Differential regulation of the tyrosine hydroxylase and enkephalin neuropeptide transmitter genes in rat PC12 cells by short chain fatty acids: Concentration-dependent effects on transcription and RNA stability

• Published in: Brain research 2007-02, Vol.1132 (1), p.42-50
• Main Authors: Parab, Santosh, Nankova, Bistra B, La Gamma, Edmund F
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Butyrate; Butyrates - metabolism; Butyrates - pharmacology; Catecholamines; Differential gene regulation; Dose-Response Relationship, Drug; Enkephalin; Enkephalins - biosynthesis; Enkephalins - genetics; Fatty Acids, Volatile - pharmacology; Fatty Acids, Volatile - physiology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Isolated neuron and nerve. Neuroglia; Nervous System - drug effects; Nervous System - metabolism; Neurology; Neurons - drug effects; Neurons - metabolism; PC12 Cells; Promoter Regions, Genetic - drug effects; Promoter Regions, Genetic - genetics; Protein Synthesis Inhibitors - pharmacology; Rats; RNA Stability - drug effects; RNA Stability - genetics; RNA, Messenger - drug effects; RNA, Messenger - metabolism; Short chain fatty acid; Transcription, Genetic - drug effects; Transcription, Genetic - genetics; Transcriptional Activation - drug effects; Transcriptional Activation - genetics; Tyrosine 3-Monooxygenase - biosynthesis; Tyrosine 3-Monooxygenase - genetics; Tyrosine hydroxylase; Up-Regulation - drug effects; Up-Regulation - genetics; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2006.11.013

Abstract At physiologic concentrations, butyrate regulates the expression of individual genes involving at least three mechanisms: (i) through induction of cis - and trans -acting butyrate-dependent transcription factors for selected genes, (ii) by inhibition of histone deacetylation and attendant chromatin remodeling and (iii) by affecting turnover of mRNAs. Our previous work illustrated gradual accumulation of mRNA for tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine biosynthesis and the neuropeptide transmitter proenkephalin (ppEnk) in butyrate-differentiated PC12 cells (Nankova, B.B., Chua, J., Mishra, R., Kobasiuk, C.D., La Gamma, E.F. 2003. Nicotinic induction of preproenkephalin and tyrosine hydroxylase gene expression in butyrate-differentiated rat PC12 cells: a model for adaptation to gut-derived environmental signals. Pediatr. Res. 53, 113–118.). However, at higher physiological concentrations (6 mM), TH mRNA levels are significantly reduced while ppEnk mRNA transcripts remained elevated. These differential effects suggest suppression of endogenous TH gene transcription, targeted degradation of TH mRNA or both. By using nuclear run-on assays, we found that transcription increased for both endogenous TH and ppEnk genes, even at time points and concentrations when reduced steady-state levels of TH mRNA were observed. The reduction in TH mRNA was blocked by cycloheximide consistent with a protein-dependent mechanism. We also observed a dose-dependent accumulation of luciferase reporter molecules driven by TH promoter in transient transfection experiments, data that provide additional support for separate regulatory pathways. Significantly, butyrate-dependent decreases in TH mRNA were also reflected in a reduction in TH protein. Our results suggest a novel mode of regulation for TH by butyrate operating via both transcriptional and post-transcriptional mechanisms. We speculate that, depending on plasma concentrations of butyrate, this naturally occurring signaling molecule can function as an in vivo molecular switch to alter levels of TH mRNA, its protein and thus the biosynthesis of endogenous catecholamines.