Coagulation process proceeds on cultured human mesangial cells via expression of factor V

BACKGROUND

In a previous clinicopathological study, we observed mesangial factor V expression accompanied by the intact form of cross-linked fibrin deposition in the active type of IgA nephropathy. The conversion of prothrombin to thrombin by factor Xa is potently accelerated more than 104-fold by the presence of factor V, which is a membrane-bound cofactor. Another membrane-bound cofactor, tissue factor, is known to play an initiating role in the coagulation cascade and to be synthesized in mesangial cells (MCs) by the stimulation of tumor necrosis factor-alpha (TNF-alpha). However, the synthesis of factor V, which plays on the terminating stage of prothrombin activation, has not been reported previously in MCs by in vitro study. Our current study tested the coagulation process via expression of factor V by the stimulation of proinflammatory cytokine, TNF-alpha, in cultured human MCs.

METHODS

To evaluate factor V protein expression, immunoperoxidase staining with densitometric evaluation and Western blot analysis were conducted after stimulation of TNF-alpha. To test factor V activity, stimulated MCs were incubated in combination with factor Xa, prothrombin, fibrinogen and factor XIII, and fibrin production on MCs was assessed after immunoperoxidase staining on the cell surface. In a blocking test using an antibody against factor V, suppression of fibrin production was evaluated to clarify the role of factor V activity. For the evaluation of factor V mRNA expression in cultured human MCs, in situ hybridization and Northern blot analysis were performed.

RESULTS

Factor V protein expression in MCs after TNF-alpha stimulation increased both time- and dose-dependently. As a marker of factor V activity with exogenous factor Xa, fibrin production on TNF-alpha-stimulated MCs was increased in a time-dependent manner and was inhibited by the addition of anti-factor V antibody. Factor V mRNA was identified in MCs by in situ hybridization and showed an increase after stimulation with TNF-alpha on Northern blot analysis.

CONCLUSIONS

Our data suggest that the coagulation process proceeds on MCs as the result of increased expression of endogenous factor V activity on its cell surface in cooperation with exogenous factor Xa.

Initial symptoms of acute radiation syndrome in the JCO criticality accident in Tokai-mura

A criticality accident occurred on September 30, 1999, at the uranium conversion plant in Tokai-mura (Tokai-village), Ibaraki Prefecture, Japan. When the criticality occurred, three workers saw a "blue-white glow," and a radiation monitor alarm was sounded. They were severely exposed to neutron and gamma-ray irradiation, and subsequently developed acute radiation syndrome (ARS). One worker reported vomiting within minutes and loss of consciousness for 10-20 seconds. This worker also had diarrhea an hour after the exposure. The other worker started to vomit almost an hour after the exposure. The three workers, including their supervisor, who had no symptoms at the time, were brought to the National Mito Hospital by ambulance. Because of the detection of gamma-rays from their body surface by preliminary surveys and decreased numbers of lymphocytes in peripheral blood, they were transferred to the National Institute of Radiological Sciences (NIRS), which has been designated as a hospital responsible for radiation emergencies. Dose estimations for the three workers were performed by prodromal symptoms, serial changes of lymphocyte numbers, chromosomal analysis, and 24Na activity. The results obtained from these methods were fairly consistent. Most of the data, such as the dose rate of radiation, its distribution, and the quality needed to evaluate the average dose, were not available when the decision for hematopoitic stem cell transplantation had to be made. Therefore, prodromal symptoms may be important in making decisions for therapeutic strategies, such as stem-cell transplantation in heavily exposed victims.

[Refractory idiopathic cold agglutinin disease successfully treated with intermittent high-dose cyclophosphamide]

A 56-year-old woman, who had been suffering from idiopathic cold agglutinin disease and treated unsuccessfully with prednisolone and cyclosporine A for 6 months, was referred to our hospital in November 1998. She was given methylprednisolone pulse therapy followed by low-dose cyclophosphamide, but her anemia did not improve. We then began administration of intermittent high-dose cyclophosphamide (1,200 mg/day, every 4 weeks), and this resulted in a dramatic increase of her hemoglobin level and improvement of her symptoms. She is currently receiving 500 mg of cyclophosphamide every 2 months and showing a good response. Intermittent high-dose cyclophosphamide therapy can be an effective treatment for refractory cold agglutinin disease.

Up-regulated TGF-beta mRNA expression in splenic T cells of high IgA-prone mice: a murine model of IgA nephropathy with glomerulosclerosis

BACKGROUND/AIMS

Recently, we established a high serum IgA-prone inbred (HIGA) mouse strain as a murine model of spontaneous IgA nephropathy by selective mating of high serum IgA ddY mice, and found that they showed enhanced production of glomerular extracellular matrix components with increased expression of TGF-beta mRNA and protein in the kidneys. In this study, we examined the roles of lymphocytes in the development of high serum IgA in this strain.

METHODS

We performed flow cytometric analyses of T and B cells in splenic mononuclear cells (SMNCs) from these mice using BALB/c mice as normal controls. We also compared serum TGF-beta1 concentrations and TGF-beta mRNA expression levels in the B-cell-depleted (T-cell-rich) fraction of SMNCs in these mice.

RESULTS

HIGA mice showed significantly fewer CD3-positive cells compared with BALB/c mice when young, but not when aged. The CD4/CD8 ratio of HIGA mice was lower than that of BALB/c mice, but this difference was not significant. Although the number of B220-positive cells did not vary significantly, the ratio of surface IgA-positive B cells was significantly increased in both young and adult HIGA mice. The B-cell-depleted SMNCs from HIGA mice exhibited higher levels of expression of TGF-beta and TGF-beta1 mRNA than controls from a young age, which were maintained throughout life, but there were no differences in PDGF, MCP-1 or bFGF expression between these two strains. In contrast to local mRNA expression, serum TGF-beta1 concentration was decreased in HIGA mice compared with BALB/c controls.

CONCLUSION

These findings suggest that the mating procedure performed to establish HIGA mice selected for a unique phenotype of local up-regulation of TGF-beta production in the kidneys, as well as T cells that may contribute to both the early and consistently high serum IgA expression and enhanced production of renal extracellular matrix components in HIGA mice. Additionally, TGF-beta1 may act locally, not systemically, in a paracrine or autocrine manner.

Statins selectively inhibit leukocyte function antigen-1 by binding to a novel regulatory integrin site

The beta2 integrin leukocyte function antigen-1 (LFA-1) has an important role in the pathophysiology of inflammatory and autoimmune diseases. Here we report that statin compounds commonly used for the treatment of hypercholesterolemia selectively blocked LFA-1-mediated adhesion and costimulation of lymphocytes. This effect was unrelated to the statins' inhibition of 3-hydroxy-3-methylglutaryl coenzyme-A reductase; instead it occurred via binding to a novel allosteric site within LFA-1. Subsequent optimization of the statins for LFA-1 binding resulted in potent, selective and orally active LFA-1 inhibitors that suppress the inflammatory response in a murine model of peritonitis. Targeting of the statin-binding site of LFA-1 could be used to treat diseases such as psoriasis, rheumatoid arthritis, ischemia/reperfusion injury and transplant rejection.

[Severe Klebsiella pneumonia improved by endotoxin adsorption and continuous hemodiafiltration]

A 57-year-old man who had past history of alcoholic hepatitis was admitted to our hospital because of fever, general malaise and dyspnea. Chest X-ray films and computed tomographic scans disclosed lobar pneumonia of the right upper lobe. Laboratory tests showed hypoxemia and renal dysfunction. Artificial ventilation, endotoxin adsorption (PMX) and continuous hemodiafiltration (CHDF) were started on the day after admission because of the appearance of progressive renal failure, hypotension and disturbance of consciousness. A diagnosis of septic multiple organ failure was made on the basis of a blood and sputum culture that revealed a K. pneumoniae infection. After the initiation of intensive therapy, the patient's general condition improved and artificial ventilation, PMX and CHDF were withdrawn. However, MRSA was isolated from sputum specimens and a lung abscess developed. In spite of vancomycin administration, the effect was limited. The patient underwent a right upper lobectomy and was discharged. The prognosis of bacteremic K. pneumoniae pneumonia in alcoholics is reported to be very poor. In our case, it is suggested that PMX and CHDF contributed to the improvement of the clinical course.

Some Lactobacillus L-lactate dehydrogenases exhibit comparable catalytic activities for pyruvate and oxaloacetate

The nonallosteric and allosteric L-lactate dehydrogenases of Lactobacillus pentosus and L. casei, respectively, exhibited broad substrate specificities, giving virtually the same maximal reaction velocity and substrate K(m) values for pyruvate and oxaloacetate. Replacement of Pro101 with Asn reduced the activity of the L. pentosus enzyme toward these alternative substrates to a greater extent than the activity toward pyruvate.

The role of alpha-galactosylceramide-activated Valpha14 natural killer T cells in the regulation of Th2 cell differentiation

Valpha14 natural killer T (NKT) cells produce large amounts of both IL-4 and IFN-gamma upon stimulation with a ligand, alpha-galactosylceramide (alpha-GalCer), and play a crucial role in various immune responses, including allergic diseases. Interestingly, Valpha14 NKT cells are not essential for the induction of IgE responses but rather induce suppression of specific IgE production upon activation. The suppression in the IgE production is not detected either in Valpha14 NKT cell-deficient mice or in IFN-gamma-deficient mice. Thus, activated Valpha14 NKT cells are likely to exert a potent suppressive activity on Th2 cell differentiation and subsequent IgE production by producing a large amount of IFN-gamma. In marked contrast, little regulatory effect of IL-4 produced by Valpha14 NKT cells on Th2 cell differentiation is suggested.

[Occurrence of angioimmunoblastic T-cell lymphoma six months after onset of Lyme disease]

A 68-year-old man, who had suffered a tick bite one week previously, consulted his home doctor because of fever and an erythematous rash around the bite scar. He underwent a skin biopsy, and Borrelia garinii was detected, from which Lyme disease was diagnosed. He received amoxicillin for two weeks and his symptoms disappeared. After 6 months he noticed swelling of his cervical, axillary and inguinal lymph nodes. A biopsy sample was taken from a left cervical lymph node, and this revealed angioimmunoblastic T-cell lymphoma. The patient achieved a complete remission after chemotherapy. The relationship between Lyme disease and lymphoma is discussed.

Mesangial factor V expression colocalized with fibrin deposition in IgA nephropathy

BACKGROUND

Factor V in its active form (Va) plays a key role at the termination of the intrinsic coagulation pathway, serving as a membrane-bound cofactor for the conversion of prothrombin to thrombin by factor Xa. Cross-linked fibrin (XFb) is often observed in mesangial areas in active types of human glomerulonephritis. In this study, to clarify contribution of factor V in intramesangial coagulation, mesangial factor V expression and its relationship to mesangial proliferation and fibrin deposition in IgA nephropathy (IgAN) were investigated.

METHODS

Twenty-two patients with IgAN were studied. XFb was detected in renal biopsy specimens using anti-d-dimer antibody combined with plasmin exposure, and factor V was detected with rabbit antibody against human factor V. Double-labeling immunohistochemistry was used to investigate the relationship of the glomerular distribution of factor V to XFb. The relationship of factor V staining to the activity index or XFb deposition was evaluated. The expression of factor V mRNA was assessed by in situ hybridization in relationship to the antigen staining of alpha-smooth muscle actin (alpha-SMA). The ultrastructural distribution of factor V in glomeruli was studied by immunoelectron microscopy.

RESULTS

XFb and factor V were observed in the mesangium and along capillary loops in seven and nine specimens, respectively. Factor V had intense, frequent expression in the proliferating and necrotizing areas, showing a significant relationship to XFb (P < 0.05). Furthermore, XFb deposition and factor V expression were markedly correlated with disease activity (P = 0.005 and P = 0.008, respectively). By double-labeling experiments, XFb and factor V were often seen colocalized in mesangial areas of the glomeruli, which showed necrotizing lesions and/or intense cellular proliferation. By in situ hybridization, factor V mRNA was detected mainly in the mesangial cells, which were positive for alpha-SMA, and partly in the endothelial cells. By immunoelectron microscopy, factor V presence was confirmed in the mesangium and endothelium.

CONCLUSION

The present findings suggest that factor V is strongly expressed in mesangial cells in active IgAN accompanied with mesangial proliferation and may exert procoagulant activity, leading to intramesangial coagulation.

Interleukin 12 induces crescentic glomerular lesions in a high IgA strain of ddY mice, independently of changes in IgA deposition

BACKGROUND

Our recently established high immunoglobulin (Ig)A inbred strain (HIGA) of ddY mice showed constantly high serum IgA levels, progressive mesangial sclerosis accompanied by IgA deposits, and elevated renal expression of transforming growth factor (TGF)-beta, mimicking IgA nephropathy. In the present study, we assessed the role of the immune system, especially of T cells, in this strain.

METHODS

The in vitro production of interferon (IFN)-gamma, interleukin (IL)-4 and TGF-beta1 by splenic CD4+ T cells was assessed in HIGA mice at 14 and 28 weeks of age by comparison with age-matched C57BL/6 and BALB/c mice, T-helper (Th) 1, and Th2 prone controls respectively. Moreover, recombinant murine IL-12 was administered intraperitoneally to HIGA mice and serum IgA and renal lesions were analysed.

RESULTS

The production of IFN-gamma by splenic CD4+ T cells was markedly upregulated in HIGA mice at both ages as compared with age-matched C57BL/6 and BALB/c mice. Although splenic CD4+ T cells from HIGA mice produced less IL-4 than those from BALB/c mice at both ages, the former produced significantly more IL-4 with age, which contrasted with the age-associated decrease in the latter. Moreover, TGF-beta1 production of these cells in HIGA mice was equal to or greater than that in the two groups of control mice at both ages. Daily intraperitoneal administration of IL-12 for 1 week significantly enhanced crescent formation with glomerular macrophage accumulation and interstitial cell infiltration, whereas it reduced the serum IgA level.

CONCLUSIONS

In HIGA mice, Th1 is markedly upregulated from a young age and there is an age-associated Th2 increase with TGF-beta1 upregulation in helper T cells. The former may be related to the exacerbation of inflammatory renal lesions on IL-12 administration, while the latter may contribute to increased IgA production, leading to glomerular IgA deposition and progressive glomerulosclerosis in HIGA mice. The pathogenic role of T cell function and fluctuation of these subsets, especially the Th1/Th2 balance, is crucial to the immunopathological phenotype of the renal lesions in HIGA mice.

Increased frequency of surface IgA-positive plasma cells in the intestinal lamina propria and decreased IgA excretion in hyper IgA (HIGA) mice, a murine model of IgA nephropathy with hyperserum IgA

Because abnormalities of mucosal immunity have been suggested in human IgA nephropathy, we examined the involvement of mucosal immunity in IgA deposition to the kidney in hyper IgA (HIGA) mice, which was established as a mouse model for human IgA nephropathy with hyperserum IgA. The number of surface IgA+B220- lymphocytes in the intestinal lamina propria (LP) of HIGA mice increased 2.7-fold at 30 wk of age as compared with those at 10 wk of age, whereas normal mice did not show such increase. The surface IgA+B220- LP lymphocytes spontaneously secreted IgA in culture. Morphological studies showed that the surface IgA+B220- lymphocytes of murine intestinal LP are identical with plasma cells (PCs). About 20% of IgA+B220- PC in LP expressed both Mac-1 and CD19, suggesting that they may derive from peritoneal B-1 cells. Cell cycle study on intestinal IgA-PCs using bromodeoxyuridine revealed no difference between HIGA mice and normal mice, suggesting that the high frequency of IgA-producing PCs in HIGA mice is not due to enhanced proliferation or prolonged survival of IgA-producing PCs in LP. In addition, IgA secretion into the gut lumen of HIGA mice decreased drastically (to one forth) with aging. These data suggest that the increased number of intestinal IgA-producing PCs and the down-regulation of IgA excretion into the intestinal lumen might synergistically contribute to the hyperserum IgA in HIGA mice and resultant IgA deposition to the kidney.

[A case of embolization to a large polycystic kidney with infection]

75 year old female who was hospitalized for abdominal pain and fever up on 12th May 1998. She had been followed as a polycystic kidney patient since few years. The swelling of the right kidney and her general condition became gradually worse. On 18th May, the embolization to the right kidney using pure alcohol and gelatin sponge was performed. Within a month, CT scan showed the reduced volume of the right kidney and her blood examination data as well as her general condition became gradually well. And on 17th June, she left our hospital without any complication.

Expression of YAV proteins and vaccination against viral ascites among cultured juvenile yellowtail

Yellowtail ascites virus (YAV) is a member of the family Birnaviridae and causes viral ascites among juvenile yellowtail (Seriola quinqueradiata). We have reported the cloning and expression of two viral cDNAs, the first being segment A encoding a polyprotein of viral capsid proteins (VP2 and VP3) and a protease (NS), and the second being VP2-epitope encoding serotype-specific epitope region on VP2, using a baculovirus expression system. Another viral cDNA encoding a polyprotein of NS and VP3 was cloned and expressed in this study. For the expression of NS/VP3 (YAV nt 1626 to 3066) in insect cells a 31-kDa protein, corresponding to VP3 was detected, indicating an appropriate posttranslational processing of NS/VP3 polypeptide by NS protease itself. The analysis of the N-terminal amino acid sequence of this protein showed that NS protease may cleave an Ala-Ser bond. A study of the potential for vaccination of yellowtail fry by injection of insect cell lysates infected with baculovirus, containing either cDNA of segment A, VP2-epitope, or NS/VP3 was undertaken. Only a vaccination with cell lysates infected with a recombinant virus carrying the full length of YAV segment A gene demonstrated approximately the same effect as that of inactivated YAV. This result suggested that all proteins VP2, VP3, and NS are required for an effective vaccination.

[Biweekly low-dose cisplatin and 5-fluorouracil combination chemotherapy for advanced gastrointestinal carcinoma]

Biweekly intravenous infusions of low-dose cisplatin (CDDP) and 5-fluorouracil (5-FU) were evaluated in 80 patients with advanced or recurrent gastric, colorectal, pancreatic or gallbladder adenocarcinoma. CDDP was given biweekly at a dose of 15 mg/m2 infused for 30 minutes, and 5-FU 375 mg/m2 was infused for 2 hours as many times as possible. The response rate among patients with gastric cancer was 26%, colorectal cancer 10%, pancreatic cancer 7.7%, and gallbladder cancer 42.9%. The response rates were not so high, but the median survival time of patients with recurrent gastric cancer was 17.3 months, pancreatic cancer 6.7 months, and gallbladder cancer 10.7 months. A patient with unresected advanced pancreatic head cancer with liver and para-aortic lymph node metastases received this therapy 38 times, and lived for 54 months. No severe side effects occurred in any of these cases. Thus, this chemotherapy could well be effective for the outcome of cases of advanced gastrointestinal carcinoma.

Nerve growth factor-induced neuronal differentiation requires generation of Rac1-regulated reactive oxygen species

Nerve growth factor (NGF) stimulation of pheochromocytoma PC12 cells transiently increased the intracellular concentration of reactive oxygen species (ROS). This increase was blocked by the chemical antioxidant N-acetylcysteine and a flavoprotein inhibitor, diphenylene iodonium. NGF responses of PC12 cells, including neurite outgrowth, tyrosine phosphorylation, and AP-1 activation, was inhibited when ROS production was prevented by N-acetylcysteine and diphenylene iodonium. The expression of dominant negative Rac1N17 blocked induction of both ROS generation and morphological differentiation by NGF. The ROS produced appears to be H(2)O(2), because the introduction of catalase into the cells abolished NGF-induced neurite outgrowth, ROS production, and tyrosine phosphorylation. These results suggest that the ROS, perhaps H(2)O(2), acts as an intracellular signal mediator for NGF-induced neuronal differentiation and that NGF-stimulated ROS production is regulated by Rac1 and a flavoprotein-binding protein similar to the phagocytic NADPH oxidase.

Multiple discontinuous ligand-mimetic antibody binding sites define a ligand binding pocket in integrin alpha(IIb)beta(3)

Integrin alpha(IIb)beta(3), a platelet fibrinogen receptor, is critically involved in thrombosis and hemostasis. However, how ligands interact with alpha(IIb)beta(3) has been controversial. Ligand-mimetic anti-alpha(IIb)beta(3) antibodies (PAC-1, LJ-CP3, and OP-G2) contain the RGD-like RYD sequence in their CDR3 in the heavy chain and have structural and functional similarities to native ligands. We have located binding sites for ligand-mimetic antibodies in alpha(IIb) and beta(3) using human-to-mouse chimeras, which we expect to maintain functional integrity of alpha(IIb)beta(3). Here we report that these antibodies recognize several discontinuous binding sites in both the alpha(IIb) and beta(3) subunits; these binding sites are located in residues 156-162 and 229-230 of alpha(IIb) and residues 179-183 of beta(3). In contrast, several nonligand-mimetic antibodies (e.g. 7E3) recognize single epitopes in either subunit. Thus, binding to several discontinuous sites in both subunits is unique to ligand-mimetic antibodies. Interestingly, these binding sites overlap with several (but not all) of the sequences that have been reported to be critical for fibrinogen binding (e.g. N-terminal repeats 2-3 but not repeats 4-7, of alpha(IIb)). These results suggest that ligand-mimetic antibodies and probably native ligands may make direct contact with these discontinuous binding sites in both subunits, which may constitute a ligand-binding pocket.

Morphologic abnormalities in the brain of chronically hemodialyzed patients without cerebrovascular disease

In this study, the authors evaluated the cerebral atrophy in 56 chronic hemodialyzed patients, who did not have clinical episodes or radiologic findings of cerebrovascular diseases, and 42 controls. Using computed tomography (CT) images, brain atrophy index (BAI), the proportion of subarachnoidal plus ventricular space in the cranial cavity, and ventricular area index (VAI), percent area of ventricle in the brain, were calculated. CT of the brain demonstrated an age-dependent increase in BAI in both hemodialyzed patients and controls. BAI and VAI were greater in hemodialyzed patients than healthy controls and the difference was significant at ages under 60 years in BAI and at ages less than 50 years in VAI. The atrophy of the frontal parts of the brain in patients on hemodialysis for 10 years or more was significantly greater than in patients dialyzed for less than 10 years. There was a significant negative correlation between BAI or VAI and hematocrit. These findings indicate that renal failure or hemodialysis itself might cause cerebral atrophy, and that the cerebral atrophy is more prominent in patients on hemodialysis for a long duration and with low hematocrit.

[Suicidal attempts in three postoperative patients with renal cancer after alpha interferon withdrawal]

We report 3 cases of suicide attempts in postoperative patients with renal cancer after alpha interferon withdrawal. In the first patient, depression occurred during interferon therapy, and remained after interferon withdrawal. A suicide attempt occurred 7 months after interferon withdrawal. In the second and third patients, depression did not occur during interferon therapy, but suicide attempts occurred 40 days and 7 months after interferon withdrawal, respectively. Depression does not always disappear after interferon is discontinued. Psychiatric supervision should be continued even more frequently after interferon withdrawal. The increased risk of psychiatric side effects due to interferon, as well as their severity, suggest that interferon should be administered with caution.

[A case of significant natriuresis and improvement of proteinuria by Temocapril, an ACE inhibitor with biliary excretion, in loop diuretics resistant edema in membranous nephropathy]

A 50-year-old man with WPW syndrome and chronic atrial fibrillation controlled by digoxin exhibited nephrotic syndrome due to membranous nephropathy in 1994. For massive edema resistant to loop diuretics, administration of 2 mg/day of Temocapril, an ACE inhibitor with biliary excretion, was started. It provided marked natriuresis and rapid improvement of massive anasarca. Moreover, 6 months later at the time of writing this report, nephrotic proteinuria has decreased and abnormally depressed Ccr level has elevated. For massive edema resistant to loop diuretics in nephrotic syndrome, Temocapril might bring about a beneficial effect possibly through the induction of natriuresis, which has been suppressed by the over-expression of angiotensin II in tubulointerstitium.

Interaction between collagen and the alpha(2) I-domain of integrin alpha(2)beta(1). Critical role of conserved residues in the metal ion-dependent adhesion site (MIDAS) region

A docking model of the alpha(2) I-domain and collagen has been proposed based on their crystal structures (Emsley, J., King, S., Bergelson, J., and Liddington, R. C. (1997) J. Biol. Chem. 272, 28512-28517). In this model, several amino acid residues in the I-domain make direct contact with collagen (Asn-154, Asp-219, Leu-220, Glu-256, His-258, Tyr-285, Asn-289, Leu-291, Asn-295, and Lys-298), and the protruding C-helix of alpha(2) (residues 284-288) determines ligand specificity. Because most of the proposed critical residues are not conserved, different I-domains are predicted to bind to collagen differently. We found that deleting the entire C-helix or mutating the predicted critical residues had no effect on collagen binding to whole alpha(2)beta(1), with the exception that mutating Asn-154, Asp-219, and His-258 had a moderate effect. We performed further studies and found that mutating the conserved surface-exposed residues in the metal ion-dependent adhesion site (MIDAS) (Tyr-157 and Gln-215) significantly blocks collagen binding. We have revised the docking model based on the mutagenesis data. In the revised model, conserved Tyr-157 makes contact with collagen in addition to the previously proposed Asn-154, Asp-219, His-258, and Tyr-285 residues. These results suggest that the collagen-binding I-domains (e.g. alpha(1), alpha(2), and alpha(10)) bind to collagen in a similar fashion.

Ultrastructural localization of dominantly increased fibronectin in the markedly thickened glomerular basement membrane in a selectively mated murine high IgA strain (HIGA mice)

To clarify which matrix component(s) contributes to glomerular sclerosis with mesangial IgA deposits in a murine high serum IgA strain (HIGA) derived from ddY mice, morphological and immunopathological analyses of glomeruli were performed in comparison with original ddY and BALB/c mice as controls. Significantly increased thickness of the glomerular basement membrane (GBM), especially the lamina densa, was observed in HIGA mice. Immunofluorescent staining showed marked increases in levels of fibronectin and laminin in both the mesangium and capillary wall in aged HIGA mice. Analysis of the distribution of immunogold-labeled antibody in GBM revealed a significant increase (p < 0.0001) and specific orientation of fibronectin in the endothelial side, which suggested that mesangial fibronectin produced at high levels due to IgA deposition extended to the endothelial side of GBM and contributed to the thickening of GBM with further development to glomerulosclerosis in the HIGA mice.