Mouse Model Of Multiple Sclerosis Research Articles

Regulatory T cells use heparanase to access IL-2 bound to extracellular matrix in inflamed tissue

Although FOXP3+ regulatory T cells (Treg) depend on IL-2 produced by other cells for their survival and function, the levels of IL-2 in inflamed tissue are low, making it unclear how Treg access this critical resource. Here, we show that Treg use heparanase (HPSE) to access IL-2 sequestered by heparan sulfate (HS) within the extracellular matrix (ECM) of inflamed central nervous system tissue. HPSE expression distinguishes human and murine Treg from conventional T cells and is regulated by the availability of IL-2. HPSE-/- Treg have impaired stability and function in vivo, including in the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis. Conversely, endowing monoclonal antibody-directed chimeric antigen receptor (mAbCAR) Treg with HPSE enhances their ability to access HS-sequestered IL-2 and their ability to suppress neuroinflammation in vivo. Together, these data identify a role for HPSE and the ECM in immune tolerance, providing new avenues for improving Treg-based therapy of autoimmunity.

Chronic demyelination interferes with normal spermatogenesis in cuprizone-intoxicant C57/BL 6 mice: An experimental study.

Due to myelin and axonal insults in multiple sclerosis individuals, motor coordination problems and endocrine imbalance may develop. This study aims to evaluate the role of chronic demyelination on the hypothalamic-pituitary-gonadal axis in the mouse model of multiple sclerosis. 20 adult C57/BL6 male mice were divided into 2 groups (n = 10/each) as follows: the control group (CONT) received a regular diet for 17 wk; and the experimental group (cuprizone [CPZ]) was fed with 0.2% CPZ for 12 wk and, then CPZ was withdrawn for 5 wk. Serum testosterone, histopathology of the brain and testis, and sperm analysis were evaluated. The hypothalamic myelin content was significantly decreased in the arcuate nucleus following the 12 wk of CPZ consumption compared to the CONT group, and the statistical difference remained until 17 wk. Testosterone levels declined significantly in the CPZ group compared to the CONT group in the 12 and 17 wk. A significant decrease was observed in the height of the seminiferous epithelium and the interstitial tissue area, and the number of seminiferous epithelial cells in the CPZ group compared to the CONT group in the 12 and 17 wk. The sperm count, motility, and viability in the CPZ group significantly decreased compared to the CONT group in the 12 and 17 wk of the study. Chronic demyelination induced by CPZ intoxication, maybe through damage to the hypothalamus arcuate nucleus, leads to the hypothalamic-pituitary-gonadal axis disturbance and damage to the testis and spermatogenesis subsequently.

Dietary Supplementation with 23-Hydroxy Ursolic Acid Reduces the Severity and Incidence of Acute Experimental Autoimmune Encephalomyelitis (EAE) in a Murine Model of Multiple Sclerosis.

23-Hydroxy ursolic acid (23-OH UA) is a potent atheroprotective and anti-obesogenic phytochemical, with anti-inflammatory and inflammation-resolving properties. In this study, we examined whether dietary 23-OH UA protects mice against the acute onset and progression of experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS). Female C57BL/6 mice were fed either a defined low-calorie maintenance diet (MD) or an MD supplemented with 0.2% wgt/wgt 23-OH UA for 5 weeks prior to actively inducing EAE and during the 30 days post-immunization. We observed no difference in the onset of EAE between the groups of mice, but ataxia and EAE disease severity were suppressed by 52% and 48%, respectively, and disease incidence was reduced by over 49% in mice that received 23-OH UA in their diet. Furthermore, disease-associated weight loss was strikingly ameliorated in 23-OH UA-fed mice. ELISPOT analysis showed no significant differences in frequencies of T cells producing IL-17 or IFN-γ between 23-OH UA-fed mice and control mice, suggesting that 23-OH UA does not appear to regulate peripheral T cell responses. In summary, our findings in EAE mice strongly suggest that dietary 23-OH UA may represent an effective oral adjunct therapy for the prevention and treatment of relapsing-remitting MS.

Microglia-derived exosomes modulate myelin regeneration via miR-615-5p/MYRF axis

Demyelination and failure of remyelination in the central nervous system (CNS) characterize a number of neurological disorders. Spontaneous remyelination in demyelinating diseases is limited, as oligodendrocyte precursor cells (OPCs), which are often present in demyelinated lesions in abundance, mostly fail to differentiate into oligodendrocytes, the myelinating cells in the CNS. In addition to OPCs, the lesions are assembled numbers of activated resident microglia/infiltrated macrophages; however, the mechanisms and potential role of interactions between the microglia/macrophages and OPCs are poorly understood. Here, we generated a transcriptional profile of exosomes from activated microglia, and found that miR-615-5p was elevated. miR-615-5p bound to 3′UTR of myelin regulator factor (MYRF), a crucial myelination transcription factor expressed in oligodendrocyte lineage cells. Mechanistically, exosomes from activated microglia transferred miR-615-5p to OPCs, which directly bound to MYRF and inhibited OPC maturation. Furthermore, an effect of AAV expressing miR-615-5p sponge in microglia was tested in experimental autoimmune encephalomyelitis (EAE) and cuprizone (CPZ)-induced demyelination model, the classical mouse models of multiple sclerosis. miR-615-5p sponge effectively alleviated disease progression and promoted remyelination. This study identifies miR-615-5p/MYRF as a new target for the therapy of demyelinating diseases.

Modulatory Effects of Hydatid Cyst Fluid on a Mouse Model of Experimental Autoimmune Encephalomyelitis.

The reduced burden of helminth parasites in industrialized countries is probably one of the reasons for the increased prevalence of autoimmune disorders such as multiple sclerosis (MS). The current study aimed to evaluate the potential preventive effects of hydatid cyst fluid (HCF) on the disease severity in an EAE mouse model of MS. EAE-induced mice were treated with HCF before and after EAE induction. An RT-PCR-based evaluation of IFN-γ, IL-1β, TNF, T-bet, IL-4, GATA3, IL-17, RoRγ, TGF-β, and FOXP3 expression levels in splenocytes and an ELISA-based analysis of IFN-γ and IL-4 levels in cell culture supernatant of splenocytes were performed. Histopathological examinations of mice during the study were also conducted. The expression levels of T-bet, IL-4, GATA3, TGF-β, and FOXP3 in EAE + HCF mice were significantly higher compared to EAE + PBS mice. In the EAE + HCF group, the expression levels of IFN-γ, IL-1β, and TNF were significantly lower than in the EAE + PBS group. The histopathological results showed significantly reduced inflammation and demyelination in EAE + HCF mice compared to EAE + PBS mice. Our study provides proof-of-concept in the EAE mouse model of MS that helminth-derived products such as HCF have a potential prophylactic effect on MS development and present a novel potential therapeutic strategy.

Chronic Inflammation Disrupts Circadian Rhythms in Splenic CD4+ and CD8+ T Cells in Mice.

Internal circadian clocks coordinate 24 h rhythms in behavior and physiology. Many immune functions show daily oscillations, and cellular circadian clocks can impact immune functions and disease outcome. Inflammation may disrupt circadian clocks in peripheral tissues and innate immune cells. However, it remains elusive if chronic inflammation impacts adaptive immune cell clock, e.g., in CD4+ and CD8+ T lymphocytes. We studied this in the experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis, as an established experimental paradigm for chronic inflammation. We analyzed splenic T cell circadian clock and immune gene expression rhythms in mice with late-stage EAE, CFA/PTx-treated, and untreated mice. In both treatment groups, clock gene expression rhythms were altered with differential effects for baseline expression and peak phase compared with control mice. Most immune cell marker genes tested in this study did not show circadian oscillations in either of the three groups, but time-of-day- independent alterations were observed in EAE and CFA/PTx compared to control mice. Notably, T cell effects were likely independent of central clock function as circadian behavioral rhythms in EAE mice remained intact. Together, chronic inflammation induced by CFA/PTx treatment and EAE immunization has lasting effects on circadian rhythms in peripheral immune cells.

The Contribution of Microglia and Brain-Infiltrating Macrophages to the Pathogenesis of Neuroinflammatory and Neurodegenerative Diseases during TMEV Infection of the Central Nervous System.

The infection of the central nervous system (CNS) with neurotropic viruses induces neuroinflammation and is associated with the development of neuroinflammatory and neurodegenerative diseases, including multiple sclerosis and epilepsy. The activation of the innate and adaptive immune response, including microglial, macrophages, and T and B cells, while required for efficient viral control within the CNS, is also associated with neuropathology. Under healthy conditions, resident microglia play a pivotal role in maintaining CNS homeostasis. However, during pathological events, such as CNS viral infection, microglia become reactive, and immune cells from the periphery infiltrate into the brain, disrupting CNS homeostasis and contributing to disease development. Theiler's murine encephalomyelitis virus (TMEV), a neurotropic picornavirus, is used in two distinct mouse models: TMEV-induced demyelination disease (TMEV-IDD) and TMEV-induced seizures, representing mouse models of multiple sclerosis and epilepsy, respectively. These murine models have contributed substantially to our understanding of the pathophysiology of MS and seizures/epilepsy following viral infection, serving as critical tools for identifying pharmacological targetable pathways to modulate disease development. This review aims to discuss the host-pathogen interaction during a neurotropic picornavirus infection and to shed light on our current understanding of the multifaceted roles played by microglia and macrophages in the context of these two complexes viral-induced disease.

Effects of the mineralocorticoid receptor antagonist eplerenone in experimental autoimmune encephalomyelitis

There is growing evidence indicating that mineralocorticoid receptor (MR) expression influences a wide variety of functions in metabolic and immune response. The present study explored if antagonism of the MR reduces neuroinflammation in the spinal cord of mice with experimental autoimmune encephalomyelitis (EAE). Eplerenone (EPLE) (100 mg/kg dissolved in 30% 2-hydroxypropyl-β-cyclodextrin) was administered intraperitoneally (i.p.) daily from EAE induction (day 0) until sacrificed on day 17 post-induction. The MR blocker (a) significantly decreased the inflammatory parameters TLR4, MYD88, IL-1β, and iNOS mRNAs; (b) attenuated HMGB1, NLRP3, TGF-β mRNAs, microglia, and aquaporin4 immunoreaction without modifying GFAP. Serum IL-1β was also decreased in the EAE+EPLE group. Moreover, EPLE treatment prevented demyelination and improved clinical signs of EAE mice. Interestingly, MR was decreased and GR remained unchanged in EAE mice while EPLE treatment restored MR expression, suggesting that a dysbalanced MR/GR was associated with the development of neuroinflammation. Our results indicated that MR blockage with EPLE attenuated inflammation-related spinal cord pathology in the EAE mouse model of Multiple Sclerosis, supporting a novel therapeutic approach for immune-related diseases.

Probing Brain Magnetic Susceptibility Alterations in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is an increasing cause of disability in the United States, characterized by autoimmune demyelinating events in the central nervous system. MS patients can present with a varying range of symptoms and disability due to the chronic inflammatory and relapsing events associated with the disease, such as impaired mobility, slowed cognitive processing, and high probability of disease progression.
 MS can be morphologically characterized by the damage to the myelin sheath that surrounds axons, oligodendrocytes that produce myelin, and axons that transmit information to different neurons. Due to the complicated mechanism of MS, the advanced MRI methods which can provide both sensitive and specific assessment of MS tissue injury hold the promise to provide critical mechanistic guidance of MS and serve as robust imaging biomarkers for MS. Several animal models have been established to understand the distinct aspects of the disease. Cuprizone, a copper chelator, creates demyelination events comparable to MS, allowing the mouse model to be a representation QSM’s ability to accurately distinguish between and predict acute and chronic demyelination events. Recently, we have demonstrated that the novel quantitative susceptibility mapping (QSM) can identify between the demyelination andremyelination process in the corpus callosum of mice treated with cuprizone. However, how early QSM can detect brain alterations has not been investigated.
 We acquired high-resolution in vivo whole-brain QSM, T-2 weighted, and magnetization transfer ratio (MTR) images at 0, 2, and 4 weeks after cuprizone administration. The corpus callosum exhibited significant changes in T2-weighted and MTR images at 4 weeks after cuprizone administration. In contrast, QSM decreased significantly in QSM at 2 weeks after cuprizone administration. Since dramatic demyelination only starts after oligodendrocytes depletion (3 weeks after cuprizone treatment), QSM may be able to detect the alteration of oligodendrocytes and serve as a sensitive biomarker even before demyelination occurs.

Curcumin and Its Semisynthetic Derivative F-Curcumin Ameliorate the Expression of Cytokines in Autoimmune Encephalomyelitis Mouse Models of Multiple Sclerosis.

Multiple sclerosis (MS) is an inflammatory disorder impacting the central nervous system, with cytokines significantly influencing its pathogenesis. This study investigates the effect of curcumin and its semisynthetic derivative F-curcumin on cytokine gene expression in autoimmune encephalomyelitis (EAE) mouse models of MS. We assessed the expression levels of specific cytokines including interleukin (IL)-1β, IL-4, IL-10, IL-17, interferon-γ (IFN-γ), and transforming growth factor-β (TGF-β), alongside key transcription factors for helper T cells (T-bet, GATA-3, RORγt, and FoxP3) in both the spinal cord and spleen. Treatment with curcumin and F-curcumin significantly ameliorated the severity and onset of EAE. Notably, mice administered with either compound showed a substantial decrease in the expression of genes encoding IL-1 (2 folds), IFN-γ (2 and 4 folds), and IL-17 (2.5 and 3.5 folds), alongside a marked increase in TGF-β (7 folds) and IL-10 (4 and 6 folds) levels. Additionally, the gene expression of T cell-derived transcription factors nearly mirrored the changes observed in pro-inflammatory and anti-inflammatory cytokines across the groups. The F-curcumin-treated group exhibited more pronounced results. In conclusion, curcumin and F-curcumin significantly modulate cytokine gene expression during EAE induction, potentially alleviating inflammation in MS, with F-curcumin showing a more substantial effect.

Ginsenoside-Re inhibits experimental autoimmune encephalomyelitis as a mouse model of multiple sclerosis by downregulating TLR4/MyD88/NF-κB signaling pathways.

Ginsenosides are main active compounds of Panax ginseng with pharmacological effects on immunological/neurological diseases. Recently, ginsenoside-Re (G-Re) has been shown to exert neuroprotective effects on neurodegenerative diseases such as Alzheimer's disease. However, whether G-Re has an effect on multiple sclerosis (MS), a representative autoimmune disease of the central nervous system (CNS), has not been revealed yet. The purpose of this study was to investigate pharmacological effects of G-Re and related molecular mechanisms using a myelin oligodendrocyte glycoprotein peptide-immunized experimental autoimmune encephalomyelitis (EAE) animal model of MS and lipopolysaccharide (LPS)-stimulated bEND.3 cells as an in vitro model of the blood-brain barrier (BBB). G-Re attenuated motor impairment of EAE, demyelination, and inflammation in spinal cords of EAE mice. G-Re reduced infiltration/activation of microglia/macrophages and decreased mRNA expression levels of pro-inflammatory cytokines (IL-1β and IL-6), chemokines (MIP-1α, MCP-1, and RANTES), and enzymes (iNOS) in spinal cords of EAE mice. G-Re inhibited alterations of BBB constituents (such as astrocytes, cell adhesion molecule (platelet endothelial cell adhesion molecule-1), and tight junctional molecules (occludin and zonula occludens-1)) and toll like receptor 4 (TLR4)/MyD88/nuclear factor kappa-B (NF-κB) signaling pathways in spinal cords of EAE mice and LPS-stimulated bEND.3 cells. Interestingly, combination treatment with G-Re and TLR4 inhibitor (TAK242) significantly inhibited the upregulation of TLR4/MyD88/NF-κB pathway in LPS-stimulated bEND.3 cells. TLR4 inhibitor- and activator-treated EAE mice showed conflicting behavior patterns. G-Re might alleviate motor impairment of EAE and its pathological/inflammatory events in the spinal cord by preventing BBB disruption via downregulation of TLR4/MyD88/NF-κB signaling pathways. These findings for the first time suggest that G-Re might be a potential therapeutic for MS through maintenance of BBB integrity.

Retinal microglia and ganglion cells in a cuprizone (CPZ) induced mouse model of multiple sclerosis (MS)

Aims/Purpose: Up to 90% of MS patients have ocular manifestations. Activated microglia (mg) are associated with age and diseases like MS. Mg change their activation states (ramified, hyper‐ramified, activated, amoeboid and rod) in response to stimuli, to exert either neuro‐protective or ‐toxic effects, leading to the rescue or loss of neurons. Here, we characterize retinal ganglion cell (RGC) densities and retinal mg morphotype proportions in eyes of a CPZ induced MS model and age‐matched controls.Methods: Male C57 mice were fed CPZ (0.2%w/w) mixed chow for 4 months (m) until sacrificed at 6 m (6mCPZ) or 28 m (28mCPZ) old. Age‐matched controls (6mCtrl; 28mCtrl) were fed normal chow. Enucleated eyes were fixed in 4% PFA. Whole retinas were dissected, stained (RBPMS+RGCs; iba‐1+mg), mounted and imaged. A published retinal mg morphotyping algorithm and an automated RBPMS counting script were used. Two‐way ANOVA with paired analysis (PA) was used (mg n: 6mCtrl = 15; 6mCPZ = 7; 28mCtrl = 7; 28mCPZ = 10; and RGC n: 6mCtrl = 4; 6mCPZ = 3; 28mCtrl = 3; 28mCPZ = 4).Results: There was a main effect of age for activated (p = 0.0282) and rod (p < 0.0001), and disease state for rod (p = 0.04) mg. PA showed higher activated mg in 28mCtrl versus 6mCtrl (p = 0.0485), and lower rod mg in 28mCtrl versus 6mCtrl (p = 0.0374) and in 28mCPZ versus 6mCPZ (p = 0.0007). There was a main effect of age (p = 0.0001) and disease state (p = 0.04) on RBPMS density. PA showed lower RGC density in 28mCtrl versus 6mCtrl (p = 0.0025) and in 28mCPZ versus 6mCPZ (p = 0.025).Conclusions: Our results show that there is age‐related loss of rod mg and RGCs in healthy and CPZ groups, supporting reports that rod mg are involved in protecting less damaged neurons. Age‐related increased activated mg may cause RGC loss as transcription factors like TNFα, bind to RGC receptors, inducing apoptosis. Further transcriptomic analysis may clarify functional interpretations.

Effects of oral and intranasal resveratrol nanoparticle administration on neurodegeneration and neuronal dysfunction in a model of multiple sclerosis

Aims/Purpose: Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease of the central nervous system. Immunomodulatory treatments seek to reduce inflammation in MS but have limited effect on neurodegeneration. Resveratrol is a natural polyphenol with antioxidant and anti‐inflammatory properties which could be neuroprotective in MS. The purpose of this study is to compare the oral and intranasal administration of resveratrol nanoparticles (RN) in an experimental autoimmune encephalomyelitis (EAE) mouse model of MS with ocular and neurological endpoints.Methods: RN were formulated using a thin rehydration technique. In the 1st experiment, 16.9 mg/kg RN (n = 6) or equivalent vehicle (n = 5) were given orally to EAE mice daily for 30 days. In the 2nd experiment, 8.44 mg/kg RN (n = 6) or vehicle (n = 6) were given intranasally to EAE mice daily for 30 days. EAE mice were assessed daily for clinical signs of ascending paralysis and weekly for visual function. After sacrifice at day 30, retinas were immunostained for brn3a to count retinal ganglion cells (RGC), and spinal cords and optic nerves were stained by H&E and luxol fast blue to assess inflammation and demyelination.Results: 16.9 mg/kg oral RN treatment reduced RGC loss compared to vehicle (4164 ± 406 vs 2422 ± 401 RGC/1.56 mm2, p < 0.05). Similarly, 8.44 mg/kg RN given intranasally reduced RGC loss compared to vehicle (3569 ± 241 vs 2280 ± 329 RGC/1.56 mm2, p < 0.05). Oral and intranasal RN showed similar neuroprotective effects (4164 ± 406 vs 3569 ± 241 RGC/1.56 mm2, p > 0.05). Although neither route of administration showed a reduction of ascending paralysis, 16.9 mg/kg oral RN reduced the severity of paralysis compared to vehicle and 8.44 mg/kg intranasal RN (survival analysis with median survival 29.5 vs 19.0 and 19.0 days, p < 0.05). Likewise, the severity of visual function loss was reduced by the administration of 16.9 mg/kg oral RN compared to vehicle and 8.44 mg/kg intranasal RN (median survival > 28.0 vs 28.0 and 21.0 days, p < 0.05). Neither oral nor intranasal administration showed a significant reduction of spinal cord or optic nerve inflammation or demyelination.Conclusions: RN were able to reduce RGC loss independent of their administration route, but oral administration demonstrated additional neuroprotective effects by reducing paralysis severity.

Potential therapeutic applications of targeting signal-transducing adaptor protein-2 in autoimmune diseases

Adaptor proteins are involved in various immune responses via the modulation of many signaling pathways. Signal-transducing adaptor protein-2 (STAP-2) is an adaptor protein that contains typical domains such as the pleckstrin homology (PH) domain, Src homology domain, and a proline-rich region from the N-terminal region. In T cells, STAP-2 positively regulates T cell receptor (TCR)-mediated signaling by associating with CD3ζ immunoreceptor tyrosine-based activation motifs (ITAMs) and lymphocyte-specific protein tyrosine kinase (LCK). Therefore, a peptide that inhibits the interaction between STAP-2 and CD3ζ ITAMs is likely to suppress TCR-mediated T cell activation, as well as T cell-mediated diseases. As expected, the peptide successfully inhibited the STAP-2/CD3ζ ITAM interaction and suppressed TCR-mediated signaling, cell proliferation, and interleukin (IL)-2 production in human/murine T cells. Furthermore, this inhibitor suppressed the pathogenesis of experimental autoimmune encephalomyelitis (EAE), which is widely recognized as a mouse model of multiple sclerosis, via the downregulation of T cell activation and infiltration of T helper (Th) 1/Th17 cells. These results suggest a new strategy for the treatment of multiple sclerosis and other immune diseases.

The mitochondriogenic but not the immunosuppressant effects of mTOR inhibitors prompt neuroprotection and delay disease evolution in a mouse model of progressive multiple sclerosis

IntroductionPurportedly, the progression of multiple sclerosis (MS) occurs when neurodegenerative processes due to derangement of axonal bioenergetics take over the autoimmune response. However, a clear picture of the causative interrelationship between autoimmunity and axonal mitochondrial dysfunction in progressive MS (PMS) pathogenesis waits to be provided. MethodsIn the present study, by adopting the NOD mouse model of PMS, we compared the pharmacological effects of the immunosuppressants dexamethasone and fingolimod with those of mTOR inhibitors rapamycin and everolimus that, in addition to immunosuppression, also regulate mitochondrial functioning. Female Non-Obese Diabetic (NOD) mice were immunized with MOG35–55 and treated with drugs to evaluate functional, immune and mitochondrial parameters during disease evolution. ResultsWe found that dexamethasone and fingolimod did not affect the pattern of progression as well as survival. Conversely, mTOR inhibitors rapamycin and everolimus delayed disease progression and robustly extended survival of immunized mice. The same effects were obtained when treatment was delayed by 30 days after immunization. Remarkably, dexamethasone and fingolimod prompted the same degree of immunosuppression of rapamycin within both spleen and spinal cord of mice. However, only rapamycin prompted mitochondriogenesis by increasing mitochondrial content, and expression of several mitochondrial respiratory complex subunits, thereby preventing mtDNA reduction in the spinal cords of immunized mice. These pharmacodynamic effects were not reproduced in healthy NOD mice, suggesting a disease context-dependent pharmacodynamic effect. DiscussionData corroborate the key role of mitochondriogenesis to treatment of MS progression, and for the first time disclose the translational potential of mTOR inhibitors in PMS therapy.

GABAA receptors as plausible molecular targets and mediators for taurine and homotaurine actions.

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 GABAA receptor (GABAAR) agonism in immune cells. While both taurine and HT are structural GABA analogs and thought to be GABA mimetics at GABAARs, there is uncertainty concerning their potency as GABA mimetics on native GABAARs. We show that HT is a very potent GABA mimetic, as it evokes GABAAR-mediated currents with an EC50 of 0.4μM (vs. 3.7μM for GABA and 116µM for taurine) in murine cerebellar granule cells in brain slices, with both taurine and HT having similar efficacy in activating native GABAARs. Furthermore, HT displaces the high affinity GABAAR ligand [3H]muscimol at similarly low concentrations (HT IC50 of 0.16μM vs. 125μM for taurine) in mouse brain homogenates. The potency of taurine and HT as GABAAR 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 GABAARs 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.

Tonabersat Significantly Reduces Disease Progression in an Experimental Mouse Model of Multiple Sclerosis.

Multiple sclerosis (MS) is a neurodegenerative disease marked by chronic neuroinflammation thought to be mediated by the inflammasome pathway. Connexin 43 (Cx43) hemichannels contribute to the activation of the inflammasome through the release of adenosine triphosphate (ATP) inflammasome activation signals. The objective of the study was to evaluate if the Cx43 hemichannel blocker, tonabersat, is effective in modulating the inflammatory response and reducing disability in the myelin oligodendrocyte glycoprotein 35-55-induced experimental autoimmune encephalomyelitis (MOG35-55 EAE) model of MS. Here, we show that the Cx43 hemichannel blocking drug, tonabersat, significantly reduced expression of neuroinflammatory markers for microglial activation (ionized calcium-binding adapter molecule 1 (Iba1)) and astrogliosis (glial fibrillary acidic protein (GFAP)) while preserving myelin basic protein (MBP) expression levels in the corpus callosum, motor cortex, and striatum regions of the brain in MOG35-55 EAE mice. Reduced NOD-like receptor protein 3 (NLRP3) inflammasome complex assembly and Caspase-1 activation confirmed the drug's mode of action. MOG35-55 EAE mice showed clinical signs of MS, but MOG35-55 EAE mice treated with tonabersat retained behavior closer to normal. These data suggest that clinical trial phase IIb-ready tonabersat may merit further investigation as a promising candidate for MS treatment.

Small-molecule targeting AMPA-mediated excitotoxicity has therapeutic effects in mouse models for multiple sclerosis.

While most research and treatments for multiple sclerosis (MS) focus on autoimmune reactions causing demyelination, it is possible that neurodegeneration precedes the autoimmune response. Hence, glutamate receptor antagonists preventing excitotoxicity showed promise in MS animal models, though blocking glutamate signaling prevents critical neuronal functions. This study reports the discovery of a small molecule that prevents AMPA-mediated excitotoxicity by targeting an allosteric binding site. A machine learning approach was used to screen for small molecules targeting the AMPA receptor GluA2 subunit. The lead candidate has potent effects in restoring neurological function and myelination while reducing the immune response in experimental autoimmune encephalitis and cuprizone MS mouse models without affecting basal neurotransmission or learning and memory. These findings facilitate development of a treatment for MS with a different mechanism of action than current immune modulatory drugs and avoids important off-target effects of glutamate receptor antagonists. This class of MS therapeutics could be useful as an alternative or complementary treatment to existing therapies.

Transient Receptor Potential Vanilloid 4-Dependent Microglial Function in Myelin Injury and Repair.

Microglia are found pathologically at all stages of multiple sclerosis (MS) lesion development and are hypothesized to contribute to both inflammatory injury and neuroprotection in the MS brain. Transient receptor potential vanilloid 4 (TRPV4) channels are widely expressed, play an important role as environmental sensors, and are involved in calcium homeostasis for a variety of cells. TRPV4 modulates myeloid cell phagocytosis in the periphery and microglial motility in the central nervous system. We hypothesized that TRPV4 deletion would alter microglia phagocytosis in vitro and lessen disease activity and demyelination in experimental autoimmune encephalitis (EAE) and cuprizone-induced demyelination. We found that genetic deletion of TRPV4 led to increased microglial phagocytosis in vitro but did not alter the degree of demyelination or remyelination in the cuprizone mouse model of MS. We also found no difference in disease in EAE following global or microglia-specific deletion of Trpv4. Additionally, lesioned and normal appearing white matter from MS brains exhibited similar TRPV4 expression compared to healthy brain tissue. Taken together, these findings indicate that TRPV4 modulates microglial activity but does not impact disease activity in mouse models of MS, suggesting a muted and/or redundant role in MS pathogenesis.

DRhQ: a novel therapeutic that improves cognition and mitochondrial function and reduces neuroinflammation in beta‐amyloid overexpressing Mice

AbstractBackgroundNeuroinflammation and mitochondrial dysfunction are central to the progression of Alzheimer’s disease (AD), provoking neuronal loss and cognitive decline. Identifying strategies for mitigating these responses could therefore be of significant therapeutic relevance. Evidence suggests that the inflammatory axis mediated by macrophage migration inhibitory factory (MIF) binding to its receptor, CD74, plays an important role in many central nervous system (CNS) disorders like AD. Our group has developed DRhQ, a novel CD74 binding construct that competitively inhibits MIF binding, blocks T‐cell and macrophage activation and migration into the CNS, enhances anti‐inflammatory microglia cell numbers and reduces pro‐inflammatory gene expression. DRhQ treatment resulted in reduced neuroinflammation and disease severity in a mouse model of multiple sclerosis. Because neuroinflammation is a prominent in the AD brain as well we hypothesized that DRhQ could be a similarly effective neuroprotective agent in the context of AD. We evaluated this hypothesis using the 5xFAD mouse model of β‐amyloid (Aβ) accumulation.MethodSix month old male and female 5xFAD mice and their wild‐type littermates will be treated with 0 or 100 ug of DRhQ subcutaneously for five days followed by a 3 day booster series weekly for the next 3 weeks. During the 4th week of treatment mice were evaluated cognitively using the novel object recognition test and brain tissue was harvested to evaluate mitochondrial function, Aβ pathology as well as markers of microglial activation and neuroinflammation.ResultDRhQ improved cognition and reduced neuroinflammatory markers in both male and female 5xFAD mice. DRhQ also significantly attenuated deficits in cortical mitochondrial function in female 5xFAD mice and elicited a similar, though non‐significant, effect in male 5xFAD mice. Aβ plaque burden was likewise reduced in the hippocampus and cortex of female 5xFAD mice but not significantly reduced in male 5xFAD animals.ConclusionThese results suggest that DRhQ attenuates Aβ pathology, mitochondrial dysfunction and neuroinflammation and improves cognitive function in 5xFAD mice. Future experiments will explore dose response effects and investigate the apparent sex differences in the magnitude of effect of DRhQ on specific endpoints in these mice as well as evaluate the effects of DRhQ in models of tauopathy.