Suppression of ulcerative colitis in mice by orally available inhibitors of sphingosine kinase

A comprehensive review of small molecules, targets, and pathways in ulcerative colitis treatment

Ulcerative colitis (UC), a chronic inflammatory bowel disease (IBD), poses significant clinical challenges because of its complex pathophysiology, long-term nature, and the limited efficacy of existing treatments. Small-molecule compounds, particularly those that are able to modulate inflammation-related signaling pathways and, in many cases, occur in nature, offer a promising alternative or supplement to conventional therapies. Studies on molecules for UC therapeutics reported in 1394 publications over the past 30 years were collected from the Web of Science (WOS) database. Only studies that verified therapeutic efficacy through animal experiments were included. Through an analysis of the molecular classes, structures, common targets, and pathways using network pharmacology, we identified 14 classes of compounds, 5 direct-target modules, and 3 crucial downstream pathways. Alkaloids, phenylpropanoids, flavonoids, and terpenes (and their derivatives) appeared most frequently and mainly targeted lipid metabolism, oxidative stress, immune regulation, signaling transduction, and cancer-related pathways. Notably, there has been an increasing trend of applying naturally sourced compounds in both preclinical and clinical trials, especially flavonoids, over the last five years. Although progress in UC research has been made, the majority of studies have focused on the overall therapeutic effects and biomarker alterations, with limited emphasis on the direct targets and underlying mechanisms. These findings highlight the need to explore novel small-molecule therapeutic strategies for UC, focusing on clearly defined targets and precise modes of action.

Colo-Protective Effects of Pentoxifylline Alone or in Combination With Mesalamine in Colitis Through Sphingosine Kinase 1/Sphingosine 1 Phosphate, and Zonula Occuldin 1 Pathways: New Molecular Approach

Multiple signaling pathways have been implicated in the pathogenesis of ulcerative colitis (UC), including Sphingosine Kinase 1 (SPHK)/Sphingosine-1-Phosphate (S1P), AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/NLR family pyrin domain-containing 3 (NLRP3), zonula occludens-1 (ZO-1), and signal transducer and activator of transcription 3 (STAT3). We aimed to investigate the Colo protective and anti-ulcerative effects of pentoxifylline (PTX) in a rat model of UC. Colitis was induced by intracolonic administration of 2 mL of 3% (v/v) acetic acid (AA). Thirty-five rats were randomly assigned to five groups (n = 7 each): normal control, colitis, mesalamine, PTX, and a combination of PTX plus mesalamine. Disease activity was assessed using the disease activity index, colon weight and length measurements, histological examination, and immunohistochemical detection of caspase-3. Colonic tissue homogenates were analyzed for interleukin-6 (IL-6), S1P, SPHK, mTOR, heme oxygenase-1 (HO-1), nuclear factor erythroid 2-related factor 2 (Nrf2), AMPK, and STAT3 levels. Gene expression of ZO-1 and NLRP3 was also evaluated. Intracolonic AA induced marked functional, biochemical, and inflammatory damage to colonic tissue. Treatment with PTX, mesalamine, or their combination significantly attenuated these effects. Specifically, all treatments reduced levels of IL-6, S1P, SPHK, mTOR, STAT3, NLRP3, and caspase-3, while increasing levels of ZO-1, HO-1, Nrf2, and AMPK. The combination treatment group exhibited near-complete restoration of normal colonic architecture, characterized by intact crypt morphology and minimal fibrosis in the lamina propria. PTX attenuated inflammation, apoptosis, and oxidative stress in colitis, supporting its potential as an adjuvant therapy in UC management.

The role of ACER2 in intestinal sphingolipid metabolism and gastrointestinal cancers

Sphingolipids, particularly sphingosine-1-phosphate (S1P), are bioactive lipids involved in regulating cellular processes such as proliferation, apoptosis, inflammation, and tumor progression. Alkaline ceramidase 2 (ACER2) plays a critical role in sphingolipid metabolism by catalyzing the hydrolysis of ceramide to sphingosine, which is subsequently converted to S1P. Dysregulation of ACER2 has been implicated in various gastrointestinal cancers, including colorectal cancer, gastric cancer, and hepatocellular carcinoma. ACER2-mediated sphingolipid signaling, particularly through the SphK/S1P pathway, influences cancer development by modulating immune responses, inflammation, and the balance between cell survival and death. This review examines the physiological functions of ACER2, and its role in sphingolipid metabolism, and its contribution to the pathogenesis of gastrointestinal cancers. Understanding the mechanisms by which ACER2 regulates tumor progression and immune modulation may open new avenues for targeted therapies in gastrointestinal malignancies.

RELT Is Upregulated in Breast Cancer and Induces Death in Breast Cancer Cells

BACKGROUND

Receptor Expressed in Lymphoid Tissues (RELT) is a TNFRSF member that has two paralogs, RELL1 and RELL2; the three proteins are collectively referred to as RELT family members (RELTfms).

METHODS

We sought to evaluate RELT expression in cancerous cells by using real-time PCR, western blotting, flow cytometry, and immunohistochemistry (IHC). The mechanism of RELT-induced cell death was assessed by western blotting, flow cytometry, luciferase assays, and morphology staining. RELT localization was detected through immunofluorescence and western blotting, and co-immunoprecipitation was used to test whether a mutated RELT interacts with the OXSR1 kinase.

RESULTS

RELT and RELL1 protein expression was significantly elevated in cell lines representing breast and lung cancer, whereas RELL2 protein expression was relatively consistent across different cell lines. The surface expression of RELT was highest in monocytes. IHC staining revealed increased RELT expression in malignant breast cancer biopsies compared to patient-matched benign tissue. RELTfm overexpression induced death in MDA-MB-231 (231) breast cancer cells, accompanied by increased phosphatidylserine externalization and Caspase-3/7 activation. The co-transfection of plasmids predicted to block the phosphorylation of RELT by the OXSR1 kinase did not abrogate RELT-induced apoptosis, indicating that the activation of p38 by RELT through the OXSR1 kinase is not required for RELT-induced cell death. Interestingly, nuclear localization of RELT was detected in 231 and HEK-293 cells.

CONCLUSIONS

These results demonstrate that RELT induces death in breast cancer cells through an apoptotic pathway that does not require OXSR1 phosphorylation and that RELT possesses the ability to translocate to the nucleus, a novel finding that warrants further investigation.

Pentoxifylline in patients with ulcerative colitis treated with mesalamine by modulation of IL-6/STAT3, ZO-1, and S1P pathways: a randomized controlled double-blinded study

BACKGROUND

Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) that lasts a long time and has a variety of causes.

AIM

The primary aim of this study was to evaluate pentoxifylline's (PTX) essential function in patients with UC.

METHODS

Fifty-two mild to moderate UC patients who matched the eligibility requirements participated in this clinical study. One gram of mesalamine (t.i.d.) and a placebo were administered to the mesalamine group (n = 26) for a duration of 24 weeks. Mesalamine 1 g t.i.d. and PTX 400 mg two times daily were administered to the PTX group (n = 26) for 24 weeks. A gastroenterologist investigated patients at the start and 6 months after the medication was given to assess disease activity index (DAI) and numeric pain rating scale (NRS). Also, interleukin-6 (IL-6), sphingosine 1 phosphate (S1P), tumor necrosis factor-alpha (TNF-α), and fecal myeloperoxidase (MPO) were measured before and after therapy. Zonula occuldin-1 (ZO-1) and signal transducer and activator of transcription factor-3 (STAT-3) expression was assessed before and after therapy as well as histological assessment. Short Form 36 Health Survey (SF-36), was assessed for each patient before and after 6 months of treatment.

RESULTS

The PTX group showed statistically lower levels of serum SIP, TNF-α, IL-6, faecal MPO, gene expression of STAT-3, and a significant increase of ZO-1 in comparison with the mesalamine group. DAI and NRS significantly decreased whereas SF-36 significantly increased in the PTX group.

CONCLUSION

PTX could alleviate inflammation in patients with UC, so it might be promising adjunctive for patients with UC.

TRIAL REGISTRATION IDENTIFIER

NCT05558761.

Myrrh Essential Oil Improves DSS-Induced Colitis by Modulating the MAPK Signaling Pathway: In vitro and in vivo Studies

Objective

To explore the mechanism and active components of the anti-colitis effects of myrrh essential oil (MEO).

Methods

In this study, we investigated the anti-inflammatory effects and molecular mechanisms of MEO on dextran sulfate sodium (DSS)-induced colitis with in vitro cell experiments, RNA-seq (RNA Sequencing), Weighted gene co-expression network analysis (WGCNA), combined with "weighting coefficient" network pharmacology, as and in vivo pharmacodynamic experiments. A 3% DSS solution was used to induce colitis in BALB/c mice and MEO was administered orally. We performed gas chromatography-mass spectrometry (GC-MS) analysis of the MEO components. The disease activity index (DAI) was evaluated by observing body weight, fecal characteristics, and blood in the stool of mice. The levels of inflammatory cytokines (TNF-α and IL-1β) in mouse serum were measured using ELISA (Enzyme-linked immunosorbent assay) kits. Additionally, the expression of MAPK-related proteins (JNK, p-JNK, ERK, and p-ERK) in mouse colonic tissues was detected by Western blotting and immunohistochemistry.

Results

MEO (0.0625-0.125µg/g, p.o). significantly inhibited the expression of the inflammatory mediator Nitric oxide (NO) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. After treatment, there was a significant increase in body weight and alleviation of diarrhea and bloody stools in colitis mice. It also reduced inflammatory cell infiltration. Furthermore, it decreased the serum levels of TNF-α and IL-1β, and reduced the activity of p-JNK and p-ERK in the MAPK pathway.

Conclusion

MEO relieved DSS-induced colitis by modulating the MAPK pathway. The experimental results indicate that the MAPK pathway might be inhibited by the synergistic effect of gamma-Muurolene, Curzerene, beta-Elemene, and Furanoeudesma 1.3-diene in MEO, which provides a novel idea for subsequent research and development of new anti-colitis drugs.

Opaganib Downregulates N-Myc Expression and Suppresses In Vitro and In Vivo Growth of Neuroblastoma Cells

Neuroblastoma (NB), the most common cancer in infants and the most common solid tumor outside the brain in children, grows aggressively and responds poorly to current therapies. We have identified a new drug (opaganib, also known as ABC294640) that modulates sphingolipid metabolism by inhibiting the synthesis of sphingosine 1-phosphate (S1P) by sphingosine kinase-2 and elevating dihydroceramides by inhibition of dihydroceramide desaturase. The present studies sought to determine the potential therapeutic activity of opaganib in cell culture and xenograft models of NB. Cytotoxicity assays demonstrated that NB cells, including cells with amplified MYCN, are effectively killed by opaganib concentrations well below those that accumulate in tumors in vivo. Opaganib was shown to cause dose-dependent decreases in S1P and hexosylceramide levels in Neuro-2a cells, while concurrently elevating levels of dihydroceramides. As with other tumor cells, opaganib reduced c-Myc and Mcl-1 protein levels in Neuro-2a cells, and also reduced the expression of the N-Myc protein. The in vivo growth of xenografts of human SK-N-(BE)2 cells with amplified MYCN was suppressed by oral administration of opaganib at doses that are well tolerated in mice. Combining opaganib with temozolomide plus irinotecan, considered the backbone for therapy of relapsed or refractory NB, resulted in increased antitumor activity in vivo compared with temozolomide plus irinotecan or opaganib alone. Mice did not lose additional weight when opaganib was combined with temozolomide plus irinotecan, indicating that the combination is well tolerated. Opaganib has additive antitumor activity toward Neuro-2a tumors when combined with the checkpoint inhibitor anti-CTLA-4 antibody; however, the combination of opaganib with anti-PD-1 or anti-PD-L1 antibodies did not provide increased antitumor activity over that seen with opaganib alone. Overall, the data demonstrate that opaganib modulates sphingolipid metabolism and intracellular signaling in NB cells and inhibits NB tumor growth alone and in combination with other anticancer drugs. Amplified MYCN does not confer resistance to opaganib, and, in fact, the drug attenuates the expression of both c-Myc and N-Myc. The safety of opaganib has been established in clinical trials with adults with advanced cancer or severe COVID-19, and so opaganib has excellent potential for treating patients with NB, particularly in combination with temozolomide and irinotecan or anti-CTLA-4 antibody.

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

Therapeutic Potential for Sphingolipids in Inflammatory Bowel Disease and Colorectal Cancer

Inflammatory bowel disease (IBD), characterized by chronic inflammation in the intestinal tract, increases the risk for the development of colorectal cancer (CRC). Sphingolipids, which have been implicated in IBD and CRC, are a class of bioactive lipids that regulate cell signaling, differentiation, apoptosis, inflammation, and survival. The balance between ceramide (Cer), the central sphingolipid involved in apoptosis and differentiation, and sphingosine-1-phosphate (S1P), a potent signaling molecule involved in proliferation and inflammation, is vital for the maintenance of normal cellular function. Altered sphingolipid metabolism has been implicated in IBD and CRC, with many studies highlighting the importance of S1P in inflammatory signaling and pro-survival pathways. A myriad of sphingolipid analogues, inhibitors, and modulators have been developed to target the sphingolipid metabolic pathway. In this review, the efficacy and therapeutic potential for modulation of sphingolipid metabolism in IBD and CRC will be discussed.

The Sphingolipid-Modulating Drug Opaganib Protects against Radiation-Induced Lung Inflammation and Fibrosis: Potential Uses as a Medical Countermeasure and in Cancer Radiotherapy

Fibrosis is a chronic pathology resulting from excessive deposition of extracellular matrix components that leads to the loss of tissue function. Pulmonary fibrosis can follow a variety of diverse insults including ischemia, respiratory infection, or exposure to ionizing radiation. Consequently, treatments that attenuate the development of debilitating fibrosis are in desperate need across a range of conditions. Sphingolipid metabolism is a critical regulator of cell proliferation, apoptosis, autophagy, and pathologic inflammation, processes that are all involved in fibrosis. Opaganib (formerly ABC294640) is the first-in-class investigational drug targeting sphingolipid metabolism for the treatment of cancer and inflammatory diseases. Opaganib inhibits key enzymes in sphingolipid metabolism, including sphingosine kinase-2 and dihydroceramide desaturase, thereby reducing inflammation and promoting autophagy. Herein, we demonstrate in mouse models of lung damage following exposure to ionizing radiation that opaganib significantly improved long-term survival associated with reduced lung fibrosis, suppression of granulocyte infiltration, and reduced expression of IL-6 and TNFα at 180 days after radiation. These data further demonstrate that sphingolipid metabolism is a critical regulator of fibrogenesis, and specifically show that opaganib suppresses radiation-induced pulmonary inflammation and fibrosis. Because opaganib has demonstrated an excellent safety profile during clinical testing in other diseases (cancer and COVID-19), the present studies support additional clinical trials with this drug in patients at risk for pulmonary fibrosis.

Altered metabolome and microbiome features provide clues in predicting recurrence of ulcerative colitis

PURPOSE

Many studies have shown that the imbalance of the intestinal flora and metabolite can lead to the development of ulcerative colitis (UC), but their role in recurrent-UC is still unclear. We studied the intestinal flora and metabolites associated with recurrent-UC to elucidate the mechanism and biomarkers of recurrent-UC.

METHODS

Ulcerative colitis (UC) models in active, remission, and recurrence stages were established, and the abundance of intestinal flora was determined by 16 S rRNA sequencing. The changes in the metabolites present in feces and serum were analyzed by UPLC-MS/MS.

RESULTS

We identified 24 metabolites in feces and serum, which might be used as diagnostic and predictive biomarkers of recurrent-UC. The dominant flora of recurrent-UC included Romboutsia, UCG-005, etc. The results of a network analysis found that long-chain fatty acids and phenylalanine were strongly correlated with Firmicutes and Proteobacteria, which indicated that the recurrence of UC might be closely related to metabolites and microorganisms.

CONCLUSION

The changes in intestinal microbiota and metabolites are closely related to the development of UC. Microbiota is an important inducer of UC, which can regulate metabolites through the 'microorganism-gut-metabolite' axis. It may provide a new method for the prediction and treatment of UC.

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.

Natural Products and Small Molecules Targeting Cellular Ceramide Metabolism to Enhance Apoptosis in Cancer Cells

Molecular targeting strategies have been used for years in order to control cancer progression and are often based on targeting various enzymes involved in metabolic pathways. Keeping this in mind, it is essential to determine the role of each enzyme in a particular metabolic pathway. In this review, we provide in-depth information on various enzymes such as ceramidase, sphingosine kinase, sphingomyelin synthase, dihydroceramide desaturase, and ceramide synthase which are associated with various types of cancers. We also discuss the physicochemical properties of well-studied inhibitors with natural product origins and their related structures in terms of these enzymes. Targeting ceramide metabolism exhibited promising mono- and combination therapies at preclinical stages in preventing cancer progression and cemented the significance of sphingolipid metabolism in cancer treatments. Targeting ceramide-metabolizing enzymes will help medicinal chemists design potent and selective small molecules for treating cancer progression at various levels.

The therapeutic potential of sphingolipids for cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide and Inflammation plays a critical role in the development of CVD. Despite considerable progress in understanding the underlying mechanisms and various treatment options available, significant gaps in therapy necessitate the identification of novel therapeutic targets. Sphingolipids are a family of lipids that have gained attention in recent years as important players in CVDs and the inflammatory processes that underlie their development. As preclinical studies have shown that targeting sphingolipids can modulate inflammation and ameliorate CVDs, targeting sphingolipids has emerged as a promising therapeutic strategy. This review discusses the current understanding of sphingolipids' involvement in inflammation and cardiovascular diseases, the existing therapeutic approaches and gaps in therapy, and explores the potential of sphingolipids-based drugs as a future avenue for CVD treatment.

A temporal classifier predicts histopathology state and parses acute-chronic phasing in inflammatory bowel disease patients

Previous studies have conducted time course characterization of murine colitis models through transcriptional profiling of differential expression. We characterize the transcriptional landscape of acute and chronic models of dextran sodium sulfate (DSS) and adoptive transfer (AT) colitis to derive temporal gene expression and splicing signatures in blood and colonic tissue in order to capture dynamics of colitis remission and relapse. We identify sub networks of patient-derived causal networks that are enriched in these temporal signatures to distinguish acute and chronic disease components within the broader molecular landscape of IBD. The interaction between the DSS phenotype and chronological time-point naturally defines parsimonious temporal gene expression and splicing signatures associated with acute and chronic phases disease (as opposed to ordinary time-specific differential expression/splicing). We show these expression and splicing signatures are largely orthogonal, i.e. affect different genetic bodies, and that using machine learning, signatures are predictive of histopathological measures from both blood and intestinal data in murine colitis models as well as an independent cohort of IBD patients. Through access to longitudinal multi-scale profiling from disease tissue in IBD patient cohorts, we can apply this machine learning pipeline to generation of direct patient temporal multimodal regulatory signatures for prediction of histopathological outcomes.

Unveiling the biological role of sphingosine-1-phosphate receptor modulators in inflammatory bowel diseases

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract that has a high epidemiological prevalence worldwide. The increasing disease burden worldwide, lack of response to current biologic therapeutics, and treatment-related immunogenicity have led to major concerns regarding the clinical management of IBD patients and treatment efficacy. Understanding disease pathogenesis and disease-related molecular mechanisms is the most important goal in developing new and effective therapeutics. Sphingosine-1-phosphate (S1P) receptor (S1PR) modulators form a class of oral small molecule drugs currently in clinical development for IBD have shown promising effects on disease improvement. S1P is a sphingosine-derived phospholipid that acts by binding to its receptor S1PR and is involved in the regulation of several biological processes including cell survival, differentiation, migration, proliferation, immune response, and lymphocyte trafficking. T lymphocytes play an important role in regulating inflammatory responses. In inflamed IBD tissue, an imbalance between T helper (Th) and regulatory T lymphocytes and Th cytokine levels was found. The S1P/S1PR signaling axis and metabolism have been linked to inflammatory responses in IBD. S1P modulators targeting S1PRs and S1P metabolism have been developed and shown to regulate inflammatory responses by affecting lymphocyte trafficking, lymphocyte number, lymphocyte activity, cytokine production, and contributing to gut barrier function.

The Sphingosine Kinase 2 Inhibitor Opaganib Protects Against Acute Kidney Injury in Mice

Introduction

Acute kidney injury (AKI) is a common multifactorial adverse effect of surgery, circulatory obstruction, sepsis or drug/toxin exposure that often results in morbidity and mortality. Sphingolipid metabolism is a critical regulator of cell survival and pathologic inflammation processes involved in AKI. Opaganib (also known as ABC294640) is a first-in-class experimental drug targeting sphingolipid metabolism that reduces the production and activity of inflammatory cytokines and, therefore, may be effective to prevent and treat AKI.

Methods

Murine models of AKI were used to assess the in vivo efficacy of opaganib including ischemia-reperfusion (IR) injury induced by either transient bilateral occlusion of renal blood flow (a moderate model) or nephrectomy followed immediately by occlusion of the contralateral kidney (a severe model) and lipopolysaccharide (LPS)-induced sepsis. Biochemical and histologic assays were used to quantify the effects of oral opaganib treatment on renal damage in these models.

Results

Opaganib suppressed the elevations of creatinine and blood urea nitrogen (BUN), as well as granulocyte infiltration into the kidneys, of mice that experienced moderate IR from transient bilateral ligation. Opaganib also markedly decreased these parameters and completely prevented mortality in the severe renal IR model. Additionally, opaganib blunted the elevations of BUN, creatinine and inflammatory cytokines following exposure to LPS.

Conclusion

The data support the hypotheses that sphingolipid metabolism is a key mediator of renal inflammatory damage following IR injury and sepsis, and that this can be suppressed by opaganib. Because opaganib has already undergone clinical testing in other diseases (cancer and Covid-19), the present studies support conducting clinical trials with this drug with surgical or septic patients at risk for AKI.

Opaganib Protects against Radiation Toxicity: Implications for Homeland Security and Antitumor Radiotherapy

Exposure to ionizing radiation (IR) is a lingering threat from accidental or terroristic nuclear events, but is also widely used in cancer therapy. In both cases, host inflammatory responses to IR damage normal tissue causing morbidity and possibly mortality to the victim/patient. Opaganib, a first-in-class inhibitor of sphingolipid metabolism, has broad anti-inflammatory and anticancer activity. Opaganib elevates ceramide and reduces sphingosine 1-phosphate (S1P) in cells, conditions that increase the antitumor efficacy of radiation while concomitantly suppressing inflammatory damage to normal tissue. Therefore, opaganib may suppress toxicity from unintended IR exposure and improve patient response to chemoradiation. To test these hypotheses, we first examined the effects of opaganib on the toxicity and antitumor activity of radiation in mice exposed to total body irradiation (TBI) or IR with partial bone marrow shielding. Oral treatment with opaganib 2 h before TBI shifted the LD75 from 9.5 Gy to 11.5 Gy, and provided substantial protection against gastrointestinal damage associated with suppression of radiation-induced elevations of S1P and TNFα in the small intestines. In the partially shielded model, opaganib provided dose-dependent survival advantages when administered 4 h before or 24 h after radiation exposure, and was particularly effective when given both prior to and following radiation. Relevant to cancer radiotherapy, opaganib decreased the sensitivity of IEC6 (non-transformed mouse intestinal epithelial) cells to radiation, while sensitizing PAN02 cells to in vitro radiation. Next, the in vivo effects of opaganib in combination with radiation were examined in a syngeneic tumor model consisting of C57BL/6 mice bearing xenografts of PAN02 pancreatic cancer cells and a cross-species xenograft model consisting of nude mice bearing xenografts of human FaDu cells. Mice were treated with opaganib and/or IR (plus cisplatin in the case of FaDu tumors). In both tumor models, the optimal suppression of tumor growth was attained by the combination of opaganib with IR (± cisplatin). Overall, opaganib substantially protects normal tissue from radiation damage that may occur through unintended exposure or cancer radiotherapy.

Recent Progress in the Development of Opaganib for the Treatment of Covid-19

The Covid-19 pandemic driven by the SARS-CoV-2 virus continues to exert extensive humanitarian and economic stress across the world. Although antivirals active against mild disease have been identified recently, new drugs to treat moderate and severe Covid-19 patients are needed. Sphingolipids regulate key pathologic processes, including viral proliferation and pathologic host inflammation. Opaganib (aka ABC294640) is a first-in-class clinical drug targeting sphingolipid metabolism for the treatment of cancer and inflammatory diseases. Recent work demonstrates that opaganib also has antiviral activity against several viruses including SARS-CoV-2. A recently completed multinational Phase 2/3 clinical trial of opaganib in patients hospitalized with Covid-19 demonstrated that opaganib can be safely administered to these patients, and more importantly, resulted in a 62% decrease in mortality in a large subpopulation of patients with moderately severe Covid-19. Furthermore, acceleration of the clearance of the virus was observed in opaganib-treated patients. Understanding the biochemical mechanism for the anti-SARS-CoV-2 activity of opaganib is essential for optimizing Covid-19 treatment protocols. Opaganib inhibits three key enzymes in sphingolipid metabolism: sphingosine kinase-2 (SK2); dihydroceramide desaturase (DES1); and glucosylceramide synthase (GCS). Herein, we describe a tripartite model by which opaganib suppresses infection and replication of SARS-CoV-2 by inhibiting SK2, DES1 and GCS. The potential impact of modulation of sphingolipid signaling on multi-organ dysfunction in Covid-19 patients is also discussed.

Sphingosine Kinase 2 Inhibitors: Rigid Aliphatic Tail Derivatives Deliver Potent and Selective Analogues

Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with five native G-protein coupled receptors (S1P1–5) to regulate cell growth, survival, and proliferation. S1P has been implicated in a variety of pathologies including cancer, kidney fibrosis, and multiple sclerosis. As key mediators in the synthesis of S1P, sphingosine kinase (SphK) isoforms 1 and 2 have attracted attention as viable targets for pharmacologic intervention. In this report, we describe the design, synthesis, and biological evaluation of sphingosine kinase 2 (SphK2) inhibitors with a focus on systematically introducing rigid structures in the aliphatic lipid tail present in existing SphK2 inhibitors. Experimental as well as molecular modeling studies suggest that conformationally restricted “lipophilic tail” analogues bearing a bulky terminal moiety or an internal phenyl ring are useful to complement the “J”-shaped sphingosine binding pocket of SphK2. We identified 14c (SLP9101555) as a potent SphK2 inhibitor (K_i = 90 nM) with 200-fold selectivity over SphK1. Molecular docking studies indicated key interactions: the cyclohexyl ring binding in the cleft deep in the pocket, a trifluoromethyl group fitting in a small side cavity, and a hydrogen bond between the guanidino group and Asp308 (amino acid numbering refers to human SphK2 (isoform c) orthologue). In vitro studies using U937 human histiocytic lymphoma cells showed marked decreases in extracellular S1P levels in response to our SphK2 inhibitors. Administration of 14c (dose: 5 mg/kg) to mice resulted in a sustained increase of circulating S1P levels, suggesting target engagement.

Opaganib in COVID-19 pneumonia: Results of a randomized, placebo-controlled Phase 2a trial

Background

Opaganib, an oral sphingosine kinase-2 inhibitor with antiviral and anti-inflammatory properties, was shown to inhibit severe acute respiratory syndrome coronavirus 2 replication in vitro. We thus considered that opaganib could be beneficial for moderate to severe coronavirus disease 2019 (COVID-19) pneumonia. The objective of the study was to evaluate the safety of opaganib and its effect on supplemental oxygen requirements and time to hospital discharge in COVID-19 pneumonia hospitalized patients requiring supplemental oxygen.

Methods

This Phase 2a, randomized, double-blind, placebo-controlled study was conducted between July and December 2020 in 8 sites in the United States. Forty-two enrolled patients received opaganib (n = 23) or placebo (n = 19) added to standard of care for up to 14 days and were followed up for 28 days after their last dose of opaganib/placebo.

Results

There were no safety concerns arising in this study. The incidence of ≥Grade 3 treatment-emergent adverse events was 17.4% and 33.3% in the opaganib and placebo groups, respectively. Three deaths occurred in each group. A numerical advantage for opaganib over placebo was observed in in this nonpowered study reflected by total supplemental oxygen requirement from baseline to Day 14, the requirement for supplemental oxygen for at least 24 hours by Day 14, and hospital discharge.

Conclusions

In this proof-of-concept study, hypoxic, hospitalized patients receiving oral opaganib had a similar safety profile to placebo-treated patients, with preliminary evidence of benefit for opaganib as measured by supplementary oxygen requirement and earlier hospital discharge. These findings support further evaluation of opaganib in this population.

Lipids in Liver Failure Syndromes: A Focus on Eicosanoids, Specialized Pro-Resolving Lipid Mediators and Lysophospholipids

Lipids are organic compounds insoluble in water with a variety of metabolic and non-metabolic functions. They not only represent an efficient energy substrate but can also act as key inflammatory and anti-inflammatory molecules as part of a network of soluble mediators at the interface of metabolism and the immune system. The role of endogenous bioactive lipid mediators has been demonstrated in several inflammatory diseases (rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, cancer). The liver is unique in providing balanced immunotolerance to the exposure of bacterial components from the gut transiting through the portal vein and the lymphatic system. This balance is abruptly deranged in liver failure syndromes such as acute liver failure and acute-on-chronic liver failure. In these syndromes, researchers have recently focused on bioactive lipid mediators by global metabonomic profiling and uncovered the pivotal role of these mediators in the immune dysfunction observed in liver failure syndromes explaining the high occurrence of sepsis and subsequent organ failure. Among endogenous bioactive lipids, the mechanistic actions of three classes (eicosanoids, pro-resolving lipid mediators and lysophospholipids) in the pathophysiological modulation of liver failure syndromes will be the topic of this narrative review. Furthermore, the therapeutic potential of lipid-immune pathways will be described.

Inactivation of AUF1 in Myeloid Cells Protects From Allergic Airway and Tumor Infiltration and Impairs the Adenosine-Induced Polarization of Pro-Angiogenic Macrophages

The four isoforms of the RNA-binding protein hnRNPD/AUF1 have been proposed to limit the use of inflammatory mRNAs in innate immune cells. Mice engineered to lack AUF1s in all tissues are sensitive to acute inflammatory assaults; however, they also manifest complex degenerations obscuring assessment of AUF1s’ roles in innate immune cells. Here, we restricted a debilitating AUF1 mutation to the mouse myeloid lineage and performed disease-oriented phenotypic analyses to assess the requirement of AUF1s in variable contexts of innate immune reactivity. Contrary to the whole-body mutants, the myeloid mutants of AUF1s did not show differences in their susceptibility to cytokine storms occurring during endotoxemia; neither in type-I cell-mediated reactions driving intestinal inflammation by chemical irritants. Instead, they were resistant to allergic airway inflammation and displayed reductions in inflammatory infiltrates and an altered T-helper balance. The ex-vivo analysis of macrophages revealed that the loss of AUF1s had a minimal effect on their proinflammatory gene expression. Moreover, AUF1s were dispensable for the classical polarization of cultured macrophages by LPS & IFNγ correlating with the unchanged response of mutant mice to systemic and intestinal inflammation. Notably, AUF1s were also dispensable for the alternative polarization of macrophages by IL4, TGFβ and IL10, known to be engaged in allergic reactions. In contrast, they were required to switch proinflammatory macrophages towards a pro-angiogenic phenotype induced by adenosine receptor signals. Congruent to this, the myeloid mutants of AUF1 displayed lower levels of vascular remodeling factors in exudates from allergen exposed lungs; were unable to support the growth and inflammatory infiltration of transplanted melanoma tumors; and failed to vascularize inert grafts unless supplemented with angiogenic factors. Mechanistically, adenosine receptor signals enhanced the association of AUF1s with the Vegfa, Il12b, and Tnf mRNAs to differentially regulate and facilitate the pro-angiogenic switch. Our data collectively demonstrates that AUF1s do not act as general anti-inflammatory factors in innate immune cells but have more specialized roles in regulons allowing specific innate immune cell transitions to support tissue infiltration and remodeling processes.

Testing the Effect of Curcumin on Proliferative Capacity of Colorectal Cancer Cells

This chapter presents a protocol for studying the effects of curcumin in a colorectal cell line and a mouse model of colitis-associated colon carcinogenesis. The protocol using the CT26 cell line incorporates cell proliferation, migration, invasion, spheroid formation, cell cycle, polymerase chain reaction (PCR), and western blot analyses. For the mouse model, this involved a macroscopic and histological examination of the colon and assays for oxidative damage markers.

Signaling through the S1P-S1PR Axis in the Gut, the Immune and the Central Nervous System in Multiple Sclerosis: Implication for Pathogenesis and Treatment

Sphingosine 1-phosphate (S1P) is a signaling molecule with complex biological functions that are exerted through the activation of sphingosine 1-phosphate receptors 1–5 (S1PR1–5). S1PR expression is necessary for cell proliferation, angiogenesis, neurogenesis and, importantly, for the egress of lymphocytes from secondary lymphoid organs. Since the inflammatory process is a key element of immune-mediated diseases, including multiple sclerosis (MS), S1PR modulators are currently used to ameliorate systemic immune responses. The ubiquitous expression of S1PRs by immune, intestinal and neural cells has significant implications for the regulation of the gut–brain axis. The dysfunction of this bidirectional communication system may be a significant factor contributing to MS pathogenesis, since an impaired intestinal barrier could lead to interaction between immune cells and microbiota with a potential to initiate abnormal local and systemic immune responses towards the central nervous system (CNS). It appears that the secondary mechanisms of S1PR modulators affecting the gut immune system, the intestinal barrier and directly the CNS, are coordinated to promote therapeutic effects. The scope of this review is to focus on S1P−S1PR functions in the cells of the CNS, the gut and the immune system with particular emphasis on the immunologic effects of S1PR modulation and its implication in MS.

S1P signaling, its interactions and cross-talks with other partners and therapeutic importance in colorectal cancer

Sphingosine-1-Phosphate (S1P) plays an important role in normal physiology, inflammation, initiation and progression of cancer. Deregulation of S1P signaling causes aberrant proliferation, affects survival, leads to angiogenesis and metastasis. Sphingolipid rheostat is crucial for cellular homeostasis. Discrepancy in sphingolipid metabolism is linked to cancer and drug insensitivity. Owing to these diverse functions and being a potent mediator of tumor growth, S1P signaling might be a suitable candidate for anti-tumor therapy or combination therapy. In this review, with a focus on colorectal cancer we have summarized the interacting partners of S1P signaling pathway, its therapeutic approaches along with the contribution of S1P signaling to various cancer hallmarks.

Synergistic effects of hydro extract of jujube fruit in combination with Mesalazine (orally) and Asacol (intra-colonic) administration in ameliorating animal model of ulcerative colitis

This study was done to investigate the synergistic impacts hydro extract of jujube fruit in combination with Mesalazine (orally) and Asacol (intra-colonic) administration in ameliorating animal model of ulcerative colitis (UC). After the induction of UC and with the development of signs, the treatment groups daily received the hydro extract of jujube fruit (200 mg/kg, orally, enema), Mesalazine (30 mg/kg, orally) and Asacol (10 mg/kg, enema). After 10 days, rats were euthanized and were studied. Findings indicated a significant increase in Myeloperoxidase (161.66 ± 10.40), Nitric oxide (216.01 ± 17.55), IL-6 (138.54 ± 7.02), and TNF-α (123.87 ± 9.80) colon tissue levels and pathological damage of positive control group compared with the negative control group. Hydro extract of jujube fruit in combination with Mesalazine (orally) and Asacol (intra-colonic) group represented a higher capability in significantly decreasing Myeloperoxidase (73.33 ± 9.07), Nitric oxide (81.66 ± 10.50), IL-6 (51.69 ± 5.19), TNF-α (30.59 ± 5.50) levels and pathological damage in compared with the other treatment groups. Considering accessibility and affordability of jujube fruit and the side effects of routine drugs, taking a combination of jujube fruit with low doses of routine pharmaceutical drugs can improve and cure ulcerative colitis disease.

Metformin alleviates inflammation in oxazolone induced ulcerative colitis in rats: plausible role of sphingosine kinase 1/sphingosine 1 phosphate signaling pathway

OBJECTIVES

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that is associated with high sphingosine kinase 1(SPHK1) expression in the colon, however its role in pathogenesis of UC is not clearly understood so, the aim of the present study was to clarify the role of SPHK1 and investigate whether the anti-inflammatory effects of metformin in UC is mediated by Sphingosine kinase 1/sphingosine 1 phosphate (S1P) signaling pathway.

MATERIAL AND METHODS

Colitis was induced in adult male wistar rats by intra rectal administration of oxazolone in the fifth and seventh days from initial presensitization. Oxazolone treated rats were divided into untreated oxazolone group, metformin and mesalazine treated groups both in a dose of 100 mg/kg/day orally for 21 days. Along with these groups normal control and saline groups were used .Colitis was assessed by colon length, disease activity index (DAI) and histological examination of colontissue. Plasma samples were used to measure S1P.SPHK1 activity, signal transducer and activator of transcription -3(STAT-3), interleukin-6 (IL-6), nitric oxide (NO), myeloperoxidase activity (MPO), reduced glutathione (GSH) and tissue expression of intracellular cell adhesion molecule -1(ICAM-1) and caspase-3 genes were measured in tissue.

RESULTS

Metformin successfully attenuated oxazolone colitis by increasing colon length, decreasing DAI and improved colon histologic picture. Metformin also induced a significant decrease in Plasma SIP, SPHK1 activity, inflammatory, oxidative stress markers, ICAM-1 and Caspase-3 genes expression compared to oxazolone group.

CONCLUSION

It is revealed that metformin alleviated inflammation and underlying mechanism may result from inhibition of SPHK1/S1P signaling pathway.

Bioactive sphingolipids: Advancements and contributions from the laboratory of Dr. Lina M. Obeid

Sphingolipids and their synthetic enzymes have emerged as critical mediators in numerous diseases including inflammation, aging, and cancer. One enzyme in particular, sphingosine kinase (SK) and its product sphingosine-1-phosphate (S1P), has been extensively implicated in these processes. SK catalyzes the phosphorylation of sphingosine to S1P and exists as two isoforms, SK1 and SK2. In this review, we will discuss the contributions from the laboratory of Dr. Lina M. Obeid that have defined the roles for several bioactive sphingolipids in signaling and disease with an emphasis on her work defining SK1 in cellular fates and pathobiologies including proliferation, senescence, apoptosis, and inflammation.

RELT stains prominently in B-cell lymphomas and binds the hematopoietic transcription factor MDFIC

Receptor Expressed in Lymphoid Tissues (RELT) is a human tumor necrosis factor receptor superfamily member (TNFRSF) that is expressed most prominently in cells and tissues of the hematopoietic system. RELL1 and RELL2 are two homologs that physically interact with RELT and co-localize with RELT at the plasma membrane. This study sought to further elucidate the function of RELT by identifying novel protein interactions with RELT family members. The transcription factor MyoD family inhibitor domain-containing (MDFIC) was identified in a yeast two-hybrid genetic screen using RELL1 as bait. MDFIC co-localizes with RELT family members at the plasma membrane; this co-localization was most prominently observed with RELL1 and RELL2. In vitro co-immunoprecipitation (Co-IP) was utilized to demonstrate that MDFIC physically interacts with RELT, RELL1, and RELL2. Co-IP using deletion mutants of MDFIC and RELT identified regions important for physical association between MDFIC and RELT family members and a computational analysis revealed that RELT family members are highly disordered proteins. Immunohistochemistry of normal human lymph nodes revealed RELT staining that was most prominent in macrophages. Interestingly, the level of RELT staining significantly increased progressively in low and high-grade B-cell lymphomas versus normal lymph nodes. RELT co-staining with CD20 was observed in B-cell lymphomas, indicating that RELT is expressed in malignant B cells. Collectively, these results further our understanding of RELT-associated signaling pathways, the protein structure of RELT family members, and provide preliminary evidence indicating an association of RELT with B-cell lymphomas.

Morpholino Analogues of Fingolimod as Novel and Selective S1P1 Ligands with In Vivo Efficacy in a Mouse Model of Experimental Antigen-Induced Encephalomyelitis

Multiple sclerosis (MS) is a chronic, inflammatory, autoimmune disease of the central nervous system (CNS) which is associated with lower life expectancy and disability. The experimental antigen-induced encephalomyelitis (EAE) in mice is a useful animal model of MS, which allows exploring the etiopathogenetic mechanisms and testing novel potential therapeutic drugs. A new therapeutic paradigm for the treatment of MS was introduced in 2010 through the sphingosine 1-phosphate (S1P) analogue fingolimod (FTY720, Gilenya®), which acts as a functional S1P1 antagonist on T lymphocytes to deplete these cells from the blood. In this study, we synthesized two novel structures, ST-1893 and ST-1894, which are derived from fingolimod and chemically feature a morpholine ring in the polar head group. These compounds showed a selective S1P1 activation profile and a sustained S1P1 internalization in cultures of S1P1-overexpressing Chinese hamster ovary (CHO)-K1 cells, consistent with a functional antagonism. In vivo, both compounds induced a profound lymphopenia in mice. Finally, these substances showed efficacy in the EAE model, where they reduced clinical symptoms of the disease, and, on the molecular level, they reduced the T-cell infiltration and several inflammatory mediators in the brain and spinal cord. In summary, these data suggest that S1P1-selective compounds may have an advantage over fingolimod and siponimod, not only in MS but also in other autoimmune diseases.

Sphingosine kinase and sphingosine-1-phosphate receptor signaling pathway in inflammatory gastrointestinal disease and cancers: A novel therapeutic target

Inflammatory gastrointestinal (GI) diseases and malignancies are associated with growing morbidity and cancer-related mortality worldwide. GI tumor and inflammatory cells contain activated sphingolipid-metabolizing enzymes, including sphingosine kinase 1 (SphK1) and SphK2, that generate sphingosine-1-phosphate (S1P), a highly bioactive compound. Many inflammatory responses, including lymphocyte trafficking, are directed by circulatory S1P, present in high concentrations in both the plasma and the lymph of cancer patients. High fat and sugar diet, disbalanced intestinal flora, and obesity have recently been linked to activation of inflammation and SphK/S1P/S1P receptor (S1PR) signaling in various GI pathologies, including cancer. SphK1 overexpression and activation facilitate and enhance the development and progression of esophageal, gastric, and colon cancers. SphK/S1P axis, a mediator of inflammation in the tumor microenvironment, has recently been defined as a target for the treatment of GI disease states, including inflammatory bowel disease and colitis. Several SphK1 inhibitors and S1PR antagonists have been developed as novel anti-inflammatory and anticancer agents. In this review, we analyze the mechanisms of SphK/S1P signaling in GI tissues and critically appraise recent studies on the role of SphK/S1P/S1PR in inflammatory GI disorders and cancers. The potential role of SphK/S1PR inhibitors in the prevention and treatment of inflammation-mediated GI diseases, including GI cancer, is also evaluated.

Design of Sphingosine Kinases Inhibitors: Challenges and Recent Developments

BACKGROUND

Sphingosine kinases (SphKs) catalyze the phosphorylation of sphingosine to form the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P). S1P is an important lipid mediator with a wide range of biological functions; it is also involved in a variety of diseases such as inflammatory diseases, Alzheimer's disease and cancer.

METHODS

This review reports the recent advancement in the research of SphKs inhibitors. Our purpose is also to provide a complete overview useful for underlining the features needed to select a specific pharmacological profile.

DISCUSSION

Two distinct mammalian SphK isoforms have been identified, SphK1 and SphK2. These isoforms are encoded by different genes and exhibit distinct subcellular localizations, biochemical properties and functions. SphK1 and SphK2 inhibition can be useful in different pathological conditions.

CONCLUSION

SphK1 and SphK2 have many common features but different and even opposite biological functions. For this reason, several research groups are interested in understanding the therapeutic usefulness of a selective or non-selective inhibitor of SphKs. Moreover, a compensatory mechanism for the two isoforms has been demonstrated, thus leading to the development of dual inhibitors.

Sphingolipids as mediators of inflammation and novel therapeutic target in inflammatory bowel disease

Morbidity of inflammatory gastrointestinal (GI) diseases continues to grow resulting in worsen quality of life and increased burden on public medical systems. Complex and heterogenous illnesses, inflammatory bowel diseases (IBDs) encompass several inflammation -associated pathologies including Crohn's disease and ulcerative colitis. IBD is often initiated by a complex interplay between host genetic and environmental factors, lifestyle and diet, and intestinal bacterial components. IBD inflammatory signature was linked to the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) signaling pathway that is currently targeted by IBD therapies. Sphingolipid signaling was identified as one of the key mediators and regulators of pro-inflammatory conditions, and, specifically, TNF-α related signaling. All GI tissues and circulating immune/blood cells contain activated sphingolipid-metabolizing enzymes, including sphingosine kinases (SphK1 and SphK2) that generate sphingosine-1-phosphate (S1P), a bioactive lipid and ligand for five G-protein coupled membrane S1P receptors (S1PRs). Numerous normal and pathogenic inflammatory responses are mediated by SphK/S1P/S1PRs signaling axis including lymphocyte trafficking and activation of cytokine signaling machinery. SphK1/S1P/S1PRs axis has recently been defined as a target for the treatment of GI diseases including IBD/colitis. Several SphK1 inhibitors and S1PRs antagonists have been developed as novel anti-inflammatory agents. In this review, we discuss the mechanisms of SphK/S1P signaling in inflammation-linked GI disorders. The potential role of SphK/S1PRs inhibitors in the prevention and treatment of IBD/colitis is critically evaluated.

Sphingosine Kinases as Druggable Targets

There is substantial evidence that the enzymes, sphingosine kinase 1 and 2, which catalyse the formation of the bioactive lipid sphingosine 1-phosphate, are involved in pathophysiological processes. In this chapter, we appraise the evidence that both enzymes are druggable and describe how isoform-specific inhibitors can be developed based on the plasticity of the sphingosine-binding site. This is contextualised with the effect of sphingosine kinase inhibitors in cancer, pulmonary hypertension, neurodegeneration, inflammation and sickling.

Effect of the Sphingosine Kinase 1 Selective Inhibitor, PF543 on Dextran Sodium Sulfate-Induced Colitis in Mice

Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease, which often affects colon or rectum or both. It is now well recognized that sphingosine kinases-1/sphingosine-1-phosphate (S1P) signaling may have a very significant potential as targets for therapeutic intervention in UC. Compared with the pure dextran sodium sulfate group, administration of PF543 significantly reduced clinical symptoms with less weight loss, diarrhea, and shortening of the colon. The severity of colitis was improved with reduced disease activity index and degree of histological damage in colon. Moreover, treatment with PF543 not only decreased S1P but also inhibited mRNA expression of proinflammatory factors such as interleukin (IL)-1β and IL-6. This suggests that PF543 might exhibit an anti-inflammatory function against colitis through inhibition of expression of proinflammatory factors.

Sphingosine 1-Phosphate Receptors and Metabolic Enzymes as Druggable Targets for Brain Diseases

The central nervous system is characterized by a high content of sphingolipids and by a high diversity in terms of different structures. Stage- and cell-specific sphingolipid metabolism and expression are crucial for brain development and maintenance toward adult age. On the other hand, deep dysregulation of sphingolipid metabolism, leading to altered sphingolipid pattern, is associated with the majority of neurological and neurodegenerative diseases, even those totally lacking a common etiological background. Thus, sphingolipid metabolism has always been regarded as a promising pharmacological target for the treatment of brain disorders. However, any therapeutic hypothesis applied to complex amphipathic sphingolipids, components of cellular membranes, has so far failed probably because of the high regional complexity and specificity of the different biological roles of these structures. Simpler sphingosine-based lipids, including ceramide and sphingosine 1-phosphate, are important regulators of brain homeostasis, and, thanks to the relative simplicity of their metabolic network, they seem a feasible druggable target for the treatment of brain diseases. The enzymes involved in the control of the levels of bioactive sphingoids, as well as the receptors engaged by these molecules, have increasingly allured pharmacologists and clinicians, and eventually fingolimod, a functional antagonist of sphingosine 1-phosphate receptors with immunomodulatory properties, was approved for the therapy of relapsing-remitting multiple sclerosis. Considering the importance of neuroinflammation in many other brain diseases, we would expect an extension of the use of such analogs for the treatment of other ailments in the future. Nevertheless, many aspects other than neuroinflammation are regulated by bioactive sphingoids in healthy brain and dysregulated in brain disease. In this review, we are addressing the multifaceted possibility to address the metabolism and biology of bioactive sphingosine 1-phosphate as novel targets for the development of therapeutic paradigms and the discovery of new drugs.

The Lipid Status in Patients with Ulcerative Colitis: Sphingolipids are Disease-Dependent Regulated

The factors that contribute to the development of ulcerative colitis (UC), are still not fully identified. Disruption of the colon barrier is one of the first events leading to invasion of bacteria and activation of the immune system. The colon barrier is strongly influenced by sphingolipids. Sphingolipids impact cell-cell contacts and function as second messengers. We collected blood and colon tissue samples from UC patients and healthy controls and investigated the sphingolipids and other lipids by LC-MS/MS or LC-QTOFMS. The expression of enzymes of the sphingolipid pathway were determined by RT-PCR and immunohistochemistry. In inflamed colon tissue, the de novo-synthesis of sphingolipids is reduced, whereas lactosylceramides are increased. Reduction of dihydroceramides was due to posttranslational inhibition rather than altered serine palmitoyl transferase or ceramide synthase expression in inflamed colon tissue. Furthermore, in human plasma from UC-patients, several sphinglipids change significantly in comparison to healthy controls. Beside sphingolipids free fatty acids, lysophosphatidylcholines and triglycerides changed significantly in the blood of colitis patients dependent on the disease severity. Our data indicate that detraction of the sphingolipid de novo synthesis in colon tissue might be an important trigger for UC. Several lipids changed significantly in the blood, which might be used as biomarkers for disease control; however, diet-related variabilities need to be considered.

Sphingosine kinase 1 knockout alleviates hepatic ischemia/reperfusion injury by attenuating inflammation and oxidative stress in mice

BACKGROUND

Hepatic ischemia/reperfusion (I/R) injury remains a significant problem in clinical practice. Sphingosine kinase 1 (SphK1) phosphorylates sphingosine to sphingosine-1-phosphate (S1P) which participates in multiple bioactive processes. However, little is known about the role of SphK1 in hepatic I/R injury. This study aimed to investigate the effect of SphK1 knockout on liver I/R injury and to explore underlying mechanisms.

METHODS

SphK1 knockout and wild type mice were subjected to 70% partial hepatic I/R. Serum alanine aminotransferase was determined to indicate the degree of liver damage. Hematoxylin-eosin staining and TUNEL assay were used to assess histological changes and hepatocellular apoptosis, respectively. Immunohistochemistry was performed to detect the expression and translocation of phosphorylated p65 and signal transducer and activator of transcription 3 (STAT3). Western blotting was used to determine the expression of S1P receptor 1 (S1PR1), phosphorylated p65 and STAT3. Real-time PCR was used to demonstrate the changes of proinflammatory cytokines. Oxidative stress markers were also determined through biochemical assays.

RESULTS

SphK1 knockout significantly ameliorated I/R-induced liver damage, mitigated liver tissue necrosis and apoptosis compared with wild type control. I/R associated inflammation was alleviated in SphK1 knockout mice as demonstrated by attenuated expression of S1PR1 and reduced phosphorylation of nuclear factor kappa B p65 and STAT3. The proinflammatory cytokines interleukin-1β, interleukin-6 and tumor necrosis factor-α were also inhibited by SphK1 genetic deletion. The oxidative stress markers were lower in SphK1 knockout mice after I/R injury than wild type mice.

CONCLUSIONS

Knockout of SphK1 significantly alleviated damage after hepatic I/R injury, possibly through inhibiting inflammation and oxidative stress. SphK1 may be a novel and potent target in clinical practice in I/R-related liver injury.

Roles of Ceramides and Other Sphingolipids in Immune Cell Function and Inflammation

Ceramides are bioactive sphingolipids that support the structure of the plasma membrane and mediate numerous cell-signaling events in eukaryotic cells. The finding that ceramides act as second messengers transducing cellular signals has attracted substantial attention in several fields of Biology. Since all cells contain lipid plasma membranes, the impact of various ceramides, ceramide synthases, ceramide metabolites, and other sphingolipids has been implicated in a vast range of cellular functions including, migration, proliferation, response to external stimuli, and death. The roles of lipids in these functions widely differ among the diverse cell types. Herein, we discuss the roles of ceramides and other sphingolipids in mediating the function of various immune cells; particularly dendritic cells, neutrophils, and macrophages. In addition, we highlight the main studies describing effects of ceramides in inflammation, specifically in various inflammatory settings including insulin resistance, graft-versus-host disease, immune suppression in cancer, multiple sclerosis, and inflammatory bowel disease.

Divergent Innate and Epithelial Functions of the RNA-Binding Protein HuR in Intestinal Inflammation

HuR is an abundant RNA-binding protein acting as a post-transcriptional regulator of many RNAs including mRNAs encoding inflammatory mediators, cytokines, death signalers and cell cycle regulators. In the context of intestinal pathologies, elevated HuR is considered to enhance the stability and the translation of pro-tumorigenic mRNAs providing the rationale for its pharmacological targeting. However, HuR also possesses specific regulatory functions for innate immunity and cytokine mRNA control which can oppose intestinal inflammation and tumor promotion. Here, we aim to identify contexts of intestinal inflammation where the innate immune and the epithelial functions of HuR converge or diverge. To address this, we use a disease-oriented phenotypic approach using mice lacking HuR either in intestinal epithelia or myeloid-derived immune compartments. These mice were compared for their responses to (a) Chemically induced Colitis; (b) Colitis- associated Cancer (CAC); (c) T-cell mediated enterotoxicity; (d) Citrobacter rodentium-induced colitis; and (e) TNF-driven inflammatory bowel disease. Convergent functions of epithelial and myeloid HuR included their requirement for suppressing inflammation in chemically induced colitis and their redundancies in chronic TNF-driven IBD and microbiota control. In the other contexts however, their functions diversified. Epithelial HuR was required to protect the epithelial barrier from acute inflammatory or infectious degeneration but also to promote tumor growth. In contrast, myeloid HuR was required to suppress the beneficial inflammation for pathogen clearance and tumor suppression. This cellular dichotomy in HuR's functions was validated further in mice engineered to express ubiquitously higher levels of HuR which displayed diminished pathologic and beneficial inflammatory responses, resistance to epithelial damage yet a heightened susceptibility to CAC. Our study demonstrates that epithelial and myeloid HuR affect different cellular dynamics in the intestine that need to be carefully considered for its pharmacological exploitation and points toward potential windows for harnessing HuR functions in intestinal inflammation.

Phytosomal curcumin inhibits tumor growth in colitis-associated colorectal cancer

Colorectal-cancer (CRC) is the third leading cause of death due to cancer, supporting the need for identification of novel anticancer drug to improve the efficacy of current-therapy. There is growing bodies of data showing the antitumor-activity of curcumin, although it is associated with low absorption. The aim of current study was explored the therapeutic-potential of novel phytosomal curcumin as well as its application in combination with 5-Flurouracil (5-FU) in a mouse-model of colitis-associated colon-cancer. The anti-proliferative-activity of phytosomal curcumin was assessed in 2- and 3-dimensional cell-culture-models as well as in a mouse-model of colitis-associated colon-cancer. The expression-levels of CyclinD1, beclin, E-cadherin, and p-GSK3a/b were investigated by qRT-PCR and/or Western-blotting. We evaluated the anti-inflammatory of this agent by pathological-evaluation and disease-activity-index (DAI). Moreover, oxidant/antioxidant activity was examined by malondialdehyde (MDA), total-thiols (T-SH), superoxide-dismutase (SOD), and catalase (CAT) activity parameters. Our data showed that phytosomal curcumin and its combination with 5-FU inhibited cell growth and invasive behavior of CRC cells through modulation of Wnt-pathway and E-cadherin. Combination of curcumin with 5-FU dramatically reduced the tumor-number and tumor-size in both distal and middle parts of colon in colitis-associated colon cancer followed by reduction in DAI. Also, curcumin suppressed the colonic inflammation and notably recovered the increased levels of MDA, decreased thiol level and reduced activity of CAT. We demonstrated the antitumor-activity of novel form of curcumin in CRC, supporting further investigations on the therapeutic-potential of this approach in colorectal-cancer.

Deficiency of alkaline SMase enhances dextran sulfate sodium-induced colitis in mice with upregulation of autotaxin

Intestinal alkaline SMase (Alk-SMase) cleaves phosphocholine from SM, platelet-activating factor (PAF), and lysophosphatidylcholine. We recently found that colitis-associated colon cancer was 4- to 5-fold enhanced in Alk-SMase KO mice. Here, we further studied the pathogenesis of colitis induced by dextran sulfate sodium (DSS) in WT and KO mice. Compared with WT mice, KO mice demonstrated greater body weight loss, more severe bloody diarrhea, broader inflammatory cell infiltration, and more serious epithelial injury. Higher levels of PAF and lower levels of interleukin (IL)10 were identified in KO mice 2 days after DSS treatment. A greater and progressive increase of lysophosphatidic acid (LPA) was identified. The change was associated with increased autotaxin expression in both small intestine and colon, which was identified by immunohistochemistry study, Western blot, and sandwich ELISA. The upregulation of autotaxin coincided with an early increase of PAF. IL6 and TNFα were increased in both WT and KO mice. At the later stage (day 8), significant decreases in IL6, IL10, and PAF were identified, and the decreases were greater in KO mice. In conclusion, deficiency of Alk-SMase enhances DSS-induced colitis by mechanisms related to increased autotaxin expression and LPA formation. The early increase of PAF might be a trigger for such reactions.

Alisma canaliculatum ethanol extract suppresses inflammatory responses in LPS-stimulated macrophages, HCl/EtOH-induced gastritis, and DSS-triggered colitis by targeting Src/Syk and TAK1 activities

ETHNOPHARMACOLOGICAL RELEVANCE

Alisma canaliculatum A.Braun & C.D.Bouché, distributed in Korea, Japan, China, and Taiwan, is a traditional medicine. In particular, the stem and root of Alisma canaliculatum A.Braun & C.D.Bouché are prescribed to relieve various inflammatory symptoms resulting from nephritis, cystitis, urethritis, and dropsy.

AIM OF STUDY

However, the curative mechanism of Alisma canaliculatum A.Braun & C.D.Bouché with respect to inflammatory symptoms is poorly understood. In this study, the curative roles of this plant in various inflammatory conditions as well as its inhibitory mechanism were aimed to examine using an ethanol extract (Ac-EE).

MATERIALS AND METHODS

Anti-inflammatory effects of Ac-EE were evaluated in lipopolysaccharide (LPS)-induced macrophages in vitro and HCl/EtOH-stimulated mouse model of gastritis and DSS-treated mouse model of colitis. To determine the potentially active anti-inflammatory components in this extracts, we employed HPLC. We also used kinase assays, reporter gene assay, immunoprecipitation analysis and target enzyme overexpressing cell analysis to analyze the molecular mechanisms and the target molecules.

RESULTS

This extract dose-dependently inhibited the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) from RAW264.7 cells and peritoneal macrophages activated by lipopolysaccharide (LPS). Additionally, Ac-EE ameliorated inflammatory symptoms resulting from gastritis and colitis. Ac-EE down-regulated the mRNA levels of inducible NO synthase (iNOS), tumor necrosis factor (TNF)-α, and cyclooxygenase-2 (COX-2). Ac-EE also blocked the nuclear translocation of nuclear factor (NF)-κB and activator protein (AP)- 1 in LPS-stimulated RAW264.7 cells. By analyzing the target signaling molecules activating these transcription factors, we found that Src and Syk, as well as molecular association between TAK1 and mitogen-activated protein kinase kinase 4/7 (MKK4/7), were targeted by Ac-EE.

CONCLUSIONS

Our data suggest that the Ac-EE NF-κB/AP-1-targeted anti-inflammatory potential is mediated by suppression of Src and Syk as well as the complex formation between TAK1 and its substrate proteins MKK4/7.

Targeting Sphingosine Kinases for the Treatment of Cancer

Sphingosine kinases (SK1 and SK2) are key, druggable targets within the sphingolipid metabolism pathway that promote tumor growth and pathologic inflammation. A variety of isozyme-selective and dual inhibitors of SK1 and SK2 have been described in the literature, and at least one compound has reached clinical testing in cancer patients. In this chapter, we will review the rationale for targeting SKs and summarize the preclinical and emerging clinical data for ABC294640 as the first-in-class selective inhibitor of SK2.

In Vitro and In Vivo Antitumor and Anti-Inflammatory Capabilities of the Novel GSK3 and CDK9 Inhibitor ABC1183

Glycogen synthase kinase-3s (GSK3α and GSK3β) are constitutively active protein kinases that target over 100 substrates, incorporate into numerous protein complexes, and regulate such vital cellular functions as proliferation, apoptosis, and inflammation. Cyclin-dependent kinase 9 (CDK9) regulates RNA production as a component of positive transcription elongation factor b and promotes expression of oncogenic and inflammatory genes. Simultaneous inhibition of these signaling nodes is a promising approach for drug discovery, although previous compounds exhibit limited selectivity and clinical efficacy. The novel diaminothiazole ABC1183 is a selective GSK3α/β and CDK9 inhibitor and is growth-inhibitory against a broad panel of cancer cell lines. ABC1183 treatment decreases cell survival through G2/M arrest and modulates oncogenic signaling through changes in GSK3, glycogen synthase, and β-catenin phosphorylation and MCL1 expression. Oral administration, which demonstrates no organ or hematologic toxicity, suppresses tumor growth and inflammation-driven gastrointestinal disease symptoms, owing in part to downregulation of tumor necrosis factor α and interleukin-6 proinflammatory cytokines. Therefore, ABC1183 is strategically poised to effectively mitigate multiple clinically relevant diseases.

Cell-intrinsic sphingosine kinase 2 promotes macrophage polarization and renal inflammation in response to unilateral ureteral obstruction

Sphingosine Kinase-2 (Sphk2) is responsible for the production of the bioactive lipid Sphingosine-1 Phosphate, a key regulator of tissue repair. Here we address the in vivo significance of Sphingosine Kinase -2 in renal inflammation/fibrosis in response to unilateral ureteral obstruction using both genetic and pharmacological strategies. Obstructed kidneys of Sphk2^-/- mice showed reduced renal damage and diminished levels of the renal injury markers TGFβ₁ and αSMA when compared to wild type controls. We found a consistently significant increase in anti-inflammatory (M2) macrophages in obstructed Sphk2^-/- kidneys by flow cytometry and a decrease in mRNA levels of the inflammatory cytokines, MCP1, TNFα, CXCL1 and ILβ₁, suggesting an anti-inflammatory bias in the absence of Sphk2. Indeed, metabolic profiling showed that the pro-inflammatory glycolytic pathway is largely inactive in Sphk2^-/- bone marrow-derived macrophages. Furthermore, treatment with the M2-promoting cytokines IL-4 or IL-13 demonstrated that macrophages lacking Sphk2 polarized more efficiently to the M2 phenotype than wild type cells. Bone marrow transplant studies indicated that expression of Sphk2^-/- on either the hematopoietic or parenchymal cells did not fully rescue the pro-healing phenotype, confirming that both infiltrating M2-macrophages and the kidney microenvironment contribute to the damaging Sphk2 effects. Importantly, obstructed kidneys from mice treated with an Sphk2 inhibitor recapitulated findings in the genetic model. These results demonstrate that reducing Sphk2 activity by genetic or pharmacological manipulation markedly decreases inflammatory and fibrotic responses to obstruction, resulting in diminished renal injury and supporting Sphk2 as a novel driver of the pro-inflammatory macrophage phenotype.