Impact of tacrolimus and mycophenolate mofetil combination on cardiovascular risk profile after kidney transplantation

Therapy in the Course of Kidney Graft Rejection-Implications for the Cardiovascular System-A Systematic Review

Kidney graft failure is not a homogenous disease and the Banff classification distinguishes several types of graft rejection. The maintenance of a transplant and the treatment of its failure require specific medications and differ due to the underlying molecular mechanism. As a consequence, patients suffering from different rejection types will experience distinct side-effects upon therapy. The review is focused on comparing treatment regimens as well as presenting the latest insights into innovative therapeutic approaches in patients with an ongoing active ABMR, chronic active ABMR, chronic ABMR, acute TCMR, chronic active TCMR, borderline and mixed rejection. Furthermore, the profile of cardiovascular adverse effects in relation to the applied therapy was subjected to scrutiny. Lastly, a detailed assessment and comparison of different approaches were conducted in order to identify those that are the most and least detrimental for patients suffering from kidney graft failure.

Hypertension in kidney transplant recipients

Kidney transplantation is considered the treatment of choice for end-stage kidney disease patients. However, the residual cardiovascular risk remains significantly higher in kidney transplant recipients (KTRs) than in the general population. Hypertension is highly prevalent in KTRs and represents a major modifiable risk factor associated with adverse cardiovascular outcomes and reduced patient and graft survival. Proper definition of hypertension and recognition of special phenotypes and abnormal diurnal blood pressure (BP) patterns is crucial for adequate BP control. Misclassification by office BP is commonly encountered in these patients, and a high proportion of masked and uncontrolled hypertension, as well as of white-coat hypertension, has been revealed in these patients with the use of ambulatory BP monitoring. The pathophysiology of hypertension in KTRs is multifactorial, involving traditional risk factors, factors related to chronic kidney disease and factors related to the transplantation procedure. In the absence of evidence from large-scale randomized controlled trials in this population, BP targets for hypertension management in KTR have been extrapolated from chronic kidney disease populations. The most recent Kidney Disease Improving Global Outcomes 2021 guidelines recommend lowering BP to less than 130/80 mmHg using standardized BP office measurements. Dihydropyridine calcium channel blockers and angiotensin-converting enzyme inhibitors/angiotensin-II receptor blockers have been established as the preferred first-line agents, on the basis of emphasis placed on their favorable outcomes on graft survival. The aim of this review is to provide previous and recent evidence on prevalence, accurate diagnosis, pathophysiology and treatment of hypertension in KTRs.

New Approaches to Cardiovascular Disease and Its Management in Kidney Transplant Recipients

Cardiovascular events, including ischemic heart disease, heart failure, and arrhythmia, are common complications after kidney transplantation and continue to be leading causes of graft loss. Kidney transplant recipients have both traditional and transplant-specific risk factors for cardiovascular disease. In the general population, modification of cardiovascular risk factors is the best strategy to reduce cardiovascular events; however, studies evaluating the impact of risk modification strategies on cardiovascular outcomes among kidney transplant recipients are limited. Furthermore, there is only minimal guidance on appropriate cardiovascular screening and monitoring in this unique patient population. This review focuses on the limited scientific evidence that addresses cardiovascular events in kidney transplant recipients. Additionally, we focus on clinical management of specific cardiovascular entities that are more prevalent among kidney transplant recipients (ie, pulmonary hypertension, valvular diseases, diastolic dysfunction) and the use of newer evolving drug classes for treatment of heart failure within this cohort of patients. We note that there are no consensus documents describing optimal diagnostic, monitoring, or management strategies to reduce cardiovascular events after kidney transplantation; however, we outline quality initiatives and research recommendations for the assessment and management of cardiovascular-specific risk factors that could improve outcomes.

Role of hypertension in kidney transplant recipients

Cardiovascular events are one of the leading causes of mortality in kidney transplant recipients. Hypertension is the most common comorbidity accompanying chronic kidney disease, with prevalence remaining as high as 90% even after kidney transplantation. It is often poorly controlled. Abnormal blood pressure profiles, such as masked or white-coat hypertension, are also extremely common in these patients. The pathophysiology of blood pressure elevation in kidney transplant recipients is complex and includes transplantation-specific risk factors, which are added to the traditional or chronic kidney disease-related factors. Despite these observations, hypertension management has been an under-researched area in kidney transplantation. Thus, relevant evidence derives either from studies in the general population or from small trials in kidney transplant recipients. Based on the relevant guidelines in the general population, lifestyle modifications should probably be applied as the first step of hypertension management in kidney transplant recipients. The optimal pharmacological management of hypertension in kidney transplant recipients is also not clear. Dihydropyridine calcium channel blockers are commonly used as first line agents because of their lack of adverse effects on the kidney, while other antihypertensive drug classes are under-utilised due to fear of the possible haemodynamic consequences on renal function. This review summarizes the existing data on the pathophysiology, diagnosis, prognostic significance and management of hypertension in kidney transplantation.

Thirty Years of Tacrolimus in Clinical Practice

Tacrolimus was discovered in 1984 and entered clinical use shortly thereafter, contributing to successful solid organ transplantation across the globe. In this review, we cover development of tacrolimus, its evolving clinical utility, and issues affecting its current usage. Since earliest use of this class of immunosuppressant, concerns for calcineurin-inhibitor toxicity have led to efforts to minimize or eliminate these agents in clinical regimens but with limited success. Current understanding of the role of tacrolimus focuses more on its efficacy in preventing graft rejection and graft loss. As we enter the fourth decade of tacrolimus use, newer studies utilizing novel combinations (as with the mammalian target of rapamycin inhibitor, everolimus, and T-cell costimulation blockade with belatacept) offer potential for enhanced benefits.

High plasma guanidinoacetate-to-homoarginine ratio is associated with high all-cause and cardiovascular mortality rate in adult renal transplant recipients

L-Arginine:glycine amidinotransferase (AGAT) is the main producer of the creatine precursor, guanidinoacetate (GAA), and L-homoarginine (hArg). We and others previously reported lower levels of circulating and urinary hArg in renal transplant recipients (RTR) compared to healthy subjects. In adults, hArg emerged as a novel risk factor for renal and cardiovascular adverse outcome. Urinary GAA was found to be lower in children and adolescents with kidney transplants compared to healthy controls. Whether GAA is also a risk factor in the renal and cardiovascular systems of adults, is not yet known. In the present study, we aimed to investigate the significance of circulating GAA and the GAA-to-hArg molar ratio (GAA/hArg) in adult RTR. We hypothesized that GAA/hArg represents a measure of the balanced state of the AGAT activity in the kidneys, and would prospectively allow assessing a potential association between GAA/hArg and long-term outcome in RTR. The median follow-up period was 5.4 years. Confounders and potential mediators of GAA/hArg associations were evaluated with multivariate linear regression analyses, and the association with all-cause and cardiovascular mortality or death-censored graft loss was studied with Cox regression analyses. The study cohort consisted of 686 stable RTR and 140 healthy kidney donors. Median plasma GAA concentration was significantly lower in the RTR compared to the kidney donors before kidney donation: 2.19 [1.77-2.70] µM vs. 2.78 [2.89-3.35] µM (P < 0.001). In cross-sectional multivariable analyses in RTR, HDL cholesterol showed the strongest association with GAA/hArg. In prospective analyses in RTR, GAA/hArg was associated with a higher risk for all-cause mortality (hazard ratio (HR): 1.35 [95% CI 1.19-1.53]) and cardiovascular mortality (HR: 1.46 [95% CI 1.24-1.73]), independent of potential confounders. GAA but not GAA/hArg was associated with death-censored graft loss in crude survival and Cox regression analyses. The association of GAA and death-censored graft loss was lost after adjustment for eGFR. Our study suggests that in the kidneys of RTR, the AGAT-catalyzed biosynthesis of GAA is decreased. That high GAA/hArg is associated with a higher risk for all-cause and cardiovascular mortality may suggest that low plasma hArg is a stronger contributor to these adverse outcomes in RTR than GAA.

Calcineurin dephosphorylates Kelch-like 3, reversing phosphorylation by angiotensin II and regulating renal electrolyte handling

Calcineurin inhibitors (CNIs) are potent immunosuppressants; hypertension and hyperkalemia are common adverse effects. Activation of the renal Na-Cl cotransporter (NCC) is implicated in this toxicity; however, the mechanism is unknown. CNIs’ renal effects mimic the hypertension and hyperkalemia resulting from mutations in WNK kinases or in KLHL3-CUL3 ubiquitin ligase. WNKs activate NCC and are degraded by ubiquitylation upon their binding to KLHL3. The binding of WNKs to KLHL3 is prevented by KLHL3 mutations or by PKC-mediated KLHL3 phosphorylation at serine 433. This work shows that calcineurin dephosphorylates KLHL3^S433, promoting WNK4 degradation. Conversely, CNIs inhibit KLHL3^S433 dephosphorylation, preventing WNK degradation. These findings implicate calcineurin in the normal regulation of KLHL3’s binding of WNK4 and identify a direct target causing CNI-induced pathology.

Calcineurin is a calcium/calmodulin-regulated phosphatase known for its role in activation of T cells following engagement of the T cell receptor. Calcineurin inhibitors (CNIs) are widely used as immunosuppressive agents; common adverse effects of CNIs are hypertension and hyperkalemia. While previous studies have implicated activation of the Na-Cl cotransporter (NCC) in the renal distal convoluted tubule (DCT) in this toxicity, the molecular mechanism of this effect is unknown. The renal effects of CNIs mimic the hypertension and hyperkalemia that result from germ-line mutations in with-no-lysine (WNK) kinases and the Kelch-like 3 (KLHL3)–CUL3 ubiquitin ligase complex. WNK4 is an activator of NCC and is degraded by binding to KLHL3 followed by WNK4’s ubiquitylation and proteasomal degradation. This binding is prevented by phosphorylation of KLHL3 at serine 433 (KLHL3^S433-P) via protein kinase C, resulting in increased WNK4 levels and increased NCC activity. Mechanisms mediating KLHL3^S433-P dephosphorylation have heretofore been unknown. We now demonstrate that calcineurin expressed in DCT is a potent KLHL3^S433-P phosphatase. In mammalian cells, the calcium ionophore ionomycin, a calcineurin activator, reduces KLHL3^S433-P levels, and this effect is reversed by the calcineurin inhibitor tacrolimus and by siRNA-mediated knockdown of calcineurin. In vivo, tacrolimus increases levels of KLHL3^S433-P, resulting in increased levels of WNK4, phosphorylated SPAK, and NCC. Moreover, tacrolimus attenuates KLHL3-mediated WNK4 ubiquitylation and degradation, while this effect is absent in KLHL3 with S433A substitution. Additionally, increased extracellular K⁺ induced calcineurin-dependent dephosphorylation of KLHL3^S433-P. These findings demonstrate that KLHL3^S433-P is a calcineurin substrate and implicate increased KLHL3 phosphorylation in tacrolimus-induced pathologies.

Beneficial effects of mycophenolate mofetil on cardiotoxicity induced by tacrolimus in wistar rats

The immunosuppressive drug tacrolimus (TAC) is used clinically to reduce the rejection rate in transplant patients. TAC has contributed to an increased prevalence of cardiovascular disease in patients receiving solid organ transplantation. Mycophenolate mofetil (MMF), a potent inhibitor of de novo purine synthesis, is known to prevent ongoing rejection in combination with TAC. In the present study, we investigated the antioxidant and antigenotoxic effect of MMF on TAC-induced cardiotoxicity in rats. Oral administration of TAC at 2.4, 24, and 60 mg/kg b.w. corresponding, respectively, to 1, 10, and 25% of LD50 for 24 h caused cardiac toxicity in a dose-dependant manner. TAC increased significantly DNA damage level in hearts of treated rats. Furthermore, it increased malondialdehyde (MDA) and protein carbonyl (PC) levels and decreased catalase (CAT) and superoxide dismutase (SOD) activities. The oral administration of MMF at 50 mg/kg b.w. simultaneously with TAC at 60 mg/kg b.w. proved a significant cardiac protection by decreasing DNA damage, MDA, and PC levels, and by increasing the antioxidant activities of CAT and SOD. Thus, our study showed, for the first time, the protective effect of MMF against cardiac toxicity induced by TAC. This protective effect was mediated via an antioxidant process.

Nebivolol Effects on Nitric Oxide Levels, Blood Pressure, and Renal Function in Kidney Transplant Patients

In hypertensive kidney transplant recipients, the effects of nebivolol vs metoprolol on nitric oxide (NO) blood level, estimated glomerular filtration rate (eGFR), and blood pressure (BP) have not been previously reported. In a 12-month prospective, randomized, open-label, active-comparator trial, hypertensive kidney transplant recipients were treated with nebivolol (n=15) or metoprolol (n=15). Twenty-nine patients (nebivolol [n=14], metoprolol [n=15]) completed the trial. The primary endpoint was change in blood NO level after 12 months of treatment. Secondary endpoints were changes in eGFR, BP, and number of antihypertensive drug classes used. After 12 months of treatment, least squares mean change in plasma NO level in the nebivolol kidney transplant recipient group younger than 50 years was higher by 68.19% (99.17% confidence interval [CI], 13.02-123.36), 69.54% (99.17% CI, 12.71-126.37), and 66.80% (99.17% CI, 12.95-120.64) compared with the metoprolol group younger than 50 years, the metoprolol group 50 years and older, and the nebivolol group 50 years and older, respectively. The baseline to month 12 change in mean arterial BP, eGFR, and number of antihypertensive drug classes used was not significantly different between the treatment groups. In hypertensive kidney transplant recipients, nebivolol use in patients younger than 50 years increased blood NO.

Increased phosphorylation of the renal Na+-Cl- cotransporter in male kidney transplant recipient patients with hypertension: a prospective cohort

Evidence in rodents suggests that tacrolimus-induced posttransplant hypertension is due to upregulation of the thiazide-sensitive Na+-Cl- cotransporter NCC. Here, we analyzed whether a similar mechanism is involved in posttransplant hypertension in humans. From January 2013 to June 2014, all adult kidney transplant recipients receiving a kidney allograft were enrolled in a prospective cohort study. All patients received tacrolimus as part of the immunosuppressive therapy. Six months after surgery, we assessed general clinical and laboratory variables, tacrolimus trough blood levels, and ambulatory 24-h blood pressure monitoring. Urinary exosomes were extracted to perform Western blot analysis using total and phospho-NCC antibodies. A total of 52 patients, including 17 women and 35 men, were followed. At 6 mo after transplantation, of the 35 men, 17 developed hypertension and 18 remained normotensive, while high blood pressure was observed in only 3 of 17 women. The hypertensive patients were significantly older than the normotensive group; however, there were no significant differences in body weight, history of acute rejection, renal function, and tacrolimus trough levels. In urinary exosomes, hypertensive patients showed higher NCC expression (1.7±0.19) than normotensive (1±0.13) (P=0.0096). Also, NCC phosphorylation levels were significantly higher in the hypertensive patients (1.57±0.16 vs. 1±0.07; P=0.0049). Our data show that there is a positive correlation between NCC expression/phosphorylation in urinary exosomes and the development of hypertension in posttransplant male patients treated with tacrolimus. Our results are consistent with the hypothesis that NCC activation plays a major role in tacrolimus-induced hypertension.

Assessment and management of hypertension in transplant patients

Hypertension in renal transplant recipients is common and ranges from 50% to 80% in adult recipients and from 47% to 82% in pediatric recipients. Cardiovascular morbidity and mortality and shortened allograft survival are important consequences of inadequate control of hypertension. In this review, we examine the epidemiology, pathophysiology, and management considerations of post-transplant hypertension. Donor and recipient factors, acute and chronic allograft injury, and immunosuppressive medications may each explain some of the pathophysiology of post-transplant hypertension. As observed in other patient cohorts, renal artery stenosis and adrenal causes of hypertension may be important contributing factors. Notably, BP treatment goals for renal transplant recipients remain an enigma because there are no adequate randomized controlled trials to support a benefit from targeting lower BP levels on graft and patient survival. The potential for drug-drug interactions and altered pharmacokinetics and pharmacodynamics of the different antihypertensive medications need to be carefully considered. To date, no specific antihypertensive medications have been shown to be more effective than others at improving either patient or graft survival. Identifying the underlying pathophysiology and subsequent individualization of treatment goals are important for improving long-term patient and graft outcomes in these patients.

Posttransplant hypertension: multipathogenic disease process

Arterial hypertension is prevalent among kidney transplant recipients. The multifactorial pathogenesis involves the interaction of the donor and the recipient's genetic backgrounds with several environmental parameters that may precede or follow the transplant procedure (eg, the nature of the renal disease, the duration of the chronic kidney disease phase and maintenance dialytic therapy, the commonly associated cardiovascular disease with atherosclerosis and arteriosclerosis, the renal mass at implantation, the immunosuppressive regimen used, life of the graft, and de novo medical and surgical complications that may occur after a transplant). Among calcineurin inhibitors, tacrolimus seems to have a better cardiovascular profile. Steroid-free protocols and calcineurin inhibitor-free regimens seem to be associated with better blood pressure control. Posttransplant hypertension is a major amplifier of the chronic kidney disease-cardiovascular disease continuum. Despite the adverse effects of hypertension on graft and patient survival, blood pressure control remains poor because of the high cardiovascular risk profile of the donor-recipient pair. Although the optimal blood pressure level remains unknown, it is recommended to maintain the blood pressure at < 130/80 mm Hg and < 125/75 mm Hg in the absence or presence of proteinuria.

Risk factors for graft loss and mortality after renal transplantation according to recipient age: a prospective multicentre study

BACKGROUND

To describe the causes of graft loss, patient death and survival figures in kidney transplant patients in Spain based on the recipient's age.

METHODS

The results at 5 years of post-transplant cardiovascular disease (CVD) patients, taken from a database on CVD, were prospectively analysed, i.e. a total of 2600 transplanted patients during 2000-2002 in 14 Spanish renal transplant units, most of them receiving their organ from cadaver donors. Patients were grouped according to the recipient's age: Group A: <40 years, Group B: 40-60 years and Group C: >60 years. The most frequent immunosuppressive regimen included tacrolimus, mycophenolate mofetil and steroids.

RESULTS

Patients were distributed as follows: 25.85% in Group A (>40 years), 50.9% in Group B (40-60 years) and 23.19% in Group C (>60). The 5-year survival for the different age groups was 97.4, 90.8 and 77.7%, respectively. Death-censored graft survival was 88, 84.2 and 79.1%, respectively, and non death-censored graft survival was 82.1, 80.3 and 64.7%, respectively. Across all age groups, CVD and infections were the most frequent cause of death. The main causes of graft loss were chronic allograft dysfunction in patients <40 years old and death with functioning graft in the two remaining groups. In the multivariate analysis for graft survival, only elevated creatinine levels and proteinuria >1 g at 6 months post-transplantation were statistically significant in the three age groups. The patient survival multivariate analysis did not achieve a statistically significant common factor in the three age groups.

CONCLUSIONS

Five-year results show an excellent recipient survival and graft survival, especially in the youngest age group. Death with functioning graft is the leading cause of graft loss in patients >40 years. Early improvement of renal function and proteinuria together with strict control of cardiovascular risk factors are mandatory.

Protein kinase CbetaII-mediated phosphorylation of endothelial nitric oxide synthase threonine 495 mediates the endothelial dysfunction induced by FK506 (tacrolimus)

FK506 [tacrolimus; hexadecahydro-5,19-dihydroxy-3-[2-(4-hydroxy-3-methoxycyclohexyl)-1-methylethenyl]-14,16-dimethoxy-4,10,12,18-tetramethyl-8-(2-propenyl)-15,19-epoxy-3H-pyrido[2,1-c][1,4]oxa-azacyclotricosine-1,7,20,21(4H,23H)-tetrone] is used clinically to reduce the incidence of allograft rejection; however, chronic administration leads to endothelial dysfunction and hypertension. We have previously shown that FK506 activates Ca(2+)/diacylglycerol-dependent conventional protein kinase C (cPKC), which phosphorylates endothelial nitric oxide synthase (eNOS) at one of its inhibitory sites, Thr495. However, which cPKC isoform is responsible for phosphorylating eNOS Thr495 is unknown. The aim of the current study was to determine the cPKC isoform that is activated by FK506, leading to decreased endothelial function. FK506 reduced endothelium-dependent relaxation responses, yet had no effect on endothelium-independent relaxation responses in aortas from control mice. Of the various cPKC isoforms, only the administration of a PKCβ(II) isoform-specific peptide inhibitor restored aortic relaxation responses to that of controls. In aortic endothelial cells, FK506 significantly increased PKCβ(II) activation compared with vehicle-treated controls, and this was prevented by a PKCβ(II) isoform-specific peptide inhibitor. In addition, a PKCβ(II) isoform-specific peptide inhibitor prevented the increase in eNOS Thr495 phosphorylation induced by FK506. Taken together, our results indicate that β(II) is the cPKC isoform responsible for phosphorylating eNOS at the inhibitory site Thr495 in response to FK506. PKCβ(II) inhibition could prove beneficial in ameliorating the endothelial dysfunction and hypertension in patients treated with FK506.

Cardiovascular diseases after kidney transplantation in Korea

Cardiovascular disease (CVD) is the leading cause of death in renal allograft recipients with functioning graft. Our study aimed to determine the incidence and the risk factors of cardiovascular disease after renal transplantation in Korea. We retrospectively analyzed 430 adult recipients who underwent kidney transplantation between January 1997 and February 2007. CVD was defined as a composite outcome of ischemic heart disease, cerebrovascular accident and peripheral vascular disease. Mean age of recipients was 40.0±11.8 yr. Mean duration of follow-up was 72±39 months. The cumulative incidence of CVD after renal transplantation was 2.4% at 5 yr, 5.4% at 10 yr and 11.4% at 12 yr. Multivariate analysis revealed that recipient's age, diabetes mellitus and duration of dialysis before transplantation were associated with post-transplant CVD (hazard ratio 1.843 [95% CI, 1.005-3.381], 3.846 [95% CI, 1.025-14.432] and 3.394 [95% CI, 1.728-6.665] respectively). In conclusion, old age, duration of dialysis and diabetes mellitus are important risk factors for post-transplant CVD, although the incidence of post-renal transplant CVD is lower in Korea than that in western countries.

Hypertension in special populations: chronic kidney disease, organ transplant recipients, pregnancy, autonomic dysfunction, racial and ethnic populations

The benefits of appropriate blood pressure (BP) control include reductions in proteinuria and possibly a slowing of the progressive loss of kidney function. Overall, medication therapy to lower BP during pregnancy should be used mainly for maternal safety because of the lack of data to support an improvement in fetal outcome. The major goal of hypertension treatment in those with baroreceptor dysfunction is to avoid the precipitous, severe BP elevations that characteristically occur during emotional stimulation. The treatment of hypertension in African Americans optimally consists of comprehensive lifestyle modifications along with pharmacologic treatments, most often with combination, not single-drug, therapy.

Renal transplantation in the modern immunosuppressive era in Spain: four-year results from a multicenter database focus on post-transplant cardiovascular disease

To evaluate cardiovascular disease (CVD) after renal transplantation we established a CVD database (no-intervention) including all patients transplanted among 2000-2002 in 14 hospitals from Spain (Renal Forum Group) (n=2600). They were prospective followed annually thereafter and we present herein the most important results concerning survival figures and CVD at four years. Mean recipient age was 49.7+/-13.7 years: 16% retransplanted and 12.5% hyperimmunized. Tacrolimus, mycophenolate mofetil, and steroids was used in 63%. Acute rejection (AR) rate at 1 year was 14.8%. Graft and patient survival at 48 months were 85.6% (death censored) and 91.7% respectively. The first cause of graft loss was vascular in the first year, death with function during the 2-3 years, and chronic allograft nephropathy at the 4th year. Donor age, time on dialysis, acute tubular necrosis (ATN), AR, SCr at 6 months, the use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers in the first year, and systolic blood pressure at 24 months were independent risk factors for graft loss at 4th year. The first cause of death was CVD (predominantly ischemic heart disease (IHD) in the first year). Recipient age, ATN, and SCr at 6 months were independent predictors of mortality. Despite worsening of donor age, comorbidity, and advanced age of recipients, survival figures at four years are considered good in our Spanish non-selected population. Cardiovascular mortality is the most important cause of death and graft loss particularly, IHD in the first year. Therefore, to decrease post-transplant mortality a careful cardiovascular evaluation and treatment in the waiting list and a close follow-up of patients after transplantation is mandatory.

Tacrolimus reduces nitric oxide synthase function by binding to FKBP rather than by its calcineurin effect

Hypertension develops in many patients receiving the immunosuppressive drug tacrolimus (FK506). One possible mechanism for hypertension is a reduction in vasodilatory nitric oxide. We found that tacrolimus and a calcineurin autoinhibitory peptide significantly decreased vascular calcineurin activity; however, only tacrolimus altered intracellular calcium release in mouse aortic endothelial cells. In mouse aortas, incubation with tacrolimus increased protein kinase C activity and basal endothelial nitric oxide synthase phosphorylation at threonine 495 but reduced basal and agonist-induced endothelial nitric oxide synthase phosphorylation at serine 1177, a mechanism known to inhibit synthase activity. While this decreased nitric oxide production and endothelial function, the calcineurin autoinhibitory peptide had no such effects. Inhibition of ryanodine receptor opening or protein kinase C blocked the effects of tacrolimus. Since it is known that the FK506 binding protein (FKBP12/12.6) interacts with the ryanodine receptor to regulate calcium release, we propose this as the mechanism by which tacrolimus alters intracellular calcium and endothelial nitric oxide synthase rather than by its effect on calcineurin. Our study shows that prevention of the tacrolimus-induced intracellular calcium leak may attenuate endothelial dysfunction and the consequent hypertension.

Lipoprotein profile changes in children after renal transplantation in the modern immunosuppression era

There are little data on prevalence of dyslipidemia in pediatric kidney TX recipients in the modern IS era. LP profiles of 38 TX recipients receiving triple IS with MMF, prednisone, and tacrolimus were compared with those of 11 children on HD using mixed model multiple linear regression analysis of repeated measures after adjusting for age, sex, ethnicity, duration of ESRD, and BMI. TC and LDL levels were significantly higher in TX compared with HD, whereas there was no difference in the HDL, VLDL, and TG levels. TC and LDL in TX children had no association with age, sex, ethnicity, and duration of ESRD, stage of chronic kidney disease, DM, BMI percentile, and gain in percentage IBW. Five children treated with atrovastatin had a significant reduction in TC, LDL, VLDL, and TG at 3-6 months post-treatment compared with pretreatment levels, whereas there was no difference in HDL or tacrolimus levels after treatment. No side effects of therapy were observed. Although dyslipidemia remains a significant problem in pediatric renal TX recipients in the modern era, the prevalence may have decreased with use of newer IS drugs.

Three-year follow-up of malignancies in tacrolimus-treated renal recipients--an analysis of European multicentre studies

Five prospective, multicentre adult renal studies of three yr duration conducted in Europe for which tacrolimus was used as the primary immunosuppressant in at least one treatment arm was identified. This was confirmed by literature review as the only source fulfilling these criteria. Our goal was to identify absolute (reported) incidences of malignancies in patients exposed to tacrolimus and relative rates as a proportion of the total malignancies recorded for three yr after transplant. The five studies provided 2435 patients in nine different treatment regimens. All regimens combined tacrolimus with azathioprine or mycophenolate mofetil and corticosteroids except for one regimen which also employed daclizumab without corticosteroids. There were 83 patients with malignancies or 3.4% of the total population. No patient experienced more than I malignancy type. Malignancy incidences relative to those patients experiencing a malignancy were: total skin 37.3%, lymphoma 15.7%, and non-skin-non-lymphoma 47.0%. Annual occurrence of all malignancies reflected a progressive increase with time. While the larger proportion of lymphoma and non-skin-non-lymphoma malignancies occurred during the first year after transplant, malignancies affecting the skin increased more linearly with time. These findings are consistent with reports in the literature, reflect the current established experience with tacrolimus to date, and should provide a robust basis for future comparisons with tacrolimus-based immunosuppression.

Tabebuia avellanedae extracts inhibit IL-2-independent T-lymphocyte activation and proliferation

In order to identify new, immune modulating compounds, aqueous extracts of plants pre-selected on ethno-pharmacological knowledge were screened for inhibitory effects in an anti-CD3 driven lymphocyte proliferation assay (MTT-assay). We found for the extract of the inner bark of Tabebuia avellanedae (Tabebuia) dose dependent and reproducible inhibitory effects on lymphocyte proliferation. We further analyzed Tabebuia in flow cytometry based whole blood T-cell function assays. We found that Tabebuia inhibited dose dependent ConA stimulated T-cell proliferation. Decreased T-lymphocyte proliferation was associated with dose dependent reduction of CD25 and CD71 expression on T-lymphocytes. In contrast Tabebuia exerted no effects on cytokine expression (Il-2 and TNF-alpha) by PMA/Ionomycin stimulated T-lymphocytes. Concentrations of Tabebuia used were not toxic for lymphocytes as verified by trypan blue exclusion assay. Further experiments showed that the immune inhibitory effects by Tabebuia were not mediated by its pharmacological lead compound beta-lapachone and only observed in aqueous but not in ethanol plant extracts.