Inhibition of DNA dependent RNA synthesis by porphyrin photosensitizers

Select porphyrin photosensitizers were studied to determine their effects on DNA-dependent RNA synthesis in the presence and absence of visible light. All of the porphyrins were found to inhibit wheat germ polymerase II to some degree in the dark. In the presence of light, the inhibitory effects of the porphyrins was found to result from both inactivation of the enzyme and impairment of the ability of DNA to serve as a template.     

Suppression of angiogenesis by the plant alkaloid, sanguinarine

Sanguinarine is a benzophenanthridine alkaloid derived from the root of Sanguinaria canadensis. Its principal pharmacologic use is in dental products where it has antibacterial, antifungal, and anti-inflammatory activities that reduce gingival inflammation and supragingival plaque formation. Angiogenesis is indispensable for inflammation, and most angiogenesis is dependent on vascular endothelial growth factor (VEGF). However, the effect of sanguinarine on angiogenesis is not known. In the present study, we examined the effect of sanguinarine on VEGF-induced angiogenesis in vitro and in vivo. Interestingly, sanguinarine markedly suppressed VEGF-induced endothelial cell migration, sprouting, and survival in vitro in a dose-dependent manner at nanomolar concentrations. Furthermore, sanguinarine potently suppressed blood vessel formation in vivo in mouse Matrigel plugs and the chorioallantoic membrane of chick embryos. Our biochemical assays indicated that sanguinarine strongly suppressed basal and VEGF-induced Akt phosphorylation, while it did not produce any changes in VEGF-induced activation of ERK1/2 and PLCγ1. Therefore, we conclude that sanguinarine is a potent antiangiogenic natural product, and its mode of action could involve the blocking of VEGF-induced Akt activation. Thus, in addition to antibacterial, antifungal, and anti-inflammatory activities, sanguinarine has a novel antiangiogenic role.     

Inhibition of HIV-1 proviral DNA synthesis and RNA accumulation by mismatched dsRNA

The antiviral activity of mismatched dsRNA of the form poly(I):poly(C12-U)n (Ampligen) against the human immunodeficiency virus type 1 (HIV-1) was investigated by RNA-RNA and RNA-DNA hybridizations. Mismatched dsRNA delayed the appearance of newly transcribed HIV-1 RNA as detected by liquid dot-blot hybridization in cultures of H9 T-lymphoblastoid cells following virus challenge. The appearance of proviral DNA as detected by Southern hybridization following virus challenge in H9 cells was also delayed. Mismatched dsRNA had no effect in syncytium inhibition assays performed by fusing MT-2 cells with H9/HTLV-IIIB cells. These results suggest that the in vitro anti-HIV-1 activity of mismatched dsRNA occurs, at least in part, at an early stage in the viral replication cycle following initial gp120-CD4 binding.     

Inhibition of RNA synthesis by oxolinic acid is unrelated to average DNA supercoiling.

Oxolinic acid reduced RNA synthesis rates whether chromosome supercoiling decreased, increased, or remained unchanged. Thus, inhibition of RNA synthesis by oxolinic acid appears to involve factors other than average DNA supercoiling level. Coumermycin A1 caused RNA synthesis rates to increase or decrease roughly in parallel with DNA supercoiling.     

Inhibition of the activity of membrane-bound Ca2+-ATPase in the sarcoplasmic reticulum fragments of rabbit skeletal muscles by the alkaloid sanguinarine

Sanguinarine, a plant DNA-intercalator, is shown to inhibit the enzyme activity of the membrane-bound Ca2+-ATPase of rabbit skeletal muscle sarcoplasmic reticulum fragments. This inhibition could be interpreted by the well known ability of this alkaloid to interact with sulphydryl groups of the enzymes. Sanguinarine is a weaker inhibitor of this reaction than a sulphydryl group poison Ag+. The I50 is 3.10(-6) M for Ag+ and 7.10(-5) M for sanguinarine in the reaction medium with NO3- substituted for Cl-. In the standard reaction medium containing Cl-, the I50 for sanguinarine is 1.8.10(-4) M. In this case sanguinarine activates Ca2+-ATPase at low concentrations presumably because of uncoupling ATP hydrolysis from Ca2+ transport through membrane. Other agents studied are: DNA-intercalators--ethidium bromide, acriflavine, acridine orange; DNA-complexing antibiotics--actinomycin D, and olivomycin, alkaloids, quinine, morphine, berberine and an uncoupler of oxidative phosphorylation 2,4-dinitrophenol. These were found not to inhibit Ca2+-ATPase activity up to the concentrations of 10(-3)-10(-4) M.