A diplotype in the lymphotoxin alpha gene is associated with differential expression of LTA mRNA induced by Gram-positive and Gram-negative bacteria

TNF-α and TNF-β Polymorphisms are Associated with Susceptibility to Osteoarthritis in a Korean Population

BACKGROUND

The tumor necrosis factor (TNF) is believed to play an important role in the pathophysiology of osteoarthritis (OA). Evidence shows that genetic polymorphisms make substantial contributions to the etiology of OA.

METHODS

We investigated the genotypes TNF-α and TNF-β in 301 OA patients and 291 healthy subjects as controls. We employed a polymerase chain reaction-restriction fragment length polymorphism and a polymerase chain reaction-single strand conformation polymorphism assay to identify the genotypes TNFA -G308A and TNFB +G252A, respectively.

RESULTS

For TNFA -G308A, the percentages of genotypes GG, AG, and AA were 26.3% (79/301), 62.5% (188/301), and 11.3% (34/301) in OA patients and 88.7% (258/291), 11.3% (33/291), and 0% (0/291) in controls. For TNFB +G252A, the percentages of genotypes GG, AG, and AA were 15.3% (46/301), 41.9% (126/301), and 42.9% (129/301) in OA patients and 12% (35/291), 52.6% (153/291), and 35.4% (103/291) in controls. There were significant differences in genotypes and alleles of TNFA -308 between OA patients and controls (p<0.0001) and in alleles of TNFB +252 (p=0.0325). The risk of OA was significantly higher for carriers of the TNFA -308A allele and the TNFB +252 AA homozygote (p=0.0224).

CONCLUSIONS

The results suggest close relationships between TNFA -G308A and TNFB +G252A polymorphisms and individual susceptibility to OA in the Korean population.

Characterisation of TNF block haplotypes affecting the production of TNF and LTA

Polymorphisms in the central major histocompatibility complex (MHC) (particularly TNF and adjacent genes) associate with several immunopathological diseases and with susceptibility to pneumonia. The MHC is characterised by strong linkage disequilibrium (LD), so identification of loci affecting disease must be based on haplotypes. We have defined 31 tumour necrosis factor (TNF) block haplotypes (denoted FV1-31) in Caucasians, Asians and Australian Aboriginals. This study correlates the carriage of TNF block haplotypes with TNF and lymphotoxin alpha (LTA) protein production by peripheral blood mononuclear cells from 205 healthy Caucasian subjects, following in vitro stimulation with Streptococcus pneumoniae (S. pneumoniae; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria) or TNF over 4, 8 and 24 h. Fifteen haplotypes were present at >1%, accounting for 94.5% of the cohort. The haplotypes were grouped into five families based on common alleles. Following stimulation, cells from carriers of the FV10 haplotype (family 2) produced less LTA compared with non-FV10 carriers. Carriers of the FV18 haplotype (family 4) produced more LTA than other donors. Induction of TNF by S. pneumoniae following 24 h stimulation was also greater in donors with FV18. The FV18 haplotype associated with the 44.1 MHC ancestral haplotype (HLA-A2, -C5, -B44, -DRB1*0401 and -DQB1*0301) that has few disease associations. FV16 occurred in the 8.1 MHC haplotype (HLA-A2, B8, DR3) that is associated with multiple immunopathological diseases. FV16 did not affect TNF or LTA levels. The findings suggest that many genetic variations critical in vivo are not effectively modelled by short-term cultures.

Lymphotoxin-α 252 A>G polymorphism: a link between disease susceptibility and dyslipidemia in rheumatoid arthritis?

OBJECTIVE

Rheumatoid arthritis (RA) is associated with higher levels of inflammatory mediators and with a more atherogenic lipid profile. Dyslipidemia can be present years before arthritis develops. Lymphotoxin-α (LTA) is a cytokine that mediates proinflammatory responses while also participating in lipid homeostasis, and its transcriptional activity is in part genetically determined. We examined the role of the single-nucleotide polymorphism at position 252 of the LTA gene in the genetic background of RA and dyslipidemia.

METHODS

The association between the LTA 252 A>G polymorphism and disease status was examined in a nested case-control study of 388 patients with RA and 269 unrelated healthy controls, all white. Demographics and disease features were assessed, fasting lipids measured, and the use of lipid-lowering agents evaluated.

RESULTS

The LTA 252 A allele was more frequent in cases compared to controls (70.5% and 64.3%, respectively; p = 0.018, OR 1.325, 95% CI 1.049-1.675), as well as the A/A genotype (50.8% vs 43.5%; p = 0.025). The A/A genotype was independently associated with dyslipidemia in patients, but not in controls. Patients with RA who had the LTA 252 G/G genotype were younger at disease onset and had higher C-reactive protein (CRP) levels.

CONCLUSION

We found the LTA 252 A allele to be associated with an increased risk for developing RA in whites. The LTA 252 A/A genotype translates to a phenotype more prone to dyslipidemia, and the G/G genotype to a phenotype with earlier onset of disease and higher levels of CRP, when RA does occur. These observations highlight a possible common genetic predisposition to RA and dyslipidemia.