fMet-Leu-Phe Stimulates Proinflammatory Cytokine Gene Expression in Human Peripheral Blood Monocytes: The Role of Phosphatidylinositol 3-Kinase

Abstract

The fMLP-stimulated release of proinflammatory cytokines such as IL-1 by human peripheral blood monocytes is an important component of the inflammatory process. The signaling mechanisms used by fMLP to stimulate the release of cytokines are still incompletely understood. We previously demonstrated that fMLP-stimulated NF-κB activation in PBMC and now we present evidence that the lipid products of phosphatidylinositol 3-kinase (PI 3-kinase) are required for fMLP-stimulated activation of NF-κB. Pretreatment with the PI 3-kinase inhibitors, wortmannin and LY294002, effectively blocked fMLP-induced IL-1β gene expression as well as NF-κB activation. Transient transfection of THP1 cells with a dominant-negative mutant of the PI 3-kinase p85 subunit also abrogated fMLP-induced κB activity. These results suggest a potential role of fMLP in the transcription of proinflammatory cytokines and provide the first evidence that such regulation may occur through PI 3-kinase activity.

Chemoattractant-stimulated NF-κB Activation Is Dependent on the Low Molecular Weight GTPase RhoA

“…Monocytes-We have previously demonstrated that fMLP stimulated PI3K activity, and this activity is required for fMLP-induced NF-B activity in human monocytes (13). Based on our current results and our previous report, the relationship between PI3K activation and activation of the RhoA appears to be an important issue.…”

“…We previously demonstrated that fMLP-induced NF-B activation required PI3K activity in human monocytes (13), and here we present evidence that RhoA activity is essential for fMLP-induced NF-B activation. To test the possibility that PI3K is a component of the fMLP-stimulated signaling pathway leading to RhoA activation, we assessed the effect of inhibiting PI3K activity on subsequent fMLP-induced RhoA activation.…”

“…Numerous stimuli can activate NF-B, including the bacterial components lipopolysaccharide, as well as other proinflammatory factors including IL-1 and TNF␣. We recently reported that chemoattractants (fMLP, PAF, C3a, and C5a) can activate the transcription factor NF-B (7,11,12) and provided the evidence that fMLP-induced NF-B activation is essential for proinflammatory cytokine synthesis in human peripheral blood monocytes (13). We further showed that fMLP-induced NF-B activation required PI3K activity, and this activation in monocytes is mediated by p85/p110 heterdimeric PI3K (13).…”

Signaling Mechanism of HIV-1 gp120 and Virion-Induced IL-1β Release in Primary Human Macrophages

“…However, some reports suggested that class IA PI3K might also be activated by GPCRs and may play a role in chemokine receptor-mediated IL-1␤ induction in primary human monocytes (35)(36)(37)(38). To define the role of specific PI3K isoforms on gp120-stimulated IL-1␤ release, we used the class IA PI3K-specific inhibitor PI-103 (39) and the class IB PI3K specific inhibitor AS605240 (40,41).…”

A Novel Protein Kinase C (PKCϵ) Is Required for fMet-Leu-Phe-induced Activation of NF-κB in Human Peripheral Blood Monocytes

“…NF-B is of considerable importance in immune cell function because of its ability to activate the transcription of many proinflammatory immediate early genes, and we have shown that it can be activated by chemoattractants such as fMLP (1)(2)(3)(4). Indeed, the fMLP-induced activation of NF-B appears essential for proinflammatory cytokine synthesis in human peripheral blood monocytes (5).…”