Discovery and Mechanisms of Small Molecule Amyloid Formation Inhibitors

Abstract

Current dogma suggests modulating or preventing amyloid assembly will prove critical to the armamentarium of therapeutic interventions that will likely be required to overcome the multifaceted pathology associated with amyloid diseases. The work described in this dissertation reveals substantial gains in understanding key aspects relating to the anti-amylin amyloid activities associated with both individual and broad groups of small molecule amyloid inhibitors. A main observation was the important role that the catechol functional group plays in modulating and preventing amyloid formation. In this context, each chapter provides unique yet complementary mechanistic insight that delineates a wide range of anti-amyloid activities associated with preventing amylin amyloid formation by mainly catechol-containing structural scaffolds. Structure activity studies show that the catechol moiety present within baicalein, oleuropein and rosmarinic acid are critical for their anti-amyloid functions, including exerting cell rescue effects against amylin induced cytotoxicity. We also demonstrate that in general, autoxidation enhances the anti-amyloid potency associated with many catechol containing amyloid inhibitors that may be mechanistically linked to a covalent mode of action. For example, we demonstrate that the O-quinone form of baicalein conjugates with amylin via a Schiff base mechanism. In contrast, we also show that catechol mediated formation of protein denaturant resistant aggregates, which requires autoxidation and that also stems from a predicted covalent mode of action, does not necessarily correlate with the enhanced anti-amyloid activities that occur upon catechol autoxidation. Regardless of the chemical mechanism(s) that drive catechol mediated anti-amyloid activity in vitro, the observed cell rescue effects exhibited by catechol containing molecules against amylin amyloid induced cytotoxicity is congruent with several recent in vivo studies that indicate polyphenols prevent toxic amyloid deposition as well as decades of population based studies that show regular consumption of diets rich in polyphenols are linked to a reduce incidence of age-related neurodegenerative amyloid disease. Indeed, advances in structure based drug discovery against amyloid formation may provide new avenues to optimize various catechol containing scaffolds that could be readily leveraged into improving diagnostic tools or perhaps accelerate the effort of discovering anti-amyloid therapeutics.