Sphingosine-1-phosphate signaling: A novel target for simultaneous adjuvant treatment of triple negative breast cancer and chemotherapy-induced neuropathic pain

FTY720/Fingolimod mitigates paclitaxel-induced Sparcl1-driven neuropathic pain and breast cancer progression

Paclitaxel is among the most active chemotherapy drugs for the aggressive triple negative breast cancer (TNBC). Unfortunately, it often induces painful peripheral neuropathy (CIPN), a major debilitating side effect. Here we demonstrate that in naive and breast tumor-bearing immunocompetent mice, a clinically relevant dose of FTY720/Fingolimod that targets sphingosine-1-phosphate receptor 1 (S1PR1), alleviated paclitaxel-induced neuropathic pain. FTY720 also significantly attenuated paclitaxel-stimulated glial fibrillary acidic protein (GFAP), a marker for activated astrocytes, and expression of the astrocyte-secreted synaptogenic protein Sparcl1/Hevin, a key regulator of synapse formation. Notably, the formation of excitatory synapses containing VGluT2 in the spinal cord dorsal horn induced by paclitaxel was also inhibited by FTY720 treatment, supporting the involvement of astrocytes and Sparcl1 in CIPN. Furthermore, in this TNBC mouse model that mimics human breast cancer, FTY720 administration also enhanced the anti-tumor effects of paclitaxel, leading to reduced tumor progression and lung metastasis. Taken together, our findings suggest that targeting the S1P/S1PR1 axis with FTY720 is a multipronged approach that holds promise as a therapeutic strategy for alleviating both CIPN and enhancing the efficacy of chemotherapy in TNBC treatment.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

Combination chemotherapy in rodents: a model for chemotherapy-induced neuropathic pain and pharmacological screening

Chemotherapy-induced neuropathic pain (CINP) remains a therapeutic challenge, with no US-FDA approved drugs or effective treatments available. Despite significant progress in unravelling the pathophysiology of CINP, the clinical translation of this knowledge into tangible outcome remains elusive. Here, we employed behavioural and pharmacological approaches to establish and validate a novel combination-based chemotherapeutic model of peripheral neuropathy. Male Sprague Dawley rats were subjected to chemotherapy administration followed by assessment of pain behaviour at different time-points post-chemotherapy. Paclitaxel-treated animals displayed an enhanced thermal and mechanical hypersensitivity from day four onwards which continued till day thirty-five post last paclitaxel injection. Notably, rats subjected to combination chemotherapy, displayed prolonged hypersensitivity that emerged on day four and persisted until day fifty-six. RT-PCR analysis revealed significant upregulation in DRG and spinal mRNA expressions of TRP channels (TRPA1, TRPV1, & TRPM8), pro-inflammatory cytokines (TNF-α & IL-1β) and neuropeptides, Substance P and CGRP in both the pain models. Interestingly, the combination chemotherapy model demonstrated a significant increase in DRG and spinal NR2B expressions compared to rats solely treated with paclitaxel. Pharmacological investigations revealed that gabapentin treatment substantially mitigates pain hypersensitivity in both the combined chemotherapy and paclitaxel-administered groups, with the simultaneous reversal of cellular and molecular changes observed in the lumbar DRG and spinal cord of rats. The findings from this study suggests that combination chemotherapy model exhibits heightened and prolonged hypersensitivity in comparison to the conventional paclitaxel-induced neuropathic pain model. This model not only recapitulates clinical biomarkers of neuropathy but also presents a potential alternative platform for screening analgesic drugs targeted at CINP.

Pain associated with breast cancer: etiologies and therapies

Pain associated with breast cancer is a prevalent problem that negatively affects quality of life. Breast cancer pain is not limited to the disease course itself but is also induced by current therapeutic strategies. This, combined with the increasing number of patients living with breast cancer, make pain management for breast cancer patients an increasingly important area of research. This narrative review presents a summary of pain associated with breast cancer, including pain related to the cancer disease process itself and pain associated with current therapeutic modalities including radiation, chemotherapy, immunotherapy, and surgery. Current pain management techniques, their limitations, and novel analgesic strategies are also discussed.

Combined signature of G protein-coupled receptors and tumor microenvironment provides a prognostic and therapeutic biomarker for skin cutaneous melanoma

BACKGROUND

G protein-coupled receptors (GPCRs) have been shown to have an important role in tumor development and metastasis, and abnormal expression of GPCRs is significantly associated with poor prognosis of tumor patients. In this study, we analyzed the GPCRs-related gene (GPRGs) and tumor microenvironment (TME) in skin cutaneous melanoma (SKCM) to construct a prognostic model to help SKCM patients obtain accurate clinical treatment strategies.

METHODS

SKCM expression data and clinical information were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Differential expression analysis, LASSO algorithm, and univariate and multivariate cox regression analysis were used to screen prognosis-related genes (GPR19, GPR146, S1PR2, PTH1R, ADGRE5, CXCR3, GPR143, and OR2I1P) and multiple prognosis-good immune cells; the data set was analyzed according to above results and build up a GPR-TME classifier. The model was further subjected to immune infiltration, functional enrichment, tumor mutational load, immunotherapy prediction, and scRNA-seq data analysis. Finally, cellular experiments were conducted to validate the functionality of the key gene GPR19 in the model.

RESULTS

The findings indicate that high expression of GPRGs is associated with a poor prognosis in patients with SKCM, highlighting the significant role of GPRGs and the tumor microenvironment (TME) in SKCM development. Notably, the group characterized by low GPR expression and a high TME exhibited the most favorable prognosis and immunotherapeutic efficacy. Furthermore, cellular assays demonstrated that knockdown of GPR19 significantly reduced the proliferation, migration, and invasive capabilities of melanoma cells in A375 and A2058 cell lines.

CONCLUSION

This study provides novel insights for the prognosis evaluation and treatment of melanoma, along with the identification of a new biomarker, GPR19.

The role of sphingosine 1-phosphate metabolism in brain health and disease

Lipids are essential structural and functional components of the central nervous system (CNS). Sphingolipids are ubiquitous membrane components which were discovered in the brain in the late 19^th century. In mammals, the brain contains the highest concentration of sphingolipids in the body. Sphingosine 1-phosphate (S1P) derived from membrane sphingolipids evokes multiple cellular responses which, depending on its concentration and localization, make S1P a double-edged sword in the brain. In the present review we highlight the role of S1P in brain development and focus on the often contrasting findings regarding its contributions to the initiation, progression and potential recovery of different brain pathologies, including neurodegeneration, multiple sclerosis (MS), brain cancers, and psychiatric illnesses. A detailed understanding of the critical implications of S1P in brain health and disease may open the door for new therapeutic options. Thus, targeting S1P-metabolizing enzymes and/or signaling pathways might help overcome, or at least ameliorate, several brain illnesses.

Targeting neuroinflammation in neuropathic pain and opioid use

Neuropathic pain arises from injuries to the nervous system. It affects 20% of the adult US population and poses a major socioeconomic burden yet remains exceedingly difficult to treat. Current therapeutic approaches have limited efficacy and a large side effect profile that impedes their ability to treat neuropathic pain effectively. Preclinical research over the last 30 yr has established the critical role that pro-inflammatory neuro-immune cell interactions have in the development and maintenance of neuropathic pain arising from various etiologies. Pro-inflammatory neuro-immune cell interactions also underlie the development of adverse side effects of opioids and the loss of their efficacy to treat pain. Evidence from work in our lab and others in preclinical animal models have shown that signaling from the bioactive sphingolipid, sphingosine-1-phosphate (S1P), through the S1P receptor subtype 1 (S1PR1) modulates neuro-immune cell interactions. Here, we discuss how targeting S1P/S1PR1 signaling with S1PR1 antagonists already Food and Drug Administration-approved or in clinical trials for multiple sclerosis can provide a viable pharmacotherapeutic approach to reduce neuro-immune cell inflammatory signaling and potentially treat patients suffering neuropathic pain and the adverse effects of opioids.

Nobiletin inhibits breast cancer cell migration and invasion by suppressing the IL-6-induced ERK-STAT and JNK-c-JUN pathways

BACKGROUND

Breast cancer is one of the most common cancers in women, affecting more than 2 million women worldwide annually. However, effective treatments for breast cancer are limited. Nobiletin is a flavonoid present in the dried mature pericarp of mandarin orange (Citrus reticulata Blanco), which is used to prepare Citri Renetulatae Pericarpium and can inhibit tumour growth and progression according to modern pharmacological studies. However, whether nobiletin exhibits an antimetastatic role in breast cancer and its potential mechanism need to be further investigated.

PURPOSE

This study aims to evaluate the inhibitory effect of nobiletin on breast cancer and to elucidate potential mechanisms against invasion and migration.

METHODS

Cell viability was determined by cell counting kit-8 and colony formation assays. Wound healing and Boyden chamber assays detected cancer cell migration and invasion capabilities. Immunoblotting and qPCR were applied to determine the protein and mRNA expression levels of extracellular signal-regulated kinases (ERK) and the c-Jun N-terminal kinase (JNK) signalling pathways. Molecular docking was used to assess the degree of nobiletin binding to phosphatidylinositol 3-kinase (PI3K). Xenografts and liver metastases were constructed in BALB/c nude mice to evaluate the anticancer effect of nobiletin in vivo. H&E staining and immunohistochemistry were used to detect proliferation and the expression of related proteins.

RESULTS

Nobiletin induced cell death in a concentration- and time-dependent manner and possessed anti-invasion and anti-migration effects on MCF-7 and T47D cells by suppressing the interleukin-6-induced ERK and JNK signalling pathways. In addition, nobiletin docked with the binding site of PI3K, and the binding score was -8.0 kcal/mol. Furthermore, the inhibition of breast cancer growth and metastasis by nobiletin was demonstrated by constructing xenografts and liver metastases in vivo.

CONCLUSION

Nobiletin inhibited liver metastasis of breast cancer by downregulating the ERK-STAT and JNK-c-JUN pathways, and its safety and efficacy were verified, indicating the potential of nobiletin as an anticancer agent.

Sphingosine-1-Phosphate Recruits Macrophages and Microglia and Induces a Pro-Tumorigenic Phenotype That Favors Glioma Progression

Glioblastoma is the most aggressive brain tumor in adults. Treatment failure is predominantly caused by its high invasiveness and its ability to induce a supportive microenvironment. As part of this, a major role for tumor-associated macrophages/microglia (TAMs) in glioblastoma development was recognized. Phospholipids are important players in various fundamental biological processes, including tumor-stroma crosstalk, and the bioactive lipid sphingosine-1-phosphate (S1P) has been linked to glioblastoma cell proliferation, invasion, and survival. Despite the urgent need for better therapeutic approaches, novel strategies targeting sphingolipids in glioblastoma are still poorly explored. Here, we showed that higher amounts of S1P secreted by glioma cells are responsible for an active recruitment of TAMs, mediated by S1P receptor (S1PR) signaling through the modulation of Rac1/RhoA. This resulted in increased infiltration of TAMs in the tumor, which, in turn, triggered their pro-tumorigenic phenotype through the inhibition of NFkB-mediated inflammation. Gene set enrichment analyses showed that such an anti-inflammatory microenvironment correlated with shorter survival of glioblastoma patients. Inhibition of S1P restored a pro-inflammatory phenotype in TAMs and resulted in increased survival of tumor-bearing mice. Taken together, our results establish a crucial role for S1P in fine-tuning the crosstalk between glioma and infiltrating TAMs, thus pointing to the S1P-S1PR axis as an attractive target for glioma treatment.

S1PR1/S1PR3-YAP signaling and S1P-ALOX15 signaling contribute to an aggressive behavior in obesity-lymphoma

BACKGROUND

Excess body weight has been found to associate with an increased risk of lymphomas and some metabolic pathways are currently recognized in lymphomagenesis. Bioactive lipid metabolites such as sphingosine-1-phosphate (S1P) have been proposed to play an important role linking obesity and lymphomas. However, the underlying mechanism(s) of S1P signaling in obesity-lymphomagenesis have not been well addressed.

METHODS

The gene expression of sphingosine kinase (SPHK), lymphoma prognosis, and S1P production were analyzed using Gene Expression Omnibus (GEO) and human lymphoma tissue array. Obesity-lymphoma mouse models and lymphoma cell lines were used to investigate the S1P/SPHK-YAP axis contributing to obesity-lymphomagenesis. By using the mouse models and a monocyte cell line, S1P-mediated polarization of macrophages in the tumor microenvironment were investigated.

RESULTS

In human study, up-regulated S1P/SPHK1 was found in human lymphomas, while obesity negatively impacted progression-free survival and overall survival in lymphoma patients. In animal study, obesity-lymphoma mice showed an aggressive tumor growth pattern. Both in vivo and in vitro data suggested the existence of S1P-YAP axis in lymphoma cells, while the S1P-ALOX15 signaling mediated macrophage polarization towards TAMs exacerbated the lymphomagenesis. In addition, treatment with resveratrol in obesity-lymphoma mice showed profound effects of anti-lymphomagenesis, via down-regulating S1P-YAP axis and modulating polarization of macrophages.

CONCLUSION

S1P/S1PR initiated the feedback loops, whereby S1P-S1PR1/S1PR3-YAP signaling mediated lymphomagenesis contributing to tumor aggressive growth, while S1P-ALOX15 signaling mediated TAMs contributing to immunosuppressive microenvironment in obesity-lymphoma. S1P-targeted therapy could be potentially effective and immune-enhancive against obesity-lymphomagenesis.

The FKBP51 Inhibitor SAFit2 Restores the Pain-Relieving C16 Dihydroceramide after Nerve Injury

Neuropathic pain is a pathological pain state with a broad symptom scope that affects patients after nerve injuries, but it can also arise after infections or exposure to toxic substances. Current treatment possibilities are still limited because of the low efficacy and severe adverse effects of available therapeutics, highlighting an emerging need for novel analgesics and for a detailed understanding of the pathophysiological alterations in the onset and maintenance of neuropathic pain. Here, we show that the novel and highly specific FKBP51 inhibitor SAFit2 restores lipid signaling and metabolism in nervous tissue after nerve injury. More specifically, we identify that SAFit2 restores the levels of the C16 dihydroceramide, which significantly reduces the sensitization of the pain-mediating TRPV1 channel and subsequently the secretion of the pro-inflammatory neuropeptide CGRP in primary sensory neurons. Furthermore, we show that the C16 dihydroceramide is capable of reducing acute thermal hypersensitivity in a capsaicin mouse model. In conclusion, we report for the first time the C16 dihydroceramide as a novel and crucial lipid mediator in the context of neuropathic pain as it has analgesic properties, contributing to the pain-relieving properties of SAFit2.

Sphingosine-1-phosphate receptor 1 activation in the central nervous system drives cisplatin-induced cognitive impairment

Cancer-related cognitive impairment (CRCI) is a major neurotoxicity affecting more than 50% of cancer survivors. The underpinning mechanisms are mostly unknown, and there are no FDA-approved interventions. Sphingolipidomic analysis of mouse prefrontal cortex and hippocampus, key sites of cognitive function, revealed that cisplatin increased levels of the potent signaling molecule sphingosine-1-phosphate (S1P) and led to cognitive impairment. At the biochemical level, S1P induced mitochondrial dysfunction, activation of NOD-, LRR-, and pyrin domain–containing protein 3 inflammasomes, and increased IL-1β formation. These events were attenuated by systemic administration of the functional S1P receptor 1 (S1PR1) antagonist FTY720, which also attenuated cognitive impairment without adversely affecting locomotor activity. Similar attenuation was observed with ozanimod, another FDA-approved functional S1PR1 antagonist. Mice with astrocyte-specific deletion of S1pr1 lost their ability to respond to FTY720, implicating involvement of astrocytic S1PR1. Remarkably, our pharmacological and genetic approaches, coupled with computational modeling studies, revealed that cisplatin increased S1P production by activating TLR4. Collectively, our results identify the molecular mechanisms engaged by the S1P/S1PR1 axis in CRCI and establish S1PR1 antagonism as an approach to target CRCI with therapeutics that have fast-track clinical application.

Integrated 16S rRNA Gene Sequencing and Metabolomics Analysis to Investigate the Important Role of Osthole on Gut Microbiota and Serum Metabolites in Neuropathic Pain Mice

Accumulating evidence suggests that neuropathic pain (NP) is closely connected to the metabolic disorder of gut microbiota, and natural products could relieve NP by regulating gut microbiota. The purpose of this study is to investigate the important regulatory effects of osthole on gut microbiota and serum metabolites in mice with chronic constriction injury (CCI). Mice's intestinal contents and serum metabolites were collected from the sham group, CCI group, and osthole treatment CCI group. The 16S rRNA gene sequencing was analyzed, based on Illumina NovaSeq platform, and ANOVA analysis were used to analyze the composition variety and screen differential expression of intestinal bacteria in the three groups. Ultra-high-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UHPLC-Q-TOF-MS) was used for analyzing the data obtained from serum specimens, and KEGG enrichment analysis was used to identify pathways of differential metabolites in the treatment of neuralgia mice. Furthermore, the Pearson method and Cytoscape soft were used to analyze the correlation network of differential metabolites, gut microbiota, and disease genes. The analysis results of 16S rRNA gene sequencing displayed that Bacteroidetes, Firmicutes, and Verrucomicrobia were highly correlated with NP after osthole treatment at the phylum level. Akkermansia, Lachnospiraceae_unclassified, Lachnospiraceae_NK4A136_group, Bacteroides, Lactobacillus, and Clostridiales_unclassified exhibited higher relative abundance and were considered important microbial members at genus level in neuralgia mice. Serum metabolomics results showed that 131 metabolites were considered to be significantly different in the CCI group compared to the sham group, and 44 metabolites were significantly expressed between the osthole treatment group and the CCI group. At the same time, we found that 29 differential metabolites in the two comparison groups were overlapping. Integrated analysis results showed that many intestinal microorganisms and metabolites have a strong positive correlation. The correlation network diagram displays that 10 genes were involved in the process of osthole alleviating NP through a metabolic pathway and gut microbiota, including IGF2, GDAP1, MYLK, IL18, CD55, MIR331, FHIT, F3, ERBB4, and ITGB3. Our findings have preliminarily confirmed that NP is closely related to metabolism and intestinal microbial imbalance, and osthole can improve the metabolic disorder of NP by acting on gut microbiota.

Vesicle Fusion as a Target Process for the Action of Sphingosine and Its Derived Drugs

The fusion of membranes is a central part of the physiological processes involving the intracellular transport and maturation of vesicles and the final release of their contents, such as neurotransmitters and hormones, by exocytosis. Traditionally, in this process, proteins, such SNAREs have been considered the essential components of the fusion molecular machinery, while lipids have been seen as merely structural elements. Nevertheless, sphingosine, an intracellular signalling lipid, greatly increases the release of neurotransmitters in neuronal and neuroendocrine cells, affecting the exocytotic fusion mode through the direct interaction with SNAREs. Moreover, recent studies suggest that FTY-720 (Fingolimod), a sphingosine structural analogue used in the treatment of multiple sclerosis, simulates sphingosine in the promotion of exocytosis. Furthermore, this drug also induces the intracellular fusion of organelles such as dense vesicles and mitochondria causing cell death in neuroendocrine cells. Therefore, the effect of sphingosine and synthetic derivatives on the heterologous and homologous fusion of organelles can be considered as a new mechanism of action of sphingolipids influencing important physiological processes, which could underlie therapeutic uses of sphingosine derived lipids in the treatment of neurodegenerative disorders and cancers of neuronal origin such neuroblastoma.

Chemotherapy and peripheral neuropathy

Chemotherapy-induced peripheral neurotoxicity (CIPN) is a major dose-limiting side effect of many anti-cancer agents, including taxanes, platinums, vinca alkaloids, proteasome inhibitors, immunomodulatory drugs, and antibody-drug conjugates. The resultant symptoms often persist post treatment completion and continue to impact on long-term function and quality of life for cancer survivors. At present, dose reduction remains the only strategy to prevent severe neuropathy, often leading clinicians to the difficult decision of balancing maximal treatment exposure and minimal long-lasting side effects. This review examines the clinical presentations of CIPN with each class of neurotoxic treatment, describing signs, symptoms, and long-term outcomes. We provide an update on the proposed mechanisms of nerve damage and review current data on clinical and genetic risk factors contributing to CIPN development. We also examine recent areas of research in the treatment and prevention of CIPN, with specific focus on current clinical trials and consensus recommendations for CIPN management.

Cell cycle arrest-mediated cell death by morin in MDA-MB-231 triple-negative breast cancer cells

BACKGROUND

Morin, a flavonoid extracted from Moraceace family and exhibits several pharmacological activities including anti-cancer activity. Although the anticancer activity of morin in breast cancer was estimated in some investigations, the pharmaceutical mechanism has not been fully elucidated. Therefore, we investigated to unveil the detail signaling pathway in morin-treated in MDA-MB-231 triple-negative breast cancer cells.

METHODS

The cytotoxicity of morin in MDA-MB-231 cells was confirmed by sulforhodamine B (SRB) assay and colony formation assay. Flow cytometry was performed to examine the cell cycle and cell death patterns and the protein expression and phosphorylation were detected by western blotting.

RESULTS

Our results showed that morin inhibited MDA-MB-231 cells proliferation in time and concentration-dependent manner. Morphological changes were observed when treated with various concentration of morin in MDA-MB-231 cells. In regard to protein expression, morin induced the phosphorylation of ERK and p-H2A.X and decreased the level of DNA repair markers, RAD51 and survivin. In addition, flow cytometry showed S and G2/M arrest by morin that was associated with the decrease in the protein expression of cyclin A2 and cyclin B1 and upregulation of p21. Interestingly, annexin V/PI staining result clearly showed that morin induced cell death without apoptosis. Furthermore, attenuated FoxM1 by morin was co-related with cell cycle regulators including p21, cyclin A2 and cyclin B1.

CONCLUSION

Taken together, our study indicates that morin-induced cell death of MDA-MB-231 is caused by sustained cell cycle arrest via the induction of p21 expression by activation of ERK and repression of FOXM1 signaling pathways.

Aging-dependent mitochondrial dysfunction mediated by ceramide signaling inhibits antitumor T cell response

We lack a mechanistic understanding of aging-mediated changes in mitochondrial bioenergetics and lipid metabolism that affect T cell function. The bioactive sphingolipid ceramide, induced by aging stress, mediates mitophagy and cell death; however, the aging-related roles of ceramide metabolism in regulating T cell function remain unknown. Here, we show that activated T cells isolated from aging mice have elevated C14/C16 ceramide accumulation in mitochondria, generated by ceramide synthase 6, leading to mitophagy/mitochondrial dysfunction. Mechanistically, aging-dependent mitochondrial ceramide inhibits protein kinase A, leading to mitophagy in activated T cells. This aging/ceramide-dependent mitophagy attenuates the antitumor functions of T cells in vitro and in vivo. Also, inhibition of ceramide metabolism or PKA activation by genetic and pharmacologic means prevents mitophagy and restores the central memory phenotype in aging T cells. Thus, these studies help explain the mechanisms behind aging-related dysregulation of T cells' antitumor activity, which can be restored by inhibiting ceramide-dependent mitophagy.

Lysophospholipids in Lung Inflammatory Diseases

The lysophospholipids (LPLs) belong to a group of bioactive lipids that play pivotal roles in several physiological and pathological processes. LPLs are derivatives of phospholipids and consist of a single hydrophobic fatty acid chain, a hydrophilic head, and a phosphate group with or without a large molecule attached. Among the LPLs, lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are the simplest, and have been shown to be involved in lung inflammatory symptoms and diseases such as acute lung injury, asthma, and chronic obstructive pulmonary diseases. G protein-coupled receptors (GPCRs) mediate LPA and S1P signaling. In this chapter, we will discuss on the role of LPA, S1P, their metabolizing enzymes, inhibitors or agonists of their receptors, and their GPCR-mediated signaling in lung inflammatory symptoms and diseases, focusing specially on acute respiratory distress syndrome, asthma, and chronic obstructive pulmonary disease.

FAM19A5/S1PR1 signaling pathway regulates the viability and proliferation of mantle cell lymphoma

Several intracellular pathological processes have been reported to be regulated by the FAM19A5/S1PR1 signaling pathway. However, the role of FAM19A5/S1PR1 signaling pathway in the viability and proliferation of mantle cell lymphoma is not been completely understood. The task of this study is to explore the influence of FAM19A5/S1PR1 signaling pathway in affecting the survival and growth of mantle cell lymphoma. shRNAs against FAM19A5 or S1PR1 were transfected into mantle cell lymphom. Cell viability and proliferation were measured through MTT assay and CCK8 assay, respectively. Our results demonstrated that loss of FAM19A5 significantly reduced the viability of mantle cell lymphom, an effect that was followed by a drop in cell proliferation capacity. Besides, inhibition of S1PR1 also impairs cell survival and interrupt mantle cell lymphom proliferation in vitro. Taken together, our results illustrate that FAM19A5/S1PR1 signaling pathway is associated with the regulation of mantle cell lymphom viability and proliferation. This finding will provide a potential target for the treatment of malignant lymphoma in the clinical practice.

The Importance of Sphingosine Kinase in Breast Cancer: A Potential for Breast Cancer Management

Breast cancer management includes a combination of surgery, radiation therapy, and chemotherapy. While this management has proven effective, it is not perfect. To expand the umbrella of management to resistant breast cancer tumors, researchers have explored the idea of sphingosine kinase (SphK) and sphingosine-1-phosphate (S1P) as a potential target for treatment. In this article, we review the mechanism of the sphingosine kinase/sphingosine-1-phosphate (SphK/S1P) axis along with its effect on the tumor microenvironment (TME) and compounds that have been studied inhibiting the SphK/S1P axis. We searched for relevant articles in the last five years in Medline and PubMed Central. Inclusion criteria, exclusion criteria, and quality checklists were applied to identify the most relevant articles. We compiled the information that has been summarized in the respective tables and figures provided in this review. The metabolism of sphingolipids was summarized, followed by the SphK/S1P upregulation in breast cancer cells. The variety of effects by upregulation of SphK led to an increase in inflammation, growth, and metastasis in breast cancer tumors. The increase in S1P also impacted the TME, including the cells and surrounding tissue, allowing the breast tumors to thrive. The final point made was a summary of the compounds and drugs that inhibited the SphK/S1P axis. They have proven their effectiveness and show even greater efficacy in combination with docetaxel and doxorubicin in preclinical studies. In conclusion, what is known about the SphK/S1P axis within breast cancer cells is immense but incomplete as we summarize what is known so far. Having a complete picture will allow a faster transition to application in the clinical field but clinical trials have not commenced as of yet.

Neuroinflammatory Process Involved in Different Preclinical Models of Chemotherapy-Induced Peripheral Neuropathy

Peripheral neuropathies are characterized by nerves damage and axonal loss, and they could be classified in hereditary or acquired forms. Acquired peripheral neuropathies are associated with several causes, including toxic agent exposure, among which the antineoplastic compounds are responsible for the so called Chemotherapy-Induced Peripheral Neuropathy (CIPN). Several clinical features are related to the use of anticancer drugs which exert their action by affecting different mechanisms and structures of the peripheral nervous system: the axons (axonopathy) or the dorsal root ganglia (DRG) neurons cell body (neuronopathy/ganglionopathy). In addition, antineoplastic treatments may affect the blood brain barrier integrity, leading to cognitive impairment that may be severe and long-lasting. CIPN may affect patient quality of life leading to modification or discontinuation of the anticancer therapy. Although the mechanisms of the damage are not completely understood, several hypotheses have been proposed, among which neuroinflammation is now emerging to be relevant in CIPN pathophysiology. In this review, we consider different aspects of neuro-immune interactions in several CIPN preclinical studies which suggest a critical connection between chemotherapeutic agents and neurotoxicity. The features of the neuroinflammatory processes may be different depending on the type of drug (platinum derivatives, taxanes, vinca alkaloids and proteasome inhibitors). In particular, recent studies have demonstrated an involvement of the immune response (both innate and adaptive) and the stimulation and secretion of mediators (cytokines and chemokines) that may be responsible for the painful symptoms, whereas glial cells such as satellite and Schwann cells might contribute to the maintenance of the neuroinflammatory process in DRG and axons respectively. Moreover, neuroinflammatory components have also been shown in the spinal cord with microglia and astrocytes playing an important role in CIPN development. Taking together, better understanding of these aspects would permit the development of possible strategies in order to improve the management of CIPN.

Vincristine- and bortezomib-induced neuropathies - from bedside to bench and back

Vincristine and bortezomib are effective chemotherapeutics widely used to treat hematological cancers. Vincristine blocks tubulin polymerization, whereas bortezomib is a proteasome inhibitor. Despite different mechanisms of action, the main non-hematological side effect of both is peripheral neuropathy that can last long after treatment has ended and cause permanent disability. Many different cellular and animal models of various aspects of vincristine and bortezomib-induced neuropathies have been generated to investigate underlying molecular mechanisms and serve as platforms to develop new therapeutics. These models revealed that bortezomib induces several transcriptional programs in dorsal root ganglia that result in the activation of different neuroinflammatory pathways and secondary central sensitization. In contrast, vincristine has direct toxic effects on the axon, which are accompanied by changes similar to those observed after nerve cut. Axon degeneration following both vincristine and bortezomib is mediated by a phylogenetically ancient, genetically encoded axon destruction program that leads to the activation of the Toll-like receptor adaptor SARM1 (sterile alpha and TIR motif containing protein 1) and local decrease of nicotinamide dinucleotide (NAD+). Here, I describe current in vitro and in vivo models of vincristine- and bortezomib induced neuropathies, present discoveries resulting from these models in the context of clinical findings and discuss how increased understanding of molecular mechanisms underlying different aspects of neuropathies can be translated to effective treatments to prevent, attenuate or reverse vincristine- and bortezomib-induced neuropathies. Such treatments could improve the quality of life of patients both during and after cancer therapy and, accordingly, have enormous societal impact.

Lipophilic tail modifications of 2-(hydroxymethyl)pyrrolidine scaffold reveal dual sphingosine kinase 1 and 2 inhibitors

The sphingosine 1-phosphate (S1P) signaling pathway is an attractive target for pharmacological manipulation due to its involvement in cancer progression and immune cell chemotaxis. The synthesis of S1P is catalyzed by the action of sphingosine kinase 1 or 2 (SphK1 or SphK2) on sphingosine and ATP. While potent and selective inhibitors of SphK1 or SphK2 have been reported, development of potent dual SphK1/SphK2 inhibitors are still needed. Towards this end, we report the structure-activity relationship profiling of 2-(hydroxymethyl)pyrrolidine-based inhibitors with 22d being the most potent dual SphK1/SphK2 inhibitor (SphK1 K_i = 0.679 μM, SphK2 K_i = 0.951 μM) reported in this series. 22d inhibited the growth of engineered Saccharomyces cerevisiae and decreased S1P levels in histiocytic lymphoma myeloid cell line (U937 cells), demonstrating inhibition of SphK1 and 2 in vitro. Molecular modeling studies of 22d docked inside the Sph binding pocket of both SphK1 and SphK2 indicate essential hydrogen bond between the 2-(hydroxymethyl)pyrrolidine head to interact with aspartic acid and serine residues near the ATP binding pocket, which provide the basis for dual inhibition. In addition, the dodecyl tail adopts a "J-shape" conformation found in crystal structure of sphingosine bound to SphK1. Collectively, these studies provide insight into the intermolecular interactions in the SphK1 and 2 active sites to achieve maximal dual inhibitory activity.

Effects of Sphingosine-1-Phosphate on Cell Viability, Differentiation, and Gene Expression of Adipocytes

Sphingosine-1-phosphate (S1P) is a highly potent sphingolipid metabolite, which controls numerous physiological and pathological process via its extracellular and intracellular functions. The breast is mainly composed of epithelial cells (mammary gland) and adipocytes (stroma). Adipocytes play an important role in regulating the normal functions of the breast. Compared to the vast amount studies on breast epithelial cells, the functions of S1P in breast adipocytes are much less known. Thus, in the current study, we used human preadipocyte cell lines SGBS and mouse preadipocyte cell line 3T3-L1 as in vitro models to evaluate the effects of S1P on cell viability, differentiation, and gene expression in adipocytes. Our results showed that S1P increased cell viability in SGBS and 3T3-L1 preadipocytes but moderately reduced cell viability in differentiated SGBS and 3T3-L1 adipocytes. S1P was also shown to inhibit adipogenic differentiation of SGBS and 3T3-L1 at concentration higher than 1000 nM. Transcriptome analyses showed that S1P was more influential on gene expression in differentiated adipocytes. Furthermore, our network analysis in mature adipocytes showed that the upregulated DEGs (differentially expressed genes) were related to regulation of lipolysis, PPAR (peroxisome proliferator-activated receptor) signaling, alcoholism, and toll-like receptor signaling, whereas the downregulated DEGs were overrepresented in cytokine-cytokine receptor interaction, focal adhesion, starch and sucrose metabolism, and nuclear receptors pathways. Together previous studies on the functions of S1P in breast epithelial cells, the current study implicated that S1P may play a critical role in modulating the bidirectional regulation of adipocyte-extracellular matrix-epithelial cell axis and maintaining the normal physiological functions of the breast.

Sphingosine-1-phosphate: From insipid lipid to a key regulator

It is a great honor to be asked to write a "Reflections" article by one of the true icons of biochemistry, Herb Tabor. I felt humbled, especially since it follows many written by biochemists I admire and whose contributions have shaped major advances in biochemistry and molecular biology in the last century. Here I present my personal reflections on my adventure with the bioactive sphingolipid metabolite sphingosine-1-phosphate intertwined with those of my family life as a wife, mother, and grandmother. These reflections brought back many memories of events in my early career that played significant roles in determining the path I have taken for more than 40 years and that brought much fun and satisfaction into my life. It has been an exciting journey so far, with many surprises along the way, that still continues.

Structure-function analysis of lipid substrates and inhibitors of sphingosine kinases

The sphingosine kinases, SK1 and SK2, catalyse the formation of the bioactive signalling lipid, sphingosine 1-phosphate (S1P), from sphingosine. SK1 and SK2 differ in their subcellular localisation, trafficking and regulation, but the isoforms are also distinct in their selectivity toward naturally occurring and synthetic ligands as substrates and inhibitors. To date, only the structure of SK1 has been determined, and a structural basis for selectivity differences in substrate handling by SK2 has yet to be established. Here we present a structural rationale, based on homology modelling and ligand docking, to account for the capacity of SK2, but not SK1, to efficiently process the pharmacologically active substances, fingolimod (FTY720) and safingol, as substrates. We propose that two key residue differences in hSK2 (Ser305/Thr584 in place of Ala175/Ala339 in hSK1) facilitate conformational switching in the lipid head group anchor residue, Asp308 (corresponding to Asp178 in hSK1), to accommodate substrate diversity for SK2. Our analysis accounts for the contrasting behaviour of fingolimod and safingol as non-turnover inhibitors of SK1, but substrates for SK2, and the observed stereoselectivity for phosphorylation of the pro-S hydroxymethyl group of fingolimod to generate (S)-FTY720-P in vivo. We also rationalise why methylation of the pro-R hydroxymethyl of FTY720 switches the behaviour of the resulting compound, (R)-FTY720 methyl ether (ROMe), to SK2-selective inhibition. Whilst the pharmacological significance of (S)-FTY720-P is firmly established, as the active principle of fingolimod in treating relapsing-remitting multiple sclerosis, the potential importance of SK-mediated phosphorylation of other substrates, such as safingol and non-canonical naturally occuring substrates such as (4E,nZ)-sphingadienes, is less widely appreciated. Thus, the contribution of SK2-derived safingol 1-phosphate to the anti-cancer activity of safingol should be considered. Similarly, the biological role of sphingadiene 1-phosphates derived from plant-based dietary sphingadienes, which we also show here are substrates for both SK1 and SK2, merits investigation.

Recent advances in the role of sphingosine 1-phosphate in cancer

Sphingosine 1-phosphate (S1P) is a bioactive lipid that binds to a family of G protein-coupled receptors (S1P_1-5 ) and intracellular targets, such as HDAC1/2, that are functional in normal and pathophysiologic cell biology. There is a significant role for sphingosine 1-phosphate in cancer underpinning the so-called hallmarks, such as transformation and replicative immortality. In this review, we survey the most recent developments concerning the role of sphingosine 1-phosphate receptors, sphingosine kinase and S1P lyase in cancer and the prognostic indications of these receptors and enzymes in terms of disease-specific survival and recurrence. We also provide evidence for identification of new therapeutic approaches targeting sphingosine 1-phosphate to prevent neovascularisation, to revert aggressive and drug-resistant cancers to more amenable forms sensitive to chemotherapy, and to induce cytotoxicity in cancer cells. Finally, we briefly describe current advances in the development of isoform-specific inhibitors of sphingosine kinases for potential use in the treatment of various cancers, where these enzymes have a predominant role. This review will therefore highlight sphingosine 1-phosphate signalling as a promising translational target for precision medicine in stratified cancer patients.

The imbalance in the aortic ceramide/sphingosine-1-phosphate rheostat in ovariectomized rats and the preventive effect of estrogen

Background

The prevalence of hypertension in young women is lower than that in age-matched men while the prevalence of hypertension in women is significantly increased after the age of 50 (menopause) and is greater than that in men. It is already known that sphingosine-1-phosphate (S1P) and ceramide regulate vascular tone with opposing effects. This study aimed to explore the effects of ovariectomy and estrogen supplementation on the ceramide/S1P rheostat of the aorta in rats, and to explore a potential mechanism for perimenopausal hypertension and a brand-new target for menopausal hormone therapy to protect vessels.

Methods

In total, 30 female adult SD rats were randomly divided into three groups: The sham operation group (SHAM), ovariectomy group (OVX) and ovariectomy plus estrogen group (OVX + E). After 4 weeks of treatment, the blood pressure (BP) of the rats was monitored by a noninvasive system; the sphingolipid content (e.g., ceramide and S1P) was detected by liquid chromatography-mass spectrometry (LC-MS); the expression of the key enzymes involved in ceramide anabolism and catabolism was measured by real-time fluorescence quantitative polymerase chain reaction (qPCR); and the expression of key enzymes and proteins in the sphingosine kinase 1/2 (SphK1/2)-S1P-S1P receptor 1/2/3 (S1P1/2/3) signaling pathway was detected by qPCR and western blotting.

Results

In the OVX group compared with the SHAM group, the systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) increased significantly, especially the SBP and PP (P < 0.001). For aortic ceramide metabolism, the mRNA level of key enzymes involved in anabolism and catabolism decreased in parallel 2–3 times, while the contents of total ceramide and certain long-chain subtypes increased significantly (P < 0.05). As for the S1P signaling pathway, SphK1/2, the key enzymes involved in S1P synthesis, decreased significantly, and the content of S1P decreased accordingly (P < 0.01). The S1P receptors showed various trends: S1P1 was significantly down-regulated, S1P2 was significantly up-regulated, and S1P3 showed no significant difference. No significant difference existed between the SHAM and OVX + E groups for most of the above parameters (P > 0.05).

Conclusions

Ovariectomy resulted in the imbalance of the aortic ceramide/S1P rheostat in rats, which may be a potential mechanism underlying the increase in SBP and PP among perimenopausal women. Besides, the ceramide/S1P rheostat may be a novel mechanism by which estrogen protects vessels.

Evaluating the antitumor activity of sphingosine-1-phosphate against human triple-negative breast cancer cells with basal-like morphology

Sphingosine-1-phosphate (S1P) is an important sphingolipid metabolite that regulates a wide range of physiological and pathophysiological processes. Our previous studies show that S1P selectively induces cell apoptosis in human breast cancer luminal A subtype cell line MCF7. In addition, S1P exhibits synergistic effects with chemotherapy drugs against both MCF7 and luminal B subtype cell line MDA-MB-361 at concentration in the high nM to low μM range. In the current study, we evaluated the effect of S1P on proliferation, apoptosis and cytotoxicity towards a panel of nine triple-negative breast cancer with basal-like morphology (TNBC-BL) cell lines (HCC1599, HCC1937, HCC1143, MDA-MB-468, HCC38, HCC70, HCC1806, HCC1187 and DU4475) in the same concentration range. S1P exhibited mild to moderate effects (<20% increase comparted to control) towards the TNBC-BL cell lines except HCC38, HCC70 and HCC1806. Furthermore, it increased cell apoptosis by ~15-20% in all the cell lines compared to the control, and elicited moderate to strong cytotoxic effect towards all cell lines except MDA-MB-468 and HCC1806. However, no synergistic/additive effect was observed between S1P and chemotherapy drug docetaxel for any TNBC-BL cell line.