Current Medicinal Chemistry - Volume 17, Issue 12, 2010

Src family tyrosine kinases (SFKs) play key roles in regulating signal transduction in cellular processes. However, hyper-activated SFKs lead to uncontrolled cell proliferation and cancers. For both Src SH2 and SH3 domains involve in the regulation of tumorigenesis signal pathways, the SH2 and SH3 inhibition strategies are expected to block the protein-protein interactions between SFKs and their corporation proteins to abolish the signal transduction. Many inhibitors of SH2 and SH3 domain have been identified. Herein, some predominant examples of these inhibitors are reviewed.

The blood-brain barrier (BBB) not only impedes the influx of intravascular substances from blood to brain, but also promotes transport of substances from blood to brain or from brain to blood through several transport systems such as carrier-mediated transport, active efflux transport, and receptor-mediated transport systems. The multidrug resistance transporter P-glycoprotein (P-gp) is an ATP-dependent efflux pump and contributes to efflux of undesirable substances such as amyloid-β (Aβ) proteins from the brain into the blood as well as many drugs such as anti-cancer drugs. The inhibition of P-gp has favorable and unfavorable effects on living bodies. P-gp deficiency at the BBB induces the increase of Aβ deposition in the brain of an Alzheimer disease mouse model. It is also known that the Aβ deposition is inversely correlated with P-gp expression in the brains of elderly non-demented humans. However, the transient inhibition of P-gp by antidepressants enables medicines such as anti-cancer drugs to enter the brain. Concerning Aβ clearance in the brain, the low-density lipoprotein receptor-related protein 1 (LRP1) is a major efflux transporter for Aβ, while the receptor for advanced glycation end products (RAGE) is a major influx transporter for Aβ across the BBB. Dysfunction of the BBB with efflux and influx transporters may contribute to the pathogenesis of some degenerative neuronal disorders. This review will focus on several transporters and discuss how medicines pass the BBB to reach the brain parenchyma.

Platensimycin, an active metabolite of Streptomyces platensis, was initially discovered by a combination of RNA interferin induced gene-silencing and library screening to microbial extracts. Platensimycin selectively inhibits β- ketoacyl-acyl carrier protein (ACP) synthase II (FabF) that is recognized as an effective broad-spectrum antibiotic against drug-resistant microorganism strains. Its novel scaffold and extraordinary antibacterial activity have drawn great attentions in recent years. So far, a number of synthetic strategies have been explored for the total synthesis of platensimycin. Moreover, many analogues have been investigated in terms of structure-activity relationships (SAR). This review provides a detailed overview of updated studies on platensimycin, focusing on various total and formal synthetic strategies, development of analogues, and the structure-activity relationships.

Dendritic cells (DCs) link innate and adaptive immunity by directly recognizing pathogen-associated molecular patterns (PAMPs) on bacteria. DCs can capture and degrade bacteria and present their antigens on MHC molecules to T cells. PAMP recognition promotes DC maturation, a phenotypic change that empowers them to prime naïve T cells. As a result, an adaptive immune response that specifically targets bacteria-derived antigens is initiated. Consequently, any impairment of DC function might contribute to bacterial survival and dissemination in the host. Therefore, the characterization of DC-bacteria interactions is required to understand the mechanisms used by virulent bacteria to avoid adaptive immunity. An example of a bacterial pathogen capable of interfering with DC function is Salmonella enterica serovar Typhimurium (S. Typhimurium), which causes a typhoid-like disease in mice. Virulent strains of S. Typhimurium are able to differentially modulate the entrance to DCs and avoid lysosomal degradation, to prevent antigen presentation on MHC molecules. These features of virulent S. Typhimurium are controlled by virulence factors encoded by Salmonella Pathogenicity Islands 1 and 2. Modulation of DC functions by the activity of these gene products is supported by several recent studies, which have shown that pathogenesis might depend on this attribute of virulent S. Typhimurium. Here we discuss recent data showing that several virulence factors from Salmonella are required to differentially modulate DC function and adaptive immunity in the host.

G protein-coupled receptors (GPCRs) mediate senses such as odor, taste, vision, and pain in mammals. In addition, important cell recognition and communication processes often involve GPCRs. Many diseases involve malfunction of GPCRs, making them important targets for drug development. Indeed, greater than 50 % of all marketed therapeutics act on those receptors. Unfortunately, the atomic-level structures are only available for rhodopsin, β2AR, β1AR, A2A adenosin and opsin. In silico computational methods, employing receptor-based modeling, offer a rational approach in the design of drugs targeting GPCRs. These approaches can be used to understand receptor selectivity and species specificity of drugs that interact with GPCRs. This review gives an overview of current computational approaches to GPCR model building; ligand-receptor interaction for drug design; and molecular mechanism of GPCR activation from simulation.

Arachidonic acid metabolites, eicosanoids, are key contributors to vascular function and improper eicosanoid regulation contributes to the progression of cardiovascular diseases. Epoxyeicosatrienoic acids (EETs) are synthesized from arachidonic acid by epoxygenase enzymes to four regioisomers, 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET. These EETs have interesting beneficial effects like vasodilation, anti-inflammation, and anti-platelet aggregation that could combat cardiovascular diseases. There is mounting evidence that each regioisomeric EET may have unique vascular effects and that the contribution of individual EETs to vascular function differs from organ to organ. Over the past decade EET analogs and antagonists have been synthesized to determine EET structure function relationships and define the contribution of each regioisomeric EET. A number of studies have demonstrated that EET analogs induce vasodilation, lower blood pressure and decrease inflammation. EET antagonists have also been used to demonstrate that endogenous EETs contribute importantly to cardiovascular function. This review will discuss EET synthesis, regulation and physiological roles in the cardiovascular system. Next we will focus on the development of EET analogs and what has been learned about their contribution to vascular function. Finally, the development of EET antagonists and how these have been utilized to determine the cardiovascular actions of endogenous epoxides will be discussed. Overall, this review will highlight the important knowledge garnered by the development of EET analogs and their possible value in the treatment of cardiovascular diseases.

Madagascar, the world's fourth biggest island has a unique biodiversity. The interest on the phytochemical investigation of Malagasy plant and marine natural products started from the isolation of the potent anti-cancerous bisindole alkaloids: vinblastine and vincristine. In this paper, work published in the last two decades (1991-2009) on 262 new natural products isolated from Malagasy higher plants, liverworts and marine organisms is reviewed. Several results on the bioassays of the isolated new natural products have been reported.