Recurrent Inhibition Research Articles

3.1 ENHANCED PARVALBUMIN NETWORK ACTIVITY PROLONGS CRITICAL PERIOD PLASTICITY

BackgroundOscillations in neuronal activity tie the pathophysiology of schizophrenia to alterations in local processing and large-scale coordination, and these alterations in turn can lead to the cognitive and perceptual disturbances observed in schizophrenia. Here, we focus on the dual role of fast-spiking, parvalbumin (PV+) networks in the generation of gamma oscillations and critical periods of brain plasticity.MethodsWe generated a mouse model of reduced recurrent inhibition only within local PV+ cell networks by selective removal of GABAA receptor alpha1 subunits (PV-α1 KO mice). Electroencephalography (EEG), PV+ immunohistochemistry, perineuronal net (PNN) labeling and redox balance were compared to cortical measures of brain plasticity (loss of visual acuity, formation of preference behaviors) that are typically limited to a critical period early in life.ResultsPV-α1 KO mice exhibit chronically enhanced gamma-oscillations and extended juvenile forms of cortical plasticity into adulthood. Acute pharmacological suppression of excitatory input restored E-I balance onto these disinhibited PV+ cells and returned baseline EEG power to normal levels, preventing the extended plasticity. Enhanced gamma oscillations were further found to compromise the integrity of perineuronal nets (PNNs) surrounding PV+ cells, elevating oxidative stress and the turnover of metallopeptidases and structural components of the PNN. All of these aspects were also reversed by pharmacological dampening of excitation onto PV+ cells.DiscussionCortical gamma oscillations are associated with plasticity and cognition. Our results provide a cellular explanation of how elevated gamma oscillations may promote ectopic brain plasticity by regulating the extracellular matrix which normally stabilizes cortical circuitry. These results carry broad implications for subjects at-risk for schizophrenia who exhibit heightened gamma oscillations prior to psychosis onset (see talk by P Uhlhaas).

α2-Adrenergic receptor activation promotes long-term potentiation at excitatory synapses in the mouse accessory olfactory bulb.

The formation of mate recognition memory in mice is associated with neural changes at the reciprocal dendrodendritic synapses between glutamatergic mitral cell (MC) projection neurons and GABAergic granule cell (GC) interneurons in the accessory olfactory bulb (AOB). Although noradrenaline (NA) plays a critical role in the formation of the memory, the mechanism by which it exerts this effect remains unclear. Here we used extracellular field potential and whole-cell patch-clamp recordings to assess the actions of bath-applied NA (10 µM) on the glutamatergic transmission and its plasticity at the MC-to-GC synapse in the AOB. Stimulation (400 stimuli) of MC axons at 10 Hz but not at 100 Hz effectively induced N-methyl-d-aspartate (NMDA) receptor-dependent long-term potentiation (LTP), which exhibited reversibility. NA paired with subthreshold 10-Hz stimulation (200 stimuli) facilitated the induction of NMDA receptor-dependent LTP via the activation of α2-adrenergic receptors (ARs). We next examined how NA, acting at α2-ARs, facilitates LTP induction. In terms of acute actions, NA suppressed GC excitatory postsynaptic current (EPSC) responses to single pulse stimulation of MC axons by reducing glutamate release from MCs via G-protein coupled inhibition of calcium channels. Consequently, NA reduced recurrent inhibition of MCs, resulting in the enhancement of evoked EPSCs and spike fidelity in GCs during the 10-Hz stimulation used to induce LTP. These results suggest that NA, acting at α2-ARs, facilitates the induction of NMDA receptor-dependent LTP at the MC-to-GC synapse by shifting its threshold through disinhibition of MCs.

Recurrent excitation between motoneurones propagates across segments and is purely glutamatergic.

Spinal motoneurones (Mns) constitute the final output for the execution of motor tasks. In addition to innervating muscles, Mns project excitatory collateral connections to Renshaw cells (RCs) and other Mns, but the latter have received little attention. We show that Mns receive strong synaptic input from other Mns throughout development and into maturity, with fast-type Mns systematically receiving greater recurrent excitation than slow-type Mns. Optical recordings show that activation of Mns in one spinal segment can propagate to adjacent segments even in the presence of intact recurrent inhibition. While it is known that transmission at the neuromuscular junction is purely cholinergic and RCs are excited through both acetylcholine and glutamate receptors, here we show that neurotransmission between Mns is purely glutamatergic, indicating that synaptic transmission systems are differentiated at different postsynaptic targets of Mns.

Self-Consistent Scheme for Spike-Train Power Spectra in Heterogeneous Sparse Networks.

Recurrent networks of spiking neurons can be in an asynchronous state characterized by low or absent cross-correlations and spike statistics which resemble those of cortical neurons. Although spatial correlations are negligible in this state, neurons can show pronounced temporal correlations in their spike trains that can be quantified by the autocorrelation function or the spike-train power spectrum. Depending on cellular and network parameters, correlations display diverse patterns (ranging from simple refractory-period effects and stochastic oscillations to slow fluctuations) and it is generally not well-understood how these dependencies come about. Previous work has explored how the single-cell correlations in a homogeneous network (excitatory and inhibitory integrate-and-fire neurons with nearly balanced mean recurrent input) can be determined numerically from an iterative single-neuron simulation. Such a scheme is based on the fact that every neuron is driven by the network noise (i.e., the input currents from all its presynaptic partners) but also contributes to the network noise, leading to a self-consistency condition for the input and output spectra. Here we first extend this scheme to homogeneous networks with strong recurrent inhibition and a synaptic filter, in which instabilities of the previous scheme are avoided by an averaging procedure. We then extend the scheme to heterogeneous networks in which (i) different neural subpopulations (e.g., excitatory and inhibitory neurons) have different cellular or connectivity parameters; (ii) the number and strength of the input connections are random (Erdős-Rényi topology) and thus different among neurons. In all heterogeneous cases, neurons are lumped in different classes each of which is represented by a single neuron in the iterative scheme; in addition, we make a Gaussian approximation of the input current to the neuron. These approximations seem to be justified over a broad range of parameters as indicated by comparison with simulation results of large recurrent networks. Our method can help to elucidate how network heterogeneity shapes the asynchronous state in recurrent neural networks.

Adenosine A1 Receptor-Mediated Attenuation of Reciprocal Dendro-Dendritic Inhibition in the Mouse Olfactory Bulb.

It is well described that A1 adenosine receptors inhibit synaptic transmission at excitatory synapses in the brain, but the effect of adenosine on reciprocal synapses has not been studied so far. In the olfactory bulb, the majority of synapses are reciprocal dendro-dendritic synapses mediating recurrent inhibition. We studied the effect of A1 receptor activation on recurrent dendro-dendritic inhibition in mitral cells using whole-cell patch-clamp recordings. Adenosine reduced dendro-dendritic inhibition in wild-type, but not in A1 receptor knock-out mice. Both NMDA receptor-mediated and AMPA receptor-mediated dendro-dendritic inhibition were attenuated by adenosine, indicating that reciprocal synapses between mitral cells and granule cells as well as parvalbumin interneurons were targeted by A1 receptors. Adenosine reduced glutamatergic self-excitation and inhibited N-type and P/Q-type calcium currents, but not L-type calcium currents in mitral cells. Attenuated glutamate release, due to A1 receptor-mediated calcium channel inhibition, resulted in impaired dendro-dendritic inhibition. In behavioral tests we tested the ability of wild-type and A1 receptor knock-out mice to find a hidden piece of food. Knock-out mice were significantly faster in locating the food. Our results indicate that A1 adenosine receptors attenuates dendro-dendritic reciprocal inhibition and suggest that they affect odor information processing.

Inhibitory Effect of Chunghyul-dan on Stroke Recurrence in Small Vessel Disease Patients: A 5-Year Observational Study.

We investigated the stroke recurrence rate and the rate of adverse effects induced by an herbal medicine, Chunghyul-dan, administered to patients over a 5-year period. We prescribed 600 mg Chunghyul-dan a day to patients with small vessel diseases and investigated stroke recurrence, adverse effects, and drug compliance for 5 years. The primary outcome was the prevalence of stroke recurrence (in 3, 4, and 5 years). The secondary outcome was the frequency of adverse effects induced by Chunghyul-dan. We recruited 400 patients. Among them, 270, 233, and 195 patients completed 3, 4, and 5 years of follow-up, respectively. Among patients who completed 3, 4, and 5 years of follow-up, cumulative recurrent stroke occurred in 7 (2.6%), 11 (4.7%), and 12 (6.2%) patients. There were no adverse effects. We suggest that Chunghyul-dan might be useful for the inhibition of stroke recurrence by reducing microangiography progression. Further study is needed to confirm our hypothesis.

Multifaceted Implantable Anticancer Device for Potential Postsurgical Breast Cancer Treatment: A Single Platform for Synergistic Inhibition of Local Regional Breast Cancer Recurrence, Surveillance, and Healthy Breast Reconstruction

AbstractAn implantable anticancer device (IAD) amenable to eradicate local regional recurrence (LRR) of breast cancer as well as to enhance the breast reconstruction during/after therapy is proposed for the first time. The IAD is fabricated by incorporating the superparamagnetic graphene oxide doxorubicin nanocomposite of size ≈200 nm in a nanofiber matrix to enable the sustained and tumor specific anticancer drug release over 60 d in vitro with a minimum initial burst release and the repeated hyperthermic capability in an alternating magnetic field to ensure the synergistic inhibition of LRR. The IAD also enriches the reconstruction of poor breast cosmesis that resulted from the surgical treatment by supporting the lipofilling of the surgical residual cavity to induce the adipogenic process. Moreover, the noninvasive monitoring capability of IAD through magnetic resonance imaging augments to the effective patient care. Thus, this work reports a new and reliable concept by introducing the multifunctional IAD possessing enhanced specificity with a real‐time monitoring capability and long‐term anticancer efficacy as a potential platform for synergistic inhibition of LRR and a great promise for the in situ breast reconstruction ability for better breast cosmesis.

Direct central nervous system effects of botulinum neurotoxin

Local intramuscular injections of botulinum neurotoxin type A (BoNT/A) are effective in the treatment of focal dystonias, muscle spasms, and spasticity. However, not all clinical effects of BoNT/A may be explained by its action at peripheral nerve terminals. For example, the therapeutic benefit may exceed the duration of the peripheral neuroparalysis induced by the neurotoxin. In cellular and animal models, evidence demonstrates retrograde transport of catalytically active BoNT/A in projection neurons. This process of long-range trafficking is followed by transcytosis and action at second-order synapses. In humans, several physiological changes have been described following intramuscular delivery of BoNT/A. In particular, clinical studies have documented a decrease in Renshaw cell-mediated inhibition (i.e., recurrent inhibition), which may be important therapeutically for normalizing uncoordinated movements and overflow of muscle activity. In this review, we present data obtained in animal and experimental models that support direct central actions of BoNT/A mediated via retrograde axonal trafficking. We also discuss the reorganization of central circuitry induced by BoNT/A in patients, and the potential contribution of these effects to the therapeutic efficacy of the neurotoxin.

Protective role of LRRC3B in preventing breast cancer metastasis and recurrence post-bupivacaine.

The present study aimed to investigate the potential effect of leucine-rich repeat containing 3B (LRRC3B) with respect to the inhibition of breast cancer recurrence and metastasis post-anesthesia. The mRNA expression of LRRC3B in breast MDA-MB-231 and MCF-7 cell lines was detected using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. The effect of bupivacaine on breast cancer cell invasion was analyzed using a Matrigel assay. LRRC3B specific small interfering (si)RNA was constructed and transfected into breast cancer cells using Lipofectamine® 2000 reagent. The influence of bupivacaine on LRRC3B expression was measured based on RT-qPCR. Additionally, the effect of LRRC3B silencing on the invasion of breast cancer cells treated with bupivacaine was analyzed. Compared with the control, LRRC3B expression significantly increased in MDA-MB-231 and in MCF-7 cells as the length of time increased (P<0.05), but the expression of the gene significantly declined in 2 types of cancer cell when the cells were transfected with siRNA-LRRC3B plasma (P<0.05). The administration of 50 µg/ml bupivacaine promoted maximum breast cancer cell invasion, and suppressed LRRC3B mRNA expression in cells. However, when LRRC3B was silenced in cancer cells, 20 µg/ml bupivacaine significantly promoted cancer cell invasion, indicating that bupivacaine suppresses the expression of LRRC3B and promotes cell invasion. The present study suggested that LRRC3B serves a protective role in preventing bupivacaine-induced breast cancer recurrence and metastasis.

Dysregulation of Long Non-coding RNAS in Hepatocellular Carcinoma-Current Implications and Perspectives

Background and Aim: Hepatocellular carcinoma (HCC), a fatal human malignancy, accounts for 90% of primary liver cancers worldwide. In conjunction with several cellular, molecular and genetic aberrations, dysregulation of a variety of non-coding RNAs such as long non-coding RNAs (LncRNAs) have been implicated in HCC. LncRNAs are endogenous cellular RNAs that play pivotal roles in the modulation of the tumor microenvironment in several malignant processes such as initiation, progression, and dissemination. A variety of LncRNAs has been reported to be dysregulated in HCC. In context, we aim to characterize the functional regulatory mechanisms of LncRNAs in HCC. Methods: The databases PubMed, Medline, Embase, and Cochrane were probed for relevant literature in English using the keywords “LncRNAs and hepatocellular carcinoma”, “LncRNA and downregulation and hepatocellular carcinoma”, and “LncRNA and upregulation and hepatocellular carcinoma”. Manuscripts pertaining to other non-coding RNAs involved in HCC were excluded. Results: Dysregulation of LncRNA expression have been associated with prognosis and metastasis of HCC. Several lines of evidence indicate that a host of LncRNAs found to be upregulated in HCC viz., HULC, H19, TUC338, MALAT1 and HOTAIR, promote cell proliferation, cell growth, tumor growth, increased liver cirrhosis, metastasis and invasion, inhibition of apoptosis and recurrence. Contrarily, LncRNAs MEG3, LncRNA-LET, PTENP1, SRHC and MTIDP are downregulated in HCC and exhibit inhibition of cancer proliferation, decreased cell proliferation, increased apoptosis, reduced hepatic invasion and metastasis. Conclusion: Recent advancements elucidate that the non-coding part of the genome, once considered as superfluous or transcriptional “noise”, play significant roles in various biological processes. Although LncRNA research is still at an early stage, extensive and in-depth inquests are imperative to establish the functional importance of lnRNA in HCC in order to ascertain whether LncRNAs can be clinically utilized as early diagnostic and prognostic marker for HCC or as potential therapeutic targets in HCC. The authors have none to declare.

Abstract 1105: A chemotherapeutic approach to kill cancer stem cell rich ovarian ascites

Abstract Purpose: More than one third of ovarian cancer patients present with cancer cells in the abdomen (also known as ascites) at diagnosis, and almost all have ascites at recurrence (Ahmed and Stenvers 2013). It is well-documented that subpopulations of the ascites show cancer stem cell-like characteristics which possess enhanced resistance to chemotherapies and the capacity for distal metastatic spread and recurrent disease. Therefore, ascites are a major source of morbidity and mortality for ovarian cancer patients. The major deficiency that currently exists is that there is no effective and safe therapy for ascites since they are rich in cancer stem cells (CSCs) and resistant to chemotherapy. To overcome this deficiency, it is our objective to develop an effective chemotherapy approach that can destroy the CSC-rich ascites and inhibit recurrence. Methods: Several established human ovarian cancer cells as well as ascites obtained from the abdomen of an ovarian cancer patient (ASCITES) were cultured. Cells were sorted by FACS Cell Sorter to determine the percentage of cancer stem cells (CSCs) in each cell line. Dose response curves of different chemotherapeutic drugs such as Cisplatin (CDDP), 6-Methylpurine (6-MP), 5-Flurouracil (5-FU), SN-38, Monomethyl auristatin E (MMAE) and Etoposide were studied in suspension culture enriched with cancer stem cells. The relative change in total CSC-rich spheroid mass which considers both number and volume of spheroids was used to determine Killing Index for each chemotherapeutic drug. To investigate inhibition of recurrence, the spheroids were monitored for 30 days post treatment and the viability of CSC-rich spheroids were studied by fluorescent microscopy. Results: Primary human ovarian A2780 and ASCITES (derived from ovarian cancer patient Ascitic fluid) were found to have CSCs with unlimited renewal capacity in suspension culture. While Cisplatin, 5-FU, 6-MP and Etoposide showed efficacy in killing CSC spheroids at effective doses around 1-10 μM, but MMAE and SN-38 showed the ability to either significantly diminish or completely eradicate CSC spheroids with effective doses as low as 10 nM. Importantly, no evidence of recurrence (repopulation of spheroids) was observed in MMAE and SN-38 treated group even after 30 days of post treatment. Conclusion: These promising results with the two chemotherapeutic drugs that show their ability to kill highly drug-resistant CSC-rich ovarian spheroids open the door to further investigate their use in the clinic. Currently, we are investigating the potential use of these two drugs in combination but at very low concentrations for the treatment of abdominal ovarian metastasis. Citation Format: Siddik Sarkar, Obeid M. Malekshah, Arash Hatefi. A chemotherapeutic approach to kill cancer stem cell rich ovarian ascites [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1105. doi:10.1158/1538-7445.AM2017-1105

Engaging and disengaging recurrent inhibition coincides with sensing and unsensing of a sensory stimulus

Even simple sensory stimuli evoke neural responses that are dynamic and complex. Are the temporally patterned neural activities important for controlling the behavioral output? Here, we investigated this issue. Our results reveal that in the insect antennal lobe, due to circuit interactions, distinct neural ensembles are activated during and immediately following the termination of every odorant. Such non-overlapping response patterns are not observed even when the stimulus intensity or identities were changed. In addition, we find that ON and OFF ensemble neural activities differ in their ability to recruit recurrent inhibition, entrain field-potential oscillations and more importantly in their relevance to behaviour (initiate versus reset conditioned responses). Notably, we find that a strikingly similar strategy is also used for encoding sound onsets and offsets in the marmoset auditory cortex. In sum, our results suggest a general approach where recurrent inhibition is associated with stimulus ‘recognition’ and ‘derecognition’.

Intrinsically-generated fluctuating activity in excitatory-inhibitory networks.

Recurrent networks of non-linear units display a variety of dynamical regimes depending on the structure of their synaptic connectivity. A particularly remarkable phenomenon is the appearance of strongly fluctuating, chaotic activity in networks of deterministic, but randomly connected rate units. How this type of intrinsically generated fluctuations appears in more realistic networks of spiking neurons has been a long standing question. To ease the comparison between rate and spiking networks, recent works investigated the dynamical regimes of randomly-connected rate networks with segregated excitatory and inhibitory populations, and firing rates constrained to be positive. These works derived general dynamical mean field (DMF) equations describing the fluctuating dynamics, but solved these equations only in the case of purely inhibitory networks. Using a simplified excitatory-inhibitory architecture in which DMF equations are more easily tractable, here we show that the presence of excitation qualitatively modifies the fluctuating activity compared to purely inhibitory networks. In presence of excitation, intrinsically generated fluctuations induce a strong increase in mean firing rates, a phenomenon that is much weaker in purely inhibitory networks. Excitation moreover induces two different fluctuating regimes: for moderate overall coupling, recurrent inhibition is sufficient to stabilize fluctuations; for strong coupling, firing rates are stabilized solely by the upper bound imposed on activity, even if inhibition is stronger than excitation. These results extend to more general network architectures, and to rate networks receiving noisy inputs mimicking spiking activity. Finally, we show that signatures of the second dynamical regime appear in networks of integrate-and-fire neurons.

Inhibitory interneuron circuits at cortical and spinal levels are associated with individual differences in corticomuscular coherence during isometric voluntary contraction

Corticomuscular coherence (CMC) is an oscillatory synchronization of 15–35 Hz (β-band) between electroencephalogram (EEG) of the sensorimotor cortex and electromyogram of contracting muscles. Although we reported that the magnitude of CMC varies among individuals, the physiological mechanisms underlying this variation are still unclear. Here, we aimed to investigate the associations between CMC and intracortical inhibition (ICI) in the primary motor cortex (M1)/recurrent inhibition (RI) in the spinal cord, which probably affect oscillatory neural activities. Firstly, we quantified ICI from changes in motor-evoked potentials induced by paired-pulse transcranial magnetic stimulation in M1 during tonic isometric voluntary contraction of the first dorsal interosseous. ICI showed a significant, negative correlation with the strength of EEG β-oscillation, but not with the magnitude of CMC across individuals. Next, we quantified RI from changes in H-reflexes induced by paired-pulse electrical nerve stimulation to the posterior tibial nerve during isometric contraction of the soleus muscle. We observed a significant, positive correlation between RI and peak CMC across individuals. These results suggest that the local inhibitory interneuron networks in cortical and spinal levels are associated with the oscillatory activity in corticospinal loop.

Regulation of Thalamic and Cortical Network Synchrony by Scn8a

Voltage-gated sodium channel (VGSC) mutations cause severe epilepsies marked by intermittent, pathological hypersynchronous brain states. Here we present two mechanisms that help to explain how mutations in one VGSC gene, Scn8a, contribute to two distinct seizure phenotypes: (1) hypoexcitation of cortical circuits leading to convulsive seizure resistance, and (2) hyperexcitation of thalamocortical circuits leading to non-convulsive absence epilepsy. We found that loss of Scn8a leads to altered RT cell intrinsic excitability and a failure in recurrent RT synaptic inhibition. We propose that these deficits cooperate to enhance thalamocortical network synchrony and generate pathological oscillations. To our knowledge, this finding is the first clear demonstration of apathological state tied to disruption of the RT-RT synapse. Our observation that loss of a single gene in the thalamus of an adult wild-type animal is sufficient to cause spike-wave discharges is striking and represents an example of absence epilepsy of thalamic origin.

Choline induces opposite changes in pyramidal neuron excitability and synaptic transmission through a nicotinic receptor-independent process in hippocampal slices.

Choline is present at cholinergic synapses as a product of acetylcholine degradation. In addition, it is considered a selective agonist for α5 and α7 nicotinic acetylcholine receptors (nAChRs). In this study, we determined how choline affects action potentials and excitatory synaptic transmission using extracellular and intracellular recording techniques in CA1 area of hippocampal slices obtained from both mice and rats. Choline caused a reversible depression of evoked field excitatory postsynaptic potentials (fEPSPs) in a concentration-dependent manner that was not affected by α7 nAChR antagonists. Moreover, this choline-induced effect was not mimicked by either selective agonists or allosteric modulators of α7 nAChRs. Additionally, this choline-mediated effect was not prevented by either selective antagonists of GABA receptors or hemicholinium, a choline uptake inhibitor. The paired pulse facilitation paradigm, which detects whether a substance affects presynaptic release of glutamate, was not modified by choline. On the other hand, choline induced a robust increase of population spike evoked by orthodromic stimulation but did not modify that evoked by antidromic stimulation. We also found that choline impaired recurrent inhibition recorded in the pyramidal cell layer through a mechanism independent of α7 nAChR activation. These choline-mediated effects on fEPSP and population spike observed in rat slices were completely reproduced in slices obtained from α7 nAChR knockout mice, which reinforces our conclusion that choline modulates synaptic transmission and neuronal excitability by a mechanism independent of nicotinic receptor activation.

局所ステロイド処置による好酸球性副鼻腔炎（ECRS）術後の再燃抑制効果

局所ステロイド処置による好酸球性副鼻腔炎（ECRS）術後の再燃抑制効果

Schizophrenia: Basic and Clinical.

Schizophrenia is a chronic severe mental disorder characterized by psychosis, cognitive impairments, and social and motivational deficits. It is associated with a progressive loss of cortical volume after onset of psychosis; nevertheless, cortical atrophy correlates with the cognitive impairments and the negative symptoms but not with the psychosis. The cortical atrophy is not primarily due to neuronal degeneration but rather to neuronal atrophy and loss of glutamatergic synapses. A downregulation of the presynaptic markers for the parvalbumin-expressing GABAergic interneurons that provide recurrent inhibition to cortical pyramidal neurons is another consistent pathologic feature. Antipsychotic drugs continue after 50 years to be the mainstay of treatment although these drugs, with the possible exception of clozapine, have negligible effects on cognition and negative symptoms. Pharmacologic challenge studies, postmortem analyses and a recent sufficiently powered genome-wide association study and copy number variant studies provide compelling evidence that NMDA receptor hypofunction is an important pathophsysiologic feature of schizophrenia. Silencing the gene encoding serine racemase, the enzyme that synthesizes the cortical-limbic NMDA receptor co-agonist, D-serine, replicates the dendritic and GABAergic pathology and cognitive deficits of schizophrenia in mice. Pharmacologic strategies to overcome NMDA receptor hypofunction hold promise of treating the disabling cognitive and negative symptoms.

Oligomeric amyloid-β peptide disrupts olfactory information output by impairment of local inhibitory circuits in rat olfactory bulb

Although early olfactory dysfunction has been found in patients with Alzheimer's disease, the underlying mechanisms remain unclear. In this study, we investigated whether and how oligomeric amyloid-β peptide (Aβ) affects the responses of mitral cells (MCs). We found that oligomeric Aβ1–42 increased spontaneous and evoked firing rates but decreased the ratio of evoked to spontaneous firings in MCs. Aβ1–42 oligomers showed no impact on the hyperactivity exerted by pharmacological blockage of GABAA receptors, suggesting an involvement of GABAergic inhibitory transmission in Aβ1 to 42–induced over-excitability. It was further determined that Aβ1–42 oligomers inhibited the frequency of spontaneous inhibitory postsynaptic currents and miniature inhibitory postsynaptic currents, as well as the amplitude of miniature inhibitory postsynaptic currents in MCs. Both recurrent and lateral inhibition of MCs, which are critical for odor discrimination, were also disrupted by Aβ1–42 oligomers. The above data indicate that Aβ impairs local inhibitory circuits and thereby leads to perturbations of olfactory information output in the olfactory bulb. This study reveals a cellular and synaptic basis of olfactory deficits associated with Alzheimer's disease.

Abstract 4657: Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis

Abstract Tumor-initiating stem-like cells (TICs) are a minor population in bulk tumors that play a critical role in tumor recurrence and therapy-resistance. We previously showed that a key stemness marker Nanog is upregulated that regulates self-renewal and pluripotency of embryonic stem cells and TICs. We demonstrated that alcohol-mediated activation of Toll-like receptor 4 (TLR4) by endotoxin resulted in increased expression of pluripotency stem cell transcription factor NANOG that metabolically reprograms tumor-initiating stem-like cells (TICs: cancer stem cells) via inhibition of oxidative phosphorylation and activation of fatty acid oxidation in our recently accepted Cell Metabolism paper. Discovery of a drug that specifically targets TICs would be a vital goal for cancer therapy. To identify selective TIC inhibitors, we conducted a high throughput screening of an FDA-approved drug library using combination of Nanog promoter-GFP-based screening with viability-based screening and their combination screening of each hit compound. Our high-throughput screening identified the best combination of repurposed FDA-approved drugs: all-trans retinoic acid (ATRA) and the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) that repressed NANOG and induces apoptosis of TICs. Treatment of ATRA inhibits self-renewal ability in vitro. To specifically target the CD133 (+) population, we encapsulated ATRA into nanoparticles conjugated with CD133 antibody using biodegradable poly(D,L-lactide-co-glycolide) (PLGA) polymer. The combination treatment significantly inhibited tumor growth compared to single drug treatments while the ATRA or SAHA monotherapy groups did not reduce or even promoted tumor growth. The combination of ATRA with SAHA specifically induces apoptosis of TICs. Targeting of TICs by NANOG antagonism increases drug susceptibility in tumor-bearing mice and achieves ∼90% tumor growth suppression. RNA-seq analysis identified that ATRA+SAHA treatment reduced expression of MicroRNA-22 (miR-22), leading to induction of PTEN and ten-eleven translocation enzymes (TET2), which demethylates DNA. PTEN induction promoted P-FOXO3A and induced BIM, leading to induction of apoptosis. The combined treatment Induced TET1/2 to demethylate p53-binding sites of NANOG promoter, leading to downregulation of NANOG. Taken together, combination treatment of ATRA with SAHA may serve as a novel avenue for HCC treatment. Novel combination of repurposed drugs is cost-effective therapeutic strategy to target microRNA for eradication of TICs, leading to inhibition of metastasis and recurrence. Citation Format: Chia-Lin Chen, Suresh Swaminathan, Ameya Kirtane, Jayanth Panyam, Keigo Machida. Selective inhibitors epigenetically modify and eradicate tumor-initiating stem-like cells through downregulating microRNA 22-mediated TET induction and apoptosis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4657.