Properties of lysosomal beta-hexosaminidase accumulated in Niemann-Pick mouse liver

Various lysosomal acid hydrolases from tissues of Niemann-Pick mice, a mutant strain of C57BL/KsJ mice (spm/spm), were examined and compared to those from control mice. Activities of beta-hexosaminidase, beta-galactosidase, acid phosphatase, and cathepsin L were elevated in the liver and spleen of the affected mice, whereas no significant changes in beta-glucosidase and acid alpha-glucosidase were observed. Alpha-Mannosidase and neutral alpha-glucosidase activities were rather decreased in the affected mouse liver. The level of beta-hexosaminidase in the Niemann-Pick mice was raised sixfold in the liver and two- to threefold in the spleen and brain, whereas its total activity was decreased in the kidney. Sixty to ninety percent of total activity of lysosomal hydrolases was solubilized with 0.1% Triton X-100 in control mice, but most of the beta-hexosaminidase activity of the Niemann-Pick mice remained associated with the membrane fraction of liver lysosomes. The beta-hexosaminidase of the Niemann-Pick mice was appreciably stable when heated at 55 degrees C, while hydrolases of the affected mice and all of the enzymes tested in control mice were heat labile. The relative content of two beta-hexosaminidase fractions separated by DEAE-cellulose column chromatography was 8% for beta-hexosaminidase I and 92% for beta-hexosaminidase II in the case of the control mouse liver. The isozyme pattern of hexosaminidases in Niemann-Pick mice was similar to that of control enzymes. However, the beta-hexosaminidase II accumulated in Niemann-Pick mouse liver was different from that of the control in optimum pH, Km values and thermostability.

Metabolism of sphingomyelin in cultured skin fibroblasts from patients with different types of Niemann-Pick disease

The metabolism of [choline-methyl-14C]sphingomyelin in cultured skin fibroblasts from patients with different types of Niemann-Pick disease was measured 1 and 3 days after uptake from the media. The cell lines obtained from type A disease had more than 95% unhydrolyzed sphingomyelin in situ on day 3 while two cell lines obtained from type B had 36.3% and 43.3% unhydrolyzed sphingomyelin on day 3. The cell line derived from one patient with the transitory type disease had 48.1% unhydrolyzed sphingomyelin on day 3, and there was no significant difference in the sphingomyelinase activity measured in vitro or in degradation of sphingomyelin in situ between the type B and transitory type disease. In three cell lines from patients with type C disease, there was 18.5%, 29.6% and 31.1% unhydrolyzed sphingomyelin on day 3, which indicates that this type has a decreased ability to metabolize sphingomyelin. Cell from type E disease metabolized sphingomyelin normally.

[Type C Niemann-Pick disease in 2 siblings. Biochemical bases of its diagnosis]

Two brothers, a seven-year-old male and a nine-year-old female are reported. Clinical features include scholar troubles and clumsiness, hepatosplenomegaly, vertical supranuclear ophthalmoplegia and ataxic gait. Moreover, the girl showed intention tremor. Foamy histiocytes were seen in bone marrow and some Niemann-Pick type Kupffer cells were present in liver. Girl's conjunctival biopsy showed lamellar inclusions. Biochemical studies were performed in girl's skin and liver biopsies. Sphingomyelinase activity assayed with 14C sphingomieline in cultured skin fibroblasts was 26% at the mean control value. Liver lipid composition did not show an appreciable increase of sphingomyelin or cholesterol, but bis (monoacylglyceryl) phosphate was clearly elevated. These data are compatible with Niemann-Pick disease type C.

Sphingomyelinases and Niemann-Pick disease

In the first part the properties of normal mammalian sphingomyelinases are reviewed: The lysosomal acid sphingomyelinase is a polymeric glycoprotein (subunit Mr between 28 000 and 70 000) which hydrolyses natural sphingomyelin, coloured and fluorescent semi-synthetic analogues (trinitrophenyl-aminolauryl-sphingomyelin and pyrenedecanoyl-sphingomyelin) and the synthetic analogue 2-N-hexadecanoylamido-nitrophenyl-phosphorylcholine. The suitability of these substrates and of synthetic fluorescent derivatives of methylumbelliferone is discussed. The effect of lipids, detergents and other effectors on the enzyme activity is also described. The neutral sphingomyelinase from brain tissue, localized in cell membranes, has a high Mr (160 000 and 600 000), is heat labile, hydrolyses sphingomyelin and its coloured and fluorescent analogues, but not 2-N-hexadecanoylamido-nitrophenyl-phosphorylcholine. A new method is available for determining enzyme activity in the intact cell through the utilization of endogenous or exogenous sphingomyelin as substrate. In the second part of the review, the classification of Niemann-Pick disease, the characteristic features of each type and the biological tools used for the diagnosis are reported. Experimental models (animal models and cellular models in culture) are reviewed with a particular attention to a new model system, Epstein-Barr virus-transformed lymphoid cell lines.

Clinical and biochemical diagnostics of Niemann-Pick disease

Niemann-Pick disease (NPD) is an inherited lysosomal storage disorder characterised biochemically by a deficiency of sphingomyelinase activity and massive accumulation of undegraded sphingomyelin. There are three main clinical types of the disorder (NPD type A, B and C). NPD type A and B is diagnosed biochemically on the basis of measuring sphingomyelinase activity in leukocytes or cultured fibroblasts. The diagnosis may be established with the chromatographic method by the high level of sphingomyelin concentration in liver samples. Because in NPD type C the decrease of sphingomyelinase activity is moderate and only occurs in fibroblasts the thin-layer chromatography of the total liver lipid extracts is necessary for establishing the diagnosis. The thin-layer chromatography of the total liver lipids is sufficient for the diagnosis of all types of NPD.

Molecular forms of sphingomyelinase and non-specific phosphodiesterases in Epstein-Barr virus-transformed lymphoid cell lines from Niemann-Pick disease types A and B

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.

Soluble sphingomyelinase from human urine as antigen for obtaining anti-sphingomyelinase antibodies

A soluble form of lysosomal sphingomyelinase was partially purified from human urine using concanavalin A-Sepharose 4B, Sephadex G-100 and octyl-Sepharose 4B chromatography. The octyl-Sepharose 4B eluate was used to immunise a rabbit. The antiserum obtained was able to precipitate about 70% of the sphingomyelinase activity present in urine from control subjects. Both the immunoprecipitable and non-precipitable activities were found to be deficient in urine from patients with Niemann-Pick disease Type A and Type B. In contrast, both activities were present in urine from patients with Niemann-Pick disease Type C. The antiserum was able to precipitate about 80% of the sphingomyelinase activity present in an aqueous extract of placenta.

Adrenal changes in Niemann-Pick disease: differences between sphingomyelinase deficiency and type C

Structural, chemical, and histochemical analyses of adrenal tissue performed in 8 cases of Niemann-Pick disease (NPD) revealed stark differences of storage between spingomyelinase (SMase) deficiency (6 cases) and type C (2 cases). In all the full-blown cases of the SMase deficiency group, pronounced sphingomyelin (SM) storage was found in all the zones of the cortical epithelium with slightly increasing centripetal gradient. The storage resulted in the reduction or even disappearance of lipofuscinogenesis in the reticular zone, in the reduction of the physiological fat content, in the generalized foamy transformation of the epithelium, and in moderate organomegaly. The storage was expressed in both A and B types and was roughly proportional to the storage in other viscera. The stromal storage was confined to the vascular endothelium, and in particular, to the macrophages. One of the cases showed the presence of typical spirolactone bodies unmodified in fine structure by the lysosomal storage. Their most conspicuous enzymatic activity was that of non-specific esterase and NADH tetrazolium reductase. The adrenals in type C were macroscopically and histologically normal except for a variable population of stromal foam cells. Chemically, there was slight increase in all phospholipids with borderline or moderate percentual increase of SM. There was also slight increase in some of the lower neutral glycosphingolipids. Electron microscopy dislosed rudimentar storage in lower cortical layer epithelium which by its fine structure and according to results of lipid histochemistry was qualitatively different from that in SMase deficiency. The stromal storage was expressed mainly in macrophages in which there was histochemically detectable amount of SM. There was no storage detectable in medullary cells in neither group of NPD complex. The results point not only to striking quantitative differences in storage intensity between the 2 basic groups of NPD showing the cortical epithelium in type C as being remarkably resistant to the metabolic disorder, but also to difference in quality of the storage very much like that found in other tissues, too.

Placental ultrasonographic biochemical and histochemical studies in human fetuses affected with Niemann-Pick disease type A

Placental ultrasonographic, bio- and histochemical studies were performed on four unrelated fetuses affected with Niemann-Pick disease Type A, following prostaglandin-induced abortion at about the 19th week of gestation. An accumulation of sphingomyelin in the placentae of affected fetuses indicates the essential role of the enzyme sphingomyelinase, even during the early stages of gestation. A fair correlation between histochemical localization of sphingomyelin in the placentae and ultrasonographic findings was found, indicating the value of ultrasonic echo wave information in the diagnosis of metabolic disorders.

New tools for the study of Niemann-Pick disease: analogues of natural substrate and Epstein-Barr virus-transformed lymphoid cell lines

Acid sphingomyelinase activity was determined in Epstein-Barr virus-transformed lymphoid cell lines (LCL) established from patients affected with Niemann-Pick disease (NPD) using several substrates: sphingomyelin derivatives, radiolabeled [14C]sphingomyelin (SM), fluorescent N-(10-(1-pyrene)decanoyl)sphingomyelin (P10-SM) or colored trinitrophenylaminolauryl-sphingomyelin, and the chromogenic non-natural substrate 2-N-(hexadecanoyl)amino-4-nitrophenylphosphoryl-choline. LCL from NPD Type A and Type B showed a severe deficiency of acid sphingomyelinase determined using either substrate, whereas LCL from normal subjects had an activity close to that of blood leukocytes. Sphingomyelinase in normal LCL had the same pH optimum (5.0-5.2) and molecular form (pI 5.8) as the enzyme from other sources; identical profiles and activity levels were obtained using the various analogues of sphingomyelin. However, among these derivatives, the assay using P10-SM appeared as the most useful and sensitive for enzymatic diagnosis of NPD. Electron microscopy of NPD LCL demonstrated the lysosomal storage. These results prove the validity of LCL as an experimental model system for NPD.

Biochemical and ultrastructural findings in a lymphoid cell line from Niemann-Pick disease type A

A lymphoid cell line (LCL) established by Epstein-Barr Virus (EBV)-transformation of blood B-lymphocytes from a patient affected with Niemann-Pick disease (NPD) Type A exhibited a severe deficiency of sphingomyelinase activity (less than 10% residual activity). Ultrastructural investigation showed in LCL from NPD type A, the presence of numerous osmiophilic, electron-dense inclusions with myelin-like figures characteristic of the accumulation of sphingomyelin (and other amphiphilic lipids) similar to those observed in tissues of patients affected with NPD.

Immunological studies on lysosomal sphingomyelinase: identification of a 28 000-Da component deficient in urine from patients with Niemann-Pick disease types A and B

The immunoblotting technique was used to identify sphingomyelinase protein in samples of tissue and urine after subjection to polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an Mr of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-Mr bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded that sphingomyelinase is composed of at least one polypeptide with an Mr of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B.

Studies on the activation of sphingomyelinase activity in Niemann-Pick type A, B, and C fibroblasts: enzymological differentiation of types A and B

Cultured skin fibroblast homogenates from patients with Niemann-Pick disease Type C, were able to degrade sphingomyelin liposomes at a normal rate. Fibroblasts from patients with Niemann-Pick disease Types A and B were less active (0.08-0.55 versus 0.96-2.93 nmol/h/mg). When fibroblasts were maintained in synthetic media (MCDB-104) devoid of fetal calf serum for a period of 21 days, sphingomyelinase activity measured at pH 3.8 increased in control and Niemann-Pick Type C (up to 15-fold) and in Niemann-Pick Type B (up to 3-fold) while Niemann-Pick Type A showed no significant increase in sphingomyelinase activity. Addition of a protein activator isolated from the spleen of a Type I Gaucher's disease patient stimulated a 2-7.5-fold increase in sphingomyelinase activity in normal, Niemann-Pick Type B and C fibroblasts, while under the same conditions the Niemann-Pick Type A fibroblast enzyme responded poorly. Our data show that the residual sphingomyelinase activity in Niemann-Pick Type A can be differentiated from that present in other phenotypic forms by its lack of response to the Gaucher activator. Furthermore, we can find no evidence to support the view that Niemann-Pick Type C sphingomyelinase differs from the normal enzyme in its response to Gaucher activator.

Liver findings in Niemann-Pick disease type C

A complex analysis of liver from a series of eight cases of Niemann-Pick disease type C showed practically generalized storage of glycolipids and phosphoglycerides by chemical and histochemical techniques. In six of the eight cases the storage process was of low degree, barely recognizable by routine histology, but well recognizable by histochemistry and electron-microscopy. In two cases it was marked and led to early functional impairment of the liver. Changes in various enzyme activities and in ultrastructural features of the storage process are described. Sphingomyelin was found to participate to a very low low degree and its accumulation was not proportional to the extent of overall storage. In two cases with prominent involvement of the liver normal levels of sphingomyelin were found. In other cases sphingomyelin was found, by lipid histochemistry, to be stored only in macrophages. To stress that the storage process in Niemann-Pick disease type C is qualitatively different a comparison was made with liver findings in sphingomyelinase-deficient patients. This feature is of practical as well as theoretical importance.

Degradation of lysophosphatidylcholine by lysosomes. Stimulation of lysophospholipase C by taurocholate and deficiency in Niemann-Pick fibroblasts

Hydrolysis of 2-[1-14C]oleoyl phosphatidylcholine and of 1-[1-14C]oleoyl lysophosphatidylcholine by lysosomes prepared from rat liver using Triton WR-1339 has been studied. At pH 5.0 sodium taurocholate stimulated the release by the soluble lysosomal fraction of labelled lysophosphatidylcholine, diacyl- and monoacylglycerol and fatty acids from [14C]phosphatidylcholine. The time course of appearance of labelled products suggested that monoacylglycerol could be released as a result of the action of phospholipase A1 followed by lysophospholipase C or by the initial action of phospholipase C followed by monoacylglycerol lipase. The hydrolysis of 1-[14C]acyl lysophosphatidylcholine was also stimulated by sodium taurocholate under similar conditions; however, only release of monoacylglycerol was increased, whereas release of fatty acid was inhibited. Mg2+ inhibited the release of labelled monoacylglycerol and of fatty acid from lysophosphatidylcholine. The detergents deoxycholate and Triton X-100 and phospholipids were strongly inhibitory. 5'-AMP almost completely suppressed release of monoacylglycerol but increased release of fatty acid. Chloroquine strongly suppressed release of monoacylglycerol and only at high concentration (1.25 mM) diminished fatty acid release. In the presence of sodium taurocholate the predominant mechanism for degradation of phosphatidylcholine by the soluble fraction of lysosomes involves phospholipase A followed by phospholipase C. Assay of release of monoacylglycerol from [14C]lysophosphatidylcholine catalyzed by extracts of fibroblasts from patients with Niemann-Pick disease and controls in the presence of taurocholate revealed that lysophospholipase C activity was lacking in those cell lines that were deficient in sphingomyelinase. This suggests that lysophospholipase C and sphingomyelinase activities may be catalyzed by one enzyme.

[Type-B Niemann-Pick disease. Apropos of a case]

A case of Niemann-Pick's disease is described. This finding is the result of infant's interstitial pneumonitis study. Anatomopathological and enzymatic results are showed.

Sphingomyelinase and nonspecific phosphodiesterase activities in Epstein-Barr virus-transformed lymphoid cell lines from Niemann-Pick disease A, B and C

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.

Studies on the activation of the enzymatic hydrolysis of sphingomyelin liposomes

Two pH optima were observed for the hydrolysis of sphingomyelin liposomes by brain and fibroblast extracts; one at pH 4.2-4.5, the other at pH 7-8. The proportion of the acidic activity in fibroblasts was affected greatly by the culturing conditions. Both the acidic and neutral enzyme activities were deficient in Niemann-Pick Type A fibroblasts, suggesting that both were genetically related. Partially purified activators from normal as well as Gaucher disease spleen stimulated the hydrolysis of sphingomyelin, at both pH values, by fibroblast and brain extracts. After further purification by DE-52 and Sephacryl 200 column chromatography the Gaucher activator retained its ability to stimulate sphingomyelinase and was active as well towards beta-glucocerebrosidase and beta-galactocerebrosidase.

Ultrastructural investigations on two lymphoid cell lines from Niemann-Pick disease type B

Lymphoid cell lines (LCL) were established by Epstein-Barr Virus (EBV) transformation of blood B-lymphocytes from two different patients affected with Niemann-Pick disease (NPD) type B. Those lines were severely deficient in sphingomyelinase activity (8% and 10% residual activity). Ultrastructural investigations showed in both these lines the presence of numerous osmiophilic, dense and pleiomorphic inclusions characteristic of lysosomal storage (due to the accumulation of amphiphilic lipids) similar to those observed in tissues from NPD.