Absorption measurements of cell monolayers relevant to mechanisms of laser phototherapy: reduction or oxidation of cytochrome c oxidase under laser radiation at 632.8 nm.

Objective: The objective of this work was a further investigation of redox mechanisms of laser phototherapy on the cellular level.

Background Data: Cytochrome c oxidase, the terminal enzyme of the mitochondrial respiratory chain, is believed to work as the photoacceptor to modulate cellular metabolism in laser phototherapy.

Materials And Methods: The changes in the absorption spectra of HeLa-cell monolayers before and after irradiation at 632.

Elementary processes in cells after light absorption do not depend on the degree of polarization: implications for the mechanisms of laser phototherapy.

Objective: The objective of this work was to evaluate the importance of the degree of light polarization in stimulation of cellular metabolism.

Background Data: Although the possible role of polarization's effects on the mechanisms of laser phototherapy is sometimes discussed in the literature, there are still no clear answers.

Material And Methods: A model system (HeLa cell suspension) was used in which the lengths of light scattering (l sc) and absorption (l a) were much larger than the thickness of the irradiated layer (L = 3 mm).

Cellular effects of low power laser therapy can be mediated by nitric oxide.

Background And Objectives: The objective of this study was to investigate the possibility of involvement of nitric oxide (NO) into the irradiation-induced increase of cell attachment. These experiments were performed with a view to exploring the cellular mechanisms of low-power laser therapy.

Study Design/materials And Methods: A suspension of HeLa cells was irradiated with a monochromatic visible-to-near infrared radiation (600-860 nm, 52 J/m2) or with a diode laser (820 nm, 8-120 J/m2) and the number of cells attached to a glass matrix was counted after 30 minute incubation at 37 degrees C.

A novel mitochondrial signaling pathway activated by visible-to-near infrared radiation.

The number of cells attached to glass substratum increases if HeLa cell suspension is irradiated with monochromatic visible-to-near infrared radiation before plating (the action spectrum with maxima at 619, 657, 675, 700, 740, 760, 800, 820, 840 and 860 nm). Treating of cell suspension with sodium azide (2 x 10(-5) M), sodium nitroprusside (5 x 10(-5) M), ouabain (1 x 10(-6) M) or amiloride (1.7 x 10(-5) M) before irradiation significantly modifies the spectrum of cell attachment enhancement.

Photobiological modulation of cell attachment via cytochrome c oxidase.

The number of cells attached to glass substrates increases if HeLa cell suspensions are irradiated with monochromatic visible-to-near infrared radiation (600-860 nm, 52 J m(-2)) prior to plating. The well-structured relationship between this biological response and the radiation wavelength (action spectrum with maxima at 620, 680, 760, and 820 nm) suggests the existence of a photoacceptor responsible for the enhancement of attachment (presumably cytochrome c oxidase, the terminal enzyme of the respiratory chain) and, secondly, the existence of signaling pathways between the mitochondria, the plasma membrane, and the nucleus of the cell. Treating the cell suspension with ouabain (a Na(+), K(+)-ATPase inhibitor), amiloride (an inhibitor of N(+)/H(+) exchangers), or sodium azide (a cytochrome c oxidase inhibitor) prior to irradiation significantly modifies the action spectrum of cell attachment enhancement.

Melatonin modulates the action of near infrared radiation on cell adhesion.

The adhesion of human cervical cancer (HeLa) cells to a glass matrix is evaluated following their irradiation in a suspension with a pulsed near-infrared (IR) light-emitting diode (wavelength 820 nm, pulse repetition frequency 10 Hz, irradiation dose 16-120 J/m2) when melatonin (4 x 10(-11) to 4 x 10(-5) m) is added to cell suspension immediately before or after the irradiation. Also, the dependence of visible-to-near-IR radiation (600-840 nm, 52 J/m2) on cell adhesion (action spectrum) is recorded in absence and presence of melatonin (4 x 10(-6) m). It is found that melatonin in pharmacological concentrations (but not in physiological range) inhibited cell adherence.