A Novel Mouse Model of Cerebral Demyelination in X-linked Adrenoleukodystrophy Highlights NLRP3 Activation in Lesion Pathogenesis
Ezzat Hashemi1, Isha Srivastava1, Alejandro Aguirre1, Ezra Yoseph1, Esha Kaushal1, Avni Awani1, Jae Ryu3, Shahrzad Talebian1, Pauline Chu2, Lawrence Steinman 1, Paul Orchard4, Troy Lund4, May Han1, Joshua Bonkowsky5, Keith Van Haren1
1Neurology, 2Stanford Human Research Histology Core, Stanford University School of Medicine, 3Gladstone Institute for Neurological Disease, 4University of Minnesota, 5University of Utah School of Medicine
Objective:
We sought to create and characterize a mouse model of cALD that facilitate the study of disease pathogenesis and therapy development. We also sought to cross-validate two potential therapeutic targets, fibrinogen and NLRP3 inflammasome activation pathways in cALD postmortem humans’ brain tissues and cALD mouse model.
Background:
X-linked adrenoleukodystrophy (ALD) is caused by mutations in the ABCD1 encoding a peroxisomal transporter. Most males with ALD develop inflammatory cerebral demyelination (cALD), but the underlying mechanisms are unknown due to the lack of cALD phenotype in the Abcd1-null mouse.
Design/Methods:
We generated a cALD phenotype in 8 week-old, male Abcd1-null mice by deploying a two-hit method combining cuprizone and experimental autoimmune encephalomyelitis (EAE) models. We employed in vivo MRI and immunohistochemistry to evaluate myelin loss, gliosis, blood-brain barrier disruption, immune cell infiltration, fibrin deposition, oxidative stress, and Nlrp3 inflammasome activation in mice. We used immunohistochemistry and bead-based immunoassay to evaluate IL-18, NLRP3 inflammasome activation, in CSF and post-mortem human cALD brain tissue.
Results:
: MRI studies revealed T2 hyperintensities and post-gadolinium enhancement in the medial corpus callosum of cALD mice, similar to human cALD lesions. Both human and mouse cALD lesions shared common histologic features of myelin phagocytosis, myelin loss, abundant microglial activation, T and B-cell infiltration, and astrocytosis. Compared to wild-type controls, Abcd1-null mice had more severe cerebral inflammation, demyelination, fibrin deposition, oxidative stress, and IL-18 activation. IL-18 immunoreactivity co-localized with macrophages/microglia in the perivascular region of both human and mouse brain tissue.
Conclusions:
This novel mouse model of cALD suggests loss of Abcd1 function predisposes to more severe cerebral inflammation, oxidative stress, fibrin deposition, and Nlrp3 pathway activation, which parallels the findings seen in patients with cALD. We expect this model to enable long-sought investigations into cALD mechanisms and accelerate development of candidate therapies for lesion prevention, cessation, and remyelination.