C3 Gene Functional Polymorphisms and C3 Serum Levels in Patients with Rheumatoid Arthritis

ABSTRACT

The complement system is a key component of the innate immunity that plays a significant role in the development and clinical presentation of Rheumatoid arthritis (RA). Complement protein C3 is a central molecule in the activation of complement with a significant role in the inflammatory processes of RA. Nevertheless, the impact of C3 gene polymorphisms in the development of RA is still unknown. The current study aimed to investigate the possible influence of C3 gene polymorphisms in the susceptibility and clinical expression of RA. Three C3 polymorphisms (rs2250656:A > G, intron 2; rs2230199:C > G [p.Arg102Gly], exon 3 and rs1047286:C > T [p.Pro314Leu], exon 9) were assessed by sequence-specific PCR in a total of 156 RA patients and 270 healthy controls from Southern Brazil. In addition, C3 levels were measured in 60 patients and 60 controls by immunoturbidimetry and clinical features were collected from medical records. The frequency of rs2230199 G allele and GG genotype was significantly higher in RA patients than controls (p_adj = 0.012 OR = 1.57 [1.11–2.31]; p_adj = 0.008, OR = 1.60 [1.35–2.33]) as well as the rs1047286 T and TT (p_adj = 0.010, OR = 1.67 [1.12–2.40]; p_adj = 0.001, OR = 1.83 [1.27–2.65] and the C3 AGT haplotype (p_adj = 0.0007 OR = 1.92 [1.32–2.80]). Moreover, C3 serum levels were higher in patients than controls (median: 169 mg/dl vs.155 mg/dl; p_adj = 0.022), as well as in RF seronegative compared with seropositive patients (172 mg/dl vs. 165 mg/dl; p_adj = 0.007). Our results suggest that the rs2230199 G (p.102Gly) and rs1047286 T (p.314Leu) alleles play a role in the pathophysiology of RA, possibly impacting complement activation by the alternative pathway.

KEYWORDS:

• Rheumatoid arthritis
• polymorphism
• gene C3
• complement system

Acknowledgments

This work was supported by grants and scholarships from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). IJMR, FAA and LS contributed with conception and design of the study; LS executed laboratory procedures; FAA and LS performed the statistical analysis; LS and FAA wrote the original draft of the manuscript; CFOT contributed with discussion of results and writing; TS performed the diagnosis of RA and the recruitment of patients. All authors contributed to manuscript revision, read and approved the submitted version.

Disclosure statement

The authors declare that there is no conflict of interest.

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Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).