Environmentally relevant concentrations of 6-PPDQ disrupt vitamin D3 adsorption and receptor function in <i>Caenorhabditis elegans</i>

As a derivative of the antioxidant of <i>N</i>-(1,3-dimethylbutyl)-<i>N'</i>-phenyl-<i>p</i>-phenylenediamine (6-PPD), 6-PPD quinone (6-PPDQ) is frequently found in environments and the bodies of organisms. Vitamin D3 is an important vitamin that needs to be absorbed from the intestine. In <i>Caenorhabditis elegans</i>, vitamin D3 content was reduced by 0.1-10 μg L^-1 of 6-PPDQ. Meanwhile, 6-PPDQ (0.1-10 μg L^-1) decreased the expressions of <i>lrp-2</i>, <i>scl-12</i>, <i>scl-13</i>, and <i>ifo-1</i>, and their RNAi decreased the vitamin D3 content in 6-PPDQ-exposed animals. 6-PPDQ (0.1-10 μg L^-1) further decreased the <i>nhr-8</i> expression and increased the <i>daf-12</i> expression, and the expression of these 2 vitamin D3 receptor genes could be changed by RNAi of <i>lrp-2</i>, <i>scl-12</i>, <i>scl-13</i>, and <i>ifo-1</i> after 6-PPDQ exposure. The 6-PPDQ toxicity was increased by the RNAi of <i>lrp-2</i>, <i>scl-12</i>, <i>scl-13</i>, <i>ifo-1</i>, and <i>nhr-8</i> and inhibited by the RNAi of <i>daf-12</i>. Moreover, after 6-PPDQ exposure, SOD-3 and HSP-6 expressions were decreased by <i>nhr-8</i> RNAi and increased by <i>daf-12</i> RNAi. Therefore, 6-PPDQ potentially caused damage to the adsorption of vitamin D3 and the function of its receptors, and these effects were related to the toxicity induction of 6-PPDQ.