Pressure Myography Research Articles

OS 21-01 NOX1 OR NOX4 DELETION PREVENTS TYPE 1 DIABETES-INDUCED ENDOTHELIAL DYSFUNCTION

Objective : The prognosis of type-1 diabetes remains poor and is primarily related to the increased risk of vascular complications. Overproduction of reactive oxygen species by NADPH oxidase (NOX) is believed to play an important role in diabetes-related vascular injury. NOX1 may play a role in the macrovascular disease, whereas NOX4 may have protective actions. Nevertheless, their role in diabetic microangiopathy is less well understood. We hypothesized that deletion of Nox1 would prevent diabetes-induced endothelial dysfunction and vascular remodeling of small arteries whereas Nox4 would exaggerate vascular injury. Design and Method : Diabetes-related vascular injury were studied in atherosclerosis-prone apolipoprotein knockout (Apoe-/-) mice. Six-week-old male Apoe-/- mice, Apoe-/- mice deficient in Nox1 (Apoe-/-/Nox1y/-) and Nox4 (Apoe-/-/Nox4-/-) were rendered diabetic by streptozotocin treatment (STZ, 55 mg/kg/day, ip) for 5 days. Mice were studied 14 weeks later. Endothelial function and vascular remodeling were assessed in mesenteric arteries (MA) using pressurized myography. Results: Apoe-/- mice presented a maximal endothelium-dependent vasodilatory response to acetylcholine of only 46%, which was further decreased by ∼50% by diabetes. In contrast, endothelium-dependent relaxations to acetylcholine were 1.5-fold higher in diabetic Apoe-/-/Nox1y/- and Apoe-/-/Nox4-/- mice compared to vehicle-treated Apoe-/- mice. Endothelium-independent relaxation responses to the nitric oxide donor, sodium nitroprusside, were similar in all groups. Diabetes decreased MA stiffness in Apoe-/- mice, as indicated by a rightward displacement of the stress-strain curves, which was blunted by Nox1 or Nox4 knockout. MA media/lumen was unaltered by diabetes. Knockout of Nox4 but not Nox1 increased MA media/lumen 1.4-fold in diabetic Apoe-/- mice. Conclusions: These results suggest that NOX1 and NOX4 play a pathophysiological role in diabetes-induced endothelial dysfunction and contribute to potentially maladaptive changes in vascular stiffness. NOX4 also seems to have dual actions on the vasculature, as it is also protective against vascular remodeling of small arteries in type 1 diabetes.

OS 15-02 MATRIX METALLOPROTEINASE 2 KNOCKOUT PROTECTS FROM ANGIOTENSIN II-INDUCED VASCULAR INJURY IN PART VIA INHIBITION OF EGFR AND ERK1/2 ACTIVATION

Objective: Matrix metalloproteinase 2 (MMP2) is involved in cardiovascular disease. Whether MMP2 plays a role in hypertension and vascular damage is unknown. We hypothesized that Mmp2 knockout will prevent angiotensin (Ang) II-induced hypertension and vascular injury. Design and Method: Mmp2 knockout (Mmp2−/−) and wild-type (WT) mice were infused with Ang II (1000 ng/kg/min, SC) for 14 days. Systolic blood pressure (SBP) was measured by telemetry, and mesenteric artery (MA) endothelial function and vascular remodeling by pressurized myography. Reactive oxygen species (ROS) generation using dihydroethidium staining, and vascular cell adhesion protein 1 (VCAM-1), monocyte chemotactic protein-1 (MCP-1) expression and monocyte/macrophage infiltration by immunofluorescence were determined in the aortic wall or perivascular fat (PVAT). Spleen T cell and monocyte profiles were assessed by flow cytometry. Vascular smooth muscle cells (VSMCs) were isolated from MA of WT and Mmp2−/− mice, stimulated 5 min with Ang II (100 nM) and epidermal growth factor receptor (EGFR) and extracellular-signal-regulated kinase 1/2 (ERK1/2) phosphorylation measured by Western blot. Results: Ang II increased SBP by 50 mmHg (P < 0.01), decreased by 50% MA vasodilator responses to acetylcholine (P < 0.01) and increased 1.7-fold MA media-to-lumen ratio (P < 0.01), 1.4-fold media cross-sectional area (P < 0.05), and stiffness (P < 0.01), as shown by a leftward shift of the stress/strain relationship, in WT. Furthermore, Ang II enhanced 12-fold aortic ROS generation (P < 0.01), 3.4-fold aortic VCAM-1 (P < 0.01), 6.5-fold MCP-1 expression (P < 0.01), 8-fold PVAT monocyte/macrophage infiltration (P < 0.05), and ∼2-fold spleen activated CD4+CD69+ and CD8+CD69+ T cells, and pro-inflammatory Ly-6Chi monocytes (P < 0.05) in WT. Ang II increased phosphorylation of EGFR 1.9-fold and ERK1/2 1.4-fold in VSMCs (P < 0.05). Mmp2 knockout prevented or reduced all of the above (P < 0.05) except SBP elevation. Conclusions: MMP2 plays an important role in Ang II-induced vascular injury, which could be mediated at least in part through EFGR and ERK1/2 activation in VSMCs.

Abstract P225: Nox1 or Nox4 Deletion Prevents Type-1 Diabetes-induced Endothelial Dysfunction

Objective: The prognosis of type-1 diabetes is in part related to the increased risk of vascular complications such as atherosclerosis. Overproduction of reactive oxygen species by NADPH oxidase (NOX) is believed to play an important role in diabetes-related vascular injury. NOX1 may play a role in the macrovascular disease, whereas NOX4 may have protective actions. Nevertheless, their role in diabetic vascular injury is less well understood. We hypothesized that deletion of Nox1 would prevent diabetes-induced endothelial dysfunction and vascular remodeling of small arteries whereas Nox4 would exaggerate vascular injury in atherosclerosis-prone apolipoprotein knockout ( Apoe -/- ) mice. Methods: Diabetes was induced by streptozotocin IP injections (STZ, 55 mg/kg/day) for 5 days in 6-week-old male Apoe -/- mice, Apoe -/- mice deficient in Nox1 ( Apoe -/- / Nox1 y/- ) and Nox4 ( Apoe -/- / Nox4 -/- ). Mice were studied 14 weeks later. Endothelial function and vascular remodeling were assessed in mesenteric arteries (MA) using pressurized myography. Results: Apoe -/- mice presented a maximal endothelium-dependent vasodilatory response (E max ) to acetylcholine of 48±8%, which was further decreased by diabetes to 20±6%. In contrast, endothelium-dependent relaxations to acetylcholine were 1.5-fold higher in diabetic Apoe -/- / Nox1 y/- and Apoe -/- / Nox4 -/- mice compared to non-diabetic Apoe -/- mice (E max : 72±9 and 70±7 vs 48±8%). Diabetes decreased MA stiffness in Apoe -/- mice, as indicated by a rightward displacement of the stress-strain curves (strain at 140 mm Hg: 1.02±0.04 vs 0.75±0.04), which was blunted by Nox1 or Nox4 knockout (strain at 140 mm Hg: 0.77±0.02 and 0.81±0.02). MA media/lumen was unaltered by diabetes. Knockout of Nox4 but not Nox1 increased MA media/lumen 1.4-fold in diabetic Apoe -/- mice (4.1±0.4 and 3.5±0.2 vs 2.9±0.2%). Conclusions: These results suggest that NOX1 and NOX4 play a pathophysiological role in diabetes-induced endothelial dysfunction and contribute to potentially maladaptive changes in vascular stiffness. NOX4 seems to have dual actions on the vasculature, as it is also protective against vascular remodeling of small arteries in type 1 diabetes.

MPS 18-02 ENDOTHELIN-1 OVEREXPRESSION PRESERVES ENDOTHELIAL FUNCTION IN MICE WITH VASCULAR SMOOTH MUSCLE CELL-SPECIFIC DELETION OF PPAR-GAMMA

Objective: Peroxisome proliferator-activated receptor γ (PPARγ) agonists reduce blood pressure (BP) and vascular injury in hypertensive rodents. Pparγ inactivation in vascular smooth muscle cells (VSMC) using a tamoxifen inducible Cre-Lox system enhanced angiotensin II-induced vascular damage. Transgenic mice overexpressing endothelin (ET)-1 in the endothelium (eET-1) exhibit endothelial dysfunction, increased oxidative stress and inflammation. We hypothesized that inactivation of the Ppar gene in VSMC (smPparγ−/−) will exaggerate ET-1-induced vascular damage. Design and Method: Eleven week-old male control, eET-1, smPparγ−/− and eET-1/smPparγ−/− mice were treated with tamoxifen (1 mg/kg/day, s.c.) for 5 days and sacrificed 4 weeks later. BP was measured by telemetry. Endothelial function and vascular remodeling using pressurized myography, reactive oxygen species (ROS) production by dihydroethidium staining, monocyte/macrophage infiltration by immunofluorescence and mRNA expression by reverse transcription-quantitative PCR were assessed in mesenteric arteries (MA) or perivascular fat (PVAT). Spleen T cell and monocyte profiles were assessed by flow cytometry. Results: Systolic BP was 20 mmHg higher in eET-1 and unaffected by Pparγ inactivation. MA vasorelaxation to acetylcholine was impaired 37% only in smPparγ−/−. Likewise, ET-1-induced contractions were enhanced only in smPparγ−/−. ROS levels were increased 1.7-fold in smPparγ−/− and 2.5-fold in eET-1/smPparγ−/−. Monocyte/macrophage infiltration in PVAT was 2-fold higher in eET-1 and smPparγ−/−, which was further increased 2-fold in eET-1/smPparγ−/−. The percentage of CD11b+ cells was increased 2.3-fold in smPparγ−/− and further increased 1.5-fold in eET-1/smPparγ−/−. The percentage of Ly-6Chi monocytes was increased ∼1.8-fold in eET-1 and smPparγ−/− but not eET-1/smPparγ−/−. The percentage of T regulatory cells was increased 1.5-fold in smPparγ−/− and decreased by 26% in eET-1, which was further decreased by 38% in eET-1/smPparγ−/−. Conclusions: These results suggest that increased ET-1 paradoxically preserves endothelial function in mice with inactivated VSMC Pparγ despite enhanced oxidative stress. Flow cytometry data indicate that infiltrating monocyte/macrophages in these mice might be anti-inflammatory.

Abstract P218: Induction of Human Endothelin-1 Overexpression for 3 Months Causes Blood Pressure Rise and Small Artery Endothelial Dysfunction and Stiffening

Background: The mechanisms of blood pressure (BP) regulation by endothelin (ET)-1 produced by endothelial cells are complex and remain unclear. Recently, we developed a transgenic mouse with tamoxifen-inducible endothelium-restricted human ET-1 overexpression (ieET-1) using Cre/loxP technology. ieET-1 mice exhibited BP rise after three weeks of induction in an ET type A (ET A ) receptor-dependent manner, in absence of vascular and kidney injury. It is unknown whether long-term exposure to ET-1 overexpression results in sustained BP elevation and vascular injury. Design and methods: Nine to 12-week old male ieET-1 mice and control ieCre mice expressing a tamoxifen-inducible Cre recombinase under the control of endothelium-specific Tie2 promoter, were treated with tamoxifen (1 mg/kg/day, s.c.) for 5 days and studied 3 months later. ieET-1 mice were treated or not with ET A receptor blocker, atrasentan (10 mg/kg/day, PO) in the last 2 weeks of the study. BP by telemetry, endothelial function and vascular remodeling by pressurized myography and reactive oxygen species (ROS) generation using dihydroethidium staining in mesenteric artery (MA) or perivascular fat (PVAT) and renal artery flow (RAF) by ultrasonography were determined. Results: Systolic BP was increased in ieET-1 and normalized by atrasentan compared to ieCre mice (141±0 and 124±4 vs 120±0 mm Hg, P &lt;0.001). Endothelium-dependent relaxation responses to acetylcholine were impaired in ieET-1 and uncorrected by atrasentan compared to ieCre (35±4 and 32±4 vs 65±8%, P &lt;0.01). Media/lumen and media cross-sectional area were unchanged, but stiffness was increased in ieET-1 and normalized by atrasentan compared to ieCre mice (strain at 140 mm Hg: 0.6±0.0 and 0.7±0.0 vs 0.7±0.0 ΔD/D, P &lt;0.05). ROS generation was enhanced in PVAT of ieET-1 and normalized with atrasentan when compared to ieCre mice (1.4±0.1 and 0.9±0.1 and vs 1.0±0.1 relative fluorescence units/μm 2 , P &lt;0.05). RAF was decreased in ieET-1 and unchanged by atrasentan compared with control (1.8±0.2 and 2.0±0.2 vs 3.0±0.3 mL/min, P &lt;0.01). Conclusions: Long-term exposure to endothelial human ET-1 overexpression caused sustained BP elevation, endothelial dysfunction and vascular stiffening and oxidative stress.

Abstract P226: Endothelin-1 Overexpression Exaggerates Diabetes-induced Endothelial Dysfunction by Altering Oxidative Stress

Objective: Increased endothelin (ET)-1 expression has been shown to cause 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 sought to determine whether ET-1 contributes to diabetes-induced endothelial dysfunction. We hypothesized that overexpression of ET-1 in the endothelium will exaggerate diabetes-induced endothelial dysfunction. Methods: Diabetes was induced by streptozotocin IP injections (STZ, 55 mg/kg/day) 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. Endothelial function and vascular remodeling using pressurized myography, reactive oxygen species (ROS) production by dihydroethidium staining and mRNA expression by reverse transcription-quantitative PCR were assessed in mesenteric arteries (MA). Results: MA endothelium-dependent vasodilatory responses to acetylcholine were reduced 24% by diabetes in WT (E max : 61±6 vs 84±3%, P &lt;0.05), and further decreased by 12% in eET-1 (E max : 49±5, P &lt;0.05). Diabetes decreased MA media/lumen in WT (2.4±0.1% vs 3.3±0.2%, P &lt;0.05) and eET-1 (2.9±0.2% vs 4.0±0.2%, P &lt;0.05), whereas ET-1 overexpression increased MA media/lumen to a similar extent in diabetic and non-diabetic WT mice ( P &lt;0.05). Vascular ROS production in MA was increased 2-fold by diabetes in WT (5.0±0.5 vs 2.5±0.3 relative fluorescence units [RFU]/μm 2 , P &lt;0.05) and further augmented 1.7-fold in eET-1 (8.5±1.2 RFU/μm 2 , P &lt;0.05). Diabetes reduced endothelial nitric oxide synthase (eNOS, Nos3) mRNA expression in eET-1 by 50% (0.7±0.1 vs 1.4±0.2, P &lt;0.05) but not in WT. Induction of diabetes caused a 50% increase in superoxide dismutase 1 ( Sod1 , 1.5±0.2 vs 1.0±0.0, P &lt;0.05) and a 30% increase in Sod2 (1.3±0.1 vs 1.0±0.0, P &lt;0.05) mRNA expression in WT but not in eET-1. Conclusions: Increased expression of ET-1 exaggerates diabetes-induced endothelial dysfunction. This may be caused by an increase in vascular oxidative stress, a decrease in eNOS expression and a decrease in antioxidant capacity.

Abstract P347: Retinol-binding Protein 7 (RBP7) is Required for PPARG-mediated Endothelial Protection via Adiponectin

PPARγ protects against endothelial dysfunction by regulation of unknown target genes. One such target, RBP7, an intracellular fatty acid-binding protein, exhibits endothelium-specific expression, but its effect on vascular function remain unknown. We hypothesize that RBP7 is endothelial protective. We examined vascular responses in basilar artery (pressurized myograph) of RBP7-knockout (KO) and wild type (WT) mice fed normal chow (ND) or high fat diet (HFD) for 8 wks. Endothelium-dependent acetylcholine (ACh)-induced relaxation was significantly impaired in HFD-fed KO mice (ACh, 100μM: 33±7% KO vs 83±10% WT, p&lt;0.05), but not in ND-fed groups. This response was ameliorated by pre-incubation with superoxide scavenger tempol (1mM) or PEG-superoxide dismutase (100 U/ml). Mean arterial pressure (measured by radiotelemetry), body weight, hepatic steatosis, fasting glucose, glucose tolerance, and insulin sensitivity were similar in HFD-fed KO and WT mice. To identify targets downstream of RBP7, RNA-Sequencing was performed on carotid arteries from 8-week HFD-fed WT and KO mice as well as ND-fed age-matched littermates. Adiponectin (AdipoQ), a PPARγ target, was increased ~6-fold in HFD-fed WT mice, a response that was markedly blunted in KO mice. RNA sequencing was confirmed by qPCR. There was no difference in plasma AdipoQ. AdipoQ protein is expressed in endothelial cells of carotid arteries and its level of expression was increased in HFD-fed WT but not KO mice (AdipoQ/CD31: 1.14±0.1 WT-HFD vs 0.82±0.1 WT-ND, p&lt;0.05; 0.79±0.1 KO-HFD vs 0.81±0.04 KO-ND). This led us to hypothesize that AdipoQ is involved in RBP7-mediated endothelial protection. Incubation of basilar artery with mouse full-length AdipoQ protein (5 μg/mL, 4 hours) significantly ameliorated endothelial dysfunction (ACh, 100 μM: 56±6% AdipoQ+KO vs 26±3% KO, p&lt;0.05) and blunted carotid artery superoxide production in HFD-fed KO mice. AdipoQ also protects against endothelial dysfunction caused by subpressor Ang-II in KO mice. We conclude that RBP7 protects the endothelium from oxidative stress-induced dysfunction through an AdipoQ-dependent mechanism. Our evidence suggests RBP7 is an essential cofactor for activation of some PPARγ target genes in the endothelium.

Abstract P212: Sphingolipid De Novo Pathway is a Novel Regulator of Blood Pressure Homeostasis

Background and objectives: Sphingolipids, particularly sphingosine 1-phosphate (S1P), play an important role in the cardiovascular homeostasis. Recently, we revealed that endothelial de novo biosynthesis of sphingolipids is very important to control vascular functions and blood pressure. We discovered that in blood vessels, particularly in endothelial cells, Nogo-B, a membrane protein of the endoplasmic reticulum, inhibits serine palmitoyltransferase (SPT), the first and rate-limiting enzyme of de novo production of sphingolipids, to impact vascular tone and blood pressure. Indeed, mice lacking Nogo-B are protected from angiotensin II-induced hypertension, and pharmacological inhibition of SPT by myriocin reinstates high blood pressure in absence of Nogo-B, suggesting that the upregulation of SPT activity exerts anti-hypertensive functions. Thus, the goal of this study is to investigate the role of SPT in vascular functions and blood pressure regulation by using novel genetic mouse models. Methods: The SBP was evaluated in 14 weeks old mice heterozygous for Sptlc2 ( Sptlc2 +/- ) or lacking Sptlc2 specifically in endothelial cells (ECKO Sptlc2 ) and smooth muscle cells (SMCKO Sptlc2 ) by using tail-cuff system. Vascular reactivity of isolated mesenteric arteries was assessed ex-vivo by using the pressure myograph system. Results: Sptlc2 +/- , ECKO Sptlc2 and SMCKO Sptlc2 mice were hypertensive compared to their respective controls ( Sptlc2 +/- 128.9±2.6 vs. WT 112.1±2.6 mmHg; ECKO Sptlc2 125.5±1.8, SMCKO Sptlc2 127.2±0.6 vs. Sptlc2 f/f 106±0.84 mmHg) and developed endothelial dysfunction as shown by the impaired vasodilation in response to acetylcholine (EC 50 Sptlc2 +/- 1.48x10 -6 M vs. WT 4.46x10 -7 M; Emax ECKO Sptlc2 73.2±3.3% vs. Sptlc2 f/f 95.3±1.1%), as well as to flow (Emax: Sptlc2 +/- 23.3±1.4 μm vs. WT 42.9±4.4 μm; ECKO Sptlc2 19.9±0.9 μm vs. Sptlc2 f/f 41.3±3.1 μm). Conclusion: This study demonstrates the important role of SPT, thus the de novo production of sphingolipids, in controlling blood flow and pressure homeostasis, and provides the ground for the development of alternative therapeutic strategies to manage high blood pressure.

Lentil consumption reduces resistance artery remodeling and restores arterial compliance in the spontaneously hypertensive rats

We previously established that lentils were able to significantly attenuate the development of hypertension in spontaneously hypertensive rats (SHRs), but the mechanism was not investigated. The current study was therefore designed to examine the effect of lentils on arterial function in relation to arterial stiffness, lipid biochemistry and activation of select aortic proteins. Seventeen-week-old male SHRs were randomly assigned to groups (n=10/group) fed (a) 30% w/w green lentils, (b) 30% red lentils, (c) 30% mixed lentils (red and green) or (d) no lentils for 8 weeks. Normotensive Wistar Kyoto (WKY) groups (n=10/group) received either the mixed lentil or no lentil diet. Blood pressure, pulse wave velocity and serum lipids were measured at baseline and 8 weeks, while pressure myography, arterial morphology and aortic proteins were measured after termination. There were no dietary-related changes in pulse wave velocity or blood pressure for any SHR or WKY group. Low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were significantly lower in only SHR red lentil and WKY mixed lentil groups compared to their controls. The lentil diets reduced the media:lumen ratio of SHRs relative to control-fed SHRs but had no effect on WKYs. Both red and green lentils reduced arterial stiffness of SHRs but not WKYs. SHR lentil groups showed lower aortic p38 mitogen-activated protein kinase (p38MAPK) phosphorylation, thus implying that p38MAPK activation is suppressed with lentil feeding. Lentil-based diets suppress pathological vascular remodeling in SHRs, while green lentils maintain the vascular function of SHRs similar to normotensive WKYs despite the presence of high blood pressure.

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

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. 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. 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. 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.

Functional and structural changes in internal pudendal arteries underlie erectile dysfunction induced by androgen deprivation.

Androgen deficiency is strongly associated with erectile dysfunction (ED). Inadequate penile arterial blood flow is one of the major causes of ED. The blood flow to the corpus cavernosum is mainly derived from the internal pudendal arteries (IPAs); however, no study has evaluated the effects of androgen deprivation on IPA's function. We hypothesized that castration impairs IPAs reactivity and structure, contributing to ED. In our study, Wistar male rats, 8-week-old, were castrated and studied 30 days after orchiectomy. Functional and structural properties of rat IPAs were determined using wire and pressure myograph systems, respectively. Protein expression was determined by Western blot and immunohistochemistry. Plasma testosterone levels were determined using the IMMULITE 1000 Immunoassay System. Castrated rats exhibited impaired erectile function, represented by decreased intracavernosal pressure/mean arterial pressure ratio. IPAs from castrated rats exhibited decreased phenylephrine- and electrical field stimulation (EFS)-induced contraction and decreased acetylcholine- and EFS-induced vasodilatation. IPAs from castrated rats exhibited decreased internal diameter, external diameter, thickness of the arterial wall, and cross-sectional area. Castration decreased nNOS and α-actin expression and increased collagen expression, p38 (Thr180/Tyr182) phosphorylation, as well as caspase 3 cleavage. In conclusion, androgen deficiency is associated with impairment of IPA reactivity and structure and increased apoptosis signaling markers. Our findings suggest that androgen deficiency-induced vascular dysfunction is an event involving hypotrophic vascular remodeling of IPAs.

Adverse vascular remodelling is more sensitive than endothelial dysfunction to hyperglycaemia in diabetic rat mesenteric arteries

Increased vascular stiffness and reduced endothelial nitric oxide (NO) bioavailability are characteristic of diabetes. Whether these are evident at a more moderate levels of hyperglycaemia has not been investigated. The objectives of this study were to examine the association between the level of glycaemia and resistance vasculature phenotype, incorporating both arterial stiffness and endothelial function. Diabetes was induced in male Sprague Dawley rats with streptozotocin (STZ; 55mg/kg i.v.) and followed for 8 weeks. One week post STZ, diabetic rats were allocated to either moderate (⿼20mM blood glucose, 6⿿7U/insulins.c. daily) or severe hyperglycaemia (⿼30mM blood glucose, 1⿿2U/insulins.c. daily as required). At study end, rats were anesthetized, and the mesenteric arcade was collected. Passive mechanical wall properties were assessed by pressure myography. Responses to the endothelium-dependent vasodilator acetylcholine (ACh) were assessed using wire myography. Our results demonstrated for the first time that mesenteric arteries from both moderate and severely hyperglycaemic diabetic rats exhibited outward hypertrophic remodelling and increased axial stiffness compared to arteries from non-diabetic rats. Secondly, mesenteric arteries from severely (⿼30mM blood glucose), but not moderately hyperglycaemic (⿼20mM blood glucose) rats exhibit a significant reduction to ACh sensitivity compared to their non-diabetic counterparts. This endothelial dysfunction was associated with significant reduction in endothelium-derived hyperpolarisation and endothelium-dependent NO-mediated relaxation. Interestingly, endothelium-derived nitroxyl (HNO)-mediated relaxation was intact. Therefore, moderate hyperglycaemia is sufficient to induce adverse structural changes in the mesenteric vasculature, but more severe hyperglycaemia is essential to cause endothelial dysfunction.

Immature endothelial cells initiate endothelin-mediated constriction of newborn arteries.

Endothelial expression and the release of endothelin-1 (ET-1) in levels sufficient to initiate vasoconstriction is considered to be a hallmark feature of pathological endothelial dysfunction. During the immediate postnatal period, arterial endothelial cells undergo remarkable structural and functional changes as they transition to a mature protective cell layer, which includes a marked increase in NO dilator activity. The present study demonstrates that endothelial cells lining newborn central arteries express high levels of ET-1 peptides and, in response to endothelial stimulation, rapidly release ET-1 and initiate powerful ET-1-mediated constriction. This activity is lost as the endothelium matures in the postnatal period. Heightened activity of ET-1 in the neonatal endothelium might contribute to inappropriate responses of immature arteries to stress or injury. Indeed, the immature endothelium resembles dysfunctional endothelial cells, and retention or re-emergence of this phenotype may contribute to the development of vascular disease. Endothelial cells lining fetal and newborn arteries have an unusual phenotype, including reduced NO activity, prominent actin stress fibres and poorly developed cellular junctions. Experiments were performed to determine whether the immature endothelium of newborn arteries also expresses and releases endothelin-1 (ET-1) and initiates endothelium-dependent constriction. Carotid arteries were isolated from newborn (postnatal day 1; P1), postnatal day 7 (P7) and postnatal day 21 (P21) mice and assessed in a pressure myograph system. Endothelial stimulation with A23187 or thrombin caused constriction in P1 arteries, no significant change in diameter of P7 arteries, and dilatation in P21 arteries. In P1 arteries, constriction to thrombin or A23187 was inhibited by endothelial-denudation, by ET-1 receptor antagonists (BQ123 plus BQ788) or by inhibition of endothelin-converting enzyme (phosphoramidon or SM19712). ET-1 receptor antagonism did not affect responses to thrombin or A23187 in more mature arteries. Exogenous ET-1 caused similar concentration-dependent constrictions of P1, P7 and P21 arteries. Endothelial stimulation with thrombin rapidly increased the endothelial release of ET-1 from P1 but not P21 aortas. Endothelial expression of ET-1 peptides, as assessed by immunofluorescence analysis, was increased in P1 compared to P21 arteries. Therefore, newborn endothelial cells express high levels of ET-1 peptides, rapidly release ET-1 in response to endothelial stimulation, and initiate ET-1-mediated endothelium-dependent constriction. This activity is diminished as the endothelium matures in the immediate postnatal period. Heightened activity of ET-1 in neonatal endothelium probably reflects an early developmental role of the peptide, although this might contribute to inappropriate responses of immature arteries to stress or injury.

Isolation and Cannulation of Cerebral Parenchymal Arterioles.

Intracerebral parenchymal arterioles (PAs), which include parenchymal arterioles, penetrating arterioles and pre-capillary arterioles, are high resistance blood vessels branching out from pial arteries and arterioles and diving into the brain parenchyma. Individual PA perfuse a discrete cylindrical territory of the parenchyma and the neurons contained within. These arterioles are a central player in the regulation of cerebral blood flow both globally (cerebrovascular autoregulation) and locally (functional hyperemia). PAs are part of the neurovascular unit, a structure that matches regional blood flow to metabolic activity within the brain and also includes neurons, interneurons, and astrocytes. Perfusion through PAs is directly linked to the activity of neurons in that particular territory and increases in neuronal metabolism lead to an augmentation in local perfusion caused by dilation of the feed PA. Regulation of PAs differs from that of better-characterized pial arteries. Pressure-induced vasoconstriction is greater in PAs and vasodilatory mechanisms vary. In addition, PAs do not receive extrinsic innervation from perivascular nerves - innervation is intrinsic and indirect in nature through contact with astrocytic endfeet. Thus, data regarding contractile regulation accumulated by studies using pial arteries does not directly translate to understanding PA function. Further, it remains undetermined how pathological states, such as hypertension and diabetes, affect PA structure and reactivity. This knowledge gap is in part a consequence of the technical difficulties pertaining to PA isolation and cannulation. In this manuscript we present a protocol for isolation and cannulation of rodent PAs. Further, we show examples of experiments that can be performed with these arterioles, including agonist-induced constriction and myogenic reactivity. Although the focus of this manuscript is on PA cannulation and pressure myography, isolated PAs can also be used for biochemical, biophysical, molecular, and imaging studies.

Current Developments on Optical Feedback Interferometry as an All-Optical Sensor for Biomedical Applications.

Optical feedback interferometry (OFI) sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of the work in progress at UPC-CD6 and LAAS-CNRS related to the application of OFI to different aspects of biosensing, both in vivo and ex vivo. This work is intended to present the variety of opportunities and potential applications related to OFI that are available in the field. The activities presented are divided into two main sensing strategies: The measurement of optical path changes and the monitoring of flows, which correspond to sensing strategies linked to the reconstruction of changes of amplitude from the interferometric signal, and to classical Doppler frequency measurements, respectively. For optical path change measurements, measurements of transient pulses, usual in biosensing, together with the measurement of large displacements applied to designing palliative care instrumentation for Parkinson disease are discussed. Regarding the Doppler-based approach, progress in flow-related signal processing and applications in real-time monitoring of non-steady flows, human blood flow monitoring and OFI pressure myograph sensing will be presented. In all cases, experimental setups are discussed and results presented, showing the versatility of the technique. The described applications show the wide capabilities in biosensing of the OFI sensor, showing it as an enabler of low-cost, all-optical, high accuracy biomedical applications.

Abstract 567: Transcription Factor Runx2 is Induced in Vascular Aging and May Promote Age-related Arterial Stiffness

Background: Arterial stiffening is a hallmark of vascular aging and may constitute a critical mechanism linking age to increased cardiovascular risk. However, up to now there is no therapy available to efficiently and specifically target age-related arterial stiffening. We recently identified the osteogenic transcription factor Runx2 as an inducer of diabetic arterial stiffness. Objective: The present study investigated the role of Runx2 in the setting of age-related arterial stiffness. Methods and Results: Aortic stiffness – quantified by ex vivo mechanical testing (pressure myography) – was markedly increased in 1-year old male C57Bl/6 mice compared to young (10 week-old) controls. At the same time, Runx2 was aberrantly upregulated in the medial layer of aged aortae, coming along with significant medial fibrosis. Additionally, we detected increased aortic expression of interleukin 6 ( Il6 ) – a key cytokine involved in vascular “inflammaging”. Mechanistically, we found IL-6-induced RUNX2 expression in aortic smooth muscle cells (SMCs) via a NFkB-dependent pathway. Conclusion: In conclusion this study suggests Runx2 as a potential mediator of age-related arterial fibrosis and stiffness warranting further interventional/therapeutic studies.

Abstract 182: Inhibitor of differentiation (Id)3 Regulation of the Vasculature in Adipose Tissue

Rationale: Over half of the U.S. is overweight or obese and excessive weight gain greatly increases one’s risk of cardiovascular disease. Adipose tissue requires new blood vessel formation to support transport of nutrients during expansion. Our lab has previously published that global loss of the helix-loop-helix transcription factor Inhibitor of differentiation 3 (Id3) results in attenuated increases in adipose depot size and microvascular blood volume in mice fed a high fat diet (HFD). Id3 has also been implicated in regulating tumor angiogenesis. Together, our results suggest that Id3 is regulating HFD-induced angiogenesis in adipose tissue. Methods and Results: To determine if Id3 is regulating angiogenesis, we performed genetic, cellular, and arterial experiments and analyses. Using bromodeoxyuridine (BrdU) treatments and flow cytometry, we found that endothelial cells within adipose tissue of mice with a global genetic knockout of Id3 (Id3 KO) had fewer proliferating (BrdU-positive) endothelial cells (0.0679% BrdU+CD31+ cells) than wild type (WT) mice (0.754% BrdU+CD31+). Using mouse adipose tissue gene expression data from the Gene Ontology Consortium database, we found that genes correlating most significantly with Id3 were functionally classified under categories of vascular development (p = 4.45E-8, correlation significance) and angiogenesis (p = 1.66E-6). Sox18, a known transcriptional regulator of blood vessel formation, shows higher relative gene expression in Id3 WT (1.42 ± 0.417) than Id3 KO (0.332 ± 0.126) adipose tissue. Finally, preliminary findings using pressure myography demonstrate that Id3 KO mice have a higher baseline arterial diameter than Id3 WT. Conclusion: Dysregulation of vascular development during adipose tissue expansion is altering arterial function in an Id3-dependent manner.

Diet supplementation with rice bran enzymatic extract restores endothelial impairment and wall remodelling of ApoE−/− mice microvessels

Background and aimsSmall mesenteric artery resistance and functionality are key factors for the maintenance of blood homeostasis. We attained to evaluate the effects of a rice bran enzymatic extract (RBEE) on structural, mechanic and myogenic alterations and endothelial dysfunction secondary to atherosclerosis disease. MethodsSeven week-old ApoE−/− mice were fed on standard (ST) or high fat (HF) diets supplemented or not with 1 or 5% RBEE (w/w) for 23 weeks. Wild-type C57BL/6J mice fed on ST diet served as controls. Small mesenteric arteries were mounted in a pressure myograph in order to evaluate structural, mechanical and myogenic properties. Vascular reactivity was assessed in the presence of different combinations of inhibitors: l-NAME, indometacin, apamin and charybdotoxin. ResultsApoE−/− mice fed on ST and HF diets showed different structural and mechanical alterations, alleviated by RBEE supplementation of ST and HF diets. C57BL/6J was characterized by increased expression of IKCa (199.3%, p = 0.023) and SKCa (133.2%, p = 0.026), resulting in higher EDHF participation (p = 0.0001). However, NO release was more relevant to ApoE−/− mice vasodilatation. HF diet reduced the amount of NO released due to 2-fold increase of eNOS phosphorylation in the inhibitory residue Thr495 (p = 0.034), which was fully counteracted by RBEE supplementation (p = 0.028), restoring ACh-induced vasodilatation (p = 0.00006). Dihydroethidium fluorescence of superoxide and picrosirius red staining of collagen were reduced by RBEE supplementation of HF diet by 76.91% (p = 0.022) and 65.87% (p = 0.030), respectively. ConclusionRBEE supplemented diet reduced vessel remodeling and oxidative stress. Moreover, RBEE supplemented diet increased NO release by downregulating p-eNOSThr495, thus, protecting the endothelial function.

Endothelial Adherens Junctions and Endothelial Dysfunction in Aging Arteries

Aging causes a systemic deterioration of the structure and function of the entire arterial network resulting in organ injury, dysfunction and failure. Endothelial dysfunction, including diminished NO activity, is thought to be a key contributor to pathological vascular aging. The normal protective phenotype of arterial endothelial cells is initiated in the immediate postnatal period and appears to be dependent on increased engagement and signaling of VE‐cadherin at Adherens Junctions (Flavahan S et al, 2013, Am J Physiol Heart Circ Physiol. 305(3):H321–9). The aim of the present study was to determine whether this process might be disrupted in aging arteries and contribute to aging‐induced endothelial dysfunction. Aortas and tail arteries were isolated from young (3 to 4 months) and old (22–24 months old) F344 rats and processed for immunofluorescent, biochemical and functional analysis. Arterial function was assessed using pressure myographs at a constant transmural pressure of 60 mmHg. During constriction with phenylephrine (to 70% of baseline), acetylcholine (1 to 1000 nM) caused dilatation that was significantly reduced in old compared to young arteries. Inhibition of NO synthase with LNAME markedly inhibited responses to acetylcholine, and there was no significant difference in the magnitude of the LNAME‐resistant dilatation between young and old arteries. There was also no significant difference in dilatation to the NO donor, DEA‐NONOate (1 to 1000 nM) between young and old arteries. These results are consistent with the presence of endothelial dysfunction and reduced endothelial NO activity in aging arteries. Immunofluorescent labeling followed by LSM analysis of VE‐cadherin demonstrated the presence of intense protein staining at endothelial Adherens Junctions in young arteries. This staining was significantly reduced in old arteries, which demonstrated a significant increase in intracellular localization of the protein. Immunoblot analysis confirmed a significant reduction in cell surface expression of VE‐cadherin in old compared to young arteries. A function‐blocking antibody to VE‐cadherin, which inhibits VE‐cadherin engagement and disrupts endothelial Adherens Junctions, significantly inhibited dilatation to acetylcholine in young but not in old arteries. A control antibody had no significant effects. After inhibition of VE‐cadherin engagement with the function‐blocking antibody, there was no longer any significant different in dilatation to acetylcholine between young and old arteries. These results demonstrate that there is morphological disruption of Adherens Junctions and reduced cell surface expression of VE‐cadherin in aging endothelial cells. Furthermore, the functional role of Adherens Junctions in contributing to endothelial dilatation is selectively lost in old arteries and likely contributes to endothelial dysfunction in these blood vessels.

Coronary Microvascular Smooth Muscle‐Endothelial Cell Communication and Notch 3 Signaling in Type 2 Diabetes

The Notch signaling pathway, via cell‐cell communication, is critical during normal vascular development and homeostasis, and it is known to regulate vascular smooth muscle (VSMC) phenotype, including proliferation. The current study tested the hypothesis that VSMC‐endothelial cell (EC) Notch 3/Jagged 1 signaling is aberrant to account for adverse remodeling and stiffness observed in type 2 diabetic coronary resistance microvessels (CRMs). Low‐passage primary coronary VMSCs were isolated from normal and type 2 diabetic db/db mice and were either mono‐ or co‐cultured with normal or type 2 diabetic human coronary microvascular endothelial cells (hCMECs), respectively (n=4–6 per group). In separate experiments, normal (n=3) and diabetic db/db CRMs (n=3) were isolated, mounted, and perfusion pressure fixed on a pressure myograph. The size and frequency of fenestrae in the internal elastic laminas of intact CRMs were assessed using Alexa Fluor 633 hydrazide on a confocal microscope. Coronary VSMCs isolated from db/db mice expressed higher Notch 3 mRNA (2.12±0.10 vs. 1.00±0.20; p&lt;0.01) compared to normal. Co‐culture of coronary VSCMs with hCMECs caused a robust induction of Notch 3 expression in normal VSMCs (3.67±0.60 vs. 1.00, p&lt;0.001), which was exacerbated in coronary VSMCs isolated from db/db mice (5.52±0.51 vs. 3.67±0.60, p&lt;0.05). Alpha‐smooth muscle actin (α‐SMA) trended lower in db/db coronary VSMCs (p=0.07), while co‐culture with hCMECs did not alter α‐SMA expression. Diabetic hCMECs expressed lower Jagged 1 mRNA compared to normal (0.58±0.04 vs. 1.00±0.07; p&lt;0.01); co‐culture of hCMECs and coronary VSMCs caused a robust reduction in Jagged 1 expression in normal cells (0.63±0.06 vs. 1.00±0.07, p&lt;0.001), while no further reduction was observed in co‐cultured diabetic cells. The number of fenestrae in the internal elastic lamina was reduced in diabetic CRMs (0.028±0.005 vs. 0.040±0.001 fen/μm2, p&lt;0.05), while the size of the fenestrae remained unchanged. These data show that Notch3/Jagged 1 expression and VSMC differentiation are altered in diabetic coronary resistance microvessel cells, and VSMC‐EC contact via co‐culture induces differential dysregulation of Notch3/Jagged1 signaling. The data further show a reduction in the number of fenestrae in db/db CRMs, suggesting that the opportunity for Notch3/Jagged1 signaling to occur in vivo may be reduced to contribute to adverse remodeling and stiffness observed in those blood vessels.Support or Funding InformationAHA 15UFEL22760002 to MK; NIH K99HL116769 and NCH to AJT.