Selective impairment of endothelium-mediated vasodilation in liver transplant recipients with cyclosporin A-induced hypertension

Vascular resistance and endothelial function in cyclosporine-treated lung transplant recipients

The majority of patients undergoing solid organ transplantation develop hypertension, to which vasoconstriction and impaired endothelial function have been suggested to contribute. We compared basal vascular resistance and nitric oxide-mediated endothelial-dependent and independent vasoreactivity between cyclosporine-treated lung transplant recipients and healthy subjects. Forearm blood flow was measured by venous occlusion plethysmography at rest and during acetylcholine, glyceryltrinitrate and N(G)-monomethyl-L-arginine acetate (L-NMMA) infusion in 11 lung transplant recipients 3-5 years after transplantation and in eight healthy subjects. Forearm vascular resistance (FVR) was calculated. Plasma levels of endothelin-1 (ET-1) and von Willebrand factor (vWf) were analysed. Basal vascular resistance was 40% lower in transplant recipients than in healthy subjects (P = 0.021). Endothelial-dependent and independent vasodilation did not differ. Plasma levels of ET-1 and vWf were higher in transplant recipients (P = 0.009 and P < 0.001 respectively). There was a significant correlation between ET-1 levels and FVR in healthy subjects (r = 0.83, P = 0.042), but not in transplant recipients (r = -0.14, P = 0.70). The findings oppose the theory of generalized vasoconstriction and impaired endothelial function in the pathogenesis of hypertension after transplantation. Increased plasma levels of ET-1 do not cause increased FVR in lung transplant recipients.

Plasma total homocysteine and cardiovascular risk in patients submitted to liver transplantation

Patients submitted to orthotopic liver transplantation (OLT) show an increased rate of cardiovascular events. OLT subjects have high homocysteine (Hcy) levels, but no data are available on the association of Hcy with cardiovascular events. In a cross-sectional analysis, 230 subjects were studied at least 6 months after OLT (159 on cyclosporine, 71 on tacrolimus). Routine laboratory data and total Hcy were recorded, as well as the history of diabetes, hypertension, dyslipidemia, and overweight. Cardiovascular events occurring in a follow-up of 2-36 months were registered. OLT subjects had higher-than-normal Hcy (median 16.7 micromol/L, range 6.1-171.8) without difference between the 2 immunosuppressive agents. The prevalence of Hcy >15 micromol/L was also similar, and significantly correlated with creatinine levels. A total of 28 arterial events occurred in 25 patients during follow-up (11 in coronary arteries, 10 in peripheral arteries, and 7 in splanchnic arteries). Deep vein thromboses occurred in 2 patients, and splanchnic vein thromboses in 4 patients. Cardiovascular events were frequently associated to high Hcy and hypertension. Cox regression analysis showed that high Hcy was significantly associated with arterial events. The risk of any arterial event, coronary artery or peripheral artery event increased by nearly 10% for any increase in Hcy of 5 micromol/L. In conclusion, high Hcy may be involved in the pathogenesis of cardiovascular events in OLT patients. The usefulness of Hcy-lowering therapy remains to be verified.

Beneficial effects of converting liver transplant recipients from cyclosporine to tacrolimus on blood pressure, serum lipids, and weight

Hypertension and hyperlipidemia are more prevalent after liver transplantation with cyclosporine as the primary immunosuppressive agent compared with tacrolimus. To determine whether blood pressure, serum lipid level, or weight improves when patients switch immunosuppression therapy, we retrospectively studied 26 liver transplant recipients with stable graft function who had been converted from cyclosporine to tacrolimus therapy with a median follow-up of 8 months. One of the 26 patients developed pruritus necessitating withdrawal of tacrolimus. The results therefore concern the remaining 25 patients. With the exception of a small decrease in bilirubin level (P <.05), there was no difference in graft or renal function after conversion. Mean systolic blood pressure decreased from 158 +/- 25 to 148 +/- 22 mm Hg over a mean of 8 +/- 3 months after conversion to tacrolimus (P =.015), whereas mean serum cholesterol level decreased from 5.3 +/- 0.9 to 4.9 +/- 0.9 mmol/L (P =.01). Sixty-eight percent of the patients lost weight, from a mean of 79.4 +/- 22.6 to 76.1 +/- 20.1 kg, in the 11 months after switching to tacrolimus therapy (P =.024). Serum triglyceride and blood glucose levels did not change, and no patient developed diabetes mellitus after conversion. These results indicate that switching from cyclosporine to tacrolimus can reduce blood pressure, serum cholesterol level, and weight after liver transplantation.

Weight gain and cardiovascular risk after organ transplantation

Organ transplantation has become a common and effective approach to the management of patients with organ failure. The improvement in long-term survival has resulted in the emergence of cardiovascular disease as the primary cause of death in renal transplant patients and a significant complication in other organ recipients. A number of factors explain this trend, including a high incidence of hypertension, posttransplant diabetes, hyperlipidemia, and obesity-risk factors that are mediated by direct effects of immunosuppressive medications. Weight gain posttransplant affects approximately 50% of patients and represents a significant problem because of the potential synergism between obesity and immunosuppressive medication-induced effects on cardiovascular disease risk factor development. This review discusses the incidence and implications of cardiovascular disease risk factors in organ transplant recipients, strategies for clinical management, and future research directions.

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.