Role Of Ceramide Research Articles

The role of ceramides in skin barrier function and the importance of their correct formulation for skincare applications.

Ceramides are a family of lipids constituted by a sphingoid base and a fatty acid. In the skin, they are mainly present in the stratum corneum where, with cholesterol and free fatty acids, they constitute the inter-corneocyte lipids. With the other lipid groups, they play a key role in the formation of dense lamellar structures between adjacent corneocytes, collectively ensuring the vital efficient barrier to water evaporation and protection from foreign agents´ penetration. Changes in ceramide level and relative composition, with potential impairment of lipid arrangement, have been evidenced in different skin conditions and skin diseases. Therefore, use of suitably formulated ceramides has been proposed for topical treatment to help re-structure damaged lipid arrangement and repair impaired skin barrier function. Nonetheless, the formulation of ceramides in products necessitates specific processes such as heating to high temperature before their introduction in the final formula. In this review on the structure, the role and the potential of ceramides for skincare, we point out the necessity of rigorous process when formulating ceramides into the final product. We demonstrate the counterproductive effects of undissolved ceramides on skin barrier repair capacity of the formulas, when assessed in different invitro models of disrupted skin barrier.

The role of ceramides in the disruption of the cutaneous permeability barrier, a common manifestation of skin disorders

The role of ceramides in the disruption of the cutaneous permeability barrier, a common manifestation of skin disorders

Oral Exposure to Titanium Dioxide E171 and Zinc Oxide Nanoparticles Induces Multi-Organ Damage in Rats: Role of Ceramide.

Food-grade titanium dioxide (E171) and zinc oxide nanoparticles (ZnO NPs) are common food additives for human consumption. We examined multi-organ toxicity of both compounds on Wistar rats orally exposed for 90 days. Rats were divided into three groups: (1) control (saline solution), (2) E171-exposed, and (3) ZnO NPs-exposed. Histological examination was performed with hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM). Ceramide (Cer), 3-nitrotyrosine (NT), and lysosome-associated membrane protein 2 (LAMP-2) were detected by immunofluorescence. Relevant histological changes were observed: disorganization, inflammatory cell infiltration, and mitochondrial damage. Increased levels of Cer, NT, and LAMP-2 were observed in the liver, kidney, and brain of E171- and ZnO NPs-exposed rats, and in rat hearts exposed to ZnO NPs. E171 up-regulated Cer and NT levels in the aorta and heart, while ZnO NPs up-regulated them in the aorta. Both NPs increased LAMP-2 expression in the intestine. In conclusion, chronic oral exposure to metallic NPs causes multi-organ injury, reflecting how these food additives pose a threat to human health. Our results suggest how complex interplay between ROS, Cer, LAMP-2, and NT may modulate organ function during NP damage.

Necessary Role of Ceramides in the Human Microvascular Endothelium During Health and Disease.

Elevated plasma ceramides and microvascular dysfunction both independently predict adverse cardiac events. Despite the known detrimental effects of ceramide on the microvasculature, evidence suggests that activation of the shear-sensitive, ceramide-forming enzyme NSmase (neutral sphingomyelinase) elicits formation of vasoprotective nitric oxide (NO). Here, we explore a novel hypothesis that acute ceramide formation through NSmase is necessary for maintaining NO signaling within the human microvascular endothelium. We further define the mechanism through which ceramide exerts beneficial effects and discern key mechanistic differences between arterioles from otherwise healthy adults (non-coronary artery disease [CAD]) and patients diagnosed with CAD. Human arterioles were dissected from discarded surgical adipose tissue (n=166), and vascular reactivity to flow and C2-ceramide was assessed. Shear-induced NO and mitochondrial hydrogen peroxide (H2O2) production were measured in arterioles using fluorescence microscopy. H2O2 fluorescence was assessed in isolated human umbilical vein endothelial cells. Inhibition of NSmase in arterioles from otherwise healthy adults induced a switch from NO to NOX-2 (NADPH-oxidase 2)-dependent H2O2-mediated flow-induced dilation. Endothelial dysfunction was prevented by treatment with sphingosine-1-phosphate (S1P) and partially prevented by C2-ceramide and an agonist of S1P-receptor 1 (S1PR1); the inhibition of the S1P/S1PR1 signaling axis induced endothelial dysfunction via NOX-2. Ceramide increased NO production in arterioles from non-CAD adults, an effect that was diminished with inhibition of S1P/S1PR1/S1P-receptor 3 signaling. In arterioles from patients with CAD, inhibition of NSmase impaired the overall ability to induce mitochondrial H2O2 production and subsequently dilate to flow, an effect not restored with exogenous S1P. Acute ceramide administration to arterioles from patients with CAD promoted H2O2 as opposed to NO production, an effect dependent on S1P-receptor 3 signaling. These data suggest that despite differential downstream signaling between health and disease, NSmase-mediated ceramide formation is necessary for proper functioning of the human microvascular endothelium. Therapeutic strategies that aim to significantly lower ceramide formation may prove detrimental to the microvasculature.

Abstract 12494: Role of Ceramide in Estrogen-Induced Oxidative Stress in Endothelial Cells From Individuals Assigned Male at Birth

Compared to cis-males and females, risk for cardiovascular disease (CVD) is elevated in trans-females undergoing estrogen-containing gender affirming therapy. We have previously shown that continuous estrogen treatment of arterioles from healthy adults assigned male at birth promotes microvascular endothelial dysfunction, however the mechanism through which estrogen contributes to endothelial damage remains unknown. Estrogen increases expression of neutral sphingomyelinase (NSmase), an enzyme responsible for the production of ceramides. Ceramides are bioactive sphingolipids that can increase cellular levels of hydrogen peroxide (H 2 O 2 ). Together, we hypothesize that estrogen increases endothelial levels of oxidative stress through NSmase-mediated ceramide formation. Primary male human umbilical vein endothelial cells (HUVECs; pooled from n=3) were seeded in 8-well microscopy plates prior to treatments. Peroxy yellow 1 (PY1) was used to measure changes in endothelial H 2 O 2 . Wells were imaged at 20x and analyzed using ImageJ. Difference between %change in fluorescence ±standard error (SE) is reported, and significance is determined using One-Way ANOVA. Treatment with 17β-estradiol (E2; 100nM, 48hrs) increased endothelial H 2 O 2 production (control, n=6 vs E2, n=7; 13.9±6.3, p=0.038), an effect diminished in the presence of the NSmase inhibitor GW4869 (GW4869, 4μM, 48hrs; control, n=6 vs E2+GW4869, n=7; 1.7±6.3, p=0.78). Signal specificity for H 2 O 2 was confirmed with PEG-catalase treatment (500U/ml, 48hrs; control, n=6 vs E2+catalase, n=3; 2.3±7.9, p=0.77). Together, these results suggest that estrogen increases oxidative stress in endothelial cells isolated from individuals assigned male at birth which can be prevented through inhibition of the ceramide-forming enzyme NSmase. This work offers mechanistic insight into how estrogen containing gender affirming therapy may potentially contribute to endothelial damage and increase CVD risk in trans-females.

1609-P: Neutral Sphingomyelinase Inhibition Limits Hepatic-Lipotoxicity and Inflammation in a Cell Model of Steatosis

Nonalcoholic fatty liver disease (NAFLD) represents a global healthcare challenge; it is the hepatic manifestation of metabolic syndrome and is strongly associated with developing type 2diabetes mellitus (T2DM). Liver fat accumulation is the first step of disease progression that triggers hepatic lipotoxicity. The role of ceramides in inducing deleterious effects on hepatic metabolism is now well-accepted. Yet, the specific role of stress responsive sphingomyelinase activation under lipotoxic conditions remains under-investigated. The complexity of NAFLD pathogenesis contributes to lack of proper investigatory model, limiting progression in developing and testing novel treatment and prevention strategies. Here, we first report a convenient in-vitro human cell-based model with great resemblance to in-vivo NAFLD hallmarks. Neutral Sphingomyelinase (nSMase2) expression and activity was found to be elevated in both the liver of high fat steatosis mouse models and in HepG2-steatosis cell models. Meanwhile, the functional inhibition of nSMase2 prevented hepatotoxicity-induced pathologies by significantly reducing intracellular lipid accumulation and prevented the upregulation of TNF-α triggered inflammation. Furthermore, inhibition of nSMase2 showed significant increase in PPARα at both gene and protein levels, while PPARα reduction was observed under the stimulation of nSMase2 activity by its agonist daunorubicin (DNR). Together the presented data highlight the role of nSMase2 in the pathogenesis of NAFLD and other disorders linked to hepatic steatosis, providing a novel therapeutic target. Disclosure F. Alrashed: None. H. Arefanian: None. S.T. Sindhu: None. F. Bahman: None. H. AlSaeed: None. A. Al Madhoun: None. F. Alzaid: None. F. Al-Mulla: None. R. Ahmad: None. Funding Kuwait Foundation for the Advancement of Sciences (RA0402021)

Mechanisms of pulmonary microvascular endothelial cells barrier dysfunction induced by LPS: The roles of ceramides and the Txnip/NLRP3 inflammasome.

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are characterized by pulmonary microvascular endothelial cells (PMVECs) barrier dysfunction and proinflammatory cytokine influx into lung tissue, resulting in pulmonary oedema. Ceramide overproduction is an important mediator of pulmonary hyperinflammation and pulmonary oedema in Acute lung injury (ALI). Ceramides induce NLRP3 inflammasome activation are essential for the hyperinflammatory response. However, the roles and specific mechanisms of ceramide-induced NLRP3 inflammasome activation, proinflammatory cytokine manufacturing and PMVECs barrier dysfunction in ALI are unclear. Herein, pretreatment with the acid sphingomyelinase (ASMase) inhibitor imipramine (but not a neutral sphingomyelinase (NSMase) inhibitor or de novo pathway inhibitor) significantly inhibited ceramide early production in rats with lipopolysaccharide (LPS)-induced ALI; Furthermore, the Txnip/NLRP3 inflammasome activation, proinflammatory cytokine release, increased PMVECs permeability and lung injury were significantly decreased. Verapamil, a Txnip inhibitor, substantially inhibited Txnip/NLRP3 inflammasome activation, proinflammatory cytokine release, increased PMVECs permeability and lung injury in rats with C8-ceramide-induced ALI. In vitro, short hairpin RNA-mediated Txnip silencing significantly inhibited C8-ceramide-induced Txnip/NLRP3 inflammasome activation in NR8383 alveolar macrophages (AMs) and early secretion of the proinflammatory cytokines IL-1β (4-12h) as well as IL-6 and TNF-α at subsequent times (later than 12h). However, C8-ceramide significantly increased the early secretion (within 8h) of the proinflammatory cytokines IL-1β, IL-6 and TNF-α in a co-culture model of NR8383 AMs and PMVECs, and Txnip silencing of NR8383 AMs inhibited the secretion of pro-inflammatory cytokines and reduced cytoskeletal rearrangements, intercellular connection breakage and hyperpermeability in PMVECs. Overall, our results suggest that in LPS-induced ALI, ceramide-mediated Txnip/NLRP3 inflammasome activation in NR8383 AMs leads to early IL-1β release, subsequently inducing PMVECs injury and release of the proinflammatory cytokines IL-6 and TNF-α, ultimately leading to PMVECs barrier dysfunction and ALI.

Lipids in Mitochondrial Macroautophagy: Phase Behavior of Bilayers Containing Cardiolipin and Ceramide

Cardiolipin (CL) is a key lipid for damaged mitochondrial recognition by the LC3/GABARAP human autophagy proteins. The role of ceramide (Cer) in this process is unclear, but CL and Cer have been proposed to coexist in mitochondria under certain conditions. Varela et al. showed that in model membranes composed of egg sphingomyelin (eSM), dioleoyl phosphatidylethanolamine (DOPE), and CL, the addition of Cer enhanced the binding of LC3/GABARAP proteins to bilayers. Cer gave rise to lateral phase separation of Cer-rich rigid domains but protein binding took place mainly in the fluid continuous phase. In the present study, a biophysical analysis of bilayers composed of eSM, DOPE, CL, and/or Cer was attempted to understand the relevance of this lipid coexistence. Bilayers were studied by differential scanning calorimetry, confocal fluorescence microscopy, and atomic force microscopy. Upon the addition of CL and Cer, one continuous phase and two segregated ones were formed. In bilayers with egg phosphatidylcholine instead of eSM, in which the binding of LC3/GABARAP proteins hardly increased with Cer in the former study, a single segregated phase was formed. Assuming that phase separation at the nanoscale is ruled by the same principles acting at the micrometer scale, it is proposed that Cer-enriched rigid nanodomains, stabilized by eSM:Cer interactions formed within the DOPE- and CL-enriched fluid phase, result in structural defects at the rigid/fluid nanointerfaces, thus hypothetically facilitatingLC3/GABARAP protein interaction.

Role of Ceramides and Sphingolipids in Parkinson's Disease

Sphingolipids, including the basic ceramide, are a subset of bioactive lipids that consist of many different species. Sphingolipids are indispensable for proper neuronal function, and an increasing number of studies have emerged on the complexity and importance of these lipids in (almost) all biological processes. These include regulation of mitochondrial function, autophagy, and endosomal trafficking, which are affected in Parkinson’s disease (PD). PD is the second most common neurodegenerative disorder and is characterized by the loss of dopaminergic neurons. Currently, PD cannot be cured due to the lack of knowledge of the exact pathogenesis. Nonetheless, important advances have identified molecular changes in mitochondrial function, autophagy, and endosomal function. Furthermore, recent studies have identified ceramide alterations in patients suffering from PD, and in PD models, suggesting a critical interaction between sphingolipids and related cellular processes in PD. For instance, autosomal recessive forms of PD cause mitochondrial dysfunction, including energy production or mitochondrial clearance, that is directly influenced by manipulating sphingolipids. Additionally, endo-lysosomal recycling is affected by genes that cause autosomal dominant forms of the disease, such as VPS35 and SNCA. Furthermore, endo-lysosomal recycling is crucial for transporting sphingolipids to different cellular compartments where they will execute their functions.This review will discuss mitochondrial dysfunction, defects in autophagy, and abnormal endosomal activity in PD and the role sphingolipids play in these vital molecular processes.

The Role of Ceramide in Inherited Retinal Disease Pathology.

Ceramide (Cer) plays an essential role in photoreceptor cell death in the retina. On the one hand, Cer accumulation emerges as a common feature during retina neurodegeneration, leading to the death of photoreceptors. On the other hand, Cer deficiency has also recently been associated with retinal dysfunction and degeneration. Although more and more evidence supports the importance of maintaining Cer homeostasis in the retina, mechanistic explanations of the observed phenotypes, especially in the context of Cer deficiency, are still lacking. An enhanced understanding of Cer's role in the retina will help us explore the underlying molecular basis for clinical phenotypes of retinal dystrophies and provide us with potential therapeutic targets.

Ceramides: correlation with cardiovascular risk factors

Despite the successes achieved, cardiovascular disease (CVD) remains the leading cause of death worldwide. With the help of traditional risk factors, it is not always possible to identify all patients with a high probability of developing cardiovascular events (CVЕ); therefore, the problem of finding new CVD biomarkers still remains relevant. Previous studies have shown the important role of excessive synthesis of ceramides in the development of obesity, insulin resistance (IR), type 2 diabetes mellitus (DM2), and liver steatosis. It is considered that ceramides are able to modulate signaling pathways involved in the regulation of glucose metabolism, triglyceride synthesis, development of apoptosis, fibrosis, and atherosclerosis. Given the wide range of metabolic effects, the study of ceramides is promising for identifying patients at high risk of CVD, as well as improving existing treatment and diagnostic strategies. This review article considers the role of ceramides in the development of atherosclerosis, the correlation with traditional risk factors, and the possibility of using them as new risk factors for early diagnosis of CVD.

Ceramides: correlation with cardiovascular risk factors

Despite the successes achieved, cardiovascular disease (CVD) remains the leading cause of death worldwide. With the help of traditional risk factors, it is not always possible to identify all patients with a high probability of developing cardiovascular events (CVЕ); therefore, the problem of finding new CVD biomarkers still remains relevant. Previous studies have shown the important role of excessive synthesis of ceramides in the development of obesity, insulin resistance (IR), type 2 diabetes mellitus (DM2), and liver steatosis. It is considered that ceramides are able to modulate signaling pathways involved in the regulation of glucose metabolism, triglyceride synthesis, development of apoptosis, fibrosis, and atherosclerosis. Given the wide range of metabolic effects, the study of ceramides is promising for identifying patients at high risk of CVD, as well as improving existing treatment and diagnostic strategies. This review article considers the role of ceramides in the development of atherosclerosis, the correlation with traditional risk factors, and the possibility of using them as new risk factors for early diagnosis of CVD.

A simple, highly sensitive, and facile method to quantify ceramide at the plasma membrane

The role of ceramide in biological functions is typically based on the elevation of cellular ceramide, measured by LC-MS in the total cell lysate. However, it has become increasingly appreciated that ceramide in different subcellular organelles regulates specific functions. In the plasma membrane, changes in ceramide levels might represent a small percentage of the total cellular ceramide, evading MS detection but playing a critical role in cell signaling. Importantly, there are currently no efficient techniques to quantify ceramide in the plasma membrane. Here, we developed a method to measure the mass of ceramide in the plasma membrane using a short protocol that is based on the hydrolysis of plasma membrane ceramide into sphingosine by the action of exogenously applied bacterial recombinant neutral ceramidase. Plasma membrane ceramide content can then be determined by measuring the newly generated sphingosine at a stoichiometry of 1:1. A key step of this protocol is the chemical fixation of cells to block cellular sphingolipid metabolism, especially of sphingosine to sphingosine 1-phosphate. We confirmed that chemical fixation does not disrupt the lipid composition at the plasma membrane, which remains intact during the time of the assay. We illustrate the power of the approach by applying this protocol to interrogate the effects of the chemotherapeutic compound doxorubicin. Here we distinguished two pools of ceramide, depending on the doxorubicin concentration, consolidating different reports. In summary, we have developed the first approach to quantify ceramide in the plasma membrane, allowing the study of new avenues in sphingolipid compartmentalization and function.

Role of Ceramides and Lysosomes in Extracellular Vesicle Biogenesis, Cargo Sorting and Release

Cells have the ability to communicate with their immediate and distant neighbors through the release of extracellular vesicles (EVs). EVs facilitate intercellular signaling through the packaging of specific cargo in all type of cells, and perturbations of EV biogenesis, sorting, release and uptake is the basis of a number of disorders. In this review, we summarize recent advances of the complex roles of the sphingolipid ceramide and lysosomes in the journey of EV biogenesis to uptake.

Role of Ceramide in insulin resistance in type 2 diabetes.

Role of Ceramide in insulin resistance in type 2 diabetes.

Abstract 1513: FASN inhibition-induced BRCAness as a therapeutic option for castration-resistant prostate cancer (CRPC)

Abstract Androgen deprivation therapy (ADT) is the primary treatment for prostate cancer. However, resistance to ADT invariably develops, leading to castration-resistant prostate cancer (CRPC). Prostate cancer progression is marked by overexpression of fatty acid synthase (FASN) and increased de novo synthesis of fatty acids. Importantly, the majority of normal tissues have low expression of FASN and rely mostly on exogenous lipids, making FASN an interesting therapeutic target for prostate cancer. Previously our group evaluated the effects of inhibiting FASN in prostate cancer, with especially promising results in CRPC models. We observed that FASN inhibition decreases DNA damage repair capability by transcriptionally modulating homologous recombination (BRCAness) and non-homologous end joining repair pathways, which leads to increased DNA damage and apoptosis. Key enzymes involved in DNA repair pathways are reduced at the protein level, and the addition of exogenous palmitate, the product of FASN, is able to rescue their expression to normal levels. Interestingly, genes involved in the synthesis of ceramide are upregulated after FASN blockade, with consequent increased cellular levels of ceramides, dihydroceramides and sphingomyelin. Additionally, we observed increased acyl chain unsaturation levels in these lipid species, in line with the uptake of polyunsaturated fatty acids (PUFA) observed when de novo lipogenesis is blocked. The inhibition of ceramide synthesis, both through genetic knock-down with siRNA or pharmacologically with an inhibitor of serine palmitoyltransferase, is capable of partially rescuing the DNA damage induced by FASN inhibition, suggesting a role of ceramides in DNA damage response modulation. Next, we investigated the synergistic effect of combining FASN inhibitor with PARP inhibitor and observed a higher inhibition of cell growth in prostate cancer cell lines in comparison to either drug alone. Human CRPC organoids when treated with PARP and FASN inhibitor in combination showed reduced diameter, as well as reduced cell proliferation, when compared with each agent alone. Overall, our data demonstrate that targeting de novo lipogenesis can increase the therapeutic efficacy of PARP inhibitors and benefit prostate cancer patients that do not harbor BRCA mutations, by pharmacologically downregulating DNA damage repair pathways, particularly HR. Citation Format: Caroline Fidalgo Ribeiro, Silvia D. Rodrigues, Debora C. Bastos, Hubert Pakula, Giorgia Zadra, Marco Foiani, Massimo Loda. FASN inhibition-induced BRCAness as a therapeutic option for castration-resistant prostate cancer (CRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1513.

Serine Palmitoyltransferase Gene Silencing Prevents Ceramide Accumulation and Insulin Resistance in Muscles in Mice Fed a High-Fat Diet.

Skeletal muscles account for ~80% of insulin-stimulated glucose uptake and play a key role in lipid metabolism. Consumption of a high-fat diet (HFD) contributes to metabolic changes in muscles, including the development of insulin resistance. The studies carried out to date indicate that the accumulation of biologically active lipids, such as long-chain acyl-CoA, diacylglycerols and ceramides, play an important role in the development of insulin resistance in skeletal muscles. Unfortunately, it has not yet been clarified which of these lipid groups plays the dominant role in inducing these disorders. In order to explore this topic further, we locally silenced the gene encoding serine palmitoyltransferase (SPT) in the gastrocnemius muscle of animals with HFD-induced insulin resistance. This enzyme is primarily responsible for the first step of de novo ceramide biosynthesis. The obtained results confirm that the HFD induces the development of whole-body insulin resistance, which results in inhibition of the insulin pathway. This is associated with an increased level of biologically active lipids in the muscles. Our results also demonstrate that silencing the SPT gene with the shRNA plasmid reduces the accumulation of ceramides in gastrocnemius muscle, which, in turn, boosts the activity of the insulin signaling pathway. Furthermore, inhibition of ceramide synthesis does not significantly affect the content of other lipids, which suggests the leading role of ceramide in the lipid-related induction of skeletal muscle insulin resistance.

Abstract P4-02-06: Exploiting ceramide homeostasis to target endocrine therapy-resistant breast cancer

Abstract Estrogen receptor (ER)-positive breast cancer accounts for the majority of breast cancer-related deaths. Current treatment includes endocrine therapy (ET), which most women respond to at first. However, up to 40% of women will eventually experience a relapse. Recurrent tumors tend to retain ER expression but no longer respond to ET. There have been multiple genomic and proteomic profiling studies between ET-sensitive and ET-resistant breast cancer cells, but lipidomic studies have been lacking. We have performed targeted and non-targeted lipidomic profiling of ET-sensitive and two models of ET-resistant MCF-7 breast cancer cells and found differences in their sphingolipid profiles, suggesting our overarching hypothesis that ceramide homeostasis is altered in ET-resistance. The current study is designed to understand the functional role of ceramides and their metabolites in ET-resistant breast cancer, with an overall goal to improve the current treatment regimens and quality of life in breast cancer patients. Detection of ceramides and other sphingolipid levels were analyzed by reverse-phase chromatography and LC-QToF-MS. C1P levels were detected by LC-QqQ-MS. Hoechst-PI staining was performed to measure cell death and Annexin-PI staining to detect apoptosis. All cytometric data analyses were performed using a Celigo cytometer. RT-qPCR was performed to analyze mRNA expression. Fold changes were calculated using the ΔΔCt method with multiple housekeeping controls. While numerous changes were observed in lipid species, the most pronounced changes were seen in the sphingolipidome. More specifically, ET-resistant breast cancer cells had lower levels of ceramides and di-hydroceramides. Along with a depletion of ceramides, we have also observed an increase in ceramide-1-phosphate (C1P) levels in the ET-resistant cells. C1P, which is produced by phosphorylation of ceramides by ceramide kinase (CERK), is known to promote cell survival and proliferation. This observation suggests that ET-resistant cells may rely on a higher degree of ceramide turnover to C1P compared to their ET-sensitive counterpart. To test this hypothesis, CERK was inhibited with a small molecule inhibitor (NVP-231), which resulted in increased apoptosis in ET-resistant cells but not in ET-sensitive cells, suggesting ET-resistant cells are more sensitive to CERK inhibition. Although NVP-231 treatment increased ceramide levels in both ET-sensitive and ET-resistant cells, only ET-resistant cells were dependent on ceramide turnover to C1P. To further understand the molecular underpinnings of the differential sensitivity to CERK inhibition, we have investigated the expression of several BCL2 family members, as evidence from the literature suggests that sphingolipids play a critical role in apoptosis by interacting with several BCL2 family members by mechanisms that are not thoroughly understood. We have observed a high positive correlation between BCL2 expression and NVP-231 sensitivity, as well as an inverse correlation between MCL-1 and NVP-231 sensitivity. This suggests that loss of BCL2 in the ET-resistant cells may be a factor for increased sensitivity to CERK inhibition and elevated MCL-1 fails to compensate for that loss. Together, our findings suggest that ET-resistant breast cancer cells have a unique ceramide homeostasis dependence, i.e., rely on a higher degree of ceramide turnover to C1P. Additionally, BCL2 family proteins may play a critical role in determining the sensitivity to CERK inhibition. The dependence of ET-resistant breast cancer cells on C1P production for survival can therefore offer a unique opportunity to increase the therapeutic efficacy and improve patient outcome for women with ET-resistant breast cancer. Citation Format: Purab Pal, Alec Millner, Ekin Atilla-Gokcumen, Jonna Frasor. Exploiting ceramide homeostasis to target endocrine therapy-resistant breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-02-06.

Role of Ceramides in the Molecular Pathogenesis and Potential Therapeutic Strategies of Cardiometabolic Diseases: What we Know so Far.

Ceramides represent a class of biologically active lipids that are involved in orchestrating vital signal transduction pathways responsible for regulating cellular differentiation and proliferation. However, accumulating clinical evidence have shown that ceramides are playing a detrimental role in the pathogenesis of several diseases including cardiovascular disease, type II diabetes and obesity, collectively referred to as cardiometabolic disease. Therefore, it has become necessary to study in depth the role of ceramides in the pathophysiology of such diseases, aiming to tailor more efficient treatment regimens. Furthermore, understanding the contribution of ceramides to the pathological molecular mechanisms of those interrelated conditions may improve not only the therapeutic but also the diagnostic and preventive approaches of the preceding hazardous events. Hence, the purpose of this article is to review currently available evidence on the role of ceramides as a common factor in the pathological mechanisms of cardiometabolic diseases as well as the mechanism of action of the latest ceramides-targeted therapies.

Sphingolipid Metabolism and Signaling in Endothelial Cell Functions.

The endothelium, inner layer of blood vessels, constitutes a metabolically active paracrine, endocrine, and autocrine organ, able to sense the neighboring environment and exert a variety of biological functions important to preserve the health of vasculature, tissues, and organs. Sphingolipids are both fundamental structural components of the eukaryotic membranes and signaling molecules regulating a variety of biological functions. Ceramide and sphingosine-1-phosphate (S1P), bioactive sphingolipids, have emerged as important regulators of cardiovascular functions in health and disease. In this review we discuss recent insights into the role of ceramide and S1P biosynthesis and signaling in regulating endothelial cell functions, in health and diseases. We also highlight advances into the mechanisms regulating serine palmitoyltransferase, the first and rate-limiting enzyme of de novo sphingolipid biosynthesis, with an emphasis on its inhibitors, ORMDL and NOGO-B. Understanding the molecular mechanisms regulating the sphingolipid de novo biosynthesis may provide the foundation for therapeutic modulation of this pathway in a variety of conditions, including cardiovascular diseases, associated with derangement of this pathway.