Angiotensin (Ang) II activates AngII type 1 (AT1) and AngII type 2 (AT2) receptors. In rodents two subtypes of AT1 have been identified (AT1A and AT1B). The vasoconstrictor and growth-stimulatory effects of Ang II are mediated by AT1. AT2 receptors are assumed to counteract these actions. To determine receptor-specific functions and possible AngII effects independent of its known receptors, we generated mice lacking one, two, or all three AngII receptor subtypes. All combinations were vital and fertile, although survival in AT1A/AT1B-double- and in the triple-knockout mice was significantly impaired. We characterized renal and cardiac histological alterations and linked them to the absence of the generated receptor combinations. Basal blood pressure was measured in anesthetized mice by carotis canulation. We determined the reactivity to AngII infusion in those mice in vivo and in a Langendorff setting. The general vascular behaviour was characterized using vasorelaxants and AngII-independent vasoconstrictors. We finally correlated identified differences in cardiovascular regulation to altered receptor expression and/or changes in endogenous AngII concentrations. Using a wide range of experimental settings we could identify specific functions for each of the three receptors in cardiovascular regulation and determined AngII effects independent of its receptors in triple knockout mice.
Objective: To study the combined effect of RAS blockade and SGLT2i in experimental diabetes. Design and method: TGR (mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic with streptozotocin for 12 weeks and treated with either vehicle, the angiotensin receptor blocker valsartan (VAL: 4 mg/kg/day), the SGLT2 inhibitor empagliflozin (EMPA: 10 mg/kg/day) or their combination during the final 3 weeks. Mean arterial blood pressure (MAP) was measured by telemetry. Results: MAP before treatment was 120 ± 14 mm Hg. Diabetes resulted in albuminuria, accompanied by glomerulosclerosis, without a change in glomerular filtration rate (GFR). EMPA did not lower MAP, while VAL did (by 29 ± 7 mm Hg), and when combined the MAP drop was largest (44 ± 6 mm Hg). Only EMPA+VAL reduced the heart weight/tibia length ratio (P = 0.04 vs. vehicle). VAL, but not EMPA, increased plasma renin, and the largest renin rise was observed during EMPA+VAL (P < 0.0001 vs. vehicle) Although both VAL and EMPA alone tended to diminish albuminuria, the reduction was significant (P = 0.01 vs. vehicle) only when both drugs were combined (vehicle, VAL, EMPA and EMPA+VAL 108 ± 18, 89 ± 24, 55 ± 8 and 26 ± 6 ug/mL, respectively). This was accompanied by a reduction in glomerulosclerosis index and no change in GFR. EMPA either alone or in combination with VAL increased water intake and urine production and induced urinary glucose loss, and as a consequence reduced blood glucose and body weight. Renal expression of the fibrosis and inflammatory markers TIMP2, collagen 1alpha 1, fibronectin, Neph1, nephrin was lowest in the dual treatment group. Conclusions: RAS blockade and SGLT2i display synergistic beneficial effects on blood pressure, kidney jury and cardiac hypertrophy in a rat with hypertension and diabetes.
Medial degeneration is a key feature of aneurysm disease and aortic dissection. In a murine aneurysm model we investigated the structural and functional characteristics of aortic wall degeneration in adult fibulin-4 deficient mice and the potential therapeutic role of the angiotensin (Ang) II type 1 (AT1) receptor antagonist losartan in preventing aortic media degeneration. Adult mice with 2-fold (heterozygous Fibulin-4+/R) and 4-fold (homozygous Fibulin-4R/R) reduced expression of fibulin-4 displayed the histological features of cystic media degeneration as found in patients with aneurysm or dissection, including elastin fiber fragmentation, loss of smooth muscle cells, and deposition of ground substance in the extracellular matrix of the aortic media. The aortic contractile capacity, determined by isometric force measurements, was diminished, and was associated with dysregulation of contractile genes as shown by aortic transcriptome analysis. These structural and functional alterations were accompanied by upregulation of TGF-β signaling in aortas from fibulin-4 deficient mice, as identified by genome-scaled network analysis as well as by immunohistochemical staining for phosphorylated Smad2, an intracellular mediator of TGF-β. Tissue levels of Ang II, a regulator of TGF-β signaling, were increased. Prenatal treatment with the AT1 receptor antagonist losartan, which blunts TGF-β signaling, prevented elastic fiber fragmentation in the aortic media of newborn Fibulin-4R/R mice. Postnatal losartan treatment reduced haemodynamic stress and improved lifespan of homozygous knockdown fibulin-4 animals, but did not affect aortic vessel wall structure. In conclusion, the AT1 receptor blocker losartan can prevent aortic media degeneration in a non-Marfan syndrome aneurysm mouse model. In established aortic aneurysms, losartan does not affect aortic architecture, but does improve survival. These findings may extend the potential therapeutic application of inhibitors of the renin-angiotensin system to the preventive treatment of aneurysm disease.
We previously modulated, by conjugating a single cholesterol, plasma protein binding and liver cell uptake of a phosphorothioate oligodeoxynucleotide (PS-ODN). In this study, we investigated the biological fate of a PS-ODN, denoted ISIS-9389 (3′,5′-bis-cholesteryl-conjugated ISIS 3082), provided with two cholesteryl moieties. After intravenous injection of into rats, [3H]ISIS-9389 was cleared from plasma with a half-life of 23.6 ± 0.3 min. After 90 min (approximately 95% cleared), the liver contained 83.0 ± 0.8% of the dose. Spleen and bone (marrow), which constitute with the liver the reticuloendothelial system, contained 3.1 ± 0.3 and 4.3 ± 0.2%, respectively. All other tissues accumulated together <5% of the dose. The hepatic uptake of [3H]ISIS-9389 occurred mainly by endothelial cells (51.9 ± 6.4% of the liver uptake). Parenchymal and Kupffer cells were responsible for 24.9 ± 7.7 and 23.3 ± 2.5%, respectively. Preinjected polyinosinic acid and polyadenylic acid reduced hepatic uptake, albeit the latter was less effective. This finding suggests implication of (multiple) scavenger receptors in liver uptake of ISIS-9389. The interaction of ISIS-9389 with plasma proteins, analyzed by size exclusion chromatography, differs from that of unconjugated PS-ODN and PS-ODN with a single cholesterol. Plasma-incubated ISIS-9389 was mainly recovered as a high molecular weight complex. In conclusion, conjugation of PS-ODNs with two cholesteryl moieties results in almost quantitative uptake by the liver. The liver targeting exceeds the already impressive gain in liver uptake achieved by conjugation of a single cholesterol, and is expected to increase the therapeutic activity against liver-associated targets and reduce side effects in nonhepatic tissues.
Combined angiotensin receptor--neprilysin inhibition (ARNI) reduces glomerulosclerosis better than single angiotensin receptor blockade (ARB) in diabetic, hypertensive rats. The renoprotective mechanism remains unknown, but may depend on superior blood pressure control, improved renal hemodynamics, suppressed renal inflammation or prevention of podocyte loss.To address this, TGR(mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic for 12 weeks and treated with vehicle (n = 10), valsartan (ARB; n = 7) or sacubitril/valsartan (ARNI; n = 8) for the final 3 weeks. Arterial pressure was measured via radiotelemetry.Sacubitril/valsartan lowered mean arterial pressure by -50 ± 4 mmHg and valsartan by -43 ± 4 mmHg (P = 0.3). Both treatments lowered albuminuria, but only sacubitril/valsartan maintained high urinary atrial natriuretic peptide, improved glycemic control and protected podocyte integrity, reflected by increased nephrin expression and suppression of transient receptor potential canonical 6 and regulator of calcineurin 1. This resulted in markedly reduced glomerulosclerosis (P < 0.05 vs. control and valsartan). Despite higher effective renal plasma flow and glomerular filtration rates, sacubitril/valsartan did neither improve filtration fraction nor renal immune cell infiltration.Sacubitril/valsartan offers drug-class-specific renoprotection in a preclinical model of diabetes and hypertension. Renoprotection is unrelated to antihypertensive efficacy, renal hemodynamics or inflammation, but may be related to protective effects of natriuretic peptides on podocyte integrity.
To investigate whether mast cells release renin in the heart, we studied renin and prorenin synthesis by such cells, using the human mast cell lines human mastocytoma 1 and LAD2, as well as fresh mast cells from mastocytosis patients. We also quantified the contribution of mast cells to cardiac renin levels in control and infarcted rat hearts. Human mastocytoma 1 cells contained and released angiotensin I-generating activity, and the inhibition of this activity by the renin inhibitor aliskiren was comparable to that of recombinant human renin. Prorenin activation with trypsin increased angiotensin I-generating activity in the medium only, suggesting release but not storage of prorenin. The adenylyl cyclase activator forskolin, the cAMP analogue 8-db-cAMP, and the degranulator compound 48/80 increased renin release without affecting prorenin. Angiotensin II blocked the forskolin-induced renin release. Angiotensin I-generating activity was undetectable in LAD2 cells and fresh mast cells. Nonperfused rat hearts contained angiotensin I-generating activity, and aliskiren blocked approximately 70% of this activity. A 30-minute buffer perfusion washed away >70% of the aliskiren-inhibitable angiotensin I-generating activity. Prolonged buffer perfusion or compound 48/80 did not decrease cardiac angiotensin I-generating activity further or induce angiotensin I-generating activity release in the perfusion buffer. Results in infarcted hearts were identical, despite the increased mast cell number in such hearts. In conclusion, human mastocytoma 1 cells release renin and prorenin, and the regulation of this release resembles that of renal renin. However, this is not a uniform property of all mast cells. Mast cells appear an unlikely source of renin in the heart, both under normal and pathophysiological conditions.
The capsular polysaccharide glucuronoxylomannan (GXM) of Cryptococcus neoformans has been shown to interfere with neutrophil migration. Although several receptors have been implied to mediate this process, the structural perspectives are unknown. Here, we assess the contribution of 6-O-acetylation and xylose substitution of the (1-->3)-alpha-d-mannan backbone of GXM, the variable structural features of GXM, to the interference with neutrophil migration. We compare chemically deacetylated GXM and acetyl- or xylose-deficient GXM from genetically modified strains with wild-type GXM in their ability to inhibit the different phases of neutrophil migration. Additionally, we verify the effects of de-O-acetylation on neutrophil migration in vivo. De-O-acetylation caused a dramatic reduction of the inhibitory capacity of GXM in the in vitro assays for neutrophil chemokinesis, rolling on E-selectin and firm adhesion to endothelium. Genetic removal of xylose only marginally reduced the ability of GXM to reduce firm adhesion. In vivo, chemical deacetylation of GXM significantly reduced its ability to interfere with neutrophil recruitment in a model of myocardial ischemia (65% reduction vs a nonsignificant reduction in tissue myeloperoxidase, respectively). Our findings indicate that 6-O-acetylated mannose of GXM is a crucial motive for the inhibition of neutrophil recruitment.
