Testosterone is necessary for the development of male pattern baldness, known as androgenetic alopecia (AGA); yet, the mechanisms for decreased hair growth in this disorder are unclear. We show that prostaglandin D2 synthase (PTGDS) is elevated at the mRNA and protein levels in bald scalp compared to haired scalp of men with AGA. The product of PTGDS enzyme activity, prostaglandin D2 (PGD2), is similarly elevated in bald scalp. During normal follicle cycling in mice, Ptgds and PGD2 levels increase immediately preceding the regression phase, suggesting an inhibitory effect on hair growth. We show that PGD2 inhibits hair growth in explanted human hair follicles and when applied topically to mice. Hair growth inhibition requires the PGD2 receptor G protein (heterotrimeric guanine nucleotide)–coupled receptor 44 (GPR44), but not the PGD2 receptor 1 (PTGDR). Furthermore, we find that a transgenic mouse, K14-Ptgs2, which targets prostaglandin-endoperoxide synthase 2 expression to the skin, demonstrates elevated levels of PGD2 in the skin and develops alopecia, follicular miniaturization, and sebaceous gland hyperplasia, which are all hallmarks of human AGA. These results define PGD2 as an inhibitor of hair growth in AGA and suggest the PGD2-GPR44 pathway as a potential target for treatment.

Abstract--The preclinical pharmacology, antitumor activity and toxicity of seven of the more important amino acid analogs, with antineoplastic activity, is discussed in this review. Three of these compounds are antagonists of L-glutamine: acivicin, DON and azaserine; and two are analogs of L-aspartic acid: PALA and L-alanosine. All five of these antimetabolites interrupt cellular nucleotide synthesis and thereby halt the formation of DNA and/or RNA in the tumor cell. The remaining two compounds, buthionine sulfoximine and difluoromethylornithine, are inhibitors of glutathione and polyamine synthesis, respectively, with limited intrinsic antitumor activity; however, because of their powerful biochemical actions and their low systemic toxicities, they are being evaluated as chemotherapeutic adjuncts to or modulators of other more toxic antineoplastic agents. CONTENTS

Apoptosis plays an important role in many physiological processes, ranging from morphogenetic events to adult tissue homeostasis, and defects in its regulation contribute to many disorders. Here we review molecular mechanisms of apoptosis in the hair follicle (HF), whose cyclical growth pattern is repeatedly interrupted by apoptosis-driven involution (catagen). We review the common mechanisms underlying apoptosis in the HF during catagen, as well as differences in the regulation of apoptosis between distinct HF cell populations. An overview is provided on the expression and function of molecules involved in the control of various phases of the apoptotic process during catagen.

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A series of dinucleotides, analogous to nicotinamide adenine dinucleotide but containing the five-membered base nucleosides tiazofurin (1a), selenazofurin (1b), ribavirin (2), and AICAR (3) in place of nicotinamide ribonucleoside, were prepared in greater than 50% yield by reacting the corresponding nucleotide imidazolidates (6a-d) with adenosine 5'-monophosphate (AMP). The symmetric dinucleotides of tiazofurin (TTD, 8e) and selenazofurin (SSD, 8f) were also prepared by a similar methodology. These dinucleotides were characterized by 1H NMR and fast atom bombardment MS and were evaluated for their inhibitory potency against a partially purified preparation of tumoral inosine monophosphate dehydrogenase (IMPD) from P388 cells. The order of potency found was SAD (8b) greater than TAD (8a) much greater than SSD (8f) congruent to TTD (8e) congruent to RAD (8c) much much greater than ZAD (8d). On kinetic analysis none of the dinucleotides produced competitive inhibition of IMPD with NAD as a variable substrate. In addition to their superior IMPD inhibitory activity, SAD and TAD appear to be the only dinucleotides, besides NAD, that are formed naturally by the NAD pyrophosphorylase from P388 lymphoblasts.

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This long-term study demonstrated sustained safety, tolerability, and efficacy of oxymetazoline for moderate-to-severe persistent erythema of rosacea.