A prospective, randomized, blind comparison between saline, calcium gluconate and diphoterine for washing skin acid injuries in rats: effects on substance P and beta-endorphin release

Activation of the δ-opioid receptor promotes cutaneous wound healing by affecting keratinocyte intercellular adhesion and migration

BACKGROUND AND PURPOSE

In addition to its analgesic functions, the peripheral opioid receptor system affects skin homeostasis by influencing cell differentiation, migration and adhesion; also, wound healing is altered in δ-opioid receptor knockout mice (DOPr^–/–). Hence, we investigated δ-opioid receptor effects on the expression of several proteins of the desmosomal junction complex and on the migratory behaviour of keratinocytes.

EXPERIMENTAL APPROACH

Expression levels of desmosomal cadherins in wild-type and DOPr^–/– mice, and the morphology of intercellular adhesion in human keratinocytes were analysed by immunofluorescence. To investigate the δ-opioid receptor activation pathway, protein expression was studied using Western blot and its effect on cellular migration determined by in vitro live cell migration recordings from human keratinocytes.

KEY RESULTS

Expression of the desmosomal cadherins, desmogleins 1 and 4, was up-regulated in skin from DOPr^–/– mice, and down-regulated in δ-opioid receptor-overexpressing human keratinocytes. The localization of desmoplakin expression was rearranged from linear arrays emanating from cell borders to puncta in cell periphery, resulting in less stable intercellular adhesion. Migration and wound recovery were enhanced in human keratinocyte monolayers overexpressing δ-opioid receptors in vitro. These δ-opioid receptor effects were antagonized by specific PKCα/β inhibition indicating they were mediated through the PKC signalling pathway. Finally, cells overexpressing δ-opioid receptors developed characteristically long but undirected protrusions containing filamentous actin and δ-opioid receptors, indicating an enhanced migratory phenotype.

CONCLUSION AND IMPLICATIONS

Opioid receptors affect intercellular adhesion and wound healing mechanisms, underlining the importance of a cutaneous neuroendocrine system in wound healing and skin homeostasis.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2

Use of a 3-D imaging technique for non-invasive monitoring of the depth of experimentally induced wounds

BACKGROUND/PURPOSE

Experimental studies of wound healing lack methods for standardized wounding and in situ depth assessment. Consequently, in this pilot study, an Erbium (Er):YAG laser has been used for wound induction with a non-invasive 3-D imaging technique as an alternative to histology.

METHODS

Erbium:YAG ablation of human skin ex vivo was performed with total fluences of 10, 50 and 200 J/cm(2), removing the stratum corneum, epidermis/papillary dermis and deeper dermis, respectively. Wound depth was measured with the 3-D method and histologically.

RESULTS

Wound depth was proportional to fluence for both techniques : 3-D, 17.7+/-1.7, 43.9+/-16 and 245.2+/-61 microm; histology, 14.6+/-1.7, 50.6+/-11.6 and 238+/-102 microm, respectively.

CONCLUSIONS

The 3-D technique compares well with and is an improvement on histological measurement, providing true wound depth measurement, avoiding shape changes inherent with histology. Furthermore, the Er:YAG laser is a highly appropriate means of wound induction due to its rapidity and precision.