Estrogen receptor dependence of lysyl oxidase expression and activity in cardiac fibroblasts

Abstract

Lysyl oxidase (LOX) is a collagen crosslinking enzyme essential for the deposition of collagen. We investigated the mechanism of estrogen mediated increases of LOX expression in rat cardiac fibroblasts and the role of estrogen receptors (ER). Adult rat cardiac fibroblasts were treated with ER‐α (MPP) and ‐β (PHTPP) specific antagonists, and a general ER inhibitor (ICI 181780), then treated with estrogen for 48 hrs. LOX protein expression was analyzed by Western blot. LOX catalytic activity was measured by fluorometric assay of cell‐conditioned media. Estrogen (1 to 50 ng/ml) increased LOX protein expression (150–290% for active form and 210–310% for proLOX vs control; P<0.05). Estrogen also increased LOX activity in media (120–140% vs media from untreated). LOX activation by estrogen was prevented by ER‐α and ‐β blockade; however ER‐β antagonism had a greater effect, reducing LOX activity below that of control (75% versus control and ER‐α block; P<0.05). ER‐β blockade also had a greater effect on LOX protein expression (58% decrease for active LOX vs estrogen treated) than ER‐α inhibitor (25%). ICI also significantly decreased LOX protein expression. These data indicate that both ER‐α and ‐β are involved in estrogen induced upregulation of LOX expression and activity in rat cardiac fibroblasts, with ER‐β playing a more significant role (Louisiana Board of Regents LEQSF2009‐12‐RDA10 and AHA #11GRNT7700002).