Inhibition of Na+/H+ exchanger 1 by cariporide reduces burn-induced intestinal barrier breakdown

Kinetics of Inflammatory Mediators in the Immune Response to Burn Injury: Systematic Review and Meta-Analysis of Animal Studies

Burns are often accompanied by a dysfunctional immune response, which can lead to systemic inflammation, shock, and excessive scarring. The objective of this study was to provide insight into inflammatory pathways associated with burn-related complications. Because detailed information on the various inflammatory mediators is scattered over individual studies, we systematically reviewed animal experimental data for all reported inflammatory mediators. Meta-analyses of 352 studies revealed a strong increase in cytokines, chemokines, and growth factors, particularly 19 mediators in blood and 12 in burn tissue. Temporal kinetics showed long-lasting surges of proinflammatory cytokines in blood and burn tissue. Significant time-dependent effects were seen for IL-1β, IL-6, TGF-β1, and CCL2. The response of anti-inflammatory mediators was limited. Burn technique had a profound impact on systemic response levels. Large burn size and scalds further increased systemic, but not local inflammation. Animal characteristics greatly affected inflammation, for example, IL-1β, IL-6, and TNF-α levels were highest in young, male rats. Time-dependent effects and dissimilarities in response demonstrate the importance of appropriate study design. Collectively, this review presents a general overview of the burn-induced immune response exposing inflammatory pathways that could be targeted through immunotherapy for burn patients and provides guidance for experimental set-ups to advance burn research.

The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity

The five plasma membrane Na⁺/H⁺ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pH_i regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na⁺ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na⁺/H⁺ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.

Exploration of Potential Molecular Targets of Dexmedetomidine in the Intestinal Repair of Burnt Rats

Background

More and more burn survivors were suffering from varying degrees of damage to the intestinal barrier. Dexmedetomidine (Dex) was frequently used as sedative in more cases, but it was found to have repair effect on intestinal barrier dysfunction recently. This study aimed to explore the potential specific targets of Dex in intestinal barrier repair in burn rats model.

Methods

Male adult SD rats were used to establish 40% TBSA III degree scald model in our study. The samples were divided into four groups: burn rats (Burn), burn rats with Dex medication (Burn-Dex), sham rats (Sham) and sham rats with Dex medication (Sham-Dex). And plasma FITC-dextran and diamine oxidase (DAO) were detected to determine the intestinal permeability. Differentially expressed proteins were further adopted to protein-protein interaction network analysis, Gene Ontology analysis (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis.

Results

It showed that 40% TBSA III degree scald model was successfully constructed. And plasma FITC-dextran and DAO decreased significantly after Dex administration. Additionally, differentially expressed genes Psmb10, Psmb7 among the experimental groups were screened, which were significantly enriched in proteasome and other several pathways.

Conclusion

The results above suggested that Q4KM35 and Q9JHW0, which are encoded by Psmb10 and Psmb7, respectively, are two possible protein targets of Dex in intestinal barrier repair.

Intestinal barrier dysfunction in severe burn injury

Severe burn injury is often accompanied by intestinal barrier dysfunction, which is closely associated with post-burn shock, bacterial translocation, systemic inflammatory response syndrome, hypercatabolism, sepsis, multiple organ dysfunction syndrome, and other complications. The intestinal epithelium forms a physical barrier that separates the intestinal lumen from the internal milieu, in which the tight junction plays a principal role. It has been well documented that after severe burn injury, many factors such as stress, ischemia/hypoxia, proinflammatory cytokines, and endotoxins can induce intestinal barrier dysfunction via multiple signaling pathways. Recent advances have provided new insights into the mechanisms and the therapeutic strategies of intestinal epithelial barrier dysfunction associated with severe burn injury. In this review, we will describe the current knowledge of the mechanisms involved in intestinal barrier dysfunction in response to severe burn injury and the emerging therapies for treating intestinal barrier dysfunction following severe burn injury.

Chitosan oligosaccharides improve the disturbance in glucose metabolism and reverse the dysbiosis of gut microbiota in diabetic mice

The aim of this study is to investigate the effect of chitosan oligosaccharides (COS) on type 2 diabetes mellitus. Wild type C57BL/6J mice or diabetic db/db mice were treated with vehicle or COS for three months. COS treatment significantly decreased the blood glucose (P < 0.01) and reversed the insulin resistance (P < 0.05) in db/db mice, which was accompanied by suppressing the inflammation mediators (P < 0.05), down-regulating the lipogenesis (P < 0.01) and inhibiting the adipocyte differentiation (P < 0.05) in white adipose tissue. Additionally, COS treatment inhibited the reduction of occludin (P < 0.01) and relieved the gut dysbiosis in diabetic mice by promoting Akkermansia (P < 0.01) and suppressing Helicobacter (P < 0.05). Spearman's correlation analysis indicates that the COS-modulated bacteria are positively correlated with inflammation, hyperglycemia and dyslipidemia. The functional profiling based on the microbiota composition implicated that COS treatment may regulate the metabolic pathways of gut microbiota. In summary, COS treatment remarkably improved the glucose metabolism and reshaped the unbalanced gut microbiota of diabetic mice. Our study provided the evidence for application of COS to the treatment of diabetes mellitus.

Effect of cariporide on ram sperm pH regulation and motility: possible role of NHE1

Sperm motility, a feature essential for in vivo fertilization, is influenced by intracellular pH (pH_i) homeostasis. Several mechanisms are involved in pH_i regulation, among which sodium-hydrogen exchangers (NHEs), a family of integral transmembrane proteins that catalyze the exchange of Na⁺ for H⁺ across lipid bilayers. A preliminary characterization of NHE activity and kinetic parameters, followed by analysis of the expression and localization of the protein in ram spermatozoa was performed. NHE activity showed an apparent K_m for external Na⁺ of 17.61 mM. Immunoblotting revealed a molecular mass of 85 kDa. Immunolocalization pattern showed some species-specific aspects, such as positive labeling at the equatorial region of the sperm head. Cariporide, a selective NHE1 inhibitor, significantly reduced pH_i recovery (85%). Similarly, exposure to cariporide significantly inhibited different motility parameters, including those related to sperm capacitation. In vitro fertilization (IVF) was not affected by cariporide, possibly due to the non-dramatic, although significant, drop in motility and velocity parameters or due to prolonged exposure during IVF, which may have caused progressive loss of its inhibitory effect. In conclusion, this is the first study documenting, in a large animal model (sheep) of well-known translational relevance, a direct functional role of NHE on sperm pH_i and motility. The postulated specificity of cariporide toward isoform 1 of the Na⁺/H⁺ exchanger seems to suggest that NHE1 may contribute to the observed effects on sperm cell functionality.

Role of epithelial ion transports in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with a complex pathogenesis. Diarrhea is a highly prevalent and often debilitating symptom of IBD patients that results, at least in part, from an intestinal hydroelectrolytic imbalance. Evidence suggests that reduced electrolyte absorption is more relevant than increased secretion to this disequilibrium. This systematic review analyses and integrates the current evidence on the roles of epithelial Na(+)-K(+)-ATPase (NKA), Na(+)/H(+) exchangers (NHEs), epithelial Na(+) channels (ENaC), and K(+) channels (KC) in IBD-associated diarrhea. NKA is the key driving force of the transepithelial ionic transport and its activity is decreased in IBD. In addition, the downregulation of apical NHE and ENaC and the upregulation of apical large-conductance KC all contribute to the IBD-associated diarrhea by lowering sodium absorption and/or increasing potassium secretion.

Protective effect of crocetin against burn-induced intestinal injury

BACKGROUND

Oxidative stress and inflammation exert central roles in burn-induced intestinal injury. Crocetin, a natural carotenoid compound from gardenia fruits and saffron, has been shown to inhibit oxidative stress and inflammatory response. However, the possibility of crocetin to be used in the treatment of intestinal injury after burn injury has not been investigated. The purpose of the present study was to investigate the effects and potential mechanisms of crocetin in burn-induced intestinal injury.

MATERIALS AND METHODS

Several free radical-generating and lipid peroxidation models were used to systematically assess the antioxidant activities of crocetin in vitro. A common burn model was used to induce the intestinal injury in rats. Changes in the levels of malondialdehyde, superoxidase dismutase, catalase, glutathione peroxidase, tumor necrosis factor α, interleukin 6, polymorphonuclear neutrophil accumulation, intestinal permeability, and intestinal histology were examined.

RESULTS

In several models of antioxidant activity, crocetin exhibited marked inhibitory action against free radicals and lipid peroxidation. Crocetin increased levels of antioxidant enzymes and reduced intestinal oxidative injury in burn models. In addition, crocetin inhibited polymorphonuclear neutrophil accumulation, ameliorated tumor necrosis factor α and interleukin 6 levels, intestinal permeability, and histological changes.

CONCLUSIONS

Crocetin treatment may protect against burn-induced small intestinal injury, possibly by inhibiting burn-induced oxidative stress and inflammatory response.