Macrophages induce apoptosis in proximal tubule cells.
Macrophages play important roles during renal inflammation. Infiltrating macrophages produce proinflammatory mediators and induce apoptosis in a variety of target cells. Because proximal tubules are frequently damaged in inflammatory processes, we investigated murine macrophages (J774) in the induction of apoptosis in murine PKSV-PR proximal tubule cells. PKSV-PR cells were co-cultured with activated or non-activated macrophages. Apoptosis was assessed by Annexin-V-FITC/propidium iodide staining and analyzed by fluorescence-activated cell sorting. Macrophages were separated from tubule cells with transwell membranes to distinguish soluble factor-mediated from direct cell-to-cell contact-mediated apoptosis. Cell supernatants from activated and non-activated macrophages were analyzed for induction of apoptosis. Activated (but not non-activated) macrophages induced tubule cell apoptosis in co-culture. Soluble factors were mainly responsible for induction of apoptosis; membrane separation and transfer of cell supernatant from activated macrophages showed similar levels of apoptosis induction. Although tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta(1), measured by ELISA, increased significantly in supernatants from activated macrophages, blocking TNF-alpha and TGF-beta did not decrease apoptosis in PKSV-PR cells co-cultured with macrophages. Moreover, exogenous addition of TNF-alpha, TGF-beta, anti-Fas antibody, or TRAIL failed to induce apoptosis in tubule cells. We conclude that inflammatory macrophages mediate proximal tubule cell death, directing apoptosis mainly via release of unidentified soluble factors.
Lange-Sperandio
Bärbel
B
Department of Pediatrics, University of Virginia, VA 22908, Charlottesville, USA.
Fulda
Simone
S
Vandewalle
Alain
A
Chevalier
Robert L
RL
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D002460:Cell Line; D018920:Coculture Techniques; D017077:Culture Media, Conditioned; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D008262:Macrophage Activation / Q000502:physiology; D008264:Macrophages / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology; D051379:Mice; D013347:Subcellular Fractions / Q000502:physiology; D053221:TNF-Related Apoptosis-Inducing Ligand; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D019014:fas Receptor / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; D017077:Culture Media, Conditioned; D008562:Membrane Glycoproteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor