Stress-induced apoptosis and the sphingomyelin pathway

Identification of Lipids and Cytokines in Plasma and Follicular Fluid before and after Follicle-Stimulating Hormone Stimulation as Potential Markers for Follicular Maturation in Cattle

The process of follicle maturation leading to ovulation is a key milestone in female fertility. It is known that circulating lipids and cytokines play a role in the follicle's ability to go through follicular maturation and the ovulatory processes. However, the specific mechanisms are not well understood. We posit that dysregulation of granulosa cells influences the ovarian environment, which tries to adapt by changing released lipids and cytokines to achieve follicular maturation. Eleven non-lactating adult females underwent estrus synchronization with two injections of PGF2α 14 days apart. Daily blood samples were collected for 28 days to monitor steroid hormone production after the second injection. To understand the potential impacts of lipids and cytokines during ovulation, a low-dose FSH stimulation (FSHLow) was performed after resynchronization of cows, and daily blood samples were collected for 14 days to monitor steroid hormone production until ovariectomies. The lipidomic analysis demonstrated increased circulating diacylglycerides and triacylglycerides during the mid-luteal phase and after FSHLow treatment. Cholesteryl esters decreased in circulation but increased in follicular fluid (FF) after FSHLow. Increased circulating concentrations of TNFα and reduced CXCL9 were observed in response to FSHLow. Therefore, specific circulating lipids and cytokines may serve as markers of normal follicle maturation.

Sphingolipids and impaired hypoxic stress responses in Huntington disease

Huntington disease (HD) is a debilitating, currently incurable disease. Protein aggregation and metabolic deficits are pathological hallmarks but their link to neurodegeneration and symptoms remains debated. Here, we summarize alterations in the levels of different sphingolipids in an attempt to characterize sphingolipid patterns specific to HD, an additional molecular hallmark of the disease. Based on the crucial role of sphingolipids in maintaining cellular homeostasis, the dynamic regulation of sphingolipids upon insults and their involvement in cellular stress responses, we hypothesize that maladaptations or blunted adaptations, especially following cellular stress due to reduced oxygen supply (hypoxia) contribute to the development of pathology in HD. We review how sphingolipids shape cellular energy metabolism and control proteostasis and suggest how these functions may fail in HD and in combination with additional insults. Finally, we evaluate the potential of improving cellular resilience in HD by conditioning approaches (improving the efficiency of cellular stress responses) and the role of sphingolipids therein. Sphingolipid metabolism is crucial for cellular homeostasis and for adaptations following cellular stress, including hypoxia. Inadequate cellular management of hypoxic stress likely contributes to HD progression, and sphingolipids are potential mediators. Targeting sphingolipids and the hypoxic stress response are novel treatment strategies for HD.

Effects of activation and assisted reproduction techniques on the composition, structure, and properties of the sauger (Sander Canadensis) spermatozoa plasma membrane

The sperm plasma membrane is a multifunctional organelle essential to fertilization. However, assisted reproduction techniques often negatively affect this structure, resulting in reduced fertility. These reductions have been attributed to plasma membrane damage in a wide array of species, including fish. Considerable research has been conducted on the fish sperm membrane, but few have examined the effect of cryopreservation and other assisted reproduction techniques (ARTs) on not only membrane composition, but also specific characteristics (e.g., fluidity) and organization (e.g., lipid rafts). Herein, we determined the effects of three ARTs (testicular harvest, strip spawning, and cryopreservation) on the sperm plasma membrane, using Sauger (Sander canadensis) sperm as a model. To this end, a combination of fluorescent dyes (e.g., merocyanine 540, filipin III, cholera toxin subunit β), liquid chromatography - mass spectroscopy (LC-MS) analysis of membrane lipids, and membrane ultracentrifugation coupled with plate assays and immunofluorescence were used to describe and compare sperm fluidity, membrane composition, as well as lipid raft composition and distribution among sperm types. Stripped sperm became more fluid following motility activation (40% increase in highly fluid cells characterized by a 2 × increase in fluorescence) and contained lipid rafts restricted to the midpiece. Testicular harvest yielded sperm with characteristics similar to stripped sperm. By contrast, cryopreservation impacted every aspect of membrane physiology. Two cell populations, one highly fluid and the other rigid, resulted from the freeze-thaw process. Cryopreservation reduced lipid raft cholesterol content by 44% and flotilin-2 (a lipid raft marker) was partially displaced owing to a decrease in buoyancy. Unlike stripped and testicular sperm, LC-MS analysis revealed increases in oxidative damage markers, membrane destabilization, and apoptotic signaling in cryopreserved sperm. Ultrastructural analysis also revealed widespread physical damage to the membrane following freeze-thaw. Sperm motility, however, was unrelated to any measure of membrane physiology used in this study. Our results demonstrate that ARTs have the potential to substantially affect the sperm plasma membrane, but not always detrimentally. These results provide multiple potential biomarkers of sperm quality as well as insight into sources of sub-fertility resulting from use of ARTs.

Lysophospholipid Mediators in Health and Disease

Lysophospholipids, exemplified by lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), are produced by the metabolism and perturbation of biological membranes. Both molecules are established extracellular lipid mediators that signal via specific G protein-coupled receptors in vertebrates. This widespread signaling axis regulates the development, physiological functions, and pathological processes of all organ systems. Indeed, recent research into LPA and S1P has revealed their important roles in cellular stress signaling, inflammation, resolution, and host defense responses. In this review, we focus on how LPA regulates fibrosis, neuropathic pain, abnormal angiogenesis, endometriosis, and disorders of neuroectodermal development such as hydrocephalus and alopecia. In addition, we discuss how S1P controls collective behavior, apoptotic cell clearance, and immunosurveillance of cancers. Advances in lysophospholipid research have led to new therapeutics in autoimmune diseases, with many more in earlier stages of development for a wide variety of diseases, such as fibrotic disorders, vascular diseases, and cancer.

Sphingomyelinases in a journey to combat arthropod-borne pathogen transmission

Ixodes scapularis ticks feed on humans and other vertebrate hosts and transmit several pathogens of public health concern. Tick saliva is a complex mixture of bioactive proteins, lipids and immunomodulators, such as I. scapularis sphingomyelinase (IsSMase)-like protein, an ortholog of dermonecrotoxin SMase D found in the venom of Loxosceles spp. of spiders. IsSMase modulates the host immune response towards Th2, which suppresses Th1-mediated cytokines to facilitate pathogen transmission. Arboviruses utilize exosomes for their transmission from tick to the vertebrate host, and exosomes derived from tick saliva/salivary glands suppress C-X-C motif chemokine ligand 12 and interleukin-8 immune response(s) in human skin to delay wound healing and repair processes. IsSMase affects also viral replication and exosome biogenesis, thereby inhibiting tick-to-vertebrate host transmission of pathogenic exosomes. In this review, we elaborate on exosomes and their biogenesis as potential candidates for developing novel control measure(s) to combat tick-borne diseases. Such targets could help with the development of an efficient anti-tick vaccine for preventing the transmission of tick-borne pathogens.

The radioprotective effects of alpha-lipoic acid on radiotherapy-induced toxicities: A systematic review

PURPOSE

Radiation therapy is one of the main cancer treatment modalities applied in 50-70% of cancer patients. Despite the many advantages of this treatment, such as non-invasiveness, organ-preservation, and spatiotemporal flexibility in tumor targeting, it can lead to complications in irradiated healthy cells/tissues. In this regard, the use of radio-protective agents can alleviate radiation-induced complications. This study aimed to review the potential role of alpha-lipoic acid in the prevention/reduction of radiation-induced toxicities on healthy cells/tissues.

METHODS

A systematic search was performed following PRISMA guidelines to identify relevant literature on the "role of alpha-lipoic acid in the treatment of radiotherapy-induced toxicity" in the electronic databases of Web of Science, Embase, PubMed, and Scopus up to January 2021. Based on the inclusion and exclusion criteria of the present study, 278 articles were screened. Finally, 29 articles were included in this systematic review.

RESULTS

The obtained results showed that in experimental in vivo models, the radiation-treated groups had decreased survival rate and body weight compared to the control groups. It was also found that radiation can induce mild to severe toxicities on gastrointestinal, circulatory, reproductive, central nervous, respiratory, endocrine, exocrine systems, etc. However, the use of alpha-lipoic acid could alleviate the radiation-induced toxicities in most cases. This radio-protective agent exerts its effects through mechanisms of anti-oxidant, anti-apoptosis, anti-inflammatory, and so on.

CONCLUSION

According to the obtained results, it can be mentioned that co-treatment of alpha-lipoic acid with radiotherapy ameliorates the radiation-induced toxicities in healthy cells/tissues.

Radiation protection by Ex-RAD: a systematic review

Protection of normal tissues against ionizing radiation-induced damages is a critical issue in clinical and environmental radiobiology. One of the ways of accomplishing radiation protection is through the use of radioprotectors. In the search for the most effective radioprotective agent, factors such as toxicity, effect on tumors, number of tissues protected, ease of administration, long-term stability, and compatibility with other drugs need to be assessed. Thus, in the present study, we systematically review existing studies on a chemical radioprotector, Ex-RAD, with the aim of examining its efficacy of radiation protection as well as underlying mechanisms. To this end, a systematic search of the electronic databases including Pubmed, Scopus, Embase, and Google Scholar was conducted to retrieve articles investigating the radioprotective effect of Ex-RAD. From an initial search of 268 articles, and after removal of duplicates as well as applying the predetermined inclusion and exclusion criteria, 10 articles were finally included for this systematic review. Findings from the reviewed studies indicated that Ex-RAD showed potentials for effective radioprotection of the studied organs with no side effect. Furthermore, the inhibition of apoptosis through p53 signaling pathway was the main mechanism of radioprotection by Ex-RAD. However, its radioprotective effect would need to be investigated for more organs in future studies.

Skin barrier lipid enzyme activity in Netherton patients is associated with protease activity and ceramide abnormalities

Individuals with Netherton syndrome (NTS) have increased serine protease activity, which strongly impacts the barrier function of the skin epidermis and leads to skin inflammation. Here, we investigated how serine protease activity in NTS correlates with changes in the stratum corneum (SC) ceramides, which are crucial components of the skin barrier. We examined two key enzymes involved in epidermal ceramide biosynthesis, β-glucocerebrosidase (GBA) and acid-sphingomyelinase (ASM). We compared in situ expression levels and activities of GBA and ASM between NTS patients and controls and correlated the expression and activities with i) SC ceramide profiles, ii) in situ serine protease activity, and iii) clinical presentation of patients. Using activity-based probe labeling, we visualized and localized active epidermal GBA, and a newly developed in situ zymography method enabled us to visualize and localize active ASM. Reduction in active GBA in NTS patients coincided with increased ASM activity, particularly in areas with increased serine protease activity. NTS patients with scaly erythroderma exhibited more pronounced anomalies in GBA and ASM activities than patients with ichthyosis linearis circumflexa. They also displayed a stronger increase in SC ceramides processed via ASM. We conclude that changes in the localization of active GBA and ASM correlate with i) altered SC ceramide composition in NTS patients, ii) local serine protease activity, and iii) the clinical manifestation of NTS.

Radioprotective Effect of Hesperidin: A Systematic Review

Background and objectives: Ionizing radiation (IR) has been of immense benefit to man, especially for medical purposes (diagnostic imaging and radiotherapy). However, the risks of toxicity in healthy normal cells, leading to cellular damage as well as early and late side effects, have been major drawbacks. The aim of this study was to evaluate the radioprotective effect of hesperidin against IR-induced damage. Materials and Methods: The preferred reporting items for systematic reviews and meta-analyses (PRISMA) were applied in reporting this study. A search was conducted using the electronic databases PubMed, Scopus, Embase, Google Scholar, and www.ClinicalTrials.gov for information about completed or ongoing clinical trials. Results: From our search results, 24 studies involving rats, mice, and cultured human and animal cells were included. An experimental case-control design was used in all studies. The studies showed that the administration of hesperidin reduced oxidative stress and inflammation in all investigated tissues. Furthermore, it increased 30-day and 60-day survival rates and protected against DNA damage. The best radioprotection was obtained when hesperidin was administered before irradiation. Conclusions: The results of the included studies support the antioxidant, anti-inflammatory, and antiapoptotic abilities of hesperidin as a potential radioprotective agent against IR-induced damage. We recommend future clinical trials for more insights.

Radiation-Induced Heart Diseases: Protective Effects of Natural Products

Cardiovascular diseases (CVDs) account for the majority of deaths worldwide. Radiation-induced heart diseases (RIHD) is one of the side effects following exposure to ionizing radiation (IR). Exposure could be from various forms such as diagnostic imaging, radiotherapy for cancer treatment, as well as nuclear disasters and nuclear accidents. RIHD is mostly observed after radiotherapy for thoracic malignancies, especially left breast cancer. RIHD may affect the supply of blood to heart muscles, leading to an increase in the risk of heart attacks to irradiated persons. Due to its dose-limiting consequence, RIHD has a negative effect on the therapeutic efficacy of radiotherapy. Several methods have been proposed for protection against RIHD. In this paper, we review the use of natural products, which have shown promising results for protection against RIHD.

Clinical application of ceramide in cancer treatment

Development of innovative strategies for cancer treatment is a pressing public health issue. Despite recent advances, the mechanisms of cancer progression and the resistance to cancer treatment have not been fully elucidated. Sphingolipids, including ceramide and sphingoshin-1-phosphate, are bioactive mediators that regulate cancer cell death and survival through the dynamic balance of what has been termed the 'sphingolipid rheostat'. Specifically, ceramide, which acts as the central hub of sphingolipid metabolism, is generated via three major pathways by many stressors, including anti-cancer treatments, environmental stresses, and cytokines. We have previously shown in breast cancer patients that elevated ceramide correlated with less aggressive cancer phenotypes, leading to a prognostic impact. Recent studies showed that ceramide have the possibility of becoming the reinforcing agent of cancer treatment as well as other roles such as nanoparticles and diagnostic biomarker. We review ceramide as one of the key molecules to investigate in overcoming resistance to current drug therapies and in becoming one of the newest cancer treatments.

Mechanisms of apoptosis modulation by curcumin: Implications for cancer therapy

Cancer incidences are growing and cause millions of deaths worldwide. Cancer therapy is one of the most important challenges in medicine. Improving therapeutic outcomes from cancer therapy is necessary for increasing patients' survival and quality of life. Adjuvant therapy using various types of antibodies or immunomodulatory agents has suggested modulating tumor response. Resistance to apoptosis is the main reason for radioresistance and chemoresistance of most of the cancers, and also one of the pivotal targets for improving cancer therapy is the modulation of apoptosis signaling pathways. Apoptosis can be induced by intrinsic or extrinsic pathways via stimulation of several targets, such as membrane receptors of tumor necrosis factor-α and transforming growth factor-β, and also mitochondria. Curcumin is a naturally derived agent that induces apoptosis in a variety of different tumor cell lines. Curcumin also activates redox reactions within cells inducing reactive oxygen species (ROS) production that leads to the upregulation of apoptosis receptors on the tumor cell membrane. Curcumin can also upregulate the expression and activity of p53 that inhibits tumor cell proliferation and increases apoptosis. Furthermore, curcumin has a potent inhibitory effect on the activity of NF-κB and COX-2, which are involved in the overexpression of antiapoptosis genes such as Bcl-2. It can also attenuate the regulation of antiapoptosis PI3K signaling and increase the expression of MAPKs to induce endogenous production of ROS. In this paper, we aimed to review the molecular mechanisms of curcumin-induced apoptosis in cancer cells. This action of curcumin could be applicable for use as an adjuvant in combination with other modalities of cancer therapy including radiotherapy and chemotherapy.

The Onus of Sphingolipid Enzymes in Cancer Drug Resistance

Chemotherapy resistance, inherent or acquired, represents a serious barrier to the successful treatment of cancer. Although drug efflux, conducted by plasma membrane-resident proteins, detoxification enzymes, cell death inhibition, and DNA damage repair are ensemble players in this unwanted biology, a full understanding of the many in concert molecular mechanisms driving drug resistance is lacking. Recent discoveries in sphingolipid (SL) metabolism have provided significant insight into the role of these lipids in cancer growth; however, considerably less is known with respect to SLs and the drug-resistant phenotype. One exception here is enhanced ceramide glycosylation, a hallmark of multidrug resistance that is believed responsible, in part, for diminishing ceramides tumor-suppressor potential. This chapter will review various aspects of SL biology that relate to chemotherapy resistance and extend this topic to acknowledge the role of chemotherapy selection pressure in promoting dysregulated SL metabolism, a characteristic in cancer and an exploitable target for therapy.

Phytosphingosine exhibits an anti-epithelial-mesenchymal transition function by the inhibition of EGFR signaling in human breast cancer cells

The lack of effective anti-metastatic drugs for the eradication of breast cancer stem cells within tumors, which are often resistant to chemotherapy and radiotherapy, creates a major obstacle during metastatic breast cancer therapy. Although D-ribo-phytosphingosine (PHS) is well known to activate protein kinase (MAPK)-mediated apoptosis, its possible role towards the metastasis signaling mechanisms underlying the epithelial-mesenchymal transition (EMT) remains largely unknown. In this report, we investigate the anti-metastatic potential of the natural sphingolipid PHS for the targeting of breast cancer cells as well as breast stem-like cells in vitro. We showed that PHS led to suppression of migratory potential, spheroid formation, CD44^high/CD24^low subpopulation as well as stem cell- and EMT-associated protein expression in basal type highly malignant breast cancer cell lines. In addition, PHS-based inhibition of EMT was attributable to the downregulation of the EGFR/JAK1/STAT3 signaling axis, as validated by immunoprecipitation assays and breast tumorigenesis mice models. This study demonstrate that PHS can target metastatic tumors with dual specificity (EMT and cancer stem-like cells) and therefore may be serve as a promising candidate for breast cancer treatments.

Altered lipid metabolism in the aging kidney identified by three layered omic analysis

Aging-associated diseases and their comorbidities affect the life of a constantly growing proportion of the population in developed countries. At the center of these comorbidities are changes of kidney structure and function as age-related chronic kidney disease predisposes to the development of cardiovascular diseases such as stroke, myocardial infarction or heart failure. To detect molecular mechanisms involved in kidney aging, we analyzed gene expression profiles of kidneys from adult and aged wild-type mice by transcriptomic, proteomic and targeted lipidomic methodologies. Interestingly, transcriptome and proteome analyses revealed differential expression of genes primarily involved in lipid metabolism and immune response. Additional lipidomic analyses uncovered significant age-related differences in the total amount of phosphatidylethanolamines, phosphatidylcholines and sphingomyelins as well as in subspecies of phosphatidylserines and ceramides with age. By integration of these datasets we identified Aldh1a1, a key enzyme in vitamin A metabolism specifically expressed in the medullary ascending limb, as one of the most prominent upregulated proteins in old kidneys. Moreover, ceramidase Asah1 was highly expressed in aged kidneys, consistent with a decrease in ceramide C16. In summary, our data suggest that changes in lipid metabolism are involved in the process of kidney aging and in the development of chronic kidney disease.

Targeting ceramide metabolism in obesity

Obesity is a major health concern that increases the risk for insulin resistance, type 2 diabetes (T2D), and cardiovascular disease. Thus, an enormous research effort has been invested into understanding how obesity-associated dyslipidemia and obesity-induced alterations in lipid metabolism increase the risk for these diseases. Accordingly, it has been proposed that the accumulation of lipid metabolites in organs such as the liver, skeletal muscle, and heart is critical to these obesity-induced pathologies. Ceramide is one such lipid metabolite that accumulates in tissues in response to obesity, and both pharmacological and genetic strategies that reduce tissue ceramide levels yield salutary actions on overall metabolic health. We will review herein why ceramide accumulates in tissues during obesity and how an increase in intracellular ceramide impacts cellular signaling and function as well as potential mechanisms by which reducing intracellular ceramide levels improves insulin resistance, T2D, atherosclerosis, and heart failure. Because a reduction in skeletal muscle ceramide levels is frequently associated with improvements in insulin sensitivity in humans, the beneficial findings reported for reducing ceramides in preclinical studies may have clinical application in humans. Therefore, modulating ceramide metabolism may be a novel, exciting target for preventing and/or treating obesity-related diseases.

Review : c-Jun and the c-Jun Amino-Terminal Kinases: Bipotential Components of the Neuronal Stress Response

Expression of the inducible transcription factor c-Jun in neurons is a common finding after neuronal injury or 'stress,' such as ischemia, excitotoxicity, axon transection, UV irradiation, stimulation by cytokines, or production of such lipid messengers as ceramide. The neuronal 'stress response' displays striking similarities to the stress response of other cell types such as lymphocytes or tumor cells and is characterized by the activation of programs that lead to apoptosis or survival. It is accepted knowledge that c-Jun can act as neuronal 'killer' under in vitro conditions (with the death inducing ligand fas-ligand as novel AP-1 controlled target gene), but there is also growing evidence that c-Jun is linked to neuronal repair or survival. The control of this dichotomous function of c-Jun is not fully understood. Similar to the expression of c-Jun, the transcriptional activation of c-Jun by amino-terminal phosphorylation and the activation of the catalyzing c- Jun amino-terminal kinases (JNK), also called stress activated protein kinases, can also be linked to both neuronal survival and apoptosis. We suggest a model for the control of gene transcription after neuronal stress with activation of JNK and phosphorylation of c-Jun as transcriptional prerequisites, and with asso ciated partners as transcriptional effectors, e.g., by the expression and/or suppression of other transcription factors as activating transcription factor 2 (ATF-2), c-Fos, or JunD. This scenario is complicated by the observation that activity of JNK does not lead automatically to c-Jun phosphorylation. This review summa rizes the role of c-Jun and JNK as down-stream mediators of neuronal stressors and places the function of these molecules in the context of other stressful stimuli and intraneuronal responses. NEUROSCIENTIST 5:147-154, 1999

Computational modeling of sphingolipid metabolism

Background

As suggested by the origin of the word, sphingolipids are mysterious molecules with various roles in antagonistic cellular processes such as autophagy, apoptosis, proliferation and differentiation. Moreover, sphingolipids have recently been recognized as important messengers in cellular signaling pathways. Notably, sphingolipid metabolism disorders have been observed in various pathological conditions such as cancer and neurodegeneration.

Results

The existing formal models of sphingolipid metabolism focus mainly on de novo ceramide synthesis or are limited to biochemical transformations of particular subspecies. Here, we propose the first comprehensive computational model of sphingolipid metabolism in human tissue. Contrary to the previous approaches, we use a model that reflects cell compartmentalization thereby highlighting the differences among individual organelles.

Conclusions

The model that we present here was validated using recently proposed methods of model analysis, allowing to detect the most sensitive and experimentally non-identifiable parameters and determine the main sources of model variance. Moreover, we demonstrate the usefulness of our model in the study of molecular processes underlying Alzheimer’s disease, which are associated with sphingolipid metabolism.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0176-9) contains supplementary material, which is available to authorized users.

Measuring brain lipids

The rapid development of analytical technology has made lipidomics an exciting new area and this review will focus more on modern approaches to lipidomics than on earlier technology. Although not fully comprehensive for all possible brain lipids, the intent is to at least provide a reference for the analysis of classes of lipids found in brain and nervous tissue. We will discuss problems posed by the brain because of its structural and functional heterogeneity, the development changes it undergoes (myelination, aging, pathology etc.) and its cellular heterogeneity (neurons, glia etc.). Section 2 will discuss the various ways in which brain tissue can be extracted to yield lipids for analysis and section 3 will cover a wide range of techniques used to analyze brain lipids such as chromatography and mass-spectrometry. In Section 4 we will discuss ways of analyzing some of the specific biologically active brain lipids found in very small amounts except in pathological conditions and section 5 looks to the future of experimental lipidomic modification in the brain. This article is part of a Special Issue entitled Brain Lipids.

Current approaches and recent developments in the management of head and neck paragangliomas

Head and neck paragangliomas (HNPGLs) are rare neuroendocrine tumors belonging to the family of pheochromocytoma/paraganglioma neoplasms. Despite advances in understanding the pathogenesis of these tumors, the growth potential and clinical outcome of individual cases remains largely unpredictable. Over several decades, surgical resection has long been the treatment of choice for HNPGLs. However, increasing experience in various forms of radiosurgery has been reported to result in curative-like outcomes, even for tumors localized in the most inaccessible anatomical areas. The emergence of such new therapies challenges the traditional paradigm for the management of HNPGLs. This review will assist and guide physicians who encounter patients with such tumors, either from a diagnostic or therapeutic standpoint. This review will also particularly emphasize current and emerging knowledge in genetics, imaging, and therapeutic options as well as the health-related quality of life for patients with HNPGLs.

Lipid mediators in diabetic nephropathy

The implications of lipid lowering drugs in the treatment of diabetic nephropathy have been considered. At the same time, the clinical efficacy of lipid lowering drugs has resulted in improvement in the cardiovascular functions of chronic kidney disease (CKD) patients with or without diabetes, but no remarkable improvement has been observed in the kidney outcome. Earlier lipid mediators have been shown to cause accumulative effects in diabetic nephropathy (DN). Here, we attempt to analyze the involvement of lipid mediators in DN. The hyperglycemia-induced overproduction of diacyglycerol (DAG) is one of the causes for the activation of protein kinase C (PKCs), which is responsible for the activation of pathways, including the production of VEGF, TGFβ1, PAI-1, NADPH oxidases, and NFҟB signaling, accelerating the development of DN. Additionally, current studies on the role of ceramide are one of the major fields of study in DN. Researchers have reported excessive ceramide formation in the pathobiological conditions of DN. There is less report on the effect of lipid lowering drugs on the reduction of PKC activation and ceramide synthesis. Regulating PKC activation and ceramide biosynthesis could be a protective measure in the therapeutic potential of DN. Lipid lowering drugs also upregulate anti-fibrotic microRNAs, which could hint at the effects of lipid lowering drugs in DN.

Sphingolipids' role in radiotherapy for prostate cancer

There are several well-established mechanisms involved in radiation-induced cell death in mammalian cell systems. The p53-mediated apoptotic pathway is the most widely recognized mechanism (Lowe et al. Nature 362:847-849, 1993), although apoptosis has long been considered a less relevant mechanism of radiation-induced cell death (Steel, Acta Oncol 40:968-975, 2001; Brown and Wouters, Cancer Res 59:1391-1399, 1999; Olive and Durand, Int J Radiat Biol 71:695-707, 1997). We and others have recently focused instead on the emerging links between radiation, apoptosis, and ceramide and showed that ceramide is a sphingolipid-derived second messenger capable of initiating apoptotic cascades in response to various stress stimuli, including radiation.Ceramide, the backbone of all sphingolipids, is synthesized by a family of ceramide synthases (CerS), each using acyl-CoAs of defined chain length for N-acylation of the sphingoid long-chain base. Six mammalian CerS homologs have been cloned that demonstrated high selectivity towards acyl-CoAs (Lahiri et al. FEBS Lett 581:5289-5294, 2007), and more recently, it was shown that their activity can be modulated by dimer formation (Mesicek et al. Cell Signal 22:1300-1307, 2010; Laviad et al. J Biol Chem 283:5677-5684, 2008).This de novo ceramide synthesis has been observed in irradiated cells through a pathway normally suppressed by ataxia telangiectasia-mutated (ATM) protein, a key component of the cellular response to DNA double-strand breaks (Liao et al. J Biol Chem 274:17908-17917, 1999). ATM is not the sole factor known to affect apoptotic potential by modulating CerS activity. Recent work has also implicated protein kinase Cα (PKCα) as a potential CerS activator (Truman et al. Cancer Biol Ther 8:54-63, 2009).In this review, we summarize involvement of CerS in sphingolipid-mediated apoptosis in irradiated human prostate cancer cells and discuss future directions in this field.

Principles of radiobiology of stereotactic radiosurgery and clinical applications in the central nervous system

Stereotactic radiosurgery (SRS) has become an important treatment option for intracranial lesions and has recently been adapted to treat lesions outside the brain. Many studies have shown the effectiveness of SRS for the treatment of benign and metastatic tumors. Although DNA damage has been thought to be the principal form of radiation-induced damage, recent studies have shown that vascular endothelial damage is perhaps more important in the setting of high radiation doses per fraction such as those used in SRS. Furthermore, it has been shown that molecular responses to radiation differ based on dose per fraction. The principles of classical radiobiology are reviewed with explanation on why fractionation of radiotherapy allows optimization of the therapeutic ratio. The current understanding of the molecular responses that occur soon after the delivery of high radiation doses per fraction is also reviewed. A summary of current clinical evidence of radiation tolerance to SRS of brain, brainstem, optic chiasm and spinal cord is also provided. Recent advances in understanding the molecular basis of SRS response have uncovered a different biological response than previously thought. Further understanding of these molecular mechanisms will allow for the development of targeted radiosensitizers and radioprotectors to optimize the therapeutic ratio.

Mixing properties of sphingomyelin ceramide bilayers: a simulation study

Ceramide is the simplest molecule in the class of glycosphingolipids composed of a sphingosine backbone and acyl moiety. It plays significant roles in cell signaling; apoptosis; binding of hormones, toxins, and viruses; and many other biologically important functions. Sphingomyelin, ceramide with a phosphotidylcholine headgroup, is another biologically vital lipid present in the myelin sheath of nerve cell axons. Regions with high concentrations of ceramide can be formed in biological membranes composed of sphingomyelin by enzymatic catalysis with sphingomyelinase. To better understand the biophysical and thermodynamic properties of these molecules and their mixtures, we have preformed NPT molecular dynamics simulations of hydrated 16:0 sphingomyelin bilayers with increasing concentrations of 16:0 ceramide at 323, 332, 340, and 358 K. From analyses of electron densities, hydrogen bonding, NMR order parameters, partial molecular volume, and partial molecular area, we have identified possible structural changes corresponding to liquid ordered and liquid disordered phases. These structural changes are the results of changes in intra- and intermolecular hydrogen bonds between SM and Cer molecules. Our results correspond to DSC experiments for sphingomyelin bilayer concentrations up to 50% Cer. Above 50% concentration, we observe conformational changes in the SM headgroup similar to that of the umbrella model for lipid cholesterol mixtures.

Ceramides as modulators of cellular and whole-body metabolism

Nearly all stress stimuli (e.g., inflammatory cytokines, glucocorticoids, chemotherapeutics, etc.) induce sphingolipid synthesis, leading to the accumulation of ceramides and ceramide metabolites. While the role of these lipids in the regulation of cell growth and death has been studied extensively, recent studies suggest that a primary consequence of ceramide accumulation is an alteration in metabolism. In both cell-autonomous systems and complex organisms, ceramides modify intracellular signaling pathways to slow anabolism, ensuring that catabolism ensues. These ceramide actions have important implications for diseases associated with obesity, such as diabetes and cardiovascular disease.

The concepts, diagnosis and management of early imaging changes after therapy for glioblastomas

Since postoperative radiotherapy plus concomitant temozolomide followed by adjuvant temozolomide has become standard treatment for glioblastoma, the phenomenon of early post-treatment enlargement of the imaged tumour volume, usually without clinical deterioration, has become widely recognised. The term pseudoprogression has been used to describe a poorly understood pathophysiological process. In this review, the pathophysiological concepts, relevance, diagnosis and management of patients with 'pseudoprogression' and 'pseudoresponse' are discussed. Guidelines are given with respect to radiological imaging modality, mode and frequency. Further biological and clinical insights into these phenomena require carefully designed prospective studies.

LC/MS analysis of stratum corneum lipids: ceramide profiling and discovery

Ceramides (CERs) in the upper layer of the skin, the stratum corneum (SC), play a key role in the skin barrier function. In human SC, the literature currently reports 11 CER subclasses that have been identified. In this paper, a novel quick and robust LC/MS method is presented that allows the separation and analysis of all known human SC CER subclasses using only limited sample preparation. Besides all 11 known and identified subclasses, a 3D multi-mass chromatogram shows the presence of other lipid subclasses. Using LC/MS/MS with an ion trap (IT) system, a Fourier transform-ion cyclotron resonance system, and a triple quadrupole system, we were able to identify one of these lipid subclasses as a new CER subclass: the ester-linked ω-hydroxy fatty acid with a dihydrosphingosine base (CER [EOdS]). Besides the identification of a new CER subclass, this paper also describes the applicability and robustness of the developed LC/MS method by analyzing three (biological) SC samples: SC from human dermatomed skin, human SC obtained by tape stripping, and SC from full-thickness skin explants. All three biological samples showed all known CER subclasses and slight differences were observed in CER profile.

Role of JNK/ATF-2 pathway in inhibition of thrombospondin-1 (TSP-1) expression and apoptosis mediated by doxorubicin and camptothecin in FTC-133 cells

Our previous studies have shown that camptothecin and doxorubicin triggered ceramide accumulation via de novo synthesis pathway. De novo ceramide generation was responsible for the drug-induced apoptosis through a caspase-3-dependent pathway and a decrease of thrombospondin-1 expression in human thyroid carcinoma FTC-133 cells. Here, we demonstrate that Jun N-terminal kinases play a critical role in camptothecin- and doxorubicin-induced down-regulation of thrombospondin-1 expression: i) de novo ceramide synthesis pathway activates Jun N-terminal kinase 1/2 resulting in activating transcription factor 2 phosphorylation; ii) cell treatment by SP600125, a Jun N-terminal kinase specific inhibitor, strongly reduced activating transcription factor 2 phosphorylation and completely abolished camptothecin and doxorubicin effects; and iii) activating transcription factor 2 expression silencing greatly attenuated camptothecin- and doxorubicin-induced down-regulation of thrombospondin-1 expression and apoptosis. The set of our data established that camptothecin- and doxorubicin-induced activation of Jun N-terminal kinase/activating transcription factor 2 pathway via de novo ceramide synthesis down-regulates thrombospondin-1 expression and apoptosis in human thyroid carcinoma FTC-133 cells. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Lipidome of narrow-band ultraviolet B irradiated keratinocytes shows apoptotic hallmarks

BACKGROUND

UV light triggers a variety of biological responses in irradiated keratinocytes that might be associated with global perturbation of their lipidome. However, lipids that are specifically affected and the exact molecular mechanisms involved remain poorly understood.

OBJECTIVES

To characterize time-dependent changes of the lipidome of cultured keratinocytes induced by narrow-band ultraviolet B (NB-UVB) irradiation.

METHODS

Immortalized human keratinocytes (HaCaT) were cultured under standard conditions, irradiated with NB-UVB light (311 nm) at 400 and 800 mJ/cm(2) and collected 1, 2, 3, 6, 12 and 24 h later for lipid extraction. Lipid extracts were separated on silica plates in chloroform/ethanol/water/triethylamine (35:40:9:35) and in n-hexane/ethylacetate (5:1) followed by quantitative shotgun lipidomics analysis.

RESULTS

Irradiation with 800 mJ/cm(2) of NB-UVB altered morphology and lipidome composition of HaCaT cells. Ceramide content increased two-fold 6- and 12-h postirradiation with 800 mJ/cm(2), followed by threefold increase in triacylglycerols (TAGs) that peaked at 24 h. In addition, we observed marked increase of various phosphatidylcholine and phosphatidylethanolamine ethers, whereas phosphatidylcholine-species with short-chain fatty acid moieties decreased. The abundance of other lipid species was altered to lesser extent or remained unchanged.

CONCLUSIONS

NB-UVB affected the cellular lipidome of keratinocytes in strictly apoptosis-specific manner.

Involvement of the sphingolipid ceramide in heat-shock-induced apoptosis of bovine oocytes

Programmed cell death via the sphingomyelin pathway has been suggested to underlie heat-shock disturbance of oocyte developmental competence. A series of experiments were performed to characterise the role of the sphingolipid ceramide in heat-shock-induced apoptosis, and to determine whether ceramide formation can be regulated. Bovine cumulus–oocyte complexes (COCs) were aspirated from ovaries collected in the cold season (November–April), in vitro-matured, fertilised and cultured for 8 days. Exposure of COCs to heat shock (41°C) during maturation reduced cleavage rate and blastocyst formation relative to the control group (38.5°C). Annexin-V binding (V-FITC assay), which is associated with the early apoptotic event of membrane phosphatidylserine turnover, was higher in oocytes exposed to short-term versus long-term heat shock, suggesting that heat-shock-induced apoptosis involves membrane alterations. Similar to heat exposure, oocyte maturation with C2-ceramide had a dose-dependent deleterious effect on the first cleavages and subsequent embryonic development in association with increased annexin-V binding. Blocking endogenous ceramide generation with fumonisin B1, a specific inhibitor of dihydroceramide synthase (i.e. de novo formation), moderated, to some extent, the effects of heat shock on oocyte developmental competence, suggesting that ceramide plays an important role in heat-shock-induced apoptosis.

Early and late administration of MnTE-2-PyP5+ in mitigation and treatment of radiation-induced lung damage

Chronic production of reactive oxygen and nitrogen species is an underlying mechanism of irradiation (IR)-induced lung injury. The purpose of this study was to determine the optimum time of delivery of an antioxidant and redox-modulating Mn porphyrin, MnTE-2-PyP(5+), to mitigate and/or treat IR-induced lung damage. Female Fischer-344 rats were irradiated to their right hemithorax (28 Gy). Irradiated animals were treated with PBS or MnTE-2-PyP(5+) (6 mg /kg/24 h) delivered for 2 weeks by sc-implanted osmotic pumps (beginning after 2, 6, 12, 24, or 72 h or 8 weeks). Animals were sacrificed 10 weeks post-IR. Endpoints were body weight, breathing frequency, histopathology, and immunohistochemistry (8-OHdG, ED-1, TGF-beta, HIF-1alpha, VEGF A). A significant radioprotective effect on functional injury, measured by breathing frequency, was observed for all animals treated with MnTE-2-PyP(5+). Treatment with MnTE-2-PyP(5+) starting 2, 6, and 12 h but not after 24 or 72 h resulted in a significant decrease in immunostaining for 8-OHdG, HIF-1alpha, TGF-beta, and VEGF A. A significant decrease in HIF-1alpha, TGF-beta, and VEGF A, as well as an overall reduction in lung damage (histopathology), was observed in animals beginning treatment at the time of fully developed lung injury (8 weeks post-IR). The catalytic manganese porphyrin antioxidant and modulator of redox-based signaling pathways MnTE-2-PyP(5+) mitigates radiation-induced lung injury when given within the first 12 h after IR. More importantly, this is the first study to demonstrate that MnTE-2-PyP(5+) can reverse overall lung damage when started at the time of established lung injury 8 weeks post-IR. The radioprotective effects are presumably mediated through its ability both to suppress oxidative stress and to decrease activation of key transcription factors and proangiogenic and profibrogenic cytokines.

Increase in sphingolipid catabolic enzyme activity during aging

AIM

To understand the contribution of sphingolipid metabolism and its metabolites to development and aging.

METHODS

A systemic analysis on the changes in activity of sphingolipid metabolic enzymes in kidney, liver and brain tissues during development and aging was conducted. The study was conducted using tissues from 1-day-old to 720-day-old rats.

RESULTS

Catabolic enzyme activities as well as the level of sphingomyelinase (SMase) and ceramidase (CDase) were higher than that of anabolic enzyme activities, sphingomyelin synthase and ceramide synthase. This suggested an accumulation of ceramide and sphingosine during development and aging. The liver showed the highest neutral-SMase activity among the tested enzymes while the kidney and brain exhibited higher neutral-SMase and ceramidase activities, indicating a high production of ceramide in liver and ceramide/sphingosine in the kidney and brain. The activities of sphingolipid metabolic enzymes were significantly elevated in all tested tissues during development and aging, although the onset of significant increase in activity varied on the tissue and enzyme type. During aging, 18 out of 21 enzyme activities were further increased on day 720 compared to day 180.

CONCLUSION

Differential increases in sphingolipid metabolic enzyme activities suggest that sphingolipids including ceramide and sphingosine might play important and dynamic roles in proliferation, differentiation and apoptosis during development and aging.

Identification of Mg2+ -dependent neutral sphingomyelinase 1 as a mediator of heat stress-induced ceramide generation and apoptosis

Neutral sphingomyelinases (SMases) are involved in the induction of ceramide-mediated proapoptotic signaling under heat stress conditions. Although ceramide is an important mediator of apoptosis, the neutral SMase that is activated under heat stress has not been identified. In this study, we cloned an Mg(2+)-dependent neutral SMase from a zebrafish embryonic cell cDNA library using an Escherichia coli expression-cloning vector. Screening of the clones using an SMase activity assay with C(6)-7-nitro-2-1,3-benzoxadiazol-4-yl-sphingomyelin as the substrate resulted in the isolation of one neutral SMase cDNA clone. This cDNA encoded a polypeptide of 420 amino acids (putative molecular weight: 46,900) containing two predicted transmembrane domains in its C-terminal region. The cloned neutral SMase 1 acted as a mediator of stress-induced apoptosis. Bacterially expressed recombinant neutral SMase 1 hydrolyzed [choline-methyl-(14)C]sphingomyelin optimally at pH 7.5 in the presence of an Mg(2+) ion. In zebrafish embryonic cells, the endogenous SMase enzyme was localized in the microsomal fraction. In FLAG-tagged SMase-overexpressing cells, neutral SMase 1 colocalized with a Golgi marker in a cytochemical analysis. Inactivation of the enzyme by an antisense phosphorothioate oligonucleotide repressed the induction of ceramide generation, caspase-3 activation, and apoptotic cell death by heat stress. Thus, neutral SMase 1 participates in an inducible ceramide-mediating, proapoptotic signaling pathway that operates in heat-induced apoptosis in zebrafish embryonic cells.

Activation of Lck is critically required for sphingosine-induced conformational activation of Bak and mitochondrial cell death

Despite extensive investigation, the molecular mechanism of anticancer activity of sphingolipid metabolites remains to be clarified. Here we demonstrate that sphingosine induces mitochondrial cell death via Lck-mediated conformational activation of Bak in Jurkat T cell lymphoma. Treatment of cells with sphingosine rapidly induced mitochondrial membrane potential loss, cytochrome c release from mitochondria, and apoptotic cell death. Sphingosine also induced conformational activation of Bak, but not Bax. siRNA targeting of Bak effectively attenuated sphingosine-induced mitochondrial cell death, indicating that Bak is involved in sphingosine-induced mitochondrial cell death. Sphingosine also induced activation of tyrosine kinase Lck. Inhibition of Lck by treatment of PP2, a Lck inhibitor or siRNA targeting of Lck suppressed sphingosine-induced conformational activation and oligomerization of Bak, mitochondrial membrane potential loss, and apoptotic cell death, implying that activation of Lck is critically required for sphingosine-induced conformational activation of Bak and mitochondrial cell death. The results elucidated in this study provide a novel cellular mechanism for the anticancer activity of sphingolipid metabolites.

Effects of flavonoids on sphingolipid turnover in the toxin-damaged liver and liver cells

BACKGROUND

The ceramide generation is an early event in the apoptotic response to numerous stimuli including the oxidative stress and ceramide analogs mimic the stress effect and induce apoptosis. Flavonoids of German chamomile are reported to exhibit the hepatoprotective effect. Flavonoids affect sphingolipid metabolism and reduce the elevated ceramide level in the aged liver. In the present paper, the ceramide content and production in the CCl4- and ethanol-treated liver and hepatocytes as well as the correction of sphingolipid metabolism in the damaged liver using the mixture of German chamomile flavonoids (chamiloflan) or apigenin-7-glucoside (AP7Glu) have been investigated.

RESULTS

The experiments were performed in either the rat liver or hepatocytes of normal, CCl4- and ethanol-treated or flavonoid- and toxin plus flavonoid-treated animals. [14C]palmitic acid and [methyl-14C-phosphorylcholine]sphingomyelin were used to investigate the sphingolipid turnover. Addition of the CCl4 or ethanol to isolated hepatocyte suspensions caused loss of cell viability and increased the lactate dehydrogenase release from the cells into supernatant and ceramide level in the cells. CCl4 administration to the rats enlarged ceramide mass as well as neutral sphingomyelinase (SMase) activity and reduced ceramide degradation by the neutral ceramidase. Pretreatment of isolated hepatocytes with flavonoids abrogated the CCl4 effects on the cell membrane integrity and normalized the ceramide content. Flavonoid administration to the rats normalized the elevated ceramide content in the damaged liver via neutral SMase inhibition and ceramidase activation.

CONCLUSION

The data obtained have demonstrated that flavonoids affect sphingolipid metabolism in the CCl4- and ethanol-damaged liver and liver cells. Flavonoids normalized activities of key enzymes of sphingolipid turnover (neutral SMase and ceramidase) and ceramide contents in the damaged liver and liver cells, and stabilized the hepatocyte membranes.

Oxidative stress, lipid rafts, and macrophage reprogramming

Oxidant stress, induced under a variety of conditions, is known to lead to the molecular reprogramming of the tissue-fixed macrophage. This reprogramming is associated with an altered response to subsequent inflammatory stimuli, such as lipopolysaccharide (LPS), leading to enhanced liberation of proinflammatory chemokines and cytokines. Due to this altered response, dysregulated immunity ensues, leading to the development of clinical syndromes such as multiple organ dysfunction syndrome (MODS). Although the mechanisms responsible for this altered macrophage activity by oxidant stress remains complex and poorly elucidated, it appears, based on recent research, that early and direct alterations within lipid rafts are responsible. This early and direct interaction with lipid rafts by oxidants leads to the mobilization of annexin VI from lipid raft constructs, leading to the release of calcium. This increased cytosolic concentration of this secondary messenger, in turn, results in the activation of calcium-dependent kinases, leading to further alterations in lipid raft lipids and eventually lipid raft proteins. Due to these lipid raft compositional changes, preassembly of receptor complexes occur, leading to enhanced proinflammatory activation. Within this review, the complexity of oxidant-induced reprogramming within the tissue fixed macrophage as currently understood is explained.

Heat stress-induced apoptosis in porcine in vitro fertilized and parthenogenetic preimplantation-stage embryos

Decades worth of research have consistently shown the adverse effects of elevated temperatures on reproductive parameters of livestock species. The objective of this study was to evaluate the developmental and apoptotic responses of porcine in vitro fertilized (IVF) and parthenogenetically activated (PA) embryos heat stressed at the late 1-cell stage. Embryos were heat stressed (HS) at 42 degrees C for 9 hr starting 22 hr after insemination or artificial activation stimulus. Non heat-stressed (NHS) control embryos were maintained at 39 degrees C for the duration of the experiments. TUNEL staining on Day 5 of development demonstrated that heat stress elicited a significant apoptotic response in IVF embryos (45.6% of HS embryos and 26.7% of NHS embryos were apoptotic; P<0.05), but not in PA embryos (51.1% and 39.9% for HS and NHS embryos, respectively; P>0.1). And, while IVF embryos were highly susceptible to heat-induced developmental perturbations (20.6% and 8.8% development to blastocyst for NHS and HS embryos, respectively; P<0.05), elevated temperatures did not affect blastocyst rates in PA embryos (22.2% for NHS PA embryos and 21.2% for HS PA embryos; P>0.1). These findings indicate that, as in other systems studied, IVF pig embryos are directly affected adversely by heat stress conditions. Parthenogenetic embryos, though, appear to be surprisingly tolerant of the elevated temperatures. The differences between IVF and PA embryos in their response to heat stress warrants further investigation.

Activation of de novo synthetic pathway of ceramides is responsible for the initiation of hydrogen peroxide-induced apoptosis in HL-60 cells

Sphingolipid metabolites in HL-60 cells were analyzed to gain an understanding of their roles in early events underlying hydrogen peroxide (H2O2)-induced apoptosis. Incubation of cells with H2O2 increased the intracellular levels of ceramides and sphinganine, but decreased those of ceramide 1-phosphates (ceramide 1-P) and sphingosine. The levels of sphingomyelins and sphingomyelinase (SMase) activities were not affected by H2O2 treatment. These results were similar to the profiles induced by daunorubicin, an activator of serine palmitoyl CoA transferase (SPT), suggesting that H2O2 stimulated the de novo synthetic pathway of ceramides. L-cycloserine and fumonisin B1 (FB1), specific inhibitors of de novo ceramide biosynthesis, suppressed the elevation of ceramides and sphinganine induced by H2O2, which consequently reduced apoptotic cell death. Collectively, these results demonstrated that H2O2 increased the intracellular concentrations of ceramides via activation of a de novo biosynthetic pathway, and the enhanced ceramides might initiate apoptosis in HL-60 cells.

Responses of normal cells to ionizing radiation

Radiation-induced alterations in cellular tissue homeostasis triggered by various molecular responses at the level of inter- and intracellular signaling processes cause both acute and late effects in normal tissue after radiation therapy. Some of the underlying molecular and cellular response pathways leading to radiation-induced tissue remodeling will be discussed, with special emphasis on vascular and parenchymal tissues.

Physiologic and pathophysiologic roles of lipid mediators in the kidney

Small lipids such as eicosanoids exert diverse and complex functions. In addition to their role in regulating normal kidney function, these lipids also play important roles in the pathogenesis of kidney diseases. Cyclooxygenase (COX)-derived prostanoids play important role in maintaining renal function, body fluid homeostasis, and blood pressure. Renal cortical COX2-derived prostanoids, particularly (PGI2) and PGE2 play critical roles in maintaining blood pressure and renal function in volume contracted states. Renal medullary COX2-derived prostanoids appear to have antihypertensive effect in individuals challenged with a high salt diet. 5-Lipoxygenase (LO)-derived leukotrienes are involved in inflammatory glomerular injury. LO product 12-hydroxyeicosatetraenoic acid (12-HETE) is associated with pathogenesis of hypertension, and may mediate angiotensin II and TGFbeta induced mesengial cell abnormality in diabetic nephropathy. P450 hydroxylase-derived 20-HETE is a potent vasoconstrictor and is involved in the pathogenesis of hypertension. P450 epoxygenase derived epoxyeicosatrienoic acids (EETs) have vasodilator and natriuretic effect. Blockade of EET formation is associated with salt-sensitive hypertension. Ceramide has also been demonstrated to be an important signaling molecule, which is involved in pathogenesis of acute kidney injury caused by ischemia/reperfusion, and toxic insults. Those pathways should provide fruitful targets for intervention in the pharmacologic treatment of renal disease.

Roles of Lipid Mediators in Kidney Injury

Small lipids such as eicosanoids exert diverse and complex functions. In addition to their role in regulating normal kidney function, these lipids also play important roles in the pathogenesis of kidney diseases. Increased glomerular cyclooxygenase (COX)1 or COX2 expression has been reported in patients with nephritis and in animal models of nephritis. COX inhibitors have shown beneficial effects on lupus nephritis and passive Heymann nephritis, but not anti-Thy1.1-induced nephritis. 5-Lipoxygenase-derived leukotrienes are involved in inflammatory glomerular injury. Lipoxygenase product 12-hydroxyeicosatetraenoic acid may mediate angiotensin II and transforming growth factor beta-induced mesangial cell abnormality in diabetic nephropathy. P450 arachidonic acid mono-oxygenase-derived 20-hydroxyeicosatetraenoic acid and epoxyeicosatrienoic acids are involved in several forms of kidney injury, including renal injury in metabolic syndrome. Ceramide also has been shown to be an important signaling molecule that is involved in the pathogenesis of acute kidney injury caused by ischemia/reperfusion and toxic insults. Those pathways should provide fruitful targets for intervention in the pharmacologic treatment of renal disease.

The induction of colonocyte differentiation in CaCo-2 cells by sodium butyrate causes an increase in glucosylceramide synthesis in order to avoid apoptosis based on ceramide

To examine the relationship between apoptosis accompanying differentiation and sphingolipid-metabolism, CaCo-2 cells were used as a model of human intestinal epithelial cells and the variation in cellular Cer/GlcCer-content and related enzyme activities during butyrate-induced differentiation were investigated. The simultaneous administration of PDMP as a GlcCer synthase inhibitor caused a significant increase in the amount of Cers, especially palmitoyl-Cer. Butyrate caused an increase in the amount of GlcCers, especially alpha-hydroxy fatty acid-GlcCers, and in cellular GlcCer synthase activity. Cellular Cer content related to apoptosis was mainly regulated by the GlcCer synthase-based metabolism of Cers.