A histochemical study on the vitamin D synthesis into the epidermis

Vitamin D toxicity related to its physiological and unphysiological supply

Vitamin D is defined as a nutrient despite its rare occurrence in food. Vitamin D status is determined mainly by solar UV light action in skin. However, the strategy to combat vitamin D deficiency has been to increase oral intake of vitamin D in greater amounts than could be obtained from food. Persistent large intakes of vitamin D can cause hypercalcaemic toxicity. Although the amounts recommended to prevent deficiency are far less than those causing such toxicity, the possibility of other toxic actions from increased intake of vitamin D has been ignored. Animal experiments have demonstrated that moderate amounts of oral vitamin D over time result in atherosclerosis. Differences in the fate of vitamin D could explain this angiotoxicity.

Considerations for development of therapies for cutaneous neurofibroma

Objective

The only therapies currently available for cutaneous neurofibromas (cNF) are procedural. The goals of the Therapies Development Working Group were to (1) summarize currently available treatment options for cNF, (2) define key considerations for drug discovery and development generally, and specifically for cNF, and (3) outline recommendations for the successful development of medical therapies for cNF.

Methods

The subgroup reviewed published and unpublished data on procedural, drug/device, and medical treatment approaches utilized for cNFs via literature search. The team defined disease- and patient-specific factors to consider for therapies development in a series of consensus meetings.

Results

The team identified 5 approaches entailing procedural and drug/device methods currently under study. There have been 4 clinical studies exploring various interventional therapies, from which outcomes were highly variable. The team identified 4 key factors to prioritize during the development of products for the treatment for cNF: safety, anatomic distribution of cNF, numbers of tumors to be treated, and route of administration.

Conclusions

The number, size, and distribution of cNF is highly variable among patients with NF1 and it is possible that different phenotypes will require different drug development paths. The nonfatal nature of the disease and relatively limited patient numbers suggest that for any product to have a higher likelihood of acceptance, it will have to (1) demonstrate an effect that is clinically meaningful, (2) have a safety profile conducive to long-term dosing, and (3) have a low manufacturing cost.

A histochemical investigation on the percutaneous absorption of vitamin D synthesized into the mammal epidermis

The vitamin D transepidermis absorption was studied by means of a histochemical technique suitable to detect this vitamin and to discriminate it from cholesterol and its esters. Such technique shows vitamin D inside the mast cell granules. As the mast cell granules contain metachromatic substances its own histochemical reactivity must be previously blocked by methylation. After this treatment the mast cell granules do not stain by toluidine blue and do not react to the peracetic acid-toluidine blue reaction. However, the granules remains reactive to alkaline permanganate-toluidine blue and to alkaline permanganate-Schiff reactions. These results show that the mast cell granules do not contain cholesterol but they contain vitamin D. The lack of cholesterol suggests that vitamin D is not synthesized inside the granules. As the mast cells may appears within the epidermis or in close relationship with the epidermis, although it is placed into the superficial dermis, it was admitted that the mast cells uptake vitamin D contained inside the epidermis intercellular compartment. In such instances, the vitamin D synthesized by the keratinocytes enter the intercellular compartment, where its synthesis accomplishes, and migrate towards the basement membrane. At the basal epidermis layer or after passing through the basement membrane the vitamin D is taken up by mast cells, where it is stored inside its granules.