Response of alveolar type II pneumocytes to mechanical stimulation
The aim of this work was to study the responses of Alveolar type II (ATII) cells to mechanical stimulation. We focused in particular on stretch induced changes in the cytoplasmic Ca2+ concentration ([Ca2+]c) and on the underlying mechanisms. To overcome the methodological problems of live cell imaging at high temporal resolution during cell stretch, suitable techniques had to be developed. The first part of this work focused on design of new stretch devices. We used a computer controlled unidirectional stretch-compression device and a system with a micro-spatula for local stimulation of ATII cells. With the micro-spatula we achieved image acquisition interval of 30 - 35 ms and without any delay after the stretch. In the second part we focused on the fast [Ca2+]c increase as a response of ATII cells to mechanical stimulation with a special interest in the TRP channel family. Pharmacological evidence but especially the silencing of TRPV2 with siRNA techniques led to a significant reduction of the stretch-induced [Ca2+]c increase and identified TRPV2 as a mechanosensitive channel in ATII cells. Moreover, we found that mechanical gating of mechano sensitive channels in ATII cells is strictly dependent on the presence of stretch stimulus, pointing at a direct gating mechanism. TRPV2 is localized in close vicinity to FA as shown by co-immuno-labeling and immunoprecipitation experiments suggesting molecular interaction of TRPV2 with FA proteins. Indeed, we can show that integrins, FA proteins, and the actin cytoskeleton play a crucial role in transducing the mechanical signal and possibly activate the mechano-sensitive channels. For the first time our study provides molecular information on the mechanically induced Ca2+ response in ATII cells. This information may be used as a basis in the search for drugs preventing mechanically induced lung diseases.
Erstellung / Fertigstellung
Normierte SchlagwörterCalcium [MeSH]
Focal adhesions [MeSH]
Mechanotransduction, cellular [MeSH]