Role of endothelin-1 in the renal handling of salt in early Type 1 diabetes mellitus

Tight control of blood glucose and blood pressure (BP) reduces cardiovascular risk in early Type 1 diabetes mellitus (T1DM). Increased BP normally increases renal medullary perfusion and sodium excretion. This is called acute pressure natriuresis. Inadequate acute pressure natriuresis disrupts circadian regulation of BP, which predicts hypertension. The peptide, endothelin-1 (ET-1), regulates BP via ETA and ETB receptors. ETA receptor antagonists reduce BP and restore its circadian rhythm. Two hypotheses were investigated. First, that acute pressure natriuresis is impaired in early T1DM, prior to established nephropathy, and this is associated with elevated BP. Second, that the mechanism is an ETA receptor-mediated blunting of medullary perfusion which can be reversed with insulin and ETA receptor antagonism. Experimental acute pressure natriuresis was induced in young, early T1DM (2-3 weeks post streptozotocin) Sprague Dawley rats and healthy controls. Despite maintaining glomerular filtration rate, early T1DM suppressed urinary flow (UV, 22.9±2.9 v. 93.7±11.1μl/min/gkw) and sodium excretion (UNaV, 3.2±0.7 v. 22.7±3.3μmol/min/gkw) rates by >80%, and reduced gradients of pressure diuresis (linear, 1.9 to 0.3) and natriuresis (non-linear k, 0.05 to 0.01) curves. Insulin treatment lowered blood glucose (16.8±1.8 to 9.3±0.6mmol/l) and restored gradients of the responses. Tissue and urine analyses did not suggest structural nephropathy. In early T1DM rats, changes in BP on radiotelemetry were consistent with impaired circadian regulation of BP and precursors of hypertension: 24–hour diastolic BP rose (92.3±0.4 to 97.1±0.5mmHg), and the circadian dip in diastolic BP fell (6±1 to 2±1%). Atrasentan (ETA receptor antagonist, 5mg/kg/day orally) reduced diastolic dipping in early T1DM (3±1 to 1±1%) while additional ETB receptor antagonism (A-192621, 10mg/kg/day orally) reversed this, suggesting that ETA, and not ETB receptors, mediate impairment of acute pressure natriuresis. To address this, renal blood flow was measured during experimental acute pressure natriuresis and ET receptor antagonism. Early T1DM suppressed the normal rise in medullary perfusion (flux, 227.2±26.7 v. 115.4±10.3%) by ~90%. Suppressed medullary flux was unaffected by insulin (112.2±6.8%), despite restoration of UV and UNaV. In controls, atrasentan reduced UV (15.7±4.9 v. 38.6±6.2μl/min/gkw), UNaV (1.7±0.5 v. 16.7±1.4μmol/min/gkw), FENa (3.4±1.4 v. 15.0±2.4%) and medullary flux (122.2±26.7%) by 60 to 90% of control values, while A-192621 increased UNaV (26.6±6.9μmol/min/gkw) and FENa (21.6±3.4%), but not medullary flux, by ~50%. ET receptor antagonism did not modify early T1DM+/-insulin effects. Diabetic status had no effect on renal ET-1 and ET receptor expression. These results support the first hypothesis but disprove the second. Early T1DM blunts medullary perfusion and acute pressure natriuresis, and increases diastolic BP. Insulin restores natriuresis but not medullary flow. Therefore, targeting medullary perfusion may reduce cardiovascular risk in early T1DM, but this is not achievable with selective ETA receptor antagonists. Novel natriuretic (ETA) and anti-natriuretic (ETB) roles for ET receptors, which are not apparent in early T1DM during severe, experimental rises in BP, appear to contribute to daily regulation of BP, and may preclude the use of selective ETA receptor antagonists in T1DM prior to nephropathy

Comparison of cellular changes in cavalier King Charles spaniel and mixed breed dogs with myxomatous mitral valve disease

Introduction: The aim of this study was to determine if there are differences in cellular changes in Cavalier King Charles spaniel (CKCS) myxomatous mitral valves compared to non-CKCS dogs. Animals: Cavalier King Charles spaniels (n = 6) and age-matched mixed breed (n = 6) with severe myxomatous mitral valve disease (MMVD), and normal mixed breed (n = 4) dogs. Materials and Methods: Immunohistochemistry staining and qualitative and quantitative analysis of mitral valves sections, examining for the presence of CD11c and CD45, vimentin, alpha smooth muscle actin (α-SMA) and embryonic smooth muscle myosin heavy chain (Smemb), von Willebrand factor and CD31 and Ki-67. Results: Vimentin positive cell numbers were increased in the MMVD dogs and distributed throughout the valve with greatest density close to the endothelium. There were no significant differences in cell marker expression for the two diseased groups, but cell numbers were significantly increased compared to controls for α-SMA (CKCS only) and Smemb (CKCS and mixed breed: p < 0.05). Alpha smooth muscle actin+ cells were primarily located at the valve edge, with Smemb+ cells similarly located, but also present throughout the valve stroma. A small number of cells close to the valve edge co-expressed α-SMA and Smemb. Endothelial von Willebrand factor expression was identified in all valves, with evidence of disrupted endothelium in the diseased, but was also found in diseased valve stroma. There was no staining for CD11c, CD45 or CD31 in any valve. Ki-67+ cells formed linear clusters at the leaflet tip and were sparsely distributed throughout both myxomatous valve groups. Conclusions: The cellular changes notes with advanced stage MMVD appear similar for CKCS when compared to mixed breed dogs

The acute pressure natriuresis response is suppressed by selective ETA receptor blockade

Hypertension is a major risk factor for cardiovascular disease. In a significant minority of people, it develops when salt intake is increased (salt-sensitivity). It is not clear whether this represents impaired vascular function or disruption to the relationship between blood pressure (BP) and renal salt-handling (pressure natriuresis, PN). Endothelin-1 (ET-1) regulates BP via ET(A) and ET(B) receptor subtypes. Blockade of ET(A) receptors reduces BP but promotes sodium retention by an unknown mechanism. ET(B) blockade increases both BP and sodium retention. We hypothesized that ET(A) blockade promotes sodium and water retention by suppressing PN. We also investigated whether suppression of PN might reflect off-target ET(B) blockade. Acute PN was induced by sequential arterial ligation in male Sprague Dawley rats. Intravenous atrasentan (ET(A) antagonist, 5 mg/kg) halved the normal increase in medullary perfusion and reduced sodium and water excretion by >60%. This was not due to off-target ET(B) blockade because intravenous A-192621 (ET(B) antagonist, 10 mg/kg) increased natriuresis by 50% without modifying medullary perfusion. In a separate experiment in salt-loaded rats monitored by radiotelemetry, oral atrasentan reduced systolic and diastolic BP by ∼10 mmHg, but additional oral A-192621 reversed these effects. Endogenous ET(A) stimulation has natriuretic effects mediated by renal vascular dilation while endogenous ET(B) stimulation in the kidney has antinatriuretic effects via renal tubular mechanisms. Pharmacological manipulation of vascular function with ET antagonists modifies the BP set-point, but even highly selective ET(A) antagonists attenuate PN, which may be associated with salt and water retention

Computed tomography diagnosis of intermittent type IV paraoesophageal hernia in a dog

Bertrand Henri, Legros Cl. Notes complémentaires sur Deronectes bertrandi Legros [Col. Dytiscidae]. In: Bulletin de la Société entomologique de France, volume 76 (7-8), Septembre-octobre 1971. pp. 193-196

Heightened immune response to autocitrullinated porphyromonas gingivalis peptidylarginine deiminase: a potential mechanism for breaching immunologic tolerance in rheumatoid arthritis

Background: Rheumatoid arthritis (RA) is characterised by autoimmunity to citrullinated proteins, and there is increasing epidemiologic evidence linking Porphyromonas gingivalis to RA. P gingivalis is apparently unique among periodontal pathogens in possessing a citrullinating enzyme, peptidylarginine deiminase (PPAD) with the potential to generate antigens driving the autoimmune response. Objectives: To examine the immune response to PPAD in patients with RA, individuals with periodontitis (PD) and controls (without arthritis), confirm PPAD autocitrullination and identify the modified arginine residues. Methods: PPAD and an inactivated mutant (C351A) were cloned and expressed and autocitrullination of both examined by immunoblotting and mass spectrometry. ELISAs using PPAD, C351A and another P gingivalis protein arginine gingipain (RgpB) were developed and antibody reactivities examined in patients with RA (n=80), individuals with PD (n=44) and controls (n=82). Results: Recombinant PPAD was a potent citrullinating enzyme. Antibodies to PPAD, but not to Rgp, were elevated in the RA sera (median 122 U/ml) compared with controls (median 70 U/ml; p<0.05) and PD (median 60 U/ml; p<0.01). Specificity of the anti-peptidyl citrullinated PPAD response was confirmed by the reaction of RA sera with multiple epitopes tested with synthetic citrullinated peptides spanning the PPAD molecule. The elevated antibody response to PPAD was abolished in RA sera if the C351A mutant was used on ELISA. Conclusions: The peptidyl citrulline-specific immune response to PPAD supports the hypothesis that, as a bacterial protein, it might break tolerance in RA, and could be a target for therapy