Monitoring of organochlorine pesticides in the urban air of Dalian,China with semipermeable membrane devices

The concentrations of 28 organochlorine pesti- cides （OCPs） in the urban air of Dalian, China were measured using semipermeable membrane devices （SPMDs） for the first time. Alpha-hexachlorocyclohexane （α-HCH）, β-HCH, pentachlorobenzene （PentCB）, hexachlorobenzene （HexCB）, 4,4＇-dichlorodiphenyltrichloroethane （4,4＇-DDT）, 4,4＇- dichlorodiphenyldichloroethene, endosulfan-I and endosul- fan-Ⅱ were the predominant OCPs in the urban air of Dalian. The concentration of OCPs sequestrated by SPMDs （CSPMD） ranged from undetected to 56,772 pg SPMD-1 and had a linear correlation with the reciprocal of the average ambient atmospheric temperature （1/T）. The CSPMD of PentCB and HexCB had negative correlations with T, whereas the other detected OCPs had a positive correlation. The source of HCHs, DDTs, HexCB, PentCB, chlordane, and endosulfan in the air were also evaluated. The OCPs in the urban air of Dalian could be attributed to the seasonal usage of pesticides,combustion, volatilization of aged OCPs from soil, water, plants, and long-range atmospheric transport.     

Comparative genome sequencing of Escherichia coli allows observation of bacterial evolution on a laboratory timescale

We applied whole-genome resequencing of Escherichia coli to monitor the acquisition and fixation of mutations that conveyed a selective growth advantage during adaptation to a glycerol-based growth medium. We identified 13 different de novo mutations in five different E. coli strains and monitored their fixation over a 44-d period of adaptation. We obtained proof that the observed spontaneous mutations were responsible for improved fitness by creating single, double and triple site-directed mutants that had growth rates matching those of the evolved strains. The success of this new genome-scale approach indicates that real-time evolution studies will now be practical in a wide variety of contexts.     

Ceramide synthase 2 deficiency aggravates AOM-DSS-induced colitis in mice: role of colon barrier integrity

Loss of intestinal barrier functions is a hallmark of inflammatory bowel disease like ulcerative colitis. The molecular mechanisms are not well understood, but likely involve dysregulation of membrane composition, fluidity, and permeability, which are all essentially regulated by sphingolipids, including ceramides of different chain length and saturation. Here, we used a loss-of-function model (CerS2^+/+ and CerS2^?/? mice) to investigate the impact of ceramide synthase 2, a key enzyme in the generation of very long-chain ceramides, in the dextran sodium salt (DSS) evoked model of UC. CerS2^?/? mice developed more severe disease than CerS2^+/+ mice in acute DSS and chronic AOM/DSS colitis. Deletion of CerS2 strongly reduced very long-chain ceramides (Cer24:0, 24:1) but concomitantly increased long-chain ceramides and sphinganine in plasma and colon tissue. In naive CerS2^?/? mice, the expression of tight junction proteins including ZO-1 was almost completely lost in the colon epithelium, leading to increased membrane permeability. This could also be observed in vitro in CerS2 depleted Caco-2 cells. The increase in membrane permeability in CerS2^?/? mice did not manifest with apparent clinical symptoms in naive mice, but with slight inflammatory signs such as an increase in monocytes and IL-10. AOM/DSS and DSS treatment alone led to a further deterioration of membrane integrity and to severe clinical symptoms of the disease. This was associated with stronger upregulation of cytokines in CerS2^?/? mice and increased infiltration of the colon wall by immune cells, particularly monocytes, CD4⁺ and Th17⁺ T-cells, and an increase in tumor burden. In conclusion, CerS2 is crucial for the maintenance of colon barrier function and epithelial integrity. CerS2 knockdown, and associated changes in several sphingolipids such as a drop in very long-chain ceramides/(dh)-ceramides, an increase in long-chain ceramides/(dh)-ceramides, and sphinganine in the colon, may weaken endogenous defense against the endogenous microbiome.     

EP4 receptor stimulation down-regulates human eosinophil function

Accumulation of eosinophils in tissue is a hallmark of allergic inflammation. Here we observed that a selective agonist of the PGE₂ receptor EP4, ONO AE1-329, potently attenuated the chemotaxis of human peripheral blood eosinophils, upregulation of the adhesion molecule CD11b and the production of reactive oxygen species. These effects were accompanied by the inhibition of cytoskeletal rearrangement and Ca²⁺ mobilization. The involvement of the EP4 receptor was substantiated by a selective EP4 antagonist, which reversed the inhibitory effects of PGE₂ and the EP4 agonist. Selective kinase inhibitors revealed that the inhibitory effect of EP4 stimulation on eosinophil migration depended upon activation of PI 3-kinase and PKC, but not cAMP. Finally, we found that EP4 receptors are expressed by human eosinophils, and are also present on infiltrating leukocytes in inflamed human nasal mucosa. These data indicate that EP4 agonists might be a novel therapeutic option in eosinophilic diseases.     

Plasmacytoid dendritic cells sense self-DNA coupled with antimicrobial peptide

Plasmacytoid dendritic cells (pDCs) sense viral and microbial DNA through endosomal Toll-like receptors to produce type 1 interferons. pDCs do not normally respond to self-DNA, but this restriction seems to break down in human autoimmune disease by an as yet poorly understood mechanism. Here we identify the antimicrobial peptide LL37 (also known as CAMP) as the key factor that mediates pDC activation in psoriasis, a common autoimmune disease of the skin. LL37 converts inert self-DNA into a potent trigger of interferon production by binding the DNA to form aggregated and condensed structures that are delivered to and retained within early endocytic compartments in pDCs to trigger Toll-like receptor 9. Thus, our data uncover a fundamental role of an endogenous antimicrobial peptide in breaking innate tolerance to self-DNA and suggest that this pathway may drive autoimmunity in psoriasis.     

Mutations in genes encoding ribonuclease H2 subunits cause Aicardi-Goutières syndrome and mimic congenital viral brain infection

Aicardi-Goutières syndrome (AGS) is an autosomal recessive neurological disorder, the clinical and immunological features of which parallel those of congenital viral infection. Here we define the composition of the human ribonuclease H2 enzyme complex and show that AGS can result from mutations in the genes encoding any one of its three subunits. Our findings demonstrate a role for ribonuclease H in human neurological disease and suggest an unanticipated relationship between ribonuclease H2 and the antiviral immune response that warrants further investigation.     

Apoptotic cell-derived factors induce arginase II expression in murine macrophages by activating ERK5/CREB

Apoptotic cell (AC)-derived factors alter the physiology of macrophages (MΦs) towards a regulatory phenotype, characterized by reduced nitric oxide (NO) production. Impaired NO formation in response to AC-conditioned medium (CM) was facilitated by arginase II (ARG II) expression, which competes with inducible NO synthase for l-arginine. Here we explored signaling pathways allowing CM to upregulate ARG II in RAW264.7 MΦs. Sphingosine-1-phosphate (S1P) was required and acted synergistically with a so far unidentified factor to elicit high ARG II expression. S1P activated S1P₂, since S1P₂ knockdown prevented ARG II upregulation. Furthermore, ERK5 knockdown attenuated CM-mediated ARG II protein induction. CREB was implicated as shown by EMSA analysis and decoy-oligonucleotides scavenging CREB in RAW264.7 MΦs, which blocked ARG II expression. We conclude that AC-derived S1P binds to S1P₂ and acts synergistically with other factors to activate ERK5 and concomitantly CREB. This signaling cascade shapes an anti-inflammatory MΦ phenotype by ARG II induction.     

Viperin mRNA is a novel target for the human RNase MRP/RNase P endoribonuclease

RNase MRP is a conserved endoribonuclease, in humans consisting of a 267-nucleotide RNA associated with 7–10 proteins. Mutations in its RNA component lead to several autosomal recessive skeletal dysplasias, including cartilage-hair hypoplasia (CHH). Because the known substrates of mammalian RNase MRP, pre-ribosomal RNA, and RNA involved in mitochondrial DNA replication are not likely involved in CHH, we analyzed the effects of RNase MRP (and the structurally related RNase P) depletion on mRNAs using DNA microarrays. We confirmed the upregulation of the interferon-inducible viperin mRNA by RNAi experiments and this appeared to be independent of the interferon response. We detected two cleavage sites for RNase MRP/RNase P in the coding sequence of viperin mRNA. This is the first study providing direct evidence for the cleavage of a mRNA by RNase MRP/RNase P in human cells. Implications for the involvement in the pathophysiology of CHH are discussed.