Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia.
Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czechia.
Front Immunol. 2022 Feb 8;13:707085. doi: 10.3389/fimmu.2022.707085. eCollection 2022.
Polymorphonuclear neutrophils (PMNs) play a key role in host defense. However, their massive accumulation at the site of inflammation can delay regenerative healing processes and can initiate pathological inflammatory processes. Thus, the efficient clearance of PMNs mediated by the induction of regulated cell death is a key process preventing the development of these pathological conditions. Myeloperoxidase (MPO), a highly abundant enzyme in PMN granules, primarily connected with PMN defense machinery, is suggested to play a role in PMN-regulated cell death. However, the contribution of MPO to the mechanisms of PMN cell death remains incompletely characterized. Herein, the process of the cell death of mouse PMNs induced by three different stimuli - phorbol 12-myristate 13-acetate (PMA), opsonized streptococcus (OST), and N-formyl-met-leu-phe (fMLP) - was investigated. MPO-deficient PMNs revealed a significantly decreased rate of cell death characterized by phosphatidylserine surface exposure and cell membrane permeabilization. An inhibitor of MPO activity, 4-aminobenzoic acid hydrazide, did not exhibit a significant effect on PMA-induced cell death compared to MPO deficiency. Interestingly, only the limited activation of markers related to apoptotic cell death was observed (e.g. caspase 8 activation, Bax expression) and they mostly did not correspond to phosphatidylserine surface exposure. Furthermore, a marker characterizing autophagy, cleavage of LC3 protein, as well as histone H3 citrullination and its surface expression was observed. Collectively, the data show the ability of MPO to modulate the life span of PMNs primarily through the potentiation of cell membrane permeabilization and phosphatidylserine surface exposure.
多形核粒细胞 (PMN) 在宿主防御中发挥关键作用。然而，它们在炎症部位的大量积累会延迟再生愈合过程，并引发病理性炎症过程。因此，通过诱导调节性细胞死亡来有效清除 PMN 是防止这些病理状况发展的关键过程。髓过氧化物酶 (MPO) 是 PMN 颗粒中含量丰富的酶，主要与 PMN 防御机制相关联，被认为在 PMN 调节性细胞死亡中发挥作用。然而，MPO 对 PMN 细胞死亡机制的贡献仍不完全清楚。本文研究了三种不同刺激物（佛波醇 12-肉豆蔻酸 13-乙酸酯 (PMA)、调理链球菌 (OST) 和 N-甲酰基甲硫氨酸亮氨酸苯丙氨酸 (fMLP)）诱导的小鼠 PMN 细胞死亡过程。MPO 缺陷型 PMN 表现出明显降低的细胞死亡率，其特征为磷脂酰丝氨酸表面暴露和细胞膜通透性增加。MPO 活性抑制剂 4-氨基苯甲酰基肼与 MPO 缺陷相比，对 PMA 诱导的细胞死亡没有显著影响。有趣的是，仅观察到与凋亡细胞死亡相关的标记物的有限激活（例如 caspase 8 激活、Bax 表达），并且它们大多与磷脂酰丝氨酸表面暴露不对应。此外，还观察到自噬的标志物，即 LC3 蛋白的切割，以及组蛋白 H3 瓜氨酸化及其表面表达。总的来说，这些数据表明 MPO 能够通过增强细胞膜通透性和磷脂酰丝氨酸表面暴露来调节 PMN 的寿命。
