Bile acids attenuate hepatic inflammation during ischemia/reperfusion injury.

Background & Aims: Persistent cholestasis has been associated with poor prognosis after orthotopic liver transplantation. In this study, we aimed to investigate how the accumulation of tauro-beta-muricholic acid (TßMCA), resulting from the reprogramming of bile acid (BA) metabolism during liver ischemia/reperfusion (IR) stress, attenuates liver inflammation. Methods: Ingenuity Pathway Analysis was performed using transcriptome data from a murine hepatic IR model. Three different models of hepatic IR (liver warm IR, bile duct separation-IR, common bile duct ligation-IR) were employed. We generated adeno-associated virus-transfected mice and CD11b-DTR mice to assess the role of BAs in regulating the myeloid S1PR2-GSDMD axis. Hepatic BA levels were analyzed using targeted metabolomics. Finally, the correlation between the reprogramming of BA metabolism and hepatic S1PR2 levels was validated through RNA-seq of human liver transplant biopsies. Results: We found that BA metabolism underwent reprogramming in murine hepatocytes under IR stress, leading to increased synthesis of TßMCA, catalyzed by the enzyme CYP2C70. The levels of hepatic TßMCA were negatively correlated with the severity of hepatic inflammation, as indicated by the serum IL-1ß levels. Inhibition of hepatic CYP2C70 resulted in reduced TßMCA production, which subsequently increased serum IL-1ß levels and exacerbated IR injury. Moreover, our findings suggested that TßMCA could inhibit canonical inflammasome activation in macrophages and attenuate inflammatory responses in a myeloid-specific S1PR2-GSDMD-dependent manner. Additionally, Gly-ßMCA, a derivative of TßMCA, could effectively attenuate inflammatory injury in vivo and inhibit human macrophage pyroptosis in vitro. Conclusions: IR stress orchestrates hepatic BA metabolism to generate TßMCA, which attenuates hepatic inflammatory injury by inhibiting the myeloid S1PR2-GSDMD axis. Bile acids have immunomodulatory functions in liver reperfusion injury that may guide therapeutic strategies. Impact and implications: Our research reveals that liver ischemia-reperfusion stress triggers reprogramming of bile acid metabolism. This functions as an adaptive mechanism to mitigate inflammatory injury by regulating the S1PR2-GSDMD axis, thereby controlling the release of IL-1ß from macrophages. Our results highlight the crucial role of bile acids in regulating hepatocyte-immune cell crosstalk, which demonstrates an immunomodulatory function in liver reperfusion injury that may guide therapeutic strategies targeting bile acids and their receptors.

Multilineage-differentiating stress-enduring cells: a powerful tool for tissue damage repair.

Multilineage-differentiating stress-enduring (Muse) cells are a type of pluripotent cell with unique characteristics such as non-tumorigenic and pluripotent differentiation ability. After homing, Muse cells spontaneously differentiate into tissue component cells and supplement damaged/lost cells to participate in tissue repair. Importantly, Muse cells can survive in injured tissue for an extended period, stabilizing and promoting tissue repair. In addition, it has been confirmed that injection of exogenous Muse cells exerts anti-inflammatory, anti-apoptosis, anti-fibrosis, immunomodulatory, and paracrine protective effects in vivo. The discovery of Muse cells is an important breakthrough in the field of regenerative medicine. The article provides a comprehensive review of the characteristics, sources, and potential mechanisms of Muse cells for tissue repair and regeneration. This review serves as a foundation for the further utilization of Muse cells as a key clinical tool in regenerative medicine.

A detrimental role of endothelial S1PR2 in cardiac ischemia-reperfusion injury via modulating mitochondrial dysfunction, NLRP3 inflammasome activation, and pyroptosis.

Sphingosine 1-phosphate (S1P), a bioactive lipid molecule, exerts multifaceted effects on cardiovascular functions via S1P receptors, but its effects on cardiac I/R injury are not fully understood. Plasma lipidomics analysis by mass spectrometry revealed that sphingosine lipids, including sphingosine 1-phosphate (S1P), were significantly down-regulated following cardiac I/R injury in mice. The reduced S1P levels were also observed in the plasma of coronary heart disease (CHD) patients after percutaneous coronary intervention (PCI) compared with those without PCI. We found that S1P exerted a cardioprotective effect via endothelial cell (EC)-S1PR1, whereas EC-S1PR2 displayed a detrimental effect on cardiac I/R. Our data showed that EC-specific S1pr2 loss-of-function significantly lessened inflammatory responses and diminished cardiac I/R injury, while EC-specific S1pr2 gain-of-function aggravated cardiac I/R injury. Mechanistically, EC-S1PR2 initiated excessive mitochondrial fission and elevated ROS production via RHO/ROCK1/DRP1 pathway, leading to NLRP3 inflammasome activation and subsequent cell pyroptosis, thereby exacerbating inflammation and I/R injuries. Furthermore, RGD-peptide magnetic nanoparticles packaging S1pr2-siRNA to specifically knockdown S1PR2 in endothelial cells significantly ameliorated cardiac I/R injury. Taken together, our investigations demonstrate that EC-S1PR2 induces excessive mitochondrial fission, which results in NLRP3 inflammasome activation and subsequently triggers cell pyroptosis, ultimately exacerbating inflammatory responses and aggravating heart injuries following I/R.

S1PR2 participates in intestinal injury in severe acute pancreatitis by regulating macrophage pyroptosis.

Background: Severe acute pancreatitis (SAP) is an inflammatory disorder affecting the gastrointestinal system. Intestinal injury plays an important role in the treatment of severe acute pancreatitis. In this study, we mainly investigated the role of S1PR2 in regulating macrophage pyroptosis in the intestinal injury of severe acute pancreatitis. Methods: The SAP model was constructed using cerulein and lipopolysaccharide, and the expression of S1PR2 was inhibited by JTE-013 to detect the degree of pancreatitis and intestinal tissue damage in mice. Meanwhile, the level of pyroptosis-related protein was detected by western blot, the level of related mRNA was detected by PCR, and the level of serum inflammatory factors was detected by ELISA. In vitro experiments, LPS+ATP was used to construct the pyroptosis model of THP-1. After knockdown and overexpression of S1PR2, the pyroptosis proteins level was detected by western blot, the related mRNA level was detected by PCR, and the level of cell supernatant inflammatory factors were detected by ELISA. A rescue experiment was used to verify the sufficient necessity of the RhoA/ROCK pathway in S1PR2-induced pyroptosis. Meanwhile, THP-1 and FHC were co-cultured to verify that cytokines released by THP-1 after damage could regulate FHC damage. Results: Our results demonstrated that JTE-013 effectively attenuated intestinal injury and inflammation in mice with SAP. Furthermore, we observed a significant reduction in the expression of pyroptosis-related proteins within the intestinal tissue of SAP mice upon treatment with JTE-013. We confirmed the involvement of S1PR2 in THP-1 cell pyroptosis in vitro. Specifically, activation of S1PR2 triggered pyroptosis in THP-1 cells through the RhoA/ROCK signaling pathway. Moreover, it was observed that inflammatory factors released during THP-1 cell pyroptosis exerted an impact on cohesin expression in FHC cells. Conclusion: The involvement of S1PR2 in SAP-induced intestinal mucosal injury may be attributed to its regulation of macrophage pyroptosis.

Hepatic LGR4 aggravates cholestasis-induced liver injury in mice.

Current therapy for hepatic injury induced by the accumulation of bile acids is limited. Leucine-rich repeat G protein-coupled receptor 4 (LGR4), also known as GPR48, is critical for cytoprotection and cell proliferation. Here, we reported a novel function for the LGR4 in cholestatic liver injury. In the bile duct ligation (BDL)-induced liver injury model, hepatic LGR4 expression was significantly downregulated. Deficiency of LGR4 in hepatocytes (Lgr4LKO) notably decreased BDL-induced liver injury measured by hepatic necrosis, fibrosis, and circulating liver enzymes and total bilirubin. Levels of total bile acids in plasma and liver were markedly reduced in these mice. However, deficiency of LGR4 in macrophages (Lyz2-Lgr4MKO) demonstrated no significant effect on liver injury induced by BDL. Deficiency of LGR4 in hepatocytes significantly attenuated S1PR2 and the phosphorylation of protein kinase B (AKT) induced by BDL. Recombinant Rspo1 and Rspo3 potentiated the taurocholic acid (TCA)-induced upregulation in S1PR2 and phosphorylation of AKT in hepatocytes. Inhibition of S1PR2-AKT signaling by specific AKT or S1PR2 inhibitors blocked the increase of bile acid secretion induced by Rspo1/3 in hepatocytes. Our studies indicate that the R-spondins (Rspos)-LGR4 signaling in hepatocytes aggravates the cholestatic liver injury by potentiating the production of bile acids in a S1PR2-AKT-dependent manner.NEW & NOTEWORTHY Deficiency of LGR4 in hepatocytes alleviates BDL-induced liver injury. LGR4 in macrophages demonstrates no effect on BDL-induced liver injury. Rspos-LGR4 increases bile acid synthesis and transport via potentiating S1PR2-AKT signaling in hepatocytes.

Is myeloid-derived growth factor a ligand of the sphingosine-1-phosphate receptor 2?

Secretory myeloid-derived growth factor (MYDGF) exerts beneficial effects on organ repair, probably via a plasma membrane receptor; however, the identity of the expected receptor has remained elusive. In a recent study, MYDGF was reported as an agonist of the sphingosine-1-phosphate receptor 2 (S1PR2), an A-class G protein-coupled receptor that mediates the functions of the signaling lipid, sphingosine-1-phosphate (S1P). In the present study, we conducted living cell-based functional assays to test whether S1PR2 is a receptor for MYDGF. In the NanoLuc Binary Technology (NanoBiT)-based ß-arrestin recruitment assay and the cAMP-response element (CRE)-controlled NanoLuc reporter assay, S1P could efficiently activate human S1PR2 overexpressed in human embryonic kidney (HEK) 293T cells; however, recombinant human MYDGF, overexpressed either from Escherichia coli or HEK293 cells, had no detectable effect. Thus, the results demonstrated that human MYDGF is not a ligand of human S1PR2. Considering the high conservation of MYDGF and S1PR2 in evolution, MYDGF is also probably not a ligand of S1PR2 in other vertebrates.

Electroacupuncture Alleviates Cerebral Ischemia-reperfusion Injury by Regulating the S1PR2/TLR4/NLRP3 Signaling Pathway via m6A Methylation of lncRNA H19.

Electroacupuncture (EA) treatment plays a protective role in cerebral ischemiareperfusion (CIR) injury. However, the underlying molecular mechanism is still not fully elucidated. METHODS: All rats were randomly divided into five groups: the SHAM group, MCAO group, MCAO+EA (MEA) group, MCAO+METTL3 overexpression+EA (METTL3) group and MCAO+lncRNA H19 overexpression+EA (lncRNA H19) group. The middle cerebral artery occlusion (MCAO) rats were established to mimic CIR injury. The overexpression of lncRNA H19 and METTL3 was induced by stereotactic injection of lentiviruses into the rat lateral ventricles. The rats in the MEA, METTL3, and lncRNA H19 groups were treated with EA therapy on "Renzhong" (DU26) and "Baihui" (DU20) acupoints (3.85/6.25Hz; 1mA). Besides, the neurological deficit scoring, cerebral infarction area, pathological changes in brain tissue, total RNA m6A level, and the expression of METTL3, S1PR2, TLR4, NLRP3 and lncRNA H19 were detected in this experiment. RESULTS: EA improved the neurological deficit scoring, cerebral infarction area, and pathological injury in MCAO rats, while these beneficial effects of EA on CIR injury were attenuated by the overexpression of METTL3 or lncRNA H19. More importantly, EA down-regulated the total RNA m6A level and the expression of METTL3, S1PR2, TLR4, NLRP3 and lncRNA H19 in MCAO rats. Instead, the overexpression of METTL3 or lncRNA H19 was found to reverse the EA-induced down-regulation. CONCLUSION: The findings indicated that EA might down-regulate the S1PR2/TLR4/NLRP3 signaling pathway via m6A methylation of lncRNA H19 to alleviate CIR injury. Our findings provide a new insight into the molecular mechanism of EA on CIR injury.

Targeting the SPHK1/S1P/S1PR2 axis ameliorates GH-secreted pituitary adenoma progression.

BACKGROUND: Growth hormone-secreted pituitary adenoma (GHPA) is a prominent subtype of pituitary adenoma (PA) associated with progressive somatic disfigurement, various complications, and elevated mortality rates. Existing treatment options have limited efficacy, highlighting the urgent need for novel pharmacological interventions. Previous studies have revealed that sphingosine kinase 1 (SphK1)/sphingosine-1-phosphate (S1P)/S1P receptors (S1PRs) signalling have critical roles in the tumour microenvironment, but their role in GHPA remains unclear. METHODS: We performed integrative analyses including bioinformatics analyses, functional studies, and clinical validation to investigate the pathological roles of SPHK1/S1P and evaluated the effectiveness of the S1P receptor 2 (S1PR2) inhibitor JTE-013 in GHPA treatment. RESULTS: SPHK1/S1P signalling is abnormally expressed in patients with GHPA. Knockdown of SPHK1 suppresses S1P-mediated cell proliferation in GH3 Cells. Mechanistically, S1P inhibits apoptosis and autophagy while promoting the secretion of Growth Hormone (GH) by binding to the S1P receptor subtype 2 (S1PR2) in GH3 cells. Moreover, the function of S1PR2 in GH3 cells is mediated by the downstream Akt-Creb pathway. We then identify the S1PR2 as a novel target for therapeutic intervention in GHPA. Systemic administration of the potent and selective S1PR2 antagonist, JTE-013, significantly reduces both tumour size and GH secretion. Importantly, we identify preoperative serum S1P levels as a biomarker predicting poor prognosis in GHPA patients at follow-up. CONCLUSION: Our study shows that blocking SPHK1/S1P/S1PR2 axis can ameliorate the progression of GHPA, providing evidence of a promising therapeutic target for GHPA.

S1PR2 Regulates Autophagy Through the AKT/mTOR Pathway to Promote Pathological Damage in Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) is a fatal and debilitating neurodegenerative disease. Sphingosine-1-phosphate receptor 2 (S1PR2), one of the receptors of S1P, is a key regulatory factor for various diseases. OBJECTIVE: This study aimed to explore the role and possible mechanism of S1PR2 in AD. METHODS: S1PR2 expression in the AD mice was detected, and after intervening S1PR2 expression with sh-S1PR2 in AD mice, the behavioral changes, pathological lesions of the hippocampus, autophagy level, and AKT/mTOR pathway activation were analyzed. Furthermore, SH-SY5Y cells were induced by Aß25-35 to construct an AD cell model, and the effects of sh-S1PR2 on proliferation, apoptosis, autophagy, and AKT/mTOR pathway of AD cells were investigated. In addition, the effects of pathway inhibitor rapamycin on model cells were further analyzed. RESULTS: The expression of S1PR2 was significantly increased in AD mice, the sh-S1PR2 significantly improved behavioral dysfunction, alleviated pathological injury of the hippocampus, increased the number of neurons, and inhibited Aß production and p-tau expression, showing a positive effect on the AD pathology. In addition, silencing of S1PR2 expression significantly promoted the autophagy level and inhibited the activation of the AKT/mTOR pathway in AD model mice. In vitro experiments further confirmed that sh-S1PR2 promoted cell proliferation, inhibited apoptosis, relieved cytopathology, promoted autophagy, and inhibited the activation of the AKT/mTOR pathway in the cell model. The use of rapamycin further confirmed the role of AKT/mTOR pathway-mediated autophagy in the regulation of AD by S1PR2. CONCLUSION: S1PR2 promoted AD pathogenesis by inhibiting autophagy through the activation of AKT/mTOR pathway.

Nogo-A is secreted in extracellular vesicles, occurs in blood and can influence vascular permeability.

Nogo-A is a transmembrane protein with multiple functions in the central nervous system (CNS), including restriction of neurite growth and synaptic plasticity. Thus far, Nogo-A has been predominantly considered a cell contact-dependent ligand signaling via cell surface receptors. Here, we show that Nogo-A can be secreted by cultured cells of neuronal and glial origin in association with extracellular vesicles (EVs). Neuron- and oligodendrocyte-derived Nogo-A containing EVs inhibited fibroblast spreading, and this effect was partially reversed by Nogo-A receptor S1PR2 blockage. EVs purified from HEK cells only inhibited fibroblast spreading upon Nogo-A over-expression. Nogo-A-containing EVs were found in vivo in the blood of healthy mice and rats, as well as in human plasma. Blood Nogo-A concentrations were elevated after acute stroke lesions in mice and rats. Nogo-A active peptides decreased barrier integrity in an in vitro blood-brain barrier model. Stroked mice showed increased dye permeability in peripheral organs when tested 2 weeks after injury. In the Miles assay, an in vivo test to assess leakage of the skin vasculature, a Nogo-A active peptide increased dye permeability. These findings suggest that blood borne, possibly EV-associated Nogo-A could exert long-range regulatory actions on vascular permeability.

JTE-013 Alleviates Pulmonary Fibrosis by Affecting the RhoA/YAP Pathway and Mitochondrial Fusion/Fission.

Pulmonary fibrosis may be due to the proliferation of fibroblasts and the aggregation of extracellular matrix, resulting in the stimulation of inflammation damage, destroying lung tissue structure, seriously affecting the patient's respiratory function, and even leading to death. We investigated the role and mechanism of JTE-013 in attenuating bleomycin (BLM)-induced pulmonary fibrosis. BLM-induced pulmonary fibrosis was established in mice. Type 2 alveolar epithelial cells (MLE-12) were stimulated with sphingosine monophosphate (S1P) in vitro. JTE-013, an S1PR2 (sphingosine 1-phosphate receptor 2) antagonist, and Verteporfin were administered in vivo and in vitro. IL-4, IL-5, TNF-α, and IFN-γ were measured by ELISA. IL-4 and IFN-γ positive cells were detected by flow cytometry. Inhibition of S1PR2 with JTE-013 significantly ameliorated BLM-induced pathological changes and inflammatory cytokine levels. JTE-013 also significantly reduced the expression of RHOA/YAP pathway proteins and mitochondrial fission protein Drp1, apoptosis, and the colocalization of α-SMA with YAP, Drp1, and Tom20, as detected by immunohistochemistry, immunofluorescence staining, TUNEL, and Western blot. In vitro, S1PR2 and YAP knockdown downregulated RHOA/YAP pathway protein expression, Drp1 phosphorylation, and Drp1 translocation, promoted YAP phosphorylation and phenotypic transformation of MFN2, and inhibited the up-regulation of mitochondrial membrane potential, reactive oxygen species production, and cell apoptosis (7.13% vs. 18.14%), protecting the integrity of the mitochondrial dynamics. JTE-013 also inhibited the expression of fibrosis markers α-SMA, MMP-9, and COL1A1, and alleviated the symptoms of pulmonary fibrosis. Conclusively, JTE-013 has great anti-pulmonary fibrosis potential by regulating RHOA/YAP and mitochondrial fusion/fission.

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 ß 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.

Proanthocyanidin B2 derived metabolites may be ligands for bile acid receptors S1PR2, PXR and CAR: an in silico approach.

Bile acids (BAs) act as signaling molecules via their interactions with various nuclear (FXR, VDR, PXR and CAR) and G-protein coupled (TGR5, M3R, S1PR2) BA receptors. Stimulation of these BA receptors influences several processes, including inflammatory responses and glucose and xenobiotic metabolism. BA profiles and BA receptor activity are deregulated in cardiometabolic diseases; however, dietary polyphenols were shown to alter BA profile and signaling in association with improved metabolic phenotypes. We previously reported that supplementing mice with a proanthocyanidin (PAC)-rich grape polyphenol (GP) extract attenuated symptoms of glucose intolerance in association with changes to BA profiles, BA receptor gene expression, and/or downstream markers of BA receptor activity. Exact mechanisms by which polyphenols modulate BA signaling are not known, but some hypotheses include modulation of the BA profile via changes to gut bacteria, or alteration of ligand-availability via BA sequestration. Herein, we used an in silico approach to investigate putative binding affinities of proanthocyanidin B2 (PACB2) and PACB2 metabolites to nuclear and G-protein coupled BA receptors. Molecular docking and dynamics simulations revealed that certain PACB2 metabolites had stable binding affinities to S1PR2, PXR and CAR, comparable to that of known natural and synthetic BA ligands. These findings suggest PACB2 metabolites may be novel ligands of S1PR2, CAR, and PXR receptors.Communicated by Ramaswamy H. Sarma.

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. 3MA 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.

Alleviating early demyelination in ischaemia/reperfusion by inhibiting sphingosine-1-phosphate receptor 2 could protect visual function from impairment.

Retinal ischaemia/reperfusion (I/R) injury is a common cause of retinal ganglion cell (RGC) apoptosis and axonal degeneration, resulting in irreversible visual impairment. However, there are no available neuroprotective and neurorestorative therapies for retinal I/R injury, and more effective therapeutic approaches are needed. The role of the myelin sheath of the optic nerve after retinal I/R remains unknown. Here, we report that demyelination of the optic nerve is an early pathological feature of retinal I/R and identify sphingosine-1-phosphate receptor 2 (S1PR2) as a therapeutic target for alleviating demyelination in a model of retinal I/R caused by rapid changes in intraocular pressure. Targeting the myelin sheath via S1PR2 protected RGCs and visual function. In our experiment, we observed early damage to the myelin sheath and persistent demyelination accompanied by S1PR2 overexpression after injury. Blockade of S1PR2 by the pharmacological inhibitor JTE-013 reversed demyelination, increased the number of oligodendrocytes, and inhibited microglial activation, contributing to the survival of RGCs and alleviating axonal damage. Finally, we evaluated the postoperative recovery of visual function by recording visual evoked potentials and assessing the quantitative optomotor response. In conclusion, this study is the first to reveal that alleviating demyelination by inhibiting S1PR2 overexpression may be a therapeutic strategy for retinal I/R-related visual impairment.

Bile acid-mediated signaling in cholestatic liver diseases.

Chronic cholestatic liver diseases, such as primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are associated with bile stasis and gradually progress to fibrosis, cirrhosis, and liver failure, which requires liver transplantation. Although ursodeoxycholic acid is effective in slowing the disease progression of PBC, it has limited efficacy in PSC patients. It is challenging to develop effective therapeutic agents due to the limited understanding of disease pathogenesis. During the last decade, numerous studies have demonstrated that disruption of bile acid (BA) metabolism and intrahepatic circulation promotes the progression of cholestatic liver diseases. BAs not only play an essential role in nutrition absorption as detergents but also play an important role in regulating hepatic metabolism and modulating immune responses as key signaling molecules. Several excellent papers have recently reviewed the role of BAs in metabolic liver diseases. This review focuses on BA-mediated signaling in cholestatic liver disease.

Liver sinusoidal endothelial S1pr2 regulates experimental liver fibrosis through YAP/TGF-ß signaling pathway.

The hepatic vascular niche plays an important role in the pathological process of liver fibrosis. Liver sinusoidal endothelial cells (LSECs) predominantly compose hepatic vascular niches. Endothelial cell (EC)-expressing sphingosine 1-phosphate receptor 2 (S1pr2) plays an essential role in the regulation of vascular functions. Nevertheless, it remains unknown whether liver LSEC-S1pr2 might modulate pathological liver fibrosis. In this study, liver fibrosis was induced by hepatotoxin carbon tetrachloride (CCl4 ). The expression of S1pr2 is significantly downregulated in liver sinusoidal endothelial cells after CCl4 treatment. The loss of S1pr2 in LSECs significantly alleviated liver fibrosis after chronic insult, whereas the overexpression of S1pr2 in LSECs accentuated liver fibrogenesis. In vivo experiments further revealed that the deficiency of S1pr2 in LSECs dampened hepatic stellate cell (HSC) activation, while overexpression of S1pr2 in LSECs enhanced HSC activation with more extracellular matrix component production. Mechanistically, LSEC-S1pr2 activates the YAP signaling pathway to potentiate the transactivation of TGF-ß, which acts on HSCs in a paracrine manner, and thus aggravated liver fibrosis. Taken together, our results uncover a novel pathological mechanism of liver fibrosis in which LSEC-S1pr2 plays an important role in modulating the development of liver fibrosis, providing a future novel therapy target against liver fibrogenesis.

The relationship between sphingosine-1-phosphate receptor 2 and epidermal growth factor in migration and invasion of oral squamous cell carcinoma.

Sphingosine-1-phosphate (S1P) is a lipid mediator and its binding to the S1P receptor 2 (S1PR2) is reported to regulate cytoskeletal organization. Epidermal growth factor (EGF) has been shown to induce migration and invasion in tumour cells. Since binding of S1P to S1PR2 and EGF to the EGF receptors exhibit some overlapping functionality, this study aimed to determine whether S1PR2 was involved in EGF-induced migration and invasion of oral squamous cell carcinoma (OSCC) lines and to identify any potential crosstalk between the two pathways. Migration was investigated using the scratch wound assay while invasion was studied using the transwell invasion and multicellular tumour spheroid (MCTS) assays. Activity of Rac1, a RhoGTPase, was measured using G-LISA (small GTPase activation assays) while S1P production was indirectly measured via the expression of sphingosine kinase (Sphk). S1PR2 inhibition with 10 µM JTE013 reduced EGF-induced migration, invasion and Rac1 activity, however, stimulation of S1PR2 with 10 µM CYM5478 did not enhance the effect of EGF on migration, invasion or Rac1 activity. The data demonstrated a crosstalk between EGF/EGFR and S1P/S1PR2 pathways at the metabolic level. S1PR2 was not involved in EGF production, but EGF promoted S1P production through the upregulation of Sphk1. In conclusion, OSCC lines could not migrate and invade without S1PR2 regulation, even with EGF stimulation. EGF also activated S1PR2 by stimulating S1P production via Sphk1. The potential for S1PR2 to control cellular motility may lead to promising treatments for OSCC patients and potentially prevent or reduce metastasis.

S1PR2 is Important for Cigarette Smoke-induced Pyroptosis in Human Bronchial Epithelial Cells.

BACKGROUND: Chronic obstructive pulmonary disease and other respiratory inflammatory diseases are often associated with cigarette smoke exposure. However, the underlying molecular mechanism remains unclear. AIM OF THE STUDY: This study aimed to investigate the role of sphingosine-1-phosphate receptor 2 (S1PR2) in cigarette smoke extract (CSE)-induced inflammation and pyroptosis in human bronchial epithelial (HBE) cells. METHODS: CSE was administered to HBE cells and inflammation and pyroptosis were assessed. The mRNA levels of S1PR2, NLRP3, IL-1ß, and IL-18 in HBE cells were detected by quantitative RT-PCR. Secreted protein levels of IL-1ß and IL-18 in the culture supernatants were detected using enzyme-linked immunosorbent assay. Western blotting was used to measure the levels of S1PR2 and pyroptosis-related proteins (NLRP3, ASC, caspase-1, GSDMD, IL-1ß, and IL-18). RESULTS: Our study revealed an upregulated expression of S1PR2, NLRP3, ASC, caspase-1, GSDMD, IL-1ß, and regulated IL-18 in HBE cells after CSE exposure. Genetic blockage of S1PR2 could reverse the increased expression of these proteins related to CSE-induced pyroptosis. Conversely, S1PR2 overexpression increased CSE-induced pyroptosis by upregulating the expression of NLRP3, ASC, caspase-1, GSDMD, IL-1ß, and IL-18 in HBE cells. CONCLUSIONS: Our results revealed that a novel S1PR2 signaling pathway may be involved in the pathogenesis of CSE-induced inflammation and pyroptosis in HBE cells. Thus, S1PR2 inhibitors could be an effective treatment for cigarette smoke-induced airway inflammation and injury.

Inhibition of Sphingosine-1-Phosphate Receptor 2 by JTE013 Enhanced Alveolar Bone Regeneration by Promoting Angiogenesis.

Sphingosine-1-phosphate receptor 2 (S1PR2) is a G protein-coupled receptor that regulates various immune responses. Herein, we report the effects of a S1PR2 antagonist (JTE013) on bone regeneration. Murine bone marrow stromal cells (BMSCs) were treated with dimethylsulfoxide (DMSO) or JTE013 with or without infection by an oral bacterial pathogen Aggregatibacter actinomycetemcomitans. Treatment with JTE013 enhanced vascular endothelial growth factor A (VEGFA), platelet derived growth factor subunit A (PDGFA), and growth differentiation factor 15 (GDF15) gene expression and increased transforming growth factor beta (TGFß)/Smad and Akt signaling. Eight-week-old male C57BL/6J mice were challenged with ligatures around the left maxillary 2nd molar for 15 days to induce inflammatory bone loss. After ligature removal, mice were treated with diluted DMSO or JTE013 in the periodontal tissues 3 times per week for 3 weeks. Calcein was also injected twice to measure bone regeneration. Micro-CT scanning of maxillary bone tissues and calcein imaging revealed that treatment with JTE013 enhanced alveolar bone regeneration. JTE013 also increased VEGFA, PDGFA, osteocalcin, and osterix gene expressions in the periodontal tissues compared to control. Histological examination of periodontal tissues revealed that JTE013 promoted angiogenesis in the periodontal tissues compared to control. Our findings support that inhibition of S1PR2 by JTE013 increased TGFß/Smad and Akt signaling; enhanced VEGFA, PDGFA, and GDF15 gene expression; and subsequently promoted angiogenesis and alveolar bone regeneration.