Sima, a Drosophila homolog of HIF-1α, in fat body tissue inhibits larval body growth by inducing Tribbles gene expression.

Limited oxygen availability impairs normal body growth, although the underlying mechanisms are not fully understood. In Drosophila, hypoxic responses in the larval fat body (FB) disturb the secretion of insulin-like peptides from the brain, inhibiting body growth. However, the cell-autonomous effects of hypoxia on the insulin-signaling pathway in larval FB have been underexplored. In this study, we aimed to examine the effects of overexpression of Sima, a Drosophila hypoxia-inducible factor-1 (HIF-1) α homolog and a key component of HIF-1 transcription factor essential for hypoxic adaptation, on the insulin-signaling pathway in larval FB. Forced expression of Sima in FB reduced the larval body growth with reduced Akt phosphorylation levels in FB cells and increased hemolymph sugar levels. Sima-mediated growth inhibition was reversed by overexpression of TOR or suppression of FOXO. After Sima overexpression, larvae showed higher expression levels of Tribbles, a negative regulator of Akt activity, and a simultaneous knockdown of Tribbles completely abolished the effects of Sima on larval body growth. Furthermore, a reporter analysis revealed Tribbles as a direct target gene of Sima. These results suggest that Sima in FB evokes Tribbles-mediated insulin resistance and consequently protects against aberrant insulin-dependent larval body growth under hypoxia.

Epicutaneous challenge with protease allergen requires its protease activity to recall TH2 and TH17/TH22 responses in mice pre-sensitized via distant skin.

Epicutaneous exposure to allergenic proteins is an important sensitization route for skin diseases like protein contact dermatitis, immunologic contact urticaria, and atopic dermatitis. Environmental allergen sources such as house dust mites contain proteases, which are frequent allergens themselves. Here, the dependency of T-helper (TH) cell recall responses on allergen protease activity in the elicitation phase in mice pre-sensitized via distant skin was investigated. Repeated epicutaneous administration of a model protease allergen, i.e. papain, to the back skin of hairless mice induced skin inflammation, serum papain-specific IgE and TH2 and TH17 cytokine responses in the sensitization sites, and antigen-restimulated draining lymph node cells. In the papain-sensitized but not vehicle-treated mice, subsequent single challenge on the ear skin with papain, but not with protease inhibitor-treated papain, up-regulated the gene expression of TH2 and TH17/TH22 cytokines along with cytokines promoting these TH cytokine responses (TSLP, IL-33, IL-17C, and IL-23p19). Up-regulation of IL-17A gene expression and cells expressing RORγt occurred in the ear skin of the presensitized mice even before the challenge. In a reconstructed epidermal model with a three-dimensional culture of human keratinocytes, papain but not protease inhibitor-treated papain exhibited increasing transdermal permeability and stimulating the gene expression of TSLP, IL-17C, and IL-23p19. This study demonstrated that allergen protease activity contributed to the onset of cutaneous TH2 and TH17/TH22 recall responses on allergen re-encounter at sites distant from the original epicutaneous sensitization exposures. This finding suggested the contribution of protease-dependent barrier disruption and induction of keratinocyte-derived cytokines to the recall responses.

Total dose defines the incidence of percutaneous IgE/IgG1 mediated immediate-type hypersensitivity caused by papain.

Assessment of human health risk requires an understanding of antigen dose metrics associated with toxicity. Whereas assessment of the human health risk for delayed-type hypersensitivity is understood, the metrics remain unclear for percutaneous immediate-type hypersensitivity (ITH) mediated by IgE/IgG1. In this work, we aimed to investigate the dose metric for percutaneous ITH mediated by IgE/IgG1 responses. Papain, which causes ITH via percutaneous sensitization in humans, was used to sensitize guinea pigs and mice. The total dose per animal or dose per unit area was adjusted to understand the drivers of sensitization. Passive cutaneous anaphylaxis (PCA) and enzyme-linked immunosorbent assay (ELISA) for papain-specific IgG1 enabled quantification of the response in guinea pigs. In mice, the number of antigen-bearing B cells in the draining lymph nodes (DLN) was calculated using flow cytometry papain-specific IgG1 and IgE levels were quantified by ELISA. PCA positive test rates and the amounts of antigen-specific antibody corresponded with total dose per animal, not dose per unit area. Furthermore, the number of B cells taking up antigen within DLN also correlated with total dose. These findings indicate that the total antigen dose is the important metric for percutaneous IgE/IgG1-mediated ITH.

Effects of aging on serum levels of lipid molecular species as determined by lipidomics analysis in Japanese men and women.

BACKGROUND: Aging is known to be associated with increased risk of lipid disorders related to the development of type 2 diabetes. Recent evidence revealed that change of lipid molecule species in blood is associated with the risk of type 2 diabetes. However, changes in lipid molecular species induced by aging are still unknown. We assessed the effects of age on the serum levels of lipid molecular species as determined by lipidomics analysis. METHODS: Serum samples were collected from ten elderly men (71.7 ± 0.5 years old) and women (70.2 ± 1.0 years old), ten young men (23.9 ± 0.4 years old), and women (23.9 ± 0.7 years old). Serum levels of lipid molecular species were determined by liquid chromatography mass spectrometry-based lipidomics analysis. RESULTS: Our mass spectrometry analysis revealed increases in the levels of multiple triacylglycerol molecular species in the serum of elderly men and women. Moreover, serum levels of total ester-linked phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were increased by aging. In contrast, serum levels of specific ether-linked PC and PE molecular species were lower in elderly individuals than in young individuals. CONCLUSIONS: Our finding indicates that specific lipid molecular species, such as ether- and ester- linked phospholipids, may be selectively altered by aging.