Enterovirus 71 induces autophagy in mice via mTOR inhibition and ERK pathway activation

Enterovirus 71 Induces Mitophagy via PINK1/Parkin Signaling Pathway to Promote Viral Replication

Enterovirus 71 (EV71) infection poses a global public health challenge, especially in infants and young children, with severe cases leading to fatal consequences. EV71 infection modulates various biological processes of the host and evades host immunity through multiple mechanisms. The balance of mitochondrial dynamics is important for cellular homeostasis. However, the mechanisms underlying EV71-induced cellular damage via mitophagy remain unclear. In the current study, we showed that EV71 infection significantly reduced the total and mitochondrial ATP contents in cells, as well as the expression of mitochondrial proteins TOM20 and TIM23. Then, EV71 infection increased the protein levels of PINK1, Parkin, and LC3B, suggesting that EV71 infection triggers the mitophagy. Silencing PINK1 caused a significant reduction in viral replication, while overexpressing Parkin promoted the replication of EV71. Moreover, CsA treatment, as a mitophagy inhibitor, alleviated pathological damage and suppressed the replication of EV71 in vivo. Mechanistic study showed that silencing PINK1 inhibited the cleavage of MAVS by EV71, while overexpressing Parkin enhanced the cleavage of MAVS by EV71, suggesting that PINK1-mediated mitophagy was involved in regulating innate immunity. Furthermore, we found that EV71 infection promoted the release of mitochondria carrying EV71 virions into the extracellular environment, which mediated infection of other cells, thus facilitating virus spreading. In addition, we also demonstrated that the extracellular mitochondria induced the degradation of MAVS and mitophagy promoted the release of mitochondria in EV71-infected HeLa cells. In conclusion, these findings suggest that EV71 infection induces PINK1-mediated mitophagy, which inhibits innate immunity and facilitates virus replication.

EV-D68 cleaves LARP1 and PABPC1 by 3Cpro to redirect host mRNA translation machinery toward its genomic RNA

Enterovirus D68 (EV-D68) is an emerging pathogen associated with severe respiratory diseases and neurological complications, such as acute flaccid myelitis. EV-D68 has developed sophisticated mechanisms to hijack host translation machinery, facilitating its replication and impairing host mRNA translation. In this study, we demonstrate that EV-D68 cleaves La-related protein 1 (LARP1) and poly(A)-binding protein cytoplasmic 1 (PABPC1) through its proteases 3Cpro and 2Apro. Our results indicate that overexpressing LARP1 and PABPC1 significantly inhibits EV-D68 replication and reduces the virus-mediated suppression of host translation. While both LARP1 and PABPC1 regulate translation, they exert antiviral effects through distinct mechanisms. We found that LARP1 interacts with the 5'UTR of EV-D68 RNA through its LAM domain, and this interaction is crucial for its antiviral function. LARP1 translation modulation is also influenced by the mTOR and CDK1 signaling pathways. Viral infection inhibits mTOR and CDK1 phosphorylation, which enhances LARP1's binding to viral RNA and inhibits viral translation. To counteract this inhibition, EV-D68 cleaves LARP1 through 3Cpro, thereby promoting efficient viral translation. We also investigated other enteroviruses, such as EV-A71 and CV-A16, which similarly target LARP1 and PABPC1, indicating a conserved mechanism across enteroviruses. Our findings offer new insights into how EV-D68 manipulates host translation and highlight the potential of targeting LARP1 and PABPC1 for antiviral interventions.

Enhancing endometrial receptivity: the roles of human chorionic gonadotropin in autophagy and apoptosis regulation in endometrial stromal cells

Inadequate endometrial receptivity often results in embryo implantation failure and miscarriage. Human chorionic gonadotropin (hCG) is a key signaling molecule secreted during early embryonic development, which regulates embryonic maternal interface signaling and promotes embryo implantation. This study aimed to examine the impact of hCG on endometrial receptivity and its underlying mechanisms. An exploratory study was designed, and endometrial samples were obtained from women diagnosed with simple tubal infertility or male factor infertile (n = 12) and recurrent implantation failure (RIF, n = 10). Using reverse transcription-quantitative PCR and western blotting, luteinizing hormone (LH)/hCG receptor (LHCGR) levels and autophagy were detected in the endometrial tissues. Subsequently, primary endometrial stromal cells (ESCs) were isolated from these control groups and treated with hCG to examine the presence of LHCGR and markers of endometrial receptivity (HOXA10, ITGB3, FOXO1, LIF, and L-selectin ligand) and autophagy-related factors (Beclin1, LC3, and P62). The findings revealed that the expressions of receptivity factors, LHCGR, and LC3 were reduced in the endometrial tissues of women with RIF compared with the control group, whereas the expression of P62 was elevated. The administration of hCG to ESCs specifically activated LHCGR, stimulating an increase in the endometrial production of HOXA10, ITGB3, FOXO1, LIF and L-selectin ligands. Furthermore, when ESCs were exposed to 0.1 IU/mL hCG for 72 h, the autophagy factors Beclin1 and LC3 increased within the cells and P62 decreased. Moreover, the apoptotic factor Bax increased and Bcl-2 declined. However, when small interfering RNA was used to knock down LHCGR, hCG was less capable of controlling endometrial receptivity and autophagy molecules in ESCs. In addition, hCG stimulation enhanced the phosphorylation of ERK1/2 and mTOR proteins. These results suggest that women with RIF exhibit lower levels of LHCGR and compromised autophagy function in their endometrial tissues. Thus, hCG/LHCGR could potentially improve endometrial receptivity by modulating autophagy and apoptosis.

Advances in anti-EV-A71 drug development research

BACKGROUND

Enterovirus A71 (EV-A71) is capable of causing hand, foot and mouth disease (HFMD), which may lead to neurological sequelae and even death. As EV-A71 is resistant to environmental changes and mutates easily, there is still a lack of effective treatments or globally available vaccines.

AIM OF REVIEW

For more than 50 years since the HFMD epidemic, related drug research has been conducted. Progress in this area can promote the further application of existing potential drugs and develop more efficient and safe antiviral drugs, and provide useful reference for protecting the younger generation and maintaining public health security.

KEY SCIENTIFIC CONCEPTS OF REVIEW

At present, researchers have identified hundreds of EV-A71 inhibitors based on screening repurposed drugs, targeted structural design, and rational modification of previously effective drugs as the main development strategies. This review systematically introduces the current potential drugs to inhibit EV-A71 infection, including viral inhibitors targeting key sites such as the viral capsid, RNA-dependent RNA polymerase (RdRp), 2C protein, internal ribosome entry site (IRES), 3C proteinase (3Cpro), and 2A proteinase (2Apro), starting from each stage of the viral life cycle. Meanwhile, the progress of host-targeting antiviral drugs and their development are summarized in terms of regulating host immunity, inhibiting autophagy or apoptosis, and regulating the cellular redox environment. In addition, the current clinical methods for the prevention and treatment of HFMD are summarized and discussed with the aim of providing support and recommendations for the treatment of enterovirus infections including EV-A71.

Cellular communication network factor 1 interlinks autophagy and ERK signaling to promote osteogenesis of periodontal ligament stem cells

OBJECTIVES

To investigate the effects of cellular communication network factor 1 (CCN1), a critical matricellular protein, on alveolar bone regeneration, and to elucidate the underlying molecular mechanism.

BACKGROUND

In the process of orthodontic tooth movement, bone deposition on the tension side of human periodontal ligament stem cells (hPDLSCs) ensured high efficiency and long-term stability of the treatment. The matricellular protein CCN1 is responsive to mechanical stimulation, exhibiting important tasks in bone homoeostasis. However, the role and mechanism of CCN1 on alveolar bone remodeling of hPDLSCs remains unclear.

METHODS

The expression and distribution of CCN1 in rat periodontal ligament were detected by immunofluorescence staining and immunohistochemical staining. ELISA verified the secretion of CCN1 triggered by stretch loading. To examine the mineralization ability of hPDLSCs induced by CCN1, Western blotting, qRT-PCR, ARS, and ALP staining were performed. CCK-8 and cell migration assay were performed to detect the cell proliferation rate and the wound healing. PI3K/Akt, MAPK, and autophagy activation were examined via Western blotting and immunofluorescence.

RESULTS

Mechanical stimuli induced the release of CCN1 into extracellular environment by hPDLSCs. Knockdown of CCN1 attenuated the osteogenesis of hPDLSCs while rhCCN1 enhanced the expression of Runx2, Col 1, ALPL, and promoted the mineralization nodule formation. CCN1 activated PI3K/Akt and ERK signaling, and blockage of PI3K/Akt signaling reversed the accelerated cell migration triggered by CCN1. The enhanced osteogenesis induced by CCN1 was abolished by ERK signaling inhibitor PD98059 or autophagy inhibitor 3-MA. Further investigation demonstrated PD98059 abrogated the activation of autophagy.

CONCLUSION

This study demonstrated that CCN1 promotes osteogenesis in hPDLSCs via autophagy and MAPK/ERK pathway.

Characterization of Pathogenesis and Inflammatory Responses to Experimental Parechovirus Encephalitis

Human parechovirus type 3 (PeV-A3) infection has been recognized as an emerging etiologic factor causing severe nerve disease or sepsis in infants and young children. But the neuropathogenic mechanisms of PeV-A3 remain unknown. To understand the pathogenesis of PeV-A3 infection in the neuronal system, PeV-A3-mediated cytopathic effects were analyzed in human glioblastoma cells and neuroblastoma cells. PeV-A3 induced interferons and inflammatory cytokine expression in these neuronal cells. The pronounced cytopathic effects accompanied with activation of death signaling pathways of apoptosis, autophagy, and pyroptosis were detected. A new experimental disease model of parechovirus encephalitis was established. In the disease model, intracranial inoculation with PeV-A3 in C57BL/6 neonatal mice showed body weight loss, hindlimb paralysis, and approximately 20% mortality. PeV-A3 infection in the hippocampus and cortex regions of the neonatal mouse brain was revealed. Mechanistic assay supported the in vitro results, indicating detection of PeV-A3 replication, inflammatory cytokine expression, and death signaling transduction in mouse brain tissues. These in vitro and in vivo studies revealed that the activation of death signaling and inflammation responses is involved in PeV-A3-mediated neurological disorders. The present results might account for some of the PeV-A3-associated clinical manifestations.