Related Experiment Videos
Cyclosporin-induced endothelial dysfunction and hypertension: are nitric oxide system abnormality and oxidative
L Calò1, A Semplicini, P A Davis
1Department of Medical and Surgical Sciences, University of Padua, Italy. renzcalo@ux1.unipd.it
Insights
Cyclosporin (CsA) treatment upregulates the nitric oxide (NO) system in transplant patients, despite causing hypertension. This protective NO mechanism may be overwhelmed by CsA-induced oxidative stress, contributing to vasoconstriction and atherosclerosis.
Area of Science:
- Cardiovascular Pharmacology
- Transplantation Medicine
- Renal Physiology
Background:
- Cyclosporin (CsA) is a widely used immunosuppressant in organ transplantation.
- Hypertension is a significant and common side effect of CsA therapy.
- The precise mechanisms underlying CsA-induced hypertension, particularly involving endothelial function, remain incompletely understood.
Purpose of the Study:
- To investigate the status of the endothelial nitric oxide synthase (ecNOS) gene and plasma nitric oxide (NO) metabolites in transplant patients experiencing CsA-induced hypertension.
- To evaluate markers of oxidative stress, including hydroperoxides and peroxynitrite, in these patients.
- To elucidate the role of the NO system in the context of CsA-induced hypertension and potential counterregulatory mechanisms.
Main Methods:
- Polymerase Chain Reaction (PCR) analysis to assess ecNOS gene status.
- Enzyme-Linked Immunosorbent Assay (ELISA) to quantify plasma levels of NO metabolites.
- High-Performance Liquid Chromatography (HPLC) to measure plasma hydroperoxides and peroxynitrite as indicators of oxidative stress.
Main Results:
- Transplant patients on CsA with hypertension showed significant upregulation of the NO system, with increased ecNOS mRNA expression and higher plasma NO metabolite levels compared to controls.
- Elevated levels of cholesterol ester and triglyceride hydroperoxides, along with detectable peroxynitrite, were observed in CsA-treated patients, indicating increased oxidative stress.
- Despite NO system upregulation, the findings suggest a potential impairment of the NO-mediated vasodilation protective mechanism.
Conclusions:
- CsA treatment induces an upregulation of the NO system in transplant patients.
- However, CsA-induced production of superoxide and free radicals may counteract the beneficial effects of NO, contributing to vasoconstriction and hypertension.
- This imbalance may predispose patients to atherosclerosis and highlights the complex interplay between CsA, NO, and oxidative stress in cardiovascular complications.
Abstract:
Hypertension is a major side effect of cyclosporin (CsA). While the mechanism(s) responsible are unclear, CsA-induced endothelial dysfunction and CsA-induced hypertension have been attributed to the CsA effect on the endothelial-derived factors controlling vasomotor tone. Endothelial nitric oxide (NO) is crucial in the maintenance of a state of basal vasodilation, and recent studies have suggested an NO-mediated counterregulatory mechanism protective from CsA-induced vasoconstriction. Our study evaluates endothelial nitric oxide synthase (ecNOS) gene status (PCR analysis) and plasma levels of NO metabolites (ELISA) in kidney and heart transplant patients under chronic CsA treatment with CsA-induced hypertension. Since CsA increases superoxide production, which metabolises NO, plasma hydroperoxides from cholesterol esters and from triglycerides and peroxynitrite were also evaluated (HPLC) as an index of the presence of superoxides and of "oxidative stress". Quantification of monocyte ecNOS mRNA and NO metabolites plasma levels from patients and controls (C) demonstrated NO system upregulation in patients notwithstanding the hypertension. The mean ecNOS to beta-actin ratio was 1.80 +/- 0.85 in patients vs 0.40 +/- 0.09 in C (P < 0.04). NO metabolites were 34.03 +/- 14.32 microM in patients vs 11.53 +/- 5.64 microM in C (P < 0.001). Hydroperoxides from cholesterol esters and from triglycerides were also increased in patients, 3.4 +/- 1.4 vs 1.3 +/- 0.6 integrated area units (i. a. u.), P < 0.007 and 10.6 +/- 6.4 vs 1.3 +/- 0.8 i. a. u., P < 0.008, respectively, as well as the peroxynitrite plasma level, 0.32 +/- 0.11 microM/l vs undetectable in C. This study confirms a CsA-induced NO system upregulation in transplanted patients. However, the NO-mediated counterregulatory system to CsA-induced vasoconstriction, present in normals, could be canceled in patients by CsA-induced superoxide (O2-) and free radical production which, by increasing NO metabolism, could contribute to CsA-induced vasoconstriction and hypertension and predispose to atherosclerosis.