[Free radical mechanisms of low-intensive laser radiation]

A hypothesis of free radical mechanisms of stimulating action of low-intensive laser radiation (LILR) used for therapy of a variety of inflammatory diseases is formulated. The main points of the above hypothesis are as follows. Endogenous porphins are a LILR chromofor in the red band (lambda = 632.8 nm). Light absorption induces the production of initiating radicals that are involved in subsequent free radical reactions, in lipid peroxidation in particular. Modified lipid peroxidation in the cell membranes causes an increase in ion permeability, including that for Ca2+. The higher levels of Ca2+ in the leukocytic cytosol result in Ca(2+)-dependent cellular priming, which appeared as the increased cell functional potential and which is seen in subsequent leukocytic stimulation of the greater production of prooxidants and other biologically active products. These products include nitric oxide and a number of cytokines involved in the regulation of microcirculation. The paper presents experimental findings that can be regarded as evidence for some points of the above hypothesis which are used to provide a chain of events underlying the free radical mechanisms of stimulating action of low-intensive laser radiation.