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Biomedical subjects

Rachel Lubart

Publications and source records attributed to Rachel Lubart.

9 recordsLinked to original sources
PubMed2006

Photochemistry and photobiology of light absorption by living cells.

In this review, we summarize a part of our research concerning photobiostimulative effects on cardiomyocytes, sperm cells, and nerve cells. We concentrate on results demonstrating that photobiostimulation can be described by the Arndt-Schultz (A.S.) curve. Results monitoring an increase in reactive oxygen species (ROS) concentration following visible light irradiation describe the ascending part of the A.S. curve, whereas those that describe the antioxidant role of photobiostimulation represent the descending part of the curve.

Animals↗
PubMed2005

Flavins are source of visible-light-induced free radical formation in cells.

BACKGROUND AND OBJECTIVES: It has been hypothesized that reactive oxygen species (ROS) are created by an endogenous photosensitizer during low energy visible light illumination of tissue, and these ROS are responsible for reported biostimulative effects. This study aims to identify the endogenous photosensitizer responsible for ROS production by visible light. STUDY DESIGN/MATERIALS AND METHODS: Electron paramagnetic resonance (EPR) spectroscopy was used to detect oxyradicals produced in cardiac and sperm cells during illumination by a halogen lamp. Oxyradical production was determined as a function of illumination wavelength, cell fraction, and molecular weight. RESULTS: Oxyradicals were created solely by the 400-500 nm range of visible light. The endogenous photosensitizer is found predominantly in the cytosol and is smaller than 12 kD. Flavin mononucleotide produces the same signal at concentrations consistent with reported intracellular free flavin concentrations. CONCLUSIONS: A small, water soluble photosensitizer active only at wavelengths shorter than 500 nm is consistent with a flavin, which reproduces cellular signals at physiological concentrations. Thus, flavins are responsible for the photosensitization of the observed oxyradicals in cells.

Animals↗
PubMed2005

Low-energy laser irradiation promotes cellular redox activity.

Low-energy visible light (LEVL) has been shown to stimulate cell functions. This is called "photobiostimulation" and has been used successfully over the last three decades for treating a range of conditions, including soft tissue injuries, severe wounds, chronic pain, and more. Nevertheless, the mechanism of photobiostimulative processes is still being debated. It is obvious that, in order to interact with the living cell, light has to be absorbed by intracellular chromophores. In a search for chromophores responsible for photobiostimulation, endogenous porphyrins, mitochondrial and membranal cytochromes, and flavoproteins were found to be suitable candidates. The above-mentioned chromophores are photosensitizers that generate reactive oxygen species (ROS) following irradiation. As the cellular redox state has a key role in maintaining the viability of the cell, changes in ROS may play a significant role in cell activation. In the present review, we summarize evidence demonstrating that various ROS and antioxidants are produced following LEVL illumination. We found that very little evidence for NO formation in illuminated non-vascular smooth muscle cells exists in the literature. We suggest that the change in the cellular redox state which plays a pivotal role in maintaining cellular activities leads to photobiostimulative processes.

Antioxidants↗
PubMed2005

Er:YAG laser promotes gingival wound repair by photo-dissociating water molecules.

OBJECTIVE: The aim of the present study was to show that rapid wound repair following Er:YAG treatment and its bactericidal effect can also be related to reactive oxygen species (ROS) generation in irradiated tissue. BACKGROUND DATA: The Er:YAG laser with a wavelength of 2,940 nm (corresponding to the vibrational OH stretch frequency of water) is of great value in dental medicine, owing to its dual ability to ablate soft and hard tissues with minimal damage to surrounding structures. The relatively rapid postoperative healing time seen after ablation of the gingiva is attributed to the very narrow zone of thermal disruption. METHODS: Water was irradiated with an Er:YAG laser at an energy of 100-130 mJ/cm(2) and 10-30-Hz pulse repetition rate The concentration of OH radicals produced following irradiation was assessed by spin trapping coupled with electron paramagnetic resonance (EPR) spectroscopy. RESULTS: We found that the Er-YAG laser dissociates water and generates OH radicals. The concentration of radicals produced was strongly dependent on the pulse repetition rate and energy density per laser pulse. CONCLUSIONS: The dissociation of water needed to generate OH radicals is possibly due to intermolecular vibrational (V-V) energy transfer in water, competing with vibrational relaxation, thus leading to water dissociation. High amounts of oxygen radicals (e.g., hydroxyl groups) have a sterilization effect, whereas low concentrations of ROS stimulate fibroblasts, causing collagen and extracellular matrix formation. ROS formation may explain the wound healing effect of the Er-YAG laser in dentistry.

Laser Therapy↗
PubMed2004

ESR detection of 1O2 reveals enhanced redox activity in illuminated cell cultures.

Low-energy visible light (LEVL) has previously been found to modulate various processes in different biological systems. One explanation for the stimulatory effect of LEVL is light-induced reactive oxygen species formation. In the present study, both sperm and skin cells were illuminated with LEVL and were found to generate singlet oxygen (1O2). The detection of 1O2 was performed using a trapping probe, 2,2,6,6-tetramethyl-4-piperidone, coupled with electron paramagnetic resonance spectroscopy. In addition, we have shown that, together with O2 generation, LEVL illumination increases the reductive capacity of the cells, which explains the difficulties encountered in 1O2 detection. The potential of visible light to change the cellular redox state may explain the recently observed biostimulative effects exerted by LEVL.

Animals↗
PubMed2004

Visible light affects chemiluminescence of carp (Cyprinus carpio) blood leukocytes.

OBJECTIVE: Visible light irradiations at doses of 5 and 12 J/cm(2) were applied to carp buffy coat leukocytes. MATERIALS AND METHODS: The leukocytes response was measured by a chemiluminescence (CL) assay as basal (spontaneous) bCL and Ca ionophore-induced stimulated CL (StCL). RESULTS: The irradiation caused a significant decrease in bCL in six out of 14 fish (susceptible fish) and rendered eight out of 14 fish unsusceptible. An inhibitory effect of light intensity dependence was more pronounced at 12 J/cm(2). Furthermore, this inhibitory effect of irradiation on bCL was found in fish which displayed higher (433 +/- 90 cpm/mL) pre-irradiation bCL, compared to unsusceptible subjects (88 +/- 30 cpm/mL, p < 0.05). Similar differences in the intensity of preirradiation StCL were found between these fish groups (13,053 +/- 5086 as compared to 1077 +/- 294, p = 0.03). Moreover, the time-to-peak of StCL was significantly shorter in susceptible fish, indicating their hyper-reactivity. CONCLUSION: These data show the inhibitory effect of visible light irradiation on blood leukocyte CL response in fish. These results suggest the prevention of host hyper-response which may occur under natural conditions of fish life. An Electron Paramagnetic Resonance (EPR) study of illuminated carp blood cells reveals the formation of Ascorbate free radicals (AFR) that may explain the decrease in reactive oxygen species (ROS) concentration following irradiation.

Animals↗
PubMed2003

Low energy visible light induces reactive oxygen species generation and stimulates an increase of intracellular calcium concentration in cardiac cells.

Low energy visible light (LEVL) irradiation has been shown to exert some beneficial effects on various cell cultures. For example, it increases the fertilizing capability of sperm cells, promotes cell proliferation, induces sprouting of neurons, and more. To learn about the mechanism of photobiostimulation, we studied the relationship between increased intracellular calcium ([Ca2+]i) and reactive oxygen species production following LEVL illumination of cardiomyocytes. We found that visible light causes the production of O2. and H2O2 and that exogenously added H2O2 (12 microm) can mimic the effect of LEVL (3.6 J/cm2) to induce a slow and transient increase in [Ca2+]i. This [Ca2+]i elevation can be reduced by verapamil, a voltage-dependent calcium channel inhibitor. The kinetics of [Ca2+]i elevation and morphologic damage following light or addition of H2O2 were found to be dose-dependent. For example, LEVL, 3.6 J/cm2, which induced a transient increase in [Ca2+]i, did not cause any cell damage, whereas visible light at 12 J/cm2 induced a linear increase in [Ca2+]i and damaged the cells. The linear increase in [Ca2+]i resulting from high energy doses of light could be attenuated into a non-linear small rise in [Ca2+]i by the presence of extracellular catalase during illumination. We suggest that the different kinetics of [Ca2+]i elevation following various light irradiation or H2O2 treatment represents correspondingly different adaptation levels to oxidative stress. The adaptive response of the cells to LEVL represented by the transient increase in [Ca2+]i can explain LEVL beneficial effects.

Animals↗