High intraluminal pressure promotes vascular inflammation via caveolin-1

The aetiology and progression of hypertension involves various endogenous systems, such as the renin angiotensin system, the sympathetic nervous system, and endothelial dysfunction. Recent data suggest that vascular inflammation may also play a key role in the pathogenesis of hypertension. This study sought to determine whether high intraluminal pressure results in vascular inflammation. Leukocyte adhesion was assessed in rat carotid arteries exposed to 1 h of high intraluminal pressure. The effect of intraluminal pressure on signaling mechanisms including reactive oxygen species production (ROS), arginase expression, and NFĸB translocation was monitored. 1 h exposure to high intraluminal pressure (120 mmHg) resulted in increased leukocyte adhesion and inflammatory gene expression in rat carotid arteries. High intraluminal pressure also resulted in a downstream signaling cascade of ROS production, arginase expression, and NFĸB translocation. This process was found to be angiotensin II-independent and mediated by the mechanosensor caveolae, as caveolin-1 (Cav1)-deficient endothelial cells and mice were protected from pressure-induced vascular inflammatory signaling and leukocyte adhesion. Cav1 deficiency also resulted in a reduction in pressure-induced glomerular macrophage infiltration in vivo. These findings demonstrate Cav1 is an important mechanosensor in pressure-induced vascular and renal inflammation.

Lack of English proficiency is associated with the characteristics of work- related injury and recovery cost in the Victorian working population

BACKGROUND

Migrant workers have been identified in Europe, North America, Asia and Australia as a particularly vulnerable working population with a higher risk of work-related injury and mortality compared to non-migrant workers. Lack of English language proficiency is associated with an increased risk of work-related injury. Whether lack of English proficiency influences post-injury recovery or return to work outcomes remains unknown.

OBJECTIVE

Using administrative data from a population based workers' compensation dataset in the state of Victoria, Australia, we aimed to examine work-related injury rates, worker characteristics and compensation outcomes in workers who were not proficient in English. We hypothesized that the use of an interpreter service would be associated with a poorer post-injury recovery profile and worse return to work outcomes.

METHODS

WorkSafe Victoria accepted non-fatal claims for injuries and illnesses reported between January 1, 2003, and December 31, 2012 by workers aged 15 to 74 (n = 402, 828 claims) were analysed. Consistent with prior research, we selected "use of an interpreter service" as the indicator of English language proficiency. The total and categorical compensable cost of recovery was used as recovery outcomes.

RESULTS

Of these claims, 16,286 (4%) involved the use of an interpreter service (LOTE workers). Our analysis revealed that Victorian injured LOTE workers have significantly different demographic, occupational and injury characteristics compared to non-LOTE injured workers. Furthermore, we present novel evidence that LOTE status was associated with poorer long-term injury outcomes, observed as a greater healthcare utilisation and larger paid income benefits, after controlling for occupation, employment status and injury type compared to non-LOTE injured workers.

CONCLUSIONS

These data suggest that English language proficiency is associated not only with the risk of work-related injury but also to the long-term recovery outcomes. We conclude that despite access to language interpreter services, injured LOTE workers experience English language proficiency dependent, and injury severity independent, recovery barriers which need to be overcome to improve long term recovery outcomes.

Y Chromosome, Hypertension and Cardiovascular Disease: Is Inflammation the Answer?

It is now becomingly increasingly evident that the functions of the mammalian Y chromosome are not circumscribed to the induction of male sex. While animal studies have shown variations in the Y are strongly accountable for blood pressure (BP), this is yet to be confirmed in humans. We have recently shown modulation of adaptive immunity to be a significant mechanism underpinning Y-chromosome-dependent differences in BP in consomic strains. This is paralleled by studies in man showing Y chromosome haplogroup is a significant predictor for coronary artery disease through influencing pathways of immunity. Furthermore, recent studies in mice and humans have shown that Y chromosome lineage determines susceptibility to autoimmune disease. Here we review the evidence in animals and humans that Y chromosome lineage influences hypertension and cardiovascular disease risk, with a novel focus on pathways of immunity as a significant pathway involved.

Accelerated age-related decline in renal and vascular function in female rats following early-life growth restriction

Many studies report sexual dimorphism in the fetal programming of adult disease. We hypothesized that there would be differences in the age-related decline in renal function between male and female intrauterine growth-restricted rats. Early-life growth restriction was induced in rat offspring by administering a low-protein diet (LPD; 8.7% casein) to dams during pregnancy and lactation. Control dams were fed a normal-protein diet (NPD; 20% casein). Mean arterial pressure (MAP) and renal structure and function were assessed in 32- and 100-wk-old offspring. Mesenteric artery function was examined at 100 wk using myography. At 3 days of age, body weight was ∼24% lower ( P < 0.0001) in LPD offspring; this difference was still apparent at 32 wk but not at 100 wk of age. MAP was not different between the male NPD and LPD groups at either age. However, MAP was greater in LPD females compared with NPD females at 100 wk of age (∼10 mmHg; P < 0.001). Glomerular filtration rate declined with age in the NPD male, LPD male and LPD female offspring (∼45%, all P < 0.05), but not in NPD female offspring. Mesenteric arteries in the aged LPD females had reduced sensitivity to nitric oxide donors compared with their NPD counterparts, suggesting that vascular dysfunction may contribute to the increased risk of disease in aged females. In conclusion, females growth-restricted in early life were no longer protected from an age-related decline in renal and arterial function, and this was associated with increased arterial pressure without evidence of renal structural damage.

Compound 21, a selective agonist of angiotensin AT2 receptors, prevents endothelial inflammation and leukocyte adhesion in vitro and in vivo

BACKGROUND AND PURPOSE

Angiotensin AT2 receptors are upregulated in disease states such as atherosclerosis and blockade of the AT2 receptors exacerbates plaque formation. Direct stimulation of these receptors is anti-atherogenic but the mechanisms and pathways involved remain unknown. We examined the effect of direct AT2 receptor stimulation with Compound 21 (C21) on the leukocyte adhesion cascade in vitro, right through to plaque formation in vivo.

EXPERIMENTAL APPROACH

Effects of C21 on TNFα-induced inflammation were assessed in human umbilical vein endothelial cells (HUVECs), activation of monocytes, polarisation of monocyte-derived macrophages and in intact mouse aortae.

KEY RESULTS

C21 attenuated TNFα-induced: monocyte adhesion to cultured HUVECs, adhesion molecule expression and abolished TNFα-induced ROS production. TNFα-induced NFκB translocation from the cytoplasm to the nucleus, essential for cytokine production, was prevented by C21. C21 did not influence monocyte activation or macrophage polarisation but did reduce TNFα and IL-6 mRNA expression in M1 macrophages. The anti-inflammatory effects of C21 were abolished by an AT2 receptor antagonist confirming that the effects of C21 were AT2 receptor-mediated. Also, leukocyte adhesion and cytokine gene expression, induced by high-fat diet (HFD), was attenuated in ApoE(-/-) mice treated with C21. Plaque size and stability were improved with C21 treatment with increased smooth muscle cell composition and decreased lipid size, compared with HFD-saline treated mice.

CONCLUSION AND IMPLICATIONS

C21 prevented TNFα-induced and HFD-induced vascular inflammation in vitro and in vivo. Our data provide strong evidence that the anti-atherosclerotic actions of C21 were due to vascular anti-inflammatory effects, mediated by AT2 receptors.

Origin of the Y chromosome influences intrarenal vascular responsiveness to angiotensin I and angiotensin (1-7) in stroke-prone spontaneously hypertensive rats

The lineage of the Y chromosome accounts for up to 15 to 20 mm Hg in arterial pressure. Genes located on the Y chromosome from the spontaneously hypertensive rat (SHR) are associated with the renin-angiotensin system. Given the important role of the renin-angiotensin system in the renal regulation of fluid homeostasis and arterial pressure, we hypothesized that the origin of the Y chromosome influences arterial pressure via interaction between the intrarenal vasculature and the renin-angiotensin system. Sixteen-week-old normotensive rats (Wistar Kyoto [WKY]), spontaneously hypertensive stroke-prone rat (SHRSP), and 2 reciprocal Y consomic rat strains, 1 comprising the WKY autosomes and X chromosome with the Y chromosome from the hypertensive rat strain (WKY.SPGlaY) and vice versa (SP.WKYGlaY), were examined. SP.WKYGlaY had lower systolic blood pressure than SHRSP (195±5 versus 227±8 mm Hg; P<0.03), whereas WKY.SPGlaY had higher systolic blood pressure compared with WKY (157±3 versus 148±3 mm Hg; P<0.05), measured by radiotelemetry. Compared with WKY rats, SHRSP had higher plasma angiotensin(1-7) (Ang (1-7)):Ang II ratio (WKY: 0.13±0.01 versus SHRSP: 1.33±0.4; P<0.005), greater angiotensin II receptor type 2 and Mas receptor mRNA expression, and a blunted renal constrictor response to intrarenal Ang I and Ang(1-7) infusions. Introgression of the normotensive Y chromosome into the SHRSP background (SP.WKYGlaY) restored responses in the SHRSP to WKY levels, evidenced by a reduction in plasma Ang(1-7):Ang II ratio (SP.WKYGlaY: 0.24±0.02; P<0.01), angiotensin II receptor type 2, and Mas receptor mRNA expression and an increased vasoconstrictor response to intrarenal Ang I and Ang(1-7) infusion. This study demonstrates that the origin of the Y chromosome significantly impacts the renal vascular responsiveness and therefore may influence the long-term renal regulation of blood pressure.

Abstract 417: AT2R Stimulation Prevents TNFa-Induced Vascular Inflammation In Vitro and Ex Vivo

Vascular inflammation, involving the recruitment, adhesion and infiltration of monocytes to the sub-endothelial space, is a critical early event in the development of atherosclerosis. The renin angiotensin system plays an important role in inflammation via activation of the angiotensin type I receptor (AT1R), which induces pro-inflammatory effects. The angiotensin II type 2 receptor (AT2R) counter-regulates the effects of the AT1R, including AT1R-mediated pro-inflammatory cytokine expression. We investigated the anti-inflammatory effects of AT2R stimulation in vascular inflammation by examining leukocyte to endothelial adhesion. We quantified the effect of AT2R stimulation (Compound 21: C21, 100μM) on TNFα (10ng/mL)-induced monocyte adhesion to cultured human umbilical vascular endothelial cells in vitro . AT2R stimulation attenuated TNFα-induced monocyte adhesion (unstimulated: 8±4% of TNFα: 100%, C21+TNFα: 59±12% of TNFα-induced adhesion). Adhesion of monocytes to the endothelial monolayer following incubation with TNFα+C21+AT2R antagonism (PD 123319, 10μM) was not different to TNFα-induced monocyte adhesion (93±5% of TNFα); demonstrating that the anti-inflammatory effects of C21 are mediated by the AT2R. Furthermore, C21 treatment attenuated TNFα-induced upregulation of adhesion molecules ICAM-1 and E-selectin and abolished TNFα-induced ROS production (unstimulated: 2±2, TNFα: 55±16, TNFα+C21: -3±5 dihydroethidium fluorescence intensity units). We quantified TNFα-induced leukocyte adhesion in intact mouse thoracic aorta ex vivo in real time in the presence and absence of AT2R activation. Consistent with our in vitro findings, we observed that direct AT2R activation (C21, 10μM) abolished TNFα-induced leukocyte adhesion (TNFα: 30±4, vs TNFα+C21: 11±4 adhered leukocytes/field of view (FOV), P<0.01) an effect which was abolished by co-incubation with PD 123319 (10μM: 31±5 adhered leukocytes/FOV). This study provides the first functional evidence that direct AT2R stimulation prevents TNFα-induced leukocyte adhesion, ICAM-1 and E-selectin expression and ROS production revealing the anti-inflammatory and therapeutic potential of the AT2R in the treatment of inflammation-induced cardiovascular disease.

Abstract 5: Intrarenal Responses to Angiotensin I and Angiotensin (1-7) in the Stroke-Prone Spontaneously Hypertensive Rat Are Y Chromosome Dependent

The Y chromosome accounts for 15-20mmHg difference in arterial pressure; the gene(s) and mechanism(s) underlying this effect remain unknown. One candidate gene, the Sry3 gene, expressed exclusively on the hypertensive SHR Y chromosome has been shown in vitro to interact with the renin angiotensin system (RAS). Using a reciprocal Y consomic rat approach, we investigated the functional consequences of this interaction in vivo ; examining the interaction of the Y chromosome with the renal vasculature. 16 week old normotensive rats (WKY), hypertensive rats (SHRSP) and two reciprocal Y consomic rat strains; one comprising the WKY autosomes and X chromosome with the hypertensive Y chromosome (WKY.SP Gla Y) and vice versa (SP.WKY Gla Y) were examined. We confirmed via radiotelemetry that systolic blood pressure (SBP) was Y chromosome dependent; SP.WKY Gla Y had lower SBP than SHRSP (195±5mmHg vs 227±8mmHg, P<0.03) and was higher in WKY.SP Gla Y compared to WKY (157±3mmHg vs 148±3mmHg, P<0.05). Compared to WKY rats, the vasodilator arm of the RAS was enhanced in SHRSP as evidenced by a higher plasma Ang(1-7):Ang II ratio (WKY:0.13±0.01 vs SHRSP:1.33±0.4, P<0.005) and a blunted renal blood flow (RBF) response to graded intrarenal Ang I and Ang(1-7) infusions. In response to 10ng/kg we observed a reduction in RBF of WKY:58±6% and 16±6% vs SHRSP: 17±6%, P<0.01 and 1±4%, P<0.05 respectively. Introgression of the normotensive Y chromosome into the SHRSP background (SP.WKY Gla Y) resulted in a reduction in plasma Ang(1-7):AngII ratio (SP.WKY Gla Y: 0.24±0.02, P<0.01) and an increased vasoconstrictor response to intrarenal Ang I and Ang(1-7) infusion. In response to 10ng/kg bolus RBF in SP.WKY Gla Y reduced by 45±14%, P<0.01 and 41±18%, P<0.005, respectively compared to SHRSP, demonstrating the blunted responsiveness in the SHRSP is Y chromosome dependent. Investigation of the interlobular arteries via wire myography revealed increased sensitivity to Ang II in SHRSP compared to WKY which was reduced following introgression of the WKY Y chromosome (SP.WKY Gla Y) confirming that the Y chromosome influences the RAS in the renal vasculature. This study provides novel evidence that the Y chromosome influences the vasodilatory arm of the RAS and intrarenal vascular function.

Endothelial dysfunction in patients with type 2 diabetes post acute coronary syndrome

This single visit study examined whether endothelial function, in addition to cardiovascular (CV) risk factors and plasma microparticle content, was normalised in 15 patients with type 2 diabetes + acute coronary syndrome (ACS) (6 weeks-6 months post cardiac event) undergoing standard clinical care compared to 16 sex- and age-matched healthy controls.

RESULTS

While total and low-density lipoprotein (LDL) cholesterol levels were well controlled in the patients with type 2 diabetes + ACS, residual CV risk profiles such as increased body mass index (BMI), systolic blood pressure, glucose levels and triglycerides and lower high-density lipoprotein (HDL) levels were still apparent. Endothelium-dependent responses to acetylcholine (ACh) were significantly lower in type 2 diabetes + ACS patients compared to controls. Correspondingly, the reactive hyperaemic index (RHI) was lower in the patient cohort. Endothelial microparticle (EMP) levels (CD31(+), CD41(-)) were 40% lower in the patient cohort. Simultaneous analysis of platelet microparticle (PMP) levels (CD41(+)) showed no difference between cohorts.

CONCLUSIONS

Patients with type 2 diabetes suffering from recent ACS exhibit residual CV risk factors despite being on standard clinical care. In addition, these patients continue to present with endothelial dysfunction despite having lower levels of EMPs.

The arterial depressor response to chronic low-dose angiotensin II infusion in female rats is estrogen dependent

The complex role of the renin-angiotensin-system (RAS) in arterial pressure regulation has been well documented. Recently, we demonstrated that chronic low-dose angiotensin II (ANG II) infusion decreases arterial pressure in female rats via an AT(2)R-mediated mechanism. Estrogen can differentially regulate components of the RAS and is known to influence arterial pressure regulation. We hypothesized that AT(2)R-mediated depressor effects evident in females were estrogen dependent and thus would be abolished by ovariectomy and restored by estrogen replacement. Female Sprague-Dawley rats underwent ovariectomy or sham surgery and were treated with 17β-estradiol or placebo. Mean arterial pressure (MAP) was measured via telemetry in response to a 2-wk infusion of ANG II (50 ng·kg(-1)·min(-1) sc) or saline. MAP significantly decreased in females treated with ANG II (-10 ± 2 mmHg), a response that was abolished by ovariectomy (+4 ± 2 mmHg) and restored with estrogen replacement (-6 ± 2 mmHg). Cardiac and renal gene expression of components of the RAS was differentially regulated by estrogen, such that overall, estrogen shifted the balance of the RAS toward the vasodilatory axis. In conclusion, estrogen-dependent mechanisms offset the vasopressor actions of ANG II by enhancing RAS vasodilator pathways in females. This highlights the potential for these vasodilator pathways as therapeutic targets, particularly in women.

Gender Differences in Pressure-Natriuresis and Renal Autoregulation

Sexual dimorphism in arterial pressure regulation has been observed in humans and animal models. The mechanisms underlying this gender difference are not fully known. Previous studies in rats have shown that females excrete more salt than males at a similar arterial pressure. The renin-angiotensin system is a powerful regulator of arterial pressure and body fluid volume. This study examined the role of the angiotensin type 2 receptor (AT 2 R) in pressure-natriuresis in male and female rats because AT 2 R expression has been reported to be enhanced in females. Renal function was examined at renal perfusion pressures of 120, 100, and 80 mm Hg in vehicle-treated and AT 2 R antagonist-treated (PD123319; 1 mg/kg/h) groups. The pressure-natriuresis relationship was gender-dependent such that it was shifted upward in female vs male rats ( P <0.001). AT 2 R blockade modulated the pressure-natriuresis relationship, shifting the curve downward in male ( P <0.01) and female ( P <0.01) rats to a similar extent. In females, AT 2 R blockade also reduced the lower end of the autoregulatory range of renal blood flow ( P <0.05) and glomerular filtration rate ( P <0.01). Subsequently, the renal blood flow response to graded angiotensin II infusion was also measured with and without AT 2 R blockade. We found that AT 2 R blockade enhanced the renal vasoconstrictor response to angiotensin II in females but not in males ( P <0.05). In conclusion, the AT 2 R modulates pressure-natriuresis, allowing the same level of sodium to be excreted at a lower pressure in both genders. However, a gender-specific role for the AT 2 R in renal autoregulation was evident in females, which may be a direct vascular AT 2 R effect.

Predictive response-relevant clustering of expression data provides insights into disease processes

This article describes and illustrates a novel method of microarray data analysis that couples model-based clustering and binary classification to form clusters of `response-relevant' genes; that is, genes that are informative when discriminating between the different values of the response. Predictions are subsequently made using an appropriate statistical summary of each gene cluster, which we call the `meta-covariate' representation of the cluster, in a probit regression model. We first illustrate this method by analysing a leukaemia expression dataset, before focusing closely on the meta-covariate analysis of a renal gene expression dataset in a rat model of salt-sensitive hypertension. We explore the biological insights provided by our analysis of these data. In particular, we identify a highly influential cluster of 13 genes—including three transcription factors (Arntl, Bhlhe41 and Npas2)—that is implicated as being protective against hypertension in response to increased dietary sodium. Functional and canonical pathway analysis of this cluster using Ingenuity Pathway Analysis implicated transcriptional activation and circadian rhythm signalling, respectively. Although we illustrate our method using only expression data, the method is applicable to any high-dimensional datasets. Expression data are available at ArrayExpress (accession number E-MEXP-2514) and code is available at http://www.dcs.gla.ac.uk/inference/metacovariateanalysis/.

Sex-differences in circadian blood pressure variations in response to chronic angiotensin II infusion in rats

1. The aim of this study was to investigate the effect of chronic angiotensin II (AngII) infusion on the circadian rhythms of arterial blood pressure, heart rate (HR) and locomotor activity (ACT) in male and female rats. 2. Radiotelemetry probes were implanted into the aorta in male and female rats and allowed 10 days for recovery. Control levels for mean arterial pressure (MAP), HR and ACT were recorded for 3 days, then AngII (400 ng/kg per min s.c. via osmotic minipump) or vehicle (saline) was infused for 10 days (n = 6 per group). Further recordings of MAP, HR and ACT were made during days 8, 9 and 10 of the infusion period. 3. In response to AngII infusion, night and day-time MAP increased significantly in female (18 +/- 2 mmHg; 28 +/- 7 mmHg) and male (27 +/- 4 mmHg; 30 +/- 3 mmHg) rats, respectively. The degree of elevation in MAP in response to AngII was attenuated in the females during the night period (P(sex) < 0.05) but not the day (P(sex) = 0.2). Control night-day differences in MAP, HR and ACT averaged 7 +/- 1 mmHg, 58 +/- 5 b.p.m. and 30 +/- 4 units in the female and 6 +/- 1 mmHg, 43 +/- 3 b.p.m. (P(sex) < 0.05) and 14 +/- 2 units (P(sex) < 0.05) in male rats, respectively. AngII infusion disrupted MAP circadian rhythm in female (-4 +/- 2 mmHg) and male rats (1 +/- 2 mmHg; P(treat) < 0.01), but did not affect heart rate or locomotor activity. 4. In conclusion, sex differences in the circadian rhythm of heart rate and locomotor activity, but not arterial pressure exist under basal conditions. Circulating AngII modulated the circadian rhythm of MAP in female and male rats but not heart rate or locomotor activity. These findings have important implications for our understanding of circadian blood pressure rhythms in states of activation of the renin angiotensin system.

Angiotensin II and nitric oxide in neural control of intrarenal blood flow

We investigated the roles of the renin-angiotensin system and the significance of interactions between angiotensin II and nitric oxide, in responses of regional kidney perfusion to electrical renal nerve stimulation (RNS) in pentobarbital sodium-anesthetized rabbits. Under control conditions, RNS (0.5–8 Hz) reduced total renal blood flow (RBF; −89 ± 3% at 8 Hz) and cortical perfusion (CBF; −90 ± 2% at 8 Hz) more than medullary perfusion (MBF; −55 ± 5% at 8 Hz). Angiotensin II type 1 (AT1)-receptor antagonism (candesartan) blunted RNS-induced reductions in RBF ( P = 0.03), CBF ( P = 0.007), and MBF ( P = 0.04), particularly at 4 and 8 Hz. Nitric oxide synthase inhibition with NG-nitro-l-arginine (l-NNA) enhanced RBF ( P = 0.003), CBF ( P = 0.001), and MBF ( P = 0.03) responses to RNS, particularly at frequencies of 2 Hz and less. After candesartan pretreatment, l-NNA significantly enhanced RNS-induced reductions in RBF ( P = 0.04) and CBF ( P = 0.007) but not MBF ( P = 0.66). Renal arterial infusion of angiotensin II (5 ng·kg−1·min−1) selectively enhanced responses of MBF to RNS in l-NNA-pretreated but not in vehicle-pretreated rabbits. In contrast, greater doses of angiotensin II (5–15 ng·kg−1·min−1) blunted responses of MBF to RNS in rabbits with intact nitric oxide synthase. These results suggest that endogenous angiotensin II enhances, whereas nitric oxide blunts, neurally mediated vasoconstriction in the renal cortical and medullary circulations. In the renal medulla, but not the cortex, angiotensin II also appears to be able to blunt neurally mediated vasoconstriction.