Yukito Kokado

Retrospective study on the impact of hepatitis C virus infection on kidney transplant patients over 20 years.

BACKGROUND The majority of chronic hepatitis is ascribable to hepatitis C virus (HCV) infection, whereas the clinical impact has not been understood in kidney transplant recipients. Our current study was carried out to assess the impact of HCV infection on kidney recipients over the long-term, and to investigate the effect and risk of interferon-alpha (IFN-alpha) therapy for chronic active hepatitis C. METHODS Hepatitis B surface antigen (HBsAg) and antibody to HCV (HCVAb) were examined prospectively and retrospectively in 280 patients, who underwent kidney transplants in the period from 1973 to 1996. The patient survival rate, the graft survival rate, the incidence of liver dysfunction and the cause of mortality among the HCV infected and noninfected groups were analyzed. IFN-alpha therapy was performed on 10 patients with chronic active hepatitis C. RESULTS Prevalence of the hepatitis virus was quite high at 34.3% (96/280): the frequency of the HBsAg carrier was 3.2% (9/280), that of the HCVAb carrier was 28.6% (80/280) and that of the both carriers was 2.5% (7/280). The other 184 cases (65.7%) were negative for both HBsAg and HCVAb. Liver dysfunction developed at the significantly higher incidence of 55% in HCVAb carriers compared to the 9.2% of the noninfected group (P<0.01). HCVAb carriers had a poor survival rate in the second decade compared to the noninfected group: 83.7% vs. 88.91% for 10-year survival (P=0.44) and 63.9% vs. 87.9% for 20-year survival (P<0.05). The poor survival rate was a result of the mortality from liver disorder. Five patients died of such disease in the infected groups whereas no noninfected patient died in the same period (p<0.01). As the result of IFN-alpha therapy, biochemical activity normalized or improved in eight cases, whereas the HCV-RNA titer was reduced only in three patients. Only one patient maintained normal biochemical markers and undetectable levels of HCV-RNA for 2 years after treatment. The therapy was discontinued for five patients with the adverse effects of acute rejection, deterioration of diabetes, and depression. CONCLUSIONS HCV infection has a significant impact on kidney transplant recipients over the long term and in particular affects them in the second decade. Our pilot study revealed only partial efficacy of IFN-alpha therapy for HCV-infected recipients, but with the high risk of acute rejection.

Human Herpesvirus 6 Infection In Renal Transplantation

The relationship between renal transplantation and human herpesvirus 6 (HHV-6) infection was studied. All 21 kidney donors examined had antibody to HHV-6 at the time of transplantation. The 21 kidney recipients also had detectable antibody to HHV-6 before transplantation--and, of these, 8 patients showed a significant increase of serum antibody titer against HHV-6 after transplantation. All these 8 recipients suffered severe kidney rejection. Furthermore, virus isolation from peripheral blood lymphocytes of 2 recipients who suffered rejection was attempted, and in both cases HHV-6 was isolated. Biopsy specimens of rejected kidneys of 9 other patients were examined for the presence of HHV-6 antigens, and in 5 of these specimens antigens were detected in the tubular epithelium, as well as in infiltrating histiocytes and lymphocytes. These results suggest that HHV-6 can infect renal tissues and that the infection may be correlated with rejection or with immunosuppressive therapy.

Changes in lipid metabolism and effect of simvastatin in renal transplant recipients induced by cyclosporine or tacrolimus

Hyperlipidemia is frequently developed following renal transplantation and results in worsening of the patients prognosis. In study 1, the effects of immunosuppressants, cyclosporine (CsA) and tacrolimus on serum lipids were compared in-patients undergoing renal transplantation. The study included 32 cases of renal transplantation recipients who randomized to the CsA treatment group (15 patients) and the tacrolimus group (17 patients). Before and 1 month after the transplantation, we assessed the serum lipid levels, apolipoprotein levels, the concentrations of cholesterol in the respective lipoprotein fractions and the enzyme activities related to lipid-metabolism. The serum lipid levels in both groups were significantly increased at 1 month after renal transplantation. In the CsA group, there were significant increases in cholesterol contents in very-low-density lipoprotein (VLDL), LDL2 and HDL2 fractions, whereas, in the tacrolimus group, cholesterol content was increased in VLDL and HDL2 fractions. In study 2, 1 month after renal transplantation, 19 patients with hypercholesterolemia (total cholesterol (TC) >200 mg/dl) and hypertriglyceridemia (triglyceride (TG) >150 mg/dl) were treated with simvastatin 5-10 mg/day for 6 months. Simvastatin treatment significantly decreased serum TC (240+/-29-200+/-22 mg/dl, P<0.001), low-density lipoprotein cholesterol (LDL-C; 114+/-20-99+/-17 mg/dl, P<0.05) and TG levels (217+/-103-130+/-38 mg/dl, P<0.01). In addition, there were significant decreases in very-low-density lipoprotein cholesterol (VLDL-C; 53+/-20-34+/-15 mg/dl, P<0.001). The Cmax and AUC of simvastatin were increased about eight-fold, when simvastatin was given in combination with CsA. In contrast, no significant changes in simvastatin levels were observed when combination with tacrolimus. Although simvastatin levels were increased with CsA, there were no abnormal changes in renal and liver functions, creatinine phosphokinase (CPK) levels or in incidence of adverse effects.

FK506-induced kidney tubular cell injury

Some renal changes associated with cyclosporine, such as tubular vacuolization and glomerular thrombosis, have also been reported with FK506. Furthermore, FK506 therapy is associated with a decrease in glomerular filtration rate and renal plasma flow and an increase in renal vascular resistance. We studied the in vitro tubular cell sensitivity to FK506 in comparison with CsA, the ultrastructural changes induced by FK506 and CsA, and the effect of both drugs on tubular cell growth in vitro. We also investigated whether FK506 and CsA induced endothelin-1 (ET-1) secretion of cultured tubular cells and whether this stimulatory effect coincided with a change in the endothelin systemic synthesis. Exposure of tubular cells to high concentrations of FK506 or CsA (10, 50, 100 μM) induced a time- and dose-dependent cell injury in vitro. The damage induced by FK506 and CsA was characterized by a direct cytotoxic effect on tubular cells, as expressed by release of 3H thymidine from prelabeled cells, N-acetyl-β-D-glu-cosaminidase release, and cell detachment. Ultrastructural changes (vacuolizations, swelling, and mitochondrial enlargement) and inhibition of the growth of cultured tubular cells were also observed at high concentrations of FK506 and CsA. Low concentrations of FK506 and CsA (1, 0.1, 0.01, 0.001 %mUM) were not cytotoxic and induced only a minimal inhibitory effect on the growth of tubular cells in vitro. We demonstrated that FK506 (1, 0.1, 0.01 μM) time-dependently stimulated the secretion of endothelin by cultured tubular cells. CsA 10, 1, 0.1, 0.01 also exerted an enhancing effect on ET-1 secretion in cultured tubular cells. We observed that the concentration of CsA that induced the most important enhancing effect was 10 or 100 times higher than that required for FK506 to observe the same effect. The concentrations of FK506 or CsA that induced ET-1 secretion were not cytolytic for tubular cells in vitro. FK506− or CsA-treated rats showed an increase in serum level of ET-1 in comparison with the control. Through the stimulatory effect on endothelin secretion by tubular cells, FK506 and CsA may induce a perturbation of renal hemodynamics. Concentrations of FK506 and CsA, higher than established serum levels but close to those reached in tissues, are cytotoxic for tubular cells and induced ultrastructural changes and a significant delayed regeneration.

Risk factors for malignancy in Japanese renal transplant recipients

Among recipients of renal transplants, the incidences of renal cancer and gastrointestinal cancer are higher and that of skin cancer is much lower in Japan than in Europe and North America.

Tacrolimus may be associated with lower osteonecrosis rates after renal transplantation.

To compare the effect of two immunosuppressive agents, cyclosporin A and tacrolimus, in terms of the development of osteonecrosis after renal transplantation, a cohort study was done. The cyclosporin A group and the tacrolimus group consisted of 32 patients each, and were matched for age, gender, and renal allograft (cadaveric or living). Four patients with osteonecrosis of the femoral head and one patient with osteonecrosis of the knee were observed in the cyclosporin A group, whereas none of the patients in the tacrolimus group had osteonecrosis. All five patients with osteonecrosis were diagnosed on magnetic resonance imaging within 2 years after renal transplantation, and were followed up for more than 3 years after diagnosis. Significant differences were observed in the number of patients with acute rejection (cyclosporin A, 16 patients versus tacrolimus, seven patients). Significant differences also were found in the dose of pulse corticosteroids at 2 weeks (cyclosporin A, 1161.1 ± 939.6 mg versus tacrolimus, 674.3 ± 587.5 mg) and 4 weeks after transplantation (1727.5 ± 1399.9 mg versus 965.0 ± 861.9 mg). The risk of osteonecrosis after renal transplantation was reduced in the patients who used tacrolimus for immunosuppression, which reduced the number of acute rejection episodes and the dose of pulse corticosteroid administration.

Rapid and simple determination of mycophenolic acid in human plasma by ion-pair RP-LC with fluorescence detection

Mycophenolic acid (MPA) is an immunosuppressive drug given as the prodrug of mycophenolate mofetil (MMF). In order to investigate the pharmacokinetics of MPA, a simple, specific, sensitive and reliable method has been established for the quantitative determination of MPA in plasma from renal transplant recipients. The method involves a single-step protein precipitation procedure and a specific determination by ion-pair reversed-phase high-performance liquid chromatography (HPLC) with fluorescence detection. Separation was achieved on a C18 column (150 x 4.6 mm, 5 microm) with a mobile phase composed of borate buffer (pH 10.0; 50 mM)--acetonitrile--tetrabutylammonium bromide (200 mM) (75:25:1, v/v/v). The fluorescence detector was set at 310 (excitation) and 430 nm (emission). Following protein precipitation with ice-cold acetonitrile, clear supernatants (50 microl) were injected into the HPLC system. The retention time of MPA was approximately 4.5 min. The HPLC run time was 8 min. The assay was linear in concentration range 0.2-20.0 microg/ml for MPA in human plasma. Precision of the assay in the concentration range examined was from 0.89 to 3.21% for the intra-assay run and from 3.01 to 4.35% for the inter-assay run. A limit of detection was 0.05 microg/ml at a signal-to-noise ratio of 3. This validated method was then applied to the determination of MPA concentrations in renal transplant recipients after oral administration of 0.75 g of MMF.

Lymphotactin: a key regulator of lymphocyte trafficking during acute graft rejection.

The attraction of leucocytes to allografts is essential for rejection. The prcocess is controlled by chemokines. In order to clarify the role of lymphotactin (a cytokine that represents a novel branch of the chemokine superfamily) in regulating leucocyte trafficking during graft rejection, we used rat renal transplantation models to examine its gene expression and the distribution of lymphotactin‐expressing cells in renal grafts. Lymphotactin mRNA was upregulated strongly in acutely rejecting renal allografts. The mRNA was undetectable in isografts, chronically rejecting renal allografts or normal kidney. Once lymphotactin was expressed, large numbers of infiltrating lymphocytes were seen. Moreover extended studies demonstrated that in cultured rat spleen cells the expression of lymphotactin mRNA was markedly induced by phytohaemagglutinin (PHA) or phorbol myristate acetate (PMA), and such induction was inhibited by the immunosuppressive drugs FK506 and cyclosporin. Collectively, these observations provide new evidence demonstrating that lymphotactin is a key regulator of lymphocyte motility and adhesiveness during acute allograft rejection. FK506 and cyclosporin inhibition of lymphotactin expression is likely to represent an important molecular mechanism of the action of the drugs.

Serum HGF levels in acute renal rejection after living related renal transplantation

Hepatocyte growth factor (HGF), a long sought-after hepatotrophic factor, has recently been shown to act as a renotrophic factor in regeneration of the kidney. We investigated serum HGF levels in 16 renal transplant patients. In patients with acute rejection, the serum HGF level was markedly increased (over 1 ng/ml), and its elevation was accompanied by an increase in serum creatinine and blood urea nitrogen (BUN). In contrast, serum HGF levels were continuously low in patients without rejection. We conclude that serum HGF may become a clinically useful marker for the assessment of acute renal rejection.

Vitamin D Deficiency Predicts Decline in Kidney Allograft Function: A Prospective Cohort Study

CONTEXT Vitamin D, often deficient in kidney transplant (KTx) recipients, has potential immunomodulatory effects. OBJECTIVE This study aimed to evaluate whether vitamin D status affects the rate of decline in kidney allograft function. DESIGN, SETTING, AND PATIENTS The study included a prospective cohort of 264 ambulatory KTx recipients at a single Japanese center. MAIN OUTCOME MEASURES We measured the baseline 25-hydroxyvitamin D (25D) concentration and examined its association with annual decline in estimated glomerular filtration rate (eGFR). Secondary outcome was rescue treatment with iv methylprednisolone (IV-MP) as an index of rejection episodes. RESULTS The mean serum 25D concentration was 17.1 (SD 6.5) ng/mL, and 68.4% patients had vitamin D inadequacy or deficiency. Time after KTx was a significant effect modifier for the association of serum 25D concentration with annual eGFR change and need for IV-MP (P for interaction < .1). We divided patients according to the median time after KTx (10 y) and found that low vitamin D was significantly associated with a rapid eGFR decline at less than 10 years after KTx but not at 10 or more years after KTx. The same was true for rescue treatment with IV-MP. Overall, propensity score matching showed independent associations of low vitamin D with both outcomes. Stratified matching confirmed pronounced associations at less than 10 years after KTx. CONCLUSIONS Vitamin D deficiency predicts a rapid decline in eGFR and need for IV-MP at less than 10 years after KTx. Future studies are warranted to evaluate the clinical efficacy of vitamin D supplementation.