Abstract: FR-PO707

Albumin Modification Leads to Altered Glomerular and Podocyte Injury

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Agrawal, Shipra, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
  • Waller, Amanda P., The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
  • Kino, Jiro, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
  • Chanley, Melinda A., The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
  • Kerlin, Bryce A., The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
  • Smoyer, William E., The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States
Background

Albuminuria is associated with an increased risk of progressive glomerular disease. However, the molecular basis for potential causative roles for albuminuria and/or its modification [free fatty acid (FFA) binding and ionic forms] in progressive glomerular disease remains poorly understood. We hypothesized that albumin modification by altering its levels, FFA binding ratio, and charge can regulate glomerular and podocyte injury.

Methods

A model of chronic glomerular disease was studied in wild type (WT), Nagase Analbuminemic Rat (NAR), and NAR-Het on a Fischer344 background female rats (~160 g, N=4-5/group) by multiple puromycin-aminonucleoside (PAN) injections (100 mg/kg i.p., every 4 weeks) over a course of 3 months, with serial measurements of proteinuria, serum creatinine, urinary podocalyxin, and N-acetyl-b-D-glucosaminidase (NAG) activity. Moreover, direct podocyte injury was compared following exposure to albumin and FFA at varying molar ratios, as well as exposure to cationic vs. regular albumin.

Results

Consistent proteinuria was induced at week 11 in WT rats, which was significantly higher vs. NAR or NAR-Het rats. Moreover, comparable plasma protein levels were observed in NAR vs. WT rats, despite complete absence of albumin in NAR. Serum creatinine levels were similarly increased in both NAR and WT rats at week 12, while podocalyxin levels were slightly increased only in WT rats, and NAG activity was not altered in either group. Since the FFA:albumin ratio is massively altered in NAR, the ability of FFA to cause direct podocyte injury in vitro was measured in the absence/presence of albumin at different molar ratios. Both the absence of albumin and exceeding the FFA binding capacity of albumin (>10:1 FFA:albumin) resulted in increased podocyte toxicity, especially for oleic acid and arachidonic acid. Additionally, cationic albumin induced dramatically greater podocyte toxicity vs. regular negatively charged albumin, even at 400 times lower concentration (0.1 g/dL, 20 hr exposure vs. 4g/dL, 4-7 days exposure).

Conclusion

Modification of albumin by altering its levels, FFA:albumin ratio, or ionic charge dramatically alters its glomerular and direct podocyte toxicity.