Pierluigi Baron

Glial activation in Alzheimer’s disease: the role of Aβ and its associated proteins

A common feature of Alzheimers disease (AD) pathology is the abundance of reactive astrocytes and activated microglia in close proximity to neuritic plaques containing amyloid-beta protein (Abeta). The relationship between glial activation and neurodegeneration remains unclear, although several cytokines and inflammatory mediators produced by activated glia have the potential to initiate or exacerbate the progression of neuropathology. Assuming that glial activation plays a central role in the development and progression of AD, a prominent feature is to understand which stimuli drive this activation in senile plaques and to define their effects in vitro. There is a growing body of evidence to suggest that deposition of Abeta and expression of its associated molecules represent important trigger factors in glial activation leading to an inflammatory reaction in the brain. Thus, unraveling the mechanisms by which these proteins exert their effect on glial cells may provide significant insight into the pathophysiology of AD, and may lead to the identification of new strategies for AD treatment.

Proinflammatory profile of cytokine production by human monocytes and murine microglia stimulated with β-amyloid[25–35]

Growing evidence indicates that amyloid (A beta) deposition and phagocyte activation participate in inflammatory reactions in the brain during the course of Alzheimers disease. To further investigate the effects of A beta-phagocyte interaction, we examined the production of proinflammatory (IL-1beta, IL-6), chemotactic (MIP-1alpha, IP-10) and inhibitory (IL-1Ra, IL-10 and TGFbeta1) cytokines by cultured human monocytes and mouse microglial cells upon stimulation with A beta[25-35]. Northern blot analysis and specific immunoassays demonstrated that A beta[25-35] triggers mRNA expression and release of IL-1beta, IL-1Ra and MIP-1alpha but not of IL-6, IL-10, TGFbeta1 and IP-10 from human monocytes. Similar results were obtained by examining the production of IL-1beta, IL-6 and IL-10 from mouse microglial cells in the same experimental conditions. Taken together, these data indicate that A beta-phagocyte interaction can drive a different response towards cytokine production by monocytes and microglia, with a particular proinflammatory trend, and further support a role for A beta deposition as a triggering factor of inflammatory events in Alzheimers disease.

Melanocortin peptides inhibit production of proinflammatory cytokines and nitric oxide by activated microglia

Inflammatory processes contribute to neurodegenerative disease, stroke, encephalitis, and other central nervous system (CNS) disorders. Activated microglia are a source of cytokines and other inflammatory agents within the CNS and it is therefore important to control glial function in order to preserve neural cells. Melanocortin peptides are pro‐opiomelanocortin‐derived amino acid sequences that include α‐melanocyte‐stimulating hormone (α‐MSH) and adrenocorticotropic hormone (ACTH). These peptides have potent and broad anti‐inflammatory effects. We tested effects of α‐MSH (1‐13), α‐MSH (11‐13), and ACTH (1‐24) on production of tumor necrosis factor α (TNF‐α), interleukin‐6 (IL‐6), and nitric oxide (NO) in a cultured murine microglial cell line (N9) stimulated with lipopolysaccharide (LPS) plus interferon γ (IFN‐γ). Melanocortin peptides inhibited production of these cytokines and NO in a concentration‐related fashion, probably by increasing intracellular cAMP. When stimulated with LPS + IFN‐γ, microglia increased release of α‐MSH. Production of TNF‐α, IL‐6, and NO was greater in activated microglia after immunoneutralization of endogenous α‐MSH. The results suggest that α‐MSH is an autocrine factor in microglia. Because melanocortin peptides inhibit production of proinflammatory mediators by activated microglia they might be useful in treatment of inflammatory/degenerative brain disorders. J. Leukoc. Biol. 63: 740–745; 1998.

Oxidative imbalance in patients with mild cognitive impairment and Alzheimer's disease

Increasing evidence supports a role of oxidative imbalance, characterized by impaired antioxidant enzymatic activity and increased reactive oxygen species (ROS) production, in mild cognitive impairment (MCI) and Alzheimers disease (AD) pathogenesis. Hyperhomocysteinemia, another risk factor for AD, also contributes to oxidative damage. Plasma total homocysteine (tHcy) and ROS levels, and total antioxidant capacity (TAC) were determined in 71 AD, 36 MCI and 28 vascular dementia (VaD) patients as well as in 44 age-matched controls. tHcy levels were significantly increased in patients with AD and VaD an a trend towards an increase in multiple domain MCI was observed. TAC was significantly decreased in AD as well as MCI, but not in VaD patients. In AD patients, a negative correlation was found between TAC and disease duration. ROS levels did not differ among groups, but were correlated with age. In conclusion, a pattern characterized by increased tHcy levels and decreased TAC is present in AD as well as MCI patients. While increased tHcy levels were also found in VaD, TAC modifications occur specifically in AD. ROS levels appear to be correlated with age rather than with a specific dementing disorder, thus leading to the hypothesis that oxidative imbalance observed in AD could be due to a decreased TAC.

Production of monocyte chemoattractant protein-1 in amyotrophic lateral sclerosis.

The presence of activated microglia in the spinal cord of amyotrophic lateral sclerosis (ALS) patients is usually accompanied by inflammatory biochemical changes, but these are largely unexplored. Monocyte chemoattractant protein‐1 (MCP‐1) is critical for recruitment of inflammatory cells of monocytic lineage after inflammation or injury to the central nervous system. MCP‐1 concentrations were measured by an enzyme‐linked immunosorbent assay in the cerebrospinal fluid (CSF) and the serum of 27 patients with ALS and 30 patients with noninflammatory neurological diseases. In ALS, circulating MCP‐1 levels were significantly increased in the serum and particularly in the CSF. Immunoreactivity for MCP‐1 in ALS spinal cord was detected mostly in astrocytes but also in microglia, neurons, and within the vasculature of the cord. Our findings suggest a role for MCP‐1 as an important molecular mediator of the injury response in ALS. Muscle Nerve, 2005

IP-10 and MCP-1 levels in CSF and serum from multiple sclerosis patients with different clinical subtypes of the disease

Interferon-gamma-inducible Protein-10 (IP-10) and Monocyte Chemotactic Protein-1 (MCP-1) levels were measured by enzyme-linked immunosorbent assay (ELISA) in the CSF and in the serum from 74 patients affected by different clinical forms of Multiple Sclerosis (MS), including 39 patients with Relapsing Remitting (RR) MS in an active phase, 14 patients in a stable phase of the disease, 12 patients with Secondary Progressive (SP) MS and 9 patients with Primary Progressive (PP) MS. IP-10 and MCP-1 levels were also determined in 19 subjects with no neurological diseases or major systemic disorders, 18 patients with non-inflammatory neurological diseases, as well as in 15 patients with other inflammatory neurological diseases.IP-10 levels were significantly elevated in CSF and serum from RR and SP, but not PP-MS patients. On the contrary, MCP-1 levels were decreased in CSF and serum of all MS patients. CSF concentrations of IP-10 and MCP-1 did not significantly correlate neither with each other, nor with CSF mononuclear cell count, albumin quotient or CSF IgG index. No correlation between disease duration, clinical course or EDSS score and chemokine levels was found.IP-10 and MCP-1 undergo modifications in different subtypes of the disease: IP-10 levels in CSF and serum samples are markedly increased when inflammation is prominent, and not in PP--MS patients, where inflammation is less evident. MCP-1 decrease in CSF and serum from MS patients could be related to the regulation of T-cell polarization.

Etiology of first‐ever ischaemic stroke in European young adults: the 15 cities young stroke study

Risk factors for IS in young adults differ between genders and evolve with age, but data on the age‐ and gender‐specific differences by stroke etiology are scare. These features were compared based on individual patient data from 15 European stroke centers.

MCP-1 in Alzheimer’s disease patients: A-2518G polymorphism and serum levels

MCP-1 levels are increased in CSF of patients with Alzheimers disease (AD) compared with controls, suggesting a role in the development of dementia. Recently, a biallelic A/G polymorphism in the MCP-1 promoter at position -2518 has been found, influencing the level of MCP-1 expression in response to an inflammatory stimulus. The distribution of the A-2518G SNP was determined in 269 AD patients and in 203 healthy age matched controls, showing no differences between the two groups. On the contrary, a significant increase of MCP-1 serum levels in AD patients carrying at least one G mutated allele was observed. Moreover, the highest peaks of MCP-1 serum levels were present in patients carrying two G alleles. Stratifying by ApoE genotype, gender or age at onset, no differences in both allele frequency and MCP-1 serum concentration were observed. The A-2518G polymorphism in MCP-1 gene does not seem to be a risk factor for the development of AD, but its presence correlates with higher levels of serum MCP-1, which can contribute to increase the inflammatory process occurring in AD.

Demographic and geographic vascular risk factor differences in european young adults with ischemic stroke: The 15 cities young stroke study

Background and Purpose— We compared among young patients with ischemic stroke the distribution of vascular risk factors among sex, age groups, and 3 distinct geographic regions in Europe. Methods— We included patients with first-ever ischemic stroke aged 15 to 49 years from existing hospital- or population-based prospective or consecutive young stroke registries involving 15 cities in 12 countries. Geographic regions were defined as northern (Finland, Norway), central (Austria, Belgium, France, Germany, Hungary, The Netherlands, Switzerland), and southern (Greece, Italy, Turkey) Europe. Hierarchical regression models were used for comparisons. Results— In the study cohort (n=3944), the 3 most frequent risk factors were current smoking (48.7%), dyslipidemia (45.8%), and hypertension (35.9%). Compared with central (n=1868; median age, 43 years) and northern (n=1330; median age, 44 years) European patients, southern Europeans (n=746; median age, 41 years) were younger. No sex difference emerged between the regions, male:female ratio being 0.7 in those aged <34 years and reaching 1.7 in those aged 45 to 49 years. After accounting for confounders, no risk-factor differences emerged at the region level. Compared with females, males were older and they more frequently had dyslipidemia or coronary heart disease, or were smokers, irrespective of region. In both sexes, prevalence of family history of stroke, dyslipidemia, smoking, hypertension, diabetes mellitus, coronary heart disease, peripheral arterial disease, and atrial fibrillation positively correlated with age across all regions. Conclusions— Primary preventive strategies for ischemic stroke in young adults—having high rate of modifiable risk factors—should be targeted according to sex and age at continental level.

Absence of P0 leads to the dysregulation of myelin gene expression and myelin morphogenesis.

P0, the major peripheral nervous system (PNS) myelin protein, is a member of the immunoglobulin supergene family of membrane proteins and can mediate homotypic adhesion. P0 is an essential structural component of PNS myelin; mice in which P0 expression has been eliminated by homologous recombination (P0−/−) develop a severe dysmyelinating neuropathy with predominantly uncompacted myelin. Although P0 is thought to play a role in myelin compaction by promoting adhesion between adjacent extracellular myelin wraps, as an adhesion molecule it could also have a regulatory function. Consistent with this hypothesis, Schwann cells in adult P0−/− mice display a novel molecular phenotype: PMP22 expression is down‐regulated, MAG and PLP expression are up‐regulated, and MBP expression is unchanged. As in quaking viable mutant mice (qkv), which have uncompacted myelin morphologically similar to that found in P0−/− mice, neither the qKI‐6 or qKI‐7 proteins are expressed in P0−/− peripheral nerve. In addition to these changes in gene expression in the P0 knockout, PLP/DM‐20 accumulates in the endoplasmic reticulum of P0−/− Schwann cells, whereas MAG accumulates in redundant loops of uncompacted myelin, not at nodes of Ranvier or Schmidt‐Lantermann incisures. Taken together, these results demonstrate that P0 is involved, either directly or indirectly, in the regulation of both myelin gene expression and myelin morphogenesis. J. Neurosci. Res. 60:714–724, 2000.