Renal fibrosis in diabetic and aortic-constricted hypertensive rats

Efficacy of shear wave elasticity for evaluating myocardial hypertrophy in hypertensive rats

Shear wave (SW) imaging is a novel ultrasound-based technique for assessing tissue characteristics. SW elasticity may be useful to assess the severity of hypertensive left ventricular (LV) hypertrophy. This study aimed to evaluate the efficacy of SW elasticity for assessing the degree of myocardial hypertrophy using hypertensive rats. Rats were divided into hypertension group and control group. SW elasticity was measured on the excised heart. Myocardial hypertrophy was assessed histologically. LV weight was greater in hypertension group. An increase in interventricular septum and LV free wall thicknesses was observed in hypertension group. SW elasticity was significantly higher in hypertension group than in control group (14.6 ± 4.3 kPa vs. 6.5 ± 1.1 kPa, P < 0.01). The cross-sectional area of cardiomyocytes was larger in hypertension group than in control group (397 ± 50 μm2 vs. 243 ± 14 μm2, P < 0.01), and SW elasticity was positively correlated with the cross-sectional area of cardiomyocytes (R = 0.96, P < 0.01). This study showed that SW elasticity was higher in hypertensive rats and was closely correlated with the degree of myocardial hypertrophy, suggesting the efficacy of SW elasticity for estimating the severity of hypertensive LV hypertrophy.

Efficacy of shear wave elastography for evaluating right ventricular myocardial fibrosis in monocrotaline-induced pulmonary hypertension rats

BACKGROUND

Right ventricular (RV) function is important for outcomes in pulmonary hypertension. Evaluation of RV myocardial characteristics is useful to assess the disease severity. Shear wave elastography (SWE) provides information of shear wave (SW) elasticity, which is related to tissue hardness, and SW dispersion slope, which reflects tissue viscosity. This study aimed to test the hypothesis that SW elasticity is increased and SW dispersion slope is decreased in the right ventricle of monocrotaline (MCT)-induced pulmonary hypertension rats.

METHODS

Rats were divided into MCT-induced pulmonary hypertension group (n = 10) and control group (n = 10). SW elasticity and SW dispersion slope were measured on excised hearts. Myocardial fibrosis was evaluated histologically.

RESULTS

RV hypertrophy was observed in the MCT group. SW elasticity of right ventricle was higher in the MCT group than in the control group (3.5 ± 0.9 kPa vs. 2.5 ± 0.4 kPa, p < 0.01). SW dispersion slope of right ventricle was lower in the MCT group than in the control group (5.3 ± 1.7 m/s/kHz vs. 7.7 ± 1.5 m/s/kHz, p < 0.01). The fibrosis area of right ventricle was increased in MCT group compared with control group (18 ± 5% vs. 8 ± 3%, p < 0.01), and was positively related to SW elasticity and negatively related to SW dispersion slope.

CONCLUSIONS

Higher SW elasticity and lower SW dispersion slope were observed in the fibrotic myocardium of right ventricle in MCT-induced pulmonary hypertension rats. SWE may have the potential to evaluate RV function by assessing myocardial characteristics.

Inhibitory Effects of Tofogliflozin on Cardiac Hypertrophy in Dahl Salt-Sensitive and Salt-Resistant Rats Fed a High-Fat Diet

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are drugs for diabetes and might prevent heart failure. In this study, we investigated the effects of tofogliflozin, an SGLT2 inhibitor, on cardiac hypertrophy and metabolism in hypertensive rats fed a high-fat diet. Dahl salt-sensitive (DS) rats, hypertensive model rats, and Dahl salt-resistant (DR) rats, non-hypertensive model rats, were fed a high-salt and high-fat diet containing tofogliflozin (0.005%) for 9 weeks to examine the effects of this drug on cardiac hypertrophy and metabolism. Tofogliflozin tended to suppress a rise of the systolic blood pressure, relative to the control, throughout the treatment period in both DR and DS rats, and significantly suppress a rise of the systolic blood pressure, relative to the control, at the 9th week in DS rats. Tofogliflozin reduced cardiac hypertrophy (heart weight/body weight) not only in DS rats but also in DR rats. Histological analysis showed that tofogliflozin significantly decreased cardiomyocyte hypertrophy and perivascular fibrosis in both DS and DR rats. Tofogliflozin significantly decreased the expression levels of genes related to cardiac hypertrophy (encoding for natriuretic peptides A and B and interleukin-6), and to cardiac fibrosis (encoding for transforming growth factor-β1 and collagen type IV), in DS rats. Recent studies have shown that hypertrophied and failing hearts shift to oxidizing ketone bodies as a significant fuel source. We also performed metabolome analysis for ventricular myocardial tissue. Tofogliflozin reduced 3-hydroxybutyrate, a ketone body, and significantly decreased the expression levels of β-hydroxybutyrate dehydrogenase 1 and 3-oxoacid CoA-transferase, which are related to ketone oxidization. In conclusion, tofogliflozin ameliorated cardiac hypertrophy and fibrosis along with reduction of ketone usage in myocardial tissue.

Effect of LCZ696, a dual angiotensin receptor neprilysin inhibitor, on isoproterenol-induced cardiac hypertrophy, fibrosis, and hemodynamic change in rats

BACKGROUND

Recent clinical studies have shown that treatment with LCZ696, a complex containing the angiotensin receptor blocker valsartan and neprilysin inhibitor sacubitril, improves the prognosis of heart failure patients with a reduced ejection fraction. This study evaluated whether LCZ696 affects left ventricular hypertrophy, fibrosis, and hemodynamics in isoproterenol (ISO)-treated rats compared with valsartan alone.

METHODS

Male Wistar rats received subcutaneous saline (n = 10), subcutaneous ISO (2.4 mg/kg/day; n = 10), subcutaneous ISO + oral LCZ696 (60 mg/kg/day; n = 20) (ISO-LCZ), or subcutaneous ISO + oral valsartan (30 mg/kg/day; n = 20) (ISO-VAL) for 7 days.

RESULTS

LCZ696 and valsartan did not significantly reduce the increased heart weight/body weight ratio in rats treated with ISO. Echocardiography showed that the deceleration time shortened by ISO was restored by LCZ696 but not valsartan alone (p = 0.01 vs. the ISO group). Histological analysis showed that cardiac interstitial fibrosis increased by ISO was decreased significantly by LCZ696 but not valsartan alone (control: 0.10 ± 0.14%; ISO: 0.41 ± 0.32%; ISO-LCZ: 0.19 ± 0.23% [p < 0.01 vs. the ISO group]; ISO-VAL: 0.34 ± 0.23% [p = 0.34 vs. the ISO group]). Quantitative polymerase chain reaction showed that mRNA expression of Tgfb1, Col1a1, Ccl2, and Anp increased by ISO was significantly attenuated by LCZ696 but not valsartan alone (p < 0.05 vs. the ISO group).

CONCLUSIONS

LCZ696 improves cardiac fibrosis, but not hypertrophy, caused by continuous exposure to ISO in rats.

Effect of vildagliptin, a dipeptidyl peptidase 4 inhibitor, on cardiac hypertrophy induced by chronic beta-adrenergic stimulation in rats

Background

Heart failure with left ventricular (LV) hypertrophy is often associated with insulin resistance and inflammation. Recent studies have shown that dipeptidyl peptidase 4 (DPP4) inhibitors improve glucose metabolism and inflammatory status. We therefore evaluated whether vildagliptin, a DPP4 inhibitor, prevents LV hypertrophy and improves diastolic function in isoproterenol-treated rats.

Methods

Male Wistar rats received vehicle (n = 20), subcutaneous isoproterenol (2.4 mg/kg/day, n = 20) (ISO), subcutaneous isoproterenol (2.4 mg/kg/day + oral vildagliptin (30 mg/kg/day, n = 20) (ISO-VL), or vehicle + oral vildagliptin (30 mg/kg/day, n = 20) (vehicle-VL) for 7 days.

Results

Blood pressure was similar among the four groups, whereas LV hypertrophy was significantly decreased in the ISO-VL group compared with the ISO group (heart weight/body weight, vehicle: 3.2 ± 0.40, ISO: 4.43 ± 0.39, ISO-VL: 4.14 ± 0.29, vehicle-VL: 3.16 ± 0.16, p < 0.05). Cardiac catheterization revealed that vildagliptin lowered the elevated LV end-diastolic pressure observed in the ISO group, but other parameters regarding LV diastolic function such as the decreased minimum dp/dt were not ameliorated in the ISO-VL group. Histological analysis showed that vildagliptin attenuated the increased cardiomyocyte hypertrophy and perivascular fibrosis, but it did not affect angiogenesis in cardiac tissue. In the ISO-VL group, quantitative PCR showed attenuation of increased mRNA expression of tumor necrosis factor-α, interleukin-6, insulin-like growth factor-l, and restoration of decreased mRNA expression of glucose transporter type 4.

Conclusions

Vildagliptin may prevent LV hypertrophy caused by continuous exposure to isoproterenol in rats.

Indapamide lowers blood pressure by increasing production of epoxyeicosatrienoic acids in the kidney

Diuretics are widely used in the treatment of hypertension, although the precise mechanisms remain unknown. Epoxyeicosatrienoic acids (EETs), cytochrome P450 (P450) epoxygenase metabolites of arachidonic acid, play critical roles in regulation of blood pressure. The present study was carried out to investigate whether EETs participate in the antihypertensive effect of thiazide diuretics [hydrochlorothiazide (HCTZ)] and thiazide-like diuretics (indapamide). Male spontaneously hypertensive rats (SHRs) were treated with indapamide or HCTZ for 8 weeks. Systolic blood pressure, measured via tail-cuff plethysmography and confirmed via intra-arterial measurements, was significantly decreased in indapamide- and HCTZ-treated SHRs compared with saline-treated SHRs. Indapamide increased kidney CYP2C23 expression, decreased soluble epoxide hydrolase expression, increased urinary and renovascular 11,12- and 14,15-EETs, and decreased production of 11,12- and 14,15-dihydroxyeicosatrienoic acids in SHRs. No effect on expression of CYP4A1 or CYP2J3, or on 20-hydroxyeicosatetraenoic acid production, was observed, suggesting indapamide specifically targets CYP2C23-derived EETs. Treatment of SHRs with HCTZ did not affect the levels of P450s or their metabolites. Increased cAMP activity and protein kinase A expression were observed in the renal microvessels of indapamide-treated SHRs. Indapamide ameliorated oxidative stress and inflammation in renal cortices by down-regulating the expression of p47phox, nuclear factor-κB, transforming growth factor-β1, and phosphorylated mitogen-activated protein kinase. Furthermore, the p47phox-lowering effect of indapamide in angiotensin II-treated rat mesangial cells was partially blocked by the presence of N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MS-PPOH) or CYP2C23 small interfering RNA. Together, these results indicate that the hypotensive effects of indapamide are mediated, at least in part, by the P450 epoxygenase system in SHRs, and provide novel insights into the blood pressure-lowering mechanisms of diuretics.

Effect of bis-1,4-dihydropyridine in the kidney of diabetic rats

The in vivo effectiveness of 4-dihydropyridine (bis-1,4-DHP), a new calcium-channel blocker, as a nephroprotector in isolated perfused kidney was evaluated by determining its effects on parameters associated with renal injury in diabetic rats. Diabetes in male Wistar rats, control, diabetic, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP, was induced by a single administration of STZ (55 mg·kg(-1), i.p.). In the drug-treated groups, treatment with bis-1,4-DHP (10 mg·kg(-1)·day(-1)) started one week before diabetes induction; bis-1,4-DHP was dissolved in DMSO (0.3%) and suspended in drinking water with carboxymethyl cellulose (3%). Parameters evaluated were body weight, blood glucose, albuminuria, proteinuria, creatinine, urea excretion, kidney's weight / body weight ratio, and kidney perfusion pressure in all rat groups at different times of diabetes (2, 4, 6, and 10 weeks). Kidney weight of diabetic rats significantly increased vs. control, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP rats at different times of diabetes. The ratios % kidney weight / 100 g body weight were different between control, control + bis-1,4-DHP, and diabetic + bis-1,4-DHP rats vs. diabetic rats (P < 0.05). Kidney perfusion pressure was decreased by diabetes, while it was partially recovered by bis-1,4-DHP treatment in response to phenylephrine. Bis-1,4-DHP had a tendency to decrease hyperglycemia vs. diabetic rats, even though glycemia was too high as compared with controls, and it ameliorated albuminuria, creatinine, and urea excretion, suggesting a favorable effect on renal haemodynamics. Bis-1,4-DHP, by inhibiting Ca(2+) entrance, induced vasodilation in renal vascular bed and thus may have a nephroprotective effect against diabetes-induced renal dysfunction, but does not have significant impact on hyperglycemia.

Etiopathology of chronic tubular, glomerular and renovascular nephropathies: clinical implications

Chronic kidney disease (CKD) comprises a group of pathologies in which the renal excretory function is chronically compromised. Most, but not all, forms of CKD are progressive and irreversible, pathological syndromes that start silently (i.e. no functional alterations are evident), continue through renal dysfunction and ends up in renal failure. At this point, kidney transplant or dialysis (renal replacement therapy, RRT) becomes necessary to prevent death derived from the inability of the kidneys to cleanse the blood and achieve hydroelectrolytic balance. Worldwide, nearly 1.5 million people need RRT, and the incidence of CKD has increased significantly over the last decades. Diabetes and hypertension are among the leading causes of end stage renal disease, although autoimmunity, renal atherosclerosis, certain infections, drugs and toxins, obstruction of the urinary tract, genetic alterations, and other insults may initiate the disease by damaging the glomerular, tubular, vascular or interstitial compartments of the kidneys. In all cases, CKD eventually compromises all these structures and gives rise to a similar phenotype regardless of etiology. This review describes with an integrative approach the pathophysiological process of tubulointerstitial, glomerular and renovascular diseases, and makes emphasis on the key cellular and molecular events involved. It further analyses the key mechanisms leading to a merging phenotype and pathophysiological scenario as etiologically distinct diseases progress. Finally clinical implications and future experimental and therapeutic perspectives are discussed.

Mechanisms of Combined Treatment With Celiprolol and Candesartan for Ventricular Remodeling in Experimental Heart Failure

BACKGROUND

Both beta-adrenergic blockers and angiotensin-II receptor blockers were reported to improve the prognosis of patients with heart failure, but the efficacy of combination therapy with these agents has not been fully elucidated. Also the efficacy of celiprolol, a beta1-selective adrenoceptor antagonist with partial beta2-agonist properties, for heart failure treatment is still controversial. We examined the cardioprotective effects and mechanisms of the therapy with celiprolol or candesartan, an angiotensin-II receptor blockers and their combination in heart failure induced by isoproterenol (ISO).

METHODS AND RESULTS

ISO 300 mg/kg was injected in rats to produce heart failure. Two months after the injection, the ISO-injected rats were divided into 4 groups (8 rats each) and treated for 4 weeks as follows: (a) vehicle; (b) celiprolol 10 mg/kg per day (BB); (c) candesartan 0.2 mg/kg per day (ARB); and (d) their combination BB+ARB. ISO significantly elevated left ventricular (LV) end-diastolic pressure, decreased peak-negative dP/dt and LV ejection fraction. BB and ARB similarly ameliorated cardiac dysfunction due to ISO, but BB+ARB were more potent than the individual therapies. Separately, ARB preserved the histological structure in LV myocardium. In contrast, BB ameliorated calcium handling, as shown by the increased ratio of SERCA2 to phospholamban protein, despite having little effect on the histology.

CONCLUSION

Both celiprolol and candesartan showed cardioprotective effects in this heart failure model. The potential use of the combination treatment in heart failure might result in a synergistic effect through the different cardioprotective mechanisms of celiprolol and candesartan.

Troglitazone induces a cellular acidosis by inhibiting acid extrusion in cultured rat mesangial cells

We studied the effect of troglitazone on cellular acid-base balance and alanine formation in isolated rat mesangial cells. Mesangial cells were grown to confluency in RPMI 1640 media on 30-mm chambers used to monitor both cellular pH using the pH-sensitive dye 2'7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein and metabolic acid production as well as glutamine metabolism. Troglitazone (10 microM) induced a spontaneous cellular acidosis (6.95 +/- 0.02 vs. 7.47 +/- 0.04, respectively; P < 0.0001) but without an increase in lactic acid production. Alanine production was reduced 64% (P < 0.01) consistent with inhibition of the glutamate transamination. These findings pointed to a decrease in acid extrusion rather than an increase in acid production as the underlying mechanism leading to the cellular acidosis. To test their acid extrusion capabilities, mesangial cells were acid loaded with NH and then allowed to recover in Krebs-Henseleit media or in Krebs-Henseleit media minus bicarbonate (HEPES substituted), and the recovery response (Delta pH(i)/min) was monitored. In the presence of 10 microM troglitazone, the recovery response to the NH acid load was virtually eliminated in the bicarbonate-buffered media (0.00 +/- 0.001 vs. 0.06 +/- 0.02 pH(i)/min, P < 0.0001 vs. control) and reduced 75% in HEPES-buffered media (0.01 +/- 0.01 vs. 0.04 +/- 0.02 pH(i)/min, P < 0.002 vs. control). These results show that troglitazone induces a spontaneous cellular acidosis resulting from a reduction in cellular acid extrusion.