L. J. Fernandez1, W. Huang1, K. P. Terracina1, M. Nagahashi3, A. Yamada2, T. Aoyagi4, S. Spiegel5, K. Takabe1,5 1Virginia Commonwealth University,Surgical Oncology,Richmond, VA, USA 2Yokohama City University,Surgery,Yokohama, , Japan 3Nigata University,Digestive And General Surgery,Nigata, , Japan 4Chiba University,Surgery,Chiba, , Japan 5Virginia Commonwealth University,Biochemistry And Molecular Biology,Richmond, VA, USA 6Chang Gung Memorial Hospital,Taipei, , Taiwan
Introduction:
There is growing evidence that sphingosine-1-phosphate (S1P), a pleiotropic bioactive sphingolipid metabolite formed inside cells by two closely related sphingosine kinases, SphK1 and SphK2, is involved in inflammation and cancer. Previously, we have reported the involvement of S1P and SphK1 in colitis and colitis-associated cancer (CAC) utilizing SphK2 knockout mice in Cancer Cell. S1P has been found to play an important role in inflammation and CAC through persistent activation of the NF-kappaB/IL-6/STAT3 axis by S1P. In this current study we sought to investigate the role of S1P in lymphangiogenesis and lymphatic vessel dilatation in a DSS colitis model.
Methods:
SphK2 knockout mice were kindly provided by Dr. Proia, NIH. Dextran Sulfate Sodium (DSS) in drinking water was used to generate accolitis model. Lymphangiogenesis and lymphatic vessel dilatation were determined by micro-vessel density and the area of the vessel with both IHC and Immunofluorescence on colon and mesenteric lymph node (MLN) samples. As methods of blocking S1P signaling, we used SK1-I, a SphK1 specific inhibitor, W146, a S1PR1 specific inhibitor, and FTY720, a S1PR1 functional antagonist
Results:
When comparing wild type (WT) and SphK2 knock out (KO) mice, SphK2 KO mice were shown to overexpress SpkK1 resulting in higher extracellular levels of S1P. We have observed that SphK2 KO mice demonstrated stronger mucosal damage compared to WT mice by histology colitis severity score when treated with DSS. Both lymphangiogenesis and lymphatic vessel dilatation were increased in SphK2 KO after DSS treatment in both colon and MLN. Morphologically, SphK2 KO mice demonstrated increased lymphatic vessel vasculature when compared to WT but the difference was much higher with DSS treated mice, which was evident both in the colon and in the MLNs. The inhibition of SphK1 by SK1-I or S1PR1 by W146 or FTY720 resulted in a significant decrease of lymphangiogenesis and dilatation of lymphatic vessels in DSS induced colitis
Conclusion:
We found that SphK1 overexpressing, thus S1P producing, animals demonstrated severe colitis with S1P mediated enhancement of lymphangiogenesis and lymphatic vessel dilatation. Considering the fact that S1P signaling blockade significantly suppressed lymphangiogenesis and lymphatic vessel dilatation, we conclude that S1P plays a critical role in inflammation-induced lymphangiogenesis and lymphatic vessel dilatation