Geraniol suppresses tumour growth and enhances chemosensitivity of 5-fluorouracil on breast carcinoma in mice: involvement of miR-21/PTEN signalling.

OBJECTIVES: Breast cancer is the most diagnosed cancer in females worldwide. Phytochemicals are among the recent compelling approaches showing anticancer activity. Geraniol is a monoterpenoid showing anti-tumoral potential in cell lines. However, its exact mechanism in breast cancer has not been elucidated. In addition, the possible chemosenstizing effect of geraniol when combined with chemotherapeutic drugs in breast carcinoma has not been previously addressed. METHODS: Therefore, the aim of the current work is to investigate the potential therapeutic as well as chemosensitizing effects of geraniol on breast carcinoma induced in mice through examination of tumour biomarkers and histopathology profile. KEY FINDINGS: Results showed a prominent suppression of tumour growth following geraniol treatment. This was accompanied with miR-21 downregulation that subsequently upregulated PTEN and suppressed mTOR levels. Geraniol was also able to activate apoptosis and inhibit autophagy. Histopathological examination revealed high necrosis areas separating malignant cells in the geraniol-treated group. Combined geraniol and 5-fluorouracil treatment induced more than 82% inhibition of tumour rate, surpassing the effect of each drug alone. CONCLUSIONS: It can be concluded that geraniol could represent a promising avenue for breast cancer treatment as well as a potential sensitizing agent when combined with chemotherapeutic drugs.

A novel investigation of statins myotoxic mechanism: effect of atorvastatin on respiratory muscles in hypoxic environment.

Myopathy is a well-known adverse effect of statins, affecting a large sector of statins users. The reported experimental data emphasized on mechanistic study of statin myopathy on large muscles. Clinically, both large muscles and respiratory muscles are reported to be involved in the myotoxic profile of statins. However, the experimental data investigating the myopathic mechanism on respiratory muscles are still lacking. The present work aimed to study the effect of atorvastatin treatment on respiratory muscles using rat isolated hemidiaphragm in normoxic & hypoxic conditions. The contractile activity of isolated hemidiaphragm in rats treated with atorvastatin for 21 days was investigated using nerve stimulated technique. Muscle twitches, train of four and tetanic stimulation was measured in normoxic, hypoxic and reoxygenation conditions. Atorvastatin significantly increased the tetanic fade, a measure of muscle fatigability, in hypoxic conditions. Upon reoxygenation, rat hemidiaphragm regains its normal contractile profile. Co-treatment with coenzyme Q10 showed significant improvement in defective diaphragmatic contractility in hypoxic conditions. This work showed that atorvastatin treatment rapidly deteriorates diaphragmatic activity in low oxygen environment. The mitochondrial respiratory dysfunction is probably the mechanism behind such finding. This was supported by the improvement of muscle contractile activity following CoQ10 co-treatment.

Neuronal Voltage Gated Potassium Channels May Modulate Nitric Oxide Synthesis in Corpus Cavernosum.

Potassium channels (K+Ch) in corpus cavernosum play an important role in the regulation of erection. Nitric oxide (NO) acts through opening of K+Ch leading to hyperpolarization and relaxation. Aim : This study aims to update knowledge about the role of voltage-gated K+Ch (KV) channels in erectile machinery and investigate their role in the control of NO action &/or synthesis in the corpus cavernosum. Methods : Tension studies using isolated rabbit corpus cavernosum (CC) strips and rat anococcygeus muscle were conducted. Results are expressed as mean ± SEM. Results : Electric field stimulation (EFS, 2-16 Hz) evoked frequency-dependent relaxations of the PE (phenylephrine)-precontracted CC strips. At 2 Hz, EFS-induced relaxation amounted to 73.17 ± 2.55% in presence 4-AP (10-3 M) compared to 41.98 ± 1.45% as control. None of the other selective K+Ch blockers tested inhibited EFS-induced relaxation. 4-AP (10-3M) significantly attenuated ACh-induced relaxation of rabbit CC where dose-response curve was clearly shifted upward, and attenuated SNP- induced relaxation, for example, to 49.28 ± 4.52% compared to 65.53 ± 3.01% as control at 10-6 M SNP. The potentiatory effect of 4-AP on EFS was abolished or reversed in presence of N G -nitro-L-arginine (L-NNA, non-selective nitric oxide synthase inhibitor, 10-5M, and 2 × 10-4M). Same results were observed in rat anococcygeus muscle which is a part of the erectile machinery in rats. Conclusion : This study provides evidence for the presence of prejunctional voltage-gated K+Ch in CC, the blockade of which may increase the neuronal synthesis of NO.

Rosuvastatin safety: An experimental study of myotoxic effects and mitochondrial alterations in rats.

Myopathy is the most commonly reported adverse effect of statins. All statins are associated with myopathy, though with different rates. Rosuvastatin is a potent statin reported to induce myopathy comparable to earlier statins. However, in clinical practice most patients could tolerate rosuvastatin over other statins. This study aimed to evaluate the myopathic pattern of rosuvastatin in rats using biochemical, functional and histopathological examinations. The possible deleterious effects of rosuvastatin on muscle mitochondria were also examined. The obtained results were compared to myopathy induced by atorvastatin in equimolar dose. Results showed that rosuvastatin induced a rise in CK, a slight increase in myoglobin level together with mild muscle necrosis. Motor activity, assessed by rotarod, showed that rosuvastatin decreased rats' performance. All these manifestations were obviously mild compared to the prominent effects of atorvastatin. Parallel results were obtained in mitochondrial dysfunction parameters. Rosuvastatin only induced a slight increase in LDH and a minor decrease in ATP (∼14%) and pAkt (∼12%). On the other hand, atorvastatin induced an increase in LDH, lactate/pyruvate ratio and a pronounced decline in ATP (∼80%) and pAkt (∼65%). These findings showed that rosuvastatin was associated with mild myotoxic effects in rats, especially when compared to atorvastatin.

Elucidation of the mechanism of atorvastatin-induced myopathy in a rat model.

Myopathy is among the well documented and the most disturbing adverse effects of statins. The underlying mechanism is still unknown. Mitochondrial dysfunction related to coenzyme Q10 decline is one of the proposed theories. The present study aimed to investigate the mechanism of atorvastatin-induced myopathy in rats. In addition, the mechanism of the coenzyme Q10 protection was investigated with special focus of mitochondrial alterations. Sprague-Dawely rats were treated orally either with atorvastatin (100mg/kg) or atorvastatin and coenzyme Q10 (100mg/kg). Myopathy was assessed by measuring serum creatine kinase (CK) and myoglobin levels together with examination of necrosis in type IIB fiber muscles. Mitochondrial dysfunction was evaluated by measuring muscle lactate/pyruvate ratio, ATP level, pAkt as well as mitochondrial ultrastructure examination. Atorvastatin treatment resulted in a rise in both CK (2X) and myoglobin (6X) level with graded degrees of muscle necrosis. Biochemical determinations showed prominent increase in lactate/pyruvate ratio and a decline in both ATP (>80%) and pAkt (>50%) levels. Ultrastructure examination showed mitochondrial swelling with disrupted organelle membrane. Co-treatment with coenzyme Q10 induced reduction in muscle necrosis as well as in CK and myoglobin levels. In addition, coenzyme Q10 improved all mitochondrial dysfunction parameters including mitochondrial swelling and disruption. These results presented a model for atorvastatin-induced myopathy in rats and proved that mitochondrial dysfunction is the main contributor in statin-myopathy pathophysiology.

Modulation of dopamine-mediated facilitation at the neuromuscular junction of Wistar rats: A role for adenosine A1/A2A receptors and P2 purinoceptors.

This study aims to understand how dopamine and the neuromodulators, adenosine and adenosine triphosphate (ATP) modulate neuromuscular transmission. Adenosine and ATP are well-recognized for their regulatory effects on dopamine in the central nervous system. However, if similar interactions occur at the neuromuscular junction is unknown. We hypothesize that the activation of adenosine A1/A2A and/or P2 purinoceptors may influence the action of dopamine on neuromuscular transmission. Using the rat phrenic nerve hemi-diaphragm, we assessed the influence of dopamine, adenosine and ATP on the height of nerve-evoked muscle twitches. We investigated how the selective blockade of adenosine A1 receptors (2.5nM DPCPX), adenosine A2A receptors (50nM CSC) and P2 purinoceptors (100µM suramin) modified the effects of dopamine. Dopamine alone increased indirect muscle contractions while adenosine and ATP either enhanced or depressed nerve-evoked muscle twitches in a concentration-dependent manner. The facilitatory effects of 256µM dopamine were significantly reduced to 29.62±2.79% or 53.69±5.45% in the presence of DPCPX or CSC, respectively, relative to 70.03±1.57% with dopamine alone. Alternatively, the action of 256µM dopamine was potentiated from 70.03±1.57, in the absence of suramin, to 86.83±4.36%, in the presence of suramin. It can be concluded that the activation of adenosine A1 and A2A receptors and P2 purinoceptors potentially play a central role in the regulation of dopamine effects at the neuromuscular junction. Clinically this study offers new insights for the indirect manipulation of neuromuscular transmission for the treatment of disorders characterized by motor dysfunction.

Selective ET(A) receptor blockade protects against cisplatin-induced acute renal failure in male rats.

The present study aims to investigate the possibility that inhibiting the physiological function of endothelin-1 (ET-1) by blocking its receptors would significantly decrease the nephrotoxic effect of cisplatin. Therefore the study was designed to investigate the effect of treatment with BQ-123, the selective endothelin receptor-A (ET(A)) blocker, and bosentan, the non-selective endothelin receptor blocker, on the cisplatin-induced structural, functional, and biochemical alterations in the rat kidney. Rats were divided into four groups: control (given a single dose of normal saline, i.p.), cisplatin (given a single dose of cisplatin, 6mg/kg, i.p.), cisplatin+BQ-123 (1mg/kg, i.p.), and cisplatin+bosentan (30mg/kg, orally via gavage). Each of the two blockers was administered in two doses; 1h before and one day after the cisplatin dose. Acute cisplatin administration resulted in significant increases in blood urea nitrogen and serum creatinine concentrations at 96h following cisplatin injection. Increased concentrations of malondialdehyde, tumor necrosis factor-α (TNF-α) and caspase-3, decreased nitric oxide (NO) production and superoxide dismutase (SOD) activity in kidney homogenates were observed at 96h following cisplatin injection, in addition to a typical 'acute tubular necrosis' pattern. BQ-123 ameliorated the structural and functional injuries caused by cisplatin mainly via restoring SOD activity, in addition to other antioxidant parameters, NO, TNF-α and caspase-3 concentrations. This study further proves that ET(A) but not ETB receptors are involved in cisplatin-induced nephrotoxicity. The selective ET(A) antagonist BQ-123 ameliorated the cisplatin-induced deleterious effects and showed reno-protective effect against cisplatin-induced acute renal damage.

Redox imbalances incite the hypertensive, baroreflex, and autonomic effects of cyclosporine in rats.

Previous studies including ours showed that cyclosporine (CSA) causes baroreflex dysfunction and hypertension. Here we tested the hypothesis that oxidative damage in central and peripheral tissues underlies the hypertensive, baroreflex and autonomic actions elicited by CSA in rats. We investigated the effects of individual and combined 7-day treatments with CSA (25 mg/kg/day, n=7) and 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol, superoxide dismutase mimetic, 100 mg/kg/day, n=7) on blood pressure, reflex heart rate responses to peripherally mediated pressor and depressor responses, and biomarkers of oxidative stress. CSA elevated blood pressure and reduced reflex bradycardic (phenylephrine) and tachycardic (sodium nitroptrusside) responses. The ability of muscarinic (atropine, 1 mg/kg i.v.) or ß-adrenoceptor blockade (propranolol, 1 mg/kg i.v.) to reduce reflex heart rate responses was reduced in CSA-treated rats, suggesting the impairment by CSA of reflex cardiac autonomic control. Concurrent administration of tempol abolished CSA-induced hypertension and normalized the associated impairment in baroreflex gain and cardiac autonomic control. Tempol also reversed the CSA-induced increases in aortic and brainstem nitrite/nitrate and malondialdehyde (MDA) and decreases in aortic superoxide dismutase (SOD). These findings implicate oxidative stress in peripheral and central cardiovascular sites in the deleterious actions of CSA on blood pressure and baroreceptor control of heart rate.

Adenosinergic modulation of the imidazoline I1-receptor-dependent hypotensive effect of ethanol in acute renal failure.

We reported that inhibition of central sympathetic pools of imidazoline I(1) receptors abolishes the hypotensive effect of ethanol in rats with glycerol-induced acute renal failure (ARF). This study investigated whether adenosine receptors modulate the ethanol-I(1)-receptor interaction. The effect of selective blockade of adenosine A(1), A(2A), or A(2B) receptors on hemodynamic responses to ethanol in the absence and presence of the I(1)-receptor agonist moxonidine was determined in ARF rats. Ethanol (1g/kg i.v.) decreased and increased blood pressure (BP) and heart rate (HR), respectively. Pretreatment with moxonidine abolished the hypotensive but not the tachycardic effect of ethanol. The hypotensive effect of ethanol remained unaltered after selective blockade of A(1), A(2A), or A(2B) receptors with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and 8-(3-chlorostyryl) caffeine (CSC) and alloxazine, respectively. Neither was ethanol hypotension affected after inhibition of adenosine uptake by dipyridamole (DPY). Alternatively, the ability of moxonidine to abolish ethanol hypotension was still evident in presence of alloxazine whereas it disappeared or weakened in rats pretreated with CSC and DPCPX, respectively. These findings implicate adenosine A(2A) receptors in the moxonidine-evoked inhibition of the hypotensive action of ethanol. A modulatory role for adenosine A(1) site in the ethanol-I(1)-receptor interaction is also possible through as yet unidentified mechanism.

Crosstalk between central pathways of nitric oxide and carbon monoxide in the hypertensive action of cyclosporine.

Although the intermediary role of central neurons in the hypertensive and sympathoexcitatory actions of cyclosporine (CSA) has been recognized in previous studies including our own, the underlying mechanism remains obscure. In this study, we tested the hypothesis that central pathways of nitric oxide (NO) and carbon monoxide (CO) modulate the blood pressure (BP) response elicited by CSA in conscious rats. Hemodynamic effects of CSA were evaluated in absence and presence of maneuvers that inhibit or facilitate biosynthesizing enzymes of NO (NOS) or CO (heme oxygenase, HO). CSA (20mg/kg i.v.) produced abrupt increases in BP that peaked in 5min and maintained for at least 45min. The hypertensive effect of CSA disappeared in rats pretreated intracisternally (i.c.) with N(ω)-nitro-l-arginine methyl ester (L-NAME, nonselective NOS inhibitor), N(5)-(1-iminoethyl)-l-ornithine (L-NIO, selective eNOS inhibitor), N(ω)-propyl-l-arginine (NPLA, selective nNOS inhibitor), or 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ, guanylate cyclase inhibitor), suggesting the importance of central eNOS/nNOS/GC cascade in CSA-induced hypertension. L-NAME also abolished the hypotension caused by the sympatholytic drug moxonidine, indicating a tonic sympathoinhibitory action for NO. The inhibition of HO activity by zinc protoporphyrin IX (ZnPP) abrogated the hypertensive action of CSA. The abolition by L-NAME or ZnPP of CSA hypertension was compromised upon simultaneous i.c. exposure to hemin (HO substrate) and l-arginine (NOS substrate), respectively. Together, the interruption of the mutually facilitated NOS/NO and HO/CO pathways and coupled GC/cGMP in central neuronal pools accounts, at least partly, for the hypertensive and perhaps sympathoexcitatory actions of CSA.

A novel COX-2 inhibitor pyrazole derivative proven effective as an anti-inflammatory and analgesic drug.

The introduction of new COX-2 inhibitors with high efficacy and enhanced safety profile would be a great achievement in the development of anti-inflammatory drugs. This study was designed to screen and assess the anti-inflammatory and analgesic activities as well as some of the expected side effects of some pyrazole derivatives, newly synthesized as potential COX-2 inhibitors at the Faculty of Pharmacy, Alexandria University and compared to indomethacin and celecoxib. Twelve compounds were screened for their anti-inflammatory activity using carrageenan-induced paw oedema and cotton pellet granuloma tests. On the basis of their apparent anti-inflammatory activity, four compounds with different substitutions were selected for the evaluation of their analgesic activity using the formalin-induced hyperalgesia and hot-plate tests. Compound AD 532, ((4-(3-(4-Methylphenyl)-4-cyano-1H-pyrazol-1-yl)benzenesulfonamide)), showed very promising results. In the single-dose and subchronic toxicity studies, compound AD 532 showed no ulcerogenic effect and produced minimal effects on renal function. Furthermore, compound AD 532 was a less potent inhibitor of COX-2 in vitro than celecoxib, which may indicate lower potential cardiovascular toxicity. It is concluded that compound AD 532 appears to be a promising and safe option for the management of chronic inflammatory conditions. This study recommends more in-depth investigation into the therapeutic effects and toxicity profile of this compound including its cardiovascular toxicity.

Facilitation of central imidazoline I(1)-site/extracellular signal-regulated kinase/p38 mitogen-activated protein kinase signalling mediates the hypotensive effect of ethanol in rats with acute renal failure.

BACKGROUND AND PURPOSE: This study investigated the role of central sympathetic activity and related mitogen-activated protein kinase (MAPK) signalling in the cardiovascular effects of ethanol in a model of acute renal failure (ARF). EXPERIMENTAL APPROACH: The effects of pharmacological interventions that inhibit peripheral or central sympathetic activity or MAPK on the cardiovascular actions of ethanol in rats with ARF induced by glycerol were evaluated. KEY RESULTS: Glycerol (50%, 10 mL.kg(-1), i.m.) caused progressive increases and decreases in blood pressure (BP) and heart rate (HR) respectively. Subsequent i.v. ethanol (0.25 or 1 g.kg(-1)) elicited dose-related changes in BP (decreases) and HR (increases). These effects were replicated after intracisternal (i.c.) administration of ethanol. Blockade of nicotinic cholinoceptors (nAChR, hexamethonium, 20 mg.kg(-1)) or alpha(1)-adrenoceptors (prazosin, 1 mg.kg(-1)) attenuated cardiovascular effects of ethanol. Ethanol hypotension was also attenuated after the centrally acting sympatholytic drug moxonidine (selective I(1)-site agonist, 100 microg.kg(-1) i.v.), but not guanabenz (selective alpha(2)-receptor agonist, 30 microg.kg(-1), i.v.), suggesting involvement of central circuits of I(1) sites in ethanol-evoked hypotension. Selective blockade I(1) sites (efaroxan) but not alpha(2) (yohimbine) adrenoceptors abolished the hypotensive response to ethanol. Intracisternal administration of PD98059 or SB203580, inhibitors of extracellular signal-regulated kinase (ERK 1/2) and p38 MAPK, respectively, reduced the hypotensive action of moxonidine or ethanol. When used simultaneously, the two MAPK inhibitors produced additive attenuation of ethanol hypotension. CONCLUSIONS AND IMPLICATIONS: Sympathoinhibitory pathways of central I(1)-sites and downstream ERK/p38 MAPK signalling were involved in the hypotensive action of ethanol in ARF.

Interruption of central neuronal pathway of imidazoline I1 receptor mediates the hypertensive effect of cyclosporine in rats.

Increased central sympathetic outflow secondary to afferent sympathetic excitation has been implicated in the hypertensive effect of the immunosuppressant drug cyclosporine (CSA). The present study investigated the roles of central alpha(2)-adrenoceptors and I(1)-imidazoline receptors in modulating the hypertensive action of CSA. The blood pressure (BP) response to CSA in conscious rats was assessed in the absence and presence of peripherally or centrally acting sympatholytic drugs. Also, the effect of selective pharmacologic blockade of alpha(2) or I(1) receptors by yohimbine and efaroxan, respectively, on the pressor response to CSA was evaluated. CSA (20 mg/kg i.v.) produced a rapid increase in BP that peaked (25+/-4 mm Hg) after approximately 4 min and continued for the 45 min study duration. Ganglionic (hexamethonium 20 mg/kg) or alpha(1)-adrenoceptor (prazosin 1 mg/kg) blockade reduced the pressor effect of CSA. Pressor responses to phenylephrine (alpha(1)-adrenoceptor agonist) were not affected by CSA, thereby eliminating a possible role for alterations of vascular alpha(1)-adrenoceptor responsiveness in CSA hypertension. CSA hypertension was attenuated in rats pretreated intravenously with drugs that reduce central sympathetic tone including clonidine (mixed alpha(2)/I(1)-receptor agonist, 30 microg/kg) or moxonidine (selective I(1)-receptor agonist, 100 microg/kg) in contrast to no effect for guanabenz (selective alpha(2)-receptor agonist, 30 microg/kg). Intracisternal (i.c.) administration of moxonidine also reduced CSA hypertension. Selective blockade of central I(1) (efaroxan, 0.15 microg/rat, i.c.) but not alpha(2) (yohimbine, 25 microg/5 microl/rat, i.c.) receptors abolished the hypertensive response to CSA. Together, these findings highlight that CSA elicits its hypertensive effect via disruption of central sympathoinhibitory pathways which include I(1)-imidazoline receptors.

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.

Relative roles of endothelial relaxing factors in cyclosporine-induced impairment of cholinergic and beta-adrenergic renal vasodilations.

Vascular toxicity is a major adverse effect for the immunosuppressant drug cyclosporine A. The present study sought to characterize the relative roles of the endothelium-derived relaxing factors (nitric oxide, endothelium-derived hyperpolarizing factor [EDHF], and prostaglandins) in the cyclosporine-induced impairment of renovascular responsiveness to acetylcholine receptor or beta-adrenoceptor activation. Changes evoked by cyclosporine in the responses to either vasorelaxant were evaluated in phenylephrine-preconstricted isolated perfused rat kidneys in the absence and presence of N(G)-nitro-l-arginine methyl ester (l-NAME, nitric oxide synthase inhibitor), tetraethylammonium (K(+) channel blocker), or diclophenac (cyclooxygenase inhibitor). Acetylcholine (0.03-2 nmol) vasodilations were significantly inhibited by prior treatment with l-NAME, tetraethylammonium, or diclophenac, suggesting a role for nitric oxide, EDHF, and prostaglandins in acetylcholine vasodilations. Isoprenaline (0.125-4 micromol) vasodilations were inhibited by l-NAME and tetraethylammonium versus no effect for diclophenac. Cyclosporine (1-4 microM) produced a concentration-related inhibition of vasodilations relaxations produced by either vasodilator. Cyclosporine-induced inhibition of acetylcholine vasodilations was attenuated in tissues pretreated with l-NAME or tetraethylammonium but not diclophenac, implicating nitric oxide and EDHF in cyclosporine-acetylcholine interaction. On the other hand, the inhibition of isoprenaline vasodilations by cyclosporine was virtually abolished by l-NAME. In cyclosporine-treated kidneys, exposure to l-arginine, the substrate of nitric oxide synthesis, fully restored isoprenaline vasodilations to control levels and significantly increased acetylcholine vasodilations. It is concluded that the identity and relative contributions of endothelial factors to renal vasodilatory responses as well as to the inhibition of these responses by cyclosporine largely depend on the vasodilator stimulus.

Testosterone depletion contributes to cyclosporine-induced chronic impairment of acetylcholine renovascular relaxations.

The immunosuppressant drug cyclosporine causes nephrotoxicity mainly via alterations of renovascular reactivity. This study investigated whether this effect of cyclosporine is modulated by the male gonadal hormone testosterone. The endothelium-dependent and -independent relaxations evoked by acetylcholine and sodium nitroprusside, respectively, were evaluated in phenylephrine-preconstricted isolated perfused kidneys obtained from sham-operated, castrated, and testosterone-replaced castrated (CAS+T) male rats in the absence and presence of cyclosporine. Compared with sham-operated values, short-term (10 days) castration or cyclosporine treatment caused significant and equivalent reductions in plasma testosterone levels and vasorelaxant responses to acetylcholine. Treatment of castrated rats with cyclosporine caused no further attenuation of acetylcholine relaxations. Testosterone replacement of castrated (CAS+T) or cyclosporine-treated castrated (CAS+CyA+T) rats restored plasma testosterone and acetylcholine relaxations to near-sham-operated levels. On the other hand, castration caused significant increases in nitroprusside relaxations versus no effect for cyclosporine. The relaxant responses to nitroprusside in castrated rats were restored to sham-operated levels after testosterone replacement. Plasma urea and creatinine were not affected by castration but were significantly increased by cyclosporine. These findings suggest that testosterone exerts directionally opposite modulatory effects on endothelium-dependent and -independent renal relaxations. Further, the results demonstrate that testosterone depletion may contribute, at least partly, to the inhibitory effect of cyclosporine on renovascular endothelial function. These data are clinically important because endothelial dysfunction contributes to vascular abnormalities associating cyclosporine therapy.