Sphingosine kinase/sphingosine 1-phosphate (S1P)/S1P receptor axis is involved in liver fibrosis-associated angiogenesis

Chaihu Guizhi Ganjiang Decoction ameliorates chronic pancreatitis by modulating the SK1/S1P signaling pathway

Chronic pancreatitis (CP) is a progressive disease characterized by injury on pancreatic acinar cells (PACs), ongoing fibrosis, and gradual loss of exocrine and endocrine functions. Sphingosine kinase 1 (SK1) expression is elevated in injured PACs, and its metabolite sphingosine-1-phosphate (S1P) promotes the activation of pancreatic stellate cell (PSC) through autophagy and pyroptosis. Chaihu Guizhi Ganjiang Decoction (CGGD), a traditional Chinese medicine is widely used in the clinical treatment of digestive diseases. However, whether CCGD affects the SK1/S1P axis and relieves pancreatic damage through this pathway remains unknown. In this study, CP rats were treated with CGGD, individually or in combination with S1P and SKI-178 for four weeks to assess the effect of CGGD on pancreatic injury, fibrosis, autophagy and pyroptosis. The results showed that SK1, S1P and S1PR2 levels were increased in the pancreatic tissues of CP rats, while CGGD reduced these levels. Treatment with S1P exacerbated histological damage, promoted fibrosis, accelerated autophagy, and induced pyroptosis. Conversely, SKI-178 suppressed these effects. Notably, CGGD mitigated histological damage, decreased serum amylase and lipase levels, and alleviated pancreatic fibrosis induced by S1P. Furthermore, CGGD downregulated autophagy and pyroptosis induced by S1P, exhibiting an effect comparable to SKI-178 in CP. In conclusion, CGGD ameliorates pancreatic damage by reducing fibrosis, inhibiting autophagy, and suppressing pyroptosis through the SK1/S1P axis.

ROS-responsive injectable hydrogels loaded with exosomes carrying miR-4500 reverse liver fibrosis

The reversal of liver fibrosis requires effective strategies to reduce oxidative stress and inhibition of hepatic stellate cell (HSC) activation. MiR-4500 regulates pathological angiogenesis and collagen mRNA stability, with the potential to inhibit fibrosis. Herein, we explored the inhibition of HSC activation in vitro by exosomes (Exos) carrying miR-4500 and encapsulated ExosmiR-4500 in an intelligent injectable hydrogel with biological activity and reactive oxygen species (ROS) responsiveness for application in oxidative stress environments. Briefly, reversible boronic ester bonds were integrated into gelatin-based hydrogels through dynamic crosslinking of quaternized chitosan (QCS) and 4-carboxyphenylboronic acid (CPBA)-modified gelatin. The QCS-CPBA-Gelatin (QCG) hydrogel scavenged excess ROS from the local microenvironment and released ExosmiR-4500 through the dissociation of boronic ester bonds, providing a favorable microenvironment and in situ sustained-release drug delivery system for ExosmiR-4500. The results showed that QCG@ExosmiR-4500 hydrogel has biocompatibility, biodegradability, and slow-release ability, which could effectively clear ROS and inhibit HSC activation and pathological angiogenesis in vitro and in vivo. Furthermore, transcriptome analysis suggests that the pharmacological mechanism of the QCG@ExosmiR-4500 hydrogel is mainly related to anti-oxidation, anti-angiogenesis, anti-fibrosis processes, and signaling pathways. Thus, our study demonstrates that an intelligently responsive ExosmiR-4500 delivery system based on injectable hydrogels is a promising strategy for the treatment of liver fibrosis.

Regulatory role of S1P and its receptors in sepsis-induced liver injury

As an immune and metabolic organ, the liver affects the progression and prognosis of sepsis. Despite the severe adverse effects of sepsis liver injury on the body, treatment options remain limited. Sphingosine-1-phosphate (S1P) is a widely distributed lipid signaling molecule that binds to five sphingosine-1-phosphate receptors (S1PR) to regulate downstream signaling pathways involved in the pathophysiological processes of sepsis, including endothelial permeability, cytokine release, and vascular tone. This review summarizes current research on the role of S1P in normal liver biology and describes the mechanisms by which changes in S1P/S1PR affect the development of liver-related diseases. At the same time, the pathological processes underlying liver injury, as evidenced by clinical manifestations during sepsis, were comprehensively reviewed. This paper focused on the mechanistic pathways through which S1P and its receptors modulate immunity, bile acid metabolism, and liver-intestinal circulation in septic liver injury. Finally, the relationships between S1P and its receptors with liver inflammation and metabolism and the use of related drugs for the treatment of liver injury were examined. By elucidating the role of S1P and its receptor in the pathogenesis of sepsis liver injury, this review established a molecular targeting framework, providing novel insights into clinical and drug development.

Sinusoidal communication in chronic liver disease

The liver sinusoid, mainly composed of liver sinusoidal endothelial cells, hepatic macrophages and hepatic stellate cells, shapes the hepatic vasculature and is key to maintaining liver homeostasis and function. During chronic liver disease (CLD), the function of sinusoidal cells is impaired, being directly involved in the progression of liver fibrosis, cirrhosis, and main clinical complications including portal hypertension and hepatocellular carcinoma. In addition to their roles in liver diseases pathobiology, sinusoidal cells' paracrine communication or cross-talk is being studied as a mechanism of disease but also as a remarkable target for treatment. The aim of this review is to gather current knowledge of intercellular signalling in the hepatic sinusoid during the progression of liver disease. We summarise studies developed in pre-clinical models of CLD, especially emphasizing those pathways characterized in human-based clinically relevant models. Finally, we describe pharmacological treatments targeting sinusoidal communication as promising options to treat CLD and its clinical complications.

Anoikis and Mitophagy-Related Gene Signature for Predicting the Survival and Tumor Cell Progression in Colon Cancer

Anoikis is a specialized form of programmed cell death and is also related mitophagy process. We aimed to identify an anoikis and mitophagy-related genes (AMRGs) prognostic model and explore the role of SPHK1 in colon cancer (CC). Bioinformatic methods were used to screen the AMRGs. Based on these genes, all the samples were divided into different subtypes. Furthermore, LASSO was conducted to optimize the AMRGs. Based on the optimal genes, a prognostic risk score model was established and evaluated. Finally, the effects of downregulated SPHK1 on the CC cell proliferation, migration, invasion, and anoikis were investigated. Based on the AMRGs, all the CC samples were divided into subtype 1 and subtype 2. An AMRGs signature containing three key genes (SPHK1, CDC25C, and VPS37A) that exhibiting predicting ability in CC survival is confirmed. Subtype2 and low-risk groups exhibited better survival and higher immune cell infiltration. Moreover, downregulated SPHK1 is related to lower cell proliferation, migration, and invasion ability, as well as higher anoikis in CC cell line (P < 0.01). The AMRGs risk score model exhibits promising predicting ability on patients with CC. SPHK1 might inhibit CC cell growth, migration, and invasion through stimulating anoikis.

An inducible sphingosine kinase 1 in hepatic stellate cells potentiates liver fibrosis

Hepatic stellate cells (HSCs) play a role in hepatic fibrosis and sphingosine kinase (SphK) is involved in biological processes. As studies on the regulatory mechanisms and functions of SphK in HSCs during liver fibrosis are currently limited, this study aimed to elucidate the regulatory mechanism and connected pathways of SphK upon HSC activation. The expression of SphK1 was higher in HSCs than in hepatocytes, and upregulated in activated primary HSCs. SphK1 was also increased in liver homogenates of carbon tetrachloride-treated or bile duct ligated mice and in transforming growth factor-β (TGF-β)-treated LX-2 cells. TGF-β-mediated SphK1 induction was due to Smad3 signaling in LX-2 cells. SphK1 modulation altered the expression of liver fibrogenesis-related genes. This SphK1-mediated profibrogenic effect was dependent on SphK1/sphingosine-1-phosphate/sphingosine-1-phosphate receptor signaling through ERK. Epigallocatechin gallate blocked TGF-β-induced SphK1 expression and hepatic fibrogenesis by attenuating Smad and MAPK activation. SphK1 induced by TGF-β facilitates HSC activation and liver fibrogenesis, which is reversed by epigallocatechin gallate. Accordingly, SphK1 and related signal transduction may be utilized to treat liver fibrosis.

Role of Sphingosine-1-Phosphate Signaling Pathway in Pancreatic Diseases

Sphingosine-1-phosphate (S1P) is a sphingolipid metabolic product produced via the phosphorylation of sphingosine by sphingosine kinases (SPHKs), serving as a powerful modulator of various cellular processes through its interaction with S1P receptors (S1PRs). Currently, this incompletely understood mechanism in pancreatic diseases including pancreatitis and pancreatic cancer, largely limits therapeutic options for these disorders. Recent evidence indicates that S1P significantly contributes to pancreatic diseases by modulating inflammation, promoting pyroptosis in pancreatic acinar cells, regulating the activation of pancreatic stellate cells, and affecting organelle functions in pancreatic cancer cells. Nevertheless, no review has encapsulated these advancements. Thus, this review compiles information about the involvement of S1P signaling in exocrine pancreatic disorders, including acute pancreatitis, chronic pancreatitis, and pancreatic cancer, as well as prospective treatment strategies to target S1P signaling for these conditions. The insights presented here possess the potential to offer valuable guidance for the implementation of therapies targeting S1P signaling in various pancreatic diseases.

Exogenous S1P via S1P receptor 2 induces CTGF expression through Src-RhoA-ROCK-YAP pathway in hepatic stellate cells

BACKGROUND

Hepatic fibrosis, a prevalent chronic liver condition, involves excessive extracellular matrix production associated with aberrant wound healing. Hepatic stellate cells (HSCs) play a pivotal role in liver fibrosis, activated by inflammatory factors such as sphingosine 1-phosphate (S1P). Despite S1P's involvement in fibrosis, its specific role and downstream pathway in HSCs remain controversial.

METHODS

In this study, we investigated the regulatory role of S1P/S1P receptor (S1PR) in Hippo-YAP activation in both LX-2 cell lines and primary HSCs. Real-time PCR, western blot, pharmacological inhibitors, siRNAs, and Rho activity assays were adopted to address the molecular mechanisms of S1P mediated YAP activation.

RESULTS

Serum and exogenous S1P significantly increased the expression of YAP target genes in HSCs. Pharmacologic inhibitors and siRNA-mediated knockdowns of S1P receptors showed S1P receptor 2 (S1PR2) as the primary mediator for S1P-induced CTGF expression in HSCs. Results using siRNA-mediated knockdown, Verteporfin, and Phospho-Tag immunoblots showed that S1P-S1PR2 signaling effectively suppressed the Hippo kinases cascade, thereby activating YAP. Furthermore, S1P increased RhoA activities in cells and ROCK inhibitors effectively blocked CTGF induction. Cytoskeletal-perturbing reagents were shown to greatly modulate CTGF induction, suggesting the important role of actin cytoskeleton in S1P-induced YAP activation. Exogeneous S1P treatment was enough to increase the expression of COL1A1 and α-SMA, that were blocked by YAP specific inhibitor.

CONCLUSIONS

Our data demonstrate that S1P/S1PR2-Src-RhoA-ROCK axis leads to Hippo-YAP activation, resulting in the up-regulation of CTGF, COL1A1 and α-SMA expression in HSCs. Therefore, S1PR2 may represent a potential therapeutic target for hepatic fibrosis.

Exploring the potential of drug repurposing for liver diseases: A comprehensive study

Drug repurposing involves the investigation of existing drugs for new indications. It offers a great opportunity to quickly identify a new drug candidate at a lower cost than novel discovery and development. Despite the importance and potential role of drug repurposing, there is no specific definition that healthcare providers and the World Health Organization credit. Unfortunately, many similar and interchangeable concepts are being used in the literature, making it difficult to collect and analyze uniform data on repurposed drugs. This research was conducted based on understanding general criteria for drug repurposing, concentrating on liver diseases. Many drugs have been investigated for their effect on liver diseases even though they were originally approved (or on their way to being approved) for other diseases. Some of the hypotheses for drug repurposing were first captured from the literature and then processed further to test the hypothesis. Recently, with the revolution in bioinformatics techniques, scientists have started to use drug libraries and computer systems that can analyze hundreds of drugs to give a short list of candidates to be analyzed pharmacologically. However, this study revealed that drug repurposing is a potential aid that may help deal with liver diseases. It provides available or under-investigated drugs that could help treat hepatitis, liver cirrhosis, Wilson disease, liver cancer, and fatty liver. However, many further studies are needed to ensure the efficacy of these drugs on a large scale.

Critical Roles of the Sphingolipid Metabolic Pathway in Liver Regeneration, Hepatocellular Carcinoma Progression and Therapy

The sphingolipid metabolic pathway, an important signaling pathway, plays a crucial role in various physiological processes including cell proliferation, survival, apoptosis, and immune regulation. The liver has the unique ability to regenerate using bioactive lipid mediators involving multiple sphingolipids, including ceramide and sphingosine 1-phosphate (S1P). Dysregulation of the balance between sphingomyelin, ceramide, and S1P has been implicated in the regulation of liver regeneration and diseases, including liver fibrosis and hepatocellular carcinoma (HCC). Understanding and modulating this balance may have therapeutic implications for tumor proliferation, progression, and metastasis in HCC. For cancer therapy, several inhibitors and activators of sphingolipid signaling, including ABC294640, SKI-II, and FTY720, have been discussed. Here, we elucidate the critical roles of the sphingolipid pathway in the regulation of liver regeneration, fibrosis, and HCC. Regulation of sphingolipids and their corresponding enzymes may considerably influence new insights into therapies for various liver disorders and diseases.

Assessment of the Effects of Sphingosine Kinase 1/Sphingosine-1-Phosphate on Microangiogenesis at Rat Myofascial Trigger Points Using Contrast-Enhanced Ultrasonography

Purpose

Few studies have assessed the effects of sphingosine kinase 1/sphingosine-1-phosphate (SPHK1/S1P) on microangiogenesis at rat myofascial trigger points (MTrPs) using contrast-enhanced ultrasonography (CEUS). This study aimed to address these deficiencies. Here, we investigated the effects of SPHK1/S1P on MTrP microangiogenesis and the value of CEUS in evaluating these effects.

Methods

Forty Sprague‒Dawley rats were subdivided into two groups: control and MTrP groups. MTrPs were established by 8 weeks of the strike procedure combined with eccentric motion and 4 weeks of recovery. All rats were euthanized after having undergone CEUS with an overdose of pentobarbital sodium. MTrP and control tissue samples were removed for haematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM) imaging. The tissue was dehydrated, cleared, and embedded before sectioning. The sections were then incubated overnight at 4°C, and immunohistochemistry was carried out with primary antibodies including rabbit anti-CD31, rabbit anti-SPHK1and rabbit anti-S1PR1.

Results

MTrP rats exhibited spontaneous electrical activity (SEA) and a local twitch response (LTR) during electromyography (EMG) examination. The CEUS time-intensity curves (TICs) showed that the perfusion intensity in the MTrPs and surrounding tissue area was increased, with faster perfusion than in normal sites, while the TICs in the control group slowly increased and then slowly decreased. The correlation coefficient between the microvessel density (MVD) and sphingosine 1-phosphate receptor 1 (S1PR1) was 0.716 (p <0.01). Spearman correlation analysis revealed that Spearman's rho (ρ) values between the MVD and peak intensity (PI), between the MVD and area under the curve (AUC), and between the MVD and SPHK1 were > 0.5 (p <0.05), > 0.7 (p <0.01), and > 0.7 (p <0.01), respectively.

Conclusion

CEUS is valuable for detecting microangiogenesis within MTrPs, and SPHK1/S1P plays an important role in promoting MTrP tissue microangiogenesis.

SPHK1/S1P/S1PR pathway promotes the progression of peritoneal fibrosis by mesothelial-mesenchymal transition

Long-term exposure to non-physiologically compatible dialysate inevitably leads to peritoneal fibrosis (PF) in patients undergoing peritoneal dialysis (PD), and there is no effective prevention or treatment for PF. Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid produced after catalysis by sphingosine kinase (SPHK) 1/2 and activates signals through the S1P receptor (S1PR) via autocrine or paracrine. However, the role of SPHK1/S1P/S1PR signaling has never been elucidated in PF. In our research, we investigated S1P levels in peritoneal effluents and demonstrated the role of SPHK1/S1P/S1PR pathway in peritoneal fibrosis. It was found that S1P levels in peritoneal effluents were positively correlated with D/P Cr (r = 0.724, p < .001) and negatively correlated with 4 h ultrafiltration volume (r = -0.457, p < .001). S1PR1 and S1PR3 on peritoneal cells were increased after high glucose exposure in vivo and in vitro. Fingolimod was applied to suppress S1P/S1PR pathway. Fingolimod restored mouse peritoneal function by reducing interstitial hyperplasia, maintaining ultrafiltration volume, reducing peritoneal transport solute rate, and mitigating the protein expression changes of fibronectin, vimentin, α-SMA, and E-cadherin induced by PD and S1P. Fingolimod preserved the morphology of the human peritoneal mesothelial cells, MeT-5A, and moderated the mesothelial-mesenchymal transition (MMT) process. We further delineated that SPHK1 was elevated in peritoneal cells after high glucose exposure and suppression of SPHK1 in MeT-5A cells reduced S1P release. Overexpression of SPHK1 in MeT-5A cells increased S1P levels in the supernatant and fostered the MMT process. PF-543 treatment, targeting SPHK1, alleviated deterioration of mouse peritoneal function. In conclusion, S1P levels in peritoneal effluent were correlated with the deterioration of peritoneal function. SPHK1/S1P/S1PR pathway played an important role in PF.

Targeting long non-coding RNAs in cancer therapy using CRISPR-Cas9 technology: A novel paradigm for precision oncology

Cancer is the second leading cause of death worldwide, despite recent advances in its identification and management. To improve cancer patient diagnosis and care, it is necessary to identify new biomarkers and molecular targets. In recent years, long non-coding RNAs (lncRNAs) have surfaced as important contributors to various cellular activities, with growing proof indicating their substantial role in the genesis, development, and spread of cancer. Their unique expression profiles within specific tissues and their wide-ranging functionalities make lncRNAs excellent candidates for potential therapeutic intervention in cancer management. They are implicated in multiple hallmarks of cancer, such as uncontrolled proliferation, angiogenesis, and immune evasion. This review article explores the innovative application of CRISPR-Cas9 technology in targeting lncRNAs as a cancer therapeutic strategy. The CRISPR-Cas9 system has been widely applied in functional genomics, gene therapy, and cancer research, offering a versatile platform for lncRNA targeting. CRISPR-Cas9-mediated targeting of lncRNAs can be achieved through CRISPR interference, activation or the complete knockout of lncRNA loci. Combining CRISPR-Cas9 technology with high-throughput functional genomics makes it possible to identify lncRNAs critical for the survival of specific cancer subtypes, opening the door for tailored treatments and personalised cancer therapies. CRISPR-Cas9-mediated lncRNA targeting with other cutting-edge cancer therapies, such as immunotherapy and targeted molecular therapeutics can be used to overcome the drug resistance in cancer. The synergy of lncRNA research and CRISPR-Cas9 technology presents immense potential for individualized cancer treatment, offering renewed hope in the battle against this disease.

Long non-coding RNA HOX transcript antisense intergenic RNA depletion protects against alcoholic hepatitis through the microRNA-148a-3p/sphingosine 1-phosphate receptor 1 axis

The aggravating role of long noncoding RNA (lncRNA) HOTAIR has been indicated in liver injury caused by hepatic ischemia/reperfusion. However, under the condition of alcoholic hepatitis (AH), its effects remain unclear. The present study aimed to examine the effect of lncRNA HOTAIR on hepatic stellate cell viability and apoptosis during liver injury caused by AH. In the liver tissues of AH rats, HOTAIR and S1PR1 were overexpressed, and microRNA (miR)-148a-3p was poorly expressed. Loss-of-function assays revealed that silencing of HOTAIR alleviated liver injury in AH by inhibiting the activated phenotype of hepatic stellate cells, inflammation, and fibrosis. Using the bioinformatics databases, dual-luciferase, RIP, and FISH assays, we observed that HOTAIR was mainly localized in the cytoplasm of hepatic stellate cells, and HOTAIR could bind specifically to miR-148a-3p. In addition, miR-148a-3p could target S1PR1 expression. Rescue experiments showed that silencing of miR-148a-3p or overexpression of S1PR1 reversed the alleviating effects of HOTAIR silencing on liver injury. Taken together, our findings revealed that HOTAIR regulates hepatic stellate cell proliferation via the miR-148a-3p/S1PR1 axis in liver injury, which may serve as the basis for developing novel therapeutic strategies to treat AH.

A comprehensive multiomics approach reveals that high levels of sphingolipids in cardiac cachexia adipose tissue are associated with inflammatory and fibrotic changes

Cardiac cachexia is a deadly consequence of advanced heart failure that is characterised by the dysregulation of adipose tissue homeostasis. Once cachexia occurs with heart failure, it prevents the normal treatment of heart failure and increases the risk of death. Targeting adipose tissue is an important approach to treating cardiac cachexia, but the pathogenic mechanisms are still unknown, and there are no effective therapies available. Transcriptomics, metabolomics, and lipidomics were used to examine the underlying mechanisms of cardiac cachexia. Transcriptomics investigation of cardiac cachexia adipose tissue revealed that genes involved in fibrosis and monocyte/macrophage migration were increased and strongly interacted. The ECM-receptor interaction pathway was primarily enriched, as shown by KEGG enrichment analysis. In addition, gene set enrichment analysis revealed that monocyte chemotaxis/macrophage migration and fibrosis gene sets were upregulated in cardiac cachexia. Metabolomics enrichment analysis demonstrated that the sphingolipid signalling pathway is important for adipose tissue remodelling in cardiac cachexia. Lipidomics analysis showed that the adipose tissue of rats with cardiac cachexia had higher levels of sphingolipids, including Cer and S1P. Moreover, combined multiomics analysis suggested that the sphingolipid metabolic pathway was associated with inflammatory-fibrotic changes in adipose tissue. Finally, the key indicators were validated by experiments. In conclusion, this study described a mechanism by which the sphingolipid signalling pathway was involved in adipose tissue remodelling by inducing inflammation and fat fibrosis in cardiac cachexia.

MicroRNAs as the critical regulators of tumor angiogenesis in liver cancer

Liver cancer is one of the most common malignancies in human digestive system. Despite the recent therapeutic methods, there is a high rate of mortality among liver cancer patients. Late diagnosis in the advanced tumor stages can be one of the main reasons for the poor prognosis in these patients. Therefore, investigating the molecular mechanisms of liver cancer can be helpful for the early stage tumor detection and treatment. Vascular expansion in liver tumors can be one of the important reasons for poor prognosis and aggressiveness. Therefore, anti-angiogenic drugs are widely used in liver cancer patients. MicroRNAs (miRNAs) have key roles in the regulation of angiogenesis in liver tumors. Due to the high stability of miRNAs in body fluids, these factors are widely used as the non-invasive diagnostic and prognostic markers in cancer patients. Regarding, the importance of angiogenesis during liver tumor growth and invasion, in the present review, we discussed the role of miRNAs in regulation of angiogenesis in these tumors. It has been reported that miRNAs mainly exert an anti-angiogenic function by regulation of tumor microenvironment, transcription factors, and signaling pathways in liver tumors. This review can be an effective step to suggest the miRNAs for the non-invasive early detection of malignant and invasive liver tumors.

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.

Integrative roles of sphingosine kinase in liver pathophysiology

Bioactive sphingolipids and enzymes that metabolize sphingolipid-related substances have been considered as critical messengers in various signaling pathways. One such enzyme is the crucial lipid kinase, sphingosine kinase (SphK), which mediates the conversion of sphingosine to the potent signaling substance, sphingosine-1-phosphate. Several studies have demonstrated that SphK metabolism is strictly regulated to maintain the homeostatic balance of cells. Here, we summarize the role of SphK in the course of liver disease and illustrate its effects on both physiological and pathological conditions of the liver. SphK has been implicated in a variety of liver diseases, such as steatosis, liver fibrosis, hepatocellular carcinoma, and hepatic failure. This study may advance the understanding of the cellular and molecular foundations of liver disease and establish therapeutic approaches via SphK modulation.

Lipidomics in pathogenesis, progression and treatment of nonalcoholic steatohepatitis (NASH): Recent advances

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disease affecting up to 30% of the general adult population. NAFLD encompasses a histological spectrum ranging from pure steatosis to non-alcoholic steatohepatitis (NASH). NASH can progress to cirrhosis and is becoming the most common indication for liver transplantation, as a result of increasing disease prevalence and of the absence of approved treatments. Lipidomic readouts of liver blood and urine samples from experimental models and from NASH patients disclosed an abnormal lipid composition and metabolism. Collectively, these changes impair organelle function and promote cell damage, necro-inflammation and fibrosis, a condition termed lipotoxicity. We will discuss the lipid species and metabolic pathways leading to NASH development and progression to cirrhosis, as well as and those species that can contribute to inflammation resolution and fibrosis regression. We will also focus on emerging lipid-based therapeutic opportunities, including specialized proresolving lipid molecules and macrovesicles contributing to cell-to-cell communication and NASH pathophysiology.

The Sphingosine 1-Phosphate Axis: an Emerging Therapeutic Opportunity for Endometriosis

Endometriosis is a common condition in women of reproductive age, but its current interventions are unsatisfactory. Recent research discovered a dysregulation of the sphingosine 1-phosphate (S1P) signaling pathway in endometriosis and showed a positive outcome by targeting it. The S1P axis participates in a series of fundamental pathophysiological processes. This narrative review is trying to expound the reported and putative (due to limited reports in this area for now) interactions between the S1P axis and endometriosis in those pathophysiological processes, to provide some perspectives for future research. In short, S1P signaling pathway is highly activated in the endometriotic lesion. The S1P concentration has a surge in the endometriotic cyst fluid and the peritoneal fluid, with the downstream dysregulation of its receptors. The S1P axis plays an essential role in the migration and activation of the immune cells, fibrosis, angiogenesis, pain-related hyperalgesia, and innervation. S1P receptor (S1PR) modulators showed an impressive therapeutic effect by targeting the different S1P receptors in the endometriosis model, and many other conditions resemble endometriosis. And several of them already got approval for clinical application in many diseases, which means a drug repurposing direction and a rapid clinical translation for endometriosis treatments.

Effects of adipocyte-conditioned cell culture media on S1P treatment of human triple-negative breast cancer cells

Sphingosine-1-phosphate (S1P) is a potent sphingolipid metabolite that regulates a wide range of biological functions such as cell proliferation, cell apoptosis and angiogenesis. Its cellular level is elevated in breast cancer, which, in turn, would promote cancer cell proliferation, survival, growth and metastasis. However, the cellular concentration of S1P is normally in the low nanomolar range, and our previous studies showed that S1P selectively induced apoptosis of breast cancer cells at high concentrations (high nanomolar to low micromolar). Thus, local administration of high-concentration S1P alone or in combination of chemotherapy agents could be used to treat breast cancer. The breast mainly consists of mammary gland and connective tissue stroma (adipose), which are dynamically interacting each other. Thus, in the current study, we evaluated how normal adipocyte-conditioned cell culture media (AD-CM) and cancer-associated adipocyte-conditioned cell culture media (CAA-CM) would affect high-concentration S1P treatment of triple-negative breast cancer (TNBC) cells. Both AD-CM and CAA-CM may suppress the anti-proliferative effect and reduce nuclear alteration/apoptosis caused by high-concentration S1P. This implicates that adipose tissue is likely to be detrimental to local high-concentration S1P treatment of TNBC. Because the interstitial concentration of S1P is about 10 times higher than its cellular level, we undertook a secretome analysis to understand how S1P would affect the secreted protein profile of differentiated SGBS adipocytes. At 100 nM S1P treatment, we identified 36 upregulated and 21 downregulated secretome genes. Most of these genes are involved in multiple biological processes. Further studies are warranted to identify the most important secretome targets of S1P in adipocytes and illustrate the mechanism on how these target proteins affect S1P treatment of TNBC.

Single-cell RNA seq identifies Plg-RKT-PLG as signals inducing phenotypic transformation of scar-associated macrophage in liver fibrosis

Hepatic macrophages play a central role in liver fibrosis. Scar-associated macrophages (SAMs), a recently identified subgroup of macrophages, play an important role in this process. However, the mechanism by which SAMs transform during liver fibrosis is still unclear. In this study, we aimed to characterize SAMs and elucidate the underlying mechanism of SAM transformation. Bile duct ligation (BDL) and carbon tetrachloride (CCl₄) were used to induce mouse liver fibrosis. Non-parenchymal cells were isolated from normal/fibrotic livers and were analyzed using single cell RNA sequencing (scRNA-seq) or mass cytometry (CyTOF). The glucan-encapsulated siRNA particles (siRNA-GeRPs) was employed to perform macrophage selective gene knockdown. The results of scRNA-seq and CyTOF revealed that SAMs, which derived from bone marrow-derived macrophages (BMMs), accumulated in mouse fibrotic livers. Further analysis showed that SAMs highly expressed genes related to fibrosis, indicating the pro-fibrotic functions of SAMs. Moreover, plasminogen receptor Plg-R_KT was highly expressed by SAMs, suggesting the role of Plg-R_KT and plasminogen (PLG) in SAM transformation. In vitro, PLG-treated BMMs transformed into SAMs and expressed SAM functional genes. Knockdown of Plg-R_KT blocked the effects of PLG. In vivo, selective knockdown of Plg-R_KT in intrahepatic macrophages of BDL- and CCl₄-treated mice reduced the number of SAMs and alleviated BDL- and CCl₄-induced liver fibrosis, suggesting that Plg-R_KT-PLG played an important role in liver fibrosis by mediating SAM transformation. Our findings reveal that SAMs are crucial participants in liver fibrosis. Inhibition of SAM transformation by blocking Plg-R_KT might be a potential therapeutic target for liver fibrosis.

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.

Therapeutic potential of the sphingosine kinase 1 inhibitor, PF-543

PF-543 is a sphingosine kinase 1（SPHK1）inhibitor developed by Pfizer and is currently considered the most potent selective SPHK1 inhibitor. SPHK1 catalyses the production of sphingosine 1-phosphate (S1P) from sphingosine. It is the rate-limiting enzyme of S1P production, and there is substantial evidence to support a very important role for sphingosine kinase in health and disease. This review is the first to summarize the role and mechanisms of PF-543 as an SPHK1 inhibitor in anticancer, antifibrotic, and anti-inflammatory processes, providing new therapeutic leads and ideas for future research and clinical trials.

Hepatic Stellate Cells: Dictating Outcome in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a fast growing, chronic liver disease affecting ∼25% of the global population. Nonalcoholic fatty liver disease severity ranges from the less severe simple hepatic steatosis to the more advanced nonalcoholic steatohepatitis (NASH). The presence of NASH predisposes individuals to liver fibrosis, which can further progress to cirrhosis and hepatocellular carcinoma. This makes hepatic fibrosis an important indicator of clinical outcomes in patients with NASH. Hepatic stellate cell activation dictates fibrosis development during NASH. Here, we discuss recent advances in the analysis of the profibrogenic pathways and mediators of hepatic stellate cell activation and inactivation, which ultimately determine the course of disease in nonalcoholic fatty liver disease/NASH.

Identifying key multifunctional components shared by critical cancer and normal liver pathways via SparseGMM

Despite the abundance of multimodal data, suitable statistical models that can improve our understanding of diseases with genetic underpinnings are challenging to develop. Here, we present SparseGMM, a statistical approach for gene regulatory network discovery. SparseGMM uses latent variable modeling with sparsity constraints to learn Gaussian mixtures from multiomic data. By combining coexpression patterns with a Bayesian framework, SparseGMM quantitatively measures confidence in regulators and uncertainty in target gene assignment by computing gene entropy. We apply SparseGMM to liver cancer and normal liver tissue data and evaluate discovered gene modules in an independent single-cell RNA sequencing (scRNA-seq) dataset. SparseGMM identifies PROCR as a regulator of angiogenesis and PDCD1LG2 and HNF4A as regulators of immune response and blood coagulation in cancer. Furthermore, we show that more genes have significantly higher entropy in cancer compared with normal liver. Among high-entropy genes are key multifunctional components shared by critical pathways, including p53 and estrogen signaling.

Molecular Advances in MAFLD—A Link between Sphingolipids and Extracellular Matrix in Development and Progression to Fibrosis

Metabolic-Associated Fatty Liver Disease (MAFLD) is a major cause of liver diseases globally and its prevalence is expected to grow in the coming decades. The main cause of MAFLD development is changed in the composition of the extracellular matrix (ECM). Increased production of matrix molecules and inflammatory processes lead to progressive fibrosis, cirrhosis, and ultimately liver failure. In addition, increased accumulation of sphingolipids accompanied by increased expression of pro-inflammatory cytokines in the ECM is closely related to lipogenesis, MAFLD development, and its progression to fibrosis. In our work, we will summarize all information regarding the role of sphingolipids e.g., ceramide and S1P in MAFLD development. These sphingolipids seem to have the most significant effect on macrophages and, consequently, HSCs which trigger the entire cascade of overproduction matrix molecules, especially type I and III collagen, proteoglycans, elastin, and also tissue inhibitors of metalloproteinases, which as a result cause the development of liver fibrosis.

Sphingosine 1-phosphate receptor, a new therapeutic direction in different diseases

Sphingosine 1-phosphate receptor (S1PR), as a kind of G protein-coupled receptor, has five subtypes, including S1PR1, S1PR2, S1PR3, S1PR4, and S1PR5. Sphingosine 1-phosphate receptor (S1P) and S1PR regulate the trafficking of neutrophils and some cells, which has great effects on immune systems, lung tissue, and liver tissue. Presently, many related reports have proved that S1PR has a strong effect on the migration of lymphocytes, tumor cells, neutrophils, and many other cells via the regulation of signals, pathways, and enzymes. In this way, S1PR can regulate the relative response of the organism. Thus, S1PR has become a possible target for the treatment of autoimmune diseases, pulmonary disease, liver disease, and cancer. In this review, we mainly focus on the research of the S1PR for the new therapeutic directions of different diseases and is expected to assist support in the clinic and drug use.

Sphingosine-1-phosphate Attenuates Endoplasmic Reticulum Stress-induced Cardiomyocyte Apoptosis Through Sphingosine-1-phosphate Receptor 1

BACKGROUND

Endoplasmic reticulum stress (ER stress) is involved in the development and progression of various forms of heart disease and may lead to myocardial apoptosis. Sphingosine-1-phosphate (S1P) possesses cardioprotective properties, including anti-apoptosis. However, little is known about the link between S1P and ER stress-induced myocardial apoptosis. This study investigated the regulatory role of S1P in ER stress-induced apoptosis in cardiomyocytes.

METHODS

ER stress and myocardial apoptosis were induced by transverse aortic constriction (TAC) or tunicamycin in mice, which were then treated with 2-acetyl-5-tetrahydroxybutyl imidazole (THI) or S1P. AC16 cells were treated with tunicamycin or thapsigargin, or pretreated with S1P, sphingosine-1-phosphate receptor (S1PR) subtype antagonists, S1PR1 agonist, and PI3K and MEK inhibitors. Cardiac function, the level of S1P in plasma and heart, ER stress markers, cell viability, and apoptosis were detected.

RESULTS

S1P reduced the expression of ER stress-related molecules and ER stress-induced myocardial apoptosis in mice subjected to TAC or an injection of tunicamycin. Furthermore, in AC16 cells exposed to thapsigargin or tunicamycin, S1P decreased the expression of ER stress-related molecules, promoting cell viability and survival. Nevertheless, the S1PR1 antagonist abrogated the protection of S1P. Subsequently, in TAC S1PR1 heterozygous (S1PR1^+/-) mice, S1P had no effect on ER stress and apoptosis in cardiomyocytes. Notably, in vitro, the impact of anti-ER stress-induced myocardial apoptosis by the S1PR1 agonist was reversed by PI3K and MEK inhibitors.

CONCLUSION

This study is the first to demonstrate that S1P relieves ER stress-induced myocardial apoptosis via S1PR1/AKT and S1PR1/ERK1/2, which are potential therapeutic targets for heart disease.

Sphingosine Kinase 1 Mediates Sexual Dimorphism in Fibrosis in a Mouse Model of NASH

OBJECTIVE

Men with non-alcoholic fatty liver disease (NAFLD) are more likely to progress to nonalcoholic steatohepatitis (NASH) and liver fibrosis than women. However, the underlying molecular mechanisms of this dimorphism is unclear. We have previously shown that mice with global deletion of SphK1, the enzyme that produces the bioactive sphingolipid metabolite sphingosine 1-phosphate (S1P), were protected from development of NASH. The aim of this study was to elucidate the role of hepatocyte-specific SphK1 in development of NASH and to compare its contribution to hepatosteatosis in male and female mice.

RESULTS

We generated hepatocyte-specific SphK1 knockout mice (SphK1-hKO). Unlike the global knockout, SphK1-hKO male mice were not protected from diet-induced steatosis, inflammation, or fibrogenesis. In contrast, female SphK1-hKO mice were protected from inflammation. Surprisingly, however, in these female mice, there was a ∼10-fold increase in the fibrosis markers Col1α1 and 2-3 fold induction of alpha smooth muscle actin and the pro-fibrotic chemokine CCL5. Because increased fibrosis in female SphK1-hKO mice occurred despite an attenuated inflammatory response, we investigated the crosstalk between hepatocytes and hepatic stellate cells, central players in fibrosis. We found that estrogen stimulated release of S1P from female hepatocytes preventing TGFβ-induced expression of Col1α1 in HSCs via S1PR3.

CONCLUSIONS

The results revealed a novel pathway of estrogen-mediated cross-talk between hepatocytes and HSCs that may contribute to sex differences in NAFLD through an anti-fibrogenic function of the S1P/S1PR3 axis. This pathway is susceptible to pharmacologic manipulation, which may lead to novel therapeutic strategies.

Dual Targeting of Angipoietin-1 and von Willebrand Factor by microRNA-671-5p Attenuates Liver Angiogenesis and Fibrosis

Angipoietin-1 (Angpt1) and von Willebrand factor (VWF) are two important angiogenic molecules that can drive pathologic angiogenesis and progression of liver fibrosis in our previous study. MicroRNAs (miRs) participate in a variety of physiological and pathological processes, including angiogenesis. However, the critical miRs targeting Angpt1 or VWF and potential molecular mechanism underlying liver fibrosis-associated angiogenesis is not clear yet. Human liver tissues were obtained from patients with different chronic liver diseases. Mouse models of liver fibrosis were induced by injection of CCl₄ or bile duct ligation (BDL) operation. MiR-671-5p was predicted to target Angpt1 and VWF from three databases (miRanda, RNA22v2, and miRwalk). MiR-671-5p expression was decreased in the fibrotic liver of human and mice, with a negative correlation with the levels of Angpt1, VWF, sphingosine kinase-1 (SphK1, the rate-limiting enzyme for sphingosine 1-phosphate [S1P] formation), transforming growth factor β1 (TGFβ1), hypoxia inducible factor (Hif)1α, Hif2α, and fibrosis markers. Importantly, miR-671-5p expression was down-regulated in fluorescence-activated cell sorted liver sinusoidal endothelial cells and hepatic stellate cells (HSCs) in CCl₄ mice compared with control mice. In vitro miR-671-5p expression was also decreased in S1P-stimulated HSCs and TGFβ1-activated liver sinusoidal endothelial cells, negatively correlated with Angpt1 and VWF expression. MiR-671-5p directly targeted Angpt1 and VWF by luciferase reporter assays. In vivo administration of miR-671-5p agomir decreased the messenger RNA and protein levels of Anpgt1 and VWF, and attenuated CCl₄ -induced or BDL-induced liver angiogenesis and fibrosis. Conclusion: We identify the negative regulation of miR-671-5p on Angpt1 and VWF and liver fibrosis-associated angiogenesis, which may provide promising targets for the prevention and treatment of liver disease.

Activated Neutrophils Secrete Chitinase-Like 1 and Attenuate Liver Inflammation by Inhibiting Pro-Inflammatory Macrophage Responses

Excessive activation and recruitment of neutrophils are generally considered to be associated with pathological aggravation of multiple diseases. However, as the role of neutrophils in tissue injury repair is receiving increasing attention, it is necessary to further explore the beneficial role of activated neutrophils in promoting the resolution of inflammation after injury. In this study, we found that activated neutrophils have a crucial function in suppressing liver inflammation. In methionine-choline-deficient and high-fat (MCDHF) diet induced liver inflammation in mice, tail vein injection of activated neutrophils (A-Neu, stimulated by sphingosine 1-phosphate) inhibited the expressions of pro-inflammatory cytokines in the liver, including C-C chemokine motif ligand 4, tumor necrosis factor and nitric oxide synthase 2, and attenuated liver injury. However, non-activated neutrophils (N-Neu) did not have these effects. In vitro, pro-inflammatory macrophages were co-cultured with N-Neu or A-Neu by transwell, respectively. A-Neu was found to suppress the pro-inflammatory phenotype of macrophages by using RT-qPCR, western blot and cytometric bead array. Microarray analysis showed that there were systematic variations in transcript expression levels between N-Neu and A-Neu. GeneVenn software was used to show the gene expression overlap between GO terms including Regulation of Cell Communication, Cytokine Secretion, Inflammatory Response and Extracellular Space clusters. We identified that Chitinase-like 1 (CHIL1) secreted by S1P activated neutrophils may be an important mediators affecting the pro-inflammatory macrophage responses. In the injured liver of mice induced by MCDHF diet, the expression of Chil1 mRNA increased and was positively correlated with the neutrophil marker Ly6g. Moreover, the secretion of CHIL1 in A-Neu increased significantly. Strikingly, the effect of A-Neu on macrophage response was reproduced by incubating pro-inflammatory macrophages with recombinant CHIL1. A-Neu conditioned medium were incubated with CHIL1 antibody-conjugated protein G beads, magnetically separated to immunodepletion CHIL1 from the A-Neu supernatant, which can partially weaken its inhibitory effect of A-Neu on the production of macrophage pro-inflammatory cytokines. Together, the conclusions indicated that A-Neu could inhibit the pro-inflammatory macrophage responses by secreting CHIL1, thereby effectively inhibiting liver inflammation.

Review article: the sphingosine 1 phosphate/sphingosine 1 phosphate receptor axis - a unique therapeutic target in inflammatory bowel disease

BACKGROUND

Ozanimod, a high selective sphingosine 1 phosphate (S1P) receptor (S1PR) 1/5 modulator was approved by the Food and Drug Administration for the treatment of adult patients with moderately to severely active ulcerative colitis. Additional S1PR modulators are being tested in clinical development programmes for both ulcerative colitis and Crohn's disease.

AIM

To provide an overview of advances in understanding S1PRs biology and summarise preclinical and clinical investigations of S1P receptor modulators in chronic inflammatory disease with special emphasis on inflammatory bowel diseases (IBD).

METHODS

We performed a narrative review using PubMed and ClinicalTrials.gov.

RESULTS

Through S1PRs, S1P regulates multiple cellular processes, including proliferation, migration, survival, and vascular barrier integrity. The S1PRs function of regulating lymphocyte trafficking is well known, but new functions of S1PRs expand our knowledge of S1PRs biology. Several S1PR modulators are in clinical development for both ulcerative colitis and Crohn's disease and have shown promise in phase II and III studies with ozanimod now being approved for ulcerative colitis.

CONCLUSIONS

S1P receptor modulators constitute a novel, promising, safe, and convenient strategy for the treatment of IBD.

Fisetin Ameliorates Alcohol-Induced Liver Injury through Regulating SIRT1 and SphK1 Pathway

Alcoholic liver disease (ALD) often leads to hepatitis, hepatic cirrhosis, and even hepatocellular carcinoma. Fisetin has been shown to confer protection against liver injury. Herein, we investigated whether fisetin could prevent ethanol-induced hepatotoxicity. Mice were fed on 5% (v/v) Lieber–DeCarli ethanol diet. Human primary hepatic stellate cells (HSCs) co-cultured with ethanol were used to verify the therapeutic effect of fisetin. The results of alanine/aspartate aminotransferase (ALT/AST), Triglyceride (TG), total cholesterol (TC) in serum, Oil O Red and Masson staining revealed that fisetin (80[Formula: see text]mg/kg) ameliorated ethanol-induced mice liver injury and fibrosis. Besides, immunofluorescence results of [Formula: see text]-SMA revealed that fisetin suppressed HSCs activation. The suppression was dose-dependent. Furthermore, fisetin promoted SIRT1-mediated autophagy and inhibited Sphk1-mediated endoplasmic reticulum stress (ER stress) both in vitro and in vivo. Molecular docking results indicated potential interaction of fisetin with SIRT1 and SphK1. The inhibitory effect of fisetin on HSCs activation was reversed on co-culturing with EX-527, a specific inhibitor against STIR1 overexpression. Thus, fisetin has the potential to ameliorate alcohol-induced liver injury through suppression of HSCs activation, SIRT1-mediated autophagy and Sphk1-mediated ER stress.

Metabolic Reprogramming of Liver Fibrosis

Liver fibrosis is an excessive and imbalanced deposition of fibrous extracellular matrix (ECM) that is associated with the hepatic wound-healing response. It is also the common mechanism that contributes to the impairment of the liver function that is observed in many chronic liver diseases (CLD). Despite the efforts, no effective therapy against fibrosis exists yet. Worryingly, due to the growing obesity pandemic, fibrosis incidence is on the rise. Here, we aim to summarize the main components and mechanisms involved in the progression of liver fibrosis, with special focus on the metabolic regulation of key effectors of fibrogenesis, hepatic stellate cells (HSCs), and their role in the disease progression. Hepatic cells that undergo metabolic reprogramming require a tightly controlled, fine-tuned cellular response, allowing them to meet their energetic demands without affecting cellular integrity. Here, we aim to discuss the role of ribonucleic acid (RNA)-binding proteins (RBPs), whose dynamic nature being context- and stimuli-dependent make them very suitable for the fibrotic situation. Thus, we will not only summarize the up-to-date literature on the metabolic regulation of HSCs in liver fibrosis, but also on the RBP-dependent post-transcriptional regulation of this metabolic switch that results in such important consequences for the progression of fibrosis and CLD.

Sphingosine 1-Phosphate Receptor 4 Promotes Nonalcoholic Steatohepatitis by Activating NLRP3 Inflammasome

BACKGROUND & AIMS

Sphingosine 1-phosphate receptors (S1PRs) are a group of G-protein-coupled receptors that confer a broad range of functional effects in chronic inflammatory and metabolic diseases. S1PRs also may mediate the development of nonalcoholic steatohepatitis (NASH), but the specific subtypes involved and the mechanism of action are unclear.

METHODS

We investigated which type of S1PR isoforms is activated in various murine models of NASH. The mechanism of action of S1PR4 was examined in hepatic macrophages isolated from high-fat, high-cholesterol diet (HFHCD)-fed mice. We developed a selective S1PR4 functional antagonist by screening the fingolimod (2-amino-2-[2-(4- n -octylphenyl)ethyl]-1,3- propanediol hydrochloride)-like sphingolipid-focused library.

RESULTS

The livers of various mouse models of NASH as well as hepatic macrophages showed high expression of S1pr4. Moreover, in a cohort of NASH patients, expression of S1PR4 was 6-fold higher than those of healthy controls. S1pr4^+/- mice were protected from HFHCD-induced NASH and hepatic fibrosis without changes in steatosis. S1pr4 depletion in hepatic macrophages inhibited lipopolysaccharide-mediated Ca⁺⁺ release and deactivated the Nod-like receptor pyrin domain-containning protein 3 (NLRP3) inflammasome. S1P increased the expression of S1pr4 in hepatic macrophages and activated NLRP3 inflammasome through inositol trisphosphate/inositol trisphosphate-receptor-dependent [Ca⁺⁺] signaling. To further clarify the biological function of S1PR4, we developed SLB736, a novel selective functional antagonist of SIPR4. Similar to S1pr4^+/- mice, administration of SLB736 to HFHCD-fed mice prevented the development of NASH and hepatic fibrosis, but not steatosis, by deactivating the NLRP3 inflammasome.

CONCLUSIONS

S1PR4 may be a new therapeutic target for NASH that mediates the activation of NLRP3 inflammasome in hepatic macrophages.

Hepatic macrophages: Key players in the development and progression of liver fibrosis

Hepatic fibrosis is a common pathological process involving persistent liver injury with various etiologies and subsequent inflammatory responses that occur in chronic liver diseases. If left untreated, liver fibrosis can progress to liver cirrhosis, hepatocellular carcinoma and eventually, liver failure. Unfortunately, to date, there is no effective treatment for liver fibrosis, with the exception of liver transplantation. Although the pathophysiology of liver fibrosis is multifactorial and includes the activation of hepatic stellate cells, which are known to drive liver fibrogenesis, hepatic macrophages have emerged as central players in the development of liver fibrosis and regression. Hepatic macrophages, which consist of resident macrophages (Kupffer cells) and monocyte-derived macrophages, have been shown to play an intricate role in the initiation of inflammatory responses to liver injury, progression of fibrosis, and promotion of fibrosis resolution. These features have made hepatic macrophages uniquely attractive therapeutic targets in the fight against hepatic fibrosis. In this review, we synthesised the literature to highlight the functions and regulation of heterogeneity in hepatic macrophages. Furthermore, using the existing findings, we attempt to offer insights into the molecular mechanisms underlying the phenotypic switch from fibrogenic macrophages to restorative macrophages, the regulation of heterogeneity, and modes of action for hepatic macrophages. A better understanding of these mechanisms may guide the development of novel anti-fibrotic therapies (eg macrophage subset-targeted treatments) to combat liver fibrosis in the future.

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

Profile of sphingolipid-related genes and its association with prognosis highlights sphingolipid metabolism in oral cancer

BACKGROUND

Sphingolipids are bioactive lipids that play a role in cancer development. However, the clinical role of sphingolipid (SPL)-related genes in oral cancer (OC) remains not fully understood.

OBJECTIVE

This study, aimed to examine the mRNA expression of 14 sphingolipid-related genes in oral cancer patients and their implication with clinicopathological features and prognosis.

METHODS

qPCR analysis was performed in 50 OC tissues and their matched surgical margins. Next, Kaplan-Meier, Cox regression, and Receiver operating characteristics (ROC) analysis were applied to evaluate the impact of sphingolipid-related genes expression on the prognosis of OC.

RESULTS

The genes SET, ACER3, SK1 and S1PR5 were predominantly up-regulated, while ABCG2, S1PR1, ABCB1 and SPNS2 were down-regulated in OC patients. Analyzing the Cancer Genome Atlas Head-Neck Squamous Cell Carcinoma (TCGA-HNSC) data, which are predominantly composed of OC samples, these genes displayed a similar profile. In OC patients, high levels of SK1 were associated with lymph node metastasis, extracapsular invasion, desmoplasia, locoregional relapse, and disease status. Low levels of SPNS2 were associated with lymph node metastasis, perineural invasion, and disease status. Furthermore, OC and HNSC patients with higher SK1 expression demonstrated shorter disease-free survival (p= 0.0037; p= 0.0087), whereas those with lower SPNS2 expression exhibited shorter overall survival (p= 0.051; p= 0.0012). High levels of ACER3 and low levels of S1PR1 were associated with shorter disease-free and overall survival in HNSC patients.

CONCLUSION

Several sphingolipid-related genes are deregulated in OC at the mRNA level and are associated with clinicopathological features and presented potencial for the prediction of poor prognosis in OC patients.

EGR2-mediated regulation of m6A reader IGF2BP proteins drive RCC tumorigenesis and metastasis via enhancing S1PR3 mRNA stabilization

Emerging discoveries of dynamic and reversible N6-methyladenosine (m⁶A) modification on RNA in mammals have revealed the key roles of the modification in human tumorigenesis. As known m⁶A readers, insulin-like growth factor 2 mRNA-binding proteins (IGF2BPs) are upregulated in most cancers and mediates the enhancement of m⁶A-modified mRNAs stability. However, the mechanisms of IGF2BPs in renal cell cancer (RCC) still remain unclear. Bioinformatic analysis and RT-qPCR were performed to evaluate the expression of IGF2BPs and m⁶A writer Wilms tumor 1-associating protein (WTAP) in RCC samples and its correlation with patient prognosis. In vitro, in vivo biological assays were performed to investigate the functions of IGF2BPs and WTAP in RCC. Chromatin immunoprecipitation-qPCR (ChIP-qPCR) combined with bioinformatics analysis and following western blot assay, dual-luciferase reporter assays were performed to validate the regulatory relationships between transcription factor (TF) early growth response 2 (EGR2) and potential target genes IGF2BPs. RNA sequencing (RNA-seq), methylated RNA immunoprecipitation-qPCR (MERIP-qPCR), RIP-qPCR, m⁶A dot blot, and dual-luciferase reporter assays combined with bioinformatics analysis were employed to screen and validate the direct targets of IGF2BPs and WTAP. Here, we showed that early growth response 2 (EGR2) transcription factor could increase IGF2BPs expression in RCC. IGF2BPs in turn regulated sphingosine-1-phosphate receptor 3 (S1PR3) expression in an m⁶A-dependent manner by enhancing the stability of S1PR3 mRNA. They also promoted kidney tumorigenesis via PI3K/AKT pathway. Furthermore, IGF2BPs and WTAP upregulation predicted poor overall survival in RCC. Our studies showed that the EGR2/IGF2BPs regulatory axis and m⁶A-dependent regulation of S1PR3-driven RCC tumorigenesis, which enrich the m⁶A-modulated regulatory network in renal cell cancer. Together, our findings provide new evidence for the role of N6-methyladenosine modification in RCC.

The role of metabolomics in hepatocellular carcinoma

Background

Hepatocellular carcinoma is the most common primary liver malignancy, with the highest incidence in the developing world, including Egypt. Hepatocellular carcinoma is usually diagnosed in the terminal stage of the disease because of the low sensitivity of the available screening tests. During the process of carcinogenesis, the cellular metabolism is altered to allow cancer cells to adapt to the hypoxic environment and therefore increase anabolic synthesis and survival and avoid the apoptotic death signals. These changes in metabolic status can be tracked by metabolomics analysis.

Main body

Metabolomics is a comprehensive approach for identifying metabolic signatures towards the screening, prediction, and earlier diagnosis of hepatocellular carcinoma with greater efficiency than the conventional diagnostic biomarker. The identification of metabolic changes associated with hepatocellular carcinoma is essential to the understanding of disease pathophysiology and enables better monitoring of high-risk individuals. However, due to the complexity of the metabolic pathways associated with hepatocellular carcinoma, the details of these perturbations are still not adequately characterized. The current status of biomarkers for hepatocellular carcinoma and their insufficiencies and metabolic pathways linked to hepatocellular carcinogenesis are briefly addressed in this mini-review. The review focused on the significantly changed metabolites and pathways associated with hepatocellular carcinoma such as phospholipids, bile acids, amino acids, reactive oxygen species metabolism, and the metabolic changes related to energy production in a cancer cell. The review briefly discusses the sensitivity of metabolomics in the prediction and prognosis of hepatocellular carcinoma and the effect of coexisting multiple etiologies of the disease.

Conclusions

Metabolomics profiling is a potentially promising tool for better predicting, diagnosis, and prognosis of hepatocellular carcinoma.

Angiogenesis-related non-coding RNAs and gastrointestinal cancer

Gastrointestinal (GI) cancers are among the main reasons for cancer death globally. The deadliest types of GI cancer include colon, stomach, and liver cancers. Multiple lines of evidence have shown that angiogenesis has a key role in the growth and metastasis of all GI tumors. Abnormal angiogenesis also has a critical role in many non-malignant diseases. Therefore, angiogenesis is considered to be an important target for improved cancer treatment. Despite much research, the mechanisms governing angiogenesis are not completely understood. Recently, it has been shown that angiogenesis-related non-coding RNAs (ncRNAs) could affect the development of angiogenesis in cancer cells and tumors. The broad family of ncRNAs, which include long non-coding RNAs, microRNAs, and circular RNAs, are related to the development, promotion, and metastasis of GI cancers, especially in angiogenesis. This review discusses the role of ncRNAs in mediating angiogenesis in various types of GI cancers and looks forward to the introduction of mimetics and antagonists as possible therapeutic agents.

Salidroside Inhibits CCl4-Induced Liver Fibrosis in Mice by Reducing Activation and Migration of HSC Induced by Liver Sinusoidal Endothelial Cell-Derived Exosomal SphK1

Sphingosine kinase 1 (SphK1)/Sphingosine-1-phosphate (S1P)/S1PRs signaling pathway is known to involve the advancement of liver fibrosis. Exosomal SphK1 promotes hepatic stellate cells (HSC) migration. Salidroside (Sal) inhibits liver fibrosis, but its mechanism is yet to be elucidated. This study was to explore the influences of Sal on the SphK/S1P/S1PRs signaling pathway in liver fibrosis induced by carbon tetrachloride (CCl₄) in vivo, and investigated the mechanism of Sal affecting the migration and activation of HSC triggered by exosomal SphK1 in vitro. Our data showed that Sal reduced the activities of alanine transaminase (ALT), aspartate aminotransferase (AST) in serum, and hydroxyproline (Hyp) content in the liver tissue. Sal subdued the expression of α-smooth muscle actin (α-SMA), fibronectin (FN) and type I collagen (Col I) of the liver. Sal also reduced mitochondria-induced hepatocyte apoptosis and to inhibit JNK activation. Furthermore, Sal remarkably eradicated the influence of SphK1, SphK2, S1P, and S1PRs triggered by CCl₄, whether stimulating or hindering. Compared with serum-derived exosomes from model group mice, serum-derived exosomes from Sal group mice expressed lower SphK1 and reduced JS 1 (mouse HSC cell line) migration. In addition, Sal was also observed to subdue Col I expression, AKT activation, and LX-2 migration induced by exosomal SphK1 from SK-HEP-1 (a kind of liver sinusoidal endothelial cells (LSEC) cell line). In conclusion, Sal could effectively alleviate liver injury, hepatocyte apoptosis, and liver fibrosis in vivo, providing supports that the protective effects of Sal might be realized by suppressing JNK activation and modulating the SphK/S1P/S1PRs axis. In vitro, it was observed that Sal might alleviate LX-2 migration and activation induced by exosomal SphK1 by inhibiting the AKT activation.

Sphingosine-1-phosphate receptor 3 signaling

Sphingosine-1-phosphate (S1P) is a bioactive lipid which regulates a series of physiological and pathological processes via binding to five S1P receptors (S1PR1-5). Although S1PR1-3 are widely expressed, the study of S1PRs, however, mainly addressed S1PR1 and S1PR2, and few studies focus on S1PR3-5. In recent years, a growing number of studies have shown that S1PR3 plays an important role in cell proliferation, differentiation, apoptosis, and migration, but its function is still controversial. This is the first comprehensive review paper about the role of S1PR3 signaling in cardiovascular function, tissue fibrosis, cancer, immune response, and neurological function. In addition, existing S1PR3 agonists and antagonists are listed at the end of the article, and we also put forward our opinion on the dispute of S1PR3 function.

NLRP3 inflammasome priming and activation in cholestatic liver injury via the sphingosine 1-phosphate/S1P receptor 2/Gα(12/13)/MAPK signaling pathway

NLRP3 inflammasome-driven inflammation represents a key trigger for hepatic fibrogenesis during cholestatic liver injury. However, whether sphingosine 1-phosphate (S1P) plays a role in NLRP3 inflammasome priming and activation remains unknown. Here, we found that the expression of NLRP3 in macrophages and NLRP3 inflammasome activation were significantly elevated in the liver injured by bile duct ligation (BDL). In vitro, S1P promoted the NLRP3 inflammasome priming and activation via S1P receptor 2 (S1PR2) in bone marrow-derived monocyte/macrophages (BMMs). Focusing on BMMs, the gene silencing of Gα12 or Gα13 by specific siRNA suppressed NLRP3 inflammasome priming and pro-inflammatory cytokine (IL-1β and IL-18) secretion, whereas Gα(i/o) and Gαq were not involved in this process. The MAPK signaling pathways (P38, ERK, and JNK) mediated NLRP3 inflammasome priming and IL-1β and IL-18 secretion, whereas blockage of PI3K, ROCK, and Rho family had no such effect. Moreover, JTE-013 (S1PR2 inhibitor) treatment markedly reduced NLRP3 inflammasome priming and activation in BDL-injured liver. Collectively, S1P promotes NLRP3 inflammasome priming and pro-inflammatory cytokines (IL-1β and IL-18) secretion via the S1PR2/Gα(12/13)/MAPK pathway, which may represent an effective therapeutic strategy for liver disease. KEY MESSAGE: • Hepatic NLRP3 expression was significantly elevated in BMMs of BDL-injured mouse liver. • S1P promoted NLRP3 inflammasome priming and activation in BMMs, depending on the S1PR2/Gα(12/13)/MAPK pathway. • Blockade of S1PR2 by JTE-013 reduced NLRP3 inflammasome priming and activation inflammasome in vivo.

Loss of sphingosine 1-phosphate receptor 3 gene function impairs injury-induced stromal angiogenesis in mouse cornea

Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid generated through sphingosine kinase1 (SPK1)-mediated phosphorylation of sphingosine. We show here that injury-induced S1P upregulation increases corneal neovascularization through stimulating S1PR3, a cognate receptor. since this response was suppressed in S1PR3-knockout mice. Furthermore, Cayman10444, a selective S1PR3 inhibitor, reduced this response in WT mice. Such reductions in neovascularization were associated with reduced vascular endothelial growth factor A (VEGF-A) mRNA expression levels in WT TKE2 corneal epithelial cells and macrophages treated with CAY10444 as well as macrophages isolated from S1PR3 KO mice. S1P increased tube-like vessel formation in human vascular endothelial cells (HUVEC) and human retinal microvascular endothelial cells (HRMECs) cells expressing S1PR3. In S1PR3 KO mice, TGFβ1-induced increases in αSMA gene expression levels were suppressed relative to those in the WT counterparts. In S1PR3 deficient macrophages, VEGF-A expression levels were lower than in WT macrophages. Transforming growth factor β1(TGFβ1) upregulated SPK1 expression levels in ocular fibroblasts and TKE2 corneal epithelial cells. CAY10444 blocked S1P-induced increases in VEGF-A mRNA expression levels in TKE2 corneal epithelial cells. Endogenous S1P signaling upregulated VEGF-A and VE-cadherin mRNA expression levels in HUVEC. Unlike in TKE2 cells, SIS3 failed to block TGFβ1-induced VEGF-A upregulation in ocular fibroblasts. Taken together, these results indicate that injury-induced TGFβ1 upregulation increases S1P generation through increases in SPK1 activity. The rise in S1P formation stimulates the S1PR3-linked signaling pathway, which in turn increases VEGF-A expression levels and angiogenesis in mouse corneas.

Sphingosine 1-phosphate signaling in uterine fibroids: implication in activin A pro-fibrotic effect

OBJECTIVE

To explore the link between sphingosine 1-phosphate (S1P) signaling and leiomyoma and the possible S1P cross-talk with the fibrotic effect of activin A.

DESIGN

Case-control laboratory study.

SETTING

University institute and university hospital.

PATIENT(S)

Patients with uterine fibroids (n = 26).

INTERVENTIONS(S)

Tissue specimens of leiomyoma and normal myometrium were obtained from patients undergoing myomectomy or total hysterectomy.

MAIN OUTCOME MEASURE(S)

Expression of mRNA levels of the enzyme involved in S1P metabolism, S1P receptors, and S1P transporter Spns2 was evaluated in matched leiomyoma/myometrium specimens and cell populations. The effects of inhibition of S1P metabolism and signaling was evaluated on activin A-induced fibrotic action in leiomyoma cell lines.

RESULT(S)

The expression of the enzymes responsible for S1P formation, sphingosine kinase (SK) 1 and 2, and S1P₂, S1P₃, and S1P₅ receptors was significantly augmented in leiomyomas compared with adjacent myometrium. In leiomyoma cells, but not in myometrial cells, activin A increased mRNA expression levels of SK1, SK2, and S1P₂. The profibrotic action of activin A was abolished when SK1/2 were inhibited or S1P_2/3 were blocked. Finally, S1P augmented by itself mRNA levels of fibrotic markers (fibronectin, collagen 1A1) and activin A in leiomyomas but not in myometrial cells.

CONCLUSION(S)

This study shows that S1P signaling is dysregulated in uterine fibroids and involved in activin A-induced fibrosis, opening new perspectives for uterine fibroid treatment.

Sphingomyelin synthase 2 loss suppresses steatosis but exacerbates fibrosis in the liver of mice fed with choline-deficient, L-amino acid-defined, high-fat diet

Sphingomyelin synthase 2 (SMS2) regulates sphingomyelin synthesis and contributes to obesity and hepatic steatosis. Here, we investigated the effect of SMS2 deficiency on liver fibrosis in mice fed with choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) or injected with carbon tetrachloride (CCl₄), respectively. SMS2 deficiency suppressed hepatic steatosis, but exacerbated fibrosis induced by CDAHFD feeding. Sphingosine 1-phosphate (S1P), which is a key lipid mediator induces fibrosis in various organs, was increased in the liver of mice fed with CDAHFD. The increase of S1P became prominent by SMS2 deficiency. Meanwhile, SMS2 deficiency had no impact on CCl₄-induced liver injury, fibrosis and S1P levels. Our findings demonstrated that SMS2 deficiency suppresses steatosis but worsens fibrosis in the liver in a specific condition with CDAHFD feeding.