A potential role for protease nexin 1 overexpression in the pathogenesis of scleroderma

Abstract

Scleroderma currently affects approximately 75,000-100,000 individuals in the United States. Fibroblasts isolated from lesional skin of scleroderma patients overexpress collagens and other matrix components, and this abnormality is maintained for multiple passages in culture. To understand the molecular basis for matrix gene overexpression, we performed a differential display comparison of fibroblasts from clinically lesional and nonlesional scleroderma skin. The results suggested that protease nexin 1 (PN1), a protease inhibitor, is overexpressed in scleroderma fibroblasts. Northern blot verification showed that lesional and nonlesional scleroderma fibroblasts had three-to five-fold increased levels of PN1 mRNA compared with healthy fibroblasts. Western analysis showed that scleroderma fibroblasts also secreted more PN1. In situ hybridization of skin biopsy specimens demonstrated PN1 expression in the dermis of four out of six scleroderma patients but no PN1 expression in the dermis of six healthy volunteers. Transient or stable overexpression of PN1 in mouse 3T3 fibroblasts increased collagen promoter activity or endogenous collagen transcript levels, respectively. PN1 mutagenized at its active site and antisense PN1 both failed to increase collagen promoter activity. These results suggest that overexpression of enzymatically active PN1 may play a pathogenic role in the development of the scleroderma phenotype.

Increased expression of protease nexin-1 in fibroblasts during idiopathic pulmonary fibrosis regulates thrombin activity and fibronectin expression

“…Upregulation of PN-1 expression has previously been shown to induce increased collagen transcript levels in mouse embryonic fibroblasts, but no data were provided for fibronectin transcripts. 8 In contrast, our results did not show any significant change for collagen expression in lung fibroblasts overexpressing PN-1. We can assume that, according to the studied tissue type, PN-1 overexpressed by fibroblasts may be involved in the upregulation of certain MEC proteins.…”

“…23 However, a major part of PN-1 immunostaining was detected in lung fibroblasts, in particular in fibrotic areas. PN-1 is known to be expressed by fibroblasts from many different tissue types, including foreskin fibroblasts, 6 skin fibroblasts, 8 or mouse embryonic fibroblasts. 24 In human foreskin fibroblasts, PN-1 expression has been shown to be upregulated by interleukin-1.…”

“…6,7 Moreover, PN-1 is thought to have a pathogenic role in the development of scleroderma, another fibrotic disease. 8 PN-1 is thus a good candidate for regulating both ECM and fibrin deposition in tissues.…”

Misregulation of gene expression in primary fibroblasts lacking poly(ADP-ribose) polymerase

“…Other genes for ECM proteins that are induced in PARP Ϫ/Ϫ cells include the genes that encode ␤ 2 -microglobulin, which is similar to APP and adopts the fibrillar configuration of ␤-amyloid in individuals with amyloidosis or carpal tunnel syndrome (73), and protease nexin-I (Table 2). This latter protein is implicated in the pathogenesis of systemic sclerosis, which together with systemic lupus erythrematosus and rheumatoid arthritis belong to a family of age-related connective tissue diseases characterized by ECM accumulation, vascular injury, and autoimmunity (74). Overexpression of the cyclindependent kinase inhibitor p21 (Waf1 or Cip1) was also observed in PARP Ϫ/Ϫ cells at both the mRNA (Table 1) and protein (Fig.…”

Persistent Down-Regulation of Fli1, a Suppressor of Collagen Transcription, in Fibrotic Scleroderma Skin

“…35,36 In healthy skin, the majority of the cells with fibroblastic morphology, as well as endothelial cells in deep dermis, express Fli1 ( Figure 6, a and b). In contrast, in clinically involved skin of SSc patients with active disease, Fli1-positive fibroblasts were either absent or only occasionally seen.…”