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Global Translational Medicine Laser influence on cytokine secretion

1. Introduction reported a reduction in the secretion of pro-inflammatory
cytokines such as interleukin (IL)-1β and tumor necrosis
The concept of utilizing light for medical purposes factor (TNF)-α using infrared lasers. 37,38,44 Infrared laser
originated long ago. Ancient Egyptian, Greek, Roman, irradiation also appears to decrease cyclooxygenase
and Arab physicians used sunlight to treat various human (COX)-2 mRNA levels and prostaglandin synthesis
1
ailments, beginning as early as 1400 B.C. However, modern in some cell types. Considering the number of laser
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phototherapy began to take form around the turn of the parameters potentially influencing cell/tissue effects
th
20 century. In 1903, Niels Ryberg Finsen received a Nobel and the complexity of the immune response, additional
Prize for his work demonstrating the bactericidal and studies are required to clarify the underlying mechanisms
tissue-stimulating effects of concentrated light. In 1960, of PBM and optimize therapeutic protocols. Although
2
3
Theodore Maiman introduced the first laser, and by the clinical investigations have suggested that laser irradiation
end of the same decade, Dr. Endre Mester demonstrated the improves wound healing in various contexts, narrowly
improvement of a biological process (hair growth) in mice
irradiated with a ruby laser. Since then, researchers have focused in vitro studies contribute to the body of evidence
4
associated laser irradiation with pain relief, 5-11 improved highlighting the underlying mechanisms. The primary
wound healing, 5,12-16 bone 17-21 and nerve regeneration, 22-26 purpose of this study was to explore the influence of a
and reduced inflammation. 5,27-38 specific laser parameter (exposure time) on cytokine
secretion in stimulated peripheral blood mononuclear cell
After Mester’s early experiments, investigators quickly (PBMC) cultures irradiated with a neodymium-doped
realized that progressively large laser exposures or “doses” yttrium aluminum garnet (Nd:YAG) laser.
did not always result in concomitant increases in the
recorded biological outcome. In fact, laser irradiation 2. Materials and methods
6
may produce either stimulatory or inhibitory responses, 2.1. Materials
depending on the applied laser parameters. Of principal
2
importance is the wavelength of the laser light, which 2.1.1. Target cells and culture conditions
determines the absorption profile within the tissue. Sprague–Dawley rat PBMCs were obtained from IQ
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Fluence (J/cm ) and irradiance (W/cm ) are also major Biosciences (Berkeley, California, USA) and maintained
2
2
determinants of the biological response. Other relevant in liquid nitrogen before culturing. Cells were initially
40
and interrelated parameters include the average power, resuspended in Hank’s balanced salt solution without
peak power, pulse duration, pulse repetition rate, exposure calcium or magnesium supplemented with 10% fetal
time, spot size, target cell type, pulse energy, total energy bovine serum (FBS). They were then pelleted and
applied, number of laser applications, and interval between resuspended in RPMI 1640 medium supplemented
laser applications. 41,42 with 10% FBS (Thermofisher Scientific, Waltham, MA,
Mester referred to the effect he observed as “laser USA). Approximately 1 × 10 cells were seeded into T-75
6
biostimulation,” and low-level laser/light therapy is another culture flasks (Fisher Scientific, Hampton, NH, USA) for
4
commonly used term for the phenomenon. In 2014, the expansion. The cells were grown at 37°C in a 5% CO
2
2
North American Association for Photobiomodulation atmosphere with ambient humidity. The medium was
(PBM) Therapy and the World Association for Laser replaced every 3 days and as required. The cells were
Therapy (WALT) jointly affirmed “photobiomodulation” evaluated through microscopy during each media change,
as the most appropriate term. WALT defines PBM and they were found to remain morphologically consistent,
as the induction of non-thermal photophysical and structurally intact, and free of debris throughout the course
photochemical events in target cells or tissues, resulting in of the study.
physiological changes at various biological scales. PBM
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responses are produced through non-thermal mechanisms 2.1.2. Laser system
and are distinguishable from the effects that result from An Nd:YAG laser (1064 nm, Lightwalker AT, Fotona,
simply heating the tissue. Typical fluence values used in Dallas, Texas, USA) was used to irradiate the cultures
2
PBM range from 1 to 20 J/cm , above which thermal according to the manufacturer’s operating instructions.
2 40
effects may predominate or partially account for the
observed responses. 2.2. Lipopolysaccharide (LPS) stimulation
Modulation of the inflammatory response is one of Near-confluent rat PBMC cultures (consisting of
6
the most consistent observations in PBM research, and 1 × 10 cells each) were exposed to one of four LPS
this effect may account for some of the clinical benefits concentrations of 0, 10, 100, or 1000 ng/mL for 1 h in
associated with laser therapy. Various researchers have the cell culture media. The cells were then transferred
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Volume 3 Issue 4 (2024) 2 doi: 10.36922/gtm.4433