Medicines associated with folate-homocysteine-methionine pathway disruption.

Folate is vital for cell development and growth. It is involved in one-carbon transfer reactions essential for the synthesis of purines and pyrimidines. It also acts in conjunction with cobalamin (vitamin B12) as a fundamental cofactor in the remethylation cycle that converts homocysteine to methionine. A deficiency in folate or vitamin B12 can lead to elevated homocysteine level, which has been identified as an independent risk factor in several health-related conditions. Adequate folate levels are essential in women of childbearing age and in pregnant women, and folate deficiency is associated with several congenital malformations. Low folate levels can be caused by dietary deficiencies, a genetic predisposition or treatment with medicines that affect folate concentration. Women who are pregnant or of child-bearing age commonly use medicines, so it is important to identify the basic biochemical mechanisms by which medicines interfere with the folate-homocysteine-methionine pathway. This review focuses on prescription medicines associated with folate disruption. It also summarizes their undesirable/toxic effects. Recommendations regarding folate supplementation during medical therapy are also reviewed.

Genome-wide gene expression profiling of low-dose, long-term exposure of human osteosarcoma cells to bisphenol A and its analogs bisphenols AF and S.

The bisphenols AF (BPAF) and S (BPS) are structural analogs of the endocrine disruptor bisphenol A (BPA), and are used in common products as a replacement for BPA. To elucidate genome-wide gene expression responses, estrogen-dependent osteosarcoma cells were cultured with 10 nM BPA, BPAF, or BPS, for 8 h and 3 months. Genome-wide gene expression was analyzed using the Illumina Expression BeadChip. Three months exposure had significant effects on gene expression, particularly for BPS, followed by BPAF and BPA, according to the number of differentially expressed genes (1980, 778, 60, respectively), the magnitude of changes in gene expression, and the number of enriched biological processes (800, 415, 33, respectively) and pathways (77, 52, 6, respectively). 'Embryonic skeletal system development' was the most enriched bone-related process, which was affected only by BPAF and BPS. Interestingly, all three bisphenols showed highest down-regulation of genes related to the cardiovascular system (e.g., NPPB, NPR3, TXNIP). BPA only and BPA/BPAF/BPS also affected genes related to the immune system and fetal development, respectively. For BPAF and BPS, the 'isoprenoid biosynthetic process' was enriched (up-regulated genes: HMGCS1, PDSS1, ACAT2, RCE1, DHDDS). Compared to BPA, BPAF and BPS had more effects on gene expression after long-term exposure. These findings stress the need for careful toxicological characterization of BPA analogs in the future.

Small molecule antagonists of integrin receptors.

The complex and widespread family of integrin receptors is involved in numerous physiological processes, such as tissue remodeling, angiogenesis, development of the immune response and homeostasis. In addition, their key role has been elucidated in important pathological disorders such as cancer, cardiovascular diseases, osteoporosis, autoimmune and inflammatory diseases and in the pathogenesis of infectious diseases, making them highly important targets for modern drug design campaigns. In this review we seek to present a concise overview of the small molecule antagonists of this diverse and highly complex receptor family. Integrin antagonists are classified according to the targeted integrin receptor and are discussed in four sections. First we present the fibrinogen alpha(IIb)beta3 and the vitronectin alpha (V)beta(3) receptor antagonists. The remaining selective integrin antagonists are examined in the third section. The final section is dedicated to molecules with dual or multiple integrin activity. In addition, the use of antibodies and peptidomimetic approaches to modulate the integrin receptors are discussed, as well providing the reader with an overall appreciation of the field.

Dual antagonists of integrins.

The roles of integrins in pathologies have been studied intensively and only partially explained. This has resulted in the development of several nanomolar antagonists to certain integrins. In most cases, the aim was to produce compounds which are highly selective towards specific integrins. This paradigm has recently shifted a little. Targeting two or more integrins with one compound has become a very attractive concept, especially since it has become clear that several severe disorders, such as pathological angiogenesis, cannot be treated just with highly specific integrin antagonists. This review is aimed to elucidate some aspects regarding the design of drugs with dual activity towards integrins. Integrin structure and tissue distribution will first be described, in order to provide the basis for their functions in various pathologies which will follow. Inhibitors of several pairs of integrins will be described.

Thrombin receptor antagonists; recent advances in PAR-1 antagonist development.

The receptor for the serine protease thrombin, the protease-activated receptor-1 (PAR-1), has been recently characterized. Its key roles in thrombin-stimulated human platelet activation, vascular endothelial and smooth muscle proliferation, inflammatory responses and neurodegeneration suggest receptor involvement in various disorders such as arterial thrombosis, atherosclerosis, restenosis, inflammation and myocardial infarction. It has been established that thrombin elicits the majority of its effects via PAR-1. PAR-1 has a novel mechanism of activation. The receptor, a member of the seven-transmembrane domain receptor family, is cleaved by thrombin at a specific site on the N-terminal extension, and a newly exposed N-terminus acts as a tethered ligand to activate the receptor itself. The need for development of a PAR-1 antagonist that may be valuable as a therapeutic agent has been recognized. An intriguing challenge is the necessity of the antagonist to compete with an intramolecular ligand while showing no intrinsic activity. The lead compounds were found to be synthetic peptides containing N-terminal hexapeptide or pentapeptide (Ser-Phe-Leu-Leu-Arg-Asn, Ser-Phe-Leu-Leu-Arg) or modified sequences (TRAPs; thrombin receptor-activating peptides), which exhibit full PAR-1 agonist activity. Selective PAR-1 antagonists have already been synthesized. Though their potency is still not enough to justify therapeutic use, it is clear that future progress will bring a novel class of drugs-thrombin receptor antagonists. The emphasis of this review, therefore, will be placed on advances in the discovery of potent and selective PAR-1 antagonists.