Cold-induced Hypertension Research Articles

Role of BKCa channels in vascular smooth muscle during the development of environmental cold-induced hypertension

Abstracts Background Cold is an important factor contributing to the high incidence of hypertension. Large conductance calcium-activated potassium (BKCa) channels modulate vascular smooth muscle tone. The objective of this study is to determine whether BKCa channels in vascular smooth muscle cells (VSMC) play a role in the development of hypertension during chronic exposure to cold. Methods Forty-eight rats were divided into cold-treated group and control group randomly, and then, rats of cold-treated group were exposed to 4±1 °C (4 h/day) and rats of another group were kept at 25±1 °C. Results Compared to control group, systolic blood pressure of the rats exposed to cold for 2, 4, 6, 8 weeks were increased by 7.14%, 20.42%, 40.54%, 28.74%, respectively. The BKCa current and BKCa peak current density in aortic VSMC increased significantly as the time of exposure to cold went until the 6th week exposure to cold. At the 6th weeks, the BKCa peak current density in the cold exposed group compared to the control group were increased 345.21% (n=6, P Conclusion Our data showed that BKCa channels have apparent change with the development of hypertension during repeated cold exposure, suggesting that BKCa channel could be thought as a new target for prevention and treating cold-induced hypertension.

BKCA CHANNEL ACT AS A NEGATIVE-FEEDBACK REGULATOR IN THE DEVELOPMENT OF COLD-INDUCED HYPERTENSION

ObjectivesCold is an important factor contributing to the high incidence of hypertension. In order to explore the mechanisms of cold-induced hypertension. This study observed whether Large conductance calcium-activated potassium channel...

AAV-Based RNAi Silencing of NADPH Oxidase gp91phox Attenuates Cold-Induced Cardiovascular Dysfunction

Clinical observations and epidemiological surveys indicated that the prevalence of hypertension and heart diseases is increased in cold regions or during winter. Cold exposure increased NADPH oxidase gp91(phox) protein expression in heart, kidneys, and aorta in rats. The aim of this study was to investigate if RNA interference (RNAi) silencing of gp91(phox) would attenuate cold-induced hypertension and cardiovascular and renal damage. The recombinant adeno-associated virus serotype 2 (AAV-2) vector carrying gp91(phox)-shRNA (gp91-shRNA) was constructed for inhibiting gp91(phox) protein expression in cold-exposed rats. Blood pressure (BP) was monitored using a telemetry system. BP was increased in the Control-shRNA and PBS groups within 1 week of exposure to moderate cold (5°C) and reached a plateau after 7 weeks. The cold-induced increase in BP was attenuated significantly by intravenous delivery of gp91-shRNA (1.25×10(10) particles/rat, 0.5 mL). One single dose of gp91-shRNA controlled hypertension for up to 10 weeks. In addition, gp91-shRNA reversed cold-induced vascular dysfunction. gp91-shRNA abolished the cold-induced up-regulation of gp91(phox) protein expression in heart, kidneys, and aorta, confirming effective silencing of gp91(phox). The cold-induced increases in NADPH oxidase activity and superoxide production were eliminated by silencing of gp91(phox), suggesting that the cold-induced up-regulation of NADPH oxidase activity may be attributed to the increased gp91(phox) protein expression. RNAi silencing of gp91(phox) abolished cold-induced cardiac and renal hypertrophy and attenuated aortic, coronary, and renal remodeling. The up-regulation of gp91(phox) may play a critical role in cold-induced cardiovascular dysfunction and organ damage. AAV delivery of gp91-shRNA may be a new and effective therapeutic approach for cold-related cardiovascular disorders.

Progressive increase in renal sympathetic nerve activity in cold‐induced hypertension in rats

The study investigated how renal sympathetic nerve activity was involved in the development of cold‐induced hypertension in rats. Male Wistar rats were chronically instrumented to allow recording of renal (RSNA), lumbar (LSNA) sympathetic nerve activity, measurement of systemic arterial pressure and infusion of vasoactive drugs. At least three days after the surgery, rats were placed in an environmental temperature of 10 °C for 96 hours. The cold exposure caused an immediate increase in arterial pressure from 103 }2 to 118 }1 mmHg (P<0.05) associated with simultaneous increases in RSNA, of 55%, LSNA, of 211% and heart rate, of 86beats/min (all P<0.05). Subsequently, RSNA increased further in a progressive manner reaching 152% at the end of the cold exposure while LSNA and heart rate remained at the initial increased levels. These data suggest that cold exposure activates RSNA in a cumulative manner, which may contribute to the development of cold‐induced hypertension in rats. JSPS Grant.

Progressive increase in renal sympathetic nerve activity during development of cold-induced hypertension in rats

Progressive increase in renal sympathetic nerve activity during development of cold-induced hypertension in rats

Effect on expression of vascular smooth muscle cell calcium channel in rats exposed in low temperature

To observe the expression of vascular smooth muscle cells calcium channel α1C subunit (LTCCα1C) in rats exposed in low temperature. Cold-induced hypertension was established and blood pressure was measured every two weeks. The mRNA expression of L type calcium channel α1C was determined by RT-PCR. The blood pressure of the rats exposed to cold environment increased. The blood pressure of experimental groups [(102.8 ± 2.25) mm Hg] began to increase from the first two weeks, compared with the control group [(89.2 ± 3.73) mm Hg], there were significant difference (P < 0.05). The blood pressure of experimental groups were (114.5 ± 4.21), (121.9 ± 3.03) mm Hg respectively at 4, 6 weeks. Compared with the control group, the expression of LTCCα1C mRNA of the cold exposure group increased significantly (P < 0.01). There was a significant correlation between the expression of LTCCα1C mRNA and the blood pressure of the rats (r = 0.86, P < 0.01). Repeated cold exposure can establish cold-induced hypertension, and the level of vascular smooth muscle cells LTCCα1C expression increase.

Ribonucleic Acid Interference Knockdown of Interleukin 6 Attenuates Cold-Induced Hypertension

The purpose of this study was to determine the role of the proinflammatory cytokine interleukin (IL) 6 in cold-induced hypertension. Four groups of male Sprague-Dawley rats were used (6 rats per group). After blood pressure was stabilized, 3 groups received intravenous delivery of adenoassociated virus carrying IL-6 small hairpin RNA (shRNA), adenoassociated virus carrying scrambled shRNA, and PBS, respectively, before exposure to a cold environment (5 degrees C). The last group received PBS and was kept at room temperature (25 degrees C, warm) as a control. Adenoassociated virus delivery of IL-6 shRNA significantly attenuated cold-induced elevation of systolic blood pressure and kept it at the control level for < or =7 weeks (length of the study). Chronic exposure to cold upregulated IL-6 expression in aorta, heart, and kidneys and increased macrophage and T-cell infiltration in kidneys, suggesting that cold exposure increases inflammation. IL-6 shRNA delivery abolished the cold-induced upregulation of IL-6, indicating effective silence of IL-6. Interestingly, RNA interference knockdown of IL-6 prevented cold-induced inflammation, as evidenced by a complete inhibition of tumor necrosis factor-alpha expression and leukocyte infiltration by IL-6 shRNA. RNA interference knockdown of IL-6 significantly decreased the cold-induced increase in vascular superoxide production. It is noted that IL-6 shRNA abolished the cold-induced increase in collagen deposition in the heart, suggesting that inflammation is involved in cold-induced cardiac remodeling. Cold exposure caused glomerular collapses, which could be prevented by knockdown of IL-6, suggesting an important role of inflammation in cold-induced renal damage. In conclusion, cold exposure increased IL-6 expression and inflammation, which play critical roles in the pathogenesis of cold-induced hypertension and cardiac and renal damage.

RNAi Inhibition of Interleukin‐6 Attenuates Cold‐Induced Hypertension

The purpose of this study was to determine the role of the pro‐inflammatory cytokine IL‐6 in cold‐induced hypertension (CIH). We hypothesized that RNAi knockdown of IL‐6 would decrease inflammatory infiltrates and attenuate CIH. Four groups of male rats were used (6 rats/group). After blood pressure (BP) was stabilized, 3 groups were injected intravenously with recombinant AAV carrying IL‐6shRNA, AAV carrying scrambled shRNA (ScrshRNA), and PBS, respectively, prior exposure to a cold environment (5°C). The last group received PBS and was kept at room temperature (25°C, warm) as a control. AAV delivery of IL‐6shRNA significantly attenuated cold‐induced elevation of BP and kept it at the control level. Chronic exposure to cold up‐regulated IL‐6 and TNF‐α expression in aorta, heart and kidneys and increased macrophage and T‐cell infiltration in kidneys, suggesting that cold exposure increases inflammation. RNAi knockdown of IL‐6 abolished cold‐induced up‐regulation of IL‐6 and TNF‐α, leukocyte infiltration, and increases in vascular superoxide production. IL‐6shRNA prevented the cold‐induced increase in collagen deposition in the heart (cardiac remodeling). Cold exposure caused glomerular collapses which could be abolished by knockdown of IL‐6. Conclusions: Cold exposure up‐regulated IL‐6 expression leading to inflammation which plays a critical role in the pathogenesis of CIH and cardiac and renal damage.

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.

Role of Phosphodiesterase 1A in Cold‐induced Hypertension and Cardiac Hypertrophy

The calcium/calmodulin‐dependent phosphodiesterase 1A (PDE1A) hydrolyzes the intracellular second messengers cAMP and cGMP. Cold exposure to (6 hr/day) results in hypertension and cardiac hypertrophy. PDE1A expression was up‐regulated in resistance arteries, kidneys and hearts of cold‐exposed rats. We hypothesized that RNAi inhibition of PDE1A would attenuate cold‐induced hypertension (CIH) and cardiac hypertrophy (CICH).We constructed AAV carrying PDE1AshRNA, ControlshRNA, and LacZ driven by a CMV promoter. Four groups received an intravenous injection of AAV.PDE1A‐shRNA, AAV.Control‐shRNA, AAV.LacZ, and PBS, respectively, before exposure to cold (5°C), while 1 group received PBS and was kept at room temperature as a control. BP was increased significantly in all cold‐exposed groups except the group treated with PDE1AshRNA, indicating that PDE1AshRNA prevented CIH. PDE1AshRNA enhanced hypothesive responses to acetylcholine in cold‐exposed rats, indicating improved endothelial dysfunction. The in vivo left ventricle wall thickness was also decreased significantly in the cold‐exposed rats treated with PDE1AshRNA. PDE1A‐shRNA attenuated the cold‐induced increases in heart weight, cardiomyocyte sizes, and vascular wall thickness. PDE1AshRNA increased intracellular cGMP and cAMP levels and decreased VSMC cell proliferation and migration. Thus, PDE1A plays a critical role in the pathogenesis of CIH and CICH.

Abstract 324: RNAi Inhibition of Phosphodiesterase 1A Prevents Cold-Induced Hypertension and Cardiac Hypertrophy

The calcium/calmodulin-dependent phosphodiesterase 1A (PDE1A) hydrolyzes the intracellular second messengers cAMP and cGMP, which are known to play an important role in regulating vascular tone and smooth muscle cell (VSMC) proliferation. Intermittent exposure to cold (6 hr/day) results in hypertension and cardiac hypertrophy. Interestingly, PDE1A expression was up-regulated in resistance arteries, kidneys and heart of rats exposed to cold. We hypothesize that RNAi inhibition of PDE1A would attenuate cold-induced hypertension (CIH) and cardiac hypertrophy (CICH). We constructed PDE1A shRNA (PDE1A-shRNA) plasmid, Control-shRNA plasmid, and LacZ plasmid driven by a CMV promoter. AAV-2 was used for in vivo gene delivery. Five groups of rats were used to test the effect of in vivo inhibition of PDE1A expression on the development of CIH and CICH. Four groups received an intravenous injection of AAV.PDE1A-shRNA, AAV.Control-shRNA, AAV.LacZ, and PBS, respectively, before intermittent exposure to moderate cold temperature (5°C), while the last group received PBS and was kept at room temperature (25°C) as a control. Blood pressure (BP), monitored using a telemetry system, was increased significantly in all cold-exposed groups except the group treated with PDE1A-shRNA, indicating that PDE1A-shRNA prevented the development of CIH. PDE1A-shRNA enhanced hypothesive responses to acetylcholine in cold-exposed rats, indicating improved endothelial dysfunction. The MRI analysis indicated that the in vivo left ventricle wall thickness was also decreased significantly in the cold-exposed rats treated with PDE1A-shRNA. All animals were sacrificed at 10 weeks after gene delivery. PDE1A-shRNA significantly attenuated the cold-induced increases in heart weight, cardiomyocyte sizes, and vascular wall thickness. PDE1A-shRNA increased intracellular cGMP and cAMP levels and decreased VSMC cell proliferation and migration. PDE1A protein expression was significantly decreased, indicating effective silence of PDE1A gene. RNAi inhibition prevented CIH, CICH and cold-induced vascular dysfunction and hypertrophy. Thus, PDE1A plays a critical role in the pathogenesis of CIH and CICH.

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 degrees 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 x 10(11) 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.

Changes of renal function and structure in rats exposed to cold

The kidney appears to play a crucial role in both initiating and maintaining the high blood pressure in cold-induced hypertension (CIH). The aim of the present study was to evaluate the changes of renal function and structure in rats exposed to cold for 2, 4 and 6 weeks. Systolic blood pressure increased significantly after 2 weeks of cold exposure and was maintained throughout the whole experiment. Upregulation of angiotensin type 1 receptor (AT 1R) expression was seen in the vascular zone and distal tubule after 4 and 6 weeks of cold exposure. This was accompanied by an increase in malondialdehyde (MDA) levels and decreases in superoxide dismutase (SOD), nitric oxide synthase (NOS) activities and nitric oxide (NO) content in kidney. Structural changes were also observed in glomeruli, tubules and arteries in cold-treated rats. These results suggest that upregulation of kidney AT 1R plays a critical role in the development of CIH, and its interaction with oxidative stress, NO and NOS may be involved in changes of renal function and structure.

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.

Systemic and Specific Delivery of Small Interfering RNAs to the Liver Mediated by Apolipoprotein A-I

Tissue-targeted delivery of small interfering RNA (siRNA) must be achieved before RNA interference (RNAi) technology can be used in practical therapeutic approaches. In this study, the potential of apolipoprotein A-I (apo A-I) for the systemic delivery of nucleic acids to the liver is demonstrated using real-time in vivo imaging. As a proof of concept, synthetic siRNAs against hepatitis B virus (HBV) were formulated into complexes of apo A-I and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP)/cholesterol (DTC-Apo) and injected intravenously (i.v.) into a mouse model carrying replicating HBV. We show that administration of these nanoparticles can significantly reduce viral protein expression by receptor-mediated endocytosis. The advantages of the apo A-I-mediated siRNA delivery method are its liver specificity, its effectiveness at low doses (< or = 2 mg/kg) in only a single treatment, and its persistent antiviral effect up to 8 days. The liver-targeted gene silencing was also shown by in vivo images, in which bioluminescent signals emitted from the liver were efficiently reduced after i.v. administration of luciferase-specific siRNA and DTC-Apo lipoplex. Thus, our unique approach to siRNA delivery creates a foundation for the development of a new class of promising therapeutics against hepatitis viruses or hepatocyte genes related to tumor growth.

Evaluation of endothelial and inducible nitric oxide synthase mRNA expression in the lung of broiler chickens with developmental pulmonary hypertension due to cold stress

1. To clarify the effect of cold-induced pulmonary hypertension on endothelial and inducible nitric oxide synthase (eNOS and iNOS) mRNA expression in the lung of broiler chickens, semi quantitative reverse transcription-PCR was performed on total RNAs isolated from lungs of the broiler chickens exposed to 5 weeks of cold stress. 2. The eNOS gene was expressed increasingly with the increasing age during the rearing period. 3. Comparing the treatment group with its related control group eNOS was expressed significantly only at d 21. 4. Expression of iNOS mRNA also increased in both control and treatment groups with increasing age until d 28 and then decreased at d 35 and 42. 5. Comparing the treatment group with its control group, iNOS mRNA level was significantly higher at 21 d of age in the cold-exposed chickens. 6. It was concluded that, although cold exposure could significantly increase eNOS and iNOS gene expression, cold-induced pulmonary hypertension is not associated with significant variations of eNOS and iNOS expression in the lungs of broiler chickens.

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. (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.

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.

Potential of Gene Therapy Strategy for the Treatment of Hypertension

Hypertension is one of the most important risk factors for cardiovascular diseases (CVDs). CVD extends across all populations and represents the leading cause of morbidity and mortality in industrialized countries. Hypertension increases the risk of peripheral arterial disease, cardiomyopathy, stroke, and renal failure. The disease affects &50 million Americans and goes undetected in at least one third of the population. In spite of the tremendous progress made by pharmacotherapy in the management and control of hypertension, there has been a steady escalation in its prevalence during the last decade. This has led many to conclude that traditional pharmacotherapy has reached an intellectual plateau and that novel and innovative approaches must be sought for the treatment, control, and possible cure of hypertension. As a result, efforts of our group and those of many others have been diverted to explore the use of gene transfer and gene therapy strategies for a long-term control of hypertension. We have argued that gene therapy offers potentially significant improvements and benefits over the use of traditional pharmacotherapy: (1) noncompliance by patients can be significantly reduced or even eliminated because of the fact that a single treatment involving gene transfer could remain effective for months or even years; (2) side effects associated with pharmacotherapy can be minimized as a result of specific targeting of a therapeutic gene in a given tissue and optimally influencing cardiovascular pathophysiology on an individual patient basis; and (3) with its potential to produce long-term beneficial outcomes in end-organ damage, the gene therapy strategy could lead to a cure of hypertension and its related pathophysiology. It is noteworthy to mention that current pharmacotherapies are often unable to reverse end-organ damage associated with hypertension. In order for the gene therapy for hypertension to be successful, one must provide conceptual support of its efficacy in …

Prolonged attenuation of cold-induced hypertension by adenoviral delivery of renin antisense

Renin has been linked to the pathogenesis of some forms of hypertension, including cold-induced hypertension (CIH). Although several antihypertensive drugs that inhibit angiotensin-converting enzyme (ACE) and angiotensin II (Ang II) type 1 (AT(1)) receptors are available, they are short-lasting and have side effects. Inhibition of renin [the first and rate-limiting step of the renin-angiotensin system (RAS)] would provide an inhibition of the entire RAS. Thus, we developed an antisense approach for specific inhibition of renin based on the genetic design. The objective of this study was to test our hypothesis that adenoviral delivery of renin antisense inhibits renin and attenuates CIH. Recombinant adenoviruses carrying rat renin antisense (rAdv.RRA) and LacZ reporter gene (rAdv.LacZ) were constructed and used for in vivo gene transfer via intravenous injection. Four groups of rats were used (six rats/group). Blood pressure did not differ among the four groups during the control period at room temperature (25 degrees C). Two groups of rats received rAdv.RRA (2.5 x 10(9) pfu/rat, intravenously), while the other two groups received the same dose of rAdv.LacZ and served as controls. After gene delivery, one rAdv.LacZ-treated and one rAdv.RRA-treated group were exposed to cold (5 degrees C), while the remaining groups were kept at 25 degrees C. Blood pressure was monitored weekly during cold exposure. A 24-hour urine sample was collected during weeks 1, 3, and 5 for measuring urinary aldosterone excretion. At the end of week 5, all animals were killed and blood was collected for measurement of plasma renin activity (PRA), total plasma renin, plasma active renin, and plasma aldosterone. Vascular Ang II contents were measured in all rats. Blood pressure of the rAdv.LacZ-treated group rose significantly within 2 weeks of exposure to cold and reached 158.2 +/- 6.4 mm Hg by week 5. In contrast, blood pressure (117.1 +/- 5.3 mm Hg) of the cold-exposed group treated with rAdv.RRA did not increase until 5 weeks after exposure to cold. Thus, a single dose of rAdv.RRA prevented CIH for at least 5 weeks. rAdv.RRA abolished the cold-induced increases in PRA, total plasma renin, plasma active renin, vascular Ang II, and plasma and urine aldosterone, indicating effective inhibition of the entire RAS. rAdv.RRA effectively inhibited the entire RAS and produced prolonged attenuation of CIH. Antisense inhibition of renin may be a novel and ideal approach for long-term control of hypertension.