Elevated expression of LCN13 through FXR activation ameliorates hepatocellular lipid accumulation and inflammation.

BACKGROUND: Lipocalin 13 (LCN13) is a member of the lipocalin family that consists of numerous secretory proteins. LCN13 high-expression has been reported to possess anti-obesity and anti-diabetic effects. Although metabolic dysfunction-associated steatotic liver diseases (MASLD) including metabolic dysfunction-associated steatohepatitis (MASH) are frequently associated with obesity and insulin resistance, the functional role of endogenous LCN13 and the therapeutic effect of LCN13 in MASH and related metabolic deterioration have not been evaluated. METHODS: We employed a methionine-choline deficient diet model and MASH cell models to investigate the role of LCN13 in MASH development. We sought to explore the effects of LCN13 on lipid metabolism and inflammation in hepatocytes under PA/OA exposure using Western blotting, real-time RT-PCR, enzyme-linked immunosorbent assay, hematoxylin and eosin staining, oil red O staining. Using RNA sequencing, chromatin immunoprecipitation assay, and luciferase reporter assays to elucidate whether farnesoid X receptor (FXR) regulates human LCN13 transcription as a transcription factor. RESULTS: Our study found that LCN13 was down-regulated in MASH patients, MASH mouse and cell models. LCN13 overexpression in hepatocyte cells significantly inhibited lipid accumulation and inflammation in vitro. Conversely, LCN13 downregulation significantly exacerbated lipid accumulation and inflammatory responses in vivo and in vitro. Mechanistically, we provided the first evidence that LCN13 was transcriptionally activated by FXR, representing a novel direct target gene of FXR. And the key promoter region of LCN13 binds to FXR was also elucidated. We further revealed that LCN13 overexpression via FXR activation ameliorates hepatocellular lipid accumulation and inflammation in vivo and in vitro. Furthermore, LCN13-down-regulated mice exhibited aggravated MASH phenotypes, including increased hepatic lipid accumulation and inflammation. CONCLUSION: Our findings provide new insight regarding the protective role of LCN13 in MASH development and suggest an innovative therapeutic strategy for treating MASH or related metabolic disorders.

Epidemiology, genetic characteristics, and association with meteorological factors of human metapneumovirus infection in children in southern China: A 10-year retrospective study.

OBJECTIVES: This study aimed to determine the epidemiological and genetic features of human metapneumovirus (HMPV) infection in children in southern China, and the effect of meteorological factors on infection. METHODS: 14,817 children (≤14 years) with acute respiratory tract infections from 2010 to 2019 were examined for HMPV and other respiratory viruses by real-time quantitative polymerase chain reaction. Full-length F gene of 54 positive samples were sequenced and subjected to phylogenetic analysis. The correlation between the HMPV-positive rate and meteorological factors was analyzed by linear regression analysis. RESULTS: HMPV was detected in 524 (3.5%) children, who were mostly younger than 1 year. The seasonal peak of HMPV prevalence mainly occurred in spring. Respiratory syncytial virus was the most common virus coinfected with HMPV (5.3%). Phylogenetic analysis revealed that the sequenced HMPV strains belonged to four sublineages, including A2b (1.9%), A2c (31.5%), B1 (50.0%), and B2 (16.7%). After adjusting for all meteorological factors, sunshine duration was inversely correlated with the HMPV-positive rate. CONCLUSION: HMPV is an important respiratory pathogen that causes acute respiratory tract infections in children in southern China, particularly in children ≤5 years old. The prevalence peak of HMPV in this area appeared in spring, and the predominant subtype was B1. Meteorological factors, especially long sunshine duration, might decrease the HMPV prevalence.

SHFL inhibits enterovirus A71 infection by triggering degradation of viral 3Dpol protein via the ubiquitin-proteasome pathway.

Enterovirus A71 (EV-A71) is a highly contagious virus that poses a major threat to global health, representing the primary etiological agent for hand-foot and mouth disease (HFMD) and neurological complications. It has been established that interferon signaling is critical to establishing a robust antiviral state in host cells, mainly mediated through the antiviral effects of numerous interferon-stimulated genes (ISGs). The host restriction factor SHFL is a novel ISG with broad antiviral activity against various viruses through diverse underlying molecular mechanisms. Although SHFL is widely acknowledged for its broad-spectrum antiviral activity, it remains elusive whether SHFL inhibits EV-A71. In this work, we validated that EV-A71 triggers the upregulation of SHFL both in cell lines and in a mouse model. Knockdown and overexpression of SHFL in EVA71-infected cells suggested that this factor could markedly suppress EV-A71 replication. Our findings further revealed an intriguing mechanism of SHFL that it could interact with the nonstructural proteins 3Dpol of EV-A71 and promoted the degradation of 3Dpol through the ubiquitin-proteasome pathway. Furthermore, the zinc-finger domain and the 36 amino acids (164-199) of SHFL were crucial to the interaction between SHFL and EV-A71 3Dpol . Overall, these findings broadened our understanding of the pivotal roles of SHFL in the interaction between the host and EV-A71.

Host factor DUSP5 potently inhibits dengue virus infection by modulating cytoskeleton rearrangement.

Cytoskeleton has been reported to play an essential role in facilitating the viral life cycle. However, whether the host can exert its antiviral effects by modulating the cytoskeleton is not fully understood. In this study, we identified that host factor DUSP5 was upregulated after dengue virus (DENV) infection. In addition, we demonstrated that overexpression of DUSP5 remarkably inhibited DENV replication. Conversely, the depletion of DUSP5 led to an increase in viral replication. Moreover, DUSP5 was found to restrain viral entry into host cells by suppressing F-actin rearrangement via negatively regulating the ERK-MLCK-Myosin IIB signaling axis. Depletion of dephosphorylase activity of DUSP5 abolished its above inhibitory effects. Furthermore, we also revealed that DUSP5 exhibited broad-spectrum antiviral effects against DENV and Zika virus. Taken together, our studies identified DUSP5 as a key host defense factor against viral infection and uncovered an intriguing mechanism by which the host exerts its antiviral effects through targeting cytoskeleton rearrangement.