Discovery of BACE1 Inhibitors for the Treatment of Alzheimer’s Disease

Alzheimer’s disease is the most common cause of dementia. According to the amyloid hypothesis, β-secretase (BACE1) is a promising molecular target for the development of anti-Alzheimer’s disease drugs. BACE1 triggers the formation of the amyloid-β (Aβ) peptides that are the main component of senile plaques in the brain of patients with Alzheimer’s disease. As BACE1 cleaves the amyloid precursor protein at the N-terminus of the Aβ domain, BACE1 inhibitors reduce the Aβ level in the brain. Previously, we designed a series of peptidic inhibitors that possessed a substrate transition-state analogue, and the structure-activity relationship of our inhibitors was evaluated, based on docking and scoring, using the docking simulation software Molecular Operating Environment (MOE). However, there was no association between the scoring values and the inhibitory activities at the P2 position. Hence, we hypothesized that the interaction of the P2 position of the inhibitor with the S2 site of BACE1 was critical for the mechanism of inhibition, and we proposed the novel concept of ‘electron donor bioisostere’ for drug discovery. Using this concept, we designed potent small molecule non-peptidic BACE1 inhibitors

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells. Adrenomedullin (AM), a potent vasorelaxant and natriuretic peptide isolated from human pheochromocytoma, is present in the kidney and secreted from endothelial cells (EC) and vascular smooth muscle cells (VSMC), but the functional role of AM is still unclear. To clarify the significance of AM as a local regulator, we investigated its secretion and action in cultured cells, and examined the effects of neutralization using a specific monoclonal antibody against AM. The prepared antibody directed against the ring structure showed a high affinity for human and rat AM. Using radioimmunoassay with this antibody, we found significant secretion from cultured rat mesangial cells (MC) of a 6-kDa mature form of AM as seen from EC and VSMC. The addition of AM into cultured cells dose-dependently increased cAMP production and potently inhibited PDGF-stimulated thymidine incorporation. Pretreatment with the monoclonal antibody completely abolished cAMP increase induced by exogenous AM. Moreover, antibody neutralization of endogenously secreted AM in cultured EC, but not in MC or VSMC, markedly (by ∼70%) reduced basal cAMP production and significantly (1.7-fold) enhanced DNA synthesis. These results indicate that AM, acting as an autocrine/paracrine regulator, exerts an antiproliferative action on EC and MC, and suggest its role as a local modulator of endothelial and mesangial function

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells

Autocrine/paracrine role of adrenomedullin in cultured endothelial and mesangial cells. Adrenomedullin (AM), a potent vasorelaxant and natriuretic peptide isolated from human pheochromocytoma, is present in the kidney and secreted from endothelial cells (EC) and vascular smooth muscle cells (VSMC), but the functional role of AM is still unclear. To clarify the significance of AM as a local regulator, we investigated its secretion and action in cultured cells, and examined the effects of neutralization using a specific monoclonal antibody against AM. The prepared antibody directed against the ring structure showed a high affinity for human and rat AM. Using radioimmunoassay with this antibody, we found significant secretion from cultured rat mesangial cells (MC) of a 6-kDa mature form of AM as seen from EC and VSMC. The addition of AM into cultured cells dose-dependently increased cAMP production and potently inhibited PDGF-stimulated thymidine incorporation. Pretreatment with the monoclonal antibody completely abolished cAMP increase induced by exogenous AM. Moreover, antibody neutralization of endogenously secreted AM in cultured EC, but not in MC or VSMC, markedly (by ∼70%) reduced basal cAMP production and significantly (1.7-fold) enhanced DNA synthesis. These results indicate that AM, acting as an autocrine/paracrine regulator, exerts an antiproliferative action on EC and MC, and suggest its role as a local modulator of endothelial and mesangial function

Myocardial Impairment Detected by Late Gadolinium Enhancement in Hypertrophic Cardiomyopathy: Comparison with 99mTc-MIBI/Tetrofosmin and 123I-BMIPP SPECT

Purpose: Myocardial fibrosis is considered to be an important factor in myocardial dysfunction and sudden cardiac death in hypertrophic cardiomyopathy (HCM). The purpose of this study was to compare myocardial fibrosis detected by late gadolinium enhancement (LGE) on cardiac MRI with myocardial perfusion and fatty acid metabolism assessed by single photon emission computed tomography in HCM.Materials and Methods: We retrospectively evaluated 20 consecutive HCM patients (female, 7; mean age, 53.4 years) who underwent LGE, technetium-99m methoxyisobutylisonitrile/tetrofosmin (99mTc-MIBI/tetrofosmin), and iodine-123 beta-methyl-iodophenylpentadecanoic acid (123I-BMIPP) imaging. We calculated the myocardium-to-lumen signal ratio (M/L) for LGE in 17 segments based on the American Heart Association statement. Scoring of 99mTc-MIBI/tetrofosmin (PI) and 123I-BMIPP (BM) was performed for each segment using a 5-point scale (0, normal; 4, highly decreased).Results: Nineteen of 20 patients (95%) and 153 of 340 segments (45%) showed LGE. M/Ls were 0.42ｱ・.16, 0.55ｱ・.17, and 0.65ｱ・.24 in PI0/BM0, PI0/BM1-4 and PI1-4/BM1-4, respectively. All M/Ls were significantly higher than that of a normal control (0.34ｱ・.14) (p<0.001).Conclusions: Myocardial fibrosis in HCM can occur despite normal perfusion and fatty acid metabolism, and is more strongly associated with disorders of fatty acid metabolism than with perfusion abnormalities. M/L may be a useful indicator of disease severity

Application of the O-N intramolecular acyl migration reaction in medicinal chemistry

The O-N intramolecular acyl migration, also named as an acyl shift or acyl transfer reaction, is well-known in organic and peptide chemistry as a simple rearrangement which proceeds under very mild aqueous conditions. Despite a long history with this reaction, its application in medicinal chemistry has only lately been proposed. In the last decade, this reaction has been intensively studied and several applications of this rearrangement in medicinal chemistry have appeared. O-N Intramolecular acyl migration has been employed in "no auxiliary, no byproduct" prodrug strategies (prodrugs of paclitaxel and other taxoids, prodrugs of HIV protease inhibitors), for the synthesis of peptides containing difficult sequences via "O-acyl isopeptide method", including Alzheimer's disease related amyloid peptide (A beta) 1-42, and in the design of pH-, photo- or enzyme-triggered click peptides, as a potential powerful tool for identifying the pathological functions of amyloid peptides in Alzheimer's disease. This review summarized recent advances in the application of O-N intramolecular acyl migration with special focus on medicinal chemistry

Small-sized BACE1 inhibitors

The determination of the three-dimensional X-ray crystal structure of b-secretase (BACE) complexed with an inhibitor has greatly facilitated the design of BACE inhibitors. Generally, BACE inhibitors can be grouped into two main families: substrate-based inhibitors designed as peptidomimetic inhibitors and nonpeptidomimetic inhibitors. This review focuses on the rational design of inhibitors based on transition-state analogues. The structural nature of peptidomimetic inhibitors usually implies relatively poor catabolic stability and low bioavailability after systemic administration due to low blood-brain barrier permeability. To overcome these drawbacks, several different approaches have been used