Protein, lipid, and DNA radicals to measure skin UVA damage and modulation by melanin

Afro-Caribbeans have a lower incidence of skin cancer than Caucasians, but the effectiveness of melanin as a photoprotective pigment is debated. We investigated the UVA and solar irradiation of ex vivo human skin and DMPO using electron spin resonance spectroscopy, to determine whether pigmented skin is protected by melanin against free radical damage. Initial ascorbate radicals in Caucasian skin were superseded by lipid and/or protein radical adducts with isotropic (a(H)=1.8 mT) and anisotropic spectra comparable to spectra in irradiated pig fat (a(H)=1.9 mT) and BSA. DNA carbon-centered radical adducts (a(H)=2.3 mT) and a broad singlet were detected in genomic DNA/melanin but were not distinguishable in irradiated Caucasian skin. Protein and lipid radicals (n=6 in Caucasian skin) were minimal in Afro-Caribbean skin (n=4) and intermediate skin pigmentations were variable (n=3). In irradiated Afro-Caribbean skin a shoulder to the melanin radical (also in UVA-irradiated pigmented melanoma cells and genomic DNA/melanin and intrinsic to pheomelanin) was detected. In this sample group, protein (but not lipid) radical adducts decreased directly with pigmentation. ESR/spin trapping methodology has potential for screening skin susceptibility to aging and cancer-related radical damage and for measuring protection afforded by melanin, sunscreens, and antiaging creams.     

Effect of primary mild stresses on resilience and resistance of the nitrate reducer community to a subsequent severe stress

The factors regulating soil microbial stability (e.g. resistance and resilience) are poorly understood, even though microorganisms are essential for ecosystem functioning. In this study, we tested whether a functional microbial community subjected to different primary mild stresses was equally resistant or resilient to a subsequent severe stress. The nitrate reducers were selected as model community and analysed in terms of nitrate reduction rates and genetic structure by narG PCR-restriction fragment length polymorphism fingerprinting. Heat, copper and atrazine were used as primary stresses and mercury at a high concentration as a severe stress. None of the primary stresses had any significant impact on the nitrate reducer community. Although primary stress with heat, copper or atrazine had no effect on the resilience of the nitrate reducer activity to mercury stress, pre-exposure to copper, another heavy metal, resulted in increased resilience. In contrast, the resistance of both structure and activity of the nitrate reducer community to severe mercury stress was not affected by any of the primary stresses tested. Our experiment suggests that the hypothetical effect of an initial stress on the response of a microbial community to an additional stress is complex and may depend on the relatedness of the two consecutive stresses and the development of positive cotolerance.     

VE-statin/egfl7 regulates vascular elastogenesis by interacting with lysyl oxidases

We previously characterized VE-statin/egfl7, a protein that is exclusively secreted by endothelial cells and modulates smooth muscle cell migration. Here, we show that VE-statin/egfl7 is the first known natural negative regulator of vascular elastogenesis. Transgenic mice, expressing VE-statin/egfl7 under the control of keratin-14 promoter, showed an accumulation of VE-statin/egfl7 in arterial walls where its presence correlated with an impaired organization of elastic fibres. In vitro, fibroblasts cultured in the presence of VE-statin/egfl7 were unable to deposit elastic fibres due to a deficient conversion of soluble tropoelastin into insoluble mature elastin. VE-statin/egfl7 interacts with the catalytic domain of lysyl oxidase (LOX) enzymes and, in endothelial cells, endogenous VE-statin/egfl7 colocalizes with LoxL2 and inhibits elastic fibre deposition. In contrast, mature elastic fibres are abundantly deposited by endothelial cells that are prevented from producing endogenous VE-statin/egfl7. We propose a model where VE-statin/egfl7 produced by endothelial cells binds to the catalytic domains of enzymes of the LOX family in the vascular wall, thereby preventing the crosslink of tropoelastin molecules into mature elastin polymers and regulating vascular elastogenesis.     

Comparison of Anopheles gambiae and Culex pipiens acetycholinesterase 1 biochemical properties

Selection of insensitive acetycholinesterase 1 (AChE1) has occurred in several mosquito species controlled with carbamate (CX) and organophosphate (OP) insecticides. In case of pyrethroid resistance, these insecticides represent an alternative for disease vector control program. Their heavy use in agriculture has selected resistant populations of Anopheles gambiae in West Africa. The evolution of resistance has to be studied to prevent, or at least slow down, the spread of resistant mosquito in wild populations. An. gambiae shares the same resistance mechanism to CX and OP insecticides as Culex pipiens, which was attributed to the G119S substitution in the AChE1 enzyme. By comparing resistant AChE1 from both species, we show here that similar resistance levels are obtained toward 10 insecticides of both classes. Moreover, similar AChE1 activity levels are recorded between either susceptible or resistant mosquitoes of both species. Enzymes belonging to both species seem thus to share identical properties. Consequently, we hypothesize that fitness cost associated with AChE1 insensitivity in C. pipiens mosquitoes should be similar in An. gambiae and thus be used in strategies to control resistant populations where malaria is prevalent.     

Square-planar and trigonal prismatic silver(I) in bipyrimidine and oxalate bridged tetranuclear complexes and one-dimensional compounds: Synthesis and crystal structures

The reaction of [Ag₄(hfac)₄(THF)₂] (hfac⁻ = 1,1,1,5,5,5-hexafluoroacetylacetonate, THF = tetrahydrofurrane) with 2,2′-bipyrimidine (bpm) leads to single crystals. They crystallise in the triclinic system, space group . Their structure consists of [Ag₄(hfac)₄(μ₂-bpm)₃] tetranuclear complexes. In this complex, Ag(I) ions adopt distorted square planar and trigonal prismatic geometries. When [Ag₄(hfac)₄(THF)₂] is replaced by monohydrated silver(I) perchlorate, a one-dimensional (1D) compound with a formula of [[Ag(μ₂-bpm)]⁺]_n, is obtained as single crystals. They crystallise in the monoclinic system, space group P2₁/c. Their structure consists of [[Ag(μ₂-bpm)]⁺]_n chains separated by non-coordinated perchlorate ions. In the chains, the Ag(I) centres adopt a square planar geometry. Finally, starting from [[Ag(μ₂-bpm)]⁺]_n, and sodium oxalate , another 1D compound with a formula of [Ag(μ₂-bpm)(μ₂-ox)]_n, 4nH₂O is obtained as single crystals. They crystallise in the triclinic system, space group . In these chains, bipyrimidine and oxalate are alternate. They generate a square planar geometry around the Ag(I) cations.     

Acetylcholine evokes an InsP3R1-dependent transient Ca2+ signal in rat duodenum myocytes

In smooth muscle myocytes, agonist-activated release of calcium ions (Ca2+) stored in the sarcoplasmic reticulum (SR) occurs via different but overlapping transduction pathways. Hence, to fully study how SR Ca2+ channels are activated, the simultaneous activation of different Ca2+ signals should be separated. In rat duodenum myocytes, we have previously characterized that acetylcholine (ACh) induces Ca2+ oscillations by binding to its M2 muscarinic receptor and activating the ryanodine receptor subtype 2. Here, we show that ACh simultaneously evokes a Ca2+ signal dependent on activation of inositol 1,4,5-trisphosphate (InsP3) receptor subtype 1. A pharmacologic approach, the use of antisense oligonucleotides directed against InsP3R1, and the expression of a specific biosensor derived from green-fluorescent protein coupled to the pleckstrin homology domain of phospholipase C, suggested that the InsP3R1-dependent Ca2+ signal is transient and due to a transient synthesis of InsP3 via M3 muscarinic receptor. Moreover, we suggest that both M2 and M3 signalling pathways are modulating phosphatidylinositol 4,5-bisphosphate and InsP3 concentration, thus describing closely interacting pathways activated by ACh in duodenum myocytes.