Association analysis of TGFBR3 gene with Behçet's disease and idiopathic intermediate uveitis in a Caucasian population.

BACKGROUND: Transforming growth factor ß (TGFß) is an important immunoregulatory cytokine in regulatory T cell (Treg) and Th17-mediated pathology, including uveitis due to Behçet's disease (BD). Of the three isoforms, TGFß2 is found at highest levels in the aqueous humour of uninflamed eyes. TGFß signals through a cell-surface receptor comprising three subunits (TGFBR1, 2 and 3). TGFBR3 is considered necessary for TGFß2 signal transduction, but not for other isoforms. A polymorphism in TGFBR3 (rs1805110) has previously been identified in Han Chinese patients with BD. We investigated the frequency of this polymorphism in a Caucasian population with BD and idiopathic intermediate uveitis (IIU). METHODS: The single-nucleotide polymorphism (SNP) rs1805110 in TGFBR3 was genotyped in 75 BD patients, 92 IIU disease controls and 85 disease-free controls. The association with both diseases was analysed using Fisher's exact test. RESULTS: No significant difference in rs1805110 allele or genotype frequency was observed. A low frequency of the T allele was observed (5.88% control, 9.33% BD, 10.33% IIU) with the TT genotype absent in patients with BD and IIU (1.18% control, 0% BD and 0% IIU). Stratification analysis according to clinical features of BD did not associate with the tested SNP. CONCLUSIONS: RS1805110 is not associated with BD or IIU in Caucasian patients. The T allele frequency is consistent with that presented for Caucasian populations in the HapMap database (p>0.05). Our results differ from the previous analysis in Han Chinese patients (p<0.0001), however, the possibility of having a much smaller effect due to the low minority frequency cannot be excluded.

Cortisol biosynthesis in the human ocular surface innate immune response.

Innate immune responses have a critical role in regulating sight-threatening ocular surface (OcS) inflammation. While glucocorticoids (GCs) are frequently used to limit tissue damage, the role of intracrine GC (cortisol) bioavailability via 11-beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) in OcS defense, remains unresolved. We found that primary human corneal epithelial cells (PHCEC), fibroblasts (PHKF) and allogeneic macrophages (M1, GM-CSF; M2, M-CSF) were capable of generating cortisol (M1>PHKF>M2>PHCEC) but in corneal cells, this was independent of Toll-like receptor (TLR) activation. While PolyI∶C induced maximal cytokine and chemokine production from both PHCEC (IFNγ, CCL2, CCL3, and (CCL4), IL6, CXCL10, CCL5, TNFα) and PHKF (CCL2, IL-6, CXCL10, CCL5), only PHKF cytokines were inhibited by GCs. Both Poly I∶C and LPS challenged-corneal cells induced M1 chemotaxis (greatest LPS-PHKF (250%), but down-regulated M1 11ß-HSD1 activity (30 and 40% respectively). These data were supported by clinical studies demonstrating reduced human tear film cortisol∶cortisone ratios (a biomarker of local 11ß-HSD1 activity) in pseudomonas keratitis (1∶2.9) versus healthy controls (1∶1.3; p<0.05). This contrasted with putative TLR3-mediated OcS disease (Stevens-Johnson Syndrome, Mucous membrane pemphigoid) where an increase in cortisol∶cortisone ratio was observed (113.8∶1; p<0.05). In summary, cortisol biosynthesis in human corneal cells is independent of TLR activation and is likely to afford immunoprotection under physiological conditions. Contribution to ocular mucosal innate responses is dependent on the aetiology of immunological challenge.

Characterization of vitamin D production by human ocular barrier cells.

PURPOSE: Vitamin D3 is a secosteroid mainly synthesized from the conversion of the skin precursor 7-dehydrocholesterol (7DHC) to vitamin D3 by ultraviolet (UV) B sunlight. Extrarenal synthesis of vitamin D3 has been reported in many tissues and cells, including barrier sites. This study characterizes the expression of components of vitamin D3 signaling in human ocular barrier cells. METHODS: Primary human scleral fibroblasts (HSF), human corneal endothelial (HCEC-12), nonpigmented ciliary body epithelial (ODM-2), and adult retinal pigment epithelial (ARPE-19) cell lines were analyzed for the expression of vitamin D receptor (VDR), the vitamin D3 activating enzymes 1α-hydroxylase (CYP27B1), 25-hydroxylases (CYP27A1 and CYP2R1), the vitamin D3 inactivating enzyme 24-hydroxylase (CYP24A1), and the endocytic receptors cubilin and megalin using a combination of RT-PCR, immunocytochemistry, and enzyme immunoassay (EIA). RESULTS: The HSF, HCEC-12, ODM-2, and ARPE-19 express mRNA and protein for all vitamin D3 synthesizing and metabolizing components. The cell types tested, except HSF, are able to convert inactive 25-hydroxyvitamin D3 (25[OH]D3) into active 1,25-hydroxyvitamin D3 (1,25[OH]2D3). CONCLUSIONS: This novel study demonstrated that ocular barrier epithelial cells express the machinery for vitamin D3 and can produce 1,25(OH)2D3. We suggest that vitamin D3 might have a role in immune regulation and barrier function in ocular barrier epithelial cells.