Urinary Interleukin-8 Is a Biomarker of Stress in Emergency Physicians,Especially with Advancing Age — The JOBSTRESS* Randomized Trial

Background

Emergency physicians are exposed to greater stress during a 24-hour shift (24 hS) than a 14-hour night shift (14 hS), with an impact lasting several days. Interleukin-8 (IL-8) is postulated to be a chronic stress biomarker. However, no studies have tracked IL-8 over several shifts or used it for monitoring short-term residual stress. The IL-8 response to the shifts may also increase with age. Conveniently, IL-8 can be measured non-intrusively from urine.

Methods

We conducted a shifts-randomized trial comparing 17 emergency physicians’ urinary IL-8 levels during a 24 hS, a 14 hS, and a control day (clerical work on return from leave). Mean levels of IL-8 were compared using a Wilcoxon matched-pairs test. Independent associations of key factors including shifts, stress, and age with IL-8 levels were further assessed in a multivariable generalized estimating equations model.

Results

Mean urinary IL-8 levels almost doubled during and after a 24 hS compared with a 14 hS or a control day. Furthermore, IL-8 levels failed to return to control values at the end of the third day after the shift despite a rest day following the 24 hS. In the multivariable model, engaging in a 24 hS, self-reported stress, and age were independently associated with higher IL-8 levels. A 24 hS significantly increased IL-8 levels by 1.9 ng (p = .007). Similarly, for every unit increase in self-reported stress, there was a 0.11 ng increase in IL-8 levels (p = .003); and for every one year advance in age of physicians, IL-8 levels also increased by 0.11 ng (p = .018).

Conclusion

The 24 hS generated a prolonged response of the immune system. Urinary IL-8 was a strong biomarker of stress under intensive and prolonged demands, both acutely and over time. Because elevated IL-8 levels are associated with cardiovascular disease and negative psychological consequences, we suggest that emergency physicians limit their exposure to 24 hS, especially with advancing age.     

Hepatic Adaptation Compensates Inactivation of Intestinal Arginine Biosynthesis in Suckling Mice

Suckling mammals, including mice, differ from adults in the abundant expression of enzymes that synthesize arginine from citrulline in their enterocytes. To investigate the importance of the small-intestinal arginine synthesis for whole-body arginine production in suckling mice, we floxed exon 13 of the argininosuccinate synthetase (Ass) gene, which codes for a key enzyme in arginine biosynthesis, and specifically and completely ablated Ass in enterocytes by crossing Ass ^fl and Villin-Cre mice. Unexpectedly, Ass ^fl/fl /VilCre ^tg/- mice showed no developmental impairments. Amino-acid fluxes across the intestine, liver, and kidneys were calculated after determining the blood flow in the portal vein, and hepatic and renal arteries (86%, 14%, and 33%, respectively, of the transhepatic blood flow in 14-day-old mice). Relative to control mice, citrulline production in the splanchnic region of Ass ^fl/fl /VilCre ^tg/- mice doubled, while arginine production was abolished. Furthermore, the net production of arginine and most other amino acids in the liver of suckling control mice declined to naught or even changed to consumption in Ass ^fl/fl /VilCre ^tg/- mice, and had, thus, become remarkably similar to that of post-weaning wild-type mice, which no longer express arginine-biosynthesizing enzymes in their small intestine. The adaptive changes in liver function were accompanied by an increased expression of genes involved in arginine metabolism (Asl, Got1, Gpt2, Glud1, Arg1, and Arg2) and transport (Slc25a13, Slc25a15, and Slc3a2), whereas no such changes were found in the intestine. Our findings suggest that the genetic premature deletion of arginine synthesis in enterocytes causes a premature induction of the post-weaning pattern of amino-acid metabolism in the liver.     

Association of the variant rs2243421 of human DOC-2/DAB2 interactive protein gene (hDAB2IP) with gastric cancer in the Chinese Han population

Human DOC-2/DAB2 interactive protein (hDAB2IP) gene is a novel member of the Ras GTPase-activating family and has been demonstrated to be a tumor-suppressor gene that inhibits cell survival and proliferation and induces cell apoptosis. It was reported that the expression level of hDAB2IP in gastric cancer tissue was highly correlated with tumor progression, however, whether hDAB2IP genetic variants are associated with the risk of gastric cancer remains yet unknown. In this case–control study, we conducted a genetic analysis for hDAB2IP variants in 311 patients with gastric cancer and 425 controls from the Chinese Han population. We found that the SNP rs2243421 of hDAB2IP gene with the minor allele C significantly revealed strong association with decreased gastric cancer susceptibility (P = 0.007, adjusted odds ratio [OR] = 0.734, 95%CI = 0.586–0.919). Haplotypes rs2243421 and rs10985332 (HaploType: CC, P = 0.012, aOR = 0.760) and haplotypes rs2243421 and rs555996 (HaploType: CG, P = 0.034, aOR = 0.788) represented the decreased risk of gastric cancer, respectively. On the contrary, rs2243421 and rs555996 showed an elevated susceptibility (HaploType: TG, P = 0.010, aOR = 1.320). Our results for the first time provided new insight into susceptibility factors of hDAB2IP gene variants in carcinogenesis of gastric cancer.     

Irreversible Changes Occur in Chromatin Structure Upon Dissociation Of Histone H1

Abstract

The role of histone H1 in the actual interactions bringing about chromatin folding is investigated by studying the reversibility of its dissociation. HI was dissociated by increase of the NaCl concentration and reassociated by dialysis, without removal from the dialysis bag. To scrutinize the fidelity of this stoichiometric form of chromatin reconstitution, we use circular dichroism, nuclease digestion, thermal denaturation and the sensitive electric birefringence method. No alteration of the repeat length and no nucleosomal sliding are observed upon the reassociation procedure. However, under all the different conditions investigated, the original value of the positive electric birefringence is never recovered, indicating an irreversible change of structure. CD and melting profiles confirm that DNA-protein interactions are modified, and orientational relaxation time measurements indicate that these structural perturbations affect the salt- induced transition of poly nucleosomal fibers. The striking conclusion of these studies is that variations of ionic concentration are sufficient to induce irreversible structural alterations affecting the higher-order folding of chromatin. It is of interest that the only sample which exhibits behavior upon reassociation comparable to that of native chromatin is the one which experienced the fastest salt transitions. We suggest that these conformational changes arise from the unbinding to DNA of certain basic tails of histone(s), and that a competition for DNA binding locations exists upon the reassociation. These results are then additional arguments (Mazen, A., Hacques, M.F. and Marion, C., J. Mol. Biol. 194, 741–745 (1987)), to suggest that dissociation of H1 might modify a direct interaction between basic tails of core histones and H1.     

Settlement Behaviour of Marine Invertebrate Larvae Measured by EthoVision 3.0

Submerged marine surfaces are rapidly colonized by fouling organisms. Current research is aimed at finding new, non-toxic, or at least environmentally benign, solutions to this problem. Barnacles are a major target organism for such control as they constitute a key component of the hard fouling community. A range of standard settlement assays is available for screening test compounds against barnacle cypris larvae, but they generally provide little information on mechanism(s) of action. Towards this end, a quick and reliable video-tracking protocol has been developed to study the behaviour of the cypris larvae of the barnacle, Balanus amphitrite, at settlement. EthoVision 3.0 was used to track individual cyprids in 30-mm Petri dishes. Experiments were run to determine the optimal conditions vis-à-vis acclimation time, tracking duration, number of replicates, temperature and lighting. A protocol was arrived at involving a two Petri dish system with backlighting, and tracking over a 5-min period after first acclimating the cyprids to test conditions for 2 min. A minimum of twenty replicates was required to account for individual variability in cyprid behaviour from the same batch of larvae. This methodology should be widely applicable to both fundamental and applied studies of larval settlement and with further refinements, to that of smaller fouling organisms such as microalgae and bacteria.     

Characterization of a Serine Hydrolase Targeted by Acyl-protein Thioesterase Inhibitors in Toxoplasma gondii

In eukaryotic organisms, cysteine palmitoylation is an important reversible modification that impacts protein targeting, folding, stability, and interactions with partners. Evidence suggests that protein palmitoylation contributes to key biological processes in Apicomplexa with the recent palmitome of the malaria parasite Plasmodium falciparum reporting over 400 substrates that are modified with palmitate by a broad range of protein S-acyl transferases. Dynamic palmitoylation cycles require the action of an acyl-protein thioesterase (APT) that cleaves palmitate from substrates and conveys reversibility to this posttranslational modification. In this work, we identified candidates for APT activity in Toxoplasma gondii. Treatment of parasites with low micromolar concentrations of β-lactone- or triazole urea-based inhibitors that target human APT1 showed varied detrimental effects at multiple steps of the parasite lytic cycle. The use of an activity-based probe in combination with these inhibitors revealed the existence of several serine hydrolases that are targeted by APT1 inhibitors. The active serine hydrolase, TgASH1, identified as the homologue closest to human APT1 and APT2, was characterized further. Biochemical analysis of TgASH1 indicated that this enzyme cleaves substrates with a specificity similar to APTs, and homology modeling points toward an APT-like enzyme. TgASH1 is dispensable for parasite survival, which indicates that the severe effects observed with the β-lactone inhibitors are caused by the inhibition of non-TgASH1 targets. Other ASH candidates for APT activity were functionally characterized, and one of them was found to be resistant to gene disruption due to the potential essential nature of the protein.     

Replication and trafficking of a plant virus are coupled at the entrances of plasmodesmata

Plant viruses use movement proteins (MPs) to modify intercellular pores called plasmodesmata (PD) to cross the plant cell wall. Many viruses encode a conserved set of three MPs, known as the triple gene block (TGB), typified by Potato virus X (PVX). In this paper, using live-cell imaging of viral RNA (vRNA) and virus-encoded proteins, we show that the TGB proteins have distinct functions during movement. TGB2 and TGB3 established endoplasmic reticulum–derived membranous caps at PD orifices. These caps harbored the PVX replicase and nonencapsidated vRNA and represented PD-anchored viral replication sites. TGB1 mediated insertion of the viral coat protein into PD, probably by its interaction with the 5′ end of nascent virions, and was recruited to PD by the TGB2/3 complex. We propose a new model of plant virus movement, which we term coreplicational insertion, in which MPs function to compartmentalize replication complexes at PD for localized RNA synthesis and directional trafficking of the virus between cells.