Suberosin inhibits proliferation of human peripheral blood mononuclear cells through the modulation of the transcription factors NF‐AT and NF‐κB

Abstract

Background and purpose: Extracts of Plumbago zeylanica containing suberosin exhibit anti-inflammatory activity. We purified suberosin from such extracts and studied its effects on a set of key regulatory events in the proliferation of human peripheral blood mononuclear cells (PBMC) stimulated by phytohemagglutinin (PHA). Experimental approach: Proliferation of PBMC in culture was measured by uptake of 3 H-thymidine; production of cytokines and cyclins by Western blotting and RT-PCR. Transcription factors NF-AT and NF-kB were assayed by immunocytochemistry and EMSA. Key results: Suberosin suppressed PHA-induced PBMC proliferation and arrested cell cycle progression from the G 1 transition to the S phase. Suberosin suppressed, in activated PBMC, transcripts of interleukin-2 (IL-2), interferon-g (IFN-g), and cyclins D3, E, A, and B. DNA binding activity and nuclear translocation of NF-AT and NF-kB induced by PHA were blocked by suberosin. Suberosin decreased the rise in intracellular Ca 2 þ concentration ([Ca 2 þ ] i ) in PBMC stimulated with PHA. Suberosin did not affect phosphorylation of p38 and JNK but did reduce activation of ERK in PHA-treated PBMC. Pharmacological inhibitors of NF-kB, NF-AT, and ERK decreased expression of mRNA for the cyclins, IL-2, and IFN-g and cell proliferation in PBMC activated by PHA. Conclusions and Implications: The inhibitory effects of suberosin on PHA-induced PBMC proliferation, were mediated, at least in part, through reduction of [Ca 2 þ ] i , ERK, NF-AT, and NF-kB activation, and early gene expression in PBMC including cyclins and cytokines, and arrest of cell cycle progression in the cells. Our observations provide an explanation for the antiinflammatory activity of P. zeylanica.

Piperine inhibits cytokine production by human peripheral blood mononuclear cells

“…Previous studies have shown that a series of cytokines such as IL-2 and IFN-γ are important in the growth of antigen-or PHA-induced PBMCs (Robb, 1984;Young, 1996;Chen et al, 2007). PHA, a T lymphocyte mitogen, stimulates the proliferation of T cells by interacting with the N-acetylgalactosamine glycoproteins expressed on the cells (Janeway et al, 1997).…”

“…The cytotoxicity of piperine on PHA-stimulated PBMCs was studied using microscopic examination to ensure that the inhibitory action of piperine was due to direct cytotoxicity. In addition, it has been previously verified by many researchers that a series of cytokines such as interleukin-2 (IL-2) and interferon-γ (IFN-γ) are important for the growth of PBMCs induced by antigens or PHA (Robb, 1984;Young, 1996;Chen et al, 2007). Therefore, the production and gene expression of both cytokines were examined in this study.…”

Interleukin-6 and Cyclooxygenase-2 Downregulation by Fatty-Acid Fractions of Ranunculus Constantinopolitanus

“…RT-PCR was carried out according to a previously described method [15]. Briefly, RNA (1 μg) was reversetranscribed to cDNA by the Advantage™ RT-for-PCR kit (Clontech, USA) according to the manufacturer's instructions.…”

Inhibition of Delayed-Type Hypersensitivity by Cucurbitacin R through the Curbing of Lymphocyte Proliferation and Cytokine Expression by Means of Nuclear Factor AT Translocation to the Nucleus

“…To determine exactly how cucurbitacin R exerts these effects, we have to examine the principal event in the generation of the immune response, namely, the activation and clonal expansion of T lymphocytes. These are spontaneously arrested in the G 0 /G 1 phase and remain quiescent for long periods until they are exposed to specific agents (Chen et al, 2007). The activation of T cells with agents such as antigens or phytohemagglutinin A triggers the biochemical events that induce resting T cells to enter into the cell cycle after proliferation and differentiation (Kuo et al, 2003), during which the transcription factor NFAT is involved.…”

“…This cycle is accompanied by the expression of a series of genes such as those for IL-2, interferon-␥, and the cyclins, which are expressed in a carefully controlled order as the cells pass through the G 0 , G 1 , and S phases (Ajchenbaum et al, 1993;Liu et al, 2004). Indeed, cell cycle activation is in part coordinated by the D-type cyclins, which are rate-limiting and essential for the progression through the G 1 phase of the cycle (Chen et al, 2007). We found that addition of cucurbitacin R affected the cell cycle of stimulated T lymphocytes without exerting any effect on cell viability.…”