A new subgroup of lectin-bound biliary proteins binds to cholesterol crystals, modifies crystal morphology, and inhibits cholesterol crystallization.

Abstract

Biliary proteins inhibiting or promoting cholesterol crystallization are assumed to play a major role in cholesterol gallstone pathogenesis. We now report a new group of biliary proteins that bind to cholesterol crystals, modify crystal morphology, and inhibit cholesterol crystallization. Various glycoprotein mixtures were extracted from abnormal human gallbladder bile using lectin affinity chromatography on concanavalin A, lentil, and Helix pomatia columns and were added to supersaturated model bile. Independent of the protein mixtures added, from the cholesterol crystals harvested, the same four GPs were isolated having molecular masses of 16, 28, 63, and 74 kD, respectively. Each protein was purified using preparative SDS-PAGE, and influence on cholesterol crystallization in model bile was tested at 10 jig/ml. Crystal growth was reduced by 76% (GP63), 65% (GP16), 55% (GP74), and 40% (GP28), respectively. Thus, these glycoproteins are the most potent biliary inhibitors of cholesterol crystallization known so far. Evidence that the inhibiting effect on cholesterol crystallization is mediated via protein-crystal interaction was further provided from scanning electron microscopy studies. Crystals grown in presence of inhibiting proteins showed significantly more ordered structures. Incidence of triclinic crystals and regular aggregates was shifted from 30 to 70% compared with controls. These observations may have important implications for understanding the role of biliary proteins in cholesterol crystallization and gallstone pathogenesis. (J. Clin. Invest. 1995. 96:3009-3015.)

Cholesterol crystal binding of biliary immuno-globulin A: visualization by fluorescence light microscopy

“…We speculate that crystal growth inhibitors like biliary IgA attach to the most rapidly growing sites l i k e s p i r a l a n d e d g e d i s l o c a t i o n s o n t h e thermodynamically stable monohydrate crystals, thus changing crystal morphology, retarding crystal growth and decreasing final crystal concentration [19] . This concept applies to many crystal growth inhibitors in biomineralization.…”

“…To remove insoluble constituents, bile samples were ultracentrifuged at 100 000 × g for 1h. Biliary protein fractions were isolated by affinity chromatography using -Concanavalin A and Helix pomatia-lectin, as described [19,20] . Biliary IgA was isolated from the bound protein fraction by immunoaffinity chromatography [20] .…”

“…However, the significance of individual protein factors for the pathogenesis of the human disease remains controversial [17,18] . By preparing crystal adsorbed proteins via sucrose density gradient centrifugation and gel electrophoresis, we identified a subgroup of human biliary proteins that bind to cholesterol crystals, modify crystal morphology and inhibit cholesterol crystallization [19] . We demonstrated that secretory immunoglobulin A (IgA) is a major constituent of this group of cholesterol crystal-binding proteins [20] .…”

Genetic evidence that apolipoprotein E4 is not a relevant susceptibility factor for cholelithiasis in two high-risk populations

“…Although the association between serum lipids and gallstones has remained controversial, decreased HDL cholesterol and increased triglyceride levels might be correlated with biliary cholesterol supersaturation and the risk for cholelithiasis (14)(15)(16). Previous studies have indicated that the interaction of sustained cholesterol supersaturation in bile with biliary proteins, such as mucins, modulates cholesterol crystallization and gallstone formation (1)(2)(3)(4)(17)(18)(19). Together, these findings suggest that abnormalities in cholesterol and lipoprotein metabolism play an important role in the pathogenesis of cholesterol cholelithiasis.…”

The role of Concanavalin A-binding fraction in cholesterol crystallization in native human bile

“…The results of these studies indicated that added immunoglobulins (6,17), cr 1 -acid glycoprotein (7), aminopeptidase N (818) and haptoglobin (19) promote cholesterol crystallization in model biles. In addition to crystallization-promoting proteins, inhibitors have been isolated from CABF (3,4,20,21).…”