Cristina Cheroni

Protein Nitration in a Mouse Model of Familial Amyotrophic Lateral Sclerosis POSSIBLE MULTIFUNCTIONAL ROLE IN THE PATHOGENESIS

Multiple mechanisms have been proposed to contribute to amyotrophic lateral sclerosis (ALS) pathogenesis, including oxidative stress. Early evidence of a role for oxidative damage was based on the finding, in patients and murine models, of high levels of markers, such as free nitrotyrosine (NT). However, no comprehensive study on the protein targets of nitration in ALS has been reported. We found an increased level of NT immunoreactivity in spinal cord protein extracts of a transgenic mouse model of familial ALS (FALS) at a presymptomatic stage of the disease compared with age-matched controls. NT immunoreactivity is increased in the soluble fraction of spinal cord homogenates and is found as a punctate staining in motor neuron perikarya of presymptomatic FALS mice. Using a proteome-based strategy, we identified proteins nitrated in vivo, under physiological or pathological conditions, and compared their level of specific nitration. α- and γ-enolase, ATP synthase β chain, and heat shock cognate 71-kDa protein and actin were overnitrated in presymptomatic FALS mice. We identified by matrix-assisted laser desorption/ionization mass spectrometry 16 sites of nitration in proteins oxidized in vivo. In particular, α-enolase nitration at Tyr43, target also of phosphorylation, brings additional evidence on the possible interference of nitration with phosphorylation. In conclusion, we propose that protein nitration may have a role in ALS pathogenesis, acting directly by inhibiting the function of specific proteins and indirectly interfering with protein degradation pathways and phosphorylation cascades.

IL28B polymorphisms predict interferon-related hepatitis B surface antigen seroclearance in genotype D hepatitis B e antigen-negative patients with chronic hepatitis B.

Interleukin (IL)28B polymorphisms have been associated with interferon (IFN)‐induced viral clearance in patients with chronic hepatitis C. Whether this is also true for patients with the difficult‐to‐cure hepatitis B e antigen (HBeAg)‐negative chronic hepatitis B (CHB) is unknown. One hundred and one HBeAg‐negative patients (92% genotype D) with compensated CHB (84% males, 46 years; hepatitis B virus [HBV] DNA: 6.0 log cp/mL; alanine aminotransferase [ALT]: 136 IU/L; 42% with cirrhosis) were followed up for a median of 11 years (range, 1‐17) after a median of 23 months (range, 10‐48) of either standard or pegylated (Peg)‐IFN‐alpha therapy. A post‐treatment response was defined as hepatitis B surface antigen (HBsAg) clearance with or without antibody to hepatitis B surface antigen (anti‐HBs) seroconversion. The rs12979860 (C>T) genotype in the IL28B locus was assessed in serum samples by using Custom TaqMan SNP Genotyping Assays (Applied Biosystems, Carlsbad, CA). During a median of 11 years of post‐treatment follow‐up, 21 patients (21%) cleared serum HBsAg, including 15 who developed >10 IU/mL of anti‐HBs titers. Forty‐eight patients (47%) had CC genotype, 42 (42%) had CT, and 11 (11%) had TT, with the allelic frequency being 68% for C allele and 32% for T allele. The rate of serum HBsAg clearance was 29% (n = 14) in CC compared to 13% (n = 7) in non‐CC, genotype carriers (P = 0.039). Baseline HBV DNA levels <6 log cp/mL (odds ratio [OR], 11.9; 95% confidence interval [CI]: 2.8‐50.6; P = 0.001), ALT levels >136 IU/L (OR, 6.5; 95% CI: 1.8‐22.5; P = 0.003), duration of IFN (OR, 1.16; 95% CI: 1.02‐1.31; P = 0.021), and genotype CC (OR, 3.9; 95% CI: 1.1‐13.2; P = 0.025) independently predicted HBsAg clearance. Conclusions: IL28B polymorphism is an additional predictor of off‐therapy IFN‐related HBsAg seroclearance to be used in the pretreatment stratification of HBeAg‐negative patients chronically infected by genotype D of HBV. (HEPATOLOGY 2013)

Functional alterations of the ubiquitin-proteasome system in motor neurons of a mouse model of familial amyotrophic lateral sclerosis†

In familial and sporadic amyotrophic lateral sclerosis (ALS) and in rodent models of the disease, alterations in the ubiquitin-proteasome system (UPS) may be responsible for the accumulation of potentially harmful ubiquitinated proteins, leading to motor neuron death. In the spinal cord of transgenic mice expressing the familial ALS superoxide dismutase 1 (SOD1) gene mutation G93A (SOD1G93A), we found a decrease in constitutive proteasome subunits during disease progression, as assessed by real-time PCR and immunohistochemistry. In parallel, an increased immunoproteasome expression was observed, which correlated with a local inflammatory response due to glial activation. These findings support the existence of proteasome modifications in ALS vulnerable tissues. To functionally investigate the UPS in ALS motor neurons in vivo, we crossed SOD1G93A mice with transgenic mice that express a fluorescently tagged reporter substrate of the UPS. In double-transgenic Ub(G76V)-GFP /SOD1G93A mice an increase in Ub(G76V)-GFP reporter, indicative of UPS impairment, was detectable in a few spinal motor neurons and not in reactive astrocytes or microglia, at symptomatic stage but not before symptoms onset. The levels of reporter transcript were unaltered, suggesting that the accumulation of Ub(G76V)-GFP was due to deficient reporter degradation. In some motor neurons the increase of Ub(G76V)-GFP was accompanied by the accumulation of ubiquitin and phosphorylated neurofilaments, both markers of ALS pathology. These data suggest that UPS impairment occurs in motor neurons of mutant SOD1-linked ALS mice and may play a role in the disease progression.

Genetic variation in the interleukin-28B gene is not associated with fibrosis progression in patients with chronic hepatitis C and known date of infection†

Polymorphisms in the interleukin‐28B (IL28B) region are associated with spontaneous and treatment‐induced viral clearance in hepatitis C virus (HCV) infection. Nevertheless, it is unknown whether genetic variation at the IL28B locus influences the natural history of chronic HCV infection. Thus, we asked whether an association between IL28B polymorphisms and liver fibrosis progression existed. We studied 247 consecutive patients with chronic HCV, an accurate estimate of the date of infection, and a liver biopsy performed before any treatment. No patient had a history of alcohol abuse or coinfection with other viruses. We assessed the role of rs8099917 and rs12979860 polymorphisms and the effect of host and environmental factors on fibrosis progression. Blood transfusion (75%) was the main modality of infection. Median age at infection was 21 years, and median interval between infection and liver biopsy was 25 years. One hundred twenty‐nine patients (52%) were infected by HCV‐1, 74 (30%) by HCV‐2, 34 (14%) by HCV‐3, and 10 (4%) by HCV‐4. Bridging fibrosis/cirrhosis (Ishak ≥4) was detected in 24% of patients. Age at infection had a marked effect on fibrosis progression by both a linear model and Cox proportional‐hazard regression (P < 2E‐16). A 12.1% increase in the hazard of advanced fibrosis was estimated for each additional year at infection, suggesting that this was the major explanatory variable in this cohort. Male gender (P < 0.05), HCV genotype 3 (P < 0.001) and steatosis (P < 0.05) were also associated with faster fibrosis progression. Conversely, the two IL28B polymorphisms had no impact on fibrosis progression. Conclusion: In HCV patients with a known date of infection, IL28B genotype was not associated with fibrosis progression rate or with the risk of developing advanced liver fibrosis. (HEPATOLOGY 2011;)

Dysfunction of constitutive and inducible ubiquitin-proteasome system in amyotrophic lateral sclerosis: Implication for protein aggregation and immune response

The ubiquitin-proteasome system (UPS) is the major intracellular proteolytic mechanism controlling the degradation of misfolded/abnormal proteins. A common hallmark in amyotrophic lateral sclerosis (ALS) and in other neurodegenerative disorders is the accumulation of misfolded/abnormal proteins into the damaged neurons, leading to the formation of cellular inclusions that are mostly ubiquitin-positive. Although proteolysis is a complex mechanism requiring the participation of different pathways, the abundant accumulation of ubiquitinated proteins strongly suggests an important contribution of UPS to these neuropathological features. The use of cellular and animal models of ALS, particularly those expressing mutant SOD1, the gene mutation most represented in familiar ALS, has provided significant evidence for a role of UPS in protein inclusions formation and motor neuron death. This review will specifically discuss this piece of evidence and provide suggestions of potential strategies for therapeutic intervention. We will also discuss the finding that, unlike the constitutive proteasome subunits, the inducible subunits are overexpressed early during disease progression in SOD1 mice models of ALS. These subunits form the immunoproteasome and generate peptides for the major histocompatibility complex class I molecules, suggesting a role of this system in the immune responses associated with the pathological features of ALS. Since recent discoveries indicate that innate and adaptive immunity may influence the disease process, in this review we will also provide evidence of a possible connection between immune-inflammatory reactions and UPS function, in the attempt to better understand the etiopathology of ALS and to identify appropriate targets for novel treatment strategies of this devastating disease.

Insoluble Mutant SOD1 Is Partly Oligoubiquitinated in Amyotrophic Lateral Sclerosis Mice

Mutations in the Cu,Zn-superoxide dismutase (SOD1) gene cause a familial form of amyotrophic lateral sclerosis (ALS) through an unknown gain-of-function mechanism. Mutant SOD1 aggregation may be the toxic property. In fact, proteinaceous inclusions rich in mutant SOD1 have been found in tissues from the familial form of ALS patients and in mutant SOD1 animals, before disease onset. However, very little is known of the constituents and mechanism of formation of aggregates in ALS. We and others have shown that there is a progressive accumulation of detergent-insoluble mutant SOD1 in the spinal cord of G93A SOD1 mice. To investigate the mechanism of SOD1 aggregation, we characterized by proteome technologies SOD1 isoforms in a Triton X-100-insoluble fraction of spinal cord from G93A SOD1 mice at different stages of the disease. This showed that at symptomatic stages of the disease, part of the insoluble SOD1 is unambiguously mono- and oligoubiquitinated, in spinal cord and not in hippocampus, and that ubiquitin branches at Lys48, the major signal for proteasome degradation. At presymptomatic stages of the disease, only insoluble unmodified SOD1 is recovered. Partial ubiquitination of SOD1-rich inclusions was also confirmed by immunohistochemical and electron microscopy analysis of lumbar spinal cord sections from symptomatic G93A SOD1 mice. On the basis of these results, we propose that ubiquitination occurs only after SOD1 aggregation and that oligoubiquitination may underline alternative mechanisms in disease pathogenesis.

Characterization of detergent-insoluble proteins in ALS indicates a causal link between nitrative stress and aggregation in pathogenesis.

Background Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease, and protein aggregation has been proposed as a possible pathogenetic mechanism. However, the aggregate protein constituents are poorly characterized so knowledge on the role of aggregation in pathogenesis is limited. Methodology/Principal Findings We carried out a proteomic analysis of the protein composition of the insoluble fraction, as a model of protein aggregates, from familial ALS (fALS) mouse model at different disease stages. We identified several proteins enriched in the detergent-insoluble fraction already at a preclinical stage, including intermediate filaments, chaperones and mitochondrial proteins. Aconitase, HSC70 and cyclophilin A were also significantly enriched in the insoluble fraction of spinal cords of ALS patients. Moreover, we found that the majority of proteins in mice and HSP90 in patients were tyrosine-nitrated. We therefore investigated the role of nitrative stress in aggregate formation in fALS-like murine motor neuron-neuroblastoma (NSC-34) cell lines. By inhibiting nitric oxide synthesis the amount of insoluble proteins, particularly aconitase, HSC70, cyclophilin A and SOD1 can be substantially reduced. Conclusion/Significance Analysis of the insoluble fractions from cellular/mouse models and human tissues revealed novel aggregation-prone proteins and suggests that nitrative stress contribute to protein aggregate formation in ALS.

Interleukin 28B polymorphism predicts pegylated interferon plus ribavirin treatment outcome in chronic hepatitis C genotype 4.

Single nucleotide polymorphisms (SNPs) near the interleukin 28B (IL28B) region are the strongest baseline predictors of a sustained virologic response (SVR) to peg‐interferon (PegIFN) and ribavirin (Rbv) in patients with hepatitis C virus (HCV) genotype 1 infection. Whether this holds true for HCV‐4 patients too is unknown. The aim was to investigate the predictive power of the rs12979860 IL28B SNP for a response to Peg‐IFN and Rbv in HCV‐4 patients. All HCV‐4 patients consecutively treated between September 2004 and June 2010 with PegIFN and Rbv at two liver centers at the Maggiore Hospital Milan (Italy) underwent TaqMan SNP Genotyping assays for testing rs12979860 genotype. Of 112 treated patients (98 males, 75 of Egyptian descent, 26 with cirrhosis) 103 were included in the final analysis; five discontinued treatment for nonvirologic reasons and four did not consent to genetic testing. Twenty‐four (23%) were genotype CC, 65 (63%) CT, and 14 (14%) TT. Overall, 50 (49%) achieved an SVR: 21 (88%) CC patients versus 29 (37%) CT/TT (P < 0.0001). CC patients more often had a rapid virologic response (RVR) than CT/TT patients (12, 50% versus 23, 29%; P = 0.08), while also showing lower relapse rates (0% [0/21] versus 36% [16/45] P = 0.0013). In non‐RVR patients, SVR rates were higher in CC than CT/TT patients (9 [75%] versus 13 [23%] P = 0.001). By logistic regression, the IL28B rs12979860 CC genotype was an independent predictor of SVR with an odds ratio of 8.0 (95% confidence interval 2.00‐32.01; P = 0.003). Conclusion: The IL28B rs12979860 SNP may have an added value in the treatment algorithm of HCV‐4 patients because it is the strongest predictor of an SVR to PegIFN/Rbv therapy. (HEPATOLOGY 2012)

Intracellular Modulation, Extracellular Disposal and Serum Increase of MiR-150 Mark Lymphocyte Activation

Activated lymphocytes release nano-sized vesicles (exosomes) containing microRNAs that can be monitored in the bloodstream. We asked whether elicitation of immune responses is followed by release of lymphocyte-specific microRNAs. We found that, upon activation in vitro, human and mouse lymphocytes down-modulate intracellular miR-150 and accumulate it in exosomes. In vivo, miR-150 levels increased significantly in serum of humans immunized with flu vaccines and in mice immunized with ovalbumin, and this increase correlated with elevation of antibody titers. Immunization of immune-deficient mice, lacking MHCII, resulted neither in antibody production nor in elevation of circulating miR-150. This study provides proof of concept that serum microRNAs can be detected, with minimally invasive procedure, as biomarkers of vaccination and more in general of adaptive immune responses. Furthermore, the prompt reduction of intracellular level of miR-150, a key regulator of mRNAs critical for lymphocyte differentiation and functions, linked to its release in the external milieu suggests that the selective extracellular disposal of microRNAs can be a rapid way to regulate gene expression during lymphocyte activation.

Genome-Wide Analysis of DNA Methylation, Copy Number Variation, and Gene Expression in Monozygotic Twins Discordant for Primary Biliary Cirrhosis

Primary biliary cirrhosis (PBC) is an uncommon autoimmune disease with a homogeneous clinical phenotype that reflects incomplete disease concordance in monozygotic (MZ) twins. We have taken advantage of a unique collection consisting of genomic DNA and mRNA from peripheral blood cells of female MZ twins (n = 3 sets) and sisters of similar age (n = 8 pairs) discordant for disease. We performed a genome-wide study to investigate differences in (i) DNA methylation (using a custom tiled four-plex array containing tiled 50-mers 19,084 randomly chosen methylation sites), (ii) copy number variation (CNV) (with a chip including markers derived from the 1000 Genomes Project, all three HapMap phases, and recently published studies), and/or (iii) gene expression (by whole-genome expression arrays). Based on the results obtained from these three approaches we utilized quantitative PCR to compare the expression of candidate genes. Importantly, our data support consistent differences in discordant twins and siblings for the (i) methylation profiles of 60 gene regions, (ii) CNV of 10 genes, and (iii) the expression of 2 interferon-dependent genes. Quantitative PCR analysis showed that 17 of these genes are differentially expressed in discordant sibling pairs. In conclusion, we report that MZ twins and sisters discordant for PBC manifest particular epigenetic differences and highlight the value of the epigenetic study of twins.