Actinomyces naeslundii is a pioneer of the oral cavity and forms a biofilm on the tooth's surface. Most bacteria require iron for survival and in pathogenic bacteria iron availability regulates virulence gene expression. Metal-dependent repressors control gene expression involved in metal transport and uptake including siderophores. Siderophores are small molecules synthesized by bacteria and fungi to acquire iron. The A. naeslundii genome was searched for a gene encoding a metal-dependent repressor. Actinomyces metal-dependent repressor or amdR was identified. The AmdR protein was examined for its ability to bind to the promoter sequence of a gene encoding the siderophore uptake (sid gene). According to gel shift assays, AmdR binds to the sid gene promoter sequences. In the authors' model, when iron is available AmdR binds to the sid promoter and represses sid gene expression. To further explore the role of AmdR, an amdR-defective strain of A. naeslundii was constructed and biofilm formation and siderophore production were evaluated. When iron is removed from the medium A. naeslundii increases biofilm and siderophore production. However, amdR-defective A. naeslundii is less sensitive to metal ion concentrations in the growth medium.

BACKGROUND: Neonatal abstinence syndrome (NAS) is a significant problem. Opioid withdrawal induces oxidative stress and disrupts glutamate and glutathione homeostasis. We hypothesized that N-acetylcysteine (NAC) administered during acute opioid withdrawal in neonatal rats would decrease withdrawal behaviors and normalize CNS glutathione and glutamate. METHODS: Osmotic minipumps with methadone (opioid dependent, OD) and saline (Sham) were implanted into Sprague Dawley dams 7 days prior to delivery. Pups were randomized to receive either naloxone plus saline or NAC (50-100 mg/kg), administered on postnatal day (PND) 7. We performed MR spectroscopy on PND6-7 before, 30 min, and 120 min after withdrawal. On PND7, we assessed withdrawal behaviors for 90 min after naloxone administration and summed scores during peak withdrawal period. RESULTS: Mean summed behavioral scores were significantly different between groups (χ 2 (2) = 10.49, p = 0.005) but not different between NAC/NAL/OD and Sham (p = 0.14): SAL/NAL/OD = 17.2 ± 4.2 (n = 10); NAC/NAL/OD = 11.3 ± 5.6 (n = 9); Sham = 6.5 ± 0.6 (n = 4). SAL/NAL/OD pups had decreased glutathione at 120 min (p = 0.01), while NAC/NAL/OD pups maintained pre-withdrawal glutathione (p = 0.26). CONCLUSION: In antenatal OD, NAC maintains CNS glutathione and mitigates acute opioid withdrawal in neonatal rats. This is the first study to demonstrate acute opioid withdrawal neurochemical changes in vivo in neonatal OD. NAC is a potential novel treatment for NAS.

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