Biochemical characterization of a glucocorticoid-induced membrane protein (RM3/1) in human monocytes and its application as model system for ranking glucocorticoid potency.

PURPOSE

Upon glucocorticoid stimulation, human mononuclear leucocytes express an antigen, RM3/1, which characterizes a subpopulation of human monocytes and macrophages evolving in late phase of inflammation. We investigated biochemical properties of the RM3/1 antigen and correlations between antigen expression and glucocorticoid potency.

METHODS

Biochemical properties were analyzed after solubilization by immunoaffinity methods and SDS-PAGE.

RESULTS

Induction of the RM3/1 antigen is a glucocorticoid receptor mediated process, in contrast, inflammatory mediators such as LPS or TPA were not able to upregulate RM3/1 expression. After SDS-PAGE, the antigen appeared as a 130 kDa (nonreduced)/150 kDa (reduced) glycoprotein with a 25 kDa N-linked glycoportion. The interdependence between antigen density and glucocorticoid efficacy was assessed by calculation of relative antigen expression induced by dexamethasone, fluticasone propionate, budesonide, triamcinolone acetonide, flunisolide, beclomethasone, prednisolone and triamcinolone. Relative antigen expression was significantly correlated with the relative receptor affinity of the glucocorticoid.

CONCLUSIONS

We described biochemical properties of the glucocorticoid-induced protein RM3/1. Though the precise role of the RM3/1 antigen in the antiinflammatory process is not fully understood yet, an useful application of the induced expression could already be demonstrated for pre-clinical screening of glucocorticoid potency.