Sphingosine 1-phosphate receptor 2 mediated early stages of pancreatic and systemic inflammatory responses via NF-kappa B activation in acute pancreatitis

Insight into modulators of sphingosine-1-phosphate receptor and implications for cardiovascular therapeutics

Cardiovascular disease is the leading cause of death worldwide, and it's of great importance to understand its underlying mechanisms and find new treatments. Sphingosine 1-phosphate (S1P) is an active lipid that exerts its effects through S1P receptors on the cell surface or intracellular signal, and regulates many cellular processes such as cell growth, cell proliferation, cell migration, cell survival, and so on. S1PR modulators are a class of modulators that can interact with S1PR subtypes to activate receptors or block their activity, exerting either agonist or functional antagonist effects. Many studies have shown that S1P plays a protective role in the cardiovascular system and regulates cardiac physiological functions mainly through interaction with cell surface S1P receptors (S1PRs). Therefore, S1PR modulators may play a therapeutic role in cardiovascular diseases. Here, we review five S1PRs and their functions and the progress of S1PR modulators. In addition, we focus on the effects of S1PR modulators on atherosclerosis, myocardial infarction, myocardial ischaemia/reperfusion injury, diabetic cardiovascular diseases, and myocarditis, which may provide valuable insights into potential therapeutic strategies for cardiovascular disease.

A rapid protocol for inducing acute pancreatitis in zebrafish models

Acute pancreatitis (AP) is an inflammatory disorder that occurs in the exocrine pancreas associated with tissue injury and necrosis. Experimental models of AP typically involve rodents, such as rats or mice. However, rodents exhibit divergent pathophysiological responses after the establishment of AP between themselves and in comparison, with human. The experiments conducted for this manuscript aimed to standardize a new AP model in zebrafish and validate it. Here, we provide a protocol for inducing AP in zebrafish through intraperitoneal injections of synthetic caerulein. Details are provided for solution preparation, pre-injection procedures, injection technique, and monitoring animal survival. Subsequently, validation was performed through biochemical and histological analyses of pancreatic tissue. The administered dose of caerulein for AP induction was 10 μg/kg applied four times in the intraperitoneal region. The histological validation study demonstrated the presence of necrosis within the first 12 h post-injection, accompanied by an excess of zymogen granules in the extracellular milieu. These observations align with those reported in conventional rodent models. We have standardized and validated the AP model in zebrafish. This model can contribute to preclinical and clinical studies of new drugs for AP treatment. Therefore, this novel model expands the toolkit for exploring faster and more effective preventive and therapeutic strategies for AP.

E3 ubiquitin ligase FBXW11 as a novel inflammatory biomarker is associated with immune infiltration and NF-κB pathway activation in pancreatitis and pancreatic cancer

BACKGROUND

Pancreatic cancer (pancreatic ductal adenocarcinoma, PDAC) is an aggressive disease with an overall poor prognosis. Pancreatitis is a major risk factor for the development of PDAC. Due to the lack of reliable and accurate biomarkers, the diagnosis, treatment, and prognosis of PDAC face great challenges. It is of great significance to elucidate the pathogenesis of PDAC and explore novel inflammatory biomarkers.

METHODS

We identified E3 ubiquitin ligases associated with pancreatic inflammation by combining multiple GEO datasets and UbiNet 2.0, and integrating the WGCNA algorithm and Limma R package. A risk score model for PDAC patients was established by using LASSO regression. We investigated the correlation between FBXW11 and immune cell infiltration using CIBERSORT, mMCP-counter, ImmuCellAI-mouse, QUANTISEQ, and TIMER algorithms, based on GEO, ArrayExpress, and TCGA datasets. We used Ubibrowser 2.0 to predict potential substrates for FBXW11. WikiPathway, MSigDB Hallmark, and Elsevier pathway analysis of FBXW11 key substrates were also performed using the EnrichR database. We detected protein expression through IHC, immunofluorescence, and western blot in the cerulein-induced acute pancreatitis mouse model.

RESULTS

We first identified that FBXW11 exhibited a clear tendency to gradually increase in normal, pancreatitis, and PDAC patients. The validation analysis revealed that the FBXW11 protein exhibited significantly high expression in cerulein-induced acute pancreatitis mice, with its distribution primarily observed in the cytoplasm. Simultaneously, we developed a risk model utilizing the genes associated with FBXW11 to forecast the outcome of patients with PDAC and the likelihood of pancreatitis advancing to pancreatic cancer. Functional analysis showed that FBXW11, as a novel inflammatory biomarker, had a significant positive correlation with macrophage infiltration and the NF-κB signaling pathway. Finally, the western blot assay of the NF-κB signaling pathway in pancreatic tissues demonstrated that high activation of NF-κB was correlated with high expression of FBXW11.

CONCLUSIONS

Our research not only provides evidence for FBXW11 as a novel inflammatory biomarker but also provides new insights into the research and clinical treatment of pancreatic cancer.

Characterization of a S1PR2 specific 11C-labeled radiotracer in streptozotocin-induced diabetic murine model

BACKGROUND

Diabetes mellitus is a chronic progressive metabolic disorder that affects millions of people worldwide. Emerging evidence suggests the important roles of sphingolipid metabolism in diabetes. In particular, sphingosine-1-phosphate (S1P) and S1P receptor 2 (S1PR2) have important metabolic functions and are involved in several metabolic diseases. In diabetes, S1PR2 can effectively preserve β cells and improve glucose/insulin tolerance in high-fat diet induced and streptozotocin (STZ)-induced diabetic mouse models. We previously developed a group of potent and selective S1PR2 ligands and radioligands.

METHODS

In this study, we continued our efforts and characterized our leading S1PR2 radioligand, [11C]TZ34125, in a STZ-induced diabetic mouse model. [11C]TZ34125 was radiosynthesized in an automated synthesis module and in vitro saturation binding assay was performed using recombinant human S1PR2 membrane. In vitro saturation autoradiography analysis was also performed to determine the binding affinity of [11C]TZ34125 against mouse tissues. Type-1 diabetic mouse model was developed following a single high dose of STZ in C57BL/6 mice. Ex vivo biodistribution was performed to evaluate the distribution and amount of [11C]TZ34125 in tissues. In vitro autoradiography analysis was performed to compare the uptake of [11C]TZ34125 between diabetic and control animals in mouse spleen and pancreas.

RESULTS

Our in vitro saturation binding assay using [11C]TZ34125 confirmed [11C]TZ34125 is a potent radioligand to recombinant human S1PR2 membrane with a Kd value of 0.9 nM. Saturation autoradiographic analysis showed [11C]TZ34125 has a Kd of 67.5, 45.9, and 25.0 nM to mouse kidney, spleen, and liver tissues respectively. Biodistribution study in STZ-induced diabetic mice showed the uptake of [11C]TZ34125 was significantly elevated in the spleen (~2 fold higher) and pancreas (~1.4 fold higher) compared to normal controls. The increased uptake of [11C]TZ34125 was further confirmed using autoradiographic analysis in the spleen and pancreases of STZ-induced diabetic mice, indicating S1PR2 can potentially act as a biomarker of diabetes in pancreases and inflammation in spleen. Future mechanistic analysis and in vivo quantitative assessment using non-invasive PET imaging in large animal model of diabetes is worthwhile.

CONCLUSIONS

Overall, our data showed an increased uptake of our lead S1PR2-specific radioligand, [11C]TZ34125, in the spleen and pancreases of STZ-induced diabetic mice, and demonstrated [11C]TZ34125 has a great potential for preclinical and clinical usage for assessment of S1PR2 in diabetes and inflammation.

S1P/S1PR2 promote pancreatic stellate cell activation and pancreatic fibrosis in chronic pancreatitis by regulating autophagy and the NLRP3 inflammasome

Sphingosine-1-phosphate (S1P) is a bioactive lipid molecule that governs various functions by embedding its receptor, S1PR, in different cells. Chronic pancreatitis (CP) is characterized by pancreatic fibrosis via activation of pancreatic stellate cells (PSCs). However, the effect of S1P on CP and PSC activation is still unknown. Here, we conducted a series of experiments to explore the effect of S1P on a CP rat model and primary cultured PSCs. In vivo, CP was induced by intravenous injection of dibutyltin dichloride. S1P was administered at a dosage of 200 μg/kg body weight per day by intraperitoneal injection. After 4 weeks, serum, plasma and pancreas samples were collected for molecular analysis and histological detection. In vitro, PSCs were isolated and cultured for treatment with different doses of S1P. 3 MA and MCC950 were used to determine the effect of S1P on PSC activation by regulating autophagy and the NLRP3 inflammasome. JTE013 and Si-S1PR2 were applied to verify that the functions of S1P were realized by combining with S1PR2. Cells were collected for RT‒PCR, western blotting and immunofluorescence. The results showed that S1P was increased in the plasma and pancreatic tissue of CP rats. When S1P was administered to CP rats, the function and histomorphology of the pancreas were severely impaired. In addition, S1P promoted PSC activation, heightened autophagy and enhanced the NLRP3 inflammasome in vivo and in vitro. Moreover, S1PR2 mediated the effect of S1P on PSC activation by regulating autophagy and the NLRP3 inflammasome sequentially. In conclusion, S1P binding to S1PR2 promoted PSC activation and pancreatic fibrosis in CP by regulating autophagy and the NLRP3 inflammasome. These findings provide a theoretical basis for targeting S1P/S1PR2 to treat pancreatic fibrosis and further suggest that considering the role of autophagy and the NLRP3 inflammasome may help with the treatment pancreatic fibrosis.