As shown inFigure 1A, WT mice challenged with bleomycin began dying at 5 days after bleomycin treatment, and reached a mortality rate of approximately 80% on Day 14, whereasLpar2/bleomycin-challenged mice began to die on Day 8, with a final mortality rate of approximately 50% on Day 14. lung tissue, as well as levels of IL-6, transforming growth factor (TGF-), and total protein in bronchoalveolar lavage fluid. In human lung fibroblasts, the knockdown of LPA2attenuated the LPA-induced expression of TGF-1 and the differentiation of lung fibroblasts to myofibroblasts, resulting in the decreased expression of FN, -SMA, and collagen, as well as decreased activation of extracellular regulated kinase 1/2, Akt, Smad3, and p38 mitogen-activated protein kinase. Moreover, the knockdown of LPA2with Dofetilide small interfering RNA also mitigated the TGF-1induced differentiation of lung fibroblasts. In addition, LPA2deficiency significantly attenuated the bleomycin-induced apoptosis of alveolar and bronchial epithelial cells in the mouse lung. Together, our data indicate that the knockdown of LPA2attenuated bleomycin-induced lung injury and pulmonary fibrosis, and this may be related to an inhibition of the LPA-induced expression of TGF- and the activation and differentiation of fibroblasts. Keywords:lysophosphatidic acid, LPA2, idiopathic pulmonary fibrosis, transforming growth factor More than five million people are afflicted with idiopathic pulmonary fibrosis (IPF), a progressive and highly devastating interstitial lung disease (1), with an average survival time of 25 years from initial diagnosis (2). The pathology of IPF is characterized by alveolar epithelial cell injury, areas of Type II cell hyperplasia, the accumulation of fibroblasts and myofibroblasts, and the deposition of smooth muscle actin (-SMA) and extracellular matrix (ECM) proteins such as fibronectin (FN) and collagen (36). Recent investigations have Rabbit polyclonal to SelectinE indicated that alveolar injury, followed by abnormal wound-healing, is involved in the pathogenesis of IPF (7,8). Subsequently, the accumulation of fibroblasts results in excessive scarring and Dofetilide changes in lung architecture, leading to a loss of lung function and death (9). However, the details underlying the pathogenesis of IPF remain elusive, and effective therapies are not yet available for patients with IPF. Lysophosphatidic acid (LPA) is a bioactive lysophospholipid that regulates numerous cellular functions, and also promotes wound healing and tissue fibrosis (10). LPA signals through its G-proteincoupled receptors, and so far, in humans, six LPA receptors (LPA16) have been cloned and characterized (1114). Recent studies have demonstrated a positive role for LPA and LPA1in the pathogenesis of fibrosis (15,16).In vitro, LPA is known Dofetilide to induce the proliferation and differentiation of lung fibroblasts (17,18), and to augment the fibroblast-mediated contraction of released collagen gels (19). Lipid profiling indicates that LPA levels were dramatically higher in bronchoalveolar lavage (BAL) fluid collected from patients with IPF, compared with their normal counterparts (16). In the bleomycin-induced pulmonary fibrosis model, LPA1deficiency conferred significant protection against bleomycin-induced fibrosis and mortality (16,20). Furthermore, LPA-induced fibroblast recruitment, vascular leakage, and epithelial cell apoptosis were also markedly reduced inLpar1/mice (16,20).In vivo, the oral administration of an LPA1antagonist dramatically prevented bleomycin- induced pulmonary fibrosis in mice (16,21), and the intraperitoneal injection of an LPA1/3antagonist ameliorated irradiation-induced lung fibrosis (22). In a renal fibrosis model, LPA1deficiency or the administration of an LPA1antagonist suppressed renal interstitial fibrosis (12,23). Moreover, LPA induced fibroblast chemotaxis through an LPA1-dependent mechanism (16). Together, these results point to LPA1receptor antagonism as a potentially useful treatment for IPF. However, the role of other LPA receptors in fibrosis remains unknown. Transforming growth factor (TGF-) is known to play critical roles in the pathogenesis of lung injury and fibrosis (24,25), and recent reports indicate that LPA2induced v6 integrinmediated TGF- activation in epithelial cells (26). We therefore hypothesized that LPA2is likely Dofetilide to play a functional role in bleomycin-induced lung fibrosis, a well-validated model of chronic pulmonary fibrosis. In this report, we show thatLpar2/mice are significantly protected against bleomycin-induced lung injury, fibrosis, and mortality, and that Dofetilide the bleomycin-induced expression of FN, -SMA, and collagen is attenuated in the lungs ofLpar2/mice. In addition, the increased levels of IL-6, TGF-1, and total protein found in the BAL fluid of wild-type (WT) control mice challenged with bleomycin are not observed in bleomycin-treated, LPA2-deficient mice. Mice deficient in LPA2are also protected from bleomycin-induced alveolar and bronchial epithelial cell apoptosis.In vitro, the LPA-induced differentiation of lung fibroblasts is characterized by an increased expression of FN, -SMA, and.