Red light emitting diode irradiation inhibits high glucose-enhanced osteoclastogenesis of rat bone marrow cells

Hyperglycemia has been implicated in the pathogenesis of diabetic bone disease. By photo-modulating the biological functions of osteoclasts, LLLI (Low level light irradiation) may be applied in the clinical treatments for diabetic osteoporosis. Light irradiation was performed at radiant exposure of 2 J/cm(2), and single or multiple exposures using a light source composed of red light emitting diodes (LEDs) with a wavelength of 660 nm and the irradiance of 10 mW/cm(2). Our results found that LLLI led to increase the number of osteoclasts differentiated from rat bone marrow monocytes. Cell cycle analysis revealed that the percentage of cells in G(0)/G(1) phase increased and that in S phase decreased following LLLI. The gene expression of RANK and cathepsin K were found to decrease after LLLI. When rat bone marrow monocytes were cultured in a medium containing high concentration of glucose, decreased viability and increased level of lactate dehydrogenase release were found. Production of reactive oxygen species (ROS) and the gene expression level of RANK, TRAP and cathepsin K elevated during high glucose incubation. Whereas LLLI was shown to lessen the effects on rat monocytes from osmotic shock due to high glucose incubation by increasing cell viability and inhibiting ROS production as well as osteoclastic gene expression. In conclusion, our findings suggest that LLLI under specific parameters may accelerate the process of bone remodeling by inhibiting osteoclastogenesis and also alleviate the enhancement of osteoclastic differentiation resulted from high glucose incubation.