Small molecule inhibitors of fungal Δ(9) fatty acid desaturase as antifungal agents against Candida auris.

Candida auris has emerged as a significant healthcare-associated pathogen due to its multidrug-resistant nature. Ongoing constraints in the discovery and provision of new antifungals create an urgent imperative to design effective remedies to this pressing global blight. Herein, we screened a chemical library and identified aryl-carbohydrazide analogs with potent activity against both C. auris and the most prevalent human fungal pathogen, C. albicans. SPB00525 [N'-(2,6-dichlorophenyl)-5-nitro-furan-2-carbohydrazide] exhibited potent activity against different strains that were resistant to standard antifungals. Using drug-induced haploinsufficient profiling, transcriptomics and metabolomic analysis, we uncovered that Ole1, a Δ(9) fatty acid desaturase, is the likely target of SPB00525. An analog of the latter, HTS06170 [N'-(2,6-dichlorophenyl)-4-methyl-1,2,3-thiadiazole-5-carbohydrazide], had a superior antifungal activity against both C. auris and C. albicans. Both SPB00525 and HTS06170 act as antivirulence agents and inhibited the invasive hyphal growth and biofilm formation of C. albicans. SPB00525 and HTS06170 attenuated fungal damage to human enterocytes and ameliorate the survival of Galleria mellonella larvae used as systemic candidiasis model. These data suggest that inhibiting fungal Δ(9) fatty acid desaturase activity represents a potential therapeutic approach for treating fungal infection caused by the superbug C. auris and the most prevalent human fungal pathogen, C. albicans.

Dihydroceramide desaturase regulates the compartmentalization of Rac1 for neuronal oxidative stress.

Disruption of sphingolipid homeostasis is known to cause neurological disorders, but the mechanisms by which specific sphingolipid species modulate pathogenesis remain unclear. The last step of de novo sphingolipid synthesis is the conversion of dihydroceramide to ceramide by dihydroceramide desaturase (human DEGS1; Drosophila Ifc). Loss of ifc leads to dihydroceramide accumulation, oxidative stress, and photoreceptor degeneration, whereas human DEGS1 variants are associated with leukodystrophy and neuropathy. In this work, we demonstrate that DEGS1/ifc regulates Rac1 compartmentalization in neuronal cells and that dihydroceramide alters the association of active Rac1 with organelle-mimicking membranes. We further identify the Rac1-NADPH oxidase (NOX) complex as the major cause of reactive oxygen species (ROS) accumulation in ifc-knockout (ifc-KO) photoreceptors and in SH-SY5Y cells with the leukodystrophy-associated DEGS1H132R variant. Suppression of Rac1-NOX activity rescues degeneration of ifc-KO photoreceptors and ameliorates oxidative stress in DEGS1H132R-carrying cells. Therefore, we conclude that DEGS1/ifc deficiency causes dihydroceramide accumulation, resulting in Rac1 mislocalization and NOX-dependent neurodegeneration.

Effects of compound-326, a selective delta-5 desaturase inhibitor, in ApoE knockout mice with two different protocols for atherosclerosis development.

PURPOSE: We previously confirmed its anti-atherosclerotic effects by pre-treatment with compound-326, a selective delta-5 desaturase (D5D) inhibitor, in Western diet-fed ApoE knockout mice. In the present study, we evaluated effects of compound-326 in ApoE knockout mice with two different protocols for atherosclerosis development. METHODS: In a post-treatment protocol, where the compound treatment started after 10 weeks pre-feeding of Western diet, compound-326 (1 and 3 mg/kg/day, p.o. for 12 weeks) significantly reduced the atherosclerotic lesion area in the aorta (24% reduction at 3 mg/kg/day). In another protocol using Paigen diet (containing 12.5% cholesterol and 5% sodium cholate), compound-326 (3 and 10 mg/kg/day, p.o. for 7 weeks) also significantly reduced the lesion area (36% reduction at 3 mg/kg/day). RESULTS: In both protocols, Compound-326 significantly reduced the hepatic ratio of arachidonic acid to dihomo-γ-linolenic acid, blood inflammatory eicosanoid production and plasma soluble intercellular adhesion molecule 1 (sICAM-1) levels, similarly to the previous pre-treatment study. CONCLUSIONS: Compound-326 exerted anti-atherosclerotic effects in ApoE knockout mice with the two different protocols for atherosclerosis development further supporting D5D inhibition as a promising strategy in treating atherosclerosis.

Novel carfilzomib-based combinations as potential therapeutic strategies for liposarcomas.

Proteasome inhibitors, such as bortezomib and carfilzomib, have shown efficacy in anti-cancer therapy in hematological diseases but not in solid cancers. Here, we found that liposarcomas (LPS) are susceptible to proteasome inhibition, and identified drugs that synergize with carfilzomib, such as selinexor, an inhibitor of XPO1-mediated nuclear export. Through quantitative nuclear protein profiling and phospho-kinase arrays, we identified potential mode of actions of this combination, including interference with ribosome biogenesis and inhibition of pro-survival kinase PRAS40. Furthermore, by assessing global protein levels changes, FADS2, a key enzyme regulating fatty acids synthesis, was found down-regulated after proteasome inhibition. Interestingly, SC26196, an inhibitor of FADS2, synergized with carfilzomib. Finally, to identify further combinational options, we performed high-throughput drug screening and uncovered novel drug interactions with carfilzomib. For instance, cyclosporin A, a known immunosuppressive agent, enhanced carfilzomib's efficacy in vitro and in vivo. Altogether, these results demonstrate that carfilzomib and its combinations could be repurposed for LPS clinical management.

Ternary complex formation of AFN-1252 with Acinetobacter baumannii FabI and NADH: Crystallographic and biochemical studies.

Acinetobacter baumannii is an opportunistic Gram-negative bacterial pathogen, associated mostly with hospital-acquired infections. The emergence of drug resistance strains made it necessary to explore new pathways for the development of more effective antibiotics. Enoyl CoA reductase (FabI), a key enzyme in the fatty acid biosynthesis (FAS) pathway, has emerged as a potential target for antibacterial drug development. Earlier reports show that the lead SaFabI inhibitor AFN-1252 can inhibit FabI from other organisms including Escherichia coli and Burkholderia pseudomallei, but with differential potency. In the present work, we show that AFN-1252 is a moderate inhibitor of AbFabI with an IC50 of 216 nM. AFN-1252 stabilized AbFabI with a 4.2°C increase in the melting temperature (Tm ) and, interestingly, the stabilization effect was significantly increased in presence of the cofactor NADH (∆Tm  = 17°C), suggesting the formation of a ternary complex AbFabI: AFN-1252: NADH. X-ray crystallography studies of AbFabI co-crystalized with AFN-1252 and NADH confirmed the ternary complex formation. The critical interactions of AFN-1252 with AbFabI and NADH identified from the co-crystal structure may facilitate the design and development of new drugs against A. baumannii infections by targeting the FAS pathway.

Sphingolipid Modulation Activates Proteostasis Programs to Govern Human Hematopoietic Stem Cell Self-Renewal.

Cellular stress responses serve as crucial decision points balancing persistence or culling of hematopoietic stem cells (HSCs) for lifelong blood production. Although strong stressors cull HSCs, the linkage between stress programs and self-renewal properties that underlie human HSC maintenance remains unknown, particularly at quiescence exit when HSCs must also dynamically shift metabolic state. Here, we demonstrate distinct wiring of the sphingolipidome across the human hematopoietic hierarchy and find that genetic or pharmacologic modulation of the sphingolipid enzyme DEGS1 regulates lineage differentiation. Inhibition of DEGS1 in hematopoietic stem and progenitor cells during the transition from quiescence to cellular activation with N-(4-hydroxyphenyl) retinamide activates coordinated stress pathways that coalesce on endoplasmic reticulum stress and autophagy programs to maintain immunophenotypic and functional HSCs. Thus, our work identifies a linkage between sphingolipid metabolism, proteostatic quality control systems, and HSC self-renewal and provides therapeutic targets for improving HSC-based cellular therapeutics.

A Novel Orally Available Delta-5 Desaturase Inhibitor Prevents Atherosclerotic Lesions Accompanied by Changes in Fatty Acid Composition and Eicosanoid Production in ApoE Knockout Mice.

Delta-5 desaturase (D5D), encoded by fatty acid desaturase 1 (Fads1), is the rate-limiting enzyme for the conversion from dihomo-γ-linolenic acid (DGLA) to arachidonic acid (AA) in the ω-6 polyunsaturated fatty acid pathway. Several AA-derived eicosanoids (e.g., prostaglandins, thromboxanes, and leukotrienes) and DGLA-derived eicosanoids are reported to promote and/or prevent atherosclerosis progression through, at least in part, its proinflammatory or anti-inflammatory effects. To elucidate the effects of D5D inhibition by a D5D inhibitor on atherosclerosis, we generated a potent, orally available and selective D5D inhibitor, 2-(2,2,3,3,3-Pentafluoropropoxy)-3-[4-(2,2,2-trifluoroethoxy) phenyl]-5,7-dihydro-3H-pyrrolo[2,3-d]pyrimidine-4,6-dione, compound-326, and examined its effects on Western-diet fed ApoE knockout (KO) mice. Oral administration of compound-326 (3-10 mg/kg per day for 15 weeks) significantly inhibited the progression of atherosclerotic lesions in the aorta without affecting plasma total cholesterol and triglyceride levels. Compound-326 significantly decreased AA levels, while it increased DGLA levels in the liver and the blood accompanied by decreases in AA-derived eicosanoid production and increases in DGLA-derived eicosanoid production from the blood cells. We conclude that compound-326 prevents the progression of atherosclerosis in Western-diet fed ApoE KO mice by modulating a profile of eicosanoid production, suggesting that D5D inhibitors can be a novel remedy for preventing atherosclerosis and subsequent cardiovascular events. SIGNIFICANCE STATEMENT: This study shows a D5D-specific and orally available potent inhibitor provided the first evidence to support the concept that D5D inhibitors will be a novel remedy for preventing the progression of atherosclerosis.

PPARα-Mediated Positive-Feedback Loop Contributes to Cold Exposure Memory.

Fluctuations in food availability and shifts in temperature are typical environmental changes experienced by animals. These environmental shifts sometimes portend more severe changes; e.g., chilly north winds precede the onset of winter. Such telltale signs may be indicators for animals to prepare for such a shift. Here we show that HEK293A cells, cultured under starvation conditions, can "memorize" a short exposure to cold temperature (15 °C), which was evidenced by their higher survival rate compared to cells continuously grown at 37 °C. We refer to this phenomenon as "cold adaptation". The cold-exposed cells retained high ATP levels, and addition of etomoxir, a fatty acid oxidation inhibitor, abrogated the enhanced cell survival. In our standard protocol, cold adaptation required linoleic acid (LA) supplementation along with the activity of Δ-6-desaturase (D6D), a key enzyme in LA metabolism. Moreover, supplementation with the LA metabolite arachidonic acid (AA), which is a high-affinity agonist of peroxisome proliferator-activated receptor-alpha (PPARα), was able to underpin the cold adaptation, even in the presence of a D6D inhibitor. Cold exposure with added LA or AA prompted a surge in PPARα levels, followed by the induction of D6D expression; addition of a PPARα antagonist or a D6D inhibitor abrogated both their expression, and reduced cell survival to control levels. We also found that the brief cold exposure transiently prevents PPARα degradation by inhibiting the ubiquitin proteasome system, and starvation contributes to the enhancement of PPARα activity by inhibiting mTORC1. Our results reveal an innate adaptive positive-feedback mechanism with a PPARα-D6D-AA axis that is triggered by a brief cold exposure in cells. "Cold adaptation" could have evolved to increase strength and resilience against imminent extreme cold temperatures.

Inhibition of fatty acid desaturation impairs cuticle differentiation in Drosophila melanogaster.

Previously, we showed that inhibition of the activity of fatty acid desaturases (Desat) perturbs signalling of the developmental timing hormone ecdysone in the fruit fly Drosophila melanogaster. To understand the impact of this effect on cuticle differentiation, a process regulated by ecdysone, we analysed the cuticle of D. melanogaster larvae fed with the Desat inhibitor CA10556. In these larvae, the expression of most of the key cuticle genes is normal or slightly elevated at day one of CA10556 feeding. As an exception, expression of twdlM coding for a yet uncharacterised cuticle protein is completely suppressed. The cuticle of these larvae appears to be normal at the morphological level. However, these animals are sensitive to desiccation, a trait that according to our data, among others, may be associated with reduced TwdlM amounts. At day two of CA10556 feeding, expression of most of the cuticle genes tested including twdlM is suppressed. Expression of cpr47Eb coding for a chitin-binding protein is, by contrast, highly elevated suggesting that Cpr47Eb participates at a specific compensation program. Overall, the cuticle of these larvae is thinner than the cuticle of control larvae. Taken together, lipid desaturation is necessary for a coordinated deployment of a normal cuticle differentiation program.

Dihomo-γ-linolenic acid inhibits xenograft tumor growth in mice bearing shRNA-transfected HCA-7 cells targeting delta-5-desaturase.

BACKGROUND: We previously demonstrated that knockdown of delta-5-desaturase via siRNA transfection together with dihomo-γ-linolenic acid supplementation inhibited colon cancer cell growth and migration, by promoting the production of the anti-cancer byproduct 8-hydroxyoctanoic acid from Cyclooxygenase-2-catalyzed dihomo-γ-linolenic acid peroxidation. Here, we extend our study to investigate the effects of delta-5-desaturase-knockdown and the resulting intensified dihomo-γ-linolenic acid peroxidation in xenograft tumor mice model. METHODS: Four-week old nude mice bearing the human colon cancer cell HCA-7/C29 vs. its delta-5-desaturase knockdown analog (via shRNA transfection) were subject to 4-week treatments of: vehicle control, dihomo-γ-linolenic acid supplementation, 5-Fluorouracil, and combination of dihomo-γ-linolenic acid and 5-Fluorouracil. Tumor growth was monitored during the treatment. At the endpoint, the mice were euthanized and the tumor tissues were collected for further mechanism analysis. RESULTS: Delta-5-desaturase knockdown (shRNA) together with dihomo-γ-linolenic acid supplementation increased 8-hydroxyoctanoic acid production to a threshold level in xenograft tumors, which consequently induced p53-dependent apoptosis and reduced tumors significantly. The promoted 8-hydroxyoctanoic acid formation was also found to suppress the tumors' metastatic potential via regulating MMP-2 and E-cadherin expressions. In addition, our in vivo data showed that delta-5-desaturase knockdown along with dihomo-γ-linolenic acid supplementation resulted in anti-tumor effects comparable to those of 5-Fluorouracil. CONCLUSIONS: We have demonstrated that our paradigm-shifting strategy of knocking down delta-5-desaturase and taking advantage of overexpressed Cyclooxygenase-2 in tumor cells can be used for colon cancer suppression. Our research outcome will lead us to develop a better and safer anti-cancer therapy for patients.

Minimizing Membrane Arachidonic Acid Content as a Strategy for Controlling Cancer: A Review.

Many cancers and pre-cancerous lesions convert membrane-bound arachidonic acid (AA) to eicosanoids that promote the survival, growth, and spread of cancer. In contrast, the long-chain omega-3s eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can competitively inhibit AA's interaction with the enzymes that give rise to eicosanoids, while acting as precursors for alternative eicosanoids which oppose cancer development and growth. Hence, minimizing the AA content of cancer membranes, while boosting that of EPA and DHA, is a rational strategy for cancer prevention and control. The former goal can be achieved by eating a plant-based diet (inherently free of AA); by avoiding foods high in linoleic acid; by down-regulating the expression of delta-6-desaturase (D6D), rate-limiting for the conversion of linoleic acid to AA; and by competitively decreasing flux of linoleic acid through D6D with a high intake of alpha-linolenic acid (ALA) from flaxseed. ALA and DHA, potent agonists for the farnesoid X receptor, can be expected to suppress D6D transcription, and AMP-activated kinase (AMPK) activators and a cholesterol-free diet also have potential in this regard. Hence, a plant-based diet low in linoleic acid, complemented by an ample intake of flaxseed and supplemental fish oil, with or without metformin and other D6D-antagonist agents, may aid prevention and control of some cancers.

Complex lipid metabolic remodeling is required for efficient hepatitis C virus replication.

The hepatitis C virus (HCV) life cycle is tightly linked to the host cell lipid metabolism with the endoplasmic reticulum-derived membranous web harboring viral RNA replication complexes and lipid droplets as virion assembly sites. To investigate HCV-induced changes in the lipid composition, we performed quantitative shotgun lipidomic studies of whole cell extracts and subcellular compartments. Our results indicate that HCV infection reduces the ratio of neutral to membrane lipids. While the amount of neutral lipids and lipid droplet morphology were unchanged, membrane lipids, especially cholesterol and phospholipids, accumulated in the microsomal fraction in HCV-infected cells. In addition, HCV-infected cells had a higher relative abundance of phosphatidylcholines and triglycerides with longer fatty acyl chains and a strikingly increased utilization of C18 fatty acids, most prominently oleic acid (FA [18:1]). Accordingly, depletion of fatty acid elongases and desaturases impaired HCV replication. Moreover, the analysis of free fatty acids revealed increased levels of polyunsaturated fatty acids (PUFAs) caused by HCV infection. Interestingly, inhibition of the PUFA synthesis pathway via knockdown of the rate-limiting Δ6-desaturase enzyme or by treatment with a high dose of a small-molecule inhibitor impaired viral progeny production, indicating that elevated PUFAs are needed for virion morphogenesis. In contrast, pretreatment with low inhibitor concentrations promoted HCV translation and/or early RNA replication. Taken together our results demonstrate the complex remodeling of the host cell lipid metabolism induced by HCV to enhance both virus replication and progeny production.

Polyunsaturated Fatty Acid Biosynthesis Involving Δ8 Desaturation and Differential DNA Methylation of FADS2 Regulates Proliferation of Human Peripheral Blood Mononuclear Cells.

Polyunsaturated fatty acids (PUFAs) are important for immune function. Limited evidence indicates that immune cell activation involves endogenous PUFA synthesis, but this has not been characterised. To address this, we measured metabolism of 18:3n-3 in quiescent and activated peripheral blood mononuclear cells (PBMCs), and in Jurkat T cell leukaemia. PBMCs from men and women (n = 34) were incubated with [1-13C]18:3n-3 with or without Concanavalin A (Con. A). 18:3n-3 conversion was undetectable in unstimulated PBMCs, but up-regulated when stimulated. The main products were 20:3n-3 and 20:4n-3, while 18:4n-3 was undetectable, suggesting initial elongation and Δ8 desaturation. PUFA synthesis was 17.4-fold greater in Jurkat cells than PBMCs. The major products of 18:3n-3 conversion in Jurkat cells were 20:4n-3, 20:5n-3, and 22:5n-3. 13C Enrichment of 18:4n-3 and 20:3n-3 suggests parallel initial elongation and Δ6 desaturation. The FADS2 inhibitor SC26196 reduced PBMC, but not Jurkat cell, proliferation suggesting PUFA synthesis is involved in regulating mitosis in PBMCs. Con. A stimulation increased FADS2, FADS1, ELOVL5 and ELOVL4 mRNA expression in PBMCs. A single transcript corresponding to the major isoform of FADS2, FADS20001, was detected in PBMCs and Jurkat cells. PBMC activation induced hypermethylation of a 470bp region in the FADS2 5'-regulatory sequence. This region was hypomethylated in Jurkat cells compared to quiescent PBMCs. These findings show that PUFA synthesis involving initial elongation and Δ8 desaturation is involved in regulating PBMC proliferation and is regulated via transcription possibly by altered DNA methylation. These processes were dysregulated in Jurkat cells. This has implications for understanding the regulation of mitosis in normal and transformed lymphocytes.

FADS2 inhibition in essential fatty acid deficiency induces hepatic lipid accumulation via impairment of very low-density lipoprotein (VLDL) secretion.

Fatty acid desaturase 2 (FADS2) is responsible for the first desaturation reaction in the synthesis of highly unsaturated fatty acids (HUFAs), such as arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3), and is involved in Mead acid (20:3n-9) production during essential fatty acid deficiency (EFAD). In this study, an obvious hepatic lipid accumulation was observed in EFAD mice treated with a FADS2 inhibitor. FADS2 inhibition in the EFAD state reduced secretion of very low-density lipoprotein (VLDL) and markedly diminished Mead acid in phosphatidylcholine (PC) in the liver and plasma. As the results, the amount of C20 HUFAs in hepatic and plasma PC dramatically reduced in the EFAD mice treated with a FADS2 inhibitor, whereas the decrease of C20 HUFA levels of PC in EFAD mice was not observed because of the increased Mead acid in PC. These results supposed that Mead acid in PC is important as a component of VLDL. It is possible that Mead acid plays the role of a substitute of HUFAs in VLDL secretion during EFAD.

Discovery of 3,5-Diphenyl-4-methyl-1,3-oxazolidin-2-ones as Novel, Potent, and Orally Available Δ-5 Desaturase (D5D) Inhibitors.

The discovery and optimization of Δ-5 desaturase (D5D) inhibitors are described. Investigation of the 1,3-oxazolidin-2-one scaffold was inspired by a pharmacophore model constructed from the common features of several hit compounds, resulting in the identification of 3,5-diphenyl-1,3-oxazolidin-2-one 5h as a novel lead showing potent in vitro activity. Subsequent optimization focused on the modification of two metabolic sites, which provided (4S,5S)-5i, a derivative with improved metabolic stability. Moreover, adding a substituent into the upper phenyl moiety further enhanced the intrinsic activity, which led to the discovery of 5-[(4S,5S)-5-(4fluorophenyl)-4-methyl-2-oxo-1,3-oxazolidin-3-yl]benzene-1,3-dicarbonitrile (4S,5S)-5n, endowed with excellent D5D binding affinity, cellular activity, and high oral bioavailability in a mouse. It exhibited robust in vivo hepatic arachidonic acid/dihomo-γ-linolenic acid ratio reduction (a target engagement marker) in an atherosclerosis mouse model. Finally, an asymmetric synthetic procedure for this compound was established.

Pomegranate seed oil influences the fatty acids profile and reduces the activity of desaturases in livers of Sprague-Dawley rats.

The aim of our study was to compare the influence of diet supplementation with pomegranate seed oil - as conjugated linolenic acids (CLnA) source, or conjugated linoleic acids (CLA) and to examine the mechanism of their activity. The content of fatty acids, levels of biomarkers of lipids' oxidation and the activity of key enzymes catalyzing lipids metabolism were measured. Obtained results revealed that conjugated fatty acids significantly decrease the activity of Δ5-desaturase (p=0.0001) and Δ6-desaturase (p=0.0008) and pomegranate seed oil reduces their activity in the most potent way. We confirmed that diet supplementation with pomegranate seed oil - a rich source of punicic acid leads to the increase of cis-9, trans-11 CLA content in livers (p=0.0003). Lack of side effects and beneficial influence on desaturases activity and fatty acids profile claim pomegranate seed oil to become interesting alternative for CLA as functional food.

From the configurational preference of dihydroceramide desaturase-1 towards Δ6-unsaturated substrates to the discovery of a new inhibitor.

Dihydroceramide desaturase 1 (Des1) catalyzes the last step of ceramide synthesis de novo, thus regulating the physiologically relevant balance between dihydrosphingolipids and sphingolipids. Here we report on the configurational preference of Des1 towards isomeric Δ6-unsaturated dihydroceramide analogs and the discovery of a potent Des1 inhibitor.

A Novel Selective Inhibitor of Delta-5 Desaturase Lowers Insulin Resistance and Reduces Body Weight in Diet-Induced Obese C57BL/6J Mice.

Obesity is now recognized as a state of chronic low-grade inflammation and is called as metabolic inflammation. Delta-5 desaturase (D5D) is an enzyme that metabolizes dihomo-γ-linolenic acid (DGLA) to arachidonic acid (AA). Thus, D5D inhibition increases DGLA (precursor to anti-inflammatory eicosanoids) while decreasing AA (precursor to pro-inflammatory eicosanoids), and could result in synergistic improvement in the low-grade inflammatory state. Here, we demonstrate reduced insulin resistance and the anti-obesity effect of a D5D selective inhibitor (compound-326), an orally active small-molecule, in a high-fat diet-induced obese (DIO) mouse model. In vivo D5D inhibition was confirmed by determining changes in blood AA/DGLA profiles. In DIO mice, chronic treatment with compound-326 lowered insulin resistance and caused body weight loss without significant impact on cumulative calorie intake. Decreased macrophage infiltration into adipose tissue was expected from mRNA analysis. Increased daily energy expenditure was also observed following administration of compound-326, in line with sustained body weight loss. These data indicate that the novel D5D selective inhibitor, compound-326, will be a new class of drug for the treatment of obese and diabetic patients.

Knockdown of delta-5-desaturase promotes the anti-cancer activity of dihomo-γ-linolenic acid and enhances the efficacy of chemotherapy in colon cancer cells expressing COX-2.

Cyclooxygenase (COX), commonly overexpressed in cancer cells, is a major lipid peroxidizing enzyme that metabolizes polyunsaturated fatty acids (ω-3s and ω-6s). The COX-catalyzed free radical peroxidation of arachidonic acid (ω-6) can produce deleterious metabolites (e.g. 2-series prostaglandins) that are implicated in cancer development. Thus, COX inhibition has been intensively investigated as a complementary therapeutic strategy for cancer. However, our previous study has demonstrated that a free radical-derived byproduct (8-hydroxyoctanoic acid) formed from COX-catalyzed peroxidation of dihomo-γ-linolenic acid (DGLA, the precursor of arachidonic acid) can inhibit colon cancer cell growth. We thus hypothesize that the commonly overexpressed COX in cancer (~90% of colon cancer patients) can be taken advantage to suppress cell growth by knocking down delta-5-desaturase (D5D, a key enzyme that converts DGLA to arachidonic acid). In addition, D5D knockdown along with DGLA supplement may enhance the efficacy of chemotherapeutic drugs. After knocking down D5D in HCA-7 colony 29 cells and HT-29 cells (human colon cancer cell lines with high and low COX levels, respectively), the antitumor activity of DGLA was significantly enhanced along with the formation of a threshold range (~0.5-1.0µM) of 8-hydroxyoctanoic acid. In contrast, DGLA treatment did not inhibit cell growth when D5D was not knocked down and only limited amount of 8-hydroxyoctanoic acid was formed. D5D knockdown along with DGLA treatment also enhanced the cytotoxicities of various chemotherapeutic drugs, including 5-fluorouracil, regorafenib, and irinotecan, potentially through the activation of pro-apoptotic proteins, e.g. p53 and caspase 9. For the first time, we have demonstrated that the overexpressed COX in cancer cells can be utilized in suppressing cancer cell growth. This finding may provide a new option besides COX inhibition to optimize cancer therapy. The outcome of this translational research will guide us to develop a novel ω-6-based diet-care strategy in combination with current chemotherapy for colon cancer prevention and treatment.

Design, synthesis, and in vivo activity of novel inhibitors of delta-5 desaturase for the treatment of metabolic syndrome.

The synthesis, SAR, and in vivo activity of inhibitors of delta-5 desaturase are described. Ring-constraint of the initial series provided access to a variety of in vitro active chemotypes, from which the indazole was selected. Examples from the indazole series displayed in vivo activity in reducing the enzymatic activity of liver delta-5 desaturase.