Biology subjects

Brachman, R. A.

Publications and source records attributed to Brachman, R. A..

3 recordsLinked to original sources

bioRxiv2023

(R,S)-ketamine's rapid-acting antidepressant effects are modulated by NR2B- containing NMDA receptors on adult-born hippocampal neurons

Standard antidepressant treatments often take weeks to reach efficacy and are ineffective for many patients. (R,S)-ketamine, an N-methyl-D-aspartate (NMDA) antagonist, has been shown to be a rapid-acting antidepressant and to decrease depressive symptoms within hours of administration. While previous studies have shown the importance of the NR2B subunit of the NMDA receptor (NMDAR) on interneurons in the medial prefrontal cortex (mPFC), no study has investigated the influence of NR2B-expressing adult-born granule cells (abGCs). In this study, we examined whether (R,S)-ketamines efficacy depends upon these adult-born hippocampal neurons using a genetic strategy to selectively ablate the NR2B subunit of the NMDAR from Nestin+ cells. To validate our findings, we also used several other transgenic lines including one in which NR2B was deleted from an interneuron (Parvalbumin (PV)+) population. We report that in male mice, NR2B expression on 6-week-old adult-born neurons is necessary for (R,S)-ketamines effects on behavioral despair in the forced swim test (FST) and on hyponeophagia in the novelty suppressed feeding (NSF) paradigm, as well on fear behavior following contextual fear conditioning (CFC). In female mice, NR2B expression is necessary for effects on hyponeophagia in the NSF. We also find that ablating neurogenesis increases fear expression in CFC, which is buffered by (R,S)-ketamine administration. In line with previous studies, these results suggest that 6-week-old adult-born hippocampal neurons expressing NR2B partially modulate (R,S)-ketamines rapid-acting effects. Future work targeting these 6-week-old adult-born neurons may prove beneficial for increasing the efficacy of (R,S)-ketamines antidepressant actions.

neuroscience↗

bioRxiv2021

Humoral immune responses against seasonal coronaviruses predict efficiency of SARS-CoV-2 spike targeting, FcγR activation, and corresponding COVID-19 disease severity

Despite SARS-CoV-2 being a "novel" coronavirus, several studies suggest that detection of anti-spike IgG early in infection may be attributable to the amplification of humoral memory responses against seasonal hCoVs in severe COVID-19 patients. In this study, we examined this concept by characterizing anti-spike IgG from a cohort of non-hospitalized convalescent individuals with a spectrum of COVID-19 severity. We observed that anti-spike IgG levels positively correlated with disease severity, higher IgG cross-reactivity against betacoronaviruses (SARS-CoV-1 and OC43), and higher levels of proinflammatory Fc gamma receptor 2a and 3a (Fc{gamma}R2a & Fc{gamma}R3a) activation. In examining the levels of IgG targeting betacoronavirus conserved and immunodominant epitopes versus disease severity, we observed a positive correlation with the levels of IgG targeting the conserved S2FP region, and an inverse correlation with two conserved epitopes around the heptad repeat (HR) 2 region. In comparing the levels of IgG targeting non-conserved epitopes, we observed that only one of three non-conserved immunodominant epitopes correlated with disease severity. Notably, the levels of IgG targeting the receptor binding domain (RBD) were inversely correlated with severity. Importantly, targeting of the RBD and HR2 regions have both been shown to mediate SARS-CoV-2 neutralization. These findings show that, aside from antibody (Ab) targeting of the RBD region, humoral memory responses against seasonal betacoronaviruses are potentially an important factor in dictating COVID-19 severity, with anti-HR2-dominant Ab profiles representing protective memory responses, while an anti-S2FP dominant Ab profiles indicate deleterious recall responses. Though these profiles are masked in whole antigen profiling, these analyses suggest that distinct Ab memory responses are detectable with epitope targeting analysis. These findings have important implications for predicting severity of SARS-CoV-2 infections (primary and reinfections), and may predict vaccine efficacy in subpopulations with different dominant antibody epitope profiles.

microbiology↗

bioRxiv2019

Ovarian hormones mediate the prophylactic efficacy of (R,S)-ketamine and (2R,6R)-hydroxynorketamine in female mice

BACKGROUNDFemales are more likely than males to develop major depressive disorder (MDD) after exposure to stress. We previously reported that the administration of (R,S)-ketamine before stress can prevent stress-induced depressive-like behavior in male mice but have yet to assess efficacy in female mice or for other compounds, such as the metabolites of (R,S)-ketamine.\n\nMETHODSWe administered (R,S)-ketamine or its metabolites (2R,6R)-hydroxynorketamine ((2R,6R)-HNK) and (2S,6S)-HNK at various doses 1 week before one of a number of stressors, including contextual fear conditioning (CFC), learned helplessness (LH), and chronic immobilization stress (CIS), in male and female 129S6/SvEv mice. To examine the interaction between ovarian hormones and stress resilience, female mice also underwent ovariectomy surgery (OVX) and a hormone replacement protocol prior to drug administration.\n\nRESULTS(R,S)-ketamine and (2S,6S)-HNK, but not (2R,6R)-HNK, attenuated learned fear in male mice. (R,S)-ketamine and (2R,6R)-HNK, but not (2S,6S)-HNK, significantly reduced stress-induced depressive-like behavior in male and female mice. (R,S)-ketamine and (2R,6R)-HNK) were prophylactically effective at a lower dose (10 mg/kg and 0.025 mg/kg, respectively) in female mice than in male mice (30 mg/kg and 0.075 mg/kg, respectively). Moreover, ovarian-derived hormones were necessary and sufficient for prophylaxis in female mice.\n\nCONCLUSIONSOur results suggest that prophylactics against stress-induced depressive-like behavior can be developed in a sex-specific manner and that ovarian hormones mediate prophylactic efficacy in females. To our knowledge, this is the first demonstration of the prophylactic efficacy of the metabolites of (R,S)-ketamine in male and female mice.

neuroscience↗