Transcranial Low-Level Laser (Light) Therapy for Brain Injury

Abstract

Background: Low-level laser therapy (LLLT) or photobiomodulation (PBM) is a possible treatment for brain injury, including traumatic brain injury (TBI). Methods: We review the fundamental mechanisms at the cellular and molecular level and the effects on the brain are discussed. There are several contributing processes that have been proposed to lead to the beneficial effects of PBM in treating TBI such as stimulation of neurogenesis, a decrease in inflammation, and neuroprotection. Both animal and clinical trials for ischemic stroke are outlined. A number of articles have shown how transcranial LLLT (tLLLT) is effective at increasing memory, learning, and the overall neurological performance in rodent models with TBI. Results: Our laboratory has conducted three different studies on the effects of tLLLT on mice with TBI. The first studied pulsed against continuous laser irradiation, finding that 10 Hz pulsed was the best. The second compared four different wavelengths, discovering only 660 and 810 nm to have any effectiveness, whereas 732 and 980 nm did not. The third looked at varying regimens of daily laser treatments (1, 3, and 14 days) and found that 14 laser applications was excessive. We also review several studies of the effects of tLLLT on neuroprogenitor cells, brain-derived neurotrophic factor and synaptogenesis, immediate early response knockout mice, and tLLLT in combination therapy with metabolic inhibitors. Conclusions: Finally, some clinical studies in TBI patients are covered.

Neuroprotective effect of a new photobiomodulation technique against Aβ25–35 peptide–induced toxicity in mice: Novel hypothesis for therapeutic approach of Alzheimer's disease suggested

“…Although this rodent model is far away from reproducing the complexity of the physiopathological characteristics of dementia in humans, its features may be of interest for better understanding some of the underlying mechanisms. The toxicity induced by the Ab [25][26][27][28][29][30][31][32][33][34][35] peptide in oligomeric form has been repeatedly shown to result 7 days after in neuroinflammation and reactive gliosis [18,19], pro-apoptotic caspases activity enhancement [18], oxidative stress [20], endogenously produced amyloid protein deposition [18], tau protein hyperphosphorylation [18], and increase of kinases [21,22], a reduction in the number of neurons measured in hippocampal pyramidal cell layers [17,23], loss of cholinergic neurons [24], and memory deficits [17,18,23,[25][26][27].…”

“…4C and 4F). However, RGn500 very significantly reduced the level of IL-1b and interleukin 6 when animals were treated simultaneously during 10 minutes on the head The injection of Ab [25][26][27][28][29][30][31][32][33][34][35] peptide oligomers produced the appearance of typical activated astrocytes ( Fig. 5B) characterized by a change in shape consisting particularly in an important ramification compared to resting astrocytes in the Sc Ab group (Fig.…”

“…The level of pro-apoptotic Bax and the anti-apoptotic Bcl2 markers were measured in the hippocampus 10 days after Ab [25][26][27][28][29][30][31][32][33][34][35] peptide oligomer i.c.v. injection in mice, by enzyme linked immunosorbent assay.…”

“…To test the hypothesis of multiple possible strategies of treatment of the pathology, RGn500 was tested, with applications both on the head and abdomen, on the neurotoxic effects produced by the intracerebroventricular (i.c.v.) injection of oligomeric amyloid b peptide 25-35 (Ab [25][26][27][28][29][30][31][32][33][34][35] in mice. That procedure has been described as reproducing some of the features of AD pathology [17] and may give some indication on the interest of this new treatment in humans.…”

Photon penetration depth in human brain for light stimulation and treatment: A realistic Monte Carlo simulation study

“…[10][11][12] Especially, in the¯eld of light stimulation and therapy, the most meaningful, challenging, and mostly-researched part of human body is human brain. [12][13][14] While the other parts of human body, like breast, leg, arm, and belly, are simple in structure which mostly can be treated as layered model, the head is of complicate three-dimensional (3D) structure and complex geometry of cerebral tissue. It is not convincing to use layered head model to study light penetration depth.…”