Role of proto-oncogenes in the regulation of proenkephalin mRNA expression induced by repeated nicotine injections in rat adrenal medulla

The nuclear transcription factor CREB: involvement in addiction, deletion models and looking forward

Addiction involves complex physiological processes, and is characterised not only by broad phenotypic and behavioural traits, but also by ongoing molecular and cellular adaptations. In recent years, increasingly effective and novel techniques have been developed to unravel the molecular implications of addiction. Increasing evidence has supported a contribution of the nuclear transcription factor CREB in the development of addiction, both in contribution to phenotype and expression in brain regions critical to various aspects of drug-seeking behaviour and drug reward. Abstracting from this, models have exploited these data by removing the CREB gene from the developing or developed mouse, to crucially determine its impact upon addiction-related processes. More recent models, however, hold greater promise in unveiling the contribution of CREB to disorders such as addiction.

Prolonged Activation of cAMP-response Element-binding Protein and ATF-2 Needed for Nicotine-triggered Elevation of Tyrosine Hydroxylase Gene Transcription in PC12 Cells

Phosphorylation (P-) of cAMP-response element-binding protein (CREB) by protein kinase A or mitogen-activated protein kinases was implicated in mediating the increased tyrosine hydroxylase (TH) gene expression after prolonged exposure to nicotine in vivo and in cell culture. We examined the time course and signaling pathways for phosphorylation of CREB and possible involvement of ATF-2. Treatment of PC12 cells with 200 microm nicotine triggered rapid but transient elevation of P-CREB followed by a second sustained rise after 2-5 h of continuous nicotine. In contrast, ERK1/2 was only phosphorylated with short term nicotine exposure. MEK inhibitor U0126 abolished nicotine-induced rise in P-ERK1/2, but not P-CREB, nor did it inhibit nicotine-evoked elevation in TH promoter activity, indicating that ERK1/2 was not needed for induction of TH gene expression by nicotine. In contrast, protein kinase A inhibitor H-89 or Ca(2+)/calmodulin-activated protein kinase inhibitor KN-93 reduced the nicotine-triggered rise in P-CREB and TH promoter activity. There was a delayed elevation of P-ATF-2 after 1 h of nicotine treatment, accompanied by increased ATF-2 protein. Upstream kinase JNK, but not p38, was phosphorylated especially after 5 min to 2 h of nicotine exposure. To examine the requirement for CREB and ATF-2, cells were transfected with dominant negative forms of ATF-2 or CREB. Both reduced the basal TH promoter activity and the response to nicotine. Knockdown of ATF-2 or CREB with siRNA did not alter basal TH promoter activity or mRNA but greatly attenuated the response to nicotine. The results suggest that both ATF-2 and CREB mediate activation of TH gene transcription by nicotine.

Experimental tooth movement upregulates preproenkephalin mRNA in the rat trigeminal nucleus caudalis and oralis

Levels of preproenkephalin mRNA expression in trigeminal subnucleus complex by noxious tooth movement stimuli were examined using in situ hybridization. At 24 h, preproenkephalin mRNA expression was significantly upregulated in the ipsilateral trigeminal subnucleus caudalis (P<0.05), and in the subnucleus oralis (P<0.05). These findings suggested that enkephalinergic inhibitory systems could be activated during tooth movement, and that subnucleus oralis may be involved in modulation of the nociception, as well as the subnucleus caudalis.

Receptor-mediated tobacco toxicity: regulation of gene expression through alpha3beta2 nicotinic receptor in oral epithelial cells

Tobacco is a known cause of oral disease but the mechanism remains elusive. Nicotine (Nic) is a likely culprit of pathobiological effects because it displaces the local cytotransmitter acetylcholine from the nicotinic receptors (nAChRs) expressed by oral keratinocytes (KCs). To gain a mechanistic insight into tobacco-induced morbidity in the oral cavity, we studied effects of exposures to environmental tobacco smoke (ETS) versus equivalent concentration of pure Nic on human and murine KCs. Both ETS and Nic up-regulated expression of cell cycle and apoptosis regulators, differentiation marker filaggrin, and signal transduction factors at both the mRNA and protein levels. These changes could be abolished in cultured human oral KCs transfected with anti-alpha3 small interfering RNA or treated with the alpha3beta2-preferring antagonist alpha-conotoxin MII. Functional inactivation of alpha3-mediated signaling in alpha3-/- mutant KCs prevented most of the ETS/Nic-dependent changes in gene expression. To determine relevance of the in vitro findings to the in vivo situation, we studied gene expression in oral mucosa of neonatal alpha3+/+ and alpha3-/- littermates delivered by heterozygous mice soon after their exposures to ETS or equivalent concentration of pure Nic in drinking water. In addition to reverse transcriptase-polymerase chain reaction and Western blot, the ETS/Nic-dependent alterations in gene expression were also detected by semiquantitative immunofluorescence assay directly in KCs comprising murine oral mucosa. Only wild-type mice consistently developed significant (P < 0.05) changes in the gene expression. These results identified alpha3beta2 nAChR as a major receptor mediating effects of tobacco products on KC gene expression. Real-time polymerase chain reaction demonstrated that in all three model systems the common genes targeted by alpha3beta2-mediated ETS/Nic toxicity were p21, Bcl-2, NF-kappaB, and STAT-1. The expression of the nAChR subunits alpha5 and beta2 and the muscarinic receptor subtypes M(2) and M(3) was also altered. This novel mechanism offers innovative solutions to ameliorate the tobacco-related cell damage and intercede in disease pathways, and may shed light on general mechanisms regulating and driving tobacco-related morbidity in human cells.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).