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Glucose enhances mesangial cell apoptosis.
Tarnjit Khera1, John Martin, Stephen Riley
1Institute of Nephrology, School of Medicine, Cardiff University, Heath Park, Cardiff, Wales, UK.
Summary
High glucose levels in diabetic nephropathy promote mesangial cell apoptosis by increasing sensitivity to TGF-beta1, not by increasing its synthesis. This pathway involves reduced NF-kappaB activation and altered Bcl-2:Bax ratios.
Area of Science:
- Nephrology
- Molecular Biology
- Cell Biology
Background:
- Diabetic nephropathy is characterized by mesangial cell apoptosis, correlating with albuminuria.
- Understanding glucose's role in mesangial cell apoptosis is crucial for diabetic kidney disease research.
Purpose of the Study:
- To elucidate the mechanism by which elevated glucose concentrations modulate mesangial cell apoptosis.
- To investigate the roles of NF-kappaB, Bcl-2/Bax ratio, and TGF-beta1 in high glucose-induced apoptosis.
Main Methods:
- Mesangial cells were cultured with varying glucose concentrations (5 mM vs. 25 mM) and subjected to serum deprivation.
- Apoptosis was assessed using Annexin-V staining and mitochondrial potential disruption.
- Gene expression (Bax, Bcl-2, NF-kappaB) and protein activation (caspase-3, NF-kappaB) were analyzed via RT-PCR and EMSA.
- The impact of TGF-beta1 and NF-kappaB inhibition (SN50) was evaluated.
Main Results:
- High glucose (25 mM) enhanced serum deprivation-induced apoptosis, caspase-3 activation, and decreased the Bcl-2:Bax ratio.
- High glucose inhibited NF-kappaB activation; SN50 treatment mimicked this, increasing apoptosis and decreasing the Bcl-2:Bax ratio.
- TGF-beta1 addition mimicked high glucose effects; blocking TGF-beta1 antibody inhibited glucose-mediated apoptosis.
- High glucose increased mesangial cell sensitivity to TGF-beta1, though de novo TGF-beta1 synthesis was not significantly increased.
Conclusions:
- Elevated glucose concentrations enhance mesangial cell apoptosis following serum deprivation.
- This effect is likely mediated by increased cellular sensitivity to endogenous TGF-beta1, coupled with inhibited NF-kappaB activation and altered Bcl-2:Bax ratio.