In vitro evaluation of the involvement of Nrf2 in maslinic acid-mediated anti-inflammatory effects in atheroma pathogenesis

Bee Kee Ooi, Su Wen Phang, Phelim Voon Chen Yong, Dinesh Kumar Chellappan, Kamal Dua, Kooi Yeong Khaw, Bey Hing Goh, Priyia Pusparajah, Wei Hsum Yap

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Aims: Maslinic acid (MA) is a naturally occurring pentacyclic triterpene known to exert cardioprotective effects. This study aims to investigate the involvement of nuclear factor erythroid 2-related factor 2 (Nrf2) for MA-mediated anti-inflammatory effects in atheroma pathogenesis in vitro, including evaluation of tumor necrosis factor-alpha (TNF-α)-induced monocyte recruitment, oxidized low-density lipoprotein (oxLDL)-induced scavenger receptors expression, and nuclear factor-kappa B (NF-ĸB) activity in human umbilical vein endothelial cells (HUVECS) and human acute monocytic leukemia cell line (THP-1) macrophages. Materials and methods: An in vitro monocyte recruitment model utilizing THP-1 and HUVECs was developed to evaluate TNF-α-induced monocyte adhesion and trans-endothelial migration. To study the role of Nrf2 for MA-mediated anti-inflammatory effects, Nrf2 inhibitor ML385 was used as the pharmacological inhibitor. The expression of Nrf2, monocyte chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule 1 (VCAM-1), cluster of differentiation 36 (CD36), and scavenger receptor type A (SR-A) in HUVECs and THP-1 macrophages were investigated using RT-qPCR and Western blotting. The NF-κB activity was determined using NF-κB (p65) Transcription Factor Assay Kit. Key findings: The results showed opposing effects of MA on Nrf2 expression in HUVECs and THP-1 macrophages. MA suppressed TNF-α-induced Nrf2 expression in HUVECs, but enhanced its expression in THP-1 macrophages. Combined effects of MA and ML385 suppressed MCP-1, VCAM-1, and SR-A expressions. Intriguingly, at the protein level, ML385 selectively inhibited SR-A but enhanced CD36 expression. Meanwhile, ML385 further enhanced MA-mediated inhibition of NF-κB activity in HUVECs. This effect, however, was not observed in THP-1 macrophages. Significance: MA attenuated foam cell formation by suppressing VCAM-1, MCP-1, and SR-A expression, as well as NF-κB activity, possibly through Nrf2 inhibition. The involvement of Nrf2 for MA-mediated anti-inflammatory effects however differs between HUVECs and macrophages. Future investigations are warranted for a detailed evaluation of the contributing roles of Nrf2 in foam cells formation.

Original languageEnglish
Article number119658
Number of pages11
JournalLife Sciences
Volume278
DOIs
Publication statusPublished - 1 Aug 2021

Keywords

  • Maslinic acid
  • Monocytes recruitment
  • NF-κB
  • Nrf2
  • Scavenger receptors
  • Transendothelial migration

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