Suppression of host p53 is critical for Plasmodium liver-stage infection

p53-regulated non-apoptotic cell death pathways and their relevance in cancer and other diseases

Programmed cell death is a mechanism that is crucial for numerous physiological and pathological processes. Whereas p53-mediated apoptosis is a major cell death pathway in cancer, accumulating evidence indicates that p53 also has crucial roles in controlling different non-apoptotic cell death (NACD) pathways, including ferroptosis, necroptosis, pyroptosis, autophagy-dependent cell death, entotic cell death, parthanatos and paraptosis, and may regulate PANoptosis, cuproptosis and disulfidptosis. Notably, the function of p53 in these NACDs substantially contributes to its biological effects, particularly in cancer development and other pathological processes. In this Review, we discuss recent advances in understanding the roles and underlying mechanisms of p53-mediated NACDs, focusing on ferroptosis, necroptosis and pyroptosis. We discuss the complex and distinct physiological settings in which NACDs are regulated by p53, and potential targeting of p53-regulated NACDs for the treatment of cancer and other human diseases. Finally, we highlight several important questions concerning p53-regulated NACDs that warrant further investigation.

Plasmodium infection downregulates hypoxia‑inducible factor 1α expression to suppress the vascularization and tumorigenesis of liver cancer

Liver cancer is characterized by hypervascularization. Anti-angiogenic agents may normalize the tumor vasculature and improve the efficacy of other treatments. The present study aims to investigate the anti-angiogenic effect of Plasmodium infection in a mouse model of implanted liver cancer cells. HepG2 cells were injected into the left liver lobe of nude mice as a model of in situ hepatic tumorigenesis. Plasmodium yoelii parasitized erythrocytes were administered in the animal model of liver cancer to introduce Plasmodium infection. The tumor growth and microvascular density were determined in the presence or absence of Plasmodium infection. The expression levels of hypoxia-inducible factor 1α (HIF-1α) and angiogenesis-related factors were evaluated using western blotting and reverse transcription-quantitative PCR analysis. The results demonstrated that Plasmodium infection suppressed tumor growth and vascularization in the mouse model of implanted HepG2 cells. Plasmodium parasites reduced the expression of pro-angiogenic factors (vascular endothelial growth factor A and angiopoietin 2), matrix metalloproteinases [(MMP)2 and MMP9] and inflammatory cytokines [tumor necrosis factor α, interleukin 6 (IL)-6) and IL-1β] in both hepatic and tumor tissues. HIF-1α was downregulated in both hepatic and tumor tissues upon Plasmodium infection, and HIF-1α overexpression rescued angiogenesis and tumor growth under the condition of Plasmodium infection. In conclusion, the results of the present study demonstrated the anti-angiogenic and anti-tumorigenic effects of Plasmodium infection on liver cancer through downregulating HIF-1α expression, indicating that Plasmodium parasites could be developed as an intervention strategy to restrain neo-angiogenesis in liver cancer.

Can artemisinin and its derivatives treat malaria in a host-directed manner?

Malaria is caused by an apicomplexan protozoan parasite, Plasmodium, and is transmitted through vectors. It remains a substantial health burden, especially in developing countries, leading to significant socioeconomic losses. Although the World Health Organization (WHO) has approved various antimalarial medications in the past two decades, the increasing resistance to these medications has worsened the situation. The development of drug resistance stems from genetic diversity among Plasmodium strains, impeding eradication efforts. Consequently, exploring innovative technologies and strategies for developing effective medications based on the host is crucial. Artemisinin and its derivatives (artemisinins) have been recommended by the WHO for treating malaria owing to their known effectiveness in killing the parasite. However, their potential to target the host for malaria treatment has not been investigated. This article concisely reviews the application of host-directed therapeutics, potential drug candidates targeting the host for treating malaria, and usage of artemisinins in numerous diseases. It underscores the importance of host-directed interventions for individuals susceptible to malaria, suggests the potential utility of artemisinins in host-directed malaria treatments, and posits that the modulation of host proteins with artemisinins may offer a means of intervening in host-parasite interactions. Further studies focusing on the host-targeting perspective of artemisinins can provide new insights into the mechanisms of artemisinin resistance and offer a unique opportunity for new antimalarial drug discovery.

Hepatocytes and the art of killing Plasmodium softly

The Plasmodium parasites that cause malaria undergo asymptomatic development in the parenchymal cells of the liver, the hepatocytes, prior to infecting erythrocytes and causing clinical disease. Traditionally, hepatocytes have been perceived as passive bystanders that allow hepatotropic pathogens such as Plasmodium to develop relatively unchallenged. However, now there is emerging evidence suggesting that hepatocytes can mount robust cell-autonomous immune responses that target Plasmodium, limiting its progression to the blood and reducing the incidence and severity of clinical malaria. Here we discuss our current understanding of hepatocyte cell-intrinsic immune responses that target Plasmodium and how these pathways impact malaria.

The antimicrobial activity of innate host-directed therapies: A systematic review

Intracellular human pathogens are the deadliest infectious diseases and are difficult to treat effectively due to their protection inside the host cell and the development of antimicrobial resistance (AMR). An emerging approach to combat these intracellular pathogens is host-directed therapies (HDT), which harness the innate immunity of host cells. HDT rely on small molecules to promote host protection mechanisms that ultimately lead to pathogen clearance. These therapies are hypothesized to: (1) possess indirect yet broad, cross-species antimicrobial activity, (2) effectively target drug-resistant pathogens, (3) carry a reduced susceptibility to the development of AMR and (4) have synergistic action with conventional antimicrobials. As the field of HDT expands, this systematic review was conducted to collect a compendium of HDT and their characteristics, such as the host mechanisms affected, the pathogen inhibited, the concentrations investigated and the magnitude of pathogen inhibition. The evidential support for the main four HDT hypotheses was assessed and concluded that HDT demonstrate robust cross-species activity, are active against AMR pathogens, clinical isolates and laboratory-adapted pathogens. However, limited information exists to support the notion that HDT are synergistic with canonical antimicrobials and are less predisposed to AMR development.

Translating p53-based therapies for cancer into the clinic

Inactivation of the most important tumour suppressor gene TP53 occurs in most, if not all, human cancers. Loss of functional wild-type p53 is achieved via two main mechanisms: mutation of the gene leading to an absence of tumour suppressor activity and, in some cases, gain-of-oncogenic function; or inhibition of the wild-type p53 protein mediated by overexpression of its negative regulators MDM2 and MDMX. Because of its high potency as a tumour suppressor and the dependence of at least some established tumours on its inactivation, p53 appears to be a highly attractive target for the development of new anticancer drugs. However, p53 is a transcription factor and therefore has long been considered undruggable. Nevertheless, several innovative strategies have been pursued for targeting dysfunctional p53 for cancer treatment. In mutant p53-expressing tumours, the predominant strategy is to restore tumour suppressor function with compounds acting either in a generic manner or otherwise selective for one or a few specific p53 mutations. In addition, approaches to deplete mutant p53 or to target vulnerabilities created by mutant p53 expression are currently under development. In wild-type p53 tumours, the major approach is to protect p53 from the actions of MDM2 and MDMX by targeting these negative regulators with inhibitors. Although the results of at least some clinical trials of MDM2 inhibitors and mutant p53-restoring compounds are promising, none of the agents has yet been approved by the FDA. Alternative strategies, based on a better understanding of p53 biology, the mechanisms of action of compounds and treatment regimens as well as the development of new technologies are gaining interest, such as proteolysis-targeting chimeras for MDM2 degradation. Other approaches are taking advantage of the progress made in immune-based therapies for cancer. In this Review, we present these ongoing clinical trials and emerging approaches to re-evaluate the current state of knowledge of p53-based therapies for cancer.

Ghrelin regulating liver activity and its potential effects on liver fibrosis and Echinococcosis

Ghrelin widely exists in the central nervous system and peripheral organs, and has biological activities such as maintaining energy homeostasis, regulating lipid metabolism, cell proliferation, immune response, gastrointestinal physiological activities, cognition, memory, circadian rhythm and reward effects. In many benign liver diseases, it may play a hepatoprotective role against steatosis, chronic inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress and apoptosis, and improve liver cell autophagy and immune response to improve disease progression. However, the role of Ghrelin in liver Echinococcosis is currently unclear. This review systematically summarizes the molecular mechanisms by which Ghrelin regulates liver growth metabolism, immune-inflammation, fibrogenesis, proliferation and apoptosis, as well as its protective effects in liver fibrosis diseases, and further proposes the role of Ghrelin in liver Echinococcosis infection. During the infectious process, it may promote the parasitism and survival of parasites on the host by improving the immune-inflammatory microenvironment and fibrosis state, thereby accelerating disease progression. However, there is currently a lack of targeted in vitro and in vivo experimental evidence for this viewpoint.

Association of apoptosis-related variants to malaria infection and parasite density in individuals from the Brazilian Amazon

BACKGROUND

In malaria infection, apoptosis acts as an important immunomodulatory mechanism that leads to the elimination of parasitized cells, thus reducing the parasite density and controlling immune cell populations. Here, it was investigated the association of INDEL variants in apoptotic genes-rs10562972 (FAS), rs4197 (FADD), rs3834129 and rs59308963 (CASP8), rs61079693 (CASP9), rs4647655 (CASP3), rs11269260 (BCL-2), and rs17880560 (TP53)-and the influence of genetic ancestry with susceptibility to malaria and parasite density in an admixed population from the Brazilian Amazon.

METHODS

Total DNA was extracted from 126 malaria patients and 101 uninfected individuals for investigation of genetic ancestries and genotypic distribution of apoptosis-related variants by Multiplex PCR. Association analyses consisted of multivariate logistic regressions, considering the following comparisons: (i) DEL/DEL genotype vs. INS/DEL + INS/INS; and (ii) INS/INS vs. INS/DEL + DEL/DEL.

RESULTS

Individuals infected by Plasmodium falciparum had significantly higher African ancestry proportions in comparison to uninfected controls, Plasmodium vivax, and mixed infections. The INS/INS genotype of rs3834129 (CASP8) seemed to increase the risk for P. falciparum infection (P = 0.038; OR = 1.867; 95% CI 0.736-3.725), while the DEL/DEL genotype presented a significant protective effect against infection by P. falciparum (P = 0.049; OR = 0.446; 95% CI 0.185-0.944) and mixed infection (P = 0.026; OR = 0.545; 95% CI 0.281-0.996), and was associated with lower parasite density in P. falciparum malaria (P = 0.009; OR = 0.383; 95% CI 0.113-1.295). Additionally, the INS/INS genotype of rs10562972 (FAS) was more frequent among individuals infected with P. vivax compared to P. falciparum (P = 0.036; OR = 2.493; 95% CI 1.104-4.551), and the DEL/DEL genotype of rs17880560 (TP53) was significantly more present in patients with mono-infection by P. vivax than in individuals with mixed infection (P = 0.029; OR = 0.667; 95% CI 0.211-1.669).

CONCLUSIONS

In conclusion, variants in apoptosis genes are associated with malaria susceptibility and parasite density, indicating the role of apoptosis-related genetic profiles in immune responses against malaria infection.

Neither the African-Centric S47 Nor P72 Variant of TP53 Is Associated With Reduced Risk of Febrile Malaria in a Malian Cohort Study

BACKGROUND

TP53 has been shown to play a role in inflammatory processes, including malaria. We previously found that p53 attenuates parasite-induced inflammation and predicts clinical protection to Plasmodium falciparum infection in Malian children. Here, we investigated whether p53 codon 47 and 72 polymorphisms are associated with differential risk of P. falciparum infection and uncomplicated malaria in a prospective cohort study of malaria immunity.

METHODS

p53 codon 47 and 72 polymorphisms were determined by sequencing TP53 exon 4 in 631 Malian children and adults enrolled in the Kalifabougou cohort study. The effects of these polymorphisms on the prospective risk of febrile malaria, incident parasitemia, and time to fever after incident parasitemia over 6 months of intense malaria transmission were assessed using Cox proportional hazards models.

RESULTS

Confounders of malaria risk, including age and hemoglobin S or C, were similar between individuals with or without p53 S47 and R72 polymorphisms. Relative to their respective common variants, neither S47 nor R72 was associated with differences in prospective risk of febrile malaria, incident parasitemia, or febrile malaria after parasitemia.

CONCLUSIONS

These findings indicate that p53 codon 47 and 72 polymorphisms are not associated with protection against incident P. falciparum parasitemia or uncomplicated febrile malaria.

Mechanism of Immune Evasion in Mosquito-Borne Diseases

In recent decades, mosquito-borne illnesses have emerged as a major health burden in many tropical regions. These diseases, such as malaria, dengue fever, chikungunya, yellow fever, Zika virus infection, Rift Valley fever, Japanese encephalitis, and West Nile virus infection, are transmitted through the bite of infected mosquitoes. These pathogens have been shown to interfere with the host's immune system through adaptive and innate immune mechanisms, as well as the human circulatory system. Crucial immune checkpoints such as antigen presentation, T cell activation, differentiation, and proinflammatory response play a vital role in the host cell's response to pathogenic infection. Furthermore, these immune evasions have the potential to stimulate the human immune system, resulting in other associated non-communicable diseases. This review aims to advance our understanding of mosquito-borne diseases and the immune evasion mechanisms by associated pathogens. Moreover, it highlights the adverse outcomes of mosquito-borne disease.

Phospholipase A and acyltransferase 4/retinoic acid receptor responder 3 at the intersection of tumor suppression and pathogen restriction

Phospholipase A and acyltransferase (PLAAT) 4 is a class II tumor suppressor with phospholipid metabolizing abilities. It was characterized in late 2000s, and has since been referred to as 'tazarotene-induced gene 3' (TIG3) or 'retinoic acid receptor responder 3' (RARRES3) as a key downstream effector of retinoic acid signaling. Two decades of research have revealed the complexity of its function and regulatory roles in suppressing tumorigenesis. However, more recent findings have also identified PLAAT4 as a key anti-microbial effector enzyme acting downstream of interferon regulatory factor 1 (IRF1) and interferons (IFNs), favoring protection from virus and parasite infections. Unveiling the molecular mechanisms underlying its action may thus open new therapeutic avenues for the treatment of both cancer and infectious diseases. Herein, we aim to summarize a brief history of PLAAT4 discovery, its transcriptional regulation, and the potential mechanisms in tumor prevention and anti-pathogen defense, and discuss potential future directions of PLAAT4 research toward the development of therapeutic approaches targeting this enzyme with pleiotropic functions.

Autophagy in protists and their hosts: When, how and why?

Pathogenic protists are a group of organisms responsible for causing a variety of human diseases including malaria, sleeping sickness, Chagas disease, leishmaniasis, and toxoplasmosis, among others. These diseases, which affect more than one billion people globally, mainly the poorest populations, are characterized by severe chronic stages and the lack of effective antiparasitic treatment. Parasitic protists display complex life-cycles and go through different cellular transformations in order to adapt to the different hosts they live in. Autophagy, a highly conserved cellular degradation process, has emerged as a key mechanism required for these differentiation processes, as well as other functions that are crucial to parasite fitness. In contrast to yeasts and mammals, protist autophagy is characterized by a modest number of conserved autophagy-related proteins (ATGs) that, even though, can drive the autophagosome formation and degradation. In addition, during their intracellular cycle, the interaction of these pathogens with the host autophagy system plays a crucial role resulting in a beneficial or harmful effect that is important for the outcome of the infection. In this review, we summarize the current state of knowledge on autophagy and other related mechanisms in pathogenic protists and their hosts. We sought to emphasize when, how, and why this process takes place, and the effects it may have on the parasitic cycle. A better understanding of the significance of autophagy for the protist life-cycle will potentially be helpful to design novel anti-parasitic strategies.

Inhibition of mycobacteria proliferation in macrophages by low cisplatin concentration through phosphorylated p53-related apoptosis pathway

BACKGROUND

Drug resistance is a prominent problem in the treatment of tuberculosis, so it is urgent to develop new anti- tuberculosis drugs. Here, we investigated the effects and mechanisms of cisplatin (DDP) on intracellular Mycobacterium smegmatis to tap the therapeutic potential of DDP in mycobacterial infection.

RESULTS

Macrophages infected with Mycobacterium smegmatis were treated with DDP alone or combined with isoniazid or rifampicin. The results showed that the bacterial count in macrophages decreased significantly after DDP (≤ 6 μg/mL) treatment. When isoniazid or rifampicin was combined with DDP, the number of intracellular mycobacteria was also significantly lower than that of isoniazid or rifampicin alone. Apoptosis of infected cells increased after 24 h of DDP treatment, as shown by flow cytometry and transmission electron microscopy detection. Transcriptome sequencing showed that there were 1161 upregulated and 645 downregulated differentially expressed genes (DEGs) between the control group and DDP treatment group. A Trp53-centered protein interaction network was found based on the top 100 significant DEGs through STRING and Cytoscape software. The expression of phosphorylated p53, Bax, JAK, p38 MAPK and PI3K increased after DDP treatment, as shown by Western blot analysis. Inhibitors of JAK, PI3K or p38 MAPK inhibited the increase in cell apoptosis and the reduction in the intracellular bacterial count induced by DDP. The p53 promoter Kevetrin hydrochloride scavenges intracellular mycobacteria. If combined with DDP, Kevetrin hydrochloride could increase the effect of DDP on the elimination of intracellular mycobacteria. In conclusion, DDP at low concentrations could activate the JAK, p38 MAPK and PI3K pathways in infected macrophages, promote the phosphorylation of p53 protein, and increase the ratio of Bax to Bcl-2, leading to cell apoptosis, thus eliminating intracellular bacteria and reducing the spread of mycobacteria.

CONCLUSION

DDP may be a new host-directed therapy for tuberculosis treatment, as well as the p53 promoter Kevetrin hydrochloride.

A spatiotemporally resolved single-cell atlas of the Plasmodium liver stage

Malaria infection involves an obligatory, yet clinically silent liver stage^1,2. Hepatocytes operate in repeating units termed lobules, exhibiting heterogeneous gene expression patterns along the lobule axis³, but the effects of hepatocyte zonation on parasite development at the molecular level remain unknown. Here we combine single-cell RNA sequencing⁴ and single-molecule transcript imaging⁵ to characterize the host and parasite temporal expression programmes in a zonally controlled manner for the rodent malaria parasite Plasmodium berghei ANKA. We identify differences in parasite gene expression in distinct zones, including potentially co-adaptive programmes related to iron and fatty acid metabolism. We find that parasites develop more rapidly in the pericentral lobule zones and identify a subpopulation of periportally biased hepatocytes that harbour abortive infections, reduced levels of Plasmodium transcripts and parasitophorous vacuole breakdown. These 'abortive hepatocytes', which appear predominantly with high parasite inoculum, upregulate immune recruitment and key signalling programmes. Our study provides a resource for understanding the liver stage of Plasmodium infection at high spatial resolution and highlights the heterogeneous behaviour of both the parasite and the host hepatocyte.

Analysis of gene expression profiles to study malaria vaccine dose efficacy and immune response modulation

Malaria is a life-threatening disease, and Africa is still one of the most affected endemic regions despite years of policy to limit infection and transmission rates. Further, studies into the variable efficacy of the vaccine are needed to provide a better understanding of protective immunity. Thus, the current study is designed to delineate the effect of each dose of vaccine on the transcriptional profiles of subjects to determine its efficacy and understand the molecular mechanisms underlying the protection this vaccine provides. Here, we used gene expression profiles of pre and post-vaccination patients after various doses of RTS,S based on samples collected from the Gene Expression Omnibus datasets. Subsequently, differential gene expression analysis using edgeR revealed the significantly (false discovery rate < 0.005) 158 downregulated and 61 upregulated genes between control vs. controlled human malaria infection samples. Further, enrichment analysis of significant genes delineated the involvement of CCL8, CXCL10, CXCL11, XCR1, CSF3, IFNB1, IFNE, IL12B, IL22, IL6, IL27, etc., genes which found to be upregulated after earlier doses but downregulated after the 3rd dose in cytokine-chemokine pathways. Notably, we identified 13 cytokine genes whose expression significantly varied during three doses. Eventually, these findings give insight into the dual role of cytokine responses in malaria pathogenesis. The variations in their expression patterns after various doses of vaccination are linked to the protection as it decreases the severe inflammatory effects in malaria patients. This study will be helpful in designing a better vaccine against malaria and understanding the functions of cytokine response as well.

Plasmodium's fight for survival: escaping elimination while acquiring nutrients

Plasmodium parasites extensively alter their host hepatocyte to evade host detection and support an unprecedented replication rate. Host cell manipulation includes association with the host early and late endomembrane systems, where Plasmodium accesses nutrients while suppressing cellular immune processes. Early endomembrane organelles provide an opportunity to sequester an abundance of lipids and proteins, but the association with late endomembrane organelles also risks autophagy-mediated elimination. While not all parasites survive, those that do benefit from a plethora of nutrients provided through this pathway. In this review, we discuss recent advances in our understanding of how Plasmodium parasites balance the need for host nutrients while avoiding elimination during the liver stage.

Active APPL1 sequestration by Plasmodium favors liver-stage development

Intracellular pathogens manipulate host cells to survive and thrive. Cellular sensing and signaling pathways are among the key host machineries deregulated to favor infection. In this study, we show that liver-stage Plasmodium parasites compete with the host to sequester a host endosomal-adaptor protein (APPL1) known to regulate signaling in response to endocytosis. The enrichment of APPL1 at the parasitophorous vacuole membrane (PVM) involves an atypical Plasmodium Rab5 isoform (Rab5b). Depletion of host APPL1 alters neither the infection nor parasite development; however, upon overexpression of a GTPase-deficient host Rab5 mutant (hRab5_Q79L), the parasites are smaller and their PVM is stripped of APPL1. Infection with the GTPase-deficient Plasmodium berghei Rab5b mutant (PbRab5b_Q91L) in this case rescues the PVM APPL1 signal and parasite size. In summary, we observe a robust correlation between the level of APPL1 retention at the PVM and parasite size during exoerythrocytic development.

Recent Advances in Host-Directed Therapies for Tuberculosis and Malaria

Tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis, and malaria, caused by parasites from the Plasmodium genus, are two of the major causes of death due to infectious diseases in the world. Both diseases are treatable with drugs that have microbicidal properties against each of the etiologic agents. However, problems related to treatment compliance by patients and emergence of drug resistant microorganisms have been a major problem for combating TB and malaria. This factor is further complicated by the absence of highly effective vaccines that can prevent the infection with either M. tuberculosis or Plasmodium. However, certain host biological processes have been found to play a role in the promotion of infection or in the pathogenesis of each disease. These processes can be targeted by host-directed therapies (HDTs), which can be administered in conjunction with the standard drug treatments for each pathogen, aiming to accelerate their elimination or to minimize detrimental side effects resulting from exacerbated inflammation. In this review we discuss potential new targets for the development of HDTs revealed by recent advances in the knowledge of host-pathogen interaction biology, and present an overview of strategies that have been tested in vivo, either in experimental models or in patients.

p53 in ferroptosis regulation: the new weapon for the old guardian

Although the conventional activities of p53 such as cell cycle arrest, senescence, and apoptosis are well accepted as the major checkpoints in stress responses, accumulating evidence implicates the importance of other tumor suppression mechanisms. Among these unconventional activities, an iron-dependent form of non-apoptotic cell death, termed ferroptosis, attracts great interest. Unlike apoptotic cell death, activation of p53 alone is not sufficient to induce ferroptosis directly; instead, through its metabolic targets, p53 is able to modulate the ferroptosis response in the presence of ferroptosis inducers such as GPX4 inhibitors or high levels of ROS. Here, we review the role of ferroptosis in p53-mediated tumor suppression, with a focus on what cellular factors are critical for p53-dependent ferroptosis during tumor suppression and how p53 modulates both the canonical (GPX4-dependent) and the non-canonical (GPX4-independent) ferroptosis pathways. We also discuss the possibility of targeting p53-mediated ferroptotic responses for the treatment of human cancers and potentially, other diseases.

Coding and Noncoding RNA Expression Profiles of Spleen CD4+ T Lymphocytes in Mice with Echinococcosis

Cystic echinococcosis (CE) is a severe and neglected zoonotic disease that poses health and socioeconomic hazards. So far, the prevention and treatment of CE are far from meeting people's ideal expectations. Therefore, to gain insight into the prevention and diagnosis of CE, we explored the changes in RNA molecules and the biological processes and pathways involved in these RNA molecules as E. granulosus infects the host. Interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-6, IL-10, IL-17A, and tumor necrosis factor (TNF)-α levels in peripheral blood serum of E. granulosus infected and uninfected female BALB/c mice were measured using the cytometric bead array mouse Th1/Th2/Th17 cytokine kit. mRNA, microRNA (miRNA), long noncoding RNA (lncRNA), and circular RNA (circRNA) profiles of spleen CD4+ T cells from the two groups of mice were analyzed using high-throughput sequencing and bioinformatics. The levels of IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-17A, and TNF-α were significantly higher in the serum of the CE mice than in control mice (P < 0.01). In total, 1,758 known mRNAs, 37 miRNAs, 175 lncRNAs, and 22 circRNAs were differentially expressed between infected and uninfected mice (|fold change| ≥ 0.585, P < 0.05). These differentially expressed molecules are involved in chromosome composition, DNA/RNA metabolism, and gene expression in cell composition, biological function, and cell function. Moreover, closely related to the JAK/STAT signaling pathways, mitogen-activated protein kinase signaling pathways, P53 signaling pathways, PI3K/AKT signaling pathways, cell cycle, and metabolic pathways. E. granulosus infection significantly increased the levels of IFN-γ, IL-2, IL-4, IL-6, IL-10, IL-17A, and TNF-α in mouse peripheral blood of mice and significantly changed expression levels of various coding and noncoding RNAs. Further study of these trends and pathways may help clarify the pathogenesis of CE and provide new insights into the prevention and treatment of this disease.

Plasmodium berghei-Mediated NRF2 Activation in Infected Hepatocytes Enhances Parasite Survival

The protozoan parasite Plasmodium, causative agent of malaria, initially invades and develops in hepatocytes where it resides in a parasitophorous vacuole (PV). A single invaded parasite develops into thousands of daughter parasites. Survival of the host cell is crucial for successful completion of liver stage development. Nuclear factor erythroid-derived 2-related factor 2 (NRF2) is a transcription factor known to induce transcription of cytoprotective genes when activated. Here we show that NRF2 is activated in Plasmodium berghei-infected hepatocytes. We observed that this NRF2 activation depends on PV membrane resident p62 recruiting KEAP1, the negative regulator of NRF2. Disrupting the NRF2 gene results in reduced parasite survival, indicating that NRF2 signaling is an important event for parasite development in hepatocytes. Together, our observations uncovered a novel mechanism of how Plasmodium parasites ensure host cell survival during liver stage development.

Elucidating Spatially-Resolved Changes in Host Signaling During Plasmodium Liver-Stage Infection

Upon transmission to the human host, Plasmodium sporozoites exit the skin, are taken up by the blood stream, and then travel to the liver where they infect and significantly modify a single hepatocyte. Low infection rates within the liver have made proteomic studies of infected hepatocytes challenging, particularly in vivo, and existing studies have been largely unable to consider how protein and phosphoprotein differences are altered at different spatial locations within the heterogeneous liver. Using digital spatial profiling, we characterized changes in host signaling during Plasmodium yoelii infection in vivo without disrupting the liver tissue. Moreover, we measured alterations in protein expression around infected hepatocytes and identified a subset of CD163⁺ Kupffer cells that migrate towards infected cells during infection. These data offer the first insight into the heterogeneous microenvironment that surrounds the infected hepatocyte and provide insights into how the parasite may alter its milieu to influence its survival and modulate immunity.

Suppression of Plasmodium MIF-CD74 signaling protects against severe malaria

The deadliest complication of infection by Plasmodium parasites, cerebral malaria, accounts for the majority of malarial fatalities. Although our understanding of the cellular and molecular mechanisms underlying the pathology remains incomplete, recent studies support the contribution of systemic and neuroinflammation as the cause of cerebral edema and blood-brain barrier (BBB) dysfunction. All Plasmodium species encode an orthologue of the innate cytokine, Macrophage Migration Inhibitory Factor (MIF), which functions in mammalian biology to regulate innate responses. Plasmodium MIF (PMIF) similarly signals through the host MIF receptor CD74, leading to an enhanced inflammatory response. We investigated the PMIF-CD74 interaction in the onset of experimental cerebral malaria (ECM) and liver stage Plasmodium development by using a combination of CD74 deficient (Cd74^-/- ) hosts and PMIF deficient parasites. Cd74^-/- mice were found to be protected from ECM and the protection was associated with the inability of brain microvessels to present parasite antigen to sequestered and pathogenic Plasmodium-specific CD8⁺ T cells. Infection of WT hosts with PMIF-deficient sporozoites or infection of Cd74^-/- hosts with WT sporozoites impacted the survival of infected hepatocytes and subsequently reduced blood-stage associated inflammation, contributing to protection from ECM. We recapitulated these finding with a novel pharmacologic PMIF-selective antagonist that reduced PMIF/CD74 signaling and fully protected mice from ECM. These findings reveal a conserved mechanism for Plasmodium usurpation of host CD74 signaling and suggest a tractable approach for new pharmacologic intervention.

Mitochondria as a Cellular Hub in Infection and Inflammation

Mitochondria are the energy center of the cell. They are found in the cell cytoplasm as dynamic networks where they adapt energy production based on the cell’s needs. They are also at the center of the proinflammatory response and have essential roles in the response against pathogenic infections. Mitochondria are a major site for production of Reactive Oxygen Species (ROS; or free radicals), which are essential to fight infection. However, excessive and uncontrolled production can become deleterious to the cell, leading to mitochondrial and tissue damage. Pathogens exploit the role of mitochondria during infection by affecting the oxidative phosphorylation mechanism (OXPHOS), mitochondrial network and disrupting the communication between the nucleus and the mitochondria. The role of mitochondria in these biological processes makes these organelle good targets for the development of therapeutic strategies. In this review, we presented a summary of the endosymbiotic origin of mitochondria and their involvement in the pathogen response, as well as the potential promising mitochondrial targets for the fight against infectious diseases and chronic inflammatory diseases.

Host-directed therapy, an untapped opportunity for antimalarial intervention

Host-directed therapy (HDT) is gaining traction as a strategy to combat infectious diseases caused by viruses and intracellular bacteria, but its implementation in the context of parasitic diseases has received less attention. Here, we provide a brief overview of this field and advocate HDT as a promising strategy for antimalarial intervention based on untapped targets. HDT provides a basis from which repurposed drugs could be rapidly deployed and is likely to strongly limit the emergence of resistance. This strategy can be applied to any intracellular pathogen and is particularly well placed in situations in which rapid identification of treatments is needed, such as emerging infections and pandemics, as starkly illustrated by the current COVID-19 crisis.

Host-targeted Interventions as an Exciting Opportunity to Combat Malaria

Terminal and benign diseases alike in adults, children, pregnant women, and others are successfully treated by pharmacological inhibitors that target human enzymes. Despite extensive global efforts to fight malaria, the disease continues to be a massive worldwide health burden, and new interventional strategies are needed. Current drugs and vector control strategies have contributed to the reduction in malaria deaths over the past 10 years, but progress toward eradication has waned in recent years. Resistance to antimalarial drugs is a substantial and growing problem. Moreover, targeting dormant forms of the malaria parasite Plasmodium vivax is only possible with two approved drugs, which are both contraindicated for individuals with glucose-6-phosphate dehydrogenase deficiency and in pregnant women. Plasmodium parasites are obligate intracellular parasites and thus have specific and absolute requirements of their hosts. Growing evidence has described these host necessities, paving the way for opportunities to pharmacologically target host factors to eliminate Plasmodium infection. Here, we describe progress in malaria research and adjacent fields and discuss key challenges that remain in implementing host-directed therapy against malaria.

Tumor suppressor p53 regulates intestinal type 2 immunity

The role of p53 in tumor suppression has been extensively studied and well-established. However, the role of p53 in parasitic infections and the intestinal type 2 immunity is unclear. Here, we report that p53 is crucial for intestinal type 2 immunity in response to the infection of parasites, such as Tritrichomonas muris and Nippostrongylus brasiliensis. Mechanistically, p53 plays a critical role in the activation of the tuft cell-IL-25-type 2 innate lymphoid cell circuit, partly via transcriptional regulation of Lrmp in tuft cells. Lrmp modulates Ca2+ influx and IL-25 release, which are critical triggers of type 2 innate lymphoid cell response. Our results thus reveal a previously unrecognized function of p53 in regulating intestinal type 2 immunity to protect against parasitic infections, highlighting the role of p53 as a guardian of immune integrity.

cAMP-Dependent Signaling Pathways as Potential Targets for Inhibition of Plasmodium falciparum Blood Stages

We review the role of signaling pathways in regulation of the key processes of merozoite egress and red blood cell invasion by Plasmodium falciparum and, in particular, the importance of the second messengers, cAMP and Ca²⁺, and cyclic nucleotide dependent kinases. cAMP-dependent protein kinase (PKA) is comprised of cAMP-binding regulatory, and catalytic subunits. The less well conserved cAMP-binding pockets should make cAMP analogs attractive drug leads, but this approach is compromised by the poor membrane permeability of cyclic nucleotides. We discuss how the conserved nature of ATP-binding pockets makes ATP analogs inherently prone to off-target effects and how ATP analogs and genetic manipulation can be useful research tools to examine this. We suggest that targeting PKA interaction partners as well as substrates, or developing inhibitors based on PKA interaction sites or phosphorylation sites in PKA substrates, may provide viable alternative approaches for the development of anti-malarial drugs. Proximity of PKA to a substrate is necessary for substrate phosphorylation, but the P. falciparum genome encodes few recognizable A-kinase anchor proteins (AKAPs), suggesting the importance of PKA-regulatory subunit myristylation and membrane association in determining substrate preference. We also discuss how Pf14-3-3 assembles a phosphorylation-dependent signaling complex that includes PKA and calcium dependent protein kinase 1 (CDPK1) and how this complex may be critical for merozoite invasion, and a target to block parasite growth. We compare altered phosphorylation levels in intracellular and egressed merozoites to identify potential PKA substrates. Finally, as host PKA may have a critical role in supporting intracellular parasite development, we discuss its role at other stages of the life cycle, as well as in other apicomplexan infections. Throughout our review we propose possible new directions for the therapeutic exploitation of cAMP-PKA-signaling in malaria and other diseases caused by apicomplexan parasites.

Unraveling Cell Death Pathways during Malaria Infection: What Do We Know So Far?

Malaria is a parasitic disease (caused by different Plasmodium species) that affects millions of people worldwide. The lack of effective malaria drugs and a vaccine contributes to this disease, continuing to cause major public health and socioeconomic problems, especially in low-income countries. Cell death is implicated in malaria immune responses by eliminating infected cells, but it can also provoke an intense inflammatory response and lead to severe malaria outcomes. The study of the pathophysiological role of cell death in malaria in mammalians is key to understanding the parasite-host interactions and design prophylactic and therapeutic strategies for malaria. In this work, we review malaria-triggered cell death pathways (apoptosis, autophagy, necrosis, pyroptosis, NETosis, and ferroptosis) and we discuss their potential role in the development of new approaches for human malaria therapies.

Theileria secretes proteins to subvert its host leukocyte

Theileria parasites are classified in the phylum Apicomplexa that includes several genera of medical and veterinary importance such as Plasmodium, Babesia, Toxoplasma and Cryptosporidium. These protozoans have evolved subtle ways to reshape their intracellular niche for their own benefit and Theileria is no exception. This tick transmitted microorganism is unique among all eukaryotes in that its intracellular schizont stage is able to transform its mammalian host leukocytes into an immortalised highly disseminating cell that phenocopies tumour cells. Here, we describe what is known about secreted Theileria-encoded host cell manipulators.

Modeling Relapsing Malaria: Emerging Technologies to Study Parasite-Host Interactions in the Liver

Recent studies of liver stage malaria parasite-host interactions have provided exciting new insights on the cross-talk between parasite and its mammalian (predominantly rodent) host. We review the latest state of the art and and zoom in on new technologies that will provide the tools necessary to investigate host-parasite interactions of relapsing parasites. Interactions between hypnozoites and hepatocytes are particularly interesting because the parasite can remain in a quiescent state for prolonged periods of time and triggers for reactivation have not been irrefutably identified. If we learn more about the cross-talk between hypnozoite and host we may be able to identify factors that encourage waking up these dormant parasite reservoirs and help to achieve the total eradication of malaria.

The host mTOR pathway and parasitic diseases pathogenesis

The mechanistic (or mammalian) target of rapamycin (mTOR) is considered as a critical regulatory enzyme involved in essential signaling pathways affecting cell growth, cell proliferation, protein translation, regulation of cellular metabolism, and cytoskeletal structure. Also, mTOR signaling has crucial roles in cell homeostasis via processes such as autophagy. Autophagy prevents many pathogen infections and is involved on immunosurveillance and pathogenesis. Immune responses and autophagy are therefore key host responses and both are linked by complex mTOR regulatory mechanisms. In recent years, the mTOR pathway has been highlighted in different diseases such as diabetes, cancer, and infectious and parasitic diseases including leishmaniasis, toxoplasmosis, and malaria. The current review underlines the implications of mTOR signals and intricate networks on pathogen infections and the modulation of this master regulator by parasites. Parasitic infections are able to induce dynamic metabolic reprogramming leading to mTOR alterations in spite of many other ways impacting this regulatory network. Accordingly, the identification of parasite effects and interactions over such a complex modulation might reveal novel information regarding the biology of the abovementioned parasites and might allow the development of therapeutic strategies against parasitic diseases. In this sense, the effects of inhibiting the mTOR pathways are also considered in this context in the light of their potential for the prevention and treatment of parasitic diseases.

Plasmodium infection inhibits tumor angiogenesis through effects on tumor-associated macrophages in a murine implanted hepatoma model

Background

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death in China. The lack of an effective treatment for this disease results in a high recurrence rate in patients who undergo radical tumor resection, and the 5-year survival rate of these patients remains low. Our previous studies demonstrated that Plasmodium infection provides a potent antitumor effect by inducing innate and adaptive immunity in a murine Lewis lung carcinoma (LLC) model.

Methods

This study aimed to investigate the inhibitory effect of Plasmodium infection on hepatocellular carcinoma in mice, and various techniques for gene expression analysis were used to identify possible signal regulation mechanisms.

Results

We found that Plasmodium infection efficiently inhibited tumor progression and prolonged survival in tumor-bearing mice, which served as a murine implanted hepatoma model. The inhibition of tumor progression by Plasmodium infection was related to suppression of tumor angiogenesis within the tumor tissue and decreased infiltration of tumor-associated macrophages (TAMs). Further study demonstrated that matrix metalloprotease 9 (MMP-9) produced by TAMs contributed to tumor angiogenesis in the tumor tissue and that the parasite-induced reduction in MMP-9 expression in TAMs resulted in the suppression of tumor angiogenesis. A mechanistic study revealed that the Plasmodium-derived hemozoin (HZ) that accumulated in TAMs inhibited IGF-1 signaling through the PI3-K and MAPK signaling pathways and thereby decreased the expression of MMP-9 in TAMs.

Conclusions

Our study suggests that this novel approach of inhibiting tumor angiogenesis by Plasmodium infection is of high importance for the development of new therapies for cancer patients.

Alterations in Phosphorylation of Hepatocyte Ribosomal Protein S6 Control Plasmodium Liver Stage Infection

Plasmodium parasites are highly selective when infecting hepatocytes and induce many changes within the host cell upon infection. While several host cell factors have been identified that are important for liver infection, our understanding of what facilitates the maintenance of infection remains incomplete. Here, we describe a role for phosphorylated ribosomal protein S6 (Ser235/236) (p-RPS6) in Plasmodium yoelii-infected hepatocytes. Blocking RPS6 phosphorylation prior to infection decreases the number of liver stage parasites within 24 h. Infected hepatocytes exhibit elevated levels of p-RPS6 while simultaneously abrogating the induction of phosphorylation of RPS6 in response to insulin stimulation. This is in contrast with the regulation of p-RPS6 by Toxoplasma gondii, which elevates levels of p-RPS6 after infection but does not alter the response to insulin. Our data support a model in which RPS6 phosphorylation is uncoupled from canonical regulators in Plasmodium-infected hepatocytes and is relied on by the parasite to maintain infection.

An epigrammatic status of the 'azole'-based antimalarial drugs

The development of multidrug resistance in the malarial parasite has sabotaged majority of the eradication efforts by restraining the inhibition profile of first line as well as second line antimalarial drugs, thus necessitating the development of novel pharmaceutics constructed on appropriate scaffolds with superior potency against the drug-resistant and drug-susceptible Plasmodium parasite. Over the past decades, the infectious malarial parasite has developed resistance against most of the contemporary therapeutics, thus necessitating the rational development of novel approaches principally focused on MDR malaria. This review presents an epigrammatic collation of the epidemiology and the contemporary antimalarial therapeutics based on the 'azole' motif.

African-centric TP53 variant increases iron accumulation and bacterial pathogenesis but improves response to malaria toxin

A variant at amino acid 47 in human TP53 exists predominantly in individuals of African descent. P47S human and mouse cells show increased cancer risk due to defective ferroptosis. Here, we show that this ferroptotic defect causes iron accumulation in P47S macrophages. This high iron content alters macrophage cytokine profiles, leads to higher arginase level and activity, and decreased nitric oxide synthase activity. This leads to more productive intracellular bacterial infections but is protective against malarial toxin hemozoin. Proteomics of macrophages reveal decreased liver X receptor (LXR) activation, inflammation and antibacterial defense in P47S macrophages. Both iron chelators and LXR agonists improve the response of P47S mice to bacterial infection. African Americans with elevated saturated transferrin and serum ferritin show higher prevalence of the P47S variant (OR = 1.68 (95%CI 1.07–2.65) p = 0.023), suggestive of its role in iron accumulation in humans. This altered macrophage phenotype may confer an advantage in malaria-endemic sub-Saharan Africa.

A polymorphism in human TP53 (P47S) that predominantly exists in individuals of African descent affects ferroptosis. Here, the authors show that this results in iron accumulation in macrophages leading to more productive infection by intracellular bacteria but improved anti-inflammatory response to the malarial toxin hemozoin.

Synthetic DNA Vaccines Adjuvanted with pIL-33 Drive Liver-Localized T Cells and Provide Protection from Plasmodium Challenge in a Mouse Model

The need for a malaria vaccine is indisputable. A single vaccine for Plasmodium pre-erythrocytic stages targeting the major sporozoite antigen circumsporozoite protein (CSP) has had partial success. Additionally, CD8+ T cells targeting liver-stage (LS) antigens induced by live attenuated sporozoite vaccines were associated with protection in human challenge experiments. To further evaluate protection mediated by LS antigens, we focused on exported pre-erythrocytic proteins (exported protein 1 (EXP1), profilin (PFN), exported protein 2 (EXP2), inhibitor of cysteine proteases (ICP), transmembrane protein 21 (TMP21), and upregulated in infective sporozoites-3 (UIS3)) expressed in all Plasmodium species and designed optimized, synthetic DNA (synDNA) immunogens. SynDNA antigen cocktails were tested with and without the molecular adjuvant plasmid IL-33. Immunized animals developed robust T cell responses including induction of antigen-specific liver-localized CD8+ T cells, which were enhanced by the co-delivery of plasmid IL-33. In total, 100% of mice in adjuvanted groups and 71%–88% in non-adjuvanted groups were protected from blood-stage disease following Plasmodium yoelii sporozoite challenge. This study supports the potential of synDNA LS antigens as vaccine components for malaria parasite infection.

Targeting liver stage malaria with metformin

Despite an unprecedented 2 decades of success, the combat against malaria - the mosquito-transmitted disease caused by Plasmodium parasites - is no longer progressing. Efforts toward eradication are threatened by the lack of an effective vaccine and a rise in antiparasite drug resistance. Alternative approaches are urgently needed. Repurposing of available, approved drugs with distinct modes of action are being considered as viable and immediate adjuncts to standard antimicrobial treatment. Such strategies may be well suited to the obligatory and clinically silent first phase of Plasmodium infection, where massive parasite replication occurs within hepatocytes in the liver. Here, we report that the widely used antidiabetic drug, metformin, impairs parasite liver stage development of both rodent-infecting Plasmodium berghei and human-infecting P. falciparum parasites. Prophylactic treatment with metformin curtails parasite intracellular growth in vitro. An additional effect was observed in mice with a decrease in the numbers of infected hepatocytes. Moreover, metformin provided in combination with conventional liver- or blood-acting antimalarial drugs further reduced the total burden of P. berghei infection and substantially lessened disease severity in mice. Together, our findings indicate that repurposing of metformin in a prophylactic regimen could be considered for malaria chemoprevention.

A Molecular Signature in Blood Reveals a Role for p53 in Regulating Malaria-Induced Inflammation

Immunity that controls parasitemia and inflammation during Plasmodium falciparum (Pf) malaria can be acquired with repeated infections. A limited understanding of this complex immune response impedes the development of vaccines and adjunctive therapies. We conducted a prospective systems biology study of children who differed in their ability to control parasitemia and fever following Pf infection. By integrating whole-blood transcriptomics, flow-cytometric analysis, and plasma cytokine and antibody profiles, we demonstrate that a pre-infection signature of B cell enrichment, upregulation of T helper type 1 (Th1) and Th2 cell-associated pathways, including interferon responses, and p53 activation associated with control of malarial fever and coordinated with Pf-specific immunoglobulin G (IgG) and Fc receptor activation to control parasitemia. Our hypothesis-generating approach identified host molecules that may contribute to differential clinical outcomes during Pf infection. As a proof of concept, we have shown that enhanced p53 expression in monocytes attenuated Plasmodium-induced inflammation and predicted protection from fever.

Genetics of Malaria Inflammatory Responses: A Pathogenesis Perspective

Despite significant progress in combating malaria in recent years the burden of severe disease and death due to Plasmodium infections remains a global public health concern. Only a fraction of infected people develops severe clinical syndromes motivating a longstanding search for genetic determinants of malaria severity. Strong genetic effects have been repeatedly ascribed to mutations and allelic variants of proteins expressed in red blood cells but the role of inflammatory response genes in disease pathogenesis has been difficult to discern. We revisited genetic evidence provided by inflammatory response genes that have been repeatedly associated to malaria, namely TNF, NOS2, IFNAR1, HMOX1, TLRs, CD36, and CD40LG. This highlighted specific genetic variants having opposing roles in the development of distinct malaria clinical outcomes and unveiled diverse levels of genetic heterogeneity that shaped the complex association landscape of inflammatory response genes with malaria. However, scrutinizing genetic effects of individual variants corroborates a pathogenesis model where pro-inflammatory genetic variants acting in early infection stages contribute to resolve infection but at later stages confer increased vulnerability to severe organ dysfunction driven by tissue inflammation. Human genetics studies are an invaluable tool to find genes and molecular pathways involved in the inflammatory response to malaria but their precise roles in disease pathogenesis are still unexploited. Genome editing in malaria experimental models and novel genotyping-by-sequencing techniques are promising approaches to delineate the relevance of inflammatory response gene variants in the natural history of infection thereby will offer new rational angles on adjuvant therapeutics for prevention and clinical management of severe malaria.

Primaquine-quinoxaline 1,4-di-N-oxide hybrids with action on the exo-erythrocytic forms of Plasmodium induce their effect by the production of reactive oxygen species

Background

The challenge in anti-malarial chemotherapy is based on the emergence of resistance to drugs and the search for medicines against all stages of the life cycle of Plasmodium spp. as a therapeutic target. Nowadays, many molecules with anti-malarial activity are reported. However, few studies about the cellular and molecular mechanisms to understand their mode of action have been explored. Recently, new primaquine-based hybrids as new molecules with potential multi-acting anti-malarial activity were reported and two hybrids of primaquine linked to quinoxaline 1,4-di-N-oxide (PQ–QdNO) were identified as the most active against erythrocytic, exoerythrocytic and sporogonic stages.

Methods

To further understand the anti-malarial mode of action (MA) of these hybrids, hepg2-CD81 were infected with Plasmodium yoelii 17XNL and treated with PQ–QdNO hybrids during 48 h. After were evaluated the production of ROS, the mitochondrial depolarization, the total glutathione content, the DNA damage and proteins related to oxidative stress and death cell.

Results

In a preliminary analysis as tissue schizonticidals, these hybrids showed a mode of action dependent on peroxides production, but independent of the activation of transcription factor p53, mitochondrial depolarization and arrest cell cycle.

Conclusions

Primaquine–quinoxaline 1,4-di-N-oxide hybrids exert their antiplasmodial activity in the exoerythrocytic phase by generating high levels of oxidative stress which promotes the increase of total glutathione levels, through oxidation stress sensor protein DJ-1. In addition, the role of HIF1a in the mode of action of quinoxaline 1,4-di-N-oxide is independent of biological activity.

Liver stage malaria infection is controlled by host regulators of lipid peroxidation

The facets of host control during Plasmodium liver infection remain largely unknown. We find that the SLC7a11-GPX4 pathway, which has been associated with the production of reactive oxygen species, lipid peroxidation, and a form of cell death called ferroptosis, plays a critical role in control of Plasmodium liver stage infection. Specifically, blocking GPX4 or SLC7a11 dramatically reduces Plasmodium liver stage parasite infection. In contrast, blocking negative regulators of this pathway, NOX1 and TFR1, leads to an increase in liver stage infection. We have shown previously that increased levels of P53 reduces Plasmodium LS burden in an apoptosis-independent manner. Here, we demonstrate that increased P53 is unable to control parasite burden during NOX1 or TFR1 knockdown, or in the presence of ROS scavenging or when lipid peroxidation is blocked. Additionally, SLC7a11 inhibitors Erastin and Sorafenib reduce infection. Thus, blocking the host SLC7a11-GPX4 pathway serves to selectively elevate lipid peroxides in infected cells, which localize within the parasite and lead to the elimination of liver stage parasites.

Plasmodium PK9 Inhibitors Promote Growth of Liver-Stage Parasites

There is a scarcity of pharmacological tools to interrogate protein kinase function in Plasmodium parasites, the causative agent of malaria. Among Plasmodium's protein kinases, those characterized as atypical represent attractive drug targets as they lack sequence similarity to human proteins. Here, we describe takinib as a small molecule to bind the atypical P. falciparum protein kinase 9 (PfPK9). PfPK9 phosphorylates the Plasmodium E2 ubiquitin-conjugating enzyme PfUBC13, which mediates K63-linkage-specific polyubiquitination. Takinib is a potent human TAK1 inhibitor, thus we developed the Plasmodium-selective takinib analog HS220. We demonstrate that takinib and HS220 decrease K63-linked ubiquitination in P. falciparum, suggesting PfPK9 inhibition in cells. Takinib and HS220 induce a unique phenotype where parasite size in hepatocytes increases, yet high compound concentrations decrease the number of parasites. Our studies highlight the role of PK9 in regulating parasite development and the potential of targeting Plasmodium kinases for malaria control.

Cancer-malaria: hidden connections

Cancer and malaria exemplify two maladies historically assigned to separated research spaces. Cancer, on the one hand, ranks among the top priorities in the research agenda of developed countries. Its rise is mostly explained by the ageing of these populations and linked to environment and lifestyle. Malaria, on the other hand, represents a major health burden for developing countries in the Southern Hemisphere. These two diseases also belong to separate fields of medicine: non-communicable diseases for cancer and communicable diseases for malaria.

Opportunities for Host-targeted Therapies for Malaria

Despite the recent successes of artemisinin-based antimalarial drugs, many still die from severe malaria, and eradication efforts are hindered by the limited drugs currently available to target transmissible gametocyte parasites and liver-resident dormant Plasmodium vivax hypnozoites. Host-targeted therapy is a new direction for infectious disease drug development and aims to interfere with host molecules, pathways, or networks that are required for infection or that contribute to disease. Recent advances in our understanding of host pathways involved in parasite development and pathogenic mechanisms in severe malaria could facilitate the development of host-targeted interventions against Plasmodium infection and malaria disease. This review discusses new opportunities for host-targeted therapeutics for malaria and the potential to harness drug polypharmacology to simultaneously target multiple host pathways using a single drug intervention.

A small molecule p53 activator attenuates Fanconi anemia leukemic stem cell proliferation

Although p53 mutations are common in solid tumors, such mutations are found at a lower frequency in hematologic malignancies. In the genetic disorder Fanconi anemia (FA), p53 has been proposed as an important pathophysiological factor for two important hematologic hallmarks of the disease: bone marrow failure and leukemogenesis. Here we show that low levels of the p53 protein enhance the capacity of leukemic stem cells from FA patients to repopulate immunodeficient mice. Furthermore, boosting p53 protein levels with the use of the small molecule Nutlin-3 reduced leukemia burden in recipient mice. These results demonstrate that the level of p53 protein plays a crucial role in FA leukemogenesis.

Host cell cytosolic immune response during Plasmodium liver stage development

Recent years have witnessed a great gain in knowledge regarding parasite-host cell interactions during Plasmodium liver stage development. It is now an accepted fact that a large percentage of sporozoites invading hepatocytes fail to form infectious merozoites. There appears to be a delicate balance between parasite survival and elimination and we now start to understand why this is so. Plasmodium liver stage parasites replicate within the parasitophorous vacuole (PV), formed during invasion by invagination of the host cell plasma membrane. The main interface between the parasite and hepatocyte is the parasitophorous vacuole membrane (PVM) that surrounds the PV. Recently, it was shown that autophagy marker proteins decorate the PVM of Plasmodium liver stage parasites and eliminate a proportion of them by an autophagy-like mechanism. Successfully developing Plasmodium berghei parasites are initially also labeled but in the course of development, they are able to control this host defense mechanism by shedding PVM material into the tubovesicular network (TVN), an extension of the PVM that releases vesicles into the host cell cytoplasm. Better understanding of the molecular events at the PVM/TVN during parasite elimination could be the basis of new antimalarial measures.

Symbiotic immuno-suppression: is disease susceptibility the price of bleaching resistance?

Accelerating anthropogenic climate change threatens to destroy coral reefs worldwide through the processes of bleaching and disease. These major contributors to coral mortality are both closely linked with thermal stress intensified by anthropogenic climate change. Disease outbreaks typically follow bleaching events, but a direct positive linkage between bleaching and disease has been debated. By tracking 152 individual coral ramets through the 2014 mass bleaching in a South Florida coral restoration nursery, we revealed a highly significant negative correlation between bleaching and disease in the Caribbean staghorn coral, Acropora cervicornis. To explain these results, we propose a mechanism for transient immunological protection through coral bleaching: removal of Symbiodinium during bleaching may also temporarily eliminate suppressive symbiont modulation of host immunological function. We contextualize this hypothesis within an ecological perspective in order to generate testable predictions for future investigation.