ABSTRACT
Adenovirus transfection technique was used in the current study to show if thioredoxin-interacting protein (TXNIP) overexpression can induce cell apoptosis and injury in H9C2 cardiomyocytes cultured in normal glucose condition. And the mechanisms were then investigated. Briefly, H9C2 cardiomyocytes in logarithmic growth phase were randomly divided into three groups: normal cultured group, empty adenovirus vector group (Ad-eGFP) and TXNIP overexpression group (Ad-TXNIP-eGFP). All cells were cultured in DMEM containing normal concentration of glucose (5 mmol/L) and lipid. 72 h after adenovirus transfection, cells and culture mediums were collected for further assay. The results showed that Ad-eGFP and Ad-TXNIP-eGFP adenovirus transfected H9C2 cells successfully, and the transfection efficiency reached the peak at 72 h. Compared with Ad-eGFP group, Ad-TXNIP-eGFP transfection significantly increased TXNIP mRNA (P < 0.05) and protein expression level (P < 0.01). TXNIP overexpression induced remarkable cell apoptosis and injury as evidenced by increased caspase-3 activity (P < 0.05), apoptotic rate (P < 0.01) and LDH activity (P < 0.01). To further analysis the mechanisms of TXNIP-induced cell apoptosis, we also determined Trx activity, Trx related free radical injury and p38 kinase activation, which are involved in free radical induced apoptosis. The results showed that, compared with those in Ad-eGFP group, Trx activity was significantly decreased (P < 0.01), while malondialdehyde (MDA), 3-nitrotyrosine contents and p38 kinase activity were significantly increased (P < 0.01) in TXNIP overexpression group. These results suggest that TXNIP overexpression alone can induce severe apoptosis and injury in H9C2 cardiomyocytes even they are cultured in normal glucose and lipid concentration conditions. The mechanism involved is that overexpressed TXNIP can bind and inhibit Trx, impairs its antioxidative and antiapoptotic function, and then increases free radical induced injury and p38 kinase dependent apoptosis.