Proteinase 3/myeloblastin as a growth factor in human kidney cells.

BACKGROUND: Numerous data support the possible role of myeloblastin/proteinase 3 (PR3) in growth and differentiation of neutrophil granulocytes and certain monocyte subtypes. However, whether PR3 is expressed in non-myeloid cells remains a matter of debate even though recent studies clearly demonstrated its expression in endothelium, kidney epithelial cells and epithelial tumor cell lines. METHODS: To survey PR3 transcript presence in human tissues, we analyzed different human tissues by dot blot and northern blot using a cloned PR3-cDNA probe. To examine the physiological function of PR3 expression in non-myeloid cells, we constructed different recombinant retroviral vectors containing human PR3-cDNA variants and expressed them in tubular epithelial cells (TEC). Using an MTT-based proliferation assay, we determined the proliferation rate of PR3-transduced kidney cells. RESULTS: The resulting expression pattern clearly indicated that PR3 transcripts are not only present in tissues known to harbor hematopoietic cells, but surprisingly PR3 was highly expressed in fetal organs including the kidney. The proliferation assay revealed that the growth rate of TEC transduced with native PR3 was significantly enhanced relative to non-transduced TEC. CONCLUSIONS: The results supported our theory that PR3 can act as a growth factor in non-hematopoietic cells, analogous to its role in hematopoietic cells. The cells, recombinant vectors and methods described here serve as a basis to investigate PR3 function in cellular differentiation and proliferation, as well as its role in autoimmune diseases.

Correlation of renal tubular epithelial cell-derived interleukin-18 up-regulation with disease activity in MRL-Faslpr mice with autoimmune lupus nephritis.

OBJECTIVE: MRL-Fas(lpr) mice spontaneously develop an autoimmune disease that mimics systemic lupus erythematosus in humans. Infiltrating T cells expressing interferon-gamma (IFNgamma) are responsible for the autoimmune kidney destruction in MRL-Fas(lpr) mice, and interleukin-18 (IL-18) released by mononuclear phagocytes stimulates T cells to produce the IFNgamma. Since MRL-Fas(lpr) T cells are characterized by an overexpression of the IL-18 receptor accessory chain, we sought to determine the impact of IL-18 on the progression of lupus nephritis in MRL-Fas(lpr) mice. METHODS: IL-18 expression in sera and kidney tissues from MRL-Fas(lpr) mice was determined by enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blotting. IL-18 production by primary cultured tubular epithelial cells (TECs) from MRL-Fas(lpr) and BALB/c mice were examined by RT-PCR, ELISA, and Western blotting. The interactions of TEC-derived IL-18 and MRL-Fas(lpr) T cells were studied in coculture assays. IL-18-related effects on TEC viability and adhesion molecule expression were determined by fluorescence-activated cell sorting and cell proliferation assays. RESULTS: Up-regulation of mature IL-18 was restricted to nephritic MRL-Fas(lpr) kidneys and increased in parallel with the severity of lupus nephritis. IL-18 expression was not confined to infiltrating monocytes but was primarily detected in TECs. Similarly, interleukin-1beta-converting enzyme expression, which is required for the processing of precursor IL-18, was localized in TECs. De novo synthesis of IL-18 by MRL-Fas(lpr) TECs was confirmed by RT-PCR and Western blotting. Functional assays revealed that activated TECs induced IFNgamma production in MRL-Fas(lpr) T cells through IL-18. IL-18, in turn, increased apoptotic TEC death and up-regulation of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1. CONCLUSION: Taken together, our findings suggest that IL-18-producing TECs may directly be involved in the pathogenesis of lupus nephritis.