Acid Sphingomyelinase Serum Activity Predicts Mortality in Intensive Care Unit Patients after Systemic Inflammation: A Prospective Cohort Study

Introduction

Acid sphingomyelinase is involved in lipid signalling pathways and regulation of apoptosis by the generation of ceramide and plays an important role during the host response to infectious stimuli. It thus has the potential to be used as a novel diagnostic marker in the management of critically ill patients. The objective of our study was to evaluate acid sphingomyelinase serum activity (ASM) as a diagnostic and prognostic marker in a mixed intensive care unit population before, during, and after systemic inflammation.

Methods

40 patients admitted to the intensive care unit at risk for developing systemic inflammation (defined as systemic inflammatory response syndrome plus a significant procalcitonin [PCT] increase) were included. ASM was analysed on ICU admission, before (PCT_before), during (PCT_peak) and after (PCT_low) onset of SIRS. Patients undergoing elective surgery served as control (N = 8). Receiver-operating characteristics curves were computed.

Results

ASM significantly increased after surgery in the eight control patients. Patients from the intensive care unit had significantly higher ASM on admission than control patients after surgery. 19 out of 40 patients admitted to the intensive care unit developed systemic inflammation and 21 did not, with no differences in ASM between these two groups on admission. In patients with SIRS and PCT peak, ASM between admission and PCT_before was not different, but further increased at PCT_peak in non-survivors and was significantly higher at PCT_low compared to survivors. Survivors exhibited decreased ASM at PCT_peak and PCT_low. Receiver operating curve analysis on discrimination of ICU mortality showed an area under the curve of 0.79 for ASM at PCT_low.

Conclusions

In summary, ASM was generally higher in patients admitted to the intensive care unit compared to patients undergoing uncomplicated surgery. ASM did not indicate onset of systemic inflammation. In contrast to PCT however, it remained high in non-surviving ICU patients after systemic inflammation.     

Knockout of LASP1 in CXCR4 expressing CML cells promotes cell persistence,proliferation and TKI resistance

Chronic myeloid leukaemia (CML) is a clonal myeloproliferative stem cell disorder characterized by the constitutively active BCR-ABL tyrosine kinase. The LIM and SH3 domain protein 1 (LASP1) has recently been identified as a novel BCR-ABL substrate and is associated with proliferation, migration, tumorigenesis and chemoresistance in several cancers. Furthermore, LASP1 was shown to bind to the chemokine receptor 4 (CXCR4), thought to be involved in mechanisms of relapse. In order to identify potential LASP1-mediated pathways and related factors that may help to further eradicate minimal residual disease (MRD), the effect of LASP1 on processes involved in progression and maintenance of CML was investigated. The present data indicate that not only overexpression of CXCR4, but also knockout of LASP1 contributes to proliferation, reduced apoptosis and migration as well as increased adhesive potential of K562 CML cells. Furthermore, LASP1 depletion in K562 CML cells leads to decreased cytokine release and reduced NK cell-mediated cytotoxicity towards CML cells. Taken together, these results indicate that in CML, reduced levels of LASP1 alone and in combination with high CXCR4 expression may contribute to TKI resistance.     

Cks1 is required for tumor cell proliferation but not sufficient to induce hematopoietic malignancies

The Cks1 component of the SCF(Skp2) complex is necessary for p27(Kip1) ubiquitylation and degradation. Cks1 expression is elevated in various B cell malignancies including Burkitt lymphoma and multiple myeloma. We have previously shown that loss of Cks1 results in elevated p27(Kip1) levels and delayed tumor development in a mouse model of Myc-induced B cell lymphoma. Surprisingly, loss of Skp2 in the same mouse model also resulted in elevated p27(Kip1) levels but exhibited no impact on tumor onset. This raises the possibility that Cks1 could have other oncogenic activities than suppressing p27(Kip1). To challenge this notion we have targeted overexpression of Cks1 to B cells using a conditional retroviral bone marrow transduction-transplantation system. Despite potent ectopic overexpression, Cks1 was unable to promote B cell hyperproliferation or B cell malignancies, indicating that Cks1 is not oncogenic when overexpressed in B cells. Since Skp2 overexpression can drive T-cell tumorigenesis or other cancers we also widened the quest for oncogenic activity of Cks1 by ubiquitously expressing Cks1 in hematopoetic progenitors. At variance with c-Myc overexpression, which caused acute myeloid leukemia, Cks1 overexpression did not induce myeloproliferation or leukemia. Therefore, despite being associated with a poor prognosis in various malignancies, sole Cks1 expression is insufficient to induce lymphoma or a myeloproliferative disease in vivo.     

Community perspectives on scabies,impetigo and mass drug administration in Fiji: A qualitative study

Scabies is endemic in Fiji and is a significant cause of morbidity. Little is known about the sociocultural beliefs and practices that affect the occurrence of scabies and impetigo, or community attitudes towards the strategy of mass drug administration that is emerging as a public health option for scabies and impetigo control in Fiji and other countries. Data were collected during semi-structured interviews with 33 community members in four locations in Fiji’s Northern Division. Thematic analysis examined participants’ lived experiences of scabies and impetigo; community knowledge and perceptions about scabies and impetigo aetiology and transmission; community-based treatment and prevention measures; and attitudes towards mass drug administration. Many indigenous Fijian (iTaukei) participants noted extensive and ongoing experience of scabies and impetigo among children in their families and communities, but only one participant of Indian descent (Indo-Fijian) identified personal childhood experience of scabies. Scabies and impetigo were perceived as diseases affecting children, impacting on school attendance and families’ quality of sleep. Awareness of scabies and impetigo was considerable, but there were major misconceptions around disease causation and transmission. Traditional remedies were preferred for scabies treatment, followed by biomedicines provided by local health centres and hospitals. Treatment of close household contacts was not prioritised. Attitudes towards mass drug administration to control scabies were mostly positive, although some concerns were noted about adverse effects and hesitation to participate in the planned scabies elimination programme. Findings from this first study to document perspectives and experiences related to scabies and impetigo and their management in the Asia Pacific region illustrate that a community-centred approach to scabies and impetigo is needed for the success of control efforts in Fiji, and most likely in other affected countries. This includes community-based health promotion messaging on the social dynamics of scabies transmission, and a campaign of education and community engagement prior to mass drug administration.     

Dynamics of trigger factor interaction with translating ribosomes

In all organisms ribosome-associated chaperones assist early steps of protein folding. To elucidate the mechanism of their action, we determined the kinetics of individual steps of the ribosome binding/release cycle of bacterial trigger factor (TF), using fluorescently labeled chaperone and ribosome-nascent chain complexes. Both the association and dissociation rates of TF-ribosome complexes are modulated by nascent chains, whereby their length, sequence, and folding status are influencing parameters. However, the effect of the folding status is modest, indicating that TF can bind small globular domains and accommodate them within its substrate binding cavity. In general, the presence of a nascent chain causes an up to 9-fold increase in the rate of TF association, which provides a kinetic explanation for the observed ability of TF to efficiently compete with other cytosolic chaperones for binding to nascent chains. Furthermore, a subset of longer nascent polypeptides promotes the stabilization of TF-ribosome complexes, which increases the half-life of these complexes from 15 to 50 s. Nascent chains thus regulate their folding environment generated by ribosome-associated chaperones.     

A Temperature-sensitive mutation in the Arabidopsis thaliana phosphomannomutase gene disrupts protein glycosylation and triggers cell death

Eukaryotic phosphomannomutases (PMMs) catalyze the interconversion of mannose 6-phosphate to mannose 1-phosphate and are essential to the biosynthesis of GDP-mannose. As such, plant PMMs are involved in ascorbic acid (AsA) biosynthesis and N-glycosylation. We report on the conditional phenotype of the temperature-sensitive Arabidopsis thaliana pmm-12 mutant. Mutant seedlings were phenotypically similar to wild type seedlings when grown at 16-18 degrees C but died within several days after transfer to 28 degrees C. This phenotype was observed throughout both vegetative and reproductive development. Protein extracts derived from pmm-12 plants had lower PMM protein and enzyme activity levels. In vitro biochemical analysis of recombinant proteins showed that the mutant PMM protein was compromised in its catalytic efficiency (K cat/K m). Despite significantly decreased AsA levels in pmm-12 plants, AsA deficiency could not account for the observed phenotype. Since, at restrictive temperature, total glycoprotein patterns were altered and glycosylation of protein-disulfide isomerase was perturbed, we propose that a deficiency in protein glycosylation is responsible for the observed cell death phenotype.     

Design and synthesis of ten biphenyl-neolignan derivatives and their in vitro inhibitory potency against cyclooxygenase-1/2 activity and 5-lipoxygenase-mediated LTB4-formation

A set of ten derivatives of methylhonokiol, an anti-inflammatory active biphenyl-type neolignan from Magnolia grandiflora, has been evaluated for their in vitro cyclooxygenase-1/2 (COX-1/2) inhibitory activity using assays with purified prostaglandin H synthase (PGHS)-1 and PGHS-2 enzymes as well as for their 5-lipoxygenase (5-LOX) mediated LTB₄ formation inhibitory activity using an assay with activated human polymorphonuclear leukocytes. The derivatization reactions included methylation, acetylation, hydrogenation, epoxydation and isomerization. Five of the derivatives are new to science. The most active compound against COX-1 and COX-2 was methylhonokiol with IC₅₀ values of 0.1 μM, whereas the most active compound against LTB₄ formation was (E)-3′-propenyl-5-(2-propenyl)-biphenyl-2,4′-diol with an IC₅₀ value of 1.0 μM. Structure–activity relationship studies showed that the polarity of the derivatives plays a crucial role in their activity towards COX-1/2 enzyme and 5-LOX mediated LTB₄ formation.     

Helicobacter pylori VacA Toxin/Subunit p34: Targeting of an Anion Channel to the Inner Mitochondrial Membrane

The vacuolating toxin VacA, released by Helicobacter pylori, is an important virulence factor in the pathogenesis of gastritis and gastroduodenal ulcers. VacA contains two subunits: The p58 subunit mediates entry into target cells, and the p34 subunit mediates targeting to mitochondria and is essential for toxicity. In this study we found that targeting to mitochondria is dependent on a unique signal sequence of 32 uncharged amino acid residues at the p34 N-terminus. Mitochondrial import of p34 is mediated by the import receptor Tom20 and the import channel of the outer membrane TOM complex, leading to insertion of p34 into the mitochondrial inner membrane. p34 assembles in homo-hexamers of extraordinary high stability. CD spectra of the purified protein indicate a content of >40% β-strands, similar to pore-forming β-barrel proteins. p34 forms an anion channel with a conductivity of about 12 pS in 1.5 M KCl buffer. Oligomerization and channel formation are independent both of the 32 uncharged N-terminal residues and of the p58 subunit of the toxin. The conductivity is efficiently blocked by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), a reagent known to inhibit VacA-mediated apoptosis. We conclude that p34 essentially acts as a small pore-forming toxin, targeted to the mitochondrial inner membrane by a special hydrophobic N-terminal signal.     

Metabolism of green tea catechins by the human small intestine

Numerous studies have shown that green tea polyphenols can be degraded in the colon, and there is abundant knowledge about the metabolites of these substances that appear in urine and plasma after green tea ingestion. However, there is very little information on the extent and nature of intestinal degradation of green tea catechins in humans. Therefore, the aim of this study was to examine in detail the microbial metabolism and chemical stability of these polyphenols in the small intestine using a well-established ex vivo model. For this purpose, fresh ileostomy fluids from two probands were incubated for 24 h under anaerobic conditions with (+)-catechin (C), (-)-epicatechin (EC), (-)-epicatechin 3-O-gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatchin 3-O-gallate (EGCG) and gallic acid (GA). After lyophilisation and extraction, metabolites were separated, identified and quantified by high performance liquid chromatography-photodiode array detection (HPLC-DAD) and HPLC-ESI-tandem mass spectrometry. Two metabolites of EC and C (3', 4', 5'-trihydroxyphenyl-γ-valerolactone and 3', 4'-dihydroxyphenyl-γ-valerolactone) were identified. In addition, 3', 4', 5'-trihydroxyphenyl-γ-valerolactone was detected as a metabolite of EGC, and (after 24-h incubation) pyrogallol as a degradation product of GA. Cleavage of the GA esters of EGCG and ECG was also observed, with variations dependent on the sources (probands) of the ileal fluids, which differed substantially microbiotically. The results provide new information about the degradation of green tea catechins in the gastrointestinal tract, notably that microbiota-dependent liberation of GA esters may occur before these compounds reach the colon.