Mechanisms Involved in the Remyelinating Effect of Sildenafil

Remyelination occurs in demyelinated lesions in multiple sclerosis (MS) and pharmacological treatments that enhance this process will critically impact the long term functional outcome in the disease. Sildenafil, a cyclic GMP (cGMP)-specific phosphodiesterase 5 inhibitor (PDE5-I), is an oral vasodilator drug extensively used in humans for treatment of erectile dysfunction and pulmonary arterial hypertension. PDE5 is expressed in central nervous system (CNS) neuronal and glial populations and in endothelial cells and numerous studies in rodent models of neurological disease have evidenced the neuroprotective potential of PDE5-Is. Using myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) as a MS model, we previously showed that daily administration of sildenafil starting at peak disease rapidly ameliorates clinical symptoms while administration at symptoms onset prevents disease progression. These beneficial effects of the drug involved down-regulation of adaptive and innate immune responses, protection of axons and oligodendrocytes (OLs) and promotion of remyelination. In this work we have investigated mechanisms involved in the remyelinating effect of sildenafil. Using demyelinated organotypic cerebellar slice cultures we demonstrate that sildenafil stimulates remyelination by direct effects on CNS cells in a nitric oxide (NO)-cGMP-protein kinase G (PKG)-dependent manner. We also show that sildenafil treatment enhances OL maturation and induces expression of the promyelinating factor ciliary neurotrophic factor (CNTF) in spinal cord of EAE mice and in cerebellar slice cultures. Furthermore, we demonstrate that sildenafil promotes a M2 phenotype in bone marrow derived macrophages (BMDM) and increases myelin phagocytosis in these cells and in M2 microglia/macrophages in the spinal cord of EAE mice. Taken together these data indicate that promotion of OL maturation directly or through induction of growth factor expression, regulation of microglia/macrophage inflammatory phenotype and clearance of myelin debris may be relevant mechanisms involved in sildenafil enhancement of remyelination in demyelinated tissue and further support the contention that this well tolerated drug could be useful for ameliorating MS pathology

The draft genome sequence of the spider Dysdera silvatica (Araneae, Dysderidae): A valuable resource for functional and evolutionary genomic studies in chelicerates

Background We present the draft genome sequence of Dysdera silvatica, a nocturnal ground-dwelling spider from a genus that has undergone a remarkable adaptive radiation in the Canary Islands. Results The draft assembly was obtained using short (Illumina) and long (PaciBio and Nanopore) sequencing reads. Our de novo assembly (1.36 Gb), which represents 80% of the genome size estimated by flow cytometry (1.7 Gb), is constituted by a high fraction of interspersed repetitive elements (53.8%). The assembly completeness, using BUSCO and core eukaryotic genes, ranges from 90% to 96%. Functional annotations based on both ab initio and evidence-based information (including D. silvatica RNA sequencing) yielded a total of 48,619 protein-coding sequences, of which 36,398 (74.9%) have the molecular hallmark of known protein domains, or sequence similarity with Swiss-Prot sequences. The D. silvatica assembly is the first representative of the superfamily Dysderoidea, and just the second available genome of Synspermiata, one of the major evolutionary lineages of the 'true spiders' (Araneomorphae). Conclusions Dysderoids, which are known for their numerous instances of adaptation to underground environments, include some of the few examples of trophic specialization within spiders and are excellent models for the study of cryptic female choice. This resource will be therefore useful as a starting point to study fundamental evolutionary and functional questions, including the molecular bases of the adaptation to extreme environments and ecological shifts, as well of the origin and evolution of relevant spider traits, such as the venom and silk