Beta-adrenoceptor blockade delays granulation tissue formation in polyurethane sponge implants

Deletion of the α2A/α2C-adrenoceptors accelerates cutaneous wound healing in mice

The α2-adrenoceptors regulate the sympathetic nervous system, controlling presynaptic catecholamine release. However, the role of the α2-adrenoceptors in cutaneous wound healing is poorly understood. Mice lacking both the α2A/α2C-adrenoceptors were used to evaluate the participation of the α2-adrenoceptor during cutaneous wound healing. A full-thickness excisional lesion was performed on the dorsal skin of the α2A/α2C-adrenoceptor knockout and wild-type mice. Seven or fourteen days later, the animals were euthanized and the lesions were formalin-fixed and paraffin-embedded or frozen. Murine skin fibroblasts were also isolated from α2A/α2C-adrenoceptor knockout and wild-type mice, and fibroblast activity was evaluated. The in vivo study demonstrated that α2A/α2C-adrenoceptor depletion accelerated wound contraction and re-epithelialization. A reduction in the number of neutrophils and macrophages was observed in the α2A/α2C-adrenoceptor knockout mice compared with wild-type mice. In addition, α2A/α2C-adrenoceptor depletion enhanced the levels of nitrite and hydroxyproline, and the protein expression of transforming growth factor-β and vascular endothelial growth factor. Furthermore, α2A/α2C-adrenoceptor depletion accelerated blood vessel formation and myofibroblast differentiation. The in vitro study demonstrated that skin fibroblasts isolated from α2A/α2C-adrenoceptor knockout mice exhibited enhanced cell migration, α-smooth muscle actin _protein expression and collagen deposition compared with wild-type skin fibroblasts. In conclusion, α2A/α2C-adrenoceptor deletion accelerates cutaneous wound healing in mice.

Propranolol impairs the closure of pressure ulcers in mice

AIMS

β-Adrenoceptors modulate acute wound healing; however, few studies have shown the effects of β-adrenoceptor blockade on chronic wounds. Therefore, this study investigated the effect of β1-/β2-adrenoceptor blockade in wound healing of pressure ulcers.

MAIN METHODS

Male mice were daily treated with propranolol (β1-/β2-adrenoceptor antagonist) until euthanasia. One day after the beginning of treatment, two cycles of ischemia-reperfusion by external application of two magnetic plates were performed in skin to induce pressure ulcer formation.

KEY FINDINGS

Propranolol administration reduced keratinocyte migration, transforming growth factor-β protein expression, re-epithelialization, and necrotic tissue loss. Neutrophil number and neutrophil elastase protein expression were increased in propranolol-treated group when compared with control group. Propranolol administration delayed macrophage mobilization and metalloproteinase-12 protein expression and reduced monocyte chemoattractant protein-1 protein expression. Myofibroblastic differentiation, angiogenesis, and wound closure were delayed in the propranolol-treated animals. Propranolol administration increased neo-epidermis thickness, reduced collagen deposition, and enhanced tenascin-C expression resulting in the formation of an immature and disorganized collagenous scar.

SIGNIFICANCE

β1-/β2-Adrenoceptor blockade delays wound healing of ischemia-reperfusion skin injury through the impairment of the re-epithelialization and necrotic tissue loss which compromise wound inflammation, dermal reconstruction, and scar formation.

Cutaneous wound healing of chronically stressed mice is improved through catecholamines blockade

Stress impairs cutaneous wound healing; however, it is unclear how beta-adrenoceptors participates in alterations induced by stress on skin wound repair. Therefore, the aim of this study was to investigate the effects of propranolol, a non-selective beta-blocker, administration on cutaneous wound healing of chronically stressed mice. Male mice were spun at 115 rpm for 15 min every hour from three days before wounding until euthanasia. Control animals were not submitted to stress. Stressed and control animals were treated with propranolol dissolved in water; controls received only water. Propranolol administration began one day before wounding and was continued daily until euthanasia. A full-thickness excisional lesion was performed. Seven and fourteen days later, animals were killed, and lesions were formalin-fixed and paraffin-embedded. Sections were stained with hematoxylin-eosin and immunostained against F4/80 to quantify macrophages, alpha-smooth muscle actin to quantify the myofibroblast density and proliferating cell nuclear antigen to quantify the cell proliferation. Furthermore, matrix metalloproteinases (MMP)-2 and MMP-9 activity, nitrite and hydroxyproline levels and tumor necrosis factor-alpha (TNF-alpha) expression were measured in wound. Stress and control + propranolol groups presented a delay in wound contraction, re-epithelialization, F4/80-positive macrophages, neutrophils and mast cells infiltration, cellular proliferation, angiogenesis, myofibroblastic differentiation, MMP-2 and MMP-9 activation and TNF-alpha expression, whereas an increase in the nitrite levels. Stress + propranolol group presented results similar to control group. In conclusion, stress impairs cutaneous wound healing in mice through beta1- adrenoceptors and beta2-adrenoceptors activation.