Pathways of lipopolysaccharide-induced prostaglandin E(2) production in human microvascular endothelial cells
Abstract
I proposed to further investigate the production of PGE$\sb2$ by microvascular endothelial cells in response to lipopolysaccharide (LPS). The goal of my studies was to determine if LPS interacts specifically with the cell membrane of microvascular endothelial cells and induces the production of PGE$\sb2$ through specific signaling pathways. I sought to identify signaling mediators which were involved in the LPS-induced production of PGE$\sb2$. I performed binding studies to investigate the nature of the interaction of LPS with the surface of the cell and in order to determine the identity of individual signaling mediators, I used inhibitors and activators of various signaling systems. By inhibiting or mimicking the different mediators and examining the effect that it had on the response of the cell to LPS, I could evaluate each mediator's participation in the LPS-induced production of PGE$\sb2.$ Initial studies were performed in a model of untransformed human adipose-derived microvascular endothelial cells. These cells were evaluated for their ability to internalize acetylated LDL and the expression of factor VIII-related antigen to confirm their identity as endothelial cells. The results of my studies show that LPS interacts with a specific binding site or sites on the surface of human microvascular endothelial cells. The specific binding of an $\sp{125}$I-labeled LPS species can be competitively inhibited with excess unlabeled LPS. Upon interaction with the cell, LPS initiates signaling which results in the stimulation of tyrosine kinase activity, and ERK and p38 MAP kinase activity. These three signaling mediators are necessary components in the signaling pathways which are responsible for the LPS-induced production of PGE$\sb2.$ Inhibition of any of these mediators results in inhibition of LPS-stimulated synthesis of PGE$\sb2.$ PKC exerts a negative modulation on the system. Inhibition of PKC activity results in a potentiation of the LPS response. Pertussis toxin was capable of partially inhibiting the LPS response which implicates a pertussis toxin-sensitive protein in the signaling pathways initiated by LPS. Under the conditions of these studies, cAMP, the sphingolipids, ceramide and sphingosine, and the microtubule system do not appear to be involved in the LPS induction of PGE$\sb2$ production. NF-$\kappa$B was demonstrated to be a transcription factor which is involved in the LPS signaling leading to PGE$\sb2$ synthesis. Inhibition of the nuclear localization of NF-$\kappa$B resulted in partial inhibition of the LPS response. These studies demonstrate that LPS interacts specifically with the cell surface of endothelial cells. Upon interaction with the cell, LPS initiates specific signaling pathways, including the activation of tyrosine kinase, the activation of the MAP kinases, ERK and p38, and intranuclear events involving NF-$\kappa$B which are responsible for the induction of PGE$\sb2$ production. (Abstract shortened by UMI.)
Subject Area
Cellular biology
Recommended Citation
Lucas, Kimberly Anne, "Pathways of lipopolysaccharide-induced prostaglandin E(2) production in human microvascular endothelial cells" (1998). ProQuest ETD Collection - Thomas Jefferson University. AAI9829087.
https://jdc.jefferson.edu/dissertations/AAI9829087
