Fibronectin turnover in human mesangial cell cultures as affected by adriamycin
1Institute of Animal Physiology, Justus-Liebig-University Giessen, Germany.
Abstract:
Fibronectin (FN) turnover and turnover changes induced by the anticancer drug Adriamycin (ADR) were measured in human mesangial cells (HMC) in vitro. HMC cultures synthesize cellular FN (2.2 +/- 0.3% of total protein synthesis; n = 12) which is secreted and incorporated into a fibrillar extracellular matrix (ECM). A 24 hr incubation of HMC with ADR (0.5-5 micrograms/ml) resulted in an accumulation of FN in the culture medium, with a maximum increase following 5 micrograms/ml (7.3 +/- 2.3 pg/cell vs. controls: 4.4 +/- 1.9 pg/cell; n = 10). Correspondingly, radioactively labeled immunoprecipitable FN was increased in a dosage-dependent manner in the culture medium up to 50% vs. controls. The incorporation of radioactively labeled FN into ECM was significantly increased following 2 micrograms ADR/ml. In accordance, immunofluorescence staining revealed an expansion of pericellular FN fibers in cultures exposed to 2 micrograms ADR/ml. Concomitant with the accumulation of extracellular FN, radioactively labeled FN in the cells was reduced by 22%. Qualitative characterization of FN patterns revealed a diminished number of degradation products in the culture medium of ADR-treated HMC. These data suggest that ADR interferes with the turnover of FN secreted by HMC in vitro in such a way that FN accumulates extracellularly. This in turn leads to a reduced FN synthesis. These findings are compatible with a loss of urinary FN degradation products accompanying the onset of proteinuria in ADR-treated rats.
Insights
Adriamycin (ADR) increases fibronectin (FN) in human mesangial cells, leading to extracellular accumulation and reduced cellular FN. This suggests ADR disrupts FN turnover, impacting extracellular matrix formation.
Area of Science:
- Cell Biology
- Pharmacology
- Nephrology
Background:
- Fibronectin (FN) is a crucial extracellular matrix (ECM) protein synthesized by human mesangial cells (HMC).
- Altered FN turnover is implicated in kidney disease pathogenesis.
- Adriamycin (ADR) is an anticancer drug with known nephrotoxic effects.
Purpose of the Study:
- To investigate the effects of Adriamycin (ADR) on fibronectin (FN) turnover in human mesangial cells (HMC) in vitro.
- To determine how ADR influences FN secretion, incorporation into the ECM, and degradation.
Main Methods:
- HMC cultures were treated with varying concentrations of ADR (0.5-5 µg/ml).
- Quantification of FN in culture medium and cells using radioisotopes and immunoprecipitation.
- Analysis of FN incorporation into the ECM and pericellular fiber organization via immunofluorescence staining.
- Assessment of FN degradation products in the culture medium.
Main Results:
- ADR treatment led to a dose-dependent accumulation of FN in the culture medium, with a significant increase at 5 µg/ml.
- Radioactive FN in the medium increased up to 50%, while intracellular radioactive FN decreased by 22%.
- ADR (≥2 µg/ml) significantly enhanced FN incorporation into the ECM and expanded pericellular FN fibers.
- A reduction in FN degradation products was observed in ADR-treated HMC cultures.
Conclusions:
- ADR interferes with fibronectin (FN) turnover in human mesangial cells (HMC) in vitro.
- ADR promotes extracellular FN accumulation and reduces intracellular FN levels.
- These findings suggest ADR disrupts FN metabolism, potentially contributing to renal pathology observed in vivo.
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