How Do Young and Old Spontaneously Hypertensive Rats Respond to Antihypertensive Therapy? Comparative Studies on the Effects of Combined Captopril and Nifedipine Treatment.

Numerous studies on the effects of antihypertensive treatment in young spontaneously hypertensive rats (SHRs) have shown that early-onset therapy may effectively reduce their blood pressure (BP) even to normotensive values. In contrast, only a few studies investigated the effects of treatment started at an advanced age. These studies revealed that antihypertensive effects are lower in adult or even in senescent SHRs compared with young SHRs. Even more, prevention of cardiac sequelae of hypertension such as hypertrophy and fibrosis is less effective when treatment starts late in life. Because, in patients, combination therapies with calcium antagonists are favored, we studied the efficacy of a combination therapy with captopril and nifedipine in young and old SHRs. We directly compared the treatment effects on BP as well as on cardiac hypertrophy and remodeling between these two animal cohorts. With antihypertensive treatment, significantly lower BP values were achieved in young SHRs despite a shorter treatment period compared with old SHRs. Although treatment effects on cardiac hypertrophy were greater in old than in young SHRs, cardiac fibrosis was significantly attenuated only in young but not in old SHRs. The results emphasize the value of antihypertensive therapy and particularly accentuate the importance of an early-onset therapy. With respect to problems such as late diagnosis and poor therapy adherence, these results may have great importance for the treatment of human hypertension.

How Effective Is a Late-Onset Antihypertensive Treatment? Studies with Captopril as Monotherapy and in Combination with Nifedipine in Old Spontaneously Hypertensive Rats.

Background: A major problem in the treatment of human hypertension is the late diagnosis of hypertension and, hence, the delayed start of treatment. Very often, hypertension has existed for a long time and cardiac damage has already developed. Therefore, we tested whether late-onset antihypertensive treatment is effective in lowering blood pressure (BP) and in reducing or even preventing left ventricular hypertrophy and fibrosis. Methods: Twenty-one male 60-week-old spontaneously hypertensive rats (SHR) were included. Fourteen rats received oral treatment with captopril (CAP) either as monotherapy or combined with nifedipine (CAP + NIF) over 22 weeks. Seven untreated SHR served as controls. We examined the therapeutic effects on BP, heart weight and histological and biochemical markers of left ventricular remodeling and fibrosis. Results: At 82 weeks of age, BP was reduced in the CAP and CAP + NIF groups by 44 and 51 mmHg, respectively (p < 0.001), but not in untreated controls. Despite the late therapy start, cardiac hypertrophy and fibrosis were attenuated compared to controls. Both treatments reduced heart weight by 1.2 mg/g (25%, p = 0.001) and collagens I and III by 66% and 60%, respectively (p < 0.001), thus proving nearly equivalent cardioprotective efficacy. Conclusion: These data clearly emphasize the benefit of antihypertensive treatment in reducing BP and mitigating the development of cardiac damage even when treatment is started late in life.

Antihypertensive and cardioprotective effects of different monotherapies and combination therapies in young spontaneously hypertensive rats - A pilot study.

Spontaneously hypertensive rats (SHR) are an established animal model for antihypertensive treatment. The aim of this pilot study was a systematic search for two lines of antihypertensive treatment - a monotherapy and a combination of two drugs - to be applied in a future study on old SHR. Originally, representatives of three drug classes recommended for antihypertensive therapy in humans should be applied, namely captopril (CAP) as an antagonist of the renin-angiotensin-aldosterone system, nifedipine (NIF) as calcium channel blocker and propranolol (PROP) as ß-adrenergic blocker. As we observed that PROP had been poorly ingested, all groups with PROP therapy were excluded from the study. CAP (60 mg kg-1 d-1), NIF (10 mg kg-1 d-1) or both were administered orally to seven-week-old SHR over 3 weeks. A further group of SHR received no treatment (SHR/CTRL). Age-matched normotensive Wistar-Kyoto rats served as normotensive controls. We examined the effect of the antihypertensive therapies on systolic blood pressure, heart weight and on histological and biochemical markers of cardiac hypertrophy and fibrosis. CAP proved to be the most effective treatment reducing blood pressure and relative heart weight significantly compared to SHR/CTRL without reaching normotensive values. Beginning cardiac fibrosis observed in SHR/CTRL was completely abrogated with CAP treatment. Similar effects were achieved with a combination of CAP and NIF. CAP as monotherapy and CAP + NIF as combination therapy were chosen for the forthcoming study on old SHR.

Effects of late-onset and long-term captopril and nifedipine treatment in aged spontaneously hypertensive rats: Echocardiographic studies.

The purpose of the present study was to analyze the changes in blood pressure, left ventricular (LV) wall thickness and LV systolic function of aged spontaneously hypertensive rats (SHRs) either with or without antihypertensive therapy. Twenty-one SHRs aged 60.5±0.25 weeks were investigated over 22 weeks. They were divided into the following three groups (7 per group): untreated controls (CTRL), treatment with captopril (CAP, 60 mg kg(-1) daily) and treatment with captopril plus nifedipine (CAP+NIF, 60+10 mg kg(-1) daily). Systolic blood pressure (SBP) was regularly measured using the tail cuff method, and an echocardiogram was repeatedly obtained to examine the LV systolic and diastolic area, LV systolic fractional area change, cardiac output and LV myocardial wall thickness. Finally, heart catheterization was performed. While SBP remained stable in the CTRL animals over the experimental period, both of the antihypertensive treatments significantly reduced SBP by 20% in the treated animals (P<0.001). Echocardiography demonstrated that both the systolic and the diastolic LV function of the untreated SHRs deteriorated over time, whereas both types of antihypertensive treatments attenuated and delayed but did not completely prevent the decline in LV systolic function. Cardiac output, as determined by pulsed wave Doppler echocardiography, remained significantly higher in the treated animals than in CTRLs until week 20, but it then decreased. Heart catheterization showed a significant decrease in LV function, as reflected by the LV systolic pressure and contractility, in the CTRLs but not in treated animals. These findings clearly indicate that late-onset antihypertensive treatment with CAP or CAP+NIF is beneficial with respect to blood pressure reduction, LV hypertrophy attenuation and LV systolic function preservation.

Is glutamine deficiency the link between inflammation, malnutrition, and fatigue in cancer patients?

PURPOSE: Evaluation of potential associations between plasma glutamine levels and the incidence of cancer related fatigue, physical performance, poor nutritional status, and inflammation in patients with solid tumors. STUDY DESIGN: Mono-center cross-sectional study recruiting 100 (34 women) consecutive patients (September 2009-March 2011; ≥18 y) with solid tumors and causal tumor therapy. METHODOLOGY: Fasting venous blood was harvested for routine clinical chemistry, amino acid (HPLC) and inflammation marker analyses. Clinical assessments included global, physical, affective and cognitive fatigue (questionnaire) and Karnofsky performance status. Nutritional status was evaluated using bioelectrical impedance analysis, the Prognostic Inflammatory and Nutritional Index and plasma protein levels. Regression analyses were performed to correlate continuous variables with plasma glutamine (95% confidence intervals). RESULTS: Nutritional status was impaired in 19% of the patients. Average plasma glutamine concentration (574.0 ± 189.6 µmol/L) was within normal range but decreased with impaired physical function. Plasma glutamine was linked to the ratio extracellular to body cell mass (p < 0.044), CRP (p < 0.001), physical (p = 0.014), affective (p = 0.041), and global fatigue (p = 0.030). Markers of inflammation increased with low physical performance. CONCLUSIONS: The data support our working hypothesis that in cancer patients systemic inflammation maintains a catabolic situation leading to malnutrition symptoms and glutamine deprivation, the latter being associated with cancer related fatigue.

Catecholamines can induce pulmonary remodeling in rats.

BACKGROUND/AIMS: Previously, we found that catecholamine (CA) infusion in rats induced pulmonary injury with edema and inflammation resembling acute lung injury in humans. Here, we examined effects of norepinephrine (NE) and of selective α- and ß-adrenergic agonists on the remodeling of pulmonary extracellular matrix. METHODS: Eighty rats were infused over 8-72 h with NE, phenylephrine (PE), isoproterenol (ISO) or NaCl solution. We investigated mRNA expression of collagen, matrix metalloproteinase (MMP)-2, its tissue inhibitor (TIMP-2) and transforming growth factor (TGF)-ß isoforms in lung tissue. Additionally, lung histology, hemodynamic function and cardiac hypertrophy were evaluated. RESULTS: After 72 h of infusion, lung histology showed beginning fibrosis and vascular hypertrophy. Collagen type I, MMP-2 and TIMP-2 mRNA expression were significantly elevated. All these effects were most pronounced with NE while PE and ISO induced weaker responses. TGF-ß mRNA expression was also elevated after 72 h, predominantly after PE infusion. Cardiac hypertrophy was most pronounced after ISO infusion. CONCLUSION: CA infusion over 72 h may induce pulmonary remodeling. Mainly α-adrenergic but also ß-adrenergic mechanisms contribute to these processes. In contrast, cardiac hypertrophy is predominantly mediated by ß-adrenergic stimulation and hence, is considered to be a direct adrenergic effect rather than a consequence of pulmonary fibrosis.

Ribose treatment reduced the infarct size and improved heart function after myocardial infarction in rats.

OBJECTIVE: In this study the effect of ribose on heart function and infarct-size was analyzed 6 h after myocardial infarction (MI) in rats. METHODS: Continuous i.v.-infusion of NaCl or ribose (200 mg/kg/h) was started one day prior to induction of MI in female Sprague-Dawley rats which was done by ligation of the left coronary artery. Six hours after MI heart function was measured with 3F tip catheter, cardiac output by thermodilution method. Thereafter the ischemic area was delineated by Evans Blue infusion, and the infarct area was visualized by triphenyltetrazolium chloride staining. The mRNA expression of interleukin (IL)-1beta, IL-6, matrix-metalloproteinase (MMP)-8, and -9 was measured by ribonuclease protection assay. RESULTS: Heart function was severely depressed 6 hours after coronary artery occlusion, but recovered significantly under the influence of ribose. Left ventricular (LV) systolic pressure (LVSP) and contractility (LVdP/dtmax) were restored to the normal levels of sham-operated animals, while parameters of LV relaxation (LVdP/dtmin and time constant of relaxation tau) were impaired compared to sham-operated animals, but significantly improved by ribose treatment compared to sham-treated MI-rats. Moreover, the infarct size was significantly smaller in the ribose treated animals despite a comparable ischemic area at risk in all MI-rats. The cytokine mRNA expression after MI was significantly reduced after ribose treatment, while there were no differences regarding MMP expression. CONCLUSION: MI size was significantly reduced and LV function significantly improved by ribose treatment at 6 h after MI. This seemed to be based on slowing the velocity of the necrotic wave front across the LV wall after MI resulting in smaller infarcts.

Crucial role of interleukin-6 in the development of norepinephrine-induced left ventricular remodeling in mice.

BACKGROUND: Elevated serum concentration of interleukin (IL)-6 is a predictor for poor prognosis in congestive heart failure. It was shown previously in rats, that IL-6 expression in the left ventricle (LV) was followed by LV hypertrophy. METHODS: Using IL-6 deficient mice (IL-6(-/-)), we studied the role of IL-6 in a model of norepinephrine (NE)-induced LV hypertrophy. RESULTS: In wild type (WT) mice, IL-6 mRNA expression and its concentration in the serum were elevated after 4 h of NE-treatment (s.c. 0.25 mg.h)./kg Further, NE-induced LV hypertrophy was detected: LV weight/body weight (LVW/BW) ratio (+12.3+/-3%, p < 0.05) and mRNA expression of atrial natriuretic peptide (ANP) in WT mice (+120+/-25%, p < 0.05) after 3 days were increased. In contrast, NE did not induce elevation of LVW/BW ratio and ANP expression in IL-6(-/-) mice. Replacement with recombinant IL-6 restored the hypertrophy-inducing effect of NE in IL-6(-/-) mice. As to the extracellular matrix (ECM) proteins, NE increased collagen type I and III expression only in WT mice and not in IL-6(-/-) mice. The addition of recombinant IL-6 elevated the expression of the ECM proteins to the WT level. CONCLUSION: IL-6 is a major player in the development of NE-induced LV hypertrophy in mice.

Cord blood cell therapy alters LV remodeling and cytokine expression but does not improve heart function after myocardial infarction in rats.

OBJECTIVE: In this study the ability of unrestricted somatic stem cells (USSC) and mononuclear cord blood cells (MN-CBC) was tested to improve heart function and left ventricular (LV) remodeling after myocardial infarction (MI). METHODS: The cells were delivered by i.v. or intramyocardial injections in rat models of MI by permanent coronary artery occlusion and by ischemia/reperfusion (I/R) injury. Heart function and remodeling was followed by recurrent echocardiography over 8 or 12 weeks after which catheterization was performed. RESULTS: Although injected labeled cells could be observed within the myocardium for up to 6 d, there was no sign of cardiac regeneration 8 or 12 weeks after MI. However, the mRNA expression of components of the extracellular matrix was attenuated in the infarct scar 12 weeks after MI and cell injection. Additionally, the expression of interleukin (IL)-6 but not of IL-1 beta increased at the site of injury and the adjacent border-zone 12 weeks after I/R and USSC-injection. However, these effects did not translate into improved heart function or attenuated LV dilatation. CONCLUSION: These data indicate that cord blood cell implantation after MI acts through paracrine mechanisms to modify remodeling rather than myocyte regeneration. The role of myofibroblasts and the optimal conditions of cell application need to be determined to translate these mechanisms into functional improvement.

Tissue inhibitor of matrix metalloproteinase-1 in norepinephrine-induced remodeling of the mouse heart.

BACKGROUND: Matrix metalloproteinases (MMPs) play an important role in myocardial remodeling. Their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). The present study analyzed the contribution of changes in functional and molecular parameters to early cardiac remodeling in mice hearts. The role that TIMPs might play in this process was specially acknowledged. METHODS: The remodeling was induced by norepinephrine (NE) given sc in balb/c mice. Varying concentrations, time and the addition of a neutralizing TIMP-1 antibody were evaluated. RESULTS: High dose NE led to insufficiency of the left ventricle (LV) as evidenced by reduced NE-induced elevation of LV systolic pressure, contractility and relaxation. Further, signs of lung congestion were seen. NE induced a concentration-dependent increase of LV weight/body weight (LVW/BW) ratio and elevated mRNA expression of atrial natriuretic peptide (ANP). This was accompanied by induction of collagen type I and III, as well as TIMP-1 expression. CONCLUSIONS: The NE-induced increase of TIMP-1 expression may induce the elevation of the antihypertrophic cardiac factor ANP since NE-induced increase of ANP expression was abolished by neutralizing TIMP-1 antibody. Thus, TIMP-1 may mediate ANP-induced attenuation of NE-induced hypertrophy in the mouse heart.

Contrast enhanced echocardiographic follow-up of cardiac remodeling and function after myocardial infarction in rats.

Echocardiography is a reliable and commonly used method to examine cardiac diseases. Recent employment of modern technologies provides new opportunities to study left ventricular (LV) remodeling after myocardial infarction (MI) also in small rodents. LV volumes as most important prognostic parameters can be estimated by noncontrast enhanced echocardiography in rats from M-mode or single cross sections only. In this study, contrast enhanced echocardiography and volume measurements by the biplane method of discs (Simpson's rule) were applied in rats to monitor remodeling and function after MI. MI was induced in female Sprague-Dawley rats (n = 26 for MI, and n = 16 for sham). LV remodeling and heart function were serially studied by contrast enhanced echocardiography for 12 to 16 wk. At the end of the observation periods hemodynamic data were additionally measured by left and right heart catheterization. LV end systolic volume (LVESV) measured by biplane method of discs correlated best with LV developed pressure as indicator for severely impaired heart function. Interestingly, LV end systolic area (LVESA) from native short axis view correlated well with LVESV (R(2) = 0.93) and was the second best predictor for depressed heart function. Moreover, left atrial size was a powerful indicator of severely impaired heart function whereas ejection fraction or fractional area change were primarily related to infarct size. In conclusion, contrast enhanced echocardiography in rats is feasible and an economical method to study time-dependent LV remodeling and deterioration of contractile function after MI.

Time course of hypoxia-induced lung injury in rats.

We investigated the effects of normobaric hypoxia on rat lungs and hypothesized that the hypoxic exposure would induce lung injury with pulmonary edema and inflammation ensued by development of fibrosis. Rats were exposed to 10% O(2) in nitrogen over 6-168h. We analyzed cardiovascular function and pulmonary changes, lung histology and mRNA expression of extracellular matrix (ECM) molecules in the lung. Significant hemodynamic changes occurred after 168h of hypoxic exposure. Moderate pulmonary edema appeared after 8h and peaked after 16h of hypoxia. It was accompanied by inflammation, fibrosis and vascular hypertrophy. mRNA expression of transforming growth factor-beta2 and -beta3 was up-regulated in lung tissue after 8h of hypoxia. After 8-16h, mRNA expression of collagen types I and III and of other ECM molecules was significantly elevated and increased further with longer exposure to hypoxia. The time course of hypoxia-induced pulmonary injury resembled that previously observed after continuous norepinephrine infusion in rats.

Effects of salt loading and various therapies on cardiac hypertrophy and fibrosis in young spontaneously hypertensive rats.

We investigated the effects of salt loading on blood pressure, cardiac hypertrophy and fibrosis as well as on the effectiveness of various antihypertensive therapies in young spontaneously hypertensive rats (SHR). Twenty-five male SHR were salt-stimulated by drinking 1% NaCl from 3 to 6 months of age. Eighteen of them were treated for the last 2 weeks of salt loading with either the angiotensin-converting enzyme inhibitor captopril, the beta-adrenergic receptor blocker propranolol or the calcium-channel antagonist verapamil. Age-matched male Wistar-Kyoto (WKY) rats and SHR drinking only water served as controls. At the age of 6 months, SHR had significantly elevated blood pressure that was unchanged by salt loading. Relative heart weight was increased in SHR without (3.3) and even more so with salt intake (3.6 vs. 2.4 in WKY). Left ventricular (LV) hypertrophy was accompanied by a 17-fold increase in the expression of mRNA for atrial natriuretic factor (ANF) both in untreated and salt-loaded SHR compared to WKY (p<0.001). Collagen I and III mRNA increased 1.7-1.8-fold in SHR without and with additional salt intake (p<0.01). None of the therapies significantly reduced blood pressure or hypertrophy. Although captopril had no antihypertensive effect, it reduced ANF, collagen I and III mRNA in LV to control level. Less pronounced effects were achieved with verapamil. These findings emphasize the cardioprotective role of captopril which may not be fully expressed in the presence of elevated salt intake.