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PubMed2004

Metabolic alteration of the N-glycan structure of a protein from patients with a heterozygous protein deficiency.

Glycosylation, an important post-translation modification, could alter biological activity or influence the clearance rates of glycoproteins. We report here the first example of a heterozygous protein deficiency leading to metabolic alteration of N-glycan structures in residual secreted protein. Analysis of C1 esterase inhibitor (C1INH) glycans from normal individuals and patients with hereditary deficiency of C1INH demonstrated identical O-glycan structures but the N-glycans of patients with a heterozygous genetic deficiency were small, highly charged and lacked sialidase releasable N-acetylneuraminic acid. Structural studies indicate that the charge character of these aberrant N-glycan structures may result from the presence of mannose-6-phosphate residues. These residues might facilitate secretion of C1INH through an alternate lysosomal pathway, possibly serving as a compensatory mechanism to enhance plasma levels of C1INH in these deficient patients.

Angioedema↗
PubMed2004

A novel RNA splice site mutation in the C1 inhibitor gene of a patient with type I hereditary angioedema.

We describe a patient with type I hereditary angioedema presenting recurrent episodes of skin swelling and abdominal pain. Laboratory examination showed reduced levels of CH50 and C4 with a normal C3 level. The C1 inhibitor was decreased to 7.0 mg/dl (normal, 10-25 mg/dl) with a remarkably reduced activity (<25%; normal, 80-125%). DNA analysis of the C1 inhibitor gene revealed a novel point mutation at the 3' acceptor mRNA splice site of the intron 5 (G-->A at nucleotide 8722). This mutation may abolish the correct splicing of the intron 5 and create unstable mRNA.

Angioedema↗
PubMed2004

Worsening fluid retention in a patient with hereditary angioedema and end-stage renal disease.

A 60-year-old woman who was diagnosed with hereditary angioedema (HAE) developed nephrotic syndrome, with end-stage renal disease (ESRD) occurring about 2.5 years later. During her slide toward ESRD, she experienced three severe episodes of angioedema that each resulted in significant fluid retention. Though the therapeutic administration of C1-inhibitor concentrate was effective in controlling her angioedema, seemed ineffective in preventing her from developing ESRD requiring hemodialysis treatment. We theorized that the patient's low colloid osmolality and glomerular perfusion were important facilitators of her attacks of angioedema.

Angioedema↗
PubMed2002

Nuclear phosphatases and the proteasome in suppression of STAT1 activity in hepatocytes.

IFN-gamma induction of C1 inhibitor (C1INH) is mediated by an IFN-gamma-activated sequence (GAS), via binding of signal transducer and activator of transcription 1 (STAT1). These studies focused on the factors responsible for down-regulation of nuclear STAT1 in hepatocytes, the primary site of synthesis of C1INH. The activity of nuclear STAT1 following stimulation with IFN-gamma was sustained with the phosphatase inhibitor, pervanadate, or the proteasome inhibitor, lactacystin. Pervanadate prolonged STAT1 activation and blocked the inactivation of nuclear STAT1. Binding of ubiquitin to phosphorylated STAT1 was detectable in cells treated with lactacystin. Staurosporine only moderately decreased the prolongation of nuclear phosphorylated STAT1 after pretreatment with pervanadate or lactacystin. An antisense mitogen-activated protein kinase phosphatase (MKP-1) oligonucleotide prolonged the accumulation of phosphorylated STAT1. These data are consistent with the hypothesis that down-regulation of IFN-gamma-mediated nuclear STAT1 binding in hepatocytes involves both dephosphorylation by MKP-1 and degradation via proteolysis by the ubiquitin-dependent proteasome pathway.

Acetylcysteine↗
PubMed2007

Coagulation cascade activation triggers early failure of pig hearts expressing human complement regulatory genes.

BACKGROUND: Hyperacute rejection (HAR) and early graft failure (EGF) have been described in a minority of pig-to-baboon heart transplants using organs transgenic for human complement regulatory proteins (hCRP). Here we investigate the role of coagulation cascade activation in the pathogenesis of HAR and EGF in a consecutive series where a high incidence of these outcomes was observed. METHODS: Twenty-eight naïve wild-caught Papio anubis baboons received heterotopic heart transplants from pigs transgenic for hDAF (n = 23) or hMCP (n = 5). Immunosuppression consisted of cyclosporine A, cyclophosphamide and MMF (n = 18) or anti-CD154 mAb (IDEC-131) and ATG (n = 10). Eleven received anti-Gal carbohydrates (GAS914, n = 8, or NEX1285, n = 3), of which four also underwent extracorporeal immunoadsorption (EIA), and 12 also received pharmacologic complement inhibitors (C1 INH, n = 9, or APT070, n = 3). RESULTS: Excluding one technical failure, 14 of 27 transplants (11 hDAF, 3 hMCP) exhibited either HAR (n = 10) or EGF (n = 4). Surprisingly, neither complement inhibition (with C1 INH or APT070) nor anti-Gal antibody depletion with GAS914, NEX1285, or additional EIA consistently prevented HAR or EGF despite low or undetectable complement deposition. Strikingly, most grafts with HAR/EGF exhibited prominent fibrinogen and platelet deposition associated with systemic coagulation cascade activation, consistent with non-physiologic intravascular coagulation, in many instances despite little evidence for antibody-mediated complement activation. CONCLUSION: We conclude that dysregulated coagulation correlates closely with and probably causes primary failure of pig hearts transgenic for hCRP. These data support efforts to define effective strategies to prevent dysregulated coagulation in pig organ xenografts.

Acute Disease↗
PubMed2002

Normal transcription of the C1 inhibitor gene is dependent upon a polypurine-polypyrimidine region within the promoter.

Analysis of the transcriptional activity of C1 inhibitor (CIINH) promoter reporter constructs with mutations in the R-Y region indicate that triplex formation by this region is not a predictor of transcriptional activity and that normal promoter function depends on the interaction of trans acting factors with specific elements within this region. Electrophoretic mobility shift assay (EMSA) of Hep3B nuclear extracts using the wild type promoter probe (nucleotides -98 to -9) yielded four major bands. Incubation of the same extracts with probes lacking the HNF-1 site resulted in the disappearance of one band. Supershift assays indicate that HNF-1alpha is the only previously identified protein that is present in the EMSA bands. Southwestern blot analysis detected four bands (M(r)s -130, 75, 65 and 20 kDa). These data suggest that the -98 to -9 region of the C1INH promoter interacts with at least four proteins, one of which is HNF-1alpha.

Blotting, Southwestern↗
PubMed2001

In vitro interaction of C1-inhibitor with thrombin.

Previous observations of increased generation of thrombin during acute attacks of angioedema in plasma of patients with C1-inhibitor (C1-INH) deficiency prompted us to evaluate the interaction of C1-INH with thrombin in both purified systems and human plasma. For this purpose, we used several methods: (1) sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting analysis; (2) enzyme-linked immunosorbent assays to measure complexes between C1-INH and thrombin and inactivated C1-INH; and (3) kinetic studies using a chromogenic assay. We found that the interaction of purified C1-INH with thrombin is associated with the formation of bimolecular complexes of molecular weight (Mr) 130 000 and 120 000 as well as with the appearance of a cleaved form of C1-INH of Mr 97 000. The kinetic studies of inhibition of thrombin by C1-INH showed an average second-order rate constant of 19/s per mol/l, which was significantly increased in the presence of heparin. The addition of thrombin to human plasma was not associated with detectable C1-INH-thrombin complex formation or with cleavage of C1-INH. In conclusion, our data demonstrate that C1-INH upon interaction with thrombin, in part, forms enzyme-inhibitor complexes and, in part, is cleaved. The low second-order rate constant and the lack of a significant interaction in plasma suggest that the inhibition of thrombin by C1-INH has a minor role in circulating blood; however, its role might be important at the endothelial surface, where high concentrations of glycosaminoglycans occur.

Complement C1 Inactivator Proteins↗
PubMed2005

Hereditary angioedema.

PURPOSE OF REVIEW: Major advances have been made in understanding the clinical signs and symptoms, the pathophysiology and the treatment of hereditary angioedema. This disease that often begins in childhood is caused by partial absence of the plasma protein C1-inhibitor. At the present time five pharmaceutical companies are planning or conducting clinical trials of a variety of agents to treat acute attacks of this illness. Here we review our current understanding of this illness and the current approaches to treatment. RECENT FINDINGS: This disease is often missed in childhood or confused with other illness. The clinical signs and symptoms are reviewed. The importance of the kinin generating pathway and bradykinin in causing edema has become central to our understanding of pathophysiology. The many new approaches to therapy all appear promising. SUMMARY: Currently we have effective chronic therapy for this disease, although available drugs have real or potential difficulties in use in children. In the future it is likely that effective therapy for acute attacks of disease will become available in the US. It is important to recognize the clinical manifestations of this potentially fatal illness and to understand the therapeutic options.

Androgens↗
PubMed1999

A 'de novo' arisen case of angioedema C1-inhibitor deficiency dependent: possible mutagenic effect of azathioprine?

It is reported that a C1-inhibitor (CI-INH) deficiency dependent angiodema case arose 'de novo' in a child without a family history of this disease. His mother was undergoing immunosuppressive therapy (50 mg of azathioprine plus 8 mg of methyl-prednisolone daily) during pregnancy, uninterrupted for seven years because of a kidney transplant. All the other known causes of acquired C1-INH deficiency were excluded. An involvement of an azathioprine-induced C1-INH gene mutation is hypothised.

Angioedema↗
PubMed1997

Degradation of C1-inhibitor by plasmin: implications for the control of inflammatory processes.

BACKGROUND: A correct balance between protease and inhibitor activity is critical in the maintenance of homoeostasis; excessive activation of enzyme pathways is frequently associated with inflammatory disorders. Plasmin is an enzyme ubiquitously activated in inflammatory disorder, and C1-inhibitor (C1-Inh) is a pivotal inhibitor of protease activity, which is particularly important in the regulation of enzyme cascades generated in plasma. The nature of the interaction between plasmin and C1-Inh is poorly understood. MATERIALS AND METHODS: C1-Inh was immunoadsorbed from the plasma of normal individuals (n = 21), from that of patients with systemic lupus erythematosus (n = 18) or adult respiratory distress syndrome (n = 9), and from the plasma and synovial fluid of patients with rheumatoid arthritis (n = 18). As plasmin is a putative enzyme responsible for C1-Inh was examined using SDS-PAGE. In addition, peptides cleaved from C1-Inh by plasmin were isolated and sequenced and the precise cleavage sites determined from the known primary sequence of C1-Inh. Homology models of C1-Inh were then constructed. RESULTS: Increased levels of cleaved and inactivated C1-Inh were found in each of the inflammatory disorders examined. Through SDS-PAGE analysis it was shown that plasmin rapidly degraded C1-Inh in vitro. The pattern of C1-Inh cleavage seen in vivo in patients with inflammatory disorders and that produced in vitro following incubation with plasmin were very similar. Homology models of C1-Inh indicate that the majority of the plasmin cleavage sites are adjacent to the reactive site of the inhibitor. CONCLUSIONS: This study suggests that local C1-Inh degradation by plasmin may be a central and critical event in the loss of protease inhibition during inflammation. These findings have important implications for our understanding of pathogenic mechanisms in inflammation and for the development of more effectively targeted therapeutic regimes. These findings may also explain the efficacy of anti-plasmin agents in the treatment of C1-Inh deficiency states, as they may diminish plasmin-mediated C1-Inh degradation.

Adult↗
PubMed2000

C1-Esterase inhibitor: an anti-inflammatory agent and its potential use in the treatment of diseases other than hereditary angioedema.

C1-esterase inhibitor (C1-Inh) therapy was introduced in clinical medicine about 25 years ago as a replacement therapy for patients with hereditary angioedema caused by a deficiency of C1-Inh. There is now accumulating evidence, obtained from studies in animals and observations in patients, that administration of C1-Inh may have a beneficial effect as well in other clinical conditions such as sepsis, cytokine-induced vascular leak syndrome, acute myocardial infarction, or other diseases. Activation of the complement system, the contact activation system, and the coagulation system has been observed in these diseases. A typical feature of the contact and complement system is that on activation they give rise to vasoactive peptides such as bradykinin or the anaphylatoxins, which in part explains the proinflammatory effects of either system. C1-Inh, belonging to the superfamily of serine proteinase inhibitors (serpins), is a major inhibitor of the classical complement pathway, the contact activation system, and the intrinsic pathway of coagulation, respectively. It is, therefore, endowed with anti-inflammatory properties. However, inactivation of C1-Inh occurs locally in inflamed tissues by proteolytic enzymes (e.g., elastase) released from activated neutrophils or bacteria thereby leading to increased local activation of the various host defense systems. Here we will give an overview on the biochemistry and biology of C1-Inh. We will discuss studies addressing therapeutic administration of C1-Inh in experimental and clinical conditions. Finally, we will provide an explanation for the therapeutic benefit of C1-Inh in so many different diseases.

Animals↗
PubMed2006

Normal C1 inhibitor mRNA expression level in type I hereditary angioedema patients: newly found C1 inhibitor gene mutations.

BACKGROUND: C1 esterase inhibitor (C1INH) plays a key role in the classical pathway of the complement cascade. Mutations in this gene cause a decreased level of antigenic (type I hereditary angioedema, HAE) or functional (type II HAE) C1INH. OBJECTIVE: To find novel mutations in C1INH and evaluate the expression of C1INH gene in HAE patients. METHODS: Direct sequencing mutation analysis was performed for genomic DNA from three unrelated families (14 HAE patients and 18 family members). Genomic DNA from one family was also analyzed for larger genomic rearrangements, using Southern blotting analysis. We used real-time quantitative polymerase chain reaction (PCR) to evaluate C1INH mRNA expression level. RESULTS: Four mutations in exons (2,311 T-->C, 14,034 G-->A, 16,830 G-->A, and 16,979-16,980 G insertion) and four in introns (738 G-->A, 8,531 A-->G, 14,254 A-->G, and 14,337-14,378 TT deletion) were found. Interestingly, all of the nine patients in one family share the same mutation of Gly345Arg (14,034 G-->A) in the seventh exon. In another family, a single base mutation near the splice site (14,254 A-->G) was found in all of the three patients. In the last family, although a significant mutation was not found by direct sequencing, patients showed an abnormal 16 kb fragment in addition to the normal allele (21 kb Bcl I fragment). The C1INH mRNA expression of HAE patients in two families was not significantly different compared with that of normal controls. CONCLUSION: The two novel exonal mutations (G-->A and A-->G) and one large gene deletion were associated with the clinical phenotypes of HAE. Considering the normal C1INH mRNA levels but below normal protein levels in two families, their phenotypes would be associated with the post-translational defect.

Adolescent↗
PubMed2001

Hereditary angioedema with a de novo mutation of exon 8 in the C1 inhibitor gene showing recurrent edema of the hands around the peripheral joints: importance for the differential diagnosis of joint swelling.

We describe a patient with hereditary angioedema (HAE), showing recurrent edema around the peripheral joints. Her symptoms began at the age of 18 with hand swelling distal to the wrist joints. Until she was referred to our hospital 3 years after her initial symptoms, she was still undiagnosed, although she was suspected of having rheumatoid arthritis. Laboratory examination showed reduced levels of CH50 and C4 with normal C3 levels. The C1 inhibitor (C1-INH) was decreased to 5 mg/ml, with remarkably reduced activity. Although these findings were compatible with a diagnosis of HAE, there were no episodes of skin edema in her family. To establish the diagnosis, we carried out DNA analysis of the C1-INH gene, which revealed a newly identified de novo mutation of G to A at nucleotide 16869 in exon 8. As described in this patient, localized edema around the peripheral joints may be the only manifestation of HAE. HAE should therefore be taken into consideration for the differential diagnosis of joint swelling.

Adolescent↗
PubMed2003

Management of oral surgery in patients with hereditary or acquired angioedemas: review and case report.

Angioedemas are a rare but significant event in simple oral surgery because they can cause an acute life-threatening laryngeal edema. We report a case of a tooth extraction in a patient with hereditary angioedema, for which the C1-inhibitor (C1-INH) concentration administered effectively controlled edema during and after extraction. We also review case reports of oral surgery management in patients with hereditary and acquired angioedemas. In 2 of 36 cases, laryngeal edema occurred after teeth extraction. One was considered to be a type 2 acquired angioedema, which tolerates replacement therapy with fresh frozen plasma. The other case was managed only with danazol, and it was suggested that this was on occasion insufficient. Safety of oral surgery on patients with angioedema depends on the type of angioedema and the availability of C1-INH concentration. An exact diagnosis of the type of angioedema is needed to know the effect of replacement therapy with C1-INH.

Angioedema↗
PubMed2005

Deficiencies of C1 inhibitor.

Hereditary and acquired deficiencies of the C1 inhibitor result in a single prominent symptom, namely angioedema. Angioedema may involve the skin, the gastrointestinal tract or the upper airway. Genetically determined defects in C1INH cause hereditary angioedema. The defect may be acquired as the result of an auto-antibody to C1INH or be due to the generation of anti-idiotypic antibody to monoclonal immunoglobulins as occurs in various B cell lymphoproliferative diseases. Androgens provide prophylaxis against attacks of angioedema. There is no widely approved treatment for acute attacks of angioedema although several promising drugs are now in the final stages of clinical trials.

Angioedema↗
PubMed2004

Influence of lactation parameters on the N-glycosylation of recombinant human C1 inhibitor isolated from the milk of transgenic rabbits.

The large-scale production of recombinant biopharmaceutical glycoproteins in the milk of transgenic animals is becoming more widespread. However, in comparison with bacterial, plant cell, or cell culture production systems, little is known about the glycosylation machinery of the mammary gland, and hence on the glycosylation of recombinant glycoproteins produced in transgenic animals. Here the influence is presented of several lactation parameters on the N-glycosylation of recombinant C1 inhibitor (rhC1INH), a human serum glycoprotein, expressed in the milk of transgenic rabbits. Enzymatically released N-glycans of series of rhC1INH samples were fluorescently labeled and fractionated by HPLC. The major N-glycan structures on rhC1INH of pooled rabbit milk were similar to those on native human C1 inhibitor and recombinant human C1 inhibitor produced in transgenic mouse milk, with only the degree of sialylation and core fucosylation being lower. Analyses of individual animals furthermore showed slight interindividual differences; a decrease in the extent of sialylation, core fucosylation, and oligomannose-type glycosylation with the progress of lactation; and a positive correlation between expression level and oligomannose-type N-glycan content. However, when large quantities of rhC1INH were isolated for preclinical and clinical studies, highly consistent N-linked glycan profiles and monosaccharide compositions were found.

Animals↗
PubMed2003

Approaches toward reversal of increased vascular permeability in C1 inhibitor deficient mice.

C1 inhibitor (C1INH) deficient mice have increased vascular permeability that can be demonstrated by the extravasation of Evans Blue dye. This vascular leak is reversed with protease inhibitors, such as C1INH itself, DX88 (a recombinant variant Kunitz domain plasma kallikrein inhibitor), and the bradykinin receptor type 2 antagonist, Hoe140. The studies described here were undertaken for the following reasons: (1) To provide a more quantitative analysis of the effects of these interventions; (2) to provide data to further test the hypothesis that increased vascular permeability results from contact system activation with kallikrein-mediated release of bradykinin; (3) to test the hypothesis that the amino terminal non-serpin domain of C1INH modulates access to complex proteases, such as kallikrein complexed with high molecular weight kininogen (HK); and (4) to determine whether attenuated androgens or estrogens exert a direct effect on C1INH synthesis. To characterize the differences in these reagents, the dose-response and the rate of reappearance of increased vascular permeability in C1INH(-/-) mice were determined for the following agents: human plasma-derived C1INH, a recombinant Kunitz domain plasma kallikrein inhibitor (DX88), a bradykinin receptor antagonist (Hoe140), and a recombinant C1INH with an amino terminal truncation at amino acid 98 and substitution of the P2 Ala with a Val (Cserp98,A443V). C1INH and Cserp98,A443V were equivalent in activity, which provides further support for the hypothesis that the vascular leak is mediated by bradykinin and suggests that the amino terminal domain neither enhances nor interferes with access to kallikrein within the kallikrein-HK complex. DX88 was effective at very low doses, as was Hoe140. The duration of action of Hoe140 was quite prolonged. The data indicate that, in the mouse, neither danazol nor estrogens have a significant effect on C1INH synthesis.

Animals↗
PubMed2006

Characterisation of a new C1 inhibitor mutant in a patient with hepatocellular carcinoma.

A patient developed the first case of hepatocarcinoma associated with hereditary angioedema within the context of a 13-year long prophylactic danazol exposure. We sought to identify the molecular defect and to test the relative contribution to the development of hepatocarcinoma of intracellular accumulation of abnormal C1 inhibitor (C1-INH) protein. The de novo mutation c.878_881delTCTA was identified, leading to a premature stop codon. Monocyte C1-INH secretions of the patient and of her affected daughter were, respectively, 26 and 18% compared to controls. Mutant transcripts compatible with the 4bp deletion were detectable as a faint RT-PCR product both in interferon-stimulated monocytes and in liver tissue, whereas total C1-INH mRNA was found nearly half the amount recovered from normal subjects. In order to study the consequences at the protein level of the low expression of the mutant allele, we analysed the intracellular fate of mutant products. COS-7 cells were transiently transfected with a C1-INH expression minigene encoding the mutant protein. In pulse-chase experiments, a faint 75,000-M(r) band was detected only within 10min. Both the c.878_881delTCTA mutant transcript and the intracellular abnormal C1-INH protein are unstable. Our data therefore rule out the hypothesis of an accumulation of the mutant protein at levels relevant for the pathology and strengthen the link between the development of hepatocarcinoma and danazol exposure.

Adult↗