RESUMEN
Platelet-derived growth factor (PDGF) and its receptor system regulate mesenchymal cell proliferation. We recently reported that emission-source fly-ash particles and asbestos fibers induce the PDGF alpha-receptor through a macrophage-dependent pathway, and upregulation of this receptor greatly enhances the mitogenic response of lung myofibroblasts to PDGF (Lindroos and colleagues, Am. J. Respir. Cell Mol. Biol. 1997;16:283-292). In the present study we investigated the effect of particulate matter <= 10 micrometers in size (PM10) from the southern, central, and northern regions of Mexico City on PDGF receptor induction and compared these urban, ambient particles with Mt. St. Helen's volcanic ash particles as a negative control. All Mexico City PM10 samples, but not volcanic ash, stimulated rat alveolar macrophages to secrete a soluble, upregulatory factor(s) for the PDGF alpha-receptor on early passage rat lung myofibroblasts. The macrophage-derived upregulatory activity was blocked by the interleukin (IL)-1 receptor antagonist. The ability of PM10 to stimulate IL-1beta release was blocked in part by a recombinant endotoxin neutralizing protein (rENP). Lipopolysaccharide/endotoxin (LPS) and vanadium, both constituents that were present within these PM10 samples, also stimulated macrophages to secrete factor(s) that upregulated PDGF-Ralpha on lung myofibroblasts. Direct exposure of myofibroblasts to PM10 also elicited upregulation of the PDGF alpha-receptor, and this effect was blocked by rENP and mimicked by LPS, but not vanadium. These findings suggest that PM10 particles induce expression of the PDGF receptor system through macrophage-dependent and -independent mechanisms involving endotoxin and metals.
Asunto(s)
Contaminantes Atmosféricos/farmacología , Pulmón/inmunología , Receptores del Factor de Crecimiento Derivado de Plaquetas/inmunología , Contaminantes Atmosféricos/inmunología , Animales , Líquido del Lavado Bronquioalveolar/química , Líquido del Lavado Bronquioalveolar/citología , Líquido del Lavado Bronquioalveolar/inmunología , Ciudades , Medios de Cultivo Condicionados/farmacología , Endotoxinas/inmunología , Fibroblastos/efectos de los fármacos , Fibroblastos/inmunología , Fibroblastos/metabolismo , Interleucina-1/inmunología , Interleucina-1/metabolismo , Pulmón/química , Macrófagos Alveolares/inmunología , Macrófagos Alveolares/metabolismo , Masculino , México , Ratas , Ratas Sprague-Dawley , Receptores del Factor de Crecimiento Derivado de Plaquetas/análisis , Regulación hacia Arriba/inmunología , Compuestos de Vanadio/inmunología , Compuestos de Vanadio/farmacología , Erupciones VolcánicasRESUMEN
Two overlapping clones containing sequences homologous to bovine, human and chicken decorin have been recovered from poly A+ RNA isolated from rat vascular smooth muscle cells (VSMC) using cDNA cloning and reverse transcription-polymerase chain reaction (PCR) methodologies. Results of nucleotide sequence analysis performed on these clones demonstrated that they encode the complete mature rat decorin protein expressed by VSMC. Within the coding region, rat decorin exhibits 76% nucleotide sequence homology to human and bovine decorin, and 69% homologous to chicken decorin indicating a significant level of conservation among these species. This level of conservation among species was also maintained at the protein level with rat decorin being 77% homologous to its human, bovine and chicken homologues. As previously observed its human homologue, rat decorin, is made up of seven, tandem, leucine-rich repeat sequences. Furthermore, within the core of these repeats was the consensus protein sequence NKISK which has been proposed to be the fibronectin binding region of decorin (G. Schmidt et al., Biochem. J. 280, 411-414 (1991)). The vast majority of amino acid substitutions within rat decorin were of the conservative type. The highest frequency of amino acid substitutions were found to be localized within a hypervariable region located near the amino terminus of the decorin core protein. Unlike rat biglycan, rat decorin mRNA levels were found to increase significantly in density-arrested VSMC cultures. In contrast to rat biglycan gene expression, no quantitative differences in rat decorin mRNA levels were observed between proliferating VSMC and VSMC made quiescent through serum depletion. Finally, specific extracellular matrix (ECM) proteins were able to regulate the expression of decorin at the mRNA level in a slightly different manner than previously observed for biglycan.