Mistletoe lectin (Viscum album coloratum) modulates proliferation and cytokine expressions in murine splenocytes

Alterations in IL-6/STAT3 Signaling by Korean Mistletoe Lectin Regulate the Self-Renewal Activity of Placenta-Derived Mesenchymal Stem Cells

Korean mistletoe (Viscum album L. var. coloratum) lectin (VCA) is known as an anticancer drug. However, it is not clear whether VCA affects the self-renewal activity of mesenchymal stem cells (MSCs). Therefore, the objectives of this study were to analyze the effect of VCA on the proliferation of MSCs and expression of stemness markers. We also evaluated the usefulness of placenta-derived MSCs (PD-MSCs) as a screening tool. VCA was stably administered to MSCs, and analyzed self-renewal activities. The effect of IL-6 signaling on MSC proliferation was explored by quantitative methylation-specific PCR (qMSP) and western blot analysis. Compared with the control condition, low concentrations of VCA (10 pg/mL) induced an increase in the self-renewal activity of MSCs. Interestingly, a low concentration of VCA promoted IL-6 signaling in PD-MSCs through altered IL-6/STAT3 gene methylation. Furthermore, inhibition of IL-6 expression in PD-MSCs using an anti-IL-6 antibody caused a decrease in their self-renewal activity through IL-6/STAT3 signaling by altering IL-6/STAT3 gene methylation. These findings provide helpful data for understanding the mechanism of MSC self-renewal via VCA and show that VCA may be useful as a functional natural product for developing efficient therapies using placenta-derived stem cells.

Liver injury induced by herbal extracts containing mistletoe and kudzu

PURPOSE

Along with the use of herbal medicines worldwide, the number of cases of reported herbal-induced hepatotoxicity has also been increasing. This report describes a case of liver injury caused by mistletoe and kudzu extracts in a patient previously in good health.

CASE

A 55-year-old man with no significant medical history was admitted to a hospital with a 10-day history of mild fever and brownish urine. The patient also had epigastric and right upper quadrant pain. The patient's liver function test results showed significantly elevated aspartate aminotransferase (AST) (958 IU/L) and alanine aminotransferase (ALT) (1000 IU/L) levels. Serologic viral hepatitis test results were negative. The patient neither consumed alcohol nor took any medications other than an antacid, which was not correlated with the elevated liver function test results. The patient reported taking mistletoe extract for 1 month and kudzu root extract for 10 days to promote his general health. Upon admission to the hospital, his AST and ALT levels were elevated to 1108 IU/L and 1528 IU/L, respectively. The total bilirubin level increased to 9.4 mg/dL on day 4. The modified Roussel Ulcaf Causality Assessment Method yielded a score of 10 points, indicating probable liver injury caused by mistletoe. Therefore, mistletoe- and kudzu-induced liver injury with a hepatocellular pattern was diagnosed. After discontinuation of the mistletoe and kudzu extracts in the hospital, the patient's liver function test values gradually decreased until day 8, with no other abnormal symptoms. The patient was discharged on hospital day 8 and had a follow-up visit at 1 week.

CONCLUSION

This case of liver injury characterized by a significant increase in AST and ALT levels was related to the use of mistletoe and kudzu extracts.

Korean mistletoe lectin promotes proliferation and invasion of trophoblast cells through regulation of Akt signaling

Recently, Viscum album var. coloratum agglutinin (VCA) was shown to have various effects on cancer cells. However, most researchers are focused on high concentrations (1-1000 ng/ml) of VCA and its anti-cancer effects. Therefore, we wanted to know whether low concentrations of VCA have an effect on proliferation and invasion of human trophoblast cells (HTR-8/SVneo cell line). Cell proliferations at low concentration of VCA (1-10 pg/ml) were increased over 2-fold relative to the control. Also, gelatinolytic activities of matrix metalloproteinase-2 were increased after VCA treatment, while TIMP-1 expression was reduced. Furthermore, the expression of integrin subunits α5 and β1 were increased 1.5-fold when cells were treated with low dose of VCA (10 pg/ml). Lastly, VCA was able to promote trophoblast invasion through activation of the Akt signaling pathway. In conclusion, low concentrations of VCA can stimulate the ability of trophoblast cells to invade through the extracellular matrix in vitro.

Korean mistletoe lectin regulates self-renewal of placenta-derived mesenchymal stem cells via autophagic mechanisms

OBJECTIVES

The balance between survival and death is a key point for regulation of physiology of stem cells. Recently, applications of natural products to enhance efficiencies in culturing and differentiation of stem cells are increasing. Korean mistletoe lectin (Viscum album L. var. coloratum agglutinin, VCA) has been known to be toxic to some cancer cells, but it is still unclear whether VCA has a cytotoxic or indeed a proliferative effect on mesenchymal stem cells (MSCs). Here, we have compared effects of VCA in naïve placenta-derived stem cells (PDSCs), immortalized PDSCs and cancer cells (HepG2), and analysed their mechanisms.

MATERIALS AND METHODS

MTT assay was performed to analyse effects of VCA on naïve PDSCs, immortalized PDSCs and HepG2. FACS, ROS, caspase-3 assay, western blotting and immunofluorescence were performed to detect signalling events involved in self-renewal of the above cell types.

RESULTS

VCA had cancer cell-specific toxicity to HepG2 cells even with low concentrations of VCA (1-5 pg/ml), toxicity was observed to immortalized PDSCs and HepG2s, while proliferation of naïve PDSCs was significantly increased (P < 0.05). ROS production by VCA treatment in naïve PDSCs was significantly lower compared to controls (P < 0.05). Furthermore, autophagy was activated in naïve PDSCs treated with VCA through increase in type II LC3 and decrease in phosphorylated mTOR.

CONCLUSIONS

VCA can promote MSC proliferation through an activated autophagic mechanism.

Fermented mistletoe extract as a multimodal antitumoral agent in gliomas

In Europe, commercially available extracts from the white-berry mistletoe (Viscum album L.) are widely used as a complementary cancer therapy. Mistletoe lectins have been identified as main active components and exhibit cytotoxic effects as well as immunomodulatory activity. Since it is still not elucidated in detail how mistle toe extracts such as ISCADOR communicate their effects, we analyzed the mechanisms that might be responsible for their antitumoral function on a molecular and functional level. ISCADOR-treated glioblastoma (GBM) cells down-regulate central genes involved in glioblastoma progression and malignancy such as the cytokine TGF-β and matrix-metalloproteinases. Using in vitro glioblastoma/immune cell co-cultivation assays as well as measurement of cell migration and invasion, we could demonstrate that in glioblastoma cells, lectin-rich ISCADOR M and ISCADOR Q significantly enforce NK-cell-mediated GBM cell lysis. Beside its immune stimulatory effect, ISCADOR reduces the migratory and invasive potential of glioblastoma cells. In a syngeneic as well as in a xenograft glioblastoma mouse model, both pretreatment of tumor cells and intratumoral therapy of subcutaneously growing glioblastoma cells with ISCADOR Q showed delayed tumor growth. In conclusion, ISCADOR Q, showing multiple positive effects in the treatment of glioblastoma, may be a candidate for concomitant treatment of this cancer.

Fructans from aged garlic extract produce a delayed immunoadjuvant response to ovalbumin antigen in BALB/c mice

Garlic (Allium sativum) is known for its innumerable biological activities including immunomodulation. Aged garlic extract (AGE), an odorless garlic preparation, has been shown to have superior immunomodulatory properties over raw garlic extract. Although garlic is a very rich source of fructans (17%, fresh weight basis), AGE contains only 0.22% of raw garlic fructans. Aged garlic fructans (AGF) have recently been shown to possess immunomodulatory activities in vitro. Natural adjuvants capable of eliciting better immune response of a model antigen are important in developing newer vaccines. In the present study, the adjuvant activity of AGF has been investigated in BALB/c mice using ovalbumin (OVA, 30 µg) as an experimental antigen. The body weights of animals did not change significantly indicating that the administration of garlic fructans is well-tolerated. AGF produce a significant humoral (serum IgG) response to OVA in BALB/c mice administered mucosally by either intranasal or oral route--a delayed response appearing on 50th day at a dose of 30 µg AGF by intranasal route. However, the serum IgG response was seen earlier on 35th day at a dose of 100 µg AGF by oral route. Higher concentrations of AGF (>50 µg) were inhibitory for adjuvant activity by intranasal administration. These observations indicate that AGF display immunoadjuvant activity for a test antigen though the humoral immune response is delayed.

Immunomodulating effects of Korean mistletoe lectin in vitro and in vivo

The immunomodulatory effects of Korean mistletoe lectin (KML), one of the major active components in Viscum album L. var. coloratum, were investigated in vitro in immune cell proliferation and natural killer (NK) cell- and macrophage-mediated cytotoxicity, and in vivo in the forced swim test and cold stress. In mitogen-induced lymphocyte proliferation of murine splenocytes, concanavalin A and lipopolysaccharide significantly increased the proliferation of T cell and B cell lymphocytes, respectively. KML exposure increased lymphocyte proliferation in response to mitogen. KML also increased the splenic NK cell and macrophage activities in vitro. Exposure to KML increased production of cytokines such as interleukin-1 and interleukin-6 by macrophages. Two-week treatment with KML (30, 100, 300 and 600 microg/kg) increased the recruitment of lymphocytes, monocytes and macrophages. In the forced swim test, the immobility time was significantly attenuated by treatment with KML (300 and 600 microg/kg). In a cold stress experiment, spleen and thymus weight increased in KML-treated mice, while the weight of adrenal gland was lower than that in vehicle-treated mice. The levels of serum aminotransferases, lactate dehydrogenase and alkaline phosphatase were decreased by KML treatment. KML treatment also induced increases in the percentages of CD4(+) and CD8(+) cells in thymus. Our results suggest that KML enhances the immune system through modulation of lymphocytes, NK cells, and macrophages.

The effect of subminimal inhibitory concentrations of antibiotics on virulence factors expressed by Staphylococcus aureus biofilms

AIMS

The effect of subminimal inhibitory concentrations (sub-MICs) of cefalexin, ciprofloxacin and roxithromycin was investigated on some virulence factors [e.g. coagulase, Toxic Shock Syndrome Toxin 1 (TSST-1) and biofilm formation] expressed by Staphylococcus aureus biofilms.

METHODS AND RESULTS

Biofilms were grown with and without the presence of 1/16 MIC of antibiotics on Sorbarod filters. Eluate supernatants were collected, and coagulase and TSST-1 production were evaluated. Coagulase production was reduced in eluates exposed to roxithromycin when compared to control, while TSST-1 production was reduced in biofilms exposed to cefalexin and to a lesser extent, ciprofloxacin. In addition, the ability of Staph. aureus to produce biofilm in microtitre plates in the presence of sub-MIC antibiotics indicated that cefalexin induced biofilm formation at a wide range of sub-MICs. TSST-1 produced from the challenged and control biofilms was purified, and its proliferative activity was studied on single cell suspension of mouse splenocytes using MTS/PMS assay. No significant difference in the activity between the treated toxin and the control has been observed.

CONCLUSIONS

Antibiotics at sub-MIC levels interfere with bacterial biofilm virulence expression depending on the type and concentration of antibiotic used.

SIGNIFICANCE AND IMPACT OF THE STUDY

The establishment of sub-MICs of antibiotics in clinical situations may result in altered virulence states in pathogenic bacteria.

In vitro immunoregulatory effects of Korean mistletoe lectin on functional activation of monocytic and macrophage-like cells

Korean mistletoe lectin (KML) is one of the major active components in Viscum album var. (coloratum), displaying various biological effects such as anti-tumor and anti-metastatic activities. Even though it has been shown to boost host immune defense mechanisms, the immunomodulatory effects of KML on specific immune responses mediated by macrophages have not been fully elucidated. Therefore, in this study, we aimed to demonstrate KML's regulatory roles on macrophage-mediated immune responses. KML clearly blocked lipopolysaccharide (LPS)-induced events [expression of interleukin (IL)-10, nitric oxide (NO) production and phagocytic uptake], and suppressed the normal expression levels of IL-10 (at 2 ng/ml) and tumor necrosis factor (TNF)-alpha (at 10 ng/ml). In contrast, (1) the expression of cytokine (TNF-alpha) and (2) the generation of reactive oxygen species (ROS) induced by LPS were significantly up-regulated with KML co-treatment. In addition, KML itself increased the mRNA levels of IL-3 and IL-23; phagocytic uptake; the surface levels of co-stimulatory molecules (CD80 and CD86), pattern recognition receptors (PRRs) [such as dectin-1 and toll like receptor (TLR)-2] and adhesion molecules [beta1-integrins (CD29) and CD43]; and CD29-mediated cell adhesion events. Finally, according to co-treatment of D-galactose with KML under LPS-induced NO production conditions, KML inhibition seems to be mediated by binding to proteins with D-galactose. Therefore, these data suggest that KML may participate in regulating various macrophage-mediated innate and adaptive responses via binding to surface protein with D-galactose and that some of these may deserve in KML's therapeutic activities such as anti-tumor and anti-microbial effects.