Krüppel-like zinc-finger transcription factor 5 (KLF5) is highly expressed in large and giant unruptured cerebral aneurysms

Exploring the latest findings on endovascular treatments for giant aneurysms: a review

Giant intracranial aneurysms represent a very challenging aspect of aneurysmal pathophysiology with very high mortality and morbidity if left untreated. Their variety in clinical presentation (subarachnoid hemorrhage, cranial nerve palsy, etc.) and pathological and imaging properties (location, anatomy, presence of collateral circulation) pose serious questions regarding the best treatment option. Admirable advances have been achieved in surgical techniques, while endovascular modalities with flow diversion techniques have become widely used. However, there is still lack of data regarding whether a single endovascular technique can be the universal treatment for such cases. In this review, we aim to summarize the current funds of knowledge concerning giant intracranial aneurysms and the role of endovascular management in their treatment.

Intracranial Fusiform and Circumferential Aneurysms of the Main Trunk: Therapeutic Dilemmas and Prospects

Intracranial fusiform and circumferential aneurysms (IFCAs), especially those located on the main trunk, are uncommon and difficult to manage. Currently, literature focused on IFCAs on the main trunk of cerebral arteries is lacking. The treatment of IFCAs is still under debate. Therefore, in this review, we further explore the treatment of this complicated entity. In addition, we also present some interesting cases. Based on the literature review and our experience, we found that IFCAs are often located in the vertebrobasilar system and that ruptured or large symptomatic IFCAs are associated with increased mortality and higher rebleeding rates. The treatment strategies for IFCAs can be classified as deconstructive and reconstructive methods via open surgery and/or endovascular treatment (EVT). Currently, EVT is a popular method and the main therapeutic choice. In particular, flow diversion has revolutionized the treatment of IFCAs. Parent artery occlusion (PAO) with or without revascularization may still be considered a suitable choice. Complex IFCAs that cannot be resolved by EVT can also be treated via open surgery with or without extracranial–intracranial bypass. Targeted embolization for the weak points of IFCAs is a temporary or palliative choice that is rarely used. In summary, despite complications, both surgical treatment and EVT are effective options for appropriately selected cases. Due to the development of endovascular implants, EVT will have better prospects in the future.

microRNA-195 attenuates neuronal apoptosis in rats with ischemic stroke through inhibiting KLF5-mediated activation of the JNK signaling pathway

BACKGROUND

Accumulating evidence has implicated the regulation of microRNAs (miRs) in ischemia stroke. The current study aimed to elucidate the role of microRNA-195 (miR-195) in neuronal apoptosis and brain plasticity in rats with ischemic stroke via the JNK signaling pathway/KLF5 axis.

METHODS

Ischemic stroke rat models were established by middle cerebral artery occlusion (MCAO), and oxygen deprivation (OGD) models were constructed in rat neuronal cells, followed by gain- or loss-of-function of miR-195 and/or KLF5 in rats and cells. Infarct volume, neuronal loss and ultrastructure, the expression of GAP-43, SYP and KLF5 protein as well as cell apoptosis were determined in the rats. Caspase-3 activity as well as the expression of miR-195, KLF5, GAP-43, SYP, JNK, phosphorylated JNK, Bax and Bcl-2 was measured in the cells.

RESULTS

The infarct size, expression of GAP-43 and SYP protein and apoptotic cells were increased in the miR-195^-/- MCAO rats, while reductions were detected in the miR-195 mimic MCAO and KLF5^-/- MCAO rats. Bcl-2 expression was increased, Bax and Caspase-3 expression as well as the ratio of phosphorylated JNK/JNK was decreased in response to miR-195 overexpression or KLF5 knockdown. Interestingly, the silencing of KLF5 reversed the effects exerted by the miR-195 inhibitor on the expression of Bcl-2, phosphorylated JNK/JNK, Bax and Caspase-3.

CONCLUSIONS

Collectively, our study unraveled that miR-195 could down-regulate KLF5 and block the JNK signaling pathway, ultimately inhibiting neuronal apoptosis in rats with ischemic stroke.

miR-448-3p controls intracranial aneurysm by regulating KLF5 expression

microRNAs (miRNAs) control several processes known to be involved in progression of aneurysm. Here, intracranial aneurysms (IAs) were surgically induced in Sprague-Dawley rats, and we found that miR-448-3p was downregulated and KLF5 was upregulated in IA rats. We identified Klf5 as a direct target of miR-448-3p in smooth muscle cells (SMCs). In addition, aneurysms size and the lumen area of the aneurysms were smaller 4 weeks after IA induction in the miR-448-3p-treated group. miR-448-3p treatment protected the wall thickness ratio and suppressed macrophage infiltration after IA induction. IAs caused a significant increase in KLF5 expression and were alleviated by miR-448-3p. Moreover, the anti-inflammatory effect of miR-448-3p was verified in lipopolysaccharide -stimulated RAW 264.7 macrophage cells. The expression levels of KLF5, MMP2, and MMP9 levels were elevated by LPS, and were attenuated by miR-448-3p. These data suggest that miR-448-3p plays the inhibitory role in IA progression, indicating that miR-448-3p overexpression is crucial for preventing the development of IA through downregulation of macrophage-mediated inflammation.

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.

Inhibition of KLF5-Myo9b-RhoA Pathway-Mediated Podosome Formation in Macrophages Ameliorates Abdominal Aortic Aneurysm

RATIONALE

Abdominal aortic aneurysms (AAAs) are characterized by pathological remodeling of the aortic wall. Although both increased Krüppel-like factor 5 (KLF5) expression and macrophage infiltration have been implicated in vascular remodeling, the role of KLF5 in macrophage infiltration and AAA formation remains unclear.

OBJECTIVE

To determine the role of KLF5 in AAA formation and macrophage infiltration into AAAs.

METHODS AND RESULTS

KLF5 expression was significantly increased in human AAA tissues and in 2 mouse models of experimental AAA. Moreover, in myeloid-specific Klf5 knockout mice (myeKlf5^-/- mice), macrophage infiltration, medial smooth muscle cell loss, elastin degradation, and AAA formation were markedly decreased. In cell migration and time-lapse imaging analyses, the migration of murine myeKlf5^-/- macrophages was impaired, and in luciferase reporter assays, KLF5 activated Myo9b (myosin IXB) transcription by direct binding to the Myo9b promoter. In subsequent coimmunostaining studies, Myo9b was colocalized with filamentous actin, cortactin, vinculin, and Tks5 in the podosomes of phorbol 12,13-dibutyrate-treated macrophages, indicating that Myo9b participates in podosome formation. Gain- and loss-of-function experiments showed that KLF5 promoted podosome formation in macrophages by upregulating Myo9b expression. Furthermore, RhoA-GTP levels increased after KLF5 knockdown in macrophages, suggesting that KLF5 lies upstream of RhoA signaling. Finally, Myo9b expression was increased in human AAA tissues, located in macrophages, and positively correlated with AAA size.

CONCLUSIONS

These data are the first to indicate that KLF5-dependent regulation of Myo9b/RhoA is required for podosome formation and macrophage migration during AAA formation, warranting consideration of the KLF5-Myo9b-RhoA pathway as a therapeutic target for AAA treatment.

Hyperhomocysteinemia induced by excessive methionine intake promotes rupture of cerebral aneurysms in ovariectomized rats

Background

Hyperhomocysteinemia (HHcy) is associated with inflammation and a rise in the expression of matrix metalloproteinase-9 (MMP-9) in the vascular wall. However, the role of HHcy in the growth and rupture of cerebral aneurysms remains unclear.

Methods

Thirteen-week-old female Sprague-Dawley rats were subject to bilateral ovariectomy and ligation of the right common carotid artery and fed an 8 % high-salt diet to induce cerebral aneurysms. Two weeks later, they underwent ligation of the bilateral posterior renal arteries. They were divided into two groups and methionine (MET) was or was not added to their drinking water. In another set of experiments, the role of folic acid (FA) against cerebral aneurysms was assessed.

Results

During a 12-week observation period, subarachnoid hemorrhage due to aneurysm rupture was observed at the anterior communicating artery (AcomA) or the posterior half of the circle of Willis. HHcy induced by excessive MET intake significantly increased the incidence of ruptured aneurysms at 6–8 weeks. At the AcomA of rats treated with MET, we observed the promotion of aneurysmal growth and infiltration by M1 macrophages. Furthermore, the mRNA level of MMP-9, the ratio of MMP-9 to the tissue inhibitor of metalloproteinase-2, and the level of interleukin-6 were higher in these rats. Treatment with FA abolished the effect of MET, suggesting that the inflammatory response and vascular degradation at the AcomA is attributable to HHcy due to excessive MET intake.

Conclusions

We first demonstrate that in hypertensive ovariectomized rats, HHcy induced by excessive MET intake may be associated with the propensity of the aneurysm wall to rupture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0634-3) contains supplementary material, which is available to authorized users.

Genetic markers and their influence on cerebrovascular malformations

Cerebrospinal vascular malformations are a group of anomalies affecting the arterial wall, the capillary arteriovenous interface, or the venous and lymphatic structures. Heritability and family studies allow identification of mutations in single genes associated with rare familial conditions causing cerebral or spinal vascular malformations, as is the case in hemorrhagic hereditary telangiectasia diseases. This article reviews the genetic and epigenetic influences increasingly reported in recent years as causal factors or triggers involved in the formation and growth of cerebromedullary vascular malformations.

BTEB2 prevents neuronal apoptosis via promoting bad phosphorylation in rat intracerebral hemorrhage model

Krüppel-like zinc-finger transcription factor 5 (KLF5), known as BTEB2 or IKLF, has several biological functions that involve cell proliferation, development and apoptosis. Previous studies demonstrated that BTEB2 had anti-apoptotic effect in multiple diseases such as esophageal cancer and non-small cell lung cancers (NSCLCs). However, the distribution and function of BTEB2 in CNS diseases remain unknown. In this study, we show that BTEB2 down-regulates neuronal apoptosis during pathophysiological processes of intracerebral hemorrhage (ICH). A rat ICH model was established by behavioral tests. Western blot and immunohistochemistry revealed a remarkable up-regulation of BTEB2 expression surrounding the hematoma after ICH. Double-labeled immunofluorescence showed BTEB2 was mostly co-localized with neurons, rarely with activated astrocytes and microglia. Furthermore, we detected that neuronal apoptosis marker active caspase-3 had co-localizations with BTEB2. In addition, KLF5 knockdown in vitro specifically resulted in increasing neuronal apoptosis coupled with reduced Bad phosphorylation at both ser112 and ser136 residues. All our findings suggested that BTEB2 down-regulated neuronal apoptosis via promoting Bad phosphorylation after ICH.