Impairment of Bilirubin Clearance and Intestinal Interleukin-6 Expression in Bile Duct-Ligated Vitamin D Receptor Null Mice

Abstract

The vitamin D receptor (VDR) mediates the physiological and pharmacological actions of 1α,25-dihydroxyvitamin D3 in bone and calcium metabolism, cellular growth and differentiation, and immunity. VDR also responds to secondary bile acids and belongs to the NR1I subfamily of the nuclear receptor superfamily, which regulates expression of xenobiotic metabolism genes. When compared to knockout mouse investigations of the other NR1I nuclear receptors, pregnane X receptor and constitutive androstane receptor, an understanding of the role of VDR in xenobiotic metabolism remains limited. We examined the effect of VDR deletion in a mouse model of cholestasis. We performed bile duct ligation (BDL) on VDR-null mice and compared blood biochemistry, mRNA expression of genes involved in bile acid and bilirubin metabolism, cytokine production, and expression of inflammatory regulators with those of wild-type mice. VDR-null mice had elevated plasma conjugated bilirubin levels three days after BDL compared with wild-type mice. Urine bilirubin levels and renal mRNA and/or protein expression of multidrug resistance-associated proteins 2 and 4 were decreased in VDR-null mice, suggesting impaired excretion of conjugated bilirubin into urine. While VDR-null kidney showed mRNA expression of interleukin-6 (IL-6) after BDL and VDR-null macrophages had higher IL-6 protein levels after lipopolysaccharide stimulation, the induction of intestinal Il6 mRNA expression and plasma IL-6 protein levels after BDL was impaired in VDR-null mice. Immunoblotting analysis showed that expression of an immune regulator, IκBα, was elevated in the jejunum of VDR-null mice, a possible mechanism for the attenuated induction of Il6 expression in the intestine after BDL. Increased expression of IκBα may be a consequence of compensatory mechanisms for VDR deletion. These results reveal a role of VDR in bilirubin clearance during cholestasis. VDR is also suggested to contribute to tissue-selective immune regulation.

Prohibitin 1 suppresses liver cancer tumorigenesis in mice and human hepatocellular and cholangiocarcinoma cells

“…We chose IL-6 because its level is higher after bile duct ligation and in patients with HCC and CCA. (28)(29)(30) We found that IL-6 (10 ng/mL) treatment of H69 cells for only 4 hours significantly reduced MAT1A and PHB1 mRNA levels by 22% and 26%, respectively, and raised c-MYC, MAFG, and c-MAF by 40%-53%. These results suggest that bile acids are not likely to be responsible for causing the changes in these genes but, rather, proinflammatory cytokines such as IL-6.…”

“…Because this is unlikely to be relevant during bile duct ligation, we then explored the possibility that IL‐6 may be involved in triggering the observed changes in gene expression during bile duct ligation. We chose IL‐6 because its level is higher after bile duct ligation and in patients with HCC and CCA . We found that IL‐6 (10 ng/mL) treatment of H69 cells for only 4 hours significantly reduced MAT1A and PHB1 mRNA levels by 22% and 26%, respectively, and raised c‐MYC , MAFG , and c‐MAF by 40%‐53%.…”

Calcipotriol Inhibits NLRP3 Signal Through YAP1 Activation to Alleviate Cholestatic Liver Injury and Fibrosis

“…Moreover, VDR governs the TGF-β/smad signal, thus playing an important role in modulating fibrosis (Ding et al, 2013;Beilfuss et al, 2015;Duran et al, 2016). In cholestasis, VDR can regulate the metabolism and transport of BA, and VDR deficiency promotes liver injury in mice (Ogura et al, 2009;Ishizawa et al, 2012;Firrincieli et al, 2013). Multiple recent studies highlight antiinflammatory effect of VDR which is very likely to serves as a potentially effective therapeutic strategy for liver diseases and urgently needs in-depth researched.…”

Lithocholic Acid Is a Vitamin D Receptor Ligand That Acts Preferentially in the Ileum

“…The VDR-null ( Vdr(−/−) ) mice and wild-type mice ( Vdr( +/+) ) mice were obtained by breeding Vdr(+/−) mice on a pure C57BL/6J background [ 52 ]. Original Vdr(−/−) mice were kindly provided by Shigeaki Kato and Chugai Pharmaceutical Co. [ 25 ].…”

“…The tissues were crushed using a Bessman Tissue Pulverizer (Spectrum Laboratories, Racho Dominguez, CA, USA), and the total RNA extraction was performed using the acid guanidium thiocyanate/phenol/chloroform method [ 52 ]. The cDNAs were synthesized using the ImProm-II Reverse Transcription system (Promega, Madison WI, USA), and the real time polymerase chain reaction was performed on the ABI PIRSM 7000 Sequence Detection System (Life Technologies Corporation, Carlsbad, CA, USA) using Power SYBR Green PCR Master Mix (Life Technologies Corporation) and primers reported previously [ 16 , 22 ].…”