Stimulation of alpha-1 adrenoceptors may intensify cutaneous inflammation in complex regional pain syndrome
School of Medical and Health Sciences
Alpha-1 adrenoceptors are overexpressed in the epidermis of a subgroup of patients with complex regional pain syndrome (CRPS). Activating α1-adrenoceptors in epidermal cells increases production of the proinflammatory cytokine interleukin-6 (IL-6), a mediator of inflammation. To investigate whether this might exacerbate inflammation in CRPS, primary keratinocytes or dermal fibroblasts were cultured from skin biopsies obtained from the affected limb of 25 patients and a similar site in 28 controls. The fundamental proinflammatory cytokine, tumor necrosis factor alpha, was administered for 24 hours to initiate inflammation. After this, cells were incubated for 6 hours with the α1-adrenoceptor agonist phenylephrine. Exposure to tumor necrosis factor alpha induced proinflammatory cytokine mRNA production and protein secretion in keratinocytes and fibroblasts and enhanced α1B-adrenoceptor mRNA expression in keratinocytes. Additional stimulation of α1adrenoceptors with phenylephrine increased the production of IL-6 mRNA and protein secretion in both cell types. Under all conditions, gene and protein α1-adrenoceptor levels and cytokine gene expression and protein secretion were similar, overall, in patients and controls, except for abnormally high α1-adrenoceptor protein levels in the keratinocytes of 3 of 17 patients. These findings suggest that persistent inflammation in CRPS is not due to dysfunction of skin cells but is a normal response to extrinsic signals. After α1-adrenoceptor stimulation of keratinocytes, increases in IL-6 mRNA but not protein were proportional to basal α1-adrenoceptor protein levels. Skin cells play an important role in persistent inflammation in CRPS. Potentially, a positive feedback loop between α1-adrenoceptors and IL-6 production in skin cells contributes to this inflammatory state.
Wijaya, L. K., Morici, M. V., Stumbles, P. A., Finch, P. M., & Drummond, P. D. (2023). Stimulation of α1-adrenoceptors may intensify cutaneous inflammation in complex regional pain syndrome. Pain, 164(4), 771-781. https://doi.org/10.1097/j.pain.0000000000002764