髙橋 和男

BACKGROUND: Maintenance of low serum urate levels is important for the management of gout. Achieving the recommended serum urate levels of less than 6.0 mg/dL is difficult in elderly (65 years of age or older) patients with renal impairment. Xanthine oxidase inhibitors allopurinol and febuxostat are used for this purpose. Although febuxostat had been shown to be efficacious in elderly patients, its safety and efficacy in elderly female patients with hyperuricemia remain unclear. OBJECTIVE: The aim of this study was to assess the efficacy and safety of febuxostat in elderly female patients. METHODS: We studied a retrospective cohort study. The study included elderly Japanese patients (65 years of age or older) who were treated with febuxostat at Fujita Health University Hospital from January 2012 to December 2013. The treatment goal was defined as achievement of serum urate levels of 6.0 mg/dL or lower within 16 weeks; this was the primary endpoint in the present study. Adverse events of febuxostat were defined as more than twofold increases in Common Terminology Criteria for adverse events scores from baseline. RESULTS: We evaluated 82 patients treated with febuxostat during the observation period and classified them into male (n=53) and female (n=29) groups. The mean time to achievement of the treatment goal was significantly shorter in the female group (53 days) than in the male group (71 days). There were no significant differences in adverse events between the 2 groups. CONCLUSION: Our findings suggest that the efficacy of febuxostat in elderly female patients is superior to that in elderly male patients and that the safety is equivalent.

BACKGROUND: To clarify the therapeutic impact of tonsillectomy and combined therapies of tonsillectomy plus steroid on the long-term prognosis of immunoglobulin A nephropathy (IgAN). METHODS: A retrospective study was conducted on 208 patients with IgAN between 1986 and 2009. According to the strategies for treatments, patients were divided into four groups: tonsillectomy and steroid pulse (TSP, n = 47), tonsillectomy and oral steroid (TOS, n = 33), tonsillectomy alone (T, n = 56), and N group (no particular therapy, n = 72). Multivariate analysis based on the Cox's regression model was used to assess the relative risk of reaching the outcome of doubling creatinine based on the influence of baseline prognostic factors. RESULTS: The mean observation periods were 53.8 months in the TSP group, 122.0 months in the TOS group, 102.9 months in the T group, and 84.6 months in the N group. During an observation period, serum creatinine levels doubled as follows: one in the TSP group (2.1 %), two in the TOS group (6.1 %), five in the T group (8.9 %), histological severity, and 22 in the N group (30.6 %). The Cox's regression proportional hazard model showed that gender, age, histological activity, dialysis induction risk and therapy were associated with doubling creatinine levels. Hazard ratios (95 % CI) and (P value) in T, TOS, and TSP groups versus N were 0.314 (0.11-0.93, P = 0.037), 0.213 (0.04-1.10, P = 0.065), and 0.032 (0.00-0.28, P = 0.002), respectively. CONCLUSION: A combination therapy of tonsillectomy and steroid pulse had the most significant therapeutic impact compared to other therapies.

IgA is the most abundantly produced antibody and plays an important role in the mucosal immune system. Human IgA is represented by two isotypes, IgA1 and IgA2. The major structural difference between these two subclasses is the presence of nine potential sites of O-glycosylation in the hinge region between the first and second constant region domains of the heavy chain. Thr(225), Thr(228), Ser(230), Ser(232) and Thr(236) have been identified as the predominant sites of O-glycan attachment. The range and distribution of O-glycan chains at each site within the context of adjacent sites in this clustered region create a complex heterogeneity of surface epitopes that is incompletely defined. We previously described the analysis of IgA1 O-glycan heterogeneity by use of high resolution LC-MS and electron capture dissociation tandem MS to unambiguously localize all amino acid attachment sites in IgA1 (Ale) myeloma protein. Here, we report the identification and elucidation of IgA1 O-glycopeptide structural isomers that occur based on amino acid position of the attached glycans (positional isomers) and the structure of the O-glycan chains at individual sites (glycan isomers). These isomers are present in a model IgA1 (Mce1) myeloma protein and occur naturally in normal human serum IgA1. Variable O-glycan chains attached to Ser(230), Thr(233) or Thr(236) produce the predominant positional isomers, including O-glycans composed of a single GalNAc residue. These findings represent the first definitive identification of structural isomeric IgA1 O-glycoforms, define the single-site heterogeneity for all O-glycan sites in a single sample, and have implications for defining epitopes based on clustered O-glycan variability.

The human UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyl-transferase 2 (GalNAc-T2) is one of the key enzymes that initiate synthesis of hinge-region O-linked glycans of human immunoglobulin A1 (IgA1). We designed secreted soluble form of human GalNAc-T2 as a fusion protein containing mouse immunoglobulin light chain kappa secretory signal and expressed it using baculovirus and mammalian expression vectors. The recombinant protein was secreted by insect cells Sf9 and human HEK 293T cells in the culture medium. The protein was purified from the media using affinity Ni-NTA chromatography followed by stabilization of purified protein in 50mM Tris-HCl buffer at pH 7.4. Although the purity of recombinant GalNAc-T2 was comparable in both expression systems, the yield was higher in Sf9 insect expression system (2.5mg of GalNAc-T2 protein per 1L culture medium). The purified soluble recombinant GalNAc-T2 had an estimated molecular mass of 65.8kDa and its amino-acid sequence was confirmed by mass-spectrometric analysis. The enzymatic activity of Sf9-produced recombinant GalNAc-T2 was determined by the quantification of enzyme-mediated attachment of GalNAc to synthetic IgA1 hinge-region peptide as the acceptor and UDP-GalNAc as the donor. In conclusion, murine immunoglobulin kappa secretory signal was used for production of secreted enzymatically active GalNAc-T2 in insect baculovirus expression system.

IgA nephropathy (IgAN) is the most common primary glomerulonephritis in the world. Aberrantly glycosylated IgA1, with galactose (Gal)-deficient hinge region (HR) O-glycans, plays a pivotal role in the pathogenesis of the disease. It is not known whether the glycosylation defect occurs randomly or preferentially at specific sites. We have described the utility of activated ion-electron capture dissociation (AI-ECD) mass spectrometric analysis of IgA1 O-glycosylation. However, locating and characterizing the entire range of O-glycan attachment sites are analytically challenging due to the clustered serine and threonine residues in the HR of IgA1 heavy chain. To address this problem, we analyzed all glycoforms of the HR glycopeptides of a Gal-deficient IgA1 myeloma protein, mimicking the aberrant IgA1 in patients with IgAN, by use of a combination of IgA-specific proteases + trypsin and AI-ECD Fourier transform ion cyclotron resonance (FT-ICR) tandem mass spectrometry (MS/MS). The IgA-specific proteases provided a variety of IgA1 HR fragments that allowed unambiguous localization of all O-glycosylation sites in the six most abundant glycoforms, including the sites deficient in Gal. Additionally, this protocol was adapted for on-line liquid chromatography (LC)-AI-ECD MS/MS and LC-electron transfer dissociation MS/MS analysis. Our results thus represent a new clinically relevant approach that requires ECD/electron transfer dissociation-type fragmentation to define the molecular events leading to pathogenesis of a chronic kidney disease. Furthermore, this work offers generally applicable principles for the analysis of clustered sites of O-glycosylation.

Human immunodeficiency virus type 1 (HIV-1) entry is mediated by the interaction between a variably glycosylated envelope glycoprotein (gp120) and host-cell receptors. Approximately half of the molecular mass of gp120 is contributed by N-glycans, which serve as potential epitopes and may shield gp120 from immune recognition. The role of gp120 glycans in the host immune response to HIV-1 has not been comprehensively studied at the molecular level. We developed a new approach to characterize cell-specific gp120 glycosylation, the regulation of glycosylation, and the effect of variable glycosylation on antibody reactivity. A model oligomeric gp120 was expressed in different cell types, including cell lines that represent host-infected cells or cells used to produce gp120 for vaccination purposes. N-Glycosylation of gp120 varied, depending on the cell type used for its expression and the metabolic manipulation during expression. The resultant glycosylation included changes in the ratio of high-mannose to complex N-glycans, terminal decoration, and branching. Differential glycosylation of gp120 affected envelope recognition by polyclonal antibodies from the sera of HIV-1-infected subjects. These results indicate that gp120 glycans contribute to antibody reactivity and should be considered in HIV-1 vaccine design.

Ten genetically modified Maackia amurensis hemagglutinin (MAH) clones at the carbohydrate-recognition loop were found to bind glycophorin A and a mucin mimetic with NeuAcalpha2-3Galbeta1-3GalNAcalpha (monosialyl-T antigen) in different relative intensity. Binding profiles of these lectins to human serum IgA1 from healthy individuals and from IgA nephropathy patients were subjected to the cluster analysis. Two large groups, one with only healthy individuals and another with all IgA nephropathy patients, were generated. The results strongly suggest that the library of genetically modified MAH is a useful tool for serum diagnosis of IgA nephropathy.

The IgA isotype of human antibodies triggers inflammatory responses via the IgA-specific receptor FcalphaRI (CD89). Structural studies have suggested that IgA1 N-glycans could modulate the interaction with FcalphaRI. We have carried out detailed biophysical analyses of three IgA1 samples purified from human serum and recombinant IgA1-Fc and compared their binding to FcalphaRI. Analytical ultracentrifugation revealed wide variation in the distribution of polymeric species between IgA1 samples, and Fourier transform ion cyclotron resonance mass spectrometry showed overlapping but distinct populations of N-glycan species between IgA1 samples. Kinetic and equilibrium data from surface plasmon resonance experiments revealed that variation in the IgA1 C H2 N-glycans had no effect on the kinetics or affinity constants for binding to FcalphaRI. Indeed, complete enzymatic removal of the IgA1 N-glycans yielded superimposable binding curves. These findings have implications for renal diseases such as IgA nephropathy.

BACKGROUND: Immunoglobulin A nephropathy (IgAN) is characterized by an aberrant structure of O-glycans in the IgA1 hinge region. Recently, under-galactosylated IgA1 has been found to be increased in Caucasian IgAN patients. Thus, we examined this in Japanese IgAN patients. METHODS: An enzyme-linked immunosorbent assay of binding between Helix aspersa (HAA) and serum IgA was performed in Japanese IgAN patients and the HAA-IgA binding levels were compared among IgAN patients (n = 41), patients with other forms of kidney disease (OKD, n = 43) and healthy controls (n = 38). The clinicopathological severity of IgAN was then analysed between patients with high and low HAA-IgA binding levels. The levels were also compared in 11 patients before and after the combination of tonsillectomy and steroid pulse therapy. Furthermore, we examined the O-glycan structure of IgA1 hinge glycopeptides by mass spectrometry (MS). RESULTS: The HAA-IgA binding levels were significantly higher in IgAN patients compared with either healthy controls (P = 0.0025) or those with OKD (P = 0.016). To reflect the absolute level of under-galactosylated IgA, we multiplied the HAA-IgA binding level by the serum IgA concentration to produce an indicative value. The specificity and sensitivity of this value were 89% and 66%, respectively. MS showed that peak distribution of IgA1 hinge glycopeptides was shifted to smaller molecular weights in high HAA-IgA-binding IgAN patients. There was no correlation between the HAA-IgA binding level and either disease severity or the use of combination therapy. CONCLUSIONS: HAA-IgA binding is significantly increased in Japanese IgAN patients. This potential IgAN marker is not affected by disease severity or therapeutic intervention.

BACKGROUND: The KM mouse lacks endogenous genes for immunoglobulins and carries the entire human IgH locus and the IgLk transgene. Therefore, human IgA1 does not provoke a hetero-immune response. We had observed mesangial IgA deposits in KM mice given desialo-degalacto (DeS/DeGal) IgA1. METHODS: In this study, the mice were immunized with synthetic IgA1 hinge (glyco-)peptide before administration of DeS/DeGal IgA1, and the effects of the pre-immunization were evaluated. Mice were divided into sHP, 5GalNAc-sHP and non-immunization groups. In two pre-immunization groups, KLH-conjugated sHP or KLH-5GalNAc-sHP, which has five GalNAc residues, was subcutaneously given three times every 2 weeks. Two weeks after the final pre-immunization, DeS/DeGal IgA1 was administered daily for 5 weeks. Serial serum levels of anti-sHP and anti-IgA1 antibodies were evaluated by ELISA. On the day of the last administration of IgA1, renal biopsy was performed. RESULTS: Mesangial IgA deposits were observed in all non-immunized mice. In pre-immunized mice, IgA deposition was not detected in 6 of 13 sHP mice and 1 of 4 5GalNAc-sHP mice. The intensities of IgA deposits were significantly different between sHP groups and non-immunized (P = 0.003) groups. There was a significant inverse correlation between the intensities of IgA deposits and the anti-sHP antibody titers (P = 0.016). CONCLUSIONS: These results suggest that the anti-IgA1 hinge peptide antibody plays a role in the inhibition of glomerular IgA deposition.

Bisphenol A [BPA, 2,2-bis(4-hydoxyphenyl)propane], an industrial chemical used in the production of polycarbonate, epoxide resin, and polyarylate, is considered to be an endocrine-disrupting chemical. BPA may be present in some hollow-fiber dialyzers used in hemodialysis. In this study, we tested the amounts of BPA eluted from various hollow fibers. Furthermore, we measured the BPA concentration in the sera of 22 renal disease predialysis patients, as well as 15 patients who were receiving hemodialysis, to see if there is BPA accumulation in these patients. The elution test of BPA showed that a much larger amount of BPA was eluted from polysulfone (PS), and polyester-polymeralloy hollow fibers. Among renal disease patients who had not undergone hemodialysis, the serum BPA concentration increased as the renal function deteriorated, showing a significant negative association. In a crossover test between PS and cellulose (Ce) dialyzers, the predialysis serum BPA concentration of PS dialyzer users decreased after changing to a Ce dialyzer, and the serum BPA increased again after switching back to PS dialyzers. In patients who were using PS dialyzers, the BPA level significantly increased after a dialysis session. However, in the Ce dialyzer users, the BPA level decreased. Since accumulation of BPA could affect the endocrine or metabolic system of the human body, it is important to perform further investigations on dialysis patients.

The aim of the study was to develop a simple and precise method for identifying glycosylation of the IgA hinge region using surface-enhanced laser desorption/ionization (SELDI)-TOFMS with a lectin-coupled ProteinChip array. Serum IgA was isolated using an anti-IgA antibody column. Following reduction, alkylation, and trypsin digestion, the IgA fragments were applied on the ProteinChip coupled with jacalin, peanut agglutinin (PNA), or Vilsa villosa lectin (VVL). The SELDI-TOFMS peaks corresponding to the fragments containing IgA1 hinge glycopeptides trapped by each lectin were compared. The jacalin-, PNA-, and VVL-immobilized ProteinChips detected 13, 4, and 2 peaks, respectively. One major peak was confirmed as a glycopeptide by MS/MS analysis. These results suggest that a lectin-immobilized ProteinChip assay can be used to simplify the procedures for the analyses of the O-glycans in IgA1 hinge. This method potentially makes it possible to identify a disease-specific glycoform by selecting the appropriate ligand-coupled ProteinChip array.

To evaluate the efficacy of cytapheresis for the treatment of rapidly progressive glomerulonephritis (RPGN) caused by myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-associated vasculitis, the renal prognosis and the mortality rate at 1 year after treatment were compared between a Cytapheresis Group and a Steroid Pulse Group. The Cytapheresis Group included 10 patients who were treated with cytapheresis and oral corticosteroids. Five had granulocytapheresis with the Adacolumn (Japan Immuno Research Laboratories Co. Ltd, Takasaki, Japan) and the remaining five had leukocytapheresis with the leukocyte removal filter, Cellsorba (Asahi Medical Co. Ltd, Tokyo, Japan). The Steroid Pulse Group was comprised of 12 patients who were treated with methylprednisolone pulse therapy and oral corticosteroids. In the Cytapheresis Group, renal function recovered in 70% of the patients and the mortality rate was 10%. In the Steroid Pulse Group, renal function recovered in 66.7% and the mortality rate was 33.3%, with infection as the cause of death. Total doses of corticosteroids converted to prednisolone dose during a 1 month period, ranged from 280 mg to 1226 mg in the Cytapheresis Group. On the other hand, these dosages ranged from 2375 mg to 8380 mg in the Steroid Pulse Group. These results indicated that the mortality rate by infection could be reduced by adding cytapheresis therapy. Concerning the mechanism of cytapheresis, anti-inflammatory factors such as soluble tumor necrosis factor receptor, and interleukin-10 reduced after cytapheresis. These changes might be responsible for the efficacy of cytapheresis. In conclusion, cytapheresis is thought to be one of the effective treatments for RPGN caused by MPO-ANCA-associated vasculitis, reducing the levels of anti-inflammatory factors.

The effects of antibody-mediated rejection on long-term graft survival have not been fully investigated. The aim of this study is to clarify the influence on long-term survival of deposition of the complement split product C4d in allografts using polyclonal anti-C4d antibody. Inclusion criteria were recipients who underwent graft biopsy during acute deterioration of graft function within the first 2 yr after transplantation. Patients whose graft did not survive more than 1 yr and who received graft from an human leucocyte antigen (HLA)-identical sibling or an ABO-incompatible donor were excluded. Among the 92 recipients investigated, 22 (23.9%) had peritubular capillary C4d deposition, 15 (16.3%) had glomerular capillary C4d deposition and seven (7.6%) had both peritubular and glomerular capillary C4d deposition. Twenty of these 22 patients revealed acute cellular rejection, including borderline changes. There was no significant relationship between pathological severity of acute rejection and presence or absence of peritubular capillary C4d deposition. Graft survival was inferior in patients with peritubular capillary C4d deposition to that in patients without C4d deposition (p = 0.0419). Graft survival in patients with glomerular C4d deposition did not differ from that in patients without C4d deposition. In conclusion, C4d deposition in peritubular capillaries has a substantial impact on long-term graft survival. Copyright © Blackwell Munksgaard 2005.

The effects of antibody-mediated rejection on long-term graft survival have not been fully investigated. The aim of this study is to clarify the influence on long-term survival of deposition of the complement split product C4d in allografts using polyclonal anti-C4d antibody. Inclusion criteria were recipients who underwent graft biopsy during acute deterioration of graft function within the first 2 yr after transplantation. Patients whose graft did not survive more than 1 yr and who received graft from an human leucocyte antigen (HLA)-identical sibling or an ABO-incompatible donor were excluded. Among the 92 recipients investigated, 22 (23.9%) had peritubular capillary C4d deposition, 15 (16.3%) had glomerular capillary C4d deposition and seven (7.6%) had both peritubular and glomerular capillary C4d deposition. Twenty of these 22 patients revealed acute cellular rejection, including borderline changes. There was no significant relationship between pathological severity of acute rejection and presence or absence of peritubular capillary C4d deposition. Graft survival was inferior in patients with peritubular capillary C4d deposition to that in patients without C4d deposition (p = 0.0419). Graft survival in patients with glomerular C4d deposition did not differ from that in patients without C4d deposition. In conclusion, C4d deposition in peritubular capillaries has a substantial impact on long-term graft survival.