Treatment with the Glycosphingolipid Modulator THI Rescues Myelin Integrity in the Striatum of R6/2 HD Mice.

Huntington's disease is one of the most common dominantly inherited neurodegenerative disorders caused by an expansion of a polyglutamine (polyQ) stretch in the N-terminal region of huntingtin (Htt). Among all the molecular mechanisms, affected by the mutation, emerging evidence proposes glycosphingolipid dysfunction as one of the major determinants. High levels of sphingolipids have been found to localize in the myelin sheaths of oligodendrocytes, where they play an important role in myelination stability and functions. In this study, we investigated any potential existing link between sphingolipid modulation and myelin structure by performing both ultrastructural and biochemical analyses. Our findings demonstrated that the treatment with the glycosphingolipid modulator THI preserved myelin thickness and the overall structure and reduced both area and diameter of pathologically giant axons in the striatum of HD mice. These ultrastructural findings were associated with restoration of different myelin marker protein, such as myelin-associated glycoprotein (MAG), myelin basic protein (MBP) and 2', 3' Cyclic Nucleotide 3'-Phosphodiesterase (CNP). Interestingly, the compound modulated the expression of glycosphingolipid biosynthetic enzymes and increased levels of GM1, whose elevation has been extensively reported to be associated with reduced toxicity of mutant Htt in different HD pre-clinical models. Our study further supports the evidence that the metabolism of glycosphingolipids may represent an effective therapeutic target for the disease.

Abnormal expression of sphingolipid-metabolizing enzymes in the heart of spontaneously hypertensive rat models.

Sphingolipids exert important roles within the cardiovascular system and related diseases. Perturbed sphingolipid metabolism was previously reported in cerebral and renal tissues of spontaneously hypertensive rats (SHR). Specific defects related to the synthesis of sphingolipids and to the metabolism of Sphingosine-1-Phospahte (S1P) were exclusively identified in the stroke-prone (SHRSP) with the respect to the stroke-resistant (SHRSR) strain. In this study, we explored any existing perturbation in either protein or gene expression of enzymes involved in the sphingolipid pathways in cardiac tissue from both SHRSP and SHRSR strains, compared to the normotensive Wistar Kyoto (WKY) strain. The two hypertensive rat models showed an overall perturbation of the expression of different enzymes involved in the sphingolipid metabolism in the heart. In particular, whereas the expression of the S1P-metabolizing-enzyme, SPHK2, was significantly reduced in both SHR strains, SGPL1 protein levels were decreased only in SHRSP. The protein levels of S1P receptors 1-3 were reduced only in the cardiac tissue of SHRSP, whereas S1PR2 levels were reduced in both SHR strains. The de novo synthesis of sphingolipids was aberrant in the two hypertensive strains. A significant reduction of mRNA expression of the Sgms1 and Smpd3 enzymes, implicated in the metabolism of sphingomyelin, was found in both hypertensive strains. Interestingly, Smpd2, devoted to sphingomyelin degradation, was reduced only in the heart of SHRSP. In conclusion, alterations in the expression of sphingolipid-metabolizing enzymes may be involved in the susceptibility to cardiac damage of hypertensive rat strains. Specific differences detected in the SHRSP, however, deserve further elucidation.