Intestinal neuropod GUCY2C regulates visceral pain

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Abstract

Visceral pain (VP) is a global problem with complex etiologies and limited therapeutic options. Guanylyl cyclase C (GUCY2C), an intestinal receptor producing cyclic GMP which regulates luminal fluid secretion, has emerged as a therapeutic target for VP. Indeed, FDA-approved GUCY2C agonists ameliorate VP in patients with chronic constipation syndromes, although analgesic mechanisms remain obscure. Here, we reveal that intestinal GUCY2C is selectively enriched in neuropod cells, a type of enteroendocrine cell that synapses with submucosal neurons in mice and humans. GUCY2CHigh neuropod cells associate with co-cultured dorsal root ganglia neurons and induce hyperexcitability, reducing the rheobase and increasing the resulting number of evoked action potentials. Conversely, the GUCY2C agonist linaclotide eliminated neuronal hyperexcitability produced by GUCY2C-sufficient, but not GUCY2C-deficient, neuropod cells, an effect independent of bulk epithelial cells or extracellular cGMP. Genetic elimination of intestinal GUCY2C amplified nociceptive signaling and VP that was comparable to chemically-induced VP but refractory to linaclotide. Importantly, eliminating GUCY2C selectively in neuropod cells also increased nociceptive signaling and VP that was refractory to linaclotide. In the context of loss of GUCY2C hormones in patients with VP, these observations suggest a specific role for neuropod GUCY2C signaling in the pathophysiology and treatment of these pain syndromes.

Authors

Joshua R. Barton, Annie K. Londregan, Tyler D. Alexander, Ariana A. Entezari, Shely Bar-Ad, Lan Cheng, Angelo C. Lepore, Adam E. Snook, Manuel Covarrubias, Scott A. Waldman

TIAM1-mediated synaptic plasticity underlies comorbid depression–like and ketamine antidepressant–like actions in chronic pain

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Abstract

Chronic pain often leads to depression, increasing patient suffering and worsening prognosis. While hyperactivity of the anterior cingulate cortex (ACC) appears to be critically involved, the molecular mechanisms underlying comorbid depressive symptoms in chronic pain remain elusive. T cell lymphoma invasion and metastasis 1 (Tiam1) is a Rac1 guanine nucleotide exchange factor (GEF) that promotes dendrite, spine, and synapse development during brain development. Here, we show that Tiam1 orchestrates synaptic structural and functional plasticity in ACC neurons via actin cytoskeleton reorganization and synaptic N-methyl-d-aspartate receptor (NMDAR) stabilization. This Tiam1-coordinated synaptic plasticity underpins ACC hyperactivity and drives chronic pain–induced depressive-like behaviors. Notably, administration of low-dose ketamine, an NMDAR antagonist emerging as a promising treatment for chronic pain and depression, induces sustained antidepressant-like effects in mouse models of chronic pain by blocking Tiam1-mediated maladaptive synaptic plasticity in ACC neurons. Our results reveal Tiam1 as a critical factor in the pathophysiology of chronic pain–induced depressive-like behaviors and the sustained antidepressant-like effects of ketamine.

Authors

Qin Ru, Yungang Lu, Ali Bin Saifullah, Francisco A. Blanco, Changqun Yao, Juan P. Cata, De-Pei Li, Kimberley F. Tolias, Lingyong Li

Thalamocortical circuits drive remifentanil-induced postoperative hyperalgesia

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Abstract

Remifentanil-induced hyperalgesia (RIH) is a severe but common postoperative clinical problem with elusive underlying neural mechanisms. Here, we discovered that glutamatergic neurons in the thalamic ventral posterolateral nucleus (VPLGlu) exhibited significantly elevated burst firing accompanied by upregulation of Cav3.1 T-type calcium channel expression and function in RIH model mice. In addition, we identified a glutamatergic neuronal thalamocortical circuit in the VPL projecting to hindlimb primary somatosensory cortex glutamatergic neurons (S1HLGlu) that mediated RIH. In vivo calcium imaging and multi-tetrode recordings revealed heightened S1HLGlu neuronal activity during RIH. Moreover, preoperative suppression of Cav3.1-dependent burst firing in VPLGlu neurons or chemogenetic inhibition of VPLGlu neuronal terminals in the S1HL abolished the increased S1HLGlu neuronal excitability while alleviating RIH. Our findings suggest that remifentanil induces postoperative hyperalgesia by upregulating T-type calcium channel-dependent burst firing in VPLGlu neurons to activate S1HLGlu neurons, thus revealing an ion channel–mediated neural circuit basis for RIH that can guide analgesic development.

Authors

Yan Jin, Yu Mao, Danyang Chen, Yingju Tai, Rui Hu, Chen-Ling Yang, Jing Zhou, Lijian Chen, Xuesheng Liu, Erwei Gu, Chunhui Jia, Zhi Zhang, Wenjuan Tao

Soluble TREM2 levels associate with conversion from mild cognitive impairment to Alzheimer’s disease

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Abstract

BACKGROUND Soluble triggering receptor expressed on myeloid cells 2 (sTREM2) plays an important role in the clearance of pathological amyloid-β (Aβ) in Alzheimer’s disease (AD). This study aimed to explore sTREM2 as a central and peripheral predictor of the conversion from mild cognitive impairment (MCI) to AD.METHODS sTREM2 and Aβ1–42 levels in cerebrospinal fluid (CSF) and florbetapir-PET (AV45) images were analyzed for healthy control (HCs), patients with MCI, and patients with AD from the ADNI database. Peripheral plasma sTREM2 and Aβ1–42 levels were determined for our Neurology database of Ruijin Hospital for Alzheimer’s Disease (NRHAD) cohort, and patients with MCI were reevaluated at follow-up visits to assess for progression to AD. The association between CSF and plasma sTREM2 levels was analyzed in data from the Chinese Alzheimer’s Biomarker and Lifestyle (CABLE) database.RESULTS The results showed that patients with MCI who had low levels of CSF sTREM2 and Aβ1–42 were more likely to develop AD. Among participants with positive Aβ deposition, as assessed by AV45 imaging, elevated CSF sTREM2 levels were associated with a decreased risk of MCI-to-AD conversion. Meanwhile, in the NRHAD cohort, individuals in the MCI group with high sTREM2 levels in plasma were at a greater risk for AD, whereas low Aβ1–42 with high sTREM2 levels in plasma were associated with a faster cognitive decline. In addition, CSF sTREM2 levels were highly correlated with plasma sTREM2 levels in the CABLE database.CONCLUSION These findings suggest that sTREM2 may be useful as a potential predictive biomarker of MCI-to-AD conversion.FUNDING This study was supported by grants from the National Natural Science Foundation of China (grant nos. 82001341, 82071415, 81873778, and 82201392); the Shanghai Sailing Program (grant no. 22YF1425100); and the China Postdoctoral Science Foundation funded project (grant no. 2021M702169).

Authors

Aonan Zhao, Yang Jiao, Guanyu Ye, Wenyan Kang, Lan Tan, Yuanyuan Li, Yulei Deng, Jun Liu, for the Alzheimer’s Disease Neuroimaging Initiative (ADNI)

Mechanisms and treatments of neuropathic itch in a mouse model of lymphoma

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Abstract

Our understanding of neuropathic itch is limited, due to the lack of relevant animal models. Patients with cutaneous T-cell lymphoma (CTCL) suffer from severe itching. Here we characterize a mouse model of chronic itch with remarkable lymphoma growth, immune cell accumulation, and persistent pruritus. Intradermal CTCL inoculation produces time-dependent changes in nerve innervations in lymphoma-bearing skin. In the early-phase (20 days), CTCL causes hyper-innervations in the epidermis. However, chronic itch is associated with loss of epidermal nerve fibers in the late-phases (40 and 60 days). CTCL is also characterized by marked nerve innervations in mouse lymphoma. Blockade of C-fibers reduced pruritus at early- and late-phases, whereas blockade of A-fibers only suppressed late-phase itch. Intrathecal gabapentin injection reduced late-phase but not early-phase pruritus. IL-31 is upregulated in mouse lymphoma, while its receptor Il31ra was persistently upregulated in Trpv1-expressing sensory neurons in CTCL mice. Intratumoral anti-IL-31 treatment effectively suppressed CTCL-induced scratching and alloknesis (mechanical itch). Finally, intrathecal administration of TLR4 antagonist attenuated pruritus in early and late phases and in both sexes. Collectively, we have established a mouse model of neuropathic and cancer itch with relevance to human disease. Our findings also suggest distinct mechanisms underlying acute, chronic, and neuropathic itch.

Authors

Ouyang Chen, Qianru He, Qingjian Han, Kenta Furutani, Yun Gu, Madelynne Olexa, Ru-Rong Ji

A human TRPV1 genetic variant within the channel gating domain regulates pain sensitivity in rodents

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Abstract

Pain signals are relayed to the brain via a nociceptive system, and in rare situations, this nociceptive system contains genetic variants that can limit pain response. Here we questioned whether a human transient receptor potential vanilloid 1 (TRPV1) missense variant causes a resistance to noxious stimuli and further if we can target this region by a cell-permeable peptide as a pain therapeutic. Initially using a computational approach, we identified a human K710N TRPV1 missense variant in an otherwise highly conserved region of mammalian TRPV1. After generating a TRPV1K710N knock-in mouse using CRISPR/Cas9, we discovered the K710N variant reduced capsaicin-induced calcium influx in dorsal root ganglion neurons. The TRPV1K710N rodents also had less acute behavioral response to chemical noxious stimuli and less hypersensitivity to nerve injury-induced pain, while leaving the response to noxious heat intact. Furthermore, blocking this K710 region in wild-type rodents by a cell-penetrating peptide limited acute behavioral responses to noxious stimuli and rescued pain hypersensitivity induced by nerve injury back to baseline. These findings identify K710 TRPV1 as a discrete site crucial for the control of nociception and provides new insights into how to leverage rare genetic variants in humans to uncover fresh strategies for developing pain therapeutics.

Authors

Shufang He, Vanessa O. Zambelli, Pritam Sinharoy, Laura Brabenec, Yang Bian, Freeborn Rwere, Rafaela C.R. Hell, Beatriz Stein Neto, Barbara Hung, Xuan Yu, Meng Zhao, Zhaofei Luo, Chao Wu, Lijun Xu, Katrin J. Svensson, Stacy L. McAllister, Creed M. Stary, Nana-Maria Wagner, Ye Zhang, Eric R. Gross

Nociception and pain in humans lacking functional TRPV1 channel

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Abstract

Chronic-pain is a debilitating illness that has become exceedingly widespread with currently limited treatments. Differences in the molecular signature of nociceptors, have been demonstrated between human and the commonly-used mouse model, suggesting functional differences in detection and transmission of noxious-stimuli. Therefore, direct understanding of pain-physiology in humans is required for pain treatment. This could be facilitated by studying humans carrying deleterious genetic mutations affecting pain sensation. The transient receptor potential vanilloid 1 (TRPV1) channel is associated with several body-functions, in particular, noxious-heat detection and inflammatory-pain. Reports of adverse effects in human trials have hinder the clinical development of TRPV1 antagonists as novel pain relievers. Hence, studies on the functional roles of TRPV1, which currently rely mainly on evidences obtained from rodents, should be extended to humans. Here, we examined humans carrying a unique missense mutation in TRPV1, rendering the channel non-functional. The affected individual demonstrated lack of aversion towards capsaicin and elevated heat-pain threshold. Surprisingly, he showed elevated cold-pain threshold and extensive neurogenic inflammatory flare and pain-responses following application of the TRPA1 channel-activator, mustard-oil. Our study provides the first direct evidence for pain-related functional-changes linked to TRPV1 in humans, which is a prime target in the development of novel pain-relievers.

Authors

Ben Katz, Rachel Zaguri, Simon Edvardson, Channa Maayan, Orly Elpeleg, Shaya Lev, Elyad Davidson, Maximilian Peters, Shlomit Kfir-Erenfeld, Esther Berger, Shifa Ghazalin, Alexander M. Binshtok, Baruch Minke

A phase 1/2 study on intracerebroventricular tralesinidase alfa in patients with Sanfilippo syndrome type B

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Abstract

BACKGROUND. Sanfilippo type B is a mucopolysaccharidosis (MPS) with a major neuronopathic component characterized by heparan sulfate (HS) accumulation due to mutations in the NAGLU gene encoding for alfa-N-acetyl-glucosaminidase. Enzyme replacement therapy for neuronopathic MPS requires efficient enzyme delivery throughout the brain in order to normalize HS, prevent brain atrophy and potentially delay cognitive decline. METHODS. In this phase 1/2, open-label study, subjects (n=22) affected with MPS IIIB were treated with tralesinidase alfa administered intracerebroventricularly (ICV). Subjects were monitored for drug exposure, total HS and HS non-reducing end (HS-NRE) levels in both cerebrospinal fluid (CSF) and plasma, anti-drug antibody response, brain, spleen and liver volumes as measured by magnetic resonance imaging and cognitive development as measured by age-equivalent (AEq) scores. RESULTS. In the Part 1 dose escalation (30, 100, and 300 mg) phase, tralesinidase alfa 300 mg was necessary to achieve normalization of HS and HS-NRE in CSF and plasma. In Part 2, tralesinidase alfa 300 mg sustained HS and HS-NRE normalization in the CSF and stabilized cortical grey matter volume (CGMV) over 48 weeks of treatment. Resolution of hepatomegaly and reduction in spleen volume were observed in most subjects. Significant correlations were also established between change in cognitive AEq and plasma drug exposure, plasma HS-NRE level and change in CGMV. CONCLUSION. ICV administration of tralesinidase alfa effectively normalized HS and HS-NRE as a prerequisite for clinical efficacy. Peripheral drug exposure data suggests a role for the glymphatic system in altering tralesinidase alfa efficacy. TRIAL REGISTRATION. Clinicaltrials.gov: NCT02754076.

Authors

Nicole Muschol, Anja Koehn, Katharina von Cossel, Ilyas Okur, Fatih Ezgu, Paul Harmatz, Maria Jose de Castro Lopez, Maria Luz Couce, Shuan-Pei Lin, Spyros Batzios, Maureen Cleary, Martha Solano, Igor Nestrasil, Brian D. Kaufman, Adam J. Shaywitz, Stephen M. Maricich, Bernice Kuca, Joseph Kovalchin, Eric H. Zanelli

Parvalbumin interneuron loss mediates repeated anesthesia-induced memory deficits in mice

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Abstract

Repeated or prolonged, but not short-term, general anesthesia during the early postnatal period causes long-lasting impairments in memory formation in various species. The mechanisms underlying long-lasting impairment in cognitive function are poorly understood. Here we showed that repeated general anesthesia in postnatal mice induces preferential apoptosis and subsequent loss of parvalbumin-positive inhibitory interneurons in the hippocampus. Each parvalbumin interneuron controls the activity of multiple pyramidal excitatory neurons, thereby regulating neuronal circuits and memory consolidation. Preventing the loss of parvalbumin neurons by deleting a pro-apoptotic protein MAPL (Mitochondrial Anchored Protein Ligase) selectively in parvalbumin neurons rescued anesthesia-induced deficits in pyramidal cell inhibition, and hippocampus-dependent long-term memory. Conversely, partial depletion of parvalbumin neurons in neonates was sufficient to engender long-lasting memory impairment. Thus, loss of parvalbumin interneurons in postnatal mice following repeated general anesthesia critically contributes to memory deficits in adulthood.

Authors

Patricia Soriano Roque, Carolina Thörn Perez, Mehdi Hooshmandi, Calvin Wong, Mohammad Javad Eslamizade, Shilan Heshmati, Nicole Brown, Vijendra Sharma, Kevin C. Lister, Vanessa Magalie Goyon, Laura E. Neagu-Lund, Cathy Shen, Nicolas Daccache, Hiroaki Sato, Tamaki Sato, Jeffrey S. Mogil, Karim Nader, Christos G. Gkogkas, Mihaela D. Iordanova, Masha Prager-Khoutorsky, Heidi M. McBride, Jean-Claude Lacaille, Linda Wykes, Thomas Schricker, Arkady Khoutorsky

Age-related differences in striatal dopamine D1 receptors mediate subjective drug effects

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Abstract

Authors

Peter Manza, Ehsan Shokri-Kojori, Sukru B. Demiral, Rui Zhang, Evan Dennis, Allison M. Johnson, Leah Vines, Diana Sotelo, Dardo Tomasi, Gene-Jack Wang, Nora D. Volkow