Effects of the Aminophenol Analogue p-Dodecylaminophenol on Mouse Skin

[Prevention and Treatment of Cancer with Vitamin A and Its Derivatives: Cell Differentiation and Proliferation]

Normal differentiation and proliferation of cells are essential for maintaining homeostasis. Following the successful completion of whole genome sequencing, protein modification has been attracted increasing attention in order to understand the roles of protein diversification in protein function and to elucidate molecular targets in mechanisms of signal transduction. Vitamin A is an essential nutrient for health maintenance. It is present as β-carotene in green and yellow vegetables and retinyl ester in animal products and absorbed into the body from the intestines. After ingestion, it is converted to retinol and oxidized in target cells to retinal, which plays critical roles in vision. It is then further oxidized to retinoic acid (RA), which exhibits a number of effects prior to being metabolized by cytochrome P450 and excreted from the body. Since RA exhibits cell differentiation-inducing actions, it is used as a therapeutic agent for patients with acute promyelocytic leukemia. The current paper describes: (1) HL60 cell differentiation and cell differentiation induction therapy by RA; (2) roles played by RA and retinal and their mechanisms of action; (3) retinoylation, post-translational protein-modified by RA, a novel non-genomic RA mechanism of action without RA receptor; (4) new actions of β-carotene and retinol in vivo and (5) potent anticancer effects of p-dodecylaminophenol (p-DDAP), a novel vitamin A derivative created from the RA derivative fenretinide. We propose that nutritional management of vitamin A can be effective at preventing and treating diseases, and that p-DDAP is a promising anticancer drug.

Examination of aminophenol-containing compounds designed as antiproliferative agents and potential atypical retinoids

Retinoic acid (RA, 1), an oxidized form of vitamin A, binds to retinoic acid receptors (RAR) and retinoid X receptors (RXR) to regulate gene expression and has important functions such as cell proliferation and differentiation. Synthetic ligands regarding RAR and RXR have been devised for the treatment of various diseases, particularly promyelocytic leukemia, but their side effects have led to the development of new, less toxic therapeutic agents. Fenretinide (4-HPR, 2), an aminophenol derivative of RA, exhibits potent antiproliferative activity without binding to RAR/RXR, but its clinical trial was discontinued due to side effects of impaired dark adaptation. Assuming that the cyclohexene ring of 4-HPR is the cause of the side effects, methylaminophenol was discovered through structure-activity relationship research, and p-dodecylaminophenol (p-DDAP, 3), which has no side effects or toxicity and is effective against a wide range of cancers, was developed. Therefore, we thought that introducing the motif carboxylic acid found in retinoids, could potentially enhance the anti-proliferative effects. Introducing chain terminal carboxylic functionality into potent p-alkylaminophenols significantly attenuated antiproliferative potencies, while a similar structural modification of weakly potent p-acylaminophenols enhanced growth inhibitory potencies. However, conversion of the carboxylic acid moieties to their methyl esters completely abolished the cell growth inhibitory effects of both series. Insertion of a carboxylic acid moiety, which is important for binding to RA receptors, abolishes the action of p-alkylaminophenols, but enhances the action of p-acylaminophenols. This suggests that the amido functionality may be important for the growth inhibitory effects of the carboxylic acids.

Effects of Post-administration of β-Carotene on Diet-induced Atopic Dermatitis in Hairless Mice

Atopic dermatitis (AD) is a cutaneous condition characterized by itchy, swollen, and dry skin, which is mediated by T helper cell-related cytokines. β-Carotene, a natural red pigment found in plants, exhibits antioxidant activity that has been shown to promote an inflammatory response. Because it is not clear whether β-carotene suppresses inflammation in AD skin tissues, we examined the effects of oral administration of β-carotene in mice induced by a low zinc/magnesium diet (HR-AD diet). Our studies found that AD-like inflammation was remarkably reduced by β-carotene. In addition, β-carotene significantly suppressed protein expression of TNF-α, IL-1β, and MCP-1 and mRNA expression of TSLP, IL-6, IL-1β, IL-4, IL-5, and Par-2 in AD-like skin tissues. It was also found that mRNA and protein expression of filaggrin (a major structural protein in epidermis) in AD-like skin was significantly elevated by β-carotene administration. Furthermore, β-carotene treatment significantly reduced the activity and/or mRNA expression of matrix metalloproteinases (MMPs), degradation of the extracellular matrix and regulation of chemokines. These results suggest that β-carotene reduces skin inflammation through the suppressed expression of inflammatory factors or the activity of MMPs as well as the promotion of filaggrin expression in AD-like skin. β-Carotene is a potent anti-inflammatory agent, which improves AD-like skin by enhancing the skin barrier function.

Anticancer efficacy of p-dodecylaminophenol against high-risk and refractory neuroblastoma cells in vitro and in vivo

Neuroblastoma is an aggressive and drug-resistant refractory cancer. The human high-risk neuroblastoma cell line, SK-N-AS (non-amplified N-myc) is derived from stromal cells and it is resistant to treatment with retinoic acid (1, RA), which is a chemotherapeutic agent used to induce neuronal cellular differentiation of neuroblastomas. We have developed p-dodecylaminophenol (3, p-DDAP), based on N-(4-hydroxyphenyl)retinamide (2, 4-HPR), a synthetic amide of 1, since 1 and 2 are associated with the side-effect of nyctalopia. In order to evaluate the effects of 3 on high-risk neuroblastomas, we employed SK-N-AS cells as well asa second high-risk human neuroblastoma cell line, IMR-32, which is derived from neuronal cells (amplified N-myc, drug sensitive). Compound 3 suppressed cell growth of SK-N-AS and IMR-32 cells more effectively than 1, 2, p-decylaminophenol (4, p-DAP), N-(4-hydroxyphenyl)dodecananamide (5, 4-HPDD) or N-(4-hydroxyphenyl)decananamide (6, 4-HPD). In SK-N-AS cells, 3 induced G₀/G₁ arrest and apoptosis to a greater extent than 1 and 2. In IMR-32 cells, 3 induced apoptosis to a similar extent as 1 and 2, potentially by inhibiting N-myc expression. In addition, i.p. administration of 3 suppressed tumor growth in SK-N-AS-implanted mice in vivo. Since 3 showed no effects on blood retinol concentrations, in contrast to reductions following the administration of 2, it exhibited excellent anticancer efficacy against high-risk neuroblastoma SK-N-AS and IMR-32 expressing distinct levels of N-myc. Compound 3 may have potential for clinical use in the treatment of refractory neuroblastoma with reduced side effects.

Active ingredients against human epidermal aging

The decisive role of the epidermis in maintaining body homeostasis prompted studies to evaluate the changes in epidermal structure and functionality over the lifetime. This development, along with the identification of molecular mechanisms of epidermal signaling, maintenance, and differentiation, points to a need for new therapeutic alternatives to treat and prevent skin aging. In addition to recovering age- and sun-compromised functions, proper treatment of the epidermis has important esthetic implications. This study reviews active ingredients capable of counteracting symptoms of epidermal aging, organized according to the regulation of specific age-affected epidermal functions: (1) several compounds, other than retinoids and derivatives, act on the proliferation and differentiation of keratinocytes, supporting the protective barrier against mechanical and chemical insults; (2) natural lipidic compounds, as well as glycerol and urea, are described as agents for maintaining water-ion balance; (3) regulation of immunological pathogen defense can be reinforced by natural extracts and compounds, such as resveratrol; and (4) antioxidant exogenous sources enriched with flavonoids and vitamin C, for example, improve solar radiation protection and epidermal antioxidant activity. The main objective is to provide a functional classification of active ingredients as regulatory elements of epidermal homeostasis, with potential cosmetic and/or dermatological applications.