Role of Phosphodiesterase PDE4 isoforms in the neuroinflammatory response of an EAE mice model

Abstract

Trabajo presentado a la Neuroscience celebrada en San Diego del 13 al 17 de noviembre de 2010.Inflammatory responses involve cAMP and pharmacological manipulation of cAMP levels by using specific phosphodiesterase (PDE) inhibitors provokes an anti-inflammatory response. Experimental autoimmune encephalomyelitis (EAE) is an animal model of the chronic inflammatory, neurodegenerative demyelinating disease multiple sclerosis (MS). Previously we demonstrated that in the brain and spinal cord of EAE rats there was a dramatic increase in the mRNA expression levels of the PDE4B isoenzyme, solely due to the splicing mRNA variant PDE4B2. This expression was found in the infiltrating T-cells and macrophage/microglia in microvessels and brain parenchima. We present here the study on the alterations in the expression of the cAMP-specific PDE4 and of several inflammatory cytokine mRNAs in the brain and spinal cord of C57BL6 EAE mice model by neuroanatomical techniques (double in situ hybridization histochemistry and immunohistochemistry), and quantitative real time RT-PCR. We observed a PDE4B2 mRNA upregulation after the onset of the EAE model, being significant 30 days post-immunization. No changes on PDE4B3 mRNA splice variant could be detected. Double in situ hybridization and immunohistochemistry studies showed that cellular infiltrates in brain and spinal cord tissues of EAE mice are overexpressing PDE4B isoform. Studies performed on PDE4A and PDE4B knockout (KO) mice showed an early onset of EAE in PDE4B KO mice, suggesting a “protective/retarding” role of PDE4B in this disease. RT-PCR experiments also detected a downregulation of some pro-inflammatory cytokines, like interferon-γ (IFNγ), in PDE4A KO mice and a trend to upregulation of interleukin 1β (IL1β) and IL6 in PDE4B KO mice. This differential response to EAE of PDE4A and PDE4B KO mice contrast with results obtained for EAE wt mice treated with a PDE4 inhibitor, rolipram. These findings support an important and distinctive role of different PDE4 isoforms during the neuroinflammatory response produced in a EAE model and their importance as a therapeutic target for the treatment of some neuroinflammatory diseases using subtype-selective PDE4 inhibitors.MICINN Grant SAF2006-10243; MICINN Grant SAF2009-11052; Sandler Foundation Grant to MC; CS IDIBAPS fellowship and EJ MICINN fellowship.Peer Reviewe