bioRxiv : the preprint server for biology
Dorman, LC;Nguyen, PT;Escoubas, CC;Vainchtein, ID;Xiao, Y;Lidsky, PV;Nakajo, H;Silva, NJ;Lagares-Linares, C;Wang, EY;Taloma, SE;Cuevas, B;Nakao-Inoue, H;Rivera, BM;Schwer, B;Condello, C;Andino, R;Nowakowski, TJ;Molofsky, AV;
PMID: 35233577 | DOI: 10.1101/2021.04.29.441889
Microglia, the innate immune cells of the brain, are exquisitely sensitive to dynamic changes in the neural environment. Using single cell RNA sequencing of the postnatal somatosensory cortex during topographic remapping, we identified a type I interferon (IFN-I) responsive microglia population that expanded with this developmental stressor. Using the marker gene IFITM3 we found that IFN-I responsive microglia were engulfing whole neurons. Loss of IFN-I signaling ( Ifnar1 -/- ) resulted in dysmorphic 'bubble' microglia with enlarged phagolysosomal compartments. We also observed a reduction in dead cells and an accumulation of neurons with double strand DNA breaks, a marker of cell stress. Conversely, IFN-I gain of function in zebrafish was sufficient to drive microglial engulfment of whole neurons. We identified IFITM3+ microglia in two murine disease models: SARS-CoV-2 infection and the 5xFAD model of Alzheimer's disease. These data reveal a novel role for IFN-I signaling in regulating efficient neuronal clearance by microglia.
The Journal of neuroscience : the official journal of the Society for Neuroscience
Zhang, J;Junigan, JM;Trinh, R;Kavelaars, A;Heijnen, CJ;Grace, PM;
PMID: 36096670 | DOI: 10.1523/JNEUROSCI.1182-22.2022
Peripheral neuropathic pain induced by the chemotherapeutic cisplatin can persist for months to years after treatment. Histone deacetylase 6 (HDAC6) inhibitors have therapeutic potential for cisplatin-induced neuropathic pain since they persistently reverse mechanical hypersensitivity and spontaneous pain in rodent models. Here, we investigated the mechanisms underlying reversal of mechanical hypersensitivity in male and female mice by a two-week treatment with an HDAC6 inhibitor, administered 3 days after the last dose of cisplatin. Mechanical hypersensitivity in animals of both sexes treated with the HDAC6 inhibitor was temporarily reinstated by a single injection of the neutral opioid receptor antagonist 6β-naltrexol or the peripherally restricted opioid receptor antagonist naloxone methiodide. These results suggest that tonic peripheral opioid ligand-receptor signaling mediates reversal of cisplatin-induced mechanical hypersensitivity after treatment with an HDAC6 inhibitor. Pointing to a specific role for delta opioid receptors (DORs), Oprd1 expression was decreased in dorsal root ganglion neurons following cisplatin administration, but normalized after treatment with an HDAC6 inhibitor. Mechanical hypersensitivity was temporarily reinstated in both sexes by a single injection of the DOR antagonist naltrindole. Consistently, HDAC6 inhibition failed to reverse cisplatin-induced hypersensitivity when DORs were genetically deleted from advillin+ neurons. Mechanical hypersensitivity was also temporarily reinstated in both sexes by a single injection of a neutralizing antibody against the DOR ligand met-enkephalin. In conclusion, we reveal that treatment with an HDAC6 inhibitor induces tonic enkephalin-DOR signaling in peripheral sensory neurons to suppress mechanical hypersensitivity.SIGNIFICANCE STATEMENT:Over a quarter of cancer survivors suffer from intractable painful chemotherapy-induced peripheral neuropathy (CIPN), which can last for months to years after treatment ends. HDAC6 inhibition is a novel strategy to reverse CIPN without negatively interfering with tumor growth, but the mechanisms responsible for persistent reversal are not well understood. We built on evidence that the endogenous opioid system contributes to the spontaneous, apparent resolution of pain caused by nerve damage or inflammation, referred to as latent sensitization. We show that blocking the delta opioid receptor or its ligand enkephalin unmasks CIPN in mice treated with an HDAC6 inhibitor (latent sensitization). Our work provides insight into the mechanisms by which treatment with an HDAC6 inhibitor apparently reverses CIPN.
Linker KE, Elabd MG, Tawadrous P, Cano M, Green KN, Wood MA, Leslie FM
PMID: 31949158 | DOI: 10.1038/s41467-019-14173-3
With the rise of e-cigarette use, teen nicotine exposure is becoming more widespread. Findings from clinical and preclinical studies show that the adolescent brain is particularly sensitive to nicotine. Animal studies have demonstrated that adolescent nicotine exposure increases reinforcement for cocaine and other drugs. However, the mechanisms that underlie these behaviors are poorly understood. Here, we report reactive microglia are critical regulators of nicotine-induced increases in adolescent cocaine self-administration. Nicotine has dichotomous, age-dependent effects on microglial morphology and immune transcript profiles. A multistep signaling mechanism involving D2 receptors and CX3CL1 mediates nicotine-induced increases in cocaine self-administration and microglial activation. Moreover, nicotine depletes presynaptic markers in a manner that is microglia-, D2- and CX3CL1-dependent. Taken together, we demonstrate that adolescent microglia are uniquely susceptible to perturbations by nicotine, necessary for nicotine-induced increases in cocaine-seeking, and that D2 receptors and CX3CL1 play a mechanistic role in these phenomena
Jung, M;Dourado, M;Maksymetz, J;Jacobson, A;Laufer, BI;Baca, M;Foreman, O;Hackos, DH;Riol-Blanco, L;Kaminker, JS;
PMID: 36690629 | DOI: 10.1038/s41467-023-36014-0
Sensory neurons of the dorsal root ganglion (DRG) are critical for maintaining tissue homeostasis by sensing and initiating responses to stimuli. While most preclinical studies of DRGs are conducted in rodents, much less is known about the mechanisms of sensory perception in primates. We generated a transcriptome atlas of mouse, guinea pig, cynomolgus monkey, and human DRGs by implementing a common laboratory workflow and multiple data-integration approaches to generate high-resolution cross-species mappings of sensory neuron subtypes. Using our atlas, we identified conserved core modules highlighting subtype-specific biological processes related to inflammatory response. We also identified divergent expression of key genes involved in DRG function, suggesting species-specific adaptations specifically in nociceptors that likely point to divergent function of nociceptors. Among these, we validated that TAFA4, a member of the druggable genome, was expressed in distinct populations of DRG neurons across species, highlighting species-specific programs that are critical for therapeutic development.
Liu, X;Wang, Y;Zeng, Y;Wang, D;Wen, Y;Fan, L;He, Y;Zhang, J;Sun, W;Liu, Y;Tao, A;
PMID: 36876522 | DOI: 10.1111/all.15699
Spinal astrocytes contribute to chronic itch via sensitization of itch-specific neurons expressing gastrin-releasing peptide receptor (GRPR). However, whether microglia-neuron interactions contribute to itch remains unclear. In this study, we aimed to explore how microglia interact with GRPR+ neurons and promote chronic itch.RNA sequencing, quantitative real-time PCR, western blot, immunohistochemistry, RNAscope ISH, pharmacologic and genetic approaches were performed to examine the roles of spinal NLRP3 (The NOD-like receptor family, pyrin-containing domain 3) inflammasome activation and IL-1β-IL1R1 signaling in chronic itch. Grpr-eGFP and Grpr KO mice were used to investigate microglia-GRPR+ neuron interactions.We observed NLRP3 inflammasome activation and IL-1β production in spinal microglia under chronic itch conditions. Blockade of microglial activation and the NLRP3/caspase-1/IL-1β axis attenuated chronic itch and neuronal activation. Type 1 IL-1 receptor (IL-1R1) was expressed in GRPR+ neurons, which are essential for the development of chronic itch. Our studies also find that IL-1β+ microglia are localized in close proximity to GRPR+ neurons. Consistently, intrathecal injection of IL1R1 antagonist or exogenous IL-1β indicate that the IL-1β-IL-1R1 signaling pathway enhanced the activation of GRPR+ neurons. Furthermore, our results demonstrate that the microglial NLRP3/caspase-1/IL-1β axis contributes to several different chronic itches triggered by small molecules and protein allergens from the environment and drugs.Our findings reveal a previously unknown mechanism in which microglia enhances the activation of GRPR+ neurons through the NLRP3/caspase-1/IL-1β/IL1R1 axis. These results will provide new insights into the pathophysiology of pruritus and novel therapeutic strategies for patients with chronic itch.
Stempel AV, Stumpf A, Zhang HY, Özdoğan T, Pannasch U, Theis AK, Otte DM, Wojtalla A, Rácz I, Ponomarenko A, Xi ZX, Zimmer A, Schmitz D.
PMID: 27133464 | DOI: 10.1016/j.neuron.2016.03.034
Endocannabinoids (eCBs) exert major control over neuronal activity by activating cannabinoid receptors (CBRs). The functionality of the eCB system is primarily ascribed to the well-documented retrograde activation of presynaptic CB1Rs. We find that action potential-driven eCB release leads to a long-lasting membrane potential hyperpolarization in hippocampal principal cells that is independent of CB1Rs. The hyperpolarization, which is specific to CA3 and CA2 pyramidal cells (PCs), depends on the activation of neuronal CB2Rs, as shown by a combined pharmacogenetic and immunohistochemical approach. Upon activation, they modulate the activity of the sodium-bicarbonate co-transporter, leading to a hyperpolarization of the neuron. CB2R activation occurred in a purely self-regulatory manner, robustly altered the input/output function of CA3 PCs, and modulated gamma oscillations in vivo. To conclude, we describe a cell type-specific plasticity mechanism in the hippocampus that provides evidence for the neuronal expression of CB2Rs and emphasizes their importance in basic neuronal transmission.
Mishra D, Richard JE, Maric I, Porteiro B, Häring M, Kooijman S, Musovic S, Eerola K, López-Ferreras L, Peris E, Grycel K, Shevchouk OT, Micallef P, Olofsson CS, Wernstedt Asterholm I, Grill HJ, Nogueiras R, Skibicka KP.
PMID: 30865890 | DOI: 10.1016/j.celrep.2019.02.044
Chronic low-grade inflammation and increased serum levels of the cytokine IL-6 accompany obesity. For brain-produced IL-6, the mechanisms by which it controls energy balance and its role in obesity remain unclear. Here, we show that brain-produced IL-6 is decreased in obese mice and rats in a neuroanatomically and sex-specific manner. Reduced IL-6 mRNA localized to lateral parabrachial nucleus (lPBN) astrocytes, microglia, and neurons, including paraventricular hypothalamus-innervating lPBN neurons. IL-6 microinjection into lPBN reduced food intake and increased brown adipose tissue (BAT) thermogenesis in male lean and obese rats by increasing thyroid and sympathetic outflow to BAT. Parabrachial IL-6 interacted with leptin to reduce feeding. siRNA-mediated reduction of lPBN IL-6 leads to increased weight gain and adiposity, reduced BAT thermogenesis, and increased food intake. Ambient cold exposure partly normalizes the obesity-induced suppression of lPBN IL-6. These results indicate that lPBN-produced IL-6 regulates feeding and metabolism and pinpoints (patho)physiological contexts interacting with lPBN IL-6.
Geraghty AC, Gibson EM, Ghanem RA, Greene JJ, Ocampo A, Goldstein AK, Ni L, Yang T, Marton RM, Paşca SP, Greenberg ME, Longo FM, Monje M.
PMID: 31122677 | DOI: 10.1016/j.neuron.2019.04.032
Activity-dependent myelination is thought to contribute to adaptive neurological function. However, the mechanisms by which activity regulates myelination and the extent to which myelin plasticity contributes to non-motor cognitive functions remain incompletely understood. Using a mouse model of chemotherapy-related cognitive impairment (CRCI), we recently demonstrated that methotrexate (MTX) chemotherapy induces complex glial dysfunction for which microglial activation is central. Here, we demonstrate that remote MTX exposure blocks activity-regulated myelination. MTX decreases cortical Bdnf expression, which is restored by microglial depletion. Bdnf-TrkB signaling is a required component of activity-dependent myelination. Oligodendrocyte precursor cell (OPC)-specific TrkB deletion in chemotherapy-naive mice results in impaired cognitive behavioral performance. A small-molecule TrkB agonist rescues both myelination and cognitive impairment after MTX chemotherapy. This rescue after MTX depends on intact TrkB expression in OPCs. Taken together, these findings demonstrate a molecular mechanism required for adaptive myelination that is aberrant in CRCI due to microglial activation
Wallace ML, Huang KW, Hochbaum D, Hyun M, Radeljic G, Sabatini BL
PMID: 32043968 | DOI: 10.7554/eLife.51271
The lateral habenula (LHb) is an epithalamic brain structure critical for processing and adapting to negative action outcomes. However, despite the importance of LHb to behavior and the clear anatomical and molecular diversity of LHb neurons, the neuron types of the habenula remain unknown. Here, we use high-throughput single-cell transcriptional profiling, monosynaptic retrograde tracing, and multiplexed FISH to characterize the cells of the mouse habenula. We find five subtypes of neurons in the medial habenula (MHb) that are organized into anatomical subregions. In the LHb, we describe four neuronal subtypes and show that they differentially target dopaminergic and GABAergic cells in the ventral tegmental area (VTA). These data provide a valuable resource for future study of habenular function and dysfunction and demonstrate neuronal subtype specificity in the LHb-VTA circuit
Maza, N;Wang, D;Kowalski, C;Stoveken, HM;Dao, M;Sial, OK;Giles, AC;Grill, B;Martemyanov, KA;
PMID: 35982154 | DOI: 10.1038/s41593-022-01135-0
Repeated exposure to opioids causes tolerance, which limits their analgesic utility and contributes to overdose and abuse liability. However, the molecular mechanisms underpinning tolerance are not well understood. Here, we used a forward genetic screen in Caenorhabditis elegans for unbiased identification of genes regulating opioid tolerance which revealed a role for PTR-25/Ptchd1. We found that PTR-25/Ptchd1 controls μ-opioid receptor trafficking and that these effects were mediated by the ability of PTR-25/Ptchd1 to control membrane cholesterol content. Electrophysiological studies showed that loss of Ptchd1 in mice reduced opioid-induced desensitization of neurons in several brain regions and the peripheral nervous system. Mice and C. elegans lacking Ptchd1/PTR-25 display similarly augmented responses to opioids. Ptchd1 knockout mice fail to develop analgesic tolerance and have greatly diminished somatic withdrawal. Thus, we propose that Ptchd1 plays an evolutionarily conserved role in protecting the μ-opioid receptor against overstimulation.
Science Translational Medicine
Frere, J;Serafini, R;Pryce, K;Zazhytska, M;Oishi, K;Golynker, I;Panis, M;Zimering, J;Horiuchi, S;Hoagland, D;Møller, R;Ruiz, A;Kodra, A;Overdevest, J;Canoll, P;Borczuk, A;Chandar, V;Bram, Y;Schwartz, R;Lomvardas, S;Zachariou, V;tenOever, B;
| DOI: 10.1126/scitranslmed.abq3059
The host response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can result in prolonged pathologies collectively referred to as post-acute sequalae of COVID-19 (PASC) or long COVID. To better understand the mechanism underlying long COVID biology, we compared the short- and long-term systemic responses in the golden hamster following either SARS-CoV-2 or influenza A virus (IAV) infection. Results demonstrated that SARS-CoV-2 exceeded IAV in its capacity to cause permanent injury to the lung and kidney and uniquely impacted the olfactory bulb (OB) and epithelium (OE). Despite a lack of detectable infectious virus, the OB and OE demonstrated myeloid and T cell activation, proinflammatory cytokine production, and an interferon response that correlated with behavioral changes extending a month post viral clearance. These sustained transcriptional changes could also be corroborated from tissue isolated from individuals who recovered from COVID-19. These data highlight a molecular mechanism for persistent COVID-19 symptomology and provide a small animal model to explore future therapeutics.
Jeon, H;Lee, H;Kwon, DH;Kim, J;Tanaka-Yamamoto, K;Yook, JS;Feng, L;Park, HR;Lim, YH;Cho, ZH;Paek, SH;Kim, J;
PMID: 35235786 | DOI: 10.1016/j.celrep.2022.110439
The subthalamic nucleus (STN) controls psychomotor activity and is an efficient therapeutic deep brain stimulation target in individuals with Parkinson's disease. Despite evidence indicating position-dependent therapeutic effects and distinct functions within the STN, the input circuit and cellular profile in the STN remain largely unclear. Using neuroanatomical techniques, we construct a comprehensive connectivity map of the indirect and hyperdirect pathways in the mouse STN. Our circuit- and cellular-level connectivities reveal a topographically graded organization with three types of indirect and hyperdirect pathways (external globus pallidus only, STN only, and collateral). We confirm consistent pathways into the human STN by 7 T MRI-based tractography. We identify two functional types of topographically distinct glutamatergic STN neurons (parvalbumin [PV+/-]) with synaptic connectivity from indirect and hyperdirect pathways. Glutamatergic PV+ STN neurons contribute to burst firing. These data suggest a complex interplay of information integration within the basal ganglia underlying coordinated movement control and therapeutic effects.
