Impact of sex differences and small molecules on proinflammatory lipid mediator biosynthesis
In the first part, the thesis examines the influence of sex on prostanoid formation. Prostaglandins (PG) are generated by cyclooxygenase (COX)-1/2, which convert arachidonic acid (AA) to PGH2 which is further metabolized to distinct PGs by terminal synthases. Recent findings suggest a sex biased regulation in animals. Hence, the regulation of the prostanoid formation in male and female human whole blood and freshly isolated cells was evaluated. Analysis of human blood cells showed higher lymphocyte and neutrophil numbers in females, whereas monocyte numbers were higher in males and long term incubations of whole blood resulted in significantly enhanced levels of PGs in males. The elevated formation in males was not influenced by pre-incubation with sex hormones, independent of COX-1/2 protein and COX-2 mRNA expression and of AA release in leukocytes. In contrast, the involvement of the 15-prostaglandin dehydrogenase and of transcellular interactions of isolated leukocytes could be shown. In the second part, potential 5-lipoxygenase (5-LO) inhibitors were evaluated. Leukotrienes (LT) are bioactive lipid mediators, which are biosynthesized involving 5-LO catalyzing the incorporation of molecular oxygen into AA. Out of three distinct series of potential 5-LO inhibitors, the two most potent compounds F-XII and F-XVI were analyzed in detail. Both compounds showed potent inhibition of 5-LO with IC50 values in the nanomolar range in cell-based and cell-free preparations (F-XII = 70 - 100 nM; F-XVI = 60 - 120 nM). 5-LO inhibition was direct, reversible and not primarily mediated due to radical scavenging and antioxidant properties. Docking simulations proposed binding to the amino acid Asp-166, which is involved in a salt bridge connecting the two domains of 5-LO. Furthermore, inhibition of 5-LO was independent of interference with cellular signals required for the 5-LO activation and were confirmed in human whole blood and in zymosan-induced peritonitis in mice.
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