A versatile transcription factor: Multiple roles of orthopedia a (otpa) beyond its restricted localization in dopaminergic systems of developing and adult zebrafish (Danio rerio) brains.

Many transcription factors boost neural development and differentiation in specific directions and serve for identifying similar or homologous structures across species. The expression of Orthopedia (Otp) is critical for the development of certain cell groups along the vertebrate neuraxis, for example, the medial amygdala or hypothalamic neurosecretory neurons. Therefore, the primary focus of the present study is the distribution of Orthopedia a (Otpa) in the larval and adult zebrafish (Danio rerio) brain. Since Otpa is also critical for the development of zebrafish basal diencephalic dopaminergic cells, colocalization of Otpa with the catecholamine synthesizing enzyme tyrosine hydroxylase (TH) is studied. Cellular colocalization of Otpa and dopamine is only seen in magnocellular neurons of the periventricular posterior tubercular nucleus and in the posterior tuberal nucleus. Otpa-positive cells occur in many additional structures along the zebrafish neuraxis, from the secondary prosencephalon down to the hindbrain. Furthermore, Otpa expression is studied in shh-GFP and islet1-GFP transgenic zebrafish. Otpa-positive cells only express shh in dopaminergic magnocellular periventricular posterior tubercular cells, and only colocalize with islet1-GFP in the ventral zone and prerecess caudal periventricular hypothalamic zone and the perilemniscal nucleus. The scarcity of cellular colocalization of Otpa in islet1-GFP cells indicates that the Shh-islet1 neurogenetic pathway is not active in most Otpa-expressing domains. Our analysis reveals detailed correspondences between mouse and zebrafish forebrain territories including the zebrafish intermediate nucleus of the ventral telencephalon and the mouse medial amygdala. The zebrafish preoptic Otpa-positive domain represents the neuropeptidergic supraopto-paraventricular region of all tetrapods. Otpa domains in the zebrafish basal plate hypothalamus suggest that the ventral periventricular hypothalamic zone corresponds to the otp-expressing basal hypothalamic tuberal field in the mouse. Furthermore, the mouse otp domain in the mammillary hypothalamus compares partly to our Otpa-positive domain in the prerecess caudal periventricular hypothalamic zone (Hc-a).

Staphylococcus aureus controls eicosanoid and specialized pro-resolving mediator production via lipoteichoic acid.

Staphylococcus aureus causes severe infections associated with inflammation, such as sepsis or osteomyelitis. Inflammatory processes are regulated by distinct lipid mediators (LMs) but how their biosynthetic pathways are orchestrated in S. aureus infections is elusive. We show that S. aureus strikingly not only modulates pro-inflammatory, but also inflammation-resolving LM pathways in murine osteomyelitis and osteoclasts as well as in human monocyte-derived macrophages (MDMs) with different phenotype. Targeted LM metabololipidomics using ultra-performance liquid chromatography-tandem mass spectrometry revealed massive generation of LM with distinct LM signature profiles in acute and chronic phases of S. aureus-induced murine osteomyelitis in vivo. In human MDM, S. aureus elevated cyclooxygenase-2 (COX-2) and microsomal prostaglandin E2  synthase-1 (mPGES-1), but impaired the levels of 15-lipoxygenase-1 (15-LOX-1), with respective changes in LM signature profiles initiated by these enzymes, that is, elevated PGE2 and impaired specialized pro-resolving mediators, along with reduced M2-like phenotypic macrophage markers. The cell wall component, lipoteichoic acid (LTA), mimicked the impact of S. aureus elevating COX-2/mPGES-1 expression via NF-κB and p38 MAPK signalling in MDM, while the impairment of 15-LOX-1 correlates with reduced expression of Lamtor1. In conclusion, S. aureus dictates LM pathways via LTA resulting in a shift from anti-inflammatory M2-like towards pro-inflammatory M1-like LM signature profiles.

Incidence and severity of G6PI-induced arthritis are not increased in genetically distinct mouse strains upon aging.

BACKGROUND: The incidence of rheumatoid arthritis is correlated with age. In this study, we analyzed the association of the incidence and severity of glucose-6-phosphate isomerase (G6PI)-induced arthritis with age in two different mouse strains. METHODS: Young and very old mice from two different arthritis-susceptible wild-type mouse strains were analyzed after a single subcutaneous injection of G6PI s.c. The metabolism and the function of synoviocytes were analyzed in vitro, the production of bioactive lipid mediators by myeloid cells and synoviocytes was assessed in vitro and ex vivo by UPLC-MS-MS, and flow cytometry was used to verify age-related changes of immune cell composition and function. RESULTS: While the severity of arthritis was independent from age, the onset was delayed in old mice. Old mice showed common signs of immune aging like thymic atrophy associated with decreased CD4+ effector T cell numbers. Despite its decrease, the effector T helper (Th) cell compartment in old mice was reactive and functionally intact, and their Tregs exhibited unaltered suppressive capacities. In homeostasis, macrophages and synoviocytes from old mice produced higher amounts of pro-inflammatory cyclooxygenase (COX)-derived products. However, this functional difference did not remain upon challenge in vitro nor upon arthritis reactions ex vivo. CONCLUSION: While old mice show a higher baseline of inflammatory functions, this does not result in increased reaction towards self-antigens in arthritis-susceptible mouse strains. Together, our data from two different mouse strains show that the susceptibility for G6PI-induced arthritis is not age-dependent.

Loss of metabolic plasticity underlies metformin toxicity in aged Caenorhabditis elegans.

Current clinical trials are testing the life-extending benefits of the diabetes drug metformin in healthy individuals without diabetes. However, the metabolic response of a non-diabetic cohort to metformin treatment has not been studied. Here, we show in C. elegans and human primary cells that metformin shortens lifespan when provided in late life, contrary to its positive effects in young organisms. We find that metformin exacerbates ageing-associated mitochondrial dysfunction, causing respiratory failure. Age-related failure to induce glycolysis and activate the dietary-restriction-like mobilization of lipid reserves in response to metformin result in lethal ATP exhaustion in metformin-treated aged worms and late-passage human cells, which can be rescued by ectopic stabilization of cellular ATP content. Metformin toxicity is alleviated in worms harbouring disruptions in insulin-receptor signalling, which show enhanced resilience to mitochondrial distortions at old age. Together, our data show that metformin induces deleterious changes of conserved metabolic pathways in late life, which could bring into question its benefits for older individuals without diabetes.

Staphylococcus aureus-Derived α-Hemolysin Evokes Generation of Specialized Pro-resolving Mediators Promoting Inflammation Resolution.

Underlying mechanisms of how infectious inflammation is resolved by the host are incompletely understood. One hallmark of inflammation resolution is the activation of specialized pro-resolving mediators (SPMs) that enhance bacterial clearance and promote tissue repair. Here, we reveal α-hemolysin (Hla) from Staphylococcus aureus as a potent elicitor of SPM biosynthesis in human M2-like macrophages and in the mouse peritoneum through selective activation of host 15-lipoxygenase-1 (15-LOX-1). S. aureus-induced SPM formation in M2 is abolished upon Hla depletion or 15-LOX-1 knockdown. Isolated Hla elicits SPM formation in M2 that is reverted by inhibition of the Hla receptor ADAM10. Lipid mediators derived from Hla-treated M2 accelerate planarian tissue regeneration. Hla but not zymosan provokes substantial SPM formation in the mouse peritoneum, devoid of leukocyte infiltration and pro-inflammatory cytokine secretion. Besides harming the host, Hla may also exert beneficial functions by stimulating SPM production to promote the resolution of infectious inflammation.

Novel benzoxanthene lignans that favorably modulate lipid mediator biosynthesis: A promising pharmacological strategy for anti-inflammatory therapy.

Lipid mediators (LM) encompass pro-inflammatory prostaglandins (PG) and leukotrienes (LT) but also specialized pro-resolving mediators (SPM) which display pivotal bioactivities in health and disease. Pharmacological intervention with inflammatory disorders such as osteoarthritis and rheumatoid arthritis commonly employs anti-inflammatory drugs that can suppress PG and LT formation, which however, possess limited effectiveness and side effects. Here, we report on the discovery and characterization of the two novel benzoxanthene lignans 1 and 2 that modulate select LM biosynthetic enzymes enabling the switch from pro-inflammatory LT to SPM biosynthesis as potential pharmacological strategy to intervene with inflammation. In cell-free assays, compound 1 and 2 inhibit microsomal prostaglandin E2 synthase-1 and leukotriene C4 synthase (IC50 ∼ 0.6-3.4 µM) and potently interfere with 5-lipoxygenase (5-LOX), the key enzyme in LT biosynthesis (IC50 = 0.04 and 0.09 µM). In human neutrophils, monocytes and M1 and M2 macrophages, compound 1 and 2 efficiently suppress LT biosynthesis (IC50 < 1 µM), accompanied by elevation of 15-LOX-derived LM including SPM. In zymosan-induced murine peritonitis, compound 1 and 2 ameliorated self-limited inflammation along with suppression of early LT formation and elevation of subsequent SPM biosynthesis in vivo. Together, these novel benzoxanthene lignans promote the LM class switch from pro-inflammatory towards pro-resolving LM to terminate inflammation, suggesting their suitability as novel leads for pharmacotherapy of arthritis and related inflammatory disorders.

Insulin-like growth factor-1 acts as a zeitgeber on hypothalamic circadian clock gene expression via glycogen synthase kinase-3ß signaling.

Brain and muscle ARNT-like protein-1 (BMAL-1) is an important component of the cellular circadian clock. Proteins such as epidermal (EGF) or nerve growth factor (NGF) affect the cellular clock via extracellular signal-regulated kinases-1/2 (ERK-1/2) in NIH3T3 or neuronal stem cells, but no such data are available for the insulin-like growth factor-1 (IGF-1). The hypothalamus expresses receptors for all three growth factors, acts as a central circadian pacemaker, and releases hormones in a circadian fashion. However, little is known about growth factor-induced modulation of clock gene activity in hypothalamic cells. Here, we investigated effects of IGF-1, EGF, or NGF on the Bmal-1 promoter in two hypothalamic cell lines. We found that only IGF-1 but not EGF or NGF enhanced activity of the Bmal-1 promoter. Inhibition of ERK-1/2 activity did not affect IGF-1-induced Bmal-1 promoter activation and all three growth factors similarly phosphorylated ERK-1/2, questioning a role for ERK-1/2 in controlling BMAL-1 promoter activity. Of note, only IGF-1 induced sustained phosphorylation of glycogen synthase kinase-3ß (GSK-3ß). Moreover, the GSK-3ß inhibitor lithium or siRNA-mediated GSK-3ß knockdown diminished the effects of IGF-1 on the Bmal-1 promoter. When IGF-1 was used in the context of temperature cycles entraining hypothalamic clock gene expression to a 24-h rhythm, it shifted the phase of Bmal-1 promoter activity, indicating that IGF-1 functions as a zeitgeber for cellular hypothalamic circadian clocks. Our results reveal that IGF-1 regulates clock gene expression and that GSK-3ß but not ERK-1/2 is required for the IGF-1-mediated regulation of the Bmal-1 promoter in hypothalamic cells.