Mechanisms of Krabbe Disease Pathobiology and Therapy

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DESCRIPTION (provided by applicant): Krabbe disease (KD) is a developmental neurological disorder characterized by excessive accumulation of psychosine and loss of oligodendrocytes (OLs) and myelin as a result of deficiency of ¿-galactosylcerebrosidase (GALC). Mechanisms of OL death in KD are not well understood, and thus therapy has been elusive. This study is designed to investigate the psychosine induced mechanism of OL loss and the identification of drugs that block the loss of OLs as potential therapy for KD. The present proposal is based on our original findings that psychosine-induced apoptotic loss of OLs is mediated via the sPLA2 signaling pathway and that inhibitors of sPLA2 protect against loss of PPAR/peroxisomal functions and loss of OLs. Since the expression of enzymatic activity for synthesis of psychosine is integral to OL differentiation, delineation of psychosine mediated mechanisms in differentiation and loss of OLs is important for understanding KD pathology. Based on these novel findings, we hypothesize that the accumulation of psychosine is associated with stage(s) specific abnormalities in OL differentiation and that activation of sPLA2 and inhibition of PPAR/ peroxisomal functions participate in dysregulation of OL differentiation and their loss in KD. Mechanism based interventions of these pathways by means of pharmacological inhibitors have therapeutic potential in KD. Therefore, the proposed studies are; 1) To investigate the effects of psychosine on differentiation and survival of OLs and to elucidate the mechanisms of psychosine-mediated dysregulation of OLs differentiation and survival. 2) To evaluate the therapeutic efficacy of inhibitor of sPLA2 (DEDA) and antioxidant (NAC) for the treatment of twitcher (TW) mice. These studies are based on the original contributions from our laboratory. The observed role of sPLA2 in psychosine induced loss of OLs in culture as well as in CNS of KD/TW and inhibition of OLs loss by sPLA2 inhibitor documents the significance of sPLA2 mediated signaling pathways in KD pathology. The fact that inhibition of sPLA2 signaling pathway protects OLs against psychosine toxicity provides us an opportunity to elucidate disease mechanisms and to identify potential therapeutics for patients with KD. Study of these novel signaling mechanisms in KD pathology are innovative and may identify drug(s) as potential candidates for effective therapy for KD. PUBLIC HEALTH RELEVANCE: Pathognomic accumulation of psychosine and psychosine-induced impaired myelination and loss of oligodendrocytes and myelin are the "hallmark" of Krabbe disease. This proposal is to evaluate the efficacy of inhibitors of sPLA2 signaling pathway to delineate disease mechanisms and to identify potential therapeutics for KD.