P. van der Valk

Severe oxidative damage in multiple sclerosis lesions coincides with enhanced antioxidant enzyme expression

Reactive oxygen species (ROS) and subsequent oxidative damage may contribute to the formation and persistence of multiple sclerosis (MS) lesions by acting on distinct pathological processes. ROS initiate lesion formation by inducing blood-brain barrier disruption, enhance leukocyte migration and myelin phagocytosis, and contribute to lesion persistence by mediating cellular damage to essential biological macromolecules of vulnerable CNS cells. Relatively little is known about which CNS cell types are affected by oxidative injury in MS lesions. Here, we show the presence of extensive oxidative damage to proteins, lipids, and nucleotides occurring in active demyelinating MS lesions, predominantly in reactive astrocytes and myelin-laden macrophages. Oxidative stress can be counteracted by endogenous antioxidant enzymes that confer protection against oxidative damage. Here, we show that antioxidant enzymes, including superoxide dismutase 1 and 2, catalase, and heme oxygenase 1, are markedly upregulated in active demyelinating MS lesions compared to normal-appearing white matter and white matter tissue from nonneurological control brains. Particularly, hypertrophic astrocytes and myelin-laden macrophages expressed an array of antioxidant enzymes. Enhanced antioxidant enzyme production in inflammatory MS lesions may reflect an adaptive defense mechanism to reduce ROS-induced cellular damage.

Epstein Barr virus is not a characteristic feature in the central nervous system in established multiple sclerosis

Sir, Although recent studies have demonstrated a clear association of Epstein-Barr virus (EBV) infection with multiple sclerosis (Zaadstra et al. , 2008; Lunemann and Munz, 2009; Salvetti et al. , 2009), there has been much debate if and where the virus acts in the pathogenic cascade of multiple sclerosis and whether the virus needs to gain entry to the central nervous system (CNS). A recent study reported in Brain by Willis et al. (2009) showed that there is little evidence for the presence of EBV in the central nervous system of people with multiple sclerosis. These findings contrast greatly with the studies by Serafini et al. (2007) that have described abundant EBV positive cells in multiple sclerosis, and the presence of ectopic B cell follicles enriched with EBV infected cells in some patients. Willis and co-workers used a variety of validated methods to determine the presence of EBV in the CNS of patients with B cell infiltrates within the meninges and parenchyma. The paper described two crucial observations. Unlike Serafini et al. (2007), Willis et al. did not find the presence of EBV to be a characteristic feature of multiple sclerosis (aptly the title of the paper). Second, ectopic follicles, suggested by Serafini et al. to harbour EBV infected B cells, were not observed, despite scrutiny of meningeal tissues where these follicles should have been present. Clearly, the issue of whether EBV is indeed present in the CNS is crucial not only to determine the impact of the virus on the disease in the CNS, but also for diagnostic pathology in general. The studies reveal the vagaries of pathological detection methods for infectious agents such as EBV. Care in the practice and interpretation of such methodologies are of course key for correct diagnosis and proving pathogenic …

BLBP-expression in astrocytes during experimental demyelination and in human multiple sclerosis lesions

Several lines of evidence indicate that remyelination represents one of the most effective mechanisms to achieve axonal protection. For reasons that are not yet understood, this process is often incomplete or fails in multiple sclerosis (MS). Activated astrocytes appear to be able to boost or inhibit endogenous repair processes. A better understanding of remyelination in MS and possible reasons for its failure is needed. Using the well-established toxic demyelination cuprizone model, we created lesions with either robust or impaired endogenous remyelination capacity. Lesions were analyzed for mRNA expression levels by Affymetrix GeneChip® arrays. One finding was the predominance of immune and stress response factors in the group of genes which were classified as remyelination-supporting factors. We further demonstrate that lesions with impaired remyelination capacity show weak expression of the radial-glia cell marker brain lipid binding protein (BLBP, also called B-FABP or FABP7). The expression of BLBP in activated astrocytes correlates with the presence of oligodendrocyte progenitor cells. BLBP-expressing astrocytes are also detected in experimental autoimmune encephalomyelitis during the remission phase. Furthermore, highest numbers of BLBP-expressing astrocytes were evident in lesions of early MS, whereas significantly less are present at the rim of (chronic)-active lesions from patients with long disease duration. Transfection experiments show that BLBP regulates growth factor expression in U87 astrocytoma cells. In conclusion, we provide evidence that expression of BLBP in activated astrocytes negatively correlates with disease duration and in parallel with remyelination failure.

Matrix metalloproteinase-19 is highly expressed in active multiple sclerosis lesions

Matrix metalloproteinases (MMPs) are proteases known for their capacity to degrade extracellular matrix (ECM) components. MMPs have been implicated in several central nervous system (CNS) diseases, including multiple sclerosis (MS). Microarray analysis has demonstrated significant increased mRNA levels of MMP‐19 in chronic MS lesions, suggesting a role of MMP‐19 in MS pathogenesis. Therefore, in this study, we investigated the expression pattern and cellular localization of MMP‐19 protein in various well‐characterized MS lesion stages. In normal control patient white matter, MMP‐19 was constitutively expressed by microglia throughout the brain parenchyma, suggesting a physiological role for this MMP family member. Likewise, MMP‐19 was expressed by microglia in (p)reactive MS lesions, albeit more intense. In highly active demyelinating MS lesions, parenchymal and perivascular myelin‐laden macrophages were strongly immunoreactive for MMP‐19, whereas reactive astrocytes were occasionally immunopositive. Astrocytes in chronic inactive lesions were weakly stained for MMP‐19. In vitro, MMP‐19 was expressed in cultures of primary human microglia, not in astrocyte cultures. As MMP‐19 is able to degrade basement membrane constituents and other ECM proteins, it is conceivable that this relatively novel MMP family member contributes to MS pathology by remodelling the ECM of the CNS, thereby influencing leucocyte infiltration, axonal regeneration and astrogliosis.

CNS myelin induces regulatory functions of DC-SIGN-expressing, antigen-presenting cells via cognate interaction with MOG

Human myelin oligodendrocyte glycoprotein is decorated with fucosylated N-glycans that are recognized by DC-SIGN+ DCs and microglia that control immune homeostasis.

What drives MRI-measured cortical atrophy in multiple sclerosis?

Background: Cortical atrophy, assessed with magnetic resonance imaging (MRI), is an important outcome measure in multiple sclerosis (MS) studies. However, the underlying histopathology of cortical volume measures is unknown. Objective: We investigated the histopathological substrate of MRI-measured cortical volume in MS using combined post-mortem imaging and histopathology. Methods: MS brain donors underwent post-mortem whole-brain in-situ MRI imaging. After MRI, tissue blocks were systematically sampled from the superior and inferior frontal gyrus, anterior cingulate gyrus, inferior parietal lobule, and superior temporal gyrus. Histopathological markers included neuronal, axonal, synapse, astrocyte, dendrite, myelin, and oligodendrocyte densities. Matched cortical volumes from the aforementioned anatomical regions were measured on the MRI, and used as outcomes in a nested prediction model. Results: Forty-five tissue blocks were sampled from 11 MS brain donors. Mean age at death was 68±12 years, post-mortem interval 4±1 hours, and disease duration 35±15 years. MRI-measured regional cortical volumes varied depending on anatomical region. Neuronal density, neuronal size, and axonal density were significant predictors of GM volume. Conclusions: In patients with long-standing disease, neuronal and axonal pathology are the predominant pathological substrates of MRI-measured cortical volume in chronic MS.

Heterogeneity of cortical lesions in multiple sclerosis Clinical and pathologic implications

Objective: Autopsy cases show that cortical lesions (CLs) in multiple sclerosis (MS) lack lymphocyte/macrophage influx, blood-brain barrier breakdown, and complement activation. However, some CLs were demonstrated to harbor activated microglia. Here, we assessed the clinical significance of microglia activation in CLs in a large autopsy sample, and we investigated possible interrelationships with other pathologic characteristics. Methods: We cross-sectionally investigated the clinicopathologic characteristics of 22 patients with MS with extensive subpial demyelination (CL group) and 19 patients with MS with only little demyelination of the cerebral cortex (non-CL group). Results: A subset of the patients in the CL group (12 patients) showed rims of activated microglia (RAM) at the border of the CLs (RAM-CL group), whereas the other 10 patients in this group did not show microglia activation (non−RAM-CL group). A subsequent comparison between groups showed that patients with MS harboring RAM-CLs were significantly younger at the time of their death (53.5 years) than patients harboring mainly non–RAM-CLs (68.7 years; p < 0.05) or patients without extensive numbers of CLs (66.9 years; p < 0.01). In addition, a significantly shorter disease duration was found for the RAM-CL group (mean 20.9 years) than for the non-CL group (mean 34.5 years; p < 0.05). We also found that the presence of RAM-CLs is associated with a higher number of chronic active white matter (WM) lesions (Spearman ρ = 0.74; p < 0.0001). Conclusions: RAM-CLs were found in a subset of patients with MS who also have more active WM inflammation and a less favorable disease course.

Retinoblastoma and optic nerve enhancement on MRI: not always extraocular tumour extension

Neoadjuvant chemotherapy is useful in the management of extensive forms of retinoblastoma with radiologically detectable optic nerve invasion at diagnosis.1 Magnetic resonance imaging (MRI) can detect various degrees of optic nerve invasion as enhancement extending from an intraocular tumour into the optic nerve. However, pretreatment false positive MRI findings based on inflammation occur occasionally.2 We describe a case of unilateral retinoblastoma and false positive MRI findings of extensive optic nerve involvement. A 3 year old girl presented with retinoblastoma of the right eye. Ophthalmic examination revealed a large exophytic growing tumour, a shallow anterior chamber, rubeosis iridis, and an elevated intraocular pressure. T2WI showed a hypointense subretinal tumour mass with similar signal intensity (SI) compared to both optic nerves (fig 1A). No delineation of the ipsilateral optic nerve with surrounding cerebrospinal fluid was possible. On additional short tau inversion recovery (STIR) MRI, the optic nerve showed an increased SI from the postlaminar part to the orbital apex. Contrast enhanced T1WI showed enhancement of the tumour mass (tumour volume 2.1 cm3). Thickening and marked enhancement …

Characterization of oxygen-tolerant Chinese hamster ovary cells. II: Energy metabolism and antioxidant status

Further characteristics of an oxygen-tolerant variant of Chinese hamster ovary cells (CHO-99) capable of stable proliferation at 99% O2/1% CO2, and O2 level that is lethal to the parental line (CHO-20), are described. Previous work has revealed that CHO-99 cells have 2- to 4-fold increased activities of superoxide dismutases, catalase and glutathione peroxidase, and substantially increased relative volumes of mitochondria and peroxisomes. To document possible additional mechanisms of O2 tolerance we compared CHO-20 cells growing at 20% O2 (normoxia) and CHO-99 cells at 99% O2 (normobaric hyperoxia). We show the following: (1) the estimated total (oxidative and glycolytic) ATP production in CHO-99 cells was 36% decreased. ATP production through oxidative phosphorylation was 52% lower in CHO-99 cells, while the relative contribution from glycolysis was increased from 6% to 30%. The ATP content was 29% lower in CHO-99 cells, the adenylate energy charge being also significantly decreased, indicating that energy production through oxidative phosphorylation is compromised in CHO-99 cells. Cyanide-resistant respiration was 4-fold higher in CHO-99 cells, probably reflecting, at least partly, the increased peroxisomal activity in these cells. (2) The level of reduced glutathione was several fold increased in CHO-99 cells, oxidized glutathione being unaltered; (NADPH + NADP+) levels were elevated 2.7-fold, while the ratio of NADPH to NADP+ was increased almost two-fold. These changes were associated with a 50% increased metabolism of glucose through the hexose monophosphate pathway. (3) No evidence was obtained for an increased steady-state level of endogenous lipid peroxidation in CHO-99 cells, in spite of a 50% increased content of polyunsaturated fatty acids in the phospholipid fraction.

International retinoblastoma staging system helps to bridge the gap.

To the Editor: The publication of an International Retinoblastoma Staging System by Chantada et al. [1] gained our specific interest since we are in the process establishing a collaboration between Indonesia and the Netherlands regarding the treatment of retinoblastoma patients, a twinning project that is supported by the Dutch Cancer Society. The aim of this project is the development of an Indonesian Centre of Expertise for Retinoblastoma (ICER). The clinical presentation of retinoblastoma patients in both collaborating countries is completely different, since Indonesian patients are characterized by advanced disease while Dutch retinoblastoma patients mainly have an early referral with mainly intra-ocular retinoblastoma. One of our basic issues for protocol development was a proper definition of different stages of disease. Standardized descriptions of disease extent are needed to register patients properly, to interpret treatment outcome and to compare Indonesian long-term treatment results with the literature. We discussed many different subtypes of advanced disease that were encountered in daily practice in Indonesia. The earlier St. Jude classification lacks differentiation in extra-ocular presentation of retinoblastoma [2]. The publication of the staging proposed by Chantada et al. offers the opportunity to discuss the staging system profoundly during our meetings. We think that this whole spectrum staging system is very worthwhile; however, we would like to propose two additional aspects to be added to the classification system (Supplemental Table I). First, we would recommend specifying the CNS extension in subclasses IVb 2a chiasmatic, IVb 2b contralateral spread, and IVb 2c other CNS mass [3]. This staging procedure should be feasible with computer tomography as well as with MRI. Such a subclassification would enable stratifying CNS patients further and, when implemented in treatment schedules, the potential differences in prognosis might become clear. Second, we think it is important to classify anterior chamber involvement separately in the subclassification of extra-retinal stages as A1 in the case of cells in the anterior chamber and as A2 in the case of tumor invasion into the tissue of the anterior chamber. This aspect needs development of histopathological consensus. We think that these recommendations may help to define specific subgroups that finally might require specific treatment adaptations. We intend to implement this adapted version of the staging system in the Indonesian treatment guidelines and are grateful to the authors for their effort to propose a whole spectrum staging system to be used internationally.