Identification of cathepsin L as a potential sex-specific biomarker for renal damage.

The renin-angiotensin system is a well-known regulator of blood pressure and plays an important role in the pathogenesis of cardiovascular disease and renal damage. Genetic factors, including single nucleotide polymorphisms and sex, are increasingly recognized as potential risk factors for the development of cardiovascular disease. Double transgenic rats (dTGRs), harboring human renin and angiotensinogen genes, were used in this study to investigate potential sex differences influencing renal function and renal gene expression. dTGR males and females had comparable increases in blood pressure, whereas body weight, albuminuria/proteinuria, and urine flow rate were higher in males. At 8 weeks of age, renal plasma flow and glomerular filtration rate were proportionally lower in males, and renal vascular resistance tended to be higher. Males developed more severe tubulointerstitial and vascular lesions. By the end of week 8, 40%of the males but none of the females had died. Genome expression studies were performed with RNA from kidneys of 7-week-old male and female dTGRs and control rats to further investigate the sex-related differences on a molecular level. Forty-five genes showed sex-dependent expression patterns in dTGRs that were significantly different compared to controls. Cathepsin L, one of the genes differentially expressed between the sexes, was also shown to be strongly associated with the degree of renal injury. In dTGRs, urinary cathepsin L at week 7 was higher in males (nanograms per 24 hours: male, 512±163; female, 132±70). These results reveal a potential new biomarker for the personalized diagnosis and management of chronic kidney disease.

Pharmacology of macitentan, an orally active tissue-targeting dual endothelin receptor antagonist.

Macitentan, also called Actelion-1 or ACT-064992 [N-[5-(4-bromophenyl)-6-(2-(5-bromopyrimidin-2-yloxy)ethoxy)-pyrimidin-4-yl]-N'-propylaminosulfonamide], is a new dual ET(A)/ET(B) endothelin (ET) receptor antagonist designed for tissue targeting. Selection of macitentan was based on inhibitory potency on both ET receptors and optimization of physicochemical properties to achieve high affinity for lipophilic milieu. In vivo, macitentan is metabolized into a major and pharmacologically active metabolite, ACT-132577. Macitentan and its metabolite antagonized the specific binding of ET-1 on membranes of cells overexpressing ET(A) and ET(B) receptors and blunted ET-1-induced calcium mobilization in various natural cell lines, with inhibitory constants within the nanomolar range. In functional assays, macitentan and ACT-132577 inhibited ET-1-induced contractions in isolated endothelium-denuded rat aorta (ET(A) receptors) and sarafotoxin S6c-induced contractions in isolated rat trachea (ET(B) receptors). In rats with pulmonary hypertension, macitentan prevented both the increase of pulmonary pressure and the right ventricle hypertrophy, and it markedly improved survival. In diabetic rats, chronic administration of macitentan decreased blood pressure and proteinuria and prevented end-organ damage (renal vascular hypertrophy and structural injury). In conclusion, macitentan, by its tissue-targeting properties and dual antagonism of ET receptors, protects against end-organ damage in diabetes and improves survival in pulmonary hypertensive rats. This profile makes macitentan a new agent to treat cardiovascular disorders associated with chronic tissue ET system activation.

Promotion of sleep by targeting the orexin system in rats, dogs and humans.

Orexins are hypothalamic peptides that play an important role in maintaining wakefulness in mammals. Permanent deficit in orexinergic function is a pathophysiological hallmark of rodent, canine and human narcolepsy. Here we report that in rats, dogs and humans, somnolence is induced by pharmacological blockade of both orexin OX(1) and OX(2) receptors. When administered orally during the active period of the circadian cycle, a dual antagonist increased, in rats, electrophysiological indices of both non-REM and, particularly, REM sleep, in contrast to GABA(A) receptor modulators; in dogs, it caused somnolence and increased surrogate markers of REM sleep; and in humans, it caused subjective and objective electrophysiological signs of sleep. No signs of cataplexy were observed, in contrast to the rodent, dog or human narcolepsy syndromes. These results open new perspectives for investigating the role of endogenous orexins in sleep-wake regulation.

Bosentan, sildenafil, and their combination in the monocrotaline model of pulmonary hypertension in rats.

The dual endothelin receptor antagonist, bosentan, and the phosphodiesterase inhibitor, sildenafil, are efficacious in experimental and clinical pulmonary hypertension (PHT). The effects of bosentan, sildenafil, and their combination were evaluated in rats with monocrotaline (MCT)-induced PHT. A first group consisted of control rats with no MCT injection. Four other groups of rats received MCT subcutaneously and were assigned to receive no treatment, 300 mg/kg/day bosentan as food admix, 100 mg/kg/day sildenafil in drinking water, or their combination for 4 weeks. The doses of bosentan and sildenafil were the maximally effective doses based on a dose-range-finding study. Mortality was 0%, 53%, 11%, 11%, and 0%, respectively, in the five different groups. Bosentan and sildenafil significantly attenuated the increase in mean pulmonary arterial pressure, and the combination had an additional effect. Similarly, bosentan, sildenafil, and, to a greater extent, their combination significantly reduced right ventricular (RV) hypertrophy. Bosentan, but not sildenafil, decreased norepinephrine and BNP plasma concentrations, reduced kidney weight, and normalized systemic hemodynamics. In conclusion, bosentan and sildenafil are efficacious in rats with chronic PHT, and their combination shows an additional effect for decreasing pulmonary arterial pressure, reducing plasma catecholamines, maintaining body weight, and reducing mortality.

The urotensin-II receptor antagonist palosuran improves pancreatic and renal function in diabetic rats.

Urotensin-II (U-II) is a cyclic peptide that acts through a specific G-protein-coupled receptor, UT receptor. Urotensin-II and UT receptors have been described in pancreas and kidney, but their function is not well understood. We studied the effects of chronic treatment of diabetic rats with the orally active selective U-II receptor antagonist palosuran. Streptozotocin treatment causes pancreatic beta-cell destruction and leads to the development of hyperglycemia, dyslipidemia, and renal dysfunction. Long-term treatment of streptozotocin-induced diabetic rats with palosuran improved survival, increased insulin, and slowed the increase in glycemia, glycosylated hemoglobin, and serum lipids. Furthermore, palosuran increased renal blood flow and delayed the development of proteinuria and renal damage. The U-II system is unique in that it plays a role both in insulin secretion and in the renal complications of diabetes. Urotensin receptor antagonism might be a new therapeutic approach for the treatment of diabetes.

[The therapeutic effects of bosentan and valsartan on renal interstitial fibrosis of chronic aristolochic acid nephropathy].

OBJECTIVE: To investigate the therapeutic effects of endothelin receptor antagonist (bosentan) and angiotensin II type 1 receptor antagonist (valsartan) on renal interstitial fibrosis of rats with chronic aristolochic acid nephropathy (CAAN). METHODS: A rat model of CAAN was established by gavage with extract of Aristolochia manshuriensis Kom intermittently, and then they were divided into the following three groups, i.e. model group, bosentan group (100 mg.kg(-1).d(-1) by gavage) and valsartan group (30 mg .kg(-1).d(-1) by gavage). Control group (CTR) only received tap water by gavage. Each group consisted of 6 rats. At the end of 1st, 4 th, 8 th, 12 th and 16 th week, urinary protein excretion, urinary beta2 microglobulin (beta2-mG) and serum creatinine (SCr) were measured. Afterwards the rats were sacrificed. The relative area of renal interstitial fibrosis on pathological section was semi-quantitatively determined. The mRNA and the protein expression of transforming growth factor-beta1 (TGF-beta1), connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), tissue inhibitor of metalloproteinase-1 (TIMP-1) and collagen I (ColI) in kidney tissue was semi-quantitatively determined with reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical staining, respectively. RESULTS: Compared with CTR, urinary protein excretion, urinary beta2-mG and Scr were significantly increased (P < 0.05 or 0.01) and relative area of interstitial fibrosis was also significantly enlarged in the model group (3.964 +/- 0.739%, CTR 0.158 +/- 0.059%, P < 0.01). Compared with CTR, the expression of TGF-beta1, CTGF, PAI-1, TIMP-1 and Col I mRNA and protein was significantly up-regulated in the model group (P < 0.01). After intervention with bosentan or valsartan the up-regulating above mentioned parameters were all significantly inhibited (P < 0.05 or 0.01). However, there was no difference between bosentan group and valsartan group. CONCLUSION: Bosentan and valsartan both can ameliorate renal interstitial fibrosis and improve renal function in rats with CAAN. These responses may result from the inhibition effects on the promoting factors of ECM synthesis (TGF-beta1, CTGF) and the antagonistic factors of ECM degradation (PAI-1, TIMP-1).

Pharmacology of the urotensin-II receptor antagonist palosuran (ACT-058362; 1-[2-(4-benzyl-4-hydroxy-piperidin-1-yl)-ethyl]-3-(2-methyl-quinolin-4-yl)-urea sulfate salt): first demonstration of a pathophysiological role of the urotensin System.

Urotensin-II (U-II) is a cyclic peptide now described as the most potent vasoconstrictor known. U-II binds to a specific G protein-coupled receptor, formerly the orphan receptor GPR14, now renamed urotensin receptor (UT receptor), and present in mammalian species. Palosuran (ACT-058362; 1-[2-(4-benzyl-4-hydroxy-piperidin-1-yl)-ethyl]-3-(2-methyl-quinolin-4-yl)-urea sulfate salt) is a new potent and specific antagonist of the human UT receptor. ACT-058362 antagonizes the specific binding of (125)I-labeled U-II on natural and recombinant cells carrying the human UT receptor with a high affinity in the low nanomolar range and a competitive mode of antagonism, revealed only with prolonged incubation times. ACT-058362 also inhibits U-II-induced calcium mobilization and mitogen-activated protein kinase phosphorylation. The binding inhibitory potency of ACT-058362 is more than 100-fold less on the rat than on the human UT receptor, which is reflected in a pD'(2) value of 5.2 for inhibiting contraction of isolated rat aortic rings induced by U-II. In functional assays of short incubation times, ACT-058362 behaves as an apparent noncompetitive inhibitor. In vivo, intravenous ACT-058362 prevents the no-reflow phenomenon, which follows renal artery clamping in rats, without decreasing blood pressure and prevents the subsequent development of acute renal failure and the histological consequences of ischemia. In conclusion, the in vivo efficacy of the specific UT receptor antagonist ACT-058362 reveals a role of endogenous U-II in renal ischemia. As a selective renal vasodilator, ACT-058362 may be effective in other renal diseases.

[The preliminary studies on the cross action between endothelin-1 and angiotensin II in kidney tissue of rats with diabetic nephropathy].

OBJECTIVE: To investigate the interrelation between endothelin-1 (ET-1) and angiotensin II (AngII) in kidney tissue of rats with diabetic nephropathy. METHODS: Wistar rats were performed a removal operation of right kidney. Two weeks later the uninephrectomized rats were given intravenous injection of streptozotocin (STZ, 35 mg/kg). The diabetic rats were randomly divided into the following four groups: DM + bos group (bosentan 100 mg/kg/d by gavage); DM + ena group (enalapril 10 mg/kg/d by gavage); DM + bos + ena group (the same doses of both bosentan and enalapril by gavage); DM + veh group (only buffer by gavage). Besides, uninephrectomized rats without STZ injection were assigned as control group. Each group consisted of 6 rats. Twenty weeks later, they were sacrificed and left kidney of each rat was harvested respectively. The mRNA expression of angiotensinogen (Ao), angiotensin type 1 receptor (AT1R), preproendothelin-1 and endothelin A receptor (ETaR), and the protein expression of AngII, AT1R, ET-1 and ETaR in kidney tissue were semi-quantitatively detected with reverse transcription- polymerase chain reaction and immunohistochemical staining respectively. RESULTS: In the diabetic group without treatment (DM + veh group), the expression of Ao (AII), AT1R and ET-AR was significantly up-regulated (1.25, 1.94 and 2.56-folds in mRNA respectively, 2.52, 3.84 and 3.30-folds in protein respectively, P < 0.01 or P < 0.05) compared with control group. In three treatment groups, i.e. DM + bos group, DM + ena group and DM + bos + ena group, the up-regulated expression of Ao (AII), AT1R and ET-AR was significantly attenuated (-38.2% to -54.8% in mRNA and -55.3% to -69.7% in protein, P < 0.05 or P < 0.01) compared with DM group. The inhibitory rates among these three treatment groups had no significant difference (P > 0.05). In this study, the expression of preproendothelin-1 mRNA and ET-1 protein was not significantly changed among all groups (P > 0.05). CONCLUSION: Either endothelin receptor antagonist or ACE inhibitor can significantly inhibit the expression of AngII, AT1R and ETaR in kidney tissue of diabetic rats, which suggest that there are close relationship and cross action between ET-1 and AngII.

Chronic endothelin receptor blockade prevents both early hyperfiltration and late overt diabetic nephropathy in the rat.

Diabetic nephropathy is associated with enhanced renal synthesis of endothelin (ET)-1. The goal of this study was to investigate the effects of dual ET receptor antagonism in the early phase (2 months) and in the late phase (5 months) of diabetic nephropathy in rats, and to compare this approach to angiotensin-converting enzyme inhibition. Four groups of uninephrectomized streptozotocin-induced diabetic rats were assigned to receive orally vehicle, bosentan, enalapril, or their combination. A fifth group consisted of nondiabetic, uninephrectomized rats. At 2 weeks, untreated diabetic rats exhibited increased glomerular filtration rate and renal plasma flow. Bosentan, enalapril, and the combination all prevented hyperfiltration and hyperperfusion. By 5 months, diabetic rats developed marked increases in mean arterial pressure and renal vascular resistance, progressive proteinuria, and renal structural damage with glomerular sclerosis and hypertrophy. Bosentan completely prevented the development of hypertension and renal vasoconstriction, and largely prevented the development of proteinuria and renal structural injury. The renal protective effect of bosentan was comparable to that of enalapril or the combination, although its anti-proteinuric effect was less. Clinical studies are warranted to assess whether ET receptor antagonism can have additive effects on top of ACE inhibition, the current treatment of choice in diabetic nephropathy.

Inhibition of inducible nitric oxide synthase during high dietary salt intake.

BACKGROUND: Previous studies indicate that nitric oxide (NO) is involved in the regulation of blood pressure (BP) and natriuresis in response to high sodium intake. We investigated the role of inducible NO synthase (iNOS) in response to an increased salt intake. METHODS: Conscious, chronically catheterized rats were exposed to a high-salt (6%) diet for 14 days while receiving vehicle or aminoguanidine ([AG]; 250 mg/kg/24 h), which selectively inhibits iNOS. A group of rats on normal salt intake + AG were also studied. RESULTS: Aminoguanidine had no impact on BP (120 +/- 2 v 116 +/- 1 mm Hg, control v day 14) or 24-h urinary nitrite and nitrate excretion (UNOxV), in rats on normal salt but prevented lipopolysaccharide-induced hypotension. High salt alone had no impact on BP (120 +/- 1 v 121 +/- 1 mm Hg), whereas UNaV (1.3 +/- 0.2 v 3.5 +/- 0.6 microeq/min, P < .001) and UNOxV increased with high salt intake. The natriuretic response persisted (1.5 +/- 0.2 v 4.3 +/- 0.8 microeq/min, P < .005), but the increase in UNOXV was prevented with chronic AG although BP fell slightly (121 +/- 1 v 115 +/- 1 mm Hg, P < .05). There was no change in plasma volume with high salt, and 24-h UNaV increased appropriately in the presence of AG. The in vitro NOS activity was not increased in kidney homogenates by high salt diet, nor was it affected by chronic AG treatment. CONCLUSION: We conclude that NO from an iNOS source is not essential for the regulation of sodium excretion and BP in the presence of a high-salt diet in a normal rat.

Chronic endothelin receptor blockade prevents renal vasoconstriction and sodium retention in rats with chronic heart failure.

OBJECTIVE: Importance of endothelin in mediating the chronic renal alterations of chronic heart failure was studied in rats chronically treated with bosentan after myocardial infarction. METHODS: Rats were subjected to coronary artery ligation and were treated for 8 weeks with placebo or bosentan, a dual ET(A) and ET(B) receptor antagonist, (approximately 100 mg/kg/day) as food admix. Sham-operated rats served as normal controls. Cardiac and renal functions were measured at the end of 8-week treatment. RESULTS: Bosentan significantly reduced the elevated left ventricular end-diastolic pressure (from 26.6+/-3.3 to 11.4+/-2.2 mmHg, P<0.001) and the increased heart-to-body-weight ratio seen in untreated rats with myocardial infarction. Bosentan prevented the marked increase in renal vascular resistance (bosentan, 7.7+/-0.6; untreated, 15.6+/-2.5 mmHg/ml/min; P<0.001). This led to a significant increase in renal plasma flow resulting in a decrease in filtration fraction. Bosentan furthermore increased urinary sodium excretion. CONCLUSIONS: Prolonged ET receptor blockade in rats with myocardial infarction has chronic renal vasodilatory effect and improves renal sodium excretory function. Thus, dual ET antagonists such as bosentan might be useful in the treatment of the progressive renal failure associated with human chronic heart failure.

Short-term endothelin receptor blockade with tezosentan has both immediate and long-term beneficial effects in rats with myocardial infarction.

OBJECTIVES: We investigated the effects of short-term tezosentan treatment on cardiac function, pulmonary edema and long-term evolution of heart failure (HF) in a rat model of myocardial infarction (MI). BACKGROUND: Endothelin (ET) may play a major role in the progression from MI to HF. Tezosentan is a new dual ET(A)/ET(B) receptor antagonist. METHODS: Rats were subjected to coronary artery ligation and were treated with either vehicle or tezosentan (10 mg/kg IV bolus) at 1 h and 24 h after MI. Cardiac hemodynamics and lung weight were measured at 48 h after MI. Survival was assessed over a five-month period. RESULTS: At 48 h after ligation, vehicle-treated rats developed HF, as evidenced by a marked increase in left ventricular end-diastolic pressure (LVEDP), reduction in dP/dt(max) and mean arterial pressure (MAP), and development of pulmonary edema. Tezosentan treatment attenuated the increase in LVEDP and in lung weight and slightly reduced MAP without affecting dP/dt(max). Infarct size was not modified by tezosentan. Despite the fact that treatment with tezosentan was stopped after 24 h, the initial tezosentan administration significantly reduced cardiac hypertrophy (22%) and decreased mortality by 51% at five months (50% survival vs. 19% survival in vehicle-treated rats, p < 0.001). CONCLUSIONS: Tezosentan administered during the first day after MI in rats, in addition to improving acutely hemodynamic conditions, markedly increases long-term survival. This increase is associated with a decrease of pulmonary edema and prevention of cardiac hypertrophy. Tezosentan could be a safe and useful therapeutic agent in the prevention and treatment of ischemic HF.