title: Effects of Tumor Necrosis Factor-α on Podocyte Expression of Monocyte Chemoattractant Protein-1 and in Diabetic Nephropathy.
abstract: OBJECTIVE
  Tumor necrosis factor (TNF)-α is believed to play a role in diabetic kidney disease. This study explores the specific effects of TNF-α with regard to nephropathy-relevant parameters in the podocyte.
  
  
  METHODS
  Cultured mouse podocytes were treated with recombinant TNF-α and assayed for production of monocyte chemoattractant protein-1 (MCP-1) by enzyme-linked immunosorbent assay (ELISA). TNF-α signaling of MCP-1 was elucidated by antibodies against TNF receptor (TNFR) 1 or TNFR2 or inhibitors of nuclear factor-kappaB (NF-κB), phosphatidylinositol 3-kinase (PI3K) or Akt. In vivo studies were done on male db/m and type 2 diabetic db/db mice. Levels of TNF-α and MCP-1 were measured by RT-qPCR and ELISA in the urine, kidney and plasma of the two cohorts and correlated with albuminuria.
  
  
  RESULTS
  Podocytes treated with TNF-α showed a robust increase (∼900%) in the secretion of MCP-1, induced in a dose- and time-dependent manner. Signaling of MCP-1 expression occurred through TNFR2, which was inducible by TNF-α ligand, but did not depend on TNFR1. TNF-α then proceeded via the NF-κB and the PI3K/Akt systems, based on the effectiveness of the inhibitors of those pathways. For in vivo relevance to diabetic kidney disease, TNF-α and MCP-1 levels were found to be elevated in the urine of db/db mice but not in the plasma.
  
  
  CONCLUSIONS
  TNF-α potently stimulates podocytes to produce MCP-1, utilizing the TNFR2 receptor and the NF-κB and PI3K/Akt pathways. Both TNF-α and MCP-1 levels were increased in the urine of diabetic db/db mice, correlating with the severity of diabetic albuminuria.
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA ; Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors: Choon Hee
authors: CH
authors: Chung
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA ; Pediatric Department, Wuhan University School of Medicine, Zhongnan Affiliated Hospital, Wuhan, P.R. China.
authors: Jingyi
authors: J
authors: Fan
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA ; Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors: Eun Young
authors: EY
authors: Lee
authors: Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors: Jeong Suk
authors: JS
authors: Kang
authors: Department of Internal Medicine, Soonchunhyang University College of Medicine, Cheonan, Korea.
authors: Seung Joo
authors: SJ
authors: Lee
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA.
authors: Petr E
authors: PE
authors: Pyagay
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA.
authors: Charbel C
authors: CC
authors: Khoury
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA.
authors: Tet-Kin
authors: TK
authors: Yeo
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA.
authors: Mark F
authors: MF
authors: Khayat
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA.
authors: Amy
authors: A
authors: Wang
authors: Division of Nephrology/Hypertension, Northwestern University, Chicago, Ill., USA ; Section of Nephrology, MD Anderson Cancer Center, Houston, Tex., USA.
authors: Sheldon
authors: S
authors: Chen
keywords: Akt or protein kinase B; Albuminuria; Diabetic rodent model; Nuclear factor-kappaB; Phosphatidylinositol 3-kinase; TNF receptor 2