Cardiomyocyte-specific deletion of TLR4 attenuates angiotensin II-induced hypertension and cardiac remodeling

Toll-like receptor 4 (TLR4) is an integral factor in the initiation of the innate immune response and plays an important role in cardiovascular diseases such as hypertension and myocardial infarction. Previous studies from our lab demonstrated that central TLR4 blockade reduced cardiac TLR4 expression, attenuated hypertension, and improved cardiac function. However, the contribution of cardiac specific TLR4 to the development of hypertension and cardiac remodeling is unknown. Therefore, we hypothesized that cardiomyocyte specific knockdown of TLR4 would have beneficial effects on hypertension, cardiac hypertrophy, and remodeling. To test this hypothesis, cardiomyocyte-specific TLR4 knockdown (cTLR4KO) mice were generated by crossing floxed TLR4 mice with Myh6-Cre mice, and subjected to angiotensin II (Ang II, 1 µg/kg/min or vehicle for 14 days) hypertension model. Blood pressure measurements using radio telemetry revealed no differences in baseline mean arterial pressure between control littermates and cTLR4KO mice (103 ± 2 vs. 105 ± 3 mmHg, p > 0.05). Ang II-induced hypertension (132 ± 2 vs. 151 ± 3 mmHg, p < 0.01) was attenuated and cardiac hypertrophy (heart/body weight; 4.7 vs. 5.8 mg/g, p < 0.01) was prevented in cTLR4KO mice when compared with control mice. In addition, the level of myocardial fibrosis was significantly reduced, and the cardiac function was improved in cTLR4KO mice infused with Ang II. Furthermore, cardiac inflammation, as evidenced by elevated gene expression of TNF, IL-6, and MCP-1 in the left ventricle, was attenuated in cTLR4KO mice infused with Ang II. Together, this data revealed a protective role for cardiomyocyte-specific deletion of TLR4 against Ang II-induced hypertension and cardiac dysfunction through inhibition of proinflammatory cytokines.

Intramyocardial hemorrhage drives fatty degeneration of infarcted myocardium

Sudden blockage of arteries supplying the heart muscle contributes to millions of heart attacks (myocardial infarction, MI) around the world. Although re-opening these arteries (reperfusion) saves MI patients from immediate death, approximately 50% of these patients go on to develop chronic heart failure (CHF) and die within a 5-year period; however, why some patients accelerate towards CHF while others do not remains unclear. Here we show, using large animal models of reperfused MI, that intramyocardial hemorrhage - the most damaging form of reperfusion injury (evident in nearly 40% of reperfused ST-elevation MI patients) - drives delayed infarct healing and is centrally responsible for continuous fatty degeneration of the infarcted myocardium contributing to adverse remodeling of the heart. Specifically, we show that the fatty degeneration of the hemorrhagic MI zone stems from iron-induced macrophage activation, lipid peroxidation, foam cell formation, ceroid production, foam cell apoptosis and iron recycling. We also demonstrate that timely reduction of iron within the hemorrhagic MI zone reduces fatty infiltration and directs the heart towards favorable remodeling. Collectively, our findings elucidate why some, but not all, MIs are destined to CHF and help define a potential therapeutic strategy to mitigate post-MI CHF independent of MI size.

Endothelial Cullin3 Mutation Impairs Nitric Oxide-Mediated Vasodilation and Promotes Salt-Induced Hypertension

Human hypertension caused by in-frame deletion of CULLIN3 exon-9 (Cul3∆9) is driven by renal and vascular mechanisms. We bred conditionally activatable Cul3∆9 transgenic mice with tamoxifen-inducible Tie2-CRE^ERT2 mice to test the importance of endothelial Cul3. The resultant mice (E-Cul3∆9) trended towards elevated nighttime blood pressure (BP) correlated with increased nighttime activity, but displayed no difference in daytime BP or activity. Male and female E-Cul3∆9 mice together exhibited a decline in endothelial-dependent relaxation in carotid artery. Male but not female E-Cul3∆9 mice displayed severe endothelial dysfunction in cerebral basilar artery. There was no impairment in mesenteric artery and no difference in smooth muscle function, suggesting the effects of Cul3∆9 are arterial bed-specific and sex-dependent. Expression of Cul3∆9 in primary mouse aortic endothelial cells decreased endogenous Cul3 protein, phosphorylated (S1177) endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) production. Protein phosphatase (PP) 2A, a known Cul3 substrate, dephosphorylates eNOS. Cul3∆9-induced impairment of eNOS activity was rescued by a selective PP2A inhibitor okadaic acid, but not by a PP1 inhibitor tautomycetin. Because NO deficiency contributes to salt-induced hypertension, we tested the salt-sensitivity of E-Cul3∆9 mice. While both male and female E-Cul3∆9 mice developed salt-induced hypertension and renal injury, the pressor effect of salt was greater in female mutants. The increased salt-sensitivity in female E-Cul3∆9 mice was associated with decreased renovascular relaxation and impaired natriuresis in response to a sodium load. Thus, CUL3 mutations in the endothelium may contribute to human hypertension in part through decreased endothelial NO bioavailability, renovascular dysfunction, and increased salt-sensitivity of BP.

Intramyocardial Hemorrhage and the "Wave Front" of Reperfusion Injury Compromising Myocardial Salvage

BACKGROUND

Reperfusion therapy for acute myocardial infarction (MI) is lifesaving. However, the benefit of reperfusion therapy can be paradoxically diminished by reperfusion injury, which can increase MI size.

OBJECTIVES

Hemorrhage is known to occur in reperfused MIs, but whether hemorrhage plays a role in reperfusion-mediated MI expansion is not known.

METHODS

We studied cardiac troponin kinetics (cTn) of ST-segment elevation MI patients (n = 70) classified by cardiovascular magnetic resonance to be hemorrhagic (70%) or nonhemorrhagic following primary percutaneous coronary intervention. To isolate the effects of hemorrhage from ischemic burden, we performed controlled canine studies (n = 25), and serially followed both cTn and MI size with time-lapse imaging.

RESULTS

CTn was not different before reperfusion; however, an increase in cTn following primary percutaneous coronary intervention peaked earlier (12 hours vs 24 hours; P < 0.05) and was significantly higher in patients with hemorrhage (P < 0.01). In hemorrhagic animals, reperfusion led to rapid expansion of myocardial necrosis culminating in epicardial involvement, which was not present in nonhemorrhagic cases (P < 0.001). MI size and salvage were not different at 1 hour postreperfusion in animals with and without hemorrhage (P = 0.65). However, within 72 hours of reperfusion, a 4-fold greater loss in salvageable myocardium was evident in hemorrhagic MIs (P < 0.001). This paralleled observations in patients with larger MIs occurring in hemorrhagic cases (P < 0.01).

CONCLUSIONS

Myocardial hemorrhage is a determinant of MI size. It drives MI expansion after reperfusion and compromises myocardial salvage. This introduces a clinical role of hemorrhage in acute care management, risk assessment, and future therapeutics.

Abstract MP14: Endothelial Cullin3 Mutation Causes Decreased Nitric Oxide (NO) Bioavailability And Vascular Dysfunction Through Protein Phosphatase 2A

Mutations in CULLIN3 gene (in-frame deletion of exon 9, termed Cul3Δ9) cause human hypertension (HT) driven by a combination of renal tubular and vascular mechanisms. To test the importance of endothelial Cul3 in vivo , we bred the conditionally activatable Cul3Δ9 mice with tamoxifen-inducible Tie2-CRE ERT2 mice. The resultant mice (E-Cul3Δ9) developed arterial stiffening (pulse wave velocity, 3.7±0.3 vs 2.7±0.1 m/s, n=5-7, p<0.05) and a trend towards elevated nighttime blood pressure (peak systolic BP, E-Cul3Δ9 136±3 vs control 128±3 mmHg, n=9-11) that were not associated with any alterations in locomotion, food/water intake or sleep/wake behaviors. No difference was seen in daytime BP. To determine whether vascular remodeling impairs baroreflex function, we performed power spectral analysis. Heart rate (HR), low frequency/high frequency ratio of HR variability, and baroreflex gain were comparable between control and E-Cul3Δ9 mice, suggesting no change in cardiac sympathetic nerve activity. However, low frequency amplitude of arterial pressure variability (16±4 vs 7±2 mmHg 2 , n=5-9, p<0.05) at night was markedly augmented in E-Cul3Δ9 mice, suggesting increased sympathetic activity in vascular tone regulation. Consistently, E-Cul3Δ9 mice exhibited impaired endothelial-dependent relaxation in carotid artery (max ACh relaxation: 69% vs 84%, n=5-7, p<0.05) and cerebral resistance basilar artery (41% vs 77%, n=4-6, p<0.05). However, no dilatory impairment in mesenteric resistance artery and no difference in smooth muscle function were observed, suggesting that the effects of Cul3Δ9 are arterial bed specific. Expression of Cul3Δ9 in primary mouse aortic endothelial cells markedly decreased wild type Cul3 protein, phosphorylated eNOS and NO production. Protein phosphatase (PP) 2A, a known Cul3 substrate, dephosphorylates eNOS. Therefore, we determined whether impaired eNOS activity was attributable to PP2A. Cul3Δ9-induced impairment of eNOS activity was rescued by a selective PP2A inhibitor okadaic acid (4nM), but not by a PP1 inhibitor tautomycetin (4nM). Thus, CUL3 mutations in the endothelium may contribute to human HT in part through decreased endothelial NO bioavailability, arterial stiffening and secondary sympathoexcitation.

Failure to vasodilate in response to salt loading blunts renal blood flow and causes salt-sensitive hypertension

AIMS

Salt-sensitive (SS) hypertension is accompanied by impaired vasodilation in the systemic and renal circulation. However, the causal relationship between vascular dysfunction and salt-induced hypertension remains controversial. We sought to determine whether primary vascular dysfunction, characterized by a failure to vasodilate during salt loading, plays a causal role in the pathogenesis of SS hypertension.

METHODS AND RESULTS

Mice selectively expressing a peroxisome proliferator-activated receptor γ dominant-negative mutation in vascular smooth muscle (S-P467L) exhibited progressive SS hypertension during a 4 week high salt diet (HSD). This was associated with severely impaired vasodilation in systemic and renal vessels. Salt-induced impairment of vasodilation occurred as early as 3 days after HSD, which preceded the onset of SS hypertension. Notably, the overt salt-induced hypertension in S-P467L mice was not driven by higher cardiac output, implying elevations in peripheral vascular resistance. In keeping with this, HSD-fed S-P467L mice exhibited decreased smooth muscle responsiveness to nitric oxide (NO) in systemic vessels. HSD-fed S-P467L mice also exhibited elevated albuminuria and a blunted increase in urinary NO metabolites which was associated with blunted renal blood flow and increased sodium retention mediated by a lack of HSD-induced suppression of NKCC2. Blocking NKCC2 function prevented the salt-induced increase in blood pressure in S-P467L mice.

CONCLUSION

We conclude that failure to vasodilate in response to salt loading causes SS hypertension by restricting renal perfusion and reducing renal NO through a mechanism involving NKCC2 in a mouse model of vascular peroxisome proliferator-activated receptor γ impairment.

Reperfused hemorrhagic myocardial infarction in rats

BACKGROUND

Intramyocardial hemorrhage following reperfusion is strongly associated with major adverse cardiovascular events in myocardial infarction (MI) patients; yet the mechanisms contributing to these outcomes are not well understood. Large animal models have been used to investigate intramyocardial hemorrhage, but they are exorbitantly expensive and difficult to use for mechanistic studies. In contrast, rat models are widely used to investigate mechanistic aspects of cardiovascular physiology, but a rat model that consistently recapitulates the characteristics of an hemorrhagic MI does not exist. To bridge this gap, we investigated the physiological conditions of MI that would create intramyocardial hemorrhage in rats so that a reliable model of hemorrhagic MI would become available for basic research.

METHODS & RESULTS

Sprague-Dawley rats underwent either a 90-minute (90-min) ischemia and then reperfusion (I/R) (n = 22) or 30-minute (30-min) I/R (n = 18) of the left anterior descending coronary artery. Sham rats (n = 12) were used as controls. 90-min I/R consistently yielded hemorrhagic MI, while 30-min I/R consistently yielded non-hemorrhagic MI. Twenty-four hours post-reperfusion, ex-vivo late-gadolinium-enhancement (LGE) and T2* cardiac MRI performed on excised hearts from 90-min I/R rats revealed colocalization of iron deposits within the scarred tissue; however, in 30-min I/R rats scar was evident on LGE but no evidence of iron was found on T2* CMR. Histological studies verified tissue damage (H&E) detected on LGE and the presence of iron (Perl's stain) observed on T2*-CMR. At week 4 post-reperfusion, gene and protein expression of proinflammatory markers (TNF-α, IL-1β and MMP-9) were increased in the 90-min I/R group when compared to 30-min I/R groups. Further, transmission electron microscopy performed on 90-min I/R myocardium that were positive for iron on T2* CMR and Perl's stain showed accumulation of granular iron particles within the phagosomes.

CONCLUSION

Ischemic time prior to reperfusion is a critical factor in determining whether a MI is hemorrhagic or non-hemorrhagic in rats. Specifically, a period of 90-min of ischemia prior to reperfusion can produce rat models of hemorrhagic MI, while 30-minutes of ischemia prior to reperfusion can ensure that the MIs are non-hemorrhagic. Hemorrhagic MIs in rats result in marked increase in iron deposition, proinflammatory burden and adverse left-ventricular remodeling compared to rats with non-hemorrhagic MIs.

Abstract P086: Endothelial Cullin3 Mutation Causes Vascular Dysfunction, Arterial Stiffening, And Hypertension

Mutations in CULLIN3 gene (causing in-frame deletion of exon 9, termed Cul3Δ9) cause human hypertension (HT), which is driven by a combination of renal tubular and vascular mechanisms. We have previously shown that disruption of Cullin3 (CUL3) in vascular smooth muscle impairs nitric oxide (NO) signaling and vasodilation through decreased cGMP bioavailability, strongly supporting a role of vascular CUL3 in blood pressure (BP) regulation. To test the importance of endothelial Cul3 in vivo , we bred the conditionally activatable Cul3Δ9 mice with tamoxifen-inducible Tie2-CRE ERT2 mice. Four weeks after tamoxifen, the resultant mice (E-Cul3Δ9) developed nocturnal HT (Night time peak systolic BP, E-Cul3Δ9: 135±3 vs Control: 124±3 mmHg) and arterial stiffening (pulse wave velocity, 3.7±0.3 vs 2.7±0.1 m/s). No difference was seen in daytime BP. To determine whether vascular remodeling impairs baroreflex function, we performed power spectral analysis. Heart rate (HR), low frequency/high frequency ratio of HR variability, and baroreflex gain were comparable between control and E-Cul3Δ9 mice, suggesting there was no change in cardiac sympathetic nerve activity. However, low frequency amplitude of arterial pressure variability (16±4 vs 7±2 mmHg 2 ) at night was markedly augmented in E-Cul3Δ9 mice, suggesting increased sympathetic activity in vascular tone regulation. Consistently, E-Cul3Δ9 mice exhibited impaired endothelial-dependent relaxation in carotid artery (Max ACh relaxation: 69% vs 84%) and cerebral resistance basilar artery (41% vs 77%). No difference in smooth muscle function was observed. Expression of Cul3Δ9 in primary mouse aortic endothelial cells markedly decreased wild type Cul3 protein, phosphorylated eNOS, and NO production. Because protein phosphatase 2A (PP2A) is a known Cul3 substrate which dephosphorylates eNOS, we determined whether impaired eNOS activity was attributable to PP2A. Cul3Δ9-induced impairment of eNOS activity was rescued by a selective PP2A inhibitor Okadaic Acid (4 nM), but not by a Protein Phosphatase 1 inhibitor Tautomycetin (4 nM). Thus, CUL3 mutations in the endothelium contribute to human HT in part through decreased NO bioavailability, endothelial dysfunction and secondary sympathoexcitation.

Fabrication of a Self-Curling Cuff with a Soft, Ionically Conducting Neural Interface

Direct current (DC) has the potential not only to excite but also to inhibit neurons. This property of DC stimulus has been used for generating peripheral nerve blocks. One translational challenge of DC-based neuromodulation technologies, especially for pain suppression, is that the commercially available cuff electrodes have metal-tissue interfaces that are incapable of delivering DC safely. Passing DC through any metal-tissue interface generates harmful electrochemical products which can damage the target nerve. To address this issue, we present a fabrication process for making self-curling silicone cuffs with paper/agar based, ionically conducting neural interface. We fabricate monopolar as well as bipolar cuffs and demonstrate that the electrode impedances can be easily controlled by modulating the paper/agar channel dimensions. Further, we perform in-vivo implantation of these electrodes on a rat sciatic nerve to qualitatively validate the self-curling action.

Increased Susceptibility of Mice Lacking Renin-b to Angiotensin II-Induced Organ Damage

Several cardiac and renal diseases are attributed to a dysregulation of the renin-angiotensin system. Renin, the rate-limiting enzyme of the renin-angiotensin system, has 2 isoforms. The classical renin isoform (renin-a) encoding preprorenin is mainly confined to the juxtaglomerular cells and released into the circulation upon stimulation. Alternatively, renin-b is predicted to remain intracellular and is expressed in the brain, heart, and adrenal gland. In the brain, ablation of renin-b (Ren-b^Null mice) results in increased brain renin-angiotensin system activity. However, the consequences of renin-b ablation in tissues outside the brain remain unknown. Therefore, we hypothesized that renin-b protects from hypertensive cardiac and renal end-organ damage in mice. Ren-b^Null mice exhibited normal blood pressure at baseline. Thus, we induced hypertension by using a slow pressor dose of Ang II (angiotensin II). Ang II increased blood pressure in both wild type and Ren-b^Null to the same degree. Although the blood pressure between Ren-b^Null and wild-type mice was elevated equally, 4-week infusion of Ang II resulted in exacerbated cardiac remodeling in Ren-b^Null mice compared with wild type. Ren-b^Null mice also exhibited a modest increase in renal glomerular matrix deposition, elevated plasma aldosterone, and a modestly enhanced dipsogenic response to Ang II. Interestingly, ablation of renin-b strongly suppressed plasma renin, but renal cortical renin mRNA was preserved. Altogether, these data indicate that renin-b might play a protective role in the heart, and thus renin-b could be a potential target to treat hypertensive heart disease.

Abstract 065: Endothelial CULLIN3 Mutation Causes Vascular Dysfunction, Arterial Stiffening, and Hypertension

Mutations in CULLIN3 gene (causing in-frame deletion of exon 9) cause human hypertension (HT), which is likely to be driven by a combination of renal tubular and vascular mechanisms. We have recently shown that smooth muscle expression of Cul3Δ9 mutant causes vascular dysfunction and HT via augmented RhoA/Rho-kinase signaling, strongly supporting a vascular role of Cul3 in BP regulation. To test the importance of endothelial Cul3 in vivo , we bred the conditionally activatable Cul3Δ9 mice with tamoxifen-inducible Tie2-CRE ERT2 mice. The resultant mice (E-Cul3Δ9) developed nocturnal hypertension (Night time peak systolic BP, E-Cul3Δ9: 138±3 vs Control: 121±4 mmHg, p<0.01) and arterial stiffening (pulse wave velocity, 3.7±0.3 vs 2.7±0.1 m/s, p<0.01). No difference was seen in daytime BP. Nitric oxide synthase (NOS) inhibitor L-NAME induced smaller increases in nocturnal peak SBP and DBP in E-Cul3Δ9 mice (15±1 vs 27±3 mmHg, p<0.01), suggesting their NOS activity is low. Of note, E-Cul3Δ9 mice exhibited impaired endothelial-dependent relaxation in carotid artery (Max ACh relaxation: 69% vs 84%, p<0.05) and cerebral resistance basilar artery (41% vs 77%, p<0.01). No difference in smooth muscle function was observed. To determine the molecular mechanisms, we isolated primary aortic endothelial cells from mice carrying the inducible Cul3Δ9 construct and induced Cul3Δ9 expression in vitro using adenovirus carrying Cre recombinase gene. Expression of Cul3Δ9 resulted in marked decreases in wild type Cul3 protein, phosphorylated eNOS, and nitric oxide production. Because protein phosphatase 2A (PP2A) is a known Cul3 substrate which dephosphorylates eNOS, we determined whether impaired eNOS activity was attributable to PP2A. Cul3Δ9-induced impairment of eNOS activity was rescued by a selective PP2A inhibitor Okadaic Acid (4 nM), but not by a Protein Phosphatase 1 inhibitor Tautomycetin (4 nM). These data define a novel regulatory pathway involving Cullin3/PP2A/phospho-eNOS in the endothelium. Selective endothelial expression of Cul3Δ9 partially phenocopies the hypertension observed in Cul3Δ9 patients, suggesting that mutations in Cullin-3 cause human hypertension in part through a vascular mechanism characterized by endothelial dysfunction.

Abstract P183: Retinol Binding Protein 7, a PPARγ Target Gene Protects Against Endothelial Dysfunction Induced by Mitochondrial Uncoupling

PPARγ is a nuclear receptor that prevents oxidative stress in the endothelium. Endothelium specific PPARγ target gene, retinol binding protein 7 (RBP7) is required for the protective effects of PPARγ. In response to a cardiovascular stressor (high fat diet or Ang II), transgenic mice carrying a dominant-negative mutation in PPARγ in the endothelium (E-V290M) and RBP7 knockout mice (RBP7KO) exhibited increased oxidative stress and endothelial dysfunction. We hypothesize that RBP7 has a protective role against endothelial dysfunction induced by the pro-oxidant effects of mitochondrial uncoupling (MU). Acetylcholine (ACh) and sodium nitroprusside (SNP) induced vasodilation response were evaluated in carotid arteries from 4 and 8 month old RBP7KO mice, infused with either saline or a sub-pressor dose of Ang II (120ng/kg/min) for 2 weeks. Ang II infusion did not alter systolic blood pressure either in wild type (WT) (4 months old: 116.2±4.2 vs 113.9±4.1 mmHg; 8 months old: 111.3±3.8 vs 109.5±2.9 mmHg) or RBP7KO (4 months old: 112.9±1.1 vs 111.8±5.2 mmHg; 8 months old: 112.2±4.2 vs 113.9±4.1 mmHg). Endothelium-dependent relaxation to ACh was not affected by Ang II in either RBP7KO (4 month old: % relaxation - saline, 89.7±1.3 vs Ang II, 93.8±2.0; 8 months old: % relaxation - saline, 80.1±6.8 vs Ang II, 74.6±10.6) or WT littermates (4 months old: % relaxation - saline, 98.1±0.3 vs Ang II, 94.5±1.7; 8 months old: % relaxation - saline, 81.4±4.7 vs Ang II, 78.6±10.4). To test if RBP7 plays a role in MU, the vessels were pre-incubated with the MU carbonyl cyanide m-chlorophenyl hydrazone (CCCP; 1uM for 30 min). Pre-incubation with CCCP did not alter the relaxation responses to ACh in 4 month old mice in all groups. However, in 8 month old mice, there is a trend towards impaired endothelial function in the carotid artery from Ang II-infused RBP7KO compared with genotype-matched saline-treated mice (% relaxation: 51.9±3.8 vs 81.8±5.3, p=0.06) as well as Ang II-treated WT mice (% relaxation: 51.9±3.8 vs 77.1±2.0 p=0.08). In conclusion, Ang II alone was not able to impair vascular function, however, in 8 month old mice, Ang II increased the susceptibility to CCCP-dependent endothelial impairment, and RBP7 was required to mediate vascular protection against mitochondrial uncoupling.

Abstract 120: Protective Role of Vascular Smooth Muscle Rho-Related BTB Domain Containing Protein 1 in Hypertension and Arterial Stiffness

Rho-related BTB domain containing protein 1 (RhoBTB1) is an atypical GTPase associated with human hypertension. RhoBTB1 was decreased in aorta from mice expressing a hypertension (HT)-causing PPARγ mutation (P467L) specifically in vascular smooth muscle (VSM, S-P467L mice). Restoration of VSM RhoBTB1 improved vasodilation, reversed arterial stiffness and HT by suppressing phosphodiesterase 5 (PDE5) activity. Here we sought to reveal the molecular function of RhoBTB1 and study its protective role in Angiotensin II (Ang II) induced hypertension. PDE5 and RhoBTB1 reciprocally co-immunoprecipitated in HEK293 cells; and notably, endogenous Cullin3 from HEK293 cells was also present in RhoBTB1/PDE5 immunoprecipitant. Whereas, RhoBTB1 was not sufficient to inhibit PDE5 activity in vitro (1.9±0.2 vs 1.7 ±0.2 nmol/min/mg, n=3), it was required for PDE5 ubiquitination in HEK293 cells. RhoBTB1-mediated PDE5 ubiquitination was blunted by pan-Cullin inhibitor MLN4924 treatment, and MLN4924 increased PDE5 activity in aorta. Thus, RhoBTB1 serves as a substrate adaptor for Cullin3-Ring ubiquitin ligase (CRL3) complex. Like mutation in PPARγ, Ang II infusion also reduced aortic RhoBTB1 expression. We generated mice with VSM specific, tamoxifen inducible RhoBTB1 (S-RhoBTB1) expression. Activation of RhoBTB1 expression with tamoxifen partially prevented Ang II induced HT and vascular dysfunction. However, activation of the RhoBTB1 transgene after 2-week of Ang II infusion did not reverse established Ang II HT and failed to reverse impaired vasodilation to acetylcholine and sodium nitroprusside in aorta and carotid artery. Remarkably however, arterial stiffness as measured by aortic Pulse Wave Velocity was decreased in S-RhoBTB1 compared to non-transgenic mice receiving Ang II infusion (4.6±0.4 vs 3.2±0.3 mm/ms, p<0.05, n=5-7). In conclusion, RhoBTB1 serves as CRL3 substrate adaptor and promotes PDE5 ubiquitination. Pretreatment with RhoBTB1 partially prevents Ang II HT, while restoration of VSM RhoBTB1 was not sufficient to reverse Ang II mediated HT but showed a potential in reducing arterial stiffness.

Conditional deletion of smooth muscle Cullin-3 causes severe progressive hypertension

Patients with mutations in Cullin-3 (CUL3) exhibit severe early onset hypertension but the contribution of the smooth muscle remains unclear. Conditional genetic ablation of CUL3 in vascular smooth muscle (S-CUL3KO) causes progressive impairment in responsiveness to nitric oxide (NO), rapid development of severe hypertension, and increased arterial stiffness. Loss of CUL3 in primary aortic smooth muscle cells or aorta resulted in decreased expression of the NO receptor, soluble guanylate cyclase (sGC), causing a marked reduction in cGMP production and impaired vasodilation to cGMP analogues. Vasodilation responses to a selective large conductance Ca2+-activated K+-channel activator were normal suggesting that downstream signals which promote smooth muscle-dependent relaxation remained intact. We conclude that smooth muscle specific CUL3 ablation impairs both cGMP production and cGMP responses and that loss of CUL3 function selectively in smooth muscle is sufficient to cause severe hypertension by interfering with the NO-sGC-cGMP pathway. Our study provides compelling evidence for the sufficiency of vascular smooth muscle CUL3 as a major regulator of BP. CUL3 mutations cause severe vascular dysfunction, arterial stiffness and hypertension due to defects in vascular smooth muscle.

Endothelial PPARγ (Peroxisome Proliferator-Activated Receptor-γ) Protects From Angiotensin II-Induced Endothelial Dysfunction in Adult Offspring Born From Pregnancies Complicated by Hypertension

Preeclampsia is a hypertensive disorder of pregnancy associated with vascular dysfunction and cardiovascular risk to offspring. We hypothesize that endothelial PPARγ (peroxisome proliferator-activated receptor-γ) provides cardiovascular protection in offspring from pregnancies complicated by hypertension. C57BL/6J dams were bred with E-V290M sires, which express a dominant-negative allele of PPARγ selectively in the endothelium. Arginine vasopressin was infused throughout gestation. Vasopressin elevated maternal blood pressure at gestational day 14 to 15 and urinary protein at day 17 consistent. Systolic blood pressure and vasodilation responses to acetylcholine were similar in vasopressin-exposed offspring compared to offspring from control pregnancies. We treated offspring with a subpressor dose of angiotensin II to test if hypertension during pregnancy predisposes offspring to hypertension. Male and female angiotensin II-treated E-V290M offspring from vasopressin-exposed but not control pregnancy exhibited significant impairment in acetylcholine-induced relaxation in carotid artery. Endothelial dysfunction in angiotensin II-treated E-V290M vasopressin-exposed offspring was attenuated by tempol, an effect which was more prominent in male offspring. Nrf2 (nuclear factor-E2-related factor) protein levels were significantly elevated in aorta from male E-V290M offspring, but not female offspring compared to controls. Blockade of ROCK (Rho-kinase) signaling and incubation with a ROCK2-specific inhibitor improved endothelial function in both male and female E-V290M offspring from vasopressin-exposed pregnancy. Our data suggest that interference with endothelial PPARγ in offspring from vasopressin-exposed pregnancies increases the risk for endothelial dysfunction on exposure to a cardiovascular stressor in adulthood. This implies that endothelial PPARγ provides protection to cardiovascular stressors in offspring of a pregnancy complicated by hypertension and perhaps in preeclampsia.

Interference With Endothelial PPAR (Peroxisome Proliferator-Activated Receptor)-γ Causes Accelerated Cerebral Vascular Dysfunction in Response to Endogenous Renin-Angiotensin System Activation

Low-salt diet is beneficial in salt-sensitive hypertension but may provoke cardiovascular risk in patients with heart failure, diabetes mellitus, or other cardiovascular abnormalities because of endogenous renin-angiotensin system activation. PPAR (peroxisome proliferator-activated receptor)-γ is a transcription factor which promotes an antioxidant pathway in the endothelium. We studied transgenic mice expressing a dominant-negative mutation in PPAR-γ selectively in the endothelium (E-V290M) to test the hypothesis that endothelial PPAR-γ plays a protective role in response to low salt-mediated renin-angiotensin system activation. Plasma renin and Ang II (angiotensin II) were significantly and equally increased in all mice fed low salt for 6 weeks. Vasorelaxation to acetylcholine was not affected in basilar artery from E-V290M at baseline but was significantly and selectively impaired in E-V290M after low salt. Unlike basilar artery, low salt was not sufficient to induce vascular dysfunction in carotid artery or aorta. Endothelial dysfunction in the basilar artery from E-V290M mice fed low salt was attenuated by scavengers of superoxide, inhibitors of NADPH oxidase, or blockade of the Ang II AT1 (angiotensin type-1) receptor. Simultaneous AT1 and AT2 receptor blockade revealed that the restoration of endothelial function after AT1 receptor blockade was not a consequence of AT2 receptor activation. We conclude that interference with PPAR-γ in the endothelium produces endothelial dysfunction in the cerebral circulation in response to low salt-mediated activation of the endogenous renin-angiotensin system, mediated at least in part, through AT1 receptor activation and perturbed redox homeostasis. Moreover, our data suggest that the cerebral circulation may be particularly sensitive to inhibition of PPAR-γ activity and renin-angiotensin system activation.

RhoBTB1 protects against hypertension and arterial stiffness by restraining phosphodiesterase 5 activity

Mice selectively expressing PPARγ dominant negative mutation in vascular smooth muscle exhibit RhoBTB1-deficiency and hypertension. Our rationale was to employ genetic complementation to uncover the mechanism of action of RhoBTB1 in vascular smooth muscle. Inducible smooth muscle-specific restoration of RhoBTB1 fully corrected the hypertension and arterial stiffness by improving vasodilator function. Notably, the cardiovascular protection occurred despite preservation of increased agonist-mediated contraction and RhoA/Rho kinase activity, suggesting RhoBTB1 selectively controls vasodilation. RhoBTB1 augmented the cGMP response to nitric oxide by restraining the activity of phosphodiesterase 5 (PDE5) by acting as a substrate adaptor delivering PDE5 to the Cullin-3 E3 Ring ubiquitin ligase complex for ubiquitination inhibiting PDE5. Angiotensin-II infusion also caused RhoBTB1-deficiency and hypertension which was prevented by smooth muscle specific RhoBTB1 restoration. We conclude that RhoBTB1 protected from hypertension, vascular smooth muscle dysfunction, and arterial stiffness in at least two models of hypertension.

Arginine vasopressin infusion is sufficient to model clinical features of preeclampsia in mice

Copeptin, a marker of arginine vasopressin (AVP) secretion, is elevated throughout human pregnancies complicated by preeclampsia (PE), and AVP infusion throughout gestation is sufficient to induce the major phenotypes of PE in mice. Thus, we hypothesized a role for AVP in the pathogenesis of PE. AVP infusion into pregnant C57BL/6J mice resulted in hypertension, renal glomerular endotheliosis, intrauterine growth restriction, decreased placental growth factor (PGF), altered placental morphology, placental oxidative stress, and placental gene expression consistent with human PE. Interestingly, these changes occurred despite a lack of placental hypoxia or elevations in placental fms-like tyrosine kinase-1 (FLT1). Coinfusion of AVP receptor antagonists and time-restricted infusion of AVP uncovered a mid-gestational role for the AVPR1A receptor in the observed renal pathologies, versus mid- and late-gestational roles for the AVPR2 receptor in the blood pressure and fetal phenotypes. These findings demonstrate that AVP is sufficient to initiate phenotypes of PE in the absence of placental hypoxia, and indicate that AVP may mechanistically (independently, and possibly synergistically with hypoxia) contribute to the development of clinical signs of PE in specific subtypes of human PE. Additionally, they identify divergent and gestational time-specific signaling mechanisms that mediate the development of PE phenotypes in response to AVP.

Abstract 133: Endothelial-Specific Interference With PPARγ Increases the Susceptibility to Angiotensin II-Induced Endothelial Dysfunction in Adult Offspring Born from AVP-Infused Pregnancies

Mutations in the ligand-activated transcription factor PPARγ result in hypertension, and synthetic agonists of PPARγ reduce blood pressure. Previously we found that mice expressing dominant-negative (DN) PPARγ driven by an endothelium-specific promoter (E-DN) exhibit vascular dysfunction. Preeclampsia (PE) is a hypertensive disorder of pregnancy which carries cardiovascular risk to offspring. PE is also associated with vascular dysfunction. We hypothesized a role for endothelial PPARγ in the pathogenesis of PE and its sequelae. C57BL/6J dams were bred with E-DN sires, and symptoms of PE were induced by infusion of vasopressin (AVP, 24 ng/hr sc) throughout gestation. Phenotypes of PE were first assessed in pregnant dams and then in adult offspring. Compared to saline infusion (SAL), AVP elevated maternal blood pressure (SBP: 116±3 vs 107±3, p<0.05) at gestational day (GD) 14-15 and urine protein (70±6 vs 27±4 mg/mL, p<0.05) at GD17. Offspring were phenotyped in adulthood. Data were stratified to sex, genotype, and exposure to AVP or SAL. At 20 weeks of age, SBP and vasorelaxation responses to acetylcholine were similar in offspring exposed to PE compared to mice born from SAL pregnancies. Adult offspring were next exposed to a sub-pressor dose of Angiotensin II (ANG; 120ng/kg/hr) for 14 days. Adult male ANG-treated E-DN born to PE pregnancies, but not NT mice exhibited significant impairment in ACh-induced relaxation in carotid artery (% relaxation: 62±10 vs 86±11, p<0.05). Adult female ANG-treated E-DN exposed to PE also exhibited a trend for impaired endothelial function compared to NT controls (% relaxation: 63±9 vs 72±10). Endothelial dysfunction in male ANG-treated E-DN born to PE pregnancies was attenuated by tempol (relaxation improved from 56±9% vs 81±12%, p<0.05), indicative of oxidative stress, and by a Rho-kinase inhibitor (relaxation improved from 73±11% vs 89±12%, p<0.05). This data suggests that interference with endothelial PPARγ in pups born from PE pregnancies increases the risk for endothelial dysfunction upon exposure to a cardiovascular stressor in adulthood. Thus, conditions which impair PPARγ activity, such as obesity and diabetes, may predispose adult offspring born from PE pregnancy to cardiovascular disease.

Abstract 036: Interference With PPARγ in the Endothelium Produces Endothelial Dysfunction in the Cerebral Circulation in Response to Activation of the Endogenous Renin-Angiotensin System

Low salt diet (LSD) is beneficial in salt-sensitive hypertension but may provoke cardiovascular risk in patients with heart failure, diabetes, or other cardiovascular abnormalities because of renin-angiotensin system (RAS) activation. PPARγ is a transcription factor which promotes an anti-oxidant pathway in the endothelium. We studied transgenic mice expressing a dominant-negative mutation in PPARγ selectively in the endothelium (E-DN) to test the hypothesis that endothelial PPARγ plays a protective role in response to LSD-mediated RAS activation. Plasma renin and angiotensin were significantly and equally increased in all mice fed LSD for 6-weeks (Renin - NT: 39±7 vs 20±1 ng/ml; E-DN: 34±1 vs 16±4 ng/ml; Ang - NT: 257±54 vs 47±6 pg/ml; E-DN: 294±69 vs 63±14 pg/ml p<0.05, n=5). Vasorelaxation to acetylcholine was not affected in basilar artery from E-DN at baseline, but was significantly and selectively impaired in E-DN after LSD (33±5 vs 69±2%, p<0.05, n=6). Unlike basilar artery, LSD was not sufficient to induce vascular dysfunction in carotid artery (carotid artery: 86±4 vs 92±3%, n=5). Endothelial dysfunction in the basilar artery from E-DN mice fed LSD was attenuated by scavengers of superoxide (improved from 29±5% to 55±7%, n=6), inhibitors of NADPH oxidase (improved from 23±3% to 54±7%, p<0.05, n=6), or blockade of the angiotensin-II AT1 receptor (improved from 31±5% to 64±9%, p<0.05, n=5). Gene expression levels of Nox2 was elevated (2.1±0.3 vs 0.4±0.1, p<0.05, n=7) while those of antioxidant enzymes catalase and SOD3 were blunted in cerebral vessels of E-DN mice on a LSD (catalase: 0.5±0.1 vs 2.5±0.2; SOD3: 0.2±0.1 vs 1.1±0.1, p<0.05, n=7). Simultaneous AT1 and AT2 receptor blockade revealed the restoration of endothelial function after AT1 receptor blockade was not a consequence of AT2 receptor activation (59±10 vs 48±2, p<0.05, n=4). We conclude that interference with PPARγ in the endothelium produces endothelial dysfunction in the cerebral circulation in response to LSD-mediated activation of the endogenous RAS, mediated at least in part, through AT1 receptor activation and perturbed redox homeostasis. Moreover, our data suggest that the cerebral circulation may be particularly sensitive to inhibition of PPARγ activity and RAS activation.

Abstract 094: Smooth Muscle PPARγ Mutation Causes Impaired Renal Blood Flow and Salt-Sensitive Hypertension

Mutations in PPARγ cause hypertension (HT) while PPARγ activation lowers blood pressure (BP) in humans. To determine if vascular smooth muscle (VSM) PPARγ regulates salt sensitivity, we studied transgenic mice selectively expressing a HT-causing PPARγ mutant in VSM (S-P467L) and non-transgenic littermates (NT) fed a 4% high salt (HS) diet for 4 weeks. Salt equally suppressed plasma renin in both strains, but S-P467L mice exhibited increased systolic BP (S-P467L 136±3 mmHg vs NT 124±2 mmHg, p<0.01) and pulse wave velocity (3.1±0.1 vs 2.7±0.1 m/s, p<0.01) in response to HS. The salt-induced HT was not associated with changes in diastolic BP, sympathetic nerve activity, heart rate, or cardiac output. Thus, the pressor effect of HS was likely due to higher peripheral vascular resistance. HS-fed S-P467L mice developed impaired acetylcholine (ACh)- and sodium nitroprusside (SNP)-induced vasorelaxation in carotid (Max ACh relaxation: 31±4.9% vs 90±1.8%, p<0.01; Max SNP relaxation: 38±2.8% vs 89±2.6%, p<0.01) and basilar artery (Max ACh relaxation: -3.2±9.3% vs 57±5.9%, p<0.01). The impaired vasodilation rapidly developed after 3-day HS diet, preceding salt-induced BP elevation. Pre-incubation with a cyclooxygenase inhibitor indomethacin normalized ACh/SNP relaxation responses, and preliminary mass spectrometry indicated HS increased prostaglandin E2 in S-P467L aortas. HS-fed S-P467L mice had smaller renal artery luminal diameter (322±21 vs 389±22 μm, p<0.05) and blunted renal blood flow (36±3.6 vs. 50±6.4 μL/min/g, p<0.05). During the 4 th week of HS diet, S-P467L mice produced 31% less nitrate/nitrite in 24 hour urine compared to NT controls (2.2±0.3 vs 3.2±0.4 μmol, p<0.05), suggesting blunted renal bioavailability of nitric oxide, a potent inhibitor of Na-K-2Cl cotransporter (NKCC2). This was associated with a declined capacity of HS-fed S-P467L mice to excrete an acute volume/Na + load, which was rescued by an NKCC2 inhibitor furosemide, but not by the Na-Cl-cotransporter inhibitor hydrochlorothiazide. Our data support the novel concept that smooth muscle PPARγ regulates systemic vascular resistance, renal perfusion and tubular sodium transport, and loss of these protective actions of PPARγ predisposes to salt sensitivity and hypertension.

Abstract 110: Vascular Smooth Muscle RhoBTB1 Protects From Hypertension and Arterial Stiffness by Cullin-3 Dependent Ubiquitination of Phosphodiesterase 5

We previously reported that vascular smooth muscle cell (VSMC) selective expression of hypertension (HT)-causing mutations in either PPARγ or the E3 Ring Ubiquitin Ligase Cullin-3 causes nitric oxide resistance and HT. Here we sought to assess the physiological role of RhoBTB1, a VSMC PPARγ target gene and Cullin-3 substrate adaptor. S-P467L mice which selectively express dominant negative PPARγ-P467L in VSMC exhibit RhoBTB1-deficiency. We bred S-P467L mice with mice inducibly expressing RhoBTB1 in response to Cre-recombinase. Inducible VSMC-specific restoration of RhoBTB1 in S-P467L mice fully corrected the HT (SBP, 141±6 vs 124±3 mmHg, p<0.01, n=8-10), arterial stiffness (Aortic Pulse Wave Velocity, 3.8±0.2 vs 2.5±0.1 mm/ms, p<0.01, n=11-13), and vasodilator function (Aorta, 46±5 vs 80±2% ACh-induced relaxation, p<0.01, n=6-9). Notably, the cardiovascular protection occurred despite preservation of increased agonist-mediated contraction and RhoA/Rho kinase activity, suggesting RhoBTB1 selectively controls vasodilation. Sodium nitroprusside-induced production of cGMP in aorta was severely impaired in S-P467L but restored by RhoBTB1. Consistent with this, phosphodiesterase 5 (PDE5) activity in aorta was augmented 2.5±0.3 fold in S-P467L but was returned to normal by RhoBTB1. PDE5 and RhoBTB1 reciprocally co-immunoprecipitated in HEK293 cells. Ubiquitination of PDE5 by Cullin-3 in HEK293 cells was RhoBTB1-dependent. Consistent with a role for Cullin-3 in mediating turnover of PDE5, PDE5 activity was augmented in MLN4924-treated aorta, a Cullin inhibitor, and abrogated by PDE5 inhibitor. The beneficial cardiovascular effect of RhoBTB1 in S-P467L mice was phenocopied by PDE5 inhibition. Angiotensin-II infusion also causes RhoBTB1-deficiency and HT which was reversed by smooth muscle specific RhoBTB1 restoration. We conclude that RhoBTB1 augments the cGMP response to nitric oxide by restraining the activity of PDE5 by acting as a substrate adaptor delivering PDE5 to the Cullin-3 E3 Ring ubiquitin ligase complex for ubiquitination and proteasomal degradation. RhoBTB1 provides protection from HT, vascular smooth muscle dysfunction, and arterial stiffness in at least two models of HT.

Blueberry supplementation attenuates oxidative stress within monocytes and modulates immune cell levels in adults with metabolic syndrome: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Blueberries (BB) have been shown to improve insulin sensitivity and endothelial function in obese and pre-diabetic humans, and decrease oxidative stress and inflammation, and ameliorate cardio-renal damage in rodents. This indicates that blueberries have a systemic effect and are not limited to a particular organ system. In order for blueberries to exert beneficial effects on the whole body, the mechanism would logically have to operate through modulation of cellular humoral factors.

OBJECTIVE

This study investigated the role of blueberries in modulating immune cell levels and attenuating circulatory and monocyte inflammation and oxidative stress in metabolic syndrome (MetS) subjects.

DESIGN

A double-blind, randomized and placebo-controlled study was conducted in adults with MetS, in which they received a blueberry (22.5 g freeze-dried) or placebo smoothie twice daily for six weeks. Free radical production in the whole blood and monocytes, dendritic cell (DC) levels, expression of cytokines in monocytes and serum inflammatory markers were assessed pre- and post-intervention.

RESULTS

Baseline free radical levels in MetS subjects' samples were not different between groups. Treatment with blueberries markedly decreased superoxide and total reactive oxygen species (ROS) in whole blood and monocytes compared to the placebo (p ≤ 0.05). The baseline DC numbers in MetS subjects' samples in both groups were not different, however treatment with blueberries significantly increased myeloid DC (p ≤ 0.05) and had no effect on plasmacytoid cells. Blueberry treatment decreased monocyte gene expression of TNFα, IL-6, TLR4 and reduced serum GMCSF in MetS subjects when compared to the placebo treatment (p ≤ 0.05).

CONCLUSIONS

The findings of the current study demonstrate that blueberries exert immunomodulatory effects and attenuate oxidative stress and inflammation in adults with MetS.

Abstract 099: Smooth Muscle PPARγ Mutation Causes Salt-sensitive Hypertension

Abnormal increase in renal salt retention is traditionally believed to be an early pathophysiological event in the causation of salt-sensitive hypertension, whereas increase in systemic vascular resistance (SVR) is a secondary response caused by autoregulation. However, recent studies show that salt-resistant subjects vasodilate and reduce SVR during salt loading, while salt-sensitive humans fail to vasodilate and exhibit salt-induced blood pressure (BP) elevation. Therefore, we tested the hypothesis that primary vascular dysfunction predisposes to salt sensitive hypertension. We used mice with smooth muscle-specific expression of a human hypertension-causing mutation in PPARγ P467L (S-P467L). S-P467L transgenic mice and non-transgenic controls (NT) were fed regular diet (0.4% salt) or high salt diet (4% salt) for 4 weeks. S-P467L mice, but not NT controls, exhibited severe impairment in acetylcholine- and sodium nitroprusside-induced vasorelaxation (31±4.9% S-P467L salt vs. 70±9.5% regular diet, maximal relaxation at 30 μM acetylcholine). This was associated with salt-induced systolic BP elevation in S-P467L mice (142±5 mmHg salt vs 127±2 mmHg regular diet), but not in NT mice (120±2.7 mmHg salt vs 115±4.0 mmHg). These changes were not due to differences in food intake, weight gain or renal sympathetic nerve activity between the two strains. In the 3 rd week of high salt diet, S-P467L mice and NT controls both had increased water intake by 3-fold compared to those on regular diet; however, S-P467L mice excreted 32% less urine and produced 36% less NO in the kidney as indicated by 24-hour urinary nitrate/nitrite. To assess renal function, mice were subjected to an acute saline challenge (10% body weight, i.p. injection). S-P467L mice exhibited a marked decline in their capacity to excrete this volume/sodium load, indicative of renal dysfunction. Of note, the impaired vasorelaxation in S-P467L occurred as early as day 3 of high salt diet, while renal dysfunction did not develop until day 10, suggesting that vascular dysfunction may serve as an initiation mechanism that reinforces salt-induced hemodynamic changes. These data supports the concept that vascular dysfunction may predispose to renal abnormalities including increased salt sensitivity.

Abstract P264: Endothelial-specific Interference With PPARγ Activity in Offspring Born From AVP-induced Preeclamptic Pregnancies Has Cardio-renal and Metabolic Consequences

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcription factor known to regulate metabolic and vascular function. Mutations in PPARγ result in hypertension, and synthetic agonists of PPARγ reduce blood pressure. Previously we found that mice expressing dominant-negative (DN) PPARγ driven by an endothelium-specific promoter (E-DN) exhibit vascular dysfunction. Preeclampsia (PE) is a hypertensive disorder of pregnancy which carries cardiovascular and metabolic risk to offspring. PE is associated with vascular dysfunction, and we therefore hypothesized a role for endothelial PPARγ in the pathogenesis of PE and its sequelae. C57BL/6J dams were bred with E-DN sires, and symptoms of PE were induced by the infusion of vasopressin (AVP, 24 ng/hr sc) throughout gestation. We assessed phenotypes of PE first in pregnant dams, and then in offspring as adults. Compared to saline infusion (SAL), AVP elevated maternal blood pressure (SBP: 116±3 vs 107±3, p<0.05) at gestational day (GD) 14-15 and urine protein (70±6 vs 27±4 mg/mL, p<0.05) at GD17. Offspring from these pregnancies were phenotyped in adulthood to assess cardiovascular and metabolic function. Data were stratified to sex, genotype, and maternal exposure to AVP vs SAL. Systolic blood pressure in adult male and female offspring born to AVP-infused pregnancies was similar to mice born to SAL pregnancies. At 20 weeks of age, vasorelaxation responses to acetylcholine were not different in offspring exposed to PE compared to mice born from SAL pregnancies. However, urinary protein levels were significantly elevated in both male (58±13 vs 32±5 mg/ml, p<0.05) and female (38±3 vs 25±2 mg/ml, p<0.05) adult E-DN born to PE pregnancies compared to E-DN controls born from SAL pregnancies. Male E-DN offspring exposed to PE showed significantly increased gain in body weight over time compared to male NT exposed to PE (ΔBW: 20±8 vs 14±2 g). These data highlight the impact of in utero exposure to elevated AVP upon cardiovascular function in the mother, and the adverse renal and metabolic consequences of PE upon offspring. Moreover, our data suggests that interference with endothelial PPARγ in pups born from PE pregnancies increases the risk for renal and metabolic dysfunction.

Abstract 140: Endogenous Renin-angiotensin System Activation Causes Accelerated Cerebral Vascular Dysfunction in Mice Expressing Dominant-negative Mutations in PPARγ in Endothelium

Abnormal activation of the renin-angiotensin system (RAS) has been implicated in cardiovascular (CV) disease. Whereas low salt diet (LSD) may be beneficial in salt-sensitive hypertension, it has been proposed to induce CV risk due to RAS activation. Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcription factor which regulates the actions of angiotensin II (ANG) in the vasculature and promotes anti-oxidant pathways. We hypothesize that endothelial PPARγ plays a protective role in the vasculature in response to RAS activation. Transgenic mice specifically expressing dominant-negative (DN) mutations in PPARγ in the endothelium (E-DN) were fed a LSD and endothelial function was measured. Plasma renin and ANG were significantly increased in both non-transgenic (NT) and E-DN mice fed a LSD for 6 weeks compared with normal chow (Renin - NT: 39±7 vs 20±1 ng/ml; E-DN: 34±1 vs 16±4 ng/ml; AngII - NT: 257±54 vs 47±6 pg/ml; E-DN: 294±69 vs 63±14 pg/ml p<0.05, n=5). At baseline, vasorelaxation to acetylcholine (ACh) was not affected in E-DN compared to NT (basilar artery: 66±12 vs 64±4%; carotid artery: 93±4 vs 91±4%, n=5). Six weeks of LSD significantly impaired ACh-mediated relaxation in basilar artery of E-DN but not in NT (42±8 vs 74±5%, p<0.05, n=5). Unlike basilar artery, 6 weeks of LSD was not sufficient to induce vascular dysfunction in carotid artery of E-DN (carotid artery: 86±4 vs 92±3%, n=5). The endothelial dysfunction observed in the basilar artery of E-DN was attenuated upon in vitro incubation with tempol (improved from 29±5% to 55±7%, n=6). Further, administration of the AT1 receptor blocker, Losartan (0.6g/L drinking water) for the last 2 weeks of LSD blunted the endothelial dysfunction observed in the basilar artery of E-DN (improved from 24±2% to 64±9%, n=5). We conclude that interference with PPARγ in the endothelium produces endothelial dysfunction in the cerebral circulation in response to LSD-mediated activation of the endogenous RAS and this dysfunction is mediated, at least in part, through AT1 receptor activation and ROS signaling pathways. Moreover, our data suggest that the basilar artery and perhaps cerebral circulation is particularly sensitive to inhibition of PPARγ activity and activation of the RAS.

Abstract 062: Vascular Dysfunction and Hypertension are Prevented by a Novel PPARγ Target Gene, RhoBTB1

RhoBTB1 is a novel peroxisome proliferator-activated receptor gamma (PPARγ) target gene expressed in smooth muscle cells (SMC) which may mediate some of the vascular protective and antihypertensive benefits of PPARγ. Here, we tested the hypothesis that RhoBTB1 can prevent angiotensin II (ANG)-induced hypertension. RhoBTB1 expression in aorta from C57BL/6 mice was decreased by 54±9% (n=16) in response to ANG infusion (490 ng/min/kg, 2 weeks). To test if RhoBTB1 expression is protective, we generated double transgenic mice with tamoxifen-inducible, Cre-dependent overexpression of RhoBTB1 specifically in SMC (S-RhoBTB1). S-RhoBTB1 and non-transgenic (NT) mice were treated with tamoxifen (Tx; 75 mg/kg, ip, 5 days) or vehicle (corn oil) and then ANG was infused. Although RhoBTB1 expression was decreased in ANG-infused control mice (p<0.01, n=8-10), RhoBTB1 expression in Tx-treated S-RhoBTB1 mice infused with ANG was restored to a level similar to NT treated with saline (n=11). Overexpression of RhoBTB1 did not alter baseline blood pressure (BP) in the absence of ANG (n=7-8). However, the increase in BP induced by ANG was significantly attenuated by RhoBTB1 restoration in S-RhoBTB1 mice with Tx compared to ANG-infused control mice (either NT with Tx, NT with corn oil, or S-RhoBTB1 with corn oil) in which RhoBTB1 was not restored (Systolic BP, 159±5 in control mice vs 132±6 mmHg in S-RhoBTB1 mice with Tx, p<0.01, n=7-8). We also observed increased heart weight in ANG-infused control mice, which was prevented in S-RhoBTB1 mice treated with Tx (p<0.05, n=8). Thoracic aorta and basilar artery from ANG-infused control mice exhibited impaired acetylcholine-induced endothelial-dependent relaxation (Aorta, 48±2%, p<0.01, n=6-8), which was prevented by restoration of RhoBTB1 in SMC (Aorta, 76±5%, p<0.01, n=6-8). Thoracic aorta from ANG-infused control mice also displayed decreased sodium nitroprusside-induced endothelial-independent relaxation with a right-shifted dose-response (76±9%, p<0.01, n=8), which was also prevented in tamoxifen-treated S-RhoBTB1 mice (95±10%, p<0.01, n=8). We conclude that the novel PPARγ target gene, RhoBTB1, functions in SMC to specifically facilitate vasodilation and mediates a protective anti-hypertensive effect.

Abstract P189: Endothelial Cullin3 Mutation Causes Vascular Dysfunction, Arterial Stiffening, and Hypertension

Mutations in CULLIN3 gene (causing in-frame deletion of exon 9) cause hypertension in humans. The hypertension phenotype is unlikely to be driven by renal tubular mechanisms, as kidney-specific deletion of Cullin3 (Cul3) in mice results in hypotension, not hypertension. We have recently shown that smooth muscle expression of Cul3Δ9 causes vascular dysfunction and elevation of blood pressure (BP) via augmented RhoA/Rho-kinase signaling, strongly supporting a vascular role of Cul3 in BP regulation. To test the importance of endothelial Cul3 in vivo , we bred the conditionally activatable Cul3α9 mice with Tek-CRE ERT2 mice specifically expressing tamoxifen-inducible Cre-recombinase in the endothelium. The resultant mice (E-Cul3α9) exhibited impaired endothelial-dependent relaxation in the basilar artery (maximal relaxation in response to 30 μM acetylcholine, 45% vs 85% in control mice) and carotid artery. No difference in smooth muscle function was observed. Moreover, E-Cul3α9 mice exhibited nocturnal hypertension as determined by radiotelemetry (night time peak BP, 141±3 mmHg vs 122±3 mmHg). However no difference was seen in daytime pressure. E-Cul3α9 mice also exhibited arterial stiffening as indicated by elevated pulse wave velocity (3.7±0.3 m/s vs 2.7±0.1 m/s). To determine the molecular mechanism of endothelial dysfunction, primary aortic endothelial cells were isolated from mice carrying the inducible Cul3α9 construct and Cul3α9 expression was robustly induced by adenovirus carrying Cre recombinase gene in vitro . Cul3α9 acted in a dominant negative manner by interfering with expression and function of wild type Cul3, leading to impaired turnover of a Cul3 substrate protein phosphatase 2A, marked reduction in phosphorylated eNOS, and decreased nitric oxide production. Treatment with a selective PP2A inhibitor Okadaic Acid (1 nM) rescued Cul3α9-induced impairment of eNOS activity. These data define a novel pathway involving Cullin-3/PP2A/phospho-eNOS in the endothelium. Selective endothelial expression of Cul3α9 partially phenocopies the hypertension observed in Cul3α9 patients, suggesting that mutations in Cullin-3 cause human hypertension in part through a vascular mechanism characterized by endothelial dysfunction.

The Anti-Inflammatory Effects of Blueberries in an Animal Model of Post-Traumatic Stress Disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a trauma and stressor-related disorder that results in a prolonged stress response. It is associated with increased oxidative stress and inflammation in the prefrontal cortex (PFC) and hippocampus (HC). The only approved therapy for PTSD is selective serotonin re-uptake inhibitors (SSRIs), but their efficacy is marginal. Recently, we demonstrated that over-production of norepinephrine (NE) as the possible reason for the lack of efficacy of SSRIs. Hence, there is a need for novel therapeutic approaches for the treatment of PTSD. In this study, we investigated the anti-inflammatory role of blueberries in modulating inflammatory markers and neurotransmitter levels in PTSD. Rats were fed either a blueberry enriched (2%) or a control diet. Rats were exposed to cats for one hour on days 1 and 11 of a 31-day schedule to simulate traumatic conditions. The rats were also subjected to psychosocial stress via daily cage cohort changes. At the end of the study, the rats were euthanized and the PFC and HC were isolated. Monoamines were measured by high-performance liquid chromatography. Reactive oxygen species (ROS), gene and protein expression levels of inflammatory cytokines were also measured. In our PTSD model, NE levels were increased and 5-HT levels were decreased when compared to control. In contrast, a blueberry enriched diet increased 5-HT without affecting NE levels. The rate limiting enzymes tyrosine hydroxylase and tryptophan hydroxylase were also studied and they confirmed our findings. The enhanced levels free radicals, gene and protein expression of inflammatory cytokines seen in the PTSD group were normalized with a blueberry enriched diet. Decreased anxiety in this group was shown by improved performance on the elevated plus-maze. These findings indicate blueberries can attenuate oxidative stress and inflammation and restore neurotransmitter imbalances in a rat model of PTSD.

Abstract P205: Endothelium-specific Interference with PPARG Causes Cerebral Vascular Dysfunction in Response to Endogenous Renin-angiotensin System Activation

Abnormal activation of the endogenous renin-angiotensin system (RAS) has been implicated in various cardiovascular (CV) disorders including hypertension, atherosclerosis and stroke. Whereas a low salt diet may be beneficial in salt-sensitive hypertension, it has been proposed to also cause CV risk due to activation of the RAS. The molecular mechanism by which RAS activation mediates vascular dysfunction remains undefined. Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand-activated transcription factor which activates anti-oxidant and anti-inflammatory processes and can regulate the actions of angiotensin II (AngII) in the vasculature. We examined endothelial function in transgenic mice specifically expressing dominant-negative (DN) mutations in PPARγ in the endothelium (E-V290M) fed a low salt diet to test the hypothesis that endothelial PPARγ plays a protective role in the vasculature in response to endogenous RAS activation. Circulating levels of renin were significantly increased in both non-transgenic (NT) and E-V290M mice fed a low-salt diet for 6 weeks compared to standard chow (NT: 39.3±7.4 vs 19.8±1.3 ng/ml; E-V290M: 34.3±0.8 vs 16.0±3.8 ng/ml, p<0.05, n=5). Under baseline conditions, responses to endothelium-dependent agonist acetylcholine were not affected in E-V290M mice compared to NT (basilar artery: 66.1±11.8 vs 63.5±3.7%; carotid artery: 93.3±3.6 vs 91.1±4.2%, n=5). Six weeks of low-salt diet significantly impaired acetylcholine-mediated dilation in the basilar artery of E-V290M mice but not in NT (41.7±7.7 vs 74.2±5.0%, p<0.05, n=5). Unlike basilar artery, 6 weeks of low salt diet was not sufficient to induce vascular dysfunction in carotid artery or aorta of E-V290M mice (carotid artery: 85.6±4.4 vs 91.9±2.5%, n=5; aorta: 80.8±5.4 vs 87.0±5.6%, n=3). The responses to endothelium-independent vasodilator sodium nitroprusside (SNP) were not different in E-V290M mice compared to NT controls. We conclude that endothelial-specific interference with PPARγ causes endothelial dysfunction in response to endogenous RAS activation induced by a low-salt diet. Moreover, the cerebral circulation is particularly susceptible to low salt diet-induced dysfunction in conjunction with PPARγ impairment.

Abstract P158: Cullin3 Regulated Endothelial Function by Modulating eNOS Activity

Pseudohypoaldosteronism type II (PHAII) patients expressing dominant negative cullin3 mutations exhibit increased renal NaCl reabsorption and develop hyperkalaemia, metabolic acidosis and hypertension. It is unclear whether loss of cullin3 function in extra-renal tissues contributes to the hypertensive phenotype. In the vasculature, endothelial Nrf2 stability is tightly regulated by cullin3-based E3 ubiquitin ligase via the redox-sensitive adaptor kelch-like ECH-associated protein 1. In the present study, we found that 24-hour treatment with a pan cullin inhibitor MLN4924 (1 μM) caused a 3-fold increase in Nrf2 protein in mouse lung endothelial cells (MLECs), while tert-butyl hydroperoxide (tBHP, 240 μM) had no effect on Nrf2 level. However, both MLN4924 and tBHP triggered time-dependent accumulation of Nrf2 in the nuclei, which peaked at 40 minutes following treatment. As a result, both treatments induced marked upregulation of antioxidant genes including NAD(P)H quinone oxidoreductase 1, heme oxygenase 1, glutamate cysteine ligase (rate-limiting enzyme in glutathione synthesis), and catalase both in MLECs and primary mouse aortic endothelial cells (MAECs). Of note, MLN4924 upregulated Nox4 expression (1.0 ± 0.15 vs 1.7 ± 0.2) and tBHP upregulated Nox1 (1.0 ± 0.2 vs 4.8 ± 1.1), while MLN4924 and tBHP both markedly increased intracellular superoxide as determined by dihydroethidium staining. In addition, intracellular nitric oxide was decreased by half in MLN4924-treated MLECs. This redox imbalance was likely due to impaired eNOS expression and activation as MLN4924 caused a 25% reduction in total eNOS and a 75% reduction in phosphorylated eNOS, while tBHP lead to a 50% reduction in phosphorylated eNOS with no effect on total eNOS. This suggests that decreased eNOS activation contributed to the oxidative stress induced by these agents. These data imply that suppression of cullin3 in arterial endothelial cells may dampen endothelium-dependent vascular relaxation and contribute to the blood pressure elevation observed in PHAII patients with global loss of cullin3 function. Although cullin3 also negatively regulates Nrf2-mediated antioxidant responses in vascular endothelial cells, this likely occurs as a compensatory mechanism.

Abstract 053: RhoBTB1 is a Novel Gene Protecting Against Hypertension

Peroxisome proliferator-activated receptor gamma (PPARγ) is a ligand activated transcription factor regulating metabolic and vascular function. We previously reported that mice (S-DN) expressing dominant-negative PPARγ in smooth muscle cells (SMC) are hypertensive, exhibit impaired vascular relaxation and enhanced contraction, and display reduced expression of a novel PPARγ target gene, RhoBTB1. We hypothesized that RhoBTB1 may play a protective role in vascular function that is disrupted in S-DN mice and in other models of hypertension. We generated double transgenic mice (termed R+) with tamoxifen-inducible, Cre-dependent expression of RhoBTB1 in SMC. R+ mice were crossed with S-DN to produce mice (S-DN/R+) in which tamoxifen-treatment (75 mg/kg, ip, 5 days) restored RhoBTB1 expression in aorta to normal. Thoracic aorta and basilar artery from S-DN showed impaired acetylcholine (ACh)-induced endothelial-dependent relaxation, which was reversed by replacement of RhoBTB1 in SMC (thoracic aorta, 43.3±4.4 vs 74.2±1.1%, p<0.01, basilar artery, 19.9±6.7 vs 48.1±12.3%, p<0.05, n=6). Aorta from S-DN mice also displayed severely decreased sodium nitroprusside (SNP)-induced endothelial-independent relaxation with a right-shifted dose-response, which was also reversed in tamoxifen-treated S-DN/R+ mice (p<0.01, n=6). Importantly, replacement of RhoBTB1 also reversed the hypertensive phenotype observed in S-DN mice (Radiotelemetry SBP, 135.9±3.9 vs 123.7±3.0 mmHg, p<0.05, n=4). To examine if overexpression of RhoBTB1 in SMC has a protective effect on other hypertensive models, Ang-II (490 ng/min/kg) was infused in tamoxifen treated R+ mice for 2 wks. RhoBTB1 expression prevented Ang-II-induced impairment of ACh relaxation in basilar artery (17.0±8.6 in control mice vs 40.7±5.3 % in R+ mice, p<0.05, n=4) and decreased SBP (166.0±7.2 in control mice vs 133.3±5.1 mmHg in R+ mice, p<0.05, n=4). We conclude that a) loss of RhoBTB1 function explains the vascular dysfunction and hypertension observed in response to interference with PPARγ in smooth muscle, and b) RhoBTB1 in SMC has an anti-hypertensive effect and facilitates vasodilatation.

Aerobic training normalizes autonomic dysfunction, HMGB1 content, microglia activation and inflammation in hypothalamic paraventricular nucleus of SHR

Exercise training (ExT) is recommended to treat hypertension along with pharmaceutical antihypertensive therapies. Effects of ExT in hypothalamic content of high mobility box 1 (HMGB1) and microglial activation remain unknown. We examined whether ExT would decrease autonomic and cardiovascular abnormalities in spontaneously hypertensive rats (SHR), and whether these effects were associated with decreased HMGB1 content, microglial activation, and inflammation in the hypothalamic paraventricular nucleus (PVN). Normotensive Wistar-Kyoto (WKY) rats and SHR underwent moderate-intensity ExT for 2 wk. After ExT, cardiovascular (heart rate and arterial pressure) and autonomic parameters (arterial pressure and heart rate variability, peripheral sympathetic activity, cardiac vagal activity, and baroreflex function) were measured in conscious and freely-moving rats through chronic arterial and venous catheterization. Cerebrospinal fluid, plasma, and brain were collected for molecular and immunohistochemistry analyses of the PVN. In addition to reduced heart rate variability, decreased vagal cardiac activity and increased mean arterial pressure, heart rate, arterial pressure variability, cardiac, and vasomotor sympathetic activity, SHR had higher HMGB1 protein expression, IκB-α phosphorylation, TNF-α and IL-6 protein expression, and microglia activation in the PVN. These changes were accompanied by higher plasma and cerebrospinal fluid levels of HMGB1. The ExT + SHR group had decreased expression of HMGB1, CXCR4, SDF-1, and phosphorylation of p42/44 and IκB-α. ExT reduced microglial activation and proinflammatory cytokines content in the PVN, and improved autonomic control as well. Data suggest that training-induced downregulation of activated HMGB1/CXCR4/microglia/proinflammatory cytokines axis in the PVN of SHR is a prompt neural adaptation to counterbalance the deleterious effects of inflammation on autonomic control.

Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells

BACKGROUND AND PURPOSE

Angiotensin II is a vaso-constrictive peptide that regulates blood pressure homeostasis. Even though the inflammatory effects of AngII in renal pathophysiology have been studied, there still exists a paucity of data with regard to the mechanism of action of AngII-mediated kidney injury. The objective of this study was to elucidate the mechanistic role of HMGB1-TLR4 signaling in AngII-induced inflammation in the kidney.

EXPERIMENTAL APPROACH

Rat tubular epithelial cells (NRK52E) were treated with AngII over a preset time-course. In another set of experiments, HMGB1 was neutralized and TLR4 was knocked down using small interfering RNA targeting TLR4. Cell extracts were subjected to RT-PCR, immunoblotting, flow cytometry, and ELISA.

KEY RESULTS

AngII-induced inflammation in NRK52E cells increased gene and protein expression of TLR4, HMGB1 and key proinflammatory cytokines (TNFα and IL1β). Pretreatment with Losartan (an AT1 receptor blocker) attenuated the AngII-induced expression of TLR4 and inflammatory cytokines. TLR4 silencing was used to elucidate the specific role played by TLR4 in AngII-induced inflammation. TLR4siRNA treatment in these cells significantly decreased the AngII-induced inflammatory effect. Consistent observations were made when the Ang II treated cells were pretreated with anti-HMGB1. Downstream activation of NFκB and rate of generation of ROS was also decreased on gene silencing of TLR4 and exposure to anti-HMGB1.

CONCLUSIONS AND IMPLICATIONS

These results indicate a key role for HMGB1-TLR4 signaling in AngII-mediated inflammation in the renal epithelial cells. Our data also reveal that AngII-induced effects could be alleviated by HMGB1-TLR4 inhibition, suggesting this pathway as a potential therapeutic target for hypertensive renal dysfunctions.

Toll-like receptor 4 promotes autonomic dysfunction, inflammation and microglia activation in the hypothalamic paraventricular nucleus: role of endoplasmic reticulum stress

BACKGROUND & PURPOSE

Toll-like receptor 4 (TLR4) signaling induces tissue pro-inflammatory cytokine release and endoplasmic reticulum (ER) stress. We examined the role of TLR4 in autonomic dysfunction and the contribution of ER stress.

EXPERIMENTAL APPROACH

Our study included animals divided in 6 experimental groups: rats treated with saline (i.v., 0.9%), LPS (i.v., 10mg/kg), VIPER (i.v., 0.1 mg/kg), or 4-PBA (i.p., 10 mg/kg). Two other groups were pretreated either with VIPER (TLR4 viral inhibitory peptide) LPS + VIPER (i.v., 0.1 mg/kg) or 4-Phenyl butyric acid (4-PBA) LPS + PBA (i.p., 10 mg/kg). Arterial pressure (AP) and heart rate (HR) were measured in conscious Sprague-Dawley rats. AP, HR variability, as well as baroreflex sensitivity (BrS), was determined after LPS or saline treatment for 2 hours. Immunofluorescence staining for NeuN, Ib1a, TLR4 and GRP78 in the hypothalamic paraventricular nucleus (PVN) was performed. TNF-α, TLR4 and GRP78 protein expression in the PVN were evaluated by western blot. Plasma norepinephrine levels were determined by ELISA.

KEY RESULTS

Acute LPS treatment increased HR and plasma norepinephrine concentration. It also decreased HR variability and high frequency (HF) components of HR variability, as well BrS. Acute LPS treatment increased TLR4 and TNF-α protein expression in the PVN. These hemodynamic and molecular effects were partially abrogated with TLR4 blocker or ER stress inhibitor pretreatment. In addition, immunofluorescence study showed that TLR4 is co-localized with GRP78in the neurons. Further inhibition of TLR4 or ER stress was able to attenuate the LPS-induced microglia activation.

CONCLUSIONS & IMPLICATIONS

TLR4 signaling promotes autonomic dysfunction, inflammation and microglia activation, through neuronal ER stress, in the PVN.

A blueberry-enriched diet improves renal function and reduces oxidative stress in metabolic syndrome animals: potential mechanism of TLR4-MAPK signaling pathway

Background

Metabolic syndrome (MetS) is characterized by a cluster of health factors that indicate a higher risk for cardio-renal diseases. Recent evidence indicates that antioxidants from berries are alternative to attenuate oxidative stress and inflammation. We tested the hypothesis that inflammation-induced renal damage is triggered by the activation of TLR4, and subsequent modulation of redox-sensitive molecules and mitogen-activated protein kinase (MAPK) pathway.

Methods

Five-week old lean and obese Zucker rats (LZR and OZR) were fed a blueberry-enriched diet or an isocaloric control diet for 15 weeks. A glucose tolerance test and acute renal clearance experiments were performed. Gene and protein expression levels for TLR4, cytokines and phosphorylation of ERK and p38MAPK were measured. Kidney redox status and urinary albumin levels were quantified. Renal pathology was evaluated histologically.

Results

Control OZR exhibited lower glucose tolerance; exacerbated renal function parameters; increased oxidative stress. Gene and protein expression levels of TLR4 were higher and this was accompanied by increased renal pathology with extensive albuminuria and deterioration in antioxidant levels in OZR. In addition, OZR had increased phosphorylation of ERK and p38MAPK. Blueberry-fed OZR exhibited significant improvements in all these parameters compared to OZR.

Conclusion

TLR4-MAPK signaling pathway is a key to the renal structural injury and dysfunction in MetS and blueberry (BB) protect against this damage by inhibiting TLR4.

Significance

This is the first study to put forth a potential mechanism of TLR4-induced kidney damage in a model of MetS and to elucidate a downstream mechanism by which blueberry exert their reno-protective effects.

Differential effects of sertraline in a predator exposure animal model of post-traumatic stress disorder

Serotonin (5-HT), norepinephrine (NE), and other neurotransmitters are modulated in post-traumatic stress disorder (PTSD). In addition, pro-inflammatory cytokines (PIC) are elevated during the progression of the disorder. Currently, the only approved pharmacologic treatments for PTSD are the selective-serotonin reuptake inhibitors (SSRI) sertraline and paroxetine, but their efficacy in treating PTSD is marginal at best. In combat-related PTSD, SSRIs are of limited effectiveness. Thus, this study sought to analyze the effects of the SSRI sertraline on inflammation and neurotransmitter modulation via a predator exposure/psychosocial stress animal model of PTSD. We hypothesized that sertraline would diminish inflammatory components and increase 5-HT but might also affect levels of other neurotransmitters, particularly NE. PTSD-like effects were induced in male Sprague-Dawley rats (n = 6/group × 4 groups). The rats were secured in Plexiglas cylinders and placed in a cage with a cat for 1 h on days 1 and 11 of a 31-day stress regimen. PTSD rats were also subjected to psychosocial stress via daily cage cohort changes. At the conclusion of the stress regimen, treatment group animals were injected intraperitoneally (i.p.) with sertraline HCl at 10 mg/kg for 7 consecutive days, while controls received i.p. vehicle. The animals were subsequently sacrificed on day 8. Sertraline attenuated inflammatory markers and normalized 5-HT levels in the central nervous system (CNS). In contrast, sertraline produced elevations in NE in the CNS and systemic circulation of SSRI treated PTSD and control groups. This increase in NE suggests SSRIs produce a heightened noradrenergic response, which might elevate anxiety in a clinical setting.

Renal cells exposed to cadmium in vitro and in vivo: normalizing gene expression data

Cadmium (Cd) is a toxic metal with a long half-life in biological systems. This half-life is partly as a result of metallothioneins (MTs), metal-binding proteins with a high affinity for Cd. The high retention properties of the kidneys reside in proximal tubular cells that possess transport mechanisms for Cd-MT uptake, ultimately leading to more Cd accumulation. Researchers have studied MT-metal interactions using various techniques including quantitative real-time PCR (qPCR), an efficient tool for quantifying gene expression. Often a poor choice of reference genes, which is represented by their instability and condition dependency, leads to inefficient normalization of gene expression data and misinterpretations. This study demonstrates the importance of an efficient normalization strategy in toxicological research. A selection of stable reference genes was proposed in order to acquire reliable and reproducible gene quantification under metal stress using MT expression as an example. Moreover, in vitro and in vivo setups were compared to identify the influence of toxicological compounds in function of the experimental design. This study shows that glyceraldehyde-3-phosphate dehydrogenase (Gapdh), tyrosine monooxygenase/tryptophan5-monooxygenase activation-protein, zeta polypeptide (Ywhaz) and beta-actin (Actb) are the most stable reference genes in a kidney proximal tubular cell line exposed to moderate and high Cd concentrations, applied as CdCl2 . A slightly different sequence in reference gene stability was found in renal cells isolated from rats in vivo exposed to Cd. It was further shown that three reference genes are required for efficient normalization in this experimental setup. This study demonstrates the importance of an efficient normalization strategy in toxicological research.

Role of TLR4 in lipopolysaccharide-induced acute kidney injury: protection by blueberry

Inflammation has been implicated in the pathophysiology of kidney disorders. Previous studies have documented the contributions of various inflammatory cascades in the development of kidney and other organ dysfunctions. The Toll-like receptor 4 (TLR4) inflammatory pathway is a major contributor of inflammation in the kidney. Interestingly, lipopolysaccharide (LPS), a specific ligand for TLR4, has been shown to induce acute kidney injury (AKI) in animal models. We have previously studied the beneficial effects of nonpharmacological agents, particularly blueberries (BB), in attenuating inflammation and oxidative stress. We hypothesize that BB protect against the LPS-induced AKI by inhibiting TLR4 activation and kidney injury markers. Twelve-week-old male Sprague-Dawley rats received a BB solution or saline intragastric gavage for 2 days. One group of BB and saline-gavaged animals was injected with LPS (10 mg/kg bw). Another group of rats was injected with VIPER (0.1 mg/kg iv), a TLR4-specific inhibitory peptide, 2 h before LPS administration. Compared to LPS-administered rats, the BB-pretreated animals exhibited improved glomerular filtration rate, elevated renal blood flow, and a reduced renal vascular resistance. In addition, a reduction in the rate of production of free radicals, namely total reactive oxygen species (ROS) and superoxide, was observed in the BB-supplemented LPS group. Gene and protein expressions for TLR4, proinflammatory cytokine, and acute kidney injury markers were also attenuated in animals that were pretreated with BB as measured by real time RT-PCR and Western blotting, respectively. These results in the BB-pretreated group were consistent with those in the VIPER-treated rats, and indicate that BB protects against AKI by inhibiting TLR4 and its subsequent effect on inflammatory and oxidative stress pathways.

Abstract 201: Mice Lacking the Gene for Toll-like Receptor 4 (TLR4) Had an Attenuated ER Stress in the Heart in Response to Ang II Infusion

Inflammatory molecule plays an important role in the pathophysiology of hypertension. Recently we showed that TLR4 inhibition in the brain attenuates hypertension. In this study we demonstrate that ANGII induced ER stress in the heart is attenuated in mice lacking the gene for TLR4. In addition, we show that ANGII induced cardiac hypertrophy is blocked by ER stress inhibitor.

Method: TLR4 knock-out (KO) mice and wild type (WT) controls were implanted with telemetry probes for mean arterial pressure (MAP) measurements. After collecting baseline MAP and left ventricular function using echocardiography, osmotic minipump containing ANGII (200ng/kg/min) or vehicle (saline) was implanted for 14 days. In another group, C57BL6 mice were injected with ER stress inhibitor 4-PBA (150mg/kg bw) given intraperitoneally with and without ANGII. At the end of the study, mice were sacrificed the LV tissue removed and analyzed for gene of interest using RT-PCR and Western blotting.

Results are tabulated. The real-time PCR values are shown as αCT values (18S - the gene of interest).

Conclusions: 1) ANGII infusion induces cardiac hypertrophy and ER stress. 2) Mice lacking the gene for TLR4 had attenuated cardiac hypertrophy and ER stress in response to ANGII. 3) ER stress inhibitor protect against ANGII induces cardiac hypertrophy. 4) TLR4 at least in part contributes to ANG II induced cardiac hypertrophy and ER stress.