Deficiency of different nitric oxide synthase isoforms activates divergent transcriptional programs in cardiac hypertrophy

Dronedarone produces early regression of myocardial remodelling in structural heart disease

Background and aims

Left ventricular hypertrophy (LVH) in hypertension is associated with a greater risk of sustained supraventricular/atrial arrhythmias. Dronedarone is an antiarrhythmic agent that was recently approved for the treatment of atrial fibrillation. However, its effect on early regression of LVH has not been reported. We tested the hypothesis that short-term administration of dronedarone induces early regression of LVH in spontaneously hypertensive rats (SHR_s).

Methods

Ten-month-old male SHR_s were randomly assigned to an intervention group (SHR-D), where animals received dronedarone treatment (100 mg/kg) for a period of 14 days, or to a control group (SHR) where rats were given vehicle. A third group with normotensive control rats (WKY) was also added. At the end of the treatment with dronedarone we studied the cardiac anatomy and function in all the rats using transthoracic echocardiogram, cardiac metabolism using the PET/CT study (2-deoxy-2[18F]fluoro-D-glucose) and cardiac structure by histological analysis of myocyte size and collagen content.

Results

The hypertensive vehicle treated SHR rats developed the classic cardiac pattern of hypertensive cardiomyopathy as expected for the experimental model, with increases in left ventricular wall thickness, a metabolic shift towards an increase in glucose use and increases in myocyte and collagen content. However, the SHR-D rats showed statistically significant lower values in comparison to SHR group for septal wall thickness, posterior wall thickness, ventricular mass, glucose myocardial uptake, size of left ventricular cardiomyocytes and collagen content. All these values obtained in SHR-D rats were similar to the values measured in the normotensive WKY control group.

Conclusion

The results suggest by three alternative and complementary ways (analysis of anatomy and cardiac function, metabolism and histological structure) that dronedarone has the potential to reverse the LVH induced by arterial hypertension in the SHR model of compensated ventricular hypertrophy.

Does the ADMA/DDAH/NO pathway modulate early regression of left ventricular hypertrophy with esmolol?

Hypertensive left ventricular hypertrophy (LVH) is a maladaptive response to chronic pressure overload and a strong independent risk factor for cardiovascular disease. Regression of LVH is associated with improved prognosis. Regression of LVH with antihypertensive therapy (angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium channel blockers, and diuretics) has been reported, although only after long-term treatment. Asymmetrical dimethylarginine (ADMA), the most potent endogenous NO synthase inhibitor, is emerging as an important cardiovascular risk factor in patients with arterial hypertension and LVH, and dimethylarginine dimethylaminohydrolase (DDAH) is the mechanism that most frequently leads to accumulation of ADMA (plasma ADMA is cleared in small part by renal excretion, although the bulk of ADMA is degraded by DDAH). Left ventricular mass is strongly modulated by the NO system. As an important inhibitor of the bioavailability of NO, ADMA is an underlying mechanism of LVH. Beta-blockers can induce regression of LVH and reduced plasma ADMA levels. Oxidative stress is increased in patients with LVH, and this in turn increases generation of ADMA. In a previous preclinical study of spontaneously hypertensive rats, we found that short-term treatment (48 h) with esmolol reverses early LVH, increases the bioavailability of NO, and improves antioxidant status in plasma. Therefore, we propose that the ADMA/DDAH/NO pathway could modulate early regression of LVH with esmolol.

Nitric oxide synthases, S-nitrosylation and cardiovascular health: from molecular mechanisms to therapeutic opportunities (review)

The understanding of nitric oxide (NO) signaling has grown substantially since the identification of endothelial derived relaxing factor (EDRF). NO has emerged as a ubiquitous signaling molecule involved in diverse physiological and pathological processes. Perhaps the most significant function, independent of EDRF, is that of NO signaling mediated locally in signaling modules rather than relying upon diffusion. In this context, NO modulates protein function via direct post-translational modification of cysteine residues. This review explores NO signaling and related reactive nitrogen species involved in the regulation of the cardiovascular system. A critical concept in the understanding of NO signaling is that of the nitroso-redox balance. Reactive nitrogen species bioactivity is fundamentally linked to the production of reactive oxygen species. This interaction occurs at the chemical, enzymatic and signaling effector levels. Furthermore, the nitroso-redox equilibrium is in a delicate balance, involving the cross-talk between NO and oxygen-derived species signaling systems, including NADPH oxidases and xanthine oxidase.

Modulation of stretch-induced myocyte remodeling and gene expression by nitric oxide: a novel role for lipoma preferred partner in myofibrillogenesis

Prolonged hemodynamic load as a result of hypertension eventually leads to maladaptive cardiac adaptation and heart failure. The signaling pathways that underlie these changes are still poorly understood. The adaptive response to mechanical load is mediated by mechanosensors that convert the mechanical stimuli into a biological response. We examined the effect of cyclic mechanical stretch on myocyte adaptation using neonatal rat ventricular myocytes with 10% (adaptive) or 20% (maladaptive) maximum strain at 1 Hz for 48 h to mimic in vivo mechanical stress. Cells were also treated with and without nitro-L-arginine methyl ester (L-NAME), a general nitric oxide synthase (NOS) inhibitor to suppress NO production. Maladaptive 20% mechanical stretch led to a significant loss of intact sarcomeres that were rescued by L-NAME (P < 0.05; n ≥ 5 cultures). We hypothesized that the mechanism was through NO-induced alteration of myocyte gene expression. L-NAME upregulated the mechanosensing proteins muscle LIM protein (MLP; by 100%; P < 0.05; n = 5 cultures) and lipoma preferred partner (LPP), a novel cardiac protein (by 80%; P < 0.05; n = 4 cultures). L-NAME also significantly altered the subcellular localization of LPP and MLP in a manner that favored growth and adaptation. These findings suggest that NO participates in stretch-mediated adaptation. The use of isoform selective NOS inhibitors indicated a complex interaction between inducible NOS and neuronal NOS isoforms regulate gene expression. LPP knockdown by small intefering RNA led to formation of α-actinin aggregates and Z bodies showing that myofibrillogenesis was impaired. There was an upregulation of E3 ubiquitin ligase (MUL1) by 75% (P < 0.05; n = 5 cultures). This indicates that NO contributes to stretch-mediated adaptation via the upregulation of proteins associated with mechansensing and myofibrillogenesis, thereby presenting potential therapeutic targets during the progression of heart failure.

Nitric oxide synthase in post-ischaemic remodelling: new pathways and mechanisms

The three isoforms of nitric oxide synthase (NOS), spatially confined in specific intracellular compartments in cardiac cells, have distinct roles in the regulation of contractility in pathophysiological situations. Recently, evidence has emerged that implicates NOS in modulating myocardial remodelling during cardiac stress, including after ischaemic insults. As long as they remain in a coupled state the NOS mostly attenuate hypertrophic remodelling through both cGMP-dependent and independent mechanisms. We review the evidence provided from the phenotype of genetic mouse models as well as from in vitro cell experiments dissecting the signalling effectors involved in the NOS-mediated regulation that justify new therapeutic interventions on the NOS-cGMP axis to attenuate the development of heart failure.

Gene expression profiles of lung adenocarcinoma linked to histopathological grading and survival but not to EGF-R status: a microarray study

BACKGROUND

Several different gene expression signatures have been proposed to predict response to therapy and clinical outcome in lung adenocarcinoma. Herein, we investigate if elements of published gene sets can be reproduced in a small dataset, and how gene expression profiles based on limited sample size relate to clinical parameters including histopathological grade and EGFR protein expression.

METHODS

Affymetrix Human Genome U133A platform was used to obtain gene expression profiles of 28 pathologically and clinically annotated adenocarcinomas of the lung. EGFR status was determined by fluorescent in situ hybridization and immunohistochemistry.

RESULTS

Using unsupervised clustering algorithms, the predominant gene expression signatures correlated with the histopathological grade but not with EGFR protein expression as detected by immunohistochemistry. In a supervised analysis, the signature of high grade tumors but not of EGFR overexpressing cases showed significant enrichment of gene sets reflecting MAPK activation and other potential signaling cascades downstream of EGFR. Out of four different previously published gene sets that had been linked to prognosis, three showed enrichment in the gene expression signature associated with favorable prognosis.

CONCLUSIONS

In this dataset, histopathological tumor grades but not EGFR status were associated with dominant gene expression signatures and gene set enrichment reflecting oncogenic pathway activation, suggesting that high immunohistochemistry EGFR scores may not necessarily be linked to downstream effects that cause major changes in gene expression patterns. Published gene sets showed association with patient survival; however, the small sample size of this study limited the options for a comprehensive validation of previously reported prognostic gene expression signatures.

alpha1G-dependent T-type Ca2+ current antagonizes cardiac hypertrophy through a NOS3-dependent mechanism in mice

In noncontractile cells, increases in intracellular Ca2+ concentration serve as a second messenger to signal proliferation, differentiation, metabolism, motility, and cell death. Many of these Ca2+-dependent regulatory processes operate in cardiomyocytes, although it remains unclear how Ca2+ serves as a second messenger given the high Ca2+ concentrations that control contraction. T-type Ca2+ channels are reexpressed in adult ventricular myocytes during pathologic hypertrophy, although their physiologic function remains unknown. Here we generated cardiac-specific transgenic mice with inducible expression of alpha1G, which generates Cav3.1 current, to investigate whether this type of Ca2+ influx mechanism regulates the cardiac hypertrophic response. Unexpectedly, alpha1G transgenic mice showed no cardiac pathology despite large increases in Ca2+ influx, and they were even partially resistant to pressure overload-, isoproterenol-, and exercise-induced cardiac hypertrophy. Conversely, alpha1G-/- mice displayed enhanced hypertrophic responses following pressure overload or isoproterenol infusion. Enhanced hypertrophy and disease in alpha1G-/- mice was rescued with the alpha1G transgene, demonstrating a myocyte-autonomous requirement of alpha1G for protection. Mechanistically, alpha1G interacted with NOS3, which augmented cGMP-dependent protein kinase type I activity in alpha1G transgenic hearts after pressure overload. Further, the anti-hypertrophic effect of alpha1G overexpression was abrogated by a NOS3 inhibitor and by crossing the mice onto the Nos3-/- background. Thus, cardiac alpha1G reexpression and its associated pool of T-type Ca2+ antagonize cardiac hypertrophy through a NOS3-dependent signaling mechanism.

Role of xanthine oxidoreductase in cardiac nitroso-redox imbalance

Emerging evidence supports the importance of nitroso-redox balance in the cardiovascular system. Xanthine oxidoreductase (XOR) is a major oxidative enzyme and increased XOR activity, leading to both increased production of reactive oxygen species and uric acid, is implicated in heart failure. Within the heart, XOR activity stimulates cardiomyocyte hypertrophy, apoptosis, and impairs matrix structure. The underpinnings of these derangements can be linked not solely to oxidative stress, but may also involve the process of nitroso-redox imbalance. In this regard, XOR interacts with nitric oxide signaling at numerous levels, including a direct protein-protein interaction with neuronal nitric oxide synthase (NOS1) in the sarcoplasmic reticulum. Deficiency or translocation of NOS1 away from this microdomain leads to increased activity of XOR, which in turn impairs excitation-contraction coupling and myofilament calcium sensitivity. There is a mounting abundance of preclinical data supporting beneficial effects of inhibiting XOR, but translation to the clinic continues to be incomplete. A growing understanding of XOR and its role in nitroso-redox imbalance has great potential to lead to improved pathophysiologic insights and possibly therapeutic advances.

The genetic contribution to heart rate and heart rate variability in quiescent mice

Recent studies have suggested a genetic component to heart rate (HR) and HR variability (HRV). However, a systematic examination of the genetic contribution to the variation in HR and HRV has not been performed. This study investigated the genetic contribution to HR and HRV using a wide range of inbred and recombinant inbred (RI) mouse strains. Electrocardiogram data were recorded from 30 strains of inbred mice and 29 RI strains. Significant differences in mean HR and total power (TP) HRV were identified between inbred strains and RI strains. Multiple significant differences within the strain sets in mean low-frequency (LF) and high-frequency (HF) power were also found. No statistically significant concordance was found between strain distribution patterns for HR and HRV phenotypes. Genomewide interval mapping identified a significant quantitative trait locus (QTL) for HR [LOD (likelihood of the odds) score = 3.763] on chromosome 6 [peak at 53.69 megabases (Mb); designated HR 1 (Hr1)]. Suggestive QTLs for TP were found on chromosomes 2, 4, 5, 6, and 14. A suggestive QTL for LF was found on chromosome 16; for HF, we found one significant QTL on chromosome 5 (LOD score = 3.107) [peak at 53.56 Mb; designated HRV-high-frequency 1 (Hrvhf1)] and three suggestive QTLs on chromosomes 2, 11 and 15. In conclusion, the results demonstrate a strong genetic component in the regulation of resting HR and HRV evidenced by the significant differences between strains. A lack of correlation between HR and HRV phenotypes in some inbred strains suggests that different sets of genes control the phenotypes. Furthermore, QTLs were found that will provide important insight to the genetic regulation of HR and HRV at rest.

Sympathetic control of heart rate in nNOS knockout mice

Inhibition of neuronal nitric oxide synthase (nNOS) in cardiac postganglionic sympathetic neurons leads to enhanced cardiac sympathetic responsiveness in normal animals, as well as in animal models of cardiovascular diseases. We used isolated atria from mice with selective genetic disruption of nNOS (nNOS(-/-)) and their wild-type littermates (WT) to investigate whether sympathetic heart rate (HR) responses were dependent on nNOS. Immunohistochemistry was initially used to determine the presence of nNOS in sympathetic [tyrosine hydroxylase (TH) immunoreactive] nerve terminals in the mouse sinoatrial node (SAN). After this, the effects of postganglionic sympathetic nerve stimulation (1-10 Hz) and bath-applied norepinephrine (NE; 10(-8)-10(-4) mol/l) on HR were examined in atria from nNOS(-/-) and WT mice. In the SAN region of WT mice, TH and nNOS immunoreactivity was virtually never colocalized in nerve fibers. nNOS(-/-) atria showed significantly reduced HR responses to sympathetic nerve activation and NE (P < 0.05). Similarly, the positive chronotropic response to the adenylate cyclase activator forskolin (10(-7)-10(-5) mol/l) was attenuated in nNOS(-/-) atria (P < 0.05). Constitutive NOS inhibition with L-nitroarginine (0.1 mmol/l) did not affect the sympathetic HR responses in nNOS(-/-) and WT atria. The paucity of nNOS in the sympathetic innervation of the mouse SAN, in addition to the attenuated HR responses to neuronal and applied NE, indicates that presynaptic sympathetic neuronal NO does not modulate neuronal NE release and SAN pacemaking in this species. It appears that genetic deletion of nNOS results in the inhibition of adrenergic-adenylate cyclase signaling within SAN myocytes.

Leptin signaling and obesity: cardiovascular consequences

Leptin, among the best known hormone markers for obesity, exerts pleiotropic actions on multiple organ systems. In this review, we summarize major leptin signaling pathways, namely Janus-activated kinase/signal transducers and activators of transcription and mitogen-activated protein kinase, including possible mechanisms of leptin resistance in obesity. The effects of leptin on the cardiovascular system are discussed in detail, including its contributions to hypertension, atherosclerosis, depressed myocardial contractile function, fatty acid metabolism, hypertrophic remodeling, and reduction of ischemic/reperfusion injury. The overall goal is to summarize current understanding of how altered leptin signaling in obesity contributes to obesity-related cardiovascular disease.

Characterization of myocardial hypertrophy in prehypertensive spontaneously hypertensive rats: interaction between adrenergic and nitrosative pathways

OBJECTIVE AND METHODS

Left ventricular hypertrophy in human and experimental hypertension is not always associated with pressure overload but seems to precede an increase in blood pressure. In this study, performed in male 5-week-old prehypertensive spontaneously hypertensive rats (SHR; n = 65) and age-matched Wistar-Kyoto rats (n = 56), the relationship between myocardial structure and activation of the adrenergic and nitric oxide systems was evaluated.

RESULTS

Body weight, blood pressure and heart rate were similar in both groups. A higher left ventricle/body weight ratio was found in SHR, as a result of greater mononuclear (+47%) and binuclear (+43%) myocyte volumes, without changes in interstitial collagen. Both adrenergic and nitric oxide pathways were activated in SHR, as expressed by higher myocardial norepinephrine content, tyrosine hydroxylase activity, myocardial nitric oxide synthase 3 expression and protein nitration, indicating greater peroxynitrite (ONOO) generation from nitric oxide and superoxide. No difference was measured in nitric oxide synthase 1 expression, whereas nitric oxide synthase 2 was undetectable. A positive correlation between myocardial tyrosine hydroxylase activity and protein nitration was observed in SHR (r = 0.328; P < 0.01). Early treatment with a superoxide dismutase mimetic, 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl, from the third to the fifth week of age, reduced ONOO generation, protein nitration and sympathetic activation in SHR without changes in myocardial structure.

CONCLUSION

In prehypertensive SHR, left ventricular hypertrophy is associated with adrenergic and nitrosative imbalance. Early superoxide dismutase mimetic treatment in SHR effectively reduces higher myocardial ONOO generation, sympathetic activation, and heart rate without affecting the development of myocardial hypertrophy.

Relevance of nitric oxide for myocardial remodeling

Endogenous myocardial nitric oxide (NO) may modulate the transition from adaptive to maladaptive remodeling leading to heart failure. In rodent models of pressure overload or myocardial infarction, the three NO synthase (NOS) isoforms were shown to play a neutral, protective, or even adverse role in myocardial remodeling, depending on the quantity of NO produced, the location of each NOS and their regulators, the prevailing oxidant stress and resultant NO/oxidant balance, as well as NOS coupling/dimerization. Beside neuronal NOS and--in specific conditions--inducible NOS isoforms, endothelial NOS (eNOS) exerts cardioprotective effects on pressure-overload, ischemia/reperfusion, and myocardial infarction-induced myocardial remodeling, provided the enzyme remains in a coupled state. Besides its effects on excitation-contraction coupling in response to stretch, eNOS acts as an "endogenous beta-blocker" by restoring the sympathovagal balance, opposing excessive hypertrophy as well as promoting vasodilatation and neoangiogenesis, thereby contributing to tissue repair. As eNOS was also shown to mediate the beneficial effects of cardiovascular drugs commonly used in patients with heart failure, strategies to increase its expression and/or coupled catalytic activity in the myocardium offer new therapeutic avenues for the treatment of this disease.

Cardioprotection in females: a role for nitric oxide and altered gene expression

A number of epidemiological and animal studies have suggested a cardioprotective role for estrogen. This review will focus on the cardioprotective role of estrogen in ischemia-reperfusion injury. Estrogen binding to receptors can lead to altered gene expression and estrogen has been shown to induce expression of a number of genes that have been suggested to be important in cardioprotection. Estrogen is reported to increase expression of the plasma membrane glucose transporter GLUT4 and to increase carbohydrate metabolism. Estrogen has also been reported to increase mitochondrial biogenesis and to alter mitochondrial generation of reactive oxygen species. Estrogen results in upregulation of cardiac eNOS and nNOS, which have been shown previously to be important mediators of cardioprotection. Nitric oxide has been shown to result in S-nitrosylation and inhibition of the L-type calcium channel, thereby reducing calcium loading during ischemia. Nitric oxide has also been reported to inhibit complex I and inhibition of complex I has been reported to reduce activation of the mitochondrial permeability transition pore. Nitric oxide has been shown to result in activation of the mitochondrial K(ATP) channel, which has been shown to be involved in cardioprotection. Estrogen can also activate rapid non-genomic pathways that activate cardioprotective-signaling pathways such as the phosphatidylinositol-3-kinase (PI-3 kinase) pathway which has also been shown to initiate protection. Taken together, estrogen by genomic and non-genomic pathways can result in the initiation of a number of signaling pathways that enhance cardioprotection.

Chronic allopurinol administration ameliorates maladaptive alterations in Ca2+ cycling proteins and beta-adrenergic hyporesponsiveness in heart failure

Xanthine oxidase (XO) activity contributes to both abnormal excitation-contraction (EC) coupling and cardiac remodeling in heart failure (HF). beta-Adrenergic hyporesponsiveness and abnormalities in Ca(2+) cycling proteins are mechanistically linked features of the HF phenotype. Accordingly, we hypothesized that XO influences beta-adrenergic responsiveness and expression of genes whose products participate in deranged EC coupling. We measured inotropic (dP/dt(max)), lusitropic (tau), and vascular (elastance; E(a)) responses to beta-adrenergic (beta-AR) stimulation with dobutamine in conscious dogs administered allopurinol (100 mg po daily) or placebo during a 4-wk induction of pacing HF. With HF induction, the decreases in both baseline and dobutamine-stimulated inotropic responses were offset by allopurinol. Additionally, allopurinol converted a vasoconstrictor effect to dobutamine to a vasodilator response and enhanced both lusitropic and preload reducing effects. To assess molecular correlates for this phenotype, we measured myocardial sarcoplasmic reticulum Ca(2+)-ATPase 2a (SERCA), phospholamban (PLB), phosphorylated PLB (P-PLB), and Na(+)/Ca(2+) transporter (NCX) gene expression and protein. Although SERCA mRNA and protein concentrations did not change with HF, both PLB and NCX were upregulated (P < 0.05). Additionally, P-PLB and protein kinase A activity were greatly reduced. Allopurinol ameliorated all of these molecular alterations and preserved the PLB-to-SERCA ratio. Preventing maladaptive alterations of Ca(2+) cycling proteins represents a novel mechanism for XO inhibition-mediated preservation of cardiac function in HF, raising the possibility that anti-oxidant therapies for HF may ameliorate transcriptional changes associated with adverse cardiac remodeling and beta-adrenergic hyporesponsiveness.

Simvastatin attenuates vascular leak and inflammation in murine inflammatory lung injury

Therapies to limit the life-threatening vascular leak observed in patients with acute lung injury (ALI) are currently lacking. We explored the effect of simvastatin, a 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase inhibitor that mediates endothelial cell barrier protection in vitro, in a murine inflammatory model of ALI. C57BL/6J mice were treated with simvastatin (5 or 20 mg/kg body wt via intraperitoneal injection) 24 h before and again concomitantly with intratracheally administered LPS (2 μg/g body wt). Inflammatory indexes [bronchoalveolar lavage (BAL) myeloperoxidase activity and total neutrophil counts assessed at 24 h with histological confirmation] were markedly increased after LPS alone but significantly reduced in mice that also received simvastatin (20 mg/kg; ∼35–60% reduction). Simvastatin also decreased BAL albumin (∼50% reduction) and Evans blue albumin dye extravasation into lung tissue (100%) consistent with barrier protection. Finally, the sustained nature of simvastatin-mediated lung protection was assessed by analysis of simvastatin-induced gene expression (Affymetrix platform). LPS-mediated lung gene expression was significantly modulated by simvastatin within a number of gene ontologies (e.g., inflammation and immune response, NF-κB regulation) and with respect to individual genes implicated in the development or severity of ALI (e.g., IL-6, Toll-like receptor 4). Together, these findings confirm significant protection by simvastatin on LPS-induced lung vascular leak and inflammation and implicate a potential role for statins in the management of ALI.

NO/redox disequilibrium in the failing heart and cardiovascular system

There is growing evidence that the altered production and/or spatiotemporal distribution of reactive oxygen and nitrogen species creates oxidative and/or nitrosative stresses in the failing heart and vascular tree, which contribute to the abnormal cardiac and vascular phenotypes that characterize the failing cardiovascular system. These derangements at the integrated system level can be interpreted at the cellular and molecular levels in terms of adverse effects on signaling elements in the heart, vasculature, and blood that subserve cardiac and vascular homeostasis.

NO/redox disequilibrium in the failing heart and cardiovascular system

There is growing evidence that the altered production and/or spatiotemporal distribution of reactive oxygen and nitrogen species creates oxidative and/or nitrosative stresses in the failing heart and vascular tree, which contribute to the abnormal cardiac and vascular phenotypes that characterize the failing cardiovascular system. These derangements at the integrated system level can be interpreted at the cellular and molecular levels in terms of adverse effects on signaling elements in the heart, vasculature, and blood that subserve cardiac and vascular homeostasis.

Transcriptional basis for exercise limitation in male eNOS-knockout mice with age: heart failure and the fetal phenotype

Endothelium-derived nitric oxide (NO) is pivotal in regulating mitochondrial O(2) consumption (Vo(2)) and glucose uptake in mice. The aim of this study was to investigate the mechanism of age- and genotype-related exercise limitation in male endothelial NO synthase (eNOS)-knockout (KO, n = 16) and wild-type (WT, n = 19) mice. Treadmill testing was performed at 12, 14, 16, 18, and 21 mo of age. Vo(2), CO(2) production, respiratory exchange ratio, and maximal running distance were determined during treadmill running. There were good linear correlations for increase of speed with increase of Vo(2). The difference between KO and WT mice was not significant at 12 mo but was significant at 18 mo. Linear regression showed that KO mice consumed more O(2) at the same absolute and relative workloads, suggesting that Vo(2) was not inhibited by NO in KO mice. KO mice performed 30-50% less work than WT mice at each age (work = vertical distance x weight). In contrast to WT mice, the work performed by KO mice significantly decreased from 17 +/- 1.4 m.kg at 12 mo to 9.4 +/- 1.7 m.kg at 21 mo. Running distance was significantly decreased from 334 +/- 27 m at 12 mo to 178 +/- 38 m at 21 mo, and maximal Vo(2), CO(2) production, and respiratory exchange ratio per work unit were significantly higher in KO than in WT mice. Gene arrays showed evidence of a fetal phenotype in KO mice at 21 mo. In conclusion, age- and genotype-related exercise limitations in maximal work performed and maximal running distance in male eNOS-KO mice indicated that fetal phenotype and age were related to onset of heart failure.

Oxidant stress from nitric oxide synthase-3 uncoupling stimulates cardiac pathologic remodeling from chronic pressure load

Cardiac pressure load stimulates hypertrophy, often leading to chamber dilation and dysfunction. ROS contribute to this process. Here we show that uncoupling of nitric oxide synthase-3 (NOS3) plays a major role in pressure load-induced myocardial ROS and consequent chamber remodeling/hypertrophy. Chronic transverse aortic constriction (TAC; for 3 and 9 weeks) in control mice induced marked cardiac hypertrophy, dilation, and dysfunction. Mice lacking NOS3 displayed modest and concentric hypertrophy to TAC with preserved function. NOS3(-/-) TAC hearts developed less fibrosis, myocyte hypertrophy, and fetal gene re-expression (B-natriuretic peptide and alpha-skeletal actin). ROS, nitrotyrosine, and gelatinase (MMP-2 and MMP-9) zymogen activity markedly increased in control TAC, but not in NOS3(-/-) TAC, hearts. TAC induced NOS3 uncoupling in the heart, reflected by reduced NOS3 dimer and tetrahydrobiopterin (BH4), increased NOS3-dependent generation of ROS, and lowered Ca(2+)-dependent NOS activity. Cotreatment with BH4 prevented NOS3 uncoupling and inhibited ROS, resulting in concentric nondilated hypertrophy. Mice given the antioxidant tetrahydroneopterin as a control did not display changes in TAC response. Thus, pressure overload triggers NOS3 uncoupling as a prominent source of myocardial ROS that contribute to dilatory remodeling and cardiac dysfunction. Reversal of this process by BH4 suggests a potential treatment to ameliorate the pathophysiology of chronic pressure-induced hypertrophy.

Pre-B-cell colony-enhancing factor as a potential novel biomarker in acute lung injury

Although the pathogenic and genetic basis of acute lung injury (ALI) remains incompletely understood, the identification of novel ALI biomarkers holds promise for unique insights. Expression profiling in animal models of ALI (canine and murine) and human ALI detected significant expression of pre-B-cell colony-enhancing factor (PBEF), a gene not previously associated with lung pathophysiology. These results were validated by real-time polymerase chain reaction and immunohistochemistry studies, with PBEF protein levels significantly increased in both bronchoalveolar lavage fluid and serum of ALI models and in cytokine- or cyclic stretch-activated lung microvascular endothelium. We genotyped two PBEF single-nucleotide polymorphisms (SNPs) in a well characterized sample of white patients with sepsis-associated ALI, patients with severe sepsis, and healthy subjects and observed that carriers of the haplotype GC from SNPs T-1001G and C-1543T had a 7.7-fold higher risk of ALI (95% confidence interval 3.01-19.75, p < 0.001). The T variant from the SNP C-1543T resulted in a significant decrease in the transcription rate (1.8-fold; p < 0.01) by the reporter gene assay. Together, these results strongly indicate that PBEF is a potential novel biomarker in ALI and demonstrate the successful application of robust genomic technologies in the identification of candidate genes in complex lung disease.

The glomerulosclerosis of aging in females: contribution of the proinflammatory mesangial cell phenotype to macrophage infiltration

Age-associated renal changes may be an important cause of renal failure. We recently found that aged female B6 mice developed progressive glomerular lesions. This was associated with macrophage infiltration, a frequent finding in glomerulosclerosis. We used these mice as a model for studying the mechanisms of glomerular aging. We compared the gene expression profile of intact glomeruli from late postmenopausal (28-month-old) mice to that of intact glomeruli from premenopausal (5-month-old) mice. We found that inflammation-related genes, especially those expressed by activated macrophages, were up-regulated in the glomeruli of 28-month-old mice, a result correlating with the histological observation of glomerular macrophage infiltration. The mechanism for macrophage recruitment could have been stable phenotypic changes in mesangial cells because we found that mesangial cells isolated from 28-month-old mice expressed higher levels of RANTES and VCAM-1 than cells from 5-month-old mice. The elevated serum tumor necrosis factor (TNF)-alpha levels present in aged mice may contribute to increased RANTES and VCAM-1 expression in mesangial cells. Furthermore, cells from 28-month-old mice were more sensitive to TNF-alpha-induced RANTES and VCAM-1 up-regulation. The effect of TNF-alpha on RANTES expression was mediated by TNF receptor 1. Interestingly, mesangial cells isolated from 28-month-old mice had increased nuclear factor-kappaB transcriptional activity. Inhibition of nuclear factor-kappaB activity decreased baseline as well as TNF-alpha-induced RANTES and VCAM-1 expression in mesangial cells isolated from 28-month-old mice. Thus, phenotypic changes in mesangial cells may predispose them to inflammatory stimuli, such as TNF-alpha, which would contribute to glomerular macrophage infiltration and inflammatory lesions in aging.

Neuronal nitric oxide synthase negatively regulates xanthine oxidoreductase inhibition of cardiac excitation-contraction coupling

Although interactions between superoxide (O(2)(.-)) and nitric oxide underlie many physiologic and pathophysiologic processes, regulation of this crosstalk at the enzymatic level is poorly understood. Here, we demonstrate that xanthine oxidoreductase (XOR), a prototypic superoxide O(2)(.-) -producing enzyme, and neuronal nitric oxide synthase (NOS1) coimmunoprecipitate and colocalize in the sarcoplasmic reticulum of cardiac myocytes. Deficiency of NOS1 (but not endothelial NOS, NOS3) leads to profound increases in XOR-mediated O(2)(.-) production, which in turn depresses myocardial excitation-contraction coupling in a manner reversible by XOR inhibition with allopurinol. These data demonstrate a unique interaction between a nitric oxide and an O(2)(.-) -generating enzyme that accounts for crosstalk between these signaling pathways; these findings demonstrate a direct antioxidant mechanism for NOS1 and have pathophysiologic implications for the growing number of disease states in which increased XOR activity plays a role.

Regulation of gene expression by cyclic GMP

Cyclic GMP, produced in response to nitric oxide and natriuretic peptides, is a key regulator of vascular smooth muscle cell contractility, growth, and differentiation, and is implicated in opposing the pathophysiology of hypertension, cardiac hypertrophy, atherosclerosis, and vascular injury/restenosis. cGMP regulates gene expression both positively and negatively at transcriptional as well as at posttranscriptional levels. cGMP-regulated transcription factors include the cAMP-response element binding protein CREB, the serum response factor SRF, and the nuclear factor of activated T cells NF/AT. cGMP can regulate CREB directly, through phosphorylation by cGMP-dependent protein kinase, or indirectly, through activation of mitogen-activated protein kinase pathways; regulation of SRF and NF/AT by cGMP is indirect, through modulation of RhoA and calcineurin signaling, respectively. Downregulation of the RNA-binding protein HuR by cGMP leads to destabilization of guanylate cyclase mRNA, but this posttranscriptional mechanism may affect many more cGMP-regulated genes. In this review, we discuss the role of cGMP-regulated gene expression in (patho)physiological processes most relevant to the cardiovascular system, such as regulation of vascular tone, cardiac hypertrophy, phenotypic modulation of vascular smooth muscle cells, and regulation of cell proliferation and apoptosis.

Cytoskeletal activation and altered gene expression in endothelial barrier regulation by simvastatin

The statins, a class of HMG-CoA reductase inhibitors, directly affect multiple vascular processes via inhibition of geranylgeranylation, a covalent modification essential for Rho GTPase interaction with cell membrane-bound activators. We explored simvastatin effects on endothelial cell actomyosin contraction, gap formation, and barrier dysfunction produced by the edemagenic agent, thrombin. Human pulmonary artery endothelial cells exposed to prolonged simvastatin treatment (5 microM, 16 h) demonstrated significant reductions in thrombin-induced (1 U/ml) barrier dysfunction ( approximately 70% inhibition) with accelerated barrier recovery, as measured by transendothelial resistance. Furthermore, simvastatin attenuated basal and thrombin-stimulated (1 U/ml, 5 min) myosin light chain diphosphorylation and stress fiber formation while dramatically increasing peripheral immunostaining of actin and cortactin, an actin-binding protein, in conjunction with increased Rac GTPase activity. As both simvastatin-induced Rac activation and barrier protection were delayed (maximal after 16 h), we assessed the role of gene expression and protein translation in the simvastatin response. Simultaneous treatment with cycloheximide (10 microg/ml, 16 h) abolished simvastatin-mediated barrier protection. Robust alterations were noted in the expression of cytoskeletal proteins (caldesmon, integrin beta4), thrombin regulatory elements (PAR-1, thrombomodulin), and signaling genes (guanine nucleotide exchange factors) in response to simvastatin by microarray analysis. These novel observations have broad clinical implications in numerous vascular pathobiologies characterized by alterations in vascular integrity including inflammation, angiogenesis, and acute lung injury.

Nitric oxide activates diverse signaling pathways to regulate gene expression

Nitric oxide signaling is crucial for effecting long lasting changes in cells, including gene expression, cell cycle arrest, apoptosis, and differentiation. We have determined the temporal order of gene activation induced by NO in mammalian cells and have examined the signaling pathways that mediate the action of NO. Using microarrays to study the kinetics of gene activation by NO, we have determined that NO induces three distinct waves of gene activity. The first wave is induced within 30 min of exposure to NO and represents the primary gene targets of NO. It is followed by subsequent waves of gene activity that may reflect further cascades of NO-induced gene expression. We verified our results using quantitative real time PCR and further validated our conclusions about the effects of NO by using cytokines to induce endogenous NO production. We next applied pharmacological and genetic approaches to determine the signaling pathways that are used by NO to regulate gene expression. We used inhibitors of particular signaling pathways, as well as cells from animals with a deleted p53 gene, to define groups of genes that require phosphatidylinositol 3-kinase, protein kinase C, NF-kappaB, p53, or combinations thereof for activation by NO. Our results demonstrate that NO utilizes several independent signaling pathways to induce gene expression.