Fungal metabolites. Part 11. A potent immunosuppressive activity found in Isaria sinclairii metabolite

The potential capacities of FTY720: Novel therapeutic functions, targets, and mechanisms against diseases

Fingolimod (FTY720), an antagonist of sphingosine-1-phosphate (S1P), functions by binding to S1P receptors (S1PRs), excluding S1PR2. It received approval from the Food and Drug Administration (FDA) for the treatment of multiple sclerosis (MS) in 2010. As the first non-selective oral agonist for S1PRs, FTY720's diverse and systemic receptor expression often leads to alterations in various signaling pathways and multiple systems, making it a subject of intense research. Recent studies have identified a wide range of novel or potential functions for FTY720 beyond its application in MS. These include effects on the blood-brain barrier (BBB), vascular system, organelles, and cell death, as well as potential applications in organ transplantation, immune disorders, oncological conditions, neurological and psychiatric disorders, viral infections, and hypersensitivity diseases. This paper reviews the novel roles, targets, and mechanisms of FTY720 that hold promise for clinical utility. Additionally, it summarizes FTY720's derivation and development process, the characterization and mechanism of the structure of FTY720-P bound to S1PRs, the clinical safety profile, future challenges, and potential strategies to address them. These insights aim to guide future research and applications of FTY720, maximizing its therapeutic potential.

Emerging paradigms for target discovery of traditional medicines: A genome-wide pan-GPCR perspective

Traditional medicines serve not only as an integral part of medical treatments prescribed by healthcare providers but also as a fundamental reservoir for novel molecular scaffolds. However, gaps remain in our understanding of the mechanisms underlying their activity. A superfamily of membrane proteins, G protein-coupled receptors (GPCRs), have been demonstrated to be potential targets for several compounds isolated from traditional medicines. Given that GPCRs serve as targets for approximately one-third of all marketed drugs, they may be compelling targets for repurposing traditional medicines. Despite this potential, research investigating their activity or potential ligands across GPCRome, the library of human GPCRs, is scarce. Drawing on the functional and structural knowledge presently available, this review contemplates prospective trends in GPCR drug discovery, proposes innovative strategies for investigating traditional medicines, and highlights ligand screening approaches for identifying novel drug-like molecules. To discover bioactive molecules from traditional medicines that either directly bind to GPCRs or indirectly modify their function, a genome-wide pan-GPCR drug discovery platform was designed for the identification of bioactive components and targets, and the evaluation of their pharmacological profiles. This platform aims to aid the exploration of all-sided relations between traditional medicines and GPCRome using advanced high-throughput screening techniques. We present various approaches used by many, including ourselves, to illuminate the previously unexplored aspects of traditional medicines and GPCRs.

The sphingosine-1-phosphate signaling pathway (sphingosine-1-phosphate and its receptor, sphingosine kinase) and epilepsy

Epilepsy is one of the common chronic neurological diseases, affecting more than 70 million people worldwide. The brains of people with epilepsy exhibit a pathological and persistent propensity for recurrent seizures. Epilepsy often coexists with cardiovascular disease, cognitive dysfunction, depression, etc., which seriously affects the patient's quality of life. Although our understanding of epilepsy has advanced, the pathophysiological mechanisms leading to epileptogenesis, drug resistance, and associated comorbidities remain largely unknown. The use of newer antiepileptic drugs has increased, but this has not improved overall outcomes. We need to deeply study the pathogenesis of epilepsy and find drugs that can not only prevent the epileptogenesis and interfere with the process of epileptogenesis but also treat epilepsy comorbidities. Sphingosine-1-phosphate (S1P) is an important lipid molecule. It not only forms the basis of cell membranes but is also an important bioactive mediator. It can not only act as a second messenger in cells to activate downstream signaling pathways but can also exert biological effects by being secreted outside cells and binding to S1P receptors on the cell membrane. Fingolimod (FTY720) is the first S1P receptor modulator developed and approved for the treatment of multiple sclerosis. More and more studies have proven that the S1P signaling pathway is closely related to epilepsy, drug-resistant epilepsy, epilepsy comorbidities, or other epilepsy-causing diseases. However, there is much controversy over the role of certain natural molecules in the pathway and receptor modulators (such as FTY720) in epilepsy. Here, we summarize and analyze the role of the S1P signaling pathway in epilepsy, provide a basis for finding potential therapeutic targets and/or epileptogenic biomarkers, analyze the reasons for these controversies, and put forward our opinions. PLAIN LANGUAGE SUMMARY: This article combines the latest research literature at home and abroad to review the sphingosine 1-phosphate signaling pathway and epileptogenesis, drug-resistant epilepsy, epilepsy comorbidities, other diseases that can cause epilepsy, as well as the sphingosine-1-phosphate signaling pathway regulators and epilepsy, with the expectation of providing a certain theoretical basis for finding potential epilepsy treatment targets and/or epileptogenic biomarkers in the sphingosine-1-phosphate signaling pathway.

Elucidation of physiological functions of sphingolipid-related molecules by chemical approaches

Sphingolipids (SLs), found in all animals, plants, and fungi and in certain prokaryotic organisms, exhibit essential physiological functions that cannot be replicated by other lipids. Although SLs and their related biomolecules behave as lipid mediators, skin barrier systems, and epitopes, their detailed biological functions have not yet been revealed, unlike those of proteins and nucleic acids, because the biosynthesis of SLs is not governed by the central dogma. Recently, SLs have been widely studied in relation to diseases such as obesity, dementia, and neuron agenesis and have attracted attention as molecules related to unmet medical needs. This review presents the recent applications of the SL chemical biology in unmet medical needs.

Safe and Orally Bioavailable Inhibitor of Serine Palmitoyltransferase Improves Age-Related Sarcopenia

The accumulation of ceramides and related metabolites has emerged as a pivotal mechanism contributing to the onset of age-related diseases. However, small molecule inhibitors targeting the ceramide de novo synthesis pathway for clinical use are currently unavailable. We synthesized a safe and orally bioavailable inhibitor, termed ALT-007, targeting the rate-limiting enzyme of ceramide de novo synthesis, serine palmitoyltransferase (SPT). In a mouse model of age-related sarcopenia, ALT-007, administered through the diet, effectively restored muscle mass and function compromised by aging. Mechanistic studies revealed that ALT-007 enhances protein homeostasis in Caenorhabditis elegans and mouse models of aging and age-related diseases, such as sarcopenia and inclusion body myositis (IBM); this effect is mediated by a specific reduction in very-long chain 1-deoxy-sphingolipid species, which accumulate in both muscle and brain tissues of aged mice and in muscle cells from IBM patients. These findings unveil a promising therapeutic avenue for developing safe ceramide inhibitors to address age-related neuromuscular diseases.

Sex-dependent efficacy of sphingosine-1-phosphate receptor agonist FTY720 in mitigating Huntington's disease

Huntington's disease (HD) is a debilitating neurodegenerative disorder characterized by severe motor deficits, cognitive decline and psychiatric disturbances. An early and significant morphological hallmark of HD is the activation of astrocytes triggered by mutant huntingtin, leading to the release of inflammatory mediators. Fingolimod (FTY), an FDA-approved sphingosine-1-phosphate (S1P) receptor agonist is used to treat multiple sclerosis (MS), a neuroinflammatory disease, and has shown therapeutic promise in other neurological conditions. Our study aimed to investigate the therapeutic potential of FTY for treating HD by utilizing a well-characterized mouse model of HD (zQ175dn) and wild-type littermates. The study design included a crossover, long-term oral treatment with 1 mg/kg to 2 mg/kg FTY from the age of 15-46 weeks (n = 128). Different motor behavior and physiological parameters were assessed throughout the study. The findings revealed that FTY rescued disease-related body weight loss in a sex-dependent manner, indicating its potential to regulate metabolic disturbances and to counteract neurodegenerative processes in HD. FTY intervention also rescued testicular atrophy, restored testis tissue structure in male mice suggesting a broader impact on peripheral tissues affected by huntingtin pathology. Histological analyses of the brain revealed delayed accumulation of activated astrocytes contributing to the preservation of the neural microenvironment by reducing neuroinflammation. The extent of FTY-related disease improvement was sex-dependent. Motor functions and body weight improved mostly in female mice with sustained estrogen levels, whereas males had to compensate for the ongoing, disease-related testis atrophy and the loss of androgen production. Our study underscores the beneficial therapeutic effects of FTY on HD involving endogenous steroid hormones and their important anabolic effects. It positions FTY as a promising candidate for therapeutic interventions targeting various aspects of HD pathology. Further studies are needed to fully evaluate its therapeutic potential in patients.

Role of dietary and nutritional interventions in ceramide-associated diseases

Ceramides are important intermediates in sphingolipid metabolism and serve as signaling molecules with independent biological significance. Elevated cellular and circulating ceramide levels are consistently associated with pathological conditions including cardiometabolic diseases, neurological diseases, autoimmune diseases, and cancers. Although pharmacological inhibition of ceramide formation often protects against these diseases in animal models, pharmacological modulation of ceramides in humans remains impractical. Dietary interventions including the Mediterranean diet, lacto-ovo-vegetarian diet, calorie-restricted diet, restriction of dairy product consumption, and dietary supplementation with polyunsaturated fatty acids, dietary fibers, and polyphenols, all have beneficial effects on modulating ceramide levels. Mechanistic insights into these interventions are discussed. This article reviews the relationships between ceramides and disease pathogenesis, with a focus on dietary intervention as a viable strategy for lowering the concentration of circulating ceramides.

Involvement of lipid-translocating exporter family proteins in determination of myriocin sensitivity in budding yeast

Myriocin is an inhibitor of serine palmitoyltransferase involved in the initial biosynthetic step for sphingolipids, and causes potent growth inhibition in eukaryotic cells. In budding yeast, Rsb1, Rta1, Pug1, and Ylr046c are known as the Lipid-Translocating Exporter (LTE) family and believed to contribute to export of various cytotoxic lipophilic compounds. It was reported that Rsb1 is a transporter responsible for export of intracellularly accumulated long-chain bases, which alleviate the cytotoxicity. In this study, it was found that LTE family genes are involved in determination of myriocin sensitivity in yeast. Analyses of effects of deletion and overexpression of LTE family genes suggested that all LTEs contribute to suppression of cytotoxicity of myriocin. It was confirmed that RSB1 overexpression suppressed reduction in complex sphingolipid levels caused by myriocin treatment, possibly exporting myriocin to outside of the cell. These results suggested that LTE family genes function as a defense mechanism against myriocin.

Lysophospholipid receptors in neurodegeneration and neuroprotection

The central nervous system (CNS) is one of the most complex physiological systems, and treatment of CNS disorders represents an area of major medical need. One critical aspect of the CNS is its lack of regeneration, such that damage is often permanent. The damage often leads to neurodegeneration, and so strategies for neuroprotection could lead to major medical advances. The G protein-coupled receptor (GPCR) family is one of the major receptor classes, and they have been successfully targeted clinically. One class of GPCRs is those activated by bioactive lysophospholipids as ligands, especially sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA). Research has been increasingly demonstrating the important roles that S1P and LPA, and their receptors, play in physiology and disease. In this review, I describe the role of S1P and LPA receptors in neurodegeneration and potential roles in neuroprotection. Much of our understanding of the role of S1P receptors has been through pharmacological tools. One such tool, fingolimod (also known as FTY720), which is a S1P receptor agonist but a functional antagonist in the immune system, is clinically efficacious in multiple sclerosis by producing a lymphopenia to reduce autoimmune attacks; however, there is evidence that fingolimod is also neuroprotective. Furthermore, fingolimod is neuroprotective in many other neuropathologies, including stroke, Parkinson's disease, Huntington's disease, Rett syndrome, Alzheimer's disease, and others that are discussed here. LPA receptors also appear to be involved, being upregulated in a variety of neuropathologies. Antagonists or mutations of LPA receptors, especially LPA1, are neuroprotective in a variety of conditions, including cortical development, traumatic brain injury, spinal cord injury, stroke and others discussed here. Finally, LPA receptors may interact with other receptors, including a functional interaction with plasticity related genes.

Self-activating chitosan-based nanoparticles for sphingosin-1 phosphate modulator delivery and selective tumor therapy

This study reports on the design and synthesis of hypoxia responsive nanoparticles (HRNPs) composed of methoxy polyethylene glycol-4,4 dicarboxylic azolinker-chitosan (mPEG-Azo-chitosan) as ideal drug delivery platform for Fingolimod (FTY720, F) delivery to achieve selective and highly enhanced TNBC therapy in vivo. Herein, HRNPs with an average size of 49.86 nm and a zeta potential of +3.22 mV were synthetized, which after PEG shedding can shift into a more positively-charged NPs (+30.3 mV), possessing self-activation ability under hypoxia situation in vitro, 2D and 3D culture. Treatment with lower doses of HRNPs@F significantly reduced MDA-MB-231 microtumor size to 15 %, induced apoptosis by 88 % within 72 h and reduced highly-proliferative 4 T1 tumor weight by 87.66 % vs. ∼30 % for Fingolimod compared to the untreated controls. To the best of our knowledge, this is the first record for development of hypoxia-responsive chitosan-based NPs with desirable physicochemical properties, and selective self-activation potential to generate highly-charged nanosized tumor-penetrating chitosan NPs. This formulation is capable of localized delivery of Fingolimod to the tumor core, minimizing its side effects while boosting its anti-tumor potential for eradication of TNBC solid tumors.

Fingolimod synergizes and reverses K. pneumoniae resistance to colistin

Klebsiella pneumoniae (K. pneumoniae) infection and the rapid spread of multi-drug resistant (MDR) bacteria pose a serious threat to global healthcare. Polymyxin E (colistin), a group of cationic antimicrobial polypeptides, is currently one of the last resort treatment options against carbapenem-resistant Gram-negative pathogens. The effectiveness of colistin has been compromised due to its intensive use. This study found that fingolimod (FLD), a natural product derivative, exhibited a significant synergistic bactericidal effect on K. pneumoniae when combined with colistin, both in vitro and in vivo. The checkerboard method was employed to assess the in vitro synergistic effect of FLD with colistin. FLD enhanced the susceptibility of bacteria to colistin and lowered effectively minimum inhibitory concentrations (MIC) when compared to colistin MIC, and the fractional inhibitory concentrations (FIC) value was less than 0.3. The time-kill curve demonstrated that the combination treatment of FLD and colistin had significant bactericidal efficacy. The in vitro concurrent administration of colistin and FLD resulted in heightening membrane permeability, compromising cell integrity, diminishing membrane fluidity, and perturbing membrane homeostasis. They also induced alterations in membrane potential, levels of reactive oxygen species, and adenosine triphosphate synthesis, ultimately culminating in bacterial death. Moreover, the combination of FLD with colistin significantly influenced fatty acid metabolism. In the mouse infection model, the survival rate of mice injected with K. pneumoniae was significantly improved to 67% and pathological damage was significantly relieved with combination treatment of FLD and colistin when compared with colistin treatment. This study highlights the potential of FLD in combining with colistin for treating infections caused by MDR isolates of K. pneumoniae.

Medicinal Chemistry Strategies for the Modification of Bioactive Natural Products

Natural bioactive compounds are valuable resources for drug discovery due to their diverse and unique structures. However, these compounds often lack optimal drug-like properties. Therefore, structural optimization is a crucial step in the drug development process. By employing medicinal chemistry principles, targeted molecular operations can be applied to natural products while considering their size and complexity. Various strategies, including structural fragmentation, elimination of redundant atoms or groups, and exploration of structure-activity relationships, are utilized. Furthermore, improvements in physicochemical properties, chemical and metabolic stability, biophysical properties, and pharmacokinetic properties are sought after. This article provides a concise analysis of the process of modifying a few marketed drugs as illustrative examples.

Metabolites analysis and new bioactive compounds from the medicine food homology product of Cordyceps chanhua on artificial media

Cordyceps chanhua on artificial media has been approved as a medicine food homology product. However, the metabolites have not been extensively studied. HPLC-HRMS analysis showed that there were 11 main metabolites in the EtOAc extract including 4 probable unknown compounds. Fumosoroseain A with anti-aging effects is the most abundant known compound and was identified from C. chanhua for the first time. The second abundant compound is N6-(2-Hydroxyethyl) adenosine, a typical metabolite of C. chanhua. All the known compounds have consistent health function with that of the fungus. HRMS, 1D and 2D NMR analyses revealed that compounds 2, 3, and 4 are new nucleosides named as chanhuanosides A, B, and C. Compound 1 is the known compound cordyrrole B isolated from C. chanhua for the first time whose structure is firstly confirmed by single crystal X-ray analysis. Bioactivity analysis revealed that 1-4 significantly inhibited pancreatic lipase activity, and strongly promoted the proliferation of RAW264.7 and 293T cells, suggesting that they might have ant-obesity, immunoregulation, and renal protection functions. Structure-bioactivity analysis revealed that the esterification on ribose can increase their bioactivity. Present metabolites study suggests that C. chanhua cultured on the artificial medium is a promising health food.

Unique Bioactives from Zombie Fungus (Cordyceps) as Promising Multitargeted Neuroprotective Agents

Cordyceps, also known as "zombie fungus", is a non-poisonous mushroom that parasitizes insects for growth and development by manipulating the host system in a way that makes the victim behave like a "zombie". These species produce promising bioactive metabolites, like adenosine, β-glucans, cordycepin, and ergosterol. Cordyceps has been used in traditional medicine due to its immense health benefits, as it boosts stamina, appetite, immunity, longevity, libido, memory, and sleep. Neuronal loss is the typical feature of neurodegenerative diseases (NDs) (Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS)) and neurotrauma. Both these conditions share common pathophysiological features, like oxidative stress, neuroinflammation, and glutamatergic excitotoxicity. Cordyceps bioactives (adenosine, N6-(2-hydroxyethyl)-adenosine, ergosta-7, 9 (11), 22-trien-3β-ol, active peptides, and polysaccharides) exert potential antioxidant, anti-inflammatory, and anti-apoptotic activities and display beneficial effects in the management and/or treatment of neurodegenerative disorders in vitro and in vivo. Although a considerable list of compounds is available from Cordyceps, only a few have been evaluated for their neuroprotective potential and still lack information for clinical trials. In this review, the neuroprotective mechanisms and safety profile of Cordyceps extracts/bioactives have been discussed, which might be helpful in the identification of novel potential therapeutic entities in the future.

Inhibiting de novo ceramide synthesis restores mitochondrial and protein homeostasis in muscle aging

Disruption of mitochondrial function and protein homeostasis plays a central role in aging. However, how these processes interact and what governs their failure in aging remain poorly understood. Here, we showed that ceramide biosynthesis controls the decline in mitochondrial and protein homeostasis during muscle aging. Analysis of transcriptome datasets derived from muscle biopsies obtained from both aged individuals and patients with a diverse range of muscle disorders revealed that changes in ceramide biosynthesis, as well as disturbances in mitochondrial and protein homeostasis pathways, are prevalent features in these conditions. By performing targeted lipidomics analyses, we found that ceramides accumulated in skeletal muscle with increasing age across Caenorhabditis elegans, mice, and humans. Inhibition of serine palmitoyltransferase (SPT), the rate-limiting enzyme of the ceramide de novo synthesis, by gene silencing or by treatment with myriocin restored proteostasis and mitochondrial function in human myoblasts, in C. elegans, and in the skeletal muscles of mice during aging. Restoration of these age-related processes improved health and life span in the nematode and muscle health and fitness in mice. Collectively, our data implicate pharmacological and genetic suppression of ceramide biosynthesis as potential therapeutic approaches to delay muscle aging and to manage related proteinopathies via mitochondrial and proteostasis remodeling.

Total Synthesis of Immunosuppressive Mycestericin E and G Enabled by a Highly Stereoselective Nitroso-Ene Cyclization

This report describes a streamlined synthesis of immunosuppressive mycestericin E and G through a highly stereoselective nitroso-ene cyclization in 11-12 steps using readily available materials. The stereochemical outcome in the formation of a Nα-quaternary stereogenic center is rationalized by a trajectory based on the polar diradical intermediate and subsequent hydrogen transfer. Julia olefination offers a facile chain elongation method that presents a viable strategy for structural derivatization in future medicinal applications.

Molecular and neuroimmune pharmacology of S1P receptor modulators and other disease-modifying therapies for multiple sclerosis

Multiple sclerosis (MS) is a neurological, immune-mediated demyelinating disease that affects people in the prime of life. Environmental, infectious, and genetic factors have been implicated in its etiology, although a definitive cause has yet to be determined. Nevertheless, multiple disease-modifying therapies (DMTs: including interferons, glatiramer acetate, fumarates, cladribine, teriflunomide, fingolimod, siponimod, ozanimod, ponesimod, and monoclonal antibodies targeting ITGA4, CD20, and CD52) have been developed and approved for the treatment of MS. All the DMTs approved to date target immunomodulation as their mechanism of action (MOA); however, the direct effects of some DMTs on the central nervous system (CNS), particularly sphingosine 1-phosphate (S1P) receptor (S1PR) modulators, implicate a parallel MOA that may also reduce neurodegenerative sequelae. This review summarizes the currently approved DMTs for the treatment of MS and provides details and recent advances in the molecular pharmacology, immunopharmacology, and neuropharmacology of S1PR modulators, with a special focus on the CNS-oriented, astrocyte-centric MOA of fingolimod.

Targeting Tyrosinase in Hyperpigmentation: Current Status, Limitations and Future Promises

Hyperpigmentation is a common and distressing dermatologic condition. Since tyrosinase (TYR) plays an essential role in melanogenesis, its inhibition is considered a logical approach along with other therapeutic methods to prevent the accumulation of melanin in the skin. Thus, TYR inhibitors are a tempting target as the medicinal and cosmetic active agents of hyperpigmentation disorder. Among TYR inhibitors, hydroquinone is a traditional lightening agent that is commonly used in clinical practice. However, despite good efficacy, prolonged use of hydroquinone is associated with side effects. To overcome these shortcomings, new approaches in targeting TYR and treating hyperpigmentation are desperately requiredessentialneeded. In line with this purpose, several non-hydroquinone lightening agents have been developed and suggested as hydroquinone alternatives. In addition to traditional approaches, nanomedicine and nanotheranostic platforms have been recently proposed in the treatment of hyperpigmentation. In this review, we discuss the available strategies for the management of hyperpigmentation with a focus on TYR inhibition. In addition, alternative treatment options to hydroquinone are discussed. Finally, we present nano-based strategies to improve the therapeutic effect of drugs prescribed to patients with skin disorders.

Recent Insight into the Role of Sphingosine-1-Phosphate Lyase in Neurodegeneration

Sphingosine-1-phosphate lyase (SPL) is a pyridoxal 5'-phosphate-dependent enzyme involved in the irreversible degradation of sphingosine-1-phosphate (S1P)-a bioactive sphingolipid that modulates a broad range of biological processes (cell proliferation, migration, differentiation and survival; mitochondrial functioning; and gene expression). Although SPL activity leads to a decrease in the available pool of S1P in the cell, at the same time, hexadecenal and phosphoethanolamine, compounds with potential biological activity, are generated. The increased expression and/or activity of SPL, and hence the imbalance between S1P and the end products of its cleavage, were demonstrated in several pathological states. On the other hand, loss-of-function mutations in the SPL encoding gene are a cause of severe developmental impairments. Recently, special attention has been paid to neurodegenerative diseases as the most common pathologies of the nervous system. This review summarizes the current findings concerning the role of SPL in the nervous system with an emphasis on neurodegeneration. Moreover, it briefly discusses pharmacological compounds directed to inhibit its activity.

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.

Compound combinations targeting longevity: Challenges and perspectives

Aging is one of the world's greatest concerns, requiring urgent, effective, large-scale interventions to decrease the number of late-life chronic diseases and improve human healthspan. Anti-aging drug therapy is one of the most promising strategies to combat the effects of aging. However, most geroprotective compounds are known to successfully affect only a few aging-related targets. Given this, there is a great biological rationale for the use of combinations of anti-aging interventions. In this review, we characterize the various types of compound combinations used to modulate lifespan, discuss the existing evidence on their role in life extension, and present some key points about current challenges and future prospects for the development of combination drug anti-aging therapy.

Plant-derived compounds for treating autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD), the most common monogenic hereditary kidney disease, is the fourth leading cause of end-stage kidney disease worldwide. In recent years, significant progress has been made in delaying ADPKD progression with different kinds of chemical drugs, such as tolvaptan, rapamycin, and somatostatin. Meanwhile, numerous plant-derived compounds have been investigated for their beneficial effects on slowing ADPKD progression. Among them, saikosaponin-d, Ganoderma triterpenes, curcumin, ginkgolide B, steviol, resveratrol, Sparganum stoloniferum Buch.-Ham, Cordyceps sinensis, triptolide, quercitrin, naringin, cardamonin, gambogic acid, and olive leaf extract have been found to retard renal cyst development by inhibiting cell proliferation or promoting cell apoptosis in renal cyst-lining epithelial cells. Metformin, a synthesized compound derived from French lilac or goat's rue (Galega officinalis), has been proven to retard the progression of ADPKD. This review focuses on the roles and mechanisms of plant-derived compounds in treating ADPKD, which may constitute promising new therapeutics in the future.

Reduced sphingolipid biosynthesis modulates proteostasis networks to enhance longevity

As the elderly population increases, chronic, age-associated diseases are challenging healthcare systems around the world. Nutrient limitation is well known to slow the aging process and improve health. Regrettably, practicing nutrient restriction to improve health is unachievable for most people. Alternatively, pharmacological strategies are being pursued including myriocin which increases lifespan in budding yeast. Myriocin impairs sphingolipid synthesis, resulting in lowered amino acid pools which promote entry into a quiescent, long-lived state. Here we present transcriptomic data during the first 6 hours of drug treatment that improves our mechanistic understanding of the cellular response to myriocin and reveals a new role for ubiquitin in longevity. Previously we found that the methionine transporter Mup1 traffics to the plasma membrane normally in myriocin-treated cells but is not active and undergoes endocytic clearance. We now show that UBI4, a gene encoding stressed-induced ubiquitin, is vital for myriocin-enhanced lifespan. Furthermore, we show that Mup1 fused to a deubiquitinase domain impairs myriocin-enhanced longevity. Broader effects of myriocin treatment on ubiquitination are indicated by our finding of a significant increase in K63-linked ubiquitin polymers following myriocin treatment. Although proteostasis is broadly accepted as a pillar of aging, our finding that ubiquitination of an amino acid transporter promotes longevity in myriocin-treated cells is novel. Addressing the role of ubiquitination/deubiquitination in longevity has the potential to reveal new strategies and targets for promoting healthy aging.

Role of the blue light receptor gene Icwc-1 in mycelium growth and fruiting body formation of Isaria cicadae

The Isaria cicadae, is well known highly prized medicinal mushroom with great demand in food and pharmaceutical industry. Due to its economic value and therapeutic uses, natural sources of wild I. cicadae are over-exploited and reducing continuously. Therefore, commercial cultivation in controlled environment is an utmost requirement to fulfill the consumer's demand. Due to the lack of knowledge on fruiting body (synnemata) development and regulation, commercial cultivation is currently in a difficult situation. In the growth cycle of macrofungi, such as mushrooms, light is the main factor affecting growth and development, but so far, specific effects of light on the growth and development of I. cicadae is unknown. In this study, we identified a blue light receptor white-collar-1 (Icwc-1) gene homologue with well-defined functions in morphological development in I. cicadae based on gene knockout technology and transcriptomic analysis. It was found that the Icwc-1 gene significantly affected hyphal growth and fruiting body development. This study confirms that Icwc-1 acts as an upstream regulatory gene that regulates genes associated with fruiting body formation, pigment-forming genes, and related genes for enzyme synthesis. Transcriptome data analysis also found that Icwc-1 affects many important metabolic pathways of I. cicadae, i.e., amino acid metabolism and fatty acid metabolism. The above findings will not only provide a comprehensive understanding about the molecular mechanism of light regulation in I. cicadae, but also provide new insights for future breeding program and improving this functional food production.

[The First 5-year Integrated Doctoral Program Exploring the Frontiers of Pharmaceutical Sciences]

To empower the next generation of students to become leaders that play active roles in various fields in society, research universities must offer attractive and meaningful doctor of philosophy (PhD) programs in their graduate schools. The Graduate School of Pharmaceutical Sciences, at Kyoto University has trained a large number of researchers who are leading drug discovery science and clinical pharmacy in academia as well as in the pharmaceutical industry, in medical organization and in government. However, due to changes in the trends of students and the evolving skill requirements of future PhD holders to handle the challenges of a changing society, it is necessary to revise the curriculum of our graduate school. Thus, we will reform the graduate and undergraduate school programs by implementing a so-called late specialization program and a double mentoring system and aim to nurture emergent researchers who will explore uncharted areas in pharmaceutical sciences. Toward this goal, we established the Division of Medical Frontier Sciences in April 2022 to replace the former Division of Bioinformatics and Chemical Genomics. This program is Japan's first five-year integrated doctoral course in the field of pharmaceutical sciences. In this review, I will introduce the background leading to its development construction and provide an overview of the characteristics of this five-year integrated doctoral program.

Ten decadal advances in fungal biology leading towards human well-being

Fungi are an understudied resource possessing huge potential for developing products that can greatly improve human well-being. In the current paper, we highlight some important discoveries and developments in applied mycology and interdisciplinary Life Science research. These examples concern recently introduced drugs for the treatment of infections and neurological diseases; application of -OMICS techniques and genetic tools in medical mycology and the regulation of mycotoxin production; as well as some highlights of mushroom cultivaton in Asia. Examples for new diagnostic tools in medical mycology and the exploitation of new candidates for therapeutic drugs, are also given. In addition, two entries illustrating the latest developments in the use of fungi for biodegradation and fungal biomaterial production are provided. Some other areas where there have been and/or will be significant developments are also included. It is our hope that this paper will help realise the importance of fungi as a potential industrial resource and see the next two decades bring forward many new fungal and fungus-derived products.

Enhancing Genome-Scale Model by Integrative Exometabolome and Transcriptome: Unveiling Carbon Assimilation towards Sphingolipid Biosynthetic Capability of Cordyceps militaris

Cordyceps militaris is an industrially important fungus, which is often used in Asia as traditional medicine. There has been a published genome-scale metabolic model (GSMM) of C. militaris useful for predicting its growth behaviors; however, lipid metabolism, which plays a vital role in cellular functions, remains incomplete in the GSMM of C. militaris. A comprehensive study on C. militaris was thus performed by enhancing GSMM through integrative analysis of metabolic footprint and transcriptome data. Through the enhanced GSMM of C. militaris (called iPC1469), it contained 1469 genes, 1904 metabolic reactions and 1229 metabolites. After model evaluation, in silico growth simulation results agreed well with the experimental data of the fungal growths on different carbon sources. Beyond the model-driven integrative data analysis, interestingly, we found key metabolic responses in alteration of lipid metabolism in C. militaris upon different carbon sources. The sphingoid bases (e.g., sphinganine, sphingosine, and phytosphingosine) and ceramide were statistically significant accumulated in the xylose culture when compared with other cultures; this study suggests that the sphingolipid biosynthetic capability in C. militaris was dependent on the carbon source assimilated for cell growth; this finding provides a comprehensive basis for the sphingolipid biosynthesis in C. militaris that can help to further redesign its metabolic control for medicinal and functional food applications.

Galleria mellonella as a Novel In Vivo Model to Screen Natural Product-Derived Modulators of Innate Immunity

Immunomodulators are drugs that either stimulate or suppress the immune system in response to an immunopathological disease or cancer. The majority of clinically approved immunomodulators are either chemically synthesised (e.g., dexamethasone) or protein-based (e.g., monoclonal antibodies), whose uses are limited due to toxicity issues, poor bioavailability, or prohibitive cost. Nature is an excellent source of novel compounds, as it is estimated that almost half of all licenced medicines are derived from nature or inspired by natural product (NP) structures. The clinical success of the fungal-derived immunosuppressant cyclosporin A demonstrates the potential of natural products as immunomodulators. Conventionally, the screening of NP molecules for immunomodulation is performed in small animal models; however, there is a growing impetus to replace animal models with more ethical alternatives. One novel approach is the use of Galleria melonella larvae as an in vivo model of immunity. Despite lacking adaptive antigen-specific immunity, this insect possesses an innate immune system comparable to mammals. In this review, we will describe studies that have used this alternative in vivo model to assess the immunomodulating activity of synthetic and NP-derived compounds, outline the array of bioassays employed, and suggest strategies to enhance the use of this model in future research.

Preparation of the sphingolipid fraction from mycelia of Cordyceps sinensis and its immunosuppressive activity

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sinensis (CS) is an herbal tonic in traditional Chinese medicine and is used to treat a wide range of disorders, including immune, kidney, respiratory, lung and cardiovascular diseases, in China. Most studies are focused mainly on nucleotides and polysaccharides from CS and consider them to be the main active ingredients, while other ingredients are often disregarded. Hundreds of sphingolipids have been identified from CS and showed inhibitory effects on mouse splenic lymphocytes.

AIM OF THE STUDY

This study aimed to establish a method for preparing a fraction of sphingolipids from the mycelial powder of CS and evaluate its immunosuppressive activity.

MATERIALS AND METHODS

Fraction of sphingolipids (Fr-SPLs) were prepared by silica gel chromatography and reversed-phase chromatography. Its components were identified and quantified by Quadrupole-Orbitrap UHPLC-MS/MS. PBMCs were prepared from human blood, and splenic lymphocytes, B cells, and T cells were prepared from mouse spleens. The inhibitory effect of Fr-SPLs on cell viability was evaluated by CCK-8 assay. PBMC apoptosis and the ratio of CD4⁺ T cells and CD8⁺ T cells were quantified by flow cytometry analysis. The expression of IL-2, IL-10, and TNF-α in PBMCs was detected by ELISA kits.

RESULTS

A fraction containing 84.83% of sphingolipids (SPLs) was prepared from the mycelia of CS and named Fr-SPLs. 15 SPLs were identified from the Fr-SPLs. Fr-SPLs significantly inhibited the viability of human peripheral blood mononuclear cells (PBMCs) with an IC₅₀ value of 9.82 μg/mL and promoted PBMC apoptosis in a dose-dependent manner. Moreover, Fr-SPLs inhibited the viability of mouse splenocytes, as well as that of B cells and T cells derived from splenocytes. Furthermore, Fr-SPLs reduced the production of IL-2, IL-10, and TNF-α in PBMCs.

CONCLUSIONS

Fr-SPLs show immunosuppressive activity, and this study will be useful for preparing immunosuppressive components from CS and its mycelia for hyperimmune disease.

Therapeutic strategy for rheumatoid arthritis by induction of myeloid-derived suppressor cells with high suppressive potential

Combination treatment using fingolimod (FTY720), an immunomodulator, and a pathogenic antigen prevents the progression of glucose-6-phosphate isomerase (GPI)_325-339-induced arthritis. In this study, we focused on myeloid-derived suppressor cells (MDSCs; CD11b⁺Gr-1⁺ cells) and investigated the effects of the combination treatment on these cells. DBA/1J mice with GPI_325-339-induced arthritis were treated using FTY720 and/or GPI_325-339 for five days. The expanded CD11b⁺Gr-1⁺ cell population and its inhibitory potential were examined. The percentage of CD369⁺CD11b⁺Gr-1⁺ cells effectively increased in the combination-treated mice. The inhibitory potential of CD369⁺CD11b⁺Gr-1⁺ cells was higher than that of cells not expressing CD369. Among bone marrow cells, the expression of CD369 in CD11b⁺Gr-1⁺ cells increased following stimulation with granulocyte-macrophage colony-stimulating factor, and the expression of CD11c increased accordingly. The increased CD11c expression indicated a decrease in the potential to suppress T cell proliferation based on the results of the suppression assay. The percentage of CD11c^-CD369⁺ cells in CD11b⁺Gr-1⁺ cells that were induced by the combination treatment also increased, and these cells tended to have a higher capacity to inhibit T cell proliferation. In conclusion, the combination treatment using FTY720 and the pathogenic antigen effectively induces MDSC, which demonstrates a high potential for suppressing T cell proliferation in the lymph nodes, thereby establishing an immune-tolerant state.

Drug Candidates for Autoimmune Diseases

Most of the immunosuppressive drugs used in the clinic to prevent organ rejection or to treat autoimmune disorders were originally isolated from fungi or bacteria. Therefore, in addition to plants, these are valuable sources for identification of new potent drugs. Many side effects of established drugs limit their usage and make the identification of new immunosuppressants necessary. In this review, we present a comprehensive overview of natural products with potent anti-inflammatory activities that have been tested successfully in different models of chronic inflammatory autoimmune diseases. Some of these candidates already have passed first clinical trials. The anti-inflammatory potency of these natural products was often comparable to those of established drugs, and they could be used at least in addition to standard therapy to reduce their dose to minimize unwanted side effects. A frequent mode of action is the inhibition of classical inflammatory signaling pathways, such as NF-κB, in combination with downregulation of oxidative stress. A drawback for the therapeutic use of those natural products is their moderate bioavailability, which can be optimized by chemical modifications and, in addition, further safety studies are necessary. Altogether, very interesting candidate compounds exist which have the potential to serve as starting points for the development of new immunosuppressive drugs.

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.

Differential Expression of the Sphingolipid Pathway Is Associated with Sensitivity to the PP2A Activator FTY720 in Colorectal Cancer Cell Lines

Protein phosphatase 2A (PP2A) is a ubiquitously expressed intracellular serine/threonine phosphatase. Deregulation of PP2A is a common event associated with adenocarcinomas of the colon and rectum. We have previously shown that breast cancer cell lines are sensitive to the PP2A activator FTY720, and that sensitivity is predicted by high Aurora kinase A (AURKA) mRNA expression. In this study, we hypothesized that high relative AURKA expression could predict sensitivity to FTY720-induced apoptosis in colorectal cancer (CRC). The CRC cell lines NCI H716, COLO320DM, DLD-1, SW480, and HT-29 show a high relative AURKA expression as compared to LS411N, T84, HCT116, SW48, and LOVO. Following viability assays, LS411N, T84, HCT116, and SW480 were shown to be sensitive to FTY720, whereas DLD-1 and HT-29 were non-sensitive. Hence, AURKA mRNA expression does not predict sensitivity to FTY720 in CRC cell lines. Differentially expressed genes (DEGs) were obtained by comparing the sensitive CRC cell lines (LS411N and HCT116) against the non-sensitive (HT-29 and DLD-1). We found that 253 genes were significantly altered in expression, and upregulation of CERS4, PPP2R2C, GNAZ, PRKCG, BCL2, MAPK12, and MAPK11 suggests the involvement of the sphingolipid signaling pathway, known to be activated by phosphorylated-FTY720. In conclusion, although AURKA expression did not predict sensitivity to FTY720, it is evident that specific CRC cell lines are sensitive to 5 µM FTY720, potentially because of the differential expression of genes involved in the sphingolipid pathway.

CHO/LY-B cell growth under limiting sphingolipid supply: Correlation between lipid composition and biophysical properties of sphingolipid-restricted cell membranes

Sphingolipids (SL) are ubiquitous in mammalian cell membranes, yet there is little data on the behavior of cells under SL-restriction conditions. LY-B cells derive from a CHO linein whichserine palmitoyl transferase (SPT), thus de novo SL synthesis, is suppressed, while maintaining the capacity of taking up and metabolizing exogenous sphingoid bases from the culture medium. In this study, LY-B cells were adapted to grow in a fetal bovine serum (FBS)-deficient medium to avoid external uptake of lipids. The lowest FBS concentration that allowed LY-B cell growth, though at a slow rate, under our conditions was 0.04%, that is, 250-fold less than the standard (10%) concentration. Cells grown under limiting SL concentrations remained viable for at least 72 hours. Enriching with sphingomyelin the SL-deficient medium allowed the recovery of growth rates analogous to those of control LY-B cells. Studies including whole cells, plasma membrane preparations, and derived lipid vesicles were carried out. Laurdan fluorescence was recorded to measure membrane molecular order, showing a significant decrease in the rigidity of LY-B cells, not only in plasma membrane but also in whole cell lipid extract, as a result of SL limitation in the growth medium. Plasma membrane preparations and whole cell lipid extracts were also studied using atomic force microscopy in the force spectroscopy mode. Force measurements demonstrated that lower breakthrough forces were required to penetrate samples obtained from SL-poor LY-B cells than those obtained from control cells. Mass-spectroscopic analysis was also a helpful tool to understand the rearrangement undergone by the LY-B cell lipid metabolism. The most abundant SL in LY-B cells, sphingomyelin, decreased by about 85% as a result of SL limitation in the medium, the bioactive lipid ceramide and the ganglioside precursor hexosylceramide decreased similarly, together with cholesterol. Quantitative SL analysis showed that a 250-fold reduction in sphingolipid supply to LY-B cells led only to a sixfold decrease in membrane sphingolipids, underlining the resistance to changes in composition of these cells. Plasma membrane compositions exhibited similar changes, at least qualitatively, as the whole cells with SL restriction. A linear correlation was observed between the sphingomyelin concentration in the membranes, the degree of lipid order as measured by laurdan fluorescence, and membrane breakthrough forces assessed by atomic force microscopy. Smaller, though significant, changes were also detected in glycerophospholipids under SL-restriction conditions.

The sphingosine-1-phosphate receptor modulator, FTY720, prevents the incidence of diabetes in Spontaneously Diabetic Torii rats

The sphingosine-1-phosphate (S1P) receptor modulator regulates lymphocyte trafficking, resulting in its depletion from circulation, which ultimately causes immunosuppression. In this study, we investigated the preventive effect of fingolimod (FTY720) in the non-obese type 2 diabetic model, Spontaneously Diabetic Torii (SDT) rats. The S1P receptor modulator, FTY720 (0.3 mg/kg p.o.), was administered for 12 weeks to SDT rats from 5 to 17 weeks of age. Based on our findings, FTY720 could suppress the incidence of diabetes in SDT rats. Further, glucose intolerance was improved in FTY720-treated SDT rats at 14 weeks of age. Based on the haematological and histological analyses performed at 17 to 18 weeks of age, a decrease in lymphocytes and monocytes in the peripheral blood and a decrease in lymphocyte and atrophy in spleen occurred in the FTY720-treated SDT rats. Furthermore, the pancreatic changes, such as inflammation, atrophy, and fibrosis in islets observed in SDT rats were improved by FTY720 treatment. These findings suggest that the immunomodulatory effects of FTY720 reduced the pancreatic lesion in SDT rats, thereby demonstrating its preventive effect against diabetes. The development of diabetes in SDT rats is related to disorders of the immune system. However, the S1P receptor modulator may be useful for treating type 2 diabetes.

Prophylactic administration of fingolimod (FTY720) ameliorated experimental autoimmune myasthenia gravis by reducing the number of dendritic cells, follicular T helper cells and antibody-secreting cells

Fingolimod (FTY720), a sphingosine 1-phosphate (S1P) receptor antagonist, possesses potent immunomodulatory activity via lymphocyte homing. The effects of FTY720 have been widely studied in various T-cell-mediated autoimmune diseases, while the immunomodulatory effects on experimental autoimmune myasthenia gravis (EAMG), a typical disease model for antibody-mediated autoimmunity, remain elusive. In the present study, FTY720 was administered to EAMG rats as prophylaxis. The clinical scores were recorded every other day, and serum antibodies at different time points were measured by enzyme-linked immunosorbent assay (ELISA). The immune cell subsets in the spleen, bone marrow, circulation, and thymus were determined by flow cytometry. The prophylactic administration alleviated EAMG symptoms by reducing the level of serum antibodies IgG and its isotype IgG2b on days 30 and 46 post immunization, as well as IgG and Ig kappa antibody-secreting cells in the spleen and bone marrow. The mitigated humoral immune response can be attributed to the decreased dendritic cells, follicular T help cells (Tfh) and Tfh subsets (Tfh1, Tfh2, and Tfh17), and T helper cell subsets (Th1, Th2, and Th17) in the spleen. The promotion of lymphocyte homing and inhibition of thymocyte egress contribute to the effects of FTY720 on these effector T cell subsets. Overall, the prophylactic administration of FTY720 ameliorated EAMG partially by regulating humoral immune response，suggesting that FTY720 could be part of a pharmacological strategy for managing myasthenia gravis.

Targeting S1PRs as a Therapeutic Strategy for Inflammatory Bone Loss Diseases-Beyond Regulating S1P Signaling

As G protein coupled receptors, sphingosine-1-phosphate receptors (S1PRs) have recently gained attention for their role in modulating inflammatory bone loss diseases. Notably, in murine studies inhibiting S1PR2 by its specific inhibitor, JTE013, alleviated osteoporosis induced by RANKL and attenuated periodontal alveolar bone loss induced by oral bacterial inflammation. Treatment with a multiple S1PRs modulator, FTY720, also suppressed ovariectomy-induced osteoporosis, collagen or adjuvant-induced arthritis, and apical periodontitis in mice. However, most previous studies and reviews have focused mainly on how S1PRs manipulate S1P signaling pathways, subsequently affecting various diseases. In this review, we summarize the underlying mechanisms associated with JTE013 and FTY720 in modulating inflammatory cytokine release, cell chemotaxis, and osteoclastogenesis, subsequently influencing inflammatory bone loss diseases. Studies from our group and from other labs indicate that S1PRs not only control S1P signaling, they also regulate signaling pathways induced by other stimuli, including bacteria, lipopolysaccharide (LPS), bile acid, receptor activator of nuclear factor κB ligand (RANKL), IL-6, and vitamin D. JTE013 and FTY720 alleviate inflammatory bone loss by decreasing the production of inflammatory cytokines and chemokines, reducing chemotaxis of inflammatory cells from blood circulation to bone and soft tissues, and suppressing RANKL-induced osteoclast formation.

Enhancing lifespan of budding yeast by pharmacological lowering of amino acid pools

The increasing prevalence of age-related diseases and resulting healthcare insecurity and emotional burden require novel treatment approaches. Several promising strategies seek to limit nutrients and promote healthy aging. Unfortunately, the human desire to consume food means this strategy is not practical for most people but pharmacological approaches might be a viable alternative. We previously showed that myriocin, which impairs sphingolipid synthesis, increases lifespan in Saccharomyces cerevisiae by modulating signaling pathways including the target of rapamycin complex 1 (TORC1). Since TORC1 senses cellular amino acids, we analyzed amino acid pools and identified 17 that are lowered by myriocin treatment. Studying the methionine transporter, Mup1, we found that newly synthesized Mup1 traffics to the plasma membrane and is stable for several hours but is inactive in drug-treated cells. Activity can be restored by adding phytosphingosine to culture medium thereby bypassing drug inhibition, thus confirming a sphingolipid requirement for Mup1 activity. Importantly, genetic analysis of myriocin-induced longevity revealed a requirement for the Gtr1/2 (mammalian Rags) and Vps34-Pib2 amino acid sensing pathways upstream of TORC1, consistent with a mechanism of action involving decreased amino acid availability. These studies demonstrate the feasibility of pharmacologically inducing a state resembling amino acid restriction to promote healthy aging.

Sphinganine-Analog Mycotoxins (SAMs): Chemical Structures, Bioactivities, and Genetic Controls

Sphinganine-analog mycotoxins (SAMs) including fumonisins and A. alternata f. sp. Lycopersici (AAL) toxins are a group of related mycotoxins produced by plant pathogenic fungi in the Fusarium genus and in Alternaria alternata f. sp. Lycopersici, respectively. SAMs have shown diverse cytotoxicity and phytotoxicity, causing adverse impacts on plants, animals, and humans, and are a destructive force to crop production worldwide. This review summarizes the structural diversity of SAMs and encapsulates the relationships between their structures and biological activities. The toxicity of SAMs on plants and animals is mainly attributed to their inhibitory activity against the ceramide biosynthesis enzyme, influencing the sphingolipid metabolism and causing programmed cell death. We also reviewed the detoxification methods against SAMs and how plants develop resistance to SAMs. Genetic and evolutionary analyses revealed that the FUM (fumonisins biosynthetic) gene cluster was responsible for fumonisin biosynthesis in Fusarium spp. Sequence comparisons among species within the genus Fusarium suggested that mutations and multiple horizontal gene transfers involving the FUM gene cluster were responsible for the interspecific difference in fumonisin synthesis. We finish by describing methods for monitoring and quantifying SAMs in food and agricultural products.

Screening of FDA-Approved Drugs Using a 384-Well Plate-Based Biofilm Platform: The Case of Fingolimod

In an effort to find new repurposed antibacterial compounds, we performed the screening of an FDA-approved compounds library against Staphylococcus aureus American Type Culture Collection (ATCC) 25923. Compounds were evaluated for their capacity to prevent both planktonic growth and biofilm formation as well as to disrupt pre-formed biofilms. One of the identified initial hits was fingolimod (FTY720), an immunomodulator approved for the treatment of multiple sclerosis, which was then selected for follow-up studies. Fingolimod displayed a potent activity against S. aureus and S. epidermidis with a minimum inhibitory concentration (MIC) within the range of 12–15 µM at which concentration killing of all the bacteria was confirmed. A time–kill kinetic study revealed that fingolimod started to drastically reduce the viable bacterial count within two hours and we showed that no resistance developed against this compound for up to 20 days. Fingolimod also displayed a high activity against Acinetobacter baumannii (MIC 25 µM) as well as a modest activity against Escherichia coli and Pseudomonas aeruginosa. In addition, fingolimod inhibited quorum sensing in Chromobacterium violaceum and might therefore target this signaling pathway in certain Gram-negative bacteria. In conclusion, we present the identification of fingolimod from a compound library and its evaluation as a potential repurposed antibacterial compound.

Cordycepin, a metabolite of Cordyceps militaris, reduces immune-related gene expression in insects

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High doses of cordycepin are lethal to G. mellonella.

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Cordycepin interacts with EPF to increase the rate of G. mellonella mortality.

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Cordycepin reduces immune-related gene expression in G. mellonella and S2r+ cells.

Hypocrealean entomopathogenic fungi (EPF) (Sordariomycetes, Ascomycota) are natural regulators of insect populations in terrestrial environments. Their obligately-killing life-cycle means that there is likely to be strong selection pressure for traits that allow them to evade the effects of the host immune system. In this study, we quantified the effects of cordycepin (3′-deoxyadenosine), a secondary metabolite produced by Cordyceps militaris (Hypocreales, Cordycipitaceae), on insect susceptibility to EPF infection and on insect immune gene expression. Application of the immune stimulant curdlan (20 µg ml⁻¹, linear beta-1,3-glucan, a constituent of fungal cell walls) to Drosophila melanogaster S2r+ cells resulted in a significant increase in the expression of the immune effector gene metchnikowin compared to a DMSO-only control, but there was no significant increase when curdlan was co-applied with 25 µg ml⁻¹ cordycepin dissolved in DMSO. Injection of cordycepin into larvae of Galleria mellonella (Lepidoptera: Pyralidae) resulted in dose-dependent mortality (LC₅₀ of cordycepin = 2.1 mg per insect 6 days after treatment). Incubating conidia of C. militaris and Beauveria bassiana (Hypocreales, Cordycipitaceae; an EPF that does not synthesize cordycepin) with 3.0 mg ml⁻¹ cordycepin had no effect on the numbers of conidia germinating in vitro. Co-injection of G. mellonella with a low concentration of cordycepin (3.0 mg ml⁻¹) plus 10 or 100 conidia per insect of C. militaris or B. bassiana caused a significant decrease in insect median survival time compared to injection with the EPF on their own. Analysis of predicted vs. observed mortalities indicated a synergistic interaction between cordycepin and the EPF. The injection of C. militaris and B. bassiana into G. mellonella resulted in increased expression of the insect immune effector genes lysozyme, IMPI and gallerimycin at 72 h post injection, but this did not occur when the EPF were co-injected with 3.0 mg ml⁻¹ cordycepin. In addition, we observed increased expression of IMPI and lysozyme at 48 h after injection with C. militaris, B. bassiana and sham injection (indicating a wounding response), but this was also prevented by application of cordycepin. These results suggest that cordycepin has potential to act as a suppressor of the immune response during fungal infection of insect hosts.

Actions of FTY720 (Fingolimod), a Sphingosine-1-Phosphate Receptor Modulator, on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-Lymphocytes

FTY720 (fingolimod), a modulator of sphingosine-1-phosphate receptors, is known to produce the immunomodulatory actions and to be beneficial for treating the relapsing multiple sclerosis. However, whether it exerts any effects on membrane ion currents in immune cells remains largely unknown. Herein, the effects of FTY720 on ionic currents in Jurkat T-lymphocytes were investigated. Cell exposure to FTY720 suppressed the amplitude of delayed-rectifier K⁺ current (I_K(DR)) in a time- and concentration-dependent manner with an IC₅₀ value of 1.51 μM. Increasing the FTY720 concentration not only decreased the I_K(DR) amplitude but also accelerated the inactivation time course of the current. By using the minimal reaction scheme, the effect of FTY720 on I_K(DR) inactivation was estimated with a dissociation constant of 3.14 μM. FTY720 also shifted the inactivation curve of I_K(DR) to a hyperpolarized potential with no change in the slope factor, and recovery from I_K(DR) became slow during the exposure to this compound. Cumulative inactivation for I_K(DR) in response to repetitive depolarizations was enhanced in the presence of FTY720. In SEW2871-treated cells, FTY720-induced inhibition of I_K(DR) was attenuated. This compound also exerted a stimulatory action on the activity of intermediate-conductance Ca²⁺-activated K⁺ channels in Jurkat T-lymphocytes. However, in NSC-34 neuronal cells, FTY720 did not modify the inactivation kinetics of KV3.1-encoded I_K(DR), although it suppressed I_K(DR) amplitude in these cells. Collectively, the perturbations by FTY720 on different types of K⁺ channels may contribute to the functional activities of immune cells, if similar findings appear in vivo.

Positron Emission Tomography in the Inflamed Cerebellum: Addressing Novel Targets among G Protein-Coupled Receptors and Immune Receptors

Inflammatory processes preceding clinical manifestation of brain diseases are moving increasingly into the focus of positron emission tomographic (PET) investigations. A key role in inflammation and as a target of PET imaging efforts is attributed to microglia. Cerebellar microglia, with a predominant ameboid and activated subtype, is of special interest also regarding improved and changing knowledge on functional involvement of the cerebellum in mental activities in addition to its regulatory role in motor function. The present contribution considers small molecule ligands as potential PET tools for the visualization of several receptors recognized to be overexpressed in microglia and which can potentially serve as indicators of inflammatory processes in the cerebellum. The sphingosine 1 phosphate receptor 1 (S1P1), neuropeptide Y receptor 2 (NPY2) and purinoceptor Y12 (P2Y12) cannabinoid receptors and the chemokine receptor CX3CR1 as G-protein-coupled receptors and the ionotropic purinoceptor P2X7 provide structures with rather classical binding behavior, while the immune receptor for advanced glycation end products (RAGE) and the triggering receptor expressed on myeloid cells 2 (TREM2) might depend for instance on further accessory proteins. Improvement in differentiation between microglial functional subtypes in comparison to the presently used 18 kDa translocator protein ligands as well as of the knowledge on the role of polymorphisms are special challenges in such developments.

Antifungal Drug Development: Targeting the Fungal Sphingolipid Pathway

Fungal infections are becoming more prevalent and problematic due to the continual rise of immune deficient patients as well as the progressive development of drug resistance towards currently available antifungal drugs. There has been a significant increase in the development of antifungal compounds with a similar mechanism of action of current drugs. In contrast, there has been very little progress in developing compounds inhibiting totally new fungal targets or/and fungal pathways. This review focuses on novel compounds recently discovered to target the fungal sphingolipids and their metabolizing enzymes.

Inhibitors of Ceramide- and Sphingosine-Metabolizing Enzymes as Sensitizers in Radiotherapy and Chemotherapy for Head and Neck Squamous Cell Carcinoma

In the treatment of advanced head and neck squamous cell carcinoma (HNSCC), including oral SCC, radiotherapy is a commonly performed therapeutic modality. The combined use of radiotherapy with chemotherapy improves therapeutic effects, but it also increases adverse events. Ceramide, a central molecule in sphingolipid metabolism and signaling pathways, mediates antiproliferative responses, and its level increases in response to radiotherapy and chemotherapy. However, when ceramide is metabolized, prosurvival factors, such as sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glucosylceramide, are produced, reducing the antitumor effects of ceramide. The activities of ceramide- and sphingosine-metabolizing enzymes are also associated with radio- and chemo-resistance. Ceramide analogs and low molecular-weight compounds targeting these enzymes exert anticancer effects. Synthetic ceramides and a therapeutic approach using ultrasound have also been developed. Inhibitors of ceramide- and sphingosine-metabolizing enzymes and synthetic ceramides can function as sensitizers of radiotherapy and chemotherapy for HNSCC.