Finerenone Reduces Intrinsic Arterial Stiffness in Munich Wistar Frömter Rats, a Genetic Model of Chronic Kidney Disease.

BACKGROUND: Development of albuminuria and arterial stiffness in Munich Wistar Frömter (MWF) rats, a model of chronic kidney disease, is related to alterations in extracellular matrix, increased oxidative stress, and endothelial dysfunction. Finerenone (FIN), a novel, nonsteroidal, potent, and selective mineralocorticoid receptor antagonist, improves endothelial dysfunction through enhancing nitric oxide (NO) bioavailability and decreasing superoxide anion levels due to an upregulation in vascular and renal superoxide dismutase activity. We hypothesize that FIN reduces arterial stiffness in this model associated to the reduction in albuminuria and matrix metalloproteinase (MMP)-2/9 activity. METHODS: Twelve-week-old MWF rats with established albuminuria and age-matched normoalbuminuric Wistar (W) rats were treated with FIN (10 mg/kg/day, once-daily oral gavage) or with vehicle (control, C) for 4 weeks. RESULTS: Arterial stiffness was significantly higher in mesenteric arteries (MA) of MWF-C as compared to W-C. FIN treatment significantly lowered ß-index, a measure of intrinsic stiffness independent of geometry, in MWF (ßMWF-FIN = 7.7 ± 0.4 vs. ßMWF-C = 9.2 ± 0.5, p < 0.05) positively correlating with urinary albumin excretion. Elastin fenestrae area in the internal elastic lamina of MA from MWF-FIN was significantly larger (+377%, p < 0.05). FIN increased plasma pro-MMP-2 and decreased plasma MMP-2 and MMP-9 activities, correlating with reductions in ß-index. MA from MWF-FIN exhibited higher NO bioavailability and reduced superoxide anion levels compared to MWF-C. CONCLUSION: FIN treatment reduces intrinsic arterial stiffness in MA from MWF rats associated with changes in elastin organization, normalization of MMP-2 and MMP-9 activities, and reduction of oxidative stress. Moreover, reduction of arterial stiffness correlates with reduction in albuminuria.

Rapid, Automated, and Specific Immunoassay to Directly Measure Matrix Metalloproteinase-9-Tissue Inhibitor of Metalloproteinase-1 Interactions in Human Plasma Using AlphaLISA Technology: A New Alternative to Classical ELISA.

The protocol describes a novel, rapid, and no-wash one-step immunoassay for highly sensitive and direct detection of the complexes between matrix metalloproteinases (MMPs) and their tissue inhibitor of metalloproteinases (TIMPs) based on AlphaLISA® technology. We describe two procedures: (i) one approach is used to analyze MMP-9-TIMP-1 interactions using recombinant human MMP-9 with its corresponding recombinant human TIMP-1 inhibitor and (ii) the second approach is used to analyze native or endogenous MMP-9-TIMP-1 protein interactions in samples of human plasma. Evaluating native MMP-9-TIMP-1 complexes using this approach avoids the use of indirect calculations of the MMP-9/TIMP-1 ratio for which independent MMP-9 and TIMP-1 quantifications by two conventional ELISAs are needed. The MMP-9-TIMP-1 AlphaLISA® assay is quick, highly simplified, and cost-effective and can be completed in less than 3 h. Moreover, the assay has great potential for use in basic and preclinical research as it allows direct determination of native MMP-9-TIMP-1 complexes in circulating blood as biofluid.

Mild and Short-Term Caloric Restriction Prevents Obesity-Induced Cardiomyopathy in Young Zucker Rats without Changing in Metabolites and Fatty Acids Cardiac Profile.

Caloric restriction (CR) ameliorates cardiac dysfunction associated with obesity. However, most of the studies have been performed under severe CR (30-65% caloric intake decrease) for several months or even years in aged animals. Here, we investigated whether mild (20% food intake reduction) and short-term (2-weeks) CR prevented the obese cardiomyopathy phenotype and improved the metabolic profile of young (14 weeks of age) genetically obese Zucker fa/fa rats. Heart weight (HW) and HW/tibia length ratio was significantly lower in fa/fa rats after 2 weeks of CR than in counterparts fed ad libitum. Invasive pressure measurements showed that systolic blood pressure, maximal rate of positive left ventricle (LV) pressure, LV systolic pressure and LV end-diastolic pressure were all significantly higher in obese fa/fa rats than in lean counterparts, which were prevented by CR. Magnetic resonance imaging revealed that the increase in LV end-systolic volume, stroke volume and LV wall thickness observed in fa/fa rats was significantly lower in animals on CR diet. Histological analysis also revealed that CR blocked the significant increase in cardiomyocyte diameter in obese fa/fa rats. High resolution magic angle spinning magnetic resonance spectroscopy analysis of the LV revealed a global decrease in metabolites such as taurine, creatine and phosphocreatine, glutamate, glutamine and glutathione, in obese fa/fa rats, whereas lactate concentration was increased. By contrast, fatty acid concentrations in LV tissue were significantly elevated in obese fa/fa rats. CR failed to restore the LV metabolomic profile of obese fa/fa rats. In conclusion, mild and short-term CR prevented an obesity-induced cardiomyopathy phenotype in young obese fa/fa rats independently of the cardiac metabolic profile.

Role of matrix metalloproteinase-9 in chronic kidney disease: a new biomarker of resistant albuminuria.

Resistant albuminuria, developed under adequate chronic blockade of the renin-angiotensin system, is a clinical problem present in a small number of patients with chronic kidney disease (CKD). The mechanism underlying this resistant albuminuria remains unknown. Matrix metalloproteinases (MMPs) are involved in the pathophysiology of cardiovascular and renal diseases. In the present study we tested the role of MMPs in resistant albuminuria. First we evaluated gelatinase MMP-2 and MMP-9 activity by zymography in the Munich Wistar Frömter (MWF) rat, a model of progressive albuminuria, and subsequently in patients with resistant albuminuria. Markers of oxidative stress were observed in the kidneys of MWF rats, together with a significant increase in pro-MMP-2 and active MMP-9 forms. These changes were normalized together with reduced albuminuria in consomic MWF-8(SHR) rats, in which chromosome 8 of MWF was replaced with the respective chromosome from spontaneously hypertensive rats. The MMP-2 and MMP-9 protein levels were similar in patients with normal and resistant albuminuria; however, high circulating levels of collagen IV, a specific biomarker of tissue collagen IV degradation, were observed in patients with resistant albuminuria. These patients showed a significant increase in gelatinase MMP-2 and MMP-9 activity, but only a significant increase in the active MMP-9 form quantified by ELISA, which correlated significantly with the degree of albuminuria. Although the expression of the tissue inhibitor of MMP-9 (TIMP)-1 was similar, a novel AlphaLISA assay demonstrated that the MMP-9-TIMP-1 interaction was reduced in patients with resistant albuminuria. It is of interest that oxidized TIMP-1 expression was higher in patients with resistant albuminuria. Therefore, increased circulating MMP-9 activity is associated with resistant albuminuria and a deleterious oxidative stress environment appears to be the underlying mechanism. These changes might contribute to the progression of CKD in these patients.

Urinary alpha-1 antitrypsin and CD59 glycoprotein predict albuminuria development in hypertensive patients under chronic renin-angiotensin system suppression.

BACKGROUND: Hypertension is a multi-factorial disease of increasing prevalence and a major risk factor for cardiovascular mortality even in the presence of adequate treatment. Progression of cardiovascular disease (CVD) occurs frequently during chronic renin-angiotensin-system (RAS) suppression, and albuminuria is a marker of CV risk. High prevalence of albuminuria in treated hypertensive patients has been demonstrated, but there are no available markers able to predict evolution. The aim of this study was the identification of novel indicators of albuminuria progression measurable in urine of diabetic and non-diabetic patients. METHODS: 1143 hypertensive patients under chronic treatment were followed for a minimum period of 3 years. Among them, 105 diabetic and non-diabetic patients were selected and classified in three groups according to albuminuria development during follow-up: (a) patients with persistent normoalbuminuria; (b) patients developing de novo albuminuria; (c) patients with maintained albuminuria. Differential urine analysis was performed by 2D gel electrophoresis (2D-DIGE) and further confirmed by liquid chromatography-mass spectrometry. Non-parametric statistical tests were applied. RESULTS: CD59 glycoprotein and alpha-1 antitrypsin (AAT) resulted already altered in patients developing albuminuria de novo, with a similar response in those with maintained albuminuria. A prospective study in a sub-group of normoalbuminuric patients who were clinically followed up for at least 1 year from urine sampling, revealed CD59 and AAT proteins significantly varied in the urine collected from normoalbuminurics who will negatively progress, serving as predictors of future albuminuria development. CONCLUSIONS: CD59 and AAT proteins are significantly altered in hypertensive patients developing albuminuria. Interestingly, CD59 and AAT are able to predict, in normoalbuminuric individuals, who will develop albuminuria in the future, being potential predictors of vascular damage and CV risk. These findings contribute to early identify patients at risk of developing albuminuria even when this classical predictor is still in the normal range, constituting a novel strategy towards a prompt and more efficient therapeutic intervention with better outcome.

Development of albuminuria and enhancement of oxidative stress during chronic renin-angiotensin system suppression.

OBJECTIVE: Albuminuria has been recently described in hypertensive patients under chronic renin-angiotensin system (RAS) suppression. We investigated whether this fact could be related to an increase in oxidative stress. METHODS: We examined normoalbuminuric and albuminuric patients in stage 2 chronic kidney disease, both with more than 2 years of RAS blockade. The relationship between albuminuria and circulating biomarkers for both oxidative damage, that is carbonyl and malondialdehyde, as well as antioxidant defense, that is reduced glutathione, thiol groups, uric acid, bilirubin, or catalase, and superoxide scavenging activity, was assessed. RESULTS: We found that only patients with albuminuria showed an important increase in carbonyls (P < 0.001) and malondialdehyde (P < 0.05) compared to normoalbuminuric patients. This increase in oxidative damage was also accompanied by a rise in catalase activity (P < 0.05) and low-molecular-weight antioxidants only when they were measured as total antioxidant capacity (P < 0.01). In order to establish the specific oxidative status of each group, new indexes of oxidative damage and antioxidant defense were calculated with all these markers following a mathematical and statistical approach. Although both pro-oxidant and antioxidant indexes were significantly increased in patients with albuminuria, only the oxidative damage index positively correlated with the increase of albumin/creatinine ratio (P = 0.0024). CONCLUSIONS: We conclude that albuminuria is accompanied by an amplified oxidative damage in patients in early stages of chronic kidney disease. These results indicate that chronic RAS protection must be directed to avoid development of albuminuria and oxidative damage.

Dissecting the genetic predisposition to albuminuria and endothelial dysfunction in a genetic rat model.

OBJECTIVE: The Munich Wistar Frömter (MWF) rat develops progressive spontaneous albuminuria largely attributable to quantitative trait loci on rat chromosome (RNO)6 and RNO8, respectively. We tested the hypothesis whether quantitative trait loci on these chromosomes are linked to both albuminuria and endothelial dysfunction. METHODS: Experiments were performed in male 12-week-old MWF, Wistar Kyoto (WKY), spontaneously hypertensive rat (SHR) and consomic MWF-6 and MWF-8 rats, in which RNO6 or RNO8 was replaced by the respective SHR chromosome (n = 10 per strain). Vascular function was assessed in aorta and vascular superoxide anion production was determined by confocal microscopy. RESULTS: Acetylcholine potency to induce relaxation was significantly reduced in MWF (6.2 ±â€Š0.1) compared with WKY (7.1 ±â€Š0.1) or SHR (7.3 ±â€Š0.1; P < 0.01). N-nitro-L-arginine methyl ester abolished relaxation to acetylcholine in all three strains, whereas indomethacin exhibited no effect in WKY and MWF. Contractions to noradrenaline and superoxide production were significantly higher in MWF compared with SHR and WKY (P < 0.05, respectively). In consomic MWF-6 and MWF-8 rats albuminuria was markedly suppressed (-85 and -92%, P < 0.005 compared with MWF, respectively). Interestingly, relaxation to acetylcholine and contraction to noradrenaline were restored to normal WKY levels only in MWF-8, but not in MWF-6, due to an increase in stimulated and basal nitric oxide availability, respectively. CONCLUSION: These data demonstrate the partial genetic independence of albuminuria and endothelial dysfunction in this model. From two known albuminuria quantitative trait loci one locus affects both albuminuria and endothelial dysfunction. Whether this observation is based on a common genetic mechanism related to NO availability warrants further investigation.