A Trichinella spiralis new born larvae-specific protein, Ts-NBL1, interacts with host's cell vimentin

The parasitic nematode Trichinella has a special relationship with its host as it has a unique intracellular location within the feeder cell which is a structure derived from skeletal muscle fiber. It has been proposed that “parakines” secreted by Trichinella larvae serve as messengers to implement communication between the parasite and the muscle cells through a molecular cross-talk to ensure permanent coexistence within the host. The Ts-NBL1 protein is considered to be a potential key “parakine” involved in the early invasion of the muscle fiber and its transformation into a feeder cell during Trichinella spiralis infection. This study used for the first time yeast two-hybrid (Y2H) technology in Trichinella to identify Ts-NBL1 interacting proteins. GST co-affinity purification experiments confirmed vimentin as an important interactor. The discovery of the new host proteins interacting with Ts-NBL1 will help to suggest that Ts-NBL1 contributes to participate in the capsule formation of feeder cells and provide ideas for understanding the molecular and cellular mechanisms involved in the survival of Trichinella in the host.

Coronary artery perforation after bioresorbable scaffold implantation treated with a new generation covered stent-OCT insights

Background

Coronary artery perforation is a rare but potentially lethal complication of percutaneous coronary intervention (PCI) with an associated mortality of 7–17%. We report the case of coronary artery perforation complicating Absorb bioresorbable vascular scaffold (BVS) implantation and the associated technical challenges with managing this life-threatening complication.

Case report

A 46-year-old male was referred to our institution and underwent PCI with an Absorb bioabsorbable vascular scaffold (BVS) to a proximal LAD long segment bifurcation lesion. Following pre-dilation and deployment of the 3.5 × 28 mm Absorb BVS, high pressure post-dilation of the distal scaffold was complicated by a large, Ellis type III coronary perforation with no flow to the distal LAD beyond the rupture, and associated with a large pericardial effusion confirmed on bedside transthoracic echocardiogram (TTE). The insult was temporised with prolonged balloon inflation within the Absorb BVS immediately proximal to the site of perforation, permitting urgent insertion of a pericardial drain. After deflation of the balloon, a 3.0 × 21 mm BeGraft covered stent was deployed across the perforation, restoring normal LAD flow and abolishing the perforation. Cardio-pulmonary resuscitation was not required and the patient remained conscious throughout the procedure. TTE demonstrated normal left ventricular function and the patient was discharged 3 days later. Repeat angiography at 3 months showed patent stents with TIMI III flow, and optical coherence tomography (OCT) showed good expansion and apposition of the proximal Absorb BVS and BeGraft. The patient has remained well 4 years after PCI with no major cardiovascular events.

Conclusion

The utility of bioresorbable scaffold technology remains controversial although meticulous implantation techniques are associated with improved clinical outcomes. Adoption of the Pre-dilatation, Sizing and Post-dilatation (‘PSP’) method of BVS implantation with routine aggressive vessel preparation and scaffold optimization however may contribute to a higher risk of vessel perforation. The case emphasises the importance of accurate sizing of the vessel with intracoronary imaging and demonstrates the value of newer generation covered stents with single-layer design and slimmer crossing profile producing improved deliverability and procedural success.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02501-3.

A232 TUFT CELLS COORDINATE RAPID EXPULSION OF THE TAPEWORM H. DIMINUTA BUT ARE NOT REQUIRED FOR ENHANCED IMMUNITY AGAINST THE NEMATODE, H. POLYGYRUS, IN MICE PREVIOUSLY INFECTED WITH H. DIMINUTA

Background

The tuft cell is an important sentinel that monitors the gut lumen and coordinates immunity against parasitic nematodes. We showed small intestinal tuft cell hyperplasia 11 days post-infection (dpi.) with the tapeworm Hymenolepis diminuta: a time when the parasite is no longer present in murine hosts. This may be a way by which the host protects itself from subsequent helminth-infections, a common phenomenon in parasite-endemic world regions. We test this supposition using Pou2f3^-/- mice that lack tuft cells.

Aims

To test the hypothesis that tuft cells are important in the anti-worm response in H. diminuta ( H.d.)-infected mice subsequently infected with the nematode parasite Heligosomoides polygyrus ( H.p.).

Methods

Male C57BL6 and Pou2f3^-/- mice (8–12 weeks) were infected with 5 H.d. cysticercoids ± 200 H.p. larvae at 10 dpi with H. diminuta (non H.p. mice - control). Upon necropsy at 24 dpi H. diminuta (i.e. 14 dpi H.p. in co-infected mice), both worms were ennumerated in small intestinal washings, H.p. granulomas examined and fecal egg counts performed. Small intestinal segments were stained for tuft (DCLK1⁺) and goblet cells (PAS⁺). As a surrogate of successful infection, IL-4 and IL-10 were measured in supernatants from concanavalin-A treated splenocytes.

Results

Wild-type (WT) mice expel H. diminuta by 11 dpi and this was delayed in Pou2f3^-/-mice, with worms readily detectable at 14 dpi and absent by 21 dpi. Despite the delayed expulsion, both WT and Pou2f3^-/- mice showed increased splenic production of IL-4 and IL-10; however, unlike WT mice, H. diminuta-infected Pou2f3^-/- mice show no increase in jejunal goblet cell numbers. Mice infected with H. diminuta displayed a degree of increased resistance to H.p.-infection defined by reduced worm and egg burdens, and increased granuloma formation in comparison to H.p.-only infected animals. In this sequential co-infection model, there were no significant differences between WT and Pou2f3^-/- mice in the response to H.p.

Conclusions

The absence of tuft cells slows expulsion of H. diminuta from its non-permissive mouse host and correlates with diminished goblet cell hyperplasia. Hypothesizing that H. diminuta-evoked tuft cell hyperplasia would enhance the immune response to a subsequent infection with an unrelated nematode parasite proved incorrect. While H. diminuta-infected mice were partially protected from H.p., response was similar in WT and Pou2f3^-/- mice. Thus tuft cells are important in worm detection: yet, our co-infection data suggests that other events initiated by the primary worm infection impact the outcome of subsequent infection with a different helminth and tuft cells have a limited, if any, role to play in this helminth-host-helminth interaction.

Funding Agencies

CIHRNSERC, Eye’s High International doctoral scholarship

A181 INFECTION WITH THE RAT TAPEWORM HYMENOLEPIS DIMINUTA REVEALS AN INTERLEUKIN-4 INDEPENDENT TUFT CELL ASSOCIATED WITH PEYER’S PATCHES

Background

Infection with the rat tapeworm Hymenolepis diminuta elicits a T helper 2 (Th2) imunity and suppresses dinitrobenzene sulphonic-acid-induced colitis in mice. However, the signaling cascade in an immunocompetent host that recognizes and mobilizies early immune events to expel the worm is poorly understood. To fully understand how helminth-infection can ameliorate concomitant disease, it is important to elucidate key cells/mediators in the detection of the worm and early events in the local anti-worm response. Here, we assess the chemosensory epithelial tuft cell and Peyer’s patches (PP) as the primary inductive sites of mucosal immunity in H. diminuta-infected mice.

Aims

To assess the role of tuft cells in PP development and worm expulsion following infection of H. diminuta.

Methods

BALB/c, BALB/c Il-4receptor-a^-/-, C57Bl/6 and C57Bl/6 pou2f3^-/- (transcription factor critial for tuft cell development) mice were infected with 5 cysticercoids of H. diminuta and necropsied 5-, 8- and 11-days post-infection (dpi); time-matched non-infected mice served as controls. PP number and size were counted and measured. Enteric tuft cells were assessed by immunostaining for the canonical marker double cortin like kinase (dclk)-1, and enumerated in PP-associated epithelium and villous epithelium distant from PP.

Results

Dclkl⁺ tuft cells were sparse throughout villus epithelium of control mice, but were notably aggregrated over PPs. Infection with H. diminuta resulted in more detectable PPs by visual inspection, but did not result in a statistically significant increase in either size or number of PP. Infected mice showed increased numbers of dclk1⁺ tuft cells in villus epithelium and PP-associated epithelium (n=3–6). Tuft cells were absent in pou2f3^-/- mice, that showed normal size and number of PPs ± infection with H. diminuta. Unexpectedly, analysis of small intestine from il4ra^-/- mice revealed dclk1⁺ tuft cells in association with PPs; perhaps a unique sub-type of this sentinel cell.

Conclusions

Analysis of tuft cells after infection with H. diminuta revealed that these cells aggregate around PPs under homeostatic conditions, and future studies will explore if this distrirbution is important for ‘M’ cell development and/or PP immune reactivity. Intrigingly, an il-4ra-independent tuft cell subtype was observed that awaits fuller characterization. Understanding the tuft cell may reveal novel aspects of development of mucosal immunity relevant to combating helminth-infection and perhaps autoinflammatory enteric disease.

Funding Agencies

NSERC

A60 THE NEURAL SIGNAL, CALCITONIN GENE-RELATED PEPTIDE (CGRG) ENHANCES A REGULATORY PHENOTYPE IN THE HUMAN IL-4 TREATED HUMAN MACROPHAGE

Background

Recent studies in pre-clinical models of disease have revealed the ability of murine and human IL-4-treated macrophages (M(IL4)) to promote wound recovery and reduce the severity of colitis. An unbiased RNA-sequence analysis of human blood-derived macrophages revealed increased expression of the RAMP1 chain of the CGRP receptor in IL-4 treated cells, raising the intriguing possibility of neural control of regulatory macrophages in the context of neuroimmune interaction in colitis. Thus, we sought to address if this mRNA signal translated into increased RAMP1 protein, if/how CGPR affected M(IL4) function, and if this applied to macrophages from patients with IBD as well as those from healthy donors.

Aims

To determine if CRGP-RAMP1 signalling in human IL-4 treated macrophages enhances a regulatory phenotype.

Methods

Peripheral blood mononuclear cells from healthy volunteers and individuals with IBD were cultured on plastic (2h, 37°C) and non-adherent cells removed. The adherent cells were cultured with recombinant hM-CSF (10 ng/ml) for 7 days. The resultant macrophages (2.5×105) were differentiated with IL-4 (48h 20 ng/mL) and assessed by qPCR and immunocytochemistry. In other cells, CGRP (10 nM) was added 24h after IL-4 and (1) cAMP (2) cytokines and (3) phagocytosis of inert FITC-beads measured, and (4) the capacity of supernatant from the cells to promote healing in wounded Caco2 epithelial monolayers tested.

Results

Compared to non-treated macrophages (M(0)), M(IL4)s from healthy individuals had increased mRNA for both chains of the CGRP-receptor (i.e. RAMP1 and CLR), and increased surface expression of the receptor as shown by immunostaining and CGRP-evoked cAMP. The IL-4 evoked RAMP1 mRNA was only detected in macrophages from 50% of the patients with active IBD. M(IL4)s treated with CGRP showed enhanced expression of the mannose receptor (CD206, allows detection of bacteria), increase phagocytosis of inert beads/macrophages. Moreover, CGRP increases VEGF and CCL18 expression in M(IL4), and soluble mediators from these cells promoted in vitro epithelial wound repair.

Conclusions

Reduced expression of CGRP and its receptor has been shown in IBD. The findings herein, demonstrating how CGRP-RAMP1 signalling can reinforce and enhance a regulatory, reparatory phenotype in human macrophages reveals another aspect of IBD pathophysiology. We speculate that loss of this neuroimmune axis (i.e. CGRP/Nerve-M(IL4) interaction) has the potential to significantly impair mucosal healing in IBD.

Funding Agencies

CCCAlberta Innovates in Health Innovation

A55 INTERLEUKIN-10 ELICITS CYTOPROTECTION VIA MITOCHONDRIAL SIGNAL TRANSDUCER AND ACTIVATORS OF TRANSCRIPTION 3 (MTSTAT3) TO PREVENT BACTERIAL PATHOBIONT EVOKED MITOCHONDRIAL FRAGMENTATION IN GUT EPITHELIA

Background

Aberrant mitochondrial function is increasingly reported in inflammatory bowel disease (IBD). We recently reported that the IBD-associated pathobiont, adherent-invasive E. coli (AIEC) (strain LF82)-evoked epithelial mitochondrial fragmentation and mitochondrial depolarization. Remarkably, the transcription factor, signal transducer and activator of transcription (STAT)-3, can migrate to mitochondria (mtSTAT3) to regulate functions such as reactive oxygen species and ATP production. This non-canonical activity is dependent on STAT3 phosphorylation at serine727. IL-10 is an important regulator of enteric homeostasis that signals via STAT-3, however whether IL-10 affects mitochondrial dynamics is unknown.

Aims

To determine (1) if IL-10 preserves mitochondrial function in E. coli-LF82-infected epithelia through mtSTAT3, and if so, (2) to identify the mechanism by which mtSTAT3 restores mitochondrial functions.

Methods

The human colon-derived T84 epithelial cells or human organoids were exposed to E. coli LF82 (10⁸ cfu/ml, 4h) ± co-treatment or an 18h pre-treatment with IL-10 (10 ng/ml). The effect of IL-10 on bacterial growth and its invasion of T84 cells were assessed by growth curve analysis and bacterial internalisation assays. We assessed mitochondrial network morphology using mito-tracker red and confocal microscopy, mitochondrial membrane potential with the fluorescent-dye TMRE and flow cytometry and fluorescence microscopy, and oxygen consumption rate (OCR) and ATP levels. STAT3 phosphorylation was analysed in whole cell protein extracts by western blot. Pharmacological inhibitors of JAK and Erk1/2 were used to examine the pathway of mtSTAT3 activation.

Results

IL-10 affected neither E. coli-LF82 growth nor invasion of T84 epithelia, but substantially reduced the AIEC-induced mitochondrial fragmentation in T84 cells and organoids. IL-10 preservation of the mitochondrial network was accompanied by increased mitochondrial membrane potential, OCR, and ATP levels in E. coli-LF82 infected T84 cells. IL-10 + E. coli-LF82-treated epithelia displayed increased phospho-S⁷²⁷ STAT3 that was reduced by inhibition of Erk1/2 but not JAK activity.

Conclusions

Mitochondria are a potential drug target in IBD, and the E. coli-LF82 pathobiont can be added to a growing list of microbial pathogens that evoke epithelial mitochondrial dysfunction. We have uncovered that IL-10 can stabilize mitochondrial function in E. coli-LF82 infected cells, possibly through mtSTAT-3. Our results underscore the role of IL-10/STAT3 signaling in preserving mitochondrial functions that could result in mitochondria-targeted therapeutics in IBD and other bacteria-driven enteropathies.

Funding Agencies

CIHRAIHS

Pericardiocentesis over 3 years at a tertiary referral Australian hospital

Funding Acknowledgements

Type of funding sources: None.

Background

 Pericardiocentesis is a lifesaving intervention performed both percutaneously or surgically. We analysed 3 years of experience in a major tertiary hospital in Sydney Australia. 

Purpose

 To examine the indications, safety and delivery of a pericardiocentesis service at a major teaching hospital. 

Methods

 We retrospectively audited consecutive patients who underwent pericardiocentesis for  pericardial effusion[PE] at a major teaching hospital from February 2018 to December 2020. Eligible patients were identified from the electronic medical records with this coding diagnosis.

Results

89 patients identified with mean age 60.8 ± 18.9years and 58.4%(51/89) male. Follow-up to August 2021 showed 41.5% had died, with an index hospitalisation mortality of 19%(17/89). Malignancy was the most common aetiology 30.3%(27/89) and attributable cause of hospitalisation death in 29.4%. Alternate causes included pericarditis 14.6%, idiopathic 13.4%, percutaneous-coronary-intervention(PCI) 5.6%(6/89) and electrophysiology 4.5%(4/89) complications. Three patients had aortic dissection (3.3%) and two were fatal. Clinical tamponade was present in 66.2%(55/89), PE identification occurred via echocardiography(TTE) in 55% cases (49/89) and incidental CT-diagnosis in 20.2%. TTE findings: right atrial collapse 54%(47/87), right ventricular collapse 60.9%(53/87), fixed and dilated inferior vena cava 64.7%. Pericardiocentesis was performed by cardiology trainees in 90.5% cases, 64.5% with consultant supervision and during working hours in 57.3% of cases. Percutaneous drainage was successful in 96%(72/75) of cases and was performed in the coronary care unit (30.3%), catheterisation laboratory (23.5%), emergency department (19.1%) and ICU (11.2%). Subxiphoid approach in 70%(62/89) was the most common then trans-apical 15%(13/89), parasternal 3%(3/89) and surgical 16%(14/89). TTE confirmed drain position in 76%(54/71), fluoroscopy in 28.5%(6/21) and agitated saline in 38.9%(30/77). Haemo-serous fluid noted in 77%(67/87) with average initial fluid drainage 480 ± 326mls and mean drain removal time 54 ± 33hrs. 17%(15/89) required re-drainage with adenocarcinoma found in 33.3%(5/15). Background antiplatelet treatment in 30.6%(27/88) and of these 67%(18/27) were on dual antiplatelets. 33%(29/89) patients were anticoagulated and 31.3%(9/29) required reversal prior to drainage. Complications were rare, 4%(3/75) had right heart chamber perforation needing emergency surgery. Two were post complex PCI (one died during admission from multiorgan failure) and one with pericarditis . 

Conclusions

 Pericardiocentesis is a safe and effective procedure for tamponade treatment and largely guided by echocardiography in our experience. Complications are rare and prognosis depends on aetiology with malignancy the most common. Drainage is often successfully performed emergently where the patient is located. Tamponade resulting from procedural complications are rare in our cohort.

Risk factors for left ventricular thrombus formation on transthoracic echocardiography in a propensity-matched case control study

Introduction

The specific risk factors for left ventricular thrombus (LVT) formation on transthoracic echocardiography (TTE) independent of age, sex, and left ventricular ejection fraction (LVEF) remain uncertain.

Purpose

To conduct a propensity-matched case control study of LVT.

Methods

We queried structured TTE report data from 113,673 patients at our institution to identify individuals with LVT on TTE, 2000–2011. Cases were matched 1:1 with controls on age, sex, LVEF, inpatient/outpatient status, image quality, test year, blood pressure, heart rate, height, and weight. using propensity scores. Risk factors for LVT formation were determined using medical chart review.

Results

Over 12 years, we identified 132 patients with LVT and 132 matched controls (mean age 62.0±16.1 years, 73.1% male, mean LVEF 27.0% ± 16.0%). Cases were similar to controls across all matched variables except height (cases vs. controls, mean height 172.2±8.8 vs. 174.8±9.3 cm, p=0.03). Compared with controls, TTEs for cases were more frequently performed for the indications of myocardial infarction (MI; 28.0% vs. 9.9%, p<0.001) and source of embolism (3.8% vs. 0.0%, p=0.008). Despite no differences between cases and controls in rates of hypertension, hyperlipidemia, diabetes, and thrombophilia (Table), a history of peripheral arterial disease was associated with a 3.4-fold increased odds of LVT formation (univariate odds ratio [OR], 3.35, 1.50–7.47, p=0.003). This association persisted despite adjustment for history of MI, stroke, height, history of recent major bleeding, and receipt of percutaneous coronary intervention (PCI) (adjusted OR, 4.33, 1.66–11.29, p=0.003). On presentation, 22.0% of cases were on anticoagulation including 20.5% on warfarin, none on a direct oral anticoagulant (DOAC), and 1.5% on heparin products. Additionally, 48.5% of cases were on antiplatelet medications. Of the 27 patients on warfarin on diagnosis of LVT, 25.9% had an International Normalized Range (INR) value <2.0. All TTE parameters were similar across groups (p>0.05 for all). Of those with LVT, 54 (40.9%) had LVT resolution over a median of 4.4 (0.9 to 13.6) months.

Conclusions

In this single center, propensity-matched case-control study of individuals with LVT on TTE, a history of peripheral arterial disease was associated with a 4.3-fold increased odds of LVT formation independent of age, sex, LVEF, history of MI, stroke, or PCI. Of those with LVT, anticoagulation was used on presentation in 22.0%. Nearly half had LVT resolution within 4.4 months.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The project was funded by a grant from the National, Heart, Lung, and Blood Institute (1K23HL144907 - Strom).

Ambient climate determines the directional trend of community stability under warming and grazing

Changes in ecological processes over time in ambient treatments are often larger than the responses to manipulative treatments in climate change experiments. However, the impacts of human-driven environmental changes on the stability of natural grasslands have been typically assessed by comparing differences between manipulative plots and reference plots. Little is known about whether or how ambient climate regulates the effects of manipulative treatments and their underlying mechanisms. We collected two datasets, one a 36-year long-term observational dataset from 1983 to 2018, and the other a 10-year manipulative asymmetric warming and grazing experiment using infrared heaters with moderate grazing from 2006 to 2015 in an alpine meadow on the Tibetan Plateau. The 36-year observational dataset shows that there was a nonlinear response of community stability to ambient temperature with a positive relationship between them due to an increase in ambient temperature in the first 25 years and then a decrease in ambient temperature thereafter. Warming and grazing decreased community stability with experiment duration through an increase in legume cover and a decrease in species asynchrony, which was due to the decreasing background temperature through time during the 10-year experiment period. Moreover, the temperature sensitivity of community stability was higher under the ambient treatment than under the manipulative treatments. Therefore, our results suggested that ambient climate may control the directional trend of community stability while manipulative treatments may determine the temperature sensitivity of the response of community stability to climate relative to the ambient treatment. Our study emphasizes the importance of the context dependency of the response of community stability to human-driven environmental changes.

Catalytically active inclusion bodies (CatIBs) induced by terminally attached self-assembling coiled-coil domains: To enhance the stability of (R)-hydroxynitrile lyase

The catalytically-active inclusion bodies (CatIBs) represent a promising strategy for immobilizing enzyme without additional carriers and chemicals, which has aroused great attention in academic and industrial communities. In this work, we discovered two natural parallel right-handed coiled-coil tetramer peptides from PDB database by a structural mining strategy. The two self-assembling peptides, NSPdoT from rotavirus and HVdoT from human Vasodilator-stimulated phosphoprotein, efficiently induced the CatIBs formation of a (R)-Hydroxynitrile lyase from Arabidopsis thaliana (AtHNL) in Escherichia coli cells. This is convenient to simultaneously purify and immobilize the target proteins as biocatalysts. As expected, HVdoT-AtHNL and NSPdoT-AtHNL possessed drastically increased tolerance toward lower pH values, which will be very critical to synthesize cyanohydrins under acidic condition for suppressing the non-enzymatic side reaction. In addition. AtHNL-CatIBs are produced at high yield in host cells as bioactive microparticles, which exhibited high thermal and pH stabilities. Therefore, the CatIBs method represent a promising application for the immobilization of enzymes in the biocatalysis field.

Efficiently Enantioselective Hydrogenation Photosynthesis of (R)-1-[3,5-Bis(trifluoromethyl)phenyl] ethanol over a CLEs-TiO2 Bioinorganic Hybrid Materials

Engineering of biological pathways with man-made materials provides inspiring blueprints for sustainable drug production. (R)-1-[3,5-Bis(trifluoromethyl)phenyl]ethanol [(R)-3,5-BTPE], as an important artificial chiral intermediate for complicated pharmaceutical drugs and biologically active molecules, is often synthesized through a hydrogenation reaction of 3,5-bis(trifluoromethyl)acetophenone (3,5-BTAP), in which enantioselectivity and sufficient active hydrogen are the key to restricting the reaction. In this work, a biohybrid photocatalytic hydrogenation system based on an artificial cross-linked enzymes (CLEs)-TiO₂-Cp*Rh(bpy) photoenzyme is developed through a bottom-up engineering strategy. Here, TiO₂ nanotubes in the presence of Cp*Rh(bpy) are used to transform NADP⁺ to NADPH during the formation of chiral alcohol intermediates from the catalytic reduction of a ketone substrate by alcohol dehydrogenase CLEs. Hydrogen and electrons, provided by water and photocatalytic systems, respectively, are transferred to reduce NADP⁺ to NADPH via [Cp*Rh(bpy)(H₂O)]²⁺. With the resulting NADPH, [(R)-3,5-BTPE] is synthesized using our efficient CLEs obtained from the cell lysate by nonstandard amino acid modification. Through this biohybrid photocatalytic system, the photoenzyme-catalyzed combined reductive synthesis of [(R)-3,5-BTPE] has a yield of 41.2% after reaction for 24 h and a very high enantiomeric excess value (>99.99%). In the case of reuse, this biohybrid system retained nearly 95% of its initial catalytic activity for synthesizing the above chiral alcohol. The excellent reusability of the CLEs and TiO₂ nanotubes hybrid catalytic materials highlights the environmental friendliness of (R)-3,5-BTPE production.

Cyanide-free synthesis of aromatic nitriles from aldoximes: Discovery and application of a novel heme-containing aldoxime dehydratase

Aromatic nitriles are important structural motifs that frequently existed in pharmaceutical drugs. Due to the convenient synthesis of aldoximes from aldehydes, the dehydration of aldoximes to corresponding nitriles by aldoxime dehydratases (Oxds) is considered as a safe and robust enzymatic production route. Although the Oxd genes are widely distributed in microbial kingdom, so far less than ten Oxds were expressed and further characterized. In this study, we found 26 predicted putative Oxd genes from the GenBank database using a genome mining strategy. The Oxd gene from Pseudomonas putida F1 was cloned and functionally expressed in Escherichia coli BL21 (DE3). The amino acid sequence of OxdF1 shows high identities of 33∼85 % to other characterized Oxds, and contained a ferrous heme as the catalytic site. The optimum reaction pH and temperature of recombinant OxdF1 were 7.0 and 35 °C, respectively. OxdF1 was stable in pH 7.0 potassium phosphate buffer at 30 °C, and its half-life was approximately 3.8 h. OxdF1 can efficiently dehydrate aromatic and heterocyclic aldoximes to nitriles, such as 2-bromobenzaldoxime, 2-chloro-6-fluorobenzaldoxime, thiophene-2-carboxaldoxime, and pyridine-3-aldoxime. Therefore, the recombinant OxdF1 shows a potential application in the cyanide-free synthesis of aromatic nitriles.

[Effects of melatonin on PBDE-47-induced abnormal autophagy and apoptosis in PC12 cells]

OBJECTIVE

To explore the effect of melatonin (MT) on 2, 2', 4, 4'-tetrabromodiphenylether (PBDE-47)-induced abnormal autophagy and apoptosis in rat adrenal medullary pheochromocytoma PC12 cells.

METHODS

PC12 cells were pretreated with a concentration gradient (12.5, 25, 50, 100, and 200 μmol/L) of melatonin for 2 h before exposure to 20 μmol/L PBDE-47 for 24 h to determine the optimal concentration of melatonin for cell treatment. In subsequent experiments, PC12 cells were treated with 0.5‰ DMSO (control group), 20 μmol/L PBDE-47, 25 μmol/L melatonin, or both PBDE-47 and melatonin. Immunofluorescence assay was used to detect the positive staining of microtubule associated protein 1 light chain 3 (LC3; a marker protein of autophagy); Western blotting was performed to determine the expression levels of the key autophagic proteins including autophagy-related protein 7 (ATG7), LC3-Ⅱ and autophagy substrate p62, and the key apoptotic proteins including active cysteine-containing aspartate specific protease-3 (active caspase-3) and cleaved poly(ADP ribose) polymerase (cleaved PARP).

RESULTS

PBDE-47 treatment significantly reduced the viability of PC12 cells (P=0.001), but pretreatment with 25 μmol/L melatonin maintained a cell viability over 80% following exposure to PBDE-47 (P=0.023). PBDE-47-treated PC12 cells showed obviously enhanced immunofluorescent staining of LC3 protein, a significantly decreased expression of ATG7 and increased expression levels of p62, LC3-Ⅱ, active caspase-3 and cleaved PARP (P < 0.001). The cells treated with both PBDE-47 and melatonin showed obviously reduced staining of LC3 protein with a signficantly increased expression level of ATG7 (P=0.034) and decreased expressions of p62 (P=0.048), LC3-Ⅱ (P=0.018), active caspase-3 (P < 0.001) and cleaved PARP (P=0.032).

CONCLUSION

PBDE-47 exposure impairs autophagy to cause autophagosome accumulation and promote apoptosis of PC12 cells. Melatonin can improve PBDE-47-induced abnormal autophagy and apoptosis and thus promote the survival of PC12 cells.