Brimonidine displays anti-inflammatory properties in the skin through the modulation of the vascular barrier function.

BACKGROUND: Rosacea is a chronic inflammatory skin disease. Characteristic vascular changes in rosacea skin include enlarged, dilated vessels of the upper dermis and blood flow increase. Brimonidine is approved for symptomatic relief of the erythema of rosacea. It acts by selectively binding to α2-adrenergic receptors present on smooth muscle in the peripheral vasculature, resulting in transient local vasoconstriction. OBJECTIVES: To provide further evidence of the anti-inflammatory potential of brimonidine across preclinical models of skin inflammation and its ability to decrease the neutrophil infiltration in human skin after ultraviolet light exposure. METHODS: The anti-inflammatory properties of brimonidine through modulation of the vascular barrier function were assessed using in vivo neurogenic vasodilation and acute inflammatory models and a well-described in vitro transmigration assay. A clinical study assessed the neutrophil infiltration in human skin after exposure to UV in 37 healthy Caucasian male subjects. RESULTS: In vitro, brimonidine affects the transmigration of human neutrophils through the endothelial barrier by modulating adhesion molecules. In vivo, in the mouse, topical treatment with brimonidine, used at a vasoconstrictive dose, confirmed its anti-inflammatory properties and prevented leucocyte recruitment (rolling and adhesion) mediated by endothelial cells. Topical pretreatment with brimonidine tartrate 0.33% gel once a day for 4 days significantly prevented neutrophil infiltration by 53.9% in human skin after exposure to UV light. CONCLUSION: Results from in vitro, in vivo and from a clinical study indicate that brimonidine impacts acute inflammation of the skin by interfering with neurogenic activation and/or recruitment of neutrophils.

Mid-infrared spectral microimaging of inflammatory skin lesions.

Skin is one of the most important organs of the human body because of its characteristics and functions. There are many alterations, either pathological or physiological, that can disturb its functioning. However, at present all methods used to investigate skin diseases, non-invasive or invasive, are based on clinical examinations by physicians. Thus, diagnosis, prognosis and therapeutic management rely on the expertise of the practitioner, the quality of the method and the accessibility of distinctive morphological characteristics of each lesion. To overcome the high sensitivity of these parameters, techniques based on more objective criteria must be explored. Vibrational spectroscopy has become as a key technique for tissue analysis in the biomedical research field. Based on a non-destructive light/matter interaction, this tool provides information about specific molecular structure and composition of the analyzed sample, thus relating to its precise physiopathological state and permitting to distinguish lesional from normal tissues. This label-free optical method can be performed directly on the paraffin-embedded tissue sections without chemical dewaxing. In this study, the potential of the infrared microspectroscopy, combined with data classification methods was demonstrated, to characterize at the tissular level different types of inflammatory skin lesions, and this independently from conventional histopathology.

Topical Treatment of Rosacea with Ivermectin Inhibits Gene Expression of Cathelicidin Innate Immune Mediators, LL-37 and KLK5, in Reconstructed and Ex Vivo Skin Models.

INTRODUCTION: Numerous intrinsic and extrinsic factors have been associated with the pathophysiology of rosacea, including dysregulation of innate immunity. A high level of cathelicidin antimicrobial peptides (e.g., LL-37) has been shown in the facial skin of patients with rosacea. Excessive production of both LL-37 and KLK5, the serine protease responsible for its cleavage, has been suggested to play a role in the pathophysiology of rosacea. Ivermectin 10 mg/g cream, indicated for the treatment of inflammatory lesions of rosacea, is reported to have dual anti-parasitic and anti-inflammatory properties. However, the exact mechanism of action of ivermectin cream in the treatment of rosacea is unknown. METHODS: This study aimed to evaluate the effect of ivermectin on the expression of KLK5 and the subsequent effect on the maturation process of cathelicidins. Experimental studies were performed either on normal human epidermal keratinocytes (NHEK), reconstructed human epidermis (RHE) or on human skin ex vivo stimulated with calcitriol (1α,25-dihydroxyvitamin D3), which is known to induce KLK5 and LL-37 expression. RESULTS: The results show that ivermectin is able to inhibit KLK5 and CAMP gene expression and protein secretion in NHEK cells stimulated with calcitriol. Those results were confirmed in 3D models of the skin (RHE and skin ex vivo). The anti-inflammatory effects of ivermectin were associated with an inhibition of IL-8, IL-6 and MCP-1 (CCL2) secretion from NHEK cells. CONCLUSIONS: These results suggest that ivermectin can prevent the inflammatory effects of rosacea triggered by abnormal LL-37 processing, through the inhibition of KLK5 gene expression in the epidermis. FUNDING: Nestlé Skin Health R&D.

Adaptation of the validated SkinEthic Reconstructed Human Epidermis (RHE) skin corrosion test method to 0.5 cm2 tissue sample.

At its 25th meeting the ECVAM Scientific Advisory Committee (ESAC) unanimously endorsed that the SkinEthic Reconstructed Human Epidermis (RHE) model could be used for distinguishing between corrosive and non-corrosive chemicals within the context of the Organisation Economic for Co-operation and Development (OECD) test guideline, TG 431 (ESAC 16-17 November 2006). Both test method development and multi-center study were performed using 0.63 cm(2) RHE tissue samples. The purpose of the present study was to demonstrate that similar results could be obtained using the validated test method adapted to 0.5cm(2) RHE tissue samples. Test method adaptation only consisted in applying a reduced volume of test substance (40 microL instead of 50 microL for liquids and 20 microL water+20mg test substance instead of 25 microL water+25mg test substance for solids) and a reduced propan-2-ol extraction volume (1.5 mL instead of 2 mL) during the MTT reduction assay. The test method was assessed with 25 representative test substances of different chemical classes. Among the latter, the 12 OECD reference test substances (6 corrosives and 6 non-corrosives) were evaluated and showed to be similarly classified as in vivo. More generally, the SkinEthic skin corrosion test adapted to 0.5 cm(2) RHE tissue samples fully complies with the OECD performance and reproducibility requirements with the 25 test substances.