Thimerosal Induces Apoptosis in a Neuroblastoma Model via the cJun N-Terminal Kinase Pathway

Abstract

The cJun N-terminal kinase (JNK)-signaling pathway is activated in response to a variety of stimuli, including environmental insults, and has been implicated in neuronal apoptosis. In this study, we investigated the role that the JNK pathway plays in neurotoxicity caused by thimerosal, an ethylmercury-containing preservative. SK-N-SH cells treated with thimerosal (0-10 microM) showed an increase in the phosphorylated (active) form of JNK and cJun with 5 and 10 microM thimerosal treatment at 2 and 4 h. To examine activator protein-1 (AP-1) transcription, cells were transfected with a pGL2 vector containing four AP-1 consensus sequences and then treated with thimerosal (0-2.5 microM) for 24 h. Luciferase studies showed an increase in AP-1 transcriptional activity upon thimerosal administration. To determine the components of the AP-1 complex, cells were transfected with a dominant negative to either cFos (A-Fos) or cJun (TAM67). Reporter analysis showed that TAM67, but not A-Fos, decreased AP-1 transcriptional activity, indicating a role for cJun in this pathway. To assess which components are essential to apoptosis, cells were treated with a cell-permeable JNK inhibitor II (SP600125) or transfected with TAM67, and the downstream effectors of apoptosis were analyzed. Cells pretreated with SP600125 showed decreases in activation of caspases 9 and 3, decreases in degradation of poly(ADP-ribose) polymerase (PARP), and decreased levels of proapoptotic Bim, in comparison to cells treated with thimerosal alone. However, cells transfected with TAM67 showed no changes in those same components. Taken together, these results indicate that thimerosal-induced neurotoxicity occurs through the JNK-signaling pathway, independent of cJun activation, leading ultimately to apoptotic cell death.

Oxidative stress regulates mitogen-activated protein kinases and c-Jun activation involved in heat stress and lipopolysaccharide-induced intestinal epithelial cell apoptosis

“…Previous studies have demonstrated that ROS mediates MAPK and c-Jun activation in various cellular stress conditions and cell types (4,26,28). To investigate the molecular mechanism underlying MAPK and c-Jun activation, cells were pretreated with an antioxidant.…”

Effect of thimerosal on Ca2+ movement and viability in human oral cancer cells

“…Subcutaneous injection of sufficient high quantities of thimerosal may cause inflammatory responses (Uchida et al, 1994). In recent years, there were several studies showing that thimerosal could induce apoptosis in a neuroblastoma model via the cJun N-terminal kinase pathway (Herdman et al, 2006). In T cells and neuronal cells, thimerosal causes apoptosis through mitochondrial pathways (Makani et al, 2002;Yel et al, 2005), and in human leukemia cells it also induced G2/M phase arrest (Woo et al, 2006).…”

Evaluation of Cytotoxicity Attributed to Thimerosal on Murine and Human Kidney Cells

“…Thimerosal alters the activity of sodium channels (Evans & Bielefeldt, 2000) and Ca 2+ -activated K + channels (Lang et al, 2000). It was reported that thimerosal induced DNA and membrane damage, caspase-3-dependent apoptosis (Baskin et al, 2003), activation of caspase-9 and caspase-3 (Makani et al, 2002), and activation of the cJun N-terminal kinase pathway (Herdman et al, 2006). Data showed that thimerosal and not thiosalicylic acid induced apoptosis in T cells (Makani et al, 2002).…”