Allosteric inhibition of phosphodiesterase 4D induces biphasic memory-enhancing effects associated with learning-activated signaling pathways

RATIONALE

Phosphodiesterase 4D negative allosteric modulators (PDE4D NAMs) enhance memory and cognitive function in animal models without emetic-like side effects. However, the relationship between increased cyclic adenosine monophosphate (cAMP) signaling and the effects of PDE4D NAM remains elusive.

OBJECTIVE

To investigate the roles of hippocampal cAMP metabolism and synaptic activation in the effects of D159687, a PDE4D NAM, under baseline and learning-stimulated conditions.

RESULTS

At 3 mg/kg, D159687 enhanced memory formation and consolidation in contextual fear conditioning; however, neither lower (0.3 mg/kg) nor higher (30 mg/kg) doses induced memory-enhancing effects. A biphasic (bell-shaped) dose-response effect was also observed in a scopolamine-induced model of amnesia in the Y-maze, whereas D159687 dose-dependently caused an emetic-like effect in the xylazine/ketamine anesthesia test. At 3 mg/kg, D159687 increased cAMP levels in the hippocampal CA1 region after conditioning in the fear conditioning test, but not in the home-cage or conditioning cage (i.e., context only). By contrast, 30 mg/kg of D159687 increased hippocampal cAMP levels under all conditions. Although both 3 and 30 mg/kg of D159687 upregulated learning-induced Fos expression in the hippocampal CA1 30 min after conditioning, 3 mg/kg, but not 30 mg/kg, of D159687 induced phosphorylation of synaptic plasticity-related proteins such as cAMP-responsive element-binding protein, synaptosomal-associated protein 25 kDa, and the N-methyl-D-aspartate receptor subunit NR2A.

CONCLUSIONS

Our findings suggest that learning-stimulated conditions can alter the effects of a PDE4D NAM on hippocampal cAMP levels and imply that a PDE4D NAM exerts biphasic memory-enhancing effects associated with synaptic plasticity-related signaling activation.

Chronic social defeat stress induces anxiety-like behaviors via downregulation of serotonin transporter in the prefrontal serotonergic system in mice

The serotonergic (5-HTergic) system is closely involved in the pathophysiology of mood and anxiety disorders and the responsibility of this system may differ for each symptom. In this study, we examined the relationship between the dysfunction of the 5-HTergic system and abnormal behaviors in the social defeat stress model, an animal model of mood and anxiety disorders and in mice with knockdown of Slc6a4, the gene encoding SERT. Monoamine content, serotonin (5-HT) release, 5-HT uptake, 5-HT transporter (SERT) protein levels, and behaviors were investigated in mice subjected to chronic social defeat stress and in mice with knockdown of Slc6a4, in 5-HTergic neurons projecting to the prefrontal cortex (PFC). Furthermore, DNA methylation of Slc6a4 was examined in mice subjected to chronic social defeat stress. Increased turnover, increased extracellular basal levels, decreased release and decreased uptake of 5-HT, and decreased SERT protein levels were observed in the PFC of the stressed mice. The decreased 5-HT uptake correlated with anxiety-like behavior characterized by decreased time spent in the open arms of the elevated plus maze. DNA methylation was increased in the CpG island of Slc6a4 in 5-HTergic neurons projecting to the PFC of the stressed mice. Similar to the stressed mice, mice with Slc6a4 knockdown in 5-HTergic neurons projecting to the PFC also showed decreased release and uptake of 5-HT in the PFC and increased anxiety-like behavior. Chronic stress may induce anxiety due to dysfunction in the prefrontal 5-HTergic system via decreased SERT expression in the PFC.

Blockade of vasoactive intestinal peptide receptor 2 (VIPR2) signaling suppresses cyclin D1-dependent cell-cycle progression in MCF-7 cells

Vasoactive intestinal peptide (VIP) receptor 2 (VIPR2) is a G protein-coupled receptor that binds to Gαs, Gαi, and Gαq proteins to regulate various downstream signaling molecules, such as protein kinase A (PKA), phosphatidylinositol 3-kinase (PI3K), and phospholipase C. In this study, we examined the role of VIPR2 in cell cycle progression. KS-133, a newly developed VIPR2-selective antagonist peptide, attenuated VIP-induced cell proliferation in MCF-7 cells. The percentage of cells in the S-M phase was decreased in MCF-7 cells treated with KS-133. KS-133 in the presence of VIP decreased the phosphorylation of extracellular signal-regulated kinase (ERK), AKT, and glycogen synthase kinase-3β (GSK3β), resulting in a decrease in cyclin D1 levels. In MCF-7 cells stably-expressing VIPR2, KS-133 decreased PI3K activity and cAMP levels. Treatment with the ERK-specific kinase (MEK) inhibitor U0126 and the class I PI3K inhibitor ZSTK474 decreased the percentage of cells in the S phase. KS-133 reduced the percentage of cells in the S phase more than treatment with U0126 or ZSTK474 alone and did not affect the effect of the mixture of these inhibitors. Our findings suggest that VIPR2 signaling regulates cyclin D1 levels through the cAMP/PKA/ERK and PI3K/AKT/GSK3β pathways, and mediates the G1/S transition to control cell proliferation.

(R)-ketamine restores anterior insular cortex activity and cognitive deficits in social isolation-reared mice

Chronic social isolation increases the risk of mental health problems, including cognitive impairments and depression. While subanesthetic ketamine is considered effective for cognitive impairments in patients with depression, the neural mechanisms underlying its effects are not well understood. Here we identified unique activation of the anterior insular cortex (aIC) as a characteristic feature in brain-wide regions of mice reared in social isolation and treated with (R)-ketamine, a ketamine enantiomer. Using fiber photometry recording on freely moving mice, we found that social isolation attenuates aIC neuronal activation upon social contact and that (R)-ketamine, but not (S)-ketamine, is able to counteracts this reduction. (R)-ketamine facilitated social cognition in social isolation-reared mice during the social memory test. aIC inactivation offset the effect of (R)-ketamine on social memory. Our results suggest that (R)-ketamine has promising potential as an effective intervention for social cognitive deficits by restoring aIC function.

A Behavioral and Electroencephalographic Study of Anesthetic State Induced by MK-801 Combined with Haloperidol, Ketamine and Riluzole in Mice

BACKGROUND

Ketamine is an intravenous anesthetic that acts as a channel blocker on the N-methyl-d-aspartate (NMDA) receptor, a glutamate receptor subtype. MK-801 is the most potent compound among noncompetitive NMDA receptor antagonists. Ketamine induces loss of the righting reflex (LORR) in rodents, which is one of the indicators of unconsciousness, whereas high doses of MK-801 produce ataxia, but not LORR. In contrast, we previously reported that MK-801 combined with a low dose of the dopamine receptor antagonist haloperidol-induced LORR in mice. To assess a neurophysiologically distinct brain state and demonstrate unconsciousness, electroencephalograms (EEG) need to be examined together with LORR. Therefore, we herein investigated EEG changes after the systemic administration of MK-801 alone or in combination with haloperidol, and compared them with those induced by ketamine, the glutamate release inhibitor riluzole, and the γ-aminobutyric acid type A receptor agonist propofol.

METHODS

All drugs were intraperitoneally administered to adult male ddY mice (n = 168). General anesthesia was evaluated based on the righting reflex test. Animals who exhibited no righting for more than 30 seconds were considered to have LORR. In a separate group of mice, EEG of the primary visual cortex was recorded before and after the administration of MK-801 (3.0 mg/kg) alone or in combination with haloperidol (0.2 mg/kg), ketamine (150 mg/kg), riluzole (30 mg/kg), or propofol (240 mg/kg). The waveforms recorded were analyzed using EEG power spectra and spectrograms.

RESULTS

The high dose of MK-801 alone did not induce LORR, whereas MK-801 combined with haloperidol produced LORR in a dose-dependent manner. Ketamine, riluzole, and propofol also dose-dependently induced LORR. In the EEG study, MK-801 alone induced a significant increase in δ power, while MK-801 plus haloperidol exerted similar effects on not only δ, but also θ and α power during LORR, suggesting that increases in δ, θ, and α power were necessary for LORR. The results obtained on MK-801 plus haloperidol were similar to those on ketamine in the behavioral and EEG studies, except for an increase in γ power by ketamine during LORR. Propofol significantly increased δ, θ, α, and β power during LORR. However, the EEG results obtained using riluzole, which produced a unique pattern of lower amplitude activity spanning most frequencies, markedly differed from those with the other drugs.

CONCLUSIONS

This study revealed differences in EEG changes induced by various sedatives. The results obtained on MK-801 alone and MK-801 plus haloperidol suggest the importance of dopamine transmission in maintaining the righting reflex.

Long-lasting anti-despair and anti-anhedonia effects of (S)-norketamine in social isolation-reared mice

Alternatives to ketamine without psychotomimetic properties for the treatment of depression have attracted much attention. Here, we examined the anti-despair and anti-anhedonia effects of the ketamine metabolites (S)-norketamine ((S)-NK), (R)-NK, (2S,6S)-hydroxynorketamine, and (2R,6R)-hydroxynorketamine in a mouse model of depression induced by social isolation. All ketamine metabolites examined had acute (30 min after administration) anti-despair-like effects in the forced swim test, but only (S)-NK showed a long-lasting (1 week) effect. Additionally, only (S)-NK improved reduced motivation both 30 min and 24 h after injection in the female encounter test. These results suggest that (S)-NK has potent and long-lasting antidepressant-like effects.

Mouse maternal odontogenic infection with Porphyromonas gingivalis induces cognitive decline in offspring

Introduction

Porphyromonas gingivalis (P. gingivalis), a major periodontal pathogen, causes intrauterine infection/inflammation. Offspring exposed to intrauterine infection/inflammation have an increased risk of neurological disorders, regardless of gestational age. However, the relationship between maternal periodontitis and offspring functional/histological changes in the brain has not yet been elucidated.

Methods

In this study, we used a gestational mouse model to investigate the effects of maternal odontogenic infection of P. gingivalis on offspring behavior and brain tissue.

Results

The step-through passive avoidance test showed that the latency of the acquisition trial was significantly shorter in the P. gingivalis group (p < 0.05), but no difference in spontaneous motor/exploratory parameters by open-field test. P. gingivalis was diffusely distributed throughout the brain, especially in the hippocampus. In the hippocampus and amygdala, the numbers of neuron cells and cyclic adenosine monophosphate response element binding protein-positive cells were significantly reduced (p < 0.05), whereas the number of ionized calcium binding adapter protein 1-positive microglia was significantly increased (p < 0.05). In the hippocampus, the number of glial fibrillary acidic protein-positive astrocytes was also significantly increased (p < 0.05).

Discussion

The offspring of P. gingivalis-infected mothers have reduced cognitive function. Neurodegeneration/neuroinflammation in the hippocampus and amygdala may be caused by P. gingivalis infection, which is maternally transmitted. The importance of eliminating maternal P. gingivalis-odontogenic infection before or during gestation in maintenance healthy brain function in offspring should be addressed in near future.

The VIPR2-selective antagonist KS-133 changes macrophage polarization and exerts potent anti-tumor effects as a single agent and in combination with an anti-PD-1 antibody

We have previously demonstrated that KS-133 is a specific and potent antagonist of vasoactive intestinal peptide receptor 2 (VIPR2). We have also shown that vasoactive intestinal peptide-VIPR2 signaling affects the polarity and activation of tumor-associated macrophages, which is another strategy for cancer immunotherapy apart from the activation of effector T cells. In this study, we aimed to examine whether the selective blockade of VIPR2 by KS-133 changes the polarization of macrophages and induces anti-tumor effects. In the presence of KS-133, genetic markers indicative of tumor-aggressive M1-type macrophages were upregulated, and conversely, those of tumor-supportive M2-type macrophages were downregulated. Daily subcutaneous administration of KS-133 tended to suppress the growth of CT26 tumors (murine colorectal cancer-derived cells) implanted subcutaneously in Balb/c mice. To improve the pharmacological efficacy and reduce the number of doses, we examined a nanoformulation of KS-133 using the US Food and Drug Administration-approved pharmaceutical additive surfactant Cremophor® EL. KS-133 nanoparticles (NPs) were approximately 15 nm in size and stable at 4°C after preparation. Meanwhile, KS-133 was gradually released from the NPs as the temperature was increased. Subcutaneous administration of KS-133 NPs once every 3 days had stronger anti-tumor effects than daily subcutaneous administration of KS-133. Furthermore, KS-133 NPs significantly enhanced the pharmacological efficacy of an immune checkpoint-inhibiting anti-PD-1 antibody. A pharmacokinetic study suggested that the enhancement of anti-tumor activity was associated with improvement of the pharmacokinetic profile of KS-133 upon nanoformulation. Our data have revealed that specific blockade of VIPR2 by KS-133 has therapeutic potential for cancer both alone and in combination with immune checkpoint inhibitors.

Overexpression of VIPR2 in mice results in microencephaly with paradoxical increased white matter volume

Large scale studies in populations of European and Han Chinese ancestry found a series of rare gain-of-function microduplications in VIPR2, encoding VPAC2, a receptor that binds vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide with high affinity, that were associated with an up to 13-fold increased risk for schizophrenia. To address how VPAC2 receptor overactivity might affect brain development, we used a well-characterized Nestin-Cre mouse strain and a knock-in approach to overexpress human VPAC2 in the central nervous system. Mice that overexpressed VPAC2 were found to exhibit a significant reduction in brain weight. Magnetic resonance imaging analysis confirmed a decrease in brain size, a specific reduction in the hippocampus grey matter volume and a paradoxical increase in whole-brain white matter volume. Sex-specific changes in behavior such as impaired prepulse inhibition and contextual fear memory were observed in VPAC2 overexpressing mice. The data indicate that the VPAC2 receptor may play a critical role in brain morphogenesis and suggest that overactive VPAC2 signaling during development plays a mechanistic role in some forms of schizophrenia.

N-methyl-d-aspartate receptors and glycinergic transmission, respectively, mediate muscle relaxation and immobility of pentobarbital in mice

Pentobarbital-induced anesthesia is believed to be mediated by enhancement of the inhibitory action of γ-aminobutyric acid (GABA)ergic neurons in the central nervous system. However, it is unclear whether all components of anesthesia induced by pentobarbital, such as muscle relaxation, unconsciousness, and immobility in response to noxious stimuli, are mediated only through GABAergic neurons. Thus, we examined whether the indirect GABA and glycine receptor agonists gabaculine and sarcosine, respectively, the neuronal nicotinic acetylcholine receptor antagonist mecamylamine, or the N-methyl-d-aspartate receptor channel blocker MK-801 could enhance pentobarbital-induced components of anesthesia. Muscle relaxation, unconsciousness, and immobility were evaluated by grip strength, the righting reflex, and loss of movement in response to nociceptive tail clamping, respectively, in mice. Pentobarbital reduced grip strength, impaired the righting reflex, and induced immobility in a dose-dependent manner. The change in each behavior induced by pentobarbital was roughly consistent with that in electroencephalographic power. A low dose of gabaculine, which significantly increased endogenous GABA levels in the central nervous system but had no effect on behaviors alone, potentiated muscle relaxation, unconsciousness, and immobility induced by low pentobarbital doses. A low dose of MK-801 augmented only the masked muscle-relaxing effects of pentobarbital among these components. Sarcosine enhanced only pentobarbital-induced immobility. Conversely, mecamylamine had no effect on any behavior. These findings suggest that each component of anesthesia induced by pentobarbital is mediated through GABAergic neurons and that pentobarbital-induced muscle relaxation and immobility may partially be associated with N-methyl-d-aspartate receptor antagonism and glycinergic neuron activation, respectively.

Vasoactive intestinal peptide receptor 2 signaling promotes breast cancer cell proliferation by enhancing the ERK pathway

Vasoactive intestinal peptide (VIP) receptor 2 (VIPR2) is a class B G protein-coupled receptor with the neuropeptide VIP as a ligand. Increased VIPR2 mRNA expression and/or VIPR2 gene copy number has been documented in several cancers including breast carcinoma. However, the pathophysiological role of increased VIPR2 in the proliferation of breast cancer cells remains largely unknown. In this study, we found that VIPR2 overexpression in MCF-7 and MDA-MB-231 cells, human breast cancer cell lines, promoted cell proliferation. Increased VIPR2 also exacerbated intraperitoneal proliferation of breast cancer MDA-MB-231 cells in a tumor nude mouse model in vivo. Treatment with KS-133, a VIPR2-selective antagonist peptide, significantly inhibited VIP-induced cell proliferation in VIPR2-overexpressing MCF-7 and MDA-MB-231 cells. Overexpressed VIPR2 caused increases in the levels of cAMP and phosphorylated extracellular signal-regulated kinase (ERK), which involves a VIPR2 signaling pathway through Gs protein. Additionally, phosphorylation of vasodilator-stimulated phosphoprotein (Ser157) and cAMP response element binding protein (Ser133) in VIPR2-overexpressing MCF-7 cells was greater than that in control cells, suggesting the increased PKA activity. Moreover, an inhibitor of mitogen-activated protein kinase kinase, U0126, attenuated tumor proliferation in exogenous VIPR2-expressing MCF-7 and MDA-MB-231 cells at the same level as observed in EGFP-expressing cells treated with U0126. Together, these findings suggest that VIPR2 controls breast tumor growth by regulating the cAMP/PKA/ERK signaling pathway, and the excessive expression of VIPR2 may lead to an exacerbation of breast carcinoma.

Suppressive effect of black tea polyphenol theaflavins in a mouse model of ovalbumin-induced food allergy

Food allergy is recognized as a global medical problem with increasing prevalence in recent years. Currently, the treatment of food allergy mainly involves avoidance of allergens and allergen-specific immunotherapy. Barring the spontaneous resolution of food allergy during the growth process, this disease is difficult to treat fundamentally. In recent years, the use of functional food ingredients derived from natural products has been attracting attention for their prophylactic use in food allergy. Theaflavins, i.e., black tea polyphenols, are potent antioxidants that have inhibitory effects on a variety of diseases. However, little is known about the preventive effect of theaflavins on food allergy. In this study, we designed a mouse model of food allergy and examined the effect of theaflavins using the severity of diarrhea, a symptom of food allergy, as an indicator. The administration of a black tea extract rich in theaflavins or theaflavin 1 (subgroup of theaflavins) to mice reduced the severity of diarrhea when compared with a normal diet. A reduction in malondialdehyde levels, a key marker of lipid peroxidation, was also observed. Overall, these data suggest that theaflavins may potentially inhibit food allergy by alleviating oxidative stress in the colon and can be a potential food material for prevention of food allergy.

Roles of the monoaminergic system in the antidepressant effects of ketamine and its metabolites

While the molecular target of (R,S)-ketamine (ketamine) is thought to be the NMDA receptor, subanesthetic doses of ketamine have been known to modulate monoaminergic neurotransmission in the central nervous system. Although the involvement of the serotonergic system in the antidepressant effects of ketamine has been reported in most studies of this topic, some recent studies have reported that the dopaminergic system plays a key role in the effects of ketamine. Additionally, several lines of evidence suggest that the antidepressant-like effects of (R)-ketamine might be independent of the monoaminergic system. Ketamine metabolites also differ considerably in their ability to regulate monoamine neurotransmitters relative to (S)-ketamine and (R)-ketamine, while (2R,6R)-hydroxynorketamine might share common serotonergic signaling mechanisms with ketamine. In the current review, we summarize the effects of ketamine and its metabolites on monoamine neurotransmission in the brain and discuss the potential roles of the monoaminergic system in the mechanism of action of ketamine.

Development of the vasoactive intestinal peptide receptor 2 (VIPR2) antagonist peptide for the treatment of schizophrenia

Schizophrenia affects approximately 24 million people worldwide. Existing medications for the treatment of schizophrenia work primarily by improving positive symptoms such as agitation, hallucinations, delusions, and aggression. They possess common mechanism of action (MOA), blocking to neurotransmitter receptors such as dopamine, serotonin, and adrenaline receptors. Although multiple agents are available for the treatment of schizophrenia, the majority do not address negative symptoms or cognitive dysfunction. In other cases, patients have drug-related adverse effects. The vasoactive intestinal peptide receptor 2 (VIPR2, also known as VPAC2 receptor) might be an attractive drug target for the treatment of schizophrenia because both clinical and preclinical studies have demonstrated a strong link between high expression/overactivation of VIPR2 and schizophrenia. Despite these backgrounds, the proof-of-concept of VIPR2 inhibitors has not been examined clinically. A reason might be that VIPR2 belongs to class-B GPCRs, and the discovery of small-molecule drugs against class-B GPCRs is generally difficult. We have developed a bicyclic peptide KS-133, which shows VIPR2 antagonist activity and suppresses cognitive decline in a mouse model relevant to schizophrenia. KS-133 has a different MOA from current therapeutic drugs and exhibits high selectivity for VIPR2 and potent inhibitory activity against a single-target molecule. Therefore, it may contribute to both the development of a novel drug candidate for the treatment of psychiatric disorders such as schizophrenia and acceleration of basic studies on VIPR2.

[A new method for assessing depressive-like behaviors in female mice]

Depression is a common mental disorder and mainly characterized by persistent sadness and a lack of interest or pleasure in previously rewarding or enjoyable activities. Despair is also a common symptom of depression, and the forced swim and tail suspension tests are widely used to measure this behavior in rodents, but the results from these tests can include the effects on stress resistance in addition to depressive-like states. Reduced motivation is an important marker of psychiatric disorders, including depression, and thus we have previously developed the female encounter test, a novel and simple procedure for assessing reward-seeking behavior in adult male mice. Importantly, female mice should be considered in the development of animal models of depression and assessment of mouse behaviors since the lifetime prevalence of a major depressive disorder in women is almost twice that in men, and around one in seven women can develop postpartum depression. In this review, we summarized our recent research on the male encounter test for assessing motivation in adult female mice and introduced new topics on animal models and therapeutic drugs for postpartum depression.

Physiological concentrations of glucocorticoids induce pathological DNA double-strand breaks

Steroid hormones induce the transcription of target genes by activating nuclear receptors. Early transcriptional response to various stimuli, including hormones, involves the active catalysis of topoisomerase II (TOP2) at transcription regulatory sequences. TOP2 untangles DNAs by transiently generating double-strand breaks (DSBs), where TOP2 covalently binds to DSB ends. When TOP2 fails to rejoin, called "abortive" catalysis, the resulting DSBs are repaired by tyrosyl-DNA phosphodiesterase 2 (TDP2) and non-homologous end-joining (NHEJ). A steroid, cortisol, is the most important glucocorticoid, and dexamethasone (Dex), a synthetic glucocorticoid, is widely used for suppressing inflammation in clinics. We here revealed that clinically relevant concentrations of Dex and physiological concentrations of cortisol efficiently induce DSBs in G1 phase cells deficient in TDP2 and NHEJ. The DSB induction depends on glucocorticoid receptor (GR) and TOP2. Considering the specific role of TDP2 in removing TOP2 adducts from DSB ends, induced DSBs most likely represent stalled TOP2-DSB complexes. Inhibition of RNA polymerase II suppressed the DSBs formation only modestly in the G1 phase. We propose that cortisol and Dex frequently generate DSBs through the abortive catalysis of TOP2 at transcriptional regulatory sequences, including promoters or enhancers, where active TOP2 catalysis occurs during early transcriptional response.

Vasoactive intestinal peptide–VIPR2 signaling regulates tumor cell migration

Phosphoinositide metabolism is critically involved in human cancer cell migration and metastatic growth. The formation of lamellipodia at the leading edge of migrating cells is regulated by metabolism of the inositol phospholipid PI(4,5)P₂ into PI(3,4,5)P₃. The synthesized PI(3,4,5)P₃ promotes the translocation of WASP family verprolin homologous protein 2 (WAVE2) to the plasma membrane and regulates guanine nucleotide exchange factor Rac-mediated actin filament remodeling. Here, we investigated if VIPR2, a receptor for vasoactive intestinal peptide (VIP), has a potential role in regulating cell migration via this pathway. We found that silencing of VIPR2 in MDA-MB-231 and MCF-7 human breast cancer cells inhibited VIP-induced cell migration. In contrast, stable expression of exogenous VIPR2 promoted VIP-induced tumor cell migration, an effect that was inhibited by the addition of a PI3-kinase (PI3K)γ inhibitor or a VIPR2-selective antagonist. VIPR2 stably-expressing cells exhibited increased PI3K activity. Membrane localization of PI(3,4,5)P₃ was significantly attenuated by VIPR2-silencing. VIPR2-silencing in MDA-MB-231 cells suppressed lamellipodium extension; in VIPR2-overexpressing cells, VIPR2 accumulated in the cell membrane on lamellipodia and co-localized with WAVE2. Conversely, VIPR2-silencing reduced WAVE2 level on the cell membrane and inhibited the interaction between WAVE2, actin-related protein 3, and actin. These findings suggest that VIP–VIPR2 signaling controls cancer migration by regulating WAVE2-mediated actin nucleation and elongation for lamellipodium formation through the synthesis of PI(3,4,5)P₃.

Phospholipase C-related catalytically inactive protein enhances cisplatin-induced apoptotic cell death

Cisplatin is one of the most widely used chemotherapeutic agents and induces caspase-9-mediated apoptosis. Here, we examined whether phospholipase C-related catalytically inactive protein (PRIP) enhances cisplatin-induced apoptosis of breast cancer cells. PRIP depletion increased expression of X-linked inhibitor of apoptosis protein (XIAP) by inhibiting protein degradation, which is downstream of the phosphatidylinositol 3-kinase/AKT pathway and inhibits apoptotic signaling by blocking caspase-9 activation. Conversely, the viability of MCF-7 cells transfected with Prip1 was significantly lower than that of control cells in the presence of cisplatin. The number of apoptotic nuclei and expression levels of cleaved caspase-9 and downstream cleaved caspase-7 and poly-ADP ribose polymerase were greater in PRIP1-expressing MCF-7 cells treated with cisplatin than in control cells. XIAP was decreased by expression of pleckstrin homology domain of PRIP1 (PRIP1-PH domain) that blocked phosphatidylinositol 4,5 bisphosphate metabolism. In an orthotopic transplantation model, combined administration of PRIP1-PH domain-containing liposomes and cisplatin reduced the size of MCF-7 tumors compared with cisplatin alone. Our findings demonstrate that PRIP promotes XIAP degradation by inhibiting PI(3,4,5)P₃/AKT signaling and enhances cisplatin-induced apoptotic cell death. Therefore, we propose that PRIP1-PH liposomes are a novel agent to avoid cisplatin resistance.

Anti-interleukin-6 receptor antibody improves allodynia and cognitive impairment in mice with neuropathic pain following partial sciatic nerve ligation

Neuropathic pain caused by nerve injury presents with severe spontaneous pain and a range of comorbidities, including deficits in higher executive functioning, none of which are adequately treated with current analgesics. Interleukin-6 (IL-6), a proinflammatory cytokine, is critically involved in the development and maintenance of central sensitization. However, the roles of IL-6 in neuropathic pain and related comorbidities have yet to be fully clarified. The present study examined the effect of MR16-1, an anti-IL-6 receptor antibody and inhibits IL-6 activity, on allodynia and cognitive impairment in mice with neuropathic pain following partial sciatic nerve ligation (PSNL). Significant upregulation of IL-6 expression was observed in the hippocampus in PSNL mice. Intranasal administration of MR16-1 significantly improved cognitive impairment but not allodynia in PSNL mice. Intranasal MR16-1 blocked PSNL-induced degenerative effects on hippocampal neurons. Intraperitoneal administration of MR16-1 suppressed allodynia but not cognitive impairment of PSNL mice. The findings suggest that cognitive impairment associated with neuropathic pain is mediated through changes in hippocampus induced by IL-6. These data also suggest that IL-6 mediated peripheral inflammation underlies allodynia, and IL-6 mediated inflammation in the central nervous system underlies cognitive impairment associated with neuropathic pain, and further suggest the therapeutic potential of blocking IL-6 functioning by blocking its receptor.

Prenatal exposure to valproic acid causes allodynia associated with spinal microglial activation

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social communication and social interaction and the presence of restricted, repetitive behaviors. Additionally, difficulties in sensory processing commonly occur in ASD. Sensory abnormalities include heightened or reduced sensitivity to pain, but the mechanism underlying sensory phenotypes in ASD remain unknown. Emerging evidence suggests that microglia play an important role in forming and refining neuronal circuitry, and thus contribute to neuronal plasticity and nociceptive signaling. In the present study, we investigated the age-dependent tactile sensitivity in an animal model of ASD induced by prenatal exposure to valproic acid (VPA) and subsequently assessed the involvement of microglia in the spinal cord in pain processing. Pregnant ICR (CD1) mice were intraperitoneally injected with either saline or VPA (500 mg/kg) on embryonic day 12.5. Male offspring of VPA-treated mothers showed mechanical allodynia at both 4 and 8 weeks of age. In the spinal cord dorsal horn in prenatally VPA-treated mice, the numbers and staining intensities of ionized calcium-binding adapter molecule 1-positive cells were increased and the cell bodies became enlarged, indicating microglial activation. Treatment with PLX3397, a colony-stimulating factor 1 receptor inhibitor, for 10 days resulted in a decreased number of spinal microglia and attenuated mechanical allodynia in adult mice prenatally exposed to VPA. Additionally, intrathecal injection of Mac-1-saporin, a saporin-conjugated anti-CD11b antibody to deplete microglia, abolished mechanical allodynia. These findings suggest that prenatal VPA treatment causes allodynia and that spinal microglia contribute to the increased nociceptive responses.

High-mobility group box 1-mediated hippocampal microglial activation induces cognitive impairment in mice with neuropathic pain

Clinical evidence indicates that cognitive impairment is a common comorbidity of chronic pain, including neuropathic pain, but the mechanism underlying cognitive impairment remains unclear. Neuroinflammation plays a critical role in the development of both neuropathic pain and cognitive impairment. High-mobility group box 1 (HMGB1) is a proinflammatory molecule and could be involved in neuroinflammation-mediated cognitive impairment in the neuropathic pain state. Hippocampal microglial activation in mice has been associated with cognitive impairment. Thus, the current study examined a potential role of HMGB1 and microglial activation in cognitive impairment in mice with neuropathic pain due to a partial sciatic nerve ligation (PSNL). Mice developed cognitive impairment over two weeks, but not one week, after nerve injury. Nerve-injured mice demonstrated decreased nuclear fraction HMGB1, suggesting increased extracellular release of HMGB1. Furthermore, two weeks after PSNL, significant microglia activation was observed in hippocampus. Inhibition of microglial activation with minocycline, local hippocampal microglia depletion with clodronate liposome, or blockade of HMGB1 with either glycyrrhizic acid (GZA) or anti-HMGB1 antibody in PSNL mice reduced hippocampal microglia activation and ameliorated cognitive impairment. Other changes in the hippocampus of PSNL mice potentially related to cognitive impairment, including decreased hippocampal neuron dendrite length and spine densities and decreased α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor (AMPAR) subunits, were prevented with anti-HMGB1 antibody treatment. The current findings suggest that neuro-inflammation involves a number of cellular-level changes and microglial activation. Blocking neuro-inflammation, particularly through blocking HMGB1 could be a novel approach to reducing co-morbidities such as cognitive impairment associated with neuropathic pain.

Physicochemical and Biochemical Evaluation of Amorphous Solid Dispersion of Naringenin Prepared Using Hot-Melt Extrusion

Naringenin (NRG) is a plant-derived flavonoid. Due to its antioxidant, anti-inflammatory, and analgesic activities it is beneficial to human health and is often used as a functional food ingredient; however, it has poor water solubility and low in vivo bioavailability. Therefore, the efficacy of NRG can be improved by enhancing its water solubility to increase gastrointestinal absorption. Conventional methods for the formulation of NRG are very complex and use toxic organic solvents, making them impractical for the production of functional foods. The objective of this study was to develop a safe and effective NRG-based functional food material. Previously, we established a technology to prepare amorphous solid dispersions (SDs) from functional food ingredients with poor water solubility and used hot-melt extrusion technology that is comparatively simple and does not involve the use of organic solvents. In this study, we prepared NRG SD and evaluated them both physicochemically and biochemically. NRG SD had superior water solubility and gastrointestinal absorption relative to native NRG and showed higher analgesic efficacy in rats than crystalline NRG. NRG SD was administered to mice in a mixed diet for 28 days, and organ weights and hematological/clinical biochemical parameters were assessed. NRG SD did not demonstrate severe adverse effects. The results suggest that NRG SD is a safe and highly efficacious formulation that can be used as a functional food material in the future.

Molecular brain (micro report) oxytocin ameliorates impaired social behavior in a mouse model of 3q29 deletion syndrome

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by specific social symptoms, restricted interests, stereotyped repetitive behaviors, and delayed language development. The 3q29 microdeletion (3q29del), a recurrent copy number variant, confers a high risk for ASD and schizophrenia, and serves as an important pathological model for investigating the molecular pathogenesis of a large number of neurodevelopmental and psychiatric conditions. Recently, mouse models carrying a deletion of the chromosomal region corresponding to the human 3q29 region (Df/+ mice) were generated and demonstrated neurodevelopmental and psychiatric conditions associated behavioral abnormalities, pointing to the relevance of Df/+ mice as a model for these conditions with high construct and face validity. Currently, the molecular pathogenesis of these behavioral phenotypes in Df/+ mice remains unclear. The oxytocin (OXT) system plays a central role in social behavior across species and has a potential role in ASD. In this study, to elucidate the molecular mechanisms behind impaired social behavior in Df/+ mice, we investigated the possible involvement of OXT signaling in impaired social behavior in Df/+ mice. We demonstrated that OXT administration restored the impaired social behavior in Df/+ mice. We also demonstrated that the number of OXT-positive cells in the paraventricular nucleus (PVN) was significantly lower in Df/+ mice than in wild-type (WT) littermates. Consistent with this, the level of OXT peptide in the cerebral cortex of Df/+ mice was lower than in WT littermates. Our study may provide important insights into the molecular pathophysiological basis of neurodevelopmental and psychiatric conditions, including ASD.

Claustrum mediates bidirectional and reversible control of stress-induced anxiety responses

The processing of stress responses involves brain-wide communication among cortical and subcortical regions; however, the underlying mechanisms remain elusive. Here, we show that the claustrum (CLA) is crucial for the control of stress-induced anxiety-related behaviors. A combined approach using brain activation mapping and machine learning showed that the CLA activation serves as a reliable marker of exposure to acute stressors. In TRAP2 mice, which allow activity-dependent genetic labeling, chemogenetic activation of the CLA neuronal ensemble tagged by acute social defeat stress (DS) elicited anxiety-related behaviors, whereas silencing of the CLA ensemble attenuated DS-induced anxiety-related behaviors. Moreover, the CLA received strong input from DS-activated basolateral amygdala neurons, and its circuit-selective optogenetic photostimulation temporarily elicited anxiety-related behaviors. Last, silencing of the CLA ensemble during stress exposure increased resistance to chronic DS. The CLA thus bidirectionally controls stress-induced emotional responses, and its inactivation can serve as a preventative strategy to increase stress resilience.

Examination of dissolution ratio of β-carotene in water for practical application of β-carotene amorphous solid dispersion

β-Carotene (BC) has an antioxidant effect that removes active oxygen in vivo and can reduce the risk of developing various diseases, but it is almost insoluble in water. Therefore, to develop highly effective BC functional food products, it is essential to increase its water solubility, which in turn can improve its absolute bioavailability. Recently, a BC amorphous solid dispersion (BC-SD) prepared using hot melt extruder technology had increased water solubility and improved absorption from the gastrointestinal tract. However, only a part of the BC in BC-SD could be dissolved in water. In this study, we evaluated whether the dissolution ratio of BC in water could be improved by examining the mixing ratio of BC and base materials in BC-SD. Results showed that by reducing the mixing ratio of BC to the base materials, the dissolution ratio of BC in water increased. It was also found that when BC-SD, which has the highest dissolution ratio, was intragastrically administered to rats, its absolute bioavailability was most increased. These results are useful findings that may help in reducing the costs associated with the BC-SD manufacturing process and will be an important part of our strategy for practical use in the future.

Generation of KS-133 as a Novel Bicyclic Peptide with a Potent and Selective VIPR2 Antagonist Activity that Counteracts Cognitive Decline in a Mouse Model of Psychiatric Disorders

Worldwide, more than 20 million people suffer from schizophrenia, but effective and definitive new therapeutic drugs/treatments have not been established. Vasoactive intestinal peptide receptor 2 (VIPR2) might be an attractive drug target for the treatment of schizophrenia because both preclinical and clinical studies have demonstrated a strong link between high expression/overactivation of VIPR2 and schizophrenia. Nevertheless, VIPR2-targeting drugs are not yet available. VIPR2 is a class-B G protein-coupled receptor that possesses high structural homology to its subtypes, vasoactive intestinal peptide receptor 1 (VIPR1) and pituitary adenylate cyclase-activating polypeptide type-1 receptor (PAC1). These biological and structural properties have made it difficult to discover small molecule drugs against VIPR2. In 2018, cyclic peptide VIpep-3, a VIPR2-selective antagonist, was reported. The aim of this study was to generate a VIpep-3 derivative for in vivo experiments. After amino acid substitution and structure optimization, we successfully generated KS-133 with 1) a VIPR2-selective and potent antagonistic activity, 2) at least 24 h of stability in plasma, and 3) in vivo pharmacological efficacies in a mouse model of psychiatric disorders through early postnatal activation of VIPR2. To the best of our knowledge, this is the first report of a VIPR2-selective antagonistic peptide that counteracts cognitive decline, a central feature of schizophrenia. KS-133 may contribute to studies and development of novel schizophrenia therapeutic drugs that target VIPR2.

Multiple alterations in glutamatergic transmission and dopamine D2 receptor splicing in induced pluripotent stem cell-derived neurons from patients with familial schizophrenia

An increasing body of evidence suggests that impaired synapse development and function are associated with schizophrenia; however, the underlying molecular pathophysiological mechanism of the disease remains largely unclear. We conducted a family-based study combined with molecular and cellular analysis using induced pluripotent stem cell (iPSC) technology. We generated iPSCs from patients with familial schizophrenia, differentiated these cells into neurons, and investigated the molecular and cellular phenotypes of the patient's neurons. We identified multiple altered synaptic functions, including increased glutamatergic synaptic transmission, higher synaptic density, and altered splicing of dopamine D2 receptor mRNA in iPSC-derived neurons from patients. We also identified patients' specific genetic mutations using whole-exome sequencing. Our findings support the notion that altered synaptic function may underlie the molecular and cellular pathophysiology of schizophrenia, and that multiple genetic factors cooperatively contribute to the development of schizophrenia.

Probing the VIPR2 Microduplication Linkage to Schizophrenia in Animal and Cellular Models

Pituitary adenylate cyclase-activating polypeptide (PACAP, gene name ADCYAP1) is a multifunctional neuropeptide involved in brain development and synaptic plasticity. With respect to PACAP function, most attention has been given to that mediated by its specific receptor PAC1 (ADCYAP1R1). However, PACAP also binds tightly to the high affinity receptors for vasoactive intestinal peptide (VIP, VIP), called VPAC1 and VPAC2 (VIPR1 and VIPR2, respectively). Depending on innervation patterns, PACAP can thus interact physiologically with any of these receptors. VPAC2 receptors, the focus of this review, are known to have a pivotal role in regulating circadian rhythms and to affect multiple other processes in the brain, including those involved in fear cognition. Accumulating evidence in human genetics indicates that microduplications at 7q36.3, containing VIPR2 gene, are linked to schizophrenia and possibly autism spectrum disorder. Although detailed molecular mechanisms have not been fully elucidated, recent studies in animal models suggest that overactivation of the VPAC2 receptor disrupts cortical circuit maturation. The VIPR2 linkage can thus be potentially explained by inappropriate control of receptor signaling at a time when neural circuits involved in cognition and social behavior are being established. Alternatively, or in addition, VPAC2 receptor overactivity may disrupt ongoing synaptic plasticity during processes of learning and memory. Finally, in vitro data indicate that PACAP and VIP have differential activities on the maturation of neurons via their distinct signaling pathways. Thus perturbations in the balance of VPAC2, VPAC1, and PAC1 receptors and their ligands may have important consequences in brain development and plasticity.

Safety and efficacy of an anti-claudin-5 monoclonal antibody to increase blood-brain barrier permeability for drug delivery to the brain in a non-human primate

Claudin-5 (CLDN-5) is an essential component of the tight junction seal in the blood-brain barrier. Previously, we showed that CLDN-5 modulation in vitro via an anti-CLDN-5 monoclonal antibody (mAb) may be useful for increasing the permeability of the blood-brain barrier for drug delivery to the brain. Based on these findings, here we examined the safety and efficacy of the anti-CLDN-5 mAb in a non-human primate. Cynomolgus monkeys were intravenously administered the anti-CLDN-5 mAb followed by fluorescein dye (376 Da), and the concentrations of the dye in the cerebrospinal fluid was examined. When the mAb was administered at 3.0 mg/kg, the concentration of dye in the cerebrospinal fluid was increased, and no behavioral changes or changes in plasma biomarkers for inflammation or liver or kidney injury were observed. However, a monkey that received the mAb at 6 mg/kg experienced convulsions, and subsequent histopathological examination of this animal revealed vasodilation in the liver, lung, and kidney; hemorrhage in the lung; and edema in the brain. Together, our data indicate that CLDN-5 might be a potential target for enhancing drug delivery to the brain, but also that the therapeutic window of the anti-CLDN-5 mAb may be narrow for separating efficacy and toxicity.

The pivotal role of pituitary adenylate cyclase-activating polypeptide for lactate production and secretion in astrocytes during fear memory

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide (PACAP) plays an essential role in the modulation of astrocyte functions. Although lactate secretion from astrocytes contributes to many forms of neuronal plasticity in the central nervous system, including fear learning and memory, the role of PACAP in lactate secretion from astrocytes is unclear.

METHODS

The amygdala and hippocampus of PACAP (+ / +) and PACAP (-/-) mice were acquired 1 h after memory acquisition and recall in the passive avoidance test. The concentration of glycogen and lactate in these regions was measured. The concentration of lactate in the hippocampus's extracellular fluid was also measured by microdialysis during memory acquisition or intracerebroventricular administration of PACAP.

RESULTS

We observed that memory acquisition caused a significant decrease in glycogen concentration and increased lactate concentration in the PACAP (+ / +) mice's hippocampus. However, memory acquisition did not increase in the lactate concentration in PACAP (-/-) mice's hippocampus. Further, memory retrieval evoked lactate production in the amygdala and the hippocampus of PACAP (+ / +) mice. Still, there was no significant increase in lactate concentration in the same regions of PACAP (-/-) mice. In vivo microdialysis in rats revealed that the hippocampus's extracellular lactate concentration increased after a single PACAP intracerebroventricular injection. Additionally, the hippocampus's extracellular lactate concentration increased with the memory acquisition in PACAP (+ / +) mice, but not in PACAP (-/-) mice.

CONCLUSIONS

PACAP may enhance lactate production and secretion in astrocytes during the acquisition and recall of fear memories.

Intranasal oxytocin administration ameliorates social behavioral deficits in a POGZWT/Q1038R mouse model of autism spectrum disorder

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder characterized by core symptoms of impaired social behavior and communication. Recent studies have suggested that the oxytocin system, which regulates social behavior in mammals, is potentially involved in ASD. Mouse models of ASD provide a useful system for understanding the associations between an impaired oxytocin system and social behavior deficits. However, limited studies have shown the involvement of the oxytocin system in the behavioral phenotypes in mouse models of ASD. We have previously demonstrated that a mouse model that carries the ASD patient-derived de novo mutation in the pogo transposable element derived with zinc finger domain (POGZ^WT/Q1038R mice), showed ASD-like social behavioral deficits. Here, we have explored whether oxytocin (OXT) administration improves impaired social behavior in POGZ^WT/Q1038R mice and found that intranasal oxytocin administration effectively restored the impaired social behavior in POGZ^WT/Q1038R mice. We also found that the expression level of the oxytocin receptor gene (OXTR) was low in POGZ^WT/Q1038R mice. However, we did not detect significant changes in the number of OXT-expressing neurons between the paraventricular nucleus of POGZ^WT/Q1038R mice and that of WT mice. A chromatin immunoprecipitation assay revealed that POGZ binds to the promoter region of OXTR and is involved in the transcriptional regulation of OXTR. In summary, our study demonstrate that the pathogenic mutation in the POGZ, a high-confidence ASD gene, impairs the oxytocin system and social behavior in mice, providing insights into the development of oxytocin-based therapeutics for ASD.

Improved Bioavailability of β-Carotene by Amorphous Solid Dispersion Technology in Rats

β-Carotene (BC) is a natural lipophilic carotenoid mainly present in vegetables and fruits. Although it has various beneficial pharmacological activities, its bioavailability is low owing to its low water solubility. Recently, we reported that BC solid dispersion prepared using hot-melt technology with polyvinylpyrrolidone and sucrose fatty acid esters was in an amorphous state and showed the highest solubility. We hypothesized that the absorption of BC solid dispersion would be better because of its increased water solubility. To verify this, we conducted a pharmacokinetic analysis of BC for application in functional foods. Crystalline or amorphous BC was orally administered to rats. Blood was collected at various time points, and the BC concentration in the plasma was measured by HPLC. Oral administration of amorphous BC showed increased absorption in rats compared with that of BC crystals. Using blood samples from rats that were intravenously injected with the plasma of rats that had been orally administered BC, pharmacokinetic parameters could be calculated without using organic solvents or surfactants. It was possible to calculate various pharmacokinetic parameters under physiological conditions according to amorphous BC characteristics. Thus, we were able to determine the bioavailability of BC after oral administration. This simple technology to improve BC solubility without the use of organic solvents can be applied not only in the pharmaceutical industry but also in the food industry, and it therefore has high utility value.

Activation of the VPAC2 Receptor Impairs Axon Outgrowth and Decreases Dendritic Arborization in Mouse Cortical Neurons by a PKA-Dependent Mechanism

Clinical studies have shown that microduplications at 7q36.3, containing VIPR2, confer significant risk for schizophrenia and autism spectrum disorder (ASD). VIPR2 gene encodes the VPAC2 receptor for vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Lymphocytes from patients with these mutations exhibited higher VIPR2 gene expression and VIP-induced cAMP responsiveness, but mechanisms by which overactive VPAC2 signaling may lead to these psychiatric disorders are unknown. We have previously found that repeated administration of a selective VPAC2 receptor agonist Ro25-1553 in the mouse during early postnatal development caused synaptic alterations in the prefrontal cortex and sensorimotor gating deficits. In this study, we aimed to clarify the effects of VPAC2 receptor activation on neurite outgrowth in cultured primary mouse cortical neurons. Ro25-1553 and VIP caused reductions in total numbers and lengths of both neuronal dendrites and axons, while PACAP38 facilitated elongation of dendrites, but not axons. These effects of Ro25-1553 and VIP were blocked by a VPAC2 receptor antagonist PG99-465 and abolished in VPAC2 receptor-deficient mice. Additionally, Ro25-1553-induced decreases in axon and dendritic outgrowth in wild-type mice were blocked by a protein kinase A (PKA) inhibitor H89, but not by a PKC inhibitor GF109203X or a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor U0126. PACAP38- induced facilitation of dendritic outgrowth was blocked by U0126. These results suggest that activation of the VPAC2 receptor impairs neurite outgrowth and decreases branching of cortical neurons by a PKA-dependent mechanism. These findings also imply that the VIPR2-linkage to mental health disorders may be due in part to deficits in neuronal maturation induced by VPAC2 receptor overactivation.

Direct visualization of an antidepressant analog using surface-enhanced Raman scattering in the brain

Detailed spatial information of low-molecular weight compound distribution, especially in the brain, is crucial to understanding their mechanism of actions. Imaging techniques that can directly visualize drugs in the brain at a high resolution will complement existing tools for drug distribution analysis. Here, we performed surface-enhanced Raman scattering (SERS) imaging using a bioorthogonal alkyne tag to visualize drugs directly in situ at a high resolution. Focusing on the selective serotonin reuptake inhibitor S-citalopram (S-Cit), which possesses a nitrile group, we substituted an alkynyl group into its structure and synthesized alkynylated S-Cit (Alk-S-Cit). The brain transitivity and the serotonin reuptake inhibition of Alk-S-Cit were not significantly different as compared with S-Cit. Alk-S-Cit was visualized in the coronal mouse brain section using SERS imaging with silver nanoparticles. Furthermore, SERS imaging combined with fluorescence microscopy allowed Alk-S-Cit to be visualized in the adjacent neuronal membranes, as well as in the brain vessel and parenchyma. Therefore, our multimodal imaging technique is an effective method for detecting low-molecular weight compounds in their original tissue environment and can potentially offer additional information regarding the precise spatial distribution of such drugs.

Valproic acid attenuates CCR2-dependent tumor infiltration of monocytic myeloid-derived suppressor cells, limiting tumor progression

Myeloid-derived suppressor cells (MDSCs) are immunosuppressive cells that promote tumor progression by inhibiting anti-tumor immunity and may be the cause of patient resistance to immune checkpoint inhibitors (ICIs). Therefore, MDSCs are a promising target for cancer immunotherapy, especially in combination with ICIs. Previous studies have shown that the anticonvulsant drug valproic acid (VPA) has additional anti-cancer and immunoregulatory activities due to its inhibition of histone deacetylases. We have previously shown that VPA can attenuate the immunosuppressive function of differentiated MDSCs in vitro. In the present study, we utilized anti-PD-1-sensitive EL4 and anti-PD-1-resistant B16-F10 tumor-bearing mouse models and investigated the effects of VPA on MDSCs with the aim of enhancing the anti-cancer activity of an anti-PD-1 antibody. We showed that VPA could inhibit EL4 and B16-F10 tumor progression, which was dependent on the immune system. We further demonstrated that VPA down-regulated the expression of CCR2 on monocytic (M)-MDSCs, leading to the reduced infiltration of M-MDSCs into tumors. Importantly, we demonstrated that VPA could relieve the immunosuppressive action of MDSCs on CD8⁺ T-cell and NK cell proliferation and enhance their activation in tumors. We also observed that the combination of VPA plus an anti-PD-1 antibody was more effective than either agent alone in both the EL4 and B16-F10 tumor models. These results suggest that VPA can effectively relieve the immunosuppressive tumor microenvironment by reducing tumor infiltration of M-MDSCs, resulting in tumor regression. Our findings also show that VPA in combination with an immunotherapeutic agent could be a potential new anti-cancer therapy.

Pathogenic POGZ mutation causes impaired cortical development and reversible autism-like phenotypes

Pogo transposable element derived with ZNF domain (POGZ) has been identified as one of the most recurrently de novo mutated genes in patients with neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD), intellectual disability and White-Sutton syndrome; however, the neurobiological basis behind these disorders remains unknown. Here, we show that POGZ regulates neuronal development and that ASD-related de novo mutations impair neuronal development in the developing mouse brain and induced pluripotent cell lines from an ASD patient. We also develop the first mouse model heterozygous for a de novo POGZ mutation identified in a patient with ASD, and we identify ASD-like abnormalities in the mice. Importantly, social deficits can be treated by compensatory inhibition of elevated cell excitability in the mice. Our results provide insight into how de novo mutations on high-confidence ASD genes lead to impaired mature cortical network function, which underlies the cellular pathogenesis of NDDs, including ASD.

De novo mutations significantly contribute to autism spectrum disorders (ASD). Here, the authors demonstrate that ASD-associated de novo mutations in the POGZ gene, one of a high-confidence ASD gene, lead to ASD-related impaired neuronal development and disrupted mature cortical network function.

Psychiatric-disorder-related behavioral phenotypes and cortical hyperactivity in a mouse model of 3q29 deletion syndrome

3q29 microdeletion, a rare recurrent copy number variant (CNV), greatly confers an increased risk of psychiatric disorders, such as schizophrenia and autism spectrum disorder (ASD), as well as intellectual disability. However, disease-relevant cellular phenotypes of 3q29 deletion syndrome remain to be identified. To reveal the molecular and cellular etiology of 3q29 deletion syndrome, we generated a mouse model of human 3q29 deletion syndrome by chromosome engineering, which achieved construct validity. 3q29 deletion (Df/+) mice showed reduced body weight and brain volume and, more importantly, impaired social interaction and prepulse inhibition. Importantly, the schizophrenia-related impaired prepulse inhibition was reversed by administration of antipsychotics. These findings are reminiscent of the growth defects and neuropsychiatric behavioral phenotypes in patients with 3q29 deletion syndrome and exemplify that the mouse model achieves some part of face validity and predictive validity. Unbiased whole-brain imaging revealed that neuronal hyperactivation after a behavioral task was strikingly exaggerated in a restricted region of the cortex of Df/+ mice. We further elucidated the cellular phenotypes of neuronal hyperactivation and the reduction of parvalbumin expression in the cortex of Df/+ mice. Thus, the 3q29 mouse model provides invaluable insight into the disease-causative molecular and cellular pathology of psychiatric disorders.

Autism-associated protein kinase D2 regulates embryonic cortical neuron development

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder, characterized by impaired social interaction, repetitive behavior and restricted interests. Although the molecular etiology of ASD remains largely unknown, recent studies have suggested that de novo mutations are significantly involved in the risk of ASD. We and others recently identified spontaneous de novo mutations in PKD2, a protein kinase D family member, in sporadic ASD cases. However, the biological significance of the de novo PKD2 mutations and the role of PKD2 in brain development remain unclear. Here, we performed functional analysis of PKD2 in cortical neuron development using in utero electroporation. PKD2 is highly expressed in cortical neural stem cells in the developing cortex and regulates cortical neuron development, including the neuronal differentiation of neural stem cells and migration of newborn neurons. Importantly, we determined that the ASD-associated de novo mutations impair the kinase activity of PKD2, suggesting that the de novo PKD2 mutations can be a risk factor for the disease by loss of function of PKD2. Our current findings provide novel insight into the molecular and cellular pathogenesis of ASD.

(R)-Ketamine Induces a Greater Increase in Prefrontal 5-HT Release Than (S)-Ketamine and Ketamine Metabolites via an AMPA Receptor-Independent Mechanism

BACKGROUND

Although recent studies provide insight into the molecular mechanisms of the effects of ketamine, the antidepressant mechanism of ketamine enantiomers and their metabolites is not fully understood. In view of the involvement of mechanisms other than the N-methyl-D-aspartate receptor in ketamine's action, we investigated the effects of (R)-ketamine, (S)-ketamine, (R)-norketamine [(R)-NK], (S)-NK, (2R,6R)-hydroxynorketamine [(2R,6R)-HNK], and (2S,6S)-HNK on monoaminergic neurotransmission in the prefrontal cortex of mice.

METHODS

The extracellular monoamine levels in the prefrontal cortex were measured by in vivo microdialysis.

RESULTS

(R)-Ketamine and (S)-ketamine acutely increased serotonin release in a dose-dependent manner, and the effect of (R)-ketamine was greater than that of (S)-ketamine. In contrast, (S)-ketamine caused a robust increase in dopamine release compared with (R)-ketamine. Both ketamine enantiomers increased noradrenaline release, but these effects did not differ. (2R,6R)-HNK caused a slight but significant increase in serotonin and noradrenaline but not dopamine release. (S)-NK increased dopamine and noradrenaline but not serotonin release. Differential effects between (R)-ketamine and (S)-ketamine were also observed in a lipopolysaccharide-induced model of depression. An α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor antagonist, 2,3-dioxo-6-nitro-1,2,3,4- tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), attenuated (S)-ketamine-induced, but not (R)-ketamine-induced serotonin release, whereas NBQX blocked dopamine release induced by both enantiomers. Local application of (R)-ketamine into the prefrontal cortex caused a greater increase in prefrontal serotonin release than that of (S)-ketamine.

CONCLUSIONS

(R)-Ketamine strongly activates the prefrontal serotonergic system through an AMPA receptor-independent mechanism. (S)-Ketamine-induced serotonin and dopamine release was AMPA receptor-dependent. These findings provide a neurochemical basis for the underlying pharmacological differences between ketamine enantiomers and their metabolites.

[Pathophysiological implication of the VPAC2 receptor in psychiatric disorders]

The advent of the genomic era has led to the discovery of linkages of several genes and pathways to schizophrenia and autism spectrum disorder (ASD) that may serve as new biomarkers or therapeutic targets for these diseases. Two large-scale genetic studies published early in 2011 provided evidence that functional microduplications at 7q36.3, containing VIPR2, are a risk factor for schizophrenia. 7q36.3 microduplications were also reported to be significantly increased in ASD. VIPR2 encodes VPAC2, a seven transmembrane heterotrimeric G protein-coupled receptor that binds two homologous neuropeptides with high affinity, PACAP and VIP. These clinical studies demonstrate a VIPR2 genetic linkage to schizophrenia and ASD and should lead to novel insights into the etiology of these mental health disorders. However, the mechanism by which overactive VPAC2 signaling may lead to schizophrenia and ASD is unknown. In the present review, we will describe recent advances in the genetics of schizophrenia and attempt to discuss the pathophysiological role of altered VPAC2 signaling in psychiatric disorders.

LY341495, an mGluR2/3 Antagonist, Regulates the Immunosuppressive Function of Myeloid-Derived Suppressor Cells and Inhibits Melanoma Tumor Growth

Myeloid-derived suppressor cells (MDSCs) are immunosuppressive myeloid cells found in patients with cancer and in mouse tumor models. They suppress anti-tumor immunity, resulting in the promotion of tumor growth. The relationship between nutrition and cancer has recently been reported by several research groups. Tumor cells rely on glutaminolysis, in which glutamine is metabolized into glutamate for energy production, and hence, glutamate levels are elevated in tumor-bearing hosts. However, the mechanism of regulation of tumor progression by glutamate still remains unclear. In this study, we found that the metabotropic glutamate receptor (mGluR) 2/3 was expressed on MDSCs, and an mGluR2/3 antagonist LY341495 attenuated the immunosuppressive activity of MDSCs. Furthermore, we observed that LY341495 treatment inhibited B16-F10 melanoma growth in vivo. Taken together, our data suggest that glutamate signaling promotes tumor growth by increasing the potency of immune suppression.

The Robo4-TRAF7 complex suppresses endothelial hyperpermeability in inflammation

Roundabout guidance receptor 4 (Robo4) is an endothelial cell-specific receptor that stabilizes the vasculature in pathological angiogenesis. Although Robo4 has been shown to suppress vascular hyperpermeability induced by vascular endothelial growth factor (VEGF) in angiogenesis, the role of Robo4 in inflammation is poorly understood. In this study, we investigated the role of Robo4 in vascular hyperpermeability during inflammation. Endotoxemia models using Robo4 ^-/- mice showed increased mortality and vascular leakage. In endothelial cells, Robo4 suppressed tumor necrosis factor α (TNFα)-induced hyperpermeability by stabilizing VE-cadherin at cell junctions, and deletion assays revealed that the C-terminus of Robo4 was involved in this suppression. Through binding and localization assays, we demonstrated that in endothelial cells, Robo4 binds to TNF receptor-associated factor 7 (TRAF7) through interaction with the C-terminus of Robo4. Gain- and loss-of-function studies of TRAF7 with or without Robo4 expression showed that TRAF7 is required for Robo4-mediated suppression of hyperpermeability. Taken together, our results demonstrate that the Robo4-TRAF7 complex is a novel negative regulator of inflammatory hyperpermeability. We propose this complex as a potential future target for protection against inflammatory diseases.

Valproic acid attenuates immunosuppressive function of myeloid-derived suppressor cells

Immune checkpoint blockade (ICB) is a promising novel therapy for multiple cancer types; however, most patients show limited or no clinical response. Accumulating evidence indicates that myeloid-derived suppressor cells (MDSCs) are a major factor responsible for immunosuppression in patients with cancer. Therefore, identifying effective therapies that deplete or modulate MDSCs is essential. In this study, we focus on the anticonvulsant drug valproic acid (VPA), which has additional activities including anticancer and immunoregulation by inhibition of histone deacetylases. We showed that VPA decreased the proportion of polymorphonuclear (PMN)-MDSCs in vitro and showed for the first time that VPA greatly attenuated the immunosuppressive function of MDSCs in a dose-dependent manner. Moreover, we demonstrated that in vitro differentiated VPA-conditioned MDSCs exhibited impaired ability to stimulate tumor progression in vivo. We also showed the possible involvement of several mechanisms in the VPA-induced attenuation of the immunosuppressive function of MDSCs, including the interleukin-4 receptor-α (IL-4Rα)/arginase axis, programmed cell death 1 ligand 1 (PD-L1) and toll-like receptor 4 (TLR4) signaling pathways, and retinoblastoma 1 (Rb1) derepression. This research highlights the potential of combining VPA with ICB in cancer treatment.