Background/Purpose:  GCA has been considered a Th1-mediated disease. In recent years it has become apparent that Th17-mediated mechanisms may also play a role in GCA pathogenesis. Interleukin-12 is a heterodimeric cytokine (p35/p40) involved in Th1 functional differentiation of T lymphocytes. When combining with p19 subunit, p40 compose IL-23, a powerful pro-inflammatory cytokine that promotes Th17 response. P40, p35 and p19 are known to be expressed in GCA lesions but their distribution, association and functional roles have not been investigated. The aims of this study were 1) to investigate IL12p40, IL12p35 and IL23p19 subunit expression in GCA lesions and their combination to conform different cytokines 2) to investigate the effect of glucocorticoid treatment on subunit expression 3) to explore functional roles of p40 by culturing temporal artery sections with a neutralizing anti-human IL12/IL23p40 antibody.

Methods:  IL-12/IL23p40, IL12p35 and IL23p19 mRNA were measured by qRT-PCR in temporal arteries from 50 patients with biopsy-proven GCA and 20 patients with negative temporal artery biopsies, eventually diagnosed with other conditions. 36 patients were treatment naïve and 14 had received glucocorticoid treatment for 7 days (range 2-12) before the performance of temporal artery biopsy. Cytokine subunit distribution was assessed by immunofluorescence. Proximity ligation assay (PLA) was used to assess spatial relationship between subunits to conform different cytokines. Temporal arteries from 10 patients and 10 controls were cultured on 3D-matrix (Matrigel) and exposed to a neutralizing goat anti-human p40 antibody (R&D Systems) or dexamethasone (0.5 μg/mL) .Mann-Whitney test was used for statistical analysis.

Results: p40 and p19 mRNA concentrations were significantly higher in patients than in controls .No significant differences were found in constitutively expressed p35 mRNA levels between patients and controls. P40 and p19 mRNA expression was significantly decreased in treated GCA patients versus those treatment-naïve. Interestingly, immunofluorescence staining revealed intense p19 expression by inflammatory cells, independent from p40 expression. Although p40 expression was less abundant than other subunits, association between subunits to conform IL-23 could be confirmed by PLA in GCA lesions. Neutralization of IL-12/IL-23p40 tended to reduce IFNg mRNA production in cultured temporal arteries from GCA patients with no effect on IL-17, TNFa or IL-6. Dexamethasone significantly down-regulated IFNg, IL-17, TNFa and IL-6 in cultured arteries.

Conclusion: p40 and p19 mRNA expression are increased in active lesions from patients with GCA and decrease with glucocorticoid treatment. P19 subunit is much more expressed than p40 in GCA temporal arteries, indicating an independent role for p19 or its potential association with unidentified subunits. Neutralization of IL12/IL23p40 seems to mainly inhibit the Th1-mediated pathway by reducing IFNg levels. Supported by SAF 2014 57708-R , PIE13/00033 and FEDER.

« Back to 2016 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/expression-and-function-of-il-1223-related-cytokine-subunits-p35-p40-and-p19-in-giant-cell-arteritis-lesions-potential-role-of-p40-in-promoting-th1-mediated-pathways/