AIBP, inflammation, and atherosclerosis

AIBP promotes cell proliferation and migration through the ERK1/2-MAPK signaling pathway in hepatocellular carcinoma

Background

As a highly aggressive cancer, hepatocellular carcinoma (HCC) is often found at an advanced stage and has a poor prognosis. Therefore, in addition to the surgical treatment of HCC, the drug therapy for HCC is still under continuous exploration. The primary apolipoprotein of high-density lipoproteins (HDLs) is apolipoprotein A-I binding protein (AIBP), which has a significant impact on cholesterol metabolism, angiogenesis, and a wide range of inflammatory disorders, including cancer. The AIBP function in HCC is, however, yet unknown. This study aims to reveal the underlying mechanisms of AIBP influencing HCC proliferation and migration through mitogen-activated protein kinase (MAPK) pathways.

Methods

AIBP expression and its clinical prognostic association were investigated using The Cancer Genome Atlas (TCGA) data. The AIBP expression was studied in human HCC tissues using immunohistochemistry (IHC) and western blotting. Colony formation assays (CFAs) and cell counting kit-8 (CCK-8) were used to determine in vitro cell proliferation. Cell migration and invasion were evaluated using wound-healing and transwell assays. A xenograft tumor model was employed to investigate HCC cell proliferation in nude mice.

Results

Tissues from HCC patients had much increased AIBP expression compared to nearby normal tissues. The prognosis for patients was bleak when AIBP expression was high. When AIBP was overexpressed in SMMC-7721 cells, the cells may become more proliferative, migrative, and invasive. In contrast, the HCC-LM3 cells' ability to proliferate, migrate, and invade was drastically decreased once AIBP was knocked down in vitro. Furthermore, in vivo research showed that AIBP overexpression may enhance cell proliferation in HCC. Finally, we discovered that AIBP could control the MAPK signaling pathway-involved genes expression, including P-MEK, MEK, c-Myc, P-ERK1/2, and ERK1/2, and that GDC-0994, a specific ERK1/2 inhibitor, could suppress the AIBP overexpression induced cell migration and proliferation abilities.

Conclusions

These findings demonstrated that the ERK/MAPK signaling pathway might be stimulated by AIBP in HCC tissues, leading to increased cell invasion, migration, and proliferation. It was hypothesized that AIBP might act as a useful prognostic and diagnostic marker for HCC.

Targeting mitochondrial function in macrophages: A novel treatment strategy for atherosclerotic cardiovascular disease?

Atherosclerotic cardiovascular disease is a major cause of morbidity and mortality due to chronic arterial injury caused by hyperlipidemia, hypertension, inflammation and oxidative stress. Recent studies have shown that the progression of this disease is associated with mitochondrial dysfunction and with the accumulation of mitochondrial alterations within macrophages of atherosclerotic plaques. These alterations contribute to processes of inflammation and oxidative stress. Among the many players involved, macrophages play a pivotal role in atherogenesis as they can exert both beneficial and deleterious effects due to their anti- and pro-inflammatory properties. Their atheroprotective functions, such as cholesterol efflux and efferocytosis, as well as the maintenance of their polarization towards an anti-inflammatory state, are particularly dependent on mitochondrial metabolism. Moreover, in vitro studies have demonstrated deleterious effects of oxidized LDL on macrophage mitochondrial function, resulting in a switch to a pro-inflammatory state and to a potential loss of atheroprotective capacity. Therefore, preservation of mitochondrial function is now considered a legitimate therapeutic strategy. This review focuses on the potential therapeutic strategies that could improve the mitochondrial function of macrophages, enabling them to maintain their atheroprotective capacity. These emerging therapies could play a valuable role in counteracting the progression of atherosclerotic lesions and possibly inducing their regression.

Mitochondrial apolipoprotein A-I binding protein alleviates atherosclerosis by regulating mitophagy and macrophage polarization

Apolipoprotein A-I binding protein (AIBP), a secreted protein, has been shown to play a pivotal role in the development of atherosclerosis. The function of intracellular AIBP, however, is not yet well characterized. Here, we found that AIBP is abundantly expressed within human and mouse atherosclerotic lesions and exhibits a distinct localization in the inner membrane of mitochondria in macrophages. Bone marrow-specific AIBP deficiency promotes the progression of atherosclerosis and increases macrophage infiltration and inflammation in low-density lipoprotein receptor-deficient (LDLR-/-) mice. Specifically, the lack of mitochondrial AIBP leads to mitochondrial metabolic disorders, thereby reducing the formation of mitophagy by promoting the cleavage of PTEN-induced putative kinase 1 (PINK1). With the reduction in mitochondrial autophagy, macrophages polarize to the M1 proinflammatory phenotype, which further promotes the development of atherosclerosis. Based on these results, mitochondrial AIBP in macrophages performs an antiatherosclerotic role by regulating of PINK1-dependent mitophagy and M1/M2 polarization. Video Abstract.

Systemic metabolite profiling reveals sexual dimorphism of AIBP control of metabolism in mice

Emerging studies indicate that APOA-I binding protein (AIBP) is a secreted protein and functions extracellularly to promote cellular cholesterol efflux, thereby disrupting lipid rafts on the plasma membrane. AIBP is also present in the mitochondria and acts as an epimerase, facilitating the repair of dysfunctional hydrated NAD(P)H, known as NAD(P)H(X). Importantly, AIBP deficiency contributes to lethal neurometabolic disorder, reminiscent of the Leigh syndrome in humans. Whereas cyclic NADPHX production is proposed to be the underlying cause, we hypothesize that an unbiased metabolic profiling may: 1) reveal new clues for the lethality, e.g., changes of mitochondrial metabolites., and 2) identify metabolites associated with new AIBP functions. To this end, we performed unbiased and profound metabolic studies of plasma obtained from adult AIBP knockout mice and control littermates of both genders. Our systemic metabolite profiling, encompassing 9 super pathways, identified a total of 640 compounds. Our studies demonstrate a surprising sexual dimorphism of metabolites affected by AIBP deletion, with more statistically significant changes in the AIBP knockout female vs male when compared with the corresponding controls. AIBP knockout trends to reduce cholesterol but increase the bile acid precursor 7-HOCA in female but not male. Complex lipids, phospholipids, sphingomyelin and plasmalogens were reduced, while monoacylglycerol, fatty acids and the lipid soluble vitamins E and carotene diol were elevated in AIBP knockout female but not male. NAD metabolites were not significantly different in AIBP knockout vs control mice but differed for male vs female mice. Metabolites associated with glycolysis and the Krebs cycle were unchanged by AIBP knockout. Importantly, polyamine spermidine, critical for many cellular functions including cerebral cortex synapses, was reduced in male but not female AIBP knockout. This is the first report of a systemic metabolite profile of plasma samples from AIBP knockout mice, and provides a metabolic basis for future studies of AIBP regulation of cellular metabolism and the pathophysiological presentation of AIBP deficiency in patients.

AIBP, Angiogenesis, Hematopoiesis, and Atherogenesis

PURPOSE OF REVIEW

The goal of this manuscript is to summarize the current understanding of the secreted APOA1 binding protein (AIBP), encoded by NAXE, in angiogenesis, hematopoiesis, and inflammation. The studies on AIBP illustrate a critical connection between lipid metabolism and the aforementioned endothelial and immune cell biology.

RECENT FINDINGS

AIBP dictates both developmental processes such as angiogenesis and hematopoiesis, and pathological events such as inflammation, tumorigenesis, and atherosclerosis. Although cholesterol efflux dictates AIBP-mediated lipid raft disruption in many of the cell types, recent studies document cholesterol efflux-independent mechanism involving Cdc42-mediated cytoskeleton remodeling in macrophages. AIBP disrupts lipid rafts and impairs raft-associated VEGFR2 but facilitates non-raft-associated NOTCH1 signaling. Furthermore, AIBP can induce cholesterol biosynthesis gene SREBP2 activation, which in turn transactivates NOTCH1 and supports specification of hematopoietic stem and progenitor cells (HSPCs). In addition, AIBP also binds TLR4 and represses TLR4-mediated inflammation. In this review, we summarize the latest research on AIBP, focusing on its role in cholesterol metabolism and the attendant effects on lipid raft-regulated VEGFR2 and non-raft-associated NOTCH1 activation in angiogenesis, SREBP2-upregulated NOTCH1 signaling in hematopoiesis, and TLR4 signaling in inflammation and atherogenesis. We will discuss its potential therapeutic applications in angiogenesis and inflammation due to selective targeting of activated cells.

Mitochondrial metabolism in regulating macrophage polarization: an emerging regulator of metabolic inflammatory diseases

As a major type of immune cells with heterogeneity and plasticity, macrophages are classically divided into inflammatory (M1) and alternative/anti-inflammatory (M2) types and play a crucial role in the progress of the inflammatory diseases. Recent studies have shown that metabolism is an important determinant of macrophage phenotype. Mitochondria, one of the most important compartments involving cell metabolism, are closely associated with the regulation of cell functions. In most types of cell, mitochondrial oxidative phosphorylation (OXPHOS) is the primary mode of cellular energy production. However, mitochondrial OXPHOS is inhibited in activated M1 macrophages, rendering them unable to be converted into M2 phenotype. Thus, mitochondrial metabolism is a crucial regulator in macrophage functions. This review summarizes the roles of mitochondria in macrophage polarization and analyzes the molecular mechanisms underlying mitochondrial metabolism and function, which may provide new approaches for the treatment of metabolic inflammatory diseases.

Upstream therapeutic strategies of valsartan and fluvastatin on hypertensive patients with non-permanent atrial fibrillation

AIM

To investigate the upstream therapeutic effects of fluvastatin and valsartan on hypertensive patients with non-permanent atrial fibrillation (AF).

METHODS

A total of 189 patients who were admitted to outpatient and inpatient department from eight medical centers in China, diagnosed as hypertension with non-permanent AF, were divided into four groups randomly: the CCBs group (group A, n = 45); CCB + fluvastatin group (group B, n = 48); valsartan group (group C, n = 46); valsartan + fluvastatin group (group D, n = 50). The four groups were followed up for 24 months. The blood routine, biochemical examination, echocardiography, high sensitive C-reactive protein (hs-CRP), N-terminal pro-brain natriuretic peptide (NT-proBNP), the maintenance rate of sinus rhythm, and the recurrence of paroxysmal AF or persistent AF incidence were observed in these groups before and after 24 months' treatment.

RESULTS

After 24 months of follow-up, there were 178 cases of patients who have completed the study. (a) There was no significant difference in blood routine, liver, and renal function in each group (P > 0.05). (b) The blood lipids level in groups B and D was significantly reduced after treatment (P < 0.01). There was no significant difference of hs-CRP level in group A (P > 0.05). The left ventricular remodeling was significantly alleviated in group C and group D (P < 0.05). The NT-ProBNP level was significantly decreased in group D (P < 0.05). (c) The sinus rhythm maintenance rate of group B, group C, and group D was higher than group A (77.78%, 70.45%, 79.17% vs 43.90%), the occurrence of persistent AF was significantly lower than group A (11.11%, 14.29%, 8.33% vs 31.71%; P < 0.05).

CONCLUSIONS

CCB plus fluvastatin and valsartan can reduce the recurrence rate of non-permanent AF and to delay the progression from non-permanent AF to permanent AF in patients with hypertension. The combined application of valsartan and fluvastatin is more effective than valsartan or CCB alone in the upstream therapies of AF.