Intracellular accumulation of unconjugated bilirubin inhibits phytohemagglutin-induced proliferation and interleukin-2 production of human lymphocytes

Blockade of PGK1 and ALDOA enhances bilirubin control of Th17 cells in Crohn's disease

Unconjugated bilirubin (UCB) confers Th17-cells immunosuppressive features by activating aryl-hydrocarbon-receptor, a modulator of toxin and adaptive immune responses. In Crohn's disease, Th17-cells fail to acquire regulatory properties in response to UCB, remaining at an inflammatory/pathogenic state. Here we show that UCB modulates Th17-cell metabolism by limiting glycolysis and through downregulation of glycolysis-related genes, namely phosphoglycerate-kinase-1 (PGK1) and aldolase-A (ALDOA). Th17-cells of Crohn's disease patients display heightened PGK1 and ALDOA and defective response to UCB. Silencing of PGK1 or ALDOA restores Th17-cell response to UCB, as reflected by increase in immunoregulatory markers like FOXP3, IL-10 and CD39. In vivo, PGK1 and ALDOA silencing enhances UCB salutary effects in trinitro-benzene-sulfonic-acid-induced colitis in NOD/scid/gamma humanized mice where control over disease activity and enhanced immunoregulatory phenotypes are achieved. PGK1 and/or ALDOA blockade might have therapeutic effects in Crohn's disease by favoring acquisition of regulatory properties by Th17-cells along with control over their pathogenic potential.

Reversing an Oncogenic Epithelial-to-Mesenchymal Transition Program in Breast Cancer Reveals Actionable Immune Suppressive Pathways

Approval of checkpoint inhibitors for treatment of metastatic triple negative breast cancer (mTNBC) has opened the door for the use of immunotherapies against this disease. However, not all patients with mTNBC respond to current immunotherapy approaches such as checkpoint inhibitors. Recent evidence demonstrates that TNBC metastases are more immune suppressed than primary tumors, suggesting that combination or additional immunotherapy strategies may be required to activate an anti-tumor immune attack at metastatic sites. To identify other immune suppressive mechanisms utilized by mTNBC, our group and others manipulated oncogenic epithelial-to-mesenchymal transition (EMT) programs in TNBC models to reveal differences between this breast cancer subtype and its more epithelial counterpart. This review will discuss how EMT modulation revealed several mechanisms, including tumor cell metabolism, cytokine milieu and secretion of additional immune modulators, by which mTNBC cells may suppress both the innate and adaptive anti-tumor immune responses. Many of these pathways/proteins are under preclinical or clinical investigation as therapeutic targets in mTNBC and other advanced cancers to enhance their response to chemotherapy and/or checkpoint inhibitors.

Retrospective analysis of T-lymphocyte subsets and cytokines in malignant obstructive jaundice before and after external and internal biliary drainage

Objective

To study changes in T lymphocyte subsets, cytokines, and liver enzymes in patients with malignant obstructive jaundice (MOJ) before and after external biliary drainage (percutaneous transhepatic cholangiography drainage, PTCD) and internal biliary drainage (percutaneous transhepatic insertion of biliary stents, PTIBS).

Methods

MOJ patients undergoing PTCD (n = 44) and PTIBS (n = 38) at our hospital were enrolled in the study from January 2017 until December 2019. Peripheral blood total bilirubin (TBIL), direct bilirubin (DBIL), aspartate aminotransferase (AST), alanine aminotransferase (ALT), CD3⁺%, CD4⁺%, CD4⁺/CD8⁺ ratio, interleukin (IL)-2, IL-6, and tumor necrosis factor (TNF)-α were measured before and 1 week after biliary drainage.

Results

There was no significant difference in any parameter between the two groups before biliary drainage. TBIL, DBIL, AST and ALT following PTCD were significantly lower than before PTCD. By contrast, CD3⁺%, CD4⁺%, CD4⁺/CD8⁺ ratio, IL-2, IL-6 and TNF-α showed no significant difference before and 1 week after PTCD. TBIL, DBIL, AST, ALT, IL-6 and TNF-α were significantly lower following PTIBS than before PTIBS. CD3⁺%, CD4⁺%, CD4⁺/CD8⁺ ratio and IL-2 were significantly higher following PTIBS than before PTIBS.

Conclusion

Both PTCD and PTIBS were effective for treatment of MOJ, but PTIBS was more beneficial for recovery of immune function.

Neonatal jaundice, phototherapy and childhood allergic diseases: An updated systematic review and meta-analysis

BACKGROUND

Neonatal jaundice and phototherapy have been associated with the development of allergic diseases. It has been suggested, however, that effect estimates of the associations might be smaller than expected. We sought to update the evidence of their associations including recently published large longitudinal studies.

METHODS

We sought published and unpublished observational studies through the major databases. We used a random-effect meta-analysis model weighted by the inverse variance estimate, the Quality in Prognosis Studies tool to assess the methodological quality for each study, and the Grading of Recommendations, Assessment, Development, and Evaluation approach to assess the certainty of evidence (COE).

RESULTS

Nineteen studies were enrolled in the qualitative syntheses, and fourteen studies were synthesized in the meta-analyses. Neonatal jaundice was associated with a higher risk of childhood-onset asthma (odds ratio [OR], 1.46; 95% confidence interval [95% CI], 1.39-1.53; COE, moderate), atopic dermatitis (AD; OR, 1.30; 95% CI, 1.07-1.57; COE, moderate), and allergic rhinitis (AR; OR, 3.01; 95% CI, 0.8810.30; COE, low). Neonatal phototherapy was also associated with a higher risk of childhood-onset asthma (OR, 1.24; 95% CI, 1.11-1.38; COE, moderate), AD (OR, 1.31; 95% CI, 1.24-1.39; COE, moderate), and AR (OR, 1.38; 95% CI, 0.93-2.04; COE, very low). There were no studies that reported effect estimates of the associations between childhood-onset food allergies and neonatal jaundice and phototherapy.

CONCLUSION

Neonatal jaundice and phototherapy were probably a prognostic factor of childhood-onset allergic diseases; however, the associations were likely to be smaller than previously estimated.

Can bilirubin nanomedicine become a hope for the management of COVID-19?

Bilirubin has been proven to possess significant anti-inflammatory, antioxidant and antiviral activities. Recently, it has been postulated as a metabolic hormone. Further, moderately higher levels of bilirubin are positively associated with reduced risk of cardiovascular diseases, diabetes, metabolic syndrome and obesity. However, due to poor solubility the therapeutic delivery of bilirubin remains a challenge. Nanotechnology offers unique advantages which may be exploited for improved delivery of bilirubin to the target organ with reduced risk of systemic toxicity. Herein, we postulate the use of intravenous administration or inhalational delivery of bilirubin nanomedicine (BNM) to combat systemic dysfunctions associated with COVID-19, owing to the remarkable preclinical efficacy and optimistic results of various clinical studies of bilirubin in non-communicable disorders. BNM may be used to harness the proven preclinical pharmacological efficacy of bilirubin against COVID-19 related systemic complications.

Decreased Bilirubin is Associated With Disease Activity of Primary Sjögren's Syndrome

Objectives

This study aims to determine the serum bilirubin levels in primary Sjögren's syndrome (pSS) patients and to explore clinical significance of bilirubin in pSS.

Patients and methods

Retrospective analysis of electronic medical records was performed in 97 pSS patients (12 males, 85 females; mean age 54±15 years; range, 15 to 91 years) and 100 healthy controls (17 males, 83 females; mean age 51±14 years; range, 25 to 75 years). Serum bilirubin and other variables were compared between pSS patients and healthy controls. The European League Against Rheumatism Sjögren's syndrome disease activity index (ESSDAI) was used to assess the disease activity of pSS, and ESSDAI ≥5 was defined as moderate to high activity. The relationship between bilirubin and ESSDAI was analyzed by Spearman's correlation analysis and multivariable logistic regression.

Results

The median level of serum bilirubin was 9 μmol/L (interquartile range (IQR), 7-13 μmol/L) in pSS patients, much lower than healthy controls (median, IQR, 13, 10-18 μmol/L) (p<0.001). It was positively correlated with age (r=0.255, p=0.012), but negatively with immunoglobulin (Ig) A (r=-0.314, p=0.003), IgG (r=-0.265, p=0.015), erythrocyte sedimentation rate (r=-0.309, p=0.002) and ESSDAI (r=-0.342, p=0.001). Multivariate analysis revealed that increased bilirubin was independently associated with decreased risk of moderate to high disease activity (odds ratio, 95% confidence interval: 0.852, 0.730-0.955).

Conclusion

Serum bilirubin is decreased in pSS patients and may be a useful biomarker for reflecting pSS disease activity.

Modulation of Inflammation and Immune Responses by Heme Oxygenase-1: Implications for Infection with Intracellular Pathogens

Heme oxygenase-1 (HO-1) catalyzes the degradation of heme molecules releasing equimolar amounts of biliverdin, iron and carbon monoxide. Its expression is induced in response to stress signals such as reactive oxygen species and inflammatory mediators with antioxidant, anti-inflammatory and immunosuppressive consequences for the host. Interestingly, several intracellular pathogens responsible for major human diseases have been shown to be powerful inducers of HO-1 expression in both host cells and in vivo. Studies have shown that this HO-1 response can be either host detrimental by impairing pathogen control or host beneficial by limiting infection induced inflammation and tissue pathology. These properties make HO-1 an attractive target for host-directed therapy (HDT) of the diseases in question, many of which have been difficult to control using conventional antibiotic approaches. Here we review the mechanisms by which HO-1 expression is induced and how the enzyme regulates inflammatory and immune responses during infection with a number of different intracellular bacterial and protozoan pathogens highlighting mechanistic commonalities and differences with the goal of identifying targets for disease intervention.

Why some organ allografts are tolerated better than others: new insights for an old question

PURPOSE OF REVIEW

There is great variability in how different organ allografts respond to the same tolerance induction protocol. Well known examples of this phenomenon include the protolerogenic nature of kidney and liver allografts as opposed to the tolerance-resistance of heart and lung allografts. This suggests there are organ-specific factors which differentially drive the immune response following transplantation.

RECENT FINDINGS

The specific cells or cell products that make one organ allograft more likely to be accepted off immunosuppression than another are largely unknown. However, new insights have been made in this area recently.

SUMMARY

The current review will focus on the organ-intrinsic factors that contribute to the organ-specific differences observed in tolerance induction with a view to developing therapeutic strategies to better prevent organ rejection and promote tolerance induction of all organs.

Heme Catabolic Pathway in Inflammation and Immune Disorders

In recent years, the heme catabolic pathway is considered to play an important regulatory role in cell protection, apoptosis, inflammation, and other physiological and pathological processes. An appropriate amount of heme forms the basic elements of various life activities, while when released in large quantities, it can induce toxicity by mediating oxidative stress and inflammation. Heme oxygenase (HO) -1 can catabolize free heme into carbon monoxide (CO), ferrous iron, and biliverdin (BV)/bilirubin (BR). The diverse functions of these metabolites in immune systems are fascinating. Decades work shows that administration of degradation products of heme such as CO and BV/BR exerts protective activities in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS) and other immune disorders. This review elaborates the molecular and biochemical characterization of heme catabolic pathway, discusses the signal transduction and immunomodulatory mechanism in inflammation and summarizes the promising therapeutic strategies based on this pathway in inflammatory and immune disorders.

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.

Hyperbilirubinemia, Phototherapy, and Childhood Asthma

OBJECTIVES

Our aim was to quantify the associations of both hyperbilirubinemia and phototherapy with childhood asthma using a population-based cohort with total serum bilirubin (TSB) levels.

METHODS

Retrospective cohort study of infants born at ≥35 weeks' gestation in the Kaiser Permanente Northern California health system (n = 109 212) from 2010 to 2014. Cox models were used to estimate hazard ratios (HRs) for a diagnosis of asthma.

RESULTS

In the study, 16.7% of infants had a maximum TSB level of ≥15 mg/dL, 4.5% of infants had a maximum TSB level of ≥18 mg/dL, and 11.5% of infants received phototherapy. Compared with children with a maximum TSB level of 3 to 5.9 mg/L, children with a TSB level of 9 to 11.9 mg/dL, 12 to 14.9 mg/dL, and 15 to 17.9 mg/dL were at an increased risk for asthma (HR: 1.22 [95% confidence interval (CI): 1.11-1.3], HR: 1.18 [95% CI: 1.08-1.29], and HR: 1.30 [95% CI: 1.18-1.43], respectively). Children with a TSB level of ≥18 mg/dL were not at an increased risk for asthma (HR: 1.04; 95% CI: 0.90-1.20). In propensity-adjusted analyses, phototherapy was not associated with asthma (HR: 1.07; 95% CI: 0.96-1.20).

CONCLUSIONS

Modest levels of hyperbilirubinemia were associated with an increased risk of asthma, but an association was not seen at higher levels. No dose-response relationship was seen. Using phototherapy to prevent infants from reaching these modest TSB levels is unlikely to be protective against asthma.

Bilirubin, a new therapeutic for kidney transplant?

In patients with end-stage renal disease, kidney transplantation has been associated with numerous benefits, including increased daily activity, and better survival rates. However, over 20% of kidney transplants result in rejection within five years. Rejection is primarily due to a hypersensitive immune system and ischemia/reperfusion injury. Bilirubin has been shown to be a potent antioxidant that is capable of potentially reversing or preventing damage from reactive oxygen species generated from ischemia and reperfusion. Additionally, bilirubin has several immunomodulatory effects that can dampen the immune system to promote organ acceptance. Increased bilirubin has also been shown to have a positive impact on renal hemodynamics, which is critical post-transplantation. Lastly, bilirubin levels have been correlated with biomarkers of successful transplantation. In this review, we discuss a multitude of potentially beneficial effects that bilirubin has on kidney acceptance of transplantation based on numerous clinical trials and animal models. Exogenous bilirubin delivery or increasing endogenous levels pre- or post-transplantation may have therapeutic benefits.

Conjugated Bilirubin Upregulates TIM-3 Expression on CD4+CD25+ T Cells: Anti-Inflammatory Implications for Hepatitis A Virus Infection

Bilirubin (BR), a metabolite with increased concentrations in plasma during viral hepatitis, has been recognized as a potential immune-modulator. We recently reported that conjugated BR (CB) augments regulatory T cell (Treg) suppressor activity during acute hepatitis A virus (HAV) infection. However, the mechanisms related to the effects of CB on Treg function in the course of hepatotropic viral diseases have not been elucidated. T cell immunoglobulin domain and mucin domain 3 (TIM-3), via its interactions with galectin-9 (GAL-9), is a receptor associated with enhanced Treg function. Thus, TIM-3 expression may be related to the crosstalk between CB and Tregs during HAV infection. Herein, in vitro treatment with high concentrations of CB upregulated TIM-3 expression on Tregs from healthy donors. CB treatment in vitro did not induce de novo Treg generation, and in vitro stimulation with TGF-β, which shows increased secretion during HAV infection, resulted in a trend toward increased TIM-3 expression on Tregs and CD4⁺ T lymphocytes (TLs) from healthy donors. Interestingly, an upregulation of TIM-3 expression on CD4⁺CD25⁺ T cells and an increase in the proportion of CD4⁺ TLs expressing GAL-9 were found in HAV-infected patients with abnormal CB values relative to healthy controls. In addition, a statistically significantly reduction in IL-17F production was observed after treatment of CD4⁺ TLs from healthy donors with high doses of CB in vitro. In summary, our results suggest that CB might regulate Treg activity via a TIM-3-mediated mechanism, ultimately leading to an anti-inflammatory hepatoprotective effect.

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.

Global Fecal and Plasma Metabolic Dynamics Related to Helicobacter pylori Eradication

Background:Helicobacter pylori colonizes the gastric mucosa of more than half of the world's population. There is increasing evidence H. pylori protects against the development of obesity and childhood asthma/allergies in which the development of these diseases coincide with transient dysbiosis. However, the mechanism underlying the association of H. pylori eradication with human metabolic and immunological disorders is not well-established. In this study, we aimed to investigate the local and systemic effects of H. pylori eradication through untargeted fecal lipidomics and plasma metabolomics approaches by liquid chromatography mass spectrometry (LC-MS).

Results: Our study revealed that eradication of H. pylori eradication (i.e., loss of H. pylori and/or H. pylori eradication therapy) changed many global metabolite/lipid features, with the majority being down-regulated. Our findings primarily show that H. pylori eradication affects the host energy and lipid metabolism which may eventually lead to the development of metabolic disorders.

Conclusion: These predictive metabolic signatures of metabolic and immunological disorders following H. pylori eradication can provide insights into dynamic local and systemic metabolism related to H. pylori eradication in modulating human health.

Neonatal risk factors of atopic dermatitis in Denmark - Results from a nationwide register-based study

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin condition with a multifactorial etiopathogenesis. Studies have suggested that several perinatal factors may influence the risk of AD in early childhood. We investigated possible neonatal risk factors such as jaundice, blue light phototherapy, birthweight, gestational age at birth, and season of birth on the risk of developing AD in the first 5 years of life.

MATERIALS & METHODS

Data were collected through Danish nationwide administrative registers. All newborn children between 1997 and 2007 (n = 673,614) were included in the cohort. Incidence rate ratios (IRRs) were estimated with 95% confidence intervals (95% CIs) by multivariate Poisson regression analyses.

RESULTS

We identified a total of 85,743 children with AD in the first 5 years of life. The risk of AD was slightly increased in children with neonatal jaundice (IRR 1.13 [95% CI 1.06-1.21]). Preterm birth was inversely associated with the risk of AD (IRR 0.74, [95% CI 0.68-0.81]) as well as low birthweight (IRR 0.68, [95% CI 0.61-0.75]). Children born in fall and winter seasons had an increased risk of AD compared to spring and summer. No association between neonatal blue light therapy and the risk of AD was found.

CONCLUSIONS

Low birthweight and preterm birth were inversely associated with AD, while neonatal jaundice and cold seasons of birth were associated with an increased risk of AD.

Neonatal jaundice and risks of childhood allergic diseases: a population-based cohort study

BACKGROUND

Only a few studies have systemically analyzed the association between neonatal jaundice and childhood-onset allergic diseases.

METHODS

From 2000 to 2007, 27,693 neonates with newly diagnosed neonatal jaundice and 55,367 matched nonneonatal jaundice cohorts were identified. The incidences and hazard ratios (HRs) of five allergic diseases, namely allergic conjunctivitis (AC), allergic rhinitis (AR), atopic dermatitis (AD), asthma, and urticaria, by the end of 2008 were calculated.

RESULTS

The incidence density and HRs of the five allergic diseases were greater in the neonatal jaundice cohort than in the nonneonatal jaundice cohort, and the HRs declined modestly with age. The HRs for AR (HR = 2.51, 95% confidence interval (CI) = 2.43-2.59) and AD (HR = 2.51, 95% CI = 2.40-2.62) were the highest, and that for urticaria was the lowest (HR = 2.06, 95% CI = 1.94-2.19). The HRs of allergic diseases were substantially greater for boys and those requiring phototherapy. The HRs of the allergic diseases, except urticaria (HR = 2.49, 95% CI = 1.57-3.97), were not significantly different between the neonatal jaundice regardless of whether the patients received exchange transfusion.

CONCLUSION

Neonatal jaundice is associated with the development of allergic diseases in early childhood.

Heme oxygenase and the immune system in normal and pathological pregnancies

Normal pregnancy is an immunotolerant state. Many factors, including environmental, socioeconomic, genetic, and immunologic changes by infection and/or other causes of inflammation, may contribute to inter-individual differences resulting in a normal or pathologic pregnancy. In particular, imbalances in the immune system can cause many pregnancy-related diseases, such as infertility, abortions, pre-eclampsia, and preterm labor, which result in maternal/fetal death, prematurity, or small-for-gestational age newborns. New findings imply that myeloid regulatory cells and regulatory T cells (Tregs) may mediate immunotolerance during normal pregnancy. Effector T cells (Teffs) have, in contrast, been implicated to cause adverse pregnancy outcomes. Furthermore, feto-maternal tolerance affects the developing fetus. It has been shown that the Treg/Teff balance affects litter size and adoptive transfer of pregnancy-induced Tregs can prevent fetal rejection in the mouse. Heme oxygenase-1 (HO-1) has a protective role in many conditions through its anti-inflammatory, anti-apoptotic, antioxidative, and anti-proliferative actions. HO-1 is highly expressed in the placenta and plays a role in angiogenesis and placental vascular development and in regulating vascular tone in pregnancy. In addition, HO-1 is a major regulator of immune homeostasis by mediating crosstalk between innate and adaptive immune systems. Moreover, HO-1 can inhibit inflammation-induced phenotypic maturation of immune effector cells and pro-inflammatory cytokine secretion and promote anti-inflammatory cytokine production. HO-1 may also be associated with T-cell activation and can limit immune-based tissue injury by promoting Treg suppression of effector responses. Thus, HO-1 and its byproducts may protect against pregnancy complications by its immunomodulatory effects, and the regulation of HO-1 or its downstream effects has the potential to prevent or treat pregnancy complications and prematurity.

Neonatal hyperbilirubinemia and childhood allergic diseases: a systematic review

Studies have found a link between neonatal hyperbilirubinemia (NNH) and/or neonatal phototherapy (NPT) and childhood allergic diseases. The present systematic review was conducted to provide updated evidence and to provide direction regarding future research. A systematic search of the published literature was carried out. Observational studies including children up to 12 yr of age were included. Data extraction was carried out using a standardized data extraction form that was designed and pilot tested a priori. The analysis was carried out with the statistical software RevMan (version 5.2) [Protocol is registered at

PROSPERO

CRD42014009943]. Of 79 citations retrieved, a total of 7 good quality studies (n = 101,499) were included in the final analysis. There was a significant increase in the odds of asthma and allergic rhinitis (AR) after NNH [asthma, OR 4.26 (95% CI 4.04-4.5); AR, OR 5.37 (95% CI 4.16-6.92)] and after NPT [asthma, OR 3.81 (95% CI 3.53-4.11); AR, OR 3.04(95% CI 2.13-4.32)]. A similar increase in the trend was noted for late onset of asthma after NNH [OR 4.1 (95% CI 2.82-5.94)], and hospitalization due to asthma after NPT [OR 3.56 (95% CI 2.93-4.33)]. The GRADE evidence generated was of 'low quality'. The current evidence finds a significant increase in the odds of childhood allergic diseases after NNH and/or NPT. As observational studies were included, the evidence generated was of 'low quality'. Future studies should try to elucidate the pathophysiologic link between NNH and/or NPT and childhood allergic diseases.

Conjugated bilirubin affects cytokine profiles in hepatitis A virus infection by modulating function of signal transducer and activator of transcription factors

Hepatitis A virus (HAV) infection is the major cause of acute liver failure in paediatric patients. The clinical spectrum of infection is variable, and liver injury is determined by altered hepatic enzyme function and bilirubin concentration. We recently reported differences in cytokine profiles between distinct HAV-induced clinical courses, and bilirubin has been recognized as a potential immune-modulator. However, how bilirubin may affect cytokine profiles underlying the variability in the course of infection has not been determined. Herein, we used a transcription factor (TF) binding site identification approach to retrospectively analyse cytokine expression in HAV-infected children and to predict the entire set of TFs associated with the expression of specific cytokine profiles. The results suggested that modulation of the activity of signal transducers and activators of transcription proteins (STATs) may play a central role during HAV infection. This led us to compare the degree of STAT phosphorylation in peripheral blood lymphoid cells (PBLCs) from paediatric patients with distinct levels of conjugated bilirubin (CB). Low CB levels in sera were associated with increased STAT-1 and STAT-5 phosphorylation. A positive correlation was observed between the serum interleukin-6 (IL-6) content and CB values, whereas higher levels of CB correlated with reduced serum IL-8 values and with a reduction in the proportion of PBLCs positive for STAT-5 phosphorylation. When CB was used to stimulate patients' PBLCs in vitro, the levels of IL-6 and tumour necrosis factor-α were increased. The data showed that bilirubin plays a role in STAT function and affects cytokine profile expression during HAV infection.

The mononuclear phagocyte system in homeostasis and disease: a role for heme oxygenase-1

SIGNIFICANCE

Heme oxygenase-1 (HO-1) is a potential therapeutic target in many diseases, especially those mediated by oxidative stress and inflammation. HO-1 expression appears to regulate the homeostatic activity and distribution of mononuclear phagocytes (MP) in lymphoid tissue under physiological conditions. It also regulates the ability of MP to modulate the inflammatory response to tissue injury.

RECENT ADVANCES

The induction of HO-1 within MP-particularly macrophages and dendritic cells-modulates the effector functions that they acquire after activation. These effector functions include cytokine production, surface receptor expression, maturation state, and polarization toward a pro- or anti-inflammatory phenotype. The importance of HO-1 in MP is emphasized by their expression of specific receptors that primarily function to ingest heme-containing substrate and deliver it to HO-1.

CRITICAL ISSUES

MP are the first immunological responders to tissue damage. They critically affect the outcome of injury to many organ systems, yet few therapies are currently available to specifically target MP during disease pathogenesis. Elucidation of the role of HO-1 expression in MP may help to direct broadly applicable therapies to clinical use that are based on the immunomodulatory capabilities of HO-1.

FUTURE DIRECTIONS

Unraveling the complexities of HO-1 expression specifically within MP will more completely define how HO-1 provides cytoprotection in vivo. The use of models in which HO-1 expression is specifically modulated in bone marrow-derived cells will allow for a more complete characterization of its immunoregulatory properties.

Neonatal jaundice is a risk factor for childhood allergic rhinitis: a retrospective cohort study

BACKGROUND

This study evaluates the association between neonatal jaundice and childhood allergic rhinitis (AR).

METHODS

Eleven thousand three hundred twenty-eight children were collected from the National Health Insurance Research Database in Taiwan. Their claims data were evaluated from birth to 10 years of age, and they were assigned to either the study (with neonatal jaundice) or the control (without neonatal jaundice) group. The diagnostic criteria for AR were at least three diagnoses of AR at outpatient services, one diagnosis of AR during an admission, or one diagnosis of AR in an emergency department. Mantel-Haenszel odds ratios (ORs) were calculated after adjustment for the following confounders: preterm/low birth weight, neonatal infection, other respiratory conditions, other birth conditions, and gender. AR rate, AR onset time, the use of oral antihistamines/nasal corticosteroids, outpatient visit frequency for AR, lower respiratory infection (LRI) rates, sinusitis/otitis media/conjunctivitis rates, and the effect of phototherapy were evaluated.

RESULTS

After adjustment for the confounding factors, the rate of AR was higher in icteric children (OR, 1.46; 95% confidence interval, 1.24∼1.72). There was a higher incidence of AR in children <4 years old with icterus. The use of oral antihistamines, LRI rates, sinusitis rates, and otitis media rates were higher in the icteric children. There was no association between phototherapy and childhood AR.

CONCLUSION

Neonatal jaundice increased the rate and complications of childhood AR in subjects aged up to 10 years and may be a risk factor for childhood AR.

The molecular basis for the immunomodulatory activities of unconjugated bilirubin

Nearly a century ago, jaundiced patients were observed to have surprising and spontaneous remissions from incurable immunologic diseases including rheumatoid arthritis, allergy, and asthma. The mystery of why this phenomenon occurred remains unresolved to this day. Bilirubin has traditionally been considered an excretory product resulting from heme metabolism with little benefit to human physiology. In the past few decades, however, the salutary role of this byproduct as a potent antioxidant has been repeatedly noted. Most recently, the molecule has been found to possess immunomodulatory properties that rival its redox capacity, possibly explaining its ability to suppress inflammation. In this review, we specifically examine unconjugated bilirubin (UCB) as an immunomodulator and explore the molecular basis for its immunosuppressive effects.

Neonatal jaundice is a risk factor for childhood asthma: a retrospective cohort study

BACKGROUND

The association between neonatal jaundice and childhood asthma is a new finding of two reports. The purpose of the study was to verify their results.

METHODS

Data from 11,321 children were collected from the National Health Insurance Research Database. Their claims data were evaluated from birth to 10 yr old. Children were analyzed as case (those with neonatal jaundice) and controls (those without neonatal jaundice). The diagnostic criteria for asthma were as follows: at least four asthma diagnoses at outpatient services and emergency department (ED), or one asthma diagnosis during an admission. In children fitting the asthma criteria, those with no asthma diagnosis after 1 yr of age were excluded. Mantel-Haenszel's odds ratios were calculated after adjustment for the following confounders: preterm/low birth weight, neonatal infection, other respiratory conditions, other birth conditions, and gender. Asthma rate, onset time, the use of drugs, upper respiratory infection and lower respiratory infection (LRI) rates, hospital admission/ED visit rates, and the effect of phototherapy were evaluated.

RESULTS

After adjustment for the confounding factors, the rate of asthma was higher in icteric children (OR: 1.64, 95% CI 1.36-1.98, p < 0.001), and the influence in females was stronger. There still was an association between neonatal jaundice and late onset asthma (asthma onset after 3 yr of age). In asthmatic children, those with neonatal jaundice have increased asthma onset rate before age 6, increased use of inhalant steroids, LRI rates, and ED visits for respiratory disease.

CONCLUSIONS

Neonatal jaundice increased the rate and severity of childhood asthma in subjects aged up to 10 yr and may be a risk factor for childhood asthma.

Immunomodulatory and immunotoxic effects of bilirubin: molecular mechanisms

The immunomodulatory and immunotoxic effects of purified UCB have not been evaluated previously at clinically relevant UCB concentrations and UCB:BSA ratios. To delineate the molecular mechanism of UCB-induced immunomodulation, immune cells were exposed to clinically relevant concentrations of UCB. It inhibited LPS-induced B cell proliferation and cytokine production from splenic macrophages. UCB (≥25 μM) was toxic to unfractionated splenocytes, splenic T cells, B cells, macrophages, LPS-stimulated CD19(+) B cells, human PBMCs, and RBCs. Purified UCB also was found to be toxic to splenocytes and human PBMCs. UCB induced necrosis and apoptosis in splenocytes. UCB activated the extrinsic and intrinsic pathways of apoptosis, as reflected by the markers, such as CD95, caspase-8, Bax, MMP, cytoplasmic Ca(+2), caspase-3, and DNA fragmentation. UCB depleted GSH and activated p38MAPK. NAC, caspase inhibitors, and p38MAPK inhibitor attenuated the UCB-induced apoptosis. In vivo administration of ≥25 mg/kbw UCB induced atrophy of spleen, depletion of bone marrow cells, and leukopenia and decreased lymphocyte count and the T and B cell response to mitogens. UCB administration to mice led to induction of oxidative stress, activation of p38MAPK, and cell death in splenocytes. These parameters were attenuated by the injection of NAC and the p38MAPK inhibitor. Our results demonstrate for the first time that clinically relevant concentrations of UCB induce apoptosis and necrosis in immune cells by depleting cellular GSH. These findings should prove useful in understanding the immunosuppression associated with hyperbilirubinemia.

Bilirubin Promotes De Novo Generation of T Regulatory Cells

We have previously demonstrated that bilirubin administration to the recipient induces tolerance towards islet cell transplants across a complete MHC mismatch in a mouse model. Here we assess the mechanisms of such protection. Bilirubin treatment of recipients improved function of islet allografts by suppressing expressions of proinflammatory and proapoptotic genes in those islets and by increasing Foxp3+ T regulatory (Treg) cells at the site of transplanted islets at various days after transplantation. No prolongation of graft survival was observed in recipients treated with bilirubin when CD4+CD25+ T cells were predepleted from those recipients, indicating that Treg cells are necessary for the protective effect of bilirubin. Adoptive transfer of Treg cells from tolerant mice into Rag1-/- recipients resulted in long-term acceptance of skin allografts in an alloantigen-specific manner, suggesting that Treg cells are sufficient to induce tolerance. In addition, bilirubin treatment promoted de novo generation of Treg cells in Rag1-/- recipients. Thus, bilirubin treatment to the recipients prolongs islet allograft survival via a Treg-dependent manner in which CD4+CD25+ Treg cells are both necessary and sufficient for tolerance induction and graft acceptance. Bilirubin treatment promotes de novo generation of Treg cells that might account for the protective effects of bilirubin given to recipients.

Therapeutic applications of bilirubin and biliverdin in transplantation

Bilirubin is the end product of heme catabolism by heme oxygenases. The inducible form of these enzymes is heme oxygenase-1 (HO-1), which is the rate-limiting enzyme that can degrade heme into equimolar quantities of carbon monoxide (CO), biliverdin, and free iron. Biliverdin is very rapidly converted to bilirubin by the enzyme biliverdin reductase, and free iron upregulates the expression of ferritin. HO-1 is a ubiquitous stress protein and is induced in many cell types by various stimuli. Induced HO-1 exerts antiinflammatory effects and modulates apoptosis. Expression of HO-1 in vivo suppresses the inflammatory responses in endotoxic shock, hyperoxia, acute pleurisy, and organ transplantation, as well as ischemia-reperfusion injury, and thereby provides salutary effects in these conditions. Accumulating evidence indicates that biliverdin/bilirubin can mediate the protective effects of HO-1 in many disease models, such as IRI and organ transplantation, via its antiinflammatory, antiapoptotic, antiproliferative, and antioxidant properties, as well as its effects on the immune response. This review attempts to summarize these protective roles as well as the molecular mechanisms by which biliverdin/bilirubin benefit IRI and solid-organ transplantation, including chronic rejection, and islet transplantation.

''Iatrogenic Gilbert syndrome''--a strategy for reducing vascular and cancer risk by increasing plasma unconjugated bilirubin

The catabolism of heme, generating biliverdin, carbon monoxide, and free iron, is mediated by heme oxygenase (HO). One form of this of this enzyme, heme oxygenase-1, is inducible by numerous agents which promote oxidative stress, and is now known to provide important antioxidant protection, as demonstrated in many rodent models of free radical-mediated pathogenesis, and suggested by epidemiology observing favorable health outcomes in individuals carrying high-expression alleles of the HO-1 gene. The antioxidant impact of HO-1 appears to be mediated by bilirubin, generated rapidly from biliverdin by ubiquitously expressed biliverdin reductase. Bilirubin efficiently scavenges a wide range of physiological oxidants by electron donation. In the process, it is often reconverted to biliverdin, but biliverdin reductase quickly regenerates bilirubin, thereby greatly boosting its antioxidant potential. There is also suggestive evidence that bilirubin inhibits the activity or activation of NADPH oxidase. Increased serum bilirubin is associated with reduced risk for atherogenic disease in epidemiological studies, and more limited data show an inverse correlation between serum bilirubin and cancer risk. Gilbert syndrome, a genetic variant characterized by moderate hyperbilirubinemia attributable to reduced hepatic expression of the UDP-glucuronosyltransferase which conjugates bilirubin, has been associated with a greatly reduced risk for ischemic heart disease and hypertension in a recent study. Feasible strategies for boosting serum bilirubin levels may include administration of HO-1 inducers, supplementation with bilirubin or biliverdin, and administration of drugs which decrease the efficiency of hepatic bilirubin conjugation. The well-tolerated uricosuric drug probenecid achieves non-competitive inhibition of hepatic glucuronidation reactions by inhibiting the transport of UDP-glucuronic acid into endoplasmic reticulum; probenecid therapy is included in the differential diagnosis of hyperbilirubinemia, and presumably could be used to induce an ''iatrogenic Gilbert syndrome''. Other drugs, such as rifampin, can raise serum bilirubin through competitive inhibition of hepatocyte bilirubin uptake--although unfortunately rifampin is not as safe as probenecid. Measures which can safely achieve moderate serum elevations of bilirubin may prove to have value in the prevention and/or treatment of a wide range of disorders in which oxidants play a prominent pathogenic role, including many vascular diseases, cancer, and inflammatory syndromes. Phycobilins, algal biliverdin metabolites that are good substrates for biliverdin reductase, may prove to have clinical antioxidant potential comparable to that of bilirubin.

Cytokine production, glutamate release and cell death in rat cultured astrocytes treated with unconjugated bilirubin and LPS

In hyperbilirubinemic newborns, sepsis is considered a risk factor for kernicterus. Evidence shows that injury to astrocytes triggers cytokine release. We examined the effects of unconjugated bilirubin (UCB) alone, or in combination with LPS, on the release of glutamate and cytokines from astrocytes in conditions inducing less than 10% of cell death. UCB leads to an increase of extracellular glutamate and highly enhances the release of TNF-alpha and IL-1beta, while inhibiting the production of IL-6. LPS potentiates immunostimulatory properties of UCB. These results point out the role of cytokines and provide a basis for the significance of sepsis in UCB encephalopathy.

Induction of long-term cardiac allograft survival by heme oxygenase-1 gene transfer

Elevated expression of heme oxygenase-1 (HO-1), an intracellular enzyme that degrades heme into carbon monoxide (CO), biliverdine and free iron, has anti-inflammatory and antiapoptotic effects in diverse models. Here, we analyzed the effects of specific overexpression of HO-1 following adenovirus-mediated (AdHO-1) gene transfer in an acute cardiac allograft rejection model. The intragraft (i.g.) injection of AdHO-1 into cardiac allografts, as well as intramuscular (i.m.) or intravenous (i.v.) administration, prolonged allograft survival with, respectively, 13.3, 62.5 and 80% of the grafts surviving long term (>100 days), whereas control grafts were rejected with acute kinetics. HO-1 overexpression was associated with inhibited allogeneic responses in MLRs using graft-infiltrating leukocytes and splenocytes, but not with lymph node cells. The inhibition of splenocyte proliferation was mediated by soluble factors and was dependent on the presence of APCs, since purified T cells proliferated normally. i.v. but not i.g. AdHO-1 administration decreased the number of graft-infiltrating leukocytes, cytokine mRNA accumulation and apoptosis in transplanted hearts, whereas i.v. and i.g. AdHO-1 did not modify normal immune responses against cognate antigens, indicating that there was no general immunosuppression. These results indicate that HO-1 overexpression prolongs the survival of vascularized allografts by promoting tolerogenic mechanisms acting on allogeneic cellular immune responses.

Biliverdin, a natural product of heme catabolism, induces tolerance to cardiac allografts

Biliverdin, a product of heme oxygenase-1 (HO-1) enzymatic action, is converted into bilirubin, which has been considered a waste product in the past. We now show that administration of biliverdin has a salutary effect in organ transplantation. A brief course of treatment with biliverdin leads to long-term survival of H-2 incompatible heart allografts. Furthermore, those recipients harboring long-surviving (>100 days) allografts were tolerant to donor antigens indicated by the acceptance of second donor strain hearts but not third-party grafts. Treatment with biliverdin decreased intragraft leukocyte infiltration and inhibited T cell proliferation. Likely related to tolerance induction, biliverdin interferes with T cell signaling by inhibiting activation of nuclear factor of activated T cells (NFAT) and nuclear factor kappaB (NF-kappaB), two transcription factors involved in interleukin-2 (IL-2) transcription and T cell proliferation, as well as suppressing Th1 interferon-gamma (IFN-gamma) production in vitro. These findings support the potential use of biliverdin, a natural product, in transplantation and other T cell mediated immune disorders.

Inhibition of ischemia/reperfusion injury and chronic graft deterioration by a single-donor treatment with cobalt-protoporphyrin for the induction of heme oxygenase-1

Today, the major problem in organ transplantation is not acute graft rejection but chronic graft deterioration. In addition to alloantigen-specific events, alloantigen independent factors like donor age, previous diseases, consequences of brain death, and perioperative events of ischemia/reperfusion injury have a major impact on long-term graft function. The induction of the stress protein heme oxygenase-1 (HO-1) protects cells from injury and apoptosis. Here, we tested the protective effects of HO-1 induction in a clinically relevant kidney transplant model. Induction of HO-1 expression following cobalt-protoporphyrin (CoPP) treatment in organ donors prolonged graft survival and long-term function remarkably following extended periods of ischemia. Positive effects were observed with both optimal and marginal grafts from old donor animals. Structural changes characteristic for chronic rejection, as well as graft infiltration by monocytes/macrophages and CD8+ T cells, were substantially reduced following HO-1 induction. Up-regulation of HO-1 expression before organ transplantation was also associated with reduced levels for tumor necrosis factor (TNF)-alpha mRNA, increased levels for interferon (IFN)-gamma, and bcl-x, and insignificant differences for CD25, interleukin (IL)-2, IL-4, IL-6, and IL-10 mRNA levels. The significant improvement of long-term graft function following induction of HO-1 expression in donor organs suggests that this strategy may be a novel clinical treatment option with particular relevance for transplantation of marginal organs.

Gene transfer of heme oxygenase-1 and carbon monoxide delivery inhibit chronic rejection

The hallmark of chronic rejection is the occlusion of the artery lumen by intima hyperplasia as a consequence of leukocyte infiltration and vascular smooth muscle cell (VSMC) migration and proliferation. Heme oxygenase-1 (HO-1) is a tissue protective molecule which degrades heme into carbon monoxide (CO), free iron and biliverdin. We analyzed the effects of HO-1 gene transfer into the vessel wall using an adenoviral vector (AdHO-1) and of CO delivery in a model of chronic allogeneic aorta rejection in rats. Carbon monoxide treatment was achieved by a new pharmacological approach in transplantation using methylene chloride (MC), which releases CO after degradation. AdHO-1-mediated gene transfer into aorta endothelial cells (ECs) or CO delivery resulted in a significant reduction in intimal thickness compared to untreated or noncoding adenovirus-treated controls. Aortas transduced with AdHO-1 or treated with CO showed a reduction in the number of leukocytes as well as in the expression of adhesion molecules, costimulatory molecules and cytokines, with the gene transfer treatment displaying a more pronounced effect than the CO treatment. Conversely, CO inhibited VSMC accumulation in the intima more efficiently than AdHO-1 treatment. Gene transfer of HO-1 and pharmacological manipulation of CO are novel approaches to the analysis and treatment of chronic rejection.

Heme oxygenase-1 overexpression protects rat livers from ischemia/reperfusion injury with extended cold preservation

This study analyzes the effects and mechanisms of heme oxygenase-1 (HO-1)-mediated cytoprotection in rat livers exposed to cold preservation. In the first series, rats were pretreated with cobalt protoporphyrin (CoPP) or zinc protoporphyrin (ZnPP), HO-1 inducer and antagonist, respectively. Livers were stored at 4 degrees C for 24 h, and then perfused ex vivo for 2 h. Livers pretreated with CoPP had significantly higher portal venous blood flow and increased total bile production, as compared with the ZnPP group. This correlated with histologic (Banff) criteria of hepatocyte injury/liver function. In the second series, rat livers were stored at 4 degrees C for 24 h or 40 h, and then transplanted into syngeneic recipients. After 24 h of preservation, 80% of rats bearing CoPP-pretreated liver grafts survived 21 days (vs. 50% in controls). After 40h of cold preservation, liver transplant survival at day 1, 7 and 21 for the CoPP group was: 100%, 71% and 57%, respectively (vs. 50%, 50% and 33% in controls). This correlated with improved hepatic function/histologic (Suzuki) criteria of hepatocyte injury after HO-1 overexpression (immunohistology/Western blots) by infiltrating macrophages. This study documents the potential utility of HO-1-inducing agents in preventing ischemia/reperfusion injury resulting from prolonged storage of liver transplants.

Endocytosis in rat cultured astrocytes is inhibited by unconjugated bilirubin

Excessive hyperbilirubinemia can cause irreversible neurological damage in the neonatal period. However, the complete understanding of the pathogenesis of unconjugated bilirubin (UCB) encephalopathy remains a matter of debate. This study investigates whether UCB inhibits the endocytosis of cationized ferritin (CF) by cultured rat astrocytes. The relationship between endocytosis and MTT reduction, as well as changes on tubulin and glial fibrillary acidic protein (GFAP) assembly, were also evaluated. Inhibition of endocytosis was complete in the presence of 171 microM UCB, while a marked decrease of CF labeling was noticed for 86 microM UCB. In addition, MTT reduction was inhibited by 60 to 76% as UCB concentrations changed from 17 to 171 microM, while alterations on both GFAP and microtubule morphology were only achieved by cell exposure to 171 microM UCB. These findings indicate that inhibition of CF endocytosis in rat cortical astrocytes by UCB is a concentration-dependent process that appears to be primarily related to a direct effect on the cell membrane and not to any alteration of cytoskeletal microtubules and intermediate filaments.

Bilirubin-induced apoptosis in cultured rat neural cells is aggravated by chenodeoxycholic acid but prevented by ursodeoxycholic acid

BACKGROUND/AIMS

Unconjugated bilirubin (UCB) can be neurotoxic in jaundiced neonates and in patients with Crigler-Najjar syndrome. UCB toxicity may culminate in cell death, however, the occurrence of apoptosis has never been investigated. Ursodeoxycholic acid (UDCA) is a strong modulator of the apoptotic threshold in both hepatic and nonhepatic cells. The aims of this study were to determine whether apoptosis plays a role in neural cell death induced by UCB, and to investigate the ability of UDCA to prevent cell death.

METHODS

Cultured rat astrocytes were incubated with UCB (17 and 86 microM) plus albumin (5.7 and 28.7 microM) for 4-22 h. In addition, astrocytes and neurones were treated with either UCB, 50 microM UDCA, or their combination for 4 h. Cultures were scored for nonviable cells by trypan blue dye exclusion. Apoptosis was assessed by Hoechst staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling assay.

RESULTS

UCB induced a concentration- and time-dependent decrease in astrocyte viability. Apoptosis was 4- and 7-fold increased after 4 h exposure to 17 and 86 microM UCB, respectively (P < 0.01). UDCA reduced apoptosis to <7%, which represents a appoximately 60% protection (P < 0.01). Cholic acid was not protective, and chenodeoxyholic acid aggravated UCB toxicity (P < 0.05). Finally, neurones showed a 1.5-fold greater sensitivity than astrocytes to UCB, while UDCA was still protective.

CONCLUSIONS

UCB is toxic to both astrocytes and neurones, causing cell death through an apoptotic process. Moreover, UDCA inhibits UCB-induced apoptosis in neural cells and this could not be mimicked by other bile acids.

Alleviation of graft-versus-host disease after conditioning with cobalt-protoporphyrin, an inducer of heme oxygenase-1

BACKGROUND

Recently, we demonstrated that elevated expression of heme oxygenase-1 (HO-1 or Hsp-32) resulted in the modulation of several immune effector functions. Here we evaluated whether induction of HO-1 after administration of cobalt protoporphyrin (CoPP) can prevent the development of acute graft-versus-host-disease (GVHD).

METHODS

Acute GVHD was initiated by injection of unfractionated spleen cells from C57BL/6 into B6D2/F1 mice.

RESULTS

Administration of CoPP resulted in increased survival: 85% of CoPP-treated animals survived for >100 days compared with only 29% of saline-treated control animals (P<0.05). In contrast, administration of ZnPP, a well-known inhibitor of HO, accelerated GVHD development. The protective effect of CoPP therapy seemed to be caused by immunomodulation of donor cells, because treatment of cell donors prevented development of acute GVHD in 80% of recipients compared with 0% in control animals. Spontaneous lymphocyte proliferation could be measured with splenocytes harvested from animals developing GVHD but not with splenocytes from recipients of CoPP-treated donor cells. CoPP-treatment had no effect on interleukin-2 or interleukin-4 synthesis but inhibited interferon-gamma production. Mice with active GVHD demonstrated a defective lympho-proliferative response to alloantigens or concanavalin A. However, spleen cells isolated from survivors (on day 100) responded normally. Flow cytometric analysis of splenic T cell populations revealed a severe reduction in recipient type (H-2b,d) cells in mice with active GVHD, whereas in protected mice the number of cells remained normal.

CONCLUSION

The results from this study confirmed our previous observation that up-regulation of HO-1 activity is associated with down-regulation of several immune effector functions. This resulted in protection from acute GVHD in a parent into F1 mouse model.

Gene transfer of immunomodulatory peptides correlates with heme oxygenase-1 induction and enhanced allograft survival

BACKGROUND

Decapeptides derived from human HLA class I sequences have been shown to prolong allograft survival. The mechanism of action of these peptides has been uncertain, because they act in an MHC unrestricted manner. Recently, it was found that these peptides bind heme oxygenase 1 (HO-1). In the present study, we sought to determine whether local delivery of these peptides through gene transfer could extend allograft survival, and to explore the underlying mechanisms.

METHODS

C57BL/6 neonatal hearts were transplanted to CBA/J recipients and the peptide, or plasmid DNA encoding the peptide, was injected directly into the allograft at the time of the transplant.

RESULTS

Direct injection of 1 microg of the B2702 peptide into the allograft did not prolong survival (13.3+/-0.8 vs. 13.4+/-0.8 days for untreated controls), but injection of 400 microg of peptide did extend survival (22.0+/-0.6). Injection of plasmid DNA encoding the B2702 peptide was superior to peptide delivery, extending graft survival to 30.8+/-1.5 days. Similar results were obtained using another plasmid encoding the rationally designed peptide BC1 (28.5+/-1.7), whereas no significant prolongation was observed using a plasmid encoding the control peptide B2705 (16.5+/-1.0). To explore the hypothesis that these peptides exert their immunosuppressive effect by altering HO-1 activity, animals were treated with iron protoporphyrin, an inducer of HO-1 activity, or tin protoporphyrin, an inhibitor of HO-1. Treatment with iron protoporphyrin alone extended graft survival (24.5+/-1.6) and did not alter the benefit in survival seen with BC1 gene transfer (28.0+/-0.8). In contrast, treatment with tin protoporphyrin abolished the benefit of BC1 gene transfer (17.0+/-0.6).

CONCLUSIONS

These results demonstrate that plasmid mediated gene transfer is an effective means for delivering immunosuppressive peptides to extend allograft survival. The experiments suggest that these peptides may act by increasing HO-1 activity and support a role for HO-1 in immune regulation and allograft survival.

Enhanced neuronal expression of the oxidoreductase--biliverdin reductase--after permanent focal cerebral ischemia

This is the first report on increased neuronal levels of biliverdin reductase (BVR) in response to ischemic brain injury. BVR is an oxidoreductase, and is unique among all enzymes characterized to date in having dual pH/dual cofactor requirements--NADH and NADPH at 6.7 and 8.7, respectively. BVR catalyses the final step in the heme metabolic pathway and reduces the heme degradation product, biliverdin, to bilirubin. Bilirubin can be both a neurotoxicant and an antioxidant depending on its ratio to protein and concentration. Bilirubin also has immunomodulatory activity. Other biologically active heme degradation products are iron and CO. This study assessed time-dependent changes in the level of BVR, following permanent middle cerebral artery occlusion (MCAo). It also examined correlation of the change in BVR expression with display of indices of ischemic tissue injury. Under halothane anesthesia and normothermic conditions, 72 DNX inbred mice were subjected to MCAo. A time-dependent enlargement of an ischemic lesion over the course of 24 h was observed and measured 55 +/- 5 mm3 at 6 h, 63 +/- 6.7 mm3 at 12 h, and 73 +/- 5 mm3 at 24 h. Six hours after MCAo, increased immunoreactivity for BVR was noted in neurons in the peri-ischemic areas, intraischemic cortical layers 3 and 5, as well as in neurons in regions distant from the borders of vascular distribution of the MCA, such as those in substantia nigra, in the Purkinje layer of the cerebellum and in the central nucleus of inferior colliculus. Twenty-four hours after MCAo, immunoreactivity for BVR remained increased in the peri-ischemia areas. At all time points staining for BVR was decreased in the ischemic core. At the 24 h time point there was an increase in Fe staining in the perimeter of the lesion and an increase in Schiff's staining for lipid peroxidation at the rim of the lesion. In situ hybridization analysis demonstrated a time dependent increase in BVR mRNA labeling in neurons of the peri-ischemic area. In the ischemic hemisphere, when compared with the contralateral hemisphere, neither measurable decreases in BVR mRNA or total protein levels nor a decrease in NADH-dependent BVR activity at pH 6.7 were observed. As judged by Northern and Western blots and activity analysis, despite the apparent loss of BVR from the ischemic core, and its increase in the peri-ischemic region, when compared with the contralateral hemisphere, the overall capacity of the ischemic hemisphere to catalyze the reduction of biliverdin was unchanged throughout the experiment. Should, in the case of ischemia, the conditions favor the antioxidant activity of bilirubin, then we suggest that increase in BVR expression in ischemic penumbra may present a cellular defense mechanism against free radical-mediated neuronal damage. Furthermore, we interpret the apparent tightly regulated expression of BVR in the ischemic hemisphere as an important factor in protection against bilirubin neurotoxicity. Data suggest that pharmacological modulation of BVR expression is a possible new direction for protecting neurons against ischemic injury and oxidative stress.

Upregulation of heme oxygenase-1 protects genetically fat Zucker rat livers from ischemia/reperfusion injury

We examined the effects of upregulation of heme oxygenase-1 (HO-1) in steatotic rat liver models of ex vivo cold ischemia/reperfusion (I/R) injury. In the model of ischemia/isolated perfusion, treatment of genetically obese Zucker rats with the HO-1 inducer cobalt protoporphyrin (CoPP) or with adenoviral HO-1 (Ad-HO-1) significantly improved portal venous blood flow, increased bile production, and decreased hepatocyte injury. Unlike in untreated rats or those pretreated with the HO-1 inhibitor zinc protoporphyrin (ZnPP), upregulation of HO-1 by Western blots correlated with amelioration of histologic features of I/R injury. Adjunctive infusion of ZnPP abrogated the beneficial effects of Ad-HO-1 gene transfer, documenting the direct involvement of HO-1 in protection against I/R injury. Following cold ischemia/isotransplantation, HO-1 overexpression extended animal survival from 40% in untreated controls to about 80% after CoPP or Ad-HO-1 therapy. This effect correlated with preserved hepatic architecture, improved liver function, and depressed infiltration by T cells and macrophages. Hence, CoPP- or gene therapy-induced HO-1 prevented I/R injury in steatotic rat livers. These findings provide the rationale for refined new treatments that should increase the supply of usable donor livers and ultimately improve the overall success of liver transplantation.

Inhibition of glutamate uptake by unconjugated bilirubin in cultured cortical rat astrocytes: role of concentration and pH

The molecular basis of bilirubin toxicity to nerve cell function is still unclear. Since astrocytes are the main transporters of synaptically released glutamate and impaired glutamate uptake results in neuronal death, we investigated the effect of unconjugated bilirubin (UCB) on [(3)H]glutamate uptake in cultured rat astrocytes and the role of bilirubin ionization on toxicity. Astrocytes were incubated for 5-15 min, with UCB concentrations from 17 to 342 microM and UCB/albumin molar ratios of 0.2-3.0, at pH 7.0, 7.4, and 8.0. Exposure of astrocytes for 15 min to 85.5 microM UCB and 28.5 microM albumin resulted in a 63.1% decrease of glutamate uptake (p < 0.01). Interestingly, the effect demonstrated to be correlated with the UCB/albumin molar ratio (r = -0.986, p < 0.01) and a significant decrease was observed for a UCB/albumin molar ratio as low as 0.8. Inhibition of glutamate transport was also pH-dependent as it occurred at 7.4 (p < 0.05) and 8.0 (p < 0.01), but not at 7.0, suggesting that the monoanionic species of UCB accounted for the inhibition. These findings indicate that UCB, and more precisely the monoanionic species, impairs a crucial function of astrocytes such as glutamate transport and support a potential role of astrocyte function in the pathogenesis of UCB-related brain damage (kernicterus).

In vitro and in vivo immunomodulatory effects of RDP1258, a novel synthetic peptide

Peptides derived from certain regions of human class I MHC molecules are known to have immunomodulatory effects. In particular, amino acid residues 75-84 of the HLA-B7 and HLA-B2702 molecules have demonstrated allele nonspecific immunosuppression in several animal transplant models. There is evidence that these effects are mediated by binding to intracellular heat shock proteins, including heme oxygenase-1. A new derivative of these peptides, RDP1258, was developed using a novel computer-assisted rational design technique. In vitro, RDP1258 peptide inhibited rat heme oxygenase activity in a dose-dependent manner. Similar to observations made with other in vitro heme oxygenase inhibitors, in vivo administration of RDP1258 peptide to naive rats resulted in upregulation of splenic heme oxygenase activity. The effects of the peptide on alloimmune responses were then tested. Addition of RDP1258 to rat and human mixed leukocyte reactions inhibited proliferation in a dose-dependent manner. In a rat renal transplantation model, peptide therapy combined with a sub-therapeutic dose of cyclosporin A significantly prolonged allograft survival. These data provide further evidence that modulation of the heat shock protein heme oxygenase by rationally designed peptides affects immune effector functions and may allow the development of novel immunomodulatory strategies in organ transplantation.