Signaling Mechanisms of Endothelial ICAM-1 Expression and Neutrophil-mediated Lung Injury

We want to know how pro-inflammatory mediators such as thrombin mediate neutrophils (PMN) sequestration and emigration in the lung and thus induce lung vascular injury.

In particular, we are interested in defining the critical signaling pathways mediating expression of intercellular adhesion molecule (CAM-1; CD54), an inducible endothelial adhesive protein that serves as a counter-receptor for beta2-integrins (CD11/CD18) present on the surface of leukocytes. Interaction of ICAM-1 with beta2-integrins enables PMN to adhere firmly and stably to the vascular endothelium, and to migrate across the endothelial barrier. PMN binding to endothelial cells by this mechanism contributes to the development of lung vascular injury and tissue edema.

We have shown that the transcription factor NF-kB is a critical regulator of endothelial ICAM-1 gene expression following thrombin activation of G-protein coupled receptor, Proteinase-Activated Receptor-1 (PAR- 1). We have further shown that protein kinase C-delta (PKC-delta) regulates thrombin-induced NF-kB activation and thereby ICAM-1 gene expression in endothelial cells via activation of p38 MAP kinase.

Our ongoing experiments are aimed to address the following questions: What are the heterotrimeric G-proteins that functionally couple to PAR-1, and thus regulate thrombin-induced NF-kB activation and ICAM-1 expression? What are the signaling events activated by PAR-1/G-protein interactions that induce NF-kB activation and ICAM-1 expression and how interfering with these signals impacts lung PMN sequestration and PMN-dependent lung vascular injury? Do specific PAR-1/G-protein interactions mediate lung PMN sequestration and PMN-dependent lung vascular injury and do other PAR-1/G-protein interactions inhibit these responses?

These studies are being carried out using cultured endothelial cells and in vivo mouse models with targeted gene deletions to address the signaling pathways mediating NF-kB activation, ICAM-1 expression, and PMN sequestration and vascular injury in lungs. We expect that the use of multidisciplinary approaches ranging from molecular biology to lung physiology will help us address these questions of fundamental importance.

Garin G, Abe J, Mohan A, Lu W, Yan C, Newby AC, Rhaman A, and Berk BC. 2007. Flow antagonizes TNF-alpha signaling in endothelial cells by inhibiting caspase-dependent PKCzeta processing. Circ Res. Jul 6;101(1):97-105

Fazal F, Minhajuddin M, Bijli KM, McGrath JL, and Rahman A 2007. Evidence for actin cytoskeleton-dependent and -independent pathways for RelA/p65 nuclear translocation in endothelial cells. J. Biol. Chem. 282:3940-3950.

Bijli KM, Minhajuddin M, Fazal F, O’Reilly MA, Platanias LC, and Rahman A. 2007. c-Src interacts with and phosphorylates RelA/p65 to promote thrombin-induced ICAM-1 expression in endothelial cells. Am J Physiol: Lung Cell Mol Physiol. 292:L396-404.

Orrington-Myers J, Gao X, Kouklis P, Broman M, Rahman A, Vogel S, Malik AB. 2006. Regulation of Lung Neutrophil Recruitment by VE-cadherin. Am. J. Physiol: Lung Cell. Mol. Physiol. 291:L764-771.

Staversky RJ, Vitiello PF, Gehen SC, Helt CE, Rahman A, Keng PC, O’Reilly MA. 2006. P21ip1/Waf1/Sdi1 protects against persistent oxidative stress by maintaining expression of BCL-XL. Free Radic. Biol. Med. 41:601-609.

Minhajuddin, M., Fazal, F., Bijli, K. M., and Rahman A. 2005. Inhibition of mammalian target of rapamycin potentiates thrombin-induced intercellular adhesion molecule-1 expression by accelerating and stabilizing NF-kappa B activation in endothelial cells. J. Immunol. 174:5823-5829.

Frey RS, Gao XP, Javaid K, Siddiqui SS, Rahman A, and Malik AB. 2006. Phosphatidylinositol 3-kinase γ signaling via PKCΖ induces NADPH oxidase-induced oxidant generation and NF-κB activation in endothelial cells. J. Biol. Chem. 281:16128-16138.

Anwar, K. N., Fazal, F., Malik, A.B., and Rahman, A. 2004. RhoA/Rho-associated kinase pathway selectively regulates thrombin-induced intercellular adhesion molecule-1 expression in endothelial cells via activation of I kappa B kinase beta and phosphorylation of RelA/p65 J. Immunol. 173:6965-6972.

Rahman, A., Anwar, K. N., Minhajuddin, M., Bijli, K. M., Javaid, K., True, A. L., and Malik, A. B. 2004. cAMP targeting of p38 MAP kinase inhibits thrombin-induced NF-kappaB activation and ICAM-1 expression in endothelial cells. Am. J. Physiol: Lung Cell. Mol. Physiol. 287: 1017-1024.

Javaid K, Rahman A, Anwar KN, Frey RS, Minshall RD, Malik AB. 2003. Tumor necrosis factor-a induces early-onset endothelial adhesivity by protein kinase C zeta-dependent activation of intercellular adhesion molecule-1. Circ. Res., 92:1089-1097.

Deb, D. K., Sassano, A., Lekmine, F., Majchrzak, B., Verma, A., Kambhampati, S., Uddin, S., Rahman, A., Fish, E. N., and Platanias, L. C. , 2003. Activation of protein kinase C delta by IFN-gamma. J. Immunol. 171:267-273.

Khambhampati, S., Verma, A., Sassano, A., Majchrzak, B., Deb, D. K., Parmar, S., Giafis, N., Kalvakolanu, D. V., Rahman, A., Uddin, S., Minucci, S., Tallman, M., Fish, E. N., and Platanias, L. C. 2003. Activation of protein kinase C delta by all-trans-retinoic acid. J. Biol. Chem. 278:32544-32551.

Ong, E. V., Gao, X. P., Xu, N., Predescue, D., Rahman, A., and Malik, A. B. , 2003. E. coli pneumonia induces CD18-independent airway neutrophil migration in the absence of increased lung vascular permeability Am. J. Physiol: Lung Cell. Mol. Physiol. 285:879-888.

Paria, B. C. Malik, A. B. Kwiateki, A. M., Rahman, A., May, M. J., Ghosh, S., and Tiruppathi, C. , 2003. Tumor necrosis factor-a induces TRPC1 expression in endothelial cells by activation of nuclear factor-kB. J. Biol. Chem. 278:37195-37203.

Fan, J., Frey, R.S., Rahman, A., and Malik, A.B. 2002. Role of neutrophil NADPH oxidase in the mechanism of TNFa-induced NF-kB activation and ICAM-1 expression in endothelial cells. J. Biol.Chem. 277:3404-3411.

Xu, N., Gao, X., Minshall, R. D., Rahman, A., and Malik, A. B. 2002. Time-dependent reversal of sepsis-induced PMN uptake and lung vascular injury by expression of CD18 antagonist. Am. J. Physiol: Lung Mol. Cell. Physiol. 282:L796-802.

Gao, X., Standiford, T. J., Rahman, A., Newstead, M., Holland, S. M., Dinauer, M. C., Liu, Q., and Malik, A. B. 2002. Role of NADPH oxidase complex in the mechanism of lung neutrophil sequestration and microvessel injury induced by Gram negative septicemia: Studies in p47phox -/- and gp91 phox -/- mice. J. Immunol. 168:3974-3982.

*Frey, R.S., *Rahman, A., Kefer, J., Minshall, R.D., and Malik, A.B. 2002. PKCzeta regulates TNF-alpha-induced activation of NADPH oxidase in endothelial cells.. Circ. Res. 90:1012-1019. (*denotes equal contribution).

Rahman A., True, A. L., Anwar, K. N., Ye, R. D., Voyno-Yasenetskaya T. A., and Malik, A. B. 2002. Galpha(q) and Gbetagamma regulate PAR-1 signaling of thrombin-induced NF-kappaB activation and ICAM-1 transcription in endothelial cells.. Circ. Res. 91:398-405, 2002.