Contributi scientifici in memoria di Antonio Fusco

Come si leggerà nell'Introduzione della sezione propriamente scientifica del Volume, il presente testo nasce dalla volontà e, soprattutto, dall'esigenza culturale di omaggiare il fu Prof. Antonio Fusco. Un debito scientifico ed umano che trova il suo locus naturale in questa prima parte del testo stesso, cui farà poi seguito la parte propriamente scientifica. In siffatta parentesi dovuta per le ragioni appena menzionate, il lettore, l'amico o l'allievo dell'opera del Prof. Fusco potranno trovare un suo sintetico Curriculum Vitae, correlato da una specifica ed accurata prosa, svolta dal già Magnifico Rettore Carlo Cipolli; il quale, oltre che evidenziare, ricordando, i meriti del collega oramai scomparso, aggiunge alsuo scritto un elemento che sarebbe imprescindibile a non trasformare lo stesso in una mera sequenza di parole: l'amicizia e l'affetto per un amico che, oramai, non c'è più. A fine lettura, evidente risuonerà il fatto che la vita di ognuno, se mossa dalla passione per ciò per cui si è predisposti cognitivamente e psicologicamente, può essere ricca di riconoscimenti, riconoscenze e soddisfazioni che, lungi dal divenire un cuscino di allori su cui adagiarsi, per una mente creativa come quella del Prof. Fusco hanno funto solo da motivazioni ad agire instancabilmente guardando sempre al futuro. Il lavoro di una vita che, materialmente, è sancito da un supporto poco più di cm 25x15: una targa. Una materialità evidente che, con grande commozione e riconoscenza, è stata affissa il 25 ottobre 2019 sull'aula fronte l'Aula Magna del Campus "La Folcara", a testimonianza che quello spirito creativo in continua evoluzione non si ferma; non si arresta neppure con la fine biologica di chi lo ha "posseduto". Rimangono le opere ed il pensiero del Prof. Fusco e restano gli affetti. A tal proposito, il lettore troverà una breve e sentita sezione su Testimonianze; coloro i quali hanno avuto modo, nell'arco della vita accademica ed umana, personale, di Fusco di conoscerlo. Ecco, allora, che i ricordi saranno i veri protagonisti di questa parentesi. Dopo di ciò, prima dei contributi prettamente scientifici dei lavori, tenutisi in occasione del Convegno Internazionale Psicologia, Arte, Letteratura. Antiche e Nuove Tendenze, seguiranno i saluti delle autorità che in quei due giorni si sono succedute a rappresentare non solo l'istituzione affiliata, ma anche la relazione di stima e di affetto che le legava al compianto Professore. Si passerà, infine, al volume tradizionalmente inteso.

The large subunit of the regulatory [NiFe]-hydrogenase from Ralstonia eutropha - a minimal hydrogenase?

Chemically synthesized compounds that are capable of facilitating the reversible splitting of dihydrogen into protons and electrons are rare in chemists' portfolio. The corresponding biocatalysts – hydrogenases – are, however, abundant in the microbial world. [NiFe]-hydrogenases represent a major subclass and display a bipartite architecture, composed of a large subunit, hosting the catalytic NiFe(CO)(CN)₂ cofactor, and a small subunit whose iron–sulfur clusters are responsible for electron transfer. To analyze in detail the catalytic competence of the large subunit without its smaller counterpart, we purified the large subunit HoxC of the regulatory [NiFe]-hydrogenase of the model H₂ oxidizer Ralstonia eutropha to homogeneity. Metal determination and infrared spectroscopy revealed a stoichiometric loading of the metal cofactor. This enabled for the first time the determination of the UV-visible extinction coefficient of the NiFe(CO)(CN)₂ cofactor. Moreover, the absence of disturbing iron–sulfur clusters allowed an unbiased look into the low-spin Fe²⁺ of the active site by Mössbauer spectroscopy. Isolated HoxC was active in catalytic hydrogen–deuterium exchange, demonstrating its capacity to activate H₂. Its catalytic activity was drastically lower than that of the bipartite holoenzyme. This was consistent with infrared and electron paramagnetic resonance spectroscopic observations, suggesting that the bridging position between the active site nickel and iron ions is predominantly occupied by water-derived ligands, even under reducing conditions. In fact, the presence of water-derived ligands bound to low-spin Ni²⁺ was reflected by the absorption bands occurring in the corresponding UV-vis spectra, as revealed by time-dependent density functional theory calculations conducted on appropriate in silico models. Thus, the isolated large subunits indeed represent simple [NiFe]-hydrogenase models, which could serve as blueprints for chemically synthesized mimics. Furthermore, our data point to a fundamental role of the small subunit in preventing water access to the catalytic center, which significantly increases the H₂ splitting capacity of the enzyme.

Spectroscopic investigation of an isolated [NiFe]-hydrogenase large subunit enables a unique view of the NiFe(CO)(CN)₂ cofactor.

Diversity of Secondary Metabolism in Aspergillus nidulans Clinical Isolates

The filamentous fungus Aspergillus nidulans has been a primary workhorse used to understand fungal genetics. Much of this work has focused on elucidating the genetics of biosynthetic gene clusters (BGCs) and the secondary metabolites (SMs) they produce. SMs are both niche defining in fungi and of great economic importance to humans. Despite the focus on A. nidulans, very little is known about the natural diversity in secondary metabolism within this species. We determined the BGC content and looked for evolutionary patterns in BGCs from whole-genome sequences of two clinical isolates and the A4 reference genome of A. nidulans Differences in BGC content were used to explain SM profiles determined using liquid chromatography-high-resolution mass spectrometry. We found that in addition to genetic variation of BGCs contained by all isolates, nine BGCs varied by presence/absence. We discovered the viridicatumtoxin BGC in A. nidulans and suggest that this BGC has undergone a horizontal gene transfer from the Aspergillus section Nigri lineage into Penicillium sometime after the sections Nigri and Nidulantes diverged. We identified the production of viridicatumtoxin and several other compounds previously not known to be produced by A. nidulans One isolate showed a lack of sterigmatocystin production even though it contained an apparently intact sterigmatocystin BGC, raising questions about other genes and processes known to regulate this BGC. Altogether, our work uncovers a large degree of intraspecies diversity in BGC and SM production in this genetic model species and offers new avenues to understand the evolution and regulation of secondary metabolism.IMPORTANCE Much of what we know about the genetics underlying secondary metabolite (SM) production and the function of SMs in the model fungus Aspergillus nidulans comes from a single reference genome. A growing body of research indicates the importance of biosynthetic gene cluster (BGC) and SM diversity within a species. However, there is no information about the natural diversity of secondary metabolism in A. nidulans We discovered six novel clusters that contribute to the considerable variation in both BGC content and SM production within A. nidulans We characterize a diverse set of mutations and emphasize how findings of single nucleotide polymorphisms (SNPs), deletions, and differences in evolutionary history encompass much of the variation observed in nonmodel systems. Our results emphasize that A. nidulans may also be a strong model to use within-species diversity to elucidate regulatory cross talk, fungal ecology, and drug discovery systems.

The tetrameric pheromone module SteC-MkkB-MpkB-SteD regulates asexual sporulation, sclerotia formation and aflatoxin production in Aspergillus flavus

For eukaryotes like fungi to regulate biological responses to environmental stimuli, various signalling cascades are utilized, like the highly conserved mitogen‐activated protein kinase (MAPK) pathways. In the model fungus Aspergillus nidulans, a MAPK pathway known as the pheromone module regulates development and the production of secondary metabolites (SMs). This pathway consists five proteins, the three kinases SteC, MkkB and MpkB, the adaptor SteD and the scaffold HamE. In this study, homologs of these five pheromone module proteins have been identified in the plant and human pathogenic fungus Aspergillus flavus. We have shown that a tetrameric complex consisting of the three kinases and the SteD adaptor is assembled in this species. It was observed that this complex assembles in the cytoplasm and that MpkB translocates into the nucleus. Deletion of steC, mkkB, mpkB or steD results in abolishment of both asexual sporulation and sclerotia production. This complex is required for the positive regulation of aflatoxin production and negative regulation of various SMs, including leporin B and cyclopiazonic acid (CPA), likely via MpkB interactions in the nucleus. These data highlight the conservation of the pheromone module in Aspergillus species, signifying the importance of this pathway in regulating fungal development and secondary metabolism.

Catalytic H2 evolution/oxidation in [FeFe]-hydrogenase biomimetics: account from DFT on the interplay of related issues and proposed solutions

A DFT overview on selected issues regarding diiron catalysts related to [FeFe]-hydrogenase biomimetic research, with implications for both energy conversion and storage strategies.

Concomitant medullary thyroid carcinoma with paraganglioma-like pattern and papillary thyroid carcinoma

SUMMARY

A 74-year-old man was referred to the Endocrinology Unit because of multinodular goiter. The dominant nodule (1.7 × 1.9 × 2.4 cm), at the medium-superior third of the left lobe, was inhomogeneously hypoechoic, with irregular margins, macrocalcifications and intranodular vascularization. Fine-needle aspiration biopsy (FNAB) was performed. The cytological diagnosis was TIR 2, benign, according to the 2013 Italian thyroid cytology classification system. Moderately high serum calcitonin (s-Ct) (61.5 pg/mL, n.r. 0-7.5) and normal CEA were detected. The Ct level in FNAB wash-out fluid (Ct-FNAB) was 1450 pg/mL. Based on s-Ct and Ct-FNAB levels, patient underwent total thyroidectomy. Macroscopically, a dominant circumscribed nodule of 2 ecm was described; the histological and immunohistochemical features identified medullary thyroid carcinoma (MTC) with paraganglioma (PG)-like pattern positive for Ct, CEA and chromogranin and negative for S-100 sustentacular cells (SC). Moreover, papillary carcinoma of 3 mm in the right lobe was also associated. No areas of hyperaccumulation of the tracer were documented at Ga68 PET/CT. No RET-proto-oncogene mutations were found. Post-surgery s-Ct levels were within normal range (4 pg/mL). Two years after thyroidectomy, the patient is still disease-free. We reported a case of sporadic and rare variant of MTC: this is the ninth described case of PG-like MTC. In this case, cytologically benign, the clinical suspicion arose from high Ct values at FNAB wash-out fluid. Even if clinical behavior of this variant seems indolent, additional studies are necessary to understand prognoses and predictive factors.

LEARNING POINTS

Several unusual histological variants of medullary thyroid carcinoma (MTC) have been described such as spindle cell, giant cell, clear cell, melanotic, squamous, angiosarcoma-like variants; even rarer is the paraganglioma (PG)-like pattern. We here describe a case of medullary PG-like thyroid carcinoma in a 74-year-old man. This is a rare histological variant of MTC hardly diagnosed by cytology, since immunohistochemical investigations are necessary. Measurement of calcitonin both in serum and in wash-out fluid from fine-needle aspiration could be an additional tool for an early and non-invasive identification of these variants.

Protonation and electrochemical properties of a bisphosphide diiron hexacarbonyl complex bearing amino groups on the phosphide bridge

A bisphosphide-bridged diiron hexacarbonyl complex 3 with NEt2 groups on the phosphide bridge was synthesized to examine a new proton relay system from the NEt2 group to the bridging hydride between the two iron centers. As a precursor of the bridging moiety, peri-Et2NP-PNEt2-bridged naphthylene 5 was synthesized by the reaction of 1,8-dilithionaphthylene with two equivalents of Cl2PNEt2 followed by reductive P-P bond formation by magnesium. The reaction of the diphosphine ligand 5 with Fe2(CO)9 gave the diiron hexacarbonyl complex 3, in which the P-P bond of the ligand was cleaved to form the bisphosphide-bridge. The molecular structure of 3 indicated that the trigonal plane of the NEt2 group was forced to face the Fe-Fe bond to avoid steric congestion with the naphthylene group linking the two phosphide groups. The NEt2 group could be protonated by p-toluenesulfonic acid. Density functional theory (DFT) calculations confirmed that the proton of the N(H)Et2 group adopted a position close to the bridging hydride. The DFT results for the ferrocene analogue 1, in which the 1,8-naphthylene group of 3 was replaced with the 1,1'-ferrocenylene group, also revealed that the most stable orientation of the protonated NHEt2 group was that in the protonated 3. As a result, electrochemical proton reduction reactions using complexes 1 and 3 proceeded with similar catalytic efficiencies. Unfortunately, the catalytic efficiencies (CEs) of these complexes were much lower than those of the complexes with a proton relay system of the terminal hydrogen, indicating that the reactive properties of the bridging hydride in the present proton relay system cannot exceed those of the terminal hydride.

P4613Long-term impact of postnatal nutritional programming on cardiac sensitivity to ischemia-reperfusion injury in vivo and on cardio-protective pathways in mice

Introduction

Nutritional disturbances during the postnatal period may be responsible for a predisposition, or “programming”, to increased cardio-metabolic risk and to a progressive alteration of left ventricular contractility in adulthood. This nutritional perinatal programming may also lead to an alteration of cellular pathways involved in cardiac protection, such as the specific RISK and SAFE pathways, highlighted during pre- and post-ischemic conditioning or those of sirtuins (SIRT), histone deacetylases involved in the regulation of essential biological process.

Purpose

Our aim was to evaluate in mice the impact of postnatal overfeeding (PNOF) on cardiac sensitivity to ischemia-reperfusion (I-R) injury in vivo and on the myocardial expression of genes involved in heart protection against ischemia.

Methods

PNOF was induced by the reduction of litter size of C57/BL6 mice immediately after birth: normally-fed group (NF) was composed of 9 male pups/mother and overfed group (OF) of 3 pups/mother. In vivo ischemia-reperfusion injury was induced by the ligation of the anterior interventricular artery for 45 minutes followed by 24 h of reperfusion in hearts from 6-months aged mice. The gene expressions of proteins of interest composing the cardioprotective pathways (RISK pathway: Akt, ERK; SAFE pathway: JAK/STAT3; Sirtuins: SIRT1) were measured by RT-qPCR in mice aged 4 and 6 months.

Results

PNOF induced in OF group an early and permanent increase in body weight (+23%, p<0.01, n=11) and a significant increase of infarct size (+32%, p<0.05, n=11) at 6 months. Hearts OF mice aged 4 months showed a decreased expression of cardioprotective pathways, represented by a reduction in the gene expression of ERK1, Akt, PI3K, STAT3 and SIRT1. At 6 months, the expression of cardioprotective pathways was also reduced in OF group, with the diminution of the gene expression of STAT3, Akt and Erk1.

Conclusion

Nutritional programming through short-term PNOF induced a long-lasting decrease in the expression of signaling pathways involved in cardiac cellular protection, which could explain why 6-months old mice show increased susceptibility to myocardial I-R injury in vivo. The mechanism of these alterations needs further exploration, but could involve alterations in cardiomyocyte's balance between apoptotic and regenerative pathways, and epigenetic modifications.

Acknowledgement/Funding

French Fundation

Depsipeptide Aspergillicins Revealed by Chromatin Reader Protein Deletion

Expression of biosynthetic gene clusters (BGCs) in filamentous fungi is highly regulated by epigenetic remodeling of chromatin structure. Two classes of histone modifying proteins, writers (which place modifications on histone tails) and erasers (which remove the modifications), have been used extensively to activate cryptic BGCs in fungi. Here, for the first time, we present activation of a cryptic BGC by a third category of histone modifying proteins, reader proteins that recognize histone tail modifications and commonly mediate writer and eraser activity. Loss of the reader SntB (Δ sntB) resulted in the synthesis of two cryptic cyclic hexa-depsipeptides, aspergillicin A and aspergillicin F, in the fungus Aspergillus flavus. Liquid chromatography, high resolution mass spectrometry, and NMR analysis coupled with bioinformatic analysis and gene deletion experiments revealed that a six adenylation (A) domain nonribosomal peptide synthetase (NRPS, called AgiA) and O-methyltransferase (AgiB) were required for metabolite formation. A proposed biosynthetic scheme illustrates the requirement for unusual NRPS domains, such as a starting condensation domain and a thiolesterase domain proposed to cyclize the depsipeptides. This latter activity has only been found in bacterial but not fungal NRPS. The agi BGC-unique to A. flavus and some closely related species (e.g., A. oryzae, A. arachidicola)-is located next to a conserved Aspergillus siderophore BGC syntenic to other fungi.

Role of the carbon defects in the catalytic oxygen reduction by graphite nanoparticles: a spectromagnetic, electrochemical and computational integrated approach

The chemical groups present at the surface of graphite have been thought for a long time to be mainly responsible for its catalytic activity in the oxygen reduction reaction. Recently, it was proposed that the surface defects of graphite also significantly contribute to promote this reaction. Although the behaviour of surface defects has been reported, only few comments have been dedicated to their involvement in the mechanism and the possible intermediate species in the oxygen reduction reaction. Herein, we aim to present a more detailed explanation of the catalytic activity of graphite particles based on the structure of their defects and their size. Structural, spectroscopic and magnetic investigation (X-ray diffraction, Raman and electron spin resonance) and electrochemical measurements were performed to describe the nature of the defects and their aptitude to transfer electrons. Computational description supplied precise details of the energy of the different defects and their ability to promote the reduction, also suggesting the structure of the intermediate adduct in the oxygen reduction. The results indicated that molecular oxygen preferentially interacts with graphite defects, which involve the π-electron system and accumulation of the spin density on the edges of the grains, in particular, on the zig-zag edges present on ball-milled graphite. This promotes the reactivity of this nanomaterial. Furthermore, the activation increases by decreasing the particle size.

Glycaemic variability is associated with severity of coronary artery disease in patients with poorly controlled type 2 diabetes and acute myocardial infarction

BACKGROUND

In patients with type 2 diabetes (T2D), glycaemic variability (GV), another component of glycaemic abnormalities, is a novel potentially aggravating factor for coronary artery disease (CAD).

OBJECTIVES

The aim of our study was to identify interactions between GV and severity of CAD in diabetes patients admitted for acute myocardial infarction (AMI).

METHODS

All patients with T2D admitted to our university hospital for AMI from March 2015 to February 2017 who received intravenous (IV) insulin therapy and underwent coronary angiography were included. GV was assessed by mean amplitude of blood glucose excursion (MAGE) values taken within 2 days of admission. Patients with higher GV (highest MAGE tertile) were compared with those with lower GV (first and second MAGE tertiles).

RESULTS

A total of 204 patients were included: median age was 72 (61-81) years; 32% were female; HbA_1c was 7.3% (6.4-8.2%); diabetes duration was 10 (2-17.5) years; and MAGE value was 0.65 (0.43-0.92) g/L. Compared with those with lower GV, patients with the highest GV were more often women, treated with previous insulin, and had higher blood glucose and HbA_1c levels. In addition, patients with elevated GV had significantly higher SYNTAX scores: 17 (10-28) vs. 12 (6-22) (P = 0.009). Indeed, SYNTAX scores (OR: 1.05, 95% CI: 1.02-1.08; P = 0.001) remained independently associated with high GV beyond HbA_1c levels (OR: 1.51, 95% CI: 1.2-1.89; P <  0.001).

CONCLUSION

In AMI patients with poorly controlled diabetes, GV is associated with CAD severity beyond chronic hyperglycaemia. Although no causality can be determined from our observational study, the results suggest that, in AMI, early evaluation of GV might contribute to the identification of those diabetes patients at high risk, and serve as a therapeutic target for both primary and secondary prevention.