title: Systemic but not local administration of retinoic acid reduces early transcript levels of pro-inflammatory cytokines after experimental spinal cord injury.
abstract: Early rises of pro-inflammatory cytokines play a key role in tissue damage and has detrimental consequences for functional outcome after spinal cord injury (SCI). All-trans retinoic acid (RA) has been shown to be a therapeutic agent reducing cytokine expression in vitro, but its use may be limited due to adverse side effects associated with systemic delivery. Local delivery of RA may circumvent adverse side effects, but may simultaneously reduce the therapeutic benefits of the therapy. Here, we investigated whether local or systemic RA treatment differentially affected pro-inflammatory cytokine expression early after rat SCI. Pro-inflammatory cytokines IL-1β, IL-6 and TNFα were investigated at 6h after moderate contusion injury of the thoracic (T9) spinal cord, when mRNA levels are known to peak. Rats were either treated with intrathecal RA (0, 2.5, 10, or 100ng) or received an intraperitoneal injection of RA (15mg/kg bodyweight). Surprisingly intrathecal RA up to amounts of 100ng did not attenuate SCI-induced increases in gene-expression of pro-inflammatory cytokines. In contrast, intraperitoneal RA rendered a 60%, 35% and 58% reduction of IL-1β, IL-6 and TNFα mRNA levels, respectively. Although local doses higher than 100ng RA may reduce pro-inflammatory cytokine gene-expression, such doses precipitate and possibly increase risks of adverse side effects. We conclude that in contrast to systemic delivery, intrathecal administration of RA up to doses of 100ng is ineffective in reducing early pro-inflammatory cytokine gene-expression. Future studies are required to investigate the effects of single intraperitoneal RA treatment on long-term SCI outcome.
authors.affiliation: Department of Anesthesiology, School for Mental Health and Neuroscience, Maastricht University Medical Center, P. Debyelaan 25, 6202 AZ, Maastricht, The Netherlands. s.vanneerven@maastrichtuniversity.nl
authors.forename: S
authors.initials: S
authors.lastname: van Neerven
authors.forename: J
authors.initials: J
authors.lastname: Mey
authors.forename: E A
authors.initials: EA
authors.lastname: Joosten
authors.forename: H W
authors.initials: HW
authors.lastname: Steinbusch
authors.forename: M
authors.initials: M
authors.lastname: van Kleef
authors.forename: M A E
authors.initials: MA
authors.lastname: Marcus
authors.forename: R
authors.initials: R
authors.lastname: Deumens
mesh_terms: D000818:Animals; D005260:Female; D007249:Inflammation / Q000378:metabolism; D007274:Injections, Intraperitoneal; D007278:Injections, Spinal; D053583:Interleukin-1beta / Q000096:biosynthesis* / Q000235:genetics; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D015213:Neuroimmunomodulation; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000276:immunology / Q000378:metabolism*; D014212:Tretinoin / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D014212:Tretinoin