Current Medicinal Chemistry - Volume 23, Issue 17, 2016

Vitamin D has been known for a long time as a major factor involved in the calcium- phosphate balance and homeostasis, along with parathyroid hormone (PTH). While vitamin D effects on calcium and phosphate are fully known, recent studies attempted to link vitamin D status and cardiovascular diseases. The involvement of vitamin D on vascular remodeling is mediated by several mechanisms such as activation of renin-angiotensin-aldosterone system (RAAS), cell proliferation and anti-apoptotic cell pathways. This correlation is highlighted by the fact that the activated form of vitamin D (1,25 (OH)2 D3) can be synthesized by the same endothelial cells, due to the constitutive presence of endothelial 1α-hydroxylase. Vitamin D reduces the expression of angiotensin 2 receptor (AT2R) on the endothelial cell surface (AT2R), leading to a cascade of events that result in the synthesis of vasodilators, such as nitric oxide. The activation of vitamin D receptors (VDRs) on endothelial cells induces changes in the metabolic activity of the endothelium and is responsible for cell survival, proliferation and neoangiogenesis. Moreover, altered signaling of VDR due to gene polymorphisms has been demonstrated in patients with cardiac disorders and chronic kidney disease (CKD). Recently, vascular access outcome has been associated with vitamin D status. Future studies will help to better define the need of vitamin D supplementation for a better cardiovascular as well as vascular access outcome in patients with CKD.

Autotaxin (ATX) has become an attractive target with a huge pharmacological and pharmacochemical interest in LPA-related diseases and to date many small organic molecules have been explored as potential ATX inhibitors. As a useful aid in the various efforts of identifying novel effective ATX inhibitors, in silico methods can serve as an important and valuable tool. Especially, Virtual Screening (VS) has recently received increased attention due to the large datasets made available, the development of advanced VS techniques and the encouraging fact that VS has contributed to the discovery of several compounds that have either reached the market or entered clinical trials. Different techniques and workflows have been reported in literature with the goal to prioritize possible potent hits. In this review article several deployed virtual screening strategies for the identification of novel potent ATX inhibitors are described.

Serum amyloid A (SAA) is, like C-reactive protein (CRP), an acute phase protein and can be used as a diagnostic, prognostic or therapy follow-up marker for many diseases. Increases in serum levels of SAA are triggered by physical insults to the host, including infection, trauma, inflammatory reactions and cancer. The order of magnitude of increase in SAA levels varies considerably, from a 10- to 100- fold during limited inflammatory events to a 1000-fold increase during severe bacterial infections and acute exacerbations of chronic inflammatory diseases. This broad response range is reflected by SAA gene duplications resulting in a cluster encoding several SAA variants and by multiple biological functions of SAA. SAA variants are single-domain proteins with simple structures and few post-translational modifications. SAA1 and SAA2 are inducible by inflammatory cytokines, whereas SAA4 is constitutively produced. We review here the regulated expression of SAA in normal and transformed cells and compare its serum levels in various disease states. At low concentrations (10-100 ng/ml), early in an inflammatory response, SAA induces chemokines or matrix degrading enzymes via Toll-like receptors and functions as an activator and chemoattractant through a G protein-coupled receptor. When an infectious or inflammatory stimulus persists, the liver continues to produce more SAA (≥ 1000 ng/ml) to become an antimicrobial agent by functioning as a direct opsonin of bacteria or by interference with virus infection of host cells. Thus, SAA regulates innate and adaptive immunity and this information may help to design better drugs to treat specific diseases.

Poly(ADP-ribose) polymerase 1 (PARP1) inhibition, increasing chemosensitization and conferring independent antiproliferation against defective homologous recombination cells, has provided a unique opportunity for anticancer therapeutic intervention. Therefore, PARP1, the best characterized enzyme among PARP family, is presently serving as a well-established target for the treatment of oncology attributed to its intimate role in DNA repair. Nowadays, intensified medicinal chemistry efforts have led to the discovery of 12 PARP1 inhibitors that have been advanced into clinical trial. In this article, we classify these candidates as three categories based on the chemical structure, including lactam type, pseudo ring type and untypical PARP1 inhibitors, for a sequential overview of them. In particular, the development of some candidates will serve the purpose for the future exploration of PARP1 inhibitors.

Tissue hypoxia may occur in many diseases, specifically during the occurrence and growth of malignant solid-tumors. Targeting hypoxia is one of the most significant characteristics of tumors in diagnosis, monitoring, and treatment. This review summarizes the current oxygen-sensitive imaging agents used to target tumor hypoxia, including positron-emission computed tomography/single photon-emission computed tomography radionuclide labeled tracers, magnetic resonance imaging contrast agents for hypoxia detection, and hypoxia-sensitive optical imaging probes. Researchers have utilized nanotechnology as a useful toolkit to improve the effects of oxygen-sensitive imaging agents. We emphasize the progress and influence of nanotechnology in these materials and technologies. This review demonstrates that hypoxia imaging agents have promising prospects, and may provide helpful information for tumor diagnosis and prognosis.