Inhibition of rho family functions by lovastatin promotes myelin repair in ameliorating experimental autoimmune encephalomyelitis

Lipid metabolism in myelinating glial cells: lessons from human inherited disorders and mouse models

The integrity of central and peripheral nervous system myelin is affected in numerous lipid metabolism disorders. This vulnerability was so far mostly attributed to the extraordinarily high level of lipid synthesis that is required for the formation of myelin, and to the relative autonomy in lipid synthesis of myelinating glial cells because of blood barriers shielding the nervous system from circulating lipids. Recent insights from analysis of inherited lipid disorders, especially those with prevailing lipid depletion and from mouse models with glia-specific disruption of lipid metabolism, shed new light on this issue. The particular lipid composition of myelin, the transport of lipid-associated myelin proteins, and the necessity for timely assembly of the myelin sheath all contribute to the observed vulnerability of myelin to perturbed lipid metabolism. Furthermore, the uptake of external lipids may also play a role in the formation of myelin membranes. In addition to an improved understanding of basic myelin biology, these data provide a foundation for future therapeutic interventions aiming at preserving glial cell integrity in metabolic disorders.

Therapeutic potential of experimental autoimmune encephalomyelitis by Fasudil, a Rho kinase inhibitor

The migration of aberrant inflammatory cells into the central nervous system plays an important role in the pathogenesis of demyelinating diseases potentially through the Rho/Rho-kinase (Rock) pathway, but direct evidence from human and animal models remains inadequate. Here we further confirm that Fasudil, a selective Rock inhibitor, has therapeutic potential in a mouse model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). The results show that Fasudil decreased the development of EAE in C57BL/6 mice. Immunohistochemistry disclosed that expression of Rock-II in the perivascular spaces and vascular endothelial cells of spleens, spinal cords, and brains was elevated in EAE and was inhibited in the Fasudil-treated group. T-cell proliferation specific to MOG(35-55) was markedly reduced, together with a significant down-regulation of interleukin (IL)-17, IL-6, and MCP-1. In contrast, secretion of IL-4 was increased, and IL-10 was slightly elevated. There were no differences in the percentages of CD4(+)CD25(+), CD8(+)CD28(-), and CD8(+)CD122(+) in mononuclear cells. Histological staining disclosed a marked decrease of inflammatory cells in spinal cord and brain of Fasudil-treated mice. These results, together with previous studies showing the inhibitory effect of Fasudil on T-cell migration, might expand its clinical application as a new therapy for multiple sclerosis by decreasing cell migration and regulating immune balance.

Simvastatin treatment in patients with relapsing-remitting multiple sclerosis receiving interferon beta 1a: a double-blind randomized controlled trial

OBJECTIVES

This study was conducted to evaluate the effect of simvastatin (40 mg/day) as an adjuvant therapy to interferon beta (IFNb 1a, 30 microg once weekly) in relapsing-remitting multiple sclerosis patients, compared with placebo.

METHODS

We enrolled 85 patients with relapsing-remitting multiple sclerosis (71% female) who were already receiving IFNb 1a (Avonex), with Expanded Disability Status Scale score of less than 5.0. The patients were assigned (in random and double-blinded fashion) into the two groups of simvastatin and placebo. All patients continued to receive their current IFNb treatment. The outcome measures were total relapse rate, Expanded Disability Status Scale score, and the number of gadolinium-enhanced (Gd+) and new T2 lesions in magnetic resonance imaging after a 1-year follow-up. We used Mann-Whitney and one-way multivariate analysis of variances to analyze the data.

RESULTS

Four patients in the placebo and two in the simvastatin group prematurely withdrew from the study due to experiencing two attacks. The total attack number in the simvastatin group was significantly lower than placebo group (moderate effect size r = 0.29) (p = 0.01). The final Expanded Disability Status Scale scores were lower in the simvastatin group (1.01 +/- 1.40, mean +/- SD) than in the placebo group (1.73 +/- 1.49, mean +/- SD), but this difference was not significant after controlling the baseline Expanded Disability Status Scale score (p = 0.07). In the simvastatin group, the mean +/- SD of gadolinium-enhanced and new T2 lesions were 0.66 +/- 1.18 and 3.39 +/- 3.55, respectively, (compared with 0.74 +/- 1.21 and 3.39 +/- 3.55 in the placebo group). Although there was a decreasing trend in lesions on magnetic resonance imaging, this difference was not statistically significant (p = 0.62). The combination therapy was safe and well tolerated, and no serious adverse effect was noted.

CONCLUSION

Our study supports the safety and efficacy of simvastatin as an add-on therapy to INFb 1a in patients with relapsing-remitting multiple sclerosis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00668343. This interventional study provides Class I evidence stating that adding simvastatin 40 mg/day to IFNb 1a 30 microg a week in patients with relapsing-remitting multiple sclerosis may reduce the relapse rate (moderate effect size r = 0.29) (p = 0.01) compared with treatment with IFNb 1a alone.

RGMA and IL21R show association with experimental inflammation and multiple sclerosis

Rat chromosome 1 harbors overlapping quantitative trait loci (QTL) for cytokine production and experimental models of inflammatory diseases. We fine-dissected this region that regulated cytokine production, myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), anti-MOG antibodies and pristane-induced arthritis (PIA) in advanced intercross lines (AILs). Analysis in the tenth and twelfth generation of AILs resolved the region in two narrow QTL, Eae30 and Eae31. Eae30 showed linkage to MOG-EAE, anti-MOG antibodies and levels of interleukin-6 (IL-6). Eae31 showed linkage to EAE, PIA, anti-MOG antibodies and levels of tumor necrosis factor (TNF) and IL-6. Confidence intervals defined a limited set of potential candidate genes, with the most interesting being RGMA, IL21R and IL4R. We tested the association with multiple sclerosis (MS) in a Nordic case-control material. A single nucleotide polymorphism in RGMA associated with MS in males (odds ratio (OR)=1.33). Polymorphisms of RGMA also correlated with changes in the expression of interferon-gamma (IFN-gamma) and TNF in cerebrospinal fluid of MS patients. In IL21R, there was one positively associated (OR=1.14) and two protective (OR=0.87 and 0.68) haplotypes. One of the protective haplotypes correlated to lower IFN-gamma expression in peripheral blood mononuclear cells of MS patients. We conclude that RGMA and IL21R and their pathways are crucial in MS pathogenesis and warrant further studies as potential biomarkers and therapeutic targets.

Differential effects of simvastatin and pravastatin on expression of Alzheimer's disease-related genes in human astrocytes and neuronal cells

Inhibitors of HMG-CoA reductase (statins) are widely used medications for reduction of cholesterol levels. Statin use significantly reduces risk of cardiovascular disease but has also been associated with lower risk of other diseases and conditions, including dementia. However, some reports suggest that statins also have detrimental effects on the brain. We provide evidence that simvastatin and pravastatin have significantly different effects on expression of genes related to neurodegeneration in astrocytes and neuroblastoma (SK-N-SH) cells in culture. Simvastatin significantly reduced expression of ABCA1 in astrocytes and neuroblastoma cells (by 79% and 97%, respectively; both P < 0.001). Pravastatin had a similar but attenuated effect on ABCA1 in astrocytes (-54%, P < 0.001) and neuroblastoma cells (-70%, P < 0.001). Simvastatin reduced expression of apolipoprotein E in astrocytes (P < 0.01). Furthermore, both statins reduced expression of microtubule-associated protein tau in astrocytes (P < 0.01), while both statins increased its expression in neuroblastoma cells (P < 0.01). In SK-N-SH cells, simvastatin significantly increased cyclin-dependent kinase 5 and glycogen synthase kinase 3beta expression, while pravastatin increased amyloid precursor protein expression. Our data suggest that simvastatin and pravastatin differentially affect expression of genes involved in neurodegeneration and that statin-dependent gene expression regulation is cell type specific.

Lovastatin induces the formation of abnormal myelin-like membrane sheets in primary oligodendrocytes

Statins, well-known inhibitors of cholesterol synthesis and protein isoprenylation, have been proposed as therapeutic drugs for multiple sclerosis (MS). As lovastatin and simvastatin, which are currently tested for their use in MS, can cross the blood-brain barrier, they may affect cellular processes in the central nervous system. This is especially relevant with respect to remyelination as a proposed additional treatment for MS, because cholesterol is a major component of myelin. Here, we show that primary oligodendrocytes, treated with lovastatin, form extensive membrane sheets, which contain galactosphingolipids. However, these membrane sheets are devoid of the major myelin proteins, myelin basic protein (MBP) and proteolipid protein (PLP). Reduced MBP protein expression was confirmed by SDS-PAGE and Western blotting, and in situ hybridization experiments revealed that lovastatin blocks MBP mRNA transport into oligodendrocyte processes. In contrast, PLP expression was only mildly affected by lovastatin. However, lovastatin treatment resulted in intracellular accumulation of PLP and prevented its translocation to the cell surface. Interestingly, another inhibitor of cholesterol synthesis (ro48-8071), which does not interfere with isoprenylation, had a similar effect on the localization of PLP, but it did not affect MBP expression and localization. These results suggest that lovastatin affects PLP transport predominantly by the inhibition of cholesterol synthesis, whereas reduced MBP expression is caused by impaired isoprenylation. Based on these results we recommend to carefully monitor the effect of statins on myelination prior to their use in demyelinating diseases.

Statins: mechanisms of neuroprotection

Clinical trials report that the class of drugs known as statins may be neuroprotective in Alzheimer's and Parkinson's disease, and further trials are currently underway to test whether these drugs are also beneficial in multiple sclerosis and acute stroke treatment. Since statins are well tolerated and have relatively few side effects, they may be considered as viable drugs to ameliorate neurodegenerative diseases. However, the mechanism of their neuroprotective effects is only partly understood. In this article, we review the current data on the neuroprotective effects of statins and their underlying mechanisms. In the first section, we detail the mechanisms by which statins affect cellular signalling. The primary action of statins is to inhibit cellular cholesterol synthesis. However, the cholesterol synthesis pathway also has several by-products, the non-sterol isoprenoids that are also important in cellular functioning. Furthermore, reduced cholesterol levels may deplete the cholesterol-rich membrane domains known as lipid rafts, which in turn could affect cellular signalling. In the second section, we summarize how the effects on signalling translate into general neuroprotective effects through peripheral systems. Statins improve blood-flow, reduce coagulation, modulate the immune system and reduce oxidative damage. The final section deals with the effects of statins on the central nervous system, particularly during Alzheimer's and Parkinson's disease, stroke and multiple sclerosis.

Combination therapy of lovastatin and rolipram provides neuroprotection and promotes neurorepair in inflammatory demyelination model of multiple sclerosis

Drug combination therapies for central nervous system (CNS) demyelinating diseases including multiple sclerosis (MS) are gaining momentum over monotherapy. Over the past decade, both in vitro and in vivo studies established that statins (HMG-CoA reductase inhibitors) and rolipram (phosphodiesterase-4 inhibitor; blocks the degradation of intracellular cyclic AMP) can prevent the progression of MS in affected individuals via different mechanisms of action. In this study, we evaluated the effectiveness of lovastatin (LOV) and rolipram (RLP) in combination therapy to promote neurorepair in an inflammatory CNS demyelination model of MS, experimental autoimmune encephalomyelitis (EAE). Combination treatment with suboptimal doses of these drugs in an established case of EAE (clinical disease score > or = 2.0) significantly attenuated the infiltration of inflammatory cells and protected myelin sheath and axonal integrity in the CNS. It was accompanied with elevated level of cyclic AMP and activation of its associated protein kinase A. Interestingly, combination treatment with these drugs impeded neurodegeneration and promoted neurorepair in established EAE animals (clinical disease score > or = 3.5) as verified by quantitative real-time polymerase chain reaction, immunohistochemistry and electron microscopic analyses. These effects of combination therapy were minimal and/or absent with either drug alone in these settings. Together, these data suggest that combination therapy with LOV and RLP has the potential to provide neuroprotection and promote neurorepair in MS, and may have uses in other related CNS demyelinating diseases.

Negative impact of statins on oligodendrocytes and myelin formation in vitro and in vivo

Statins are widely prescribed drugs in cardiovascular diseases. Recent studies also demonstrated anti-inflammatory and immunomodulatory properties of statins by modulating the activity of small GTPases. Statins are thus considered as potential therapeutic drug for the inflammatory demyelinating disease multiple sclerosis (MS). However, little is known about the effects of statins on myelin-forming oligodendrocytes. Here, we show that statins hamper process and myelin formation in vitro by interfering with Ras and Rho signaling in mature oligodendrocytes and provide evidence that statins impair ongoing remyelination in vivo. Our findings may have significant implications for the application of statins in MS patients and in other demyelinating diseases of the CNS.

Combined medication of lovastatin with rolipram suppresses severity of experimental autoimmune encephalomyelitis

Combinations of new medications or existing therapies are gaining momentum over monotherapy to treat central nervous system (CNS) demyelinating diseases including multiple sclerosis (MS). Recent studies established that statins (HMG-CoA reductase inhibitors) are effective in experimental autoimmune encephalomyelitis (EAE), an MS model and are promising candidates for future MS medication. Another drug, rolipram (phosphodiesterase-4 inhibitor) ameliorates the clinical severity of EAE via induction of various anti-inflammatory and neuroprotective activities. In this study, we tested whether combining the suboptimal doses of these drugs can suppress the severity of EAE. Prophylactic studies revealed that combined treatment with suboptimal doses of statins perform better than their individually administered optimal doses in EAE as evidenced by delayed clinical scores, reduced disease severity, and rapid recovery. Importantly, combination therapy suppressed the progression of disease in an established EAE case via attenuation of inflammation, axonal loss and demyelination. Combination treatment attenuated inflammatory T(H)1 and T(H)17 immune responses and induced T(H)2-biased immunity in the peripheral and CNS as revealed by serological, quantitative, and immunosorbant assay-based analyses. Moreover, the expansion of T regulatory (CD25(+)/Foxp3(+)) cells and self-immune tolerance was apparent in the CNS. These effects of combined drugs were reduced or minimal with either drug alone in this setting. In conclusion, our findings demonstrate that the combination of these drugs suppresses EAE severity and provides neuroprotection thereby suggesting that this pharmacological approach could be a better future therapeutic strategy to treat MS patients.