In previous studies, we showed that interleukin-4 (IL-4) suppressed porcine (p) macrophage Superoxide production and that the mechanism of suppression involved down-regulation of the superoxide-generating enzyme NADPH oxidase heavy-chain 91-kDa subunit mRNA (gp91-phox) expression. In order to examine the effect of IL-4 on expression of the gene encoding the porcine NADPH oxidase light-chain 22-kDa subunit (p22-phox), we cloned the p22-phox cDNA from a macrophage library. The p22-phox cDNA is 786 bp in length and contains a 576-bp open reading frame which predicts a primary translation product of 192 amino acids (aa). Comparison of the porcine and human 22-phox cDNAs showed a high degree of similarity between the two species in their nucleotide (85%) and deduced aa (83%) sequences, as well as in their hydropathy profiles. Notable features, including a high proline content and an iron-coordinating His94, are conserved in both the porcine and human 22-Phox. A single species of mRNA of about 1 kb was detected in macrophages. The mRNA levels remained unchanged in cells treated with lipopolysaccharide (LPS) or with IL-4 at various concentrations from 0-50 ng/ml. Prolonged treatment with LPS or IL-4 did not enhance the effect of these substances on p22-phox mRNA expression. The effect of IL-4 on p22-phox mRNA expression was also compared with another immunosuppressive cytokine, transforming growth factor-β1 (TGFß1). No change in mRNA expression was found in the cells with or without TGFß1 treatment. The results indicated that the heavy and light chains of NADPH oxidase are independently regulated by IL-4 in macrophages.
- gene regulation