Bilirubin-Induced Oxidative Stress Leads to DNA Damage in the Cerebellum of Hyperbilirubinemic Neonatal Mice and Activates DNA Double-Strand Break Repair Pathways in Human Cells

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.

Hematological changes, oxidative stress assessment, and dysregulation of aquaporin-3 channel, prolactin, and oxytocin receptors in kidneys of lactating Wistar rats treated with monosodium glutamate

High consumption of locally produced delicacies could expose nursing mothers to high monosodium glutamate (MSG) levels, frequently used as a necessary condiment in low-income countries. Thus, this study evaluated some novel preliminary changes in renal hormonal receptors, the aquaporin-3 channel, oxidative stress markers, and hematological indices induced by monosodium glutamate in lactating rats. Post-parturition, twenty-four (24) lactating Wistar rats were divided into four (4) groups of six rats each (n = 6). Oral administration of distilled water and MSG started three (3) days postpartum as follows: group 1: distilled water (1 ml/kg BW), group 2: MSG (925 mg/kg BW), group 3: MSG (1850 mg/kg BW), and group 4: MSG (3700 mg/kg BW). At the end of the experiment, which lasted fourteen (14) days, animals were sacrificed and samples of blood and tissues were obtained for biochemical analysis. MSG administration significantly (p < 0.05) increased ROS and MDA, with a significant (p < 0.05) decrease in kidney antioxidants. Serum creatinine, total, conjugated, and unconjugated bilirubin significantly (p < 0.05) increased with MSG administration. The prolactin receptor was significantly reduced (p < 0.05), while the oxytocin receptor and aquaporin-3 channel were significantly (p < 0.05) increased in the MSG-administered groups. There were significant (p < 0.05) changes in the hematological indices of the MSG-administered animals. Thus, the findings of this study suggest that high MSG consumption causes hematological alterations and may alter renal function via increased ROS production and dysregulation of the AQP-3 channel, prolactin, and oxytocin receptors in the kidneys of lactating Wistar rats.

Effect of hyperbilirubinemia and phototherapy on apoptotic microparticle levels in neonates

OBJECTIVE

We aimed to evaluate the effect of hyperbilirubinemia and phototherapy on total apoptotic, platelet-derived, endothelial-derived, and tissue factor (TF)-positive apoptotic microparticle (MP) levels in neonates with nonhemolytic pathologic hyperbilirubinemia.

METHODS

Thirty-three term neonates with nonhemolytic pathologic hyperbilirubinemia and 25 healthy term neonates were included. MP levels were analyzed by flow cytometry using peripheral blood samples only once for the neonates in the control group and twice for the neonates in the study group (before and after phototherapy). Annexin V-positive MPs were defined as apoptotic MPs. Platelet-derived MPs were defined as those containing CD31. MPs containing CD144 were defined as endothelial-derived MPs, and MPs expressing TF were identified as those containing CD142.

RESULTS

The rates of total apoptotic and endothelial-derived apoptotic MPs were significantly higher in the study group than the control group before phototherapy (P = 0.012 and P = 0.003, respectively) and after phototherapy (P = 0.046 and P = 0.001, respectively). Total apoptotic, platelet-derived, endothelial-derived, and TF-positive apoptotic MPs did not show any significant differences before and after phototherapy in the study group (P = 0.908, P = 0.823, P = 0.748, and P = 0.437, respectively).

CONCLUSIONS

Our study demonstrated that total apoptotic and endothelial-derived apoptotic MPs are increased in cases of nonhemolytic pathologic hyperbilirubinemia. We showed that phototherapy does not have a significant effect on apoptotic MP levels. Further studies are needed to evaluate the risk of elevated apoptotic MPs on the development of thromboembolism in neonates with nonhemolytic pathologic hyperbilirubinemia.

Uridine diphosphate glucuronosyltransferase 1A1 prevents the progression of liver injury

BACKGROUND

Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) plays a crucial role in metabolizing and detoxifying endogenous and exogenous substances. However, its contribution to the progression of liver damage remains unclear.

AIM

To determine the role and mechanism of UGT1A1 in liver damage progression.

METHODS

We investigated the relationship between UGT1A1 expression and liver injury through clinical research. Additionally, the impact and mechanism of UGT1A1 on the progression of liver injury was analyzed through a mouse model study.

RESULTS

Patients with UGT1A1 gene mutations showed varying degrees of liver damage, while patients with acute-on-chronic liver failure (ACLF) exhibited relatively reduced levels of UGT1A1 protein in the liver as compared to patients with chronic hepatitis. This suggests that low UGT1A1 levels may be associated with the progression of liver damage. In mouse models of liver injury induced by carbon tetrachloride (CCl4) and concanavalin A (ConA), the hepatic levels of UGT1A1 protein were found to be increased. In mice with lipopolysaccharide or liver steatosis-mediated liver-injury progression, the hepatic protein levels of UGT1A1 were decreased, which is consistent with the observations in patients with ACLF. UGT1A1 knockout exacerbated CCl4- and ConA-induced liver injury, hepatocyte apoptosis and necroptosis in mice, intensified hepatocyte endoplasmic reticulum (ER) stress and oxidative stress, and disrupted lipid metabolism.

CONCLUSION

UGT1A1 is upregulated as a compensatory response during liver injury, and interference with this upregulation process may worsen liver injury. UGT1A1 reduces ER stress, oxidative stress, and lipid metabolism disorder, thereby mitigating hepatocyte apoptosis and necroptosis.

Ferroptosis contributes to hemolytic hyperbilirubinemia‑induced brain damage in vivo and in vitro

Ferroptosis is driven by iron‑dependent accumulation of lipid hydroperoxides, and hemolytic hyperbilirubinemia causes accumulation of unconjugated bilirubin and iron. The present study aimed to assess the role of ferroptosis in hemolytic hyperbilirubinemia‑induced brain damage (HHIBD). Rats were randomly divided into the control, phenylhydrazine (PHZ) and deferoxamine (DFO) + PHZ groups, with 12 rats in each group. Ferroptosis‑associated biochemical and protein indicators were measured in the brain tissue of rats. We also performed tandem mass tag‑labeled proteomic analysis. The levels of iron and malondialdehyde were significantly higher and levels of glutathione (GSH) and superoxide dismutase activity significantly lower in the brain tissues of the PHZ group compared with those in the control group. HHIBD also resulted in significant increases in the expression of the ferroptosis‑related proteins acyl‑CoA synthetase long‑chain family member 4, ferritin heavy chain 1 and transferrin receptor and divalent metal transporter 1, as well as a significant reduction in the expression of ferroptosis suppressor protein 1. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis demonstrated that the differentially expressed proteins of rat brain tissues between the control and PHZ groups were significantly involved in ferroptosis, GSH metabolism and fatty acid biosynthesis pathways. Pretreatment with DFO induced antioxidant activity and alleviated lipid peroxidation‑mediated HHIBD. In addition, PC12 cells treated with ferric ammonium citrate showed shrinking mitochondria, high mitochondrial membrane density, and increased lipid reactive oxygen species and intracellular ferrous iron, which were antagonized by pretreatment with ferrostatin‑1 or DFO, which was reversed by pretreatment with ferrostatin‑1 or DFO. The present study demonstrated that ferroptosis is involved in HHIBD and provided novel insights into candidate proteins that are potentially involved in ferroptosis in the brain during hemolytic hyperbilirubinemia.

Deficiency of ligase IV leads to reduced NHEJ, accumulation of DNA damage, and can sensitize cells to cancer therapeutics

Ligase IV is a key enzyme involved during DNA double-strand breaks (DSBs) repair through nonhomologous end joining (NHEJ). However, in contrast to Ligase IV deficient mouse cells, which are embryonic lethal, Ligase IV deficient human cells, including pre-B cells, are viable. Using CRISPR-Cas9 mediated genome editing, we have generated six different LIG4 mutants in cervical cancer and normal kidney epithelial cell lines. While the LIG4 mutant cells showed a significant reduction in NHEJ, joining mediated through microhomology-mediated end joining (MMEJ) and homologous recombination (HR) were significantly high. The reduced NHEJ joining activity was restored by adding purified Ligase IV/XRCC4. Accumulation of DSBs and reduced cell viability were observed in LIG4 mutant cells. LIG4 mutant cells exhibited enhanced sensitivity towards DSB-inducing agents such as ionizing radiation (IR) and etoposide. More importantly, the LIG4 mutant of cervical cancer cells showed increased sensitivity towards FDA approved drugs such as Carboplatin, Cisplatin, Paclitaxel, Doxorubicin, and Bleomycin used for cervical cancer treatment. These drugs, in combination with IR showed enhanced cancer cell death in the background of LIG4 gene mutation. Thus, our study reveals that mutation in LIG4 results in compromised NHEJ, leading to sensitization of cervical cancer cells towards currently used cancer therapeutics.

Elevated Serum Total Bilirubin Might Indicate Poor Coronary Conditions for Unstable Angina Pectoris Patients beyond as a Cardiovascular Protector

Backgrounds

Serum total bilirubin (STB) is recently more regarded as an antioxidant with vascular protective effects. However, we noticed that elevated STB appeared in unstable angina pectoris (UAP) patients with diffused coronary lesions. We aimed to explore STB's roles in UAP patients, which have not been reported by articles.

Methods and Results

1120 UAP patients were retrospectively screened, and 296 patients were finally enrolled. They were grouped by Canadian Cardiovascular Society (CCS) angina grades. The synergy between PCI with TAXUS stent and cardiac surgery score (SYNTAX score) and corrected thrombolysis in myocardial infarction flow count (CTFC) were adopted to profile coronary features. The results showed that STB, mean platelet volume (MPV), hs-CRP, fasting blood glucose (FBG), red blood cell width (RDW), and CTFC elevated significantly in the CCS high-risk group. STB (B = 0.59, 95% CI: 0.39-0.74, P < 0.01) and MPV (B = 0.86, 95% CI: 0.42-1.31, P < 0.01) could indicate SYNTAX score changes for these patients. STB (≥21.7 μmol/L) could even indicate a coronary slow flow condition (AUC: 0.88, 95% CI: 0.84-0.93, P < 0.01). Moreover, UAP patients with elevated STB had a lower event-free survival rate by the Kaplan-Meier curve. STB ≥21.7 μmol/L could reflect a poor coronary flow status and indicate 1-year poor outcomes for these patients (HR: 2.01, 95% CI: 1.06-3.84, P < 0.01).

Conclusion

Elevated STB in UAP patients has a close relationship with changes in SYNTAX score. STB (over 21.7 μmol/L) could even indicate a coronary slow flow condition and poor outcomes for the UAP patients.

Effects of Repetitive Transcranial Magnetic Stimulation on Pallidum GABAergic Neurons and Motor Function in Rat Models of Kernicterus

Kernicterus is a serious complication of hyperbilirubinemia, caused by neuronal injury due to excessive unconjugated bilirubin (UCB) in specific brain areas. This injury induced by this accumulation in the globus pallidus can induce severe motor dysfunction. Repetitive transcranial magnetic stimulation (rTMS) has shown neuroprotective effects in various neurological diseases. This study aimed to investigate the effects of rTMS on pallidal nerve damage and motor dysfunction in a rat model of kernicterus. Rats were divided into a sham group (n = 16), a model group (bilirubin with sham rTMS; n = 16) and an rTMS group (bilirubin with rTMS; n = 16). High-frequency rTMS (10 Hz) was applied starting from 24 h postmodeling for 7 days. The rotarod test, western blotting and immunohistochemical staining were performed to measure motor function and protein expression levels. The rTMS mitigated the negative effects of UCB on the general health of kernicterus-model rats and improved their growth and development. Furthermore, the rTMS alleviated UCB-induced motor dysfunction and increased the expression of GABAergic neuronal marker GAD67 in the globus pallidus. Notably, it also inhibited apoptosis-related protein caspase-3 activation. In conclusion, rTMS could alleviate motor dysfunction by inhibiting apoptosis and increasing globus pallidus GAD67 in kernicterus rat models, indicating that it may be a promising treatment for kernicterus.

Association between Serum Total Bilirubin Level and Patients with Primary Open-Angle Glaucoma in China: A Cross-Sectional, Case-Control Study

Objective

To investigate the relationship between peripheral blood total bilirubin (TBIL) levels and the risk of primary open-angle glaucoma (POAG).

Methods

This study was a cross-sectional, case-control study design. Between April 2021 and January 2022, 198 POAG patients and 205 healthy subjects were recruited from the EENT Hospital of Fudan University. Their clinical information (intraocular pressure, central corneal thickness, vertical cup-disk ratios (VCDR), and axial length) and demographic data were collected. Serum levels of TBIL were measured in enzymes using a Roche C702 biochemical analyzer. The POAG subgroups were classified by gender and VCDR: mild (VCDR ≤ 0.64), moderate (VCDR ≤ 0.85), and severe (VCDR > 0.85). Univariate and multivariate logistic regression analyses were performed.

Results

The level of TBIL (11.58 ± 5.16 μmol/L) in the POAG group was higher than that in the control group (10.18 ± 3.38 μmol/L; p < 0.05). In the male subgroup, TBIL was also significantly higher than in the normal control group; TBIL levels were lower in the mild subgroup (10.82 ± 4.48 μmol/L), followed by the moderate subgroup (12.00 ± 5.55 μmol/L) and the severe subgroup (14.47 ± 5.45 μmol/L). The results of the multivariate logistic regression analysis showed that high TBIL levels were a risk factor for male POAG, at 1.126 (95% CI 1.009-1.256). Pearson's analysis revealed that TBIL was positively correlated with intraocular pressure (r = 0.134, p = 0.012), VCDR (r = 0.142, p = 0.046), anterior chamber depth (r = 0.190, p = 0.014), and axial length (r = 0.179, p = 0.019) in the patients. However, no statistical difference (p < 0.05) was observed in the female patients with POAG.

Conclusion

The results showed that high levels of TBIL may be related to the pathogenesis of POAG and that the severity of the disease is positively correlated, especially in male patients.

Time progression and regional expression of brain oxidative stress induced by obstructive jaundice in rats

BACKGROUND

Obstructive jaundice induces oxidative changes in the brain parenchyma and plays significant role in clinical manifestations of hepatic encephalopathy. We aim to study the progression of the brain oxidative status over time and the differences of its pattern over the hemispheres, the brainstem and the cerebellum. We use an experimental model in rats and measuring the oxidative stress (OS) specific biomarkers protein malondialdehyde (PrMDA) and protein carbonyls (PrC = O).

RESULTS

Hyperbilirubinemia has been confirmed in all study groups as the result of common bile duct obstruction. We confirmed increase in both PrMDA and PrC = O biomarkers levels with different type of changes over time. We also confirmed that the oxidative process develops differently in each of the brain areas in study.

CONCLUSIONS

The present study confirms the progressive increase in OS in all brain areas studied using markers indicative of cumulative protein modification.

Models of bilirubin neurological damage: lessons learned and new challenges

OBJECTIVE

Jaundice (icterus) is the visible manifestation of the accumulation of bilirubin in the tissue and is indicative of potential toxicity to the brain. Since its very first description more than 2000 years ago, many efforts have been undertaken to understand the molecular determinants of bilirubin toxicity to neuronal cells to reduce the risk of neurological sequelae through the use of available chemicals and in vitro, ex vivo, in vivo, and clinical models. Although several studies have been performed, important questions remain unanswered, such as the reasons for regional sensitivity and the interplay with brain development. The number of new molecular effects identified has increased further, which has added even more complexity to the understanding of the condition. As new research challenges emerged, so does the need to establish solid models of prematurity.

METHODS

This review critically summarizes the key mechanisms of severe neonatal hyperbilirubinemia and the use of the available models and technologies for translational research.

IMPACT

We critically review the conceptual dogmas and models used for studying bilirubin-induced neurotoxicity. We point out the pitfalls and translational gaps, and suggest new clinical research challenges. We hope to inform researchers on the pro and cons of the models used, and to help direct their experimental focus in a most translational research.

Hyperbilirubinemia after surgical repair for acute type a aortic dissection: A propensity score-matched analysis

Background: Inflammation and oxidative stress are known to participate in the pathogenesis of hyperbilirubinemia. It has been known that acute type A aortic dissection (ATAAD) surgical repair often associates with complications which might affect the long-term prognosis. However, the clinical significance of postoperative hyperbilirubinemia (PH) has not been evaluated. Here in this study, we examined the incidence, risk factors, and prognosis of PH after ATAAD surgery.

Methods: This retrospective study enrolled a total of 970 patients who received ATAAD surgical repair from January 2014 to December 2019. PH was defined as serum total bilirubin >3.0 mg/dl within the first week after the surgery. Propensity score matching was used to reduce selection bias and eliminate potential confounding factors. Kaplan–Meier survival and Cox proportional hazards regression analyses were conducted to explore the association between PH and postoperative long-term survival.

Results: Development of PH (183 patients) was associated with a higher 30-Day mortality (20.8% vs. 9.0%, p < 0.001). Advanced age [odds ratio (OR) 1.538, p = 0.006], higher baseline total bilirubin level (OR 1.735, p = 0.026), preoperative pericardial tamponade (OR 3.192, p = 0.024), prolonged cardiopulmonary bypass (CPB) duration (OR 2.008, p = 0.005), and elevated postoperative central venous pressure (CVP) level (OR 2.183, p < 0.001) were associated with PH. The Kaplan-Meier analysis showed patients who developed PH were associated with poor long-term survival (p = 0.044). Cox analysis showed that the presence of PH (hazard ratio 2.006, p = 0.003) was an independent risk factor for increased mortality.

Conclusion: PH is a common complication in patients undergoing ATAAD surgical repair that associates with worse short- and long-term prognosis. Our data indicated that age, preoperative total bilirubin level, pericardial tamponade, CPB duration, and postoperative CVP level were risk factors for the development of PH.

Network Pharmacology-Based Analysis on the Potential Biological Mechanisms of Yinzhihuang Oral Liquid in Treating Neonatal Hyperbilirubinemia

Objective

Neonatal hyperbilirubinemia is caused by the excessive production of bilirubin and decreased excretion ability in the neonatal period. It leads to a concentration of blood bilirubin that exceeds a certain threshold. Yinzhihuang oral liquid (YZH) is a traditional Chinese medicine mixture used in the treatment of neonatal hyperbilirubinemia in China. This article systematically explores the pharmacological mechanisms by which YZH acts in the treatment of neonatal hyperbilirubinemia through network pharmacology at the molecular level.

Methods

We adopted the method of network pharmacology, which includes active component prescreening, target gene prediction, gene enrichment analysis, and network analysis.

Results

According to the network pharmacological analysis, 8 genes (STAT3, AKT1, MAPK14, JUN, TP53, MAPK3, ESR1, and RELA) may be targets of YZH in the treatment of neonatal hyperbilirubinemia. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that YZH may regulate antioxidation, modulate lipid metabolism, and have anti-infective properties.

Conclusion

In this study, the pharmacological action and molecular mechanisms of YZH were predicted as a whole. It was found that YZH is a promising drug for treating oxidative stress due to bilirubin, as it reduces immunosuppression and helps to eliminate virus infection.

Bilirubin-Induced Neurological Damage: Current and Emerging iPSC-Derived Brain Organoid Models

Bilirubin-induced neurological damage (BIND) has been a subject of studies for decades, yet the molecular mechanisms at the core of this damage remain largely unknown. Throughout the years, many in vivo chronic bilirubin encephalopathy models, such as the Gunn rat and transgenic mice, have further elucidated the molecular basis of bilirubin neurotoxicity as well as the correlations between high levels of unconjugated bilirubin (UCB) and brain damage. Regardless of being invaluable, these models cannot accurately recapitulate the human brain and liver system; therefore, establishing a physiologically recapitulating in vitro model has become a prerequisite to unveil the breadth of complexities that accompany the detrimental effects of UCB on the liver and developing human brain. Stem-cell-derived 3D brain organoid models offer a promising platform as they bear more resemblance to the human brain system compared to existing models. This review provides an explicit picture of the current state of the art, advancements, and challenges faced by the various models as well as the possibilities of using stem-cell-derived 3D organoids as an efficient tool to be included in research, drug screening, and therapeutic strategies for future clinical applications.

Lipoxin alleviates oxidative stress: a state-of-the-art review

OBJECTIVE

This review aims to summarize the capability of lipoxin in regulating oxidative stress.

BACKGROUND

Oxidative stress is defined as an imbalance between the production of free radicals and the antioxidant system, and it is associated with the existence of a large number of oxidation products, such as reactive oxygen species (ROS) and reaction nitrogen species (RNS), causing damage to human tissues through immunoinflammatory responses. Therefore, reducing oxidative stress is vital to alleviate pathological damage. Lipoxin, an acronym for lipoxygenase interaction product, is a bioactive autacoid metabolite of arachidonic acid made by various cell types. Previous studies have shown that lipoxin is associated with a variety of biological functions, including anti-inflammatory, regulating immune responses, promoting the repair of damaged cells, etc. The deficiency of lipoxin is a critical pathological mechanism in different diseases. Moreover, the ability of lipoxin to attenuate oxidative stress is noteworthy, thereby protecting the human body from diverse diseases.

METHODS

We searched papers from PubMed database using search terms, such as lipoxin, lipoxin A4, oxidative stress, and other relevant terms.

RESULTS

A total of 103 articles published over the past 20 years were identified for inclusion. We summarized the capability of lipoxin in regulating oxidative stress and mechanism.

CONCLUSION

Lipoxin is provided with a protective role in attenuating oxidative stress.

Vascular network expansion, integrity of blood-brain interfaces, and cerebrospinal fluid cytokine concentration during postnatal development in the normal and jaundiced rat

BACKGROUND

Severe neonatal jaundice resulting from elevated levels of unconjugated bilirubin in the blood induces dramatic neurological impairment. Central oxidative stress and an inflammatory response have been associated with the pathophysiological mechanism. Cells forming the blood-brain barrier and the choroidal blood-CSF barrier are the first CNS cells exposed to increased plasma levels of unconjugated bilirubin. These barriers are key regulators of brain homeostasis and require active oxidative metabolism to fulfill their protective functions. The choroid plexus-CSF system is involved in neuroinflammatory processes. In this paper, we address the impact of neonatal hyperbilirubinemia on some aspects of brain barriers. We describe physiological changes in the neurovascular network, blood-brain/CSF barriers integrities, and CSF cytokine levels during the postnatal period in normobilirubinemic animals, and analyze these parameters in parallel in Gunn rats that are deficient in bilirubin catabolism and develop postnatal hyperbilirubinemia.

METHODS

Gunn rats bearing a mutation in UGT1a genes were used. The neurovascular network was analyzed by immunofluorescence stereomicroscopy. The integrity of the barriers was evaluated by [14C]-sucrose permeability measurement. CSF cytokine levels were measured by multiplex immunoassay. The choroid plexus-CSF system response to an inflammatory challenge was assessed by enumerating CSF leukocytes.

RESULTS

In normobilirubinemic animals, the neurovascular network expands postnatally and displays stage-specific regional variations in its complexity. Network expansion is not affected by hyperbilirubinemia. Permeability of the blood-brain and blood-CSF barriers to sucrose decreases between one- and 9-day-old animals, and does not differ between normobilirubinemic and hyperbilirubinemic rats. Cytokine profiles differ between CSF and plasma in all 1-, 9-, and 18-day-old animals. The CSF cytokine profile in 1-day-old animals is markedly different from that established in older animals. Hyperbilirubinemia perturbs these cytokine profiles only to a very limited extent, and reduces CSF immune cell infiltration triggered by systemic exposure to a bacterial lipopeptide.

CONCLUSION

The data highlight developmental specificities of the blood-brain barrier organization and of CSF cytokine content. They also indicate that a direct effect of bilirubin on the vascular system organization, brain barriers morphological integrity, and inflammatory response of the choroid plexus-CSF system is not involved in the alteration of brain functions induced by severe neonatal jaundice.

A Potential Role of Keratinocyte-Derived Bilirubin in Human Skin Yellowness and Its Amelioration by Sucrose Laurate/Dilaurate

Sallow and/or dull skin appearance is greatly attributable to the yellow components of skin tone. Bilirubin is a yellow chromophore known to be made in the liver and/or spleen and is transported throughout the body via the blood stream. Recent publications suggest bilirubin may be synthesized in other cells/organs, including the skin. We found human keratinocytes express the transcripts involved in bilirubin biosynthesis. In parallel, we also found human keratinocytes could indeed synthesize bilirubin in monolayer keratinocytes and in a 3D human skin-equivalent model. The synthesized amount was substantial enough to contribute to skin yellowness. In addition, oxidative stress enhanced bilirubin production. Using UnaG, a protein that forms a fluorescent species upon binding to bilirubin, we also visualized the intracellular expression of bilirubin in keratinocytes. Finally, we screened a compound library and discovered that the sucrose laurate/dilaurate (SDL) combination significantly reduced bilirubin levels, as well as bilirubin-mediated yellowness. In conclusion, bilirubin is indeed synthesized in epidermal keratinocytes and can be upregulated by oxidative stress, which could contribute to chronic or transient yellow skin tone appearance. Application of SDL diminishes bilirubin generation and may be a potential solution to mitigate yellowish and/or dull skin appearance.

Bilirubin Encephalopathy

PURPOSE OF REVIEW

Hyperbilirubinemia is commonly seen in neonates. Though hyperbilirubinemia is typically asymptomatic, severe elevation of bilirubin levels can lead to acute bilirubin encephalopathy and progress to kernicterus spectrum disorder, a chronic condition characterized by hearing loss, extrapyramidal dysfunction, ophthalmoplegia, and enamel hypoplasia. Epidemiological data show that the implementation of universal pre-discharge bilirubin screening programs has reduced the rates of hyperbilirubinemia-associated complications. However, acute bilirubin encephalopathy and kernicterus spectrum disorder are still particularly common in low- and middle-income countries.

RECENT FINDINGS

The understanding of the genetic and biochemical processes that increase the susceptibility of defined anatomical areas of the central nervous system to the deleterious effects of bilirubin may facilitate the development of effective treatments for acute bilirubin encephalopathy and kernicterus spectrum disorder. Scoring systems are available for the diagnosis and severity grading of these conditions. The treatment of hyperbilirubinemia in newborns relies on the use of phototherapy and exchange transfusion. However, novel therapeutic options including deep brain stimulation, brain-computer interface, and stem cell transplantation may alleviate the heavy disease burden associated with kernicterus spectrum disorder. Despite improved screening and treatment options, the prevalence of acute bilirubin encephalopathy and kernicterus spectrum disorder remains elevated in low- and middle-income countries. The continued presence and associated long-term disability of these conditions warrant further research to improve their prevention and management.

From dried bear bile to molecular investigation: A systematic review of the effect of bile acids on cell apoptosis, oxidative stress and inflammation in the brain, across pre-clinical models of neurological, neurodegenerative and neuropsychiatric disorders

Bile acids, mainly ursodeoxycholic acid (UDCA) and its conjugated species glycoursodeoxycholic acid (GUDCA) and tauroursodeoxycholic acid (TUDCA) have long been known to have anti-apoptotic, anti-oxidant and anti-inflammatory properties. Due to their beneficial actions, recent studies have started to investigate the effect of UDCA, GUDCA, TUDCA on the same mechanisms in pre-clinical models of neurological, neurodegenerative and neuropsychiatric disorders, where increased cell apoptosis, oxidative stress and inflammation in the brain are often observed. A total of thirty-five pre-clinical studies were identified through PubMed/Medline, Web of Science, Embase, PsychInfo, and CINAHL databases, investigating the role of the UDCA, GUDCA and TUDCA in the regulation of brain apoptosis, oxidative stress and inflammation, in pre-clinical models of neurological, neurodegenerative and neuropsychiatric disorders. Findings show that UDCA reduces apoptosis, reactive oxygen species (ROS) and tumour necrosis factor (TNF)-α production in neurodegenerative models, and reduces nitric oxide (NO) and interleukin (IL)-1β production in neuropsychiatric models; GUDCA decreases lactate dehydrogenase, TNF-α and IL-1β production in neurological models, and also reduces cytochrome c peroxidase production in neurodegenerative models; TUDCA decreases apoptosis in neurological models, reduces ROS and IL-1β production in neurodegenerative models, and decreases apoptosis and TNF-α production, and increases glutathione production in neuropsychiatric models. In addition, findings suggest that all the three bile acids would be equally beneficial in models of Huntington's disease, whereas UDCA and TUDCA would be more beneficial in models of Parkinson's disease and Alzheimer's disease, while GUDCA in models of bilirubin encephalopathy and TUDCA in models of depression. Overall, this review confirms the therapeutic potential of UDCA, GUDCA and TUDCA in neurological, neurodegenerative and neuropsychiatric disorders, proposing bile acids as potential alternative therapeutic approaches for patients suffering from these disorders.

Ursodeoxycholic acid as a potential alternative therapeutic approach for neurodegenerative disorders: Effects on cell apoptosis, oxidative stress and inflammation in the brain

Ursodeoxycholic acid (UDCA) is a bile acid component with anti-apoptotic, anti-oxidant and anti-inflammatory properties. It has been used in clinical medicine for liver diseases for centuries. In neurodegenerative diseases, increased cell apoptosis, oxidative stress and inflammation are frequently observed as well. Due to those beneficial effects of UDCA, recent studies have started to investigate the effects of UDCA in pre-clinical models of neurodegeneration. On this account, I review the data reported so far to investigate the role of UDCA in regulating apoptosis, oxidative stress and inflammation in pre-clinical models of neurodegeneration, as well as in homeostatic state. Evidence have shown that UDCA can reduce apoptosis, inhibit reactive oxygen species and tumor necrosis factor - α production in neurodegenerative models. In addition, UDCA is able to induce apoptosis of brain blastoma cells in homeostatic conditions. Overall, this review suggests the therapeutic potential of UDCA in neurodegenerative disorders, proposing UDCA as a potential alternative therapeutic approach for patients suffering from these diseases.

M2 macrophage accumulation contributes to pulmonary fibrosis, vascular dilatation, and hypoxemia in rat hepatopulmonary syndrome

Hepatopulmonary syndrome (HPS) markedly increases the mortality of patients. However, its pathogenesis remains incompletely understood. Rat HPS develops in common bile duct ligation (CBDL)-induced, but not thioacetamide (TAA)-induced cirrhosis. We investigated the mechanisms of HPS by comparing these two models. Pulmonary histology, blood gas exchange, and the related signals regulating macrophage accumulation were assessed in CBDL and TAA rats. Anti-polymorphonuclear leukocyte (antiPMN) and anti-granulocyte-macrophage colony stimulating factor (antiGM-CSF) antibodies, clodronate liposomes (CL), and monocyte chemoattractant protein 1 (MCP1) inhibitor (bindarit) were administrated in CBDL rats, GM-CSF, and MCP1 were administrated in bone marrow-derived macrophages (BMDMs). Pulmonary inflammatory cell recruitment, vascular dilatation, and hypoxemia were progressively developed by 1 week after CBDL, but only occurred at 4 week after TAA. Neutrophils were the primary inflammatory cells within 3 weeks after CBDL and at 4 week after TAA. M2 macrophages were the primary inflammatory cells, meantime, pulmonary fibrosis, GM-CSFR, and CCR2 were specifically increased from 4 week after CBDL. AntiPMN antibody treatment decreased neutrophil and macrophage accumulation, CL or the combination of antiGM-CSF antibody and bindarit treatment decreased macrophage recruitment, resulting in pulmonary fibrosis, vascular dilatation, and hypoxemia in CBDL rats alleviated. The combination treatment of GM-CSF and MCP1 promoted cell migration, M2 macrophage differentiation, and transforming growth factor-β1 (TGF-β1) production in BMDMs. Conclusively, our results highlight neutrophil recruitment mediates pulmonary vascular dilatation and hypoxemia in the early stage of rat HPS. Further, M2 macrophage accumulation induced by GM-CSF/GM-CSFR and MCP1/CCR2 leads to pulmonary fibrosis and promotes vascular dilatation and hypoxemia, as a result, HPS develops.

The influence of hyperbilirubinemia on indexes of kidney function in neonates

BACKGROUND

To study the influence of hyperbilirubinemia on indexes of neonatal kidney function.

METHODS

A prospective cohort study was conducted September 2019 to March 2020 in Neonatology Department of Xuzhou Central Hospital. Neonates with gestational age ≥ 35 weeks and aged ≤ 7 days were included and divided into mild, moderate, and severe groups according to total serum bilirubin level. Epidemiologic and demographic data and daily urine output were recorded. Total serum bilirubin, serum creatinine, serum cystatin C, serum neutrophil gelatinase-associated lipocalin (NGAL), urine NGAL, and kidney injury molecule-1 were tested before and 12~18 h after phototherapy. Parameters of kidney function were compared between groups.

RESULTS

Fifty-three, 52, and 49 neonates were included in the mild, moderate, and severe groups, respectively. Urine NGAL was higher in severe (1.36 ± 0.24 μg/L) compared to moderate (1.22 ± 0.19 μg/L) and mild groups (1.16 ± 0.19 μg/L), and differences were statistically significant (P = 0.004 and < 0.001, respectively). Urine NGAL was not significantly different between moderate and mild groups (P > 0.05). No significant differences in other kidney function indexes were observed between the three groups (all P > 0.05). Significant reduction in urine NGAL levels 12~18 h after stopping phototherapy was found in severe group ((1.17 ± 0.28) μg/L vs. (1.35 ± 0.23) μg/L, P < 0.001). Urine NGAL positively correlated with total serum bilirubin (r = 0.575, P < 0.001). Among all cases, neither serum creatinine nor daily urine output met neonatal acute kidney injury diagnostic criteria.

CONCLUSION

Severe hyperbilirubinemia may temporarily impair renal tubular reabsorption functions in full-term and near-term neonates, which is likely reversible. However, it has little effect on glomerular filtration function. A higher resolution version of the Graphical abstract is available as Supplementary information.

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.

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.

Oxidative stress in vascular calcification

Vascular calcification (VC), which is closely associated with significant mortality in cardiovascular disease, chronic kidney disease (CKD), and/or diabetes mellitus, is characterized by abnormal deposits of hydroxyapatite minerals in the arterial wall. The impact of oxidative stress (OS) on the onset and progression of VC has not been well described. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, xanthine oxidases, myeloperoxidase (MPO), nitric oxide synthases (NOSs), superoxide dismutase (SOD) and paraoxonases (PONs) are relevant factors that influence the production of reactive oxygen species (ROS). Furthermore, excess ROS-induced OS has emerged as a critical mediator promoting VC through several mechanisms, including phosphate balance, differentiation of vascular smooth muscle cells (VSMCs), inflammation, DNA damage, and extracellular matrix remodeling. Because OS is a significant regulator of VC, antioxidants may be considered as novel treatment options.

Decreased serum bilirubin levels in children with lead poisoning

Objective

Lead is a toxic heavy metal, which causes irreversible damage in children. Oxidative stress is the underlying mechanism of lead toxicity, and monitoring oxidative stress of lead poisoning children in vivo is important. Our study aimed to investigate blood serum levels of biochemical parameters, including albumin, bilirubin, creatinine, and uric acid, which are regarded as non-enzymatic antioxidants, in children with lead poisoning.

Methods

We studied 355 children with lead poisoning and 355 age- and sex-matched controls. We analyzed clinical characteristics and measured serum levels of total protein, globulin, albumin, bilirubin, aspartate aminotransferase (AST), alanine aminotransferase, urea, and creatinine.

Results

We found that albumin, bilirubin, urea, and creatinine levels were significantly lower and AST, total protein, and globulin levels were higher in children with lead poisoning than in controls. Direct bilirubin, albumin, total protein, urea, creatinine, and AST levels were associated with lead poisoning after adjustment for other covariates. Spearman analysis showed that direct bilirubin, albumin, and urea levels were independent indicators (i.e., not related to hemoglobin or weight), while creatinine levels showed a moderate correlation with weight.

Conclusion

Lead interferes with the non-enzymatic antioxidant system in children, and lead poisoning results in a decrease in serum bilirubin levels.

Challenges of phototherapy for neonatal hyperbilirubinemia (Review)

Phototherapy is universally recognized as the first option for treating neonatal jaundice due to its unparalleled efficiency and safety in reducing the high serum free bilirubin levels and limiting its neurotoxic effects. However, several studies have suggested that phototherapy may elicit a series of short- and long-term adverse reactions associated with pediatric diseases, including hemolysis, allergic diseases, DNA damage or even cancer. The aim of the present review was to summarize the etiology, mechanism, associated risks and therapeutic strategies for reducing high neonatal serum bilirubin levels. In order to shed light on the negative effects of phototherapy and to encourage implementation of a reasonable and standardized phototherapy scheme in the clinic, the present review sought to highlight the current understanding of the adverse reactions of phototherapy, as it is necessary to further study the mechanism underlying the development of the adverse effects of phototherapy in infants in order to explore novel therapeutic alternatives.

Brassica juncea L. (Mustard) Extract Silver NanoParticles and Knocking off Oxidative Stress, ProInflammatory Cytokine and Reverse DNA Genotoxicity

Detoxification is one of the main vital tasks performed by the liver. The purpose of this study was to investigate whether mustard in its normal or nanoparticles could confer a protective/therapeutic effect against TAA-induced acute liver failure in experimental animal models. Mustard ethanolic extract was analyzed by HPLC/MS. To induce liver failure, male rats were injected with 350 mg/kg bw TAA IP, then treated orally with a dose of 100 mg/kg for 15 d of mustard extract and its nanoform before and following induction. The levels of serum liver functions, total cholesterol (TCHo), total glyceride (TG), total bilirubin (TBIL), hepatic malonaldhyde (MDA) and nitric oxide (NO),glutathione (GSH), sodium oxide dismutase (SOD), as well as tumor necrosis factor (TNF-α,) and interleukin 6 (IL-6), were estimated. DNA genotoxicity and hepatic pathology, and immunohistologic (IHC) changes were assayed. The antioxidant content of Phenolic acids, flavonoids in mustard ethanolic extract substantially decreased the levels of ALT, AST, ALP and rehabilitated the histopathological alterations. In addition, nanoforms of mustard ethanol extract have notably increased the levels of GSH, SOD and significantly reduced the levels of MDA. The expression levels of TNF-α and IL-6 in serum and tissue were markedly downregulated. DNA genotoxicity was significantly reversed. Mustard introduced a protective and medicinal effect against TAA in both its forms.

The role of microbiota in neonatal hyperbilirubinemia

Hyperbilirubinemia accounts for about 60% of full-term and 80% of preterm neonates globally, which is characterized by physiologically elevated unconjugated bilirubin in serum, but abnormally high levels of bilirubin have potential neurotoxic effects. Several factors contribute to the development of neonatal hyperbilirubinemia, including isoimmunization, dysregulated gut flora, genetic alteration and environmental factors. Animal studies have pinpointed the causal roles of several bacteria in bilirubin metabolism. Human studies have revealed microbiota composition in hyperbilirubinemia and found that gut microbiota affect newborns with different severity of hyperbilirubinemia. However, dysbiosis and subsequent changes in microbiota-related metabolic processes are not always considered. This review aims to describe the critical microbiota signatures for neonatal hyperbilirubinemia and focus on the underlying pathogenetic mechanism. These scientific bases give a new and accurate therapeutic strategy for the application of gut microbiota.

Oxidative Stress and Inflammation in COVID-19-Associated Sepsis: The Potential Role of Anti-Oxidant Therapy in Avoiding Disease Progression

Since the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak emerged, countless efforts are being made worldwide to understand the molecular mechanisms underlying the coronavirus disease 2019 (COVID-19) in an attempt to identify the specific clinical characteristics of critically ill COVID-19 patients involved in its pathogenesis and provide therapeutic alternatives to minimize COVID-19 severity. Recently, COVID-19 has been closely related to sepsis, which suggests that most deceases in intensive care units (ICU) may be a direct consequence of SARS-CoV-2 infection-induced sepsis. Understanding oxidative stress and the molecular inflammation mechanisms contributing to COVID-19 progression to severe phenotypes such as sepsis is a current clinical need in the effort to improve therapies in SARS-CoV-2 infected patients. This article aims to review the molecular pathogenesis of SARS-CoV-2 and its relationship with oxidative stress and inflammation, which can contribute to sepsis progression. We also provide an overview of potential antioxidant therapies and active clinical trials that might prevent disease progression or reduce its severity.

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.

Endogenous toxic metabolites and implications in cancer therapy

It is well recognized that many metabolic enzymes play essential roles in cancer cells in producing building blocks such as nucleotides, which are required in greater amounts due to their increased proliferation. On the other hand, the significance of enzymes in preventing the accumulation of their substrates is less recognized. Here, we outline the evidence and underlying mechanisms for how many metabolites normally produced in cells are highly toxic, such as metabolites containing reactive groups (e.g., methylglyoxal, 4-hydroxynonenal, and glutaconyl-CoA), or metabolites that act as competitive analogs against other metabolites (e.g., deoxyuridine triphosphate and l-2-hydroxyglutarate). Thus, if a metabolic pathway contains a toxic intermediate, then we may be able to induce accumulation and poison a cancer cell by targeting the downstream enzyme. Furthermore, this poisoning may be cancer cell selective if this pathway is overactive in a cancer cell relative to a nontransformed cell. We describe this concept as illustrated in selenocysteine metabolism and other pathways and discuss future directions in exploiting toxic metabolites to kill cancer cells.

Microglia Susceptibility to Free Bilirubin Is Age-Dependent

Increased concentrations of unconjugated bilirubin (UCB), namely its free fraction (Bf), in neonatal life may cause transient or definitive injury to neurons and glial cells. We demonstrated that UCB damages neurons and glial cells by compromising oligodendrocyte maturation and myelination, and by activating astrocytes and microglia. Immature neurons and astrocytes showed to be especially vulnerable. However, whether microglia susceptibility to UCB is also age-related was never investigated. We developed a microglia culture model in which cells at 2 days in vitro (2DIV) revealed to behave as the neonatal microglia (amoeboid/reactive cells), in contrast with those at 16DIV microglia that performed as aged cells (irresponsive/dormant cells). Here, we aimed to unveil whether UCB-induced toxicity diverged from the young to the long-cultured microglia. Cells were isolated from the cortical brain of 1- to 2-day-old CD1 mice and incubated for 24 h with 50/100 nM Bf levels, which were associated to moderate and severe neonatal hyperbilirubinemia, respectively. These concentrations of Bf induced early apoptosis and amoeboid shape in 2DIV microglia, while caused late apoptosis in 16DIV cells, without altering their morphology. CD11b staining increased in both, but more markedly in 2DIV cells. Likewise, the gene expression of HMGB1, a well-known alarmin, as well as HMGB1 and GLT-1–positive cells, were enhanced as compared to long-maturated microglia. The CX3CR1 reduction in 2DIV microglia was opposed to the 16DIV cells and suggests a preferential Bf-induced sickness response in younger cells. In conformity, increased mitochondrial mass and NO were enhanced in 2DIV cells, but unchanged or reduced, respectively, in the 16DIV microglia. However, 100 nM Bf caused iNOS gene overexpression in 2DIV and 16DIV cells. While only arginase 1/IL-1β gene expression levels increased upon 50/100 nM Bf treatment in long-maturated microglia, MHCII/arginase 1/TNF-α/IL-1β/IL-6 (>10-fold) were upregulated in the 2DIV microglia. Remarkably, enhanced inflammatory-associated microRNAs (miR-155/miR-125b/miR-21/miR-146a) and reduced anti-inflammatory miR-124 were found in young microglia by both Bf concentrations, while remained unchanged (miR/21/miR-125b) or decreased (miR-155/miR-146a/miR-124) in aged cells. Altogether, these findings support the neurodevelopmental susceptibilities to UCB-induced neurotoxicity, the most severe disabilities in premature babies, and the involvement of immune-inflammation neonatal microglia processes in poorer outcomes.

Experimental models assessing bilirubin neurotoxicity

The molecular and cellular events leading to bilirubin-induced neurotoxicity, the mechanisms regulating liver and intestine expression in neonates, and alternative pathways of bilirubin catabolism remain incompletely defined. To answer these questions, researchers have developed a number of model systems to closely recapitulate the main characteristics of the disease, ranging from tissue cultures to engineered mouse models. In the present review we describe in vitro, ex vivo, and in vivo models developed to study bilirubin metabolism and neurotoxicity, with a special focus on the use of engineered animal models. In addition, we discussed the most recent studies related to potential therapeutic approaches to treat neonatal hyperbilirubinemia, ranging from anti-inflammatory drugs, activation of nuclear receptor pathways, blockade of bilirubin catabolism, and stimulation of alternative bilirubin-disposal pathways.