Increased concentration of endothelin messenger RNA in the mesenteric arteries of cyclosporine-induced hypertensive rats

H2S Prevents Cyclosporine A-Induced Vasomotor Alteration in Rats

Cyclosporine A (CsA) induces hypertension after transplantation. Hydrogen sulfide (H₂S) was found to have hypotensive/vasoprotective effects in the cardiovascular system. The present study aims to investigate the role of H₂S on CsA-induced vascular function disorder in rats. Rats were subcutaneously injected with CsA 25 mg/kg for 21 days. Blood pressure was measured by the tail-cuff method. Vasomotion was determined using a sensitive myograph. Western blotting and immunohistochemistry were used to quantify the protein expression of endothelin type A (ET_A) receptor and essential MAPK pathway molecules. Vascular superoxide anion production and serum contents of malondialdehyde were determined. The results showed that sodium hydrosulfide (NaHS), a H₂S donor, significantly attenuated the increase of blood pressure and contractile responses, and the upregulation of ET_A receptor induced by CsA. In addition, NaHS could restore the CsA decreased acetylcholine-induced vasodilatation. Furthermore, NaHS blocked the CsA-induced elevation of reactive oxygen species level, extracellular signal-regulated kinase and p38 MAPK activities. In conclusion, H₂S prevents CsA-induced vasomotor dysfunction. H₂S attenuates CsA-induced ET_A receptor upregulation, which may be associated with MAPK signal pathways. H₂S ameliorates endothelial-dependent relaxation, which may be through antioxidant activity.

Vascular synthesis of aldosterone: role in hypertension

The author showed direct evidence that blood vessels are aldosteronogenic. The expression of CYP11B2 mRNA and synthesis of vascular aldosterone were decreased in rats treated with angiotensin converting enzyme inhibitor. Angiotensin II increased production of aldosterone in blood vessels. Vascular aldosterone and CYP11B2 mRNA levels of 2-week-old SHRSPs were significantly increased compared with that in WKY rats of the same age. High sodium intake develops and accelerates vascular injury and cardiac hypertrophy in SHRSP. Plasma aldosterone concentrations and plasma renin concentration were decreased by high salt intake in SHRSP. Aldosterone production, the expression of CYP11B2 mRNA and type I angiotensin II receptor (ATiR) mRNA in blood vessels were significantly increased by high salt intake. These results suggest that high salt intake increases aldosterone production and expression of the ATiR mRNA in the vascular tissue in SHRSP, which may contribute to the development of malignant hypertension in salt-loaded SHRSP.

Imbalance in endothelial vasoactive factors as a possible cause of cyclosporin toxicity: a role for endothelin-converting enzyme

Cyclosporin A (CsA) is a powerful, widely used immunosuppressant, but it is not devoid of serious clinical side effects such as hypertension and nephrotoxicity. To clarify the mechanisms involved in the genesis of these side effects, we studied the effects of chronic CsA administration on the expression of some endothelial vasoactive factors in the aorta and kidney. For this purpose rats were treated for 30 days with 50 mg/kg/day CsA, and hypertension and renal insufficiency developed. In rats receiving CsA, the mRNA expression of pre-pro-endothelin-1 increased, whereas that of endothelial nitric oxide (NO) synthase decreased, both in the aorta and in the renal cortex (increases in pre-pro-endothelin-1 mRNA in aorta and renal cortex, respectively: 275%+/-18%, 300%+/-27%; decreases in endothelial NO synthase mRNA in aorta and renal cortex respectively: 40%+/-8%, 42%+/-6%). Moreover, long-term CsA treatment also induced an up-regulation of the endothelin-converting enzyme 1 mRNA expression (156% vs. control rats) in the renal cortex, with a significantly increased protein content and enzyme activity. In contrast, no changes were detected in endothelin-converting enzyme 1 mRNA expression in aortas from rats receiving the drug. This imbalance between endothelin-1 and NO systems could explain the hypertension and the deranged kidney function observed after long-term CsA treatment in rats.

Effects of chronic neutral endopeptidase inhibition in rats with cyclosporine-induced hypertension

OBJECTIVE

Cyclosporine (CysA), a potent immunosuppressant, is associated with hypertension and nephrotoxicity. Neutral endopeptidase (NEP) degrades vasoactive peptides, including the natriuretic peptides and endothelin-1 (ET-1). We conducted the present study to determine whether or not the NEP inhibitor, ecadotril, prevents cyclosporine-induced hypertension and to clarify the mechanisms responsible for the hypotensive effects of ecadotril.

DESIGN AND METHODS

We studied the chronic effects of ecadotril (30 mg/kg per day) on blood pressure; the production of ET-1 and C-type natriuretic peptide (CNP); endothelial nitric oxide synthase (eNOS) activity; and the expression of messenger RNA (mRNA), for each substance in blood vessels of CysA-induced hypertensive rats.

RESULTS

CysA (25 mg/kg per day) given for 4 weeks increased the blood pressure from 116 +/- 14 mmHg to 159 +/- 15 mmHg, in rats. This increase was blunted by the co-administration of ecadotril (blood pressure: 134 +/- 14 mmHg). CysA increased plasma NEP activity. CysA increased the production of ET-1 and the expression of ET-1 mRNA without affecting CNP synthesis and endothelin converting enzyme (ECE)-1 mRNA expression. CysA decreased the eNOS activity and eNOS mRNA levels. Addition of the NEP inhibitor decreased the synthesis of ET-1 and ET-1 mRNA levels and increased the eNOS activity and the eNOS mRNA levels. Vascular CNP synthesis and ECE-1 mRNA expression in rats treated with ecadotril did not differ from those in rats treated with CysA and ecadotril.

CONCLUSION

These results indicate that chronic NEP inhibition may prevent the CysA-induced hypertension by decreasing local ET-1 synthesis and partly increasing vascular nitric oxide production.

Enalapril and valsartan improve cyclosporine A-induced vascular dysfunction in spontaneously hypertensive rats

Cyclosporine A causes hypertension and nephrotoxicity in spontaneously hypertensive rats (SHR). In the present study, arterial function was investigated using in vitro vascular preparations after long-term treatment with cyclosporine A. SHR received cyclosporine A (5 mg kg(-1) day(-1) s.c.) and high-Na(+) diet for 6 weeks during the developmental phase of hypertension. Part of the rats were treated concomitantly either with the angiotensin converting enzyme inhibitor enalapril (30 mg kg(-1) day(-1) p.o.) or with an angiotensin AT(1) receptor antagonist valsartan (3 or 30 mg kg(-1) day(-1) p.o.). In renal arteries, contractile responses to noradrenaline and angiotensin II, as well as relaxation responses to acetylcholine (endothelium-dependent) and to sodium nitroprusside (endothelium-independent), were severely impaired by cyclosporine A-treatment. There was also a trend for the dysfunction of the mesenteric arteries, but the impairment did not reach statistical difference. Enalapril and valsartan improved the impaired renal arterial functions. Cyclosporine A-induced hypertension and nephrotoxicity seem to be associated with renal arterial dysfunction in SHR on high-Na(+) diet. Antagonism of the renin-angiotensin system protects from vascular toxicity of cyclosporine A.

Mechanisms of FK 506-induced hypertension in the rat

-Tacrolimus (FK 506) is a powerful, widely used immunosuppressant. The clinical utility of FK 506 is complicated by substantial hypertension and nephrotoxicity. To clarify the mechanisms of FK 506-induced hypertension, we studied the chronic effects of FK 506 on the synthesis of endothelin-1 (ET-1), the expression of mRNA of ET-1 and endothelin-converting enzyme-1 (ECE-1), the endothelial nitric oxide synthase (eNOS) activity, and the expression of mRNA of eNOS and C-type natriuretic peptide (CNP) in rat blood vessels. In addition, the effect of the specific endothelin type A receptor antagonist FR 139317 on FK 506-induced hypertension in rats was studied. FK 506, 5 mg. kg-1. d-1 given for 4 weeks, elevated blood pressure from 102+/-13 to 152+/-15 mm Hg and increased the synthesis of ET-1 and the levels of ET-1 mRNA in the mesenteric artery (240% and 230%, respectively). Little change was observed in the expression of ECE-1 mRNA and CNP mRNA. FK 506 decreased eNOS activity and the levels of eNOS mRNA in the aorta (48% and 55%, respectively). The administration of FR 139317 (10 mg. kg-1. d-1) prevented FK 506-induced hypertension in rats. These results indicate that FK 506 may increase blood pressure not only by increasing ET-1 production but also by decreasing NO synthesis in the vasculature.

Bosentan ameliorates cyclosporin A-induced hypertension in rats and primates

Cyclosporine-induced hypertension is a major problem in transplant therapy. The pathophysiology of this disease is unclear. Cyclosporine increases endothelin synthesis and release, which may contribute to this hypertension. We examined the effects of chronic endothelin receptor blockade with the novel nonpeptide endothelin receptor antagonist bosentan in two animal models of cyclosporine-induced hypertension. Cyclosporine was administered daily to female Wistar rats (10 mg/kg per day SC for 30 days) and marmosets (30 mg/kg per day PO for 20 days). Control rats received vehicle. Tail-cuff systolic pressure was significantly elevated in the cyclosporine-treated animals before the last week of treatment. Bosentan (100 mg/kg) in arabic gum or arabic gum alone was given daily to the rats by gavage during the last 5 days of cyclosporine treatment and to the marmosets for the last 7 days of cyclosporine treatment. Tail-cuff systolic pressure was measured daily during bosentan treatment. Bosentan but not gum alone significantly lowered blood pressure in the cyclosporine-hypertensive rats from 134 +/- l to 122 +/- 3 mm Hg (P<.Ol) and in the cyclosporine-hypertensive marmosets from 156 +/- 2 to 139+/- 4 mm Hg (P<.Ol). There were no differential effects on plasma creatinine concentration, endothelin concentration, or end-organ weights. Bosentan had no effect in the vehicle-treated rats. These data provide further evidence to support a role for endothelin in cyclosporine-induced hypertension and demonstrate the effectiveness of endothelin receptor antagonism as a novel treatment in cyclosporine-induced hypertension.

Effects of cyclosporin A on the synthesis, excretion, and metabolism of endothelin in the rat

Increasing evidence suggests that endothelin, a potent vasoconstrictor, is implicated in cyclosporin A (CsA)-induced nephrotoxicity. Increased levels of urinary and circulating endothelin have been described in CsA-treated humans and animals. The exact mechanisms by which CsA induces these increases are still unknown, and no data indicate whether these elevated levels reflect increased synthesis or decreased clearance of endothelin. In the present study, we investigated the effects of CsA administration (50 mg/kg per day i.p. for 6 days) to rats on plasma and urinary levels of endothelin; expression of endothelin-1 (ET-1), ET-3, and endothelin-converting enzyme in renal tissue; clearance of infused 125I-ET-1; and degradation of 125I-ET-1 by recombinant neutral endopeptidase. Rats given CsA for 6 days developed severe renal insufficiency, as shown by a 74% decrease in creatinine clearance rate (Ccr) (P < .006). Ccr was remarkably improved in CsA-treated rats that received bosentan, the combined antagonist of both endothelin A and endothelin B receptors. Urinary excretion of endothelin increased from an undetectable level to 31.7 +/- 6.0 pg/24 h (P < .001), and plasma levels of endothelin were unchanged (2.8 +/- 0.2 to 3.1 +/- 0.2 pg/mL). Reverse transcription followed by quantitative polymerase chain reaction revealed that ET-1 mRNA in the renal medulla increased by 59% (P < .006), whereas the expression of both ET-3 and endothelin-converting enzyme was unchanged. In other rats, neither acute nor chronic treatment with CsA affected either the clearance of 125I-ET-1 from the blood or the renal and pulmonary uptake of the peptide. Moreover, CsA did not affect the degradation of 125I-ET-1 by highly purified recombinant neutral endopeptidase, a well-known endothelinase. Taken together, these data suggest that the elevated urinary endothelin levels obtained after CsA treatment originate from the kidney and reflect increased renal synthesis of ET-1. Moreover, the production of endothelin appears to be regulated at the mRNA transcription level, and expressions of ET-1 and ET-3 are regulated independently.

Effects of an endothelin receptor antagonist in rats with cyclosporine-induced hypertension

Cyclosporine, a potent immunosuppressant, is associated with the development of hypertension and nephrotoxicity. We have previously shown that endothelin release from the arteries is increased in rats with cyclosporine-induced hypertension. We conducted the present study to determine whether the specific endothelin type A (ETA) receptor antagonist FR 139317 prevents cyclosporine-induced hypertension and whether cyclosporine increases ETA receptor mRNA in blood vessels. Cyclosporine (25 mg/kg per day) given for 4 weeks increased blood pressure from 98 +/- 12 to 156 +/- 14 mm Hg; this increase was blunted by coadministration of 10 mg/kg per day FR 139317 (ie, blood pressure was 138 +/- 14 mm Hg) in Wistar-Kyoto rats. Cyclosporine induced greater vasoconstrictor responses to norepinephrine and angiotensin II in isolated mesenteric arteries. FR 139317 normalized the vasoconstrictor responses to angiotensin II and norepinephrine. Cyclosporine (25 mg/kg per day) given for 4 weeks increased ETA receptor mRNA expression in the rat aorta and mesenteric artery (170% and 176%, respectively). Little change was observed in ETB receptor mRNA. These results indicate that cyclosporine may increase blood pressure by increasing not only endothelin production but also ETA receptor in the vasculature. The specific ETA receptor antagonist FR 139317 may prevent the hypertension induced by cyclosporine.

Gene expression of endothelin receptors in aortic cells from cyclosporine-induced hypertensive rats

1. We examined preproendothelin-1, ETA and ETB receptor mRNA levels in aortic endothelial and smooth muscle cells from cyclosporine (CyA)-induced hypertensive rats using the reverse transcription polymerase chain reaction method. 2. Aortic endothelial preproendothelin-1 mRNA expression was about 1.5-fold higher, while that of ETB receptor mRNA was markedly decreased in CyA-treated rats compared with those in controls. 3. The expression of ETA receptor mRNA in smooth muscle cells from CyA-induced hypertensive rats was increased about two-fold over that in cells from control animals. 4. Thus, increased endothelial preproendothelin-1, and ETA receptor mRNA levels in smooth muscle cells, which are concomitant with the decrease in ETB receptor mRNA levels in endothelium, may contribute to CyA-induced hypertension in rats.

Gene expression of 11 beta-hydroxysteroid dehydrogenase in the mesenteric arteries of genetically hypertensive rats

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) modulates the access of corticosteroids to their receptors and plays an important role in controlling blood pressure. We determined 11 beta-HSD activity and mRNA levels in the mesenteric arteries of genetically hypertensive rats, the Dahl salt-sensitive hypertensive rat, and compared them with Dahl salt-resistant and Sprague-Dawley rats. 11 beta-HSD activity was expressed as the percent conversion of [3H]corticosterone to [3H]11-dehydrocorticosterone. 11 beta-HSD activity was significantly decreased in the mesenteric arteries of 8-week-old Dahl salt-sensitive hypertensive rats (11.4 +/- 1.4%) compared with Dahl salt-resistant rats (17.4 +/- 1.4%) or Sprague-Dawley rats (18.0 +/- 1.5%) of the same age (P < .05). There were no significant differences in 11 beta-HSD activity between 4-week-old Dahl salt-sensitive hypertensive and Dahl salt-resistant rats of the same age (15.3 +/- 1.3% and 15.1 +/- 1.9%, respectively). The concentration of 11 beta-HSD mRNA in the mesenteric arteries of 8-week-old Dahl salt-sensitive hypertensive rats was significantly lower than in Dahl salt-resistant or Sprague-Dawley rats of the same age (P < .05). There were no significant differences in the concentration of 11 beta-HSD mRNA in the mesenteric arteries of 4-week-old Dahl salt-sensitive hypertensive rats, Dahl salt-resistant rats, and Sprague-Dawley rats. These results indicate that 11 beta-HSD in the vascular wall may play a role in the pathogenesis of hypertension in this rat model.

Vascular endothelin responsiveness and receptor characteristics in vitro and effects of endothelin receptor blockade in vivo in cyclosporin hypertension

1. The aim of these studies was to determine the role of endothelin in cyclosporin A ([CsA], 10 mg/kg per day, s.c., for 30 days) hypertension in the rat. 2. There were no significant differences in plasma endothelin concentrations, in vitro mesenteric vascular membrane [125I]-endothelin-1 (ET-1) binding characteristics or myographic vascular responses to endothelin-1 between the CsA and control groups (systolic blood pressure 135 +/- 1 vs 127 +/- 1 mmHg, respectively, P < 0.001). 3. Twenty-four hours after selective endothelin type A receptor blockade in vivo with BQ123, blood pressure in CsA hypertensive rats was lowered to levels of normotensive controls. 4. These results suggest that changes in endothelin synthesis rather than changes in vascular sensitivity and/or ET-1 receptor characteristics may contribute to CsA-induced hypertension.