Gas chromatography/mass spectrometric assay of endogenous cellular lipid peroxidation products: quantitative analysis of 9- and 10-hydroxystearic acids

Effects of Regioisomerism on the Antiproliferative Activity of Hydroxystearic Acids on Human Cancer Cell Lines

A series of regioisomers of the hydroxystearic acid (HSA) was prepared, and the effect of the position of the hydroxyl group along the chain on a panel of human cancer cell lines was investigated. Among the various regioisomers, those carrying the hydroxyl at positions 5, 7, and 9 had growth inhibitor activity against various human tumor cell lines, including CaCo-2, HT29, HeLa, MCF7, PC3, and NLF cells. 10-HSA and 11-HSA showed a very weak effect. 8-HSA did not show inhibitory activity in all cell lines. The biological role of 7-HSA and 9-HSA is widely recognized, while little is known about the effects of 5-HSA. Therefore, the biological effects of 5-HSA in HeLa, HT29, MCF7, and NLF cell lines were investigated using the Livecyte's ptychography technology, which allows correlating changes in proliferation, motility, and morphology as a function of treatment at the same time. 5-HSA not only reduces cell proliferation but also induces changes in cell displacement, directionality, and speed. It is important to characterize the biological effects of 5-HSA, this molecule being an important component of fatty acyl esters of hydroxy fatty acids (FAHFA), a class of endogenous mammalian lipids with noticeable anti-diabetic and anti-inflammatory effects.

Divinylcarbinol Desymmetrization Strategy: A Concise and Reliable Approach to Chiral Hydroxylated Fatty Acid Derivatives

By the aid of the catalytic desymmetrization of divinylcarbinol as one-pot asymmetric induction and protection of olefin, asymmetric total syntheses of two chiral hydroxylated fatty acid derivatives were successfully achieved. The desired stereoisomers could be concisely prepared in mild conditions in a highly convergent manner. Thus, this novel strategy can help stereochemical elucidations of natural products, which have difficulties in spectroscopic stereochemical analyses due to their local symmetries in the vicinities of the stereogenic secondary hydroxyl units.

Synthesis of Novel Tryptamine Derivatives and Their Biological Activity as Antitumor Agents

We synthesized five novel tryptamine derivatives characterized by the presence of an azelayl chain or of a 1,1,1-trichloroethyl group, in turn connected to another heterocyclic scaffold. The combination of tryptamin-, 1,1,1-trichloroethyl- and 2-aminopyrimidinyl- moieties produced compound 9 identified as the most active compound in hematological cancer cell lines (IC₅₀ = 0.57-65.32 μM). Moreover, keeping constant the presence of the tryptaminic scaffold and binding it to the azelayl moiety, the compounds maintain biological activity. Compound 13 is still active against hematological cancer cell lines and shows a selective effect only on HT29 cells (IC₅₀ = 0.006 µM) among solid tumor models. Compound 14 loses activity on all leukemic lines, while showing a high level of toxicity on all solid tumor lines tested (IC₅₀ 0.0015-0.469 µM).

Synthesis of Novel Structural Hybrids between Aza-Heterocycles and Azelaic Acid Moiety with a Specific Activity on Osteosarcoma Cells

Nine compounds bearing pyridinyl (or piperidinyl, benzimidazolyl, benzotriazolyl) groups bound to an azelayl moiety through an amide bond were synthesized. The structural analogy with some histone deacetylase inhibitors inspired their syntheses, seeking new selective histone deacetylase inhibitors (HDACi). The azelayl moiety recalls part of 9-hydroxystearic acid, a cellular lipid showing antiproliferative activity toward cancer cells with HDAC as a molecular target. Azelayl derivatives bound to a benzothiazolyl moiety further proved to be active as HDACi. The novel compounds were tested on a panel of both normal and tumor cell lines. Non-specific induction of cytotoxicity was observed in the normal cell line, while three of them induced a biological effect only on the osteosarcoma (U2OS) cell line. One of them induced a change in nuclear shape and size. Cell-cycle alterations are associated with post-transcriptional modification of both H2/H3 and H4 histones. In line with recent studies, revealing unexpected HDAC7 function in osteoclasts, molecular docking studies on the active molecules predicted their proneness to interact with HDAC7. By reducing side effects associated with the action of the first-generation inhibitors, the herein reported compounds, thus, sound promising as selective HDACi.

Synthesis of 9-Hydroxystearic Acid Derivatives and Their Antiproliferative Activity on HT 29 Cancer Cells

9-Hydroxystearic acid (9-HSA) is an endogenous cellular lipid that possesses antiproliferative and selective effects against cancer cells. A series of derivatives were synthesized in order to investigate the effect of the substituent in position 9 and on the methyl ester functionality on the biological activity. The two separate enantiomers of methyl 9-hydroxystearate and of methyl 9-aminostearate showed antiproliferative activity against the HT29 cell line. This indicates the importance of position 9 groups being able to make hydrogen bonding with the molecular target. Further, this effect must be preserved when the carboxy group of 9-HSA is esterified. The biological tests showed that the amines, contrarily to methyl esters, resulted in cytotoxicity. A deep investigation on the effect of methyl (R)-9-hydroxystearate on HT29 cells showed an antiproliferative effect acting through the CDKN1A and MYCBP gene expression.

N-methylformamide and 9-hydroxystearic acid: two anti-proliferative and differentiating agents with different modes of action in colon cancer cells

N-methylformamide (NMF) is an anti-proliferative, differentiating agent studied in several cell lines as well as in preclinical and clinical trials, whose mechanisms of action are still unclear. 9-Hydroxystearic acid (9-HSA) is an endogenous product of lipid peroxidation recently identified as a new histone deacetylase 1 inhibitor. Both agents show the same anti-proliferative effects by arresting colon cancer cell growth in G0/G1. We addressed two questions. (i) Do they act by regulating G0/G1 checkpoint proteins? (ii) Does 9-HSA have differentiating effects comparable to those of NMF? The effects of NMF and 9-HSA on growth, differentiation and invasiveness of HT29, a colon cancer cell line, have been compared by using immunoprecipitation analysis, confocal microscopy, enzyme assays and invasiveness tests. The results show that the G1 arrest caused by NMF is a cell cycle exit due to p27 induction, whereas 9-HSA has no effect on the induction of this inhibitor. Evidence is presented that the arrest in early G0/G1 induced by 9-HSA is associated with the conversion of HT29 characteristics to those of a more benign phenotype, whereas the arrest in the late G1 in response to NMF is not followed by a decrease in tumorigenicity. The failure of NMF in cancer therapy indicates that both anti-proliferative and differentiating characteristics are required for an anti-tumoral agent to be effective.

The production of 10-hydroxystearic and 10-ketostearic acids is an alternative route of oleic acid transformation by the ruminal microbiota in cattle

The formation of hydroxystearic acid (HSA) and ketostearic acid (KSA) from oleic acid transformation has been documented in a variety of microbial species, including several isolated from the rumen of domesticated ruminant species. However, their ruminal production rates have not been established as influenced by fatty acid source. Dosing continuous cultures of mixed ruminal microorganisms with 1-(13C)-oleic acid increased the 13C enrichment of both HSA and KSA at 24 h postdosing, and showed that the majority (96 and 85%, respectively) of the HSA and KSA present in the 24-h samples originated from oleic acid. Several experiments using batch cultures of ruminal microorganisms showed that production of HSA and KSA was directly related to oleic acid input but was not affected by elaidic acid input, and that HSA was further metabolized to KSA but not to other fatty acids. When continuous cultures of ruminal microorganisms were supplemented with soybean oil or canola oil, production of 10-HSA + 10-KSA was related to oleic acid input but not to linoleic acid input. Daily production of 10-HSA + 10-KSA across treatments was 14.4 micromol/100 micromol oleic acid input into the cultures or 31.1 micromol/100 micromol oleic acid net loss. The results of this study quantify the formation of 10-HSA and 10-KSA from oleic acid transformation by ruminal microorganisms, and show that their accumulation in ruminal contents is directly related to the extent of oleic acid input and biotransformation by the rumen microbiota.

Fluorescein conjugates of 9- and 10-hydroxystearic acids: synthetic strategies, photophysical characterization, and confocal microscopy applications

Different strategies are presented to conjugate a fluorescein moiety to 9- and 10-hydroxystearic acids (HSAs). 5-Amino-fluorescein (5-AF) was used as a starting reagent. When reacted with acyl-chloride-modified HSAs, 5-AF gave rise to stable amide derivatives with a 75% reaction yield. These products exhibited the typical steady-state and time-resolved fluorescence properties of the fluorescein chromophore with absorption at 494 nm and emission at 519 nm. Flow cytometry studies confirmed the distinct proapoptotic effect of underivatized 9-HSA on Jurkat cells and revealed a comparable ability of its amide derivative. Confocal microscopy imaging studies showed that green fluorescence could stain intracellular membranous structures. Moreover, dual-dye labeling with Mito Tracker Red, followed by colocalization analysis, revealed that HSA can move to the mitochondria. Thus, fluorescent derivatives of HSA can be used to monitor the localization of these biologically active molecules in living cells and can provide a useful tool for linking biochemical investigation with optical visualization methods. In contrast, when unmodified HSAs were used, the reaction gave monoesterified and diesterified fluorescein derivatives. These products exhibited unusual steady-state and time-resolved fluorescence properties with the excitation wavelength at 342 nm and the emission wavelength at 432 nm. It is shown that the synthesized HSA amides of fluorescein provide all of the typical photophysical and instrumental advantages of this popular dye, whereas the unusual luminescence and excitation properties of the monoester and diester of the 5-aminofluorescein would make these dyes interesting to explore as potential candidates for two photon excitation applications.

Histone deacetylase 1: a target of 9-hydroxystearic acid in the inhibition of cell growth in human colon cancer

Recent studies have shown that an endogenous lipoperoxidation product, 9-hydroxystearic acid (9-HSA), acts in colon carcinoma cells (HT29) as a growth inhibitor by inducing p21(WAF1) in an immediate-early, p53-independent manner and that p21(WAF1) is required for 9-HSA-mediated growth arrest in HT29 cells. It is conceivable, therefore, to hypothesize that the cytostatic effect induced by this agent is at least partially associated with a molecular mechanism that involves histone deacetylase 1 (HDAC1) inhibition, as demonstrated for sodium butyrate and other specific inhibitors, such as trichostatin A and hydroxamic acids. Here, we show that, after administration, 9-HSA causes an accumulation of hyperacetylated histones and strongly inhibits the activity of HDAC1. The interaction of 9-HSA with the catalytic site of the enzyme has been highlighted by computational modeling of the human HDAC1, using its homolog from the hyperthermophilic Aquifex aeolicus as a template. Consistent with the experimental data, we find that 9-HSA can bind to the active site of the protein, showing that the inhibition of the enzyme can be explained at the molecular level by the ligand-protein interaction.

9-Hydroxystearic acid upregulates p21(WAF1) in HT29 cancer cells

Growing evidence supports the critical role of lipid peroxidation products in the control of cell proliferation. In previous studies we demonstrated the efficient restriction of the proliferation rate in several cell lines resulting from the in vitro treatment with endogenous lipid polar components of cell membranes. Among these, 9-hydroxystearic acid (9-HSA), a primary intermediate of lipid peroxidation, induced a significant arrest in G0/G1 in HT29 colon cancer cells. In response to 9-HSA treatment of HT29 we observed cell growth arrest and increase in p21(WAF1) expression both at the transcriptional and the translational levels. Growth of p21(WAF1)-deleted HCT116 human colon carcinoma cells was not inhibited by 9-HSA. We present evidence that p21(WAF1) is required for 9-HSA mediated growth arrest in human colon carcinoma cells.