Lissinda H. Du Plessis

Review of Natural Compounds for Potential Skin Cancer Treatment

Most anti-cancer drugs are derived from natural resources such as marine, microbial and botanical sources. Cutaneous malignant melanoma is the most aggressive form of skin cancer, with a high mortality rate. Various treatments for malignant melanoma are available, but due to the development of multi-drug resistance, current or emerging chemotherapies have a relatively low success rates. This emphasizes the importance of discovering new compounds that are both safe and effective against melanoma. In vitro testing of melanoma cell lines and murine melanoma models offers the opportunity for identifying mechanisms of action of plant derived compounds and extracts. Common anti-melanoma effects of natural compounds include potentiating apoptosis, inhibiting cell proliferation and inhibiting metastasis. There are different mechanisms and pathways responsible for anti-melanoma actions of medicinal compounds such as promotion of caspase activity, inhibition of angiogenesis and inhibition of the effects of tumor promoting proteins such as PI3-K, Bcl-2, STAT3 and MMPs. This review thus aims at providing an overview of anti-cancer compounds, derived from natural sources, that are currently used in cancer chemotherapies, or that have been reported to show anti-melanoma, or anti-skin cancer activities. Phytochemicals that are discussed in this review include flavonoids, carotenoids, terpenoids, vitamins, sulforaphane, some polyphenols and crude plant extracts.

Combination therapy of Western drugs and herbal medicines: recent advances in understanding interactions involving metabolism and efflux

Introduction: While complementary and alternative medicine markets prosper with an increasing number of consumers of herbal medicines, there is an associated likelihood for herb–drug interactions to occur. Modulation of the activity of metabolic enzymes and/or active transporters by chemical constituents of herbal medicines may influence the therapeutic outcomes of coadministered allopathic medicines due to changes in their pharmacokinetic profiles. Although valuable information on herb–drug interactions is obtained by in vitro studies, such as the mechanisms of interaction, clinical significance of interactions is ultimately demonstrated by in vivo data. Areas covered: The authors outline the mechanisms of herb–drug pharmacokinetic interactions briefly and discuss pharmacokinetic interactions between different therapeutic classes of Western drugs and herbal medicines. Furthermore, the authors also discuss herb–drug interactions from both in vitro and in vivo studies with specific focus on recent findings. Expert opinion: Basic and clinical researches have contributed to the comprehension of the underlying mechanisms involved as well as the practical implications of herb–drug interactions. This provides a foundation for development of guidelines to inform patients about herb–drug interactions that can affect their health.

Nasal and rectal delivery of insulin with chitosan and N-trimethyl chitosan chloride

The aim of this study was to evaluate the ability of TMC, with different degrees of quaternization, to increase insulin absorption in vivo following nasal and rectal administration in rats. Two batches of TMC with different degrees of quaternization (TMC-L, 12.3% quaternized and TMC-H, 61.2% quaternized) and chitosan hydrochloride were administered intranasally (0.25 and 0.5% w/v) and rectally (0.5% w/v) with insulin (4 IU/kg body weight), at a pH of 4.40 and 7.40, in rats. Blood samples were taken over a period of 2 h for measurement of blood glucose levels and plasma insulin levels. Local toxicity evaluation was done by histological examination of the nasal and rectal epithelia. At pH 4.40 all these polymers were able to increase nasal and rectal insulin absorption, compared to the control groups. However, at a pH of 7.40, only TMC-H was able to increase the nasal and rectal absorption of insulin. These results relate to the insolubility of chitosan hydrochloride at neutral pH values, while the charge density of TMC-L is still too low for any significant interaction at pH 7.40. Histological evaluation of the nasal and rectal eptihelia shows no changes in the morphology of the cells after exposure to these polymers. Only slight congestion of the nasal submucosa was observed and all these polymers led to a mild increase in mucus secretion at pH 4.40. Highly quaternized TMC proves to be a potent absorption enhancer in vivo, especially at neutral pH values where chitosan salts are ineffective.

Flow Cytometric Analysis of the Oxidative Status in Human Peripheral Blood Mononuclear Cells of Workers Exposed to Welding Fumes

Flow cytometry is a simple analytical technique that identifies, counts, and characterizes cells. The oxidative status of cells is influenced by many exogenous sources, such as occupational exposure to welding fumes. This study evaluated flow cytometry as a method to determine the oxidative status of male welders (n = 15) occupationally exposed to welding fumes. Flow cytometric analysis of reactive oxygen species (ROS) was carried out in peripheral blood mononuclear cells (PBMC) by using the probe 2, 7-dichlorodihydrofluorescein diacetate (DCFH-DA). Lipid peroxidation was measured by the decrease of fluor-DHPE fluorescence and intracellular glutathione (GSH) levels by using mercury orange. All of the parameters were also observed under a confocal microscope. The oxidative stress ratio was calculated from the oxidative damage and the antioxidant capacity to give an accurate account of the cellular oxidative status. ROS and lipid peroxidation levels were elevated by ∼ 87% and ∼ 96%, respectively, and GSH levels lowered ∼ 96% in PBMC of workers exposed to welding fumes compared with non-exposed controls. The oxidative stress ratio was significantly higher (p < 0.001) in the exposed group. Flow cytometry can be useful for the measurement of cellular oxidative stress in somatic cells of workers exposed to welding fumes and other occupational settings. Calculating an oxidative stress index may be useful in predicting disease outcomes and whether preventative control measures are efficient.

Absorption of the novel artemisinin derivatives artemisone and artemiside: potential application of Pheroid™ technology

Artemisinins have low aqueous solubility that results in poor and erratic absorption upon oral administration. The poor solubility and erratic absorption usually translate to low bioavailability. Artemisinin-based monotherapy and combination therapies are essential for the management and treatment of uncomplicated as well as cerebral malaria. Artemisone and artemiside are novel artemisinin derivatives that have very good antimalarial activities. Pheroid™ technology is a patented drug delivery system which has the ability to entrap, transport and deliver pharmacologically active compounds. Pharmacokinetic models were constructed for artemisone and artemiside in Pheroid™ vesicle formulations. The compounds were administered at a dose of 50.0mg/kg bodyweight to C57 BL/6 mice via an oral gavage tube and blood samples were collected by means of tail-bleeding. Drug concentrations in the samples were determined using an LC/MS/MS method. There was 4.57 times more artemisone in the blood when the drug was entrapped in Pheroid™ vesicles in comparison to the drug only formulation (p < 0.0001). The absorption of artemiside was not dramatically enhanced by the Pheroid™ delivery system.

Characterization of the cell-free DNA released by cultured cancer cells

The most prominent factor that delays the translation of cell-free DNA (cfDNA) analyses to clinical practice is the lack of knowledge regarding its origin and composition. The elucidation of the former is complicated by the seemingly random fluctuation of quantitative and qualitative characteristics of cfDNA in the blood of healthy and diseased individuals. Besides methodological discrepancies, this could be ascribed to a web of cellular responses to various environmental cues and stressors. Since all cells release cfDNA, it follows that the cfDNA in the blood of cancer patients is not only representative of tumor derived DNA, but also of DNA released by healthy cells under different conditions. Additionally, cfDNA released by malignant cells is not necessarily just aberrant, but likely includes non-mutated chromosomal DNA fragments. This may cause false positive/negative results. Although many have acknowledged that this is a major problem, few have addressed it. We propose that many of the current stumbling blocks encountered in in vivo cfDNA studies can be partially circumvented by in vitro models. Accordingly, the purpose of this work was to evaluate the release of cfDNA from cultured cells and to gauge its potential use for elucidating the nature of cfDNA. Results suggest that the occurrence of cfDNA is not a consequence of apoptosis or necrosis, but primarily a result of actively secreted DNA, perhaps in association with a protein complex. This study demonstrates the potential of in vitro cell culture models to obtain useful information about the phenomenon of cfDNA.

In vitro anti-cancer effects of artemisone nano-vesicular formulations on melanoma cells

UNLABELLED Artemisone is a 10-amino-artemisinin derivative that is markedly superior in vitro and in vivo to current artemisinins against malaria and also possesses antitumor activity. In seeking to capitalise on the last property, we have examined the encapsulation of artemisone in nano-vesicular niosomes and solid lipid nanoparticles, and have evaluated efficacies of the free and encapsulated artemisone against human melanoma A-375 cells and effects on human keratinocytes (HaCaT). Artemisone is successfully encapsulated into the nano-vesicles with encapsulation efficiencies of 67±6% and 79±5%, and with average particle sizes being 211±10nm and 295±18nm respectively. The formulations displayed highly selective cytotoxicity towards the melanoma cells with negligible toxicity towards the normal skin cells. The artemisone-loaded nano-vesicles almost completely inhibited the melanoma cells compared to the free drug. The results overall suggest a potentially more useful therapeutic strategy that needs to be evaluated for the treatment of melanoma and other cancers. FROM THE CLINICAL EDITOR Apart from being an effective anti-malarial drug, a surprising action of artemisone also has antitumor activity. Nonetheless, its low water solubility and bioavailability has limited its clinical use. In this article, the authors enacapsulated artemisone in nano- vesicles and solid lipid nano-particles (SLNs). In-vitro studies confirmed the selective cytotoxicity towards melanoma cells. Further in-vivo and pre-clinical studies are awaited.

Evaluation of the cytotoxic properties, gene expression profiles and secondary signalling responses of cultured cells exposed to fumonisin B1, deoxynivalenol and zearalenone mycotoxins

Abstract Mycotoxins are toxic secondary metabolites produced by a range of fungi and are common contaminants of agricultural crops. These toxins are chemically diverse and structurally stable, enabling them to enter the food chain which can lead to numerous adverse health effects in animals and humans. Although mycotoxin exposure is associated with the development of several cancers, it has proved challenging to show a direct connection between exposure and oncogenic change. This study investigates the in vitro cytotoxicity, molecular mechanisms and secondary signalling responses associated with the exposure to three major mycotoxins, fumonisin B1 (FB1), deoxynivalenol (Don) and zearalenone (Zea). The cytotoxicity of FB1, Don and Zea were investigated in cultured HepG2 and Caco-2 cells using cell viability assays as well as flow cytometry. FB1 proved to be less cytotoxic than its counterparts, while Don and Zea demonstrated high cytotoxicity through an apoptotic mechanism. Expression profiles of 84 genes involved in mediating communication between tumour cells and the cellular mediators of inflammation as well as the innate immune system were also studied. The expression profiles associated with the different mycotoxins were further explored for functional networks, biological functions, canonical pathways, toxicological association as well as to predict network associations between the differentially expressed genes. RT-qPCR revealed the significant differential expression of 46 genes, including the expression of several genes strongly associated with cancer and aberrant inflammatory signalling, after mycotoxin exposure. Aberrant inflammatory signalling seems to be a credible contributing factor that initiates the malignant change observed in cells exposed to mycotoxins.

Synthesis and in vitro biological evaluation of aminoacridines and artemisinin–acridine hybrids

During this study, 9-aminoacridine and artemisinin-acridine hybrid compounds were synthesized and the in vitro for antimalarial activity against both the chloroquine sensitive but also gametocytocidal strain (NF54), and chloroquine resistant (Dd2) strains of Plasmodium falciparum was determined. In vitro cytotoxicity against CHO cells, apoptosis of HepG2 and SH-SY5Y as well as anticancer activity against HeLa cell lines were assessed. The hybrids were synthesized, using a microwave-assisted radiation method by covalently linking artemisinin and acridine pharmacophores by means of a liable, aminoethyl ether linker. The synthesized compounds were found active against both the Plasmodium strains and displayed superior selective toxicity towards the parasitic cells. Hybrid 7, however, containing ethylenediamine linker, proved the most active of all of the synthesized compounds. It had seven-fold higher antigametocytocidal activity compared to chloroquine and was also found to be seven-fold more potent than chloroquine against the Dd2 strain, with highly selective action towards the parasitic cells. This hybrid also showed favourable anti-cancer activity against the HeLa cells, three- and eight-fold higher than those of chloroquine and melphalan, respectively. This hybrid may therefore stand as drug candidate for further investigation in the search for new and effective drugs against malaria and cervical cancer.

Nasal delivery of recombinant human growth hormone: In vivo evaluation with pheroid technology and N-Trimethyl chitosan chloride

PURPOSE It was the aim of this study to investigate the possible enhancement of the absorption of recombinant human growth hormone (rhGH) in the nasal cavity, in the presence of a polymeric absorption enhancer, N-trimethyl chitosan chloride (TMC) and a fatty acid-based delivery system, Pheroid. METHODS Two types of Pheroid formulations, Pheroid vesicles and Pheroid microsponges were characterized and evaluated with regard to particle size and morphology. In vivo bioavailability studies in rats were performed and the nasal bioavailability of Pheroid vesicles and Pheroid microsponges were compared relative to subcutaneous administration. The results were also compared with different N-trimethyl chitosan chloride (TMC) formulations, TMC H-L and TMC H-H, well studied absorption enhancers. RESULTS Pheroid vesicles and Pheroid microsponges showed a size distribution of approxiamately 2-3 microm and 3-4 microm for Pheroid vesicles and Pheroid microsponges respectively. Using specific RIA, the relative bioavailability of rhGH after comparison with subcutaneous injection was determined to be 38.9, 128.5, 39.9, 136.3, and 8.3 % for Pheroid microsponges, Pheroid vesicles, TMC H-H, TMC H-L and control group (intranasal rhGH alone), respectively. All the enhancers showed significant absorption enhancement (P < 0.05) with the highest effect observed with TMC H-L. CONCLUSIONS All the enhancers may have promising potential as safe and effective nasal absorption enhancers of rhGH.