A Caenorhabditis elegans–based assay recognizes immunoglobulin light chains causing heart amyloidosis

Abstract

Key Points• C elegans specifically recognizes cardiotoxic LCs as toxicants.• This is an innovative model for studying the heart-specific toxicity of amyloidogenic LCs and developing new therapeutic strategies.Poor prognosis and limited therapeutic options characterize immunoglobulin light-chain (AL) amyloidosis with major heart involvement. Reliable experimental models are needed to study light-chain (LC)/heart interactions and to explore strategies for prevention of cardiac damage. We have exploited the nematode Caenorhabditis elegans as a novel tool, because its pharynx is evolutionarily related to the vertebrate heart. Our data demonstrate that the pharyngeal pumping of C elegans is significantly and selectively reduced by LCs from AL patients suffering from cardiomyopathy, but not by amyloid LCs with different organ tropism or nonamyloidogenic LCs from multiple myeloma. This functional alteration is dependent on the LC concentration and results in persistent pharyngeal dysfunction and in a significant reduction of the worms' lifespan. These manifestations are paralleled by an increase of mitochondrial reactive oxygen species and can be prevented by treatment with antioxidant agents. In conclusion, these data indicate that this nematode-based assay is a promising surrogate model for investigating the heart-specific toxicity of amyloidogenic LCs and for a rapid screening of new therapeutic strategies. (Blood. 2014;123(23):3543-3552)

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

“…25 The results obtained indicated that, contrary to what observed with the Ab proteins, the pharyngeal dysfunction caused by cardiotoxic LC was not related to a peculiar protein folding, oligomerization propensity nor to different size; instead, it was due to their peculiar ability to continuously generate reactive oxygen species (ROS). 25 This renders these proteins recognizable as stressors from C. elegans, which reacts by ceasing the feeding. Once ingested, LC produce cellular oxidative damage and increase mitochondrial ROS, which contribute to sustaining the permanent pharyngeal dysfunction and shorting their lifespans 25 ( Fig.…”

“…Interestingly, we observed that only amyloidogenic LC that are cardiotoxic in AL patients caused a specific impairment of the pharyngeal pumping in C. elegans. 25 This effect is dose-dependent and is maximal at concentrations comparable to those commonly found in blood of patients with AL amyloidosis. 25,19,20 We also observed that the pharynx functionality is selectively impaired and, since the C. elegans external cuticle is quite impermeable, it cannot be dismissed that the restriction of the effect only to this organ is due to the high local concentration of the toxic LC.…”

“…25 This renders these proteins recognizable as stressors from C. elegans, which reacts by ceasing the feeding. Once ingested, LC produce cellular oxidative damage and increase mitochondrial ROS, which contribute to sustaining the permanent pharyngeal dysfunction and shorting their lifespans 25 ( Fig. 1).…”

“…[21][22][23][24] We hypothesized that LC damaging vertebrate heart can similarly affect C. elegans' pharyngeal muscles and that, by scoring the pumping rate, we can easily determine the potential LC cardiotoxicity. 25 The reaction of worms to the administration of soluble amyloidogenic LC with different organ tropisms obtained from AL patients, and non-amyloidogenic LC from multiple myeloma subjects 26,27 was investigated. Interestingly, we observed that only amyloidogenic LC that are cardiotoxic in AL patients caused a specific impairment of the pharyngeal pumping in C. elegans.…”

Melphalan and dexamethasone with or without bortezomib in newly diagnosed AL amyloidosis: a matched case–control study on 174 patients

“…3 Clinical and experimental evidence indicate that cardiac damage in AL amyloidosis is mainly determined by a direct toxicity exerted by the circulating amyloidogenic free light chain (FLC). [4][5][6][7][8] Thus, therapy of AL amyloidosis is aimed at obtaining a rapid and profound FLC reduction by targeting the amyloidogenic plasma cell clone with chemotherapy, while attentively supporting involved organ function. Treatment approaches are derived from multiple myeloma and are adapted to the fragile amyloid patients, and novel agents are finding their place in the therapeutic armamentarium for AL amyloidosis.…”