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Pentacyclic triterpenoids as antibiofilm agents against methicillin-resistant and biofilm-forming Staphylococcus aureus (MRSA)

Chung PY, Gan MY, Chin BY

Curr Pharm Biotechnol, 2021 Aug 05.
PMID: 34365946 DOI: 10.2174/1389201022666210806092643

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) has been constantly evolving and developing resistance against conventional antibiotics. One of the key features of MRSA that enables it to develop resistance to antibiotics and host immune system is its ability to form biofilm in indwelling medical devices. In previous studies, the antimicrobial activity and mechanisms of action of three known pentacyclic triterpenoids α-amyrin, betulinic acid and betulinaldehyde against planktonic cells of MRSA were determined and elucidated.
OBJECTIVE: This study was carried out to evaluate the ability of the three compounds to significantly reduce the biomass of pre-formed biofilms of MRSA and metabolic activity of the bacterial cells in the biofilm.
METHODS: The anti-biofilm activity of α-amyrin, betulinic acid and betulinaldehyde, individually and in combination with oxacillin or vancomycin, against reference strain of MRSA in pre-formed biofilm were evaluated using the crystal violet and resazurin assays.
RESULTS: α-amyrin and betulinic acid significantly reduced the biomass of pre-formed biofilms of MRSA as individual compounds and in combination with oxacillin or vancomycin. Although betulinaldehyde individually increased the biomass, selected combinations with oxacillin and vancomycin were able to reduce the biomass. All three compounds did not show cytotoxic properties on normal mammalian cells.
CONCLUSION: The three pentacyclic triterpenoids could significantly reduce pre-formed biofilm of MRSA with no cytotoxic effects on normal mammalian cells. These findings demonstrated that pentacyclic triterpenoids have the potential to be developed further as antibiofilm agents against MRSA cells in biofilms, to combat infections caused by multidrug-resistant and biofilm-forming S. aureus.
Lactoferrin modulates the biofilm formation and bap gene expression of methicillin-resistant Staphylococcus epidermidis

Khanum R, Chung PY, Clarke SC, Chin BY

Can J Microbiol, 2023 Feb 01;69(2):117-122.
PMID: 36265186 DOI: 10.1139/cjm-2022-0135

Lactoferrin is an innate glycoprotein with broad antibacterial and antibiofilm properties. The autonomous antibiofilm activity of lactoferrin against Gram-positive bacteria is postulated to involve the cell wall and biofilm components. Thus, the prevention of biomass formation and eradication of preformed biofilms by lactoferrin was investigated using a methicillin-resistant Staphylococcus epidermidis (MRSE) strain. Additionally, the ability of lactoferrin to modulate the expression of the biofilm-associated protein gene (bap) was studied. The bap gene regulates the production of biofilm-associated proteins responsible for bacterial adhesion and aggregation. In the in vitro biofilm assays, lactoferrin prevented biofilm formation and eradicated established biofilms for up to 24 and 72 h, respectively. Extensive eradication of MRSE biofilm biomass was accompanied by the significant upregulation of bap gene expression. These data suggest the interaction of lactoferrin with the biofilm components and cell wall of MRSE, including the biofilm-associated protein.
Fulltext Lipopolysaccharide (LPS) stimulation of Pancreatic Ductal Adenocarcinoma (PDAC) and macrophages activates the NLRP3 inflammasome that influences the levels of pro-inflammatory cytokines in a co-culture model

Sivam HGP, Chin BY, Gan SY, Ng JH, Gwenhure A, Chan EWL

Cancer Biol Ther, 2023 Dec 31;24(1):2284857.
PMID: 38018872 DOI: 10.1080/15384047.2023.2284857

Modified macrophages, tumor-associated macrophages (TAMs), are key contributors to the survival, growth, and metastatic behavior of pancreatic ductal adenocarcinoma (PDAC) cells. Central to the role of inflammation and TAMs lies the NLRP3 inflammasome. This study investigated the effects of LPS-stimulated inflammation on cell proliferation, levels of pro-inflammatory cytokines, and the NLRP3 inflammasome pathway in a co-culture model using PDAC cells and macrophages in the presence or absence of MCC950, a NLRP3-specific inhibitor. The effects of LPS-stimulated inflammation were tested on two PDAC cell lines (Panc 10.05 and SW 1990) co-cultured with RAW 264.7 macrophages. Cell proliferation was determined using the MTT assay. Levels of pro-inflammatory cytokines, IL-1β, and TNF-α were determined by ELISA. Western blot analyses were used to examine the expression of NLRP3 in both PDAC cells and macrophages. The co-culture and interaction between PDAC cell lines and macrophages led to pro-inflammatory microenvironment under LPS stimulation as evidenced by high levels of secreted IL-1β and TNF-α. Inhibition of the NLRP3 inflammasome by MCC950 counteracted the effects of LPS stimulation on the regulation of the NLRP3 inflammasome and pro-inflammatory cytokines in PDAC and macrophages. However, MCC950 differentially modified the viability of the metastatic vs primary PDAC cell lines. LPS stimulation increased PDAC cell viability by regulating the NLRP3 inflammasome and pro-inflammatory cytokines in the tumor microenvironment of PDAC cells/macrophages co-cultures. The specific inhibition of the NLRP inflammasome by MCC950 effectively counteracted the LPS-stimulated inflammation.
Fulltext Carbon Monoxide Suppresses Neointima Formation in Transplant Arteriosclerosis by Inhibiting Vascular Progenitor Cell Differentiation

Sakihama H, Lee GR, Chin BY, Csizmadia E, Gallo D, Qi Y, et al.

Arterioscler Thromb Vasc Biol, 2021 Jun;41(6):1915-1927.
PMID: 33853347 DOI: 10.1161/ATVBAHA.120.315558

[Figure: see text].