Dipalmitoylphosphatidylcholine, (DP-PtdCho), the major phospholipid component of lung surfactant is biosynthesized via a de novo pathway, the last step of which is catalyzed by CDP-choline:cholinephosphotransferase (CPT) and two remodeling steps: a deacylation and a reacylation one, catalyzed by an acidic, Ca²⁺-independent phospholipase A₂ (aiPLA₂) and a lyso-phosphatidylcholine acyltransferase (LPCAT), respectively. The aim of our study was to investigate whether a low magnitude, non-injurious static mode of mechanical stretch can induce phosphatidylcholine (PtdCho) biosynthesis and its remodeling to DP-PtdCho in the A549 cell-line, a model of alveolar type II cells. The deformation of A549 cells did not cause any release of lactate dehydrogenase, or phospholipids into the cell culture supernatants. An increase in PtdCho levels was observed after 1 h of static stretching, especially among the DP-PtdCho molecular species, as indicated by targeted lipidomics approach and site-directed fatty acyl-chain analysis. Moreover, although sphingomyelin (CerPCho) levels were unaffected, the DP-PtdCho/CerPCho ratio increased. Induction was observed in CPT, LPCAT and aiPLA₂ enzymatic activities and gene expression. Finally, incubation of the cells with MJ33 suppressed aiPLA₂ activity and DP-PtdCho production. Our data suggest that mild static mechanical stretch can promote the biosynthesis of PtdCho and its remodeling to DP-PtdCho in lung epithelial cells. Thus, low magnitude stretch could contribute to protective mechanisms rather than to injurious ones.
e16083 Background: In the prostatic epithelium endothelin-1 (ET-1), fibroblast growth factor-2 (FGF2) and hepatocyte growth factor (HGF) are involved in cell proliferation and inhibition of apoptosis. The aim of this study is to investigate whether neuropeptides such as ET-1 and growth factors such as FGF and HGF may constitute an alternate pathway to intracellular steroidogenesis. Methods: PC3 cells, an androgen independent prostate cancer cell line were cultured in RPMI 1640, fully supplemented with FBS 10% and in serum free conditions. The cells were incubated with ET-1(10nM, 3 hrs incubation), FGF-2 (10 ng/ml, 3 hrs incubation) and HGF(33 ng/ml, 3 hrs incubation), and then progesterone, 17-OH progesterone and aldosterone were measured in cell lysates by LC-MS using LTQ Orbitrap XL MS 2.5.5 SP1 (Thermo-Fisher) equipped with Accela AS 2.2.1, Accela pump. The data were analysed by Xcalibur 2.1.0 Software. Results: In baseline conditions PC3 cells produce no progesterone but high amounts of 17-OH progesterone and small amounts of aldosterone. Upon stimulation with endothelin there was a significant increase in progesterone, significant decrease in 17-OH progesterone and a very significant increase in aldosterone. Similarly stimulation with both HGF and FGF resulted in significant decreases in 17-OH progesterone and increases in aldosterone. Conclusions: Our results imply that in androgen deprivation conditions intracellular steroidogenesis can still take place by stimulation via seven membrane and tyrosine kinase receptors, contributing in part to a steroid dependent phenotype in addition to a steroid independent one, thus implying the potential for new therapeutic interventions.
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