Guoren Huang

Salidroside attenuates LPS-induced pro-inflammatory cytokine responses and improves survival in murine endotoxemia

Salidroside is a major component isolated from the Rhodiola rosea. In the present study, we investigated the anti-inflammatory effects of salidroside on cytokine production by lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages in vitro, and the results showed that salidroside reduced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) secretions. This inspired us to further study the effects of salidroside in vivo. Salidroside significantly attenuated TNF-α, IL-1β and IL-6 productions in serum from mice challenged with LPS, and consistent with the results in vitro. In the murine model of endotoxemia, mice were treated with salidroside prior to or after LPS challenge. The results showed that salidroside significantly increased mouse survival. Further studies revealed that salidroside could downregulate LPS-induced nuclear transcription factor-қB (NF-қB) DNA-binding activation and ERK/MAPKs signal transduction pathways production in RAW 264.7 macrophages. These observations indicated that salidroside modulated early cytokine responses by blocking NF-қB and ERK/MAPKs activation, and thus, increased mouse survival. These effects of salidroside may be of potential usefulness in the treatment of inflammation-mediated endotoxemia.

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.

Gossypol suppresses mouse T lymphocytes via inhibition of NFκB, NFAT and AP-1 pathways.

Abstract Gossypol is a kind of yellow polyphenolic compounds extracted from root stem and seed of the cotton plant. In the present study, we investigated its immunosuppressive mechanism by using BALB/c mouse T lymphocytes in vitro. When mouse splenocytes was incubated with gossypol, the extract effectively suppress the overproduction of the cell stimulated by concanavalin A (ConA) in a dose manner. This inhibitive activity was mainly due to interfering Th1 and Th2 cytokines production and decreasing CD4+ T cell populations and ratio of CD4+/CD8+. Furthermore, we also showed that signal transduction via NF-κB, NFAT and AP-1 are critical to the ConA-induced T cell activation in mice. The data revealed that gossypol could down-regulate activation of ConA-induced NF-κB, NFAT and AP-1 signal transduction pathways in mouse T lymphocyte. These observations indicated that gossypol exhibited immunosuppressive effects by inhibition T lymphocyte activation in vitro.

Immunosuppressive activity of 8-gingerol on immune responses in mice.

8-Gingerol is one of the principal components of ginger, which is widely used in China and elsewhere as a food, spice and herb. It shows immunosuppressive activity on the immune responses to ovalbumin (OVA) in mice. In the present study, we found that 8-gingerol suppressed lipopolysaccharide (LPS) and concanavalin A (ConA)-stimulated splenocyte proliferation in vitro. In vivo, 8-gingerol not only significantly suppressed Con A-, LPS- and OVA-induced splenocyte proliferation (P < 0.05) but also decreased the percentage of CD19+ B cells and CD3+ T cell (P < 0.05) at high doses (50, 100 mg/kg). Moreover, OVA-specific IgG, IgG1 and IgG2b levels in OVA-immunized mice were reduced by 8-gingerol at doses of 50, 100 mg/kg. These results suggest that 8-gingerol could suppress humoral and cellular immune responses in mice. The mechanism might be related to direct inhibition of sensitized T and B lymphocytes.

Suppressive effects of fisetin on mice T lymphocytes in vitro and in vivo

BACKGROUND Most of the immunosuppressive drugs have satisfactory therapeutic effects on organ transplantation and autoimmune disease. However, their clinical application is limited by side effects. Therefore, new and safe immunosuppressive drugs against acute and chronic rejections are eagerly awaited. Fisetin, a flavonoid present in various types of vegetables and fruits, has few side effects and low level of toxicity, which would be a desirable clinical feature. In the present study, we investigated the immunosuppressive effects and underlying mechanisms of fisetin against T-cell activation in vitro and in vivo. METHODS We measured the effect of fisetin on T-lymphocyte proliferation, T-cell subsets, cell cycle progression, cytokine production, and nuclear factor activation in vitro, as well as its influence on T cell-mediated delayed-type hypersensitivity reaction in vivo. RESULTS In vitro, the results showed that fisetin significantly suppressed mouse splenocytes proliferation, Th1 and Th2 cytokine production, cell cycle and the ratio of CD4(+)/CD8(+) T cells. Furthermore, fisetin exerts an immunosuppressive effect in mouse T lymphocytes through the suppression of nuclear factor kappa B activation and nuclear factor of activated T cells signaling in a dose-dependent manner. In vivo, fisetin treatment also significantly inhibited the dinitrofluorobenzene-induced delayed-type hypersensitivity reactions in mice. CONCLUSIONS Fisetin had strong immunosuppressive activity in vitro and in vivo, suggesting a potential role for fisetin as an immunosuppressive agent.

1,3-Dichloro-2-propanol induced hyperlipidemia in C57BL/6J mice via AMPK signaling pathway

1,3-Dichloro-2-propanol (1,3-DCP) is a well-known contaminant that has been detected in a wide range of foods. Dietary intake represents the greatest source of exposure to 1,3-DCP. In the study, we first found 1,3-DCP could induce hyperlipidemia in C57BL/6J mice below 1 mg/kg/day. We investigated serum lipid profile, liver total cholesterol (TC) and triglyceride (TG), histopathology of Liver and adipose tissue. The results showed 1,3-DCP dose dependently increased serum TG, TC and low-density lipoprotein cholesterol (LDL-C), decreased serum high-density lipoprotein cholesterol (HDL-C), increased relative liver weight, liver TG and TC, relative adipose tissue weight and enlarged the size of adipose cells. Because AMPK signal pathway is important in the process of lipid metabolism, we further investigated the effects of 1,3-DCP on AMPK signaling pathway in murine models. The results showed that 1,3-DCP (0.1-1 mg/kg/day) decreased p-AMPK/tAMPK ratio, p-ACC/tACC ratio, PPARα expression, but increased FAT, SREBP1, HMGCR and FAS expression. These observations indicated that 1,3-DCP induced hyperlipidemia in C57BL/6J mice at least partially through regulating AMPK signaling pathway.

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.

Salidroside Attenuates Hydrogen Peroxide-Induced Cell Damage Through a cAMP-Dependent Pathway

Salidroside, a major component of Rhodiola rosea L., has shown various pharmacological functions, including antioxidant effects, but the signal transduction pathway of its antioxidant effects is not very clear. In this study, we found that salidroside could attenuate hydrogen peroxide (H2O2)-induced HL-7702 cell damage, inhibit H2O2-induced cytosolic free Ca2+ ([Ca2+]i) elevation, scavenge reactive oxygen species (ROS) and increase 3’-5’-cyclic adenosine monophosphate (cAMP) level in a dose-dependent manner, but it couldn’t influence 3’-5’-cyclic guanosine monophosphate (cGMP) levels. Therefore, these results indicated that the antioxidant effects of salidroside were associated with down-regulation of [Ca2+]i, ROS occur via a cAMP-dependent pathway.

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.