The amyloid β protein precursor (AβPP) is sequentially processed by β-and γ-secretases to generate the Aβ peptide. The biochemical * B.P. and L.P. have equally contributed to this work.

N-terminally truncated amyloid-b (Ab) peptides are present in early and diffuse plaques of individuals with Alzheimer's disease (AD), are overproduced in early onset familial AD and their amount seems to be directly correlated to the severity and the progression of the disease in AD and Down's syndrome (DS). The pyroglutamate-containing isoforms at position 3 [AbN3(pE))40/42] represent the prominent form among the N-truncated species, and may account for more than 50% of Ab accumulated in plaques. In this study, we compared the toxic properties, fibrillogenic capabilities, and in vitro degradation profile of Ab1-40, Ab1-42, AbN3(pE))40 and AbN3(pE))42. Our data show that fibre morphology of Ab peptides is greatly influenced by the C-terminus while toxicity, interaction with cell membranes and degradation are influenced by the N-terminus. AbN3(pE))40 induced significantly more cell loss than the other species both in neuronal and glial cell cultures. Aggregated AbN3(pE) peptides were heavily distributed on plasma membrane and within the cytoplasm of treated cells. AbN3(pE))40/42 peptides showed a significant resistance to degradation by cultured astrocytes, while fulllength peptides resulted partially degraded. These findings suggest that formation of N-terminally modified peptides may enhance b-amyloid aggregation and toxicity, likely worsening the onset and progression of the disease.

The mechanism of neurodegeneration caused by ␤-amyloid in Alzheimer disease is controversial. Neuronal toxicity is exerted mostly by various species of soluble ␤-amyloid oligomers that differ in their N-and C-terminal domains. However, abundant accumulation of ␤-amyloid also occurs in the brains of cognitively normal elderly people, in the absence of obvious neuronal dysfunction. We postulated that neuronal toxicity depends on the molecular composition, rather than the amount, of the soluble ␤-amyloid oligomers. Here we show that soluble ␤-amyloid aggregates that accumulate in Alzheimer disease are different from those of normal aging in regard to the composition as well as the aggregation and toxicity properties.A series of evidence indicates that progressive cerebral accumulation of ␤-amyloid (A␤), 2 a proteolytic product of transmembrane protein APP, is the primary pathogenic event of Alzheimer disease (AD) (1). Recent clues indicate that small, soluble A␤ aggregates produce more severe synaptic dysfunction and neuronal damage than do A␤ polymers (2-5). This behavior is common to all known pathogenic and nonpathogenic amyloidogenic peptides (6, 7). Soluble A␤ is detectable early in the cerebral cortex of subjects at risk for AD pathology, several years before the formation and deposition of amyloid fibrils (8). Hence, the analysis of soluble A␤ in brain tissue allows the characterization of the toxic form of the peptide.A strong argument against the amyloid hypothesis is the abundant and constant deposition of A␤ in the brains of elderly subjects, in the absence of signs of neuronal degeneration and dementia (9 -11). The reasons for the absence of pathogenic effect exerted by A␤ in normal aging are unknown. The issue has important therapeutic implications, because the major strategies to prevent and cure AD are focused on halting A␤ accumulation (12).In brains from Alzheimer disease (AD) and Down syndrome patients, three major species of soluble A␤ have been identified by mass spectrometry: the full-length form, A␤1-42, which has a relative molecular mass of 4.5 kDa, and two N-terminal peptides truncated at residue 3 (A␤3-42) and residue 11 (A␤11-42) with relative molecular masses of 4.2 and 3.5 kDa, respectively (13, 14). The 4.2-and 3.5-kDa bands are more prominent in familial AD carrying presenilin 1 mutations than in sporadic AD, suggesting that the ratio of soluble A␤ species may dictate the toxicity of the aggregates (15).We predicted that the composition of soluble A␤ underlies the different effect exerted by the molecule in AD and in normal aging. To investigate this hypothesis, we studied the composition and properties of aggregation and toxicity as well as the damage produced on artificial membranes of soluble A␤, comparing these areas in sporadic AD and cognitively normal elderly subjects with abundant amyloid plaques in cerebral cortex. MATERIALS AND METHODSTissues-We used frozen blocks and formalin-fixed sections of frontal cortex from 14 cases with late onset sporadic AD (mean age at death 80 Ϯ ...

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BACKGROUND AND PURPOSEPalmitoylethanolamide (PEA) is an endogenous fatty acid amide displaying anti-inflammatory and analgesic actions. To investigate the molecular mechanism responsible for these effects, the ability of PEA and of pain-inducing stimuli such as capsaicin (CAP) or bradykinin (BK) to influence intracellular calcium concentrations ([Ca 2+ ]i) in peripheral sensory neurons, has been assessed in the present study. The potential involvement of the transcription factor PPARa and of TRPV1 channels in PEA-induced effects was also studied. [Ca 2+ ]i was evaluated by single-cell microfluorimetry in differentiated F11 cells. Activation of TRPV1 channels was assessed by imaging and patch-clamp techniques in CHO cells transiently-transfected with rat TRPV1 cDNA. EXPERIMENTAL APPROACH KEY RESULTSIn F11 cells, PEA (1-30 mM) dose-dependently increased [Ca 2+ ]i. The TRPV1 antagonists capsazepine (1 mM) and SB-366791 (1 mM), as well as the PPARa antagonist GW-6471 (10 mM), inhibited PEA-induced [Ca 2+ ]i increase; blockers of cannabinoid receptors were ineffective. PEA activated TRPV1 channels heterologously expressed in CHO cells; this effect appeared to be mediated at least in part by PPARa. When compared with CAP, PEA showed similar potency and lower efficacy, and caused stronger TRPV1 currents desensitization. Sub-effective PEA concentrations, closer to those found in vivo, counteracted CAPand BK-induced [Ca 2+ ]i transients, as well as CAP-induced TRPV1 activation. CONCLUSIONS AND IMPLICATIONSActivation of PPARa and TRPV1 channels, rather than of cannabinoid receptors, largely mediate PEA-induced [Ca 2+ ]i transients in sensory neurons. Differential TRPV1 activation and desensitization by CAP and PEA might contribute to their distinct pharmacological profile, possibly translating into potentially relevant clinical differences.