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W E Van Nostrand

Publications and source records attributed to W E Van Nostrand.

At least 19 recordsLinked to original sources
PubMed2006

Metallothionein-I and -III expression in animal models of Alzheimer disease.

Previous studies have described altered expression of metallothioneins (MTs) in neurodegenerative diseases like multiple sclerosis (MS), Down syndrome, and Alzheimer's disease (AD). In order to gain insight into the possible role of MTs in neurodegenerative processes and especially in human diseases, the use of animal models is a valuable tool. Several transgenic mouse models of AD amyloid deposits are currently available. These models express human beta-amyloid precursor protein (AbetaPP) carrying different mutations that subsequently result in a varied pattern of beta-amyloid (Abeta) deposition within the brain. We have evaluated the expression of MT-I and MT-III mRNA by in situ hybridization in three different transgenic mice models of AD: Tg2576 (carrying AbetaPP harboring the Swedish K670N/M671L mutations), TgCRND8 (Swedish and the Indiana V717F mutations), and Tg-SwDI (Swedish and Dutch/Iowa E693Q/D694N mutations). MT-I mRNA levels were induced in all transgenic lines studied, although the pattern of induction differed between the models. In the Tg2576 mice MT-I was weakly upregulated in cells surrounding Congo Red-positive plaques in the cortex and hippocampus. A more potent induction of MT-I was observed in the cortex and hippocampus of the TgCRND8 mice, likely reflecting their higher amyloid plaques content. MT-I upregulation was also more significant in Tg-SwDI mice, especially in the subiculum and hippocampus CA1 area. Immunofluorescence stainings demonstrate that astrocytes and microglia/macrophages surrounding the plaques express MT-I&II. In general, MT-I regulation follows a similar but less potent response than glial fibrillary acidic protein (GFAP) expression. In contrast to MT-I, MT-III mRNA expression was not significantly altered in any of the models examined suggesting that the various MT isoforms may have different roles in these experimental systems, and perhaps also in human AD.

Alzheimer Disease↗
PubMed2006

NO synthase 2 (NOS2) deletion promotes multiple pathologies in a mouse model of Alzheimer's disease.

Alzheimer's disease is characterized by two primary pathological features: amyloid plaques and neurofibrillary tangles. The interconnection between amyloid and tau aggregates is of intense interest, but mouse models have yet to reveal a direct interrelationship. We now show that NO may be a key factor that connects amyloid and tau pathologies. Genetic removal of NO synthase 2 in mice expressing mutated amyloid precursor protein results in pathological hyperphosphorylation of mouse tau, its redistribution to the somatodendritic compartment in cortical and hippocampal neurons, and aggregate formation. Lack of NO synthase 2 in the amyloid precursor protein Swedish mutant mouse increased insoluble beta-amyloid peptide levels, neuronal degeneration, caspase-3 activation, and tau cleavage, suggesting that NO acts at a junction point between beta-amyloid peptides, caspase activation, and tau aggregation.

Alzheimer Disease↗
PubMed2001

Pathogenic effects of D23N Iowa mutant amyloid beta -protein.

Cerebral amyloid beta-protein angiopathy (CAA) is a key pathological feature of patients with Alzheimer's disease and certain related disorders. In these conditions the CAA is characterized by the deposition of Abeta within the cerebral vessel wall and, in severe cases, hemorrhagic stroke. Several mutations have been identified within the Abeta region of the Abeta protein precursor (AbetaPP) gene that appear to enhance the severity of CAA. We recently described a new mutation within the Abeta region (D23N) of AbetaPP that is associated with severe CAA in an Iowa kindred (Grabowski, T. J., Cho, H. S., Vonsattel, J. P. G., Rebeck, G. W., and Greenberg, S. M. (2001) Ann. Neurol. 49, 697-705). In the present study, we investigated the effect of this new D23N mutation on the processing of AbetaPP and the pathogenic properties of Abeta. Neither the D23N Iowa mutation nor the E22Q Dutch mutation affected the amyloidogenic processing of AbetaPP expressed in H4 cells. The A21G Flemish mutation, in contrast, resulted in a 2.3-fold increase in secreted Abeta peptide. We also tested synthetic wild-type and mutant Abeta40 peptides for fibrillogenesis and toxicity toward cultured human cerebrovascular smooth muscle (HCSM) cells. The E22Q Dutch, D23N Iowa, and E22Q,D23N Dutch/Iowa double mutant Abeta40 peptides rapidly assembled in solution to form fibrils, whereas wild-type and A21G Flemish Abeta40 peptides exhibited little fibril formation. Similarly, the E22Q Dutch and D23N Iowa Abeta40 peptides were found to induce robust pathologic responses in cultured HCSM cells, including elevated levels of cell-associated AbetaPP, proteolytic breakdown of smooth muscle cell alpha-actin, and cell death. Double mutant E22Q,D23N Dutch/Iowa Abeta40 was more potent than either single mutant form of Abeta in causing pathologic responses in HCSM cells. These data suggest that the different CAA mutations in AbetaPP may exert their pathogenic effects through different mechanisms. Whereas the A21G Flemish mutation appears to enhance Abeta production, the E22Q Dutch and D23N Iowa mutations enhance fibrillogenesis and the pathogenicity of Abeta toward HCSM cells.

Amino Acid Sequence↗
PubMed2001

Disruption of pathologic amyloid beta-protein fibril assembly on the surface of cultured human cerebrovascular smooth muscle cells.

Cerebral amyloid beta-protein (Abeta) angiopathy (CAA) is a common pathological feature of Alzheimer's disease and several related disorders. In this condition, the accumulation offibrillar Abeta deposits is associated with degeneration of smooth muscle cells within the cerebral blood vessel wall. We have been using primary cultures of human cerebrovascular smooth muscle (HCSM) cells to investigate pathogenic mechanisms of Abeta in CAA. The specific assembly of Abeta fibrils on the surface of these cell types initiates several pathologic responses including increased expression and cell surface accumulation of the Abeta precursor protein (AbetaPP) and induction of apoptotic cell death. These pathologic responses are not observed with preparations of Abeta that are assembled into fibrils in solution, further underscoring the significance of the fibril assembly process on the cell surface. Since cell surface Abeta fibril assembly is the key initiator of the cerebrovascular cellular pathology that is observed in vitro, inhibition of this process remains an attractive therapeutic target for CAA. We have tested the efficacy of a variety of compounds that have been reported to inhibit Abeta fibril assembly in solution and block the neurotoxic properties of Abeta in vitro. The vast majority of these agents were ineffective in inhibiting the cell surface fibrillar assembly of Abeta and the subsequent pathologic responses in the cultured HCSM cells. This emphasizes the likely requirement of therapeutic compounds that are effective in disrupting cell surface-driven Abeta fibril assembly in the treatment of CAA.

Alzheimer Disease↗
PubMed2000

Protease nexin-2/Amyloid beta-protein precursor regulates factor VIIa and the factor VIIa-tissue factor complex.

Protease nexin-2/amyloid beta-protein precursor (PN-2/AbetaPP) and its Kunitz protease inhibitory (KPI) domain were characterized as inhibitors of factor VIIa (FVIIa) and factor VIIa-tissue factor complex (FVIIa-TF). PN-2/AbetaPP and KPI domain inhibited FVIIa with an apparent K(i) of 1.1+/-0.2x 10(-7) M and 1.5+/-0.1x10(-7) M, respectively. When soluble tissue factor (TF(1-219)) was present, there was increased FVIIa inhibition by PN-2/AbetaPP or KPI domain (K(i)=7.8+/-0.3x10(-8) M and 6.8+/-0.6x10(-8) M, respectively). When relipidated tissue factor (TF(1-243)) was present, the K(i) of FVIIa inhibition by PN-2/AbetaPP increased 4.7-fold further. PN-2/AbetaPP complexed with FVIIa, as shown on gel filtration and solid phase binding assay. The apparent second-order rate constant of inhibition of FVIIa by PN-2/AbetaPP in the absence of TF(1-219) was less than that of the FVIIa-TF(1-219) complex. Antithrombin in the absence of TF(1-219) also had a lower apparent second-order rate constant of inhibition than in its presence. In a mixture that included FVIIa, relipidated TF(1-243) and factor X, PN-2/AbetaPP or KPI domain had an IC(50) at 65 and 250 nM, respectively; antithrombin and heparin (1 U/mL) had an IC(50) of 12.8 nM. These data indicate that tissue factor promoted the inhibition of FVIIa by PN-2/AbetaPP or KPI domain, but antithrombin was a better inhibitor of soluble FVIIa-TF in extrinsic tenase.

Amyloid beta-Protein Precursor↗
PubMed2000

Fibrillar amyloid beta-protein binds protease nexin-2/amyloid beta-protein precursor: stimulation of its inhibition of coagulation factor XIa.

Cerebrovascular deposition of fibrillar 39-42 amino acid amyloid beta-protein (Abeta), a condition known as cerebral amyloid angiopathy (CAA), is a key pathological feature of Alzheimer's disease and related disorders including hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Severe cases of CAA, particularly in HCHWA-D, lead to recurrent and often fatal hemorrhagic strokes. Although the reasons for this pathological consequence remain unclear, alterations in proteolytic hemostasis mechanisms have been implicated. For example, the Abeta parent molecule protease nexin-2/amyloid beta-protein precursor (PN-2/AbetaPP), which is elevated in HCHWA-D cerebral vessels with Abeta deposits, is a potent inhibitor of coagulation factor XIa (FXIa). Here we show that fibrillar HCHWA-D Abeta binds PN-2/AbetaPP, but not its isolated Kunitz-type proteinase inhibitor (KPI) domain, in a saturable, dose-dependent manner with a K(d) of approximately 28 nM. Neither PN-2/AbetaPP nor its KPI domain bound to nonfibrillar HCHWA-D Abeta. The fibrillar Abeta binding domain on PN-2/AbetaPP was localized to residues 18-119. PN-2/AbetaPP that bound to fibrillar HCHWA-D Abeta immobilized either in plastic wells or on the surface of cultured cerebrovascular smooth muscle cells was active in inhibiting FXIa. Quantitative kinetic measurements revealed that fibrillar HCHWA-D Abeta caused a >5-fold enhancement of FXIa inhibition by PN-2/AbetaPP. Similar stimulatory effects on FXIa inhibition by PN-2/AbetaPP were also observed with fibrillar wild-type Abeta. However, fibrillar Abeta had no effect on the inhibition of trypsin by PN-2/AbetaPP. These findings suggest that fibrillar Abeta deposits in cerebral vessels can effectively localize and enhance the anticoagulant functions of PN-2/AbetaPP, thereby contributing to a microenvironment conducive to hemorrhaging.

Amyloid beta-Peptides↗
PubMed2000

Fibrillar amyloid beta-protein mediates the pathologic accumulation of its secreted precursor in human cerebrovascular smooth muscle cells.

Cerebrovascular deposition of the amyloid beta-protein (Abeta) is a key pathologic lesion seen in patients with Alzheimer's disease and certain related disorders, including hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D). The deposition of Abeta has pronounced deleterious effects on smooth muscle cells within the cerebral vessel wall. We have previously shown that Abeta(1-40) possessing the E22Q HCHWA-D mutation extensively assembles into fibrils on the surface of cultured human cerebrovascular smooth muscle (HCSM) cells. This cell-surface Abeta fibril formation induces a series of pathologic responses in cultured HCSM cells, including a marked increase in the levels of cell-associated amyloid beta-protein precursor (AbetaPP) and cell death. In the present study, we investigated the relationship between HCSM cell-surface Abeta fibril formation and the striking increase in cell-associated AbetaPP. Time course studies showed that cell-surface HCHWA-D Abeta(1-40) fibril formation occurred rapidly, whereas both the increase in cell-associated AbetaPP and loss of cell viability were delayed responses. Domain analysis using site-specific antibodies indicated that the vast majority of the increase in cell-associated AbetaPP was secreted AbetaPP (sAbetaPP). Localization studies showed that the sAbetaPP was present on the HCSM cell surface. This result raised the possibility that sAbetaPP may bind back to HCSM cell-surface fibrils formed by HCHWA-D Abeta(1-40). Indeed, binding of biotinylated sAbetaPP to fibrillar HCHWA-D Abeta(1-40) was demonstrated by transmission electron microscopy. Furthermore, solid-phase binding assays showed that biotinylated sAbetaPP exhibited dose-dependent, saturable binding to fibrillar (but not soluble) HCHWA-D Abeta(1-40) with k(d) approximately 28 nM. Exon deletion experiments further defined a fragment of sAbetaPP (AbetaPP(18-119)), encoded by AbetaPP exons 2 and 3, to contain the fibrillar Abeta-binding domain. In addition, AbetaPP(18-119) effectively blocked the cell-surface accumulation of sAbetaPP and subsequent cell death in HCSM cells treated with pathogenic Abeta. Together, these findings could explain the accumulation of AbetaPP in cerebrovascular Abeta deposits observed both in vitro and in vivo and may contribute to the pathologic responses evoked by pathogenic forms of Abeta in HCSM cells.

Amino Acid Sequence↗
PubMed2000

Charge alterations of E22 enhance the pathogenic properties of the amyloid beta-protein.

Cerebral amyloid angiopathy (CAA) due to amyloid beta-protein (Abeta) is a key pathological feature of patients with Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis, Dutch-type (HCHWA-D). The CAA in these disorders is characterized by deposition of Abeta in the smooth muscle cells within the cerebral vessel wall. Recently, a new mutation in Abeta, E22K, was identified in several Italian families that, like HCHWA-D, is associated with CAA and hemorrhagic stroke. These two similar disorders, stemming from amino acid substitutions at position 22 of Abeta, implicate the importance of this site in the pathology of HCHWA. Previously we showed that HCHWA-D Abeta(1-40) containing the E22Q substitution induces robust pathologic responses in cultured human cerebrovascular smooth muscle cells (HCSM cells), including highly elevated levels of cell-associated Abeta precursor (AbetaPP) and cell death. In the present study, a series of E22 mutant Abeta(1-40) peptides were synthesized, and their pathogenic properties toward cultured HCSM cells were evaluated. Quantitative fluorescence analyses showed that mutant Abeta(1-40) peptides either containing a loss of charge (E22Q and E22A) or a change of charge (E22K) bind to the surface of HCSM cells and form amyloid fibrils. Similarly, this same group of E22 mutant Abeta(1-40) peptides caused enhanced pathologic responses in HCSM cells. In contrast, wild-type E22 or the charge-preserving E22D Abeta(1-40) peptides were devoid of any of these pathogenic properties. These data suggest that a change or loss of charge at position 22 of Abeta enhances the pathogenic effects of the peptide toward HCSM cells and may contribute to the pathogenesis of the phenotypically related HCHWA disorders.

Amino Acid Substitution↗
PubMed2000

Cerebrovascular smooth muscle cell surface fibrillar A beta. Alteration of the proteolytic environment in the cerebral vessel wall.

Cerebrovascular deposition of the amyloid beta-protein (A beta) is a common pathologic event in patients with Alzheimer's disease (AD) and certain related disorders including hereditary cerebral hemorrhage with amyloidosis Dutch-type (HCHWA-D). A beta deposition occurs primarily in the medial layer of the cerebral vessel wall in an assembled fibrillar state. These deposits are associated with several pathological responses including degeneration of the smooth muscle cells in the cerebral vessel wall. Severe cases of cerebrovascular A beta deposition are also accompanied by loss of vessel wall integrity and hemorrhagic stroke. Although the reasons for this pathological consequence are unclear, altered proteolytic mechanisms within the cerebral vessel wall may be involved. Recent studies from our laboratory have shown that cell-surface assembly of A beta into fibrillar structures causes cellular degeneration via an apoptotic pathway and creates an altered proteolytic microenvironment on the cell surface of human cerebrovascular smooth muscle cells (HCSM cells). For example, HCSM cell-surface A beta fibrils serve as a site for tight binding of cell-secreted amyloid beta-precursor protein (A beta PP). Since A beta PP is a potent inhibitor of key proteinases of coagulation cascade, its enhanced localization on the A beta fibrils would provide an strong anticoagulant environment. In addition, HCSM cell-surface A beta fibrils are potent stimulators of tissue plasminogen activator (tPA) creating a profibrinolytic milieu. Our findings indicate that A beta fibril assembly on the HCSM cell surface causes cellular degeneration and results in both a strong anticoagulant and fibrinolytic environment. Together, these altered proteolytic events could create a setting that is conducive to loss of vessel wall integrity and hemorrhagic stroke.

Alzheimer Disease↗
PubMed2000

Amyloid-beta-induced degeneration of human brain pericytes is dependent on the apolipoprotein E genotype.

Amyloid-beta (A beta) deposition in cerebral vessels (cerebral amyloid angiopathy, CAA) is accompanied by degeneration of vascular cells, including pericytes and smooth muscle cells. Previous studies indicated that specific A beta protein isoforms are toxic for cultured human brain pericytes and smooth muscle cells. In particular, A beta 1-40 carrying the E22Q mutation, as in hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), is toxic. We investigated the effects of the A beta-binding protein apolipoprotein E (ApoE) on the toxicity of A beta for cultured human brain pericytes. We compared the toxicity of HCHWA-D A beta 1-40 for pericyte cultures with different ApoE genotypes, studied the accumulation of A beta and ApoE in these different cell cultures, and investigated the effects of exogenous ApoE. Pericyte cultures with an ApoE epsilon 2/epsilon 3 genotype were more resistant to HCHWA-D A beta 1-40 treatment than cultures with a epsilon 3/epsilon 3 or epsilon 3/epsilon 4 genotype. Cell death was highest in cultures homozygous for ApoE epsilon 4. The extent to which both A beta ApoE accumulated at the cell surface was parallel to the degree of toxicity. The addition of purified ApoE resulted in a decrease in cell death. These data suggest that ApoE4 may direct A beta more efficiently than other ApoE isoforms into a pathological interaction with the HBP cell surface. The results of this study are in line with the observations that inheritance of the ApoE epsilon 4 allele increases the risk of developing Alzheimer's disease, and that the ApoE epsilon 2 allele has a relatively protective effect.

Aged↗
PubMed1999

Plasmin cleavage of the amyloid beta-protein: alteration of secondary structure and stimulation of tissue plasminogen activator activity.

Cerebrovascular amyloid beta-protein (A beta) deposition, a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis Dutch-type, can lead to intracerebral hemorrhage; however, the mechanism for this remains unclear. Assembled A beta is a potent stimulator of tissue-type plasminogen activator (tPA) in vitro. Herein, we investigated the stimulation of tPA by freshly solubilized A beta 1-40. The rate of tPA stimulation by A beta 1-40 increased dramatically over time, suggesting that A beta may be altered during the course of the reaction. SDS-PAGE analysis showed that A beta 1-40 was cleaved during the course of the reaction. Subsequent studies showed that it was plasmin, the product of tPA activation of plasminogen, that specifically cleaved A beta 1-40 in the amino terminal region between Arg5 and His6. Plasmin effectively cleaved a chromogenic substrate corresponding to this cleavage site in A beta. Circular dichroism spectral analysis showed that A beta 6-40 adopted a strong beta-sheet secondary structure. This truncated A beta 6-40 peptide was a potent stimulator of tPA in vitro. Our results indicate that beta-sheet secondary structure of A beta, which can be promoted by plasmin cleavage, stimulates tPA activity. These findings suggest that pathologic interactions between A beta, tPA, and plasmin in the cerebral vessel wall could result in excessive proteolysis contributing to intracerebral hemorrhages.

Amyloid beta-Peptides↗
PubMed1999

Pathogenic amyloid beta-protein induces apoptosis in cultured human cerebrovascular smooth muscle cells.

The amyloid beta-protein (A beta) pathologically accumulates in cerebral vascular and senile plaque deposits in the brains of patients with Alzheimer's disease (AD) and related disorders including hereditary cerebral hemorrhage with amyloidosis Dutch type (HCHWA-D). The cerebrovascular deposits are accompanied by degeneration and eventual loss of smooth muscle cells in cerebral vessel wall. Similarly, we have shown that pathogenic forms of A beta cause cell death in cultured human cerebrovascular smooth muscle (HCSM) cells in vitro. Here we show that pathogenic A beta induces a number of structural changes in HCSM cells including shrinkage of cell bodies, retraction of processes, disruption of the intracellular actin network, and nuclear condensation and fragmentation. These changes were accompanied by a number of biochemical alterations in the cells shown by in situ end labeling of nuclear DNA, proteolytic breakdown of smooth muscle cell a actin, and proteolytic activation of the proteinase caspase 3. Together, these characteristics are consistent with an apoptotic mechanism of cell death in HCSM cells in response to pathogenic A beta.

Actins↗
PubMed1998

Pathologic amyloid beta-protein cell surface fibril assembly on cultured human cerebrovascular smooth muscle cells.

Cerebrovascular amyloid beta-protein (A beta) deposition is a key pathological feature of Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). A beta(1-40) containing the E22Q HCHWA-D mutation, but not wild-type A beta(1-40), potently induces several pathologic responses in cultured human cerebrovascular smooth muscle cells, including cellular degeneration and a robust increase in the levels of cellular A beta precursor. In the present study, we show by several quantitative criteria, including thioflavin T fluorescence binding, circular dichroism spectroscopy, and transmission electron microscopic analysis, that at a concentration of 25 microM neither HCHWA-D A beta(1-40) nor wild-type A beta(1-40) appreciably assembles into beta-pleated sheet-containing fibrils in solution over a 6-day incubation period. In contrast, at the same concentrations, HCHWA-D A beta(1-40), but not wild-type A beta(1-40), selectively binds and assembles into abundant fibrils on the surfaces of cultured human cerebrovascular smooth muscle cells. The simultaneous addition of an equimolar concentration of the dye Congo red prevents the cell surface fibril assembly of HCHWA-D A beta(1-40). Moreover, Congo red effectively blocks the key pathologic responses induced by HCHWA-D A beta(1-40) in these cells. The present findings suggest that the surface of human cerebrovascular smooth muscle cells may selectively orchestrate the assembly of pathogenic A beta fibrils and that cell surface A beta fibril formation plays an important role in causing the pathologic responses in these cells.

Amyloid beta-Peptides↗
PubMed1997

The mechanism by which heparin promotes the inhibition of coagulation factor XIa by protease nexin-2.

Previous kinetic studies have shown that protease nexin-2 is a potent, reversible, and competitive inhibitor of factor XIa. Here we show that high molecular weight heparin potentiates the ability of protease nexin-2 to inhibit factor XIa with a parabolic concentration dependence, predominantly because of an increase of the association rate constant with little perturbation of the dissociation rate constant. No effect on factor XIa inhibition by protease nexin-2 was observed with heparin preparations of 6-22 saccharide units (0.1 nM-10 microM), whereas heparin preparations with 32-64 saccharide units potentiated factor XIa inhibition by protease nexin-2 in a size- and concentration-dependent manner. We propose a model wherein heparin exerts this effect by providing a template for the assembly of factor XIa-protease nexin-2 complexes, and only heparin polymers consisting of greater than 32 saccharide units (Mr approximately 10,000) are sufficiently long to provide a template to which factor XIa and protease nexin-2 molecules can bind simultaneously. Heparin-mediated enhancement of factor XIa inhibition by protease nexin-2 was partially abrogated by high molecular weight kininogen, suggesting that high molecular weight kininogen may play a role in regulating factor XIa activity.

Amyloid beta-Protein Precursor↗
PubMed1997

Progress curve analysis of the kinetics with which blood coagulation factor XIa is inhibited by protease nexin-2.

Protease nexin-2 (PN-2), a soluble form of amyloid beta-protein precursor (APP) containing a Kunin protease inhibitor domain, has been shown to be a potent, reversible and competitive inhibitor of blood coagulation factor XIa (FXIa). We have analyzed progress curves of the hydrolysis of a sensitive fluorogenic substrate by FXIa in the presence of PN-2 to ascertain the kinetic rate constants governing the inhibition of FXIa by PN-2. The mechanism of this inhibition is best described as a slow equilibration between the free enzyme and inhibitor directly, without prior formation of a loosely-associated complex. The association rate constant (kon) and the dissociation rate constant (koff) were found to be 2.1 +/- 0.2 x 10(6) M-1 s-1 and 8.5 +/- 0.8 x 10(-4) s-1, respectively (n = 23). The inhibition constant calculated from these parameters (Ki) is 400 pM, in good agreement with previous reports. High molecular weight kininogen (HK) and Zn2+ ions exert opposite effects on the inhibition of FXIa by PN-2. HK protects FXIa from inactivation in a dose dependent and saturable manner (EC50 = 61 nM) whereas Zn2+ augments the ability of PN-2 to inhibit FXIa. When both Zn2+ ions and HK are present, only the accessory effect of Zn2+ is observed. PN-2 is known to be an abundant platelet alpha-granule protein (Van Nostrand et al., 1990a; Smith & Broze, 1992). We conducted sensitive measurements of FXIa activity in the presence of human platelets before and after their being activated with the thrombin receptor agonist peptide, SFLLRN-amide. We found that platelet activation, and ostensibly the release of PN-2, limits the lifetime of FXIa activity within the locus of activated platelets. As in the purified system, HK protects FXIa from inactivation and Zn2+ increases the inactivation of FXIa. However, when HK and Zn2+ are both present, it is the protective effect of HK which predominates and prolongs the lifetime of FXIa after platelet activation.

Amyloid beta-Protein Precursor↗
PubMed1997

Rapid degeneration of cultured human brain pericytes by amyloid beta protein.

Amyloid beta protein (A beta) deposition in the cerebral arterial and capillary walls is one of the major characteristics of brains from patients with Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis-Dutch type (HCHWA-D). Vascular A beta deposition is accompanied by degeneration of smooth muscle cells and pericytes. In this study we found that A beta 1-40 carrying the "Dutch" mutation (HCHWA-D A beta 1-40) as well as wild-type A beta 1-42 induced degeneration of cultured human brain pericytes and human leptomeningeal smooth muscle cells, whereas wild-type A beta 1-40 and HCHWA-D A beta 1-42 were inactive. Cultured brain pericytes appeared to be much more vulnerable to A beta-induced degeneration than leptomeningeal smooth muscle cells, because in brain pericyte cultures cell viability already decreased after 2 days of exposure to HCHWA-D A beta 1-40, whereas in leptomeningeal smooth muscle cell cultures cell death was prominent only after 4-5 days. Moreover, leptomeningeal smooth muscle cell cultures were better able to recover than brain pericyte cultures after short-term treatment with HCHWA-D A beta 1-40. Degeneration of either cell type was preceded by an increased production of cellular amyloid precursor protein. Both cell death and amyloid precursor protein production could be inhibited by the amyloid-binding dye Congo red, suggesting that fibril assembly of A beta is crucial for initiating its destructive effects. These data imply an important role for A beta in inducing perivascular cell pathology as observed in the cerebral vasculature of patients with Alzheimer's disease or HCHWA-D.

Amyloid beta-Peptides↗