Abstract5-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 pathogenesis 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.
Keywordsγ-secretase; Tg2576; Aβ; amyloid-β precursor protein; leukotrienes Alzheimer's disease (AD) is a neurodegenerative disorder that causes progressive loss of cognitive function and dementia. The pathological hallmarks in the AD brains are amyloid plaques in the extracellular parenchyma consisting mainly of Amyloid-β (Aβ) peptides (1), and intraneuronal tangles made of abnormally phosphorylated microtubule-associated tau protein (2).Increasing evidence from human and mouse models suggests that inflammation is an important player in the pathogenesis of AD (3). Eicosanoids, including prostaglandins and leukotrienes, derive from arachidonic acid by the action of cyclooxygenase (COX-1 and COX-2), lipoxygenase (12/15 lipoxygenase (12/15LO), and 5-lipoxygenase (5LO) enzymes. They have important proinflammatory functions and a large array of other biological activities (4). The roles of cyclooxygenases (5-8) and 12/15LO (9,10) in AD have been studied, but much less attention has been directed to the 5LO (11). Previously, it has been shown that 5LO is present in the central nervous system (CNS) in neurons and other cell types in mice (12) and rats (13,14). 5LO and leukotrienes in the CNS have neuromodulatory and neuroendocrine functions (14-16) and might play an important role in aging-associated neurodegenerative diseases (12,13). 5LO and its metabolites have been also been reported to be associated with excitotoxic injury (17,18) and cerebral ischemia (19). Taken together, these data would indirectly indicate that 5LO may have also a role in neurodegeneration, but only few studies have directly addressed this issue. It has been shown that 5LO promoter mutations cause a lower 5LO expression compared to wild-type (20). In a pilot study on the association of 5LO promoter polymorphism and the age of onset of AD, a trend toward higher frequency of wild-type 5LO promoter was f...
Although hepatic cell transplantation (CT) holds the promise of bridging patients with end-stage chronic liver failure to whole liver transplantation, suitable cell populations are under debate. In addition to hepatic cells, mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) are being considered as alternative cell sources for initial clinical cell work. Fetal liver (FL) tissue contains potential progenitors for all these cell lineages. Based on the collagenase incubation of tissue fragments, traditional isolation techniques yield only a fraction of the number of available cells. We report a 5-step method in which a portal vein in situ perfusion technique is used for tissue from the late second trimester. This method results in the high viabilities known for adult liver vascular perfusion, addresses the low cell yields of conventional digestion methods, and reduces the exposure of the tissue to collagenase 4-fold. We used donated tissue from gestational weeks 18 to 22, Additional Supporting Information may be found in the online version of this article.
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 (CiC3-1a59–76) also promoted hemocyte chemotaxis. Furthermore, the CiC3-1a terminal Arg was not crucial for chemotactic activity, because the desArg peptide (CiC3-1a59–75) 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 Gi 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.
Background: 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).
Lipoxygenases (LOs) are members of a large family of non-heme iron-containing dioxygenases that insert molecular oxygen into polyunsaturated fatty acids.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.