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46: Presence of misfolded soluble oligomers in urine of women with severe preeclampsia classifies preeclampsia as a protein conformational disorder

      Objective

      Protein conformational disorders such as Alzheimer′s, light chain amyloidosis and prion diseases are propagated by amyloid fibril formation and aggregation due to defective folding of cellular proteins into aberrant 3D structures. A novel observation is that soluble pre-amyloid oligomers (intermediates in fibril assembly) have proteotoxic effects leading to endothelial damage and oxidative stress. As these processes play pathogenic roles in severe preeclampsia (sPE), our aim was to identify and characterize the nature of urinary soluble pre-amyloid oligomers in this pregnancy-specific condition.

      Study Design

      We analyzed 111 urine samples from women enrolled in 3 groups: sPE (n=49, GA: 28±1 wks), chronic hypertension (cHTN n=12, GA: 29±1 wks) and normotensive controls (CRL n=50, GA: 28±1 wks). Equal amounts of urine protein was subjected to dot blot using 3 conformation-specific antibodies recognizing prefibrillar soluble oligomers (A11), ring-shaped protofibrils (Officer) or fibrils (OC). Specificity was confirmed by omitting the primary antibodies. Identity of aggregated component proteins was sought by mass spectrometry and validated by Western blot with sequence-specific antibodies.

      Results

      1) Women with sPE had increased A11 and Officer (sPE: 42±8 vs. cHTN: 9±6 vs. CRL: 3±1 U/μg, P<0.001) but not OC urine immunoreactivity, independent of GA; 2) Urine A11 and Officer dot blot staining intensity correlated with severity of hypertension (P=0.007) and proteinuria (P=0.005); 3) Soluble oligomers in sPE urine were identified as light and heavy immunoglobulin chains, ceruloplasmin and the newly described 6-16 protein (G1P3), which is known to interact with Alzheimer′s presenilin-2 protein to regulate apoptosis.

      Conclusion

      This is the first observation that PE is a conformational disorder characterized by amyloid-like assembly of proteins. Concurrent A11 and Officer staining suggests that the misfolded intermediates have a propensity to assemble into pore-like structures (amyloid channels) that may play a role in clinical disease manifestations.