Myocardial morphology and cardiac function in rats with renal failure

Synergistic effects of Ficus Carica extract and extra virgin olive oil against oxidative injury, cytokine liberation, and inflammation mediated by 5-Fluorouracil in cardiac and renal tissues of male albino rats

5-Fluorouracil (5-FU), a chemotherapeutic drug, has adverse effects on heart and kidney functions. Ficus Carica (fig) and extra virgin olive oil (EVOO) are natural sources which have antioxidant effects. This study investigated the synergistic effects of fig extract and EVOO against cardiac and renal damage induced by 5-FU. Forty rats were equally divided into five groups and treated with physiological saline (control), five intravenous injections of 5-FU (40 mg/kg b.w) (5-FU), fig (1 g/kg b.w/day, orally) with 5-FU (Fig/5-FU), EVOO (7 g/kg b.w/day, orally) with 5-FU (EVOO/5-FU), combined treatment of fig and EVOO with five 5-FU injections (Fig/EVOO/5-FU). After 30 days, blood and tissue samples (Heart and kidney) were collected to be used in the examinations. 5-FU significantly increased serum creatine kinase activity, renal biomarkers, cholesterol, triglycerides, C-reactive protein, tumor necrosis factor-α, and interleukin-1β as well as cardiac and renal lipid peroxides (malondialdehyde). Meanwhile, serum levels of immunoglobulins, interleukins (IL-10, IL-12), and antioxidants of heart and kidney tissues were significantly decreased in 5-FU group. It also downregulated cardiac and renal Bcl2, and upregulated cardiac troponin and renin gene expressions. As well, histological alterations clarified that 5-FU induced cardiac cell damage, distorted renal corpuscles and tubules, inflammatory cell infiltrations, and severe congestion and hemorrhage in the blood vessels. The treatment with fig and olive oil, especially the combined treatment, modulated the toxic effect of 5-FU on the heart and kidney. Our results revealed that fig extract and EVOO have a powerful antioxidant and many protective effects against cardiac and renal toxicity induced by 5-FU, especially when using fig and EVOO together as a combined treatment.

Cardiac function and tolerance to ischemia-reperfusion injury in chronic kidney disease

BACKGROUND

Cardiac dysfunction is an independent risk factor of ischemic heart disease and mortality in chronic kidney disease (CKD) patients, yet the relationship between impaired cardiac function and tolerance to ischemia-reperfusion (IR) injury in experimental CKD remains unclear.

METHODS

Cardiac function was assessed in 5/6 ablation-infarction (AI) and sham male Sprague-Dawley rats at 20 weeks of age, 8 weeks post-surgery using an isolated working heart system. This included measures taken during manipulation of preload and afterload to produce left ventricular (LV) function curves as well as during reperfusion following a 15-min ischemic bout. In addition, LV tissue was used for biochemical tissue analysis.

RESULTS

Cardiac function was impaired in AI animals during preload and afterload manipulations. Cardiac functional impairments persisted post-ischemia in the AI animals, and 36% of AI animals did not recover sufficiently to achieve aortic overflow following ischemia (versus 0% of sham animals). However, for those animals able to withstand the ischemic perturbation, no difference was observed in percent recovery of post-ischemic cardiac function between groups. Urinary NOx (nitrite + nitrate) excretion was lower in AI animals and accompanied by reduced LV endothelial nitric oxide synthase and NOx. LV antioxidants superoxide dismutase-1 and -2 were reduced in AI animals, whereas glutathione peroxidase-1/2 as well as NADPH-oxidase-4 and H(2)O(2) were increased in these animals.

CONCLUSIONS

Impaired cardiac function appears to predispose AI rats to poor outcomes following short-duration ischemic insult. These findings could be, in part, mediated by increased oxidative stress via nitric oxide-dependent and -independent mechanisms.

Target organ cross talk in cardiorenal syndrome: animal models

The combination of chronic kidney disease (CKD) and heart failure (HF) is associated with an adverse prognosis. Although clinical studies hint at a specific bidirectional interaction between HF and CKD, insight into the pathogenesis of cardiorenal syndrome (CRS) remains limited. We review available evidence on cardiorenal interactions from animal models of CKD and HF and discuss several studies that employed a "double-hit" model to research organ cross talk between the heart and kidneys. Regarding cardiac changes in CKD models, parameters of cardiac remodeling are equivocal and cardiac systolic function generally remains preserved. Structural changes include hypertrophy, fibrosis, and microvasculopathy. In models of HF, data on renal pathology are mostly limited to functional hemodynamic changes. Most double-hit models were unable to show that combined renal and cardiac injury induces additive damage to both organs, perhaps because of the short study duration or absence of organ failure. Because of this lack of "dual-failure" models, we have developed two rat models of combined CKD and HF in which renal dysfunction induced by a subtotal nephrectomy preceded cardiac dysfunction. Cardiac dysfunction was induced either functionally by nitric oxide depletion or structurally by myocardial infarction. In both models, we found that cardiac remodeling and failure were worse in CKD rats compared with controls undergoing the same cardiac insult. Variables of renal damage, like glomerulosclerosis and proteinuria, were also further worsened by combined cardiorenal injury. These studies show that target organ cross talk does occur in CRS. These models may be useful for interventional studies in rats.

Subtotal nephrectomy plus coronary ligation leads to more pronounced damage in both organs than either nephrectomy or coronary ligation

Coexistence of chronic kidney disease (CKD) and heart failure (HF) in humans is associated with poor outcome. We hypothesized that preexistent CKD worsens cardiac outcome after myocardial infarction, and conversely that ensuing HF worsens progression of CKD. Subtotally nephrectomized (SNX) or sham-operated (CON) rats were subjected to coronary ligation (CL) or sham surgery in week 9 to realize four groups: CON, SNX, CON + CL, and SNX + CL. Blood pressure and renal function were measured in weeks 8, 11, 13, and 15. In week 16, cardiac hemodynamics and end-organ damage were assessed. Blood pressure was significantly lower in SNX + CL vs. SNX. Despite this, glomerulosclerosis was more severe in SNX + CL vs. SNX. Two weeks after CL, SNX + CL had more cardiac dilatation compared with CON + CL (end-diastolic volume index: 0.28 ± 0.04 vs. 0.19 ± 0.03 ml/100 g body wt; mean ± SD, P < 0.001), although infarct size was similar. During follow-up in SNX + CL, ejection fraction declined. Mortality was only observed in SNX + CL (2 out of 9). In SNX + CL, end-diastolic pressure (18 ± 4 mmHg) and tau (29 ± 9 ms), the time constant of active relaxation, were significantly higher compared with SNX (13 ± 3 mmHg, 20 ± 4 ms; P < 0.01) and CON + CL (11 ± 5 mmHg, 17 ± 2 ms; P < 0.01). The diameter of small arterioles in the myocardium was significantly decreased in SNX + CL vs. CON + CL (P < 0.01). Urinary excretion of NO metabolites was significantly lower in SNX + CL compared with both CL and SNX. This study demonstrates the existence of more heart and more kidney damage in a new model of combined CKD and HF than in the individual models. Such enhanced damage appears to be separate from systemic hemodynamic changes. Reduced nitric oxide availability may have played a role in both worsened glomerulosclerosis and cardiac diastolic function and appears to be a connector in the cardiorenal syndrome.

Renal failure induces telomere shortening in the rat heart

BACKGROUND

Renal failure aggravates pathological cardiac remodelling induced by myocardial infarction (MI). Cardiac remodelling is associated with telomere shortening, a marker for biological ageing. We investigated whether mild and severe renal failure shorten cardiac telomeres and excessively shorten telomeres after MI.

METHODS

Rats were subjected to sham, unilateral (UNX) or 5/6th nephrectomy (5/6NX) to induce none, mild or severe renal failure. MI was induced by left coronary artery ligation. Renal function parameters and blood pressure were measured. DNA was isolated from non-infarcted cardiac tissue. Telomere length was assessed by quantitative polymerase chain reaction (PCR).

RESULTS

Proteinuria was unchanged in UNX and MI compared with control, but strongly increased in 5/6NX, UNX+MI and 5/6NX+MI. Serum creatinine levels were increased fourfold in 5/6NX and tenfold in 5/6NX+MI. 5/6NX and groups with both renal failure and MI showed an approximate 20% reduction of telomere length, similar to the MI group. No excess telomere shortening was observed in hearts from rats with renal ablation after MI.

CONCLUSION

Severe renal failure, but not mild renal failure, leads to shortening of cardiac telomeres to a similar extent as found after MI. Renal failure did not induce excessive telomere shortening after MI. (Neth Heart J 2009;17:190-4.).

Coronary revascularization improves long-term prognosis in diabetic and nondiabetic end-stage renal disease

To test the hypothesis that coronary revascularization improves long-term prognosis in patients with hemodialysis, 80 of 121 patients (66%) on maintenance hemodialysis who had undergone initial coronary angiography had bypass surgery, catheter angioplasty, or both between 1983 and 1999. Multivessel disease was more frequent (p=0.01) and the duration of hemodialysis therapy was shorter (p=0.01) in patients with diabetes (n=61), than in nondiabetic patients (n=60). Of the patients who underwent revascularization, complete revascularization was achieved in 75% of those with diabetic nephropathy (30/40) and 83% in a similar number of nondiabetic patients (33/40). The 5-year survival rate from initiation of hemodialysis was 79% in diabetic and 96% in non-diabetic patients (p<0.01), exceeding published Japanese (53% vs 70%) and US (26% vs 60%) survival rates. When survival was studied from the date of revascularization, predictors of outcome were age and achievement of complete revascularization. Surprisingly, diabetes was not a predictor of survival outcome. Complete revascularization improves long-term survival in both diabetic and nondiabetic patients.

Cardiac beta-adrenoceptor desensitization due to increased beta-adrenoceptor kinase activity in chronic uremia

Patients with chronic renal failure develop an autonomic dysfunction with impaired baroreflex control and attenuated cardiovascular beta-adrenoceptor response to noradrenaline. In rats that underwent 5/6-nephrectomy (SNX), cardiac beta-adrenoceptor responsiveness was reduced as well. Therefore, the aim of this study was to further investigate the mechanism underlying cardiac beta-adrenoceptor desensitization in SNX rats. For this purpose, right and left ventricular beta-adrenoceptor density, activity of the G-protein-coupled receptor kinase, and activity and density of the neuronal noradrenaline transporter (uptake1) were assessed in SNX rats. Seven weeks after SNX, rats had developed left heart hypertrophy. Plasma creatinine, urea, and noradrenaline levels were significantly increased; left and right ventricular noradrenaline content was significantly decreased when compared with sham-operated control rats. In these SNX rats, left, but not right, ventricular beta-adrenoceptor density was significantly reduced, and membrane-associated G-protein-coupled receptor kinase activity was significantly increased compared with sham-operated rats. Although right and left ventricular activity of uptake1 was unchanged, the neuronal noradrenaline transporter density was significantly reduced in both ventricles of SNX versus sham-operated rats. An increase in left ventricular G-protein-coupled receptor kinase activity, possibly triggered by enhanced cardiac noradrenaline release, might be responsible for the decrease in left ventricular beta-adrenoceptor responsiveness in SNX rats.