Olive Leaf Extract Attenuates Inflammatory Activation and DNA Damage in Human Arterial Endothelial Cells

Blaž Burja; Tadeja Kuret; Tea Janko; Dijana Topalović; Lada Živković; Katjuša Mrak-Poljšak; Biljana Spremo-Potparević; Polona Žigon; Oliver Distler; Saša Čučnik; Snezna Sodin-Semrl; Katja Lakota; Mojca Frank-Bertoncelj

doi:10.3389/fcvm.2019.00056

Olive Leaf Extract Attenuates Inflammatory Activation and DNA Damage in Human Arterial Endothelial Cells

Front Cardiovasc Med. 2019 May 16:6:56. doi: 10.3389/fcvm.2019.00056. eCollection 2019.

Authors

Blaž Burja^{1

2}, Tadeja Kuret^{1

3}, Tea Janko⁴, Dijana Topalović⁵, Lada Živković⁵, Katjuša Mrak-Poljšak¹, Biljana Spremo-Potparević⁵, Polona Žigon¹, Oliver Distler², Saša Čučnik^{1

3}, Snezna Sodin-Semrl^{1

4}, Katja Lakota^{1

4}, Mojca Frank-Bertoncelj²

Affiliations

¹ Department of Rheumatology, University Medical Centre, Ljubljana, Slovenia.
² Department of Rheumatology, Center of Experimental Rheumatology, University Hospital Zurich, Zurich, Switzerland.
³ Chair of Clinical Biochemistry, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia.
⁴ Faculty of Mathematics, Natural Science and Information Technology, University of Primorska, Koper, Slovenia.
⁵ Department of Pathobiology, Faculty of Pharmacy, University of Belgrade, Belgrade, Serbia.

Abstract

Olive leaf extract (OLE) is used in traditional medicine as a food supplement and as an over-the-counter drug for a variety of its effects, including anti-inflammatory and anti-atherosclerotic ones. Mechanisms through which OLE could modulate these pathways in human vasculature remain largely unknown. Serum amyloid A (SAA) plays a causal role in atherosclerosis and cardiovascular diseases and induces pro-inflammatory and pro-adhesive responses in human coronary artery endothelial cells (HCAEC). Within this study we explored whether OLE can attenuate SAA-driven responses in HCAEC. HCAEC were treated with SAA (1,000 nM) and/or OLE (0.5 and 1 mg/ml). The expression of adhesion molecules VCAM-1 and E-selectin, matrix metalloproteinases (MMP2 and MMP9) and microRNA 146a, let-7e, and let-7g (involved in the regulation of inflammation) was determined by qPCR. The amount of secreted IL-6, IL-8, MIF, and GRO-α in cell culture supernatants was quantified by ELISA. Phosphorylation of NF-κB was assessed by Western blot and DNA damage was measured using the COMET assay. OLE decreased significantly released protein levels of IL-6 and IL-8, as well as mRNA expression of E-selectin in SAA-stimulated HCAEC and reduced MMP2 levels in unstimulated cells. Phosphorylation of NF-κB (p65) was upregulated in the presence of SAA, with OLE significantly attenuating this SAA-induced effect. OLE stabilized SAA-induced upregulation of microRNA-146a and let-7e in HCAEC, suggesting that OLE could fine-tune the SAA-driven activity of NF-κB by changing the microRNA networks in HCAEC. SAA induced DNA damage and worsened the oxidative DNA damage in HCAEC, whereas OLE protected HCAEC from SAA- and H₂O₂-driven DNA damage. OLE significantly attenuated certain pro-inflammatory and pro-adhesive responses and decreased DNA damage in HCAEC upon stimulation with SAA. The reversal of SAA-driven endothelial activation by OLE might contribute to its anti-inflammatory and anti-atherogenic effects in HCAEC.

Keywords: DNA damage; HCAEC; OLE; SAA; atherosclerosis; inflammation; microRNA.