Transthyretin (TTR) amyloidoses comprise a wide spectrum of acquired and hereditary diseases triggered by extracellular deposition of toxic TTR aggregates in various organs. Despite recent advances regarding the elucidation of the molecular mechanisms underlying TTR misfolding and pathogenic self-assembly, there is still no effective therapy for treatment of these fatal disorders. Recently, the "molecular tweezers", CLR01, has been reported to inhibit self-assembly and toxicity of different amyloidogenic proteins in vitro, including TTR, by interfering with hydrophobic and electrostatic interactions known to play an important role in the aggregation process. In addition, CLR01 showed therapeutic effects in animal models of Alzheimer's disease and Parkinson's disease. Here, we assessed the ability of CLR01 to modulate TTR misfolding and aggregation in cell culture and in an animal model. In cell culture assays we found that CLR01 inhibited TTR oligomerization in the conditioned medium and alleviated TTR-induced neurotoxicity by redirecting TTR aggregation into the formation of innocuous assemblies. To determine whether CLR01 was effective in vivo, we tested the compound in mice expressing TTR V30M, a model of familial amyloidotic polyneuropathy, which recapitulates the main pathological features of the human disease. Immunohistochemical and Western blot analyses showed a significant decrease in TTR burden in the gastrointestinal tract and the peripheral nervous system in mice treated with CLR01, with a concomitant reduction in aggregate-induced endoplasmic reticulum stress response, protein oxidation, and apoptosis. Taken together, our preclinical data suggest that CLR01 is a promising lead compound for development of innovative, disease-modifying therapy for TTR amyloidosis.

Many polyphenols have been proposed as broad-spectrum inhibitors of amyloid formation. To investigate structure-activity relationships relevant for the interaction of flavonoids with transthyretin (TTR), the protein associated with familial amyloid polyneuropathy (FAP), we compared the effects of major tea catechins and their larger polymers theaflavins, side-by-side, on TTR amyloid formation process.

Familial amyloidotic polyneuropathy (FAP) is a neurodegenerative disease caused by the extracellular deposition of mutant transthyretin (TTR), with special involvement of the peripheral nervous system (PNS). Currently, hepatic transplantation is considered the most efficient therapy to halt the progression of clinical symptoms in FAP since more than 95% of TTR is produced by the liver. However, less invasive and more reliable therapeutic approaches have been proposed for FAP therapy, namely based on drugs acting as inhibitors of amyloid formation or as amyloid disruptors. We have recently reported that epigallocatechin-3-gallate (EGCG), the most abundant catechin in green tea, is able to inhibit TTR aggregation and fibril formation, "in vitro" and in a cellular system, and is also able to disrupt pre-formed amyloid fibrils "in vitro".

The transthyretin amyloidoses (ATTR) are devastating diseases characterized by progressive neuropathy and/or cardiomyopathy for which novel therapeutic strategies are needed. We have recently shown that curcumin (diferuloylmethane), the major bioactive polyphenol of turmeric, strongly suppresses TTR fibril formation in vitro, either by stabilization of TTR tetramer or by generating nonfibrillar small intermediates that are innocuous to cultured neuronal cells. In the present study, we aim to assess the effect of curcumin on TTR amyloidogenesis in vivo, using a well characterized mouse model for familial amyloidotic polyneuropathy (FAP). Mice were given 2% (w/w) dietary curcumin or control diet for a six week period. Curcumin supplementation resulted in micromolar steady-state levels in plasma as determined by LC/MS/MS. We show that curcumin binds selectively to the TTR thyroxine-binding sites of the tetramer over all the other plasma proteins. The effect on plasma TTR stability was determined by isoelectric focusing (IEF) and curcumin was found to significantly increase TTR tetramer resistance to dissociation. Most importantly, immunohistochemistry (IHC) analysis of mice tissues demonstrated that curcumin reduced TTR load in as much as 70% and lowered cytotoxicity associated with TTR aggregation by decreasing activation of death receptor Fas/CD95, endoplasmic reticulum (ER) chaperone BiP and 3-nitrotyrosine in tissues. Taken together, our results highlight the potential use of curcumin as a lead molecule for the prevention and treatment of TTR amyloidosis.