Omentin-1 ameliorates the attachment of the leukocyte THP-1 cells to HUVECs by targeting the transcriptional factor KLF2

https://doi.org/10.1016/j.bbrc.2018.02.012Get rights and content

Highlights

  • Omentin-1 inhibited ox-LDL-induced THP-1 attachment to HUVECs.

  • Omentin-1 mitigated ox-LDL-induced expression of VCAM-1 and E-selectin.

  • Omentin-1 attenuated ox-LDL-induced reduction of KLF2 and its target genes.

  • The effects of omentin-1 on the expression of KLF2 are mediated by p53.

Abstract

Oxidation of low-density lipoproteins (ox-LDL) plays a critical role in endothelial dysfunction and the pathological progression of atherosclerosis by causing leukocyte attachment to endothelial surfaces. Omentin-1, an important adipokine primarily secreted by stromal vascular cells, has displayed various biological functions in diverse tissues. However, little information regarding the effects of omentin-1 on ox-LDL- induced endothelial dysfunction has been reported before. In the current study, we found that omentin-1 significantly reduced the attachment of the leukocyte THP-1 cells to human umbilical vein endothelial cells (HUVECs) in a dose dependent manner. Additionally, omentin-1 treatment prevented the expression of cell adhesion molecules such as VCAM-1 and E-selectin at both the mRNA level and the protein level. Notably, we found that omentin-1 significantly restored ox-LDL-induced reduction of KLF2, an important transcriptional factor and regulator of endothelial function. Also, omentin-1 promoted the expression of KLF2 target genes eNOS and PAI-1. Mechanistically, our results indicate that the effects of omentin-1 on KLF2 expression are mediated by p53. These results highlight the potential of omentin-1 in preventing endothelial dysfunction and atherosclerosis.

Introduction

Endothelial dysfunction is an important pathological status of endothelium in the wall of vessels. Endothelial dysfunction has been involved in the pathogenesis of various vascular diseases, including atherosclerosis [1]. In the past few decades, oxidation of low density lipoproteins (ox-LDL) has been widely investigated and reported as an essential regulator which contributes to vascular diseases and endothelial dysfunction [2]. Ox-LDL has been revealed to promote endothelial inflammation and to contribute to atherosclerosis in many stages including plaque formation, progression and destabilization [3,4]. Excessive oxidative stress and inflammatory insults caused by ox-LDL in arterial wall have been considered as crucial mechanisms of atherosclerosis [5]. One of the initial and critical events in the endothelium's response to ox-LDL stimuli is the expression of adhesion molecules such as vascular cell adhesion molecule (VCAM)-1 and E-selectin. These molecules cause the early attachment and rolling of leukocyte on the endothelial surface [6], and finally lead to the formation of atherosclerosis. Induction of VCAM-1 and E-selectin by ox-LDL is regulated by transcriptional factors in endothelium. The kruppel-like factor 2 (KLF2) is an important member of the kruppel-like factor family member [7]. KLF2 is extensively distributed in the nucleus of endothelium and acts as a “molecular switch” to regulate critical aspects of endothelial cell function in inflammatory disease states [8,9]. Interestingly, studies demonstrate that KLF2 is able to inhibit the pro-inflammatory cytokines-induced expression of adhesion molecules such as E-selectin and VCAM-1 [6].

Omentin-1, an important adipokine primarily secreted by stromal vascular cells in visceral adipose tissue, has been reported to distribute in diverse tissues, including heart, placenta, and pancreas [10]. Omentin-1 has been involved in different types of physiological processes including redox homeostasis, cardiovascular action, and anti-inflammatory response [11]. Omentin-1 is beneficial for enhancing insulin-stimulated glucose uptake by activating Akt signaling, which regulates downstream events such as glucose metabolism [12]. Moreover, decreased serum omentin-1 levels have been found to be associated with the presence and disease activity of inflammatory bowel disease (IBD) [13]. Importantly, counteractive effects of omentin-1 on atherosclerosis and ischemia-induced revascularization have been reported before [14]. High levels of plasma omentin have been found to be linked to the improvement of heart damage and function after reperfusion therapy in patients with acute myocardial infarction. Administration of human recombinant omentin ameliorated acute ischemic injury in the heart by suppressing myocyte apoptosis through both Adenosine 5‘-monophosphate (AMP)-activated protein kinase (AMPK)- and Akt-dependent mechanisms in a rodent disease model [15]. Intravenous administration of adenoviral vectors encoding human omentin (Ad-omentin) in mice attenuated neointimal formation after arterial injury and suppressed vascular smooth muscle cells (VSMCs) growth [16]. Systemic delivery of Ad-omentin enhanced blood flow recovery and capillary density in ischemic limbs of wild-type mice through stimulating an Akt and endothelial nitric oxide synthase (eNOS) signaling pathway [17]. In the current study, we aimed to investigate the effects of omentin-1 on ox-LDL- induced endothelial inflammation and to clarify the underlying mechanisms.

Section snippets

Cell culture, treatment, and transfection

Human umbilical vein endothelial cells (HUVECs) were purchased from ATCC, USA. Cells were maintained in endothelial cell growth medium (Lonza, USA) containing 2% fetal calf serum (FCS) and endothelial cell growth factors. Human recombinant omentin-1 produced in HEK 293 cells was obtained from Enzo Life Sciences, USA. HUVECs were treated with ox-LDL (100 mg/l) in the presence or absence of omentin-1 (150, 300 ng/ml) for 12 h or 24 h. For “Loss-of-function” experiments, HUVECs were transfected

Result

It is well known that attachment of monocytes to the surface of endothelial cells plays a pivotal role in the pathogenesis of atherosclerosis. Therefore, we set out to find out whether omentin-1 had an influence on adhesion of monocytes to HUVECs. As shown in Fig. 1, the numbers of THP-1 cells adhered to HUVECs were significantly increased by treatments with ox-LDL. However, omentin-1 significantly decreased the adhesion of THP-1 cells to the surface of HUVECs in a dose dependent manner.

Discussion

It is well known that the atherosclerotic lesion is characterized by an accumulation of lipids carried by lipoproteins, such as low-density lipoprotein (LDL). LDL becomes susceptible to (non) enzymatic oxidative modifications when retained in the artery wall. Ox-LDL plays a critical role in endothelial dysfunction and contributes to the atherosclerotic plaque formation, progression and destabilization [19,20]. Blockage of ox-LDL- induced endothelial inflammation has been considered as an

References (29)

  • C. Wu et al.

    Aβ(1-42) disrupts the expression and function of KLF2 in Alzheimer's disease mediated by p53

    Biochem. Biophys. Res. Commun.

    (2013)
  • J.E. Deanfield et al.

    Endothelial function and dysfunction: testing and clinical relevance

    Circulation

    (2007)
  • H.M. Ahmad et al.

    Higher circulating levels of OxLDL % of LDL are associated with subclinical atherosclerosis in female patients with systemic lupus erythematosus

    Rheumatol. Int.

    (2014)
  • Y. Shen et al.

    Increased serum ox-LDL levels correlated with lung function, inflammation, and oxidative stress in COPD

    Mediat. Inflamm.

    (2013)
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