Bilirubin Links Heme Metabolism to Neuroprotection by Scavenging Superoxide

Exploring the causal association between genetically determined circulating metabolome and hemorrhagic stroke

Background

Hemorrhagic stroke (HS), a leading cause of death and disability worldwide, has not been clarified in terms of the underlying biomolecular mechanisms of its development. Circulating metabolites have been closely associated with HS in recent years. Therefore, we explored the causal association between circulating metabolomes and HS using Mendelian randomization (MR) analysis and identified the molecular mechanisms of effects.

Methods

We assessed the causal relationship between circulating serum metabolites (CSMs) and HS using a bidirectional two-sample MR method supplemented with five ways: weighted median, MR Egger, simple mode, weighted mode, and MR-PRESSO. The Cochran Q-test, MR-Egger intercept test, and MR-PRESSO served for the sensitivity analyses. The Steiger test and reverse MR were used to estimate reverse causality. Metabolic pathway analyses were performed using MetaboAnalyst 5.0, and genetic effects were assessed by linkage disequilibrium score regression. Significant metabolites were further synthesized using meta-analysis, and we used multivariate MR to correct for common confounders.

Results

We finally recognized four metabolites, biliverdin (OR 0.62, 95% CI 0.40-0.96, PMVMR = 0.030), linoleate (18. 2n6) (OR 0.20, 95% CI 0.08-0.54, PMVMR = 0.001),1-eicosadienoylglycerophosphocholine* (OR 2.21, 95% CI 1.02-4.76, PMVMR = 0.044),7-alpha-hydroxy-3 -oxo-4-cholestenoate (7-Hoca) (OR 0.27, 95% CI 0.09-0.77, PMVMR = 0.015) with significant causal relation to HS.

Conclusion

We demonstrated significant causal associations between circulating serum metabolites and hemorrhagic stroke. Monitoring, diagnosis, and treatment of hemorrhagic stroke by serum metabolites might be a valuable approach.

iLight2: A near-infrared optogenetic tool for gene transcription with low background activation

Optogenetic tools (OTs) operating in the far-red and near-infrared (NIR) region offer advantages for light-controlling biological processes in deep tissues and spectral multiplexing with fluorescent probes and OTs acting in the visible range. However, many NIR OTs suffer from background activation in darkness. Through shortening linkers, we engineered a novel NIR OT, iLight2, which exhibits a significantly reduced background activity in darkness, thereby increasing the light-to-dark activation contrast. The resultant optimal configuration of iLight2 components suggests a molecular mechanism of iLight2 action. Using a biliverdin reductase knock-out mouse model, we show that iLight2 exhibits advanced performance in mouse primary cells and deep tissues in vivo. Efficient light-controlled cell migration in wound healing cellular model demonstrates the possibility of using iLight2 in therapy and, overall, positions it as a valuable addition to the NIR OT toolkit for gene transcription applications.

Heme metabolism and HO-1 in the pathogenesis and potential intervention of endometriosis

Endometriosis (EM) is one of the diseases related to retrograded menstruation and hemoglobin. Heme, released from hemoglobin, is degraded by heme oxygenase-1 (HO-1). In EM lesions, heme metabolites regulate processes such as inflammation, redox balance, autophagy, dysmenorrhea, malignancy, and invasion, where macrophages (Mø) play a fundamental role in their interactions. Regulation occurs at molecular, cellular, and pathological levels. Numerous studies suggest that heme is an indispensable component in EM and may contribute to its pathogenesis. The regulatory role of heme in EM encompasses cytokines, signaling pathways, and kinases that mediate cellular responses to external stimuli. HO-1, a catalytic enzyme in the catabolic phase of heme, mitigates heme's cytotoxicity in EM due to its antioxidant, anti-inflammatory, and anti-proliferative properties. Certain compounds may intervene in EM by targeting heme metabolism, guiding the development of appropriate treatments for all stages of endometriosis.

Associations of apolipoprotein E ε4 allele, regional cerebral blood flow, and serum liver function markers in patients with cognitive impairment

Introduction

The ε4 allele of the apolipoprotein E gene (APOE4) is expressed abundantly in both the brain and peripheral circulation as a genetic risk factor for Alzheimer's disease (AD). Cerebral blood flow (CBF) dysfunction is an essential feature of AD, and the liver plays an important role in the pathogenesis of dementia. However, the associations of APOE4 with CBF and liver function markers in patients with cognitive impairment remains unclear. We aimed to evaluate the associations of APOE4 with CBF measured by arterial spin labeling (ASL) magnetic resonance imaging (MRI) and serum liver function markers in participants who were diagnosed with cognitive impairment.

Methods

Fourteen participants with AD and sixteen with amnestic mild cognitive impairment (MCI) were recruited. In addition to providing comprehensive clinical information, all patients underwent laboratory tests and MRI. All participants were divided into carriers and noncarriers of the ε4 allele, and T-tests and Mann-Whitney U tests were used to observe the differences between APOE4 carriers and noncarriers in CBF and liver function markers.

Results

Regarding regional cerebral blood flow (rCBF), APOE4 carriers showed hyperperfusion in the bilateral occipital cortex, bilateral thalamus, and left precuneus and hypoperfusion in the right lateral temporal cortex when compared with noncarriers. Regarding serum liver function markers, bilirubin levels (including total, direct, and indirect) were lower in APOE4 carriers than in noncarriers.

Conclusion

APOE4 exerts a strong effect on CBF dysfunction by inheritance, representing a risk factor for AD. APOE4 may be related to bilirubin metabolism, potentially providing specific neural targets for the diagnosis and treatment of AD.

Production of biliverdin by biotransformation of exogenous heme using recombinant Pichia pastoris cells

Biliverdin, a bile pigment hydrolyzed from heme by heme oxygenase (HO), serves multiple functions in the human body, including antioxidant, anti-inflammatory, and immune response inhibitory activities. Biliverdin has great potential as a clinical drug; however, no economic and efficient production method is available currently. Therefore, the production of biliverdin by the biotransformation of exogenous heme using recombinant HO-expressing yeast cells was studied in this research. First, the heme oxygenase-1 gene (HO1) encoding the inducible plastidic isozyme from Arabidopsis thaliana, with the plastid transport peptide sequence removed, was recombined into Pichia pastoris GS115 cells. This resulted in the construction of a recombinant P. pastoris GS115-HO1 strain that expressed active HO1 in the cytoplasm. After that, the concentration of the inducer methanol, the induction culture time, the pH of the medium, and the concentration of sorbitol supplied in the medium were optimized, resulting in a significant improvement in the yield of HO1. Subsequently, the whole cells of GS115-HO1 were employed as catalysts to convert heme chloride (hemin) into biliverdin. The results showed that the yield of biliverdin was 132 mg/L when hemin was added to the culture of GS115-HO1 and incubated for 4 h at 30 °C. The findings of this study have laid a good foundation for future applications of this method for the economical production of biliverdin.

Neuroprotective Roles of the Biliverdin Reductase-A/Bilirubin Axis in the Brain

Biliverdin reductase-A (BVRA) is a multi-functional enzyme with a multitude of important roles in physiologic redox homeostasis. Classically, BVRA is well known for converting the heme metabolite biliverdin to bilirubin, which is a potent antioxidant in both the periphery and the brain. However, BVRA additionally participates in many neuroprotective signaling cascades in the brain that preserve cognition. Here, we review the neuroprotective roles of BVRA and bilirubin in the brain, which together constitute a BVRA/bilirubin axis that influences healthy aging and cognitive function.

High-normal unconjugated bilirubin is associated with decreased risk of chronic kidney disease in type 2 diabetes: A real-world study

OBJECTIVE

To investigate the association between serum unconjugated bilirubin (UCB) within normal limits and chronic kidney disease (CKD) in T2DM patients.

METHOD

This cross-sectional, real-world study was performed in 8661 hospitalised T2DM patients. The subjects were stratified into quintiles based on serum UCB levels. The clinical characteristics and CKD prevalence were compared among the UCB quantile groups. The associations of serum UCB levels and quintiles with CKD were also analysed by binary logistic regression.

RESULTS

After controlling for age, sex, and diabetes duration (DD), the CKD prevalence (20.4%, 12.2%, 10.6%, 8.3%, and 6.4% for the first, second, third, fourth, and fifth quintiles, respectively, p < 0.001 for trend) was significantly decreased across the serum UCB quintiles. The fully adjusted regression model showed negative associations of serum UCB levels (OR: 0.660, 95% CI: 0.585-0.744; p < 0.001 for trend) and quintiles (p < 0.001) with the presence of CKD. Compared with the subjects in the lowest UCB quintile, the risk of CKD decreased by 36.2%, 54.3%, 53.8%, and 62.1%, respectively, in those from the second to the highest UCB quintile. Additionally, C-reactive protein (CRP) levels were significantly higher in the subjects with CKD than in those without CKD (p < 0.001), and significantly decreased across the UCB quintiles (p < 0.001 for trend).

CONCLUSIONS

Serum UCB levels within the normal range were significantly and negatively linked to CKD in T2DM patients. High-normal UCB may be an independent protective factor for CKD by its antioxidant and the following anti-inflammatory activities through its signalling activity, which was indicated by clearly decreased CRP levels across the UCB quintiles.

Biliverdin modulates the Nrf2/A20/eEF1A2 axis to alleviate cerebral ischemia-reperfusion injury by inhibiting pyroptosis

This study aimed to examine whether Biliverdin, which is a common metabolite of haem, can alleviate cerebral ischemia reperfusion injury (CIRI) by inhibiting pyroptosis. Here, CIRI was induced by middle cerebral artery occlusion-reperfusion (MCAO/R) in C57BL/6 J mice and modelled by oxygen and glucose deprivation/reoxygenation (OGD/R) in HT22 cells, it was treated with or without Biliverdin. The spatiotemporal expression of GSDMD-N and infarction volumes were assessed by immunofluorescence staining and triphenyltetrazolium chloride (TTC), respectively. The NLRP3/Caspase-1/GSDMD pathway, which is central to the pyroptosis process, as well as the expression of Nrf2, A20, and eEF1A2 were determined by Western-blots. Nrf2, A20, and eEF1A2 interactions were verified using dual-luciferase reporter assays, chromatin immunoprecipitation, or co-immunoprecipitation. Additionally, the role of Nrf2/A20/eEF1A2 axis in modulating the neuroprotective properties of Biliverdin was investigated using A20 or eEF1A2 gene interference (overexpression and/or silencing). 40 mg/kg of Biliverdin could significantly alleviate CIRI both in vivo and in vitro, promoted the activation of Nrf2, elevated A20 expression, but decreased eEF1A2 expression. Nrf2 can bind to the promoter of A20, thereby transcriptionally regulating the expression of A20. A20 can furthermore interacted with eEF1A2 through its ZnF4 domain to ubiquitinate and degrade it, leading to the downregulation of eEF1A2. Our studies have also demonstrated that either the knock-down of A20 or over-expression of eEF1A2 blunted the protective effect of Biliverdin. Rescue experiments further confirmed that Biliverdin could regulate the NF-κB pathway via the Nrf2/A20/eEF1A2 axis. In summary, our study demonstrates that Biliverdin ameliorates CIRI by inhibiting the NF-κB pathway via the Nrf2/A20/eEF1A2 axis. Our findings can help identify novel therapeutic targets for the treatment of CIRI.

Antioxidative Stress Metabolic Pathways in Moderately Active Individuals

Physical activity (PA) is known to have beneficial effects on health, primarily through its antioxidative stress properties. However, the specific metabolic pathways that underlie these effects are not fully understood. This study aimed to investigate the metabolic pathways that are involved in the protective effects of moderate PA in non-obese and healthy individuals. Data on 305 young, non-obese participants were obtained from the Qatar Biobank. The participants were classified as active or sedentary based on their self-reported PA levels. Plasma metabolomics data were collected and analyzed to identify differences in metabolic pathways between the two groups. The results showed that active participants had increased activation of antioxidative, stress-related pathways, including lysoplasmalogen, plasmalogen, phosphatidylcholine, vitamin A, and glutathione. Additionally, there were significant associations between glutathione metabolites and certain clinical traits, including bilirubin, uric acid, hemoglobin, and iron. This study provides new insights into the metabolic pathways that are involved in the protective effects of moderate PA in non-obese and healthy individuals. The findings may have implications for the development of new therapeutic strategies that target these pathways.

Nanomedicine-Based Therapeutics for Myocardial Ischemic/Reperfusion Injury

Myocardial ischemic/reperfusion (IR) injury is a global cardiovascular disease with high mortality and morbidity. Therapeutic interventions for myocardial ischemia involve restoring the occluded coronary artery. However, reactive oxygen species (ROS) inevitably impair the cardiomyocytes during the ischemic and reperfusion phases. Antioxidant therapy holds great promise against myocardial IR injury. The current therapeutic methodologies for ROS scavenging depend predominantly on administering antioxidants. Nevertheless, the intrinsic drawbacks of antioxidants limit their further clinical transformation. The use of nanoplatforms with versatile characteristics greatly benefits drug delivery in myocardial ischemic therapy. Nanoplatform-mediated drug delivery significantly improves drug bioavailability, increases therapeutic index, and reduces systemic toxicity. Nanoplatforms can be specifically and reasonably designed to enhance molecule accumulation at the myocardial site. The present review initially summarizes the mechanism of ROS generation during the process of myocardial ischemia. The understanding of this phenomenon will facilitate the advancement of innovative therapeutic strategies against myocardial IR injury. The latest developments in nanomedicine for treating myocardial ischemic injury are then discussed. Finally, the current challenges and perspectives in antioxidant therapy for myocardial IR injury are addressed.

Bilirubin and Redox Stress in Age-Related Brain Diseases

Cellular redox status has a crucial role in brain physiology, as well as in pathologic conditions. Physiologic senescence, by dysregulating cellular redox homeostasis and decreasing antioxidant defenses, enhances the central nervous system's susceptibility to diseases. The reduction of free radical accumulation through lifestyle changes, and the supplementation of antioxidants as a prophylactic and therapeutic approach to increase brain health, are strongly suggested. Bilirubin is a powerful endogenous antioxidant, with more and more recognized roles as a biomarker of disease resistance, a predictor of all-cause mortality, and a molecule that may promote health in adults. The alteration of the expression and activity of the enzymes involved in bilirubin production, as well as an altered blood bilirubin level, are often reported in neurologic conditions and neurodegenerative diseases (together denoted NCDs) in aging. These changes may predict or contribute both positively and negatively to the diseases. Understanding the role of bilirubin in the onset and progression of NCDs will be functional to consider the benefits vs. the drawbacks and to hypothesize the best strategies for its manipulation for therapeutic purposes.

Association between total bilirubin and gender-specific incidence of fundus arteriosclerosis in a Chinese population: a retrospective cohort study

To investigate the gender-specific relationship between total bilirubin (TBIL) and fundus arteriosclerosis in the general population, and to explore whether there is a dose-response relationship between them. In a retrospective cohort study, 27,477 participants were enrolled from 2006 to 2019. The TBIL was divided into four groups according to the quartile. The Cox proportional hazards model was used to estimate the HRs with 95% CIs of different TBIL level and fundus arteriosclerosis in men and women. The dose-response relationship between TBIL and fundus arteriosclerosis was estimated using restricted cubic splines method. In males, after adjusting for potential confounders, the Q2 to Q4 level of TBIL were significantly associated with the risk of fundus arteriosclerosis. The HRs with 95% CIs were 1.217 (1.095-1.354), 1.255 (1.128-1.396) and 1.396 (1.254-1.555), respectively. For females, TBIL level was not associated with the incidence of fundus arteriosclerosis. In addition, a linear relationship between TBIL and fundus arteriosclerosis in both genders (P < 0.0001 and P = 0.0047, respectively). In conclusion, the incidence of fundus arteriosclerosis is positively correlated with serum TBIL level in males, but not in females. In addition, there was a linear dose-response relationship between TBIL and incidence of fundus arteriosclerosis.

CEACAM6 as a Novel Therapeutic Target to Boost HO-1-mediated Antioxidant Defense in COPD

Rationale: Tobacco smoking and air pollution are primary causes of chronic obstructive pulmonary disease (COPD). However, only a minority of smokers develop COPD. The mechanisms underlying the defense against nitrosative/oxidative stress in nonsusceptible smokers to COPD remain largely unresolved. Objectives: To investigate the defense mechanisms against nitrosative/oxidative stress that possibly prevent COPD development or progression. Methods: Four cohorts were investigated: 1) sputum samples (healthy, n = 4; COPD, n = 37), 2) lung tissue samples (healthy, n = 13; smokers without COPD, n = 10; smoker+COPD, n = 17), 3) pulmonary lobectomy tissue samples (no/mild emphysema, n = 6), and 4) blood samples (healthy, n = 6; COPD, n = 18). We screened 3-nitrotyrosine (3-NT) levels, as indication of nitrosative/oxidative stress, in human samples. We established a novel in vitro model of a cigarette smoke extract (CSE)-resistant cell line and studied 3-NT formation, antioxidant capacity, and transcriptomic profiles. Results were validated in lung tissue, isolated primary cells, and an ex vivo model using adeno-associated virus-mediated gene transduction and human precision-cut lung slices. Measurements and Main Results: 3-NT levels correlate with COPD severity of patients. In CSE-resistant cells, nitrosative/oxidative stress upon CSE treatment was attenuated, paralleled by profound upregulation of heme oxygenase-1 (HO-1). We identified carcinoembryonic antigen cell adhesion molecule 6 (CEACAM6) as a negative regulator of HO-1-mediated nitrosative/oxidative stress defense in human alveolar type 2 epithelial cells (hAEC2s). Consistently, inhibition of HO-1 activity in hAEC2s increased the susceptibility toward CSE-induced damage. Epithelium-specific CEACAM6 overexpression increased nitrosative/oxidative stress and cell death in human precision-cut lung slices on CSE treatment. Conclusions: CEACAM6 expression determines the hAEC2 sensitivity to nitrosative/oxidative stress triggering emphysema development/progression in susceptible smokers.

Dynamic Changes of BVRA Protein Levels Occur in Response to Insulin: A Pilot Study in Humans

Biliverdin reductase-A (BVRA) is involved in the regulation of insulin signaling and the maintenance of glucose homeostasis. Previous research showed that BVRA alterations are associated with the aberrant activation of insulin signaling in dysmetabolic conditions. However, whether BVRA protein levels change dynamically within the cells in response to insulin and/or glucose remains an open question. To this aim, we evaluated changes of intracellular BVRA levels in peripheral blood mononuclear cells (PBMC) collected during the oral glucose tolerance test (OGTT) in a group of subjects with different levels of insulin sensitivity. Furthermore, we looked for significant correlations with clinical measures. Our data show that BVRA levels change dynamically during the OGTT in response to insulin, and greater BVRA variations occur in those subjects with lower insulin sensitivity. Changes of BVRA significantly correlate with indexes of increased insulin resistance and insulin secretion (HOMA-IR, HOMA-β, and insulinogenic index). At the multivariate regression analysis, the insulinogenic index independently predicted increased BVRA area under curve (AUC) during the OGTT. This pilot study showed, for the first time, that intracellular BVRA protein levels change in response to insulin during OGTT and are greater in subjects with lower insulin sensitivity, supporting the role of BVR-A in the dynamic regulation of the insulin signaling pathway.

Increased Risk of Aging-Related Neurodegenerative Disease after Traumatic Brain Injury

Traumatic brain injury (TBI) survivors frequently suffer from chronically progressive complications, including significantly increased risk of developing aging-related neurodegenerative disease. As advances in neurocritical care increase the number of TBI survivors, the impact and awareness of this problem are growing. The mechanisms by which TBI increases the risk of developing aging-related neurodegenerative disease, however, are not completely understood. As a result, there are no protective treatments for patients. Here, we review the current literature surrounding the epidemiology and potential mechanistic relationships between brain injury and aging-related neurodegenerative disease. In addition to increasing the risk for developing all forms of dementia, the most prominent aging-related neurodegenerative conditions that are accelerated by TBI are amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Parkinson's disease (PD), and Alzheimer's disease (AD), with ALS and FTD being the least well-established. Mechanistic links between TBI and all forms of dementia that are reviewed include oxidative stress, dysregulated proteostasis, and neuroinflammation. Disease-specific mechanistic links with TBI that are reviewed include TAR DNA binding protein 43 and motor cortex lesions in ALS and FTD; alpha-synuclein, dopaminergic cell death, and synergistic toxin exposure in PD; and brain insulin resistance, amyloid beta pathology, and tau pathology in AD. While compelling mechanistic links have been identified, significantly expanded investigation in the field is needed to develop therapies to protect TBI survivors from the increased risk of aging-related neurodegenerative disease.

Metabolomic study combined with the low-level light therapy of Chinese acupuncture points and combined oral contraceptives in treatment of primary dysmenorrhea: A prospective, multicenter, randomized controlled study

Objective

To compare the changes of metabolites between Low-level light therapy (LLLT) and combined oral contraceptive (COC) after treatment of primary dysmenorrhea (PD), and to compare and analyze the biological and biochemical effects of the two treatments by analyzing the differences in metabolite profiles.

Methods

A multicenter, double-blind, prospective, parallel, randomized controlled study was conducted on 69 women aged 16-35 years old with PD who were randomly divided into COC treatment group or LLLT treatment group. Low-level light therapy with light-emitting diodes (LED) was applied on two acupoints named "Guanyuan" (CV4) and "Qihai" (CV6). After 12 weeks of treatment intervention, blood samples were collected before and after treatment for metabolomic analysis. We used UPLC-MS/MS analysis to compare the differences in metabolite changes between LLLT and COC before and after treatment.

Results

76 differential metabolites were detected in the LLLT group, and 92 differential metabolites were detected in the COC group, which were up-regulated or down-regulated (p < 0.001). Prostaglandin D2 (PG D2) was down-regulated and biliverdin was up-regulated after LLLT treatment, 4a-Hydroxytetrahydrobiopterin, Prostaglandin D2, 5-Hydroxy-l-tryptophan, Cholic acid were down-regulated and cortisol was up-regulated after COC treatment, and the differences were statistically significant. Cortisol and testosterone glucuronide in LLLT group were significantly lower than those in COC group. The metabolic pathways affected were glycerophospholipid metabolism, linoleic acid metabolism and arachidonic acid metabolism in the LLLT group, and glycerophospholipid metabolism, folate biosynthesis, arachidonic-acid-metabolism, and tryptophan metabolism in the COC group. The differential metabolic pathway were linoleic acid metabolism, steroid hormone biosynthesis, and alpha-Linolenic acid metabolism after the comparison of LLLT with COC.

Conclusion

LLLT and COC might relieve dysmenorrhea by down-regulating PGD2, and LLLT might also relieve dysmenorrhea by up-regulating biliverdin. The level of cortisol and testosterone glucuronide after LLLT treatment was lower than that after COC treatment, which might lead to the difference in the clinical efficacy of the two treatments for dysmenorrhea.

Nomogram including indirect bilirubin for the prediction of post-stroke depression at 3 months after mild acute ischemic stroke onset

Background

Post-stroke depression (PSD) has been proven to be associated with stroke severity. Thus, we hypothesized that the prevalence of PSD would be lower in patients with mild stroke. We aim to explore predictors of depression at 3 months after mild acute ischemic stroke (MAIS) onset and to develop a practical and convenient prediction model for the early identification of patients at high risk.

Methods

A total of 519 patients with MAIS were consecutively recruited from three hospitals in Wuhan city, Hubei province. MAIS was defined as a National Institute of Health Stroke Scale (NIHSS) score of ≤5 at admission. Meeting the DSM-V diagnostic criteria and a 17-item Hamilton Rating Scale for Depression (HAMD-17) score of >7 at their 3-month follow-up were considered the primary outcomes. A multivariable logistic regression model was used to determine the factors adjusted for potential confounders, and all independent predictors were brought into the construction of a nomogram to predict PSD.

Results

The prevalence of PSD is up to 32% at 3 months after MAIS onset. After adjusting for potential confounders, indirect bilirubin (p = 0.029), physical activity (p = 0.001), smoking (p = 0.025), hospitalization days (p = 0.014), neuroticism (p < 0.001), and MMSE (p < 0.001) remained independently and significantly related with PSD. The concordance index (C-index) of the nomogram jointly constructed by the aforementioned six factors was 0.723 (95% CI: 0.678-0.768).

Conclusion

The prevalence of PSD seems equally high even if the ischemic stroke is mild, which calls for great concern from clinicians. In addition, our study found that a higher level of indirect bilirubin can lower the risk of PSD. This finding may provide a potential new approach to PSD treatment. Furthermore, the nomogram including bilirubin is convenient and practical to predict PSD after MAIS onset.

Effects of bilirubin on the development and electrical activity of neural circuits

In the past several decades, bilirubin has attracted great attention for central nervous system (CNS) toxicity in some pathological conditions with severely elevated bilirubin levels. CNS function relies on the structural and functional integrity of neural circuits, which are large and complex electrochemical networks. Neural circuits develop from the proliferation and differentiation of neural stem cells, followed by dendritic and axonal arborization, myelination, and synapse formation. The circuits are immature, but robustly developing, during the neonatal period. It is at the same time that physiological or pathological jaundice occurs. The present review comprehensively discusses the effects of bilirubin on the development and electrical activity of neural circuits to provide a systematic understanding of the underlying mechanisms of bilirubin-induced acute neurotoxicity and chronic neurodevelopmental disorders.

Heme Oxygenase-1 and Blood Bilirubin Are Gradually Activated by Oral D-Glyceric Acid

It has been shown that small doses of oral D-glyceric acid (DGA) activate mitochondrial metabolism and reduce inflammation among 50-60-year-old healthy volunteers. The present results with the same small doses reveal that after a 4-day DGA regimen, a dose of DGA activated the HO-1 pathway acutely, while enhanced inflammatory status after the 4-day DGA regimen seemed to be able to downregulate the HO-1 pathway in non-acute measurement. Blood bilirubin was strongly upregulated towards the end of the altogether 21-day study period with positive associations towards improved inflammation and reduced blood triglycerides. After the 4-day DGA regimen, hepatic inflow of blood bilirubin with albumin as the carrier was clearly upregulated in the lower-aerobic-capacity persons. At the same time also, blood triglycerides were down, pointing possibly to the activation of liver fatty acid oxidation. The combination of activated aerobic energy metabolism with transient HO-1 pathway activation and the upregulation of blood bilirubin may reduce the risks of chronic diseases, especially in aging. Furthermore, there exist certain diseases with unsatisfactorily-met medical needs, such as fatty and cholestatic liver diseases, and Parkinson's disease, that can be possibly ameliorated with the whole-body mechanism of the action of the DGA regimen.

A New Product of Bilirubin Degradation by H2O2 and Its Formation in Activated Neutrophils and in an Inflammatory Mouse Model

Bilirubin (BR) is a tetrapyrrolic compound stemming from heme catabolism with diverse physiological functions. It can be oxidized by H₂O₂ to form several degradation products, some of which have been detected in vivo and may contribute to the pathogenesis of certain diseases. However, the oxidative degradation of BR is complex and the conditions that BR degradation occurs pathophysiologically remain obscure. Neutrophils are known to generate large amounts of reactive oxygen species, including H₂O₂, upon activation and they are mobilized to inflammatory sites; therefore, we hypothesized that activated neutrophils could cause BR degradation, which could occur at inflammatory sites. In the present study, we investigated BR degradation by H₂O₂ and identified hematinic acid (BHP1) and a new product BHP2, whose structure was characterized as 2,5-diformyl-4-methyl-1H-pyrrole-3-propanoic acid. An LC-MS/MS method for the quantitation of the two compounds was then established. Using the LC-MS/MS method, we observed the concentration-dependent formation of BHP1 and BHP2 in mouse neutrophils incubated with 10 and 30 μM of BR with the yields being 16 ± 3.2 and 31 ± 5.9 pmol/10⁶ cells for BHP1, and 25 ± 4.4 and 71 ± 26 pmol/10⁶ cells for BHP2, respectively. After adding phorbol 12-myristate 13-acetate, a neutrophil agonist, to 30 μM of BR-treated cells, the BHP1 yield increased to 43 ± 6.6 pmol/10⁶ cells, whereas the BHP2 one decreased to 47 ± 9.2 pmol/10⁶ cells. The two products were also detected in hemorrhagic skins of mice with dermal inflammation and hemorrhage at levels of 4.5 ± 1.9 and 0.18 ± 0.10 nmol/g tissue, respectively, which were significantly higher than those in the non-hemorrhagic skins. BHP2 was neurotoxic starting at 0.10 μM but BHP1 was not, as assessed using Caenorhabditis elegans as the animal model. Neutrophil-mediated BR degradation may be a universally pathophysiological process in inflammation and can be particularly important under pathological conditions concerning hemorrhage.

Identification of the NRF2 transcriptional network as a therapeutic target for trigeminal neuropathic pain

Trigeminal neuralgia, historically dubbed the "suicide disease," is an exceedingly painful neurologic condition characterized by sudden episodes of intense facial pain. Unfortunately, the only U.S. Food and Drug Administration (FDA)-approved medication for trigeminal neuralgia carries substantial side effects, with many patients requiring surgery. Here, we identify the NRF2 transcriptional network as a potential therapeutic target. We report that cerebrospinal fluid from patients with trigeminal neuralgia accumulates reactive oxygen species, several of which directly activate the pain-transducing channel TRPA1. Similar to our patient cohort, a mouse model of trigeminal neuropathic pain also exhibits notable oxidative stress. We discover that stimulating the NRF2 antioxidant transcriptional network is as analgesic as inhibiting TRPA1, in part by reversing the underlying oxidative stress. Using a transcriptome-guided drug discovery strategy, we identify two NRF2 network modulators as potential treatments. One of these candidates, exemestane, is already FDA-approved and may thus be a promising alternative treatment for trigeminal neuropathic pain.

Biliverdin Reductase A Protects Lens Epithelial Cells against Oxidative Damage and Cellular Senescence in Age-Related Cataract

Age-related cataract (ARC) is the common cause of blindness globally. Reactive oxygen species (ROS), one of the greatest contributors to aging process, leads to oxidative damage and senescence of lens epithelial cells (LECs), which are involved in the pathogenesis of ARC. Biliverdin reductase A (BVRA) has ROS-scavenging ability by converting biliverdin (BV) into bilirubin (BR). However, little is known about the protective effect of BVRA against ARC. In the present study, we measured the expression level of BVRA and BR generation in human samples. Then, the antioxidative property of BVRA was compared between the young and senescent LECs upon stress condition. In addition, we evaluated the effect of BVRA on attenuating H₂O₂-induced premature senescence in LECs. The results showed that the mRNA expression level of BVRA and BR concentration were decreased in both LECs and lens cortex of age-related nuclear cataract. Using the RNA interference technique, we found that BVRA defends LECs against oxidative stress via (i) restoring mitochondrial dysfunction in a BR-dependent manner, (ii) inducing heme oxygenase-1 (HO-1) expression directly, and (iii) promoting phosphorylation of ERK1/2 and nuclear delivery of nuclear factor erythroid 2-related factor 2 (Nrf2). Intriguingly, the antioxidative effect of BVRA was diminished along with the reduced BR concentration and repressed nuclear translocation of BVRA and Nrf2 in senescent LECs, which would be resulted from the decreased BVRA activity and impaired nucleocytoplasmic trafficking. Eventually, we confirmed that BVRA accelerates the G1 phase transition and prevents against H₂O₂-induced premature senescence in LECs. In summary, BVRA protects LECs against oxidative stress and cellular senescence in ARC by converting BV into BR, inducing HO-1 expression, and activating the ERK/Nrf2 pathway. This trial is registered with ChiCTR2000036059.

Beneficial and Detrimental Roles of Heme Oxygenase-1 in the Neurovascular System

Heme oxygenase (HO) has both beneficial and detrimental effects via its metabolites, including carbon monoxide (CO), biliverdin or bilirubin, and ferrous iron. HO-1 is an inducible form of HO that is upregulated by oxidative stress, nitric oxide, CO, and hypoxia, whereas HO-2 is a constitutive form that regulates vascular tone and homeostasis. In brains injured by trauma, ischemia-reperfusion, or Alzheimer’s disease (AD), the long-term expression of HO-1 can be detected, which can lead to cytotoxic ferroptosis via iron accumulation. In contrast, the transient induction of HO-1 in the peri-injured region may have regenerative potential (e.g., angiogenesis, neurogenesis, and mitochondrial biogenesis) and neurovascular protective effects through the CO-mediated signaling pathway, the antioxidant properties of bilirubin, and the iron-mediated ferritin synthesis. In this review, we discuss the dual roles of HO-1 and its metabolites in various neurovascular diseases, including age-related macular degeneration, ischemia-reperfusion injury, traumatic brain injury, Gilbert’s syndrome, and AD.

Role of Biliverdin Reductase A in the Regulation of Insulin Signaling in Metabolic and Neurodegenerative Diseases: An Update

Insulin signaling is a conserved pathway that orchestrates glucose and lipid metabolism, energy balance, and inflammation, and its dysregulation compromises the homeostasis of multiple systems. Insulin resistance is a shared hallmark of several metabolic diseases, including obesity, metabolic syndrome, and type 2 diabetes, and has been associated with cognitive decline during aging and dementia. Numerous mechanisms promoting the development of peripheral and central insulin resistance have been described, although most of them were not completely clarified. In the last decades, several studies have highlighted that biliverdin reductase-A (BVR-A), over its canonical role in the degradation of heme, acts as a regulator of insulin signaling. Evidence from human and animal studies show that BVR-A alterations are associated with the aberrant activation of insulin signaling, metabolic syndrome, liver steatosis, and visceral adipose tissue inflammation in obese and diabetic individuals. In addition, recent findings demonstrated that reduced BVR-A levels or impaired BVR-A activation contribute to the development of brain insulin resistance and metabolic alterations in Alzheimer’s disease. In this narrative review, we will provide an overview on the literature by focusing on the role of BVR-A in the regulation of insulin signaling and how BVR-A alterations impact on cell dysfunctions in both metabolic and neurodegenerative disorders.

Biliverdin reductase bridges focal adhesion kinase to Src to modulate synaptic signaling

Synapses connect discrete neurons into vast networks that send, receive, and encode diverse forms of information. Synaptic function and plasticity, the neuronal process of adapting to diverse and variable inputs, depend on the dynamic nature of synaptic molecular components, which is mediated in part by cell adhesion signaling pathways. Here, we found that the enzyme biliverdin reductase (BVR) physically links together key focal adhesion signaling molecules at the synapse. BVR-null (BVR^-/-) mice exhibited substantial deficits in learning and memory on neurocognitive tests, and hippocampal slices in which BVR was postsynaptically depleted showed deficits in electrophysiological responses to stimuli. RNA sequencing, biochemistry, and pathway analyses suggested that these deficits were mediated through the loss of focal adhesion signaling at both the transcriptional and biochemical level in the hippocampus. Independently of its catalytic function, BVR acted as a bridge between the primary focal adhesion signaling kinases FAK and Pyk2 and the effector kinase Src. Without BVR, FAK and Pyk2 did not bind to and stimulate Src, which then did not phosphorylate the N-methyl-d-aspartate (NMDA) receptor, a critical posttranslational modification for synaptic plasticity. Src itself is a molecular hub on which many signaling pathways converge to stimulate NMDAR-mediated neurotransmission, thus positioning BVR at a prominent intersection of synaptic signaling.

Wasp Venom Ameliorates Scopolamine-Induced Learning and Memory Impairment in Mice

This study investigated the effects of wasp venom (WV) from the yellow-legged hornet, Vespa velutina, on scopolamine (SCO)-induced memory deficits in mice, as well as the antioxidant activity in HT22 murine hippocampal neuronal cells in parallel comparison with bee venom (BV). The WV was collected from the venom sac, freeze-dried. Both venoms exhibited free radical scavenging capabilities in a concentration-dependent manner. In addition, the venom treatment enhanced cell viability at the concentrations of ≤40 µg/mL of WV and ≤4 µg/mL of BV in glutamate-treated HT22 cells, and increased the transcriptional activity of the antioxidant response element (ARE), a cis-acting enhancer which regulates the expression of nuclear factor erythroid 2-related factor 2 (Nrf2)-downstream antioxidant enzymes. Concurrently, WV at 20 µg/mL significantly increased the expression of a key antioxidant enzyme heme oxygenase 1 (HO-1) in HT22 cells despite no significant changes observed in the nuclear level of Nrf2. Furthermore, the intraperitoneal administration of WV to SCO-treated mice at doses ranged from 250 to 500 µg/kg body weight ameliorated memory impairment behavior, reduced histological injury in the hippocampal region, and reduced oxidative stress biomarkers in the brain and blood of SCO-treated mice. Our findings demonstrate that WV possess the potential to improve learning and memory deficit in vivo while further study is needed for the proper dose and safety measures and clinical effectiveness.

Nomogram for Persistent Post-Stroke Depression and Decision Curve Analysis

Purpose

Patients and Methods

Results

Conclusion

Understanding Cellular Redox Homeostasis: A Challenge for Precision Medicine

Living organisms use a large repertoire of anabolic and catabolic reactions to maintain their physiological body functions, many of which include oxidation and reduction of substrates. The scientific field of redox biology tries to understand how redox homeostasis is regulated and maintained and which mechanisms are derailed in diverse pathological developments of diseases, where oxidative or reductive stress is an issue. The term “oxidative stress” is defined as an imbalance between the generation of oxidants and the local antioxidative defense. Key mediators of oxidative stress are reactive species derived from oxygen, nitrogen, and sulfur that are signal factors at physiological concentrations but can damage cellular macromolecules when they accumulate. However, therapeutical targeting of oxidative stress in disease has proven more difficult than previously expected. Major reasons for this are the very delicate cellular redox systems that differ in the subcellular compartments with regard to their concentrations and depending on the physiological or pathological status of cells and organelles (i.e., circadian rhythm, cell cycle, metabolic need, disease stadium). As reactive species are used as signaling molecules, non-targeted broad-spectrum antioxidants in many cases will fail their therapeutic aim. Precision medicine is called to remedy the situation.

Long-Term Effects of Biliverdin Reductase a Deficiency in Ugt1-/- Mice: Impact on Redox Status and Metabolism

Accumulation of neurotoxic bilirubin due to a transient neonatal or persistent inherited deficiency of bilirubin glucuronidation activity can cause irreversible brain damage and death. Strategies to inhibit bilirubin production and prevent neurotoxicity in neonatal and adult settings seem promising. We evaluated the impact of Bvra deficiency in neonatal and aged mice, in a background of unconjugated hyperbilirubinemia, by abolishing bilirubin production. We also investigated the disposal of biliverdin during fetal development. In Ugt1^−/− mice, Bvra deficiency appeared sufficient to prevent lethality and to normalize bilirubin level in adults. Although biliverdin accumulated in Bvra-deficient fetuses, both Bvra^−/− and Bvra^−/−Ugt1^−/− pups were healthy and reached adulthood having normal liver, brain, and spleen histology, albeit with increased iron levels in the latter. During aging, both Bvra^−/− and Bvra^−/−Ugt1^−/− mice presented normal levels of relevant hematological and metabolic parameters. Interestingly, the oxidative status in erythrocytes from 9-months-old Bvra^−/− and Bvra^−/−Ugt1^−/− mice was significantly reduced. In addition, triglycerides levels in these 9-months-old Bvra^−/− mice were significantly higher than WT controls, while Bvra^−/−Ugt1^−/− tested normal. The normal parameters observed in Bvra^−/−Ugt1^−/− mice fed chow diet indicate that Bvra inhibition to treat unconjugated hyperbilirubinemia seems safe and effective.

Redox-mediated carbon monoxide release from a manganese carbonyl-implications for physiological CO delivery by CO releasing moieties

The dynamics of hydrogen peroxide reactions with metal carbonyls have received little attention. Given reports that therapeutic levels of carbon monoxide are released in hypoxic tumour cells upon manganese carbonyls reactions with endogenous H2O2, it is critical to assess the underlying CO release mechanism(s). In this context, a quantitative mechanistic investigation of the H2O2 oxidation of the water-soluble model complex fac-[Mn(CO)3(Br)(bpCO2)]2-, (A, bpCO2 2- = 2,2'-bipyridine-4,4'-dicarboxylate dianion) was undertaken under physiologically relevant conditions. Characterizing such pathways is essential to evaluating the viability of redox-mediated CO release as an anti-cancer strategy. The present experimental studies demonstrate that approximately 2.5 equivalents of CO are released upon H2O2 oxidation of A via pH-dependent kinetics that are first-order both in [A] and in [H2O2]. Density functional calculations were used to evaluate the key intermediates in the proposed reaction mechanisms. These pathways are discussed in terms of their relevance to physiological CO delivery by carbon monoxide releasing moieties.

Redox imbalance links COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome

Although most patients recover from acute COVID-19, some experience postacute sequelae of severe acute respiratory syndrome coronavirus 2 infection (PASC). One subgroup of PASC is a syndrome called "long COVID-19," reminiscent of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). ME/CFS is a debilitating condition, often triggered by viral and bacterial infections, leading to years-long debilitating symptoms including profound fatigue, postexertional malaise, unrefreshing sleep, cognitive deficits, and orthostatic intolerance. Some are skeptical that either ME/CFS or long COVID-19 involves underlying biological abnormalities. However, in this review, we summarize the evidence that people with acute COVID-19 and with ME/CFS have biological abnormalities including redox imbalance, systemic inflammation and neuroinflammation, an impaired ability to generate adenosine triphosphate, and a general hypometabolic state. These phenomena have not yet been well studied in people with long COVID-19, and each of them has been reported in other diseases as well, particularly neurological diseases. We also examine the bidirectional relationship between redox imbalance, inflammation, energy metabolic deficits, and a hypometabolic state. We speculate as to what may be causing these abnormalities. Thus, understanding the molecular underpinnings of both PASC and ME/CFS may lead to the development of novel therapeutics.

Sex differences between serum total bilirubin levels and cognition in patients with schizophrenia

BACKGROUND

Cognitive deficits are common in patients with schizophrenia (SCZ). Abnormal serum total bilirubin (TBIL) levels have been involved in cognitive deficits associated with neuropsychiatric diseases such as mild cognitive impairment and subcortical ischemic vascular disease. However, this relationship has not yet been fully investigated in patients with SCZ. Therefore, the aim of this study was to investigate the association between the serum TBIL concentration and cognitive deficits in SCZ patients and to determine whether a sex difference exists in the association.

METHODS

A total of 455 participants were eligible and included in this cross-sectional study. Cognition was evaluated using the Montreal Cognitive Assessment. Serum TBIL concentration was measured with an automatic biochemistry analyzer according to the routine protocol in the hospital medical laboratory.

RESULTS

Serum TBIL levels were lower in the cognition impairment group than in the cognition normal group in male patients. In contrast, serum TBIL levels tended to be increased in the cognition impairment group in female patients, although the difference was not significant. Further stepwise multiple regression analysis stratified by sex showed that serum TBIL was independently and positively associated with cognitive function in male patients but not in female patients. Moreover, the association between serum TBIL level and cognitive function was also identified by the propensity score matching (PSM) method in male patients, but not in female patients.

CONCLUSION

These findings suggest that lower serum TBIL levels may be associated with cognitive impairment in male SCZ patients.

Near-infrared and far-red genetically encoded indicators of neuronal activity

Genetically encoded fluorescent indicators of neuronal activity are ultimately developed to dissect functions of neuronal ensembles during behavior in living animals. Recent development of near-infrared shifted calcium and voltage indicators moved us closer to this goal and enabled crosstalk-free combination with blue light-controlled optogenetic tools for all-optical control and readout. Here I discuss designs of recent near-infrared and far-red calcium and voltage indicators, compare their properties and performance, and overview their applications to spectral multiplexing and in vivo imaging. I also provide perspectives for further development.

Bilirubin Oxidation End Products (BOXes) Induce Neuronal Oxidative Stress Involving the Nrf2 Pathway

Delayed ischemic neurological deficit (DIND) is a severe complication after subarachnoid hemorrhage (SAH). Previous studies have suggested that bilirubin oxidation end products (BOXes) are probably associated with the DIND after SAH, but there is a lack of direct evidence yet even on cellular levels. In the present study, we aim to explore the potential role of BOXes and the involved mechanisms in neuronal function. We synthesized high-purity (>97%) BOX A and BOX B isomers. The pharmacokinetics showed they are permeable to the blood-brain barrier. Exposure of a moderate concentration (10 or 30 μM) of BOX A or BOX B to isolated primary cortical neurons increased the production of reactive oxygen species. In the human neuroblastoma SH-SY5Y cells, BOX A and BOX B decreased the mitochondrial membrane potential and enhanced nuclear accumulation of the protein Nrf2 implicated in oxidative injury repair. In addition, both chemicals increased the mRNA and protein expression levels of multiple antioxidant response genes including Hmox1, Gsta3, Blvrb, Gclm, and Srxn1, indicating that the antioxidant response element (ARE) transcriptional cascade driven by Nrf2 is activated. In conclusion, we demonstrated that primary cortical neurons and neuroblastoma cells undergo an adaptive response against BOX A- and BOX B-mediated oxidative stress by activation of multiple antioxidant responses, in part through the Nrf2 pathway, which provides in-depth insights into the pathophysiological mechanism of DIND after SAH or other neurological dysfunctions related to cerebral hemorrhage.

Programmed cell death protein-1 (PD-1) protects liver damage by suppressing IFN-γ expression in T cells in infants and neonatal mice

Background

Biliary atresia (BA) is a severe cholangiopathy possibly resulting from virus-induced and immune-mediated injury of the biliary system. IFN-γ, secreted from CD4⁺ Th1 cells and CD8⁺ cytotoxic T cells, is a major mediator of liver pathology. Programmed death protein-1 (PD-1) signaling suppresses T cell function. However, how PD-1 modify T cell function in BA remains incompletely understood.

Methods

Frequencies of PD-1 expressing CD4⁺ and CD8⁺ T cells were analyzed in the liver and blood from BA and control subjects. Associations of PD-1⁺CD4⁺/CD8⁺T cell abundances with liver function indices were measured. Function of PD-1 was measured by administration of an anti-PD-1 antibody in a Rhesus Rotavirus (RRV)-induced BA model. Survival, histology, direct bilirubin, liver immune cell subsets and cytokine production were analyzed.

Results

PD-1 was significantly upregulated in CD4⁺ and CD8⁺ T cells in patients with BA compared with control subjects. PD-1 expression in T cells was negatively associated with IFN-γ concentration in liver (PD-1⁺CD4⁺T cells in liver vs. IFN-γ concentration, r = − 0.25, p = 0.05; PD-1⁺CD8⁺T cells in liver vs. IFN-γ concentration, r = − 0.39, p = 0.004). Blockade of PD-1 increased IFN-γ expression in CD4⁺ T and CD8⁺ T cells (RRV vs. anti-PD-1 treated RRV mice: 11.59 ± 3.43% vs. 21.26 ± 5.32% IFN-γ⁺ in hepatic CD4⁺T cells, p = 0.0003; 9.33 ± 4.03% vs. 22.55 ± 7.47% IFN-γ⁺ in hepatic CD8⁺T cells, p = 0.0001), suppressed bilirubin production (RRV vs. anti-PD-1 treated RRV mice: 285.4 ± 47.93 vs. 229.8 ± 45.86 μmol/L total bilirubin, p = 0.01) and exacerbated liver immunopathology.

Conclusions

PD-1 plays a protective role in infants with BA by suppressing IFN-γ production in T cells. Increasing PD-1 signaling may serve as a therapeutic strategy for BA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02794-x.

Effect of Silymarin Treatment on Circulating Bilirubin and Cardiovascular Disease Risk Factors in Healthy Men: A Single-Blind, Randomized Crossover Trial

This clinical trial (ACTRN12619001296123) investigated the impact of silymarin (Legalon®) on circulating bilirubin concentration, lipid status, systemic inflammation, and antioxidant status. The study design was a randomized, placebo-controlled, single-blind crossover trial of healthy men (18-65 years), conducted at Griffith University, Gold Coast, Australia. Participants were recruited from Griffith University and were randomized to silymarin (140 mg silymarin capsules thrice daily) or placebo (3 capsules containing mannitol taken daily) for 14 days followed by a ≥4-week washout and crossover to the other arm. The main outcomes were whether silymarin treatment would increase serum bilirubin concentration by >0.29 mg/dL, change serum lipid status (cholesterol and triglycerides), inflammation (c-reactive protein), and antioxidant capacity (ferric reducing ability of plasma) compared with baseline. Silymarin consumption (n = 17) did not affect serum concentrations of unconjugated bilirubin (0.73 versus 0.67 mg/dL, P = .79), cholesterol (185 versus 189 mg/dL, P = .19), triglycerides (94.2 versus 92.3 mg/dL, P = .79), c-reactive protein (0.17 versus 0.09 mg/dL, P = .23), or antioxidant status (6.61 versus 6.67 mg Fe²⁺ /dL, P = .40). These findings challenge previous reports and manufacturer claims of hyperbilirubinemia following silymarin treatment and are critical to guiding researchers toward an effective means to mildly elevate bilirubin, which evidence suggests could protect from cardiovascular disease.

Bilirubin: A Promising Therapy for Parkinson's Disease

Following the increase in life expectancy, the prevalence of Parkinson's disease (PD) as the most common movement disorder is expected to rise. Despite the incredibly huge efforts in research to find the definitive biomarker, to date, the diagnosis of PD still relies mainly upon clinical symptoms. A wide range of treatments is available for PD, mainly alleviating the clinical symptoms. However, none of these current therapies can stop or even slow down the disease evolution. Hence, disease-modifying treatment is still a paramount unmet medical need. On the other side, bilirubin and its enzymatic machinery and precursors have offered potential benefits by targeting multiple mechanisms in chronic diseases, including PD. Nevertheless, only limited discussions are available in the context of neurological conditions, particularly in PD. Therefore, in this review, we profoundly discuss this topic to understand bilirubin's therapeutical potential in PD.

Heme oxygenase 1: a novel oncogene in multiple gynecological cancers

Heme oxygenase 1 (HO-1), also known as heat shock protein 32 (HSP32), is a stress-inducible enzyme. In the past, it was believed to participate in maintaining cell homeostasis, reducing oxidative stress damage and exerting anti-apoptotic effects. When exposed to noxious stimulation, the expression of HO-1 in the body will increase, antagonizing these oxidative stresses and protecting our bodies. Recently, many studies showed that HO-1 was also highly-expressed in multiple gynecological cancers (such as ovarian cancer, cervical cancer and endometrial cancer), suggesting that it should be closely related to cell proliferation, metastasis, immune regulation and angiogenesis as an oncogene. This review summarizes the different effects of HO-1 under normal and diseased conditions with a brief discussion of its implications on the diagnosis and treatment of gynecological cancers, aiming to provide a new clue for prevention and treatment of diseases.

Unconjugated Bilirubin Attenuates DSS-Induced Colitis Potentially via Enhancement of Bilirubin Reabsorption

Studies increasingly show that ulcerative colitis (UC) is a consequence of an imbalance between oxidative stress and antioxidant capacity. Bilirubin exerts an anti-inflammatory effect by scavenging reactive oxygen species (ROS), although the exact mechanism is not completely understood. The aim of this study was to determine the role of serum bilirubin in UC using patient data and a mouse model of dextran sodium sulfate (DSS)-induced colitis. We found that low levels of serum bilirubin correlated to a higher risk of UC in a retrospective case-control population. Pre-treatment with exogenous unconjugated bilirubin (UCB) significantly enhanced colonic bilirubin absorption in mice, and attenuated the DSS-induced body weight loss, colon shortening and histopathological damage. Mechanistically, bilirubin prevented the infiltration of inflammatory cells, and decreased the levels of myeloperoxidase and pro-inflammatory cytokines in the serum and colon. Moreover, bilirubin inhibited ROS and malondialdehyde production, scavenged superoxide anions (O₂^·−) from the colon and enhanced the total antioxidant capacity. In conclusion, exogenous UCB attenuated DSS-induced colitis by directly scavenging O₂^·− and enhancing bilirubin reabsorption in the colon via enterohepatic cycling.

Quantitative measurement of reactive oxygen species in ex vivo mouse brain slices

Evaluating redox homeostasis involves gauging the levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) directly in tissues and cells. The brain is especially metabolically active and is particularly vulnerable to excessive ROS and RNS. Here, we describe a methodology to quantitatively measure ROS in ex vivo mouse brain slices at baseline and after neural stimulation. Evaluating ROS in slices provides a more complete picture of neural redox signaling than when measured in isolated neurons or astrocytes. For complete details on the use and execution of this protocol, please refer to Vasavda et al. (2019).

Associations of Serum Liver Function Markers With Brain Structure, Function, and Perfusion in Healthy Young Adults

Background: Previous neuroimaging studies have demonstrated brain abnormalities in patients with hepatic diseases. However, the identified liver-brain associations are largely limited to disease-affected populations, and the nature and extent of such relations in healthy subjects remain unclear. We hypothesized that serum liver function markers within a normal level would affect brain properties. Method: One hundred fifty-seven healthy young adults underwent structural, resting-state functional, and arterial spin labeling MRI scans. Gray matter volume (GMV), regional homogeneity (ReHo), and cerebral blood flow (CBF) analyses were performed to assess brain structure, function, and perfusion, respectively. Peripheral venous blood samples were collected to measure serum liver function markers. Correlation analyses were conducted to test potential associations between liver function markers and brain imaging parameters. Results: First, serum proteins showed relations to brain structure characterized by higher albumin associated with increased GMV in the parahippocampal gyrus and amygdala and lower globulin and a higher albumin/globulin ratio with increased GMV in the olfactory cortex and parahippocampal gyrus. Second, serum bilirubin was linked to brain function characterized by higher bilirubin associated with increased ReHo in the precuneus, middle cingulate gyrus, inferior parietal lobule, and supramarginal gyrus and decreased ReHo in the caudate nucleus. Third, serum alanine transaminase (ALT) was related to brain perfusion characterized by higher ALT associated with increased CBF in the superior frontal gyrus and decreased CBF in the middle occipital gyrus, angular gyrus, precuneus, and middle temporal gyrus. More importantly, we found that CBF in the superior frontal gyrus was a significant mediator of the association between serum ALT level and working memory performance. Conclusion: These findings may not only expand existing knowledge about the relationship between the liver and the brain but also have clinical implications for studying brain impairments secondary to liver diseases as well as providing potential neural targets for their diagnosis and treatment.

An effective enzymatic assay for pH selectively measuring direct and total bilirubin concentration by using of CotA

In this study, we aimed to develop B. subtilis spore coat protein A (CotA) for the enzymatic determination of bilirubin. Firstly, molecular docking and oxidation kinetic analysis confirmed the feasibility of CotA for oxidizing bilirubin. Secondly, CotA showed pH-preferable oxidization performance to direct bilirubin (DB) in acidic conditions and an alkaline-catalytic oxidation capacity to total bilirubin (TB). Mechanism analysis results confirm that the conformational changes of CotA, DB and UB caused by pH changes are responsible for the selective oxidation of DB and TB by CotA. Then, CotA exhibits better structural characteristics and enzymatic performance than M. verrucaria-derived bilirubin oxidase (Mv-BOD). Besides, the strong anti-interference ability helps CotA adapt to complex catalytic environment in the detection of DB and TB. Our results prove that CotA can be used as a promising candidate bio-enzymatic detection reagent for DB and TB.

Human Plasma Metabolomics for Biomarker Discovery: Targeting the Molecular Subtypes in Breast Cancer

Simple Summary

Breast cancer is the leading cause of female cancer-related deaths worldwide. New technologies with enhanced sensitivity and specificity for early diagnosis and tailored monitoring are in critical demand. Thus, metabolomics appears to be a growing tool in order to detect molecular differences between distinct groups. In this case, an untargeted analytical approach was used to identify metabolomics differences between molecular subtypes of breast cancer in comparison with healthy matched controls. Footprints for each breast cancer subtype provided diagnostic capacities with an area under the receiver-operating characteristic curve above 0.85, which suggests that our results may represent a major advance towards the improvement of personalized medicine and precise targeted therapies for the various breast cancer phenotypes. To validate these molecular profiling as potential therapeutic strategies for the different breast cancer subtypes, further analysis and larger cohorts would be necessary in the near future.

Abstract

Purpose: The aim of this study is to identify differential metabolomic signatures in plasma samples of distinct subtypes of breast cancer patients that could be used in clinical practice as diagnostic biomarkers for these molecular phenotypes and to provide a more individualized and accurate therapeutic procedure. Methods: Untargeted LC-HRMS metabolomics approach in positive and negative electrospray ionization mode was used to analyze plasma samples from LA, LB, HER2+ and TN breast cancer patients and healthy controls in order to determine specific metabolomic profiles through univariate and multivariate statistical data analysis. Results: We tentatively identified altered metabolites displaying concentration variations among the four breast cancer molecular subtypes. We found a biomarker panel of 5 candidates in LA, 7 in LB, 5 in HER2 and 3 in TN that were able to discriminate each breast cancer subtype with a false discovery range corrected p-value < 0.05 and a fold-change cutoff value > 1.3. The model clinical value was evaluated with the AUROC, providing diagnostic capacities above 0.85. Conclusion: Our study identifies metabolic profiling differences in molecular phenotypes of breast cancer. This may represent a key step towards therapy improvement in personalized medicine and prioritization of tailored therapeutic intervention strategies.

Transkingdom interactions between Lactobacilli and hepatic mitochondria attenuate western diet-induced diabetes

Western diet (WD) is one of the major culprits of metabolic disease including type 2 diabetes (T2D) with gut microbiota playing an important role in modulating effects of the diet. Herein, we use a data-driven approach (Transkingdom Network analysis) to model host-microbiome interactions under WD to infer which members of microbiota contribute to the altered host metabolism. Interrogation of this network pointed to taxa with potential beneficial or harmful effects on host's metabolism. We then validate the functional role of the predicted bacteria in regulating metabolism and show that they act via different host pathways. Our gene expression and electron microscopy studies show that two species from Lactobacillus genus act upon mitochondria in the liver leading to the improvement of lipid metabolism. Metabolomics analyses revealed that reduced glutathione may mediate these effects. Our study identifies potential probiotic strains for T2D and provides important insights into mechanisms of their action.

Heme Degradation in Pathophysiology of and Countermeasures to Inflammation-Associated Disease

The class of tetrapyrrol "coordination complexes" called hemes are prosthetic group components of metalloproteins including hemoglobin, which provide functionality to these physiologically essential macromolecules by reversibly binding diatomic gasses, notably O₂, which complexes to ferrous (reduced/Fe(II)) iron within the heme porphyrin ring of hemoglobin in a pH- and PCO₂-dependent manner-thus allowing their transport and delivery to anatomic sites of their function. Here, pathologies associated with aberrant heme degradation are explored in the context of their underlying mechanisms and emerging medical countermeasures developed using heme oxygenase (HO), its major degradative enzyme and bioactive metabolites produced by HO activity. Tissue deposits of heme accumulate as a result of the removal of senescent or damaged erythrocytes from circulation by splenic macrophages, which destroy the cells and internal proteins, including hemoglobin, leaving free heme to accumulate, posing a significant toxicogenic challenge. In humans, HO uses NADPH as a reducing agent, along with molecular oxygen, to degrade heme into carbon monoxide (CO), free ferrous iron (FeII), which is sequestered by ferritin protein, and biliverdin, subsequently metabolized to bilirubin, a potent inhibitor of oxidative stress-mediated tissue damage. CO acts as a cellular messenger and augments vasodilation. Nevertheless, disease- or trauma-associated oxidative stressors sufficiently intense to overwhelm HO may trigger or exacerbate a wide range of diseases, including cardiovascular and neurologic syndromes. Here, strategies are described for counteracting the effects of aberrant heme degradation, with a particular focus on "bioflavonoids" as HO inducers, shown to cause amelioration of severe inflammatory diseases.

Mitochondrial oxidative function in NAFLD: Friend or foe?

Background

Mitochondrial oxidative function plays a key role in the development of non-alcoholic fatty liver disease (NAFLD) and insulin resistance (IR). Recent studies reported that fatty liver might not be a result of decreased mitochondrial fat oxidation caused by mitochondrial damage. Rather, NAFLD and IR induce an elevation in mitochondrial function that covers the increased demand for carbon intermediates and ATP caused by elevated lipogenesis and gluconeogenesis. Furthermore, mitochondria play a role in regulating hepatic insulin sensitivity and lipogenesis by modulating redox-sensitive signaling pathways.

Scope of review

We review the contradictory studies indicating that NAFLD and hyperglycemia can either increase or decrease mitochondrial oxidative capacity in the liver. We summarize mechanisms regulating mitochondrial heterogeneity inside the same cell and discuss how these mechanisms may determine the role of mitochondria in NAFLD. We further discuss the role of endogenous antioxidants in controlling mitochondrial H₂O₂ release and redox-mediated signaling. We describe the emerging concept that the subcellular location of cellular antioxidants is a key determinant of their effects on NAFLD.

Major conclusions

The balance of fat oxidation versus accumulation depends on mitochondrial fuel preference rather than ATP-synthesizing respiration. As such, therapies targeting fuel preference might be more suitable for treating NAFLD. Similarly, suppressing maladaptive antioxidants, rather than interfering with physiological mitochondrial H₂O₂-mediated signaling, may allow the maintenance of intact hepatic insulin signaling in NAFLD. Exploration of the subcellular compartmentalization of different antioxidant systems and the unique functions of specific mitochondrial subpopulations may offer new intervention points to treat NAFLD.

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Mitochondrial function has been reported to be increased or decreased in NAFLD.

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Functionally independent subpopulations of mitochondria can clarify the conundrum of these conflicting reports.

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Maladaptive antioxidants decreasing mitochondrial H₂O₂ and promoting NAFLD are discussed.

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Therapies targeting mitochondria to treat NAFLD are discussed.

Improvement of Phycocyanobilin Synthesis for Genetically Encoded Phytochrome-Based Optogenetics

Optogenetics is a powerful technique using photoresponsive proteins, and the light-inducible dimerization (LID) system, an optogenetic tool, allows to manipulate intracellular signaling pathways. One of the red/far-red responsive LID systems, phytochrome B (PhyB)-phytochrome interacting factor (PIF), has a unique property of controlling both association and dissociation by light on the second time scale, but PhyB requires a linear tetrapyrrole chromophore such as phycocyanobilin (PCB), and such chromophores are present only in higher plants and cyanobacteria. Here, we report that we further improved our previously developed PCB synthesis system (SynPCB) and successfully established a stable cell line containing a genetically encoded PhyB-PIF LID system. First, four genes responsible for PCB synthesis, namely, PcyA, HO1, Fd, and Fnr, were replaced with their counterparts derived from thermophilic cyanobacteria. Second, Fnr was truncated, followed by fusion with Fd to generate a chimeric protein, tFnr-Fd. Third, these genes were concatenated with P2A peptide cDNAs for polycistronic expression, resulting in an approximately 4-fold increase in PCB synthesis compared with the previous version. Finally, we incorporated the PhyB, PIF, and SynPCB system into drug inducible lentiviral and transposon vectors, which enabled us to induce PCB synthesis and the PhyB-PIF LID system by doxycycline treatment. These tools provide a new opportunity to advance our understanding of the causal relationship between intracellular signaling and cellular functions.

The Role of Bilirubin and the Other "Yellow Players" in Neurodegenerative Diseases

Bilirubin is a yellow endogenous derivate of the heme catabolism. Since the 1980s, it has been recognized as one of the most potent antioxidants in nature, able to counteract 10,000× higher intracellular concentrations of H2O2. In the recent years, not only bilirubin, but also its precursor biliverdin, and the enzymes involved in their productions (namely heme oxygenase and biliverdin reductase; altogether the "yellow players"-YPs) have been recognized playing a protective role in diseases characterized by a chronic prooxidant status. Based on that, there is an ongoing effort in inducing their activity as a therapeutic option. Nevertheless, the understanding of their specific contributions to pathological conditions of the central nervous system (CNS) and their role in these diseases are limited. In this review, we will focus on the most recent evidence linking the role of the YPs specifically to neurodegenerative and neurological conditions. Both the protective, as well as potentially worsening effects of the YP's activity will be discussed.

Biliverdin and bilirubin sulfonate inhibit monosodium urate induced sterile inflammation in the rat

BACKGROUND

Biliverdin, a by-product of haem catabolism, possesses potent endogenous antioxidant and anti-inflammatory properties. Bilirubin-C10-sulfonate (BRS), an active metabolite formed after enteral administration of BV in the rat, also possess antioxidant properties. Therefore, we investigated the anti-inflammatory and antioxidant activity of BV and BRS in an in vivo model of monosodium urate induced sterile inflammation.

METHODS

Subcutaneous air pouches were created on the dorsal flanks of Wistar rats (10-12 weeks of age). Prior to stimulation of the 6-day old pouch with monosodium urate (25 mg), groups were pre-treated with intraperitoneal BRS (27 mg/kg) and BV (27 mg/kg). Total and differential leukocyte counts were determined in pouch fluid aspirate at 1, 6, 12, 24 and 48 h after monosodium urate stimulation. Biliverdin (BV), BRS and unconjugated bilirubin (UCB) concentrations in the serum and pouch fluid were quantified using liquid chromatography-mass spectrometry. Pouch fluid cytokine concentrations (IL-1β, IL-1α, TNF-α, IL-17A, IL-12, GM-CSF, IL-33, IFN-γ, IL-18, IL-10, MCP-1, CXCL-1 and IL-6) were assessed after 6 h. In addition, 24 h protein carbonyl and chloramine concentrations were assessed in pouch fluid using ELISA and spectrophotometry, respectively.

RESULTS

BRS and BV significantly (p < 0.05) inhibited leukocyte (total, neutrophil and macrophage) infiltration into the pouch fluid from 6 to 48 h. For example, after 6 h neutrophil counts decreased following BRS (0.32 ± 0.11 × 10⁶ cells mL^-1) and BV (0.17 ± 0.03 × 10⁶ cells mL^-1) compared to MSU only (3.51 ± 1.07 × 10⁶ cells mL^-1). Both BV and BRS significantly (p < 0.05) reduced pouch GM-CSF (BV: 5.8 ± 1.2 pg mL^-1, BRS: 6.9 ± 1.5 pg mL^-1 vs MSU only: 13.0 ± 1.9 pg mL^-1) and MCP-1 concentrations at 6 h (BV: 1804 ± 269 pg mL^-1, BRS: 7927 ± 2668 pg mL^-1 vs MSU only: 17,290 ± 4503 pg ml^-1), whilst BV additionally inhibited IL-6 (4354 ± 977 pg mL^-1 vs MSU only: 25,070 ± 5178 pg mL^-1) and IL-18 (17.6 ± 2.0 pg mL^-1 vs MSU only: 81.5 ± 19.9 pg mL^-1) concentrations at 6 h (p < 0.05). Despite these differences, no change in pouch chloramine or protein carbonyl concentrations occurred at 24 h (p > 0.05). Serum BV concentrations rapidly diminished over 6 h, however, BRS was readily detected in the serum over 48 h, and in pouch fluid over 12 h.

CONCLUSIONS

This study is the first to elucidate anti-inflammatory activity of BRS and the efficacy of BV administration in a model of gouty inflammation. Reduced leukocyte infiltration and cytokine production in response to sterile inflammation further support the importance of these molecules in physiology and their therapeutic potential in sterile inflammation.

BVR-A Deficiency Leads to Autophagy Impairment through the Dysregulation of AMPK/mTOR Axis in the Brain-Implications for Neurodegeneration

Biliverdin reductase-A (BVR-A) impairment is associated with increased accumulation of oxidatively-damaged proteins along with the impairment of autophagy in the brain during neurodegenerative disorders. Reduced autophagy inhibits the clearance of misfolded proteins, which then form neurotoxic aggregates promoting neuronal death. The aim of our study was to clarify the role for BVR-A in the regulation of the mTOR/autophagy axis by evaluating age-associated changes (2, 6 and 11 months) in cerebral cortex samples collected from BVR-A knock-out (BVR-A^−/−) and wild-type (WT) mice. Our results show that BVR-A deficiency leads to the accumulation of oxidatively-damaged proteins along with mTOR hyper-activation in the cortex. This process starts in juvenile mice and persists with aging. mTOR hyper-activation is associated with the impairment of autophagy as highlighted by reduced levels of Beclin-1, LC3β, LC3II/I ratio, Atg5–Atg12 complex and Atg7 in the cortex of BVR-A^−/− mice. Furthermore, we have identified the dysregulation of AMP-activated protein kinase (AMPK) as a critical event driving mTOR hyper-activation in the absence of BVR-A. Overall, our results suggest that BVR-A is a new player in the regulation of autophagy, which may be targeted to arrive at novel therapeutics for diseases involving impaired autophagy.