A second look with prone SPECT myocardial perfusion imaging reduces the need for angiography in patients at low risk for cardiac death or MI

BACKGROUND

Correction for soft tissue signal attenuation can improve the diagnostic accuracy of single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). The aim of this study was to correlate SPECT-MPI findings with clinical outcomes in patients who underwent stress imaging in the supine position, who also underwent "second look" stress imaging in the prone position.

METHODS

Patients without perfusion abnormalities were considered Normal (N = 270). Those with apparent supine stress perfusion abnormalities which all resolved during prone imaging formed the Normal-Prone group (N = 309). Patients with matched perfusion abnormalities during both supine and prone stress imaging were considered Abnormal (N = 169).

RESULTS

During follow-up (187 ± 96 days), utilization rates for invasive coronary angiography were similar for Normal vs Normal-Prone patients (3.5% vs 3.8%; P = NS), but were significantly higher in Abnormal patients (42.4%, P < .0001). Coronary revascularization occurred in 0.78%, 0.64%, and 17.7% of Normal, Normal-Prone, and Abnormal patients, respectively (P < .001). Cardiac death or myocardial infarction occurred in 2.2%, 2.3%, and 6.3% of Normal, Normal-Prone, and Abnormal patients, respectively (P = .02).

CONCLUSIONS

Second look SPECT-MPI identifies patients at low risk for death or myocardial infarction, who infrequently require invasive coronary angiography.

Effect of Chronic Heart Rate Reduction by If Current Inhibitor Ivabradine on Left Ventricular Remodeling and Systolic Performance in Middle-Aged Rats With Postmyocardial Infarction Heart Failure

Background:

A large myocardial infarction (MI) initiates progressive cardiac remodeling that leads to systolic heart failure (HF). Long-term heart rate reduction (HRR) induced by the I f current inhibitor ivabradine (IVA) ameliorates left ventricular (LV) remodeling and improves systolic performance in young post-MI rats. However, the beneficial effects of chronic IVA treatment in middle-aged rats remain to be determined.

Methods:

A large MI was induced in 12-month-old rats by left coronary artery ligation. Rats were treated with IVA via osmotic pumps intraperitoneal in a dose of 10.5 mg/kg/d (MI + IVA) and compared with MI and sham-operated animals 12 weeks after MI.

Results:

Heart rate in MI + IVA rats was on average 29% lower than that of rats in the MI group. Left ventricular remodeling was comparable between post-MI groups, although MI + IVA rats did not show the compensatory thickening of the noninfarcted myocardium. Chronic HRR had no effect on transverse cardiac myocyte size and capillary growth, but it reduced the collagen content in noninfarcted myocardium. Left ventricular systolic performance remained similarly impaired in MI and MI + IVA rats. Moreover, abrupt IVA withdrawal led to worsening HF and reduction of coronary reserve.

Conclusion:

Our data reveal that chronic IVA-induced HRR does not provide sustainable benefits for LV systolic performance in middle-aged rats with post-MI HF.

Cardiovascular magnetic resonance characterization of left ventricular non-compaction provides independent prognostic information in patients with incident heart failure or suspected cardiomyopathy

BACKGROUND

With recent advances in imaging methods, detection of LVNC is increasingly common. Concomitantly, the prognostic importance of LVNC is less clear.

METHODS

We followed 42 patients (63% male, age 44 ± 15 years) with incident heart failure or suspected cardiomyopathy, in whom cardiovascular magnetic resonance (CMR) yielded a diagnosis of LVNC, for 27 ± 16 months.

RESULTS

LVNC was preferentially distributed among posterolateral segments, with apical predominance. Patients with maximum non-compacted-to-compacted thickness ratio (NC:C) < 3 improved by 0.9 ± 0.7 NYHA Class, compared to 0.3 ± 0.8 for patients with NC:C > 3 (p = 0.001). In 29 patients with baseline LVEF < 0.40, there was an inverse correlation between NC:C ratio, and the change in LVEF during follow-up. Tachyarrhythmias were observed in 42% of patients with LGE, and in 0% of patients without LGE (p = 0.02). In multivariate analysis, arrhythmia incidence was significantly higher in patients with LGE, even when adjusted for LVEF and RVEF.

CONCLUSIONS

CMR assessments of myocardial morphology provide important prognostic information for patients with LVNC who present with incident heart failure or suspected cardiomyopathy.

Abstract 414: Inhibition of Mitogen-Activated Protein Kinase (MAPK) Signaling Ameliorates Endoplasmic Reticulum (ER) Stress, Inflammation and Sympathetic Nerve Activity in Heart Failure Rats

Heart failure (HF) is characterized by increased sympathetic nerve activity, driven in part by increases in brain inflammation and renin-angiotensin system activity. Angiotensin II (ANG II) and pro-inflammatory cytokines (PICs) activate neuronal MAPK signaling, which has been implicated in sympathetic activation in HF. ANG II and PICs can also activate ER stress, which plays an important role in regulating sympathetic drive and cardiovascular function in ANG II hypertension. The present study was designed to determine whether ER stress occurs in cardiovascular regions of the brain in HF, and if so how MAPK signaling interacts with ER stress. HF and SHAM (n=6) rats were produced by coronary ligation or sham ligation, respectively. HF rats received a chronic (4 wk) intracerebroventricular (ICV) infusion (0.25 μl/hr) of vehicle (Veh, n=6) or an inhibitor (0.25μg/μl, n=6 in each group) selective for p44/42 MAPK (PD98059), JNK (SP600125), or p38 MAPK (SB203580). ER stress markers (GRP78, ATF-6, P58 IPK and CHOP) and NF-κB components (NF-κB p65 and IκB-α) were measured in the subfornical organ (SFO) and the hypothalamic paraventricular nucleus (PVN) by real time PCR. Plasma norepinephrine (NE) was measured by ELISA. Compared with SHAM rats, Veh-treated HF rats had significantly (*p<0.05) higher mRNA levels for the ER stress markers in SFO (2-3 folds) and PVN (1.8-2.5 folds); these levels were lower (28-55%*) in the HF rats treated with the MAPK inhibitors, with SB203580 being most effective in SFO and PD98059 most effective in PVN. Veh-treated HF rats had higher (95 ± 11 %*) NF-κB p65 mRNA level and lower (46 ± 5 %*) IκB-α mRNA level in SFO and PVN, compared with SHAM rats; these indicators of increased inflammation did not occur in the HF rats treated with the MAPK inhibitors. The plasma NE level (ng/ml) was higher in Veh-treated HF (36.93 ± 2.60*) than SHAM (17.90 ± 2.59) rats; this increase was attenuated in the HF rats treated with PD98059 (13.64 ± 0.92*) and SB203580 (24.68 ± 2.71*). These data demonstrate that ER stress increases in the SFO and PVN of rats with ischemia-induced HF. Inhibition of brain MAPK signaling reduces brain ER stress and inflammation and decreases sympathetic excitation in HF. Brain MAPK signaling is a potential target for therapeutic intervention in HF.

Aortic valve sclerosis in mice deficient in endothelial nitric oxide synthase

Risk factors for fibrocalcific aortic valve disease (FCAVD) are associated with systemic decreases in bioavailability of endothelium-derived nitric oxide (EDNO). In patients with bicuspid aortic valve (BAV), vascular expression of endothelial nitric oxide synthase (eNOS) is decreased, and eNOS(-/-) mice have increased prevalence of BAV. The goal of this study was to test the hypotheses that EDNO attenuates profibrotic actions of valve interstitial cells (VICs) in vitro and that EDNO deficiency accelerates development of FCAVD in vivo. As a result of the study, coculture of VICs with aortic valve endothelial cells (vlvECs) significantly decreased VIC activation, a critical early phase of FCAVD. Inhibition of VIC activation by vlvECs was attenuated by N(G)-nitro-l-arginine methyl ester or indomethacin. Coculture with vlvECs attenuated VIC expression of matrix metalloproteinase-9, which depended on stiffness of the culture matrix. Coculture with vlvECs preferentially inhibited collagen-3, compared with collagen-1, gene expression. BAV occurred in 30% of eNOS(-/-) mice. At age 6 mo, collagen was increased in both bicuspid and trileaflet eNOS(-/-) aortic valves, compared with wild-type valves. At 18 mo, total collagen was similar in eNOS(-/-) and wild-type mice, but collagen-3 was preferentially increased in eNOS(-/-) mice. Calcification and apoptosis were significantly increased in BAV of eNOS(-/-) mice at ages 6 and 18 mo. Remarkably, these histological changes were not accompanied by physiologically significant valve stenosis or regurgitation. In conclusion, coculture with vlvECs inhibits specific profibrotic VIC processes. In vivo, eNOS deficiency produces fibrosis in both trileaflet and BAVs but produces calcification only in BAVs.

Microtubule-mediated defects in junctophilin-2 trafficking contribute to myocyte transverse-tubule remodeling and Ca2+ handling dysfunction in heart failure

BACKGROUND

Cardiac dysfunction in failing hearts of human patients and animal models is associated with both microtubule densification and transverse-tubule (T-tubule) remodeling. Our objective was to investigate whether microtubule densification contributes to T-tubule remodeling and excitation-contraction coupling dysfunction in heart disease.

METHODS AND RESULTS

In a mouse model of pressure overload-induced cardiomyopathy by transaortic banding, colchicine, a microtubule depolymerizer, significantly ameliorated T-tubule remodeling and cardiac dysfunction. In cultured cardiomyocytes, microtubule depolymerization with nocodazole or colchicine profoundly attenuated T-tubule impairment, whereas microtubule polymerization/stabilization with taxol accelerated T-tubule remodeling. In situ immunofluorescence of heart tissue sections demonstrated significant disorganization of junctophilin-2 (JP2), a protein that bridges the T-tubule and sarcoplasmic reticulum membranes, in transaortic banded hearts as well as in human failing hearts, whereas colchicine injection significantly preserved the distribution of JP2 in transaortic banded hearts. In isolated mouse cardiomyocytes, prolonged culture or treatment with taxol resulted in pronounced redistribution of JP2 from T-tubules to the peripheral plasma membrane, without changing total JP2 expression. Nocodazole treatment antagonized JP2 redistribution. Moreover, overexpression of a dominant-negative mutant of kinesin 1, a microtubule motor protein responsible for anterograde trafficking of proteins, protected against JP2 redistribution and T-tubule remodeling in culture. Finally, nocodazole treatment improved Ca(2+) handling in cultured myocytes by increasing the amplitude of Ca(2+) transients and reducing the frequency of Ca(2+) sparks.

CONCLUSION

Our data identify a mechanistic link between microtubule densification and T-tubule remodeling and reveal microtubule-mediated JP2 redistribution as a novel mechanism for T-tubule disruption, loss of excitation-contraction coupling, and heart failure.

Nox1 NADPH oxidase is necessary for late but not early myocardial ischaemic preconditioning

AIMS

Ischaemic preconditioning (IPC) is an adaptive mechanism that renders the myocardium resistant to injury from subsequent hypoxia. Although reactive oxygen species (ROS) contribute to both the early and late phases of IPC, their enzymatic source and associated signalling events have not yet been understood completely. Our objective was to investigate the role of the Nox1 NADPH oxidase in cardioprotection provided by IPC.

METHODS AND RESULTS

Wild-type (WT) and Nox1-deficient mice were treated with three cycles of brief coronary occlusion and reperfusion, followed by prolonged occlusion either immediately (early IPC) or after 24 h (late IPC). Nox1 deficiency had no impact on the cardioprotection afforded by early IPC. In contrast, deficiency of Nox1 during late IPC resulted in a larger infarct size, cardiac remodelling, and increased myocardial apoptosis compared with WT hearts. Furthermore, expression of Nox1 in WT hearts increased in response to late IPC. Deficiency of Nox1 abrogated late IPC-mediated activation of cardiac nuclear factor-κB (NF-κB) and induction of tumour necrosis factor-α (TNF-α) in the heart and circulation. Finally, knockdown of Nox1 in cultured cardiomyocytes prevented TNF-α induction of NF-κB and the protective effect of IPC on hypoxia-induced apoptosis.

CONCLUSIONS

Our data identify a critical role for Nox1 in late IPC and define a previously unrecognized link between TNF-α and NF-κB in mediating tolerance to myocardial injury. These findings have clinical significance considering the emergence of Nox1 inhibitors for the treatment of cardiovascular disease.

Surface-modified nanoparticles enhance transurothelial penetration and delivery of survivin siRNA in treating bladder cancer

Penetration of the bladder permeability barrier (BPB) is a major challenge when treating bladder diseases via intravesical delivery. To increase transurothelial migration and tissue and tumor cell uptake, poly(lactic-co-glycolic acid; PLGA) nanoparticles (NP) were modified by addition of a low molecular weight (2.5 or 20 kDa) positively charged mucoadhesive polysaccharide, chitosan, to the NP surface. In designing these NPs, we balanced the adhesive properties of chitosan with the release and bioactivity of the siRNA. Chitosan-functionalized NPs demonstrated increased binding to and uptake in intravesically instilled mouse bladders and human ureter at 10 times the level of unmodified NPs. Furthermore, we extended the bioactivity of survivin siRNA in vitro for up to 9 days and demonstrated a decrease in proliferation when using chitosan-modified NPs relative to unmodified NPs. In addition, treatment of xenograft tumors with chitosan-modified NPs that encapsulate survivin siRNA (NP-siSUR-CH2.5) resulted in a 65% reduction in tumor volume and a 75% decrease in survivin expression relative to tumors treated with blank chitosan NPs (NP-Bk-CH2.5). Our low molecular weight chitosan delivery system has the capacity to transport large amounts of siRNA across the urothelium and/or to the tumor site, thus increasing therapeutic response.

Fibrocalcific aortic valve disease: opportunity to understand disease mechanisms using mouse models

Studies in vitro and in vivo continue to identify complex-regulated mechanisms leading to overt fibrocalcific aortic valve disease (FCAVD). Assessment of the functional impact of those processes requires careful studies of models of FCAVD in vivo. Although the genetic basis for FCAVD is unknown for most patients with FCAVD, several disease-associated genes have been identified in humans and mice. Some gene products which regulate valve development in utero also protect against fibrocalcific disease during postnatal aging. Valve calcification can occur via processes that resemble bone formation. But valve calcification can also occur by nonosteogenic mechanisms, such as formation of calcific apoptotic nodules. Anticalcific interventions might preferentially target either osteogenic or nonosteogenic calcification. Although FCAVD and atherosclerosis share several risk factors and mechanisms, there are fundamental differences between arteries and the aortic valve, with respect to disease mechanisms and responses to therapeutic interventions. Both innate and acquired immunity are likely to contribute to FCAVD. Angiogenesis is a feature of inflammation, but may also contribute independently to progression of FCAVD, possibly by actions of pericytes that are associated with new blood vessels. Several therapeutic interventions seem to be effective in attenuating the development of FCAVD in mice. Therapies which are effective early in the course of FCAVD, however, are not necessarily effective in established disease.

Oxidized Ca(2+)/calmodulin-dependent protein kinase II triggers atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is a growing public health problem without adequate therapies. Angiotensin II and reactive oxygen species are validated risk factors for AF in patients, but the molecular pathways connecting reactive oxygen species and AF are unknown. The Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) has recently emerged as a reactive oxygen species-activated proarrhythmic signal, so we hypothesized that oxidized CaMKIIδ could contribute to AF.

METHODS AND RESULTS

We found that oxidized CaMKII was increased in atria from AF patients compared with patients in sinus rhythm and from mice infused with angiotensin II compared with mice infused with saline. Angiotensin II-treated mice had increased susceptibility to AF compared with saline-treated wild-type mice, establishing angiotensin II as a risk factor for AF in mice. Knock-in mice lacking critical oxidation sites in CaMKIIδ (MM-VV) and mice with myocardium-restricted transgenic overexpression of methionine sulfoxide reductase A, an enzyme that reduces oxidized CaMKII, were resistant to AF induction after angiotensin II infusion.

CONCLUSIONS

Our studies suggest that CaMKII is a molecular signal that couples increased reactive oxygen species with AF and that therapeutic strategies to decrease oxidized CaMKII may prevent or reduce AF.

The multifunctional Ca²⁺/calmodulin-dependent kinase IIδ (CaMKIIδ) regulates arteriogenesis in a mouse model of flow-mediated remodeling

Objective

Sustained hemodynamic stress mediated by high blood flow promotes arteriogenesis, the outward remodeling of existing arteries. Here, we examined whether Ca²⁺/calmodulin-dependent kinase II (CaMKII) regulates arteriogenesis.

Methods and Results

Ligation of the left common carotid led to an increase in vessel diameter and perimeter of internal and external elastic lamina in the contralateral, right common carotid. Deletion of CaMKIIδ (CaMKIIδ−/−) abolished this outward remodeling. Carotid ligation increased CaMKII expression and was associated with oxidative activation of CaMKII in the adventitia and endothelium. Remodeling was abrogated in a knock-in model in which oxidative activation of CaMKII is abolished. Early after ligation, matrix metalloproteinase 9 (MMP9) was robustly expressed in the adventitia of right carotid arteries of WT but not CaMKIIδ−/− mice. MMP9 mainly colocalized with adventitial macrophages. In contrast, we did not observe an effect of CaMKIIδ deficiency on other proposed mediators of arteriogenesis such as expression of adhesion molecules or smooth muscle proliferation. Transplantation of WT bone marrow into CaMKIIδ−/− mice normalized flow-mediated remodeling.

Conclusion

CaMKIIδ is activated by oxidation under high blood flow conditions and is required for flow-mediated remodeling through a mechanism that includes increased MMP9 expression in bone marrow-derived cells invading the arterial wall.

Critical roles of junctophilin-2 in T-tubule and excitation-contraction coupling maturation during postnatal development

AIMS

Emerging evidence indicates a critical role for junctophilin-2 (JP2) in T-tubule integrity and assembly of cardiac dyads in adult ventricular myocytes. In the postnatal stage, one of the critical features of myocyte maturation is development of the T-tubule system, though the mechanisms remain poorly understood. In this study, we aim to determine whether JP2 is required for normal cardiac T-tubule maturation.

METHODS AND RESULTS

Using in situ confocal imaging of intact murine hearts, we found T-tubules were absent in both left- and right-ventricular myocytes at postnatal Day 8 and did not appear until Day 10. Quantification of T-tubule structural integrity using the T-tubule power (TT(power)) index revealed a progressive increase in TT(power) between postnatal Days 10 and 19. By postnatal Day 19, TT(power) was similar to that in adult murine cardiomyocytes, indicative of a nearly matured T-tubule network. JP2 levels increased dramatically during development, reaching levels observed in adult hearts by postnatal Day 14. Deficiency of JP2, using a mouse model in which a JP2-specific shRNA is expressed during embryonic development, severely impaired T-tubule maturation, with equivalent decreases in the left- and right-ventricular TT(power). We also detected a gradual increase in the density of transverse but not longitudinal tubules during development, and JP2 deficiency abolished the increase in the density of transverse elements. Alterations in T-tubules caused significant reduction in Ca(2+) transient amplitude and marked increase in Ca(2+) release dyssynchrony, Ca(2+) alternans, and spontaneous Ca(2+) waves, leading to contractile failure.

CONCLUSION

Our data identify a critical role for JP2 in T-tubule and excitation-contraction coupling maturation during development.

Nanoparticles for urothelium penetration and delivery of the histone deacetylase inhibitor belinostat for treatment of bladder cancer

Nearly 40% of patients with non-invasive bladder cancer will progress to invasive disease despite locally-directed therapy. Overcoming the bladder permeability barrier (BPB) is a challenge for intravesical drug delivery. Using the fluorophore coumarin (C6), we synthesized C6-loaded poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs), which were surface modified with a novel cell penetrating polymer, poly(guanidinium oxanorbornene) (PGON). Addition of PGON to the NP surface improved tissue penetration by 10-fold in intravesically-treated mouse bladder and ex vivo human ureter. In addition, NP-C6-PGON significantly enhanced intracellular uptake of NPs compared to NPs without PGON. To examine biological activity, we synthesized NPs that were loaded with the histone deacetylase (HDAC) inhibitor belinostat (NP-Bel-PGON). NP-Bel-PGON exhibited a significantly lower IC50 in cultured bladder cancer cells, and sustained hyperacetylation, when compared to unencapsulated belinostat. Xenograft tumors treated with NP-Bel-PGON showed a 70% reduction in volume, and a 2.5-fold higher intratumoral acetyl-H4, when compared to tumors treated with unloaded NP-PGON.

FROM THE CLINICAL EDITOR

These authors demonstrate that PLGA nanoparticles with PGON surface functionalization result in greatly enhanced cell penetrating capabilities, and present convincing data from a mouse model of bladder cancer for increased chemotherapy efficacy.

Differential control of calcium homeostasis and vascular reactivity by Ca2+/calmodulin-dependent kinase II

The multifunctional Ca(2+)/calmodulin-dependent kinase II (CaMKII) is activated by vasoconstrictors in vascular smooth muscle cells (VSMC), but its impact on vasoconstriction remains unknown. We hypothesized that CaMKII inhibition in VSMC decreases vasoconstriction. Using novel transgenic mice that express the inhibitor peptide CaMKIIN in smooth muscle (TG SM-CaMKIIN), we investigated the effect of CaMKII inhibition on L-type Ca(2+) channel current (ICa), cytoplasmic and sarcoplasmic reticulum Ca(2+), and vasoconstriction in mesenteric arteries. In mesenteric VSMC, CaMKII inhibition significantly reduced action potential duration and the residual ICa 50 ms after peak amplitude, indicative of loss of L-type Ca(2+) channel-dependent ICa facilitation. Treatment with angiotensin II or phenylephrine increased the intracellular Ca(2+) concentration in wild-type but not TG SM-CaMKIIN VSMC. The difference in intracellular Ca(2+) concentration was abolished by pretreatment with nifedipine, an L-type Ca(2+) channel antagonist. In TG SM-CaMKIIN VSMC, the total sarcoplasmic reticulum Ca(2+) content was reduced as a result of diminished sarcoplasmic reticulum Ca(2+) ATPase activity via impaired derepression of the sarcoplasmic reticulum Ca(2+) ATPase inhibitor phospholamban. Despite the differences in intracellular Ca(2+) concentration, CaMKII inhibition did not alter myogenic tone or vasoconstriction of mesenteric arteries in response to KCl, angiotensin II, and phenylephrine. However, it increased myosin light chain kinase activity. These data suggest that CaMKII activity maintains intracellular calcium homeostasis but is not required for vasoconstriction of mesenteric arteries.

Osteoprotegerin inhibits aortic valve calcification and preserves valve function in hypercholesterolemic mice

BACKGROUND

There are no rigorously confirmed effective medical therapies for calcific aortic stenosis. Hypercholesterolemic Ldlr (-/-) Apob (100/100) mice develop calcific aortic stenosis and valvular cardiomyopathy in old age. Osteoprotegerin (OPG) modulates calcification in bone and blood vessels, but its effect on valve calcification and valve function is not known.

OBJECTIVES

To determine the impact of pharmacologic treatment with OPG upon aortic valve calcification and valve function in aortic stenosis-prone hypercholesterolemic Ldlr (-/-) Apob (100/100) mice.

METHODS

Young Ldlr (-/-) Apob (100/100) mice (age 2 months) were fed a Western diet and received exogenous OPG or vehicle (N = 12 each) 3 times per week, until age 8 months. After echocardiographic evaluation of valve function, the aortic valve was evaluated histologically. Older Ldlr (-/-) Apob (100/100) mice were fed a Western diet beginning at age 2 months. OPG or vehicle (N = 12 each) was administered from 6 to 12 months of age, followed by echocardiographic evaluation of valve function, followed by histologic evaluation.

RESULTS

In Young Ldlr (-/-) Apob (100/100) mice, OPG significantly attenuated osteogenic transformation in the aortic valve, but did not affect lipid accumulation. In Older Ldlr (-/-) Apob (100/100) mice, OPG attenuated accumulation of the osteoblast-specific matrix protein osteocalcin by ∼80%, and attenuated aortic valve calcification by ∼ 70%. OPG also attenuated impairment of aortic valve function.

CONCLUSIONS

OPG attenuates pro-calcific processes in the aortic valve, and protects against impairment of aortic valve function in hypercholesterolemic aortic stenosis-prone Ldlr (-/-) Apob (100/100) mice.

A novel polymer-coated nanoparticle (NP) for urothelium penetration and drug delivery

e15543

Background: Up to 40% of patients with non-invasive bladder cancer (BC) will develop invasive disease progression despite locally-directed therapy. Overcoming the urothelial barrier is a challenge for intravesical drug delivery. We designed a biodegradable poly(lactide-co-glycolide) (PLGA) NP coated with a novel cell penetrating polymer, poly (guanidinium oxanorbornene) (PGON) for testing against BC in vitro and in vivo. We chose to deliver the HDAC inhibitor belinostat (bel) for its BC cell cytotoxicity and inhibition of invasion & migration pathways; key mechanisms that enable progression of BC. Methods: Fluorophore (C6) or bel was encapsulated in PLGA using an oil/water nanoemulsion method, and surface coated with PGON, and then characterized for morphology, size, and loading. BC cell lines UM-UC-3 and T24 were treated with belinostat or NP-bel-PGON vs controls for assessment of cytotoxicity and acetyl-H4 histone expression over time. In vivo murine bladder and ex vivo human ureter were treated with NP-C6-PGON, and compared to NPs coated with chitosan or PEG for urothelial penetration using FACS analysis, tissue extraction, and fluorescence microscopy. UM-UC-3 murine flank xenografts were treated locally biweekly with NP-bel-PGON or controls and assessed for tumor size and acetyl-H4 expression. Results: C6 extraction of intravesically treated mouse bladder and ex-vivo human ureter showed uptake improved ten-fold in NP-C6-PGON compared to other NPs and corroborated by fluorescent microscopy. In vitro, NP-bel-PGON and bel had similar IC50 of ~2.0 μM in UM-UC-3 & T24 lines, and no effect from PGON. Significantly, the NP-bel-PGON treated groups retained 30% of max H4 hyperacetylation whereas bel groups declined to basal at 12hr post wash, which supports a mechanism of intracellular NP release and activity. In vivo, xenografts treated with NP-bel-PGON showed tumor volume reduced 70% and had 2.5 fold higher intratumoral acetyl-H4 expression compared to vehicle three days post final treatment. Conclusions: NP-bel-PGON penetrates the urothelium, is taken up by BC cells, sustains HDAC inhibition, and causes tumor regression. These data demonstrate the potential for NP-bel-PGON as an intravesical nanotherapy of BC.

CD14 directs adventitial macrophage precursor recruitment: role in early abdominal aortic aneurysm formation

Background

Recruitment of macrophage precursors to the adventitia plays a key role in the pathogenesis of abdominal aortic aneurysms (AAAs), but molecular mechanisms remain undefined. The innate immune signaling molecule CD14 was reported to be upregulated in adventitial macrophages in a murine model of AAA and in monocytes cocultured with aortic adventitial fibroblasts (AoAf) in vitro, concurrent with increased interleukin‐6 (IL‐6) expression. We hypothesized that CD14 plays a crucial role in adventitial macrophage precursor recruitment early during AAA formation.

Methods and Results

CD14^−/− mice were resistant to AAA formation induced by 2 different AAA induction models: aortic elastase infusion and systemic angiotensin II (AngII) infusion. CD14 gene deletion led to reduced aortic macrophage infiltration and diminished elastin degradation. Adventitial monocyte binding to AngII‐infused aorta in vitro was dependent on CD14, and incubation of human acute monocytic leukemia cell line‐1 (THP‐1) monocytes with IL‐6 or conditioned medium from perivascular adipose tissue (PVAT) upregulated CD14 expression. Conditioned medium from AoAf and PVAT induced CD14‐dependent monocyte chemotaxis, which was potentiated by IL‐6. CD14 expression in aorta and plasma CD14 levels were increased in AAA patients compared with controls.

Conclusions

These findings link CD14 innate immune signaling via a novel IL‐6 amplification loop to adventitial macrophage precursor recruitment in the pathogenesis of AAA.

Brg1 determines urothelial cell fate during ureter development

Developing and adult ureters express the epigenetic regulator Brg1, but the role of Brg1 in ureter development is not well understood. We conditionally ablated Brg1 in the developing ureter using Hoxb7-Cre and found that Brg1 expression is upstream of p63, Pparγ, and sonic hedgehog (Shh) expression in the ureteral epithelium. In addition, epithelial stratification in the basal cells required Brg1-dependent p63 expression, whereas terminal differentiation of the umbrella cells required Brg1-dependent Pparγ expression. Furthermore, the loss of ureteric Brg1 resulted in failure of Shh expression, which correlated with reduced smooth muscle cell development and hydroureter. Taken together, we conclude that Brg1 expression unifies three aspects of ureter development: maintenance of the basal cell population, guidance for terminal differentiation of urothelial cells, and proper investment of ureteral smooth muscle cells.

Diabetes increases mortality after myocardial infarction by oxidizing CaMKII

Diabetes increases oxidant stress and doubles the risk of dying after myocardial infarction, but the mechanisms underlying increased mortality are unknown. Mice with streptozotocin-induced diabetes developed profound heart rate slowing and doubled mortality compared with controls after myocardial infarction. Oxidized Ca(2+)/calmodulin-dependent protein kinase II (ox-CaMKII) was significantly increased in pacemaker tissues from diabetic patients compared with that in nondiabetic patients after myocardial infarction. Streptozotocin-treated mice had increased pacemaker cell ox-CaMKII and apoptosis, which were further enhanced by myocardial infarction. We developed a knockin mouse model of oxidation-resistant CaMKIIδ (MM-VV), the isoform associated with cardiovascular disease. Streptozotocin-treated MM-VV mice and WT mice infused with MitoTEMPO, a mitochondrial targeted antioxidant, expressed significantly less ox-CaMKII, exhibited increased pacemaker cell survival, maintained normal heart rates, and were resistant to diabetes-attributable mortality after myocardial infarction. Our findings suggest that activation of a mitochondrial/ox-CaMKII pathway contributes to increased sudden death in diabetic patients after myocardial infarction.

G-protein inactivator RGS6 mediates myocardial cell apoptosis and cardiomyopathy caused by doxorubicin

Clinical use of the widely used chemotherapeutic agent doxorubicin is limited by life-threatening cardiotoxicity. The mechanisms underlying doxorubicin-induced cardiomyopathy and heart failure remain unclear but are thought to involve p53-mediated myocardial cell apoptosis. The tripartite G-protein inactivating protein RGS6 has been implicated in reactive oxygen species (ROS) generation, ATM/p53 activation, and apoptosis in doxorubicin-treated cells. Thus, we hypothesized that RGS6, the expression of which is enriched in cardiac tissue, might also be responsible for the pathologic effects of doxorubicin treatment in heart. In this study, we show that RGS6 expression is induced strongly by doxorubicin in the ventricles of mice and isolated ventricular myocytes via a posttranscriptional mechanism. While doxorubicin-treated wild-type (WT) mice manifested severe left ventricular dysfunction, loss of heart and body mass, along with decreased survival 5 days after doxorubicin administration, mice lacking RGS6 were completely protected against these pathogenic responses. Activation of ATM/p53 apoptosis signaling by doxorubicin in ventricles of WT mice was also absent in their RGS6(-/-) counterparts. Doxorubicin-induced ROS generation was dramatically impaired in both the ventricles and ventricular myocytes isolated from RGS6(-/-) mice, and the apoptotic response to doxorubicin in ventricular myocytes required RGS6-dependent ROS production. These results identify RGS6 as an essential mediator of the pathogenic responses to doxorubicin in heart, and they argue that RGS6 inhibition offers a rational means to circumvent doxorubicin cardiotoxicity in human patients with cancer.

Genetic inhibition of Na+-Ca2+ exchanger current disables fight or flight sinoatrial node activity without affecting resting heart rate

RATIONALE

The sodium-calcium exchanger 1 (NCX1) is predominantly expressed in the heart and is implicated in controlling automaticity in isolated sinoatrial node (SAN) pacemaker cells, but the potential role of NCX1 in determining heart rate in vivo is unknown.

OBJECTIVE

To determine the role of Ncx1 in heart rate.

METHODS AND RESULTS

We used global myocardial and SAN-targeted conditional Ncx1 knockout (Ncx1(-/-)) mice to measure the effect of the NCX current on pacemaking activity in vivo, ex vivo, and in isolated SAN cells. We induced conditional Ncx1(-/-) using a Cre/loxP system. Unexpectedly, in vivo and ex vivo hearts and isolated SAN cells showed that basal rates in Ncx1(-/-) (retaining ≈20% of control level NCX current) and control mice were similar, suggesting that physiological NCX1 expression is not required for determining resting heart rate. However, increases in heart rate and SAN cell automaticity in response to isoproterenol or the dihydropyridine Ca(2+) channel agonist BayK8644 were significantly blunted or eliminated in Ncx1(-/-) mice, indicating that NCX1 is important for fight or flight heart rate responses. In contrast, the pacemaker current and L-type Ca(2+) currents were equivalent in control and Ncx1(-/-) SAN cells under resting and isoproterenol-stimulated conditions. Ivabradine, a pacemaker current antagonist with clinical efficacy, reduced basal SAN cell automaticity similarly in control and Ncx1(-/-) mice. However, ivabradine decreased automaticity in SAN cells isolated from Ncx1(-/-) mice more effectively than in control SAN cells after isoproterenol, suggesting that the importance of NCX current in fight or flight rate increases is enhanced after pacemaker current inhibition.

CONCLUSIONS

Physiological Ncx1 expression is required for increasing sinus rates in vivo, ex vivo, and in isolated SAN cells, but not for maintaining resting heart rate.

Pioglitazone attenuates valvular calcification induced by hypercholesterolemia

OBJECTIVE

Development of calcific aortic valve stenosis involves multiple signaling pathways, which may be modulated by peroxisome proliferator-activated receptor-γ). This study tested the hypothesis that pioglitazone (Pio), a ligand for peroxisome proliferator-activated receptor-γ, inhibits calcification of the aortic valve in hypercholesteremic mice.

METHODS AND RESULTS

Low density lipoprotein receptor(-/-)/apolipoprotein B(100/100) mice were fed a Western-type diet with or without Pio (20 mg/kg per day) for 6 months. Pio attenuated lipid deposition and calcification in the aortic valve, but not aorta. In the aortic valve, Pio reduced levels of active caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Valve function (echocardiography) was significantly improved by Pio. To determine whether changes in gene expression are associated with differential effects of Pio on aortic valves versus aorta, Reversa mice were fed Western diet with or without Pio for 2 months. Several procalcific genes were increased by Western diet, and the increase was attenuated by Pio, in aortic valve, but not aorta.

CONCLUSIONS

Pio attenuates lipid deposition, calcification, and apoptosis in aortic valves of hypercholesterolemic mice, improves aortic valve function, and exhibits preferential effects on aortic valves versus aorta. We suggest that Pio protects against calcific aortic valve stenosis, and Pio or other peroxisome proliferator-activated receptor-γ ligands may be useful for early intervention to prevent or slow stenosis of aortic valves.