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A-type cranberry proanthocyanidins (AC-PACs) have recently been reported to be beneficial for human health, especially urinary tract health. The effect of these proanthocyanidins on periodontitis, a destructive disease of tooth-supporting tissues, needs to be investigated. The purpose of this study was to investigate the effects of AC-PACs on various virulence determinants of Porphyromonas gingivalis as well as on the inflammatory response of oral epithelial cells stimulated by this periodontopathogen. We examined the effects of AC-PACs on P. gingivalis growth and biofilm formation, adherence to human oral epithelial cells and protein-coated surfaces, collagenase activity, and invasiveness. We also tested the ability of AC-PACs to modulate the P. gingivalis-induced inflammatory response by human oral epithelial cells. Our results showed that while AC-PACs neutralized all the virulence properties of P. gingivalis in a dose-dependent fashion, they did not interfere with growth. They also inhibited the secretion of interleukin-8 (IL-8) and chemokine (C-C motif) ligand 5 (CCL5) but did not affect the secretion of IL-6 by epithelial cells stimulated with P. gingivalis. This anti-inflammatory effect was associated with reduced activation of the nuclear factor-kappaB (NF-kappaB) p65 pathway. AC-PACs may be potentially valuable bioactive molecules for the development of new strategies to treat and prevent P. gingivalis-associated periodontal diseases.

The Tf1 element of Schizosaccharomyces pombe is a long terminal repeat-containing retrotransposon that encodes functional protease, reverse transcriptase, and integrase proteins. Although these proteins are known to be necessary for protein processing, reverse transcription, and integration, respectively, the function of the protein thought to be Gag has not been determined. We present here the first electron microscopy of Tf1 particles. We tested whether the putative Gag of Tf1 was required for particle formation, packaging of RNA, and reverse transcription. We generated deletions of 10 amino acids in each of the four hydrophilic domains of the protein and found that all four mutations reduced transposition activity. The N-terminal deletion removed a nuclear localization signal and inhibited nuclear import of the transposon. The two mutations in the center of Gag destabilized the protein and resulted in no virus-like particles. The C-terminal deletion caused a defect in RNA packaging and, as a result, low levels of cDNA. The electron microscopy of cells expressing a truncated Tf1 showed that Gag alone was sufficient for the formation of virus-like particles. Taken together, these results indicate that Tf1 encodes a Gag protein that is a functional equivalent of the Gag proteins of retroviruses.

In Saccharomyces cerevisiae, carbon and nitrogen metabolisms are connected via the incorporation of ammonia into glutamate; this reaction is catalyzed by the NADP-dependent glutamate dehydrogenase (NADP-GDH) encoded by the GDH1 gene. In this report, we show that the GDH1 gene requires the CCAAT box-binding activator (HAP complex) for optimal expression. This conclusion is based on several lines of evidence: (1) overexpression of GDH1 can correct the growth defect of hap2 and hap3 mutants on ammonium sulfate as a nitrogen source, (ii) Northern (RNA) blot analysis shows that the steady-state level of GDH1 mRNA is strongly lowered in a hap2 mutant, (iii) expression of a GDH1-lacZ fusion is drastically reduced in hap mutants, (iv) NADP-GDH activity is several times lower in the hap mutants compared with that in the isogenic wild-type strain, and finally, (v) site-directed mutagenesis of two consensual HAP binding sites in the GDH1 promoter strongly reduces expression of GDH1 and makes it HAP independent. Expression of GDH1 is also regulated by the carbon source, i.e., expression is higher on lactate than on ethanol, glycerol, or galactose, with the lowest expression being found on glucose. Finally, we show that a hap2 mutation does not affect expression of other genes involved in nitrogen metabolism (GDH2, GLN1, and GLN3 encoding, respectively, the NAD-GDH, glutamine synthetase, and a general activator of several nitrogen catabolic genes). The HAP complex is known to regulate expression of several genes involved in carbon metabolism; its role in the control of GDH1 gene expression, therefore, provides evidence for a cross-pathway regulation between carbon and nitrogen metabolisms.