Su-Hyun Mun

Synergistic antibacterial effect of curcumin against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) are spread among infected patients, with infection rates increasing at an alarming rate. Furthermore, increased resistance to antibiotics has resulted in serious challenges in the treatment of infectious diseases worldwide. Under the selection pressure of exposure to antibiotics, microorganisms evolve to survive against the new conditions imposed by therapy. Therefore, there exists a need to develop alternative natural or combination drug therapies. Curcumin (CCM), a natural polyphenolic flavonoid isolated from the rhizome of a plant, Curcuma longa Linné., has been found to possess many beneficial biological activities. The aim of this study was to investigate the synergistic effect of curcumin and antibiotics as well as to determine the antibacterial activity of CCM against specific MRSA strains. The antibacterial activity of CCM was assessed by the broth microdilution method (by calculating the minimal inhibitory concentration [MIC]), checkerboard dilution test, and time-kill assay. Antimicrobial activity of CCM was observed against all tested strains. The MICs of CCM against 10 strains of S. aureus ranged from 125 to 250 μg/ml. In the checkerboard test, CCM markedly reduced the MICs of the antibiotics oxacillin (OXI), ampicillin (AMP), ciprofloxacin (CIP), and norfloxacin (NOR) used against MRSA. The time-kill curves showed that a combined CCM and OXI treatment reduced the bacterial counts below the lowest detectable limit after 24h. This study suggested that CCM reduced the MICs of several antibiotics tested, notably of OXI, AMP, CIP, and NOR, and that CCM in combination with antibiotics could lead to the development of new combination of antibiotics against MRSA infection.

Quercetin prevents adipogenesis by regulation of transcriptional factors and lipases in OP9 cells

With the industrialization of society, the increase in the prevalence of obesity and metabolic disorders has become an important health concern in a number of countries. Quercetin (3,30,40,5,7-pentahydroxyflavone) is well known as a bioactive flavonoid in a variety of biological resources. The aim of the present study was to explore the machanisms responsible for the anti-adipogenic activity of quercetin and its effects on the lipolysis in OP9 mouse stromal cells which rapidly differentiate into adipocytes. The differentiation of OP9 cells into adipocytes was evaluated by the measurement of lipid accumulation by Oil Red O (ORO) staining; lipid accumulation was significantly impaired by treatment with quercetin. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis were used to measure the expression levels of CCAAT/enhancer binding protein α (C/EBPα), proliferator-activated receptor γ (PPARγ), sterol regulatory element-binding protein-1 (SREBP-1) and fatty acid synthase (FAS). The mRNA expression levels of lipases, such as adipose triglyceride lipase (ATGL), hormone sensitive lipase (HSL) and lipoprotein lipase (LPL) were also measured by RT-PCR. Quercetin significantly decreased the expression of transcription factors, including C/EBPα, PPARγ and SREBP-1c both at the protein and mRNA level. The results from the present study demonstrate that quercetin prevents adipogenesis by upregulating ATGL and HSL expression and downregulating FAS, LPL and adipocyte fatty acid-binding protein (aP2) expression, as well as the expression of transcription factors. Our data suggest that quercetin has therapeutic potential by regulating the expression of transcriptional factors and enzymes associated with adipogenesis.

Gomisin N has anti-allergic effect and inhibits inflammatory cytokine expression in mouse bone marrow-derived mast cells

Gomisin N is a bioactive compound and a prominent anti-allergic agent found in the fruits of tree Schizandra chinensis. However, its effects on the bone marrow-derived mast cell (BMMC)-mediated allergy and inflammation mechanism remain unknown. In this study, the biological effects of gomisin were evaluated while focusing on its effects on the allergic mediator in PMA + A23187-stimulated BMMCs. The anti-allergic effect of gomisin has shown that inhibited PMA + A23187-induced interleukin-6 (IL-6) production. An investigation was also conducted to determine its effects on the production of several allergic mediators including prostaglandin D2 (PGD2), leukotriene C4 (LTC4), β-hexosaminidase (β-Hex), and cyclooxygenase-2 (COX-2) protein. The results revealed that gomisin inhibited the PMA + A23187-induced production of IL-6, PGD2, LTC4, β-Hex, and COX-2 protein. Taken together, these findings indicate that gomisin N has the potential for use in the treatment of allergy.

Tetrandrine suppresses pro-inflammatory mediators in PMA plus A23187-induced HMC-1 cells

Tetrandrine (TET), a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, is known to possess antitumor activity in various malignant neoplasms. However, the precise mechanism of TET-mediated immune modulation remains to be clarified. One of the possible mechanisms for its protective properties is by downregulation of the inflammatory responses. In the present study, the human mast cell line (HMC-1) was used to investigate this effect. TET significantly inhibited the induction of inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8 by phorbol 12-myristate 13-acetate (PMA) plus A23187. Moreover, TET attenuated expression of cyclooxygenase (COX)-2. In activated HMC-1 cells, the phosphorylation of extra-signal response kinase (ERK1/2) and c-jun N-terminal Kinase (JNK1/2), but not p38 mitogen-activated protein kinase, was decreased by treatment of the cells with TET. TET inhibited PMA plus A23187-induced nuclear factor (NF)-κB activation, IκB degradation and phosphorylation. Furthermore, TET suppressed the expression of TNF-α, IL-8, IL-6 and COX-2 through suppression of the ERK1/2, JNK1/2, IκBα degradation and phosphorylation, and NF-κB activation. These results indicated that TET exerted a regulatory effect on inflammatory reactions mediated by mast cells.

The Antibacterial Assay of Tectorigenin with Detergents or ATPase Inhibitors against Methicillin-Resistant Staphylococcus aureus

Tectorigenin (TTR) is an O-methylated isoflavone derived from the rhizome of Belamacanda chinensis (L.) DC. It is known to perform a wide spectrum of biological activities such as antioxidant, anti-inflammatory, anti-tumor. The aim of this study is to examine the mechanism of antibacterial activity of TTR against methicillin-resistant Staphylococcus aureus (MRSA). The anti-MRSA activity of TTR was analyzed in combination assays with detergent, ATPase inhibitors, and peptidoglycan (PGN) derived from S. aureus. Transmission electron microscopy (TEM) was used to monitor survival characteristics and changes in S. aureus morphology. The MIC values of TTR against all the tested strains were 125 μg/mL. The OD(600) of each suspension treated with a combination of Triton X-100, DCCD, and NaN3 with TTR (1/10 × MIC) had been reduced from 68% to 80%, compared to the TTR alone. At a concentration of 125 μg/mL, PGN blocked antibacterial activity of TTR. This study indicates that anti-MRSA action of TTR is closely related to cytoplasmic membrane permeability and ABC transporter, and PGN at 125 μg/mL directly bind to and inhibit TTR at 62.5 μg/mL. These results can be important indication in study on antimicrobial activity mechanism against multidrug resistant strains.

Combination Therapy of Sophoraflavanone B against MRSA: In Vitro Synergy Testing

Sophoraflavanone B (SPF-B), a known prenylated flavonoid, was isolated from the roots of Desmodium caudatum. The aim of this study was to determine the antimicrobial synergism of SPF-B combined with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). MRSA, a multidrug-resistant pathogen, causes both hospital- and community-acquired infections worldwide. The antimicrobial activity of SPF-B was assessed by the broth microdilution method, checkerboard dilution test, and time-kill curve assay. The MIC of SPF-B for 7 strains of S. aureus ranges from 15.6 to 31.25 μg/mL determined. In the checkerboard method, the combinations of SPF-B with antibiotics had a synergistic effect; SPF-B markedly reduced the MICs of the β-lactam antibiotics: ampicillin (AMP) and oxacillin (OXI); aminoglycosides gentamicin (GET); quinolones ciprofloxacin (CIP) and norfloxacin (NOR) against MRSA. The time-kill curves assay showed that a combined SPF-B and selected antibiotics treatment reduced the bacterial counts below the lowest detectable limit after 24 h. These data suggest that the antibacterial activity of SPF-B against MRSA can be effectively increased through its combination with three groups of antibiotics (β-lactams, aminoglycosides, and quinolones). Our research can be a valuable and significant source for the development of a new antibacterial drug with low MRSA resistance.

The mechanism of antibacterial activity of tetrandrine against Staphylococcus aureus.

Tetrandrine (TET) is a bis-benzylisoquinoline alkaloid derived from the radix of Stephania tetrandra S. Moore. TET performs a wide spectrum of biological activities. The radix of S. tetrandrae has been used traditionally in Asia, including Korea, to treat congestive circulatory disorders and inflammatory diseases. The aim of this study was to examine the mechanism of antibacterial activity of tetrandrine against Staphylococcus aureus. The mechanism was investigated by studying the effects of TET in combination with detergent or membrane potential un-couplers. In addition, the direct involvement of peptidoglycan (PGN) was assessed in titration assays. TET activity against S. aureus was 125-250 μg/mL, and the minimum inhibitory concentration (MIC) of the two reference strains was 250 μg/mL. The OD(600) of each suspension treated with a combination of ethylenediaminetetraacetic acid (EDTA), tris(hydroxymethyl) aminomethane (TRIS), and Triton X-100 (TX) with TET (0.25×MIC) had been reduced from 43% to 96%. Additional structure-function studies on the antibacterial activity of TET in combination with other agents may lead to the discovery of more effective antibacterial agents.

In Vitro Potentiation of Ampicillin, Oxacillin, Norfloxacin, Ciprofloxacin, and Vancomycin by Sanguinarine Against Methicillin-Resistant Staphylococcus aureus

Few new drugs are available against methicillin-resistant Staphylococcus aureus (MRSA), because MRSA has the ability to acquire resistance to most antibiotics, which consequently increases the cost of medication. The objective of this study is to evaluate the potentiation of sanguinarine (SN) with selected antibiotics (ampicillin [AC], oxacillin [OX], norfloxacin [NR], ciprofloxacin [CP], and vancomycin [VC]) against MRSA. Minimum inhibitory concentration was determined by using the broth microdilution method and the synergistic effect of AC, OX, NR, CP, and VC in combination with SN was examined by the checkerboard dilution test. The results of the checkerboard test suggested that all combinations exhibited some synergy, partial synergy, or additivity. None of the combinations showed an antagonism effect. The combination of SN plus CP exhibited maximum synergistic effect in 11/13 strains, followed by SN plus NR in 9/13 strains, and AC and OX in 7/13 strains each. The combination of SN with VC, however, mostly showed partial synergy in 11/13 strains. The time-kill assay showed that SN in combination with other antibiotics reduced the bacterial count by 10(2)-10(3) colony forming units after 4 h and to less than the lowest detectable limit after 24 h. Although in vivo synergy and clinical efficacy of SN cannot be predicted, it can be concluded that SN has the potential to restore the effectiveness of the selected antibiotics, and it can be considered in an alternative MRSA treatment.

The inhibition effect of Chlorpromazine against the β-lactam resistance of MRSA.

OBJECTIVE To investigate the gene related to β-lactam resistance and to confirm the mechanism about a synergy effect between CPZ and β-lactam antibiotics. METHODS To measure antibacterial activity, we performed a minimum inhibitory concentration (MIC) and synergy test. Transmission electron microscopy (TEM) was used in morphological analysis. To analyze gene expression, we conducted reverse transcriptase polymerase chain reaction (PCR). RESULTS We confirmed a synergy effect between CPZ and β-lactam antibiotics. Furthermore, we observed that CPZ affect the cell envelope of MRSA by using TEM. At the gene level, CPZ reduced the expression of resistance genes. CONCLUSIONS Through this result, we hypothesize that a decrease of resistance factor expressions was caused by CPZ because it disrupts the activity of a sensor protein located in the cell membrane.

Punicalagin suppresses methicillin resistance of Staphylococcus aureus to oxacillin

Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen that is cross-resistant to most β-lactam antibiotics. We investigated whether oxacillin, which is a β-lactam antibiotic, alone or in combination with punicalagin can affect the penicillin binding protein 2a (PBP2a)-mediated resistance of MRSA. Susceptibility testing of punicalagin with oxacillin was performed using the microdilution and checkerboard assay and the growth curve assay. Binding affinity of punicalagin for cell wall peptidoglycan (PGN) was confirmed by an increased concentration of PGN in bacterial cultures containing punicalagin. The level of PBP2a was analyzed by western blotting. Punicalagin exhibited antimicrobial activity in the viability assay and increased the susceptibility of MRSA to oxacillin. PGN interfered with the antimicrobial activity of punicalagin and prevented the synergistic activity of punicalagin and oxacillin. Increasing the concentration of punicalagin and maintaining a constant concentration of oxacillin resulted in synergistic suppression of the expression of the mec operon (mecA, mecI, and mecR1). The production of PBP2a was suppressed by the addition of punicalagin to oxacillin. Our findings demonstrate that punicalagin potentiates the effect of oxacillin on MRSA by reducing the transcription of mecA (a gene marker for methicillin resistance), which resulted in a reduced level of PBP2a.