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Biomedical subjects

M D Tilson

Publications and source records attributed to M D Tilson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Elastin degradation products induce adventitial angiogenesis in the Anidjar/Dobrin rat aneurysm model.

BACKGROUND: Infusion of the abdominal aorta with pancreatic elastase induces aneurysms in a rat model (Anidjar/Dobrin). Because elastolysis liberates elastin degradation products (EDPs), the present experiment was carried out to test the hypothesis that an EDP alone could induce features of aneurysm disease. METHODS: The EDP val/gly/val/ala/pro/gly (VGVAPG), elastase, or saline solution was infused into infrarenal aorta (n = 4/group). After 1 week aortic diameters were measured, and the tissues were prepared for histologic examination. Adventitial capillaries (vessels per high-power field) were counted over a standardized preparation of aorta. Wall thickness was measured by means of computer-aided planimetry. RESULTS: There was an increase of greater than 100-fold in mean vessels per high-power field in aortas receiving VGVAPG or elastase versus saline controls (4.10 +/- 0.68 SEM or 4.48 +/- 0.49 SEM versus 0.03 +/- 0.03 SEM, respectively, p < 0.05). The VGVAPG-perfused group had a 26% +/- 4% SEM increase in diameter from baseline that was statistically significant (p < 0.01), but the aortas did not reach aneurysmal dimensions. CONCLUSIONS: Although no aneurysms occurred at 1 week after the infusion of EDP, the results demonstrate that the EDP VGVAPG can induce a characteristic feature of aneurysm disease. The model permits study of the earliest stages of experimental aneurysm formation and raises interesting questions regarding the role of the vasa vasorum in this pathologic process.

Animals↗
PubMed1997

Molecular cloning of the complementary DNA for an additional member of the family of aortic aneurysm antigenic proteins.

PURPOSE: We have purified and partially sequenced a protein from the adventitia of the human aorta (aortic aneurysm antigenic protein 40 kDa; AAAP-40) that has homologies to bovine aortic microfibril-associated glycoprotein (MAGP-36). It is immunoreactive with immunoglobulin G (IgGs) purified from the serum and aortic wall of patients with abdominal aortic aneurysms. AAAP-40 and MAGP-36 have fibrinogen-like and vitronectin-like motifs. Screening an expression library constructed from human aortic adventitial messenger RNA has resulted in the cloning of three complementary DNAs whose gene products are immunoreactive with immunoglobulin G from patients with abdominal aortic aneurysms. Two strongly resemble each other and have been described separately. The purpose of this article is to report the third clone. METHODS: Messenger RNA from a specimen of human aortic aneurysmal adventitia was reverse-transcribed for insertion into the phagemid Uni Zap XR (Stratagene). A strain of Escherichia coli, engineered for expression (XL 1-Blue MFR', Stratagene), was transfected, and rabbit antihuman vitronectin antibody as used to identify positive clones. Sequencing of the positive clones was performed by the Core Laboratories at Columbia University. RESULTS: The hypothetical protein of rAAAP-CL4 (clone 4) shares sequence motifs with known microfibril-associated glycoproteins (MAGPs). The recombinant protein (rAAAP-CL4) is immunoreactive with serum from patients (three of four abdominal aortic aneurysm sera). In addition, similarities have been detected with immunoglobulins of the kappa family and with a protein from cytomegalovirus that is a potential molecular mimic. CONCLUSIONS: There may several members of a novel family of human aortic autoantigenic proteins implicated in abdominal aortic aneurysm disease.

Amino Acid Sequence↗
PubMed1997

The nitrite/elastin reaction: implications for in vivo degenerative effects.

Nitrite ion is a by-product of nitrogen oxides (nitric oxide and nitrogen dioxide) from cigarette smoke and is used as a preservative for curing meats. Therefore, study of the reaction of nitrite with elastin in vitro was undertaken. By colorimetric assay, reactivity of nitrite with insoluble elastin at neutral pH, 37 degrees C, and physiologic concentration was confirmed. In histochemical studies on in situ human aortic elastin, nitrite-treated sections displayed marked structural disruptions. Determinations of fluorescence and absorbance on nitrite-treated soluble bovine elastin revealed marked alterations of fluorescence, and increased UV and visible absorbance. Amino acid analysis confirmed that it reacted with tyrosine. The findings indicate that non-enzymatic nitration by nitrite may have deleterious effects on elastin in vivo and may provide insights into the pathogenesis of chronic elastin degenerative processes, including aortic aneurysms, pulmonary emphysema, and premature skin wrinkling, all of which have been well known to have associations with cigarette smoking.

Amino Acids↗
PubMed1997

Three-dimensional modeling and molecular evolution of Matrix Cell Adhesion Molecule #2: MAT-CAM 2.

Our research group has recently reported the partial amino acid sequence of an aortic adventitial collagen-associated fibrillar protein, which may be the target of an autoimmune response in patients with abdommal aortic aneurysms (AAA). Its apparent molecular weight is approximately 40 kDa, so we have named it aneurysm-associated antigenic protein-40 kDa (AAAP-40). It has similarities to microfibril-associated glycoprotein-36 kDa (MAGP-36), which was reported by Kobayashi et al. to have a tissue distribution limited to the aorta in pig; unlike other microfibrillar proteins which appear to distribute ubiquitously throughout the body with elastin. Accordingly, if AAAP-40 is the human homolog of MAGP-36, it would explain how an autoimmune reaction against this protein might have consequences more or less limited to the aorta and its branches.

Journal Article↗
PubMed1996

Two hypothetical proteins of human aortic adventitia, with Ig kappa, collagenous, and aromatic-rich motifs.

Two of five clones, selected from an expression library of aortic adventitia, encode unique hypothetical proteins sharing sequences of Ig kappa, gly/pro rich (collagenous) motifs, and aromatic motifs that occur in several proteins of the extracellular matrix. Both proteins have a similar domain structure with at least 8 regions: (1) Ig kappa (84-120 residues in length); (2) ser/thr-rich motif (44-63); (3) a second Ig kappa motif (9-12); (4) either a possible calcium-binding motif or a gly/pro rich sequence (35-43); (5) an aromatic rich sequence (6-7); (6) another gly/pro rich sequence (62-72); (7) a third Ig kappa sequence (26-28); and (8) a C-terminal 68-70 residue sequence with another aromatic motif.

Amino Acid Sequence↗
PubMed1996

Partial amino acid sequence of a novel 40-kDa human aortic protein, with vitronectin-like, fibrinogen-like, and calcium binding domains: aortic aneurysm-associated protein-40 (AAAP-40) [human MAGP-3, proposed].

A microfibrillar protein (40 kDa) purified from the adventitia of the human abdominal aorta is immunoreactive with IgG harvested from the wall of abdominal aortic aneurysms. We have partially sequenced this protein and found that it has fibrinogen alpha-, beta-, and gamma-like domains, a vitronectin-like domain, and a possible site for binding calcium. Because of homologies with other microfibril-associated glycoproteins and because it is the third member of the family to be characterized in man, we suggest the name MAGP-3.

Amino Acid Sequence↗
PubMed1996

Features of autoimmunity in the abdominal aortic aneurysm.

PURPOSE: Previous work has revealed that nonspecific abdominal aortic aneurysms (AAAs) have a prominent infiltration of inflammatory cells and that soluble extracts of AAA tissue are rich in immunoglobulins. These observations raise the question whether autoimmune mechanisms play a role in the pathogenesis or progression of AAA disease. The hypothesis of this investigation was that IgG purified from aneurysmal specimens would be immunoreactive with normal components of the aortic wall (by means of immunohistochemistry) and with soluble proteins extracted from normal aortic tissue (by Western immunoblotting methods). METHODS: Immunoglobulin G extracted from AAA homogenates was used to detect immunohistochemical reactivity to connective tissue components in fixed sections of normal aorta obtained from an organ donor. Immunoblotting techniques were used to compare the reactivity of IgG (detected with secondary goat antihuman antibody) from 14 patients with AAA with soluble proteins extracted from normal and aneurysmal aortas. Immunoglobulins G purified from extracts obtained from nine patients with no AAA were used for control experiments. RESULTS: A unique band at approximately 80 kd was visualized when the filters were probed with IgG from 11 (79%) of 14 patients with AAA compared with only one (11%) of nine control subjects (P = .002 by Fisher's exact test). Immunoglobulins G from patients with AAA codistributed with matrix fibers in normal aortic sections, particularly in the adventitia (suggestive of a microfibrillar component). CONCLUSION: Our findings suggest that there are autoimmune features of AAA disease that might not only be informative in terms of AAA origin but also lead to more precise forms of pharmacologic down-regulation of disease progression.

Aortic Aneurysm, Abdominal↗
PubMed1996

A novel hypothesis to explain the hemorrhagic and connective tissue manifestations of Ebola virus infection.

The hemorrhagic and connective tissue complications of infection with Ebola virus are poorly understood. While searching for homologies and motifs of the aortic aneurysm-associated autoantigenic protein 40 kDa (AAAP-40), we have noted some short sequences (possibly shared epitopes) that occur in the envelope glycoprotein (40 kDa) of the Ebola virus. As a first step toward determining whether molecular mimicry of human matrix proteins by the Ebola virus protein might explain some of the severe connective tissue manifestations of infection, we have tested whether immunoglobulin (IgG) purified from the sera of patients with abdominal aortic aneurysm (AAA) are immunoreactive with the 40-kDa protein of the Ebola virus. Immunoblots of soluble Ebola proteins (strain Mayinga/Zaire) were probed with IgG's purified from the sera of eight patients with AAA and two healthy young control volunteers. The proteins were also probed with IgG extracted from the walls of two surgical aneurysm specimens. Serum IgG from eight consecutively studied AAA patients was immunoreactive with an Ebola virus protein of 40 kDa, consistent with the envelope glycoprotein. IgG's extracted from the walls of two AAAs were also reactive. The control sera were not reactive. In addition to the Ebola sequences in AAAP-40, an Ebola sequence also occurs in the microfibril-associated glycoprotein-4 (MAGP-4), which is distributed ubiquitously throughout connective tissue with elastin. We hypothesize that the catastrophic hemorrhagic and connective tissue complications of Ebola virus infection may be the result of these shared epitopes.

Aged↗
PubMed1996

Complement activation and subclassification of tissue immunoglobulin G in the abdominal aortic aneurysm.

Features of autoimmunity in abdominal aortic aneurysm (AAA) have been described, including increases in IgG content. The present experiments were carried out to determine (1) whether the increases in IgG are subclass specific and (2) whether the IgG complex is associated with an increase in the isoforms of complement C3. Seven AAA, four athero-occlusive (AOD), and two normal (NL) aortic tissue extracts were evaluated for immunoreactive complement (C3) components, both by ELISA and by Western immunoblots (probed with a polyclonal goat anti-human C3). The extracts were also assayed for each of the four subclasses of IgG by ELISA (monoclonal mouse anti-human IgGs). Compared to the amounts of IgG by subclass in normal aorta, AAAs had increases of 193-fold in IgG1, 160-fold in IgG2, 389-fold in IgG3, and 627-fold in IgG4. Increases relative to AOD by subclass were smaller, but each subclass was statistically significantly elevated (P < 0.01) over NL or over AOD. There was a 125-fold increase in immunoreactive C3 by ELISA in AAA vs NL, and Western immunoblotting techniques revealed the presence of multiple C3 degradation products. Increases in IgG1, 2, and 3 may be responsible for activation of complement in AAA by the classical pathway. Since the complement system is one of the major effector pathways of inflammation, the presence of complement-fixing IgG subclasses along with increased C3 in the aneurysm wall may be an important mechanism promoting matrix proteolysis in AAA.

Aorta, Abdominal↗
PubMed1995

Similarities of an autoantigen in aneurysmal disease of the human abdominal aorta to a 36-kDa microfibril-associated bovine aortic glycoprotein.

Immunoglobulin G (IgG) from human aneurysmal aorta was used to partially purify an aortic protein with an apparent MW approximately 80 kDa. Amino acid sequencing of a tryptic digest revealed two sequences with homology to mouse tenascin-X. The autoimmune IgG was then shown to react with purified human tenascin, and a rabbit polyclonal anti-human tenascin antibody was found to react with the purified autoantigen. These observations suggest that the autoantigen of abdominal aortic aneurysm disease may be homologous to a calcium-binding member of the tenascin superfamily that has been identified by others in pig and cow.

Amino Acid Sequence↗
PubMed1994

The elastase infusion model of experimental aortic aneurysms: synchrony of induction of endogenous proteinases with matrix destruction and inflammatory cell response.

PURPOSE: Perfusion of the isolated aorta of the rat with a saline solution containing pancreatic elastase induces an abdominal aortic aneurysm (AAA). An interesting feature of this model is the phenomenon of latency, suggesting that additional steps beyond the initial injury are required for AAA formation. This study was performed to determine whether the latency period for aortic dilation to aneurysmal proportions is correlated with the appearance of proteinases of endogenous origin and the interval for infiltration of inflammatory cells. METHODS: Twenty Wistar rat aortas were perfused with the test solution, and 20 with normal saline solution. Laparotomy was performed on days 1, 2, 3, and 6 for measurement and harvest of the aorta. Histochemical studies were performed to analyze changes in matrix proteins, and substrate gel enzymography was used to determine the appearance of endogenous proteinases. Immunohistochemical studies were performed with monoclonal antibodies to T cells (CD-4, -5, and -8), monocytes/macrophages (ED-2), B cells (LC-A), immunoglobulin G, and immunoglobulin M. RESULTS: The exogenously administered elastase was not detectable beyond day 2, but the aortic diameter did not progress to aneurysmal dimensions until the interval between days 3 and 6. During the period from day 3 to day 6, multiple endogenous matrix proteinases became detectable in the aortic tissue preparations. Immunohistochemical study revealed progressive infiltration of the aorta with various subsets of inflammatory cells. CONCLUSION: The results suggest that the latency in AAA formation in this model corresponds with a complex sequence of biochemical and cellular events. The model provides an "early window" into these interesting early phases leading to aneurysm formation.

Animals↗
PubMed1994

Cellular localization of matrix metalloproteinases in the abdominal aortic aneurysm wall.

PURPOSE: This study explores the source(s) of the matrix-degrading proteinases, matrix metalloproteinase 1 (MMP-1; interstitial collagenase), matrix metalloproteinase 3 (MMP-3; stromelysin 1), and matrix metalloproteinase 9 (MMP-9; gelatinase B), previously implicated in abdominal aortic aneurysm (AAA) development. The possible involvement of the plasmin cascade in the activation of these proteinases was also explored by examining the presence of the urokinase-type plasminogen activator (uPA) in aneurysm wall. METHODS: Immunohistochemical techniques were used to detect the presence of MMP-1, MMP-3 and MMP-9 proteins and uPA in fixed, paraffin-embedded tissue sections from AAA (n = 10) and control (n = 2) aortas. RESULTS: The MMP-9 protein was localized to mononuclear cells in the AAA wall. Dual-labeling techniques confirmed the identity of these cells as macrophages. The MMP-3 protein and uPA were also detected primarily in the macrophage-like mononuclear cells infiltrating the aneurysmal aorta. Immunoreactive material to MMP-1 was demonstrated in mesenchymal cells of the AAA wall suggesting alternative expression and delivery of this enzyme in AAA. CONCLUSIONS: This work establishes the role of macrophages in the delivery, expression, and possible activation of matrix destructive proteinases during AAA pathogenesis and suggests a role for the activation of MMPs in the progression of the disease.

Antibodies, Monoclonal↗
PubMed1994

Identification of matrix metalloproteinases 3 (stromelysin-1) and 9 (gelatinase B) in abdominal aortic aneurysm.

A prominent metalloproteinase activity with an apparent molecular mass of 80 kD and additional activities at 67 through 70, 50, and 32 kD have been observed on casein, gelatin, and elastin gel zymography in extracts from abdominal aortic aneurysms (AAAs). The forms at 80, 50, and 32 kD were isolated by affinity to recombinant tissue inhibitor of metalloproteinases, and the 80-kD and 50-kD components were shown to be derived from matrix metalloproteinase-9 (MMP-9). The relative electrophoretic mobility of these forms under reducing and nonreducing conditions corresponds to those of MMP-9 generated by MMP-3 (stromelysin-1) cleavage, and the active forms of MMP-3 at 45 and 35 kD were detected in aneurysmal extracts under reducing conditions by using specific antibody. Confirmation that the major proteolytic activity observed at 80 kD is MMP-9 was also demonstrated by immunoprecipitation of the activity with specific antibody. Comparative immunoblots of tissue extracts from 10 typical AAA patients, using specific antibody against MMP-9, revealed bands at 92, 82, 67, 51 through 53, 27, 23, and 20 kD under reducing conditions; six aortic control specimens displayed negligible immunoreactivity. This report is the first to show that known activated forms of MMP-3 and MMP-9 are present in the aneurysmal aortic wall and that they may play a role in the destruction of aortic matrix in AAA disease.

Aorta, Abdominal↗