Cyclosporine and the renin-angiotensin axis

Role of cyclosporin A in the treatment of kidney disease and nephrotoxicity

The clinical use of cyclosporin A (CsA) has led to significant advances and achievements in the field of transplantation and immune diseases. However, the nephrotoxicity of CsA is a major concern in current immunosuppression regimens. CsA causes abnormal kidney function while treating kidney disease, causing problems for clinicians and patients. Evidence of CsA nephrotoxicity is almost always present in transplant recipients after long-term CsA administration (up to 10 years), and similar phenomena occur with other calcineurin inhibitors. In this review, we summarize the mechanisms and influencing factors of CsA for the treatment of primary nephrotic syndrome. The mechanisms of CsA nephrotoxicity, clinical-pathological features, diagnosis, prevention strategies, and risk factors are summarized. We discuss the correlates and mechanisms of the switch between kidney disease prevention and nephrotoxicity of CsA to better understand the function of CsA in the kidney and to provide a basis for the prevention and treatment of CsA nephrotoxicity.

Role of (Pro)Renin Receptor in Cyclosporin A-Induced Nephropathy

Calcineurin inhibitors (CNIs) such as cyclosporin A (CsA) have been widely used to improve graft survival following solid-organ transplantation. However, the clinical use of CsA is often limited by its nephrotoxicity. The present study tested the hypothesis that activation of (pro)renin receptor (PRR) contributes to CsA-induced nephropathy by activating the renin-angiotensin system (RAS). Renal injury in male Sprague-Dawley rats was induced by a low-salt diet combined with CsA as evidenced by elevated plasma creatinine and BUN levels, decreased creatinine clearance and induced renal inflammation, apoptosis as well as interstitial fibrosis, elevated urinary N-acetyl-β-D-glucosaminidase activity and urinary kidney injury molecular 1 content. Each index of renal injury was attenuated following a 2-wk treatment with a PRR decoy inhibitor PRO20. While CsA rats with kidney injury displayed increased renal sPRR abundance, plasma sPRR, renin activity, Ang II, and heightened urinary total prorenin/renin content; RAS activation was attenuated by PRO20. Exposure of cultured human renal proximal tubular HK-2 cells to CsA induced expression of fibronectin and sPRR production, but the fibrotic response was attenuated by PRO20 and siRNA-mediated PRR knockdown. These findings support the hypothesis that activation of PRR contributes to CsA-induced nephropathy by activating the RAS in rats. Of importance, we provide strong proof of concept that targeting PRR offers a novel therapeutic strategy to limit nephotoxic effects of immunosuppressant drugs.

A physiology-based approach to a patient with hyperkalemic renal tubular acidosis

Hyperkalemic renal tubular acidosis is a non-anion gap metabolic acidosis that invariably indicates an abnormality in potassium, ammonium, and hydrogen ion secretion. In clinical practice, it is usually attributed to real or apparent hypoaldosteronism caused by diseases or drug toxicity. We describe a 54-year-old liver transplant patient that was admitted with flaccid muscle weakness associated with plasma potassium level of 9.25 mEq/L. Additional investigation revealed type 4 renal tubular acidosis and marked hypomagnesemia with high fractional excretion of magnesium. Relevant past medical history included a recent diagnosis of Paracoccidioidomycosis, a systemic fungal infection that is endemic in some parts of South America, and his outpatient medications contained trimethoprim-sulfamethoxazole, tacrolimus, and propranolol. In the present acid-base and electrolyte case study, we discuss a clinical approach for the diagnosis of hyperkalemic renal tubular acidosis and review the pathophysiology of this disorder.

Does Mineralocorticoid Receptor Antagonism Prevent Calcineurin Inhibitor-Induced Nephrotoxicity?

Calcineurin inhibitors have markedly reduced acute rejection rates in renal transplantation, thus significantly improved short-term outcome. The beneficial effects are, however, tampered by acute and chronic nephrotoxicity leading to interstitial fibrosis and tubular atrophy, which impairs long-term allograft survival. The mineralocorticoid hormone aldosterone induces fibrosis in numerous organs, including the kidney. Evidence from animal models suggests a beneficial effect of aldosterone antagonism in reducing calcineurin inhibitor-induced nephrotoxicity. This review summarizes current evidence of mineralocorticoid receptor antagonism in animal models of calcineurin inhibitor-induced nephrotoxicity and the results from studies of mineralocorticoid antagonism in renal transplant patients.

Impact of immunosuppressive therapy on arterial stiffness in kidney transplantation: are all treatments the same?

Arterial stiffness is a biologic process related to ageing and its relationship with cardiovascular risk is well established. Several methods are currently available for non-invasive measurement of arterial stiffness that provide valuable information to further assess patients’ vascular status in real time. In kidney transplantation recipients, several factors could accelerate the stiffness process, such as the use of calcineurin inhibitors (CNIs), the presence of chronic kidney disease and other classical cardiovascular factors, which would explain, at least in part, the high cardiovascular mortality and morbidity. Despite the importance of arterial stiffness as a biomarker of cardiovascular risk, and unlike other cardiovascular risk factors (e.g. left ventricular hypertrophy), only a few clinical trials or retrospective studies of kidney recipients have evaluated its impact. In this review we describe the clinical impact of arterial stiffness as a prognostic marker of cardiovascular disease and the effects of different immunosuppressive regimens on its progression, focusing on the potential benefits of CNI-sparing protocols and supporting the rationale for individualization of immunosuppression in patients with lower arterial elasticity. Among the immunosuppressive drugs, a belatacept-based regimen seems to offer better vascular protection compared with CNIs, although further studies are needed to confirm the preliminary positive results.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Pathophysiological mechanisms of calcineurin inhibitor-induced nephrotoxicity and arterial hypertension

Solid organ transplantation is an established treatment modality in patients with end-stage organ damage in cases where other therapeutic options fail. The long-term outcomes of solid organ transplant recipients have improved considerably since the introduction of the first calcineurin inhibitor (CNI) - cyclosporine. In 1984, the potent immunosuppressive properties of another CNI, tacrolimus, were discovered. The immunosuppressive effects of CNIs result from the inhibition of interleukin-2 synthesis and reduced proliferation of T cells due to calcineurin blockade. The considerable side effects that are associated with CNIs therapy include arterial hypertension and nephrotoxicity. The focus of this article was to review the available literature on the pathophysiological mechanisms of CNIs that induce chronic nephrotoxicity and arterial hypertension. CNIs lead to activation of the major vasoconstriction systems, such as the renin-angiotensin and endothelin systems, and increase sympathetic nerve activity. On the other hand, CNIs are known to inhibit NO synthesis and NO-mediated vasodilation and to increase free radical formation. Altogether, these processes cause endothelial dysfunction and contribute to the impairment of organ function. A better insight into the mechanisms underlying CNI nephrotoxicity could assist in developing more targeted therapies of arterial hypertension or preventing CNI nephrotoxicity in organ transplant recipients, including heart transplantation.

Calcineurin-inhibition Results in Upregulation of Local Renin and Subsequent Vascular Endothelial Growth Factor Production in Renal Collecting Ducts

BACKGROUND

Tacrolimus (Tac) and Cyclosporine A (CyA) calcineurin inhibitors (CNIs) are 2 effective immunosuppressants which are essential to prevent allograft rejection. Calcineurin inhibitors are known to be nephrotoxic. However, the precise mechanism of nephrotoxicity is not fully understood. In this study, we investigated the in vivo effects of CNIs on the local renal renin-angiotensin system in the collecting duct (CD).

METHODS

Three-week-old mice were treated with either vehicle, CyA (2 mg/kg per day), Tac (0.075 mg/kg per day), CyA + Aliskiren (25 mg/kg per day), or Tac + Aliskiren for 3 weeks. Serum creatinine was measured. Renin and vascular endothelial growth factor (VEGF) contents in CD were evaluated with flow cytometry and multiphoton microscopy. The diameter of vessels was assessed with multiphoton microscopy, and the amount of renal collagen was determined by real-time polymerase chain reaction and Masson staining.

RESULTS

The elevated level of serum creatinine in CNI groups was abolished by Aliskiren. Flow cytometric analysis found elevated renin content in principal cells, which was prevented by Aliskiren. This result was further confirmed with multiphoton microscopy. The VEGF content in CD correlated with reduced capillary diameter and with the formation of fibrotic islands.

CONCLUSIONS

Calcineurin inhibitors induce production of renin in the CD that may contribute to decreased renal blood flow. In turn, CD responds with increased VEGF production, resulting in disproportional vessel growth, further worsening the local hypoxia and striped fibrosis surrounding the CDs. Aliskiren, a direct renin inhibitor blocks these effects and improves CNI-induced nephropathy by decreasing renin production in the CDs. Our data suggest that Aliskiren may be used for the prevention of CNI nephrotoxicity.

Biomarkers of calcineurin inhibitor nephrotoxicity in transplantation

Over 35 years of use has demonstrated the revolutionary therapeutic benefits of calcineurin inhibitors (CNI) in not only preventing transplant rejection, but also the renal and nonrenal toxicity of CNI. Acute reversible and insidious irreversible forms of CNI nephrotoxicity have been identified, with ischemia from an imbalance between vasoconstrictors and vasodilators playing an important role. The ongoing search to define toxicity pathways has been enriched by ‘Omics’ studies. Changes in proteins including those involved in activation of pro-inflammatory responses, oxidative stress, ER stress and the unfolded protein response have been identified, and these may serve as biomarkers of toxicity. However, the current standard of CNI toxicity, histology, lacks specificity, which creates challenges for biomarker validation. This review focuses on progress in nephrotoxic pathway identification of CNI and biomarker validation.

A randomized cross-over comparison of short-term exposure of once-daily extended release tacrolimus and twice-daily tacrolimus on renal function in healthy volunteers

Calcineurin inhibitor nephrotoxicity remains an issue for transplant recipients. The pharmacokinetic profile (PK) of the once-daily tacrolimus extended release (Tac-ER) includes equivalent exposure [AUC(0-24 h) ] but lower Cmax versus twice-daily tacrolimus immediate release (Tac-IR). We hypothesized that the unique PK profiles would result in pharmacodynamic differences in renal function. Nineteen healthy male subjects were allocated to once-daily Tac-ER and twice-daily Tac-IR in a prospective, randomized, two period, cross-over study. Tacrolimus was titrated to achieve trough levels of 8-12 ng/ml. Twenty four hours ERPF and GFR estimated by para-aminohippurate and sinistrin clearance were performed at baseline and at the end of each 10-day dosing period. Mean Tac C0 was 11.0 ± 2.2 and 11.3 ± 1.8 ng/ml for Tac-ER and Tac-IR, respectively. The mean Effective 24 h renal plasma flow (ERPF) was significantly higher with Tac-ER compared with Tac-IR (658 ± 127 vs. 610 ± 93 ml/min/1.73 m(2) , P = 0.046). There was a trend to a greater mean GFR over 24 h for Tac-ER at 114.5 ± 13.6 ml/min/1.73 m(2) compared with 108.9 ± 9.7 ml/min/1.73 m(2) for Tac-IR, P = 0.116. Under controlled physiological conditions, ERPF was significantly improved with Tac-ER compared with Tac-IR, likely owing to the differing PKs of these tacrolimus preparations (ClinicalTrials.gov Identifier: NCT01681134).

Hypertension: The Neglected Complication of Transplantation

Arterial hypertension and transplantation are closely linked, and its association may promote impaired graft and overall survival. Since the introduction of calcineurin inhibitors, it is observed in 50–80% of transplanted patients. However, many pathophysiological mechanisms are involved in its genesis. In this review, we intend to provide an updated overview of these mechanisms, dealing with the causes common to all kinds of transplantation and emphasizing special cases with distinct features, and to give a perspective on the pharmacological approach, in order to help clinicians in the management of this frequent complication.

Arterial hypertension in liver transplant recipients

Hypertension is an important cardiovascular risk factor that influences patient survival. This study sought to evaluate hypertension incidence and circadian rhythms of blood pressure (BP) among liver transplant recipients during the first posttransplant month. We also compared hypertension incidence according to clinical and automated blood pressure monitoring methods. BP was determined by clinical blood pressure monitoring (CBPM) methods and by automated blood pressure monitoring (ABPM) using the SpaceLabs device. We also assessed blood biochemistry, particularly kidney function parameters and immunosuppressive drug blood trough levels, among 32 white subjects (10 women and 22 men) of average age 47.58±14.19 years. The leading cause for transplantation was liver insufficiency due to viral hepatitis B and/or C infection (43.75%). The majority (93.75%) of patients was prescribed immunosuppressive treatment with tacrolimus. Although we observed hypertension in 28 patients (87.5%) by ABPM measurements and in 25 (78.12%) using CBPM method, the difference did not reach statistical significance. However, BP control was inadequate in 28 patients (87.5%) by ABPM assessment versus 3 (9.38%) according to CBPM readings (P=.025). The BP circadian rhythm was altered in 30 patients (93.75%) including 15 with higher nighttime BP readings. There was no correlation between tacrolimus blood levels and BP values or with kidney function as assessed by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. We concluded that prevalence of arterial hypertension among liver transplant recipients within 1 month after transplantation is high. The majority of the patients show disturbed circadian rhythms in the early period after liver transplantation with loss or even reversal of the normal nocturnal decrease in BP. Owing to the fact that ABPM enables more adequate daily assessment of BP values, it is an optimal method to adjust antihypertensive therapy to optimal levels.

Genomic-derived markers for early detection of calcineurin inhibitor immunosuppressant-mediated nephrotoxicity

Calcineurin inhibitor (CI) therapy has been associated with chronic nephrotoxicity, which limits its long-term utility for suppression of allograft rejection. In order to understand the mechanisms of the toxicity, we analyzed gene expression changes that underlie the development of CI immunosuppressant-mediated nephrotoxicity in male Sprague-Dawley rats dosed daily with cyclosporine (CsA; 2.5 or 25 mg/kg/day), FK506 (0.6 or 6 mg/kg/day), or rapamycin (1 or 10 mg/kg/day) for 1, 7, 14, or 28 days. A significant increase in blood urea nitrogen was observed in animals treated with CsA (high) or FK506 (high) for 14 and 28 days. Histopathological examination revealed tubular basophilia and mineralization in animals given CsA (high) or FK506 (low and high). We identified a group of genes whose expression in rat kidney is correlated with CI-induced kidney injury. Among these genes are two genes, Slc12a3 and kidney-specific Wnk1 (KS-Wnk1), that are known to be involved in sodium transport in the distal nephrons and could potentially be involved in the mechanism of CI-induced nephrotoxicity. The downregulation of NCC (the Na-Cl cotransporter coded by Slc12a3) in rat kidney following CI treatment was confirmed by immunohistochemical staining, and the downregulation of KS-Wnk1 was confirmed by quantitative real-time-polymerase chain reaction (qRT-PCR). We hypothesize that decreased expression of Slc12a3 and KS-Wnk1 could alter the sodium chloride reabsorption in the distal tubules and contribute to the prolonged activation of the renin-angiotensin system, a demonstrated contributor to the development of CI-induced nephrotoxicity in both animal models and clinical settings. Therefore, if validated as biomarkers in humans, SLC12A3 and KS-WNK1 could potentially be useful in the early detection and reduction of CI-related nephrotoxicity in immunosuppressed transplant patients when monitoring the health of kidney xenographs in clinical practice.

A comparison of short-term exposure of once-daily extended release tacrolimus and twice-daily cyclosporine on renal function in healthy volunteers

BACKGROUND

Calcineurin inhibitor nephrotoxicity remains an issue for recipients of solid organ transplants. After cyclosporine A (CsA) microemulsion administration, effective renal plasma flow (ERPF) and glomerular filtration rate(GFR) are decreased coincident with the maximal concentration (Cmax) of CsA. The pharmacokinetic (PK) profile of the once-daily formulation of tacrolimus extended release (Tac ER) includes an equivalent AUCPK 0-24 hr and a lower Cmax versus twice-daily Tac immediate release.

METHODS

Eighteen healthy subjects were allocated once-daily Tac ER and twice-daily CsA in a prospective, randomized,open-label, two-period, two-sequence single crossover study. CsA was targeted to C2 of 700 to 1400 ng/mL, and Tac ER was targeted to C0 of 5 to 10 ng/mL. Pharmacodynamic (PD) assessments were conducted preexposure, and PD and PK were assessed during a 6-hr postdose period after 10-day exposure.

RESULTS

The achieved mean C(o) Tac and CsA were 6.4 +/- 1.16 and 201 +/- 57 ng/mL, respectively. At Cmax, the change in ERPF was +30 +/- 127 vs. -70 +/- 96 mL/min/1.73 m2 relative to baseline for Tac ER and CsA (P=0.0085). The ERPF and GFR AUC (PD 0-6) hr were 3645 +/- 887 vs. 3210 +/- 582 mL/1.73 m2 (P=0.027) and 604 +/- 98 vs. 543+/- 79 mL/1.73 m2(P=0.023) for Tac ER versus CsA, respectively. Both systolic and diastolic blood pressures were significantly greater with exposure to CsA compared with Tac ER.

CONCLUSIONS

Acute reductions in ERPF and GFR are attenuated with Tac ER compared with CsA and may correlate with the differing PK profiles of these calcineurin inhibitors.

Cardiovascular risk factors following orthotopic liver transplantation: predisposing factors, incidence and management

BACKGROUND

Liver transplantation is the standard of care for acute and chronic causes of end-stage liver disease. Advances in medical therapy and surgical techniques have led to improvement of patient and graft survival rates following orthotopic liver transplantation. However, the prevalence of post-transplant cardiovascular complications has been rising with increased life expectancy after liver transplantation.

AIMS

To determine the incidences, risk factors, and treatment for hypertension, hyperlipidaemia, diabetes, and obesity in the post-liver transplantation population.

METHODS

We performed a review of relevant studies available on the PubMed database that provided information on the incidence, risk factors and treatment for cardiovascular complications that develop in the post-liver transplantation population.

RESULTS

Current immunosuppressive agents have improved patient and graft survival rates. However, long-term exposure to these agents has been associated with development of systemic and metabolic complications including hypertension, hyperlipidaemia, diabetes mellitus and obesity. Cardiovascular disease remains one of the most common causes of death in liver transplant patients with functional grafts.

CONCLUSIONS

Liver transplant recipients have a higher risk of cardiovascular complications compared with the nontransplant population. Post-transplant cardiac risk stratification and aggressive treatment of cardiovascular complications, including modification of risk factors and tailoring of immunosuppressive regimen, is imperative to prevent serious complications.

Hypertension after pediatric cardiac transplantation: detection, etiology, implications and management

While it may rescue children with end-stage heart failure from impending catastrophe, cardiac transplantation leaves 50-70% of pediatric recipients with new-onset hypertension. Given the unique vulnerability of the heart and kidneys in these children, we can expect long-term uncontrolled hypertension to shorten both graft and patient survival. In this review we discuss the multi-factorial etiology of post-transplant hypertension, highlighting current uncertainties and emphasizing mechanisms specific to cardiac recipients. We consider the optimal means of monitoring BP and in particular, the advantages of 24 h-ABP over intermittent clinic measurements. We also review BP treatment after cardiac transplantation, drawing attention to specific cautions appropriate when prescribing antihypertensive agents in these circumstances.

The pathophysiology of chronic graft failure in the cardiac transplant patient

Following cardiac transplantation, many patients develop chronic deterioration of graft function, which may lead to a clinical syndrome similar to native chronic heart failure (CHF). This condition of chronic cardiac graft failure (CGF) may also share pathophysiological processes comparable with that of CHF. However, the unique environment following cardiac transplantation may also contribute with a variety of unique mechanisms, deserved of special attention. This review article discusses the complex pathophysiology of CGF after cardiac transplantation, an important yet neglected condition of transplant medicine.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Nephrotoxicity as a cause of acute kidney injury in children

Many different drugs and agents may cause nephrotoxic acute kidney injury (AKI) in children. Predisposing factors such as age, pharmacogenetics, underlying disease, the dosage of the toxin, and concomitant medication determine and influence the severity of nephrotoxic insult. In childhood AKI, incidence, prevalence, and etiology are not well defined. Pediatric retrospective studies have reported incidences of AKI in pediatric intensive care units (PICU) of between 8% and 30%. It is widely recognized that neonates have higher rates of AKI, especially following cardiac surgery, severe asphyxia, or premature birth. The only two prospective studies in children found incidence rates of 4.5% and 2.5% of AKI in children admitted to PICU, respectively. Nephrotoxic drugs account for about 16% of all AKIs most commonly associated with AKI in older children and adolescents. Nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, amphotericin B, antiviral agents, angiotensin-converting enzyme (ACE) inhibitors, calcineurin inhibitors, radiocontrast media, and cytostatics are the most important drugs to indicate AKI as significant risk factor in children. Direct pathophysiological mechanisms of nephrotoxicity include constriction of intrarenal vessels, acute tubular necrosis, acute interstitial nephritis, and-more infrequently-tubular obstruction. Furthermore, AKI may also be caused indirectly by rhabdomyolysis. Frequent therapeutic measures consist of avoiding dehydration and concomitant nephrotoxic medication, especially in children with preexisting impaired renal function.

ACE inhibitors and persistent left ventricular hypertrophy after renal transplantation: a randomized clinical trial

BACKGROUND

Interventional studies of left ventricular hypertrophy (LVH) in renal transplant recipients are scarce and to date evaluated only patients immediately after renal transplantation.

STUDY DESIGN

Randomized controlled trial that assessed the effectiveness of angiotensin-converting enzyme (ACE) inhibitors in regressing persistent LVH after successful transplantation.

SETTING & PARTICIPANTS

70 renal transplant recipients (47 men; age, 30 to 68 years) without diabetes previously randomly assigned to either cyclosporine or tacrolimus therapy, with LVH persisting 3 to 6 months after transplantation.

INTERVENTION

Subjects were randomly assigned to either lisinopril (ACE-inhibitor group; 36 patients) or no therapy (control group; 34 subjects).

OUTCOMES

Main outcome was change in left ventricular mass index (LVMi) at month 18.

RESULTS

A consistent decrease in both systolic (SBP) and diastolic blood pressure (DBP) was observed in both groups (between-group differences, -1.7 +/- 3.3 mm Hg; 95% confidence interval [CI], -4.8 to 8.2; P = 0.6 for SBP; 0.3 +/- 2.2 mm Hg; 95% CI, -4.8 to 4.1; P = 0.9 for DBP), whereas LVMi regressed more in the ACE-inhibitor group (between-group difference, 10.1 +/- 16.3 g/m(2.7); 95% CI, 4.2 to 16.1; P < 0.01). A significant interaction of ACE inhibitors with cyclosporine in affecting LVMi change was shown by means of post hoc multiple regression analysis (P < 0.01; differences between cyclosporine and tacrolimus group, 13.3 +/- 3.9 g/m(2.7); 95% CI, 5.3 to 21.2; P < 0.01 in the ACE-inhibitor group; 3.7 +/- 4.2 g/m(2.7); 95% CI, -4.7 to 12.2; P = 0.4 in the control group).

LIMITATIONS

Single-center study with small sample size. Interaction of ACE inhibitors with cyclosporine treatment emerged from post hoc analysis.

CONCLUSION

A prolonged course of ACE-inhibitor therapy is effective in regressing the persistent LVH of renal transplant recipients by mechanisms independent of effects on BP. This regression seems to be at least in part the effect of an interaction between ACE inhibitors and cyclosporine.

Review article: medical management of the liver transplant recipient - a primer for non-transplant doctors

BACKGROUND

Survival 10 years after orthotopic liver transplantation now approaches 65%. Consequently, community doctors must manage the metabolic and neoplastic complications of orthotopic liver transplantation in an ageing population.

AIMS

To review common sources of morbidity and mortality in long-term orthotopic liver transplantation recipients, and to make evidence-based recommendations regarding their management.

METHODS

Pertinent studies and reviews were identified by literature search through PubMed. Where evidence-based recommendations could not be gleaned from the literature, expert opinion was obtained from syllabi of national meetings.

RESULTS

The two most common causes of morbidity and mortality in orthotopic liver transplantation recipients are atherosclerotic vascular disease and de novo malignancy. The pathogenesis of many complications begins before orthotopic liver transplantation, and many are potentially modifiable. Most complications, however, can be directly ascribed to immunosuppressive agents. Despite improvements in our understanding of the pathogenesis and epidemiology of the metabolic and neoplastic complications of orthotopic liver transplantation, remarkably few randomized-controlled studies exist to define their optimal management.

CONCLUSIONS

Orthotopic liver transplantation recipients experience and succumb to the same afflictions of old age as non-transplant patients, but with greater frequency and at an earlier age. Most recommendations regarding surveillance for, and treatment of, medical complications of orthotopic liver transplantation remain based upon expert opinion rather than evidence-based medicine.

Differential expression of tissue factor (TF) in calcineurin inhibitor-induced nephrotoxicity and rejection—implications for development of a possible diagnostic marker

Deposition of fibrin in the form of fibrinoid necrosis is a common feature of severe acute renal allograft rejection. The role of the coagulation system and its initiator tissue factor (TF) during this process is, however, still poorly understood. In this study, we analyzed the expression of TF in 88 renal transplants afflicted with different forms of rejection and calcineurin inhibitor-induced nephrotoxicity, to see whether there was differential expression of this protein. TF immunoreactivity was evaluated semiquantitatively in six different renal structures: the podocytes, Bowman epithelium, the endothelium of the glomeruli, the brush border of tubular cells, the thin ascending loop of Henle, and small arteries/arterioles. The TF expression of normal renal tissue (n=6) was restricted to the glomerular podocytes and Bowman epithelium, and to some extent the ascending loop of Henle. Renal allografts undergoing acute rejection (AR) of grades I-III, (n=13, n=17 and n=12, respectively) did not show any altered TF expression in the glomeruli or vascular endothelium. In the ascending loop of Henle, a reduced expression could be seen (ARI, p=0.015; and ARII, p=0.043). TF staining of the brush border of renal transplants undergoing acute cyclosporin A (CsA) nephrotoxicity (n=18) was significantly higher than in normal kidneys (p=0.0003), as well as in transplants undergoing various degrees of acute rejection (ARI, p=0.027; ARII, p=0.0012; and ARIII, p=0.0001). Tubular brush border-expressed TF was also evident in 10 of 15 allografts suffering from chronic CsA nephrotoxicity, compared to 4 out of 13 cases with chronic allograft vasculopathy (CAV), but the increase was not statistically significant relative to normal kidneys. The majority of the grafts afflicted with either of the two chronic conditions displayed a TF-positive arterial endothelium (CAV, p=0.0034; and chronic CsA nephrotoxicity, p=0.0026) relative to controls. In conclusion, these results indicate that vascular TF expression is not altered during acute rejection, but may be of importance in chronic allograft nephropathy. Furthermore, TF immunoreactivity in the tubular brush border may be specific to acute CsA nephrotoxicity and might be used as a biomarker for this condition. Further studies are required to evaluate the possible role of brush border-expressed TF in the pathogenesis of CsA nephrotoxicity.

Hypertension in Kidney Transplantation

Arterial hypertension in renal transplant patients plays a major role in the progression to chronic allograft failure, and in morbidity and mortality associated with cardiovascular disease. Its cause is diverse, with contributions not only from donor and/or recipient factors, but it also is influenced strongly by the type of immunosuppressive regimen. Despite increased awareness of the adverse effects of hypertension in both graft and patient survival, long-term studies have shown that arterial hypertension in the transplant population has not been controlled adequately. Ambulatory blood pressure measurements provide the advantage of a better assessment of the diurnal blood pressure variation, a predictor of target organ damage and cardiovascular morbidity and mortality events. Although the available data do not support the recommendation of any class of antihypertensive medication as preferred agents for blood pressure management in the transplant population, angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers have shown beneficial effects beyond their antihypertensive effects. Clinical data in transplant recipients are emerging that suggest that applying interventions proven to be effective in reducing cardiovascular morbidity and mortality in the general population may be effective for the transplant population.

Different effect of cyclosporine A and mycophenolate mofetil on passive Heymann nephritis in the rat

BACKGROUND

While cyclosporine A (CsA) is an effective therapy for nephrotic syndrome, it has nephrotoxic side effects. We compared the anti-proteinuric effects and nephrotoxicity in rats with passive Heymann nephritis (PHN) of CsA and mycophenolate mofetil (MMF).

METHODS

PHN was induced in female Wistar rats. Two treatment groups consisting of 8 rats each received either 25 mg of CsA or 25 mg of MMF/kg body weight/day and were compared with untreated controls. Kidney function and proteinuria were monitored over 4 weeks. Western blots were used for densitometric analysis of renal cyclooxygenase-2 (COX-2) protein expression. Thromboxane B2 (TxB2) and 6-keto-PGF(1alpha) were determined by radioimmunoassays (RIAs) in renal tissue and urine.

RESULTS

Rats with PHN exhibited a marked proteinuria of 12.76 +/- 4.42 vs. 0.73 +/- 0.28 mg/24 h (p < 0.01) and showed increased glomerular concentrations of TxB2 and 6-keto-PGF(1alpha) (992.6 +/- 216.9 and 1,187.0 +/- 54.2 pg/mg protein, respectively) compared with healthy controls (595 +/- 196.17 and 729 +/- 297.84, respectively) and a strongly induced COX-2 protein expression. CsA and MMF treatment reduced PHN-related proteinuria to 2.10 +/- 1.47 and 1.47 +/- 7.2 mg/24 h, respectively. In rats with PHN, CsA induced a significant deterioration of renal function and enhanced urine excretion of thromboxane A2, paralleled by a significant, twofold increase in COX-2 protein expression and renal prostaglandins. By contrast, MMF treatment in rats with PHN was not nephrotoxic and had no effect on prostaglandin production. COX-2 protein expression under MMF was suppressed.

CONCLUSION

While the antiproteinuric efficacy of MMF and CsA in PHN was comparable, the absence of nephrotoxicity might favor MMF in the treatment of nephrotic syndrome. The CsA-induced increase in COX-2 expression and COX-2-dependent prostacyclin may indicate a mechanism that compensates nephrotoxicity in the diseased and CsA-exposed kidney.

Nephrotoxic aspects of cyclosporine

Over the last 20 years cyclosporine (CsA) has improved the survival of kidney, heart, and liver transplants. However, with increasing use, evidence has accumulated that CsA therapy carries a variety of side effects, the most important being renal toxicity. CsA can lead to a wide spectrum of renal function impairments, including a marked and rapidly reversible decrease in renal hemodynamics (acute CsA nephrotoxicity), and a chronic form of renal damage that potentially progress irreversibly to end-stage renal disease (chronic CsA nephrotoxicity). All these manifestations are the consequence of the drug toxic effects on renal vessels and the tubulointerstitium. A proper diagnosis of CsA toxicity at early stages, the combination of low CsA doses with non-nephrotoxic immunosuppressants, and the development of more feasible strategies to monitor daily CsA exposure may contribute to a better CsA management, improve quality of life of transplant recipients, and prolong graft survival.

Scleroderma renal crisis: new insights and developments

Scleroderma renal crisis (SRC) was once a uniformly fatal complication of systemic sclerosis (SSc). With the introduction of angiotensin-converting enzyme inhibitors as treatment, outcomes have improved significantly, though 39% to 50% of SSc patients who develop SRC continue to have poor outcomes, including permanent dialysis and death. Early recognition and treatment with angiotensin-converting enzyme inhibitors are important in the effective management of SRC, though given the continuing morbidity and mortality caused by SRC, they are clearly not sufficient. Newer therapies based on the pathophysiologic mechanisms underlying the development and perpetuation of SRC are needed. This article reviews the epidemiology, pathogenesis, risk factors, clinical features, and treatment of SRC, with an emphasis on recent insights and developments.

Impact of renal transplantation on small vessel reactivity

BACKGROUND

The function of large arteries is altered after renal transplantation. Whether transplantation also induces agonist-dependent functional changes in small arterial renal and extrarenal vessels has not yet been studied.

METHODS

Chronic rejection was induced by grafting Lewis rats with kidneys from Fischer rats (FL). Rats that underwent transplantation were bilaterally nephrectomized. Rats that underwent syngeneic transplantation, uninephrectomized rats, uninephrectomized rats with denervated kidneys or with kidneys made ischemic, and native rats served as controls. All animals were treated with cyclosporine for 10 days. Eighteen weeks after surgery, the reactivity of small arteries (220-270 microm) was tested by myography.

RESULTS

Weight gain, glomerular filtration rate, and arterial pressure were similar in all groups, whereas proteinuria was elevated in FL. Only kidneys from FL showed glomerular lesions, tubular atrophy, and vasculopathy. Responsiveness of coronary, mesenteric, and femoral resistance vessels to both constrictor and dilator agonists was similar in transplanted and nontransplanted animals. Resistance vessels obtained from both allogeneically and syngeneically transplanted kidneys were more sensitive to norepinephrine, phenylephrine, angiotensin II, and vasopressin than renal vessels from weight-matched controls. Vasodilation in response to acetylcholine and sodium nitroprusside was mitigated in transplanted versus nontransplanted kidneys.

CONCLUSIONS

In rat renal transplantation, renal resistance vessel responsiveness to constrictor or dilator stimuli is altered. Extrarenal small vessel function is not affected. The changes in function of renal resistance vessels are not explained by reduction of nephron mass, denervation, ischemia, or chronic rejection.

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.

Cyclosporine A suppresses cyclooxygenase-2 expression in the rat kidney

On the basis of recent evidence that the cyclooxygenase-2 (COX-2) gene promoter contains functional binding sites for the nuclear factor of activated T cells (NFAT) and that COX-2 is expressed in a regulated fashion in the kidney, this study aimed to assess the effect of immunosuppressants on COX-2 expression in the kidney. Therefore, Wistar-Kyoto rats were treated with cyclosporine A (CsA; 15 mg/kg per day) or tacrolimus (5 mg/kg per day) for 7 d each. Both drugs markedly lowered COX-2 expression while COX-1 expression remained unaltered. Furthermore, CsA blunted the increase of renocortical COX-2 expression in response to low salt intake or a combination of low-salt diet with the ACE inhibitor ramipril (10 mg/kg per day), which strongly stimulates renocortical COX-2 expression. At the same time, calcineurin inhibitors moderately enhanced basal as well as stimulated renin secretion and renin gene expression. These findings suggest that inhibition of calcineurin could be a crucial determinant for the regulated expression of COX-2 in the kidney. Inhibition of COX-2 expression may therefore at least in part account for the well-known adverse effects of immunosuppressants in the kidney. Moreover, our data suggest that the stimulation of the renin system by low salt and by ACE inhibitors is not essentially mediated by COX-2 activity.

Recombinant human growth hormone post-renal transplantation in children: a randomized controlled study of the NAPRTCS

BACKGROUND

Growth retardation persists in renal allograft recipients despite successful transplantation. The etiology is multi-factorial including the adverse effects of corticosteroids, suboptimal allograft function, and perturbations of the GH/GF axis. Recombinant human growth hormone (rhGH) has been effective in improving growth velocity; however, allograft dysfunction has been reported. Therefore, a randomized controlled study was undertaken.

METHODS

Sixty-eight growth retarded pediatric renal allograft recipients were enrolled in a one-year randomized controlled study to determine the efficacy and safety of rhGH. A protocol biopsy was performed prior to enrollment.

RESULTS

After one year, the delta SDS (standardized height) was +0.49 +/- 0.10 in the treatment group (N = 30) compared to -0.10 +/- 0.08 in the control group (N = 22; P < 0.001). During the first year, there were no rejection episodes in the treatment group and three in the control group. After the first year, when all recipients were receiving rhGH, there were three patients in the treatment group and two patients in the control group who experienced an acute rejection episode. Prior to enrollment, more than one acute rejection episode was predictive of a subsequent rejection following enrollment. There was no difference in adverse events between the two groups.

CONCLUSION

In conclusion, rhGH is effective in improving the growth velocity of pediatric renal allograft recipients and is not associated with an increase in adverse events.

Angiotensin-converting enzyme inhibition induces apoptosis in erythroid precursors and affects insulin-like growth factor-1 in posttransplantation erythrocytosis

A number of studies suggest that erythropoietin (Ep), angiotensin II, and insulin-like growth factor (IGF-1) are involved in the pathogenesis of posttransplantation erythrocytosis (PTE). Angiotensin-converting enzyme inhibitors (ACEI) are the treatment of choice in PTE, but their mechanism of action is unclear. It was shown previously that ACEI added directly to cultures of erythroid precursors from patients with PTE inhibit colony growth. In this report, the effect of ACEI on CD34+ erythroid precursor apoptosis was studied, as were hematocrit (Hct), Ep, IGF-1, and IGF-binding protein 3 (IGF-BP3) levels. Ten patients with PTE, 10 transplant control patients, and 7 normal control subjects were studied. Peripheral blood CD34+ cells were isolated, and apoptosis was assessed by annexin assay and DNA laddering before and during ACEI therapy. At the same time, Hct, Ep, IGF-1, and IGF-BP3 levels were measured. Baseline CD34+ cell number, CD34+ apoptosis, Ep, IGF-1, and IGF-BP3 levels were the same between PTE and transplant control subjects. ACEI therapy was associated with a striking increase in CD34+ cell apoptosis and a decrease in Hct in both groups. In contrast to control subjects, patients with PTE on ACEI showed a significant decrease in IGF-1 levels and a greater percentage decrease in Hct. In normal control subjects, ACEI therapy was associated with a fall in Hct but no change in CD34+ cell apoptosis. In PTE, ACEI-related increase in erythroid progenitor apoptosis may partially explain the ACEI-associated decrease in Hct. However, it is not clear that erythroid precursor apoptosis is related to changes in IGF-1 or IGF-BP3.

Effects of losartan and amlodipine on intrarenal hemodynamics and TGF-beta(1) plasma levels in a crossover trial in renal transplant recipients

Hypertension and hyperfiltration are two important risk factors for the development of chronic allograft nephropathy. Transforming growth factor-beta(1) (TGF-beta(1)) is the main cytokine involved in the fibrotic process that is involved in chronic rejection. Angiotensin II upregulates TGF-beta(1) production. Angiotensin II receptor antagonists therefore could not only control BP but also reduce TGF-beta(1) production in renal transplant patients. The aim of this study was to compare the effects of losartan and amlodipine on renal hemodynamics, as well as TGF-beta(1) and endothelin-1 (ET-1) plasma levels in a group of renal transplant patients who had normal renal function and who were treated with cyclosporine. Seventeen renal transplant patients who were receiving cyclosporine and who had normal graft function were included in a random 2 x 2 crossover trial with amlodipine and losartan (6 wk with each therapy). Three studies were performed (at baseline and at the end of both treatment periods) to determine renal hemodynamics, TGF-beta(1), and ET-1. Both treatments controlled BP to a similar degree, but only amlodipine increased GFR through an increase in the estimated glomerular hydrostatic pressure and filtration fraction. In contrast, losartan maintained GFR and reduced estimated glomerular hydrostatic pressure and filtration fraction significantly. Losartan and amlodipine had opposite effects on TGF-beta(1). Amlodipine did not affect TGF-beta(1) concentrations. In contrast, losartan reduced the plasma levels of TGF-beta(1) by approximately by 50% (from baseline, 5.2 to 2.6 ng/ml; P: = 0.01); the majority of the patients reached normal levels of TGF-beta(1). ET-1 concentrations were significantly higher during amlodipine compared with losartan treatment. The present study documents that with similar control of BP, losartan and amlodipine have opposite effects on renal hemodynamics and on TGF-beta1 concentrations. These differences could be important for the management of chronic allograft nephropathy.

Calcineurin blockade prevents cardiac mitogen-activated protein kinase activation and hypertrophy in renovascular hypertension

Chronic stimulation of the renin-angiotensin system induces an elevation of blood pressure and the development of cardiac hypertrophy via the actions of its effector, angiotensin II. In cardiomyocytes, mitogen-activated protein kinases as well as protein kinase C isoforms have been shown to be important in the transduction of trophic signals. The Ca(2+)/calmodulin-dependent phosphatase calcineurin has also been suggested to play a role in cardiac growth. In the present report, we investigate possible cross-talks between calcineurin, protein kinase C, and mitogen-activated protein kinase pathways in controlling angiotensin II-induced hypertrophy. Angiotensin II-stimulated cardiomyocytes and mice with angiotensin II-dependent renovascular hypertension were treated with the calcineurin inhibitor cyclosporin A. Calcineurin, protein kinase C, and mitogen-activated protein kinase activations were determined. We show that cyclosporin A blocks angiotensin II-induced mitogen-activated protein kinase activation in cultured primary cardiomyocytes and in the heart of hypertensive mice. Cyclosporin A also inhibits specific protein kinase C isoforms. In vivo, cyclosporin A prevents the development of cardiac hypertrophy, and this effect appears to be independent of hemodynamic changes. These data suggest cross-talks between the calcineurin pathway, the protein kinase C, and the mitogen-activated protein kinase signaling cascades in transducing angiotensin II-mediated stimuli in cardiomyocytes and could provide the basis for an integrated model of cardiac hypertrophy.

Immunohistochemical analysis of renin activity in chronic cyclosporine nephropathy in childhood nephrotic syndrome

Although the pivotal role of activation of the intrarenal renin-angiotensin system (RAS) has been demonstrated in the rat model of chronic cyclosporine (CyA) nephropathy, it is still unclear whether intrarenal RAS activation is responsible for chronic CyA nephropathy in humans. Therefore, the distribution of renin in formalin-fixed, paraffin-embedded renal biopsy specimens obtained from 26 children who had idiopathic nephrotic syndrome (NS) and who were treated with long-term moderate-dose CyA was examined with the use of immunohistochemistry with rabbit polyclonal anti-human renin antibody. Nineteen patients had steroid-dependent NS, and 7 had steroid-resistant NS. However, CyA treatment led all of the latter patients into complete remission. All of the patients underwent renal biopsies at the start and the end of CyA treatment. In the pre-CyA specimens, immunoreactivity to renin was detected mainly in those parts of arterioles within the anatomically well-defined juxtaglomerular apparatus. In the post-CyA specimens, it was also detected in those parts of the vessels upstream from the juxtaglomerular apparatus. Moreover, the ratio of the number of renin-positive cells to the number of glomeruli (histologic renin index) increased significantly with long-term CyA treatment (from 1.26+/-0.24 to 4.30+/-0.40, P<0.0001). Eleven of the post-CyA specimens showed mild or moderate CyA-associated arteriolopathy (CAA), whereas 15 showed no CAA. The histologic renin index was significantly higher in specimens with CAA than in those without CAA (5.16+/-0.59 versus 3.67+/-0.48, P = 0.031). Seven CAA-positive patients underwent repeat biopsies 6 to 12 mo after discontinuing the CyA. Their specimens showed an improvement in the CAA and significantly lower histologic renin index compared with the post-CyA (from 4.18+/-0.69 to 2.10+/-0.25, P = 0.018). Eleven of the post-CyA specimens showed mild to moderate interstitial fibrosis, and 15 showed no fibrosis. There was no significant difference in immunoreactivity to renin between the specimens with interstitial fibrosis and those without. However, patients with interstitial fibrosis had significantly longer periods of heavy proteinuria during CyA therapy, because of either steroid-resistant NS or frequent relapses of NS (83+/-18 versus 35+/-12 d, P = 0.030). These findings indicate that long-term CyA treatment for idiopathic NS in children may stimulate renin production in arterioles. They also suggest that CyA-stimulated intrarenal RAS activation is responsible for the development of CAA and that CyA-induced interstitial fibrosis is potentiated by long-term heavy proteinuria and is at least partly independent of CyA-stimulated intrarenal RAS activation.

Regression of left ventricular hypertrophy by lisinopril after renal transplantation: role of ACE gene polymorphism

BACKGROUND

Cardiac complications are the main cause of death in renal transplantation (RT), and left ventricular hypertrophy (LVH) may play an important role in these patients. The unfavorable genotype of the angiotensin-converting enzyme (ACE) gene has been associated with cardiovascular disease, including LVH. ACE inhibitors (ACEIs) reduce LVH, but little is known about the effects of ACEIs on LVH in RT patients with different insertion/deletion (I/D) genotypes of the ACE gene.

METHODS

We prospectively studied 57 stable nondiabetic RT patients with hypertension and echocardiographic LVH as well as a functional graft for 69.5 +/- 5.6 months. Patients randomly received either lisinopril 10 mg/day (group A, N = 29; 5 were excluded due to reversible acute renal failure) or placebo (group B, N = 28) for 12 months. Echocardiography (M-mode, 2-B, and color flow Doppler) was performed at baseline and 6 and 12 months later by the same examiner without previous knowledge of the genetic typing. The ACE genotype (I or D alleles) was ascertained by polymerase chain reaction (PCR; group A, DD = 10 and ID/II = 14; group B, DD = 15 and ID/II = 13).

RESULTS

All patients maintained a good renal function (serum creatinine <2.5 mg/dL) during the follow-up and both groups received a similar proportion of antihypertensive drugs (beta-blockers 83 vs. 79%; Ca antagonists 66 vs. 68%; alpha1-adrenoreceptor antagonists 50 vs. 67%) during the study. As expected, mean arterial blood pressure and hemoglobin levels showed a higher percentage reduction in group A versus group B (-4 +/- 2.8 vs. 2.1 +/- 2.6%, P = 0.07, and -11.5 +/- 1.5 vs. -0.5 +/- 2.3%, P < 0.01, respectively). Group A patients showed a significantly higher decrement in LV mass index (LVMI) than group B at the end of follow-up, after adjusting for age, baseline LVMI, time after grafting and changes in systolic blood pressure, renal function, and hemoglobin levels (group A, -9.5 +/- 3.5% vs. group B, 3 +/- 3.2%, P < 0.05). As a result, 46% of group A and only 7% of group B patients showed a reduction of LVMI >/=15% (P < 0.01). The beneficial effect of lisinopril on LVMI reduction was more evident in DD patients (placebo DD, 8.4 +/- 4.1% vs. lisinopril DD, -7.2 +/- 5.3, P < 0.05), and a trend was observed in patients with other genotypes (placebo ID/II, 2.8 +/- 5.4% vs. lisinopril ID/II, -11.4 +/- 5%, P = 0.33).

CONCLUSIONS

Lisinopril decreases LVM in renal transplant patients with hypertension and LVH, and the ACE gene polymorphism may predict the beneficial effect of this therapy. This finding may be important in targeting prophylactic interventions in this population.

CyA-mediated renal interstitial and vascular lesions in the rat under low-sodium diet

Nephrotoxicity of CyA was analyzed histologically in rats fed a low-sodium diet. CyA was subcutaneously administered daily at a dose of 15 mg/kg for 10 or 35 days with or without prior uninephrectomy (UNT) in male Sprague-Dawley rats receiving a low-sodium diet (0.03% sodium). CyA-administered rats showed impaired renal function as well as tubulo-interstitial lesions, such as edema, tubular basement membrane changes, and tubular atrophy, in the cortex, especially in the subcapsular portion, within 10 days. On day 35, the tubulo-interstitial lesions were advanced with mild focal interstitial fibrosis. These lesions were mild in the UNT group compared to the non-UNT group. Immunohistochemically, CyA treatment caused an increase in number of renin-positive cells in the afferent arteriolar wall at juxtaglomerular area. These cells lost the expression of calponin, which is a marker of mature smooth muscle cells. In addition, in afferent arterioles and interlobular arteries, electron-dense fibrous bodies were found in the smooth muscle cells on days 10 and 35. Immunoelectron microscopically, these bodies showed scattered positive staining for calponin and alpha-actinin, were negative or only peripherally positive for alpha-SMA and vimentin, and were completely negative for desmin. This study revealed that CyA could cause interstitial lesions starting in the subcapsular portion of the renal cortex and vascular lesions of the preglomerular artery. Increases in number of renin granules and formation of cytoplasmic fibrous bodies in smooth muscle cells could be the forerunner of severe arteriolar wall damage.

Renin-angiotensin system gene expression in post-transplant hypertension predicts allograft function

BACKGROUND

Registry analyses and single-center studies have demonstrated that hypertension significantly increases the risk for chronic graft loss. The graft itself may contribute to posttransplant hypertension, and intragraft vasoactive hormones therefore, may be dysregulated in posttransplant hypertension.

METHODS

We used the reverse-transcription polymerase chain reaction to assess the intragraft regulation of renin-angiotensin system transcripts in biopsy samples from 42 stable renal transplant patients with posttransplant hypertension. We also examined mRNA expression of inducible nitric oxide synthase, transforming growth factor-beta (TGF-beta), select cytokines, and metalloproteinase transcripts in biopsy tissue. Polymerase chain reaction products were quantitated using high performance liquid chromatography and normalized to beta-actin mRNA expression. Serum creatinine, glomerular filtration rate or creatinine clearance and tubular atrophy on biopsy were concurrently assessed.

RESULTS

Renin and select Thl cytokine mRNA expression correlated with blood pressure. Type 1 angiotensin II receptor mRNA expression significantly correlated with glomerular filtration rate or creatinine clearance (P = 0.034) and inversely correlated with Th1 cytokines, inducible nitric oxide synthase, and cyclooxygenase-1 mRNA expression (P< or =0.013 for each). Type 1 angiotensin II receptor mRNA also approached a significant inverse correlation with TGF-beta mRNA expression (P = 0.09). Conversely, angiotensin-converting enzyme mRNA expression directly correlated with Thl cytokine (P< or =0.008 for each) and TGF-beta mRNA expression (P = 0.006). Type 1 angiotensin II receptor mRNA expression also correlated with matrix metalloproteinase-1 promoter region, tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) and tissue inhibitor of matrix metalloproteinase-3 mRNA expression. Notably, matrix metalloproteinase-1 promoter region, tissue inhibitor of matrix metalloproteinase-2, and tissue inhibitor of matrix metalloproteinase-3 inversely correlated with TGF-beta mRNA expression (P< or =0.0027 for each). Type 1 angiotensin II receptor mRNA expression at biopsy directly correlated with glomerular filtration rate at 2 year's follow-up. However, angiotensin-converting enzyme mRNA expression at biopsy inversely correlated with glomerular filtration rate at 2 year's follow-up.

CONCLUSIONS

These data suggest that allograft-level RAS gene expression may be predictive of future graft function in the setting of diastolic hypertension.

Endothelial dysfunction in renal transplant recipients maintained on cyclosporine

BACKGROUND

Hypertension is almost universal following renal transplantation and may contribute to the already poor cardiovascular prognosis of this group. Cyclosporine-induced hypertension is a particular problem and has variously been attributed to increased sympathetic nerve activity, salt and water retention, and increased circulating endothelin levels. However, the effects of cyclosporine on the L-arginine/nitric oxide (NO) system in vivo in humans are unknown. In this present study, we examined basal and stimulated NO production from the vascular endothelium in cyclosporine-treated renal transplant recipients using the technique of forearm venous plethysmography.

METHODS

In study 1, stimulated NO production was assessed in 9 cyclosporine-treated renal transplant recipients (CsA), 7 azathioprine-treated renal transplant recipients (AZA), and 12 controls, using carbachol (an endothelium-dependent vasodilator) and sodium nitroprusside (an endothelium-independent vasodilator). In study 2, basal NO production was assessed in 9 cyclosporine-treated patients and 11 controls using L-NMMA (inhibits NO synthase), with norepinephrine as a control vasoconstrictor. Drugs were infused into the nondominant forearm through a sterile 27-gauge needle, and changes in forearm blood flow (FBF) were measured using venous occlusion plethysmography.

RESULTS

In study 1, sodium nitroprusside caused a similar dose-dependent increase in FBF in all groups. However, the median (range) percentage increase FBF to carbachol (3 micrograms/min) was markedly reduced in the CsA patients (188.8; 72.5 to 385.1) compared with AZA patients (378.1; 124.0 to 548.9; P = 0.042) and to controls (303.8; 124.8 to 813.3; P = 0.028). In study 2, the maximum percentage reduction in FBF to L-NMMA (4 mumol/min) was less pronounced in CsA patients (-19.5; -4.7 to -63.1) compared with controls (-39.5; -15.7 to -52.8; P = 0.056), and while controls vasoconstricted to the maximum dose of norepinephrine (240 pmol/min) as expected (-26.9; -1.4 to -38.6), CsA patients as a group tended to vasodilate (7.9; -36.8 to 92.6; P = 0.02).

CONCLUSION

These data demonstrate impaired stimulated and basal NO production in CsA patients, indicating endothelial dysfunction. This may predispose patients to atherosclerosis and may be involved in the etiology of post-transplant hypertension.

Vasoactive substances in renal transplantation

During and after transplantation the kidney experiences a variety of insults that result in functional impairment and structural damage. These changes are mediated or influenced by hormones, cytokines, enzymes and growth factors, which are excreted by endothelial, graft parenchymal as well as by graft infiltrating cells. This review evaluates the pathophysiological role of vasoactive substances (for example, the vasoconstrictors angiotensin II and endothelin, as well as vasodilators such as nitric oxide, adrenomedullin and atrial natriuretic peptide) in kidney transplantation and summarizes recent reports that indicate that targeting vasoactive substances may represent effective therapeutic strategies for the achievement of long-term allograft survival.

Cyclosporine-induced interstitial fibrosis and arteriolar TGF-beta expression with preserved renal blood flow

BACKGROUND

Cyclosporine A (CsA)-induced chronic nephrotoxicity is characterized by interstitial fibrosis and afferent arteriole hyalinosis. CsA lesion has been linked to maintained renal vasoconstriction and narrowing of the afferent arteriole lumen diameter, leading to preglomerular ischemia. We investigated the role of renal hemodynamics in CsA-induced transforming growth factor (TGF-beta) expression and interstitial fibrosis.

METHODS

Groups of rats fed a low salt diet were given CsA 5 mg/kg/day (CsA) or the vehicle (olive oil, [VH]) s.c. and had the renal blood flow (RBF), glomerular filtration rate (GFR), mean arterial pressure, renal vascular resistance, renal histologic changes, and immunohistochemical features for macrophages and TGF-beta evaluated after 1, 2, and 8 weeks of treatment.

RESULTS

At week 1, despite normal renal hemodynamics and MAP, there was a significant macrophage interstitial influx in CsA-treated rats (70+/-16 vs. 29+/-4 cells+/0.5 mm2, in CsA vs. VH, P=0.02) that was progressive with treatment (80+/-13 vs. 32+/-8 cells+/0.5 mm2, P=0.016 and 197+/-36 vs. 23+/-3 cells+/0.5 mm2, P=0.0002, CsA vs. VH at 2 and 8 weeks, respectively). After 2 weeks of treatment, CsA animals developed a significant interstitial fibrosis, with preserved RBF, even when it was assessed 2 hr after CsA injection. There was a significant increase in the immunostaining for TGF-beta in the juxtaglomerular arterioles in CsA-treated rats (48.6+/-3.8 vs. 35.1+/-1.1%, CsA vs. VH at 2 weeks, P<0.05 and 59.0+/-3.2 vs. 37.0+/-2.1%, CsA vs. VH at 8 weeks, P=0.0001). A significant and progressive GFR decrease followed the renal structural injury of CsA treatment. Arteriolar and glomerular anatomic injury were not found throughout the study.

CONCLUSIONS

Low CsA doses might generate interstitial fibrosis without any decrease in RBF or structural arteriolar lesion evidence, possibly through early macrophage influx and increased TGF-beta expression. It clearly seems that CsA-induced ischemia and tubulointerstitial injury may occur independently, suggesting that chronic CsA nephrotoxicity may be very hard to prevent or even not be preventable at all.

Effects of nitric oxide blockade and cyclosporin A on cardiovascular and renal function in normal man

OBJECTIVE

The present study investigated whether the nitric oxide (NO) system is involved in cyclosporin A (CsA)-induced changes in cardiovascular and renal function in man.

SUBJECTS AND METHODS

Ten healthy volunteers were investigated twice--with and without intake of a single dose of CsA (8 mg/kg). N(G)-monomethyl-L-arginine (L-NMMA; 3 mg/kg) was injected 4 h after study start on each day.

RESULTS

There was no change in glomerular filtration rate (GFR) on the day without CsA. CsA alone did not change GFR, but after L-NMMA injection, GFR decreased significantly from 101 +/- 4 to 91 +/- 4 ml/min. L-NMMA increased renal vascular resistance with no difference between the two study days. CsA increased significantly the diastolic blood pressure (BP) by 8 +/- 2% and the heart rate (HR) by 30 +/- 4%, without changes in cardiac output L-NMMA further increased BP by around 8%, and decreased HR by 11% and cardiac output by 20% on both study days. L-NMMA decreased urinary flow rate by around 25% and renal sodium clearance from 1.1 to approximately 0.6 ml/min on both study days. CsA decreased plasma renin significantly and increased the urinary excretion rate of prostaglandin E2 (PgE2), 6-keto-prostaglandin F1alpha (6-keto-PgF1alpha) and thromboxane B2(TxB2) when compared to the control day. The urinary excretion rate of NOx and cGMP declined gradually on the control day. In contrast, there was a minor, non-significant increase in NOx and cGMP excretion after CsA, followed by a decrease (29 +/- 2 and 16 +/- 4%, respectively) after L-NMMA in parallel with the decrease in GFR.

CONCLUSION

The present findings suggest that NO does not play a major role during acute CsA-induced changes in cardiovascular function and renal haemodynamics in man. Renal NO synthesis, however, may attenuate the acute CsA-induced decrease in GFR.

Correlation between angiotensin-converting enzyme gene insertion/deletion polymorphism and kidney graft long-term outcome in pediatric recipients: a single-center analysis

BACKGROUND

Despite numerous advances in the areas of organ preservation, histocompatibility, and immunosuppression, chronic deterioration of organ allograft function, referred to as "chronic rejection," still remains the main obstacle to long-term graft survival. The common feature of chronic rejection is a concentric generalized graft arteriosclerosis associated with interstitial fibrosis that reflects an allogeneic injury to graft arteries, possibly worsened by other alloantigen-independent risk factors. The presence of the angiotensin I-converting enzyme (ACE) gene-deleted (D) allele has been associated, when in homozygosity, with increased risk of cardiovascular diseases and with an accelerated progression of organ damage in a variety of kidney diseases. In this study, we analyzed whether the insertion/deletion polymorphism of the ACE gene, because of its negative prognostic impact on cardiovascular and renal pathology, could have any influence on kidney graft survival in pediatric recipients.

METHODS

DNA was isolated from peripheral blood mononuclear cells from 146 pediatric dialysis patients (mean age: 12.9 years) who received a first kidney graft at our center between December 1985 and July 1997. To rule out any bias due to acute graft losses, only 119 patients who reached a minimum of 12 months of graft survival were considered for statistical analysis. The insertion/deletion polymorphism of the ACE gene was detected using a polymerase chain reaction technique with two flanking primers.

RESULTS

The results demonstrated that (i) the distribution of DD and non-DD (ID + II) genotypes was 36.1% (43 patients) and 63.8% (76 patients), respectively; (ii) actuarial graft survival at 7, 8, 9, and 10 years in patients with non-DD genotype was significantly higher than that in patients with DD genotype (7 years: 94.6% vs. 72.4%, P<0.05; 8 years: 94.6% vs. 62%, P<0.025; 9 years: 87.3% vs. 51.4%, P<0.025; 10 years: 76.3% vs. 25.7%, P<0.01).

CONCLUSIONS

In conclusion, the above data indicate that DD genotype is associated in pediatric kidney graft recipients with a shorter long-term kidney graft survival and suggest a possible role of this genotype as a cofactor in the progression of nonimmunological injuries leading to chronic kidney graft failure.

Aluminum exacerbates cyclosporin induced nephrotoxicity in rats

Cyclosporin (CSA) has been universally used as an immunosuppressant for the management of allotransplantation and autoimmune diseases. However, nephrotoxicity of CSA limits its use to optimum level. Aluminum (Al) is an extensively distributed element in the environment and human exposure to this metal is unavoidable. Recent studies suggest that even a slight impairment of renal function may increase the Al body burden significantly, which may lead to neurotoxicity, nephrotoxicity, osteodystrophy or hypochromic anemia. In the present study, an attempt was made to study the effect of concomitant use of Al and CSA on structure and function of kidney in rats. This study was undertaken in two steps. In the first set of experiments, the effect of single dose of Al (1% Al2(SO4)3 18H2O) on the nephrotoxicity of multiple doses of CSA (12.5 mg/kg, 25 mg/kg and 50 mg/kg) was studied, where as in the second set of experiments the effect of multiple doses of Al (0.25%, 0.5% and 1%) on single dose of CSA (50 mg/kg) was undertaken. Male Sprague-Dawley rats (weighing 230 +/- 20 g) were used in this study. CSA was given once a day by gavage for seven days, where as Al was given in drinking water for the same period. Twenty four hours after the last dose of CSA, animals were sacrificed and blood and kidney were collected for biochemical and histopathological studies. The bio-chemical parameters included blood urea nitrogen (BUN), serum creatinine (SCr), CSA and Al levels. The kidney homogenates were assayed for malondialdehyde (MDA) and lipid hydroperoxides (LPH). Treatment of rats with CSA alone produced dose-dependent structural and functional changes in kidney. Although Al alone failed to produce any deleterious effect on renal function, it significantly increased the bioavailability and nephrotoxicity of CSA. Al also exacerbated CSA induced increase in oxidative stress (as evident by increased MDA and LPH). Thus, the exacerbation of CSA nephrotoxicity by Al may be attributed to increased bioavailability of CSA and excessive generation of free radicals following concomitant use of these drugs.

Treatment of hypertension after renal transplantation: long-term efficacy of verapamil, enalapril, and doxazosin

Normal blood pressure is a good marker of graft survival after renal transplantation, and effective antihypertensive treatment reduces the progression of graft damage. We conducted a long-term follow-up study of 88 hypertensive renal transplant recipients, all of whom were taking sustained cyclosporine A (CsA) immunosuppression. The patients were treated for at least three years, and initially received 240 mg/day of verapamil (N = 24, group I), 5 mg/day of enalapril (N = 24, group II) or 1 mg/day of doxazosin (N = 40, group III). Baseline creatinine did not differ in the three groups, but proteinuria was higher in the enalapril group (7 patients had proteinuria > 1.5 g/day). Treatment was withdrawn in 5 patients in the verapamil group, 5 in the enalapril group and 2 in the doxazosin group due to drug-related side effects. Blood pressure (BP) control at three years was equivalent in the three groups (systolic BP, group I 157 +/- 12; group II 149 +/- 19; group III 154 +/- 21; diastolic BP, group I 90 +/- 8.7, group II 84 +/- 9.8, group III 90.5 +/- 16; mean BP, group I 113 +/- 7, group II 106 +/- 10, group III 106 +/- 29). Two patients in group I, 3 in group II and 15 in group III required additional antihypertensive drugs. CsA levels increased in the verapamil-treated patients, allowing for an early decrease in CsA doses (1 year doses, 3.3 +/- 1 mg/kg body wt/day in group I, 4.3 +/- 1.6 in group II, 3.7 +/- 1.6 in group III). Six cardiovascular events occurred, 3 in group I, 1 in group II, and 2 in group III patients. One patient died in the enalapril group and another in the doxazosin group. Eight verapamil-treated patients, 8 enalapril-treated patients and 4 doxazosin-treated patients lost their grafts due to biopsy-proven chronic transplant nephropathy. In conclusion, the three antihypertensive agents are effective in reducing blood pressure, with no clear advantage of one above any other. Verapamil allows the CsA dose to be reduced, thus decreasing the cost of immunosupression. Enalapril can be a more effective antiproteinuric agent, but hyperkalemia or impaired allograft function may occur in patients with non-optimal allograft function. Doxazosin offers an excellent safety and efficacy profile, and when not efficient by itself in controlling blood pressure, is an ideal concomitant agent in hypertensive renal transplant patients.