Monosubstituted tricationic Zn(II) phthalocyanine enhances antimicrobial photodynamic inactivation (aPDI) of methicillin-resistant Staphylococcus aureus (MRSA) and cytotoxicity evaluation for topical applications: in vitro and in vivo study

Antimicrobial photodynamic therapy (aPDT) is an innovative approach to combat multi-drug resistant bacteria. It is known that cationic Zn(II) phthalocyanines (ZnPc) are effective in mediating aPDT against methicillin-resistant Staphylococcus aureus (MRSA). Here we used ZnPc-based photosensitizer named ZnPcE previously reported by our research group to evaluate its aPDT efficacy against broad spectrum of clinically relevant MRSAs. Remarkably, in vitro anti-MRSA activity was achieved using near-infrared (NIR, >610 nm) light with minimal bactericidal concentrations ranging <0.019-0.156 µM against the panel of MRSAs. ZnPcE was not only significantly (p < .05) more potent than methylene blue, which is a clinically approved photosensitizer but also demonstrated low cytotoxicity against human fibroblasts cell line (Hs-27) and human immortalized keratinocytes cell line (HaCaT). The toxicity was further evaluated on human 3-D skin constructs and found ZnPcE did not manifest in vivo skin irritation at ≤7.8 µM concentration. In the murine MRSA wound model, ZnPcE with PDT group demonstrated > 4 log10 CFU reduction and the value is significantly higher (p < .05) than all test groups except positive control. To conclude, results of present study provide a scientific basis for future clinical evaluation of ZnPcE-PDT on MRSA wound infection.

Synthesis and In Vitro Photodynamic Activity of Cationic Boron Dipyrromethene-Based Photosensitizers against Methicillin-Resistant Staphylococcus aureus

A series of cationic boron dipyrromethene (BODIPY) derivatives were synthesized and characterized with various spectroscopic methods. Having the ability to generate singlet oxygen upon irradiation, these compounds could potentially serve as photosensitizers for antimicrobial photodynamic therapy. Of the five BODIPYs being examined, the dicationic aza-BODIPY analogue (compound 5) demonstrated the highest potency against a broad spectrum of clinically relevant methicillin-resistant Staphylococcus aureus (MRSA), including four ATCC-type strains (ATCC 43300, ATCC BAA-42, ATCC BAA-43, and ATCC BAA-44), two strains carrying specific antibiotic resistance mechanisms [-AAC(6')-APH(2") and RN4220/pUL5054], and ten non-duplicate clinical strains from hospital- and community-associated MRSAs of the important clonal types ST239, ST30, and ST59, which have previously been documented to be prevalent in Hong Kong and its neighboring countries. The in vitro anti-MRSA activity of compound 5 was achieved upon irradiation with near-infrared light (>610 nm) with minimal bactericidal concentrations (MBCs) ranging from 12.5 to 25 µM against the whole panel of MRSAs, except the hospital-associated MRSAs for which the MBCs were in the range of 50-100 µM. Compound 5 was significantly (p < 0.05) more potent than methylene blue, which is a clinically approved photosensitizer, indicating that it is a promising antimicrobial agent that is worthy of further investigation.

IL33: Roles in Allergic Inflammation and Therapeutic Perspectives

Interleukin (IL)-33 belongs to IL-1 cytokine family which is constitutively produced from the structural and lining cells including fibroblasts, endothelial cells, and epithelial cells of skin, gastrointestinal tract, and lungs that are exposed to the environment. Different from most cytokines that are actively secreted from cells, nuclear cytokine IL-33 is passively released during cell necrosis or when tissues are damaged, suggesting that it may function as an alarmin that alerts the immune system after endothelial or epithelial cell damage during infection, physical stress, or trauma. IL-33 plays important roles in type-2 innate immunity via activation of allergic inflammation-related eosinophils, basophils, mast cells, macrophages, and group 2 innate lymphoid cells (ILC2s) through its receptor ST2. In this review, we focus on the recent advances of the underlying intercellular and intracellular mechanisms by which IL-33 can regulate the allergic inflammation in various allergic diseases including allergic asthma and atopic dermatitis. The future pharmacological strategy and application of traditional Chinese medicines targeting the IL-33/ST2 axis for anti-inflammatory therapy of allergic diseases were also discussed.

Anti-Inflammatory Activities of Pentaherbs Formula, Berberine, Gallic Acid and Chlorogenic Acid in Atopic Dermatitis-Like Skin Inflammation

Atopic dermatitis (AD) is a common allergic skin disease, characterized by dryness, itchiness, thickening and inflammation of the skin. Infiltration of eosinophils into the dermal layer and presence of edema are typical characteristics in the skin biopsy of AD patients. Previous in vitro and clinical studies showed that the Pentaherbs formula (PHF) consisting of five traditional Chinese herbal medicines, Flos Lonicerae, Herba Menthae, Cortex Phellodendri, Cortex Moutan and Rhizoma Atractylodis at w/w ratio of 2:1:2:2:2 exhibited therapeutic potential in treating AD. In this study, an in vivo murine model with oxazolone (OXA)-mediated dermatitis was used to elucidate the efficacy of PHF. Active ingredients of PHF water extract were also identified and quantified, and their in vitro anti-inflammatory activities on pruritogenic cytokine IL-31- and alarmin IL-33-activated human eosinophils and dermal fibroblasts were evaluated. Ear swelling, epidermis thickening and eosinophils infiltration in epidermal and dermal layers, and the release of serum IL-12 of the murine OXA-mediated dermatitis were significantly reduced upon oral or topical treatment with PHF (all p < 0.05). Gallic acid, chlorogenic acid and berberine contents (w/w) in PHF were found to be 0.479%, 1.201% and 0.022%, respectively. Gallic acid and chlorogenic acid could suppress the release of pro-inflammatory cytokine IL-6 and chemokine CCL7 and CXCL8, respectively, in IL-31- and IL-33-treated eosinophils-dermal fibroblasts co-culture; while berberine could suppress the release of IL-6, CXCL8, CCL2 and CCL7 in the eosinophil culture and eosinophils-dermal fibroblasts co-culture (all p < 0.05). These findings suggest that PHF can ameliorate allergic inflammation and attenuate the activation of eosinophils.

Combating against methicillin-resistant Staphylococcus aureus - two fatty acids from Purslane (Portulaca oleracea L.) exhibit synergistic effects with erythromycin

OBJECTIVES

The aims of this study were to identify the active ingredients from Portulaca oleracea L. (PO) that could provide synergism with antibiotics against methicillin-resistant Staphylococcus aureus (MRSA) and their possible mechanisms of resistance inhibition.

METHODS

High-speed counter-current chromatography (HSCCC) coupled with gas chromatography-mass spectrometry and a panel of laboratory MRSA strains were used for checkerboard and efflux inhibitory assays.

KEY FINDINGS

Linoleic and oleic acids were identified from HSCCC fraction 18 of PO with synergistic antibacterial activity when combined with erythromycin against RN4220/pUL5054. Ethidium bromide efflux inhibitory studies revealed that linoleic and oleic acids may interfere the activity of MsrA pump. By comparing among a panel of linoleic and oleic acids analogues, unsaturated fatty acids in salt form with cis configuration and an increase in number of double bonds were found to further increase the antibacterial activity when used alone or in combination with antibiotics.

CONCLUSION

This study reported for the first time that two active ingredients, namely linoleic and oleic acids, were identified from PO with synergistic antibacterial activity when combined with erythromycin against MRSA RN4220/pUL5054 and possibly act by inhibiting the efflux pumps of the bacteria cells.

Immunomodulatory activities of Ganoderma sinense polysaccharides in human immune cells

Medicinal mushrooms have been traditionally used as food nutrient supplements in China for thousands of years. The present study aimed to evaluate the immunomodulatory activities of Ganoderma sinense (GS), an allied species of G. lucidum, using human peripheral blood mononuclear cells (PBMC). Our results showed that the polysaccharide-enriched fraction of GS hot water extract (400 μg/ml) exhibited significant stimulatory effects on PBMC proliferation. When the fruiting bodies of GS were divided into pileus and stipe parts and were separately extracted, the GS stipe polysaccharide-enriched fraction (50-400 μg/ml) showed concentration-dependent immunostimulating effects in PBMC. The productions of tumor necrosis factor-α, interleukin (IL)-10, and transforming growth factor -β were significantly enhanced by this fraction. In addition, the proportion of CD14(+) monocyte subpopulation within the PBMC was specifically increased. The IL-10 and IL-12 productions in monocyte-derived dendritic cells were significantly enhanced by GS stipe fraction. The composition of monosaccharides of this fraction was determined by ultra performance liquid chromatography and ion exchange chromatography. Our study demonstrated for the first time the immunostimulatory effects of GS stipe polysaccharide-enriched fraction on PBMC and dendritic cells. The findings revealed the potential use of GS (especially including the stipes of fruiting bodies) as adjuvant nutrient supplements for patients, who are receiving immunosuppressive chemotherapies.

Synergistic effects of diosmetin with erythromycin against ABC transporter over-expressed methicillin-resistant Staphylococcus aureus (MRSA) RN4220/pUL5054 and inhibition of MRSA pyruvate kinase

Increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) worldwide with limited therapeutic options is a growing public health concern. Natural products have been shown to possess antibacterial actions against MRSA. Flavonoids from natural products have been shown to possess antibacterial actions against MRSA by antagonizing its resistance mechanisms. Diosmin and diosmetin are natural flavonoids found in a variety of citrus fruits. The aim of this study was to investigate whether diosmin and diosmetin could inhibit the growth of MRSA and the in vitro enzymatic activity of a newly discovered MRSA drug target, pyruvate kinase (PK). By using a panel of MRSA strains with known resistant mechanisms, neither diosmin nor diosmetin was shown to possess direct antibacterial activities against all tested MRSA strains. However, in checkerboard assay, we found that diosmetin together with erythromycin, could synergistically inhibit the growth of ABC-pump overexpressed MRSA-RN4220/pUL5054, and time kill assay also showed that the antibacterial activities of diosmetin with erythromycin were bactericidal. Diosmetin was further shown to significantly suppress the MRSA PK activities in a dose dependent manner. In conclusion, the inhibition of MRSA PK by diosmetin could lead to a deficiency of ATP and affect the bacterial efflux pump which might contribute to the antibacterial actions of diosmetin against MRSA.

Anti-angiogenesis and immunomodulatory activities of an anti-tumor sesquiterpene bigelovin isolated from Inula helianthus-aquatica

Bigelovin is a sesquiterpene lactone isolated from the plant Inula helianthus-aquatica which was traditionally used in cancer treatment in Yunnan, China. The potent apoptotic activities of bigelovin in human leukemia U937 cells were shown in our previous study. The present study investigated the anti-angiogenic and immunomodulatory effects of bigelovin using transgenic zebrafish Tg(fli1a:EGFP)y1 with fluorescent blood vessels and human peripheral blood mononuclear cells (PBMCs), respectively. Furthermore, the inhibitory activities of bigelovin on the human endothelial cell adhesion molecules (CAMs) were also examined. Our results showed that the growth of subintestinal vessels of the bigelovin-treated zebrafish embryos was significantly inhibited and the gene expressions in angiogenesis signaling pathways (e.g. Ang2 and Tie2) of the zebrafish were down-regulated after bigelovin treatment. Besides, the proliferation and Th1 cytokines productions (e.g. IFN-γ, IL-2 and IL-12) were suppressed in bigelovin-treated PBMCs. On the other hand, bigelovin was shown to significantly inhibit the human monocyte adhesion to human endothelial cells and the gene expressions of inflammation-related CAMs (e.g. ICAM-1, VCAM-1 and E-selectin) were significantly down-regulated in bigelovin-treated human endothelial cells. In summary, our data provide the first evidence that bigelovin possesses anti-angiogenic and immunomodulatory activities, suggesting bigelovin may exert multi-target functions against cancer in animal models.

Synergistic effects of baicalein with ciprofloxacin against NorA over-expressed methicillin-resistant Staphylococcus aureus (MRSA) and inhibition of MRSA pyruvate kinase

ETHNOPHARMACOLOGICAL RELEVANCE

Baicalein, the active constituent derived from Scutellaria baicalensis Georgi., has previously been shown to significantly restore the effectiveness of β-lactam antibiotics and tetracycline against methicillin-resistant Staphylococcus aureus (MRSA). With multiple therapeutic benefits, the antibacterial actions of baicalein may also be involved in overcoming other bacterial resistance mechanisms. The aim of the present study was to further investigate antibacterial activities of baicalein in association with various antibiotics against selected Staphylococcus aureus strains with known specific drug resistance mechanisms.

MATERIAL AND METHODS

A panel of clinical MRSA strains was used for further confirmation of the antibacterial activities of baicalein. The effect of baicalein on inhibiting the enzymatic activity of a newly discovered MRSA-specific pyruvate kinase (PK), which is essential for Staphylococcus aureus growth and survival was also examined.

RESULTS

In the checkerboard dilution test and time-kill assay, baicalein at 16 μg/ml could synergistically restore the antibacterial actions of ciprofloxacin against the NorA efflux pump overexpressed SA-1199B, but not with the poor NorA substrate, pefloxacin. Moreover, synergistic effects were observed when baicalein was combined with ciprofloxacin against 12 out of 20 clinical ciprofloxacin resistant strains. For MRSA PK studies, baicalein alone could inhibit the enzymatic activity of MRSA PK in a dose-dependent manner.

CONCLUSION

Our results demonstrated that baicalein could significantly reverse the ciprofloxacin resistance of MRSA possibly by inhibiting the NorA efflux pump in vitro. The inhibition of MRSA PK by baicalein could lead to a deficiency of ATP which might further contribute to the antibacterial actions of baicalein against MRSA.