Aerial exposure (emersion) due to the periodical ebb and flow of tides is a major stressor for intertidal organisms and a key environmental factor in shaping their local communities. Oysters are among the most emersion-tolerant mollusk species and can survive for several days under aerial exposure. Noticeably, overwhelming inflammation responses could occur during the emersion stress. However, mechanisms beneath the activation and modulation of emersion-induced inflammation response have remained largely unknown. Ca2+ is an important intracellular second messenger that plays indispensable roles in inflammation response by cooperation with calmodulin (CaM) genes. Here, we showed that intracellular Ca2+ accumulates rapidly in oyster hemocytes during emersion stress along with the changes in the protein levels of three CaM genes, which function as intracellular sensors of Ca2+. As downstream effector of Ca2+/CaM complex, nitric oxide synthase (NOS) activity in hemocytes was enhanced during the emersion stress, facilitating a greater production of nitrite oxide (NO). Augmentation of NO concentration was associated with the increased mRNA expression levels of two oyster cytokines (CgTNFs) during aerial exposure. The robust accumulation of cytokines and severe injury of tissues in oysters have been regarded as potential cause and marker of their death in prolonged emersion stress. Here, both the expression levels of CgTNFs and the tissue injuries of oysters were attenuated when Ca2+/CaM complex or NOS activity were repressed in vivo during the emersion stress. These findings indicate that Ca2+/CaM-NOS/NO-CgTNFs pathway is critically involved in the emersion-induced inflammation response in oysters and plays a role in the resistance against long-term aerial exposure.

中文翻译：

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Ca2+/钙调蛋白-NOS/NO-TNFs 通路标志着牡蛎在空气暴露期间的炎症反应

由于潮汐的周期性涨落而导致的空中暴露（涌现）是潮间带生物的主要压力源，也是塑造当地社区的关键环境因素。牡蛎是最耐重生的软体动物之一，在空中暴露下可以存活数天。值得注意的是，在出现压力期间可能会发生压倒性的炎症反应。然而，激活和调节再现诱导的炎症反应的机制在很大程度上仍然未知。Ca2+ 是一种重要的细胞内第二信使，通过与钙调蛋白 (CaM) 基因合作，在炎症反应中发挥不可或缺的作用。在这里，我们表明，随着三个 CaM 基因蛋白质水平的变化，在出现应激期间细胞内 Ca2+ 在牡蛎血细胞中迅速积累，其作为 Ca2+ 的细胞内传感器起作用。作为 Ca2+/CaM 复合物的下游效应物，血细胞中的一氧化氮合酶 (NOS) 活性在出现应激期间增强，从而促进亚硝酸氧化物 (NO) 的产生。在空中暴露期间，NO 浓度的增加与两种牡蛎细胞因子 (CgTNF) 的 mRNA 表达水平增加有关。牡蛎体内细胞因子的大量积累和组织的严重损伤被认为是它们在长时间的出水胁迫下死亡的潜在原因和标志。在这里，当 Ca2+/CaM 复合物或 NOS 活性在再现应激期间在体内受到抑制时，CgTNFs 的表达水平和牡蛎的组织损伤都会减弱。