Mechanistic insights into light chain-associated cardiotoxicity: from amyloidosis patient-derived light chains to animal models

Background and aims Light chain amyloidosis (AL), is a plasma cell dyscrasia in which cardiac involvement determines the prognosis. Immunoglobulin light chains (LCs) have been suggested to provoke cardiotoxicity. We aimed to characterize the underlying mechanisms of LC-mediated cardiotoxicity in vitro and in vivo and identify possible protective therapies. Methods The amyloidogenic LCs from seven patients with AL and cardiac involvement, and the respective isotype LCs from two healthy volunteers were biotechnologically produced and characterized for folding and amyloidogenic tendency. LC cardiotoxicity was initially assessed on primary adult ventricular murine cardiomyocytes (pAVMCs). Male (n=36) C57BL6 mice received the LCs or vehicle via intramyocardial injection (IMC, 1mg/mouse). Male and female (n=40) NOD-scid IL2Rγnull (NSG) mice received AL_2718LV2 LC (200 μg) or vehicle (daily, intraperitoneally) for one or two months. Echocardiography, histology, assessment of circulating markers of toxicity, and molecular analysis were performed on both animal models. Based on the underlying mechanisms of cardiotoxicity, several agents were evaluated in vitro. Results Five AL-derived LCs significantly decreased pAVMCs viability and formed amyloids in vitro. In vivo, IMC administration led to histology features of cardiac damage. Lambda-type LCs significantly reduced ejection fraction compared to vehicle treated mice, while kappa-type did not alter systolic function. AL-LCs cardiotoxicity upon IMC administration was associated with enhanced endoplasmic reticulum stress (ERS) via IRE-1 and NF-kB signaling. LC-treated NSG mice had prolonged isovolumic contraction time, a marked increase of NT-proBNP and significantly elevated urea and creatinine at 2 months compared to control. LC treated mice demonstrated microvascular damage and perivascular fibrosis. Proteomic analysis on the myocardium of NSG mice revealed that Vascular Cell Adhesion Molecule-1 (VCAM-1) was increased along with NF-kB-p38-Intercellular Adhesion Molecule-1 (ICAM-1) pathway. None of the animals bared amyloid deposits. In vitro, treatment with the IRE-1a inhibitor STF-083010 targeting ERS and TUDCA targeting ERS and NFkB restored the LCs-induced cardiotoxicity. Conclusions AL-derived LCs induce cardiotoxicity in vitro and in vivo via ERS and NF-kB-p38-ICAM pathways. Our results provide insights into AL pathophysiology, enhance our understanding of the mechanisms of cardiac toxicity and suggest future therapeutic directions.