Virus-encoded G-protein-coupled receptors: constitutively active (dys)regulators of cell function and their potential as drug target.

G-protein-coupled receptors encoded by herpesviruses such as EBV, HCMV and KSHV are very interesting illustrations of the (patho)physiological importance of constitutive GPCR activity. These viral proteins are expressed on the cell surface of infected cells and often constitutively activate a variety of G-proteins. For some virus-encoded GPCRs, the constitutive activity has been shown to occur in vivo, i.e., in infected cells. In this paper, we will review the occurrence of virus-encoded GPCRs and describe their known signaling properties. Moreover, we will also review the efforts, directed towards the discovery of small molecule antagonist, that so far have been mainly focused on the HCMV-encoded GPCR US28. This virus-encoded receptor might be involved in cardiovascular diseases and cancer and seems an interesting target for drug intervention.

New synthetic flavonoids as potent protectors against doxorubicin-induced cardiotoxicity.

A series of 3,7-disubstituted-2(3',4'-dihydroxyphenyl) flavones has been studied as potential cardioprotective agents in doxorubicin antitumor therapy. The influence of substituents on the 3 and 7 position of the flavone nucleus on antioxidant activity cytotoxicity and cardioprotective properties was explored to improve the activity of our lead compound 7-monohydroxyethylrutoside. In the protection against Fe(2+)/vitamin C-induced microsomal lipid peroxidation (LPO assay), IC(50) values ranged from 0.2 to 37 microM. In general, the 3-substituted flavones were the most potent compounds in this assay. The cytotoxicity of the new compounds was tested (up to 250 microM) in hepatocytes. LDH leakage ranged from 2.6-29.2%, whereas the GSH concentrations decreased to 87.3-41.3%. Only four compounds out of this series protected the isolated mouse left atrium against doxorubicin-induced toxicity. Because of the positive inotropic effect of 8d (N-(3-(3',4'-dihydroxyflavon-7-yl)oxypropyl)-N,N,N-trimethylammonium chloride) and 10c (3-hydroxyethoxy-7,3',4'-trihydroxyflavone) on the atrium, compounds 9i (3',4'-dihydroxy-3-glucosylflavone) and 10d (N-(3-(7,3',4'-trihydroxyflavon-3-yl)oxypropyl)-N,N,N-trimethylammonium chloride) were selected to be evaluated as cardioprotective agents in vivo.