Monocyte chemoattractant protein 1 gene regulatory region polymorphism and serum levels of monocyte chemoattractant protein 1 in Japanese patients with Kawasaki disease
Kawasaki disease (KD) is an acute febrile vasculitic syndrome of unknown etiology (1) that preferentially affects Japanese children (2). To date, no specific genetic marker has been found to be a risk factor for this disease. It has been suggested that proinflammatory cytokines and chemokines are key players during acute KD, including interleukin-1โฃ (IL-1โฃ) (3), tumor necrosis factor โฃ (3), and monocyte chemoattractant protein 1 (MCP-1) (4,5). We reported an enhanced expression of MCP-1 in the coronary vessels infiltrated by macrophages in fatal KD (4). The MCP-1 gene expression levels in the peripheral blood mononuclear cells (PBMC) were significantly elevated in patients with acute KD (5), suggesting a role of MCP-1 in the pathogenesis of KD.
Recently, the polymorphism at position ฯช2518 (G or A) relative to the major transcriptional start site of the MCP-1 gene was shown to influence the level of MCP-1 production in response to IL-1โค in vitro (6). We reproduced this in vitro effect of MCP-1 production with the aid of 18 Japanese healthy volunteers. PBMC from Japanese individuals who carried the ฯช2518 G allele (high production of MCP-1) produced more MCP-1 than PBMC from homozygotes for the A allele (low production of MCP-1) (P ฯฝ 0.01 by unpaired Welch's t-test) (Figure ), consistent with findings of an earlier study (6). It was preliminarily reported that the G allele frequency was increased in Asian populations, although the numbers analyzed were quite small (n ฯญ 16 patients) (6). The A allele was found to be predominant among Caucasian and African American populations (6), suggesting a possible ethnic variation. The G/A polymorphism in the Japanese population has not been investigated. Since there is a role for MCP-1 in the pathogenesis of KD, which preferentially affects Japanese, it is of great importance to determine the effects of this polymorphism on the pathogenesis of KD. Informed consent was obtained from all subjects before the beginning of the study. All data are expressed as the mean ฯฎ SD. The statistical analyses were conducted with Prism Software version 3.0 (GraphPad Software, San Diego, CA). P values less than 0.05 were considered significant.
First, we determined the G/A polymorphism in 253 unrelated Japanese subjects, consisting of 153 KD patients and 100 control individuals with no history of KD. A 930-bp segment of the MCP-1 5ะ-flanking region between nucleotides ฯช1817 and ฯช2746 relative to the major transcriptional start site was analyzed according to the method previously described (6). This segment contains the distal regulatory region of the MCP-1 gene and has been found to be important for cytokine induction of MCP-1 transcription (6-9). The polymerase chain reaction products from genomic DNA using the forward primer 5ะ-CCGAGATGTTCCCAGCACAG-3ะ and the reverse primer 5ะ-CTGCTTTGCTTGTGCCTCTT-3ะ were digested with Pvu II (6). The G allele gives 2 fragments (708 bp and 222 bp), while the A allele gives a single 930-bp fragment.