Redox regulation of glial inflammatory response to lipopolysaccharide and interferongamma

Astrocytes and microglia, the two immune-regulatory cells of the central nervous system (CNS), are activated by a variety of pathogens and cytokines to elicit rapid transcriptional responses. This program of activation is initiated by a set of intracellular signaling cascades that includes mitogen-activated protein kinase (MAPK), nuclear factor (NF) kappaB, and Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways. This study defines the critical role that NADPH oxidase(Phox)-derived reactive oxygen species (ROS) play in lipopolysaccharide (LPS)- and interferon (IFN)gamma-induced signaling cascades leading to gene expression in glial cells. Treatment of rat microglia and astrocytes with LPS and IFNgamma resulted in a rapid activation of Phox and the release of ROS followed by an induction of inducible nitric oxide synthase (iNOS) expression. iNOS induction was blocked by inhibitors of Phox, i.e., diphenylene iodonium chloride (DPI) and 4-(2-aminoethyl) benzenesulfonylfluoride (AEBSF), suggesting an involvement of ROS signaling in iNOS gene expression. Exogenous catalase but not superoxide dismutase suppressed the basal activity and completely blocked induced levels of NO/iNOS, suggesting that hydrogen peroxide is the ROS involved. Phox inhibitors and catalase also suppressed LPS/IFNgamma-induced expression of cytokines, i.e., interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)alpha and blocked LPS activation of MAP kinases (i.e., p38 MAPK, c-Jun N-terminal kinase and extracellular signal-regulated kinase), NFkappaB, and IFNgamma-induced STAT1 phosphorylation. A microglial cell line stably transfected with a mutant form of Phox subunit, i.e., p47(phox) W(193)R, and primary astrocytes derived from Phox-deficient mice showed attenuated ROS production and induction of iNOS in response to LPS/IFNgamma, further strengthening the notion that Phox-derived ROS are crucial for proinflammatory gene expression in glial cells.

Definition and Consensus Diagnostic Criteria for Neurosarcoidosis: From the Neurosarcoidosis Consortium Consensus Group

Importance

The Neurosarcoidosis Consortium Consensus Group, an expert panel of physicians experienced in the management of patients with sarcoidosis and neurosarcoidosis, engaged in an iterative process to define neurosarcoidosis and develop a practical diagnostic approach to patients with suspected neurosarcoidosis. This panel aimed to develop a consensus clinical definition of neurosarcoidosis to enhance the clinical care of patients with suspected neurosarcoidosis and to encourage standardization of research initiatives that address this disease.

Observations

The work of this collaboration included a review of the manifestations of neurosarcoidosis and the establishment of an approach to the diagnosis of this disorder. The proposed consensus diagnostic criteria, which reflect current knowledge, provide definitions for possible, probable, and definite central and peripheral nervous system sarcoidosis. The definitions emphasize the need to evaluate patients with findings suggestive of neurosarcoidosis for alternate causal factors, including infection and malignant neoplasm. Also emphasized is the need for biopsy, whenever feasible and advisable according to clinical context and affected anatomy, of nonneural tissue to document the presence of systemic sarcoidosis and support a diagnosis of probable neurosarcoidosis or of neural tissue to support a diagnosis of definite neurosarcoidosis.

Conclusions and Relevance

Diverse disease presentations and lack of specificity of relevant diagnostic tests contribute to diagnostic uncertainty. This uncertainty is compounded by the absence of a pathognomonic histologic tissue examination. The diagnostic criteria we propose are designed to focus investigations on NS as accurately as possible, recognizing that multiple pathophysiologic pathways may lead to the clinical manifestations we currently term NS. Research recognizing the clinical heterogeneity of this diagnosis may open the door to identifying meaningful biologic factors that may ultimately contribute to better treatments.

Presentations and outcomes of neurosarcoidosis: a study of 54 cases

OBJECTIVE

To report on the clinical presentations, laboratory abnormalities, treatment and outcomes in 54 patients with neurosarcoidosis (NS).

BACKGROUND

Sarcoidosis is an inflammatory granulomatous disease affecting multiple organ systems. Neurosarcoidosis (CNS involvement) is seen in approximately 25% of patients with systemic sarcoidosis, although it is subclinical in most of these cases. Because of its rarity, exposure of neurologists to the clinical spectrum of NS is limited to case reports or short case series.

PATIENTS AND METHODS

A database of 3900 patients treated at the Vanderbilt Multiple Sclerosis Clinic between 1995 and 2008 was searched for 'neurosarcoidosis', 'neurosarcoid', 'sarcoidosis' and 'sarcoid'. Of the 162 patient records that were retrieved, 54 patients were found to meet the criteria for definite, probable or possible neurosarcoidosis and were reviewed, including their clinical presentation, Cerebrospinal fluid (CSF) findings, Magnetic resonance imaging (MRIs), biopsy results, treatment, and where available, outcomes 4 months to 20 years after onset of the presenting illness.

RESULTS

Clinical presentations and imaging findings in NS were varied. Cranial nerve abnormalities were the most common clinical presentation and involvement of the optic nerve in particular was associated with a poor prognosis for visual recovery. Isolated involvement of lower cranial nerves had a more favorable outcome. T(2) hyperintense parenchymal lesions were the most common imaging finding followed by meningeal enhancement. Long-term treatment consisted of prednisone and/or other immunomodulators (azathioprine, methotrexate or mycophenolate mofetil).

CONCLUSION

Unlike systemic sarcoidosis, there is difficulty in making tissue diagnosis when involvement of CNS is suspected. MRI and CSF studies are sensitive in the detection of CNS inflammation but lack specificity, making the ascertainment of neurosarcoidosis a clinical challenge. In addition the low prevalence of the disease makes clinical trials difficult and therapeutic decisions are likely to be made from careful reporting from case studies.

Infliximab for the treatment of CNS sarcoidosis: A multi-institutional series

OBJECTIVE

To describe clinical and imaging responses in neurosarcoidosis to infliximab, a monoclonal antibody against tumor necrosis factor-α.

METHODS

Investigators at 6 US centers retrospectively identified patients with CNS sarcoidosis treated with infliximab, including only patients with definite or probable neurosarcoidosis following rigorous exclusion of other causes.

RESULTS

Of 66 patients with CNS sarcoidosis (27 definite, 39 probable) treated with infliximab for a median of 1.5 years, the mean age was 47.5 years at infliximab initiation (SD 11.7, range 24-71 years); 56.1% were female; 62.1% were white, 37.0% African American, and 3% Hispanic. Sarcoidosis was isolated to the CNS in 19.7%. Using infliximab doses ranging from 3 to 7 mg/kg every 4-8 weeks, MRI evidence of a favorable treatment response was observed in 82.1% of patients with imaging follow-up (n = 56), with complete remission of active disease in 51.8% and partial MRI improvement in 30.1%; MRI worsened in 1 patient (1.8%). There was clinical improvement in 77.3% of patients, with complete neurologic recovery in 28.8%, partial improvement in 48.5%, clinical stability in 18.2%, worsening in 3%, and 1 lost to follow-up. In 16 patients in remission when infliximab was discontinued, the disease recurred in 9 (56%), typically in the same neuroanatomic location.

CONCLUSIONS

Most patients with CNS sarcoidosis treated with infliximab exhibit favorable imaging and clinical treatment responses, including some previously refractory to other immunosuppressive treatments.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for patients with CNS sarcoidosis infliximab is associated with favorable imaging and clinical responses.

Diagnostic and therapeutic aspects of Hashimoto's encephalopathy

OBJECTIVE

To share our experience on clinical presentation and management of patients diagnosed with Hashimoto's Encephalopathy (HE) at Vanderbilt Medical Center between 1999 and 2012.

BACKGROUND

HE is a rare disorder characterized by encephalopathy and central nervous system (CNS) dysfunction, elevated antithyroid antibodies, the absence of infection or structural abnormalities in the CNS, and a response to treatment with steroids. The relationship between thyroid antibodies and encephalopathy has remained unresolved.

DESIGN/METHODS

Retrospective chart review.

RESULTS

We identified 13 patients who met the criteria for the diagnosis of HE. The median age was 49 years (range, 2-66) and all except one were women. Encephalopathy in the form of altered mental status, stroke-like symptoms or seizures, with prompt resolution of symptoms upon receiving steroids, was the commonest presentation, seen in 7 patients. The second commonest presentation was subacute progressive decrease in cognitive function, which reversed within days to weeks after steroid therapy, seen in 4 patients. Electroencephalogram (EEG) was available in 12 patients and was abnormal in 8, showing nonspecific cerebral dysfunction in all 8 and epileptiform activity in 3. Treatment consisted of steroids in the acute phase for 12 of 13 patients with rapid improvement in symptoms. Maintenance therapy was rituximab in 7 patients, intravenous immunoglobulin (IVIg) in 7, azathioprine in 4, mycophenolate mofetil in 3, and methotrexate in 1 (some patients received sequential therapy with different agents). There was complete or near complete resolution of symptoms in 12 of the 13 patients.

CONCLUSIONS

We present a cohort of patients in whom CNS dysfunction was associated with elevated antithyroid antibodies and reversal of disease followed immunomodulatory therapies.

Extended interval dosing of natalizumab in multiple sclerosis

BACKGROUND

Natalizumab (NTZ), a monoclonal antibody to human α4β1/β7 integrin, is an effective therapy for multiple sclerosis (MS), albeit associated with progressive multifocal leukoencephalopathy (PML). Clinicians have been extending the dose of infusions with a hypothesis of reducing PML risk. The aim of the study is to evaluate the clinical consequences of reducing NTZ frequency of infusion up to 8 weeks 5 days.

METHODS

A retrospective chart review in 9 MS centres was performed in order to identify patients treated with extended interval dosing (EID) regimens of NTZ. Patients were stratified into 3 groups based on EID NTZ treatment schedule in individual centres: early extended dosing (EED; n=249) every 4 weeks 3 days to 6 weeks 6 days; late extended dosing (LED; n=274) every 7 weeks to 8 weeks 5 days; variable extended dosing (n=382) alternating between EED and LED. These groups were compared with patients on standard interval dosing (SID; n=1093) every 4 weeks.

RESULTS

17% of patients on SID had new T2 lesions compared with 14% in EID (p=0.02); 7% of patients had enhancing T1 lesions in SID compared with 9% in EID (p=0.08); annualised relapse rate was 0.14 in the SID group, and 0.09 in the EID group. No evidence of clinical or radiographic disease activity was observed in 62% of SID and 61% of EID patients (p=0.83). No cases of PML were observed in EID group compared with 4 cases in SID cohort.

CONCLUSIONS

Dosing intervals up to 8 weeks 5 days did not diminish effectiveness of NTZ therapy. Further monitoring is ongoing to evaluate if the risk of PML is reduced in patients on EID.

Neurosarcoidosis: Pathophysiology, Diagnosis, and Treatment

Although often regarded as a protean illness with myriad clinical and imaging manifestations, neurosarcoidosis typically presents as recognizable syndromes that can be approached in a rational, systematic fashion. Understanding of neurosarcoidosis has progressed significantly in recent years, including updated diagnostic criteria and advances in treatment. The diagnosis of neurosarcoidosis is established by the clinical syndrome, imaging and histopathological findings, and exclusion of other causes. Mounting evidence supports the use of tumor necrosis factor inhibitors as an important addition to the therapeutic armamentarium, along with glucocorticoids and steroid-sparing cytotoxic immunosuppressants. In this narrative review, we summarize recent advances in the diagnosis and treatment of neurosarcoidosis.

Development of chemical exchange saturation transfer at 7 T

Chemical exchange saturation transfer (CEST) MRI is a molecular imaging method that has previously been successful at reporting variations in tissue protein and glycogen contents and pH. We have implemented amide proton transfer (APT), a specific form of chemical exchange saturation transfer imaging, at high field (7 T) and used it to study healthy human subjects and patients with multiple sclerosis. The effects of static field inhomogeneities were mitigated using a water saturation shift referencing method to center each z-spectrum on a voxel-by-voxel basis. Contrary to results obtained at lower fields, APT imaging at 7 T revealed significant contrast between white and gray matters, with a higher APT signal apparent within the white matter. Preliminary studies of multiple sclerosis showed that the APT asymmetry varied with the type of lesion examined. An increase in APT asymmetry relative to healthy tissue was found in some lesions. These results indicate the potential utility of APT at high field as a noninvasive biomarker of white matter pathology, providing complementary information to other MRI methods in current clinical use.

Extended interval dosing of natalizumab: a two-center, 7-year experience

BACKGROUND

The enthusiasm for natalizumab, a highly efficacious agent in the treatment of multiple sclerosis (MS), has been tempered by the risks of progressive multifocal leukoencephalopathy associated with its use, and strategies to minimize those risks are of great interest. Extended interval dosing (EID) has been proposed as a way to maintain the efficacy of natalizumab while reducing exposure to it. We reviewed a cohort of patients who received natalizumab at 6-8-week intervals instead of the typical infusions every 4 weeks with the goal to assess if patients on EID had an increase in clinical relapses.

METHODS

This is a retrospective review of all patients with MS treated with natalizumab at two MS centers where patients were offered the opportunity to switch to an EID every 6 or 8 weeks.

RESULTS

A total of 361 patients received natalizumab for 22 ± 13 months (minimum duration 6 months). Of these, 96 patients received EID natalizumab at some point for 20 ± 11 months (minimum duration 6 months). Over the study period, there was no significant difference between the relapse rate in the monthly dosing (13%) and the EID (13%) groups of patients.

CONCLUSION

Natalizumab is effective in controlling MS as very few clinical relapses were observed in our dataset. We found that EID did not compromise the treatment effect as measured by relapse rate and no significant breakthrough disease activity was observed. EID is an optional regimen for maintenance natalizumab therapy, but prospective studies are warranted to determine its efficacy.

Comparison of switching to 6-week dosing of natalizumab versus continuing with 4-week dosing in patients with relapsing-remitting multiple sclerosis (NOVA): a randomised, controlled, open-label, phase 3b trial

BACKGROUND

Treatment with natalizumab once every 4 weeks is approved for patients with relapsing-remitting multiple sclerosis, but is associated with a risk of progressive multifocal leukoencephalopathy. Switching to extended-interval dosing is associated with lower progressive multifocal leukoencephalopathy risk, but the efficacy of this approach is unclear. We aimed to assess the safety and efficacy of natalizumab once every 6 weeks compared with once every 4 weeks in patients with relapsing-remitting multiple sclerosis.

METHODS

We did a randomised, controlled, open-label, phase 3b trial (NOVA) at 89 multiple sclerosis centres across 11 countries in the Americas, Europe, and Western Pacific. Included participants were aged 18-60 years with relapsing-remitting multiple sclerosis and had been treated with intravenous natalizumab 300 mg once every 4 weeks with no relapses for at least 12 months before randomisation, with no missed doses in the previous 3 months. Participants were randomly assigned (1:1), using a randomisation sequence generated by the study funder and contract personnel with interactive response technology, to switch to natalizumab once every 6 weeks or continue with once every 4 weeks. The centralised MRI reader, independent neurology evaluation committee, site examining neurologists, site backup examining neurologists, and site examining technicians were masked to study group assignments. The primary endpoint was the number of new or newly enlarging T2 hyperintense lesions at week 72, assessed in all participants who received at least one dose of assigned treatment and had at least one postbaseline MRI, relapse, or neurological examination or efficacy assessment. Missing primary endpoint data were handled under prespecified primary and secondary estimands: the primary estimand included all data, regardless of whether participants remained on the assigned treatment; the secondary estimand classed all data obtained after treatment discontinuation or study withdrawal as missing. Safety was assessed in all participants who received at least one dose of study treatment. Study enrolment is closed and an open-label extension study is ongoing. This study is registered with EudraCT, 2018-002145-11, and ClinicalTrials.gov, NCT03689972.

FINDINGS

Between Dec 26, 2018, and Aug 30, 2019, 605 patients were assessed for eligibility and 499 were enrolled and assigned to receive natalizumab once every 6 weeks (n=251) or once every 4 weeks (n=248). After prespecified adjustments for missing data, mean numbers of new or newly enlarging T2 hyperintense lesions at week 72 were 0·20 (95% CI 0·07-0·63) in the once every 6 weeks group and 0·05 (0·01-0·22) in the once every 4 weeks group (mean lesion ratio 4·24 [95% CI 0·86-20·85]; p=0·076) under the primary estimand, and 0·31 (95% CI 0·12-0·82) and 0·06 (0·01-0·31; mean lesion ratio 4·93 [95% CI 1·05-23·20]; p=0·044) under the secondary estimand. Two participants in the once every 6 weeks group with extreme new or newly enlarging T2 hyperintense lesion numbers (≥25) contributed most of the excess lesions. Adverse events occurred in 194 (78%) of 250 participants in the once every 6 weeks group and 190 (77%) of 247 in the once every 4 weeks group, and serious adverse events occurred in 17 (7%) and 17 (7%), respectively. No deaths were reported. There was one case of asymptomatic progressive multifocal leukoencephalopathy (without clinical signs) in the once every 6 weeks group, and no cases in the once every 4 weeks group; 6 months after diagnosis, the participant was without increased disability and remained classified as asymptomatic.

INTERPRETATION

We found a numerical difference in the mean number of new or newly enlarging T2 hyperintense lesions at week 72 between the once every 6 weeks and once every 4 weeks groups, which reached significance under the secondary estimand, but interpretation of statistical differences (or absence thereof) is limited because disease activity in the once every 4 weeks group was lower than expected. The safety profiles of natalizumab once every 6 weeks and once every 4 weeks were similar. Although this trial was not powered to assess differences in risk of progressive multifocal leukoencephalopathy, the occurrence of the (asymptomatic) case underscores the importance of monitoring and risk factor consideration in all patients receiving natalizumab.

FUNDING

Biogen.

C-Jun N-terminal kinase (JNK) regulation of iNOS expression in glial cells: predominant role of JNK1 isoform

The mitogen-activated protein kinases (MAPKs) play a central role in mediating the activation and transcriptional responses of diverse cells, including glia. c-Jun N-terminal kinase (JNK), a member of the MAPK family, is activated by a variety of stress and proinflammatory signals and in turn phosphorylates its downstream substrates including nuclear factors, leading to transcriptional activation of target genes. There are at least three subtypes of JNK (i.e., JNKs 1-3) that may play isoform-specific roles. This study examined the role of JNK isoforms in the induction of inducible nitric oxide synthase (iNOS) in astrocytes in response to lipopolysachharide (LPS) and interferon (IFN)-gamma. While an inhibitor of the JNK pathway (SP600125) inhibited iNOS expression, ectopic expression of a constitutively active form of MEKK1 (MAPK/ERK kinase kinase- 1), an upstream activator of JNK, led to an induction of co-transfected iNOS promoter activity and, in the presence of LPS, to an enhanced expression of iNOS. RNA knockdown studies with JNK subtype-specific short-interfering RNA (siRNA), indicated that JNK1- but not JNK2- nor JNK3-specific siRNA, interfered with LPS/IFNgamma induction of iNOS. It is concluded that, of the three JNK forms, JNK1 is the major mediator of iNOS induction and perhaps, inflammatory signaling in general, in glial cells.

Amide proton transfer CEST of the cervical spinal cord in multiple sclerosis patients at 3T

PURPOSE

The ability to evaluate pathological changes in the spinal cord in multiple sclerosis (MS) is limited because T₁ - and T₂ -w MRI imaging are not sensitive to biochemical changes in vivo. Amide proton transfer (APT) chemical exchange saturation transfer (CEST) can indirectly detect amide protons associated with proteins and peptides, potentially providing more pathological specificity. Here, we implement APT CEST in the cervical spinal cord of healthy and MS cohorts at 3T.

METHODS

APT CEST of the cervical spinal cord was obtained in a cohort of 10 controls and 10 MS patients using a novel respiratory correction methodology. APT was quantified using two methods: 1) APT_w , based off the conventional magnetization transfer ratio asymmetry, and 2) ΔAPT, a spatial characterization of APT changes in MS patients relative to the controls.

RESULTS

Respiratory correction yielded highly reproducible z-spectra in white matter (intraclass correlation coefficient = 0.82). APT_w signals in normal-appearing white matter (NAWM) of MS patients were significantly different from healthy controls (P = 0.04), whereas ΔAPT of MS patients highlighted large APT differences in NAWM.

CONCLUSION

Respiration correction in the spinal cord is necessary to accurately quantify APT CEST, which can provide unique biochemical information regarding disease processes within the spinal cord. Magn Reson Med 79:806-814, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Magnetic resonance imaging of the cervical spinal cord in multiple sclerosis at 7T

BACKGROUND

The clinical course of multiple sclerosis (MS) is mainly attributable to cervical and upper thoracic spinal cord dysfunction. High-resolution, 7T anatomical imaging of the cervical spinal cord is presented. Image contrast between gray/white matter and lesions surpasses conventional, clinical T1- and T2-weighted sequences at lower field strengths.

OBJECTIVE

To study the spinal cord of healthy controls and patients with MS using magnetic resonance imaging at 7T.

METHODS

Axial (C2-C5) T1- and T2*-weighted and sagittal T2*-/spin-density-weighted images were acquired at 7T in 13 healthy volunteers (age 22-40 years), and 15 clinically diagnosed MS patients (age 19-53 years, Extended Disability Status Scale, (EDSS) 0-3) in addition to clinical 3T scans. In healthy volunteers, a high-resolution multi-echo gradient echo scan was obtained over the same geometry at 3T. Evaluation included signal and contrast to noise ratios and lesion counts for healthy and patient volunteers, respectively.

RESULTS/CONCLUSION

High-resolution images at 7T exceeded resolutions reported at lower field strengths. Gray and white matter were sharply demarcated and MS lesions were more readily visualized at 7T compared to clinical acquisitions, with lesions apparent at both fields. Nerve roots were clearly visualized. White matter lesion counts averaged 4.7 vs 3.1 (52% increase) per patient at 7T vs 3T, respectively (p=0.05).

Multiple sclerosis lesions affect intrinsic functional connectivity of the spinal cord

Patients with multiple sclerosis present with focal lesions throughout the spinal cord. There is a clinical need for non-invasive measurements of spinal cord activity and functional organization in multiple sclerosis, given the cord's critical role in the disease. Recent reports of spontaneous blood oxygenation level-dependent fluctuations in the spinal cord using functional MRI suggest that, like the brain, cord activity at rest is organized into distinct, synchronized functional networks among grey matter regions, likely related to motor and sensory systems. Previous studies looking at stimulus-evoked activity in the spinal cord of patients with multiple sclerosis have demonstrated increased levels of activation as well as a more bilateral distribution of activity compared to controls. Functional connectivity studies of brain networks in multiple sclerosis have revealed widespread alterations, which may take on a dynamic trajectory over the course of the disease, with compensatory increases in connectivity followed by decreases associated with structural damage. We build upon this literature by examining functional connectivity in the spinal cord of patients with multiple sclerosis. Using ultra-high field 7 T imaging along with processing strategies for robust spinal cord functional MRI and lesion identification, the present study assessed functional connectivity within cervical cord grey matter of patients with relapsing-remitting multiple sclerosis (n = 22) compared to a large sample of healthy controls (n = 56). Patient anatomical images were rated for lesions by three independent raters, with consensus ratings revealing 19 of 22 patients presented with lesions somewhere in the imaged volume. Linear mixed models were used to assess effects of lesion location on functional connectivity. Analysis in control subjects demonstrated a robust pattern of connectivity among ventral grey matter regions as well as a distinct network among dorsal regions. A gender effect was also observed in controls whereby females demonstrated higher ventral network connectivity. Wilcoxon rank-sum tests detected no differences in average connectivity or power of low frequency fluctuations in patients compared to controls. The presence of lesions was, however, associated with local alterations in connectivity with differential effects depending on columnar location. The patient results suggest that spinal cord functional networks are generally intact in relapsing-remitting multiple sclerosis but that lesions are associated with focal abnormalities in intrinsic connectivity. These findings are discussed in light of the current literature on spinal cord functional MRI and the potential neurological underpinnings.

Glutamate-sensitive imaging and evaluation of cognitive impairment in multiple sclerosis

BACKGROUND

Cognitive impairment (CI) profoundly impacts quality of life for patients with multiple sclerosis (MS). Dysfunctional regulation of glutamate in gray matter (GM) has been implicated in the pathogenesis of MS by post-mortem pathological studies and in CI by in vivo magnetic resonance spectroscopy, yet GM pathology is subtle and difficult to detect using conventional T₁- and T₂-weighted magnetic resonance imaging (MRI). There is a need for high-resolution, clinically accessible imaging techniques that probe molecular changes in GM.

OBJECTIVE

To study cortical GM pathology related to CI in MS using glutamate-sensitive chemical exchange saturation transfer (GluCEST) MRI at 7.0 Tesla (7T).

METHODS

A total of 20 patients with relapsing-remitting MS and 20 healthy controls underwent cognitive testing, anatomical imaging, and GluCEST imaging. Glutamate-sensitive image contrast was quantified for cortical GM, compared between cohorts, and correlated with clinical measures of CI.

RESULTS AND CONCLUSION

Glutamate-sensitive contrast was significantly increased in the prefrontal cortex of MS patients with accumulated disability (p < 0.05). In addition, glutamate-sensitive contrast in the prefrontal cortex was significantly correlated with symbol digit modality test (r_S = -0.814) and choice reaction time (r_S = 0.772) scores in patients (p < 0.05), suggesting that GluCEST MRI may have utility as a marker for GM pathology and CI.

Chemical exchange saturation transfer of the cervical spinal cord at 7 T

High-magnetic-field (7 T) chemical exchange saturation transfer (CEST) MRI provides information on the tissue biochemical environment. Multiple sclerosis (MS) affects the entire central nervous system, including the spinal cord. Optimal CEST saturation parameters found via simulation were implemented for CEST MRI in 10 healthy controls and 10 patients with MS, and the results were examined using traditional asymmetry analysis and a Lorentzian fitting method. In addition, T1 - and T2 *-weighted images were acquired for lesion localization and the transmitted B1 (+) field was evaluated to guide imaging parameters. Distinct spectral features for all tissue types studied were found both up- and downfield from the water resonance. The z spectra in healthy subjects had the expected z spectral shape with CEST effects apparent from 2.0 to 4.5 ppm. The z spectra from patients with MS demonstrated deviations from this expected normal shape, indicating this method's sensitivity to known pathology as well as to tissues appearing normal on conventional MRI. Examination of the calculated CESTasym revealed increased asymmetry around the amide proton resonance (Δω = 3.5 ppm), but it was apparent that this measure is complicated by detail in the CEST spectrum upfield from water, which is expected to result from the nuclear Overhauser effect. The z spectra upfield (negative ppm range) were also distinct between healthy and diseased tissue, and could not be ignored, particularly when considering the conventional asymmetry analysis used to quantify the CEST effect. For all frequencies greater than +1 ppm, the Lorentzian differences (and z spectra) for lesions and normal-appearing white matter were distinct from those for healthy white matter. The increased frequency separation and signal-to-noise ratio, in concert with prolonged T1 at 7 T, resulted in signal enhancements necessary to detect subtle tissue changes not possible at lower field strengths. This study presents CEST imaging metrics that may be sensitive to the extensive and temporally varying biochemical neuropathology of MS in the spinal cord. Copyright © 2016 John Wiley & Sons, Ltd.

Expression, characterization, and purification of C-terminally hexahistidine-tagged thromboxane A2 receptors

Thromboxane A2 (TxA2) receptors belong to the class of G-protein-coupled receptors. Knowledge of the relationship of structure to function for TxA2 receptors is limited because of their low levels of expression, lengthy purification procedures and poor recoveries. A C-terminal hexahistidine-tag (C-His) was ligated to the alpha-isoform of TxA2 receptors and expressed in COS-7 and Chinese hamster ovary cells. The C-His-TxA2 receptors bound the radioligands 125I-7-[(1R,2S,3S,5R)-6, 6-dimethyl-3-(4-benzenesulfonylamino)bicyclo[3.1. 1]hept-2-yl]-5(Z)-heptenoic acid, an antagonist, and 125I-[1S-1alpha, 2beta(5Z),3alpha(1E,3S*), 4alpha]-7-[3[(3-hydroxy-4-(4'-phenoxy)-1butenyl)-7-oxabicycl o-[2.2. 1]heptan-2-yl]-5-heptanoic acid, an agonist, with affinities not significantly different from those of the wild type (wt)-TxA2 receptors. LipofectAMINE transfection of the cDNAs resulted in high levels of expression (Bmax = 95 +/- 6 pmol/mg) of the C-His-TxA2 receptors. In competition binding studies the IC50 values of five different ligands were not significantly different between C-His-TxA2 and wt-TxA2 receptors. Agonist-induced stimulation of cAMP and total inositol phosphate formation were not significantly different between the two receptors. Purification on a Ni2+-NTA column resulted in a rapid (within 4 h) purification with a 36 +/- 2% recovery and a 30 +/- 6-fold purification (n = 5). The partially purified receptors were resolved on SDS-polyacrylamide gel electrophoresis, transferred to a nitrocellulose membrane, dissolved in acetone/trifluoroacetic acid/hexafluoroisopropanol/sinapinic acid, and successfully subjected to matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis. The results suggest that the combination of a high level of expression of C-His-TxA2 receptors and a rapid purification procedure followed by SDS- polyacrylamide gel electrophoresis may provide a useful approach for mass-spectrometry based structure-function and other studies of TxA2 receptors.

Selective Inversion Recovery Quantitative Magnetization Transfer Brain MRI at 7T: Clinical and Postmortem Validation in Multiple Sclerosis

BACKGROUND AND PURPOSE

An imaging biomarker of myelin integrity is an unmet need in multiple sclerosis (MS). Selective inversion recovery (SIR) quantitative magnetization transfer imaging (qMT) provides assays of myelin content in the human brain. We previously translated the SIR method to 7T and incorporated a rapid turbo field echo (TFE) readout for whole-brain imaging within clinically acceptable scan times. We herein provide histological validation and test in vivo feasibility and applicability of the SIR-TFE protocol in MS.

METHODS

Clinical (T₁ - and T₂ -weighted) and SIR-TFE MRI scans were performed at 7T in a postmortem MS brain and MRI data were acquired in 10 MS patients and 14 heathy volunteers in vivo. The following parameters were estimated from SIR data: the macromolecular-to-free water pool-size-ratio (PSR), the spin-lattice relaxation rate of water (R_1f ), and the MT exchange rate (k_mf ). Differences in SIR parameters across tissue types, eg, white matter lesions (WM-Ls) and normal appearing WM (NAWM) in patients, and normal white matter (NWM) in heathy volunteers were evaluated. Associations between SIR parameters and disability scores were assessed.

RESULTS

For postmortem scans, correspondence was observed between WM-Ls and NAWM from histology and PSR/R_1f values. In vivo differences were detected for PSR, R_1f , and k_mf between WM-Ls and NWM (P ≤ .041). Associations were seen between WM-Ls/ NAWM PSR and disability scores (r ≤ -.671, P ≤ .048).

CONCLUSIONS

SIR-qMT at 7T provides sensitive, quantitative measures of myelin integrity for clinical and research applications.

The role of infections in the pathogenesis and course of multiple sclerosis

Interplay between susceptibility genes and environmental factors is considered important player in the genesis of multiple sclerosis (MS). Among environmental factors, a role for an infectious pathogen has long been considered central to the disease process. This opinion has support both from epidemiological data and the findings of immunological abnormalities in spinal fluid that reflect an immune response to an as yet undetermined antigen, possibly a pathogen, in the cerebrospinal fluid. Our review will outline the current understanding of the role of infection in the causation and progression of MS. We will review the data that point to an infectious cause of MS and consider the specific agents Chlamydophila (Chlamydia) pneumoniae, Human Herpes Virus 6, and Epstein-Barr Virus, that are implicated in either the development or progression of MS.

Effectiveness of alternative dose fingolimod for multiple sclerosis

Background

Fingolimod is a daily oral medication used to treat relapsing multiple sclerosis (MS). Clinicians often adopt less frequent dosing for patients with profound drug-induced lymphopenia or other adverse events. Data on the effectiveness of alternate dose fingolimod are limited.

Methods

We conducted a multicenter, retrospective, observational study at 14 sites and identified 170 patients with MS taking alternate doses of fingolimod for ≥1 month. Clinical and radiologic outcomes were collected and compared during daily and alternate fingolimod dosing.

Results

Profound lymphopenia (77%), liver function abnormalities (9%), and infections (7%) were the most common reasons for patients to switch to alternate fingolimod dosing. The median follow-up was 12 months on daily dose and 14 months on alternate dose. Most patients (64%) took fingolimod every other day during alternate dosing. Disease activity was similar on alternate dose compared to daily dose: annualized relapse rate was 0.1 on daily dose vs 0.2 on alternate dose (p = 0.25); proportion of patients with contrast-enhancing MRI lesions was 7.6% on daily vs 9.4% on alternate (p = 0.55); proportion of patients with cumulative MS activity (clinical and radiologic disease) was 13.5% on daily vs 18.2% on alternate (p = 0.337). Patients who developed contrast-enhancing lesions while on daily dose were at higher risk for breakthrough disease while on alternate dose fingolimod (odds ratio 11.4, p < 0.001).

Conclusions

These data support the clinical strategy of alternate dosing of fingolimod in patients with good disease control but profound lymphopenia or other adverse events while on daily dose.

Classification of Evidence

This study provides Class IV evidence that for patients with MS on daily dose fingolimod with adverse events, alternate dose fingolimod is associated with disease activity similar to daily dose fingolimod.

Improved diffusion tensor imaging of the optic nerve using multishot two-dimensional navigated acquisitions

PURPOSE

A diffusion-weighted multishot echo-planar imaging approach combined with SENSE and a two-dimensional (2D) navigated motion correction was investigated as an alternative to conventional single-shot counterpart to obtain optic nerve images at higher spatial resolution with reduced artifacts.

METHODS

Fifteen healthy subjects were enrolled in the study. Six of these subjects underwent a repeated acquisition at least 2 weeks after the initial scan session to address reproducibility. Both single-shot and multishot diffusion tensor imaging studies of the human optic nerve were performed with matched scan time. Effect of subject motions were corrected using 2D phase navigator during multishot image reconstruction. Tensor-derived indices from proposed multishot were compared against conventional single-shot approach. Image resolution difference, right-left optic nerve asymmetry, and test-retest reproducibility were also assessed.

RESULTS

In vivo results of acquired multishot images and quantitative maps of diffusion properties of the optic nerve showed significantly reduced image artifacts (e.g., distortions and blurring), and the derived diffusion indices were comparable to those from other studies. Single-shot scans presented larger variability between right and left optic nerves than multishot scans. Multishot scans also presented smaller variations across scans at different time points when compared with single-shot counterparts.

CONCLUSION

The multishot technique has considerable potential for providing improved information on optic nerve pathology and may also be translated to higher fields.

Isolated longitudinal myelitis: a report of six cases

STUDY DESIGN

Retrospective chart review.ObjectiveTo report six patients with isolated longitudinal myelitis (LM).

SETTING

Outpatients at Multiple Sclerosis Center/Clinic Vanderbilt University Medical Center.

METHODS

1.

PATIENTS

PATIENTS treated for LM in whom evidence for multiple sclerosis (MS), neuromyelitis optica (NMO) and systemic inflammatory disorders such as systemic lupus erythematosus (SLE) was lacking. 2.

INTERVENTIONS

Clinical, laboratory and imaging data, treatment and outcomes were reviewed. 3.

MAIN OUTCOME MEASURES

LM in the absence of optic neuritis, normal or nonspecific brain magnetic resonance imaging (MRI) findings, the absence of NMO antibody.

RESULTS

All presented with monophasic myelitis with variable loss of motor, sensory and bowel/bladder functions. MRIs of the brain were normal (five cases), and in the sixth showed a single T2 hyperintense lesion, which was interpreted as an ischemic lesion due to small-vessel disease. MRIs of the spinal cord of all patients showed swelling and T2 hyperintense lesions with patchy contrast enhancement that extended from the cervicomedullary junction to the conus medullaris. Two of these patients received rituximab with clinical benefit. Another patient received one dose of rituximab, developed an allergic reaction, received further treatments with azathioprine and also made a good recovery. In one patient, approval for rituximab was obtained several months after the inflammation had subsided, and she has shown only a minimal improvement. The two patients who did not receive rituximab made no significant recovery from their maximal neurological deficits.

CONCLUSIONS

Isolated LM may be a new clinical syndrome, or a variant of NMO.