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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Enzyme-Linked Immunosorbent Assay, Feedback, Physiological, Fluorescent Antibody Technique, Gene Expression, Interleukin-18, Kidney, Kidney Cortex, Kidney Tubules, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Polymerase Chain Reaction, RNA, Messenger, Receptors, Interleukin-18, Ureteral Obstruction.
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Does interleukin-18 stimulate a positive feedback loop during renal obstruction via interleukin-18 receptor? Context: 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. 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. 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.
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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. Final Decision: yes