Peeling agents and irritants, unlike tretinoin, do not stimulate collagen synthesis in the photoaged hairless mouse

Comparative effects of retinoic acid or glycolic acid vehiculated in different topical formulations

Retinoids and hydroxy acids have been widely used due to their effects in the regulation of growth and in the differentiation of epithelial cells. However, besides their similar indication, they have different mechanisms of action and thus they may have different effects on the skin; in addition, since the topical formulation efficiency depends on vehicle characteristics, the ingredients of the formulation could alter their effects. Thus the objective of this study was to compare the effects of retinoic acid (RA) and glycolic acid (GA) treatment on the hairless mouse epidermis thickness and horny layer renewal when added in gel, gel cream, or cream formulations. For this, gel, gel cream, and cream formulations (with or without 6% GA or 0.05% RA) were applied in the dorsum of hairless mice, once a day for seven days. After that, the skin was analyzed by histopathologic, morphometric, and stereologic techniques. It was observed that the effects of RA occurred independently from the vehicle, while GA had better results when added in the gel cream and cream. Retinoic acid was more effective when compared to glycolic acid, mainly in the cell renewal and the exfoliation process because it decreased the horny layer thickness.

Safety Evaluation and Anti-wrinkle Effects of Retinoids on Skin

Retinoids have many beneficial effects on dermatological applications. But, retinoids cause skin irritation. In this study, the safety of retinoids was clarified via both primary skin irritation test in rabbits and sensitization study using an integrated model for the differentiation of chemical-induced allergic and irritant skin reaction (IMDS) , an alternative method to sensitization test. The effects of retinoids on the change of ultraviolet A (UVA) -induced matrix metalloproteinase-1 (MMP-1) in human skin fibroblasts and the modulation of type-1 pN collagen synthesis in hairless mice were examined to clarify the anti-wrinkle effects. All-trans retinol (t-ROL) and its derivative, all-trans retinoic acid (t-RA) , showed mild skin irritation but did not induce the sensitization. t-ROL and t-RA exerted anti-wrinkle effects by inhibiting the UVA-induced MMP-1 in human skin fibroblasts and increasing the type-1 pN collagen synthesis in hairless mice. These findings suggest that retinoids do not induce the allergy, and show anti-wrinkle effects by decreasing MMP-1 activation and increasing collagen synthesis.

Epidermal Hyperplasia and Elevated HB-EGF are More Prominent in Retinoid Dermatitis Compared with Irritant Contact Dermatitis Induced by Benzalkonium Chloride

BACKGROUND

'Retinoid dermatitis' is a retinoid-induced irritant contact dermatitis (ICD). The mechanism of retinoid dermatitis may be different from that of other ICDs. However, it remains uncertain how topical retinoid induce ICD.

OBJECTIVE

We compared several aspects of contact dermatitis induced by topical retinol and benzalkonium chloride (BKC) on hairless mice skin.

METHODS

2% retinol or 2.5% BKC was applied to hairless mice and transepidermal water loss (TEWL), ear thickness, histologic and immunohistochemical findings were compared. We also compared mRNA expression of inflammatory cytokines, epidermal differential markers, cyclooxygenases (COXs) and heparin binding epidermal growth factor like growth factor (HB-EGF).

RESULTS

Topical application of 2% retinol and 2.5% BKC increased TEWL and ear thickness in similar intensity. Epidermal hyperplasia was more prominent in retinol treated skin. Proliferating cell nuclear antigen, involucrin and loricrin expression were higher in retinol-treated skin than in BKC-treated skin. Filaggrin, however, was more expressed in BKC-treated skin. The mRNA expression of IL-8, TNF-alpha, COX-2, involucrin, loricrin and filaggrin were increased in both retinol- and BKC-treated skin in similar intensity. HB-EGF was more significantly increased in retinol-treated skin.

CONCLUSION

Elevated HB-EGF and epidermal hyperplasia are more prominent features of retinoid dermatitis than in BKC-induced ICD.

Comparison of epidermal morphologic response to commercial antiwrinkle agents in the hairless mouse

BACKGROUND

A large number of commercial antiwrinkle and antiaging compounds are available to consumers for rejuvenation of facial skin ravaged by age or solar radiation. Experimental data on the histological effects of these commercial products in laboratory models are sparse.

OBJECTIVES

To compare the efficacy of topical application of five commercially available antiaging compounds (retinoic acid, glycolic acid, vitamin C, estrogen, and soy) on the dorsal skin.

METHODS AND MATERIALS

The effects were examined using light microscopic analysis of the epidermis in the normal nonirradiated hairless mouse. The agents were applied daily to dorsal tattooed areas for 2 weeks before histological assessment; neighboring untreated surface areas were used as control. Morphometric measurements of total epidermal width, nuclear volume of keratinocytes in three layers, and index of proliferating cell nuclear antigen according to immunohistochemistry were obtained and statistically analyzed.

RESULTS

Significant histomorphometric effects were noticed with all five agents, but more pronounced changes were obtained with glycolic acid, estrogen, and retinoic acid product.

CONCLUSIONS

These baseline data will be useful for future studies on the effect of ultraviolet radiation to cause photoaging and reparative effects of similar agents in this animal. The information contained in the report may provide guidelines to consumers and clinicians.

Some non-equilibrium phenomena in the malic acid/water/Polysorbate 81 system

Topical formulations undergo radical structural changes after application and the action on the skin is not directly related to the original structure of the formulation. This fact has been well established in the scientific literature. However, and more essential, is the fact that these changes in the formulation structure are not equilibrium ones. Especially so, with the hydroxy acids, which are widely used in cosmetic and dermatological treatment of skin. The article reports the first investigation into the non-equilibrium conditions in a hydroxy acid system. Different phases in the title system, which were not in mutual equilibrium, were brought in contact while avoiding convection. The transfer of substance between them was estimated from the changes in volume of each phase. The results showed, unexpectedly, that the systems were far from equilibrium even after prolonged times in contact. The kinetics of the changes varied to significant degree, from extremely slow, when solid phases were involved to fast for liquid phases. In one case was observed a separated layer, which was not found in the phase diagram under equilibrium conditions.

Phase behavior of beta hydroxy-acids with laureth 4

The colloidal structures of beta carboxylic acid topical vesicle formulations were determined and the changes during evaporation after applications were estimated from phase diagrams. The results showed significant difference during evaporation between salicylic acid on one hand and three water soluble acids; malic, tartaric, and citric acid, on the other. The water soluble acids showed an increase in the acid concentration in the aqueous solution to levels that must be considered harmful, while salicylic acid showed no increase in concentration in the individual phases even after 99% evaporation of water.

Combined tretinoin and glycolic acid treatment improves mouth opening for postburn patients

Postburn tissue repair progresses late, with changes in the skin's physical properties. Clinically, the skin appears dry, scaly, and dyschromic, with diminished elasticity, particularly in the presence of hypertrophic scars. Improvement of postburn skin can be obtained by using topical agents normally used in pathologies such as acne and photoaging. This study analyzed 77 patients, ages 6 to 46 years, with late perioral burn sequelae. The resulting integument was classified as grafted or restored when it epithelialized spontaneously. Topical treatment consisted of tretinoin (0.01-0.05%) and glycolic acid (5-7%) over a 3-month period. With the mouth opened maximally, the interdental (D) and interlabial (L) distances were measured using a digital caliper. Significant increases in D and L distances were observed after treatment, as compared with controls (p < 0.01). These results were similar in the restored and skin-grafted groups.

Effect of retinoids on LPS-induced COX-2 expression and COX-2 associated PGE(2) release from mouse peritoneal macrophages and TNF-alpha release from rat peripheral blood mononuclear cells

Anti-inflammatory activity of retinoids has been demonstrated earlier, but their mechanism is poorly understood. In this study, we examined the effects of retinoids on lipopolysaccharide (LPS)-induced prostaglandin (PG) E(2) production, an indicator of cyclooxygenase (COX) activity, and COX-2 protein expression in mouse peritoneal macrophages, and tumor necrosis factor (TNF)-alpha release in rat peripheral blood mononuclear cell (PBMC) to elucidate their possible mechanism for anti-inflammation. All-trans retinoic acid (t-RA) and all-trans retinol significantly inhibited a LPS-induced PGE(2) production as assessed by enzyme-linked immunosorbant assay (ELISA) and COX-2 protein expression as assessed by Western blot assay in mouse peritoneal macrophages, after knocking out the COX-1 activity by aspirin. All-trans retinoic acid, but not all-trans retinol, inhibited LPS-induced TNF-alpha release as assessed by ELISA in rat PBMC. These findings suggest that the modulation of COX-2 and TNF-alpha release could be one of the possible pathways by which retinoids function as anti-inflammatory agents.

The effect of glycolic acid on photoaged albino hairless mouse skin

BACKGROUND

Several clinical reports have suggested that alpha hydroxy acids (AHAs), including glycolic acid, may improve photoaging. However, the mechanism of action of glycolic acid is not well understood.

OBJECTIVE

In order to investigate the mechanism of action of glycolic acid in improving photoaged skin, we observed the effect of glycolic acid on collagen metabolism and wrinkle effacement in chronically ultraviolet B (UVB) irradiated mice.

METHODS

Skh:HR-1 mice were exposed to UVB for 10 weeks and then treated topically with 15% glycolic acid for 10 weeks. We assessed the improvement in wrinkling, the depth of the dermal repair zone, and the extent of the increase in collagen synthesis.

RESULTS

At treatment week 10, the glycolic acid-treated mice showed a significant decrease in wrinkle score, an increased thickness of the dermal repair zone, and an increase in the amount of collagen synthesized compared to vehicle (hydrophilic ointment base) treated mice.

CONCLUSION

Topically applied glycolic acid may improve photoaging through modulation of collagen production.

Intermittent therapy for melasma in Asian patients with combined topical agents (retinoic acid, hydroquinone and hydrocortisone): clinical and histological studies

Melasma is a common problem in Asians, but treatments have not been satisfactory. In the present study, we evaluated the efficacy of a new formula containing 0.1% tretinoin, 5% hydroquinone, and 1% hydrocortisone (RHQ) in Korean patients with melasma. Twenty-five Korean females with therapy recalcitrant melasma applied RHQ on their faces for 4 months and were evaluated before and 4 weeks after treatment clinically and histologically. They were also evaluated clinically 4 months after treatment. To minimize unavoidable side effects (erythema or peeling), we applied RHQ twice a week instead of the usual daily application. However, we obtained clinical and histological results comparable to other reports from white populations. Statistically significant depigmentation in clinical and histological studies and increased subepidermal collagen synthesis were observed in this study. These effects were seen as early as 4 weeks after treatment with RHQ. We used mMASI scoring, a modified version of the original MASI, to quantify the effects of RHQ more objectively and easily.

Photoaging therapy with topical tretinoin: an evidence-based analysis

Topical tretinoin is established as an effective treatment for photoaging. Yet some confusion still exists about the proper way to use this medication, confusion that can misguide physicians in their clinical approaches and patients in their treatment regimens. Most of the misinformation about tretinoin has been perpetuated from the early days of the drug, when its efficacy for treating the effects of photoaging was still in dispute. Significant advances in clinical and basic research in this area have dispelled much of the confusion, clearing the way for an evidence-based medical approach to tretinoin therapy for photoaging. This review summarizes recent relevant advances in tretinoin therapy to guide physicians in treating patients with this safe and effective hormone. To date, tretinoin remains the only therapeutic agent proved to repair photodamage.