Featured Article: Immunomodulatory effect of hemozoin on pneumocyte apoptosis via CARD9 pathway, a possibly retarding pulmonary resolution

Hemozoin-induced IFN-γ production mediates innate immune protection against sporozoite infection

Hemozoin is a crystal synthesized by Plasmodium parasites during hemoglobin digestion in the erythrocytic stage. The hemozoin released when the parasites egress from the red blood cell, which is complexed with parasite DNA, is cleared from the circulation by circulating and tissue-resident monocytes and macrophages, respectively. Recently, we reported that intravenous administration of purified hemozoin complexed with Plasmodium berghei DNA (HzPbDNA) resulted in an innate immune response that blocked liver stage development of sporozoites that was dose-dependent and time-limited. Here, we further characterize the organismal, cellular, and molecular events associated with this protective innate response in the liver and report that a large proportion of the IV administered HzPbDNA localized to F4/80+ cells in the liver and that the rapid and strong protection against liver-stage development waned quickly such that by 1 week post-HzPbDNA treatment animals were fully susceptible to infection. RNAseq of the liver after IV administration of HzPbDNA demonstrated that the rapid and robust induction of genes associated with the acute phase response, innate immune activation, cellular recruitment, and IFN-γ signaling observed at day 1 was largely absent at day 7. RNAseq analysis implicated NK cells as the major cellular source of IFN-γ. In vivo cell depletion and IFN-γ neutralization experiments supported the hypothesis that tissue-resident macrophages and NK cells are major contributors to the protective response and the NK cell-derived IFN-γ is key to induction of the mechanisms that block sporozoite development in the liver. These findings advance our understanding of the innate immune responses that prevent liver stage malaria infection.

Mass Spectrometry-Based Metabolomics Revealed Effects of Metronidazole on Giardia duodenalis

Giardia duodenalis is a significant protozoan that affects humans and animals. An estimated 280 million G. duodenalis diarrheal cases are recorded annually. Pharmacological therapy is crucial for controlling giardiasis. Metronidazole is the first-line therapy for treating giardiasis. Several metronidazole targets have been proposed. However, the downstream signaling pathways of these targets with respect to their antigiardial action are unclear. In addition, several giardiasis cases have demonstrated treatment failures and drug resistance. Therefore, the development of novel drugs is an urgent need. In this study, we performed a mass spectrometry-based metabolomics study to understand the systemic effects of metronidazole in G. duodenalis. A thorough analysis of metronidazole processes helps identify potential molecular pathways essential for parasite survival. The results demonstrated 350 altered metabolites after exposure to metronidazole. Squamosinin A and N-(2-hydroxyethyl)hexacosanamide were the most up-regulated and down-regulated metabolites, respectively. Proteasome and glycerophospholipid metabolisms demonstrated significant differential pathways. Comparing glycerophospholipid metabolisms of G. duodenalis and humans, the parasite glycerophosphodiester phosphodiesterase was distinct from humans. This protein is considered a potential drug target for treating giardiasis. This study improved our understanding of the effects of metronidazole and identified new potential therapeutic targets for future drug development.

CARD9 in host immunity to fungal, bacterial, viral, and parasitic infections: An update

Microbial infection, caused by fungi, bacteria, viruses, and parasites, significantly contributes to the global death burden and health costs. The innate and adaptive immune systems orchestrate a multifaceted signaling response to invading pathogens as the human antimicrobial system. In this process, caspase recruitment domain-containing protein 9 (CARD9) emerges as a critical intermediary adaptor molecule to participate in regulating a series of antimicrobial immune reactions. Previous publications have confirmed that CARD9 plays a crucial role in fungal, bacterial, viral, and parasitic infections. In this study, we aim to provide an update on the recent clinical and basic studies where the mechanism and function of CARD9 have been further studied and understood. In addition, we summarize the latest treatment and prevention strategies based on CARD9 and discuss the current perspectives and future direction of CARD9.

Role of sphingosine kinase and sphingosine-1-phosphate receptor in the liver pathology of mice infected with Plasmodium berghei ANKA

Decreased serum sphingosine 1-phosphate (S1P) has been reported in severe malaria patients, but the expression of receptors and enzymes associated with S1P has not been investigated in the liver of malaria patients. Therefore, this study aimed to investigate the expression of sphingosine kinase (SphK) and S1P receptors (S1PRs) in the liver of malaria-infected mice. C57BL/6 male mice were divided into a control group (n = 10) and a Plasmodium berghei (PbA)-infected group (n = 10). Mice in the malaria group were intraperitoneally injected with 1×10⁶P. berghei ANKA-infected red blood cells, whereas control mice were intraperitoneally injected with normal saline. Liver tissues were collected on Day 13 of the experiment to evaluate histopathological changes by hematoxylin and eosin staining and to investigate SphK and S1PR expression by immunohistochemistry and real-time PCR. Histological examination of liver tissues from the PbA-infected group revealed sinusoidal dilatation, hemozoin deposition, portal tract inflammation and apoptotic hepatocytes, which were absent in the control group. Immunohistochemical staining showed significant increases in the expression of SphK1 and SphK2 and significant decreases in the expression of S1PR1, S1PR2, and S1PR3 in the endothelium, hepatocytes, and Kupffer cells in liver tissue from the PbA-infected group compared with the control group. Real-time PCR analysis showed the upregulation of SphK1 and the downregulation of S1PR1, S1PR2, and S1PR3 in the liver in the PbA-infected group compared with the control group. In conclusion, this study demonstrates for the first time that SphK1 mRNA expression is upregulated and that S1PR1, S1PR2, and S1PR3 expression is decreased in the liver tissue of PbA-infected mice. Our findings suggest that the decreased levels of S1PR1, S1PR2, and S1PR3 might play an important role in liver injury during malaria infection.

Hemozoin: a Complex Molecule with Complex Activities

Purpose of Review

Malaria is a disease caused by parasites that reside in host red blood cells and use hemoglobin as a nutrient source. Heme released by hemoglobin catabolism is modified by the parasite to produce hemozoin (HZ), which has toxic effects on the host. Experimentation aiming to elucidate how HZ contributes to malaria pathogenesis has utilized different preparations of this molecule, complicating interpretation and comparison of findings. We examine natural synthesis and isolation of HZ and highlight studies that have used multiple preparations, including synthetic forms, in a comparative fashion.

Recent Findings

Recent work utilizing sophisticated imaging and detection techniques reveals important molecular characteristics of HZ synthesis and biochemistry. Other recent studies further refine understanding of contributions of HZ to malaria pathogenesis yet highlight the continuing need to characterize HZ preparations and contextualize experimental conditions in the in vivo infection milieu.

Summary

This review highlights the necessity of collectively determining what is physiologically relevant HZ. Characterization of isolated natural HZ and use of multiple preparations in each study are recommended with application of in vivo studies whenever possible. Adoption of such practices is expected to improve reproducibility of results and elucidate the myriad of ways that HZ participates in malaria pathogenesis.

Protective Effect of an Anti-HMGB-1 Neutralizing Antibody on Hemozoin-Induced Alveolar Epithelial Cell in a Model of Malaria Associated ALI/ARDS

Background:

We aimed to determine whether neutralizing high mobility group box-1 (HMGB-1) prevents the release of HMGB-1 and proinflammatory cytokines on hemozoin (Hz)-induced alveolar epithelial cell in a model of malaria associated ALI/ARDS.

Methods:

This study was conducted in the Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand in 2020. Human pulmonary alveolar epithelial cells (HPAEpiCs) were exposed to medium alone or 20 μM Hz for 24 h and incubated with different concentrations (1, 5, and 10 μg/ml) of anti-HMGB-1 monoclonal antibody (mAb) for various times (0, 4, 12, 24, and 48 h). The levels of HMGB-1, TNF-α and IFN-γ in the supernatants were measured by ELISA. The mRNA expression of RAGE, TLR-2 and TLR-4 were analyzed by real-time PCR.

Results:

The HPAEpiCs treated with 10 μg/ml anti-HMGB-1 mAb showed a significant reduction in HMGB-1 release into the supernatant compared with those treated with 1 and 5 μg/ml anti-HMGB-1 mAb. The levels of TNF-α and IFN-γ were significantly decreased in the supernatant of HPAEpiCs treated with 1, 5, and 10 μg/ml anti-HMGB-1 mAb for 4, 12, 24, and 48 h compared with those stimulated with Hz alone. The mRNA expression levels of RAGE, TLR-2, and TLR-4 were significantly decreased after 24 h of anti-HMGB-1 antibody treatment at all concentrations.

Conclusion:

An anti-HMGB-1 antibody could be an effective agent for inhibiting the release of HMGB-1, TNF-α and IFN-γ. Furthermore, a neutralizing anti-HMGB-1 antibody could be applicable for the treatment of malaria-associated ALI/ARDS.

Streptozotocin induces alpha-2u globulin nephropathy in male rats during diabetic kidney disease

BACKGROUND

Alpha-2u globulin nephropathy mainly shows toxicological pathology only in male rats induced by certain chemicals and drugs, such as levamisole (antiparasitic and anticancer drugs). Streptozotocin (STZ) is also an anticancer-antibiotic agent that has been used for decades to induce a diabetic kidney disease model in rodents. The purpose of this study is to determine if STZ causes alpha-2u globulin nephropathy in male rats during an advanced stage of diabetic kidney disease. Alpha-2u globulin nephropathy, water absorption and filtration capacities (via aquaporin [AQP]-1, - 2, - 4 and - 5) and mitochondrial function (through haloacid dehalogenase-like hydrolase domain-containing protein [HDHD]-3 and NADH-ubiquinone oxidoreductase 75 kDa subunit [NDUFS]-1 proteins) were examined in STZ-induced diabetic Wistar rat model.

RESULTS

More than 80% of severe clinical illness rats induced by STZ injection simultaneously exhibited alpha-2u globulin nephropathy with mitochondrial degeneration and filtration apparatus especially pedicels impairment. They also showed significantly upregulated AQP-1, - 2, - 4 and - 5, HDHD-3 and NDUFS-1 compared with those of the rats without alpha-2u globulin nephropathy.

CONCLUSIONS

STZ-induced alpha-2u globulin nephropathy during diabetic kidney disease in association with deterioration of pedicels, renal tubular damage with adaptation and mitochondrial driven apoptosis.

Hemozoin Promotes Lung Inflammation via Host Epithelial Activation

Respiratory distress (RD) is a complication of severe malaria associated with a particularly high risk for death in African children infected with the parasite Plasmodium falciparum. The pathophysiology underlying RD remains poorly understood, and the condition is managed supportively.

Respiratory distress in severe malaria is associated with high mortality, but its pathogenesis remains unclear. The malaria pigment hemozoin (HZ) is abundant in target organs of severe malaria, including the lungs, and is known to be a potent innate immune activator of phagocytes. We hypothesized that HZ might also stimulate lung epithelial activation and thereby potentiate lung inflammation. We show here that airway epithelium stimulated with HZ undergoes global transcriptional reprogramming and changes in cell surface protein expression that comprise an epithelial activation phenotype. Proinflammatory signaling is induced, and key cytoadherence molecules are upregulated, including several associated with severe malaria, such as CD36 and ICAM1. Epithelial and extracellular matrix remodeling pathways are transformed, including induction of key metalloproteases and modulation of epithelial junctions. The overall program induced by HZ serves to promote inflammation and neutrophil transmigration, and is recapitulated in a murine model of HZ-induced acute pneumonitis. Together, our data demonstrate a direct role for hemozoin in stimulating epithelial activation that could potentiate lung inflammation in malaria.

Case Report: The First Direct Evidence of Gnathostoma spinigerum Migration through Human Lung

Gnathostomiasis is a helminthic infection caused by the third-stage larvae of nematodes of the genus Gnathostoma. The life cycle in humans starts with an enteric phase, with the worm perforating the gastric or intestinal mucosa to reach the peritoneal cavity and migrating through the human body. Subsequent penetration through the diaphragm may produce pleuropulmonary symptoms. We herein present a previously healthy 56-year-old Thai man from Southern Thailand who was an ex-smoker presented with chronic dry cough progressing to hemoptysis after consuming grilled swamp eels and freshwater fish. Chest computed tomography showed consolidation at the lingular segment, and the differential diagnosis was primary lung cancer and pulmonary tuberculosis. The lung tissue biopsied during bronchoscopy displayed segments of organisms with the phenotypic characteristics of Gnathostoma spp., and abundant eosinophils were seen in the alveolar tissue. Gnathostoma spinigerum infection was confirmed by a Western blot assay for G. spinigerum-specific 24-kDa reactive band. The patient received albendazole, and a follow-up chest radiograph revealed improvement in the consolidation in the lung and reduction in hemoptysis. We report the first direct evidence including pathology and immunohistochemistry of Gnathostoma invasion via the human lung, with clinical and radiographic presentations mimicking either malignancy or chronic infection.

Hemozoin in Malarial Complications: More Questions Than Answers

Plasmodium parasites contain various virulence factors that modulate the host immune response. Malarial pigment, or hemozoin (Hz), is an undegradable crystalline product of the hemoglobin degradation pathway in the parasite and possesses immunomodulatory properties. An association has been found between Hz accumulation and severe malaria, suggesting that the effects of Hz on the host immune response may contribute to the development of malarial complications. Although the immunomodulatory roles of Hz have been widely investigated, many conflicting data exist, likely due to the variability between experimental set-ups and technical limitations of Hz generation and isolation methods. Here, we critically assess the potential immunomodulatory effects of Hz, its role in malarial complications, and its potential effects after parasite clearance.

Evaluating the effect of rice (Oryza sativa L.: SRNC05053-6-2) crude extract on psoriasis using in vitro and in vivo models

Psoriasis is mainly caused because of inappropriate immune responses in the epidermis. Rice (Oryza sativa L.: SRNC05053-6-2) consists of anthocyanin, which exhibits strong antioxidative and anti-inflammatory properties. This study aimed to evaluate the role of this black-coloured rice crude extract in alleviating the symptoms of psoriasis using human psoriatic artificial skin and an imiquimod-induced rat psoriasis model. Psoriasis-related genes, cytokines and chemokines were examined; in addition, the antioxidative and anti-inflammatory properties and the immunohistopathological features of this condition were studied. The results showed that the rice extract reduced the severity of psoriasis by (1) decreasing the epidermal thickness, acanthosis, hyperkeratosis, epidermal inflammation and degree of apoptosis induction via caspase-3, (2) increasing the expression levels of anti-inflammatory cytokines (IL-10 and TGF-β), (3) reducing the levels of pro-inflammatory cytokines (IL-6, IL-8, IL-20, IL-22 and TNF-α), chemokines (CCL-20) and anti-microbial peptides (psoriasin and β-defensin), (4) enhancing the antioxidative property (Nrf-2), (5) downregulating the levels of psoriasis-associated genes (psoriasin, β-defensin, koebnerisin 15L and koebnerisin 15S) and (6) upregulating the levels of psoriasis-improving genes (caspase-14, involucrin and filaggrin). Thus, the extract appears to exert therapeutic effects on psoriasis through its antioxidative and immunomodulatory properties.

Heme on Pulmonary Malaria: Friend or Foe?

Malaria is a hemolytic disease that, in severe cases, can compromise multiple organs. Pulmonary distress is a common symptom observed in severe malaria caused by Plasmodium vivax or Plasmodium falciparum. However, biological components involved in the development of lung malaria are poorly studied. In experimental models of pulmonary malaria, it was observed that parasitized red blood cell-congested pulmonary capillaries are related to intra-alveolar hemorrhages and inflammatory cell infiltration. Thus, it is very likely that hemolysis participates in malaria-induced acute lung injury. During malaria, heme assumes different biochemical structures such as hemin and hemozoin (biocrystallized structure of heme inside Plasmodium sp.). Each heme-derived structure triggers a different biological effect: on the one hand, hemozoin found in lung tissue is responsible for the infiltration of inflammatory cells and consequent tissue injury; on the other hand, heme stimulates heme oxygenase-1 (HO-1) expression and CO production, which protect mice from severe malaria. In this review, we discuss the biological mechanism involved in the dual role of heme response in experimental malaria-induced acute lung injury.

Physiological and Pathological Functions of CARD9 Signaling in the Innate Immune System

Caspase recruitment domain protein 9 (CARD9) forms essential signaling complexes in the innate immune system that integrate cues from C-type lectin receptors and specific intracellular pattern recognition receptors. These CARD9-mediated signals are pivotal for host defense against fungi, and they mediate immunity against certain bacteria, viruses and parasites. Furthermore, CARD9-regulated pathways are involved in sterile inflammatory responses critical for immune homeostasis and can control pro- and antitumor immunity in cancer microenvironments. Consequently, multiple genetic alterations of human CARD9 are connected to primary immunodeficiencies or prevalent inflammatory disorders in patients. This review will summarize our current understanding of CARD9 signaling in the innate immune system, its physiological and pathological functions and their implications for human immune-mediated diseases.

Effect of urea-extracted sericin on melanogenesis: potential applications in post-inflammatory hyperpigmentation

Background

Hyperpigmentation disorders such as post-inflammatory hyperpigmentation are major concerns not only in light-skinned people but also in Asian populations with darker skin. The anti-tyrosinase and immunomodulatory effects of sericin have been known for decades. However, the therapeutic effects of sericin on hyperpigmentation disorders have not been well documented.

Methods

In this study, we used an in vitro model to study the anti-tyrosinase, tolerogenic, and anti-melanogenic effects of sericin on Staphylococcus aureus peptidoglycan (PEG)-stimulated melanocytes, dendritic cells (DCs), and artificial skin (MelanoDerm™). Enzyme-linked immunosorbent assay, conventional and immunolabeled electron microscopy, and histopathological studies were performed.

Results

The results revealed that urea-extracted sericin has strong anti-tyrosinase properties as shown by a reduction of tyrosinase activity in melanin pigments both 48 h and 10 days after allergic induction with PEG. Anti-inflammatory cytokines including interleukin (IL)-4, IL-10, and transforming growth factor-β were upregulated upon sericin treatment (10, 20, and 50 µg/mL), whereas production of allergic chemokines, CCL8 and CCL18, by DCs was diminished 48 h after allergic induction with PEG. Moreover, sericin lowered the expression of micropthalmia-associated transcription factor (MITF), a marker of melanogenesis regulation, in melanocytes and keratinocytes, which contributed to the reduction of melanin size and the magnitude of melanin deposition. However, sericin had no effect on melanin transport between melanocytes and keratinocytes, as demonstrated by a high retention of cytoskeletal components.

Conclusion

In summary, sericin suppresses melanogenesis by inhibition of tyrosinase activity, reduction of inflammation and allergy, and modulation of MITF function.

Malaria pigment accelerates MTT - formazan exocytosis in human endothelial cells

Haemozoin is a by-product of haemoglobin digestion by intraerythrocytic malaria parasites, which induces immunologic responses on different tissues, including endothelial cells. In the present paper, the incubation of human microvascular endothelial cells with haemozoin significantly inhibited MTT reduction, a measure of cytotoxicity, without increasing the release of cytoplasmic lactate dehydrogenase. Moreover, haemozoin did not induce apoptosis or cell cycle arrest nor decreased the number of live cells, suggesting that cells viability itself was not affected and that the inhibition of MTT reduction was only apparent and probably due to accelerated MTT-formazan exocytosis. After 30 min of MTT addition, a significant increase in the % of cells exocytosing MTT formazan crystals was observed in haemozoin-treated cells compared with control cells. Such an effect was partially reversed by the addition of genistein, an inhibitor of MTT-formazan exocytosis. The rapid release of CXCL-8, a preformed chemokine contained in Weibel-Palade bodies, confirmed that haemozoin induces a perturbation of the intracellular endothelial trafficking, including the exocytosis of MTT-formazan containing vesicles. The haem moiety of haemozoin is responsible for the observed effect. Moreover, this work underlines that MTT assay should not be used to measure cytotoxicity induced by haemozoin and other methods should be preferred.