Reflux induces DNA strand breaks and expression changes of MMP1+9+14 in a human miniorgan culture model

Gastroesophageal reflux disease has been implicated in the pathogenesis of adenocarcinoma of the oesophagus. The same applies to laryngopharyngeal reflux (LPR) and squamous cell cancer of the head and neck, but so far, this link has not been proven. The impact of low pH and bile acids has not been studied extensively in cells other than oesophageal cancer cell lines and tissue. The aims of this study were to investigate the pathogenic potential of reflux and its single components on the mucosa of the upper respiratory tract. We measured DNA stability in human miniorgan cultures (MOCs) and primary epithelial cell cultures (EpCs) in response to reflux by the alkaline comet assay. As matrix metalloproteinases (MMPs) are involved in extracellular matrix remodelling processes and may contribute to cancer progression, we studied the expression of MMP1, -9, and -14 in MOCs, EpC, UM-SCC-22B, and FADU_DD. DNA strand breaks (DNA-SBs) increased significantly at low pH and after incubation with human or artificial gastric juice. Single incubation with glycochenodeoxycholic acid also showed a significant increase in DNA-SBs. In epithelial cell cultures, human gastric juice increased the number of DNA-SBs at pH 4.5 and 5.5. Artificial gastric juice significantly up regulated the gene expression of MMP9. Western blot analysis confirmed the results of gene expression analysis, but the up regulation of MMP1, -9, and -14 was donor-specific. Reflux has the ability to promote genomic instability and may contribute to micro environmental changes suitable for the initiation of malignancy. Further functional gene analysis may elucidate the role of laryngopharyngeal reflux in the development of head neck squamous cell carcinoma (HNSCC).     

The GIY-YIG Type Endonuclease Ankyrin Repeat and LEM Domain-Containing Protein 1 (ANKLE1) Is Dispensable for Mouse Hematopoiesis

Ankyrin repeat and LEM-domain containing protein 1 (ANKLE1) is a GIY-YIG endonuclease with unknown functions, mainly expressed in mouse hematopoietic tissues. To test its potential role in hematopoiesis we generated Ankle1-deficient mice. Ankle1^Δ/Δ mice are viable without any detectable phenotype in hematopoiesis. Neither hematopoietic progenitor cells, myeloid and lymphoid progenitors, nor B and T cell development in bone marrow, spleen and thymus, are affected in Ankle1^Δ/Δ-mice. Similarly embryonic stress erythropoiesis in liver and adult erythropoiesis in bone marrow and spleen appear normal. To test whether ANKLE1, like the only other known GIY-YIG endonuclease in mammals, SLX1, may contribute to Holliday junction resolution during DNA repair, Ankle1-deficient cells were exposed to various DNA-damage inducing agents. However, lack of Ankle1 did not affect cell viability and, unlike depletion of Slx1, Ankle1-deficiency did not increase sister chromatid exchange in Bloom helicase-depleted cells. Altogether, we show that lack of Ankle1 does neither affect mouse hematopoiesis nor DNA damage repair in mouse embryonic fibroblasts, indicating a redundant or non-essential function of ANKLE1 in mouse.     

Multiple stressors: using the honeybee model BEEHAVE to explore how spatial and temporal forage stress affects colony resilience

The causes underlying the increased mortality of honeybee Apis mellifera colonies observed over the past decade remain unclear. Since so far the evidence for monocausal explanations is equivocal, involvement of multiple stressors is generally assumed. We here focus on various aspects of forage availability, which have received less attention than other stressors because it is virtually impossible to explore them empirically. We applied the colony model BEEHAVE, which links within‐hive dynamics and foraging, to stylized landscape settings to explore how foraging distance, forage supply, and “forage gaps”, i.e. periods in which honeybees cannot find any nectar and pollen, affect colony resilience and the mechanisms behind. We found that colony extinction was mainly driven by foraging distance, but the timing of forage gaps had strongest effects on time to extinction. Sensitivity to forage gaps of 15 days was highest in June or July even if otherwise forage availability was sufficient to survive. Forage availability affected colonies via cascading effects on queen's egg‐laying rate, reduction of new‐emerging brood stages developing into adult workers, pollen debt, lack of workforce for nursing, and reduced foraging activity. Forage gaps in July led to reduction in egg‐laying and increased mortality of brood stages at a time when the queen's seasonal egg‐laying rate is at its maximum, leading to colony failure over time. Our results demonstrate that badly timed forage gaps interacting with poor overall forage supply reduce honeybee colony resilience. Existing regulation mechanisms which in principle enable colonies to cope with varying forage supply in a given landscape and year, such as a reduction in egg‐laying, have only a certain capacity. Our results are hypothetical, as they are obtained from simplified landscape settings, but they are consistent with existing empirical knowledge. They offer ample opportunities for testing the predicted effects of forage stress in controlled experiments.     

Involvement of the Adhesion GPCRs Latrophilins in the Regulation of Insulin Release

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IRAG is essential for relaxation of receptor-triggered smooth muscle contraction by cGMP kinase

Signalling by cGMP-dependent protein kinase type I (cGKI) relaxes various smooth muscles modulating thereby vascular tone and gastrointestinal motility. cGKI-dependent relaxation is possibly mediated by phosphorylation of the inositol 1,4,5-trisphosphate receptor I (IP(3)RI)-associated protein (IRAG), which decreases hormone-induced IP(3)-dependent Ca(2+) release. We show now that the targeted deletion of exon 12 of IRAG coding for the N-terminus of the coiled-coil domain disrupted in vivo the IRAG-IP(3)RI interaction and resulted in hypomorphic IRAG(Delta12/Delta12) mice. These mice had a dilated gastrointestinal tract and a disturbed gastrointestinal motility. Carbachol- and phenylephrine-contracted smooth muscle strips from colon and aorta, respectively, of IRAG(Delta12/Delta12) mice were not relaxed by cGMP, while cAMP-mediated relaxation was unperturbed. Norepinephrine-induced increases in [Ca(2+)](i) were not decreased by cGMP in aortic smooth muscle cells from IRAG(Delta12/Delta12) mice. In contrast, cGMP-induced relaxation of potassium-induced smooth muscle contraction was not abolished in IRAG(Delta12/Delta12) mice. We conclude that cGMP-dependent relaxation of hormone receptor-triggered smooth muscle contraction essentially depends on the interaction of cGKI-IRAG with IP(3)RI.     

Synthesis of dimeric acridine derived antivirals

A series of antiviral compounds consisting of an intercalating acridine derived part, a spacer region and a reactive EDTA derived conjugate was synthesized in an easy sequence starting from 1,omega-alkyldiamines. As shown in model screenings, in the presence of ascorbic acid the Fe-complexes of these compounds reduced the phage-titer of MS2-phages by >8 logarithmic decades.     

Pxl1p, a paxillin-like protein in Saccharomyces cerevisiae, may coordinate Cdc42p and Rho1p functions during polarized growth

Rho-family GTPases Cdc42p and Rho1p play critical roles in the budding process of the yeast Saccharomyces cerevisiae. However, it is not clear how the functions of these GTPases are coordinated temporally and spatially during this process. Based on its ability to suppress cdc42-Ts mutants when overexpressed, a novel gene PXL1 was identified. Pxl1p resembles mammalian paxillin, which is involved in integrating various signaling events at focal adhesion. Both proteins share amino acid sequence homology and structural organization. When expressed in yeast, chicken paxillin localizes to the sites of polarized growth as Pxl1p does. In addition, the LIM domains in both proteins are the primary determinant for targeting the proteins to the cortical sites in their native cells. These data strongly suggest that Pxl1p is the "ancient paxillin" in yeast. Deletion of PXL1 does not produce any obvious phenotype. However, Pxl1p directly binds to Rho1p-GDP in vitro, and inhibits the growth of rho1-2 and rho1-3 mutants in a dosage-dependent manner. The opposite effects of overexpressed Pxl1p on cdc42 and rho1 mutants suggest that the functions of Cdc42p and Rho1p may be coordinately regulated during budding and that Pxl1p may be involved in this coordination.