Knockdown of the NHR-8 nuclear receptor enhanced sensitivity to the lipid-reducing activity of alkaloids in <i>Caenorhabditis elegans</i>

<div><p><i>Caenorhabditis elegans</i> is a versatile, whole-organism model for bioactivity screening. However, this worm has extensive defensive mechanisms against xenobiotics which limit its use for screening of pharmacologically active compounds. In this study, we report that knockdown of <i>nhr</i>-8, a gene involved in the xenobiotic response, increased the worm’s sensitivity to the lipid-reducing effects of some isoquinoline alkaloids, especially berberine. On the other hand, crude extract of rhizome and cultured cells showed enhanced biological activity compared to the pure alkaloids in wild type worm, but this enhanced activity was not detected in <i>nhr</i>-8 RNAi worm, suggesting that some components in cell extracts might interfere with the defense response in this worm. The possibility of using <i>C. elegans</i> as a model for screening bioactive chemicals is discussed.</p>