CsA-induced Hypertension Research Articles

Cyclosporin-induced hypertension is associated with the up-regulation of Na+-K+-2Cl- cotransporter (NKCC2).

The use of cyclosporin A (CsA) is hampered by the development of nephrotoxicity including hypertension, which is partially dependent on renal sodium retention. To address this issue, we have investigated in vivo sodium reabsorption in different nephron segments of CsA-treated rats through micropuncture study coupled to expression analyses of sodium transporters. To translate the findings in rats to human, kidney-transplanted patients having CsA treatment were enrolled in the study. Adult male Sprague-Dawley rats were treated with CsA (15 mg/kg/day) for 21days, followed by micropuncture study and expression analyses of sodium transporters. CsA-treated kidney-transplanted patients with resistant hypertension were challenged with 50mg furosemide. CsA-treated rats developed hypertension associated with reduced glomerular filtration rate. In vivo microperfusion study demonstrated a significant decrease in rate of absolute fluid reabsorption in the proximal tubule but enhanced sodium reabsorption in the thick ascending limb of Henle's loop (TAL). Expression analyses of sodium transporters at the same nephron segments further revealed a reduction in Na+-H+ exchanger isoform 3 (NHE3) in the renal cortex, while TAL-specific, furosemide-sensitive Na+-K+-2Cl- cotransporter (NKCC2) and NHE3 were significantly upregulated in the inner stripe of outer medulla. CsA-treated patients had a larger excretion of urinary NKCC2 protein at basal condition, and higher diuretic response to furosemide, showing increased FeNa+, FeCl- and FeCa2+ compared with both healthy controls and FK506-treated transplanted patients. Altogether, these findings suggest that up-regulation of NKCC2 along the TAL facilitates sodium retention and contributes to the development of CsA-induced hypertension.

NaHS or Lovastatin Attenuates Cyclosporine A-Induced Hypertension in Rats by Inhibiting Epithelial Sodium Channels.

The use of cyclosporine A (CsA) in transplant recipients is limited due to its side effects of causing severe hypertension. We have previously shown that CsA increases the activity of the epithelial sodium channel (ENaC) in cultured distal nephron cells. However, it remains unknown whether ENaC mediates CsA-induced hypertension and how we could prevent hypertension. Our data show that the open probability of ENaC in principal cells of split-open cortical collecting ducts was significantly increased after treatment of rats with CsA; the increase was attenuated by lovastatin. Moreover, CsA also elevated the levels of intracellular cholesterol (Cho), intracellular reactive oxygen species (ROS) via activation of NADPH oxidase p47phox, serum- and glucocorticoid-induced kinase isoform 1 (Sgk1), and phosphorylated neural precursor cell–expressed developmentally downregulated protein 4–2 (p-Nedd4-2) in the kidney cortex. Lovastatin also abolished CsA-induced elevation of α-, ß-, and γ-ENaC expressions. CsA elevated systolic blood pressure in rats; the elevation was completely reversed by lovastatin (an inhibitor of cholesterol synthesis), NaHS (a donor of H2S which ameliorated CsA-induced elevation of reactive oxygen species), or amiloride (a potent ENaC blocker). These results suggest that CsA elevates blood pressure by increasing ENaC activity via a signaling cascade associated with elevation of intracellular ROS, activation of Sgk1, and inactivation of Nedd4-2 in an intracellular cholesterol-dependent manner. Our data also show that NaHS ameliorates CsA-induced hypertension by inhibition of oxidative stress.

Lovastatin attenuates hypertension induced by renal tubule-specific knockout of ATP-binding cassette transporter A1, by inhibiting epithelial sodium channels.

We have shown that cholesterol is synthesized in the principal cells of renal cortical collecting ducts (CCD) and stimulates the epithelial sodium channels (ENaC). Here we have determined whether lovastatin, a cholesterol synthesis inhibitor, can antagonize the hypertension induced by activated ENaC, following deletion of the cholesterol transporter (ATP-binding cassette transporter A1; ABCA1). We selectively deleted ABCA1 in the principal cells of mouse CCD and used the cell-attached patch-clamp technique to record ENaC activity. Western blot and immunofluorescence staining were used to evaluate protein expression levels. Systolic BP was measured with the tail-cuff method. Specific deletion of ABCA1 elevated BP and ENaC single-channel activity in the principal cells of CCD in mice. These effects were antagonized by lovastatin. ABCA1 deletion elevated intracellular cholesterol levels, which was accompanied by elevated ROS, increased expression of serum/glucocorticoid regulated kinase 1 (Sgk1), phosphorylated neural precursor cell-expressed developmentally down-regulated protein 4-2 (Nedd4-2) and furin, along with shorten the primary cilium, and reduced ATP levels in urine. These data suggest that specific deletion of ABCA1 in principal cells increases BP by stimulating ENaC channels via a cholesterol-dependent pathway which induces several secondary responses associated with oxidative stress, activated Sgk1/Nedd4-2, increased furin expression, and reduced cilium-mediated release of ATP. As ABCA1 can be blocked by cyclosporine A, these results suggest further investigation of the possible use of statins to treat CsA-induced hypertension.

Intracellular cholesterol stimulates ENaC by interacting with phosphatidylinositol‑4,5‑bisphosphate and mediates cyclosporine A-induced hypertension

We have previously shown that blockade of ATP-binding cassette transporter A1 (ABCA1) with cyclosporine A (CsA) stimulates the epithelial sodium channel (ENaC) in cultured distal nephron cells. Here we show that CsA elevated systolic blood pressure in both wild-type and apolipoprotein E (ApoE) knockout (KO) mice to a similar level. The elevated systolic blood pressure was completely reversed by inhibition of cholesterol (Cho) synthesis with lovastatin. Inside-out patch-clamp data show that intracellular Cho stimulated ENaC in cultured distal nephron cells by interacting with phosphatidylinositol‑4,5‑bisphosphate (PIP2), an ENaC activator. Confocal microscopy data show that both α‑ENaC and PIP2 were localized in microvilli via a Cho-dependent mechanism. Deletion of membrane Cho reduced the levels of γ‑ENaC in the apical membrane. Reduced ABCA1 expression and elevated intracellular Cho were observed in old mice, compared to young mice. In parallel, cell-attached patch-clamp data from the split-open cortical collecting ducts (CCD) show that ENaC activity was significantly increased in old mice. These data suggest that elevation of intracellular Cho due to blockade of ABCA1 stimulates ENaC, which may contribute to CsA-induced hypertension. This study also implies that reduced ABCA1 expression may mediate age-related hypertension by increasing ENaC activity via elevation of intracellular Cho.

Cyclosporin A Induces Hypertension via a Cholesterol‐ and ENaC‐Dependent Mechanism

Hypertension related to the use of immunosuppressive drugs, particularly cyclosporin A (CsA), presents one of the major problems in the management of transplant recipients. Our recent studies suggest a hypothesis that CsA may cause hypertension by stimulating the renal epithelial sodium channel (ENaC) via a pathway associated with elevated intracellular cholesterol (Cho). To further determine the mechanism, we performed confocal microscopy and patch‐clamp experiments using cultured cortical collecting duct (CCD) principal cells and measured the blood pressure in mice. Confocal data show that CsA and Cho increased both the length of microvilli of CCD cells where ENaC is located and the levels of phosphatidylinositol‐4,5‐bisphosphate (PIP2) in microvilli. Conversely, inhibition of Cho synthesis with lovastatin decreased the levels of PIP2, a well‐known ENaC activator. Patch‐clamp data shows that Cho increased ENaC activity in a PIP2‐dependent manner. Interestingly, CsA elevated the blood pressure in mice and the elevation was abolished by either inhibition of Cho synthesis with lovastatin or blockade of ENaC with amiloride. These results suggest that CsA increases the blood pressure of mice by stimulating ENaC via a pathway associated with the elevation of intracellular Cho and PIP2 in the principal cells of CCD. However, it remains to be determined whether statins or amiloride can be used for the treatment of CsA‐induced hypertension.Support or Funding Information(Supported by NIH R01DK100582 to H.M.)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Myeloid-Derived Suppressor Cells Ameliorate Cyclosporine A-Induced Hypertension in Mice.

The calcineurin inhibitor cyclosporine A (CsA) suppresses the immune system but promotes hypertension, vascular dysfunction, and renal damage. CsA decreases regulatory T cells and this contributes to the development of hypertension. However, CsA's effects on another important regulatory immune cell subset, myeloid-derived suppressor cells (MDSCs), is unknown. We hypothesized that augmenting MDSCs would ameliorate the CsA-induced hypertension and vascular and renal injury and dysfunction and that CsA reduces MDSCs in mice. Daily interleukin-33 treatment, which increased MDSC levels, completely prevented CsA-induced hypertension and vascular and renal toxicity. Adoptive transfer of MDSCs from control mice into CsA-treated mice after hypertension was established dose-dependently reduced blood pressure and vascular and glomerular injury. CsA treatment of aortas and kidneys isolated from control mice for 24 hours decreased relaxation responses and increased inflammation, respectively, and these effects were prevented by the presence of MDSCs. MDSCs also prevented the CsA-induced increase in fibronectin in microvascular and glomerular endothelial cells. Last, CsA dose-dependently reduced the number of MDSCs by inhibiting calcineurin and preventing cell proliferation, as other direct calcineurin signaling pathway inhibitors had the same dose-dependent effect. These data suggest that augmenting MDSCs can reduce the cardiovascular and renal toxicity and hypertension caused by CsA.

Nebivolol suppresses asymmetric dimethylarginine and attenuates cyclosporine-induced nephrotoxicity and endothelial dysfunction in rats.

Cyclosporine A (CsA)-induced nephrotoxicity is a challenging problem complicating its chronic use in a large array of autoimmune diseases, as well as in organ transplantation. A considerable body of evidence points to the involvement of nitric oxide (NO) and its endogenous synthesis inhibitor, asymmetric dimethylarginine (ADMA), in CsA-induced renal and cardiovascular adverse effects. In this study, the potential of the third generation β-blocker, nebivolol, to modify the NO/ADMA system is hypothesized to play a role in protection against CsA-induced renal injury and endothelial dysfunction. Both in vivo and in vitro studies were carried out on 36 male Wistar rats randomly divided into three groups; normal control, CsA (30mg/kg/day)-treated or CsA+nebivolol (30mg/kg and 1mg/kg daily, respectively)-treated groups. After four weeks, blood pressure, lipid profile, renal functions, renal oxidative status, NO, inducible NO synthase and ADMA were assessed. In vitro evaluation of vascular relaxant responses of norepinephrine pre-contracted aortic rings to acetylcholine (ACh) and sodium nitroprusside were evaluated. Concurrent nebivolol treatment significantly attenuated CsA-induced hypertension, impairment of renal functions, oxidative stress and restored the balance in renal NO system with lowering of the elevated ADMA. This was associated with favourable effects on lipid profile. Nebivolol treatment also abrogated the CsA-induced impairment of relaxant responses of aortic rings to ACh. Nebivolol possesses multifaceted actions that make it advantageous to combat the CsA-induced toxic effects on renal and endothelial functions.

Cyclosporine-A, but not tacrolimus significantly increases reactivity of vascular smooth muscle cells.

Application of cyclosporine-A (CsA) or tacrolimus is associated with numerous side effects. One of the main reasons for restricting usage of CsA is hypertension. In tacrolimus treated subjects the frequency of these phenomena is significantly lower. The known molecular mechanism of action of tacrolimus and cyclosporine-A seems to be the same, thus we decided to compare modulatory effect of drugs on vascular smooth muscle contractility. Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force was measured by increased degree of perfusion pressure with a constant flow rate. Concentration-response curves for agonist in the presence CsA were significantly shifted to the left with increase in maximal responses. This effect was due to increased calcium influx from extracellular calcium stores whereas there were no significant changes in calcium influx in the presence of tacrolimus; concentration-response curve was comparable to controls. Our results strongly support the idea that main difference between effects on smooth muscle contractility of calcineurin-dependent immunosuppressants: CsA and tacrolimus is related to the different level of extracellular calcium influx to the cytoplasm. The elucidation of these mechanisms may permit the identification of new therapeutic strategies against CsA-induced hypertension.

Abstract P183: Myeloid-Derived Suppressor Cells Prevent Cyclosporine A-Induced Hypertension, Endothelial Dysfunction, and Renal Injury in Mice

Cyclosporine A (CsA) is an immunosuppressive drug used to treat focal segmental glomerulosclerosis, reduce autoimmune diseases, and prevent allograft rejection; however a limitation of CsA is that it can induce vascular and renal injury as well as hypertension. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature granulocytes, macrophages, and dendritic cells that suppress pro-inflammatory immune responses by secreting anti-inflammatory cytokines, inhibiting innate and adaptive immune cells, and inducing regulatory T cells (Tregs). We hypothesized that adoptive transfer of MDSCs would prevent CsA-induced vascular and renal injury and hypertension. Daily treatment of male C57BL6/J mice for 1 week with CsA (50 mg/kg/day, i.p. injection) significantly increased systolic blood pressure (Day 7 SBP in mmHg: Con=97±2 vs. CsA=145±3, p<0.05 vs. Con), decreased aortic endothelium-dependent relaxation responses, increased aortic fibronectin levels, increased renal glomerular mesangial expansion, increased renal fibronectin levels, and decreased splenic Treg levels. Adoptive transfer of 1 million MDSCs by i.p. injection on days 1, 4, and 7 partially prevented the CsA-induced rise in systolic blood pressure (CsA+1M MDSCs=120±3 mmHg) and the detrimental vascular and renal effects. However, adoptive transfer of 2 million MDSCs fully prevented the CsA-induced hypertension (CsA+2M MDSCs=105±1 mmHg) and vascular and renal effects. The anti-hypertensive and vascular and renal protective effects of 2 million MDSCs were independent of Treg induction as splenic Treg levels remained significantly decreased. These data suggest that MDSCs can prevent the hypertension and toxicity caused by CsA independent of Tregs and may be a therapeutic target for CsA-treated patients.

Cyclosporin A upregulates ETB receptor in vascular smooth muscle via activation of mitogen-activating protein kinases and NF-κB pathways

Hypertension is one of the most frequent complications of solid organ transplantation, and cyclosporin A (CsA) plays a predominant role in the pathophysiology of post-transplant hypertension. However, the exact molecular mechanisms of CsA-induced hypertension remain obscure. We previously showed that CsA increased the mRNA expression and contractile function of endothelin B (ETB) receptor in vascular smooth muscle cells. The present study was designed to investigate the underlying mechanisms of CsA-induced upregulation of ETB receptor in vasculature. Rat mesenteric arteries were incubated with CsA in an organ culture system, and results showed that CsA enhanced ETB receptor mRNA in the time- and dose-dependent manner, and increased protein expression levels of ETB receptor after treatment with CsA 10−5M for 6h. Furthermore, CsA induced phosphorylation of extracellular regulated protein kinases 1 and 2 (ERK1/2), p38, and translocation of nuclear factor-kappaB (NF-κB) p65 in vasculature. Blocking ERK1/2, p38, or NF-κB activation with their specific inhibitors markedly attenuated CsA-induced upregulation of ETB receptor mRNA expression and protein levels, and ETB receptor-mediated contraction. In summary, this study showed that mitogen-activating protein kinases (ERK1/2 and p38) and the downstream transcriptional factor NF-κB pathways were involved in CsA-induced upregulation of ETB receptor in arterial smooth muscle cells.

Prevention of nephrotoxicity induced by cyclosporine-A: role of antioxidants.

Cyclosporine A (CsA) is a powerful immunosuppressive drug used to prevent allograft rejection after organ transplantation as well as in human and veterinary medicine. Unfortunately, its use is hampered by its nephrotoxic effects. The mechanisms of CsA-induced hypertension and nephrotoxicity are not clear, but several studies suggest the possible involvement of free radicals. In this review we have summarized the effect of some antioxidants that we have used in the recent years, in combination with CsA, to better understand the exact mechanism of action of CsA and to try to open new perspectives in the treatment of CsA nephrotoxicity.

Pharmacokinetic drug-drug interaction of calcium channel blockers with cyclosporine in hematopoietic stem cell transplant children.

Cyclosporine (CsA) is frequently responsible for hypertension in bone marrow transplant children. Calcium channel blockers (CCBs) are considered to be the best treatment for CsA-induced hypertension, but they may alter the exposure and the effect of CsA by inhibiting the CYP3A4 pathway of CsA metabolism or P-gp. However, the inhibitory effect on CYP3A4 may vary among CCBs. This study aimed to quantify the pharmacokinetic drug-drug interaction between CsA and nicardipine, amlodipine, and lacidipine. In all, 51 children who received CsA and CCB concomitantly were included. Dose-normalized CsA trough blood concentrations significantly increased in patients treated with nicardipine and amlodipine, whereas they remained stable in patients treated with lacidipine. Because lacidipine appears to have no effect on CsA exposure, it may be the best option among CCBs for treating high blood pressure caused by CsA in children.

Renal Sodium Transporters Are Increased in Urinary Exosomes of Cyclosporine-Treated Kidney Transplant Patients

Background/Aims: Cyclosporine (CsA) is a calcineurin inhibitor widely used as an immunosuppressant in organ transplantation. Previous studies demonstrated the relationship between CsA and renal sodium transporters such as the Na-K-2Cl cotransporter in the loop of Henle (NKCC2). Experimental models of CsA-induced hypertension have shown an increase in renal NKCC2. Methods: Using immunoblotting of urinary exosomes, we investigated in CsA-treated kidney transplant patients (n = 39) the excretion of NKCC2 and Na-Cl cotransporter (NCC) and its association with blood pressure (BP) level. We included 8 non-CsA-treated kidney transplant patients as a control group. Clinical data, immunosuppression and hypertension treatments, blood and 24-hour urine tests, and 24-hour ambulatory BP monitoring were recorded. Results: CsA-treated patients tended to excrete a higher amount of NKCC2 than non-CsA-treated patients (mean ± SD, 175 ± 98 DU and 90 ± 70.3 DU, respectively; p = 0.05) and showed higher BP values (24-hour systolic BP 138 ± 17 mm Hg and 112 ± 12 mm Hg, p = 0.003; 24-hour diastolic BP, 83.8 ± 9.8 mm Hg and 72.4 ± 5.2 mm Hg, p = 0.015, respectively). Within the CsA-treated group, there was no correlation between either NKCC2 or NCC excretion and BP levels. This was confirmed by a further analysis including potential confounding factors. On the other hand, a significant positive correlation was observed between CsA blood levels and the excretion of NKCC2 and NCC. Conclusion: Overall, these results support the hypothesis that CsA induces an increase in NKCC2 and NCC in urinary exosomes of renal transplant patients. The fact that the increase in sodium transporters in urine did not correlate with the BP level suggests that in kidney transplant patients, other mechanisms could be implicated in CsA-induced hypertension.

Vasomotor Dysfunction in the Mesenteric Artery after Organ Culture with Cyclosporin A

Cyclosporin A (CsA) is a widely used immunosuppressive agent that also causes hypertension. However, the molecular basis for CsA-induced hypertension remains elusive. In this study, we established an in vitro model for CsA-induced pathological changes in vasculature. Rat mesenteric arteries were incubated with CsA for 24hr in an organ culture system. Both vasocontraction and vasorelaxation in mesenteric artery were studied using myograph technology, and mRNA expressions of the contractile receptors were determined by real-time PCR. The results showed that CsA increased the mRNA expression and contractile function of several G-protein-coupled receptors (GPCRs), such as endothelin receptor type B (ETB ), 5-hydroxytryptamine type 1B (5-HT1B ) and 1D (5-HT1D ), in vascular smooth muscle cells. In addition, both nitric oxide (NO)-mediated vasorelaxation and endothelium-independent relaxation were impaired by CsA. In summary, this study showed the enhanced GPCRs-mediated contraction and reduced vasorelaxation in mesenteric artery after organ culture with CsA, which mimicked the CsA-induced pathological changes in the vascular system in vivo. Furthermore, this organ culture system would be an ideal in vitro tool to study the molecular mechanisms of CsA-induced hypertension.

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 (25mg/kg/day, n=7) and 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol, superoxide dismutase mimetic, 100mg/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, 1mg/kg i.v.) or β-adrenoceptor blockade (propranolol, 1mg/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.

Abstract 448: Cyclosporine A-Induced Increases in Th17 Cells, Endothelial Dysfunction, and Blood Pressure are Prevented by IL-17 Inhibition

The immunosuppressive drug cyclosporine A (CsA) decreases anti-inflammatory regulatory T cells (Tregs); however its effect on pro-inflammatory Th17 cells and whether IL-17 secreted by Th17 cells plays a role in the development of CsA-induced endothelial dysfunction and hypertension are unknown. We hypothesized that CsA causes endothelial dysfunction and hypertension in part by increasing Th17 cells and these effects can be prevented by IL-17 inhibition. Daily treatment of male C57BL6/J mice for 1 week with CsA (50 mg/kg/day, ip) significantly increased SBP compared to vehicle-treated controls (Con: 99±3 mmHg vs. CsA: 138±3 mmHg; p<0.05) and significantly decreased maximal aortic endothelium-dependent relaxation responses (Con: 69±3% vs. CsA: 25±2%; p<0.05). These effects were associated with a significant increase in both splenic and circulating levels of Th17 cells and a significant decrease in both splenic and circulating Tregs. Injections of an IL-17 neutralizing antibody (nAb) on days 0, 3, and 6 of CsA treatment normalized SBP (108±9 mmHg) and aortic endothelium-dependent relaxation responses (68±2%). IL-17 nAb treatment also decreased both splenic and circulating levels of Th17 cells and increased both splenic and circulating levels of Tregs. Injections of an isotype nAb on days 0, 3, and 6 had no effects on SBP in either CsA-treated (141±3 mmHg) or vehicle-treated (98±6 mmHg) mice. The isotype nAb also had no effects on aortic relaxation responses, splenic or circulating levels of Th17 cells, or splenic or circulating levels of Tregs in either CsA-treated or vehicle-treated mice. Together, these data suggest that the hypertension and endothelial dysfunction caused by the immunosuppressive drug CsA is mediated in part by increased Th17 cells and IL-17. Inhibition of IL-17 may have beneficial cardiovascular effects in CsA-treated patients.

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 Nω-nitro-l-arginine methyl ester (L-NAME, nonselective NOS inhibitor), N5-(1-iminoethyl)-l-ornithine (L-NIO, selective eNOS inhibitor), Nω-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.

Amelioration By Tempol Of The Hypertensive And Baroreflex Depressant Effects Of Cyclosporine In Conscious Rats: Role Of Cardiac Autonomic Control

Previous studies including ours showed that cyclosporine (CSA) causes hypertension and baroreflex dysfunction. This study tested the hypothesis that increased oxidative damage mediates CSA effects. Experiments were undertaken in rats to investigate the effects of individual and combined 7‐day treatments with CSA (25 mg/kg/day) and tempol (superoxide dismutase mimetic, 100 mg/kg/day) on BP, reflex HR responses to peripherally mediated pressor and depressor responses, and biomarkers of oxidative stress. The role of cardiac autonomic control in cyclosporine‐tempol interaction was also investigated. CSA elevates blood pressure and reduced reflex bradycardic (phenylephrine) and tachycardic (sodium nitroptrusside) responses. The ability of muscarinic (atropine) or β‐adrenoceptors (propranolol) blockade to reduce reflex HR responses was reduced in CSA‐treated rats, suggesting impairment by CSA of cardiac autonomic control. Concurrent administration of tempol abolished CSA‐induced hypertension, baroreflex dysfunction, and autonomic impairment. Tempol also reversed the CSA‐induced increases in aortic and brainstem nitrite/nitrate and malondialdehyde and decreases in aortic superoxide dismutase. These findings implicate oxidative stress, at peripheral and central sites, in CSA‐induced hypertension and baroreflex dysfunction.

Cyclosporine stimulates the renal epithelial sodium channel by elevating cholesterol

Cyclosporine A (CsA) is an efficient immunosuppressant used for reducing allograft rejection but with a severe side effect of causing hypertension. We hypothesize that the renal epithelial sodium channel (ENaC) may participate in CsA-induced hypertension. In the present study, we used the patch-clamp cell-attached configuration to examine whether and how CsA stimulates ENaC in A6 distal nephron cells. The data showed that CsA significantly increased ENaC open probability. Since CsA is an inhibitor of the ATP-binding cassette A1 (ABCA1) transporter, we employed 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), another ABCA1 inhibitor, and found that DIDS mimicked the effects of CsA on ENaC basal and cholesterol-induced activity but without any additive effect if combined with CsA. CsA and DIDS also had an identical effect on reduced ENaC activity caused by cholesterol extraction. ABCA1 protein was detected in A6 cells by Western blot analysis. Confocal microscopy data showed that both CsA and DIDS facilitated A6 cells to uptake cholesterol. Since enhanced ENaC activity is known to cause hypertension, these data together suggest that CsA may cause hypertension by stimulating ENaC through a pathway associated with inhibition of ABCA1 and consequent elevation of cholesterol in the cells.

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.