The fumonisins are mycotoxins produced by fungi that contaminate primarily corn and are toxic through interruption of intracellular sphingolipid synthesis. Several reports have indicated that fumonisin B1 concentrations decreased when heated in aqueous solutions of reducing sugars. The incubation of fumonisin B1 with d-glucose resulted in the formation of N-(carboxymethyl)fumonisin B1, which was characterized by NMR and electrospray mass spectroscopy. We determined the methylene carbon of the carboxymethyl group is derived from C1 on glucose, while the carbonyl carbon is derived from the C2 of glucose, using 13C glucose. Apparently N-(carboxymethyl)fumonisin B1 arises from Schiff's base formation, Amadori rearrangement to a β-ketoamine, and oxidation with molecular oxygen. N-(Carboxymethyl)fumonisin B1 formation is favored by alkaline conditions (pH >7), requires molecular oxygen, and is catalyzed by several reducing sugars. N-(carboxymethyl)fumonisin B1 was detected in raw corn samples that contained fumonisin B1 (0.5−1.4 ppm) at an average of 4% of the fumonisin B1 levels. Keywords: Fumonisin B1; fumonisins; N-(carboxymethyl)fumonisin B1; detoxification; Amadori rearrangement; Maillard reaction; reducing sugars; mycotoxin

Sertraline, a selective serotonin reuptake inhibitor, has been used for the treatment of depression. Although it is generally considered safe, cases of sertraline-associated liver injury have been documented; however, the possible mechanism of sertraline-associated hepatotoxicity is entirely unknown. Here, we report that mitochondrial impairment may play an important role in liver injury induced by sertraline. In mitochondria isolated from rat liver, sertraline uncoupled mitochondrial oxidative phosphorylation and inhibited the activities of oxidative phosphorylation complexes I and V. Additionally, sertraline induced Ca(2+)-mediated mitochondrial permeability transition (MPT), and the induction was prevented by bongkrekic acid (BA), a specific MPT inhibitor targeting adenine nucleotide translocator (ANT), implying that the MPT induction is mediated by ANT. In freshly isolated rat primary hepatocytes, sertraline rapidly depleted cellular adenosine triphosphate (ATP) and subsequently induced lactate dehydrogenase leakage; both were attenuated by BA. Our results, including ATP depletion, induction of MPT, inhibition of mitochondrial respiration complexes, and uncoupling oxidative phosphorylation, indicate that sertraline-associated liver toxicity is possibly via mitochondrial dysfunction.

Sertraline is generally used for the treatment of depression and is also approved for the treatment of panic, obsessive-compulsive, and posttraumatic stress disorders. Previously, using rat primary hepatocytes and isolated mitochondria, we demonstrated that sertraline caused hepatic cytotoxicity and mitochondrial impairment. In the current study, we investigated and characterized molecular mechanisms of sertraline toxicity in human hepatoma HepG2 cells. Sertraline decreased cell viability and induced apoptosis in a dose- and time-dependent manner. Sertraline activated the intrinsic checkpoint protein caspase-9 and caused the release of cytochrome c from mitochondria to cytosol; this process was Bcl-2 family dependent because antiapoptotic Bcl-2 family proteins were decreased. Pretreatment of the HepG2 cells with caspase-3, caspase-8, and caspase-9 inhibitors partially but significantly reduced the release of lactate dehydrogenase, indicating that sertraline-induced apoptosis is mediated by both intrinsic and extrinsic apoptotic pathways. Moreover, sertraline markedly increased the expression of tumor necrosis factor (TNF) and the phosphorylation of JNK, extracellular signal-regulated kinase (ERK1/2), and p38. In sertraline-treated cells, the induction of apoptosis and cell death was shown to be the result of activation of JNK, but not ERK1/2 or p38 in the mitogen-activated protein kinase (MAPK) pathway. Furthermore, silencing MAP4K4, the upstream kinase of JNK, attenuated both apoptosis and cell death caused by sertraline. Taken together, our findings suggest that sertraline induced apoptosis in HepG2 cells at least partially via activation of the TNF-MAP4K4-JNK cascade signaling pathway.