Kyu Ha Huh

Mycophenolic Acid Inhibits Platelet-Derived Growth Factor-Induced Reactive Oxygen Species and Mitogen-Activated Protein Kinase Activation in Rat Vascular Smooth Muscle Cells

Vascular smooth muscle cell (VSMC) proliferation is the major pathologic feature associated with chronic allograft nephropathy, and mycophenolic acid (MPA) inhibits VSMC proliferation. Since the role of inosine monophosphate dehydrogenase (IMPDH)‐dependent de novo guanosine synthesis is limited in VSMCs, we examined the effects of MPA on platelet‐derived growth factor (PDGF)‐induced cellular ROS and mitogen‐actived protein kinases (MAPK) activation in VSMCs. Primary cultured rat VSMCs were stimulated with PDGF‐BB in the presence or absence of MPA. Cell proliferation was assessed by [3H]‐thymidine incorporation, ROS by flow cytometry and MAPK activation by Western blot analysis. PDGF increased cell proliferation, cellular ROS and extracellular‐regulated protein kinase (ERK) 1/2 and p38 MAPK activation by 3.4‐, 1.6‐, 3.3‐ and 3.9‐fold, respectively. MPA at above 1 μM inhibited PDGF‐induced cellular ROS and ERK 1/2 and p38 MAPK activation, as well as proliferation. Structurally different anti‐oxidants and inhibitor of ERK or p38 MAPK blocked PDGF‐induced proliferation. Anti‐oxidants also inhibited ERK 1/2 and p38 MAPK activation. Exogenous guanosine partially recovered the inhibitory effect of MPA on VSMC proliferation. These results suggest that MPA may inhibit PDGF‐induced VSMC proliferation partially through inhibiting cellular ROS, and subsequent ERK 1/2 and p38 MAPK activation in addition to inhibiting IMPDH.

Exchange living-donor kidney transplantation: merits and limitations.

Background. The shortage of donor organs is one of the major barriers to transplantation worldwide. After the success of the direct exchange donor (swap) program in Korea since 1991, we have developed a swap-around program. However, reports on the long-term outcomes of exchange donor programs are scarce. Methods. From September 1995 to September 2006, we performed 1193 cases of renal transplantation, including 398 cases from living-unrelated donors. The living-unrelated donors included 129 exchange donors and 269 nonexchange donors. We compared the outcomes of the exchange program with that of the nonexchange program, and examined the merits and limitations of the exchange program. Results. The reasons for the exchange program were ABO incompatibility (n=84, 65.1%), human leukocyte antigen mismatching beyond our criteria (n=39, 30.2%), or positive lymphocyte crossmatch (n=6, 4.7%). The overall 10-year graft survival (86.3%) of exchange transplantation was comparable with that of nonexchange (82.3%) or one- haplotype matched living-related (81.2%) transplantation (P=0.2994). In multivariate analysis, exchange versus nonexchange donors did not affect graft survival. The proportion of blood-type O donors was much lower in the exchange group (29.5%) than in the nonexchange group (42.4%; P=0.026). Blood-type O kidneys were preferentially allocated to blood-type O recipients (78.9%) in the exchange group as compared with the nonexchange group (54.4%; P=0.007). Conclusion. We achieved excellent outcomes by using a donor exchange program as an option to reduce the donor organ shortage. However, the exchange donor program has no added benefit for blood-type O recipients.

The RhoGDI-α/JNK signaling pathway plays a significant role in mycophenolic acid- induced apoptosis in an insulin-secreting cell line

Mycophenolic acid (MPA)-induced beta-cell toxicity is an important factor for islet graft function. The signal transduction mechanisms underlying this process have not been fully explored. Using a proteomics approach, we examined protein expression patterns in MPA-treated RIN-5 cells and found that RhoGDI-alpha expression is altered by MPA-treatment. We examined the relationship between RhoGDI-alpha expression and activated JNK during MPA-induced apoptosis. Cells were treated with N-acetyl-cysteine (NAC), caspase inhibitor, JNK inhibitor, guanosine or GTP for 1 h before being treated with MPA. To investigate the regulatory effects of RhoGDI-alpha on JNK activity, we examined cells showing either elevated or reduced expression of RhoGDI-alpha as a result of transfection with cDNA or siRNA constructs, respectively. MPA significantly increased cell death, caspase-3 expression and JNK activation, but it decreased the expression of a protein spot 25 observed by two-dimensional electrophoresis. This protein 25 was identified as RhoGDI-alpha by mass spectrometry. MPA-induced cell death and down-regulation of RhoGDI-alpha were prevented by guanosine, GTP or a JNK inhibitor. However, MPA-induced cell death was partially restored by treatment with a caspase inhibitor, but not by NAC treatment. RhoGDI-alpha expression was not affected by treatment with NAC or caspase inhibitor. Over-expression of RhoGDI-alpha increased cell viability and decreased activated JNK expression following exposure to MPA, whereas knockdown of RhoGDI-alpha enhanced MPA-induced cell death and increased the activation of JNK. In conclusion, MPA induces significant apoptosis in insulin-secreting cells via down-regulation of RhoGDI-alpha linked with increased JNK expression. This RhoGDI-alpha/JNK pathway might be the focus of therapeutic target for the prevention of MPA-induced islet apoptosis.

Sirolimus-Induced Pneumonitis After Renal Transplantation: A Single-Center Experience

PURPOSE Sirolimus is a potent immunosuppressive agent used with increasing frequency in kidney transplantation. However, sirolimus can increase the rate of unexplained interstitial pneumonitis. The aim of this study was to evaluate the clinical characteristics of sirolimus-induced pneumonitis and the therapeutic results in renal transplant recipients. PATIENTS AND METHODS Seventy-two patients received sirolimus, conversion or de novo regimen, at our center between January 2007 and April 2011. Twelve of the 72 patients (16.7%) developed interstitial pneumonitis. The patients were divided into three groups according to the following indications of sirolimus use: de novo, early conversion, and late conversion groups. RESULTS The mean duration of follow-up was 11.0 ± 11.5 months. The mean blood level of sirolimus measured by microparticulate enzyme immunoassay was 16.5 ± 7.4 ng/mL at the time of diagnosis. The mean time from the start of sirolimus to pneumonitis onset was 14.7 ± 8.0 months. The clinical presentation included fever, cough, dyspnea, general weakness, and periorbital edema. In most cases, radiological imaging tests revealed bilateral lower-lobe involvement. Bronchoalveolar lavage was performed in three patients and two patients showed lymphocytic alveolitis. Sirolimus was discontinued or reduced for the treatment of pneumonitis. All cases of pneumonitis were resolved within 2 to 4 weeks. CONCLUSION Sirolimus blood level should be monitored tightly and early intervention is important when sirolimus-induced pneumonitis is suspected.

A 6-Month, Multicenter, Single-Arm Pilot Study to Evaluate the Efficacy and Safety of Generic Tacrolimus (TacroBell) After Primary Renal Transplantation

OBJECTIVE Tacrolimus has been shown to be an important immunosuppressive agent in organ and bone marrow transplantation. Previously, we reported that there were no statistically significant differences between the pharmacokinetic parameters of the oral formulation of generic tacrolimus (TacroBell) and the conventional formulation (Prograf). This study was designed to evaluate the efficacy and safety of oral capsules of TacroBell in de novo renal transplantation. METHODS Ninety-six renal transplant recipients from 9 transplantation centers in South Korea were enrolled between November 2005 and July 2007. De novo renal recipients ranged from 19-65 years old. Ninety-four patients who underwent renal transplantation were administered study drug at least one time in the intent-to-treat (ITT) analysis. This phase 4 clinical trial was a 26-week, open-label, noncomparative, multicenter study. RESULTS An acute rejection episode developed in 10/94 recipients (10.6%, 95% confidence interval, 4.4%-16.9%). There were no patient deaths during the study. The 6-month graft survival rate was 96.8%. CONCLUSION Based on this study, treatment with TacroBell is considered to be efficient and safe after primary renal transplantation.

The clinicopathological relevance of pretransplant anti-angiotensin II type 1 receptor antibodies in renal transplantation

Background Anti-angiotensin II type 1 receptor antibodies (AT1R-Abs) have been suggested as a risk factor for graft failure and acute rejection (AR). However, the prevalence and clinical significance of pretransplant AT1R-Abs have seldom been evaluated in Asia. Methods In this multicenter, observational cohort study, we tested the AT1R-Abs in pretransplant serum samples obtained from 166 kidney transplant recipients. Statistical analysis was used to set a threshold AT1R-Abs level at 9.05 U/mL. Results Pretransplant AT1R-Abs were detected in 98/166 (59.0%) of the analyzed recipients. No graft loss or patient death was reported during the study period. AT1R-Abs (+) patients had a significantly higher incidence of biopsy-proven AR than AT1R-Abs (-) patients (27.6 versus 10.3%, P = 0.007). Recipients with pretransplant AT1R-Abs had a 3.2-fold higher risk of AR within a year of transplantation (P = 0.006). Five study subjects developed microcirculation inflammation (score ≥2). Four of them were presensitized to AT1R-Abs. In particular, three patients had a high titer of anti-AT1R-Abs (>22.7 U/mL). Conclusions Pretransplant AT1R-Abs is an independent risk factor for AR, especially acute cellular rejection, and is possibly associated with the risk of antibody-mediated injury. Pretransplant assessment of AT1R-Abs may be useful for stratifying immunologic risks.

Chronologically different incidences of post‐transplant malignancies in renal transplant recipients: single center experience

The incidence of malignancy in transplant recipients is known to be higher than the same in the general population. However, the types of malignancies vary geographically, and the relative risks (RR) for malignancy in transplant recipients, compared with that of the general population, also differ country‐by‐country. In this study, we investigated the incidence and characteristics of malignancies after renal transplantation in a single center. A total of 2630 renal recipients who underwent surgery between April 1979 and June 2007 were enrolled in this study. The cumulative and interval incidences of malignancies were calculated for every 3 years post‐transplantation. One‐hundred ninety cases of postrenal transplant malignancies among 177 recipients (6.73%) were reported until 2007. The post‐transplant malignancies were detected from 6 to 290 months after transplantation, with a mean duration of 112.6 ± 66.0 months. Skin cancer [35 (18.4%)] was the most common post‐transplant malignancy, followed by thyroid [25 (13.2%)], stomach [22 (11.6%)], colorectal [22 (11.6%)], and urologic cancers [19 (10.0%)]. As the post‐transplant period increased, the interval incidence of malignancy correspondingly increased. Virus‐related malignancies, such as Kaposi’s sarcoma and cervical cancer, developed earlier within the post‐transplant period, while urologic cancer, colorectal cancer developed late in the post‐transplant period. The recipient’s age at the time of transplantation was the sole independent risk factor for post‐transplant malignancy based on the multivariate analysis (RR = 2.723, P < 0.0001 in the >50‐year‐old age group). We should establish strategies for post‐transplant malignancy‐screening based on the recipient’s age at the time of transplantation, the post‐transplant interval, and the national trend of post‐transplant malignancy.

Safety and efficacy of the early introduction of everolimus with reduced-exposure cyclosporine a in de novo kidney recipients.

Background Everolimus and cyclosporine A (CsA) exhibit synergistic immunosuppressive activity when used in combination. We examined the safety and efficacy of the use of everolimus with a cyclosporine-sparing strategy in de novo renal transplant recipients. Methods A comparative, parallel, randomized, open-label 1-year study has been performed in 148 patients from five transplant centers to compare the efficacy and tolerability of everolimus and reduced exposure CsA (the investigational group) or enteric-coated mycophenolate sodium and standard-exposure CsA (the control group) in combination with basiliximab and steroids. The eligible subjects were randomly assigned at 1 month after transplantation. Efficacy failure (biopsy-proven acute rejection, death, graft loss, or loss to follow-up), safety, and renal function were evaluated. Results One graft loss has been reported in the control group and no patient death were reported in either group. The incidence of biopsy-proven acute rejection until 12 months after transplantation of the investigational group was 7.5%, compared to 11.1% of the control group (P=0.565). The mean estimated glomerular filtration rates of the investigational group at 12 months after transplantation was significantly higher (68.1±16.8 ml/min/1.73 m2) than that of the control group (60.6±15.8 ml/min/1.73 m2; P=0.016). There was no significant difference (P>0.05) in the incidence of discontinuations and serious adverse events between the groups. Conclusion The results of this study provide the evidences that (1) the calcineurin inhibitor (CNI) minimization by the introduction of everolimus after 1-month posttransplantation keeps the incidences of acute rejection and addtional risks as low as the conventional immunosuppression; (2) it allows minimizing CNI exposure, consequently reducing CNI nephrotoxicity and preserving renal function.

ABO incompatible living donor kidney transplantation in Korea: highly uniform protocols and good medium-term outcome

The organ shortage is as serious in Korea as in other parts of the world. As about one‐third of the potential living donors are ABO incompatible (ABOi), transplantation across the blood group barrier can help overcome this shortage. One hundred and twenty‐five ABOi kidney transplantations (KTs) were performed between 2007 and 2010 in Korea. We collected the perioperative and follow‐up data for 118 of these patients until September 2011. The preconditioning and immunosuppressive protocols were almost identical across the different transplant centers, with rituximab but no splenectomy; pre‐transplant plasmapheresis (PP) with target anti‐A/B titer 8 or 16 on transplant day, on‐demand, rather than routine, post‐transplant PP, and tacrolimus‐based immunosuppressants. The number of patients and participating centers showed a rapid increase over time, and in 2010, ABOi KT (n = 79) comprised 10% of all the living donor KTs in Korea. The mean follow‐up period was 21 months (range, 1–56 months). Sixteen (14%) patients developed acute rejection, and three of these had antibody‐mediated rejection (AMR). Two‐yr patient and graft survival were 99.2% and 97.5%, respectively. No graft was lost due to AMR. ABOi KT is rapidly expanding in Korea with excellent medium‐term outcome and will help mitigate the organ shortage.

Is the Affinity Column–Mediated Immunoassay Method Suitable as an Alternative to the Microparticle Enzyme Immunoassay Method as a Blood Tacrolimus Assay?

BACKGROUND Tacrolimus is a potent immunosuppressive drug used in organ transplantation. Because of its substantial toxic effects, narrow therapeutic index, and interindividual pharmacokinetic variability, therapeutic drug monitoring of whole-blood tacrolimus concentrations has been recommended. We investigated the comparability of the results of 2 immunoassay systems, affinity column-mediated immunoassay (ACMIA) and microparticle enzyme immunoassay (MEIA), comparing differences in the tacrolimus concentrations measured by the 2 methods in relation to the hematologic and biochemical values of hepatic and renal functions. METHODS A total of 154 samples from kidney or liver transplant recipients were subjected to Dimension RxL HM with a tacrolimus Flex reagent cartilage for the ACMIA method and IMx tacrolimus II for the MEIA method. RESULTS Tacrolimus concentrations measured by the ACMIA method (n = 154) closely correlated with those measured by the MEIA method (r = 0.84). The Bland-Altman plot using concentration differences between the 2 methods and the average of the 2 methods showed no specific trends. The tacrolimus levels determined by both the MEIA method and the ACMIA method were not influenced by hematocrit levels, but the difference between the 2 methods (ACMIA - MEIA) tended to be larger in low hematocrit samples (P < .001). CONCLUSION The ACMIA method used for a tacrolimus assay is precise and has advantages, including the lack of a required pretreatment procedure. Furthermore, it is only slightly influenced by the hematologic or biochemical status of the samples.