The potential role of Hippo pathway regulates cellular metabolism via signaling crosstalk in disease-induced macrophage polarization

Macrophages polarized into distinct phenotypes play vital roles in inflammatory diseases by clearing pathogens, promoting tissue repair, and maintaining homeostasis. Metabolism serves as a fundamental driver in regulating macrophage polarization, and understanding the interplay between macrophage metabolism and polarization is crucial for unraveling the mechanisms underlying inflammatory diseases. The intricate network of cellular signaling pathway plays a pivotal role in modulating macrophage metabolism, and growing evidence indicates that the Hippo pathway emerges as a central player in network of cellular metabolism signaling. This review aims to explore the impact of macrophage metabolism on polarization and summarize the cell signaling pathways that regulate macrophage metabolism in diseases. Specifically, we highlight the pivotal role of the Hippo pathway as a key regulator of cellular metabolism and reveal its potential relationship with metabolism in macrophage polarization.

Hepatic inflammation and liver fibrogenesis: A potential target for the treatment of cystic echinococcosis-associated hepatic injury

To investigate the effect of cystic echinococcosis (CE) on liver damage, we developed a secondary experimental echinococcosis in Swiss mice by intraperitoneal inoculation of viable protoscoleces. Mice were randomly allocated into three groups: Ctrl group, PBS group, and CE group. Mice were euthanized and associated indications were investigated to evaluate inflammatory and fibrotic responses in liver. Hepatic damage and fibrotic reaction were histologically analyzed. The hepatic expression of iNOS, TNF-α, NF-κβ, vimentin, Bcl-2 and CD68 was evaluated by Immunohistochemical examinations. Interestingly, a significant iNOS, TNF-α, NF-κβ, vimentin, Bcl-2 and CD68 increase levels was observed in liver tissue and pericystic layer of hepatic hydatid cyst and correlate with the abundance of collagen and reticulin fibers. These observations could promote a potential target for the treatment of CE-associated hepatic injury.

A combination of pirfenidone and TGF-β inhibition mitigates cystic echinococcosis-associated hepatic injury

Cystic echinococcosis (CE) occurs in the intermediate host's liver, assuming a bladder-like structure surrounded by the host-derived collagen capsule mainly derived from activated hepatic stellate cells (HSCs). However, the effect of CE on liver natural killer (NK) cells and the potential of transforming growth factor-β (TGF-β) signalling inhibition on alleviating CE-related liver damage remain to be explored. Here, by using the CE-mouse model, we revealed that the inhibitory receptors on the surface of liver NK cells were up-regulated, whereas the activating receptors were down-regulated over time. TGF-β1 secretion was elevated in liver tissues and mainly derived from macrophages. A combination of TGF-β signalling inhibitors SB525334 and pirfenidone could reduce the expression of TGF-β1 signalling pathway-related proteins and collagen production. Based on the secretion of TGF-β1, only the pirfenidone group showed a depressing effect. Also, the combination of SB525334 and pirfenidone exhibited a higher potential in effectively alleviating the senescence of the hepatocytes and restoring liver function. Together, TGF-β1 may be a potential target for the treatment of CE-associated liver fibrosis.

Extracellular vesicles from Echinococcus granulosus larval stage: Isolation, characterization and uptake by dendritic cells

The secretion of extracellular vesicles (EVs) in helminth parasites is a constitutive mechanism that promotes survival by improving their colonization and adaptation in the host tissue. In the present study, we analyzed the production of EVs from supernatants of cultures of Echinococcus granulosus protoscoleces and metacestodes and their interaction with dendritic cells, which have the ability to efficiently uptake and process microbial antigens, activating T lymphocytes. To experimentally increase the release of EVs, we used loperamide, a calcium channel blocker that increases the cytosolic calcium level in protoscoleces and EV secretion. An exosome-like enriched EV fraction isolated from the parasite culture medium was characterized by dynamic light scattering, transmission electron microscopy, proteomic analysis and immunoblot. This allowed identifying many proteins including: small EV markers such as TSG101, SDCBP, ALIX, tetraspanins and 14-3-3 proteins; proteins involved in vesicle-related transport; orthologs of mammalian proteins involved in the immune response, such as basigin, Bp29 and maspardin; and parasite antigens such as antigen 5, P29 and endophilin-1, which are of special interest due to their role in the parasite-host relationship. Finally, studies on the EVs-host cell interaction demonstrated that E. granulosus exosome-like vesicles were internalized by murine dendritic cells, inducing their maturation with increase of CD86 and with a slight down-regulation in the expression of MHCII molecules. These data suggest that E. granulosus EVs could interfere with the antigen presentation pathway of murine dendritic cells inducing immunoregulation in the host. Further studies are needed to better understand the role of these vesicles in parasite survival and as diagnostic markers and new vaccines.

Human cystic echinococcosis, caused by chronic infection with the larval stage of Echinococcus granulosus, affects over 1 million people worldwide. This helminth parasite secretes numerous excretory/secretory products that are in contact with host tissues where it establishes hydatid cysts. In this study, we comprehensively characterized extracellular vesicles (EVs) from E. granulosus protoscoleces and metacestodes, and demonstrated for the first time that the exosome-like vesicles from helminths can interact with host dendritic cells and carry several immunoregulatory proteins. This study provides valuable data on cestode-host immune communication. Nevertheless, further research on EVs is needed to fully understand their role in the parasite-host interface and obtain new data concerning their function as therapeutic markers and diagnostic tools.

In vivo treatment with IL-17A attenuates hydatid cyst growth and liver fibrogenesis in an experimental model of echinococcosis

We aimed to assess the effect of exogenous Interleukin (IL)-17A in experimental model of echinococcosis. Swiss mice were inoculated intra-peritoneally with viable protoscoleces (PSCs). Then, IL-17A was administered at 100, 125 or 150 pg/mL two weeks after cystic echinococcosis (CE) induction. Cyst development and hepatic damage were macroscopically and histologically analyzed. We observed that in vivo IL-17A treatment at 100, 125, and 150 pg/mL, reduced metacestode growth by 72.3%, 93.8%, and 96.9%, respectively. Interestingly an amelioration of liver architecture was noted at 125 pg/mL without toxic effect. In this context, we showed less fibrosis reaction and reduced expression of iNOS, TNF-α, NF-κb and CD68 in hepatic parenchyma of treated mice by 125 pg/mL of IL-17A. Collectively, our results indicate an antihydatic effect and immunoprotective properties of IL-17A and suggest its potential therapeutic value against Echinococcus granulosus infection.

Macrophage plasticity, polarization, and function in health and disease

Macrophages are heterogeneous and their phenotype and functions are regulated by the surrounding micro-environment. Macrophages commonly exist in two distinct subsets: 1) Classically activated or M1 macrophages, which are pro-inflammatory and polarized by lipopolysaccharide (LPS) either alone or in association with Th1 cytokines such as IFN-γ, GM-CSF, and produce pro-inflammatory cytokines such as interleukin-1β (IL-1β), IL-6, IL-12, IL-23, and TNF-α; and 2) Alternatively activated or M2 macrophages, which are anti-inflammatory and immunoregulatory and polarized by Th2 cytokines such as IL-4 and IL-13 and produce anti-inflammatory cytokines such as IL-10 and TGF-β. M1 and M2 macrophages have different functions and transcriptional profiles. They have unique abilities by destroying pathogens or repair the inflammation-associated injury. It is known that M1/M2 macrophage balance polarization governs the fate of an organ in inflammation or injury. When the infection or inflammation is severe enough to affect an organ, macrophages first exhibit the M1 phenotype to release TNF-α, IL-1β, IL-12, and IL-23 against the stimulus. But, if M1 phase continues, it can cause tissue damage. Therefore, M2 macrophages secrete high amounts of IL-10 and TGF-β to suppress the inflammation, contribute to tissue repair, remodeling, vasculogenesis, and retain homeostasis. In this review, we first discuss the basic biology of macrophages including origin, differentiation and activation, tissue distribution, plasticity and polarization, migration, antigen presentation capacity, cytokine and chemokine production, metabolism, and involvement of microRNAs in macrophage polarization and function. Secondly, we discuss the protective and pathogenic role of the macrophage subsets in normal and pathological pregnancy, anti-microbial defense, anti-tumor immunity, metabolic disease and obesity, asthma and allergy, atherosclerosis, fibrosis, wound healing, and autoimmunity.

Melanomacrophage functions in the liver of the caecilian Siphonops annulatus

Melanomacrophages are phagocytes that synthesize melanin. They are found in the liver and spleen of ectothermic vertebrates, and in the kidney of fish. In agnathan and elasmobranch fish, melanomacrophages are seen as isolated cells, and forming clusters in all the other vertebrates. The natural phagocytic activity of melanomacrophages is poorly characterized, as most of the research works have focused on induced phagocytic activity only. Furthermore, little is known about amphibian melanomacrophages, mainly about those in caecilians - wormlike amphibians in the order of Gymnophiona, which is the least known group of terrestrial vertebrates. The present research work aimed at the structure and function of hepatic melanomacrophages of Siphonops annulatus, a species largely found in South America. We identified the role of these cells in the control of circulating basophils (pro-melanogenic cells), in the turnover of liver collagen stroma and in the hemocatheresis, interrelated physiological mechanisms.

Corilagin Counteracts IL-13Rα1 Signaling Pathway in Macrophages to Mitigate Schistosome Egg-Induced Hepatic Fibrosis

The IL-13Rα1 signaling pathway and M2 macrophages play crucial roles in schistosome egg-induced hepatic fibrosis via the expression of pro-fibrotic molecules. This study aims to investigate the inhibitory effect and mechanism of action of corilagin on schistosome egg-induced hepatic fibrosis via the IL-13Rα1 signaling pathway in M2 macrophages in vitro and in vivo. The mRNA and protein expression of IL-13Rα1, PPARγ, KLF4, SOCS1, STAT6, p-STAT6, and TGF-β was measured in vitro with corilagin treatment after IL-13 stimulation and in vivo corilagin treatment after effectively killing the adult schistosomes in schistosome-infected mice. Histological analysis of liver tissue was assessed for the degree of hepatic fibrosis. The results revealed that corilagin significantly reduced the expression of PPARγ, KLF4, SOCS1, p-STAT6, and TGF-β compared with model group and praziquantel administration (p < 0.01 or p < 0.05) in vivo and in vitro, which indicated a strong inhibitory effect of corilagin on IL-13Rα1 signaling pathway. As well, the inhibitory effect of corilagin showed a significant dose-dependence (p < 0.05). The area of fibrosis and distribution of M2 macrophages in mouse liver tissue were reduced significantly and dose-dependently with corilagin treatment compared to model group or praziquantel administration (p < 0.01 or p < 0.05), indicating that corilagin suppressed IL-13Rα1 signaling pathway and M2 macrophage polarization effectively in vivo. Furthermore, the anti-fibrogenic effect persisted even when IL-13Rα1 was up- or down-regulated in vitro. In conclusion, corilagin can suppress schistosome egg-induced hepatic fibrosis via inhibition of M2 macrophage polarization in the IL-13Rα1 signaling pathway.

Comparison of serological assessments in the diagnosis of liver fibrosis in bile duct ligation mice

Liver fibrosis assessment is essential to make a prognosis and to determine the appropriate anti-fibrosis treatment. Non-invasive serum markers are widely studied in patients to assess liver fibrosis due to the limitations of liver biopsy. When using animal models to study the mechanism and intervention of hepatic fibrosis, serum markers might be useful for the continuous assessment of liver fibrosis in individual animals, which could avoid the influence of biological differences between individuals. However, it is unclear whether serum markers can assess hepatic fibrosis in the animal model. In the present study, we evaluated and compared the ability of four serum markers to assess liver fibrosis in bile duct ligation mice. According to the stages of liver fibrosis assessed by pathological changes, mice in this study were divided into five groups (F0, F1, F2, F3, and F4). Subsequently, four serum markers, aspartate aminotransferase-to-alanine aminotransferase ratio (AAR), aspartate aminotransferase-to-platelet ratio index (APRI), fibrosis index based on the 4 factors (FIB-4), and Forns Index, were calculated for each group. Furthermore, the correlations between serum markers and pathological stages and the ability of serological markers to evaluate liver fibrosis were analyzed. AAR, APRI, FIB-4, and Forns Index could significantly distinguish F0-2 from F3-4 mice. APRI, FIB-4, and Forns Index could detect F0-3 from F4 mice. Among these four markers, FIB-4 was the best able to distinguish ≥F2 and ≥F3, with area under the curve values of 0.882 and 0.92, respectively. Forns Index was best for diagnosing F4 with area under the curve value of 0.879. These results demonstrated that serum markers could be used for assessing liver fibrosis in bile duct ligation mice, and therefore, these markers might lead to more accurate diagnostic and therapeutic studies through continuous monitoring in individual animals. Impact statement The assessment of liver fibrosis is essential for making a prognosis and determining the appropriate anti-fibrosis treatment. In studies focusing on the mechanism and treatment of liver fibrosis using animal models, it would be more accurate to continuously evaluate liver fibrosis in a single animal to avoid individual biological differences. Unfortunately, it is difficult to perform continuous assessment through liver biopsy in the most commonly used rodent models. It is unclear whether serum markers, which have been used in hepatic fibrosis patients, could be used in animal models. Our results demonstrate that serum markers could be used for assessing liver fibrosis in bile duct ligation mice. This study might contribute to more accurate diagnostic and therapeutic studies through continuous monitoring in individual animals.

Immunology of Alveolar and Cystic Echinococcosis (AE and CE)

Cystic and alveolar echinococcosis are severe chronic helminthic diseases caused by the cystic growth or the intrahepatic tumour-like growth of the metacestode of Echinococcus granulosus or Echinococcus multilocularis, respectively. Both parasites have evolved sophisticated strategies to escape host immune responses, mainly by manipulating and directing this immune response towards anergy and/or tolerance. Recent research studies have revealed a number of respective immunoregulatory mechanisms related to macrophages and dendritic cell as well as T cell activities (regulatory T cells, Tregs). A better understanding of this complex parasite-host relationship, and the elucidation of specific crucial events that lead to disease, represents targets towards the development of novel treatment strategies and options.

Diagnostic accuracy of APRI and FIB-4 for predicting hepatitis B virus-related liver fibrosis accompanied with hepatocellular carcinoma

BACKGROUND

Aspartate aminotransferase to platelet ratio index (APRI) and the fibrosis index based on four factors (FIB-4) are the two most focused non-invasive models to assess liver fibrosis.

AIMS

We aimed to examine the validity of these two models for predicting hepatitis B virus (HBV)-related liver fibrosis accompanied with hepatocellular carcinoma (HCC).

METHODS

We enrolled HBV-infected patients with liver cancer who had received hepatectomy. The accuracy of APRI and FIB-4 for diagnosing liver fibrosis was assessed based on their sensitivity, specificity, diagnostic efficiency, positive predictive value (PPV), negative predictive value (NPV), kappa (κ) value and area under the receiver-operating characteristic curve (AUC).

RESULTS

Finally 2176 patients were included, with 1682 retrospective subjects and 494 prospective subjects. APRI (rs=0.310) and FIB-4 (rs=0.278) were positively correlated with liver fibrosis. And χ(2) analysis demonstrated that APRI and FIB-4 values correlated with different levels of liver fibrosis with all P values less than 0.01. The AUC values for APRI and FIB-4 were 0.685 and 0.626 (P=0.73) for predicting significant fibrosis, 0.681 and 0.648 (P=0.81) for differentiation of advanced fibrosis and 0.676 and 0.652 (P=0.77) for diagnosing cirrhosis.

CONCLUSION

APRI and FIB-4 correlate with liver fibrosis. However these two models have low accuracy for predicting HBV-related liver fibrosis in HCC patients.

In vitro anti-hydatic and immunomodulatory effects of ginger and [6]-gingerol

OBJECTIVE

To study in vitro anti-hydatic and immunomodulatory effects of ginger and [6]-gingerol as an alternative therapy for cystic echinococcosis.

METHODS

Effect of a commonly used herbal product and ginger (Zingiber officinale) towards protoscoleces (PSC) and cyst wall in vitro was studied. The effect of [6]-gingerol, and the pungent constituent of ginger, was also evaluated on PSC culture. Furthermore, the activity of both extracts in association with interferon-gamma (IFN-γ) on PSC co-cultured with mononuclear cells of hydatic patients was evaluated. The nitric oxide (NO) production was measured in each co-culture.

RESULTS

Ginger exhibited a concentration- and time-dependent cytotoxic effect against PSC and cyst wall. Interestingly, ginger was more effective than the [6]-gingerol. Moreover, additional parasitic effect between extracts and IFN-γ are also observed in co-cultures. Furthermore, both extracts attenuated the NO production elicited by this infection or by the IFN-γ.

CONCLUSIONS

Ginger has an important anti-hydatic effect in vitro. This effect is amplified in the presence of IFN-γ. Moreover, this herbal product may protect against host's cell death by reducing the high levels of NO. Ginger may act, at least, through the [6]-gingerol. All our data suggest the promising use of ginger in the treatment of Echinococcus granulosus infection.

Antihydatic and immunomodulatory effects of Punica granatum peel aqueous extract in a murine model of echinococcosis

OBJECTIVE

To investigate the effect of pomegranate peel aqueous extract (PGE) on the development of secondary experimental echinococcosis and on the viability of Echinococcus granulosus protoscoleces, and the immunomodulatory properties of PGE.

METHODS

Swiss mice were inoculated intraperitoneally with viable protoscoleces. Then, PGE was orally administered daily during cystic echinococcosis development. Cyst development and hepatic damage were macroscopically and histologically analyzed. The production of nitric oxide and TNF-α was assessed in plasma and the hepatic expression of iNOS, TNF-α, NF-κB and CD68 was examined. Moreover, protoscoleces were cultured and treated with different concentrations of PGE.

RESULTS

It was observed that in vitro treatment of protoscoleces caused a significant decrease in viability in a PGE-dose-dependent manner. In vivo, after treatment of cystic echinococcosis infected mice with PGE, a significant decrease in nitric oxide levels (P < 0.0001) and TNF-α levels (P < 0.001) was observed. This decline was strongly related to the inhibition of cyst development (rate of hydatid cyst growth inhibition = 63.08%) and a decrease in CD68 expression in both the pericystic layer of hepatic hydatid cysts and liver tissue (P < 0.0001). A significant diminution of iNOS, TNF-α and NF-κB expression was also observed in liver tissue of treated mice (P < 0.0001).

CONCLUSIONS

Our results indicate an antihydatic scolicidal effect and immunomodulatory properties of PGE, suggesting its potential therapeutic role against Echinococcus granulosus infection.

Macrophage polarization in pathology

Macrophages are cells of the innate immunity constituting the mononuclear phagocyte system and endowed with remarkable different roles essential for defense mechanisms, development of tissues, and homeostasis. They derive from hematopoietic precursors and since the early steps of fetal life populate peripheral tissues, a process continuing throughout adult life. Although present essentially in every organ/tissue, macrophages are more abundant in the gastro-intestinal tract, liver, spleen, upper airways, and brain. They have phagocytic and bactericidal activity and produce inflammatory cytokines that are important to drive adaptive immune responses. Macrophage functions are settled in response to microenvironmental signals, which drive the acquisition of polarized programs, whose extremes are simplified in the M1 and M2 dichotomy. Functional skewing of monocyte/macrophage polarization occurs in physiological conditions (e.g., ontogenesis and pregnancy), as well as in pathology (allergic and chronic inflammation, tissue repair, infection, and cancer) and is now considered a key determinant of disease development and/or regression. Here, we will review evidence supporting a dynamic skewing of macrophage functions in disease, which may provide a basis for macrophage-centered therapeutic strategies.

Inhibition of Granulomatous Inflammation and Prophylactic Treatment of Schistosomiasis with a Combination of Edelfosine and Praziquantel

BACKGROUND

Schistosomiasis is the third most devastating tropical disease worldwide caused by blood flukes of the genus Schistosoma. This parasitic disease is due to immunologic reactions to Schistosoma eggs trapped in tissues. Egg-released antigens stimulate tissue-destructive inflammatory and granulomatous reactions, involving different immune cell populations, including T cells and granulocytes. Granulomas lead to collagen fibers deposition and fibrosis, resulting in organ damage. Praziquantel (PZQ) is the drug of choice for treating all species of schistosomes. However, PZQ kills only adult Schistosoma worms, not immature stages. The inability of PZQ to abort early infection or prevent re-infection, and the lack of prophylactic effect prompt the need for novel drugs and strategies for the prevention of schistosomiasis.

METHODOLOGY/PRINCIPAL FINDINGS

Using in vitro and in vivo approaches, we have found that the alkylphospholipid analog edelfosine kills schistosomula, and displays anti-inflammatory activity. The combined treatment of PZQ and edelfosine during a few days before and after cercariae infection in a schistosomiasis mouse model, simulating a prophylactic treatment, led to seven major effects: a) killing of Schistosoma parasites at early and late development stages; b) reduction of hepatomegaly; c) granuloma size reduction; d) down-regulation of Th1, Th2 and Th17 responses at late post-infection times, thus inhibiting granuloma formation; e) upregulation of IL-10 at early post-infection times, thus potentiating anti-inflammatory actions; f) down-regulation of IL-10 at late post-infection times, thus favoring resistance to re-infection; g) reduction in the number of blood granulocytes in late post-infection times as compared to infected untreated animals.

CONCLUSIONS/SIGNIFICANCE

Taken together, these data suggest that the combined treatment of PZQ and edelfosine promotes a high decrease in granuloma formation, as well as in the cellular immune response that underlies granuloma development, with changes in the cytokine patterns, and may provide a promising and effective strategy for a prophylactic treatment of schistosomiasis.

Macrophage plasticity and polarization in liver homeostasis and pathology

Resident and recruited macrophages are key players in the homeostatic function of the liver and in its response to tissue damage. In response to environmental signals, macrophages undergo polarized activation to M1 or M2 or M2-like activation states. These are extremes of a spectrum in a universe of activation states. Progress has been made in understanding the molecular mechanisms underlying the polarized activation of mononuclear phagocytes. Resident and recruited macrophages are a key component of diverse homeostatic and pathological responses of hepatic tissue. Polarized macrophages interact with hepatic progenitor cells, integrate metabolic adaptation, mediate responses to infectious agents, orchestrate fibrosis in a yin-yang interaction with hepatic stellate cells, and are a key component of tumor-promoting inflammation.

CONCLUSION

A better understanding of macrophage diversity and plasticity in liver homeostasis and pathology may pave the way to innovative diagnostic and therapeutic approaches.

Kupffer Cells in Health and Disease

Kupffer cells (KC), the resident macrophages of the liver, represent the largest population of mononuclear phagocytes in the body. Phenotypic, developmental, and functional aspects of these cells in steady state and in different diseases are the focus of this review. Recently it has become evident that KC precursors seed the liver already early in fetal development, and the population can be maintained independently from circulating monocytes. However, inflammatory conditions allow rapid differentiation of monocytes into mature cells that are indistinguishable from genuine KC. KC are located in the lumen of sinusoids that receive blood both from the portal vein, carrying nutrients and microbial products from the gut, and from the hepatic artery. This positions KC ideally for their prime function, namely surveillance and clearance of the circulation. As such, they are important in iron recycling by phagocytosing effete erythrocytes, for instance. The immunophenotype of KC, characterized by a wide variety of endocytic receptors, is indicative of this scavenger function. In maintaining homeostasis, KC have an ambivalent response to exogenous triggers. On the one hand, their surveillance function requires alert responses to potentially hazardous substances. On the other hand, continuous exposure of the cells to the trigger-rich content of blood originating from the gut dampens their responsiveness to further stimuli. This ambivalence is also reflected in their diverse roles in disease pathogenesis. For the latter, we sketch the contribution of KC by giving examples of their role in metabolic disease, infections, and liver injury.

Inflammation, wound repair, and fibrosis: reassessing the spectrum of tissue injury and resolution

Estimates from various disease-specific registries suggest that chronic inflammatory and fibrotic disorders affect a large proportion of the world's population, yet therapies for these conditions are largely ineffective. Recent advances in our collective understanding of mechanisms underlying both physiological and pathological repair of tissue injury are informing new clinical approaches to deal with various human inflammatory and fibrotic diseases. This 2013 Annual Review Issue of The Journal of Pathology offers an up-to-date glimpse of ongoing research in the fields of inflammation, wound healing, and tissue fibrosis, and highlights novel pathways and mechanisms that may be exploited to provide newer, more effective treatments to patients worldwide suffering from these conditions.