Bilirubin inhibits the up-regulation of inducible nitric oxide synthase by scavenging reactive oxygen species generated by the toll-like receptor 4-dependent activation of NADPH oxidase

Serum metabolites and hypercholesterolemia: insights from a two-sample Mendelian randomization study

Background

Hypercholesterolemia, a critical contributor to cardiovascular disease, is not fully understood in terms of its relationship with serum metabolites and their role in disease pathogenesis.

Methods

This study leveraged GWAS data to explore the relationship between serum metabolites and hypercholesterolemia, pinpointing significant metabolites via Mendelian Randomization (MR) and KEGG pathway enrichment analysis. Data on metabolites were sourced from a European population, with analysis focusing on individuals diagnosed with hypercholesterolemia.

Results

Out of 486 metabolites analyzed, ten showed significant associations with hypercholesterolemia, categorized into those enhancing risk and those with protective effects. Specifically, 2-methoxyacetaminophen sulfate and 1-oleoylglycerol (1-monoolein) were identified as risk-enhancing, with odds ratios (OR) of 1.545 (95% CI: 1.230-1.939; P_FDR = 3E-04) and 1.462 (95% CI: 1.036-2.063; P_FDR = 0.037), respectively. On the protective side, 3-(cystein-S-yl)acetaminophen, hydroquinone sulfate, and 2-hydroxyacetaminophen sulfate demonstrated ORs of 0.793 (95% CI: 0.735-0.856; P_FDR = 6.18E-09), 0.641 (95% CI: 0.423-0.971; P_FDR = 0.042), and 0.607 (95% CI: 0.541-0.681; P_FDR = 5.39E-17), respectively. In addition, KEGG pathway enrichment analysis further revealed eight critical pathways, comprising "biosynthesis of valine, leucine, and isoleucine", "phenylalanine metabolism", and "pyruvate metabolism", emphasizing their significant role in the pathogenesis of hypercholesterolemia.

Conclusion

This study underscores the potential causal links between particular serum metabolites and hypercholesterolemia, offering innovative viewpoints on the metabolic basis of the disease. The identified metabolites and pathways offer promising targets for therapeutic intervention and warrant further investigation.

ROS-scavenging materials for skin wound healing: advancements and applications

The intricate healing process of skin wounds includes a variety of cellular and molecular events. Wound healing heavily relies on reactive oxygen species (ROS), which are essential for controlling various processes, including inflammation, cell growth, angiogenesis, granulation, and the formation of extracellular matrix. Nevertheless, an overabundance of reactive oxygen species (ROS) caused by extended oxidative pressure may result in the postponement or failure of wound healing. It is crucial to comprehend the function of reactive oxygen species (ROS) and create biomaterials that efficiently eliminate ROS to enhance the healing process of skin wounds. In this study, a thorough examination is presented on the role of reactive oxygen species (ROS) in the process of wound healing, along with an exploration of the existing knowledge regarding biomaterials employed for ROS elimination. In addition, the article covers different techniques and substances used in the management of skin wound. The future prospects and clinical applications of enhanced biomaterials are also emphasized, highlighting the potential of biomaterials that scavenge active oxygen to promote skin repair. This article seeks to enhance the understanding of the complex processes of ROS in the healing of wounds and the application of ROS-scavenging materials. Its objective is to create novel strategies for effective treatment skin wounds.

Challenges and opportunities in the islet transplantation microenvironment: a comprehensive summary of inflammatory cytokine, immune cells, and vascular endothelial cells

It is now understood that islet transplantation serves as a β-cell replacement therapy for type 1 diabetes. Many factors impact the survival of transplanted islets, especially those related to the microenvironment. This review explored microenvironmental components, including vascular endothelial cells, inflammatory cytokines, and immune cells, and their profound effects on post-islet transplantation survival rates. Furthermore, it revealed therapeutic strategies aimed at targeting these elements. Current evidence suggests that vascular endothelial cells are pivotal in facilitating vascularization and nutrient supply and establishing a new microcirculation network for transplanted islets. Consequently, preserving the functionality of vascular endothelial cells emerges as a crucial strategy to enhance the survival of islet transplantation. Release of cytokines will lead to activation of immune cells and production and release of further cytokines. While immune cells hold undeniable significance in regulating immune responses, their activation can result in rejection reactions. Thus, establishing immunological tolerance within the recipient's body is essential for sustaining graft functionality. Indeed, future research endeavors should be directed toward developing precise strategies for modulating the microenvironment to achieve higher survival rates and more sustained transplantation outcomes. While acknowledging certain limitations inherent to this review, it provides valuable insights that can guide further exploration in the field of islet transplantation. In conclusion, the microenvironment plays a paramount role in islet transplantation. Importantly, we discuss novel perspectives that could lead to broader clinical applications and improved patient outcomes in islet transplantation.

Atazanavir-induced unconjugated hyperbilirubinemia prevents vascular hyporeactivity during experimental human endotoxemia

Objective

Inflammation-induced free radical release is important in the pathogenesis of several diseases, including atherosclerosis and sepsis. Heme oxygenase (HO) breaks down heme into carbon monoxide, iron, and biliverdin. Biliverdin IXα is directly converted to bilirubin by biliverdin reductase. Unconjugated bilirubin is a powerful antioxidant, and elevated levels have beneficial effects in preclinical models and human cardiovascular disease. However, its impact during acute inflammation in humans is unknown. In the present study, we investigated the impact of atazanavir-induced (unconjugated) hyperbilirubinemia on antioxidant capacity, inflammation, and vascular dysfunction in human experimental endotoxemia.

Approach and results

Following double-blinded four-day treatment with atazanavir 2dd300 mg (or placebo), twenty healthy male volunteers received 2 ng/kg Escherichia coli lipopolysaccharide intravenously. Blood was drawn to determine the bilirubin levels, antioxidant capacity, and cytokine response. It was demonstrated that following atazanavir treatment, total bilirubin concentrations increased to maximum values of 4.67 (95%CI 3.91-5.59) compared to 0.82 (95%CI 0.64-1.07) mg/dL in the control group (p<0.01). Furthermore, the anti-oxidant capacity, as measured by the ferric-reducing ability of plasma (FRAP), was significantly increased with 36% in hyperbilirubinemia subjects (p<0.0001), and FRAP concentrations correlated strongly to bilirubin concentrations (R2 = 0.77, p<0.001). Hyperbilirubinemia attenuated the release of interleukin-10 from 377 (95%CI 233-609) to 219 (95%CI 152-318) pg/mL (p=0.01), whereas the release of pro-inflammatory cytokines remained unaltered. In vitro, in the absence of hyperbilirubinemia, atazanavir did not influence lipopolysaccharide-induced cytokine release in a whole blood assay. Vascular function was assessed using forearm venous occlusion plethysmography after intra-arterial infusion of acetylcholine and nitroglycerin. Hyperbilirubinemia completely prevented the LPS-associated blunted vascular response to acetylcholine and nitroglycerin.

Conclusions

Atazanavir-induced hyperbilirubinemia increases antioxidant capacity, attenuates interleukin-10 release, and prevents vascular hyporesponsiveness during human systemic inflammation elicited by experimental endotoxemia.

Clinical trial registration

http://clinicaltrials.gov, identifier NCT00916448.

PGC-1α in osteoarthritic chondrocytes: From mechanism to target of action

Osteoarthritis (OA) is one of the most common degenerative joint diseases, often involving the entire joint. The degeneration of articular cartilage is an important feature of OA, and there is growing evidence that the mitochondrial biogenesis master regulator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) exert a chondroprotective effect. PGC-1α delays the development and progression of OA by affecting mitochondrial biogenesis, oxidative stress, mitophagy and mitochondrial DNA (mtDNA) replication in chondrocytes. In addition, PGC-1α can regulate the metabolic abnormalities of OA chondrocytes and inhibit chondrocyte apoptosis. In this paper, we review the regulatory mechanisms of PGC-1α and its effects on OA chondrocytes, and introduce potential drugs and novel nanohybrid for the treatment of OA which act by affecting the activity of PGC-1α. This information will help to further elucidate the pathogenesis of OA and provide new ideas for the development of therapeutic strategies for OA.

Gut-liver axis in the progression of nonalcoholic fatty liver disease: From the microbial derivatives-centered perspective

Nonalcoholic fatty liver disease (NAFLD) is one of the world's most common chronic liver diseases. However, its pathogenesis remains unclear. With the deepening of research, NAFLD is considered a metabolic syndrome associated with the environment, heredity, and metabolic disorders. Recently, the close relationship between the intestinal microbiome and NAFLD has been discovered, and the theory of the "gut-liver axis" has been proposed. In short, the gut bacteria directly reach the liver via the portal vein through the damaged intestinal wall or indirectly participate in the development of NAFLD through signaling pathways mediated by their components and metabolites. This review focuses on the roles of microbiota-derived lipopolysaccharide, DNA, peptidoglycan, bile acids, short-chain fatty acids, endogenous ethanol, choline and its metabolites, indole and its derivatives, and bilirubin and its metabolites in the progression of NAFLD, which may provide significative insights into the pathogenesis, diagnosis, and treatment for this highly prevalent liver disease.

Neonatal asphyxia as an inflammatory disease: Reactive oxygen species and cytokines

Neonatologists resuscitate asphyxiated neonates by every available means, including positive ventilation, oxygen therapy, and drugs. Asphyxiated neonates sometimes present symptoms that mimic those of inflammation, such as fever and edema. The main pathophysiology of the asphyxia is inflammation caused by hypoxic-ischemic reperfusion. At birth or in the perinatal period, neonates may suffer several, hypoxic insults, which can activate inflammatory cells and inflammatory mediator production leading to the release of larger quantities of reactive oxygen species (ROS). This in turn triggers the production of oxygen stress-induced high mobility group box-1 (HMGB-1), an endogenous damage-associated molecular patterns (DAMPs) protein bound to toll-like receptor (TLR) -4, which activates nuclear factor-kappa B (NF-κB), resulting in the production of excess inflammatory mediators. ROS and inflammatory mediators are produced not only in activated inflammatory cells but also in non-immune cells, such as endothelial cells. Hypothermia inhibits pro-inflammatory mediators. A combination therapy of hypothermia and medications, such as erythropoietin and melatonin, is attracting attention now. These medications have both anti-oxidant and anti-inflammatory effects. As the inflammatory response and oxidative stress play a critical role in the pathophysiology of neonatal asphyxia, these drugs may contribute to improving patient outcomes.

Oxybaphus himalaicus Mitigates Lipopolysaccharide-Induced Acute Kidney Injury by Inhibiting TLR4/MD2 Complex Formation

Acute kidney injury (AKI) is described as the abrupt decrease in kidney function always accompanied by inflammation. The roots of Oxybaphus himalaicus Edgew. have long been used in Tibetan folk medicine for the treatment of nephritis. Nevertheless, modern pharmacological studies, especially about the underlying mechanism of O. himalaicus medications, are still lacking. Here, in lipopolysaccharide (LPS)-induced RAW264.7 macrophages, the O. himalaicus extract (OE) showed significant anti-inflammatory activity with the dose dependently reducing the LPS-stimulated release of nitric oxide and the mRNA level and protein expression of inflammatory cytokines and reversed the activation of nuclear factor kappa B (NF-κB). Co-immunoprecipitation assay indicated that OE inhibited Toll-like receptor 4/myeloid differentiation factor 2 (TLR4/MD2) complex formation and further suppressed both myeloid differentiation factor 88 (MyD88)-dependent and TIR-domain-containing adapter-inducing interferon-β (TRIF)-dependent cascades activation. In addition, OE could restrain NADPH oxidase 2 (NOX2) endocytosis by blocking TLR4/MD2 complex formation to prevent reactive oxygen species production. In LPS-induced AKI mice, OE treatment mitigated renal injury and inflammatory infiltration by inhibiting TLR4/MD2 complex formation. UPLC-MS/MS analysis tentatively identified 41 components in OE. Our results indicated that OE presented significant anti-inflammatory activity by inhibiting TLR4/MD2 complex formation, which alleviated LPS-induced AKI in mice.

Serum metabolomics reveal pathways associated with protective effect of ginsenoside Rg3 on immune stress

Our previous study has demonstrated that administration of ginsenoside Rg3 ameliorates immune stress by inhibiting inflammatory responses, reducing oxidative damage and upregulating mRNA expression of mTOR, SOD-1, and HO-1. However, the specific mechanism in relation to the protective effect of ginsenoside Rg3 on stressed broilers especially the metabolites alteration remains obscure. The present study aimed to investigate the underlined mechanism in relation to the pathogenesis and protective effect of ginsenoside Rg3 on stressed broilers using liquid chromatograph-mass spectrometry profiling. Eighteen broiler chicks were randomly allocated to 3 treatments: Control, Model and Rg3. Chickens in Rg3 group received intraperitoneally administered 1 mg/kg Rg3 2 h before LPS challenge. Then the broilers were intraperitoneally injection of 250 µg/kg LPS at the age of 12, 14, 33, and 35 d to induce immune stress. Control group was injected with an equivalent amount of sterile saline. At the end of the experiment, the serum was obtained for metabolomics analysis. The changes in serum metabolic profiles were investigated with the application of metabolomics approach. Distinct changes in metabolite patterns in serum were observed by orthogonal partial least square-discriminate analysis. In total, 35 metabolites were identified, among which 17 differential metabolites were found between Control and Model group, and 18 differential metabolites were identified between Model and Rg3 group. Metabolic pathway analysis revealed potential serum metabolites involved in oxidative stress and inflammation, degradation of lipid and protein in broiler chicks with immune stress. In addition, the protective effect of Rg3 on the stressed chicks may be largely mediated by BCAA metabolism, apoptosis and mTOR signaling pathway. These results suggested the potential biomarkers involved in pathogenesis and prevention of stress induced by Escherichia coli lipopolysaccharide.

Bile Duct Ligation Impairs Function and Expression of Mrp1 at Rat Blood-Retinal Barrier via Bilirubin-Induced P38 MAPK Pathway Activations

Liver injury is often associated with hepatic retinopathy, resulting from accumulation of retinal toxins due to blood-retinal barrier (BRB) dysfunction. Retinal pigment epithelium highly expresses MRP1/Mrp1. We aimed to investigate whether liver injury affects the function and expression of retinal Mrp1 using bile duct ligation (BDL) rats. Retinal distributions of fluorescein and 2,4-dinitrophenyl-S-glutathione were used for assessing Mrp1 function. BDL significantly increased distributions of the two substrates and bilirubin, downregulated Mrp1 protein, and upregulated phosphorylation of p38 and MK2 in the retina. BDL neither affected the retinal distribution of FITC-dextran nor expressions of ZO-1 and claudin-5, demonstrating intact BRB integrity. In ARPE-19 cells, BDL rat serum or bilirubin decreased MRP1 expression and enhanced p38 and MK2 phosphorylation. Both inhibiting and silencing p38 significantly reversed the bilirubin- and anisomycin-induced decreases in MRP1 protein. Apparent permeability coefficients of fluorescein in the A-to-B direction (Papp, A-to-B) across the ARPE-19 monolayer were greater than Papp, B-to-A. MK571 or bilirubin significantly decreased Papp, A-to-B of fluorescein. Bilirubin treatment significantly downregulated Mrp1 function and expression without affecting integrity of BRB and increased bilirubin levels and phosphorylation of p38 and MK2 in rat retina. In conclusion, BDL downregulates the expression and function of retina Mrp1 by activating the p38 MAPK pathway due to increased bilirubin levels.

RND3 attenuates oxidative stress and vascular remodeling in spontaneously hypertensive rat via inhibiting ROCK1 signaling

Superoxide and vascular smooth muscle cells (VSMCs) migration and proliferation play crucial roles in the vascular remodeling. Vascular remodeling contributes to the development and complications of hypertension. Rho family GTPase 3 (RND3 or RhoE), an atypical small Rho-GTPase, is known to be involved in cancer development and metastasis. However, the roles of RND3 in superoxide production and cardiovascular remodeling are unknown. Here, we uncovered the critical roles of RND3 in attenuating superoxide production, VSMCs migration and proliferation, and vascular remodeling in hypertension and its underline mechanisms. VSMCs were isolated and prepared from thoracic aorta of Male Wistar-Kyoto rat (WKY) and spontaneously hypertensive rat (SHR). RND3 mRNA and protein expressions in arteries and VSMCs were down-regulated in SHR. RND3 overexpression in VSMCs reduced NAD(P)H oxidase (NOX) activity, NOX1 and NOX2 expressions, mitochondria superoxide generation, and H2O2 production in SHR. Moreover, the RND3 overexpression inhibited VSMCs migration and proliferation in SHR, which were similar to the effects of NOX1 inhibitor ML171 plus NOX2 inhibitor GSK2795039. Rho-associated kinase 1 (ROCK1) and RhoA expressions and myosin phosphatase targeting protein 1 (MYPT1) phosphorylation in VSMCs were increased in SHR, which were prevented by RND3 overexpression. ROCK1 overexpression promoted NOX1 and NOX2 expressions, superoxide and H2O2 production, VSMCs migration and proliferation in both WKY and SHR, which were attenuated by RND3 overexpression. Adenoviral-mediated RND3 overexpression in SHR attenuated hypertension, vascular remodeling and oxidative stress. These results indicate that RND3 attenuates VSMCs migration and proliferation, hypertension and vascular remodeling in SHR via inhibiting ROCK1-NOX1/2 and mitochondria superoxide signaling.

β2-and β3-Adrenergic Receptors Contribute to Cancer-Evoked Pain in a Mouse Model of Osteosarcoma via Modulation of Neural Macrophages

The mechanisms involved in the development and maintenance of cancer pain remain largely unidentified. Recently, it has been reported that β-adrenergic receptors (β-ARs), mainly β2-and β3-ARs, contribute to tumor proliferation and progression and may favor cancer-associated pain and neuroinflammation. However, the mechanism underlying β-ARs in cancer pain is still unknown. Here, we investigated the role of β1-, β2-and β3-ARs in a mouse model of cancer pain generated by the para-tibial injection of K7M2 osteosarcoma cells. Results showed a rapid tumor growth in the soft tissue associated with the development of mechanical allodynia in the hind paw ipsilateral to the injected site. In addition to reduce tumor growth, both propranolol and SR59230A, β1-/β2-and β3-AR antagonists, respectively, attenuated mechanical allodynia, the number of macrophages and an oxidative stress by-product accumulated in the ipsilateral tibial nerve. The selective β1-AR antagonist atenolol was able to slightly reduce the tumor growth but showed no effect in reducing the development of mechanical allodynia. Results suggest that the development of the mechanical allodynia in K7M2 osteosarcoma-bearing mice is mediated by oxidative stress associated with the recruitment of neural macrophages, and that antagonism of β2-and β3-ARs contribute not solely to the reduction of tumor growth, but also in cancer pain. Thus, the targeting of the β2-and β3-ARs signaling may be a promising therapeutic strategy against both tumor progression and the development of cancer-evoke pain in osteosarcoma.

The Protective Role of the Heme Catabolic Pathway in Hepatic Disorders

Significance: As the central metabolic organ, the liver is exposed to a variety of potentially cytotoxic, proinflammatory, profibrotic, and carcinogenic stimuli. To protect the organism from these deleterious effects, the liver has evolved a number of defense systems, which include antioxidant substrates and enzymes, anti-inflammatory tools, enzymatic biotransformation systems, and metabolic pathways. Recent Advances: One of the pivotal systems that evolved during phylogenesis was the heme catabolic pathway. Comprising the important enzymes heme oxygenase and biliverdin reductase, this complex pathway has a number of key functions including enzymatic activities, but also cell signaling, and DNA transcription. It further generates two important bile pigments, biliverdin and bilirubin, as well as the gaseous molecule carbon monoxide. These heme degradation products have potent antioxidant, immunosuppressive, and cytoprotective effects. Recent data suggest that the pathway participates in the regulation of metabolic and hormonal processes implicated in the pathogenesis of hepatic and other diseases. Critical Issues: This review discusses the impact of the heme catabolic pathway on major liver diseases, with particular focus on the involvement of cellular targeting and signaling in the pathogenesis of these conditions. Future Directions: To utilize the biological consequences of the heme catabolic pathway, several unique therapeutic strategies have been developed. Research indicates that pharmaceutical, nutraceutical, and lifestyle modifications positively affect the pathway, delivering potentially long-term clinical benefits. However, further well-designed studies are needed to confirm the clinical benefits of these approaches. Antioxid. Redox Signal. 35, 734-752.

In Vitro Electrochemical Detection of Hydrogen Peroxide in Activated Macrophages via a Platinum Microelectrode Array

Oxidative stress, an excess of endogenous or exogenous reactive oxygen species (ROS) in the human body, is closely aligned with inflammatory responses. ROS such as hydrogen peroxide (H₂O₂), superoxide, and radical hydroxyl ions serve essential functions in fighting infection; however, chronic elevation of these species irreversibly damages cellular components. Given the central role of inflammation in a variety of diseases, including Alzheimer’s disease and rheumatoid arthritis, a low-cost, extracellular, non-invasive assay of H₂O₂ measurement is needed. This work reports the use of a platinum microelectrode array (Pt MEA)-based ceramic probe to detect time- and concentration-dependent variations in H₂O₂ production by activated RAW 264.7 macrophages. First, these cells were activated by lipopolysaccharide (LPS) to induce oxidative stress. Chronoamperometry was then employed to detect the quantity of H₂O₂ released by cells at various time intervals up to 48 h. The most stimulatory concentration of LPS was identified. Further experiments assessed the anti-inflammatory effect of dexamethasone (Dex), a commonly prescribed steroid medication. As expected, the probe detected significantly increased H₂O₂ production by LPS-doped macrophages, subsequently diminishing the pro-inflammatory effect in LPS-doped cells treated with Dex. These results strongly support the use of this probe as a non-invasive, robust, point-of-care test of inflammation, with a high potential for multiplexing in further studies.

Reactive-oxygen-species-scavenging nanomaterials for resolving inflammation

Reactive oxygen species (ROS) mediate multiple physiological functions; however, the over-accumulation of ROS causes premature aging and/or death and is associated with various inflammatory conditions. Nevertheless, there are limited clinical treatment options that are currently available. The good news is that owing to the considerable advances in nanoscience, multiple types of nanomaterials with unique ROS-scavenging abilities that influence the temporospatial dynamic behaviors of ROS in biological systems have been developed. This has led to the emergence of next-generation nanomaterial-controlled strategies aimed at ameliorating ROS-related inflammatory conditions. Accordingly, herein we reviewed recent progress in research on nanotherapy based on ROS scavenging. The underlying mechanisms of the employed nanomaterials are emphasized. Furthermore, important issues in developing cross-disciplinary nanomedicine-based strategies for ROS-based inflammatory conditions are discussed. Our review of this increasing interdisciplinary field will benefit ongoing studies and clinical applications of nanomedicine based on ROS scavenging.

Carnosine Protects Macrophages against the Toxicity of Aβ1-42 Oligomers by Decreasing Oxidative Stress

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide has well-known antioxidant, anti-inflammatory, and anti-aggregation activities, and it may be useful for treatment of neurodegenerative disorders such as Alzheimer’s disease (AD). In this disease, peripheral infiltrating macrophages play a substantial role in the clearance of amyloid beta (Aβ) peptides from the brain. Correspondingly, in patients suffering from AD, defects in the capacity of peripheral macrophages to engulf Aβ have been reported. The effects of carnosine on macrophages and oxidative stress associated with AD are consequently of substantial interest for drug discovery in this field. In the present work, a model of stress induced by Aβ1-42 oligomers was investigated using a combination of methods including trypan blue exclusion, microchip electrophoresis with laser-induced fluorescence, flow cytometry, fluorescence microscopy, and high-throughput quantitative real-time PCR. These assays were used to assess the ability of carnosine to protect macrophage cells, modulate oxidative stress, and profile the expression of genes related to inflammation and pro- and antioxidant systems. We found that pre-treatment of RAW 264.7 macrophages with carnosine counteracted cell death and apoptosis induced by Aβ1-42 oligomers by decreasing oxidative stress as measured by levels of intracellular nitric oxide (NO)/reactive oxygen species (ROS) and production of peroxynitrite. This protective activity of carnosine was not mediated by modulation of the canonical inflammatory pathway but instead can be explained by the well-known antioxidant and free-radical scavenging activities of carnosine, enhanced macrophage phagocytic activity, and the rescue of fractalkine receptor CX3CR1. These new findings obtained with macrophages challenged with Aβ1-42 oligomers, along with the well-known multimodal mechanism of action of carnosine in vitro and in vivo, substantiate the therapeutic potential of this dipeptide in the context of AD pathology.

Bilirubin as a metabolic hormone: the physiological relevance of low levels

Recent research on bilirubin, a historically well-known waste product of heme catabolism, suggests an entirely new function as a metabolic hormone that drives gene transcription by nuclear receptors. Studies are now revealing that low plasma bilirubin levels, defined as "hypobilirubinemia," are a possible new pathology analogous to the other end of the spectrum of extreme hyperbilirubinemia seen in patients with jaundice and liver dysfunction. Hypobilirubinemia is most commonly seen in patients with metabolic dysfunction, which may lead to cardiovascular complications and possibly stroke. We address the clinical significance of low bilirubin levels. A better understanding of bilirubin's hormonal function may explain why hypobilirubinemia might be deleterious. We present mechanisms by which bilirubin may be protective at mildly elevated levels and research directions that could generate treatment possibilities for patients with hypobilirubinemia, such as targeting of pathways that regulate its production or turnover or the newly designed bilirubin nanoparticles. Our review here calls for a shift in the perspective of an old molecule that could benefit millions of patients with hypobilirubinemia.

Cartilage-targeting peptide-modified dual-drug delivery nanoplatform with NIR laser response for osteoarthritis therapy

Cartilage-targeting delivery of therapeutic agents is still an effective strategy for osteoarthritis (OA) therapy. Recently, scavenging for reactive oxygen species (ROS) and activating autophagy have been increasingly reported to treat OA effectively. In this study, we designed, for the first time, a dual-drug delivery system based on metal organic framework (MOF)-decorated mesoporous polydopamine (MPDA) which composed of rapamycin (Rap) loaded into the mesopores and bilirubin (Br) loaded onto the shell of MOF. The collagen II-targeting peptide (WYRGRL) was then conjugated on the surface of above nanocarrier to develop a cartilage-targeting dual-drug delivery nanoplatform (RB@MPMW). Our results indicated the sequential release of two agents from RB@MPMW could be achieved via near-infrared (NIR) laser irritation. Briefly, the rapid release of Br from the MOF shell exhibited excellent ROS scavenging ability and anti-apoptosis effects, however responsively reduced autophagy activity, to a certain extent. Meanwhile, following the NIR irradiation, Rap was rapidly released from MPDA core and further enhanced autophagy activation and chondrocyte protection. RB@MPMW continuously phosphorylated AMPK and further rescued mitochondrial energy metabolism of chondrocytes following IL-1β stimulation via activating SIRT1-PGC-1α signaling pathway. Additionally, the cartilage-targeting property of peptide-modified nanocarrier could be monitored via Magnetic Resonance (MR) and IVIS imaging. More significantly, RB@MPMW effectively delayed cartilage degeneration in ACLT rat model. Overall, our findings indicated that the as-prepared dual-drug delivery nanoplatform exerted potent anti-inflammation and anti-apoptotic effects, rescued energy metabolism of chondrocytes in vitro and prevented cartilage degeneration in vivo, which thereby showed positive performance for OA therapy.

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Collagen type II-targeting peptide and positive surface potential endow RB@MPMW with a fine cartilage affinity ability.

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RB@MPMW possess superb biological functions of scavenging free radicals and autophagy induction.

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RB@MPMW effectively promotes chondrocyte mitochondrial energy metabolism in the inflammatory microenvironment.

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RB@MPMW has a good MR imaging ability, which could monitor its therapeutic effects in vivo.

Serum Bilirubin Level Is Increased in Metabolically Healthy Obesity

OBJECTIVES

Bilirubin is a biochemical substance with metabolic benefits. The objective of this research was to elucidate the association between serum bilirubin levels and metabolic alterations in different obesity phenotypes.

METHODS

In total, 1,042 drug-naive participants were included in the study. Of them, 541 were obese patients and 501 were age-matched and sex-matched healthy control subjects. The obese patients were divided into metabolically healthy obesity (MHO) group and metabolically unhealthy obesity (MUHO) group according to the levels of fasting plasma glucose (FBG), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and blood pressure (BP). Clinical and biochemical parameters including total bilirubin (TBil), indirect bilirubin (IBil) and direct bilirubin (DBil) were measured. ANOVA or Kruskal-Wallis H test was used to test differences among the three groups. Pearson and Spearman correlations were used to analyze the relationships between two parameters. The relationships between bilirubin and other variables were analyzed using Multivariate regression analysis.

RESULTS

MHO group had favorable blood pressure, glucose and lipids profiles, along with increased TBil and DBil, and decreased high-sensitivity C-reactive protein (hsCRP) and homeostasis model assessment of insulin resistance (HOMA-IR) levels when compared to MUHO group (P < 0.05 for all). TBil and DBil were negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), fasting insulin (FINS), hsCRP and HOMA-IR, even after adjusted for age, gender and BMI (all P <0.01). Multivariate regression analysis demonstrated that HOMA-IR was independently correlated with TBil and DBIi levels (β = -0.400, P < 0.01).

CONCLUSION

MHO group harbors increased bilirubin level compared with MUHO group. HOMA-IR was independently correlated with TBil and DBIi levels.

AhR activation attenuates calcium oxalate nephrocalcinosis by diminishing M1 macrophage polarization and promoting M2 macrophage polarization

Calcium oxalate (CaOx) crystal can trigger kidney injury, which contributes to the pathogenesis of nephrocalcinosis. The phenotypes of infiltrating macrophage may impact CaOx-mediated kidney inflammatory injury as well as crystal deposition. How aryl hydrocarbon receptor (AhR) regulates inflammation and macrophage polarization is well understood; however, how it modulates CaOx nephrocalcinosis remains unclear.

Methods: Mice were intraperitoneally injected with glyoxylate to establish CaOx nephrocalcinosis model with or without the treatment of AhR activator 6-formylindolo(3,2-b)carbazole (FICZ). Positron emission tomography computed tomography (PET-CT) imaging, Periodic acid-Schiff (PAS) staining, and polarized light optical microscopy were used to evaluate kidney injury and crystal deposition in mice kidney. Western blotting, immunofluorescence, chromatin immunoprecipitation, microRNA-fluorescence in situ hybridization, and luciferase reporter assays were applied to analyze polarization state and regulation mechanism of macrophage.

Results: AhR expression was significantly upregulated and negatively correlated with interferon-regulatory factor 1 (IRF1) and hypoxia inducible factor 1-alpha (HIF-1α) levels in a murine CaOx nephrocalcinosis model following administration of FICZ. Moreover, AhR activation suppressed IRF1 and HIF-1α levels and decreased M1 macrophage polarization in vitro. In terms of the mechanism, bioinformatics analysis and chromatin immunoprecipitation assay confirmed that AhR could bind to miR-142a promoter to transcriptionally activate miR-142a. In addition, luciferase reporter assays validated that miR-142a inhibited IRF1 and HIF-1α expression by directly targeting their 3'-untranslated regions.

Conclusions: Our results indicated that AhR activation could diminish M1 macrophage polarization and promote M2 macrophage polarization to suppress CaOx nephrocalcinosis via the AhR-miR-142a-IRF1/HIF-1α pathway.

Role of taurine, its haloamines and its lncRNA TUG1 in both inflammation and cancer progression. On the road to therapeutics? (Review)

For one century, taurine is considered as an end product of sulfur metabolism. In this review, we discuss the beneficial effect of taurine, its haloamines and taurine upregulated gene 1 (TUG1) long non‑coding RNA (lncRNA) in both cancer and inflammation. We outline how taurine or its haloamines (N‑Bromotaurine or N‑Chlorotaurine) can induce robust and efficient responses against inflammatory diseases, providing insight into their molecular mechanisms. We also provide information about the use of taurine as a therapeutic approach to cancer. Taurine can be combined with other chemotherapeutic drugs, not only mediating durable responses in various malignancies, but also circumventing the limitations met from chemotherapeutic drugs, thus improving the therapeutic outcome. Interestingly, the lncRNA TUG1 is regarded as a promising therapeutic approach, which can overcome acquired resistance of cancer cells to selected strategies. In this regard, we can translate basic knowledge about taurine and its TUG1 lncRNA into potential therapeutic options directed against specific oncogenic signaling targets, thereby bridging the gap between bench and bedside.

Glucocorticoid versus traditional therapy for hepatitis B virus-related acute-on-chronic liver failure: A systematic review and meta-analysis

OBJECTIVE

This meta-analysis aimed to assess the efficacy and safety of glucocorticoid versus traditional therapy for hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF).

METHODS

PubMed, Cochrane Central Register of Clinical Trials, and EMBASE were searched. All clinical studies, including randomized controlled studies and cohort studies, comparing glucocorticoids with traditional treatments (until November 1, 2018), were included.

RESULTS

A total of 3 randomized controlled trials and 5 cohort studies (including 3 retrospective cohort studies), involving 538 patients, were subjected to the meta-analysis. The total bilirubin levels before treatment were not significantly different (odds ratio [OR]: -0.97; 95% confidence interval [CI]: -2.56 to 0.62; P = .23), and, however, they were significantly reduced after treatment in the corticosteroid group compared with the traditional treatment group (OR: -8.83; 95% CI: -14.99 to 2.67; P = .005). Moreover, prothrombin time was significantly long before treatment in either group, with no significant differences (OR: 0.28; 95% CI: -0.79 to 1.34; P = 0.61). However, after treatment, prothrombin time was significantly shortened in the traditional treatment group (OR: 31.71; 95% CI: 3.62-59.81; P = .03). Furthermore, inpatient mortality (OR: 0.23; 95% CI: 0.08-0.67; P = .007) and ascites events (OR: 0.35; 95% CI: 0.18-0.67; P = .90) were significantly lower in the corticosteroid treatment group.

CONCLUSIONS

Glucocorticoid is more effective for reducing the T-bili level, significantly decreasing in-hospital mortality and ascites events in HBV-related ACLF patients. Moreover, bilirubin may play a pivotal role in the early stage of HBV-related ACLF progression to advanced liver failure.

Nutraceuticals Targeting Generation and Oxidant Activity of Peroxynitrite May Aid Prevention and Control of Parkinson's Disease

Parkinson's disease (PD) is a chronic low-grade inflammatory process in which activated microglia generate cytotoxic factors-most prominently peroxynitrite-which induce the death and dysfunction of neighboring dopaminergic neurons. Dying neurons then release damage-associated molecular pattern proteins such as high mobility group box 1 which act on microglia via a range of receptors to amplify microglial activation. Since peroxynitrite is a key mediator in this process, it is proposed that nutraceutical measures which either suppress microglial production of peroxynitrite, or which promote the scavenging of peroxynitrite-derived oxidants, should have value for the prevention and control of PD. Peroxynitrite production can be quelled by suppressing activation of microglial NADPH oxidase-the source of its precursor superoxide-or by down-regulating the signaling pathways that promote microglial expression of inducible nitric oxide synthase (iNOS). Phycocyanobilin of spirulina, ferulic acid, long-chain omega-3 fatty acids, good vitamin D status, promotion of hydrogen sulfide production with taurine and N-acetylcysteine, caffeine, epigallocatechin-gallate, butyrogenic dietary fiber, and probiotics may have potential for blunting microglial iNOS induction. Scavenging of peroxynitrite-derived radicals may be amplified with supplemental zinc or inosine. Astaxanthin has potential for protecting the mitochondrial respiratory chain from peroxynitrite and environmental mitochondrial toxins. Healthful programs of nutraceutical supplementation may prove to be useful and feasible in the primary prevention or slow progression of pre-existing PD. Since damage to the mitochondria in dopaminergic neurons by environmental toxins is suspected to play a role in triggering the self-sustaining inflammation that drives PD pathogenesis, there is also reason to suspect that plant-based diets of modest protein content, and possibly a corn-rich diet high in spermidine, might provide protection from PD by boosting protective mitophagy and thereby aiding efficient mitochondrial function. Low-protein diets can also promote a more even response to levodopa therapy.

Integrated network pharmacology and targeted metabolomics to reveal the mechanism of nephrotoxicity of triptolide

Triptolide (TP) is one of the important active components in Tripterygium wilfordii Hook. F., which shows strong anti-inflammatory and immunomodulatory effects. However, a large number of literature studies have reported that TP is the main component causing nephrotoxicity, and the mechanism of nephrotoxicity has not yet been revealed. Therefore, it is of great practical significance to clarify the toxicity mechanism of TP. This study integrated network pharmacology and targeted metabolomics to reveal the nephrotoxicity mechanism of TP. Firstly, network pharmacology screening of 61 action targets related to TP induced nephrotoxicity, with 39 direct targets and 22 indirect targets, was performed. Subsequently, based on a large-scale protein-protein interaction (PPI) and molecular docking validation, the core targets were identified. Based on the above targets and enrichment analysis, the purine metabolism, Toll-like receptor signaling pathway and NF-κB signaling pathway were found play a pivotal role in TP-induced nephrotoxicity. Literature investigation showed that purine and pyrimidine metabolism pathways were closely related to kidney diseases. Therefore, by using the quantitative method of determining endogenous purine and pyrimidine previously established in the laboratory, a targeted metabolomic analysis of TP was carried out. Finally, six nephrotoxicity biomarkers, dihydroorotate, thymidine, 2-deoxyinosine, uric acid, adenosine and xanthine, were found. Combining the above results, the mechanisms underlying the nephrotoxicity of TP were speculated to be due to the over-consumption of xanthine and uric acid, which would result in enormous ROS being released in response to oxidative stress in the body. Furthermore, activation of the Toll-like receptor signalling pathway can promotes the phosphorylation of the downstream protein NF-κB and causes an inflammatory response that ultimately leads to nephrotoxicity.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.

Organosilica-Based Hollow Mesoporous Bilirubin Nanoparticles for Antioxidation-Activated Self-Protection and Tumor-Specific Deoxygenation-Driven Synergistic Therapy

A major concern about glucose oxidase (GOx)-mediated cancer starvation therapy is its ability to induce serious oxidative damage to normal tissues through the massive production of H₂O₂ byproducts in the oxygen-involved glucose decomposition reaction, which may be addressed by using a H₂O₂ scavenger, known as an antioxidation agent. Surprisingly, H₂O₂ removal accelerates the aerobic glycometabolism of tumors by activating the H₂O₂-dependent "redox signaling" pathway of cancer cells. Simultaneous oxygen depletion further aggravates tumor hypoxia to increase the toxicity of a bioreductive prodrug, such as tirapazamine (TPZ), thereby improving the effectiveness of cancer starvation therapy and bioreductive chemotherapy. Herein, a "nitrogen-protected silica template" method is proposed to design a nanoantioxidant called an organosilica-based hollow mesoporous bilirubin nanoparticle (HMBRN), which can act as an excellent nanocarrier to codeliver GOx and TPZ. In addition to efficient removal of H₂O₂ for self-protection of normal tissues via antioxidation, GOx/TPZ-coloaded HMBRN can also rapidly deplete intratumoral glucose/oxygen to promote a synergistic starvation-enhanced bioreductive chemotherapeutic effect for the substantial suppression of solid tumor growth. Distinct from the simple combination of two treatments, this study introduces antioxidation-activated self-protection nanotechnology for the significant improvement of tumor-specific deoxygenation-driven synergistic treatment efficacy without additional external energy input, thus realizing the renaissance of precise endogenous cancer therapy with negligible side effects.

Effect of conjugated bilirubin on clinical outcomes in infective endocarditis

Liver dysfunction is associated with adverse events in infective endocarditis (IE). However, few studies have explored the predictive value of conjugated bilirubin (CB) in IE. We aimed to investigate the nature of the link between CB and adverse prognosis in patients with IE. Consecutive patients with IE between January 2009 and July 2015 were enrolled. Multivariate analysis was performed to confirm whether CB was an independent risk factor for adverse outcomes. In all, 1010 patients were included and divided into two groups according to admission CB level (μmol/L): normal (≤ 7.0, n = 820) and elevated (> 7.0, n = 190) CB groups. In-hospital mortality (5.0% vs. 22.1%, p < 0.001) and major adverse cardiac events (16.8% vs. 36.3%, p < 0.001) were significantly higher in patients with increased CB. A possible J-shaped relationship was found between CB and in-hospital events. Further, CB had more predictive power than total bilirubin in predicting in-hospital death (AUC 0.715 vs. 0.674, p = 0.010). Elevated CB was an independent predictor of in-hospital death (adjusted OR = 2.62, 95%CI 1.40-4.91, p = 0.003). Moreover, CB (increment 1 μmol/L) was independently associated with higher long-term mortality. Kaplan-Meier curves indicated that patients with elevated CB were associated with higher cumulative rate of long-term death (log-rank = 21.47, p < 0.001). CB, a biomarker of liver function, was a relatively powerful predictor of in-hospital and long-term adverse prognosis of IE and could likely comprise a novel risk evaluation strategy.

Carnosine Decreases PMA-Induced Oxidative Stress and Inflammation in Murine Macrophages

Carnosine is an endogenous dipeptide composed of β-alanine and L-histidine. This naturally occurring molecule is present at high concentrations in several mammalian excitable tissues such as muscles and brain, while it can be found at low concentrations in a few invertebrates. Carnosine has been shown to be involved in different cellular defense mechanisms including the inhibition of protein cross-linking, reactive oxygen and nitrogen species detoxification as well as the counteraction of inflammation. As a part of the immune response, macrophages are the primary cell type that is activated. These cells play a crucial role in many diseases associated with oxidative stress and inflammation, including atherosclerosis, diabetes, and neurodegenerative diseases. In the present study, carnosine was first tested for its ability to counteract oxidative stress. In our experimental model, represented by RAW 264.7 macrophages challenged with phorbol 12-myristate 13-acetate (PMA) and superoxide dismutase (SOD) inhibitors, carnosine was able to decrease the intracellular concentration of superoxide anions (O2-•) as well as the expression of Nox1 and Nox2 enzyme genes. This carnosine antioxidant activity was accompanied by the attenuation of the PMA-induced Akt phosphorylation, the down-regulation of TNF-α and IL-6 mRNAs, and the up-regulation of the expression of the anti-inflammatory mediators IL-4, IL-10, and TGF-β1. Additionally, when carnosine was used at the highest dose (20 mM), there was a generalized amelioration of the macrophage energy state, evaluated through the increase both in the total nucleoside triphosphate concentrations and the sum of the pool of intracellular nicotinic coenzymes. Finally, carnosine was able to decrease the oxidized (NADP+)/reduced (NADPH) ratio of nicotinamide adenine dinucleotide phosphate in a concentration dependent manner, indicating a strong inhibitory effect of this molecule towards the main source of reactive oxygen species in macrophages. Our data suggest a multimodal mechanism of action of carnosine underlying its beneficial effects on macrophage cells under oxidative stress and inflammation conditions.

Correlations between the serum bilirubin level and ulcerative colitis: a case-control study

OBJECTIVE

To analyze whether the bilirubin level is a protective factor in ulcerative colitis (UC) and the predictive value of the bilirubin level.

PATIENTS AND METHODS

We compared the bilirubin levels of 100 UC patients and 140 healthy controls as well as those of the subgroups of patients with different UC severities and then analyzed the correlation between the bilirubin level and UC and the correlations among the erythrocyte sedimentation rate (ESR), high sensitivity C-reactive protein (hs-CRP) level, UC severity, and bilirubin level. The predictive value of the bilirubin level for UC was determined by constructing a receiver operating characteristic (ROC) curve.

RESULTS

The mean levels of the total bilirubin (TBIL) and indirect bilirubin (IBIL) in the UC were lower in comparison with the mean TBIL and IBIL levels in the control group, and the TBIL and IBIL levels were significantly higher in the mild activity subgroup than in the moderate and severe activity subgroups (P<0.05). TBIL (P<0.001, 95% confidence interval: 0.794-0.918) and especially IBIL (P<0.001, 95% confidence interval: 0.646-0.809) were independent protective factors for UC. There were also significant differences in the serum ESR and hs-CRP levels between the patients with different UC severities (ESR=χ: 23.975; hs-CRP=χ: 26.626, P<0.001), and there was a positive correlation between these two parameters (ESR=r: 0.472; hs-CRP=r: 0.495, P<0.001). However, the TBIL and IBIL levels were correlated negatively with the ESR (rtotal=-0.429, rindirect=-0.461, P<0.001) and hs-CRP (rtotal=-0.289, rindirect=-0.25, P<0.05) levels. The ROC curve showed that the threshold values of TBIL and IBIL were 8.87 and 6.735 µmol/l, the areas under the maximum ROC curve were 0.664 and 0.716, the sensitivities were 0.450 and 0.61, and the specificities were 0.800 and 0.786, respectively.

CONCLUSION

TBIL and especially IBIL may be independent protective factors for UC because of their antioxidant and anti-inflammatory effects. A low level of IBIL has a moderate predictive value for UC, and an IBIL level less than 6.735 µmol/l can be used as a defining index for predicting UC.

Hyperbilirubinemia in Gunn Rats is Associated with Decreased Inflammatory Response in LPS-Mediated Systemic Inflammation

Decreased inflammatory status has been reported in subjects with mild unconjugated hyperbilirubinemia. However, mechanisms of the anti-inflammatory actions of bilirubin (BR) are not fully understood. The aim of this study is to assess the role of BR in systemic inflammation using hyperbilirubinemic Gunn rats as well as their normobilirubinemic littermates and further in primary hepatocytes. The rats were treated with lipopolysaccharide (LPS, 6 mg/kg intraperitoneally) for 12 h, their blood and liver were collected for analyses of inflammatory and hepatic injury markers. Primary hepatocytes were treated with BR and TNF-α. LPS-treated Gunn rats had a significantly decreased inflammatory response, as evidenced by the anti-inflammatory profile of white blood cell subsets, and lower hepatic and systemic expressions of IL-6, TNF-α, IL-1β, and IL-10. Hepatic mRNA expression of LPS-binding protein was upregulated in Gunn rats before and after LPS treatment. In addition, liver injury markers were lower in Gunn rats as compared to in LPS-treated controls. The exposure of primary hepatocytes to TNF-α with BR led to a milder decrease in phosphorylation of the NF-κB p65 subunit compared to in cells without BR. In conclusion, hyperbilirubinemia in Gunn rats is associated with an attenuated systemic inflammatory response and decreased liver damage upon exposure to LPS.

Gut microbiota analysis and its significance in vasovagal syncope in children

BACKGROUND

Vasovagal syncope (VVS) is common in children and greatly affect both physical and mental health. But the mechanisms have not been completely explained. This study was designed to analyze the gut microbiota in children with VVS and explore its clinical significance.

METHODS

Fecal samples from 20 VVS children and 20 matched controls were collected, and the microbiota were analyzed by 16S rRNA gene sequencing. The diversity and microbiota compositions of the VVS cases and controls were compared with the independent sample t test or Mann-Whitney U test. The correlation between the predominant bacteria and clinical symptoms was analyzed using Pearson or Spearman correlation test.

RESULTS

No significant differences in diversity were evident between VVS and controls (P > 0.05). At the family level, the relative abundance of Ruminococcaceae was significantly higher in VVS children than in controls (median [Q1, Q3]: 22.10% [16.89%, 27.36%] vs. 13.92% [10.31%, 20.18%], Z = -2.40, P < 0.05), and LEfSe analysis revealed Ruminococcaceae as a discriminative feature (linear discriminant analysis [LDA] score > 4, P < 0.05). The relative abundance of Ruminococcaceae in VVS patients was positively correlated with the frequency of syncope (r = 0.616, P < 0.01). In terms of its correlation with hemodynamics, we showed that relative abundance of Ruminococcaceae was negatively correlated with the systolic and diastolic pressure reduction at the positive response in head-up tilt test (HUTT; r = -0.489 and -0.448, all P < 0.05), but was positively correlated with the mean pressure drop and decline rate (r = 0.489 and 0.467, all P < 0.05) as well as diastolic pressure drop and decline rate at the HUTT positive response (r = 0.579 and 0.589, all P < 0.01) in VVS patients.

CONCLUSION

Ruminococcaceae was the predominant gut bacteria and was associated with the clinical symptoms and hemodynamics of VVS, suggesting that gut microbiota might be involved in the development of VVS.

Heme oxygenase-1 prevents glucocorticoid and hypoxia-induced apoptosis and necrosis of osteocyte-like cells

Glucocorticoids and hypoxia is considered to promote osteocyte apoptosis and necrosis, which are observed in glucocorticoid-associated osteonecrosis and osteoporosis. Heme oxygenase-1 (HO-1) induced by hemin is reported to have cytoprotective effects in ischemic diseases. The objective of this study was to evaluate the effect of HO-1 on osteocyte death caused by glucocorticoids and hypoxia. We confirmed that hemin induced HO-1 expression in MLO-Y4 mouse osteocytes. MLO-Y4 was cultured with dexamethasone (Dex) under hypoxia (DH group). Furthermore, these cells were cultured with hemin (DH-h group) or hemin and zinc protoporphyrin IX (an HO-1 inhibitor) (DH-h-PP group). The rates of apoptosis and necrosis of these groups were analyzed by flow cytometry and compared with cells cultured under normal condition. Both apoptosis and necrosis increased in the DH group. Hemin administration significantly reduced cell death caused by glucocorticoids and hypoxia in the DH-h group, and its effect was attenuated by the HO-1 inhibitor in DH-h-PP group. Capase-3 activity significantly decreased in the DH-h group. This implied that the cell death inhibition effect due to hemin is mediated by HO-1 and caspase-3. HO-1 induction may be useful in the treatment of glucocorticoid-associated osteonecrosis and osteoporosis.

Sub-acute restraint stress progressively increases oxidative/nitrosative stress and inflammatory markers while transiently upregulating antioxidant gene expression in the rat hippocampus

We have previously demonstrated that acute stress decreases neuronal nitric oxide synthase (NOS) expression in the hippocampus despite increased concentrations of nitric oxide which may indicate feedback inhibition of neuronal NOS expression via inducible NOS-derived nitric oxide. Moreover, the hippocampus undergoes an initial oxidative/nitrosative insult that is rapidly followed by upregulation of protective antioxidants, including the zinc-binding metallothioneins, in order to counter this and restore redox balance following acute stress exposure. In the present study, we have utilized indicators of oxidative/nitrosative stress, members of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway, antioxidant metallothioneins, and neuroinflammatory markers to observe the changes occurring in the hippocampus following short term repeated stress exposure. Male Wistar rats were subjected to control conditions or 6 h of restraint stress applied for 1, 2, or 3 days (n = 8 per group) after which the hippocampus was isolated for redox assays and relative gene expression. The hippocampus showed increased oxidative stress, transient dys-homeostasis of total zinc, and increased expression of the Nrf2 pathway members. Moreover, repeated stress increased nitrosative status, nitric oxide metabolites, and 3-nitrotyrosine, indicative of nitrosative stress in the hippocampus. However, levels of neuronal NOS decreased over all stress treatment groups, while increases were observed in inducible NOS and xanthine dehydrogenase. In addition to inducible NOS, mRNA expression of other inflammatory markers including interleukin-6 and interleukin-1β also increased even in the presence of increased anti-inflammatory glucocorticoids. Together, these results demonstrate that despite increases in antioxidant expression, sub-acute stress causes an inflammatory phenotype in the hippocampus by inducing oxidative/nitrosative stress, zinc dys-homeostasis, and the accumulation of nitrotyrosinated proteins which is likely driven by increased inducible NOS signaling.

Peroxidase-Mimicking Nanoassembly Mitigates Lipopolysaccharide-Induced Endotoxemia and Cognitive Damage in the Brain by Impeding Inflammatory Signaling in Macrophages

Oxidative stress during sepsis pathogenesis remains the most-important factor creating imbalance and dysregulation in immune-cell function, usually observed following initial infection. Hydrogen peroxide (H₂O₂), a potentially toxic reactive oxygen species (ROS), is excessively produced by pro-inflammatory immune cells during the initial phases of sepsis and plays a dominant role in regulating the pathways associated with systemic inflammatory immune activation. In the present study, we constructed a peroxide scavenger mannosylated polymeric albumin manganese dioxide (mSPAM) nanoassembly to catalyze the decomposition of H₂O₂ responsible for the hyper-activation of pro-inflammatory immune cells. In a detailed manner, we investigated the role of mSPAM nanoassembly in modulating the expression and secretion of pro-inflammatory markers elevated in bacterial lipopolysaccharide (LPS)-mediated endotoxemia during sepsis. Through a facile one-step solution-phase approach, hydrophilic bovine serum albumin reduced manganese dioxide (BM) nanoparticles were synthesized and subsequently self-assembled with cationic mannosylated disulfide cross-linked polyethylenimine (mSP) to formulate mSPAM nanoassembly. In particular, we observed that the highly stable mSPAM nanoassembly suppressed HIF1α expression by scavenging H₂O₂ in LPS-induced macrophage cells. Initial investigation revealed that a significant reduction of free radicals by the treatment of mSPAM nanoassembly has reduced the infiltration of neutrophils and other leukocytes in a local endotoxemia animal model. Furthermore, therapeutic studies in a systemic endotoxemia model demonstrated that mSPAM treatment reduced TNF-α and IL-6 inflammatory cytokines in serum, in turn circumventing organ damage done by the inflammatory macrophages. Interestingly, we also observed that the reduction of these inflammatory cytokines by mSPAM nanoassembly further prevented IBA-1 immuno-positive microglial cell activation in the brain and consequently improved the cognitive function of the animals. Altogether, the administration of mSPAM nanoassembly scavenged H₂O₂ and suppressed HIF1α expression in LPS-stimulated macrophages and thereby inhibited the progression of local and systemic inflammation as well as neuroinflammation in an LPS-induced endotoxemia model. This mSPAM nanoassembly system could serve as a potent anti-inflammatory agent, and we further anticipate its successful application in treating various inflammation-related diseases.

Bilirubin in the Liver-Gut Signaling Axis

Bilirubin is a component of the heme catabolic pathway that is essential for liver function and has been shown to reduce hepatic fat accumulation. High plasma bilirubin levels are reflective of liver disease due to an injurious effect on hepatocytes. In healthy liver, bilirubin is conjugated and excreted to the intestine and converted by microbes to urobilinoids, which are reduced to the predominant pigment in feces, stercobilin, or reabsorbed. The function of urobilinoids in the gut or their physiological relevance of reabsorption is not well understood. In this review, we discuss the relationship of hepatic bilirubin signaling to the intestinal microbiota and its regulation of the liver-gut axis, as well as its capacity to mediate these processes.

Association of serum bilirubin with longevity: Evidence from a retrospective longitudinal study and cross-sectional data

Bilirubin is a potent antioxidant and an important anti-inflammatory factor. Therefore, there has been an increasing focus on serum bilirubin as a negative risk factor of cardiovascular mortality in men and an indicator of improved survival in both sexes, but the direct mechanisms of these links and the causes of sex differences are not well understood. Moreover, the evidence from longitudinal studies on effects of bilirubin on longevity is limited. In this study, we retrospectively analyzed two groups of older adults to explore age-dependent changes in serum bilirubin levels and their associations with long-term survival in both sexes. Longitudinal data from 142 individuals (68 men and 74 women) aged 45 to 70 years were compared with cross-sectional data from 225 individuals (113 men and 112 women). The latter group was divided into four categories of survival, i.e. 53, 63, 68, and 76+ based on data on lifespan. ANOVA, t-test, and regression analysis were run. The analysis of the longitudinal data showed an increase in serum total bilirubin levels in men (0.3038e0.093x, R2 = 0.667) and women (0.1838e0.0187x, R2 = 0.950), while the analysis of cross-sectional data revealed a U-shaped pattern of age-related changes in men (0.001x2 - 0.1263x + 4.4524, R2 = 0.999) but an inverted U-shaped pattern in women (0.0006x2 + 0.072x - 1.6924, R2 = 0.195). On balance, these results suggest that elevated but normal bilirubin levels might confer a survival advantage in older men but not women. Alternatively, the positive relationship between serum total bilirubin and lifespan was not causal but coincidental. Further studies are needed to elucidate the direct mechanisms of the association between serum bilirubin levels and longevity in elderly people of both sexes.

Elevated bilirubin levels and risk of developing chronic kidney disease: a dose-response meta-analysis and systematic review of cohort studies

AIMS

Previous studies have indicated the link of bilirubin levels and risk of developing chronic kidney disease (CKD); however, the findings were inconsistent.

METHODS

We searched for cohort studies examining bilirubin as an exposure and CKD as an outcome in the Medline, EMBASE, and Web of Science databases from inception through November 31, 2016. A generalized least-squares approach was applied to assess the dose-response relationship between them by pooling rate ratios with 95% confidence intervals. Subgroup analyses, sensitivity analysis, meta-regression, and publication bias were also conducted.

RESULTS

Seven cohort studies with 1316 cases and 21,076 participants were identified for inclusion in the meta-analysis. The combined RR for the highest versus lowest bilirubin level was 0.36 (95% CI 0.19-0.68; P _{heterogeneity} = 0.001; Power = 0.72; n = 6). In the linear dose-response analysis, each 1-μmol/L increase in bilirubin was associated with a 5% reduced risk of CKD (RR = 0.95; 95% CI 0.92-0.97; P for trend test = 0.113; P _{heterogeneity} = 0.001; Power = 0.99; n = 7). The subgroup analyses and sensitivity analyses showed consistent results, and publication bias may exist.

CONCLUSION

This meta-analysis suggests that elevated bilirubin level may be associated with decreased risk of developing CKD.

Quercetin alleviates pulmonary angiogenesis in a rat model of hepatopulmonary syndrome

Quercetin shows protective effects against hepatopulmonary syndrome (HPS), as demonstrated in a rat model. However, whether these effects involve pulmonary vascular angiogenesis in HPS remains unclear. Therefore, this study aimed to assess the effect of quercetin on pulmonary vascular angiogenesis and explore the underlying mechanisms. Male Sprague-Dawley rats weighing 200-250 g underwent sham operation or common bile duct ligation (CBDL). Two weeks after surgery, HIF-1α and NFκB levels were assessed in rat lung tissue by immunohistochemistry and western blot. Then, CBDL and sham-operated rats were further divided into 2 subgroups each to receive intraperitoneal administration of quercetin (50 mg/kg daily) or 0.2% Tween for two weeks: Sham (Sham+Tween; n=8), CBDL (CBDL+Tween; n=8), Q (Sham+quercetin; n=8), and CBDL+Q (CBDL+quercetin; n=8). After treatment, lung tissue specimens were assessed for protein (immunohistochemistry and western blot) and/or gene expression (quantitative real-time PCR) levels of relevant disease markers, including VEGFA, VEGFR2, Akt/p-Akt, HIF-1α, vWf, and IκB/p-IκB. Finally, arterial blood was analyzed for alveolar arterial oxygen pressure gradient (AaPO₂). Two weeks after CBDL, HIF-1α expression in the lung decreased, but was gradually restored at four weeks. Treatment with quercetin did not significantly alter HIF-1α levels, but did reduce AaPO₂ as well as lung tissue NF-κB activity, VEGFA gene and protein levels, Akt activity, and angiogenesis. Although hypoxia is an important feature in HPS, our findings suggest that HIF-1α was not the main cause for the VEGFA increase. Interestingly, quercetin inhibited pulmonary vascular angiogenesis in rats with HPS, with involvement of Akt/NF-κB and VEGFA/VEGFR-2 pathways.

Bilirubin suppresses Th17 immunity in colitis by upregulating CD39

Unconjugated bilirubin (UCB), a product of heme oxidation, has known immunosuppressant properties but the molecular mechanisms, other than antioxidant effects, remain largely unexplored. We note that UCB modulates T helper type 17 (Th17) immune responses, in a manner dependent upon heightened expression of CD39 ectonucleotidase. UCB has protective effects in experimental colitis, where it enhances recovery after injury and preferentially boosts IL-10 production by colonic intraepithelial CD4+ cells. In vitro, UCB confers immunoregulatory properties on human control Th17 cells, as reflected by increased levels of FOXP3 and CD39 with heightened cellular suppressor ability. Upregulation of CD39 by Th17 cells is dependent upon ligation of the aryl hydrocarbon receptor (AHR) by UCB. Genetic deletion of CD39, as in Entpd1-/- mice, or dysfunction of AHR, as in Ahrd mice, abrogates these UCB salutary effects in experimental colitis. However, in inflammatory bowel disease (IBD) samples, UCB fails to confer substantive immunosuppressive properties upon Th17 cells, because of decreased AHR levels under the conditions tested in vitro. Immunosuppressive effects of UCB are mediated by AHR resulting in CD39 upregulation by Th17. Boosting downstream effects of AHR via UCB or enhancing CD39-mediated ectoenzymatic activity might provide therapeutic options to address development of Th17 dysfunction in IBD.

Bilirubin Prevents Atherosclerotic Lesion Formation in Low-Density Lipoprotein Receptor-Deficient Mice by Inhibiting Endothelial VCAM-1 and ICAM-1 Signaling

Background

Numerous epidemiological studies support an inverse association between serum bilirubin levels and the incidence of cardiovascular disease; however, the mechanism(s) by which bilirubin may protect against atherosclerosis is undefined. The goals of the present investigations were to assess the ability of bilirubin to prevent atherosclerotic plaque formation in low‐density lipoprotein receptor‐deficient (Ldlr^−/−) mice and elucidate the molecular processes underlying this effect.

Methods and Results

Bilirubin, at physiological concentrations (≤20 μmol/L), dose‐dependently inhibits THP‐1 monocyte migration across tumor necrosis factor α–activated human umbilical vein endothelial cell monolayers without altering leukocyte binding or cytokine production. A potent antioxidant, bilirubin effectively blocks the generation of cellular reactive oxygen species induced by the cross‐linking of endothelial vascular cell adhesion molecule 1 (VCAM‐1) or intercellular adhesion molecule 1 (ICAM‐1). These findings were validated by treating cells with blocking antibodies or with specific inhibitors of VCAM‐1 and ICAM‐1 signaling. When administered to Ldlr^−/− mice on a Western diet, bilirubin (30 mg/kg intraperitoneally) prevents atherosclerotic plaque formation, but does not alter circulating cholesterol or chemokine levels. Aortic roots from bilirubin‐treated animals exhibit reduced lipid and collagen deposition, decreased infiltration of monocytes and lymphocytes, fewer smooth muscle cells, and diminished levels of chlorotyrosine and nitrotyrosine, without changes in VCAM‐1 or ICAM‐1 expression.

Conclusions

Bilirubin suppresses atherosclerotic plaque formation in Ldlr^−/− mice by disrupting endothelial VCAM‐1‐ and ICAM‐1‐mediated leukocyte migration through the scavenging of reactive oxygen species signaling intermediaries. These findings suggest a potential mechanism for the apparent cardioprotective effects of bilirubin.

Reciprocal regulation of eNOS, H2S and CO-synthesizing enzymes in human atheroma: Correlation with plaque stability and effects of simvastatin

The molecular and cellular mechanisms underlying plaque destabilization remain obscure. We sought to elucidate the correlation between NO, H₂S and CO-generating enzymes, nitro-oxidative stress and plaque stability in carotid arteries. Carotid atherosclerotic plaques were collected from 62 patients who had undergone endarterectomy due to internal artery stenosis. Following histological evaluation the plaques were divided into stable and unstable ones. To investigate the impact of simvastatin we divided patients with stable plaques, into those receiving and to those not receiving simvastatin. Expression and/or levels of p-eNOS/eNOS, pAkt/t-Akt, iNOS, cystathionine beta synthase (CBS), cystathionine gamma lyase (CSE), heme oxygenase-1(HO-1), soluble guanyl cyclase sGCα1, sGCβ1, NOX-4 and HIF-1α were evaluated. Oxidative stress biomarkers malondialdehyde (MDA) and nitrotyrosine (NT) were measured. NT levels were decreased in stable plaques with a concomitant increase of eNOS phosphorylation and expression and Akt activation compared to unstable lesions. An increase in HIF-1α, NOX-4, HO-1, iNOS, CBS and CSE expression was observed only in unstable plaques. 78% of patients under simvastatin were diagnosed with stable plaques whereas 23% of those not receiving simvastatin exhibited unstable plaques. Simvastatin decreased iNOS, HO-1, HIF-1α and CSE whilst it increased eNOS phosphorylation. In conclusion, enhanced eNOS and reduced iNOS and NOX-4 were observed in stable plaques; CBS and CSE positively correlated with plaque vulnerability. Simvastatin, besides its known effect on eNOS upregulation, reduced the HIF-1α and its downstream targets. The observed changes might be useful in developing biomarkers of plaque stability or could be targets for pharmacothepary against plaque vulnerability.

BGP-15 Protects against Oxidative Stress- or Lipopolysaccharide-Induced Mitochondrial Destabilization and Reduces Mitochondrial Production of Reactive Oxygen Species

Reactive oxygen species (ROS) play a critical role in the progression of mitochondria-related diseases. A novel insulin sensitizer drug candidate, BGP-15, has been shown to have protective effects in several oxidative stress-related diseases in animal and human studies. In this study, we investigated whether the protective effects of BGP-15 are predominantly via preserving mitochondrial integrity and reducing mitochondrial ROS production. BGP-15 was found to accumulate in the mitochondria, protect against ROS-induced mitochondrial depolarization and attenuate ROS-induced mitochondrial ROS production in a cell culture model, and also reduced ROS production predominantly at the complex I-III system in isolated mitochondria. At physiologically relevant concentrations, BGP-15 protected against hydrogen peroxide-induced cell death by reducing both apoptosis and necrosis. Additionally, it attenuated bacterial lipopolysaccharide (LPS)-induced collapse of mitochondrial membrane potential and ROS production in LPS-sensitive U-251 glioma cells, suggesting that BGP-15 may have a protective role in inflammatory diseases. However, BGP-15 did not have any antioxidant effects as shown by in vitro chemical and cell culture systems. These data suggest that BGP-15 could be a novel mitochondrial drug candidate for the prevention of ROS-related and inflammatory disease progression.

Dimethyl ester of bilirubin exhibits anti-inflammatory activity through inhibition of secretory phospholipase A2, lipoxygenase and cyclooxygenase

Overproduction of arachidonic acid (AA) mediated by secretory phospholipase A2 group IIA (sPLA2IIA) is a hallmark of many inflammatory disorders. AA is subsequently converted into pro-inflammatory eicosanoids through 5-lipoxygenase (5-LOX) and cyclooxygenase-1/2 (COX-1/2) activities. Hence, inhibition of sPLA2IIA, 5-LOX and COX-1/2 activities is critical in regulating inflammation. We have previously reported unconjugated bilirubin (UCB), an endogenous antioxidant, as sPLA2IIA inhibitor. However, lipophilic UCB gets conjugated in liver with glucuronic acid into hydrophilic conjugated bilirubin (CB). Since hydrophobicity is pre-requisite for sPLA2IIA inhibition, conjugation reduces the efficacy of UCB. In this regard, UCB was chemically modified and derivatives were evaluated for sPLA2IIA, 5-LOX and COX-1/2 inhibition. Among the derivatives, BD1 (dimethyl ester of bilirubin) exhibited ∼ 3 fold greater inhibitory potency towards sPLA2IIA compared to UCB. Both UCB and BD1 inhibited human 5-LOX and COX-2 activities; however only BD1 inhibited AA induced platelet aggregation. Molecular docking studies demonstrated BD1 as better inhibitor of aforesaid enzymes than UCB and other endogenous antioxidants. These data suggest that BD1 exhibits strong anti-inflammatory activity through inhibition of AA cascade enzymes which is of great therapeutic importance.

Edema, Hyperpigmentation, Induration: 3 Skin Signs Heralding Danger in Patients on Maintenance Hemodialysis

Skin changes are common in patients on dialysis. This study focused on putative associations of specific skin findings with comorbidities and mortality.We performed a retrospective analysis of data from 508 patients on maintenance hemodialysis therapy in 7 centers in the German State of North Rhine Westphalia. Data had been collected by interview, from patient files, and from targeted physical examination in an earlier prospective study screening hemodialysis patients for the presence of nephrogenic systemic fibrosis. While on dialysis, patients' extremities had been examined for any of the following: edematous skin at the lower extremities, hyperpigmentation, induration, and xerosis cutis. Our present data analyses focused on associated mortality and comorbidities.Five hundred eight patients (median age 71 years, range 20.0-95.9; n = 292 men) had agreed to participate in the initial study: 48% (n = 243) were diabetics and 46% (n = 232) had been diagnosed with coronary heart disease. On examination, 86% of patients (n = 439) presented with at least 1 of the prespecified skin changes. Skin edema (n = 89; 18%), hyperpigmentation (n = 74; 15%), and induration (n = 9; 2%) were independently associated with increased mortality over 24 months (P < 0.002, P < 0.030, and P < 0.020, respectively).In our study, prespecified skin changes indicated an increased mortality risk in patients on chronic hemodialysis. Routinely assessing the skin of dialysis patients represents a simple, reliable, and cost effective means of identifying those at greatest risk.

Bilirubin acts as an endogenous regulator of inflammation by disrupting adhesion molecule-mediated leukocyte migration

There is a growing body of evidence that bilirubin, which is generated during the physiological breakdown of heme, exerts potent anti-inflammatory effects. Previous work by our group suggests that bilirubin is able to suppress inflammatory responses by preventing the migration of leukocytes into target tissues through disruption of vascular cell adhesion molecule-1 (VCAM-1)-dependent cell signaling. As VCAM-1 is an important mediator of tissue injury in the dextran sodium sulfate (DSS) murine model of inflammatory colitis, we examined whether bilirubin prevents colonic injury in DSS-treated mice. As anticipated, bilirubin-treated animals manifested significantly less colonic injury and reduced infiltration of inflammatory cells into colon tissues. We further observed that bilirubin administration was associated with a reduced number of eosinophils and monocytes in the small intestine, with a corresponding increase in peripheral blood eosinophilia, regardless of whether mice received DSS. These findings suggest that bilirubin impairs the normal migration of eosinophils into intestinal tissues, as supported by in vitro experiments showing that bilirubin blocks the VCAM-1-dependent movement of Jurkat cells across human endothelial cell monolayers. Taken together, our findings support that bilirubin ameliorates DSS-induced colitis and disrupts the physiological trafficking of leukocytes to the intestine by preventing transmigration across the vascular endothelium, potentially through the inhibition VCAM-1-mediated signaling. Our findings raise the possibility that bilirubin functions as an endogenous regulator of inflammatory responses.

SjCa8, a calcium-binding protein from Schistosoma japonicum, inhibits cell migration and suppresses nitric oxide release of RAW264.7 macrophages

Background

Schistosomiasis is considered second only to malaria as the most devastating parasitic disease in tropical countries. Schistosome cercariae invade the host by penetrating the skin and migrate though the lungs and portal circulation to their final destination in the hepatic portal system and eventually the mesenteric veins. Previous studies have shown that the cytotoxic pathways that target schistosomulum in the lung-stage involve nitric oxide (NO) produced by macrophages. By contrast, skin-stage schistosomulas can evade clearance, indicating that they might be freed from macrophage NO-mediated cytotoxicity to achieve immune evasion; however, the critical molecules and mechanisms involved remain unknown.

Methods

Recombinant SjCa8 (rSjCa8), an 8-kDa calcium-binding protein that is stage-specifically expressed in cercaria and early skin-stage schistosomulas of Schistosoma japonicum, was incubated with mouse RAW264.7 macrophages. Effects on macrophage proliferation were determined using Cell Counting Kit-8. Next, transwell assay was carried out to further investigate the role of rSjCa8 in macrophage migration. The effects of rSjCa8 on macrophage apoptosis were evaluated using confocal microscopy and flow cytometry. Additional impacts of rSjCa8 on NO release by lipopolysaccharide (LPS)-stimulated macrophages as well as the underlying mechanisms were explored using fluorescent probe, nitric oxide signaling pathway microarray, quantitative real-time PCR, mutagenesis, and neutralizing antibody approaches.

Results

rSjCa8 exhibited a striking inhibitory effect on macrophage migration, but did not markedly increase cell proliferation or apoptosis. Additionally, rSjCa8 potently inhibited NO release by LPS-stimulated macrophages in a dose- and time-dependent manner, and the inhibitory mechanism was closely associated with intracellular Ca²⁺ levels, the up-regulation of catalase expression, and the down-regulation of the expression of 47 genes, including Myc, Gadd45a, Txnip, Fas, Sod2, Nos2, and Hmgb1. Vaccination with rSjCa8 increased NO concentration in the challenging skin area of infected mice and reduced the number of migrated schistosomula after skin penetration by cercariae.

Conclusions

Our findings indicate that SjCa8 might be a novel molecule that plays a critical role in immune evasion by S. japonicum cercaria during the process of skin penetration. The inhibitory impacts of rSjCa8 on macrophage migration and [Ca²⁺]_i-dependent NO release suggest it might represent a novel vaccine candidate and chemotherapeutic target for the prevention and treatment of schistosomiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1119-4) contains supplementary material, which is available to authorized users.