Investigating heart-specific toxicity of amyloidogenic immunoglobulin light chains: A lesson from C. elegans

Abstract

Abnormalities in protein folding are involved in many localized and systemic diseases, all of which are characterized by insoluble amyloid formation and deposition. In immunoglobulin light chain (LC) amyloidosis, the most frequent systemic form of amyloidosis, the amyloid involvement of the heart dictates the prognosis and the elucidation of the mechanism of heart targeting and toxicity is essential for designing and testing new effective treatments. To this end, the availability of an appropriate animal model is crucial. We recently described the use of C. elegans as an innovative experimental system to investigate in vivo the pathogenic effects of monoclonal LC. This idea stems from the knowledge that the worm's pharynx is an "ancestral heart" with the additional ability to recognize stressor compounds. The feeding of worms with LC purified from patients suffering from cardiomyopathy, selectively and permanently impaired the pharyngeal function. This irreversible damage resulted in time, in a significant reduction in the lifespan of worms. We also reported that the ability of LC to generate reactive oxygen species was associated with their toxic effects and was counteracted by anti-oxidant compounds. This new nematode-based assay represents a promising model for elucidating the heart-specific toxicity of LC and for a rapid screening of new therapeutic strategies.

Keywords: C. elegans; amyloidosis; cardiotoxicity; immunoglobulin light chains; pharynx.

Figure 1.

Schematic representation of the redox-mediated recognition of cardiotoxic LC by C. elegans. Amyloidogenic cardiotoxic LC continuously generate consistent amount of reactive oxygen species (ROS) which render the proteins recognizable as “chemical stressor” by the C. elegans pharynx. This results in a reduction of the pharyngeal pumping and in a tissue-specific stress response with an increase in reactive radicals in mitochondria. Antioxidant compounds counteracted this dysfunction.