Linli Xu

Immunosuppressive activity of daphnetin, one of coumarin derivatives, is mediated through suppression of NF-κB and NFAT signaling pathways in mouse T cells.

Daphnetin, a plant-derived dihydroxylated derivative of coumarin, is an effective compound extracted from a plant called Daphne Korean Nakai. Coumarin derivates were known for their antithrombotic, anti-inflammatory, and antioxidant activities. The present study was aimed to determine the immunosuppressive effects and the underlying mechanisms of daphnetin on concanavalin A (ConA) induced T lymphocytes in mice. We showed that, in vitro, daphnetin suppressed ConA-induced splenocyte proliferation, influenced production of the cytokines and inhibited cell cycle progression through the G0/G1 transition. The data also revealed that daphnetin could down-regulate activation of ConA induced NF-κB and NFAT signal transduction pathways in mouse T lymphocyte. In vivo, daphnetin treatment significantly inhibited the 2, 4- dinitrofluorobenzene (DNFB) -induced delayed type hypersensitivity (DTH) reactions in mice. Collectively, daphnetin had strong immunosuppressive activity both in vitro and in vivo, suggesting a potential role for daphnetin as an immunosuppressive agent, and established the groundwork for further research on daphnetin.

Investigation of effects of farrerol on suppression of murine T lymphocyte activation in vitro and in vivo.

Farrerol, a new type of 2,3-dihydro-flavonoid, has been isolated from the leaves of Rhododendron dauricum L. In the present study, we found that farrerol exerted potent immunosuppressive effects on murine T cells both in vitro and in vivo. In vitro, farrerol markedly suppressed concanavalin A (ConA)-induced lymphocyte proliferation, Th1 and Th2 cytokine production, cluster of differentiation 4-positive (CD4(+)) T cell populations, and the ratio of CD4(+)/cluster of differentiation 8-positive (CD8(+)) T cells. Moreover, farrerol significantly inhibited the T cell-mediated delayed-type hypersensitivity (DTH) reaction in vivo. In addition, we investigated signal transduction mechanisms to determine the effects of farrerol by Western blotting. The data revealed that farrerol could downregulate the activation of the nuclear factor κB (NF-қB) and nuclear factor of activated T cells 2 (NFAT2) signal transduction pathways. These findings suggested that farrerol has potential effects on the regulation of the immune system and could be developed as a practicable immunosuppressive compound.

Tyrosol exhibits negative regulatory effects on LPS response and endotoxemia.

Tyrosol, a phenolic compound, was isolated from wine, olive oil and other plant-derived products. In the present study, we first investigated the negative regulatory effects of tyrosol on cytokine production by lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages in vitro, and the results showed that tyrosol reduced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) secretion. This inspired us to further study the effects of tyrosol in vivo. Tyrosol significantly attenuated TNF-α, IL-1β and IL-6 production in serum from mice challenged with LPS, and consistent with the results in vitro. In the murine model of endotoxemia, mice were treated with tyrosol prior to or after LPS challenge. The results showed that tyrosol significantly increased mice survival. We further investigated signal transduction ways to determine how tyrosol works. The data revealed that tyrosol shocked LPS-induced mitogen activated protein kinases (MAPKs) and nuclear transcription factor-κB (NF-κB) signal transduction pathways in RAW 264.7 macrophages. These observations indicated that tyrosol exerted negative regulatory effects on LPS response in vitro and in vivo through suppressing NF-κB and p38/ERK MAPK signaling pathways.

Inhibitory Effects of Salidroside on Nitric Oxide and Prostaglandin E2 Production in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages

The aim of this study was to evaluate the effect of salidroside on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E₂ (PGE₂) production in RAW 264.7 macrophages and related anti-inflammatory mechanism. PGE₂ production was measured by enzyme-linked immunosorbent assay (ELISA); NO production was tested by Griess reagent. Inducible nitric oxidesynthase (iNOS) and COX-2 were determined by RT-PCR and Western blot analysis; IκB and P-IκB protein express were detected by Western blot analysis; cytosolic free Ca²⁺ ([Ca²⁺](i)) was measured by a fluorescent microscope. The data showed salidroside inhibited LPS-induced NO and PGE₂ production and reduced iNOS and COX-2 protein expression in RAW 264.7 macrophages. Consistent with these observations, salidroside inhibited LPS-induced cytosolic free Ca²⁺ concentration ([Ca²⁺](i)) elevation. In addition, we further investigated signal transduction mechanisms and found that the activation of NF-κB was suppressed by salidroside in a dose-dependent manner. These results suggest that salidroside suppresses NO and PGE₂ production by inhibiting iNOS and COX-2 protein expression, level of [Ca²⁺](i), and activation of NF-κB signal transduction pathway.

Phytochemical composition and toxicity of an antioxidant extract from Pimpinella brachycarpa (Kom.) Nakai.

Pimpinella brachycarpa (Kom.) Nakai (PB) is one of the most favored edible greens grown in Asian regions. In our previously study, we found PB extract had antioxidant effects in vitro. In the present study, an EtOAc soluble extract (PBet) was isolated from PB. Then the antioxidant properties at cellular level, phytochemical composition and toxicity of PBet were examined. The results indicated that PBet (0.5-2mg/mL) could protect Bel-7404 cells from H(2)O(2) induced cell damage through scavenging of intracellular ROS. Moreover, myristic acid, 24ζ-methyl-5α-lanosta-25-one, β-sitosterol, pregnenolone and β-daucosterol were firstly isolated from PB. In addition, PBet (0.75g/kg BW, ig) had no acute toxicity and it (0.03-0.12g/kg BW, ig, 7 d) could not influence the rate of bone marrow polychromatic erythrocytes micronucleus and chromosome aberration in KM mice. All above findings suggested that PBet could be considered as a safe functional food with antioxidant activities.

The inhibition of 2,3-dichloro-1-propanol on T cell in vitro and in vivo.

2,3-Dichloro-1-propanol (2,3-DCP) is a member of a group of chemicals known as chloropropanols. Currently, immunotoxicity of 2,3-DCP has not been reported. In the present study, we studied its inhibitory effects on T cell both in vivo and in vitro. The results showed that 2,3-DCP markedly inhibited ConA-induced splenocyte proliferation, Th1 and Th2 cytokine production, CD4(+) T cell populations, and the ratio of CD4(+)/CD8(+) T cells and cell cycle arrest in vitro. In addition, 2,3-DCP markedly suppressed DNFB-induced T-cell-mediated delayed-type hypersensitivity (DTH) reaction in mice. Furthermore, Western blot was used to study how 2,3-DCP affects signal transduction mechanisms. The data revealed that 2,3-DCP could down regulate activation of ConA-induced NF-κB and NFAT signal transduction pathways. These observations indicated that 2,3-DCP exhibited negative regulatory effects by directly suppressing T-cell-mediated immune responses in vitro and in vivo.

The toxic effects of benzo[a]pyrene on activated mouse T cells in vitro

Abstract Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon contaminant that is widely present in environmental sources, including food. This study aims to clarify the effects of B[a]P toxicity on activated mouse T cells in vitro. Our results show that B[a]P markedly inhibited Concanavalin A (ConA)-induced T lymphocyte proliferation and suppressed the production of the cytokines Interferon (IFN)-γ, Interleukin (IL)-2 and IL-4. Western blot and protein-DNA interaction assays were used to study how B[a]P affects signal transduction. The results revealed that B[a]P suppressed the ConA-induced activation of the Ca2+/CaM/NFκB and Ca2+/CaM/CaN/NFAT signal transduction pathways. These observations indicate that B[a]P has toxic effects on activated mouse T cells in vitro.

The toxicity of 3-monochloro-1,2-propanediol (+) to activated T cells in mice

ABSTRACT 3-monochloro-1,2-propanediol (3-MCPD) is a member of a group of chemicals known as chloropropanols that has been detected in a wide range of foods. In the present study, we found that its α-chlorohydrin structure (3-MCPD(+)) has toxic effects on activated T cells in mice. Specifically, the data showed that 1, 2, and 4 mM 3-MCPD(+) markedly inhibited ConA-induced T cell proliferation and Th1/Th2 cytokine production. Furthermore, Western blotting was used to study the mechanism of action of 3-MCPD(+). The data revealed that 3-MCPD(+) inhibited the activation of the Ca2+/CaM/I-κB-NF-κB and Ca2+/CaM/CaN/NFAT signaling pathways. In vivo, 3-MCPD(+) treatment significantly inhibited 2,4-dinitrofluorobenzene-induced delayed-type hypersensitivity reactions in mice. These observations indicated that 3-MCPD(+) is toxic to activated mouse T cells in vitro and in vivo.