Identification of the sulfotransferase iso-enzyme primarily responsible for the bio-activation of topical minoxidil.

Pattern hair loss (i.e., androgenetic alopecia) is a common condition afflicting approximately fifty percent of men and women by the age of fifty. Currently, topical minoxidil is the only US FDA approved drug for the treatment of pattern hair loss in men and women.

The effect of topical minoxidil treatment on follicular sulfotransferase enzymatic activity.

Minoxidil is the only US FDA-approved topical drug for the treatment of female and male pattern hair loss. Previously, it was demonstrated that topical minoxidil is metabolized to its active metabolite, minoxidil sulfate, by sulfotransferase enzymes located in the outer root sheath of hair follicles. The expression of sulfotransferase in the scalp varies greatly between individuals, and this difference in expression explains the varied response to minoxidil treatment. Previously, we have demonstrated the clinical utility of detecting sulfotransferase in plucked hair follicles to predict minoxidil response in pattern hair loss patients. Typically, exogenous exposure to substrates affects the expression of the enzymatic system responsible for their metabolism. For example, Phase I metabolizing enzymes, such as the cytochrome P450 family of enzymes, are known to be up-regulated in the presence of xenobiotic substrates. However, it is not known if Phase II metabolizing enzymes, such as the sulfotransferase family of enzymes, are similarly affected by the presence of substrates. In this study, we recruited 120 subjects and analyzed their sulfotransferase enzymatic activity before and after treatment with topical minoxidil. Adjusting the results for biologic (within subject) variability, we discovered that the sulfotransferase enzymatic system expression is stable over the course of minoxidil treatment. To the best of our knowledge, this is the first study to demonstrate the stability of sulfotransferase, a Phase II metabolizing enzyme, over the course of minoxidil treatment.

Social selection favours offspring prone to the development of androgenetic alopecia.

In recent years, dermatologists have observed an increase in the incidence of male androgenetic alopecia (AGA). In a survey of 41 dermatologists, 88% reported an increase in incidence of AGA in men younger than 30 years. This phenomenon has no apparent explanation. However, due to the strong genetic inheritance component of AGA, a social or environmental factor which favours the inheritance of genes that increase the risk of developing AGA is suspected. To date, the strongest predictor of AGA in men has been the length of the CAG repeat located in the androgen receptor gene (AR gene) on the X chromosome. The same genetic variant in women is associated with ovulation at a later age, higher antral follicle count, and lower risk for premature ovarian failure. This led us to theorize that, due to social pressure to conceive later in life, women carriers of the short CAG repeat in the AR gene would have a selective advantage to conceive later in life and would thus favour male offspring exhibiting AGA.

Mechanism of action of minoxidil in the treatment of androgenetic alopecia is likely mediated by mitochondrial adenosine triphosphate synthase-induced stem cell differentiation.

Topical minoxidil is the only topical drug approved by the US Food and Drug Administration (FDA) for the treatment of androgenetic alopecia. However, the exact mechanism by which minoxidil stimulates anagen phase and promotes hair growth is not fully understood. In the late telegen phase of the hair follicle growth cycle, stem cells located in the bulge region differentiate and re-enter anagen phase, a period of growth lasting 2-6 years. In androgenetic alopecia, the anagen phase is shortened and a progressive miniaturization of hair follicles occurs, eventually leading to hair loss. Several studies have demonstrated that minoxidil increases the amount of intracellular Ca2+, which has been shown to up-regulate the enzyme adenosine triphosphate (ATP) synthase. A recent study demonstrated that ATP synthase, independent of its role in ATP synthesis, promotes stem cell differentiation. As such, we propose that minoxidil induced Ca2+ influx can increase stem cell differentiation and may be a key factor in the mechanism by which minoxidil facilitates hair growth. Based on our theory, we provide a roadmap for the development of a new class of drugs for the treatment of androgenetic alopecia.