Genetic and environmental influences on serum oxylipins, endocannabinoids, bile acids and steroids

Lipid bioactivity is a result of direct action and the action of lipid mediators including oxylipins, endocannabinoids, bile acids and steroids. Understanding the factors contributing to biological variation in lipid mediators may inform future approaches to understand and treat complex metabolic diseases. This research aims to determine the contribution of genetic and environmental influences on lipid mediators involved in the regulation of inflammation and energy metabolism. This study recruited 138 monozygotic (MZ) and dizygotic (DZ) twins aged 18-65 years and measured serum oxylipins, endocannabinoids, bile acids and steroids using liquid chromatography mass-spectrometry (LC-MS). In this classic twin design, the similarities and differences between MZ and DZ twins are modelled to estimate the contribution of genetic and environmental influences to variation in lipid mediators. Heritable lipid mediators included the 12-lipoxygenase products 12-hydroxyeicosatetraenoic acid [0.70 (95% CI: 0.12,0.82)], 12-hydroxyeicosatetraenoic acid [0.73 (95% CI: 0.30,0.83)] and 14‑hydroxy-docosahexaenoic acid [0.51 (95% CI: 0.07,0.71)], along with the endocannabinoid docosahexaenoy-lethanolamide [0.52 (95% CI: 0.15,0.72)]. For others such as 13-hydroxyoctadecatrienoic acid and lithocholic acid the contribution of environment to variation was stronger. With increased understanding of lipid mediator functions in health, it is important to understand the factors contributing to their variance. This study provides a comprehensive analysis of lipid mediators and extends pre-existing knowledge of the genetic and environmental influences on the human lipidome.

Changes in expression of 15-lipoxygenase and prostaglandin-H synthase during differentiation of human tracheobronchial epithelial cells

The purpose of our studies was to examine differentiation-dependent expression of 15-lipoxygenase (15-LO) and prostaglandin H synthase (PGHS) isoforms in cultured normal human tracheobronchial epithelial cells. In the presence of retinoic acid (RA) the cultures differentiated into a mucociliary epithelium. When cultured in RA-depleted media, the cultures differentiated into a squamous epithelium. In the absence of RA the cultures did not express 15-LO or either of the PGHS isoforms. The PGHS-1 isoform was not expressed in RA-sufficient cultures, but both PGHS-2 messenger RNA (mRNA) and protein were strongly expressed, and prostaglandin E2 (PGE2) was produced during the predifferentiation phase. No PGHS-2 expression or PGE2 could be detected in fully differentiated mucociliary cultures. 15-LO showed the opposite expression pattern: neither mRNA nor protein were detected during the predifferentiation stage, but both were strongly expressed once mucous differentiation had occurred. Cytosolic phospholipase A2 protein was expressed throughout all stages of growth and differentiation. The cultures generated no 15-LO metabolites when incubated with 10 microM to 50 microM arachidonic acid (AA) and stimulated with ionophore. However, lysates prepared from such cultures generated 15-hydroxyeicosatetraenoic acid (15-HETE) and 12-HETE from AA, indicating that the cells contained active enzyme. When cultures expressing 15-LO protein were incubated with 10 microM linoleic acid (LA) instead of AA, and were stimulated with ionophore, they generated 13-hydroxy-9,11-octadecadienoic acid. LA rather than AA appeared to be the preferred substrate for the 15-LO enzyme. Our studies indicated that the expression of 15-LO and PGHS-2 is differentiation dependent in airway epithelial cells.

Effect of the PAF-receptor antagonist SM-12502 on human platelets

We analyzed the effect of the PAF receptor antagonist (+)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride (SM-12502) on human platelet aggregation as well as mediator release. After incubation of human platelet with different concentrations of SM-12502 the cells were subsequently stimulated with either the Ca ionophore A23187, with human thrombin, or with an activator of heterotrimeric G-proteins, sodium fluoride (NaF, in the presence of Al3+). Preincubation of platelets with the PAF receptor antagonist led to an inhibition of 12-lipoxygenase derived 12(S)-HETE and cyclooxygenase derived 12(S)-HHT. Pretreatment of platelets with the PAF receptor antagonist SM-12502 prior to activation with the Ca ionophore A23187 or PAF also inhibited platelet aggregation. Our data clearly indicate an inhibitory effect of the new PAF receptor antagonist SM-12502 on the formation of platelet derived inflammatory mediators of the lipoxygenase pathway as well as of the cyclooxygenase pathway, and furtherone, treatment with the PAF receptor antagonist diminished platelet aggregation after subsequent specific and unspecific activation.

Nitric oxide enhances 12-HETE versus LTB4 generation in pancreatic transplantation

The role of nitric oxide in lipoxygenase metabolism after a process of ischemia-reperfusion in pancreas transplantation has been evaluated in this study. Sprague-Dawley rats were randomized into three groups, as follows: Group I--Control animals not surgically manipulated; Group II.--Pancreas transplantation, after 12 h of organ preservation; Group III.--Same as II but with administration of NG-nitro-L-arginine methyl esther (a nitric oxide synthase inhibitor) (10 mg/Kg) prior to organ revascularization. The results show post-transplantation increases in leukotriene B4 and 12-hydroxyeicosatraenoic acid levels in pancreatic tissue. Nitric oxide synthase inhibition reversed the increases in 12-hydroxyeicosatetraenoic acid, but was unable to modify leukotriene B4 increases suggesting the existence of a direct effect of nitric oxide on the 12-lipoxygenase metabolism in pancreas transplantation.