High Serum Iron level is Associated with Increased Mortality in Patients with Sepsis.

Iron is an essential nutrient for bacterial survival and thus higher iron levels may precipitate bacterial infections. We investigated the association between the serum iron level and prognosis in patients with sepsis by using the single-centre Medical Information Mart for Intensive Care III (MIMIC-III) database. Sepsis patients with iron parameters measured on ICU admission were included and stratified according to quartiles of serum iron levels. A total of 1,891 patients diagnosed with sepsis according to the Sepsis-3 criteria were included in this study, 324 of whom were septic shock. After adjusting for confounding variables, higher iron quartile was associated with an increase in 90-day mortality in the Cox regression analysis. Moreover, a stepwise increase in the risk of 90-day mortality was observed as the quartiles of serum iron levels increased in the patients with sepsis. In conclusion, higher serum iron levels were independently associated with increased 90-day mortality in this large cohort of patients with sepsis.

Characterization of the Bombyx mori Cecropin A1 promoter regulated by IMD pathway.

Cecropin A1 (CecA1) promoter from Bombyx mori was cloned and characterized to provide insight into the transcriptional control of this antimicrobial peptide gene upon immune challenges. Reporter gene assays demonstrated that both Escherichia coli and lipopolysaccharide could induce expression in BmE cells but B. bombyseptieus or peptidoglycan failed, and the induction pattern of the reporter gene was coincident with the endogenous CecA1. Analysis of deletion and mutation constructs revealed that the regulatory region was the κB motif located between -176 and -166, and no other predicted elements on CecA1 promoter affected its inducibility. Insertion of additional κB motifs increased the activity of CecA1 promoter. Furthermore, binding of Relish to κB motif was confirmed by electrophoretic mobility shift assay. These findings indicate the regulatory mechanism of CecA1 expression in IMD pathway and suggest an approach of engineering antimicrobial peptide promoter with enhanced activities that may lead to broad applications.

[Construction of the recQ double mutants and analysis of adversity in Deinococcus radiodurans].

As a subfamily member of SF1 superfamily, the RecO helicases are highly conserved in evolution and are required for maintaining genome stability in all organisms. Loss of RecO helicase function leads to a breakdown in the maintenance of genome integrity, in particular hyper-recombination. Named after the recQ gene of Escherichia coli, lower eukaryotic species generally only contain a single RecQ family representative; for example, Sgsl in the budding yeast, Saccharomyces cerevisiae, and Rqhl in the fission yeast, Schizosaccharomyces pombe. There are, however, multiple members in most higher organisms, with five being present in humans. Defects in three of these human RecQ helicases give rise to defined clinical disorders associated with cancer predisposition and variable aspects of premature aging. Deinococcus radiodurans encodes two recQ genes with unusual domain: DR1289 and DR2444, whose functions, however, remain obscure currently. DR1289 contains three tandem copies of the C-terminal helicase-RNase D (HRDC) domain, instead of the single copy present in all other bacteria except Neisseria that similarly possesses three copies. DR2444 contains a HRDC domain and a domain homologous to cystathionine gamma-lyase; this is the first example of an HRDC domain that is not associated with either a helicase or a nuclease. In this study, a fusion DNA fragment carrying kanamycin resistance gene with the D. radiodurans groEL promoter, chloramphenicol resistance gene with KAT promoter was cloned by PCR amplification and reversely inserted into the recQ locus in the genome of the wild-type strain RI. Three resulting recQ-deficient strains, designated deltaDR1289, deltaDR2444 and deltarecQ (double mutation), were constructed. Results show that deltaDR1289 and delta recQ were very sensitive to ionizing radiation and H2O2, while delta DR2444 and wild strain R1 were not. The phenotype of delta DR1289 was similar to many RecQ helicase mutants. Therefore, it was presumed that DR1289 was the necessary gene in maintaining the extreme resistance to DNA damaging agents, whereas DR2444 was not. Further research based on genetic and biochemical approaches should help to gain a better understanding of the genes involved in DNA repair.

Functional analysis of helicase and three tandem HRDC domains of RecQ in Deinococcus radiodurans.

RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose function, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.