Shoichi Ozaki

Isolation and Characterization of CA XIV, a Novel Membrane-bound Carbonic Anhydrase from Mouse Kidney

Carbonic anhydrase (CA) is involved in various physiological processes such as acid-base balance and transport of carbon dioxide and ions. In this study, we have succeeded in the isolation of a novel CA from the mouse kidney by use of the signal sequence trap method. It is a 337-amino acid polypeptide with a calculated molecular mass of 37.5 kDa, consisting of a putative amino-terminal signal sequence, a CA domain, a transmembrane domain, and a short hydrophilic carboxyl terminus, which we designated CA XIV.1 The CA domain of CA XIV is highly homologous with those of known CAs, especially extracellular CAs including CA XII, IX, VI, and IV. The expression study of an epitope-tagged protein has suggested that CA XIV is located on the plasma membrane. When expressed in COS-7 cells, CA XIV exhibits CA activity that is predominantly associated with the membrane fraction. By Northern blot analysis, the gene expression of CA XIV is most abundant in the kidney and heart, followed by the skeletal muscle, brain, lung, and liver. In situ hybridization has revealed that, in the kidney, the gene is expressed intensely in the proximal convoluted tubule, which is the major segment for bicarbonate reabsorption and also in the outer border of the inner stripe of the outer medulla. In conclusion, we have cloned a functional cDNA encoding a novel membrane-bound CA. This study will bring new insights into our understanding of carbon dioxide metabolism and acid-base balance.

ANCA-associated Vasculitis: Diagnostic and Therapeutic Strategy

Among small-vessel vasculitides, microscopic polyangiitis (MPA), Wegeners granulomatosis (WG), and allergic granulomatous angiitis (AGA) are known collectively as ANCA-associated vasculitis (AAV) because of the involvement of anti-neutrophil cytoplasmic antibodies (ANCA) as the common pathogenesis. Major target antigens of ANCA associated with vasculitis are myeloperoxidase (MPO) and proteinase 3 (PR3). MPO-ANCA is related to MPA and AGA, and PR3-ANCA is the marker antibody in WG. MPO-ANCA-associated vasculitis is more frequent in Japan, whereas PR3-ANCA-associated vasculitis is more common in Europe and USA. ANCA appears to induce vasculitis by directly activating neutrophils. Therefore, no immunoglobulins or complement components are detected in the vasculitis lesions; hence, AAV is called pauci-immune vasculitis (pauci=few/little). Untreated patients with severe AAV with multi-organ involvement have a poor prognosis, which is improved by combination therapy with cyclophosphamide and high-dose corticosteroid. Randomized controlled trials (RCT) regarding induction and maintenance of remission of AAV indicated that the rate of remission induction by the standard regimen is approximately 90% in 6 months, that maintenance of remission can be achieved with oral azathioprine as well as cyclophosphamide, and that methotrexate can be used only for non-renal mild AAV. As these data were obtained mostly in patients positive for PR3-ANCA, caution must be taken in applying these findings to Japanese patients, most of whom are positive for MPO-ANCA. A prospective study is now underway to clarify the effectiveness of the standard regimen in Japanese patients with MPOANCA-associated vasculitis. This article describes the diagnostic criteria and the recent evidence-based therapeutic strategy of AAV.

Involvement of Th1 cells and heat shock protein 60 in the pathogenesis of intestinal Behcet's disease.

Involvement of excessive Th1 cell functions and heat shock protein expression in the pathogenesis of Behçets disease (BD) has been reported. In this study we have characterized immune responses in intestinal lesions of BD. Peripheral blood lymphocytes (PBL) of BD and healthy controls (HC) and tissue specimens of intestinal Behçets disease (intestinal BD), Crohns disease (CD) and ulcerative colitis (UC) were analysed for mRNA and protein expression by reverse transcriptase‐polymerase chain reaction (PCR) and immunohistochemistry, respectively. PBL of BD patients expressed the Th1‐related chemokine receptor, CCR5 and CXCR3 preferentially compared with those of healthy controls. Intestinal lesions of BD expressed interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α and interleukin (IL)‐12 mRNA, indicating Th1 skewed responses in vivo. mRNA of Txk, a Tec family tyrosine kinase specific to Th1 cells, was expressed in the lesions, suggesting its contribution to the Th1‐dominant responses. In the intestinal samples, CCR5 was detected in all the cases with BD, whereas Th2‐related CCR3 and CCR4 were detected randomly, mainly in the cases with inactive BD and those receiving large amounts of prednisolone, indicating the Th1‐dominant immune responses in the intestinal lesions. As the ligands of CCR5, MIP1α and MIP1β were detected, whereas RANTES was not. Heat shock protein (HSP) 60 was expressed in PBL and intestinal tissues of BD. Th1‐dominant immune responses and HSP60 expression may induce the inflammatory responses and thus be associated with the pathogenesis of intestinal BD.

Prevalence and characterization of perinuclear anti-neutrophil cytoplasmic antibodies (P-ANCA) directed against HMG1 and HMG2 in ulcerative colitis (UC)

In a previous study, we reported that the high mobility group (HMG) non‐histone chromosomal proteins HMG1 and HMG2 were novel target antigens of P‐ANCA. In this study, we determined the immunodiagnostic value of anti‐HMG1/HMG2 antibodies in patients with UC. Sixty sera from patients with UC were tested for reactivity with HMG1 and HMG2 by means of ELISA. Anti‐HMG1 antibody was detected in 32% of patients (40% of P‐ANCA+ patients). Anti‐HMG2 antibody was detected in 33% (40% of P‐ANCA+ patients). Thirty‐five percent of sera were positive for antibody to either HMG1 or HMG2 (43% of P‐ANCA+ patients). P‐ANCA+ patients expressed anti‐HMG1/HMG2 antibodies with significantly greater frequency compared with P‐ANCA− patients. Furthermore, the anti‐HMG1/HMG2 antibodies were significantly related to disease activity in UC. Sixteen of the 18 UC patients, who had high titres of anti‐HMG1 or ‐HMG2 antibody during the active phase, showed lower titres in the inactive phase. Anti‐HMG1/HMG2 antibodies appear to be useful as a marker for disease activity in UC.

High mobility group (HMG) non-histone chromosomal proteins HMG1 and HMG2 are significant target antigens of perinuclear anti-neutrophil cytoplasmic antibodies in autoimmune hepatitis

BACKGROUND High mobility group (HMG) non-histone chromosomal proteins HMG1 and HMG2 have been identified as novel antigens of perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCAs), and the existence of anti-HMG1 and anti-HMG2 antibodies in a population of patients with ulcerative colitis has been reported. AIMS To investigate whether HMG1 and HMG2 are target antigens for p-ANCAs in autoimmune hepatitis (AIH). PATIENTS Serum samples from 28 patients with AIH, 44 patients with primary biliary cirrhosis (PBC), 27 patients with chronic hepatitis C, and 23 patients with chronic hepatitis B were tested. METHODS ANCAs were detected by routine indirect immunofluorescence (IIF). Anti-HMG1 and anti-HMG2 antibodies were assayed by enzyme linked immunosorbent assay. RESULTS p-ANCAs were detected in 89% (25/28) of patients with AIH, 36% (16/44) of patients with PBC, 11% (3/27) of patients with chronic hepatitis C, and 13% (3/23) of patients with chronic hepatitis B. Anti-HMG1 and/or anti-HMG2 antibodies were detected in 89% (25/28) of patients with AIH, 70% (31/44) with PBC, 26% (7/27) with chronic hepatitis C, and 9% (2/23) with chronic hepatitis B. In AIH, anti-HMG1 and/or anti-HMG2 antibodies were detected in 96% (24/25) of p-ANCA positive patients. The p-ANCA staining pattern detected by IIF using sera from patients with AIH disappeared or decreased in titre after preincubation with a mixture of HMG1/HMG2. The presence and titres of those antibodies in AIH correlated significantly with those of p-ANCA, but not with those of anti-nuclear antibody or anti-smooth muscle antibody. CONCLUSIONS HMG1 and HMG2 are significant target antigens of p-ANCA in AIH.

Longterm Survival and Associated Risk Factors in Patients with Adult-onset Idiopathic Inflammatory Myopathies and Amyopathic Dermatomyositis: Experience in a Single Institute in Japan

Objective. To analyze clinical characteristics, survival, causes of death, and risk factors associated with mortality in patients with adult-onset idiopathic inflammatory myopathies (IIM) in Japan. Methods. We retrospectively investigated 197 patients diagnosed with adult-onset IIM at our hospital from 1984 to 2009 according to Bohan and Peter criteria for polymyositis (PM)/dermatomyositis (DM) and modified Sontheimer’s criteria for clinically amyopathic DM (ADM). Results. Survival in the whole group at 1, 5, and 10 years was 85%, 75%, and 67%, respectively. Mortality in cancer-associated myositis was the worst (25% at 5 yrs), followed by clinically ADM (61% at 5 yrs) and primary DM (77% at 5 yrs). Primary DM had significantly low survival compared to primary PM (91% at 5 yrs; p = 0.0427). Among the 53 patients who died were 6 patients with ADM (11%) and 20 patients with primary DM (38%). Interstitial lung disease (ILD) was the main cause of death in clinically ADM (71%) and primary DM (60%), most of which occurred within the first few months. Fewer patients died in primary PM (9%) and overlap myositis (13%). Independent risk factors for death were older age (HR 1.031; 95% CI 1.009–1.053) and skin ulcers (HR 3.018; 95% CI 1.340–6.796) in the whole group and ILD with mild serum creatine kinase levels (< 500 IU/l; HR 3.537; 95% CI 1.260–9.928) in primary DM. Conclusion. Survival of clinically ADM and primary DM was low, mainly due to fatal ILD, compared to primary PM. Establishing therapeutic strategy for ILD may improve the survival in our patient population.

DIP2 disco-interacting protein 2 homolog A (Drosophila) is a candidate receptor for follistatin-related protein/follistatin-like 1--analysis of their binding with TGF-β superfamily proteins.

Follistatin‐related protein (FRP)/follistatin‐like 1 (FSTL1) is a member of the follistatin protein family, all of which share a characteristic structure unit found in follistatin, called the FS domain. Developmental studies have suggested that FRP regulates organ tissue formation in embryos. Immunological studies showed that FRP modifies joint inflammation in arthritic disease, and modulates allograft tolerance. However, the principle physiological function of FRP is currently unknown. To address this issue, we cloned four FRP‐associated proteins using a two‐hybrid cloning method: disco‐interacting protein 2 homolog A from Drosophila (DIP2A), CD14, glypican 1 and titin. Only DIP2A was expected to be a membrane receptor protein with intracellular regions. Over‐expression of FLAG epitope‐tagged DIP2A augmented the suppressive effect of FRP on FBJ murine osteosarcoma viral oncogene homolog (FOS) expression, and the Fab fragment of IgG to FLAG blocked this effect. Knockdown of Dip2a leaded to Fos gene up‐regulation, and this was not affected by exogenous FRP. These in vitro experiments confirmed that DIP2A could be a cell‐surface receptor protein and mediate a FOS down‐regulation signal of FRP. Moreover, molecular interaction analyses using Biacore demonstrated that FRP bound to DIP2A and CD14, and also with proteins of the TGF‐β superfamily, i.e. activin, TGF‐β, bone morphogenetic protein 2/4 (BMP‐2/4), their receptors and follistatin. FRP binding to DIP2A was blocked by CD14, follistatin, activin and BMP‐2. FRP blocked the ligand–receptor binding of activin and BMP‐2, but integrated itself with that of BMP‐4. This multi‐specific binding may reflect the broad physiological activity of FRP.

Genetic regulation of the class conversion of dsDNA-specific antibodies in (NZB×NZW) F1 hybrid

To investigate the possible effects of NZW genes on the class conversion of dsDNA-specific antibodies in NZB × NZW (B/W) F1 hybrids, we measured IgM, IgGl, and IgG2 dsDNA-specific antibodies, using the Crithidia luciliae kinetoplast immunofluorescence test, in NZB, NZW, B/W F1 hybrid, B/W F1 × NZB backcross, and B/W F1 × NZW backcross mice at 4, 7, and 10 months of age. The highest serum levels of IgM dsDNA-specific antibodies were observed in NZB mice at the ages tested; however, the amounts of IgG1 and IgG2 antibodies were scanty. In contrast, a large amount of both IgG1 and IgG2 dsDNA-specific antibodies was produced in B/W F1 hybrids, in which the serum IgM antibodies were lower than those observed in NZB mice. NZW mice were virtually negative for these antibodies. Progeny testing suggested that a combined effect of two unlinked dominant genes of the NZB strain determines the production of dsDNA-specific antibodies and that these genes only act to produce IgM antibodies. These traits are to a great degree modified by the NZW loci in B/W F1 hybrids, and a combined effect of two unlinked dominant genes leads to conversion of the class of the antibodies from IgM to IgG, which, in turn, increases the serum levels of dsDNA-specific antibodies. The F1 hybrid of C57BL/6 and NZW strains produced no dsDNA-specific antibodies, indicating that the relevant NZB predisposing genes are required for the NZW gene action. Linkage studies showed that one of such NZW genes is to some extent linked to the H-2 complex on chromosome 17, but not to Mup-1 (chromosome 4) or a coat color locus (chromosome 2). The appearance of IgG dsDNA-specific antibodies correlated well with the incidence of renal disease in B/W F1 × NZB backcross mice.

Cutaneous polyarteritis nodosa: revisiting its definition and diagnostic criteria

Polyarteritis nodosa (PN) is a classical collagen disease with poor prognosis that demonstrates systemic necrotizing vasculitis of small and medium-sized arteries. Cutaneous symptoms are observed in 25–60% of PN patients. On other hand, cutaneous polyarteritis nodosa (CPN) is designated for the cutaneous limited form of PN and demonstrates benign prognosis. However, there has been much debate on whether or not CPN can progress to PN. Although CPN lesions are fundamentally limited to skin, some CPN cases show extracutaneous symptoms such as peripheral neuropathy and myalgia. According to PN diagnostic criteria, which were established by the Ministry of Health, Labour and Welfare of Japan, a disease with both cutaneous and at least one extracutaneous symptom with appropriate histopathological findings can be diagnosed as PN. The same is true according to diagnostic criteria established by the American College of Rheumatology. In addition, there are no specific diagnostic criteria for CPN. In this study, CPN cases were retrospectively collected from multiple Japanese clinics, and analyzed for detailed clinical and histopathological manifestations, in order to redefine the clinical entity of CPN and to propose appropriate diagnostic criteria for CPN and PN. According to the CPN description in Rook’s Textbook of Dermatology, we collected 22 cases with appropriate histopathological findings. Of the 22 cases, none progressed to PN or death during the follow-up period, 32% had peripheral neuropathy and 27% had myalgia. Regarding extracutaneous symptoms with CPN, 17 dermatological specialists in vasculitis sustained the opinion that CPN can be accompanied by peripheral neuropathy and myalgia but these symptoms are limited to the same area as skin lesions. Based on these results, we devised new drafts for CPN and PN diagnostic criteria. Our study shows the efficacy of these criteria and most dermatologists recognized that our new diagnostic criteria for CPN and PN are appropriate at the present time. In conclusion, this study suggests that CPN does not progress to PN, and introduces new drafts for CPN and PN diagnostic criteria.

Cloning of novel soluble gp130 and detection of its neutralizing autoantibodies in rheumatoid arthritis

In an attempt to isolate disease-associated autoantigens in rheumatoid arthritis (RA), we cloned a new autoantigen named gp130-RAPS, which is a novel soluble form of the IL-6 signal-transducing molecule gp130. gp130-RAPS is a 50-kDa protein translated from alternatively spliced mRNA and has a truncated form of gp130 with a unique sequence, Asn-Ile-Ala-Ser-Phe (NIASF), in its COOH-terminus. We observed serum antibodies to this NIASF sequence frequently in patients with RA, but not in those with other systemic rheumatic diseases or in healthy subjects. In RA, detection of those antibodies was significantly associated with disease activity indices such as serum C-reactive protein (CRP) levels, erythrocyte sedimentation rate, blood platelet counts, and serum IL-6 concentration. In vitro experiments revealed that gp130-RAPS inhibited IL-6 activity, and this inhibition was neutralized by antibodies to the COOH-terminus of gp130-RAPS derived from patients with RA. Thus, autoantibody to gp130-RAPS may play an important role in the progression of RA by promoting IL-6 activity. Inspection of autoantibodies to gp130-RAPS may become a practical clinical test for RA. gp130-RAPS and its autoantibody provide a new clue to the complicated pathogenesis of RA.