Dihydroartemisinin enhances the inhibitory effect of sorafenib on HepG2 cells by inducing ferroptosis and inhibiting energy metabolism.

Although sorafenib (Sora) shows improved efficacy in clinical liver cancer therapy, its therapeutic efficacy is still greatly limited due to side effects as well as drug resistance. Thus new drug intervention strategies are imperative. Our research showed the combined application of Dihydroartemisinin (DHA) and Sora had a synergistic inhibitory effect on HepG2 and SW480 cells, and DHA enhanced Sora efficacy on xenograft tumor in nude mice. DHA and Sora significantly inhibited the cell energy metabolism by decreasing the ATP synthesis rate of oxidative phosphorylation and glycolysis rate, and induced ferroptosis by increasing the level of lipid reactive oxygen species (L-ROS), labile iron pool (LIP) as well as malondialdehyde (MDA) and decreasing the level of glutathione (GSH) in HepG2 cells. In addition, DHA and Sora significantly decreased the levels of SLC7A11 (xCT), GCLC, GPX4, and HO-1 protein in HepG2 cells. Importantly, the above-mentioned indicators changed more significantly after the combined application of DHA and Sora as compared with Sora. In conclusion, DHA and Sora had the same mechanism, and the combined application of them could have a synergistic anti-tumor effect by inducing ferroptosis and inhibiting energy metabolism in HepG2 cells.

Effects of dihydroartemisinin, a metabolite of artemisinin, on colon cancer chemoprevention and adaptive immune regulation.

BACKGROUND: Artemisinin (ART) is an anti-malaria natural compound with a moderate anticancer action. As a metabolite of ART, dihydroartemisinin (DHA) may have stronger anti-colorectal cancer (CRC) bioactivities. However, the effects of DHA and ART on CRC chemoprevention, including adaptive immune regulation, have not been systematically evaluated and compared. METHODS: Coupled with a newly-established HPLC analytical method, enteric microbiome biotransformation was conducted to identify if the DHA is a gut microbial metabolite of ART. The anti-CRC potential of these compounds was compared using two different human CRC cell lines for cell cycle arrest, apoptotic induction, and anti-inflammation activities. Naive CD4+ T cells were also obtained for testing the compounds on the differentiation of Treg, Th1 and Th17. RESULTS: Using compound extraction and analytical methods, we observed for the first time that ART completely converted into its metabolites by gut microbiome within 24 h, but no DHA was detected. Although ART did not obviously influence cancer cell growth in the concentration tested, DHA very significantly inhibited the cancer cell growth at relatively low concentrations. DHA included G2/M cell cycle arrest via upregulation of cyclin A and apoptosis. Both ART and DHA downregulated the pro-inflammatory cytokine expression. The DHA significantly promoted Treg cell proliferation, while both ART and DHA inhibited Th1 and Th17 cell differentiation. CONCLUSIONS: As a metabolite of ART, DHA possessed stronger anti-CRC activities. The DHA significantly inhibited cell growth via cell cycle arrest, apoptosis induction and anti-inflammation actions. The adaptive immune regulation is a related mechanism of actions for the observed effects.

Study towards improving artemisinin-based combination therapies.

Covering: Up to 2020 Artemisinin has made a significant contribution towards global malaria control since its initial discovery. Countless lives have been saved by this unique and miraculous molecule. In 2006, artemisinin-based combination therapies (ACTs) were recommended by the World Health Organization (WHO) as the first-line treatment for uncomplicated malaria infection and have since remained as the mainstays of the antimalarial treatment. Even so, substantial efforts to pursue better curative effects for the treatment of malaria have never ceased, particularly with regards to the circumstances surrounding the appearance of delayed clearance of malaria parasites by 3 day ACT treatments in South-East Asian countries. Strategies to further optimize artemisinin-based therapies, including synthesizing better artemisinin derivatives, developing advanced drug delivery systems, and diversifying artemisinin partner drugs, have been proposed over the past few years. Here, we provide an updated account of the continuous efforts in improving ACTs for better efficacy in curing malarial infection.

Analysis of spleen histopathology, splenocyte composition and haematological parameters in four strains of mice infected with Plasmodium berghei K173.

BACKGROUND: Malaria is a fatal disease that presents clinically as a continuum of symptoms and severity, which are determined by complex host-parasite interactions. Clearance of infection is believed to be accomplished by the spleen and mononuclear phagocytic system (MPS), independent of artemisinin treatment. The spleen filters infected red blood cells (RBCs) from circulation through immune-mediated recognition of the infected RBCs followed by phagocytosis. This study evaluated the tolerance of four different strains of mice to Plasmodium berghei strain K173 (P. berghei K173), and the differences in the role of the spleen in controlling P. berghei K173 infection. METHODS: Using different strains of mice (C57BL/6, BALB/C, ICR, and KM mice) infected with P. berghei K173, the mechanisms leading to splenomegaly, histopathology, splenocyte activation and proliferation, and their relationship to the control of parasitaemia and host mortality were examined and evaluated. RESULTS: Survival time of mice infected with P. berghei K173 varied, although the infection was uniformly lethal. Mice of the C57BL/6 strain were the most resistant, while mice of the strain ICR were the most susceptible. BALB/c and KM mice were intermediate. In the course of P. berghei K173 infection, all infected mice experienced significant splenomegaly. Parasites were observed in the red pulp at 3 days post infection (dpi) in all animals. All spleens retained late trophozoite stages as well as a fraction of earlier ring-stage parasites. The percentages of macrophages in infected C57BL/6 and KM mice were higher than uninfected mice on 8 dpi. Spleens of infected ICR and KM mice exhibited structural disorganization and remodelling. Furthermore, parasitaemia was significantly higher in KM versus C57BL/6 mice at 8 dpi. The percentages of macrophages in ICR infected mice were lower than uninfected mice, and the parasitaemia was higher than other strains. CONCLUSIONS: The results presented here demonstrate the rate of splenic mechanical filtration and that splenic macrophages are the predominant roles in controlling an individual's total parasite burden. This can influence the pathogenesis of malaria. Finally, different genetic backgrounds of mice have different splenic mechanisms for controlling malaria infection.

[Reasearch on lipid metabolism of Plasmodium and antimalarial mechanism of artemisinin].

As a unicellular organism, Plasmodium displays a panoply of lipid metabolism pathways that are seldom found together in a unicellular organism. These pathways mostly involve the Plasmodium-encoded enzymatic machinery and meet the requirements of membrane synthesis during the rapid cell growth and division throughout the life cycle. Different lipids have varied synthesis and meta-bolism pathways. For example, the major phospholipids are synthesized via CDP-diacylglycerol-dependent pathway in prokaryotes and de novo pathway in eukaryotes, and fatty acids are synthesized mainly via type Ⅱ fatty acid synthesis pathway. The available studies have demonstrated the impacts of artemisinin and its derivatives, the front-line compounds against malaria, on the lipid metabolism of Plasmodium. Therefore, this article reviewed the known lipid metabolism pathways and the effects of artemisinin and its derivatives on these pathways, aiming to deepen the understanding of lipid synthesis and metabolism in Plasmodium and provide a theoretical basis for the research on the mechanisms and drug resistance of artemisinin and other anti-malarial drugs.

Inhibitory Mechanisms of DHA/CQ on pH and Iron Homeostasis of Erythrocytic Stage Growth of Plasmodium Falciparum.

Malaria is an infectious disease caused by Plasmodium group. The mechanisms of antimalarial drugs DHA/CQ are still unclear today. The inhibitory effects (IC50) of single treatments with DHA/CQ or V-ATPase inhibitor Baf-A1 or combination treatments by DHA/CQ combined with Baf-A1 on the growth of Plasmodium falciparum strain 3D7 was investigated. Intracellular cytoplasmic pH and labile iron pool (LIP) were labeled by pH probe BCECF, AM and iron probe calcein, AM, the fluorescence of the probes was measured by FCM. The effects of low doses of DHA (0.2 nM, 0.4 nM, 0.8 nM) on gene expression of V-ATPases (vapE, vapA, vapG) located in the membrane of DV were tested by RT-qPCR. DHA combined with Baf-A1 showed a synergism effect (CI = 0.524) on the parasite growth in the concentration of IC50. Intracellular pH and irons were effected significantly by different doses of DHA/Baf-A1. Intracellular pH was decreased by CQ combined with Baf-A1 in the concentration of IC50. Intracellular LIP was increased by DHA combined with Baf-A1 in the concentration of 20 IC50. The expression of gene vapA was down-regulated by all low doses of DHA (0.2/0.4/0.8 nM) significantly (p < 0.001) and the expression of vapG/vapE were up-regulated by 0.8 nM DHA significantly (p < 0.001). Interacting with ferrous irons, affecting the DV membrane proton pumping and acidic pH or cytoplasmic irons homeostasis may be the antimalarial mechanism of DHA while CQ showed an effect on cytoplasmic pH of parasite in vitro. Lastly, this article provides us preliminary results and a new idea for antimalarial drugs combination and new potential antimalarial combination therapies.

[Research progress on heme metabolism in intraerythrocytic plasmodium].

Heme is a key metabolic factor in all life. Malaria parasite has de novo heme-biosynthetic pathway, however the growth and development of parasite depend on the hemoglobin-derived heme metabolism process during the intraerythrocytic stages, such as the ingestion and degradation of hemoglobin in the food vacuole. The hemoglobin metabolism in the food vesicles mainly includes four aspects: hemoglobin transport and intake, hemoglobin enzymolysis to produce heme, heme polymerization into malarial pigment, and heme transport via the food vacuole. The potential mechanisms of antimalarial drugs,such as chloroquine, artemisinin and atovaquone may be related to this process. The main four aspects of this metabolic process, key metabolic enzymes, effects of antimalarial drugs on the process and their potential mechanism of action would be summarized in this paper, providing ideas for rational use and mechanism exploration of similar drugs.

[Ferroptosis pathway and its intervention regulated by Chinese materia medica].

Ferroptosis is a new form of regulated cell death which is different from apoptosis, necrosis and autophagy, and results from iron-dependent lipidperoxide accumulation. Now, it is found that ferroptosis is involved in multiple physiological and pathological processes, such as cancer, arteriosclerosis, neurodegenerative diseases, diabetes, antiviral immune response, acute renal failure, hepatic and heart ischemia/reperfusion injury. On the one hand, it could be found the appropriate drugs to promote ferroptosis to clear cancer cells and virus infected cells, etc. On the other hand, we could inhibit ferroptosis to protect healthy cells. China has a wealth of traditional Chinese medicine resources. Chinese medicine contains a variety of active ingredients that regulate ferroptosis. Here, this paper reported the research of ferroptosis pathway, targets of its inducers and inhibitors that have been discovered, and the regulatory effects of the discovered Chinese herbs and its active ingredients on ferroptosis to help clinical and scientific research.