The scaffolding A-kinase anchoring protein 150 (AKAP150) is critically involved in kinase and phosphatase regulation of synaptic transmission/plasticity, and neuronal excitability. Emerging evidence also suggests that AKAP150 signaling may play a key role in brain’s processing of rewarding/aversive experiences, however its role in the lateral habenula (LHb, as an important brain reward circuitry) is completely unknown. Using whole cell patch clamp recordings in LHb of male wildtype and ΔPKA knockin mice (with deficiency in AKAP-anchoring of PKA), here we show that the genetic disruption of PKA anchoring to AKAP150 significantly reduces AMPA receptor-mediated glutamatergic transmission and prevents the induction of presynaptic endocannabinoid-mediated long-term depression in LHb neurons. Moreover, ΔPKA mutation potentiates GABA A receptor-mediated inhibitory transmission while increasing LHb intrinsic excitability through suppression of medium afterhyperpolarizations. ΔPKA mutation-induced suppression of medium afterhyperpolarizations also blunts the synaptic and neuroexcitatory actions of the stress neuromodulator, corticotropin releasing factor (CRF), in mouse LHb. Altogether, our data suggest that AKAP150 complex signaling plays a critical role in regulation of AMPA and GABA A receptor synaptic strength, glutamatergic plasticity and CRF neuromodulation possibly through AMPA receptor and potassium channel trafficking and endocannabinoid signaling within the LHb.

Current treatments of anxiety and depressive disorders are plagued by considerable side effects and limited efficacies, underscoring the need for additional molecular targets that can be leveraged to improve medications. Here, we have identified a molecular cascade triggered by chronic stress that exacerbates anxiety- and depressive-like behaviors. Specifically, chronic stress enhances Src kinase activity and tyrosine phosphorylation of calmodulin, which diminishes MyosinVa (MyoVa) interaction with Neuroligin2 (NL2), resulting in decreased inhibitory transmission and heightened anxiety-like behaviors. Importantly, pharmacological inhibition of Src reinstates inhibitory synaptic deficits and effectively reverses heightened anxiety-like behaviors in chronically stressed mice, a process requiring the MyoVa–NL2 interaction. These data demonstrate the reversibility of anxiety- and depressive-like phenotypes at both molecular and behavioral levels and uncover a therapeutic target for anxiety and depressive disorders.

Tumor cells are characterized by aberrant signal transduction and cell cycle control pathways that lead to unchecked cell proliferation. Unchecked tumor cell proliferation, as well as macrophage proliferation, contributes to tumor growth and spread. Inhibitors of PI3K or MEK signaling pathways can initially inhibit tumor growth until resistance due to upregulation of the alternative pathway develops. We identified a novel allosteric cKIT/FLT3/CSF1R inhibitor that induces synthetic lethality in AML, lung carcinoma, pancreatic carcinoma and other tumor cells and in proliferating macrophages in vitro and in tumors in vivo by simultaneously inhibiting the MEK-ERK and PI3K-AKT pathways and activating stress activated kinase-mediated cell cycle arrest. A series of related cKIT/FLT3/CSF1R/PDGFR allosteric inhibitors suppressed receptor tyrosine phosphorylation as well as downstream MEK-ERK and PI3K-AKT signaling and mTorc1 and cMyc gene expression pathways that control cell growth. Select cKIT/FLT3/CSF1R/PDGFR inhibitors with a unique positioning of a single side chain also inhibited CDK8/19 and stimulated phosphorylation and activation of JNK and p38. JNK activation promoted sustained ATF-2 and cJun-mediated p53 and Chk1/Chk2 activation, thereby promoting cell cycle arrest in G2/M and ultimately, apoptosis. These inhibitors potently suppressed tumor growth in vivo by halting tumor cell and macrophage proliferation in G2/M. They synergized with anti-PD-1 and anti-CTLA-4 and led to tumor eradication and immunological memory formation. These studies identify novel allosteric inhibitors with potent synthetically lethal anti-tumor activity. Citation Format: Hui Chen, Marc Paradise, Ryan Shepard, Judith Varner. In vitro and in vivo synthetic lethality: Potent tumor suppression by a novel FLT3/cKIT/CSF1R/CDK19 inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1669.

GABA-A receptors (GABA A Rs) are crucial for development and function of the brain. Altered GABAergic transmission is hypothesized to be involved in neurodevelopmental disorders. Recently, we identified Shisa7 as a GABA A R auxiliary subunit that modulates GABA A R trafficking and GABAergic transmission. However, the underlying molecular mechanisms remain elusive. Here we generated a knock-in (KI) mouse line that is phospho-deficient at a phosphorylation site in Shisa7 (S405) and combined with electrophysiology, imaging and behavioral assays to illustrate the role of this site in GABAergic transmission and plasticity as well as behaviors. We found that expression of phospho-deficient mutants diminished α2-GABA A R trafficking in heterologous cells. Additionally, α1/α2/α5-GABA A R surface expression and GABAergic inhibition were decreased in hippocampal neurons in KI mice. Moreover, chemically induced inhibitory long-term potentiation was abolished in KI mice. Lastly, KI mice exhibited hyperactivity, increased grooming and impaired sleep homeostasis. Collectively, our study reveals a phosphorylation site critical for Shisa7-dependent GABA A Rs trafficking which contributes to behavioral endophenotypes displayed in neurodevelopmental disorders.

Adverse events and childhood trauma increase the susceptibility towards developing psychiatric disorders (substance use disorder, anxiety, depression, etc.) in adulthood. Although there are treatment strategies that have utility in combating these psychiatric disorders, little attention is placed on how to therapeutically intervene in children exposed to early life stress (ELS) to prevent the development of later psychopathology. The lateral habenula (LHb) has been a topic of extensive investigation in mental health disorders due to its prominent role in emotion and mood regulation through modulation of brain reward and motivational neural circuits. Importantly, rodent models of ELS have been shown to promote LHb dysfunction. Moreover, one of the potential mechanisms contributing to LHb neuronal and synaptic dysfunction involves endocannabinoid (eCB) signaling, which has been observed to critically regulate emotion/mood and motivation. Many pre-clinical studies targeting eCB signaling suggest that this neuromodulatory system could be exploited as an intervention therapy to halt maladaptive processes that promote dysfunction in reward and motivational neural circuits involving the LHb. In this perspective article, we report what is currently known about the role of eCB signaling in LHb function and discuss our opinions on new research directions to determine whether the eCB system is a potentially attractive therapeutic intervention for the prevention and/or treatment of ELS-associated psychiatric illnesses.

Early life stress (ELS) presents an important risk factor for drug addiction and comorbid depression and anxiety through persistent effects on the mesolimbic dopamine (DA) pathways 1 . Using an ELS model for child neglect (a single 24 h episode of maternal deprivation, MD) in rats, recent published works from our lab show that MD induces dysfunction in ventral tegmental area (VTA) DA neurons 2–4 and its negative controller, the lateral habenula (LHb) 5–7 . In regard to LHb, MD-induced potentiation of glutamatergic synaptic transmission onto LHb neurons shifts the coordination of excitation/inhibition (E/I) balance towards excitation, resulting in an increase in the overall spontaneous neuronal activity with elevation in bursting and tonic firing, and intrinsic excitability of LHb neurons in early adolescent male rats 5–7 . Here, we explored how MD affects intravenous morphine self-administration (MSA) acquisition and sucrose preference as well as glutamatergic synaptic function in LHb neurons of adult male rats self-administering morphine. We found that MD-induced increases in LHb neuronal and glutamatergic synaptic activity and E/I ratio persisted into adulthood. Moreover, MD significantly reduced morphine intake, triggered anhedonia-like behavior in the sucrose preference test (SPT), and was associated with persistent glutamatergic potentiation 24h after the last MSA session. MSA also triggered postsynaptic glutamatergic potentiation in LHb neurons of control rats during this time period. Our data highlights that ELS-induced glutamatergic plasticity in LHb may dampen the positive reinforcing properties of natural rewards and opioids, and contribute to the development of anhedonic and dysphoric states associated with opioids.

The vast majority of fast inhibitory transmission in the brain is mediated by GABA acting on GABAA receptors (GABAARs), which provides inhibitory balance to excitatory drive and controls neuronal output. GABAARs are also effectively targeted by clinically important drugs for treatment in a number of neurological disorders. It has long been hypothesized that function and pharmacology of GABAARs are determined by the channel pore-forming subunits. However, recent studies have provided new dimensions in studying GABAARs due to several transmembrane proteins that interact with GABAARs and modulate their trafficking and function. In this review, we summarize recent findings on these novel GABAAR transmembrane regulators and highlight a potential avenue to develop new GABAAR psychopharmacology by targeting these receptor-associated membrane proteins.

Sleep is a fundamental physiological process conserved across most species. As such, deficits in sleep can result in a myriad of psychological and physical health issues. However, the mechanisms underlying the induction of sleep are relatively unknown. Interestingly, general anesthetics cause unconsciousness by positively modulating GABA-A receptors (GABA A Rs). Based on this observation, it is hypothesized that GABA A Rs play a critical role in modulating circuits involved in sleep to promote unconsciousness. Recently, the lateral habenula (LHb) has been demonstrated to play a role in sleep physiology and sedation. Specifically, propofol has been shown to excite LHb neurons to promote sedation. However, the mechanism by which this occurs is unknown. Here, we utilize whole-cell voltage and current clamp recordings from LHb neurons obtained from 8-10 week old male mice to determine the physiological mechanisms for this phenomenon. We show that bath application of 1.5μM propofol is sufficient to increase LHb neuronal excitability involving synaptic transmission, but not through modulation of intrinsic properties. Additionally, although there is increased LHb neuronal excitability, GABA A Rs localized postsynaptically on LHb neurons are still responsive to propofol, as indicated by an increase in the decay time. Lastly, we find that propofol increases the synaptic drive onto LHb neurons involving enhanced presynaptic release of both glutamate and GABA. However, the greatest contributor to the potentiated synaptic drive is the increased release of glutamate which shifts the balance of synaptic transmission towards greater excitation. Taken together, this study is the first to identify the physiological basis for why LHb neurons are excited by propofol, rather than inhibited, and as a result promote sedation.

Diverse populations of GABAA receptors (GABAARs) throughout the brain mediate fast inhibitory transmission and are modulated by various endogenous ligands and therapeutic drugs. Deficits in GABAAR signaling underlie the pathophysiology behind neurological and neuropsychiatric disorders such as epilepsy, anxiety, and depression. Pharmacological intervention for these disorders relies on several drug classes that target GABAARs, such as benzodiazepines and more recently neurosteroids. It has been widely demonstrated that subunit composition and receptor stoichiometry impact the biophysical and pharmacological properties of GABAARs. However, current GABAAR-targeting drugs have limited subunit selectivity and produce their therapeutic effects concomitantly with undesired side effects. Therefore, there is still a need to develop more selective GABAAR pharmaceuticals, as well as evaluate the potential for developing next-generation drugs that can target accessory proteins associated with native GABAARs. In this review, we briefly discuss the effects of benzodiazepines and neurosteroids on GABAARs, their use as therapeutics, and some of the pitfalls associated with their adverse side effects. We also discuss recent advances toward understanding the structure, function, and pharmacology of GABAARs with a focus on benzodiazepines and neurosteroids, as well as newly identified transmembrane proteins that modulate GABAARs.

The lateral habenula (LHb) is an epithalamic brain region associated with value-based decision making and stress evasion through its modulation of reward circuitry. Increased activity of the LHb is associated with drug addiction and stress-related mood disorders. Dynorphin (DYN)/Kappa opioid receptor (KOR) signaling is an endogenous mediator of stress response in reward circuitry. Previously, we have shown a novel functional role of DYN/KOR signaling within LHb and its dysregulation by a severe early life stress (maternal deprivation, MD). Specifically, KOR stimulation has distinct effects on LHb neuronal excitability in distinct neuronal populations identified by the presence of hyperpolarizing current (Ih) that were absent following MD. Namely, KOR stimulation through the KOR agonist, U50,488, significantly decreases excitability of Ih negative (Ih-) LHb neurons while simultaneously increasing excitability of Ih positive (Ih+) LHb neurons. Additionally, KOR-induced alteration in LHb excitability is dependent on both presynaptic glutamatergic and GABAergic signaling likely through presynaptic KORs on inputs to LHb neurons. Given that LHb inputs from the entopeduncular nucleus (EP) and lateral hypothalamus (LH) have been implicated in stress-induced mood disorders through modulation of LHb excitability, we hypothesize that the presynaptic effects of KOR stimulation on LHb neuronal activity may be driven by one or both of these inputs. Using selective in vitro optical stimulation of either EP or LH inputs to LHb neurons in brain slices from rats, our pilot study suggests that KOR activation of EP and LH inputs may differentially affect optically evoked action potential generation across Ih- and Ih+ LHb subpopulations. Moreover, our data from MD rats suggest that there may be an imbalance of excitation to inhibition at EP synapses onto LHb neurons. Given that MD increases immunolabeled DYN (the endogenous KOR agonist) labeling in neuronal fibers in LHb while significantly decreasing mRNA levels of KORs in LHb, we also investigated MD-induced modulation of a KOR-specific downstream signaling (p38 MAPK). Our molecular data indicate that decreased KOR expression may be a homeostatic response to higher basal activation of KORs by MD-induced increases in DYN and p38 expression in the LHb. Ih- and Ih+ neurons molecular identification is further investigated following electrophysiological recordings by combining ionophoresis labeling during electrophysiology experiments and post-hoc immunohistochemistry to verify the glutamatergic (VGLUT+) and GABAergic (somatostatin, SST+ or parvalbumin, PV) nature of LHb neurons. Collectively, our current studies provide evidence for input- and cell-specific regulation of LHb neurons by KOR signaling that could be modulated by MD and highlights a future hotspot for pharmacological intervention of KOR-mediated mood disorders through dysregulation of specific LHb neural circuits.

Traumatic early life stress (ELS) is linked to dopamine (DA) dysregulation which increases the probability of developing psychiatric disorders in adolescence and adulthood. Our prior studies demonstrated that a severe early life stressor, a 24-hr maternal deprivation (MD) in juvenile male rats, could lead to altered DA signaling from the ventral tegmental area (VTA) due to impairment of GABAergic synaptic plasticity (promoting GABAergic long-term depression, LTD) with concomitant changes in the abundance of synaptic regulators including A-kinase anchoring protein (AKAP150). Importantly, these MD-induced synaptic changes in the VTA were accompanied by upregulation of histone deacetylase 2, histone hypoacetylation, and were reversible by HDAC inhibition. Using cell-attached and whole-cell patch clamp recordings, we found that MD stress also increased spontaneous VTA DA neuronal activity and excitability in juvenile male rats without affecting intrinsic excitability. Postsynaptic chemical disruption of AKAP150 and protein kinase A interaction increased VTA DA neuronal excitability in control non-MD rats mimicking the effects of MD on DA cell excitability with similar changes in membrane properties. Interestingly, this disruption decreased MD-induced VTA DA hyperexcitability. This MD-induced DA neuronal hyperexcitability could also be normalized at 24 hr after injection of the class 1 HDAC inhibitor, CI-994. Altogether, our data suggest that AKAP150 plays a critical role in the regulation of VTA DA neuronal excitability and that HDAC-mediated targeting of AKAP150 signaling could normalize VTA DA dysfunction following ELS thereby providing novel therapeutic targets for prevention of later life psychopathology.

Exposure to stress is recognized to be a triggering factor in several mood disorders, including depression and anxiety. There is very little understanding of why female subjects have a significantly higher risk for these conditions than males. Recent findings in male rodents indicated that prophylactic ketamine can prevent the development of a stress-induced depressive-like phenotype, providing a pharmacological tool to study the mechanisms underlying stress resilience. Unfortunately, none of these studies incorporated female subjects, nor did they provide a mechanistic understanding of the effects of ketamine on stress resilience. Our previous work identified the prefrontal glutamatergic and parvalbumin (PV) systems as potential molecular mechanisms underlying sex differences in susceptibility to stress-induced emotional deregulations. To further address this point, we treated male and female mice with a single dose of ketamine before exposure to a chronic stress paradigm to determine whether stress-resilience induced by a pre-exposure to ketamine is similar in males and females and whether modulation of the prefrontal glutamatergic and PV systems by ketamine is associated with these behavioral effects. Ketamine prevented chronic stress-induced changes in behaviors in males, which was associated with a reduction in expression of PV and the NMDA receptor NR1 subunit. Ketamine did not protect females against the effects of chronic stress and did not change significantly prefrontal gene expression. Our data highlight fundamental sex differences in the sustained effects of ketamine. They also further implicate prefrontal glutamatergic transmission and PV in resilience to chronic stress.

The lateral habenula (LHb) is an epithalamic brain region associated with value-based decision making and stress evasion through its modulation of dopamine (DA)-mediated reward circuitry. Specifically, increased activity of the LHb is associated with drug addiction, schizophrenia and stress-related disorders such as depression, anxiety and posttraumatic stress disorder. Dynorphin (Dyn)/Kappa opioid receptor (KOR) signaling is a mediator of stress response in reward circuitry. Previously, we have shown that maternal deprivation (MD), a severe early life stress, increases LHb spontaneous neuronal activity and intrinsic excitability while blunting the response of LHb neurons to extrahypothalamic corticotropin-releasing factor (CRF) signaling, another stress mediator. CRF pathways also interact with Dyn/KOR signaling. Surprisingly, there has been little study of direct KOR regulation of the LHb despite its distinct role in stress, reward and aversion processing. To test the functional role of Dyn/KOR signaling in the LHb, we utilized ex-vivo electrophysiology combined with pharmacological tools in rat LHb slices. We show that activation of KORs by a KOR agonist (U50,488) exerted differential effects on the excitability of two distinct sub-populations of LHb neurons that differed in their expression of hyperpolarization-activated cation currents (HCN, Ih). Specifically, KOR stimulation increased neuronal excitability in LHb neurons with large Ih currents (Ih+) while decreasing neuronal excitability in small/negative Ih (Ih-) neurons. We found that an intact fast-synaptic transmission was required for the effects of U50,488 on the excitability of both Ih- and Ih+ LHb neuronal subpopulations. While AMPAR-, GABAAR-, or NMDAR-mediated synaptic transmission alone was sufficient to mediate the effects of U50,488 on excitability of Ih- neurons, either GABAAR- or NMDAR-mediated synaptic transmission could mediate these effects in Ih+ neurons. Consistently, KOR activation also altered both glutamatergic and GABAergic synaptic transmission where stimulation of presynaptic KORs uniformly suppressed glutamate release onto LHb neurons while primarily decreased or in some cases increased GABA release. We also found that MD significantly increased immunolabeled Dyn (the endogenous KOR agonist) labeling in neuronal fibers in LHb while significantly decreasing mRNA levels of KORs in LHb tissues compared to those from non-maternally deprived (non-MD) control rats. Moreover, the U50,488-mediated increase in LHb neuronal firing observed in non-MD rats was absent following MD. Altogether, this is the first demonstration of the existence of functional Dyn/KOR signaling in the LHb that can be modulated in response to severe early life stressors such as MD.

Psychiatric illnesses are a major public health concern due to their prevalence and heterogeneity of symptom presentation resulting from a lack of efficacious treatments. Although dysregulated dopamine (DA) signaling has been observed in a myriad of psychiatric conditions, different pathophysiological mechanisms have been implicated which impede the development of adequate treatments that work across all patient populations. The ventral tegmental area (VTA), a major source of DA neurons in the brain reward pathway, has been shown to have altered activity that contributes to reward dysregulation in mental illnesses and drug addiction. It has now become better appreciated that epigenetic mechanisms contribute to VTA DA dysfunction, such as through histone modifications, which dynamically regulate transcription rates of critical genes important in synaptic plasticity underlying learning and memory. Here, we provide a focused review on differential histone modifications within the VTA observed in both humans and animal models, as well as their relevance to disease-based phenotypes, specifically focusing on epigenetic dysregulation of histones in the VTA associated with early life stress (ELS) and drugs of abuse. Locus- and cell-type-specific targeting of individual histone modifications at specific genes within the VTA presents novel therapeutic targets which can result in greater efficacy and better long-term health outcomes in susceptible individuals that are at increased risk for substance use and psychiatric disorders.

Introduction: Tumor-associated macrophages promote immunosuppressive microenvironment in head and neck squamous cell carcinoma (HNSCC). We previously reported that macrophage PI3-kinase γ (PI3Kγ) controls a critical switch between immune stimulation and suppression during inflammation and cancer. The aim of the present study was to investigate the effect of PI3Kγ inhibition on T-cell immune response, especially on T-cell memory and exhaustion status using mouse models of HNSCC. Materials and Methods: Wild-type (WT) or Pik3cg-/- 6- to 8-week-old male syngeneic C57Bl/6J mice were implanted with HPV+ MEER tumor cells (mouse HPV+ HNSCC cell line) by subcutaneous injection. Tumors, draining lymph nodes and spleens were isolated, then analyzed using flow cytometry or mass cytometry. Mice that completely cleared tumors were reinjected with tumor cells and tumor growth was monitored. CD90.2+ T cells or CD19+ B cells that were harvested from spleens of WT or Pik3cg-/- tumor-inoculated mice were mixed 1:1 with viable tumor cells and injected into the flanks of naive WT mice. Results: Mice lacking PI3Kγ exhibited suppressed growth of implanted HPV+ MEER tumors. The proportion of T cells, especially CD8+ T cells, significantly increased in tumors from Pik3c-/- mice. T cells from Pik3cg-/- tumors expressed significantly more granzyme B and less T-cell exhaustion markers. The proportion of CD8+ effector memory T cells significantly increased in spleens from Pik3cg-/- mice. Mice that were implanted with both tumor cells and T cells from spleens of tumor-bearing Pik3cg-/- mice exhibited significant suppression of tumor growth. All mice that had previously cleared tumors dramatically suppressed tumor growth when rechallenged with tumor cells and remained cancer-free. Conclusion:Pik3cg-/- mice showed more activated T-cell immune response and T-cell memory than WT, resulting in significant suppression of tumor growth. These results suggest that PI3Kγ-targeted therapy might enhance the activity of checkpoint inhibitors through the activation of T-cell immune response in patients with HNSCC. Citation Format: Hideyuki Takahashi, Paulina Pathria, Ryan Shepard, Ann Shih, Tiani L. Louis, Judith A. Varner. PI3Kγ inhibition activates T cell memory and relieves T cell exhaustion [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr A86.

Dysfunction of prefrontal parvalbumin (PV+) interneurons has been linked with severe cognitive deficits as observed in several neurodevelopmental disorders including schizophrenia. However, whether a specific aspect of PV+ neurons deregulation, or a specific molecular mechanism within PV+ neurons is responsible for cognitive deficits and other behavioral impairments remain to be determined. Here, we induced cognitive deficits and altered the prefrontal PV system in mice by exposing them neonatally to the NMDA receptor antagonist ketamine. We observed that the cognitive deficits and hyperactivity induced by neonatal ketamine were associated with a downregulation of Npas4 expression specifically in PV+ neurons. To determine whether Npas4 downregulation-induced dysfunction of PV+ neurons could be a molecular contributor to the cognitive and behavioral impairments reported after neonatal ketamine, we used a transgenic Cre-Lox approach. Reduced Npas4 expression within PV+ neurons replicates deficits in short-term memory observed after neonatal ketamine, but does not reproduce disturbances in general activity. Our data show for the first time that the brain-specific transcription factor Npas4 may be an important contributor to PV+ neurons dysfunction in neurodevelopmental disorders, and thereby could contribute to the cognitive deficits observed in diseases characterized by abnormal functioning of PV+ neurons such as schizophrenia. These findings provide a potential novel therapeutic target to rescue the cognitive impairments of schizophrenia that remain to date unresponsive to treatments.

Reduced activity of the prefrontal cortex (PFC) is seen in mood disorders including depression and anxiety. The mechanisms of this hypofrontality remain unclear. Because of their specific physiological properties, parvalbumin-expressing (PV+) inhibitory interneurons contribute to the overall activity of the PFC. Our recent work using a chronic stress mouse model showed that stress-induced increases in prefrontal PV expression correlates with increased anxiety-like behaviors in female mice. Our goal is now to provide a causal relationship between changes in prefrontal PV+ cells and changes in emotional behaviors in mice. We first show that, in addition to increasing overall level of PV expression, chronic stress increases the activity of prefrontal PV+ cells. We then used a chemogenetic approach to mimic the effects of chronic stress and specifically increase the activity of prefrontal PV+ cells. We observed that chemogenetic activation of PV+ cells caused an overall reduction in prefrontal activity, and that chronic activation of PV+ cells lead to increased anxiety-related behaviors in female mice only. These results demonstrate that activity of prefrontal PV+ cells could represent a novel sex-specific modulator of anxiety-related behaviors, potentially through changes in overall prefrontal activity. The findings also support the idea that prefrontal PV+ cells are worth further investigation to better understand mood disorders that are more prevalent in female populations.

Myeloid cells are recruited to damaged tissues where they can resolve infections and tumor growth or stimulate wound healing and tumor progression. Recruitment of these cells is regulated by integrins, a family of adhesion receptors that includes integrin CD11b. Here we report that, unexpectedly, integrin CD11b does not regulate myeloid cell recruitment to tumors but instead controls myeloid cell polarization and tumor growth. CD11b activation promotes pro-inflammatory macrophage polarization by stimulating expression of microRNA Let7a . In contrast, inhibition of CD11b prevents Let7a expression and induces cMyc expression, leading to immune suppressive macrophage polarization, vascular maturation, and accelerated tumor growth. Pharmacological activation of CD11b with a small molecule agonist, Leukadherin 1 (LA1), promotes pro-inflammatory macrophage polarization and suppresses tumor growth in animal models of murine and human cancer. These studies identify CD11b as negative regulator of immune suppression and a target for cancer immune therapy.