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.

中文翻译：

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Brugada 综合征患者外周血唾液酸化途径改变的证据

资金致谢 资金来源类型：公共拨款——仅限国家预算。主要资金来源：意大利卫生部 RICERCA CORRENTE 背景 Brugada 综合征 (BrS) 是一种与心源性猝死 (SCD) 风险增加相关的心律失常。BrS被认为是一种遗传性疾病，最常见的突变基因是SCN5A，它编码电压门控心脏钠通道(NaV1.5)的α亚基。SCN5A 的突变通常会导致 NaV1.5 功能受损，从而导致动作电位的改变。然而，SCN5A 突变仅导致 30% 的 BrS 病例。因此，可以想象其他机制，如翻译后修饰 (PTM) 可能会影响 NaV1.5 的活性。其中，唾液酸化可以通过携带带负电荷的糖来改变离子通道活性。唾液酸化的改变以前曾在几种心血管疾病中被描述过，包括心肌梗塞、恰加斯病和先天性糖基化障碍，这是一种影响心脏的疾病。出于这些原因，目的是研究 BrS 患者唾液酸化的变化，以获得有关 BrS 发病机制的新信息。材料与方法 外周血单个核细胞 (PBMC) 采集自 BrS 患者和健康对照。为了表征 PBMC 的蛋白质唾液酸化状态，通过蛋白质印迹和流式细胞术使用 SNA 凝集素，它是唾液酸结合蛋白。参与生物合成、活化、转移、降解的酶的基因表达，通过实时 PCR 检测 PBMC 中唾液酸的再循环。结果 BrS 患者和对照组的 PBMCs 的细胞外和细胞内唾液酸化水平存在差异。特别是，CD3+/CD4+ T 细胞表现出较低的显着量的唾液酸。此外，与对照组相比，参与唾液酸生物合成和活化的酶的基因表达在患者中下调。相比之下，唾液酸转移酶 St3Gal1、St3Gal4 和 St6Gal2，负责将唾液酸结合到蛋白质表面的酶，在 BrS 患者和对照之间显示出显着的酶特异性差异。此外，唾液酸转移酶和唾液酸化蛋白的水平与心脏病理基质的心外膜区域和潜在持续时间呈负相关，BrS严重程度的两个临床指标。讨论 这些初步结果表明唾液酸化参与 BrS 综合征，并表明唾液酸化过程的损害可能与 BrS 的发作和/或表现有关。此外，首次报道了 BrS 免疫系统细胞的生化改变，支持了 BrS 是一种全身性疾病，其最终表现是 SCD 风险增加的假设。