The association between subgingival periodontal pathogens and systemic inflammation.

AIM: To investigate associations between periodontal disease pathogens and levels of systemic inflammation measured by C-reactive protein (CRP). METHODS: A representative sample of dentate 60-70-year-old men in Northern Ireland had a comprehensive periodontal examination. Men taking statins were excluded. Subgingival plaque samples were analysed by quantitative real time PCR to identify the presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia. High-sensitivity CRP (mg/l) was measured from fasting blood samples. Multiple linear regression analysis was performed using log-transformed CRP concentration as the dependent variable, with the presence of each periodontal pathogen as predictor variables, with adjustment for various potential confounders. RESULTS: A total of 518 men (mean age 63.6 SD 3.0 years) were included in the analysis. Multiple regression analysis showed that body mass index (p < 0.001), current smoking (p < 0.01), the detectable presence of P. gingivalis (p < 0.01) and hypertension (p = 0.01), were independently associated with an increased CRP. The detectable presence of P. gingivalis was associated with a 20% (95% confidence interval 4-35%) increase in CRP (mg/l) after adjustment for all other predictor variables. CONCLUSION: In these 60-70-year-old dentate men, the presence of P. gingivalis in subgingival plaque was significantly associated with a raised level of C-reactive protein.

Retinopathy is reduced during experimental diabetes in a mouse model of outer retinal degeneration.

PURPOSE: Diabetic patients who also have retinitis pigmentosa (RP) appear to have fewer and less severe retinal microvascular lesions. Diabetic retinopathy may be linked to increased inner retinal hypoxia, with the possibility that this is exacerbated by oxygen usage during the dark-adaptation response. Therefore, patients with RP with depleted rod photoreceptors may encounter proportionately less retinal hypoxia, and, when diabetes is also present, there may be fewer retinopathic lesions. This hypothesis was tested in rhodopsin knockout mice (Rho-/-) as an RP model in which the diabetic milieu is superimposed. The study was designed to investigate whether degeneration of the outer retina has any impact on hypoxia, to examine diabetes-related retinal gene expression responses, and to assess lesions of diabetic retinopathy. METHODS: Streptozotocin-induced diabetes was created in male C57Bl6 (wild-type; WT) and Rho-/- mice, and hyperglycemia was maintained for 5 months. The extent of diabetes was confirmed by measurement of glycated hemoglobin (%GHb) and accumulation of advanced glycation end products (AGEs). Retinal hypoxia was assessed using the bioreductive drug pimonidazole. The retinal microvasculature was studied in retinal flatmounts stained by the ADPase reaction, and the outer retina was evaluated histologically in paraffin-embedded sections. Retinal gene expression of VEGF-A, TNF-alpha, and mRNAs encoding basement membrane component proteins were quantified by real-time RT-PCR. RESULTS: The percentage GHb increased significantly in the presence of diabetes (P < 0.001) and was not different between WT or Rho-/- mice. Hypoxia increased in the retina of WT diabetic animals when compared with controls (P < 0.001) but this diabetes-induced change was absent in Rho-/- mice. Retinal gene expression of VEGF-A was significantly increased in WT mice with diabetes (P < 0.05), but was unchanged in Rho-/- mice. TNF-alpha gene expression significantly increased (4.9-fold) in WT mice with diabetes (P < 0.05) and also increased appreciably in Rho-/- mice but to a reduced extent (1.5 fold; P < 0.05). The outer nuclear layer in nondiabetic Rho-/- mice was reduced to a single layer after 6 months, but when diabetes was superimposed on this model, there was less degeneration of photoreceptors (P < 0.05). Vascular density was attenuated in diabetic WT mice compared with the nondiabetic control (P < 0.001); however, this diabetes-related disease was not observed in Rho-/- mice. CONCLUSIONS: Loss of the outer retina reduces the severity of diabetic retinopathy in a murine model. Oxygen usage by the photoreceptors during dark adaptation may contribute to retinal hypoxia and exacerbate the progression of diabetic retinopathy.

Rod photoreceptor loss in Rho-/- mice reduces retinal hypoxia and hypoxia-regulated gene expression.

PURPOSE: This study was conducted to evaluate whether regions of the retinal neuropile become hypoxic during periods of high oxygen consumption and whether depletion of the outer retina reduces hypoxia and related changes in gene expression. METHODS: Retinas from rhodopsin knockout (Rho-/-) mice were evaluated along with those of wild-type (WT) control animals. Retinas were also examined at the end of 12-hour dark or light periods, and a separate group was treated with l-cis-diltiazem at the beginning of a 12-hour dark period. Hypoxia was assessed by deposition of hypoxyprobe (HP) and HP-protein adducts were localized by immunohistochemistry and quantified using ELISA. Also, hypoxia-regulated gene expression and transcriptional activity were assessed alongside vascular density. RESULTS: Hypoxia was observed in the inner nuclear and ganglion cell layers in WT retina and was significantly reduced in Rho-/- mice (P < 0.05). Retinal hypoxia was significantly increased during dark adaptation in WT mice (P < 0.05), whereas no change was observed in Rho-/- or with l-cis-diltiazem-treated WT mice. Hypoxia-inducible factor (HIF)-1alpha DNA-binding and VEGF mRNA expression in Rho-/- retina was significantly reduced in unison with outer retinal depletion (P < 0.05). Retina from the Rho-/- mice displayed an extensive intraretinal vascular network after 6 months, although there was evidence that capillary density was depleted in comparison with that in WT retinas. CONCLUSIONS: Relative hypoxia occurs in the inner retina especially during dark adaptation. Photoreceptor loss reduces retinal oxygen usage and hypoxia which corresponds with attenuation of the retinal microvasculature. These studies suggest that in normal physiological conditions and diurnal cycles the adult retina exists in a state of borderline hypoxia, making this tissue particularly susceptible to even subtle reductions in perfusion.