Learning to program the liver.

Half a century ago, people were learning to program computers. Similarly, we have been trying to learn how to program the liver to protect us from chemicals. We have given various chemicals that activate transcription factors such as the nuclear receptors: These ligand-activated nuclear receptors enter the nucleus of liver cells (hepatocytes) and bind to their specific motifs in DNA to increase the transcription of various genes that protect against chemical-induced injury. Several examples from our laboratory are given to demonstrate this detoxification process: (a) a steroid chemical that increases the expression of a hepatic transporter to enhance the elimination of other chemicals and thus decrease their toxicity, (b) a metal that decreases its own toxicity by increasing the production of a protein to which it binds, and (c) an herbal chemical that activates a transcription factor that serves as a sensor of oxidative stress and electrophiles to protect against cytotoxicity by increasing the expression of numerous antioxidant proteins. In addition, at the present time, we are investigating which bile acids that are synthesized in the liver and altered by bacteria in the intestine may be used to alter the programming of the liver, as well as how the liver reprograms itself after birth in the transition from a hematopoietic organ to one that decreases the toxicity of chemicals.