Low-Power Laser Irradiation Promotes Cell Proliferation by Activating PI3K/Akt Pathway

Low-power laser irradiation (LPLI) can stimulate cell proliferation through a wide network of signals. Akt is an important protein kinase in modulating cell proliferation. In this study, using real-time single-cell analysis, we investigated the activity of Akt and its effects on cell proliferation induced by LPLI in African green monkey SV40-transformed kidney fibroblast cells (COS-7). We utilized a recombinant fluorescence resonance energy transfer (FRET) Akt probe (BKAR) to dynamically detect the activation of Akt after LPLI treatment. Our results show that LPLI induced a gradual and continuous activation of Akt. Moreover, the activation of Akt can be completely abolished by wortmannin, a specific inhibitor of PI3K, suggesting that the activation of Akt caused by LPLI is a PI3K-dependent event. Src family is involved in Akt activation as demonstrated by the part inhibition of Akt activity in samples treated with PP I (an inhibitor of Src family). In contrast, loading Go 6983, a PKC inhibitor, did not affect this response. Further experiments performed using GFP-Akt fluorescence imaging and Western blot analysis demonstrate that, the activation of Akt is a multi-step process in response to LPLI, involving membrane recruitment, phosphorylation, and membrane detachment. LPLI promotes cell proliferation through PI3K/Akt activation since the cell viability was significantly inhibited by PI3K inhibitor. All these studies create a concernful conclusion that PI3K/Akt signaling pathway is well involved in LPLI triggered cell proliferation that acts as a time- and dose-dependent manner.