Imbalance between production and scavenging of hydroxyl radicals in patients maintained on hemodialysis.

BACKGROUND: Reactive oxygen species are as being related to the pathophysiology of endstage renal disease (ESRD). We measured the plasma hydroxyl radical (.OH)-producing ability and .OH-scavenging activity in patients with ESRD to clarify the pathophysiological states involved. METHODS: We used electron spin resonance to measure plasma N-t-butyl-alpha-phenylnitron radical spin adduct (pPBN rsa) as .OH-producing ability and plasma 3,3,5,5-tetramethyl-1-pyrroline-N-oxide radical spin adduct (pM4PO rsa) as .OH-scavenging activity. Oxidative injuries were evaluated by determining oxidised low-density lipoprotein (Ox-LDL). RESULTS: The pPBN rsa of the ESRD patients was lower than that of the controls (1.83 vs 2.94 micromol/g protein). The pM4PO rsa of the ESRD patients was higher than that of the controls (3.85 vs 3.15 mmol L: -ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl hydrogen phosphate] potassium salt (EPC-K1)/g protein). The pPBN rsa and pM4PO rsa were correlated, both in the ESRD patients and in the controls (r = 0.47 and r = 0.53). Ox-LDL was correlated with hemodialysis (HD) duration (r = 0.49) and was negatively correlated with pPBN rsa (r = -0.54), which indicates that oxidative stress was increased as HD therapy was prolonged and suppressed pPBN rsa. CONCLUSIONS: There was an imbalance between .OH-producing ability and .OH-scavenging activity, in the ESRD patients, and this may be responsible for compromising the health of ESRD patients.

More stable and reliable pharmacokinetics with preprandial administration of cyclosporine compared with postprandial administration in patients with refractory nephrotic syndrome.

STUDY OBJECTIVE: To compare the absorption profile of cyclosporine after preprandial administration with that after postprandial administration, and to determine which administration time resulted in a more stable absorption profile and the timing of the drug concentration that was the most reliable marker for monitoring drug absorption. DESIGN: Prospective analysis. SETTING: University teaching hospital in Japan. PATIENTS: Sixteen patients with refractory nephrotic syndrome. INTERVENTION: Thirteen patients received cyclosporine after breakfast (postprandial group) and eight received the drug 30 minutes before breakfast (preprandial group). MEASUREMENTS AND MAIN RESULTS: Blood cyclosporine concentration was measured 5 times serially: before administration (C 0 ) and at 1-hour intervals until 4 hours after administration of cyclosporine (C 1 -C 4 ). Also, area under the concentration-time curve from 0-4 hours (AUC 0-4 ) was calculated. Of the 13 patients in the postprandial group, six (46%) showed fair absorption and exhibited a peak concentration at C 1 or C 2 (high-absorption pattern); seven (54%) showed poor absorption and did not reach the peak concentration within the 4-hour period (low-absorption pattern). Five of the seven patients with the low-absorption pattern were switched from postprandial to preprandial administration. All patients in the preprandial administration group showed a high-absorption pattern and reached the peak cyclosporine concentration at C 1 . The C 2 value showed the best correlation with AUC 0-4 in both groups, and the C 0 parameter did not correlate with AUC 0-4 in either group. CONCLUSION: Preprandial administration provided a more stable absorption profile of cyclosporine compared with postprandial administration. From the correlation with AUC 0-4 , we concluded that C 2 , and not C 0 , is a reliable marker for monitoring cyclosporine exposure.

Hypertension-linked mutation in the adducin alpha-subunit leads to higher AP2-mu2 phosphorylation and impaired Na+,K+-ATPase trafficking in response to GPCR signals and intracellular sodium.

Alpha-adducin polymorphism in humans is associated with abnormal renal sodium handling and high blood pressure. The mechanisms by which mutations in adducin affect the renal set point for sodium excretion are not known. Decreases in Na+,K+-ATPase activity attributable to endocytosis of active units in renal tubule cells by dopamine regulates sodium excretion during high-salt diet. Milan rats carrying the hypertensive adducin phenotype have a higher renal tubule Na+,K+-ATPase activity, and their Na+,K+-ATPase molecules do not undergo endocytosis in response to dopamine as do those of the normotensive strain. Dopamine fails to promote the interaction between adaptins and the Na+,K+-ATPase because of adaptin-mu2 subunit hyperphosphorylation. Expression of the hypertensive rat or human variant of adducin into normal renal epithelial cells recreates the hypertensive phenotype with higher Na+,K+-ATPase activity, mu2-subunit hyperphosphorylation, and impaired Na+,K+-ATPase endocytosis. Thus, increased renal Na+,K+-ATPase activity and altered sodium reabsorption in certain forms of hypertension could be attributed to a mutant form of adducin that impairs the dynamic regulation of renal Na+,K+-ATPase endocytosis in response to natriuretic signals.

Aquaporin-1 is recruited to the plasma membrane by hyperosmotic stimuli via a protein kinase A-dependent pathway in rat peritoneal mesothelial cells.

Aquaporin-1 (AQP1) has been reported to play an important role in water permeability in peritoneal dialysis. To determine the mechanism involved in this process, we used cultured rat peritoneal mesothelial cells (RPMCs) to examine the glucose-induced translocation of AQP1 to the plasma membrane. Cultured RPMCs obtained from male Sprague-Dawley rats were incubated in a combination of Dulbecco modified Eagle medium (DMEM) and F12 medium at 37 degrees C for 15 minutes. The plasma membrane of the RPMCs was separated by Percoll gradient, and the quantity of AQP1 in the membrane fraction was determined by Western blot analysis. The amount of AQP1 was significantly increased by the addition of 5% glucose (139.5% +/- 38.7% of control, p < 0.05) or of dibutyryl cyclic adenosine monophosphate (db-cAMP), a cAMP analog to the medium (139.5% +/- 21.9% of control, p < 0.05). However glucose-induced enhancement of AQP1 disappeared with the addition of H-89, a protein kinase A (PKA)--specific inhibitor (103% +/- 17.5% of control, p < 0.05 as compared with 5% glucose). We also examined the effect of 5% glucose on PKA activity separately in the cytosol fraction, the crude membrane fraction, and the pure plasma membrane fraction. In the cytosol fraction of 5% glucose-stimulated RPMCs, PKA activity was decreased (70.5% +/- 11.5% of control, p < 0.01), but in the crude membrane fraction, it was significantly increased (143.9% +/- 52.9% of control, p < 0.01). In the pure plasma membrane fraction, PKA activity did not change. From those findings, we hypothesize that 5% glucose augments the PKA-dependent translocation of AQP1 to the plasma membrane, mediated by PKA translocation to the intracellular AQP1 store.

[Takotsubo cardiomyopathy thought to be induced by MRSA meningitis and cervical epidural abscess in a maintenance-hemodialysis patient: case report].

A 65-year-old man was admitted to our hospital for high fever and severe left shoulder pain. He was initiated on maintenance hemodialysis for end-stage renal failure caused by diabetic nephropathy 9 years previously. On admission, the serum CRP level was 29.3 mg/d/l and the white blood cell count was 29,000/mm3. Bacterial examination of blood and spinal fluid revealed MRSA colonization. On the 6th hospital day, a giant negative T wave in the V2-6 leads of an electrocardiogram asymptomatically appeared. Ultracardiogram revealed apical systolic paradoxical centrifugal motion. None of the cardiogenic enzymes, such as creatine kinase, lactate dehydrogenase and glutamic oxaloacetic transaminase was elevated. Cardiac thallium-201-chloride (201Tl-Cl) and I-123 beta-metyl iodophenyl-pentadecanoic acid (123I-BMIPP) scintigraphy revealed a decreased accumulation of isotopes in the apex. From these findings, we diagnosed Takotsubo cardiomyopathy induced by MRSA meningitis. Vancomycin was administrated and the inflammatory signs decreased. On the 46th hospital day, tetraplegia and respiratory suppression occurred. A cervical spinal magnetic resonance image revealed cervical spondylodiscitis and cervical epidural abscess, which compressed the medulla oblongata. Surgical spinal decompression and drainage of the abscess were performed. The giant negative T wave in the electrocardiogram improved after the operation. Two months after the operation, cardiac 201Tl-Cl scintigraphy revealed improvement in the accumulation of isotopes in the apex. Takotsubo cardiomyopathy is secondary cardiomyopathy presenting with apical systolic paradoxical centrifugal motion without coronary stenotic disease. It has been reported to be induced by severe mental stress or intracranial disease. In the present patient, it was predicted that stress on the central nerve system caused by the MRSA meningitis and the cervical epidural abscess induced the Takotsubo cardiomyopathy.

Hypertension accelerates diabetic nephropathy in Wistar fatty rats, a model of type 2 diabetes mellitus, via mitogen-activated protein kinase cascades and transforming growth factor-beta1.

Although it is known that diabetic nephropathy is accelerated by hypertension, the mechanisms involved in this process are not clear. In this study we aimed to clarify these mechanisms using male Wistar fatty rats (WFR) as a type 2 diabetic model and male Wistar lean rats (WLR) as a control. Each group was fed a normal or high sodium diet from the age of 6 to 14 weeks. We determined the blood pressure and urinary albumin excretion (UAE). At the end of the study, the expressions of mitogen-activated protein kinases (MAPK) and transforming growth factor-beta1 (TGF-beta1) were examined in the isolated glomeruli by Western blot analysis, and the number of glomerular lesions was determined by conventional histology. High sodium load caused hypertension and a marked increase in UAE in the WFR but not in the WLR. Glomerular volume was increased in the hypertensive WFR. There was no difference among the four groups in the expression of c-Jun-NH2-terminal kinase (JNK). In contrast, the expressions of extracellular signal-regulated kinase 1/2 (ERK1/2) and its upstream regulator, MAPK/ERK kinase 1 (MEK1), were augmented in the hypertensive WFR. Expression of p38 MAPK was increased in the normotensive WFR, and further enhanced in the hypertensive WFR. Moreover, administration of high sodium load to WFR augmented the expression of TGF-beta1. In conclusion, systemic hypertension in WFR accelerates the diabetic nephropathy in type 2 diabetes via MEK-ERK and p38 MAPK cascades. TGF-beta1 is also involved in this mechanism.

Alteration of energy production by the heart in CRF patients undergoing peritoneal dialysis.

Cardiovascular disease is commonly observed in patients with chronic renal failure and this is a leading cause of death in patients with end-stage renal disease undergoing maintenance dialysis. Myocardial energy production is a very crucial aspect of cardiac function. Therefore, to evaluate energy metabolism of myocardial muscle in peritoneal dialysis (PD) patients, we carried out the following study using Magnetic resonance spectroscopy (MRS). Fourteen chronic renal failure patients and eight healthy volunteers were enrolled. The ratio of the phosphocreatine peak to the beta-phosphate to ATP peak (PCr/beta-ATP) was calculated from their MR spectra obtained by 31P-MR spectroscopy (Gyroscan S15, Philips). To determine the correlation between cardiac function and energy status, the left atrial diameter, the left ventricular (LV) end-diastolic diameter, the ejection fraction, the fraction of shortening and the LV mass index were measured by echocardiography. Peripheral blood sampling was also performed for creatinine, blood urea nitrogen, hematocrit, hemoglobin, beta2-microglobuline, intact parathyroid hormone. PCr/beta-ATP was significantly lower in PD (1.03 +/- 0.15 vs. 1.40 +/- 0.18: p = 0.0002), although all patients showed normal systolic function. No correlation was found between PCr/beta-ATP and cardiac function or hematological or biochemical markers. A negative correlation was present between PCr/beta-ATP and dialysis duration (r = 0.57, p < 0.05). Altered energy status of the myocardium in PD should be considered even if the patients did not show any systolic dysfunction. 31P-MRS is a useful tool to evaluate the energy status of the myocardium.