[Pathogenesis and therapy for transthyretin related amyloidosis]

Abstract

Transthyretin (TTR) is a beta-sheet rich protein whose plasma half life is 1.9 days. It behaves as a tetramer and binds to retinol binding protein (RBP) and thyroxin in plasma. Since TTR is a tryptophan-rich-protein, the protein is used as a useful marker protein for nutrition supporting team (NST). However, TTR is also an anti-acute phase protein, and its concentration is influenced by various conditions, such as inflammation and infection. Mutated forms of TTR are the precursor protein of familial amyloidotic polyneuropathy (FAP). Since plasma TTR is predominantly synthesized by the liver, liver transplantation has been performed as an effective therapy for FAP. However, the surgery has several problems, so we must develop novel essential therapies for FAP. Single stranded oligonucleotides (SSOs) or short interference RNA (SiRNA) is a promising option for an essential therapy for FAP. In mutated TTR, instability of tetrameric form of TTR occurs, resulting in misfolding of TTR molecule, which lead to amyloid fibril formation. Since mutated TTR exposes criptic epitopes on the surface of TTR molecule, induction of an antibody for the epitopes was thought to be effective. We synthesized ATTR Y78P, a spontaneously misfolded TTR, and injected it to amyloid laden transgenic mice having human ATTR V30M to induce the antibody for amyloid fibrils. As we expected, amyloid deposition was significantly reduced by the injection of ATTR Y78P to the mice. These therapies may become novel strategies for essential FAP therapy instead of liver transplantation.