PDE4 inhibition in EAE mice: cAMP-PDEs and inflammatory cytokines mRNA expression analyses in spinal cord

Abstract

Experimental autoimmune encephalomyelitis (EAE) is an animal model of multiple sclerosis that courses with neuroinflammation, axonal damage and demyelination, characterized by T- and B-cell responses to myelin oligodendrocyte glycoprotein which produce a wide range of pro- and anti-inflammatory cytokines. PDE4B gene has been related to the inflammatory immune response in mice. We have previously shown that in the brain and spinal cord of EAE rats and mice there was a dramatic increase in the mRNA expression levels of the PDE4B2 mRNA splicing variant in infiltrating cells. We analyzed the expression of mRNA coding for PDE4A, PDE4B, PDE4D, PDE7A, PDE7B, pro-inflammatory and anti-inflammatory cytokines and several cellular markers by semiquantitative real-time PCR in spinal cord from EAE mice and compared it with animals treated with a “classic” PDE4 inhibitor, roflumilast along the different stages of the disease. Animals were treated i.p. daily with 10 mg/kg roflumilast from day 5 after the onset of the disease, and sacrificed at 10, 17, 21 and 40 days p.i. Mice chronically treated with roflumilast showed a slight lessening of clinical score compared to control and vehicle treated animals. We observed that roflumilast treatment maintained elevated expression levels of PDE4 and PDE7 mRNAs analyzed along treatment, especially at day 40. TNFalpha, COX-2, TGFbeta, IL-6 and IL-1beta mRNA levels were high at day 40 after roflumilast treatment. Alterations on expression of Tbx21 and IFNgamma (proinflammatory Th1 cells); Rorc and IL-17 (proinflammatory Th17 cells); FoxP3 and IL-10 (Treg) and Gata3 and IL-4 (anti-inflammatory Th2 response) were observed at day 40 for Th1 and Treg response. We will discuss on the relevance of PDE4 isozymes as therapeutic targets for the treatment of some neuroinflammatory diseases.