Overexpression of BCL-2 in the Intestinal Epithelium Prevents Sepsis-Induced Gut Barrier Dysfunction via Altering Tight Junction Protein Expression

Marine red yeast supplementation improves laying performance by regulating small intestinal homeostasis in aging chickens

Recent studies have shown that age-related aging evolution is accompanied by imbalances in intestinal homeostasis. Marine red yeast (MRY) is a functional probiotic that has been shown to have antioxidant, immune and other properties. Therefore, we chose 900 healthy Hy-Line Brown hens at 433 d old as the research subjects and evaluated the correlation between intestinal health, laying performance, and egg quality in aged hens through the supplementation of MRY. These laying hens were assigned into 5 groups and received diet supplementation with 0%, 0.5%, 1.0%, 1.5%, and 2% MRY for 12 weeks. The results showed that MRY supplementation increased egg production rate, average egg weight, and egg quality, and decreased feed conversion ratio and daily feed intake (P < 0.05). The MRY supplement improved antioxidant indicators such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), stimulated villus height, and increased the villus height to crypt depth ratio (V/C ratio) in the intestine (P < 0.05). It also regulated the expression of intestinal inflammatory factors (transforming growth factor-β [TGF-β], interleukin [IL]-1β, IL-8, tumor necrosis factor-α [TNF-α]) while increasing serum immunoglobulin G (IgG) levels (P < 0.05). Furthermore, MRY supplementation upregulated the mRNA expression of tight junction proteins (occludin and zonula occludens-1 [ZO-1]), anti-apoptotic gene (Bcl-2), and autophagy-related proteins (beclin-1 and light chain 3I [LC3I]) in the intestine (P < 0.05). The MRY supplement also led to an increase in the concentration of short-chain fatty acids in the cecum, and the relative abundance of the phylum Bacteroidetes, and genera Bacteroides and Rikenellaceae_RC9_gut_group. The LEfSe analysis revealed an enrichment of Sutterella and Akkermansia muciniphila. In conclusion, the results of this experiment indicated that the additional supplementation of MRY can improve the production performance of laying hens and may contribute to the restoration and balance of intestinal homeostasis, which supports the application potential of MRY as a green and efficient feed additive for improving the laying performance in chickens.

Emamectin benzoate-induced toxicity affects intestinal epithelial integrity involving apoptosis

The frequency presence of emamectin benzoate in agricultural production highlights the need for studying their toxicity against human intestinal epithelial barrier (IEB). Herein, we combined a Caco-2 cell model with transcriptome analysis to assess the intestinal toxicity of emamectin benzoate and its disease-causing potential. Results showed that the half maximal inhibitory concentration (IC50) of emamectin benzoate on Caco-2 cell viability after 24, 48, and 72 h of exposure were 18.1, 9.9, and 8.3 μM, respectively. Emamectin benzoate exposure enhanced the Caco-2 monolayer paracellular permeability, damaged the IEB, and increased cellular apoptosis. Key driver gene analysis of 42 apoptosis - related DEGs, identified 10 genes (XIAP, KRAS, MCL1, NRAS, PIK3CA, CYCS, MAPK8, CASP3, FADD, and TNFRSF10B) with the strongest correlation with emamectin benzoate - induced apoptosis. Transcriptomics identified 326 differentially expressed genes (DEGs, 204 upregulated and 122 downregulated). The functional terms of neurodegeneration - multiple diseases was enriched with the most number of DEGs, and the Parkinson disease pathway had the highest enrichment degree. Our findings provided support for environmental toxicology studies and the health risk assessment of emamectin benzoate.

Claudin-2 upregulation enhances intestinal permeability, immune activation, dysbiosis, and mortality in sepsis

Intestinal epithelial expression of the tight junction protein claudin-2, which forms paracellular cation and water channels, is precisely regulated during development and in disease. Here, we show that small intestinal epithelial claudin-2 expression is selectively upregulated in septic patients. Similar changes occurred in septic mice, where claudin-2 upregulation coincided with increased flux across the paracellular pore pathway. In order to define the significance of these changes, sepsis was induced in claudin-2 knockout (KO) and wild-type (WT) mice. Sepsis-induced increases in pore pathway permeability were prevented by claudin-2 KO. Moreover, claudin-2 deletion reduced interleukin-17 production and T cell activation and limited intestinal damage. These effects were associated with reduced numbers of neutrophils, macrophages, dendritic cells, and bacteria within the peritoneal fluid of septic claudin-2 KO mice. Most strikingly, claudin-2 deletion dramatically enhanced survival in sepsis. Finally, the microbial changes induced by sepsis were less pathogenic in claudin-2 KO mice as survival of healthy WT mice injected with cecal slurry collected from WT mice 24 h after sepsis was far worse than that of healthy WT mice injected with cecal slurry collected from claudin-2 KO mice 24 h after sepsis. Claudin-2 upregulation and increased pore pathway permeability are, therefore, key intermediates that contribute to development of dysbiosis, intestinal damage, inflammation, ineffective pathogen control, and increased mortality in sepsis. The striking impact of claudin-2 deletion on progression of the lethal cascade activated during sepsis suggests that claudin-2 may be an attractive therapeutic target in septic patients.

Dynamic changes in the migratory microbial components of colon tissue during different periods of sepsis in an LPS-induced rat model

Previous studies have shown that bacterial translocation may play an important role in worsening gastrointestinal injury during sepsis. However, the dynamics of specific microbiota components in intestinal tissues at different sepsis stages remain unclear. Rats receiving intraperitoneal lipopolysaccharide (LPS) were sacrificed at 12 h and 48 h post-injection. Routine blood, serum cytokines, and microbiota in colon tissue, colonic contents, and lung tissue at different time points were assessed. Migratory microbial components in colonic tissue at 12 h and 48 h post-LPS were identified using source tracking, characteristic component identification, and abundance difference analyses. Colonic tissue microbiota changed dynamically over time after LPS injection, involving translocation of microbial components from colon contents and lung tissue at different time points. Bacteria migrating to colon tissue at 12 h sepsis were mainly from colonic contents, while those at 48 h were predominantly from the lung tissue. The migratory microbial components in colon tissue were widely associated with blood indicators and colonizing genus abundance and microbiota functionality in colon tissue. In this study, the temporal dynamics of bacterial translocation from various sources into colon tissues at different sepsis progression stages were characterized for the first time, and the species composition of these migrating microbes was delineated. These bacterial migrants may contribute to the pathophysiological processes in sepsis through direct interactions or indirectly by modulating colonic microbiota community structure and function.

Systemic cytokines inhibition with Imp7 siRNA nanoparticle ameliorates gut injury in a mouse model of ventilator-induced lung injury

Mechanical ventilation (MV) may negatively affect the lungs and cause the release of inflammatory mediators, resulting in extra-pulmonary organ dysfunction. Studies have revealed systemically elevated levels of proinflammatory cytokines in animal models of ventilator-induced lung injury (VILI); however, whether these cytokines have an effect on gut injury and the mechanisms involved remain unknown. In this study, VILI was generated in mice with high tidal volume mechanical ventilation (20 ml/kg). Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 concentrations in serum and gut measured by ELISA showed significant elevation in the VILI mice. Significant increases in gut injury and PANoptosis were observed in the VILI mice, which were positively correlated with the serum levels of TNF-α, IL-1β, and IL-6. The VILI mice displayed intestinal barrier defects, decreased expressions of occludin and zonula occludin-1 (ZO-1), and increased expression of claudin-2 and the activation of myosin light chain (MLC). Importantly, intratracheal administration of Imp7 siRNA nanoparticle effectively inhibited cytokines production and protected mice from VILI-induced gut injury. These data provide evidence of systemic cytokines contributing to gut injury following VILI and highlight the possibility of targeting cytokines inhibition via Imp7 siRNA nanoparticle as a potential therapeutic intervention for alleviating gut injury following VILI.

CHRONIC ETHANOL USE WORSENS GUT PERMEABILITY AND ALTERS TIGHT JUNCTION EXPRESSION IN A MURINE SEPSIS MODEL

ABSTRACT

Alcohol use disorder is associated with increased mortality in septic patients. Murine studies demonstrate that ethanol/sepsis is associated with changes in gut integrity. This study examined intestinal permeability after ethanol/sepsis and investigated mechanisms responsible for alterations in barrier function. Mice were randomized to drink either 20% ethanol or water for 12 weeks and then were subjected to either sham laparotomy or cecal ligation and puncture (CLP). Intestinal permeability was disproportionately increased in ethanol/septic mice via the pore, leak, and unrestricted pathways. Consistent with increased permeability in the leak pathway, jejunal myosin light chain (MLC) kinase (MLCK) expression and the ratio of phospho-MLC to total MLC were both increased in ethanol/CLP. Gut permeability was altered in MLCK -/- mice in water/CLP; however, permeability was not different between WT and MLCK -/- mice in ethanol/CLP. Similarly, jejunal IL-1β levels were decreased while systemic IL-6 levels were increased in MLCK -/- mice in water/CLP but no differences were identified in ethanol/CLP. While we have previously shown that mortality is improved in MLCK -/- mice after water/CLP, mortality was significantly worse in MLCK -/- mice after ethanol/CLP. Consistent with an increase in the pore pathway, claudin 4 levels were also selectively decreased in ethanol/CLP WT mice. Furthermore, mRNA expression of jejunal TNF and IFN-γ were both significantly increased in ethanol/CLP. The frequency of CD4 + cells expressing TNF and IL-17A and the frequency of CD8 + cells expressing IFN-γ in Peyer's Patches were also increased in ethanol/CLP. Thus, there is an ethanol-specific worsening of gut barrier function after CLP that impacts all pathways of intestinal permeability, mediated, in part, via changes to the tight junction. Differences in the host response in the setting of chronic alcohol use may play a role in future precision medicine approaches toward the treatment of sepsis.

Gut Microbiome in Sepsis

Abstract The gut has been hypothesized to be the "motor" of multiple organ dysfunction in sepsis. Although there are multiple ways in which the gut can drive systemic inflammation, increasing evidence suggests that the intestinal microbiome plays a more substantial role than previously appreciated. An English language literature review was performed to summarize the current knowledge of sepsis-induced gut microbiome dysbiosis. Conversion of a normal microbiome to a pathobiome in the setting of sepsis is associated with worsened mortality. Changes in microbiome composition and diversity signal the intestinal epithelium and immune system resulting in increased intestinal permeability and a dysregulated immune response to sepsis. Clinical approaches to return to microbiome homeostasis may be theoretically possible through a variety of methods including probiotics, prebiotics, fecal microbial transplant, and selective decontamination of the digestive tract. However, more research is required to determine the efficacy (if any) of targeting the microbiome for therapeutic gain. The gut microbiome rapidly loses diversity with emergence of virulent bacteria in sepsis. Restoring normal commensal bacterial diversity through various therapies may be an avenue to improve sepsis mortality.

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

The gut–liver axis in sepsis: interaction mechanisms and therapeutic potential

Sepsis is a potentially fatal condition caused by dysregulation of the body's immune response to an infection. Sepsis-induced liver injury is considered a strong independent prognosticator of death in the critical care unit, and there is anatomic and accumulating epidemiologic evidence that demonstrates intimate cross talk between the gut and the liver. Intestinal barrier disruption and gut microbiota dysbiosis during sepsis result in translocation of intestinal pathogen-associated molecular patterns and damage-associated molecular patterns into the liver and systemic circulation. The liver is essential for regulating immune defense during systemic infections via mechanisms such as bacterial clearance, lipopolysaccharide detoxification, cytokine and acute-phase protein release, and inflammation metabolic regulation. When an inappropriate immune response or overwhelming inflammation occurs in the liver, the impaired capacity for pathogen clearance and hepatic metabolic disturbance can result in further impairment of the intestinal barrier and increased disruption of the composition and diversity of the gut microbiota. Therefore, interaction between the gut and liver is a potential therapeutic target. This review outlines the intimate gut–liver cross talk (gut–liver axis) in sepsis.

Inhibition of platelet activation suppresses reactive enteric glia and mitigates intestinal barrier dysfunction during sepsis

BACKGROUND

Intestinal barrier dysfunction, which is associated with reactive enteric glia cells (EGCs), is not only a result of early sepsis but also a cause of multiple organ dysfunction syndrome. Inhibition of platelet activation has been proposed as a potential treatment for septic patients because of its efficacy in ameliorating the organ damage and barrier dysfunction. During platelet activation, CD40L is translocated from α granules to the platelet surface, serving as a biomarker of platelet activation a reliable predictor of sepsis prognosis. Given that more than 95% of the circulating CD40L originate from activated platelets, the present study aimed to investigate if inhibiting platelet activation mitigates intestinal barrier dysfunction is associated with suppressing reactive EGCs and its underlying mechanism.

METHODS

Cecal ligation and puncture (CLP) was performed to establish the sepsis model. 24 h after CLP, the proportion of activated platelets, the level of sCD40L, the expression of tight-junction proteins, the intestinal barrier function and histological damage of septic mice were analyzed. In vitro, primary cultured EGCs were stimulated by CD40L and LPS for 24 h and EGCs-conditioned medium were collected for Caco-2 cells treatment. The expression of tight-junction proteins and transepithelial electrical resistance of Caco-2 cell were evaluated.

RESULTS

In vivo, inhibiting platelet activation with cilostazol mitigated the intestinal barrier dysfunction, increased the expression of ZO-1 and occludin and improved the survival rate of septic mice. The efficacy was associated with reduced CD40L+ platelets proportion, decreased sCD40L concentration, and suppressed the activation of EGCs. Comparable results were observed upon treatment with compound 6877002, a blocker of CD40L-CD40-TRAF6 signaling pathway. Also, S-nitrosoglutathione supplement reduced intestinal damage both in vivo and in vitro. In addition, CD40L increased release of TNF-α and IL-1β while suppressed the release of S-nitrosoglutathione from EGCs. These EGCs-conditioned medium reduced the expression of ZO-1 and occludin on Caco-2 cells and their transepithelial electrical resistance, which could be reversed by CD40-siRNA and TRAF6-siRNA transfection on EGCs.

CONCLUSIONS

The inhibition of platelet activation is related to the suppression of CD40L-CD40-TRAF6 signaling pathway and the reduction of EGCs activation, which promotes intestinal barrier function and survival in sepsis mice. These results might provide a potential therapeutic strategy and a promising target for sepsis.

Inhibition of platelet activation suppresses reactive enteric glia and mitigates intestinal barrier dysfunction during sepsis

BACKGROUND

Intestinal barrier dysfunction, which is associated with reactive enteric glia cells (EGCs), is not only a result of early sepsis but also a cause of multiple organ dysfunction syndrome. Inhibition of platelet activation has been proposed as a potential treatment for septic patients because of its efficacy in ameliorating the organ damage and barrier dysfunction. During platelet activation, CD40L is translocated from α granules to the platelet surface, serving as a biomarker of platelet activation a reliable predictor of sepsis prognosis. Given that more than 95% of the circulating CD40L originate from activated platelets, the present study aimed to investigate if inhibiting platelet activation mitigates intestinal barrier dysfunction is associated with suppressing reactive EGCs and its underlying mechanism.

METHODS

Cecal ligation and puncture (CLP) was performed to establish the sepsis model. 24 h after CLP, the proportion of activated platelets, the level of sCD40L, the expression of tight-junction proteins, the intestinal barrier function and histological damage of septic mice were analyzed. In vitro, primary cultured EGCs were stimulated by CD40L and LPS for 24 h and EGCs-conditioned medium were collected for Caco-2 cells treatment. The expression of tight-junction proteins and transepithelial electrical resistance of Caco-2 cell were evaluated.

RESULTS

In vivo, inhibiting platelet activation with cilostazol mitigated the intestinal barrier dysfunction, increased the expression of ZO-1 and occludin and improved the survival rate of septic mice. The efficacy was associated with reduced CD40L+ platelets proportion, decreased sCD40L concentration, and suppressed the activation of EGCs. Comparable results were observed upon treatment with compound 6,877,002, a blocker of CD40L-CD40-TRAF6 signaling pathway. Also, S-nitrosoglutathione supplement reduced intestinal damage both in vivo and in vitro. In addition, CD40L increased release of TNF-α and IL-1β while suppressed the release of S-nitrosoglutathione from EGCs. These EGCs-conditioned medium reduced the expression of ZO-1 and occludin on Caco-2 cells and their transepithelial electrical resistance, which could be reversed by CD40-siRNA and TRAF6-siRNA transfection on EGCs.

CONCLUSIONS

The inhibition of platelet activation is related to the suppression of CD40L-CD40-TRAF6 signaling pathway and the reduction of EGCs activation, which promotes intestinal barrier function and survival in sepsis mice. These results might provide a potential therapeutic strategy and a promising target for sepsis.

The importance of a sepsis layered early warning system for critical patients

Critical illness, particularly sepsis, is associated with high mortality, so prevention is more important than effective therapy. Advances in medical science have provided more opportunities for early warning and early intervention to avoid the development of critical illness. Existing early warning systems (EWS) have the advantages of high efficiency and convenience. However, with the development of medical technology, they do not completely meet clinical needs. EWS should contain elements that meet many dimensions of clinical requirements, including risk warning, response warning, injury warning, critical warning, and death warning. By summarizing previous studies, we outlined a layered EWS that follows RISK bundles. RISK represents different warning sign categories: R: host response, I: organ injury, S: changes in vital signs, and K: gradual appearance of "killed" organs. We plan to construct a complete layered EWS to guide clinical activities and subsequent clinical studies in the near future.

Junctional adhesion molecule-A deletion increases phagocytosis and improves survival in a murine model of sepsis

Expression of the tight junction–associated protein junctional adhesion molecule-A (JAM-A) is increased in sepsis, although the significance of this is unknown. Here, we show that septic JAM-A ^–/– mice have increased gut permeability, yet paradoxically have decreased bacteremia and systemic TNF and IL-1β expression. Survival is improved in JAM-A^–/– mice. However, intestine-specific JAM-A^–/– deletion does not alter mortality, suggesting that the mortality benefit conferred in mice lacking JAM-A is independent of the intestine. Septic JAM-A^–/– mice have increased numbers of splenic CD44^hiCD4⁺ T cells, decreased frequency of TNF⁺CD4⁺ cells, and elevated frequency of IL-2⁺CD4⁺ cells. Septic JAM-A^–/– mice have increased numbers of B cells in mesenteric lymph nodes with elevated serum IgA and intraepithelial lymphocyte IgA production. JAM-A^–/– × RAG^–/– mice have improved survival compared with RAG^–/– mice and identical mortality as WT mice. Gut neutrophil infiltration and neutrophil phagocytosis are increased in JAM-A^–/– mice, while septic JAM-A^–/– mice depleted of neutrophils lose their survival advantage. Therefore, increased bacterial clearance via neutrophils and an altered systemic inflammatory response with increased opsonizing IgA produced through the adaptive immune system results in improved survival in septic JAM-A^–/– mice. JAM-A may be a therapeutic target in sepsis via immune mechanisms not related to its role in permeability.

The Severity of Acute Kidney and Lung Injuries Induced by Cecal Ligation and Puncture Is Attenuated by Menthol: Role of Proliferating Cell Nuclear Antigen and Apoptotic Markers

Objective

Sepsis-induced acute lung injury (ALI) and acute kidney injury (AKI) are major causes of mortality. Menthol is a natural compound that has anti-inflammatory and antioxidative actions. Since exaggerated inflammatory and oxidative stress are characteristics of sepsis, the aim of this study was to evaluate the effect of menthol against sepsis-induced mortality, ALI, and AKI.

Methods

The cecal ligation and puncture (CLP) procedure was employed as a model of sepsis. Rats were grouped into sham, sham-Menthol, CLP, and CLP-Menthol (100 mg/kg, p.o).

Key Findings

A survival study showed that menthol enhanced the survival after sepsis from 0% in septic group to 30%. Septic rats developed histological evidence of ALI and AKI. Menthol markedly suppressed sepsis induced elevation of tissue TNF-a, ameliorated sepsis-induced cleavage of caspase-3 and restored the antiapoptotic marker Bcl2.

Significance

We introduced a role of the proliferating cell nuclear antigen (PCNA) in these tissues with a possible link to the damage induced by sepsis. PCNA level was markedly reduced in septic animals and menthol ameliorated this effect. Our data provide novel evidence that menthol protects against organ damage and decreases mortality in experimental sepsis.

Chlorothalonil induces the intestinal epithelial barrier dysfunction in Caco-2 cell-based in vitro monolayer model by activating MAPK pathway

The widespread use of chlorothalonil (CTL) has caused environmental residues and food contamination. Although the intestinal epithelial barrier (IEB) is directly involved in the metabolism and transportation of various exogenous compounds, there are few studies on the toxic effects of these compounds on the structure and function of IEB. The disassembly of tight junction (TJ) is a major cause of intestinal barrier dysfunction under exogenous compounds intake, but the precise mechanisms are not well understood. Here, we used Caco-2 cell monolayers as an in vitro model of human IEB to evaluate the toxicity of CTL exposure on the structure and function of IEB. Results showed that CTL exposure increased the paracellular permeability of the monolayers and downregulated mRNA levels of the TJ genes (ZO-1, OCLN, and CLDN1), polarity marker gene (SI), and anti-apoptosis gene (BCL-2) but upregulated the mRNA levels of apoptosis-related genes, including BAD, BAX, CASP3, and CASP8. Western blot analysis and immunofluorescence assay results showed the decreased levels and disrupted distribution of TJ protein network, including ZO-1 and CLDN1 in CTL-exposed IEB. In addition, the accumulation of intracellular reactive oxygen species, decreased mitochondrial membrane potential, and increased active CASP3 expression were observed in treated IEB. The result of TUNEL assay further confirmed the occurrence of cell apoptosis after CTL exposure. In addition, the phosphorylation of mitogen-activated protein kinases, including ERK, JNK and p38, was increased in CTL-exposed IEB. In summary, our results demonstrated that CTL exposure induced IEB dysfunction in Caco-2 cell monolayers by activating the mitogen-activated protein kinase pathway.

Crosstalk between gut microbiota and sepsis

Sepsis is an overwhelming inflammatory response to microbial infection. Sepsis management remains a clinical challenge. The role of the gut microbiome in sepsis has gained some attention. Recent evidence has demonstrated that gut microbiota regulate host physiological homeostasis mediators, including the immune system, gut barrier function and disease susceptibility pathways. Therefore, maintenance or restoration of microbiota and metabolite composition might be a therapeutic or prophylactic target against critical illness. Fecal microbiota transplantation and supplementation of probiotics are microbiota-based treatment methods that are somewhat limited in terms of evidence-based efficacy. This review focuses on the importance of the crosstalk between the gastrointestinal ecosystem and sepsis to highlight novel microbiota-targeted therapies to improve the outcomes of sepsis treatment.

Membrane Permeant Inhibitor of Myosin Light Chain Kinase Worsens Survival in Murine Polymicrobial Sepsis

ABSTRACT

Sepsis-induced intestinal hyperpermeability is mediated by disruption of the epithelial tight junction, which is closely associated with the peri-junctional actin-myosin ring. Genetic deletion of myosin light chain kinase (MLCK) reverses intestinal hyperpermeability and improves survival in a murine model of intra-abdominal sepsis. In an attempt to determine whether these findings could be translated using a more clinically relevant strategy, this study aimed to determine if pharmacologic inhibition of MLCK using the membrane permeant inhibitor of MLCK (PIK) improved gut barrier function and survival following sepsis. C57BL/6 mice underwent cecal ligation and puncture to induce sepsis and were then randomized to receive either PIK or vehicle. Unexpectedly, PIK significantly worsened 7-day survival following sepsis (24% vs. 62%). The three pathways of intestinal permeability were then interrogated by orally gavaging septic mice with creatinine (6Å), FD-4 (28Å), and rhodamine70 (120Å) and assaying their appearance in the bloodstream. PIK led to increased permeability in the leak pathway with higher levels of FD-4 in the bloodstream compared to septic mice given vehicle. In contrast, no differences were detected in the pore or unrestricted pathways of permeability. Examination of jejunal tight junctions for potential mechanisms underlying increased leak permeability revealed that mice that received PIK had increased phosphorylated MLC without alterations in occludin, ZO-1, or JAM-A. PIK administration was not associated with significant differences in systemic or peritoneal bacterial burden, cytokines, splenic or Peyer's Patches immune cells or intestinal integrity. These results demonstrate that pharmacologic inhibition of MLCK unexpectedly increases mortality, associated with worsened intestinal permeability through the leak pathway, and suggest caution is required in targeting the gut barrier as a potential therapy in sepsis.

Effect of silymarin on intestinal injury and PI3K/Akt and NF-κB signaling pathways in rats with severe acute pancreatitis

BACKGROUND

Acute pancreatitis is a very common clinical acute abdomen. Excessive release of inflammatory factors can damage the intestinal mucosa, induce cell apoptosis, and accelerate the course of the disease. Silymarin has anti-oxidative, immunoregulatory, anti-inflammatory, liver-protecting, anti-tissue fibrosis, and other effects. However, there is no relevant research on the effect of silymarin on the intestinal injury in severe acute pancreatitis.

AIM

To study the effects of silymarin on intestinal injury and PI3K/Akt and NF-κB signaling pathways in rats with severe acute pancreatitis.

METHODS

Rats were divided into a control group, a severe acute pancreatitis (SAP) model group, and low-, medium, and high-dose silymarin groups (severe acute pancreatitis rats given 60, 120 , and 240 mg/kg silymarin, respectively). Rats treated with glutamine (1.5 g/kg) were used as positive controls. The death of rats was recorded. Serum amylase and lipase levels were detected using an automatic biochemical analyzer. Serum IL-1β and TNF-α levels were detected by ELISA. Pancreatic and ileal pathology scores were scalculated. The expression of Bcl-2, Bax, PI3K, p-PI3K, Akt, p-Akt, NF-κBp65, and Bcl-2 in ileal tissues was detected by Western blot. TUNEL method was used to detect cell apoptosis in ileal tissues.

RESULTS

The SAP group, control group, and low-, medium, and high-dose silymarin groups had 3, 0, 2, 1, and 0 deaths, respectively. Compared with the control group, the levels of serum amylase, lipase, IL-1β, and TNF-α , the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65, and the apoptosis index increased, while Bcl-2 protein expression decreased in the SAP group. Compared with the SAP group, the levels of serum amylase, lipase, IL-1β, and TNF-αased, the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65 protein levels, and the apoptosis index gradually decreased, while Bcl-2 protein expression gradually increased in the low-, medium, and high-dose silymarin groups. Compared with the SAP group, the serum levels of amylase, lipase, IL-1β, and TNF-α, the pancreatic and ileal pathology scores, the levels of Bax, p-PI3K/PI3K, p-Akt/Akt, and NF-κBp65, and the apoptosis index decreased, while Bcl-2 protein expression increased in the glutamine group.

CONCLUSION

Silymarin can reduce intestinal injury in rats with SAP, inhibit inflammation, reduce cell apoptosis, and inhibit the activation of the PI3K/Akt and NF-κB signaling pathways.

Ghrelin Alleviates Intestinal Dysfunction in Sepsis Through the KLF4/MMP2 Regulatory Axis by Activating SIRT1

Intestinal barrier dysfunction is an important contributor to morbidity caused by sepsis. This study investigates the molecular mechanism by which Ghrelin affects intestinal dysfunction in rat model of sepsis. A rat model of sepsis was established by cecal ligation and puncture (CLP), revealing that Ghrelin was downregulated when sepsis occurs. Increases in the levels of inflammatory factors tumor necrosis factor α (TNF-α), interleukin-1 (IL-1β), IL-6, gastrin, γ-H2AX and 8-OHdG was also detected in this model system, as was an overall increase in oxidative stress. Introduction of exogenous Ghrelin inhibited these increases in inflammatory response and oxidative stress, leading to a reduction of overall sepsis-induced intestinal dysfunction. Ghrelin was then shown to activate SIRT1 expression in vitro, while SIRT1 was found to co-express with KLF4, which in turn was predicted to bind to matrix metalloproteinase 2 (MMP2) promoter. Finally, gain- and loss-of-function experiment demonstrated that SIRT1 upregulated the expression of KLF4 to downregulate MMP2. Collectively, Ghrelin inhibits the oxidative stress and intestinal dysfunction to attenuate sepsis by activating SIRT1 and regulating a KLF4/MMP2 regulatory axis.

The microbiome and the immune system in critical illness

PURPOSE OF REVIEW

Although the gut microbiome plays a crucial role in the maintenance of health, it is hypothesized to drive morbidity and mortality in critically ill patients. This review describes the relationship between the gut microbiome and the immune system in critical illness.

RECENT FINDINGS

The gut microbiome is converted to a pathobiome in the ICU, characterized by decreased microbial diversity and pathogen predominance. These changes are induced by a pathologic microenvironment and are further exacerbated by common medical treatments initiated in the ICU. The conversion of the microbiome to a pathobiome has direct consequences on the regulation of inflammation and immunity by loss of beneficial host responses and initiation of maladaptive changes that can further propagate critical illness.

SUMMARY

The gut microbiome is dramatically altered in the ICU. In light of constant crosstalk between the microbiome and the host immune system, the pathobiome may play a key mechanistic role in driving a maladaptive response in critically ill patients. The pathobiome represents a potential therapeutic target in the management of critical illness whereby restoration of a healthier microbiome may directly alter the host inflammatory response, which could lead to improved patient outcomes.

Contributions of HO-1-Dependent MAPK to Regulating Intestinal Barrier Disruption

The mitogen-activated protein kinase (MAPK) pathway controls intestinal epithelial barrier permeability by regulating tight junctions (TJs) and epithelial cells damage. Heme oxygenase-1 (HO-1) and carbon monoxide (CO) protect the intestinal epithelial barrier function, but the molecular mechanism is not yet clarified. MAPK activation and barrier permeability were studied using monolayers of Caco-2 cells treated with tissue necrosis factor α (TNF-α) transfected with FUGW-HO-1 or pLKO.1-sh-HO-1 plasmid. Intestinal mucosal barrier permeability and MAPK activation were also investigated using carbon tetrachloride (CCl₄) administration with CoPP (a HO-1 inducer), ZnPP (a HO-1 inhibitor), CO releasing molecule 2 (CORM-2), or inactived-CORM-2-treated wild-type mice and mice with HO-1 deficiency in intestinal epithelial cells. TNF-α increased epithelial TJ disruption and cleaved caspase-3 expression, induced ERK, p38, and JNK phosphorylation. In addition, HO-1 blocked TNF-α-induced increase in epithelial TJs disruption, cleaved caspase-3 expression, as well as ERK, p38, and JNK phosphorylation in an HO-1-dependent manner. CoPP and CORM-2 directly ameliorated intestinal mucosal injury, attenuated TJ disruption and cleaved caspase-3 expression, and inhibited epithelial ERK, p38, and JNK phosphorylation after chronic CCl₄ injection. Conversely, ZnPP completely reversed these effects. Furthermore, mice with intestinal epithelial HO-1 deficient exhibited a robust increase in mucosal TJs disruption, cleaved caspase-3 expression, and MAPKs activation as compared to the control group mice. These data demonstrated that HO-1-dependent MAPK signaling inhibition preserves the intestinal mucosal barrier integrity by abrogating TJ dysregulation and epithelial cell damage. The differential targeting of gut HO-1-MAPK axis leads to improved intestinal disease therapy.