Low-level laser (light) therapy (LLLT) is a fast-growing technology used to treat a multitude of conditions that require stimulation of healing, relief of pain and inflammation, and restoration of function.

Although skin is naturally exposed to light more than any other organ, it still responds well to red and near-infrared wavelengths. The photons are absorbed by mitochondrial chromophores in skin cells. Consequently, electron transport, adenosine triphosphate nitric oxide release, blood flow, reactive oxygen species increase, and diverse signaling pathways are activated. Stem cells can be activated, allowing increased tissue repair and healing.

In dermatology, LLLT has beneficial effects on wrinkles, acne scars, hypertrophic scars, and healing of burns. LLLT can reduce UV damage both as a treatment and as a prophylactic measure.

In pigmentary disorders such as vitiligo, LLLT can increase pigmentation by stimulating melanocyte proliferation and reduce depigmentation by inhibiting autoimmunity.

Inflammatory diseases such as psoriasis and acne can also be managed. The noninvasive nature and almost complete absence of side effects encourage further testing in dermatology.

This review will cover the use of LLLT as possibly the ultimate non-invasive approach to treating the skin.

SOURCE: US National Institute of Health’s National Library of Medicine
READ FULL TEXT: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4126803/

. . .  LLLT, phototherapy or photobiomodulation refers to the use of photons at a non-thermal irradiance to alter biological activity. LLLT uses either coherent light sources (lasers) or non-coherent light sources consisting of filtered lamps or light-emitting diodes (LED) or, on occasion, a combination of both. The main medical applications of LLLT are reducing pain and inflammation, augmenting tissue repair and promoting regeneration of different tissues and nerves, and preventing tissue damage in situations where it is likely to occur., In the last few decades, non-ablative laser therapies have been used increasingly for the aesthetic treatment of fine wrinkles, photoaged skin and scars, a process known as photorejuvenation (Table 1). More recently, this approach has also been used for inflammatory acne (Table 1). LLLT involves exposing cells or tissue to low-levels of red and near infrared (NIR) light. This process is referred to as ‘low-level’ because the energy or power densities employed are low compared to other forms of laser therapy such as ablation, cutting, and thermally coagulating tissue. Recently, medical treatment with LLLT at various intensities has been found to stimulate or inhibit an assortment of cellular processes.

The mechanism associated with the cellular photobiostimulation by LLLT is not yet fully understood. From observation, it appears that LLLT has a wide range of effects at the molecular, cellular, and tissue levels. The basic biological mechanism behind the effects of LLLT is thought to be through absorption of red and NIR light by mitochondrial chromophores, in particular cytochrome c oxidase (CCO) which is contained in the respiratory chain located within the mitochondria, and perhaps also by photoacceptors in the plasma membrane of cells. Consequently a cascade of events occur in the mitochondria, leading to biostimulation of various processes (Figure 1). Absorption spectra obtained for CCO in different oxidation states were recorded and found to be very similar to the action spectra for biological responses to the light. It is hypothesized that this absorption of light energy may cause photodissociation of inhibitory nitric oxide from CCO leading to enhancement of enzyme activity, electron transport, mitochondrial respiration and adenosine triphosphate (ATP) production (Figure 1). In turn, LLLT alters the cellular redox state which induces the activation of numerous intracellular signaling pathways, and alters the affinity of transcription factors concerned with cell proliferation, survival, tissue repair and regeneration (Figure 1).,,,, . . . .

Tissue penetration depths of various wavelengths:

. . . LED which is a novel light source for non-thermal, non-ablative skin rejuvenation has been shown to be effective for improving wrinkles and skin laxity (Figure 3). It is not a new phenomenon since the first reports of LLLT effects on increased collagen go back to 1987. Studies by Abergel et al. and Yu et al. reported an increase in production of pro-collagen, collagen, basic fibroblast growth factors (bFGF) and proliferation of fibroblasts after exposure to low-energy laser irradiation in vitro and in vivo animal models (Figure 4)., Furthermore, LLLT was already known to increase microcirculation, vascular perfusion in the skin, alter platelet-derived growth factor (PDGF), transforming growth factor (TGF-β1) and inhibit apoptosis (Figure 4).,,   . . .

. . . Phototherapy (light, lasers, and photodynamic therapy) has been proposed as an alternative therapeutic modality to treat acne vulgaris and was proposed to have less side effects compared to other treatment options. Exposure of sunlight was reported to be highly effective for treatment of acne with efficacy up to 70%. The sunlight decreases the androgenic hormones in the sebaceous gland, but the unwanted effect of exposure to UVA and UVB limits sunlight for the treatment of acne. Recently, phototherapy with visible light (mainly blue light, red light or combination of both) started being used in the treatment of acne (Figure 3). One mechanism of action of phototherapy for acne is through the absorption of light (specifically blue light) by porphyrins that have been produced by P. acnes as a part of its normal metabolism, and that act as endogenous photosensitizers. , This process causes a photochemical reaction and forms reactive free radicals and Singlet oxygen species which in turn lead to bacterial destruction (Figure 5)., Red light is known to penetrate deeper in tissues when compared to blue light. It has been demonstrated that red light can affect the sebum secretion of sebaceous glands and change keratinocyte behavior. Furthermore, red light might also exert its effects by modulating cytokines from macrophages and other cells, which in turn could reduce inflammation.,. . . 

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