Naoki Fujitani

Publications (2)11.96 Total impact

• Article: Interruption of glycosphingolipid synthesis enhances osteoarthritis development in mice.

  Naoki Seito, Tadashi Yamashita, Yukinori Tsukuda, Yuichiro Matsui, Atsushi Urita, Tomohiro Onodera, Takeomi Mizutani, Hisashi Haga, Naoki Fujitani, Yasuro Shinohara, Akio Minami, Norimasa Iwasaki
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  ABSTRACT: Glycosphingolipids (GSLs) are ubiquitous membrane components that modulate transmembrane signaling and mediate cell-to-cell and cell-to-matrix interactions. GSL expression is decreased in the articular cartilage of humans with osteoarthritis (OA). This study was undertaken to determine the functional role of GSLs in cartilage metabolism related to OA pathogenesis in mice. We generated mice with knockout of the chondrocyte-specific Ugcg gene, which encodes an initial enzyme of major GSL synthesis, using the Cre/loxP system (Col2-Ugcg(-/-) mice). In vivo OA and in vitro cartilage degradation models were used to evaluate the effect of GSLs on the cartilage degradation process. Although Col2-Ugcg(-/-) mice developed and grew normally, OA changes in these mice were dramatically enhanced with aging, through the overexpression of matrix metalloproteinase 13 and chondrocyte apoptosis, compared to their wild-type (WT) littermates. Col2-Ugcg(-/-) mice showed more severe instability-induced pathologic OA in vivo and interleukin-1α (IL-1α)-induced cartilage degradation in vitro. IL-1α stimulation of chondrocytes from WT mice significantly increased Ugcg messenger RNA expression and up-regulated GSL metabolism. Our results indicate that GSL deficiency in mouse chondrocytes enhances the development of OA. However, this deficiency does not affect the development and organization of cartilage tissue in mice at a young age. These findings indicate that GSLs maintain cartilage molecular metabolism and prevent disease progression, although GSLs are not essential for chondrogenesis of progenitor and stem cells and cartilage development in young mice. GSL metabolism in the cartilage is a potential target for developing a novel treatment for OA.
  Arthritis & Rheumatism 03/2012; 64(8):2579-88. · 7.87 Impact Factor
• Source

  Available from: Yasuro Shinohara

  Article: Ganglioside GM3 has an essential role in the pathogenesis and progression of rheumatoid arthritis.

  Yukinori Tsukuda, Norimasa Iwasaki, Naoki Seito, Masashi Kanayama, Naoki Fujitani, Yasuro Shinohara, Yasuhiko Kasahara, Tomohiro Onodera, Koji Suzuki, Tsuyoshi Asano, Akio Minami, Tadashi Yamashita
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  ABSTRACT: Rheumatoid arthritis (RA), a chronic systemic inflammatory disorder that principally attacks synovial joints, afflicts over 2 million people in the United States. Interleukin (IL)-17 is considered to be a master cytokine in chronic, destructive arthritis. Levels of the ganglioside GM3, one of the most primitive glycosphingolipids containing a sialic acid in the structure, are remarkably decreased in the synovium of patients with RA. Based on the increased cytokine secretions observed in in vitro experiments, GM3 might have an immunologic role. Here, to clarify the association between RA and GM3, we established a collagen-induced arthritis mouse model using the null mutation of the ganglioside GM3 synthase gene. GM3 deficiency exacerbated inflammatory arthritis in the mouse model of RA. In addition, disrupting GM3 induced T cell activation in vivo and promoted overproduction of the cytokines involved in RA. In contrast, the amount of the GM3 synthase gene transcript in the synovium was higher in patients with RA than in those with osteoarthritis. These findings indicate a crucial role for GM3 in the pathogenesis and progression of RA. Control of glycosphingolipids such as GM3 might therefore provide a novel therapeutic strategy for RA.
  PLoS ONE 01/2012; 7(6):e40136. · 4.09 Impact Factor