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

Gut microbes of the cecum versus the colon drive more severe lethality and multi-organ damage

Intestinal perforations lead to a high risk of sepsis-associated morbidity and multi-organ dysfunctions. A perforation allows intestinal contents (IC) to enter the peritoneal cavity, causing abdominal infections. Right- and left-sided perforations have different prognoses in humans, but the mechanisms associated with different cecum and colon perforations remain unclear. This study investigates how gut flora influences outcomes from perforations at different sites in mice. Using fecal-induced peritonitis mouse model, isolated IC from the cecum or colon was injected peritoneally at 2 mg/kg. Bacterial burden was quantified with quantitative PCR, and microbial communities were analyzed using 16S rRNA gene sequencing. Survival rates were monitored, and blood biochemical indices, histological changes, cytokines expression, immunological signaling and multiple-organ damage were assessed at 16 h post-injections. The results showed cecum IC developed more severe sepsis than colon IC, with shorter median survival time and greater multi-organ damage. Mice treated with cecum IC displayed elevated tissue damage markers in the liver, heart, and kidneys, contributing to worsened pathology. This was likely driven by systematic inflammatory cytokines production and lung inflammation. Mechanistically, cecum IC triggered stronger cGAS-STING and TBK1-NF-κB signaling, promoting systemic inflammation compared to the colon IC. Moreover, bacterial analysis demonstrated that cecum IC carry a higher bacterial burden than colon IC and exhibit a different microbial community. A detailed microbiome comparison revealed an increased abundance of potentially pathogenic bacteria in the cecum IC. These findings suggest that the site of intestinal perforation influences sepsis severity, with the cecum being associated with a higher bacterial burden and a relatively increased abundance of potentially pathogenic bacteria compared to the colon. Our findings first compared the lethality associated with the microbial composition of the cecum and colon, indicating the perforation site could help providers predict the severity of sepsis, thereby introducing a novel perspective to microbiology and sepsis research.

Metabolomic and lipidomic pathways in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) results in a complex systemic response that is critical to the pathophysiology of late complications and has important effects on outcomes. Omics techniques have expanded our investigational scope and depth into this phenomenon. In particular, metabolomics-the study of small molecules, such as blood products, carbohydrates, amino acids, and lipids-can provide a snapshot of dynamic subcellular processes and thus broaden our understanding of molecular-level pathologic changes that lead to the systemic response after aSAH. Lipids are especially important due to their abundance in the circulating blood and numerous physiological roles. They are comprised of a wide variety of subspecies and are critical for cellular energy metabolism, the integrity of the blood-brain barrier, the formation of cell membranes, and intercellular signaling including neuroinflammation and ferroptosis. In this review, metabolomic and lipidomic pathways associated with aSAH are summarized, centering on key metabolites from each metabolomic domain.

Phosphatidylserine improves aging sepsis survival, modulates gut microbiome, and prevents sepsis-associated encephalopathy

Aged adults are prone to both short- and long-term complications following sepsis due to ineffective therapy. Phosphatidylserine (PS) is a membrane nutrient supplement known to enhance cognition and brain function, but its potential effects in treating sepsis are not well-documented. Our study aimed to explore the potential of PS in improving outcomes in sepsis and sepsis-associated encephalopathy (SAE). Middle-aged mice were administered PS for two months following induction of sepsis by lipopolysaccharides. The results indicated a significant increase in the survival rate of mice treated with PS after sepsis. Surviving mice underwent open field and shuttle box tests 45 days post-sepsis, revealing potential alleviation of neurobehavioral impairments due to PS pretreatment. Analysis at 60 days post-sepsis euthanasia showed reduced cleaved-caspase 3 in neurons and glial cell markers in the PS-treated group compared to the untreated sepsis group. Furthermore, PS administration effectively reduced proinflammatory cytokine gene expression in the hippocampus of mice with SAE, potentially inhibiting the TBK1/NLRP3/ASC signaling pathway. In the gut, PS pretreatment modulated β-diversity while maintaining jejunal morphology and colon ZO-1 expression, without significantly affecting α-diversity indices. Our findings suggest that PS administration improves survival rates, modulates the gut microbiome, preserves gut integrity, and ameliorates brain pathology in survived mice after sepsis. Importantly, these findings have significant implications for sepsis treatment and cognitive function preservation in aging individuals, providing new insights and sparking further interest and investigation into the potential of PS in sepsis treatment.

Comprehensive analysis of biological landscape of oxidative stress-related genes in diabetic erectile dysfunction

Oxidative stress plays a pivotal role in the pathogenesis of diabetic erectile dysfunction, while specific mechanisms have not been illuminated. The study aims to reveal the genetic expression patterns of oxidative stress in diabetic erectile dysfunction. Transcriptome data of diabetic erectile dysfunction and oxidative stress-related genes (OSRGs) in the Gene Expression Omnibus database were downloaded and analyzed based on differential expression. Functional enrichment analyses were conducted to clarify the biological functions. A protein interaction framework was established, and significant gene profiles were validated in the cavernous endothelial cells, clinical patients, and rat models. A miRNA-OSRGs network was predicted and validated. The results were analyzed using Student's t-test. The analysis screened 203 differentially expressed OSRGs (p < 0.05), which had a close association with oxidoreductase activities, glutathione metabolism, and autophagy. A four-gene signature comprised of EPS8L2 (p = 0.044), GSTA3 (p = 0.015), LOX (p < 0.001) and MGST1 (p = 0.002) was well validated and regarded as the hub OSRGs. Compared with the control group, notable increases and decreases were observed in the expressions of GSTA3 (3.683 ± 0.636 vs. 0.416 ± 0.507) and LOX (2.104 ± 1.895 vs. 18.804 ± 2.751) in the validated diabetic erectile dysfunction group. The hub OSRGs-related miRNAs participated in smooth muscle cell proliferation. Besides, miR-125a-3p (p = 0.034) and miR-138-2-3p (p = 0.012) were validated as promising oxidative stress-related miRNA biomarkers. Our findings revealed the genetic alternations of oxidative stress in diabetic erectile dysfunction. These results will be instructive to explore the molecular landscape and the potential treatment for diabetic erectile dysfunction.

A Platform for the Synthesis of Oxidation Products of Bilirubin

Bilirubin is the principal product of heme catabolism. High concentrations of the pigment are neurotoxic, yet slightly elevated levels are beneficial. Being a potent antioxidant, oxidative transformations of bilirubin occur in vivo and lead to various oxidized fragments. The mechanisms of their formation, intrinsic biological activities, and potential roles in human pathophysiology are poorly understood. Degradation methods have been used to obtain samples of bilirubin oxidation products for research. Here, we report a complementary, fully synthetic method of preparation. Our strategy leverages repeating substitution patterns in the parent tetracyclic pigment. Functionalized ready-to-couple γ-lactone, γ-lactam, and pyrrole monocyclic building blocks were designed and efficiently synthesized. Subsequent modular combinations, supported by metal-catalyzed borylation and cross-coupling chemistries, translated into the concise assembly of the structurally diverse bilirubin oxidation products (BOXes, propentdyopents, and biopyrrins). The discovery of a new photoisomer of biopyrrin A named lumipyrrin is reported. Synthetic bilirubin oxidation products made available in sufficient purity and quantity will support future in vitro and in vivo investigations.

High total bilirubin-to-uric acid ratio predicts poor sleep quality after acute ischemic stroke: a prospective nested case-control study

BACKGROUND

Sleep disorders are prevalent after stroke, resulting in high recurrence rates and mortality. But the biomarkers of sleep disorders in stroke patients remain to be elucidated. This study aimed to explore the relationship between total bilirubin-to-uric acid ratio (TUR) and sleep quality after acute ischemic stroke (AIS).

METHODS

Three hundred twenty-six AIS patients were recruited and followed up 1 month after stroke in our study. Serum total bilirubin and uric acid levels were obtained within 24 h after admission. The Pittsburgh Sleep Quality Index (PSQI) was used to evaluate sleep quality 1 month after stroke. We conducted receiver operating characteristic (ROC) curve analysis and screened the optimal biomarker to differentiate sleep disorders after stroke. Then the TUR was stratified according to the best cut-off value (0.036) of the ROC and further analysed by binary logistic regression analysis. Additionally, the interaction was used to explore the difference in its effect on post-stroke sleep quality in different subgroups.

RESULTS

Three hundred thirty-one patients (40.2%) were considered as having poor sleep quality during the one-month follow-up. Compared to patients with good sleep, patients with poor sleep were more likely to have higher TUR (IQR), 0.05 (0.03-0.06) versus 0.03 (0.02-0.04), P < 0.001. After adjusting for confounding factors, binary regression analysis demonstrated that a high TUR (≥0.036) was independently related to post-stroke poor sleep quality (OR = 3.75, 95% CI = 2.02-6.96, P < 0.001).

CONCLUSIONS

High TUR is associated with an increased risk of poor sleep quality in AIS patients, especially in females, diabetics, and patients with hyperlipidaemia.

Integrated transcriptomic and metabolomic analysis of cortical neurons reveals dysregulated lipid metabolism, enhanced glycolysis and activated HIF-1 signaling pathways in acute hypoxia

The brain is the main oxygen-consuming organ and is vulnerable to ischemic shock or insufficient blood perfusion. Brain hypoxia has a persistent and detrimental effect on resident neurons. Previous studies have identified alterations in genes and metabolites in ischemic brain shock by single omics, but the adaptive systems that neurons use to cope with hypoxia remain uncovered. In the present study, we constructed an acute hypoxia model and performed a multi-omics analysis from RNA-sequencing and liquid chromatography-mass spectrometry (LC-MS)-based metabolomics on exploring potentially differentially expressed genes (DEGs) and metabolites (DEMs) in primary cortical neurons under severe acute hypoxic conditions. The TUNEL assay showed acute hypoxia-induced apoptosis in cortical neurons. Omics analysis identified 564 DEGs and 46 DEMs categorized in the Kyoto encyclopedia of genes and genomes (KEGG) database. Integrative pathway analysis highlighted that dysregulated lipid metabolism, enhanced glycolysis, and activated HIF-1 signaling pathways could regulate neuron physiology and pathophysiology under hypoxia. These findings may help us understand the transcriptional and metabolic mechanisms by which cortical neurons respond to hypoxia and identify potential targets for neuron protection.

Multi-omics analysis reveals neuroinflammation, activated glial signaling, and dysregulated synaptic signaling and metabolism in the hippocampus of aged mice

Aging is an intricate biological event that occurs in both vertebrates and invertebrates. During the aging process, the brain, a vulnerable organ, undergoes structural and functional alterations, resulting in behavioral changes. The hippocampus has long been known to be critically associated with cognitive impairment, dementia, and Alzheimer’s disease during aging; however, the underlying mechanisms remain largely unknown. In this study, we hypothesized that altered metabolic and gene expression profiles promote the aging process in the hippocampus. Behavioral tests showed that exploration, locomotion, learning, and memory activities were reduced in aged mice. Metabolomics analysis identified 69 differentially abundant metabolites and showed that the abundance of amino acids, lipids, and microbiota-derived metabolites (MDMs) was significantly altered in hippocampal tissue of aged animals. Furthermore, transcriptomic analysis identified 376 differentially expressed genes in the aged hippocampus. A total of 35 differentially abundant metabolites and 119 differentially expressed genes, constituting the top 200 correlations, were employed for the co-expression network. The multi-omics analysis showed that pathways related to inflammation, microglial activation, synapse, cell death, cellular/tissue homeostasis, and metabolism were dysregulated in the aging hippocampus. Our data revealed that metabolic perturbations and gene expression alterations in the aged hippocampus were possibly linked to their behavioral changes in aged mice; we also provide evidence that altered MDMs might mediate the interaction between gut and brain during the aging process.

Integrated transcriptomics and metabolomics analysis of the hippocampus reveals altered neuroinflammation, downregulated metabolism and synapse in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is an intricated complication of sepsis that brings abnormal emotional and memory dysfunction and increases patients’ mortality. Patients’ alterations and abnormal function seen in SAE occur in the hippocampus, the primary brain region responsible for memory and emotional control, but the underlying pathophysiological mechanisms remain unclear. In the current study, we employed an integrative analysis combining the RNA-seq-based transcriptomics and liquid chromatography/mass spectrometry (LC-MS)-based metabolomics to comprehensively obtain the enriched genes and metabolites and their core network pathways in the endotoxin (LPS)-injected SAE mice model. As a result, SAE mice exhibited behavioral changes, and their hippocampus showed upregulated inflammatory cytokines and morphological alterations. The omics analysis identified 81 differentially expressed metabolites (variable importance in projection [VIP] &gt; 1 and p &lt; 0.05) and 1747 differentially expressed genes (Foldchange &gt;2 and p &lt; 0.05) were detected in SAE-grouped hippocampus. Moreover, 31 compounds and 100 potential target genes were employed for the Kyoto Encyclopedia of Genes and Genomes (KEGG) Markup Language (KGML) network analysis to explore the core signaling pathways for the progression of SAE. The integrative pathway analysis showed that various dysregulated metabolism pathways, including lipids metabolism, amino acids, glucose and nucleotides, inflammation-related pathways, and deregulated synapses, were tightly associated with hippocampus dysfunction at early SAE. These findings provide a landscape for understanding the pathophysiological mechanisms of the hippocampus in the progression of SAE and pave the way to identify therapeutic targets in future studies.

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

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

Bilirubin oxidation end product B prevents CoCl2-induced primary cortical neuron apoptosis by promoting cell survival Akt/mTOR/p70S6K signaling pathway

Bilirubin oxidation end products (BOXes) are associated with the late-developing neurological deficits after subarachnoid hemorrhage (SAH) possibly by direct constricting the cerebral arteries, but their specific impacts on neurons especially in the state of hypoxia, a prominent feature during the late stage of SAH, remain unclear. Here, we explored the effects of BOXes on the primary cortical neurons subjected to CoCl₂-induced hypoxia by evaluating the morphological and apoptotic changes of neurons. The present study showed that Z-BOX B but not Z-BOX A greatly alleviated CoCl₂-induced neuronal cell deterioration and apoptosis. Immunocytochemical staining assay showed Z-BOX B significantly increased neurite length, the numbers of both secondary and tertiary branches, and the protein level of Synaptophysin. Caspase 3/7 apoptosis assay and DAPI staining showed that Z-BOX B markedly reduced primary cortical neurons apoptosis. The expression of cleaved Caspase-3 was suppressed by Z-BOX B treatment, while the expression of Bcl-xL was upregulated. To further discover the mechanism of the neuroprotective effect observed in Z-BOX B, we found Z-BOX B increased the expression of p-mTOR, p-Akt, and p-p70S6K. In general, our results implicated Z-BOX B may prevent CoCl₂-induced primary cortical neurons apoptosis by activating sAkt/mTOR/p70S6K signaling pathway. Hence, the present data may provide new insights into the pathophysiological mechanism of delayed neurological dysfunction after SAH and novel targets for treating SAH.