Laboratory of Immunothrombosis, Department of Biochemistry, Institute of Biological Sciences, Federal University of Juiz de Fora, Juiz de Fora, Brazil.
Laboratory of Immunopharmacology, Oswaldo Cruz Institute, Oswaldo Cruz Foundation (FIOCRUZ), Rio de Janeiro, Brazil.
Front Immunol. 2022 Dec 7;13:1029213. doi: 10.3389/fimmu.2022.1029213. eCollection 2022.
Dengue is an arthropod-born disease caused by dengue virus (DENV), that may manifest as a mild illness or severe form, characterized by hemorrhagic fever and shock. Nitric oxide (NO) is a vasodilator signaling molecule and an inhibitor of platelet aggregation known to be increased in platelets from dengue patients. However, the mechanisms underlying NO synthesis by platelets during dengue are not yet elucidated. IL-1β is a pro-inflammatory cytokine able to induce iNOS expression in leukocytes and present in dengue patients at high levels. Nevertheless, the role of IL-1β in platelet activation, especially regarding iNOS expression, are not clear.
We prospectively followed a cohort of 28 dengue-infected patients to study NO synthesis in platelets and its relationship with disease outcomes. We used in vitro infection and stimulation models to gain insights on the mechanisms.
We confirmed that platelets from dengue patients express iNOS and produce higher levels of NO during the acute phase compared to healthy volunteers, returning to normal levels after recovery. Platelet NO production during acute dengue infection was associated with the presence of warning signs, hypoalbuminemia and hemorrhagic manifestations, suggesting a role in dengue pathophysiology. By investigating the mechanisms, we evidenced increased iNOS expression in platelets stimulated with dengue patients´ plasma, indicating induction by circulating inflammatory mediators. We then investigated possible factors able to induce platelet iNOS expression and observed higher levels of IL-1β in plasma from patients with dengue, which were correlated with NO production by platelets. Since platelets can synthesize and respond to IL-1β, we investigated whether IL-1β induces iNOS expression and NO synthesis in platelets. We observed that recombinant human IL-1β enhanced iNOS expression and dose-dependently increased NO synthesis by platelets. Finally, platelet infection with DENV in vitro induced iNOS expression and NO production, besides the secretion of both IL-1α and IL-1β. Importantly, treatment with IL-1 receptor antagonist or a combination of anti-IL-1α and anti-IL-1β antibodies prevented DENV-induced iNOS expression and NO synthesis. Our data show that DENV induces iNOS expression and NO production in platelets through mechanisms depending on IL-1 receptor signaling.
登革热是一种由登革病毒（DENV）引起的虫媒病，可能表现为轻度疾病或严重形式，其特征为出血性发热和休克。一氧化氮（NO）是一种血管扩张信号分子和血小板聚集抑制剂，已知在登革热患者的血小板中增加。然而，登革热期间血小板中 NO 合成的机制尚不清楚。白细胞介素-1β（IL-1β）是一种促炎细胞因子，能够诱导白细胞中的诱导型一氧化氮合酶（iNOS）表达，并在登革热患者中高水平存在。然而，IL-1β在血小板激活中的作用，特别是关于 iNOS 表达，尚不清楚。
我们前瞻性地随访了 28 例登革热感染患者的队列，以研究血小板中 NO 的合成及其与疾病结局的关系。我们使用体外感染和刺激模型来深入了解机制。
我们证实，与健康志愿者相比，登革热患者的血小板在急性期表达 iNOS 并产生更高水平的 NO，在恢复后恢复正常水平。急性登革热感染期间血小板产生的 NO 与预警信号、低白蛋白血症和出血表现有关，提示其在登革热病理生理学中的作用。通过研究机制，我们发现，用登革热患者的血浆刺激血小板后，iNOS 表达增加，表明循环炎症介质诱导了这种表达。然后，我们研究了可能诱导血小板 iNOS 表达的因素，并观察到登革热患者血浆中 IL-1β水平升高，与血小板产生的 NO 相关。由于血小板可以合成和对 IL-1β做出反应，我们研究了 IL-1β 是否诱导血小板中的 iNOS 表达和 NO 合成。我们观察到重组人白细胞介素-1β增强了 iNOS 表达，并呈剂量依赖性地增加了血小板中的 NO 合成。最后，体外用 DENV 感染血小板诱导了 iNOS 表达和 NO 产生，以及白细胞介素-1α和白细胞介素-1β的分泌。重要的是，用白细胞介素-1 受体拮抗剂或抗白细胞介素-1α和抗白细胞介素-1β抗体的联合治疗可预防 DENV 诱导的 iNOS 表达和 NO 合成。我们的数据表明，DENV 通过依赖白细胞介素-1 受体信号的机制诱导血小板中的 iNOS 表达和 NO 产生。
