Genetic variants within the MAP kinase signalling network and anti-TNF treatment response in rheumatoid arthritis patients.

BACKGROUND: Rheumatoid arthritis (RA) does not always respond to available treatments, including tumour necrosis factor (TNF) antagonists. A study was undertaken to investigate whether genetic variation within genes, encoding proteins in the p38 signalling network, contributes to the variable response to TNF antagonists. METHODS: 1102 UK Caucasian patients with RA receiving anti-TNF therapy (infliximab, adalimumab and etanercept) were genotyped for 38 pairwise-tagging single nucleotide polymorphisms (SNPs) spanning 12 candidate genes from the p38 network. Regression analyses were performed to test association between genotype and treatment response at 6 months using both absolute change in DAS28 (Disease Activity Score across 28 joints) and European League Against Rheumatism (EULAR) improvement criteria. Stratified analyses were performed to investigate association with individual therapies. RESULTS: Seven SNPs, in five genes, were associated with improvement in DAS28 at 6 months at a nominal 0.1 significance level, jointly explaining 3% of variance in outcome in a model adjusting for other predictors. These encoded proteins both upstream (MKK6) and downstream (MAPKAPK2, MSK1, MSK2) of p38, and MAPK14, the p38-α isoform of p38 MAPK. One SNP (rs2716191 in MAP2K6) was associated with EULAR response at the 0.1 level. SNPs generally showed greater correlation with response to infliximab and adalimumab, but not to etanercept. CONCLUSIONS: More SNPs than would be expected by chance, mapping to the p38 signalling network, showed association with the anti-TNF response as a whole, and particularly with the response to infliximab and adalimumab. Validation of these findings in independent cohorts is warranted.

Vitamin D3 down-regulates intracellular Toll-like receptor 9 expression and Toll-like receptor 9-induced IL-6 production in human monocytes.

OBJECTIVE: To determine whether vitamin D(3) modulates monocytic expression of intracellular Toll-like receptors (TLRs) 3, 7 and 9. METHODS: Human monocytes were isolated from peripheral blood and cultured with 100 nM vitamin D(3) for 24, 48 and 72 h. Expression of CD14 and TLR2, TLR3, TLR4, TLR7 and TLR9 were examined by flow cytometry. Monocytes exposed to vitamin D(3) for 48 h were then stimulated with a TLR9 agonist for a further 24 h. The level of IL-6 secretion was measured by ELISA. RESULTS: CD14 was up-regulated, whereas TLR2, TLR4 and TLR9 expression was down-regulated by vitamin D(3) exposure in a time-dependent manner. TLR3 expression was unaffected by vitamin D(3) and there was no measurable expression of TLR7 on the monocytes. TLR9-induced IL-6 production was impaired in monocytes treated with vitamin D(3) compared with untreated cells. CONCLUSION: The intracellular TLRs are differentially regulated by vitamin D(3), with TLR9 being down-regulated by vitamin D(3) exposure whereas TLR3 was unaffected. This decreased TLR9 expression in monocytes had a downstream functional effect as these cells subsequently secreted less IL-6 in response to TLR9 challenge. This may have significant biological relevance and may be a factor in the association of vitamin D deficiency with susceptibility to autoimmune disease.

p38(MAPK): stress responses from molecular mechanisms to therapeutics.

The p38(MAPK) protein kinases affect a variety of intracellular responses, with well-recognized roles in inflammation, cell-cycle regulation, cell death, development, differentiation, senescence and tumorigenesis. In this review, we examine the regulatory and effector components of this pathway, focusing on their emerging roles in biological processes involved in different pathologies. We summarize how this pathway has been exploited for the development of therapeutics and discuss the potential obstacles of targeting this promiscuous protein kinase pathway for the treatment of different diseases. Furthermore, we discuss how the p38(MAPK) pathway might be best exploited for the development of more effective therapeutics with minimal side effects in a range of specific disease settings.