Effect of conjugated linoleic acids on the activity and mRNA expression of 5- and 15-lipoxygenases in human macrophages

Pretreatment with zinc protects Kupffer cells following administration of microbial products

BACKGROUND

Systemic inflammation and severe fibrosis can reduce serum zinc levels, while zinc supplementation is reported to improve the prognosis of patients with chronic liver disease (CLD).

OBJECTIVES

We aimed to investigate the clinical application of serum zinc in patients with CLD and the anti-infective mechanism of zinc supplementation.

METHODS

Based on the serum zinc level, 149 CLD patients were divided into 3 groups and their clinical parameters were compared. In in-vitro experiments, microbial isolates derived from patients were used to stimulate human liver non-parenchymal cells, and the zinc sulfate solution was added in certain experiments. The effect of zinc was compared by LDH and thromboxane A₂ levels in the cell supernatant.

RESULT

Compared with other groups, patients with low serum zinc levels had significantly higher C-reactive protein (CRP), total bilirubin, INR, creatinine, and MELD scores, while albumin and GOT levels were reduced. Only CRP and albumin were significantly correlated with serum zinc in both low and normal-zinc groups. Bacterial isolates significantly increased LDH levels in Kupffer cells (KCs) and stellate cells but had no effect on sinusoidal endothelial cells, whereas zinc pretreatment protected KCs but not stellate cells. Thromboxane A₂ secreted by KCs can also be induced by bacterial stimulation, accompanied by increased gene expression of Myd88, MAPK and NF-kB, while zinc pretreatment can attenuate that.

CONCLUSION

Serum zinc levels can be used to estimate infection and liver fibrosis in CLD patients. As a new antibacterial weapon, zinc supplementation acts on KCs through Myd88-MAPK related pathways.

Cross-Classification of Human Urinary Lipidome by Sex, Age, and Body Mass Index

Technological advancements in past decades have led to the development of integrative analytical approaches to lipidomics, such as liquid chromatography-mass spectrometry (LC/MS), and information about biogenic lipids is rapidly accumulating. Although several cohort-based studies have been conducted on the composition of urinary lipidome, the data on urinary lipids cross-classified by sex, age, and body mass index (BMI) are insufficient to screen for various abnormalities. To promote the development of urinary lipid metabolome-based diagnostic assay, we analyzed 60 urine samples from healthy white adults (young (c.a., 30 years) and old (c.a., 60 years) men/women) using LC/MS. Women had a higher urinary concentration of omega-3 12-lipoxygenase (LOX)-generated oxylipins with anti-inflammatory activity compared to men. In addition, young women showed increased abundance of poly-unsaturated fatty acids (PUFAs) and cytochrome P450 (P450)-produced oxylipins with anti-hypertensive activity compared with young men, whereas elderly women exhibited higher concentration of 5-LOX-generated anti-inflammatory oxylipins than elderly men. There were no significant differences in urinary oxylipin levels between young and old subjects or between subjects with low and high BMI. Our findings suggest that sex, but neither ages nor BMI could be a confounding factor for measuring the composition of urinary lipid metabolites in the healthy population. The information showed contribute to the development of reliable biomarker findings from urine.

Arachidonic and linoleic acid derivatives impact oocyte ICSI fertilization--a prospective analysis of follicular fluid and a matched oocyte in a 'one follicle--one retrieved oocyte--one resulting embryo' investigational setting

Objective

To evaluate human oocyte ability to undergo fertilization and subsequent preimplantation embryonic development in relation to a wide panel of follicular fluid (FF) arachidonic acid derivatives (AAD) and linoleic acid derivatives (LAD) of prospectively selected patients undergoing intracytoplasmic sperm injection (ICSI).

Methodology

Study was designed as a two center (a university clinic and a private clinic) prospective study. 54 women of 181 consecutive couples undergoing ICSI were prospectively found to be eligible for analysis. 'One follicle – one retrieved oocyte – one resulting embryo' approach was used. Each individual follicle was aspirated independently and matched to an oocyte growing in this particular follicular milieu. FF samples were assessed for AAD and LAD by high-performance liquid chromatography; additionally, activity of secretory phospholipase A (sPLA₂) was determined by enzyme-linked immunosorbent assay.

Principal Findings

Increased activity of sPLA₂ and significantly higher AAD and LAD levels were found in FF of oocytes that did not show two pronuclei or underwent degeneration after ICSI in comparison to oocytes with the appearance of two pronuclei. Receiver operating characteristics curve analysis identified acids with the highest sensitivity and specificity: 5oxo-hydroxyeicosatetraenoic, 16-hydroxyeicosatetraenoic, 9-hydroxyoctadecadieneoic and 12-hydroxyeicosatetraenoic. No significant differences between AAD and LAD related to embryo quality were found.

Conclusions/Significance

Our study demonstrates for the first time that elevated concentrations of AAD and LAD in FF at the time of oocyte retrieval significantly decrease the ability of oocytes to form pronuclei after ICSI. This may serve as a new tool for non-invasive assessment of oocyte developmental capacity. However, levels of AAD and LAD are not associated with subsequent embryo quality or pregnancy rate, and therefore more studies are needed to determine their usefulness in human IVF procedure.

Dietary polyunsaturated fatty acids and inflammation: the role of phospholipid biosynthesis

The composition of fatty acids in the diets of both human and domestic animal species can regulate inflammation through the biosynthesis of potent lipid mediators. The substrates for lipid mediator biosynthesis are derived primarily from membrane phospholipids and reflect dietary fatty acid intake. Inflammation can be exacerbated with intake of certain dietary fatty acids, such as some ω-6 polyunsaturated fatty acids (PUFA), and subsequent incorporation into membrane phospholipids. Inflammation, however, can be resolved with ingestion of other fatty acids, such as ω-3 PUFA. The influence of dietary PUFA on phospholipid composition is influenced by factors that control phospholipid biosynthesis within cellular membranes, such as preferential incorporation of some fatty acids, competition between newly ingested PUFA and fatty acids released from stores such as adipose, and the impacts of carbohydrate metabolism and physiological state. The objective of this review is to explain these factors as potential obstacles to manipulating PUFA composition of tissue phospholipids by specific dietary fatty acids. A better understanding of the factors that influence how dietary fatty acids can be incorporated into phospholipids may lead to nutritional intervention strategies that optimize health.

Lipidic last breath of life in patients with alcoholic liver disease

Alcoholic liver disease (ALD) begins with the accumulation of lipid droplets in the liver. Lipids which accumulate in the liver can stimulate inflammation, and the fatty acid derivatives, hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecadienoic acids (HODEs), may play an important role in this process. We evaluated the concentrations of linoleic and arachidonic acid derivatives in the plasma of patients with ALD, non-alcoholic fatty liver disease (NAFLD) and healthy individuals. The groups consisted of 173 subjects: 63 patients with ALD, 90 with NAFLD and 20 healthy volunteers. Plasma 12-, 15-, and 5-HETE as well as 9- and 13-HODE were assessed using HPLC and isoprostane 8-epi-PGF 2α III was evaluated with an ELISA. In addition the mRNA expression of lipoxygenases (5-LOX, 15-LOX-1, 15-LOX-2) in the liver samples of patients with ALD cirrhosis was measured. A significant difference between the plasma concentrations of the analyzed derivatives was found when divided according to gender. The most significant differences were found between healthy individuals and ALD patients, as well as ALD and NAFLD individuals regardless of gender. The increased plasma HODEs and HETEs concentrations were in line with the increase in 5- and 15-LOX-1 and 15-LOX-2 mRNA in liver samples from ALD cirrhosis patients. LOXs expression and peroxidation of polyunsaturated fatty acids by free radical-propagated chemical oxidation may be contributing factors in liver necroinflammatory injury in ALD.

Fluoride in low concentration modifies expression and activity of 15 lipoxygenase in human PBMC differentiated monocyte/macrophage

Epidemiological and experimental evidences demonstrate positive correlation between environmental and occupational fluoride exposure and risk to various cardio-respiratory disorders. That fore we decided to examine the effect of fluorides on activity and expression of 15LOX enzyme which is implicated in biosynthesis of inflammatory mediators. Expression of 15LOX-1 and -2 enzymes mRNA and protein was analyzed using RT PCT and immunoblotting methods respectively whereas HPLC method was used to measure the levels of 15 lipoxygenases end products. Additionally AA and LA concentration in cells was measured using GC method. We observed that fluoride in small concentration may significantly decrease activity of 15LOX-1 and -2 in human PBMC macrophages and then concentration of its end products: 15-HETE, 12-HETE and 9+13-HODE, what may cause development of inflammation through the cholesterol arrest into the macrophages and its differentiation to foam cell. Noted by our team overexpression of the 15LOX-1 enzyme in macrophages after addition of lowest fluoride concentrations (1 and 3 μM) may be aimed at fighting inflammation development and excessive intracellular lipid accumulation. But highest fluoride concentrations (6 and 10 μM) added to cell culture slowly declined expression of this enzyme probably because of developing inflammation. Additional 15LOX-2 expression in macrophages after fluoride addition was low in 1 and 3 μM concentrations, but increased significantly after 10 μM fluoride addition what may suggest developing acute inflammation, because 15LOX-2 is associated to increased local hypoxia. This study indicated that even in small concentrations fluorides changes the amounts and activity of 15 LOX-1 and -2 enzymes taking part in the development of inflammatory process.

Influence of conjugated linoleic acids on functional properties of vascular cells

Conjugated linoleic acids (CLA) are biologically highly active lipid compounds that inhibit the development of atherosclerotic plaques in experimental animals. The underlying mechanisms of action, however, are only poorly understood. Since cell-culture experiments are appropriate to provide a detailed view into the mechanisms of action of a compound, the present review summarises results fromin vitrostudies dealing with the effects of CLA isomers and CLA mixtures on functional properties of cells of the vascular wall, such as endothelial cells, smooth muscle cells and monocyte-derived macrophages, which are amongst the major cells contributing to atherosclerotic lesion development. Based on these studies, it can be concluded that CLA exert several beneficial actions in cells of the vascular wall through the activation of nuclear PPAR. These actions of CLA, which may, at least partially, explain the inhibition of atherogenesis by dietary CLA, include modulation of vasoactive mediator release from endothelial cells, inhibition of inflammatory and fibrotic processes in activated smooth muscle cells, abrogation of inflammatory responses in activated macrophages, and reduction of cholesterol accumulation in macrophage-derived foam cells.

15(S)-Lipoxygenase-1 associates with neutral lipid droplets in macrophage foam cells: evidence of lipid droplet metabolism

15(S)-lipoxygenase-1 (15-LO-1) was present in the whole-cell homogenate of an acute human monocytic leukemia cell line (THP-1). Additionally, 15-LO-1 was detected on neutral lipid droplets isolated from THP-1 foam cells. To investigate if 15-LO-1 is active on lipid droplets, we used the mouse leukemic monocytic macrophage cell line (RAW 264.7), which are stably transfected with human 15-LO-1. The RAW 15-LO-1 cells were incubated with acetylated low density lipoprotein to generate foam cells. 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE], the major 15-LO-1 metabolite of arachidonic acid, was produced in the 15-LO-1 RAW but not in the mock transfected cells when incubated with arachidonic acid. Lipid droplets were isolated from the cells and incubated with arachidonic acid, and production of 15(S)-HETE was measured over 2 h. 15(S)-HETE was produced in the incubations with the lipid droplets, and this production was attenuated when the lipid droplet fraction was subjected to enzyme inactivation through heating. Efflux of 15(S)-HETE from cholesteryl ester-enriched 15-LO RAW cells, when lipid droplets are present, was significantly reduced compared with that from cells enriched with free cholesterol (lipid droplets are absent). We propose that 15-LO-1 is present and functional on cytoplasmic neutral lipid droplets in macrophage foam cells, and these droplets may act to accumulate the anti-inflammatory lipid mediator 15(S)-HETE.

cis-9,trans-11-Conjugated linoleic acid activates AMP-activated protein kinase in attenuation of insulin resistance in C2C12 myotubes

Obesity is a key risk factor in the development of insulin resistance (IR). This study is to investigate the IR attenuating effect and the molecular mechanism of cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA). This study was performed with a palmitate-induced IR model using C(2)C(12) myotubes and showed that c9,t11-CLA increased insulin-stimulated and basal (non-insulin-stimulated) glucose uptake of IR myotubes. c9,t11-CLA also up-regulated the levels of phosphorglycogen synthase, phosphoracetyl CoA carboxylase, and carnitine palmitoyltransferase-1 while down-regulating the level of pyruvate dehydrogenase kinase 4 under insulin-stimulated and basal conditions. However, c9,t11-CLA did not affect protein kinase B/Akt (Akt). These results suggested that c9,t11-CLA induced an insulin-independent enhancement of glucose and fatty acid metabolism. Furthermore, there was a dose- and time-dependent increase in the expression of phosphor-AMP-activated protein kinase (AMPK), whereas LKB1, the upstream kinase of AMPK, was unchanged. Collectively, c9,t11-CLA attenuated palmitate-induced IR by increasing the consumption of glucose and fatty acid, the mechanism involving the direct activation of AMPK.

Overexpression of human 15(S)-lipoxygenase-1 in RAW macrophages leads to increased cholesterol mobilization and reverse cholesterol transport

OBJECTIVE

The purpose of this study was to determine the effect of 15-lipoxygenase-1 (15-LO-1) on cholesterol mobilization from macrophages.

METHODS AND RESULTS

Overexpression of human 15-LO-1 in RAW mouse macrophages led to enhanced cholesterol efflux, increased cholesteryl ester (CE) hydrolysis, and increased reverse cholesterol transport (RCT). Efflux studies comparing 15-LO-1 overexpressing cells to mock-transfected RAW macrophages resulted in a 3- to 7-fold increase in cholesterol efflux to apolipoprotein A-I and a modest increase in efflux to HDL. Additional experiments revealed an increase in mRNA and protein levels of ABCA1 and ABCG1 in the RAW expressing 15-LO-1 compared to controls. Efforts to examine whether the arachidonic acid metabolite of 15-LO-1, (15S)-hydroxyeicosatetraenoic acid (HETE), was responsible for the enhanced efflux revealed this eicosanoid metabolite did not play a role. Enhanced steryl ester hydrolysis was observed in 15-LO-1 overexpressing cells suggesting that the CE produced in the 15-LO-1 expressing cells was readily mobilized. To measure RCT, RAW macrophages overexpressing 15-LO-1 or mock-transfected cells were cholesterol enriched by exposure to acetylated low-density lipoprotein and [(3)H]-cholesterol. These macrophages were injected into wild-type animals and RCT was measured as a percent of injected dose of (3)H appearing in the feces at 48 hours. We found 7% of the injected (3)H in the feces of mice that received macrophages overexpressing 15-LO-1 and 4% in the feces of mice that received mock-transfected cells.

CONCLUSIONS

These data are consistent with a model in which overexpression of human 15-LO-1 in RAW macrophages promotes RCT through increased CE hydrolysis and ABCA1-mediated cholesterol efflux.