Vasopressin Use in the Support of Organ Donors: Physiological Rationale and Review of the Literature.

The objective of this review was to depict the physiological and clinical rationale for the use of vasopressin in hemodynamic support of organ donors. After summarizing the physiological, pharmacological concepts and preclinical findings, regarding vasopressin's pathophysiological impacts, we will present the available clinical data. DATA SOURCES: Detailed search strategies in PubMed, OVID Medline, and EMBASE were undertaken using Medical Subject Headings and Key Words. STUDY SELECTION: Physiological articles regarding brain death, and preclinical animal and human studies about the use of vasopressin or analogs, as an intervention in organ support for donation, were considered. DATA EXTRACTION: Two authors independently screened titles, abstracts, and full text of articles to determine eligibility. Data encompassing models, population, methodology, outcomes, and relevant concepts were extracted. DATA SYNTHESIS: Following brain death, profound reduction in sympathetic outflow is associated with reduced cardiac output, vascular tone, and hemodynamic instability in donors. In addition to reducing catecholamine needs and reversing diabetes insipidus, vasopressin has been shown to limit pulmonary injury and decrease systemic inflammatory response in animals. Several observational studies show the benefit of vasopressin on hemodynamic parameters and catecholamine sparing in donors. Small trials suggest that vasopressin increase organ procurement and have some survival benefit for recipients. However, the risk of bias is overall concerning, and therefore the quality of the evidence is deemed low. CONCLUSIONS: Despite potential impact on graft outcome and a protective effect through catecholamine support sparing, the benefit of vasopressin use in organ donors is based on low evidence. Well-designed observational and randomized controlled trials are warranted.

Endothelium-restricted endothelin-1 overexpression in type 1 diabetes worsens atherosclerosis and immune cell infiltration via NOX1.

AIMS: NADPH oxidase (NOX) 1 but not NOX4-dependent oxidative stress plays a role in diabetic vascular disease, including atherosclerosis. Endothelin (ET)-1 has been implicated in diabetes-induced vascular complications. We showed that crossing mice overexpressing human ET-1 selectively in endothelium (eET-1) with apolipoprotein E knockout (Apoe-/-) mice enhanced high-fat diet-induced atherosclerosis in part by increasing oxidative stress. We tested the hypothesis that ET-1 overexpression in the endothelium would worsen atherosclerosis in type 1 diabetes through a mechanism involving NOX1 but not NOX4. METHODS AND RESULTS: Six-week-old male Apoe-/- and eET-1/Apoe-/- mice with or without Nox1 (Nox1-/y) or Nox4 knockout (Nox4-/-) were injected intraperitoneally with either vehicle or streptozotocin (55 mg/kg/day) for 5 days to induce type 1 diabetes and were studied 14 weeks later. ET-1 overexpression increased 2.5-fold and five-fold the atherosclerotic lesion area in the aortic sinus and arch of diabetic Apoe-/- mice, respectively. Deletion of Nox1 reduced aortic arch plaque size by 60%; in contrast, Nox4 knockout increased lesion size by 1.5-fold. ET-1 overexpression decreased aortic sinus and arch plaque alpha smooth muscle cell content by ∼35% and ∼50%, respectively, which was blunted by Nox1 but not Nox4 knockout. Reactive oxygen species production was increased two-fold in aortic arch perivascular fat of diabetic eET-1/Apoe-/- and eET-1/Apoe-/-/Nox4-/- mice but not eET-1/Apoe-/-/Nox1y/- mice. ET-1 overexpression enhanced monocyte/macrophage and CD3+ T-cell infiltration ∼2.7-fold in the aortic arch perivascular fat of diabetic Apoe-/- mice. Both Nox1 and Nox4 knockout blunted CD3+ T-cell infiltration whereas only Nox1 knockout prevented the monocyte/macrophage infiltration in diabetic eET-1/Apoe-/- mice. CONCLUSION: Endothelium ET-1 overexpression enhances the progression of atherosclerosis in type 1 diabetes, perivascular oxidative stress, and inflammation through NOX1.

Chromosome 2 Fragment Substitutions in Dahl Salt-Sensitive Rats and RNA Sequencing Identified Enpep and Hs2st1 as Vascular Inflammatory Modulators.

Chromosome 2 introgression from normotensive Brown Norway (BN) rats into hypertensive Dahl salt-sensitive (SS) background (SS-chromosome 2BN/Mcwi; consomic S2B) reduced blood pressure and vascular inflammation under a normal-salt diet (NSD). We hypothesized that BN chromosome 2 contains anti-inflammatory genes that could reduce blood pressure and vascular inflammation in rats fed NSD or high-salt diet (HSD). Four- to 6-week old male SS and congenic rats containing the BN chromosome 2 distal portion (SS.BN-[rs13453786-rs66377062]/Aek; S2Ba) and middle segment (SS.BN-[rs106982173-rs65057186]/Aek; S2Bb) were fed NSD or HSD (4% NaCl) up to age 12 to 13 weeks. Systolic blood pressure determined by telemetry was higher in SS rats fed HSD versus NSD. Systolic blood pressure was lower in both congenic rats than in SS under NSD, but similar under HSD versus SS. Reactive oxygen species generation using dihydroethidium staining, expression of vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, and immune cell infiltration by immunofluorescence demonstrated that S2Ba rats present less inflammation under NSD and more under HSD versus SS rats. RNA sequencing and reverse transcription-quantitative PCR identified 2 differentially expressed genes encoded within BN chromosome 2 distal portion that could act as regulators of vascular inflammation. These were downregulated glutamyl aminopeptidase (Enpep) that was anti-inflammatory under NSD and upregulated heparan sulfate 2-O-sulfotransferase 1 (Hs2st1) that was proinflammatory under HSD. In conclusion, 2 differentially expressed genes encoded within introgressed BN chromosome 2 distal fragment were identified: Enpep associated with reduced vascular inflammation under NSD, and Hs2st1, associated with increased vascular inflammation under HSD.

miR-431-5p Knockdown Protects Against Angiotensin II-Induced Hypertension and Vascular Injury.

Vascular injury is an early manifestation in hypertension and a cause of end-organ damage. MicroRNAs play an important role in cardiovascular disease, but their implication in vascular injury in hypertension remains unclear. This study revealed using an unbiased approach, microRNA and mRNA sequencing with molecular interaction analysis, a microRNA-transcription factor coregulatory network involved in vascular injury in mice made hypertensive by 14-day Ang II (angiotensin II) infusion. A candidate gene approach identified upregulated miR-431-5p encoded in the conserved 12qF1 (14q32 in humans) microRNA cluster, whose expression correlated with blood pressure, and which has been shown to be upregulated in human atherosclerosis, as a potential key regulator in Ang II-induced vascular injury. Gain- and loss-of-function in human vascular smooth muscle cells demonstrated that miR-431-5p regulates in part gene expression by targeting ETS homologous factor. In vivo miR-431-5p knockdown delayed Ang II-induced blood pressure elevation and reduced vascular injury in mice, which demonstrated its potential as a target for treatment of hypertension and vascular injury.

Three-Month Endothelial Human Endothelin-1 Overexpression Causes Blood Pressure Elevation and Vascular and Kidney Injury.

Endothelium-derived endothelin (ET)-1 has been implicated in the development of hypertension and end-organ damage, but its exact role remains unclear. We have shown that tamoxifen-inducible endothelium-restricted human ET-1 overexpressing (ieET-1) mice exhibited blood pressure rise after a 3-week induction in an ET type A (ETA) receptor-dependent manner, in absence of vascular and renal injury. It is unknown whether long-term ET-1 overexpression results in sustained blood pressure elevation and vascular and renal injury. Adult male ieET-1 and control tamoxifen-inducible endothelium-restricted Cre recombinase (ieCre) mice were induced with tamoxifen and 2.5 months later, were treated with or without the ETA receptor blocker atrasentan for 2 weeks. Three-month induction of endothelial human ET-1 overexpression increased blood pressure (P<0.01), reduced renal artery flow (P<0.001), and caused mesenteric small artery stiffening (P<0.05) and endothelial dysfunction (P<0.01). These changes were accompanied by enhanced mesenteric small artery Col1A1 and Col3A1 expression, and perivascular adipose tissue oxidative stress (P<0.05) and monocyte/macrophage infiltration (P<0.05). Early renal injury was demonstrated by increased kidney injury molecule-1 expression in renal cortex tubules (P<0.05), with, however, undetectable lesions using histochemistry staining and unchanged urinary albumin. There was associated increased myeloid (CD11b+) and myeloid-derived suppressive cell (CD11b+Gr-1+) renal infiltration (P<0.01) and greater frequency of myeloid and renal cells expressing the proinflammatory marker CD36 (P<0.05). Atrasentan reversed or reduced all of the above changes (P<0.05) except the endothelial dysfunction and collagen expression and reduced renal artery flow. These results demonstrate that long-term exposure to endothelial human ET-1 overexpression causes sustained blood pressure elevation and vascular and renal injury via ETA receptors.

Matrix metalloproteinase-2 knockout prevents angiotensin II-induced vascular injury.

AIMS: Matrix metalloproteinases (MMPs) have been implicated in the development of hypertension in animal models and humans. Mmp2 deletion did not change Ang II-induced blood pressure (BP) rise. However, whether Mmp2 knockout affects angiotensin (Ang) II-induced vascular injury has not been tested. We sought to determine whether Mmp2 knockout will prevent Ang II-induced vascular injury. METHODS AND RESULTS: A fourteen-day Ang II infusion (1000 ng/kg/min, SC) increased systolic BP, decreased vasodilatory responses to acetylcholine, induced mesenteric artery (MA) hypertrophic remodelling, and enhanced MA stiffness in wild-type (WT) mice. Ang II enhanced aortic media and perivascular reactive oxygen species generation, aortic vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 expression, perivascular monocyte/macrophage and T cell infiltration, and the fraction of spleen activated CD4+CD69+ and CD8+CD69+ T cells, and Ly-6Chi monocytes. Study of intracellular signalling showed that Ang II increased phosphorylation of epidermal growth factor receptor and extracellular-signal-regulated kinase 1/2 in vascular smooth muscle cells isolated from WT mice. All these effects were reduced or prevented by Mmp2 knockout, except for systolic BP elevation. Ang II increased Mmp2 expression in immune cells infiltrating the aorta and perivascular fat. Bone marrow (BM) transplantation experiments revealed that in absence of MMP2 in immune cells, Ang II-induced BP elevation was decreased, and that when MMP2 was deficient in either immune or vascular cells, Ang II-induced endothelial dysfunction was blunted. CONCLUSIONS: Mmp2 knockout impaired Ang II-induced vascular injury but not BP elevation. BM transplantation revealed a role for immune cells in Ang II-induced BP elevation, and for both vascular and immune cell MMP2 in Ang II-induced endothelial dysfunction.

γδ T Cells Mediate Angiotensin II-Induced Hypertension and Vascular Injury.

BACKGROUND: Innate antigen-presenting cells and adaptive immune T cells have been implicated in the development of hypertension. However, the T-lymphocyte subsets involved in the pathophysiology of hypertension remain unclear. A small subset of innate-like T cells expressing the γδ T cell receptor (TCR) rather than the αß TCR could play a role in the initiation of the immune response in hypertension. We aimed to determine whether angiotensin (Ang) II caused kinetic changes in γδ T cells; deficiency in γδ T cells blunted Ang II-induced hypertension, vascular injury, and T-cell activation; and γδ T cells are associated with human hypertension. METHODS: Male C57BL/6 wild-type and Tcrδ-/- mice, which are devoid of γδ T cells, or wild-type mice injected IP with control isotype IgG or γδ T cell-depleting antibodies, were infused or not with Ang II for 3, 7, or 14 days. T-cell profiling was determined by flow cytometry, systolic blood pressure (SBP) by telemetry, and mesentery artery endothelial function by pressurized myography. TCR γ constant region gene expression levels and clinical data of a whole blood gene expression microarray study, including normotensive and hypertensive subjects, were used to demonstrate an association between γδ T cells and SBP. RESULTS: Seven- and 14-day Ang II infusion increased γδ T-cell numbers and activation in the spleen of wild-type mice (P<0.05). Fourteen days of Ang II infusion increased SBP (P<0.01) and decreased mesenteric artery endothelial function (P<0.01) in wild-type mice, both of which were abrogated in Tcrδ-/- mice (P<0.01). Anti-TCRγδ antibody-induced γδ T-cell depletion blunted Ang II-induced SBP rise and endothelial dysfunction (P<0.05), compared with isotype antibody-treated Ang II-infused mice. Ang II-induced T-cell activation in the spleen and perivascular adipose tissue was blunted in Tcrδ-/- mice (P<0.01). In humans, the association between SBP and γδ T cells was demonstrated by a multiple linear regression model integrating whole blood TCR γ constant region gene expression levels and age and sex (R2=0.12, P<1×10-6). CONCLUSIONS: γδ T cells mediate Ang II-induced SBP elevation, vascular injury, and T-cell activation in mice. γδ T cells might contribute to the development of hypertension in humans.

Vascular smooth muscle cell peroxisome proliferator-activated receptor γ protects against endothelin-1-induced oxidative stress and inflammation.

AIMS: Peroxisome proliferator-activated receptor γ (PPARγ) agonists reduce blood pressure and vascular injury in hypertensive rodents. Pparγ inactivation in vascular smooth muscle cells (VSMC) enhances vascular injury. Transgenic mice overexpressing endothelin (ET)-1 selectively in the endothelium (eET-1) exhibit endothelial dysfunction, increased oxidative stress and inflammation. We hypothesized that inactivation of the Pparγ gene in VSMC (smPparγ-/-) would exaggerate ET-1-induced vascular injury. METHODS AND RESULTS: eET-1, smPparγ-/- and eET-1/smPparγ-/- mice were treated with tamoxifen for 5 days and studied 4 weeks later. SBP was higher in eET-1 and unaffected by smPparγ inactivation. Mesenteric artery vasodilatory responses to acetylcholine were impaired only in smPparγ-/-. N(omega)-Nitro-L-arginine methyl ester abrogated relaxation responses, and the Ednra/Ednrb mRNA ratio was decreased in eET-1/smPparγ-/-, which could indicate that nitric oxide production was enhanced by ET-1 stimulation of endothelin type B receptors. Mesenteric artery media/lumen was greater only in eET-1/smPparγ-/-. Mesenteric artery reactive oxygen species increased in smPparγ and were further enhanced in eET-1/smPparγ-/-. Perivascular fat monocyte/macrophage infiltration was higher in eET-1 and smPparγ and increased further in eET-1/smPparγ-/-. Spleen CD11b+ cells were increased in smPparγ-/- and further enhanced in eET-1/smPparγ-/-, whereas Ly-6C(hi) monocytes increased in eET-1 and smPparγ-/- but not in eET-1/smPparγ-/-. Spleen T regulatory lymphocytes increased in smPparγ and decreased in eET-1, and decreased further in eET-1/smPparγ-/-. CONCLUSION: VSMC Pparγ inactivation exaggerates ET-1-induced vascular injury, supporting a protective role for PPARγ in hypertension through modulation of pro-oxidant and proinflammatory pathways. Paradoxically, ET-1 overexpression preserved endothelial function in smPparγ-/- mice, presumably by enhancing nitric oxide through stimulation of endothelin type B receptors.

Endothelin-1 Overexpression Exaggerates Diabetes-Induced Endothelial Dysfunction by Altering Oxidative Stress.

BACKGROUND: Increased endothelin (ET)-1 expression causes endothelial dysfunction and oxidative stress. Plasma ET-1 is increased in patients with diabetes mellitus. Since endothelial dysfunction often precedes vascular complications in diabetes, we hypothesized that overexpression of ET-1 in the endothelium would exaggerate diabetes-induced endothelial dysfunction. METHODS: Diabetes was induced by streptozotocin treatment (55mg/kg/day, i.p.) for 5 days in 6-week-old male wild type (WT) mice and in mice overexpressing human ET-1 restricted to the endothelium (eET-1). Mice were studied 14 weeks later. Small mesenteric artery (MA) endothelial function and vascular remodeling by pressurized myography, reactive oxygen species (ROS) production by dihydroethidium staining and mRNA expression by reverse transcription/quantitative PCR were determined. RESULTS: Endothelium-dependent vasodilatory responses to acetylcholine of MA were reduced 24% by diabetes in WT ( P < 0.05), and further decreased by 12% in eET-1 ( P < 0.05). Diabetes decreased MA media/lumen in WT and eET-1 ( P < 0.05), whereas ET-1 overexpression increased MA media/lumen similarly in diabetic and nondiabetic WT mice ( P < 0.05). Vascular ROS production was increased 2-fold by diabetes in WT ( P < 0.05) and further augmented 1.7-fold in eET-1 ( P < 0.05). Diabetes reduced endothelial nitric oxide synthase (eNOS, Nos3 ) expression in eET-1 by 31% ( P < 0.05) but not in WT. Induction of diabetes caused a 52% ( P < 0.05) increase in superoxide dismutase 1 ( Sod1 ) and a 32% ( P < 0.05) increase in Sod2 expression in WT but not in eET-1. CONCLUSIONS: Increased expression of ET-1 exaggerates diabetes-induced endothelial dysfunction. This may be caused by decrease in eNOS expression, increase in vascular oxidative stress, and decrease in antioxidant capacity.

Aldosterone-Induced Vascular Remodeling and Endothelial Dysfunction Require Functional Angiotensin Type 1a Receptors.

We investigated the role of angiotensin type 1a receptors (AGTR1a) in vascular injury induced by aldosterone activation of mineralocorticoid receptors in Agtr1a(-/-) and wild-type (WT) mice infused with aldosterone for 14 days while receiving 1% NaCl in drinking water. Aldosterone increased systolic blood pressure (BP) by ≈30 mm Hg in WT mice and ≈50 mm Hg in Agtr1a(-/-) mice. Aldosterone induced aortic and small artery remodeling, impaired endothelium-dependent relaxation in WT mice, and enhanced fibronectin and collagen deposition and vascular inflammation. None of these vascular effects were observed in Agtr1a(-/-) mice. Aldosterone effects were prevented by the AGTR1 antagonist losartan in WT mice. In contrast to aldosterone, norepinephrine caused similar BP increase and mesenteric artery remodeling in WT and Agtr1a(-/-) mice. Agtr1a(-/-) mice infused with aldosterone did not increase sodium excretion in response to a sodium chloride challenge, suggesting that sodium retention could contribute to the exaggerated BP rise induced by aldosterone. Agtr1a(-/-) mice had decreased mesenteric artery expression of the calcium-activated potassium channel Kcnmb1, which may enhance myogenic tone and together with sodium retention, exacerbate BP responses to aldosterone/salt in Agtr1a(-/-) mice. We conclude that although aldosterone activation of mineralocorticoid receptors raises BP more in Agtr1a(-/-) mice, AGTR1a is required for mineralocorticoid receptor stimulation to induce vascular remodeling and inflammation and endothelial dysfunction.