Elevated tissue polypeptide antigen as a risk factor for carpal tunnel syndrome in haemodialyzed patients

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Beta 2 microglobulin isoforms in healthy individuals and in amyloid deposits

beta 2 microglobulin (beta 2m) is classically known to have isoforms with isoelectric points (pI) 5.7 and 5.3. New isoforms of beta 2m with lower pI, probably due to modifications with advanced glycation end products, were found in the amyloid deposits of dialysis related amyloidosis (DRA), and they were proposed as the amyloidogenic forms of beta 2m. The other modifications in beta 2m from amyloid deposits are partial proteolysis and single amino acid replacement (Asn by ASp at position 17). However, there are no data on the sequence of the different isoforms of beta 2 m from amyloid deposits. Amyloid deposits surgically obtained from the carpal tunnel from 13 dialysis treated patients and urine from 10 healthy volunteers and 5 living-related kidney donors were analyzed for beta 2m content. Two-dimensional gel electrophoresis (2D-PAGE) of beta 2m from amyloid deposits showed the presence of four or more isoforms with pIs < 5.7. All the spots migrating at 12 kDa Mr region and between 4 and 6 pH reacted with rabbit anti-human beta 2m antibody by Western blotting, confirming that they were beta 2m isoforms. beta 2m isoforms from the amyloid deposits were then separately purified with an IEF column (PB94, Pharmacia) for analysis. Enough quantities of three pure beta 2m isoforms could be obtained in two cases. The sequence analysis showed an intact N-terminus in all the isoforms. There was Asn in the 17th residue in all the isoforms sequenced. 2D-PAGE of urine from 8 out of the 10 healthy volunteers showed the presence of beta 2m. In two of them beta 2m also displayed four different isoforms. At least four isoforms were observed in urine of all the kidney donors. The present study shows that the elution peaks of three different beta 2m isoforms in gel isoelectrofocusing contain beta 2m with intact N-terminus. None of them have deamidated their 17th residue. More importantly, the beta 2m isoforms with lower pI are not specific for amyloidosis as they were found in urine from kidney donors and in normal volunteers. These results bring into question the hypothesis that dialysis related amyloidosis is due to the known modifications on beta 2m. They suggest that the precipitation of beta 2m into amyloid fibrils should result from the interaction of beta 2m with other factors with amyloid enhancing activity.