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Professor, Department of Medical Microbiology & Immunology
Dr. Stepkowski’s interests are in cellular and organ transplantation, with research focused on improvement of long-term allograft survival and development of new immunosuppressive modalities. Activation of T lymphocytes requires three overlapping and sequential signals, with signal 3 delivered by multiple cytokines that regulate cell proliferation, differentiation, and survival/death. Cytokines binding to their receptors engages two key molecular families, namely, Janus tyrosine kinases (Jaks) and signal transducers and activators of transcription (Stats). Among Jaks, gamma-cytokines bind to cytokine receptors consisting gamma-chain, thereby engaging Jak3/Stat5 cascade leading to proliferation and differentiation of T cells. Recently, novel tyrosine (Y905 and Y935) phosphorylation sites are investigating on Jak3 and their role in T cell function. Mice with mutated these tyrosines are being produced to examine in vivo impact on development and function in T cells. Similarly, Stat3 and Stat5 are investigated for their role in regulating T cells. Binding of cytokines to cytokine receptors attracts and activates one or more of the Jaks, which are tyrosine phosphorylated themselves and phosphorylate tyrosines on the cytokine receptor sites thereby creating active docking sites for Stats. Among Stats, recent evidence suggests that Stat3 is involved in the generation of a new population of T helper 17 (Th17) cells, and in the regulation of dendritic cell function and the process of angiogenesis. We are investigating whether Stat3 deficiency may affect the regulation of Th17 cells and other functions. Based on screening of multiple compounds from NIH data base, novel and selective inhibitor of Jak3, NC1153, has been developed. It has been shown that NC1153 may inhibit kidney allograft rejection in rats and cynomolgus monkeys. Most of this work has been published in the Journal of Immunology, Blood, and Transplantation.
Dr. Stepkowski had investigated a sphingosin-1-phosphate receptor (S1P) agonist, FTY720 (2-amino-2-2-[4[octylphenyl]ethyl)propane-1,3-diol hygrochloride), but this promising compound was abandoned following clinical kidney trials because of its side effects, and in particular bradycardia. Physiologically, S1P (a bioreactive lysolipid) acts through the family of G protein-coupled receptors, namely S1P1, S1P2, S1P3, S1P4 and S1P5. While S1P1 expression was shown to be restricted to the vascular endothelium, S1P3 was abundantly expressed in cardiomyocytes of perivascular smooth muscle cells. Consequently, activation of S1P1 receptor correlated with lymphopenia and increased entrapment of lymphocytes in the lymphoid compartment, while activation of S1P3 correlated with bradycardia and hypertension. The latter symptoms occurred because of poor selectivity as FTY720 was able to engage S1P1, S1P3, S1P4 and S1P5. Over the last 2 years we have tested a novel compound, KRP203 (2-amino-2-propanediol hydrochloride), that was shown to have selective agonist activity on S1P1 but not on S1P3. Our results showed that KRP203 not only extended allograft survival of kidney allgrafts but also induced transplantation tolerance to islet allografts when combined with local infusion of T regulatory cells. At present this work is in preparation for publication.
Dr. Stepkowski was educated in Warsaw, Poland (Veterinary Medicine), trained at Radium Hospital in Oslo, Norway (PhD), Dalhousie University in Halifax, Canada (postdoctoral), and at the University of Texas in Houston, USA (DSc). He considers the United States his home and the best place to perform the most advanced research.
Mierzejewska B, Baum C, Schroder PA, Durlik M, Lisik W, Rees M, Stepkowski SM. Diversity in kidney paired donation programs accommodates local requirements. Annals of Transplantation 2013 in press
Khattar M, Deng R, Kahan BD, Schroder PM, Phan T, Rutzky LP, Stepkowski SM. Novel sphingosin-1-phosphate receptor modulator KRP203 combined with locally-delivered regulatory T cells induces permanent acceptance of pancreatic islet allografts. Transplantation 2013 in press
Guo Z,Khattar M, Schroder PM, Miyahara Y, Wang G,He X, Chen W, Stepkowski SM. A dynamic dual role of IL-2 signaling in the two-step differentiation process of adaptive regulatory T cells. Journal of Immunology 2013 in press
Miyahara Y, Khattar M, Schroder P, Mierzejewska B, Deng R, Han R, Hancock WW, Chen W, Stepkowski SM. An anti-TCRb monoclonal antibody induces long-term allograft survival by reducing antigen-reactive T cells and sparing regulatory T cells. American J Transplantation 12:1409-18, 2012
Li J, Chen G, Ye P, Wang S, Zhang K, Chen W‡, Stepkowski SM, Junhua Li J, Zhong S, Xia J. CCR5 Blockade in Combination with Cyclosporine Increased Cardiac Graft Survival and Generated Alternatively Activated Macrophages in Primates. J. Immunol. 186:3753-61, 2011.
Khattar M, Chen W, Stepkowski SM. Expanding and converting regulatory T cells. Arch. Immunol. Ther. Exp. 57:199, 2009.
Wang G, Khattar M, Guo Z, Miyahara Y, Linkes SP, Sun Z, He X, Stepkowski SM, Chen W. IL-2-deprivation and TGF-beta are two non-redundant suppressor mechanisms of CD4(+)CD25(+)
regulatory T cell which jointly restrain CD4(+)CD25(-) cell activation. Immunol Lett.
2010 June 8. [Epub ahead of print].
Wang G, Miyahara Y, Guo Z, Khattar M, Stepkowski SM, Chen W. (2010) Default generation of neonatal regulatory T cells. J Immunol. 185:71-78 .
Khattar M, Chen W, Stepkowski SM (2009) Expanding and converting regulatory T cells: a horizon for immunotherapy. Arch Immunol Ther Exp (Warsz).57(3): 199-204.
Chen W, Diao J, Stepkowski SM, Zhang L. Both infiltrating regulatory T cells and insufficient antigen presentation are involved in long-term cardiac xenograft survival. J Immunology 179(3):1542-8, 2007.
Razeghi P, Wang ME, Youker KA, Golfman L, Stepkowski S, Taegtmeyer H. Lack of NF-kappaB1 (p105/p150) attenuates unloading-induced downregulation of PPARalpha and PPARalpha-regulated gene expression in rodent heart. Cardiovasc Res 74:133, 2007.
Razeghi P, Volpini KC, Wang ME, Youker KA, Stepkowski S, Polonsky KS, Taegtmeyer H. Mechanical unloading of the heart activates the calpain system. J Mol & Cellular Cardiol 42:449, 2007.
Stepkowski SM, Phan T, Zhang H, Bilinski Sz, Kloc M, Yuhua Qi Y, Katz SM, Rutzky LP. Immature syngeneic dendritic cells (DC) potentiate tolerance to islet allografts depleted of passenger DC by culturing in bioreactors. Transplantation 82:1756, 2006.
Nagy ZS, Rui H, Stepkowski SM, Karras J, Kirken RA. A preferential role for STAT5, not constitutively active STAT3, in promoting survival of human lymphoid tumor. J Immunol 177:5032-5040, 2006.
Razeghi P, Buksinska-Lisik M, Palanichamy N, Stepkowski SM, Frazier OH, Taegtmeyer H. Transcriptional regulators of ribosomal biogenesis are increased in the unloaded
heart. FASEB Journal, 20:1090-6, 2006.