Hyposalivation and periodontal disease as oral non-articular characteristics in rheumatoid arthritis.

OBJECTIVE: To investigate the association among rheumatoid arthritis (RA), saliva production, and periodontal status. METHODS: An observational study was carried out on 103 subjects with RA and 103 without RA matched by sex and age. Rheumatologic evaluation included serological and clinical variables. A full mouth periodontal examination was performed according to the American Academy of Periodontology (1999). Resting and stimulated whole salivary flows were determined after spiting during 5 min. RESULTS: RA was associated with a higher prevalence of severe periodontitis (12% vs. 4%), with a marked reduction in resting and stimulated saliva production, and with a higher prevalence of resting (19% vs. 0%) and also stimulated hyposalivation (54% vs. 10%), compared with the control group. The differences in mean resting and stimulated salivary flows between RA and control groups persisted after the exclusion of people with hyposalivation. Saliva production was not associated with the presence or the severity of periodontal disease, or with the rheumatic clinical characteristics of the patients. CONCLUSIONS: More than 50% of people with RA have some degree of reduction in their salivary flows, an affection not associated with the periodontal status or rheumatic activity, which are the expression of the two related inflammatory diseases. The influence of autonomic dysfunction on hyposalivation can be considered. While periodontitis would be a disease-associated comorbidity of RA, poor saliva production should be included among the extra-articular manifestations. Key Points • Rheumatoid arthritis patients are more prone to suffer from periodontitis and/or hyposalivation. • Periodontal disease is more prevalent in people with rheumatoid arthritis and also an association was found between the severities of both pathologies. • More than 50% of people with RA would have some degree of reduction in their salivary flows, an affection not associated with the periodontal status or rheumatic activity. • Reduced saliva production in rheumatoid arthritis patients should be included among the extra-articular manifestations.

Disease activity and subcutaneous nodules are associated to severe periodontitis in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) was significantly associated with increased overall risk of periodontitis, both chronic, inflammatory pathologies leading to connective tissue breakdown and bone destruction. To identify clinical and/or serological variables routinely evaluated during follow-up of people with RA which are associated with the severity of their periodontal disease. An observational, cross-sectional study was carried out, which included RA patients according to ACR/EULAR 2010 criteria having chronic periodontal disease. RA clinical parameters (disease duration, erythrocyte sedimentation rate, serum C-reactive protein, disease activity (DAS28) and rheumatoid factor, presence of bone erosions and rheumatic nodules) and also corticosteroid therapy were considered. Periodontitis was evaluated according to the American Academy of Periodontology (1999) and chronic periodontitis was assessed by full mouth periapical radiographic examination, periodontal probing depth, clinical attachment level and bleeding index. A total of 110 subjects with RA and chronic periodontitis were included. The female/male relation was 5.1, and no significant differences between genres were found in rheumatic or oral variables. RA patients with longer disease duration, higher disease activity and with rheumatic nodules had significantly greater periodontitis severity. Multivariate analysis confirmed that severe periodontitis was associated with DAS283 4.1 (OR 51.4, CI 95% 9.4-281.5) and the presence of rheumatic nodules (OR 6.4, CI 95% 1.3-31.6). Disease activity and rheumatic nodules were strongly associated with severe periodontitis. Based on these findings it would be desirable to include interdisciplinary management at an early stage of RA to ensure comprehensive treatment of both pathologies.

Salivary extracellular vesicles can modulate purinergic signalling in oral tissues by combined ectonucleoside triphosphate diphosphohydrolases and ecto-5'-nucleotidase activities.

We reported previously that the rat submandibular gland is able to release nanovesicles capable to hydrolyse millimolar concentrations of ATP, ADP and AMP in vitro. Here, we show that rat saliva also contains nanovesicles with the ability to hydrolyse ATP. Our aim was to identify and characterize vesicular nucleotidases by using kinetic, immunological and in silico approaches. Nucleotidase activity in the absence or presence of specific inhibitors allowed us to assume the participation of NTPDase1, -2 and -3, together with ecto-5'-nucleotidase, confirmed using specific antibodies. At neutral pH, initial ATPase activity would be mostly due to NTPDase2, which was thereafter inactivated, leaving NTPDase1 and NTPDase3 to hydrolyse ATP and ADP with an efficacy ATPase/ADPase around 2. Ecto-5'nucleotidase would be mainly responsible for AMP hydrolysis and adenosine accumulation. We proposed a kinetic model for NTPDase2 as a tool to isolate and analyse the turnover of this enzyme in the presence of different ATP concentrations, including those expected in extracellular media. Our study characterizes the ectonucleotidases carried by extracellular vesicles which contribute to modulate ATP and adenosine concentrations in the oral cavity, essential players in purinergic signalling.

Rat submandibular glands secrete nanovesicles with NTPDase and 5'-nucleotidase activities.

Extracellular nucleotides modulate a wide number of biological processes such as neurotransmission, platelet aggregation, muscle contraction, and epithelial secretion acting by the purinergic pathway. Nucleotidases as NTPDases and ecto-5'-nucleotidase are membrane-anchored proteins that regulate extracellular nucleotide concentrations. In a previous work, we have partially characterized an NTPDase-like activity expressed by rat submandibular gland microsomes, giving rise to the hypothesis that membrane NTPDases could be released into salivary ducts to regulate luminal nucleotide concentrations as was previously proposed for ovarian, prostatic, and pancreatic secretions. Present results show that rat submandibular glands incubated in vitro release membrane-associated NTPDase and ecto-5'-nucleotidase activities. Electron microscopy images show that released membranes presenting nucleotidase activity correspond to exosome-like vesicles which are also present at microsomal fraction. Both exosome release and nucleotidase activities are raised by adrenergic stimulation. Nucleotidase activities present the same kinetic characteristics than microsomal nucleotidase activity, corresponding mainly to the action of NTPDase2 and NTPDase3 isoforms as well as 5'-nucleotidase. This is consistent with Western blot analysis revealing the presence of these enzymes in the microsomal fraction.

Stoichiometry of ATP and metal cofactor interaction with the sarcoplasmic reticulum Ca(2+)-ATPase: a binding model accounting for radioisotopic and fluorescence results.

Sarcoplasmic reticulum Ca-ATPase belongs to the P-type ATPases family and transports calcium at the expense of ATP hydrolysis. For years, a complex pattern of activity has been observed as a function of ATP and metal cofactor concentrations, leaving the stoichiometry of both metal and ATP in the active site as an open question. In agreement with recent structural studies we present here-using Mn as analogue of Mg-radioisotopic and fluorescence results showing that two metal ions bind to the Ca-ATPase favoring ATP binding. We further show that low ATP concentration favors the binding of these ions, whereas high ATP concentration is inhibitory. We propose a binding model for ATP and metal ions, which permits simulation of our data. Finally, we suggest that (i) the contribution of two metal ions as cofactors of ATP is essential to get maximal activity; (ii) the contribution of two ATP molecules can activate or inhibit the Ca-ATPase depending on metal concentration.