Early life stress in male mice blunts responsiveness in a translationally-relevant reward task

Early-life stress (ELS) leaves signatures upon the brain that persist throughout the lifespan and increase the risk of psychiatric illnesses including mood and anxiety disorders. In humans, myriad forms of ELS-including childhood abuse, bullying, poverty, and trauma-are increasingly prevalent. Understanding the signs of ELS, including those associated with psychiatric illness, will enable improved treatment and prevention. Here, we developed a novel procedure to model human ELS in mice and identify translationally-relevant biomarkers of mood and anxiety disorders. We exposed male mice (C57BL/6 J) to an early-life (juvenile) chronic social defeat stress (jCSDS) and examined social interaction and responsivity to reward during adulthood. As expected, jCSDS-exposed mice showed a socially avoidant phenotype in open-field social interaction tests. However, sucrose preference tests failed to demonstrate ELS-induced reductions in choice for the sweetened solution, suggesting no effect on reward function. To explore whether other tasks might be more sensitive to changes in motivation, we tested the mice in the Probabilistic Reward Task (PRT), a procedure often used in humans to study reward learning deficits associated with depressive illness. In a touchscreen PRT variant that was reverse-translated to maximize alignment with the version used in human subjects, mice exposed to jCSDS displayed significant reductions in the tendency to develop response biases for the more richly-rewarded stimulus, a hallmark sign of anhedonia when observed in humans. Our findings suggest that translationally-relevant procedures that utilize the same endpoints across species may enable the development of improved model systems that more accurately predict outcomes in humans.

Histone H3 serotonylation dynamics in dorsal raphe nucleus contribute to stress- and antidepressant-mediated gene expression and behavior

Background

Major depressive disorder (MDD), along with related mood disorders, is a debilitating illness that affects millions of individuals worldwide. While chronic stress increases incidence levels of mood disorders, stress-mediated disruptions in brain function that precipitate these illnesses remain elusive. Serotonin-associated antidepressants (ADs) remain the first line of therapy for many with depressive symptoms, yet low remission rates and delays between treatment and symptomatic alleviation have prompted skepticism regarding precise roles for serotonin in the precipitation of mood disorders. Our group recently demonstrated that serotonin epigenetically modifies histone proteins (H3K4me3Q5ser) to regulate transcriptional permissiveness in brain. However, this phenomenon has not yet been explored following stress and/or AD exposures.

Methods

We employed a combination of genome-wide and biochemical analyses in dorsal raphe nucleus (DRN) of male and female mice exposed to chronic social defeat stress to examine the impact of stress exposures on H3K4me3Q5ser dynamics, as well as associations between the mark and stress-induced gene expression. We additionally assessed stress-induced regulation of H3K4me3Q5ser following AD exposures, and employed viral-mediated gene therapy to reduce H3K4me3Q5ser levels in DRN and examine the impact on stress-associated gene expression and behavior.

Results

We found that H3K4me3Q5ser plays important roles in stress-mediated transcriptional plasticity. Chronically stressed mice displayed dysregulated H3K4me3Q5ser dynamics in DRN, with both AD- and viral-mediated disruption of these dynamics proving sufficient to rescue stress-mediated gene expression and behavior.

Conclusions

These findings establish a neurotransmission-independent role for serotonin in stress-/AD-associated transcriptional and behavioral plasticity in DRN.

Automatically annotated motion tracking identifies a distinct social behavioral profile following chronic social defeat stress

Severe stress exposure increases the risk of stress-related disorders such as major depressive disorder (MDD). An essential characteristic of MDD is the impairment of social functioning and lack of social motivation. Chronic social defeat stress is an established animal model for MDD research, which induces a cascade of physiological and behavioral changes. Current markerless pose estimation tools allow for more complex and naturalistic behavioral tests. Here, we introduce the open-source tool DeepOF to investigate the individual and social behavioral profile in mice by providing supervised and unsupervised pipelines using DeepLabCut-annotated pose estimation data. Applying this tool to chronic social defeat in male mice, the DeepOF supervised and unsupervised pipelines detect a distinct stress-induced social behavioral pattern, which was particularly observed at the beginning of a novel social encounter and fades with time due to habituation. In addition, while the classical social avoidance task does identify the stress-induced social behavioral differences, both DeepOF behavioral pipelines provide a clearer and more detailed profile. Moreover, DeepOF aims to facilitate reproducibility and unification of behavioral classification by providing an open-source tool, which can advance the study of rodent individual and social behavior, thereby enabling biological insights and, for example, subsequent drug development for psychiatric disorders.

Genome-wide transcriptomics of the amygdala reveals similar oligodendrocyte-related responses to acute and chronic alcohol drinking in female mice

Repeated excessive alcohol consumption is a risk factor for alcohol use disorder (AUD). Although AUD has been more common in men than women, women develop more severe behavioral and physical impairments. However, relatively few new therapeutics targeting development of AUD, particularly in women, have been validated. To gain a better understanding of molecular mechanisms underlying alcohol intake, we conducted a genome-wide RNA-sequencing analysis in female mice exposed to different modes (acute vs chronic) of ethanol drinking. We focused on transcriptional profiles in the amygdala including the central and basolateral subnuclei, brain areas previously implicated in alcohol drinking and seeking. Surprisingly, we found that both drinking modes triggered similar changes in gene expression and canonical pathways, including upregulation of ribosome-related/translational pathways and myelination pathways, and downregulation of chromatin binding and histone modification. In addition, analyses of hub genes and upstream regulatory pathways revealed that voluntary ethanol consumption affects epigenetic changes via histone deacetylation pathways, oligodendrocyte and myelin function, and the oligodendrocyte-related transcription factor, Sox17. Furthermore, a viral vector-assisted knockdown of Sox17 gene expression in the amygdala prevented a gradual increase in alcohol consumption during repeated accesses. Overall, these results suggest that the expression of oligodendrocyte-related genes in the amygdala is sensitive to voluntary alcohol drinking in female mice. These findings suggest potential molecular targets for future therapeutic approaches to prevent the development of AUD, due to repeated excessive alcohol consumption, particularly in women.

Blood levels of T-Cell Receptor Excision Circles (TRECs) provide an index of exposure to traumatic stress in mice and humans

Exposure to stress triggers biological changes throughout the body. Accumulating evidence indicates that alterations in immune system function are associated with the development of stress-associated illnesses such as major depressive disorder and post-traumatic stress disorder, increasing interest in identifying immune markers that provide insight into mental health. Recombination events during T-cell receptor rearrangement and T-cell maturation in the thymus produce circular DNA fragments called T-cell receptor excision circles (TRECs) that can be utilized as indicators of thymic function and numbers of newly emigrating T-cells. Given data suggesting that stress affects thymus function, we examined whether blood levels of TRECs might serve as a quantitative peripheral index of cumulative stress exposure and its physiological correlates. We hypothesized that chronic stress exposure would compromise thymus function and produce corresponding decreases in levels of TRECs. In male mice, exposure to chronic social defeat stress (CSDS) produced thymic involution, adrenal hypertrophy, and decreased levels of TRECs in blood. Extending these studies to humans revealed robust inverse correlations between levels of circulating TRECs and childhood emotional and physical abuse. Cell-type specific analyses also revealed associations between TREC levels and blood cell composition, as well as cell-type specific methylation changes in CD4T + and CD8T + cells. Additionally, TREC levels correlated with epigenetic age acceleration, a common biomarker of stress exposure. Our findings demonstrate alignment between findings in mice and humans and suggest that blood-borne TRECs are a translationally-relevant biomarker that correlates with, and provides insight into, the cumulative physiological and immune-related impacts of stress exposure in mammals.

PACAP-PAC1R modulates fear extinction via the ventromedial hypothalamus

Exposure to traumatic stress can lead to fear dysregulation, which has been associated with posttraumatic stress disorder (PTSD). Previous work showed that a polymorphism in the PACAP-PAC1R (pituitary adenylate cyclase-activating polypeptide) system is associated with PTSD risk in women, and PACAP (ADCYAP1)-PAC1R (ADCYAP1R1) are highly expressed in the hypothalamus. Here, we show that female mice subjected to acute stress immobilization (IMO) have fear extinction impairments related to Adcyap1 and Adcyap1r1 mRNA upregulation in the hypothalamus, PACAP-c-Fos downregulation in the Medial Amygdala (MeA), and PACAP-FosB/ΔFosB upregulation in the Ventromedial Hypothalamus dorsomedial part (VMHdm). DREADD-mediated inhibition of MeA neurons projecting to the VMHdm during IMO rescues both PACAP upregulation in VMHdm and the fear extinction impairment. We also found that women with the risk genotype of ADCYAP1R1 rs2267735 polymorphism have impaired fear extinction.

Neurobiological Bases of Alcohol Consumption After Social Stress

The urge to seek and consume excessive alcohol is intensified by prior experiences with social stress, and this cascade can be modeled under systematically controlled laboratory conditions in rodents and non-human primates. Adaptive coping with intermittent episodes of social defeat stress often transitions to maladaptive responses to traumatic continuous stress, and alcohol consumption may become part of coping responses. At the circuit level, the neural pathways subserving stress coping intersect with those for alcohol consumption. Increasingly discrete regions and connections within the prefrontal cortex, the ventral and dorsal striatum, thalamic and hypothalamic nuclei, tegmental areas as well as brain stem structures begin to be identified as critical for reacting to and coping with social stress while seeking and consuming alcohol. Several candidate molecules that modulate signals within these neural connections have been targeted in order to reduce excessive drinking and relapse. In spite of some early clinical failures, neuropeptides such as CRF, opioids, or oxytocin continue to be examined for their role in attenuating stress-escalated drinking. Recent work has focused on neural sites of action for peptides and steroids, most likely in neuroinflammatory processes as a result of interactive effects of episodic social stress and excessive alcohol seeking and drinking.

Hypoactive Thalamic Crh+ Cells in a Female Mouse Model of Alcohol Drinking After Social Trauma

BACKGROUND

Comorbid stress-induced mood and alcohol use disorders are increasingly prevalent among female patients. Stress exposure can disrupt salience processing and goal-directed decision making, contributing to persistent maladaptive behavioral patterns; these and other stress-sensitive cognitive and behavioral processes rely on dynamic and coordinated signaling by midline and intralaminar thalamic nuclei. Considering the role of social trauma in the trajectory of these debilitating psychopathologies, identifying vulnerable thalamic cells may provide guidance for targeting persistent stress-induced symptoms.

METHODS

A novel behavioral protocol traced the progression from social trauma to the development of social defensiveness and chronically escalated alcohol consumption in female mice. Recent cell activation-measured as cFos-was quantified in thalamic cells after safe social interactions, revealing stress-sensitive corticotropin-releasing hormone-expressing (Crh+) anterior central medial thalamic (aCMT) cells. These cells were optogenetically stimulated during stress-induced social defensiveness and abstinence-escalated binge drinking.

RESULTS

Crh+ aCMT neurons exhibited substantial activation after social interactions in stress-naïve but not in stressed female mice. Photoactivating Crh+ aCMT cells dampened stress-induced social deficits, whereas inhibiting these cells increased social defensiveness in stress-naïve mice. Optogenetically activating Crh+ aCMT cells diminished abstinence-escalated binge alcohol drinking in female mice, regardless of stress history.

CONCLUSIONS

This work uncovers a role for Crh+ aCMT neurons in maladaptive stress-induced social interactions and in binge drinking after forced abstinence in female mice. This molecularly defined thalamic cell population may serve as a critical stress-sensitive hub for social deficits caused by exposure to social trauma and for patterns of excessive alcohol drinking in female populations.

Fighting Females: Neural and Behavioral Consequences of Social Defeat Stress in Female Mice

BACKGROUND

Despite the twofold higher prevalence of major depressive and posttraumatic stress disorders in women compared with men, most clinical and preclinical studies have focused on male subjects. We used an ethological murine model to study several cardinal symptoms of affective disorders in the female targets of female aggression.

METHODS

Intact Swiss Webster (CFW) female resident mice were housed with castrated male mice and tested for aggression toward female intruders. For 10 days, aggressive CFW female residents defeated C57BL/6J (B6) female intruders during 5-minute encounters. Measures of corticosterone, c-Fos activation in hypothalamic and limbic structures, and species-typical behaviors were collected from defeated and control females. Ketamine (20 mg/kg) was tested for its potential to reverse stress-induced social deficits.

RESULTS

Housed with a castrated male mouse, most intact resident CFW females readily attacked unfamiliar B6 female intruders, inflicting >40 bites in a 5-minute encounter. Compared with controls, defeated B6 females exhibited elevated plasma corticosterone and increased c-Fos activation in the medial amygdala, ventral lateral septum, ventromedial hypothalamus, and hypothalamic paraventricular nucleus. Chronically defeated females also showed vigilance-like behavior and deficits in social interactions, novel object investigation, and nesting. The duration of social interactions increased 24 hours after chronically defeated female mice received a systemic dose of ketamine.

CONCLUSIONS

These findings demonstrate that CFW female mice living with male conspecifics can be used as aggressive residents in an ethological model of female social defeat stress. These novel behavioral methods will encourage further studies of sex-specific neural, physiological, and behavioral adaptations to chronic stress and the biological bases for interfemale aggression.

Translational models of adaptive and excessive fighting: an emerging role for neural circuits in pathological aggression

Aggression is a phylogenetically stable behavior, and attacks on conspecifics are observed in most animal species. In this review, we discuss translational models as they relate to pathological forms of offensive aggression and the brain mechanisms that underlie these behaviors. Quantifiable escalations in attack or the development of an atypical sequence of attacks and threats is useful for characterizing abnormal variations in aggression across species. Aggression that serves as a reinforcer can be excessive, and certain schedules of reinforcement that allow aggression rewards also allow for examining brain and behavior during the anticipation of a fight. Ethological attempts to capture and measure offensive aggression point to two prominent hypotheses for the neural basis of violence. First, pathological aggression may be due to an exaggeration of activity in subcortical circuits that mediate adaptive aggressive behaviors as they are triggered by environmental or endogenous cues at vulnerable time points. Indeed, repeated fighting experiences occur with plasticity in brain areas once considered hardwired. Alternatively, a separate "violence network" may converge on aggression circuitry that disinhibits pathological aggression (for example, via disrupted cortical inhibition). Advancing animal models that capture the motivation to commit pathological aggression remains important to fully distinguish the neural architecture of violence as it differs from adaptive competition among conspecifics.

Social defeat stress and escalation of cocaine and alcohol consumption: Focus on CRF

Both the ostensibly aversive effects of unpredictable episodes of social stress and the intensely rewarding effects of drugs of abuse activate the mesocorticolimbic dopamine systems. Significant neuroadaptations in interacting stress and reward neurocircuitry may underlie the striking connection between stress and substance use disorders. In rodent models, recurring intermittent exposure to social defeat stress appears to produce a distinct profile of neuroadaptations that translates most readily to the repercussions of social stress in humans. In the present review, preclinical rodent models of social defeat stress and subsequent alcohol, cocaine or opioid consumption are discussed with regard to: (1) the temporal pattern of social defeat stress, (2) male and female protocols of social stress-escalated drug consumption, and (3) the neuroplastic effects of social stress, which may contribute to escalated drug-taking. Neuroadaptations in corticotropin-releasing factor (CRF) and CRF modulation of monoamines in the ventral tegmental area and the bed nucleus of the stria terminalis are highlighted as potential mechanisms underlying stress-escalated drug consumption. However, the specific mechanisms that drive CRF-mediated increases in dopamine require additional investigation as do the stress-induced neuroadaptations that may contribute to the development of compulsive patterns of drug-taking.

The Urge to Fight: Persistent Escalation by Alcohol and Role of NMDA Receptors in Mice

Alcohol drinking, in some individuals, culminates in pathologically aggressive and violent behaviors. Alcohol can escalate the urge to fight, despite causing disruptions in fighting performance. When orally administered under several dosing conditions the current study examined in a mouse model if repeated alcohol escalates the motivation to fight, the execution of fighting performance, or both. Specifically, seven daily administrations of alcohol (0, 1.8, or 2.2 g/kg) determined if changes in the motivation to initiate aggressive acts occur with, or without, shifts in the severity of fighting behavior. Responding under the control of a fixed interval (FI) schedule for aggression reinforcements across the initial daily sessions indicated the development of tolerance to alcohol's sedative effect. By day 7, alcohol augmented FI response rates for aggression rewards. While alcohol escalated the motivation to fight, fighting performance remained suppressed across the entire 7 days. Augmented FI responding for aggression rewards in response to a low dose of alcohol (1.0 g/kg) proved to be persistent, as we observed sensitized rates of responding for more than a month after alcohol pretreatment. In addition, this sensitization of motivated aggression did not occur with a general enhancement of motor activity. Antagonism of NMDA or AMPA receptors with ketamine, dizocilpine, or NBQX during later challenges with alcohol were largely serenic without having any notable impact on the expression of alcohol-escalated rates of FI responding. The current dissociation of appetitive and performance measures indicates that discrete neural mechanisms controlling aggressive arousal can be distinctly sensitized by alcohol.

Persistent escalation of alcohol consumption by mice exposed to brief episodes of social defeat stress: suppression by CRF-R1 antagonism

RATIONALE

Episodic bouts of social stress can precede the initiation, escalation, or relapse to disordered alcohol intake. Social stress may engender neuroadaptations in the hypothalamic-pituitary-adrenal (HPA) axis and in extrahypothalamic stress circuitry to promote the escalation of alcohol intake.

OBJECTIVES

We aimed to (1) confirm a pattern of escalated drinking in socially defeated mice and to (2) test drugs that target distinct aspects of the HPA axis and extrahypothalamic neural substrates for their effectiveness in reducing murine, stress-escalated drinking.

METHODS

Male C57BL/6J (B6) mice were socially defeated by resident Swiss-derived males for ten consecutive days receiving 30 bites/day. Ten days after the final defeat, cohorts of B6 mice received continuous or intermittent access to 20% EtOH (w/v) and water. After 4 weeks of drinking, mice were injected with weekly, systemic doses of the CRF-R1 antagonist, CP376395; the glucocorticoid receptor antagonist, mifepristone; the 11-beta-hydroxylase inhibitor, metyrapone; or the 5-alpha-reductase inhibitor, finasteride.

RESULTS

Prior to drug treatments, defeated mice reliably consumed more EtOH than non-defeated controls, and mice given alcohol intermittently consumed more EtOH than those with continuous access. CP376395 (17-30 mg/kg) reduced continuous, but not intermittent EtOH intake (g/kg) in socially defeated mice. Mifepristone (100 mg/kg), however, increased drinking by defeated mice with intermittent access to alcohol while reducing drinking during continuous access. When administered finasteride (100 mg/kg) or metyrapone (50 mg/kg), all mice reduced their EtOH intake while increasing their water consumption.

CONCLUSIONS

Mice with a history of episodic social defeat stress were selectively sensitive to the effects of CRF-R1 antagonism, suggesting that CRF-R1 may be a potential target for treating alcohol use disorders in individuals who escalate their drinking after exposure to repeated bouts of psychosocial stress. Future studies will clarify how social defeat stress may alter the expression of extrahypothalamic CRF-R1 and glucocorticoid receptors.

A Role for Prefrontal Cortical NMDA Receptors in Murine Alcohol-Heightened Aggression

Alcohol is associated with nearly half of all violent crimes committed in the United States; yet, a potential neural basis for this type of pathological aggression remains elusive. Alcohol may act on N-methyl-d-aspartate receptors (NMDARs) within cortical circuits to impede processing and to promote aggression. Here, male mice were characterized as alcohol-heightened (AHAs) or alcohol non-heightened aggressors (ANAs) during resident-intruder confrontations after self-administering 1.0 g/kg alcohol (6% w/v) or water. Alcohol produced a pathological-like pattern of aggression in AHAs; these mice shifted their bites to more vulnerable locations on the body of a submissive animal, including the anterior back and ventrum after consuming alcohol. In addition, through immunoblotting, we found that AHAs overexpressed the NMDAR GluN2D subunit in the prefrontal cortex (PFC) as compared to ANAs while the two phenotypes expressed similar levels of GluN1, GluN2A and GluN2B. After identifying several behavioral and molecular characteristics that distinguish AHAs from ANAs, we tested additional mice for their aggression following preferential antagonism of GluN2D-containing NMDARs. In these experiments, groups of AHAs and ANAs self-administered 1.0 g/kg alcohol (6% w/v) or water before receiving intraperitoneal (i.p.) doses of ketamine or memantine, or infusions of memantine directly into the prelimbic (PLmPFC) or infralimbic medial PFC (ILmPFC). Moderate doses of IP ketamine, IP memantine, or intra-PLmPFC memantine increased aggression in AHAs, but only in the absence of alcohol. Prior alcohol intake blocked the pro-aggressive effects of ketamine or memantine. In contrast, only memantine, administered systemically or intra-PLmPFC, interacted with prior alcohol intake to escalate aggression in ANAs. Intra-ILmPFC memantine had no effect on aggression in either AHAs or ANAs. In sum, this work illustrates a potential role of GluN2D-containing NMDARs in the PLmPFC in alcohol-heightened aggression. GluN2D-containing NMDARs are highly expressed on cortical parvalbumin-containing interneurons, suggesting that, in a subset of individuals, alcohol may functionally alter signal integration within cortical microcircuits to dysregulate threat reactivity and promote aggression. This work suggests that targeting GluN2D-NMDARs may be of use in reducing the impact of alcohol-related violence in the human population.

Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice

BACKGROUND

Alcohol use disorders are associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABA_A receptor α2-subunit in humans. Deficient GABAergic functioning is linked to impulse control disorders, intermittent explosive disorder, and to drug abuse and dependence, yet it remains unclear whether α2-containing GABA_A receptor sensitivity to endogenous ligands is involved in excessive alcohol drinking.

METHODS

Male wild-type (Wt) C57BL/6J and point-mutated mice rendered insensitive to GABAergic modulation by benzodiazepines (BZD; H101R), allopregnanolone (ALLO) or tetrahydrodeoxycorticosterone (THDOC; Q241M), or high concentrations of ethanol (EtOH) (S270H/L277A) at α2-containing GABA_A receptors were assessed for their binge-like, moderate, or escalated chronic drinking using drinking in the dark, continuous access (CA) and intermittent access (IA) to alcohol protocols, respectively. Social approach by mutant and Wt mice in forced alcohol abstinence was compared to approach by EtOH-naïve controls. Social deficits in forced abstinence were treated with allopregnanolone (0, 3.0, 10.0 mg/kg, intraperitoneal [i.p.]) or midazolam (0, 0.56, 1.0 mg/kg, i.p.).

RESULTS

Mice with BZD-insensitive α2-containing GABA_A receptors (H101R) escalated their binge-like drinking. Mutants harboring the Q241M point substitution in Gabra2 showed blunted chronic intake in the CA and IA protocols. S270H/L277A mutants consumed excessive amounts of alcohol but, unlike wild-types, they did not show forced abstinence-induced social deficits.

CONCLUSIONS

These findings suggest a role for: (i) H101 in species-typical binge-like drinking, (ii) Q241 in escalated chronic drinking, and (iii) S270 and/or L277 in the development of forced abstinence-associated social deficits. Clinical findings report reduced BZD-binding sites in the cortex of dependent patients; the present findings suggest a specific role for BZD-sensitive α2-containing receptors. In addition, amino acid residue 241 in Gabra2 is necessary for positive modulation and activation of GABA_A receptors by ALLO and THDOC; we postulate that neurosteroid action on α2-containing receptor may be necessary for escalated chronic EtOH intake.

Alcohol and violence: neuropeptidergic modulation of monoamine systems

Neurobiological processes underlying the epidemiologically established link between alcohol and several types of social, aggressive, and violent behavior remain poorly understood. Acute low doses of alcohol, as well as withdrawal from long-term alcohol use, may lead to escalated aggressive behavior in a subset of individuals. An urgent task will be to disentangle the host of interacting genetic and environmental risk factors in individuals who are predisposed to engage in escalated aggressive behavior. The modulation of 5-hydroxytryptamine impulse flow by gamma-aminobutyric acid (GABA) and glutamate, acting via distinct ionotropic and metabotropic receptor subtypes in the dorsal raphe nucleus during alcohol consumption, is of critical significance in the suppression and escalation of aggressive behavior. In anticipation and reaction to aggressive behavior, neuropeptides such as corticotropin-releasing factor, neuropeptide Y, opioid peptides, and vasopressin interact with monoamines, GABA, and glutamate to attenuate and amplify aggressive behavior in alcohol-consuming individuals. These neuromodulators represent novel molecular targets for intervention that await clinical validation. Intermittent episodes of brief social defeat during aggressive confrontations are sufficient to cause long-lasting neuroadaptations that can lead to the escalation of alcohol consumption.

Aggression and increased glutamate in the mPFC during withdrawal from intermittent alcohol in outbred mice

RATIONALE

Disrupted social behavior, including occasional aggressive outbursts, is characteristic of withdrawal from long-term alcohol (EtOH) use. Heavy EtOH use and exaggerated responses during withdrawal may be treated using glutamatergic N-methyl-D-aspartate receptor (NMDAR) antagonists.

OBJECTIVES

The current experiments explore aggression and medial prefrontal cortex (mPFC) glutamate as consequences of withdrawal from intermittent access to EtOH and changes in aggression and mPFC glutamate caused by NMDAR antagonists memantine and ketamine.

METHODS

Swiss male mice underwent withdrawal following 1-8 weeks of intermittent access to 20 % EtOH. Aggressive and nonaggressive behaviors with a conspecific were measured 6-8 h into EtOH withdrawal after memantine or ketamine (0-30 mg/kg, i.p.) administration. In separate mice, extracellular mPFC glutamate after memantine was measured during withdrawal using in vivo microdialysis.

RESULTS

At 6-8 h withdrawal from EtOH, mice exhibited more convulsions and aggression and decreased social contact compared to age-matched water controls. Memantine, but not ketamine, increased withdrawal aggression at the 5-mg/kg dose in mice with a history of 8 weeks of EtOH but not 1 or 4 weeks of EtOH or in water drinkers. Tonic mPFC glutamate was higher during withdrawal after 8 weeks of EtOH compared to 1 week of EtOH or 8 weeks of water. Five milligrams per kilogram of memantine increased glutamate in 8-week EtOH mice, but also in 1-week EtOH and water drinkers.

CONCLUSIONS

These studies reveal aggressive behavior as a novel symptom of EtOH withdrawal in outbred mice and confirm a role of NMDARs during withdrawal aggression and for disrupted social behavior.

NMDA receptor antagonism: escalation of aggressive behavior in alcohol-drinking mice

RATIONALE

Memantine is a potential treatment for alcoholic patients, yet few studies investigate the effect of concurrent treatment with memantine and ethanol on aggression. We evaluated aggressive behavior following ethanol consumption and treatment with glutamatergic drugs to characterize interactions between these compounds.

OBJECTIVE

This study aimed to use rodent models of aggression to examine interactions between glutamatergic compounds and ethanol.

MATERIALS AND METHODS

Once male CFW mice reliably self-administered 1 g/kg ethanol or water, they were assessed for aggression in resident-intruder confrontations. Alternatively, aggression was evaluated following a social-instigation procedure. Animals were then injected with memantine, ketamine, neramexane, MTEP, or LY379268 before aggressive confrontations. Effects of the pharmacological manipulations on salient aggressive and non-aggressive behaviors were analyzed.

RESULTS

Moderate doses of memantine, neramexane, and MTEP interacted with ethanol to increase the frequency of attack bites while ketamine did not. The highest dose of LY379268, an mGluR(2/3) agonist, reduced both aggressive and non-aggressive behaviors after water and ethanol self-administration. Attack bites increased with social instigation and decreased with administration of high doses of MTEP and LY379268. Memantine and MTEP both reduced attack bite frequency in the instigation condition without reducing locomotor behavior.

CONCLUSIONS

Memantine and neramexane interacted with ethanol to heighten aggression. The binding characteristics of these compounds allow for 'partial trapping' by which some NMDARs are unblocked between depolarizations. We propose that this feature may contribute to the differential aggression-heightening interactions between these compounds and ethanol. MTEP also interacted with ethanol to escalate aggression, possibly through inhibition of mGluR(5) modulation of NMDARs.

Cytotoxicity of electro-surgical smoke produced in an anoxic environment

BACKGROUND

The effect on cell viability of smoke produced during high-frequency electro-surgery has not been previously reported. The aim of this study was to produce smoke in vitro, in a closed environment similar to that encountered in minimal access surgery, and to test its cytotoxic effects on cultured cells.

METHODS

Pig liver was cut repeatedly with an electro-surgical hook knife, and the smoke generated was collected and equilibrated with cell culture medium. MCF-7 human breast carcinoma cells were exposed briefly to various dilutions of this medium and tested for clonogenicity.

RESULTS

Electro-surgical smoke produced in a helium environment reduced the clonogenicity of the MCF-7 human breast carcinoma cells in a dose-dependent manner, falling to 30% when the cells were exposed to undiluted medium for 15 minutes.

CONCLUSIONS

We conclude that electro-surgical smoke is cytotoxic. The sublethal effects at lower dilutions are currently being investigated.

Time-dependent photodynamic damage to blood vessels: correlation with serum photosensitizer levels

We have used the technique of dynamic capillaroscopy to study the time-course of photodynamic vascular occlusion in mice injected intraperitoneally with either of two photosensitizers; hematoporphyrin esters (HPE) or meso-tetrahydroxyphenyl chlorin (mTHPC). The peak of vascular occlusion induced by HPE coincided in time with peak serum levels of this photosensitizer (about 3 h after injection). However, there was also a second peak of occlusive activity at about 12 h after injection, at which time serum HPE was falling monotonically. In the case of mTHPC, no peak of occlusive activity was seen at 3 h after injection, even though the serum levels of this photosensitizer, like those of HPE, were highest around this time. Instead, a steady rise in photosensitizing activity was observed, peaking at 11 h. This decoupling between serum drug levels and vascular photosensitization--partial for HPE and complete for mTHPC-suggests that direct photosensitization of endothelial cells is unlikely wholly to explain the vascular collapse. Instead, there must be either another compartment that accumulates photosensitizer more slowly and in which photodynamic activity has an indirect effect on the blood capillaries or a slow metabolic transformation of mTHPC into a more active sensitizer.

Photosensitizer targeting in photodynamic therapy. II. Conjugates of haematoporphyrin with serum lipoproteins

Conjugates between haematoporphyrin (HP) and human low-density lipoprotein (LDL), human high-density lipoprotein (HDL) and bovine HDL have been prepared, purified and characterized. HP-LDL is aggregated possibly via interparticle apoB protein cross-linking. HP-HDL human and bovine conjugates show different degrees of intraparticle apoA polypeptide cross-linking. Receptor-mediated endocytosis of HP-LDL by NIH 3T3 cells is inferred from the increased uptake observed when LDL receptors are upregulated. HP-LDL uptake into HT29 cells faces competition from unlabelled LDL, albeit at rather high doses. HP-HDL uptake is also inhibited by LDL, suggesting that both lipoprotein conjugates may have cell-surface binding sites in addition to the specific LDL (apoB) receptor. J774.2 macrophages avidly accumulate HP-LDL, retaining most of the fluorescence and some of the protein while degrading the remainder. Oxidized LDL species compete in these processes, with the major effect on protein degradation. Chloroquine has little effect on the fluorescence uptake but inhibits protein degradation (and hence enhances protein accumulation). HP-HDL is also avidly taken up by J774.2 cells, but in the case of the bovine material with a sigmoidal concentration dependence. This is consistent with prior aggregation before the particles can be endocytosed. P388.D1 cells, which appear to be less activated than the J774.2 line, take up less fluorescence and retain and degrade less protein, but still to higher extents than observed for non-phagocytic cells. We conclude that photosensitizer-lipoprotein conjugates can be taken up in large amounts by cells possessing scavenger receptors and/or phagocytic activity, and that this may be a means of targeting photodynamic therapy.

Photosensitizer targeting in photodynamic therapy. I. Conjugates of haematoporphyrin with albumin and transferrin

Conjugates of haematoporphyrin (HP) with serum albumin and transferrin were prepared, purified by gel filtration and characterized by high performance liquid chromatography (HPLC), polyacrylamide gel electrophoresis (PAGE) and spectroscopy. Although the fluorescence was somewhat quenched, the conjugates had similar singlet oxygen quantum yields to free porphyrin. The albumin conjugate (HP-BSA) could be divided into monomeric and cross-linked fractions. In NIH 3T3 and HT29 cells, native albumin could not compete with the uptake of HP-BSA and the uptake was greatly enhanced in the absence of serum and in the presence of poly-L-lysine. We infer that the conjugate was mostly associated with the plasma membrane in these cells. The uptake of HP-transferrin showed evidence of a receptor-mediated component in that it was partially inhibited by native protein and increased when transferrin receptors were upregulated by an iron chelator. J774 macrophage-like cells accumulated fluorescence from HP-BSA to a much higher degree than HT29 cells, even though the protein was extensively degraded (HT29 cells did not appear to degrade the protein). The time course of the photocytotoxicity of HP-BSA was prolonged in J774 cells, although their response to free porphyrins was similar to that seen in HT29 cells. Chloroquine inhibited protein degradation without having an effect on the fluorescence uptake. J774 cells acquired more fluorescence and degraded more protein when supplied with cross-linked HP-BSA compared with monomeric fraction. For a given fluorescence uptake, the cross-linked fraction was also more photocytotoxic. We conclude that macrophages can acquire photosensitizer-protein conjugates avidly and that these are delivered to the lysosomes. These types of conjugate may have applications in targeting fluorescent molecules for diagnostic imaging and for the photodynamic treatment of macrophage malignancies.

The prognostic significance of the accumulation of p53 tumour-suppressor gene protein in gastric adenocarcinoma

We have studied the expression of p53 in 206 patients with gastric adenocarcinomas. A standard immunohistochemical technique employing the CM-1 anti-p53 polyclonal antibody was applied to the routinely fixed and paraffin-embedded material from these tumours; overexpression of p53 was defined as positive nuclear staining: 46% (94/206) of gastric carcinomas expressed high levels of p53. There was no significant correlation between p53 positivity and the tumour grade, growth pattern, the Lauren type or lymph node metastases. Correlation with disease stage was only marginally significant (P = 0.05). Life table analysis revealed a highly significant association between p53 expression and survival (P = 0.0062), the odds ratio of death being 1.89 (95% confidence interval 1.33-2.69). The overall 5-year survival of patients with p53-positive tumours was 3% compared with 16% for those with p53-negative tumours (median survival time being 5.6 and 11.4 months respectively). These data suggest that overexpression of the p53 oncoprotein is an independent marker of shortened survival in gastric cancer patients.

On the mechanism of the tumour-localising effect in photodynamic therapy

The proposed mechanisms by which tumours concentrate photosensitisers are reviewed. Tumour-associated macrophages have been shown by others to accumulate up to nine times the level of porphyrins as do tumour cells. Macrophages also take up and degrade oxidised or otherwise modified low-density lipoprotein (LDL). We propose that the interaction of photosensitisers with LDL is an important factor, leading to accumulation in macrophages. Uptake into these cells via liposomes and high-density lipoprotein is also possible. There may be three separate mechanisms for tumour destruction in photodynamic therapy: (i) direct damage to tumour cells; (ii) damage to the endothelial cells of the tumour microvasculature; and (iii) macrophage-mediated immune infiltration of the tumour. The association of photosensitisers with lipoproteins may accentuate the latter two (endothelial cells can also accumulate modified lipoproteins). Accumulation in macrophages may also largely explain the high porphyrin retention observed in atheromatous plaques.

Immunoscintigraphy of primary colorectal cancers with indium-111 monoclonal antibody B72.3

Immunoscintigraphy with CYT-103, an 111indium-labelled immunoconjugate of B72.3, was evaluated in 10 patients before surgery for suspected or biopsy-proven primary colorectal cancer. The imaging results were compared with computed tomography (CT) findings at surgery, histopathology and immunohistochemistry. There were no adverse reactions following the administration of 1.0 mg 111In-CYT-103. Surgical and pathological findings identified 15 sites of disease (10 primary and five metastatic) and all but one lesion (severe dysplasia) were malignant. CT detected nine of 14 sites of malignancy compared to 12 as identified by immunoscintigraphy. It failed to detect two primary lesions and one case of peritoneal metastasis, all of which were imaged by CYT-103. Both imaging modalities failed to detect two of three cases with lymph node metastases and the dysplastic lesion (true negatives). The results indicate that 111In-CYT-103 imaging exhibits high sensitivity and specificity in the detection of primary and secondary lesions in patients with colorectal cancer.

Dynamic capillaroscopy: a minimally invasive technique for assessing photodynamic effects in vivo

A noninvasive method for visualizing the microvasculature in the mouse tail is described, consisting of a custom-built microscope with through-lens illumination. The microscope is fitted with a television camera and images can be recorded on videotape and displayed on a television monitor. Blood vessels are imaged as columns of red blood cells, in which flow is clearly observed. Administration of photosensitizers and illumination with the standard light source produces no observable photodynamic effect on blood flow. The combination of photosensitizer and a more intense light source (either broadband light from a filtered mercury arc or red light from a laser) causes photodynamic cessation of flow within a few minutes. The magnitude of the effect is dependent on the dose and nature of the photosensitizer, the delay after photosensitization and the match between the laser light and the absorption spectra of the photosensitizers in the red region. We conclude that the technique yields results consistent with the known photodynamic effects of the photosensitizers in tumors and propose its use as an initial screening method in vivo, as a means of conducting pharmacokinetic experiments and as an assay of prolonged cutaneous photosensitivity.

Enzyme-linked immunosorbent assay for p53 in gastrointestinal malignancy: comparison with immunohistochemistry

Mutations in the p53 nuclear oncogene occur frequently in a wide spectrum of human malignancies and the mutant protein may prove to be a useful diagnostic or prognostic marker. It can be detected in fixed tissues by immunohistochemistry, but the type of fixative and conditions of fixation used can introduce variability. For routine clinical use, a method of analysis which is more easily standardized would, therefore, be of benefit. A two-site enzyme-linked immunosorbent assay (ELISA) was used to measure the level of p53 protein in soluble extracts from 20 gastrointestinal cancers (11 colonic, nine gastric). Immunohistochemistry was also performed on the paraffin-embedded sections of these tumours and the results of the two assays were compared. ELISA detected p53 at various levels in 10 cases, all of which were also positive by immunohistochemistry. Of the other 10, eight were immunohistochemically negative but two were positive. When the immunohistochemically positive specimens were ranked by scoring the degree of staining, there was a highly significant correlation with the quantitative ELISA results. Our study shows that the ELISA is sensitive and highly specific. It offers an alternative and simple method of assessing the p53 status in human tissues.

Monoclonal antibodies to cytoskeletal proteins: an immunohistochemical investigation of human colon cancer

Monoclonal antibodies raised to a number of microfilament-associated proteins were shown to recognize the appropriate proteins in extracts from human colon tissue. They were then used in an immunohistochemical study of normal colonic mucosa, adenomas, and adenocarcinomas. A strong reaction was seen in stromal cells within the tumours (both adenomas and adenocarcinomas) when frozen sections were stained with antibodies to filamin and caldesmon. In addition, a similar reaction was seen in the adenocarcinomas when stained with antibodies to talin and gelsolin. We believe that immunohistochemical staining with these antibodies reveals a tumour-induced process in the surrounding cells, possibly related to a host response to tumours.

Expression of p53 protein in normal, dysplastic, and malignant gastric mucosa: an immunohistochemical study

Mutations in the p53 nuclear oncogene are the most frequent genetic abnormalities encountered in human malignancies. Using the polyclonal antibody CM-1, we have examined the expression of the p53 oncoprotein immunohistochemically in archival material of normal, dysplastic, and malignant gastric mucosa. Abnormal expression of this protein was not observed in biopsies of normal gastric tissue (n = 30) but was detected in 22 of the 36 gastric cancers analysed (61 per cent). Nuclear staining was diffuse in 15 of the positive cancer cases, the remaining seven showing a more varied heterogeneous staining pattern. Abnormal p53 protein was not detected in mild (n = 14) or moderate (n = 16) gastric dysplasia but was present in 3 out of 15 severe dysplasia cases. The results suggest that expression of the p53 oncoprotein is a common finding in gastric cancer and occurs as a late event in the malignant transformation process.

Tamoxifen metabolism is altered by simultaneous administration of medroxyprogesterone acetate in breast cancer patients

We have measured the levels of tamoxifen and three of its metabolites in the blood of patients receiving tamoxifen alone or combination therapy with tamoxifen and medroxyprogesterone acetate. Our results indicate that addition of the progestogen significantly alters the metabolism of tamoxifen over a six-month period. We suggest that the interaction between these drugs may involve additional sites (probably hepatic) besides the desired target tumour.

Semi-permeable microcapsules for cell culture: ultra-structural characterization

Microcapsules made from alginate-poly(L-lysine)-alginate membranes have been studied as vehicles for cell culture in a number of laboratories. We have examined their permeability, robustness and ultrastructure in detail. Permeability to globular proteins could be controlled by using poly-lysine of different mean MW in their construction. However, this parameter also affected the degree to which microencapsulated living cells leaked out of the capsules during and after preparation. Poly-lysine of low MW produced a relatively permeable and robust membrane whereas a high MW produced capsules with the reverse characteristics. A MW of 22,000 appears to be optimal in forming robust capsules which are relatively impermeable to high MW species such as immunoglobulins. The structure of the semipermeable membrane was investigated by electron microscopy and found to be complex but entirely consistent with the data on protein permeability and cell leakage. Microcapsules were not disrupted by gentle treatment with trypsin or chelating agents but dissolved with the addition of heparin, sodium dodecyl sulphate or sodium hydroxide. Empty microcapsules implanted into the peritoneal cavity of rats elicited a host cellular reaction but remained intact for at least three months.

Microencapsulation of human cells: its effects on growth of normal and tumour cells in vitro

The growth kinetics of established human colorectal tumour cell lines (HT29, HT115 and COLO 320DM) and human diploid fibroblasts (Flow 2002) were studied in conventional culture and in microcapsules formed from alginate-poly(L-lysine)-alginate membranes. The tumour lines grew rapidly in microcapsules but, in the case of the substrate-adherent lines HT29 and HT115, only after a prolonged lag phase. This phase was reduced by serial passage in microcapsules. The anchorage-independent line COLO 320DM showed no lengthening in lag phase. Microencapsulated fibroblasts underwent negligible growth but remained viable. Some evidence for functional differentiation (microvilli, cell-cell junctions) of the tumour line HT115 within the microcapsules was observed. We conclude that the use of microcapsules provides an alternative system with some advantages for the study of human cancer and its metastases in vitro.

Bradykinin blocks the action of EGF, but not PDGF, on fibroblast division

Quiescent fibroblasts derived from human fetal lung can be stimulated to reinitiate DNA synthesis by sequential addition of 3 nM IGF-1 and a low concentration (8 pM) of EGF or by continuous exposure to 10% fetal calf serum or 10 ng/ml PDGF. Bradykinin blocks the IGF-1 and EGF-dependent signals without affecting the response to serum or PDGF. It activates protein kinase C and its anti-mitogenic effect is abolished after this kinase has been down-regulated. Bradykinin has no effect on the binding affinity of the EGF receptor whereas phorbol ester induces its 'transmodulation' to low affinity.

Mu-receptor specificity of the opioid peptide irreversible reagent, [3H]DALECK

A novel affinity reagent DALECK, i.e. D-Ala2-Leu5-enkephalin with a C-terminal chloromethyl ketone group, was previously synthesized in normal and in tritiated form and shown to react irreversibly at opioid receptors, with some evidence for selectivity for the mu subtype. DALECK tritiated in its phenolic group has been synthesized at 13-fold higher specific radioactivity than in the previous study. In the irreversible reaction of this product at pH 8.1 with rat brain membranes it was confirmed that only one polypeptide there is labelled, of apparent Mr 58,000. Competition between this reaction and ligands highly selective for the mu, delta or kappa binding sites yielded curves demonstrating the very high selectivity of the DALECK irreversible reaction for the mu site. The results provide evidence that the mu opioid receptor protein contains only one type of binding subunit, whose apparent Mr is 58,000, this size being dependent upon the conditions used in the gel electrophoresis and being higher when stringent conditions which would reduce all internal disulphide bonds are applied.

Differential recovery of antibody production potential after sublethal, whole-body irradiation of mice

Mice were given single injections of sheep erythrocytes (SE) or polyvinylpyrrolidone (PVP) at various times after sublethal, whole-body irradiation (550 rad 60CO) and direct, antigen-specific, plaque-forming cell (PFC) responses were quantified. Irradiated mice did not respond to SE or PVP when immunized 15 d postirradiation (PI); by day 30 PI, the responses by irradiated mice were 40-126% of normal to SE and 3-38% of normal to PVP. The impaired recovery after irradiation of immune responses to PVP was not due to altered antigen dose requirements or altered time of peak PFC response and occurred after irradiation of mice by doses as low as 200 rad. Both athymic and euthymic mice had impaired responses to PVP after whole-body irradiation. The impaired response of irradiated mice to PVP was repaired by adoptive transfer of normal bone marrow, fetal liver, or spleen cells and also by spleen cell preparations enriched in Ig+ cells but not by spleen cell preparations enriched in Thy.1+ or Ig- cells. With the aid of additional antigens it was observed that by day 30 PI, mice had recovered ability to respond to the T-cell-dependent antigen SE and the T-cell-independent type-1 antigens 2,4,6-trinitrophenyl-Brucella abortus and butanol-extracted bacterial lipopolysaccharide, but at that time they gave impaired responses to the T-cell-independent type-2 antigens PVP, type III pneumococcal polysaccharide, and phenol-extracted bacterial lipopolysaccharide; they had an immune response pattern similar to that of CBA/N mice having an X-linked immunodeficiency.

Identification of an opioid receptor subunit carrying the mu binding site

The enkephalin affinity reagent [3H]Tyr-D-Ala-Gly-Phe-Leu-CH2Cl [( 3H]DALECK) was synthesized. It exhibited high-affinity reversible binding, at pH 7.4, to both mu and delta opioid receptor sites in rat brain membranes. At pH 8.1, nanomolar levels of [3H]DALECK produced an irreversible labeling in synaptic membranes, essentially only in one subunit of 58 000 daltons. The irreversible phase of the reaction reduced the subsequent binding of a mu-selective enkephalin derivative but not that of a delta-selective one. It is concluded that a mu subunit of the opioid receptor exists, can be alkylated specifically, and is of Mr 58 000.

Sizes of opioid receptor types in rat brain membranes

The sizes of the receptors binding opiates and enkephalins in rat brain membranes were investigated by the radiation inactivation technique. By comparison with enzymes of known size added as internal standards, the mu and delta binding sites both gave a molecular weight of about 110000. Other opiate-binding components, which may include the kappa site, showed a much lower rate of inactivation when in reducing conditions, implying a subunit molecular weight of the order of 30000 for such a site.