Oxidative stress is a hallmark of Alzheimer’s disease (AD). We propose that rather than causing damage because of the action of free radicals, oxidative stress deranges signaling pathways leading to tau hyperphosphorylation, a hallmark of the disease. Indeed, incubation of neurons in culture with 5 µM beta-amyloid peptide (Aβ) causes an activation of p38 MAPK (p38) that leads to tau hyperphosphorylation. Inhibition of p38 prevents Aβ-induced tau phosphorylation. Aβ-induced effects are prevented when neurons are co-incubated with trolox (the water-soluble analog of vitamin E).We have confirmed these results in vivo, in APP/PS1 double transgenic mice of AD. We have found that APP/PS1 transgenic mice exhibit a high level of P-p38 in the hippocampus but not in cortex and this is prevented by feeding animals with a diet supplemented with vitamin E.Our results underpin the role of oxidative stress in the altered cell signaling in AD pathology and suggest that antioxidant prevention may be useful in AD therapeutics.

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Amyloid-β peptide (Aβ) toxicity and tau hyperphosphorylation are hallmarks of Alzheimer’s disease (AD). How their molecular relationships may affect the etiology, progression, and severity of the disease, however, has not been elucidated. We now report that incubation of foetal rat cortical neurons with Aβ up-regulates expression of the Regulator of Calcineurin gene RCAN1, and this is mediated by Aβ-induced oxidative stress. Calcineurin (PPP3CA) is a serine-threonine phosphatase that dephosphorylates tau. RCAN1 proteins inhibit this phosphatase activity of calcineurin. Increased expression of RCAN1 also causes up-regulation of glycogen synthase kinase-3beta (GSK3β), a tau kinase. Thus, increased RCAN1 expression might be expected to decrease phospho-tau dephosphorylation (via calcineurin inhibition) and increase tau phosphorylation (via increased GSK3β activity). We find that, indeed, incubation of primary cortical neurons with Aβ results in increased phosphorylation of tau, unless RCAN1 gene expression is silenced, or antioxidants are added. Thus we propose a mechanism to link Aβ toxicity and tau hyperphosphorylation in AD: In our hypothesis, Aβ causes mitochondrial oxidative stress and increases production of reactive oxygen species, which result in an up-regulation of RCAN1 gene expression. RCAN1 proteins then both inhibit calcineurin and induce expression of GSK3β. Both mechanisms shift tau to a hyperphosphorylated state. We also find that lymphocytes from persons whose ApoE genotype is ε4/ε4 (with high risk of developing AD) show higher levels of RCAN1 and phospho-tau than those carrying the ApoE ε3/ε3 or ε3/ε4 genotypes. Thus up-regulation of RCAN1 may be a valuable bio-marker for Alzheimer’s disease risk.

Current hypotheses of the etiology of fibromyalgia (FM) include inflammatory disorders. We evaluated the effect of a pool-aquatic exercise program (8 months, two weekly 60-min sessions) on the inflammatory cytokine production by isolated monocytes, and on the serum concentration of C-reactive protein (CRP), in a group of female FM patients. Monocytes from FM patients released more IL-1β, TNFα, IL-6, and IL-10 than those from an age-matched control group of healthy women (HW). This inflammatory disorder in FM women was also manifested by high circulating concentrations of CRP. Increased IL-6 with a concomitant decreased TNFα spontaneous release was found after 4 months (midway through) of the exercise program. At the end of the program (8 months), monocytes from FM patients showed diminished spontaneous production of pro-/anti-inflammatory cytokines, with a similar spontaneous release of IL-1β and IL-6 to that of HW, but a lower production of TNFα and higher of IL-10. Lipopolysaccharide-induced production of IL-1β, TNFα, IL-6, and IL-10 also decreased at the end of the exercise program, although IL-10 remained higher than HW. The anti-inflammatory effect of the exercise program was also corroborated by a decrease in the circulating CRP concentration. Exercise also improved the health-related quality of life of FM patients.