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SummaryStem cells reside in specialized microenvironments known as niches. During Drosophila development, glial cells provide a niche that sustains the proliferation of neural stem cells (neuroblasts) during starvation. We now find that the glial cell niche also preserves neuroblast proliferation under conditions of hypoxia and oxidative stress. Lipid droplets that form in niche glia during oxidative stress limit the levels of reactive oxygen species (ROS) and inhibit the oxidation of polyunsaturated fatty acids (PUFAs). These droplets protect glia and also neuroblasts from peroxidation chain reactions that can damage many types of macromolecules. The underlying antioxidant mechanism involves diverting PUFAs, including diet-derived linoleic acid, away from membranes to the core of lipid droplets, where they are less vulnerable to peroxidation. This study reveals an antioxidant role for lipid droplets that could be relevant in many different biological contexts.

Increased lipoprotein-associated phospholipase A 2 (Lp-PLA 2 ) activity is associated with increased risk of cardiac events, but it is not known whether Lp-PLA 2 is a causative agent. Here we show that selective inhibition of Lp-PLA 2 with darapladib reduced development of advanced coronary atherosclerosis in diabetic and hypercholesterolemic swine. Darapladib markedly inhibited plasma and lesion Lp-PLA 2 activity and reduced lesion lysophosphatidylcholine content. Analysis of coronary gene expression showed that darapladib exerted a general anti-inflammatory action, substantially reducing the expression of 24 genes associated with macrophage and T lymphocyte functioning. Darapladib treatment resulted in a considerable decrease in plaque area and, notably, a markedly reduced necrotic core area and reduced medial destruction, resulting in fewer lesions with an unstable phenotype. These data show that selective inhibition of Lp-PLA 2 inhibits progression to advanced coronary atherosclerotic lesions and confirms a crucial role of vascular inflammation independent from hypercholesterolemia in the development of lesions implicated in the pathogenesis of myocardial infarction and stroke.Atherosclerosis, the most common cause of myocardial infarction, stroke and cardiovascular death, is an inflammatory-immunomodulatory disease 1,2 . A key early step in its development is the accumulation and subsequent oxidation of low-density lipoproteins COMPETING INTERESTS STATEMENTThe authors declare competing financial interests: details accompany the full-text HTML version of the paper at http://www.nature.com/naturemedicine/. Lp-PLA 2 , also known as platelet-activating factor acetylhydrolase or type VIIA PLA 2 , is a calcium-independent phospholipase A 2 . In humans, Lp-PLA 2 is secreted by leukocytes and is associated with circulating LDL and macrophages in atherosclerotic plaques. Although some have hypothesized that Lp-PLA 2 has a protective role in atherosclerotic lesion development 9,10 , the preponderance of recent data suggests that Lp-PLA 2 has an active role in atherosclerotic development and progression [11][12][13] . Elevated circulating Lp-PLA 2 activity predicts increased cardiovascular risk 14 . A proatherogenic role for Lp-PLA 2 has been postulated on the basis of its ability to generate two key proinflammatory mediators, lysophosphatidylcholine (LPC) and oxidized nonesterified fatty acids (oxNEFAs), through the cleavage of oxidized or polar phospholipids generated during LDL oxidation 15,16 . Evidence exists for a regulatory role of these proinflammatory lipids, particularly of LPC 12,13,17 , in promoting atherosclerotic plaque development that can ultimately lead to the formation of a necrotic core. These steps include recruitment and activation of leukocytes 12,18 , induction of apoptosis 12,19 and impaired removal of dead cells 20,21 . The demonstration that Lp-PLA 2 is highly upregulated in macrophages undergoing apoptosis within the necrotic core and fibrous cap of vulnerable and ruptured plaques, ...

Plant pollens are an important source of environmental antigens that stimulate allergic responses. In addition to acting as vehicles for foreign protein antigens, they contain lipids that incorporate saturated and unsaturated fatty acids, which are necessary in the reproduction of higher plants. The CD1 family of nonpolymorphic major histocompatibility complex–related molecules is highly conserved in mammals, and has been shown to present microbial and self lipids to T cells. Here, we provide evidence that pollen lipids may be recognized as antigens by human T cells through a CD1-dependent pathway. Among phospholipids extracted from cypress grains, phosphatidyl-choline and phosphatidyl-ethanolamine were able to stimulate the proliferation of T cells from cypress-sensitive subjects. Recognition of phospholipids involved multiple cell types, mostly CD4+ T cell receptor for antigen (TCR)αβ+, some CD4−CD8− TCRγδ+, but rarely Vα24i + natural killer–T cells, and required CD1a+ and CD1d+ antigen presenting cell. The responding T cells secreted both interleukin (IL)-4 and interferon-γ, in some cases IL-10 and transforming growth factor-β, and could provide help for immunoglobulin E (IgE) production. Responses to pollen phospholipids were maximally evident in blood samples obtained from allergic subjects during pollinating season, uniformly absent in Mycobacterium tuberculosis–exposed health care workers, but occasionally seen in nonallergic subjects. Finally, allergic, but not normal subjects, displayed circulating specific IgE and cutaneous weal and flare reactions to phospholipids.

Clustering based on clinicophysiologic parameters yielded 4 stable and reproducible clusters that associate with different pathobiological pathways.