Cutting Edge: EPHB2 Is a Coreceptor for Fungal Recognition and Phosphorylation of Syk in the Dectin-1 Signaling Pathway

Preclinical and Toxicology Assessment of ALW-II-41-27, an Inhibitor of the Eph Receptor A2 (EphA2)

BACKGROUND AND OBJECTIVE

The EphA2 receptor inhibitor ALW-II-41-27 has proven to be an effective in vitro antagonist of Pneumocystis β-glucan-induced proinflammatory signaling. This suggests its potential as a candidate for initial anti-inflammatory drug testing in the rodent model of Pneumocystis pneumonia (PCP).

METHODS

Initially, single-dose intraperitoneal (IP) injections of ALW-II-41-27 were administered at concentrations of 0, 10, 15, 20, and 30 mg/kg over a 24-h treatment period. Pharmacokinetics were assessed in plasma, bronchoalveolar lavage fluid (BALF), and epithelial lining fluid (ELF). Following these assessments, a final single mg/kg dosing was determined. Mice received daily IP injections of either vehicle or 20.0 mg/kg of ALW-II-41-27 for 10 days, with their weights recorded daily. On day 11, mice were weighed and euthanized. Lungs, liver, and kidneys were harvested for H&E staining and pathology scoring. Lung samples were further analyzed for proinflammatory cytokines using enzyme-linked immunosorbent assay (ELISA) and extracellular matrix production using quantitative PCR (qPCR). Postmortem blood collection was conducted for complete blood count (CBC) blood chemistry analysis. Lastly, ALW-II-41-27 was administered to mice prior to fungal β-glucans challenge to determine in vivo effects on lung inflammation.

RESULTS

This report describes the PK assessment of ALW-II-41-27 given via IP in C57BL/6 mice. After PK data were generated, we tested ALW-II-41-27 at 20 mg/kg IP in mice and noted no significant changes in daily or final weight gain. ELISA results of proinflammatory cytokines from lung tissues showed no major differences in the respective groups. qPCR analysis of extracellular matrix transcripts were statistically similar. Examination and pathology scoring of H&E slides from lung, liver, and kidney in all groups and subsequent pathology scoring showed no significant toxicity. Blood chemistry and CBC analyses revealed no major abnormalities. Additionally, administering ALW-II-41-27 before intratracheal inoculation of fungal β-glucans, known to induce a strong proinflammatory response in the lungs, significantly reduced lung tissue IL-1β levels.

CONCLUSIONS

In our initial general safety and toxicology assessments, ALW-II-41-27 displayed no inherent safety concerns in the analyzed parameters. These data support broader in vivo testing of the inhibitor as a timed adjunct therapy to the deleterious proinflammatory host immune response often associated with anti-Pneumocystis therapy.

Candida albicans and Candida glabrata: global priority pathogens

SUMMARYA significant increase in the incidence of Candida-mediated infections has been observed in the last decade, mainly due to rising numbers of susceptible individuals. Recently, the World Health Organization published its first fungal pathogen priority list, with Candida species listed in medium, high, and critical priority categories. This review is a synthesis of information and recent advances in our understanding of two of these species-Candida albicans and Candida glabrata. Of these, C. albicans is the most common cause of candidemia around the world and is categorized as a critical priority pathogen. C. glabrata is considered a high-priority pathogen and has become an increasingly important cause of candidemia in recent years. It is now the second most common causative agent of candidemia in many geographical regions. Despite their differences and phylogenetic divergence, they are successful as pathogens and commensals of humans. Both species can cause a broad variety of infections, ranging from superficial to potentially lethal systemic infections. While they share similarities in certain infection strategies, including tissue adhesion and invasion, they differ significantly in key aspects of their biology, interaction with immune cells, host damage strategies, and metabolic adaptations. Here we provide insights on key aspects of their biology, epidemiology, commensal and pathogenic lifestyles, interactions with the immune system, and antifungal resistance.

Pathology and molecular mechanisms of Schistosoma japonicum-associated liver fibrosis

Schistosomiasis has been widely disseminated around the world, and poses a significant threat to human health. Schistosoma eggs and soluble egg antigen (SEA) mediated inflammatory responses promote the formation of egg granulomas and liver fibrosis. With continuous liver injuries and inflammatory stimulation, liver fibrosis can develop into liver cirrhosis and liver cancer. Therefore, anti-fibrotic therapy is crucial to increase the survival rate of patients. However, current research on antifibrotic treatments for schistosomiasis requires further exploration. In the complicated microenvironment of schistosome infections, it is important to understand the mechanism and pathology of schistosomiasis-associated liver fibrosis(SSLF). In this review, we discuss the role of SEA in inhibiting liver fibrosis, describe its mechanism, and comprehensively explore the role of host-derived and schistosome-derived microRNAs (miRNAs) in SSLF. Inflammasomes and cytokines are significant factors in promoting SSLF, and we discuss the mechanisms of some critical inflammatory signals and pro-fibrotic cytokines. Natural killer(NK) cells and Natural killer T(NKT) cells can inhibit SSLF but are rarely described, therefore, we highlight their significance. This summarizes and provides insights into the mechanisms of key molecules involved in SSLF development.

IL-23 signaling prevents ferroptosis-driven renal immunopathology during candidiasis

During infection the host relies on pattern-recognition receptors to sense invading fungal pathogens to launch immune defense mechanisms. While fungal recognition and immune effector responses are organ and cell type specific, during disseminated candidiasis myeloid cells exacerbate collateral tissue damage. The β-glucan receptor ephrin type-A 2 receptor (EphA2) is required to initiate mucosal inflammatory responses during oral Candida infection. Here we report that EphA2 promotes renal immunopathology during disseminated candidiasis. EphA2 deficiency leads to reduced renal inflammation and injury. Comprehensive analyses reveal that EphA2 restrains IL-23 secretion from and migration of dendritic cells. IL-23 signaling prevents ferroptotic host cell death during infection to limit inflammation and immunopathology. Further, host cell ferroptosis limits antifungal effector functions via releasing the lipid peroxidation product 4-hydroxynonenal to induce various forms of cell death. Thus, we identify ferroptotic cell death as a critical pathway of Candida-mediated renal immunopathology that opens a new avenue to tackle Candida infection and inflammation.

DOCK2 regulates antifungal immunity by regulating RAC GTPase activity

Fungal infections cause ~1.5 million deaths each year worldwide, and the mortality rate of disseminated candidiasis currently exceeds that of breast cancer and malaria. The major reasons for the high mortality of candidiasis are the limited number of antifungal drugs and the emergence of drug-resistant species. Therefore, a better understanding of antifungal host defense mechanisms is crucial for the development of effective preventive and therapeutic strategies. Here, we report that DOCK2 (dedicator of cytokinesis 2) promotes indispensable antifungal innate immune signaling and proinflammatory gene expression in macrophages. DOCK2-deficient macrophages exhibit decreased RAC GTPase (Rac family small GTPase) activation and ROS (reactive oxygen species) production, which in turn attenuates the killing of intracellular fungi and the activation of downstream signaling pathways. Mechanistically, after fungal stimulation, activated SYK (spleen-associated tyrosine kinase) phosphorylates DOCK2 at tyrosine 985 and 1405, which promotes the recruitment and activation of RAC GTPases and then increases ROS production and downstream signaling activation. Importantly, nanoparticle-mediated delivery of in vitro transcribed (IVT) Rac1 mRNA promotes the activity of Rac1 and helps to eliminate fungal infection in vivo. Taken together, this study not only identifies a critical role of DOCK2 in antifungal immunity via regulation of RAC GTPase activity but also provides proof of concept for the treatment of invasive fungal infections by using IVT mRNA.