Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Kozina, A.
Acyl-chain dependent effect of lysophosphatidylcholine on endothelial nitric oxide synthase and nitric oxide bioavailability in endothelial cells
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Medical University of Graz; 2014. pp. 94
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- Autor*innen der Med Uni Graz:
- Kirsch Andrijana
- Betreuer*innen:
- Frank Sasa
- Kratky Dagmar
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- Abstract:
- Although it is known that LPC 16:0 modulates eNOS synthesis, NO production and promotes or impairs endothelium-dependent relaxation, little is known about unsaturated LPC species. Previous studies showed that the capacity of LPC 16:0, 18:1, 18:2 and 20:4 to induce endothelial prostacyclin production, interleukin-8 and cyclooxygenase-2 expression as well as potency of attenuating vasorelaxation were different depending on the acyl-chain length and degree of saturation. The present doctoral thesis aimed to elucidate the possible acyl-chain dependent effects of LPC species, namely LPC 16:0, 18:1, 18:2 and 20:4 on endothelial nitric oxide synthase function and NO bioavailability in endothelial EA.hy 926 cell line. The cells were acutely (15 minutes and 1 hour) exposed to 60 μM LPC species in a 5% FBS-containing medium, followed by examination of eNOS phosphorylation, dimer formation and activity, as well as quantification of nitrite levels, ROS formation and examination of NO bioavailability by functional bio-assays ex vivo. Although LPC species caused no change in eNOS phosphorylation at both time points, the dimer to monomer ratio was decreased after exposure to LPC 16:0 and 18:1 at the 15-minute time point, and after exposure to LPC 16:0, 18:1 and 18:2 at the 1 hour time point. The change in dimer formation did not however affect the eNOS activity. The decrease in nitrite levels was observed at the 15-minute time point, but only LPC 18:1 caused a statistically significant decrease. Significant intracellular ROS formation was found after the 15- minute treatment of cells with LPC 16:0 and 18:1, but not with LPC 18:2 and 20:4. No elevation in ROS formation was observed at the 1-hour time point. The LPC 16:0-induced intracellular ROS was sensitive to NADPH oxidase inhibitor, and was localized predominately in the mitochondria. The LPC 16:0-induced ROS comprised of superoxide and other types of ROS, most probably hydrogen peroxide. The LPC 18:1-induced ROS was sensitive to NADPH oxidase, eNOS, xanthine oxidase and COX inhibitors, and localized in the mitochondria and cytoplasm. Intracellular and extracellular superoxide were predominant ROS triggered by LPC 18:1. The decrease in nitrite levels observed upon exposure of cells to LPC 18:1 could be ameliorated with the addition of Tiron, a superoxide scavenger. The bio-assay ex vivo experiments showed that LPC 18:1 induced a marked decrease in NO bioavailability and impaired endothelium-dependent relaxation in mouse aortic rings. Those detrimental effects of LPC could be counteracted with Tiron. The findings of this work denote LPC 18:1 as a potential inducer of endothelial dysfunction and suggest its role in subjects with high pathophysiological concentrations of LPC.