Melatonin and its indoles derivatives are central in the synchronization of malaria parasites. In this research, we discovered that melatonin is unable to increase the parasitemia in the human malaria Plasmodium falciparum that lacks the kinase PfeIK1. The PfeIK1 knockout strain is a valuable tool in the screening of indol‐related compound that blocks the melatonin effect in wild‐type (WT) parasite development. The assays were performed by using flow cytometry with simultaneous labeling for mitochondria viability with MitoTracker Deep Red and nucleus staining with SYBR Green. We found that Melatotosil leads to an increase in parasitemia in P. falciparum and blocks melatonin effect in the WT parasite. Using microscopy imaging system, we found that Melatotosil at 500 nM is able to induce cytosolic calcium rise in transgenic PfGCaMP3 parasites. On the contrary, the compound Triptiofen blocks P. falciparum cell cycle with IC₅₀ 9.76 µM ± 0.6, inhibits melatonin action, and does not lead to a cytosolic calcium rise in PfGCaMP3 parasites. We also found that the synthetic indol‐related compounds arrested parasite cycle for PfeIK1 knockout and (WT) P. falciparum (3D7) in 72 hours culture assays with the IC₅₀ values slighting lower for the WT strain. We concluded that the kinase PfeIK1 is central for melatonin downstream signaling pathways involved in parasite cell cycle progression. More importantly, the indol‐related compounds block its cycle as an upstream essential mechanism for parasite survival. Our data clearly show that this class of compounds emerge as an alternative for the problem of resistance with the classical antimalarials.

中文翻译：

---

恶性疟原虫 eIK1 激酶 (PfeIK1) 是人类疟原虫褪黑激素同步的核心。Melatotosil 阻断褪黑激素对寄生虫细胞周期的作用。

褪黑激素及其吲哚衍生物是疟疾寄生虫同步的核心。在这项研究中，我们发现褪黑激素无法增加缺乏激酶 PfeIK1的人类疟疾恶性疟原虫的寄生虫血症。PfeIK1 敲除菌株是筛选抑制野生型 (WT) 寄生虫发育中的褪黑激素作用的吲哚相关化合物的宝贵工具。这些测定是通过使用流式细胞术进行的，同时使用 MitoTracker Deep Red 标记线粒体活力，并使用 SYBR Green 进行细胞核染色。我们发现 Melatotosil 导致恶性疟原虫的寄生虫血症增加并阻止 WT 寄生虫中的褪黑激素作用。使用显微镜成像系统，我们发现 500 nM 的 Melatotosil 能够诱导转基因 PfGCaMP3 寄生虫的细胞溶质钙升高。相反，化合物 Triptiofen以 IC ₅₀ 9.76 µM ± 0.6阻断 恶性疟原虫细胞周期，抑制褪黑激素作用，并且不会导致 PfGCaMP3 寄生虫的细胞溶质钙升高。我们还发现，在使用 IC _{50 的}72 小时培养测定中，合成的吲哚相关化合物阻止了 PfeIK1 敲除和（WT）恶性疟原虫（3D7）的寄生虫周期WT 应变的值略低。我们得出结论，激酶 PfeIK1 是参与寄生虫细胞周期进程的褪黑激素下游信号通路的核心。更重要的是，吲哚相关化合物阻断了其作为寄生虫生存上游基本机制的循环。我们的数据清楚地表明，这类化合物是解决经典抗疟药耐药问题的替代方案。