Transforming growth factor beta 1 (TGF-beta1) plays an important role in the development of radiation- and drug-induced organ diseases. Proteinases-activated receptor 1 (PAR-1) is involved in many pathophysiologic processes after its activation by serine proteases. The aim of the present study was to determine messenger RNA (mRNA) production of TGF-beta1 and PAR-1 in the lungs after local irradiation. Mice of C57BL/6 and C3H/J strains with different susceptibility to fibrosis development were exposed to a of 15Gy. Non-irradiated mice of both strains were used as negative controls. Control (irradiated) and irradiated angiotensin-converting enzyme (ACE) inhibitor-treated animals were examined simultaneously. The ACE inhibitor group was given butylaminiperindopril for 9 days after irradiation (15Gy) at a daily dose of 0.1 or 0.2mg/kg per rectum. On day 9, all mice were sacrificed, and the production of mRNA TGF-beta1 and PAR-1 in lung tissue was determined semiquantitatively using reverse transcriptase polymerase chain reaction, and immunohistochemical analysis of PAR-1 expression in pulmonary tissue was performed. In the fibrosing murine strain C57Bl/6, there was an increase in the mRNA TGF-beta1 and PAR-1 levels in lungs 9 days after irradiation as compared with non-irradiated controls and non-fibrosing murine strain C3H/J. In butylaminiperindopril-treated mice, a decrease in transcript of TGF-beta1 and PAR-1 was observed. Thus, PAR-1 is involved in radiation-induced lung fibrosis in correlation with TGF-beta1 production. Administration of ACEI influences PAR-1 and TGF-beta1 expression.

Department of Pathology Thomayer Teaching Hospital Vídenská 800 Prague 4 Krc 14059 Prague Czech Republic

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Cytokines and radiation-induced pulmonary injuries