Abstract
Autophagy is the main cellular route for degradation of long-lived proteins and cytoplasmic organelles and its dysregulation contributes to the pathogenesis of different disease. In some settings it seems to be interconnected with apoptosis. In this regard the binding of the anti-apoptotic protein Bcl-2 with a key regulator of autophagy as Beclin 1 seems to down-regulate both apoptosis and autophagy. It is known that fibroblasts in idiopathic pulmonary fibrosis (IPF) acquire resistance to apoptosis but no data are available about the regulation of autophagy in IPF. Here we examined the expression of Beclin 1 and Bcl-2 in human IPF fibroblasts before and after cisplatin exposure.
We performed immunohistochemistry for Beclin 1 on sections of lung biopsies obtained from patients affected with IPF (n=25) histologically normal (n=5) or with emphysema (n=5). In 4 IPF, 2 normal and 2 emphysema the tissue was used to isolate lung fibroblasts. We performed Western Blot analysis and co-immunoprecipitation for Bcl2 and Beclin 1 on cultured fibroblasts before and after cisplatin exposure.
Expression of Beclin 1 in fibroblasts from IPF was down-regulated in comparison with normal and emphysema while the anti-apoptotic protein Bcl-2 was over-expressed. Treatment of fibroblast cell cultures with cisplatin induced a significant increase in Beclin 1 but a reduction in Bcl-2 expression in IPF fibroblasts. The immunoprecipitation of Bcl-2 and the following immunodetection of Beclin 1 indicate that Bcl-2 is mainly bound to Beclin 1.
The modified expression of Beclin 1 and Bcl-2 in human IPF fibroblasts in comparison with normal ones seems to suggest the possibility of an autophagic/apoptosis system dysfunction.
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