Formation of intranuclear crystalloids and proliferation of the smooth endoplasmic reticulum in schwann cells induced by tellurium treatment: Association with overexpression of HMG CoA reductase and HMG CoA synthase mRNA

• Published in: Glia Vol. 29; no. 3; pp. 246 - 259
• Main Authors: Berciano, Maria T., Fernandez, Rosario, Pena, Emma, Calle, Ester, Villagra, Nuria T., Rodriguez-Rey, Jose C., Lafarga, Miguel
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 01.02.2000; Wiley-Liss
• Subjects: Animals; Biological and medical sciences; Cell Nucleus - metabolism; cholesterol deficit; Cytoplasm - physiology; endomembrane biogenesis; Endoplasmic Reticulum, Smooth - physiology; Fundamental and applied biological sciences. Psychology; Hydroxymethylglutaryl CoA Reductases - genetics; Hydroxymethylglutaryl-CoA Synthase - genetics; Inclusion Bodies - ultrastructure; Isolated neuron and nerve. Neuroglia; lamellar bodies; Lipid Metabolism; Male; Microspheres; Rats; Rats, Sprague-Dawley; RNA, Messenger - metabolism; Schwann Cells - drug effects; Schwann Cells - physiology; Te-neuropathy; tellurium; Tellurium - pharmacology; Vertebrates: nervous system and sense organs; Cell proliferation; Rat; Enzyme; Neuroglia; Hydroxymethylglutaryl-CoA synthase; Rodentia; Gene overexpression; Lipids; Lyases; Cholesterol; Tellurium; Oxo-acid-lyases; Carbon-carbon lyases; Vertebrata; Mammalia; Schwann cell; Crystalloid solution; Demyelination; Hydroxymethylglutaryl-CoA reductase; Oxidoreductases; Endoplasmic reticulum
• ISSN: 0894-1491; 1098-1136
• DOI: 10.1002/(SICI)1098-1136(20000201)29:3<246::AID-GLIA6>3.0.CO;2-L

Administration of tellurium (Te) in weaning rats causes a well‐established demyelinating neuropathy induced by the inhibition in myelinating Schwann cells (SC) of the synthesis of cholesterol, a major component of the myelin sheath, at the level of squalene epoxidase. We have used this experimental model of Te neuropathy to study the biogenesis and reorganization of the endomembranes of the nuclear envelope and endoplasmic reticulum (ER) in response to Te treatment by ultrastructural analysis and in situ hybridization for the detection of HMG CoA reductase and synthase mRNA, which encode key enzymes in cholesterol synthesis. The adaptive response of myelinating SC to cholesterol depletion includes cell hypertrophy, the formation of tubular invaginations of proliferating nuclear membranes giving rise to peculiar nuclear inclusions termed crystalloids, and, at the cytoplasmic level, the formation of lamellar bodies of rough ER, proliferation of the smooth ER, and overexpression of HMG CoA reductase and synthase mRNAs. The changes revert after withdrawal of Te treatment. Our results show that the biogenesis and structural organization of both endomembrane systems change dynamically upon Te‐induced cholesterol depletion, indicating that this constituent plays a critical role in the organization of nuclear envelope and ER compartments in SC. The results also suggest that the HMG CoA reductase, an integral membrane protein of ER, provides the signal for the extensive membrane assembly. While the physiological meaning of crystalloid remains to be clarified, the hypertrophy of the smooth ER may represent a cytoprotective mechanism involved in detoxification of the neurotoxic agent or its metabolic derivates. GLIA 29:246–259, 2000. © 2000 Wiley‐Liss, Inc.