Low-Dose Propranolol Improves Cutaneous Wound Healing of Burn-Injured Rats:

Mechanism and application of β-adrenoceptor blockers in soft tissue wound healing

Soft tissue damage stimulates sympathetic nerves to release large amounts of catecholamine hormones which bind to β-adrenergic receptors (β-ARs) on the cell membrane surface. It activates the downstream effector molecules and impairs soft tissue wound healing. β-blockers specifically inhibit β-ARs activation in acute/chronic skin lesions and ulcerative hemangiomas. They also accelerate soft tissue wound healing by shortening the duration of inflammation, speeding keratinocyte migration and reepithelialization, promoting wound contraction and angiogenesis, and inhibiting bacterial virulence effects. In addition, β-blockers shorten wound healing periods in patients with severe thermal damage by reducing the hypermetabolic response. While β-blockers promote/inhibit corneal epithelial cell regeneration and restores limbal stem/progenitor cells function, it could well accelerate/delay corneal wound healing. Given these meaningful effects, a growing number of studies are focused on examining the efficacy and safety of β-blockers in soft tissue wound repair, including acute and chronic wounds, severe thermal damage, ulcerated infantile hemangioma, corneal wounds, and other soft tissue disorders. However, an intensive investigation on their acting mechanisms is imperatively needed. The purpose of this article is to summerize the roles of β-blockers in soft tissue wound healing and explore their clinical applications.

In Vivo Study of the Effects of Propranolol, Timolol, and Minoxidil on Burn Wound Healing in Wistar Rats

Propranolol, timolol, and minoxidil have all shown benefits in treatment of burn injury and other skin wounds. The study evaluated their effects on full-thickness thermal skin burns in a Wistar rat model. Performed on 50 female rats; two dorsal skin burns were created on each animal. On the next day, the rats were divided into 5 groups (n = 10); each has received a specific treatment daily for 14 days: group I-topical vehicle (control), group II-topical silver sulfadiazine (SSD), group III-oral propranolol (5.5 mg) associated with topical vehicle, group IV-topical timolol 1% cream, and group V-topical minoxidil 5% cream. Wound contraction rates, malondialdehyde (MDA), glutathione (GSH, GSSG), and catalase activity in skin and/or serum were evaluated, and histopathological analyses were performed. Propranolol did not show advantages in necrosis prevention and wound contraction and healing, and did not reduce oxidative stress. It impaired keratinocyte migration, and promoted ulceration, chronic inflammation, and fibrosis, yet reducing the necrotic zone. Timolol prevented necrosis and promoted contraction and healing, increased antioxidant capacity and promoted keratinocyte migration and neo capillarization in comparison to the other treatments. Minoxidil reduced necrosis and enhanced contraction, resulting in positive outcomes after 1 week of treatment regarding local antioxidant defense, keratinocyte migration, neo capillarization, chronic inflammation, and fibrosis rates. However, after 2 weeks, it resulted in contrasting outcomes. In conclusion, topical timolol promoted wound contraction and healing, reducing local oxidative stress and improving keratinocyte migration, bringing arguments for potential benefits in skin epithelization.

Efficacy of stromal vascular fraction and enzyme-free mechanical isolation therapy in experimental full thickness burn wounds

BACKGROUND

Autologous cell suspensions obtained by a stromal vascular fraction (SVF) and enzyme-free mechanical isolation (EMI) are an alternative in the treatment of burn wounds. In this study, we aimed to investigate the effect of autologous cell suspensions obtained by SVF and EMI on full-thickness skin burn wounds.

METHODS

A total of 45 male Sprague-Dawley rats were divided into three groups, SVF group, EMI group, and SVF + EMI group. The groups were also classified as the first, second, and third week of the burn to reveal the effect of the treatment on the burn in the early, middle, and late stages. For treatment, 0.2 ml SVF or 0.2 ml EMI was injected subcutaneously into the burn lesions of the subjects. Histopathological examination was performed on the burn wounds taken at the end of the experiment, and Ki67, CD44, CD73, CD90, and CK17 expressions were evaluated.

RESULTS

Histological examination revealed that there was no improvement in the control samples, but the skin was multicellular, vascularization was present. Histologic scores in all groups was significantly better than control, and SVF + EMI was the best group in terms of recovery (p < 0.05). Ki67, CK17, CD44, CD73, and CD90 expressions were significantly higher in the treatment groups compared to the control (p < 0.05).

CONCLUSION

We found in our study that both applications significantly increased the healing of the burn wound. Moreover, SVF + EMI application provided more improvement than SVF or EMI alone.

The use of propranolol in adult burn patients: Safety and outcome influence

OBJECTIVES

This study investigated safety and effect of propranolol on adult patients with severe burn.

METHODS

A prospective study was conducted on 124 severely adult burn patients who were randomly divided into propranolol and non-propranolol group. Propranolol was given by nasogastric tube to achieve the target of lowering 15-20% of initial heart rate.

RESULTS

Average dose of propranolol was 1.9 ± 0.5 mg/kg/day ranging from 0.9 to 3.3 mg/kg/day and was not affected by burn extent and inhalation injury. Mean heart rate reduced by 21.2% during the 28 day period. Recorded adverse events included hypotension (11.9%), bradycardia (1.6%), hypoglycemia (17.7%) and total number of held events was 8 occurring in 7 (11.3%) patients. Serum levels of glucose, total protein, albumin, cholesterol and triglyceride at different times were not significantly different between the two groups. Significantly lower resting energy expenditure on the 7^th and 14^th day were seen in propranolol group (p < 0.05). After 3 weeks, liver size in the propranolol group did not change significantly from admission, while in the non-propranolol group, liver size increased significantly (p < 0.05). The complete healing time of partial-thickness burns and donor sites were significantly shorter in propranolol group (p < 0.01). Duration of ventilation, length of stay in intensive care unit and in hospital, number of operations, rate of multiple organ failure, and death were not different between the two groups (p > 0.05).

CONCLUSION

For severely burned adults, propranolol was safe and effective on reducing energy expenditure, limited hepatomegaly, and accelerated partial burn wound and donor site closure, but does not affect length of stay in ICU, hospitalization, complication ormortality rate.

A case series of platelet rich plasma in chronic venous ulcers

INTRODUCTION

Venous ulcers are the most common type of leg wounds (80%) and the main cause is chronic venous insufficiency. Autologous platelet-rich plasma (PRP) is a potential wound healing treatment due to its great variety of growth factors. The aim of this study was to describe in a case series the results of poor-leukocyte PRP (P-PRP) or saline for the treatment of chronic non-healing ulcers of the lower extremity.

METHODS

Eight patients were treated according to the topical therapy: saline solution or P-PRP gel. All patients used double compression stocks and were assisted by a vascular practitioner for up to 12 months or until wound healing. The treatment was performed weekly with cleaning of the affected area, macroscopic evaluation (area measurement and photos) and P-PRP or saline application, and closure with Tegaderm®. Trial Registration: Retrospectively approved by Brazilian Clinical Trials, register number RBR-7zhgb3 (http://www.ensaiosclinicos.gov.br/rg/RBR-7zhgb3/).

RESULTS

All patients showed signs of wound healing with a reduction in wound size and ulcer numbers, but more evident with P-PRP application.

CONCLUSIONS

The results suggested that P-PRP presented a better result when compared to saline solution in the healing process of long clinical course chronic venous ulcers, when associated to compressive stocks and topical care.

Beta-Adrenergic Blockade in Critical Illness

Catecholamine upregulation is a core pathophysiological feature in critical illness. Sustained catecholamine β-adrenergic induction produces adverse effects relevant to critical illness management. β-blockers (βB) have proposed roles in various critically ill disease states, including sepsis, trauma, burns, and cardiac arrest. Mounting evidence suggests βB improve hemodynamic and metabolic parameters culminating in decreased burn healing time, reduced mortality in traumatic brain injury, and improved neurologic outcomes following cardiac arrest. In sepsis, βB appear hemodynamically benign after acute resuscitation and may augment cardiac function. The emergence of ultra-rapid βB provides new territory for βB, and early data suggest significant improvements in mitigating atrial fibrillation in persistently tachycardic septic patients. This review summarizes the evidence regarding the pharmacotherapeutic role of βB on relevant pathophysiology and clinical outcomes in various types of critical illness.

The Adrenergic System in Plastic and Reconstructive Surgery: Physiology and Clinical Considerations

ABSTRACT

The primary organ systems and tissues concerning plastic and reconstructive surgery include the integument, vasculature, subcutis, and peripheral nerves, because these may individually or collectively be injured requiring reconstruction, or indeed be used in reconstruction themselves through grafts, flaps, or anastomoses. Adrenergic receptors are present throughout these anatomic components on the vasculature, adipose, platelets, immune cells, keratinocytes, melanocytes, fibroblasts, peripheral nerves, and tendons. Herein, the influence of adrenergic signaling on the physiology of anatomic components related to plastic surgery is discussed, along with clinical considerations of this systems involvement in procedures, such as free flap reconstruction, skin grafting, fat grafting, and other areas relevant to plastic and reconstructive surgery. Current evidence as well as potential for further investigation is discussed.

Propranolol Is an Effective Topical and Systemic Treatment Option for Experimental Epidermolysis Bullosa Acquisita

Propranolol is an ADRB2 blocker that regulates heart muscle contractions, smooth muscle relaxation, and glycogenolysis. In addition, an increasing number of applications in dermatology have been described, most prominently, the use as a first-line treatment for infantile hemangiomas. We here show that propranolol enhances IL-8-induced neutrophil chemotaxis and reduces the release of ROS after immune complex stimulation. To obtain further molecular insights into the modulatory effects of propranolol in activated neutrophils, we performed RNA sequencing of immune complex-stimulated neutrophils in the absence and presence of the drug. We identified the transcriptomic signature of propranolol and demonstrated an ADR2-independent immunomodulatory effect. To determine if the anti-inflammatory transcriptomic signature of propranolol also translates into clinical effects, we next evaluated the impact of propranolol in a prototypical neutrophil-dependent skin disease, specifically, antibody transfer-induced epidermolysis bullosa acquisita in mice. To validate the identified propranolol gene signature obtained in human neutrophils, we analyzed a selection of genes by RT-PCR in mouse epidermolysis bullosa acquisita skin and confirmed TNF, among others, to be differentially regulated by propranolol treatment. Our data clearly indicate that, based on its molecular impact on immune complex-activated neutrophils, propranolol is a potential treatment option for neutrophil-mediated inflammatory skin diseases.

Freeze-dried versus fresh platelet-rich plasma in acute wound healing of an animal model

Aim: To compare freeze-dried and fresh platelet-rich plasma (PRP) preparations, in a pre-clinical study. Materials & methods: 30 Wistar male rats were used to compare and characterize human PRP which was applied at the perilesional area in an acute wound model, evaluated by macroscopical and histological analysis. Results: Despite the increased growth factor concentration after the freeze-drying process, no change in the healing kinetics was observed in vivo. Nevertheless, a significant increased number of myofibroblasts was demonstrated in comparison with the fresh PRP group. We also demonstrated a significant increased percentage of blood vessels in comparison with controls in both the superficial and deep epidermis. Conclusion: These results encourage randomized clinical trials to evaluate the effectiveness of freeze-dried PRP for skin ulcer treatment.

Reduced Postburn Hypertrophic Scarring and Improved Physical Recovery With Yearlong Administration of Oxandrolone and Propranolol

BACKGROUND

Massive burns induce a hypermetabolic response that leads to total body wasting and impaired physical and psychosocial recovery. The administration of propranolol or oxandrolone positively affects postburn metabolism and growth. The combined administration of oxandrolone and propranolol (OxProp) for 1 year restores growth in children with large burns. Here, we investigated whether the combined administration of OxProp for 1 year would reduce scarring and improve quality of life compared with control.

STUDY DESIGN

Children with large burns (n = 480) were enrolled into this institutional review board-approved study; patients were randomized to control (n = 226) or administration of OxProp (n = 126) for 1 year postburn. Assessments were conducted at discharge and 6, 12, and 24 months postburn. Scar biopsies were obtained for histology. Physical scar assessments and patient reported outcome measures of physical and psychosocial function were obtained.

RESULTS

Reductions in cellularity, vascular structures, inflammation, and abnormal collagen (P < 0.05) occurred in OxProp-treated scars. With OxProp, scar severity was attenuated and pliability increased (both P < 0.05). Analyses of patient-reported outcomes showed improved general and emotional health within the OxProp-treated group (P < 0.05).

CONCLUSIONS

Here, we have shown improvements in objective and subjective measures of scarring and an increase in overall patient-reported physical function. The combined administration of OxProp for up to a year after burn injury should be considered for the reduction of postburn scarring and improvement of long-term psychosocial outcomes in children with massive burns.

β-Blockade use for Traumatic Injuries and Immunomodulation: A Review of Proposed Mechanisms and Clinical Evidence

Sympathetic nervous system activation and catecholamine release are important events following injury and infection. The nature and timing of different pathophysiologic insults have significant effects on adrenergic pathways, inflammatory mediators, and the host response. Beta adrenergic receptor blockers (β-blockers) are commonly used for treatment of cardiovascular disease, and recent data suggests that the metabolic and immunomodulatory effects of β-blockers can expand their use. β-blocker therapy can reduce sympathetic activation and hypermetabolism as well as modify glucose homeostasis and cytokine expression. It is the purpose of this review to examine either the biologic basis for proposed mechanisms or to describe current available clinical evidence for the use of β-blockers in traumatic brain injury, spinal cord injury, hemorrhagic shock, acute traumatic coagulopathy, erythropoietic dysfunction, metabolic dysfunction, pulmonary dysfunction, burns, immunomodulation, and sepsis.

Pathophysiologic Mechanisms and Current Treatments for Cutaneous Sequelae of Burn Wounds

Burn injuries are a pervasive clinical problem. Extensive thermal trauma can be life-threatening or result in long-lasting complications, generating a significant impact on quality of life for patients as well as a cost burden to the healthcare system. The importance of addressing global or systemic issues such as resuscitation and management of inhalation injuries is not disputed but is beyond the scope of this review, which focuses on cutaneous pathophysiologic mechanisms for current treatments, both in the acute and long-term settings. Pathophysiological mechanisms of burn progression and wound healing are mediated by highly complex cascades of cellular and biochemical events, which become dysregulated in slow-healing wounds such as burns. Burns can result in fibroproliferative scarring, skin contractures, or chronic wounds that take weeks or months to heal. Burn injuries are highly individualized owing to wound-specific differences such as burn depth and surface area, in addition to patient-specific factors including genetics, immune competency, and age. Other extrinsic complications such as microbial infection can complicate wound healing, resulting in prolonged inflammation and delayed re-epithelialization. Although mortality is decreasing with advancements in burn care, morbidity from postburn deformities continues to be a challenge. Optimizing specialized acute care and late burn outcome intervention on a patient-by-patient basis is critical for successful management of burn wounds and the associated pathological scar outcome. Understanding the fundamentals of integument physiology and the cellular processes involved in wound healing is essential for designing effective treatment strategies for burn wound care as well as development of future therapies. Published 2018. Compr Physiol 8:371-405, 2018.

Reversal of Growth Arrest With the Combined Administration of Oxandrolone and Propranolol in Severely Burned Children

BACKGROUND

The hypercatabolic response in severely burned pediatric patients is associated with increased production of catecholamines and corticosteroids, decreased formation of testosterone, and reduced strength alongside growth arrest for up to 2 years after injury. We have previously shown that, in the pediatric burned population, the administration of the testosterone analog oxandrolone improves lean body mass accretion and bone mineral content and that the administration of the β1-, β2-adrenoceptor antagonist propranolol decreases cardiac work and resting energy expenditure while increasing peripheral lean mass. Here, we determined whether the combined administration of oxandrolone and propranolol has added benefit.

METHODS

In this prospective, randomized study of 612 burned children [52% ± 1% of total body surface area burned, ages 0.5-14 years (boys); ages 0.5-12 years (girls)], we compared controls to the individual administration of these drugs, and the combined administration of oxandrolone and propranolol at the same doses, for 1 year after burn. Data were recorded at discharge, 6 months, and 1 and 2 years after injury.

RESULTS

Combined use of oxandrolone and propranolol shortened the period of growth arrest by 84 days (P = 0.0125 vs control) and increased growth rate by 1.7 cm/yr (P = 0.0024 vs control).

CONCLUSIONS

Combined administration of oxandrolone and propranolol attenuates burn-induced growth arrest in pediatric burn patients. The present study is registered at clinicaltrials.gov: NCT00675714 and NCT00239668.

The efficacy and safety of adrenergic blockade after burn injury: A systematic review and meta-analysis

BACKGROUND

The hypermetabolic state after severe burns is a major problem that can lead to several pathophysiologic changes and produce multiple sequelae. Adrenergic blockade has been widely used to reverse these changes and improve outcomes in burned patients but has not been rigorously evaluated. The aim of this systematic review was to investigate the efficacy and safety of the use of adrenergic blockade after burn injury.

METHODS

The databases MEDLINE via OVID, PubMed, EMBASE, CINAHL, Cochrane Library, and Web of Science were searched from inception to December 2014 with search terms including burns and beta-blockers with appropriate synonyms. Articles were restricted to those published in English, French, or Spanish. Randomized controlled trials, nonrandomized controlled trials, and systematic reviews were screened. After an independent screening and full-text review, 10 articles were selected, and an appraisal of risk of bias was performed.

RESULTS

From 182 articles screened, 9 randomized controlled trials and 1 nonrandomized controlled trial met the inclusion criteria. Pooled analyses were performed to calculate effect sizes and 95% confidence intervals (CIs). There was a positive effect favoring propranolol use that significantly decreased resting energy expenditure (g = -0.64; 95% CI, -0.8 to -0.5; p < 0.001) and trunk fat (g = -0.3; 95% CI, -0.4 to -0.1; p < 0.001) as well as improved peripheral lean mass (g = 0.45; 95% CI, 0.3-0.6; p < 0.001) and insulin resistance (g = -1.35; 95% CI, -2.0 to -0.6; p < 0.001). Occurrence of adverse events was not significantly different between the treated patients the and controls.

CONCLUSION

Limited evidence suggests beneficial effects of propranolol after burn injury, and its use seems safe. However, further trials on adult population with a broader range of outcome measures are warranted.

LEVEL OF EVIDENCE

Systematic review and meta-analysis, level III.

Shouldn't Propranolol Be Used to Treat All Haemangiomas?

INTRODUCTION

Infantile haemangioma is the most common childhood tumour. These tumours can cause significant functional and cosmetic problems. While there are many treatment modalities, propranolol is increasingly being recognised as the first-line treatment of problematic haemangiomas. This study investigates the use of oral propranolol for the treatment of all haemangiomas at a tertiary children's hospital.

METHOD

This is a retrospective study evaluating 15 children (3 boys and 12 girls) presenting at a tertiary children's hospital with infantile haemangioma during a 24-month period. The protocol consisted of pre-treatment ultrasonic evaluation of the lesion, followed by the commencement of propranolol therapy (2 mg/kg orally in two divided doses), with repeat imaging performed at 16-24 weeks in order to document the dimensional changes. Adverse effects of propranolol were documented. Intralesional bleomycin was utilised as a second-line modality of treatment for large or problematic haemangiomas with inadequate regression in size after oral propranolol therapy.

RESULT

Fifteen (15) patients with a mean age of 7 months (Range: 3-14 months) presented with haemangiomas. Ten patients presented with lesions affecting the head and neck region (67%). Three patients presented with an ulcerated haemangioma, which responded to propranolol and simple dressings and all healed completely. The average decrease in size between the ultrasonography procedures was 48.87%. Only one patient showed no improvement. No side effects were reported. Concomitant bleomycin treatment was reserved for large problematic haemangiomas and proved successful at speeding up the involution process.

CONCLUSION

This study suggests that propranolol become the first-line treatment of choice for all haemangiomas. It has proven to be effective and safe for reducing the size of all haemangiomas during the proliferative phase.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Neuroendocrine regulation of inflammation

The interaction between the sympathetic nervous system and the immune system has been documented over the last several decades. In this review, the neuroanatomical, cellular, and molecular evidence for neuroimmune regulation in the maintenance of immune homeostasis will be discussed, as well as the potential impact of neuroimmune dysregulation in health and disease.

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.

β-Adrenoceptors differentially regulate vascular tone and angiogenesis of rat aorta via ERK1/2 and p38

β-Adrenoceptors (β-ARs) modulate ERK1/2 and p38 in different cells, but little is known about the contribution of these signaling pathways to the function of β-ARs in vascular tissue. Immunoblotting analysis of rat aortic rings, primary endothelial (ECs) and smooth muscle cells (SMCs) isolated from aorta showed that β-AR stimulation with isoprenaline activated p38 in aortic rings and in both cultured cell types, whereas it had a dual effect on ERK1/2 phosphorylation, decreasing it in ECs while increasing it in SMCs. These effects were reversed by propranolol, which by itself increased p-ERK1/2 in ECs. Isoprenaline β-AR mediated vasodilation of aortic rings was potentiated by the ERK1/2 inhibitor, U0126, in the presence or absence of endothelium or L-NAME, whereas inhibition of p38 had no impact. Isoprenaline moderately decreased sprouting from aorta rings in the Matrigel angiogenesis assay; conversely propranolol not only prevented isoprenaline inhibition, but stimulated angiogenesis. ERK1/2 inhibition decreased angiogenesis, while a dramatic stimulation was observed by p38 blockade. Our results suggest that ERK1/2 activation after β-ARs stimulation in the smooth muscle hinders the vasodilator effect of isoprenaline, but in the endothelium β-ARs decreases ERK1/2 and increases p38 activity reducing therefore angiogenesis.

Stromal vascular fraction improves deep partial thickness burn wound healing

OBJECTIVE

The practice of early burn wound excision and wound closure by immediate autologous skin or skin substitutes is the preferred treatment in extensive deep partial and full-thickness burns. To date there is no proven definite medical treatment to decrease burn wound size and accelerate burn wound healing in modern clinical practice. Stromal vascular fraction is an autologous mixture that has multiple proven beneficial effects on different kinds of wounds. In our study, we investigated the effects of stromal vascular fraction on deep partial-thickness burn wound healing.

METHODS

In this study, 20 Wistar albino rats were used. Inguinal adipose tissue of the rats was surgically removed and stromal vascular fraction was isolated. Thereafter, deep second-degree burns were performed on the back of the rats by hot water. The rats were divided into two groups in a randomized fashion. The therapy group received stromal vascular fraction, whereas the control group received only physiologic serum by intradermal injection. Assessment of the burn wound healing between the groups was carried out by histopathologic and immuno-histochemical data.

RESULTS

Stromal vascular fraction increased vascular endothelial growth factor, proliferating cell nuclear antigen index, and reduced inflammation of the burn wound. Furthermore, vascularization and fibroblastic activity were achieved earlier and observed to be at higher levels in the stromal vascular fraction group.

CONCLUSIONS

Stromal vascular fraction improves burn wound healing by increasing cell proliferation and vascularization, reducing inflammation, and increasing fibroblastic activity.

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.

The endocrine response to severe burn trauma

The endocrine system is frequently altered after a major burn trauma. Besides the endocrine response to stress characterized by hypercortisolism, several hypothalamus-hypophysis-target gland axes are rapidly perturbed within a few days. These alterations can persist in the long term and deserve an appropriate treatment. Disturbances in water clearance and glucidic metabolism are also common and need to be diagnosed and corrected to decrease morbidity in such patients. Bone and mineral metabolism is deeply compromised and requires correction of mineral abnormalities in order to improve symptoms and prevent bone loss. No large prospective and/or intervention trials are available to date to elaborate age-related, evidence-based recommendations to monitor and treat burn-related endocrine alterations.

Burns: an update on current pharmacotherapy

INTRODUCTION

The worldwide occurrence of burn injuries remains high despite efforts to reduce injury incidence through public awareness campaigns and improvements in living conditions. In 2004, almost 11 million people experienced burns severe enough to warrant medical treatment. Advances over the past several decades in aggressive resuscitation, nutrition, excision and grafting have reduced morbidity and mortality. Incorporation of pharmacotherapeutics into treatment regimens may further reduce complications of severe burn injuries.

AREAS COVERED

Severe burn injuries, as well as other forms of stress and trauma, trigger a hypermetabolic response that, if left untreated, impedes recovery. In the past two decades, use of anabolic agents, β-adrenergic receptor antagonists and anti-hyperglycemic agents has successfully counteracted post-burn morbidities including catabolism, the catecholamine-mediated response and insulin resistance. Here, the authors review the most up-to-date information on currently used pharmacotherapies in the treatment of these sequelae of severe burns and the insights that have expanded the understanding of the pathophysiology of severe burns.

EXPERT OPINION

Existing drugs offer promising advances in the care of burn injuries. Continued gains in the understanding of the molecular mechanisms driving the hypermetabolic response will enable the application of additional existing drugs to be broadened to further attenuate the hypermetabolic response.

Propranolol treatment of infantile hemangioma endothelial cells: A molecular analysis

Infantile hemangiomas (IHs) are non-malignant, largely cutaneous vascular tumors affecting approximately 5-10% of children to varying degrees. During the first year of life, these tumors are strongly proliferative, reaching an average size ranging from 2 to 20 cm. These lesions subsequently stabilize, undergo a spontaneous slow involution and are fully regressed by 5 to 10 years of age. Systemic treatment of infants with the non-selective β-adrenergic receptor blocker, propranolol, has demonstrated remarkable efficacy in reducing the size and appearance of IHs. However, the mechanism by which this occurs is largely unknown. In this study, we sought to understand the molecular mechanisms underlying the effectiveness of β blocker treatment in IHs. Our data reveal that propranolol treatment of IH endothelial cells, as well as a panel of normal primary endothelial cells, blocks endothelial cell proliferation, migration, and formation of the actin cytoskeleton coincident with alterations in vascular endothelial growth factor receptor-2 (VEGFR-2), p38 and cofilin signaling. Moreover, propranolol induces major alterations in the protein levels of key cyclins and cyclin-dependent kinase inhibitors, and modulates global gene expression patterns with a particular affect on genes involved in lipid/sterol metabolism, cell cycle regulation, angiogenesis and ubiquitination. Interestingly, the effects of propranolol were endothelial cell-type independent, affecting the properties of IH endothelial cells at similar levels to that observed in neonatal dermal microvascular and coronary artery endothelial cells. This data suggests that while propranolol markedly inhibits hemangioma and normal endothelial cell function, its lack of endothelial cell specificity hints that the efficacy of this drug in the treatment of IHs may be more complex than simply blockage of endothelial function as previously believed.

Urinary matrix metalloproteinases-2/9 in healthy infants and haemangioma patients prior to and during propranolol therapy

The mechanism of therapeutic success of propranolol for severe infantile haemangioma remains unclear. Propranolol was shown to modify matrix metalloproteinase (MMP) levels, which are associated with tumour pathogenesis. We hypothesized that urinary MMP2/9 is higher in patients with infantile haemangioma compared to healthy infants and that propranolol reduces MMP2/9 levels and thus leads to an involution of the haemangioma. In this case, MMP2/9 could be used as a marker of indicated therapy or therapeutic success. Urinary samples were taken before, 2 weeks after, and 2 months after the beginning of propranolol treatment in haemangioma patients and once in healthy controls. Activity of MMP2/9 was determined by commercially available activity kits. Urine of 22 haemangioma patients and 21 control subjects was obtained. Propranolol therapy had significant success in all patients. MMP2/9 was present in most samples, the younger the children the higher the MMP2 levels. Haemangioma patients showed lower levels of MMP2. The MMP2 levels were significantly higher after 2 weeks of propranolol than prior to therapy. There were no differences in MMP9 levels.

CONCLUSIONS

Presence of MMP2/9 in the urine of infants <1 year can be explained by high rate of physiological tissue remodelling. Unexpectedly, MMP2 was lower in the urine of haemangioma patients and higher 2 weeks after propranolol treatment. Taking this and the diverse results in literature into account, the correlation between MMPs, proliferation, and regression of haemangiomas and propranolol remains unclear.

β2AR antagonists and β2AR gene deletion both promote skin wound repair processes

Skin wound healing is a complex process requiring the coordinated, temporal orchestration of numerous cell types and biological processes to regenerate damaged tissue. Previous work has demonstrated that a functional β-adrenergic receptor autocrine/paracrine network exists in skin, but the role of β2-adrenergic receptor (β2AR) in wound healing is unknown. A range of in vitro (single-cell migration, immunoblotting, ELISA, enzyme immunoassay), ex vivo (rat aortic ring assay), and in vivo (chick chorioallantoic membrane assay, zebrafish, murine wild-type, and β2AR knockout excisional skin wound models) models were used to demonstrate that blockade or loss of β2AR gene deletion promoted wound repair, a finding that is, to our knowledge, previously unreported. Compared with vehicle-only controls, β2AR antagonism increased angiogenesis, dermal fibroblast function, and re-epithelialization, but had no effect on wound inflammation in vivo. Skin wounds in β2AR knockout mice contracted and re-epithelialized faster in the first few days of wound repair in vivo. β2AR antagonism enhanced cell motility through distinct intracellular signalling mechanisms and increased vascular endothelial growth factor secretion from keratinocytes. β2AR antagonism promoted wound repair processes in the early stages of wound repair, revealing a possible new avenue for therapeutic intervention.

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.

Rotational stress-induced increase in epinephrine levels delays cutaneous wound healing in mice

Stress impairs wound healing of cutaneous lesions; however, the mechanism is still unclear. The aim of this study was to evaluate the effects of rotational stress on cutaneous wound healing in mice and propose a mechanism. Male mice were spun at 45 rpm for 15 min every hour beginning 3 days before wounding until euthanasia. Control animals were not subjected to stress. To confirm that catecholamines participate in stress-induced delay of wound healing, mice were treated daily with propranolol. An excisional lesion was created and measured. Seven and 14 days later, animals were killed and lesions collected. Sections were stained with hematoxylin-eosin and immunostained for alpha-smooth muscle actin and proliferating cell nuclear antigen. Matrix metalloproteinase (MMP)-2 and -9 activity, nitrite levels, and tumor necrosis factor-alpha (TNF-alpha) expression were measured in the wounds. In addition, murine skin fibroblast cultures were treated with high levels of epinephrine and fibroblast activity was evaluated. Stressed mice exhibited reduced locomotor activity and increased normetanephrine plasma levels. Rotational stress was associated with decreased wound contraction, reduced re-epithelialization, reduced MMP-2 and MMP-9 activation, but with strongly increased nitrite levels. Furthermore, inflammatory cell infiltration, TNF-alpha expression, myofibroblastic differentiation, and angiogenesis were all delayed in the stress group. Propranolol administration reversed the deleterious effects of stress on wound contraction and re-epithelialization. High epinephrine concentrations increased murine skin fibroblast proliferation and nitric oxide synthesis, and strongly inhibited skin fibroblast migration and both pro- and active MMP-2. In conclusion, rotational stress impairs cutaneous wound healing due to epinephrine increased levels.

The year in burns 2008

For 2008, approximately 1200 original burn research articles were published in scientific journals using the English language. This article reviews those with the most impact on burn treatment according to the Editor of one of the major journals (Burns). As in the previous year's review, articles were divided into the following topic areas: epidemiology, wound characterisation, critical care physiology, inhalation injury, infection, metabolism and nutrition, psychological considerations, pain management, rehabilitation, and burn reconstruction. Each selected article is mentioned briefly with editorial comment.

Simultaneous blockade of alpha and beta adrenoceptors impairs cutaneous wound healing in rats

BACKGROUND

Recent studies showed that propranolol administration (beta-antagonist), but not phentolamine administration (alpha-antagonist), delays cutaneous wound healing. However, alpha adrenoceptor activation may be participating in propranolol-induced alterations.

OBJECTIVE

This study aims to investigate the effects of simultaneous blockade of beta and alpha adrenoceptors on cutaneous wound healing.

METHODS

Rats were treated with propranolol plus phentolamine dissolved in water. An excisional lesion was done and measured. Lesions were formalin-fixed and paraffin-embedded 21 days after wounding. Sections were stained with haematoxylin and eosin, toluidine blue and Sirius red, and immunostained for alpha-smooth muscle actin or proliferating cell nuclear antigen.

RESULTS

Administration of propranolol plus phentolamine reduced wound contraction and re-epithelialization, but increased cellular proliferation and the number of mast cells. There was no difference in myofibroblast density, collagen fibre organization and polymorphonuclear number between the control and treated groups.

CONCLUSION

Simultaneous blockade of beta and alpha adrenoceptors impairs cutaneous wound healing. Furthermore, propranolol-induced impairment on cutaneous wound healing does not occur through alpha adrenoceptor activation.