Evidence of Sialylation pathways alteration in peripheral blood of Brugada Syndrome patients

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): RICERCA CORRENTE, Italian Ministry of Health

Background

Brugada syndrome (BrS) is a cardiac arrhythmia associated with an increased risk of sudden cardiac death (SCD). BrS is considered a genetic disorder, and the most commonly mutated gene is SCN5A, which encodes the alpha subunit of the voltage-gated cardiac sodium channel (NaV1.5). Mutations of SCN5A generally cause impairment of NaV1.5 function, resulting in alteration of the action potential. However, mutations of SCN5A are responsible for only 30% of BrS cases. Therefore, it is conceivable that other mechanisms such as post-translational modifications (PTMs) could affect NaV1.5 activity. Among others, sialylation may alter ion channel activity by carrying a sugar with a negative charge. Alterations in sialylation have previously been described in several cardiovascular diseases, including myocardial infarction, Chagas disease, and congenital disorders of glycosylation, a family of diseases affecting the heart. For these reasons, the aim was to study alterations in sialylation in BrS patients to get new information about the pathogenesis of BrS.

Materials and Methods

Peripheral blood mononuclear cells (PBMCs) were collected from BrS patients and healthy controls. To characterize the protein sialylation status of PBMCs, SNA lectin, which is sialic acid-binding proteins, was used by Western blot and flow cytometry. Gene expression of enzymes involved in the biosynthesis, activation, transfer, degradation, and recycling of sialic acid was examined in PBMCs by real-time PCR.

Results

The extracellular and intracellular sialylation levels of PBMCs differed between BrS patients and controls. In particular, CD3+/CD4+ T cells exhibited a lower significant amount of sialic acid. Moreover, gene expression of enzymes involved in the biosynthesis and activation of sialic acid was downregulated in patients compared to controls. In contrast, the sialyltransferases St3Gal1, St3Gal4, and St6Gal2, enzymes responsible for binding sialic acid to the protein surface, showed significant enzyme-specific differences between BrS patients and controls. Moreover, the levels of sialyltransferases and sialylated proteins are inversely correlated with the epicardial area of the cardiac pathological substrate and with potential duration, two clinical indicators of BrS severity.

Discussion

These preliminary results demonstrate the involvement of sialylation in BrS syndrome and suggest that impairment of the sialylation process may be associated with the onset and/or manifestation of BrS. In addition, biochemical alteration of cells of the BrS immune system was reported for the first time, supporting the hypothesis that BrS is a systemic disease whose final manifestation is an increased risk of SCD.

Synthesis and chemical characterization of several perfluorinated sialic acid glycals and evaluation of their in vitro antiviral activity against Newcastle disease virus

Newcastle Disease Virus (NDV), belonging to the Paramyxoviridae family, causes a serious infectious disease in birds, resulting in severe losses in the poultry industry every year. Haemagglutinin neuraminidase glycoprotein (HN) has been recognized as a key protein in the viral infection mechanism, and its inhibition represents an attractive target for the development of new drugs based on sialic acid glycals, with the 2-deoxy-2,3-didehydro-d-N-acetylneuraminic acid (Neu5Ac2en) as their backbone. Herein we report the synthesis of several Neu5Ac2en glycals and of their perfluorinated C-5 modified derivatives, including their respective stereoisomers at C-4, together with evaluation of their in vitro antiviral activity. While all synthesized compounds were found to be active HN inhibitors in the micromolar range, we found that their potency was influenced by the chain-length of the C-5 perfluorinated acetamido functionality. Thus, the binding modes of the inhibitors were also investigated by performing a docking study. Moreover, the perfluorinated glycals were found to be more active than the corresponding normal C-5 acylic derivatives. Finally, cell-cell fusion assays on NDV infected cells revealed that the addition of a newly synthesized C-4α heptafluorobutyryl derivative almost completely inhibited NDV-induced syncytium formation.

Reversine increases multipotent human mesenchymal cells differentiation potential

Among different human stem cell sources, adult mesenchymal stem cells from bone marrow (BMSCs), and more recently from adipose tissues (ASCs), have shown their capability to differentiate into a variety of different cell types, including osteoblasts, adipocytes, and muscle cells. However, mesenchymal stem cell differentiation toward certain cell types (including skeletal and cardiac muscle), while shown to be achievable, still suffers of low yields and needs to be greatly improved before any therapeutic application could be foreseen. A possible way of achieving this goal is by using a chemical-pharmacological approach to increase stem cell plasticity. Along this line, we envisioned the possibility of pre-treating BMSCs and ASCs with reversine, a synthetic purine that has been shown to induce adult cells de-differentiation. In the current study we tested reversine effects on both BMSCs and ASCs to increase their differentiation toward osteoblasts, smooth and skeletal muscle cells. Reversine pre-treatment, at very low concentration (50 nM), caused a marked increase in the differentiation yields of both BMSCs and ASCs.

Cell reprogramming: expectations and challenges for chemistry in stem cell biology and regenerative medicine

The possibility of reprogramming adult somatic cells into pluripotent stem cells (iPSCs) has generated a renewed interest into stem cell research and promises to overcome several key issues, including the ethical concerns of using human embryonic stem cells and the difficulty of obtaining large numbers of adult stem cells (Belmonte et al., Nat Rev Genet, 2009). This approach is also not free from challenges like the mechanism of the reprogramming process, which has yet to be elucidated, and the warranties for safety of generated pluripotent cells, especially in view of their possible therapeutic use. Very recently, several new reprogramming methods have surfaced, which seem to be more appropriate than genetic reprogramming. Particularly, chemically induced pluripotent cells (CiPSs), obtained with recombinant proteins or small synthetic molecules, may represent a valid approach, simpler and possibly safer than the other ones.

Highly satisfactory procedures for the Pd-catalyzed cross coupling of aryl electrophiles with in situ generated alkynylzinc derivatives

[reaction: see text] Two new and very efficient procedures (Procedures A and B) are reported for the Pd-catalyzed cross coupling of aryl electrophiles with terminal alkynes via their in situ conversion into alkynylzinc derivatives. Procedure A is particularly valuable in cases where electron-deficient alkynes are used, while Procedure B is operationally simple and very satisfactory in less demanding cases.