circFLNA promotes intestinal injury during abdominal sepsis through Fas-mediated apoptosis pathway by sponging miR-766-3p

BACKGROUND

Intra-abdominal infections are the second most common cause of sepsis in the intensive care unit. Intestinal epithelial injury due to abdominal sepsis results in a variety of pathological changes, such as intestinal bacteria and toxins entering the blood, leading to persistent systemic inflammation and multiple organ dysfunction. The increased apoptosis of intestinal epithelial cells induced by sepsis further exacerbates the progression of sepsis. Although several studies have revealed that circRNAs are involved in intestinal epithelial injury in sepsis, few studies have identified the roles of circRNAs in intestinal epithelial apoptosis.

METHODS

We used laser capture microdissection to obtain purified epithelial cells located in intestinal crypts from four patients with abdominal sepsis induced by intestinal perforation and four samples from age and sex-matched non-septic patients. Microarray analysis of circRNAs was conducted to assess differentially expressed circRNAs between patients with and without sepsis. Lastly, in vitro and in vivo assays were performed to study the mechanism of circFLNA in intestinal epithelial apoptosis during sepsis.

RESULTS

circFLNA was upregulated in the intestinal epithelium after abdominal sepsis induced by intestinal perforation. Inhibition of miR-766-3p impaired si-circFLNA-mediated inhibition of apoptosis and inflammation factor levels in lipopolysaccharide (LPS)-treated HIEC-6 cells. circFLNA aggravated apoptosis and inflammation through the Fas-mediated apoptosis pathway in both LPS-treated HIEC-6 cells and a mouse cecal ligation and puncture model.

CONCLUSION

Our findings showed that circFLNA promotes intestinal injury in abdominal sepsis through the Fas-mediated apoptosis pathway by sponging miR-766-3p. The circFLNA/miR-766-3p/Fas axis has potential as a novel therapeutic target for treating intestinal injury in sepsis.

IL-36 signalling enhances a pro-tumorigenic phenotype in colon cancer cells with cancer cell growth restricted by administration of the IL-36R antagonist

The IL-36 cytokines are a recently described subset of the IL-1 family of cytokines, shown to play a role in the pathogenesis of intestinal diseases such as Inflammatory Bowel Disease (IBD). Given the link between IBD and colitis -associated cancer, as well as the involvement of other IL-1 family members in intestinal tumorigenesis, the aim of this work was to investigate whether IL-36 cytokines play a role in the pathogenesis of colon cancer. Whilst research to date has focused on the role of IL-36 family members in augmenting the immune response to induce tumour rejection, very little remains known about IL-36R signalling in tumour cells in this context. In this study we demonstrate that expression of IL-36 family member mRNA and protein are significantly increased in colorectal cancer tissue compared to adjacent non-tumour. In vitro assays showed stimulation of colon cancer cell lines with IL-36R agonists resulted in the activation of the pro-tumorigenic phenotypes of increased cellular migration, invasion and proliferation in both 2D and 3D models. In addition, the IL-36 cytokines induced strong expression of pro-inflammatory chemokines in both human and murine cell lines. Intraperitoneal injection of IL-36Ra significantly reduced tumour burden using the subcutaneous CT26 tumour model in syngeneic Balb/mice, and this was associated with a decrease in Ki-67 expression by tumour cells in the IL-36Ra- treated group relative to untreated, suggesting the inhibition of the pro-proliferative signalling of IL-36 agonists resulted in the decreased tumour size. Moreover, colon cancer cells lacking the IL-36R also showed reduced tumour growth and reduced Ki-67 expression in vivo. Taken together, this data suggests that targeting IL-36R signalling may be a useful targeted therapy for colorectal cancer patients with IL-36R⁺ tumour cells.

E2f2 Attenuates Apoptosis of Activated T Lymphocytes and Protects from Immune-Mediated Injury through Repression of Fas and FasL

Targeted disruption of E2f2 in mice causes T-cell hyperactivation and a disproportionate cell cycle entry upon stimulation. However, E2f2^−/− mice do not develop a lymphoproliferative condition. We report that E2f2 plays a Fas-dependent anti-apoptotic function in vitro and in vivo. TCR-stimulated murine E2f2^−/− T cells overexpress the proapoptotic genes Fas and FasL and exhibit enhanced apoptosis, which is prevented by treatment with neutralizing anti-FasL antibodies. p53 pathway is activated in TCR-stimulated E2f2^−/− lymphocytes, but targeted disruption of p53 in E2f2^−/− mice does not abrogate Fas/FasL expression or apoptosis, implying a p53-independent apoptotic mechanism. We show that E2f2 is recruited to Fas and FasL gene promoters to repress their expression. in vivo, E2f2^−/− mice are prone to develop immune-mediated liver injury owing to an aberrant lymphoid Fas/FasL activation. Taken together, our results suggest that E2f2-dependent inhibition of Fas/FasL pathway may play a direct role in limiting the development of immune-mediated pathologies.

Maternal antibiotic treatment affects offspring gastric sensing for umami taste and ghrelin regulation in the pig

Background

Scarce is knowledge on the process regulating the development of acid secretion, orexigenic signaling, and chemosensing in the stomach of young pigs. Changes of early microbial encounters by suckling pigs can interact with the gut maturation, by the induction of different molecular signaling. Our goal was to assess if the age of offspring and the maternal environment, influenced by sow antibiotic treatment peripartum, could affect gastric morphology and the expression of genes involved in the control of hydrochloric secretion, feed intake, taste, and inflammation in offspring stomach.

Methods

84 pigs from sows fed a diet with amoxicillin (on –d10 to +d21 from farrowing, ANT) or without (CON) were sacrificed at d14, d21, d28 (weaning) or d42. Samples of oxyntic (OXY), pyloric (PY) and cardiac mucosae close to OXY were collected and parietal and enteroendocrine cells (EECs) were counted. Relative gene expression of a set of 11 key genes (ATP4A, SSTR2, GAST, GHRL, MBOAT4, PCSK1, GNAT1, TAS1R1, TAS1R3, IL8 and TNF) was assessed by qRT-PCR. In addition, 40 offspring obtained from the same ANT and CON sows were offered a normal or a fat-enriched diet for 4 weeks between 140 and 169 d of age, and then OXY and PY were sampled.

Results

The number of parietal and EECs increased with age (P < 0.001). ATP4A increased with age (within suckling, P = 0.043, post-weaning vs. suckling, P < 0.001), SSTR2 increased only after weaning (P < 0.001). In OXY, GHRL increased during suckling (P = 0.012), and post-weaning as a trend (P = 0.088). MBOAT4 tended to increase during suckling (P = 0.062). TAS1R1 increased from suckling to post-weaning period (P =0.001) and was lower in ANT offspring (P = 0.013). GNAT1 in PY was higher in ANT offspring (P = 0.041). Antibiotic treatment of sows peripartum increased expression of GHRL and MBOAT4 in OXY of growing-finishing offspring aged 5 months.

Conclusions

Data show that sensing for umami taste and ghrelin regulation can be affected by maternal environment, but the development of acid secretion, orexigenic signaling and taste perception in the stomach are mostly developmentally controlled.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00557-3.

Engagement of Fas differentially regulates the production of LPS-induced proinflammatory cytokines and type I interferons

Fas (CD95) signalling is best known for its role in apoptosis, however, recent reports have shown it to be involved in other cellular responses as well, including inflammation. Fas and its adaptor protein FADD are known to negatively regulate LPS-induced proinflammatory responses, but their role in LPS-induced type I interferon production is unknown. Here, we demonstrate that Fas engagement on macrophages, using an agonistic Fas antibody CH11, augments LPS-induced NF-κB responses, causing increased production of TNFα, IL-8, IL-6 and IL-12. Conversely, costimulation with both LPS and CH11 causes a significant reduction in the level of interferon-beta (IFNβ) production. This differential effect involves the Fas adaptor FADD because while LPS-induced IL-6 production increased in FADD^-/- murine embryonic fibroblasts, LPS-induced IFNβ production was significantly reduced in these cells. Overexpression of a dominant negative form of FADD (FADD-DD) inhibits LPS-induced IFNβ luciferase but not LPS-induced NF-κB luciferase. In contrast, overexpression of full-length FADD inhibited LPS-induced NF-κB luciferase activation but was seen to augment LPS-induced IFNβ luciferase. Moreover, FADD-DD inhibits TRIF-, TRAM-, IKKε-, TBK-1- and TRAF3-induced IFNβ luciferase production, with coimmunoprecipitation experiments demonstrating an interaction between FADD and TRIF. These data identify FADD as a novel component of the noncanonical Toll-like receptor 4/IFNβ signalling pathway and demonstrate that both Fas and its adaptor FADD can differentially regulate the production of LPS-induced proinflammatory cytokines and type I interferons.

Enterobacter cloacae administration induces hepatic damage and subcutaneous fat accumulation in high-fat diet fed mice

Accumulating evidence indicates that gut microbiota plays a significant role in obesity, insulin resistance and associated liver disorders. Family Enterobacteriaceae and especially Enterobacter cloacae strain B29 have been previously linked to obesity and hepatic damage. The underlying mechanisms, however, remain unclear. Therefore, we comprehensively examined the effects of E. cloacae subsp. cloacae (ATCC® 13047™) administration on host metabolism of mice fed with high-fat diet (HFD). C57BL/6N mice were randomly divided into HFD control, chow control, and E. cloacae treatment groups. The E. cloacae treatment group received live bacterial cells in PBS intragastrically twice a week, every other week for 13 weeks. Both control groups received PBS intragastrically. After the 13-week treatment period, the mice were sacrificed for gene and protein expression and functional analyses. Our results show that E. cloacae administration increased subcutaneous fat mass and the relative proportion of hypertrophic adipocytes. Both subcutaneous and visceral fat had signs of decreased insulin signaling and elevated lipolysis that was reflected in higher serum glycerol levels. In addition, E. cloacae -treated mice had significantly higher hepatic AST and AST/ALT ratio, and their liver histology indicated fibrosis, demonstrating that E. cloacae subsp. cloacae administration promotes hepatic damage in HFD fed mice.

Lipopolysaccharide Upregulated Intestinal Epithelial Cell Expression of Fn14 and Activation of Fn14 Signaling Amplify Intestinal TLR4-Mediated Inflammation

TLR4 in intestinal epithelial cells has been shown both inflammatory and homeostatic roles following binding of its cognate ligand lipopolysaccharide (LPS). TWEAK-Fn14 axis plays an important role in pathologies caused by excessive or abnormal inflammatory responses. This study aimed to evaluate potential cross-talk between TLR4 and TWEAK/Fn14 system in porcine small intestinal epithelial cells. Our in vivo results showed that, compared with the age-matched normal control piglets, increased expression of Fn14 in epithelium and decreased TWEAK expression in lamina propria were detected in the small intestinal of piglets stimulated with LPS. Consistent with this finding, treatment with LPS increased the expression of Fn14 and TLR4 while decreased TWEAK expression in porcine small intestinal epithelial cell lines SIEC02. Interestingly, modulating Fn14 activation using agonistic anti-Fn14 decreased TLR4-mediated TNF-α production by SIEC02. In addition, pretreatment of LPS-stimulated SIEC02 with recombinant TWEAK protein suppresses the expression of Fn14 and TNF-α and inhibits the negative impact of LPS on the tight junctional protein occludin expression. In conclusion, this study demonstrates that the TWEAK-independent Fn14 activation augments TLR4-mediated inflammatory responses in the intestine of piglets. Furthermore, the TWEAK-dependent suppression of Fn14 signaling may play a role in intestinal homeostasis.

Bovine milk-based formula leads to early maturation-like morphological, immunological, and functional changes in the jejunum of neonatal piglets

Artificial rearing and formula feeding is coming more into the focus due to increasing litter sizes and limited nursing capacity of sows. The formula composition is important to effectively support the development of the gut and prevent intestinal dysfunction in neonatal piglets. In this study, newborn piglets ( = 8 per group) were fed a bovine milk-based formula (FO), containing skimmed milk and whey as the sole protein and carbohydrate sources, or were suckled by the sow (sow milk [SM]). After 2 wk, tissue from the jejunum was analyzed for structural (i.e., morphometry) and functional (i.e., disaccharidase activity, glucose transport, permeability toward macromolecules, and immune cell presence) changes and concomitant expression of related genes. Formula-fed piglets had more liquid feces ( < 0.05) over the entire experimental period. Although FO contained twice as much lactose (46% on a DM basis) as SM (21%) and no maltose or starch, the lactase activity was lower ( < 0.05) and glucose transport capacity was higher ( < 0.05) in FO-fed pigs. The relative proportion of intraepithelial natural killer cells and proinflammatory cytokine gene expression (, , and ) was higher in FO-fed pigs ( < 0.05). Piglets fed FO had deeper crypts, larger villus area, and higher expression of caspase 3 and proliferating cell nuclear antigen ( < 0.05). Epithelial permeability toward fluorescein isothiocyanate-dextran was higher and expression of claudin-4 was lower in FO-fed piglets ( < 0.05). The data suggest an early response to bovine milk-based compounds in the FO accompanied with early onset of functional maturation and impaired barrier function. Whether lactose, absence of species-specific protective factors, or antigenicity of foreign proteins lead to to the observed intestinal reactions requires further clarification.

Inhibition of MAPK and NF-κB signaling pathways alleviate carbon tetrachloride (CCl4)-induced liver fibrosis in Toll-like receptor 5 (TLR5) deficiency mice

Current researches showed that TLR family plays an important role in liver fibrosis, yet the molecular mechanism by which this occurs is not fully explained. In this study, we investigated the role of TLR5 in carbon tetrachloride-induced liver fibrosis, and further examined wether TLR5 knockout attenuated tetrachloride-induced liver fibrosis by inhibiting hepatic stellate cells activation via modulating NF-κB and MAPK signaling pathways. Our results found that carbon tetrachloride induced liver function injury in WT mice with a inflammatory responses through the activation of NF-κB and MAPK signaling pathways, resulting in hepatic stellate cells activation. In contrast, TLR5 deficiency mice after carbon tetrachloride administration reduced NF-κB and MAPK signaling pathways activation, which down regulated hepatic stellate cells activation. In addition, alpha smooth muscle-actin as marker of hepatic stellate cells further indicated that TLR5 knockout mice have a lower collagen accumulation in liver tissue than WT mice after carbon tetrachloride administration, resulting in inhibition of NF-κB and MAPK signaling pathways activation. Moreover, in vitro experiment of hepatic stellate cells challenged with LPS or TGF-β, further indicated that NF-κB and MAPK were involved in liver fibrosis development, leading to α-SMA expression and inflammation infiltration. However, cells from TLR5(-)(/-) may weaken phosphorylation levels of signal pathways, finally suppress progress of collagen accumulation and inflammatory responses. These results suggest a new therapeutic approach or target to protect against fibrosis caused by chronic liver diseases.

Engagement of Fas on Macrophages Modulates Poly I:C induced cytokine production with specific enhancement of IP-10

Viral double-stranded RNA (dsRNA) is recognised by pathogen recognition receptors such as Toll-Like Receptor 3 (TLR3) and retinoic acid inducible gene-I (RIG-I), and results in cytokine and interferon production. Fas, a well characterised death receptor, has recently been shown to play a role in the inflammatory response. In this study we investigated the role of Fas in the anti-viral immune response. Stimulation of Fas on macrophages did not induce significant cytokine production. However, activation of Fas modified the response of macrophages to the viral dsRNA analogue poly I:C. In particular, poly I:C-induced IP-10 production was significantly enhanced. A similar augmentation of IP-10 by Fas was observed following stimulation with both poly A:U and Sendai virus. Fas activation suppressed poly I:C-induced phosphorylation of the MAP kinases p38 and JNK, while overexpression of the Fas adaptor protein, Fas-associated protein with death domain (FADD), activated AP-1 and inhibited poly I:C-induced IP-10 production. Consistent with an inhibitory role for AP-1 in IP-10 production, mutation of the AP-1 binding site on the IP-10 promoter resulted in augmented poly I:C-induced IP-10. These results demonstrate that engagement of the Fas receptor plays a role in modifying the innate immune response to viral RNA.