at modulating the fate of tumor cells by controlling or inducing autophagy substrates necessitate meticulous monitoring of these mediators' functions within the tumor microenvironment to make informed decisions regarding their activation or inactivation. This review provides an updated perspective on the roles of autophagy in cancer, and discusses the potential challenges associated with autophagy-related cancer treatment. The article also highlights currently available strategies and identifies questions that require further investigation in the future.

The interplay between probiotics and host autophagy: mechanisms of action and emerging insights

Autophagy, a lysosome-dependent protein degradation mechanism, is a highly conserved catabolic process seen in all eukaryotes. This cell protection system, which is present in all tissues and functions at a basic level, can be up- or downregulated in response to various stresses. A disruption in the natural route of the autophagy process is frequently followed by an interruption in the inherent operation of the body's cells and organs. Probiotics are live bacteria that protect the host through various mechanisms. One of the processes through which probiotics exert their beneficial effects on various cells and tissues is autophagy. Autophagy can assist in maintaining host homeostasis by stimulating the immune system and affecting numerous physiological and pathological responses. In this review, we particularly focus on autophagy impairments occurring in several human illnesses and investigate how probiotics affect the autophagy process under various circumstances.Abbreviation: AD: Alzheimer disease; AKT: AKT serine/threonine kinase; AMPK: 5'AMP-activated protein kinase; ATG: autophagy related; CCl4: carbon tetrachloride; CFS: cell-free supernatant; CMA: chaperone-mediated autophagy; CRC: colorectal cancer; EPS: L. plantarum H31 exopolysaccharide; HD: Huntington disease; HFD: high-fat diet; HPV: human papillomavirus; IFNG/IFN-γ: interferon gamma; IL6: interleukin 6; LGG: L. rhamnosus GG; LPS: lipopolysaccharide; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; PD: Parkinson disease; Pg3G: pelargonidin-3-O-glucoside; PI3K: phosphoinositide 3-kinase; PolyQ: polyglutamine; ROS: reactive oxygen species; SCFAs: short-chain fatty acids; SLAB51: a novel formulation of lactic acid bacteria and bifidobacteria; Slp: surface layer protein (of acidophilus NCFM); SNCA: synuclein alpha; ULK1: unc-51 like autophagy-activating kinase 1; YB: B. longum subsp. infantis YB0411; YFP: yeast fermentate prebiotic.

Targeting secretory autophagy in solid cancers: mechanisms, immune regulation and clinical insights

Secretory autophagy is a classical form of unconventional secretion that integrates autophagy with the secretory process, relying on highly conserved autophagy-related molecules and playing a critical role in tumor progression and treatment resistance. Traditional autophagy is responsible for degrading intracellular substances by fusing autophagosomes with lysosomes. However, secretory autophagy uses autophagy signaling to mediate the secretion of specific substances and regulate the tumor microenvironment (TME). Cytoplasmic substances are preferentially secreted rather than directed toward lysosomal degradation, involving various selective mechanisms. Moreover, substances released by secretory autophagy convey biological signals to the TME, inducing immune dysregulation and contributing to drug resistance. Therefore, elucidating the mechanisms underlying secretory autophagy is essential for improving clinical treatments. This review systematically summarizes current knowledge of secretory autophagy, from initiation to secretion, considering inter-tumor heterogeneity, explores its role across different tumor types. Furthermore, it proposes future research directions and highlights unresolved clinical challenges.

Autophagy in cancer immunotherapy: Perspective on immune evasion and cell death interactions

Both the innate and adaptive immune systems work together to produce immunity. Cancer immunotherapy is a novel approach to tumor suppression that has arisen in response to the ineffectiveness of traditional treatments like radiation and chemotherapy. On the other hand, immune evasion can diminish immunotherapy's efficacy. There has been a lot of focus in recent years on autophagy and other underlying mechanisms that impact the possibility of cancer immunotherapy. The primary feature of autophagy is the synthesis of autophagosomes, which engulf cytoplasmic components and destroy them by lysosomal degradation. The planned cell death mechanism known as autophagy can have opposite effects on carcinogenesis, either increasing or decreasing it. It is autophagy's job to maintain the balance and proper functioning of immune cells like B cells, T cells, and others. In addition, autophagy controls whether macrophages adopt the immunomodulatory M1 or M2 phenotype. The ability of autophagy to control the innate and adaptive immune systems is noteworthy. Interleukins and chemokines are immunological checkpoint chemicals that autophagy regulates. Reducing antigen presentation to induce immunological tolerance is another mechanism by which autophagy promotes cancer survival. Therefore, targeting autophagy is of importance for enhancing potential of cancer immunotherapy.

Targeted Mevalonate Pathway and Autophagy in Antitumor Immunotherapy

Tumors of the digestive system are currently one of the leading causes of cancer-related death worldwide. Despite considerable progress in tumor immunotherapy, the prognosis for most patients remains poor. In the tumor microenvironment (TME), tumor cells attain immune escape through immune editing and acquire immune tolerance. The mevalonate pathway and autophagy play important roles in cancer biology, antitumor immunity, and regulation of the TME. In addition, there is metabolic crosstalk between the two pathways. However, their role in promoting immune tolerance in digestive system tumors has not previously been summarized. Therefore, this review focuses on the cancer biology of the mevalonate pathway and autophagy, the regulation of the TME, metabolic crosstalk between the pathways, and the evaluation of their efficacy as targeted inhibitors in clinical tumor immunotherapy.

Immunization of BALB/c Mice with Killed Tachyzoites of Toxoplasma gondii against Acute Toxoplasmosis

Background

Toxoplasma gondii with widespread distribution infects over one third of human populations in the world and can cause serious life-threatening diseases especially for the immunodeficient patients in acute toxoplasmosis. As the clinical pharmaceutical drugs with severe side effects for treatment and non-ideal extant vaccines for prevention, more work starves to be done for keeping advantages in the athletics.

Methods

Aluminum adjuvant and hybrid formaldehyde-killed tachyzoites of T. gondii RH and GT1 isolates were prepared to intramuscularly immunize BALB/c mice for five times at 0, 3, 7, 14 and 21 days post first injection. The triggered humoral and cellular immune responses at two weeks post the last immunization and the survival times of infected mice were examined for the hybrid immunization scheme judgement.

Results

The anti-RH and anti-GT1 specific antibodies were both increased at one week prior to challenge (P < 0.05), and the survival times of immunized mice (7.33 ± 0.71 d for RH, 7.22 ± 0.97 d for GT1) against acute toxoplasmosis were significantly prolonged by the immunizations performed in the study compared to blank control (6.67 ± 0.50 d for RH, 6.33 ± 0.71 d for GT1; P < 0.05), with the higher IFN-γ, IL-2 and IL-12p70 in sera, the elevated CD3e+CD4+ T and CD3e+CD8a+ T cells, and the enhanced lymphocyte proliferation in spleen (P < 0.05).

Conclusion

The hybrid killed tachyzoites with aluminum adjuvant induced humoral and cellular immune responses of mice, and offered mildly protective efficacy against acute toxoplasmosis.

Ferroptosis, autophagy, tumor and immunity

Ferroptosis was first proposed in 2012, a new form of cell death. Autophagy plays a crucial role in cell clearance and maintaining homeostasis. Autophagy is involved in the initial step of ferroptosis under the action of histone elements such as NCOA4, RAB7A, and BECN1. Ferroptosis and autophagy are involved in tumor progression, treatment, and drug resistance in the tumor microenvironment. In this review, we described the mechanisms of ferroptosis, autophagy, and tumor and immunotherapy, respectively, and emphasized the relationship between autophagy-related ferroptosis and tumor.

Overview of Apoptosis, Autophagy, and Inflammatory Processes in Toxoplasma gondii Infected Cells

Toxoplasma gondii (T. gondii) is an obligate intracellular parasite. During the parasitic invasion, T. gondii creates a parasitophorous vacuole, which enables the modulation of cell functions, allowing its replication and host infection. It has effective strategies to escape the immune response and reach privileged immune sites and remain inactive in a controlled environment in tissue cysts. This current review presents the factors that affect host cells and the parasite, as well as changes in the immune system during host cell infection. The secretory organelles of T. gondii (dense granules, micronemes, and rhoptries) are responsible for these processes. They are involved with proteins secreted by micronemes and rhoptries (MIC, AMA, and RONs) that mediate the recognition and entry into host cells. Effector proteins (ROP and GRA) that modify the STAT signal or GTPases in immune cells determine their toxicity. Interference byhost autonomous cells during parasitic infection, gene expression, and production of microbicidal molecules such as reactive oxygen species (ROS) and nitric oxide (NO), result in the regulation of cell death. The high level of complexity in host cell mechanisms prevents cell death in its various pathways. Many of these abilities play an important role in escaping host immune responses, particularly by manipulating the expression of genes involved in apoptosis, necrosis, autophagy, and inflammation. Here we present recent works that define the mechanisms by which T. gondii interacts with these processes in infected host cells.

Host autophagy limits Toxoplasma gondii proliferation in the absence of IFN-γ by affecting the hijack of Rab11A-positive vesicles

Introduction

Autophagy has been recognized as a bona fide immunological process. Evidence has shown that this process in IFN-γ stimulated cells controls Toxoplasma gondii proliferation or eliminates its infection. However, little is known about the effect of T. gondii infection on the host cell autophagy in the absence of IFN-γ.

Methods

Multiple autophagy detection methods and CRISPR/CAS9 technology were used to study T. gondii-induced autophagy in HeLa and several other mammalian cell lines.

Results

Here, we report increased LC3 II, autophagosome-like membrane structures, enhanced autophagic flux, and decreased lysosomes in a range of mammalian cell lines without IFN-γ treatment after T. gondii infection. Specifically, disruption of host atg5 (a necessary gene for autophagy) in HeLa cells promoted the intracellular replication of T. gondii, with the transcript level of rab11a increased, compared with that in wild-type cells. Further, after T. gondii infection, the abundance of Rab11A remained stable in wild-type HeLa cells but decreased in atg5 -/- mutant. Disruption of rab11a in the HeLa cells compromised the proliferation of T. gondii, and increased the transcription of gra2 in the parasite. Compared to the T. gondii wild-type RH∆ku80 strain, the ∆gra2 mutant induces enhanced host autophagy in HeLa cells, and results in slower replication of the parasite.

Discussion

Collectively, these results indicate that host cell autophagy can limit T. gondii proliferation in an IFN-γ independent manner, possibly by affecting the hijack of host Rab11A-positive vesicles by the parasite which involved TgGRA2. The findings provide novel insights into T. gondii infection in host cells and toxoplasmosis research.

Autophagy in Cancer Immunotherapy

Autophagy is a stress-induced process that eliminates damaged organelles and dysfunctional cargos in cytoplasm, including unfolded proteins. Autophagy is involved in constructing the immunosuppressive microenvironment during tumor initiation and progression. It appears to be one of the most common processes involved in cancer immunotherapy, playing bidirectional roles in immunotherapy. Accumulating evidence suggests that inducing or inhibiting autophagy contributes to immunotherapy efficacy. Hence, exploring autophagy targets and their modifiers to control autophagy in the tumor microenvironment is an emerging strategy to facilitate cancer immunotherapy. This review summarizes recent studies on the role of autophagy in cancer immunotherapy, as well as the molecular targets of autophagy that could wake up the immune response in the tumor microenvironment, aiming to shed light on its immense potential as a therapeutic target to improve immunotherapy.

Autophagy in Tumor Immunity and Viral-Based Immunotherapeutic Approaches in Cancer

Autophagy is a fundamental catabolic process essential for the maintenance of cellular and tissue homeostasis, as well as directly contributing to the control of invading pathogens. Unsurprisingly, this process becomes critical in supporting cellular dysregulation that occurs in cancer, particularly the tumor microenvironments and their immune cell infiltration, ultimately playing a role in responses to cancer therapies. Therefore, understanding "cancer autophagy" could help turn this cellular waste-management service into a powerful ally for specific therapeutics. For instance, numerous regulatory mechanisms of the autophagic machinery can contribute to the anti-tumor properties of oncolytic viruses (OVs), which comprise a diverse class of replication-competent viruses with potential as cancer immunotherapeutics. In that context, autophagy can either: promote OV anti-tumor effects by enhancing infectivity and replication, mediating oncolysis, and inducing autophagic and immunogenic cell death; or reduce OV cytotoxicity by providing survival cues to tumor cells. These properties make the catabolic process of autophagy an attractive target for therapeutic combinations looking to enhance the efficacy of OVs. In this article, we review the complicated role of autophagy in cancer initiation and development, its effect on modulating OVs and immunity, and we discuss recent progress and opportunities/challenges in targeting autophagy to enhance oncolytic viral immunotherapy.

Toxoplasma gondii profilin and tachyzoites RH strain may manipulate autophagy via downregulating Atg5 and Atg12 and upregulating Atg7

BACKGROUND

Autophagy process is an important defense mechanism against intracellular infection. This process plays a critical role in limiting the development of Toxoplasma gondii. This study aimed to investigate the effects of T. gondii profilin and tachyzoites on the expression of autophagy genes.

METHODS AND RESULTS

PMA-activated THP-1 cell line was incubated with T. gondii profilin and tachyzoites for 6 h. After RNA extraction and cDNA synthesis, the expression of Atg5, Atg7, Atg12, and LC3b was evaluated using real-time PCR. The results revealed statistically significant downregulation of Atg5 for 1.43 (P-value = 0.0062) and 4.15 (P-value = 0.0178) folds after treatment with T. gondii profilin and tachyzoites, respectively. Similar to Atg 5, Atg 12 revealed a statistically significant downregulation for profilin (1.41 fold; P-value = 0.0047) and T. gondii tachyzoites (3.25 fold; P-value = 0.011). The expression of Atg7 elevated in both T. gondii profilin (2.083 fold; P-value = 0.0087) and tachyzoites (1.64 fold; P-value = 0.206). T. gondii profilin and tachyzoites downregulated (1.04 fold; P-value = 0.0028) and upregulated (twofold; P-value = 0.091) the expression of LC3b, respectively.

CONCLUSIONS

Our findings suggest that T. gondii and profilin may manipulate autophagy via preventing from the formation of Atg5-12-16L complex to facilitate replication of T. gondii and development of toxoplasmosis.

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.

Emerging Autophagy Functions Shape the Tumor Microenvironment and Play a Role in Cancer Progression - Implications for Cancer Therapy

The tumor microenvironment (TME) is a complex environment where cancer cells reside and interact with different types of cells, secreted factors, and the extracellular matrix. Additionally, TME is shaped by several processes, such as autophagy. Autophagy has emerged as a conserved intracellular degradation pathway for clearance of damaged organelles or aberrant proteins. With its central role, autophagy maintains the cellular homeostasis and orchestrates stress responses, playing opposite roles in tumorigenesis. During tumor development, autophagy also mediates autophagy-independent functions associated with several hallmarks of cancer, and therefore exerting several effects on tumor suppression and/or tumor promotion mechanisms. Beyond the concept of degradation, new different forms of autophagy have been described as modulators of cancer progression, such as secretory autophagy enabling intercellular communication in the TME by cargo release. In this context, the synthesis of senescence-associated secretory proteins by autophagy lead to a senescent phenotype. Besides disturbing tumor treatment responses, autophagy also participates in innate and adaptive immune signaling. Furthermore, recent studies have indicated intricate crosstalk between autophagy and the epithelial-mesenchymal transition (EMT), by which cancer cells obtain an invasive phenotype and metastatic potential. Thus, autophagy in the cancer context is far broader and complex than just a cell energy sensing mechanism. In this scenario, we will discuss the key roles of autophagy in the TME and surrounding cells, contributing to cancer development and progression/EMT. Finally, the potential intervention in autophagy processes as a strategy for cancer therapy will be addressed.

Autophagy in the control and pathogenesis of parasitic infections

Background

Autophagy has a crucial role in the defense against parasites. The interplay existing between host autophagy and parasites has varied outcomes due to the kind of host cell and microorganism. The presence of autophagic compartments disrupt a significant number of pathogens and are further cleared by xenophagy in an autolysosome. Another section of pathogens have the capacity to outwit the autophagic pathway to their own advantage.

Result

To comprehend the interaction between pathogens and the host cells, it is significant to distinguish between starvation-induced autophagy and other autophagic pathways. Subversion of host autophagy by parasites is likely due to differences in cellular pathways from those of ‘classical’ autophagy and that they are controlled by parasites in a peculiar way. In xenophagy clearance at the intracellular level, the pathogens are first ubiquitinated before autophagy receptors acknowledgement, followed by labeling with light chain 3 (LC3) protein. The LC3 in LC3-associated phagocytosis (LAP) is added directly into vacuole membrane and functions regardless of the ULK, an initiation complex. The activation of the ULK complex composed of ATG13, FIP200 and ATG101causes the initiation of host autophagic response. Again, the recognition of PAMPs by conserved PRRs marks the first line of defense against pathogens, involving Toll-like receptors (TLRs). These all important immune-related receptors have been reported recently to regulate autophagy.

Conclusion

In this review, we sum up recent advances in autophagy to acknowledge and understand the interplay between host and parasites, focusing on target proteins for the design of therapeutic drugs. The target host proteins on the initiation of the ULK complex and PRRs-mediated recognition of PAMPs may provide strong potential for the design of therapeutic drugs against parasitic infections.

Targeting Autophagy in Innate Immune Cells: Angel or Demon During Infection and Vaccination?

Innate immune cells are the "doorkeepers" in the immune system and are important for the initiation of protective vaccine responses against infection. Being an essential regulatory component of the immune system in these cells, autophagy not only mediates pathogen clearance and cytokine production, but also balances the immune response by preventing harmful overreaction. Interestingly, recent literature indicates that autophagy is positively or negatively regulating the innate immune response in a cell type-specific manner. Moreover, autophagy serves as a bridge between innate and adaptive immunity. It is involved in antigen presentation by delivering pathogen compounds to B and T cells, which is important for effective immune protection. Upon infection, autophagy can also be hijacked by some pathogens for replication or evade host immune responses. As a result, autophagy seems like a double-edged sword to the immune response, strongly depending on the cell types involved and infection models used. In this review, the dual role of autophagy in regulating the immune system will be highlighted in various infection models with particular focus on dendritic cells, monocytes/macrophages and neutrophils. Targeting autophagy in these cells as for therapeutic application or prophylactic vaccination will be discussed considering both roles of autophagy, the "angel" enhancing innate immune responses, antigen presentation, pathogen clearance and dampening inflammation or the "demon" enabling viral replication and degrading innate immune components. A better understanding of this dual potential will help to utilize autophagy in innate immune cells in order to optimize vaccines or treatments against infectious diseases.

Activation of autophagy and IL-10 production are regulated by Jun N-terminal kinase 1 and 2 and p38 mitogen activated protein kinase signaling pathways during Talaromyces marneffei infection within dendritic cells

Previous study have shown that Talaromyces marneffei (T. marneffei) induced activation of autophagy. Therefore, we explore signaling pathway that regulates activation of autophagy by intracellular signaling mechanisms during T. marneffei infection. Further, we examine c-Jun N-terminal kinase 1 and 2 (JNK1/2) and p38 signaling pathways that regulate IL-1β and IL-10 production and activation of autophagy during T. marneffei infection in human dendritic cells (DCs). We found that T. marneffei induced activation of JNK1/2 and p38 in human DCs. Furthermore, the inhibition of JNK1/2 and p38 increased activation of autophagy and decreased the replication of T. marneffei in T. marneffei-infected human DCs. Moreover, IL-1β secretion in T. marneffei-infected human DCs was dependent on JNK1/2 and autophagy pathways, whereas IL-10 secretion was dependent on JNK1/2, p38 and autophagy pathways. These data suggest that JNK1/2 and p38 pathways play critical roles in activation of autophagy, the multiplication of T. marneffei and subsequent cytokine production during T. marneffei infection.

Toxoplasma and Dendritic Cells: An Intimate Relationship That Deserves Further Scrutiny

Toxoplasma gondii (Tg), an obligate intracellular parasite of the phylum Apicomplexa, infects a wide range of animals, including humans. A hallmark of Tg infection is the subversion of host responses, which is thought to favor parasite persistence and propagation to new hosts. Recently, a variety of parasite-secreted modulatory effectors have been uncovered in fibroblasts and macrophages, but the specific interplay between Tg and dendritic cells (DCs) is just beginning to emerge. In this review, we summarize the current knowledge on Tg-DC interactions, including innate recognition, cytokine production, and antigen presentation, and discuss open questions regarding how Tg-secreted effectors may shape DC functions to perturb innate and adaptive immunity.

CD40 in Endothelial Cells Restricts Neural Tissue Invasion by Toxoplasma gondii

Little is known about whether pathogen invasion of neural tissue is affected by immune-based mechanisms in endothelial cells. We examined the effects of endothelial cell CD40 on Toxoplasma gondii invasion of the retina and brain, organs seeded hematogenously. T. gondii circulates in the bloodstream within infected leukocytes (including monocytes and dendritic cells) and as extracellular tachyzoites. After T. gondii infection, mice that expressed CD40 restricted to endothelial cells exhibited diminished parasite loads and histopathology in the retina and brain. These mice also had lower parasite loads in the retina and brain after intravenous (i.v.) injection of infected monocytes or dendritic cells. The protective effect of endothelial cell CD40 was not explained by changes in cellular or humoral immunity, reduced transmigration of leukocytes into neural tissue, or reduced invasion by extracellular parasites. Circulating T. gondii-infected leukocytes (dendritic cells used as a model) led to infection of neural endothelial cells. The number of foci of infection in these cells were reduced if endothelial cells expressed CD40. Infected dendritic cells and macrophages expressed membrane-associated inducible Hsp70. Infected leukocytes triggered Hsp70-dependent autophagy in CD40⁺ endothelial cells and anti-T. gondii activity dependent on ULK1 and beclin 1. Reduced parasite load in the retina and brain not only required CD40 expression in endothelial cells but was also dependent on beclin 1 and the expression of inducible Hsp70 in dendritic cells. These studies suggest that during endothelial cell-leukocyte interaction, CD40 restricts T. gondii invasion of neural tissue through a mechanism that appears mediated by endothelial cell anti-parasitic activity stimulated by Hsp70.

Decreased Autophagy Impairs Decidualization of Human Endometrial Stromal Cells: A Role for ATG Proteins in Endometrial Physiology

During the menstrual cycle, the endometrium undergoes cyclic changes of cellular proliferation, differentiation, and death, an essential preparation of the endometrium for its interaction with the implanting embryo. In particular, the differentiation of endometrial stromal cells, named decidualization, ensures the formation of a proper feto-maternal interface for a regulated trophoblast invasion and correct placental orientation and growth. Interestingly, autophagy, an intracellular degradation process of great importance for the maintenance of cellular homeostasis, plays an important role in cell proliferation, differentiation, and growth. In the endometrium, increased detection of autophagy markers correlates with the progression of the menstrual cycle. However, until now, it was unknown whether autophagy contributes to the proper function of the endometrium. In this study, we show that autophagy is increased during in vitro decidualization of human endometrial stromal cells. Furthermore, we demonstrate that the knockdowns of two important autophagy-related (ATG) proteins, ATG7 and ATG5, impaired decidualization, confirming a positive role of these proteins and of autophagy for the correct decidualization of human endometrial stromal cells. In conclusion, in this work, we describe a previously unknown functional connection between autophagy and endometrial physiology.

Interplay Between Toxoplasma gondii, Autophagy, and Autophagy Proteins

Survival of Toxoplasma gondii within host cells depends on its ability of reside in a vacuole that avoids lysosomal degradation and enables parasite replication. The interplay between immune-mediated responses that lead to either autophagy-driven lysosomal degradation or disruption of the vacuole and the strategies used by the parasite to avoid these responses are major determinants of the outcome of infection. This article provides an overview of this interplay with an emphasis on autophagy.

The relationship between autophagy and the immune system and its applications for tumor immunotherapy

Autophagy is a genetically well-controlled cellular process that is tightly controlled by a set of core genes, including the family of autophagy-related genes (ATG). Autophagy is a “double-edged sword” in tumors. It can promote or suppress tumor development, which depends on the cell and tissue types and the stages of tumor. At present, tumor immunotherapy is a promising treatment strategy against tumors. Recent studies have shown that autophagy significantly controls immune responses by modulating the functions of immune cells and the production of cytokines. Conversely, some cytokines and immune cells have a great effect on the function of autophagy. Therapies aiming at autophagy to enhance the immune responses and anti-tumor effects of immunotherapy have become the prospective strategy, with enhanced antigen presentation and higher sensitivity to CTLs. However, the induction of autophagy may also benefit tumor cells escape from immune surveillance and result in intrinsic resistance against anti-tumor immunotherapy. Increasing studies have proven the optimal use of either ATG inducers or inhibitors can restrain tumor growth and progression by enhancing anti-tumor immune responses and overcoming the anti-tumor immune resistance in combination with several immunotherapeutic strategies, indicating that induction or inhibition of autophagy might show us a prospective therapeutic strategy when combined with immunotherapy. In this article, the possible mechanisms of autophagy regulating immune system, and the potential applications of autophagy in tumor immunotherapy will be discussed.

Impact of Autophagy of Innate Immune Cells on Inflammatory Bowel Disease

Autophagy, an intracellular degradation mechanism, has many immunological functions and is a constitutive process necessary for maintaining cellular homeostasis and organ structure. One of the functions of autophagy is to control the innate immune response. Many studies conducted in recent years have revealed the contribution of autophagy to the innate immune response, and relationships between this process and various diseases have been reported. Inflammatory bowel disease is an intractable disorder with unknown etiology; however, immunological abnormalities in the intestines are known to be involved in the pathology of inflammatory bowel disease, as is dysfunction of autophagy. In Crohn's disease, many associations with autophagy-related genes, such as ATG16L1, IRGM, NOD2, and others, have been reported. Abnormalities in the ATG16L1 gene, in particular, have been reported to cause autophagic dysfunction, resulting in enhanced production of inflammatory cytokines by macrophages as well as abnormal function of Paneth cells, which are important in intestinal innate immunity. In this review, we provide an overview of the autophagy mechanism in innate immune cells in inflammatory bowel disease.

The role of host autophagy machinery in controlling Toxoplasma infection

Toxoplasma gondii is an obligate intracellular parasitic protist that infects a wide range of warm-blooded vertebrates. Although this parasite can cause serious complications, infections are often asymptomatic, allowing T. gondii to persist in its host and possibly enhancing the chances of its transmission. T. gondii has thus evolved multiple mechanisms of host manipulation to establish chronic infection. This persistence involves a balance between host immunity and parasite evasion of this immune response. This review highlights recent investigations that have demonstrated the important role played by the autophagy machinery in this balance, both in parasite control by the host, and in host exploitation by the parasite.

Autophagy and proinflammatory cytokines: Interactions and clinical implications

Autophagy is a ubiquitous cellular process that regulates cell growth, survival, development and death. Its process is closely associated with diverse conditions, such as liver diseases, neurodegenerative diseases, myopathy, heart diseases, cancer, immunization, and inflammatory diseases. Thus, understanding the modulation of autophagy may provide novel insight into potential therapeutic targets. Autophagy is closely intertwined with inflammatory and immune responses, and cytokines may help mediate this interaction. Autophagy has been shown to regulate, and be regulated by, a wide range of proinflammatory cytokines. This review aims to summarize recent progress in elucidating the interplay between autophagy and proinflammatory cytokines, including IFN-γ, TNF-α, IL-17, and cytokines of the IL-1 family (e.g., IL-1α, IL-1β, IL-33, and IL-36).

Autophagy in dendritic cells

Autophagy and immunity share the property of being auto-protective for the organism. Autophagy is an important degradation pathway that buffers nutrient deprivation by recycling macromolecules in organisms from yeast to man. Perturbations in autophagy are associated with inflammation and cancer development. Emerging studies have characterized the molecular details regarding how autophagy is controlled by immune cells. Among these, dendritic cells (DCs) are one of the most potent professional antigen-presenting cells critical for the activation of naïve T cells to maintain immune tolerance and drive protective immunity to infection and cancer. DCs undergo functional maturation that can either lead to an immunostimulatory phenotype, as in the context of infection, or to a tolerogenic phenotype associated with immunosuppression to self-antigens, as well as to cancer. An increasing number of recent studies has characterized the involvement of autophagy in DC functions in various physiological and pathological contexts. Here, we provide a comprehensive review of these outcomes and discuss the limitation of the models used and the forefront of the knowledge concerning the crosstalk between autophagy and DC biology.

Autophagy-independent increase of ATG5 expression in T cells of multiple sclerosis patients

Autophagy, a process of controlled self-digestion which regulates cell homeostasis, is involved in innate and adaptive immunity. We investigated the expression of autophagy genes and autophagic activity in distinct lymphocyte populations in treatment-naive MS patients. The mRNA and protein levels of autophagy-related (ATG)5, required for autophagosome formation, were increased in CD4⁺ and CD4^- T cells, but not B cells of MS patients compared to control subjects. The expression of other investigated autophagy genes, as well as the autophagic activity, did not significantly differ between the two groups. ATG5 mRNA levels in CD4⁺ T cells from MS patients were positively correlated with those of the proinflammatory cytokine tumor necrosis factor. These data suggest that autophagy-independent increase in ATG5 expression might be associated with the proinflammatory capacity of T cells in multiple sclerosis.

Autophagy: A Potential Therapeutic Target for Reversing Sepsis-Induced Immunosuppression

Sepsis remains the leading cause of mortality in intensive care units and an intractable condition due to uncontrolled inflammation together with immune suppression. Dysfunction of immune cells is considered as a major cause for poor outcome of septic patients but with little specific treatments. Currently, autophagy that is recognized as an important self-protective mechanism for cellular survival exhibits great potential for maintaining immune homeostasis and alleviating multiple organ failure, which further improves survival of septic animals. The protective effect of autophagy on immune cells covers both innate and adaptive immune responses and refers to various cellular receptors and intracellular signaling. Multiple drugs and measures are reportedly beneficial for septic challenge by inducing autophagy process. Therefore, autophagy might be an effective target for reversing immunosuppression compromised by sepsis.

Apicomplexan autophagy and modulation of autophagy in parasite-infected host cells

Apicomplexan parasites are responsible for a number of important human pathologies. Obviously, as Eukaryotes they share a number of cellular features and pathways with their respective host cells. One of them is autophagy, a process involved in the degradation of the cell's own components. These intracellular parasites nonetheless seem to present a number of original features compared to their very evolutionarily distant host cells. In mammals and other metazoans, autophagy has been identified as an important contributor to the defence against microbial pathogens. Thus, host autophagy also likely plays a key role in the control of apicomplexan parasites, although its potential manipulation and subversion by intracellular parasites creates a complex interplay in the regulation of host and parasite autophagy. In this mini-review, we summarise current knowledge on autophagy in both parasites and their host cells, in the context of infection by three Apicomplexa: Plasmodium, Toxoplasma, and Theileria.

Crosstalk between autophagy and inflammatory signalling pathways: balancing defence and homeostasis

Autophagy has broad functions in immunity, ranging from cell-autonomous defence to coordination of complex multicellular immune responses. The successful resolution of infection and avoidance of autoimmunity necessitates efficient and timely communication between autophagy and pathways that sense the immune environment. The recent literature indicates that a variety of immune mediators induce or repress autophagy. It is also becoming increasingly clear that immune signalling cascades are subject to regulation by autophagy, and that a return to homeostasis following a robust immune response is critically dependent on this pathway. Importantly, examples of non-canonical forms of autophagy in mediating immunity are pervasive. In this article, the progress in elucidating mechanisms of crosstalk between autophagy and inflammatory signalling cascades is reviewed. Improved mechanistic understanding of the autophagy machinery offers hope for treating infectious and inflammatory diseases.

Identification of Signaling Pathways by Which CD40 Stimulates Autophagy and Antimicrobial Activity against Toxoplasma gondii in Macrophages

CD40 is an important stimulator of autophagy and autophagic killing of Toxoplasma gondii in host cells. In contrast to autophagy induced by nutrient deprivation or pattern recognition receptors, less is known about the effects of cell-mediated immunity on Beclin 1 and ULK1, key regulators of autophagy. Here we studied the molecular mechanisms by which CD40 stimulates autophagy in macrophages. CD40 ligation caused biphasic Jun N-terminal protein kinase (JNK) phosphorylation. The second phase of JNK phosphorylation was dependent on autocrine production of tumor necrosis factor alpha (TNF-α). TNF-α and JNK signaling were required for the CD40-induced increase in autophagy. JNK signaling downstream of CD40 caused Ser-87 phosphorylation of Bcl-2 and dissociation between Bcl-2 and Beclin 1, an event known to stimulate the autophagic function of Beclin 1. However, TNF-α alone was unable to stimulate autophagy. CD40 also stimulated autophagy via a pathway that included calcium/calmodulin-dependent kinase kinase β (CaMKKβ), AMP-activated protein kinase (AMPK), and ULK1. CD40 caused AMPK phosphorylation at its activating site, Thr-172. This effect was mediated by CaMKKβ and was not impaired by neutralization of TNF-α. CD40 triggered AMPK-dependent Ser-555 phosphorylation of ULK1. CaMKKβ, AMPK, and ULK1 were required for CD40-induced increase in autophagy. CD40-mediated autophagic killing of Toxoplasma gondii is known to require TNF-α. Knockdown of JNK, CaMKKβ, AMPK, or ULK1 prevented T. gondii killing in CD40-activated macrophages. The second phase of JNK phosphorylation-Bcl-2 phosphorylation-Bcl-2-Beclin 1 dissociation and AMPK phosphorylation-ULK1 phosphorylation occurred simultaneously at ∼4 h post-CD40 stimulation. Thus, CaMKKβ and TNF-α are upstream molecules by which CD40 acts on ULK1 and Beclin 1 to stimulate autophagy and killing of T. gondii.

Development of T-cell tolerance utilizes both cell-autonomous and cooperative presentation of self-antigen

The development of T-cell self-tolerance in the thymus is important for establishing immune homeostasis and preventing autoimmunity. Here, we review the components of T-cell tolerance, which includes T-cell receptor (TCR) self-reactivity, costimulation, cytokines, and antigen presentation by a variety of antigen-presenting cells (APCs) subsets. We discuss the current evidence on the process of regulatory T (Treg) cell and negative selection and the importance of TCR signaling. We then examine recent evidence showing unique roles for bone marrow (BM)-derived APCs and medullary thymic epithelial cells (mTECs) on the conventional and Treg TCR repertoire, as well as emerging data on the role of B cells in tolerance. Finally, we review the accumulating data that suggest that cooperative antigen presentation is a prominent component of T -ell tolerance. With the development of tools to interrogate the function of individual APC subsets in the medulla, we have gained greater understanding of the complex cellular and molecular events that determine T-cell tolerance.

Links of Autophagy Dysfunction to Inflammatory Bowel Disease Onset

INTRODUCTION

Autophagy is a cellular stress response that plays key roles in physiological processes, such as adaptation to starvation, degradation of aberrant proteins or organelles, anti-microbial defense, protein secretion, and innate and adaptive immunity. Dysfunctional autophagy is recognized as a contributing factor in many chronic inflammatory diseases, including inflammatory bowel disease (IBD). Genetic studies have identified multiple IBD-associated risk loci that include genes required for autophagy, and several lines of evidence demonstrate that autophagy is impaired in IBD patients. How dysfunctional autophagy contributes to IBD onset is currently under investigation by researchers.

KEY MESSAGES

Dysfunctional autophagy has been identified to play a role in IBD pathogenesis by altering processes that include (1) intracellular bacterial killing, (2) anti-microbial peptide secretion by Paneth cells, (3) pro-inflammatory cytokine production by macrophages, (4) antigen presentation by dendritic cells, (5) goblet cell function, and (6) the endoplasmic reticulum stress response in enterocytes. The overall effect of dysregulation of these processes varies by cell type, stimulus, as well as cellular context. Manipulation of the autophagic pathway may provide a new avenue in the search for effective therapies for IBD.

CONCLUSION

Autophagy plays multiple roles in IBD pathogenesis. A better understanding of the role of autophagy in IBD patients may provide better subclassification of IBD phenotypes and novel approaches to disease management.

Dendritic Cell Autophagy Contributes to Herpes Simplex Virus-Driven Stromal Keratitis and Immunopathology

Herpetic stromal keratitis (HSK) is a blinding ocular disease that is initiated by HSV-1 and characterized by chronic inflammation in the cornea. Although HSK immunopathology of the cornea is well documented in animal models, events preceding this abnormal inflammatory cascade are poorly understood. In this study, we have examined the activation of pathological CD4⁺ T cells in the development of HSK. Dendritic cell autophagy (DC-autophagy) is an important pathway regulating major histocompatibility complex class II (MHCII)-dependent antigen presentation and proper CD4⁺ T cell activation during infectious diseases. Using DC-autophagy-deficient mice, we found that DC-autophagy significantly and specifically contributes to HSK disease without impacting early innate immune infiltration, viral clearance, or host survival. Instead, the observed phenotype was attributable to the abrogated activation of CD4⁺ T cells and reduced inflammation in HSK lesions. We conclude that DC-autophagy is an important contributor to primary HSK immunopathology upstream of CD4⁺ T cell activation.

Herpetic stromal keratitis (HSK) is the leading cause of infectious blindness in the United States and a rising cause worldwide. HSK is induced by herpes simplex virus 1 but is considered a disease of inappropriately sustained inflammation driven by CD4⁺ T cells. In this study, we investigated whether pathways preceding CD4⁺ T cell activation affect disease outcome. We found that autophagy in dendritic cells significantly contributed to the incidence of HSK. Dendritic cell autophagy did not alter immune control of the virus or neurological disease but specifically augmented CD4⁺ T cell activation and pathological corneal inflammation. This study broadens our understanding of the immunopathology that drives HSK and implicates the autophagy pathway as a new target for therapeutic intervention against this incurable form of infectious blindness.

Role of Autophagy in the Maintenance of Intestinal Homeostasis

Genome-wide association studies of inflammatory bowel disease have identified several risk loci in genes that regulate autophagy, and studies have provided insight into the functional effects of these polymorphisms. We review the mechanisms by which autophagy contributes to intestinal homeostasis, focusing on its cell type-specific roles in regulating gut ecology, restricting pathogenic bacteria, and controlling inflammation. Based on this information, we are beginning to understand how alterations in autophagy can contribute to intestinal inflammation.