Effect of roflumilast on inflammatory cells in the lungs of cigarette smoke-exposed mice

Abstract

<p>Abstract</p> <p>Background</p> <p>We reported that roflumilast, a phosphodiesterase 4 inhibitor, given orally at 5 mg/kg to mice prevented the development of emphysema in a chronic model of cigarette smoke exposure, while at 1 mg/kg was ineffective. Here we investigated the effects of roflumilast on the volume density (V_V) of the inflammatory cells present in the lungs after chronic cigarette smoke exposure.</p> <p>Methods</p> <p>Slides were obtained from blocks of the previous study and V_Vwas assessed immunohistochemically and by point counting using a grid with 48 points, a 20× objective and a computer screen for a final magnification of 580×. Neutrophils were marked with myeloperoxidase antibody, macrophages with Mac-3, dendritic cells with fascin, B-lymphocytes with B220, CD4+ T-cells with CD4+ antibody, and CD8+T-cells with CD8-α. The significance of the differences was calculated using one-way analysis of variance.</p> <p>Results</p> <p>Chronic smoke exposure increased neutrophil V_Vby 97%, macrophage by 107%, dendritic cell by 217%, B-lymphocyte by 436%, CD4+ by 524%, and CD8+ by 417%. The higher dose of roflumilast prevented the increase in neutrophil V_Vby 78%, macrophage by 82%, dendritic cell by 48%, B-lymphocyte by 100%, CD4+ by 98% and CD8+ V_Vby 88%. The lower dose of roflumilast did not prevent the increase in neutrophil, macrophage and B-cell V_Vbut prevented dendritic cells by 42%, CD4+ by 55%, and CD8+ by 91%.</p> <p>Conclusion</p> <p>These results indicate (<it>i</it>) chronic exposure to cigarette smoke in mice results in a significant recruitment into the lung of inflammatory cells of both the innate and adaptive immune system; (<it>ii</it>) roflumilast at the higher dose exerts a protective effect against the recruitment of all these cells and at the lower dose against the recruitment of dendritic cells and T-lymphocytes; (<it>iii</it>) these findings underline the role of innate immunity in the development of pulmonary emphysema and (<it>iiii</it>) support previous results indicating that the inflammatory cells of the adaptive immune system do not play a central role in the development of cigarette smoke induced emphysema in mice.</p