Inhibitory mechanisms of tea polyphenols on the ultraviolet B-activated phosphatidylinositol 3-kinase-dependent pathway.

In this study, we investigated the effect of tea polyphenols, (-)-epigallocatechin-3-gallate or theaflavins, on UVB-induced phosphatidylinositol 3-kinase (PI3K) activation in mouse epidermal JB6 Cl 41 cells. Pretreatment of cells with these polyphenols inhibited UVB-induced PI3K activation. Furthermore, UVB-induced activation of Akt and ribosomal p70 S6 kinase (p70 S6-K), PI3K downstream effectors, were also attenuated by the polyphenols. In addition to LY294002, a PI3K inhibitor, pretreatment with a specific mitogen-activated protein/extracellular signal-regulated protein kinases (Erks) kinase 1 inhibitor, U0126, or a specific p38 kinase inhibitor, SB202190, blocked UVB-induced activation of both Akt and p70 S6-K. Pretreatment with LY294002 restrained UVB-induced phosphorylation of Erks, suggesting that in UVB signaling, the Erk pathway is mediated by PI3K. Moreover, pretreatment with rapamycin, an inhibitor of p70 S6-K, inhibited UVB-induced activation of p70 S6-K, but UVB-induced activation of Akt did not change. Interestingly, UVB-induced p70 S6-K activation was directly blocked by the addition of (-)-epigallocatechin-3-gallate or theaflavins, whereas these polyphenols showed only a weak inhibition on UVB-induced Akt activation. Because PI3K is an important factor in carcinogenesis, the inhibitory effect of these polyphenols on activation of PI3K and its downstream effects may further explain the anti-tumor promotion action of these tea constituents.

Proteinase inhibitors I and II from potatoes block UVB-induced AP-1 activity by regulating the AP-1 protein compositional patterns in JB6 cells.

Proteinase inhibitor I (Inh I) and proteinase inhibitor II (Inh II) from potato tubers are effective proteinase inhibitors of chymotrypsin and trypsin. Inh I and Inh II were shown to suppress irradiation-induced transformation in mouse embryo fibroblasts suggesting that they possess anticarcinogenic characteristics. We have previously demonstrated that Inh I and Inh II could effectively block UV irradiation-induced activation of transcription activator protein 1 (AP-1) in mouse JB6 epidermal cells, which mechanistically may explain their anticarcinogenic actions. In the present study, we investigated the effects of Inh I and Inh II on the expression and composition pattern of the AP-1 complex following stimulation by UV B (UVB) irradiation in the JB6 model. We found that Inh I and Inh II specifically inhibited UVB-induced AP-1, but not NFkappaB, activity in JB6 cells. Both Inh I and Inh II up-regulated AP-1 constituent proteins, JunD and Fra-2, and suppressed c-Jun and c-Fos expression and composition in bound AP-1 in response to UVB stimulation. This regulation of the AP-1 protein compositional pattern in response to Inh I or Inh II may be critical for the inhibition of UVB-induced AP-1 activity by these agents found in potatoes.

Alterations in ICAM-1 and ELAM-1 expression in psoriatic lesions following various treatments.

The expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) and intercellular adhesion molecule-1 (ICAM-1) in psoriatic lesions was immunohistochemically examined before and after various single and combination therapies. The increased staining intensity of both adhesion molecules on the proliferated papillary venules in pretreated lesion was markedly reduced after cyclosporin-A monotherapy and etretinate therapy combined with oral eicosapentaenoic acid (EPA), psoralen plus ultraviolet-A radiation (PUVA) or ultraviolet-B radiation (UVB). Less pronounced alterations were observed with etretinate, EPA, PUVA, UVB, and topical corticosteroid alone. The epidermal expression of ICAM-1, on the other hand, faded out completely following any of the treatment measures. The findings suggest that cyclosporin-A monotherapy and the etretinate combination therapies have greater inhibitory effects on the endothelial expression of the adhesion molecules than the other monotherapies. Loss of the epidermal expression of ICAM-1 may be nonspecific to the treatment.

HIV-1 reverse transcriptase inhibitor from Phyllanthus niruri.

An aqueous extract of Phyllanthus niruri (Euphorbiaceae) inhibited human immunodeficiency virus type-1 reverse transcriptase (HIV-1-RT). The inhibitor against HIV-1-RT in this plant was purified by combination of three column chromatographies, Sephadex LH-20, cellulose, and reverse-phase high-performance liquid chromatography. The inhibitor was then identified by nuclear magnetic resonance (NMR) spectra as repandusinic acid A monosodium salt (RA) which was originally isolated from Mallotus repandus. The 50% inhibitory doses (ID50) of RA on HIV-1-RT and DNA polymerase alpha (from HeLa cells) were 0.05 microM and 0.6 microM, respectively, representing approximately a 10-fold more sensitivity of HIV-1-RT compared with DNA polymerase alpha. RA was shown to be a competitive inhibitor with respect to the template-primer while it was a noncompetitive inhibitor with respect to the substrate. RA as low as 10.1 microM inhibited HIV-1-induced cytopathogenicity in MT-4 cells. In addition, 4.5 microM of RA inhibited HIV-1-induced giant cell formation of SUP-T1 approximately 50%. RA (2.5 microM) inhibited up to 90% of HIV-1 specific p24 antigen production in a Clone H9 cell system.

Reduced cleavage by sodium hydroxide of methyladenine in DNA sequencing.

When the Maxam and Gilbert DNA sequencing method which is modified by Bencini et al. (Biotechniques Jan/Feb pp4-5, 1984) is applied to DNA containing methylated adenine in a GATC sequence, the cleavage reaction by sodium hydroxide is found to be greatly reduced in comparison to that of non-methylated adenine. Thus, a faint band in A greater than C reaction suggests a methyl adenine and can be used for its detection. That the faint band corresponds to a methyladenine was confirmed by Sanger sequencing of the same fragment and further by Maxam and Gilbert sequencing of the complementary strand of DNA, which was replicated in an E. coli strain either having or lacking methylation enzymes.