Disassembly of amyloid beta-protein fibril by basement membrane components.

Amyloid beta-protein (A3) fibril in senile plaque may be related to the pathogenesis of Alzheimer's disease (AD). Basement membrane (BM) components are associated with the plaques in AD brain. It suggests that the BM components may play an important role in the deposition of the plaque. We investigated the potential of BM components, such as type IV collagen (collagen IV) and entactin, to induce disassembly of preformed Abeta1-42 (Abeta42) fibrils in direct comparison to laminin. Thioflavin T assays revealed that these BM components disrupted preformed Abeta42 fibrils in a dose-dependent manner. The high concentration of BM components, 100 microg/mL laminin, 50 microg/mL collagen IV and 50 microg/mL entactin, had most effect on disassembly of preformed Abeta42 fibrils (Molar ratio; Abeta42:laminin = 90:1, Abeta42:collagen IV = 34:1, Abeta42:entactin = 20:1). Circular dichroism spectroscopy data indicated that the high concentration of BM components induced structural transition in Abeta42 from beta-sheet to random structures. These results suggest that collagen IV and entactin, as well as laminin, are effective inducers of disassembly of Abeta42 fibrils. The ability of these BM components to induce random structures may be linked to the disassembly of preformed Abeta42 fibrils.

Effect of TTC-909 in a middle cerebral artery thrombosis model in stroke-prone spontaneously hypertensive rats.

We investigated the effect of TTC-909, a preparation of the stable prostaglandin I(2) analogue clinprost (isocarbacyclin methylester; methyl 5-[(1S,5S,6R,7R)-7-hydroxy-6-[(E)-(S)-3-hydroxy-1-octenyl] bicyclo[3.3.0]oct-2-en-3-yl] pentanoate) incorporated into lipid microspheres, on infarct volume 24 h after photochemically induced thrombotic occlusion of the middle cerebral artery in stroke-prone spontaneously hypertensive rats (SHR). Under anesthesia, the photosensitizing dye rose bengal (20 mg/kg) was administered intravenously and photoirradiation with green light (wavelength 540 nm) on the middle cerebral artery above the rhinal fissure was achieved using a xenon lamp for 10 min. Infarct volume 24 h after the photochemically induced thrombotic occlusion of the middle cerebral artery was significantly larger in stroke-prone SHR than in Wistar rats. When TTC-909 in doses of 100, 300 and 900 ng/kg/h was intravenously infused for 3 h, starting immediately after the end of the 10-min photoirradiation, the infarct volume was dose-dependently reduced and was statistically significant at a dose of 900 ng/kg/h (p < 0.05). Ozagrel, a thromboxane A(2) synthetase inhibitor, significantly reduced the infarct volume. The model of photochemically induced thrombotic occlusion of the middle cerebral artery in stroke-prone SHR is very useful, because the cerebral infarction is large enough and reproducible. TTC-909 may be effective for the treatment of acute ischemic stroke.

Type IV collagen prevents amyloid beta-protein fibril formation.

The potential of targeting through molecular therapeutics the underlying amyloid beta-protein (A beta) fibrillogenesis causing the initiation and progression of Alzheimer's disease (AD) offers an opportunity to improve the disease. Type IV collagen (collagen IV) is localized in senile plaques in patients with AD. By using thioflavin T fluorescence spectroscopy and electron microscopy, we found that collagen IV inhibited A beta1-40 (A beta40) fibril formation. The critical concentration of collagen IV for this inhibition was 5 microg/mL. Circular dichroism data indicate that collagen IV prevents formation of a beta-structured aggregate of A beta40. These studies demonstrated that collagen IV is apparently a potent inhibitor of A beta fibril formation.