Immunomodulatory and anti-oxidative effect of the direct TRPV1 receptor agonist capsaicin on Schwann cells.

BACKGROUND: Only few studies describe the impact of nutritive factors on chronic inflammatory demyelinating polyneuropathy (CIDP), an inflammatory disease of the peripheral nervous system. The active component of chili pepper, capsaicin, is the direct agonist of the transient receptor potential channel vanilloid subfamily member 1. Its anti-inflammatory effect in the animal model experimental autoimmune neuritis (EAN) has been previously demonstrated. METHODS: In the present study, we describe the anti-inflammatory and anti-oxidative influence of capsaicin on Schwann cells (SCs) in an in vitro setting. Hereby, we analyze the effect of capsaicin on Schwann cells' gene expression pattern, major histocompatibility complex class II (MHC-II) presentation, and H2O2-induced oxidative stress. Furthermore, the effect of capsaicin on myelination was examined in a SC-dorsal root ganglia (DRG) coculture by myelin basic protein staining. Finally, in order to investigate the isolated effect of capsaicin on SCs in EAN pathology, we transplant naïve and capsaicin pre-treated SCs intrathecally in EAN immunized rats and analyzed clinical presentation, electrophysiological parameters, and cytokine expression in the sciatic nerve. RESULTS: In SC monoculture, incubation with capsaicin significantly reduces interferon gamma-induced MHC-II production as well as toll-like receptor 4 and intercellular adhesion molecule 1 mRNA expression. Calcitonin gene-related peptide mRNA production is significantly upregulated after capsaicin treatment. Capsaicin reduces H2O2-induced oxidative stress in SC in a preventive, but not therapeutic setting. In a SC-DRG coculture, capsaicin does not affect myelination rate. After intrathecal transplantation of naïve and capsaicin pre-treated SCs in EAN-immunized rats, naïve, but not capsaicin pre-treated intrathecal SCs, ameliorated EAN pathology in rats. CONCLUSIONS: In conclusion, we were able to demonstrate a direct immunomodulatory and anti-oxidative effect of capsaicin in a SC culture by reduced antigen presentation and expression of an anti-inflammatory profile. Furthermore, capsaicin increases the resistance of SCs against oxidative stress. A primary effect of capsaicin on myelination was not proven. These results are in concordance with previous data showing an anti-inflammatory effect of capsaicin, which might be highly relevant for CIDP patients.

Intrathecal triamcinolone acetonide exerts anti-inflammatory effects on Lewis rat experimental autoimmune neuritis and direct anti-oxidative effects on Schwann cells.

BACKGROUND: Corticosteroids dominate in the treatment of chronic autoimmune neuropathies although long-term use is characterized by devastating side effects. METHODS: We introduce the intrathecal application of the synthetic steroid triamcinolone (TRIAM) as a novel therapeutic option in experimental autoimmune neuritis in Lewis rats RESULTS: After immunization with neuritogenic P2 peptide, we show a dose-dependent therapeutic effect of one intrathecal injection of 0.3 or 0.6 mg/kg TRIAM on clinical and electrophysiological parameters of neuritis with a lower degree of inflammatory infiltrates (T cells and macrophages) and demyelination in the sciatic nerve. In vitro studies in Schwann cell cultures showed an increased expression of IL-1 receptor antagonist and reduced expression of Toll-like receptor 4 after incubation with TRIAM as well as a protective effect of TRIAM against oxidative stress after H2O2 exposure. CONCLUSION: Intrathecal TRIAM application could be a novel immunomodulatory and potentially neuroprotective option for autoimmune neuropathies with a direct effect on Schwann cells.

Capsaicin-enriched diet ameliorates autoimmune neuritis in rats.

BACKGROUND: Autoimmune neuropathies are common PNS disorders and effective treatment is challenging. Environmental influence and dietary components are known to affect the course of autoimmune diseases. Capsaicin as pungent component of chili-peppers is common in human nutrition. An influence of capsaicin on autoimmune diseases has been postulated. METHODS: We tested capsaicin in the animal model of experimental autoimmune neuritis (EAN) in Lewis rat. Rats were immunized with P2-peptide and were treated with capsaicin in different preventive settings. Electrophysiological, histological, and molecular biological analyses of the sciatic nerve were performed to analyze T-cell and macrophage cell count, TRPV1, and cytokine expression. Moreover, FACS analyses including the intestinal immune system were executed. RESULTS: We observed an immunomodulatory effect of an early preventive diet-concept, where a physiological dosage of oral capsaicin was given 10 days before immunization in EAN. A reduced inflammation of the sciatic nerve was significant detectable clinically, electrophysiologically (CMAPs reduced in control group p < 0.01; increase of nerve conduction blocks in control group p < 0.05), histologically (significant reduction of T-cells, macrophages and demyelination), and at cytokine level. In contrast, this therapeutic effect was missing with capsaicin given from the day of immunization onwards. As possible underlying mechanism, we were able to show changes in the expression of the capsaicin receptor in the sciatic nerve and the small intestine, as well as altered immune cell populations in the small intestine. CONCLUSION: This is the first report about the immunomodulatory effect of the common nutrient, capsaicin, in an experimental model for autoimmune neuropathies.

Fingolimod attenuates experimental autoimmune neuritis and contributes to Schwann cell-mediated axonal protection.

BACKGROUND: Fingolimod, a sphingosine-1-phosphate receptor modulator with well-described immunomodulatory properties involving peripheral immune cell trafficking, was the first oral agent approved for the treatment of relapsing remitting multiple sclerosis. Analogous immunomodulatory treatment options for chronic peripheral autoimmune neuropathies are lacking. METHODS: We tested fingolimod in the animal model of experimental autoimmune neuritis in Lewis rat. Six to eight-week-old female rats were immunized with P2 peptide and from this day on treated with fingolimod. Histology of the sciatic nerve was done to analyze T cell and macrophage cell count, intercellular adhesion molecule (ICAM) and amyloid precursor protein (APP) expression, as well as apoptotic Schwann cell counts. RESULTS: Preventive oral treatment with 0.1 mg/kg up to 3 mg/kg fingolimod once daily dissolved in rapeseed oil completely ameliorated clinical neuritis signs. It reduced circulating peripheral blood T cells and infiltrating T cells and macrophages in the sciatic nerve, whereas at the same time, it preserved blood-nerve barrier impermeability. Most importantly, fingolimod showed beneficial properties on the pathogenic process as indicated by fewer apoptotic Schwann cells and a lower amount of amyloid precursor protein indicative of axonal damage at the peak of disease course. CONCLUSIONS: Taken together, orally administered low-dose fingolimod showed an impressive immunomodulatory effect in the rat model of experimental autoimmune neuritis. Our current observations introduce fingolimod as an attractive treatment option for neuritis patients.

Teriflunomide and monomethylfumarate target HIV-induced neuroinflammation and neurotoxicity.

HIV-associated neurocognitive disorders (HAND) affect about 50% of infected patients despite combined antiretroviral therapy (cART). Ongoing compartmentalized inflammation mediated by microglia which are activated by HIV-infected monocytes has been postulated to contribute to neurotoxicity independent from viral replication. Here, we investigated effects of teriflunomide and monomethylfumarate on monocyte/microglial activation and neurotoxicity. Human monocytoid cells (U937) transduced with a minimal HIV-Vector were co-cultured with human microglial cells (HMC3). Secretion of pro-inflammatory/neurotoxic cytokines (CXCL10, CCL5, and CCL2: p < 0.001; IL-6: p < 0.01) by co-cultures was strongly increased compared to microglia in contact with HIV-particles alone. Upon treatment with teriflunomide, cytokine secretion was decreased (CXCL10, 3-fold; CCL2, 2.5-fold; IL-6, 2.2-fold; p < 0.001) and monomethylfumarate treatment led to 2.9-fold lower CXCL10 secretion (p < 0.001). Reduced toxicity of co-culture conditioned media on human fetal neurons by teriflunomide (29%, p < 0.01) and monomethylfumarate (27%, p < 0.05) indicated functional relevance. Modulation of innate immune functions by teriflunomide and monomethylfumarate may target neurotoxic inflammation in the context of HAND.

Clozapine Regulates Microglia and Is Effective in Chronic Experimental Autoimmune Encephalomyelitis.

Objective: Progressive multiple sclerosis is characterized by chronic inflammation with microglial activation, oxidative stress, accumulation of iron and continuous neurodegeneration with inadequate effectiveness of medications used so far. We now investigated effects of iron on microglia and used the previously identified neuroprotective antipsychotic clozapine in vitro and in chronic experimental autoimmune encephalomyelitis (EAE). Methods: Microglia were treated with iron and clozapine followed by analysis of cell death and response to oxidative stress, cytokine release and neuronal phagocytosis. Clozapine was investigated in chronic EAE regarding optimal dosing and therapeutic effectiveness in different treatment paradigms. Animals were scored clinically by blinded raters. Spinal cords were analyzed histologically for inflammation, demyelination, microglial activation and iron accumulation and for transcription changes of regulators of iron metabolism and inflammation. Effects on immune cells were analyzed using flow cytometry. Results: Iron impaired microglial function in vitro regarding phagocytosis and markers of inflammation; this was regulated by clozapine, reflected in reduced release of IL-6 and normalization of neuronal phagocytosis. In chronic EAE, clozapine dose-dependently attenuated clinical signs and still had an effect if applied in a therapeutic setting. Early mild sedative effects habituated over time. Histologically, demyelination was reduced by clozapine and positive effects on inflammation strongly correlated with reduced iron deposition. This was accompanied by reduced expression of DMT-1, an iron transport protein. Conclusions: Clozapine regulates microglial function and attenuates chronic EAE, even in a therapeutic treatment paradigm. This well-defined generic medication might therefore be considered as promising add-on therapeutic for further development in progressive MS.

Is APOE ε4 associated with cognitive performance in early MS?

OBJECTIVE: To assess the impact of APOE polymorphisms on cognitive performance in patients newly diagnosed with clinically isolated syndrome (CIS) or relapsing-remitting MS (RRMS). METHODS: This multicenter cohort study included 552 untreated patients recently diagnosed with CIS or RRMS according to the 2005 revised McDonald criteria. The single nucleotide polymorphisms rs429358 (ε4) and rs7412 (ε2) of the APOE haplotype were assessed by allelic discrimination assays. Cognitive performance was evaluated using the 3-second paced auditory serial addition test and the Multiple Sclerosis Inventory Cognition (MUSIC). Sum scores were calculated to approximate the overall cognitive performance and memory-centered cognitive functions. The impact of the APOE carrier status on cognitive performance was assessed using multiple linear regression models, also including demographic, clinical, MRI, and lifestyle factors. RESULTS: APOE ε4 homozygosity was associated with lower overall cognitive performance, whereas no relevant association was observed for APOE ε4 heterozygosity or APOE ε2 carrier status. Furthermore, higher disability levels, MRI lesion load, and depressive symptoms were associated with lower cognitive performance. Patients consuming alcohol had higher test scores than patients not consuming alcohol. Female sex, lower disability, and alcohol consumption were associated with better performance in the memory-centered subtests of MUSIC, whereas no relevant association was observed for APOE carrier status. CONCLUSION: Along with parameters of a higher disease burden, APOE ε4 homozygosity was identified as a potential predictor of cognitive performance in this large cohort of patients with CIS and early RRMS.

Longitudinal prevalence and determinants of pain in multiple sclerosis: results from the German National Multiple Sclerosis Cohort study.

Pain is frequent in multiple sclerosis (MS) and includes different types, with neuropathic pain (NP) being most closely related to MS pathology. However, prevalence estimates vary largely, and causal relationships between pain and biopsychosocial factors in MS are largely unknown. Longitudinal studies might help to clarify the prevalence and determinants of pain in MS. To this end, we analyzed data from 410 patients with newly diagnosed clinically isolated syndrome or relapsing-remitting MS participating in the prospective multicenter German National MS Cohort Study (NationMS) at baseline and after 4 years. Pain was assessed by self-report using the PainDETECT Questionnaire. Neuropsychiatric assessment included tests for fatigue, depression, and cognition. In addition, sociodemographic and clinical data were obtained. Prevalence of pain of any type was 40% and 36% at baseline and after 4 years, respectively, whereas prevalence of NP was 2% and 5%. Pain of any type and NP were both strongly linked to fatigue, depression, and disability. This link was even stronger after 4 years than at baseline. Moreover, changes in pain, depression, and fatigue were highly correlated without any of these symptoms preceding the others. Taken together, pain of any type seems to be much more frequent than NP in early nonprogressive MS. Moreover, the close relationship between pain, fatigue, and depression in MS should be considered for treatment decisions and future research on a possible common pathophysiology.

Antineuroinflammatory drugs in HIV-associated neurocognitive disorders as potential therapy.

Today, HIV-infected (HIV+) patients can be treated efficiently with combined antiretroviral therapy (cART), leading to long-term suppression of viral load, in turn increasing life expectancy. While cART reduced the occurrence of HIV-associated dementia, the prevalence of subtle forms of HIV-associated neurocognitive disorders (HAND) is unchanged. This is related to persistent immune activation within the CNS, which is not addressed by cART. Pathologic processes leading to HAND consist of the release of proinflammatory cytokines, chemokines, reactive oxygen metabolites and glutamate, and the release of HIV proteins. Some of those processes can be targeted using medications with immunomodulatory and neuroprotective properties such as dimethyl fumarate, teriflunomide, or minocycline. In this review, we will summarize the knowledge about key pathogenic processes involved in HAND and potential therapeutic avenues to target HAND.

Can we predict cognitive decline after initial diagnosis of multiple sclerosis? Results from the German National early MS cohort (KKNMS).

BACKGROUND: Cognitive impairment (CI) affects approximately one-third of the patients with early multiple sclerosis (MS) and clinically isolated syndrome (CIS). Little is known about factors predicting CI and progression after initial diagnosis. METHODS: Neuropsychological screening data from baseline and 1-year follow-up of a prospective multicenter cohort study (NationMS) involving 1123 patients with newly diagnosed MS or CIS were analyzed. Employing linear multilevel models, we investigated whether demographic, clinical and conventional MRI markers at baseline were predictive for CI and longitudinal cognitive changes. RESULTS: At baseline, 22% of patients had CI (impairment in ≥2 cognitive domains) with highest frequencies and severity in processing speed and executive functions. Demographics (fewer years of academic education, higher age, male sex), clinical (EDSS, depressive symptoms) but no conventional MRI characteristics were linked to baseline CI. At follow-up, only 14% of patients showed CI suggesting effects of retesting. Neither baseline characteristics nor initiation of treatment between baseline and follow-up was able to predict cognitive changes within the follow-up period of 1 year. CONCLUSIONS: Identification of risk factors for short-term cognitive change in newly diagnosed MS or CIS is insufficient using only demographic, clinical and conventional MRI data. Change-sensitive, re-test reliable cognitive tests and more sophisticated predictors need to be employed in future clinical trials and cohort studies of early-stage MS to improve prediction.

Treatment choices and neuropsychological symptoms of a large cohort of early MS.

OBJECTIVE: To assess clinical characteristics, distribution of disease-modifying treatments (DMTs), and neuropsychological symptoms in a large cohort of patients with early-stage MS. METHODS: The German National MS Cohort is a multicenter prospective longitudinal cohort study that has recruited DMT-naive patients with clinically isolated syndrome (CIS) and relapsing-remitting MS (RRMS) since 2010. We evaluated their baseline characteristics and the prevalence of neuropsychological symptoms. RESULTS: Of 1,124 patients, with a 2.2:1 female-to-male ratio and median age at onset of 31.71 years (interquartile range [IQR]: 26.06-40.33), 44.6% and 55.3% had CIS and RRMS, respectively. The median Expanded Disability Status Scale (EDSS) score at baseline was 1.5 (IQR: 1.0-2.0). A proportion of 67.8% of patients started DMT after a median time of 167.0 days (IQR 90.0-377.5) since the first manifestation. A total of 64.7% and 70.4% of the 762 patients receiving early DMT were classified as CIS and RRMS, respectively. Fatigue, depressive symptoms, and cognitive dysfunction were detected in 36.5%, 33.5%, and 14.7% of patients, respectively. CONCLUSION: Baseline characteristics of this large cohort of patients with early, untreated MS corroborated with other cohorts. Most patients received early DMT within the first year after disease onset, irrespective of a CIS or RRMS diagnosis. Despite the low EDSS score, neuropsychological symptoms affected a relevant proportion of patients.

Dimethyl Fumarate Ameliorates Lewis Rat Experimental Autoimmune Neuritis and Mediates Axonal Protection.

BACKGROUND: Dimethyl fumarate is an immunomodulatory and neuroprotective drug, approved recently for the treatment of relapsing-remitting multiple sclerosis. In view of the limited therapeutic options for human acute and chronic polyneuritis, we used the animal model of experimental autoimmune neuritis in the Lewis rat to study the effects of dimethyl fumarate on autoimmune inflammation and neuroprotection in the peripheral nervous system. METHODS AND FINDINGS: Experimental autoimmune neuritis was induced by immunization with the neuritogenic peptide (amino acids 53-78) of P2 myelin protein. Preventive treatment with dimethyl fumarate given at 45 mg/kg twice daily by oral gavage significantly ameliorated clinical neuritis by reducing demyelination and axonal degeneration in the nerve conduction studies. Histology revealed a significantly lower degree of inflammatory infiltrates in the sciatic nerves. In addition, we detected a reduction of early signs of axonal degeneration through a reduction of amyloid precursor protein expressed in axons of the peripheral nerves. This reduction correlated with an increase of nuclear factor (erythroid derived 2)-related factor 2 positive axons, supporting the neuroprotective potential of dimethyl fumarate. Furthermore, nuclear factor (erythroid derived 2)-related factor 2 expression in Schwann cells was only rarely detected and there was no increase of Schwann cells death during EAN. CONCLUSIONS: We conclude that immunomodulatory and neuroprotective dimethyl fumarate may represent an innovative therapeutic option in human autoimmune neuropathies.

Laquinimod exerts strong clinical and immunomodulatory effects in Lewis rat experimental autoimmune neuritis.

Laquinimod is an immunomodulatory drug with neuroprotective potential. We used the animal model of experimental autoimmune neuritis (EAN) in the Lewis rat to study the effects of laquinimod treatment. After immunization with the neuritogenic peptide aa 53-78 of P2 myelin protein, preventive therapy with 12.5mg/kg laquinimod once daily inhibited neuritis in clinical and electrophysiological terms. Histology corroborated a lower degree of inflammatory lesions and demyelination in the sciatic nerve. The proportion of FoxP3-positive regulatory T cells in the peripheral lymph nodes of treated rats remained unchanged. We conclude that laquinimod may represent a therapeutic option in human autoimmune neuropathies.

Cytoplasmic HIV-RNA in monocytes determines microglial activation and neuronal cell death in HIV-associated neurodegeneration.

Despite highly active antiretroviral therapy, HIV-associated neurocognitive disorders (HAND) are still highly prevalent. Direct neurotoxicity of microglia activated by HIV-infected monocytes independent from viral replication may account for this observation. To investigate underlying molecular and viral determinants, human monocytoid cells (U937) transduced with HIV-particles were co-cultured with primary human microglia or astrocytes. Using genetically-engineered HIV-particles key steps of infection were examined. Levels of pro-inflammatory/neurotoxic cytokines were investigated in co-culture supernatants by flow cytometry. Neurotoxicity mediated by the supernatants was analysed using primary cortical rat neurons. To corroborate our findings, cytokine profiles in cerebrospinal fluid (CSF) of neuropsychologically asymptomatic HIV positive (HIV(+)) patients (n=45) were correlated with neurofilament H (NfH) as surrogate of neuronal/axonal degeneration. In contrast to direct exposure of HIV to microglia, only the presence of HIV-transduced monocytoid cells strongly activated human microglia as evidenced by enhanced secretion of CXCL10, CCL5, CCL2, and IL-6 (1.3-7.1-fold; p<0.01) leading to two-fold increased neurotoxicity (p<0.001). In direct comparison, astrocyte activation by HIV-transduced monocytoid cells was limited. Using different mutant HIV-particles we show that the presence of cytoplasmic HIV-RNA in monocytoid cells is the viral determinant for this unique microglial activation pattern and subsequent neuronal cell death; reverse transcription and expression of viral genes were not essential. In CSF of presymptomatic HIV(+) patients, CXCL10, CCL5 and IL-6 were correlated with NfH as surrogate marker of neurodegeneration as well as CSF-pleocytosis. In conclusion, cytosolic viral RNA in monocytes is mandatory for subsequent microglial activation and neurotoxicity; activated astrocytes may augment neuroinflammation. In addition, neuroinflammation and neurodegeneration occur even in preclinical HIV(+) patients and are associated with cytokines regulated in vitro. Our data may aid in the development of biomarkers and glia-directed therapeutic approaches of HAND.