Abstract
In the medical laser field, apart from the traditional medical lasers which use immediately absorption of great amount of heat to destroy the tissue, there is another field of laser application, called “Low Energy Laser Irradiation” (LELI). In the clinical use, LELI has been used to sport injury, laser acupuncture and arthritis, etc. In spite of more than 40 years of investigation and application, the precise biological mechanisms induced by LELI in cell physiological level are not well elucidated. The effects of LELI are still controversial. The aim of this in vitro study focused on detecting metabolic changes of the cultured human fibroblasts after irradiating with Nd:YAG (1064 nm) as following doses (25 mJ * 2 pulses, 50 mJ * 1 pulse, 25 mJ * 4 pulses, 50 mJ * 2 pulses, 100 mJ * 1 pulse) using a 600 MHz NMR spectrometer. These metabolic variations would help to speculate responses of the cells after laser irradiation. In addition, survival rate of laser irradiated cells was estimated by trypan blue exclusion method to make sure that cells were not dead due to overdosed laser irradiation. The results showed that the morphology of control group (non-irradiation) cells were well spread and randomly oriented. Upon laser irradiation with higher radiant exposure, the cells appeared more severe contraction. This appearance revealed cells had been damaged after laser irradiation. NMR spectra of extracts from irradiation cells, glucose concentration decreased substantially whereas lactate concentration increased, based on the [glucose] / [lactate] ratio. (The ratios of radiation groups were 0.11 ~0.314, lower than the ratio of control 0.859) The decreased glucose / lactate ratio suggested that glycolysis pathway was rapidly triggered after laser irradiation on fibroblasts. The result caused glucose decreased and lactate increased. The energy-related metabolites such as acetate; as well as certain amino acids, alanine, valine, glutamine, glutamate were all increased in fibroblasts after laser irradiation. Alanine can be transaminated to pyruvate, then into citric acid cycle. Valine is a precursor of succinyl-CoA. Glutamate and glutamine can be transaminated to form □-ketoglutarate into citric acid cycle. These metabolites variations suggest that cells might need large amount of energy immediately after low energy laser irradiation.