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Communications Biology Oct 2023Pyroptosis is a cell death process that causes inflammation and contributes to numerous diseases. Pyroptosis is mediated by caspase-1 family proteases that cleave the...
Pyroptosis is a cell death process that causes inflammation and contributes to numerous diseases. Pyroptosis is mediated by caspase-1 family proteases that cleave the pore-forming protein gasdermin D, causing plasma membrane rupture and release of pathogenic cellular contents. We previously identified muscimol as a small molecule that prevents plasma membrane rupture during pyroptosis via an unidentified mechanism. Here, we show that muscimol has reversible activity to prevent cellular lysis without affecting earlier pyroptotic events. Although muscimol is a well-characterized agonist for neuronal GABA receptors, muscimol protection is not altered by GABA receptor antagonists or recapitulated by other GABA agonists, suggesting that muscimol acts via a novel mechanism. We find that muscimol blocks oligomerization of ninjurin-1, which is required for plasma membrane rupture downstream of gasdermin D pore formation. Our structure-activity relationship studies reveal distinct molecular determinants defining inhibition of pyroptotic lysis compared to GABA binding. In addition, we demonstrate that muscimol reduces lethality during LPS-induced septic shock. Together, these findings demonstrate that ninjurin-1-mediated plasma membrane rupture can be pharmacologically modulated and pave the way toward identification of therapeutic strategies for pathologic conditions associated with pyroptosis.
Topics: Pyroptosis; Muscimol; Gasdermins; Intracellular Signaling Peptides and Proteins; Cell Membrane; Receptors, GABA-A; gamma-Aminobutyric Acid
PubMed: 37798443
DOI: 10.1038/s42003-023-05354-4 -
Neuron Oct 2023The persistence of play after decortication points to a subcortical mechanism of play control. We found that global blockade of the rat periaqueductal gray with either...
The persistence of play after decortication points to a subcortical mechanism of play control. We found that global blockade of the rat periaqueductal gray with either muscimol or lidocaine interfered with ticklishness and play. We recorded vocalizations and neural activity from the periaqueductal gray of young, playful rats during interspecific touch, play, and tickling. Rats vocalized weakly to touch and more strongly to play and tickling. Periaqueductal gray units showed diverse but strong modulation to tickling and play. Hierarchical clustering based on neuronal responses to play and tickling revealed functional clusters mapping to different periaqueductal gray columns. Specifically, we observed play-neutral/tickling-inhibited and tickling/play-neutral units in dorsolateral and dorsomedial periaqueductal gray columns. In contrast, strongly play/tickling-excited units mapped to the lateral columns and were suppressed by anxiogenic conditions. Optogenetic inactivation of lateral periaqueductal columns disrupted ticklishness and play. We conclude that the lateral periaqueductal gray columns are decisive for play and laughter.
Topics: Rats; Animals; Periaqueductal Gray; Touch; Neurons; Touch Perception
PubMed: 37516112
DOI: 10.1016/j.neuron.2023.06.018 -
European Neuropsychopharmacology : the... Nov 2023Alzheimer's Disease (AD) is a currently incurable but increasingly prevalent fatal and progressive neurodegenerative disease, demanding consideration of therapeutically... (Review)
Review
Alzheimer's Disease (AD) is a currently incurable but increasingly prevalent fatal and progressive neurodegenerative disease, demanding consideration of therapeutically relevant natural products and their synthetic analogues. This paper reviews evidence for effectiveness of natural and synthetic psychedelics in the treatment of AD causes and symptoms. The plastogenic effects of serotonergic psychedelics illustrate that they have efficacy for addressing multiple facets of AD pathology. We review findings illustrating neuroplasticity mechanisms of classic (serotonergic) and non-classic psychedelics that indicate their potential as treatments for AD and related dementias. Classic psychedelics modulate glutamatergic neurotransmission and stimulate synaptic and network remodeling that facilitates synaptic, structural and behavioral plasticity. Up-regulation of neurotrophic factors enable psychedelics to promote neuronal survival and glutamate-driven neuroplasticity. Muscimol modulation of GABAR reduces Aβ-induced neurotoxicity and psychedelic Sig-1R agonists provide protective roles in Aβ toxicity. Classic psychedelics also activate mTOR intracellular effector pathways in brain regions that show atrophy in AD. The potential of psychedelics to treat AD involves their ability to induce structural and functional neural plasticity in brain circuits and slow or reverse brain atrophy. Psychedelics stimulate neurotrophic pathways, increase neurogenesis and produce long-lasting neural changes through rewiring pathological neurocircuitry. Psychedelic effects on 5-HT receptor target genes and induction of synaptic, structural, and functional changes in neurons and networks enable them to promote and enhance brain functional connectivity and address diverse mechanisms underlying degenerative neurological disorders. These findings provide a rationale for immediate investigation of psychedelics as treatments for AD patients.
Topics: Humans; Alzheimer Disease; Hallucinogens; Neurodegenerative Diseases; Brain; Atrophy
PubMed: 37451163
DOI: 10.1016/j.euroneuro.2023.07.003 -
IBRO Neuroscience Reports Jun 2024There is evidence that both the GABAergic system and serotonin reuptake inhibitor (SSRI) such as citalopram are involved in the modulation of anxiety and depression...
BACKGROUND
There is evidence that both the GABAergic system and serotonin reuptake inhibitor (SSRI) such as citalopram are involved in the modulation of anxiety and depression processes. In this research, we examined the effects of GABA receptor agents and citalopram on anxiety- and depression-related behaviors and their interaction in male mice.
METHODS
For intracerebroventricular (i.c.v.) infusion, a guide cannula was implanted in the left lateral ventricle. Anxiety and depression behaviors were evaluated using the elevated plus-maze (EPM) and forced swimming test (FST).
RESULTS
The results revealed that i.c.v. microinjection of muscimol (1 µg/mouse) enhanced % OAT (open arm time) and % OAE (open arm entries) in the EPM test and decreased immobility time in the FST without affecting locomotor activity, presenting anxiolytic- and antidepressant-like behaviors in the EPM and FST, respectively. On the other hand, i.c.v. microinjection of bicuculline (1 µg/mouse) reduced % OAT and % OAE without affecting locomotor activity and immobility time, presenting an anxiogenic-like effect. Moreover, i.p. administration of citalopram (8 mg/kg) increased %OAT and %OAE and reduced immobility time with no effect on locomotor activity, showing anxiolytic- and antidepressant-like responses in male mice. Furthermore, i.c.v. infusion of an ineffective dosage of muscimol potentiated the anxiolytic- and antidepressant-like responses induced by i.p. injection of citalopram in male mice. When citalopram and bicuculline were co-injected, a non-significant dose of bicuculline reversed the anxiolytic-like effect of citalopram in male mice. Also, the data revealed synergistic anxiolytic- and antidepressant-like behaviors between citalopram and muscimol in male mice.
CONCLUSIONS
The results suggested an interaction between citalopram and GABAergic agents on the modulation of anxiety and depression behaviors in male mice.
PubMed: 38415182
DOI: 10.1016/j.ibneur.2024.02.003 -
Frontiers in Pharmacology 2023Dementia and autoimmune diseases are prevalent conditions with limited treatment options. Taurine and homotaurine (HT) are naturally occurring sulfonate amino acids,...
Dementia and autoimmune diseases are prevalent conditions with limited treatment options. Taurine and homotaurine (HT) are naturally occurring sulfonate amino acids, with taurine being highly abundant in animal tissues, but declining with age in the blood. HT is a blood-brain barrier permeable drug under investigation for Alzheimer's disease. HT also has beneficial effects in a mouse model of multiple sclerosis likely through an anti-inflammatory mechanism mediated by GABA receptor (GABAR) agonism in immune cells. While both taurine and HT are structural GABA analogs and thought to be GABA mimetics at GABARs, there is uncertainty concerning their potency as GABA mimetics on native GABARs. We show that HT is a very potent GABA mimetic, as it evokes GABAR-mediated currents with an EC of 0.4 μM (vs. 3.7 μM for GABA and 116 µM for taurine) in murine cerebellar granule cells in brain slices, with both taurine and HT having similar efficacy in activating native GABARs. Furthermore, HT displaces the high affinity GABAR ligand [H]muscimol at similarly low concentrations (HT IC of 0.16 μM vs. 125 μM for taurine) in mouse brain homogenates. The potency of taurine and HT as GABAR agonists aligns with endogenous concentrations of taurine in the blood and with HT concentrations achieved in the brain following oral administration of HT or the HT pro-drug ALZ-801. Consequently, we discuss that GABARs subtypes, similar to the ones we studied here in neurons, are plausible targets for mediating the potential beneficial effects of taurine in health and life-span extension and the beneficial HT effects in dementia and autoimmune conditions.
PubMed: 38155909
DOI: 10.3389/fphar.2023.1271203 -
Antiviral Research Sep 2023Macrophages display functional phenotypic plasticity. Hepatitis B virus (HBV) infection induces polarizations of liver macrophages either to M1-like pro-inflammatory...
Macrophages display functional phenotypic plasticity. Hepatitis B virus (HBV) infection induces polarizations of liver macrophages either to M1-like pro-inflammatory phenotype or to M2-like anti-inflammatory phenotype. Gamma-aminobutyric acid (GABA) signaling exists in various non-neuronal cells including hepatocytes and some immune cells. Here we report that macrophages express functional GABAergic signaling components and activation of type A GABA receptors (GABARs) promotes M2-polarization thus advancing HBV replication. Notably, intraperitoneal injection of GABA or the GABAR agonist muscimol increased HBV replication in HBV-carrier mice that were generated by hydrodynamical injection of adeno-associated virus/HBV1.2 plasmids (pAAV/HBV1.2). The GABA-augmented HBV replication in HBV-carrier mice was significantly reduced by the GABAR inhibitor picrotoxin although picrotoxin had no significant effect on serum HBsAg levels in control HBV-carrier mice. Depletion of liver macrophages by liposomal clodronate treatment also significantly reduced the GABA-augmented HBV replication. Yet adoptive transfer of liver macrophages isolated from GABA-treated donor HBV-carrier mice into the liposomal clodronate-pretreated recipient HBV-carrier mice restored HBV replication. Moreover, GABA or muscimol treatment increased the expression of "M2" cytokines in macrophages, but had no direct effect on HBV replication in the HepG2.2.15 cells, HBV1.3-transfected Huh7, HepG2, or HepaRG cells, or HBV-infected Huh7-NTCP cells. Taken together, these results suggest that increasing GABA signaling in the liver promotes HBV replication in HBV-carrier mice by suppressing the immunity of liver macrophages, but not by increasing the susceptibility of hepatocytes to HBV infection. Our study shows that a previously unknown GABAergic system in liver macrophage has an essential role in HBV replication.
Topics: Mice; Animals; Hepatitis B virus; Muscimol; Clodronic Acid; Picrotoxin; Hepatitis B; gamma-Aminobutyric Acid; Macrophages; Virus Replication
PubMed: 37494980
DOI: 10.1016/j.antiviral.2023.105680 -
IScience Jun 2024The cerebral cortex is widely considered part of the neural substrate of consciousness, but direct causal evidence is missing. Here, we tested in mice whether...
The cerebral cortex is widely considered part of the neural substrate of consciousness, but direct causal evidence is missing. Here, we tested in mice whether optogenetic activation of cortical neurons in posterior parietal cortex (PtA) or medial prefrontal cortex (mPFC) is sufficient for arousal from three behavioral states characterized by progressively deeper unresponsiveness: sleep, a coma-like state induced by muscimol injection in the midbrain, and deep sevoflurane-dexmedetomidine anesthesia. We find that cortical stimulation always awakens the mice from both NREM sleep and REM sleep, with PtA requiring weaker/shorter light pulses than mPFC. Moreover, in most cases light pulses produce both cortical activation (decrease in low frequencies) and behavioral arousal (recovery of the righting reflex) from brainstem coma, as well as cortical activation from anesthesia. These findings provide evidence that direct activation of cortical neurons is sufficient for behavioral and/or cortical arousal from sleep, brainstem coma, and anesthesia.
PubMed: 38812551
DOI: 10.1016/j.isci.2024.109919 -
Frontiers in Pharmacology 2024The plant-based alkaloid muscimol is a potent agonist of inhibitory GABA-neurotransmitter receptors. GABA receptors are a heterogeneous family of pentameric complexes,...
The plant-based alkaloid muscimol is a potent agonist of inhibitory GABA-neurotransmitter receptors. GABA receptors are a heterogeneous family of pentameric complexes, with 5 out of 19 subunits assembling around the central anion pore. Muscimol is considered to bind to all receptor subtypes at the orthosteric drug binding site at the β+/α- interface. Recently, we observed that the antipsychotic drugs clozapine (CLZ), loxapine (LOX) and chlorpromazine (CPZ) although exerting functional inhibition on multiple GABA receptor subtypes showed diverging results in displacing 3H-muscimol. While a complete displacement could be observed in hippocampal membranes by bicuculline (BIC), and no displacement with CPZ, the compounds CLZ and LOX competed partially. Non-sigmoidal, complex dose response curves were indicative of multiple sites. In the current study we now aimed to investigate more extensively this heterogeneity of bicuculline sensitive muscimol sites in rat brain. We tested membranes from four different brain regions (hippocampus, cerebellum, thalamus and striatum) and selected recombinantly expressed subunit combinations with displacement assays. 3H-muscimol displacement was tested with BIC, LOX, CLZ and CPZ. ligand structural analysis and computational docking was performed. We observed a unique pharmacology of each tested compound in the studied brain regions. Combining two of the tested ligands suggests that in striatum all CLZ sites are contained in the pool of LOX sites, while the CPZ sites may in part be non-overlapping with LOX sites. Experiments on recombinantly expressed receptors indicate, that BIC can displace 3H-muscimol from all tested receptors, while LOX and CLZ display different and variable competition indicative of multiple sites. Molecular docking produced structural correlates of the observed diversity of muscimol sites on the basis of bicuculline bound experimental structures. These findings indicate that 3H-muscimol binding sites in rat brain are heterogeneous, with different populations of receptors, which are CPZ, LOX or CLZ sensitive or insensitive. These binding sites show a varying distribution in different rat brain regions. Molecular docking suggests that the so-called loop F region of α subunits drives the observed differences.
PubMed: 38549678
DOI: 10.3389/fphar.2024.1368527 -
BioRxiv : the Preprint Server For... Nov 2023We often exert greater cognitive resources (i.e., listening effort) to understand speech under challenging acoustic conditions. This mechanism can be overwhelmed in...
UNLABELLED
We often exert greater cognitive resources (i.e., listening effort) to understand speech under challenging acoustic conditions. This mechanism can be overwhelmed in those with hearing loss, resulting in cognitive fatigue in adults, and potentially impeding language acquisition in children. However, the neural mechanisms that support listening effort are uncertain. Evidence from human studies suggest that the cingulate cortex is engaged under difficult listening conditions, and may exert top-down modulation of the auditory cortex (AC). Here, we asked whether the gerbil cingulate cortex (Cg) sends anatomical projections to the AC that facilitate perceptual performance. To model challenging listening conditions, we used a sound discrimination task in which stimulus parameters were presented in either 'Easy' or 'Hard' blocks (i.e., long or short stimulus duration, respectively). Gerbils achieved statistically identical psychometric performance in Easy and Hard blocks. Anatomical tracing experiments revealed a strong, descending projection from layer 2/3 of the Cg1 subregion of the cingulate cortex to superficial and deep layers of primary and dorsal AC. To determine whether Cg improves task performance under challenging conditions, we bilaterally infused muscimol to inactivate Cg1, and found that psychometric thresholds were degraded for only Hard blocks. To test whether the Cg-to-AC projection facilitates task performance, we chemogenetically inactivated these inputs and found that performance was only degraded during Hard blocks. Taken together, the results reveal a descending cortical pathway that facilitates perceptual performance during challenging listening conditions.
SIGNIFICANCE STATEMENT
Sensory perception often occurs under challenging conditions, such a noisy background or dim environment, yet stimulus sensitivity can remain unaffected. One hypothesis is that cognitive resources are recruited to the task, thereby facilitating perceptual performance. Here, we identify a top-down cortical circuit, from cingulate to auditory cortex in the gerbils, that supports auditory perceptual performance under challenging listening conditions. This pathway is a plausible circuit that supports effortful listening, and may be degraded by hearing loss.
PubMed: 38014324
DOI: 10.1101/2023.11.10.566668 -
Regulation of vagally-evoked respiratory responses by the lateral parabrachial nucleus in the mouse.Respiratory Physiology & Neurobiology Oct 2023Vagal sensory inputs to the brainstem can alter breathing through the modulation of pontomedullary respiratory circuits. In this study, we set out to investigate the...
Vagal sensory inputs to the brainstem can alter breathing through the modulation of pontomedullary respiratory circuits. In this study, we set out to investigate the localised effects of modulating lateral parabrachial nucleus (LPB) activity on vagally-evoked changes in breathing pattern. In isoflurane-anaesthetised and instrumented mice, electrical stimulation of the vagus nerve (eVNS) produced stimulation frequency-dependent changes in diaphragm electromyograph (dEMG) activity with an evoked tachypnoea and apnoea at low and high stimulation frequencies, respectively. Muscimol microinjections into the LPB significantly attenuated eVNS-evoked respiratory rate responses. Notably, muscimol injections reaching the caudal LPB, previously unrecognised for respiratory modulation, potently modulated eVNS-evoked apnoea, whilst muscimol injections reaching the intermediate LPB selectively modulated the eVNS-evoked tachypnoea. The effects of muscimol on eVNS-evoked breathing rate changes occurred without altering basal eupneic breathing. These results highlight novel roles for the LPB in regulating vagally-evoked respiratory reflexes.
Topics: Animals; Mice; Respiratory Rate; Apnea; Muscimol; Parabrachial Nucleus; Tachypnea
PubMed: 37597796
DOI: 10.1016/j.resp.2023.104141