Endothelin-1 and Endothelin-3 Induce Chemotaxis and Replication of Pulmonary Artery Fibroblasts

Publisher Website
Google Scholar
Abstract
The remodeling of pulmonary vessels that occurs in association with pulmonary hypertension involves, in part, thickening of the adventitia. The stimulus for this process is not understood. One explanation is that endothelial cells secrete a growth factor that expands the local population of fibroblasts by acting as a chemoattractant and mitogen. Endothelins are a family of potent newly discovered vasoactive peptides. One of these compounds, endothelin-1 (ET-1), is secreted by endothelial cells and is known to constrict pulmonary vessels. Another, endothelin-3 (ET-3), is not secreted by endothelial cells and is less potent as a pulmonary vasoconstrictor. We hypothesized that the endothelins may have the capacity both to constrict these vessels and to initiate fibroblast chemotaxis and replication. Here we investigated the effects of both ET-1 and ET-3 on the chemotaxis and replication of fibroblasts derived from pulmonary vessels. Cells were isolated from rat pulmonary arteries, cultured in medium and 10% newborn calf serum, and used between passages 2 and 5. Chemotaxis was assessed using a modified Boyden chamber with a polycarbonate filter (pore size, 8 µm) separating cells in the upper chambers from endothelin in the lower chambers. Replication was assessed both by direct cell counts and by a colorimetric assay based on uptake and subsequent release of methylene blue. Both ET-1 and ET-3 induced chemotaxis of pulmonary artery fibroblasts and did so in a dose-dependent fashion. The maxima for both peptides occurred at a concentration of about 10-7 M, when chemotaxis was greatest for ET-1 (22 ± 1.4 versus 14 ± 1.8 cells/grid [mean ± SEM], P < 0.05). Both endothelins also induced fibroblast replication, but once again the effect of ET-1 was greater. Maximal mitogenic response occurred at a concentration of about 10-5 M and was 35 ± 3.1% above control for ET-1 and 20 ± 1% above control for ET-3. These results were obtained in the presence of 2% newborn calf serum, but results were very similar in the absence of serum. This study suggests that the endothelins, known to be vasoconstrictors, also have the capacity to attract fibroblasts and stimulate their replication. This may have important implications in pulmonary hypertension, suggesting a possible link between pulmonary vasoconstriction and an important component of vascular remodeling.