Cytokines, properties and role during wound healing and response to photomodulation

Cytokine is a generic name used for a diverse group of soluble low molecular mass, biochemically distinct glycoproteins, found in most cells and tissue types. They are similar to peptide hormones since they have the ability to facilitate communication, trigger specific receptor signaling and modulate the function of various cells and tissues at a very low concentration (nano to picomolar). Being pleiotropic and functionally redundant, cytokines can be classified into six distinct groups namely, Interleukins (ILs); Colony Stimulating Factors (CSFs); Tumour Necrosis Factors (TNFs); Interferons (IFNs); Transforming Growth Factors (TGFs) and Chemokines. Cytokines undergo physiological changes during infection or tissue damage in order to play a role in defense or repair processes. Therefore, their function is to trigger cellular responses. However, there are some cytokines which can potently facilitate harmful cellular responses; but there are also compounds, i.e. antagonists, that can prevent or limit such harmful effects. Controlled release of these glycoproteins into the micro-environment is essential for their mode of action, functioning and stability. Although most cytokine receptors are multi-subunit structures that bind to ligands, they also have the ability to function as signal transducers due to intrinsic Tyrosine Kinase (TK) activity. Signal transduction components can be shared by different receptors which explains functional redundancy. Various cytokines have been associated with carcinogenesis or an ability to promote cancer as well as other abnormalities. Therefore, perturbations in the production and activity of cytokines may lead to unfavorable effects on cellular homeostasis. Multiple cytokines and growth factors including Interleukin (IL)-1, IL-6 and TNF alpha (TNF-α) are involved in wound healing. In abnormal or diseased state(s) such as diabetes mellitus (DM) or psoriasis, production of these growth factors or cytokines is altered such that inflammatory cytokines are usually elevated. Phototherapy has been reported to accelerate wound healing, attenuate pain and cease inflammation. However, the effect of phototherapy on cytokine modulation has not been explored extensively, especially under various stress mechanisms. Furthermore, the pathway that Photomodulation induces pro-inflammatory cytokines has not been clearly elucidated. This chapter explores the basic classification and function of cytokines focusing on their role during diseased states such as wound healing, and finally identifies the possible contribution of Photomodulation in up-regulation of specific cytokines involved in wound healing process.