title: Phosphodiesterase-5 inhibition promotes remyelination by MCP-1/CCR-2 and MMP-9 regulation in a cuprizone-induced demyelination model.
abstract: While it has recently been shown that sildenafil (Viagra®) has a protective effect on myelination/remyelination, the mechanism of this protection is still unknown. In general, cytokines, chemokines and metalloproteinases have a pro-inflammatory action, but can also exert a role in modulating glial cell activation, contributing to the balance of cell response. Investigating these molecules can contribute to clarifying the mechanisms of sildenafil neuroprotection. In addition, it is not known whether sildenafil is able to restore an already installed neurodegenerative process or if the treatment period is critical for its action. The aim of the present study was to evaluate, in a cuprizone (CPZ)-induced demyelination model, the effects and mechanisms of time-dependent treatment with sildenafil (beginning 15 days after neurodegeneration and continuing for 15 days, or starting concomitantly with neurodegeneration and continuing for 30 days) on neuroinflammation and remyelination. Neuroinflammation and demyelination induced by CPZ in rodents has been widely used as a model of multiple sclerosis (MS). In the present study, five male C57BL/6 mice aged 7-10 weeks were used per group. For four weeks, the groups received either cuprizone (CPZ) 0.2% mixed in feed or CPZ combined with the administration of sildenafil (Viagra®, Pfizer, 25 mg/kg) orally in drinking water, starting concurrently with (sild-T0) or 15 days (sild-T15) after the start of CPZ treatment. Control animals received pure food and water. The cerebella were dissected and processed for immunohistochemistry, immunofluorescence (frozen), Western blotting, Luxol fast blue staining and transmission electron microscopy. Magnetic resonance was performed for live animals, after the same treatment, using CPZ 0.3%. CPZ induced an increase in the expression of IL-1β and a decrease in MCP-1, CCR-2, MBP and GST-pi, as well as promoting damage in the structure and ultra-structure of the myelin sheath. Interestingly, the administering of sild-T0 promoted a further increase of MMP-9, MCP-1, and CCR-2, possibly contributing to changes in the microglia phenotype, which becomes more phagocytic, cleaning myelin debris. It was also observed that, after sild-T0 treatment, the expression of GST-pi and MBP increased and the myelin structure was improved. However, sild-T15 was not efficient in all aspects, probably due to the short treatment period and to starting after the installation of the degenerative process. Therefore, the present study shows that sildenafil modulates inflammation, with the involvement of MMP-9, MCP-1, and CCR-2, and also contributes to myelin repair. These protective effects were dependent on the therapeutic strategy used. This clarification can strengthen research proposals into the mechanism of action of sildenafil and contribute to the control of neurodegenerative diseases such as MS.
authors.affiliation: Laboratory of Ultrastructure, Aggeu Magalhães Research Center (CPqAM), Recife, PE, Brazil; Federal University of Pernambuco, Brazil. Electronic address: nunes.aks@gmail.com.
authors.forename: Ana Karolina de Santana
authors.initials: AK
authors.lastname: Nunes
authors.affiliation: Department of Biochemistry and Tissue Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Catarina
authors.initials: C
authors.lastname: Rapôso
authors.affiliation: Laboratory of Ultrastructure, Aggeu Magalhães Research Center (CPqAM), Recife, PE, Brazil; Federal University of Pernambuco, Brazil.
authors.forename: Wilma Helena
authors.initials: WH
authors.lastname: de Oliveira
authors.affiliation: Department of Structural and Functional Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Thomé
authors.affiliation: Department of Structural and Functional Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: Liana
authors.initials: L
authors.lastname: Verinaud
authors.affiliation: D'Or Institute for Research and Education (IDOR) and Institute of Biomedical Sciences (ICB); and National Center of Structural Biology and Bioimaging (CENABIO), Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Tovar-Moll
authors.affiliation: Laboratory of Ultrastructure, Aggeu Magalhães Research Center (CPqAM), Recife, PE, Brazil.
authors.forename: Christina Alves
authors.initials: CA
authors.lastname: Peixoto
mesh_terms: D000818:Animals; D018932:Chemokine CCL2 / Q000378:metabolism*; D003471:Cuprizone; D003711:Demyelinating Diseases / Q000139:chemically induced / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D009103:Multiple Sclerosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D009186:Myelin Sheath / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D054390:Receptors, CCR2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D000068677:Sildenafil Citrate / Q000494:pharmacology*
chemical_list: C491768:Ccl2 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D058986:Phosphodiesterase 5 Inhibitors; D054390:Receptors, CCR2; D003471:Cuprizone; D000068677:Sildenafil Citrate; D020780:Matrix Metalloproteinase 9
keywords: Cuprizone; Demyelination; Neuroinflammation; Oligodendrocyte; Sildenafil