Total flavonoids of Hedyotis diffusa Willd inhibit inflammatory responses in LPS-activated macrophages via suppression of the NF-κB and MAPK signaling pathways

Abstract

Abstract. Nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways play a central role in inflammatory responses. Total flavonoids of Hedyotis diffusa Willd (TFHDW) are active compounds derived from Hedyotis diffusa Willd, which has been long used in Chinese traditional medicine for the treatment of various inflammatory diseases, including ulcerative colitis and bronchitis; however, the precise mechanisms underlying the effects of TFHDW are largely unknown. In the present study, the anti-inflammatory effect of TFHDW was evaluated and the underlying molecular mechanisms were investigated in an in vitro inflammatory model comprising lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. The results indicated that TFHDW inhibited the inflammatory response as it significantly reduced the LPS-induced expression of pro-inflammatory nitric oxide, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β in a concentration-dependent manner, without causing cytotoxicity. In addition, the mRNA expression of inducible nitric oxide synthase, TNF-α, IL-6 and IL-1β was suppressed by treatment with TFHDW in LPS-stimulated RAW 264.7 cells. Moreover, TFHDW treatment significantly inhibited the LPS-induced activation of NF-κB via the suppression of inhibitor of κB (IκB) phosphorylation, and reduced the phosphorylation of MAPK signaling molecules (p38, c-Jun N-terminal protein kinase and extracellular signal-regulated kinase 1/2), which resulted in the inhibition of cytokine expression. These findings suggest that TFHDW exerted anti-inflammatory activity via suppression of the NF-κB and MAPK signaling pathways. IntroductionInflammation is an orchestrated biological process, induced by tissue injury or microbial infection, which protects the body from these inflammatory stimuli. However, persistent or excessive inflammation is associated with a variety of pathological conditions, including rheumatoid arthritis, bacterial sepsis and skin inflammation (1,2). Macrophages play a key role in the host defense against noxious substances and are involved in numerous inflammatory diseases (3). The activation of macrophages by inflammatory stimuli can generate reactive oxygen species, such as H 2 O 2 and superoxide, and induce the expression of various genes such as interleukin (IL)-6 and tumor necrosis factor (TNF)-α, in addition to other inflammatory mediators, including nitric oxide (NO) and prostaglandin E2 (PGE2), which are synthesized by inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, respectively. Inflammatory cytokines and mediators contribute to the pathogenesis of numerous inflammation-associated human diseases (4). Lipopolysaccharide (LPS) from gram-negative bacteria induces inflammation and is frequently used to stimulate macrophages in order to study inflammation and the mechanisms of action of potential anti-inflammatory agents.The anti-inflammatory actions of various phytochemicals have been found to be mediated through suppression of the NF-κB pathway (5). NF-κB is a key regu...

Olive oil bioactives protect pigs against experimentally-induced chronic inflammation independently of alterations in gut microbiota

“…Treating macrophages with OBE before the stimulation with LPS partly counteracted such responses by about 30%. These results are similar to findings from recent studies demonstrating anti-inflammatory properties of polyphenols and other plant bioactives in cell cultures [52; 53] and farm animals [54]. Furthermore, our in vivo and in vitro results indicate that inhibition of IL1B production is a key component of the OBE anti-inflammatory action.…”

The Hedyotis diffusa Willd. (Rubiaceae): A Review on Phytochemistry, Pharmacology, Quality Control and Pharmacokinetics

“…To date, twenty-three phenolic acids (87-109) have been identified from the herb of H. Diffusa, including four benzoic acid derivatives (87)(88)(89)(90), coumaric acid (91) …”

“…Moreover, two main chemotypes, including eight flavonoids and four iridoid glycosides were found in renal tissues after H. diffusa treatment, indicating that the anti-inflammatory effect may be due to these constituents [87]. In vitro, Chen et al found that the flavonoids extract treatment (50´100 µg/mL) on LPS-stimulated RAW 264.7 cells reduced expression of iNOS, TNF-α, IL-6 and IL-1β, as well as suppressing phosphorylation of IκB p38, JNK and ERK1/2 in a concentration-dependent manner, indicating that the anti-inflammatory activity of total flavonoids had a close relationship with the NF-κB-and MAPK-signaling pathways [88].…”

Chloroform extract of Hedyotis diffusa Willd inhibits viability of human colorectal cancer cells via suppression of AKT and ERK signaling pathways

“…Belonging to the Rubiaceae family of plants, HDW is widely distributed in Northeast Asia. It is used in TCM to clear away heat and toxic material (7,8), to promote blood circulation and has long been used clinically to treat various types of cancer, including breast (10), colorectal (11) and liver (12) cancer. Our previous studies demonstrated that HDW inhibited the growth of CRC, possibly by inducing cancer cell apoptosis and inhibiting cell proliferation and tumor angiogenesis (13)(14)(15)(16)(17).…”

“…Hedyotis diffusa Willd (HDW) is a well-known herbal medicine, which exhibits a variety of bioactivities, including anti-inflammatory, antioxidative, immune-modulating and anticancer properties (7)(8)(9). Belonging to the Rubiaceae family of plants, HDW is widely distributed in Northeast Asia.…”