Interferons and dermal fibrotic disorders: Nitric oxide production and transforming growth factor-beta1 gene expression by normal and hypertrophic dermal fibroblasts and tissues after interferon treatment

Accumulating evidence indicates that cytokines and other bioactive molecules produced by leukocytes and fibroblasts play a critical role in regulation of wound healing and scar remodeling. Among the cytokines involved in wound healing and hypertrophic scar (HSc) formation, transforming growth factor-beta (TGF-{dollar}beta{dollar}) and interferons are important in that they appear to act in opposition in regulating extracellular matrix metabolism. Among the other bioactive molecules produced by living cells, nitric oxide (NO) seems to be of special interest due to its functional activities in collagen synthesis and degradation. This study was designed to obtain more information about the involvement of these molecules in wound healing and HSc formation.; It was shown that human dermal fibroblasts express both endothelial and inducible NO synthases (NOS) and produce NO in vitro. These results indicate that fibroblasts, like platelets and leukocytes, are involved in the inflammatory response and that NO may play a role in the wound healing process. Furthermore, it was found that HSc fibroblasts produce less NO and express less endothelial NOS than normal cells, suggesting that NO may be involved in HSc formation. Interestingly, HSc tissues also possess less endothelial NOS protein than normal skin, indicating that NO may participate in regulation of HSc formation in vivo.; A new procedure was developed to construct gene-specific internal standards for quantitative reverse transcription-polymerase chain reaction (RT-PCR) to quantify TGF-{dollar}beta{dollar}1 gene expression in small numbers of cells or small amounts of tissue. This method was validated by Northern analysis for TGF-{dollar}beta{dollar}1 mRNA and supported by ELISA for TGF-{dollar}beta{dollar} protein production by dermal fibroblasts. The results showed that HSc fibroblasts and tissues express more TGF-{dollar}beta1{dollar} mRNA and protein than normal controls, suggesting that overexpression of TGF-{dollar}beta{dollar} by fibroblasts in tissues may be responsible for HSc formation. Autoinduction of TGF-{dollar}beta{dollar} may be one of the mechanisms for the over-expression of TGF-{dollar}beta{dollar} in HSc cells and tissues. Treatment of fibroblasts with TGF-{dollar}beta{dollar} stimulates their proliferation and collagen synthesis, while treatment of the cells with interferon-{dollar}alpha{dollar}2b (IFN-{dollar}alpha{dollar}2b) and -{dollar}gamma{dollar} inhibits proliferation and collagen synthesis. It is of interest that IFN reduces TGF-{dollar}beta{dollar} mRNA expression and protein synthesis. Treatment of HSc patients with IFN-{dollar}alpha{dollar}2b also reduces TGF-{dollar}beta{dollar} mRNA in the tissues and protein in the serum. These observations indicate opposite actions for TGF-{dollar}beta{dollar} and IFNs in the regulation of extracellular matrix metabolism.; In conclusion, human dermal fibroblasts synthesize NO and this is enhanced by IFN-{dollar}gamma{dollar} and bacterial lipopolysaccharide. HSc fibroblasts and tissues express more TGF-{dollar}beta{dollar} but less NO. TGF-{dollar}beta{dollar} stimulates whereas IFNs inhibit fibroblast proliferation and collagen synthesis. The inhibitory action of IFNs on TGF-{dollar}beta{dollar} expression and their antagonistic effects of IFNs on TGF-{dollar}beta{dollar}-stimulated cell proliferation and collagen synthesis indicate a new mechanism for the anti-fibrogenic activities of IFNs, i.e., IFNs block the autocrine effects and autoinduction of TGF-{dollar}beta{dollar}.