TBK1 and GABARAP family members suppress Coxsackievirus B infection by limiting viral production and promoting autophagic degradation of viral extracellular vesicles

Common Chemical Plasticizer Di(2-Ethhylhexyl) Phthalate Exposure Exacerbates Coxsackievirus B3 Infection

Di(2-ethhylhexyl) phthalate (DEHP) is a common plastic rubberizer. DEHP leaches from plastic matrices and is under increasing scrutiny as numerous studies have linked it to negative human health manifestations. Coxsackievirus B3 (CVB) is a human pathogen that typically causes subclinical infections but can sometimes cause severe diseases such as pancreatitis, myocarditis, and meningoencephalitis. Though CVB infections are common, severe illness is relatively rare, and it is unclear what factors mediate disease severity. In this study, we sought to determine the effects that DEHP has on CVB infection in a variety of human cell types to evaluate whether this plastic-derived pollutant could represent a proviral environmental factor.

METHODS

HeLa cervical cancer cells, human induced pluripotent stem cell-derived brain-like endothelial cells (iBECs), and Caco-2 colon carcinoma cells were exposed to 40 µg/mL DEHP for 24 h prior to infecting with enhanced green fluorescent protein (EGFP)-expressing CVB. The severity of the infection was evaluated via fluorescence microscopy and flow cytometry-based viral EGFP detection, viral plaque assay on tissue culture media, and Western blotting to detect VP1 viral capsid protein. Interferon-associated proteins such as interferon regulatory factor (IRF) 3, IRF7, interferon-induced transmembrane (IFITM) 2, and IFITM3 were measured by Western blotting. The roles of IFITM2 and IFITM3 in the context of CVB infection were evaluated via siRNA silencing.

RESULTS

We found that DEHP drastically increased CVB infection in each of the cell types we tested, and, while the cellular processes underlying DEHP's proviral properties were not entirely clear, we observed that DEHP may subvert CVB-induced interferon signaling and elevate levels of IFITMs, which appeared to bolster CVB infection.

CONCLUSIONS

DEHP may represent a major environmental factor associated with the severity of CVB infection. Further understanding of how DEHP exacerbates infection may better elucidate its potential role as a proviral environmental factor.

Immune modulation through secretory autophagy

Autophagy is a central mechanism of cellular homeostasis through the degradation of a wide range of cellular constituents. However, recent evidence suggests that autophagy actively provides information to neighboring cells via a process called secretory autophagy. Secretory autophagy couples the autophagy machinery to the secretion of cellular content via extracellular vesicles (EVs). EVs carry a variety of cargo, that reflect the pathophysiological state of the originating cells and have the potential to change the functional profile of recipient cells, to modulate cell biology. The immune system has evolved to maintain local and systemic homeostasis. It is able to sense a wide array of molecules signaling disturbed homeostasis, including EVs and their content. In this review, we explore the emerging concept of secretory autophagy as a means to communicate cellular, and in total tissue pathophysiological states to the immune system to initiate the restoration of tissue homeostasis. Understanding how autophagy mediates the secretion of immunogenic factors may hold great potential for therapeutic intervention.

Crosstalk Between Innate Immunity and Autophagy in Viral Myocarditis Leading to Dilated Cardiomyopathy

Viral myocarditis, characterised by inflammation of the heart muscle, presents a significant challenge to global public health, particularly affecting younger individuals and often progressing to dilated cardiomyopathy (DCM), a leading cause of heart failure. Despite ongoing research efforts, viable treatments for this condition remain elusive. Recent studies have shed light on the complex interplay between the innate immune response and autophagy mechanisms, revealing their pivotal roles in the pathogenesis of viral myocarditis and subsequent DCM development. This review aims to delve into the recent advancements in understanding the molecular mechanisms and pathways that intersect innate immunity and autophagy in the context of viral myocarditis. Furthermore, it explores the potential therapeutic implications of these findings, offering insights into promising avenues for the management and treatment of this debilitating condition.

N-Acetylcysteine Inhibits Coxsackievirus B3 Replication by Downregulating Eukaryotic Translation Elongation Factor 1 Alpha 1

Group B Coxsackieviruses (CVB) are one of the causative pathogens of myocarditis, which may progress to cardiomyopathy. The pathogenesis of CVB is not fully understood, and effective antiviral therapy is not available. N-acetylcysteine (NAC), the classic antioxidant, has been used in clinical practice for several decades to treat various medical conditions. In this study, the anti-CVB effect of NAC was investigated. We show that NAC dramatically suppressed viral replication and alleviated cardiac injury induced by CVB3. To further study the antiviral mechanism of NAC, RNA-sequencing was performed for CVB3-infected cells with NAC treatment. We found that eukaryotic elongation factor 1 alpha 1 (EEF1A1) is one of the most upregulated genes in CVB3-infected cells. However, EEF1A2, the highly homologous isoform of EEF1A1, remains unchanged. EEF1A1 expression was significantly suppressed by NAC treatment in CVB3-infected cells, while EEF1A2 was not affected. eEF1A1 knockdown significantly inhibited CVB3 replication, implicating that eEF1A1 facilitates viral replication. Importantly, we show that eEF1A1, which was not expressed in the myocardia of newborn mice, was significantly upregulated by CVB3 infection. NAC markedly downregulated the expression of eEF1A1 but not eEF1A2 in the myocardia of CVB3-infected mice. Furthermore, NAC accelerated eEF1A1 degradation by promoting autophagy in CVB3-infected cells. We show that p62, one of the critical adaptors of autophagic targets, interacts with eEF1A1 and was downregulated in CVB3-infected cells upon NAC treatment. Taken together, this study demonstrated that NAC shows a potent anti-CVB effect through the downregulation of eEF1A1.

The complexity of extracellular vesicles: Bridging the gap between cellular communication and neuropathology

Brain-derived extracellular vesicles (EVs) serve a prominent role in maintaining homeostasis and contributing to pathology in health and disease. This review establishes a crucial link between physiological processes leading to EV biogenesis and their impacts on disease. EVs are involved in the clearance and transport of proteins and nucleic acids, responding to changes in cellular processes associated with neurodegeneration, including autophagic disruption, organellar dysfunction, aging, and other cell stresses. In neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, etc.), EVs contribute to the spread of pathological proteins like amyloid β, tau, ɑ-synuclein, prions, and TDP-43, exacerbating neurodegeneration and accelerating disease progression. Despite evidence for both neuropathological and neuroprotective effects of EVs, the mechanistic switch between their physiological and pathological functions remains elusive, warranting further research into their involvement in neurodegenerative disease. Moreover, owing to their innate ability to traverse the blood-brain barrier and their ubiquitous nature, EVs emerge as promising candidates for novel diagnostic and therapeutic strategies. The review uniquely positions itself at the intersection of EV cell biology, neurophysiology, and neuropathology, offering insights into the diverse biological roles of EVs in health and disease.

Mitochondrial extracellular vesicles, autoimmunity and myocarditis

For many decades viral infections have been suspected as 'triggers' of autoimmune disease, but mechanisms for how this could occur have been difficult to establish. Recent studies have shown that viral infections that are commonly associated with viral myocarditis and other autoimmune diseases such as coxsackievirus B3 (CVB3) and SARS-CoV-2 target mitochondria and are released from cells in mitochondrial vesicles that are able to activate the innate immune response. Studies have shown that Toll-like receptor (TLR)4 and the inflammasome pathway are activated by mitochondrial components. Autoreactivity against cardiac myosin and heart-specific immune responses that occur after infection with viruses where the heart is not the primary site of infection (e.g., CVB3, SARS-CoV-2) may occur because the heart has the highest density of mitochondria in the body. Evidence exists for autoantibodies against mitochondrial antigens in patients with myocarditis and dilated cardiomyopathy. Defects in tolerance mechanisms like autoimmune regulator gene (AIRE) may further increase the likelihood of autoreactivity against mitochondrial antigens leading to autoimmune disease. The focus of this review is to summarize current literature regarding the role of viral infection in the production of extracellular vesicles containing mitochondria and virus and the development of myocarditis.

Porcine Sapovirus Protease Controls the Innate Immune Response and Targets TBK1

Human sapoviruses (HuSaVs) and noroviruses are considered the leading cause of acute gastroenteritis worldwide. While extensive research has focused on noroviruses, our understanding of sapoviruses (SaVs) and their interactions with the host's immune response remains limited. HuSaVs have been challenging to propagate in vitro, making the porcine sapovirus (PSaV) Cowden strain a valuable model for studying SaV pathogenesis. In this study we show, for the first time, that PSaV Cowden strain has mechanisms to evade the host's innate immune response. The virus 3C-like protease (NS6) inhibits type I IFN production by targeting TBK1. Catalytically active NS6, both during ectopic expression and during PSaV infection, targets TBK1 which is then led for rapid degradation by the proteasome. Moreover, deletion of TBK1 from porcine cells led to an increase in PSaV titres, emphasizing its role in regulating PSaV infection. Additionally, we successfully established PSaV infection in IPEC-J2 cells, an enterocytic cell line originating from the jejunum of a neonatal piglet. Overall, this study provides novel insights into PSaV evasion strategies, opening the way for future investigations into SaV-host interactions, and enabling the use of a new cell line model for PSaV research.

Autophagy suppression facilitates macrophage M2 polarization via increased instability of NF-κB pathway in hepatocellular carcinoma

The tumor microenvironment is a highly heterogeneous circumstance composed of multiple components, while tumor-associated macrophages (TAMs) are major innate immune cells with highly plastic and are always educated by tumor cells to structure an advantageous pro-tumor immune microenvironment. Despite emerging evidence focalizing the role of autophagy in other immune cells, the regulatory mechanism of autophagy in macrophage polarization remains poorly understood. Herein, we demonstrated that hepatocellular carcinoma (HCC) cells educated macrophages toward M2-like phenotype polarization under the condition of coculture. Moreover, we observed that inhibition of macrophage autophagy promoted M2-like macrophage polarization, while the tendency was impeded when autophagy was motivated. Mechanistically, macrophage autophagy inhibition inactivates the NF-κB pathway by increasing the instability of TAB3 via ubiquitination degradation, which leads to the M2-like phenotype polarization of macrophages. Both immunohistochemistry staining using human HCC tissues and experiment in vivo verified autophagy inhibition is correlated with M2 macrophage polarization. Altogether, we illustrated that macrophage autophagy was involved in the process of HCC cells domesticating M2 macrophage polarization via the NF-κB pathway. These results provide a new target to interfere with the polarization of macrophages to M2-like phenotype during HCC progression.

Identification of multifunctionality of grass carp (Ctenopharyngodon idella) TBK1 during bacterial infection

TBK1 is an atypical IκB kinase family member with a set of functions. It is involved in congenital immunization and autophagy in mammals. In this study, we reported that grass carp TBK1 gene expression could be upregulated by bacterial infection. Overexpression of TBK1 could decrease the number of adhesive bacteria in CIK cells. TBK1 could promote cellular migration, proliferation, vitality, and anti-apoptosis ability. Furthermore, the expression of TBK1 could activate the NF-κB signaling pathway by inducing inflammatory cytokines. In addition, we found that the grass carp TBK1 could cause the autophagy level of CIK cells within the decreasing level of p62 protein. Our finding indicated that TBK1 participated in grass carp innate immune progress and autophagy. This study provides evidence of the positive regulation of TBK1 in teleost innate immunity with its multiple functions. It thus may provide important information about the defense and immune mechanisms used by teleost against pathogens.