The α4β1 (Very Late Antigen (VLA)-4, CD49d/CD29) and α5β1 (VLA-5, CD49e/CD29) Integrins Mediate β2 (CD11/CD18) Integrin-Independent Neutrophil Recruitment to Endotoxin-Induced Lung Inflammation

Abstract

The β2 integrin cell adhesion molecules (CAM) mediate polymorphonuclear leukocyte (PMNL) emigration in most inflamed tissues, but, in the lung, other yet to be identified CAMs appear to be involved. In Lewis rats, the intratracheal injection of Escherichia coli-LPS induced acute (6-h) PMNL accumulation in the lung parenchyma (280 × 106 by myeloperoxidase assay; PBS control = 35 × 106) and bronchoalveolar lavage fluid (BALF = 27 × 106; PBS = 0.1 × 106). Parenchymal accumulation was not inhibited by a blocking Ab to β2 integrins and only minimally inhibited (20.5%; p < 0.05) in BALF. We examined the role of α4β1 and α5β1 integrins and of selectins in this PMNL recruitment. Treatment with mAbs to α4β1 or α5β1, even in combination, had no effect on PMNL accumulation induced by intratracheal LPS. However, anti-α4 combined with anti-β2 mAbs inhibited PMNL recruitment to the parenchyma by 56% (p < 0.001) and to BALF by 58% (p < 0.01). The addition of anti-α5 mAb to β2 plus α4 blockade inhibited PMNL accumulation further (by 79%; p < 0.05). In contrast, blockade of L-, P-, and E-selectins in combination or together with β2, α4, and α5 integrins had no effect. LPS-induced BALF protein accumulation was not inhibited by treatment with anti-β2 plus α4 mAbs, but was prevented when α5β1 was also blocked. Thus, while selectins appear to play no role, α4β1 and α5β1 function as major alternate CAMs to the β2 integrins in mediating PMNL migration to lung and to pulmonary vascular and epithelial permeability.

Lipopolysaccharide-Induced Leukocyte-Endothelial Cell Interactions: A Role for CD14 Versus Toll-Like Receptor 4 Within Microvessels

“…6A), which may reflect our work (Fig. 2) and previous reports of leukocytopenia (3,13). By contrast, LPS did not alter the flux of rolling cells in either CD14 Ϫ/Ϫ or TLR4 d mice treated with LPS (Fig.…”

“…There are numerous reports to suggest that inhibition of adhesion molecules in lungs is not sufficient to prevent leukocyte accumulation into this tissue (12,13). This is thought to be due to physical trapping of activated leukocytes within this microvascular bed due to the more narrow architecture of pulmonary capillaries (26,27).…”

“…There may also be a direct increase in leukocyte rigidity in response to LPS and thereby increased sequestration within the pulmonary microvascular bed (30). Clearly, it is not surprising that some studies have reported only partial or no decrease in LPS-induced leukocyte sequestration with anti-adhesion therapy (13,31). In this study, we for the first time have identified a genetic intervention (CD14 Ϫ/Ϫ or TLR4 d ) that completely prevents any systemic LPS-induced leukocyte sequestration into the pulmonary microvasculature.…”

“…Although we were able to delay leukocyte rolling and subsequent adhesion in mesentery with antiselectins, ultimately, inhibition of one of the integrins (␣ 4 integrin) was also necessary to prevent all leukocyte adhesion in response to LPS (11). Further complexity was identified in tissues like liver and lung where adhesion molecule inhibitor regimen did not reduce leukocyte adhesion in response to LPS (12)(13)(14).…”

Integrin characterization in pulmonary bronchioles

“…553837), and this is a functional h 1 blocking antibody (Burns et al, 2001;Noto et al, 1995). h 4 antibody (AB1922, Chemicon) was used at a concentration of 1/100, while a 5 , a v , a 6 , h 1 , and h 3 antibodies were used at a concentration of 1/10.…”