Feedback inhibition of CREB signaling by p38 MAPK contributes to the negative regulation of steroidogenesis

Jiaxin Li,Zhuang Ma,Wen-Jun Shen,Zhigang Hu,Meina Wang,Zhigang Guo,Salman Azhar,Qian Zhou

doi:10.1186/s12958-017-0239-4

Abstract

BackgroundSteroidogenesis is a complex, multi-steps biological process in which, cholesterol precursor is converted to steroids in a tissue specific and tropic hormone dependent manner. Given that steroidogenesis is achieved by coordinated functioning of multiple tissue specific enzymes, many steroids intermediates/metabolites are generated during this process. Both the steroid products as well as major lipoprotein cholesterol donor, high-density lipoprotein 3 (hHDL3) have the potential to negatively regulate steroidogenesis via increased oxidative stress/reactive oxygen species (ROS) generation.MethodsIn the current study, we examined the effects of treatment of a mouse model of steroidogenesis, Y1-BS1 adrenocortical tumor cells with pregnenolone, 22(R)-Hydroxycholesterol [22(R)-diol] or hHDL3 on ROS production, phosphorylation status of p38 MAPK and cAMP response element-binding protein (CREB), CREB transcriptional activity and mRNA expression of StAR, CPY11A1/P450scc and antioxidant enzymes, superoxide dismutases [Cu,ZnSOD (SOD1), MnSOD (SOD2)], catalase (CAT) and glutathione peroxidase 1 (GPX1). We also detected the steroid product in p38 MAPK inhibitor treated Y1 cells by HPLC-MS / MS.ResultsTreatment of Y1 cells with H2O2 greatly enhanced the phosphorylation of both p38 MAPK and CREB protein. Likewise, treatment of cells with pregnenolone, 22(R) diol or hHDL3 increased ROS production measured with the oxidation-sensitive fluorescent probe 2′,7′-Dichlorofluorescin diacetate (DCFH-DA). Under identical experimental conditions, treatment of cells with these agents also increased the phosphorylation of p38 MAPK and CREB. This increased CREB phosphorylation however, was associated with its decreased transcriptional activity. The stimulatory effects of pregnenolone, 22(R)-diol and hHDL3 on CREB phosphorylation was abolished by a specific p38 MAPK inhibitor, SB203580. Pregnenolone, and 22(R) diol but not hHDL3 upregulated the mRNA expression of SOD1, SOD2 and GPX1, while down-regulated the mRNA levels of StAR and CYP11A1. The p38 inhibitor SB203580 could increase the steroid production in HDL3, 22(R)-diol or pregnenolone treated cells.ConclusionOur data demonstrate induction of a ROS/p38 MAPK -mediated feedback inhibitory pathway by oxy-cholesterol and steroid intermediates and products attenuates steroidogenesis via inhibition of CREB transcriptional activity.

Highlights

Steroidogenesis is a complex, multi-steps biological process in which, cholesterol precursor is converted to steroids in a tissue specific and tropic hormone dependent manner
The cholesterol required for steroid hormone synthesis can be theoretically obtained from several different potential sources including de novo synthesis from acetate, cholesteryl esters stored in the form of lipid droplets or can be obtained from circulating lipoproteins via low-density lipoprotein (LDL) receptor/endocytic pathway or Scavenger Receptor Class B (SR-BI)/selective uptake pathway [3, 4]. steroidogenic process is subjected to a dual regulation—acute and chronic regulation [5], both are under the control of tissue-specific tropic hormone
H2O2 stimulates the phosphorylation of p38 MAPK and cAMP responsive cAMP response element-binding protein (CREB) transcription factor Increasing evidence suggests that reactive oxygen species (ROS) such as O2, OH and H2O2, promote the phosphorylation and activation of MAPK, among which p38 MAPK is highly responsive to oxidant stress which has important roles in cell signaling and homeostasis [31,32,33,34]

Summary

Introduction

Steroidogenesis is a complex, multi-steps biological process in which, cholesterol precursor is converted to steroids in a tissue specific and tropic hormone dependent manner. Given that steroidogenesis is achieved by coordinated functioning of multiple tissue specific enzymes, many steroids intermediates/metabolites are generated during this process Both the steroid products as well as major lipoprotein cholesterol donor, highdensity lipoprotein 3 (hHDL3) have the potential to negatively regulate steroidogenesis via increased oxidative stress/ reactive oxygen species (ROS) generation. Tropic hormones, ACTH and LH stimulate steroid synthesis in steroidogenic cells of their target tissues and promote ROS production, which in turn can cause DNA damage, protein oxidation and membrane lipid peroxidation in steroidogenic cells [8, 9]. We demonstrated that aging leads to a significant reduction in enzymatic and non-enzymatic antioxidant systems and increased membrane lipid peroxidation in steroidogenic cells of adrenal gland and testis [10]

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Discussion

Conclusion