Host Cell Autophagy Research Articles

Nanomaterial-mediated host directed therapy of tuberculosis by manipulating macrophage autophagy.

Tuberculosis (TB), induced by Mycobacterium tuberculosis (Mtb) infection, remains a major public health issue worldwide. Mtb has developed complicated strategies to inhibit the immunological clearance of host cells, which significantly promote TB epidemic and weaken the anti-TB treatments. Host-directed therapy (HDT) is a novel approach in the field of anti-infection for overcoming antimicrobial resistance by enhancing the antimicrobial activities of phagocytes through phagosomal maturation, autophagy and antimicrobial peptides. Autophagy, a highly conserved cellular event within eukaryotic cells that is effective against a variety of bacterial infections, has been shown to play a protective role in host defense against Mtb. In recent decades, the introduction of nanomaterials into medical fields open up a new scene for novel therapeutics with enhanced efficiency and safety against different diseases. The active modification of nanomaterials not only allows their attractive targeting effects against the host cells, but also introduce the potential to regulate the host anti-TB immunological mechanisms, such as apoptosis, autophagy or macrophage polarization. In this review, we introduced the mechanisms of host cell autophagy for intracellular Mtb clearance, and how functional nanomaterials regulate autophagy for disease treatment. Moreover, we summarized the recent advances of nanomaterials for autophagy regulations as novel HDT strategies for anti-TB treatment, which may benefit the development of more effective anti-TB treatments.

Immune System Responses against Mycobacterium tuberculosis and its Mechanisms to Escape from the Immune System

Background: Mycobacterium tuberculosis (MTB) employs a variety of strategies to evade the host immune response, enabling its persistence and the development of tuberculosis. These evasion tactics involve thwarting lysosome formation, manipulating intracellular pH, and disrupting apoptosis and autophagy processes within host cells. Specifically, MTB interferes with lysosome acidification by modulating calcium ions (Ca2+), iron ions, and hydrogen ions (H+ ), creating an optimal environment for its survival within host cells. Furthermore, MTB inhibits host cell apoptosis and autophagy, critical defense mechanisms against intracellular pathogens. Understanding these immunological escape mechanisms is paramount for developing effective tuberculosis therapies. Future research should focus on targeting MTB evasion strategies to pave the way for innovative tuberculosis treatments. Conclusion: There is still a long road ahead of us to understand the immunological escape mechanism used by MTB. Over the past 50 years, numerous studies have looked into the immune response and the pathogenic processes of MTB.

Effect of natural products on host cell autophagy induced by Influenza A virus infection.

Influenza A virus (IAV) can cause seasonal epidemics and global pandemics, posing serious threats to public health, making a deeper understanding of its biological characteristics and effective countermeasure strategies essential. Autophagy not only maintains cellular homeostasis but also plays an important role in host defense against IAV infection. However, the relationship between IAV and autophagy is complex, and effective antiviral drugs are not yet available. Natural products have shown excellent potential in disease control due to their diversity and multi-targeting. This review focuses on the relationship between IAV and autophagy and discusses the potential of targeting autophagic pathways for the development of new antiviral therapies. Particularly, the use of plant extracts as autophagy modulators has garnered attention due to their non-toxic nature and cost-effectiveness, which provides strong support for the development of future antiviral drugs that can help to inhibit viral infections and slow down disease progression.

Autophagy promotes replication of Bombyx mori Nucleopolyhedrovirus in insect cells

BmNPV is a pathogen that infects silkworms exclusively. Although the interaction between BmNPV and the silkworm has been widely noticed and studied, its specific mechanism has still not been elucidated. In this study, we investigated whether BmNPV infection induces the onset of host cell autophagy to enhance viral replication. We observed a significant increase in double- or single-membrane vesicles and an accumulation of enhanced green fluorescent protein eGFP-ATG8 spots in virus-infected cells 72 h after BmNPV infection, accompanied by a conversion of ATG8 to ATG8-PE. In addition, we observed changes in the mitochondrial morphology of BmN cells after BmNPV infection by transmission electron microscopy. By detecting the mitochondrial membrane potential, we found that BmNPV infection resulted in the decrease of mitochondrial membrane potential, and that eGFP-ATG8 was able to co-localise with mitochondria after virus infection of the cells. Moreover, the use of drugs to regulate the occurrence of autophagy affects the replication of cellular BmNPV. Our data demonstrates that BmNPV infection induces host cell autophagy and leads to cellular mitochondrial damage, which in turn may lead to mitochondrial autophagy, and that BmNPV-induced host autophagy promotes its replication in cells. These findings will provide clues for further understanding of host-virus interactions.

An Intrinsic Host Defense against HSV-1 Relies on the Activation of Xenophagy with the Active Clearance of Autophagic Receptors.

Autophagy engulfs cellular components in double-membrane-bound autophagosomes for clearance and recycling after fusion with lysosomes. Thus, autophagy is a key process for maintaining proteostasis and a powerful cell-intrinsic host defense mechanism, protecting cells against pathogens by targeting them through a specific form of selective autophagy known as xenophagy. In this context, ubiquitination acts as a signal of recognition of the cargoes for autophagic receptors, which direct them towards autophagosomes for subsequent breakdown. Nevertheless, autophagy can carry out a dual role since numerous viruses including members of the Orthoherpesviridae family can either inhibit or exploit autophagy for its own benefit and to replicate within host cells. There is growing evidence that Herpes simplex virus type 1 (HSV-1), a highly prevalent human pathogen that infects epidermal keratinocytes and sensitive neurons, is capable of negatively modulating autophagy. Since the effects of HSV-1 infection on autophagic receptors have been poorly explored, this study aims to understand the consequences of HSV-1 productive infection on the levels of the major autophagic receptors involved in xenophagy, key proteins in the recruitment of intracellular pathogens into autophagosomes. We found that productive HSV-1 infection in human neuroglioma cells and keratinocytes causes a reduction in the total levels of Ub conjugates and decreases protein levels of autophagic receptors, including SQSTM1/p62, OPTN1, NBR1, and NDP52, a phenotype that is also accompanied by reduced levels of LC3-I and LC3-II, which interact directly with autophagic receptors. Mechanistically, we show these phenotypes are the result of xenophagy activation in the early stages of productive HSV-1 infection to limit virus replication, thereby reducing progeny HSV-1 yield. Additionally, we found that the removal of the tegument HSV-1 protein US11, a recognized viral factor that counteracts autophagy in host cells, enhances the clearance of autophagic receptors, with a significant reduction in the progeny HSV-1 yield. Moreover, the removal of US11 increases the ubiquitination of SQSTM1/p62, indicating that US11 slows down the autophagy turnover of autophagy receptors. Overall, our findings suggest that xenophagy is a potent host defense against HSV-1 replication and reveals the role of the autophagic receptors in the delivery of HSV-1 to clearance via xenophagy.

EV71 5’UTR interacts with 3D protein affecting replication through the AKT-mTOR pathway

BackgroundEV71 is one of the important pathogens of Hand-foot-and-mouth disease (HFMD), which causes serious neurological symptoms. Several studies have speculated that there will be interaction between 5′UTR and 3D protein. However, whether 5′UTR interacts with the 3D protein in regulating virus replication has not been clarified.MethodsFour 5'UTR mutation sites (nt88C/T, nt90-102-3C, nt157G/A and nt574T/A) and two 3D protein mutation sites (S37N and R142K) were mutated or co-mutated using virulent strains as templates. The replication of these mutant viruses and their effect on autophagy were determined.Results5'UTR single-point mutant strains, except for EGFP-EV71(nt90-102-3C), triggered replication attenuation. The replication ability of them was weaker than that of the parent strain the virulent strain SDLY107 which is the fatal strain that can cause severe neurological complications. While the replication level of the co-mutant strains showed different characteristics. 5 co-mutant strains with interaction were screened: EGFP-EV71(S37N-nt88C/T), EGFP-EV71(S37N-nt574T/A), EGFP-EV71(R142K-nt574T/A), EGFP-EV71(R142K-nt88C/T), and EGFP-EV71(R142K-nt157G/A). The results showed that the high replicative strains significantly promoted the accumulation of autophagosomes in host cells and hindered the degradation of autolysosomes. The low replicative strains had a low ability to regulate the autophagy of host cells. In addition, the high replicative strains also significantly inhibited the phosphorylation of AKT and mTOR.ConclusionsEV71 5'UTR interacted with the 3D protein during virus replication. The co-mutation of S37N and nt88C/T, S37N and nt574T/ A, R142K and nt574T/A induced incomplete autophagy of host cells and promoted virus replication by inhibiting the autophagy pathway AKT-mTOR. The co-mutation of R142K and nt88C/T, and R142K and nt157G/A significantly reduced the inhibitory effect of EV71 on the AKT-mTOR pathway and reduced the replication ability of the virus.

Role of Macrophage PIST Protein in Regulating Leishmania major Infection.

PDZ protein interacting specifically with Tc10 or PIST is a mammalian trans-Golgi resident protein that regulates subcellular sorting of plasma membrane receptors. PIST has recently emerged as a key player in regulating viral pathogenesis. Nevertheless, the involvement of PIST in parasitic infections remains unexplored. Leishmania parasites infiltrate their host macrophage cells through phagocytosis, where they subsequently multiply within the parasitophorous vacuole (PV). Host cell autophagy has been found to be important in regulating this parasite infection. Since PIST plays a pivotal role in triggering autophagy through the Beclin 1-PI3KC3 pathway, it becomes interesting to identify the status of PIST during Leishmania infection. We found that while macrophage cells are infected with Leishmania major (L. major), the expression of PIST protein remains unaltered; however, it traffics from the Golgi compartment to PV. Further, we identified that in L. major-infected macrophage cells, PIST associates with the autophagy regulatory protein Beclin 1 within the PVs; however, PIST does not interact with LC3. Reduction in PIST protein through siRNA silencing significantly increased parasite burden, whereas overexpression of PIST in macrophages restricted L. major infectivity. Together, our study reports that the macrophage PIST protein is essential in regulating L. major infectivity.

The Chinese herbal prescription JZ-1 promotes extracellular vesicle production and protects against herpes simplex virus type 2 infection in vitro

ObjectiveGenital herpes, primarily caused by HSV-2 infection, remains a widespread sexually transmitted ailment. Extracellular vesicles play a pivotal role in host-virus confrontation. Recent research underscores the influence of Chinese herbal prescriptions on extracellular vesicle production and composition. This study aims to probe the impact of JieZe-1 (JZ-1) on extracellular vesicle components, elucidating its mechanisms against HSV-2 infection via extracellular vesicles. MethodsThe JZ-1's anti-HSV-2 effects were assessed using CCK-8 assay. Extracellular vesicles were precisely isolated utilizing ultracentrifugation and subsequently characterized through TEM, NTA, and Western Blot analyses. The anti-HSV-2 activity of extracellular vesicles was gauged using CCK-8, Western Blot, and immunofluorescence. Additionally, high-throughput sequencing was employed to detect miRNAs from extracellular vesicles, unraveling the potential antiviral mechanisms of JZ-1. ResultsAntiviral efficacy of JZ-1 was shown in VK2/E6E7, HeLa, and Vero cells. The samples extracted from cell supernatant by ultracentrifugation were identified as extracellular vesicles. In VK2/E6E7 cells, extracellular vesicles from JZ-1 group enhanced cell survival rates and diminished the expression of intracellular viral protein gD, contrasting with the inert effect of control group vesicles. Extracellular vesicles from JZ-1 treated Vero cells demonstrated a weaker yet discernible anti-HSV-2 effect. Conversely, extracellular vesicles of HeLa cells exhibited no anti-HSV-2 effect from either group. High-throughput sequencing of VK2/E6E7 cell extracellular vesicles unveiled significant upregulation of miRNA-101, miRNA-29a, miRNA-29b, miRNA-29c, and miRNA-637 in JZ-1 group vesicles. KEGG pathway analysis suggested that these miRNAs may inhibit PI3K/AKT/mTOR signaling pathway and induce autophagy of host cells to protect against HSV-2. Western blot confirmed the induction of autophagy and inhibition of AKT/mTOR in VK2/E6E7 cells with JZ-1 group extracellular vesicles treatment. ConclusionJZ-1 had an anti-HSV-2 efficacy. After JZ-1 stimulation, VK2/E6E7 cells secreted extracellular vesicles which protect host cells from HSV-2 infection. High-throughput sequencing showed that these extracellular vesicles contained a large number of miRNAs targeting PI3K/AKT/mTOR pathway. JZ-1 group extracellular vesicles could inhibit the activation of AKT/mTOR pathway and induce the host cells autophagy.

Ehrlichia chaffeensis Etf-3 Induces Host RAB15 Upregulation for Bacterial Intracellular Growth.

Ehrlichia chaffeensis infects human monocytes or macrophages and causes human monocytic ehrlichiosis (HME), an emerging life-threatening zoonosis. After internalization, E. chaffeensis resides in membrane-bound inclusions, E. chaffeensis-containing vesicles (ECVs), which have early endosome-like characteristics and fuse with early autophagosomes but not lysosomes, to evade host innate immune microbicidal mechanisms and obtain nutrients for bacterial intracellular growth. The mechanisms exploited by E. chaffeensis to modulate intracellular vesicle trafficking in host cells have not been comprehensively studied. Here, we demonstrate that E. chaffeensis type IV secretion system (T4SS) effector Etf-3 induces RAB15 upregulation in host cells and that RAB15, which is localized on ECVs, inhibits ECV fusion with lysosomes and induces autophagy. We found that E. chaffeensis infection upregulated RAB15 expression using qRT-PCR, and RAB15 was colocalized with E. chaffeensis using confocal microscopy. Silence of RAB15 using siRNA enhanced ECV maturation to late endosomes and fusion with lysosomes, as well as inhibited host cell autophagy. Overexpression of Etf-3 in host cells specifically induced RAB15 upregulation and autophagy. Our findings deepen the understanding of E. chaffeensis pathogenesis and adaptation in hosts as well as the function of RAB15 and facilitate the development of new therapeutics for HME.

A genome-wide CRISPR screen identified host genes essential for intracellular Brucella survival.

Brucella is a zoonotic intracellular bacterium that poses threats to human health and economic security. Intracellular infection is a hallmark of the agent Brucella and a primary cause of distress, through which the bacterium regulates the host intracellular environment to promote its own colonization and replication, evading host immunity and pharmaceutical killing. Current studies of Brucella intracellular processes are typically premised on bacterial phenotype such as intracellular bacterial survival, followed by biochemical or molecular biological approaches to reveal detailed mechanisms. While such processes can deepen the understanding of Brucella-host interaction, the insights into host alterations in infection would be easily restricted to known pathways. In the current study, we applied CRISPR Cas9 screen to identify host genes that are most affected by Brucella infection on cell viability at the genomic level. As a result of CRISPR screening, we firstly identified that knockout of the negatively selected genes GOLGA6L6, DEFB103B, OR4F29, and ERCC6 attenuate the viability of both the host cells and intracellular Brucella, suggesting these genes to be potential therapeutic targets for Brucella control. In particular, knockout of DEFB103B diminished Brucella intracellular survival by altering host cell autophagy. Conversely, knockout of positive screening genes promoted intracellular proliferation of Brucella. In summary, we screened host genes at the genomic level throughout Brucella infection, identified host genes that are previously not recognized to be involved in Brucella infection, and provided targets for intracellular infection control.IMPORTANCEBrucella is a Gram-negative bacterium that infects common mammals causing arthritis, myalgia, neuritis, orchitis, or miscarriage and is difficult to cure with antibiotics due to its intracellular parasitism. Therefore, unraveling the mechanism of Brucella-host interactions will help controlling Brucella infections. CRISPR-Cas9 is a gene editing technology that directs knockout of individual target genes by guided RNA, from which genome-wide gene-knockout cell libraries can be constructed. Upon infection with Brucella, the cell library would show differences in viability as a result of the knockout and specific genes could be revealed by genomic DNA sequencing. As a result, genes affecting cell viability during Brucella infection were identified. Further testing of gene function may reveal the mechanisms of Brucella-host interactions, thereby contributing to clinical therapy.

Exploring and exploiting the host cell autophagy during Mycobacterium tuberculosis infection.

Tuberculosis, caused by Mycobacterium tuberculosis, is a fatal infectious disease that prevails to be the second leading cause of death from a single infectious agent despite the availability of multiple drugs for treatment. The current treatment regimen involves the combination of several drugs for 6 months that remain ineffective in completely eradicating the infection because of several drawbacks, such as the long duration of treatment and the side effects of drugs causing non-adherence of patients to the treatment regimen. Autophagy is an intracellular degradative process that eliminates pathogens at the early stages of infection. Mycobacterium tuberculosis's unique autophagy-blocking capability makes it challenging to eliminate compared to usual pathogens. The present review discusses recent advances in autophagy-inhibiting factors and mechanisms that could be exploited to identify autophagy-inducing chemotherapeutics that could be used as adjunctive therapy with the existing first-line anti-TB agent to shorten the duration of therapy and enhance cure rates from multidrug-resistant tuberculosis (MDR-TB) and extreme drug-resistant tuberculosis (XDR-TB).

Innate immune escape and adaptive immune evasion of African swine fever virus: A review

African swine fever virus (ASFV) causes hemorrhagic fever in domestic and wild pigs. The continued spread of the virus in Africa, Europe and Asia threatens the global pig industry. The lack of an effective vaccine limits disease control. ASFV has evolved a variety of encoded immune escape proteins and can evade host adaptive immunity, inducing cellular inflammation, autophagy, or apoptosis in host cells. Frequent persistent infections hinder the development of a viral vaccine and impose technical barriers. Currently, knowledge of the virulence-related genes, main pathogenic genes and immunoregulatory mechanism of ASFV is not comprehensive. We explain that ASFV invades the host to regulate its inflammatory response, interferon production, antigen presentation and cellular immunity. Furthermore, we propose potential ideas for ASFV vaccine target design, such as knocking out high-virulence genes in ASFV and performing data mining to identify the main genes that induce antiviral responses. To support a rational strategy for vaccine development, a better understanding of how ASFV interacts with the host and regulates the host's response to infection is needed. We review the current knowledge about ASFV targeting of host innate and adaptive immunity and the mechanisms by which the affected immune pathways are suppressed.

Grp94 Inhibitor HCP1 Suppressed the Replication of SVA in BHK-21 Cells and PK-15 Cells.

Glucoregulatory protein 94 (Grp94) is necessary for the post-viral life cycle and plays a quality control role in viral proteins, but the role of Grp94 in regulating viral replication in host cells is not well known. Therefore, finding a compound that can regulate Grp94 will help us to study the mechanism of viral replication. Previously, we synthesized a coumarin pyrazoline derivative HCP1 that is an effective inhibitor of Grp94. We suppose that HCP1 may inhibit viral replication. This study aimed to investigate the effect of HCP1 on the replication ability of Senecavirus A (SVA), so as to provide a target and a leading compound for revealing the pathogenic mechanism of the virus and developing antiviral drugs. Rat cell lines BHK-21 and porcine cell lines PK-15 were infected with SVA, and the infected cells were treated with different concentrations of HCP1. The cell viability (CCK-8), virus titer (TCID50), autophagy level, and Grp94 expression were measured. The results showed that a low concentration of HCP1 decreased viral titer and viral load in BHK-21 and PK-15 cells, and 5μM HCP1 significantly decreased the expression of SVA VP2 protein. In addition, SVA infection can lead to an increased level of autophagy, and HCP1 can inhibit host cell autophagy caused by SVA infection, thereby inhibiting viral replication and infection. These findings reveal that Grp94 is a key factor in controlling SVA replication, and its inhibitor HCP1 suppresses SVA replication by inhibiting the increase of Grp94 protein level and autophagy induced by SVA. This study will contribute to the development of a new class of small-molecule antiviral drugs.

NDV-induced autophagy enhances inflammation through NLRP3/Caspase-1 inflammasomes and the p38/MAPK pathway

Newcastle disease (ND), caused by the Newcastle disease virus (NDV), is a highly virulent infectious disease of poultry. Virulent NDV can cause severe autophagy and inflammation in host cells. While studies have shown a mutual regulatory relationship between autophagy and inflammation, this relationship in NDV infection remains unclear. This study confirmed that NDV infection could trigger autophagy in DF-1 cells to promote cytopathic and viral replication. NDV-induced autophagy was positively correlated with the mRNA levels of inflammatory cytokines such as IL-1β, IL-8, IL-18, CCL-5, and TNF-α, suggesting that NDV-induced autophagy promotes the expression of inflammatory cytokines. Further investigation demonstrated that NLRP3 protein expression, Caspase-1 activity, and p38 phosphorylation level positively correlated with autophagy, suggesting that NDV-induced autophagy could promote the expression of inflammatory cytokines through NLRP3/Caspase-1 inflammasomes and p38/MAPK pathway. In addition, NDV infection also triggered mitochondrial damage and mitophagy in DF-1 cells, but did not result in a large leakage of reactive oxygen species (ROS) and mitochondrial DNA (mtDNA), indicating that mitochondrial damage and mitophagy do not contribute to the inflammation response during NDV infection.

Critical Role of Viral Protein Hexon in Hypervirulent Fowl Adenovirus Serotype-4-Induced Autophagy by Interaction with BAG3 and Promotion of Viral Replication in LMH Cells.

Hepatitis-pericardial syndrome (HHS) is an acute highly infectious avian disease caused by fowl adenovirus serotype 4 (FAdV-4), characterized by fulminant hepatitis and hydropericardium in broilers. Since 2015, a widespread epidemic has occurred in China due to the emergence of hypervirulent FAdV-4 (HPFAdV-4), causing huge losses to the stakeholders. However, the pathogenesis of HPFAdV-4 and the host responses to its infection remain elusive. Here, we show that infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy in cells and that the autophagy induced by recombinant HPFAdV-4-ON1 (rHPFAdV-4-ON1), a viral strain generated by replacing the hexon gene of wild-type HPFAdV-4 (HPFAdV-4-WT) with the one of nonpathogenic strain FAdV-4-ON1, was remarkably mitigated compared to that of the rHPFAdV-4-WT control, suggesting that HPFAdV-4 hexon is responsible for virus-induced autophagy. Importantly, we found that hexon interacted with a cellular protein, BAG3, a host protein that initiates autophagy, and that BAG3 expression increased in cells infected with HPFAdV-4. Furthermore, knockdown of BAG3 by RNA interference (RNAi) significantly inhibited HPFAdV-4- or hexon-induced autophagy and suppressed viral replication. On the contrary, expression of hexon markedly upregulated the expression of BAG3 via activating the P38 signaling pathway, triggering autophagy. Thus, these findings reveal that HPFAdV-4 hexon interacts with the host protein BAG3 and promotes BAG3 expression by activating P38 signaling pathway, thereby inducing autophagy and enhancing viral proliferation, which immensely furthers our understanding of the pathogenesis of HPFAdV-4 infection. IMPORTANCE HHS, mainly caused by HPFAdV-4, has caused large economic losses to the stakeholders in recent years. Infection of leghorn male hepatocellular (LMH) cells by HPFAdV-4 induced complete autophagy that is essential for HPFAdV-4 replication. By a screening strategy, the viral protein hexon was found responsible for virus-induced autophagy in cells. Importantly, hexon was identified as a factor promoting viral replication by interaction with BAG3, an initiator of host cell autophagy. These findings will help us to better understand the host response to HPFAdV-4 infection, providing a novel insight into the pathogenesis of HPFAdV-4 infection.

Type III secretory protein SINC of Chlamydia psittaci promotes host cell autophagy by activating the MAPK/ERK signaling pathway

To investigate the effects of SINC, a secreted protein of Chlamydia psittaci, on autophagy of host cells and the role of MAPK/ERK signaling pathway in mediating SINC-induced autophagy. RAW 264.7 cells treated with recombinant SINC were examined for changes in expression levels of LC3-II, Beclin-1, phosphorylated and total ERK1/2 using Western blotting. The expression level of LC3 in the treated cells was detected using immunofluorescence analysis, and the formation of autophagosomes and autolysosomes was observed with transmission electron microscopy (TEM). The effect of pretreatment with U0126 (a specific ERK inhibitor) on the expression levels of LC3-II and Beclin-1 in RAW 264.7 cells exposed to different concentrations of SINC was examined using Western blotting, and LC3 puncta in the cells was detected with immunofluorescence analysis. The expression levels of LC3-II and Beclin-1 were the highest in RAW 264.7 cells treated with 2 μg/mL SINC for 12h. Immunofluorescence analysis showed exposure to SINC significantly increased the number of cells containing LC3 puncta, where the presence of autophagosomes and autolysosomes was detected. Exposure to 2 μg/mL SINC for 15 min resulted in the most significant increase of the ratios of p-ERK1/2/ERK1/2 in RAW 264.7 cells. Pretreatment of the cells with U0126 prior to SINC exposure significantly decreased the ratio of p-ERK1/2/ERK1/2, lowered the expression levels of LC3-II and Beclin-1, and decreased LC3 aggregation in the cells. SINC exposure can induce autophagy in RAW 264.7 cells by activating the MAPK/ERK signaling pathway.

Pathogenic mechanism of Eimeria tenella autophagy activation of chicken embryo cecal epithelial cells induced by Eimeria tenella

Eimeria tenella mainly invades and develops into cecal epithelial cells of chickens, resulting in cecal epithelial cell damage. Infectious intracellular pathogens possibly act by influencing the autophagy process after invading cells. The interaction between E. tenella and the autophagy of host cells was explored by infecting E. tenella with chick embryo cecal epithelial cells. Transmission electron microscopy, laser confocal microscopy, and Western blot analysis were used to demonstrate that E. tenella infection could induce autophagy in host cells. Results showed that infection with E. tenella induced the formation of autophagosomes in cells. The expression of ATG 5, Beclin-1, and LC3B-II proteins were significantly (P < 0.01) increased after E. tenella infected host cells. Expression of p62 protein levels were significantly (P < 0.01) decreased in host cells infected with E. tenella. Chloroquine (CQ) significantly (P < 0.01) increased the expression levels of LC3B-II and P62 in E. tenella-infected host cells. Rapamycin (RAPA) induced autophagy in host cells, thus reducing the intracellular infection of E. tenella. By contrast, the infection rate of E. tenella increased in cells treated with 3-Methyladenine (3-MA). Hence, E. tenella sporozoite infection could induce autophagy activation in chick embryo cecal epithelial cells, and enhanced autophagy could reduce the infection rate of E. tenella.

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

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

MicroRNAs as immune regulators and biomarkers in tuberculosis.

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), is one of the most lethal infectious disease worldwide, and it greatly affects human health. Some diagnostic and therapeutic methods are available to effectively prevent and treat TB; however, only a few systematic studies have described the roles of microRNAs (miRNAs) in TB. Combining multiple clinical datasets and previous studies on Mtb and miRNAs, we state that pathogens can exploit interactions between miRNAs and other biomolecules to avoid host mechanisms of immune-mediated clearance and survive in host cells for a long time. During the interaction between Mtb and host cells, miRNA expression levels are altered, resulting in the changes in the miRNA-mediated regulation of host cell metabolism, inflammatory responses, apoptosis, and autophagy. In addition, differential miRNA expression can be used to distinguish healthy individuals, patients with TB, and patients with latent TB. This review summarizes the roles of miRNAs in immune regulation and their application as biomarkers in TB. These findings could provide new opportunities for the diagnosis and treatment of TB.

Modulation of autophagy as a therapeutic strategy for Toxoplasma gondii infection.

Toxoplasma gondii infection is a severe health threat that endangers billions of people worldwide. T. gondii utilizes the host cell membrane to form a parasitophorous vacuole (PV), thereby fully isolating itself from the host cell cytoplasm and making intracellular clearance difficult. PV can be targeted and destroyed by autophagy. Autophagic targeting results in T. gondii killing via the fusion of autophagosomes and lysosomes. However, T. gondii has developed many strategies to suppress autophagic targeting. Accordingly, the interplay between host cell autophagy and T. gondii is an emerging area with important practical implications. By promoting the canonical autophagy pathway or attenuating the suppression of autophagic targeting, autophagy can be effectively utilized in the development of novel therapeutic strategies against T gondii. Here, we have illustrated the complex interplay between host cell mediated autophagy and T. gondii. Different strategies to promote autophagy in order to target the parasite have been elucidated. Besides, we have analyzed some potential new drug molecules from the DrugBank database using bioinformatics tools, which can modulate autophagy. Various challenges and opportunities focusing autophagy mediated T. gondii clearance have been discussed, which will provide new insights for the development of novel drugs against the parasite.