Sex-specific GABAergic microcircuits that switch vulnerability into resilience to stress and reverse the effects of chronic stress exposure.

Clinical and preclinical studies have identified somatostatin (SST)-positive interneurons as key elements that regulate the vulnerability to stress-related psychiatric disorders. Conversely, disinhibition of SST neurons in mice results in resilience to the behavioral effects of chronic stress. Here we established a low-dose chronic chemogenetic protocol to map these changes in positively and negatively motivated behaviors to specific brain regions. AAV-hM3Dq mediated chronic activation of SST neurons in the prelimbic cortex (PLC) had antidepressant drug-like effects on anxiety- and anhedonia-related motivated behaviors in male but not female mice. Analogous manipulation of the ventral hippocampus (vHPC) had such effects in female but not male mice. Moreover, activation of SST neurons in the PLC of male and the vHPC of female mice resulted in stress resilience. Activation of SST neurons in the PLC reversed prior chronic stress-induced defects in motivated behavior in males but was ineffective in females. Conversely, activation of SST neurons in the vHPC reversed chronic stress-induced behavioral alterations in females but not males. Quantitation of c-Fos + and FosB + neurons in chronic stress-exposed mice revealed that chronic activation of SST neurons leads to a paradoxical increase in pyramidal cell activity. Collectively, these data demonstrate that GABAergic microcircuits driven by dendrite targeting interneurons enable sex- and brain-region-specific neural plasticity that promotes stress resilience and reverses stress-induced anxiety- and anhedonia-like motivated behavior. Our studies provide a mechanistic rationale for antidepressant efficacy of dendrite-targeting, low-potency GABA A receptor agonists, independent of sex and despite striking sex differences in the relevant brain substrates.

Disinhibition of somatostatin interneurons confers resilience to stress in male but not female mice.

Chronic stress represents a vulnerability factor for anxiety and depressive disorders and has been widely used to model aspects of these disorders in rodents. Disinhibition of somatostatin (SST)-positive GABAergic interneurons in mice by deletion of γ2 GABAA receptors selectively from these cells (SSTCre:γ2f/f mice) has been shown to result in behavioral and biochemical changes that mimic the responses to antidepressant doses of ketamine. Here we explored the extent to which SSTCre:γ2f/f mice exhibit resilience to unpredictable chronic mild stress (UCMS). We found that male SSTCre:γ2f/f mice are resilient to UCMS-induced (i) reductions in weight gain, (ii) reductions in SST-immuno-positive cells in medial prefrontal cortex (mPFC), (iii) increases in phosphorylation of eukaryotic elongation factor 2 (eEF2) in mPFC, and (iv) increased anxiety in a novelty suppressed feeding test. Female SSTCre:γ2f/f mice were resilient to UCMS-induced reductions in SST-immuno-positive cells indistinguishably from males. However, in contrast to males, they showed no UCMS effects on weight gain independent of genotype. Moreover, in mPFC of female γ2f/f control mice, UCMS resulted in paradoxically reduced p-EF2 levels without stress effects in the SSTCre:γ2f/f mutants. Lastly, female SSTCre:γ2f/f mice showed increased rather than reduced UCMS induced anxiety compared to γ2f/f controls. Thus, disinhibition of SST interneurons results in behavioral resilience to UCMS selectively in male mice, along with cellular resilience of SST neurons to UCMS independent of sex. Thus, mechanisms underlying vulnerability and resilience to stress are sex specific and map to mPFC rather than hippocampus but appear unrelated to changes in expression of SST as a marker of corresponding interneurons.

Antidepressant mechanisms of ketamine: Focus on GABAergic inhibition.

There has been much recent progress in understanding of the mechanism of ketamine's rapid and enduring antidepressant effects. Here we review recent insights from clinical and preclinical studies, with special emphasis of ketamine-induced changes in GABAergic synaptic transmission that are considered essential for its antidepressant therapeutic effects. Subanesthetic ketamine is now understood to exert its initial action by selectively blocking a subset of NMDA receptors on GABAergic interneurons, which results in disinhibition of glutamatergic target neurons, a surge in extracellular glutamate and correspondingly elevated glutamatergic synaptic transmission. This surge in glutamate appears to be corroborated by the rapid metabolism of ketamine into hydroxynorketamine, which acts at presynaptic sites to disinhibit the release of glutamate. Preclinical studies indicate that glutamate-induced activity triggers the release of BDNF, followed by transient activation of the mTOR pathway and increased expression of synaptic proteins, along with functional strengthening of glutamatergic synapses. This drug-on phase lasts for approximately 2h and is followed by a period of days characterized by structural maturation of newly formed glutamatergic synapses and prominently enhanced GABAergic synaptic inhibition. Evidence from mouse models with constitutive antidepressant-like phenotypes suggests that this phase involves strengthened inhibition of dendrites by somatostatin-positive GABAergic interneurons and correspondingly reduced NMDA receptor-mediated Ca2+ entry into dendrites, which activates an intracellular signaling cascade that converges with the mTOR pathway onto increased activity of the eukaryotic elongation factor eEF2 and enhanced translation of dendritic mRNAs. Newly synthesized proteins such as BDNF may be important for the prolonged therapeutic effects of ketamine.

Residual Learning for Salient Object Detection.

Recent deep learning based salient object detection methods improve the performance by introducing multi-scale strategies into fully convolutional neural networks (FCNs). The final result is obtained by integrating all the predictions at each scale. However, the existing multi-scale based methods suffer from several problems: 1) it is difficult to directly learn discriminative features and filters to regress high-resolution saliency masks for each scale; 2) rescaling the multi-scale features could pull in many redundant and inaccurate values, and this weakens the representational ability of the network. In this paper, we propose a residual learning strategy and introduce to gradually refine the coarse prediction scale-by-scale. Concretely, instead of directly predicting the finest-resolution result at each scale, we learn to predict residuals to remedy the errors between coarse saliency map and scale-matching ground truth masks. We employ a Dilated Convolutional Pyramid Pooling (DCPP) module to generate the coarse prediction and guide the the residual learning process through several novel Attentional Residual Modules (ARMs). We name our network as Residual Refinement Network (R2Net). We demonstrate the effectiveness of the proposed method against other state-of-the-art algorithms on five released benchmark datasets. Our R2Net is a fully convolutional network which does not need any post-processing and achieves a real-time speed of 33 FPS when it is run on one GPU.

Angptl8 mediates food-driven resetting of hepatic circadian clock in mice.

Diurnal light-dark cycle resets the master clock, while timed food intake is another potent synchronizer of peripheral clocks in mammals. As the largest metabolic organ, the liver sensitively responds to the food signals and secretes hepatokines, leading to the robust regulation of metabolic and clock processes. However, it remains unknown which hepatokine mediates the food-driven resetting of the liver clock independent of the master clock. Here, we identify Angptl8 as a hepatokine that resets diurnal rhythms of hepatic clock and metabolic genes in mice. Mechanistically, the resetting function of Angptl8 is dependent on the signal relay of the membrane receptor PirB, phosphorylation of kinases and transcriptional factors, and consequently transient activation of the central clock gene Per1. Importantly, inhibition of Angptl8 signaling partially blocks food-entrained resetting of liver clock in mice. We have thus identified Angptl8 as a key regulator of the liver clock in response to food.

Gluconate suppresses seizure activity in developing brains by inhibiting CLC-3 chloride channels.

Neonatal seizures are different from adult seizures, and many antiepileptic drugs that are effective in adults often fail to treat neonates. Here, we report that gluconate inhibits neonatal seizure by inhibiting CLC-3 chloride channels. We detect a voltage-dependent outward rectifying Cl- current mediated by CLC-3 Cl- channels in early developing brains but not adult mouse brains. Blocking CLC-3 Cl- channels by gluconate inhibits seizure activity both in neonatal brain slices and in neonatal animals with in vivo EEG recordings. Consistently, neonatal neurons of CLC-3 knockout mice lack the outward rectifying Cl- current and show reduced epileptiform activity upon stimulation. Mechanistically, we demonstrate that activation of CLC-3 Cl- channels alters intracellular Cl- homeostasis and enhances GABA excitatory activity. Our studies suggest that gluconate can suppress neonatal seizure activities through inhibiting CLC-3 Cl- channels in developing brains.

Reversal of a Treatment-Resistant, Depression-Related Brain State with the Kv7 Channel Opener Retigabine.

Neuroinflammation is associated with increased vulnerability to diverse psychiatric conditions, including treatment-resistant major depressive disorder (MDD). Here we assessed whether high fat diet (HFD) induced neuroinflammation may be suitable to model a treatment-resistant depressive-like brain state in mice. Male and female mice were fed a HFD for 18 weeks, followed by quantitation of glucose tolerance, inflammatory markers of brain tissue (TNFα, IL-6, IL-1ß, Iba-1), neural excitability in the prelimbic cortex (PLC), as well as assessment of emotional reactivity and hedonic behavior in a battery of behavioral tests. In addition, we assessed the behavioral responsiveness of mice to fluoxetine, desipramine, ketamine, and the Kv7 channel opener and anticonvulsant retigabine. HFD exposure led to glucose intolerance and neuroinflammation in male mice, with similar but non-significant trends in females. Neuroinflammation of males was associated with anxious-depressive-like behavior and defects in working memory, along with neural hyperexcitability and increased Ih currents of pyramidal cells in the PLC. The behavioral changes were largely resistant to chronic treatment with fluoxetine and desipramine, as well as ketamine. By contrast, retigabine (also known as ezogabine) normalized neural excitability and Ih currents recorded from slices of HFD-treated animals and significantly ameliorated most of the behavioral impairments, without effects in control diet exposed animals. Thus, treatment resistant depressive-like brain states that are associated with chronic neuroinflammation may involve hyperexcitability of pyramidal neurons and may be effectively treated by retigabine.

Ketamine normalizes binge drinking-induced defects in glutamatergic synaptic transmission and ethanol drinking behavior in female but not male mice.

Ketamine is a fast acting experimental antidepressant with significant therapeutic potential for emotional disorders such as major depressive disorder and alcohol use disorders. Of particular interest is binge alcohol use, which during intermittent withdrawal from drinking involves depressive-like symptoms reminiscent of major depressive disorder. Binge drinking has been successfully modeled in mice with the Drinking in the Dark (DID) paradigm, which involves daily access to 20% ethanol, for a limited duration and selectively during the dark phase of the circadian light cycle. Here we demonstrate that DID exposure reduces the cell surface expression of NMDA- and AMPA-type glutamate receptors in the prelimbic cortex (PLC) of female but not male mice, along with reduced activity of the mammalian target of rapamycin (mTOR) signaling pathway. Pretreatment with an acute subanesthetic dose of ketamine suppresses binge-like ethanol consumption in female but not male mice. Lastly, DID-exposure reduces spontaneous glutamatergic synaptic transmission in the PLC of both sexes, but synaptic transmission is rescued by ketamine selectively in female mice. Thus, ketamine may have therapeutic potential as an ethanol binge suppressing agent selectively in female subjects.

An Unsupervised Game-Theoretic Approach to Saliency Detection.

We propose a novel unsupervised game-theoretic salient object detection algorithm that does not require labeled training data. First, saliency detection problem is formulated as a non-cooperative game, hereinafter referred to as Saliency Game, in which image regions are players who choose to be "background" or "foreground" as their pure strategies. A payoff function is constructed by exploiting multiple cues and combining complementary features. Saliency maps are generated according to each region's strategy in the Nash equilibrium of the proposed Saliency Game. Second, we explore the complementary relationship between color and deep features and propose an Iterative Random Walk algorithm to combine saliency maps produced by the Saliency Game using different features. Iterative random walk allows sharing information across feature spaces, and detecting objects that are otherwise very hard to detect. Extensive experiments over 6 challenging datasets demonstrate the superiority of our proposed unsupervised algorithm compared to several state of the art supervised algorithms.

Genipin alleviates high-fat diet-induced hyperlipidemia and hepatic lipid accumulation in mice via miR-142a-5p/SREBP-1c axis.

Hyperlipidemia is a chronic disorder which plays an important role in the development of cardiovascular diseases, type 2 diabetes, atherosclerosis, hypertension, and nonalcoholic fatty liver disease. Genipin (GNP) is a metabolite from genipioside, which is an active component of the traditional Chinese medicine Gardenia jasminoides Ellis, and has been recognized as a beneficial compound against metabolic disorders. However, whether it can correct overnutrition-induced dyslipidemia is still unknown. In this study, the effects of GNP on attenuating hyperlipidemia and hepatic lipid accumulation were investigated using normal and obese mice induced with a high-fat diet (HFD) and primary hepatocytes treated with free fatty acids. We also sought to identify potential targets of GNP to mediate its effects in the liver. We found that obese mice treated with GNP showed a decrease in the body weight, serum lipid levels, as well as hepatic lipid accumulation. Besides, GNP regulated hepatic expression levels of lipid metabolic genes, which are important in maintaining systemic lipid homeostasis. At the molecular level, GNP increased the expression levels of miR-142a-5p, which bound to 3' untranslated region of Srebp-1c, an important regulator of lipogenesis, which thus led to the inhibition of lipogenesis. Collectively, our data demonstrated that GNP effectively antagonized HFD-induced hyperlipidemia and hepatic lipid accumulation in mice. Such effects were achieved by regulating miR-142a-5p/SREBP-1c axis.

Vanishing point attracts gaze in free-viewing and visual search tasks.

Several structural scene cues such as gist, layout, horizontal line, openness, and depth have been shown to guide scene perception (e.g., Oliva & Torralba, 2001); Ross & Oliva, 2009). Here, to investigate whether vanishing point (VP) plays a significant role in gaze guidance, we ran two experiments. In the first one, we recorded fixations of 10 observers (six male, four female; mean age 22; SD = 0.84) freely viewing 532 images, out of which 319 had a VP (shuffled presentation; each image for 4 s). We found that the average number of fixations at a local region (80 × 80 pixels) centered at the VP is significantly higher than the average fixations at random locations (t test; n = 319; p < 0.001). To address the confounding factor of saliency, we learned a combined model of bottom-up saliency and VP. The AUC (area under curve) score of our model (0.85; SD = 0.01) is significantly higher than the base saliency model (e.g., 0.8 using attention for information maximization (AIM) model by Bruce & Tsotsos, 2005, t test; p = 3.14e-16) and the VP-only model (0.64, t test; p < 0.001). In the second experiment, we asked 14 subjects (10 male, four female; mean age 23.07, SD = 1.26) to search for a target character (T or L) placed randomly on a 3 × 3 imaginary grid overlaid on top of an image. Subjects reported their answers by pressing one of the two keys. Stimuli consisted of 270 color images (180 with a single VP, 90 without). The target happened with equal probability inside each cell (15 times L, 15 times T). We found that subjects were significantly faster (and more accurate) when the target appeared inside the cell containing the VP compared to cells without the VP (median across 14 subjects 1.34 s vs. 1.96 s; Wilcoxon rank-sum test; p = 0.0014). These findings support the hypothesis that vanishing point, similar to face, text (Cerf, Frady, & Koch, 2009), and gaze direction Borji, Parks, & Itti, 2014) guides attention in free-viewing and visual search tasks.

Dissociation of Golgi-associated DHHC-type Zinc Finger Protein (GODZ)- and Sertoli Cell Gene with a Zinc Finger Domain-ß (SERZ-ß)-mediated Palmitoylation by Loss of Function Analyses in Knock-out Mice.

The γ2 subunit of GABA type A receptors (GABAARs) is thought to be subject to palmitoylation by both Golgi-associated DHHC-type zinc finger protein (GODZ; also known as DHHC3) and its paralog Sertoli cell gene with a zinc finger domain-ß (SERZ-ß; DHHC7) based on overexpression of enzymes and substrates in heterologous cells. Here we have further investigated the substrate specificity of these enzymes by characterization of GODZ and SERZ-ß knock-out (KO) mice as well as double KO (DKO) neurons. Palmitoylation of γ2 and a second substrate, growth-associated protein of 43 kDa, that is independently implicated in trafficking of GABAARs was significantly reduced in brain of GODZ KO versus wild-type (WT) mice but unaltered in SERZ-ß KO mice. Accumulation of GABAARs at synapses, GABAergic innervation, and synaptic function were reduced in GODZ KO and DKO neurons to a similar extent, indicating that SERZ-ß does not contribute to palmitoylation or trafficking of GABAARs even in the absence of GODZ. Notably, these effects were seen only when mutant neurons were grown in competition with WT neurons, thereby mimicking conditions of shRNA-transfected neurons previously used to characterize GODZ. However, GABA-evoked whole-cell currents of DKO neurons and the GABAAR cell surface expression in DKO neurons and GODZ or SERZ-ß KO brain slices were unaltered, indicating that GODZ-mediated palmitoylation selectively controls the pool of receptors at synapses. The different substrate specificities of GODZ and SERZ-ß in vivo were correlated with their differential localization to cis- versus trans-Golgi compartment, a mechanism that was compromised by overexpression of GODZ.

Identification of sturgeon IgD bridges the evolutionary gap between elasmobranchs and teleosts.

IgD has been found in almost all jawed vertebrates, including cartilaginous and teleost fish. However, IgD is missing in acipenseriformes, a branch that is evolutionarily positioned between elasmobranchs and teleost fish. Here, by analyzing transcriptome data, we identified a transcriptionally active IgD-encoding gene in the Siberian sturgeon (Acipenser baerii). Phylogenetic analysis indicated that it is orthologous to mammalian IgD and closely related to the IgD of other fish. The lengths of sturgeon membrane-bound IgD transcripts ranged from 1.2kb to 6.2kb, encoding 3-19 CH domains. As in teleosts, the first CH domain of the sturgeon IgD transcript is also derived from µCH1 by RNA splicing. However, the variable region of the expressed sturgeon IgD shows limited V(D)J usage. In addition to IgD, three IgM variants were also identified in this species, whereas no IgT/Z-encoding genes were observed. This study bridges the gap in Ig evolution between elasmobranchs and teleosts and provides significant insight into the early evolution of immunoglobulins.