Hyperuricemia and Acute Renal Failure in Renal Transplant Recipients Treated With High-Dose Mizoribine.

BACKGROUND: Hyperuricemia is a common adverse event frequently found in renal transplant recipients with mizoribine (MZ). Hyperuricemia itself will be a cause of renal dysfunction, and renal dysfunction also will be a cause of hyperuricemia simultaneously. This study investigates frequency of hyperuricemia and renal failure in renal transplant recipients treated with high-dose MZ. PATIENTS AND METHODS: From December 2007 to October 2015, there was a total of 32 living related renal transplant recipients treated with high-dose MZ. Of the 32 patients, 28 were treated with urate-lowering medications. RESULTS: One patient received allopurinol (AP) and 13 patients received benzbromarone (BB). For 6 of them, their urate-lowering medications were converted to febuxostat (FX) form AP or BB. In the remaining 14 patients, FX was administered from the beginning. In 2 cases of ABO-incompatible living related renal transplant recipients who were maintained with high-dose MZ and BB, severe hyperuricemia and acute renal failure occurred. One patient was a 48-year-old man, and his creatinine (Cr) level increased to 8.14 mg/dL and his serum uric acid (UA) was 24.6 mg/dL. Another patient was a 57-year-old man, and his Cr level increased to 3.59 mg/dL and his UA was 13.2 mg/dL. In both cases Cr and UA were improved, and no finding of acute rejection and drug toxicity was observed in graft biopsy specimens. BB was switched to FX and discontinuance or reduction of MZ was done. CONCLUSION: Combination of MZ and BB has the risk of acute renal dysfunction after renal transplantation. Latent renal dysfunction should be watched for in renal transplant recipients receiving high-dose MZ.

Cardiac-specific overexpression of mouse cardiac calsequestrin is associated with depressed cardiovascular function and hypertrophy in transgenic mice.

Calsequestrin is a high capacity Ca2+-binding protein in the sarcoplasmic reticulum (SR) lumen. To elucidate the functional role of calsequestrin in vivo, transgenic mice were generated that overexpressed mouse cardiac calsequestrin in the heart. Overexpression (20-fold) of calsequestrin was associated with cardiac hypertrophy and induction of a fetal gene expression program. Isolated transgenic cardiomyocytes exhibited diminished shortening fraction (46%), shortening rate (60%), and relengthening rate (60%). The Ca2+ transient amplitude was also depressed (45%), although the SR Ca2+ storage capacity was augmented, as suggested by caffeine application studies. These alterations were associated with a decrease in L-type Ca2+ current density and prolongation of this channel's inactivation kinetics without changes in Na+-Ca2+ exchanger current density. Furthermore, there were increases in protein levels of SR Ca2+-ATPase, phospholamban, and calreticulin and decreases in FKBP12, without alterations in ryanodine receptor, junctin, and triadin levels in transgenic hearts. Left ventricular function analysis in Langendorff perfused hearts and closed-chest anesthetized mice also indicated depressed rates of contraction and relaxation of transgenic hearts. These findings suggest that calsequestrin overexpression is associated with increases in SR Ca2+ capacity, but decreases in Ca2+-induced SR Ca2+ release, leading to depressed contractility in the mammalian heart.