hymecromone and Niemann-Pick-Diseases

Human lymphoid cell lines established from normal subjects and from a Niemann-Pick disease type C patient were investigated from a triple point of view of enzymology, metabolism and ultrastructure: Sphingomyelinase activities, isoenzyme electrofocusing profiles and properties of the major enzyme were quite similar in type C and normal lymphoid cell lines. Similarly, no significant difference was observed in non-specific phosphodiesterases hydrolysing bis(methylumbelliferyl)phosphate and bis(methylumbelliferyl)pyrophosphate. The study of the lipid composition of type C cells showed no obvious accumulation of sphingomyelin or other phospholipid, but only a higher amount of glycolipids (mainly GlcCer and GbOse3Cer), as visualized by bidimensional thin-layer chromatography. Ultrastructural studies demonstrated, in type C cells, the presence of an obvious lysosomal storage of amphiphilic lipids quite similar to that observed in tissues of type C patients. These studies, which demonstrate the validity of lymphoid cell lines as an experimental model system for type C disease, agree with the current opinion that an impairment of sphingomyelin catabolism is not the primary defect in type C disease.

Topics: Cell Line; Cell Transformation, Viral; Herpesvirus 4, Human; Humans; Hydrogen-Ion Concentration; Hymecromone; Isoenzymes; Lipids; Lymphocytes; Microscopy, Electron; Niemann-Pick Diseases; Phosphoric Diester Hydrolases; Sphingomyelin Phosphodiesterase; Sphingomyelins; Umbelliferones

Molecular forms of sphingomyelinase and phosphodiesterases from lymphocytes- and Epstein-Barr virus-transformed lymphoid cell lines were separated by preparative electrofocusing in granulated gels. In either type of cell derived from normal individuals, sphingomyelinase focused as a single peak (pI = 5.60 +/- 0.1) while phosphodiesterases hydrolyzing bis(4-methylumbelliferyl)phosphate and bis(4-methylumbelliferyl)diphosphate separated into seven and three molecular forms respectively; one of the latter showed sphingomyelinase as well as phosphodiesterase activities. Lymphoid cell lines derived from patients with Niemann-Pick disease, types A or B, were practically devoid of sphingomyelinase activity; this was not so for the phosphodiesterases which focussed essentially as normal. The protein peak, which in normal cells contained the three activities, had phosphodiesterase but no sphingomyelinase activity in the Niemann-Pick cells. In normal cells, sphingomyelinase and phosphodiesterase activities of this peak showed different responses to heating and several effectors. These data suggest that in lymphoid cell lines, which are a useful model for studies of Niemann-Pick disease, sphingomyelinase and phosphodiesterases are subject to separate genetic coding and that the latter activities are not a reliable measure for diagnosing Niemann-Pick disease.

Topics: Cell Line; Cell Transformation, Viral; Herpesvirus 4, Human; Humans; Hymecromone; Isoelectric Focusing; Lymphocytes; Niemann-Pick Diseases; Phosphoric Diester Hydrolases; Protein Denaturation; Sphingomyelin Phosphodiesterase; Umbelliferones

Acid sphingomyelinase activity determined using the natural substrate, [choline-methyl-14C]sphingomyelin, or the chromogenic synthetic analogue, 2-N-(hexadecanoyl)amino-4-nitrophenylphosphorylcholine, was deficient in Epstein-Barr virus-transformed lymphoid cell lines from Niemann-Pick disease types A and B. In contrast, lines from Niemann-Pick disease type C and "sea-blue histiocyte syndrome" showed a sphingomyelinase activity within the normal range. Bis(4-methylumbelliferyl)phosphate and bis(4-methylumbelliferyl)pyrophosphate phosphodiesterase activities were not deficient in any Niemann-Pick disease cell line. These results demonstrate the validity of such cell lines as an experimental model system for enzymatic studies of Niemann-Pick disease.

Topics: Adult; Cell Line; Cell Transformation, Viral; Herpesvirus 4, Human; Humans; Hymecromone; Lymphocytes; Niemann-Pick Diseases; Phosphoric Diester Hydrolases; Sphingomyelin Phosphodiesterase; Sphingomyelins; Umbelliferones