Endothelial and vascular smooth muscle function after chronic treatment with cyclosporin A

UGT1A1 morpholino antisense oligonucleotides produce mild unconjugated hyperbilirubinemia in cyclosporine A-induced cardiovascular disorders in BLC57 mice

This study aimed to investigate the induction of mild unconjugated hyperbilirubinemia in hepatic UGT1A1 inhibition by Morpholinos antisense in CsA-treated BLC57 mice in comparison with the efficacy of chitosan (CH) as an anti-hypolipidemic natural product. Antisense morpholino oligonucleotides were injected intravenously into CsA-treated mice for 14 days thrice a week. Serum biochemical parameters, antioxidant status, and gene expression analysis of eNOS, PPAR-α, NF-kB, cFn, AT1-R, and ETA-R were determined in cardiac tissues with confirmation by histopathology. Inhibition of UGT1A1 significantly elevated serum unconjugated bilirubin within a physiological range. Furthermore, induced mild hyperbilirubinemia reduces hyperlipidemia, improves antioxidant status, and significantly increases the expression of the cardiac PPAR-α gene while decreasing, ETA-R, iNOS, NF-kB, cFn and AT1-R gene expression in CsA-treated mice. Importantly, mild unconjugated hyperbilirubinemia within physiological ranges may be used as a novel therapeutic strategy to lower hyperlipidemia, atherosclerosis, hypertension, and the CVD outcomes in CsA- treated transplant recipients.

Coronary endothelial vasomotor function and vascular remodeling in heart transplant recipients randomized for tacrolimus or cyclosporine immunosuppression

OBJECTIVES

This study aimed to compare changes in coronary endothelial function, systemic endothelin-1 (ET-1) levels, and vascular remodeling in heart transplant recipients randomized to cyclosporin A (CyA) or tacrolimus (Tac) immunosuppression.

BACKGROUND

Functional endothelial abnormalities and intimal thickening are sensitive measures of early cardiac allograft vasculopathy (CAV).

METHODS

The randomized, prospective study was performed in two groups of 22 patients, maintained on Tac or CyA and mycophenolate mofetil immunosuppression, 1 and 12 months after heart transplantation. We investigated epicardial luminal diameter, coronary blood flow velocity, and ET-1 plasma levels at 1 and 12 months after transplantation. Structural coronary alterations were determined using intravascular ultrasound.

RESULTS

Epicardial vasomotor function at baseline and during follow-up was comparable between the groups. Deterioration of microvascular endothelial function during follow-up was significantly enhanced in the CyA versus Tac group (p < 0.05). Circulating ET-1 concentration increased in the CyA group but significantly decreased over time in the Tac group (CyA +17% vs. Tac -25%; p < 0.05). The time-dependent increase in mean intimal area was significantly enhanced in the CyA versus Tac group, whereas the vessel area significantly increased during follow-up in the Tac compared with the CyA group.

CONCLUSIONS

Epicardial endothelial function is comparable between CyA- and Tac-treated patients. Microvascular endothelial function deteriorates more in CyA-treated patients, a finding that correlates with enhanced ET-1 concentration and an increased intimal area during follow-up. The mean vessel area in the Tac group increased over time, indicating positive vascular remodeling. Tac is superior to CyA with respect to microvascular endothelial function, intimal thickening, and vascular remodeling.

Amelioration of cyclosporine nephrotoxicity by irbesartan, A selective AT1 receptor antagonist

Cyclosporine A (CsA), a fungal undecapeptide, is the most common immunosuppressive drug used in organ transplantation and autoimmune diseases. However, nephrotoxicity is the major adverse effect of CsA use. The molecular mechanisms of CsA nephrotoxicity are not well characterized, but more recent studies suggest an involvement of angiotensin II (ANG II) and reactive oxygen species in the development of cyclosporine nephrotoxicity. Induction of heat shock proteins (HSPs) is one of the best-described cellular responses to heat stress, hypoxia, and exposure to oxidants. HSPs have beneficial roles in protein processing and protection against cell injury. There is emerging evidence that ANG II induces oxidative stress in vitro and in vivo. This study was thus designed to investigate the role of Angiotensin II type I (AT1) receptor antagonist, irbesartan, on CsA-induced nephrotoxicity. Five groups of rats were employed in this study: group 1 served as control, group 2 rats were treated with CsA (20 mg kg(-1), subcutaneously for 21 days), and groups 3, 4, and 5 received CsA along with irbesartan (10, 25, and 50 mg kg(-1), perorally 24 hr before and 21 days concurrently), respectively. Renal function was assessed by measuring serum creatinine, blood urea nitrogen, creatinine, and urea clearance. The renal oxidative stress was measured by renal malondialdehyde levels, reduced glutathione levels, and enzymatic activity of catalase, glutathione reductase, and superoxide dismutase. Renal morphological alterations were assessed by histopathological examination. CsA administration for 21 days resulted in a marked renal oxidative stress and significantly deranged the renal functions as well as renal morphology. All these factors were significantly improved by irbesartan (50 mg kg(-1)) treatment. HSP72, HSP47, and HSP25 were clearly induced and expressed in CsA-treated animals. The induction and expression of HSP25 was markedly protected by treatment with irbesartan, whereas the induction and expression of HSP47 and HSP72 remained unaltered with the irbesartan treatment. These results clearly demonstrate the pivotal role of ANG II-induced oxidative stress and therapeutic potential of AT, receptor antagonist in ameliorating CsA-induced nephrotoxicity.

Cryopreservation alters antigenicity of allografts in a porcine model of transplant vasculopathy

The need for arterial grafts in coronary surgery to complement autologous vessels has generated interest in cryopreservation of small diameter allografts. We evaluated functional and histologic changes occurring in cryopreserved allografts 3 months after porcine femoral artery transplants.

METHODS

Twenty recipient and 15 donor pigs included a control group of 16 fresh and 12 cryopreserved nonimplant arteries were used. Fresh (n=5) and cryopreserved (n=5) autografts were implanted to assess cryopreservation effects in the absence of rejection. Fresh allografts with or without treatment with cyclosporine (CsA) (n=6 of 8) and cryopreserved allografts with or without treatment with CsA (n=6 of 10) were performed to study the antigenicity of cryopreserved allografts. Arteries were stained with hematoxylin and eosin, Masson's trichrome, and orcein for morphometric analyses and immunostained to identify endothelial cells, smooth muscle cells, T lymphocytes, and macrophages.

RESULTS

Among nonimplant arteries, cryopreservation reduced alpha-actin expression and increased the luminal area. All implanted autografts were patent. Cryopreserved autografts showed reduced alpha-actin expression and developed intimal hyperplasia compared to fresh autografts. Treatment with CsA improved the patency of fresh allografts from 0% to 83% (P <.01) and of cryopreserved allografts from 40% to 100% (P <.05). Cryopreserved allografts showed substantial intimal hyperplasia, and fresh allografts had more T lymphocyte infiltration in the intimal layer with aneurysmal dilatation.

CONCLUSIONS

Cryopreservation reduces the deposition of inflammatory cells and prevents the thrombosis or aneurysmal lesions observed in fresh allografts. Therefore, cryopreservation modifies the antigenicity of vascular allografts.

Regional and endothelial differences in cyclosporine attenuation of adenosine receptor-mediated vasorelaxations

The present study investigated the acute effects of the immunosuppressant drug cyclosporine A on vasorelaxations evoked via activation of adenosine receptors in the phenylephrine-preconstricted rat perfused kidney and isolated aorta. The roles of endothelial relaxing factors in this interaction were also evaluated. The adenosine analogue 5'-N-ethylcarboxamidoadenosine (NECA; kidney, 6 x 10(-9)-1 x 10(-7) mol; aorta, 1 x 10(-9)-1 x 10(-5) M) elicited dose-dependent vasorelaxations. In the perfused kidney, NECA responses were similarly and significantly attenuated by N-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor) or tetraethylammonium (K channel blocker) versus no effect for diclophenac (cyclooxygenase inhibitor). NECA relaxations in the aorta were reduced by the three inhibitors; the reduction in the response evoked by the highest dose of NECA (1 x 10(-5) M) amounted to 37.7 +/- 2.0% (L-NAME), 19.8 +/- 1.7% (tetraethylammonium), and 29.4 +/- 1.1% (diclophenac). A combination of the three inhibitors almost abolished NECA relaxations in the two preparations. Cyclosporine (2 microM) reduced NECA relaxations in the two preparations. In the aorta, cyclosporine attenuation of NECA responses was significantly reduced after exposure to L-NAME or diclophenac but not tetraethyl-ammonium, suggesting selective involvement of nitric oxide and vasodilator prostanoids in the interaction. In contrast, the cyclosporine attenuation of NECA responses in the kidney was reduced by L-NAME or tetraethylammonium. L-arginine, a nitric oxide substrate, partially restored NECA relaxations in cyclosporine-treated preparations. These findings demonstrate that cyclosporine attenuates endothelium-dependent vasorelaxations elicited via activation of adenosine receptors and highlight the interesting possibility that the relative contribution of the endothelial relaxing factors to cyclosporine-NECA interaction is largely region dependent.

Cyclosporin effect on noradrenaline release from the sympathetic nervous endings of rat aorta

Arterial hypertension is one of the main side effects of cyclosporin treatment and seems to be due to activation of the sympathetic nervous system. Some authors hypothesized that cyclosporin may act on the sympathetic nervous endings increasing catecholamine release, in agreement with our previous works which demonstrated an increase in rat plasma catecholamine levels after 30 mg/kg per day cyclosporin treatment for 7 weeks. Therefore, the aim of this work was to study the cyclosporin mechanism responsible for that increase in plasma catecholamines. Male Wistar rats were used. Noradrenaline release was performed in vitro experiments after loading rat aorta abdominal segments with 3H-noradrenaline (3H-NA). The release of 3H-NA was measured after electrical stimulation in the presence of 10(-6)M cyclosporin. In another set of experiments electrical stimulation was replaced by a pulse addition of cyclosporin (10(-6)M). Another group of rats was treated with 30 mg/kg per day cyclosporin for 7 weeks and catecholamine contents in aorta abdominal segments and adrenals were measured by high performance liquid chromatography system with electrochemical detection (HPLC-ECD). An increase in the 3H-NA release was observed in both types of in vitro experiments. Since cocaine abolished these cyclosporin effects, the obtained results suggest that cyclosporin may act on the catecholamine transporter across the membrane. In addition, after the 7 weeks of cyclosporin treatment, a significant decrease in catecholamine aorta contents was verified but in adrenals there was no difference regarding to controls. However, the dopamine synthesis/degradation ratio measured by the DA/DOPAC ratio suggests an increase in dopamine synthesis. These facts are in agreement with the enhanced plasma catecholamine levels and with the hypothesis of tissue catecholamine depletion. However, they do not explain the increase in plasma adrenaline levels, since adrenaline is a reflex of adrenal activity. The synthesized dopamine in adrenals seems to be unable to reach vesicles and to be metabolized in adrenaline. The observed decrease in HVA adrenal levels may be a consequence of extraneuronal uptake inhibition or inhibition by cyclosporin of the direct o-methylation of DOPAC. In conclusion, our results suggest that cyclosporin increases catecholamine release from the sympathetic nervous endings by a tyramine-like effect, i.e. by acting directly on the catecholamine transporter of the membrane.

Role of metoprolol, B1-adrenoceptor antagonist, thromboxane A2 and nitric oxide in CsA-induced hypertension

Chronic treatment with cyclosporine A (CsA), a potent immunosuppressive agent, is associated with the development of arterial hypertension. The effect of CsA on vascular responses was determined in Sprague-Dawley rats and rat aortic rings. Male rats weighing 250-300 g were given either CsA (25mg/kg/day) in olive oil or vehicle by intraperitoneal (ip) injection for 7 days. CsA administration produced a 42% increase (P<0.001) in mean arterial pressure (MAP) which reached a plateau after 3 days. The level of both nitrate/nitrite (NO(2)/NO(3)), metabolites of nitric oxide (NO), decreased by 50% (P<0.001), but the level of thromboxane A2 (TBXA2) increased by 75% (P<0.001), in the urine. When 10(-9)M of CsA was added acutely to intact aortic rings from untreated rats, NO(2)/NO(3) production decreased by 83% (P<0.011), but TBXA2 production increased by 86% (P<0.001). The effects of CsA were reversed both in vivo and in vitro by pretreatment with metoprolol (15 mg/kg/day ip), B1-adrenoceptor antagonist. There were no changes in MAP and tension in rats treated with metoprolol alone. In addition, in aorta of rats that were treated with CsA ip for 7 days, CsA significantly activated protein kinase C (PKC) translocation. This suggests that PKC mediate, in part, CsA-induced hypertension. In summary, CsA inhibits endothelial NO formation, activate PKC, and increase TBXA2 production, with resulting increase in MAP, and this changes can be overcome by pretreatment with metoprolol.

Impairment of vascular and platelet levels of nitric oxide and cyclic guanosine-3',5'-monophosphate in cyclosporin A-induced hypertensive rats

The therapeutic use of the immunosuppressive agent cyclosporin A (CsA) is associated with arterial hypertension and increased risk of thromboembolism. Impaired endothelium-mediated relaxation is one of the main hypotheses explaining the CsA-induced vascular hyper-reactivity. Since nitric oxide (NO) modulates both vascular and platelet activity, we studied the effects of CsA on the levels of arterial and platelet NO as well as 3',5'-cyclic guanosine monophosphate (cGMP) levels which are influenced by NO. An animal model of CsA-induced hypertension was used. Wistar rats were treated with a clinically relevant, oral dose of 5 mg/kg CsA, daily, for 4 weeks. CsA increased both systolic and diastolic blood pressures compared to non-treated rats (P < 0.01). Nitrite, a NO metabolite, decreased in the entire aorta wall (30%, P < 0.05) and in the aorta wall without the endothelial layer (70 %, P < 0.05) in CsA-treated vs. control groups. cGMP content was also decreased in the CsA-treated group (67%, P < 0.01) vs. control. Taken together, these results suggest a defect on the endothelial NO generation, acceleration of breakdown and/or consumption of NO, as well as marked alterations directly on cGMP metabolism. Conversely, platelet nitrite and cGMP content significantly increased in the CsA-treated rats, which was also observed in in vitro studies of platelet nitrite release following CsA treatment. This suggests a platelet self-regulation mechanism against CsA-induced platelet hyper-reactivity, which, in turn, could compensate vascular impairment.

Dephosphorylation of endothelial nitric-oxide synthase by vascular endothelial growth factor. Implications for the vascular responses to cyclosporin A

The endothelial isoform of nitric-oxide synthase (eNOS) is a key determinant of vascular tone. eNOS, a Ca(2+)/camodulin-dependent enzyme, is also regulated by a variety of agonist-activated protein kinases, but the role and regulation of the protein phosphatase pathways involved in eNOS dephosphorylation are much less well understood. Treatment of endothelial cells with vascular endothelial growth factor (VEGF), a potent eNOS agonist, leads to the activation of calcineurin, a Ca(2+)/camodulin-dependent protein phosphatase. In these studies, we used a phosphorylation state-specific antibody to show that VEGF promotes dephosphorylation of eNOS at serine residue 116 in cultured endothelial cells. Cyclosporin A, an inhibitor of calcineurin, completely blocks VEGF-induced eNOS dephosphorylation; under identical conditions, cyclosporin A also inhibits VEGF-induced eNOS activation. VEGF-induced eNOS dephosphorylation shows an EC(50) of 2 ng/ml and is maximal 30 min after agonist addition. eNOS phosphorylation at serine 116 is completely blocked by the protein kinase C inhibitor calphostin but is blocked by neither wortmannin (an inhibitor of phosphatidylinositide 3-kinase) nor the MAP kinase pathway inhibitor U0126. A phosphorylation-deficient mutant of eNOS in which serine 116 is changed to an alanine residue (S116A) shows significantly enhanced enzyme activity compared with the wild-type enzyme. Taken together, these findings indicated that VEGF-induced eNOS dephosphorylation at serine 116 leads to enzyme activation. Cyclosporin A is widely used as an immunosuppressive drug for which hypertension is an important dose-limiting side effect. Our results suggest that cyclosporin A-induced hypertension may involve, at least in part, the attenuation of endothelium-derived NO production through a calcineurin-sensitive pathway regulating eNOS dephosphorylation.

Cyclosporin effect on rat aorta alpha(1)-adrenoceptors and their transduction mechanisms

A possible explanation for cyclosporin-induced arterial hypertension may be its action on the adrenergic system. In spite of the controversial results reported in literature, it seems that cyclosporin changes the vascular response to noradrenaline. Therefore, after observation that two cyclosporin doses increase rat blood pressure and vascular reactivity in response to noradrenaline, the aim of this work was to study the cellular mechanisms beside the cyclosporin-induced changes in response to noradrenaline. Therefore, the cyclosporin influence on alpha(1)-adrenoceptors as well as on their transduction mechanism in smooth muscle cells was studied. Through Scatchard analysis of specific [(3)H]-prazosin binding, the alpha(1)-adrenoceptor number and related affinity were studied, before and after cyclosporin exposure. The cyclosporin influence on alpha1-adrenoceptor transduction mechanisms was also evaluated by the quantification of intracellular free calcium contents [Ca2+]i and inositol phosphate (InsP) turnover. All in vitro experiments were performed in rat aortic smooth muscle cells in culture. Results showed that both cyclosporin concentrations (10(-6) and 10(-7) M) changed alpha1-adrenoceptor number but only 10(-7) M cyclosporin increased its affinity for [(3)H]-prazosin. Compared with control cells, only 10(-7) M cyclosporin increased InsP levels. Stimulation by noradrenaline increased InsP in 10(-7) M cyclosporin-treated cells but decreased InsP in the presence of 10(-6) M cyclosporin. Both cyclosporin concentrations increased [Ca2+]i in basal conditions and after noradrenaline stimulation. The results suggest that after noradrenaline stimulation cyclosporin increases [Ca2+]i, probably through different mechanisms, depending on the cyclosporin concentration used. However, 10(-7) M cyclosporin increases alpha1-adrenoceptor affinity and their related transduction mechanisms. The higher cyclosporin concentration (10(-6) M) seems to induce downregulation of alpha1-adrenoceptors, probably by activation of protein kinase C.

Selective angiotensin II type 1 receptor blockade ameliorates cyclosporine nephrotoxicity

Nephrotoxicity associated with cyclosporine A (CsA) administration is characterized by marked renal vasoconstriction, interstitial fibrosis and arteriolar hypertrophy. The molecular mechanisms of CsA nephrotoxicity are not well characterized, but previous studies have demonstrated that angiotensin II (Ang II), the primary mediator of renin-angiotensin system (RAS) cascade plays a role in its pathogenesis. Recent studies also suggest an involvement of reactive oxygen species (ROS) in CsA nephrotoxicity. There is emerging evidence that Ang II induces oxidative stress in vitro and in vivo. The aims of this study were to investigate the role of Ang II-induced oxidative stress in CsA nephrotoxicity, and to examine the effects of the insurmountable Ang II type 1 (AT (1)) receptor antagonist, candesartan on CsA-induced nephrotoxicity in rats. Candesartan cilexetil (1.0 mg kg (-1), perorally (p.o.), once a day) was administered 24 h before and 21 days concurrently with CsA (20 mg kg(-1), subcutaneously (s.c.)). Tissue lipid peroxidation was measured as thiobarbituric acid reacting substances (TBARS). Renal function was assessed by estimating serum creatinine, blood urea nitrogen (BUN), creatinine and urea clearance. Renal morphological alterations were assessed by histopathological examination of Haematoxylin-Eosin, PAS and Mason's trichome stained sections of the kidneys. CsA (20 mg kg (-1), s.c.) administration for 21 days produced elevated levels of TBARS and deteriorated the renal function as assessed by increased serum creatinine, BUN and decreased creatinine and urea clearance as compared to vehicle treated rats. The kidneys of CsA-treated rats showed severe striped interstitial fibrosis, arteriolopathy, glomerular basement thickening, tubular vacuolisation and hyaline casts. Candesartan cilexetil (1.0 mg kg (-1)) markedly reduced elevated levels of TBARS, significantly attenuated renal dysfunction and morphological changes in CsA-treated rats. These results clearly demonstrate the pivotal role of Ang II-induced oxidative stress and the therapeutic potential of AT (1)receptor antagonists in ameliorating CsA-induced nephrotoxicity.

Superoxide limits cyclosporine-A-induced formation of peroxynitrite in endothelial cells(2)

Peroxynitrite (ONOO(-)) is a potent oxidant formed by the nonenzymatic reaction between superoxide anion (O(2)(*-)) and nitric oxide (NO*) in a one-to-one stoichiometry. Accumulated evidence suggests that endothelial dysfunction coincides with an enhanced NO* synthase expression and O(2)(*-) production, facilitating ONOO(-) formation. In vivo, formation of ONOO(-) has been associated with atherosclerosis and vascular aging. The immunosuppressor Cyclosporine A (CsA) has been associated to human endothelial dysfunction and accelerated atherosclerosis. We have previously shown that CsA induced a transcriptionally mediated increase of the eNOS gene expression and that CsA induced the formation of nitric oxide, O(2)(*-), and ONOO(-) in vascular endothelial cells. In this work, we evaluate the CsA-induced relative amounts of formation of O(2)(*-) and NO*, providing data consistent with a role of O(2)(*-), and not NO*, as the limiting factor in the CsA-dependent intracellular formation of ONOO(-) in vascular endothelial cells. Furthermore, when endothelial cells were treated with CsA in a situation of increased generation of superoxide such as that provided by high glucose levels, a further increase in the formation of peroxynitrite was detected. The temporal availability of O(2)(*-) for peroxynitrite formation may thus become critical in the pathophysiological scenarios where reactive nitrogen intermediates are operative.

Nitric oxide in CsA-induced hypertension: role of beta-adrenoceptor antagonist and thromboxane A2

Cyclosporine A (CsA) is an immunosuppressive agent, which also causes hypertension. The effect of CsA on vascular responses was determined in Sprague-Dawley rats and rat aortic rings. Male rats weighing 250-300 g were given either CsA (25 mg/kg/day) in olive oil or vehicle by intraperitoneal (ip) injection for 7 days. CsA administration produced a 42% increase (P < 0.001) in mean arterial pressure (MAP) which reached a plateau after 3 days. The level of both nitrate/nitrite (NO2/NO3), metabolites of nitric oxide (NO), decreased by 50% (P < 0.001), but the level of thromboxane A2 (TBXA2) increased by 75% (P < 0.001), in the urine. When 10(-9) M of CsAwas added acutely to intact aortic rings from untreated rats, NO2/NO3 production decreased by 83% (P < 0.011), but TBXA2 production increased by 86% (P < 0.001). The effects of CsA were reversed both in vivo and in vitro by pretreatment with propranolol (15 mg/kg/day ip), beta-adrenoceptor antagonist. There were no changes in MAP and tension in rats treated with prop alone. In addition, in aorta of rats that were treated with CsA ip for 7 days, CsA significantly activated protein kinase C (PKC) translocation. This suggests that PKC mediate, in part, CsA-induced hypertension. In summary, CsA inhibits endothelial NO formation, activate PKC, and increaseTBXA2 production, with resulting increase in MAP, and this changes can be overcome by pretreatment with propranolol.

Involvement of tyrosine hydroxylase upregulation in cyclosporine-induced hypertension

To identify the mechanism of cyclosporine-induced hypertension, we studied the effect of cyclosporine on the catecholamine synthetic pathway in rats. We administered cyclosporine (10 mg/kg per day, s.c.) for 3 days to 10-week-old male Wistar rats. Systolic blood pressure increased significantly in the cyclosporine-treated group in comparison to that in the control group. Norepinephrine and epinephrine levels in the adrenal medulla and plasma of cyclosporine-treated rats were also significantly higher than levels in the control rats. Moreover, tyrosine hydroxylase (TH) activity and TH mRNA expression in the adrenal medulla of cyclosporine-treated rats were significantly elevated. Administration of the TH inhibitor alphamethyl-p-tyrosine (200 mg/kg, b.i.d., s.c.) for 3 days significantly suppressed cyclosporine-induced increases in systolic blood pressure. Phosphorylation of cyclic AMP responsive element-binding protein (CREB) and its binding activity to DNA in the nuclear fraction from the adrenal medulla of cyclosporine-treated rats were much higher than that of the control rats. Calcineurin protein expression of cyclosporine-treated rats was less than that of the control rats. These results suggest that cyclosporine increased blood pressure via activation of the catecholamine synthetic pathway due to the activation of transcription factor CREB.

Upregulation of vasopressin V1A receptor mRNA and protein in vascular smooth muscle cells following cyclosporin A treatment

1. The major side effects of the immunosuppressive drug cyclosporin A (CsA) are hypertension and nephrotoxicity. It is likely that both are caused by local vasoconstriction. 2. We have shown previously that 20 h treatment of rat vascular smooth muscle cells (VSMC) with therapeutically relevant CsA concentrations increased the cellular response to [Arg8]vasopressin (AVP) by increasing about 2 fold the number of vasopressin receptors. 3. Displacement experiments using a specific antagonist of the vasopressin V1A receptor (V1AR) showed that the vasopressin binding sites present in VSMC were exclusively receptors of the V1A subtype. 4. Receptor internalization studies revealed that CsA (10(-6) M) did not significantly alter AVP receptor trafficking. 5. V1AR mRNA was increased by CsA, as measured by quantitative polymerase chain reaction. Time-course studies indicated that the increase in mRNA preceded cell surface expression of the receptor, as measured by hormone binding. 6. A direct effect of CsA on the V1AR promoter was investigated using VSMC transfected with a V1AR promoter-luciferase reporter construct. Surprisingly, CsA did not increase, but rather slightly reduced V1AR promoter activity. This effect was independent of the cyclophilin-calcineurin pathway. 7. Measurement of V1AR mRNA decay in the presence of the transcription inhibitor actinomycin D revealed that CsA increased the half-life of V1AR mRNA about 2 fold. 8. In conclusion, CsA increased the response of VSMC to AVP by upregulating V1AR expression through stabilization of its mRNA. This could be a key mechanism in enhanced vascular responsiveness induced by CsA, causing both hypertension and, via renal vasoconstriction, reduced glomerular filtration.

Coronary vasomotor dysfunction in the cardiac allograft: impact of different immunosuppressive regimens

Immunosuppression may have an important impact on early graft coronary endothelial injury. We investigated functional and morphologic coronary alterations, myocardial expression, and cardiac release of possible mediators of allograft vasculopathy within 6 months after cardiac transplantation with respect to different immunosuppressive regimens. Epicardial and microvascular endothelium-dependent and endothelium-independent vasomotor function and epicardial intimal thickening were measured in 8 transplant recipients treated with cyclosporin A (CyA), azathioprine, and prednisone (group 1), 9 transplant recipients treated with tacrolimus (TKL), azathioprine, and prednisone (group 2), and 14 patients treated with TKL, mycophenolate mofetil (MMF), and prednisone (group 3). The gene expressions of inducible and endothelial nitric oxide synthase (iNOS and eNOS), endothelin-1, prostacyclinsynthase, and thromboxansynthase were analyzed in endomyocardial biopsy specimens using semiquantitative reverse transcription polymerase chain reaction. Transcardiac cytokine release, endothelin-1, and nitrate-release were determined from plasma samples. Epicardial endothelial dysfunction (vasoconstriction to acetylcholine > 10%) and microvascular smooth muscle cell dysfunction (flow velocity increase to adenosine and nifedipine < 2.0) were enhanced in heart transplant recipients immunosuppressed with TKL, azathioprine, and prednisone. The prevalence of epicardial dysfunction was 78% in group 2 versus 44% and 46% in group 1 and 3 (p < 0.05), respectively. The prevalence of microvascular dysfunction was 56% in group 2 versus 13% and 7% in group 1 and 3 (p < 0.02), respectively. Coronary vasomotor dysfunction was associated with increased myocardial iNOS expression (p < 0.05), decreased eNOS expression (p < 0.05), and enhanced cardiac immunoreactive interleukin-6 (p < 0.01). Coronary intimal thickening was not different between the groups. The combination of TKL and MMF appears to be superior to TKL and azathioprine (and comparable to CyA and azathioprine) concerning preservation of early coronary vasomotor function, eNOS expression, iNOS suppression as well as cardiac interleukin-6 release. This may have an important impact on subsequent development of transplant coronary atherosclerosis.

Platelet activation is increased in cyclosporin A-induced hypertensive rats

One of the most severe side effects of the immunosuppressive agent, cyclosporin A (CsA), is increased risk of thromboembolic complications and drug-related hypertension. Because platelets might be involved in these processes, we tested the possibility of CsA affecting platelet activation, which might contribute to these adverse drug reactions. The experiments were done using Wistar rats, treated or not (control) with CsA (Sandimmun Neoral), 5 and 30 mg/kg/day, for 7 weeks. Systolic, diastolic, and mean blood pressures, intracellular free calcium concentration ([Ca2+]i), platelet serotonin (5-HT) contents, and aggregation were determined, at weeks 0, 2, and 7 of treatment. Inositol phosphates (InsP) production, platelet thromboxane A2 (TXA2) generation, and morphology of platelets, through electron microscopy studies, also were compared. It was demonstrated that blood pressures increased in the CsA-treated groups, when compared with the control group, after 2 and 7 weeks of administration. CsA at both "attack" and "maintenance" doses increased basal, 5-HT, and thrombin-evoked [Ca2+]i after 2 and 7 weeks versus the control group. However, basal and evoked InsP production was stimulated by 5 mg/kg of CsA, but inhibited by 30 mg/kg, when compared with the control. Platelet 5-HT contents decreased significantly after 2 and 7 weeks in the CsA-treated groups, when compared with the control group. Collagen-induced whole blood platelet aggregation increased drastically in the "attack" CsA-treated group, whereas adenosine diphosphate (ADP)-induced platelet aggregation did not reach statistical significance. Finally, in vitro basal, collagen-, and ADP-evoked platelet TXA2 generation increased in both CsA concentrations, versus the control. In conclusion, our study demonstrates that both CsA doses alter platelet calcium homeostasis (even affecting the calcium fluxes differently), 5-HT and TXA2 contents and aggregation, which might contribute to the development and/or maintenance of high blood pressures and increased risk of thromboembolic complications.

Comparison of enalapril and valsartan in cyclosporine A-induced hypertension and nephrotoxicity in spontaneously hypertensive rats on high-sodium diet

1. We compared the effects of the angiotensin converting enzyme (ACE) inhibitor enalapril and the angiotensin AT(1) receptor antagonist valsartan in cyclosporine A (CsA)-induced hypertension and nephrotoxicity in spontaneously hypertensive rats (SHR). 2. SHR (8 - 9 weeks old) on high-sodium diet were given CsA (5 mg kg(-1)d (-1) s.c. ) for 6 weeks. The rats were treated concomitantly either with enalapril (30 mg kg(-1)d (-1) p.o.) or valsartan (3 or 30 mg kg(-1) d (-1) p.o.). To evaluate the role of bradykinin in the action of enalapril, some rats received a bradykinin B(2) receptor antagonist icatibant (HOE 140, 500 microg kg(-1) d (-1) s.c.) during the last 2 weeks of enalapril treatment. 3. Blood pressure was recorded every second week by tail cuff method. Renal function was measured by serum creatinine, creatinine clearance and urinary excretion of proteins at the end of the experiment. The activity of the renal kallikrein-kinin system was estimated by urinary kallikrein excretion. 4. CsA caused hypertension, impaired renal function and induced morphological nephrotoxicity with glomerular damage and interstitial fibrosis. Enalapril and the lower dose of valsartan attenuated the CsA-induced hypertension to the same extent, while the higher dose of valsartan totally abolished it. Icatibant did not reduce the antihypertensive effect of enalapril. Urinary kallikrein excretion was similar in all groups. 5. Enalapril and valsartan equally prevented the CsA-induced deterioration of kidney function and morphology. 6. The renin-angiotensin but not the kallikrein-kinin system plays a crucial role in CsA-toxicity during high intake of sodium in SHR.

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.

Early alterations of myocardial blood flow reserve in heart transplant recipients with angiographically normal coronary arteries

BACKGROUND

The evaluation of the coronary reserve provides valuable information on the status of coronary vessels. Therefore, we studied with positron emission tomography (PET) and 13N-ammonia the myocardial blood flow (MBF) reserve in heart transplant recipients free of allograft rejection and with angiographically normal coronary arteries early after heart transplantation (HTx). The MBF reserve was calculated as the ratio between MBF after dipyridamole injection and basal MBF normalized for the rate-pressure product.

METHODS

Patients were studied within 3 months (group A, n = 12) or more than 9 months (group B, n = 12) after HTx. Five patients have been studied both during the early and late period after HTx. Results were compared to those obtained in 7 normal volunteers (NL).

RESULTS

Group A recipients had a significantly lower dipyridamole MBF (in ml/min/100 gr of tissue) than that of group B recipients (142+/-34 vs 195+/-59, p<0.05). This resulted in a significant decrease in MBF reserve early after HTx (group A: 1.82+/- 0.33) and a restoration to normal values thereafter (group B: 2.52+/- 0.53 vs NL: 2.62+/-0.51, p = ns). Separate analysis of 5 patients studied twice is consistent with these results.

CONCLUSION

This study shows that in heart transplant recipients free of allograft rejection and with normal coronary angiography, MBF reserve is impaired early after HTx. Restoration within one year suggests that this abnormality does not represent an early stage of cardiac allograft vasculopathy.

Cyclosporine A-induced prostacyclin release is maintained by extracellular calcium in rat aortic endothelial cells: role of protein kinase C

Chronic treatment with the immunosuppressive drug Cyclosporine A (CsA) is associated with increased intracellular calcium in vascular smooth muscle cells, which may activate phospholipase A2. We used rat aortic endothelial cells to investigate the role of protein kinase C (PKC) in CsA-induced prostacyclin (PGI2) release. CsA (10(-9) M) produced a significant increase in PGI2 release. CsA-induced PGI2 release were inhibited 80-85% by 10(-9) M, and 99-100% by 10(-6) M pretreatment doses of any of three different PKC inhibitors, i.e. 1-(5-isoquinolinesulfonylmethyl)piperazine(H7), staurosporine or 1-(5-isoquinolinesulfonyl)piperazine. Pretreatment with (10(-9) M) of diltiazem (a voltage-sensitive L-type calcium channel blocker) completely inhibited both CsA-induced PGI2 release. Conversely, pretreatment with (10(-9) M) of thapsigargin (an intracellular calcium channel blocker) did not alter the action of CsA. These results strongly suggest that PKC, in association with an influx of extracellular calcium, mediates CsA-induced PGI2 release in rat aortic endothelial cells.

Nitric oxide in cyclosporine A-induced hypertension: endothelin receptors gene expression

Cyclosporine A (CsA) is an immunosuppressive agent, which also causes hypertension. The effect of CsA on vascular responses was determined in spontaneously hypertensive rats and isolated rat aortic rings. Male rats weighing 250-300 g were given either CsA (25 mg/kg/day) in olive oil or vehicle by i.p. injection for 7 days. CsA administration produced a 27% increase (P < 0.001) in mean arterial pressure (MAP) which reached a plateau after 3 days. Conversely, the level of nitrate/nitrite, metabolites of nitric oxide (NO), decreased by 44% (P < 0.001) in the urine. In the presence of endothelin (ET) 10(-9) M, thoracic aortic rings from rats treated with olive oil, L-Arginine (L-Arg) or L-Arg+CsA showed a 100% increase (P < 0.001) in tension compared to the aortic rings from rats treated with CsA alone; aortic rings from rats treated with CsA alone did not respond to ET. The effects of CsA were reversed in both in vivo and in vitro by pretreatment with L-Arg (10 mg/kg/day ip), the precursor of NO. There were no changes in MAP and tension in rats treated with L-Arg alone. Possible explanation for lack of response to ET of aortic rings from CsA treated rats may be that CsA affected ET signalling pathway; ET receptors mRNA (messenger ribonucleic acid) gene expression was inhibited in aortic rings of rats treated with CsA. In summary, CsA inhibits endothelial NO formation, with resulting increases in MAP, and this inhibition can be overcome by parenteral administration of L-Arg.

Role of nitric oxide in cyclosporine A-induced hypertension

Cyclosporine A (CsA) is an immunosuppressive agent that also causes hypertension. The effect of CsA on vascular responses was determined in Sprague-Dawley rats and isolated rat aortic rings. Male rats weighing 250 to 300 g were given either CsA (25 mg. kg-1. d-1) in olive oil or vehicle by intraperitoneal injection for 7 days. CsA administration produced a 42% increase (P<0.001) in mean arterial pressure (MAP) that reached a plateau after 3 days. Conversely, the levels of both nitrate/nitrite, metabolites of nitric oxide (NO), and cGMP, which mediates NO action, decreased by 50% (P<0.001) and 35% (P<0.001), respectively, in the urine. Thoracic aortic rings from rats treated with CsA and precontracted with endothelin (10(-9) mol/L) showed a 35% increase (P<0.001) in tension, whereas endothelium-dependent relaxation induced by acetylcholine (ACh, 10(-9) mol/L) was inhibited 65% (P<0.001) compared with that in untreated rats. This response was similar to that of endothelium-denuded aortic rings from untreated rats in which ACh-induced relaxation was completely abolished (P<0.001), but relaxation induced by S-nitroso-N-acetylpenicillamine (SNAP, 10(-8) mol/L) was unaffected (P<0.001). ACh-induced formation of both nitrate/nitrite and cGMP by both denuded and CsA-treated aortic rings was inhibited 95% (P<0.001) and 65% (P<0.001), respectively, compared with intact aortic rings. The effects of CsA were reversed both in vivo and in vitro by pretreatment with L-arginine (10 mg. kg-1. d-1 IP), the precursor of NO. There were no changes in MAP and tension in rats treated with L-arginine alone. In summary, CsA inhibits endothelial NO activity, with resulting increases in MAP and tension, and this inhibition can be overcome by parenteral administration of L-arginine.

Cyclosporin A has low potency as a calcineurin inhibitor in cells expressing high levels of P-glycoprotein

Cyclosporin A (CsA) is a widely-used immunosuppressant drug whose therapeutic and toxic actions are mediated through inhibition of calcineurin (CN), a calcium- and calmodulin-dependent phosphatase. Inhibition of CN by CsA requires drug binding to its protein cofactor in the inhibition, cyclophilin. Because cyclophilin is a high affinity target for CsA it is expected that this protein can act as a reservoir for the drug in the cell and may be able to inhibit cellular efflux of CsA. P-glycoprotein (P-gp) is known to increase the rate of CsA efflux from CsA loaded cells but it is not clear if the P-gp drug efflux pump can compete effectively with cyclophilin at therapeutically relevant concentrations of CsA. To test the hypothesis that increased expression of P-gp confers protection against CsA-dependent inhibition of CN phosphatase activity, KB-V cells expressing varying levels of P-gp were analyzed to determine the potency of CsA as a CN inhibitor. When intact cells were treated with CsA, a positive correlation was observed between P-gp expression and resistance to CsA-dependent inhibition of CN: the IC50 is approximately 20-fold higher in the multidrug resistant epidermal carcinoma cell line, KB-V, which expresses P-gp at a high level than in the parental, KB, cell line expressing very low levels of P-gp. The resistance displayed by KB-V cells is abrogated by co-administration of the P-gp inhibitor verapamil, whereas verapamil has no effect on CsA potency in control KB cells. In cell lysates from KB-V cells with different amounts of P-gp CsA exhibits equivalent potency, indicating that the difference in sensitivity to CsA among the cell types requires maintenance of cell integrity. These observations support the view that resistance to CN inhibition by CsA occurs in cells with moderately elevated P-gp activity. Therefore, P-gp activity appears to be an important determinant of CsA cellular specificity for both therapeutic and toxic effects.

Aerobic endurance training program improves exercise performance in lung transplant recipients

STUDY OBJECTIVE

To determine whether an aerobic endurance training program (AET) in comparison to normal daily activities improves exercise capacity in lung transplant recipients.

PATIENTS AND STUDY DESIGN

Nine lung transplant recipients (12+/-6 months after transplant) were examined. All patients underwent incremental bicycle ergometry with the work rate increased in increments of 20 W every 3 min. Identical exercise tests were performed after 11+/-5 weeks of normal daily activities and then after a 6-week AET. The weekly aerobic training time increased from 60 min at the beginning to 120 min during the last week. Training intensity ranged from 30 to 60% of the maximum heart rate reserve.

RESULTS

Normal daily activities had no effect on exercise performance. The AET induced a significant decrease in resting minute ventilation from 14+/-5 to 11+/-3 L/min. At an identical, submaximal level of exercise, a significant decrease in minute ventilation from 47+/-14 L/min to 39+/-13 L/min and heart rate from 144+/-12 to 133+/-17 beats/min, before and after the AET, was noted. The increase in peak oxygen uptake after AET was statistically significant (1.13+/-0.32 to 1.26+/-0.27 L/min).

CONCLUSIONS

These data demonstrate that normal daily activities do not affect exercise performance in lung transplant recipients > or = 6 months after lung transplantation. An AET improves submaximal and peak exercise performance significantly.

Forearm vasorelaxation in hypertensive renal transplant patients: the impact of withdrawal of cyclosporine

OBJECTIVE

To determine whether cyclosporine A-induced hypertension in renal transplant recipients is accompanied by impairment of endothelium-dependent vasodilatation, which has been suggested by in-vitro and in-vivo animal experiments.

DESIGN AND METHODS

In-vivo endothelium-dependent and endothelium-independent vasodilatation, and plasma concentrations of vasoactive hormones in 16 renal transplant patients were determined while they were being treated with cyclosporine A, and 16 weeks later, after their treatment had been changed to azathioprine therapy. The vasodilator response of the forearm vascular bed was measured by strain gauge venous occlusion plethysmography during intra-arterial infusion of acetylcholine (endothelium-dependent vasodilatation) and nitroprusside (endothelium-independent vasodilatation). Postischemic reactive flow was measured after 10 min of arterial occlusion. In addition, plasma concentrations of norepinephrine, and the prostanoids prostaglandin E2 and thromboxane B2, and also concentration of cyclosporine A in blood, were measured. Glomerular filtration rate and renal blood flow were estimated 1 day before the plethysmography study during each treatment period.

RESULTS

Upon changing from cyclosporine A to azathioprine treatment, mean arterial pressure fell significantly by 12+/-3% (P< 0.05). Glomerular filtration rate and renal blood flow increased by 13+/-5 and 19+/-8%, respectively (both P< 0.05), while renal vascular resistance fell by 48+/-11% (P< 0.01). Both baseline forearm blood flow and baseline forearm resistance did not change after conversion (5.7+/-0.7 versus 4.9+/-0.6 ml/100 ml/min, and 27.3+/-4.2 versus 26.2+/-3.2 arbitrary units). The absolute and relative forearm blood flow responses, and forearm vascular resistance responses to infusions of acetylcholine and nitroprusside were similar during treatments with cyclosporine A and azathioprine. Peak postischaemic forearm blood flow was 42+/-12% higher during cyclosporine A treatment than it was during azathioprine treatment (P< 0.05), but the minimal postischaemic forearm vascular resistance did not differ for these treatments. Plasma prostaglandin E2 and thromboxane B2 levels decreased by 34+/-7 and 45+/-8%, respectively, after changing treatment, but norepinephrine levels did not change.

CONCLUSIONS

Our data indicate that cyclosporine A-induced hypertension in renal transplant recipients is not accompanied by an increase in forearm vascular resistance. In addition, changing from cyclosporine A to azathioprine treatment did not cause changes in endothelial vasodilator functioning, although mean arterial pressure decreased significantly. Our results do not support the hypothesis that attenuation of endothelial vasodilator functioning contributes to the development of cyclosporine A-induced hypertension.

Regulation of aortic wall structure by the renin-angiotensin system in Wistar rats

The effects of long-term angiotensin-converting enzyme (ACE) inhibition, angiotensin II (AT1)-receptor blockade, calcium-entry blockade, or cyclosporin A treatment on rat aortic wall structure were investigated to determine the role of the renin-angiotensin system in the physiologic regulation of vascular structure in vivo. Groups of 15 Wistar rats were treated for 6 weeks either with the ACE inhibitors lisinopril or fosinopril or with the AT1-antagonists D 8731 or losartan (each 10 mg/kg/day) or with the calcium antagonist isradipine, 60 mg/kg/day, or cyclosporin A, 15 mg/kg/day, or a combination of cyclosporin with one of the vasodilators. Media thickness, vascular smooth-muscle cell density, and intima thickening were measured in histologic sections of the abdominal aorta. In addition, aortic contractility and heart weight were determined. Long-term ACE inhibition, AT1-receptor blockade, and calcium-entry blockade reduced aortic media thickness and increased media smooth-muscle cell density. Only ACE inhibition significantly reduced the extent of intima lesions. Media thickness correlated well with the maximal aortic contraction to phenylephrine and serotonin but not to angiotensin II. ACE inhibition and AT1-receptor blockade decreased heart weight, whereas calcium antagonism increased it. Cyclosporin treatment was without effect on any of these parameters. The data demonstrate a significant long-term influence of the renin-angiotensin system on aortic wall structure and function in Wistar rats.

Effect of cyclosporine A on the release of tissue factor pathway inhibitor from endothelial cells in heart transplant patients and cell culture

We investigated the influence of cyclosporine A on the concentration of tissue factor pathway inhibitor and von Willebrand factor antigen in plasma of heart transplant outpatients. Tissue factor pathway inhibitor was quantified in plasma of blood donors (n = 50) and heart transplant outpatients (n = 50) by a chromogenic substrate assay with a mean of 32.4 micrograms/l and 98.2 micrograms/l, respectively. Von Willebrand factor antigen was determined with an enzyme-linked immunoassay with a mean of 90.9% for blood donors and 184.5% in plasma of heart transplant recipients. In addition, we investigated the effect of cyclosporine A on endothelial cell cultures over an incubation period of four days. A dose-dependent effect of cyclosporine A on the release of endothelial tissue factor pathway inhibitor and von Willebrand factor antigen was determined in a concentration range from 100 to 200 micrograms/l cyclosporine A. The tissue factor pathway inhibitor and von Willebrand factor antigen concentrations in the cell culture supernatant increased during the incubation time according to the cyclosporine A concentration 2-3 fold and 2 fold, respectively. For a further elucidation of the cyclosporine A effect we investigated the influence of cremophor EL, the vehicle of cyclosporine A. Cremophor EL alone did not increase the tissue factor pathway inhibitor release. However, the release was enhanced 2-4 fold after co-stimulation with the calcium ionophore A 23187 (10(-4) mol/l) in a concentration-dependent mode. We conclude that a generalized endothelial damage or activation is most probably caused by cyclosporine A and its vehicle cremophor EL. This process probably depends upon the increase of cytosolic free calcium, as described for the liberation of von Willebrand factor by endothelial cells.

Cyclosporine impairs the ability of human platelets to mediate vasodilation

Cyclosporine causes various platelet abnormalities. Whether it affects the ability of platelets to mediate vasodilation is unknown. Platelets were isolated from healthy volunteers and 13 heart transplant patients on cyclosporine. When perfused through preconstricted normal rabbit carotid arteries, activated platelets from transplant patients failed to cause vasorelaxation, whereas normal platelets produced significant vasodilation (-4.0 +/- 1.9% versus 30 +/- 3% [P < .0001] change in vessel diameter, respectively). When normal platelets were exposed to cyclosporine in vitro, they lost their ability to cause vasodilation in a dose- and time-dependent fashion. However, when activated and perfused through quiescent, N omega-nitro-L-arginine-pretreated arteries, platelets from transplant patients and normal platelets caused similar degrees of vasoconstriction. The amount of adenosine triphosphate in the supernatant from activated cyclosporine-exposed and control platelets was similar (1.7 +/- 0.4 versus 1.5 +/- 0.3 mumol/L [P = NS], respectively). However, concomitant perfusion of activated platelets from transplant patients impaired acetylcholine-mediated, endothelium-dependent vasodilation but perfusion of normal platelets did not. Although cyclosporine-exposed platelets showed an impaired ability to produce vasorelaxation, supernatant from the same platelets caused near normal vasodilation. Human platelets exposed to cyclosporine have an impaired ability to mediated vasodilation. This is not due to increased platelet-mediated vasoconstriction or a decrease in the release of platelet-derived nucleotides but rather to a short-acting compound released by cyclosporine-exposed platelets that interferes with endothelium-dependent vasodilation.

Vascular remodelling in intramyocardial resistance vessels in hypertensive human cardiac transplant recipients

OBJECTIVE

Cardiac transplant recipients often develop hypertension as a side effect of immunosuppressive treatment. The aim of this study was to use the serial endomyocardial biopsies taken to monitor rejection to study the early and sequential arterial changes in human myocardial resistance arteries as hypertension develops.

METHODS

At least 14 biopsies were studied from each of 23 patients, divided into a normotensive group (12 patients with a diastolic pressure never greater than 90 mm Hg) and a hypertensive group (11 patients with more than 10% of diastolic pressure measurements above 100 mm Hg). Morphometric analysis of between 30 and 50 arteries and arterioles in two widely separated histological levels from each biopsy was undertaken using an Optomax image analyser.

RESULTS

There was a correlation between blood pressure, particularly diastolic pressure, and rate of medial thickening of intramyocardial coronary resistance arteries and arterioles (P = 0.0025). There was also a correlation between serum cyclosporin A concentrations and mean artery wall thickness (P = 0.003).

CONCLUSIONS

Hypertension and cyclosporin A treatment are associated with significant wall thickening of intramyocardial resistance vessels in cardiac allograft recipients. These changes may be functionally and clinically important.

Reduced coronary flow reserve during exercise in cardiac transplant recipients

BACKGROUND

Coronary flow reserve (CFR) is reduced in a majority of patients after heart transplantation (HTx). Pharmacological interventions, however, provide only limited information on CFR under physiological conditions. Thus, CFR during exercise was evaluated in the present study.

METHODS AND RESULTS

Coronary angiography was performed at rest and during supine bicycle exercise in 35 patients early (2 to 3 months; n = 10) or late (1 to 6 years; mean, 2.5 years; n = 25) after HTx and in 8 controls (C). CFR was determined by parametric imaging after administration of 10 mg intracoronary papaverine, during exercise, and after 1.6 mg sublingual nitroglycerin. Epicardial coronary artery size was measured by quantitative coronary angiography. CFR after papaverine was normal early (3.6 +/- 0.5 versus C, 3.6 +/- 0.7; P = NS) and late (3.8 +/- 1.3 P = NS) after HTx. During exercise, CFR was normal early (3.1 +/- 0.6 versus C, 3.9 +/- 0.9; P = NS) but decreased late (2.3 +/- 0.6; P < .01) after HTx. The increase in coronary cross-sectional area during exercise was also diminished late after HTx (14 +/- 10% versus C, 22 +/- 10%; P < .05). Both exercise-induced CFR (r = -.39, P < .05) and coronary vasodilation (r = -.44, P < .01) were inversely correlated with time after HTx.

CONCLUSIONS

CFR during exercise is normal early but reduced late after HTx, whereas CFR after papaverine administration is maintained. This difference between physiological and pharmacological vasodilation suggests progressive endothelial dysfunction after HTx.

Cyclosporine A-induced contractions and prostacyclin release are maintained by extracellular calcium in rat aortic rings: role of protein kinase C

Chronic treatment with the immunosuppressive drug, Cyclosporine A (CsA), is associated with increased intracellular calcium in vascular smooth muscle cells, which may cause vasoconstriction and/or activate phospholipase A2. We used rat aortic rings to investigate the role of protein kinase C (PKC) in CsA-induced contractions and secondary prostacyclin (PGI2) release. CsA (10(-9) M) produced a sustained contraction in rat aortic rings. Both CsA-induced contractions and PGI2 release were inhibited 84 to 89% by 10(-9) M, and 99 to 100% by 10(-6) M pretreatment doses of any of three different PKC inhibitors, i.e. 1-(5-isoquinolinesulfonylmethyl) piperazine (H7), staurosporine or 1-(5-isoquinolinesulfonyl) piperazine. Pretreatment with (10(-9) M) of diltiazem (a voltage-sensitive L-type calcium channel blocker) completely inhibited both CsA-induced contractions and PGI2 release. Conversely, pretreatment with (10(-9) M) of thapsigargin (an intracellular calcium channel blocker) did not alter the action of CsA. These results strongly suggest that PKC, in association with an influx of extracellular calcium mediates CsA-induced contractions and secondary PGI2 release in rat aortic rings.

Chronic treatment with cyclosporine A in New Zealand rabbit: aortic and erectile tissue alterations

Transplanted patients frequently present erectile impotence. In order to test any interference by cyclosporine A (CsA), which is commonly used in the post-transplantation management, we investigated the in vitro contractile and relaxant responses of corpus cavernosum and aorta from rabbits chronically treated with CsA. Male New Zealand White rabbits 6 months of age were treated with CsA (25 mg/kg per day s.c.) or solvent (corn oil) for 3 weeks. Descending thoracic aorta and erectile tissue were studied in vitro at the end of treatment. Isometric tension was recorded. In thoracic aorta, noradrenaline (0.1-30 mM) induced a concentration-dependent contraction with no difference between the two groups. Acetylcholine (30 nM-3 mM) produced relaxation (52 +/- 4% at 1 mM) that was significantly reduced in comparison to controls (67 +/- 4%, P < 0.05). ATP (3-10 mM) relaxation was not significantly different (maximal 78 +/- 10% and 62 +/- 12% in CsA-treated and controls). The relaxation produced by sodium nitrite was reduced in CsA-treated rabbits (at 10 mM and 0.1 mM concentrations). In erectile tissue, no significant variation in the response of isolated erectile tissue to the above drugs was observed between CsA-treated and control animals. These data indicate that chronic treatment with CsA in rabbits, despite alteration of the in vitro response of thoracic aorta, does not directly influence the function of penile tissue with relaxants.

Effect of dietary supplementation with fish oil on cyclosporine A-induced vascular toxicity

We wished to determine whether dietary supplementation with fish oil prevents the vascular toxicity of cyclosporine (Cx). In a first set of experiments, we assessed the endothelial function of aortas isolated from rats supplemented for 6 weeks with fish oil (FO), administered by gavage, and providing 150 mg/kg/day of eicosapentaenoic acid and 100 mg/kg/day of docosahexaenoic acid. FO treatment altered neither acetylcholine- and histamine-induced relaxations, nor serotonin-induced contractions (NS vs. control group). Thereafter, three groups of rats were treated in parallel. Group 1 received FO supplementation (by gavage) for 6 weeks, and Cx (10 mg/kg/day po) was added during the last 2 weeks, group 2 received Cx only (10 mg/kg/day po) for 2 weeks, and group 3 served as a control. Both acetylcholine-and histamine-induced relaxations were reduced in group 2 compared with the control group, as indicated by the area under the curve (AUC), which was significantly higher: 296 +/- 17 vs. 138 +/- 32, and 392 +/- 38 vs. 318 +/- 25 for acetylcholine and histamine, respectively. In group 1, AUC for acetylcholine remained significantly different from the control (241 +/- 31 vs. 138 +/- 32), whereas AUC for histamine was 367 +/- 28 (NS vs. control). The serotonin-induced contractions were also enhanced in group 2 compared with those of the control group, and this alteration was not attenuated in group 1. After mechanical removal of the endothelium, the increased responsiveness to serotonin persisted in groups 1 and 2, suggesting this functional alteration to be located in the smooth muscle cells. Thus, in the rat the attenuation of Cx-induced vascular toxicity by fish oil supplementation is only partial, that is, it involves a slight improvement in endothelial function, but with persistence of functional changes in smooth muscle.

Effect of cyclosporin A and analogues on cytosolic calcium and vasoconstriction: possible lack of relationship to immunosuppressive activity

1. The full therapeutic potential of the main immunosuppressive drug, cyclosporin A (CsA), is limited because of its side effects, namely nephrotoxicity and hypertension. Several lines of evidence suggest that the origin of both side effects could be CsA-induced vasoconstriction. However, the underlying molecular mechanisms are not well understood. 2. Diameter measurements of rat isolated mesenteric arteries showed an increase in noradrenaline- and [Arg]8vasopressin-induced vasoconstriction when arteries were pretreated with CsA. 3. Measurements in cultured vascular smooth muscle cells (VSMC) of either cytosolic calcium concentration or of 45Ca2+ efflux showed that CsA potentiated the calcium influx to several vasoconstrictor hormones: [Arg]8vasopressin, angiotensin II, endothelin-1 and 5-hydroxytryptamine. On the other hand, 45Ca2+ efflux in response to thapsigargin, which depletes calcium from intracellular pools, was not potentiated by CsA. 45Ca2+ uptake was not altered by CsA or by any of the analogues tested. 4. Time-course studies in cultured VSMC showed that maximal CsA-induced Ca2+ potentiation occurred after ca. 20 h and this effect was reversed over approximately the next 20 h. 5. To investigate the possible role played by the known intracellular targets of CsA, namely cyclophilin and calcineurin, CsA derivatives with variable potencies with respect to their immunosuppressive activity, were tested on the calcium influx to [Arg]8vasopressin. Derivatives devoid of immunosuppressive activity (cyclosporin H, PSC-833) potentiated calcium signalling, while the potent immunosuppressant, FK520, a close derivative of FK506, and MeVal4CsA, an antagonist of the immunosuppressive effect of CsA did not. The latter compound was unable to reverse the calcium potentiating effect of CsA. 6. Our results show that CsA increases the calcium influx to vasoconstrictor hormones in smooth muscle cells, which presumably increases vasoconstriction. Loading of the intracellular calcium pools appears not to be involved. Experiments with derivatives of CsA and FK520 suggest that interactions with cyclophilins and calcineurin are not the mechanism involved. This indicates, for the first time, that the immunosuppressive activity can be dissociated from the calcium potentiating effect of CsA in vascular smooth muscle.

Coronary vasomotor responses in cyclosporine-treated piglets

Chronic treatment with cyclosporine A (Cx) seems to produce a decreased ability of the endothelium to secrete nitric oxide. However, its effect on the coronary arterial system remains controversial. Therefore, coronary arteries isolated from piglets treated by intramuscular injections of Cx (10 mg/kg/day, IM, for 22 days) were studied in organ baths and compared with those isolated from control animals (IM injections of the Cx solvent). Depolarization-induced contractions (KCl 120 mM) were similar in both groups, whereas the acetylcholine-induced contractions (percent of 120 mM KCl) were enhanced: The area under the curve (AUC) was 245 +/- 51 in the Cx group versus 110 +/- 15 in the control group (p < 0.05). Removal of the endothelium did not significantly modify the acetylcholine-induced contractions in both groups and, therefore, did not attenuate the enhanced responsiveness to acetylcholine in the Cx group. On unrubbed rings contracted with prostaglandin F2 alpha, the endothelium-dependent relaxations from serotonin (in the presence of 1 microM ketanserin) were reduced: The AUC was 479 +/- 24 in the Cx group versus 385 +/- 22 in the control group (p < 0.02). Larger AUC values were also found for bradykinin and substance P in the Cx group: 158 +/- 18 versus 55 +/- 17 (in the control group, p < 0.01) and 198 +/- 8 versus 145 +/- 12 (p < 0.01), respectively. Nevertheless, no alteration in calcium ionophore-induced relaxations was observed: The AUC was 217 +/- 10 in the Cx group and 224 +/- 18 in the control group (NS). Indomethacin incubation (10 microM) did not prevent the impairment in endothelium-dependent relaxations and did not attenuate the cyclosporine-induced augmentation of acetylcholine-induced contractions. Thus, chronic administration of cyclosporine to piglets impairs the coronary endothelial function and produces functional changes in smooth muscle cells. These alterations may play a role in the occurrence of cardiac graft vasculopathy.

Effect of cyclosporin A on isolated rabbit bladder and urethral smooth muscle

BACKGROUND

The effects of Cyclosporin A (CsA) on vascular smooth muscle inducing hypertension have been established. However, there is no information available concerning the effects of CsA on urinary smooth muscle. Therefore, the effects of CsA were investigated on the bladder and urethral smooth muscle in rabbits.

METHODS

CsA (10 mg/kg/day, intravenously) was given to rabbits for 14 days. Rabbit bladder and urethral smooth muscles were then isolated and evaluated using a muscle bath technique.

RESULTS

10(-10)-5 x 10(-6)M CsA alone had no direct effect on bladder or urethral smooth muscles. The Emax (maximum contractile response) and ED50 values for acetylcholine-induced contractions and the Emax (maximum relaxation response) for isoproterenol-induced relaxation in bladder smooth muscles were not significantly different between CsA-treated and control groups. The ED50 for isoproterenol-induced relaxation was significantly lower in the CsA group (P < 0.05). The Emax for phenylephrine- and clonidine-induced contractions in urethral smooth muscle was significantly higher in the CsA-treated group (P < 0.05). The ratio of the maximum response of the urethral smooth muscle to phenylephrine and clonidine in Ca+2-free solution to the normal solution in the CsA group (13.42% and 4.40%, respectively) was significantly higher than the maximal response ratios in the control group (6.34% and 3.00%, respectively; P < 0.05).

CONCLUSIONS

CsA treatment augments the relaxation response of the bladder to isoproterenol and the contractile response of the urethra to phenylephrine and clonidine. In addition, CsA increases the filling of intracellular stores of releasable Ca+2, and also increases the permeability of Ca+2 in rabbit urethral smooth muscle. Thus, it is suggested that CsA may cause a urinary disturbance in patients treated with CsA via increased urethral resistance.

Regional differences in vasculotoxic effects of cyclosporin in rats

Studies on cyclosporin-induced vasculotoxicity often yielded discrepant results, possibly as a result of differences in study protocols. The aim of the present study was to analyse cyclosporin-induced vasculotoxicity in arteries of different size and origin. Therefore, rats were treated with cyclosporin, 20 mg.kg-1.day-1, by gastric gavage for 10 days. In our previous studies, this treatment schedule induced renal functional impairment in vivo and an impaired relaxation response of thoracic aortic rings in vitro. Relaxation of various arteries (thoracic and abdominal aorta and carotid, renal, and interlobar arteries) from cyclosporin-treated and control rats in response to endothelium-dependent and -independent vasodilators was analysed. The thoracic aorta showed diminished endothelium-dependent and -independent relaxations; in the abdominal aorta no impairment was observed. Moreover, the dysfunction of the thoracic aorta seemed to be homogeneous along its length and showed an abrupt termination at the level of the diaphragm. In all other segments studied, no impairment of the relaxation responses was found. A similar pattern of vascular damage was found in rats treated with a very toxic cyclosporin treatment (50 mg.Kg-1.day-1 s.c. x 7 days). The results indicate regional differences in cyclosporin-induced vasculotoxicity. The thoracic aorta, and in view of the fall of the renal blood flow, most likely also the renal resistance vessels, could be more susceptible than other vessels to cyclosporin-induced vascular dysfunction.

Selective downregulation of rat cardiac beta 1-adrenoceptors by cyclosporine A: prevention by diltiazem or angiotensin-converting enzyme inhibitors

OBJECTIVES

This study attempted to determine whether long-term treatment with cyclosporine A in rats affects cardiac beta 1-adrenoceptors and whether this can be prevented by angiotensin-converting enzyme inhibitors or calcium-entry blocking agents.

BACKGROUND

In the transplanted human heart the density of beta 1-adrenoceptors decreases with time after transplantation, whereas that of beta 2-adrenoceptors does not. Because heart transplant recipients are treated with cyclosporine A, we studied whether administration of cyclosporine A in rats might cause this beta 1-adrenoceptor downregulation.

METHODS

We performed two studies. First, we treated groups of 10 male normotensive Wistar rats orally with 30 mg/kg body weight per day of cyclosporine A, 10 mg/kg per day of enalapril and 60 mg/kg per day of diltiazem, alone or in combination, for 6 weeks each. Second, we treated groups of 15 male normotensive Wistar rats orally with 15 mg/kg per day of cyclosporine A and 10 mg/kg per day of lisinopril, alone or in combination, for 6 weeks each. At the end of each treatment regimen, cardiac beta-adrenoceptor density and subtype distribution were assessed by (-)-[125I]iodocyanopindolol binding.

RESULTS

Both doses of cyclosporine A caused a significant decrease in cardiac beta 1-adrenoceptor density without affecting beta 2-adrenoceptor density. Although diltiazem and the angiotensin-converting enzyme inhibitors alone did not affect cardiac beta-adrenoceptors, they prevented the cyclosporine A-induced downregulation of beta 1-adrenoceptors.

CONCLUSIONS

In normotensive Wistar rats, cyclosporine A causes a significant decrease in cardiac beta 1-adrenoceptors without affecting beta 2-adrenoceptors. This can be prevented by diltiazem or angiotensin-converting enzyme inhibitors. In heart transplant recipients, who undergo long-term treatment with cyclosporine A, there is a very similar beta 1-adrenoceptor down-regulation with time after transplantation. Thus, administration of cyclosporine A may cause these beta-adrenoceptor subtype alterations.

Prevention of glomerulosclerosis by early cyclosporine treatment of experimental lupus nephritis

The influence of cyclosporine A (CsA) treatment on the development of glomerulonephritis and glomerulosclerosis was investigated in chronic graft-versus-host disease (GvHD), a murine model for lupus nephritis. The renal disease is characterized by the formation of IgG-containing electron-dense deposits along the glomerular basement membrane (GBM) and in the mesangium, followed by the onset of proteinuria which starts, varying per individual mouse, about six weeks after the induction of the disease. Glomerular mRNA levels for matrix molecules were increased from week 4, preceding mesangial matrix expansion and GBM thickening which occurred from week 6. These initial events finally led to development of glomerulosclerosis, and end-stage renal failure. Groups of mice received three intraperitoneal (i.p.) injections per week with different doses of CsA, and treatment was started 2, 4, or 6 weeks after induction of the disease. Treatment with 10 or 50 mg CsA/kg/week did not influence the development of glomerulonephritis or glomerulosclerosis. Injection of 100 mg CsA/kg/week delayed the onset of proteinuria only when treatment was started in week 2. In week 6 some mice had already developed proteinuria whereas others had not. Treatment with 250 mg CsA/kg/week starting in week 6 abrogated glomerulonephritis and glomerulosclerosis only in those animals which were not yet proteinuric at that time. This, despite comparable increased autoantibody levels against DNA, GBM, and renal tubular epithelium (RTE) in both treated and untreated GvHD mice. Further increase in proteinuria and development of glomerulosclerosis could not be prevented if the mice already had developed proteinuria when CsA treatment was started. Dot blot analysis and in situ hybridization showed significantly decreased mRNA levels for alpha 1(I) and alpha 1(IV) collagen in kidneys of CsA-treated mice as compared to those of untreated mice 12 weeks after induction of the disease, if the highest dose of CsA was administered before the onset of proteinuria. No effect on these whole-kidney mRNA levels was observed in mice which had already developed proteinuria before CsA injections were started. Increased mRNA expression for matrix molecules in this group and in untreated GvHD mice was observed mainly in the interstitium. The kidneys of the treated GvHD mice and those of mice injected with 250 mg CsA/kg/week without induction of GvHD showed no morphological signs of CsA nephrotoxicity. We conclude that treatment with 250 mg CsA/kg/week prevents the development of glomerulonephritis and glomerulosclerosis in this model of lupus nephritis, if started before the onset of proteinuria.(ABSTRACT TRUNCATED AT 400 WORDS)

Vasomotor responses in cyclosporin A-treated rats after chronic angiotensin blockade

Chronic angiotensin-converting enzyme (ACE) inhibition prevents endothelial dysfunction in hypertension and hypercholesterolemia. Long-term treatment with cyclosporin A impairs endothelium-dependent relaxations and augments contractions to angiotensin II in the rat aorta. The present study compares vasomotor responses to several vasoconstrictor and dilator stimuli after 6 weeks of oral treatment with either the angiotensin-converting enzyme inhibitor lisinopril (10 mg/kg per day), the angiotensin subtype 1 receptor antagonist D 8731 (10 mg/kg per day), cyclosporin A (15 mg/kg per day), or a combination of cyclosporin A with lisinopril or D 8731 (n = 15 rats per group). Twenty-four hours after the last treatment, aortic rings were mounted in organ chambers for measurement of isometric force. Endothelium-dependent relaxations to acetylcholine and calcium ionophore were impaired by cyclosporin A but not affected by the vasodilators. Cyclosporin A-induced endothelial dysfunction was prevented by cotreatment with lisinopril or D 8731. Relaxations to nitroglycerin, SIN-1, and forskolin were not affected by any treatment. Contractions to phenylephrine and serotonin were reduced by lisinopril but not by D 8731. In contrast, contractions to angiotensin II were augmented by cyclosporin A, lisinopril, and the combination of both but not by D 8731 or D 8731 plus cyclosporin A. The data suggest a role for angiotensin II in cyclosporin A-induced endothelial dysfunction. Chronic ACE inhibition reduces overall smooth muscle contractility. The selective augmentation of angiotensin II effects by ACE inhibition and cyclosporin A suggests upregulation of angiotensin receptors in the aortic smooth muscle by these treatments. Chronic angiotensin subtype 1 receptor blockade does not appear to affect angiotensin receptor function.

Cyclosporine produces endothelial dysfunction by increased production of superoxide

Vasoconstriction and hypertension are major side effects of cyclosporine therapy. The mechanism or mechanisms responsible for the vascular effects of cyclosporine are unclear. The vascular effects of cyclosporine may arise as a consequence of endothelial dysfunction induced by the agent. To test this possibility, we compared in vessels prepared in myographs endothelium-mediated relaxations of mesenteric resistance arteries of Wistar-Kyoto rats treated for 21 to 28 days with subcutaneous injections of cyclosporine (25 mg/kg per day), or vehicle. Endothelium-dependent relaxations in response to acetylcholine were impaired in arteries from cyclosporine-treated rats; the concentrations of acetylcholine required to produce 50% relaxation of norepinephrine activation (pD2) were 31.6 +/- 0.1 versus 5 +/- 0.1 nmol/L in control arteries (P < .05). Nitro-L-arginine produced comparable 10-fold decreases in sensitivity to acetylcholine in arteries from both rat groups, indicating that the relaxations were mediated by endothelium-derived nitric oxide. Acetylcholine-induced relaxations in cyclosporine-treated arteries were normalized by pretreatment of the arteries with superoxide dismutase (150 IU/mL; pD2, 3.6 +/- 0.1; P < .05); superoxide dismutase had no effect on relaxations in control arteries. SQ 29,548, an inhibitor of prostaglandin H2/thromboxane A2 receptors; H-7, an inhibitor of protein kinase C; and indomethacin did not alter relaxations in response to acetylcholine in either group of arteries. Cyclosporine-treated arteries were more sensitive than control arteries to nitroprusside, an agent that induces relaxation via nitric oxide (pD2, 1.3 and 6.2 mumol/L, respectively; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Preventive effects of diltiazem on cyclosporin A-induced vascular smooth muscle dysfunction

Cyclosporin A may cause vascular smooth muscle dysfunction due to calcium overload as a consequence of chronically augmented calcium influx. In the present study, the responsiveness to vasocontrictors was investigated in rats after chronic treatment for 6 weeks with placebo, cyclosporin A (30 mg/kg per day), diltiazem (60 mg/kg per day), or cyclosporin A plus diltiazem. Twenty-four hours after the last oral treatment the animals were sacrificed and rings of the thoracic aorta were suspended in organ chambers under isometric conditions in the absence of cyclosporin A or diltiazem. Chronic treatment with cyclosporin A significantly augmented contractions to angiotensin II (10(-9)-10(-5) M). This effect was prevented by cotreatment with diltiazem. Diltiazem did not affect the cyclosporin A-induced reduction in the response to potassium chloride (10-80 mM). The contractions to phenylephrine (10(-9)-10(-6) M) and endothelin-1 (10(-9)-10(-7) M) were not significantly different in the four groups. The preventive effect of diltiazem against the cyclosporin A-induced hypersensitivity to angiotensin II supports the hypothesis of increased calcium influx during cyclosporin A therapy. The results may provide an additional rationale for the use of calcium antagonists in the treatment of the vascular side effects of cyclosporin A.