Involvement of laminin beta-2 subunit in lung smooth muscle contraction and remodelling

Smooth muscle (SM) displays a contractile phenotype when express laminin alpha (a) 2 and beta (b) 1 subunits. Laminin b-2 subunit is the most common chain in laminin trimer formation and is highly expressed in lung SM, mainly during development; however, the function of laminin b-2 subunit in mature SM is not clear. Therefore, we investigated the role of laminin b-2 subunit in airway and intrapulmonary artery (IA) SM of ovalbumin sensitized adult guinea pigs (GP) that exhibit broncho-obstruction after 3 (acute) or 12 (chronic) allergen challenges (R: responders; n=6), and in sensitized GP that never displays such responses (NR: nonresponders; n=6). Allergen challenges were administrated at ten-day intervals and airway hyperresponsiveness (AHR) to histamine and the immunohistopathology of the airway and IA-SM were evaluated at the last challenge. Control group received saline solution (n=6). The AHR to histamine was observed in both R groups and in the acute NR group. All R and NR groups showed no hypertrophy either hyperplasia in the airway SM, whereas chronic R and NR groups developed hyperplasia in the IA-SM. Laminin b-2 subunit was upregulated in the airway and IA –SM of chronic NR group (p=0.001). Furthermore, the expression of laminin receptors, integrins a-1 b-1 and a-2 b-1, as well as integrin a-6 subunit were increased in chronic R and NR groups (p=0.05). These results suggest that the expression of laminin b-2 subunit might be involved in downregulation of allergen-induced broncho-obstructive response and AHR. In addition, laminin b-2 subunit might has none role in SM remodelling. This work was partly supported by SEP-CONACYT Ciencia Básica (256197)