NRF2-Independent Regulation of Intestinal Constitutive Androstane Receptor by the Pro-Oxidants Cadmium and Isothiocyanate inhUGT1Mice

Abstract

Environmental toxicants such as heavy metals from contaminated water or soil and isothiocyanates (ITC) from dietary sources act as pro-oxidants by directly generating reactive oxygen species (ROS) or through depleting cellular antioxidants such as glutathione. Toxicants can alter drug metabolism, and it was reported that CYP2B10 and UGT1A1 are induced by phenethyl isothiocyanate (PEITC) through the constitutive androstane receptor (CAR). The possibility that nuclear factor erythroid 2-related factor 2 (NRF2), the master regulator of the antioxidant response, could coactivate CAR was investigated in neonatal hUGT1/Nrf2 2/2 mice. Neonatal mice were treated with PEITC or cadmium (Cd 21 ) by oral gavage for 2 days. Both PEITC and Cd 21 induced UGT1A1 RNA and protein in intestinal tissues in both hUGT1/Nrf2 1/2 and hUGT1/Nrf2 2/2 neonates, indicating NRF2independent regulation of UGT1A1. Increases in CYP2B10 RNA in intestinal tissues were observed following PEITC or Cd 21 exposure. Activation of intestinal CAR by Cd 21 exposure was directly assessed by nuclear fractionation and Western blot analyses at 0.5, 1, 2, and 4 hours after treatment in hUGT1 neonates and after 48 hours in hUGT1/Nrf2 1/2 and hUGT1/Nrf2 2/2 neonates. CAR localized to the nucleus independently of NRF2 48 hours after exposure. Substantial CAR localization to the nucleus occurred at the 2-and 4-hour time points, coinciding with a decrease in phosphorylation of cytoplasmic extracellular signal-regulated kinases 1 and 2 and a nuclear increase in P38/p-P38 content. This suggests that a novel oxidative stress-MAPK-CAR axis exists with phenotypic consequences. SIGNIFICANCE STATEMENTPro-oxidant toxicants can alter drug metabolism through activation of CAR, independent of the NRF2-KEAP1 signaling pathway. Changes in proteins associated with drug metabolism and linked to increases in intestinal maturation are mediated through an oxidative stress-MAPK-CAR axis.s This article has supplemental material available at dmd.aspetjournals.org.

Regulation of Intestinal UDP-Glucuronosyltransferase 1A1 by the Farnesoid X Receptor Agonist Obeticholic Acid Is Controlled by Constitutive Androstane Receptor through Intestinal Maturation

“…The induction of intestinal UGT1A1 by OCA catalyzes the metabolism of serum bilirubin, similar for what we have shown when intestinal UGT1A1 is induced following oral administration of other agents such as cadmium (Liu et al, 2016;Paszek and Tukey, 2020), arsenic (Liu et al, 2016), isothiocyanates (Yoda et al, 2017;Paszek and Tukey, 2020), and formula (Fujiwara et al, 2012). Induction of intestinal UGT1A1 is sufficient, in the absence of any regulation of liver UGT1A1, to metabolize and clear serum bilirubin.…”

“…Our laboratory previously reported that UGT1A1 can be transcriptionally induced by several nuclear receptors like PXR (Chen et al, 2012), CAR (Yoda et al, 2017;Paszek and Tukey, 2020), peroxisome proliferator-activated receptor alpha (PPARα) (Senekeo-Effenberger et al, 2007), liver X receptor alpha (LXRα) (Hansmann et al, 2020), the environmental sensors aryl hydrocarbon receptor (AhR) (Yueh et al, 2003), nuclear factor erythroid-2 related factor 2 (Nrf2) (Yueh and Tukey, 2007;Yoda et al, 2017) and following activation of the IKK/NFκB pathway (Liu et al, 2016). A recent clinical report suggested that obeticholic acid (OCA) treatment, an FXR activator, lowers serum bilirubin levels (Parés et al, 2020).…”

“…One of the CNS patterns that develops in these mice is a dramatic reduction in nerve myelination, an event that we had speculated contributes to the seizure pattern (Barateiro et al, 2016). The human UGT1A1 gene is regulated by events that leads to activation of the pregnane-X-receptor (PXR) (Chen et al, 2012), constitutive androstane receptor (CAR) (Yoda et al, 2017;Paszek and Tukey, 2020), and the peroxisome proliferator receptor α (PPARα) (Senekeo-Effenberger et al, This article has not been copyedited and formatted. The final version may differ from this version.…”

Cadmium exposure modulates the gut-liver axis in an Alzheimer’s disease mouse model

“…Another study showed that an acute testicular toxic dose of Cd (2.0 mg/kg i.p) reduced hepatic microsomal aryl hydrocarbon hydroxylase (now known as Cyp1a) and aminopyrine N-demethylase (now known as Cyp3a) activities more in male rats than in female rats in a testosterone-dependent manner 21 . In the intestine of mice, acute Cd exposure activated the xenobiotic-sensing nuclear receptor constitutive androstane receptor (CAR) and upregulated its target gene Cyp2b10 22 . However, chronic Cd exposure in drinking water has not been shown to produce a significant effect on hepatic drug metabolism (up to 200 mg/L and up to 12 weeks) 18 , 19 .…”

Fifty Years of Aryl Hydrocarbon Receptor Research as Reflected in the Pages ofDrug Metabolism and Disposition

“…A CYP1A2-knockout rat model generated via a CRISPR-Cas9 approach shows no change in hepatic AHR mRNA levels but a strong compensatory increase in CYP1A1 expression (Sun et al, 2021). The induction of intestinal CYP1A1 by cadmium in UGT1humanized mice is lost in this mouse model lacking Nrf2 (Paszek and Tukey, 2020). Hepatic AHR mRNA levels and expression of AHR target genes are induced in a peroxisome proliferator-activated receptor-α (PPARα)-dependent fashion by the Olea europaea constituent oleuropein (Malliou et al, 2021).…”