Browsing by Author "Meldrum, Kirstan K."

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    IL-18 Activation is Dependent on Toll Like Receptor 4 during Renal Obstruction
    (Elsevier, 2013) Rhee, Audrey C.; Cain, Alexandra L.; Hile, Karen L.; Zhang, Hongji; Matsui, Futoshi; Meldrum, Kirstan K.; Urology, School of Medicine
    Purpose: Interleukin 18 (IL-18) is a critical mediator of obstruction-induced renal injury. Although previous studies have demonstrated that IL-18 participates in a positive feedback loop via the IL-18 receptor (IL-18R) and localized renal IL-18 and IL-18R production to tubular epithelial cells (TEC), the mechanism of IL-18 activation during obstruction remains unclear. We hypothesized that IL-18 activation is dependent on Toll-like receptor 4 (TLR4) signaling during renal obstruction. Materials and methods: Male C57BL6 TLR4 knockout (TLR4KO) and wild-type (WT) mice were subjected to unilateral ureteral obstruction versus sham operation for 1 wk. The animals were sacrificed, and renal cortical tissue was harvested and analyzed for TLR4 expression (Western blot), active IL-18 production (enzyme-linked immunosorbent assay, real-time polymerase chain reaction), IL-18 receptor expression (real-time polymerase chain reaction), and TLR4/IL-18 versus IL-18R cellular localization (dual immunofluorescent staining). Results: Renal TLR4 expression increased significantly in WT mice in response to obstruction, but remained at sham treatment levels in TLR4KO mice. IL-18 and IL-18R gene expression and active IL-18 production were similarly increased in WT mice in response to obstruction, but decreased significantly to sham treatment levels in the absence of TLR4. Dual immunofluorescent staining revealed co-localization of TLR4 and IL-18 to renal TEC during obstruction. Conclusion: IL-18 production and activation during renal obstruction is dependent on intact TLR4 signaling. Co-localization of IL-18 and TLR4 production to TEC during obstruction suggests that TEC are the primary site of IL-18 production and activation. Further characterization of the pathway may be necessary to develop targeted therapy in obstruction-induced renal injury.
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    Interleukin-18 stimulates a positive feedback loop during renal obstruction via interleukin-18 receptor
    (Elsevier, 2011-10) VanderBrink, Brian A.; Asanuma, Hiroshi; Hile, Karen; Zhang, Honji; Rink, Richard C.; Meldrum, Kirstan K.; Urology, School of Medicine
    PURPOSE: Interleukin-18 is a proinflammatory cytokine that is an important mediator of obstruction induced renal tubulointerstitial fibrosis independent of tumor necrosis factor-α and β1 activity. We hypothesized that interleukin-18 stimulates a positive feedback loop during obstruction via interleukin-18 receptor to increase interleukin-18 gene expression and protein production. MATERIALS AND METHODS: Male C57BL6 interleukin-18 receptor knockout (The Jackson Laboratory, Bar Harbor, Maine) and control wild-type mice underwent unilateral ureteral obstruction or sham operation and were sacrificed 1 week after surgery. Renal cortical tissue samples were harvested and analyzed for interleukin-18 protein by enzyme-linked immunosorbent assay, and for interleukin-18 and interleukin-18 receptor gene expression by quantitative polymerase chain reaction. The specific cellular localization of interleukin-18 and interleukin-18 receptor expression during obstruction was assessed using dual labeling immunofluorescence staining. RESULTS: Renal interleukin-18 receptor expression increased significantly in wild-type mice in response to obstruction but remained at sham operation levels in interleukin-18 receptor knockout mice. Similarly while interleukin-18 protein and gene expression were significantly increased in wild-type mice in response to obstruction, interleukin-18 levels and gene expression were significantly decreased during obstruction in knockout mice. Obstruction induced interleukin-18 and interleukin-18 receptor production were localized predominantly to tubular epithelial cells and to a lesser extent to the renal interstitium. CONCLUSIONS: Results reveal that interleukin-18 stimulates a positive feedback loop via interleukin-18 receptor during renal obstruction to stimulate interleukin-18 production and gene expression. The predominant cellular source of interleukin-18 production during renal obstruction appears to be tubular epithelial cells rather than infiltrating macrophages.
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    Mesenchymal stem cells protect against obstruction-induced renal fibrosis by decreasing STAT3 activation and STAT3-dependent MMP-9 production
    (American Physiological Society, 2017-01-01) Matsui, Futoshi; Babitz, Stephen A.; Rhee, Audrey; Hile, Karen L.; Zhang, Hongji; Meldrum, Kirstan K.; Urology, School of Medicine
    STAT3 is a transcription factor implicated in renal fibrotic injury, but the role of STAT3 in mesenchymal stem cell (MSC)-induced renoprotection during renal fibrosis remains unknown. We hypothesized that MSCs protect against obstruction-induced renal fibrosis by downregulating STAT3 activation and STAT3-induced matrix metalloproteinase-9 (MMP-9) expression. Male Sprague-Dawley rats underwent renal arterial injection of vehicle or MSCs (1 × 106/rat) immediately before sham operation or induction of unilateral ureteral obstruction (UUO). The kidneys were harvested after 4 wk and analyzed for collagen I and III gene expression, collagen deposition (Masson's trichrome), fibronectin, α-smooth muscle actin, active STAT3 (p-STAT3), MMP-9, and tissue inhibitor of matrix metalloproteinases 1 (TIMP-1) expression. In a separate arm, the STAT3 inhibitor S3I-201 (10 mg/kg) vs. vehicle was administered to rats intraperitoneally just after induction of UUO and daily for 14 days thereafter. The kidneys were harvested after 2 wk and analyzed for p-STAT3 and MMP-9 expression, and collagen and fibronectin deposition. Renal obstruction induced a significant increase in collagen, fibronectin, α-SMA, p-STAT3, MMP-9, and TIMP-1 expression while exogenously administered MSCs significantly reduced these indicators of obstruction-induced renal fibrosis. STAT3 inhibition with S3I-201 significantly reduced obstruction-induced MMP-9 expression and tubulointerstitial fibrosis. These results demonstrate that MSCs protect against obstruction-induced renal fibrosis, in part, by decreasing STAT3 activation and STAT3-dependent MMP-9 production.