News and Publications

Regulation of Inflammation in Allergic Diseases

B.L. Zuraw, Z.K. Pan, K.M. Woessner, S.C. Christiansen, R.D. Ye*

* Department of Immunology, TSRI

Inflammation plays a critical role in the pathogenesis of many allergic diseases, including asthma and rhinitis. Additionally, deficiencies in C1 inhibitor result in angioedema due to poorly regulated generation of inflammatory mediators. Our studies focus on the molecular mechanisms that regulate both the generation and effects of inflammatory mediators, particularly kinins.

C1 INHIBITOR MUTATIONS

Hereditary angioedema is an autosomal dominant disease caused by a mutation of the gene for C1 inhibitor and characterized by recurrent angioedema. Our studies have implicated activation of the plasma contact system and generation of bradykinin as causal factors in angioedema. We have identified a variety of new mutations of the gene for C1 inhibitor in patients with hereditary angioedema. To assess the relationship between the different genomic mutations and the variable clinical phenotypes, we transfected the cloned mutant cDNAs into COS-7 cells and analyzed the intracellular and extracellular expression and function of the C1 inhibitor proteins. Relative expression of the wild-type and mutant alleles is also being compared in monocytes from patients with different C1 inhibitor mutations. We are also characterizing the functional effect of polymorphisms that may play a disease-modifying role in hereditary angioedema.

EFFECT OF KININS ON GENE TRANSCRIPTION

Kinins are potent peptide mediators that are rapidly generated during inflammation. Two types of bradykinin receptors are recognized: a B2 bradykinin receptor whose ligand is bradykinin, and a B1 bradykinin receptor whose ligand is Lys-des-Arg-bradykinin. Both receptors are members of the family of 7-transmembrane G protein--coupled receptors. Bradykinin, acting through B2 bradykinin receptors, mediates most of the classic inflammatory effects of kinins, including vasodilation, vascular permeability, pain, synthesis of eicosanoids, and smooth muscle contraction.

We showed that bradykinin also potently activates the transcription factor NF-B, and thereby stimulates synthesis of IL-1ß and other cytokines. The capacity of bradykinin to stimulate activation of NF-B in epithelial cells indicates a novel mechanism that could account for the ability of bradykinin to mediate the development of chronic airway inflammation. We are studying the relevant signal transduction pathways and have shown that bradykinin-induced activation of NF-B is mediated through pertussis-sensitive heterotrimeric G proteins and requires activity of both the small G protein RhoA and phosphatidylinositol 3-kinase.

We recently showed that the B1 bradykinin receptor agonist Lys-des-Arg-bradykinin activates the transcription factor activator protein-1 in cultured epithelial cells and fibroblasts. Activator protein-1 regulates both basal and inducible transcription of many genes involved in cellular proliferation and differentiation. Although little to no B1 bradykinin receptor is expressed in normal tissue, inflammation results in a rapid upregulation of expression of the receptor in rodent tissues. We showed that expression of B1 bradykinin receptors in nasal epithelial cells is greater in subjects with allergic rhinitis than in control subjects without allergic rhinitis. These studies suggest that B1 bradykinin receptors may contribute to chronic airway inflammation. Ongoing studies are designed to elaborate the pathophysiologic consequences of expression of B1 bradykinin receptors in allergic rhinitis and asthma.

EXPRESSION OF INFLAMMATORY GENES IN THE EPITHELIUM IN ALLERGIC RHINITIS

Epithelial cells may play an active role in the regulation of airway inflammation. To understand the ordered expression of inflammatory gene products during the initiation of allergic inflammation, we developed sensitive and quantitative assays to measure the expression of multiple genes in airway epithelial cells obtained by nasal scraping. Using this technique, we showed that levels of interleukin-8 and intracellular adhesion molecule-1 mRNA are higher in patients with allergic rhinitis than in control subjects. We are using both ribonuclease protection assays and in situ hybridization to measure the ordered expression of several genes that encode inflammatory products in nasal epithelial cells obtained from allergic subjects after nasal challenge with allergen.

PUBLICATIONS

Lung, C.C., Jagels, M.A., Daffern, P.J., Tan, E.M., Zuraw, B.L. Induction of human B2 bradykinin receptor mRNA and membrane receptors by interferon gamma. Immunopharmacology, in press.

Pan, Z.K., Ye, R.D., Christiansen, S.C., Jagels, M.A., Bokoch, G.M., Zuraw, B.L. Role of the Rho GTPase in bradykinin stimulated NF-/kappapub/B activation and interleukin-1ß gene expression in cultured human epithelial cells. J. Immunol. 160:3038, 1998.

Zuraw, B.L. Urticaria, angioedema and autoimmunity. Med. Clin. North Am. 17:559, 1997.

Zuraw, B.L., Christiansen, S.C. Kinins. In: Inflammatory Mechanisms in Asthma. Claude Lenfant Series Lung Biology in Health and Disease. Holgate, S.T., Busse, W. (Eds.). Marcel Dekker, New York, 1998, p. 783.