Quercetin inhibits expression of inflammatory cytokines through attenuation of NF-kappaB and p38 MAPK in HMC-1 human mast cell line.

OBJECTIVE AND DESIGN: Mast cell-mediated allergic inflammation is involved in many diseases such as asthma, sinusitis, and rheumatoid arthritis. Mast cells induce production of pro-inflammatory cytokines with immune regulatory properties. We investigated the effect of quercetin on the expression of pro-inflammatory cytokines in human mast cell line, HMC-1. METHODS: HMC-1 cells were stimulated with phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187 (PMACI). RESULTS: Quercetin decreased the gene expression and production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, and IL-8 in PMACI-stimulated HMC-1 cells. Quercetin attenuated PMACI-induced activation of NF-kappaB and p38 mitogen-activated protein kinase. CONCLUSION: Our study provides evidence that quercetin may suitable for the treatment of mast cell-derived allergic inflammatory diseases.

Double-edged sword of chemosensitizer: increase of multidrug resistance protein (MRP) in leukemic cells by an MRP inhibitor probenecid.

The multidrug resistance protein (MRP) is a drug efflux membrane pump conferring multidrug resistance to tumor cells. Clinical trials have been undertaken to improve the effectiveness of chemotherapy by adding an MRP inhibitor to the treatment regimen. This study attempted not only to determine novel resistance mechanisms in MRP-overexpressing AML cells (AML-2/DX100) by chronic exposure to doxorubicin in the presence of an MRP inhibitor probenecid but also to find out whether probenecid could increase MRP levels. AML-2/DXPBA cultured in the presence of probenecid (600 microM) and doxorubicin (100 ng/ml) showed a higher level of the multidrug resistance (MDR) phenotype when compared to AML-2/DX100. AML-2/DXPBA showed increased levels of MRP compared to those of AML-2/DX100. Probenecid increased the MRP levels without an increase in MRP mRNA in AML-2/WT in both a time- and dose-dependent manner. Of the MRP inhibitors including probenecid, ofloxacin, erythromycin, and rifampicin used in this study, only probenecid showed a marked chemosensitizing effect in AML-2/DX100 but not in HL-60/Adr, suggesting that the chemosensitizing effects of the MRP inhibitors vary according to the type of resistant cells. The maximum noncytotoxic concentrations of these MRP inhibitors increased the MRP levels to various degrees in both AML-2/WT and HL-60/WT. However, the chemosensitizing effects of the MRP inhibitors were not correlated with their MRP-increasing effects. Altogether, MRP inhibitors such as probenecid have been shown to function as a double-edged sword, indicating that they are not only an effective chemosensitizer of MRP-associated MDR tumor cells but also an MRP activator. Therefore caution should be taken whenever using MRP inhibitors to reverse MRP-mediated multidrug resistance in clinical cancer chemotherapy as well as when used to inhibit MRP expression in vitro.

Reactive oxygen species-specific mechanisms of drug resistance in paraquat-resistant acute myelogenous leukemia sublines.

Reactive oxygen species (ROS)-specific mechanisms of drug resistance were explored in paraquat (PQ)-resistant acute myelogenous leukemia cell (OCI/AML-2) sublines. For this, PQ-resistant AML sublines, AML-2/PQ100 and AML-2/PQ400, were selected in the presence of PQ concentrations of 100 microg/ml and 400 microg/ml, respectively. They showed a moderate level of cross resistance to cisplatin and doxorubicin. They were also slightly more resistant than the parental cell (AML-2/WT) to etoposide, camptothecin and daunorubicin. The resistance of PQ-resistant AML-2 sublines to cisplatin seemed to be due to increased amounts of metallothionein, which was not only supported by reversal of resistance to cisplatin by propargylglycin (an inhibitor of metallothionein synthesis) but also confirmed by Western blot analysis and reverse transcription-PCR assay. In addition, both AML-PQ100 and /PQ400 sublines showed increased activities of Cu-, Zn-containing superoxide dismutase (Cu,Zn-SOD) and Mn-containing superoxide dismutase (Mn-SOD), whereas AML-2/PQ400, but not AML-2/PQ100, showed increased glutathione S-transferase activity as compared to that of AML-2/WT. However, there was no difference in other ROS-related cellular antioxidants between AML-2/WT and its PQ-resistant sublines. Taken together, these results strongly suggest that increases in levels of metallothionein, glutathione S-transferase, Cu,Zn-SOD and Mn-SOD play important roles in protective mechanisms against toxicity of PQ or ROS in AML cells.

Drug concentration-dependent expression of multidrug resistance-associated protein and P-glycoprotein in the doxorubicin-resistant acute myelogenous leukemia sublines.

The multidrug resistance of cancer cells can be mediated by an overexpression of the human MDR1 and MRP genes, which encode the transmembrane efflux pumps, the 170 kDa P-glycoprotein (Pgp) and the 190 kDa multidrug resistance-associated protein (MRP), respectively. In this study, we investigate which protein is preferentially overexpressed in the function of doxorubicin concentrations in the acute myelogenous leukemia cell line (OCI/AML-2). Multidrug-resistant AML-2 sublines were isolated in doxorubicin concentrations of 20, 100, 250, and 500 ng/ml. MRP was at first expressed at low concentrations of less than 5 x IC50 (100 ng/ml) of doxorubicin followed by the overexpression of Pgp with concentrations of more than 12.5 x IC50 (250 ng/ml) of doxorubicin. In addition, it appeared that increased amounts of MRP and its mRNA in AML-2/DX20 and /DX100 decreased gradually in both AML-2/DX250 and /DX500 overexpressing Pgp. In conclusion, it is thought that the overexpression of MRP or Pgp is dependent upon drug concentrations. It could be implicated that the overexpression of MRP might be negatively related to that of Pgp.

Vascular endothelial growth factor expression is higher in differentiated thyroid cancer than in normal or benign thyroid.

Vascular endothelial growth factor (VEGF) is an angiogenic factor, and its expression has been rarely demonstrated in thyroid tumors. We, therefore, investigated the expression of VEGF messenger RNA (mRNA) and production of VEGF protein in cell lines from human primary and metastatic follicular (FTC-133, FTC-236, and FTC-238), papillary (TPC-1), Hürthle cell (XTC-1), and medullary thyroid cancers (MTC-1.1 and MTC-2.2), and in human thyroid tissues (papillary, follicular, medullary, and Hürthle cell cancers, follicular adenomas, and Graves' thyroid tissue) by Northern blot, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) studies. All thyroid cell lines expressed a 4.2-kilobase VEGF mRNA. The VEGF mRNA levels were higher in the thyroid cancer cell lines than in primary cultures of normal thyroid cells, and higher in thyroid cancers of follicular than those of parafollicular cell origin. The VEGF mRNA levels were similar in primary and metastatic thyroid tumors. Immunohistochemical staining and Northern blot analysis of the cell lines correlated positively, thus thyroid cancer cell lines stained more intensely than normal thyroid cells and follicular tumor cells more intensely than parafollicular tumor cells. Again, no difference was noted in VEGF staining between primary and metastatic thyroid tumors. Deparafinized sections of papillary, follicular, and Hürthle cell cancers also stained much stronger than those of medullary thyroid cancers, benign, or hyperplastic (Graves' disease) thyroid tissue. Thyroid cancer cell lines (XTC-1 > TPC-1 > FTC-133 > MTC-1.1) also secreted more VEGF protein as measured by ELISA than did normal thyroid cells. VEGF secretion of cell lines derived from primary and metastatic thyroid tumors were similar. VEGF mRNA is therefore expressed, and VEGF protein is secreted by normal, hyperplastic, and neoplastic thyroid tissues. The higher levels of VEGF expression in differentiated thyroid cancers of follicular cell origin suggests a role in oncogenesis.