Protective effects of HTD4010, a Reg3α/PAP-derived peptide, in mouse model of acute pancreatitis via toll-like receptor 4 pathway

Reg2 treatment is protective but the induced Reg2 autoantibody is destructive to the islets in NOD mice

Regenerating family protein 2 (Reg2) is a trophic factor which stimulates β-cell replication and resists islet destruction. However, Reg2 also serves as an islet autoantigen, which makes it complicated to judge the effectiveness in treating diabetes. How Reg2 treatment behaves in non-obese diabetic (NOD) mice is to be investigated. NOD mice were treated with recombinant Reg2 protein, Complete Freund's adjuvant (CFA) + PBS and CFA+Reg2 vaccinations, CFA+PBS- and CFA+Reg2-immunized antisera, and single chain variable fragment (scFv)-Reg2 and mIgG2a-Reg2 antibodies. Glycemic level, bodyweight, serum Reg2 antibody titer, glucose tolerance, and insulin secretion were determined. Islet morphological characteristics, insulitis, cell apoptosis, islet cell components, and T cell infiltration were analyzed by histological examinations. The autoantigenicity of constructed Reg2C and Reg2X fragments was determined in healthy BALB/c mice, and the bioactivity in stimulating cell proliferation and survival was assessed in insulinoma MIN6 cells. Reg2 administration alleviated diabetes in NOD mice with improved glucose tolerance and insulin secretion but elevated serum Reg2 autoantibodies. Histomorphometry showed reduced inflammatory area, TUNEL signal and CD8 + T cell infiltration, and increased β-cell proportion in support of the islet-protective effect of Reg2 treatment. CFA+PBS and CFA+Reg2 immunizations prevented diabetic onset and alleviated insulitis while injections of the antisera offered mild protections. Antibody treatments accelerated diabetic onset without increasing the overall incidence. Reg2C fragment depletes antigenicity, but reserves protective activity in streptozotocin (STZ)-treated MIN6 cells. In conclusion, Reg2 treatment alleviates type 1 diabetes (T1D) by preserving islet β-cells, but induces Reg2 autoantibody production which poses a potential risk of accelerating diabetic progression.

[Role of superoxide dismutase in acute pancreatitis: from antioxidant protection to gene regulation]

We present modern data on the role of superoxide dismutase (SOD) in antioxidant protection and gene regulation in acute pancreatitis. Antioxidant enzymes are essential in pathogenesis of numerous diseases. SOD is one of the key enzymes of antioxidant system. In this review, we analyzed activity of this enzyme depending on various factors, mechanisms and role in physiological and pathological processes, in particular, acute pancreatitis. SOD is significantly less active in patients with severe acute pancreatitis accompanied by renal failure, severe circulatory disorders and high mortality. There are some SOD gene polymorphisms, in particular, acute destructive pancreatitis R213G, contributing to acute inflammation. Thus, SOD is not only one of the key antioxidant enzymes, but also potential transcription factor regulating activity of signaling pathways. These aspects can underlie new therapies for diseases.

Fabp5 is a common gene between a high-cholesterol diet and acute pancreatitis

Background and aims

Hypercholesterolemia has been identified as risk factor for severe acute pancreatitis (AP). We aimed to identify the common differentially expressed genes (DEGs) between a high-cholesterol diet and AP.

Methods

We retrived gene expression profiles from the GEO database. DEGs were assessed using GEO2R. For AP hub genes, we conducted functional enrichment analysis and protein-protein interaction (PPI) analysis. GeneMANIA and correlation analysis were employed to predict potential DEG mechanisms. Validation was done across various healthy human tissues, pancreatic adenocarcinoma, peripheral blood in AP patients, and Sprague-Dawley rats with AP.

Results

The gene "Fabp5" emerged as the sole common DEG shared by a high-cholesterol diet and AP. Using the 12 topological analysis methods in PPI network analysis, Rela, Actb, Cdh1, and Vcl were identified as hub DEGs. GeneMANIA revealed 77.6% physical interactions among Fabp5, TLR4, and Rela, while genetic correlation analysis indicated moderate associations among them. Peripheral blood analysis yielded area under the ROC curve (AUC) values of 0.71, 0.63, 0.74, 0.64, and 0.91 for Fabp5, TLR4, Actb, Cdh1 genes, and artificial neural network (ANN) model respectively, in predicting severe AP. In vivo immunohistochemical analysis demonstrated higher Fabp5 expression in the hyperlipidemia-associated AP group compared to the AP and control groups.

Conclusion

Fabp5 emerged as the common DEG connecting a high-cholesterol diet and AP. Rela was highlighted as a crucial hub gene in AP. Genetic interactions were observed among Fabp5, TLR4, and Rela. An ANN model consisting of Fabp5, TLR4, Actb, and Cdh1 was helpful in predicting severe AP.

Toll-Like Receptor 9 Signaling Pathway Contributes to Intestinal Mucosal Barrier Injury in Mice With Severe Acute Pancreatitis

OBJECTIVES

The purpose of this study was to investigate the role and mechanism of toll-like receptor 9 (TLR9) in intestinal mucosal barrier injury in mice with severe acute pancreatitis (SAP).

METHODS

The mice were randomly divided into 3 groups: control group, SAP group, and TLR9 antagonist-treated group. The expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, diamine oxidase, and endotoxin core antibodies were detected by enzyme-linked immunosorbent assay. The protein expression of zonula occluden-1 (ZO)-1, occludin, TLR9, myeloid differentiation factor 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), p-nuclear factor (NF)-κB p65, and NF-κB p65 were detected by Western blot. TdT-mediated dUTP nick-end labeling staining was used for detecting intestinal epithelial cell apoptosis.

RESULTS

The expression of TLR9 and its related pathway proteins MyD88, TRAF6, and p-NF-κB p65 in the intestinal tract of SAP mice were significantly increased compared with that of control mice. Inhibition of the TLR9 expression could reduce the level of serum proinflammatory cytokines, reduce the apoptosis of intestinal epithelial cells, improve intestinal permeability, and ultimately reduce the damage of intestinal mucosal barrier function in SAP.

CONCLUSIONS

Toll-like receptor 9/MyD88/TRAF6/NF-κB signaling pathway plays an important role in intestinal mucosal barrier injury of SAP.

The Role of Pancreatic Infiltrating Innate Immune Cells in Acute Pancreatitis

Acute pancreatitis (AP) is a leading cause of gastrointestinal-related hospital admissions with significant morbidity and mortality. Although the underlying pathophysiology of AP is rather complex, which greatly limits the treatment options, more and more studies have revealed that infiltrating immune cells play a critical role in the pathogenesis of AP and determine disease severity. Thus, immunomodulatory therapy targeting immune cells and related inflammatory mediators is expected to be a novel treatment modality for AP which may improve the prognosis of patients. Cells of the innate immune system, including macrophages, neutrophils, dendritic cells, and mast cells, represent the majority of infiltrating cells during AP. In this review, an overview of different populations of innate immune cells and their role during AP will be discussed, with a special focus on neutrophils and macrophages.

Asiaticoside ameliorates acinar cell necrosis in acute pancreatitis via toll-like receptor 4 pathway

Acinar cell necrosis is one of the most prominent pathophysiological changes of acute pancreatitis (AP). Asiaticoside (AS) is a triterpene compound with confirmed apoptosis-and necrosis-related activities. However, the specific effects of AS on AP have not been determined. In this study, we aimed to investigate the protective effect of AS on AP using two mouse models. In the caerulein-induced mild acute pancreatitis (MAP) model, We found that AS administration reduced serum amylase levels and alleviated the histopathological manifestations of pancreatic tissue in a dose-dependent manner. And the levels of toll-like receptor 4 (TLR4) and necrotic related proteins (RIP3 and p-MLKL) of pancreatic tissue were reduced after AS administration. In addition, TLR4 deficiency eliminated the protective effect of AS on AP induced by caerulein in mice. Correspondingly, we elucidated the effect of AS in vitro and found that AS protected against pancreatic acinar cells necrosis and TAK-242 counteracted this protective effect. Meanwhile, we found that AS ameliorated the severity of pancreatic tissue injury and pancreatitis-associated lung injury in a severe acute pancreatitis model induced by l-arginine. Furthermore, Molecular docking results revealed interaction between AS and TLR4. Taken together, our data for the first time confirmed the protective effects of AS on AP in mice via TLR4 pathway.

High-Fat Diet Aggravates Acute Pancreatitis via TLR4-Mediated Necroptosis and Inflammation in Rats

High-fat diet (HFD) often increases oxidative stress and enhances inflammatory status in the body. Toll-like receptor 4 (TLR4) is widely expressed in the pancreatic tissues and plays an important role in pancreatitis. This study is aimed at investigating the effect of HFD on acute pancreatitis (AP) and the role of TLR4-mediated necroptosis and inflammation in this disease. Weight-matched rats were allocated for an 8-week feeding on the standard chow diet (SCD) or HFD, and then, the AP model was induced by infusion of 5% sodium taurocholate into the biliopancreatic duct. Rats were sacrificed at an indicated time point after modeling. Additionally, inhibition of TLR4 signaling by TAK-242 in HFD rats with AP was conducted in vivo. The results showed that the levels of serum free fatty acid (FFA) in HFD rats were higher than those in SCD rats. Moreover, HFD rats were more vulnerable to AP injury than SCD rats, as indicated by more serious pathological damage and much higher pancreatic malondialdehyde (MDA) and lipid peroxidation (LPO) levels as well as lower pancreatic superoxide dismutase (SOD) activities and reduced glutathione (GSH) contents and more intense infiltration of MPO-positive neutrophils and CD68-positive macrophages. In addition, HFD markedly increased the expressions of TLR4 and necroptosis marker (RIP3) and aggravated the activation of NF-κB p65 and the expression of TNF-α in the pancreas of AP rats at indicated time points. However, TLR4 inhibition significantly attenuated the structural and functional damage of the pancreas induced by AP in HFD rats, as indicated by improvement of the above indexes. Taken together, these findings suggest that HFD exacerbated the extent and severity of AP via oxidative stress, inflammatory response, and necroptosis. Inhibition of TLR4 signaling by TAK-242 alleviated oxidative stress and decreased inflammatory reaction and necroptosis, exerting a protective effect during AP in HFD rats.

Murine Models of Acute Pancreatitis: A Critical Appraisal of Clinical Relevance

Acute pancreatitis (AP) is a severe disease associated with high morbidity and mortality. Clinical studies can provide some data concerning the etiology, pathophysiology, and outcomes of this disease. However, the study of early events and new targeted therapies cannot be performed on humans due to ethical reasons. Experimental murine models can be used in the understanding of the pancreatic inflammation, because they are able to closely mimic the main features of human AP, namely their histologic glandular changes and distant organ failure. These models continue to be important research tools for the reproduction of the etiological, environmental, and genetic factors associated with the pathogenesis of this inflammatory pathology and the exploration of novel therapeutic options. This review provides an overview of several murine models of AP. Furthermore, special focus is made on the most frequently carried out models, the protocols used, and their advantages and limitations. Finally, examples are provided of the use of these models to improve knowledge of the mechanisms involved in the pathogenesis, identify new biomarkers of severity, and develop new targeted therapies.