The present study indicated that PPPs could be used in foods as natural antioxidants with strong antioxidant activity. Copyright © 2007 Society of Chemical Industry.

Previously pleiotrophin (PTN) was identified among proteins secreted by Swiss 3T3 cells as a mitogen for cultured adult rat hepatocytes. The present study showed that the growth of rat hepatocytes was enhanced when cultured with rat hepatic stellate cells (HSCs). HSCs expressed PTN mRNA and secreted its protein in the co-cultures. Recombinant PTN enhanced the growth of hepatocytes in culture, suggesting that HSCs stimulate the growth of hepatocytes through the action of PTN. To know the biological role of PTN in the growth of hepatocytes in vivo, we examined the expression of PTN in four regeneration models of adult liver and embryonic liver of rat. The expression of PTN mRNA in the liver was markedly up-regulated by the treatment with D-galactosamine (GalN) or with acetylaminofluorene followed by partial hepatectomy. HSCs expressed PTN mRNA in response to GalN treatment and its protein was found on hepatocytes. The mRNA expression of N-syndecan, a PTN receptor, was up-regulated in GalN-treated hepatocytes. The mesenchymal cells in the septum transversum enclosing the embryonic liver, but not embryonic HSCs, expressed PTN mRNA. We suggest that PTN is secreted from activated adult HSCs and embryonic mesenchymal cells as a mitogen of parenchymal cells in adult and embryonic liver, respectively.

The protective effects of hen egg yolk phosvitin phosphopeptides (PPPs) against hydrogen peroxide (H2O2)-induced oxidative stress were evaluated in an in vitro assay using human intestinal epithelial cells. Caco-2 cells were stimulated with 1 mM H2O2 for 6 h, and the secretion of IL-8, a proinflammatory mediator, was determined by ELISA as a biomarker of oxidative stress. The inhibition of H2O2-induced IL-8 secretion from Caco-2 cells was observed by pretreatment for 2 h with PPPs, but not with phosvitin. PPPs also suppressed the formation of malondialdehyde in H2O2-treated Caco-2 cells. Furthermore, intracellular glutathione levels and glutathione reductase activity were elevated by the addition of PPPs. The protective effects of PPPs against H2O2-induced oxidative stress were almost the same as that of glutathione, and PPPs with a high content of phosphorus exhibited higher protective activity than PPPs without phosphorus; however, phosphoserine itself did not show any significant antioxidative stress activity. These findings suggest that oligophosphopeptides from hen egg yolk phosvitin possess novel antioxidative activity against oxidative stress in intestinal epithelial cells and that phosphorus and peptide structure seem to have a key role in the activity.

Chlorogenic acid (CGA) is a natural chemical ester composed of caffeic acid and (-)-quinic acid, and is further metabolized into active compounds in the living body. Here, we aimed to provide fundamental information on the antimicrobial action of CGA and related compounds against the Gram-negative bacterium Escherichia coli IFO 3301. Bacteriostatic effects were assessed by spectrophotometry, and bactericidal effects were determined by enumerating viable cells on MacConkey agar plates. CGA and related compounds exhibited specific antimicrobial activity and corresponding reduction in log survival ratio, in which ferulic, isoferulic, benzoic, and hydroxybenzoic acids exhibited obvious antimicrobial activity against E. coli. In a timekill assay, it was observed that bactericidal effects were associated with treatment time, temperature, and dose. A reduction in log survival ratio was observed at low pH as well as under thermal stress condition. Thus, we demonstrated that CGA and related compounds have not only bacteriostatic effects but also bactericidal effects. Keywords bactericidal effect • bacteriostatic effect • chlorogenic acid • polyphenol Materials and MethodsMaterials. Dimethyl sulfoxide, quinic acid, and ferulic acid were purchased from WAKO Pure Chemical Industries Ltd. (Japan). Luria broth (LB), and benzoic, hydroxybenzoic, caffeic, and hippuric acids were purchased from SIGMA-ALDRICH (Japan).