Homocysteine-induced toxicity increases TG2 expression in Neuro2a cells

High levels of homocysteine promote cell damage mainly through induction of oxidative stress, endoplasmic reticulum (ER) stress, and activation of pro-inflammatory factors. The effects of homocysteine were here examined in the continuously dividing neuroblastoma cell line Neuro2a. Cell treatment with homocysteine (100-500 microM) for 4 h increased ROS production while reducing cell viability in a dose-dependent manner. Cell exposure to 250 microM homocysteine was able to induce transglutaminase 2 up-regulation and increased in situ transglutaminase activity. These effects were prevented by the incubation with the transglutaminase activity inhibitor cystamine. Homocysteine also induced NF-kappaB activation that seemed associated with transglutaminase 2 up-regulation since the specific NF-kappaB inhibition by SN50 was able to reduce transglutaminase expression and activity levels. In the light of these observations, it may be postulated that TG2 up-regulation is involved in cell response to homocysteine-induced stress, in which NF-kappaB activation plays also a pivotal role.