title: Sphingosine-1-phosphate in the lymphatic fluid determined by novel methods.
abstract: BACKGROUND
  Sphingosine-1-phosphate (S1P) is a pleiotropic bioactive lipid mediator that regulates many physiological and pathological processes. It has been suggested that S1P gradient with high concentrations in the blood and lymphatic fluid and low concentrations in the peripheral tissue plays important roles in immune cell trafficking and potentially cancer progression. However, only a few reports have assessed S1P levels in the lymphatic fluid due to lack of an established easy-to-use method. Here, we report a simple technique for collection of lymphatic fluid to determine S1P.
  
  
  METHODS
  Lymphatic fluid was collected directly with a catheter needle (classical method) or was absorbed onto filter paper after incision of cisterna chyli (new method) in murine models. Blood, lymphatic fluid and mesenteric lymph nodes were corrected from wild type and sphingosine kinase 2 (SphK2) knockout mice to determine S1P levels by mass spectrometry.
  
  
  RESULTS
  The volume of lymphatic fluid collected by the new method was at least three times greater than those collected by the classical method. S1P concentrations in lymphatic fluid are lower than in blood and higher than in lymph nodes. Interestingly, S1P levels in lymphatic fluid from SphK2 knockout mice were significantly higher than those in wild type, suggesting an important role of SphK2 and/or SphK1 to regulate S1P levels in lymphatic fluid.
  
  
  CONCLUSIONS
  In agreement with the previous theory, our results confirm "S1P gradient" among blood, lymphatic fluid and peripheral lymphatic tissues. Convenient methods for collection and measurement of sphingolipids in lymphatic fluid are expected to provide new insights on functions of sphingolipids.
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, 951-8510, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nagahashi
authors.affiliation: Division of Surgical Oncology, Department of Biochemistry and Molecular Biology, and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0011, USA.
authors.forename: Akimitsu
authors.initials: A
authors.lastname: Yamada
authors.affiliation: Division of Surgical Oncology, Department of Biochemistry and Molecular Biology, and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0011, USA.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Aoyagi
authors.affiliation: Department of Biochemistry and Molecular Biology, and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0011, USA.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Allegood
authors.affiliation: Division of Digestive and General Surgery, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, 951-8510, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Wakai
authors.affiliation: Department of Biochemistry and Molecular Biology, and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Virginia 23298-0011, USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Spiegel
authors.affiliation: Breast Surgery, Department of Surgical Oncology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA; Department of Surgery, University at Buffalo, The State University of New York, Jacobs School of Medicine and Biomedical Sciences, New York.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Takabe
keywords: Biochemistry; Cancer research; Cell biology; Immunology; Oncology; Surgery