Biological effects and activity optimization of small-molecule, drug-like synthetic anion transporters.

The balance of normal anion concentrations in cells provides basis for maintaining cellular morphology and function. Disrupting the homeostasis of cellular anions and lysosomal pH, in particular with high selectivity for cancer cells over normal cells may serve as a promising approach for the treatment of cancers. Small-molecule organic compounds with transmembrane anion transport activity, namely synthetic anion transporters are able to destroy the homeostasis of cellular anions, in particular chloride anions to trigger cell death and thus may be developed as a new class of anti-tumor drugs. This paper reviews the latest advance in the investigation into the in vitro anion transport, promising anti-tumor activity and probable mechanism of biological action of synthetic anion transporters. The strategies for optimizing the biological activity of synthetic anion transporters and improving the selectivity for cancer cells over normal cells are also discussed.

[A non-infectious and quantitative cell-based bioassay for screening HIV entry inhibitors targeting HIV envelope proteins].

OBJECTIVE: To develop an objective bioassay for quantitative detection of HIV-induced cell-cell fusion for screening HIV entry inhibitors. METHODS: HL2/3 cells expressing HIV envelope proteins gp120/gp41, Tat, and other HIV proteins were co-cultured with HeLa-CD4-LTR-beta-gal cells expressing CD4 receptor and HIV LTR triggered reporter gene beta-galactosidase. The enzyme activities of beta-galactosidase were detected by a chromogenic substrate, chlorophenol red-beta-galactopyranoside (CPRG). Specific HIV entry inhibitors were used to validate the established detecting method. RESULTS: No syncytium was formed by mixing HL2/3 and HeLa-CD4-LTR-beta-gal cells. However, the membrane could be fused and the Tat expressed by HL2/3 cells could bind to HIV LTR on HeLa-CD4-LTR-beta-gal cells and trigger the expression of beta-galactosidase. CPRG allowed quantitative and sensitive detection of the activity of beta-galactosidase. Further studies showed that HIV entry inhibitors could inhibit the activity of beta-galactosidase in a dose-dependent manner. CONCLUSION: We have developed a simple, cheap, objective and quantitative non-infectious cell-cell fusion bioassay that can be used to screen for anti-HIV agents targeting the virus entry from natural and synthetic compound libraries.

[Study of the mechanism of caffeoyl glucopyranoses in inhibiting HIV-1 entry using pseudotyped virus system].

OBJECTIVE: To investigate the inhibitory activities of caffeoyl glucopyranoses purified from Balanophora japonica Makino on HIV entry and their mechanism. METHODS: HIV-1 Env pseudovirus was used to evaluate the anti-HIV-1 activity of those compounds. ELISA and molecular docking were used to study the mechanism of the actions of the active compounds. RESULTS: We used the HIV-1 Env pseudovirus to test the anti-HIV-1 activity of the six phenolic compounds (final concentration 25 microg/ml), and found that only 1,2,6-Tri-O-caffeoyl-beta-D-glucopyranose (TCGP) and 1,3-Di-O-caffeoyl-4-O-galloyl-beta-D- glucopyranose (DCGGP) could effectively inhibit the entry of HIV-1 Env pseudovirus into the target cells in a dose-dependent manner, with IC(50) values of 5.5-/+0.2 and 5.3-/+0.1 microg/ml, respectively. These two compounds could also blocked the gp41 six-helix bundle formation. Molecular docking analysis suggested that they might bind to the hydrophobic cavity of the gp41 N-trimeric coiled-coil. CONCLUSION: TCGP and DCGGP are potent HIV-1 entry inhibitors targeting gp41 and can serve as lead compounds for developing novel anti-HIV-1 microbicides for prevention of sexual HIV-1 transmission.

[Inhibition of HIV-1 mediated cell-cell fusion by saponin fraction from Psidium guajava leaf].

OBJECTIVE: To investigate the effects of the total saponin of Psidium guajava leaf (TSGL) on HIV-1 envelop proteins (env) mediated virus entry into target cells. METHODS: The TSGL was purified and concentrated using SA-1 macropore resin. The effect of TSGL on HIV-1 entry into target cells was tested using a cell-cell fusion assay by mixing CHO-WT and MT-2 cells. The cytotoxicity of TSGL was measured by MTT assay. The activity of TSGL on blocking the HIV-1 gp41 six helical bundle (6-HB) formation was analyzed by ELISA and Native-PAGE (N-PAGE). RESULTS: The TSGL could inhibit HIV env mediated cell-cell fusion with an IC50 of (7.33 +/- 0.40) microg/mL, and displayed little cytotoxicity at that concentration. ELISA assay showed that the TSGL could prevent gp41 6-HB formation with inhibitory activity of 95.93% at 25 microg/mL. N-PAGE study confirmed the inhibitory effect of TSGL on gp41 6-HB formation. CONCLUSIONS: The TSGL can inhibit HIV entry target cells by interfering the envelop subunit gp41 form the critical 6-HB structure.