1,721,069 research outputs found
Inflammation and neurodegeneration: identification of the acute phase protein haptoglobin as a potential modulator of apolipoprotein E-mediated regulation of brain cholesterol and beta-amyloid homeostasis
No full textState of the art: Alterations in cholesterol metabolism play a role in the pathogenesis of neurodegenerative diseases. Apolipoprotein E, the main lipid carrier in the brain, is a risk factor for Alzheimer’s disease. How brain cholesterol homeostasis may be related to Apolipoprotein E as a risk factor needs further clarification. A strategy might be to focus on factors that may modulate the Apolipoprotein E function. In this frame, we obtained experimental evidences that the acute-phase protein Haptoglobin binds Apolipoprotein E.
Objectives and Rationale: Haptoglobin was found in cerebral spinal fluid and suggested as a marker of blood-brain barrier dysfunction. Our main goal is to study whether Haptoglobin, because of its binding with Apolipoprotein E, might influence the apolipoprotein function in cholesterol and beta-amyloid metabolism.
Experimental plan: The Hpt effect on Apolipoprotein E activity in beta-amyloid aggregation or clearance, and on the Apolipoprotein E-stimulated cholesterol incorporation or efflux from neurons, astrocytes and microglia will be evaluated. Peptides or molecules able to influence the Haptoglobin binding to Apolipoprotein E will be screened. The Haptoglobin/Apolipoprotein E ratio will be evaluated in AD patients, as a potential diagnostic marker to monitor disease activity or the efficiency of a treatment.
Expected results and their relevance: The Haptoglobin influence on Apolipoprotein E key roles in brain will be elucidated. Modulators of the Haptoglobin-Apolipoprotein E interaction are expected to be identified. The results of this study might provide new tools to set up diagnostic methods, or design molecules for therapeutic approaches in disease treatment
Quantitative variations of the isoforms in Haptoglobin 1-2 and 2-2 individual phenotypes.
No full textHaptoglobin is a hemoglobin-binding protein presenting in humans three distinct phenotypes (Hpt 1-1, Hpt 1-2, or Hpt 2-2). The Hpt 1-2 and Hpt 2-2 phenotypes are in turn represented by populations of isoforms. The relative amount of the major isoforms of Hpt 1-2 and Hpt 2-2 was found different not only in different individuals, but also in the same individual before and after a physical effort. Exercise-dependent changes in the plasma concentration of ascorbate, urate, a-tocopherol, retinol, and glutathione were also observed, but correlations between such changes and those of the amount for any isoform were not found. Samples of Hpt 1-2 or Hpt 2-2 were challenged with oxidants (H2O2 with ferrous ions, spermine–NO, KO2, and 3-morpholinosydnonimine), but the isoform levels were not altered. Hpt 2-2 isoforms were present in Hpt 1-2, as minor species. Furthermore, different isoforms exhibited different hemoglobin binding abilities. Thus, these parameters should also be taken into consideration in studies correlating Hpt phenotypes prevalence with pathologies or functional differences
Haptoglobin Modulates Beta-Amyloid Uptake by U-87 MG Astrocyte Cell Line
No full textAccumulation of beta-amyloid (Aβ) in the extracellular
space, which is one of the hallmarks of Alzheimer’s
disease (AD), depends on the balance between its synthesis
and clearance. The physiological role of extracellular chaperones,
capable of affecting early events in the amyloid cascade,
is increasingly being investigated by many research groups.
Among these proteins, we focused on haptoglobin, which we
recently found to form a complex with beta-amyloid in brain
tissues or cerebrospinal fluids from patients with AD.We also
previously reported that haptoglobin increases with age in rat
hippocampus. Major aimof this study was to evaluate whether
haptoglobin influences Aβ interaction with astrocytes and its
internalization into these cells. Haptoglobin effect on Aβ-
induced cell death was also explored. We report here that
haptoglobin impairs Aβ uptake by human glioblastoma–astrocytoma
cell line U-87 MG and limits the toxicity of this
peptide on these cells. Of note, our data also show that Aβ can
stimulate haptoglobin release by astrocyte cell lines. The study
of the risk of developing AD should be focused not only on
the analysis ofAβ but also on the level of critical ligands, such
as haptoglobin, able to influence peptide aggregation or
clearance
The Haptoglobin binding to Apolipoprotein A-I: Influence of Hemoglobin and Concanavalin A.
No full textHaptoglobin (Hp) can be purified by affinity chromatography using hemoglobin(Hb)-linked Sepharose. Elution with 8 M urea is generally performed, resulting in Hp heavy contamination by the apolipoprotein AI (ApoAI), and partial loss of Hb binding activity. Hp, separated from ApoAI, was recovered by elution with glycine-HCl at pH 3. Complexes of the isolated protein with Hb or ApoAI were detected by enzyme-linked immunosorbent assay (ELISA). Competition between the two ligands in their interaction with Hp was observed. Concanavalin A (ConA), which binds the Hp carbohydrate chains, did not influence the Hp binding to ApoAI. The results suggest that changes in the plasma level of ApoAI or Hb affect the Hp role in regulating the cholesterol reverse transport or preventing Hb-dependent oxidative damages
The Haptoglobin binding to Apolipoprotein A-I: Influence of Hemoglobin and Concanavalin A.
No full textHaptoglobin (Hp) can be purified by affinity chromatography using hemoglobin(Hb)-linked Sepharose. Elution with 8 M urea is generally performed, resulting in Hp heavy contamination by the apolipoprotein AI (ApoAI), and partial loss of Hb binding activity. Hp, separated from ApoAI, was recovered by elution with glycine-HCl at pH 3. Complexes of the isolated protein with Hb or ApoAI were detected by enzyme-linked immunosorbent assay (ELISA). Competition between the two ligands in their interaction with Hp was observed. Concanavalin A (ConA), which binds the Hp carbohydrate chains, did not influence the Hp binding to ApoAI. The results suggest that changes in the plasma level of ApoAI or Hb affect the Hp role in regulating the cholesterol reverse transport or preventing Hb-dependent oxidative damages
Uso dell'aptoglobina, peptidi leganti l'aptoglobina, polimeri contenenti gli stessi e loro uso
No full textSono stati sintetizzati peptidi mimetici del dominio dell'apolipoproteina E (ApoE), che è legato dall'aptoglobina (Hpt). Questi peptidi possono essere utilizzati per fini diagnostici, per titolare Hpt come marker della fase acuta dell'infiammazione. Poiché i peptidi spiazzano ApoE da Hpt, essi possono anche essere usati per liberare ApoE da complessi con Hpt e permetterne, quindi, la massima attività di stimolazione sull'attività di LCAT (un enzima che svolge un ruolo chiave nel trasporto inverso del colesterolo e, quindi, nella prevenzione di malattie cardiovascolari)
Nitric oxide stimulates the erythrocyte for ascorbate recycling. Nitric Oxide
No full textS-nitrosothiols act as carrier and reservoir of nitric oxide (NO), and release NO under stimulation of Ascorbate (Asc). Erythrocyte can regenerate Asc from its oxidised products, thus saving this powerful antioxidant. In this paper the effect of donors of NO, superoxide and peroxynitrite (SpNONOate, KO2, and SIN-1, respectively) on the erythrocyte production of Asc was investigated. We report here that NO stimulated, while superoxide and peroxynitrite decreased, the Asc recycling. The NO-stimulating effect on the erythrocyte production of Asc was confirmed by using GSNO, a natural occurring S-nitrosothiol, as NO donor. These data highlight a new property of NO, that is the stimulation of erythrocytes for their Asc recycling. Such a property might contribute to regenerate Asc from its oxidised forms, thus preventing its depletion in the circulation. Temperature and pH significantly affected, both in absence and presence of NO, the recycling of Asc by erythrocytes. We propose that a positive feedback, involving the reciprocal stimulation between Asc and S-nitrosothiols, might enhance productions of Asc by erythrocytes and NO release by circulating S-nitrosothiols
- …
