Structural analysis of a simplified model reproducing SARS-CoV-2 S RBD/ACE2 binding site

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an RNA virus identified as the cause of the coronavirus outbreak in December 2019 (COVID-19). Like all the RNA viruses, SARS-CoV-2 constantly evolves through mutations in its genome, accumulating 1–2 nucleotide changes every month, giving the virus a selective advantage through enhanced transmissibility, greater pathogenicity, and the possibility of circumventing immunity previously acquired by an individual either by natural infection or by vaccination. Several SARS-CoV-2 variants of concern (VoC) have been identified, among which we find Alpha (Lineage B.1.1.7), Beta (Lineage B.1.351), and Gamma (Lineage P.1) variants. Most of the mutations occur in the spike (S) protein, a surface glycoprotein that plays a crucial role in viral infection; the S protein binds the host cell receptor, the angiotensin-converting enzyme of type 2 (ACE2) via the receptor binding domain (RBD) and catalyzes the fusion of the viral membrane with the host cell. In this work, we present the development of a simplified system that would afford to study the change in the SARS-CoV-2 S RBD/ACE2 binding related to the frequent mutations. In particular, we synthesized and studied the structure of short amino acid sequences, mimicking the two proteins’ critical portions. Variations in the residues were easily managed through the one-point alteration of the sequences. Nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopies provide insights into ACE2 and SARS-CoV-2 S RBD structure with its related three variants (Alpha, Beta, and Gamma). Spectroscopy data supported by molecular dynamics lead to the description of an ACE2/RBD binding model in which the effect of a single amino acid mutation in changing the binding of S protein to the ACE2 receptor is predictable

Microgravity Promotes Differentiation and Meiotic Entry of Postnatal Mouse Male Germ Cells

A critical step of spermatogenesis is the entry of mitotic spermatogonia into meiosis. Progresses on these topics are hampered by the lack of an in vitro culture system allowing mouse spermatogonia differentiation and entry into meiosis. Previous studies have shown that mouse pachytene spermatocytes cultured in simulated microgravity (SM) undergo a spontaneous meiotic progression. Here we report that mouse mitotic spermatogonia cultured under SM with a rotary cell culture system (RCCS) enter into meiosis in the absence of any added exogenous factor or contact with somatic cells. We found that isolated Kit-positive spermatogonia under the RCCS condition enter into the prophase of the first meiotic division (leptotene stage), as monitored by chromosomal organization of the synaptonemal complex 3 protein (Scp3) and up-regulation of several pro-meiotic genes. SM was found to activate the phosphatidyl inositol 3 kinase (PI3K) pathway and to induce in Kit-positive spermatogonia the last round of DNA replication, typical of the preleptotene stage. A PI3K inhibitor abolished Scp3 induction and meiotic entry stimulated by RCCS conditions. A positive effect of SM on germ cell differentiation was also observed in undifferentiated (Kit-negative) spermatogonia, in which RCCS conditions stimulate the expression of Kit and Stra8. In conclusion, SM is an artificial environmental condition which promotes postnatal male germ cell differentiation and might provide a tool to study the molecular mechanisms underlying the switch from mitosis to meiosis in mammals

Pectin-based bioinks for 3D models of neural tissue produced by a pH-controlled kinetics

Introduction:In the view of 3D-bioprinting with cell models representative of neural cells, we produced inks to mimic the basic viscoelastic properties of brain tissue. Moving from the concept that rheology provides useful information to predict ink printability, this study improves and expands the potential of the previously published 3D-reactive printing approach by introducing pH as a key parameter to be controlled, together with printing time. Methods:The viscoelastic properties, printability, and microstructure of pectin gels crosslinked with CaCO3 were investigated and their composition was optimized (i.e., by including cell culture medium, HEPES buffer, and collagen). Different cell models representative of the major brain cell populations (i.e., neurons, astrocytes, microglial cells, and oligodendrocytes) were considered. Results and Discussion:The outcomes of this study propose a highly controllable method to optimize the printability of internally crosslinked polysaccharides, without the need for additives or post-printing treatments. By introducing pH as a further parameter to be controlled, it is possible to have multiple (pH-dependent) crosslinking kinetics, without varying hydrogel composition. In addition, the results indicate that not only cells survive and proliferate following 3D-bioprinting, but they can also interact and reorganize hydrogel microstructure. Taken together, the results suggest that pectin-based hydrogels could be successfully applied for neural cell culture

The Metabolomic Profile in Amyotrophic Lateral Sclerosis Changes According to the Progression of the Disease: An Exploratory Study

Amyotrophic lateral sclerosis (ALS) is a multifactorial neurodegenerative pathology of the upper or lower motor neuron. Evaluation of ALS progression is based on clinical outcomes considering the impairment of body sites. ALS has been extensively investigated in the pathogenetic mechanisms and the clinical profile; however, no molecular biomarkers are used as diagnostic criteria to establish the ALS pathological staging. Using the source-reconstructed magnetoencephalography (MEG) approach, we demonstrated that global brain hyperconnectivity is associated with early and advanced clinical ALS stages. Using nuclear magnetic resonance (1H-NMR) and high resolution mass spectrometry (HRMS) spectroscopy, here we studied the metabolomic profile of ALS patients’ sera characterized by different stages of disease progression—namely early and advanced. Multivariate statistical analysis of the data integrated with the network analysis indicates that metabolites related to energy deficit, abnormal concentrations of neurotoxic metabolites and metabolites related to neurotransmitter production are pathognomonic of ALS in the advanced stage. Furthermore, analysis of the lipidomic profile indicates that advanced ALS patients report significant alteration of phosphocholine (PCs), lysophosphatidylcholine (LPCs), and sphingomyelin (SMs) metabolism, consistent with the exigency of lipid remodeling to repair advanced neuronal degeneration and inflammatio

Nusinersen Induces Disease-Severity-Specific Neurometabolic Effects in Spinal Muscular Atrophy

Intrathecal delivery of Nusinersen-an antisense oligonucleotide that promotes survival motor neuron (SMN) protein induction-is an approved therapy for spinal muscular atrophy (SMA). Here, we employed nuclear magnetic resonance (NMR) spectroscopy to longitudinally characterize the unknown metabolic effects of Nusinersen in the cerebrospinal fluid (CSF) of SMA patients across disease severity. Modulation of amino acid metabolism is a common denominator of biochemical changes induced by Nusinersen, with distinct downstream metabolic effects according to disease severity. In severe SMA1 patients, Nusinersen stimulates energy-related glucose metabolism. In intermediate SMA2 patients, Nusinersen effects are also related to energy homeostasis but involve ketone body and fatty acid biosynthesis. In milder SMA3 patients, Nusinersen mainly modulates amino acid metabolism. Moreover, Nusinersen modifies the CSF metabolome of a more severe clinical group towards the profile of untreated SMA patients with milder disease. These findings reveal disease severity-specific neurometabolic signatures of Nusinersen treatment, suggesting a selective modulation of peripheral organ metabolism by this CNS-directed therapy in severe SMA patients

Analytical characterization of an inulin-type fructooligosaccharide from root-tubers of Asphodelus ramosus L

Plant-based systems continue to play a pivotal role in healthcare, and their use has been extensively documented. Asphodelus L. is a genus comprising various herbaceous species, known by the trivial name Asphodelus. These plants have been known since antiquity for both food and therapeutic uses, especially for treating several diseases associated with inflammatory and infectious skin disorders. Phytochemical studies revealed the presence of different constituents, mainly anthraquinones, triterpenoids, phenolic acids, and flavonoids. Although extensive literature has been published on these constituents, a paucity of information has been reported regarding the carbohydrate composition, such as fructans and fructan-like derivatives. The extraction of watersoluble neutral polysaccharides is commonly performed using water extraction, at times assisted by microwaves and ultrasounds. Herein, we reported the investigation of the alkaline extraction of roottubers of Asphodelus ramosus L., analyzing the water-soluble polysaccharides obtained by precipitation from the alkaline extract and its subsequent purification by chromatography. A polysaccharide was isolated by alkaline extraction; the HPTLC study to determine its composition showed fructose as the main monosaccharide. FT-IR analysis showed the presence of an inulin-type structure, and NMR analyses allowed us to conclude that A. ramosus roots contain polysaccharide with an inulin-type fructooligosaccharide with a degree of polymerization of 7-8

Beta-amyloid-acetylcholine structural interaction: evidence for neuroprotective effects of acetylcholine in neural cells

Alzheimer’s disease (AD) is regarded as a multifactorial disease characterized by a complex pathogenesis including a cholinergic deficit - due to degeneration of cholinergic projections from the basal forebrain - and the extracellular accumulation of amyloid beta (Aβ) peptide. Aβ containing 39 to 42 amino acids is the predominant component of the senile plaques that, together with neurofibrillary tangles, are regarded as the neuropathological hallmarks of AD (Sorrentino et al. 2014). Aβ may assume different conformations changing from random coil or α-helical monomers to β-sheet structures forming toxic oligomers and/or β-sheet mature fibrils. In this framework, we studied the effect of acetylcholine (ACh) on the conformation of Aβ by circular dichroism analysis. Moreover we investigated the ability of ACh to protect neuronal cells from the toxic action of amyloid peptide and to modulate the neuroinflammatory response occurring via the phospholipase A2 (PLA2). Results show that the amount of Aβ(25-35) β-strand raised linearly in absence of ACh, whereas it remained almost constant in presence of ACh. In addition, in a micelle solution mimicking the membrane environment ACh was found effective in increasing and stabilizing the soluble and not toxic helical content of Aβ(25-35) suggesting that ACh is capable to preserve the soluble form of Aβ(25-35), reducing the incipit of Aβ aggregation. In order to assess the neuro-protective ability of ACh against toxic Aβ(25-35) accumulation, we used neural cell (NCC) cultures containing both astrocytes and glial cells prepared from brains embryos from timed pregnant Wistar rats and infused ACh for 48h. By immunostaining, we observed that ACh reduced Aβ(25-35)-induced cell death. Then, we tested the protective effect of ACh on inflammation induced by Aβ administration. NCC were challenged with Aβ(25-35) in the presence and absence of ACh and immunostained for astroglial and neuronal markers: results showed a reduction of the morphological features of astrogliosys in ACh treated cells. PLA2 expression analysis corroborated these data also underlying that ACh can negatively regulate inflammation pathways in glial cells

1,4-Disubstituted-[1,2,3]triazolyl-Containing Analogues of MT-II: Design, Synthesis, Conformational Analysis, and Biological Activity

Side chain-to-side chain cyclizations represent a strategy to select a family of bioactive conformations by reducing the entropy and enhancing the stabilization of functional ligand-induced receptor conformations. This structural manipulation contributes to increased target specificity, enhanced biological potency, improved pharmacokinetic properties, increased functional potency, and lowered metabolic susceptibility. The CuI-catalyzed azide–alkyne 1,3-dipolar Huisgen’s cycloaddition, the prototypic click reaction, presents a promising opportunity to develop a new paradigm for an orthogonal bioorganic and intramolecular side chain-to-side chain cyclization. In fact, the proteolytic stable 1,4- or 4,1-disubstituted [1,2,3]triazolyl moiety is isosteric with the peptide bond and can function as a surrogate of the classical side chain-to-side chain lactam forming bridge. Herein we report the design, synthesis, conformational analysis, and functional biological activity of a series of i-to-i+5 1,4- and 4,1-disubstituted [1,2,3]triazole-bridged cyclopeptides derived from MT-II, the homodetic Asp5 to Lys10 side chain-to-side chain bridged heptapeptide, an extensively studied agonist of melanocortin receptors