IL-13 and IL-1beta promote lung fibroblast growth through coordinated up-regulation of PDGF-AA and PDGF-Ralpha.

Peribronchiolar fibrosis is a prominent feature of airway remodeling in asthma and involves fibroblast growth and collagen deposition. Interleukin-13 (IL-13), a T-helper 2 cytokine, is a key mediator of airway remodeling in asthma, yet the mechanism through which IL-13 promotes fibroblast growth has not been investigated. In this study, we show that IL-13 stimulates the mitogenesis of mouse, rat, and human lung fibroblasts through release of a soluble mitogen that we identified as PDGF-AA. The IL-13-induced growth of human lung fibroblasts was attenuated by an anti-PDGF-AA neutralizing antibody, and IL-13 stimulated human lung fibroblasts to secrete PDGF-AA. Fibroblasts derived from mouse embryos possessing the lethal Patch mutation, which lack the PDGF-Ralpha, showed no mitogenic response to IL-13. However, Patch cells did exhibit IL-13-induced STAT-6 phosphorylation. Stable transfection of the PDGF-Ralpha into Patch cells restored the growth response to PDGF-AA and IL-13. Through the use of lung fibroblasts from STAT-6-deficient mice, we showed that IL-13-induced PDGF-AA release is STAT-6 dependent, but PDGF-AA-induced growth is STAT-6 independent. Finally, we showed that IL-1beta enhanced IL-13-induced mitogenesis of rat lung fibroblasts through up-regulation of the PDGF-Ralpha. Our findings indicate that IL-13 acts in synergy with IL-1beta to stimulate growth by coordinately up-regulating PDGF-AA and the PDGF-Ralpha, respectively.

Sodium arsenite-induced stress-related gene expression in normal human epidermal, HaCaT, and HEL30 keratinocytes.

Arsenic is a carcinogen that poses a significant health risk in humans. Based on evidence that arsenic has differential effects on human, rodent, normal, and transformed cells, these studies addressed the relative merits of using normal human epidermal keratinocytes (NHEK) and immortalized human (HaCaT) and mouse (HEL30) keratinocytes when examining stress-induced gene expression that may contribute to carcinogenesis. We hypothesize that redox-related gene expression is differentially modulated by arsenic in normal versus immortalized keratinocytes. To test the hypothesis, we exposed keratinocytes to sodium arsenite for 4 or 24 hr, at which time serine threonine kinase-25 (stk25) and nicotine adenine dinucleotide phosphate [nad(p)h] quinone oxidoreductase gene expression were measured. The effect of glutathione reduction on arsenite-induced cytotoxicity and gene expression in NHEK also was evaluated by addition of l-buthionine-[S,R]-sulfoximine (BSO) to culture media. Results indicate the term LC(50) for arsenite is approximately 10-15 microM in NHEK and HEL30 keratinocytes and 30 microM in HaCaT keratinocytes. Compared with HaCaT and HEL30 keratinocytes, a nontoxic concentration of arsenite (2.5 microM) increases stk25 and nad(p)h quinone oxidoreductase gene expression in NHEK, an effect partially attenuated by BSO. These data indicate that NHEK and HaCaT/HEL30 keratinocytes have similar sensitivities toward arsenite-induced cytotoxicity but unique gene expression responses. They also suggest that arsenite modulates gene expression in NHEK involved in cellular signaling and other aspects of intermediary metabolism that may contribute to the carcinogenic process.

Alteration in regulation of inflammatory response to influenza a virus and endotoxin in suckling rat pups: a potential relationship to sudden infant death syndrome.

Data increasingly implicate a possible role of immune and inflammatory responses to infection in sudden infant death syndrome (SIDS). We have previously described a dual challenge model that results in pathology, organ damage, vascular collapse and unexplained death similar to that seen in SIDS. In this study, we examined changes in inflammatory cytokine mRNA in the lung and liver and regulation of pathways associated with nitric oxide production. Our data suggest that priming of the immune system by mild viral infection disturbs normal inflammatory response to endotoxin. This results in an increased nitric oxide synthase production, most likely the cause of liver pathology and clotting abnormalities.