Koji Sumiyoshi

Smad3 Deficiency in Mast Cells Provides Efficient Host Protection against Acute Septic Peritonitis

Mast cells play an important role in innate immunity as well as in allergic reaction. However, regulatory mechanisms underlying mast cell-mediated innate immune responses remain largely unknown. Here we determined whether Smad3, a major signal transducer of TGF-β, regulates innate immune response by mast cells against Gram-negative bacteria. Bone marrow-derived mast cells (BMMC) obtained from Smad3 null mutant mice showed augmented capacity to produce proinflammatory cytokines upon stimulation with a Gram-negative bacteria-associated product, LPS. In acute septic peritonitis model induced by cecal ligation and puncture, mast cell-deficient W/Wv mice reconstituted with Smad3 null BMMC had significantly higher survival rate than W/Wv mice reconstituted with wild-type BMMC, which was associated with higher production of proinflammatory cytokines in the peritoneal cavity. These in vitro and in vivo results suggest that Smad3 in mast cells functions as inhibitory for mast cell-mediated innate immune response against Gram-negative bacteria. Suppression of Smad3 expression in mast cells may thus have therapeutic potential for Gram-negative bacterial infection such as acute septic peritonitis by augmenting innate immune responses of mast cells.

Transforming growth factor‐bβ1 suppresses atopic dermatitis‐like skin lesions in NC/Nga mice

Atopic dermatitis is a chronic, relapsing inflammatory disorder characterized by pruritic and eczematous skin lesions. Transforming growth factor (TGF)‐β1 has been implicated in the suppression of inflammatory responses.

IFN-γ fails to antagonize fibrotic effect of TGF-β on keloid-derived dermal fibroblasts

Abstract Background: Interferon-γ (IFN-γ) has been noted as a potential therapeutic agent for various fibrotic disorders, in part, through its antagonistic effect on a fibrogenic cytokine, transforming growth factor-β (TGF-β). Keloid is a fibrotic skin disorder that results in an excessive deposition of extracellular matrix, which is associated with altered-expression of or -responses to TGF-β in dermal fibroblasts. Objective: We sought to determine whether IFN-γ antagonized TGF-β-mediated fibrotic response in keloid-derived dermal fibroblasts. Methods: Type I collagen production, fibroblast contractile activity, and α-smooth muscle actin (α-SMA) expression were assessed by using Western blotting, an in vitro type I collagen gel contraction assay, and immunofluorescence study in normal and keloid-derived human dermal fibroblasts in the presence or absence of IFN-γ and/or TGF-β. Results: In contrast to normal dermal fibroblasts, IFN-γ did not inhibit TGF-β-induced type I collagen production, contractile activity, and α-SMA expression in keloid-derived dermal fibroblasts. In addition, keloid-derived dermal fibroblasts constitutively expressed type I collagen and α-SMA with increased capacity to contract a collagen matrix. Conclusion: IFN-γ failed to antagonize TGF-β-mediated fibrotic response in keloid-derived dermal fibroblasts. Thus, IFN-γ may not be therapeutically useful for keloid and clarification of the molecular mechanisms underlying the IFN-γ resistance should be investigated for therapeutic application of IFN-γ for keloid.

TGF-β/Smad signaling inhibits IFN-γ and TNF-α-induced TARC (CCL17) production in HaCaT cells

Abstract Background: A Th2 chemokine, thymus and activation regulated chemokine (TARC/CCL17), produced by keratinocytes, is implicated in the development of atopic dermatitis by recruiting CLA+CCR4+ lymphocytes into lesional skin and its expression was induced by proinflammatory cytokines such as interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). However, it remains unknown how TARC expression is negatively regulated in keratinocytes. Objective: We sought to determine whether transforming growth factor-β1 (TGF-β1) regulated TARC expression in keratinocytes. Methods: The effect of TGF-β1 on mRNA and protein expression of IFN-γ and TNF-α-induced TARC in a human keratinocyte cell line, HaCaT cells, was evaluated by using RT-PCR and ELISA. Adenovector-mediated gene transfer was used to determine the effect of Smad proteins on TARC expression in HaCaT cells. Results: TGF-β1 inhibited mRNA and protein expression of IFN-γ and TNF-α-induced TARC in HaCaT cells. The inhibitory effect of TGF-β1 on the TARC expression was suppressed by overexpression of Smad7, a major inhibitory regulator of Smad pathway for transforming growth factor-β (TGF-β) signaling, but not by PD98059, an inhibitor for ERK/mitogen-activated protein kinase (MAPK) pathway. In addition, overexpression of Smad2 or Smad3, major signal transducing Smads, was sufficient to inhibite the IFN-γ and TNF-α-induced TARC production in HaCaT cells. Conclusion: TGF-β1 inhibited IFN-γ and TNF-α-induced TARC production in HaCaT cells via Smad2/3, suggesting that modulation of TGF-β/Smad signaling pathway may be beneficial for the treatment of atopic dermatitis.

Smads regulate collagen gel contraction by human dermal fibroblasts

Background  Transforming growth factor (TGF)‐β induces fibroblast contraction that is implicated in efficient wound healing. The Smad family of proteins mediates signal transduction of the TGF‐β superfamily. However, its role in fibroblast contraction remains unclear.