CD14 in the TLRs signaling pathway is associated with the resistance to E. coli F18 in Chinese domestic weaned piglets

Butyrate Derivatives Exhibited Anti-Inflammatory Effects and Enhanced Intestinal Barrier Integrity in Porcine Cell Culture Models

Butyrate and its derivatives may influence inflammatory status and physiology in a variety of organisms and organ systems. Inflammatory conditions of the gastrointestinal tract, such as post-weaning diarrhea, negatively impact swine. Dietary intervention with butyrate-based compounds should be considered a strategy to improve disease resistance in pigs. We aimed to assess the properties of different forms of butyrate treatments using porcine cell culture experiments. This assessment may inform future in vivo feed experiments designed to determine its potential application of the dietary supplements for pigs. An intestinal porcine enterocyte cell line, IPEC-J2, was seeded at 5 × 103 cells/mL in 96-well plates to confirm cell viability by MTT assay for each dose range used in the current experiments (0, 0.5, 1, 2, 4 mM butyric acid or tributyrin; 0, 1, 2, 4, 8 mM sodium butyrate or monobutyrin). For transepithelial electrical resistance (TEER) analysis, IPEC-J2 was seeded at 5 × 105 cells/mL in 12-well transwell inserts and treated with 5 levels of each butyrate derivative after adherence (n = 5). TEER was measured at 24, 48, and 72 h post-treatment to quantify intestinal barrier integrity of IPEC-J2 monolayers. Butyric acid, sodium butyrate, and monobutyrin significantly increased (p < 0.05) TEER in IPEC-J2 at different time points compared with control. Further, porcine alveolar macrophages (PAMs) were harvested from donor weaned piglets (n = 6) via bronchoalveolar lavage and isolated for primary culture (6 × 105 cells/well, 6-well plates). PAMs were treated with five levels of each butyrate derivative with or without lipopolysaccharide (LPS, 1 μg/mL) challenge. The concentrations of TNF-α and IL-1β in cell culture supernatants were measured by enzyme-linked immunosorbent assay (ELISA). Butyric acid and sodium butyrate treatments reduced the production of TNF-α in LPS-challenged PAMs (linear; p < 0.05). Different butyrate derivatives exerted anti-inflammatory properties and improved intestinal barrier integrity.

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.

Oxidized β-Carotene Is a Novel Phytochemical Immune Modulator That Supports Animal Health and Performance for Antibiotic-Free Production

Oxidized β-carotene (OxBC), a phytochemical that occurs naturally in plants, is formed by the spontaneous reaction of β-carotene with ambient oxygen. Synthetic OxBC, obtained by full oxidation of β-carotene with air, shows considerable promise as an in-feed antimicrobial alternative additive that enhances health and performance in livestock. OxBC is predominantly composed of β-carotene-oxygen copolymers that have beneficial immune-modulating effects that occur within the innate immune system by priming it to face microbial challenges and by mitigating the inflammatory response. OxBC does not have any direct anti-bacterial activity. Further, unlike traditional immune stimulants, OxBC modulates but does not stimulate and utilize the animal's energy stores unless directly stress-challenged. These immune effects occur by mechanisms distinct from the provitamin A or antioxidant pathways commonly proposed as explanations for β-carotene's actions. Trials in poultry, swine, and dairy cows with low parts-per-million in-feed OxBC supplementation have shown performance benefits over and above those of feeds containing regular vitamin and mineral premixes. Through its ability to enhance immune function, health, and performance, OxBC has demonstrated utility not only as a viable alternative to in-feed antimicrobials but also in its ability to provide tangible health and performance benefits in applications where antimicrobial usage is precluded.

Characterization of Intestinal Microbiota in Lambs with Different Susceptibility to Escherichia coli F17

Diarrhea is one of the most commonly reported diseases in young farm animals. Escherichia coli (E. coli) F17 is one of the major pathogenic bacteria responsible for diarrhea. However, the pathogenicity of diarrhea in lambs involving E. coli F17 strains and how E. coli F17 infection modifies lambs' intestinal microbiota are largely unknown. To evaluate diarrhea in newborn lambs with an infection of E. coli F17, 50 lambs were selected for challenge experiments and divided into four groups, namely, a high-dose challenge group, low-dose challenge group, positive control group, and negative control group. The E. coli F17 challenge experiments caused diarrhea and increased mortality in the experimental lamb population, with a higher prevalence (90%), mortality (35%), and rapid onset time (4-12 h) being observed in the high-dose challenge group than the results observed in the low-dose challenge group (75%, 10%, 6-24 h, respectively). After the challenge experiment, healthy lambs in the high-dose challenge group and severely diarrheic lamb in the low-dose challenge group were identified as lambs sensitive/resistant to E. coli F17 (E. coli F17 -resistant/-sensitive candidate, AN/SE) according to the histopathological detection. Results of intestinal contents bacteria plate counting revealed that the number of bacteria in the intestinal contents of SE lambs was 10^2~3-fold greater than that of the AN lambs, especially in the jejunum. Then, 16S rRNA sequencing was conducted to profile the intestinal microbiota using the jejunal contents, and the results showed that SE lambs had higher Lactococcus and a lower Bacteroidetes:Firmicutes ratio and intestinal microbiota diversity in the jejunum than AN lambs. Notably, high abundance of Megasphaera elsdenii was revealed in AN lambs, which indicated that Megasphaera elsdenii may serve as a potential probiotic for E. coli F17 infection. Our study provides an alternative challenge model for the identification of E. coli F17-sensitive/-resistant lambs and contributes to the basic understandings of intestinal microbiota in lambs with different susceptibilities to E. coli F17.

Comprehensive Analysis Revealed the Potential Roles of N6-Methyladenosine (m6A) Mediating E. coli F18 Susceptibility in IPEC-J2 Cells

Post-weaning diarrhea caused by enterotoxigenic Escherichia coli F18 (E. coli F18) causes significant economic losses for pig producers. N6-methyladenosine (m6A) is a highly abundant epitranscriptomic marker that has been found to be involved in regulating the resistance of host cells to pathogenic infection, but its potential role in E. coli F18-exposed intestinal porcine epithelial cells (IPEC-J2) remains undetermined. Here, we demonstrated that m6A and its regulators modulate E. coli F18 susceptibility. Briefly, we revealed that the Wilms’ tumor 1-associating protein (WTAP) expressions were markedly elevated in IPEC-J2 cells upon E. coli F18 exposure. WTAP are required for the regulation of E. coli F18 adhesion in IPEC-J2 cells. Additionally, WTAP knockdown significantly suppressed m6A level at N-acetyllactosaminide beta-1,6-N-acetylglucosaminyl-transferase (GCNT2) 3′UTR, resulting in the enhancement of TH N6-methyladenosine RNA binding protein 2 (YTHDF2)-mediated GCNT2 mRNA stability. Subsequently, the altered GCNT2 expressions could inhibit the glycosphingolipid biosynthesis, thus improving resistance to E. coli F18 infection in IPEC-J2. Collectively, our analyses highlighted the mechanism behind the m6A-mediated management of E. coli F18 susceptibility, which will aid in the development of novel approaches that protect against bacterial diarrhea in piglets.

Identification of a 5-Methylcytosine Site (mC-7) That May Inhibit CXCL11 Expression and Regulate E. coli F18 Susceptibility in IPEC-J2 Cells

The primary pathogen causing post-weaning diarrhea in piglets is Escherichia coli F18 (E. coli F18), hence it is essential to investigate the mechanism governing E. coli F18 resistance in native pig breeds. Based on the previous RNA-seq results of the duodenum from E. coli F18-resistant and -susceptible Meishan piglets, CXCL11, an important functional gene, was preliminarily screened. In this investigation, in order to further examine the expression regulation mechanism of E. coli F18 in intestinal porcine epithelial cells (IPEC-J2) against E. coli F18 infection, CXCL11 gene expression on IPEC-J2 cells infected by E. coli F18 was detected, which was significantly downregulated (p < 0.01). Secondly, the overexpression on the IPEC-J2 cell line was successfully structured, and a relative quantification method of the PILIN, bacteria enumeration, and immunofluorescence assay indicated that the CXCL11 overexpression significantly reduced the ability of E. coli F18 to interact with IPEC-J2 in vitro. The promoter region of the CXCL11 gene was predicted to contain a CpG island (−619 ~ −380 bp) of which 13 CpG sites in the sequencing region were methylated to varying degrees, and the methylation level of one CPG site (mC-7) positively linked negatively with the expression of the CXCL11 gene (p < 0.05). Meanwhile, a dual luciferase assay detected the mutation of the mC-7 site that significantly inhibited the luciferase activity of the CXCL11 gene promoter (p < 0.01). Transcription factor prediction and expression verification indicated that mC-7 is located in the OSR1-binding domain, and that its expression level is related to E. coli F18 susceptibility. We speculated that methylation modification of the mC-7 site of the CpG island in the promoter region of the CXCL11 gene might inhibit the binding of transcription factor OSR1 with the mC-7 site, and then affect its expression level to regulate the susceptibility to E. coli F18.

CDK7/GRP78 signaling axis contributes to tumor growth and metastasis in osteosarcoma

Osteosarcoma derives from primitive bone-forming mesenchymal cells and is the most common primary bone malignancy. Therapeutic targeting of osteosarcoma has been unsuccessful; therefore, identifying novel osteosarcoma pathogenesis could offer new therapeutic options. CDK7 is a subunit within the general transcription factor TFIIH. We aim to explore the new mechanism by which CDK7 regulates osteosarcoma and our studies may provide new theoretical support for the use of CDK7 inhibitors in the treatment of osteosarcoma. Here, we investigate the molecular mechanism underlying the association between CDK7 and GRP78 in osteosarcoma. Specifically, we find that an E3 ubiquitin ligase TRIM21 binds and targets GRP78 for ubiquitination and degradation, whereas CDK7 phosphorylates GRP78 at T69 to inhibit TRIM21 recruitment, leading to GRP78 stabilization. Notably, a CDK7-specific inhibitor, THZ1, blunts osteosarcoma growth and metastasis. Combination treatment with CDK7 and GRP78 inhibitors yield additive effects on osteosarcoma growth and progression inhibition. Thus, simultaneous suppression of CDK7 and GRP78 activity represents a potential new approach for the treatment of osteosarcoma. In conclusion, the discovery of this previously unknown CDK7/GRP78 signaling axis provides the molecular basis and the rationale to target human osteosarcoma.

Combined Transcriptomics and Metabolomics Analyses in Grass Carp Under Anesthetic Stress

Ctenopharyngodon Idella, as a common freshwater bony fish, is more susceptible to various diseases than other carp species, so it has been proposed as a test organism for toxicological analysis In this study, C. idella were anesthetized with MS-222 and 2-PE, and the related anesthetic mechanism and toxic effects were revealed by transcriptomics and metabolomics analyses. When the concentration of MS-222 was 80 mg/L and 200 mg/L, 179 and 887 differentially expressed genes (DEGs), respectively, were identified in the brain tissue of C. idella. When the concentration of 2-PE was 0.6 mL/L and 1.2 mL/L, 498 and 514 DEGs were identified. The DEGs associated with MS-222 treatment were enriched in immune pathways, lipid metabolism, amino acid metabolism, and various signaling pathways; DEGs associated with 2-PE treatment were enriched in immunity and amino acid metabolism. In total, 304 metabolites were identified using a combination of positive and negative ion modes in mass spectrometry. The common differential metabolites identified in the MS-222 high and low concentration groups were 20-HETE and 12(R)-HETE; the common significant differential metabolite identified in the 2-PE high and low concentration groups was salidroside. In combination with the transcriptomics analysis and metabolomics analysis, the results showed that with the MS-222 and 2-PE concentrations used in this experiment, the metabolism of arachidonic acid in C. idella was inhibited by MS-222, and 2-PE affected the upstream and downstream metabolic pathways of arachidonic acid metabolism, thereby affecting the metabolism of arachidonic acid. Both anesthetics induce sedation by affecting related metabolites that affect stress response and autoimmunity. Metabolomics results showed that neither anesthetic had a significant effect on cortisol expression.

Insight into mechanisms of pig lncRNA FUT3-AS1 regulating E. coli F18-bacterial diarrhea

Escherichia coli F18 is a common conditional pathogen that is associated with a variety of infections in humans and animals. LncRNAs have emerged as critical players in pathogen infection, but their role in the resistance of the host to bacterial diarrhea remains unknown. Here, we used piglets as animal model and identified an antisense lncRNA termed FUT3-AS1 as a host regulator related to E. coli F18 infection by RNA sequencing. Downregulation of FUT3-AS1 expression contributed to the enhancement of E. coli F18 resistance in IPEC-J2 cells. FUT3-AS1 knockdown reduced FUT3 expression via decreasing the H4K16ac level of FUT3 promoter. Besides, the FUT3-AS1/miR-212 axis could act as a competing endogenous RNA to regulate FUT3 expression. Functional analysis demonstrated that target FUT3 plays a vital role in the resistance of IPEC-J2 cells to E. coli F18 invasion. A Fut3-knockout mice model was established and Fut3-knockout mice obviously improved the ability of resistance to bacterial diarrhea. Interestingly, FUT3 could enhance E. coli F18 susceptibility by activating glycosphingolipid biosynthesis and toll-like receptor signaling which are related to receptor formation and immune response, respectively. In summary, we have identified a novel biomarker FUT3-AS1 that modulates E. coli F18 susceptibility via histone H4 modifications or miR-212/FUT3 axis, which will provide theoretical guidance to develop novel strategies for combating bacterial diarrhea in piglets.

Characterization, mRNA expression profile, subcellular distribution and association analysis with piglet diarrhea of porcine matrix metallopeptidase 7 (pMMP7)

Matrix metalloproteinase 7 (MMP7) is involved in the degradation of extracellular matrix in disease processes and therefore plays an important role in host disease resistance/susceptibility. To better understanding the effects of porcine MMP7 (pMMP7) on piglets diarrhea trait, we characterized pMMP7 gene, identified genetic variations in pMMP7 and explored the relationship between pMMP7 polymorphisms and piglets diarrhea in Min pig and Landrace populations. The complete coding sequence of pMMP7 is 804 bp encoding a protein of 267 amino acids. Sequence alignment showed that the identity between pMMP7 and human MMP7 was approximately 80%. The expression of pMMP7 in the gut of healthy piglets were weak and the distribution of the pMMP7-EGFP fusion protein was observed mainly in the cytoplasm. After the identification of 21 genetic variations in 5' flanking region and exons, Hae III and Eco72 Ⅰ PCR-RFLP were established to genotype SNP rs327380117 and rs329429922, respectively. Statistical analysis indicated that Landrace piglets with a TT genotype at rs327380117 had a lower diarrhea score and day-14 wt than TC piglets (p < 0.05); the diarrhea score of AA Landrace animals with rs329429922 was lower than that of GG individuals (p < 0.05). The findings presented here contribute to the understanding of the biological function of pMMP7 and may provide new molecular markers for pig breeding.

Insights Into Long Non-Coding RNA and mRNA Expression in the Jejunum of Lambs Challenged With Escherichia coli F17

It has long been recognized that enterotoxigenic Escherichia coli (ETEC) is the major pathogen responsible for vomiting and diarrhea. E. coli F17, a main subtype of ETEC, is characterized by high morbidity and mortality in young livestock. However, the transcriptomic basis underlying E. coli F17 infection has not been fully understood. In the present study, RNA sequencing was conducted to explore the expression profiles of mRNAs and long non-coding RNAs (lncRNAs) in the jejunum of lambs who were identified as resistant or sensitive to E. coli F17 that was obtained in a challenge experiment. A total of 772 differentially expressed (DE) mRNAs and 190 DE lncRNAs were detected between the E. coli F17—resistance and E. coli F17-sensitive lambs (i.e., TFF2, LOC105606142, OLFM4, LYPD8, REG4, APOA4, TCONS_00223467, and TCONS_00241897). Then, a two-step machine learning approach (RX) combination Random Forest and Extreme Gradient Boosting were performed, which identified 16 mRNAs and 17 lncRNAs as potential biomarkers, within which PPP2R3A and TCONS_00182693 were prioritized as key biomarkers involved in E. coli F17 infection. Furthermore, functional enrichment analysis showed that peroxisome proliferator-activated receptor (PPAR) pathway was significantly enriched in response to E. coli F17 infection. Our finding will help to improve the knowledge of the mechanisms underlying E. coli F17 infection and may provide novel targets for future treatment of E. coli F17 infection.

DNA Methylation of Pig FUT3 Promoter Alters mRNA Expression to Regulate E. coli F18 Susceptibility

Post-weaning diarrhea (PWD) is frequently associated with E. coli F18 infections in piglets. However, the underlying molecular mechanism concerning the resistance of E. coli F18 in local weaned piglets in China is not clearly understood. In the present study, by a comparative analysis of the transcriptome, a-1,3-fucosyltransferase (FUT3) was evaluated as a key candidate correlated with resistance to E. coli F18 in Sutai and Meishan piglets. Functional analysis demonstrated that FUT3 acts as a key positive regulator of E. coli F18 susceptibility in newly food accustomed piglets. However, the core promoter of FUT3 was present at −500–(−206) bp (chr.2: g.73171117–g.73171616), comprising of 9 methylated CpG sites. Among these, the methylation levels of the two CpG sites (mC-3, mC-5) located in HIF1A and Sp1 transcription factor (TF) considerably associated with mRNA expression of FUT3 (p < 0.05). Our findings indicated that the methylation of mC-3 and mC-5 sites has certain inhibitory effect on FUT3 expression and promotes the resistance of E. coli F18 in piglets. The underlined study may explore FUT3 as a new candidate target in E. coli F18 infection in Chinese local weaned piglets.

Staphylococcus aureus induces COX-2-dependent proliferation and malignant transformation in oral keratinocytes

The COX-2/PGE₂ axis can play roles in mediating the progression of tumor. COX-2 induction was observed in oral cancer. In our previous study, we found Staphylococcus aureus, a pathogen prevalent in oral cancer, can activate the COX-2/PGE₂ pathway in human oral keratinocyte (HOK) cells. Here, we investigated the proliferation of HOK cells affected by COX-2 induction and the role of COX-2 induction in the malignant transformation of HOK cells. We found S. aureus was able to facilitate HOK cell proliferation through upregulating COX-2 expression. With the induction of COX-2, expression of oral cancer-associated genes cyclin D1 was upregulated and p16 was downregulated. Transcriptome analysis showed that the “NF−kappa B signaling pathway” and “TNF signaling pathway” had the highest enrichment of differentially expressed genes (DEGs) with COX-2 over-expression. Seven upregulated genes (jun, tlr4, cxcl1, lif, cxcl3, tnfrsf1β, and il1β) in these two pathways were critical for the increased proliferation of HOK cells and might be associated with COX-2. Malignant transformation of cells was evaluated by soft agar colony formation assay and S. aureus infection promoted HOK cell colony formation. These results suggest the potential of S. aureus to induce the infection-associated malignant transformation of oral epitheliums through COX-2 activation.

Transcriptional profiling of Auricularia cornea in selenium accumulation

Auricularia cornea is a widely cultivated edible fungus with substantial nutritive value. This study aimed to enrich the multifunctional bionutrient element selenium in A. cornea to improve its quality and explore the accumulation of selenium in the fungus using high-throughput RNA-Seq technology. In general, the treatment group with a 100 µg/g supply of selenium outperformed the other treatment groups in terms of high yield, rich crude polysaccharides and a high total selenium concentration. Additional evidences demonstrated the budding and mature phases were two typical growth stages of A. cornea and were important for the accumulation of selenium. Therefore, the budding and mature phase tissues of A. cornea in the treatment group with a 100 µg/g supply of selenium were used for transcriptome analysis and compared to those of a control group that lacked additional selenium. A total of 2.56 × 105 unigenes from A. cornea transcriptome were assembled and annotated to five frequently used databases including NR, GO, KEGG, eggNOG and SwissProt. GO and KEGG pathway analysis revealed that genes involved in metabolic process and translation were up-expressed at the budding stage in response to selenium supplementation, including amino acid metabolism, lipid metabolism, ribosome. In addition, the differential gene expression patterns of A. cornea suggested that the up-expressed genes were more likely to be detected at the budding stage than at the mature stage. These results provide insights into the transcriptional response of A. cornea to selenium accumulation.

New Insight into the Molecular Mechanism of the FUT2 Regulating Escherichia coli F18 Resistance in Weaned Piglets

Escherichia coli (E. coli) F18 is the main pathogen responsible for post-weaning diarrhea (PWD) in piglets. Resistance to E. coli F18 depends on the expression of the cognate receptors in the intestinal epithelial cells. However, the molecular mechanism of E. coli F18 resistance in weaned piglets remains unclear. Here, we performed a comparative transcriptome study of the duodenal tissue from Sutai E. coli F18 sensitive and resistant pigs by RNA-seq, and pig α(1,2) fucosyltransferase 2 (FUT2) was identified as a host differentially expressed gene controlling the E. coli F18 infection. Function analysis showed that the FUT2 expression was high in the duodenum and jejunum, with higher levels detected in sensitive individuals than in resistant individuals (p < 0.01). Expression levels of FUT2 were upregulated in IPEC-J2 cells after lipopolysaccharide (LPS)-induction or E. coli stimulation. FUT2 knockdown decreased the adhesion of E. coli F18 to IPEC-J2 cells (p < 0.05). FUT2 overexpression markedly increased the adhesion of E. coli F18 to IPEC-J2 cells (p < 0.05 or p < 0.01). Furthermore, the FUT2 mRNA levels correlated with methylation levels of the mC-22 site in the specificity protein 1 (Sp1) transcription factor (p < 0.05). Electrophoretic mobility shift assays (EMSA) showed that Sp1 interacts with the wild-type FUT2 promoter DNA, but not with methylated DNA. Our data suggested that FUT2 methylation at the mC-22 site inhibits Sp1 binding to the FUT2 promoter, thereby reducing FUT2 expression and enhancing E. coli F18 resistance in weaned piglets. These observations highlight FUT2 as a promising new target for combating E. coli F18 susceptibility in weaned piglets.

Transcriptional profiling provides new insights into the role of nitric oxide in enhancing Ganoderma oregonense resistance to heat stress

Ganoderma is well known for its use in traditional Chinese medicine and is widely cultivated in China, Korea, and Japan. Increased temperatures associated with global warming are negatively influencing the growth and development of Ganoderma. Nitric oxide is reported to play an important role in alleviating fungal heat stress (HS). However, the transcriptional profiling of Ganoderma oregonense in response to HS, as well as the transcriptional response regulated by NO to cope with HS has not been reported. We used RNA-Seq technology to generate large-scale transcriptome data from G. oregonense mycelia subjected to HS (32 °C) and exposed to concentrations of exogenous NO. The results showed that heat shock proteins (HSPs), "probable stress-induced proteins", and unigenes involved in "D-amino-acid oxidase activity" and "oxidoreductase activity" were significantly up-regulated in G. oregonense subjected to HS (P < 0.05). The significantly up-regulated HSPs, "monooxygenases", "alcohol dehydrogenase", and "FAD/NAD(P)-binding domain-containing proteins" (P < 0.05) regulated by exogenous NO may play important roles in the enhanced HS tolerance of G. oregonense. These results provide insights into the transcriptional response of G. oregonense to HS and the mechanism by which NO enhances the HS tolerance of fungi at the gene expression level.

Escherichia coli aggravates endoplasmic reticulum stress and triggers CHOP-dependent apoptosis in weaned pigs

Intestinal cells can sense the presence of pathogens and trigger many important signaling pathways to maintain tissue homeostasis and normal function. Escherichia coli and lipopolysaccharides (LPS) are the main pathogenic factors of intestinal disease in pigs. However, the roles of endoplasmic reticulum stress (ERS) and its mediated apoptosis in intestinal malfunction induced by E. coli or LPS remain unclear. In the present study, we aimed to evaluate whether ERS could be activated by E. coli fed to piglets and whether the underlying mechanisms of this disease process could be exploited. Eighteen weaned pigs (21 days old) were randomly assigned to one of two treatment groups (n = 9 per group). After pre-feeding for 1 week, the diets of the piglets in one group were supplemented with E. coli (W25 K, 10⁹ cells kg^-1 diet) for 7 days. At the end of the experiment, all piglets were slaughtered to collect jejunum and ileum samples. Western blotting and immunofluorescence experiments were used to determine the expression levels and histological locations of ERS and its downstream signaling proteins. The intestinal porcine epithelial cell line J2 (IPEC-J2) was used as in vitro model to investigate the possible mechanism. The results showed that E. coli supplementation in the diet increased the GRP78 expression in the jejunum and ileum, especially in the jejunal epithelium and ileac germinal center, and elevated the expression levels of CHOP (in both the jejunum and ileum) and caspase-11 (in the ileum), indicating that ERS and CHOP-caspase-11 dependent apoptosis were activated in the porcine small intestine. Moreover, as demonstrated by in vitro experiments, the CHOP inhibitor 4-phenylbutyrate alleviated the damage to IPEC-J2 cells induced by LPS derived from E. coli. Taken together, these data strongly suggest that ERS can be triggered in the small intestine by dietary supplementation with E. coli and that CHOP-caspase-11 dependent apoptosis may play a key role in maintaining normal homeostasis of the intestine in response to pathogenic factors.

Identification of microRNAs regulating Escherichia coli F18 infection in Meishan weaned piglets

Background

Escherichia coli F18 is mainly responsible for post-weaning diarrhea (PWD) in piglets. The molecular regulation of E. coli F18 resistance in Chinese domestic weaned piglets is still obscure. We used Meishan piglets as model animals to test their susceptibility to E. coli F18. Small RNA duodenal libraries were constructed for E. coli F18-sensitive and -resistant weaned piglets challenged with E. coli F18 and sequenced using Illumina Solexa high-throughput sequencing technology.

Results

Sequencing results showed that 3,475,231 and 37,198,259 clean reads were obtained, with 311 known miRNAs differently expressed in resistant and sensitive groups, respectively. Twenty-four miRNAs, including 15 up-regulated and 9 down-regulated, demonstrated more than a 2-fold differential expression between the F18-resistant and -sensitive piglets. Stem-loop RT-qPCR showed that miR-136, miR-196b, miR-499-5p and miR-218-3p significantly expressed in intestinal tissue (p < 0.05). KEGG pathway analysis for target genes revealed that differently expressed miRNAs were involved in infectious diseases, signal transduction and immune system pathways. Interestingly, the expression of miR-218-3p in intestinal tissue had a very significant negative correlation with target DLG5 (P < 0.01).

Conclusions

Based on the expression correlation between miRNA and target genes analysis, we speculate that miR-218-3p targeting to DLG5, appears to be very promising candidate for miRNAs involved in response to E. coli F18 infection. The present study provides improved database information on pig miRNAs, better understanding of the genetic basis of E. coli F18 resistance in local Chinese pig breeds and lays a new foundation for identifying novel markers of E. coli F18 resistance.

Reviewers

This article was reviewed by Neil R Smalheiser and Weixiong Zhang.

Electronic supplementary material

The online version of this article (doi:10.1186/s13062-016-0160-3) contains supplementary material, which is available to authorized users.