Clostridium perfringens beta2 toxin induced in vitro oxidative damage and its toxic assessment in porcine small intestinal epithelial cell lines

Mechanisms of intestinal epithelial cell damage by Clostridiumperfringens

Clostridium perfringens, a Gram-positive bacterium, causes intestinal diseases in humans and livestock through its toxins, related to alpha toxin (CPA), beta toxin (CPB), C. perfringens enterotoxin (CPE), epsilon toxin (ETX), Iota toxin (ITX), and necrotic enteritis B-like toxin (NetB). These toxins disrupt intestinal barrier, leading to various cell death mechanisms such as necrosis, apoptosis, and necroptosis. Additionally, non-toxin factors like adhesins and degradative enzymes contribute to virulence by enhancing colonization and survival of C. perfringens. A vicious cycle of intestinal barrier breach, misregulated cell death, and subsequent inflammation is at the heart of chronic inflammatory and infectious gastrointestinal diseases. Understanding these mechanisms is essential for developing targeted therapies against C. perfringens-associated intestinal diseases.

Data-driven energy landscape reveals critical genes in cancer progression

The evolution of cancer is a complex process characterized by stable states and transitions among them. Studying the dynamic evolution of cancer and revealing the mechanisms of cancer progression based on experimental data is an important topic. In this study, we aim to employ a data-driven energy landscape approach to analyze the dynamic evolution of cancer. We take Kidney renal clear cell carcinoma (KIRC) as an example. From the energy landscape, we introduce two quantitative indicators (transition probability and barrier height) to study critical shifts in KIRC cancer evolution, including cancer onset and progression, and identify critical genes involved in these transitions. Our results successfully identify crucial genes that either promote or inhibit these transition processes in KIRC. We also conduct a comprehensive biological function analysis on these genes, validating the accuracy and reliability of our predictions. This work has implications for discovering new biomarkers, drug targets, and cancer treatment strategies in KIRC.

Molecular characterization and function of JAK/STAT pathway in IPEC-J2 cells during Clostridium perfringens beta2 toxin stimulation

Intestinal infection with C. perfringens is responsible for outbreaks of diarrhea in piglets. Janus kinase / signal transducer and activator of transcription (JAK/STAT) is a vital signaling pathway that regulates cellular activity and inflammatory response, closely correlated with multiple diseases development and advances. Currently, the potential effect of JAK/STAT on C. perfringens beta2 (CPB2) treatment on porcine intestinal epithelial (IPEC-J2) cells has not been explored. The expression of JAK/STAT genes or proteins in IPEC-J2 cells induced by CPB2 were observed by qRT-PCR and Western blot, and further used WP1066 to explore the effect of JAK2/STAT3 on mechanism employed by CPB2 on apoptosis, cytotoxicity, oxidative stress and inflammatory cytokines of IPEC-J2 cells. JAK2, JAK3, STAT1, STAT3, STAT5A and STAT6 were highly expressed in CPB2-induced IPEC-J2 cells, among which STAT3 had the highest expression. Moreover, apoptosis, cytotoxicity and oxidative stress were attenuated via blocking the activation of JAK2/STAT3 by using WP1066 in CPB2-treated IPEC-J2 cells. Furthermore, WP1066 significantly suppressed the secretion of interleukin (IL)-6, IL-1β and TNF-α induced by CPB2 in IPEC-J2 cells.Our findings provide some insights into the functional roles of JAK2/STAT3 in piglets against to C. perfringens infection.

Overexpression of SIRT1 alleviates oxidative damage and barrier dysfunction in CPB2 toxin-infected IPEC-J2 cells

Clostridium perfringens (C. perfringens) beta2 (CPB2) toxin may induce necrotizing enteritis (NE) in pigs. Sirtuin1 (SIRT1) is involved in inflammatory intestinal diseases and affects intestinal barrier function. However, the effects of SIRT1 on piglet intestinal disease caused by CPB2 toxin are unclear. This study revealed the role of pig SIRT1 in CPB2 toxin-exposed intestinal porcine epithelial cells (IPEC-J2). Herein, we manifested that SIRT1 was dramatically decreased in IPEC-J2 cells infected with CPB2 toxin. Subsequently, we silenced and overexpressed SIRT1 using siRNA and a overexpression vector in CPB2 toxin-treated IPEC-J2 cells. The results indicated that overexpression of SIRT1 suppressed reactive oxygen species (ROS) generates, the expression tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and Bax, nuclear factor-kappa B (NF-κB p65), phospho (p)-NF-kB p65 and lactate dehydrogenase (LDH) activity and apoptosis in CPB2 toxin-treated IPEC-J2 cells, and increased IL-10, mitochondrial membrane potential (ΔΨm), Bcl-2, Claudin1 and Occludin levels and cell viability. These results indicated that SIRT1 protects IPEC-J2 cells against CPB2 toxin-induced oxidative damage and tight junction (TJ) disruption, which provides a theoretical basis for further study of the molecular regulatory mechanism of SIRT1 in C. perfringens-infected NE in piglets.

Identification of a Novel lncRNA LNC_001186 and Its Effects on CPB2 Toxin-Induced Apoptosis of IPEC-J2 Cells

The Clostridium perfringens (C. perfringen) beta2 (CPB2) toxin produced by C. perfringens type C (CpC) can cause necrotizing enteritis in piglets. Immune system activation in response to inflammation and pathogen infection is aided by long non-coding RNAs (lncRNAs). In our previous work, we revealed the differential expression of the novel lncRNA LNC_001186 in CpC-infected ileum versus healthy piglets. This implied that LNC_001186 may be a regulatory factor essential for CpC infection in piglets. Herein, we analyzed the coding ability, chromosomal location and subcellular localization of LNC_001186 and explored its regulatory role in CPB2 toxin-induced apoptosis of porcine small intestinal epithelial (IPEC-J2) cells. RT-qPCR results indicated that LNC_001186 expression was highly enriched in the intestines of healthy piglets and significantly increased in CpC-infected piglets' ileum tissue and CPB2 toxin-treated IPEC-J2 cells. The total sequence length of LNC_001186 was 1323 bp through RACE assay. CPC and CPAT, two online databases, both confirmed that LNC_001186 had a low coding ability. It was present on pig chromosome 3. Cytoplasmic and nuclear RNA isolation and RNA-FISH assays showed that LNC_001186 was present in the nucleus and cytoplasm of IPEC-J2 cells. Furthermore, six target genes of LNC_001186 were predicted using cis and trans approaches. Meanwhile, we constructed ceRNA regulatory networks with LNC_001186 as the center. Finally, LNC_001186 overexpression inhibited IPEC-J2 cells' apoptosis caused by CPB2 toxin and promoted cell viability. In summary, we determined the role of LNC_001186 in IPEC-J2 cells' apoptosis caused by CPB2 toxin, which assisted us in exploring the molecular mechanism of LNC_001186 in CpC-induced diarrhea in piglets.

lnc001776 Affects CPB2 Toxin-Induced Excessive Injury of Porcine Intestinal Epithelial Cells via Activating JNK/NF-kB Pathway through ssc-let-7i-5p/IL-6 Axis

Piglet diarrhea caused by Clostridium perfringens (C. perfringens) type C (CpC) seriously endangers the development of the pig production industry. C. perfringens beta2 (CPB2) toxin is a virulent toxin produced by CpC. Long non-coding RNAs (lncRNAs) are key regulators in the immune inflammatory response to bacterial infection. Nevertheless, the functional mechanism of lncRNAs in bacterial piglet diarrhea is unclear. Herein, a novel lncRNA lnc001776 expression was confirmed to be substantially elevated in the ileum tissue of CpC-infected diarrhea piglets and in CPB2 toxin-treated porcine small intestinal epithelial cells (IPEC-J2). lnc001776 knockdown restrained CPB2 toxin-induced apoptosis, inflammatory injury, barrier dysfunction and activation of JNK/NF-kB pathway in IPEC-J2 cells. Additionally, ssc-let-7i-5p was identified as sponge for lnc001776. Overexpression of ssc-let-7i-5p repressed CPB2-induced injury in IPEC-J2 cells. Interleukin 6 (IL-6), a target gene of ssc-let-7i-5p, was enhanced in CPB2 toxin-treated IPEC-J2 cells. Rescue experiments demonstrated that a ssc-let-7i-5p mimic reversed the effect of lnc001776 overexpression on CPB2 toxin-induced IPEC-J2 cell injury and JNK/NF-kB pathway, whereas IL-6 overexpression partially restored the impact of lnc001776. Overall, lnc001776 overexpression exacerbated CPB2 toxin-induced IPEC-J2 cell damage by sponging ssc-let-7i-5p to regulate IL-6 to activate JNK/NF-kB pathway, indicating that lnc001776 could be a key target for piglet resistance to CpC-induced diarrhea.

METTL3-Mediated LncRNA EN_42575 m6A Modification Alleviates CPB2 Toxin-Induced Damage in IPEC-J2 Cells

Long non-coding RNAs (lncRNAs) modified by n6-methyladenosine (m6A) have been implicated in the development and progression of several diseases. However, the mechanism responsible for the role of m6A-modified lncRNAs in Clostridium perfringens type C piglet diarrhea has remained largely unknown. We previously developed an in vitro model of CPB2 toxin-induced piglet diarrhea in IPEC-J2 cells. In addition, we previously performed RNA immunoprecipitation sequencing (MeRIP-seq), which demonstrated lncRNA EN_42575 as one of the most regulated m6A-modified lncRNAs in CPB2 toxin-exposed IPEC-J2 cells. In this study, we used MeRIP-qPCR, FISH, EdU, and RNA pull-down assays to determine the function of lncRNA EN_42575 in CPB2 toxin-exposed IPEC-J2 cells. LncRNA EN_42575 was significantly downregulated at different time points in CPB2 toxin-treated cells. Functionally, lncRNA EN_42575 overexpression reduced cytotoxicity, promoted cell proliferation, and inhibited apoptosis and oxidative damage, whereas the knockdown of lncRNA EN_42575 reversed these results. Furthermore, the dual-luciferase analysis revealed that METTL3 regulated lncRNA EN_42575 expression in an m6A-dependent manner. In conclusion, METTL3-mediated lncRNA EN_42575 exerted a regulatory effect on IPEC-J2 cells exposed to CPB2 toxins. These findings offer novel perspectives to further investigate the function of m6A-modified lncRNAs in piglet diarrhea.

Virulence assessment of four Glaesserella parasuis strains isolated in Liaoning province of China

Glaesserella parasuis (G. parasuis) is a part of the normal upper respiratory microbiota of healthy swine. In many studies, the serovars 1, 4, 5, and 12 of G. parasuis are considered to be highly virulent and its serovars 3, 6, 7, 9, and 11 are considered to be non-virulent. Until now, researchers have found that non-virulent strains of G. parasuis cause an increasing number of diseases. However, little is known concerning why non-virulent strains cause disease with the virulence changes. In present study, four G. parasuis strains were evaluated for their cytotoxicity property, which aims to compare their virulence. The results showed that highly virulent strains XX0306 and CY1201, as well as, non-virulent strains HLD0115 and YK1603 caused a series of pathological changes, increased lactate dehydrogenase (LDH) release, and decreased cell activity. In addition, compared to the control group, both highly and non-virulent strains showed similar trends, demonstrating that the method of classifying the virulence of G. parasuis based on its serovar is worth further deliberation. Hence, we investigated the adhesion capacity and invasion rate of G. parasuis, the results indicated that XX0306 and HLD0115 had the strongest adhesion and invasion ability, which contradicts the classification of the virulence of G. parasuis based on its serovar. The apoptosis degree induced by highly virulent strains was more intensive than non-virulent strains, as measured by annexin V and propidium iodide (PI) double staining. Through testing the expression of apoptosis-related genes Bcl-2 and Bax, we found highly virulent strains induced apoptosis by inhibiting the expression of Bcl-2.

Decreased S100A9 expression alleviates Clostridium perfringens beta2 toxin-induced inflammatory injury in IPEC-J2 cells

Background

S100 calcium-binding protein A9 (S100A9) is a commonly known pro-inflammatory factor involved in various inflammatory responses. Clostridium perfringens (C. perfringens ) type C is known to cause diarrhea in piglets. However, the role of S100A9 in C. perfringens type C-induced infectious diarrhea is unclear.

Methods

Here, the S100A9 gene was overexpressed and knocked down in the IPEC-J2 cells, which were treated with C. perfringens beta2 (CPB2) toxin. The role of S100A9 in CPB2 toxin-induced injury in IPEC-J2 cells was assessed by measuring the levels of inflammatory cytokines, reactive oxygen species (ROS), lactate dehydrogenase (LDH), cell proliferation, and tight junction-related proteins.

Results

The results showed elevated expression of S100A9 in diarrhea-affected piglet tissues, and the elevation of S100A9 expression after CPB2 toxin treatment of IPEC-J2 was time-dependent. In CPB2 toxin-induced IPEC-J2 cells, overexpression of S100A9 had the following effects: the relative expression of inflammatory factors IL-6, IL8, TNF-α, and IL-1β was increased; the ROS levels and LDH viability were significantly increased; cell viability and proliferation were inhibited; the G0/G1 phase cell ratio was significantly increased. Furthermore, overexpression of S100A9 reduced the expression of tight junction proteins in CPB2-induced IPEC-J2 cells. The knockdown of S100A9 had an inverse effect. In conclusion, our results confirmed that S100A9 exacerbated inflammatory injury in CPB2 toxin-induced IPEC-J2 cells, inhibited cell viability and cell proliferation, and disrupted the tight junctions between cells. Thus, decreased S100A9 expression alleviates CPB2 toxin-induced inflammatory injury in IPEC-J2 cells.

S100A9 plays a key role in Clostridium perfringens beta2 toxin-induced inflammatory damage in porcine IPEC-J2 intestinal epithelial cells

BACKGROUND

As an important regulator of autoimmune responses and inflammation, S100A9 may serve as a therapeutic target in inflammatory diseases. However, the role of S100A9 in Clostridium perfringens type C infectious diarrhea is poorly studied. The aim of our study was to screen downstream target genes regulated by S100A9 in Clostridium perfringens beta2 (CPB2) toxin-induced IPEC-J2 cell injury. We constructed IPEC-J2 cells with S100A9 knockdown and a CPB2-induced cell injury model, screened downstream genes regulated by S100A9 using RNA-Seq technique, and performed functional enrichment analysis. The function of S100A9 was verified using molecular biology techniques.

RESULTS

We identified 316 differentially expressed genes (DEGs), of which 221 were upregulated and 95 were downregulated. Functional enrichment analysis revealed that the DEGs were significantly enriched in cilium movement, negative regulation of cell differentiation, immune response, protein digestion and absorption, and complement and coagulation cascades. The key genes of immune response were TNF, CCL1, CCR7, CSF2, and CXCL9. When CPB2 toxin-induced IPEC-J2 cells overexpressed S100A9, Bax expression increased, Bcl-2 expression and mitochondrial membrane potential decreased, and SOD activity was inhibited.

CONCLUSION

In conclusion, S100A9 was involved in CPB2-induced inflammatory response in IPEC-J2 cells by regulating the expression of downstream target genes, namely, TNF, CCL1, CCR7, CSF2, and CXCL9; promoting apoptosis; and aggravating oxidative cell damage. This study laid the foundation for further study on the regulatory mechanism underlying piglet diarrhea.

LncRNA EN-90756 promotes CPB2-induced proliferation and inhibits apoptosis in IPEC-J2 cells by affecting the JAK-STAT signaling pathway activation

Background

Long non-coding RNAs (lncRNAs), as key regulators, are closely associated with the development of a variety of disease. However, the mechanisms by which lncRNAs regulate Clostridium perfringens type C induced piglet diarrhea are unclear.

Methods

In the present study, we explored the expression and characterization of lncRNAs in a C. perfringens beta2 (CPB2) toxin-treated intestinal porcine epithelial cell line-J2 (IPEC-J2) using RNA-sequencing (RNA-seq).

Results

A total of 6,558 lncRNAs were identified, of which 49 lncRNAs were significantly differentially expressed between the control and CPB2 groups. Functional enrichment analysis showed that the target genes of differentially expressed lncRNA EN-90756 were mainly associated with defense response to virus, and negative regulation of apoptotic process. LncRNA EN-90756 was significantly up-regulated in IPEC-J2 cells at different time points after CPB2 treatment. Functionally, knockdown of lncRNA EN-90756 might regulate the proliferation and apoptosis of IPEC-J2 cells by affecting the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway. LncRNA EN-90756 may be involved in CPB2 toxin-induced piglet diarrhea by regulating the expression of its target gene MX1 (encoding MX dynamin like GTPase 1).

Conclusion

Long non-coding RNA EN-90756 affected the antiviral ability of IPEC-J2 cells by regulating the expression of MX1. Meanwhile, lncRNA EN-90756 might regulate cell proliferation and apoptosis by affecting JAK-STAT signaling pathway activation. These findings provide novel perspectives and directions for further exploration of the regulatory mechanisms of lncRNAs on CPB2 toxin-induced diarrhea in piglets.

METTL3 Regulates the Inflammatory Response in CPB2 Toxin-Exposed IPEC-J2 Cells through the TLR2/NF-κB Signaling Pathway

Clostridium perfringens beta2 (CPB2) toxin is one of the main pathogenic toxins produced by Clostridium perfringens, which causes intestinal diseases in animals and humans. The N6-methyladenosine (m6A) modification is the most common reversible modification in eukaryotic disease processes. Methyltransferase-like 3 (METTL3) regulates immunity and inflammatory responses induced by the bacterial infections in animals. However, METTL3's involvement in CPB2-treated intestinal porcine epithelial cell line-J2 (IPEC-J2) remains unclear. In the current study, we used methylated RNA immunoprecipitation-quantitative polymerase chain reaction, Western blotting and immunofluorescence assay to determine the role of METTL3 in CPB2-exposed IPEC-J2 cells. The findings revealed that m6A and METTL3 levels were increased in CPB2 treated IPEC-J2 cells. Functionally, METTL3 overexpression promoted the release of inflammatory factors, increased cytotoxicity, decreased cell viability and disrupted tight junctions between cells, while the knockdown of METTL3 reversed these results. Furthermore, METTL3 was involved in the inflammatory response of IPEC-J2 cells by activating the TLR2/NF-κB signaling pathway through regulating TLR2 m6A levels. In conclusion, METTL3 overexpression triggered the TLR2/NF-κB signaling pathway and promoted CPB2-induced inflammatory responses in IPEC-J2 cells. These findings may provide a new strategy for the prevention and treatment of diarrhea caused by Clostridium perfringens.

Identification and Characterization of Clostridium perfringens Atypical CPB2 Toxin in Cell Cultures and Field Samples Using Monoclonal Antibodies

A direct sandwich enzyme-linked immunosorbent assay (sELISA) was developed for the detection of the atypical β2-toxin (CPB2) of Clostridium perfringens. Polyclonal (PAbs) and monoclonal (MAbs) antibodies were previously obtained employing recombinant CPB2 produced in the baculovirus system as antigen. In the current study, PAbs were used as capture molecules, while purified MAbs conjugated to horseradish peroxidase (MAbs-HRP) were used for the detection of atypical CPB2 toxin. MAbs 5C11E6 and 2G3G6 showed high reactivity, sensitivity and specificity when tested on 232 C. perfringens cell culture isolates. In addition, a reactivity variation among different strains producing atypical CPB2 toxin was observed using the conformation-dependent MAb 23E6E6, suggesting the hypothesis of high instability and/or the existence of different three-dimensional structures of this toxin. Results obtained by sELISA and Western blotting performed on experimentally CPB2-contaminated feces revealed a time-dependent proteolytic degradation as previously observed with the consensus allelic form of CPB2. Finally, the sELISA and an end-point PCR, specific for the atypical cpb2 gene, were used to test field samples (feces, rectal swabs and intestinal contents) from different dead animal species with suspected or confirmed clostridiosis. The comparison of sELISA data with those obtained with end-point PCR suggests this method as a promising tool for the detection of atypical CPB2 toxin.

Antimicrobial susceptibility and multilocus sequence typing of Clostridium perfringens isolated from yaks in Qinghai-Tibet plateau, China

Clostridium perfringens (C. perfringens) is an opportunistic pathogen that cause necrotic enteritis, food poisoning and even death in animals. In this study, we explored the prevalence, antibiotic resistance and genetic diversity of Clostridium perfringens isolated from yak in the Qinghai-Tibet plateau, China. A total of 744 yak fecal samples were collected and assessed for toxin genes, antimicrobial susceptibility and multilocus sequence typing (MLST). Results indicated that 144 out of 744 (19.35%) yak fecal samples were tested to be positive for C. perfringens, 75% (n = 108, 108/144) were C. perfringens type A, 17.36% (n = 25, 25/144) were C. perfringens type C, 2.78% (n = 4, 4/144) were C. perfringens type D, and 4.86% (n = 7, 7/144) were C. perfringens type F. In addition, 2.78% (n = 4, 4/144) of the isolates were positive for cpb2 toxin gene. Antimicrobial susceptibility testing revealed that 98.61% (142/144) of the isolates showed multiple-antibiotic resistance. According to MLST and phylogenetic tree, 144 yak-derived C. perfringens isolates had an average of 12.95 alleles and could be divided into 89 sequence types (STs) and clustered in 11 clonal complexes (CCs). The most of isolates belong to type A with a considerable genetic diversity, having Simpson index up to 0.9754. MLST and phylogenetic analysis showed that the isolates under the same clade came from multiple regions. Cross-transmission among isolates and interconnectedness were observed in the genetic evolution. According to the study, the most of the isolates exhibited broad-spectrum antibacterial resistance, diverse alleles, and multiple lethal toxin genes of C. perfringens.

Clostridium perfringens associated with dairy farm systems show diverse genotypes

Clostridium perfringens is a bacterial species of importance to both public and animal health. Frequently found in food system environments, it presents a risk to food animal health such as dairy herds, and may cross contaminate associated ingredients or food products, with potential to cause sporadic and outbreaks of disease in human populations, including gastroenteric illness. In this study, we characterized C. perfringens isolated from bovine, caprine, and ovine dairy farm systems (n = 8, 11 and 4, respectively). Isolates were phenotypically screened for antimicrobial sensitivity profiling, and subjected to whole genome sequencing to elucidate related genetic markers, as well as examine virulence gene markers, mobile genetic elements, and other features. Both toxin type A and type D isolates were identified (78 % and 22 % of isolates, respectively), including 20 novel sequence types. Resistance to clindamycin was most prevalent among antibiotics screened (30 %), followed by erythromycin (13 %), then penicillin and tetracycline (4 %), although an additional 3 isolates were non-susceptible to tetracycline. Most isolates harboured plasmids, which mobilised virulence markers such as etx, cpb2, and resistance markers tetA(P), tetB(P), and erm(Q), on conjugative plasmids. The presence of type D isolates on caprine farms emphasizes the need for control efforts to prevent infection and potential enterotoxemia. Clostridium perfringens enterotoxin (cpe) was not identified, suggesting lower risk of gastrointestinal illness from contaminated foods, the presence of other virulence and antimicrobial resistance markers suggests farm hygiene remains an important consideration to help ensure food safety of associated dairy foods produced.

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.

FTO Regulates Apoptosis in CPB2-Treated IPEC-J2 Cells by Targeting Caspase 3 Apoptotic Protein

N6-methyladenosine (m6A) modification can accommodate mRNA processing, stability, and translation in mammals, and fat mass and obesity associated protein (FTO) is a vital demethylase in the m6A modification pathway. Clostridium perfringens type C (C. perfringens type C) causes diarrhea in piglets and has a serious impact on the pig industry. However, our understanding of the effect of m6A in the process of C. perfringens type C infectious piglet diarrhea (CPTCIPD) is limited. Here, an in vitro model of CPTCIPD was constructed by treating the intestinal porcine epithelial cell line-J2 (IPEC-J2) with Clostridium perfringens beta2 (CPB2) toxin, and the role of FTO was analyzed using quantitative real-time polymerase chain reaction, Western blotting, and flow cytometry. The results revealed that the overall RNA m6A contents at the tissue and cell levels were significantly up-regulated after C. perfringens infection (p < 0.05). FTO expression was significantly reduced in CPB2-treated IPEC-J2 cells. Functionally, FTO knockdown in the treated cells inhibited their proliferation and promoted apoptosis and the inflammation phenotype, whereas FTO overexpression had the opposite effects. Inhibiting FTO prolonged the half-life and up-regulated the expression of Caspase 3, leading to apoptosis. Therefore, this work explored the regulation of FTO in IPEC-J2 cells after CPB2 treatment and enhanced our understanding of the effect of the m6A modification in CPTCIPD.

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.

ssc-microRNA-132 targets DACH1 to exert anti-inflammatory and anti-apoptotic effects in Clostridium perfringens beta2 toxin-treated porcine intestinal epithelial cells

Clostridium perfringens (C. perfringens) type C (CPC) is one of the chief pathogens that causes diarrhea in piglets, and C. perfringens beta2 (CPB2) toxin is the main virulence factor of CPC. Our previous research demonstrated that ssc-microR-132 was differentially expressed in ileal tissues of CPC-mediated diarrheic piglets and healthy piglets, which implied a potential role of ssc-microR-132 in this process. Here, we found that ssc-microR-132 was notably down-regulated in CPB2-exposed intestinal porcine epithelial cells (IPEC-J2), which was consistent with the ileal tissue expression. Moreover, ssc-microR-132 upregulation alleviated CPB2-induced inflammatory damage and apoptosis in IPEC-J2, whereas ssc-microR-132 knockdown presented the opposite effects. Furthermore, the dual-luciferase reporter assay indicated that ssc-microR-132 directly targeted Dachshund homolog 1 (DACH1). Moreover, DACH1 overexpression intensified CPB2-induced inflammatory injury and apoptosis in IPEC-J2. Remarkably, the introduction of DACH1 weakened the anti-inflammatory and anti-apoptotic effects of ssc-microR-132 in CPB2-exposed IPEC-J2. Overall, the results reveal that ssc-microR-132 targeted DACH1 to alleviate CPB2-mediated inflammation and apoptosis in IPEC-J2.

Clostridium perfringens Beta2 toxin forms highly cation-selective channels in lipid bilayers

Clostridium perfringens is a potent producer of a variety of toxins. Well studied from these are five toxins (alpha, Beta (CPB), epsilon, iota and CPE) that are produced by seven toxinotype strains (A–G) of C. perfringens. Besides these toxins, C. perfringens produces also another toxin that causes necrotizing enterocolitis in piglets. This toxin termed consensus Beta2 toxin (cCPB2) has a molecular mass of 27,620 Da and shows only little homology to CPB and no one to the other toxins of C. perfringens. Its primary action on cells remained unknown to date. cCPB2 was heterogeneously expressed as fusion protein with GST in Escherichia coli and purified to homogeneity. Although cCPB2 does not exhibit the typical structure of beta-stranded pore-forming proteins and contains no indication for the presence of amphipathic alpha-helices we could demonstrate that cCPB2 is a pore-forming component with an extremely high activity in lipid bilayers. The channels have a single-channel conductance of about 700 pS in 1 M KCl and are highly cation-selective as judged from selectivity measurements in the presence of salt gradients. The high cation selectivity is caused by the presence of net negative charges in or near the channel that allowed an estimate of the channel size being about 1.4 nm wide. Our measurements suggest that the primary effect of cCPB2 is the formation of cation-selective channels followed by necrotic enteritis in humans and animals. We searched in databases for homologs of cCPB2 and constructed a cladogram representing the phylogenetic relationship to the next relatives of cCPB2.

N6-Methyladenosine Methylation Analysis of Long Noncoding RNAs and mRNAs in IPEC-J2 Cells Treated With Clostridium perfringens beta2 Toxin

Background

The n6-methyladenosine (m6A) modification is present widely in mRNAs and long non-coding RNAs (lncRNAs), and is related to the occurrence and development of certain diseases. However, the role of m6A methylation in Clostridium perfringens type C infectious diarrhea remains unclear.

Methods

Here, we treated intestinal porcine jejunum epithelial cells (IPEC-J2 cells) with Clostridium perfringens beta2 (CPB2) toxin to construct an in vitro model of Clostridium perfringens type C (C. perfringens type C) infectious diarrhea, and then used methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) to identify the methylation profiles of mRNAs and lncRNAs in IPEC-J2 cells.

Results

We identified 6,413 peaks, representing 5,825 m6A-modified mRNAs and 433 modified lncRNAs, of which 4,356 m6A modified mRNAs and 221 m6A modified lncRNAs were significantly differential expressed between the control group and CPB2 group. The motif GGACU was enriched significantly in both the control group and the CPB2 group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis showed that the differentially methylated modified mRNAs were mainly enriched in Hippo signaling pathway and Wnt signaling pathway. In addition, the target genes of the differentially m6A modified lncRNAs were related to defense response to virus and immune response. For example, ENSSSCG00000042575, ENSSSCG00000048701 and ENSSSCG00000048785 might regulate the defense response to virus, immune and inflammatory response to resist the harmful effects of viruses on cells.

Conclusion

In summary, this study established the m6A transcription profile of mRNAs and lncRNAs in IPEC-J2 cells treated by CPB2 toxin. Further analysis showed that m6A-modified RNAs were related to defense against viruses and immune response after CPB2 toxin treatment of the cells. Threem6A-modified lncRNAs, ENSSSCG00000042575, ENSSSCG00000048785 and ENSSSCG00000048701, were most likely to play a key role in CPB2 toxin-treated IPEC-J2 cells. The results provide a theoretical basis for further research on the role of m6A modification in piglet diarrhea.

Protective Effects of Lactobacillus plantarum Lac16 on Clostridium perfringens Infection-Associated Injury in IPEC-J2 Cells

Clostridium perfringens (C. perfringens) causes intestinal injury through overgrowth and the secretion of multiple toxins, leading to diarrhea and necrotic enteritis in animals, including pigs, chickens, and sheep. This study aimed to investigate the protective effects of Lactobacillus plantarum (L. plantarum) Lac16 on C. perfringens infection-associated injury in intestinal porcine epithelial cell line (IPEC-J2). The results showed that L. plantarum Lac16 significantly inhibited the growth of C. perfringens, which was accompanied by a decrease in pH levels. In addition, L. plantarum Lac16 significantly elevated the mRNA expression levels of host defense peptides (HDPs) in IPEC-J2 cells, decreased the adhesion of C. perfringens to IPEC-J2 cells, and attenuated C. perfringens-induced cellular cytotoxicity and intestinal barrier damage. Furthermore, L. plantarum Lac16 significantly suppressed C. perfringens-induced gene expressions of proinflammatory cytokines and pattern recognition receptors (PRRs) in IPEC-J2 cells. Moreover, L. plantarum Lac16 preincubation effectively inhibited the phosphorylation of p65 caused by C. perfringens infection. Collectively, probiotic L. plantarum Lac16 exerts protective effects against C. perfringens infection-associated injury in IPEC-J2 cells.

Comprehensive Analysis of Transcriptome-wide m6A Methylome Upon Clostridium perfringens Beta2 Toxin Exposure in Porcine Intestinal Epithelial Cells by m6A Sequencing

Piglet diarrhea is a swine disease responsible for serious economic impacts in the pig industry. Clostridium perfringens beta2 toxin (CPB2), which is a major toxin of C. perfringens type C, may cause intestinal diseases in many domestic animals. N6-methyladenosine (m6A) RNA methylation plays critical roles in many immune and inflammatory diseases in livestock and other animals. However, the role of m6A methylation in porcine intestinal epithelial (IPEC-J2) cells exposed to CPB2 has not been studied. To address this issue, we treated IPEC-J2 cells with CPB2 toxin and then quantified methylation-related enzyme expression by RT-qPCR and assessed the m6A methylation status of the samples by colorimetric N6-methyladenosine quantification. The results showed that the methylation enzymes changed to varying degrees while the m6A methylation level increased (p < 0.01). On this basis, we performed N6-methyladenosine sequencing (m6A-seq) and RNA sequencing (RNA-seq) to examine the detailed m6A modifications and gene expression of the IPEC-J2 cells following CPB2 toxin exposure. Our results indicated that 1,448 m6A modification sites, including 437 up-regulated and 1,011 down-regulated, differed significantly between CPB2 toxin exposed cells and non-exposed cells (p < 0.05). KEGG pathway analysis results showed that m6A peaks up-regulated genes (n = 394) were mainly enriched in cancer, Cushing syndrome and Wnt signaling pathways, while m6A peaks down-regulated genes (n = 920) were mainly associated with apoptosis, small cell lung cancer, and the herpes simplex virus 1 infection signaling pathway. Furthermore, gene expression (RNA-seq data) analysis identified 1,636 differentially expressed genes (DEGs), of which 1,094 were up-regulated and 542 were down-regulated in the toxin exposed group compared with the control group. In addition, the down-regulated genes were involved in the Hippo and Wnt signaling pathways. Interestingly, the combined results of m6A-seq and RNA-seq identified genes with up-regulated m6A peaks but with down-regulated expression, here referred to as "hyper-down" genes (n = 18), which were mainly enriched in the Wnt signaling pathway. Therefore, we speculate that the genes in the Wnt signaling pathway may be modified by m6A methylation in CPB2-induced IPEC-J2 cells. These findings provide new insights enabling further exploration of the mechanisms underlying piglet diarrhea caused by CPB2 toxin.

Pyrroloquinoline quinone regulates the redox status in vitro and in vivo of weaned pigs via the Nrf2/HO-1 pathway

Background

Oxidative stress is a main cause of piglet gut damage and diarrhea. Pyrroloquinoline quinone (PQQ), is a novel redox cofactor with antioxidant properties. However, the effect and mechanism that PQQ supplementation decreases oxidative injury in weaned pigs is not understood. Therefore, the aim of this study is to confirm the effect of PQQ on regulating redox status in weaned pigs and the mechanism for antioxidant function by porcine intestinal epithelial cell line (IPEC-J2) challenged with H₂O₂.

Results

Experiment 1, 144 Duroc × Landrace × Yorkshire pigs (weaned at 28 d) were allocated to four groups: received a basal diet (control) and diets supplemented with 0.15%, 0.30% and 0.45% PQQ, respectively. On d 28, growth performance, diarrhea incidence and redox factors were measured. Experiment 2, IPEC-J2 were treated with or without PQQ in the presence or absence of H₂O₂ for indicated time points. Experiment 3, IPEC-J2 were transfected with or without Nrf2 siRNA, then treated according to Experiment 2. The cell viability, redox factors, protein of tight junctions and Nrf2 pathway were determined.

In vivo, PQQ supplementation demonstrated dose-related improvements in average daily gain, and gain to feed ratio (Linear P < 0.05). During d 0–28, compared to controls, 0.45% PQQ supplementation for pigs decreased diarrhea incidence and MDA content in liver and jejunum, and increased concentration of SOD in liver; 0.3% PQQ supplementation decreased ileal and liver MDA concentration; and 0.15% PQQ supplementation decreased ileal MDA concentration (P < 0.05). In vitro, compared to cells cultured with H₂O₂, pre-treatment with PQQ increased cell viability, tight junction proteins expression including ZO-1, ZO-2, Occludin and Claudin-1; and decreased ROS concentration and level of Caspase-3 (P < 0.05); as well as upregulated the ratio of Bcl-2 to Bax and protein expression of nuclear Nrf2, HO-1. Notably, Nrf2 knockdown by transfection with Nrf2 siRNA largely abrogated the positive effects of PQQ pretreatment on H₂O₂-induced intracellular changes.

Conclusions

PQQ administration attenuated oxidative stress in weaned pigs which is associated with activation of Nrf2/HO-1 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00595-x.

Effects of miR-204 on apoptosis and inflammatory response of Clostridium perfringens beta2 toxin induced IPEC-J2 cells via targeting BCL2L2

Clostridium perfringens beta2 (CPB2) toxin can cause intestinal damage and inflammatory responses in a variety of animals, which seriously endanger the healthy development of animal husbandry. Increasing evidence has demonstrated that microRNAs (miRNAs) can play an important regulatory role in the process of pathogenic infection. In our previous study, we found that miR-204 was highly expressed in the ileum tissues of the susceptible group diarrhea piglets after infection with Clostridium perfringens (C. perfringens) type C. In this study, we found that miR-204 was also up-regulated in different time points after CPB2 toxin treatment. Overexpression of miR-204 promoted apoptosis and inflammatory response of intestinal porcine epithelial cells (IPEC-J2), whereas the opposite results were displayed after transfected with miR-204 inhibitor. Furthermore, the luciferase reporter assays confirmed that BCL2L2 was a direct target gene of miR-204. Interestingly, we found that overexpression BCL2L2 attenuated the apoptosis and inflammatory response of CPB2 toxin induced IPEC-J2 cells. In conclusion, these results find that miR-204 promotes the apoptosis and intensify inflammatory response of CPB2 toxin induced IPEC-J2 cells via targeting BCL2L2. These data provide a valuable reference for the piglets resistance diarrhea at the molecular level.

Epigenetic upregulation of ssc-miR-124a following treatment with Clostridium perfringens beta2-toxin attenuates both apoptosis and inflammation in intestinal porcine epithelial cells

Clostridium perfringens (C. perfringens) is a globally recognized zoonotic pathogen. It has been reported that the beta2-toxin produced by C. perfringens can cause a variety of gastrointestinal diseases and even systemic inflammation. MicroRNA-124a (miR-124a) has been reported to play important roles in the host response to pathogenic infection. Although C. perfringens beta2-toxin induced injury in intestinal porcine epithelial (IPEC-J2) cells has been established, the underlying molecular mechanism is not completely unraveled. Here we show that a significant upregulation of ssc-miR-124a in IPEC-J2 cells after beta2-toxin stimulation was associated with the MiR-124A-1 and MiR-124A-2 gene promoter demethylation status. Importantly, overexpression of ssc-miR-124a significantly increased cell proliferation and decreased apoptosis and cytotoxicity in beta2-toxin treated IPEC-J2 cells. Transfection of IPEC-J2 cells with ssc-miR-124a mimic suppressed beta2-toxin induced inflammation. On the contrary, ssc-miR-124a inhibitor promoted aggravation of cell apoptosis and excessive damage. Furthermore, rho-associated coiled-coil-containing protein kinase 1 (ROCK1) was identified as the direct target gene of ssc-miR-124a in IPEC-J2 cells and its siRNA transfection reversed the promotion of apoptosis and aggravation of cellular damage induced by ssc-miR-124a inhibitor. Overall, we speculated that the miR-124A-1/2 gene was epigenetically regulated in IPEC-J2 cells after beta2-toxin treatment. Upregulation of ssc-miR-124a may restrain ROCK1, and attenuate apoptosis and inflammation induced by beta2-toxin that prevent IPEC-J2 cells from severe damages. We discover a new molecular mechanism by which IPEC-J2 cells counteract beta2-toxin-induced damage through the ssc-miR-124a/ROCK1 axis partially.