Human eNOS gene delivery attenuates cold-induced elevation of blood pressure in rats

Directed evolution of AAV accounting for long-term and enhanced transduction of cardiovascular endothelial cells in vivo

Cardiac endothelial cells (ECs) are important targets for cardiovascular gene therapy. However, the approach of stably transducing ECs in vivo using different vectors, including adeno-associated virus (AAV), remains unexamined. Regarding this unmet need, two AAV libraries from DNA shuffling and random peptide display were simultaneously screened in a transgenic mouse model. Cardiac ECs were isolated by cell sorting for salvage of EC-targeting AAV. Two AAV variants, i.e., EC71 and EC73, enriched in cardiac EC, were further characterized for their tissue tropism. Both of them demonstrated remarkably enhanced transduction of cardiac ECs and reduced infection of liver ECs in comparison to natural AAVs after intravenous injection. Significantly, persistent transgene expression was maintained in mouse cardiac ECs in vivo for at least 4 months. The EC71 vector was selected for delivery of the endothelial nitric oxide synthase (eNOS) gene into cardiac ECs in a mouse model of myocardial infarction. Enhanced eNOS activity was observed in the mouse heart and lung, which was correlated with partially improved cardiac function. Taken together, two AAV capsids were evolved with more efficient transduction in cardiovascular endothelium in vivo, but their endothelial tropism might need to be further optimized for practical application to cardiac gene therapy.

MicroRNA 379 Regulates Klotho Deficiency-Induced Cardiomyocyte Apoptosis Via Repression of Smurf1

[Figure: see text].

Dysregulation of nitric oxide synthases during early and late pathophysiological conditions of diabetes mellitus leads to amassing of microvascular impedement

Diabetes is a major killer worldwide and its unprecedented rise poses a serious threat to mankind. According to recent estimation, 387 million people worldwide are affected from the disease with a prevalence rate of 8.3 and 46.3 % still remains undiagnosed. Important characteristics of diabetes are abnormalities of the physiological signalling functions of reactive oxygen species and reactive nitrogen species. Increased oxidative stress contributes to the activation of stress-sensitive intracellular signalling pathways and the development of gene products that trigger cellular damage and contribute to the vascular complications of diabetes. Growing evidence from studies into many diseases suggests that the pathogenesis of diabetes, obesity, cancer, ageing, inflammation, neurodegenerative disorders, hypertension, apoptosis, cardiovascular diseases, and heart failure are correlated with oxidative stress. This leads to cell metabolism and cell-cell homeostasis to be complexly dysregulated. This review focuses to investigate the status of oxidative stress, nitric oxide and reactive species in early and diabetes. Significance of nitric oxide synthases Evidences has accumulated indicating that the generation of reactive oxygen species (oxidative stress) may play an important role in the etiology of diabetic complications thus attention was given on the reactive oxygen and reactive nitrogen species and their potential role in pathogenesis. Additionally, the therapeutic advances in diabetes management are included. Nanotechnology, statins and stem cell technology are some techniques which can be considered to have a possible future in the treatment sector of diabetes.

Klotho Deficiency Causes Heart Aging via Impairing the Nrf2-GR Pathway

RATIONALE

Cardiac aging is an important contributing factor for heart failure, which affects a large population but remains poorly understood.

OBJECTIVE

The purpose of this study is to investigate whether Klotho plays a role in cardiac aging.

METHODS AND RESULTS

Heart function declined in old mice (24 months), as evidenced by decreases in fractional shortening, ejection fraction, and cardiac output. Heart size and weight, cardiomyocyte size, and cardiac fibrosis were increased in old mice, indicating that aging causes cardiac hypertrophy and remodeling. Circulating Klotho levels were dramatically decreased in old mice, which prompted us to investigate whether the Klotho decline may cause heart aging. We found that Klotho gene mutation (KL-/-) largely decreased serum klotho levels and impaired heart function. Interestingly, supplement of exogenous secreted Klotho prevented heart failure, hypertrophy, and remodeling in both old mice and KL (-/-) mice. Secreted Klotho treatment inhibited excessive cardiac oxidative stress, senescence and apoptosis in old mice and KL (-/-) mice. Serum phosphate levels in KL (-/-) mice were kept in the normal range, suggesting that Klotho deficiency-induced heart aging is independent of phosphate metabolism. Mechanistically, Klotho deficiency suppressed GR (glutathione reductase) expression and activity in the heart via inhibition of transcription factor Nrf2 (nuclear factor-erythroid 2 p45-related factor 2). Furthermore, cardiac-specific overexpression of GR prevented excessive oxidative stress, apoptosis, and heart failure in both old and KL (-/-) mice.

CONCLUSIONS

Klotho deficiency causes cardiac aging via impairing the Nrf2-GR pathway. Supplement of exogenous secreted Klotho represents a promising therapeutic strategy for aging-associated cardiomyopathy and heart failure.

Identification of Hub Genes Associated with Hypertension and Their Interaction with miRNA Based on Weighted Gene Coexpression Network Analysis (WGCNA) Analysis

Background

Hypertension is one of the most widespread health conditions in the world, and the molecular mechanism of it is still unclear. In this study, we identified the hub genes (hub miRNA genes) associated with hypertension and explored the relationship between hypertension miRNA-gene by constructing a mRNA co-expression network and a miRNA co-expression network, which can help to reveal the mechanism and predict the prognosis of hypertension progression.

Material/Methods

Based on gene expression profile data of hypertensive samples from the Gene Expression Omnibus database, WGCNA was used to detect hypertension-related biomarkers and key mRNA and miRNA modules. Then, DAVID was used to perform gene-annotation enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) and miRPath were used for pathway analysis of mRNA and miRNAs genes.

Results

We identified 3 key modules relating to hypertension, 2 mRNA modules named M_saddlebrown and M_greenyellow and 1 miRNA module named M_salmon. In addition, 12 hub genes (RPL21, RPS28, LOC442727/PTGAP10, LOC100129599/RPS29P14, TBXAS1, FCER1G, CFP, FURIN, PECAM1, IGSF6, NCF1C, and LOC285296/UNC93B3) and 7 hub miRNAs (hsa-miR-1268a/b, hsa-miR-513c-3p, hsa-miR-4799-5p, hsa-miR-296-3p, hsa-miR-5195-5p, hsa-miR-219-2-3p, and hsa-miR-548d-5p) relating to hypertension were identified. HIF-1 signaling pathway and insulin signaling pathway were closely related to the 3 key modules. We also discovered 4 miRNAs (hsa-miR-548am-3p, hsa-miR-513c-3p, hsa-miR-182-5p, and hsa-miR-548d-5p) and 6 genes (IGF1R, GSK3B, FOXO1, PRKAR2B, HIF1A, and PIK3R1) were the core nodes in the hypertension-related miRNA-gene network, and hsa-miR-548am-3p was at the center of the network.

Conclusions

These findings will help improve the understanding of the pathogenesis of hypertension, and the discovered genes can serve as signatures for early diagnosis of hypertension.

AAV Delivery of Endothelin-1 shRNA Attenuates Cold-Induced Hypertension

Cold temperatures are associated with increased prevalence of hypertension. Cold exposure increases endothelin-1 (ET1) production. The purpose of this study is to determine whether upregulation of ET1 contributes to cold-induced hypertension (CIH). In vivo RNAi silencing of the ET1 gene was achieved by adeno-associated virus 2 (AAV2) delivery of ET1 short-hairpin small interfering RNA (ET1-shRNA). Four groups of male rats were used. Three groups were given AAV.ET1-shRNA, AAV.SC-shRNA (scrambled shRNA), and phosphate-buffered saline (PBS), respectively, before exposure to a moderately cold environment (6.7 ± 2°C), while the last group was given PBS and kept at room temperature (warm, 24 ± 2°C) and served as a control. We found that systolic blood pressure of the PBS-treated and SC-shRNA-treated groups increased significantly within 2 weeks of exposure to cold, reached a peak level (145 ± 4.8 mmHg) by 6 weeks, and remained elevated thereafter. By contrast, blood pressure of the ET1-shRNA-treated group did not increase, suggesting that silencing of ET1 prevented the development of CIH. Animals were euthanized after 10 weeks of exposure to cold. Cold exposure significantly increased the left ventricle (LV) surface area and LV weight in cold-exposed rats, suggesting LV hypertrophy. Superoxide production in the heart was increased by cold exposure. Interestingly, ET1-shRNA prevented cold-induced superoxide production and cardiac hypertrophy. ELISA assay indicated that ET1-shRNA abolished the cold-induced upregulation of ET1 levels, indicating effective silencing of ET1. In conclusion, upregulation of ET1 plays a critical role in the pathogenesis of CIH and cardiac hypertrophy. AAV delivery of ET1-shRNA is an effective therapeutic strategy for cold-related cardiovascular disease.

Inhibition of phosphodiesterase-1 attenuates cold-induced pulmonary hypertension

Chronic exposure to cold caused pulmonary arterial hypertension (cold-induced pulmonary hypertension [CIPH]) and increased phosphodiesterase-1C (PDE-1C) expression in pulmonary arteries (PAs) in rats. The purpose of this study is to investigate a hypothesis that inhibition of PDE-1 would decrease inflammatory infiltrates and superoxide production leading to attenuation of CIPH. Three groups of male rats were exposed to moderate cold (5±1°C) continuously, whereas 3 groups were maintained at room temperature (23.5±1°C, warm; 6 rats/group). After 8-week exposure to cold, 3 groups in each temperature condition received continuous intravenous infusion of 8-isobutyl-methylxanthine (8-IBMX) (PDE-1 inhibitor), apocynin (NADPH oxidase inhibitor) or vehicle, respectively, for 1 week. Cold exposure significantly increased right-ventricular systolic pressure compared with warm groups (33.8±3.2 versus 18.6±0.3 mm Hg), indicating that animals developed CIPH. Notably, treatment with 8-IBMX significantly attenuated the cold-induced increase in right ventricular pressure (23.5±1.8 mm Hg). Cold exposure also caused right-ventricular hypertrophy, whereas 8-IBMX reversed cold-induced right ventricular hypertrophy. Cold exposure increased PDE-1C protein expression, macrophage infiltration, NADPH oxidase activity, and superoxide production in PAs and resulted in PA remodeling. 8-IBMX abolished cold-induced upregulation of PDE-1C in PAs. Interestingly, inhibition of PDE-1 eliminated cold-induced macrophage infiltration, NADPH oxidase activation, and superoxide production in PAs and reversed PA remodeling. Inhibition of NADPH oxidase by apocynin abolished cold-induced superoxide production and attenuated CIPH and PA remodeling. In conclusion, inhibition of PDE-1 attenuated CIPH and reversed cold-induced PA remodeling by suppressing macrophage infiltration and superoxide production, suggesting that upregulation of PDE-1C expression may be involved in the pathogenesis of CIPH.

Klotho gene delivery suppresses Nox2 expression and attenuates oxidative stress in rat aortic smooth muscle cells via the cAMP-PKA pathway

Klotho is a recently discovered anti-aging gene. The purpose of this study was to investigate whether klotho gene transfer attenuates superoxide production and oxidative stress in rat aorta smooth muscle (RASM) cells. RASM cells were transfected with AAV plasmids carrying mouse klotho full-length cDNA (mKL) or LacZ as a control. Klotho gene transfer increased klotho expression in RASM cells. Notably, klotho gene expression decreased Nox2 NADPH oxidase protein expression but did not affect Nox2 mRNA expression, suggesting that the inhibition may occur at the posttranscriptional level. Klotho gene transfer decreased intracellular superoxide production and oxidative stress in RASM cells. Klotho gene expression also significantly attenuated the angiotensin II (AngII)-induced superoxide production, oxidative damage, and apoptosis. Interestingly, klotho gene delivery dose dependently increased the intracellular cAMP level and PKA activity in RASM cells. Rp-cAMP, a competitive inhibitor of cAMP, abolished the klotho-induced increase in PKA activity, indicating that klotho activated PKA via cAMP. Notably, inhibition of cAMP-dependent PKA activity by RP-cAMP abolished klotho-induced inhibition of Nox2 protein expression, suggesting an important role of cAMP-dependent PKA in this process. This finding revealed a previously unidentified role of klotho in regulating Nox2 protein expression in RASM cells. Klotho not only downregulated Nox2 protein expression and intracellular superoxide production but also attenuated AngII-induced superoxide production, oxidative damage, and apoptosis. The klotho-induced suppression of Nox2 protein expression may be mediated by the cAMP-PKA pathway.

Klotho gene delivery suppresses Nox2 expression and attenuates oxidative stress in rat aortic smooth muscle cells via the cAMP-PKA pathway

Klotho is a recently discovered anti-aging gene. The purpose of this study was to investigate whether klotho gene transfer attenuates superoxide production and oxidative stress in rat aorta smooth muscle (RASM) cells. RASM cells were transfected with AAV plasmids carrying mouse klotho full-length cDNA (mKL) or LacZ as a control. Klotho gene transfer increased klotho expression in RASM cells. Notably, klotho gene expression decreased Nox2 NADPH oxidase protein expression but did not affect Nox2 mRNA expression, suggesting that the inhibition may occur at the posttranscriptional level. Klotho gene transfer decreased intracellular superoxide production and oxidative stress in RASM cells. Klotho gene expression also significantly attenuated the angiotensin II (AngII)-induced superoxide production, oxidative damage, and apoptosis. Interestingly, klotho gene delivery dose dependently increased the intracellular cAMP level and PKA activity in RASM cells. Rp-cAMP, a competitive inhibitor of cAMP, abolished the klotho-induced increase in PKA activity, indicating that klotho activated PKA via cAMP. Notably, inhibition of cAMP-dependent PKA activity by RP-cAMP abolished klotho-induced inhibition of Nox2 protein expression, suggesting an important role of cAMP-dependent PKA in this process. This finding revealed a previously unidentified role of klotho in regulating Nox2 protein expression in RASM cells. Klotho not only downregulated Nox2 protein expression and intracellular superoxide production but also attenuated AngII-induced superoxide production, oxidative damage, and apoptosis. The klotho-induced suppression of Nox2 protein expression may be mediated by the cAMP-PKA pathway.

eNOS gene delivery prevents hypertension and reduces renal failure and injury in rats with reduced renal mass

BACKGROUND

Impaired nitric oxide (NO) release in chronic renal failure has been implicated in the pathogenesis of hypertension and the progression of renal insufficiency. We investigated whether gene delivery of the endothelial NO synthase (eNOS) improves NO release and reduces blood pressure and renal failure and injury in rats with reduced renal mass.

METHODS

Renal failure was induced by renal artery branches ligation. Two weeks later, rats with renal failure were divided into three groups and received an intravenous injection of the vehicle or the adenovirus that expresses eNOS or β-galactosidase (β-gal). Systolic blood pressure, renal parameters and histopathology were assessed at Week 4 after gene delivery.

RESULTS

At the end of the study, systolic blood pressures, serum creatinine, proteinuria, urinary endothelin-1 (ET-1) excretion and renal cortex ET-1 levels were increased, whereas plasma and urine NO(2)/NO(3) were reduced in renal failure rats as compared to normal controls. Renal injury comprised blood vessel media hypertrophy, focal and segmental glomerular sclerosis, tubular atrophy and interstitial fibrosis. Gene delivery of eNOS, but not β-gal, prevented an increase in systolic blood pressure and proteinuria, and a reduction in plasma and urine NO(2)/NO(3). eNOS gene delivery also reduced a rise in serum creatinine, urinary ET-1 excretion and renal cortex ET-1 levels, and the renal vascular, glomerular and tubular injury.

CONCLUSION

This study indicates that eNOS gene delivery in rats with renal failure improves NO release, which likely prevents the aggravation of hypertension and slows down the progression of renal failure and injury.

Thyroid hormone induces artery smooth muscle cell proliferation: discovery of a new TRalpha1-Nox1 pathway

Thyroid hormone (T3) can stimulate protein synthesis and cell growth. NOX1 is a mitogenic oxidase. The aim of this study was to test a novel hypothesis that T3 induces artery smooth muscle cell proliferation by up-regulating NOX1. Immunofluoresence confocal microscopy was used to visualize the sub-cellular localization of NOX1 and TRα1 in rat aorta smooth muscle (RASM) cells. Optical sectioning showed that TRα1 and NOX1 co-localized around the nucleus. T3 promoted RASM cell proliferation as determined by the fact that T3 significantly increased the number of cytokinesis cells, proliferating cellular nuclear antigen (PCNA) and smooth muscle α-actin (SM α-actin). T3 increased NOX1 expression at both the transcription (mRNA) and translation (protein) levels as evaluated by RT-PCR and Western blot, respectively. T3 also significantly increased the intracellular ROS production based on the oxidation of 2’,7’-dichlorodihydrofluoresein (H₂DCF) to a fluorescent 2’,7’-dichlorofluoresein (DCF). RNAi silence of TRα1 or NOX1 abolished T3-induced intracellular ROS generation and PCNA and SM α-actin expression, indicating that TRα1 and NOX1 mediated T3-induced RASM cell proliferation. Notably, RNAi silence of TRα1 blocked the T3-induced increase in NOX1 expression, whereas silence of NOX1 did not affect TRα1 expression, disclosing a new pathway, i.e. T3-TRα1-NOX1-cell proliferation. TRα1 and NOX1 co-localized around the nucleus. T3 induced RASM cell proliferation by up-regulating NOX1 in a TRα1-dependent manner.

The association of remotely-sensed outdoor temperature with blood pressure levels in REGARDS: a cross-sectional study of a large, national cohort of African-American and white participants

BACKGROUND

Evidence is mounting regarding the clinically significant effect of temperature on blood pressure.

METHODS

In this cross-sectional study the authors obtained minimum and maximum temperatures and their respective previous week variances at the geographic locations of the self-reported residences of 26,018 participants from a national cohort of blacks and whites, aged 45+. Linear regression of data from 20,623 participants was used in final multivariable models to determine if these temperature measures were associated with levels of systolic or diastolic blood pressure, and whether these relations were modified by stroke-risk region, race, education, income, sex hypertensive medication status, or age.

RESULTS

After adjustment for confounders, same-day maximum temperatures 20 °F lower had significant associations with 1.4 mmHg (95% CI: 1.0, 1.9) higher systolic and 0.5 mmHg (95% CI: 0.3, 0.8) higher diastolic blood pressures. Same-day minimum temperatures 20 °F lower had a significant association with 0.7 mmHg (95% CI: 0.3, 1.0) higher systolic blood pressures but no significant association with diastolic blood pressure differences. Maximum and minimum previous-week temperature variabilities showed significant but weak relationships with blood pressures. Parameter estimates showed effect modification of negligible magnitude.

CONCLUSIONS

This study found significant associations between outdoor temperature and blood pressure levels, which remained after adjustment for various confounders including season. This relationship showed negligible effect modification.

RNAi silencing of brain klotho potentiates cold-induced elevation of blood pressure via the endothelin pathway

Klotho is a recently identified antiaging gene. Brain endothelin-1 (ET1) is important in the regulation of blood pressure (BP). We hypothesized that silence of brain klotho potentiates cold-induced elevation of BP via the endothelin pathway. To silence brain klotho, we constructed adeno-associated virus (AAV) carrying rat klotho small interference hairpin RNA (KL-shRNA). AAV carrying ET1-shRNA was used to silence brain ET1. Scrambled shRNA was used as Control-shRNA. Three groups of male Sprague-Dawley rats (6 rats/group) received KL-shRNA, KL-shRNA plus ET1-shRNA, and Control-shRNA, respectively, via intracerebroventricular injection. BP was monitored daily using a telemetry system. All animals were exposed to a moderate cold environment (5°C) at 12 days after gene delivery. KL-shRNA significantly increased BP by 9 days of exposure to cold, while BP in the Control-shRNA group remained unchanged. ET1-shRNA abolished KL-shRNA-induced elevation of BP during cold exposure. Interestingly, KL-shRNA increased brain ET1 expression and plasma norepinephrine level, suggesting that silencing of brain klotho increased ET1 production and the sympathetic nervous activity. The KL-shRNA-induced increase in sympathetic nervous activity was mediated by ET1 because it could be abolished by silencing of ET1. These results demonstrated that silencing of brain klotho potentiated and expedited cold-induced elevation of BP by upregulation of ET1 and the subsequent activation of the sympathetic nervous system.

Cardiovascular responses to cold exposure

The prevalence of hypertension is increased in winter and in cold regions of the world. Cold temperatures make hypertension worse and trigger cardiovascular complications (stroke, myocardial infarction, heart failure, etc.). Chronic or intermittent exposure to cold causes hypertension and cardiac hypertrophy in animals. The purpose of this review is to provide the recent advances in the mechanistic investigation of cold-induced hypertension (CIH). Cold temperatures increase the activities of the sympathetic nervous system (SNS) and the renin-angiotensin system (RAS). The SNS initiates CIH via the RAS. Cold exposure suppresses the expression of eNOS and formation of NO, increases the production of endothelin-1 (ET-1), up-regulates ETA receptors, but down-regulates ETB receptors. The roles of these factors and their relations in CIH will be reviewed.

Cardiac sarcoplasmic reticulum Ca2+-ATPase: heat production and phospholamban alterations promoted by cold exposure and thyroid hormone

Short-term response to cold promotes a small but significant rise in serum T3 in euthyroid rabbits, where the heart is an important target of T3 action. In this work, we measured changes in sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a) and phospholamban (PLB) in hearts of hypo- and hyperthyroid rabbits and compared them with modifications induced by short- and long-term cold exposure. Short-term cold exposure promotes a small increase in T3 and, similar to hyperthyroidism, induces an increase of heart SERCA2a expression. The total PLB content does not change in hyperthyroidism, but short-term cold exposure promotes a significant decrease in total PLB and an increase in the ratio between phosphorylated and total PLB. The temperature of a given tissue depends on the balance between the heat provided by blood circulation and the rate of heat production by the tissue. In an attempt to evaluate the heat contribution of cardiac tissue, we measured mitochondrial respiration in permeabilized cardiac muscle and heat produced by cardiac sarcoplasmic reticulum (SR) during Ca2+ transport. We observed that there was an increase in oxygen consumption and heat production during Ca2+ transport by cardiac SR in both hyperthyroidism and short-term cold exposure. In contrast, both the mitochondrial respiration rate and heat derived from Ca2+ transport were decreased in hypothyroid rabbits. The heart changes in oxygen consumption, SERCA2a-PLB ratio, and Ca2+-ATPase activity detected during short-term cold exposure were abolished after cold adaptation. We hypothesize that the transient rise in serum T3 contributes to the short-term response to cold exposure.

Klotho gene delivery prevents the progression of spontaneous hypertension and renal damage

Klotho is a recently discovered antiaging gene. The objective of this study was to test the hypothesis that klotho gene delivery attenuates the progression of spontaneous hypertension and renal damage in spontaneous hypertensive rats (SHRs). An adeno-associated virus (AAV) carrying mouse klotho full-length cDNA (AAV.mKL) was constructed for in vivo expression of klotho. Four groups of male SHRs and 1 group of sex- and age-matched Wistar-Kyoto rats (5 rats per group) were used. Blood pressure was measured twice in all of the animals before gene delivery. Four groups of SHRs received an IV injection of AAV.mKL, AAV.LacZ, AAV.GFP, and PBS, respectively. The Wistar-Kyoto group received PBS and served as a control. AAV.mKL stopped the further increase in blood pressure in SHRs, whereas blood pressures continued to increase in other SHR groups. One single dose of AAV.mKL prevented the progression of spontaneous hypertension for at least 12 weeks (length of the study). Klotho expression and production were suppressed in SHRs, which were reverted by AAV.mKL. AAV.mKL increased plasma interleukin 10 levels but decreased Nox2 expression, NADPH oxidase activity, and superoxide production in kidneys and aortas in SHRs. AAV.mKL abolished renal tubular atrophy and dilation, tubular deposition of proteinaceous material, glomerular collapse, and collagen deposition seen in SHRs, indicating that klotho gene delivery attenuated renal damage. Therefore, the suppressed klotho expression may play a role in the progression of spontaneous hypertension and renal damage in SHRs. AAV delivery of klotho may offer a new approach for the long-term control of hypertension and for renoprotection.

RNAi inhibition of mineralocorticoid receptors prevents the development of cold-induced hypertension

The objective was to determine whether the mineralocorticoid receptor (MR) plays a role in the initiation and development of cold-induced hypertension (CIH) by testing the hypothesis that the RNA interference (RNAi) inhibition of the MR attenuates CIH. The recombinant adeno-associated virus (AAV) carrying a short-hairpin small-interference RNA for MR (MRshRNA) or a scrambled sequence (ControlshRNA) was constructed. Six groups of albino mice were used (6 mice/group). Three groups were exposed to cold (6.7°C), whereas the remaining three groups were kept at room temperature (RT; warm) as controls. In each temperature condition, three groups received an intravenous injection of MRshRNA, ControlshRNA, or virus-free PBS, respectively, before exposure to cold. The viral complexes (0.35 × 1011 particles/mouse, 0.5 ml) or PBS (0.5 ml) was delivered into the circulation via the tail vein. The blood pressure (BP) of the mice treated with ControlshRNA or PBS increased significantly during exposure to cold, whereas the BP of the cold-exposed MRshRNA-treated mice did not increase and remained at the level of the control group kept at RT. Thus AAV delivery of MRshRNA prevented the initiation of CIH. MRshRNA significantly attenuated cardiac and renal hypertrophy. MRshRNA decreased the cold-induced increase in MR protein expression to the control level in the hypothalamus, kidneys, and heart, indicating an effective prevention of the cold-induced upregulation of MR. RNAi inhibition of MR resulted in significant decreases in the plasma level of norepinephrine, plasma renin activity, and plasma level of aldosterone in cold-exposed mice. MR played a critical role in the initiation and development of CIH. AAV delivery of MRshRNA may serve as a new approach for the prevention of cold-induced hypertension.

Heart-specific inhibition of protooncogene c-myc attenuates cold-induced cardiac hypertrophy

The protooncogene c-myc is involved in the regulation of cell growth. Although increased c-Myc expression is found in hypertrophied hearts, the role of c-Myc in the development of cardiac hypertrophy (CH) has never been determined. The aim of this study was to test the effect of heart-specific inhibition of c-Myc expression on the development of cold-induced cardiac hypertrophy (CICH). We hypothesized that heart-specific inhibition of c-Myc expression attenuates CICH. We constructed c-Myc antisense (c-MycAS) plasmid and green fluorescent protein (GFP) plasmid driven by a heart-specific promoter, alpha-myosin heavy chain (MHC). The cell culture study indicated that c-MycAS can effectively inhibit c-Myc expression and that GFP can express in the rat heart cells. Four groups of rats were used to test the effect of in vivo inhibition of cardiac c-Myc expression on the development of CICH. Three groups received an intravenous injection of c-MycAS, GFP and buffer, respectively, at the beginning of exposure to moderate cold (6.7 degrees C), while the last group received buffer and was kept at room temperature (25 degrees C) to serve as a control. Blood pressure (BP) of the cold-exposed groups receiving buffer or GFP increased significantly, whereas BP of the c-MycAS group did not increase until 28 days after exposure to cold. Thus, c-MycAS delayed and attenuated cold-induced hypertension (CIH). The antihypertensive effect of c-MycAS was probably due to the decreased cardiac output. Magnetic resonance imaging (MRI) showed that the in vivo left ventricle wall thickness of cold-exposed rats was decreased significantly by c-MycAS. Consistently, the cold-induced increase in heart weight was attenuated by inhibition of cardiac c-Myc expression. The heart specificity of alpha-MHC promoter was confirmed by the selective inhibition of c-Myc expression in the heart and by the selective expression of both GFP mRNA and GFP protein in the heart. Heart-specific inhibition of c-Myc expression attenuated the development of CICH. The increased c-Myc expression may play a critical role in the pathogenesis of CICH. Thus, heart-specific inhibition of c-Myc expression may be a new and effective approach for the control of CH.

Reduced pulmonary vascular reactivity after cold exposure to acute hypoxia: a role of nitric oxide (NO)

Exposure to high altitude causes pulmonary hypertension and alterations in pulmonary vascular reactivity. Among the environmental factors, cold exposure has been suggested to be involved in the development of pulmonary hypertension. However, little information is available about pulmonary vascular reactivity after cold exposure. We examined whether cold exposure can cause changes in pulmonary vascular reactivity to acute hypoxia and the possible participation of endogenous nitric oxide. We measured mean systemic (Psa) and pulmonary artery pressures (Ppa) in conscious rats after 1-week cold exposure (3.5 +/- 1.0 degrees C). Subsequently, we investigated hypoxic pulmonary vasoconstriction (HPV) with and without endogenous NO inhibition using N(G)-nitro-L-arginine methyl ester (3 mg/kg) or 7-nitroindazole (1 mg/kg). Cold exposure for 1 week caused a small but significant increase in Ppa, but not in Psa. Neither Ppa nor Psa showed significant changes after both NO inhibitions in rats exposed to cold. However, cold exposure caused a blunted HPV and an increase in plasma nitrite-nitrate concentration compared with rats kept in a neutral environment (24.0 +/- 1.0 degrees C). In addition, NO inhibition by N(G)-nitro-L-arginine methyl ester partially restored the blunted HPV in rats exposed to cold, but not 7-nitroindazole, a selective inhibitor of neuronal NO synthase. We concluded that cold exposure alters pulmonary vascular reactivity to acute hypoxia, and augmented endothelial NO bioactivity plays a counterregulatory role in response to acute hypoxia during cold exposure in rats.

Effects of chronic cold exposure on the endothelin system

Cold temperatures have adverse effects on the human cardiovascular system. Endothelin (ET)-1 is a potent vasoconstrictor. We hypothesized that cold exposure increases ET-1 production and upregulates ET type A (ETA) receptors. The aim of this study was to determine the effect of cold exposure on regulation of the ET system. Four groups of rats (6–7 rats/group) were used: three groups were exposed to moderate cold (6.7 ± 2°C) for 1, 3, and 5 wk, respectively, and the remaining group was maintained at room temperature (25°C) and served as control. Cold exposure significantly increased ET-1 levels in the heart, mesenteric arteries, renal cortex, and renal medulla. Cold exposure increased ETA receptor protein expression in the heart and renal cortex. ET type B (ETB) receptor expression, however, was decreased significantly in the heart and renal medulla of cold-exposed rats. Cold exposure significantly increased the ratio of ETA to ETB receptors in the heart. An additional four groups of rats (3 rats/group) were used to localize changes in ETA and ETB receptors at 1, 3, and 5 wk of cold exposure. Immunohistochemical analysis showed an increase in ETA, but a decrease in ETB, receptor immunoreactivity in cardiomyocytes of cold-exposed rats. Increased ETA receptor immunoreactivity was also found in vascular smooth muscle cells of cold-exposed rats. Cold exposure increased ETA receptor immunoreactivity in tubule epithelial cells in the renal cortex but decreased ETB receptor immunoreactivity in tubule epithelial cells in the renal medulla. Therefore, cold exposure increased ET-1 production, upregulated ETA receptors, and downregulated ETB receptors.

AAV delivery of mineralocorticoid receptor shRNA prevents progression of cold-induced hypertension and attenuates renal damage

The aim of this study was to determine the effect of RNA interference inhibition of mineralocorticoid receptor (MR) on cold-induced hypertension (CIH) and renal damage. Recombinant adeno-associated virus (AAV) carrying short hairpin small interference (si)RNA for MR (AAV.MR-shRNA) was constructed and tested for the ability to inhibit renal MR and to control CIH. Three groups of rats with CIH received AAV.MR-shRNA (1.25 x 10(9) particles/rat, intravenous), AAV carrying scrambled shRNA (AAV.Control-shRNA) (1.25 x 10(9) particles/rat, intravenous) and phosphate buffer solution (PBS), respectively. All rats were kept in a cold chamber (6.7 degrees C) throughout the experiment. Adeno-associated virus delivery of MR-shRNA prevented progression of CIH. Blood pressure (BP) of the AAV.MR-shRNA-treated group did not increase and remained at 145+/-3 mm Hg, whereas BP of the AAV.Control-shRNA-treated and PBS-treated group increased to 167+/-4 and 161+/-3 mm Hg, respectively, at 3 weeks after gene delivery. Thus, the antihypertensive effect of a single injection of AAV.MR-shRNA lasted for at least 3 weeks (length of the study). Adeno-associated virus carrying short hairpin siRNA for MR significantly increased urinary sodium excretion and decreased proteinuria. It also decreased serum creatinine and blood urea nitrogen, suggesting enhanced renal function. Both Western blot and immunohistochemical analysis showed that MR expression was decreased significantly in the kidney in the AAV.MR-shRNA-treated rats, confirming that renal MR is effectively inhibited by AAV.MR-shRNA. Adeno-associated virus carrying short hairpin siRNA for MR also significantly attenuated renal hypertrophy. In addition, AAV delivery of MR-shRNA prevented atrophy and dilation of renal tubules and abolished tubular deposition of proteinaceous material seen in CIH rats.

CONCLUSIONS

(1) AAV delivery of MR-shRNA effectively silenced MR in vivo. (2) RNA interference inhibition of MR may open a new avenue for the long-term control of hypertension and renal damage.

Overview of recent advances in molecular cardiology

Molecular cardiology is a new and fast-growing area of cardiovascular medicine that aims to apply molecular biology techniques for the mechanistic investigation, diagnosis, prevention and treatment of cardiovascular disease. As an emerging discipline, it has changed conceptual thinking of cardiovascular development, disease etiology and pathophysiology. Although molecular cardiology is still at a very early stage, it has opened a promising avenue for understanding and controlling cardiovascular disease. With the rapid development and application of molecular biology techniques, scientists and clinicians are closer to curing heart diseases that were thought to be incurable 20 years ago. There clearly is a need for a more thorough understanding of the molecular mechanisms of cardiovascular diseases to promote the advancement of stem cell therapy and gene therapy for heart diseases. The present paper briefly reviews the state-of-the-art techniques in the following areas of molecular cardiology: gene analysis in the diseased heart; transgenic techniques in cardiac research; gene transfer and gene therapy for cardiovascular disease; and stem cell therapy for cardiovascular disease.

Genetic AVP deficiency abolishes cold-induced diuresis but does not attenuate cold-induced hypertension

Chronic cold exposure causes hypertension and diuresis. The aim of this study was to determine whether vasopressin (AVP) plays a role in cold-induced hypertension and diuresis. Two groups of Long-Evans (LE) and two groups of homozygous AVP-deficient Brattleboro (VD) rats were used. Blood pressure (BP) was not different among the four groups during a 2-wk control period at room temperature (25 degrees C, warm). After the control period, one LE group and one VD group were exposed to cold (5 degrees C); the remaining groups were kept at room temperature. BP and body weight were measured weekly during exposure to cold. Food intake, water intake, urine output, and urine osmolality were measured during weeks 1, 3, and 5 of cold exposure. At the end of week 5, all animals were killed and blood was collected for measurement of plasma AVP. Kidneys were removed for measurement of renal medulla V2 receptor mRNA and aquaporin-2 (AQP-2) protein expression. BP of LE and VD rats increased significantly by week 2 of cold exposure and reached a high level by week 5. BP elevations developed at approximately the same rate and to the same degree in LE and VD rats. AVP deficiency significantly increased urine output and solute-free water clearance and decreased urine osmolality. Chronic cold exposure increased urine output and solute-free water clearance and decreased urine osmolality in LE rats, indicating that cold exposure caused diuresis in LE rats. Cold exposure failed to affect these parameters in VD rats, suggesting that the AVP system is responsible for cold-induced diuresis. Cold exposure did not alter plasma AVP in LE rats. Renal medulla V2 receptor mRNA and AQP-2 protein expression levels were decreased significantly in the cold-exposed LE rats, suggesting that cold exposure inhibited renal V2 receptors and AVP-inducible AQP-2 water channels. We conclude that 1) AVP may not be involved in the pathogenesis of cold-induced hypertension, 2) the AVP system plays a critical role in cold-induced diuresis, and 3) cold-induced diuresis is due to suppression of renal V2 receptors and the associated AQP-2 water channels, rather than inhibition of AVP release.