PTPN22 +788 G>A (R263Q) Polymorphism is Associated with mRNA Expression but it is not a Susceptibility Marker for Rheumatoid Arthritis Patients from Western Mexico.

PTPN22 represents an important non-HLA gene that has been strongly associated with rheumatoid arthritis (RA) pathogenesis. Several studies have reported a specific genetic variant for PTPN22 (+788 G>A; rs33996649) that might be associated with decreased RA risk in Caucasian population; nevertheless, its specific role in western Mexican population has not been yet described. A case-control study with 443 RA patients and 317 control subjects (CS) was conducted. The genotyping was performed by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) technique and the PTPN22 mRNA expression was determined by SYBR Green-based real-time quantitative-PCR assay. No association between the PTPN22 +788 G>A polymorphism and RA susceptibility in western Mexican population was found when comparing genotype and allelic frequencies between RA patients and CS (G/G vs. G/A: OR 0.55, p = 0.14, 95% CI 0.22-1.32; G vs. A: OR 0.56, p = 0.14, 95% CI 0.23-1.36). The PTPN22 mRNA expression increased 4.6-fold more in RA patients than in CS, and RA patients, carriers of PTPN22 +788 G/A genotype, expressed 15.6-fold more than RA patients carrying the homozygous G/G genotype. Overall, these results showed that the PTPN22 +788 G>A polymorphism is not associated with RA susceptibility in western Mexican population, whereas the presence of G/A genotype is associated with increased PTPN22 mRNA expression in RA patients.

Association of 86 bp variable number of tandem repeat (VNTR) polymorphism of interleukin-1 receptor antagonist (IL1RN) with susceptibility and clinical activity in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic, systemic disease of unknown etiology. Several studies have reported a variable number of tandem repeat (VNTR) 86 bp (rs2234663) in the intron 2 of IL1RN gene with RA risk. The present study was designed to determine the frequencies of this polymorphism in patients with RA and control subjects (CS) and its association with RA in a western Mexican population. An analytical cross-sectional study was performed, in which 350 patients with RA and 307 CS were included. The identification of IL1RN VNTR polymorphism was carried out by polymerase chain reaction (PCR), and genotypes were associated with clinical variables (DAS28 and CRP). The presence of A1/A2 genotype was associated with RA risk (p = 0.03, OR = 1.45, 95% CI = 1.02-2.05). Also, results indicate that the presence of heterozygote genotypes which include A2 was associated with RA risk (p = 0.01, OR = 1.5, 95% CI = 1.07-2.11). Patients carrier of A2/A2 genotype have a higher score of DAS28 (5.64 [4.49-6.70]). A-/A- has higher level of CRP (2.30 [0.62-9.10]) in comparison with A2/A- (1.06 [0.37-2.82]). A1/A2 genotype was associated with susceptibility to RA in a western Mexican population. The presence of the A2/A2 genotype in RA is associated with increased disease activity.

High expression of interleukine-1 receptor antagonist in rheumatoid arthritis: Association with IL1RN*2/2 genotype.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation and pro-inflammatory cytokines production. IL-1Ra is an anti-inflammatory cytokine codified by IL1RN gene that blocks IL-1 signalling. A VNTR polymorphism of 86 bp in IL1RN gene has been associated with RA risk and regulation of IL-1Ra expression. In this study, we determined mRNA and protein expression of IL-1Ra in RA patients and control subjects (CS). This study included 85 RA patients classified according to the ACR/EULAR 2010 criteria and 67 CS. Polymerase chain reaction was used to identify IL1RN VNTR polymorphism, the expression of sIL-1Ra (secreted isoform) mRNA was determined by SYBR Green-based real time quantitave-PCR assay, and IL-1Ra soluble levels quantification was evaluated by ELISA test. RA patients had higher soluble levels of IL-1Ra than CS (p < .01), sIL-1Ra mRNA expression was higher in RA patients compared to CS (p < .01). Carriers of IL1RN*2/2 homozygous genotype show increased IL-1Ra soluble levels compared to IL1RN*long/long and IL1RN*2/long genotypes (p < .05) in the CS group, whereas mRNA expression in carriers of IL1RN*2/2 genotype was 1.2 times higher compared to IL1RN*long/long genotypes in the same group. Regarding RA patients, high expression of sIL-1Ra mRNA on carriers of IL1RN*long/long genotype was observed. Nevertheless, in RA patients IL-1Ra soluble levels among genotypes did not show significant differences. High expression of IL-1Ra in RA patients under treatment or not with antirheumatic drugs was detected. Additionally, carriers of IL1RN*2/2 genotype had higher IL-1Ra expression than carriers of other genotypes.