BACKGROUND Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is hallmarked by a significant reduction in natural killer (NK) cell cytotoxicity, a mechanism tightly regulated by calcium (Ca2+). Interestingly, interleukin-2 (IL-2) increases NK cell cytotoxicity. Transient receptor potential melastatin 2 (TRPM2) ion channels are fundamental for Ca2+ signalling in NK cells. This pilot investigation aimed to characterise TRPM2 and CD38 surface expression in vitro on NK cells in ME/CFS patients. This investigation furthermore examined the pharmaceutical effect of 8-bromoadenosine phosphoribose (8-Br-ADPR) and N6-Benzoyladenosine-3',5'-cyclic monophosphate (N6-Bnz-cAMP) on TRPM2 and CD38 surface expression and NK cell cytotoxicity between ME/CFS and healthy control (HC) participants. METHODS Ten ME/CFS patients (43.45 ± 12.36) and 10 HCs (43 ± 12.27) were age and sex-matched. Isolated NK cells were labelled with fluorescent antibodies to determine baseline and drug-treated TRPM2 and CD38 surface expression on NK cell subsets. Following IL-2 stimulation, NK cell cytotoxicity was measured following 8-Br-ADPR and N6-Bnz-cAMP drug treatments by flow cytometry. RESULTS Baseline TRPM2 and CD38 surface expression was significantly higher on NK cell subsets in ME/CFS patients compared with HCs. Post IL-2 stimulation, TRPM2 and CD38 surface expression solely decreased on the CD56DimCD16+ subset. 8-Br-ADPR treatment significantly reduced TRPM2 surface expression on the CD56BrightCD16Dim/- subset within the ME/CFS group. Baseline cell cytotoxicity was significantly reduced in ME/CFS patients, however no changes were observed post drug treatment in either group. CONCLUSION Overexpression of TRPM2 on NK cells may function as a compensatory mechanism to alert a dysregulation in Ca2+ homeostasis to enhance NK cell function in ME/CFS, such as NK cell cytotoxicity. As no improvement in NK cell cytotoxicity was observed within the ME/CFS group, an impairment in the TRPM2 ion channel may be present in ME/CFS patients, resulting in alterations in [Ca2+]i mobilisation and influx, which is fundamental in driving NK cell cytotoxicity. Differential expression of TRPM2 between NK cell subtypes may provide evidence for their role in the pathomechanism involving NK cell cytotoxicity activity in ME/CFS.

中文翻译：

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在肌性脑脊髓炎/慢性疲劳综合征患者中，瞬时受体潜在的褪黑素2通道过表达。

背景技术肌炎性脑脊髓炎/慢性疲劳综合症（ME / CFS）的特征在于自然杀伤（NK）细胞的细胞毒性显着降低，而自然杀伤（NK）细胞的毒性由钙（Ca2 +）严格调节。有趣的是，白介素2（IL-2）增加了NK细胞的细胞毒性。瞬时受体电位褪黑素2（TRPM2）离子通道是NK细胞中Ca2 +信号传导的基础。这项初步研究旨在表征ME / CFS患者中NK细胞在体外的TRPM2和CD38表面表达的特征。这项研究进一步检查了8-溴腺苷磷酸核糖（8-Br-ADPR）和N6-苄基腺苷-3'，5'-环一磷酸酯（N6-Bnz-cAMP）对TRPM2和CD38表面表达以及NK细胞之间的细胞毒性的药理作用ME / CFS和健康控制（HC）参与者。方法10例ME / CFS患者（43.45±12。年龄和性别相匹配的人中有36位）和10位HC（43±12.27）岁。用荧光抗体标记分离的NK细胞，以确定在NK细胞亚群上的基线以及经药物处理的TRPM2和CD38表面表达。在IL-2刺激后，通过流式细胞仪检测8-Br-ADPR和N6-Bnz-cAMP药物治疗后，NK细胞的细胞毒性。结果与HC相比，ME / CFS患者NK细胞亚群的基线TRPM2和CD38表面表达明显更高。IL-2刺激后，TRPM2和CD38表面表达仅在CD56DimCD16 +子集上降低。8-Br-ADPR治疗显着降低了ME / CFS组CD56BrightCD16Dim /-亚组上TRPM2表面的表达。ME / CFS患者的基线细胞毒性明显降低，但是两组药物治疗后均未观察到变化。结论NK细胞上TRPM2的过度表达可能是一种补偿机制，可提醒Ca2 +稳态失调，从而增强ME / CFS中NK细胞的功能，例如NK细胞的细胞毒性。由于在ME / CFS组中未观察到NK细胞的细胞毒性改善，因此ME / CFS患者中TRPM2离子通道可能受损，导致[Ca2 +] i动员和内流改变，这是驱动NK的基础细胞的细胞毒性。NK细胞亚型之间TRPM2的差异表达可能为它们在涉及ME / CFS中NK细胞细胞毒性活性的病理机制中的作用提供证据。由于在ME / CFS组中未观察到NK细胞的细胞毒性改善，因此ME / CFS患者中TRPM2离子通道可能受损，导致[Ca2 +] i动员和内流改变，这是驱动NK的基础细胞的细胞毒性。NK细胞亚型之间TRPM2的差异表达可能为它们在涉及ME / CFS中NK细胞细胞毒性活性的病理机制中的作用提供证据。由于在ME / CFS组中未观察到NK细胞的细胞毒性改善，因此ME / CFS患者中TRPM2离子通道可能受损，导致[Ca2 +] i动员和内流改变，这是驱动NK的基础细胞的细胞毒性。NK细胞亚型之间TRPM2的差异表达可能为它们在涉及ME / CFS中NK细胞细胞毒性活性的病理机制中的作用提供证据。