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Hepatic ischemia/reperfusion injury is a complication of liver surgery that involves mitochondrial dysfunction resulting from mitochondrial permeability transition pore (mPTP) opening. Cyclophilin D (PPIF or CypD) is a peptidyl-prolyl cis - trans isomerase that regulates mPTP opening in the inner mitochondrial membrane. We investigated whether and how recently created small-molecule inhibitors of CypD prevent opening of the mPTP in hepatocytes and the resulting effects in cell models and livers of mice undergoing ischemia/reperfusion injury. We measured the activity of 9 small-molecule inhibitors of cyclophilins in an assay of CypD activity. The effects of the small-molecule CypD inhibitors or vehicle on mPTP opening were assessed by measuring mitochondrial swelling and calcium retention in isolated liver mitochondria from C57BL/6J (wild-type) and Ppif –/– (CypD knockout) mice and in primary mouse and human hepatocytes by fluorescence microscopy. We induced ischemia/reperfusion injury in livers of mice given a small-molecule CypD inhibitor or vehicle before and during reperfusion and collected samples of blood and liver for histologic analysis. The compounds inhibited peptidyl-prolyl isomerase activity (half maximal inhibitory concentration values, 0.2–16.2 μmol/L) and, as a result, calcium-induced mitochondrial swelling, by preventing mPTP opening (half maximal inhibitory concentration values, 1.4–132 μmol/L) in a concentration-dependent manner. The most potent inhibitor (C31) bound CypD with high affinity and inhibited swelling in mitochondria from livers of wild-type and Ppif –/– mice (indicating an additional, CypD-independent effect on mPTP opening) and in primary human and mouse hepatocytes. Administration of C31 in mice with ischemia/reperfusion injury before and during reperfusion restored hepatic calcium retention capacity and oxidative phosphorylation parameters and reduced liver damage compared with vehicle. Recently created small-molecule inhibitors of CypD reduced calcium-induced swelling in mitochondria from mouse and human liver tissues. Administration of these compounds to mice during ischemia/reperfusion restored hepatic calcium retention capacity and oxidative phosphorylation parameters and reduced liver damage. These compounds might be developed to protect patients from ischemia/reperfusion injury after liver surgery or for other hepatic or nonhepatic disorders related to abnormal mPTP opening. [ABSTRACT FROM AUTHOR]

The NS5B RNA-dependent RNA polymerase (RdRp) is a key enzyme for Hepatitis C Virus (HCV) replication. In addition to the catalytic site, this enzyme is characterized by the presence of at least four allosteric pockets making it an interesting target for development of inhibitors as potential anti-HCV drugs. Based on a previous study showing the potential of the naturally occurring aurones as inhibitors of NS5B, we pursued our efforts to focus on pseudodimeric aurones that have never been investigated so far. Hence, 14 original compounds characterized by the presence of a spacer between the benzofuranone moieties were synthesized and investigated as HCV RdRp inhibitors by means of an in vitro assay. The most active inhibitor, pseudodimeric aurone 4 , induced high inhibition activity (IC 50 = 1.3 μM). Mutagenic and molecular modeling studies reveal that the binding site for the most active derivatives probably is the palm pocket I instead of the thumb pocket I as for the monomeric derivatives. [ABSTRACT FROM AUTHOR]

Summary During the early phase of replication, HIV reverse transcribes its RNA and crosses the nuclear envelope while escaping host antiviral defenses. The host factor Cyclophilin A (CypA) is essential for these steps and binds the HIV capsid; however, the mechanism underlying this effect remains elusive. Here, we identify related capsid mutants in HIV-1, HIV-2, and SIVmac that are restricted by CypA. This antiviral restriction of mutated viruses is conserved across species and prevents nuclear import of the viral cDNA. Importantly, the inner nuclear envelope protein SUN2 is required for the antiviral activity of CypA. We show that wild-type HIV exploits SUN2 in primary CD4 + T cells as an essential host factor that is required for the positive effects of CypA on reverse transcription and infection. Altogether, these results establish essential CypA-dependent functions of SUN2 in HIV infection at the nuclear envelope. [ABSTRACT FROM AUTHOR]

Abstract: Following our recent report showing the potential of naturally occurring aurones (2-benzylidenebenzofuran-3(2H)-ones) as anti-hepatitis C virus (HCV) agents, efforts were continued in order to refine the structural requirements for the inhibitory effect on HCV RNA-dependent RNA polymerase (RdRp). In this study, we targeted the B-ring moiety of aurones with the aim to improve structural features associated with higher inhibition of the targeted polymerase. In vitro evaluation of the RdRp inhibitory activity of the 37 newly synthesized compounds pointed out that the replacement of the B-ring with an N-substituted indole moiety induced the highest inhibitory effect. Of these, compounds 31, 40 and 41 were found to be the most active (IC50 = 2.3–2.4 μM). Docking experiments performed with the most active compounds revealed that the allosteric thumb pocket I of RdRp is the binding pocket for aurone analogues. [Copyright &y& Elsevier]

Background & Aims: Silymarin is a mixture of flavonolignans extracted from the milk thistle. Silymarin contains several molecules, including silibinin A, silibinin B, isosilibinin A, isosilibinin B, silicristin, and silidianin. Intravenous infusion of silibinin induces dose-dependent reduction of hepatitis C virus (HCV) RNA levels. The aim of this study was to test the principal isomers contained in silymarin preparations for their ability to inhibit HCV enzymatic functions and replication in different models. Methods: The inhibitory activity of silymarin components was tested in HCV RNA-dependent RNA polymerase and NS3/4A protease enzyme assays. Their ability to inhibit replication of an HCV genotype 1b replicon model and the JFH1 infectious HCV model in cell culture was also studied. Results: Silibinin A, silibinin B, their water-soluble dihydrogen succinate forms and Legalon SIL, a commercially available intravenous preparation of silibinin, inhibited HCV RNA-dependent RNA polymerase function, with inhibitory concentrations 50% of the order of 75−100 μM. Silibinin A and silibinin B also inhibited HCV genotype 1b replicon replication and HCV genotype 2a strain JFH1 replication in cell culture. None of these compounds inhibited HCV protease function. Conclusions: Silibinin A and silibinin B, as well as Legalon SIL, inhibit HCV replicon and JFH1 replication in cell culture. This effect is at least partly explained by the ability of these compounds to inhibit HCV RNA-dependent RNA polymerase activity. Our results provide a basis for the optimization and subsequent development of members of the Flavonoid family as specific HCV antivirals. [Copyright &y& Elsevier]

Abstract: The breast cancer resistance protein (BCRP, ABCG2) is among the latest discovered ABC proteins to be involved in MDR phenotype and for which only few inhibitors are known. In continuing our program aimed at discovering efficient multidrug resistance modulators, we conceived and synthesized new acridones as ABCG2 inhibitors. The design of target molecules was based on earlier results dealing with ABCG2 inhibition with flavone and chromone derivatives. The human wild-type (R482) ABCG2-transfected cells were used for rational screening of inhibitory acridones. The synthesis of target compounds, the inhibitory activity against ABCG2, and structure–activity relationships are described. One of the acridones was even more potent than the reference inhibitor, GF120918, as shown by its ability to inhibit mitoxantrone efflux. [Copyright &y& Elsevier]