Polysaccharides to combat viruses (Covid-19) and microbes: New updates

COVID-19, which is speedily distributed across the world and presents a significant challenge to public health, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Following MERS coronavirus (MERS-CoV) and SARS, this is the third severe coronavirus outbreak in less than 20 years. To date, there are no exact agents and vaccines available for the treatment of COVID-19 that are clinically successful. Antimicrobial medications are effective in controlling infectious diseases. However, the extensive use of antibiotics makes microbes more resistant to drugs and demands novel bioactive agents’ development. Polysaccharides are currently commonly used in the biomedical and pharmaceutical industries for their remarkable applications. Polysaccharides appear to have a wide range of anti-virus (anti-coronavirus) and antimicrobial applications. Polysaccharides are able to induce bacterial cell membrane disruption as they demonstrate potency in binding onto the surfaces of microbial cells. Here, the antiviral mechanisms of such polysaccharides and their success in the application of antiviral infections are reviewed. Additionally, this report provides a summary of current advancements of well-recognized polysaccharides as antimicrobial and anti-biofilm agents.

Prothrombotic Phenotype in COVID-19: Focus on Platelets

COVID-19 infection is associated with a broad spectrum of presentations, but alveolar capillary microthrombi have been described as a common finding in COVID-19 patients, appearing as a consequence of a severe endothelial injury with endothelial cell membrane disruption. These observations clearly point to the identification of a COVID-19-associated coagulopathy, which may contribute to thrombosis, multi-organ damage, and cause of severity and fatality. One significant finding that emerges in prothrombotic abnormalities observed in COVID-19 patients is that the coagulation alterations are mainly mediated by the activation of platelets and intrinsically related to viral-mediated endothelial inflammation. Beyond the well-known role in hemostasis, the ability of platelets to also release various potent cytokines and chemokines has elevated these small cells from simple cell fragments to crucial modulators in the blood, including their inflammatory functions, that have a large influence on the immune response during infectious disease. Indeed, platelets are involved in the pathogenesis of acute lung injury also by promoting NET formation and affecting vascular permeability. Specifically, the deposition by activated platelets of the chemokine platelet factor 4 at sites of inflammation promotes adhesion of neutrophils on endothelial cells and thrombogenesis, and it seems deeply involved in the phenomenon of vaccine-induced thrombocytopenia and thrombosis. Importantly, the hyperactivated platelet phenotype along with evidence of cytokine storm, high levels of P-selectin, D-dimer, and, on the other hand, decreased levels of fibrinogen, von Willebrand factor, and thrombocytopenia may be considered suitable biomarkers that distinguish the late stage of COVID-19 progression in critically ill patients.

A Dense Magnetic Coil Array with Multi-locus and Multi-site Patterning

<p>· We propose multi-loci and multi-site current patterning (sequential or simultaneous) for precise, rapid and repeatable steering for improved neuronal targeting.</p><p>· Here we demonstrate these improvements by using a unique pixel cell for excitation synthesis as enabled by a three-layer dense magnetic coil array that is mapped to a hexagonal grid with cubic coordinates.</p><p>· We validate the theory with supporting simulations, experimental results and a scalable electronics design that can address a relevant range of larger coil diameters, higher power levels and topologies.</p><p><a></a></p><p>· Precise, rapid and repeatable patterns potentially offer new modalities for noninvasive neuromodulation (suprathreshold and subthreshold) and adjacent biomagnetic applications such as tumor cell membrane disruption [1], and magnetic drug delivery [2].</p>

A Dense Magnetic Coil Array with Multi-locus and Multi-site Patterning

<p>· We propose multi-loci and multi-site current patterning (sequential or simultaneous) for precise, rapid and repeatable steering for improved neuronal targeting.</p><p>· Here we demonstrate these improvements by using a unique pixel cell for excitation synthesis as enabled by a three-layer dense magnetic coil array that is mapped to a hexagonal grid with cubic coordinates.</p><p>· We validate the theory with supporting simulations, experimental results and a scalable electronics design that can address a relevant range of larger coil diameters, higher power levels and topologies.</p><p><a></a></p><p>· Precise, rapid and repeatable patterns potentially offer new modalities for noninvasive neuromodulation (suprathreshold and subthreshold) and adjacent biomagnetic applications such as tumor cell membrane disruption [1], and magnetic drug delivery [2].</p>

Heterozygous Arrhythmogenic Cardiomyopathy-desmoplakin Mutation Carriers Exhibit a Subclinical Cutaneous Phenotype with Cell Membrane Disruption and Lack of Intercellular Adhesion

Genetic variants that result in truncation in desmoplakin (DSP) are a known cause of arrhythmogenic cardiomyopathy (AC). In homozygous carriers, the combined involvement of skin and heart muscle is well defined, however, this is not the case in heterozygous carriers. The aim of this work is to describe cutaneous findings and analyze the molecular and ultrastructural cutaneous changes in this group of patients. Four women and eight men with a mean age of 48 ± 14 years were included. Eight met definitive criteria for AC, one was borderline and three were silent carriers. No relevant macroscopic changes in skin and hair were detected. However, significantly lower skin temperature (29.56 vs. 30.97 °C, p = 0.036) and higher transepidermal water loss (TEWL) (37.62 vs. 23.95 g m 2 h 1, p = 0.028) were observed compared to sex- and age-matched controls. Histopathology of the skin biopsy showed widening of intercellular spaces and acantholysis of keratinocytes in the spinous layer. Immunohistochemistry showed a strongly reduced expression of DSP in all samples. Trichogram showed regular nodules (thickening) compatible with pseudomonilethrix. Therefore, regardless of cardiac involvement, heterozygous patients with truncation-type variants in DSP have lower skin temperature and higher TEWL, constant microscopic skin involvement with specific patterns and pseudomonilethrix in the trichogram.

Cytotoxicity of snake venom Lys49 PLA2-like myotoxin on rat cardiomyocytes ex vivo does not involve a direct action on the contractile apparatus

Viperid snake venoms contain a unique family of cytotoxic proteins, the Lys49 PLA2 homologs, which are devoid of enzymatic activity but disrupt the integrity of cell membranes. They are known to induce skeletal muscle damage and are therefore named ‘myotoxins’. Single intact and skinned (devoid of membranes and cytoplasm but with intact sarcomeric proteins) rat cardiomyocytes were used to analyze the cytotoxic action of a myotoxin, from the venom of Bothrops asper. The toxin induced rapid hypercontraction of intact cardiomyocytes, associated with an increase in the cytosolic concentration of calcium and with cell membrane disruption. Hypercontraction of intact cardiomyocytes was abrogated by the myosin inhibitor para-aminoblebbistatin (AmBleb). No toxin-induced changes of key parameters of force development were observed in skinned cardiomyocytes. Thus, although myosin is a key effector of the observed hypercontraction, a direct effect of the toxin on the sarcomeric proteins -including the actomyosin complex- is not part of the mechanism of cytotoxicity. Owing to the sensitivity of intact cardiomyocytes to the cytotoxic action of myotoxin, this ex vivo model is a valuable tool to explore in further detail the mechanism of action of this group of snake venom toxins.

The In Vitro Anti-Pseudomonal Activity of Cu2+, Strawberry Furanone, Gentamicin, and Lytic Phages Alone and in Combination: Pros and Cons

In this study, we investigated the anti-pseudomonal activity of cupric ions (Cu2+), strawberry furanone (HDMF), gentamicin (GE), and three lytic Pseudomonas aeruginosa bacteriophages (KT28, KTN4, LUZ19), separately and in combination. HDMF showed an anti-virulent effect but only when applied with Cu2+ or GE. GE, at a sub-minimal inhibitory concentration, slowed down phage progeny production due to protein synthesis inhibition. Cu2+ significantly reduced both the bacterial cell count and the number of infective phage particles, likely due to its genotoxicity or protein inactivation and cell membrane disruption effects. Furthermore, Cu2+‘s probable sequestration by phage particles led to the reduction of free toxic metal ions available in the solution. An additive antibacterial effect was only observed for the combination of GE and Cu2+, potentially due to enhanced ROS production or to outer membrane permeabilization. This study indicates that possible interference between antibacterial agents needs to be carefully investigated for the preparation of effective therapeutic cocktails.

Analyses of cell death mechanisms related to amino acid substitution at position 95 in the rabies virus matrix protein

We previously reported that the avirulent fixed rabies virus strain Ni-CE induces a clear cytopathic effect in mouse neuroblastoma cells, whereas its virulent progenitor, the Nishigahara strain, does not. Infection with Nishigahara and Ni-CE mutants containing a single amino acid substitution in the matrix protein (M) demonstrated that the amino acid at position 95 of M (M95) is a cytopathic determinant. The characteristics of cell death induced by Ni-CE infection resemble those of apoptosis (rounded and shrunken cells, DNA fragmentation), but the intracellular signalling pathway for this process has not been fully investigated. In this study, we aimed to elucidate the mechanism by which M95 affects cell death induced by human neuroblastoma cell infection with the Nishigahara, Ni-CE and M95-mutated strains. We demonstrated that the Ni-CE strain induced DNA fragmentation, cell membrane disruption, exposure of phosphatidylserine (PS), activation of caspase-3/7 and anti-poly (ADP-ribose) polymerase 1 (PARP-1) cleavage, an early apoptosis indicator, whereas the Nishigahara strain did not induce DNA fragmentation, caspase-3/7 activation, cell membrane disruption, or PARP-1 cleavage, but did induce PS exposure. We also demonstrated that these characteristics were associated with M95 using M95-mutated strains. However, we found that Ni-CE induced cell death despite the presence of a caspase inhibitor, Z-VAD-FMK. In conclusion, our data suggest that M95 mutation-related cell death is caused by both the caspase-dependent and -independent pathways.

Development of Antimicrobial Stapled Peptides Based on Magainin 2 Sequence

Magainin 2 (Mag2), which was isolated from the skin of the African clawed frog, is a representative antimicrobial peptide (AMP) that exerts antimicrobial activity via microbial membrane disruption. It has been reported that the helicity and amphipathicity of Mag2 play important roles in its antimicrobial activity. We investigated and recently reported that 17 amino acid residues of Mag2 are required for its antimicrobial activity, and accordingly developed antimicrobial foldamers containing α,α-disubstituted amino acid residues. In this study, we further designed and synthesized a set of Mag2 derivatives bearing the hydrocarbon stapling side chain for helix stabilization. The preferred secondary structures, antimicrobial activities, and cell-membrane disruption activities of the synthesized peptides were evaluated. Our analyses revealed that hydrocarbon stapling strongly stabilized the helical structure of the peptides and enhanced their antimicrobial activity. Moreover, peptide 2 stapling between the first and fifth position from the N-terminus showed higher antimicrobial activity than that of Mag2 against both gram-positive and gram-negative bacteria without exerting significant hemolytic activity. To investigate the modes of action of tested peptides 2 and 8 in antimicrobial and hemolytic activity, electrophysiological measurements were performed.

Quercetin in attenuation of ischemic/reperfusion injury: A review

Background: Ischemia/reperfusion (I/R) injury is a serious pathologic event that occurs due to restriction in blood supply to an organ, followed by hypoxia. This condition leads to enhanced levels of pro-inflammatory cytokines such as IL-6 and TNF-, and stimulation of oxidative stress via enhancing reactive oxygen species (ROS) levels. Upon reperfusion, blood supply increases, but it deteriorates condition, and leads to generation of ROS, cell membrane disruption and finally, cell death. Plant derived-natural compounds are well-known due to their excellent antioxidant and anti-inflammatory activities. Quercetin is a flavonoid exclusively found in different vegetables, herbs, and fruits. This naturally occurring compound possesses different pharmacological activities making it appropriate option in disease therapy. Quercetin can also demonstrate therapeutic effects via affecting molecular pathways such as NF-B, PI3K/Akt and so on. Methods: In the present review, we demonstrate that quercetin administration is beneficial in ameliorating I/R injury via reducing ROS levels, inhibition of inflammation, and affecting molecular pathways such as TLR4/NF-B, MAPK and so on. Results and conclusion: Quercetin can improve cell membrane integrity via decreasing lipid peroxidation. Apoptotic cell death is inhibited by quercetin via down-regulation of Bax, and caspases, and upregulation of Bcl-2. Quercetin is able to modulate autophagy (inhibition/induction) in decreasing I/R injury. Nanoparticles have been applied for delivery of quercetin, enhancing its bioavailability and efficacy in alleviation of I/R injury. Noteworthy, clinical trials have also confirmed the capability of quercetin in reducing I/R injury.