Article

Distinct PKC isoforms mediate cell survival and DNA synthesis in thrombin-induced myofibroblasts

Division of Rheumatology and Immunology, Dept. of Medicine, Medical University of South Carolina, Charleston, SC 29425, USA.
AJP Lung Cellular and Molecular Physiology (Impact Factor: 4.04). 02/2005; 288(1):L190-201. DOI: 10.1152/ajplung.00448.2003
Source: PubMed

ABSTRACT Thrombin activates protease-activated receptor (PAR)-1 and induces a myofibroblast phenotype in normal lung fibroblasts that resembles the phenotype of scleroderma lung fibroblasts. We now demonstrate that PAR-1 expression is dramatically increased in lung tissue from scleroderma patients, where it is associated with inflammatory and fibroproliferative foci. We also observe that thrombin induces resistance to apoptosis in normal lung fibroblasts, and this process is regulated by protein kinase C (PKC)-epsilon but not by PKC-alpha. Overexpression of a constitutively active (c-a) form of PAR-1 or PKC-epsilon significantly inhibits Fas ligand-induced apoptosis in lung fibroblasts, whereas scleroderma lung fibroblasts are resistant to apoptosis de novo. Thrombin translocates p21Cip1/WAF1, a signaling molecule downstream of PKC, from the nucleus to cytoplasm in normal lung fibroblasts mimicking the localization of p21Cip1/WAF1 in scleroderma lung fibroblasts. Overexpression of c-a PKC-alpha or PKC-epsilon results in accumulation of p21Cip1/WAF1 in the cytoplasm. Depletion of PKC-alpha or inhibition of mitogen-activated protein kinase (MAPK) blocks thrombin-induced DNA synthesis in lung fibroblasts. Inhibition of PKC by calphostin or PKC-alpha, but not PKC-epsilon, by antisense oligonucleotides prevents thrombin-induced MAPK phosphorylation and accumulation of G(1) phase regulatory protein cyclin D1, suggesting that PKC-alpha, MAPK, and cyclin D1 mediate lung fibroblast proliferation. These data demonstrate that two distinct PKC isoforms mediate thrombin-induced resistance to apoptosis and proliferation and suggest that p21Cip1/WAF1 promotes both phenomena.

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    • "Fibroblasts express the protease activated receptor PAR1 that enables fibroblast responsiveness to activated thrombin. PAR1 receptor expression is upregulated in IPF (Howell et al., 2005) and in lung tissue of SSc patients (Bogatkevich et al., 2005). Further, PAR1 knockout mice resist bleomycin-induced lung fibrosis (Howell et al., 2005). "
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    • "There is increasing evidence that VEGF-mediated activation of PKC can also induce protection against damaging insults (e.g. radiation, inflammatory diseases, hyperoxia) [16,26-28]. Our phospho-PKC antibody detected two PKC species that were activated in response to Vegf165, migrating at ranges between 80 and 90 kDa, respectively (Figure  9C-E). "
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    • "Elevated expression of PAR-1 has been shown in patients with IPF and in a murine model of bleomycin-induced lung fibrosis (Chambers, 2008; Howell et al., 2005). In previous studies we demonstrated that PAR-1 expression is also dramatically increased in lung tissue from scleroderma patients, mainly in lung parenchyma in context with myofibroblasts present in inflammatory and fibroproliferative foci (Bogatkevich et al., 2005). PAR-1 expression diminishes in the later stages of pulmonary fibrosis (Fig. 3 "
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