Platelet activation is increased in cyclosporin A-induced hypertensive rats

Drug- not carrier-dependent haematological and biochemical changes in a repeated dose study of cyclosporine encapsulated polyester nano- and micro-particles: size does not matter

Biodegradable nanoparticles are being considered more often as drug carriers to address pharmacokinetic/pharmacodynamic issues, yet nano-product safety has not been systematically proven. In this study, haematological, biochemical and histological parameters were examined on 28 day daily dosing of rats with nano- or micro-particle encapsulated cyclosporine (CsA) to confirm if any changes observed were drug or carrier dependent. CsA encapsulated poly(lactide-co-glycolide) [PLGA] nano- (nCsA) and micro-particles (mCsA) were prepared by emulsion techniques. CsA (15, 30, 45 mg/kg) were administered by oral gavage to Sprague Dawley (SD) rats over 28 days. Haematological and biochemical metrics were followed with tissue histology performed on sacrifice. Whether presented as nCsA or mCsA, 45 mg/kg dose caused significant loss of body weight and lowered food consumption compared to untreated control. Across the doses, both nCsA and mCsA produce significant decreases in lymphocyte numbers compared to controls, commensurate with the proprietary product, Neoral(®) 15. Dosing with nCsA showed higher serum drug levels than mCsA presumably owing to the smaller particle size facilitating absorption. The treatment had no noticeable effects on inflammatory/oxidative stress markers or antioxidant enzyme levels, except an increase in ceruloplasmin (CP) levels for high dose nCsA/mCsA group. Further, only subtle, sub-lethal changes were observed in histology of nCsA/mCsA treated rat organs. Blank (drug-free) particles did not induce changes in the parameters studied. Therefore, it is extremely important that the encapsulated drug in the nano-products is considered when safety of the overall product is assessed rather than relying on just the particle size. This study has addressed some concerns surrounding particulate drug delivery, demonstrating safe delivery of CsA whilst achieving augmented serum concentrations.

Serum and renal tissue markers of nephropathy in rats under immunosuppressive therapy: cyclosporine versus sirolimus

Cyclosporin (CsA) has been progressively replaced by other drugs with putatively fever side effects, including nephrotoxicity and hypertension. Sirolimus (SRL) is one of the main options for management of kidney transplant patients in the post-CsA era. It shows identical efficacy with apparently less cardiorenal side effects than CsA. However, doubts remain concerning the mechanisms of putative renoprotection by SRL as well as the best serum and/or tissue markers for nephropathy, as assessed in this study employing CsA- and SRL-treated rats. Three groups (n = 6) were treated orally during a 6-week protocol: control (vehicle); CsA (5 mg/kg body weight per day Sandimmun Neoral); SRL (1 mg/kg body weight per day Rapamune). Blood pressure and heart rate were assessed with a "tail cuff". Renal dysfunction and morphology were characterized using serum creatinine and blood urea nitrogen (BUN) levels as well as hematoxylin and eosin and periodic acid Schiff staining, respectively. We examined serum concentrations of interleukin (IL)-2, IL-1β, high-sensitivity C-reactive protein, tumor necrosis factor TNF-α, and vascular endothelial growth factor and kidney mRNA expression of interleukin-1β (IL-1β), tumor protein 53 (TP53), mammalian target of rapamycin (mTOR) and proliferating cell nuclear antigen (PCNA), as well as markers of lipid peroxidation in the kidney and serum. Both CsA and SRL induced significant increases in systolic and diastolic blood pressure, but only CsA caused tachycardia. CsA-treated rats also displayed increased serum creatinine and BUN levels, accompanied by mild renal lesions, which were almost absent among SRL-treated rats, which presented hyperlipidemic and hyperglycemic profiles. CsA-induced nephrotoxicity was accompanied by kidney overexpression of inflammatory and proliferative mRNA markers (IL-1β, mTOR and PCNA), which were absent among SRL group. In conclusion, the antiproliferative and antifibrotic character of SRL may explain its less nephrotoxic profile. Renal over expression of mTOR in the CsA-treated group, associated with renal dysfunction and structural damage, reinforces the potential beneft of SRL as a strategy to reduce CsA-evoked nephrotoxicity.

Dual effect of nitrate therapy for cyclosporine-induced hypertension on vascular and platelet morphofunctional markers; an animal model

The present study sought to evaluate the prevention and reversion effects of isosorbide-5-mononitrate (Is-5-Mn) on the development of hypertension (HT) and on the underlying vascular and platelet morphofunctional disturbances, using an animal model of cyclosporine (CsA)-induced HT. The following rat groups (n = 8) were tested: (1) a control group (orange juice, for 7 weeks); (2) the CsA group (5 mg/kg/d for 7 weeks); (3) the Is-5-Mn group (150 mg/kg/d, twice a day for 7 weeks); (4) the prevention group (Is-5-Mn + CsA) treated for 2 weeks with Is-5-Mn only and thereafter with both drugs for 7 weeks; (5) the curative group (CsA + Is-5-Mn) beginning 7 weeks after CsA and following thereafter with both drugs for 5 weeks. Blood pressure, lipid profile, vascular lesion, platelet aggregation and morphology, and platelet thromboxane A(2)/vascular prostacyclin equilibrium were evaluated. Is-5-Mn + CsA therapy prevented (systolic blood pressure [SBP]: 114.3 +/- 1.9 mm Hg, P < .001; diastolic blood pressure [DBP]: 97.0 +/- 3.3 mm Hg, P < .001) the CsA-induced HT (SBP: 146.2 +/- 4.5 mm Hg, P < .001; DBP: 124.9 +/- 4.5 mm Hg, P < .001 vs control: SBP: 111.6 +/- 0.7 mm Hg; DBP: 94.6 +/- 1.0 mm Hg), as well as the vascular lesion and the platelet morphofunctional disturbances. The curative group did not show attenuated CsA-induced BP increase; it showed further enhancement of the HT effect (SBP: 159.7 +/- 5.5 mm Hg, P < .05; DBP: 132.8 +/- 2.8 mm Hg), as well as worsened vascular lesions and platelet function, namely a disruption in the TXA(2)/PGI(2) equilibrium. Our data suggested that Is-5-Mn therapy may be a valid choice to prevent the morphofunctional changes associated with CsA-induced HT, when used as a preventive therapy. A careful evaluation of the impact of nitrate therapy should be considered, particularly the negative effect on cardiovascular hemodynamics, when considering its use after previous CsA disturbances have been established.

Plasma serotonin levels and the platelet serotonin transporter

Serotonin (5HT) is a platelet-stored vasoconstrictor. Altered concentrations of circulating 5HT are implicated in several pathologic conditions, including hypertension. The actions of 5HT are mediated by different types of receptors and terminated by a single 5HT transporter (SERT). Therefore, SERT is a major mechanism that regulates plasma 5HT levels to prevent vasoconstriction and thereby secure a stable blood flow. In this study, the response of platelet SERT to the plasma 5HT levels was examined within two models: (i) in subjects with chronic hypertension or normotension; (ii) on platelets isolated from normotensive subjects and pretreated with 5HT at various concentrations. The platelet 5HT uptake rates were lower during hypertension due to a decrease in Vmax with a similar Km; also, the decrease in Vmax was primarily due to a decrease in the density of SERT on the platelet membrane, with no change in whole cell expression. Additionally, while the platelet 5HT content decreased 33%, the plasma 5HT content increased 33%. Furthermore, exogenous 5HT altered the 5HT uptake rates by changing the density of SERT molecules on the plasma membrane in a biphasic manner. Therefore, we hypothesize that in a hypertensive state, the elevated plasma 5HT levels induces a loss in 5HT uptake function in platelets via a decrease in the density of SERT molecules on the plasma membrane. Through the feedback effect of this proposed mechanism, plasma 5HT controls its own concentration levels by modulating the uptake properties of platelet SERT.

Curative isosorbide-5-mononitrate treatment, in opposition to the beneficial preventive one, aggravates the prothrombotic and proconstrictor state in cyclosporine-induced hypertensive rats

1. The aim of the present study was to evaluate the effect of preventive and curative isosorbide-5-mononitrate (Is-5-Mn) treatment on the development of hypertension, cGMP content, thromboxane (TX) A(2)/prostaglandin (PG) I2 balance, the peripheral serotonergic system, platelet activation, lipid peroxidation and plasma lipids in cyclosporine A (CsA)-induced hypertensive rats. 2. Control, CsA (5 mg/kg per day) and Is-5-Mn (150 mg/kg per day, b.i.d.) rat groups were treated orally over a period of 7 weeks. The preventive Is-5-Mn group (Is-5-Mn + CsA) was first treated for 2 weeks with Is-5-Mn, followed by 7 weeks with both drugs; the curative Is-5-Mn group (CsA + Is-5-Mn) was treated for a period of 7 weeks with CsA and with both drugs for an additional 5 weeks. The control group received oral vehicle. 3. Whereas in the group undergoing preventive treatment the CsA-induced increase in blood pressure (BP), compared with the control group, was avoided, in the group undergoing curative treatment, the increase in BP was even higher. The decreased arterial cGMP content in the CsA group was prevented and reverted when Is-Mn was administered either preventatively or curatively with CsA. Platelet TXA2 production, although unaffected in the Is-5-Mn + CsA group, was significantly higher in the CsA + Is-5-Mn group compared with the group receiving CsA alone. Furthermore, plasma TXA2 was reduced following preventive Is-5-Mn treatment, but was worsened in the group undergoing curative therapy. Aortic PGI2 synthesis was identical in all groups. Consequently, the TXA2/PGI2 ratio was only altered in the CsA + Is-5-Mn group, demonstrating a markedly higher value. In both groups treated simultaneously with CsA and Is-5-Mn, a higher platelet 5-hydroxytryptamine (5-HT) content was obtained compared with CsA treatment alone, but only preventive treatment with Is-5-Mn resulted in a significant reduction in plasma 5-HT. Changes in ADP and collagen-induced platelet aggregation paralleled those of plasma 5-HT and TXA2: the hyperaggregation profile of the CsA group, although partially prevented, was not reverted by simultaneous treatment with Is-5-Mn and CsA. Lipid peroxidation and lipid profile values also worsened in the CsA + Is-5-Mn group compared with the group administered CsA alone. 4. In conclusion, the beneficial effects of concomitant Is-5-Mn and CsA treatment were demonstrated when Is-5-Mn was administered preventatively because not only was arterial hypertension prevented, but platelet aggregation and plasma TXA2 and 5-HT levels were also reduced. In contrast, following curative treatment, the BP, platelet/vascular vasoconstrictor balance, lipid peroxidation and plasma lipids were aggravated, recommending a judicious evaluation of the impact of nitrate therapy throughout the period of its administration.

Morphological and functional differences in haemostatic axis between kidney transplanted and end-stage renal disease patients

End-stage renal disease (ESRD) is characterized by several atherothrombotic abnormalities, and kidney transplant seems to improve most of them. However, because it is not clear which mechanism is responsible for such improvement, our purpose was to clarify that point.We conducted a cross sectional study involving 30 ESRD patients, 30 ESRD kidney-transplanted patients (Ktx) and 30 healthy controls (C) to evaluate platelet morphology and function, atherothrombotic profile, endothelial abnormalities and cytokine levels involved in the insulin resistance/endothelial dysfunction. (i) Platelet morphology: The ESRD group showed platelet size similar to the other two groups (ESRD=3518x10(3)+/-549x10(3) nm2, C=3075x10(3)+/-197x10(3) nm2, Ktx=2862x10(3)+/-205x10(3) nm2) with similar platelet granules and number. (ii) Platelet surface glycoprotein: The CD41 and P-Selectin were similar between groups. (iii) Platelet intracellular calcium: Resting intracellular calcium was statistically higher in ESRD compared to the C group (ESRD=182.1+/-34.5, Ktx=126.7+/-14.1, C=72.0+/-11.0 nM, P<0.01). (iv) Hypercoagulability markers and natural anticoagulants: The Ktx and ESRD groups showed higher levels of hypercoagulability markers compared to the C group. A reduction in antithrombin activity was evident in ESRD compared to the Ktx group (P=0.03). (v) Endothelial morphology: The ESRD group showed a thickened vessel basal membrane compared to the Ktx and C groups with more endothelial sufference. (vi) Insulin resistance and pro-inflammatory cytokine profile: The ESRD showed a higher homeostasis model assessment provided equations for estimating insulin resistance (HOMA-IR) compared to the Ktx and C groups (ESRD=2.6+/-0.3, Ktx=1.8+/-0.2, C=1.1+/-0.1, P=0.005) and increased soluble tumor neurosis factor alpha (sTNFalpha) (P<0.05) and soluble vascular cell adhesion molecule (sVCAM) levels (P<0.01). Positive correlations were evident among HOMA-IR and sTNFalpha (P<0.001) and sVCAM (P=0.01), respectively. In a small subgroup of ESRD who underwent Ktx (five pts), our findings were confirmed at 1 year of follow-up, suggesting an improvement of almost haemostatic abnormalities. Kidney transplant is associated with a better atherothrombotic profile in ESRD, platelet intracellular calcium and cytokines seem to be most influenced by the transplant, while most morphological abnormalities are retained.

Cyclosporin A does not affect platelets in children with idiopathic nephrotic syndrome

The immunosuppressive agents administered to maintain the remission of idiopathic nephrotic syndrome (INS) may have a deleterious effect on several cell types. The aim of this study was to analyze platelet activation and reactivity in children with INS treated with cyclosporin A (CyA). The study groups comprised 16 children with remission of INS induced by CyA and 16 children with glucocorticosteroid-induced remission 8 weeks from the onset of INS relapse. Fifteen healthy children served as controls. Surface expression of CD61, CD62P, and CD42b on resting and thrombin-stimulated platelets was analyzed with flow cytometry. No differences between groups were found in CD61, CD62P, and CD42b surface expression, but markers of the coagulation cascade and fibrinolysis or endothelial injury (F1+2 prothrombin fragments, tissue plasminogen activator inhibitor 1) were elevated in patients treated with CyA compared with children on steroids and healthy controls. No correlations between markers of platelet function and CyA concentration were found. We postulate that CyA administration in nephrotic patients causes an activation of thrombinogenesis but does not influence platelet activation and reactivity in INS.

Isosorbide-5-mononitrate treatment prevents cyclosporin A-induced platelet hyperactivation and the underlying nitric oxide-cyclic guanosine-3',5'-monophosphate disturbances

INTRODUCTION

The clinical use of cyclosporin A (CsA) is commonly associated with the development of hypertension and increased risk of thromboembolic events. Decreased endothelium-dependent relaxation and increased platelet activation seems to be involved on those side effects, but the underlying mechanisms are not yet elucidated. The present study aimed to evaluate the CsA effect on the platelet NO-cyclic guanosine-3',5'-monophosphate (cGMP) pathway and the putative benefits of concomitant isosorbide-5-mononitrate (IS-5-MN) administration on CsA-induced hypertension and on platelet hyperactivation.

MATERIALS AND METHODS

Blood pressures, platelet NO synthase activity and cGMP content, intracellular free calcium concentration ([Ca2+]i) and whole blood platelet aggregation were assessed in three rat groups orally treated, during 7 weeks, with the following diets: orange juice (control group), 5 mg/kg/day of CsA (CsA group) and 150 mg/kg/day, b.i.d., of IS-5-MN for 2 weeks and IS-5-MN plus 5 mg/kg/day of CsA for 7 weeks (IS-5-MN+CsA group).

RESULTS

IS-5-MN treatment has prevented hypertension development obtained in the solely CsA-treated rats. CsA treatment has inhibited NOS activity, which was reverted by the concomitant IS-5-MN and CsA administration. On the contrary, platelets from CsA-treated rats had cGMP content increased when compared with the control rats. The variation obtained when ISMN was present was less predominant. Therefore, the organic nitrate treatment has prevented platelet hyperactivation, namely, by decreasing thrombin-evoked [Ca2+]i and collagen-evoked platelet aggregation, when compared with the solely CsA-treated group. The preventive effect of IS-5-MN was reinforced by electron microscopy studies of platelet activation.

CONCLUSIONS

By increasing [Ca2+]i and aggregation, CsA induces platelet hyperactivation and simultaneously increases cGMP content, which might represent a compensatory inhibitory mechanism. The concomitant IS-5-MN treatment prevents the above-mentioned platelet hyperreactivity and tends to normalize the NO-cGMP pathway as well as the development of hypertension.

Impairment of vascular and platelet levels of nitric oxide and cyclic guanosine-3',5'-monophosphate in cyclosporin A-induced hypertensive rats

The therapeutic use of the immunosuppressive agent cyclosporin A (CsA) is associated with arterial hypertension and increased risk of thromboembolism. Impaired endothelium-mediated relaxation is one of the main hypotheses explaining the CsA-induced vascular hyper-reactivity. Since nitric oxide (NO) modulates both vascular and platelet activity, we studied the effects of CsA on the levels of arterial and platelet NO as well as 3',5'-cyclic guanosine monophosphate (cGMP) levels which are influenced by NO. An animal model of CsA-induced hypertension was used. Wistar rats were treated with a clinically relevant, oral dose of 5 mg/kg CsA, daily, for 4 weeks. CsA increased both systolic and diastolic blood pressures compared to non-treated rats (P < 0.01). Nitrite, a NO metabolite, decreased in the entire aorta wall (30%, P < 0.05) and in the aorta wall without the endothelial layer (70 %, P < 0.05) in CsA-treated vs. control groups. cGMP content was also decreased in the CsA-treated group (67%, P < 0.01) vs. control. Taken together, these results suggest a defect on the endothelial NO generation, acceleration of breakdown and/or consumption of NO, as well as marked alterations directly on cGMP metabolism. Conversely, platelet nitrite and cGMP content significantly increased in the CsA-treated rats, which was also observed in in vitro studies of platelet nitrite release following CsA treatment. This suggests a platelet self-regulation mechanism against CsA-induced platelet hyper-reactivity, which, in turn, could compensate vascular impairment.

Enhancement by cyclosporine A and tacrolimus of serotonin-induced formation of small platelet aggregation

Cyclosporine A (CsA) may increase the incidence of thrombotic events, but whether tacrolimus (Tc) has such effects is still unclear. The serotonergic system has been linked to the thrombotic effects of CsA, but a direct effect of CsA on serotonin-induced platelet aggregation has not been demonstrated because of methodological difficulties. We measured the effects of CsA and Tc on serotonin-induced platelet aggregate formation by particle counting using light scattering. CsA and Tc both enhanced serotonin-induced formation of small platelet aggregates, however, neither CsA nor Tc affected aggregation induced by high or low concentrations of ADP, with or without addition of a serotonin receptor antagonist. Both CsA and Tc enhance platelet aggregation induced via the serotonin pathway.