Treatment options to reduce disease activity after natalizumab: paradoxical effects of corticosteroids.

AIM: Natalizumab (NTZ) discontinuation leads to multiple sclerosis (MS) recurrence, but represents the only known strategy to limit the risk of progressive multifocal leukoencephalopathy (PML) in JCV seropositive patients. Here, we compared the clinical and imaging features of three groups of patients who discontinued NTZ treatment. METHODS: We treated 25 patients with subcutaneous INFß-1b (INF group), 40 patients with glatiramer acetate (GA group), and 40 patients with GA plus pulse steroid (GA+CS group). RESULTS: Six of 25 patients (24%) of the INF group were relapse-free 6 months after NTZ suspension. In GA group, a significant higher proportion of patients (26 of 40 patients, 65%) were relapse-free (P<0.05). Far from improving the clinical effects of GA in post-NTZ setting, combination of GA+CS was associated with lower relapse-free rate than GA alone (40% vs. 65%, P=0.04). Also on MRI parameters, combination of GA+CS was associated with worse outcome than GA alone, as 22 of 26 subjects (84.6%) had MRI evidence of disease activity 6 months after NTZ discontinuation. CONCLUSION: Corticosteroids should not be used in combination with GA to prevent post-NTZ disease recurrence.

Cerebrospinal fluid detection of interleukin-1ß in phase of remission predicts disease progression in multiple sclerosis.

BACKGROUND: Absence of clinical and radiological activity in relapsing-remitting multiple sclerosis (RRMS) is perceived as disease remission. We explored the role of persisting inflammation during remission in disease evolution. METHODS: Cerebrospinal fluid (CSF) levels of interleukin 1ß (IL-1ß), a major proinflammatory cytokine, were measured in 170 RRMS patients at the time of clinical and radiological remission. These patients were then followed up for at least 4 years, and clinical, magnetic resonance imaging (MRI) and optical coherence tomography (OCT) measures of disease progression were recorded. RESULTS: Median follow-up of RRMS patients was 5 years. Detection of CSF IL-1ß levels at the time of remission did not predict earlier relapse or new MRI lesion formation. Detection of IL-1ß in the CSF was instead associated with higher progression index (PI) and Multiple Sclerosis Severity Scale (MSSS) scores at follow-up, and the number of patients with sustained Expanded Disability Status Scale (EDSS) or Multiple Sclerosis Functional Composite worsening at follow-up was higher in individuals with detectable levels of IL-1ß. Patients with undetectable IL-1ß in the CSF had significantly lower PI and MSSS scores and a higher probability of having a benign MS phenotype. Furthermore, patients with undetectable CSF levels of IL-1ß had less retinal nerve fiber layer thickness and macular volume alterations visualized by OCT compared to patients with detectable IL-1ß. CONCLUSIONS: Our results suggest that persistence of a proinflammatory environment in RRMS patients during clinical and radiological remission influences midterm disease progression. Detection of IL-1ß in the CSF at the time of remission appears to be a potential negative prognostic factor in RRMS patients.

Opposite roles of NMDA receptors in relapsing and primary progressive multiple sclerosis.

Synaptic transmission and plasticity mediated by NMDA receptors (NMDARs) could modulate the severity of multiple sclerosis (MS). Here the role of NMDARs in MS was first explored in 691 subjects carrying specific allelic variants of the NR1 subunit gene or of the NR2B subunit gene of this glutamate receptor. The analysis was replicated for significant SNPs in an independent sample of 1548 MS subjects. The C allele of rs4880213 was found to be associated with reduced NMDAR-mediated cortical excitability, and with increased probability of having more disability than the CT/TT MS subjects. MS severity was higher in the CC group among relapsing-remitting MS (RR-MS) patients, while primary progressive MS (PP-MS) subjects homozygous for the T allele had more pronounced clinical worsening. Mean time to first relapse, but not to an active MRI scan, was lower in the CC group of RR-MS patients, and the number of subjects with two or more clinical relapses in the first two years of the disease was higher in CC compared to CT/TT group. Furthermore, the percentage of relapses associated with residual disability was lower in subjects carrying the T allele. Lesion load at the MRI was conversely unaffected by the C or T allele of this SNP in RR-MS patients. Axonal and neuronal degeneration at the optical coherence tomography was more severe in the TT group of PP-MS patients, while reduced retinal nerve fiber thickness had less consequences on visual acuity in RR-MS patients bearing the T allele. Finally, the T allele was associated with preserved cognitive abilities at the Rao's brief repeatable neuropsychological battery in RR-MS. Signaling through glutamate NMDARs enhances both compensatory synaptic plasticity and excitotoxic neurodegeneration, impacting in opposite ways on RR-MS and PP-MS pathophysiological mechanisms.

Association between a genetic variant of type-1 cannabinoid receptor and inflammatory neurodegeneration in multiple sclerosis.

Genetic ablation of type-1 cannabinoid receptors (CB1Rs) exacerbates the neurodegenerative damage of experimental autoimmune encephalomyelitis, the rodent model of multiple sclerosis (MS). To address the role on CB1Rs in the pathophysiology of human MS, we first investigated the impact of AAT trinucleotide short tandem repeat polymorphism of CNR1 gene on CB1R cell expression, and secondly on the inflammatory neurodegeneration process responsible for irreversible disability in MS patients. We found that MS patients with long AAT repeats within the CNR1 gene (≥12 in both alleles) had more pronounced neuronal degeneration in response to inflammatory white matter damage both in the optic nerve and in the cortex. Optical Coherence Tomography (OCT), in fact, showed more severe alterations of the retinal nerve fiber layer (RNFL) thickness and of the macular volume (MV) after an episode of optic neuritis in MS patients carrying the long AAT genotype of CNR1. MS patients with long AAT repeats also had magnetic resonance imaging (MRI) evidence of increased gray matter damage in response to inflammatory lesions of the white matter, especially in areas with a major role in cognition. In parallel, visual abilities evaluated at the low contrast acuity test, and cognitive performances were negatively influenced by the long AAT CNR1 genotype in our sample of MS patients. Our results demonstrate the biological relevance of the (AAT)n CNR1 repeats in the inflammatory neurodegenerative damage of MS.

Loss of striatal cannabinoid CB1 receptor function in attention-deficit / hyperactivity disorder mice with point-mutation of the dopamine transporter.

Abnormal dopamine (DA) transmission in the striatum plays a pivotal role in attention-deficit/hyperactivity disorder (ADHD). As striatal DA signalling modulates the endocannabinoid system (ECS), the present study was aimed at investigating cannabinoid CB1 receptor (CB1R) function in a model of ADHD obtained by triple point-mutation in the dopamine transporter (DAT) gene in mice, making them insensitive to cocaine [DAT cocaine-insensitive (DAT-CI) mice]. DAT-CI mice had a marked hyperactive phenotype, and neurophysiological recordings revealed that the sensitivity of CB1Rs controlling GABA-mediated synaptic currents [CB1Rs((GABA)) ] in the striatum was completely lost. In contrast, CB1Rs modulating glutamate transmission [CB1Rs((Glu)) ], and GABA(B) receptors were not affected in this model of ADHD. In DAT-CI mice, the blockade of CB1R((GABA)) function was complete even after cocaine or environmental manipulations activating the endogenous DA-dependent reward system, which are known to sensitize these receptors in control animals. Conversely, the hedonic property of sucrose was intact in DAT-CI mice, indicating normal sweet perception in these animals. Our results point to CB1Rs as novel molecular players in ADHD, and suggest that therapeutic strategies aimed at interfering with the ECS might prove effective in this disorder.

Proposed chronic cerebrospinal venous insufficiency criteria do not predict multiple sclerosis risk or severity.

OBJECTIVE: It is still unclear whether chronic cerebrospinal venous insufficiency (CCSVI) is associated with multiple sclerosis (MS), because substantial methodological differences have been claimed by Zamboni to account for the lack of results of other groups. Furthermore, the potential role of venous malformations in influencing MS severity has not been fully explored. This information is particularly relevant, because uncontrolled surgical procedures are increasingly offered to MS patients to treat their venous stenoses. METHODS: In the present study, CCSVI was studied in 84 MS patients and in 56 healthy subjects by applying the Zamboni method for CCSVI identification. RESULTS: We found no significant differences (p = 0.12) in CCSVI frequency between MS and control subjects. Furthermore, no differences were found between CCSVI-positive and CCSVI-negative patients in terms of relevant clinical variables such as disease duration, time between onset and first relapse, relapsing or progressive disease course, and risk of secondary progression course. Statistically significant differences were not found between CCSVI-positive and CCSVI-negative MS subjects by analyzing direct measures of disability such as mean Expanded Disability Status Scale (EDSS) (p = 0.07), mean progression index (p > 0.1), and mean MS severity score (p > 0.1). The percentage of subjects who reached EDSS 4.0 and 6.0 milestones was not different among CCSVI-negative and CCSVI-positive subjects, and no significant correlation was found between severity of disability and number of positive CCSVI criteria. INTERPRETATION: Our results indicate that CCSVI has no role in either MS risk or MS severity.

Cognitive and cortical plasticity deficits correlate with altered amyloid-ß CSF levels in multiple sclerosis.

Cognitive dysfunction is of frequent observation in multiple sclerosis (MS). It is associated with gray matter pathology, brain atrophy, and altered connectivity, and recent evidence showed that acute inflammation can exacerbate mental deficits independently of the primary functional system involved. In this study, we measured cerebrospinal fluid (CSF) levels of amyloid-ß(1-42) and τ protein in MS and in clinically isolated syndrome patients, as both proteins have been associated with cognitive decline in Alzheimer's disease (AD). In AD, amyloid-ß(1-42) accumulates in the brain as insoluble extracellular plaques, possibly explaining why soluble amyloid-ß(1-42) is reduced in the CSF of these patients. In our sample of MS patients, amyloid-ß(1-42) levels were significantly lower in patients cognitively impaired (CI) and were inversely correlated with the number of Gadolinium-enhancing (Gd+) lesions at the magnetic resonance imaging (MRI). Positive correlations between amyloid-ß(1-42) levels and measures of attention and concentration were also found. Furthermore, abnormal neuroplasticity of the cerebral cortex, explored with θ burst stimulation (TBS), was observed in CI patients, and a positive correlation was found between amyloid-ß(1-42) CSF contents and the magnitude of long-term potentiation-like effects induced by TBS. No correlation was conversely found between τ protein concentrations and MRI findings, cognitive parameters, and TBS effects in these patients. Together, our results indicate that in MS, central inflammation is able to alter amyloid-ß metabolism by reducing its concentration in the CSF and leading to impairment of synaptic plasticity and cognitive function.

The (AAT)n repeat of the cannabinoid CB1 receptor gene influences disease progression in relapsing multiple sclerosis.

BACKGROUND: Genetic and pharmacological inactivation of cannabinoid CB(1) receptors (CB(1)Rs) exacerbates disease course in experimental autoimmune encephalomyelitis, suggesting that CB(1)Rs might play a role in the neurodegenerative damage associated with multiple sclerosis (MS). OBJECTIVES: To see whether CNR1 gene polymorphism could influence disease progression in relapsing-remitting MS. METHODS: The genotype of 350 patients for the number of AAT repeats was characterized and correlation studies were performed with measures of disease severity and progression. RESULTS: MS patients with the homozygous genotype for long AAT repeats in the CNR1 gene had more severe disease and higher risk of progression. These subjects had significantly higher scores on both the progression index and the MS severity scale. Furthermore, the percentage of patients with MS functional composite score progression or Bayesian Risk Estimate for MS (BREMS) score ≥ 2 (considered at very high risk of secondary progression) was significantly higher in the AAT long group than in the short group, while the frequency of patients with BREMS score ≤-0.63 (very likely to remain progression-free) was not significantly different between the two groups, although lower in the long group. Finally, the frequency of patients prescribed a second-line treatment was significantly higher among subjects of the AAT long group, providing a further, indirect indication of higher disease severity. CONCLUSIONS: The results of the present investigation point to CB(1)R as an important modulator of disease severity in relapsing MS subjects.

Brain-derived neurotrophic factor controls cannabinoid CB1 receptor function in the striatum.

The role of brain-derived neurotrophic factor (BDNF) in emotional processes suggests an interaction with the endocannabinoid system. Here, we addressed the functional interplay between BDNF and cannabinoid CB(1) receptors (CB(1)Rs) in the striatum, a brain area in which both BDNF and CB(1)s play a role in the emotional consequences of stress and of rewarding experiences. BDNF potently inhibited CB(1)R function in the striatum, through a mechanism mediated by altered cholesterol metabolism and membrane lipid raft function. The effect of BDNF was restricted to CB(1)Rs controlling GABA-mediated IPSCs (CB(1)R(GABA)), whereas CB(1)Rs modulating glutamate transmission and GABA(B) receptors were not affected. The action of BDNF on CB(1)R(GABA) function was tyrosine kinase dependent and was complete even after receptor sensitization with cocaine or environmental manipulations activating the dopamine (DA)-dependent reward system. In mice lacking one copy of the BDNF gene (BDNF(+/-)), CB(1)R(GABA) responses were potentiated and were preserved from the action of haloperidol, a DA D(2) receptor (D(2)R) antagonist able to fully abolish CB(1)R(GABA) function in rewarded animals. Haloperidol also enhanced BDNF levels in the striatum, suggesting that this neurotrophin may act as a downstream effector of D(2)Rs in the modulation of cannabinoid signaling. Accordingly, 5 d cocaine exposure both reduced striatal BDNF levels and increased CB(1)R(GABA) activity, through a mechanism dependent on D(2)Rs. The present study identifies a novel mechanism of CB(1)R regulation mediated by BDNF and cholesterol metabolism and provides some evidence that DA D(2)R-dependent modulation of striatal CB(1)R activity is mediated by this neurotrophin.

Preservation of striatal cannabinoid CB1 receptor function correlates with the antianxiety effects of fatty acid amide hydrolase inhibition.

The endocannabinoid anandamide (AEA) plays a crucial role in emotional control, and inhibition of its degradation by the fatty acid amide hydrolase (FAAH) has a potent antianxiety effect. The mechanism by which the magnification of AEA activity reduces anxiety is still largely undetermined. By using FAAH mutant mice and both intraperitoneal and intracerebroventricular administration of the FAAH inhibitor (3'-(aminocarbonyl)[1,1'-biphenyl]-3-yl)-cyclohexylcarbamate (URB597), we found that enhanced AEA signaling reversed, via central cannabinoid CB1 receptors (CB1Rs), the anxious phenotype of mice exposed to social defeat stress. This behavioral effect was associated with preserved activity of CB1Rs regulating GABA transmission in the striatum, whereas these receptors were dramatically down-regulated by stress in control animals. The hypothalamic-pituitary-adrenal (HPA) axis was not involved in the antistress effects of FAAH inhibition, although the HPA axis is a biological target of endogenous AEA. We also provided some physiological indications that striatal CB1Rs regulating GABA synapses are not the receptor targets of FAAH inhibition, which rather resulted in the stimulation of striatal CB1Rs regulating glutamate transmission. Collectively, our findings suggest that preservation of cannabinoid CB1 receptor function within the striatum is a possible synaptic correlate of the antianxiety effects of FAAH inhibition.

Voluntary exercise and sucrose consumption enhance cannabinoid CB1 receptor sensitivity in the striatum.

The endogenous cannabinoid system is involved in the regulation of the central reward pathway. Running wheel and sucrose consumption have rewarding and reinforcing properties in rodents, and share many neurochemical and behavioral characteristics with drug addiction. In this study, we investigated whether running wheel or sucrose consumption altered the sensitivity of striatal synapses to the activation of cannabinoid CB1 receptors. We found that cannabinoid CB1 receptor-mediated presynaptic control of striatal inhibitory postsynaptic currents was remarkably potentiated after these environmental manipulations. In contrast, the sensitivity of glutamate synapses to CB1 receptor stimulation was unaltered, as well as that of GABA synapses to the stimulation of presynaptic GABAB receptors. The sensitization of cannabinoid CB1 receptor-mediated responses was slowly reversible after the discontinuation of running wheel or sucrose consumption, and was also detectable following the mobilization of endocannabinoids by metabotropic glutamate receptor 5 stimulation. Finally, we found that the upregulation of cannabinoid transmission induced by wheel running or sucrose had a crucial role in the protective effects of these environmental manipulations against the motor and synaptic consequences of stress.