Secreted protein acidic and rich in cysteine (SPARC) induces apoptosis of human brain vascular smooth muscle cells through regulating HK2 in intracranial aneurysm.

Background: Vascular smooth muscle cell (VSMC) dysfunction is one of the crucial pathologic processes in the development of intracranial aneurysm (IA). Secreted protein acidic and rich in cysteine (SPARC), a multifunctional glycoprotein, is overexpressed in many tumor, but its underlying mechanism in vascular disease has not been elucidated. The aim of this study is to evaluate the potential function of SPARC in IA generation and regulation of mitochondrial function in VSMC. Methods: Human brain vascular smooth muscle cells were treated with recombinant SPARC to detect apoptosis-related markers. The downstream targets affecting mitochondrial dysfunction after SPARC treatment were explored by transcriptome sequencing and bioinformatics analysis, and verified using by immunohistochemistry and western blot. Further in vitro experiments verified the role of downstream targets in regulating VSMC mitochondrial function. Results: Secreted protein acidic and rich in cysteine (SPARC) expression was associated with the risk of IA rupture. SPARC induces mitochondrial pathway apoptosis in human brain VSMC. We screened 40 differentially expressed genes related to mitochondrial function after SPARC treatment. Hexokinase 2 (HK2) was identified as a downstream target of mitochondrial pathway apoptosis in VSMC induced by SPARC. In addition, immunohistochemical results confirmed that the difference between SPARC and HK2 expression is located mainly in the smooth muscle layer of IA. Overexpression of HK2 reversed the SPARC-induced increase in apoptosis and mitochondrial damage in VSMC. Conclusion: Secreted protein acidic and rich in cysteine (SPARC) regulated mitochondrial function in VSMC and induced apoptosis through HK2, which plays an important role in the formation and rupture of IA. Targeting SPARC may be a novel strategy to delay the development of intracranial aneurysms.

Aneurysm Wall Enhancement in Unruptured Intracranial Aneurysms: A Histopathological Evaluation.

Background Unruptured intracerebral aneurysm wall enhancement (AWE) on vessel wall magnetic resonance imaging scans may be a promising predictor for rupture-prone intracerebral aneurysms. However, the pathophysiology of AWE remains unclear. To this end, the association between AWE and histopathological changes was assessed in this study. Methods and Results A total of 35 patients with 41 unruptured intracerebral aneurysms who underwent surgical clipping were prospectively enrolled. A total of 27 aneurysms were available for histological evaluation. The macroscopic and microscopic features of unruptured intracerebral aneurysms with and without enhancement were assessed. The microscopic features studied included inflammatory cell invasion and vasa vasorum, which were assessed using immunohistochemical staining with CD68, CD3, CD20, and myeloperoxidase for the former and CD34 for the latter. A total of 21 (51.2%) aneurysms showed AWE (partial AWE, n=7; circumferential AWE, n=14). Atherosclerotic and translucent aneurysms were identified in 17 and 14 aneurysms, respectively. Aneurysm size, irregularity, and atherosclerotic and translucent aneurysms were associated with AWE on univariate analysis (P<0.05). Multivariate logistic regression analysis showed that atherosclerosis was the only factor significantly and independently associated with AWE (P=0.027). Histological assessment revealed that inflammatory cell infiltration, intraluminal thrombus, and vasa vasorum were significantly associated with AWE (P<0.05). Conclusions Though AWE on vessel wall magnetic resonance imaging scans may be associated with the presence of atherosclerotic lesions in unruptured intracerebral aneurysms, inflammatory cell infiltration within atherosclerosis, intraluminal thrombus, and vasa vasorum may be the main pathological features associated with AWE. However, the underlying pathological mechanism for AWE still needs to be further studied.

Induction of SPARC on Oxidative Stress, Inflammatory Phenotype Transformation, and Apoptosis of Human Brain Smooth Muscle Cells Via TGF-ß1-NOX4 Pathway.

Secreted protein acidic and rich in cysteine (SPARC) has a close association with inflammatory response and oxidative stress in tissues and is widely expressed in intracranial aneurysms (IAs), especially in smooth muscle cells. Therefore, it is inferred that SPARC might be involved in the formation and development of IAs through the inflammatory response pathway or oxidative stress pathway. The aim of this study is to investigate the pathological mechanism of SPARC in oxidative stress, inflammation, and apoptosis during the formation of IAs, as well as the involvement of TGF-ß1 and NOX4 molecules. Human brain vascular smooth muscle cells (HBVSMCs) were selected as experimental objects. After the cells were stimulated by recombinant human SPARC protein in vitro, the ROS level in the cells was measured using an ID/ROS fluorescence analysis kit combined with fluorescence microscope and flow cytometry. The related protein expression in HBVSMCs was measured using western blotting. The mitochondrial membrane potential change was detected using a mitochondrial membrane potential kit and laser confocal microscope. The mechanism was explored by intervention with reactive oxygen scavengers N-acetylcysteine (NAC), TGF-ß1 inhibitor (SD-208), and siRNA knockout. The results showed that SPARC upregulated the expression of NOX4 through the TGF-ß1-dependent signaling pathway, leading to oxidative stress and pro-inflammatory matrix behavior and apoptosis in HBVSMCs. These findings demonstrated that SPARC may promote the progression of IAs.

SPARC induces phenotypic modulation of human brain vascular smooth muscle cells via AMPK/mTOR-mediated autophagy.

Secreted protein acidic and rich in cysteine (SPARC) was widely expressed in VSMCs of human IAs and could reduce the capability of self-repair. This indicates that SPARC may play a role in the promotion of IAs formation and progression, but the mechanism remains unclear. In this study, we further investigated whether SPARC could induce phenotypic modulation of Human Brain Vascular Smooth Muscle Cells (HBVSMCs) and sought to elucidate the role of SPARC-mediated autophagy involved in it. The results demonstrated that SPARC inhibited the expression of contractile genes in HBVSMCs and induced a synthetic phenotype. More importantly, SPARC significantly up-regulated multiple proteins including autophagy marker microtubule-associated protein light chain 3-II (LC3-II), Beclin-1, and autophagy-related gene 5(ATG5). Furthermore, SPARC could promote p62 degradation. The autophagy inhibitor 3- methyladenine (3-MA) significantly blocked SPARC-induced phenotypic modulation of HBVSMCs. We further sought to elucidate the molecular mechanism involved in SPARC-induced autophagy, and found that SPARC could activate the AMPK/mTOR signaling pathway in HBVSMCs. AMPK could be pharmacologically inhibited by Compound C (CC), which significantly decreased the phosphorylation of AMPK into p-AMPK, increased the phosphorylation of mTOR into p-mTOR, and decreased LC3-II, Beclin-1 and ATG5 levels. This suggested that activated AMPK/ mTOR signaling is related to SPARC-mediated autophagy. These results indicated that SPARC plays a role in the phenotypic modulation of HBVSMCs through autophagy activation by AMPK/mTOR signaling pathway.

Nitrogen-Doped Mesoporous Carbon-Encapsulated MoO2 Nanobelts as a High-Capacity and Stable Host for Lithium-Ion Storage.

N-doped mesoporous carbon-capped MoO2 nanobelts (designated as MoO2 @NC) were synthesized and applied to lithium-ion storage. Owing to the stable core-shell structural framework and conductive mesoporous carbon matrix, the as-prepared MoO2 @NC shows a high specific capacity of around 700 mA h g-1 at a current of 0.5 A g-1 , excellent cycling stability up to 100 cycles, and superior rate performance. The N-doped mesoporous carbon can greatly improve the conductivity and provide uninhibited conducting pathways for fast charge transfer and transport. Moreover, the core-shell structure improved the structural integrity, leading to a high stability during the cycling process. All of these merits make the MoO2 @NC to be a suitable and promising material for lithium ion battery.