Received for publication May 14, 2007.
Revised January 22, 2008.
Accepted for publication January 23, 2008.

TNF- enhances neutrophil adhesiveness: Induction of VCAM-1 via activation of Akt and CaM kinase II and modification of HAT and HDAC4 in human tracheal smooth muscle cells

Abstract

Up-regulation of VCAM-1 involves adhesions between both circulating and resident leukocytes and the human tracheal smooth muscle cells (HTSMCs) during airway inflammatory reaction. We have previously demonstrated that TNF--induced VCAM-1 expression is regulated by MAPKs, NF-B and p300 activation in HTSMCs. In addition to this pathway, phosphorylation of Akt and CaM kinase II has been implicated in HAT and HDAC4 activation. Here, we investigated whether these different mechanisms participating in TNF--induced VCAM-1 expression and enhanced neutrophils adhesion. TNF- significantly increased HTSMCs-neutrophil adhesions, and this effect was associated with increased expression of VCAM-1 on the HTSMCs and was blocked by the selective inhibitors of Src (PP1), EGFR (AG1478), PI3K (LY294002 and wortmannin), calcium (BAPTA/AM), PI-PLC (U73122), PKC (GO976, rottlerin, and Ro 31-8220), CaM (calmidazolium chloride), CaM kinase II (KT5926 and KN62), p300 (curcumin), and HDAC (trichostatin A) or transfection with siRNAs for Src, Akt, PKC, PKCµ, CaM kinase II and HDAC4. At gene regulation level, RT-PCR and promoter assays revealed that expression of VCAM-1 was also attenuated by these signaling molecule inhibitors. Moreover, TNF- induced Akt and CaM kinase II phosphorylation via cascades through Src/EGFR/PI3K and PLC/calcium/CaM, respectively. Finally, activation of Akt and CaM kinase II may eventually lead to the acetylation of histone residues and phosphorylation of histone de-acetylase. These findings revealed that TNF- induced VCAM-1 expression via multiple signaling pathways. Blockade of these pathways may be selectively targeted to reduce neutrophil adhesion via VCAM-1 suppression and attenuation of the inflammatory responses in airway diseases.

Key words: NGF/EGF, Tumor necrosis factor, Calcium (G Protein Coupled Signals), Protein Kinase C, Src and other nonreceptor tyrosine kinases, NFkappaB, Transcriptional coactivators, Signaling network analyses, Regulation of gene expression