PubMed · 15317109
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National Toxicology Program. 2002. Acetaldehyde.. https://pubmed.ncbi.nlm.nih.gov/15317109/
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We have addressed critical challenges in probiotic design to develop a commercially viable bacterial strain capable of removing the intestinal toxin, acetaldehyde. In this study, we report the engineering of the hag locus, a σD-dependent flagellin expression site, as a stable location for robust enzyme production. We demonstrate constitutive gene expression in relevant conditions driven by the endogenous hag promoter, following a deletion of the gene encoding a post-translational regulator of σD, FlgM, and a point mutation to abrogate the binding of the translational inhibitor CsrA. Reporter constructs demonstrate activity at the hag locus after germination, with a steady increase in heterologous expression throughout outgrowth and vegetative growth. To evaluate the chassis as a spore-based probiotic solution, we identified the physiologically relevant ethanol metabolic pathway and the subsequent accumulation of gut-derived acetaldehyde following alcohol consumption. We integrated a Cupriavidus necator aldehyde dehydrogenase gene (acoD) into the hag locus under the control of the flagellin promoter and observed a rapid reduction in acetaldehyde levels in gut-simulated conditions post-germination. This work demonstrates a promising approach for the development of genetically engineered spore-based probiotics.
The meso-limbic dopamine (DA) system has an important role in regulating alcohol drinking. Previous findings from our laboratory indicated that Wistar rats self-administered ethanol (EtOH) directly into the posterior, but not anterior, ventral tegmental area (VTA), and that coadministration of a DA D(2,3) receptor agonist or a serotonin-3 (5-HT3) receptor antagonist blocked EtOH self-administration. In addition, we reported that alcohol-preferring (P) rats self-administered acetaldehyde (ACD), the first metabolite of EtOH, into the posterior VTA. The objectives of this study were to compare the reinforcing effects of EtOH and ACD within the VTA of P rats to examine the possibility that the reinforcing effects of EtOH within the VTA may be mediated by its conversion to ACD. Adult female P rats were stereotaxically implanted with guide cannulae aimed at either the posterior or anterior VTA. At 1 week after surgery, rats were placed in standard two-lever (active and inactive) experimental chambers for a total of seven to eight sessions. The 4-h sessions were conducted every other day. The results indicated that (a) 75-300 mg% (17-66 mM) EtOH and 6-90 microM ACD were self-administered into the posterior, but not anterior, VTA; (b) the self-administration of 150 mg% EtOH was not altered by coinfusion of a catalase inhibitor; (c) coadministration of the D(2/3) agonist quinpirole (100 microM) blocked the self-infusions of 150 mg% EtOH and 23 microM ACD into the posterior VTA; and (d) coadministration of 200 microM ICS205,930 (5-HT3 receptor antagonist) prevented the self-infusion of 150 mg% EtOH, whereas concentrations of ICS 205,930 up to 400 microM had no effect on the self-infusion of 23 microM ACD into the posterior VTA. Overall, the results of this study indicate that EtOH and ACD can independently produce reinforcing effects within the posterior VTA, and that activation of DA neurons mediates these effects. Furthermore, activation of 5-HT3 receptors within the posterior VTA is involved in the self-infusion of EtOH, but not ACD.
Tobacco use has one of the highest rates of addiction and relapse of any abused drug. Paradoxically, however, in animal models of reinforcement nicotine appears weak compared to other abused drugs. We report here that acetaldehyde, a major component of tobacco smoke, enhances nicotine self-administration. Juvenile and adult male rats were implanted with intravenous catheters and tested for self-administration 4 days later at postnatal day 27 or 90, respectively. Animals were tested, without prior response training, in five daily 3-h sessions where each nose-poke delivered an intravenous injection followed by a 60-s timeout. Animals (11-13/group) were offered one of the following solutions: nicotine (30 microg/kg/injection), acetaldehyde (16 microg/kg/inj), nicotine (30 microg/kg/inj)+acetaldehyde (16 microg/kg/inj), or saline. The youngest animals responded significantly more for nic+acet than for saline or for either drug alone. Responding at the reinforced hole was significantly higher than at the nonreinforced hole or at the reinforced hole during noncontingent injections of nic+acet. Tests with receptor antagonists indicated that these drug effects are mediated by central, but not peripheral, nicotinic receptors. There was an age-related decline in self-administration of nic+acet, but not for cocaine. Taken together, these results indicate that acetaldehyde, at the low concentrations found in tobacco smoke, interacts with nicotine to increase responding in a stringent self-administration acquisition test where nicotine alone is only weakly reinforcing, and that adolescent animals are more sensitive to these actions than adults. Animal models of tobacco addiction could be improved by combining acetaldehyde, and possibly other smoke components, with nicotine to more accurately reflect the pharmacological profile of tobacco smoke.