Toxic Prediction of Pyrrolizidine Alkaloids and Structure‐Dependent Induction of Apoptosis in HepaRG Cells

Abstract

Pyrrolizidine alkaloids (PAs) are common phytotoxins and could cause liver genotoxicity/carcinogenicity following metabolic activation. However, the toxicity of different structures remains unclear due to the wide variety of PAs. In this study, the absorption, distribution, metabolism, excretion, and toxicity (ADMET) of 40 PAs were analyzed, and their toxicity was predicted by Komputer Assisted Technology (TOPKAT) using Discovery Studio software. The in silico results showed that all PAs except retronecine had good intestinal absorption, and all PAs were predicted to have different toxicity ranges. To verify the predictive results, 4 PAs were selected to investigate cell injury and possible mechanisms of the differentiation in HepaRG cells, including retronecine type of twelve-membered cyclic diester (retrorsine), eleven-membered cyclic diester (monocrotaline), noncyclic diester (retronecine), and platynecine type (platyphylline). After 24 h exposure, retronecine-type PAs exhibited concentration-dependent cytotoxicity. The high-content screening assay showed that cell oxidative stress, mitochondrial damage, endoplasmic reticulum stress, and the concentration of calcium ions increased, and neutral lipid metabolism was changed notably in HepaRG cells. Induced apoptosis by PAs was indicated by cell cycle arrest in the G2/M phase, disrupting the mitochondrial membrane potential. Overall, our study revealed structure-dependent cytotoxicity and apoptosis after PA exposure, suggesting that the prediction results of in silico have certain reference values for compound toxicity. A 1,2-membered cyclic diester seems to be a more potent apoptosis inducer than other PAs.

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“…In addition, heliothrin inhibits thymine uptake by all cell types, the higher the concentration of the alkaloid, the higher the inhibition; without the possibility of thymine uptake, cells are unable to synchronize the early G1/S phase and cell replication. 4,[38][39][40][41] On the other hand, the compound heliotridine together with helindicin and lasiocarpine have been shown to cause liver, kidney, and lung toxicities, inducing both tumors and carcinomas in the parts in contact with it, being one of the most dangerous compounds of the plant. 21,42,43 The N-oxide of indicin has anticancer activity preventing proliferation in solid tumors and helping in the control of acute leukemias, although it has also been investigated for inducing liver toxicity in some patients treated with this compound.…”

Structure-Dependent Toxicokinetics of Selected Pyrrolizidine Alkaloids In Vitro

“…Moreover, PAs were demonstrated to induce genotoxic effects [ 31 , 32 , 33 ]. In vitro assays indicate a structure-dependency in the effect strength of PA-induced cytotoxicity and genotoxicity [ 22 , 26 , 27 , 34 ]. For the induction of toxic effects in a target tissue, uptake of PAs over the intestinal barrier into the body is a prerequisite.…”

Pyrrolizidine Alkaloids in Tea (Camellia sinensis L.) from Weeds through Weed–Soil–Tea Transfer and Risk Assessment of Tea Intake

“…9,15−17 The major harm to humans refers to veno-occlusive dysfunction, hepatocellular damage, and liver cirrhosis. 10,18,19 Human exposure to PAs was reported in consequence of the consumption of the PAscontaminated food and teas. 20−22 It was initially thought that a main source of PAs in herbal teas was coharvested PAscontaining weeds.…”

“…Toxic PAs and their corresponding N -oxides (PANOs) are produced as secondary metabolites in a large number of plants widely distributed in the plant kingdom. , Up to now, more than 660 PAs and PANOs have been known in more than 6000 plant species worldwide. , Most of these PAs-containing plants belong to the Fabaceae ( Crotalaria ), Asteraceae ( Eupatorium and Senecio ), and Boraginaceae ( Echium, Heliotropium , and Symphytum ) families. , PAs show high acute and chronic toxicity as well as cytotoxic, genotoxic, and mutagenic activity. ,− The major harm to humans refers to veno-occlusive dysfunction, hepatocellular damage, and liver cirrhosis. ,, Human exposure to PAs was reported in consequence of the consumption of the PAs-contaminated food and teas. − It was initially thought that a main source of PAs in herbal teas was coharvested PAs-containing weeds. However, when green tea or black tea (one bud with two leaves) is harvested by hand picking, the contamination caused by coharvest of PAs-containing weeds can be minimized or avoided .…”