5‐Lipoxygenase (5LO), by producing leukotrienes, is a proinflammatory enzyme, and there is evidence suggesting that it is up‐regulated with aging and may be involved in Alzheimer's disease (AD). In this paper, we studied the effect of 5LO‐targeted gene disruption on the amyloid phenotype of a transgenic mouse model of AD, the Tg2576. Amyloid‐β (Aβ) deposition in the brains of Tg2576 mice lacking 5LO was reduced by 64–80% compared with Tg2576 controls. This reduction was associated with a similar significant decrease in Aβ levels measured by sandwich ELISA. Absence of 5LO did not induce any significant change in amyloid‐β precursor protein (APP) levels and processing, or Aβ catabolic pathways. Furthermore, in vitro studies showed that 5LO activation or 5LO metabolites increase, whereas 5LO inhibition decreases, Aβ formation, secondary to correspondent changes in γ‐secretase activity. These data establish for the first time a novel functional role for 5LO in the pathogen‐esis of AD‐like amyloidosis, thereby modulating γ‐secretase activity. Our work suggests that pharmacological inhibition of 5LO could provide a novel therapeutic tool for AD. Firuzi, O., Zhuo, J., Chinnici, C. M., Wisniewski, T., Pratico, D. 5‐Lipoxygenase gene disruption reduces amyloid‐β pathology in a mouse model of Alzheimer's disease. FASEB J. 22, 1169–1178 (2008)

An increasing body of evidence implicates both brain inflammation and oxidative stress in the pathogenesis of Alzheimer's disease (AD). The relevance of their interaction in vivo, however, is unknown. Previously, we have shown that separate pharmacological targeting of these two components results in amelioration of the amyloidogenic phenotype of a transgenic mouse model of AD-like brain amyloidosis (Tg2576). In the present study, we investigated the therapeutic effects of a combination of an anti-inflammatory agent, indomethacin, and a natural anti-oxidant, vitamin E, in the Tg2576 mice. For this reason, animals were treated continuously from 8 (prior to Aβ deposition) through 15 (when Aβ deposits are abundant) months of age. At the end of the study, these therapeutic interventions suppressed brain inflammatory and oxidative stress responses in the mice. This effect was accompanied by significant reductions of soluble and insoluble Aβ1-40 and Aβ1-42 in neocortex and hippocampus, wherein the burden of Aβ deposits also was significantly decreased. The results of the present study support the concept that brain oxidative stress and inflammation coexist in this animal model of AD-like brain amyloidosis, but they represent two distinct therapeutic targets in the disease pathogenesis. We propose that a combination of anti-inflammatory and anti-oxidant drugs may be a useful strategy for treating AD.

Deuterostome invertebrates possess complement genes, and in limited instances complement-mediated functions have been reported in these organisms. However, the organization of the complement pathway(s), as well as the functions exerted by the cloned gene products, are largely unknown. To address the issue of the presence of an inflammatory pathway in ascidians, we expressed in Escherichia coli the fragment of Ciona intestinalis C3-1 corresponding to mammalian complement C3a (rCiC3-1a) and assessed its chemotactic activity on C. intestinalis hemocytes. We found that the migration of C. intestinalis hemocytes toward rCiC3-1a was dose dependent, peaking at 500 nM, and was specific for CiC3-1a, being inhibited by an anti-rCiC3-1a-specific Ab. As is true for mammalian C3a, the chemotactic activity of C. intestinalis C3-1a was localized to the C terminus, because a peptide representing the 18 C-terminal amino acids (CiC3-1a^59–76) also promoted hemocyte chemotaxis. Furthermore, the CiC3-1a terminal Arg was not crucial for chemotactic activity, because the desArg peptide (CiC3-1a^59–75) retained most of the directional hemocyte migration activity. The CiC3-1a-mediated chemotaxis was inhibited by pretreatment of cells with pertussis toxin, suggesting that the receptor molecule mediating the chemotactic effect is G_i protein coupled. Immunohistochemical analysis with anti-rCiC3-1a-specific Ab and in situ hybridization experiments with a riboprobe corresponding to the 3′-terminal sequence of CiC3-1, performed on tunic sections of LPS-injected animals, showed that a majority of the infiltrating labeled hemocytes were granular amebocytes and compartment cells. Our findings indicate that CiC3-1a mediates chemotaxis of C. intestinalis hemocytes, thus suggesting an important role for this molecule in inflammatory processes.