Biliverdin administration regulates the microRNA-mRNA expressional network associated with neuroprotection in cerebral ischemia reperfusion injury in rats

Macrophage polarization in spinal cord injury repair and the possible role of microRNAs: A review

The prevention, treatment, and rehabilitation of spinal cord injury (SCI) have always posed significant medical challenges. After mechanical injury, disturbances in microcirculation, edema formation, and the generation of free radicals lead to additional damage, impeding effective repair processes and potentially exacerbating further dysfunction. In this context, inflammatory responses, especially the activation of macrophages, play a pivotal role. Different phenotypes of macrophages have distinct effects on inflammation. Activation of classical macrophage cells (M1) promotes inflammation, while activation of alternative macrophage cells (M2) inhibits inflammation. The polarization of macrophages is crucial for disease healing. A non-coding RNA, known as microRNA (miRNA), governs the polarization of macrophages, thereby reducing inflammation following SCI and facilitating functional recovery. This study elucidates the inflammatory response to SCI, focusing on the infiltration of immune cells, specifically macrophages. It examines their phenotype and provides an explanation of their polarization mechanisms. Finally, this paper introduces several well-known miRNAs that contribute to macrophage polarization following SCI, including miR-155, miR-130a, and miR-27 for M1 polarization, as well as miR-22, miR-146a, miR-21, miR-124, miR-223, miR-93, miR-132, and miR-34a for M2 polarization. The emphasis is placed on their potential therapeutic role in SCI by modulating macrophage polarization, as well as the present developments and obstacles of miRNA clinical therapy.

Proteomic analysis of Biliverdin protected cerebral ischemia-reperfusion injury in rats

Biliverdin, a heme metabolite, has been previously reported to alleviate cerebral ischemic reperfusion injury (CIRI). However, the alterations of brain proteome profiles underlying this treatment remain elusive. The objective of this study is to analyze the differential protein expression profile in cerebral cortex of rats involved in anti-CIRI effects of Biliverdin, providing experimental foundation for searching specific marker proteins. Rat model of MCAO/R was established, HE staining, TTC staining, TUNEL staining, and neurological behavioral examination, corner turning test, adhesive removal test, were performed to validate the effects of Biliverdin, and the results indicated that Biliverdin plays a significant role in alleviating CIRI. Furthermore, proteomic analysis of brain tissues of rats subjected to CIRI following Biliverdin treatment was performed using an integrated TMT-based quantitative proteomic approach coupled with LC-MS/MS technology to clarify the comprehensive mechanisms of Biliverdin in CIRI. First, we conducted strict quality control data for TMT experiments. Finally, a total of 7366 proteins were identified, of which 95 proteins were differentially expressed (DEPs) between the CIRI group and the Sham group and 52 between the CIRI and BV groups. In addition, two overlapping proteins among the 147 DEPs, Atg4c and Camlg, were validated by RT-qPCR and western blotting, and their levels were consistent with the results of TMT analysis. Taken together, the current findings firstly mapped comprehensive proteomic changes after CIRI treated with Biliverdin, providing a foundation for developing potentially therapeutic targets of anti-CIRI of Biliverdin and clinically prognostic biomarkers of stroke.

MicroRNA-204-5p Ameliorates Neurological Injury via the EphA4/PI3K/AKT Signaling Pathway in Ischemic Stroke

Ischemic stroke has extremely high mortality and disability rates worldwide. miR-204-5p has been reported to be associated with neurological diseases. However, the relationship linking miR-204-5p to ischemic stroke and its molecular mechanism remain unclear. Herein, we found that expression of miR-204-5p was significantly decreased while EphA4 increased in vivo and vitro, which reached the peak at 24 h after cerebral ischemia/reperfusion. Then, we altered miR-204-5p expression in rats by cerebroventricular injection. Our study showed that miR-204-5p overexpression obviously reduced the brain infarction area and neurological score. We successfully cultured neurons to investigate the downstream mechanism. Upregulation of miR-204-5p increased cell viability and suppressed the release of LDH. Moreover, the proportion of apoptotic cells tested by TUNEL and flow cytometry and protein expression of Cleaved Caspase3 and Bax were inhibited. The relative expression of IL-6, TNF-α, and IL-1β was repressed. In contrary, knockdown of miR-204-5p showed the opposite results. Bioinformatics and a dual luciferase assay illustrated that EphA4 was a target gene. Further research studies demonstrated that the neuroprotective effects of miR-204-5p could be partially mitigated by upregulating EphA4. Next, we proved that the miR-204-5p/EphA4 axis furtherly activated the PI3K/AKT pathway. We thoroughly illustrated the role of neuroinflammation and apoptosis. However, whether there are other mechanisms associated with the EphA4/PI3K/AKT pathway needs further investigation. Altogether, the miR-204-5p axis ameliorates neurological injury via the EphA4/PI3K/AKT pathway, which is expected to serve as an effective treatment for ischemic stroke.

MicroRNA-27a-3p relieves inflammation and neurologic impairment after cerebral ischemia reperfusion via inhibiting LITAF and the TLR4/NF-κB pathway

Cerebral ischemia reperfusion (CIR) affects microRNA (miR) expression and causes substantial inflammation. Here, we investigated the influence and underlying mechanism of miR-27a-3p in rats with CIR. Firstly, Biliverdin treatment relieved cerebral infarction and decreased the levels of serum interleukin (IL)-1β, IL-6 and TNF-α. Through our previous study, we found key miR-27a-3p and its targeted gene LITAF might involve in the molecular mechanism of CIR. Then, the regulation between miR-27a-3p and LITAF was verified by the temporal miR-27a-3p and LITAF expression profiles and luciferase assay. Moreover, intracerebroventricular injection of the miR-27a-3p mimic significantly decreased the LITAF, TLR4, NF-κB and IL-6 levels at 24h post-surgery, whereas miR-27a-3p inhibitor reversed these effects. Furthermore, miR-27a-3p mimic could relieve cerebral infarct and neurologic deficit after CIR. In addition, injection of miR-27a-3p mimic decreased neuronal damage induced by CIR. Taken together, our results suggest that miR-27a-3p protect against CIR by relieving inflammation, neuronal damage and neurologic deficit via regulating LITAF and the TLR4/NF-κB pathway.

Remote ischemic preconditioning protects against cerebral ischemia injury in rats by upregulating miR-204-5p and activating the PINK1/Parkin signaling pathway

Remote ischemic preconditioning (RiPC) is the process where preconditioning ischemia protects the organs against the subsequent index ischemia. RiPC is a protective method for brain damage. This study is to explore the effect and mechanism of RiPC in cerebral ischemia injury in rats through regulation of miR-204-5p/BRD4 expression. Middle cerebral artery occlusion (MCAO) rat model and glucose deprivation (OGD) neuron model were established. The effect of RiPC on neurological deficits, cerebral infarct size, autophagy marker, inflammatory cytokines and apoptosis was evaluated. miR-204-5p expression was analyzed using RT-qPCR, and then downregulated using miR-204-5p antagomir to estimate its effect on MCAO rats. The downstream mechanism of miR-204-5p was explored. RiPC promoted autophagy, reduced cerebral infarct volume and neurological deficit score, and alleviated apoptosis and cerebral ischemia injury in rats, with no significant effects on healthy rat brains. RiPC up-regulated miR-204-5p expression in MCAO rats. miR-204-5p knockdown partially reversed the effect of RiPC. RiPC promoted autophagy in OGD cells, and attenuated inflammation and apoptosis. miR-204-5p targeted BRD4, which partially reversed the effect of miR-204-5p on OGD cells. RiPC activated the PINK1/Parkin pathway via the miR-204-5p/BRD4 axis. In conclusion, RiPC activated the PINK1/Parkin pathway and prevented cerebral ischemia injury by up-regulating miR-204-5p and inhibiting BRD4.

Comprehensive Analysis of the Effect of 20(R)-Ginsenoside Rg3 on Stroke Recovery in Rats via the Integrative miRNA–mRNA Regulatory Network

MicroRNAs (miRNAs) are a class of small, endogenous, noncoding RNAs. Recent research has proven that miRNAs play an essential role in the occurrence and development of ischemic stroke. Our previous studies confirmed that 20(R)-ginsenosideRg3 [20(R)-Rg3] exerts beneficial effects on cerebral ischemia–reperfusion injury (CIRI), but its molecular mechanism has not been elucidated. In this study, we used high-throughput sequencing to investigate the differentially expressed miRNA and mRNA expression profiles of 20(R)-Rg3 preconditioning to ameliorate CIRI injury in rats and to reveal its potential neuroprotective molecular mechanism. The results show that 20(R)-Rg3 alleviated neurobehavioral dysfunction in MCAO/R-treated rats. Among these mRNAs, 953 mRNAs were significantly upregulated and 2602 mRNAs were downregulated in the model group versus the sham group, whereas 437 mRNAs were significantly upregulated and 35 mRNAs were downregulated in the 20(R)-Rg3 group in contrast with those in the model group. Meanwhile, the expression profile of the miRNAs showed that a total of 283 differentially expressed miRNAs were identified, of which 142 miRNAs were significantly upregulated and 141 miRNAs were downregulated in the model group compared with the sham group, whereas 34 miRNAs were differentially expressed in the 20(R)-Rg3 treatment group compared with the model group, with 28 miRNAs being significantly upregulated and six miRNAs being significantly downregulated. Furthermore, 415 (391 upregulated and 24 downregulated) differentially expressed mRNAs and 22 (17 upregulated and 5 downregulated) differentially expressed miRNAs were identified to be related to 20(R)-Rg3′s neuroprotective effect on stroke recovery. The Kyoto Encyclopedia of Genes and Genomes (KEGG) results showed that 20(R)-Rg3 could modulate multiple signaling pathways related to these differential miRNAs, such as the cGMP-PKG, cAMP and MAPK signaling pathways. This study provides new insights into the protective mechanism of 20(R)-Rg3 against CIRI, and the mechanism may be partly associated with the regulation of brain miRNA expression and its target signaling pathways.

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.

Biliverdin Protects Against Cerebral Ischemia/Reperfusion Injury by Regulating the miR-27a-3p/Rgs1 Axis

BACKGROUND

We have previously demonstrated that biliverdin has neuroprotective effects that ameliorate cerebral ischemia/reperfusion (I/R) injury in rats. However, the underlying mechanism is unknown. This study aimed at elucidating on the modulatory role of miR-27a-3p on Rgs1 as a mechanism by which biliverdin affects cerebral I/R injury.

METHODS

Middle cerebral artery occlusion/reperfusion (MCAO/R) was used to establish I/R rat models while oxygen glucose deprivation/reoxygenation (OGD/R) was used to induce hippocampal neurons to establish I/R models in vitro. Infarct volume was assessed by TTC staining. Apoptotic analyses of ischemic cortical neurons and cells were performed by TUNEL staining and flow cytometry, respectively. Cell viability was assessed by the CCK-8 assay while the target of miR-27a-3p was determined by double luciferase reporter assay. Relative expression levels of miR-27a-3p and Rgs1 (in vivo and in vitro) as well as markers of inflammation and apoptosis (in vitro) were detected by RT-qPCR. Then, Elisa and western blot were used to assess protein expression levels of inflammatory and apoptotic markers in vitro.

RESULTS

Biliverdin suppressed inflammation and apoptosis in hippocampal neurons upon OGD/R, and reduced cerebral infarction volume as well as apoptosis in the MCAO/R rat model. Furthermore, biliverdin upregulated miR-27a-3p and downregulated hippocampal neuron Rgs1 after OGD/R as well as in rat brain tissues after cerebral I/R. Bioinformatic analysis revealed an miR-27a-3p docking site in the 3'-UTR region of Rgs1. Luciferase reporter assays showed that Rgs1 is an miR-27a-3p target. Moreover, miR-27a-3p upregulation inhibited OGD/R-triggered inflammation and suppressed neuronal apoptosis. Rgs1 knockdown suppressed OGD/R-triggered inflammation and decreased neuronal apoptosis while miR-27a-3p downregulation reversed the protective effect of Rgs1 knockdown. Moreover, miR-27a-3p overexpression and Rgs1 silencing suppressed NF-κB (p65) expression.

CONCLUSION

Biliverdin protects against cerebral I/R injury by regulating the miR-27a-3p/Rgs1 axis, thereby inhibiting inflammation and apoptosis.

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.

Heme Oxygenase Dependent Bilirubin Generation in Vascular Cells: A Role in Preventing Endothelial Dysfunction in Local Tissue Microenvironment?

Among antioxidants in the human body, bilirubin has been recognized over the past 20 years to afford protection against different chronic conditions, including inflammation and cardiovascular disease. Moderate increases in plasma concentration and cellular bilirubin generation from metabolism of heme via heme oxygenase (HMOX) in virtually all tissues can modulate endothelial and vascular function and exert antioxidant and anti-inflammatory roles. This review aims to provide an up-to-date and critical overview of the molecular mechanisms by which bilirubin derived from plasma or from HMOX1 activation in vascular cells affects endothelial function. Understanding the molecular actions of bilirubin may critically improve the management not only of key cardiovascular diseases, but also provide insights into a broad spectrum of pathologies driven by endothelial dysfunction. In this context, therapeutic interventions aimed at mildly increasing serum bilirubin as well as bilirubin generated endogenously by endothelial HMOX1 should be considered.