BACKGROUND. Methodology for estimation of cerebrospinal fluid (CSF) tracer clearance could have wide clinical application in predicting excretion of intrathecal drugs and metabolic solutes from brain metabolism, and for diagnostic work-up of cerebrospinal fluid disturbances. METHODS. The magnetic resonance imaging (MRI) contrast agent gadobutrol (Gadovist) was utilized as CSF tracer and injected into the lumbar CSF. Gadobutrol is contained outside blood vessels of the central nervous system (CNS) and is thus eliminated along extra-vascular pathways, analogous to many CNS metabolites and intrathecal drugs. Tracer enrichment was verified and assessed in CSF by MRI at level of the cisterna magna in parallel with obtaining blood samples through 48 hours. RESULTS. In a reference patient cohort (REF; n=29), both enrichment within CSF and blood coincided in time. Blood concentration profiles of gadobutrol through 48 hours varied between patients diagnosed with CSF leakage (n=4), idiopathic normal pressure hydrocephalus dementia (iNPH; n=7), pineal cysts (n=8), and idiopathic intracranial hypertension (IIH; n=4). CONCLUSION. Assessment of CSF tracer clearance is clinically feasible and may provide a way to predict extra-vascular clearance of intrathecal drugs and endogenous metabolites from the CNS. The peak concentration in blood (at about 10 hrs) preceded by far peak tracer enhancement at MRI in extra-cranial lymphatic structures (at about 24 hrs) as shown in previous studies, indicating a major role of the spinal canal in CSF clearance capacity. FUNDING. The work was supported by Department of Neurosurgery, Oslo university hospital, and Norwegian Institute for Air Research, Kjeller, Norway, and University of Oslo.
Per K. Eide, Espen Mariussen, Hilde Uggerud, Are H. Pripp, Aslan Lashkarivand, Bjørnar Hassel, Hege Christensen, Markus Herberg Hovd, Geir Ringstad
Acute high fat diet (HFD) exposure induces a brief period of hyperphagia before caloric balance is restored. Previous studies have demonstrated this period of regulation is associated with activation of synaptic NMDA receptors (NMDARs) on dorsal motor nucleus of the vagus (DMV) neurons, which increases vagal control of gastric functions. Our aim was to test the hypothesis that activation of DMV NMDARs occurs subsequent to activation of extrasynaptic NMDA receptors (NMDARex). Sprague-Dawley rats were fed control or HFD for 3-5 days prior to experimentation. Whole cell patch clamp recordings from gastric-projecting DMV neurons, in vivo recordings of gastric motility, tone, compliance, and emptying, as well as food intake studies were used to assess the effects of NMDAR antagonism on caloric regulation. Following acute HFD exposure, inhibition of NMDARex prevented the NMDARs-mediated increase in glutamatergic transmission to DMV neurons, as well as the increase in gastric tone and motility, while chronic NMDARex inhibition attenuated the regulation of caloric intake. Following acute HFD exposure, the regulation of food intake involves NMDARs-mediated currents, which occur in response to NMDARex activation. Understanding these events may provide a mechanistic basis for hyperphagia and identify potential novel therapeutic targets for the treatment of obesity.
Courtney Clyburn, R. Alberto Travagli, Amy C. Arnold, Kirsteen N. Browning
Intracerebral hemorrhage (ICH) is a devastating form of stroke with a high mortality rate and few treatment options. Discovery of therapeutic interventions has been slow given the challenges associated with studying acute injury in the human brain. Inflammation induced by exposure of brain tissue to blood appears to be a major part of brain tissue injury. Here, we longitudinally profiled blood and cerebral hematoma effluent from a patient enrolled in the Minimally Invasive Surgery with Thrombolysis in Intracerebral Hemorrhage Evacuation trial, offering a rare window into the local and systemic immune responses to acute brain injury. Using single-cell RNA-Seq (scRNA-Seq), this is the first report to our knowledge that characterized the local cellular response during ICH in the brain of a living patient at single-cell resolution. Our analysis revealed shifts in the activation states of myeloid and T cells in the brain over time, suggesting that leukocyte responses are dynamically reshaped by the hematoma microenvironment. Interestingly, the patient had an asymptomatic rebleed that our transcriptional data indicated occurred prior to detection by CT scan. This case highlights the rapid immune dynamics in the brain after ICH and suggests that sensitive methods such as scRNA-Seq would enable greater understanding of complex intracerebral events.
Brittany A. Goods, Michael H. Askenase, Erica Markarian, Hannah E. Beatty, Riley S. Drake, Ira Fleming, Jonathan H. DeLong, Naomi H. Philip, Charles C. Matouk, Issam A. Awad, Mario Zuccarello, Daniel F. Hanley, J. Christopher Love, Alex K. Shalek, Lauren H. Sansing, the ICHseq Investigators
To identify small molecules that shield mammalian sensory hair cells from the ototoxic side effects of aminoglycoside antibiotics we screened 10,240 compounds, selecting those that protected against neomycin and gentamicin in zebrafish lateral-line hair cells and, when retested in mouse cochlear cultures, prevented gentamicin-induced death of outer hair cells (OHCs). Of 64 compounds that protected zebrafish hair cells, 8 protect OHCs from gentamicin in vitro. These hits share structural features and all block, to varying degrees, the OHC’s mechano-electrical transducer (MET) channel, a known route of aminoglycoside entry into hair cells. Further characterisation of one of the strongest MET-channel blockers, UoS-7692, revealed it additionally protects against kanamycin and tobramycin, and does not abrogate the bactericidal activity of gentamicin. UoS-7692 behaves, like the aminoglycosides, as a permeant blocker of the MET channel, significantly reduces gentamicin-Texas Red loading into OHCs, and preserves lateral-line function in neomycin-treated zebrafish. Trans-tympanic injection of UoS-7692 protects mouse OHCs from furosemide-kanamycin exposure in vivo and partially preserves hearing. The results confirm the hair-cell MET channel as a viable target for the identification of compounds that protect the cochlea from aminoglycosides, and provide a series of hit compounds that will inform the design of future otoprotectants.
Emma J. Kenyon, Nerissa K. Kirkwood, Siân R. Kitcher, Richard J. Goodyear, Marco Derudas, Daire M. Cantillon, Sarah Baxendale, Antonio de la Vega de León, Virginia N. Mahieu, Richard T. Osgood, Charlotte Donald Wilson, James C. Bull, Simon J. Waddell, Tanya T. Whitfield, Simon E. Ward, Corné J. Kros, Guy P. Richardson.
Parkinson’s disease (PD) is a prevalent neurodegenerative disease with no approved disease-modifying therapies. Multiplications, mutations, and single nucleotide polymorphisms in the SNCA gene, encoding α-synuclein (aSyn) protein, either cause or increase risk for PD. Intracellular accumulations of aSyn are pathological hallmarks of PD. Taken together, reduction of aSyn production may provide a disease-modifying therapy for PD. We show that antisense oligonucleotides (ASOs) reduce production of aSyn in rodent preformed fibril (PFF) models of PD. Reduced aSyn production leads to prevention and removal of established aSyn pathology and prevents dopaminergic cell dysfunction. In addition, we address the translational potential of the approach through characterization of human SNCA-targeting ASOs that efficiently suppress the human SNCA transcript in vivo. We demonstrate broad activity and distribution of the human SNCA ASOs throughout the nonhuman primate brain and a corresponding decrease in aSyn cerebral spinal fluid (CSF) levels. Taken together, these data suggest that, by inhibiting production of aSyn, it may be possible to reverse established pathology; thus, these data support the development of SNCA ASOs as a potential disease-modifying therapy for PD and related synucleinopathies.
Tracy A. Cole, Hien Zhao, Timothy J. Collier, Ivette Sandoval, Caryl E. Sortwell, Kathy Steece-Collier, Brian F. Daley, Alix Booms, Jack Lipton, Mackenzie Welch, Melissa Berman, Luke Jandreski, Danielle Graham, Andreas Weihofen, Stephanie Celano, Emily Schulz, Allyson Cole-Strauss, Esteban Luna, Duc Quach, Apoorva Mohan, C. Frank Bennett, Eric E. Swayze, Holly B. Kordasiewicz, Kelvin C. Luk, Katrina L. Paumier
Functional dyspepsia (FD) is associated with both chronic gastrointestinal distress and anxiety and depression. Here, we hypothesized that aberrant gastric signals, transmitted by the vagus nerve, may alter key brain regions modulating affective and pain behavior. Using a previously validated rat model of FD characterized by gastric hypersensitivity, depression- and anxiety-like behavior, we found that vagal activity in response to gastric distention was increased in FD rats. The FD phenotype was associated with gastric mast cell hyperplasia and increased expression of corticotrophin-releasing factor (CRF) and decreased brain-derived neurotrophic factor in the central amygdala. Subdiaphragmatic vagotomy reversed these changes and restored affective behavior to that of controls. Vagotomy partially attenuated pain responses to gastric distention, which may be mediated by central reflexes in the periaqueductal gray, as determined by local injection of lidocaine. Ketotifen, a mast cell stabilizer, reduced vagal hypersensitivity, normalized affective behavior and attenuated gastric hyperalgesia. In conclusion, vagal activity, partially driven by gastric mast cells, induces long-lasting changes in CRF signaling in the amygdala that may be responsible for enhanced pain and anxiety- and depression-like behaviors. Together, these results support a “bottom-up” pathway involving the gut-brain axis in the pathogenesis of both gastric pain and psychiatric co-morbidity in FD.
Zachary A. Cordner, Qian Li, Liansheng Liu, Kellie L. Tamashiro, Aditi Bhargava, Timothy H. Moran, Pankaj J. Pasricha
Spinocerebellar ataxia type 1 (SCA1) is an adult-onset neurodegenerative disorder characterized by motor incoordination, mild cognitive decline, respiratory dysfunction, and early lethality. It is caused by the expansion of the polyglutamine (polyQ) tract in Ataxin-1 (ATXN1), which stabilizes the protein, leading to its toxic accumulation in neurons. Previously, we showed that serine 776 (S776) phosphorylation is critical for ATXN1 stability and contributes to its toxicity in cerebellar Purkinje cells. Still, the therapeutic potential of disrupting S776 phosphorylation on noncerebellar SCA1 phenotypes remains unstudied. Here, we report that abolishing S776 phosphorylation specifically on the polyQ-expanded ATXN1 of SCA1-knockin mice reduces ATXN1 throughout the brain and not only rescues the cerebellar motor incoordination but also improves respiratory function and extends survival while not affecting the hippocampal learning and memory deficits. As therapeutic approaches are likely to decrease S776 phosphorylation on polyQ-expanded and WT ATXN1, we further disrupted S776 phosphorylation on both alleles and observed an attenuated rescue, demonstrating a potential protective role of WT allele. This study not only highlights the role of S776 phosphorylation to regulate ATXN1 levels throughout the brain but also suggests distinct brain region–specific disease mechanisms and demonstrates the importance of developing allele-specific therapies for maximal benefits in SCA1.
Larissa Nitschke, Stephanie L. Coffin, Eder Xhako, Dany B. El-Najjar, James P. Orengo, Elizabeth Alcala, Yanwan Dai, Ying-Wooi Wan, Zhandong Liu, Harry T. Orr, Huda Y. Zoghbi
The metabotropic glutamate receptor 7 (mGlu7) is a G protein-coupled receptor that has been recently linked to neurodevelopmental disorders. This association is supported by the identification of GRM7 variants in patients with autism spectrum disorder, attention deficit hyperactivity disorder, and severe developmental delay. One GRM7 mutation previously reported in two patients results in a single amino acid change, I154T, within the mGlu7 ligand-binding domain. Here, we report two new patients with this mutation who present with severe developmental delay and epilepsy. Functional studies of the mGlu7-I154T mutant reveal that this substitution results in significant loss of mGlu7 protein expression in HEK293A cells and in mice. We show that this occurs post-transcriptionally at the level of protein expression and trafficking. Similar to mGlu7 global knockout mice, mGlu7-I154T animals exhibit reduced motor coordination, deficits in contextual fear learning, and seizures. This provides the first functional evidence that a disease-associated mutation affecting the mGlu7 receptor is sufficient to cause neurological dysfunction in mice and further validates GRM7 as a disease-causing gene in the human population.
Nicole M. Fisher, Aqeela AlHashim, Aditi B. Buch, Hana Badivuku, Manar M. Samman, Kelly M. Weiss, Gabriela I. Cestero, Mark D. Does, Jerri M. Rook, Craig W. Lindsley, P. Jeffrey Conn, Rocco G. Gogliotti, Colleen M. Niswender
Hair cell loss is the leading cause of hearing and balance disorders in humans. It can be caused by many factors, including noise, aging, and therapeutic agents. Previous studies have shown the therapeutic potential of quinoxaline against drug-induced ototoxicity. Here, we screened a library of 68 quinoxaline derivatives for protection against aminoglycoside-induced damage of hair cells from the zebrafish lateral line. We identified Qx28 as the best quinoxaline derivative that provides robust protection against both aminoglycosides and cisplatin in zebrafish and mouse cochlear explants. FM1-43 and aminoglycoside uptake, as well as antibiotic efficacy studies, reveal that Qx28 is neither blocking the mechanotransduction channels nor interfering with aminoglycoside antibacterial activity, suggesting that it may be protecting the hair cells by directly counteracting the ototoxin’s mechanism of action. Only when animals were incubated with higher doses of Qx28 we observed a partial blockage of the mechanotransduction channels. Finally, we assessed the regulation of NF-κB pathway in vitro in mouse embryonic fibroblasts and in vivo in zebrafish larvae. Those studies showed that Qx28 protects hair cells by blocking NF-κB canonical pathway activation. Thus, Qx28 is a promising and versatile otoprotectant that can act across different species and toxins.
Marisa Zallocchi, Santanu Hati, Zhenhang Xu, William Hausman, Huizhan Liu, David Z. He, Jian Zuo
The CNS is regarded as an immunoprivileged organ, evading routine immune surveillance; however, the coordinated development of immune responses profoundly influences outcomes after brain injury. Innate lymphoid cells (ILCs) are cytokine-producing cells that are critical for the initiation, modulation, and resolution of inflammation, but the functional relevance and mechanistic regulation of ILCs are unexplored after acute brain injury. We demonstrate increased proliferation of all ILC subtypes within the meninges for up to 1 year after experimental traumatic brain injury (TBI) while ILCs were present within resected dura and elevated within cerebrospinal fluid (CSF) of moderate-to-severe TBI patients. In line with energetic derangements after TBI, inhibition of the metabolic regulator, AMPK, increased meningeal ILC expansion, whereas AMPK activation suppressed proinflammatory ILC1/ILC3 and increased the frequency of IL-10–expressing ILC2 after TBI. Moreover, intracisternal administration of IL-33 activated AMPK, expanded ILC2, and suppressed ILC1 and ILC3 within the meninges of WT and Rag1–/– mice, but not Rag1–/– IL2rg–/– mice. Taken together, we identify AMPK as a brake on the expansion of proinflammatory, CNS-resident ILCs after brain injury. These findings establish a mechanistic framework whereby immunometabolic modulation of ILCs may direct the specificity, timing, and magnitude of cerebral immunity.
Babak Baban, Molly Braun, Hesam Khodadadi, Ayobami Ward, Katelyn Alverson, Aneeq Malik, Khoi Nguyen, Skon Nazarian, David C. Hess, Scott Forseen, Alexander F. Post, Fernando L. Vale, John R. Vender, Md. Nasrul Hoda, Omid Akbari, Kumar Vaibhav, Krishnan M. Dhandapani
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