Repetitive hyperthermia attenuates progression of left ventricular hypertrophy and increases telomerase activity in hypertensive rats

2012 ◽  
Vol 302 (10) ◽  
pp. H2092-H2101 ◽  
Author(s):  
Jun-ichi Oyama ◽  
Toyoki Maeda ◽  
Makoto Sasaki ◽  
Yoshihiro Higuchi ◽  
Koichi Node ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Telomerase Activity ◽  
Hsp90 Inhibitor ◽  
Left Ventricular ◽  
High Salt ◽  
Hypertensive Rats ◽  
High Salt Diet ◽  
Blood Pressure Elevation ◽  
Salt Diet ◽  
Group A

We investigated the hypothesis that repetitive hyperthermia (RHT) attenuates the progression of cardiac hypertrophy and delays the transition from hypertensive cardiomyopathy to heart failure in Dahl salt-sensitive (DS) hypertensive rats. Six-week-old DS rats were divided into the following five groups: a normal-salt diet (0.4% NaCl) (NS group), a normal-salt diet plus RHT by daily immersion for 10 min in 40°C water (NS+RHT group), a high-salt diet (8% NaCl) (HS group), a high-salt diet (8% NaCl) plus RHT (HS+RHT group), and high-salt diet (8% NaCl) plus RHT with 17-DMAG (HSP90 inhibitor) administration (HS+RHT+17-DMAG group). All rats were killed at 10 wk. Cardiac hypertrophy and fibrosis were noted in the HS group, whereas RHT attenuated salt-induced cardiac hypertrophy, myocardial and perivascular fibrosis, and blood pressure elevation. The phosphorylated endothelial nitric oxide synthase (eNOS) and Akt were decreased in the HS group compared with the NS group, but these changes were not observed in the HS+RHT group. The levels of HSP60, 70, and 90 were elevated by RHT. Moreover, the increased levels of iNOS, nitrotyrosine, Toll-like receptor-4, BNP, PTX3, and TBARS in the HS group were inhibited by RHT. Telomeric DNA length, telomerase activity, and telomere reverse transcriptase (TERT) were reduced in the HS group; however, these changes were partially prevented by hyperthermia. In conclusion, RHT attenuates the development of cardiac hypertrophy and fibrosis and preserves telomerase, TERT activity and the length of telomere DNA in salt-induced hypertensive rats through activation of eNOS and induction of HSPs.

Increased cardiac ppENK mRNA in cardiac hypertrophy and effects on blood pressure of its peptide products

1997 ◽  
Vol 272 (6) ◽  
pp. H2885-H2894 ◽  
Author(s):  
J. M. Hao ◽  
S. W. Rabkin
Keyword(s):  
Blood Pressure ◽  
Cardiac Hypertrophy ◽  
Isolated Heart ◽  
Left Ventricular ◽  
High Salt ◽  
Heart Weight ◽  
Mrna Levels ◽  
High Salt Diet ◽  
Salt Diet ◽  
Heart Preparation

The objective of this study was to examine the expression of preproenkephalin (ppENK) in the heart in cardiac hypertrophy and the effects on cardiac contractility and blood pressure regulation of its peptide products. The ppENK-derived peptides Leu5-enkephalin (LE), Met5-enkephalin (ME), Met5-enkephalin-Arg6-Gly7-Leu8 (MEAGL), and Met5-enkephalin-Arg6-Phe7 (MEAP) were administered intravenously to unanesthetized Sprague-Dawley rats and to an isolated heart preparation from the same species. LE, ME, MEAGL, or MEAP (360 nmol iv) produced an immediate decrease in heart rate, reaching its maximum within 10 s and returning to baseline by 30 s. The blood pressure response for each enkephalin was a small initial decrease followed by a marked and significant increase (P < 0.05 for MEAP). In the isolated heart preparation, neither LE, ME, MEAGL, nor MEAP altered left ventricular contractility. Cardiac hypertrophy was produced in the Dahl salt-dependent model of hypertension with a significantly greater heart weight-to-body weight ratio in the Dahl salt-sensitive (S) compared with the Dahl salt-resistant (R) rat on a high-salt diet (P < 0.05). Tissue RNA was extracted, and Northern blot analysis identified and quantitated mRNA with a 0.93-kilobase cDNA of ppENK A. There was more ppENK mRNA in the left than in the right ventricle and much less in the atria than in the ventricles. The amount of ppENK mRNA was markedly and significantly increased in the left ventricle of the Dahl S compared with the Dahl R rat (P < 0.05). In contrast, there were no differences in ppENK mRNA levels in different brain regions between the R and S rats on a high-salt diet. Interestingly, a larger ppENK mRNA of 1.75 kilobases was abundantly expressed in testicular tissue. These data showing increased ppENK expression raise the possibilities of 1) an autocrine/paracrine role for enkephalins in cardiac hypertrophy and 2) an endocrine role for the hypertrophic heart, with an increased production of enkephalins, especially MEAP, that produces vasoconstriction and further increases in blood pressure.

scholarly journals AT1 receptor participates in the cardiac hypertrophy induced by resistance training in rats

2008 ◽  
Vol 295 (2) ◽  
pp. R381-R387 ◽  
Author(s):  
Valerio G. Barauna ◽  
Flávio C. Magalhaes ◽  
Jose E. Krieger ◽  
Edilamar M. Oliveira
Keyword(s):  
Resistance Training ◽  
Left Ventricle ◽  
Cardiac Hypertrophy ◽  
Receptor Gene ◽  
Weight Ratio ◽  
High Salt ◽  
Receptor Expression ◽  
Ang Ii ◽  
High Salt Diet ◽  
Salt Diet

Resistance training is accompanied by cardiac hypertrophy, but the role of the renin-angiotensin system (RAS) in this response is elusive. We evaluated this question in 36 male Wistar rats divided into six groups: control ( n = 6); trained ( n = 6); control + losartan (10 mg·kg−1·day−1, n = 6); trained + losartan ( n = 6); control + high-salt diet (1%, n = 6); and trained + high-salt diet (1%, n = 6). High salt was used to inhibit the systemic RAS and losartan to block the AT1 receptor. The exercise protocol consisted of: 4 × 12 bouts, 5×/wk during 8 wk, with 65–75% of one repetition maximum. Left ventricle weight-to-body weight ratio increased only in trained and trained + high-salt diet groups (8.5% and 10.6%, P < 0.05) compared with control. Also, none of the pathological cardiac hypertrophy markers, atrial natriuretic peptide, and αMHC (α-myosin heavy chain)-to-βMHC ratio, were changed. ACE activity was analyzed by fluorometric assay (systemic and cardiac) and plasma renin activity (PRA) by RIA and remained unchanged upon resistance training, whereas PRA decreased significantly with the high-salt diet. Interestingly, using Western blot analysis and RT-PRC, no changes were observed in cardiac AT2 receptor levels, whereas the AT1 receptor gene (56%, P < 0.05) and protein (31%, P < 0.05) expressions were upregulated in the trained group. Also, cardiac ANG II concentration evaluated by ELISA remained unchanged (23.27 ± 2.4 vs. 22.01 ± 0.8 pg/mg, P > 0.05). Administration of a subhypotensive dose of losartan prevented left ventricle hypertrophy in response to the resistance training. Altogether, we provide evidence that resistance training-induced cardiac hypertrophy is accompanied by induction of AT1 receptor expression with no changes in cardiac ANG II, which suggests a local activation of the RAS consistent with the hypertrophic response.

Response of resistance arteries to reduced PO2 and vasodilators during hypertension and elevated salt intake

1997 ◽  
Vol 273 (2) ◽  
pp. H869-H877 ◽  
Author(s):  
Y. Liu ◽  
K. T. Fredricks ◽  
R. J. Roman ◽  
J. H. Lombard
Keyword(s):  
Skeletal Muscle ◽  
Salt Intake ◽  
High Salt ◽  
Nitric Oxide Donor ◽  
Resistance Arteries ◽  
Hypertensive Rats ◽  
High Salt Diet ◽  
Membrane Function ◽  
Salt Diet ◽  
Spontaneously Hypertensive

This study assessed vasodilator responses in skeletal muscle resistance arteries (100-250 microns) from rats with chronic (4-8 wk) reduced renal mass (RRM) hypertension and normotensive sham-operated controls on a high (4% NaCl; HSSHAM)- or low (0.4% NaCl; LSSHAM)-salt diet. Arteries from RRM hypertensive rats [normal and high-salt diet (HSRRM)] and a separate group of spontaneously hypertensive rats exhibited an impaired dilation in response to reduced PO2 compared with those of their normotensive controls. Prostacyclin release, assessed by radio-immunoassay for 6-ketoprostaglandin F1 alpha, increased significantly in response to reduced PO2, but was unaffected by hypertension or salt intake. Dilator responses to acetylcholine and the prostacyclin analog iloprost were significantly reduced in both HSRRM and HSSHAM compared with LSSHAM rats. Dilation in response to direct activation of adenylate cyclase with forskolin or guanylate cyclase with the nitric oxide donor sodium nitroprusside was not significantly different in HSRRM, HSSHAM, and LSSHAM rats. These results indicate that hypoxic dilation is impaired in skeletal muscle resistance arteries of hypertensive rats and that chronic high-salt diet alone leads to impaired vasodilator responses in resistance arteries of normotensive animals, possibly via abnormalities in membrane function or G protein signaling rather than impaired second-messenger function.

scholarly journals Association of a Disrupted Dipping Pattern of Blood Pressure with Progression of Renal Injury during the Development of Salt-Dependent Hypertension in Rats

2020 ◽  
Vol 21 (6) ◽  
pp. 2248 ◽  
Author(s):  
Abu Sufiun ◽  
Asadur Rahman ◽  
Kazi Rafiq ◽  
Yoshihide Fujisawa ◽  
Daisuke Nakano ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Circadian Rhythm ◽  
Renal Injury ◽  
Tissue Injury ◽  
Renal Tissue ◽  
High Salt ◽  
Hypertensive Rats ◽  
High Salt Diet ◽  
Salt Diet ◽  
The Difference

The aim of the present study is to investigate whether a disruption of the dipping pattern of blood pressure (BP) is associated with the progression of renal injury in Dahl salt-sensitive (DSS) hypertensive rats. Seven-week-old DSS rats were fed a high salt diet (HSD; 8% NaCl) for 10 weeks, followed by a transition to a normal salt diet (NSD; 0.3% NaCl) for 4 weeks. At baseline, NSD-fed DSS rats showed a dipper-type circadian rhythm of BP. By contrast, HSD for 5 days caused a significant increase in the difference between the active and inactive periods of BP with an extreme dipper type of BP, while proteinuria and renal tissue injury were not observed. Interestingly, HSD feeding for 10 weeks developed hypertension with a non-dipper pattern of BP, which was associated with obvious proteinuria and renal tissue injury. Four weeks after switching to an NSD, BP and proteinuria were significantly decreased, and the BP circadian rhythm returned to the normal dipper pattern. These data suggest that the non-dipper pattern of BP is associated with the progression of renal injury during the development of salt-dependent hypertension.

scholarly journals Fetal programming effects of pentaerythritol tetranitrate in a rat model of superimposed preeclampsia

2020 ◽  
Vol 98 (9) ◽  
pp. 1287-1299
Author(s):  
Andy W. C. Man ◽  
Min Chen ◽  
Yawen Zhou ◽  
Zhixiong Wu ◽  
Gisela Reifenberg ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Glucose Tolerance ◽  
Fetal Growth ◽  
Rat Model ◽  
High Salt ◽  
Pentaerythritol Tetranitrate ◽  
High Salt Diet ◽  
Blood Pressure Elevation ◽  
Salt Diet ◽  
Normal Chow

Abstract Preeclampsia is a common medical condition during pregnancy and a major cause of maternal and prenatal mortality. The present study was conducted to investigate the effects of maternal treatment with pentaerythritol tetranitrate (PETN) in Dahl salt-sensitive rats (DSSR), a model of superimposed preeclampsia. F0 parental DSSR were treated with PETN (50 mg/kg) from the time point of mating to the end of lactation. Maternal PETN treatment improved fetal growth and had no effect on blood pressure in DSSR offspring fed with normal chow or high-salt diet. Upon high-fat diet (HFD) feeding, offspring from PETN-treated mother showed improved glucose tolerance despite similar weight gain. Unexpectedly, maternal PETN treatment significantly potentiated the HFD-induced blood pressure elevation in male DSSR offspring. Endothelium-derived hyperpolarization factor (EDHF)-mediated vasodilation was similar between NCD-fed and HFD-fed control offspring but was markedly reduced in HFD-fed PETN offspring. EDHF genes were downregulated in the vasculature of HFD-fed PETN offspring, which was associated with epigenetic changes in histone modifications. In conclusion, maternal PETN treatment in DSSR shows both beneficial and unfavorable effects. It improves fetal growth and ameliorates glucose tolerance in the offspring. Although maternal PETN treatment has no effect on blood pressure in offspring fed with normal chow or high-salt diet, the offspring is at higher risk to develop HFD-induced hypertension. PETN may potentiate the blood pressure response to HFD by epigenetic modifications of EDHF genes. Key messages The core findings of this article suggest that maternal PETN treatment of DSSR, a rat model of a spontaneous superimposed preeclampsia, leads to • Improvement of fetal growth; • No changes of maternal blood pressure or markers of preeclampsia; • Amelioration of HFD-induced glucose intolerance in adult offspring; • No changes in blood pressure development of the offspring on normal chow or high salt-diet; • Potentiation of blood pressure elevation of the offspring on HFD.

scholarly journals Discharge of RVLM vasomotor neurons is not increased in anesthetized angiotensin II-salt hypertensive rats

2013 ◽  
Vol 305 (12) ◽  
pp. H1781-H1789 ◽  
Author(s):  
Gustavo R. Pedrino ◽  
Alfredo S. Calderon ◽  
Mary Ann Andrade ◽  
Sergio L. Cravo ◽  
Glenn M. Toney
Keyword(s):  
Sympathetic Nerve Activity ◽  
High Salt ◽  
Ventrolateral Medulla ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Nerve Activity ◽  
High Salt Diet ◽  
Salt Diet ◽  
Salt Hypertension ◽  
Single Unit Recordings

Neurons of the rostral ventrolateral medulla (RVLM) are critical for generating and regulating sympathetic nerve activity (SNA). Systemic administration of ANG II combined with a high-salt diet induces hypertension that is postulated to involve elevated SNA. However, a functional role for RVLM vasomotor neurons in ANG II-salt hypertension has not been established. Here we tested the hypothesis that RVLM vasomotor neurons have exaggerated resting discharge in rats with ANG II-salt hypertension. Rats in the hypertensive (HT) group consumed a high-salt (2% NaCl) diet and received an infusion of ANG II (150 ng·kg−1·min−1 sc) for 14 days. Rats in the normotensive (NT) group consumed a normal salt (0.4% NaCl) diet and were infused with normal saline. Telemetric recordings in conscious rats revealed that mean arterial pressure (MAP) was significantly increased in HT compared with NT rats ( P < 0.001). Under anesthesia (urethane/chloralose), MAP remained elevated in HT compared with NT rats ( P < 0.01). Extracellular single unit recordings in HT ( n = 28) and NT ( n = 22) rats revealed that barosensitive RVLM neurons in both groups (HT, 23 cells; NT, 34 cells) had similar cardiac rhythmicity and resting discharge. However, a greater ( P < 0.01) increase of MAP was needed to silence discharge of neurons in HT (17 cells, 44 ± 5 mmHg) than in NT (28 cells, 29 ± 3 mmHg) rats. Maximum firing rates during arterial baroreceptor unloading were similar across groups. We conclude that heightened resting discharge of sympathoexcitatory RVLM neurons is not required for maintenance of neurogenic ANG II-salt hypertension.

scholarly journals Time course of decompensation after angiotensin II and high-salt diet in Balb/CJ mice suggests pulmonary hypertension-induced cardiorenal syndrome

2019 ◽  
Vol 316 (5) ◽  
pp. R563-R570 ◽  
Author(s):  
Mediha Becirovic-Agic ◽  
Sofia Jönsson ◽  
Maria K. Tveitarås ◽  
Trude Skogstrand ◽  
Tine V. Karlsen ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Angiotensin Ii ◽  
Cardiac Function ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
High Salt ◽  
Ang Ii ◽  
Salt Treatment ◽  
High Salt Diet ◽  
Salt Diet

The genetic background of a mouse strain determines its susceptibility to disease. C57BL/6J and Balb/CJ are two widely used inbred mouse strains that we found react dramatically differently to angiotensin II and high-salt diet (ANG II + Salt). Balb/CJ show increased mortality associated with anuria and edema formation while C57BL/6J develop arterial hypertension but do not decompensate and die. Clinical symptoms of heart failure in Balb/CJ mice gave the hypothesis that ANG II + Salt impairs cardiac function and induces cardiac remodeling in male Balb/CJ but not in male C57BL/6J mice. To test this hypothesis, we measured cardiac function using echocardiography before treatment and every day for 7 days during treatment with ANG II + Salt. Interestingly, pulsed wave Doppler of pulmonary artery flow indicated increased pulmonary vascular resistance and right ventricle systolic pressure in Balb/CJ mice, already 24 h after ANG II + Salt treatment was started. In addition, Balb/CJ mice showed abnormal diastolic filling indicated by reduced early and late filling and increased isovolumic relaxation time. Furthermore, Balb/CJ exhibited lower cardiac output compared with C57BL/6J even though they retained more sodium and water, as assessed using metabolic cages. Left posterior wall thickness increased during ANG II + Salt treatment but did not differ between the strains. In conclusion, ANG II + Salt treatment causes early restriction of pulmonary flow and reduced left ventricular filling and cardiac output in Balb/CJ, which results in fluid retention and peripheral edema. This makes Balb/CJ a potential model to study the adaptive capacity of the heart for identifying new disease mechanisms and drug targets.

scholarly journals Salt-sensitive hypertension and cardiac hypertrophy in mice deficient in the ubiquitin ligase Nedd4-2

2008 ◽  
Vol 295 (2) ◽  
pp. F462-F470 ◽  
Author(s):  
Peijun P. Shi ◽  
Xiao R. Cao ◽  
Eileen M. Sweezer ◽  
Thomas S. Kinney ◽  
Nathan R. Williams ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Critical Role ◽  
Specific Inhibitor ◽  
Normal Diet ◽  
High Salt ◽  
High Salt Diet ◽  
Salt Diet ◽  
Ww Domains ◽  
Salt Sensitive Hypertension

Nedd4-2 has been proposed to play a critical role in regulating epithelial Na+ channel (ENaC) activity. Biochemical and overexpression experiments suggest that Nedd4-2 binds to the PY motifs of ENaC subunits via its WW domains, ubiquitinates them, and decreases their expression on the apical membrane. Phosphorylation of Nedd4-2 (for example by Sgk1) may regulate its binding to ENaC, and thus ENaC ubiquitination. These results suggest that the interaction between Nedd4-2 and ENaC may play a crucial role in Na+ homeostasis and blood pressure (BP) regulation. To test these predictions in vivo, we generated Nedd4-2 null mice. The knockout mice had higher BP on a normal diet and a further increase in BP when on a high-salt diet. The hypertension was probably mediated by ENaC overactivity because 1) Nedd4-2 null mice had higher expression levels of all three ENaC subunits in kidney, but not of other Na+ transporters; 2) the downregulation of ENaC function in colon was impaired; and 3) NaCl-sensitive hypertension was substantially reduced in the presence of amiloride, a specific inhibitor of ENaC. Nedd4-2 null mice on a chronic high-salt diet showed cardiac hypertrophy and markedly depressed cardiac function. Overall, our results demonstrate that in vivo Nedd4-2 is a critical regulator of ENaC activity and BP. The absence of this gene is sufficient to produce salt-sensitive hypertension. This model provides an opportunity to further investigate mechanisms and consequences of this common disorder.

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