CHCHD4 binding affects the active site of apoptosis inducing factor (AIF): Structural determinants for allosteric regulation

Apoptosis-inducing factor (AIF), which is confined to mitochondria of normal healthy cells, is the first identified caspase-independent cell death effector. Moreover, AIF is required for the optimal functioning of the respiratory chain machinery. Recent findings have revealed that AIF fulfills its pro-survival function by interacting with CHCHD4, a soluble mitochondrial protein which promotes the entrance and the oxidative folding of different proteins in the inner membrane space. Here, we report the crystal structure of the ternary complex involving the N-terminal 27-mer peptide of CHCHD4, NAD+, and AIF harboring its FAD (flavin adenine dinucleotide) prosthetic group in oxidized form. Combining this information with biophysical and biochemical data on the CHCHD4/AIF complex, we provide a detailed structural description of the interaction between the two proteins, validated by both chemical cross-linking mass spectrometry analysis and site-directed mutagenesis.

Abstract 3237: Combining PARP inhibition with the polo-like kinase 1 (PLK1) inhibitor onvansertib overcomes PARP inhibitor resistance

Background: BRCA1/2 mutant tumors cells are deficient for homologous recombination (HR)-mediated DNA repair and are particularly sensitive to PARP inhibitors (PARPi). PARPi have proved efficacy in breast, ovarian, prostate, and pancreatic cancers, particularly in HR-deficient tumors, while their activity is limited in HR-proficient tumors. However, PARPi resistance is inevitable and therapeutic resistance resulting from restoration of HR repair is a pressing clinical problem. Identifying combination treatments to sensitize tumors cells to PARPi and/or overcome PARPi resistance is critical to expand the benefit of these therapies. The Polo-like kinase 1 (PLK1), a serine threonine kinase, is a master regulator of mitosis, overexpressed in many cancers. PLK1 is also involved in the DNA damage response through the promotion of HR-mediated DNA repair and the recovery from the G2/M checkpoint. PLK1 roles in HR repair suggest that PLK1 inhibition may reverse PARPi resistance.

Methods: To test the effect of PLK1 and PARP inhibitors combination, we used onvansertib, a highly selective, ATP-competitor PLK1 inhibitor currently in clinical development and the FDA-approved PARPi olaparib. The antitumor effect of the single and combined drug treatments was tested in 2 BRCA1 mutated high-grade serous ovarian cancer (HGSOC) patient derived (PDX) models resistant to olaparib. Orthotopically PDX transplanted mice were treated for 4 weeks and followed for survival.

Results: The combination of onvansertib and olaparib was well tolerated and showed strong anti-tumor activity in both PDX models. The combination significantly increased mice survival in comparison to vehicle, olaparib and onvansertib, and showed that onvansertib can re-sensitize PARPi-resistant tumors to olaparib. Median survival increased by 2.7-fold and 8.1-fold respectively in the 2 PDX models in the combination group versus vehicle and the Kaplan Meyer survival curves of mice treated with the combination showed a statistically survival advantage versus control and single agent treated mice. Pharmacodynamic analyses showed an increase in mitotic, apoptotic and DNA damage markers in tumors treated with the combination versus vehicle.

Conclusions: The combination of the PLK1 inhibitor onvansertib and the PARPi olaparib showed potent anti-tumor activity in olaparib-resistant BRAC1 mutant HGSOC PDX models. Additional studies are ongoing to further assess the potential of the combination in BRCA wild-type and mutant ovarian, prostate, pancreatic and breast cancer preclinical models.

Citation Format: Michela Chiappa, Federica Guffanti, Alessandra Decio, Alessandro Aliverti, Francesca Ricci, Eugenio Scanziani, Federica Camin, Ilaria Craparotta, Maria Chiara Barbera, Marco Bolis, Maya Ridinger, Giovanna Damia. Combining PARP inhibition with the polo-like kinase 1 (PLK1) inhibitor onvansertib overcomes PARP inhibitor resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3237.

Breathing patterns recognition: A functional data analysis approach

BACKGROUND AND OBJECTIVE

The ongoing pandemic proved fundamental is to assess a subject's respiratory functionality and breathing pattern measurement during quiet breathing is feasible in almost all patients, even those uncooperative. Breathing pattern consists of tidal volume and respiratory rate in an individual assessed by data tracks of lung or chest wall volume over time. State-of-art analysis of these data requires operator-dependent choices such as individuation of local minima in the track, elimination of anomalous breaths and individuation of breath clusters corresponding to different breathing patterns.

METHODS

A semi-automatic, robust and reproducible procedure was proposed to pre-process and analyse respiratory tracks, based on Functional Data Analysis (FDA) techniques, to identify representative breath curve and the corresponding breathing patterns. This was achieved through three steps: 1) breath separation through precise localization of the minima of the volume trace; 2) functional outlier breaths detection according to time-duration, magnitude and shape; 3) breath clustering to identify different pattern of interest, through K-medoids with Alignment. The method was firstly validated on simulated tracks and then applied to real data in conditions of clinical interest: operational volume change, exercise, mechanical ventilation, paradoxical breathing and age.

RESULTS

The total error in the accuracy of minima detection and in was less than 5%; with the artificial outliers being almost completely removed with an accuracy of 99%. During incremental exercise and independently on the bike resistance level, five clusters were identified (quiet breathing; recovery phase; onset of exercise; maximal and intermediate levels of exercise). During mechanical ventilation, the procedure was able to separate the non-ventilated from the ventilatory-supported breathing and to identify the worsening of paradoxical breathing due to the disease progression and the breathing pattern changes in healthy subjects due to age.

CONCLUSIONS

We proposed a robust validated automatic breathing patterns identification algorithm that extracted representative curves that could be implemented in clinical practice for objective comparison of the breathing patterns within and between subjects. In all case studies the identified patterns proved to be coherent with the clinical conditions and the physiopathology of the subjects, therefore enforcing the potential clinical translational value of the method.

Covalent inhibition of P. falciparum ferredoxin-NADP+ reductase: Exploring alternative strategies for the development of new antimalarial drugs

The protozoan Plasmodium falciparum is the main aetiological agent of tropical malaria. Characteristic of the phylum is the presence of a plastid-like organelle which hosts several homologs of plant proteins, including a ferredoxin (PfFd) and its NADPH-dependent reductase (PfFNR). The PfFNR/PfFd redox system is essential for the parasite, while mammals share no homologous proteins, making the enzyme an attractive target for novel and much needed antimalarial drugs. Based on previous findings, three chemically reactive residues important for PfFNR activity were identified: namely, the active-site Cys99, responsible for hydride transfer; Cys284, whose oxidation leads to an inactive dimeric form of the protein; and His286, which is involved in NADPH binding. These amino acid residues were probed by several residue-specific reagents and the two cysteines were shown to be promising targets for covalent inhibition. The quantitative and qualitative description of the reactivity of few compounds, including a repurposed drug, set the bases for the development of more potent and specific antimalarial leads.

Computational Fluid Dynamics (CFD) Analysis of Subject-specific Bronchial Tree Models in Lung Cancer Patients

Lung resection is the only potentially curative treatment for lung cancer. The inevitable partial removal of functional lung tissue along with the tumoral mass requires a careful and structured pre-operative condition of patients. In particular, the postoperative residual functionality of the lung needs to be predicted. Clinically, this is assessed through algorithms based on pulmonary function tests (PFTs). However, these approaches neglect the local airway segment's functionality and provide a globally averaged evaluation. CFD was demonstrated to provide patient-specific, quantitative, and local information on flow dynamics and regional ventilation in the bronchial tree. This study aims to apply CFD to characterize the flow dynamics in 12 patients affected by lung cancer and evaluate the effects of the tumoral masses on flow parameters and lobar flow distribution. Patient-specific airway models were reconstructed from CT images, and the tumoral masses were manually segmented. Measurements of lungs and tumor volumes were collected. A peripherality index was defined to describe tumor distance from the parenchyma. CFD simulations were performed in Fluent^®, and the results were analyzed in terms of flow parameters and lobar volume flow rate (VFR). The predicted postoperative forced expiratory volume in 1s (ppoFEV1) was estimated and compared to the current clinical algorithm. The patients under analysis showed relatively small tumoral masses located close to the lung parenchyma. CFD results did not highlight lobar alterations of flow parameters, whereas the flow to the lung affected by the tumor was found to be significantly lower (p=0.026) than the contralateral lung. The estimation ppoFEV1 obtained through the results of the simulations showed a high correlation (ρ=0.993, p<0.001) with the clinical formula.Clinical Relevance- The proposed study establishes the efficacy and applicability of CFD for the pre-operative characterization of patients undergoing lobectomy surgery. This technique can provide additional information on local functionality and flow dynamics to support patients' operability.

Texture-based classification of lung disease patterns in chronic hypersensitivity pneumonitis and comparison to clinical outcomes

Computer-aided detection algorithms applied to CT lung imaging have the potential to objectively quantify pulmonary pathology. We aim to develop an automatic classification method based on textural features able to classify healthy and pathological patterns on CT lung images and to quantify the extent of each disease pattern in a group of patients with chronic hypersensitivity pneumonitis (cHP), in comparison to pulmonary function tests (PFTs).27 cHP patients were scanned via high resolution CT (HRCT) at full-inspiration. Regions of interest (ROIs) were extracted and labeled as normal (NOR), ground glass opacity (GGO), reticulation (RET), consolidation (C), honeycombing (HB) and air trapping (AT). For each ROI, statistical, morphological and fractal parameters were computed. For automatic classification, we compared two classification methods (Bayesian and Support Vector Machine) and three ROI sizes. The classifier was therefore applied to the overall CT images and the extent of each class was calculated and compared to PFTs. Better classification accuracy was found for the Bayesian classifier and the 16x16 ROI size: 92.1±2.7%. The extent of GGO, HB and NOR significantly correlated with forced vital capacity (FVC) and the extent of NOR with carbon monoxide diffusing capacity (DLCO).Clinical Relevance- Texture analysis can differentiate and objectively quantify pathological classes in the lung parenchyma and may represent a quantitative diagnostic tool in cHP.

The denatured state of HIV-1 protease under native conditions

The denatured state of several proteins has been shown to display transient structures that are relevant for folding, stability, and aggregation. To detect them by nuclear magnetic resonance (NMR) spectroscopy, the denatured state must be stabilized by chemical agents or changes in temperature. This makes the environment different from that experienced in biologically relevant processes. Using high‐resolution heteronuclear NMR spectroscopy, we have characterized several denatured states of a monomeric variant of HIV‐1 protease, which is natively structured in water, induced by different concentrations of urea, guanidinium chloride, and acetic acid. We have extrapolated the chemical shifts and the relaxation parameters to the denaturant‐free denatured state at native conditions, showing that they converge to the same values. Subsequently, we characterized the conformational properties of this biologically relevant denatured state under native conditions by advanced molecular dynamics simulations and validated the results by comparison to experimental data. We show that the denatured state of HIV‐1 protease under native conditions displays rich patterns of transient native and non‐native structures, which could be of relevance to its guidance through a complex folding process.

Plasmodium falciparum Ferredoxin-NADP+ Reductase-Catalyzed Redox Cycling of Plasmodione Generates Both Predicted Key Drug Metabolites: Implication for Antimalarial Drug Development

Plasmodione (PD) is a potent antimalarial redox-active 3-benzyl-menadione acting at low nanomolar range concentrations on different malaria parasite stages. The specific bioactivation of PD was proposed to occur via a cascade of redox reactions starting from one-electron reduction and then benzylic oxidation, leading to the generation of several key metabolites including corresponding benzylic alcohol (PD-bzol, for PD benzhydrol) and 3-benzoylmenadione (PDO, for PD oxide). In this study, we showed that the benzylic oxidation of PD is closely related to the formation of a benzylic semiquinone radical, which can be produced under two conditions: UV photoirradiation or catalysis by Plasmodium falciparum apicoplast ferredoxin-NADP⁺ reductase (PfFNR) redox cycling in the presence of oxygen and the parent PD. Electrochemical properties of both PD metabolites were investigated in DMSO and in water. The single-electron reduction potential values of PD, PD-bzol, PDO, and a series of 3-benzoylmenadiones were determined according to ascorbate oxidation kinetics. These compounds possess enhanced reactivity toward PfFNR as compared with model quinones. Optimal conditions were set up to obtain the best conversion of the starting PD to the corresponding metabolites. UV irradiation of PD in isopropanol under positive oxygen pressure led to an isolated yield of 31% PDO through the transient semiquinone species formed in a cascade of reactions. In the presence of PfFNR, PDO and PD-bzol could be observed during long lasting redox cycling of PD continuously fueled by NADPH regenerated by an enzymatic system. Finally, we observed and quantified the effect of PD on the production of oxidative stress in the apicoplast of transgenic 3D7^{[Api-roGFP2-hGrx1]} P. falciparum parasites by using the described genetically encoded glutathione redox sensor hGrx1-roGFP2 methodology. The observed fast reactive oxygen species (ROS) pulse released in the apicoplast is proposed to be mediated by PD redox cycling catalyzed by PfFNR.

Ligand Binding in Allosteric Flavoproteins: Part 2. Quantitative Analysis of the Redox-Dependent Interaction of the Apoptosis-Inducing Factor (AIF) with Its Protein Partner

To perform their action usually flavoproteins interact transiently with a variety of molecular partners, whose binding is reciprocally affected and often controlled by the redox state of the bound flavin cofactor. As a case study, here we describe an approach for the quantitative characterization of the redox-controlled interaction of the mammalian apoptosis inducing factor (AIF) with one of its known protein partners, namely, the mitochondrial coiled-coil-helix-coiled-coil-helix domain-containing protein 4 (CHCHD4). In particular, we report a protocol for the titration of the flavoprotein in both in its oxidized and reduced states with CHCHD4, using an implementation of the MicroScale Thermophoresis (MST) technique.

Ligand Binding in Allosteric Flavoproteins: Part 1. Quantitative Analysis of the Interaction with NAD+ of the Apoptosis Inducing Factor (AIF) Harboring FAD in the Reduced State

To perform their action, flavoproteins usually interact with a variety of low molecular weight partners, including electron transporters, yielding transient complexes whose tightness is often controlled by the redox state of the bound flavin cofactor. As a case study, here we describe the quantitative analysis of the redox-dependent interaction of the mammalian apoptosis inducing factor (AIF) with its NAD+ ligand. In particular, we report a protocol for the spectrophotometric titration of AIF in its reduced state under anaerobic conditions with NAD+, in order to determine the dissociation constant of the resulting complex.

A Multidisciplinary Evaluation of Patients with DMD in An Italian Tertiary Care Center

With more widespread prolonged survival, Duchenne muscular dystrophy patients progressively experience multisystem complications. We retrospectively reviewed the charts of 132 Duchenne patients (112 alive/20 dead, age 3.5÷32.3 years) with the aims: 1) to provide a comprehensive description of the clinical status considering different aspects of the disease; 2) to propose a new scoring tool able to consider and pool together heterogeneous different functional. Five functions were analyzed: cardiac, respiratory, nutritional, ambulation and scoliosis. For each function, different items were considered and classified according to clinical severity (as indicated by international guidelines) and an incremental scoring was assigned. In addition, a global score incorporating all functions was defined. The scoring system confirmed that despite the significant protective role of steroids, all functions deteriorated with age. The severity of the global score became significantly higher since the age of 13 years. The severity of cardiac, respiratory and nutritional dysfunction was higher since 18 years. Deceased patients were characterized by significantly worse cardiac function, absence of steroid therapy and later use of respiratory assistive devices. The index proposed in this pilot study is a promising tool able to aggregate and correlate heterogeneous functions. It could become either an individual prognostic indicator of decline or a global score to evaluate changes in clinical trials therefore allowing multicenter studies, optimizing the management of both the primary and the secondary complications of the disease and understanding their relative impact.

Virtual reality for COPD rehabilitation: a technological perspective

Virtual Reality (VR) is a promising technology for implementing personalized, motivating and controlled rehabilitation scenarios. Although its clear potential benefits, VR has been poorly investigated in pulmonary rehabilitation. This review analyses the state of the art, by searching the scientific and grey literature, regarding the use of VR for the rehabilitation of patients with chronic obstructive pulmonary disease, providing a technological perspective. First, the main characteristics of the included systems are presented in terms of visualization devices, way of interaction and type of feedback they provide. Then, results of the selected studies are reported considering feasibility, safety, usability and user experience as outcomes. Finally, the main findings are discussed and future directions for research are outlined.

Reactions of Plasmodium falciparum Ferredoxin:NADP+ Oxidoreductase with Redox Cycling Xenobiotics: A Mechanistic Study

Ferredoxin:NADP⁺ oxidoreductase from Plasmodium falciparum (PfFNR) catalyzes the NADPH-dependent reduction of ferredoxin (PfFd), which provides redox equivalents for the biosynthesis of isoprenoids and fatty acids in the apicoplast. Like other flavin-dependent electrontransferases, PfFNR is a potential source of free radicals of quinones and other redox cycling compounds. We report here a kinetic study of the reduction of quinones, nitroaromatic compounds and aromatic N-oxides by PfFNR. We show that all these groups of compounds are reduced in a single-electron pathway, their reactivity increasing with the increase in their single-electron reduction midpoint potential (E¹₇). The reactivity of nitroaromatics is lower than that of quinones and aromatic N-oxides, which is in line with the differences in their electron self-exchange rate constants. Quinone reduction proceeds via a ping-pong mechanism. During the reoxidation of reduced FAD by quinones, the oxidation of FADH^. to FAD is the possible rate-limiting step. The calculated electron transfer distances in the reaction of PfFNR with various electron acceptors are similar to those of Anabaena FNR, thus demonstrating their similar “intrinsic” reactivity. Ferredoxin stimulated quinone- and nitro-reductase reactions of PfFNR, evidently providing an additional reduction pathway via reduced PfFd. Based on the available data, PfFNR and possibly PfFd may play a central role in the reductive activation of quinones, nitroaromatics and aromatic N-oxides in P. falciparum, contributing to their antiplasmodial action.

Antiplasmodial Activity of Nitroaromatic Compounds: Correlation with Their Reduction Potential and Inhibitory Action on Plasmodium falciparum Glutathione Reductase

With the aim to clarify the mechanism(s) of action of nitroaromatic compounds against the malaria parasite Plasmodium falciparum, we examined the single-electron reduction by P. falciparum ferredoxin:NADP⁺ oxidoreductase (PfFNR) of a series of nitrofurans and nitrobenzenes (n = 23), and their ability to inhibit P. falciparum glutathione reductase (PfGR). The reactivity of nitroaromatics in PfFNR-catalyzed reactions increased with their single-electron reduction midpoint potential (E¹₇). Nitroaromatic compounds acted as non- or uncompetitive inhibitors towards PfGR with respect to NADPH and glutathione substrates. Using multiparameter regression analysis, we found that the in vitro activity of these compounds against P. falciparum strain FcB1 increased with their E¹₇ values, octanol/water distribution coefficients at pH 7.0 (log D), and their activity as PfGR inhibitors. Our data demonstrate that both factors, the ease of reductive activation and the inhibition of PfGR, are important in the antiplasmodial in vitro activity of nitroaromatics. To the best of our knowledge, this is the first quantitative demonstration of this kind of relationship. No correlation between antiplasmodial activity and ability to inhibit human erythrocyte GR was detected in tested nitroaromatics. Our data suggest that the efficacy of prooxidant antiparasitic agents may be achieved through their combined action, namely inhibition of antioxidant NADPH:disulfide reductases, and the rapid reduction by single-electron transferring dehydrogenases-electrontransferases.

Evaluating human basal metabolism: the erroneous and misleading use of so-called "prediction equations"

Prediction (regression) equations are widely used, but their reliability as predictive tools is questionable as they provide contradicting results. The key point is that values calculated by regression equations are not precisely defined numbers but lie within a range of possible values in the standard deviation interval, none of which can be considered as the most probable. Ignoring this point leads to illicit/improper calculations, generating wrong results, which may have adverse consequences for human health. To demonstrate this, we applied the equations of Harris and Benedict in a reverse method, i.e. calculating (predicting) the daily energy expenditure in the same subjects used to obtain the equations and comparing values with the original measured data. We used the Bland-Altman and frequency distribution analyses. We found large differences in both individual data and population characteristics, showing that prediction equations are not predictive tools.

Specific anesthesia-induced lung volume changes from induction to emergence: a pilot study

BACKGROUND

Studies aimed at maintaining intraoperative lung volume to reduce post-operative pulmonary complications have been inconclusive because they mixed up the effect of general anesthesia and the surgical procedure. Our aims were to study: (1) lung volume during the entire course of anesthesia without the confounding effects of surgical procedures; (2) the combination of three interventions to maintain lung volume; and (3) the emergence phase with focus on the restored activation of the respiratory muscles.

METHODS

Eighteen ASA I-II patients undergoing ENT surgery under general anesthesia without muscle relaxants were randomized to an intervention group, receiving lung recruitment maneuver (LRM) after induction, 7 cmH₂ O positive end-expiratory pressure (PEEP) during anesthesia and continuous positive airway pressure (CPAP) during emergence with 0.4 inspired oxygen fraction (FiO₂ ) or a control group, ventilated without LRM, with 0 cmH₂ O PEEP, and 1.0 FiO₂ during emergence without CPAP application. End-expiratory lung volume (EELV) was continuously estimated by opto-electronic plethysmography. Inspiratory and expiratory ribcage muscles electromyography was measured in a subset of seven patients.

RESULTS

End-expiratory lung volume decreased after induction in both groups. It remained low in the control group and further decreased at emergence, because of active expiratory muscle contraction. In the intervention group, EELV increased after LRM and remained high after extubation.

CONCLUSION

A combined intervention consisting of LRM, PEEP and CPAP during emergence may effectively maintain EELV during anesthesia and even after extubation. An unexpected finding was that the activation of the expiratory muscles may contribute to EELV reduction during the emergence phase.

Cellulose production is coupled to sensing of the pyrimidine biosynthetic pathway via c-di-GMP production by the DgcQ protein of Escherichia coli

Production of cellulose, a stress response-mediated process in enterobacteria, is modulated in Escherichia coli by the activity of the two pyrimidine nucleotide biosynthetic pathways, namely, the de novo biosynthetic pathway and the salvage pathway, which relies on the environmental availability of pyrimidine nitrogenous bases. We had previously reported that prevalence of the salvage over the de novo pathway triggers cellulose production via synthesis of the second messenger c-di-GMP by the DgcQ (YedQ) diguanylate cyclase. In this work, we show that DgcQ enzymatic activity is enhanced by UTP, whilst being inhibited by N-carbamoyl-aspartate, an intermediate of the de novo pathway. Thus, direct allosteric control by these ligands allows full DgcQ activity exclusively in cells actively synthesizing pyrimidine nucleotides via the salvage pathway. Inhibition of DgcQ activity by N-carbamoyl-aspartate appears to be favoured by protein-protein interaction between DgcQ and PyrB, a subunit of aspartate transcarbamylase, which synthesizes N-carbamoyl-aspartate. Our results suggest that availability of pyrimidine bases might be sensed, somehow paradoxically, as an environmental stress by E. coli. We hypothesize that this link might have evolved since stress events, leading to extensive DNA/RNA degradation or lysis of neighbouring cells, can result in increased pyrimidine concentrations and activation of the salvage pathway.

High-resolution studies of hydride transfer in the ferredoxin:NADP+ reductase superfamily

Ferredoxin: NADP⁺ reductase (FNR) is an FAD-containing enzyme best known for catalysing the transfer of electrons from ferredoxin (Fd) to NADP⁺ to make NADPH during photosynthesis. It is also the prototype for a broad enzyme superfamily, including the NADPH oxidases (NOXs) that all catalyse similar FAD-enabled electron transfers between NAD(P)H and one-electron carriers. Here, we define further mechanistic details of the NAD(P)H ⇌ FAD hydride-transfer step of the reaction based on spectroscopic studies and high-resolution (~ 1.5 Å) crystallographic views of the nicotinamide-flavin interaction in crystals of corn root FNR Tyr316Ser and Tyr316Ala variants soaked with either nicotinamide, NADP⁺ , or NADPH. The spectra obtained from FNR crystal complexes match those seen in solution and the complexes reveal active site packing interactions and patterns of covalent distortion of the FAD that imply significant active site compression that would favour catalysis. Furthermore, anisotropic B-factors show that the mobility of the C4 atom of the nicotinamide in the FNR:NADP⁺ complex has a directionality matching that expected for boat-like excursions of the nicotinamide ring thought to enhance hydride transfer. Arguments are made for the relevance of this binding mode to catalysis, and specific consideration is given to how the results extrapolate to provide insight to structure-function relations for the membrane-bound NOX enzymes for which little structural information has been available.

DATABASES

Structural data are available in the PDB database under the accession numbers 3LO8 (wild-type), 5VW4 [Y316S:nicotinamide (P3₂ 21)], 5VW9 [Y316S:nicotinamide (P3₁ 21)], 5VW3 [Y316S:NADP⁺ (P3₂ 21)], 5VW8 [Y316S:NADP⁺ (P3₁ 21)], 5VW2 [Y316S:NADPH (P3₂ 21)], 5VW5 [Y316A:nicotinamide (P3₂ 21)], 5VW6 [Y316A:NADP⁺ (P3₂ 21)], 5VW7 [Y316A:NADPH (P3₂ 21)], 5VWA [Y316F (P3₂ 21)], and 5VWB [Y316F:NADP⁺ (P3₁ 21)]. Enzyme Commission number: ferredoxin:NADP⁺ reductase - E C1.18.1.2.

Efficacy of lung volume optimization maneuver monitored by optoelectronic pletismography in the management of congenital diaphragmatic hernia

Newborns affected by congenital diaphragmatic hernia (CDH) need cardio-respiratory stabilization before undergoing surgical repair. Open lung strategy is a well-established approach to optimize lung volume in preterm infants with Respiratory Distress Syndrome (RDS), using both High Frequency Oscillatory Ventilation (HFOV) and Conventional Mechanical Ventilation (CMV).

We report a case of left CDH with severe lung hypoplasia, managed applying open lung strategy in HFOV (pre-surgery period) and in Assist-Control with Volume Guarantee (post-surgery period), guided by SpO₂ changes, TcPO₂ and TcPCO₂ monitoring. Opto-electronic plethysmography was used to measure end-expiratory chest wall volume changes (ΔEEcw) related to lung volume variations occurring during pressure changes. OEP confirmed the efficacy of using SpO₂ and transcutaneous gas monitoring during this recruitment maneuver.

Structural bases of the altered catalytic properties of a pathogenic variant of apoptosis inducing factor

The apoptosis-inducing factor (AIF) is a FAD-containing protein playing critical roles in caspase-independent apoptosis and mitochondrial respiratory chain biogenesis and maintenance. While its lethal role is well known, the details of its mitochondrial function remain elusive. So far, nineteen allelic variants of AIF have been associated to human diseases, mainly affecting the nervous system. A strict correlation is emerging between the degree of impairment of its ability to stabilize the charge-transfer (CT) complex between FAD and NAD⁺ and the severity of the resulting pathology. Recently, we demonstrated that the G307E replacement in murine AIF (equivalent to the pathogenic G308E in the human protein) dramatically decreases the rate of CT complex formation through the destabilization of the flavoprotein interaction with NAD(H). To provide further insights into the structural bases of its altered functional properties, here we report the first crystal structure of an AIF pathogenic mutant variant in complex with NAD⁺ (murine AIF-G307E^CT) in comparison with its oxidized form. With respect to wild type AIF, the mutation leads to an altered positioning of NAD⁺ adenylate moiety, which slows down CT complex formation. Moreover, the altered balance between the binding of the adenine/nicotinamide portions of the coenzyme determines a large drop in AIF-G307E ability to discriminate between NADH and NADPH.

Recovery of monosaccharides from lignocellulosic hydrolysates by ion exclusion chromatography

The production of sugars from lignocellulosic biomass is the key to a sustainable, renewable chemical industry. Glucose, xylose and other monosaccharides can be easily produced by hydrolyzing cellulose and hemicellulose, the primary polysaccharides in biomass. However, the hydrolysis of biomass generates byproducts that, together with the mineral acid normally added in the hydrolysis step, have to be removed before the downstream conversion processes. In this work, the recovery of monosaccharides from lignocellulosic hydrolysates by means of Ion Exclusion Chromatography (IEC) has been studied. The analyzed process relies on new pretreatment and hydrolysis steps, involving the neutralization of the hydrolysate with sodium hydroxide. The adsorption behavior of the main components involved in the separation has been experimentally investigated. Pulse tests at the high loading encountered in preparative conditions have been performed for a selected group of model components found in the hydrolysates. For all the electrolytes, the retention volume fraction was always between the interparticle porosity and the total column porosity, confirming that ion exclusion was the dominant retention mechanism. On the other hand, sugars eluted before the total column porosity, indicating partial steric exclusion from the resin pores. This observation was then confirmed by size-exclusion experiments with polyethylene glycol standards, from which the distribution coefficient of the studied sugars has been determined. The comparison between the elution profiles of the same sugars in pure form and as a mixture present in the hydrolysate showed differences in both peak shape and retention times. Therefore, an investigation of the influence of the main electrolytes contained in the hydrolysates on sugars adsorption has been performed through the pulse on a plateau method. The electrolytes were found to enhance the sugars retention by promoting their adsorption onto the resin. However, this effect was not sufficient to explain the observed differences, which were effectively explained in terms of viscous fingering, due to the high viscosity differences between the eluent and the sample. A previously developed model for IEC has been updated to take into account all the observed phenomena and applied to simulate the experimental results. The proposed model was in good agreement with the batch-column elution profiles both for the pure components and for the actual hydrolysate, allowing a quantitative description of the separation.

Computer aided design and NMR characterization of an oligopeptide targeting the Ebola virus VP24 protein

The nona-peptide RS, designed on the basis of computational studies, is able to interact with Ebola VP24 and potentially inhibit its interaction with KPNA.

Recombinant human dihydroxyacetonephosphate acyl-transferase characterization as an integral monotopic membrane protein

Although the precise functions of ether phospholipids are still poorly understood, significant alterations in their physiological levels are associated either to inherited disorders or to aggressive metastatic cancer. The essential precursor, alkyl-dihydroxyacetone phosphate (DHAP), for all ether phospholipids species is synthetized in two consecutive reactions performed by two enzymes sitting on the inner side of the peroxisomal membrane. Here, we report the characterization of the recombinant human DHAP acyl-transferase, which performs the first step in alkyl-DHAP synthesis. By exploring several expression systems and designing a number of constructs, we were able to purify the enzyme in its active form and we found that it is tightly bound to the membrane through the N-terminal residues.

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Human DHAPAT is associated to peroxisomal membrane through the N-terminal region.

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Recombinant human DHAPAT expressed and purified from P. pastoris cells is active.

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Evidence of the in vitro reconstitution of DHAPAT/ADPS enzymatic complex.

Spontaneous Breathing Pattern as Respiratory Functional Outcome in Children with Spinal Muscular Atrophy (SMA)

Introduction

SMA is characterised by progressive motor and respiratory muscle weakness. We aimed to verify if in SMA children 1)each form is characterized by specific ventilatory and thoraco-abdominal pattern(VTAp) during quiet breathing(QB); 2)VTAp is affected by salbutamol therapy, currently suggested as standard treatment, or by the natural history(NH) of SMA; 3)the severity of global motor impairment linearly correlates with VTAp.

Materials and methods

VTAp was analysed on 32 SMA type I (SMA1,the most severe form), 51 type II (SMA2,the moderate), 8 type III (SMA3,the mildest) and 20 healthy (HC) using opto-electronic plethysmography. Spirometry, cough and motor function were measured in a subgroup of patients.

Results

In SMA1, a normal ventilation is obtained in supine position by rapid and shallow breathing with paradoxical ribcage motion. In SMA2, ventilation is within a normal range in seated position due to an increased respiratory rate(p<0.05) with reduced tidal volume(p<0.05) secondary to a poor contribution of pulmonary ribcage(%ΔV_RC,P, p<0.001). Salbutamol therapy had no effect on VTAp during QB(p>0.05) while tachypnea occurred in type I NH. A linear correlation(p<0.001) was found between motor function scales and VTAp.

Conclusion

A negative or reduced %ΔV_RC,P, indicative of ribcage muscle weakness, is a distinctive feature of SMA1 and SMA2 since infancy. Its quantitative assessment represents a non-invasive, non-volitional index that can be obtained in all children, even uncollaborative, and provides useful information on the action of ribcage muscles that are known to be affected by the disease.Low values of motor function scales indicate impairment of motor but also of respiratory function.

Alterations of diaphragm and rib cage morphometry in severe COPD patients by CT analysis

Although it is known that in patients with COPD acute hyperinflation determines shortening of the inspiratory muscles, its effects on both diaphragm and rib cage morphology are still to be investigated. In this preliminary study the relationships between hyperinflation, emphysema, diaphragm and rib cage geometry were studied in 5 severe COPD patients and 5 healthy subjects. An automatic software was developed to obtain the 3-D reconstruction of diaphragm and rib cage from CT scans taken at total lung capacity (TLC) and residual volume (RV). Dome surface area (Ado), radius of curvature, length (Ld) and position (referred to xiphoid level) of the diaphragm and antero-posterior (A-P) and transverse (T) diameters of rib cage were calculated at both volumes. Ado and Ld were similar in COPD and controls when compared at similar absolute lung volumes. Radius of curvature was significantly higher in COPD than in controls only at TLC. In COPD, the range of diaphragm position was invariantly below the xiphoid level, while in controls the top of diaphragm dome was always above it. Rib cage diameters were not different at TLC. A-P diameter was greater in COPD than in controls at RV, while T diameters were similar. In conclusion, in severe COPD diaphragm and rib cage geometry is altered at RV. The lower position of diaphragm is associated to smaller A-P but not transversal rib cage diameters, such that rib cage adopts a more circular shape.

Key Role of the Adenylate Moiety and Integrity of the Adenylate-Binding Site for the NAD(+)/H Binding to Mitochondrial Apoptosis-Inducing Factor

Apoptosis-inducing factor (AIF) is a mitochondrial flavoprotein with pro-life and pro-death activities, which plays critical roles in mitochondrial energy metabolism and caspase-independent apoptosis. Defects in AIF structure or expression can cause mitochondrial abnormalities leading to mitochondrial defects and neurodegeneration. The mechanism of AIF-induced apoptosis was extensively investigated, whereas the mitochondrial function of AIF is poorly understood. A unique feature of AIF is the ability to form a tight, air-stable charge-transfer (CT) complex upon reaction with NADH and to undergo a conformational switch leading to dimerization, proposed to be important for its vital and lethal functions. Although some aspects of interaction of AIF with NAD(+)/H have been analyzed, its precise mechanism is not fully understood. We investigated how the oxidized and photoreduced wild-type and G307A and -E variants of murine AIF associate with NAD(+)/H and nicotinamide mononucleotide (NMN(+)/H) to determine the role of the adenylate moiety in the binding process. Our results indicate that (i) the adenylate moiety of NAD(+)/H is crucial for the association with AIF and for the subsequent structural reorganization of the complex, but not for protein dimerization, (ii) FAD reduction rather than binding of NAD(+)/H to AIF initiates conformational rearrangement, and (iii) alteration of the adenylate-binding site by the G307E (equivalent to a pathological G308E mutation in human AIF) or G307A replacements decrease the affinity and association rate of NAD(+)/H, which, in turn, perturbs CT complex formation and protein dimerization but has no influence on the conformational switch in the regulatory peptide.

Discovery of Inhibitors for the Ether Lipid-Generating Enzyme AGPS as Anti-Cancer Agents

Dysregulated ether lipid metabolism is an important hallmark of cancer cells. Previous studies have reported that lowering ether lipid levels by genetic ablation of the ether lipid-generating enzyme alkyl-glycerone phosphate synthase (AGPS) lowers key structural and oncogenic ether lipid levels and alters fatty acid, glycerophospholipid, and eicosanoid metabolism to impair cancer pathogenicity, indicating that AGPS may be a potential therapeutic target for cancer. In this study, we have performed a small-molecule screen to identify candidate AGPS inhibitors. We have identified several lead AGPS inhibitors and have structurally characterized their interactions with the enzyme and show that these inhibitors bind to distinct portions of the active site. We further show that the lead AGPS inhibitor 1a selectively lowers ether lipid levels in several types of human cancer cells and impairs their cellular survival and migration. We provide here the first report of in situ-active pharmacological tools for inhibiting AGPS, which may provide chemical scaffolds for future AGPS inhibitor development for cancer therapy.

Effect of lung resection on pleuro-pulmonary mechanics and fluid balance

The aim of the study was to determine in human patients the effect of lung resection on lung compliance and on pleuro-pulmonary fluid balance. Pre and post-operative values of compliance were measured in anesthetized patients undergoing resection for lung cancer (N=11) through double-lumen bronchial intubation. Lung compliance was measured for 10-12 cm H2O increase in alveolar pressure from 5 cm H2O PEEP in control and repeated after resection. No air leak was assessed and pleural fluid was collected during hospital stay. A significant negative correlation (r(2)=0.68) was found between compliance at 10 min and resected mass. Based on the pre-operative estimated lung weight, the decrease in compliance following lung resection exceeded by 10-15% that expected from resected mass. Significant negative relationships were found by relating pleural fluid drainage flow to the remaining lung mass and to post-operative lung compliance. Following lung re-expansion, data suggest a causative relationship between the decrease in compliance and the perturbation in pleuro-pulmonary fluid balance.

Registration of lung CT images acquired in different respiratory ranges with 4DCT and HRCT

Pulmonary image registration is challenging because of the unique structure of the lung, its high deformability and its non-uniform intensity change with breathing. In the present work we propose a new method for pulmonary image registration, based on the reconstruction and the combination of the main pulmonary structures to modify parenchyma intensity prior to the application of the registration algorithm. The algorithm has been applied to both four dimensional CT and multi-volume high resolution CT demonstrating an increased accuracy of the results with the application of the pulmonary structure enhancement, evaluated both on landmarks distance in 4DCT and structures' surface distance in HRCT.

An improved expression system for the VC1 ligand binding domain of the receptor for advanced glycation end products in Pichia pastoris

The receptor for the advanced glycation end products (RAGE) is a type I transmembrane glycoprotein belonging to the immunoglobulin superfamily and binds a variety of unrelated ligands sharing a negative charge. Most ligands bind to the extracellular V or VC1 domains of the receptor. In this work, V and VC1 of human RAGE were produced in the methylotrophic yeast Pichia pastoris and directed to the secretory pathway. Fusions to a removable C-terminal His-tag evidenced proteolytic processing of the tag by extracellular proteases and also intracellular degradation of the N-terminal portion of V-His. Expression of untagged forms was attempted. While the V domain was retained intracellularly, VC1 was secreted into the medium and was functionally active in binding AGEs. The glycosylation state of VC1 was analyzed by mass spectrometry and peptide-N-glycosidase F digestion. Like RAGE isolated from mammalian sources, the degree of occupancy of the N-glycosylation sites was full at Asn25 and partial at Asn81 which was also subjected to non-enzymatic deamidation. A simple procedure for the purification to homogeneity of VC1 from the medium was developed. The folded state of the purified protein was assessed by thermal shift assays. Recombinant VC1 from P. pastoris showed a remarkably high thermal stability as compared to the protein expressed in bacteria. Our in vivo approach indicates that the V and C1 domains constitute a single folding unit. The stability and solubility of the yeast-secreted VC1 may be beneficial for future in vitro studies aimed to identify new ligands or inhibitors of RAGE.

Frequency dependence of lung volume changes during superimposed high-frequency jet ventilation and high-frequency jet ventilation

BACKGROUND

Superimposed high-frequency jet ventilation (SHFJV) has proved to be safe and effective in clinical practice. However, it is unclear which frequency range optimizes ventilation and gas exchange. The aim of this study was to systematically compare high-frequency jet ventilation (HFJV) with HFJV by assessing chest wall volume variations (ΔEEV(CW)) and gas exchange in relation to variable high frequency.

METHODS

SHFJV or HFJV were used alternatively to ventilate the lungs of 10 anaesthetized pigs (21-25 kg). The low-frequency component was kept at 16 min(-1) in SHFJV. In both modes, high frequencies ranging from 100 to 1000 min(-1) were applied in random order and ventilation was maintained for 5 min in all modalities. Chest wall volume variations were obtained using opto-electronic plethysmography. Airway pressures and arterial blood gases were measured repeatedly.

RESULTS

SHFJV increased ΔEEV(CW) compared with HFJV; the difference ranged from 43 to 68 ml. Tidal volume (V(T)) was always >240 ml during SHFJV whereas during HFJV ranged from 92 ml at the ventilation frequency of 100 min(-1) to negligible values at frequencies >300 min(-1). We observed similar patterns for Pa(O₂) and Pa(CO₂). SHFJV provided generally higher, frequency-independent oxygenation (Pa(O₂) at least 32.0 kPa) and CO₂ removal (Pa(CO₂) ∼5.5 kPa), whereas HFJV led to hypoxia and hypercarbia at higher rates (Pa(O₂) <10 kPa and Pa(CO₂)>10 kPa at f(HF)>300 min(-1)).

CONCLUSIONS

In a porcine model, SHFJV was more effective in increasing end-expiratory volume than single-frequency HFJV, but both modes may provide adequate ventilation in the absence of airway obstruction and respiratory disease, except for HFJV at frequencies ≥300 min(-1).

Variations of thoracoabdominal volumes after lung transplantation measured by opto-electronic plethysmography

BACKGROUND

Lung function after lung transplantation (LTx) has been widely studied. On the contrary, the thoracoabdominal volume rearrangement after LTx has yet to be investigated.

METHODS

Patients with cystic fibrosis and listed for double LTx at our institution were enrolled for the prospective study to explore the effects of LTx on the rearrangement of respiratory volumes in patients affected by cystic fibrosis, by utilizing the opto-electronic plethysmography (OEP), a noninvasive method to study the volume and motion of the human trunk. Rib cage and abdominal volumes were tested with OEP (OEP system, BTS, Milano, Italy).

RESULTS

Eight patients were enrolled (male-to-female ratio: 1:3; mean age 29.3 ± 7.8 years). After LTx the volume changes analyzed with OEP revealed a significant decrease of the total lung capacity (TLC) as well as the functional residual capacity and residual volume when the chest wall volume was considered. Dividing the whole respiratory volume in the three compartments showed different trends.

CONCLUSIONS

We consider OEP a particularly useful device in patients with severe respiratory disease, in that it allows a noninvasive estimate of the volume change of the chest wall. This study demonstrates a significant reduction of thoracoabdominal volumes in patients affected by cystic fibrosis treated with bilateral LTx. Abdomen and upper rib cage were congruent with the volume reduction, while the lower rib cage showed an opposite tendency.

Centaurin-α₂ interacts with β-tubulin and stabilizes microtubules

Centaurin-α₂ is a GTPase-activating protein for ARF (ARFGAP) showing a diffuse cytoplasmic localization capable to translocate to membrane, where it binds phosphatidylinositols. Taking into account that Centaurin-α₂ can localize in cytoplasm and that its cytoplasmatic function is not well defined, we searched for further interactors by yeast two-hybrid assay to investigate its biological function. We identified a further Centaurin-α₂ interacting protein, β-Tubulin, by yeast two-hybrid assay. The interaction, involving the C-terminal region of β-Tubulin, has been confirmed by coimmunoprecipitation experiments. After Centaurin-α₂ overexpression in HeLa cells and extraction of soluble (αβ dimers) and insoluble (microtubules) fractions of Tubulin, we observed that Centaurin-α₂ mainly interacts with the polymerized Tubulin fraction, besides colocalizing with microtubules (MTs) in cytoplasm accordingly. Even following the depolimerizing Tubulin treatments Centaurin-α₂ remains mainly associated to nocodazole- and cold-resistant MTs. We found an increase of MT stability in transfected HeLa cells, evaluating as marker of stability the level of MT acetylation. In vitro assays using purified Centaurin-α₂ and tubulin confirmed that Centaurin-α₂ promotes tubulin assembly and increases microtubule stability. The biological effect of Centaurin-α₂ overexpression, assessed through the detection of an increased number of mitotic HeLa cells with bipolar spindles and with the correct number of centrosomes in both dividing and not dividing cells, is consistent with the Centaurin-α₂ role on MT stabilization. Centaurin-α₂ interacts with β-Tubulin and it mainly associates to MTs, resistant to destabilizing agents, in vitro and in cell. We propose Centaurin-α₂ as a new microtubule-associated protein (MAP) increasing MT stability.

A single tyrosine hydroxyl group almost entirely controls the NADPH specificity of Plasmodium falciparum ferredoxin-NADP+ reductase

Plasmodium falciparum ferredoxin-NADP(+) reductase (FNR) is a FAD-containing enzyme that, in addition to be a promising target of novel antimalarial drugs, represents an excellent model of plant-type FNRs. The cofactor specificity of FNRs depends on differences in both k(cat) and K(m) values for NADPH and NADH. Here, we report that deletion of the hydroxyl group of the conserved Y258 of P. falciparum FNR, which interacts with the 2'-phosphate group of NADPH, selectively decreased the k(cat) of the NADPH-dependent reaction by a factor of 2 to match that of the NADH-dependent one. Rapid-reaction kinetics, active-site titrations with NADP(+), and anaerobic photoreduction experiments indicated that this effect may be the consequence of destabilization of the catalytically competent conformation of bound NADPH. Moreover, because the Y258F replacement increased the K(m) for NADPH 4-fold and decreased that for NADH 3-fold, it led to a drop in the ability of the enzyme to discriminate between the coenzymes from 70- to just 1.5-fold. The impact of the Y258F change was not affected by the presence of the H286Q mutation, which is known to enhance the catalytic activity of the enzyme. Our data highlight the major role played by the Y258 hydroxyl group in determining the coenzyme specificity of P. falciparum FNR. From the general standpoint of engineering the kinetic properties of plant-type FNRs, although P. falciparum FNR is less strictly NADPH-dependent than its homologues, the almost complete abolishment of coenzyme selectivity reported here has never been accomplished before through a single mutation.

Comparison of superimposed high-frequency jet ventilation with conventional jet ventilation for laryngeal surgery

BACKGROUND

New ventilators have simplified the use of supraglottic superimposed high-frequency jet ventilation (SHFJV(SG)), but it has not been systematically compared with other modes of jet ventilation (JV) in humans. We sought to investigate whether SHFJV(SG) would provide more effective ventilation compared with single-frequency JV techniques.

METHODS

A total of 16 patients undergoing minor laryngeal surgery under general anaesthesia were included. In each patient, four different JV techniques were applied in random order for 10-min periods: SHFJV(SG), supraglottic normal frequency (NFJV(SG)), supraglottic high frequency (HFJV(SG)), and infraglottic high-frequency jet ventilation (HFJV(IG)). Chest wall volume variations were continuously measured with opto-electronic plethysmography (OEP), intratracheal pressure was recorded and blood gases were measured.

RESULTS

Chest wall volumes were normalized to NFJV(SG) end-expiratory level. The increase in end-expiratory chest wall volume (EEV(CW)) was 239 (196) ml during SHFJV(SG) (P<0.05 compared with NFJV(SG)). EEV(CW) was 148 (145) and 44 (106) ml during HFJV(SG) and HFJV(IG), respectively (P<0.05 compared with SHFJV(SG)). Tidal volume (V(T)) during SHFJV(SG) was 269 (149) ml. V(T) was 229 (169) ml (P=1.00 compared with SHFJV(SG)), 145 (50) ml (P<0.05), and 110 (33) ml (P<0.01) during NFJV(SG), HFJV(SG), and HFJV(IG), respectively. Intratracheal pressures corresponded well to changes in both EEV(CW) and V(T). All JV modes resulted in adequate oxygenation. However, was lowest during HFJV(SG) [4.3 (1.3) kPa; P<0.01 compared with SHFJV(SG)].

CONCLUSION

SHFJV(SG) was associated with increased EEV(CW) and V(T) compared with the three other investigated JV modes. All four modes provided adequate ventilation and oxygenation, and thus can be used for uncomplicated laryngeal surgery in healthy patients with limited airway obstruction.

Quantum dots nanoparticle-based lateral flow assay for rapid detection of Mycobacterium species using anti-FprA antibodies

A lateral flow (LF) device combined with quantum dots (QDs) technology was developed for rapid detection of a specific mycobacterial flavoprotein reductase (<em>fprA</em>). In order to develop the LF assay based on a double-antibody sandwich format, two monoclonal antibodies recognizing different epitopes located in separated <em>fprA</em> domains were identified. The first monoclonal antibody was immobilized onto the detection zone of a porous nitrocellulose membrane, whereas another monoclonal antibody was conjugated to QDs nanoparticles as a detection system. Using these monoclonal antibodies we recorded a good fluorescence signal, the intensity of which was directly proportional to the concentration of <em>fprA</em> protein. The use of antibodies conjugated with fluorescent semiconductor QDs via biotin-streptavidin bridge, allowed the detection of <em>fprA</em> protein at concentrations as low as 12.5 pg/μL in less than 10 min. The reported technology could be useful in the diagnostic investigation of <em>Mycobacterium tuberculosis</em> and other human pathogens in clinical specimens.

Low abdominal contribution to breathing as daytime predictor of nocturnal desaturation in adolescents and young adults with Duchenne Muscular Dystrophy

In the respiratory management of DMD patients it is still under debate what parameter should indicate the correct timing for institution of nocturnal non-invasive ventilation (NIV), in addition to forced vital capacity, which is generally considered as a prognostic marker of disease progression. The aim of this study was to determine if volume variations of rib cage and abdominal compartments measured by Opto-Electronic Plethysmography can be helpful to distinguish between those patients who are in the early stages of nocturnal oxygen desaturation development and those who do not yet. Pulmonary function, abdominal contribution to tidal volume and to inspiratory capacity (%Abd IC) and a set of breathing pattern indexes were assessed in 40 DMD patients older than 14 years and not yet under nocturnal NIV. ROC analysis revealed that among all the considered parameters, %Abd IC in supine position was the best discriminator between DeSat (at least 10% of the night time with SpO(2) < 95%) and NonDeSat patients, providing an area under the curve with 95%CI equal to 0.752. In conclusion, in adolescents and adults DMD patients who present either no sign or only mild nocturnal oxygen desaturation, a reduced abdominal contribution to inspiratory capacity is a marker of the onset of diaphragm weakness and should be considered to identify the correct timing for the institution of nocturnal NIV.