Phosphorylation of eukaryotic initiation factor-2α in response to endoplasmic reticulum and nitrosative stress in the human protozoan parasite, Entamoeba histolytica

Acrylamide-Aggravated Liver Injury by Activating Endoplasmic Reticulum Stress in Female Mice with Diabetes

Acrylamide (ACR) is a common industrial contaminant with endocrine-disrupting toxicity. Numerous studies have indicated that females and diabetics are more sensitive to environmental contaminants. However, it remains unknown whether female diabetics are susceptible to ACR-induced toxicity and its potential mechanisms. Thus, the female ACR-exposure diabetic Balb/c mice model was established to address these issues. Results showed that ACR could induce liver injury in normal mice and cause more serious inflammatory cell infiltration, hepatocyte volume increase, and fusion in diabetic mice liver. Meanwhile, ACR could lead to exacerbation of diabetic symptoms in diabetic mice by disturbing the glucose and lipid metabolism in the liver, which mainly manifests as the accumulation of liver glycogen and liver lipids, the reduction of the activity/content of glycolytic and metabolizing enzyme as well as pentose phosphatase, upregulation of the gene expression in fatty acid transporter and gluconeogenesis, and downregulation of the gene expression in fatty acid synthesis and metabolism. Moreover, ACR exposure could induce oxidative stress, inflammation, and endoplasmic reticulum stress in the liver by a decrease in hepatic antioxidant enzyme activity and antioxidant content, an increase in inflammatory factor levels, and a change in the related protein expression of endoplasmic reticulum stress (ERS) and apoptosis-related pathways in diabetic mice. Statistical analysis results revealed that ACR-induced liver injury was highly correlated with inflammation and oxidative stress, and ERS and diabetic mice had a higher risk of liver injury than normal mice. Overall results suggested that female diabetic mice easily suffer from ACR-induced toxicity, and the reason was that ACR could induce further damage to the liver by worsening the condition of inflammation, oxidative stress, and ERS in the liver.

Encystation and Stress Responses under the Control of Ubiquitin-like Proteins in Pathogenic Amoebae

Amoebae found in aquatic and terrestrial environments encompass various pathogenic species, including the parasite Entamoeba histolytica and the free-living Acanthamoeba castellanii. Both microorganisms pose significant threats to public health, capable of inducing life-threatening effects on humans. These amoebae exist in two cellular forms: trophozoites and cysts. The trophozoite stage is the form used for growth and reproduction while the cyst stage is the resistant and disseminating form. Cysts occur after cellular metabolism slowdown due to nutritional deprivation or the appearance of environmental conditions unfavourable to the amoebae's growth and division. The initiation of encystation is accompanied by the activation of stress responses, and scarce data indicate that encystation shares factors and mechanisms identified in stress responses occurring in trophozoites exposed to toxic compounds derived from human immune defence. Although some "omics" analyses have explored how amoebae respond to diverse stresses, these studies remain limited and rarely report post-translational modifications that would provide knowledge on the molecular mechanisms underlying amoebae-specific stress responses. In this review, we discuss ubiquitin-like proteins associated with encystation and cell survival during oxidative damage. We aim to shed light on the signalling pathways involved in amoebic defence mechanisms, with a focus on their potential clinical implications against pathogenic amoebae, addressing the pressing need for effective therapies.

Eukaryotic Initiation Factor 2α Kinases Regulate Virulence Functions, Stage Conversion, and the Stress Response in Entamoeba invadens

Entamoeba histolytica is a protozoan parasite that causes amoebic dysentery and liver abscess. This pathogen possesses a two-stage life cycle consisting of an environmentally stable cyst and a pathogenic amoeboid trophozoite. Since infection is acquired by ingestion of cysts from contaminated food and water, this parasite is prevalent in underdeveloped countries. A reptilian pathogen, Entamoeba invadens, which can encyst in culture, has long served as a surrogate to study stage conversion. In the host, Entamoeba species must manage stress, including nutrient deprivation and host immune pressure. In many systems, the stress response is characterized by downregulation of translation, which is initiated by the phosphorylation of eukaryotic initiation factor-2 alpha (eIF2α). In mammalian cells, this phosphorylation is carried out by a family of eIF2α kinases. A canonical eIF2α translational control system exists in Entamoeba species; however, no eIF2α kinases have been characterized. In this study, we identified two eIF2α kinases in E. invadens, EiIF2K-A and EiIF2K-B. Their identity as eIF2α kinases was validated using a heterologous yeast system. We used an RNA interference (RNAi) trigger-mediated silencing system to reduce expression of EiIF2K-A, which also reduced expression of EiIF2K-B. Parasites with decreased kinase expression exhibited decreased phosphorylation of eIF2α and increased sensitivity to oxidative stress. Diminished kinase expression also correlated with an increased rate of encystation, a decreased rate of excystation, and an increase in several virulence functions, erythrophagocytosis and adhesion to host cells. Taken together, these data suggest that EiIF2K-A and EiIF2K-B are authentic eIF2α kinases that may regulate the Entamoeba stress response.

IMPORTANCEEntamoeba histolytica is a human pathogen that causes dysentery and affects millions of people worldwide. This parasite possesses a two-stage life cycle: an environmentally stable cyst and the pathogenic trophozoite. Cysts are ingested from contaminated food and water; thus, this parasite in prevalent in underdeveloped countries. Current therapies commonly cause adverse side effects; therefore, new treatments are needed. In the host, Entamoeba experiences stress brought on, in part, by the host immune system. Understanding stage conversion and the stress response of this pathogen may lead to new drug therapies. Using the model organism E. invadens, we identified two kinases similar to those involved in stress and stage conversion in other systems. We determined that these kinases may regulate the oxidative stress response, stage conversion, and virulence. This work is significant, as it will inform future studies on the life cycle and pathogenicity of Entamoeba species.

Endoplasmic Reticulum Stress, a Target for Drug Design and Drug Resistance in Parasitosis

Endoplasmic reticulum stress (ER stress) can be induced when cellular protein homeostasis is damaged, and cells can activate the unfolded protein response (UPR) to restore protein homeostasis or induce cell death to facilitate the survival of the whole system. Globally, parasites are a constant threat to human health and are therefore considered a serious public health problem. Parasitic infection can cause ER stress in host cells, and parasites also possess part or all of the UPR under ER stress conditions. In this review, we aim to clarify the role of ER stress pathways and related molecules in parasites for their survival and development, the pathogenesis of parasitosis in hosts, and the artemisinin resistance of Plasmodium, which provides some potential drug design targets to inhibit survival of parasites, relieves pathological damage of parasitosis, and solves the problem of artemisinin resistance.

FAM134B-mediated endoplasmic reticulum autophagy protects against sepsis myocardial injury in mice

Reticulophagy regulator 1 (RETEG1, also known as FAM134B) plays a crucial role in endoplasmic reticulum autophagy. We aimed to explore the effect of FAM134B-mediated endoplasmic reticulum autophagy in sepsis myocardial injury in mice. Sepsis myocardial injury mice were established via cecal ligation and puncture procedures. The expression of FAM134B and LC3-II/I was determined using immunohistochemistry. Myocardial tissue morphological changes and apoptosis were examined using hematoxylin and eosin (H&E) staining and TUNEL analysis. The effects of FAM134B knockdown or overexpression on mice with sepsis myocardial injury were also studied. The levels of TNF-α, IL-6, IL-8, and IL-10 were evaluated using enzyme-linked immunosorbent assay (ELISA). Autophagy- and apoptosis-related protein expression was detected using western blotting. The effect of FAM134B on Lipopolysaccharide (LPS) -induced cardiomyocytes was also studied. The expression of FAM134B and LC3-II/I increased in sepsis mice and lipopolysaccharide (LPS)-treated cardiomyocytes. 3-Methyladenine (3-MA) significantly inhibited FAM134B and LC3-II/I expression and promoted myocardial injury, inflammation response, and cardiomyocyte apoptosis. The overexpression of FAM134B could minimize myocardial injury, inflammation, and apoptosis, whereas FAM134B knockdown showed opposite effects. FAM134B-mediated endoplasmic reticulum autophagy had a protective effect on sepsis myocardial injury in mice by reducing inflammation and tissue apoptosis, which may provide new insights for sepsis myocardial injury therapies.

Entamoeba histolytica-Gut Microbiota Interaction: More Than Meets the Eye

Amebiasis is a disease caused by the unicellular parasite Entamoeba histolytica. In most cases, the infection is asymptomatic but when symptomatic, the infection can cause dysentery and invasive extraintestinal complications. In the gut, E. histolytica feeds on bacteria. Increasing evidences support the role of the gut microbiota in the development of the disease. In this review we will discuss the consequences of E. histolytica infection on the gut microbiota. We will also discuss new evidences about the role of gut microbiota in regulating the resistance of the parasite to oxidative stress and its virulence.