Expression of CX3C chemokine, fractalkine, and its receptor CX3CR1 in experimental autoimmune anterior uveitis.
OBJECTIVE
To demonstrate the expression and location of CX3C chemokine, fractalkine, and its receptor, CX3CR1, in the iris/ciliary body and thus establish their roles in experimental autoimmune anterior uveitis, an animal model of human acute anterior uveitis.


METHODS
Uveitis was induced in Lewis rats by injection of melanin associated antigen into the peritoneum and footpad. At defined times, fractalkine and its receptor CX3CR1 mRNA expression in the iris/ciliary body were measured by using a semiquantitative polymerase chain reaction method. Fractalkine in aqueous humor was determined by enzyme linked immunosorbent assay. The cellular sources of fractalkine were determined by immunhistochemical staining. In a separate experiment, NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC; 200 mg/kg/day) was administrated intraperitoneally daily after immunization. The rats were sacrificed on day 14 of immunization. Fractalkine mRNA in iris/ciliary body and fractalkine concentration in aqueous humor were determined after PDTC treatment.


RESULTS
Fractalkine mRNA was found to be upregulated in the iris/ciliary body nine days after immunization, preceding clinical disease onset. CX3CR1 mRNA exhibited peak levels at day 14, coincident with disease onset. Fractalkine in aqueous humor showed an expression profile similar to mRNA expression. PDTC (200 mg/kg) markedly inhibited the expression of fractalkine mRNA in the iris/ciliary body, and fractalkine protein in aqueous humor. Immunohistochemical staining revealed that fractalkine was expressed on vascular endothelial cells and infiltrated inflammatory cells. Treatment with PDTC significantly reduced both the number of leukocyte infiltrations in the iris/ciliary body and fractalkine expression on vascular endothelial cells.


CONCLUSIONS
The sequential expression of fractalkine may direct distinct CX3CR1 receptor expressing mononuclear cell subsets to inflammatory sites. Fractalkine expression is modulated, at least in part, through the NF-kappaB signaling pathway. These findings provide new insight into the molecular mechanisms of acute anterior uveitis and suggest fractalkine or NF-kappaB as a new drug target for uveitis therapy.
Fang
I-Mo
IM
Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.
Lin
Chang-Pin
CP
Yang
Chung-May
CM
Chen
Muh-Shy
MS
Yang
Chang-Hao
CH
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D001327:Autoimmune Diseases / Q000378:metabolism*; D000073883:CX3C Chemokine Receptor 1; D002417:Cattle; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C / Q000235:genetics* / Q000378:metabolism; D002924:Ciliary Body / Q000378:metabolism; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D007150:Immunohistochemistry; D007498:Iris / Q000378:metabolism; D007962:Leukocytes / Q000378:metabolism; D008543:Melanins; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000502:physiology; D011392:Proline / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D018121:Receptors, Cytokine / Q000235:genetics* / Q000378:metabolism; D015728:Receptors, HIV / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013859:Thiocarbamates / Q000494:pharmacology; D015854:Up-Regulation; D014606:Uveitis, Anterior / Q000378:metabolism*
D000073883:CX3C Chemokine Receptor 1; C515538:CX3CL1 protein, human; D054428:Chemokine CX3CL1; D020523:Chemokines, CX3C; C515540:Cx3cl1 protein, rat; D008543:Melanins; D008565:Membrane Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D015728:Receptors, HIV; D013859:Thiocarbamates; C066229:prolinedithiocarbamate; D011392:Proline