beta-Amyloid-(1-42) is a major component of cerebrovascular amyloid deposits: implications for the pathology of Alzheimer disease.

Abstract

Reinvestigation of the chemical structure of (-amyloid nonpathological by-product of cellular metabolism, whereas A3-(1-42) may have the more important role in the formation of neuritic plaques.With this in mind, we reexamined amyloid from the cerebrovasculature of AD brains and found that A,B-(1-42) is also the major form in these deposits. Interestingly, the amount of racemization and isomerization at aspartyl residues is much less than in neuritic plaque Af-(1-42). The localization of these undegradable aggregates suggests that their deposition might be linked to a compromised blood-brain barrier. MATERIALS AND METHODSHuman brains obtained at autopsy met the diagnostic criteria for AD established by the National Institutes of Health Neuropathology Panel (10) and by the Consortium to Establish a Registry for AD (CERAD) (11). Morphometric analyses identified brains that contained large amounts of AP in compact cores and in the blood vessels. Left hemispheres were analyzed histopathologically, while right hemispheres were stored at -70°C for subsequent A,3 isolation.Purification of A,B from Leptomeningeal Blood Vessels. The leptomeninges were gently pulled from the surface of 1-cmthick coronal sections with the aid of a dissecting microscope and immersed in 0.1 M Tris HCl (pH 8.0; TB) at 4°C. Blood vessels larger than 1 mm in diameter were discarded, and the remaining tissue was cut with scissors into 1-to 2-mm pieces. The tissue was washed eight times with 1 liter of TB at 4°C with continuous stirring for 10 min and was collected by filtration (45-,um mesh). After resuspension of this material in 20 vol of 2 mM CaCl2 in TB, 0.3 mg of collagenase (Worthington) and 10 p.g of DNase I (Worthington) were added per ml, and the suspension was shaken for 18 hr at 37°C. Large debris was removed by filtration (350-,gm mesh), and the smaller insoluble material was recovered by centrifugation at 6000 x g for 15 min. The resulting pellet was resuspended in 100 vol of 2% SDS in TB and incubated for 2 hr at room temperature, after which the insoluble material was again recovered by centrifugation (see above) and washed twice with distilled water. The pellet was then dissolved with 8 vol of 98% (vol/vol) glass-distilled formic acid (15 min at room temperature) and centrifuged at 430,000x g for 15 min in Polyallomer tubes in a TLA 100.2 rotor (Beckman). Pure A8 was isolated from the clear supernatant by size-exclusion chromatography with a Superose 12 column (10 x 300 mm) on a Pharmacia-LKB fast protein liquid chromatography (FPLC) system with a running buffer of 75%

Amyloid-β peptide–Receptor for Advanced Glycation Endproduct interaction elicits neuronal expression of macrophage-colony stimulating factor: A proinflammatory pathway in Alzheimer disease

“…2 A and B; synthetic A␤ had no detectable lipopolysaccharide and addition of polymyxin B had no effect on A␤-induced M-CSF production). Similar results were observed when either synthetic A␤ 25-35 or A␤ purified from AD brain, mainly A␤ 1-42 (22), was studied, and in a limited number of experiments with primary cultures of rat cortical neurons (data not shown). Two critical steps in the pathway through which A␤ induced M-CSF included interaction of amyloid-␤ peptide with RAGE on the neuronal cell surface and subsequent induction of cellular oxidant stress; M-CSF expression was blocked by anti-RAGE IgG, but not nonimmune IgG, and by the antioxidant N-acetylcysteine (NAC) (Fig.…”

Alpha 1-antichymotrypsin regulates Alzheimer beta-amyloid peptide fibril formation.

“…Preliminary experiments with synthetic f3-amyloid peptide, which is believed to be the main component of cerebral vascular amyloid (27) and forms fibrils more rapidly, have demonstrated a similar type of serpin interaction (S. J. and S. E., unpublished data). Although the exact mechanism remains to be explained, it is intimately associated with a conformational transition of ACT and not necessarily with its role as a proteinase inhibitor.…”

Neurovascular function in Alzheimer's disease patients and experimental models

“…In AD, aggregated forms of Ab 1À40 and Ab 1À42 settle within vessel walls of small to medium arteries, leading to cerebral amyloid angiopathy (CAA) (Roher et al, 1993). The deposition of amyloid in circumferential bands is consistent with smooth muscle cell synthesis (Roher et al, 1993); however, initial deposits on the abluminal side of the smooth muscle also suggest a neuronal origin. As the amyloid makes its way toward capillaries and arterioles, faulty clearance across the blood-brain barrier, and increased arterial stiffness hindering vessel pulsations that drive perivascular Ab drainage would result in abluminal deposition (Herzig et al, 2006;Weller et al, 2008).…”