Kamitakahara A, Wu HH, Levitt P.
PMID: 28758209 | DOI: 10.1002/cne.24294
Detailed anatomical tracing and mapping of the viscerotopic organization of the vagal motor nuclei has provided insight into autonomic function in health and disease. To further define specific cellular identities, we paired information based on visceral connectivity with a cell-type specific marker of a subpopulation of neurons in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (nAmb) that express the autism-associated MET receptor tyrosine kinase. As gastrointestinal disturbances are common in children with autism spectrum disorder (ASD), we sought to define the relationship between MET-expressing (MET+) neurons in the DMV and nAmb, and the gastrointestinal tract. Using wholemount tissue staining and clearing, or retrograde tracing in a METEGFP transgenic mouse, we identify three novel subpopulations of EGFP+ vagal brainstem neurons: 1) EGFP+ neurons in the nAmb projecting to the esophagus or laryngeal muscles, 2) EGFP+ neurons in the medial DMV projecting to the stomach, and 3) EGFP+ neurons in the lateral DMV projecting to the cecum and/or proximal colon. Expression of the MET ligand, hepatocyte growth factor (HGF), by tissues innervated by vagal motor neurons during fetal development reveal potential sites of HGF-MET interaction. Furthermore, similar cellular expression patterns of MET in the brainstem of both the mouse and nonhuman primate suggest that MET expression at these sites is evolutionarily conserved. Together, the data suggest that MET+ neurons in the brainstem vagal motor nuclei are anatomically positioned to regulate distinct portions of the gastrointestinal tract, with implications for the pathophysiology of gastrointestinal comorbidities of ASD.
Castro, RW;Lopes, MC;Settlage, RE;Valdez, G;
PMID: 37154159 | DOI: 10.1172/jci.insight.168448
Spinal motor neurons have been implicated in the loss of motor function that occurs with advancing age. However, the cellular and molecular mechanisms that impair the function of these neurons during aging remain unknown. Here, we show that motor neurons do not die in old female and male mice, rhesus monkeys, and humans. Instead, these neurons selectively and progressively shed excitatory synaptic inputs throughout the soma and dendritic arbor during aging. Thus, aged motor neurons contain a motor circuitry with a reduced ratio of excitatory to inhibitory synapses that may be responsible for the diminished ability to activate motor neurons to commence movements. An examination of the motor neuron translatome (ribosomal transcripts) in male and female mice reveals genes and molecular pathways with roles in glia-mediated synaptic pruning, inflammation, axonal regeneration, and oxidative stress that are upregulated in aged motor neurons. Some of these genes and pathways are also found altered in motor neurons affected with amyotrophic lateral sclerosis (ALS) and responding to axotomy, demonstrating that aged motor neurons are under significant stress. Our findings show mechanisms altered in aged motor neurons that could serve as therapeutic targets to preserve motor function during aging.
CNS Neuroscience and Therapeutics
Grabon, W;Bodennec, J;Belmeguenai, A;Bezin, L;
: The endocannabinoid system is recognized as an important player in neuromodulation in the central nervous system (CNS). It comprises cannabinoid receptors, endogenous molecules called endocannabinoids (eCBs) that activate these receptors, and enzymes that synthesize and degrade eCBs. 1 The most abundant eCBs are anandamide and 2-arachidoylglycerol. Many effects of eCBs are mediated by type 1 (CB1R) and type 2 (CB2R) cannabinoid receptors, which are the best known and involved in the homeostatic control of several physiological functions in the brain and other organs. 2 CB1R and CB2R are G protein-coupled receptors (GPCRs) that, in addition to interacting with eCBs, are also activated by synthetic and plantderived cannabinoids. Both were cloned in the early 1990s from human leukemia cells. 3,4 However, it is important to note here that we must take a much broader view of this system. Indeed, studies over the last decade have revealed the existence of a wide range of lipid mediators with eCB-like properties, novel enzymes, and new receptors, effectively complicating our picture of the endocannabinoid system and justifying the use of endocannabinoidome to describe it. 5 CB1R is the most prevalent GPCR in the CNS and is expressed extensively by most neuron types. 6 This receptor is the major mediator of the psychoactive effects of Cannabis sativa and its derivatives.
Proceedings of the National Academy of Sciences of the United States of America
Caligiuri, SPB;Howe, WM;Wills, L;Smith, ACW;Lei, Y;Bali, P;Heyer, MP;Moen, JK;Ables, JL;Elayouby, KS;Williams, M;Fillinger, C;Oketokoun, Z;Lehmann, VE;DiFeliceantonio, AG;Johnson, PM;Beaumont, K;Sebra, RP;Ibanez-Tallon, I;Kenny, PJ;
PMID: 36346845 | DOI: 10.1073/pnas.2209870119
Hedgehog-interacting protein (HHIP) sequesters Hedgehog ligands to repress Smoothened (SMO)-mediated recruitment of the GLI family of transcription factors. Allelic variation in HHIP confers risk of chronic obstructive pulmonary disease and other smoking-related lung diseases, but underlying mechanisms are unclear. Using single-cell and cell-type-specific translational profiling, we show that HHIP expression is highly enriched in medial habenula (MHb) neurons, particularly MHb cholinergic neurons that regulate aversive behavioral responses to nicotine. HHIP deficiency dysregulated the expression of genes involved in cholinergic signaling in the MHb and disrupted the function of nicotinic acetylcholine receptors (nAChRs) through a PTCH-1/cholesterol-dependent mechanism. Further, CRISPR/Cas9-mediated genomic cleavage of the <i>Hhip</i> gene in MHb neurons enhanced the motivational properties of nicotine in mice. These findings suggest that HHIP influences vulnerability to smoking-related lung diseases in part by regulating the actions of nicotine on habenular aversion circuits.
Downs, AM;Donsante, Y;Jinnah, HA;Hess, EJ;
PMID: 35314320 | DOI: 10.1016/j.nbd.2022.105699
Trihexyphenidyl (THP), a non-selective muscarinic receptor (mAChR) antagonist, is commonly used for the treatment of dystonia associated with TOR1A, otherwise known as DYT1 dystonia. A better understanding of the mechanism of action of THP is a critical step in the development of better therapeutics with fewer side effects. We previously found that THP normalizes the deficit in striatal dopamine (DA) release in a mouse model of TOR1A dystonia (Tor1a+/ΔE knockin (KI) mice), revealing a plausible mechanism of action for this compound, considering that abnormal DA neurotransmission is consistently associated with many forms of dystonia. However, the mAChR subtype(s) that mediate the rescue of striatal dopamine release remain unclear. In this study we used a combination of pharmacological challenges and cell-type specific mAChR conditional knockout mice of either sex to determine which mAChR subtypes mediate the DA release-enhancing effects of THP. We determined that THP acts in part at M4 mAChR on striatal cholinergic interneurons to enhance DA release in both Tor1a+/+ and Tor1a+/ΔE KI mice. Further, we found that the subtype selective M4 antagonist VU6021625 recapitulates the effects of THP. These data implicate a principal role for M4 mAChR located on striatal cholinergic interneurons in the mechanism of action of THP and suggest that subtype selective M4 mAChR antagonists may be effective therapeutics with fewer side effects than THP for the treatment of TOR1A dystonia.
Neurogastroenterol Motil. 2018 Oct 12:e13479.
Russell JP, Mohammadi E, Ligon C, Latorre R, Johnson AC, Hoang B, Krull D, Ho MW, Eidam HS, DeMartino MP, Cheung M, Oliff AI, Kumar S, Greenwood-Van Meerveld B.
PMID: 30311722 | DOI: 10.1111/nmo.13479
Abstract BACKGROUND: The expression of RET in the developing enteric nervous system (ENS) suggests that RET may contribute to adult intestinal function. ENS cholinergic nerves play a critical role in the control of colonic function through the release of acetylcholine (ACh). In the current study, we hypothesized that a RET-mediated mechanism may regulate colonic ion transport and motility through modulation of cholinergic nerves. METHODS: The effect of RET inhibition on active ion transport was assessed electrophysiologically in rat colonic tissue mounted in Ussing chambers via measurements of short circuit current (Isc) upon electrical field stimulation (EFS) or pharmacologically with cholinergic agonists utilizing a gastrointestinal (GI)-restricted RET inhibitor. We assessed the effect of the RET inhibitor on propulsive motility via quantification of fecal pellet output (FPO) induced by the acetylcholinesterase inhibitor neostigmine. KEY RESULTS: We found that enteric ganglia co-expressed RET and choline acetyltransferase (ChAT) transcripts. In vitro, the RET kinase inhibitor GSK3179106 attenuated the mean increase in Isc induced by either EFS or carbachol but not bethanechol. In vivo, GSK3179106 significantly reduced the prokinetic effect of neostigmine. CONCLUSION AND INFERENCES: Our findings provide evidence that RET-mediated mechanisms regulate colonic function by maintaining cholinergic neuronal function and enabling ACh-evoked chloride secretion and motility. We suggest that modulating the cholinergic control of the colon via a RET inhibitor may represent a novel target for the treatment of intestinal disorders associated with increased secretion and accelerated GI transit such as irritable bowel syndrome with diarrhea (IBS-D).
Proc Natl Acad Sci U S A. 2014 Nov 3.
Zhang HY, Gao M, Liu QR, Bi GH, Li X, Yang HJ, Gardner EL, Wu J, Xi ZX.
PMID: 25368177 | DOI: 201413210
Cannabinoid CB2 receptors (CB2Rs) have been recently reported to modulate brain dopamine (DA)-related behaviors; however, the cellular mechanisms underlying these actions are unclear. Here we report that CB2Rs are expressed in ventral tegmental area (VTA) DA neurons and functionally modulate DA neuronal excitability and DA-related behavior. In situ hybridization and immunohistochemical assays detected CB2 mRNA and CB2R immunostaining in VTA DA neurons. Electrophysiological studies demonstrated that activation of CB2Rs by JWH133 or other CB2R agonists inhibited VTA DA neuronal firing in vivo and ex vivo, whereas microinjections of JWH133 into the VTA inhibited cocaine self-administration. Importantly, all of the above findings observed in WT or CB1 -/- mice are blocked by CB2R antagonist and absent in CB2 -/- mice. These data suggest that CB2R-mediated reduction of VTA DA neuronal activity may underlie JWH133's modulation of DA-regulated behaviors.
Ortega-de San Luis C, Sanchez-Garcia MA, Nieto-Gonzalez JL, García-Junco-Clemente P, Montero-Sanchez A, Fernandez-Chacon R, Pascual A.
PMID: 30058223 | DOI: 10.1111/acel.12821
The striatum integrates motor behavior using a well-defined microcircuit whose individual components are independently affected in several neurological diseases. The glial cell line-derived neurotrophic factor (GDNF), synthesized by striatal interneurons, and Sonic hedgehog (Shh), produced by the dopaminergic neurons of the substantia nigra (DA SNpc), are both involved in the nigrostriatal maintenance but the reciprocal neurotrophic relationships among these neurons are only partially understood. To define the postnatal neurotrophic connections among fast-spiking GABAergic interneurons (FS), cholinergic interneurons (ACh), and DA SNpc, we used a genetically induced mouse model of postnatal DA SNpc neurodegeneration and separately eliminated Smoothened (Smo), the obligatory transducer of Shh signaling, in striatal interneurons. We show that FS postnatal survival relies on DA SNpc and is independent of Shh signaling. On the contrary, Shh signaling but not dopaminergic striatal innervation is required to maintain ACh in the postnatal striatum. ACh are required for DA SNpc survival in a GDNF-independent manner. These data demonstrate the existence of three parallel but interdependent neurotrophic relationships between SN and striatal interneurons, partially defined by Shh and GDNF. The definition of these new neurotrophic interactions opens the search for new molecules involved in the striatal modulatory circuit maintenance with potential therapeutic value.
Pancani, T;Day, M;Tkatch, T;Wokosin, DL;González-Rodríguez, P;Kondapalli, J;Xie, Z;Chen, Y;Beaumont, V;Surmeier, DJ;
PMID: 36914640 | DOI: 10.1038/s41467-023-36556-3
Huntington's disease (HD) is a progressive, neurodegenerative disease caused by a CAG triplet expansion in huntingtin. Although corticostriatal dysfunction has long been implicated in HD, the determinants and pathway specificity of this pathophysiology are not fully understood. Here, using a male zQ175+/- knock-in mouse model of HD we carry out optogenetic interrogation of intratelencephalic and pyramidal tract synapses with principal striatal spiny projection neurons (SPNs). These studies reveal that the connectivity of intratelencephalic, but not pyramidal tract, neurons with direct and indirect pathway SPNs increased in early symptomatic zQ175+/- HD mice. This enhancement was attributable to reduced pre-synaptic inhibitory control of intratelencephalic terminals by striatal cholinergic interneurons. Lowering mutant huntingtin selectively in striatal cholinergic interneurons with a virally-delivered zinc finger repressor protein normalized striatal acetylcholine release and intratelencephalic functional connectivity, revealing a node in the network underlying corticostriatal pathophysiology in a HD mouse model.
Brain : a journal of neurology
Wlaschin, JJ;Donahue, C;Gluski, J;Osborne, JF;Ramos, LM;Silberberg, H;Le Pichon, CE;
PMID: 36342754 | DOI: 10.1093/brain/awac415
Amyotrophic lateral sclerosis or ALS is a devastating and fatal neurodegenerative disease of motor neurons with very few treatment options. We had previously found that motor neuron degeneration in a mouse model of ALS can be delayed by deleting the axon damage sensor MAP3K12 or Dual Leucine Zipper Kinase (DLK)1. However, DLK is also involved in axon regeneration2-5, prompting us to ask whether combining DLK deletion with a way to promote axon regeneration would result in greater motor neuron protection. To achieve this, we used a mouse line that constitutively expresses ATF3, a master regulator of regeneration in neurons6,7. Although there is precedence for each individual strategy in the SOD1G93A mouse model of ALS1,8, these have not previously been combined. By several lines of evidence including motor neuron electrophysiology, histology and behavior, we observed a powerful synergy when combining DLK deletion with ATF3 expression. The combinatorial strategy resulted in significant protection of motor neurons with fewer undergoing cell death, reduced axon degeneration, and preservation of motor function and connectivity to muscle. This study provides a demonstration of the power of combinatorial therapy to treat neurodegenerative disease.
Marinelli, S;Marrone, MC;Di Domenico, M;Marinelli, S;
PMID: 36222019 | DOI: 10.1002/glia.24281
Microglia, the innate immune cells of the central nervous system (CNS), execute their sentinel, housekeeping and defense functions through a panoply of genes, receptors and released cytokines, chemokines and neurotrophic factors. Moreover, microglia functions are closely linked to the constant communication with other cell types, among them neurons. Depending on the signaling pathway and type of stimuli involved, the outcome of microglia operation can be neuroprotective or neurodegenerative. Accordingly, microglia are increasingly becoming considered cellular targets for therapeutic intervention. Among signals controlling microglia activity, the endocannabinoid (EC) system has been shown to exert a neuroprotective role in many neurological diseases. Like neurons, microglia express functional EC receptors and can produce and degrade ECs. Interestingly, boosting EC signaling leads to an anti-inflammatory and neuroprotective microglia phenotype. Nonetheless, little evidence is available on the microglia-mediated therapeutic effects of EC compounds. This review focuses on the EC signals acting on the CNS microglia in physiological and pathological conditions, namely on the CB1R, CB2R and TRPV1-mediated regulation of microglia properties. It also provides new evidence, which strengthens the understanding of mechanisms underlying the control of microglia functions by ECs. Given the broad expression of the EC system in glial and neuronal cells, the resulting picture is the need for in vivo studies in transgenic mouse models to dissect the contribution of EC microglia signaling in the neuroprotective effects of EC-derived compounds.
Morris, C;Watkins, D;Shah, N;Pennington, T;Hens, B;Qi, G;Doud, E;Mosley, A;Atwood, B;Baucum, A;
| DOI: 10.1016/j.biopsych.2022.12.008
Background Grooming dysfunction is a hallmark of the obsessive-compulsive spectrum disorder, trichotillomania. Numerous preclinical studies have utilized SAPAP3 deficient mice for understanding the neurobiology of repetitive grooming, suggesting excessive grooming is caused by increased metabotropic glutamate receptor 5 (mGluR5) activity in striatal direct- and indirect pathway medium spiny neurons (dMSNs and iMSNs, respectively). However, MSN subtype-specific signaling mechanisms that mediate mGluR5-dependent adaptations underlying excessive grooming are not fully understood. Here, we investigate the MSN subtype-specific roles of the striatal signaling hub protein, spinophilin, in mediating repetitive motor dysfunction associated with mGluR5 function. Methods Quantitative proteomics and immunoblotting were utilized to identify how spinophilin impacts mGluR5 phosphorylation and protein interaction changes. Plasticity and repetitive motor dysfunction associated with mGluR5 action was measured using our novel conditional spinophilin mouse model that had spinophilin knocked out from striatal dMSNs or/and iMSNs. Results Loss of spinophilin only in iMSNs decreased performance of a novel motor repertoire, but loss of spinophilin in either MSN subtype abrogated striatal plasticity associated with mGluR5 function and prevented excessive grooming caused by SAPAP3 knockout mice or treatment with the mGluR5-specific positive allosteric modulator (VU0360172) without impacting locomotion-relevant behavior. Biochemically, we determined the spinophilin-mGluR5 interaction correlates with grooming behavior and loss of spinophilin shifts mGluR5 interactions from lipid-raft associated proteins toward postsynaptic density (PSD) proteins implicated in psychiatric disorders. Conclusions These results identify spinophilin as a novel striatal signaling hub molecule in MSNs that cell subtype-specifically mediates behavioral, functional, and molecular adaptations associated with repetitive motor dysfunction in psychiatric disorders.
