Interferon gamma up-regulates a novel protein in vascular smooth muscle cells

Purpose: By means of the technique of messenger RNA (mRNA) differential dis play, we previously isolated a partial DNA clone found to be down-regulated at the polytetrafluoroethylene (PTFE) hyperplastic arterial anastomosis co mpared with the normal artery. The partial DNA gene sequence tvas found to be homologous with interferon gamma up-regulated protein (IGUP) first found in human psoriatic keratinocytes. We cloned the entire IGUP gene from huma n vascular smooth muscle cells (VSMCs) to determine its regulation by gamma interferon (gamma-IFN) and other cytokines in cultured human VSMCs. Methods: By means of polymerase chain reaction, the IGUP gene was amplified from a QUICK-Clone complementary DNA human aorta kit using 5' and 3' oligo nucleotide primers to the known IGUP sequence. Immunohistocytochemistry stu dies compared normal artery and distal anastomotic IH. Human VSMCs were sti mulated with 1000 U/mL of gamma-IFN, 5 ng/mL of platelet-derived growth fac tor BE (PDGF-BB), 3.2 ng/mL basic fibroblast growth factor, 3.3 ng/mL trans forming growth factor beta(TGF-beta), 10 ng/mL of vascular endothelial grow th factor, and 10% fetal bovine serum (FBS) for zero, 24, 48 and 72 hours. Western blot analysis of lysates of the stimulated VSMCs was performed to d etermine up-regulation of IGUP. Results: DNA sequencing confirmed the cloning of the entire coding region o f the IGUP gene with 100% homology to the known IGUP DNA sequence. There wa s strong expression of IGUP in quiescent VSMCs and marked reduction of expr ession of IGUP in proliferating smooth muscle cells. gamma-IFN was the only cytokine, of the cytokines evaluated, to up-regulate production of IGUP in VSMCs. Conclusion: IGUP is a novel protein in VSMCs found to be down-regulated in areas of anastomotic IH, as compared with a normal artery. We have now show n IGUP to be up-regulated only by gamma-IFN in human VSMCs. IGUP may, there fore, be the intermediary for the known gamma-IFN inhibition of human VSMC proliferation.