Chronic Oral Infection with Porphyromonas gingivalis Accelerates Atheroma Formation by Shifting the Lipid Profile

BACKGROUND: Recent studies have suggested that periodontal disease increases the risk of atherothrombotic disease. Atherosclerosis has been characterized as a chronic inflammatory response to cholesterol deposition in the arteries. Although several studies have suggested that certain periodontopathic bacteria accelerate atherogenesis in apolipoprotein E-deficient mice, the mechanistic link between cholesterol accumulation and periodontal infection-induced inflammation is largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: We orally infected C57BL/6 and C57BL/6.KOR-Apoe(shl) (B6.Apoeshl) mice with Porphyromonas gingivalis, which is a representative periodontopathic bacterium, and evaluated atherogenesis, gene expression in the aorta and liver and systemic inflammatory and lipid profiles in the blood. Furthermore, the effect of lipopolysaccharide (LPS) from P. gingivalis on cholesterol transport and the related gene expression was examined in peritoneal macrophages. Alveolar bone resorption and elevation of systemic inflammatory responses were induced in both strains. Despite early changes in the expression of key genes involved in cholesterol turnover, such as liver X receptor and ATP-binding cassette A1, serum lipid profiles did not change with short-term infection. Long-term infection was associated with a reduction in serum high-density lipoprotein (HDL) cholesterol but not with the development of atherosclerotic lesions in wild-type mice. In B6.Apoeshl mice, long-term infection resulted in the elevation of very low-density lipoprotein (VLDL), LDL and total cholesterols in addition to the reduction of HDL cholesterol. This shift in the lipid profile was concomitant with a significant increase in atherosclerotic lesions. Stimulation with P. gingivalis LPS induced the change of cholesterol transport via targeting the expression of LDL receptor-related genes and resulted in the disturbance of regulatory mechanisms of the cholesterol level in macrophages. CONCLUSIONS/SIGNIFICANCE: Periodontal infection itself does not cause atherosclerosis, but it accelerates it by inducing systemic inflammation and deteriorating lipid metabolism, particularly when underlying hyperlidemia or susceptibility to hyperlipidemia exists, and it may contribute to the development of coronary heart disease

Cognitive and Socio-Emotional Deficits in Platelet-Derived Growth Factor Receptor-β Gene Knockout Mice

Platelet-derived growth factor (PDGF) is a potent mitogen. Extensive in vivo studies of PDGF and its receptor (PDGFR) genes have reported that PDGF plays an important role in embryogenesis and development of the central nervous system (CNS). Furthermore, PDGF and the β subunit of the PDGF receptor (PDGFR-β) have been reported to be associated with schizophrenia and autism. However, no study has reported on the effects of PDGF deletion on mice behavior. Here we generated novel mutant mice (PDGFR-β KO) in which PDGFR-β was conditionally deleted in CNS neurons using the Cre/loxP system. Mice without the Cre transgene but with floxed PDGFR-β were used as controls. Both groups of mice reached adulthood without any apparent anatomical defects. These mice were further examined by conducting several behavioral tests for spatial memory, social interaction, conditioning, prepulse inhibition, and forced swimming. The test results indicated that the PDGFR-β KO mice show deficits in all of these areas. Furthermore, an immunohistochemical study of the PDGFR-β KO mice brain indicated that the number of parvalbumin (calcium-binding protein)-positive (i.e., putatively γ-aminobutyric acid-ergic) neurons was low in the amygdala, hippocampus, and medial prefrontal cortex. Neurophysiological studies indicated that sensory-evoked gamma oscillation was low in the PDGFR-β KO mice, consistent with the observed reduction in the number of parvalbumin-positive neurons. These results suggest that PDGFR-β plays an important role in cognitive and socioemotional functions, and that deficits in this receptor may partly underlie the cognitive and socioemotional deficits observed in schizophrenic and autistic patients

Sequence Analysis of the Ribosomal DNA Intergenic Spacer 1 Regions of Trichosporon Species

We determined the sequence of the intergenic spacer (IGS) 1 region, which is located between the 26S and 5S rRNA genes, in 25 species of the genus Trichosporon. IGS 1 sequences varied in length from 195 to 719 bp. Comparative sequence analysis suggested that the divergence of IGS 1 sequences has been greater than that of the internal transcribed spacer regions. We also identified five genotypes of T. asahii, which is a major causative agent of deep-seated trichosporonosis, based on the IGS 1 sequences of 43 strains. Most of the isolates that originated in Japan were of genotype 1, whereas the American isolates were of genotype 3 or 5. Our results suggest that analysis of IGS regions provides a powerful method to distinguish between phylogenetically closely related species and that a geographic substructure may exist among T. asahii clinical isolates

Generation of STZ-induced diabetic mice.

<p>Eleven week-old wild type (WT) (n = 10) and SRR-KO (KO) mice (n = 10) were injected with STZ (60 mg/ kg) for 3 consecutive days. Body weight (A) and blood glucose levels (B) were measured for 24 weeks post-STZ treatment.</p

Expression of SRR in mouse retina.

<p>(A) Western blot analysis of retina proteins in control (non-treated) WT and KO mice using anti-SRR (upper) and anti-actin (lower) antibodies. The position of protein size markers are indicated on the right side. (B) Immunofluorescence staining of mouse retina from non-treated (Control) and STZ-induced diabetes mellitus (DM) mice using anti-SRR antibody (magenta). Nuclei were counterstained with DRAQ5 (blue). Five retinas per group were examined. Arrows indicate the SRR-immunopositive signals. Scale bar = 50 μm. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer.</p

STZ-induced microvascular changes in diabetic (DM) WT and SRR-KO mice.

<p>(A) The retinal vasculature were dual-labeled with isolectin-B4 (green) and anti-collagen IV antibodies (red) in flat-mount retinas. Arrows in the merged images indicate collagen IV positive and isolectin negative acellular capillaries. (B) Graph shows mean number of acellular capillaries in diabetic WT and SRR-KO mice. We counted the number of acellular capillaries in a 0.09 mm² field area. Scale bar = 50 μm. Data are presented as mean ± S. E. M. n = 15 fields/mouse, 5 mice per group. *<i>p</i> < 0.05; two-tailed Student’s <i>t</i>-test.</p

Brn3-immunopositive retinal ganglion cells in non-treated (control) and diabetic (DM) WT and SRR-KO mice.

<p>Immunofluorescence staining of retinal ganglion cells in flat-mount retinas using anti-Brn3 antibody. (A) Brn3-labeled retinal ganglion cells in the posterior retina in Control and DM mice. (B) Graph shows the number of Brn3-immunopositive cells in the posterior retina in Control and DM mice. (C) Brn3-labeled retinal ganglion cells in the peripheral retina in Control and DM mice. (D) Graph shows the number of Brn3-immunopositive cells in the peripheral retina in Control and DM mice. We counted the number of Brn3 positive cells in a 0.09 mm² field area. Scale bar = 100 μm. Data are presented as mean ± S. E. M. n = 5 mice per group. *<i>p</i> < 0.05; one-way Analysis of Variance (ANOVA).</p