Association of the polymorphisms in the promoter region of tumor necrosis factor alpha and interleukin 6 genes with schizophrenia

Objective To investigate the relationship between the -308G/A, -857C/T and -1031T/C of tumor necrosis factor α gene (TNF-α), -174G/C and -572C/G of interleukin-6 gene (IL-6)polymorphisms and schizophrenia. Methods Genomic DNA was isolated from the venous blood leukocytes of 346 unrelated patients with schizophrenia and 323 healthy unrelated individuals (control group). All of the polymorphisms were genotyped by PCR-restriction fragment length polymorphisms (PCR-RFLP).Genotype and allele frequencies were analyzed by SPSS13. 0 software. Results There were significant differences in both allele and genotype frequencies of -857C/T of TNF-α gene between the schizophrenia and control groups (P＜0. 05). The allele T of -857C/T in schizophrenia group was significantly higher than that in control group (x2 = 9.414, P= 0. 002, OR= 1.511, 95% CI: 1. 160-1. 969). In addition, there were significant differences in the positive and negative syndrome scale (PANSS) total score and negative symptoms between the patients with different -857C/T genotypes, and the negative symptom score of TT genotype was significantly higher than that of CC genotype (P＜0.05). Conclusion There is an association between -857C/T of TNF-α gene and schizophrenia, individuals with T allele of -857C/T are susceptible to schizophrenia, and there is an association between -857C/T and negative symptom score. Key words: schizophrenia;  tumor necrosis factor-α;  interleukin-6;  genetic polymorphism