Hypertension in children after renal transplantation

Isolated nocturnal hypertension in pediatric kidney transplant recipients

BACKGROUND

Isolated nocturnal hypertension (INH) is defined as nighttime hypertension in the setting of normal daytime blood pressure (BP), diagnosed by ambulatory BP monitoring (ABPM).

METHODS AND RESULTS

Hypertension affects 60%-80% of pediatric kidney transplant recipients, and INH is the most common type of ambulatory hypertension. INH is associated with an increased prevalence of hypertension-mediated target organ damage such as left ventricular hypertrophy in adults and in pediatric kidney transplant recipients.

CONCLUSION

Ambulatory BP monitoring should be performed annually in all pediatric kidney transplant recipients to diagnose hypertension phenotypes that are not detectable by office BP such as masked hypertension, white-coat hypertension, or INH. Isolated nocturnal hypertension in pediatric transplant patients requires study as a treatment target.

Clinical value of ambulatory blood pressure in pediatric patients after renal transplantation

Hypertension is a highly prevalent co-morbidity in pediatric kidney transplant recipients. Undertreated hypertension is associated with cardiovascular complications and negatively impacts renal graft survival. Thus, the accurate measurement of blood pressure is of the utmost importance for the correct diagnosis and subsequent management of post-renal transplant hypertension. Data derived from the general population, and to a lesser extent from the pediatric population, indicates that ambulatory blood pressure monitoring (ABPM) is superior to blood pressure measurements taken in the clinical setting for the evaluation of true mean blood pressure, identification of patients requiring antihypertensive treatment, and in the prediction of cardiovascular outcome. This Educational Review will discuss the clinical value of ABPM in the identification of individual blood pressure phenotypes, i.e., normotension, new-onset hypertension, white-coat hypertension, masked hypertension, controlled blood pressure, and undertreated/uncontrolled hypertension in pediatric kidney transplant recipients. Finally, we examine the utility of performing repeated ABPM for treatment monitoring of post-renal transplant hypertension and on surrogate markers related to relevant clinical cardiovascular outcomes. Taken together, our review highlights the clinical value of the routine use of ABPM as a tool for identifying and monitoring hypertension in pediatric kidney transplant recipients.

Renal transplantation increases angiotensin II receptor-mediated vascular contractility associated with changes of epigenetic mechanisms

Hypertension is one of the most common complications following renal transplantation, and it increases the risk of graft loss and other cardiovascular diseases. Previous studies have revealed that the use of angiotensin II (Ang II) blockers for preventing and treating hypertension is closely associated with higher survival following renal transplantation. However, the cellular and molecular mechanisms by which the vascular contractility of the recipient is altered in response to Ang II following renal transplantation have not been fully elucidated. In the present study, using the Fisher‑Lewis rat kidney transplantation model, the blood pressure (BP) of the conscious transplant recipient was measured following the intravenous administration of Ang II. In addition, the mechanisms underlying the Ang II-mediated vascular contractility via the type 1 and type 2 Ang II receptors (AT1R and AT2R, respectively) in large and small-resistance blood vessels were determined in the recipient after renal transplantation. The results showed that renal transplantation significantly increased the Ang II-stimulated BP of the rats. Additionally, ex vivo contractility experiments using aorta and mesenteric arteries revealed that the contractions induced by Ang II were significantly strengthened in the recipient following renal transplantation, and were associated with an increased intracellular Ca2+ concentration. Losartan almost eradicated the Ang II-induced contractions whereas PD-123319 had no apparent effects on the Ang II-induced contractions in the aorta and mesenteric arteries of the recipient. Furthermore, the expression levels of AT1R but not AT2R were significantly increased in the vasculature of the recipient following renal transplantation, which exhibited a close association with selective DNA demethylation detected in the promoter region of the vascular AT1aR gene. These results indicate that changes of recipient vascular AT1R gene expression, occurring through a mechanism involving DNA methylation, increase the vascular contractility in response to Ang II. This may lead to the increased risk of hypertension following renal transplantation.