Prepulse inhibition (PPI) is a compelling endophenotype (biological markers) for mental disorders including schizophrenia. In a previous study, we identified Fabp7, a fatty acid binding protein 7 as one of the genes controlling PPI in mice and showed that this gene was associated with schizophrenia. We also demonstrated that disrupting Fabp7 dampened hippocampal neurogenesis. In this study, we examined a link between neurogenesis and PPI using different animal models and exploring the possibility of postnatal manipulation of neurogenesis affecting PPI, since gene-deficient mice show biological disturbances from prenatal stages. In parallel, we tested the potential for dietary polyunsaturated fatty acids (PUFAs), arachidonic acid (ARA) and/or docosahexaenoic acid (DHA), to promote neurogenesis and improve PPI. PUFAs are ligands for Fabp members and are abundantly expressed in neural stem/progenitor cells in the hippocampus. Our results are: (1) an independent model animal, Pax6 (+/−) rats, exhibited PPI deficits along with impaired postnatal neurogenesis; (2) methylazoxymethanol acetate (an anti-proliferative drug) elicited decreased neurogenesis even in postnatal period, and PPI defects in young adult rats (10 weeks) when the drug was given at the juvenile stage (4–5 weeks); (3) administering ARA for 4 weeks after birth promoted neurogenesis in wild type rats; (4) raising Pax6 (+/−) pups on an ARA-containing diet enhanced neurogenesis and partially improved PPI in adult animals. These results suggest the potential benefit of ARA in ameliorating PPI deficits relevant to psychiatric disorders and suggest that the effect may be correlated with augmented postnatal neurogenesis.

BackgroundThe importance of arachidonic acid (ARA) among the elderly has recently gained increased attention. The effects of ARA supplementation in the elderly are not fully understood, although ARA is considered to be associated with various diseases. We investigate whether ARA supplementation to Japanese elderly subjects affects clinical parameters involved in cardiovascular, inflammatory, and allergic diseases. We also examine the levels of ARA metabolites such as prostanoids during intervention.MethodsWe conducted a randomized, double-blind and placebo-controlled parallel group intervention trial. ARA-enriched oil (240 or 720 mg ARA per day) or placebo was administered to Japanese healthy men and women aged 55-70 years for 4 weeks followed by a 4-week washout period. The fatty acid contents of plasma phospholipids, clinical parameters, and ARA metabolites were determined at baseline, 2, 4, and 8 weeks.ResultsThe ARA content in plasma phospholipids in the ARA-administrated groups increased dose-dependently and was almost the same at 2 weeks and at 4 weeks. The elevated ARA content decreased to nearly baseline during a 4-week washout period. During the supplementation and washout periods, no changes were observed in eicosapentaenoic acid and docosahexaenoic acid contents. There were no changes in clinical blood parameters related to cardiovascular, inflammatory and allergic diseases. ARA supplementation did not alter the level of ARA metabolites such as urinary 11-dehydro thromboxane B2, 2,3-dinor-6-keto prostaglandin (PG) F1α and 9,15-dioxo-11α-hydroxy-13,14-dihydro-2,3,4,5-tetranor-prostan-1,20-dioic acid (tetranor-PGEM), and plasma PGE2 and lipoxin A4. ARA in plasma phospholipids was not correlated with ARA metabolite levels in the blood or urine.ConclusionThese results indicate that ARA supplementation, even at a relatively high dose, does not increase ARA metabolites, and suggest that it does not induce cardiovascular, inflammatory or allergic diseases in Japanese elderly individuals.

SummaryPorphyromonas gingivalis, a Gram-negative anaerobe, is known to be involved in the pathogenesis of periodontitis. P. gingivalis fimbriae, which are proteinaceous appendages extending from the cell surface, may contribute to the adherence of the organism to the host cell surface. We previously suggested that arginine-specific protease produced by P. gingivalis enhanced the adherence of purified fimbriae to fibroblasts or matrix proteins. In this study, we have revealed the mechanism of the enhanced binding of fimbriae by the protease in more detail. Arg-specific protease and fimbriae were obtained from P. gingivalis 381 cells and purified. We then analysed the interaction of fimbriae and immobilized fibronectins (intact or partially degraded fibronectin by the purified protease) by using the real-time biomolecular interaction analysis (BIAcore) system with an optical biosensor based on the principles of surface plasmon resonance. BIAcore profiles demonstrated an enhanced interaction between fimbriae and protease-degraded fibronectin. We also showed specific binding of fimbriae to the degraded fibronectin by means of BIAcore analysis. The binding of biotinylated fimbriae to immobilized fibronectin was examined by enzymelinked biotin-avidin assay. The purified protease enhanced the fimbrial binding to the immobilized fibronectin. The enhancement was inhibited by the addition of L-Arg, or oligopeptides containing the Arg residue at the C-terminus in the fimbrial binding reaction, suggesting that the P. gingivalis fimbriae may potentially have an ability to bind tightly to the Arg residue at C-terminus. Taken together, these studies indicate that P. gingivalis arginine-specific protease can expose a cryptitope in the matrix protein molecules, i.e. the C-terminal Arg residue of the host matrix proteins, so that the organism can adhere to the surface layer in the oral cavity through fimbriae-Arg interaction (a novel host-parasite relationship).

It has been shown that Porphyromonas gingivalis 381, a suspected periodontopathogen, possesses fimbriae on its cell surface. The organism is also known to produce proteases which can degrade the host cell surface matrix proteins. In this study, we investigated the effect of protease on the binding of the purified P. gingivalis fimbriae to cultured fibroblasts or matrix proteins. A protease that can hydrolyze benzoyl-L-arginine p-nitroanilide was obtained from P. gingivalis 381 cells by sonication in phosphate-buffered 0.2% Triton X-100 and was purified by column chromatography. The molecular size of the protease was estimated to be 55 kDa by gel filtration or 47 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The enzyme activity was markedly inhibited by sulfhydryl reagents, antipain, and leupeptin. The protease degraded various host proteins, including collagen and fibronectin, and cleaved the COOH terminus of the arginine residue in peptides such as benzoyl-L-arginine p-nitroanilide. However, P. gingivalis fimbriae were not degraded by this protease activity. The enzyme activity was enhanced in the presence of reducing agents or CaCl 2. When cultured fibroblasts were partially treated with the protease, the binding of the purified P. gingivalis fimbriae to the fibroblast monolayer was increased significantly. However, this enhancing effect was suppressed upon the addition of antipain and leupeptin. Similarly, binding of the fimbriae to the collagen or fibronectin immobilized on the microtiter wells was also enhanced. Addition of these host matrix proteins efficiently inhibited the binding of fimbriae to the fibroblast monolayer. The binding assay of fimbriae using dipeptidyl ligand affinity column chromatography demonstrated a clear interaction between fimbriae and the arginine residue. Taken together, these results indicate that the P. gingivalis protease at least partially degrades the host matrix proteins, which, in turn, may lead to an increased exposure of the cryptic ligands that can result in enhanced fimbria-mediated binding of this organism to periodontal tissues. Porphyromonas gingivalis, a black-pigmented gram-negative anaerobe, has been recognized as an important pathogenic organism in adult periodontitis, a chronic inflammatory disease (23). P. gingivalis possesses fine fibrillar proteinaceous appendages, fimbriae, which are arranged peritrichously, emerging from the cell surface (14). Bacterial adherence to the host tissue is an essential step in the initiation of infectious diseases, and an adhesive function held by many pathogenic bacteria is now well recognized and documented (29). It has been suggested that P. gingivalis fimbriae are involved in adherence to host cells (16, 26, 30). P. gingivalis produces various enzymes such as protease, collagenase, gelatinase, peptidase, and hyaluronidase, which are now recognized as virulence factors of this organism. Among these enzymes, proteolytic enzymes are thought to be most important, since they degrade host tissue protein...