Role of CREB on heme oxygenase-1 induction in adrenal cells: involvement of the PI3K pathway

Abstract

In addition to the well-known function of ACTH as the main regulator of adrenal steroidogenesis, we have previously demonstrated its effect on the transcriptional stimulation of HO-1 expression, a component of the cellular antioxidant defense system. In agreement, we hereby demonstrate that, in adrenocortical Y1 cells, HO-1 induction correlates with a significant prevention of the generation of reactive oxygen species induced by H 2 O 2 /Fe 2+ . ACTH/cAMP-dependent activation of redox-imbalanced related factors such as NRF2 or NFκB and the participation of MAPKs in this mechanism was, however, discarded based on results with specific inhibitors and reporter plasmids. We suggest the involvement of CREB in HO-1 induction by ACTH/cAMP, as transfection of cells with a dominant-negative isoform of CREB (DN-CREB-M1) decreased, while overexpression of CREB increased HO-1 protein levels. Sequence screening of the murine HO-1 promoter revealed CRE-like sites located at −146 and −37 of the transcription start site and ChIP studies indicated that this region recruits phosphorylated CREB (pCREB) upon cAMP stimulation in Y1 cells. In agreement, H89 (PKA inhibitor) or cotransfection with DN-CREB-M1 prevented the 8Br-cAMP-dependent increase in luciferase activity in cells transfected with pHO-1[−295/+74].LUC. ACTH and cAMP treatment induced the activation of the PI3K/Akt signaling pathway in a PKA-independent mechanism. Inhibition of this pathway prevented the cAMP-dependent increase in HO-1 protein levels and luciferase activity in cells transfected with pHO-1[−295/+74].LUC. Finally, here we show a crosstalk between the cAMP/PKA and PI3K pathways that affects the binding of p-CREB to its cognate element in the murine promoter of the Hmox1 gene. CREB mediates adrenal HO-1 induction by cAMPf astort, e m repetto and others (Gallo-Payet 2016). In turn, stimulation of PKA activity is involved in the phosphorylation and activation of several transcription factors engaged in the transcriptional stimulation of steroidogenic-related genes. Among them, the cAMP response element binding protein (CREB), the GATA-4 binding protein, the steroidogenic factor 1 (SF1) and the CAAT enhancer binding protein (C/EBP) could be included (Manna et al. 2003a,b, Stocco et al. 2005.Glucocorticoid synthesis in the adrenal cortex is a multistep process where mitochondrial and microsomal cytochrome P450 enzymes, mixed function oxidases, catalyze the hydroxylation of steroids and the reduction of O 2 to water. Even under physiological conditions, ACTHstimulated steroidogenesis generates oxidative stress, as incomplete reduction in O 2 leads to the production of reactive oxygen species (ROS), lipoperoxides and other oxygenated species (Hanukoglu 2006, Prasad et al. 2014. To cope with the potentially damaging effects associated with oxidative stress, adrenal cells activate several antioxidant mechanisms (Chinn et al. 2002, Hanukoglu 2006, Battista et al. 2009). Among them, we have previously shown that the ACTH-dependent induction of heme oxygenase...

Chronic Nicotine Exposure Reduces Antioxidant Function of Simvastatin in Renal Proximal Tubule Cells

“…Chronic nicotine exposure suppressed simvastatin-mediated CREB activation via p66shc. Since both the HO1 (5) and MnSOD (7) promoters are induced, at least partly, by the CREB transcription factor, NRK52E cells were cotransfected with a CRE and a renilla luciferase plasmid and treated with 200 μΜ nicotine for 24 h followed by treatment with 10 μΜ simvastatin. Luciferase activities were determined 24 h later.…”

“…Since both the HO1 (5) and MnSOD (7) promoters are regulated, at least partly, via CREB, we also determined the activity of a CRE-luciferase reporter. Figure 2A shows that CRE-luc activity was highly stimulated by simvastatin, the extent of which diminished on pretreatment with nicotine.…”

“…Previously, we reported that simvastatin elicits protective antioxidant responses by transcriptionally inducing the promoter of the antioxidant gene heme oxygenase-1 (HO1) via the cAMP response element binding (CREB) protein in cultured renal proximal tubule cells (4). CREB is a transcription factor that regulates promoter activity of several genes including HO1 (4,5) and manganese superoxide dismutase (MnSOD) (6,7).…”

KLF14 potentiates oxidative adaptation via modulating HO-1 signaling in castrate-resistant prostate cancer

“…Endocrine-Related Cancer been previously identified in the HMOX1 promoter region including −146 to −37 bp for CREB (Astort et al 2016), −44 bp for Nrf2 (Potteti et al 2016) and −1036 to +1 bp for Sp1 and p53 (Tung et al 2015). In contrast, the promoter region of HMOX1 bound by KLF14 (−645 to −641 bp) was not included in the above-mentioned cis-acting elements.…”

Towards Targeting PI3K-Dependent Regulation of Gene Expression in Brain Cancer

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