KLF11 mediates PPARγ cerebrovascular protection in ischaemic stroke

Endothelial KLF11 is a novel protector against diabetic atherosclerosis

BACKGROUND

Atherosclerotic cardiovascular diseases remain the leading cause of mortality in diabetic patients, with endothelial cell (EC) dysfunction serving as the initiating step of atherosclerosis, which is exacerbated in diabetes. Krüppel-like factor 11 (KLF11), known for its missense mutations leading to the development of diabetes in humans, has also been identified as a novel protector of vascular homeostasis. However, its role in diabetic atherosclerosis remains unexplored.

METHODS

Diabetic atherosclerosis was induced in both EC-specific KLF11 transgenic and knockout mice in the Ldlr-/- background by feeding a diabetogenic diet with cholesterol (DDC). Single-cell RNA sequencing (scRNA-seq) was utilized to profile EC dysfunction in diabetic atherosclerosis. Additionally, gain- and loss-of-function experiments were conducted to investigate the role of KLF11 in hyperglycemia-induced endothelial cell dysfunction.

RESULTS

We found that endothelial KLF11 deficiency significantly accelerates atherogenesis under diabetic conditions, whereas KLF11 overexpression remarkably inhibits it. scRNA-seq profiling demonstrates that loss of KLF11 increases endothelial-to-mesenchymal transition (EndMT) during atherogenesis under diabetic conditions. Utilizing gain- and loss-of-function approaches, our in vitro study reveals that KLF11 significantly inhibits EC inflammatory activation and TXNIP-induced EC oxidative stress, as well as Notch1/Snail-mediated EndMT under high glucose exposure.

CONCLUSION

Our study demonstrates that endothelial KLF11 is an endogenous protective factor against diabetic atherosclerosis. These findings indicate that manipulating KLF11 could be a promising approach for developing novel therapies for diabetes-related cardiovascular complications.

Krüppel-like factors family in health and disease

Krüppel-like factors (KLFs) are a family of basic transcription factors with three conserved Cys2/His2 zinc finger domains located in their C-terminal regions. It is acknowledged that KLFs exert complicated effects on cell proliferation, differentiation, survival, and responses to stimuli. Dysregulation of KLFs is associated with a range of diseases including cardiovascular disorders, metabolic diseases, autoimmune conditions, cancer, and neurodegenerative diseases. Their multidimensional roles in modulating critical pathways underscore the significance in both physiological and pathological contexts. Recent research also emphasizes their crucial involvement and complex interplay in the skeletal system. Despite the substantial progress in understanding KLFs and their roles in various cellular processes, several research gaps remain. Here, we elucidated the multifaceted capabilities of KLFs on body health and diseases via various compliable signaling pathways. The associations between KLFs and cellular energy metabolism and epigenetic modification during bone reconstruction have also been summarized. This review helps us better understand the coupling effects and their pivotal functions in multiple systems and detailed mechanisms of bone remodeling and develop potential therapeutic strategies for the clinical treatment of pathological diseases by targeting the KLF family.

Loss of microRNA-15a/16-1 function promotes neuropathological and functional recovery in experimental traumatic brain injury

The diffuse axonal damage in white matter and neuronal loss, along with excessive neuroinflammation, hinder long-term functional recovery after traumatic brain injury (TBI). MicroRNAs (miRs) are small noncoding RNAs that negatively regulate protein-coding target genes in a posttranscriptional manner. Recent studies have shown that loss of function of the miR-15a/16-1 cluster reduced neurovascular damage and improved functional recovery in ischemic stroke and vascular dementia. However, the role of the miR-15a/16-1 cluster in neurotrauma is poorly explored. Here, we report that genetic deletion of the miR-15a/16-1 cluster facilitated the recovery of sensorimotor and cognitive functions, alleviated white matter/gray matter lesions, reduced cerebral glial cell activation, and inhibited infiltration of peripheral blood immune cells to brain parenchyma in a murine model of TBI when compared with WT controls. Moreover, intranasal delivery of the miR-15a/16-1 antagomir provided similar brain-protective effects conferred by genetic deletion of the miR-15a/16-1 cluster after experimental TBI, as evidenced by showing improved sensorimotor and cognitive outcomes, better white/gray matter integrity, and less inflammatory responses than the control antagomir-treated mice after brain trauma. miR-15a/16-1 genetic deficiency and miR-15a/16-1 antagomir also significantly suppressed inflammatory mediators in posttrauma brains. These results suggest miR-15a/16-1 as a potential therapeutic target for TBI.

No-reflow after recanalization in ischemic stroke: From pathomechanisms to therapeutic strategies

Endovascular reperfusion therapy is the primary strategy for acute ischemic stroke. No-reflow is a common phenomenon, which is defined as the failure of microcirculatory reperfusion despite clot removal by thrombolysis or mechanical embolization. It has been reported that up to 25% of ischemic strokes suffer from no-reflow, which strongly contributes to an increased risk of poor clinical outcomes. No-reflow is associated with functional and structural alterations of cerebrovascular microcirculation, and the injury to the microcirculation seriously hinders the neural functional recovery following macrovascular reperfusion. Accumulated evidence indicates that pathology of no-reflow is linked to adhesion, aggregation, and rolling of blood components along the endothelium, capillary stagnation with neutrophils, astrocytes end-feet, and endothelial cell edema, pericyte contraction, and vasoconstriction. Prevention or treatment strategies aim to alleviate or reverse these pathological changes, including targeted therapies such as cilostazol, adhesion molecule blocking antibodies, peroxisome proliferator-activated receptors (PPARs) activator, adenosine, pericyte regulators, as well as adjunctive therapies, such as extracorporeal counterpulsation, ischemic preconditioning, and alternative or complementary therapies. Herein, we provide an overview of pathomechanisms, predictive factors, diagnosis, and intervention strategies for no-reflow, and attempt to convey a new perspective on the clinical management of no-reflow post-ischemic stroke.

Hypoxia exposure blunts angiogenic signaling and upregulates the antioxidant system in endothelial cells derived from elephant seals

BACKGROUND

Elephant seals exhibit extreme hypoxemic tolerance derived from repetitive hypoxia/reoxygenation episodes they experience during diving bouts. Real-time assessment of the molecular changes underlying protection against hypoxic injury in seals remains restricted by their at-sea inaccessibility. Hence, we developed a proliferative arterial endothelial cell culture model from elephant seals and used RNA-seq, functional assays, and confocal microscopy to assess the molecular response to prolonged hypoxia.

RESULTS

Seal and human endothelial cells exposed to 1% O2 for up to 6 h respond differently to acute and prolonged hypoxia. Seal cells decouple stabilization of the hypoxia-sensitive transcriptional regulator HIF-1α from angiogenic signaling. Rapid upregulation of genes involved in glutathione (GSH) metabolism supports the maintenance of GSH pools, and intracellular succinate increases in seal but not human cells. High maximal and spare respiratory capacity in seal cells after hypoxia exposure occurs in concert with increasing mitochondrial branch length and independent from major changes in extracellular acidification rate, suggesting that seal cells recover oxidative metabolism without significant glycolytic dependency after hypoxia exposure.

CONCLUSIONS

We found that the glutathione antioxidant system is upregulated in seal endothelial cells during hypoxia, while this system remains static in comparable human cells. Furthermore, we found that in contrast to human cells, hypoxia exposure rapidly activates HIF-1 in seal cells, but this response is decoupled from the canonical angiogenesis pathway. These results highlight the unique mechanisms that confer extraordinary tolerance to limited oxygen availability in a champion diving mammal.

[Upregulating KLF11 ameliorates intestinal inflammation in mice with 2, 4, 6-trinitrobenesulfonic acid-induced colitis by inhibiting the JAK2/STAT3 signaling pathway]

OBJECTIVE

To investigate the expression level of Kruppel-like transcription factor family member KLF11 in intestinal mucosal tissues of Crohn's disease (CD) and its regulatory effect on intestinal inflammation in CD-like colitis.

METHODS

We examined KLF11 expression levels in diseased and normal colon mucosal tissues from 12 CD patients and 12 patients with colorectal cancer using immunofluorescence staining. KLF11 expression was also detected in the colon mucosal tissues of a mouse model of 2, 4, 6-trinitrobenesulfonic acid (TNBS)-induced colitis. A recombinant adenoviral vector was used to upregulate KLF11 expression in the mouse models and the changes in intestinal inflammation was observed. A Caco-2 cell model with stable KLF11 overexpression was constructed by lentiviral infection. The effect of KLF11 overexpression on expressions of JAK2/STAT3 signaling pathway proteins was investigated using immunoblotting in both the mouse and cell models. The mouse models were treated with coumermycin A1, a JAK2/STAT3 signaling pathway agonist, and the changes in intestinal inflammatory responses were observed.

RESULTS

The expression level of KLF11 was significantly lowered in both the clinical specimens of diseased colon mucosal tissues and the colon tissues of mice with TNBS-induced colitis (P < 0.05). Adenovirus-mediated upregulation of KLF11 significantly improved intestinal inflammation and reduced the expression levels of inflammatory factors in the intestinal mucosa of the colitis mouse models (P < 0.05). Overexpression of KLF11 significantly inhibited the expression levels of p-JAK2 and p-STAT3 in intestinal mucosal tissues of the mouse models and in Caco-2 cells (P < 0.05). Treatment with coumermycin A1 obviously inhibited the effect of KLF11 upregulation for improving colitis and significantly increased the expression levels of inflammatory factors in the intestinal mucosa of the mouse models (P < 0.05).

CONCLUSION

KLF11 is downregulated in the intestinal mucosa in CD, and upregulation of KLF11 can improve intestinal inflammation and reduce the production of inflammatory factors probably by inhibiting the JAK2/STAT3 signaling pathway.

miR-10a-5p Regulates the Proliferation and Differentiation of Porcine Preadipocytes Targeting the KLF11 Gene

In the swine industry, meat quality, color, and texture are influenced by the excessive differentiation of fat cells. miRNAs have emerged as integral regulators of adipose development. This study delves into the influence of miR-10a-5b on the proliferation and differentiation of pig preadipocytes. Our findings reveal that miR-10a-5b is prevalent across various tissues. It hinders preadipocyte proliferation, amplifies the expression of adipogenic genes, promotes lipid accumulation, and, as a result, advances preadipocyte differentiation. We predict that KLF11 is the target gene of miRNA. A dual-fluorescence reporter assay was conducted to validate the binding sites of miR-10a-5b on the 3'UTR of the KLF11 mRNA. Results showed that miR-10a-5b targeted KLF11 3'UTR and reduced the fluorescence activity of the dual-fluorescent reporter vector. Our research also indicates that miR-10a-5b targets and downregulates the expression of both mRNA and the protein levels of KLF11. During the differentiation of the preadipocytes, KLF11 inhibited adipose differentiation and was able to suppress the promotion of adipose differentiation by miR-10a-5b. This underscores miR-10a-5b's potential as a significant regulator of preadipocyte behavior by modulating KLF11 expression, offering insights into the role of functional miRNAs in fat deposition.

Hypoxia blunts angiogenic signaling and upregulates the antioxidant system in elephant seal endothelial cells

Elephant seals experience extreme hypoxemia during diving bouts. Similar depletions in oxygen availability characterize pathologies including myocardial infarction and ischemic stroke in humans, but seals manage these repeated episodes without injury. However, the real-time assessment of the molecular changes underlying protection against hypoxic injury in seals remains restricted by their at-sea inaccessibility. Hence, we developed a proliferative arterial endothelial cell culture system to assess the molecular response to prolonged hypoxia. Seal and human cells exposed to 1% O 2 for up to 6 h demonstrated differential responses to both acute and prolonged hypoxia. Seal cells decouple stabilization of the hypoxia-sensitive transcriptional regulator HIF-1α from angiogenic signaling at both the transcriptional and cellular level. Rapid upregulation of genes involved in the glutathione (GSH) metabolism pathway supported maintenance of GSH pools and increases in intracellular succinate in seal but not human cells during hypoxia exposure. High maximal and spare respiratory capacity in seal cells after hypoxia exposure occurred in concert with increasing mitochondrial branch length and independent from major changes in extracellular acidification rate, suggesting seal cells recover oxidative metabolism without significant glycolytic dependency after hypoxia exposure. In sum, our studies show that in contrast to human cells, seal cells adapt to hypoxia exposure by dampening angiogenic signaling, increasing antioxidant protection, and maintaining mitochondrial morphological integrity and function.

The tissue-specific transcriptional landscape underlines the involvement of endothelial cells in health and disease

Endothelial cells (ECs) that line vascular and lymphatic vessels are being increasingly recognized as important to organ function in health and disease. ECs participate not only in the trafficking of gases, metabolites, and cells between the bloodstream and tissues but also in the angiocrine-based induction of heterogeneous parenchymal cells, which are unique to their specific tissue functions. The molecular mechanisms regulating EC heterogeneity between and within different tissues are modeled during embryogenesis and become fully established in adults. Any changes in adult tissue homeostasis induced by aging, stress conditions, and various noxae may reshape EC heterogeneity and induce specific transcriptional features that condition a functional phenotype. Heterogeneity is sustained via specific genetic programs organized through the combinatory effects of a discrete number of transcription factors (TFs) that, at the single tissue-level, constitute dynamic networks that are post-transcriptionally and epigenetically regulated. This review is focused on outlining the TF-based networks involved in EC specialization and physiological and pathological stressors thought to modify their architecture.

Genetic deletion of Krüppel-like factor 11 aggravates traumatic brain injury

BACKGROUND

The long-term functional recovery of traumatic brain injury (TBI) is hampered by pathological events, such as parenchymal neuroinflammation, neuronal death, and white matter injury. Krüppel-like transcription factor 11 (KLF 11) belongs to the zinc finger family of transcription factors and actively participates in various pathophysiological processes in neurological disorders. Up to now, the role and molecular mechanisms of KLF11 in regulating the pathogenesis of brain trauma is poorly understood.

METHODS

KLF11 knockout (KO) and wild-type (WT) mice were subjected to experimental TBI, and sensorimotor and cognitive functions were evaluated by rotarod, adhesive tape removal, foot fault, water maze, and passive avoidance tests. Brain tissue loss/neuronal death was examined by MAP2 and NeuN immunostaining, and Cresyl violet staining. White matter injury was assessed by Luxol fast blue staining, and also MBP/SMI32 and Caspr/Nav1.6 immunostaining. Activation of cerebral glial cells and infiltration of blood-borne immune cells were detected by GFAP, Iba-1/CD16/32, Iba-1/CD206, Ly-6B, and F4/80 immunostaining. Brian parenchymal inflammatory cytokines were measured with inflammatory array kits.

RESULTS

Genetic deletion of KLF11 worsened brain trauma-induced sensorimotor and cognitive deficits, brain tissue loss and neuronal death, and white matter injury in mice. KLF11 genetic deficiency in mice also accelerated post-trauma astrocytic activation, promoted microglial polarization to a pro-inflammatory phenotype, and increased the infiltration of peripheral neutrophils and macrophages into the brain parenchyma. Mechanistically, loss-of-KLF11 function was found to directly increase the expression of pro-inflammatory cytokines in the brains of TBI mice.

CONCLUSION

KLF11 acts as a novel protective factor in TBI. KLF11 genetic deficiency in mice aggravated the neuroinflammatory responses, grey and white matter injury, and impaired long-term sensorimotor and cognitive recovery. Elucidating the functional importance of KLF11 in TBI may lead us to discover novel pharmacological targets for the development of effective therapies against brain trauma.

Exosomes in subarachnoid hemorrhage: A scoping review

INTRODUCTION

Vasospasm is a common complication following subarachnoid hemorrhage (SAH), causing increased ischemia and tissue injury, and is implicated as a major risk factor for poor outcomes. The success of current treatments for vasospasm is limited, with limited efficacy and unclear clinical benefits. Exosomes, vesicles that carry small molecules such as miRNA, have been theorized as a potential vasospasm treatment. In this study, we aim to survey the current literature discussing the role of exosomes in the setting of SAH.

METHODS

Following PRISMA guidelines, we performed a scoping review evaluating the role of exosomes in the treatment of SAH. The search was conducted using PubMed and Scopus, and all original research papers studying exosomal profiles of SAH research subjects or SAH therapy were eligible for inclusion.

RESULTS

After screening and full text review, seven papers were selected for final inclusion. Of these, two studies analyzed the expression profile of endogenous exosomes after SAH. Four papers identified and characterized miRNA-based exosomal therapies to attenuate early brain injury (EBI) after SAH. One paper discussed the role of protein overexpression in exosome delivery of miRNA for EBI after SAH. Interestingly, all identified papers studying exosomal therapy demonstrated anti-apoptotic or anti-inflammatory effects of miRNA exosomes acting via the BDNF/TrkB/CREB or HDAC3/NF-κB pathways.

CONCLUSION

Identified studies demonstrate potential neuroprotective benefits of miRNA-based exosomal treatment of EBI and SAH. Findings warrant further research investigating the anti-inflammatory and anti-apoptotic role of exosomal miRNA delivery in SAH models, specifically targeting the common pathway identified by the authors.

Krüppel-like factors family regulation of adipogenic markers genes in bovine cattle adipogenesis

Intramuscular fat (IMF) content is a crucial determinant of meat quality traits in livestock. A network of transcription factors act in concert to regulate adipocyte formation and differentiation, which in turn influences intramuscular fat. Several genes and associated transcription factors have been reported to influence lipogenesis and adipogenesis during fetal and subsequent growth stage. Specifically in cattle, Krüppel-like factors (KLFs), which represents a family of transcription factors, have been reported to be involved in adipogenic differentiation and development. KLFs are a relatively large group of zinc-finger transcription factors that have a variety of functions in addition to adipogenesis. In mammals, the participation of KLFs in cell development and differentiation is well known. Specifically in the context of adipogenesis, KLFs function either as positive (KLF4, KLF5, KLF6, KLF8, KLF9, KLF10, KLF11, KLF12, KLF13, KLF14 and KLF15) or negative organizers (KLF2, KLF3 and KLF7), by a variety of different mechanisms such as crosstalk with C/EBP and PPARγ. In this review, we aim to summarize the potential functions of KLFs in regulating adipogenesis and associated pathways in cattle. Furthermore, the function of known bovine adipogenic marker genes, and associated transcription factors that regulate the expression of these marker genes is also summarized. Overall, this review will provide an overview of marker genes known to influence bovine adipogenesis and regulation of expression of these genes, to provide insights into leveraging these genes and transcription factors to enhance breeding programs, especially in the context of IMF deposition and meat quality.

MiR-128-1-5p regulates differentiation of ovine stromal vascular fraction by targeting the KLF11 5'-UTR

Fat content is an important index to evaluate the individual performance of livestock animals such as sheep for meat production purposes. Reducing the subcutaneous and visceral fat while increasing the intramuscular fat is a valuable goal to achieve for the meat production industry. Here, we investigated the effect of miR-128-1-5p on adipogenesis of subcutaneous fat by targeting 5'-UTR in KLF11, a rare mechanism where most miRNAs bind the 3'-UTR of mRNAs. A dual fluorescence reporter assay was conducted to validate the binding sites of miR-128-1-5p on 5'-UTR of KLF11 mRNA. Roles of miR-128-1-5p in KLF11 expression were measured through co-transfecting miRNA mimics with KLF11-expressing vectors (CDSs together with or without the 5'-UTR) into ovine stromal vascular fractions (SVF). Additionally, functional roles of miR-128-1-5p, and KLF11 in adipogenesis of ovine subcutaneous fat were investigated. Results showed that miR-128-1-5p targeted KLF11 5'-UTR, reduced the fluorescence activity of the dual fluorescent reporter vector, as well as KLF11 mRNA, and protein expression levels. During the differentiation of SVF, disturbing the expression of miR-128-1-5p and KLF11 changed the adipogenic differentiation of SVF as observed in the lipid formation, and adipogenic marker genes. This study indicates that miR-128-1-5p promotes the expression of lipogenic marker genes and the formation of lipid droplets by targeting KLF11 5'-UTR. Furthermore, overexpression, and inhibition of KLF11 indicate that KLF11 inhibited SVF differentiation. In summary, the 5'-UTR binding mechanism discovered in this study extends the understanding of miRNA functions. Key roles of miR-128-1-5p and KLF11 in the adipogenesis of sheep subcutaneous fat have potential values for improving the meat and/or fat ratio of domestic animals.

KLF11 Is a Novel Endogenous Protectant against Renal Ischemia-Reperfusion Injury

Discovering new nephroprotectants may provide therapeutic strategies in AKI.This study provides the first evidence that KLF11, a member of the Krüppel-like factor (KLF) family of proteins, protects against AKI.In the absence of KLF11, exaggerated induction of endothelin-1 and IL-6 occurs after ischemic renal injury and may contribute to worse AKI.

KLF11 Protects against Venous Thrombosis via Suppressing Tissue Factor Expression

Krüppel-like factors (KLFs) play essential roles in multiple biological functions, including maintaining vascular homeostasis. KLF11, a causative gene for maturity-onset diabetes of the young type 7, inhibits endothelial activation and protects against stroke. However, the role of KLF11 in venous thrombosis remains to be explored. Utilizing stasis-induced murine deep vein thrombosis (DVT) model and cultured endothelial cells (ECs), we identified an increase of KLF11 expression under prothrombotic conditions both in vivo and in vitro. The expression change of thrombosis-related genes was determined by utilizing gain- and loss-of-function approaches to alter KLF11 expression in ECs. Among these genes, KLF11 significantly downregulated tumor necrosis factor-α (TNF-α)-induced tissue factor (TF) gene transcription. Using reporter gene assay, chromatin immunoprecipitation assay, and co-immunoprecipitation, we revealed that KLF11 could reduce TNF-α-induced binding of early growth response 1 (EGR1) to TF gene promoter in ECs. In addition, we demonstrated that conventional Klf11 knockout mice were more susceptible to developing stasis-induced DVT. These results suggest that under prothrombotic conditions, KLF11 downregulates TF gene transcription via inhibition of EGR1 in ECs. In conclusion, KLF11 protects against venous thrombosis, constituting a potential molecular target for treating thrombosis.

MALAT1 improves functional recovery after traumatic brain injury through promoting angiogenesis in experimental mice

As a highly evolutionary conserved lncRNA, MALAT1 was first demonstrated to associate with metastasis of lung tumor by promoting angiogenesis. Activated vasculature was recently indicated to assist neurogenesis by secreting neurotrophic factor Ang1 (Angiopoietin-1). The purpose of this study is to investigate the potential role of MALAT1 in angiogenesis following traumatic brain injury (TBI). Adult male mice were subjected to controlled cortical impact (CCI) and brain microvascular endothelial cells were exposed to oxygen-glucose deprivation (OGD). MALAT1 RNA levels were quantified by qRT-PCR in different cells of CNS and located by RNA-FISH. Angiogenesis were measured by cell viability, migration assay, tube formation assay in vitro, and immunohistochemistry in vivo. Expression of Angiopoietin-1 was assessed by Western blot. Neurological functions were performed by NSS, Wire grip and MWM tests. Our results indicated that 1) MALAT1 RNA was localized in cerebral endothelium, enhanced by OGD stimuli. 2) Inhibition of MALAT1 by siRNA suppressed angiogenesis, as indicated by endothelial viability, tube formation, migration, and functional vessel density. 3) MALAT1 inhibition further decreased Ang1 expression in the endothelium. 4) Mice with MALAT1 inhibition exhibited worse behavioral performances (NSS, wire grip, Morris water maze), as compared to control. MALAT1 could promote angiogenesis, subsequently contributing to the Ang1 synthesis from active vasculature. It may eventually benefit to functional recovery following TBI.

Essential role of MALAT1 in reducing traumatic brain injury

As a highly evolutionary conserved long non-coding RNA, metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was first demonstrated to be related to lung tumor metastasis by promoting angiogenesis. To investigate the role of MALAT1 in traumatic brain injury, we established mouse models of controlled cortical impact and cell models of oxygen-glucose deprivation to mimic traumatic brain injury in vitro and in vivo. The results revealed that MALAT1 silencing in vitro inhibited endothelial cell viability and tube formation but increased migration. In MALAT1-deficient mice, endothelial cell proliferation in the injured cortex, functional vessel density and cerebral blood flow were reduced. Bioinformatic analyses and RNA pull-down assays validated enhancer of zeste homolog 2 (EZH2) as a downstream factor of MALAT1 in endothelial cells. Jagged-1, the Notch homolog 1 (NOTCH1) agonist, reversed the MALAT1 deficiency-mediated impairment of angiogenesis. Taken together, our results suggest that MALAT1 controls the key processes of angiogenesis following traumatic brain injury in an EZH2/NOTCH1-dependent manner.

Nuclear Receptors in Myocardial and Cerebral Ischemia-Mechanisms of Action and Therapeutic Strategies

Nearly 18 million people died from cardiovascular diseases in 2019, of these 85% were due to heart attack and stroke. The available therapies although efficacious, have narrow therapeutic window and long list of contraindications. Therefore, there is still an urgent need to find novel molecular targets that could protect the brain and heart against ischemia without evoking major side effects. Nuclear receptors are one of the promising targets for anti-ischemic drugs. Modulation of estrogen receptors (ERs) and peroxisome proliferator-activated receptors (PPARs) by their ligands is known to exert neuro-, and cardioprotective effects through anti-apoptotic, anti-inflammatory or anti-oxidant action. Recently, it has been shown that the expression of aryl hydrocarbon receptor (AhR) is strongly increased after brain or heart ischemia and evokes an activation of apoptosis or inflammation in injury site. We hypothesize that activation of ERs and PPARs and inhibition of AhR signaling pathways could be a promising strategy to protect the heart and the brain against ischemia. In this Review, we will discuss currently available knowledge on the mechanisms of action of ERs, PPARs and AhR in experimental models of stroke and myocardial infarction and future perspectives to use them as novel targets in cardiovascular diseases.

Nitro-oleic acid-mediated blood-brain barrier protection reduces ischemic brain injury

Nitro-oleic acid (OA-NO₂), a nitroalkene formed in nitric oxide-dependent oxidative reactions, has been found in human plasma and is thought to regulate pathophysiological functions. Recently, accumulating evidence suggests that OA-NO₂ may function as an anti-inflammatory mediator, and ameliorate the progression of diabetes and cardiovascular diseases. However, the role of OA-NO₂ in ischemic brain injury remains unexplored. In this study, C57BL/6 mice were subjected to 1 h transient middle cerebral artery occlusion (MCAO) and followed by 1- 7 days of reperfusion. These mice were treated with vehicle, OA, or OA-NO₂ (10 mg/kg) via tail vein injection at 2 h after the onset of MCAO. Our results show that intravenous administration of OA-NO₂ led to reduced BBB leakage in ischemic brains, reduced brain infarct, and improved sensorimotor functions in response to ischemic insults when compared to OA and vehicle controls. Also, OA-NO₂ significantly reduced BBB leakage-triggered infiltration of neutrophils and macrophages in the ischemic brains. Moreover, OA-NO₂ treatment reduced the M1-type microglia and increased M2-type microglia. Mechanistically, OA-NO₂ alleviated the decline of mRNA and protein level of major endothelial TJs including ZO-1 in stroke mice. Treatment of OA-NO₂ also significantly inhibited stroke-induced inflammatory mediators, iNOS, E-selectin, P-selectin, and ICAM1, in mouse brains. In conclusion, OA-NO₂ preserves BBB integrity and confers neurovascular protection in ischemic brain damage. OA-NO₂-mediated brain protection may help us to develop a novel therapeutic strategy for the treatment of ischemic stroke.

KLF11 protects against abdominal aortic aneurysm through inhibition of endothelial cell dysfunction

Abdominal aortic aneurysm (AAA) is a life-threatening degenerative vascular disease. Endothelial cell (EC) dysfunction is implicated in AAA. Our group recently demonstrated that Krüppel-like factor 11 (KLF11) plays an essential role in maintaining vascular homeostasis, at least partially through inhibition of EC inflammatory activation. However, the functions of endothelial KLF11 in AAA remain unknown. Here we found that endothelial KLF11 expression was reduced in the ECs from human aneurysms and was time dependently decreased in the aneurysmal endothelium from both elastase- and Pcsk9/AngII-induced AAA mouse models. KLF11 deficiency in ECs markedly aggravated AAA formation, whereas EC-selective KLF11 overexpression markedly inhibited AAA formation. Mechanistically, KLF11 not only inhibited the EC inflammatory response but also diminished MMP9 expression and activity and reduced NADPH oxidase 2-mediated production of reactive oxygen species in ECs. In addition, KLF11-deficient ECs induced smooth muscle cell dedifferentiation and apoptosis. Overall, we established endothelial KLF11 as a potentially novel factor protecting against AAA and a potential target for intervention in aortic aneurysms.

Spatially mapped single-cell chromatin accessibility

High-throughput single-cell epigenomic assays can resolve cell type heterogeneity in complex tissues, however, spatial orientation is lost. Here, we present single-cell combinatorial indexing on Microbiopsies Assigned to Positions for the Assay for Transposase Accessible Chromatin, or sciMAP-ATAC, as a method for highly scalable, spatially resolved, single-cell profiling of chromatin states. sciMAP-ATAC produces data of equivalent quality to non-spatial sci-ATAC and retains the positional information of each cell within a 214 micron cubic region, with up to hundreds of tracked positions in a single experiment. We apply sciMAP-ATAC to assess cortical lamination in the adult mouse primary somatosensory cortex and in the human primary visual cortex, where we produce spatial trajectories and integrate our data with non-spatial single-nucleus RNA and other chromatin accessibility single-cell datasets. Finally, we characterize the spatially progressive nature of cerebral ischemic infarction in the mouse brain using a model of transient middle cerebral artery occlusion.

Spatial orientation of cells in an interconnected network is lost in high-throughput single-cell epigenomic assays. Here the authors present sciMAP-ATAC to produce spatially resolved single-cell ATAC-seq data.

Current knowledge of Krüppel-like factor 5 and vascular remodeling: providing insights for therapeutic strategies

Vascular remodeling is a pathological basis of various disorders. Therefore, it is necessary to understand the occurrence, prevention, and treatment of vascular remodeling. Krüppel-like factor 5 (KLF5) has been identified as a significant factor in cardiovascular diseases during the last two decades. This review provides a mechanism network of function and regulation of KLF5 in vascular remodeling based on newly published data and gives a summary of its potential therapeutic applications. KLF5 modulates numerous biological processes, which play essential parts in the development of vascular remodeling, such as cell proliferation, phenotype switch, extracellular matrix deposition, inflammation, and angiogenesis by altering downstream genes and signaling pathways. Considering its essential functions, KLF5 could be developed as a potent therapeutic target in vascular disorders.

Inhibiting ferroptosis: A novel approach for stroke therapeutics

Stroke ranks as the second leading cause of death across the globe. Despite advances in stroke therapeutics, no US Food and Drug Administration (FDA)-approved drugs that can minimize neuronal injury and restore neurological function are clinically available. Ferroptosis, a regulated iron-dependent form of nonapoptotic cell death, has been shown to contribute to stroke-mediated neuronal damage. Inhibitors of ferroptosis have also been validated in several stroke models of ischemia or intracerebral hemorrhage. Herein, we review the therapeutic activity of inhibitors of ferroptosis in stroke models. We further summarize previously reported neuroprotectants that show protective effects in stroke models that have been recently validated as ferroptosis inhibitors. These findings reveal new mechanisms for neuroprotection and highlight the importance of ferroptosis during stroke processes.

Genome-wide CRISPR-Cas9 screen identified KLF11 as a druggable suppressor for sarcoma cancer stem cells

Cancer stem cells (CSCs) are involved in tumorigenesis, recurrence, and therapy resistance. To identify critical regulators of sarcoma CSCs, we performed a reporter-based genome-wide CRISPR-Cas9 screen and uncovered Kruppel-like factor 11 (KLF11) as top candidate. In vitro and in vivo functional annotation defined a negative role of KLF11 in CSCs. Mechanistically, KLF11 and YAP/TEAD bound to adjacent DNA sites along with direct interaction. KLF11 recruited SIN3A/HDAC to suppress the transcriptional output of YAP/TEAD, which, in turn, promoted KLF11 transcription, forming a negative feedback loop. However, in CSCs, this negative feedback was lost because of epigenetic silence of KLF11, causing sustained YAP activation. Low KLF11 was associated with poor prognosis and chemotherapy response in patients with sarcoma. Pharmacological activation of KLF11 by thiazolidinedione effectively restored chemotherapy response. Collectively, our study identifies KLF11 as a negative regulator in sarcoma CSCs and potential therapeutic target.

Role of peroxisome proliferator-activated receptors in stroke prevention and therapy-The best is yet to come?

Role of peroxisome proliferator-activated receptors (PPARs) in the pathophysiology of stroke and protective effects of PPAR ligands have been widely investigated in the last 20 years. Activation of all three PPAR isoforms, but especially PPAR-γ, was documented to limit postischemic injury in the numerous in vivo, as well as in in vitro studies. PPARs have been demonstrated to act on multiple mechanisms and were shown to activate multiple protective pathways related to inflammation, apoptosis, BBB protection, neurogenesis, and oxidative stress. The aim of this review was to summarize two decades of PPAR research in stroke with emphasis on in vivo animal studies. We focus on each PPAR receptor separately and detail their implication in stroke. This review also discusses recent clinical efforts in the field and the epidemiological data with regard to role of PPAR polymorphisms in susceptibility to stroke, and tries to draw conclusions and describe future perspectives.

Neurovascular protection by peroxisome proliferator-activated receptor α in ischemic stroke

Ischemic stroke is a leading cause of death and disability worldwide. Currently, the only pharmacological therapy for ischemic stroke is thrombolysis with tissue plasminogen activator that has a narrow therapeutic window and increases the risk of intracerebral hemorrhage. New pharmacological treatments for ischemic stroke are desperately needed, but no neuroprotective drugs have successfully made it through clinical trials. Beneficial effects of peroxisome proliferator-activated receptor alpha (PPARα) activation on vascular integrity and function have been reported, and PPARα agonists have clinically been used for many years to manage cardiovascular disease. Thus, PPARα has gained interest in recent years as a target for neurovascular disease such as ischemic stroke. Accumulating preclinical evidence suggests that PPARα activation modulates several pathophysiological hallmarks of stroke such as oxidative stress, blood-brain barrier (BBB) dysfunction, and neuroinflammation to improve functional recovery. Therefore, this review summarizes the various actions PPARα exerts in neurovascular health and disease and the potential of employing exogenous PPARα agonists for future pharmacological treatment of ischemic stroke.

Endothelium-targeted overexpression of Krüppel-like factor 11 protects the blood-brain barrier function after ischemic brain injury

Microvascular endothelial cell (EC) injury and the subsequent blood-brain barrier (BBB) breakdown are frequently seen in many neurological disorders, including stroke. We have previously documented that peroxisome proliferator-activated receptor gamma (PPARγ)-mediated cerebral protection during ischemic insults needs Krüppel-like factor 11 (KLF11) as a critical coactivator. However, the role of endothelial KLF11 in cerebrovascular function and stroke outcome is unclear. This study is aimed at investigating the regulatory role of endothelial KLF11 in BBB preservation and neurovascular protection after ischemic stroke. EC-targeted overexpression of KLF11 significantly mitigated BBB leakage in ischemic brains, evidenced by significantly reduced extravasation of BBB tracers and infiltration of peripheral immune cells, and less brain water content. Endothelial cell-selective KLF11 transgenic (EC-KLF11 Tg) mice also exhibited smaller brain infarct and improved neurological function in response to ischemic insults. Furthermore, EC-targeted transgenic overexpression of KLF11 preserved cerebral tight junction (TJ) levels and attenuated the expression of pro-inflammatory factors in mice after ischemic stroke. Mechanistically, we demonstrated that KLF11 directly binds to the promoter of major endothelial TJ proteins including occludin and ZO-1 to promote their activities. Our data indicate that KLF11 functions at the EC level to preserve BBB structural and functional integrity, and therefore, confers brain protection in ischemic stroke. KLF11 may be a novel therapeutic target for the treatment of ischemic stroke and other neurological conditions involving BBB breakdown and neuroinflammation.

Endothelium-targeted deletion of the miR-15a/16-1 cluster ameliorates blood-brain barrier dysfunction in ischemic stroke

The blood-brain barrier (BBB) maintains a stable brain microenvironment. Breakdown of BBB integrity during cerebral ischemia initiates a devastating cascade of events that eventually leads to neuronal loss. MicroRNAs are small noncoding RNAs that suppress protein expression, and we previously showed that the miR-15a/16-1 cluster is involved in the pathogenesis of ischemic brain injury. Here, we demonstrated that when subjected to experimentally induced stroke, mice with an endothelial cell (EC)-selective deletion of miR-15a/16-1 had smaller brain infarcts, reduced BBB leakage, and decreased infiltration of peripheral immune cells. These mice also showed reduced infiltration of proinflammatory M1-type microglia/macrophage in the peri-infarct area without changes in the number of resolving M2-type cells. Stroke decreases claudin-5 abundance, and we found that EC-selective miR-15a/16-1 deletion enhanced claudin-5 mRNA and protein abundance in ischemic mouse brains. In cultured mouse brain microvascular ECs (mBMECs), the miR-15a/16-1 cluster directly bound to the 3' untranslated region (3'UTR) of Claudin-5, and lentivirus-mediated ablation of miR-15a/16-1 diminished oxygen-glucose deprivation (OGD)-induced down-regulation of claudin-5 mRNA and protein abundance and endothelial barrier dysfunction. These findings suggest that genetic deletion of endothelial miR-15a/16-1 suppresses BBB pathologies after ischemic stroke. Elucidating the molecular mechanisms of miR-15a/16-1-mediated BBB dysfunction may enable the discovery of new therapies for ischemic stroke.

Endothelium-Targeted Deletion of microRNA-15a/16-1 Promotes Poststroke Angiogenesis and Improves Long-Term Neurological Recovery

RATIONALE

Angiogenesis promotes neurological recovery after stroke and is associated with longer survival of stroke patients. Cerebral angiogenesis is tightly controlled by certain microRNAs (miRs), such as the miR-15a/16-1 cluster, among others. However, the function of the miR-15a/16-1 cluster in endothelium on postischemic cerebral angiogenesis is not known.

OBJECTIVE

To investigate the functional significance and molecular mechanism of endothelial miR-15a/16-1 cluster on angiogenesis in the ischemic brain.

METHODS AND RESULTS

Endothelial cell-selective miR-15a/16-1 conditional knockout (EC-miR-15a/16-1 cKO) mice and wild-type littermate controls were subjected to 1 hour middle cerebral artery occlusion followed by 28-day reperfusion. Deletion of miR-15a/16-1 cluster in endothelium attenuates post-stroke brain infarction and atrophy and improves the long-term sensorimotor and cognitive recovery against ischemic stroke. Endothelium-targeted deletion of the miR-15a/16-1 cluster also enhances post-stroke angiogenesis by promoting vascular remodeling and stimulating the generation of newly formed functional vessels, and increases the ipsilateral cerebral blood flow. Endothelial cell-selective deletion of the miR-15a/16-1 cluster up-regulated the protein expression of pro-angiogenic factors VEGFA (vascular endothelial growth factor), FGF2 (fibroblast growth factor 2), and their receptors VEGFR2 (vascular endothelial growth factor receptor 2) and FGFR1 (fibroblast growth factor receptor 1) after ischemic stroke. Consistently, lentiviral knockdown of the miR-15a/16-1 cluster in primary mouse or human brain microvascular endothelial cell cultures enhanced in vitro angiogenesis and up-regulated pro-angiogenic proteins expression after oxygen-glucose deprivation, whereas lentiviral overexpression of the miR-15a/16-1 cluster suppressed in vitro angiogenesis and down-regulated pro-angiogenic proteins expression. Mechanistically, miR-15a/16-1 translationally represses pro-angiogenic factors VEGFA, FGF2, and their receptors VEGFR2 and FGFR1, respectively, by directly binding to the complementary sequences within 3'-untranslated regions of those messenger RNAs.

CONCLUSIONS

Endothelial miR-15a/16-1 cluster is a negative regulator for postischemic cerebral angiogenesis and long-term neurological recovery. Inhibition of miR-15a/16-1 function in cerebrovascular endothelium may be a legitimate therapeutic approach for stroke recovery.

Involvement of Epigenetic Mechanisms and Non-coding RNAs in Blood-Brain Barrier and Neurovascular Unit Injury and Recovery After Stroke

Cessation of blood flow leads to a complex cascade of pathophysiological events at the blood-vascular-parenchymal interface which evolves over time and space, and results in damage to neural cells and edema formation. Cerebral ischemic injury evokes a profound and deleterious upregulation in inflammation and triggers multiple cell death pathways, but it also induces a series of the events associated with regenerative responses, including vascular remodeling, angiogenesis, and neurogenesis. Emerging evidence suggests that epigenetic reprograming could play a pivotal role in ongoing post-stroke neurovascular unit (NVU) changes and recovery. This review summarizes current knowledge about post-stroke recovery processes at the NVU, as well as epigenetic mechanisms and modifiers (e.g., DNA methylation, histone modifying enzymes and microRNAs) associated with stroke injury, and NVU repair. It also discusses novel drug targets and therapeutic strategies for enhancing post-stroke recovery.

Angiotensin II type 2 receptor stimulation with compound 21 improves neurological function after stroke in female rats: a pilot study

The angiotensin II type 2 receptor (AT2R) agonist, compound 21 (C21), has been shown to be neurovascularly protective after ischemic stroke in male rats. In the current study, we aim to study the impact of C21 treatment on female rats. Young female Wistar rats were subjected to different durations of middle cerebral artery occlusion (MCAO) (3 h, 2 h, and 1 h) using a silicone-coated monofilament, treated at reperfusion with 0.03 mg/kg ip of C21 and followed up for different times (1, 3, and 14 days) after stroke. Behavioral tests were performed (Bederson, paw grasp, beam walk, and rotarod), and animals were euthanized for infarct size analysis and Western blot analysis. In vitro, primary male and female brain microvascular endothelial cells (ECs) were grown in culture, and the expression of the AT2R was compared between males and females. At 1 day, C21 treatment resulted in an improvement in Bederson scores. However, at 3 days and 14 days, the impact of C21 on stroke outcomes was less robust. In vitro, the expression of the AT2R was significantly higher in female ECs compared with male ECs. In conclusion, C21 improves Bederson scores after stroke in female rats when administered early at reperfusion. The ability of C21 to exert its neuroprotective effects might be affected by fluctuating levels of female hormones. NEW & NOTEWORTHY The present study shows the neuroprotective impact of C21 on ischemic stroke in female rats and how the protective effects of C21 can be influenced by the hormonal status of female rodents.

MicroRNAs in brain development and cerebrovascular pathophysiology

MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs with 21-25 nucleotides in length and play an important role in regulating gene expression at the posttranscriptional level via base-paring with complementary sequences of the 3'-untranslated region of the target gene mRNA, leading to either transcript degradation or translation inhibition. Brain-enriched miRNAs act as versatile regulators of brain development and function, including neural lineage and subtype determination, neurogenesis, synapse formation and plasticity, neural stem cell proliferation and differentiation, and responses to insults. Herein, we summarize the current knowledge regarding the role of miRNAs in brain development and cerebrovascular pathophysiology. We review recent progress of the miRNA-based mechanisms in neuronal and cerebrovascular development as well as their role in hypoxic-ischemic brain injury. These findings hold great promise, not just for deeper understanding of basic brain biology but also for building new therapeutic strategies for prevention and treatment of pathologies such as cerebral ischemia.

KLF11 (Krüppel-Like Factor 11) Inhibits Arterial Thrombosis via Suppression of Tissue Factor in the Vascular Wall

Objective- Mutations in Krüppel like factor-11 ( KLF11), a gene also known as maturity-onset diabetes mellitus of the young type 7, contribute to the development of diabetes mellitus. KLF11 has anti-inflammatory effects in endothelial cells and beneficial effects on stroke. However, the function of KLF11 in the cardiovascular system is not fully unraveled. In this study, we investigated the role of KLF11 in vascular smooth muscle cell biology and arterial thrombosis. Approach and Results- Using a ferric chloride-induced thrombosis model, we found that the occlusion time was significantly reduced in conventional Klf11 knockout mice, whereas bone marrow transplantation could not rescue this phenotype, suggesting that vascular KLF11 is critical for inhibition of arterial thrombosis. We further demonstrated that vascular smooth muscle cell-specific Klf11 knockout mice also exhibited significantly reduced occlusion time. The expression of tissue factor (encoded by the F3 gene), a main initiator of the coagulation cascade, was increased in the artery of Klf11 knockout mice, as determined by real-time quantitative polymerase chain reaction and immunofluorescence. Furthermore, vascular smooth muscle cells isolated from Klf11 knockout mouse aortas showed increased tissue factor expression, which was rescued by KLF11 overexpression. In human aortic smooth muscle cells, small interfering RNA-mediated knockdown of KLF11 increased tissue factor expression. Consistent results were observed on adenovirus-mediated overexpression of KLF11. Mechanistically, KLF11 downregulates F3 at the transcriptional level as determined by reporter and chromatin immunoprecipitation assays. Conclusions- Our data demonstrate that KLF11 is a novel transcriptional suppressor of F3 in vascular smooth muscle cells, constituting a potential molecular target for inhibition of arterial thrombosis.

MicroRNAs as Diagnostic and Prognostic Biomarkers in Ischemic Stroke-A Comprehensive Review and Bioinformatic Analysis

Stroke is the second-most common cause of death worldwide. The pathophysiology of ischemic stroke (IS) is related to inflammation, atherosclerosis, blood coagulation, and platelet activation. MicroRNAs (miRNAs) play important roles in physiological and pathological processes of neurodegenerative diseases and progression of certain neurological diseases, such as IS. Several different miRNAs, and their target genes, are recognized to be involved in the pathophysiology of IS. The capacity of miRNAs to simultaneously regulate several target genes underlies their unique value as diagnostic and prognostic markers in IS. In this review, we focus on the role of miRNAs as diagnostic and prognostic biomarkers in IS. We discuss the most common and reliable detection methods available and promising tests currently under development. We also present original results from bioinformatic analyses of published results, identifying the ten most significant genes (HMGB1, YWHAZ, PIK3R1, STAT3, MAPK1, CBX5, CAPZB, THBS1, TNFRSF10B, RCOR1) associated with inflammation, blood coagulation, and platelet activation and targeted by miRNAs in IS. Additionally, we created miRNA-gene target interaction networks based on Gene Ontology (GO) information derived from publicly available databases. Among our most interesting findings, miR-19a-3p is the most widely modulated miRNA across all selected ontologies and might be proposed as novel biomarker in IS to be tested in future studies.

Crosstalk between MicroRNAs and Peroxisome Proliferator-Activated Receptors and Their Emerging Regulatory Roles in Cardiovascular Pathophysiology

Peroxisome proliferator-activated receptors (PPARs) play vital roles in cardiovascular pathophysiology, such as energy balance, cell proliferation/apoptosis, inflammatory response, and adipocyte differentiation. These vital roles make PPARs potential targets for therapeutic prevention of cardiovascular diseases (CVDs). Emerging evidence indicates that the crosstalk of microRNAs (miRNAs) and PPARs contributes greatly to CVD pathogenesis. PPARs are inhibited by miRNAs at posttranscriptional mechanisms in the progress of pulmonary hypertension and vascular dysfunction involving cell proliferation/apoptosis, communication, and normal function of endothelial cells and vascular smooth muscle cells. In the development of atherosclerosis and stroke, the activation of PPARs could change the transcripts of target miRNA through miRNA signalling. Furthermore, the mutual regulation of PPARs and miRNAs involves cell proliferation/apoptosis, cardiac remodeling, and dysfunction in heart diseases. In addition, obesity, an important cardiovascular risk, is modulated by the regulatory axis of PPARs/miRNAs, including adipogenesis, adipocyte dysfunction, insulin resistance, and macrophage polarization in adipose tissue. In this review, the crosstalk of PPARs and miRNAs and their emerging regulatory roles are summarized in the context of CVDs and risks. This provides an understanding of the underlying mechanism of the biological process related to CVD pathophysiology involving the interaction of PPARs and miRNAs and will lead to the development of PPARs/miRNAs as effective anti-CVD medications.

Motor neuron loss and neuroinflammation in a model of α-synuclein-induced neurodegeneration

Mechanisms underlying α-synuclein (αSyn) mediated neurodegeneration are poorly understood. Intramuscular (IM) injection of αSyn fibrils in human A53T transgenic M83+/- mice produce a rapid model of α-synucleinopathy with highly predictable onset of motor impairment. Using varying doses of αSyn seeds, we show that αSyn-induced phenotype is largely dose-independent. We utilized the synchrony of this IM model to explore the temporal sequence of αSyn pathology, neurodegeneration and neuroinflammation. Longitudinal tracking showed that while motor neuron death and αSyn pathology occur within 2 months post IM, astrogliosis appears at a later timepoint, implying neuroinflammation is a consequence, rather than a trigger, in this prionoid model of synucleinopathy. Initiating at 3 months post IM, immune activation dominates the pathologic landscape in terminal IM-seeded M83+/- mice, as revealed by unbiased transcriptomic analyses. Our findings provide insights into the role of neuroinflammation in αSyn mediated proteostasis and neurodegeneration, which will be key in designing potential therapies.

Inhibition of calcium/calmodulin-dependent protein kinase kinase (CaMKK) exacerbates impairment of endothelial cell and blood-brain barrier after stroke

Brain microvascular endothelial cells play an essential role in maintaining blood-brain barrier (BBB) integrity, and disruption of the BBB aggravates the ischemic injury. CaMKK (α and β) is a major kinase activated by elevated intracellular calcium. Previously, we demonstrated that inhibition of CaMKK exacerbated outcomes, conversely, overexpression reduced brain injury after stroke in mice. Interestingly, CaMKK has been shown to activate a key endothelial protector, sirtuin 1 (SIRT1). We hypothesized that CaMKK protects brain endothelial cells via SIRT1 activation after stroke. In this study, Oxygen-Glucose Deprivation (OGD) was performed in human brain microvascular endothelial cells. Stroke was induced by middle cerebral artery occlusion (MCAO) in male mice. Knockdown of CaMKK β using siRNA increased cell death following OGD. Inhibition of CaMKK β by STO-609 significantly and selectively down-regulated levels of phosphorylated SIRT1 after OGD. Changes in the downstream targets of SIRT1 were observed following STO-609 treatment. The effect of STO-609 on cell viability after OGD was absent, when SIRT1 was concurrently inhibited. We also demonstrated that STO-609 increased endothelial expression of the pro-inflammatory proteins ICAM-1 and VCAM-1 and inhibition of CaMKK exacerbated OGD-induced leukocyte-endothelial adhesion. Finally, intracerebroventricular injection of STO-609 exacerbated endothelial apoptosis and reduced BBB integrity after 24-hr reperfusion following MCAO in vivo. Collectively, these results demonstrated that CaMKK inhibition reduced endothelial cell viability, exacerbated inflammatory responses and aggravated BBB impairment after ischemia. CaMKK activation may attenuate ischemic brain injury via protection of the microvascular system and a reduction in the infiltration of pro-inflammatory factors.

Genome-Wide Expression Profiles for Ischemic Stroke: A Meta-Analysis

BACKGROUND

Genome-wide expression studies (GWES), using microarray platforms, have allowed a deeper understanding of the molecular factors involved in the pathophysiology of ischemic stroke (IS), one of the main global causes of mortality and disability.

METHODS

In the current work, we carried out a meta-analysis of available GWES for IS. Bioinformatics and computational biology analyses were applied to identify enriched functional categories and convergence with other genomic datasets for IS.

RESULTS

Three primary datasets were included and in the meta-analyses for GWES and IS, 41 differentially expressed (DE) genes were identified using a random effects model. Thirteen of these genes were downregulated and 28 were upregulated. An analysis of functional categories found a significant enrichment for the Gene Ontology Term "Inflammatory Response" and for binding sites for the PAX2 transcription factor.

CONCLUSIONS

The list of DE genes identified in this meta-analysis of GWES for IS is useful for future genetic and molecular studies, which would allow the identification of novel mechanisms involved in the pathophysiology of IS. Several of the DE genes found in this meta-analysis have known functional roles related to mechanisms involved in the pathophysiology of IS. It is recognized the role of the inflammatory response in the pathophysiology of IS.

Krüppel-like factors and vascular wall homeostasis

Cardiovascular diseases (CVDs) are major causes of death worldwide. Identification of promising targets for prevention and treatment of CVDs is paramount in the cardiovascular field. Numerous transcription factors regulate cellular function through modulation of specific genes and thereby are involved in the physiological and pathophysiological processes of CVDs. Although Krüppel-like factors (KLFs) have a similar protein structure with a conserved zinc finger domain, they possess distinct tissue and cell distribution patterns as well as biological functions. In the vascular system, KLF activities are regulated at both transcriptional and posttranscriptional levels. Growing in vitro, in vivo, and genetic epidemiology studies suggest that specific KLFs play important roles in vascular wall biology, which further affect vascular diseases. KLFs regulate various functional aspects such as cell growth, differentiation, activation, and development through controlling a whole cluster of functionally related genes and modulating various signaling pathways in response to pathological conditions. Therapeutic targeting of selective KLF family members may be desirable to achieve distinct treatment effects in the context of various vascular diseases. Further elucidation of the association of KLFs with human CVDs, their underlying molecular mechanisms, and precise protein structure studies will be essential to define KLFs as promising targets for therapeutic interventions in CVDs.

Krüppel-Like Factors in Vascular Inflammation: Mechanistic Insights and Therapeutic Potential

The role of inflammation in vascular disease is well recognized, involving dysregulation of both circulating immune cells as well as the cells of the vessel wall itself. Unrestrained vascular inflammation leads to pathological remodeling that eventually contributes to atherothrombotic disease and its associated sequelae (e.g., myocardial/cerebral infarction, embolism, and critical limb ischemia). Signaling events during vascular inflammation orchestrate widespread transcriptional programs that affect the functions of vascular and circulating inflammatory cells. The Krüppel-like factors (KLFs) are a family of transcription factors central in regulating vascular biology in states of homeostasis and disease. Given their abundance and diversity of function in cells associated with vascular inflammation, understanding the transcriptional networks regulated by KLFs will further our understanding of the pathogenesis underlying several pervasive health concerns (e.g., atherosclerosis, stroke, etc.) and consequently inform the treatment of cardiovascular disease. Within this review, we will discuss the role of KLFs in coordinating protective and deleterious responses during vascular inflammation, while addressing the potential targeting of these critical transcription factors in future therapies.

Krüppel-like factors: Crippling and un-crippling metabolic pathways

Krüppel-like factors (KLFs) are DNA-binding transcriptional factors that regulate various pathways that control metabolism and other cellular mechanisms. Various KLF isoforms have been associated with cellular, organ or systemic metabolism. Altered expression or activation of KLFs has been linked to metabolic abnormalities, such as obesity and diabetes, as well as with heart failure. In this review article we summarize the metabolic functions of KLFs, as well as the networks of different KLF isoforms that jointly regulate metabolism in health and disease.

Peroxisome proliferator activating receptor-γ and the podocyte

Over the past two decades it has become clear that the glomerular podocyte is a key cell in preventing albuminuria, kidney failure and cardiovascular morbidity. Understanding the key pathways that protect the podocyte in times of glomerular stress, which can also be therapeutically manipulated, are highly attractive. In the following review we assess the evidence that the peroxisome proliferator activating receptor (PPAR) agonists are beneficial for podocyte and kidney function with a focus on PPAR-γ. We explain our current understanding of the mechanisms of action of these agonists and the evidence they are beneficial in diabetic and non-diabetic kidney disease. We also outline why these drugs have not been widely used for kidney disease in the past but they may be in the future.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

Altered Expression of MicroRNA-15a and Kruppel-Like Factor 4 in Cerebrospinal Fluid and Plasma After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Cerebral vasospasm (CVS) is a major determinant of prognosis in patients with subarachnoid hemorrhage (SAH). Alteration in the vascular phenotype contributes to development of CVS. However, little is known about the role of microRNAs (miRNAs) in the phenotypic alteration after SAH. We investigated the expression profile of miRNAs and the chronologic changes in the expression of microRNA-15a (miR-15a) and Kruppel-like factor 4 (KLF4), a potent regulator of vascular phenotype modulation that modulates the expression of miR-15a, in the plasma and cerebrospinal fluid (CSF) of patients with SAH.

METHODS

Peripheral blood and CSF samples were collected from 8 patients with aneurysmal SAH treated with endovascular obliteration. Samples obtained from 3 patients without SAH were used as controls in the analysis. Exosomal miRNAs were isolated and subjected to microarray analysis with the three-dimensional-gene miRNA microarray kit. The time course of the expression of miR-15a and KLF4 was analyzed using quantitative real-time polymerase chain reaction.

RESULTS

Microarray analysis showed that 12 miRNAs including miR-15a were upregulated or downregulated both in the CSF and in plasma after SAH within 3 days. Quantitative real-time polymerase chain reaction showed that miR-15a expression was significantly increased in both the CSF and plasma, with a peak around 3-5 days after SAH, whereas the expression of KLF4 was significantly decreased around 1-3 days after SAH and remained lower than in controls.

CONCLUSIONS

Our results suggest that an early and persistent decrease in KLF4 followed by an increase in miR-15a may contribute to the altered vascular phenotype, resulting in development of CVS.

The Transcription Factor IRF6 Co-Represses PPARγ-Mediated Cytoprotection in Ischemic Cerebrovascular Endothelial Cells

Activation of peroxisome proliferator-activated receptor gamma (PPARγ) in the cerebrovascular endothelium is a key suppressor of post-stroke brain damage. However, the role of PPARγ’s co-regulators during cerebral ischemia remains largely unknown. Here, we show that the transcription factor IRF6 is a novel PPARγ co-regulator that directly binds to and suppresses PPARγ activity in murine cerebrovascular endothelial cells. Moreover, IRF6 was also revealed to be a transcriptional target of PPARγ suppression, with PPARγ silencing significantly promoting IRF6 expression in cerebrovascular endothelial cells. In addition, IRF6 silencing significantly promoted pioglitazone’s cytoprotective effects in ischemic murine cerebrovascular endothelial cells. Mechanistically, IRF6 significantly suppressed PPARγ’s transcriptional inhibition of the ischemia-induced, pro-apoptotic microRNA miR-106a. In conclusion, we identified IRF6 as a novel PPARγ co-suppressor that serves a key role in suppressing PPARγ-mediated cerebrovascular endothelial cytoprotection following ischemia. Further investigation into IRF6 and other PPARγ co-regulators should provide additional insights into PPARγ’s cytoprotective role in the cerebrovascular endothelium following stroke.