Ultraviolet A photosensitivity profile of dexchlorpheniramine maleate and promethazine-based creams: Anti-inflammatory, antihistaminic, and skin barrier protection properties

Ex Vivo Human Skin: An Alternative Test System for Skin Irritation and Corrosion Assays

Native human skin has been reported in the literature as being an important experimental model for studying skin biology. Studies performed by our group have shown that ex vivo skin, from elective plastic surgery, maintains the biological characteristics of native skin under specific culture conditions. As such, it might be a feasible model for the safety and efficacy testing of topical substances. While Brazil is at the forefront of global regulation implementation, Brazilian researchers are not always able to transfer certain widely used protocols to their laboratories, particularly protocols that involve the use of reconstructed tissues with limited viability, such as those for skin corrosion (OECD TG 431) and irritation testing (OECD TG 439). In this study, we investigated the applicability of the ex vivo skin model to the evaluation of irritation and corrosion potential of a number of proficiency substances described in TG 431 and TG 439. The skin fragments were standardised in size and diameter, and placed into cell culture inserts. The experimental protocol was conducted according to TG 431 and TG 439. The results obtained show that ex vivo skin could represent a promising tool for the evaluation of irritation and corrosion potential of substances (subject to inclusion and exclusion criteria), as recommended by OECD guidelines. While this is a proof-of-concept study, the use of ex vivo skin should be considered for such testing.

Invitro effect of pine bark extract on melanin synthesis, tyrosinase activity, production of endothelin-1, and PPAR in cultured melanocytes exposed to Ultraviolet, Infrared, and Visible light radiation

BACKGROUND

French maritime pine bark (Pinus pinaster) extract (PBE), the registered trade name of which is Pycnogenol^® , has been studied for its depigmenting action due to its antioxidant, anti-inflammatory, and anti-melanogenic activity. However, the mechanisms through which PBE are still not fully clear.

OBJECTIVE

Evaluate the impact of PBE on four in vitro parameters closely associated with cutaneous pigmentation, including melanin synthesis, tyrosinase activity, endothelin-1 (ED1), and production of peroxisome proliferator-activated receptor α, δ, and γ (PPAR α, δ, and γ), by studying the modulation of action of ultraviolet radiation A (UVA)/ultraviolet radiation B (UVB), infrared-A (IR-A), visible light (VL), and association of UVA/UVB, IR-A, and VL (ASS).

METHODS

Human melanocytes were incubated in a dry extract solution of PBE, exposed to UVA/UVB, IR-A, VL, and ASS for subsequent quantification of melanin, ED1, and PPAR α, δ, and γ. The effects of PBE on inhibition of tyrosinase activity were also performed by monophenolase activity assay.

RESULTS

UVA/UVB, IR-A, VL, and ASS radiation caused significant increases in the synthesis of melanin, ED1, and PPAR α, δ, and γ when compared to baseline control. However, PBE significantly reduced the production of melanin, ED1, and PPAR α, δ, and γ, as well as reducing about 66.5% of the tyrosinase activity.

CONCLUSIONS

PBE reduces in vitro melanin production by downregulating tyrosinase and reducing pigmentation-related mediators, such as ED1 and PPAR α, δ, and γ, therefore contributing to the inhibition of pathways associated with skin hyperpigmentation.

The Ex Vivo Skin Model as an Alternative Tool for the Efficacy and Safety Evaluation of Topical Products

The development of alternative approaches for safety and efficacy testing that avoid the use of animals is a worldwide trend, which relies on the improvement of current models and tools so that they better reproduce human biology. Human skin from elective plastic surgery is a promising experimental model to test the effects of topically applied products. As the structure of native skin is maintained, including cell population (keratinocytes, melanocytes, Langerhans cells and fibroblasts) and dermal matrix (containing collagen, elastin, glycosaminoglycans, etc.), it most closely matches the effects of substances on in vivo human skin. In this review, we present a collection of results that our group has generated over the last years, involving the use of human skin and scalp explants, demonstrating the feasibility of this model. The development of a test system with ex vivo skin explants, of standard size and thickness, and cultured at the air–liquid interface, can provide an important tool for understanding the mechanisms involved in several cutaneous disorders.