Inhibition of endotoxin-induced uveitis and potentiation of local TNF-alpha and interleukin-6 mRNA expression by interleukin-13.
OBJECTIVE
To investigate the effect of systemic injections of interleukin (IL)-13 on the development of endotoxin-induced uveitis (EIU) in the rat.


METHODS
EIU was induced in Lewis rats by a single footpad injection of lipopolysaccharide (LPS; 350 microg/kg) from Salmonella typhimurium. Rats were treated with a subcutaneous injection in the back of recombinant human IL-13 (50 microg/kg in 0.2 ml of saline) performed 30 minutes before LPS injection and 6 and 10 hours afterward. At 23 hours after LPS injection, EIU was evaluated by slit-lamp examination and by counts of inflammatory cells on cryostat sections after specific immunostaining. The expression of nitric oxide synthase (NOS)-II in ocular tissues was determined by dual immunofluorescent staining and the release of nitrite in aqueous humor by Griess reaction. Cytokine gene expression in the iris/ciliary body, choroid, and retina was evaluated by reverse transcription-polymerase chain reaction.


RESULTS
At 24 hours after LPS injection, significant clinical inhibition of ocular inflammation and fibrin deposition in the eye was observed in IL-13-treated rats. Quantitative analysis of ocular tissues revealed a significant decrease of OX42+ cells (microglia, activated macrophages, dendritic cells, and polymorphonuclear leukocytes) and ED-1+ cells (monocytes/macrophages and dendritic cells). No effect on ED2+ cells (resident tissue macrophages) was found. Treatment with IL-13 decreased nitrite levels in aqueous humor and enhanced the expression of tumor necrosis factor-alpha (TNF-alpha) and IL-6 mRNA in ocular tissues.


CONCLUSIONS
Interleukin-13 treatment inhibits LPS-induced ocular inflammation with inhibition of nitrite release and increased TNF and IL-6 production in the eye. These results confirm the role of the NO pathway in the pathogenesis of EIU and suggest the involvement of TNF and IL-6 in the downregulation of ocular inflammation.
Marie
O
O
INSERM U450, Development, Aging and Pathology of the Retina, Paris, France.
Thillaye-Goldenberg
B
B
Naud
M C
MC
de Kozak
Y
Y
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D017931:DNA Primers / Q000737:chemistry; D005123:Eye / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D018793:Interleukin-13 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics*; D008070:Lipopolysaccharides; D008297:Male; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012486:Salmonella typhimurium; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation; D014605:Uveitis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*
D017931:DNA Primers; D018793:Interleukin-13; D015850:Interleukin-6; D008070:Lipopolysaccharides; D009573:Nitrites; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019001:Nitric Oxide Synthase