Polymerase delta-interacting protein 2 deficiency protects against blood-brain barrier permeability in the ischemic brain

Blood-brain barrier disruption: a culprit of cognitive decline?

Cognitive decline covers a broad spectrum of disorders, not only resulting from brain diseases but also from systemic diseases, which seriously influence the quality of life and life expectancy of patients. As a highly selective anatomical and functional interface between the brain and systemic circulation, the blood-brain barrier (BBB) plays a pivotal role in maintaining brain homeostasis and normal function. The pathogenesis underlying cognitive decline may vary, nevertheless, accumulating evidences support the role of BBB disruption as the most prevalent contributing factor. This may mainly be attributed to inflammation, metabolic dysfunction, cell senescence, oxidative/nitrosative stress and excitotoxicity. However, direct evidence showing that BBB disruption causes cognitive decline is scarce, and interestingly, manipulation of the BBB opening alone may exert beneficial or detrimental neurological effects. A broad overview of the present literature shows a close relationship between BBB disruption and cognitive decline, the risk factors of BBB disruption, as well as the cellular and molecular mechanisms underlying BBB disruption. Additionally, we discussed the possible causes leading to cognitive decline by BBB disruption and potential therapeutic strategies to prevent BBB disruption or enhance BBB repair. This review aims to foster more investigations on early diagnosis, effective therapeutics, and rapid restoration against BBB disruption, which would yield better cognitive outcomes in patients with dysregulated BBB function, although their causative relationship has not yet been completely established.

Endothelial dysfunction: Pathophysiology and therapeutic targets for sepsis-induced multiple organ dysfunction syndrome

Sepsis and septic shock are critical medical conditions characterized by a systemic inflammatory response to infection, significantly contributing to global mortality rates. The progression to multiple organ dysfunction syndrome (MODS) represents the most severe complication of sepsis and markedly increases clinical mortality. Central to the pathophysiology of sepsis, endothelial cells play a crucial role in regulating microcirculation and maintaining barrier integrity across various organs and tissues. Recent studies have underscored the pivotal role of endothelial function in the development of sepsis-induced MODS. This review aims to provide a comprehensive overview of the pathophysiology of sepsis-induced MODS, with a specific focus on endothelial dysfunction. It also compiles compelling evidence regarding potential small molecules that could attenuate sepsis and subsequent multi-organ damage by modulating endothelial function. Thus, this review serves as an essential resource for clinical practitioners involved in the diagnosing, managing, and providing intensive care for sepsis and associated multi-organ injuries, emphasizing the importance of targeting endothelial cells to enhance outcomes of the patients.

YTHDF2-regulated matrilin-3 mitigates post-reperfusion hemorrhagic transformation in ischemic stroke via the PI3K/AKT pathway

Hemorrhagic transformation can complicate ischemic strokes after recanalization treatment within a time window that requires early intervention. To determine potential therapeutic effects of matrilin-3, rat cerebral ischemia-reperfusion was produced using transient middle cerebral artery occlusion (tMCAO); intracranial hemorrhage and infarct volumes were assayed through hemoglobin determination and 2,3,5-triphenyltetrazoliumchloride (TTC) staining, respectively. Oxygen-glucose deprivation (OGD) modeling of ischemia was performed on C8-D1A cells. Interactions between matrilin-3 and YTH N6-methyladenosine RNA binding protein F2 (YTHDF2) were determined using RNA immunoprecipitation assay and actinomycin D treatment. Reperfusion after tMCAO modeling increased hemorrhage, hemoglobin content, and infarct volumes; these were alleviated by matrilin treatment. Matrilin-3 was expressed at low levels and YTHDF2 was expressed at high levels in ischemic brains. In OGD-induced cells, matrilin-3 was negatively regulated by YTHDF2. Matrilin-3 overexpression downregulated p-PI3K/PI3K, p-AKT/AKT, ZO-1, VE-cadherin and occludin, and upregulated p-JNK/JNK in ischemic rat brains; these effects were reversed by LY294002 (a PI3K inhibitor). YTHDF2 knockdown inactivated the PI3K/AKT pathway, inhibited inflammation and decreased blood-brain barrier-related protein levels in cells; these effects were reversed by matrilin-3 deficiency. These results indicate that YTHDF2-regulated matrilin-3 protected ischemic rats against post-reperfusion hemorrhagic transformation via the PI3K/AKT pathway and that matrilin may have therapeutic potential in ischemic stroke.

Crosstalk Among Glial Cells in the Blood-Brain Barrier Injury After Ischemic Stroke

Blood-brain barrier (BBB) is comprised of brain microvascular endothelial cells (ECs), astrocytes, perivascular microglia, pericytes, neuronal processes, and the basal lamina. As a complex and dynamic interface between the blood and the central nervous system (CNS), BBB is responsible for transporting nutrients essential for the normal metabolism of brain cells and hinders many toxic compounds entering into the CNS. The loss of BBB integrity following stroke induces tissue damage, inflammation, edema, and neural dysfunction. Thus, BBB disruption is an important pathophysiological process of acute ischemic stroke. Understanding the mechanism underlying BBB disruption can uncover more promising biological targets for developing treatments for ischemic stroke. Ischemic stroke-induced activation of microglia and astrocytes leads to increased production of inflammatory mediators, containing chemokines, cytokines, matrix metalloproteinases (MMPs), etc., which are important factors in the pathological process of BBB breakdown. In this review, we discussed the current knowledges about the vital and dual roles of astrocytes and microglia on the BBB breakdown during ischemic stroke. Specifically, we provided an updated overview of phenotypic transformation of microglia and astrocytes, as well as uncovered the crosstalk among astrocyte, microglia, and oligodendrocyte in the BBB disruption following ischemic stroke.

Role of Crosstalk between Glial Cells and Immune Cells in Blood-Brain Barrier Damage and Protection after Acute Ischemic Stroke

Blood-brain barrier (BBB) damage is the main pathological basis for acute ischemic stroke (AIS)-induced cerebral vasogenic edema and hemorrhagic transformation (HT). Glial cells, including microglia, astrocytes, and oligodendrocyte precursor cells (OPCs)/oligodendrocytes (OLs) play critical roles in BBB damage and protection. Recent evidence indicates that immune cells also have an important role in BBB damage, vasogenic edema and HT. Therefore, regulating the crosstalk between glial cells and immune cells would hold the promise to alleviate AIS-induced BBB damage. In this review, we first introduce the roles of glia cells, pericytes, and crosstalk between glial cells in the damage and protection of BBB after AIS, emphasizing the polarization, inflammatory response and crosstalk between microglia, astrocytes, and other glia cells. We then describe the role of glial cell-derived exosomes in the damage and protection of BBB after AIS. Next, we specifically discuss the crosstalk between glial cells and immune cells after AIS. Finally, we propose that glial cells could be a potential target for alleviating BBB damage after AIS and we discuss some molecular targets and potential strategies to alleviate BBB damage by regulating glial cells after AIS.

New insights in the molecular regulation of the NADPH oxidase 2 activity: Negative modulation by Poldip2

Poldip2 was shown to be involved in oxidative signaling to ensure certain biological functions. It was proposed that, in VSMC, by interaction with the Nox4-associated membrane protein p22^phox, Poldip2 stimulates the level of reactive oxygen species (ROS) production. In vitro, with fractionated membranes from HEK393 cells over-expressing Nox4, we confirmed the up-regulation of NADPH oxidase 4 activity by the recombinant and purified Poldip2. Besides Nox4, the Nox1, Nox2, or Nox3 isoforms are also established partners of the p22^phox protein raising the question of their regulation by Poldip2 and of the effect in cells expressing simultaneously different Nox isoforms. In this study, we have addressed this issue by investigating the potential regulatory role of Poldip2 on NADPH oxidase 2, present in phagocyte cells. Unexpectedly, the effect of Poldip2 on phagocyte NADPH oxidase 2 was opposite to that observed on NADPH oxidase 4. Using membranes from circulating resting neutrophils, the ROS production rate of NADPH oxidase 2 was down-regulated by Poldip2 (2.5-fold). The down-regulation effect could not be correlated to the interaction of Poldip2 with p22^phox but rather, to the interaction of Poldip2 with the p47^phox protein, one of the regulatory proteins of the phagocyte NADPH oxidase. Our results show that the interaction of Poldip2 with p47^phox constitutes a novel regulatory mechanism that can negatively modulate the activity of NADPH oxidase 2 by trapping the so-called "adaptor" subunit of the complex. Poldip2 could act as a tunable switch capable of specifically regulating the activities of NADPH oxidases. This selective regulatory role of Poldip2, positive for Nox4 or negative for Nox2 could orchestrate the level and the type of ROS generated by Nox enzymes in the cells.

The polymerase δ-interacting protein family and their emerging roles in diseases

The polymerase δ-interacting protein (POLDIP) family is a new family that can interact with DNA polymerase δ (delta). The members of the POLDIP family include POLDIP1, POLDIP2, and POLDIP3. Screened by the two-hybrid method, POLDIP1, POLDIP2, and POLDIP3 were initially discovered and named for their ability to bind to the p50 subunit of DNA polymerase δ. Recent studies have confirmed that POLDIPs are involved in the regulation of signal transduction pathways in neurodevelopment, neuropsychiatric diseases, cardiovascular diseases, tumors, and other diseases. However, each protein participates in different signaling pathways. In this review, we elucidate upon the family in terms of their genes and protein structures, their biological functions, in addition to the pathways that they are involved in during the development of diverse diseases. Finally, to provide new insights to the scientific community, we used the TCGA database to analyze and summarize the gene expressions of POLDIP family members in various tumors, as well as the correlations between their expressions and the overall survival times of tumor patients. Our data summary will give researchers working on cancer new concepts.

Endothelial Poldip2 regulates sepsis-induced lung injury via Rho pathway activation

AIMS

Sepsis-induced lung injury is associated with significant morbidity and mortality. Previously, we showed that heterozygous deletion of polymerase δ-interacting protein 2 (Poldip2) was protective against sepsis-induced lung injury. Since endothelial barrier disruption is thought to be the main mechanism of sepsis-induced lung injury, we sought to determine if the observed protection was specifically due to the effect of reduced endothelial Poldip2.

METHODS AND RESULTS

Endothelial-specific Poldip2 knock-out mice (EC-/-) and their wild-type littermates (EC+/+) were injected with saline or lipopolysaccharide (18 mg/kg) to model sepsis-induced lung injury. At 18 h post-injection mice, were euthanized and bronchoalveolar lavage (BAL) fluid and lung tissue were collected to assess leucocyte infiltration. Poldip2 EC-/- mice showed reduced lung leucocyte infiltration in BAL (0.21 ± 0.9×106 vs. 1.29 ± 1.8×106 cells/mL) and lung tissue (12.7 ± 1.8 vs. 23 ± 3.7% neutrophils of total number of cells) compared to Poldip2 EC+/+ mice. qPCR analysis of the lung tissue revealed a significantly dampened induction of inflammatory gene expression (TNFα 2.23 ± 0.39 vs. 4.15 ± 0.5-fold, IκBα 4.32 ± 1.53 vs. 8.97 ± 1.59-fold), neutrophil chemoattractant gene expression (CXCL1 68.8 ± 29.6 vs. 147 ± 25.7-fold, CXCL2 65 ± 25.6 vs. 215 ± 27.3-fold) and a marker of endothelial activation (VCAM1 1.25 ± 0.25 vs. 3.8 ± 0.38-fold) in Poldip2 EC-/- compared to Poldip2 EC+/+ lungs. An in vitro model using human pulmonary microvascular endothelial cells was used to assess the effect of Poldip2 knock-down on endothelial activation and permeability. TNFα-induced endothelial permeability and VE-cadherin disruption were significantly reduced with siRNA-mediated knock-down of Poldip2 (5 ± 0.5 vs. 17.5 ± 3-fold for permeability, 1.5 ± 0.4 vs. 10.9 ± 1.3-fold for proportion of disrupted VE-cadherin). Poldip2 knock-down altered expression of Rho-GTPase-related genes, which correlated with reduced RhoA activation by TNFα (0.94 ± 0.05 vs. 1.29 ± 0.01 of relative RhoA activity) accompanied by redistribution of active-RhoA staining to the centre of the cell.

CONCLUSION

Poldip2 is a potent regulator of endothelial dysfunction during sepsis-induced lung injury, and its endothelium-specific inhibition may provide clinical benefit.

Characterization of Poldip2 knockout mice: Avoiding incorrect gene targeting

POLDIP2 is a multifunctional protein whose roles are only partially understood. Our laboratory previously reported physiological studies performed using a mouse gene trap model, which suffered from three limitations: perinatal lethality in homozygotes, constitutive Poldip2 inactivation and inadvertent downregulation of the adjacent Tmem199 gene. To overcome these limitations, we developed a new conditional floxed Poldip2 model. The first part of the present study shows that our initial floxed mice were affected by an unexpected mutation, which was not readily detected by Southern blotting and traditional PCR. It consisted of a 305 kb duplication around Poldip2 with retention of the wild type allele and could be traced back to the original targeted ES cell clone. We offer simple suggestions to rapidly detect similar accidents, which may affect genome editing using both traditional and CRISPR-based methods. In the second part of the present study, correctly targeted floxed Poldip2 mice were generated and used to produce a new constitutive knockout line by crossing with a Cre deleter. In contrast to the gene trap model, many homozygous knockout mice were viable, in spite of having no POLDIP2 expression. To further characterize the effects of Poldip2 ablation in the vasculature, RNA-seq and RT-qPCR experiments were performed in constitutive knockout arteries. Results show that POLDIP2 inactivation affects multiple cellular processes and provide new opportunities for future in-depth study of its functions.

Immune Cells in the BBB Disruption After Acute Ischemic Stroke: Targets for Immune Therapy?

Blood-Brain Barrier (BBB) disruption is an important pathophysiological process of acute ischemic stroke (AIS), resulting in devastating malignant brain edema and hemorrhagic transformation. The rapid activation of immune cells plays a critical role in BBB disruption after ischemic stroke. Infiltrating blood-borne immune cells (neutrophils, monocytes, and T lymphocytes) increase BBB permeability, as they cause microvascular disorder and secrete inflammation-associated molecules. In contrast, they promote BBB repair and angiogenesis in the latter phase of ischemic stroke. The profound immunological effects of cerebral immune cells (microglia, astrocytes, and pericytes) on BBB disruption have been underestimated in ischemic stroke. Post-stroke microglia and astrocytes can adopt both an M1/A1 or M2/A2 phenotype, which influence BBB integrity differently. However, whether pericytes acquire microglia phenotype and exert immunological effects on the BBB remains controversial. Thus, better understanding the inflammatory mechanism underlying BBB disruption can lead to the identification of more promising biological targets to develop treatments that minimize the onset of life-threatening complications and to improve existing treatments in patients. However, early attempts to inhibit the infiltration of circulating immune cells into the brain by blocking adhesion molecules, that were successful in experimental stroke failed in clinical trials. Therefore, new immunoregulatory therapeutic strategies for acute ischemic stroke are desperately warranted. Herein, we highlight the role of circulating and cerebral immune cells in BBB disruption and the crosstalk between them following acute ischemic stroke. Using a robust theoretical background, we discuss potential and effective immunotherapeutic targets to regulate BBB permeability after acute ischemic stroke.

Poldip2 controls leukocyte infiltration into the ischemic brain by regulating focal adhesion kinase-mediated VCAM-1 induction

Stroke is a multiphasic process involving a direct ischemic brain injury which is then exacerbated by the influx of immune cells into the brain tissue. Activation of brain endothelial cells leads to the expression of adhesion molecules such vascular cell adhesion molecule 1 (VCAM-1) on endothelial cells, further increasing leukocyte recruitment. Polymerase δ-interacting protein 2 (Poldip2) promotes brain vascular inflammation and leukocyte recruitment via unknown mechanisms. This study aimed to define the role of Poldip2 in mediating vascular inflammation and leukocyte recruitment following cerebral ischemia. Cerebral ischemia was induced in Poldip2+/+ and Poldip2+/- mice and brains were isolated and processed for flow cytometry or RT-PCR. Cultured rat brain microvascular endothelial cells were used to investigate the effect of Poldip2 depletion on focal adhesion kinase (FAK)-mediated VCAM-1 induction. Poldip2 depletion in vivo attenuated the infiltration of myeloid cells, inflammatory monocytes/macrophages and decreased the induction of adhesion molecules. Focusing on VCAM-1, we demonstrated mechanistically that FAK activation was a critical intermediary in Poldip2-mediated VCAM-1 induction. In conclusion, Poldip2 is an important mediator of endothelial dysfunction and leukocyte recruitment. Thus, Poldip2 could be a therapeutic target to improve morbidity following ischemic stroke.

The effects of sepsis on endothelium and clinical implications

ABSTRACT

Sepsis accounts for nearly 700 000 deaths in Europe annually and is caused by an overwhelming host response to infection resulting in organ failure. The endothelium is an active contributor to sepsis and as such represents a major target for therapy. During sepsis, endothelial cells amplify the immune response and activate the coagulation system. They are both a target and source of inflammation and serve as a link between local and systemic immune responses. In response to cytokines produced by immune cells, the endothelium expresses adhesion molecules and produces vasoactive compounds, inflammatory cytokines, and chemoattractants, thus switching from an anticoagulant to procoagulant state. These responses contribute to local control of infection, but systemic activation can lead to microvascular thrombosis, capillary permeability, hypotension, tissue hypoxia, and ultimately tissue damage. This review focuses on the role of the endothelium in leucocyte adhesion and transmigration as well as production of reactive oxygen and nitrogen species, microRNAs and cytokines, formation of signalling microparticles, and disseminated intravascular coagulation. We also discuss alterations in endothelial permeability and apoptosis. Finally, we review the diagnostic potential of endothelial markers and endothelial pathways as therapeutic targets for this devastating disease.

Poldip2 mediates blood-brain barrier disruption and cerebral edema by inducing AQP4 polarity loss in mouse bacterial meningitis model

Background

Specific highly polarized aquaporin‐4 (AQP4) expression is reported to play a crucial role in blood‐brain barrier (BBB) integrity and brain water transport balance. The upregulation of polymerase δ‐interacting protein 2 (Poldip2) was involved in aggravating BBB disruption following ischemic stroke. This study aimed to investigate whether Poldip2‐mediated BBB disruption and cerebral edema formation in mouse bacterial meningitis (BM) model occur via induction of AQP4 polarity loss.

Methods and Results

Mouse BM model was induced by injecting mice with group B hemolytic streptococci via posterior cistern. Recombinant human Poldip2 (rh‐Poldip2) was administered intranasally at 1 hour after BM induction. Small interfering ribonucleic acid (siRNA) targeting Poldip2 was administered by intracerebroventricular (i.c.v) injection at 48 hours before BM induction. A specific inhibitor of matrix metalloproteinases (MMPs), UK383367, was administered intravenously at 0.5 hour before BM induction. Western blotting, immunofluorescence staining, quantitative real‐time PCR, neurobehavioral test, brain water content test, Evans blue (EB) permeability assay, transmission electron microscopy (TEM), and gelatin zymography were carried out. The results showed that Poldip2 was upregulated and AQP4 polarity was lost in mouse BM model. Both Poldip2 siRNA and UK383367 improved neurobehavioral outcomes, alleviated brain edema, preserved the integrity of BBB, and relieved the loss of AQP4 polarity in BM model. Rh‐Poldip2 upregulated the expression of MMPs and glial fibrillary acidic protein (GFAP) and downregulated the expression of β‐dystroglycan (β‐DG), zonula occludens‐1 (ZO‐1), occludin, and claudin‐5; whereas Poldip2 siRNA downregulated the expression of MMPs and GFAP, and upregulated β‐DG, ZO‐1, occludin, and claudin‐5. Similarly, UK383367 downregulated the expression of GFAP and upregulated the expression of β‐DG, ZO‐1, occludin, and claudin‐5.

Conclusion

Poldip2 inhibition alleviated brain edema and preserved the integrity of BBB partially by relieving the loss of AQP4 polarity via MMPs/β‐DG pathway.

Novel Insights into the Protective Properties of ACTH(4-7)PGP (Semax) Peptide at the Transcriptome Level Following Cerebral Ischaemia-Reperfusion in Rats

Cerebral ischaemia is the most common cause of impaired brain function. Biologically active peptides represent potential drugs for reducing the damage that occurs after ischaemia. The synthetic melanocortin derivative, ACTH_(4-7)PGP (Semax), has been used successfully in the treatment of patients with severe impairment of cerebral blood circulation. However, its molecular mechanisms of action within the brain are not yet fully understood. Previously, we used the transient middle cerebral artery occlusion (tMCAO) model to study the damaging effects of ischaemia-reperfusion on the brain transcriptome in rats. Here, using RNA-Seq analysis, we investigated the protective properties of the Semax peptide at the transcriptome level under tMCAO conditions. We have identified 394 differentially expressed genes (DEGs) (>1.5-fold change) in the brains of rats at 24 h after tMCAO treated with Semax relative to saline. Following tMCAO, we found that Semax suppressed the expression of genes related to inflammatory processes and activated the expression of genes related to neurotransmission. In contrast, ischaemia-reperfusion alone activated the expression of inflammation-related genes and suppressed the expression of neurotransmission-related genes. Therefore, the neuroprotective action of Semax may be associated with a compensation of mRNA expression patterns that are disrupted during ischaemia-reperfusion conditions.

Poldip2 mediates blood-brain barrier disruption in a model of sepsis-associated encephalopathy

Background

Sepsis-associated encephalopathy (SAE), a diffuse cerebral dysfunction in the absence of direct CNS infection, is associated with increased rates of mortality and morbidity in patients with sepsis. Increased cytokine production and disruption of the blood-brain barrier (BBB) are implicated in the pathogenesis of SAE. The induction of pro-inflammatory mediators is driven, in part, by activation of NF-κΒ. Lipopolysaccharide (LPS), an endotoxin produced by gram-negative bacteria, potently activates NF-κΒ and its downstream targets, including cyclooxygenase-2 (Cox-2). Cox-2 catalyzes prostaglandin synthesis and in the brain prostaglandin, E2 is capable of inducing endothelial permeability. Depletion of polymerase δ-interacting protein 2 (Poldip2) has previously been reported to attenuate BBB disruption, possibly via regulation of NF-κΒ, in response to ischemic stroke. Here we investigated Poldip2 as a novel regulator of NF-κΒ/cyclooxygenase-2 signaling in an LPS model of SAE.

Methods

Intraperitoneal injections of LPS (18 mg/kg) were used to induce BBB disruption in Poldip2^+/+ and Poldip2^+/− mice. Changes in cerebral vascular permeability and the effect of meloxicam, a selective Cox-2 inhibitor, were assessed by Evans blue dye extravasation. Cerebral cortices of Poldip2^+/+ and Poldip2^+/− mice were further evaluated by immunoblotting and ELISA. To investigate the role of endothelial Poldip2, immunofluorescence microscopy and immunoblotting were performed to study the effect of siPoldip2 on LPS-mediated NF-κΒ subunit p65 translocation and Cox-2 induction in rat brain microvascular endothelial cells. Finally, FITC-dextran transwell assay was used to assess the effect of siPoldip2 on LPS-induced endothelial permeability.

Results

Heterozygous deletion of Poldip2 conferred protection against LPS-induced BBB permeability. Alterations in Poldip2^+/+ BBB integrity were preceded by induction of Poldip2, p65, and Cox-2, which was not observed in Poldip2^+/− mice. Consistent with these findings, prostaglandin E2 levels were significantly elevated in Poldip2^+/+ cerebral cortices compared to Poldip2^+/− cortices. Treatment with meloxicam attenuated LPS-induced BBB permeability in Poldip2^+/+ mice, while having no significant effect in Poldip2^+/− mice. Moreover, silencing of Poldip2 in vitro blocked LPS-induced p65 nuclear translocation, Cox-2 expression, and endothelial permeability.

Conclusions

These data suggest Poldip2 mediates LPS-induced BBB disruption by regulating NF-κΒ subunit p65 activation and Cox-2 and prostaglandin E2 induction. Consequently, targeted inhibition of Poldip2 may provide clinical benefit in the prevention of sepsis-induced BBB disruption.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1575-4) contains supplementary material, which is available to authorized users.

Poldip2 knockdown inhibits vascular smooth muscle proliferation and neointima formation by regulating the expression of PCNA and p21

Polymerase delta-interacting protein 2 (Poldip2) is a multi-functional protein with numerous roles in the vasculature, including the regulation of cell apoptosis and migration, as well as extracellular matrix deposition; however, its role in VSMC proliferation and neointimal formation is unknown. In this study, we investigated the role of Poldip2 in intraluminal wire-injury induced neointima formation and proliferation of vascular smooth muscle cells in vitro and in vivo. Poldip2 expression was observed in the intima and media of human atherosclerotic arteries, where it colocalized with proliferating cell nuclear antigen (PCNA). Wire injury of femoral arteries of Poldip2^+/+ mice induced robust neointimal formation after 2 weeks, which was impaired in Poldip2^+/‒ mice. PCNA expression was significantly reduced and expression of the cell cycle inhibitor p21 was significantly increased in wire-injured arteries of Poldip2^+/‒ animals compared to wild-type controls. No difference was observed in apoptosis. Downregulation of Poldip2 in rat aortic smooth muscle cells significantly reduced serum-induced proliferation and PCNA expression, but upregulated p21 expression. Downregulation of p21 using siRNA reversed the inhibition of proliferation induced by knockdown of Poldip2. These results indicate that Poldip2 plays a critical role in the proliferation of VSMCs.

Poldip2 deficiency protects against lung edema and vascular inflammation in a model of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) in a deadly disease that can be brought on by endotoxins such as lipopolysaccharide (LPS). ARDS is characterized by vascular permeability, a severe inflammatory response, lung leukocyte infiltration, and resultant lung edema. Polymerase δ-interacting protein 2 (Poldip2) is a novel regulator of blood-brain barrier permeability; however, its role in regulating lung permeability and vascular inflammation is unknown. Here, the role of Poldip2 in regulating vascular permeability and inflammation in a mouse model of ARDS was assessed. Heterozygous deletion of Poldip2 was found to reduce LPS-induced mortality within 20 h, lung inflammatory signaling, and leukocyte infiltration. Moreover, reduced Poldip2-suppressed LP-induced vascular cell adhesion molecule (VCAM)-1 induction, leukocyte recruitment, and mitochondrial reactive oxygen species (ROS) production in vitro These data indicate that Poldip2 is an important regulator of the debilitating consequences of ARDS, potentially through the regulation of mitochondrial ROS-induced inflammatory signaling. Consequently, inhibition of Poldip2 may be a viable option for therapeutic discovery moving forward.

Genome-wide transcriptome analysis using RNA-Seq reveals a large number of differentially expressed genes in a transient MCAO rat model

Background

The transient middle cerebral artery occlusion (tMCAO) model is used for studying the molecular mechanisms of ischemic damage and neuroprotection. Numerous studies have demonstrated the role of individual genes and associated signaling pathways in the pathogenesis of ischemic stroke. Here, the tMCAO model was used to investigate the genome-wide response of the transcriptome of rat brain tissues to the damaging effect of ischemia and subsequent reperfusion.

Results

Magnetic resonance imaging and histological examination showed that the model of focal ischemia based on endovascular occlusion of the right middle cerebral artery for 90 min using a monofilament, followed by restoration of the blood flow, led to reproducible localization of ischemic damage in the subcortical structures of the brain. High-throughput RNA sequencing (RNA-Seq) revealed the presence of differentially expressed genes (DEGs) in subcortical structures of rat brains resulting from hemisphere damage by ischemia after tMCAO, as well as in the corresponding parts of the brains of sham-operated animals. Real-time reverse transcription polymerase chain reaction expression analysis of 20 genes confirmed the RNA-Seq results. We identified 469 and 1939 genes that exhibited changes in expression of > 1.5-fold at 4.5 and 24 h after tMCAO, respectively. Interestingly, we found 2741 and 752 DEGs under ischemia–reperfusion and sham-operation conditions at 24 h vs. 4.5 h after tMCAO, respectively. The activation of a large number of genes involved in inflammatory, immune and stress responses, apoptosis, ribosome function, DNA replication and other processes was observed in ischemia–reperfusion conditions. Simultaneously, massive down-regulation of the mRNA levels of genes involved in the functioning of neurotransmitter systems was recorded. A Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that dozens of signaling pathways were associated with DEGs in ischemia–reperfusion conditions.

Conclusions

The data obtained revealed a global profile of gene expression in the rat brain sub-cortex under tMCAO conditions that can be used to identify potential therapeutic targets in the development of new strategies for the prevention and treatment of ischemic stroke.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5039-5) contains supplementary material, which is available to authorized users.

Beneficial Role of Rosuvastatin in Blood-Brain Barrier Damage Following Experimental Ischemic Stroke

Hemorrhage transformation is the most challenging preventable complication in thrombolytic therapy and is related to recombinant tissue plasminogen activator (rt-PA)-induced blood–brain barrier (BBB) damage. Intraperitoneal injections of normal or high doses of rosuvastatin were administered to Balb/c mice 20 min prior to middle cerebral artery occlusion (MCAO) surgery for 3 h followed by reperfusion with rt-PA thrombolytic therapy and cerebral blood flow monitoring to investigate whether a high or normal dose of rosuvastatin reduces BBB damage after brain ischemia and rt-PA reperfusion. The integrity of the BBB was ameliorated by normal and high doses of rosuvastatin as determined from Evans blue staining, ultrastructure assessments and immunochemistry at 24 h after reperfusion. The levels of TJ proteins were preserved, potentially by targeting platelet-derived growth factor receptor α (PDGFR-α) and low-density lipoprotein receptor-related protein 1 (LRP1) to inhibit the expression of matrix metalloproteinase proteins (MMPs) by reducing the levels of phosphorylated c-jun-N-terminal kinase (pJNK), phosphorylated mitogen-activated protein kinase (MAPK) p38 (pP38) and increasing the levels of phosphorylated extracellular regulated protein kinases (pERK), and tissue inhibitor of metalloproteinases (TIMPs), as inferred from Western blotting and molecular docking analyses. In summary, rosuvastatin reduced rt-PA therapy-associated BBB permeability by PDGFR-α- and LRP1-associated MAPK pathways to reduce the mortality of mice, and a normal dose of rosuvastatin exerted greater preventative effects on reducing BBB damage than did a high dose in the time window of thrombolytic therapy.