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Complement (C5b-9) induces glomerular epithelial cell DNA synthesis but not proliferation in vitro
S J Shankland1, J W Pippin, W G Couser
1Department of Medicine, University of Washington, Seattle 98195, USA. stuartjs@u.washington.edu
Kidney International
|August 5, 1999
Summary
The complement C5b-9 attack enhances DNA synthesis in glomerular cells by regulating cell cycle proteins. However, it prevents cell division, suggesting a G2/M phase arrest.
Area of Science:
- Immunology
- Cell Biology
- Nephrology
Background:
- The complement system's C5b-9 membrane attack complex (MAC) mediates antibody-induced glomerular injury.
- In experimental membranous nephropathy, C5b-9 triggers DNA synthesis without cytokinesis in visceral epithelial cells (VECs).
Purpose of the Study:
- To investigate if C5b-9 increases VEC DNA synthesis in vitro.
- To define the underlying molecular mechanisms of C5b-9-induced VEC cell cycle modulation.
Main Methods:
- Rat VECs were exposed to C5b-9 generated by antibody and complement.
- DNA synthesis, mitosis, and cytokinesis were assessed.
- Expression of cell cycle regulators (cyclin A, CDK2, p21, p27, cyclin B, cdc2) was analyzed via immunostaining and Western blot.
Main Results:
- Sublytic C5b-9 attack significantly augmented growth factor-induced DNA synthesis by 50% in VECs.
- This was associated with increased cyclin A and CDK2, and decreased p27 levels.
- C5b-9 reduced M-phase proteins (cyclin B, cdc2), leading to decreased mitosis and cytokinesis.
Conclusions:
- C5b-9 enhances VEC entry into S-phase via specific cell cycle protein regulation.
- Antibody and complement-mediated C5b-9 attack inhibits VEC mitosis and cytokinesis, indicating a G2/M phase delay or arrest.