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Seya M, Aokage T, Nojima T, Nakao A, Naito H. Bile pigments in emergency and critical care medicine. Eur J Med Res 2022; 27:224. [PMID: 36309733 PMCID: PMC9618204 DOI: 10.1186/s40001-022-00863-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/20/2022] [Indexed: 12/04/2022] Open
Abstract
Bile pigments, such as bilirubin and biliverdin, are end products of the heme degradation pathway in mammals and are widely known for their cytotoxic effects. However, recent studies have revealed that they exert cytoprotective effects through antioxidative, anti-inflammatory, and immunosuppressive properties. All these mechanisms are indispensable in the treatment of diseases in the field of emergency and critical care medicine, such as coronary ischemia, stroke, encephalomyelitis, acute lung injury/acute respiratory distress syndrome, mesenteric ischemia, and sepsis. While further research is required before the safe application of bile pigments in the clinical setting, their underlying mechanisms shed light on their utilization as therapeutic agents in the field of emergency and critical care medicine. This article aims to summarize the current understanding of bile pigments and re-evaluate their therapeutic potential in the diseases listed above.
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Heme Oxygenase-1: An Anti-Inflammatory Effector in Cardiovascular, Lung, and Related Metabolic Disorders. Antioxidants (Basel) 2022; 11:antiox11030555. [PMID: 35326205 PMCID: PMC8944973 DOI: 10.3390/antiox11030555] [Citation(s) in RCA: 58] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 02/24/2022] [Accepted: 03/10/2022] [Indexed: 12/12/2022] Open
Abstract
The heme oxygenase (HO) enzyme system catabolizes heme to carbon monoxide (CO), ferrous iron, and biliverdin-IXα (BV), which is reduced to bilirubin-IXα (BR) by biliverdin reductase (BVR). HO activity is represented by two distinct isozymes, the inducible form, HO-1, and a constitutive form, HO-2, encoded by distinct genes (HMOX1, HMOX2, respectively). HO-1 responds to transcriptional activation in response to a wide variety of chemical and physical stimuli, including its natural substrate heme, oxidants, and phytochemical antioxidants. The expression of HO-1 is regulated by NF-E2-related factor-2 and counter-regulated by Bach-1, in a heme-sensitive manner. Additionally, HMOX1 promoter polymorphisms have been associated with human disease. The induction of HO-1 can confer protection in inflammatory conditions through removal of heme, a pro-oxidant and potential catalyst of lipid peroxidation, whereas iron released from HO activity may trigger ferritin synthesis or ferroptosis. The production of heme-derived reaction products (i.e., BV, BR) may contribute to HO-dependent cytoprotection via antioxidant and immunomodulatory effects. Additionally, BVR and BR have newly recognized roles in lipid regulation. CO may alter mitochondrial function leading to modulation of downstream signaling pathways that culminate in anti-apoptotic, anti-inflammatory, anti-proliferative and immunomodulatory effects. This review will present evidence for beneficial effects of HO-1 and its reaction products in human diseases, including cardiovascular disease (CVD), metabolic conditions, including diabetes and obesity, as well as acute and chronic diseases of the liver, kidney, or lung. Strategies targeting the HO-1 pathway, including genetic or chemical modulation of HO-1 expression, or application of BR, CO gas, or CO donor compounds show therapeutic potential in inflammatory conditions, including organ ischemia/reperfusion injury. Evidence from human studies indicate that HO-1 expression may represent a biomarker of oxidative stress in various clinical conditions, while increases in serum BR levels have been correlated inversely to risk of CVD and metabolic disease. Ongoing human clinical trials investigate the potential of CO as a therapeutic in human disease.
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Bulmer AC, Bakrania B, Du Toit EF, Boon AC, Clark PJ, Powell LW, Wagner KH, Headrick JP. Bilirubin acts as a multipotent guardian of cardiovascular integrity: more than just a radical idea. Am J Physiol Heart Circ Physiol 2018; 315:H429-H447. [PMID: 29600900 DOI: 10.1152/ajpheart.00417.2017] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Bilirubin, a potentially toxic catabolite of heme and indicator of hepatobiliary insufficiency, exhibits potent cardiac and vascular protective properties. Individuals with Gilbert's syndrome (GS) may experience hyperbilirubinemia in response to stressors including reduced hepatic bilirubin excretion/increased red blood cell breakdown, with individuals usually informed by their clinician that their condition is of little consequence. However, GS appears to protect from all-cause mortality, with progressively elevated total bilirubin associated with protection from ischemic heart and chronic obstructive pulmonary diseases. Bilirubin may protect against these diseases and associated mortality by reducing circulating cholesterol, oxidative lipid/protein modifications, and blood pressure. In addition, bilirubin inhibits platelet activation and protects the heart from ischemia-reperfusion injury. These effects attenuate multiple stages of the atherosclerotic process in addition to protecting the heart during resultant ischemic stress, likely underpinning the profound reduction in cardiovascular mortality in hyperbilirubinemic GS. This review outlines our current knowledge of and uses for bilirubin in clinical medicine and summarizes recent progress in revealing the physiological importance of this poorly understood molecule. We believe that this review will be of significant interest to clinicians, medical researchers, and individuals who have GS.
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Affiliation(s)
- Andrew C Bulmer
- School of Medical Science and Menzies Health Institute Queensland, Griffith University , Gold Coast, Queensland , Australia
| | - Bhavisha Bakrania
- Department of Physiology and Biophysics, University of Mississippi Medical Centre , Jackson, Mississippi
| | - Eugene F Du Toit
- School of Medical Science and Menzies Health Institute Queensland, Griffith University , Gold Coast, Queensland , Australia
| | - Ai-Ching Boon
- School of Medical Science and Menzies Health Institute Queensland, Griffith University , Gold Coast, Queensland , Australia
| | - Paul J Clark
- QIMR-Berghofer Medical Research Institute, School of Medicine, University of Queensland and Princess Alexandra and Mater Hospitals , Brisbane, New South Wales , Australia
| | - Lawrie W Powell
- The Centre for the Advancement of Clinical Research, Royal Brisbane and Women's Hospital, The University of Queensland Centre for Clinical Research , Brisbane, Queensland , Australia
| | - Karl-Heinz Wagner
- Department of Nutritional Science, University of Vienna , Vienna , Austria
| | - John P Headrick
- School of Medical Science and Menzies Health Institute Queensland, Griffith University , Gold Coast, Queensland , Australia
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Wang D, Tosevska A, Heiß EH, Ladurner A, Mölzer C, Wallner M, Bulmer A, Wagner KH, Dirsch VM, Atanasov AG. Bilirubin Decreases Macrophage Cholesterol Efflux and ATP-Binding Cassette Transporter A1 Protein Expression. J Am Heart Assoc 2017; 6:JAHA.117.005520. [PMID: 28455345 PMCID: PMC5524097 DOI: 10.1161/jaha.117.005520] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Mild but chronically elevated circulating unconjugated bilirubin is associated with reduced total and low-density lipoprotein cholesterol concentration, which is associated with reduced cardiovascular disease risk. We aimed to investigate whether unconjugated bilirubin influences macrophage cholesterol efflux, as a potential mechanism for the altered circulating lipoprotein concentrations observed in hyperbilirubinemic individuals. METHODS AND RESULTS Cholesterol efflux from THP-1 macrophages was assessed using plasma obtained from normo- and hyperbilirubinemic (Gilbert syndrome) humans (n=60 per group) or (heterozygote/homozygote Gunn) rats (n=20 per group) as an acceptor. Hyperbilirubinemic plasma from patients with Gilbert syndrome and Gunn rats induced significantly reduced cholesterol efflux compared with normobilirubinemic plasma. Unconjugated bilirubin (3-17.1 μmol/L) exogenously added to plasma- or apolipoprotein A1-supplemented media also decreased macrophage cholesterol efflux in a concentration- and time-dependent manner. We also showed reduced protein expression of the ATP-binding cassette transporter A1 (ABCA1), a transmembrane cholesterol transporter involved in apolipoprotein A1-mediated cholesterol efflux, in THP-1 macrophages treated with unconjugated bilirubin and in peripheral blood mononuclear cells obtained from hyperbilirubinemic individuals. Furthermore, we demonstrated that bilirubin accelerates the degradation rate of the ABCA1 protein in THP-1 macrophages. CONCLUSIONS Cholesterol efflux from THP-1 macrophages is decreased in the presence of plasma obtained from humans and rats with mild hyperbilirubinemia. A direct effect of unconjugated bilirubin on cholesterol efflux was demonstrated and is associated with decreased ABCA1 protein expression. These data improve our knowledge concerning bilirubin's impact on cholesterol transport and represent an important advancement in our understanding of bilirubin's role in cardiovascular disease.
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Affiliation(s)
- Dongdong Wang
- Department of Pharmacognosy, University of Vienna, Austria.,Institute of Genetics and Animal Breeding of the Polish Academy of Sciences, Jastrzebiec, Poland
| | - Anela Tosevska
- Research Platform Active Ageing, University of Vienna, Austria.,Department of Nutritional Sciences, University of Vienna, Austria.,Department of Molecular, Cell and Developmental Biology, UCLA, Los Angeles, CA
| | - Elke H Heiß
- Department of Pharmacognosy, University of Vienna, Austria
| | | | - Christine Mölzer
- Department of Nutritional Sciences, University of Vienna, Austria.,School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, United Kingdom
| | - Marlies Wallner
- Department of Nutritional Sciences, University of Vienna, Austria.,Institute of Dietetics and Nutrition, University of Applied Sciences FH JOANNEUM, Graz, Austria
| | - Andrew Bulmer
- School of Medical Science and Menzies Health Institute Queensland, Gold Coast, Australia
| | - Karl-Heinz Wagner
- Research Platform Active Ageing, University of Vienna, Austria.,Department of Nutritional Sciences, University of Vienna, Austria
| | | | - Atanas G Atanasov
- Department of Pharmacognosy, University of Vienna, Austria .,Institute of Genetics and Animal Breeding of the Polish Academy of Sciences, Jastrzebiec, Poland
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Boon AC, Bulmer AC, Coombes JS, Fassett RG. Circulating bilirubin and defense against kidney disease and cardiovascular mortality: mechanisms contributing to protection in clinical investigations. Am J Physiol Renal Physiol 2014; 307:F123-36. [DOI: 10.1152/ajprenal.00039.2014] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Unconjugated bilirubin is an endogenous circulating antioxidant, bound to albumin, and therefore is retained in the vascular compartment. Bilirubin has well-documented neurotoxic effects in infants; however, current evidence indicates mildly elevated bilirubin is associated with protection from cardiovascular disease and all-cause mortality in adults. Recent clinical studies show mildly elevated bilirubin is associated with protection from kidney damage and dysfunction, in addition to cardiovascular events and all-cause mortality in patients undergoing hemodialysis. This is the first review to examine the clinical evidence and summarize the potential mechanisms of action that link bilirubin to protection from kidney damage, subsequent kidney failure, and dialysis-related mortality. With this understanding, it is hoped that new therapies will be developed to prevent renal dysfunction and mortality from cardiovascular disease in at-risk individuals.
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Affiliation(s)
- Ai-Ching Boon
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, Australia; and
| | - Andrew C. Bulmer
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, Australia; and
| | - Jeff S. Coombes
- School of Human Movement Studies, University of Queensland, St Lucia, Australia
| | - Robert G. Fassett
- School of Human Movement Studies, University of Queensland, St Lucia, Australia
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Bisht K, Tampe J, Shing C, Bakrania B, Winearls J, Fraser J, Wagner KH, Bulmer AC. Endogenous Tetrapyrroles Influence Leukocyte Responses to Lipopolysaccharide in Human Blood: Pre-Clinical Evidence Demonstrating the Anti-Inflammatory Potential of Biliverdin. ACTA ACUST UNITED AC 2014; 5:1000218. [PMID: 25177524 PMCID: PMC4145741 DOI: 10.4172/2155-9899.1000218] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Sepsis is associated with abnormal host immune function in response to pathogen exposure, including endotoxin (lipopolysaccharide; LPS). Cytokines play crucial roles in the induction and resolution of inflammation in sepsis. Therefore, the primary aim of this study was to investigate the effects of endogenous tetrapyrroles, including biliverdin (BV) and unconjugated bilirubin (UCB) on LPS-induced cytokines in human blood. Biliverdin and UCB are by products of haem catabolism and have strong cytoprotective, antioxidant and anti-inflammatory effects. In the present study, whole human blood supplemented with BV and without was incubated in the presence or absence of LPS for 4 and 8 hours. Thereafter, whole blood was analysed for gene and protein expression of cytokines, including IL-1β, IL-6, TNF, IFN-γ, IL-1Ra and IL-8. Biliverdin (50 μM) significantly decreased the LPS-mediated gene expression of IL-1β, IL-6, IFN-γ, IL-1Ra and IL-8 (P<0.05). Furthermore, BV significantly decreased LPS-induced secretion of IL-1β and IL-8 (P<0.05). Serum samples from human subjects and, wild type and hyperbilirubinaemic Gunn rats were also used to assess the relationship between circulating bilirubin and cytokine expression/production. Significant positive correlations between baseline UCB concentrations in human blood and LPS-mediated gene expression of IL-1β (R=0.929), IFN-γ (R=0.809), IL-1Ra (R=0.786) and IL-8 (R=0.857) were observed in blood samples (all P<0.05). These data were supported by increased baseline IL-1β concentrations in hyperbilirubinaemic Gunn rats (P<0.05). Blood samples were also investigated for complement receptor-5 (C5aR) expression. Stimulation of blood with LPS decreased gene expression of C5aR (P<0.05). Treatment of blood with BV alone and in the presence of LPS tended to decrease C5aR expression (P=0.08). These data indicate that supplemented BV inhibits the ex vivo response of human blood to LPS. Surprisingly, however, baseline UCB was associated with heighted inflammatory response to LPS. This is the first study to explore the effects of BV in a preclinical human model of inflammation and suggests that BV could represent an anti-inflammatory target for the prevention of LPS mediated inflammation in vivo.
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Affiliation(s)
- Kavita Bisht
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, QLD, Australia
| | - Jens Tampe
- Griffith Enterprise, Griffith University, Nathan, QLD, Australia
| | - Cecilia Shing
- School of Health Sciences, University of Tasmania, Launceston, Tasmania, Australia
| | - Bhavisha Bakrania
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, QLD, Australia
| | - James Winearls
- Gold Coast University Hospital Intensive Care Unit and Gold Coast University Hospital Critical Care Research Group, Gold Coast, QLD, Australia
| | - John Fraser
- Critical Care Research Group, The Prince Charles Hospital, University of Queensland, QLD, Australia
| | - Karl-Heinz Wagner
- Emerging Field Oxidative Stress and DNA Stability and Research Platform Active Aging, Department of Nutritional Science, University of Vienna, Vienna, Austria
| | - Andrew C Bulmer
- Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, QLD, Australia ; Gold Coast University Hospital Intensive Care Unit and Gold Coast University Hospital Critical Care Research Group, Gold Coast, QLD, Australia
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