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Abstract
CYP2S1 is an evolutionarily conserved, mainly extra-hepatic member of the CYP2 family and proposed to be regulated by the aryl hydrocarbon receptor (AhR).
The present study explores AhR’s regulation of CYP2S1 in male Sprague Dawley rats using PCB126 (3,3′,4,4′,5-pentachlorobiphenyl), the most potent AhR agonist among the PCBs. Additionally, CYP2S1 expression was examined after treatments with the classic CYP-inducers β-naphthoflavone (β-NF, AhR activator), phenobarbital (PB, CAR activator) and dexamethasone (Dex, PXR activator). CYP2S1 and CYP1A1/2, CYP1B1, CYP2B and CYP3A mRNAs were measured in liver, lung, spleen, stomach, kidney, and thymus at different time points.
Constitutive CYP2S1 was expressed at comparable levels to other CYPs with the highest expression levels in stomach, kidney and lung. CYP2S1 mRNA was only non-significantly elevated by β-NF in liver tissues. PCB126 did not increase CYP2S1 mRNA in any organ and at any time point examined despite a significant induction of CYP1 genes. PCB126 reduced CYP2S1 mRNA by 40% (not significant) from the 7th post-exposure day in thymus. PB and Dex had no effect on CYP2S1 mRNA levels.
These observations show that in this model CYP2S1 is not, or only weakly, regulated by AhR and not induced by CAR or PXR activators.
Acknowledgments
The authors thank Dr. Gregor Luthe, Feodor Lynen fellow of the A. von Humbold Foundation, for the synthesis of PCB 126, Dr. Stelvio Bandiera for helpful discussions and comments.
Declaration of interest
This work was supported by the Iowa Superfund Research Program grant from the National Institute of Environmental Health Sciences (P42 ES013661). Research funds were also available from the Environmental Health Sciences Research Center (P30 ES 05605). The authors state no conflicts of interest.