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

Enhanced lipoxygenase/LTD4 signaling accounts for the exaggerated hypertensive and nephrotoxic effects of cyclosporine plus indomethacin in rats

The combined use of cyclosporine (CSA) and nonsteroidal antiinflammatory drugs (NSAIDs) causes exaggerated rises in systolic blood pressure (SBP) and nephrotoxicity. We examined whether these influences relate to the arachidonate/5-lipoxygenase (LOX) pathway. Rats were treated with CSA (20 mg kg^-1 day^-1), indomethacin (5 mg kg^-1 day^-1), or their combination for 10 days. Changes in SBP and renal biochemical/histopathological characteristics along with leukotriene levels were determined in rats treated with or without LT receptor antagonists. CSA or indomethacin caused: (i) renal tubular atrophy and interstitial fibrosis, (ii) increases in serum creatinine, blood urea nitrogen (BUN), and renal LTD4, LTB4, TNF-α, TGF-β1, and caspase-3, and (iii) decreases in renal PGE2 and total antioxidant capacity (TAC). SBP measured by tail-cuff plethysmography was increased by CSA but not indomethacin. These effects were mostly intensified in rats treated with CSA plus indomethacin. The co-treatment with montelukast (cysteinyl LT receptor blocker), but not ONO-4057 (LTB4 receptor blocker), ameliorated CSA/indomethacin-evoked hypertension, renal structural/biochemical deterioration, and LTD4 levels. Moreover, montelukast exhibited a greater capacity in reversing inflammatory, oxidative, apoptotic, and fibrotic abnormalities induced by CSA/indomethacin. Overall, lipoxygenase/LTD4 upregulation contributes to the exaggerated hypertension and nephrotoxicity caused by CSA/indomethacin. The therapeutic potential of cysteinyl LT receptor antagonism in rectifying CSA/NSAIDs-evoked anomalies is warranted.

Celecoxib, but not indomethacin, ameliorates the hypertensive and perivascular fibrotic actions of cyclosporine in rats: role of endothelin signaling

The immunosuppressant drug cyclosporine (CSA) is used with nonsteroidal antiinflammatory drugs (NSAIDs) in arthritic conditions. In this study, we investigated whether NSAIDs modify the deleterious hypertensive action of CSA and the role of endothelin (ET) receptors in this interaction. Pharmacologic, protein expression, and histopathologic studies were performed in rats to investigate the roles of endothelin receptors (ETA/ETB) in the hemodynamic interaction between CSA and two NSAIDs, indomethacin and celecoxib. Tail-cuff plethysmography measurements showed that CSA (20 mg kg(-1) day(-1), 10 days) increased systolic blood pressure (SBP) and heart rate (HR). CSA hypertension was associated with renal perivascular fibrosis and divergent changes in immunohistochemical signals of renal arteriolar ETA (increases) and ETB (decreases) receptors. While these effects of CSA were preserved in rats treated concomitantly with indomethacin (5 mg kg(-1) day(-1)), celecoxib (10 mg kg(-1) day(-1)) abolished the pressor, tachycardic, and fibrotic effects of CSA and normalized the altered renal ETA/ETB receptor expressions. Selective blockade of ETA receptors by atrasentan (5 mg kg(-1) day(-1)) abolished the pressor response elicited by CSA or CSA plus indomethacin. Alternatively, BQ788 (ETB receptor blocker, 0.1 mg kg(-1) day(-1)) caused celecoxib-sensitive elevations in SBP and potentiated the pressor response evoked by CSA. Together, the improved renovascular fibrotic and endothelin receptor profile (ETA downregulation and ETB upregulation) mediate, at least partly, the protective effect of celecoxib against the hypertensive effect of CSA. Clinically, the use of celecoxib along with CSA in the management of arthritic conditions might provide hypertension-free regimen.

Vascular endothelial dysfunction in cyclosporine-treated rat aortas is not associated with serum total homocysteine levels

OBJECTIVES

Elevation of serum total homocysteine (tHcy) is considered to contribute to endothelial cell dysfunction, which is considered to be the initial event in posttransplant vascular disease. We sought to investigate whether an association existed between serum tHcy levels and vascular endothelial function during cyclosporine (CsA) treatment.

MATERIALS AND METHODS

Endothelium-dependent and -independent relaxation responses (to acetylcholine [ACh] and sodium nitroprusside [SNP]) were determined on thoracic aortae from CsA-treated rats (5 mg kg/d, subcutaneously, for 14 days). A correlation analysis was performed between ACh responses and tHcy levels.

RESULTS

CsA decreased the responses to ACh and the pD(2) values of the concentration-response curves compared with controls (P < .05). Responses to SNP and serum tHcy levels were unchanged among the groups. tHcy negatively correlated with the ACh pD(2) values among control (r = -0.69; P < .05) and vehicle (r = -0.73; P < .05) groups, indicating that the increase in tHcy was associated with decreased sensitivity to ACh. In CsA-treated rats, no association was observed between these parameters. Also, no correlation was noted between CsA concentrations and tHcy levels.

CONCLUSION

These data suggested a possible link between serum tHcy and decreased vascular sensitivity to endothelium-dependent vasorelaxation in control aortae, but CsA-induced vascular endothelial dysfunction was not associated with an effect of the drug on homocysteine metabolism.

The α1-adrenergic receptor not the DA1-dopaminergic receptor mediates cyclosporine–SKF38393 renovascular interaction

In this study, we investigated the effect of acute exposure to cyclosporine A (CyA) on renal vasodilations evoked by the DA1 dopaminergic agonist SKF38393 and whether dopamine DA1 receptors are directly involved in the interaction. Changes evoked by CyA in SKF38393 vasodilations were evaluated in phenylephrine-preconstricted isolated perfused rat kidneys in the absence and presence of SCH23390, a DA1 receptor antagonist. SKF38393 (3 × 10–8 to 3 × 10–6 mol) produced dose-dependent reductions in the renal perfusion pressure that were significantly attenuated in tissues pretreated with SCH23390 or CyA. Unlike SKF38393, the vasodilatory action of sodium nitroprusside, a nitrovasodilator, was not altered by CyA. The attenuating effect of CyA on SKF38393 vasodilations was preserved in preparations pretreated with SCH23390, suggesting that sites other than DA1 receptors may be involved in CyA–SKF38393 interaction. The study was then extended to investigate the possible involvement of renal α1-adrenoceptors in the interaction. Blockade of α1-adrenoceptors by prazosin (30 nmol/L) significantly reduced the vasodilatory effect of SKF38393 and virtually abolished the CyA-induced attenuation of SKF38393 responses. Further, CyA failed to alter SKF38393 vasodilations when the renal tone was raised with prostaglandin F2α (PGF2α), a vasoconstrictor whose effect is independent of α1-adenoceptors. Together, these findings support earlier reports that both DA1 and α1-receptors mediate the renal vasodilatory action of SKF38393 and suggest that CyA interacts selectively with the α1-receptor component to compromise SKF38393 responses.