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Depressed renal and vascular nitric oxide synthase expression in cyclosporine-induced hypertension
1Department of Medicine, University of California, Irvine, USA. tabotten@uci.edu
Insights
Cyclosporine (CsA) treatment increases blood pressure by reducing nitric oxide (NO) production, specifically impairing inducible NO synthase (iNOS) in kidneys and blood vessels. This suggests NO restoration could mitigate CsA-induced hypertension.
Area of Science:
- Nephrology
- Pharmacology
- Cardiovascular Science
Background:
- Cyclosporine (CsA) improves organ transplant outcomes but can cause nephrotoxicity and hypertension (HTN).
- The link between CsA-induced HTN and nitric oxide (NO) production remains unclear.
Purpose of the Study:
- To investigate the hypothesis that CsA-induced hypertension is associated with reduced nitric oxide (NO) production.
Main Methods:
- Assessed urinary nitric oxide metabolites (NOx) and NO synthase (NOS) protein/mRNA expression in rat kidneys and aortas.
- Measured aorta inducible NO synthase (iNOS) activity in CsA-treated and placebo groups.
Main Results:
- CsA significantly increased blood pressure and decreased urinary NOx excretion.
- A significant reduction in kidney and aorta iNOS protein and mRNA was observed in CsA-treated rats.
- Endothelial NO synthase (eNOS) protein levels remained unchanged.
Conclusions:
- CsA treatment for three weeks leads to hypertension and reduced NO production, linked to decreased iNOS expression.
- Impaired NO production may contribute to CsA-induced hypertension.
- Strategies to enhance NO availability could potentially mitigate CsA-associated vascular complications.
Background:
Introduction of cyclosporine (CsA) for clinical use has greatly enhanced the outcome of organ transplantation. However, CsA can cause nephrotoxicity and hypertension (HTN). This study was designed to test the hypothesis that CsA-induced HTN is related to depressed nitric oxide (NO) production.
Methods:
Urinary excretion of NO metabolites (NOx) and endothelial and inducible NO synthase (eNOS and iNOS) proteins were determined in thoracic aortas and kidneys of CsA-treated (given CsA 18 mg/kg/day for 3 weeks) and placebo-treated rats. In addition, renal tissue eNOS and iNOS mRNA and aorta iNOS activity were measured.
Results:
CsA administration resulted ina significant rise in arterial blood pressure (BP) coupled with a steady decline in urinary NOx excretion, suggesting depressed NO production. This was accompanied by a significant reduction in iNOS protein abundance in the kidney and thoracic aorta but no change in eNOS protein abundance. The fall in renal iNOS protein in CsA-treated rats was accompanied by a parallel decline in iNOS mRNA abundance and enzymatic activity.
Conclusion:
Administration of CsA for three weeks resulted in a significant rise in BP together with marked reductions in urinary NOx excretion, and renal and vascular iNOS expression. These observations suggest that CsA-induced HTN may be, in part, related to impaired NO production. If true, strategies designed to restore NO availability may mitigate HTN and other vascular complications of CsA therapy.