Retinoids: unapproved uses or indications

Cellular retinol-binding protein-1 expression increases with increasing clinical severity of alopecia areata

BACKGROUND

Alopecia areata (AA) is multifactorial disease mostly autoimmune affecting anagen hair follicles. Many researchers hypothesize that adequate retinoic acid (RA) levels are important for proper hair follicle behavior. Previous animal studies revealed increase in RA synthesis proteins and decrease in RA degradation proteins in AA patients when compared with controls.

OBJECTIVE

To evaluate cellular retinol-binding protein-1 expression in lesional skin of alopecia areata in comparison with controls, in an attempt to know its role in the pathogenesis of alopecia areata .

METHODS

Immunohistochemical expression of cellular retinol-binding protein-1 CRBP1 was evaluated in skin biopsies taken from lesions of alopecia areata in 30 patients and 10 normal biopsy specimens taken from skin of healthy controls (HC) who were within the same age and sex.

RESULTS

CRBP1 expression was significantly increased in lesional alopecia areata skin in comparison with normal skin of controls (P < 0.001*). Significant positive correlation was found between expression of CRBP-1 and percentage of hair loss in the scalp (SALT score; r = 0.840, P = <0.001).

CONCLUSION

These results may enhance the idea of the possible role of CRBP1 in the pathogenesis of AA, and ensuring the importance of its level in AA treatment.

Endogenous retinoids in the pathogenesis of alopecia areata

Alopecia areata (AA) is an autoimmune disease that attacks anagen hair follicles. Gene array in graft-induced C3H/HeJ mice revealed that genes involved in retinoic acid (RA) synthesis were increased, whereas RA degradation genes were decreased in AA compared with sham controls. This was confirmed by immunohistochemistry in biopsies from patients with AA and both mouse and rat AA models. RA levels were also increased in C3H/HeJ mice with AA. C3H/HeJ mice were fed a purified diet containing one of the four levels of dietary vitamin A or an unpurified diet 2 weeks before grafting and disease progression followed. High vitamin A accelerated AA, whereas mice that were not fed vitamin A had more severe disease by the end of the study. More hair follicles were in anagen in mice fed high vitamin A. Both the number and localization of granzyme B-positive cells were altered by vitamin A. IFNγ was also the lowest and IL13 highest in mice fed high vitamin A. Other cytokines were reduced and chemokines increased as the disease progressed, but no additional effects of vitamin A were seen. Combined, these results suggest that vitamin A regulates both the hair cycle and immune response to alter the progression of AA.

Adapalene vs. metronidazole gel for the treatment of rosacea

BACKGROUND

Rosacea is a common, chronic dermatosis that requires long-term therapy. Oral isotretinoin and topical and/or oral antibiotics are effective, but their usage may be limited due to side-effects.

OBJECTIVE

The goal of the study was to compare the efficacy of topical adapalene gel (0.1%) and topical metronidazole gel (0.75%) in the treatment of patients with papulopustular rosacea.

METHODS

This study included 55 patients with papulopustular rosacea. Diagnostic efforts were focused on clinical and histological features. Patients were randomly assigned to the adapalene (n = 30) and metronidazole (n = 25) groups. Sunlight protection factor 20 cream was used to protect all patients from sunlight. The characteristics and numbers of inflammatory papules, pustules, erythema and telangiectasia were scored at baseline and after 2, 4, 8 and 12 weeks. Side-effects were recorded at each visit.

RESULTS

Fifty patients, 27 in the adapalene group and 25 in the metronidzaole group, completed the study. Significant reductions in the total number of inflammatory lesions were found in the adapalene group compared with the metronidazole group. There was no significant difference in the scores of erythema and telangiectasia in the adapalene group. However, a significant reduction in erythema was seen in the metronidazole group.

CONCLUSIONS

Adapalene gel is well tolerated and can be used as an alternative for topical treatment of papulopustular rosacea.

Retinoids: fascinating up-and-coming scenario

Retinoids have been in sharp focus ever since their introduction 30 years ago. They include any drug (s) that bind to retinoid receptors and elicit a biological response. Enormous information on the subject seems to embroil the recent literature. Practically it is impossible to clearly comprehend the undercurrents. The meticulously dispensing text envisages surmounting the perspective reader's predicaments. Accordingly, retinoids and their related facets namely retinoid receptors, classification, mode of action, and the pharmacological diversity have been precisely defined. Commonly used systemic retinoids too have been given a substantial fresh look along with their monitoring. Overall, adverse effects and relative and absolute contraindications have been scrupulously incorporated. Human immuno deficiency virus (HIV) and isoretinoid for acne, in particular, have been highlighted. Micronized isotretinoin formulations have also been taken care so also commonly used topical retinoids. Tretinoin and their newer formulation have also been accounted for along with tretinoin polymer cream. Adapalene, a new chemical entity possessing a unique physico-chemical activity similar to that of tretinoin has also been dealt with. Newer retinoids are likely to be a subject of intrigue. A focus on future potentials of retinoids is its special ingredient. The inclusion of details of rexinoid the most recent introduction in their purview is likely to invoke interest to further consolidate its reckoning in future. All in all the text of the paper should provide an insight into the current rumbling around retinoids.

Retinoids--which dermatological indications will benefit in the near future?

Retinoids are compounds with pleiotropic functions and a relatively selective targeting of certain skin structures. They are vitamins, because retinol (vitamin A) is not synthesized in the body and must be derived from diet, but also hormones with intracrine activity, because retinol is transformed into molecules that bind to nuclear receptors, exhibit their activity, and are subsequently inactivated. Retinoids exert their effects on target cells by binding and activating nuclear retinoid receptors. Retinoid receptors bind their ligands in form of dimers. Heterodimers can be formed between two different retinoid receptor molecules but also between retinoid X receptors and the vitamin D receptor as well as the triiodothyronin receptor. This fact indicates complex interactions between retinoids and further hormonal signal transduction molecules. Interaction of retinoid receptors with transcriptional factors activated by other signal transduction mechanisms, e.g. AP-1, may provide dissociation of the retinoid effects. Retinoids can exhibit agonistic activity but also be neutral antagonists and inverse agonists. Topical and oral retinol, tretinoin, isotretinoin, and bexarotene, topical alitretinoin, retinaldehyde, motretinide, adapalene, tazarotene, and systemin acitretin compose the list of launched retinoids. Psoriasis and related disorders, congenital disorders of keratinization, acne, photoaging and hypovitaminosis A are classical approved indications of retinoid treatment, whereas cutaneous T-cell lymphoma, AIDS-associated Kaposi's sarcoma, acute promyelocytic leukemia and actinic lentigines were currently confirmed. In addition, retinoids have been successfully used in several other dermatoses, e.g. epithelial precanceroses and tumors, seborrhea, rosacea and acneiform dermatoses, lichen planus, eosinophilic folliculitis, condylomata accuminata, lichen sclerosus and atrophicus. Highly receptor selective molecules, retinoic acid receptor-beta-inducers, AP-1 complex antagonists, and inverse agonists will be probably lead the retinoid development in the near future. New, more effective and less toxic retinoids, alone or in combination with other drugs and new delivery systems may provide therapeutic solutions for benign and malignant proliferative skin diseases, such as psoriasis and non-melanoma tumors, cancer chemoprevention and differentiation therapy.