Tobacco use is associated with low peripheral beta-arrestin 1 levels in major depression: A preliminary report.

BACKGROUND: Understanding mechanisms associated with depressed smokers is a relevant question given that tobacco use disorder with comorbid major depressive disorder (MDD) has worse outcomes. The beta-arrestin 1 (ARRB1) pathway is a suggested biomarker for major depressive disorder and is involved in both antidepressant mechanism of action and tobacco addiction. We aimed to assess the association between smoking and peripheral ARRB1 expression in participants who exhibited MDD with current major depressive episode (MDE). BASIC PROCEDURES: 61 participants who exhibited MDD with current MDE with a score above 17 on the Hamilton Depression Rating Scale (HDRS), and who were free from antidepressant drug treatment for at least one month before inclusion, were assessed for tobacco use and cigarettes/day. Peripheral ARRB1 expression was assessed by sandwich ELISA from peripheral blood mononuclear cells (PBMC). FINDINGS: In participants who exhibited MDD with current MDE, peripheral ARRB1 expression was lower in tobacco users (n = 20, mean (SD) 4.795 (1.04) ng/mg of total protein) compared to non-tobacco users (n = 41, mean (SD) 6.19 (1.56) ng/mg; FDR p-value= 0.0044). Higher daily tobacco consumption was associated with lower peripheral ARRB1 expression (r = -0.314; FDR p-value=0.037). CONCLUSIONS: Tobacco consumption should be considered in studies of ARRB1 in participants who exhibit MDD. ARRB1 signaling is a new target of interest with a potential clinical implication for people with MDD and tobacco use disorder.

Sex-specific neurobiological actions of prophylactic (R,S)-ketamine, (2R,6R)-hydroxynorketamine, and (2S,6S)-hydroxynorketamine.

Enhancing stress resilience in at-risk populations could significantly reduce the incidence of stress-related psychiatric disorders. We have previously reported that the administration of (R,S)-ketamine prevents stress-induced depressive-like behavior in male mice, perhaps by altering α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated transmission in hippocampal CA3. However, it is still unknown whether metabolites of (R,S)-ketamine can be prophylactic in both sexes. We administered (R,S)-ketamine or its metabolites (2R,6R)-hydroxynorketamine ((2R,6R)-HNK) and (2S,6S)-hydroxynorketamine ((2S,6S)-HNK) at various doses 1 week before one of a number of stressors in male and female 129S6/SvEv mice. Patch clamp electrophysiology was used to determine the effect of prophylactic drug administration on glutamatergic activity in CA3. To examine the interaction between ovarian hormones and stress resilience, female mice also underwent ovariectomy (OVX) surgery and a hormone replacement protocol prior to drug administration. (2S,6S)-HNK and (2R,6R)-HNK protected against distinct stress-induced behaviors in both sexes, with (2S,6S)-HNK attenuating learned fear in male mice, and (2R,6R)-HNK preventing stress-induced depressive-like behavior in both sexes. (R,S)-ketamine and (2R,6R)-HNK, but not (2S,6S)-HNK, attenuated large-amplitude AMPAR-mediated bursts in hippocampal CA3. All three compounds reduced N-methyl-D-aspartate receptor (NMDAR)-mediated currents 1 week after administration. Furthermore, ovarian-derived hormones were necessary for and sufficient to restore (R,S)-ketamine- and (2R,6R)-HNK-mediated prophylaxis in female mice. Our data provide further evidence that resilience-enhancing prophylactics may alter AMPAR-mediated glutamatergic transmission in CA3. Moreover, we show that prophylactics against stress-induced depressive-like behavior can be developed in a sex-specific manner and demonstrate that ovarian hormones are necessary for the prophylactic efficacy of (R,S)-ketamine and (2R,6R)-HNK in female mice.

S 38093, a histamine H3 antagonist/inverse agonist, promotes hippocampal neurogenesis and improves context discrimination task in aged mice.

Strategies designed to increase adult hippocampal neurogenesis (AHN) may have therapeutic potential for reversing memory impairments. H3 receptor antagonists/inverse agonists also may be useful for treating cognitive deficits. However, it remains unclear whether these ligands have effects on AHN. The present study aimed to investigate the effects of a 28-day treatment with S 38093, a novel brain-penetrant antagonist/inverse agonist of H3 receptors, on AHN (proliferation, maturation and survival) in 3-month-old and in aged 16-month-old mice. In addition, the effects of S 38093 treatment on 7-month-old APPSWE Tg2576 transgenic mice, a model of Alzheimer's disease, were also assessed. In all tested models, chronic treatment with S 38093 stimulated all steps of AHN. In aged animals, S 38093 induced a reversal of age-dependent effects on hippocampal brain-derived neurotrophic factor (BDNF) BDNF-IX, BDNF-IV and BDNF-I transcripts and increased vascular endothelial growth factor (VEGF) expression. Finally, the effects of chronic administration of S 38093 were assessed on a neurogenesis-dependent "context discrimination (CS) test" in aged mice. While ageing altered mouse CS, chronic S 38093 treatment significantly improved CS. Taken together, these results provide evidence that chronic S 38093 treatment increases adult hippocampal neurogenesis and may provide an innovative strategy to improve age-associated cognitive deficits.