氧化還原調節作用在very late antigen-4 integrin所媒介的白血球活化與toluene diisocyanate所誘發的肺部發炎反應中所扮演的角色

Abstract

The trafficking of leukocytes from the blood into peripheral tissues through a multiple-step intercellular adhesion process is essential for selective recruitment of leukocytes to the inflammation sites. Like other immune reactions, a central question regarding the initiation and progression of allergic inflammation which leads to diseases like asthma is how cells responsible for stimulations are selectively recruited to the airway. We suggest that reactive oxygen species in the tissue microenvironments may participate in the regulation of immune responses by redox modulation and use in vitro and in vivo systems to address whether leukocyte-produced reactive oxygen species play an important role in leukocytes activation and allergic disease. Activation of leukocyte integrin is important for selective recruitment of cells to tissues. Our previous studies showed that the binding between the integrin very late antigen-4 (VLA-4) and vascular cell adhesion molecule-1 (VCAM-1) is modulated by reactive oxygen species. Here, we investigated the molecular nature of redox modulation on the activation states of VLA-4 induced exposure of sulfhydryl groups on the alpha 4 peptide. Low concentrations of exogenous hydrogen peroxide (5-10M) enhanced the ligand binding ability of VLA-4 to VCAM-1 and cell rolling on VCAM-1, while higher concentrations of hydrogen peroxide (100M) inhibited the binding ability. Low concentration hydrogen peroxide induced the S-glutathionylation on VLA-4 and the VLA-4 ligand binding activity modulated by redox modulation and required outside-in signaling and cytoskeleton rearrangement. These findings indicated that ligand binding of VLA-4 involves redox modulations which may play a pivotal role in regulating the activation states of VLA-4 in inflammatory tissues and hence direct leukocyte trafficking. To address the role of leukocyte-produced oxidants in airway inflammation, toluene diisocyanate, a low molecular weight compound noted for inducing occupational asthma, was used to induce airway inflammation in a mouse model. NADPH oxidase highly expressed in leukocytes has been known to be critical in reactive oxygen species production during tissue inflammation. Wild type B6 mice and NADPH oxidase deficiency (Ncf1-/-) mice were sensitized by intranasal sensitization and challenged by inhalation with toluene diisocyanate. Cell infiltration in lung tissue and leukocytes in bronchoalveolar lavage markedly decreased in the Ncf1-/- animals. Airway reactivity to methacholine challenge also was reduced to baseline level in Ncf1-/- mice. Toluene diisocyanate-induced inflammatory cytokines expression and redox-sensitvie nuclear factor activation in the lung tissue markedly decreased in NADPH oxidase deficient mice. Our findings suggest that leukocyte NADPH oxidase may be an essential regulator in toluene diisocyanate-induced airway inflammation.