Inhibition of Citrinin-Induced Apoptotic Biochemical Signaling in Human Hepatoma G2 Cells by Resveratrol

Abstract

The mycotoxin citrinin (CTN), a natural contaminant in foodstuffs and animal feeds, exerts cytotoxic and genotoxic effects on various mammalian cells. CTN causes cell injury, including apoptosis, but its precise regulatory mechanisms of action are currently unclear. Resveratrol, a member of the phytoalexin family found in grapes and other dietary plants, possesses antioxidant and anti-tumor properties. In the present study, we examined the effects of resveratrol on apoptotic biochemical events in Hep G2 cells induced by CTN. Resveratrol inhibited CTN-induced ROS generation, activation of JNK, loss of mitochondrial membrane potential (MMP), as well as activation of caspase-9, caspase-3 and PAK2. Moreover, resveratrol and the ROS scavengers, NAC and α-tocopherol, abolished CTN-stimulated intracellular oxidative stress and apoptosis. Active JNK was required for CTN-induced mitochondria-dependent apoptotic biochemical changes, including loss of MMP, and activation of caspases and PAK2. Activation of PAK2 was essential for apoptosis triggered by CTN. These results collectively demonstrate that CTN stimulates ROS generation and JNK activation for mitochondria-dependent apoptotic signaling in Hep G2 cells, and these apoptotic biochemical events are blocked by pretreatment with resveratrol, which exerts antioxidant effects.

Presence of Citrinin in Grains and Its Possible Health Effects

“…CTN occurs in different plant products, especially in grains (Flajs & Peraica 2009, Főllmann et al 2014, and also in beans, fruit, vegetables, herbs and spices. Often, the co-occurrence with other mycotoxins is observed, especially ochratoxin A (OTA) Besides its nephrotoxicity, which has been proved by various studies, there is also proof that CTN is involved in induction of apoptosis through oxidative stress, although the precise regulatory mechanism is yet to be determined (Chen & Chan 2009). CTN induces micronucleus formation of centromeres while OTA damages chromosomes in HepG2 cells.…”

Possible Carcinogenic Mechanisms Underlying Renal Carcinogens in Food

“…Accordingly, it seems likely that the activity of the HGF/c-Met pathway following renal epithelial cell injury is responsible for ERK activation in the high CTN dose group. Nevertheless, 8-OHdG levels as a measure of oxidized DNA damage and TBARS levels as a marker of lipid peroxidation were not changed by CTN treatment 115) , despite the capacity of CTN to generate oxidative stress in cultured cells and mouse skin 122,130) . Alternatively, activation of PKC signaling may contribute to CTN-induced cell cycle progression due to CTN-mediated increases in intracellular calcium concentrations 131) .…”

“…Thus, the proliferative effects of CTN at carcinogenic doses may involve compensatory mechanisms, but also the direct mitogenic activity of CTN may exert additional effects on cell cycle progression, which thereby contributes to renal carcinogenesis. ERK, which is constitutively activated via phosphorylation in many human cancer cells, was reported to be activated by CTN treatment in HEK293 and HeLa cells 122,123) . Also, CTN treatment led to ERK phosphorylation in vivo, especially in the COR as a carcinogenic target site 115) .…”

Low doses of the mycotoxin citrinin protect cortical neurons against glutamate-induced excitotoxicity

“…Therefore, the neuroprotective effect of citrinin against glutamate induced excitotoxicity can not be explained by the prevention of calcium overload. There have been repeated reports that high-dose citrinin application induces the production of ROS and subsequent cell death (Chen and Chan, 2009;Kumar et al, 2011;Máté et al, 2014). Conversely, citrinin and its predicted precursor and metabolites have been reported as antioxidants (Li et al, 2006;Zhang et al, 2007).…”