Interplay of cysteinyl leukotrienes and TGF-β in the activation of hepatic stellate cells from Schistosoma mansoni granulomas

20-Hydroxytetraenoic acid induces hepatic fibrosis via the TGF-β1/Smad3 signaling pathway

Hepatic fibrosis is caused by excessive accumulation of extracellular matrix (ECM) due to repeated liver injury. Hepatic stellate cells (HSCs) play a key role in the pathogenesis and progression of hepatic fibrosis. A study showed that CYP4A14 gene defect can inhibit hepatic fibrosis, but the specific mechanism was not clear. In this experiment, patients with hepatic fibrosis, LX-2 cells (a human HSCs line), and mice with liver fibrosis induced by carbon tetrachloride (CCl₄) were used to study the effect of 20-Hydroxytetraenoic acid (20-HETE), one of the main metabolites of arachidonic acid (AA) catalyzed by CYP4A enzyme, on hepatic fibrosis and its mechanism. Our experimental results showed that the 20-HETE of patients with hepatic fibrosis is significantly higher than that of normal people and is closely related to the degree of fibrosis. 20-HETE could induce activation of LX-2 cells and 20-HETE antagonist could inhibit the induction of 20-HETE. 20-HETE was significantly increased in CCl₄-induced liver fibrosis mice and inhibition of 20-HETE production could attenuate hepatic fibrosis. 20-HETE induced hepatic fibrosis mainly via the TGF- β1/Smad3 signal pathway. In conclusion, the results suggest that 20-HETE plays an important role in hepatic fibrosis and may be a possible target for the clinical treatment of hepatic fibrosis.

Changing our view of the Schistosoma granuloma to an ecological standpoint

Schistosomiasis, a neglected parasitic tropical disease that has plagued humans for centuries, remains a major public health burden. A primary challenge to understanding schistosomiasis is deciphering the most remarkable pathological feature of this disease, the granuloma - a highly dynamic and self-organized structure formed by both host and parasite components. Granulomas are considered a remarkable example of how parasites evolved with their hosts to establish complex and intimate associations. However, much remains unclear regarding life within the granuloma, and strategies to restrain its development are still lacking. Here we explore current information on the hepatic Schistosoma mansoni granuloma in the light of Ecology and propose that this intricate structure acts as a real ecosystem. The schistosomal granuloma is formed by cells (biotic component), protein scaffolds, fibres, and chemical compounds (abiotic components) with inputs/outputs of energy and matter, as complex as in classical ecosystems. We review the distinct cell populations ('species') within the granuloma and examine how they integrate with each other and interact with their microenvironment to form a multifaceted cell community in different space-time frames. The colonization of the hepatic tissue to form granulomas is explained from the point of view of an ecological succession whereby a community is able to modify its physical environment, creating conditions and resources for ecosystem construction. Remarkably, the granuloma represents a dynamic evolutionary system that undergoes progressive changes in the 'species' that compose its community over time. In line with ecological concepts, we examine the granuloma not only as a place where a community of cells is settled (spatial niche or habitat) but also as a site in which the functional activities of these combined populations occur in an orchestrated way in response to microenvironmental gradients such as cytokines and egg antigens. Finally, we assert how the levels of organization of cellular components in a granuloma as conventionally defined by Cell Biology can fit perfectly into a hierarchical structure of biological systems as defined by Ecology. By rethinking the granuloma as an integrating and evolving ecosystem, we draw attention to the inner workings of this structure that are central to the understanding of schistosomiasis and could guide its future treatment.

Inhibition of 5-Lipoxygenase in Hepatic Stellate Cells Alleviates Liver Fibrosis

Background and Purpose: Activation of hepatic stellate cells (HSC) is a central driver of liver fibrosis. 5-lipoxygenase (5-LO) is the key enzyme that catalyzes arachidonic acid into leukotrienes. In this study, we examined the role of 5-LO in HSC activation and liver fibrosis.

Main Methods: Culture medium was collected from quiescent and activated HSC for target metabolomics analysis. Exogenous leukotrienes were added to culture medium to explore their effect in activating HSC. Genetic ablation of 5-LO in mice was used to study its role in liver fibrosis induced by CCl₄ and a methionine-choline-deficient (MCD) diet. Pharmacological inhibition of 5-LO in HSC was used to explore the effect of this enzyme in HSC activation and liver fibrosis.

Key Results: The secretion of LTB₄ and LTC₄ was increased in activated vs. quiescent HSC. LTB₄ and LTC₄ contributed to HSC activation by activating the extracellular signal-regulated protein kinase pathway. The expression of 5-LO was increased in activated HSC and fibrotic livers of mice. Ablation of 5-LO in primary HSC inhibited both mRNA and protein expression of fibrotic genes. In vivo, ablation of 5-LO markedly ameliorated the CCl₄- and MCD diet-induced liver fibrosis and liver injury. Pharmacological inhibition of 5-LO in HSC by targeted delivery of the 5-LO inhibitor zileuton suppressed HSC activation and improved CCl₄- and MCD diet-induced hepatic fibrosis and liver injury. Finally, we found increased 5-LO expression in patients with non-alcoholic steatohepatitis and liver fibrosis.

Conclusion: 5-LO may play a critical role in activating HSC; genetic ablation or pharmacological inhibition of 5-LO improved CCl₄-and MCD diet-induced liver fibrosis.

Generation and phenotype analysis of CysLTR1 L118F mutant mice

Cysteinyl leukotrienes (CysLTs) are a group of eicosanoids that regulate the pathogenesis of various human diseases, mainly by signaling through the cysteinyl leukotriene receptor 1 (CysLTR1). The aim of this study was to generate and examine the phenotype of CysLTR1 L118F mutant mice. CysLTR1 L118F mutant mice were generated by the simultaneous microinjection of single guide RNA, Cas9 messenger RNA, and donor plasmid into fertilized mouse eggs. The morphological and behavioral characteristics of the resultant CysLTR1 L118F mutant mice were analyzed using an animal phenotype analysis platform, which included the assessment of body length, tail length, grip strength, and locomotor activity. Immunoprecipitation coupled with mass spectrometry was performed to identify CysLTR1-interacting proteins, and the intracellular calcium levels were determined using fluorometric imaging plate reader assays. The body length and tail length of CysLTR1 L118F mutant mice were significantly increased compared with wild-type mice. In addition, the grip strength and locomotor activity were remarkably elevated in L118F mutant mice compared with wild-type mice. Only three proteins were found to interact with both wild-type and CysLTR1 L118F proteins, whereas 4 and 13 additional proteins interacted exclusively with wild-type and mutant CysLTR1, respectively. Lastly, the responsiveness of cardiac muscle cells to CysLTs were significantly impaired by the L118F substitution in CysLTR1 proteins. The CysLTR1 L118F point mutation induced significant changes in the mouse morphology and behavior, which might be mediated by alterations of its protein interaction profile.

Schistosomal Lipids Activate Human Eosinophils via Toll-Like Receptor 2 and PGD2 Receptors: 15-LO Role in Cytokine Secretion

Parasite-derived lipids may play important roles in host-pathogen interactions and immune evasion mechanisms. Remarkable accumulation of eosinophils is a characteristic feature of inflammation associated with parasitic disease, especially caused by helminthes. Infiltrating eosinophils are implicated in the pathogenesis of helminth infection by virtue of their capacity to release an array of tissue-damaging and immunoregulatory mediators. However, the mechanisms involved in the activation of human eosinophils by parasite-derived molecules are not clear. Here we investigated the effects and mechanisms of schistosomal lipids-induced activation of human eosinophils. Our results showed that stimulation of human eosinophils in vitro with total lipid extracts from adult worms of S. mansoni induced direct activation of human eosinophils, eliciting lipid droplet biogenesis, synthesis of leukotriene (LT) C₄ and eoxin (EX) C₄ (14,15 LTC₄) and secretion of eosinophil pre-formed TGFβ. We demonstrated that main eosinophil activating components within S. mansoni lipid extract are schistosomal-derived lysophosphatidylcholine (LPC) and prostaglandin (PG)D₂. Moreover, TLR2 is up-regulated in human eosinophils upon stimulation with schistosomal lipids and pre-treatment with anti-TLR2 inhibited both schistosomal lipids- and LPC-, but not PGD₂-, induced lipid droplet biogenesis and EXC₄ synthesis within eosinophils, indicating that TLR2 mediates LPC-driven human eosinophil activation. By employing PGD₂ receptor antagonists, we demonstrated that DP1 receptors are also involved in various parameters of human eosinophil activation induced by schistosomal lipids, but not by schistosomal LPC. In addition, schistosomal lipids and their active components PGD₂ and LPC, triggered 15-LO dependent production of EXC₄ and secretion of TGFβ. Taken together, our results showed that schistosomal lipids contain at least two components—LPC and PGD₂—that are capable of direct activation of human eosinophils acting on distinct eosinophil-expressed receptors, noticeably TLR2 as well as DP1, trigger human eosinophil activation characterized by production/secretion of pro-inflammatory and immunoregulatory mediators.

In vitro inhibition of hepatic stellate cell activation by the autophagy-related lipid droplet protein ATG2A

Clinical studies have found that moderate intake of retinol or oleic acid can enlarge the lipid droplets of hepatic stellate cells and suppress their activation. However, the link between lipid droplets and cell activation is unknown. This study compared the dynamics of lipid droplet-associated protein expression between activated and reverted stellate cells. Reversion of the activated human stellate cell line LX-2 and inhibition of primary mouse stellate cell activation were induced by retinol or oleic acid, which resulted in larger lipid droplets and the downregulation of cell activation markers. Quantitative proteomics and immunoblotting were performed to compare lipid-droplet protein profiles between activated and reverted LX-2 cells. Compared to expression in activated cells, 50 lipid-droplet proteins were upregulated, whereas 28 were downregulated upon reversion. ATG2A was significantly enriched in lipid droplets of retinol/oleic acid-treated LX-2 cells and quiescent primary stellate cells. Reduced expression of α-SMA, increased expression of perilipin-3, enlarged lipid droplets, and suppression of autophagic flux were observed in ATG2A-deficient LX2 cells. Lipid-droplet protein profile changes during the reversion of activated stellate cells might provide new insights into the molecular mechanisms linking lipid droplets to liver fibrosis. ATG2A could represent a potential new drug target for hepatic fibrosis.

Lipid Droplet, a Key Player in Host-Parasite Interactions

Lipid droplets (lipid bodies, LDs) are dynamic organelles that have important roles in regulating lipid metabolism, energy homeostasis, cell signaling, membrane trafficking, and inflammation. LD biogenesis, composition, and functions are highly regulated and may vary according to the stimuli, cell type, activation state, and inflammatory environment. Increased cytoplasmic LDs are frequently observed in leukocytes and other cells in a number of infectious diseases. Accumulating evidence reveals LDs participation in fundamental mechanisms of host-pathogen interactions, including cell signaling and immunity. LDs are sources of eicosanoid production, and may participate in different aspects of innate signaling and antigen presentation. In addition, intracellular pathogens evolved mechanisms to subvert host metabolism and may use host LDs, as ways of immune evasion and nutrients source. Here, we review mechanisms of LDs biogenesis and their contributions to the infection progress, and discuss the latest discoveries on mechanisms and pathways involving LDs roles as regulators of the immune response to protozoan infection.

Galectin-3, histone deacetylases, and Hedgehog signaling: Possible convergent targets in schistosomiasis-induced liver fibrosis

Schistosomiasis affects approximately 240 million people in the world. Schistosoma mansoni eggs in the liver induce periportal fibrosis and hepatic failure driven by monocyte recruitment and macrophage activation, resulting in robust Th2 response. Here, we suggested a possible involvement of Galectin-3 (Gal-3), histone deacetylases (HDACs), and Hedgehog (Hh) signaling with macrophage activation during Th1/Th2 immune responses, fibrogranuloma reaction, and tissue repair during schistosomiasis. Gal-3 is highly expressed by liver macrophages (Kupffer cells) around Schistosoma eggs. HDACs and Hh regulate macrophage polarization and hepatic stellate cell activation during schistosomiasis-associated fibrogenesis. Previously, we demonstrated an abnormal extracellular matrix distribution in the liver that correlated with atypical monocyte-macrophage differentiation in S. mansoni-infected, Gal-3-deficient (Lgals3-/-) mice. New findings explored in this review focus on the chronic phase, when wild-type (Lgals3+/+) and Lgals3-/- mice were analyzed 90 days after cercariae infection. In Lgals3-/- infected mice, there was significant inflammatory infiltration with myeloid cells associated with egg destruction (hematoxylin and eosin staining), phagocytes (specifically Kupffer cells), numerically reduced and diffuse matrix extracellular deposition in fibrotic areas (Gomori trichrome staining), and severe disorganization of collagen fibers surrounding the S. mansoni eggs (reticulin staining). Granuloma-derived stromal cells (GR cells) of Lgals3-/- infected mice expressed lower levels of alpha smooth muscle actin (α-SMA) and eotaxin and higher levels of IL-4 than Lgals3+/+ mice (real-time PCR). The relevant participation of macrophages in these events led us to suggest distinct mechanisms of activation that culminate in defective fibrosis in the liver of Lgals3-/- infected mice. These aspects were discussed in this review, as well as the possible interference between Gal-3, HDACs, and Hh signaling during progressive liver fibrosis in S. mansoni-infected mice. Further studies focused on macrophage roles could elucidate these questions and clear the potential utility of these molecules as antifibrotic targets.

5-lipoxygenase pathway is essential for the control of granuloma extension induced by Schistosoma mansoni eggs in lung

According to WHO, it is estimated that approximately 2 billion people are infected with intestinal helminths worldwide and the number of people who are cured of these diseases is relatively low, resulting in a large percentage of chronically infected individuals. Schistosomiasis is one of the most important parasitic diseases present in developing countries configuring it as a serious public health problem, directly related to poverty and social disadvantage. Once the parasite infection is established, Schistosoma mansoni eggs fall into the bloodstream and are trapped in the liver microcirculation where a strong granulomatous response and fibrosis formation occurs. In the experimental model, granulomas develop in the mouse lung after intravenous injection of purified eggs. Here we aim to understand how leukotrienes are involved in the granuloma formation. Leukotrienes are lipid mediators derived from arachidonic acid metabolites via 5-lipoxygenase (5LO) enzyme. They are potent proinflammatory agents and induce recruitment, cell activation, regulation of microbicidal activity of polymorphonuclear and mononuclear cells. In this study, 5LO deficient mice (5LO(-/-)) were inoculated with S. mansoni eggs for evaluation of immunopathological parameters involved in the induction of type 2 granulomas. We showed that in the absence of leukotrienes, the size of granulomas were decreased comparing to the wild type mice and the inflammatory compromised areas had a lower extension. In 5LO(-/-) mice granulomas presented extensive areas of fibrosis, detected by α-SMA expression along the lesions, indicating remodeling in attempt to reestablish the normal tissue. Also, comparing to WT mice we detected decrease of IL-4 and IL-13 and increase of TGF-β in the lung of 5LO(-/-), but these mice failed to produce protective IFN-γ and IL-12. These results evidenced 5-Lipoxygenase as an important pathway during lung injury due to Schistosoma-eggs injection.

Hepatic myofibroblasts derived from Schistosoma mansoni-infected mice are a source of IL-5 and eotaxin: controls of eosinophil populations in vitro

Background

Hepatic myofibroblasts are relevant for pathogenesis of S. mansoni infection. In normal liver, these perisinusoidal cells are quiescent, express the lipocyte phenotype, and are located in the Disse’s space, being the major site of vitamin A storage. When activated, they convert to myofibroblasts and contribute to granulomatous and diffuse liver fibrosis. In the present work, we observed that myofibroblasts obtained from granulomatous periovular inflammatory reactions in schistosome-infected mice (GR-MF) produce in vitro immunomodulatory cytokines for eosinophil activation: IL-5 and eotaxin.

Methods and results

The secretory activity of GR-MF was detected after TGF-β and IL-13 stimulation using 2D and 3D cell culture systems. In a mixed co-culture system using GR-MF with hematopoietic bone marrow cells from infected mice, we observed eosinophil survival that was dependent upon IL-5 and eotaxin, since antibodies against this cytokines decreased eosinophil population, as measured by eosinophil peroxidase activity.

Conclusion

These results indicate that GR-MF may contribute to maintenance of local eosinophilia in schistosomal hepatic granulomas, and can function as immunoregulatory cells, besides their role in production of fibrosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1197-3) contains supplementary material, which is available to authorized users.

Melatonin suppresses activation of hepatic stellate cells through RORα-mediated inhibition of 5-lipoxygenase

Liver fibrosis is scar tissue resulting from an uncontrolled wound-healing process in response to chronic liver injury. Liver damage generates an inflammatory reaction that activates hepatic stellate cells (HSC) that transdifferentiate from quiescent cells that control retinol metabolism to proliferative and migratory myofibroblasts that produce excessive amounts of extracellular matrix proteins, in particular collagen 1a1 (COL1A1). Although liver fibrosis is reversible, no effective drug therapy is available to prevent or reverse HSC activation. Melatonin has potent hepatoprotective properties in a variety of acute and chronic liver injury models and suppresses liver fibrosis. However, it remains unclear whether melatonin acts indirectly or directly on HSC to prevent liver fibrosis. Here, we studied the effect of melatonin on culture-activated rat HSC. Melatonin dose-dependently suppressed the expression of HSC activation markers Col1a1 and alpha-smooth muscle actin (αSMA, Acta2), as well as HSC proliferation and loss of lipid droplets. The nuclear melatonin sensor retinoic acid receptor-related orphan receptor-alpha (RORα/Nr1f1) was expressed in quiescent and activated HSC, while the membranous melatonin receptors (Mtrn1a and Mtrn1b) were not. The synthetic RORα agonist SR1078 more potently suppressed Col1a1 and αSma expression, HSC proliferation, and lipid droplet loss, while the RORα antagonist SR1001 blocked the antifibrotic features of melatonin. Melatonin and SR1078 inhibited the expression of Alox5, encoding 5-lipoxygenase (5-LO). The pharmacological 5-LO inhibitor AA861 reduced Acta2 and Col1a1 expression in activated HSC. We conclude that melatonin directly suppresses HSC activation via RORα-mediated inhibition of Alox5 expression, which provides novel drug targets to treat liver fibrosis.

Hepatic lipid droplet biology: Getting to the root of fatty liver

Hepatic steatosis is defined by the accumulation of lipid droplets (LDs). Once thought to be only inert energy storage depots, LDs are increasingly recognized as organelles that have important functions in hepatocytes beyond lipid storage. The lipid and protein composition of LDs is highly dynamic and influences their intrinsic metabolism and signaling properties, which ultimately links them to the changes in hepatic function. This concise review highlights recent discoveries in LD biology and unique aspects of hepatic LDs and their role in liver disease.

Tissue Transglutaminase-Regulated Transformed Growth Factor-β1 in the Parasite Links Schistosoma japonicum Infection with Liver Fibrosis

Transforming growth factor (TGF-β1) is among the strongest factors of liver fibrogenesis, but its association with Schistosoma-caused liver fibrosis is controversial. Tissue transglutaminase (tTG) is the principal enzyme controlling TGF-β1 maturation and contributes to Sj-infected liver fibrosis. Here we aim to explore the consistency between tTG and TGF-β1 and TGF-β1 source and its correlation with liver fibrosis after Sj-infection. TGF-β1 was upregulated at weeks 6 and 8 upon liver fibrosis induction. During tTG inhibition, TGF-β1 level decreased in sera and liver of infected mice. TGF-β1 showed positive staining in liver containing Sj adult worms and eggs. TGF-β1 was also detected in Sj adult worm sections, soluble egg antigen and Sj adult worm antigen, and adult worms' culture medium. The TGF-β1 mature peptide cDNA sequence and its extended sequence were amplified through RT-PCR and RACE-PCR using adult worms as template, and sequence is analyzed and loaded to NCBI GenBank (number GQ338152.1). TGF-β1 transcript in Sj eggs was higher than in adult worms. In Sj-infected liver, transcriptional level of TGF-β1 from Sj, but not mouse liver, correlated with liver fibrosis extent. This study provides evidence that tTG regulates TGF-β1 and illustrates the importance of targeting tTG in treating Sj infection-induced fibrosis.

Schistosome infection-derived Hepatic Stellate Cells are cellular source of prostaglandin D₂: role in TGF-β-stimulated VEGF production

Hepatic Stellate Cells (HSCs) play a crucial role in pathogenesis of liver inflammation and fibrosis. During chronic liver injury, HSCs lose vitamin A and transform into myofibroblastic cells. In schistosomal granulomas, these activated HSCs are called GR-HSCs. Schistosomal-triggered hepatic fibrogenesis has TGF-β as the most potent fibrogenic stimulus, that also controls gene expression of the angiogenic molecule VEGF in HSCs. COX-dependent production of prostaglandins (PGs) also play role in angiogenic processes. Besides angiogenic roles, prostanoids control immunomodulation of Schistosoma mansoni infection. Specifically, schistosoma-derived PGD2 has emerged as a key parasite regulator of immune defense evasion, while no role is still established to host PGD2. Therefore, the aim of this work is to investigate the ability of GR-HSCs to synthesize COX-derived PGD2 and a potential role of this prostanoid in VEGF production by GR-HSCs in vitro. Here, we confirmed that GR-HSCs express COX-2, which displayed perinuclear localization. While unstimulated GR-HSCs produce basal levels of PGD2, TGF-β stimulation besides increasing COX2- mRNA levels, enhanced synthesis/secretion of PGD2 in GR-HSCs supernatant. Moreover, GR-HSCs-derived PGD2 mediate VEGF production by TGF-β-stimulated GR-HSCs, since the pre-treatment with HQL-79, an inhibitor of hematopoietic PGD synthase inhibited both PGD2 synthesis and VEGF secretion by TGF-β-stimulated GR-HSCs. All together, our findings show an autocrine/paracrine activity of GR-HSCs-derived PGD2 on TGF-β-induced VEGF production by GR-HSCs, unveiling a role for PGD2 as important regulator of HSCs activation in hepatic granulomas from schistosome infected mice.

Exogenous bone morphogenetic protein-7 reduces hepatic fibrosis in Schistosoma japonicum-infected mice via transforming growth factor-β/Smad signaling

AIM: To investigate the antifibrotic effects of bone morphogenetic protein-7 (BMP-7) on Schistosoma japonicum (S. japonicum)-induced hepatic fibrosis in BALB/C mice.

METHODS: Sixty BALB/C mice were randomly divided into three groups, including a control group (group A, n = 20), model group (group B, n = 20) and BMP-7 treated group (group C, n = 20). The mice in group B and group C were abdominally infected with S. japonicum cercariae to induce a schistosomal hepatic fibrosis model. The mice in group C were administered human recombinant BMP-7. Liver samples were extracted from mice sacrificed at 9 and 15 wk after modeling. Hepatic histopathological changes were assessed using Masson’s staining. Transforming growth factor-beta 1 (TGF-β1), alpha-smooth muscle actin (α-SMA), phosphorylated Smad2/3 (pSmad2/3) and Smad7 protein levels and localization were measured by Western blotting and immunohistochemistry, respectively, and their mRNA expressions were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: The schistosomal hepatic fibrosis mouse model was successfully established, as the livers of mice in group B and group C showed varying degrees of typical schistosomal hepatopathologic changes such as egg granuloma and collagen deposition. The degree of collagen deposition in group C was higher than that in group A (week 9: 22.95 ± 6.66 vs 2.02 ± 0.76; week 15: 12.84 ± 4.36 vs 1.74 ± 0.80; P < 0.05), but significantly lower than that in group B (week 9: 22.95 ± 6.66 vs 34.43 ± 6.96; week 15: 12.84 ± 4.36 vs 18.90 ± 5.07; P < 0.05) at both time points. According to immunohistochemistry data, the expressions of α-SMA, TGF-β1 and pSmad2/3 protein in group C were higher than those in group A (α-SMA: week 9: 21.24 ± 5.73 vs 0.33 ± 0.20; week 15: 12.42 ± 4.88 vs 0.34 ± 0.27; TGF-β1: week 9: 37.00 ± 13.74 vs 3.73 ± 2.14; week 15: 16.71 ± 9.80 vs 3.08 ± 2.35; pSmad2/3: week 9: 12.92 ± 4.81 vs 0.83 ± 0.48; week 15: 7.87 ± 4.09 vs 0.90 ± 0.45; P < 0.05), but significantly lower than those in group B (α-SMA: week 9: 21.24 ± 5.73 vs 34.39 ± 5.74; week 15: 12.42 ± 4.88 vs 25.90 ± 7.01; TGF-β1: week 9: 37.00 ± 13.74 vs 55.66 ± 14.88; week 15: 16.71 ± 9.80 vs 37.10 ± 12.51; pSmad2/3: week 9: 12.92 ± 4.81 vs 19.41 ± 6.87; week 15: 7.87 ± 4.09 vs 13.00 ± 4.98; P < 0.05) at both time points; the expression of Smad7 protein in group B was higher than that in group A and group C at week 9 (8.46 ± 3.95 vs 1.00 ± 0.40 and 8.46 ± 3.95 vs 0.77 ± 0.42; P < 0.05), while there were no differences in Smad7 expression between the three groups at week 15 (1.09 ± 0.38 vs 0.97 ± 0.42 vs 0.89 ± 0.39; P > 0.05). Although minor discrepancies were observed, the results of RT-PCR and Western blotting were mainly consistent with the immunohistochemical results.

CONCLUSION: Exogenous BMP-7 significantly decreased the degree of hepatic fibrosis in both the acute and chronic stages of hepato-schistosomiasis, and the regulatory mechanism may involve the TGF-β/Smad signaling pathway.

Transforming growth factor β1-induced astrocyte migration is mediated in part by activating 5-lipoxygenase and cysteinyl leukotriene receptor 1

BACKGROUND

Transforming growth factor-β 1 (TGF-β 1) is an important regulator of cell migration and plays a role in the scarring response in injured brain. It is also reported that 5-lipoxygenase (5-LOX) and its products, cysteinyl leukotrienes (CysLTs, namely LTC₄, LTD₄ and LTE₄), as well as cysteinyl leukotriene receptor 1 (CysLT₁R) are closely associated with astrocyte proliferation and glial scar formation after brain injury. However, how these molecules act on astrocyte migration, an initial step of the scarring response, is unknown. To clarify this, we determined the roles of 5-LOX and CysLT₁R in TGF-β 1-induced astrocyte migration.

METHODS

In primary cultures of rat astrocytes, the effects of TGF-β 1 and CysLT receptor agonists on migration and proliferation were assayed, and the expression of 5-LOX, CysLT receptors and TGF-β1 was detected. 5-LOX activation was analyzed by measuring its products (CysLTs) and applying its inhibitor. The role of CysLT₁R was investigated by applying CysLT receptor antagonists and CysLT₁R knockdown by small interfering RNA (siRNA). TGF-β 1 release was assayed as well.

RESULTS

TGF-β 1-induced astrocyte migration was potentiated by LTD₄, but attenuated by the 5-LOX inhibitor zileuton and the CysLT₁R antagonist montelukast. The non-selective agonist LTD₄ at 0.1 to 10 nM also induced a mild migration; however, the selective agonist N-methyl-LTC₄ and the selective antagonist Bay cysLT2 for CysLT₂R had no effects. Moreover, CysLT₁R siRNA inhibited TGF-β 1- and LTD₄-induced astrocyte migration by down-regulating the expression of this receptor. However, TGF-β 1 and LTD4 at various concentrations did not affect astrocyte proliferation 24 h after exposure. On the other hand, TGF-β 1 increased 5-LOX expression and the production of CysLTs, and up-regulated CysLT1R (not CysLT₂R), while LTD4 and N-methyl-LTC4 did not affect TGF-β 1 expression and release.

CONCLUSIONS

TGF-β 1-induced astrocyte migration is, at least in part, mediated by enhanced endogenous CysLTs through activating CysLT₁R. These findings indicate that the interaction between the cytokine TGF-β 1 and the pro-inflammatory mediators CysLTs in the regulation of astrocyte function is relevant to glial scar formation.

Role of leukotrienes on protozoan and helminth infections

Leukotrienes (LTs), formed by the 5-lipoxygenase-(5-LO-) catalyzed oxidation of arachidonic acid, are lipid mediators that have potent proinflammatory activities. Pharmacologic or genetic inhibition of 5-LO biosynthesis in animals is associated with increased mortality and impaired clearance of bacteria, fungi, and parasites. LTs play a role in the control of helminth and protozoan infections by modulating the immune system and/or through direct cytotoxicity to parasites; however, LTs may also be associated with pathogenesis, such as in cerebral malaria and schistosomal granuloma. Interestingly, some proteins from the saliva of insect vectors that transmit protozoans and secreted protein from helminth could bind LTs and may consequently modulate the course of infection or pathogenesis. In addition, the decreased production of LTs in immunocompromised individuals might modulate the pathophysiology of helminth and protozoan infections. Herein, in this paper, we showed the immunomodulatory and pathogenic roles of LTs during the helminth and protozoan infections.

The combined treatment of praziquantel with osteopontin immunoneutralization reduces liver damage in Schistosoma japonicum-infected mice

The aim of this study was to evaluate the therapeutic effects of osteopontin neutralization treatment on schistosome-induced liver injury in BALB/C mice. We randomly divided 100 BALB/C mice into groups A, B, C, D and group E. Mice in all groups except group A were abdominally infected with schistosomal cercariae to induce a schistosomal hepatopathological model. Mice in group C, D and group E were respectively administered with praziquantel, praziquantel plus colchicine and praziquantel plus neutralizing osteopontin antibody. We extracted mouse liver tissues at 3 and 9 weeks after the 'stool-eggs-positive' day, observed liver histopathological changes by haematoxylin-eosin and Masson trichrome staining and detected the expression of osteopontin, alpha-smooth muscle actin (α-SMA) and transforming growth factor-beta (TGF-β1) by immunohistochemistry, RT-PCR and Western blot. We found that praziquantel plus neutralizing osteopontin antibody treatment significantly decreased the granuloma dimension, the percentage of collagen and the expression of osteopontin, α-SMA and TGF-β1 compared to praziquantel plus colchicine treatment in both the acute and chronic stage of schistosomal liver damage (P<0·05). So we believe that the combined regimen of osteopontin immunoneutralization and anti-helminthic treatment can reduce the granulomatous response and liver fibrosis during the schistosomal hepatopathologic course.

Lipid body function in eicosanoid synthesis: an update

Eicosanoids (prostaglandins, leukotrienes and lipoxins) are signaling lipids derived from arachidonic acid metabolism that have important roles in physiological and pathological processes. Lately, intracellular compartmentalization of eicosanoid-synthetic machinery has emerged as a key component in the regulation of eicosanoid synthesis and functions. Over the past years substantial progresses have been made demonstrating that precursors and enzymes involved in eicosanoid synthesis localize at lipid bodies (also known as lipid droplets) and lipid bodies are distinct sites for eicosanoid generation. Here we will review the current knowledge on the functions of lipid bodies as specialized intracellular sites of compartmentalization of signaling with major roles in eicosanoid formation within cells engaged in inflammatory, infectious and neoplastic process.