Aiming to contribute to the understanding of molecular and cellular mechanisms involved in photobiomodulation, the present studies were undertaken to monitor short and long term laser irradiation effects in metabolically intact and metabolically impaired human T cells. We used AlGaInP/GaAs lasers with emission wavelengths in the range 600 - 900 nm and exposed T leukemia lymphoblasts and peripheral blood derived adherent and non-adherent mononuclear cells, cultured in normal and in energy/nutrient restriction caused stress conditions, to doses and irradiation regimes of therapeutic significance (total incident doses up to 15 μJ/cell). Energy/nutrient restriction was realized by serum starvation, glucose deprivation or blockade of glycolysis/oxidative phosphorylation. Selecting appropriate molecular reporters, we traced changes occurring in characteristics of cell signaling key players, and rates of cellular proliferation and apoptosis induction. Cell cycle progression, percentage of apoptotic/necrotic cells, and intracellular calcium and ERK phosphorylation levels, were assessed in single cell and cell suspension measurements. The data obtained by conventional, phase contrast, and fluorescence microscopy, steady-state fluorimetry, electrophoresis/imunoblotting, and flow cytometry demonstrate significant cell type, cell state, irradiation regime, radiation dose, radiation wavelength, and treatment duration dependent soft laser effects in human T lymphocytes and leukemia lymphoblasts.

Partial financial support of the Romanian Ministry of Education, Research and Innovation (grant 42139/2008 "REUMALAS") is gratefully acknowledged.