Friday, May 15, 2015

Treatment of globoid cell leukodystrophy

Hawkins-Salsbury JA, Shea L, Jiang X, Hunter DA, Guzman AM, Reddy AS, Qin EY,
Li Y, Gray SJ, Ory DS, Sands MS. Mechanism-based combination treatment
dramatically increases therapeutic efficacy in murine globoid cell
leukodystrophy. J Neurosci. 2015 Apr 22;35(16):6495-505.

Globoid cell leukodystrophy (GLD, Krabbe disease) is a lysosomal storage disease (LSD) caused by a deficiency in galactocerebrosidase (GALC) activity. In the absence of GALC activity, the cytotoxic lipid, galactosylsphingosine (psychosine), accumulates in the CNS and peripheral nervous system. Oligodendrocytes and Schwann cells are particularly sensitive to psychosine, thus leading to a demyelinating phenotype. Although hematopoietic stem-cell transplantation provides modest benefit in both presymptomatic children and the murine model (Twitcher), there is no cure for GLD. In addition, GLD has been relatively refractory to virtually every experimental therapy attempted. Here, Twitcher mice were simultaneously treated with CNS-directed gene therapy, substrate reduction therapy, and bone marrow transplantation to target the primary pathogenic mechanism (GALC deficiency) and two secondary consequences of GALC deficiency (psychosine accumulation and neuroinflammation). Simultaneously treating multiple pathogenic targets resulted in an unprecedented increase in life span with improved motor function, persistent GALC expression, nearly normal psychosine levels, and decreased neuroinflammation. Treating the primary pathogenic mechanism and secondary targets will likely improve therapeutic efficacy for other LSDs with complex pathological and clinical presentations.

Li Y, Sands MS. Experimental therapies in the murine model of globoid cell
leukodystrophy. Pediatr Neurol. 2014 Nov;51(5):600-6.

Globoid cell leukodystrophy or Krabbe disease, is a rapidly progressive childhood lysosomal storage disorder caused by a deficiency in galactocerebrosidase. Galactocerebrosidase deficiency leads to the accumulation of galactosylsphingosine (psychosine), a cytotoxic lipid especially damaging to oligodendrocytes and Schwann cells. The progressive loss of cells involved in myelination results in a dysmyelinating phenotype affecting both the central and peripheral nervous systems. Current treatment for globoid cell leukodystrophy is limited to bone marrow or umbilical cord blood transplantation. However, these therapies are not curative and simply slow the progression of the disease. The Twitcher mouse is a naturally occurring biochemically faithful model of human globoid cell leukodystrophy that has been used extensively to study globoid cell leukodystrophy pathophysiology and experimental treatments. In this review, we present the major single and combination experimental therapies targeting specific aspects of murine globoid cell leukodystrophy.
Literature review and analysis.
The evidence suggests that even with the best available therapies, targeting a single pathogenic mechanism provides minimal clinical benefit. More recently, combination therapies have demonstrated the potential to further advance globoid cell leukodystrophy treatment by synergistically increasing life span. However, such therapies must be designed and evaluated carefully because not all combination therapies yield such positive results.
A more complete understanding of the underlying pathophysiology and the interplay between various therapies holds the key to the discovery of more effective treatments for globoid cell leukodystrophy.

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