Autophagy in the immune system

Mycobacterium vaccae attenuates airway inflammation by inhibiting autophagy and activating PI3K/Akt signaling pathway in OVA-induced allergic airway inflammation mouse model

PURPOSE

The etiology of asthma remains elusive, with no known cure. Based on accumulating evidence, autophagy, a self-degradation process that maintains cellular metabolism and homeostasis, participates in the development of asthma. Mycobacterium vaccae vaccine (M. vaccae), an immunomodulatory agent, has previously been shown to effectively alleviate airway inflammation and airway remodeling. However, its therapeutic effect on asthma via the regulation of autophagy remains unknown. Therefore, this study aimed to investigate the impact of M. vaccae in attenuating asthma airway inflammation via autophagy-mediated pathways.

METHODS

Balb/c mice were used to generate an ovalbumin (OVA)-immunized allergic airway model and were subsequently administered either M. vaccae or M. vaccae + rapamycin (an autophagy activator) prior to each challenge. Next, airway inflammation, mucus secretion, and airway remodeling in mouse lung tissue were assessed via histological analyses. Lastly, the expression level of autophagy proteins LC3B, Beclin1, p62, and autolysosome was determined both in vivo and in vitro, along with the expression level of p-PI3K, PI3K, p-Akt, and Akt in mouse lung tissue.

RESULTS

The findings indicated that aerosol inhalation of M. vaccae in an asthma mouse model has the potential to decrease eosinophil counts, alleviate airway inflammation, mucus secretion, and airway remodeling through the inhibition of autophagy. Likewise, M. vaccae could reduce the levels of OVA-specific lgE, IL-5, IL-13, and TNF-α in asthma mouse models by inhibiting autophagy. Furthermore, this study revealed that M. vaccae also suppressed autophagy in IL-13-stimulated BEAS-2B cells. Moreover, M. vaccae may activate the PI3K/Akt signaling pathway in the lung tissue of asthmatic mice.

CONCLUSION

In summary, the present study suggests that M. vaccae may contribute to alleviating airway inflammation and remodeling in allergic asthma by potentially modulating autophagy and the PI3K/Akt signaling pathway. These discoveries offer a promising avenue for the development of therapeutic interventions targeting allergic airway inflammation.

Mononuclear Phagocytes, Cellular Immunity, and Nobel Prizes: A Historic Perspective

The mononuclear phagocyte system includes monocytes, macrophages, some dendritic cells, and multinuclear giant cells. These cell populations display marked heterogeneity depending on their differentiation from embryonic and bone marrow hematopoietic progenitors, tissue location, and activation. They contribute to tissue homeostasis by interacting with local and systemic immune and non-immune cells through trophic, clearance, and cytocidal functions. During evolution, they contributed to the innate host defense before effector mechanisms of specific adaptive immunity emerged. Mouse macrophages appear at mid-gestation and are distributed throughout the embryo to facilitate organogenesis and clear cells undergoing programmed cell death. Yolk sac, AGM, and fetal liver-derived tissue-resident macrophages persist throughout postnatal and adult life, supplemented by bone marrow-derived blood monocytes, as required after injury and infection. Nobel awards to Elie Metchnikoff and Paul Ehrlich in 1908 drew attention to cellular phagocytic and humoral immunity, respectively. In 2011, prizes were awarded to Jules Hoffmann and Bruce Beutler for contributions to innate immunity and to Ralph Steinman for the discovery of dendritic cells and their role in antigen presentation to T lymphocytes. We trace milestones in the history of mononuclear phagocyte research from the perspective of Nobel awards bearing directly and indirectly on their role in cellular immunity.

Autophagy: A Silent Protagonist in Kidney Transplantation

Autophagy is a lysosome-dependent regulated mechanism that recycles unnecessary cytoplasmic components. It is now known that autophagy dysfunction may have a pathogenic role in several human diseases and conditions, including kidney transplantation. Both defective and excessive autophagy may induce or aggravate several complications of kidney transplantation, such as ischemia-reperfusion injury, alloimmune response, and immunosuppressive treatment and side effects. Although it is still complicated to measure autophagy levels in clinical practice, more attention should be paid to the factors that may influence autophagy. In kidney transplantation, the association of low doses of a mammalian target of rapamycin inhibitor with low doses of a calcineurin inhibitor may be of benefit for autophagy modulation. However, further studies are needed to explore the role of other autophagy regulators.

Role of microglia in stroke

Microglia play key roles in the post-ischemic inflammatory response and damaged tissue removal reacting rapidly to the disturbances caused by ischemia and working to restore the lost homeostasis. However, the modified environment, encompassing ionic imbalances, disruption of crucial neuron-microglia interactions, spreading depolarization, and generation of danger signals from necrotic neurons, induce morphological and phenotypic shifts in microglia. This leads them to adopt a proinflammatory profile and heighten their phagocytic activity. From day three post-ischemia, macrophages infiltrate the necrotic core while microglia amass at the periphery. Further, inflammation prompts a metabolic shift favoring glycolysis, the pentose-phosphate shunt, and lipid synthesis. These shifts, combined with phagocytic lipid intake, drive lipid droplet biogenesis, fuel anabolism, and enable microglia proliferation. Proliferating microglia release trophic factors contributing to protection and repair. However, some microglia accumulate lipids persistently and transform into dysfunctional and potentially harmful foam cells. Studies also showed microglia that either display impaired apoptotic cell clearance, or eliminate synapses, viable neurons, or endothelial cells. Yet, it will be essential to elucidate the viability of engulfed cells, the features of the local environment, the extent of tissue damage, and the temporal sequence. Ischemia provides a rich variety of region- and injury-dependent stimuli for microglia, evolving with time and generating distinct microglia phenotypes including those exhibiting proinflammatory or dysfunctional traits and others showing pro-repair features. Accurate profiling of microglia phenotypes, alongside with a more precise understanding of the associated post-ischemic tissue conditions, is a necessary step to serve as the potential foundation for focused interventions in human stroke.

HIV Infection: Shaping the Complex, Dynamic, and Interconnected Network of the Cytoskeleton

HIV-1 has evolved a plethora of strategies to overcome the cytoskeletal barrier (i.e., actin and intermediate filaments (AFs and IFs) and microtubules (MTs)) to achieve the viral cycle. HIV-1 modifies cytoskeletal organization and dynamics by acting on associated adaptors and molecular motors to productively fuse, enter, and infect cells and then traffic to the cell surface, where virions assemble and are released to spread infection. The HIV-1 envelope (Env) initiates the cycle by binding to and signaling through its main cell surface receptors (CD4/CCR5/CXCR4) to shape the cytoskeleton for fusion pore formation, which permits viral core entry. Then, the HIV-1 capsid is transported to the nucleus associated with cytoskeleton tracks under the control of specific adaptors/molecular motors, as well as HIV-1 accessory proteins. Furthermore, HIV-1 drives the late stages of the viral cycle by regulating cytoskeleton dynamics to assure viral Pr55Gag expression and transport to the cell surface, where it assembles and buds to mature infectious virions. In this review, we therefore analyze how HIV-1 generates a cell-permissive state to infection by regulating the cytoskeleton and associated factors. Likewise, we discuss the relevance of this knowledge to understand HIV-1 infection and pathogenesis in patients and to develop therapeutic strategies to battle HIV-1.

Exosomes loading Tapasin enhance T cell immune response by autophagy to inhibit HBV replication

Hepatitis B virus (HBV) specific T cell immune response plays a vital role in viral clearance. Dendritic cell derived exosomes (Dexs) can activate T cell immunity effectively. Tapasin (TPN) is involved in antigen processing and specific immune recognition. In the present study, we elucidated that Dexs loading TPN (TPN-Dexs) could enhance CD8⁺ T cell immune response and inhibit virus replication in HBV transgenic mice. T cell immune response and the ability of inhibiting HBV replication were measured in HBV transgenic mice immunized with TPN-Dexs. Meanwhile, CD8⁺ T cell autophagy and specific T cell immune responses were measured in vitro and vivo, and the mechanisms probably involved in were explored. Purified TPN-Dexs could be taken up into the cytoplasm of DCs and upregulate CD8⁺ T cell autophagy to enhance specific T cell immune response. In addition, TPN-Dexs could increase the expression of AKT and decrease the expression of mTOR in CD8⁺ T cells. Further research confirmed that TPN-Dexs could inhibit virus replication and decrease the expression of HBsAg in the liver of HBV transgenic mice. Nevertheless, those also could elicit mice hepatocytes damage. In conclusion, TPN-Dexs could enhance specific CD8⁺ T cell immune responses via the AKT/mTOR pathway to regulate the autophagy and exert the antiviral effect in HBV transgenic mice.

Modulation of long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression in the liver of Beagle dogs by Toxocara canis infection

BACKGROUND

Long non-coding RNAs (lncRNAs) and messenger RNAs (mRNAs) play crucial roles in regulating various physiological and pathological processes. However, the role of lncRNAs and mRNAs in mediating the liver response during Toxocara canis infection remains incompletely understood.

METHODS

In the present study, the expression profile of lncRNAs and mRNAs was investigated in the liver of Beagle dogs infected by T. canis using high-throughput RNA sequencing.

RESULTS

Compared with the control groups, 876 differentially expressed (DE) lncRNAs and 288 DEmRNAs were identified at 12 h post-infection (hpi), 906 DElncRNAs and 261 DEmRNAs were identified at 24 hpi, and 876 DElncRNAs and 302 DEmRNAs were identified at 36 days post-infection (dpi). A total of 16 DEmRNAs (e.g. dpp4, crp and gnas) were commonly identified at the three infection stages. Enrichment and co-localization analyses identified several pathways involved in immune and inflammatory responses during T. canis infection. Some novel DElncRNAs, such as LNC_015756, LNC_011050 and LNC_011052, were also associated with immune and inflammatory responses. Also, LNC_005105 and LNC_005401 were associated with the secretion of anti-inflammatory cytokines, which may play a role in the healing of liver pathology at the late stage of infection.

CONCLUSIONS

Our data provided new insight into the regulatory roles of lncRNAs and mRNAs in the pathogenesis of T. canis and improved our understanding of the contribution of lncRNAs and mRNAs to the immune and inflammatory response of the liver during T. canis infection.

The crosslinks between ferroptosis and autophagy in asthma

Autophagy is an evolutionarily conserved cellular process capable of degrading various biological molecules and organelles via the lysosomal pathway. Ferroptosis is a type of oxidative stress-dependent regulated cell death associated with the iron accumulation and lipid peroxidation. The crosslinks between ferroptosis and autophagy have been focused on since the dependence of ferroptosis on autophagy was discovered. Although the research and theories on the relationship between autophagy and ferroptosis remain scattered and fragmented, the crosslinks between these two forms of regulated cell death are closely related to the treatment of various diseases. Thereof, asthma as a chronic inflammatory disease has a tight connection with the occurrence of ferroptosis and autophagy since the crosslinked signal pathways may be the crucial regulators or exactly regulated by cells and secretion in the immune system. In addition, non-immune cells associated with asthma are also closely related to autophagy and ferroptosis. Further studies of cross-linking asthma inflammation with crosslinked signaling pathways may provide us with several key molecules that regulate asthma through specific regulators. The crosslinks between autophagy and ferroptosis provide us with a new perspective to interpret and understand the manifestations of asthma, potential drug discovery targets, and new therapeutic options to effectively intervene in the imbalance caused by abnormal inflammation in asthma. Herein, we introduce the main molecular mechanisms of ferroptosis, autophagy, and asthma, describe the role of crosslinks between ferroptosis and autophagy in asthma based on their common regulatory cells or molecules, and discuss potential drug discovery targets and therapeutic applications in the context of immunomodulatory and symptom alleviation.

Evidence of the Autophagic Process during the Fish Immune Response of Skeletal Muscle Cells against Piscirickettsia salmonis

Autophagy is a fundamental cellular process implicated in the health of the cell, acting as a cytoplasmatic quality control machinery by self-eating unfunctional organelles and protein aggregates. In mammals, autophagy can participate in the clearance of intracellular pathogens from the cell, and the activity of the toll-like receptors mediates its activation. However, in fish, the modulation of autophagy by these receptors in the muscle is unknown. This study describes and characterizes autophagic modulation during the immune response of fish muscle cells after a challenge with intracellular pathogen Piscirickettsia salmonis. For this, primary cultures of muscle cells were challenged with P. salmonis, and the expressions of immune markers il-1β, tnfα, il-8, hepcidin, tlr3, tlr9, mhc-I and mhc-II were analyzed through RT-qPCR. The expressions of several genes involved in autophagy (becn1, atg9, atg5, atg12, lc3, gabarap and atg4) were also evaluated with RT-qPCR to understand the autophagic modulation during an immune response. In addition, LC3-II protein content was measured via Western blot. The challenge of trout muscle cells with P. salmonis triggered a concomitant immune response to the activation of the autophagic process, suggesting a close relationship between these two processes.

Subunit microparticulate vaccine delivery using microneedles trigger significant SARS-spike-specific humoral and cellular responses in a preclinical murine model

The objective of this "proof-of-concept" study was to evaluate the synergistic effect of a subunit microparticulate vaccine and microneedles (MN) assisted vaccine delivery system against a human coronavirus. Here, we formulated PLGA polymeric microparticles (MPs) encapsulating spike glycoprotein (GP) of SARS-CoV as the model antigen. Similarly, we formulated adjuvant MPs encapsulating Alhydrogel® and AddaVax™. The antigen/adjuvant MPs were characterized and tested in vitro for immunogenicity. We found that the antigen/adjuvant MPs were non-cytotoxic in vitro. The spike GP MPs + Alhydrogel® MPs + AddaVax™ MPs showed enhanced immunogenicity in vitro as confirmed through the release of nitrite, autophagy, and antigen presenting molecules with their co-stimulatory molecules. Next, we tested the in vivo efficacy of the spike GP MP vaccine with and without adjuvant MPs in mice vaccinated using MN. The spike GP MPs + Alhydrogel® MPs + AddaVax™ MPs induced heightened spike GP-specific IgG, IgG1 and IgG2a antibodies in mice. Also, spike GP MPs + Alhydrogel® MPs + AddaVax™ MPs enhanced expression of CD4+ and CD8+ T cells in secondary lymphoid organ like spleen. These results indicated spike GP-specific humoral immunity and cellular immunity in vivo. Thus, we employed the benefits of both the subunit vaccine MPs and dissolving MN to form a non-invasive and effective vaccination strategy against human coronaviruses.

The multifunctional roles of autophagy in the innate immune response: Implications for regulation of transplantation rejection

Organ transplantation is the main treatment for end-stage organ failure, which has rescued tens of thousands of lives. Immune rejection is the main factor affecting the survival of transplanted organs. How to suppress immune rejection is an important goal of transplantation research. A graft first triggers innate immune responses, leading to graft inflammation, tissue injury and cell death, followed by adaptive immune activation. At present, the importance of innate immunity in graft rejection is poorly understood. Autophagy, an evolutionarily conserved intracellular degradation system, is proven to be involved in regulating innate immune response following graft transplants. Moreover, there is evidence indicating that autophagy can regulate graft dysfunction. Although the specific mechanism by which autophagy affects graft rejection remains unclear, autophagy is involved in innate immune signal transduction, inflammatory response, and various forms of cell death after organ transplantation. This review summarizes how autophagy regulates these processes and proposes potential targets for alleviating immune rejection.

ROS function as an inducer of autophagy to promote granulocyte proliferation in Pacific oyster Crassostrea gigas

Hematopoiesis is the biological process to generate new blood cells in the living body and reactive oxygen species (ROS) contribute significantly to the regulation of haematopoietic cell homeostasis. In the present study, the involvement of ROS in the proliferation of haemocytes was examined in Pacific oyster Crassostrea gigas. The ROS content in haemocytes increased significantly after lipopolysaccharide (LPS) treatment, but decreased after the treatment with antioxidant N-Acetyl-L-cysteine (NAC, a scavenger of ROS). The percentage of 5-ethynyl-2'-deoxyuridine labeled (EdU⁺) granulocytes in total haemocytes significantly increased at 12 h (4.12-fold, p < 0.001) and 24 h (2.36-fold, p < 0.001) after LPS treatment, while decreased at 12 h (0.26-fold, p < 0.001) and 24 h (0.61-fold, p < 0.05) after NAC treatment, respectively. Meanwhile, the percentage of haemocytes with autophagosome positive signals significantly increased at 12 h (1.17-fold, p < 0.01) and 24 h (1.19-fold, p < 0.05) after LPS treatment, but significantly reduced at 12 h (0.41-fold, p < 0.001) and 24 h (0.28-fold, p < 0.001) after the NAC treatment, respectively. After ammonium chloride (NH₄Cl) treatment, the percentage of haemocytes with autophagosome and EdU⁺ granulocytes significantly increased at 12 h, which was 1.27-fold (p < 0.01) and 1.70-fold (p < 0.01) of control group, respectively. These results collectively suggested that ROS produced after LPS treatment could act as an inducer for autophagy and involved in regulating the proliferation of some granulocytes in C. gigas.

MERS-CoV ORF4b is a virulence factor involved in the inflammatory pathology induced in the lungs of mice

No vaccines or specific antiviral drugs are authorized against Middle East respiratory syndrome coronavirus (MERS-CoV) despite its high mortality rate and prevalence in dromedary camels. Since 2012, MERS-CoV has been causing sporadic zoonotic infections in humans, which poses a risk of genetic evolution to become a pandemic virus. MERS-CoV genome encodes five accessory proteins, 3, 4a, 4b, 5 and 8b for which limited information is available in the context of infection. This work describes 4b as a virulence factor in vivo, since the deletion mutant of a mouse-adapted MERS-CoV-Δ4b (MERS-CoV-MA-Δ4b) was completely attenuated in a humanized DPP4 knock-in mouse model, resulting in no mortality. Attenuation in the absence of 4b was associated with a significant reduction in lung pathology and chemokine expression levels at 4 and 6 days post-infection, suggesting that 4b contributed to the induction of lung inflammatory pathology. The accumulation of 4b in the nucleus in vivo was not relevant to virulence, since deletion of its nuclear localization signal led to 100% mortality. Interestingly, the presence of 4b protein was found to regulate autophagy in the lungs of mice, leading to upregulation of BECN1, ATG3 and LC3A mRNA. Further analysis in MRC-5 cell line showed that, in the context of infection, MERS-CoV-MA 4b inhibited autophagy, as confirmed by the increase of p62 and the decrease of ULK1 protein levels, either by direct or indirect mechanisms. Together, these results correlated autophagy activation in the absence of 4b with downregulation of a pathogenic inflammatory response, thus contributing to attenuation of MERS-CoV-MA-Δ4b.

How Can We Improve the Vaccination Response in Older People? Part II: Targeting Immunosenescence of Adaptive Immunity Cells

The number of people that are 65 years old or older has been increasing due to the improvement in medicine and public health. However, this trend is not accompanied by an increase in quality of life, and this population is vulnerable to most illnesses, especially to infectious diseases. Vaccination is the best strategy to prevent this fact, but older people present a less efficient response, as their immune system is weaker due mainly to a phenomenon known as immunosenescence. The adaptive immune system is constituted by two types of lymphocytes, T and B cells, and the function and fitness of these cell populations are affected during ageing. Here, we review the impact of ageing on T and B cells and discuss the approaches that have been described or proposed to modulate and reverse the decline of the ageing adaptive immune system.

Surface layer protein A from hypervirulent Clostridioides difficile ribotype 001 can induce autophagy process in human intestinal epithelial cells

Clostridioides difficile is the leading cause of nosocomial diarrhea with high morbidity and mortality worldwide. C. difficile strains produce a crystalline surface layer protein A (SlpA), which is an absolute necessity for its pathogenesis. However, its pathogenic mechanisms and its pro-inflammatory behavior are not yet fully elucidated. Herein, we report for the first time that SlpA extracted from C. difficile can induce autophagy process in Caco-2 cells. SlpA protein was purified from two C. difficile strains (RT001 and ATCC 700075). The cell viability of Caco-2 cells after exposure with different concentrations (15, 20, 25 μg/mL) of SlpA at various time points (3, 6, 12, 24 h) was measured by MTT assay. Acridine orange staining was used to visualize the hypothetical acidic vesicular organelles. The gene expression of autophagy mediators including LC3B, Atg5, Atg16L, and Beclin-1 was determined by quantitative real-time PCR assay. Western blotting assay was used to detect the expression of LC3B protein. MTT assay showed that different concentrations of SlpA did not induce significant changes in the viability of Caco-2 cells. SlpA at concentration of 20 μg/mL enhanced the formation of acidic vesicular organelles in Caco-2 cells after 12 h of exposure. Moreover, SlpA treatment significantly increased the expression of autophagy-associated genes, and increased the expression of LC3B protein in Caco-2 cells. In conclusion, our study demonstrated that SlpA is capable to induce autophagy in intestinal epithelial cells. These findings reveal a novel mechanism for the pathogenesis of C. difficile mediated by its SLPs.

Novel microparticulate Zika vaccine induces a significant immune response in a preclinical murine model after intramuscular administration

Despite the detrimental effects associated with Zika infection, there are no approved treatments or vaccines available. To address the need for a safe and effective vaccine for Zika, we formulated poly(lactic-co-glycolic) acid (PLGA) polymeric vaccine microparticles (MP) encapsulating the inactivated Zika virus, along with adjuvant MP encapsulating Alhydrogel® and MPL-A®. We characterized the vaccine MP for size, surface charge, morphology, encapsulation efficiency, and antigen integrity. Further, we evaluated immunogenicity and cytotoxicity of vaccine MP in vitro in murine dendritic cells. Vaccine MP with adjuvants induced significantly higher production of nitric oxide, a marker of innate immunity, when compared to the untreated cells. In addition, vaccine MP with or without adjuvants induced increased autophagy in murine dendritic cells when compared to inactivated Zika virus, which is critical in antigen presentation. Next, we evaluated in vivo efficacy of vaccine MP with and without adjuvants in a preclinical murine model by measuring the immune response after intramuscular administration. Vaccine MP with adjuvants induced significant IgG, Ig2a, and IgG1 titers as compared to the control group of untreated mice. Thus, this study provided the 'proof-of-concept' for a microparticulate Zika vaccine.

Transcriptome analysis uncovers the autophagy-mediated regulatory patterns of the immune microenvironment in dilated cardiomyopathy

The relationship between autophagy and immunity has been well studied. However, little is known about the role of autophagy in the immune microenvironment during the progression of dilated cardiomyopathy (DCM). Therefore, this study aims to uncover the effect of autophagy on the immune microenvironment in the context of DCM. By investigating the autophagy gene expression differences between healthy donors and DCM samples, 23 dysregulated autophagy genes were identified. Using a series of bioinformatics methods, 13 DCM‐related autophagy genes were screened and used to construct a risk prediction model, which can well distinguish DCM and healthy samples. Then, the connections between autophagy and immune responses including infiltrated immunocytes, immune reaction gene‐sets and human leukocyte antigen (HLA) genes were systematically evaluated. In addition, two autophagy‐mediated expression patterns in DCM were determined via the unsupervised consensus clustering analysis, and the immune characteristics of different patterns were revealed. In conclusion, our study revealed the strong effect of autophagy on the DCM immune microenvironment and provided new insights to understand the pathogenesis and treatment of DCM.

Nanoparticle formulation of the fusion protein virus like particles of respiratory syncytial virus stimulates enhanced in vitro antigen presentation and autophagy

Respiratory Syncytial Virus (RSV) is one of the leading causes of bronchiolitis and pneumonia in childrenunder one year globally. As a result, RSV poses a severe burden on healthcare services. Thus, a vaccine for RSV is a global need. Utilizing polymeric nanoparticles as a delivery system for vaccine antigen holds a lot of promise. In this study, the virus like particles of RSV fusion protein (F-VLP) was encapsulated in poly (D, L-lactide-co-glycolide) (PLGA) nanoparticles (NP). The F-VLP NP was formulated using a double emulsion solvent evaporation technique. The optimized NPs had a particle size of 525 ± 10.5 nm and an antigen encapsulation efficiency of 73% ± 10.5. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the F-VLP was stable post formulation. The F-VLP NP showed a sustained release of the F-VLP antigen for up to a week. In vitro study revealed that the F-VLP NP were non-cytotoxic, and the cellular uptake of the NPs by dendritic cells was observed within 3 h. The F-VLP NP with adjuvant monophosphoryl lipid A (MPL) NP and without MPL NP showed enhanced expression of antigen presentation molecule major histocompatibility complex (MHC)-I and autophagosomes in dendritic cells. In summary, the sustained release of the antigen from the F-VLP NP and the particulate nature of the vaccine resulted in enhanced antigen presentation and induction of autophagy in antigen-presenting cells (APCs).

Autophagy Hijacking in PBMC From COVID-19 Patients Results in Lymphopenia

Autophagy is a homeostatic process responsible for the self-digestion of intracellular components and antimicrobial defense by inducing the degradation of pathogens into autophagolysosomes. Recent findings suggest an involvement of this process in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, the role of autophagy in the immunological mechanisms of coronavirus disease 2019 (COVID-19) pathogenesis remains largely unexplored. This study reveals the presence of autophagy defects in peripheral immune cells from COVID-19 patients. The impairment of the autophagy process resulted in a higher percentage of lymphocytes undergoing apoptosis in COVID-19 patients. Moreover, the inverse correlation between autophagy markers levels and peripheral lymphocyte counts in COVID-19 patients confirms how a defect in autophagy might contribute to lymphopenia, causing a reduction in the activation of viral defense. These results provided intriguing data that could help in understanding the cellular underlying mechanisms in COVID-19 infection, especially in severe forms.

A Novel Risk Model Based on Autophagy-Related LncRNAs Predicts Prognosis and Indicates Immune Infiltration Landscape of Patients With Cutaneous Melanoma

Cutaneous melanoma (CM) is a malignant tumor with a high incidence rate and poor prognosis. Autophagy plays an essential role in the development of CM; however, the role of autophagy-related long noncoding RNAs (lncRNAs) in this process remains unknown. Human autophagy-related genes were extracted from the Human Autophagy Gene Database and screened for autophagy-related lncRNAs using Pearson correlation. Multivariate Cox regression analysis was implemented to identify ten autophagy-related lncRNAs associated with prognosis, and a risk model was constructed. The Kaplan-Meier survival curve showed that the survival probability of the high-risk group was lower than that of the low-risk group. A novel predictive model was constructed to investigate the independent prognostic value of the risk model. The nomogram results showed that the risk score was an independent prognostic signature that distinguished it from other clinical characteristics. The immune infiltration landscape of the low-risk and high-risk groups was further investigated. The low-risk groups displayed higher immune, stromal, and ESTIMATE scores and lower tumor purity. The CIBERSORT and single sample gene set enrichment analysis (ssGSEA) algorithms indicated a notable gap in immune cells between the low- and high-risk groups. Ten autophagy-related lncRNAs were significantly correlated with immune cells. Finally, Gene Set Enrichment Analysis (GSEA) and Gene Set Variation Analysis (GSVA) results demonstrated that autophagy-related lncRNA-mediated and immune-related signaling pathways are crucial factors in regulating CM. Altogether, these data suggest that constructing a risk model based on ten autophagy-related lncRNAs can accurately predict prognosis and indicate the tumor microenvironment of patients with CM. Thus, our study provides a new perspective for the future clinical treatment of CM.

Combination Therapy of Ledipasvir and Itraconazole in the Treatment of COVID-19 Patients Coinfected with Black Fungus: An In Silico Statement

The manuscript mainly aimed at providing clues on improving the innate immunity of coronavirus patients and safeguarding them from both new mutant strains and black fungus infections. Coronavirus is readily mutating from one variant to another. Among the several variants, we selected SARS-CoV-2 B.1.1.7 in this study. Upon infection of any virus, ideally, the phagocytic cells of the host engulf and destroy the virus by a mechanism called phagocytosis. However, compromised immunity impairs phagocytosis, and thus, restoring the immune system is crucial for a speedy recovery of infected patients. The autophagy and activation of Toll-like receptor-4 are the only ways to restore innate immunity. Recently, immunocompromised COVID-19 patients have been suffering from the coinfection of black fungus. Rhizomucor, a black fungus species, causes more than 75% of cases of mucormycosis. Here, we present the results of molecular docking studies of sixty approved antiviral drugs targeting receptors associated with the SARS-CoV-2 B 1.1.7 variant (PDB id: 7NEH), activating the innate immune system (PDB id: 5YEC and 5IJC). We also studied the twenty approved antifungal drugs with Rhizomucor miehei lipase propeptide (PDB id: 6QPR) to identify the possible combination therapy for patients coinfected with coronavirus and black fungus. The ledipasvir showed excellent docking interactions with the 7NEH, 5YEC, and 5IJC, indicating that it is a perfect candidate for the treatment of COVID-19 patients. Itraconazole showed significant interaction with 6QPR of Rhizomucor miehei, suggesting that itraconazole can treat black fungus infections. In conclusion, the combination therapy of ledipasvir and itraconazole can be a better alternative for treating COVID-19 patients coinfected with black fungus.

Autophagy takes it all - autophagy inducers target immune aging

Autophagy, as the key nutrient recycling pathway, enables eukaryotic cells to adapt to surging cellular stress during aging and, thereby, delays age-associated deterioration. Autophagic flux declines with age and, in turn, decreases in autophagy contribute to the aging process itself and promote senescence. Here, we outline how autophagy regulates immune aging and discuss autophagy-inducing interventions that target senescent immune cells, which are major drivers of systemic aging. We examine how cutting-edge technologies, such as single-cell omics methods hold the promise to capture the complexity of molecular and cellular phenotypes associated with aging, driving the development of suitable putative biomarkers and clinical bioassays. Finally, we debate the urgency to initiate large-scale human clinical trials. We give special preference to small molecule probes and to dietary interventions that can extend healthy lifespan and are affordable for most of the world's population.

MHC class I antigen cross-presentation mediated by PapMV nanoparticles in human antigen-presenting cells is dependent on autophagy

Nanoparticles made of the coat protein of papaya mosaic virus (PapMV) and a single-strand RNA were previously shown to be an efficient antigen presentation system for the trigger of cellular immunity. Engineering of PapMV nano with a cytotoxic T lymphocyte epitope was previously shown activating specific T lymphocytes through a proteasome-independent major histocompatibility complex class I (MHC-I) cross-presentation. In this study, we provide new insights into the mechanism of the MHC-I cross-presentation mediated by PapMV nanoparticles. We demonstrate that PapMV nanoparticles do not require the transporter associated with antigen presentation (TAP), but rather depend on lysosome acidification and cathepsin S protease activity for presentation of the T cell epitope. We have also linked the induction of autophagy with this vacuolar MHC-I cross-presentation process. Interestingly, autophagy is induced in antigen-presenting cells after PapMV nanoparticles exposure and inhibition of autophagy reduce MHC-I cross-presentation. This study demonstrates that autophagy is associated with TAP- and proteasome-independent MHC-I cross-presentation. A deeper understanding of the autophagy-dependent MHC-I cross-presentation will be useful in designing vaccination platforms that aim to trigger an efficient cytotoxic T lymphocyte response.

Dexmedetomidine Restores Autophagic Flux, Modulates Associated microRNAs and the Cholinergic Anti-inflammatory Pathway upon LPS-Treatment in Rats

Infections and perioperative stress can lead to neuroinflammation, which in turn is linked to cognitive impairments such as postoperative delirium or postoperative cognitive dysfunctions. The α2-adrenoceptor agonist dexmedetomidine (DEX) prevents cognitive impairments and has organo-protective and anti-inflammatory properties. Macroautophagy (autophagy) regulates many biological processes, but its role in DEX-mediated anti-inflammation and the underlying mechanism of DEX remains largely unclear. We were interested how a pretreatment with DEX protects against lipopolysaccharide (LPS)-induced inflammation in adult male Wistar rats. We used Western blot and activity assays to study how DEX modulated autophagy- and apoptosis-associated proteins as well as molecules of the cholinergic anti-inflammatory pathway, and qPCR to analyse the expression of autophagy and inflammation-associated microRNAs (miRNA) in the spleen, cortex and hippocampus at different time points (6 h, 24 h, 7 d). We showed that a DEX pretreatment prevents LPS-induced impairments in autophagic flux and attenuates the LPS-induced increase in the apoptosis-associated protein cleaved poly(ADP-ribose)-polymerase (PARP) in the spleen. Both, DEX and LPS altered miRNA expression and molecules of the cholinergic anti-inflammatory pathway in the spleen and brain. While only a certain set of miRNAs was up- and/or downregulated by LPS in each tissue, which was prevented or attenuated by a DEX pretreatment in the spleen and hippocampus, all miRNAs were up- and/or downregulated by DEX itself - independent of whether or not they were altered by LPS. Our results indicate that the organo-protective effect of DEX may be mediated by autophagy, possibly by acting on associated miRNAs, and the cholinergic anti-inflammatory pathway. Preventive effects of DEX on LPS-induced inflammation. DEX restores the LPS-induced impairments in autophagic flux, attenuates PARP cleavage and alters molecules of the cholinergic system in the spleen. Furthermore, DEX alters and prevents LPS-induced miRNA expression changes in the spleen and brain along with LPS.

LC3 and NLRC5 interaction inhibits NLRC5-mediated MHC class I antigen presentation pathway in endometrial cancer

The major histocompatibility complex class I (MHC-I) transactivator, nucleotide binding oligomerization domain-like receptor family caspase recruitment domain containing 5 (NLRC5), serves as a target for immune evasion in many cancers, including endometrial cancer (EC). An inhibition of autophagy can contribute to immunotherapy by assisting the MHC-I-mediated antigen presentation in cancer. However, the underlying mechanism for autophagy-regulated MHC-I in EC remains unclear. In this study, we found that autophagy was upregulated in EC tissues when compared to that in normal endometrial tissues. MHC I and NLRC5 expressions were lower in EC endometrium than in normal endometrium. Autophagy inhibited the MHC-I genes expression in vitro. Furthermore, a negative correlation was found between NLRC5 and LC3 levels, and LC3 interacted with NLRC5 to inhibit NLRC5-mediated MHC-I antigen presentation pathway in vitro and in vivo. Thus, our findings demonstrated that an upregulation of LC3 in EC patients may contribute to tumor immune escape by restricting the NLRC5-mediated MHC-I antigen presentation pathway, signifying inhibiting LC3 and promoting NLRC5 may be a promising immunotherapy strategy in the management of EC.

Curcumin protects human umbilical vein endothelial cells against high oxidized low density lipoprotein-induced lipotoxicity and modulates autophagy

Objectives

Endothelial dysfunction is a precursor of cardiovascular disease, and protecting endothelial cells from damage is a treatment strategy for atherosclerosis (AS). Curcumin, a natural polyphenolic compound, has been shown to protect endothelial cells from dysfunction. In the present study, we investigated whether curcumin could ameliorate high oxidized low-density lipoprotein (ox-LDL)-induced endothelial lipotoxicity by inducing autophagy in human umbilical vein endothelial cells (HUVECs).

Materials and Methods

HUVECs were treated with 50 μM high ox-LDL alone or in combination with 5 μM curcumin for 24 hr. Cell viability and function were assessed by the cell counting kit-8 (CCK-8) assay, tube formation assay and cell migration experiments. Oil red O staining was used to detect lipid droplet accumulation in HUVECs. The change in reactive oxygen species (ROS) levels in HUVECs was measured with the probe DCFH-DA. Quantitative real-time PCR (qPCR) and Western blotting were used to evaluate the mRNA and protein levels of several inflammatory and autophagy-related factors.

Results

Cell viability was restored, tube formation and migration ability were increased, and lipid accumulation, oxidative stress and inflammatory responses were decreased in the curcumin-treated group compared with the high ox-LDL group. Furthermore, high ox-LDL inhibited HUVEC autophagy, and this effect was reversed by curcumin. Moreover, curcumin regulated the expression of several key proteins involved in the AMPK/mTOR/p70S6K signaling pathway.

Conclusion

Our findings suggest that curcumin is able to reduce endothelial lipotoxicity and modulate autophagy and that the AMPK/mTOR/p70S6K pathway might play a key role in these effects.

CD36 and LC3B initiated autophagy in B cells regulates the humoral immune response

Scavenger receptors are pattern recognition receptors that recognize both foreign and self-ligands, and initiate different mechanisms of cellular activation, often as co-receptors. The function of scavenger receptor CD36 in the immune system has mostly been studied in macrophages but it is also highly expressed by innate type B cells where its function is less explored. Here we report that CD36 is involved in macro-autophagy/autophagy in B cells, and in its absence, the humoral immune response is impaired. We found that CD36-deficient B cells exhibit a significantly reduced plasma cell formation, proliferation, mitochondrial mobilization and oxidative phosphorylation. These changes were accompanied by impaired initiation of autophagy, and we found that CD36 regulated autophagy and colocalized with autophagosome membrane protein MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3). When we investigated T-cell-dependent immune responses, we found that mice with CD36 deficiency, specifically in B cells, exhibited attenuated germinal center responses, class switching, and antibody production as well as autophagosome formation. These findings establish a critical role for CD36 in B cell responses and may also contribute to our understanding of CD36-mediated autophagy in other cells as well as in B cell lymphomas that have been shown to express the receptor.Abbreviations: AICDA/AID: activation-induced cytidine deaminase; ATG5: autophagy related 5; ATP: adenosine triphosphate; BCR: B-cell receptor; CPG: unmethylated cytosine-guanosine; CQ: chloroquine; DC: dendritic cells; FOB: follicular B cells; GC: germinal center; Ig: immunoglobulin; LPS: lipopolysaccharide; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MFI: mean fluorescence intensity; MZB: marginal zone B cells; NP-CGG: 4-hydroxy-3-nitrophenylacetyl-chicken gamma globulin; OCR: oxygen consumption rate; oxLDL: oxidized low-density lipoprotein; PC: plasma cells; Rapa: rapamycin; SQSTM1/p62: sequestosome 1; SRBC: sheep red blood cells; Tfh: follicular helper T cells; TLR: toll-like receptor.

Inborn Errors in the LRR Domain of Nod2 and Their Potential Consequences on the Function of the Receptor

The innate immune system plays a critical role in the early detection of pathogens, primarily by relying on pattern-recognition receptor (PRR) signaling molecules. Nucleotide-binding oligomerization domain 2 (NOD2) is a cytoplasmic receptor that recognizes invading molecules and danger signals inside the cells. Recent studies highlight the importance of NOD2′s function in maintaining the homeostasis of human body microbiota and innate immune responses, including induction of proinflammatory cytokines, regulation of autophagy, modulation of endoplasmic reticulum (ER) stress, etc. In addition, there is extensive cross-talk between NOD2 and the Toll-like receptors that are so important in the induction and tuning of adaptive immunity. Polymorphisms of NOD2′s encoding gene are associated with several pathological conditions, highlighting NOD2′s functional importance. In this study, we summarize NOD2′s role in cellular signaling pathways and take a look at the possible consequences of common NOD2 polymorphisms on the structure and function of this receptor.

Rice black-streaked dwarf virus P10 promotes phosphorylation of GAPDH (glyceraldehyde-3-phosphate dehydrogenase) to induce autophagy in Laodelphax striatellus

Macroautophagy/autophagy is an important innate and adaptive immune response that can clear microbial pathogens through guiding their degradation. Virus infection in animals and plants is also known to induce autophagy. However, how virus infection induces autophagy is largely unknown. Here, we provide evidence that the early phase of rice black-streaked dwarf virus (RBSDV) infection in Laodelphax striatellus can also induce autophagy, leading to suppression of RBSDV invasion and accumulation. We have determined that the main capsid protein of RBSDV (P10) is the inducer of autophagy. RBSDV P10 can specifically interact with GAPDH (glyceraldehyde-3-phosphate dehydrogenase), both in vitro and in vivo. Silencing of GAPDH in L. striatellus could significantly reduce the activity of autophagy induced by RBSDV infection. Furthermore, our results also showed that both RBSDV infection and RBSDV P10 alone can promote phosphorylation of AMP-activated protein kinase (AMPK), resulting in GAPDH phosphorylation and relocation of GAPDH from the cytoplasm into the nucleus in midgut cells of L. striatellus or Sf9 insect cells. Once inside the nucleus, phosphorylated GAPDH can activate autophagy to suppress virus infection. Together, these data illuminate the mechanism by which RBSDV induces autophagy in L. striatellus, and indicate that the autophagy pathway in an insect vector participates in the anti-RBSDV innate immune response.

Autophagy: Instructions from the extracellular matrix

In recent years, extensive research has uncovered crucial regulatory roles for the extracellular matrix (ECM) in regulating autophagy. Autophagy is a ubiquitous and highly conserved catabolic process that allows the selective removal and recycling of cytosolic components via lysosomal or vacuolar degradation. Due to its pivotal role in cellular homeostasis, the impairment of autophagy is involved in the pathophysiology of numerous diseases, comprising infectious diseases, immune and neurodegenerative disorders, renal and hepatic diseases, intervertebral and cartilage disorders, as well as fibrosis and cancer. Several ECM-derived proteoglycans and proteins, including decorin, biglycan, endorepellin, endostatin, collagen VI, and plasminogen kringle 5, have been identified as strong inducers of autophagy. In contrast, laminin α2, perlecan, and lumican exert opposite function by suppressing autophagy. Importantly, by direct interaction with various receptors, which interplay with their co-receptors and adhesion molecules, the ECM is able to direct autophagy in a molecular and cell context-specific manner. Thus, vast pharmacological potential resides in translating this knowledge into the development of ECM-derived therapeutics selectively regulating autophagy.

Autophagy as a Target for Drug Development Of Skin Infection Caused by Mycobacteria

Pathogenic mycobacteria species may subvert the innate immune mechanisms and can modulate the activation of cells that cause disease in the skin. Cutaneous mycobacterial infection may present different clinical presentations and it is associated with stigma, deformity, and disability. The understanding of the immunopathogenic mechanisms related to mycobacterial infection in human skin is of pivotal importance to identify targets for new therapeutic strategies. The occurrence of reactional episodes and relapse in leprosy patients, the emergence of resistant mycobacteria strains, and the absence of effective drugs to treat mycobacterial cutaneous infection increased the interest in the development of therapies based on repurposed drugs against mycobacteria. The mechanism of action of many of these therapies evaluated is linked to the activation of autophagy. Autophagy is an evolutionary conserved lysosomal degradation pathway that has been associated with the control of the mycobacterial bacillary load. Here, we review the role of autophagy in the pathogenesis of cutaneous mycobacterial infection and discuss the perspectives of autophagy as a target for drug development and repurposing against cutaneous mycobacterial infection.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Autophagy in Viral Development and Progression of Cancer

Autophagy is a complex degradative process by which eukaryotic cells capture cytoplasmic components for subsequent degradation through lysosomal hydrolases. Although this catabolic process can be triggered by a great variety of stimuli, action in cells varies according to cellular context. Autophagy has been previously linked to disease development modulation, including cancer. Autophagy helps suppress cancer cell advancement in tumor transformation early stages, while promoting proliferation and metastasis in advanced settings. Oncoviruses are a particular type of virus that directly contribute to cell transformation and tumor development. Extensive molecular studies have revealed complex ways in which autophagy can suppress or improve oncovirus fitness while still regulating viral replication and determining host cell fate. This review includes recent advances in autophagic cellular function and emphasizes its antagonistic role in cancer cells.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Effect of an Antagonistic Peptide of CCR5 on the Expression of Autophagy-related Genes and β-Arrestin 2 in Lung Tissues of Asthmatic Mice

Purpose

The mechanisms of CC chemokine receptor 5 (CCR5) in the process of autophagy remain unknown. In this study, we examined the role of HY peptide, which is an antagonistic peptide specifically binding the second extracellular loop of CCR5, in the expression of autophagy genes and β-arrestin 2 in lung tissues of asthmatic mice.

Methods

Experimental asthmatic mice were treated with HY peptide and dexamethasone sodium phosphate (Dex). Airway inflammation, autophagy-related genes, autophagic vacuoles (AVs) and β-arrestin 2 were examined in lung tissues, and the correlation between β-arrestin 2 and LC3 expression was assessed.

Results

HY peptide and Dex treatments alleviate airway inflammation. The expression of autophagy-related genes, such as BECN1, ATG5 and LC3, was decreased in the lung tissues of the asthmatic mice. However, HY peptide and Dex treatments increased the expression of these genes as well as the formation of AVs. Additionally, the expression of the β-arrestin 2 protein was significantly increased in the HY peptide-treated group, and positive cells expressing β-arrestin 2 were mainly located in the membrane and cytoplasm of bronchial epithelial cells. The β-arrestin 2 expression was positively correlated with the expression of LC3 in the model and HY peptide-treated groups.

Conclusions

HY peptide inhibits airway inflammation, autophagic dysfunction exists in asthmatic mice, and targeting HY peptide increases the expression of autophagy-related genes. Thus, β-arrestin 2 may participate in the mechanisms underlying these processes.

ATG5-Dependent Autophagy Uncouples T-cell Proliferative and Effector Functions and Separates Graft-versus-Host Disease from Graft-versus-Leukemia

Autophagy is a vital cellular process whose role in T immune cells is poorly understood, specifically, in its regulation of allo-immunity. Stimulation of wild-type T cells in vitro and in vivo with allo-antigens enhances autophagy. To assess the relevance of autophagy to T-cell allo-immunity, we generated T-cell-specific Atg5 knock-out mice. Deficiency of ATG5-dependent autophagy reduced T-cell proliferation and increased apoptosis following in vitro and in vivo allo-stimulation. The absence of ATG5 in allo-stimulated T cells enhanced their ability to release effector cytokines and cytotoxic functions, uncoupling their proliferation and effector functions. Absence of autophagy reduced intracellular degradation of cytotoxic enzymes such as granzyme B, thus enhancing the cytotoxicity of T cells. In several in vivo models of allo-HSCT, ATG5-dependent dissociation of T-cell functions contributed to significant reduction in graft-versus-host disease (GVHD) but retained sufficient graft versus tumor (GVT) response. Our findings demonstrate that ATG5-dependent autophagy uncouples T-cell proliferation from its effector functions and offers a potential new strategy to enhance outcomes after allo-HSCT. SIGNIFICANCE: These findings demonstrate that induction of autophagy in donor T-cell promotes GVHD, while inhibition of T-cell autophagy mitigates GVHD without substantial loss of GVL responses.

Cytoplasmic Cargo Receptor p62 Inhibits Avibirnavirus Replication by Mediating Autophagic Degradation of Viral Protein VP2

Avibirnavirus causes severe immunosuppression and mortality in young chickens. VP2, the capsid protein of avibirnavirus, is responsible for virus assembly, maturation, and replication. Previous study showed that avibirnavirus particles could be engulfed into the autophagosome and degradation of virus particles took apart. Selective autophagy is a highly specific and regulated degradation pathway for the clearance of damaged or unwanted cytosolic components and superfluous organelles as well as invading microbes. However, whether and how selective autophagy removes avibirnavirus capsids is largely unknown. Here, we have shown that selective autophagy specifically clears ubiquitinated avibirnavirus protein VP2 by p62 recognition and that p62 is an inhibitor of avibirnavirus replication, highlighting the role of p62 as a potential drug target for mediating the removal of ubiquitinated virus components from cells.

Selective autophagy regulates the degradation of cytoplasmic cargos, such as damaged organelles, invading pathogens, and aggregated proteins. Furthermore, autophagy is capable of degrading avibirnavirus, but the mechanism responsible for this process is unclear. Here, we show that autophagy cargo receptor p62 regulates the degradation of the avibirnavirus capsid protein VP2. Binding of p62 to VP2 enhances autophagic induction and promotes autophagic degradation of viral protein VP2. Further study showed that the interaction of p62 with viral protein VP2 is dependent on ubiquitination at the K411 site of VP2 and the ubiquitin-associated domain of p62. Mutation analysis showed that the K411R mutation of viral protein VP2 prohibits its p62-mediated degradation. Consistent with this finding, p62 lacking the ubiquitin-associated domain or the LC3-interacting region no longer promoted the degradation of VP2. Virus production revealed that the knockout of p62 but not the overexpression of p62 promotes the replication of avibirnavirus. Collectively, our findings suggest that p62 mediates selective autophagic degradation of avibirnavirus protein VP2 in a ubiquitin-dependent manner and is an inhibitor of avibirnavirus replication.

IMPORTANCE Avibirnavirus causes severe immunosuppression and mortality in young chickens. VP2, the capsid protein of avibirnavirus, is responsible for virus assembly, maturation, and replication. Previous study showed that avibirnavirus particles could be engulfed into the autophagosome and degradation of virus particles took apart. Selective autophagy is a highly specific and regulated degradation pathway for the clearance of damaged or unwanted cytosolic components and superfluous organelles as well as invading microbes. However, whether and how selective autophagy removes avibirnavirus capsids is largely unknown. Here, we have shown that selective autophagy specifically clears ubiquitinated avibirnavirus protein VP2 by p62 recognition and that p62 is an inhibitor of avibirnavirus replication, highlighting the role of p62 as a potential drug target for mediating the removal of ubiquitinated virus components from cells.

Autophagy in Multiple Sclerosis: Two Sides of the Same Coin

Multiple sclerosis (MS) is a complex auto-immune disorder of the central nervous system (CNS) that involves a range of CNS and immune cells. MS is characterized by chronic neuroinflammation, demyelination, and neuronal loss, but the molecular causes of this disease remain poorly understood. One cellular process that could provide insight into MS pathophysiology and also be a possible therapeutic avenue, is autophagy. Autophagy is an intracellular degradative pathway essential to maintain cellular homeostasis, particularly in neurons as defects in autophagy lead to neurodegeneration. One of the functions of autophagy is to maintain cellular homeostasis by eliminating defective or superfluous proteins, complexes, and organelles, preventing the accumulation of potentially cytotoxic damage. Importantly, there is also an intimate and intricate interplay between autophagy and multiple aspects of both innate and adaptive immunity. Thus, autophagy is implicated in two of the main hallmarks of MS, neurodegeneration, and inflammation, making it especially important to understand how this pathway contributes to MS manifestation and progression. This review summarizes the current knowledge about autophagy in MS, in particular how it contributes to our understanding of MS pathology and its potential as a novel therapeutic target.

Effects of the linoleic acid/docosahexaenoic acid ratio and concentration inducing autophagy in Raw264.7 cells against Staphylococcus aureus

Our study was to understand the autophagy induce by different ratios and concentrations of LA/DHA on Raw264.7 cell, and then to investigate the effect of Raw264.7 autophagy on the clearance of Staphylococcus aureus. Raw264.7 cells was treated by LA/DHA in different concentrations (50/100 µmol/L) and ratios (4:1, 6:1, 8:1, 1:4, 1:6 and 1:8) for 6/12/24 h, cell viability assay was assessed by Cell Counting Kit-8, LC3B, p62, P-mTOR, P-Akt, P-PI3K and BECN 1 were detected by the Western blot. LA/DHA could induce autophagy of Raw264.7 cells through the PI3K-Akt-mTOR signaling pathway, the strong effect on autophagy by the concentration is 100 µmol/L, the ratio is 6:1 of LA/DHA, and the treatment time is 24 h. Compared with the images in the control group obtained by merging red and green fluorescence channels, the treatment of LA, DHA in a ratio of 6:1 at a concentration of 100 µmol/L for 24 h significantly lead to a substantial number of autophagosomes (yellow) as well as autolysosomes (red), enhancing autophagy flux. Autophagy induce by LA/DHA can devour and damage intracellular and extracellular Staphylococcus aureus. These results indicate that LA/DHA cloud induce autophagy and enhance the phagocytosis and killing ability of macrophages to intracellular parasitic bacteria.

MiRNAs in tuberculosis: Their decisive role in the fate of TB

Tuberculosis (TB) is one of the most lethal global infectious diseases. Despite the availability of much higher levels of technology in health and medicine, tuberculosis still remains a serious global health problem. Mycobacterium tuberculosis has the capacity for prolonged survival inside macrophages by exploiting host metabolic and energy pathways and perturbing autophagy and apoptosis of infected cells. The mechanism(s) underlying this process are not completely understood but evidence suggests that mycobacteria subvert the host miRNA network to enable mycobacterial survival. We present here a comprehensive review on the role of miRNAs in TB immune escape mechanisms and the potential for miRNA-based TB therapeutics. Further validation studies are required to (i) elucidate the precise effect of TB on host miRNAs, (ii) determine the inhibition of mycobacterial burden using miRNA-based therapies and (iii) identify novel miRNA biomarkers that may prove useful in TB diagnosis and treatment monitoring.

Arsenic induces mTOR-dependent autophagy, whereas it impairs the autophagy-lysosome pathway and the potential role of TFEB in cultured dendritic cells

Arsenic is a toxic metalloid, which also compromises immunity and causes various immunological disorders. Exposure to arsenic exerts the immunosuppressive properties of dendritic cells (DCs). Autophagy is a self-renewal process of cells, which degrades damaged macromolecules and organelles through the lysosomal pathway. Thus, herein, we attempt to clarify the impacts of autophagy and the autophagy-lysosome pathway on arsenic-exposed DCs. Bone marrow-derived dendritic cells (BMDCs) were exposed to different concentrations of arsenic (0.25, 0.5 and 1 μM) with or without LPS stimulation. Initially, we observed that arsenic induced autophagosome accumulation, significantly enhanced the LC3 II and p62 expressions and down-regulated the p-mTOR protein levels. We also determined that arsenic-induced autophagy occurred via an mTOR pathway. The results further revealed that arsenic inhibited autophagic flux in LPS-stimulated BMDCs using the autophagy inhibitor chloroquine (CQ). Meanwhile, arsenic significantly decreased the number of lysosomes, protein expression of lysosomal-specific markers LAMP1 and LAMP2, and the protein levels of lysosomal cysteine cathepsins (CTSD and CTSL). Moreover, the overexpression of transcription factor EB (TFEB), the master transcriptional regulator of autophagy and lysosome biogenesis, partially relieved arsenic-inhibited lysosomal CTSD and CTSL expressions, recovered the disorder of autophagic flux, promoted the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-12, and reduced anti-inflammatory cytokine IL-10 secretion. In summary, our results support the idea that arsenic induces autophagy through an mTOR-dependent pathway in cultured BMDCs. Meanwhile, arsenic weakens the process of autophagic flux, which may be partially due to lysosomal dysfunction. Furthermore, we also suggest that TFEB can positively act on the autophagy-lysosome pathway and influence the expression of immunocytokines in DCs.

The RUFYs, a Family of Effector Proteins Involved in Intracellular Trafficking and Cytoskeleton Dynamics

Intracellular trafficking is essential for cell structure and function. In order to perform key tasks such as phagocytosis, secretion or migration, cells must coordinate their intracellular trafficking, and cytoskeleton dynamics. This relies on certain classes of proteins endowed with specialized and conserved domains that bridge membranes with effector proteins. Of particular interest are proteins capable of interacting with membrane subdomains enriched in specific phosphatidylinositol lipids, tightly regulated by various kinases and phosphatases. Here, we focus on the poorly studied RUFY family of adaptor proteins, characterized by a RUN domain, which interacts with small GTP-binding proteins, and a FYVE domain, involved in the recognition of phosphatidylinositol 3-phosphate. We report recent findings on this protein family that regulates endosomal trafficking, cell migration and upon dysfunction, can lead to severe pathology at the organismal level.

Partial impairment of late-stage autophagic flux in murine splenocytes leads to sqstm1/p62 mediated nrf2-keap1 antioxidant pathway activation and induced proteasome-mediated degradation in malaria

Splenomegaly, a major symptom in Plasmodium infection, is extensively studied for its immunopathological role in mice malaria model infected with Plasmodium berghei ANKA. The status of autophagic regulation in hosts in malaria pathogenesis remains unreported till date. This study demonstrated the autophagy, proteasomal degradation and NRF2-KEAP1 antioxidant pathway status in the host during Plasmodium infection taking murine spleen as our organ of interest. Initial staining and autophagic gene expression indicate a possibility of autophagic pathway activation. Although the conversion of LC3A to LC3B and lysosome-autophagosome fusion increases, the final degradation step remains incomplete. Resultant upregulation of p62 and its altered phosphorylated status enhances its binding to keap1 causing NRF2 translocation to the nucleus. NRF2 act as transcription factor upregulating p62 level itself leading to an autoinduction loop of p62 expression. Interestingly, enhancement of P62 interaction with proteasome subunit RPT1 indicates a possible role in transporting ubiquitinated cargo to proteasome complex. Ubiquitination level increased with subsequent upregulation of all three modes of proteasomal degradation i.e trypsin-like, caspase-like and especially chymotrypsin-like. Sqstm1/p62 plays a critical central role in regulating autophagy, proteasomal degradation, and NRF2-KEAP1 pathway. The incomplete autophagic flux in the final step may be a key therapeutic target, as autophagic degradation and subsequent pathogenic peptide presentation is of utmost necessity for downstream immune response.

Spermine and spermidine modulate T-cell function in older adults with and without cognitive decline ex vivo

The global increase in neurodegenerative disorders is one of the most crucial public health issues. Oral polyamine intake was shown to improve memory performance which is thought to be mediated at least in part via increased autophagy induced in brain cells. In Alzheimer’s Disease, T-cells were identified as important mediators of disease pathology. Since autophagy is a central regulator of cell activation and cytokine production, we investigated the influence of polyamines on T-cell activation, autophagy, and the release of Th1/Th2 cytokines from blood samples of patients (n=22) with cognitive impairment or dementia in comparison to healthy controls (n=12) ex vivo. We found that spermine downregulated all investigated cytokines in a dose-dependent manner. Spermidine led to an upregulation of some cytokines for lower dosages, while high dosages downregulated all cytokines apart from upregulated IL-17A. Autophagy and T-cell activation increased in a dose-dependent manner by incubation with either polyamine. Although effects in patients were seen in lower concentrations, alterations were similar to controls.

We provide novel evidence that supplementation of polyamines alters the function of T-cells. Given their important role in dementia, these data indicate a possible mechanism by which polyamines would help to prevent structural and cognitive decline in aging.

Sulfated glycolipid PG545 induces endoplasmic reticulum stress and augments autophagic flux by enhancing anticancer chemotherapy efficacy in endometrial cancer

The sulfated glycolipid PG545 shows promising antitumor activity in various cancers. This study was conducted to explore the effects and the mechanism of PG545 action in endometrial cancer (EC). PG545 exhibited strong synergy as assessed by the Chou-Talalay-Method in vitro when combined with cisplatin, or paclitaxel in both type I (Hec1B) and type II (ARK2) EC cell lines. While PG545 showed antitumor activity as monotherapy, a combination of PG545 with paclitaxel and cisplatin was highly effective in reducing the tumor burden and significantly prolonged survival of both Hec1B and ARK2 xenograft bearing mice. Mechanistically, PG545 elicits ER stress as an early response with resultant induction of autophagy. Our data demonstrated an increase in pERK, Bip/Grp78, IRE1α, Calnexin and CHOP/GADD153 within 6-24 hrs of PG545 treatment in EC cells. In parallel, PG545 also blocked FGF2 and HB-EGF mediated signaling in EC cells. Moreover, melatonin-mediated ER stress inhibition reduced PG545-mediated autophagy and PG545 in combination with cisplatin further heightened this stress response. Collectively these data indicate that PG545 exhibits strong synergistic effects with chemotherapeutics in vitro and showed promising antitumor activity in vivo. Our preclinical data indicates that in future studies PG545 can be a useful adjunct to chemotherapy in endometrial cancer.

Epithelial cells expressed IL-33 to promote degranulation of mast cells through inhibition on ST2/PI3K/mTOR-mediated autophagy in allergic rhinitis

Nasal epithelial cells are the first barrier against allergen infiltration in allergic rhinitis (AR), and the relationship between nasal epithelial cells and mast cell-mediated hypersensitivity remains unclear. This study aimed to investigate the possible association between allergen-challenged nasal epithelial cells (AR-HNEpC) and mast cell degranulation in AR. Our data revealed that calcium influx and degranulation were increased in AR-HNEpC-co-cultured mast cells. Expression of IL-33, a factor that binds to ST2 receptors on mast cells and regulates their degranulation, was elevated in AR-HNEpC. Blocking IL-33/ST2 pathway activated autophagy and inhibited degranulation and inflammatory factor release in mast cells. Furthermore, PI3K/mTOR was increased in IL-33-treated mast cells. Inhibition on PI3K/mTOR pathway enhanced autophagy and inhibited degranulation. Analysis using an in vivo AR model supported the above findings. In conclusion, IL-33 from epithelial cells promotes degranulation of mast cells in AR through inhibition on ST2/PI3K/mTOR-mediated autophagy, which provides a potential therapeutic target for the disease.Abbreviations: AR: allergic rhinitis; IL: interleukin; TNF-α: tumor necrosis factor-alpha; INF-γ: interferon-gamma; HNEpC: human nasal epithelial cell line; ATCC: American Type Culture Collection; C48/80: compound 48/80; 3-MA: 3-methyladenine; qPCR: quantitative PCR; AR-HNEpC: dust mite allergen-treated nasal epithelial cells; IgE: immunoglobulin E; Atg7: autophagy-related gene 7.

Deleting key autophagy elongation proteins induces acquirement of tumor-associated phenotypes via ISG15

Autophagy is a cellular catabolic process that maintains intracellular homeostasis using lysosomal degradation systems. We demonstrate that inhibiting autophagy by depleting essential autophagy elongation proteins, Atg5 or Atg7, induces ISG15 expression through STING-mediated cytosolic dsDNA response. Genome stability is impaired in ATG5- or ATG7-depleted cells, and thus, double-strand breakages of DNA increase and cytosolic dsDNA accumulates. Accumulated cytosolic dsDNA induces the STING pathway to activate type I IFN signals which induce STAT1 activity and downregulate ATF3. When depletion of ATG5 or ATG7 inhibits autophagy, ATF3 is downregulated and STAT1 is upregulated. Furthermore, inhibiting autophagy induces ISG15 expression through STAT1 activation, which promotes acquisition of tumor-associated phenotypes such as migration, invasion, and proliferation. In conclusion, it appears that via the STING-mediated cytosolic dsDNA response, the STAT1-ISG15 axis mediates the relationship between autophagy and the immune system in relation to tumor progression. Moreover, combined with autophagy control, regulating ISG15 expression could be a novel strategy for cancer immunotherapy.

Autophagy regulation as a promising approach for improving cancer immunotherapy

Autophagy plays a critical role in intracellular metabolism and maintaining cellular homeostasis. Certain tumor cells present a higher basal autophagy rate and autophagy inhibition can lead to impaired metabolic dysfunction in autophagy-dependent tumor cells. Autophagy status in immune cells dictates their fate and response to antigen; however, autophagy in immune cells may be beneficial or detrimental depending on the developmental stage of the cell and more specifically its degree of differentiation. Autophagy-deficient hosts present variations in many metabolites, proteins and enzymes that may have tumor-promoting or -inhibiting effects. The centrality of autophagy in the metabolism of some cancers and immune cells poses as a critical target whose mechanisms must be further unraveled to optimize patient response and prevent tumor recurrence.

Autophagy Promotes Porcine Parvovirus Replication and Induces Non-Apoptotic Cell Death in Porcine Placental Trophoblasts

Autophagy plays important roles in the infection and pathogenesis of many viruses, yet the regulatory roles of autophagy in the process of porcine parvovirus (PPV) infection remain unclear. Herein, we show that PPV infection induces autophagy in porcine placental trophoblasts (PTCs). Induction of autophagy by rapamycin (RAPA) inhibited the occurrence of apoptotic cell death, yet promoted viral replication in PPV-infected cells; inhibition of autophagy by 3-MA or ATG5 knockdown increased cellular apoptosis and reduced PPV replication. Interestingly, we found that in the presence of caspase-inhibitor zVAD-fmk, PPV induces non-apoptotic cell death that was characterized by lysosomal damage and associated with autophagy. Induction of complete autophagy flux by RAPA markedly promoted PPV replication compared with incomplete autophagy induced by RAPA plus bafilomycin (RAPA/BAF) in the early phase of PPV infection (24 h.p.i.). Meanwhile, induction of complete autophagy with RAPA increased lysosomal damage and non-apoptotic cell death in the later phase of PPV infection. Therefore, our data suggest that autophagy can enhance PPV replication and promote the occurrence of lysosomal-damage-associated non-apoptotic cell death in PPV-infected porcine placental trophoblasts.