Department of Pediatrics, Peking University First Hospital, Beijing, China.
Research Unit of Clinical Diagnosis and Treatment of Pediatric Syncope and Cardiovascular Diseases, Chinese Academy of Medical Sciences, Beijing, China.
J Adv Res. 2020 Sep 8;29:55-65. doi: 10.1016/j.jare.2020.08.017. eCollection 2021 Mar.
Mast cell (MC) degranulation is an important step in the pathogenesis of inflammatory reactions and allergies; however, the mechanism of stabilizing MC membranes to reduce their degranulation is unclear.
SO content in MC culture supernatant was measured by HPLC-FD. The protein and mRNA expressions of the key enzymes aspartate aminotransferase 1 (AAT1) and AAT2 and intracellular AAT activity were detected. The cAMP level in MCs was detected by immunofluorescence and ELISA. The release rate of MC degranulation marker β-hexosaminidase was measured. The expression of AAT1 and cAMP, the MC accumulation and degranulation in lung tissues were detected.
To exam whether an endogenous sulfur dioxide (SO) pathway exists in MCs and if it serves as a novel endogenous MC stabilizer.
We firstly show the existence of the endogenous SO/AAT pathway in MCs. Moreover, when AAT1 was knocked down in MCs, MC degranulation was significantly increased, and could be rescued by a SO donor. Mechanistically, AAT1 knockdown decreased the cyclic adenosine monophosphate (cAMP) content in MCs, while SO prevented this reduction in a dose-independent manner. Pretreatment with the cAMP-synthesizing agonist forskolin or the cAMP degradation inhibitor IBMX significantly blocked the increase in AAT1 knockdown-induced MC degranulation. Furthermore, in hypoxia-stimulated MCs, AAT1 protein expression and SO production were markedly down regulated, and MC degranulation was activated, which were blunted by AAT1 overexpression. The cAMP synthesis inhibitor SQ22536 disrupted the suppressive effect of AAT1 overexpression on hypoxia-induced MC degranulation. In a hypoxic environment, mRNA and protein expression of AAT1 was significantly reduced in lung tissues of rats. Supplementation of SO elevated the cAMP level and reduced perivascular MC accumulation and degranulation in lung tissues of rats exposed to a hypoxic environment .
SO serves as an endogenous MC stabilizer via upregulating the cAMP pathway under hypoxic circumstance.
肥大细胞（MC）脱颗粒是炎症反应和过敏发病机制中的重要步骤；然而，稳定 MC 膜以减少脱颗粒的机制尚不清楚。
通过 HPLC-FD 测量 MC 培养上清液中的 SO 含量。检测关键酶天冬氨酸氨基转移酶 1（AAT1）和 AAT2 的蛋白和 mRNA 表达以及细胞内 AAT 活性。通过免疫荧光和 ELISA 检测 MC 中的 cAMP 水平。测量 MC 脱颗粒标志物β-己糖胺酶的释放率。检测 AAT1 和 cAMP 的表达、肺组织中的 MC 聚集和脱颗粒。
检查 MC 中是否存在内源性二氧化硫（SO）途径，以及它是否作为一种新型内源性 MC 稳定剂。
我们首先在 MC 中显示了内源性 SO/AAT 途径的存在。此外，当 MC 中的 AAT1 被敲低时，MC 脱颗粒明显增加，SO 供体可以挽救这种增加。机制上，AAT1 敲低降低了 MC 中的环磷酸腺苷（cAMP）含量，而 SO 以剂量非依赖性方式防止这种减少。用 cAMP 合成激动剂 forskolin 或 cAMP 降解抑制剂 IBMX 预处理可显著阻断 AAT1 敲低诱导的 MC 脱颗粒增加。此外，在缺氧刺激的 MC 中，AAT1 蛋白表达和 SO 产生明显下调，MC 脱颗粒被激活，而过表达 AAT1 则减弱了这种激活。cAMP 合成抑制剂 SQ22536 破坏了 AAT1 过表达对缺氧诱导的 MC 脱颗粒的抑制作用。在缺氧环境中，大鼠肺组织中 AAT1 的 mRNA 和蛋白表达明显降低。补充 SO 可提高 cAMP 水平并减少缺氧环境中大鼠肺组织中的血管周围 MC 聚集和脱颗粒。
SO 通过在低氧环境下上调 cAMP 途径作为内源性 MC 稳定剂。
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