Effects of gap junction intercellular communication on the docetaxel-induced cytotoxicity in rat hepatocytes

Abstract

The effect of gap junction intercellular communication (GJIC) on docetaxel-induced hepatotoxicity and its underlying mechanisms are largely unknown. The present study involved investigating the effect of downregulating GJs derived from connexin (Cx) 32 in BRL-3A cells by three different mechanisms: Using a low-density culture; suppression of Cx32 using small interfering RNA; and use of the chemical inhibitor 2-aminoethoxydiphenyl borate (2-APB), all of which led to attenuated docetaxel hepatotoxicity. In order to investigate the relevant mechanisms involved, apoptosis and caspase activities of BRL-3A cells were determined. The increase of apoptosis and the activation of caspase-3 and caspase-9, but not caspase-8, were detected following cell exposure with docetaxel, demonstrating that the mitochondrial-mediated apoptosis pathway is largely responsible for docetaxel hepatotoxicity. However, reduced apoptosis and caspase-3, and -9 activities were observed following docetaxel application when BRL-3A GJIC was defcient from the knockdown of Cx32 expression or pretreatment with 2-APB. These observations illustrate that GJs are important in docetaxel-induced hepatotoxicity. Furthermore, inhibition of GJIC could prevent amplifcation of toxicity to docetaxel. Due to GJIC blockage, this hepatoprotection was associated, in part, with decreasing apoptosis of BRL-3A cells through the mitochondrial pathway. The present study provides evidence for potential therapeutic targets for the treatment of docetaxel-induced liver injury.