Hypericum triquetrifolium—Derived Factors Downregulate the Production Levels of LPS-Induced Nitric Oxide and Tumor Necrosis Factor-αin THP-1 Cells

Abstract

Based on knowledge from traditional Arab herbal medicine, thisin vitrostudy aims to examine the anti-inflammatory mechanism ofHypericum triquetrifoliumby measuring the expression and release of pro-inflammatory cytokines, tumor necrosis factor-α(TNF-α) and interleukine-6 (IL-6), and inducible nitric oxide synthase (iNOS) in human monocytic cells, THP-1. The effects were assessed by measuring the levels of secretory proteins and mRNA of TNF-αand IL-6, the levels of nitric oxide (NO) secretion and the expression of iNOS in THP-1 cells. Cells were treated with 5 μg lipopolysaccharide/ml (LPS) in the presence and absence of increasing concentrations of extracts from the aerial parts ofH. triquetrifolium. During the entire experimental period, we used extract concentrations (up to 250 μg mL−1) that had no cytotoxic effects, as measured with MTT and LDH assays.Hypericum triquetrifoliumextracts remarkably suppressed the LPS-induced NO release, significantly attenuated the LPS-induced transcription of iNOS and inhibited in a dose-dependent manner the expression and release of TNF-α. No significant effects were observed on the release of IL-6. Taken together, these results suggest thatH. triquetrifoliumprobably exerts anti-inflammatory effects through the suppression of TNF-αand iNOS expressions.