Propolis in correlation to cytokines - Part II

By Ahmed Hegazi

Professor of Microbiology and Immunology
National Research Center , Dokki, Giza , Egypt  
Member of Apitherapy Commission, APIMONDIA  
E mail: ahmedgaffer@mailer.eun.eg and ahmedhegazi128@gmail.com

Propolis, the resinous product collected by honey bees from plants, is used as folk medicine since ancient time. During the last ten years, immunoregulatory and anti-inflammatory properties of propolis have been published.

Cytokines (Greek cyto-, cell; and -kinos, movement) are a category of signaling molecules that are used extensively in cellular communication . They are proteins , peptides , or glycoproteins . The term cytokine encompasses a large and diverse family of polypeptide regulators that are produced widely throughout the body by cells of diverse embryological origin. (Gilman et al., 2001). Cytokines are small secreted proteins which mediate and regulate immunity, inflammation, and hematopoiesis.

Cytokine is a general name; other names include lymphokine (cytokines made by lymphocytes), monokine (cytokines made by monocytes), chemokine (cytokines with chemotactic activities), and interleukin (cytokines made by one leukocyte and acting on other leukocytes).

Apitherapy (the term comes from the Latin apis, which means "bee."), or bee therapy, is the use of honeybee venom for therapeutic purposes. Bee venom, bee pollen, raw honey, royal jelly, and propolis are products from bees that are generally considered to have medicinal effects. The history of apitherapy extends back to ancient  Egypt  (Hegazi, 1998), China (Yu,.1999) and  Greece . Apitherapy had been well documented in traditional Chinese medicine for treating systemic immune diseases, allergic diseases, viral diseases and organic-specific inflammatory diseases since more than one thousand years (Yu,.1999) , although few scientific studies have proved their benefits.

The detailed mechanisms of actions of propolis and its components on immune cells, however, are still unknown. Inflammatory cytokines and oxidative stress have a central role in the pathogenesis of acute pancreatitis. Propolis has anti-inflammatory and anti-oxidant effects. Büyükberber et al., (2009) investigated the therapeutic role of ethanolic extract of propolis on a cerulein-induced acute pancreatitis model in rats. In the acute pancreatitis group, serum amylase and lipase levels were found to be elevated and the histopathological evaluation of the tissue revealed massive edema and inflammation with less fatty necrosis when compared to the sham and control groups. In the ethanolic extract of propolis group, in particular, tissue edema was improved markedly (p=0.001). Tissue inflammation and fatty necrosis were decreased with ethanolic extract of propolis treatment.

In most of the diseases which are considered to benefit from propolis, cellular immune reaction is activated, neopterin levels in body fluids are increased and enhanced tryptophan degradation is observed. Girgin et al., (2009) studied, the immunomodulatory effects of six Turkish propolis samples were evaluated by using the in vitro model of peripheral blood mononuclear cells (PBMC). Concentrations of neopterin, tryptophan, kynurenine and pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were determined. In PBMC treated with mitogen phytohaemagglutinin, neopterin production and tryptophan degradation by enzyme indoleamine 2,3-dioxygenase (IDO) as well as release of cytokines was significantly enhanced and upon treatment with propolis extracts all these effects were dose-dependently suppressed.

CAPE is a biologically active component of propolis, a resinous material obtained from bee hives. The effect of CAPE on lipopolysaccharide (LPS)-induced inflammatory reactions is not known. Song et al., (2008) evaluated the anti-inflammatory effect of CAPE on cultured human middle ear epithelial cells (HMEECs). They suggested that the anti-inflammatory effect of caffeic acid phenethyl ester ( CAPE ) is due to its inhibition of tumor necrosis factor (TNF)-alpha expression and interleukin (IL)-8 production. The anti-inflammatory effect of CAPE is possibly through the inhibition of nuclear factor (NF)-kappaB via the suppression of inhibitor-kappaB-alpha (IkappaB-alpha) degradation.

Caffeic acid phenethyl ester ( CAPE ) is an active component of honeybee propolis extracts. It has several positive effects, including anti-inflammatory, anti-oxidation, anti-cancer, anti-bacterial, anti-viral, anti-fungal, and immunomodulatory effects. In particular, the suppressive effect of NF-kappaB may disrupt a component of allergic induction. Jung et al., (2008) determined whether treatment with CAPE results in significant inhibition of asthmatic reactions in a mouse model. An increase in the number of eosinophils in bronchoalveolar lavage (BAL) fluid; a marked influx of inflammatory cells into the lung around blood vessels and airways, and airway luminal narrowing; the development of airway hyperresponsiveness (AHR); the presence of tumor necrosis factor-alpha (TNF-alpha) and Th2 cytokines, including IL-4 and IL- 5, in the BAL fluid; and the presence of allergen-specific IgE in the serum.

Choi and,  Choi (2008) reported that (i) CAPE exerts its anti-inflammatory action (inhibition of tumor necrosis factor-induced expression of intercellular adhesion molecule-1 and CC chemokine ligand-2) via NF-kappaB inhibition by two distinct molecular mechanisms in a cell-specific manner: CAPE inhibited downstream pathways of inhibitor kappaB (IkappaB) degradation in monocytic cells, while activation of upstream IkappaB kinase was suppressed by CAPE pre-treatment in astroglial cells; and (ii) CAPE paradoxically activates the c-Jun N-terminal kinase (JNK) pathway, which might be responsible for its pro-apoptotic action and divergent regulation of proinflammatory mediators such as CXC chemokine ligand-8.

Park et al., (2008) evaluated the effects of CAPE on the active systemic anaphylaxis induced by ovalbumin (OVA) challenge in mice. Histopathological analysis, nuclear factor (NF)-kappaB activation, and the plasma levels of histamine and total IgE after allergen challenge were evaluated. After challenges, all of the sham-treated mice developed anaphylactic symptoms, increased plasma levels of histamine and OVA-specific IgE, marked vascular leakage, NF-kappaB activation, platelet-activating factor (PAF) production, and histological changes. Sy et al., (2006) found that the higher dose of propolis extracts decreases the level of IL- 5 in BALF. The splenocytes from mice administered with propolis extracts (low- and high-dose groups) exhibit a strong inhibition of IL-10 secretion and up-regulation of IFN-gamma secretion in splenocytes stimulated with concanavalin A (ConA). In addition, cytokine (IFN-gamma, IL-6, and IL-10) secretion in OVA-stimulated splenocytes from the propolis groups was significantly lower than that in the control group. These results suggest that propolis extracts may be a potential novel therapeutic agent for asthma.

Furthermore, CAPE suppressed H. pylori-induced cell proliferation and production of the cytokines TNF-alpha and IL- 8. In addition, CAPE blocked H. pylori-induced COX-2 expression. The inhibition of such transcription by CAPE could result in suppression of many genes during H. pylori-induced inflammation, and also provide new insights into the anti-cancer and anti-inflammatory properties of CAPE(Abdel-Latif et al., 2005). Márquez et al., (2004) evaluated the immunosuppressive activity of CAPE in human T-cells, discovering that this phenolic compound is a potent inhibitor of early and late events in T-cell receptor-mediated T-cell activation. They found that CAPE specifically inhibited both interleukin (IL)-2 gene transcription and IL-2 synthesis in stimulated T-cells. To further characterize the inhibitory mechanisms of CAPE at the transcriptional level.

Takagi et al., (2005) focused on immune stimulation by Propolis, and examined changes in the effect of irradiation after Propolis administration. They found that cytokines released from macrophages in mouse peripheral blood after Propolis administration activated helper T-cells to proliferate. In addition, activated macrophages in association with the secondary T-lymphocyte activation increased IFN-gamma production and stimulated proliferation of cytotoxic T-cells and suppressor T-cells, indicating the activation of cell-mediated immune responses.
Blonska et al., (2004) indicated that EEP exerts its inhibitory effect on the IL-1beta and iNOS gene expression in J774A.1 macrophages at the transcriptional level. Tested flavone derivatives contribute to the anti-inflammatory activity of propolis. The cytokine, IL-2, IL-4 and IFN-gamma were significantly increased at the dose of 20 mg/kg CAPE group. These results suggest that CAPE could have immunomodulatory effects in vivo (Park et al., 2004).

Ansorge et al., (2003) studied the effects of different propolis extracts, of the flavonoids hesperidin and quercetin as well as of caffeic acid phenethyl ester (CAPE) on basic human immune cell functions by measuring the effects on DNA synthesis and production of different types of cytokines, namely IL-1beta, IL-12, IL-2, IL-4, IL-10 and TGF-beta1, of mitogen-activated peripheral blood mononuclear cells (PBMC) as well as of purified T lymphocytes. The data clearly showed that propolis was capable of dose-dependently suppressing phythemagglutinin (PHA)-induced DNA synthesis of PBMC and T cells. Moreover, cytokines produced by monocytes/macrophages (IL-1beta, IL-12), by Th1 type (IL-2) as well as Th2 type (IL-4) lymphocytes were found to be also suppressed, whereas the production of TGF-beta1 by T regulatory cells was ascertained to be increased.

The immune system has a variety of regulatory/suppressive processes, which are decisive for the development of a healthy or an allergic immune response to allergens. NK1 and NK2 subsets have been demonstrated to display counterregulatory and provocative roles in immune responses, similar to Th1 and Th2 cells. T regulatory cells suppressing both Th1 and Th2 responses have been the focus of intensive research during the last decade. Deniz et al., (2008) investigated the regulatory NK cells in humans, by characterization of NK cell subsets according to their IL-10 secretion property. Freshly purified IL-10-secreting NK cells expressed up to 40-fold increase in IL-10. The effect of IL-10+ NK cells on Ag-specific T cell proliferation has been examined in bee venom major allergen, phospholipase A2- and purified protein derivative of Mycobecterium bovis-induced T cell proliferation. IL-10+ NK cells significantly suppressed both allergen/Ag-induced T cell proliferation and secretion of IL-13 and IFN-gamma, particularly due to secreted IL-10 as demonstrated by blocking of the IL-10 receptor. These results demonstrate that a distinct small fraction of NK cells display regulatory functions in humans.

References:

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Ansorge S , Reinhold D , Lendeckel U . (2003) Propolis and some of its constituents down-regulate DNA synthesis and inflammatory cytokine production but induce TGF-beta1 production of human immune cells. Z Naturforsch C. 58(7-8):580-9.

Blonska M , Bronikowska J , Pietsz G , Czuba ZP , Scheller S , Krol W . (2004) Effects of ethanol extract of propolis (EEP) and its flavones on inducible gene expression in J774A.1 macrophages. J Ethnopharmacol. 91(1):25-30.

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