The consequences of cerebral ischemia were studied in three different strains (BDF, CFW, and BALB/C) of mice. The different strains exhibited significant differences in susceptibility to 24-h focal ischemia. Following middle cerebral artery occlusion (MCAO), infarct volumes (mm3) were 5 +/- 3 in BDF, 15 +/- 5 in CFW, and 23 +/- 3 in BALB/C mice (p < 0.05). MCAO plus ipsilateral common carotid artery occlusion (CCAO) resulted in infarct volumes of 15 +/- 9 in BDF, 38 +/- 10 in CFW, and 72 +/- 12 in BALB/C mice (p < 0.05). In addition, MCAO plus CCAO produced death by 24 h in 42% of CFW and 67% of BALB/C mice, but not in any BDF mice (p < 0.05). CCAO alone produced multifocal hemispheric infarctions in 36% of BALB/C mice but not in the other two strains. Brains of all mouse strains subjected to sham surgery were free of any ischemic injury. Arterial blood pressures, blood gases, and blood cell profiles were relatively similar for the three mouse strains. However, carbon black studies of the cerebrovascular anatomy revealed an incomplete circle of Willis (i.e., a significant decrease in the frequency of patent posterior communicating arteries) for BALB/C compared with BDF mice (p < 0.05), with CFW mice being intermediary. Based on these anatomical data, BALB/C mice also were evaluated following transient global brain ischemia produced by bilateral CCAO. BALB/C mice exhibited a > 85% reduction in cortical microvascular perfusion and EEG power within 1 min of bilateral CCAO. Also, hippocampal neuronal CA1 damage and mortality over 7 days were related to the duration of global brain ischemia (p < 0.05). These data demonstrate a significant difference between mouse strains in their sensitivity to cerebral ischemia that appears to be related, at least in part, to the functional vascular anatomy at the level of the posterior communicating arteries. In particular, we point out the potential usefulness of BALB/C mice as a sensitive and reproducible model of focal and global ischemia.

Background-Numerous pathological mediators of cardiac hypertrophy (eg, neurohormones, cytokines, and stretch) have been shown to activate p38 MAPK. The purpose of the present study was to examine p38 MAPK activation and the effects of its long-term inhibition in a model of hypertensive cardiac hypertrophy/dysfunction and end-organ damage. Methods and Results-In spontaneously hypertensive stroke-prone (SP) rats receiving a high-salt/high-fat diet (SFD), myocardial p38 MAPK was activated persistently during the development of cardiac hypertrophy and inactivated during decompensation. Long-term oral treatment of SFD-SP rats with a selective p38 MAPK inhibitor (SB239063) significantly enhanced survival over an 18-week period compared with the untreated group (100% versus 50%). Periodic echocardiographic analysis revealed a significant reduction in LV hypertrophy and dysfunction in the SB239063-treatment groups. Little or no difference in blood pressure was noted in the treatment or vehicle groups. Basal and stimulated (lipopolysaccharide) plasma tumor necrosis factor-␣ concentrations were reduced in the SB239063-treatment groups. In vitro vasoreactivity studies demonstrated a significant preservation of endothelium-dependent relaxation in animals treated with the p38 MAPK inhibitor without effects on contraction or NO-mediated vasorelaxation. Proteinuria and the incidence of stroke (53% versus 7%) were also reduced significantly in the SB239063-treated groups. Conclusions-These results demonstrate a crucial role for p38 MAPK in hypertensive cardiac hypertrophy and end-organ damage. Interrupting its function with a specific p38 MAPK inhibitor halts clinical deterioration. (Circulation. 2001;

1 The eect of carvedilol on renal function, structure and expression of TGFb and the matrix proteins ®bronectin, collagen I and collagen III, was evaluated in spontaneously hypertensive strokeprone (SHR-SP) rats fed a high fat, high salt diet. 2 Carvedilol treatment for 11 to 18 weeks did not alter systolic blood pressure in SHR-SP rats, however, it resulted in a signi®cant reduction in heart rate. 3 Carvedilol treatment reduced renal ®brosis and total, active and chronic renal damage to levels approaching those of WKY rats on a normal diet. 4 Urinary protein excretion was higher in SHR-SP rats (51+10 mg day 71 ) than WKY rats (18+2 mg day 71) and this was further increased when SHR-SP rats were fed a high fat, high salt diet (251+120 mg day 71). Treatment with carvedilol resulted in signi®cantly lower urinary protein excretion (37+15 mg day 71). 5 The expression of TGFb mRNA was signi®cantly higher in SHR-SP rats compared to WKY rats and a further increase was observed when rats were fed a high fat, high salt diet. Renal TGFb expression was signi®cantly reduced by treatment with carvedilol. The expression of ®bronectin and collagen I and collagen III mRNA showed a pattern similar to that observed with TGFb mRNA expression. Collagen I mRNA expression followed a pattern similar to renal ®brosis. 6 These data indicate that carvedilol can provide signi®cant renal protection in the absence of any antihypertensive activity and that the mechanisms involved in this action may include reduced expression of pro®brotic factors such as TGFb.

These data indicate that carvedilol provides remarkable cardioprotection, by suppressing severe hypertension-induced cardiac remodeling and myopathies at doses that do not reduce systemic blood pressure.

No abstract

The effects of the angiotensin type 1 (AT 1 ) receptor antagonist, eprosartan, were studied in a model of severe, chronic hypertension. Treatment of male spontaneously hypertensive stroke prone rats (SHR-SP) fed a high-fat, high-salt diet with eprosartan (60 mg/kg/day i.p.) for 12 weeks resulted in a lowering of blood pressure (250 Ϯ 9 versus 284 Ϯ 8 mm Hg), renal expression of transforming growth factor-␤ mRNA (1.5 Ϯ 0.2 versus 5.4 Ϯ 1.4) and the matrix components: plasminogen activator inhibitor-1 (5.2 Ϯ 1.4 versus 31.4 Ϯ 10.7), fibronectin (2.2 Ϯ 0.6 versus 8.2 Ϯ 2.2), collagen I-␣1 (5.6 Ϯ 2.0 versus 23.8 Ϯ 7.3), and collagen III (2.7 Ϯ 0.9 versus 7.6 Ϯ 2.1). Data were corrected for rpL32 mRNA expression and expressed relative to Wistar Kyoto (WKY) rats [ϭ1.0]. Expression of fibronectin protein was also lowered by eprosartan (0.8 Ϯ 0.1 versus 1.9 Ϯ 0.5), relative to WKY rats. Eprosartan provided significant renoprotection to SHR-SP rats as measured by decreased proteinuria (22 Ϯ 2 versus 127 Ϯ 13 mg/day) and histological evidence of active renal damage (5 Ϯ 2 versus 195 Ϯ 6) and renal fibrosis (5.9 Ϯ 0.7 versus 16.4 Ϯ 1.9) in vehicle-versus eprosartantreated rats, respectively. Our results demonstrated that AT 1 receptor blockade with eprosartan can reduce blood pressure and preserve renal structure and function in this model of severe, chronic hypertension. These effects were accompanied by a decreased renal expression of transforming growth factor-␤1, plasminogen activator inhibitor-1, and several other extracellular matrix proteins compared with vehicle-treated SHR-SP.The renin-angiotensin system is a major regulator of blood pressure within the body, through the maintenance of vascular tone and sodium homeostasis. The renin-angiotensin system has, however, also been implicated in a number of diseases, characterized by remodeling and fibrosis, including forms of progressive renal disease. The generation of angiotensin II can lead to organ damage through both mitogenic activity and profibrotic remodeling. Eprosartan is a potent (K i ϭ 1.4 nM) angiotensin II receptor antagonist selective for the AT 1 subtype. AT 1 receptor antagonists have been shown to attenuate the effects of exogenous angiotensin II (Wang et al., 1997) and to be renoprotective in the partial nephrectomy model of renal failure (Gandhi et al., 1999), as measured by its ability to attenuate the hypertension, proteinuria, and up-regulation in the expression of several profibrotic genes associated with this model (Wong et al., 2000). TGF-␤ gene expression has been shown to be upregulated in a number of animal models of fibrotic disease, including renal disease (Border and Noble, 1998) and can be induced by several different vasoactive mitogens, including angiotensin II (Klahr and Morrissey, 2000). This profibrotic cytokine mediates the up-regulation of several extracellular matrix component genes, including fibronectin and collagen, leading to increased synthesis of the extracellular matrix (Ignotz and Massague, 1986). Furthermore, TGF...

Evidence suggests that endothelin receptor antagonists may have therapeutic potential for the chronic treatment of heart failure. In the current study, the effects of an orally active mixed endothelin-A/endothelin-B (ETA /ETB ) receptor antagonist (enrasentan) were assessed in a model of cardiac hypertrophy and dysfunction (spontaneously hypertensive stroke prone rats) maintained on a high-salt/high-fat diet. Echocardiography was used to quantify cardiac performance and left ventricular dimensions. Enrasentan (1,200 and 2,400 parts per million in the high-salt/high-fat diet) had no significant effects on body weight and systolic blood pressure. However, increases in heart rate were not observed in the enrasentan-treated groups at 12 weeks (p < 0.05). Enrasentan-treated groups exhibited significantly improved survival (90-95% vs. 30% [control rats] at 18 weeks; p < 0.001). Enrasentan treatments also increased stroke volume (at 8, 12, and 16 weeks) and cardiac index (at 8 and 16 weeks) 33-50% and 45-63%, respectively. Enrasentan treatments reduced the relative wall thickness (14-27% at 8 and 12 weeks), ratio of left ventricular mass to body weight (20% at 12 weeks), and ratio of terminal heart weight to body weight (16-23%, p < 0.05). Finally, circulating aldosterone concentration (54-57%) and proANF fragment (33%) were reduced in enrasentan-treated groups (54-57% and 33%, respectively). Mixed ETA /ETB receptor antagonism improves cardiac performance and attenuates ventricular remodeling and premature mortality in an aggressive hypertension model.

Background/Aims: Histological studies have provided evidence that carvedilol can prevent cardiac hypertrophy in spontaneously hypertensive-stroke prone rats (SP) fed a high-fat and -salt diet. However, the effects of carvedilol on cardiac function have not been studied in these animals. In addition, the ability of carvedilol to reverse established cardiac hypertrophy and dysfunction under these conditions remains to be determined. Here we have evaluated the ability of carvedilol to prevent and reverse cardiac hypertrophy and progressive dysfunction using echocardiography. Methods: Two echocardiology studies were conducted to determine the effects of carvedilol treatment on cardiac hypertrophy and dysfunction. In the first prevention study, four groups of rats were evaluated. SP were fed a high-fat (24.5% in food) and high-salt (1% in water) diet (SFD) without (SP-SFD control group) or with carvedilol (SP-SFD carvedilol group; carvedilol concentration 2,400 parts per million) for 18 weeks. Carvedilol was administered in the food at an optimum concentration (i.e. known to provide clinically relevant blood concentrations and reduce cardiac hypertrophy determined from previous studies). In addition, SP and WKY rats were fed a normal diet (SP normal diet group and WKY normal diet group). These groups are known to not develop the same significant cardiac hypertrophy and dysfunction within this limited time of study, and provided two more normal control groups for comparison. In the second reversal study, one group of SP was fed SFD for 12 weeks (SP-SFD pretreatment period) to induce cardiac hypertrophy. Carvedilol (2,400 parts per million) was then added to the diet for an additional 6 weeks (SP-SFD carvedilol treatment period). Results: In the first prevention study, carvedilol prolonged longevity (p < 0.05) and prevented left-ventricular hypertrophy and dysfunction (p < 0.05; SP-SFD control vs. SP-SFD carvedilol group). M-mode-measured and -calculated parameters demonstrated that carvedilol treatment in the SP-SFD carvedilol group prevented increases in left-ventricular wall thickness (p < 0.05) and decreases in diastolic chamber diameter and volume, stroke volume, ejection fraction and cardiac output (all p < 0.05) that occurred in the SP-SFD control group. Further, cardiac measurements in the SP-SFD carvedilol group were normalized to levels similar to those in the SP and WKY normal diet groups. All SFD-fed groups exhibited similar, significantly elevated blood pressure during the study. In the second reversal study, carvedilol treatment for 6 weeks reversed the cardiac hypertrophy and dysfunction that developed in SP-fed SFD for 12 weeks prior to carvedilol intervention. Under these conditions, carvedilol improved/normalized left-ventricular wall thickness, diastolic ventricular-chamber diameter and volume, stroke volume, ejection fraction and cardiac output (all p < 0.05). Conclusions: These data indicate that carvedilol provides protection from and facilitates reversal of progressive cardiac remodeling and dysfu...