Angiopoietin‐1 but not angiopoietin‐2 induces IL‐8 synthesis and release by human neutrophils

Abstract

We previously reported Tie2 receptor expression on human neutrophils, which promote chemotactic activities upon activation by both angiopoietins (Ang1 and Ang2). Moreover, we observed that neutrophil pretreatment with Ang1 or Ang2 enhances interleukin-8 (IL-8) chemotactic effect. Therefore, we assessed the capacity of Ang1 and/or Ang2 to modulate neutrophil IL-8 synthesis and release. Neutrophils isolated from healthy donors were stimulated in a time- (1-6 h) and concentration-(10(-10) -10(-8) M) dependent manner with both angiopoietins. IL-8 mRNA production was measured by RT-qPCR, whereas its protein synthesis and release from neutrophils was assessed by ELISA. Ang1 (10(-8) M) induced a significant and maximal increase of IL-8 mRNA (4.7-fold) within 1 h, and promoted maximal IL-8 protein synthesis (3.6-fold) and release (5.5-fold) within 2 h as compared to control PBS-treated neutrophils. Treatment with Ang2 alone did not modulate IL-8 synthesis or release, and its combination to Ang1 did not affect Ang1 activity. Neutrophil pretreatment with a protein synthesis inhibitor (CHX) increased IL-8 mRNA synthesis by 18-fold, and reduced Ang1-mediated IL-8 protein synthesis and release by 96% and 92%, respectively. Pretreatment with a transcription inhibitor (ActD) reduced IL-8 mRNA synthesis by 54% and IL-8 protein synthesis and release by 52% and 79%, respectively. Using specific kinase inhibitors, we observed that Ang1-driven IL-8 mRNA and protein synthesis is p42/44 MAPK-dependent and -independent from p38 MAPK and PI3K activity. Our study is the first to report the capacity of Ang1 (as opposed to Ang2) to promote neutrophil IL-8 synthesis and release through the activation of p42/44 MAPK pathway.

Adenovirus-delivered angiopoietin-1 suppresses NF-κB and p38 MAPK and attenuates inflammatory responses in phosgene-induced acute lung injury

“…Ang1, as opposed to Ang2, promotes neutrophil IL-8 synthesis and release through the activation of the p42/44 MAPK pathway (Neagoe et al, 2012). NF-kB is a family of DNA-binding proteins that is required for the transcription of many pro-inflammatory mediators and plays an important role in the pathogenesis of ALI (Kim et al, 2006;Liu et al, 2008).…”

Growth Hormone Releasing Peptide-2 Attenuation of Protein Kinase C-Induced Inflammation in Human Ovarian Granulosa Cells

“…Besides the mRNA stability aspect, in lung epithelial H292 cells, CHX was also shown to enhance IL-8 mRNA transcription with the involvement of two important responsive elements AP-1 and NF-κB, resulting in IL-8 mRNA superinduction [65]. In HL-60 promyelocytic leukemia cell line, IL-8 mRNA was rapidly induced at high levels by PKC activator phorbol 12-myristate 13-acetate and unidentified negatively-acting transcriptional regulator(s) was suggested to involve in the modulatory effect of CHX on IL-8 mRNA induction [66], and consistently in human PMN, the IL-8 mRNA superinduction effect by CHX was also proposed to be due to its ability to prevent the de novo protein synthesis of NRF, a protein shown to repress IL-8 mRNA synthesis [67]. Interestingly in human keratinocytes, it was reported that CHX, but not another protein synthesis inhibitor puromycin, was able to induce IL-8 mRNA expression [68].…”

Angiopoietin-1 Upregulates De Novo Expression of Il-1β and Il1-Ra, and the Exclusive Release of Il1-Ra from Human Neutrophils

“…In stark contrast, Ang1 exerts certain pro-inflammatory activities: Ang1 through Tie2 activation increases endothelial P-selectin translocation, a protein that mediates the rolling of leukocytes onto the endothelium under inflammatory conditions[11]. Ang1 has also the ability to directly impact leukocyte behavior, stimulating neutrophil IL-8 synthesis and release [12], and acting in a Tie2-dependent manner to recruit neutrophils and eosinophils, to increase neutrophil lifespan, and to promote neutrophil adhesion onto extracellular matrix [3], [4], [13]–[15]. The contribution of Ang2 to acute inflammation is even less defined, with some evidence of pro-inflammatory properties such as enhancing TNF-α-dependent adhesion of leukocytes to EC monolayers, as well as TNF-α-induced expression of ICAM-1 and VCAM-1 [16].…”

“…The contribution of Ang2 to acute inflammation is even less defined, with some evidence of pro-inflammatory properties such as enhancing TNF-α-dependent adhesion of leukocytes to EC monolayers, as well as TNF-α-induced expression of ICAM-1 and VCAM-1 [16]. Ang2 alone also promotes a transient endothelial P-selectin translocation and its effects on neutrophil adhesion and chemoattraction are Tie2-dependent and similar to those of Ang1 [4], [15]; however, unlike Ang1, Ang2 fails to promote neutrophil IL-8 synthesis and/or release, to increase neutrophil survival, or to counteract the effects of Ang1 on the aforementioned processes [12], [13]. Thus, the distinct contributions of Ang1 and Ang2 to acute inflammation remain to be clearly delineated.…”

“…They contribute substantially to inflammation through their ability to produce proteases, reactive oxygen species [17], [18], and to a lesser extent, cytokines including interleukin (IL)-6, TNF-α and IL-1 receptor antagonist (IL-1RA) [19]–[23]. Building on our recent findings that Ang1 promotes significant IL-8 production in human neutrophils in vitro in a time-dependent manner [12], we broadened our investigation to 84 other pro-inflammatory cytokines and their receptors, and looked at changes in their mRNA expression following angiopoietins stimulation. The first part of this study identified three related targets, all belonging to the IL-1 family of inflammatory cytokines, IL-1α, IL-1β, and IL-1RA, as well as a number of other potential interests unrelated to the IL-1 family.…”