Matrine triggers cardiotoxicity via apoptosis induced by reduction of GSH synthesis through the ATF4/CTH pathway

Matrine (MT), an alkaloid extracted from Sophora flavescens , is widely used in traditional Chinese medicine. However, its clinical application is limited by its toxic effects. In this study, we explored the function of the activating transcription factor 4 /cystathionine γ-lyase (ATF4/CTH) pathway in MT-induced cardiac injury. Our results indicated that MT significantly decreased cysteine (Cys) and glutathione (GSH) levels, leading to mitochondrial dysfunction and apoptosis characterised by ROS accumulation, mPTP opening, ΔΨm disruption, and caspase-9/3 activation. However, caspase-3 inhibition and GSH supplementation alleviated these toxic effects. NAC similarly protected against MT-induced apoptosis by providing Cys as a substrate for GSH synthesis, whereas BSO abolished this protection by inhibiting GSH biosynthesis. Additionally, MT suppressed both ATF4 expression and its transcriptional activity, leading to reduced mRNA and protein levels of the downstream target gene CTH, and consequently diminished CTH-dependent Cys production. Overexpression of either ATF4 or CTH attenuated MT-induced apoptosis by restoring intracellular Cys and GSH levels. CTH knock-down completely abrogated the protective effects of ATF4 overexpression, whereas CTH overexpression retained its efficacy, even in the absence of ATF4. These results indicated that MT-induced suppression of the ATF4/CTH pathway causes GSH deficiency, leading to mitochondria-dependent apoptosis and cardiotoxicity.