Stereospecific Regulation of Tyrosine Hydroxylase and Proenkephalin Genes by Short-Chain Fatty Acids in Rat PC12 Cells

Abstract

Circulating short-chain fatty acids (SCFAs) are primarily derived from bacterial fermentation of carbohydrates in the colon where they function as physiologic modulators of epithelial cell maturation. Butyrate has been shown to induce tyrosine hydroxylase, the rate-limiting enzyme of catecholamine synthesis, and enkephalin neuropeptide gene transcription, suggesting a role in perinatal sympathoadrenal stress-adaptation. We sought to determine whether there were SCFA structural requirements for this effect. Nine biologically relevant SCFAs and butyrate derivatives were tested in an in vitro model (PC12, rat pheochromocytoma cells) for their ability to regulate neurotransmitter-related gene expression. Our results revealed that among all the studied SCFAs, only propionate and butyrate increased tyrosine hydroxylase and proenkephalin mRNA levels. The functional activity was selective to the carbon atom chain length and associated with the presence of an ethyl moiety in the carbon atom backbone chain. Modifications or absence of this domain affected the gene induction response, suggesting a receptor-mediated mechanism(s). Moreover, propionate, butyrate, and the drug 4-phenylbutyrate were each shown to regulate transmitter genes via at least three independent mechanisms: histone hyperacetylation, cAMP signaling, or peroxisome proliferator-activated receptor gamma-mediated pathways. Thus, the biologic impact of SCFAs on catecholaminergic and opioid systems depend on the activation of SCFA-specific, dose-specific, and gene-specific molecular mechanisms. We speculate that 1) circulating levels of SCFAs may influence sympathoadrenal transmitter biosynthesis and hence whole animal stress-adaptive responsiveness after birth, and 2) the adverse effects of antibiotics on delayed acquisition of postnatal gut flora may affect this apparent evolutionary advantage of gut colonization. Sympathoadrenal transmitter systems mature to adult capacity a week or more after birth in response to progressive cholinergic innervation, exposure to growth factors, and hormonal influences from both the hypothalamic-pituitary-adrenal cortical and thyroid hormonal systems (1-6). Although the importance of these conventional control mechanisms is well established, the evolutionary significance of other exogenous stimuli can be considered in a broader view of environmentally derived signal-transduction. For example, the delayed period of adrenal transmitter accumulation after birth coincides with the time taken to establish full enteral feedings, colonization of the intestine, and attendant production of SCFA (7). Moreover, in the rat (as well as in humans), this time frame is far longer than the capacity of the chromaffin cell to rapidly induce biosynthesis of either catecholamines or enkephalins, which can occur in a matter of hours (8)

Enteric Bacterial Metabolites Propionic and Butyric Acid Modulate Gene Expression, Including CREB-Dependent Catecholaminergic Neurotransmission, in PC12 Cells - Possible Relevance to Autism Spectrum Disorders

“…in [3]. In this study, we demonstrate that PPA can induce TH gene transcription over a wide dose range (0.1 mM to 10 mM) in PC12 cells, similar to the effects of BA [63], [75]. The general transcription factor CREB (or CREB-related proteins) and signaling pathways converging on it are involved in the transcriptional regulation of the TH gene by PPA or BA.…”

“…Emerging evidence links SCFA from diet, cellular metabolism or pharmacological treatments with regulation of neuronal gene expression, attendant neuronal function and even behavior [34], [35], [36], [37], [38], [45], [39], [41], [42], [27], [43], [44], [64], [58], [63], [75], rev. in [3].…”

Overconsumption of dietary fat and alcohol: Mechanisms involving lipids and hypothalamic peptides

“…This is demonstrated by results revealing a strong and consistent association between the opioids and a marked rise in circulating TG levels induced by fat consumption as well as injection of Intralipid [29,45]. Although the molecular mechanisms elevating ENK and DYN transcripts in response to fat remain to be characterized, evidence demonstrates a direct stimulatory effect of short-chain fatty acids on ENK gene expression in PC12 rat cells via an intact PKA signaling pathway, with a possible involvement of lipid-activated transcription factors [52]. Fatty acids may also modulate the binding of opioid peptides to their receptor [53].…”

A Novel Rodent Model of Autism: Intraventricular Infusions of Propionic Acid Increase Locomotor Activity and Induce Neuroinflammation and Oxidative Stress in Discrete Regions of Adult Rat Brain

“…Moreover, PPA is commonly used as a food preservative in wheat and dairy food products [45] . A number of effects have been shown following PPA treatment, including catecholamine and proenkephalin gene induction [46] , cytoskeletal phosphorylation [47] , histone modulation [48] , second messenger metabolism [49] , impaired mitochondrial respiratory transport chain function [50,51] , modulation of gap junctions [52] and immune system activation [53] . There is also evidence of variable PPA metabolism in a number of metabolic disorders such as propionic and methylmalonic acidemia [54] , disorders of biotin [55] and B12 metabolism [56] , as well as following valproate [57] and ethanol exposure [58] .…”