Triptolide Modulates the Expression of Inflammation-Associated lncRNA-PACER and lincRNA-p21 in Mycobacterium tuberculosis-Infected Monocyte-Derived Macrophages.

Ousman Tamgue,Frank Brombacher,Julius Ebua Chia

doi:10.3389/fphar.2021.618462

Abstract

Triptolide is a diterpene triepoxide, which performs its biological activities via mechanisms including induction of apoptosis, targeting of pro-inflammatory cytokines, and reshaping of the epigenetic landscape of target cells. However, the targeting of long non-coding RNAs (lncRNAs) by triptolide has not yet been investigated, despite their emerging roles as key epigenetic regulators of inflammation and immune cell function during Mycobacterium tuberculosis (Mtb) infection. Hence, we investigated whether triptolide targets inflammation-associated lncRNA-PACER and lincRNA-p21 and how this targeting associates with Mtb killing within monocyte-derived macrophages (MDMs).Using RT-qPCR, we found that triptolide induced the expression of lincRNA-p21 but inhibited the expression of lncRNA-PACER in resting MDMs in a dose- and time-dependent manner. Moreover, Mtb infection induced the expression of lincRNA-p21 and lncRNA-PACER, and exposure to triptolide before or after Mtb infection led to further increase of Mtb-induced expression of these lncRNAs in MDMs. We further found that contrary to lncRNA-PACER, triptolide time- and dose-dependently upregulated Ptgs-2, which is a proximal gene regulated by lncRNA-PACER. Also, low-concentration triptolide inhibited the expression of cytokine IL-6, a known target of lincRNA-p21. Mtb infection induced the expression of IL-6 and Ptgs-2, and triptolide treatment further increased IL-6 but decreased Ptgs-2 expression in Mtb-infected MDMs. The inverse relation between the expression of these lncRNAs and their target genes is concordant with the conception that these lncRNAs mediate, at least partially, the cytotoxic and/or anti-inflammatory activities of triptolide in both resting and activated MDMs. Using the CFU count method, we found that triptolide decreased the intracellular growth of Mtb HN878. The alamarBlue assay showed that this decreased Mtb HN878 growth was not as a result of direct targeting of Mtb HN878 by triptolide, but rather evoking MDMs’ intracellular killing mechanisms which we speculate could include triptolide-induced enhancement of MDMs’ effector killing functions mediated by lncRNA-PACER and lincRNA-p21. Altogether, these results provide proof of the modulation of lncRNA-PACER and lincRNA-p21 expression by triptolide, and a possible link between these lncRNAs, the enhancement of MDMs’ effector killing functions and the intracellular Mtb-killing activities of triptolide. These findings prompt for further investigation of the precise contribution of these lncRNAs to triptolide-induced activities in MDMs.

Highlights

Triptolide is one of the active compounds of the medicinal herb Tripterygium wilfordii Hook f., which has been widely used in China to treat various conditions and diseases including rheumatoid arthritis, nephritic syndrome, lupus, and Behcet’s disease
We provide first evidences that triptolide modulates the expression of long noncoding RNAs (lncRNAs) p50associated COX-2 extragenic RNA (PACER) and lincRNA-p21 in both resting and Mycobacterium tuberculosis (Mtb)-infected human macrophages, which was associated with the modulation of their target genes IL-6 and prostaglandin synthase-2 (Ptgs-2)
We investigated whether triptolide (Trip) modulates the expression of lincRNA-p21 and lncRNA-PACER in monocytederived macrophages (MDMs)

Summary

Introduction

Triptolide is one of the active compounds of the medicinal herb Tripterygium wilfordii Hook f., which has been widely used in China to treat various conditions and diseases including rheumatoid arthritis, nephritic syndrome, lupus, and Behcet’s disease This diterpene triepoxide possesses antitumor, immunesuppressive, and anti-inflammatory activities which it exerts via several mechanisms in a tissue-, context-, and disease-specific manner (Zhao et al, 2010a; Zhao et al, 2010b; Liu, 2011; Carter et al, 2012; Tamgue et al, 2013; Wu et al, 2013; Hou et al, 2017; Tamgue and Lei, 2017; Chen et al, 2018; Yang et al, 2018; Huang et al, 2019; Yuan et al, 2019; Zhao et al, 2019). The discovery of long noncoding RNAs (lncRNAs) has added another layer of complexity on the regulation of these inflammatory genes expression and activities

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