Summary Homeostasis of the gut microbiota critically influences host health and aging. Developing genetically engineered probiotics holds great promise as a new therapeutic paradigm to promote healthy aging. Here, through screening 3,983 Escherichia coli mutants, we discovered that 29 bacterial genes, when deleted, increase longevity in the host Caenorhabditis elegans. A dozen of these bacterial mutants also protect the host from age-related progression of tumor growth and amyloid-beta accumulation. Mechanistically, we discovered that five bacterial mutants promote longevity through increased secretion of the polysaccharide colanic acid (CA), which regulates mitochondrial dynamics and unfolded protein response (UPRmt) in the host. Purified CA polymers are sufficient to promote longevity via ATFS-1, the host UPRmt-responsive transcription factor. Furthermore, the mitochondrial changes and longevity effects induced by CA are conserved across different species. Together, our results identified molecular targets for developing pro-longevity microbes, and a bacterial metabolite acting on host mitochondria to promote longevity.

To study the function of ␥-glutamyl leukotrienase (GGL), a newly identified member of the ␥-glutamyl transpeptidase (GGT) family, we generated null mutations in GGL (GGL tm1 ) and in both GGL and GGT (GGL tm1 -GGT tm1 ) by a serial targeting strategy using embryonic stem cells. Mice homozygous for GGL tm1 show no obvious phenotypic changes. Mice deficient in both GGT and GGL have a phenotype similar to the GGT-deficient mice, but ϳ70% of these mice die before 4 weeks of age, at least 2 months earlier than mice deficient only in GGT. These double-mutant mice are unable to cleave leukotriene C 4 (LTC 4 ) to LTD 4 , indicating that this conversion is completely dependent on the two enzymes, and in some organs (spleen and uterus) deletion of GGL alone abolished more than 90% of this activity. In an experimental model of peritonitis, GGL alone is responsible for the generation of peritoneal LTD 4 . Further, during the development of peritonitis, GGL-deficient mice show an attenuation in neutrophil recruitment but not of plasma protein influx. These findings demonstrate an important role for GGL in the inflammatory response and suggest that LTC 4 and LTD 4 have distinctly different functions in the inflammatory process.Leukotrienes (LT) are a group of biologically active metabolites of arachidonic acid and have been implicated in the pathophysiology of many inflammatory diseases, including asthma, arthritis, psoriasis, and inflammatory bowel disease (8,17,20). Unlike many other inflammatory mediators, LT are not stored but synthesized de novo in response to inflammatory stimuli (17). Synthesis of LT is an intracellular process initiated by the conversion of free arachidonic acid to LTA 4 , an epoxide intermediate, by the key enzyme 5-lipoxygenase and the accessory protein 5-lipoxygenase-activating protein. LTA 4 can be converted to LTB 4 by LTA 4 hydrolase or conjugated with glutathione (GSH) by LTC 4 synthase to form LTC 4 . LTC 4 is then transported to the extracellular microenvironment where it is converted to LTD 4 (the cysteinyl glycine conjugate of LTA 4 ) and then to LTE 4 (the cysteinyl conjugate of LTA 4 ).LTC 4 and its metabolites, LTD 4 and LTE 4 , are referred to as cysteinyl LT and were originally identified as the active components of the slow reacting substance of anaphylaxis. They are known to stimulate a wide spectrum of inflammatory processes, including vasoconstriction, increases in postcapillary venule permeability, local recruitment of eosinophils, bronchoconstriction, and mucous secretion (8,9,17,19,20). LT have been the focus of extensive investigation in recent years because of the potency of their inflammatory effects, particularly in asthma, and promising therapeutic results with novel inhibitors of their synthesis and/or antagonists of their receptors (9,19).Cysteinyl LT exert their effects through specific receptors;however, there has been significant uncertainty about the interaction of cysteinyl LT with their receptors and the relative potencies of individual cysteinyl LT. In vivo studies...

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Gut microbial metabolism is associated with host longevity. However, because it requires direct manipulation of microbial metabolism in situ, establishing a causal link between these two processes remains challenging. We demonstrate an optogenetic method to control gene expression and metabolite production from bacteria residing in the host gut. We genetically engineer an Escherichia coli strain that secretes colanic acid (CA) under the quantitative control of light. Using this optogenetically-controlled strain to induce CA production directly in the Caenorhabditis elegans gut, we reveal the local effect of CA in protecting intestinal mitochondria from stress-induced hyper-fragmentation. We also demonstrate that the lifespan-extending effect of this strain is positively correlated with the intensity of green light, indicating a dose-dependent CA benefit on the host. Thus, optogenetics can be used to achieve quantitative and temporal control of gut bacterial metabolism in order to reveal its local and systemic effects on host health and aging.

The metabolism of cysteinyl leukotrienes in vivo and the pathophysiological effects of individual cysteinyl leukotrienes are primarily unknown. Recently we identified an additional member of the gamma-glutamyl transpeptidase (GGT) family, gamma-glutamyl leukotrienase (GGL), and developed mice deficient in this enzyme. Here we show that in vivo GGL, and not GGT as previously believed, is primarily responsible for conversion of leukotriene C(4) to leukotriene D(4), the most potent of the cysteinyl leukotrienes and the immediate precursor of leukotriene E(4). GGL is a glycoprotein consisting of two polypeptide chains encoded by one gene and is attached at the amino terminus of the heavy chain to endothelial cell membranes. In mice it localizes to capillaries and sinusoids in most organs and in lung to larger vessels as well. In contrast to wild-type and GGT-deficient mice, GGL-deficient mice do not form leukotriene D(4) in vivo either in blood when exogenous leukotriene C(4) is administered intravenously or in bronchoalveolar lavage fluid of Aspergillus fumigatus extract-induced experimental asthma. Further, GGL-deficient mice show leukotriene C(4) accumulation and significantly more airway hyperreponsiveness than wild-type mice in the experimental asthma, and induction of asthma results in increased GGL protein levels and enzymatic activity. Thus GGL plays an important role in leukotriene D(4) synthesis in vivo and in inflammatory processes.

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Curcumin, an agent traditionally utilized for its preventative action against tumorigenesis, oxidation, inflammation, apoptosis and hyperlipemia, has also been used in the treatment of Alzheimer's disease (AD). Recent advances in the study of AD have revealed astrocytes (AS) as being key factors in the early pathophysiological changes in AD. Glial fibrillary acidic protein (GFAP), a marker specific to AS, is markedly more manifest during morphological modifications and neural degeneration signature during the onset of AD. Several studies investigating the functionality of curcumin have shown that it not only inhibits amyloid sedimentation but also accelerates the disaggregation of amyloid plaque. Thus, we are interested in the relationship between curcumin and spatial memory in AD. In this study, we intend to investigate the effects of curcumin in amyloid-β (Aβ(1-40)) induced AD rat models on both the behavioral and molecular levels, that is to say, on their spatial memory and on the expression of GFAP in their hippocampi. Our results were statistically significant, showing that the spatial memory of AD rats improved following curcumin treatment (p < 0.05), and that the expression of GFAP mRNA and the number of GFAP positive cells in the curcumin treated rats was decreased relative to the AD group rats (p < 0.05). Furthermore, the expression level of GFAP mRNA in hippocampal AS in the AD rats significantly increased when compared with that in the sham control (p < 0.05). Taken together, these results suggest that curcumin improves the spatial memory disorders (such disorders being symptomatic of AD) in Aβ(1-40)-induced rats by down regulating GFAP expression and suppressing AS activity.

Pupal diapause (dormancy) in the flesh fly, Sarcophaga bullata, is induced by short-day photoperiods and low temperature. In this study, the inheritance mode of diapause was investigated by crossing a nondiapausing (nd) strain of S. bullata with 2 diapausing strains having different diapause capacities. The results consistently indicated that diapause incidence is inherited in a simple Mendelian pattern, thus a single gene or a small gene cluster linked to the photoperiodic clock controls the seasonal response of diapause. The fact that the nd strain lacked daily rhythmicity in adult eclosion and showed altered expression of 2 circadian clock genes suggests that the photoperiodic and circadian clocks are related through a shared molecular component in S. bullata.