Bilirubin and brain: A pharmacological approach

Utilizing stimuli-responsive nanoparticles to deliver and enhance the anti-tumor effects of bilirubin

Bilirubin (BR) is among the most potent endogenous antioxidants that originates from the heme catabolic pathway. Despite being considered as a dangerous and cytotoxic waste product at high concentrations, BR has potent antioxidant effects leading to the reduction of oxidative stress and inflammation, which play an important role in the development and progression of cancer. The purpose of this study is to introduce PEGylated BR nanoparticles (NPs), themselves or in combination with other anti-cancer agents. BR is effective when loaded into various nanoparticles and used in cancer therapy. Interestingly, BRNPs can be manipulated to create stimuli-responsive carriers providing a sustained and controlled, as well as on-demand, release of drug in response to internal or external factors such as reactive oxygen species, glutathione, light, enzymes, and acidic pH. This review suggests that BRNPs have the potential as tumor microenvironment-responsive delivery systems for effective targeting of various types of cancers.

Inhibition of human UDP-glucuronosyltransferase (UGT) enzymes by darolutamide: Prediction of in vivo drug-drug interactions

Darolutamide is a potent second-generation, selective nonsteroidal androgen receptor inhibitor (ARI), which has been approved by the US Food and Drug Administration (FDA) in treating castrate-resistant, non-metastatic prostate cancer (nmCRPC). Whether darolutamide affects the activity of UDP-glucuronosyltransferases (UGTs) is unknown. The purpose of the present study is to evaluate the inhibitory effect of darolutamide on recombinant human UGTs and pooled human liver microsomes (HLMs), and explore the potential for drug-drug interactions (DDIs) mediated by darolutamide through UGTs inhibition. The product formation rate of UGTs substrates with or without darolutamide was determined by HPLC or UPLC-MS/MS to estimate the inhibitory effect and inhibition modes of darolutamide on UGTs were evaluated by using the inhibition kinetics experiments. The results showed that 100 μM darolutamide exhibited inhibitory effects on most of the 12 UGTs tested. Inhibition kinetic studies of the enzyme revealed that darolutamide noncompetitively inhibited UGT1A1 and competitively inhibited UGT1A7 and 2B15, with the Ki of 14.75 ± 0.78 μM, 14.05 ± 0.42 μM, and 6.60 ± 0.08 μM, respectively. In particular, it also potently inhibited SN-38, the active metabolite of irinotecan, glucuronidation in HLMs with an IC50 value of 3.84 ± 0.46 μM. In addition, the in vitro-in vivo extrapolation (IVIVE) method was used to quantitatively predict the risk of darolutamide-mediated DDI via inhibiting UGTs. The prediction results showed that darolutamide may increase the risk of DDIs when administered in combination with substrates of UGT1A1, UGT1A7, or UGT2B15. Therefore, the combined administration of darolutamide and drugs metabolized by the above UGTs should be used with caution to avoid the occurrence of potential DDIs.

The U-shaped association between serum direct bilirubin and incident mild cognitive impairment in hemodialysis patients: a multicenter study

BACKGROUND

Previous studies have suggested an association between low serum bilirubin concentrations and increased risk of cognitive impairment. This study aimed to explore the association and dose-response relationship between serum direct bilirubin (DBIL) concentrations and mild cognitive impairment (MCI) among hemodialysis patients.

METHODS

This is a multicenter cross-sectional study with patients undergoing hemodialysis from 22 dialysis centers in Guizhou Province, China. The outcome was mild cognitive impairment (MCI), measured with a Mini-Mental State Examination. The association and dose-response relationship between serum DBIL and MCI incidence were examined using multivariate logistic regression analysis, restricted cubic spline, and subgroup analysis to explore the association of serum DBIL concentrations with MCI.

RESULTS

Of the 4223 enrolled patients (mean age 55.2 ± 15.3 years, 60.4% males), 1187 (28.1%) had MCI. Serum DBIL of 0.10-1.67umol/L [multivariable-adjusted odds ratios (OR) 1.32, 95% confidence interval (CI): 1.08-1.60, P = 0.005], 2.31-3.20umol/L (OR = 1.22, 95%CI: 1.00-1.49, P = 0.047), and > 3.21umol/L (OR = 1.32, 95%CI: 1.08-1.61, P = 0.006) had increased risk of MCI compared with 1.68-2.30umol/L. The dose-response analysis between serum DBIL and MCI showed a U-shaped relationship (P for non-linearity = 0.009), and the serum DBIL concentrations with the lowest risk of MCI was 2.01umol/L. As the serum DBIL concentrations were lower than the reference, the risk of MCI decreased by 49% per standard deviation (SD) increase in serum DBIL (OR = 0.51, 95%CI: 0.29-0.89, P < 0.001); when the concentration exceeds 2.01umol/L, a rise per SD increased the risk of MCI by 9% (OR = 1.09, 95%CI:1.01-1.17, P < 0.001).

CONCLUSION

Our findings suggest a U-shaped association between serum DBIL and MCI among hemodialysis patients.

Exploring the inverse relationship between serum total bilirubin and systemic immune-inflammation index: insights from NHANES data (2009-2018)

BACKGROUND

Bilirubin is known for its multifaceted attributes, including antioxidant, anti-inflammatory, immunomodulatory, and antiapoptotic properties. The systemic immune-inflammation index (SII) is a recent marker that reflects the balance between inflammation and immune response. Despite the wealth of information available on bilirubin's diverse functionalities, the potential correlation between the total bilirubin (TB) levels and SII has not been investigated so far.

METHODS

Leveraging data from the National Health and Nutrition Examination Survey spanning 2009-2018, the TB levels were categorized using tertiles. Employing the chi-squared test with Rao and Scott's second-order correction and Spearman's rank correlation analysis, the association between TB and SII was examined. The potential nonlinearities between TB and SII were evaluated using restricted cubic spline (RCS) analysis. Weighted linear regression, adjusted for covariates, was used to explore the correlation between TB and SII, with further subgroup analyses.

RESULTS

A total of 16,858 participants were included, and the findings revealed significant SII variations across TB tertiles (p < 0.001). The third tertile (Q3) exhibited the lowest SII level at 495.73 (295.00) 1000 cells/µL. Spearman rank correlation disclosed the negative association between TB and SII. RCS analysis exposed the lack of statistically significant variations in the nonlinear relationship (p > 0.05), thereby providing support for a linear relationship. Weighted linear regression analysis underscored the negative correlation between TB and SII (β 95% CI - 3.9 [- 5.0 to  - 2.9], p < 0.001). The increase in the TB levels is associated with a significant linear trend toward decreasing SII. After controlling for relative covariates, this negative correlation increased (p < 0.001). Subgroup analysis confirmed the significant negative TB-SII association.

CONCLUSION

A notable negative correlation between TB and SII implies the potential protective effects of bilirubin in inflammation-related diseases.

Bilirubin Distribution in Plants at the Subcellular and Tissue Levels

In heterotrophs, heme degradation produces bilirubin, a tetrapyrrole compound that has antioxidant activity. In plants, heme is degraded in plastids and is believed to be converted to phytochromobilin rather than bilirubin. Recently, we used the bilirubin-inducible fluorescent protein UnaG to reveal that plants produce bilirubin via a non-enzymatic reaction with NADPH. In the present study, we used an UnaG-based live imaging system to visualize bilirubin accumulation in Arabidopsis thaliana and Nicotiana benthamiana at the organelle and tissue levels. In chloroplasts, bilirubin preferentially accumulated in the stroma, and the stromal bilirubin level increased upon dark treatment. Investigation of intracellular bilirubin distribution in leaves and roots showed that it accumulated mostly in plastids, with low levels detected in the cytosol and other organelles, such as peroxisomes, mitochondria and the endoplasmic reticulum. A treatment that increased bilirubin production in chloroplasts decreased the bilirubin level in peroxisomes, implying that a bilirubin precursor is transported between the two organelles. At the cell and tissue levels, bilirubin showed substantial accumulation in the root elongation region but little or none in the root cap and guard cells. Intermediate bilirubin accumulation was observed in other shoot and root tissues, with lower levels in shoot tissues. Our data revealed the distribution of bilirubin in plants, which has implications for the transport and physiological function of tetrapyrroles.

Association between bilirubin and chronic kidney disease in hypertensive patients: The China hypertension registry study

Limited data exists on the association between Direct bilirubin (DBIL) and Indirect bilirubin (IBIL) with the risk of chronic kidney disease (CKD) among patients with hypertension. This study aimed to assess the relationship between DBIL and IBIL with the risk of CKD in a cohort of Chinese adults diagnosed with hypertension. This study included 14 182 Chinese patients with hypertension between the ages of 27 and 96. CKD, the outcome variable, was defined by an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 . The study employed multivariate linear and multivariate logistic regression analysis to evaluate the correlation between DBIL and IBIL with the risk of CKD. The prevalence of CKD in the study population was 9.77%. Multivariate logistic regression analysis showed that the increase in DBIL (OR: 0.66; 95% CI: 0.61, 0.71) and IBIL (OR: 0.75; 95% CI: 0.71, 0.81) were independently and negatively correlated with CKD. Further analyses using a restricted cubic spline (smooth-fitting curve) confirmed the linearly negative association between DBIL and IBIL with the risk of CKD. The subgroup analysis showed that the correlation between IBIL and CKD was stronger among men and populations <65 years of age (p for interaction <.05). DBIL and IBIL were independently and negatively associated with CKD. Furthermore, the correlation between DBIL and IBIL with CKD in the hypertensive population is more significant in those under 65 years of age. These findings may inform future strategies for the management of CKD.

Heme oxygenase-1: The roles of both good and evil in neurodegenerative diseases

Heme oxygenase-1 (HO-1) is the only way for cells to decompose heme. It can cleave heme to produce carbon monoxide (CO), ferrous iron (Fe2+ ), and biliverdin (BV). BV is reduced to bilirubin (BR) by biliverdin reductase(BVR). In previous studies, HO-1 was considered to have protective effects because of its anti-inflammatory, anti-apoptosis, and antiproliferation functions. However, emerging experimental studies have found that the metabolites derived from HO-1 can cause increase iin intracellular oxidative stress, mitochondrial damage, iron death, and autophagy. Because of its particularity, it is very meaningful to understand its exact mechanism. In this review, we summarized the protective and toxic effects of HO-1, its potential mechanism, its role in neurodegenerative diseases and related drug research. This knowledge may be beneficial to the development of new therapies for neurodegenerative diseases and is crucial to the development of new therapeutic strategies and biomarkers.

Biliverdin as a disease-modifying agent: An integrated viewpoint

Biliverdin is one of the three by-products of heme oxygenase (HO) activity, the others being ferrous iron and carbon monoxide. Under physiological conditions, once formed in the cell, BV is reduced to bilirubin (BR) by the biliverdin reductase (BVR). However, if BVR is inhibited by either genetic variants, as occurs in the Inuit ethnicity, or dioxin intoxication, BV accumulates in cells giving rise to a clinical syndrome known as green jaundice. Preclinical studies have demonstrated that BV not only has a direct antioxidant effect by scavenging free radicals, but also targets many signal transduction pathways, such as BVR, soluble guanylyl cyclase, and the aryl hydrocarbon receptor. Through these direct and indirect mechanisms, BV has shown beneficial roles in ischemia/reperfusion-related diseases, inflammatory diseases, graft-versus-host disease, viral infections and cancer. Unfortunately, no clinical data are available to confirm these potential therapeutic effects and the kinetics of exogenous BV in humans is unknown. These limitations have so far excluded the possibility of transforming BV from a mere by-product of heme degradation into a disease-modifying agent. A closer collaboration between basic and clinical researchers would be advantageous to overcome these issues and promote translational research on BV in free radical-induced diseases.

A Biomimetic Nanoparticle Exerting Protection against Acute Liver Failure by Suppressing CYP2E1 Activity and Scavenging Excessive ROS

Acute liver failure (ALF) is a severe liver disease caused by many reasons. One of them is the overdosed acetaminophen (APAP), which is metabolized into N-acetyl-p-benzoquinone imine (NAPQI), an excessive toxic metabolite, by CYP2E1, resulting in excessive reactive oxygen species (ROS), exhausted glutathione (GSH), and thereafter hepatocyte necrosis. N-acetylcysteine is the Food and Drug Administration-approved drug for detoxification of APAP, but it has limited clinical application due to the short therapeutic time window and concentration-related adverse effects. In this study, a carrier-free and bilirubin dotted nanoparticle (B/BG@N) is developed, which is formed using bilirubin and 18β-Glycyrrhetinic acid, and bovine serum albumin (BSA) is then adsorbed to mimic the in vivo behavior of the conjugated bilirubin for hitchhiking. The results demonstrate that B/BG@N can effectively reduce the production of NAPQI as well as exhibit antioxidant effects against intracellular oxidative stress via regulating the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signal axis and reducing the production of inflammatory factors. In vivo study shows that B/BG@N can effectively improve the clinical symptom of the mice model. This study suggests that B/BG@N own increases circulation half-life, improves accumulation in the liver, and dual detoxification, providing a promising strategy for clinical ALF treatment.

Bilirubin is produced nonenzymatically in plants to maintain chloroplast redox status

Bilirubin, a potent antioxidant, is a product of heme catabolism in heterotrophs. Heterotrophs mitigate oxidative stress resulting from free heme by catabolism into bilirubin via biliverdin. Although plants also convert heme to biliverdin, they are generally thought to be incapable of producing bilirubin because they lack biliverdin reductase, the enzyme responsible for bilirubin biosynthesis in heterotrophs. Here, we demonstrate that bilirubin is produced in plant chloroplasts. Live-cell imaging using the bilirubin-dependent fluorescent protein UnaG revealed that bilirubin accumulated in chloroplasts. In vitro, bilirubin was produced nonenzymatically through a reaction between biliverdin and reduced form of nicotinamide adenine dinucleotide phosphate at concentrations comparable to those in chloroplasts. In addition, increased bilirubin production led to lower reactive oxygen species levels in chloroplasts. Our data refute the generally accepted pathway of heme degradation in plants and suggest that bilirubin contributes to the maintenance of redox status in chloroplasts.

A nomogram model for assessing predictors and prognosis of postoperative delirium in patients receiving acute type A aortic dissection surgery

BACKGROUND

Postoperative delirium (POD) complicates the postoperative course. There is limited information on POD-related risk factors (RFs) and prognosis in patients with acute type A aortic dissection (ATAAD) after modified triple-branched stent graft implantation (MTBSG) surgery.

METHODS

We retrospectively examined consecutive ATAAD patients who received MTBSG surgery in our hospital between January 2013 and December 2019. We employed univariate and multivariate analyses to identify stand-alone RFs for POD. A nomogram was next generated to estimate POD occurrence. The primary outcome was the development of POD, and the secondary outcomes were intensive care unit (ICU) and hospital stays, hospitalization costs, and in-hospital and follow-up mortality.

RESULTS

We selected 692 patients, of whom 220 experienced POD (31.8%). Based on our analysis, the following factors enhanced the likelihood of POD development: alcohol consumption (p < 0.001), acute physiology and chronic health evaluation II score (p = 0.023), serum total bilirubin (p = 0.007), stage 3 acute kidney injury (p < 0.001), serum interleukin-6 (p = 0.031), post-operative analgesics usage (p = 0.015), and ventilation duration (p = 0.008). POD patients had significantly longer ventilator times (p = 0.003), ICU stays (p < 0.001), and hospital stays (p = 0.038), together with increased hospitalization costs (p < 0.001) and in-hospital mortality (p = 0.019). However, POD was not a RF for mortality during follow-up (log-rank p = 0.611).

CONCLUSIONS

We demonstrated a strong link between POD and poor prognosis in ATAAD patients. We also constructed a prognosis estimator model which will benefit early management guidance to minimize the incidence of POD.

The impact of heme oxygenase-2 on pharmacological research: A bibliometric analysis and beyond

Heme oxygenase (HO-2) is an enzyme mainly involved in the physiologic turnover of heme and intracellular gas sensing, and it is very abundant in the brain, testes, kidneys and vessels. Since 1990, when HO-2 was discovered, the scientific community has underestimated the role of this protein in health and disease, as attested by the small amount of articles published and citations received. One of the reason that have contributed to the lack of interest in HO-2 was the difficulty in upregulating or inhibiting this enzyme. However, over the last 10 years, novel HO-2 agonists and antagonists have been synthesized, and the availability of these pharmacological tools should increase the appeal of HO-2 as drug target. In particular, these agonists and antagonists could help explain some controversial aspects, such as the neuroprotective versus neurotoxic roles of HO-2 in cerebrovascular diseases. Furthermore, the discovery of HO-2 genetic variants and their involvement in Parkinson's disease, in particular in males, opens new avenues for pharmacogenetic studies in gender medicine.

Causal relationships of neonatal jaundice, direct bilirubin and indirect bilirubin with autism spectrum disorder: A two-sample Mendelian randomization analysis

Background

Multiple systematic reviews and meta-analyses have examined the association between neonatal jaundice and autism spectrum disorder (ASD) risk, but their results have been inconsistent. This may be because the included observational studies could not adjust for all potential confounders. Mendelian randomization study can overcome this drawback and explore the causal relationship between the both.

Methods

We used the data of neonatal jaundice, direct bilirubin (DBIL), indirect bilirubin (IBIL), and ASD collected by genome-wide association study (GWAS) to evaluate the effects of neonatal jaundice, DBIL and IBIL on ASD by using a two-sample Mendelian randomized (MR). The inverse variance-weighted method (IVW) was the main method of MR analysis in this study. Weighted median method, MR-Egger regression and mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) test were used for sensitivity analysis.

Results

There was no evidence of an effect of neonatal jaundice (OR, 1.002, 95% CI, 0.977-1.027), DBIL (OR, 0.970, 95% CI, 0.884-1.064) and IBIL (OR, 1.074, 95% CI, 0.882-1.308) on ASD risk by IVW test. In the weighted median method, MR-Egger regression and leave-one-out analysis, the results were robust and no heterogeneity or pleiotropy was observed.

Conclusions

We found that neonatal jaundice, DBIL and IBIL were not associated with ASD in this study. However, this paper did not explore the effect of severity and duration of jaundice on ASD in different ethnic populations, which may require further research.

Neuroprotective potential of curcuminoids in modulating Alzheimer's Disease via multiple signaling pathways

Alzheimer's disease (AD) is a progressive and frequent neurodegenerative disease of elderly people. In the 21st century, owing to the increasing prevalence of AD, there is a crucial need for finding better and effective pharmacotherapeutic approaches. This review article demonstrated the various sources and possible metabolic pathways of curcuminoids obtained from Curcuma longa herb, to prevent and treat AD but the information related to the metabolic fate of curcuminoids is deficient. Different in vitro and in vivo research studies demonstrating the mechanisms by which curcuminoids attenuated AD have been summarized. Administration of curcuminoids has been indicated to inhibit hyperphosphorylation of tau protein, deposition, and oligomerization of amyloid beta plaques in several AD models. Curcuminoids also chelate metals and form complexes, have antioxidant properties, mediates neuroinflammatory signaling pathways by modifying microglial cells activity, inhibit acetylcholinesterase activities and also modulates other associated signaling pathways including insulin signaling pathways and heme-oxygenase pathway. Briefly curcuminoids exhibit the capability to be more productive and efficacious compared to many recent treatments due to their antioxidant, delayed neuron degeneration and anti-inflammatory potential. Although their effectiveness as a curative agent is considered to be reduced due to their low bioavailability, If the issue of curcuminoids' low bioavailability is resolved then curcuminoid-based medications are hopefully on the horizon against AD.

The brain heme oxygenase/biliverdin reductase system as a target in drug research and development

INTRODUCTION

The heme oxygenase/biliverdin reductase (HO/BVR) system is involved in heme metabolism. The inducible isoform of HO (HO-1) and BVR both exert cytoprotective effects by enhancing cell stress response. In this context, some xenobiotics, which target HO-1, including herbal products, behave as neuroprotectants in several experimental models of neurodegeneration. Despite this, no drug having either HO-1 or BVR as a main target is currently available.

AREAS COVERED

After a description of the brain HO/BVR system, the paper analyzes the main classes of drugs acting on the nervous system, with HO as second-level target, and their neuroprotective potential. Finally, the difficulties that exist for the development of drugs acting on HO/BVR and the possible ways to overcome these hurdles are examined.

EXPERT OPINION

Although the limited clinical evidence has restricted the translational research on the HO/BVR system, mainly because of the dual nature of its by-products, there has been growing interest in the therapeutic potential of these enzymes. Scientists should boost the translational research on the HO/BVR system which could be supported by the significant evidence provided by preclinical studies.

The effects of clofibrate on neonatal jaundice: A systematic review

Background:

Neonatal jaundice is a prevalent disease that causes many complications, including kernicterus and even death. Previous studies have shown that clofibrate as an aryloxy isobutyric acid derivate can be effectively applied for the treatment of neonatal jaundice. Thus, this review was carried out to investigate the effects and mechanism of action of clofibrate on neonatal jaundice.

Methods:

The keywords such as “Clofibrate” in combination with “Neonatal jaundice” or “Neonatal hyperbilirubinemia” or “Newborn Jaundice” were used to search for relevant publications indexed in the Institute for Scientific Information (ISI), Scopus, PubMed, and Google Scholar databases. Finally, after reviewing the studies, 24 papers were included in this study.

Results:

Results showed that the processes of albumin-bound bilirubin transfer to the hepatocytes, hepatic uptake, and storage via ligandin, hepatic conjugation via uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1), conjugation into the bile via MRP2 represent the main action mechanism of clofibrate that turns it into the bilirubin conjugates and expels it from the bile. Besides, clofibrate has been shown to reduce the level of Total Serum Bilirubin (TSB) in infants even at a dosage of 25 mg/kg without leaving side effects.

Conclusions:

The results of this review revealed that clofibrate effectively reduces TSB in short-term usage and can even have a promising effect at the dosage of 25 mg/kg in full-term infants. Most studies have shown this property over a short period in term infants, and there is no evidence about long-term usage in this regard.

Serum Total Bilirubin Level Is Associated With Hospital Mortality Rate in Adult Critically Ill Patients: A Retrospective Study

Background: Serum bilirubin level has been suggested to be associated with mortality for patients with severe sepsis. This study aimed to investigate the association of serum total bilirubin level with hospital mortality rate in adult critically ill patients.

Method: Data were extracted from the Medical Information Mart for Intensive Care-III (MIMIC-III) database. Patients with measured serum total bilirubin levels that recorded within 24 h after admission were involved in this study. Association of serum total bilirubin level and hospital mortality rate was assessed using logistic regression analysis. Propensity score-matching (PSM) was used to minimize differences between different groups.

Results: A total of 12,035 critically ill patients were herein involved. In patients with serum total bilirubin level ≥ 2 mg/dL, the hospital mortality rate was 31.9% compared with 17.0% for patients with serum total bilirubin level < 2 mg/dL (546/1714 vs. 1750/10321, P < 0.001). The results of multivariable logistic regression analysis showed that the odds ratio of mortality in patients with serum total bilirubin level ≥ 2 mg/dL was 1.654 [95% confidence interval (CI): 1.307, 2.093, P < 0.001]. After propensity score matching, in patients with serum total bilirubin level ≥ 2 mg/dL, the weighted hospital mortality rate was 32.2% compared with 24.8% for patients with serum total bilirubin level < 2 mg/dL, P = 0.001).

Conclusions: Serum total bilirubin concentration was found to be independently associated with hospital mortality rate in adult critically ill patients.

Biliverdin reductase as a target in drug research and development: Facts and hypotheses

Biliverdin reductase-A (BVR) catalyzes the reduction of heme-derived biliverdin into bilirubin, this latter being a powerful endogenous free radical scavenger. Furthermore, BVR is also endowed with both serine/threonine/tyrosine kinase and scaffold activities, through which it interacts with the insulin receptor kinase, conventional and atypical protein kinase C isoforms, mitogen-activated protein kinases as well as the phosphatidylinositol-3 kinase/Akt system. By regulating this complex array of signal transduction pathways, BVR is involved in the pathogenesis of neurodegenerative, metabolic, cardiovascular and immune-inflammatory diseases as well as in cancer. In addition, both BVR and BVR-B, this latter being an alternate isozyme predominant during fetal development but sometimes detectable through adulthood, have been studied as peripheral biomarkers for an early detection of Alzheimer's disease, atherosclerosis and some types of cancer. However, despite these interesting lines of evidence, to date BVR has not been considered as an appealing drug target. Only limited evidence supports the neuroprotective effects of atorvastatin and ferulic acid through BVR regulation in the aged canine brain and human neuroblastoma cells, whereas interesting results have been reported regarding the use of BVR-based peptides in preclinical models of cardiac diseases and cancer.

UGT1A1 dysfunction increases liver burden and aggravates hepatocyte damage caused by long-term bilirubin metabolism disorder

UGT1A1 is the only enzyme that can metabolize bilirubin, and its encoding gene is frequently mutated. UGT1A1*6 (G71R) is a common mutant in Asia which leads to the decrease of UGT1A1 activity and abnormal bilirubin metabolism. However, it is not clear whether low UGT1A1 activity-induced bilirubin metabolism disorder increases hepatocyte fragility. ugt1a^+/- mice were used to simulate the UGT1A1*6 (G71R) population. Under the same CCl₄ induction condition, ugt1a^+/- mice showed severer liver damage and fibrosis, indicating that ugt1a1 dysfunction increased liver burden and aggravated hepatocyte damage. In the animal experiment with a continuous intraperitoneal injection of bilirubin, the ugt1a^+/- mice livers had more serious unconjugated bilirubin accumulation. The accumulated bilirubin leads to hyperphosphorylation of IκB-α, Ikk-β, and p65 and a significant increase of inflammatory factor. The α-SMA and Collagen I proteins markedly up-regulated in the ugt1a^+/- mice livers. Immunofluorescence and confocal microscopy showed that hepatic stellate cells and Kupffer cells were activated in ugt1a^+/- mice. Comprehensive results show that there was a crosstalk relationship between low UGT1A1 activity-bilirubin-liver damage. Furthermore, cell experiments confirmed that unconjugated bilirubin activated the NF-κB pathway and induced DNA damage in hepatocytes, leading to the significant increase of inflammatory factors. UGT1A1 knockdown in hepatocytes aggravated the toxicity of unconjugated bilirubin. Conversely, overexpression of UGT1A1 had a protective effect on hepatocytes. Finally, Schisandrin B, an active ingredient with hepatoprotective effects, extracted from a traditional Chinese medicinal herb, which could protect the liver from bilirubin metabolism disorders caused by ugt1a1 deficiency by downregulating p65 phosphorylation, inhibiting Kupffer cells, reducing inflammation levels. Our data clarified the mechanism of liver vulnerability caused by cross-talk between low UGT1A1 activity bilirubin, and provided a reference for individualized prevention of liver fragility in Gilbert's syndrome.

Heme oxygenase-1 modulation: A potential therapeutic target for COVID-19 and associated complications

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to infect hundred thousands of people every day worldwide. Since it is a novel virus, research continues to update the possible therapeutic targets when new evidence regarding COVID-19 are gathered. This article presents an evidence-based hypothesis that activating the heme oxygenase-1 (HO-1) pathway is a potential target for COVID-19. Interferons (IFNs) have broad-spectrum antiviral activity including against SARS-CoV-2. Induction of HO-1 and increase in the heme catabolism end-product confer antiviral activity. IFN activation results in inhibition of viral replication in various viral infections. COVID-19 induced inflammation as well as acute respiratory distress syndrome (ARDS), and coagulopathies are now known major causes of mortality. A protective role of HO-1 induction in inflammation, inflammation-induced coagulation, and ARDS has been reported. Based on an association of HO-1 promoter polymorphisms and disease severity, we propose an evaluation of the status of these polymorphisms in COVID-19 patients who become severely ill. If an association is established, it might be helpful in identifying patients at high risk. Hence, we hypothesize that HO-1 pathway activation could be a therapeutic strategy against COVID-19 and associated complications.

Targeting NRF2 to suppress ferroptosis in brain injury

Brain injury is accompanied by serious iron metabolism disorder and oxidative stress. As a novel form of regulated cell death (RCD) depending on lipid peroxidation caused by iron overload, ferroptosis (FPT) further aggravates brain injury, which is different from apoptosis, autophagy and other traditional cell death in terms of biochemistry, morphology and genetics. Noteworthy, transcriptional regulator NRF2 plays a key role in the cell antioxidant system, and many genes related to FPT are under the control of NRF2, including genes for iron regulation, thiol-dependent antioxidant system, enzymatic detoxification of RCS and carbonyls, NADPH regeneration and ROS sources from mitochondria or extra-mitochondria, which place NRF2 in the key position of regulating the ferroptotic death. Importantly, NRF2 can reduce iron load and resist FPT. In the future, it is expected to open up a new way to treat brain injury by targeting NRF2 to alleviate FPT in brain.

Radioprotective effect of chloropyllin, protoporphyrin-IX and bilirubin compared with amifostine® in Drosophila melanogaster

The identification of substances that prevent or minimize the detrimental effects of ionizing radiation is an essential undertaking. The aim of this paper was to evaluate and compare the radioprotective potential of chlorophyllin, protoporphyrin and bilirubin, with amifostine®, an US Food & Drug Administration approved radioprotector Using the somatic mutation and recombination assay in the Drosophila melanogaster wing, it was found that pretreatment (1-9 h) with any of the porphyrins or amifostine® alone, did not affect the larva-adult viability or the basal frequency of mutation. However, they were associated with significant reductions in frequency of somatic mutation and recombination compared with the gamma-irradiated (20 Gy) control as follows: bilirubin (69.3 %)> chlorophyllin (40.0 %)> protoporphyrin (39.0 %)> amifostine® (19.7 %). Bilirubin also caused a 16 % increase in larva-adult viability with 3 h of pretreatment respect to percentage induced in 20 Gy control group. Whilst amifostine® was associated with lower genetic damage after pre-treatment of 1 and 3 h, this did not attain significance. These findings suggest that the tested porphyrins may have some potential as radioprotectant agents.

Nonlinear relationship between serum total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation

Objective

This study aimed to examine the relationship between total bilirubin levels and initial ischemic stroke in patients with non-valvular atrial fibrillation.

Methods

This was a retrospective study. Atrial fibrillation was diagnosed by 24-hour Holter electrocardiography and serum total bilirubin levels were divided into quintiles. Ischemic stroke was diagnosed by symptoms, signs, and a medical image examination. The multivariate Cox proportional hazards model and survival analysis were used to estimate the association of total bilirubin with initial ischemic stroke.

Results

We studied 316 patients with non-valvular atrial fibrillation. During follow-up, there were 42 (13.29%) first ischemic strokes. After multivariate adjustment, for each 1 µmol/L increase in total bilirubin, the risk of first ischemic stroke increased by 4% (95% confidence interval [CI]: 1.01, 1.07). When using the first quintile as the reference, from the second to fifth quintiles, the risks of first ischemic stroke were 0.52 (95% CI: 0.17, 1.65), 0.23 (95% CI: 0.06, 0.87), 0.92 (95% CI: 0.32, 2.67), and 1.33 (95% CI: 1.09, 4.41), respectively. The optimal cut-off point of total bilirubin for the lowest risk of ischemic stroke was 17.0 µmol/L.

Conclusions

Total bilirubin levels are nonlinearly associated with initial ischemic stroke in patients with non-valvular atrial fibrillation.

Celecoxib Exerts Neuroprotective Effects in β-Amyloid-Treated SH-SY5Y Cells Through the Regulation of Heme Oxygenase-1: Novel Insights for an Old Drug

The formation and aggregation of amyloid-β-peptide (Aβ) into soluble and insoluble species represent the pathological hallmarks of Alzheimer’s disease (AD). Over the last few years, however, soluble Aβ (sAβ) prevailed over fibrillar Aβ (fAβ) as determinant of neurotoxicity. One of the main therapeutic strategies for challenging neurodegeneration is to fight against neuroinflammation and prevent free radical-induced damage: in this light, the heme oxygenase/biliverdin reductase (HO/BVR) system is considered a promising drug target. The aim of this work was to investigate whether or not celecoxib (CXB), a selective inhibitor of the pro-inflammatory cyclooxygenase-2, modulates the HO/BVR system and prevents lipid peroxidation in SH-SY5Y neuroblastoma cells. Both sAβ (6.25–50 nM) and fAβ (1.25–50 nM) dose-dependently over-expressed inducible HO (HO-1) after 24 h of incubation, reaching statistical significance at 25 and 6.25 nM, respectively. Interestingly, CXB (1–10 μM, for 1 h) further enhanced Aβ-induced HO-1 expression through the nuclear translocation of the transcriptional factor Nrf2. Furthermore, 10 μM CXB counteracted the Aβ-induced ROS production with a mechanism fully dependent on HO-1 up-regulation; nevertheless, 10 μM CXB significantly counteracted only 25 nM sAβ-induced lipid peroxidation damage in SH-SY5Y neurons by modulating HO-1. Both carbon monoxide (CORM-2, 50 nM) and bilirubin (50 nM) significantly prevented ROS production in Aβ-treated neurons and favored both the slowdown of the growth rate of Aβ oligomers and the decrease in oligomer/fibril final size. In conclusion, these results suggest a novel mechanism through which CXB is neuroprotective in subjects with early AD or mild cognitive impairment.

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.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Baicalin Suppresses Bilirubin-Induced Apoptosis and Inflammation by Regulating p38 Mitogen-Activated Protein Kinases (MAPK) Signaling in Neonatal Neurons

Background

Hyperbilirubinemia is associated with central nervous system damage in preterm neonates due to the neurotoxicity of bilirubin. This study explored the possible mechanisms of bilirubin’s neurotoxicity, and the protective effect of baicalin (BAI) was also investigated.

Material/Methods

Isolated neonatal rat hippocampal neurons were exposed to free bilirubin (Bf). BAI was used to treat these neurons. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the cell viability. Terminal deoxynucleotidyl transferase-dUTP nick-end labeling (TUNEL) assay was used to detect apoptosis. Contents of inflammatory cytokines were determined by enzyme-linked immunosorbent assay (ELISA). Protein expression and phosphorylation levels were assessed by Western blotting. Nuclear translocation was observed by immunofluorescent staining.

Results

Bf incubation significantly induced apoptosis and decreased viabilities of neurons. The phosphorylation levels of MAP kinase kinase (MKK)3, MKK6, p38 mitogen-activated protein kinases (MAPK), nuclear translocation level of p65, and the expression levels of cleaved caspase3 and tumor necrosis factor (TNF)α were found to be dramatically higher in Bf-incubated neurons. BAI pre-treatment, however, increased cell viability by reducing cell apoptosis. BAI pre-treatment also reduced phosphorylation levels of MKK3, MKK6, p38 MAPK, and nuclear translocation level of p65, as well as the expression levels of cleaved caspase3 and TNFα, in Bf-incubated neurons.

Conclusions

BAI suppressed bilirubin-induced neuron apoptosis and inflammation by deactivating p38 MAPK signaling.

Baseline Serum Bilirubin and Risk of First Stroke in Hypertensive Patients

Background

Data on the association between serum bilirubin and the risk of stroke are limited and inconclusive. We aimed to evaluate the association between serum bilirubin and the risk of first stroke and to examine any possible effect modifiers in hypertensive patients.

Methods and Results

Our study was a post hoc analysis of the CSPPT (China Stroke Primary Prevention Trial). A total of 19 906 hypertensive patients were included in the final analysis. Cox proportional hazards models were used to estimate the hazard ratios (HRs) and 95% CIs for the risk of first stroke associated with serum bilirubin levels. The median follow‐up period was 4.5 years. When serum total bilirubin was assessed as tertiles, the adjusted HR of first ischemic stroke for participants in tertile 3 (12.9–34.1 μmol/L) was 0.75 (95% CI, 0.59–0.96), compared with participants in tertile 1 (<9.3 μmol/L). When direct bilirubin was assessed as tertiles, a significantly lower risk of first ischemic stroke was also found in participants in tertile 3 (2.5–24.8 μmol/L) (adjusted HR, 0.77; 95% CI, 0.60–0.98), compared with those in tertile 1 (<1.6 μmol/L). However, there was no significant association between serum total bilirubin (tertile 3 versus 1: adjusted HR, 1.45; 95% CI, 0.89–2.35) or direct bilirubin (tertile 3 versus 1: adjusted HR, 1.27; 95% CI, 0.76–2.11) and first hemorrhagic stroke.

Conclusions

In this sample of Chinese hypertensive patients, there was a significant inverse association between serum total bilirubin or direct bilirubin and the risk of first ischemic stroke.

Liver Transplant Patients with High Preoperative Serum Bilirubin Levels Are at Increased Risk of Postoperative Delirium: A Retrospective Study

Postoperative delirium is a common complication after liver transplantation (LT). A high model for end-stage liver disease (MELD) score is an independent risk factor for postoperative delirium, but it is unclear which of the components of this score are risk indicators. The aim of this study was to analyze the incidence of postoperative delirium according to the preoperative serum bilirubin level, a component of the MELD score, in patients who underwent LT. The medical records of 325 patients who underwent LT from January 2010 to February 2019 at a single university hospital were retrospectively reviewed. The patients were divided into two groups: those who experienced postoperative delirium (Delirium group, n = 69) and those who did not (Control group, n = 256). Data on the patients’ demographic characteristics, perioperative management, and postoperative complications were collected. Mean preoperative bilirubin level was higher in the Delirium group than in the Control group (p < 0.0001). In the Delirium group, 54 (78.26%) patients had preoperative bilirubin levels above 3.5 mg/dL. In the multivariate analysis, preoperative bilirubin above 3.5 mg/dL was associated with postoperative delirium (p = 0.002). Therefore, preoperative hyperbilirubinemia is an independent risk factor for postoperative delirium.

Tat-Biliverdin Reductase A Exerts a Protective Role in Oxidative Stress-Induced Hippocampal Neuronal Cell Damage by Regulating the Apoptosis and MAPK Signaling

Reactive oxygen species (ROS) is major risk factor in neuronal diseases including ischemia. Although biliverdin reductase A (BLVRA) plays a pivotal role in cell survival via its antioxidant function, its role in hippocampal neuronal (HT-22) cells and animal ischemic injury is not clearly understood yet. In this study, the effects of transducible fusion protein Tat-BLVRA on H₂O₂-induced HT-22 cell death and in an animal ischemia model were investigated. Transduced Tat-BLVRA markedly inhibited cell death, DNA fragmentation, and generation of ROS. Transduced Tat-BLVRA inhibited the apoptosis and mitogen activated protein kinase (MAPK) signaling pathway and it passed through the blood-brain barrier (BBB) and significantly prevented hippocampal cell death in an ischemic model. These results suggest that Tat-BLVRA provides a possibility as a therapeutic molecule for ischemia.

BRUP-1, an intracellular bilirubin modulator, exerts neuroprotective activity in a cellular Parkinson's disease model

Bilirubin, the end product of heme redox metabolism, has cytoprotective properties and is an essential metabolite associated with cardiovascular disease, inflammatory bowel disease, type 2 diabetes, and neurodegenerative diseases including Parkinson's disease (PD). PD is characterized by progressive degeneration of nigral dopaminergic neurons and is associated with elevated oxidative stress due to mitochondrial dysfunction. In this study, using a ratiometric bilirubin probe, we revealed that the mitochondrial inhibitor, rotenone, which is widely used to create a PD model, significantly decreased intracellular bilirubin levels in HepG2 cells. Chemical screening showed that BRUP-1 was a top hit that restored cellular bilirubin levels that were lowered by rotenone. We found that BRUP-1 up-regulated the expression level of heme oxygenase-1 (HO-1), one of the rate-limiting enzyme of bilirubin production via nuclear factor erythroid 2-related factor 2 (Nrf2) activation. In addition, we demonstrated that this Nrf2 activation was due to a direct inhibition of the interaction between Nrf2 and Kelch-like ECH-associated protein 1 (Keap1) by BRUP-1. Both HO-1 up-regulation and bilirubin restoration by BRUP-1 treatment were significantly abrogated by Nrf2 silencing. In neuronal PC12D cells, BRUP-1 also activated the Nrf2-HO-1 axis and increased bilirubin production, resulted in the suppression of neurotoxin-induced cell death, reactive oxygen species production, and protein aggregation, which are hallmarks of PD. Furthermore, BRUP-1 showed neuroprotective activity against rotenone-treated neurons derived from induced pluripotent stem cells. These findings provide a new member of Keap1-Nrf2 direct inhibitors and suggest that chemical modulation of heme metabolism using BRUP-1 may be beneficial for PD treatment.

The Heme Oxygenase/Biliverdin Reductase System as Effector of the Neuroprotective Outcomes of Herb-Based Nutritional Supplements

Over the last few years, several preclinical studies have shown that some herbal products, such as ferulic acid, Ginkgo biloba, and resveratrol, exert neuroprotective effects through the modulation of the heme oxygenase/biliverdin reductase system. Unfortunately, sufficient data supporting the shift of knowledge from preclinical studies to humans, particularly in neurodegenerative diseases, are not yet available in the literature. The purpose of this review is to summarize the studies and the main results achieved on the potential therapeutic role of the interaction between the heme oxygenase/biliverdin reductase system with ferulic acid, G. biloba, and resveratrol. Some critical issues have also been reported, mainly concerning the safety profile and the toxicological sequelae associated to the supplementation with the herbs mentioned above, based on both current literature and specific reports issued by the competent Regulatory Authorities.

Curcumin, Hormesis and the Nervous System

Curcumin is a polyphenol compound extracted from the rhizome of Curcuma longa Linn (family Zingiberaceae) commonly used as a spice to color and flavor food. Several preclinical studies have suggested beneficial roles for curcumin as an adjuvant therapy in free radical-based diseases, mainly neurodegenerative disorders. Indeed, curcumin belongs to the family of hormetins and the enhancement of the cell stress response, mainly the heme oxygenase-1 system, is actually considered the common denominator for this dual response. However, evidence-based medicine has clearly demonstrated the lack of any therapeutic effect of curcumin to contrast the onset or progression of neurodegeneration and related diseases. Finally, the curcumin safety profile imposes a careful analysis of the risk/benefit balance prior to proposing chronic supplementation with curcumin.

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

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

Association of circulating total bilirubin level with ischemic stroke: a systemic review and meta-analysis of observational evidence

Background

Circulating total bilirubin is a biomarker of ischemic stroke and may serve as a potential prognostic factor. It is imperative to systemically evaluate the correlation between circulating total bilirubin and risk for stroke. This systematic review and meta-analysis investigated the relationship between total serum bilirubin and risk for stroke.

Methods

Studies published before 30 June 2017 were searched in four databases (PubMed, EMBASE, Web of Science and Cochrane Central). Additional studies were searched by reviewing references and contacting authors. Cohort, cross-sectional and case-control studies in adults that examined the association between serum total bilirubin and stroke were included irrespective of language and date of publication. The primary outcome of this study was ischemic stroke, and the secondary outcome was stroke. Abstract and full-text were reviewed by two independent reviewers, and disagreement was resolved by consulting a third reviewer. Data were extracted by two independent reviewers using a pre-designed data collection form.

Results

Eleven observational studies (5 prospective and 6 cross-sectional studies) involving 131,450 subjects were included for analysis. In four studies with 83,380 subjects, the relationship between circulating total bilirubin and ischemic stroke was investigated, ischemic stroke was found in 2,496 patients, and the total odds ratio (OR) of the highest bilirubin and the lowest bilirubin for the occurrence of ischemic stroke was 0.66 (95% CI: 0.58-0.74). Eleven studies with 131,450 subjects explored the correlation between bilirubin and stroke, stroke was reported in 5,060 patients, and the total OR of the highest bilirubin and the lowest bilirubin for the occurrence of stroke was 0.73 (95% CI: 0.68-0.79). A stratified analysis based on the gender showed that the total bilirubin level in males correlated with ischemic stroke or stroke, which was not noted in females.

Conclusions

The available studies support an inverse association between circulating total bilirubin and risk for ischemic stroke and stroke in males. Prospective studies with large sample size are needed to establish the role of circulating bilirubin in the prevention of stroke.

Curcumin and Heme Oxygenase: Neuroprotection and Beyond

Curcumin is a natural polyphenol component of Curcuma longa Linn, which is currently considered one of the most effective nutritional antioxidants for counteracting free radical-related diseases. Several experimental data have highlighted the pleiotropic neuroprotective effects of curcumin, due to its activity in multiple antioxidant and anti-inflammatory pathways involved in neurodegeneration. Although its poor systemic bioavailability after oral administration and low plasma concentrations represent restrictive factors for curcumin therapeutic efficacy, innovative delivery formulations have been developed in order to overwhelm these limitations. This review provides a summary of the main findings involving the heme oxygenase/biliverdin reductase system as a valid target in mediating the potential neuroprotective properties of curcumin. Furthermore, pharmacokinetic properties and concerns about curcumin's safety profile have been addressed.

Neurotoxicity of Unconjugated Bilirubin in Mature and Immature Rat Organotypic Hippocampal Slice Cultures

BACKGROUND

The physiopathology of bilirubin-induced neurological disorders is not completely understood.

OBJECTIVES

The aim of our study was to assess the effect on bilirubin neurotoxicity of the maturity or immaturity of exposed cells, the influence of different unconjugated bilirubin (UCB) and human serum albumin (HSA) concentrations, and time of UCB exposure.

METHODS

Organotypic hippocampal slices were exposed for 48 h to different UCB and HSA concentrations after 14 (mature) or 7 (immature) days of in vitro culture. Immature slices were also exposed to UCB and HSA for 72 h. The different effects of exposure time to UCB on neurons and astrocytes were evaluated.

RESULTS

We found that 48 h of UCB exposure was neurotoxic for mature rat organotypic hippocampal slices while 72 h of exposure was neurotoxic for immature slices. Forty-eight-hour UCB exposure was toxic for astrocytes but not for neurons, while 72-h exposure was toxic for both astrocytes and neurons. HSA prevented UCB toxicity when the UCB:HSA molar ratio was ≤1 in both mature and immature slices.

CONCLUSIONS

We confirmed UCB neurotoxicity in mature and immature rat hippocampal slices, although immature ones were more resistant. HSA was effective in preventing UCB neurotoxicity in both mature and immature rat hippocampal slices.

Regenerative Effects of Heme Oxygenase Metabolites on Neuroinflammatory Diseases

Heme oxygenase (HO) catabolizes heme to produce HO metabolites, such as carbon monoxide (CO) and bilirubin (BR), which have gained recognition as biological signal transduction effectors. The neurovascular unit refers to a highly evolved network among endothelial cells, pericytes, astrocytes, microglia, neurons, and neural stem cells in the central nervous system (CNS). Proper communication and functional circuitry in these diverse cell types is essential for effective CNS homeostasis. Neuroinflammation is associated with the vascular pathogenesis of many CNS disorders. CNS injury elicits responses from activated glia (e.g., astrocytes, oligodendrocytes, and microglia) and from damaged perivascular cells (e.g., pericytes and endothelial cells). Most brain lesions cause extensive proliferation and growth of existing glial cells around the site of injury, leading to reactions causing glial scarring, which may act as a major barrier to neuronal regrowth in the CNS. In addition, damaged perivascular cells lead to the breakdown of the blood-neural barrier, and an increase in immune activation, activated glia, and neuroinflammation. The present review discusses the regenerative role of HO metabolites, such as CO and BR, in various vascular diseases of the CNS such as stroke, traumatic brain injury, diabetic retinopathy, and Alzheimer's disease, and the role of several other signaling molecules.

Neuroprotective Effect of ω-3 Polyunsaturated Fatty Acids on Bilirubin Encephalopathy In Vitro and In Vivo

Background

Bilirubin encephalopathy is a serious complication in neonatal jaundice and is associated with high mortality and disability in newborns. The present study aimed to investigate the neuroprotective effects of omega-3 polyunsaturated fatty acids (ω-3 PUFA) on bilirubin encephalopathy in vitro and in vivo.

Material/Methods

The cytotoxicity of unconjugated bilirubin (UCB) to neurons and neuroprotection of ω-3 PUFA were investigated using MTT assays and apoptosis evaluations. Superoxide dismutase (SOD) and catalase (CAT) enzyme activity were measured to investigate the anti-oxidative effect of ω-3 PUFA. The differences between eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were also compared. The in vivo neuroprotective effect of DHA was demonstrated in neonatal rats with bilirubin encephalopathy by bilirubin monitoring, neuron-specific enolase (NSE) monitoring, H&E staining of brain tissue, and apoptosis rate evaluations.

Results

Omega-3 PUFA reduced the rate of apoptosis induced by UCB and increased SOD and CAT enzyme activity for anti-oxidation. DHA did not reduce the bilirubin in the serum of neonatal rats with bilirubin encephalopathy, but did reduce the damage caused by bilirubin with decreased NSE and apoptosis rate as well as improved neuron morphology.

Conclusions

Omega-3 PUFA, particularly DHA, can reduce neurological damage in neonatal rats with bilirubin encephalopathy by increasing anti-apoptosis and anti-oxidation effects against UCB, providing a theoretical basis for the clinical treatment of bilirubin encephalopathy in newborns.

Redox Functions of Heme Oxygenase-1 and Biliverdin Reductase in Diabetes

In patients with diabetes, the hyperglycemia-driven excess generation of reactive oxygen species (ROS) induces oxidative stress (OS) in a variety of tissues. OS is closely associated with chronic inflammation and has a key role in the pathogenesis of vascular complications. The enzymes that generate ROS and gasotransmitters are redox regulated and are implicated in cellular signaling. As a result of cellular metabolism, cells produce significant amounts of carbon monoxide (CO), mainly from heme degradation catalyzed by heme oxygenases (HOs). These reactions also generate biliverdin, bilirubin (BR), and iron. The conversion of biliverdin to BR is catalyzed by biliverdin reductase-A (BVR-A). In this review, we focus on the importance of the HO-1/CO system and BVR in the pathophysiology and therapy of inflammation associated with diabetes.

Independent and combined effect of bilirubin and smoking on the progression of chronic kidney disease

Objective

Whether serum bilirubin and cigarette smoking affect the risk of renal function decline remains inconclusive. We aimed to test the independent and combined effects of bilirubin and cigarette smoking on the progression of chronic kidney disease (CKD) in hypertensive adults.

Methods

The study population consisted of 12,633 patients in the renal sub-study of the China Stroke Primary Prevention Trial. The primary outcome was progression of CKD, defined as a decrease in estimated glomerular filtration rate (eGFR) of ≥30% and to a level of <60 mL/min/1.73 m² if baseline eGFR was ≥60 mL/min/1.73 m², or a decrease in eGFR of ≥50% if baseline eGFR was <60 mL/min/1.73 m², or end-stage renal disease. The secondary outcomes included 1) rapid decline in renal function and 2) annual rate of eGFR decline.

Results

The median follow-up duration was 4.4 years. Cigarette smoking had no significant effect on the progression of CKD (odds ratio [OR]: 1.11, 95% confidence interval [95% CI]: 0.78-1.57). However, a significantly lower risk of the primary event (OR: 0.72, 95% CI: 0.55-0.95) was found in participants in tertile 3 compared to those in tertiles 1-2 for total bilirubin (TBiL) levels. More importantly, there was an interaction between TBiL and smoking status on the primary outcome (P for interaction =0.013). Among ever smokers, TBiL levels had no significant effect on the primary outcome. However, among never smokers, higher TBiL levels were significantly associated with a lower risk of the primary outcome (tertile 3 vs 1-2; OR: 0.53, 95% CI: 0.36-0.78). Similar trends were observed for direct bilirubin and secondary outcomes.

Conclusion

Among hypertensive patients, bilirubin was inversely associated with the progression of CKD in never smokers, but not in ever smokers.

Mechanisms of redox interactions of bilirubin with copper and the effects of penicillamine

Toxic effects of unconjugated bilirubin (BR) in neonatal hyperbilirubinemia have been related to redox and/or coordinate interactions with Cu²⁺. However, the development and mechanisms of such interactions at physiological pH have not been resolved. This study shows that BR reduces Cu²⁺ to Cu¹⁺ in 1:1 stoichiometry. Apparently, BR undergoes degradation, i.e. BR and Cu²⁺ do not form stable complexes. The binding of Cu²⁺ to inorganic phosphates, liposomal phosphate groups, or to chelating drug penicillamine, impedes redox interactions with BR. Cu¹⁺ undergoes spontaneous oxidation by O₂ resulting in hydrogen peroxide accumulation and hydroxyl radical production. In relation to this, copper and BR induced synergistic oxidative/damaging effects on erythrocytes membrane, which were alleviated by penicillamine. The production of reactive oxygen species by BR and copper represents a plausible cause of BR toxic effects and cell damage in hyperbilirubinemia. Further examination of therapeutic potentials of copper chelators in the treatment of severe neonatal hyperbilirubinemia is needed.

Ozone therapy: an overview of pharmacodynamics, current research, and clinical utility

The use of ozone (O₃) gas as a therapy in alternative medicine has attracted skepticism due to its unstable molecular structure. However, copious volumes of research have provided evidence that O₃'s dynamic resonance structures facilitate physiological interactions useful in treating a myriad of pathologies. Specifically, O₃ therapy induces moderate oxidative stress when interacting with lipids. This interaction increases endogenous production of antioxidants, local perfusion, and oxygen delivery, as well as enhances immune responses. We have conducted a comprehensive review of O₃ therapy, investigating its contraindications, routes and concentrations of administration, mechanisms of action, disinfectant properties in various microorganisms, and its medicinal use in different pathologies. We explore the therapeutic value of O₃ in pathologies of the cardiovascular system, gastrointestinal tract, genitourinary system, central nervous system, head and neck, musculoskeletal, subcutaneous tissue, and peripheral vascular disease. Despite compelling evidence, further studies are essential to mark it as a viable and quintessential treatment option in medicine.

Kernicterus in a boy with ornithine transcarbamylase deficiency: A case report

Ornithine transcarbamylase deficiency (OTCD) is an X-linked urea cycle defect associated with severe and usually fatal hyperammonemia. This study describes a patient with early onset lethal OTCD due to a known pathogenic variant (c.298+1G>A), as well as the novel autopsy finding of kernicterus with relatively low blood concentration of unconjugated bilirubin (UCB) (11.55 mg/dL). The patient was a full-term male with a family history of two previous male siblings who died as newborns after acute neurologic deterioration. The patient's symptoms began at 24 h of life with lethargy that rapidly progressed to coma upon admission to the neonatal intensive care unit. Although hyperammonemia and hyperbilirubinemia were documented, hemofiltration could not be performed. OTCD diagnosis was biochemically established. Despite nutritional intervention and treatment for hyperammonemia, the patient died on the sixth day of life. At autopsy, external brain examination revealed a marked yellow pigmentation typical of kernicterus that included gray matter, particularly the thalamus and basal ganglia; dentate nuclei of the cerebellum and brain stem gray matter were also affected. Microscopic findings were consistent with the classical description of tissue damage in OTCD, including the presence of Alzheimer type II astrocytes in basal ganglia, necrosis, neuronal loss with spongiform degeneration and macrophage infiltration surrounded by astroglia. This condition may be an important comorbidity in newborns with hyperammonemia.