SPA70 is a potent antagonist of human pregnane X receptor

Hemorrhagic shock (HS) is a life‐threatening condition associated with tissue hypoperfusion and often leads to injury of multiple organs including the liver. Pregnane X receptor (PXR) is a species‐specific xenobiotic receptor that regulates the expression of drug‐metabolizing enzymes (DMEs) such as the cytochrome P450 (CYP) 3A. Many clinical drugs, including those often prescribed to trauma patients, are known to activate PXR and induce CYP3A. The goal of this study is to determine whether PXR plays a role in the regulation of DMEs in the setting of HS and whether activation of PXR is beneficial or detrimental to HS‐induced hepatic injury. PXR transgenic, knockout, and humanized mice were subject to HS, and the liver injury was assessed histologically and biochemically. The expression and/or activity of PXR and CYP3A were manipulated genetically or pharmacologically in order to determine their effects on HS‐induced liver injury. Our results showed that genetic or pharmacological activation of PXR sensitized wild‐type and hPXR/CYP3A4 humanized mice to HS‐induced hepatic injury, whereas knockout of PXR protected mice from HS‐induced liver injury. Mechanistically, the sensitizing effect of PXR activation was accounted for by PXR‐responsive induction of CYP3A and increased oxidative stress in the liver. The sensitizing effect of PXR was attenuated by ablation or pharmacological inhibition of CYP3A, treatment with the antioxidant N‐acetylcysteine amide, or treatment with a PXR antagonist. Conclusion: We have uncovered a function of PXR in HS‐induced hepatic injury. Our results suggest that the unavoidable use of PXR‐activating drugs in trauma patients has the potential to exacerbate HS‐induced hepatic injury, which can be mitigated by the coadministration of antioxidative agents, CYP3A inhibitors, or PXR antagonists.

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“…A). Treatment with SPA70 efficiently blocked RIF‐responsive induction of CYP3A4 as reported (Fig. B).…”

Section: Resultssupporting

confidence: 81%

Activation of Pregnane X Receptor Sensitizes Mice to Hemorrhagic Shock–Induced Liver Injury

Xie

Deng

et al. 2019

Hepatology

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“…Ketoconazole Ketoconazole, L-sulforaphane, coumestrol, SPA70 (Cherian et al, 2018;Forman et al, 1998;Huang et al, 2007;Lemmen, Tozakidis, Bele, & Galla, 2013;Lin et al, 2017;Wang et al, 2008;Yeung, Sueyoshi, Negishi, & Chang, 2008) Biological (Aleksunes & Klaassen, 2012;Chen, Ferguson, Negishi, & Goldstein, 2003;Ferguson, Chen, LeCluyse, Negishi, & Goldstein, 2005;Ferguson, LeCluyse, Negishi, & Goldstein, 2002;Goodwin, Hodgson, D'Costa, Robertson, & Liddle, 2002;Maglich et al, 2004;Xu, Wang, & Staudinger, 2009;Yoshinari, Yoda, Toriyabe, & Yamazoe, 2010;Zhang, Huang, Chua, Wei, & Moore, 2002) UGTs Ugt1a1, Ugt1a9, Ugt2b34, Ugt2b35, Ugt2b36 UGT1A1 Ugt1a1, Ugt1a5, Ugt1a9 UGT1A1, UGT1A6, UGT1A3, UGT1A4 (Aleksunes & Klaassen, 2012;Maglich et al, 2004;…”

Section: Cinpa-1 Meclizinementioning

confidence: 99%

The constitutive androstane receptor and pregnane X receptor in the brain

Torres-Vergara

Espinoza

et al. 2020

British J Pharmacology

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Since their discovery, the orphan nuclear receptors constitutive androstane receptor (CAR;NR1I3) and pregnane X receptor (PXR;NR1I2) have been regarded as master regulators of drug disposition and detoxification mechanisms. They regulate the metabolism and transport of endogenous mediators and xenobiotics in organs including the liver, intestine and brain. However, with proposals of new physiological functions for NR1I3 and NR1I2, there is increasing interest in the role of these receptors in influencing brain function. This review will summarise key findings regarding the expression and function of NR1I3 and NR1I2 in the brain, hereby highlighting the need for further research in this field.

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“…6), where BEL maintains its typical nature of interaction. Additionally, recent studies (Lin et al, 2017) have shown that the ligand interaction with residues of helix a12, a shared region between the LBP and the AF2 region (Supplemental Fig. 5; residues 420-429), is found to be critical for determining the agonist/antagonist activity of a compound.…”

Section: Belinostat Antagonizes Hpxr Target Gene Expressionmentioning

confidence: 98%

“…For example, sulforaphane antagonizes hPXR in vitro, but the concentrations needed to sustain this effect were not achieved in vivo, resulting in lack of an hPXR antagonistic effect in in vivo (Poulton et al, 2013). Recently, a novel hPXR antagonist has been discovered (Lin et al, 2017). However, the pharmacokinetics and safety profile of this compound in humans is unknown.…”

Section: Belinostat Antagonizes Hpxr Target Gene Expressionmentioning

confidence: 99%

Belinostat, at Its Clinically Relevant Concentrations, Inhibits Rifampicin-Induced CYP3A4 and MDR1 Gene Expression

et al. 2019

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Activation of pregnane X receptor (PXR) by clinical compounds during multidrug chemotherapy results in upregulation of the expression of PXR target genes, including cytochrome p450 3A4 (CYP3A4) and multidrug resistance protein 1 (MDR1), leading to chemoresistance. It is possible to overcome the PXR‐mediated chemoresistance by downregulating the upregulated PXR target genes by inhibiting the activated PXR. However, a selective and less‐toxic PXR antagonist has yet to be developed. In this regard, a clinical anticancer drug, with selective PXR antagonistic activity at its less‐toxic concentrations, would be beneficial. We sought to determine whether belinostat, a clinically‐used histone deacetylase inhibitor, inhibits the PXR target gene expression at its clinically relevant plasma concentrations (< ~100 μM) in human hepatocytes (primary hepatocytes & hepatocells) and intestinal cells (LS174T colon cancer cells). Rifampicin, an agonist of human PXR, was used to activate PXR. Cell viability and CYQUANT cell proliferation assays were performed to determine cytotoxicity and cell proliferation, respectively. Quantitative RT‐PCR assays were conducted to study the gene expression. CYP3A4 p450‐Glo and Rhodamine‐123 intracellular accumulation assays were performed to determine the function of CYP3A4 and MDR1, respectively. Belinostat, at its unbound therapeutic plasma concentrations (< ~5 μM) did not affect the viability of LS174T cells and the hepatocytes. Belinostat (1 & 3 μM) not only inhibited rifampicin‐induced gene expression of CYP3A4 and MDR1, but also attenuated rifampicin‐induced activity of CYP3A4 and MDR1. However, belinostat alone did not affect CYP3A4 or MDR1 gene expression. These results suggest that belinostat does not affect the basal expression of PXR target genes but downregulates the upregulated PXR target genes by inhibiting the ligand‐activated PXR. Notably, belinostat, at its PXR inhibiting concentrations, decreased rifampicin‐induced proliferation of LS174T cells, suggesting that belinostat suppresses PXR‐mediated proliferation of the cancer cells. Interestingly, belinostat failed to inhibit rodent PXR agonist pregnenolone‐16 alpha‐carbonitrile (PCN)‐induced expression of CYP3A1 (the rat analog of human CYP3A4) in rat primary hepatocytes, suggesting that belinostat exhibits species‐specific inhibition of PXR at unbound plasma therapeutic concentrations. Taken together, these results are consistent with the conclusion that belinostat, at its less‐toxic and clinically relevant unbound plasma concentrations, inhibits the ligand‐activated human PXR target gene expression. Future studies will determine the mechanisms of belinostat inhibition of PXR, and belinostat sensitization of the cancer cells to chemotherapy drugs with PXR agonistic activity. Support or Funding Information The authors would like to thank Drs. Coleman, Schwartz, and Tao for sharing their research facilities. This work was supported by the Auburn University Research Initiative in Cancer Grant, Animal Health and Disease Research Grant...

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SPA70 is a potent antagonist of human pregnane X receptor

Cited by 86 publications

References 61 publications

Activation of Pregnane X Receptor Sensitizes Mice to Hemorrhagic Shock–Induced Liver Injury

Activation of Pregnane X Receptor Sensitizes Mice to Hemorrhagic Shock–Induced Liver Injury

The constitutive androstane receptor and pregnane X receptor in the brain

Belinostat, at Its Clinically Relevant Concentrations, Inhibits Rifampicin-Induced CYP3A4 and MDR1 Gene Expression

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