Stress-Mediated Increases in Systemic and Local Epinephrine Impair Skin Wound Healing: Potential New Indication for Beta Blockers

Abstract

BackgroundStress, both acute and chronic, can impair cutaneous wound repair, which has previously been mechanistically ascribed to stress-induced elevations of cortisol. Here we aimed to examine an alternate explanation that the stress-induced hormone epinephrine directly impairs keratinocyte motility and wound re-epithelialization. Burn wounds are examined as a prototype of a high-stress, high-epinephrine, wound environment. Because keratinocytes express the β2-adrenergic receptor (β2AR), another study objective was to determine whether β2AR antagonists could block epinephrine effects on healing and improve wound repair.Methods and FindingsMigratory rates of normal human keratinocytes exposed to physiologically relevant levels of epinephrine were measured. To determine the role of the receptor, keratinocytes derived from animals in which the β2AR had been genetically deleted were similarly examined. The rate of healing of burn wounds generated in excised human skin in high and low epinephrine environments was measured. We utilized an in vivo burn wound model in animals with implanted pumps to deliver β2AR active drugs to study how these alter healing in vivo. Immunocytochemistry and immunoblotting were used to examine the up-regulation of catecholamine synthetic enzymes in burned tissue, and immunoassay for epinephrine determined the levels of this catecholamine in affected tissue and in the circulation. When epinephrine levels in the culture medium are elevated to the range found in burn-stressed animals, the migratory rate of both cultured human and murine keratinocytes is impaired (reduced by 76%, 95% confidence interval [CI] 56%–95% in humans, p < 0.001, and by 36%, 95% CI 24%–49% in mice, p = 0.001), and wound re-epithelialization in explanted burned human skin is delayed (by 23%, 95% CI 10%–36%, p = 0.001), as compared to cells or tissues incubated in medium without added epinephrine. This impairment is reversed by β2AR antagonists, is absent in murine keratinocytes that are genetically depleted of the β2AR, and is reproduced by incubation of keratinocytes with other β2AR-specific agonists. Activation of the β2AR in cultured keratinocytes signals the down-regulation of the AKT pathway, accompanied by a stabilization of the actin cytoskeleton and an increase in focal adhesion formation, resulting in a nonmigratory phenotype. Burn wound injury in excised human skin also rapidly up-regulates the intra-epithelial expression of the epinephrine synthesizing enzyme phenylethanolamine-N-methyltransferase, and tissue levels of epinephrine rise dramatically (15-fold) in the burn wounded tissue (values of epinephrine expressed as pg/ug protein ± standard error of the mean: unburned control, 0.6 ± 0.36; immediately postburn, 9.6 ± 1.58; 2 h postburn, 3.1 ± 1.08; 24 h post-burn, 6.7 ± 0.94). Finally, using an animal burn wound model (20% body surface in mice), we found that systemic treatment with βAR antagonists results in a significant increase (44%, 95% CI 27%–61%, p < 0.00000001) in the rate of burn wound re-epithe...

Adrenergic Signaling in Human Oral Keratinocytes and Wound Repair

“…While the role of adrenergic signaling has been investigated in skin and corneal epithelia (Chen et al, 2002;Pullar et al, 2006bPullar et al, , 2007Ghoghawala et al, 2008;Sivamani et al, 2009b), surprisingly, this receptor-mediated signaling pathway has not been explored in oral epithelium. Here, we demonstrate for the first time the existence of an adrenergic receptor signaling pathway in oral epithelial keratinocytes, report on the consequences of receptor activation and blockade, and suggest a role for endogenous catecholamine ligands in the physiology of healing wounds within the oral cavity.…”

“…β 2 -AR blockade with receptor-specific antagonists reverses this effect and also, even in the absence of exogenously added agonists, accelerates wound healing in vitro (Pullar et al, 2006b) and in vivo in wound models (Ghoghawala et al, 2008;Sivamani et al, 2009b). AR antagonists, notably to the β 2 -AR, have therefore been proposed as therapeutic agents to improve healing, and are currently used in the care of burn wound patients (Pereira et al, 2007;Zhang et al, 2009).…”

Live Imaging of Protein Kinase Activities in Transgenic Mice Expressing FRET Biosensors

“…This observation suggested that the immediate response in PKA was caused by heat, and that the sustained activation was the result of chemical mediators. Epinephrine, for example, is known to activate PKA via the β2-adrenergic receptor in keratinocytes (Sivamani et al, 2009). In transgenic mice expressing the negative control FRET biosensor, no increase in FRET/CFP ratio was observed in the squamous epithelium (Fig.…”

Preventing, minimizing, and managing pain in patients with chronic wounds: challenges and solutions

“…Raised levels of cortisol can also lead to myopathy, fatigue, weakness, and a decrease in immune function. 11 In a study of patients with acute surgical wounds, Broadbent et al 12 found that a high level of preoperative stress was associated with reduced levels of proinflammatory cytokines, which are essential in clearing debris and infection. In a sample of patients undergoing gastric bypass surgery, McGuire et al 13 revealed that persistent postsurgery pain was an important predictor of healing time.…”