The Beneficial Role of Photobiomodulation in Neurodegenerative Diseases

Abstract

Photobiomodulation (PBM), also known as Low-level Laser Therapy (LLLT), involves the use of light from a laser or light-emitting diode (LED) in the treatment of various disorders and it has recently gained increasing interest. Progressive neuronal loss with attendant consequences such as cognitive and/or motor decline characterize neurodegenerative diseases. The available therapeutic drugs have only been able to provide symptomatic relief and may also present with some side effects, thus precluding their use in treatment. Recently, there has been an exponential increase in interest and attention in the use of PBM as a therapy in various neurodegenerative diseases in animal studies. Because of the financial and social burden of neurodegenerative diseases on the sufferers and the need for the discovery of potential therapeutic inventions in their management, it is pertinent to examine the beneficial effects of PBM and the various cellular mechanisms by which it modulates neural activity. Here, we highlight the various ways by which PBM may possess beneficial effects on neural activity and has been reported in various neurodegenerative conditions (Alzheimer's disease, Parkinson's disease, epilepsy, TBI, stroke) with the hope that it may serve as an alternative therapy in the management of neurodegenerative diseases because of the biological side effects associated with drugs currently used in the treatment of neurodegenerative diseases.

Keywords: light-emitting diode (LED); low laser light therapy; neurodegenerative diseases; photobiomodulation; therapy.

Figure 1

The electromagnetic spectrum (gamma rays, X-rays, ultraviolet rays, infrared rays, and radio waves) with two optical properties showing an inverse relationship (increasing wavelength with decreasing energy (photons) and vice-versa). The visible light spectrum between ultraviolet and infrared rays is magnified. Photobiomodulation utilizes wavelength within the red light to near infra red light spectrum for therapeutic purposes.

Figure 2

Schematic representation of photobiomodulatory effects through its action on the mitochondrial cytochrome C oxidase and activation of several signaling molecules. Following photobiostimulation, the mitochondrial chromophore, cytochrome C oxidase lead to ROS generation which in turn activates the PI3K/Akt pathway, while the effector enzyme, adenylyl cyclase, converts ATP to cyclic AMP (cAMP). cAMP could either activate pKA and RAS which further leads SIRT and ERK Signaling to promote cell survival, inhibit inflammatory processes, and apoptosis. NO release could also lead to NO-mediated vasodilation.

Figure 3

Schematic summary of the reported beneficial effects of photobiomodulation on neurodegenerative diseases (AD, PD, TBI, epilepsy) and the need to research other neurodegenerative diseases (frontotemporal lobe degeneration, ALS, and Huntington’s disease) for which there is presently a paucity of information.

Figure 4

A graphical abstract showing the effects of photobiomodulation (PBM) in neurodegenerative diseases (neurotrophic factors secretion, pathologic protein clearance, anti-apoptotic, anti-inflammatory, and improvement in blood flow) and future directions on its application (FTLD, ALS, HD).