Reduction In Cardiac Fibrosis Research Articles

Pirfenidone controls the feedback loop of the AT1R/p38 MAPK/renin-angiotensin system axis by regulating liver X receptor-\u03b1 in myocardial infarction-induced cardiac fibrosis

Pirfenidone (PFD), an anti-fibrotic small molecule drug, is used to treat fibrotic diseases, but its effects on myocardial infarction (MI)-induced cardiac fibrosis are unknown. The aim of this study was to determine the effects of PFD on MI-induced cardiac fibrosis and the possible underlying mechanisms in rats. After establishment of the model, animals were administered PFD by gavage for 4 weeks. During the development of MI-induced cardiac fibrosis, we found activation of a positive feedback loop between the angiotensin II type 1 receptor (AT1R)/phospho-p38 mitogen-activated protein kinase (p38 MAPK) pathway and renin-angiotensin system (RAS), which was accompanied by down-regulation of liver X receptor-α (LXR-α) expression. PFD attenuated body weight, heart weight, left ventricular weight, left ventricular systolic pressure, and ±dp/dtmax changes induced by MI, which were associated with a reduction in cardiac fibrosis, infarct size, and hydroxyproline concentration. Moreover, PFD inhibited the AT1R/p38 MAPK pathway, corrected the RAS imbalance [decreased angiotensin-converting enzyme (ACE), angiotensin II, and angiotensin II type 1 receptor expression, but increased ACE2 and angiotensin (1-7) activity and Mas expression] and strongly enhanced heart LXR-α expression. These results indicate that the cardioprotective effects of PFD may be due, in large part, to controlling the feedback loop of the AT1R/p38 MAPK/RAS axis by activation of LXR-α.

PP.31.10] ENDOTHELIAL CELL GROWTH SUPPLEMENT IMPROVES CARDIAC FUNCTION FOLLOWING MOUSE MYOCARDIAL INFARCTION

Objective: Myocardial infarction (MI) and subsequent heart failure is a leading cause of death in high or middle income countries. Development of treatments that stimulate heart tissue regeneration and revascularization/angiogenesis is important to improve the prognosis of these patients. Our recent work demonstrated that endothelial cell growth supplement (ECGS)-containing medium stimulates endothelial differentiation of c-kit positive cardiac progenitor cells in vitro. The objective of the current work was to test whether ECGS can activate endogenous cardiac progenitor cells and improve cardiac function in a mouse MI model. Design and method: Ligation of the left anterior descending (LAD) artery was performed on mice at 2 months of age under anesthetization and intubation. After displacing the pericardium, a 7–0 silk suture was passed under the LAD artery 2 mm below the left atrium and permanently tied, to eliminate blood flow to the area distal to the suture. ECGS or saline (as control) were injected intramyocardially to the ligation area through a sterile Hamilton syringe with a 30 gauge needle immediately after the ligation. Mice that survived the procedure were maintained for 3 weeks. Echocardiography was performed to monitor the cardiac function prior to organ collection. Results: The results showed that MI increased c-kit positive cells and blood vessel formation as well as massive fibrosis in the infarcted area 3 weeks post-surgery. ECGS treatment significantly reduced cardiac fibrosis, especially in the non-infarcted area and border zone (1.96 ± 0.28 % in ECGS treated group vs 4.54 ± 1.08 % in saline treated control group, p < 0.05). ECGS also improved ejection fraction in these animals compared to the saline treated control group (49.9 ± 2.9 % ECGS treated vs 37.4 ± 4.6 % saline treated, p < 0.05). However, ECGS had no significant effect on infarct size in these animals. Conclusions: The current study demonstrates a reduction in cardiac fibrosis and improvement of cardiac function with ECGS in a mouse MI model, which may link to our in vitro observation that ECGS can activate endothelial differentiation of cardiac progenitor cells.

Human Endomyocardial Biopsy Specimen-Derived Stromal Cells Modulate Angiotensin II-Induced Cardiac Remodeling.

Despite effective pharmacological treatment with angiotensin II type I receptor antagonists or angiotensin II-converting enzyme inhibitors, morbidity and mortality associated with heart failure are still substantial, prompting the search of novel therapeutic strategies. There is accumulating evidence supporting the use of cell therapy for cardiac repair. This study demonstrates that cells derived from human endomyocardial biopsies, cardiac-derived adherent proliferating cells (CardAPs), have the potential to reduce angiotensin II-induced cardiac remodeling and improve left ventricular function in angiotensin II mice. The mechanism involves antifibrotic and antihypertrophic effects via paracrine actions and immunomodulatory properties. These findings support the potential of CardAPs for the treatment of heart failure.

Sodium-glucose cotransporter 2 inhibition: cardioprotection by treating diabetes-a translational viewpoint explaining its potential salutary effects.

Diabetes is a growing epidemic worldwide characterized by an elevated concentration of blood glucose, associated with a high incidence of cardiovascular disease and mortality. Although in general reduction of hyperglycaemia is considered a therapeutic goal, hypoglycaemic therapies do not necessarily reduce cardiovascular mortality and may even aggravate cardiovascular risk factors, such as body weight. A new class of antidiabetic drugs acts by inhibition of the sodium-glucose cotransporter 2 (SGLT2), which (partially) prevents reabsorption of glucose from the renal filtrate. The induction of glucose excretion via the urine (glycosuria) was turned into an effective strategy to reduce blood glucose. Ancillary advantages are the caloric and volumetric loss and thereby the reduction of body weight and blood pressure. Additionally, SGLT2 inhibition has been suggested to exert direct cardioprotective effects by the reduction of cardiac fibrosis, inflammation, and oxidative stress. This article summarizes the functional consequences of SGLT2 inhibition on the diabetic and hyperglycaemic organism. We especially focused on the effects on the kidney and the cardiovascular system as described in experimental studies. The interesting observations in experimental studies may extend to clinical medicine, as a recent trial reported a decrease in heart failure outcomes in patients at high cardiovascular risk. In conclusion, SGLT2 inhibition represents a novel treatment, which might be a promising target not only to (further) reduce blood glucose but also to target other cardiovascular risk factors. More research and long-term follow-ups will reveal the specific influence of SGLT2 inhibition on the circulatory system and cardiovascular outcomes.

Moderate intensity exercise prevents diabetic cardiomyopathy associated contractile dysfunction through restoration of mitochondrial function and connexin 43 levels in db/db mice

AimsAlthough the cardiovascular benefits of exercise are well known, exercise induced effects and mechanisms in prevention of cardiomyopathy are less clear during obesity associated type-2 diabetes. The current study assessed the impact of moderate intensity exercise on diabetic cardiomyopathy by examining cardiac function and structure and mitochondrial function. MethodsObese-diabetic (db/db), and lean control (db/+) mice, were subjected to a 5 week, 300 m run on a tread-mill for 5 days/week at the speeds of 10–11 m/min. Various physiological parameters were recorded and the heart function was evaluated with M-mode echocardiography. Contraction parameters and calcium transits were examined on isolated cardiomyocytes. At the molecular level: connexin 43 and 37 (Cx43 and 37) levels, mitochondrial biogenesis regulators: Mfn2 and Drp-1 levels, mitochondrial trans-membrane potential and cytochrome c leakage were assessed through western blotting immunohistochemistry and flow cytometry. Ability of exercise to reverse oxygen consumption rate (OCR), tissue ATP levels, and cardiac fibrosis were also determined. ResultsThe exercise regimen was able to prevent diabetic cardiac functional deficiencies: ejection fraction (EF) and fractional shortening (FS). Improvements in contraction velocity and contraction maximum were noted with the isolated cardiomyocytes. Restoration of interstitial and micro-vessels associated Cx43 levels and improved gap junction intercellular communication (GJIC) were observed. The decline in the Mfn2/Drp-1 ratio in the db/db mice hearts was prevented after exercise. The exercise regimen further attenuated transmembrane potential decline and cytochrome c leakage. These corrections further led to improvements in OCR and tissue ATP levels and reduction in cardiac fibrosis. ConclusionsModerate intensity exercise produced significant cardiovascular benefits by improving mitochondrial function through restoration of Cx43 networks and mitochondrial trans-membrane potential and prevention of excessive mitochondrial fission.

HDACs Regulate miR-133a Expression in Pressure Overload-Induced Cardiac Fibrosis.

MicroRNAs (miRNAs) and histone deacetylases (HDACs) serve a significant role in the pathogenesis of a variety of cardiovascular diseases. The transcriptional regulation of miRNAs is poorly understood in cardiac hypertrophy. We investigated whether the expression of miR-133a is epigenetically regulated by class I and IIb HDACs during hypertrophic remodeling. Transverse aortic constriction (TAC) was performed in CD1 mice to induce pressure overload hypertrophy. Mice were treated with class I and IIb HDAC inhibitor (HDACi) via drinking water for 2 and 4 weeks post TAC. miRNA expression was determined by real-time polymerase chain reaction. Echocardiography was performed at baseline and post TAC end points for structural and functional assessment. Chromatin immunoprecipitation was used to identify HDACs and transcription factors associated with miR-133a promoter. miR-133a expression was downregulated by 0.7- and 0.5-fold at 2 and 4 weeks post TAC, respectively, when compared with vehicle control (P<0.05). HDAC inhibition prevented this significant decrease 2 weeks post TAC and maintained miR-133a expression near vehicle control levels, which coincided with (1) a decrease in connective tissue growth factor expression, (2) a reduction in cardiac fibrosis and left atrium diameter (marker of end-diastolic pressure), suggesting an improvement in diastolic function. Chromatin immunoprecipitation analysis revealed that HDAC1 and HDAC2 are present on the miR-133a enhancer regions. The results reveal that HDACs play a role in the regulation of pressure overload-induced miR-133a downregulation. This work is the first to provide insight into an epigenetic-miRNA regulatory pathway in pressure overload-induced cardiac fibrosis.

Aldehyde dehydrogenase-2 protects against myocardial infarction-related cardiac fibrosis through modulation of the Wnt/β-catenin signaling pathway.

BackgroundAldehyde dehydrogenase-2 (ALDH2) has a protective effect on ischemic heart disease. Here, we examined the protective effects of ALDH2 on cardiac fibrosis through modulation of the Wnt/β-catenin signaling pathway in a rat model of myocardial infarction (MI).MethodsWistar rats were divided into the sham (control), MI (model), and ALDH2 activator (Alda-1) groups. After 10 days of treatment, the left ventricular (LV) remodeling parameters of each animal were evaluated by echocardiography. Myocardial fibrosis was evaluated by Masson’s trichrome staining and Sirius Red staining. Expression levels of collagen types I and III and α-smooth muscle actin (α-SMA) were examined. Finally, the expression and activity of ALDH2 and the levels of several Wnt-related proteins and genes, such as phosphoglycogen synthase kinase (GSK)-3β, GSK-3β, β-catenin, Wnt-1, WNT1-inducible signaling-pathway protein 1, and tumor necrosis factor (TNF)-α, were also analyzed.ResultsAfter MI, the heart weight/body weight ratio, LV dimension at end diastole, and LV dimension at end systole were decreased, while the LV ejection fraction and LV fractional shortening were increased in the Alda-1 group. Myocardial fibrosis was also reduced in the Alda-1 group, accompanied by decreased expression collagen types I and III and α-SMA. β-Catenin, phosphorylated GSK-3β, and Wnt-1 levels were significantly increased in the model group. Interestingly, this alteration was partly reversed by Alda-1 treatment. Immunohistochemical staining showed that numerous WNT1-inducible signaling-pathway protein 1 (WISP-1)- and TNF-α-positive cells were found in the model group. However, few WISP-1- and TNF-α-positive cells were detected in the Alda-1 group.ConclusionThe reduction of cardiac fibrosis and the down-regulation of β-catenin, phosphorylated GSK-3β, Wnt-1, and WISP-1 may be mediated by increased ALDH2 activity, leading to reduction of MI-related cardiac fibrosis.

The Novel Extracellular Cyclophilin A (CyPA) - Inhibitor MM284 Reduces Myocardial Inflammation and Remodeling in a Mouse Model of Troponin I -Induced Myocarditis.

Cyclophilins are a group of highly conserved cytosolic enzymes that have a peptidylprolyl cis/trans isomerase activity. Cyclophilin A (CyPA) can be secreted in the extracellular space by inflammatory cells and upon cell death. The presence of CyPA in patients with non-ischemic cardiomyopathy is associated with poor clinical prognosis. Here, we investigated the inhibition of extracellular CyPA in a mouse model of troponin I-induced autoimmune myocarditis using the strictly extracellular CyPA-inhibitor MM284. Since A/J mice develop severe inflammation and fibrosis after immunization with murine cardiac troponin I (mcTn I), we used this model to analyze the effects of an extracellular CyPA inhibition. As extracellular CyPA-inhibitor we used the recently described CsA-derivate MM284. In vitro studies confirmed that MM284 inhibits CyPA-induced monocytic migration and adhesion. A/J mice immunized with mcTnI were treated with MM284 or vehicle every second day. After 28 days, we found a considerable reduction of myocardial injury and fibrosis. Further analysis revealed a reduced myocardial presence of T-cells and macrophages compared to control treated animals. Whereas MMP-9 expression was reduced significantly by MM284, we observed no significant reduction of inflammatory cytokines such as IL-6 or TNFα. Extracellular CyPA plays an important role in autoimmune myocarditis for myocardial damage and fibrosis. Our data suggest a new pharmacological approach for the treatment of myocardial inflammation and reduction of cardiac fibrosis by inhibition of extracellular CyPA.

Nox isoforms in thickened tissue.

Nox isoforms in thickened tissue.

L-Carnitine protects against arterial hypertension-related cardiac fibrosis through modulation of PPAR-γ expression

Cardiac fibrosis is a pathogenic factor in a variety of cardiovascular diseases and is characterized by an abnormal accumulation of extracellular matrix protein that leads to cardiac dysfunction. l-Carnitine (LC) plays an essential role in the β-oxidation of long-chain fatty acids in lipid metabolism. We have previously demonstrated the beneficial effects of LC in hypertensive rats. The aim of this study was to analyze the effect of LC on arterial hypertension-associated cardiac fibrosis and to explore the mechanisms of LC action. To this end, four groups of rats were used: Wistar (control), rats treated with 400mg/kg/day of LC, rats treated with 25mg/kg/day of l-NAME (to induce hypertension), and rats treated with LC+l-NAME simultaneously. We found an elevation in the myocardial expression of profibrotic factors (TGF-β1 and CTGF), types I and III of collagen, and NADPH oxidase subunits (NOX2 and NOX4), in hypertensive rats when compared with normotensive ones. In addition, an increase in myocardial fibrosis was also found in the l-NAME group. These results were accompanied by a down-regulation of PPAR-γ in the heart of hypertensive animals. When hypertensive rats were treated with LC, all these alterations were reversed. Moreover, a significant negative correlation was observed between myocardial interstitial fibrosis and mRNA expression of PPAR-γ. In conclusion, the reduction of cardiac fibrosis and the down-regulation of NOX2, NOX4, TGF-β1 and CTGF induced by LC might be, at least in part, mediated by an upregulation of PPAR-γ, which leads to a reduction on hypertension-related cardiac fibrosis.

An ACE Up Your Sleeve

Although the renin angiotensin system (RAS) is a well established regulator of blood pressure and intravascular volume,1 considerable evidence has emerged demonstrating the importance of the RAS directly on the cardiovascular system (please refer to the Figure for description of the enzymatic pathways involved in RAS regulation). Indeed, angiotensin converting enzyme (ACE) inhibitors, which prevent the conversion of angiotensin I into angiotensin II (Ang II), and Ang II receptor type 1 (AT1R) antagonists, which inhibit the receptor-mediated actions of Ang II, have demonstrated direct favorable effects on the heart. These include a reduction in cardiac fibrosis during hypertensive left ventricular (LV) hypertrophy, protection against LV enlargement following myocardial infarction, and reduced LV remodeling following coronary artery bypass graft surgery.2 Hence, ACE1 is generally thought of as a villain contributing to the development of cardiovascular disease due to its generation of Ang II. Fortunately, the RAS may also have a potential hero in ACE2, which can counter many of the negative consequences of ACE1-produced Ang II. In this issue of Circulation Research , Patel et al3 demonstrate an important role for the RAS in the development of diabetic cardiomyopathy. If diabetic Akita mice are deficient for ACE2 (Akita/ACE2KO), the enzyme responsible for converting Ang II into Ang 1–7, a progressive systolic dysfunction occurred that is associated with oxidative stress, excessive extracellular matrix degradation, vascular dysfunction, and impairment of the Akt-signaling pathway. Ang II activation of the AT1R was implicated in these actions, since a 1-month treatment with the AT1R antagonist, irbesartan, reversed this systolic dysfunction, oxidative stress, vascular dysfunction, and Akt signaling in the Akita/ACE2KO mice. Figure. Angiotensin converting enzyme (ACE)1 and 2 in the renin angiotensin system. The ACE isoforms 1 and 2 play a critical role in renin angiotensin system regulation. ACE1 …

Monoclonal antibody against marinobufagenin reverses cardiac fibrosis in rats with chronic renal failure

Cardiotonic steroids (CTS) are implicated in pathophysiology of uremic cardiomyopathy. In the present study, we tested whether a monoclonal antibody (mAb) against the bufadienolide CTS, marinobufagenin (MBG), alleviates cardiac hypertrophy and fibrosis in partially nephrectomized (PNx) rats. In PNx rats, we compared the effects of 3E9 anti-MBG mAb and of Digibind, an affinity-purified digoxin antibody, on blood pressure and cardiac hypertrophy and fibrosis following 4 weeks after the surgery. In PNx rats, a fourfold elevation in plasma MBG levels was associated with hypertension, increased cardiac levels of carbonylated protein, cardiac hypertrophy, a reduction in cardiac expression of a nuclear transcription factor which is a negative regulator of collagen synthesis, Friend leukemia integration-1 (Fli-1), and an increase in the levels of collagen-1. A single intraperitoneal administration of 3E9 mAb to PNx rats reduced blood pressure by 59 mm Hg for 7 days and produced a significant reduction in cardiac weight and cardiac levels of oxidative stress, an increase in the expression of Fli-1, and a reduction in cardiac fibrosis. The effects of Digibind were similar to those of 3E9 mAb, but were less pronounced. In experimental chronic renal failure, elevated levels of MBG contribute to hypertension and induce cardiac fibrosis via suppression of Fli-1, representing a potential target for therapy.

Cilnidipine, An L-/N-Type Calcium Channel Blocker, Changes the Circulating Angiotensin–(1-7)/Angiotensin II Ratio

Objective:It is well known that cilnidipine, which is a L/N-type calcium channel blocker (CCB), has Angiotensin (Ang) II lowering effects that result in organ protective effects compared to L-type CCBs. However, a recent study indicated that angiotensin-converting enzyme (ACE) 2, which is expressed in the heart and kidney, metabolizes Ang II to Ang-(1-7), which is a peptide that has organ-protective effects. In this study, we compared the effects of the L-/N-type CCB cilnidipine and the L-type CCB amlodipine on plasma Ang peptides in a rat hypertensive model. Methods:Eight-week-old Sprague-Dawley rats were administered a chronic infusion of Ang II through an osmotic mini-pump, along with vehicle, cilnidipine, or amlodipine for 28 days, and the plasma renin-angiotensin-aldosterone system (RAAS) levels were examined. Results:Cilnidipine and amlodipine exerted equivalent antihypertensive effects. As for Ang peptides, amlodipine induced increases in Ang I levels and decreases in Ang-(1-7)/Ang I ratios. However, the cilnidipine group showed significantly higher Ang-(1-7)/Ang II ratios than the control group. As for gene expression, amlodipine significantly decreased the ratio of ACE2/ACE. Moreover, only cilnidipine treatment resulted in a significant reduction in cardiac fibrosis. Conclusions:The results of the present study demonstrate that the L-/N-type CCB cilnidipine changed the balance between Ang-(1-7) and Ang II and increased the proportion of Ang-(1-7). Taken together, these results suggest that the suppressing the expansion of the area of cardiac fibrosis of cilnidipine is due to increases in the activity of the ACE2-Ang-(1-7) arm.

Abstract 9679: Fast/Glycolytic Skeletal Muscle Growth Attenuates Cardiac Dysfunction and Remodeling After Experimental Myocardial Infarction

Introduction: It is appreciated that aerobic endurance exercise can attenuate unfavorable myocardial remodeling post myocardial infarction (MI). In contrast, little is known about the effect of resistance exercise on these processes, partly because animal models that can assess the relationship between glycolytic muscle fiber growth and cardiac remodeling have been lacking. Hypothesis: Fast/glycolytic skeletal muscle growth attenuates cardiac dysfunction and remodeling after MI. Methods: We utilized skeletal muscle-specific, conditional Akt1 transgenic (TG) mice, that can induce the growth of functional fast/glycolytic skeletal muscle by switching Akt1 signaling on in muscle fibers. Male non-induced TG mice and their non-transgenic littermates (control) were subjected to left anterior descending coronary artery ligation. Two days after surgery, mice were provided doxycycline in their drinking water to activate Akt1 transgene expression in a skeletal muscle-specific manner. Cardiac function and remodeling were assessed by micromanometer catheter, echocardiography, histology and gene expression analyses at 2 and 4 weeks after surgery. Results: Activation of Akt1 signaling in myofibers led to a modest increase in skeletal muscle mass. Skeletal muscle-specific activation of Akt1 led to diminished left ventricular dilation and reduced contractile dysfunction compared with control mice at 4 weeks after MI. The increase in heart weight/BW ratio and lung wet weight/BW ratio was significantly diminished in Akt1 TG mice compared to control mice, consistent with an improvement in heart function. Improved cardiac function in Akt1 TG mice was coupled to diminished myocyte hypertrophy, decreased interstitial fibrosis in the infarct border zone, and increased capillary density in the remote zone. Comprehensive protein array analysis showed that panels of angiogenic factors were increased in skeletal muscle in TG mice. An ELISA analysis demonstrated that serum VEGF levels were upregulated in Akt1 TG mice compared with control mice. Conclusions: Akt1-mediated skeletal muscle growth attenuates cardiac remodeling after MI, and this is associated with increased capillary density in the heart and a reduction in cardiac fibrosis.

Chronic Losartan Administration Reduces Mortality and Preserves Cardiac but Not Skeletal Muscle Function in Dystrophic Mice

Duchenne muscular dystrophy (DMD) is a degenerative disorder affecting skeletal and cardiac muscle for which there is no effective therapy. Angiotension receptor blockade (ARB) has excellent therapeutic potential in DMD based on recent data demonstrating attenuation of skeletal muscle disease progression during 6–9 months of therapy in the mdx mouse model of DMD. Since cardiac-related death is major cause of mortality in DMD, it is important to evaluate the effect of any novel treatment on the heart. Therefore, we evaluated the long-term impact of ARB on both the skeletal muscle and cardiac phenotype of the mdx mouse. Mdx mice received either losartan (0.6 g/L) (n = 8) or standard drinking water (n = 9) for two years, after which echocardiography was performed to assess cardiac function. Skeletal muscle weight, morphology, and function were assessed. Fibrosis was evaluated in the diaphragm and heart by Trichrome stain and by determination of tissue hydroxyproline content. By the study endpoint, 88% of treated mice were alive compared to only 44% of untreated (p = 0.05). No difference in skeletal muscle morphology, function, or fibrosis was noted in losartan-treated animals. Cardiac function was significantly preserved with losartan treatment, with a trend towards reduction in cardiac fibrosis. We saw no impact on the skeletal muscle disease progression, suggesting that other pathways that trigger fibrosis dominate over angiotensin II in skeletal muscle long term, unlike the situation in the heart. Our study suggests that ARB may be an important prophylactic treatment for DMD-associated cardiomyopathy, but will not impact skeletal muscle disease.

Gene Deletion of the Kinin Receptor B1 Attenuates Cardiac Inflammation and Fibrosis During the Development of Experimental Diabetic Cardiomyopathy

OBJECTIVEDiabetic cardiomyopathy is associated with increased mortality in patients with diabetes. The underlying pathology of this disease is still under discussion. We studied the role of the kinin B1 receptor on the development of experimental diabetic cardiomyopathy.RESEARCH DESIGN AND METHODSWe utilized B1 receptor knockout mice and investigated cardiac inflammation, fibrosis, and oxidative stress after induction of streptozotocin (STZ)-induced diabetes. Furthermore, the left ventricular function was measured by pressure-volume loops after 8 weeks of diabetes.RESULTSB1 receptor knockout mice showed an attenuation of diabetic cardiomyopathy with improved systolic and diastolic function in comparison with diabetic control mice. This was associated with a decreased activation state of the mitogen-activated protein kinase p38, less oxidative stress, as well as normalized cardiac inflammation, shown by fewer invading cells and no increase in matrix metalloproteinase-9 as well as the chemokine CXCL-5. Furthermore, the profibrotic connective tissue growth factor was normalized, leading to a reduction in cardiac fibrosis despite severe hyperglycemia in mice lacking the B1 receptor.CONCLUSIONSThese findings suggest that the B1 receptor is detrimental in diabetic cardiomyopathy in that it mediates inflammatory and fibrotic processes. These insights might have useful implications on future studies utilizing B1 receptor antagonists for treatment of human diabetic cardiomyopathy.

Inhibition of left ventricular fibrosis by tranilast in rats with renovascular hypertension.

Growth factors such as transforming growth factor-beta (TGF beta) are believed to have an essential role in cardiac fibrosis. Tranilast (N(3,4-dimethoxycinnamoyl) anthranilic acid) attenuates the increased expression of TGF beta mRNA in vitro. To investigate whether tranilast reduces cardiac fibrosis in rats with two-kidney, one-clip (2K1C) renovascular hypertension. In addition, we tested the in-vitro effects of tranilast on cardiac myocytes and non-myocyte cells. We analysed hearts from four groups of rats: sham-operated controls; rats with 2K1C renovascular hypertension; rats with 2K1C renovascular hypertension treated for 12 weeks with the angiotensin converting enzyme (ACE) inhibitor, quinapril (6 mg/kg per day); rats with 2K1C renovascular hypertension treated for 12 weeks with tranilast (400 mg/kg per day). Systolic blood pressure was reduced after quinapril treatment. Tranilast did not alter blood pressure (2K1C: 223 +/- 19 mmHg; 2K1C + quinapril: 149 +/- 15 mmHg (P < 0.01 compared with 2K1C); 2K1C + tranilast: 204 +/- 32 mmHg). Left ventricular weight was likewise reduced significantly by quinapril, but not significantly by tranilast (2K1C: 1.52 +/- 0.2 g; 2K1C + quinapril: 1.26 +/- 0.18 g (P < 0.05 compared with 2K1C); 2K1C + tranilast: 1.37 +/- 0.27 g). Using a computer-aided image analysis system, we demonstrated that tranilast prevented cardiac fibrosis in a blood-pressure-independent manner (P < 0.01 compared with 2K1C). Determination of the cardiac hydroxyproline content similarly revealed a significant reduction in cardiac fibrosis by tranilast (2K1C: 4.92 +/- 0.48 mg/mg; 2K1C + tranilast: 3.97 +/- 0.46 mg/mg; P < 0.05). The effect of tranilast on cardiac fibrosis was comparable to the effects of a blood-pressure-decreasing dose of the ACE inhibitor, quinapril. Cell culture experiments revealed that tranilast significantly decreased the proliferation of cardiac non-myocyte cells. Proliferation of cardiac myocytes was not altered. This study revealed that long-term treatment with tranilast markedly attenuated left ventricular fibrosis in rats with renovascular hypertension. This was most probably the result of an antiproliferative effect of tranilast on cardiac non-myocyte cells. Tranilast thus offers a unique new therapeutic approach to the reduction of TGF beta-mediated cardiac fibrosis in vivo.