Aryl Hydrocarbon Receptor-Dependent Retention of Nuclear HuR Suppresses Cigarette Smoke-Induced Cyclooxygenase-2 Expression Independent of DNA-Binding

作者：Zago Michela; Sheridan Jared A; Nair Parameswaran; de Souza Angela Rico; Gallouzi Imed Eddine; Rousseau Simon; Di Marco Sergio; Hamid Qutayba; Eidelman David H; Baglole Carolyn J^*

来源：PLos One, 2013, 8(9): e74953.

DOI：10.1371/journal.pone.0074953

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to man-made environmental toxicants, has emerged as an endogenous regulator of cyclooxygenase-2 (Cox-2) by a mechanism that is poorly understood. In this study, we first used AhR-deficient (AhR(-/-)) primary pulmonary cells, together with pharmacological tools to inhibit new RNA synthesis, to show that the AhR is a prominent factor in the destabilization of Cox-2 mRNA. The destabilization of Cox-2 mRNA and subsequent suppression of cigarette smoke-induced COX-2 protein expression by the AhR was independent of its ability to bind the dioxin response element (DRE), thereby differentiating the DRE-driven toxicological AhR pathway from its anti-inflammatory abilities. We further describe that the AhR destabilizes Cox-2 mRNA by sequestering HuR within the nucleus. The role of HuR in AhR stabilization of Cox-2 mRNA was confirmed by knockdown of HuR, which resulted in rapid Cox-2 mRNA degradation. Finally, in the lungs of AhR(-/-) mice exposed to cigarette smoke, there was little Cox-2 mRNA despite robust COX-2 protein expression, a finding that correlates with almost exclusive cytoplasmic HuR within the lungs of AhR(-/-) mice. Therefore, we propose that the AhR plays an important role in suppressing the expression of inflammatory proteins, a function that extends beyond the ability of the AhR to respond to man-made toxicants. These findings open the possibility that a DRE-independent AhR pathway may be exploited therapeutically as an anti-inflammatory target.

• 出版日期2013-9-27