Molecular mechanisms of reduced expression of the angiostatic chemokine IP-10 in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal lung disorder characterised by irreversible scarring of the lung and has no effective therapy. Excessive fibroblast (a cell type) growth and scar formation are the most important features of the disease and require new blood vessel formation to accommodate the nutritional need. In normal lung the new blood vessel formation is inhibited by an inhibitor protein called IP-10. However, in IPF lung, IP-10 production is reduced, leading to new blood vessel formation and unopposed fibroblast growth and scar formation. Why IP-10 expression is faulty in IPF lung is unclear and is an important area to study. We believe that key processes in IP-10 expression are defective in IPF. In the studies proposed here we will compare fibroblasts from IPF patients with normal cells to examine the molecular mechanisms regulating the IP-10 expression and identify the defective processes in IPF. This will help us to understand the disease better and may lead to the development of approaches to restore IP-10 expression as a new treatment for IPF.

Idiopathic pulmonary fibrosis (IPF) is a severe, progressive and lethal fibrotic lung disorder with less than a 50% five-year survival rate. IPF is characterised by dysregulated repair of inflammatory injury, fibroproliferation, and excessive collagen deposition. The etiology of IPF is unknown and the main therapy with anti-inflammatory corticosteroids is ineffective. Thus novel therapeutic strategies to modulate specific mechanistic pathways that lead to fibrosis are needed.
Angiogenesis, the formation of new blood vessels from pre-existing vasculature, is critical in both physiological and pathological processes. Fibroblast proliferation and excessive collagen deposition are the most important pathological hallmarks of IPF and increasing evidence suggests that angiogenesis is a critical event that supports these processes. Angiogenesis is regulated by an opposing balance between angiogenic and angiostatic factors. IL-8 and interferon (IFN) ?-inducible protein of 10 kD (IP-10) of the CXC chemokine subfamily possess potent angiogenic and angiostatic properties, respectively. Recently, an imbalance in the levels of angiogenic (i.e. IL-8) and angiostatic (i.e. IP-10) chemokines that favours net angiogenesis has been demonstrated in both animal models and tissue specimens from patients with IPF and a key role of IP-10 in regulating angiogenesis in IPF has been suggested. In our preliminary studies using fibroblasts from IPF patients (F-IPF) and control subjects with nonfibrotic lung (F-NL) we have shown that compared to F-NL, cytokine-induced IP-10 protein production, mRNA expression and mRNA stability are reduced in F-IPF, but the molecular mechanisms remain to be explored.
We hypothesise that key processes in IP-10 gene transcriptional and posttranscriptional regulation are defective in IPF. We will use primary cultures of F-IPF and F-NL and compare their responses to IFN? and TNFa to test the hypothesis and identify the sites(s) of the defect(s). In the transcriptional studies, we will explore the expression, activation and IP-10 promoter binding of transcription factors and the expression, activity and recruitment to the IP-10 promoter of histone acetyltransferases and histone deacetylases. In the posttranscriptional mechanism studies, we will explore the expression, activation and RNA binding of AU-rich element (ARE) binding proteins and the involvement of the intracellular kinase pathways.
This application builds on our expertise in molecular studies of gene expression and will answer fundamental questions regarding IPF pathogenesis. The understanding of the molecular mechanisms of reduced IP-10 expression may identify specific therapeutic targets and lead to the development of molecular approaches to restore IP-10 expression as a novel therapy for IPF.