Pathogenesis and management of hypertension after kidney transplantation

Immunosuppressive Agents-Effects on the Cardiovascular System and Selected Metabolic Aspects: A Review

The widespread use of immunosuppressive drugs makes it possible to reduce inflammation in autoimmune diseases, as well as prevent transplant rejection in organ recipients. Despite their key action in blocking the body's immune response, these drugs have many side effects. These actions primarily affect the cardiovascular system, and the incidence of complications in patients using immunosuppressive drugs is significant, being associated with a higher incidence of cardiovascular incidents such as myocardial infarction and stroke. This paper analyzes the mechanisms of action of commonly used immunosuppressive drugs and their impact on the cardiovascular system. The adverse effect of immunosuppressive drugs is associated with toxicity within the cardiovascular system, which may be a problem in the clinical management of patients after transplantation. Immunosuppressants act on the cardiovascular system in a variety of ways, including fibrosis and myocardial remodeling, endothelium disfunction, hypertension, atherosclerosis, dyslipidemia or hyperglycaemia, metabolic syndrome, and hyperuricemia. The use of multidrug protocols makes it possible to develop regimens that can reduce the incidence of cardiovascular events. A better understanding of their mechanism of action and the range of complications could enable physicians to select the appropriate therapy for a given patient, as well as to reduce complications and prolong life.

Pregnancy and medications for inflammatory bowel disease: An updated narrative review

Inflammatory bowel disease (IBD) is often diagnosed during the peak reproductive years of young women. Women with active IBD around conception are at a significantly increased risk of disease relapse during pregnancy, which is associated with poor pregnancy and neonatal outcomes. Given these substantial risks, it is prudent that disease remission should ideally be achieved before conception. Unfortunately, some patients may experience a disease flare-up even if they are in a state of remission before pregnancy. Patients must continue their IBD medications to reduce the risk of disease flare and subsequent poor outcomes during the gestational and postpartum periods. When treating IBD flare-ups during pregnancy, the management is quite similar to the therapeutic approach for non-pregnant patients with IBD, including 5-aminosalicylate, steroids, calcineurin inhibitors (CNIs), and biologic therapies. While the data regarding the safety of CNIs in pregnant women with IBD is limited, the findings in our recent meta-analysis suggest that CNIs may be safer to use in those with IBD than in solid organ transplant recipients. There are several types of biologics and small-molecule therapies currently approved for IBD, and physicians should thoroughly understand their clinical benefits and safety profiles when utilizing these treatments in the context of pregnancy. This review highlights recent studies, including our systematic review and meta-analysis, and discusses the clinical advantages and safety considerations of biologics and small molecules for pregnant women with IBD.

Tracing angiotensin II's yin-yang effects on cardiovascular-renal pathophysiology

Adverse changes in cardiovascular and renal systems are major contributors to overall morbidity and mortality. Human cardiovascular and renal systems exhibit a complex network of positive and negative feedback that is reflected in the control of vascular tone via angiotensin II (Ang II) based signaling. This review will examine in some depth, the multiple components and processes that control the status and reflect the health of these various cardiovascular and renal systems, such as pathways associated to monomeric G proteins, RhoA/Rho kinase system and ERK, oxidative stress and NO balance. It will specifically emphasize the "yin-yang" nature of Ang II signaling by comparing and contrasting the effects and activity of various systems, pathways and components found in hypertension to those found in Gitelman's and Bartter's syndromes (GS/BS), two rare autosomal recessive tubulopathies characterized by electrolytic imbalance, metabolic alkalosis, sodium wasting and prominent activation of the renin-angiotensin-aldosterone system. Notwithstanding the activation of the renin-angiotensin-aldosterone system, GS/BS are normo-hypotensive and protected from cardiovascular-renal remodeling and therefore can be considered the mirror image, the opposite of hypertension.

Cardiovascular Risk after Kidney Transplantation: Causes and Current Approaches to a Relevant Burden

Background. Cardiovascular disease is a frequent complication after kidney transplantation and represents the leading cause of mortality in this population. Material and Methods. We searched for the relevant articles in the National Institutes of Health library of medicine, transplant, cardiologic and nephrological journals. Results. The pathogenesis of cardiovascular disease in kidney transplant is multifactorial. Apart from non-modifiable risk factors, such as age, gender, genetic predisposition and ethnicity, several traditional and non-traditional modifiable risk factors contribute to its development. Traditional factors, such as diabetes, hypertension and dyslipidemia, may be present before and may worsen after transplantation. Immunosuppressants and impaired graft function may strongly influence the exacerbation of these comorbidities. However, in the last years, several studies showed that many other cardiovascular risk factors may be involved in kidney transplantation, including hyperuricemia, inflammation, low klotho and elevated Fibroblast Growth Factor 23 levels, deficient levels of vitamin D, vascular calcifications, anemia and poor physical activity and quality of life. Conclusions. The timely and effective treatment of time-honored and recently discovered modifiable risk factors represent the basis of the prevention of cardiovascular complications in kidney transplantation. Reduction of cardiovascular risk can improve the life expectancy, the quality of life and the allograft function and survival.

Pregnancy and neonatal outcomes in women receiving calcineurin inhibitors: A systematic review and meta-analysis

AIM

Calcineurin inhibitors (CNIs) are often used for solid organ transplantation recipients or patients with immune-mediated diseases. This systematic review and meta-analysis aims to understand how CNIs affect pregnancy and neonatal outcomes.

METHODS

Electronic databases were searched for observational studies assessing pregnancy and neonatal outcomes in CNI-treated patients. The pooled rate of each outcome was determined. Meta-regression was conducted to identify contributing factors to the outcomes.

RESULTS

We analyzed 98 studies with a total of 5,355 pregnancies in 4,450 CNI-treated patients. The pooled rates of live birth and spontaneous abortion were 82.1% (95% CI 76.7%-86.4%) and 11.7% (95% CI 8.7%-15.5%), respectively. The rates of preterm delivery (33.2%, 95% CI 29.2%-37.5%), low birth weight (35.8%, 95% CI 27.7%-44.8%), and preeclampsia (13.5%, 95% CI 9.4%-19.2%) were 3-4 times higher than the rates of general population. Nearly half of the CNI-treated patients required C-section (43.5%, 95% CI 36.9%-50.3%). The rates of stillbirth, neonatal, and maternal death were 4.2% (95% CI 2.8%-6.2%), 2.9% (95% CI 1.8%-4.8%), and 2.3% (95% CI 1.3%-4.1%), respectively. Meta-regression showed preeclampsia was significantly associated with the risks of preterm delivery and low birth weight. Older maternal age, pre-pregnancy hypertension, and cyclosporine use increased the risk of preeclampsia.

CONCLUSION

Given the higher mortalities in CNI-treated patients and their children than the general averages, their pregnancy is considered high risk. The risks of preterm delivery and low birth weight were primarily attributed to preeclampsia. Since pre-pregnancy hypertension increased its risk, an appropriate preconception blood pressure management may improve their outcomes.

Update on Treatment of Hypertension After Renal Transplantation

PURPOSE OF REVIEW

To incorporate novel findings on pathophysiology and treatment of posttransplant hypertension.

RECENT FINDINGS

(1) The sodium retaining effects of CNIs are mediated by stimulation of the thiazide-sensitive sodium chloride co-transporter in the distal convoluted tubule and in this regard chlorthalidone was proven to be an effective antihypertensive drug in renal transplantation. (2) Local and not systemic activation of the renin-angiotensin-aldosterone system plays a crucial role in the pathogenesis of posttransplant hypertension. (3) Recent randomized controlled trials failed to prove the presumed superiority of renin-angiotensin blockers in kidney transplantation. (4) Steroid-free and mammalian target of rapamycin-based immunosuppressive drug combinations did not show favorable effects on blood pressure control. (5) In a recent report the risk of non-melanoma skin cancer was higher with thiazide diuretics. But the increased cancer risk in transplant recipients is mainly attributed to comorbidities, such as diabetes and hypertension and of course to the transplantation condition itself or the obligatory application of immunosuppression, and has little to do with the antihypertensive medication Actual recommendations about BP targets in adult renal transplant recipients are coming from a post hoc analysis of a large randomized trial with another primary endpoint. Unless convincing studies on treatment of hypertension after renal transplantation are available, the ESC/ESH Guidelines 2018 should apply for these patients.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

Antihypertensive Treatment in Kidney Transplant Recipients-A Current Single Center Experience

Arterial hypertension affects the survival of the kidney graft and the cardiovascular morbidity and mortality of the recipient after kidney transplantation (KTx). Thus, antihypertensive treatment is necessary for a vast majority of these patients. Long-term data on antihypertensive drugs and their effects on allograft function after KTx is still limited, and further investigation is required. We retrospectively analyzed a cohort of 854 recipients who received a kidney transplant at our transplant center between 2007 and 2015 with regard to antihypertensive treatment and its influence on graft function and survival. 1-y after KTx, 95.3% patients were treated with antihypertensive therapy. Of these, 38.6% received mono- or dual-drug therapy, 38.0% received three to four drugs and 8.1% were on a regimen of ≥5 drugs. Beta-blockers were the most frequently used antihypertensive agents (68.1%). Neither the use of angiotensin-converting enzyme inhibitor/angiotensin receptor blockers (51.9%) and calcium channel blockers (51.5%), nor the use the use of loop diuretics (38.7%) affected allograft survival. Arterial hypertension and the number of antihypertensive agents were associated with unfavorable allograft outcomes (each p < 0.001). In addition to the well-known risk factors of cold ischemic time and acute rejection episodes, the number of antihypertensive drugs after one year, which reflects the severity of hypertension, is a strong predictor of unfavorable allograft survival.

Approach and Management of Hypertension After Kidney Transplantation

Hypertension is one of the most common cardiovascular co-morbidities after successful kidney transplantation. It commonly occurs in patients with other metabolic diseases, such as diabetes mellitus, hyperlipidemia, and obesity. The pathogenesis of post-transplant hypertension is complex and is a result of the interplay between immunological and non-immunological factors. Post-transplant hypertension can be divided into immediate, early, and late post-transplant periods. This classification can help clinicians determine the etiology and provide the appropriate management for these complex patients. Volume overload from intravenous fluid administration is common during the immediate post-transplant period and commonly contributes to hypertension seen early after transplantation. Immunosuppressive medications and donor kidneys are associated with post-transplant hypertension occurring at any time point after transplantation. Transplant renal artery stenosis (TRAS) and obstructive sleep apnea (OSA) are recognized but common and treatable causes of resistant hypertension post-transplantation. During late post-transplant period, chronic renal allograft dysfunction becomes an additional cause of hypertension. As these patients develop more substantial chronic kidney disease affecting their allografts, fibroblast growth factor 23 (FGF23) increases and is associated with increased cardiovascular and all-cause mortality in kidney transplant recipients. The exact relationship between increased FGF23 and post-transplant hypertension remains poorly understood. Blood pressure (BP) targets and management involve both non-pharmacologic and pharmacologic treatment and should be individualized. Until strong evidence in the kidney transplant population exists, a BP of <130/80 mmHg is a reasonable target. Similar to complete renal denervation in non-transplant patients, bilateral native nephrectomy is another treatment option for resistant post-transplant hypertension. Native renal denervation offers promising outcomes for controlling resistant hypertension with no significant procedure-related complications. This review addresses the epidemiology, pathogenesis, and specific etiologies of post-transplant hypertension including TRAS, calcineurin inhibitor effects, OSA, and failed native kidney. The cardiovascular and survival outcomes related to post-transplant hypertension and the utility of 24-h blood pressure monitoring will be briefly discussed. Antihypertensive medications and their mechanism of actions relevant to kidney transplantation will be highlighted. A summary of guidelines from different professional societies for BP targets and antihypertensive medications as well as non-pharmacological interventions, including bilateral native nephrectomy and native renal denervation, will be reviewed.

Outcome and Prognosis of Patients With Lupus Nephritis Submitted to Renal Transplantation

This stydy aimed to evaluate the epidemiological and clinical profile and outcome of patients with lupus nephritis (LN) submitted to renal transplantation. Retrospective cohort study based on the records of 35 LN patients submitted to renal transplantation at a single center in Brazil between July 1996 and May 2016. The Kaplan-Meier method was used to estimate 6-month, 1-year and 5-year graft survival. The sample included 38 transplantations (3 of which retransplantations). The mean age at the time of SLE diagnosis was 23.7 ± 9.0 years. Most patients were female (94.7%) and 68.4% were non-Caucasian. Twenty-two (57.9%) underwent renal biopsy prior to transplantation. The mean time from SLE diagnosis to transplantation was 10.3 ± 6.4 years. The mean pre-transplantation dialysis time was 3.8 ± 3.7 years. The grafts came from living related (n = 11) or deceased (n = 27) donors. Three (7.9%) patients experienced acute rejection in the first year. Graft and patient survival rates were, respectively, 97.1% and 100% at 6 months, 84.9% and 96.9% at 1 year, and 76.3% and 92.5% at 5 years. One (2.6%) patient had SLE recurrence. Venous thrombosis (p = 0.017) and antiphospholipid syndrome (APS) (p = 0.036) were more prevalent in patients with graft loss. In our cohort of LN patients submitted to renal transplantation, the 5-year survival rate was high, and APS was an important predictor of poor renal outcome (graft loss).

Intrarenal Renin-Angiotensin-System Dysregulation after Kidney Transplantation

Angiotensin-converting enzyme inhibitors (ACEis) are beneficial in patients with chronic kidney disease (CKD). Yet, their clinical effects after kidney transplantation (KTx) remain ambiguous and local renin-angiotensin system (RAS) regulation including the ‘classical’ and ‘alternative’ RAS has not been studied so far. Here, we investigated both systemic and kidney allograft-specific intrarenal RAS using tandem mass-spectrometry in KTx recipients with or without established ACEi therapy (n = 48). Transplant patients were grouped into early (<2 years), intermediate (2–12 years) or late periods after KTx (>12 years). Patients on ACEi displayed lower angiotensin (Ang) II plasma levels (P < 0.01) and higher levels of Ang I (P < 0.05) and Ang-(1–7) (P < 0.05) compared to those without ACEi independent of graft vintage. Substantial intrarenal Ang II synthesis was observed regardless of ACEi therapy. Further, we detected maximal allograft Ang II synthesis in the late transplant vintage group (P < 0.005) likely as a consequence of increased allograft chymase activity (P < 0.005). Finally, we could identify neprilysin (NEP) as the central enzyme of ‘alternative RAS’ metabolism in kidney allografts. In summary, a progressive increase of chymase-dependent Ang II synthesis reveals a transplant-specific distortion of RAS regulation after KTx with considerable pathogenic and therapeutic implications.

Oxidative stress - chronic kidney disease - cardiovascular disease: A vicious circle

Chronic kidney disease patient's progression to end-stage renal disease as well as their high mortality are linked to cardiovascular disease. However, the high incidence rate of cardiovascular morbidity and mortality in these patients is not fully accounted for by traditional cardiovascular risk factors such as diabetes, hypertension and obesity. Renal disease and CVD are associated with endothelial dysfunction, inflammation and oxidative stress and in this review we will examine what is known regarding their similar roles in both CVD and chronic kidney disease, specifically focusing on the interconnections between oxidative stress, inflammation and endothelial dysfunction. These interconnections are best visualized as a vicious circle wherein these entities coexist and communicate with each other, thereby exacerbating the processes underpinning these different entities with the end result of the high morbidity and mortality that characterize CKD patients. By exploring this vicious circle i.e. the mode and extent of the interrelationships as well as some of the underlying mechanisms involved, this review aims at outlining our current understanding as well as highlighting future avenues for research and potential targets for therapeutic intervention.

Chlorthalidone Versus Amlodipine for Hypertension in Kidney Transplant Recipients Treated With Tacrolimus: A Randomized Crossover Trial

BACKGROUND

Chlorthalidone is a very effective antihypertensive drug, but it has not been studied prospectively in kidney transplant recipients with hypertension. Recent data indicate that calcineurin inhibitors activate the thiazide-sensitive sodium chloride cotransporter, providing further rationale to test thiazides in this population.

STUDY DESIGN

Randomized noninferiority crossover trial (noninferiority margin, -2.8mmHg).

SETTING & PARTICIPANTS

Hypertensive kidney transplant recipients using tacrolimus (median duration, 2.4 years after transplantation; mean estimated glomerular filtration rate, 63±27 [SD] mL/min/1.73m²; mean systolic blood pressure [SBP], 151±12mmHg).

INTERVENTION

Amlodipine (5-10mg) and chlorthalidone (12.5-25mg) for 8 weeks (separated by 2-week washout).

OUTCOMES

Average daytime (9 am to 9 pm) ambulatory SBP.

MEASUREMENTS

Blood pressure and laboratory parameters.

RESULTS

88 patients underwent ambulatory blood pressure monitoring, of whom 49 (56%) with average daytime SBP>140mmHg were enrolled. 41 patients completed the study. Amlodipine and chlorthalidone both reduced ambulatory SBP after 8 weeks (mean changes of 150±12 to 137±12 [SD] vs 151±12 to 141±13mmHg; effect size, -4.2 [95% CI, -7.3 to 1.1] mmHg). Despite these similar blood pressure responses, chlorthalidone reduced proteinuria by 30% (effect size, -65 [95% CI, -108 to -35] mg/g) and also reduced physician-assessed peripheral edema (22% to 10%; P<0.05 for both). In contrast, chlorthalidone temporarily reduced kidney function and increased both serum uric acid and glycated hemoglobin levels.

LIMITATIONS

Open-label design, short follow-up, per-protocol analysis.

CONCLUSIONS

Chlorthalidone is an antihypertensive drug equally effective as amlodipine after kidney transplantation.

Hypertension in the Pediatric Intensive Care Unit

Hypertension in the pediatric intensive care unit (PICU) is common and it contributes to the overall morbidity and mortality. Patients may present with hypertensive emergencies or hypertension can manifest itself later in PICU course. Although hypertension can be seen in most patients during hospitalization, patients with some specific diseases and conditions are more prone to hypertension. Hypertension should be recognized promptly and treated accordingly. Different pathophysiologic mechanisms can be responsible for the hypertension and management differs based on the underlying etiology. Any patient with a hypertensive emergency must be admitted to PICU, and treatment and diagnostic workup should be initiated immediately.

The impact of kidney transplantation on 24-hour ambulatory blood pressure in end-stage renal disease patients

In this study, we prospectively investigated the impact of kidney transplantation (KT) on the status of hypertension, including circadian rhythm in end-stage renal disease (ESRD) patients. We performed 24-hour ambulatory blood pressure (BP) monitoring and office BP measurement in 48 patients before and 1 year after KT. According to the nocturnal reduction in systolic BP (ΔSBP), the patients were divided into dippers, non-dippers, and reverse dippers. After KT, the mean BP value in office BP and 24-hour ambulatory BP monitoring did not change, but the proportion of patients taking anti-hypertensive drugs and the pill number significantly decreased. In contrast, the mean ΔSBP significantly decreased, and the proportion of non-dippers and reverse dippers did not decrease. Decrease in ΔSBP after KT was associated with inferior allograft function during follow-up. Our study suggests that KT improved the overall BP level, but it did not affect abnormal circadian rhythm in ESRD patients.

Hypertension, living kidney donors, and transplantation: where are we today?

Hypertension is a prevalent problem in kidney transplant recipients that is known to be a "traditional" risk factor for atherosclerotic cardiovascular disease leading to premature allograft failure and death. Donor, peritransplant, and recipient factors affect hypertension risk. Blood pressure control after transplantation is inversely associated with glomerular filtration rate (GFR). Calcineurin inhibitors, the most commonly used class of immunosuppressives, cause endothelial dysfunction, increase vascular tone, and sodium retention via the renin-angiotensin-aldosterone system resulting in systemic hypertension. Steroid withdrawal seems to have little impact on blood pressure control. Newer agents like belatacept appear to be associated with less hypertension. Transplant renal artery stenosis is an important, potentially treatable cause of hypertension. Dihydropyridine calcium channel blockers mitigate calcineurin inhibitor nephrotoxicity and may be associated with improved estimated GFR. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are not recommended in the first 3 to 6 months given their effects on reduced estimated GFR, anemia, and hyperkalemia. The use of ß-blockers may be associated with improved patient survival, even for patients without cardiovascular disease. Living donation may increase blood pressure by 5 mm Hg or more. Some transplant centers accept Caucasian living donors with well-controlled hypertension on a single agent if they agree to close follow-up.

Calcineurin inhibitors and hypertension: a role for pharmacogenetics?

Hypertension is a common side effect of calcineurin inhibitors (CNIs), which are drugs used to prevent rejection after transplantation. Hypertension after kidney transplantation has been associated with earlier graft failure and higher cardiovascular mortality in the recipient. Recent data indicate that enzymes and transporters involved in CNI pharmacokinetics and pharmacodynamics, including CYP3A5, ABCB1, WNK4 and SPAK, are also associated with salt-sensitive hypertension. These insights raise the question whether polymorphisms in the genes encoding these proteins increase the risk of CNI-induced hypertension. Predicting who is at risk for CNI-induced hypertension may be useful for when selecting specific interventions, including dietary salt restriction, thiazide diuretics or a CNI-free immunosuppressive regimen. This review aims to explore the pharmacogenetics of CNI-induced hypertension, highlighting the knowns and unknowns.

Hypertension after kidney transplantation: a pathophysiologic approach

Post-transplant hypertension is associated with decreased graft and patient survival and cardiovascular morbidity. Unfortunately, post-transplant hypertension is often poorly controlled. Important risk factors include immunosuppressive medications, complications of the transplant surgery, delayed graft function, rejection, and donor and recipient risk factors. The effects of immunosuppressive medications are multifactorial including increased vascular and sympathetic tone and salt and fluid retention. The immunosuppressive agents most commonly associated with hypertension are glucocorticoids and calcineurin inhibitors. Drug therapy for hypertension should be based on the comorbidities and pathophysiology. Evidence-based approaches to defining and treating hypertension in renal transplant recipients are predominantly extrapolated from large-scale studies performed in the general population. Thus, there continues to be a need for larger studies examining the pathophysiology, diagnosis and treatment of hypertension in renal transplant recipients.

Cardiovascular death in kidney recipients treated with renin-angiotensin system blockers

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) are widely prescribed after kidney transplantation, but evidence for an improvement in outcomes is mixed. A recent trial demonstrated a significantly lower incidence of major cardiovascular events in ACEI-treated recipients.

METHODS

Collaborative Transplant Study data on cardiovascular death during years 2 to 10 after kidney transplantation in patients with a functioning graft were analyzed according to whether ACEI/ARB or other antihypertensive therapy (excluding diuretics) was administered at year 1.

RESULTS

Of 39,251 transplants analyzed, 15,250 (38.9%) received ACEI/ARB and 24,001 (61.1%) received other antihypertensive therapy at year 1 after transplantation. The mean duration of follow-up was 5.8 years. During years 2 to 10 after transplantation, cardiovascular death occurred in 918 patients (cumulative incidence=4.7%) with a functioning graft. The rate of cardiovascular death was similar in patients who received ACEI/ARB therapy or other antihypertensive treatment overall and in subpopulations of patients who were considered by the transplant center to be at an increased cardiovascular risk, had no pretransplant risk factors, were aged 60 years and older, were treated for diabetes at year 1, or had serum creatinine of 130 μmol/L or higher at year 1. Multivariable Cox regression analysis confirmed that treatment with ACEI/ARB did not confer a beneficial effect beyond that conferred by other antihypertensive treatments on the cumulative incidence of cardiovascular death during years 2 to 10 (hazard ratio=1.1, P=0.24).

CONCLUSIONS

This large-scale retrospective analysis of prospectively collected data shows that the rate of cardiovascular death in kidney transplant recipients receiving ACEI/ARB or other antihypertensive medications is virtually identical.

Kidney transplantation down-regulates expression of organic cation transporters, which translocate β-blockers and fluoroquinolones

Kidney transplanted patients are often treated with immunosuppressive, antihypertensive, and antibiotic drugs such as cyclosporine A (CsA), β-blockers, and fluoroquinolones, respectively. Organic cation transporters (OCT) expressed in the basolateral membrane of proximal tubules represent an important drug excretion route. In this work, the renal expression of OCT after syngeneic and allogeneic kidney transplantation in rats with or without CsA immunosuppression was studied. Moreover, the interactions of CsA, β-blockers (pindolol/atenolol), and fluoroquinolones (ofloxacin/norfloxacin) with rOCT1, rOCT2, hOCT1, and hOCT2 in stably transfected HEK293-cells were studied. Kidney transplantation was associated with reduced expression of rOCT1, while rOCT2 showed only reduced expression after allogeneic transplantation. All drugs interacted subtype- and species-dependently with OCT. However, only atenolol, pindolol, and ofloxacin were transported by hOCT2, the main OCT in human kidneys. While CsA is not an OCT substrate, it exerts a short-term effect on OCT activity, changing their affinity for some substrates. In conclusion, appropriate drug dosing in transplanted patients is difficult partly because OCT are down-regulated and because concomitant CsA treatment may influence the affinity of the transporters. Moreover, drug-drug competition at the transporter can also alter drug excretion rate.

Pathogenesis of calcineurin inhibitor-induced hypertension

This article reviews the current understanding of the mechanisms of calcineurin inhibitor-induced hypertension. Already early after the introduction of cyclosporine in the 1980s, vasoconstriction, sympathetic excitation and sodium retention by the kidney had been shown to play a role in this form of hypertension. The vasoconstrictive effects of calcineurin inhibitors are related to interference with the balance of vasoactive substances, including endothelin and nitric oxide. Until recently, the renal site of the sodium-retaining effect of calcineurin inhibitors was unknown. We and others have shown that calcineurin inhibitors increase the activity of the thiazide-sensitive sodium chloride cotransporter through an effect on the kinases WNK and SPAK. Here, we review the pertinent literature on the hypertensinogenic effects of calcineurin inhibitors, including neural, vascular and renal effects, and we propose an integrated model of calcineurin inhibitor-induced hypertension.