miR-129a-3p Inhibits PEDV Replication by Targeting the EDA-Mediated NF-κB Pathway in IPEC-J2 Cells

miRNA Expression Analysis of IPEC-J2 Cells Damaged by Soybean 7S Globulin Reveals ssc-miR-221-5p as the Factor Alleviating Cell Damage

The most significant and sensitive antigen protein that causes diarrhea in weaned pigs is soybean 7S globulin. Therefore, identifying the primary target for minimizing intestinal damage brought on by soybean 7S globulin is crucial. MicroRNA (miRNA) is closely related to intestinal epithelium's homeostasis and integrity. However, the change of miRNAs' expression and the function of miRNAs in Soybean 7S globulin injured-IPEC-J2 cells are still unclear. In this study, the miRNAs' expression profile in soybean 7S globulin-treated IPEC-J2 cells was investigated. Fifteen miRNAs were expressed differently. The differentially expressed miRNA target genes are mainly concentrated in signal release, cell connectivity, transcriptional inhibition, and Hedgehog signaling pathway. Notably, we noticed that the most significantly decreased miRNA was ssc-miR-221-5p after soybean 7S globulin treatment. Therefore, we conducted a preliminary study on the mechanisms of ssc-miR-221-5p in soybean 7S globulin-injured IPEC-J2 cells. Our research indicated that ssc-miR-221-5p may inhibit ROS production to alleviate soybean 7S globulin-induced apoptosis and inflammation in IPEC-J2 cells, thus protecting the cellular mechanical barrier, increasing cell proliferation, and improving cell viability. This study provides a theoretical basis for the prevention and control of diarrhea of weaned piglets.

METTL3 enhances E. coli F18 resistance by targeting IKBKG/NF-κB signaling via an m6A-YTHDF1-dependent manner in IPEC-J2 cells

Post-weaning diarrhea caused by enterotoxigenic E. coli F18 introduces enormous losses to the porcine industry. N6-methyladenosine (m6A) is a ubiquitous epitranscriptomic biomarker that modulates host cell resistance to pathogen infection, however, its significance in E. coli F18-treated IPEC-J2 cells remains unexplored. Herein, we revealed that m6A and associated modulators strongly controlled E. coli F18 susceptibility. The data indicated an enhancement of METTL3 contents in E. coli F18-treated IPEC-J2 cells. METTL3 is known to be a major modulator of E. coli F18 adhesion within IPEC-J2 cells. As expected, METTL3 deficiency was observed to reduce m6A content at the IKBKG 5'-UTR, leading to critical suppression of YTHDF1-dependent IKBKG translation. Therefore, the activation of the NF-κB axis was observed, which enhanced IPEC-J2 resistance to E. coli F18 infection. Taken together, these findings uncover a potential mechanism underlying the m6A-mediated control of E. coli F18 susceptibility. This information may contribute to the establishment of new approaches for combating bacteria-induced diarrhea in piglets.

KPNA2 suppresses porcine epidemic diarrhea virus replication by targeting and degrading virus envelope protein through selective autophagy

IMPORTANCE

Porcine epidemic diarrhea, characterized by vomiting, dehydration, and diarrhea, is an acute and highly contagious enteric disease caused by porcine epidemic diarrhea virus (PEDV) in neonatal piglets. This disease has caused large economic losses to the porcine industry worldwide. Thus, identifying the host factors involved in PEDV infection is important to develop novel strategies to control PEDV transmission. This study shows that PEDV infection upregulates karyopherin α 2 (KPNA2) expression in Vero and intestinal epithelial (IEC) cells. KPNA2 binds to and degrades the PEDV E protein via autophagy to suppress PEDV replication. These results suggest that KPNA2 plays an antiviral role against PEDV. Specifically, knockdown of endogenous KPNA2 enhances PEDV replication, whereas its overexpression inhibits PEDV replication. Our data provide novel KPNA2-mediated viral restriction mechanisms in which KPNA2 suppresses PEDV replication by targeting and degrading the viral E protein through autophagy. These mechanisms can be targeted in future studies to develop novel strategies to control PEDV infection.

Water Extract of Portulaca Oleracea Inhibits PEDV Infection-Induced Pyrolysis by Caspase-1/GSDMD

Porcine epidemic diarrhea virus (PEDV) belongs to the coronavirus family and the coronavirus genus, causing contact enteric infection in pigs. It is one of the most serious diseases that threatens the pig industry. However, there is currently no specific drug to prevent and treat the disease, indicating that we need to be vigilant about the spread of the disease and the development of anti-PEDV drugs. The dried aerial parts of the plant Portulaca oleracea in the family Portulacaceous, whose decoction can be used to treat acute enteritis, dysentery, diarrhea, and other diseases. This study explored the potential mechanism of water extract of Portulaca oleracea (WEPO) in PEDV-induced pyroptosis in Vero cells. PEDV decreased the viability of Vero cells in a dose- and time-dependent manner, causing cell damage, upregulating the level of intracellular Nlrp3, and inhibiting the level of Gasdermin D (GSDMD) and the activation of Caspase-1. WEPO can inhibit PEDV-induced pyroptosis, reduce the elevation of inflammatory factors caused by infection, and exhibit a dose-dependent effect. Knockdown of Caspase-1 and GSDMD separately can induce the production of the inflammatory factor IL-1β to significantly decrease and increase, respectively. These results suggest that WEPO can inhibit cell pyroptosis caused by PEDV and that the Caspase-1 and GSDMD pathways play an important role in this process.

Identification of niclosamide as a novel antiviral agent against porcine epidemic diarrhea virus infection by targeting viral internalization

Porcine epidemic diarrhea virus (PEDV), an enteropathogenic coronavirus, has catastrophic impacts on the global pig industry. However, there remain no effective drugs against PEDV infection. In this study, we utilized a recombinant PEDV expressing renilla luciferase (PEDV-Rluc) to screen potential anti-PEDV agents from an FDA-approved drug library in Vero cells. Four compounds were identified that significantly decreased luciferase activity of PEDV-Rluc. Among them, niclosamide was further characterized because it exhibited the most potent antiviral activity with the highest selectivity index. It can efficiently inhibit viral RNA synthesis, protein expression and viral progeny production of classical and variant PEDV strains in a dose-dependent manner. Time of addition assay showed that niclosamide exhibited potent anti-PEDV activity when added simultaneously with or after virus infection. Furthermore, niclosamide significantly inhibited the entry stage of PEDV infection by affecting viral internalization rather than viral attachment to cells. In addition, a combination with other small molecule inhibitors of endosomal acidification enhanced the anti-PEDV effect of niclosamide in vitro. Taken together, these findings suggested that niclosamide is a novel antiviral agent that might provide a basis for the development of novel drug therapies against PEDV and other related pathogenic coronavirus infections.

miR-214-5p/C1QTNF1 axis enhances PCV2 replication through promoting autophagy by targeting AKT/mTOR signaling pathway

Porcine circovirus type 2 (PCV2) is the causative agent of PCV2-associated disease, which causes a relevant economic impact on the global swine industry. Accumulating data have indicated host microRNAs play essential roles in numerous virus replication of pigs, while their roles in PCV2 replication remain unclear. Herein, we demonstrated that PCV2 infection downregulated the expression of miR-214-5p in PK15 cells, and miR-214-5p promoted PCV2 replication. C1q/tumor necrosis factor-related protein 1 (C1QTNF1) was then identified as a target gene of miR-214-5p, and C1QTNF1 suppressed PCV2 replication. Interestingly, miR-214-5p/C1QTNF1 axis negatively regulated AKT/mTOR signaling, and then enhanced PCV2 replication through promoting autophagy in PK15 cells. Collectively, our findings provide insight into the mechanism of PCV2 replication and highlight miR-214-5p and C1QTNF1 as potential novel targets for the treatment of PCV2 infection.

miR-615 facilitates porcine epidemic diarrhea virus replication by targeting IRAK1 to inhibit type III interferon expression

Porcine epidemic diarrhea virus (PEDV) in the Coronavirus family is a highly contagious enteric pathogen in the swine industry, which has evolved mechanisms to evade host innate immune responses. The PEDV-mediated inhibition of interferons (IFNs) has been linked to the nuclear factor-kappa B (NF-κB) pathway. MicroRNAs (miRNAs) are involved in virus-host interactions and IFN-I regulation. However, the mechanism by which the PEDV regulates IFN during PEDV infection has not yet been investigated in its natural target cells. We here report a novel mechanism of viral immune escape involving miR-615, which was screened from a high-throughput sequencing library of porcine intestinal epithelial cells (IECs) infected with PEDV. PEDV infection altered the profiles of miRNAs and the activities of several pathways involved in innate immunity. Overexpression of miR-615 increased PEDV replication, inhibited IFN expression, downregulated the NF-κB pathway, and blocked p65 nuclear translocation. In contrast, knockdown of miR-615 enhanced IFN expression, suppressed PEDV replication, and activated the NF-κB pathway. We further determined that IRAK1 is the target gene of miR-615 in IECs. Our findings show that miR-615 suppresses activation of the NF-κB pathway by suppressing the IRAK1 protein and reducing the generation of IFN-IIIs, which in turn facilitates PEDV infection in IECs. Moreover, miR-615 inhibited PEDV replication and NF-κB pathway activation in both IECs and MARC-145 cells. These findings support an important role for miR-615 in the innate immune regulation of PEDV infections and provide a novel perspective for developing new treatments.

Differential expression analysis of mRNAs, lncRNAs, and miRNAs expression profiles and construction of ceRNA networks in PEDV infection

BACKGROUND

Porcine Epidemic Diarrhea Virus (PEDV) is a coronavirus that seriously affects the swine industry. MicroRNAs and long noncoding RNAs are two relevant non-coding RNAs (ncRNAs) class and play crucial roles in a variety of physiological processes. Increased evidence indicates a complex interaction between mRNA and ncRNA. However, our understanding of the function of ncRNA involved in host-PEDV interaction is limited.

RESULTS

A total of 1,197 mRNA transcripts, 539 lncRNA transcripts, and 208 miRNA transcripts were differentially regulated at 24 h and 48 h post-infection. Gene ontology (GO) and KEGG pathway enrichment analysis showed that DE mRNAs and DE lncRNAs were mainly involved in biosynthesis, innate immunity, and lipid metabolism. Moreover, we constructed a miRNA-mRNA-pathway network using bioinformatics, including 12 DE mRNAs, 120 DE miRNAs, and 11 pathways. Finally, the target genes of DE miRNAs were screened by bioinformatics, and we constructed immune-related lncRNA-miRNA-mRNA ceRNA networks. Then, the selected DE genes were validated by qRT-PCR, which were consistent with the results from RNA-Seq data.

CONCLUSIONS

This study provides the comprehensive analysis of the expression profiles of mRNAs, lncRNAs, and miRNAs during PEDV infection. We characterize the ceRNA networks which can provide new insights into the pathogenesis of PEDV.

LncRNA ALDB-898 modulates intestinal epithelial cell damage caused by Clostridium perfringens type C in piglet by regulating ssc-miR-122-5p/OCLN signaling

Diarrhea of piglets caused by Clostridium perfringens type C (C. perfringens type C) infection is a global problem afflicting piglet production. Long noncoding RNA (LncRNA) and microRNA (miRNA) have emerged as critical regulators of this pathological process, but the underlying molecular mechanisms remain unclear. In this study, we first observed the expression changes of ALDBSSCG0000000898 (ALDB-898) and ssc-miR-122-5p in infected ileum tissue of piglets with C. perfringens type C, and then used C. perfringens beta2 toxin (CPB2) to induce intestinal porcine epithelial cells (IPEC-J2) to construct an injury model. Cytometry kit 8 (CCK-8), lactate dehydrogenase (LDH), real-time quantitative polymerase chain reaction (RT-qPCR), Western blot, flow cytometry and fluorescein isothiocyanate-dextran 4 (FITC-Dextran 4) flux assays were performed to study the effect of ALDB-898 and ssc-miR-122-5p in apoptosis, inflammation and intestinal barrier damage and inflammatory in IPEC-J2 cells induced by CPB2. In addition, dual-luciferase reporter gene analysis was performed to confirm the relationship between ssc-miR-122-5p and ALDB-898 or ssc-miR-122-5p and occludin (OCLN), respectively. There were lower expression levels of ALDB-898 and OCLN and higher expression levels of ssc-miR-122-5p in diarrhea piglets caused by Clostridium perfringens type C. ALDB-898 and OCLN were significantly decreased and ssc-miR-122-5p was increased in IPEC-J2 after exposure to the CPB2 in a dose- and time-dependent manner. ALDB-898 overexpression mitigated CPB2-induced cell injury by promoting viability, restraining apoptosis, cytotoxicity, and inflammatory response, as well as weakening the destruction of the intestinal barrier. Further mechanisms disclosed that ALDB-898 functioned as a competing endogenous RNA (ceRNA) via binding to ssc-miR-122-5p, and OCLN was a target of ssc-miR-122-5p. Importantly, the ssc-miR-122-5p mimic led to abolishing the protective function of ALDB-898 on CPB2-induced IPEC-J2 cell damage, and the addition of OCLN reversed the negative impact of ssc-miR-122-5p, thereby restoring the protection of ALDB-898. Our data showed that ALDB-898 could enhance the expression of OCLN through competitive binding ssc-miR-122-5p to suppress CPB2-induced damage. The ALDB-898/ssc-miR-122-5p/OCLN signaling may be a candidate therapeutic pathway for diarrhea of piglets.

miR-30d Inhibition Protects IPEC-J2 Cells Against Clostridium perfringens Beta2 Toxin-Induced Inflammatory Injury

Clostridium perfringens beta2 (CPB2) toxin, one of the virulence factors of Clostridium perfringens (C. perfringens), can cause necrotizing enterocolitis in piglets. Accumulating pieces of evidence indicate that microRNAs (miRNAs) refer to the regulation of inflammatory processes. Previously, we have discovered that miR-30d was differentially expressed between the ileum of normal piglets and C. perfringens type C-infected diarrheal piglets. Here, we found that miR-30d expression was lowered in CPB2 toxin-treated intestinal porcine epithelial cells (IPEC-J2) at different time points. Subsequently, we determined that miR-30d inhibitor attenuated CPB2 toxin revulsive inflammatory damage in IPEC-J2 cells and promoted cell proliferation and cell cycle progression, whereas miR-30d mimic had opposite results. In addition, we confirmed that Proteasome activator subunit 3 (PSME3) was a downstream target gene of miR-30d via a dual luciferase reporter assay, qPCR, and western blot. We also found that overexpression of PSME3 suppressed CPB2 toxin-induced inflammatory damage and promoted cell proliferation and cycle progression. Our results demonstrate that miR-30d aggravates CPB2 toxin revulsive IPEC-J2 cells inflammatory injury via targeting PSME3, thereby providing a novel perspective for the prevention and treatment of piglet diarrhea at the molecular level.

m6A Demethylase ALKBH5 Restrains PEDV Infection by Regulating GAS6 Expression in Porcine Alveolar Macrophages

Porcine epidemic diarrhea virus (PEDV) is a burdensome coronavirus for the global pig industry. Although its fecal-oral route has been well-recognized, increasing evidence suggests that PEDV can also spread through airborne routes, indicating that the infection may also occur in the respiratory tract. N⁶-methyladenosine (m⁶A) has been known to regulate viral replication and host immunity, yet its regulatory role and molecular mechanism regarding PEDV infection outside the gastrointestinal tract remain unexplored. In this study, we demonstrate that PEDV can infect porcine lung tissue and the 3D4/21 alveolar macrophage cell line, and the key m⁶A demethylase ALKBH5 is remarkably induced after PEDV infection. Interestingly, the disruption of ALKBH5 expression remarkably increases the infection’s capacity for PEDV. Transcriptome profiling identified dozens of putative targets of ALKBH5, including GAS6, which is known to regulate virus infectivity. Further, MeRIP-qPCR and mRNA stability analyses suggest that ALKBH5 regulates the expression of GAS6 via an m⁶A-YTHDF2-dependent mechanism. Overall, our study demonstrates that PEDV can infect porcine lung tissue and 3D4/21 cells and reveals the crucial role of ALKBH5 in restraining PEDV infections, at least partly, by influencing GAS6 through an m⁶A-YTHDF2-dependent mechanism.