Sphingosine 1-phosphate signaling in ischemia and reperfusion injury

Sphingosine 1-phosphate protective effect on human proximal tubule cells submitted to an in vitro ischemia model: the role of JAK2/STAT3

Acute kidney injury is a serious public health problem worldwide, being ischemia and reperfusion (I/R) the main lesion-aggravating factor that contributes to the evolution towards chronic kidney disease. Nonetheless, intervention approaches currently available are just considered palliative options. In order to offer an alternative treatment, it is important to understand key factors involved in the development of the disease including the rescue of the affected cells and/or the release of paracrine factors that are crucial for tissue repair. Bioactive lipids such as sphingosine 1-phosphate (S1P) have significant effects on the modulation of signaling pathways involved in tissue regeneration, such as cell survival, proliferation, differentiation, and migration. The main objective of this work was to explore the protective effect of S1P using human kidney proximal tubule cells submitted to a mimetic I/R lesion, via ATP depletion. We observed that the S1P pre-treatment increases cell survival by 50% and preserves the cell proliferation capacity of injured cells. We showed the presence of different bioactive lipids notably related to tissue repair but, more importantly, we noted that the pre-treatment with S1P attenuated the ischemia-induced effects in response to the injury, resulting in higher endogenous S1P production. All receptors but S1PR3 are present in these cells and the protective and proliferative effect of S1P/S1P receptors axis occur, at least in part, through the activation of the SAFE pathway. To our knowledge, this is the first time that S1PR4 and S1PR5 are referred in these cells and also the first indication of JAK2/STAT3 pathway involvement in S1P-mediated protection in an I/R renal model.

1-Phosphate receptor agonists: A promising therapeutic avenue for ischemia-reperfusion injury management

Ischemia-reperfusion injury (IRI) - a complex pathological condition occurring when blood supply is abruptly restored to ischemic tissues, leading to further tissue damage - poses a significant clinical challenge. Sphingosine-1-phosphate receptors (S1PRs), a specialized set of G-protein-coupled receptors comprising five subtypes (S1PR1 to S1PR5), are prominently present in various cell membranes, including those of lymphocytes, cardiac myocytes, and endothelial cells. Increasing evidence highlights the potential of targeting S1PRs for IRI therapeutic intervention. Notably, preconditioning and postconditioning strategies involving S1PR agonists like FTY720 have demonstrated efficacy in mitigating IRI. As the synthesis of a diverse array of S1PR agonists continues, with FTY720 being a prime example, the body of experimental evidence advocating for their role in IRI treatment is expanding. Despite this progress, comprehensive reviews delineating the therapeutic landscape of S1PR agonists in IRI remain limited. This review aspires to meticulously elucidate the protective roles and mechanisms of S1PR agonists in preventing and managing IRI affecting various organs, including the heart, kidney, liver, lungs, intestines, and brain, to foster novel pharmacological approaches in clinical settings.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Immediate major dynamic changes in the T- and NK-cell subset composition after cardiac transplantation

Early kinetics of lymphocyte subsets involved in tolerance and rejection following heart transplantation (HTx) are barely defined. Here, we aimed to delineate the early alloimmune response immediately after HTx. Therefore, blood samples from 23 heart-transplanted patients were collected before (pre-), immediately (T0), 24 hours (T24), and 3 weeks (3 wks) after HTx. Immunophenotyping was performed using flow cytometry. A significant increase was detected for terminally differentiated (TEMRA) CD4+ or CD8+ T cells and CD56dim CD16+ NK cells immediately after HTx linked to a decrease in naïve CD8+ and CM CD4+ T as well as CD56bright CD16- NK cells, returning to baseline levels at T24. More detailed analyses revealed increased CD69+ CD25- and diminished CD69- CD25- CD4+ or CD8+ T-cell proportions at T0 associated with decreasing S1PR1 expression. Passenger T and NK cells were found at low frequencies only in several patients at T0 and did not correlate with lymphocyte alterations. Collectively, these results suggest an immediate, transient shift toward memory T and NK cells following HTx. Opposite migratory properties of naïve versus memory T and NK cells occurring in the early phase after HTx could underlie these observations and may impinge on the development of allo-specific immune responses.

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Microvascular Leakage as Therapeutic Target for Ischemia and Reperfusion Injury

Reperfusion injury is a very common complication of various indicated therapies such as the re-opening of vessels in the myocardium or brain as well as reflow in hemodynamic shutdown (cardiac arrest, severe trauma, aortic cross-clamping). The treatment and prevention of reperfusion injury has therefore been a topic of immense interest in terms of mechanistic understanding, the exploration of interventions in animal models and in the clinical setting in major prospective studies. While a wealth of encouraging results has been obtained in the lab, the translation into clinical success has met with mixed outcomes at best. Considering the still very high medical need, progress continues to be urgently needed. Multi-target approaches rationally linking interference with pathophysiological pathways as well as a renewed focus on aspects of microvascular dysfunction, especially on the role of microvascular leakage, are likely to provide new insights.

Effect of albumin solutions on endothelial oxidant injury: A microfluidic study

BACKGROUND

Studies have suggested a beneficial effect of early plasma-based resuscitation in patients following trauma-hemorrhagic shock. The underlying mechanism(s) are unknown but may be owing to protective effects of plasma components on the endothelium and its glycocalyx layer. Albumin, the major protein in plasma, influences vascular integrity and has antioxidant properties in vivo. Sphingosine 1-phosphate is a bioactive sphingolipid with diverse signaling functions, which include endothelial barrier protection in part owing to preservation of the glycocalyx. Sphingosine 1-phosphate is bound mainly to albumin and high-density lipids in the plasma. Debate continues about the beneficial effect of albumin solutions in shock resuscitation. Pharmacologic preparations may modify constituents of albumin solutions for clinical use. We examined the relative effects of sphingosine 1-phosphate concentrations in albumin solutions on the endothelial-glycocalyx barrier in an in vitro microfluidic platform.

METHODS

Endothelial cell monolayers were established in microfluidic perfusion devices and exposed to control or biomimetic shock conditions followed by 5% plasma or different albumin solutions ± exogenous sphingosine 1-phosphate perfusion. Biomarkers of endothelial and glycocalyx activation, damage, and oxidant injury were then determined.

RESULTS

Endothelial cell and glycocalyx barriers were damaged after biomimetic shock conditions. Plasma and sphingosine 1-phosphate loaded albumin solutions protected against barrier injury. Modest protective effects were noted with albumin alone; the efficacy varied with sphingosine 1-phosphate content of the albumin solution.

CONCLUSION

The protective effect of albumin on the endothelia-glycocalyx barrier against oxidant injury was dependent on its sphingosine 1-phosphate concentration. Our data may help explain the discrepancies regarding the effectiveness of albumin solutions in shock resuscitation.

Determination of endogenous sphingolipid content in stroke rats and HT22 cells subjected to oxygen-glucose deprivation by LC‒MS/MS

BACKGROUND

Stroke is the leading cause of death in humans worldwide, and its incidence increases every year. It is well documented that lipids are closely related to stroke. Analyzing the changes in lipid content in the stroke model after absolute quantification and investigating whether changes in lipid content can predict stroke severity provides a basis for the combination of clinical stroke and quantitative lipid indicators.

METHODS

This paper establishes a rapid, sensitive, and reliable LC‒MS/MS analytical method for the detection of endogenous sphingolipids in rat serum and brain tissue and HT22 cells and quantifies the changes in sphingolipid content in the serum and brain tissue of rats from the normal and pMCAO groups and in cells from the normal and OGD/R groups. Using sphingosine (d17:1) as the internal standard, a chloroform: methanol (9:1) mixed system was used for protein precipitation and lipid extraction, followed by analysis by reversed-phase liquid chromatography coupled to triple quadrupole mass spectrometry.

RESULTS

Based on absolute quantitative analysis of lipids in multiple biological samples, our results show that compared with those in the normal group, the contents of sphinganine (d16:0), sphinganine (d18:0), and phytosphingosine were significantly increased in the model group, except sphingosine-1-phosphate, which was decreased in various biological samples. The levels of each sphingolipid component in serum fluctuate with time.

CONCLUSION

This isotope-free and derivatization-free LC‒MS/MS method can achieve absolute quantification of sphingolipids in biological samples, which may also help identify lipid biomarkers of cerebral ischemia.

Berberine: A Review of its Pharmacokinetics Properties and Therapeutic Potentials in Diverse Vascular Diseases

Traditional Chinese medicine plays a significant role in the treatment of various diseases and has attracted increasing attention for clinical applications. Vascular diseases affecting vasculature in the heart, cerebrovascular disease, atherosclerosis, and diabetic complications have compromised quality of life for affected individuals and increase the burden on health care services. Berberine, a naturally occurring isoquinoline alkaloid form Rhizoma coptidis, is widely used in China as a folk medicine for its antibacterial and anti-inflammatory properties. Promisingly, an increasing number of studies have identified several cellular and molecular targets for berberine, indicating its potential as an alternative therapeutic strategy for vascular diseases, as well as providing novel evidence that supports the therapeutic potential of berberine to combat vascular diseases. The purpose of this review is to comprehensively and systematically describe the evidence for berberine as a therapeutic agent in vascular diseases, including its pharmacological effects, molecular mechanisms, and pharmacokinetics. According to data published so far, berberine shows remarkable anti-inflammatory, antioxidant, antiapoptotic, and antiautophagic activity via the regulation of multiple signaling pathways, including AMP-activated protein kinase (AMPK), nuclear factor κB (NF-κB), mitogen-activated protein kinase silent information regulator 1 (SIRT-1), hypoxia-inducible factor 1α (HIF-1α), vascular endothelial growth factor phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), janus kinase 2 (JAK-2), Ca²⁺ channels, and endoplasmic reticulum stress. Moreover, we discuss the existing limitations of berberine in the treatment of vascular diseases, and give corresponding measures. In addition, we propose some research perspectives and challenges, and provide a solid evidence base from which further studies can excavate novel effective drugs from Chinese medicine monomers.

Histone methyltransferase Smyd2 contributes to blood-brain barrier breakdown in stroke

BACKGROUND

The blood-brain barrier (BBB) plays a principal role in the healthy and diseased central nervous systems, and BBB disruption after ischaemic stroke is responsible for increased mortality. Smyd2, a member of the SMYD-methyltransferase family, plays a vital role in disease by methylation of diverse substrates; however, little is known about its role in the pathophysiology of the brain in response to ischaemia-reperfusion injury.

METHODS

Using oxygen glucose deprivation and reoxygenation (OGD/R)-induced primary brain microvascular endothelial cells (BMECs) and Smyd2 knockdown mice subjected to middle cerebral artery occlusion, we evaluated the role of Smyd2 in BBB disruption. We performed loss-of-function and gain-of-function studies to investigate the biological function of Smyd2 in ischaemic stroke.

RESULTS

We found that Smyd2 was a critical factor for regulating brain endothelial barrier integrity in ischaemia-reperfusion injury. Smyd2 is upregulated in peri-ischaemic brains, leading to BBB disruption via methylation-mediated Sphk/S1PR. Knockdown of Smyd2 in mice reduces BBB permeability and improves functional recovery. Using OGD/R-induced BMECs, we demonstrated that Sphk/S1PR methylation modification by Smyd2 affects ubiquitin-dependent degradation and protein stability, which may disrupt endothelial integrity. Moreover, overexpression of Smyd2 can damage endothelial integrity through Sphk/S1PR signalling.

CONCLUSIONS

Overall, these results reveal a novel role for Smyd2 in BBB disruption in ischaemic stroke, suggesting that Smyd2 may represent a new therapeutic target for ischaemic stroke.

Ceramide-1-Phosphate as a Potential Regulator of the Second Sodium Pump from Kidney Proximal Tubules by Triggering Distinct Protein Kinase Pathways in a Hierarchic Way

Kidney proximal tubules are a key segment in the reabsorption of solutes and water from the glomerular ultrafiltrate, an essential process for maintaining homeostasis in body fluid compartments. The abundant content of Na⁺ in the extracellular fluid determines its importance in the regulation of extracellular fluid volume, which is particularly important for different physiological processes including blood pressure control. Basolateral membranes of proximal tubule cells have the classic Na⁺ + K⁺-ATPase and the ouabain-insensitive, K⁺-insensitive, and furosemide-sensitive Na⁺-ATPase, which participate in the active Na⁺ reabsorption. Here, we show that nanomolar concentrations of ceramide-1 phosphate (C1P), a bioactive sphingolipid derived in biological membranes from different metabolic pathways, promotes a strong inhibitory effect on the Na⁺-ATPase activity (C1P₅₀ ≈ 10 nM), leading to a 72% inhibition of the second sodium pump in the basolateral membranes. Ceramide-1-phosphate directly modulates protein kinase A and protein kinase C, which are known to be involved in the modulation of ion transporters including the renal Na⁺-ATPase. Conversely, we did not observe any effect on the Na⁺ + K⁺-ATPase even at a broad C1P concentration range. The significant effect of ceramide-1-phosphate revealed a new potent physiological and pathophysiological modulator for the Na⁺-ATPase, participating in the regulatory network involving glycero- and sphingolipids present in the basolateral membranes of kidney tubule cells.

Aquaporin 4 inhibition alleviates myocardial ischemia-reperfusion injury by restraining cardiomyocyte pyroptosis

Myocardial injury caused by ischemia-reperfusion is the main pathological manifestation of coronary artery disease (CAD), which is characterized by high mortality and morbidity. Thus, there’s an urgent need to develop efficacious strategies and elucidate the underlying mechanisms to prevent or alleviate myocardial ischemia-reperfusion injury to improve the clinical outcomes in patients. In this study, we took advantage of a typical myocardial cell line of mice (HL-1) and cultured with or without an aquaporin 4 inhibitor (TGN-20 denoted as AQP4i) under normal conditions (NC), ischemia (IS) and ischemia reperfusion (IR), respectively. The cytomorphology, ultrastructure, cell vitality and expression pattern of apoptotic proteins were verified with scanning electron microscope (SEM), immunofluorescence staining, flow cytometry, quantitative real-time PCR and western-blotting analysis, respectively. HL-1 under IS or IR condition revealed higher expression of Aquaporin 4 (Aqp4) compared to the NC group, whereas showed similarity in cytomorphology and ultrastructure. Aqp4 inhibition was sufficient to improve the apoptotic cells in HL-1 while showed minimal effects to the other cellular vitality. Furthermore, the expression pattern of apoptotic proteins and anti-apoptotic proteins together with proinflammatory factors in HL-1 was effectively rescued by Aqp4i treatment both at the mRNA level and protein level. Ischemia and ischemia reperfusion caused higher expression of Aqp4 and resultant increase of cardiomyocyte pyroptosis. Myocardial ischemia-reperfusion injury of HL-1 was effectively alleviated by Aqp4 and pyroptosis inhibition. Our findings provided new references for myocardial ischemia-reperfusion injury management via targeting Aqp4-mediated pyroptosis of cardiomyocyte.

Serum Sphingosine-1-Phosphate Levels Are Associated With Severity and Outcome in Patients With Cerebral Ischemia

BACKGROUND AND PURPOSE

The aim of this study was to examine whether sphingosine-1-phosphate (S1P) levels in patients with acute stroke are associated with stroke severity and outcome.

METHODS

In a prospective stroke cohort (MARK-STROKE), 374 patients with acute ischemic stroke or transient ischemic attack were enrolled (mean age: 67.9±13.0 years, sex: 64.7% male), and serum-S1P at admission was analyzed with tandem mass spectrometry. In addition to cross-sectional analyses, 79 adverse events (death, stroke, myocardial infarction, rehospitalization) were recorded in 270 patients during follow-up. Regression analyses were adjusted for age, sex, low-density lipoprotein cholesterol, and vascular risk factors. Results were validated in an independent stroke cohort with 219 patients with acute ischemic stroke (CIRCULAS).

RESULTS

Low serum-S1P was associated with higher National Institutes of Health Stroke Scale score at admission and with anterior circulation nonlacunar infarcts determined by multivariate regression analyses. During a follow-up of 294±170 days, patients with S1P in the lowest tertile (<1.33 µmol/L) had more adverse events (Kaplan-Meier analysis, P=0.048 for trend). In adjusted Cox regression analysis, the lowest S1P tertile was associated with a worse outcome after stroke (hazard ratio, HR 0.51 [95% confidence interval 0.28-0.92]). Results were confirmed in an independent cohort, ie, low S1P levels were associated with higher National Institutes of Health Stroke Scale, larger infarct volumes and worse outcome after 90 days (β-coefficient: -0.03, P=0.026; β-coefficient: -0.099, P=0.009 and odds ratio 0.52 [0.28-0.96], respectively).

CONCLUSIONS

Our findings imply a detrimental role of low S1P levels in acute stroke and therefore underpin the therapeutic potential of S1P-mimics.

The role of lipid-based signalling in wound healing and senescence

Lipid-based signalling modulates several cellular processes and intercellular communication during wound healing and tissue regeneration. Bioactive lipids include but are not limited to the diverse group of eicosanoids, phospholipids, and extracellular vesicles and mediate the attraction of immune cells, initiation of inflammatory responses, and their resolution. In aged individuals, wound healing and tissue regeneration are greatly impaired, resulting in a delayed healing process and non-healing wounds. Senescent cells accumulate with age in vivo, preferably at sites implicated in age-associated pathologies and their elimination was shown to alleviate many age-associated diseases and disorders. In contrast to these findings, the transient presence of senescent cells in the process of wound healing exerts beneficial effects and limits fibrosis. Hence, clearance of senescent cells during wound healing was repeatedly shown to delay wound closure in vivo. Recent findings established a dysregulated synthesis of eicosanoids, phospholipids and extracellular vesicles as part of the senescent phenotype. This intriguing connection between cellular senescence, lipid-based signalling, and the process of wound healing and tissue regeneration prompts us to compile the current knowledge in this review and propose future directions for investigation.

Sphingosine 1-phosphate and its receptors in ischemia

Sphingosine 1-phosphate (S1P), a metabolite of sphingolipids, is mainly derived from red blood cells (RBCs), platelets and endothelial cells (ECs). It plays important roles in regulating cell survival, vascular integrity and inflammatory responses through its receptors. S1P receptors (S1PRs), including 5 subtypes (S1PR1-5), are G protein-coupled receptors and have been proved to mediate various and complex roles of S1P in atherosclerosis, myocardial infarction (MI) and ischemic stroke by regulating endothelial function and inflammatory response as well as immune cell behavior. This review emphasizes the functions of S1PRs in atherosclerosis and ischemic diseases such as MI and ischemic stroke, enabling mechanistic studies and new S1PRs targeted therapies in atherosclerosis and ischemia in the future.

The Endothelial Glycocalyx as a Target of Ischemia and Reperfusion Injury in Kidney Transplantation-Where Have We Gone So Far?

The damage of the endothelial glycocalyx as a consequence of ischemia and/or reperfusion injury (IRI) following kidney transplantation has come at the spotlight of research due to potential associations with delayed graft function, acute rejection as well as long-term allograft dysfunction. The disintegration of the endothelial glycocalyx induced by IRI is the crucial event which exposes the denuded endothelial cells to further inflammatory and oxidative damage. The aim of our review is to present the currently available data regarding complex links between shedding of the glycocalyx components, like syndecan-1, hyaluronan, heparan sulphate, and CD44 with the activation of intricate immune system responses, including toll-like receptors, cytokines and pro-inflammatory transcription factors. Evidence on modes of protection of the endothelial glycocalyx and subsequently maintenance of endothelial permeability as well as novel nephroprotective molecules such as sphingosine-1 phosphate (S1P), are also depicted. Although advances in technology are making the visualization and the analysis of the endothelial glycocalyx possible, currently available evidence is mostly experimental. Ongoing progress in understanding the complex impact of IRI on the endothelial glycocalyx, opens up a new era of research in the field of organ transplantation and clinical studies are of utmost importance for the future.

Untargeted metabolomics reveals the synergistic mechanisms of Yuanhu Zhitong oral liquid in the treatment of primary dysmenorrhea

Primary dysmenorrhea is a prevalent gynecological disorder that severely affects the quality of life in women. Yuanhu Zhitong oral liquid (YZOL) is a standardized herbal preparation frequently used in clinical practice and is a promising alternative therapy for primary dysmenorrhea. The findings of previous studies show that YZOL exhibits significant analgesic and spasmolytic effects, however, the involved mechanism remains unclear. Herein, we performed an untargeted plasma metabolomic analysis on a mouse model of oxytocin-induced primary dysmenorrhea to investigate the underlying mechanism of YZOL. We used multivariate and pathway-driven analyses to uncover the treatment targets linked with YZOL therapy and verified the possible mechanisms through biochemical assays. Therefore, we identified 47 plasma biomarkers primarily associated with sphingolipid metabolism, amino acid metabolism, arachidonic acid metabolism, and biosynthesis of steroid hormone as well as primary bile acid. We established that the analgesic effect of YZOL on primary dysmenorrhea relies on multiple constituents that act on multiple targets in multiple pathways. Our correlation analysis showed significant correlations between the biomarkers and biochemical indicators, which is of considerable significance in elucidating the YZOL mechanisms. Moreover, we identified some novel prospective biomarkers linked to primary dysmenorrhea, including bile acids. Collectively, these data provide new insights into the mechanism of YZOL and provide evidence for the analgesic effect of YZOL in the treatment of primary dysmenorrhea.

An Insight into Molecular Mechanisms and Novel Therapeutic Approaches in Epileptogenesis

Epilepsy is the second most common neurological disease with abnormal neural activity involving the activation of various intracellular signalling transduction mechanisms. The molecular and system biology mechanisms responsible for epileptogenesis are not well defined or understood. Neuroinflammation, neurodegeneration and Epigenetic modification elicit epileptogenesis. The excessive neuronal activities in the brain are associated with neurochemical changes underlying the deleterious consequences of excitotoxicity. The prolonged repetitive excessive neuronal activities extended to brain tissue injury by the activation of microglia regulating abnormal neuroglia remodelling and monocyte infiltration in response to brain lesions inducing axonal sprouting contributing to neurodegeneration. The alteration of various downstream transduction pathways resulted in intracellular stress responses associating endoplasmic reticulum, mitochondrial and lysosomal dysfunction, activation of nucleases, proteases mediated neuronal death. The recently novel pharmacological agents modulate various receptors like mTOR, COX-2, TRK, JAK-STAT, epigenetic modulators and neurosteroids are used for attenuation of epileptogenesis. Whereas the various molecular changes like the mutation of the cell surface, nuclear receptor and ion channels focusing on repetitive episodic seizures have been explored by preclinical and clinical studies. Despite effective pharmacotherapy for epilepsy, the inadequate understanding of precise mechanisms, drug resistance and therapeutic failure are the current fundamental problems in epilepsy. Therefore, the novel pharmacological approaches evaluated for efficacy on experimental models of epilepsy need to be identified and validated. In addition, we need to understand the downstream signalling pathways of new targets for the treatment of epilepsy. This review emphasizes on the current state of novel molecular targets as therapeutic approaches and future directions for the management of epileptogenesis. Novel pharmacological approaches and clinical exploration are essential to make new frontiers in curing epilepsy.

Sphingosine 1-phosphate in sepsis and beyond: Its role in disease tolerance and host defense and the impact of carrier molecules

Sphingosine 1-phosphate (S1P) is an important immune modulator responsible for physiological cellular responses like lymphocyte development and function, positioning and emigration of T and B cells and cytokine secretion. Recent reports indicate that S1P does not only regulate immunity, but can also protect the function of organs by inducing disease tolerance. S1P also influences the replication of certain pathogens, and sphingolipids are also involved in pathogen recognition and killing. Certain carrier molecules for S1P like serum albumin and high density lipoproteins contribute to the regulation of S1P effects. They are able to associate with S1P and modulate its signaling properties. Similar to S1P, both carrier molecules are also decreased in sepsis patients and likely contribute to sepsis pathology and severity. In this review, we will introduce the concept of disease tolerance and the involvement of S1P. We will also discuss the contribution of S1P and its precursor sphingosine to host defense mechanisms against pathogens. Finally, we will summarize current data demonstrating the influence of carrier molecules for differential S1P signaling. The presented data may lead to new strategies for the prevention and containment of sepsis.

Endothelial-protective effects of a G-protein-biased sphingosine-1 phosphate receptor-1 agonist, SAR247799, in type-2 diabetes rats and a randomized placebo-controlled patient trial

Aims

SAR247799 is a G‐protein‐biased sphingosine‐1 phosphate receptor‐1 (S1P₁) agonist designed to activate endothelial S1P₁ and provide endothelial‐protective properties, while limiting S1P₁ desensitization and consequent lymphocyte‐count reduction associated with higher doses. The aim was to show whether S1P₁ activation can promote endothelial effects in patients and, if so, select SAR247799 doses for further clinical investigation.

Methods

Type‐2 diabetes patients, enriched for endothelial dysfunction (flow‐mediated dilation, FMD <7%; n = 54), were randomized, in 2 sequential cohorts, to 28‐day once‐daily treatment with SAR247799 (1 or 5 mg in ascending cohorts), placebo or 50 mg sildenafil (positive control) in a 5:2:2 ratio per cohort. Endothelial function was assessed by brachial artery FMD. Renal function, biomarkers and lymphocytes were measured following 5‐week SAR247799 treatment (3 doses) to Zucker diabetic fatty rats and the data used to select the doses for human testing.

Results

The maximum FMD change from baseline vs placebo for all treatments was reached on day 35; mean differences vs placebo were 0.60% (95% confidence interval [CI] −0.34 to 1.53%; P = .203) for 1 mg SAR247799, 1.07% (95% CI 0.13 to 2.01%; P = .026) for 5 mg SAR247799 and 0.88% (95% CI −0.15 to 1.91%; P = .093) for 50 mg sildenafil. Both doses of SAR247799 were well tolerated, did not affect blood pressure, and were associated with minimal‐to‐no lymphocyte reduction and small‐to‐moderate heart rate decrease.

Conclusion

These data provide the first human evidence suggesting endothelial‐protective properties of S1P₁ activation, with SAR247799 being as effective as the clinical benchmark, sildenafil. Further clinical testing of SAR247799, at sub‐lymphocyte‐reducing doses (≤5 mg), is warranted in vascular diseases associated with endothelial dysfunction.

Impact of S1P Mimetics on Mesenteric Ischemia/Reperfusion Injury

Mesenteric ischemia/reperfusion (I/R), following the transient deprivation of blood flow to the gut, triggers an acute flogistic process involving the disruption of endothelial and epithelial barriers integrity, the activation of immune cells, and the abundant release of inflammatory mediators. Among them, the lipid mediator sphingosine-1-phosphate (S1P) is involved in maintaining epithelial and endothelial barrier integrity and in governing the migration of immune cells through the interaction with S1P_1–5 receptors. Therefore, the present work aims to investigate the involvement of S1P signaling in intestinal I/R-induced injury by studying the effects of FTY720, the non-selective S1P_1,3–5 agonist, and comparing them with the responses to ozanimod, selective S1P_1,5 agonist, in a murine model of gut I/R. Intestinal edema, gut and lung neutrophil infiltration, and oxidative stress were evaluated through biochemical and morphological assays. The collected results highlight the protective action of FTY720 against the inflammatory cascade elicited by mesenteric I/R injury, mainly through the control of vascular barrier integrity. While these beneficial effects were mimicked by ozanimod and can be therefore attributed largely to the effects exerted by FTY720 on S1P₁, the recruitment of myeloid cells to the injured areas, limited by FTY720 but not by ozanimod, rather suggests the involvement of other receptor subtypes.