Method for the Assessment of Effects of a Range of Wavelengths and Intensities of Red/near-infrared Light Therapy on Oxidative Stress In Vitro

Summary

Non-coherent Xenon light was passed through narrow-band interference and neutral density filters to deliver light of varying wavelength and intensity to cultured cells. This protocol was used to assess the effects of red/near-infrared light therapy on production of reactive species in vitro: no effects were observed using the tested parameters.

Abstract

Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of central nervous system injuries in vivo, possibly by reducing oxidative stress. However, effects of R/NIR-LT on oxidative stress have been shown to vary depending on wavelength or intensity of irradiation. Studies comparing treatment parameters are lacking, due to absence of commercially available devices that deliver multiple wavelengths or intensities, suitable for high through-put in vitro optimization studies. This protocol describes a technique for delivery of light at a range of wavelengths and intensities to optimize therapeutic doses required for a given injury model. We hypothesized that a method of delivering light, in which wavelength and intensity parameters could easily be altered, could facilitate determination of an optimal dose of R/NIR-LT for reducing reactive oxygen species (ROS) in vitro.

Non-coherent Xenon light was filtered through narrow-band interference filters to deliver varying wavelengths (center wavelengths of 440, 550, 670 and 810nm) and fluences (8.5 x 10^-3 to 3.8 x 10^-1 J/cm²) of light to cultured cells. Light output from the apparatus was calibrated to emit therapeutically relevant, equal quantal doses of light at each wavelength. Reactive species were detected in glutamate stressed cells treated with the light, using DCFH-DA and H₂O₂ sensitive fluorescent dyes. 

We successfully delivered light at a range of physiologically and therapeutically relevant wavelengths and intensities, to cultured cells exposed to glutamate as a model of CNS injury. While the fluences of R/NIR-LT used in the current study did not exert an effect on ROS generated by the cultured cells, the method of light delivery is applicable to other systems including isolated mitochondria or more physiologically relevant organotypic slice culture models, and could be used to assess effects on a range of outcome measures of oxidative metabolism.

Introduction

Reactive oxygen species (ROS) are required for a range of signal transduction pathways and normal reactions of cellular metabolism, including those of neuroprotection ¹. However, when endogenous antioxidant mechanism are unable to control the production of ROS, cells may succumb to oxidative stress ^2,3. Following injury to the CNS, the associated increases in the presence of ROS and oxidative stress are thought to play a substantial role in the progression of damage ^4,5. Despite the extensive number of strategies for attenuating oxidative stress that have been assessed, there are currently no completely effective, clinically relevant a....

Protocol

1. Optical Calibration: Measuring Light Output

1. To prepare the light delivery apparatus, connect a broadband light source (e.g., Xenon or tungsten lamp) to an appropriate power supply. Position a collimating lens in front of the light source to produce a collimated beam of light. Pass the light through a liquid heat filter to remove most of the heat from the light beam. Depending on the application, focus the collimated beam on to the entrance aperture of a liquid light guide, which provides for more flexible delivery of the light (e.g., into an incubator).
2. At the other end of the liquid light guide, position a second collimating....

Results

The output of light delivered at a wavelength of 670nm was calibrated using neutral density filters in order to irradiate cells with a range of fluences encompassing a dose of 670nm light previously shown to be beneficial in vivo (0.3 J/cm²) ²⁰. As the number of neutral density filters in front of the light source increased, the intensity (W/m²) decreased, allowing less light to pass to the target area. Table 1 presents the calibration data of 670nm light generated from the light.......

Discussion

We have successfully adapted a precise and calibrated light delivery system to provide a mechanism for study of optimization of R/NIR-LT in vitro. Wavelength and intensity parameters of R/NIR-LT are able to be manipulated accurately and effectively using this system. We established that light treatment of the cells did not lead to cell death, although ROS were not reduced at the wavelengths and dosages delivered, in the cell types tested. The maximum intensities achieved by the current system at 670nm (20.11W/m<.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
OxiSelect Intracellular ROS Assay Kit (Green Fluorescence)	Cell Biolabs	STA-342
Amplex UltraRed Reagent	Molecular Probes	A36006
300 Watt Xenon Arc Lamp	Newport Corporation	6258	Very intense light source, do not look directly into the lamp. Ensure there is sufficient cooling to the lamp whilst it is switched on
USB4000-FL Fluorescence Spectrometer	Ocean Optics
CC-3-UV Cosine Corrector for Emission Collection	Ocean Optics
200μm diameter quartz fibre optic	Ocean Optics
SpectraSuite Spectroscopy Platform	Ocean Optics
2300 EnSpire Multimode Plate Reader	Perkin Elmer
Pierce BCA Protein Assay Kit	Thermo Scientific	23225
Triton X-100	Sigma-Aldrich	9002-93-1	Acute toxicity, wear gloves when handling.
L-Glutamic acid monosodium salt hydrate	Sigma-Aldrich	142-47-2 (anhydrous)
Pheochromocytoma rat adrenal medulla (PC12) cells	American Type Culture Collection	CRL-2522
Roswell Park Memorial Institute (RPMI1640) Media	Gibco	11875-119
Fetal Bovine Serum, certified, heat inactivated, US origin	Gibco	10082-147	Warm to 37 °C in water bath before use
Horse Serum, New Zealand origin	Gibco	16050-122	Warm to 37 °C in water bath before use
GlutaMAX Supplement	Gibco	35050-061	Warm to 37 °C in water bath before use
100 mM Sodium Pyruvate	Gibco	11360-070	Warm to 37 °C in water bath before use
Penicillin-Streptomycin (10,000 U/mL)	Gibco	15140-122	Warm to 37 °C in water bath before use
100X MEM Non-Essential Amino Acids Solution	Gibco	11140-050	Warm to 37 °C in water bath before use
Retinal Muller (rMC1) cells	University of California, San Diego
Dulbecco's Modified Eagle Medium (DMEM)	Gibco	11965-118	Warm to 37 °C in water bath before use
75 cm2 Flasks	BD Biosciences	B4-BE-353136
Poly-L-lysine hydrobromide	Sigma-Aldrich	25988-63-0	Aliquot and store at -20 °C
Hank's Balanced Salt Solution (HBSS)	Gibco	14025-134	Warm to 37 °C in water bath before use
Phosphate-Buffered Saline (PBS)	Gibco	10010-049	Warm to 37 °C in water bath before use
Laminin Mouse Protein, Natural	Gibco	23017-015	Aliquot and store at -20 °C
1X Neurobasal Medium	Gibco	21103-049	Warm to 37 °C in water bath before use
Trypan Blue Solution, 0.4%	Gibco	15250-061
165U Papain	Worthington
L-Cysteine	Sigma-Aldrich	W326305
Corning 96 well plates, clear bottom, black	Corning	CLS3603-48EA
Costar Clear Polystyrene 96-Well Plates Untreated; Well shape: Round; Sterile.	Costar	07-200-103
Seesaw Rocker	Standard lab epuipment
Centrifuge	Standard lab epuipment
Neutral Density Filter Paper (0.3)	THORLABS
442 nm Bandpass Filter	THORLABS	FL441.6-10
550 nm Bandpass Filter	THORLABS	FB550-10
670 nm Bandpass Filter	THORLABS	FB670-10
810 nm Bandpass Filter	THORLABS	FB810-10e
Unmounted Ø25 mm Absorptive Neutral Density Filters (0.1)	THORLABS	NE01B
Unmounted Ø25 mm Absorptive Neutral Density Filters (0.2)	THORLABS	NE02B
Unmounted Ø25 mm Absorptive Neutral Density Filters (0.3)	THORLABS	NE03B
Unmounted Ø25 mm Absorptive Neutral Density Filters (0.5)	THORLABS	NE05B
Unmounted Ø25 mm Absorptive Neutral Density Filters (0.6)	THORLABS	NE06B
Unmounted Ø25 mm Absorptive Neutral Density Filters (1.0)	THORLABS	NE10B