Tumor Necrosis Factor-α Induces Early-Onset Endothelial Adhesivity by Protein Kinase Cζ–Dependent Activation of Intercellular Adhesion Molecule-1

Abstract

We tested the hypothesis that TNF-alpha induces early-onset endothelial adhesivity toward PMN by activating the constitutive endothelial cell surface ICAM-1, the beta2-integrin (CD11/CD18) counter-receptor. Stimulation of human pulmonary artery endothelial cells with TNF-alpha resulted in phosphorylation of ICAM-1 within 1 minute, a response that was sustained up to 15 minutes after TNF-alpha challenge. We observed that TNF-alpha induced 10-fold increase in PMN adhesion to endothelial cells in an ICAM-1-dependent manner and that this response paralleled the rapid time course of ICAM-1 phosphorylation. We also observed that the early-onset TNF-alpha-induced endothelial adhesivity was protein synthesis-independent and associated with cell surface ICAM-1 clustering. Pretreatment of cells with the pan-PKC inhibitor, chelerythrine, prevented the activation of endothelial adhesivity. As PKCzeta, an atypical PKC isoform abundantly expressed in endothelial cells, is implicated in signaling TNF-alpha-induced ICAM-1 gene transcription, we determined the possibility that PKCzeta was involved in mediating endothelial adhesivity through ICAM-1 expression. We observed that TNF-alpha stimulation of endothelial cells induced PKCzeta activation and its association with ICAM-1. Inhibition of PKCzeta by pharmacological and genetic approaches prevented the TNF-alpha-induced phosphorylation and the clustering of the cell surface ICAM-1 as well as activation of endothelial adhesivity. Thus, TNF-alpha induces early-onset, protein synthesis-independent expression of endothelial adhesivity by PKCzeta-dependent phosphorylation of cell surface ICAM-1 that precedes the de novo ICAM-1 synthesis. The rapid ICAM-1 expression represents a novel mechanism for promoting the stable adhesion of PMN to endothelial cells that is needed to facilitate the early-onset transendothelial migration of PMN.

ANG II stimulates phospholipase D through PKCζ activation in VSMC: implications in adhesion, spreading, and hypertrophy

“…This rapid pattern of activation has also been reported in endothelial cells (16). However, we were unable to measure an increase in PKC phosphorylation using phosphoantibodies due to an elevated basal phosphorylation in rat VSMC.…”

“…PKC is a critical component of mitogenic signaling in many cell types, mediating ANG II-induced activation of ERK in VSMC (22). Moreover, PKC mediates polymorphonuclear neutrophil adhesion and chemotaxis (20) and endothelial adhesion through phosphorylation of intercel-lular adhesion molecule-1 (16). However, the involvement of PKC or PLD in VSMC adhesion or spreading is not known.…”

Ezrin/Radixin/Moesin Proteins Are Phosphorylated by TNF-α and Modulate Permeability Increases in Human Pulmonary Microvascular Endothelial Cells

“…This peptide inhibits the translocation and function of PKC␣ and PKC␤ in cultured cells (18,19). The inhibitory peptides for PKC, PKC, and PKC are pseudosubstrates, and they specifically inhibit the isoform activity in various cells including ECs (20,21). All of the peptides are myristoylated, which enables them to cross the cell membrane.…”

PKCζ at the crossroad of NF-κB and Jak1/Stat6 signaling pathways

“…In fact, the loss of PKCz inhibits most of the signs of asthma in this model, including the recruitment of eosinophils in the bronchoalveolar fluid, as well as secretion of Th2 cytokines by activated T cells, strongly suggesting that PKCz can be considered a therapeutic target in asthma. 48 However, it has been shown that PKCz is required for NF-kB activation in response to TNFa in pulmonary artery endothelial cells, 50 a critical parameter in the expression of leukocyte adhesion molecules. Therefore, it could be argued that this function of PKCz in lung-resident cells could also contribute to its role during asthma.…”