sirolimus and Demyelinating-Diseases

Despite evidence for prominent metabolic dysfunction within multiple sclerosis (MS) lesions, the mechanisms controlling metabolic shifts in oligodendroglia are poorly understood. The cuprizone model of demyelination and remyelination is a valuable tool for assessing metabolic insult during oligodendrocyte death and myelin degradation, closely resembling the distal oligodendrogliopathy seen in Pattern III MS lesions. In this review we discuss how metabolic processes in oligodendrocytes are disrupted in both MS and the cuprizone model, as well as the evidence for mechanistic target of rapamycin (mTOR) signaling as a key regulator of oligodendroglial metabolic function and efficient remyelination.

Topics: Animals; Cuprizone; Demyelinating Diseases; Humans; Mice; Mice, Inbred C57BL; Multiple Sclerosis; Oligodendroglia; Remyelination; Sirolimus; TOR Serine-Threonine Kinases

We have shown in vivo and in vitro previously that psychosine causes dysfunction of autophagy and the ubiquitin-proteasome system underlying the pathogenesis of globoid cell leukodystrophy (GLD), a devastating lysosomal storage disease complicated by global demyelination. Here, we investigated the therapeutic efficacy of the mTOR inhibitor rapamycin in twitcher mice, a murine model of infantile GLD, in biochemical, histochemical, and clinical aspects. Administration of rapamycin to twitcher mice inhibited mTOR signaling in the brains, and significantly reduced the accumulation of insoluble ubiquitinated protein and the formation of ubiquitin aggregates. The astrocytes and microglia reactivity were attenuated in that reactive astrocytes, ameboid microglia, and globoid cells were reduced in the brains of rapamycin-treated twitcher mice. Furthermore, rapamycin improved the cortical myelination, neurite density, and rescued the network complexity in the cortex of twitcher mice. The therapeutic action of rapamycin on the pathology of the twitcher mice's brains prolonged the longevity of treated twitcher mice. Overall, these findings validate the therapeutic efficacy of rapamycin and highlight enhancing degradation of aggregates as a therapeutic strategy to modulate neuroinflammation, demyelination, and disease progression of GLD and other leukodystrophies associated with intracellular aggregates.

Topics: Animals; Demyelinating Diseases; Galactosylceramidase; Leukodystrophy, Globoid Cell; Mice; Neuroinflammatory Diseases; Protein Aggregates; Sirolimus; TOR Serine-Threonine Kinases; Ubiquitins

Surgical decompression after spinal cord injury (SCI) is a conventional treatment. Although it has been proven to have clinical effects, there are certain limitations, such as the surgical conditions that must be met and the invasive nature of the treatment. Therefore, there is an urgent need to develop a simple and maneuverable therapy for the emergency treatment of patients with SCI before surgery. Rapamycin (RAPA) has been reported to have potential as a therapeutic agent for SCI. In this study, we observed the therapeutic effects of rapamycin and surgical decompression, in combination or separately, on the histopathology in rabbits with SCI. After combination therapy, intramedullary pressure (IMP) decreased significantly, autophagic flux increased, and apoptosis and demyelination were significantly reduced. Compared with RAPA/surgical decompression alone, the combination therapy had a significantly better effect. In addition, we evaluated the effects of mechanical pressure on autophagy after SCI by assessing changes in autophagic initiation, degradation, and flux. Increased IMP after SCI inhibited autophagic degradation and impaired autophagic flux. Decompression improved autophagic flux after SCI. Our findings provide novel evidence of a promising strategy for the treatment of SCI in the future. The combination therapy may effectively improve emergency treatment after SCI and promote the therapeutic effect of decompression. This study also contributes to a better understanding of the effects of mechanical pressure on autophagy after neurotrauma.

Topics: Animals; Apoptosis; Autophagy; Cell Count; Decompression, Surgical; Demyelinating Diseases; Disease Models, Animal; Female; Neurons; Rabbits; Sirolimus; Spinal Cord; Spinal Cord Injuries

Demyelination occurs following many neurological insults, most notably in multiple sclerosis (MS). Therapeutics that promote remyelination could slow the neurological decline associated with chronic demyelination; however, in vivo testing of candidate small molecule drugs and signaling cascades known to impact myelination is expensive and labor intensive. Here, we describe the development of a novel zebrafish line which uses the putative promoter of Myelin Protein Zero (mpz), a major structural protein in myelin, to drive expression of Enhanced Green Fluorescent Protein (mEGFP) specifically in the processes and nascent internodes of myelinating glia. We observe that changes in fluorescence intensity in Tg(mpz:mEGFP) larvae are a reliable surrogate for changes in myelin membrane production per se in live larvae following bath application of drugs. These changes in fluorescence are strongly predictive of changes in myelin-specific mRNAs [mpz, 36K and myelin basic protein (mbp)] and protein production (Mbp). Finally, we observe that certain drugs alter nascent internode number and length, impacting the overall amount of myelin membrane synthesized and a number of axons myelinated without significantly changing the number of myelinating oligodendrocytes. These studies demonstrate that the Tg(mpz:mEGFP) reporter line responds effectively to positive and negative small molecule regulators of myelination, and could be useful for identifying candidate drugs that specifically target myelin membrane production in vivo. Combined with high throughput cell-based screening of large chemical libraries and automated imaging systems, this transgenic line is useful for rapid large scale whole animal screening to identify novel myelinating small molecule compounds in vivo.

Topics: Animals; Animals, Genetically Modified; Culture Media, Conditioned; Demyelinating Diseases; Disease Models, Animal; Embryo, Nonmammalian; Embryonic Stem Cells; Gene Expression Regulation, Developmental; Green Fluorescent Proteins; Immunosuppressive Agents; Larva; Luminescent Proteins; Myelin Basic Protein; Myelin P0 Protein; Myelin Sheath; Neuroglia; Oligodendroglia; Red Fluorescent Protein; Sirolimus; SOXE Transcription Factors; Spinal Cord; Zebrafish; Zebrafish Proteins

Persistent demyelination has been implicated in axon damage and functional deficits underlying neurodegenerative diseases such as multiple sclerosis. The cuprizone diet model of demyelination allows for the investigation of mechanisms underlying timed and reproducible demyelination and remyelination. However, spontaneous oligodendrocyte (OL) progenitor (OPC) proliferation, OPC differentiation, and axon remyelination during cuprizone diet may convolute the understanding of remyelinating events. The Akt (a serine/threonine kinase)/mTOR (the mammalian target of rapamycin) signaling pathway in OLs regulates intermediate steps during myelination. Thus, in an effort to inhibit spontaneous remyelination, the mTOR inhibitor rapamycin has been administered during cuprizone diet. Intrigued by the potential for rapamycin to optimize the cuprizone model by producing more complete demyelination, we sought to characterize the effects of rapamycin on axonal function and myelination. Functional remyelination was assessed by callosal compound action potential (CAP) recordings along with immunohistochemistry in mice treated with rapamycin during cuprizone diet. Rapamycin groups exhibited similar myelination, but significantly increased axonal damage and inflammation compared to non-rapamycin groups. There was minimal change in CAP amplitude between groups, however, a significant decrease in conduction velocity of the slower, non-myelinated CAP component was observed in the rapamycin group relative to the non-rapamycin group. During remyelination, rapamycin groups showed a significant decrease in OPC proliferation and mature OLs, suggesting a delay in OPC differentiation kinetics. In conclusion, we question the use of rapamycin to produce consistent demyelination as rapamycin increased inflammation and axonal damage, without affecting myelination.

Topics: Animals; Axons; Cell Differentiation; Corpus Callosum; Cuprizone; Demyelinating Diseases; Male; Mice, Inbred C57BL; Myelin Sheath; Oligodendroglia; Sirolimus; TOR Serine-Threonine Kinases

The immunomodulatory and anti-inflammatory properties of bone marrow-derived mesenchymal stem cells (BM-MSCs) have been considered as an appropriate candidate for treatment of autoimmune diseases. Previous studies have revealed that treatment with BM-MSCs may modulate immune responses and alleviate the symptoms in experimental autoimmune encephalomyelitis (EAE) mice, an animal model of multiple sclerosis. Therefore, the present study was designed to examine immunomodulatory effects of BM-MSCs in the treatment of myelin oligodendrocyte glycoprotein (MOG) 35-55-induced EAE in C57BL/6 mice. MSCs were obtained from the bone marrow of C57BL mice, cultured with DMEM/F12, and characterized with flow cytometry for the presence of cell surface markers for BM-MSCs. Following three passages, BM-MSCs were injected intraperitoneally into EAE mice alone or in combination with rapamycin. Immunological and histopathological effects of BM-MSCs and addition of rapamycin to BM-MSCs were evaluated. The results demonstrated that adding rapamycin to BM-MSCs transplantation in EAE mice significantly reduced inflammation infiltration and demyelination, enhanced the immunomodulatory functions, and inhibited progress of neurological impairments compared to BM-MSC transplantation and control groups. The immunological effects of rapamycin and BM-MSC treatments were associated with the inhibition of the Ag-specific lymphocyte proliferation, CD8+ cytolytic activity, and the Th1-type cytokine (gamma-interferon (IFN-γ)) and the increase of Th-2 cytokine (interleukin-4 (IL-4) and IL-10) production. Addition of rapamycin to BM-MSCs was able to ameliorate neurological deficits and provide neuroprotective effects in EAE. This suggests the potential of rapamycin and BM-MSC combined therapy to play neuroprotective roles in the treatment of neuroinflammatory disorders.

Topics: Animals; Anti-Inflammatory Agents; Cell Differentiation; Cell Proliferation; Demyelinating Diseases; Encephalomyelitis, Autoimmune, Experimental; Female; Immunomodulation; Inflammation; Mesenchymal Stem Cell Transplantation; Mesenchymal Stem Cells; Mice, Inbred C57BL; Sirolimus; T-Lymphocytes, Cytotoxic

Used in combination with immunomodulatory therapies, remyelinating therapies are a viable therapeutic approach for treating individuals with multiple sclerosis. Studies of postmortem MS brains identified greater remyelination in demyelinated cerebral cortex than in demyelinated brain white matter and implicated reactive astrocytes as an inhibitor of white matter remyelination. An animal model that recapitulates these phenotypes would benefit the development of remyelination therapeutics. We have used a modified cuprizone protocol that causes a consistent and robust demyelination of mouse white matter and cerebral cortex. Spontaneous remyelination occurred significantly faster in the cerebral cortex than in white matter and reactive astrocytes were more abundant in white matter lesions. Remyelination of white matter and cerebral cortex was therapeutically enhanced by daily injections of thyroid hormone triiodothyronine (T3). In summary, we describe an in vivo demyelination/remyelination paradigm that can be powered to determine efficacy of therapies that enhance white matter and cortical remyelination.

Topics: Animals; Axons; Brain; Calcium-Binding Proteins; Cuprizone; Demyelinating Diseases; Disease Models, Animal; Glial Fibrillary Acidic Protein; Gliosis; Immunosuppressive Agents; In Vitro Techniques; Male; Mice; Mice, Inbred C57BL; Microfilament Proteins; Monoamine Oxidase Inhibitors; Myelin Proteolipid Protein; Regeneration; Sirolimus; Time Factors; Triiodothyronine; White Matter

In the central nervous system, demyelinating diseases, such as multiple sclerosis, result in devastating long-term neurologic damage, in part because of the lack of effective remyelination in the adult human brain. One model used to understand the mechanisms regulating remyelination is cuprizone-induced demyelination, which allows investigation of remyelination mechanisms in adult animals following toxin-induced demyelination. Unfortunately, the degree of demyelination in the cuprizone model can vary, which complicates understanding the process of remyelination. Previous work in our laboratory demonstrated that the Akt/mTOR pathway regulates active myelination. When given to young postnatal mice, the mTOR inhibitor, rapamycin, inhibits active myelination. In the current study, the cuprizone model was modified by the addition of rapamycin during cuprizone exposure. When administered together, cuprizone and rapamycin produced more complete demyelination and provided a longer time frame over which to investigate remyelination than treatment with cuprizone alone. The consistency in demyelination will allow a better understanding of the mechanisms initiating remyelination. Furthermore, the slower rate of remyelination provides a longer window of time in which to investigate the diverse contributing factors that regulate remyelination. This new model of cuprizone-induced demyelination could potentially aid in identification of new therapeutic targets to enhance remyelination in demyelinating diseases.

Topics: Analysis of Variance; Animals; Basic Helix-Loop-Helix Transcription Factors; Body Weight; Brain; Cuprizone; Demyelinating Diseases; Disease Models, Animal; Immunosuppressive Agents; Ki-67 Antigen; Male; Mice; Mice, Inbred C57BL; Monoamine Oxidase Inhibitors; Myelin Sheath; Myelin-Oligodendrocyte Glycoprotein; Nerve Tissue Proteins; Oligodendrocyte Transcription Factor 2; Oligodendroglia; Receptor, Platelet-Derived Growth Factor alpha; Sirolimus

Hippocampal demyelination, a common feature of postmortem multiple sclerosis (MS) brains, reduces neuronal gene expression and is a likely contributor to the memory impairment that is found in >40% of individuals with MS. How demyelination alters neuronal gene expression is unknown.. To explore whether loss of hippocampal myelin alters expression of neuronal microRNAs (miRNAs), we compared miRNA profiles from myelinated and demyelinated hippocampi from postmortem MS brains and performed validation studies.. A network-based interaction analysis depicts a correlation between increased neuronal miRNAs and decreased neuronal genes identified in our previous study. The neuronal miRNA miR-124 was increased in demyelinated MS hippocampi and targets mRNAs encoding 26 neuronal proteins that were decreased in demyelinated hippocampus, including the ionotrophic glutamate receptors AMPA2 and AMPA3. Hippocampal demyelination in mice also increased miR-124, reduced expression of AMPA receptors, and decreased memory performance in water maze tests. Remyelination of the mouse hippocampus reversed these changes.. We establish here that myelin alters neuronal gene expression and function by modulating the levels of the neuronal miRNA miR-124. Inhibition of miR-124 in hippocampal neurons may provide a therapeutic approach to improve memory performance in MS patients.

Topics: Animals; Cuprizone; Demyelinating Diseases; Disease Models, Animal; Gene Expression Regulation; Hippocampus; Humans; Immunosuppressive Agents; Memory Disorders; Mice; MicroRNAs; Monoamine Oxidase Inhibitors; Multiple Sclerosis; Neurons; Postmortem Changes; Receptors, AMPA; RNA, Messenger; Sirolimus

Misexpression and cytosolic retention of peripheral myelin protein 22 (PMP22) within Schwann cells (SCs) is associated with a genetically heterogeneous group of demyelinating peripheral neuropathies. PMP22 overproducer C22 and spontaneous mutant Trembler J (TrJ) mice display neuropathic phenotypes and affected nerves contain abnormally localized PMP22. Nutrient deprivation-induced autophagy is able to suppress the formation of PMP22 aggregates in a toxin-induced cellular model, and improve locomotor performance and myelination in TrJ mice. As a step toward therapies, we assessed whether pharmacological activation of autophagy by rapamycin (RM) could facilitate the processing of PMP22 within neuropathic SCs and enhance their capacity to myelinate peripheral axons. Exposure of mouse SCs to RM induced autophagy in a dose- and time-dependent manner and decreased the accumulation of poly-ubiquitinated substrates. The treatment of myelinating dorsal root ganglion (DRG) explant cultures from neuropathic mice with RM (25 nm) improved the processing of PMP22 and increased the abundance and length of myelin internodes, as well as the expression of myelin proteins. Notably, RM is similarly effective in both the C22 and TrJ model, signifying that the benefit overlaps among distinct genetic models of PMP22 neuropathies. Furthermore, lentivirus-mediated shRNA knockdown of the autophagy-related gene 12 (Atg12) abolished the activation of autophagy and the increase in myelin proteins, demonstrating that autophagy is critical for the observed improvement. Together, these results support the potential use of RM and other autophagy-enhancing compounds as therapeutic agents for PMP22-associated demyelinating neuropathies.

Topics: Animals; Autophagy; Demyelinating Diseases; Female; Gene Knockdown Techniques; Male; Mice; Mice, Neurologic Mutants; Myelin Sheath; Nerve Fibers, Myelinated; Neuralgia; Organ Culture Techniques; Sirolimus

Liver transplantation is associated with a number of neurological complications. We herein report a case of chronic inflammatory demyelinating polyneuropathy associated with the use of sirolimus-based immunosuppression. The patient was treated by converting the immunosuppression from sirolimus to cyclosporine and by a short course of oral steroids. Following this, we observed almost complete clinical and electrophysiologic resolution of this syndrome. We believe that this is the first described case of such a complication occurring in association with sirolimus. This immunosuppressive agent can, therefore, lead to neurological complications similar to the ones that have been observed with calcineurin inhibitors.

Topics: alpha 1-Antitrypsin Deficiency; Cyclosporine; Demyelinating Diseases; Humans; Immunosuppressive Agents; Liver Transplantation; Male; Middle Aged; Polyneuropathies; Sirolimus

We describe the first case of sirolimus-induced drug fever in a female liver transplant recipient, with a history of hepatitis C-induced end-stage liver cirrhosis in 1999. In 2005, six years after transplantation, she developed calcineurin inhibitor-induced renal function impairment. Immunosuppression was switched from tacrolimus to sirolimus. Two days after the intake of sirolimus, she developed daily fever spikes, but no infectious focus was found. Antibiotic therapy had no influence on the fever. After fourteen days, sirolimus was switched back to tacrolimus and the fever disappeared. In history, the patient developed ciclosporin-induced generalized seizures eleven days after liver transplantation, followed by the development of a motoric speech disorder. Magnetic resonance imaging (MRI) findings were consistent with leucoencephalopathy, therefore immunosuppressive therapy was changed from ciclosporin to tacrolimus and the neurologic symptoms improved significantly. Our case is the first reported case of sirolimus-induced drug fever. In addition, the patient showed the rare occurrence of ciclosporin-induced leukencephalopathy with seizures.

Topics: Cyclosporine; Demyelinating Diseases; Female; Fever; Humans; Immunosuppressive Agents; Liver Transplantation; Middle Aged; Sirolimus