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The lipid-containing alveolar interstitial fibroblast (lipofibroblast) is known to be critically involved in rodent lung development, homeostasis, and injury/repair. However, there is lack of information on their presence and function in the human lung. Based on a number of morphological (lipid staining), molecular (presence of characteristic lipogenic and absence of myogenic markers), and functional (triglyceride uptake) characteristics that are the hallmarks of the rodent lung lipofibroblast, using human lung fibroblasts of embryonic (WI-38) and adult origin and lung tissue from human autopsy specimens, the authors for the first time clearly demonstrate the presence of lipofibroblasts in the human lung. [ABSTRACT FROM AUTHOR]

We recently suggested that alveolar interstitial fibroblast-to-myofibroblast transdifferentiation may be a key mechanism underlying in utero nicotine-induced lung injury. However, the effects of in utero nicotine exposure on fetal alveolar type II (ATII) cells have not been fully determined. Placebo, nicotine (1 mg/kg), or nicotine (1 mg/kg) + the peroxisome proliferator-activated receptor (PPAR)-γ agonist prostaglandin J2 (PGJ2, 0.3 mg/kg) was administered intraperitoneally once daily to time-mated pregnant Sprague-Dawley rats from embryonic day 6 until their death on embryonic day 20. Fetal ATII cells were isolated, and ATII cell proliferation, differentiation (surfactant synthesis), and metabolism (metabolic profiling with the stable isotope [1,2-13C2]-D-glucose) were determined after nicotine exposure in utero or in vitro. In utero nicotine exposure significantly stimulated ATII cell proliferation, differentiation, and metabolism. Although the effects on ATII cell proliferation and metabolism were almost completely prevented by concomitant treatment with PGJ2, the effects on surfactant synthesis were not. On the basis of in utero and in vitro data, we conclude that surfactant synthesis is stimulated by nicotine's direct effect on ATII cells, whereas cell proliferation and metabolism are affected via a paracrine mechanism(s) secondary to its effects on the adepithelial fibroblasts. These data provide evidence for direct and indirect effects of in utero nicotine exposure on fetal ATII cells that could permanently alter the ‘developmental program’ of the developing lung. More importantly, concomitant administration of PPAR-γ agonists can effectively attenuate many of the effects of in utero exposure to nicotine on ATII cells. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that in vitro nicotine exposure disrupts specific epithelial-mesenchymal paracrine signaling pathways and results in pulmonary interstitial lipofibroblast (LIF)-to-myofibroblast (MYF) transdifferentiation, resulting in altered pulmonary development and function. Studies were done to determine whether nicotine induces LIF-to-MYF transdifferentiation and to elucidate underlying molecular mechanism(s) involved and to determine whether nicotine-induced LIF-to-MYF transdifferentiation could be prevented by stimulating specific alveolar interstitial fibroblast lipogenic pathway. WI38 cells, a human embryonic pulmonary fibroblast cell line, were treated with nicotine with or without specific agonists of alveolar fibroblast lipogenic pathway, PTHrP, DBcAMP, or the potent PPARγ, stimulant rosiglitazone (RGZ) for 7 days. Expression of key lipogenic and myogenic markers was examined by RT-PCR, Western hybridization, and immunohistochemistry. The effect of nicotine on triglyceride uptake by WI38 cells and PTHrP binding to its receptor was also determined. Finally, the effect of transfecting WI38 cells with a PPARγ expression vector on nicotine-induced LIF-to-MYF transdifferentiation was determined. Nicotine treatment resulted in significantly decreased expression of lipogenic and increased expression of myogenic markers in a dose-dependent manner, indicating nicotine-induced LIF-to-MYF transdifferentiation. This was accompanied by decreased PTHrP receptor binding to its receptor. The nicotine-induced LIF-to-MYF transdifferentiation was completely prevented by concomitant treatment with PTHrP, DBcAMP, RGZ, and by transiently overexpressing PPARγ. Our data suggest nicotine induces alveolar LIF-to-MYF transdifferentiation through a mechanism involving downregulation of lipogenic PTHrP-mediated, cAMP-dependent PKA signaling pathway, which can be prevented using specific molecular targets. Potential therapeutic implications of these observations against in utero nicotine-induced lung injury remain to be tested. [ABSTRACT FROM AUTHOR]

Stearoyl-CoA desaturase (SCD) is a key enzyme in the conversion of stearate to oleate (C18:0 to C18:1), and palmitate to palmitoleate (C16:0 to C16:1). There are two mouse SCD genes (SCD1 and SCD2). While SCD 1 is the isoform of SCD highly expressed in the liver and adipose tissue, and its expression is induced during adipocyte differentiation with dexamethasone and insulin, SCD2 is constitutively expressed in preadipocytes. The objective of the study is to evaluate the effect of SCD inhibition on fatty acid composition and turnover in NIH3T3 preadipocytes. NIH3T3 preadipocytes were grown in culture for 72 hours with [U-[sup 13]C] stearate and [1, 2 [sup 13]C]-acetate with 1) DMSO or 2) 0.8 µM of SCD inhibitor 06811M1005 (generously provided by CompleGen, Inc.). Analysis of fatty acid mass isotopomers was performed by gas chromatography/mass spectroscopy (GCMS). Fatty acid composition and the desaturation indices were calculated from the gas chromatogram. In cells cultured with SCD inhibitor 06811M1005 in [U-[sup 13]C]-stearate and [1,2 [sup 13]C]-acetate, the desaturation index for C18:1 n-9 was significantly reduced by ∼30% (p<0.03). There was a reduction in the conversion of U-stearate to U-oleate from 64% to 38% (p<0.04) when SCD was inhibited. While 13C isotopomer enrichment of palmitate and stearate reached the same plateau levels in treated and untreated cells, 13C isotopomer enrichment of oleate in the treated cells was significantly lower than control suggesting reduced oleate turnover during the study period. We conclude: NIH3T3 preadipocytes differentiate either in the presence of dexamethasone and insulin or PPAR υ agonist into adipocytes with phenotypes having different expression of SCD1. SCD inhibitor 06811M 1005 probably acts equally on SCD1 and SCD2 in the preadipocytes resulting in a change in desaturation index. Contrary to the expectation of reduced de novo lipogenesis, SCD inhibition primarily reduced on the conversion of stearate to oleate and the turnover of oleate without affecting the uptake and de novo synthesis of palmitate or stearate. [ABSTRACT FROM AUTHOR]