A novel mouse model of cerebral adrenoleukodystrophy highlights NLRP3 activity in lesion pathogenesis.

Objective: We sought to create and characterize a mouse model of the inflammatory, cerebral demyelinating phenotype of X-linked adrenoleukodystrophy (ALD) that would facilitate the study of disease pathogenesis and therapy development. We also sought to cross-validate potential therapeutic targets such as fibrin, oxidative stress, and the NLRP3 inflammasome, in post-mortem human and murine brain tissues. Background: ALD is caused by mutations in the gene ABCD1 encoding a peroxisomal transporter. More than half of males with an ABCD1 mutation develop the cerebral phenotype (cALD). Incomplete penetrance and absence of a genotype-phenotype correlation imply a role for environmental triggers. Mechanistic studies have been limited by the absence of a cALD phenotype in the Abcd1-null mouse. Methods: We generated a cALD phenotype in 8-week-old, male Abcd1-null mice by deploying a two-hit method that combines cuprizone (CPZ) and experimental autoimmune encephalomyelitis (EAE) models. We employed in vivo MRI and post-mortem immunohistochemistry to evaluate myelin loss, astrogliosis, blood-brain barrier (BBB) disruption, immune cell infiltration, fibrin deposition, oxidative stress, and Nlrp3 inflammasome activation in mice. We used bead-based immunoassay and immunohistochemistry to evaluate IL-18 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 astrogliosis. 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. Interpretation: 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 humans 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.

Presence of a deletion mutation (c.716delA) in the ligand binding domain of the vitamin D receptor in an Indian patient with vitamin D-dependent rickets type II.

Vitamin D-dependent rickets type II (VDDR-type II) is a rare disorder caused by mutations in the vitamin D receptor (VDR) gene. Here, we describe a patient with VDDR-type II with severe alopecia and rickets. She had hypocalcemia, hypophosphatemia, secondary hyperparathyroidism, and elevated serum alkaline phosphatase and 1,25-dihydroxyvitamin D(3). Sequence analysis of the lymphocyte VDR cDNA revealed deletion mutation c.716delA. Sequence analysis of her genomic DNA fragment amplified from exon 6 of the VDR gene incorporating this mutation confirmed the presence of the mutation in homozygous form. This frameshift mutation in the ligand binding domain (LBD) resulted in premature termination (p.Lys240Argfs) of the VDR protein. The mutant protein contained 246 amino acids, with 239 normal amino acids at the N terminus, followed by seven changed amino acids resulting in complete loss of its LBD. The mutant VDR protein showed evidence of 50% reduced binding with VDR response elements on electrophoretic mobility assay in comparison to the wild-type VDR protein. She was treated with high-dose calcium infusion and oral phosphate. After 18 months of treatment, she gained 6 cm of height, serum calcium and phosphorus improved, alkaline phosphatase levels decreased, and intact PTH normalized. Radiologically, there were signs of healing of rickets. Her parents and one of her siblings had the same c.716delA mutation in heterozygous form. Despite the complete absence of LBD, the rickets showed signs of healing with intravenous calcium.

Biochemical Evaluation of Human DNA-Lysine Photoadduct Treated with Peroxynitrite.

ABSTRACT Peroxynitrite is a reactive oxidant produced from nitric oxide ((.)NO) and superoxide anion (O(2)(.-)). It is produced by the body in response to environmental toxins, stress, ultraviolet light, ischemia/reperfusion, inflammation, etc. In vivo, peroxynitrite is formed in macrophages, endothelial cells, platelets, leukocytes, and neurons. It reacts with a variety of biomolecules including proteins, lipids, and DNA. We have investigated the photochemical addition of lysine to native DNA in view of its potential importance in the photo-cross-linking of histones to DNA in chromatin. Lysine-and arginine-rich histone H1 in nucleosome on modification by physical, chemical, or environmental agents forms histone-DNA adducts. We have characterized the photoadducts by absorption, fluorescence, and chromatographic methods. The UV absorption spectra of the DNA-lysine photoadduct showed hyperchromism, indicating structural distortions in DNA either due to single-strand breaks or opening of the double helix at the site of lysine conjugation. On peroxynitrite treatment, the melting temperature (T(m)) of the DNA-lysine adduct increased by 15 degrees C compared to the native DNA-lysine adduct. A decrease in the fluorescence intensity of the DNA-lysine photoadduct with respect to the modified adduct was observed. The gel filtration profile of the peroxynitrite-modified adduct was also found to be different from that of the native DNA and DNA-lysine photoadduct. Hence, the peroxynitrite-modified photoadduct may have important implications in toxicology, mutagenesis, and carcinogenesis.

Gastric corticotropin-releasing factor influences mast cell infiltration in a rat model of functional dyspepsia.

Functional gastrointestinal disorders (FGIDs) are characterized by dysregulated gut-brain interactions. Emerging evidence shows that low-grade mucosal inflammation and immune activation contribute to FGIDs, including functional dyspepsia (FD). Stress plays an important role in the onset of FD symptoms. In human subjects with FD, presence of gastric mast cells has been reported, but factors that influence mast cell infiltration remain uncharacterized. Corticotropin-releasing factor (CRF) initiates the body's stress response and is known to degranulate mast cells. In this study, we delineated the role of the CRF system in the pathogenesis of FD in a rat model. Gastric irritation in neonate rat pups with iodoacetamide (IA) was used to induce FD-like symptoms. RNA interference (RNAi) was used to silence gastric CRF expression. Mast cell infiltrate in the stomach increased by 54% in IA-treated rats compared to controls and CRF-RNAi tended to decrease gastric mast cell infiltrate. Sucrose intake decreased in IA-treated rats and mast cell numbers showed a negative association with sucrose intake. IA treatment and transient silencing of gastric CRF increased hypothalamic CRF levels. In IA-treated rats, gastric levels of CRF receptor 2 (CRF2) decreased by ~76%, whereas hypothalamic CRF receptor 1 (CRF1) levels increased. Plasma levels of TNF-α showed a positive correlation with plasma CRF levels. Levels of phosphorylated p38 and ERK1/2 in the stomach showed a positive correlation with gastric CRF levels. Thus, CRF may contribute to low grade inflammation via modulating mast cell infiltration, cytokine levels, MAPK signaling, and the gut-brain axis.

Prevalence and significance of NALP5 autoantibodies in patients with idiopathic hypoparathyroidism.

CONTEXT: Role of parathyroid autoimmunity in idiopathic hypoparathyroidism (IH) is not clear. Recently, parathyroid-specific NACHT leucine-rich-repeat protein 5 (NALP5) autoantibodies (Ab) have been reported in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome. OBJECTIVE: Our objective was to assess prevalence and significance of NALP5 Ab in patients with IH. DESIGN AND SETTING: This was a case-control study at a tertiary care hospital. SUBJECTS: Subjects included 145 patients with IH recruited from 1998-2011 and 152 healthy controls. METHODS: Immunoprecipitation (IP) and Western blot (WB) assays were performed using ³5S-labeled NALP5 protein produced by in vitro transcription-translation and recombinant NALP5 protein in Escherichia coli, respectively. AIRE gene sequencing was performed in NALP5 Ab-positive patients. RESULTS: One of 145 patients (0.69%) and none of the 152 controls had NALP5 Ab on IP assay. Nine of 147 patients (6.12%) and four of 152 controls (2.63%) had NALP5 Ab on WB. One patient with NALP5 Ab on IP (36.6 sd score), also positive on WB, had a frameshift p.Ala386Serfs*38 AIRE gene mutation and adrenocortical Ab. Eight subjects with NALP5 Ab detected on WB had normal AIRE gene sequence. CONCLUSIONS: IP is currently the best assay to detect clinically relevant NALP5 Ab. Presence of NALP5 Ab in only one patient with IH who also had AIRE gene mutation suggests that these Ab are exceptionally rare in IH (0.69%) and, when present, occur in context of the autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome.