Examining communication between ultraviolet (UV)-damaged cutaneous nerve cells and epidermal keratinocytes in vitro

The exposure of the skin to Ultraviolet (UV) radiation is a stressful event and the skin has multiple innate defense mechanisms to counter this threat. For instance, oxidatively damaged nerve cells will express neuroglobin, a hexa-coordinate heme protein, to scavenge free radicals such as nitric oxide (NO). Likewise, keratinocytes will express various anti-oxidant enzymes such as superoxide dismutase (SOD), which will defend the cells against oxidative threats. Nonetheless, cells will still express free radicals during excessive irradiation. A fundamental question that needs to be asked is: what do these cells communicate to one another during such stressful events? This paper will present results of an in vitro study in which dorsal root ganglion were irradiated with UV radiation to elicit oxidative events such as release of NO and calcitonin gene-related peptide (CGRP), a potent neuropeptide. Cell survival was also examined using the standard MTT assay. A plant-based neuroglobin mimic called phytoglobin was used as an NO scavenger to see if control of NO would influence CGRP expression and cell survival. Results of this study demonstrate that control of NO expression in irradiated nerve cells can influence CGRP expression and can also increase cell survival rates. Following this preliminary study, controlled amounts of the nerve cell growth media were added to cultures of normal human keratinocytes and the keratinocytes were allowed to interact with the nerve cell media for 24 h. Following this treatment period, human microarrays were run on the keratinocytes to see what genes were influenced in the keratinocytes as a result of contact with the irradiated nerve cell growth media. It was found that several critical genes expressed by the keratinocytes including NO synthase (NOS1), superoxide dismutase 1 (SOD1), transglutaminase 1 and 3 (TGM1 and TGM3), metallopeptidase inhibitor 1 (TIMP1), and filaggrin (FLG) were clearly influenced by the damaged nerve cells.