An exploratory study on the effect of kynurenine metabolites on sEnd-2 endothelioma cells.

Cancer is the second leading cause of mortality worldwide. The development of anticancer therapy plays a crucial role in mitigating tumour progression and metastasis. Epithelioid hemangioendothelioma is a very rare cancer, however, with a high systemic involvement. Kynurenine metabolites which include l-kynurenine, 3-hydroxykynurenine, 3-hydroxyanthranilic acid and quinolinic acid have been shown to inhibit T-cell proliferation resulting in a decrease in cell growth of natural killer cells and T cells. Furthermore, metabolites such as  l-kynurenine have been shown to inhibit proliferation of melanoma cells in vitro. Considering these metabolite properties, the present study aimed to explore the in vitro effects of  l-kynurenine, quinolinic acid and kynurenic acid on endothelioma sEnd-2 cells and on endothelial (EA. hy926 cells) (control cell line). The in vitro effect at 24, 48, and 72 h exposure to a range of 1-4 mM of the respective kynurenine metabolites on the two cell lines in terms of cell morphology, cell cycle progression and induction of apoptosis was assessed. The half inhibitory concentration (IC50), as determined using nonlinear regression, for  l-kynurenine, quinolinic acid and kynurenic acid was 9.17, 15.56, and 535.40 mM, respectively. Optical transmitted light differential interference contrast and hematoxylin and eosin staining revealed cells blocked in metaphase, formation of apoptotic bodies and compromised cell density in  l-kynurenine-treated cells. A statistically significant increase in the number of cells present in the sub-G1 phase was observed in  l-kynurenine-treated sample. To our knowledge, this was the first in vitro study conducted to investigate the mechanism of action of kynurenine metabolites on endothelioma sEnd-2 cells. It can be concluded that  l-kynurenine exerts an antiproliferative effect on the endothelioma sEnd-2 cell line by decreasing cell growth and proliferation as well as a metaphase block. These hallmarks suggest cell death via apoptosis. Further research will be conducted on  l-kynurenine to assess the effect on cell adhesion in vitro and in vivo as cell-cell adhesion has been shown to increase metastasis to distant organs therefore, the inhibition of adhesion may lead to a decrease in metastasis.

In vitro effects and mathematical modelling of CTCE-9908 (a chemokine receptor 4 antagonist) on melanoma cell survival.

CTCE-9908, a CXC chemokine receptor 4 (CXCR4) antagonist, prevents CXCR4 phosphorylation and inhibits the interaction with chemokine ligand 12 (CXCL12) and downstream signalling pathways associated with metastasis. This study evaluated the in vitro effects of CTCE-9908 on B16 F10 melanoma cells with the use of mathematical modelling. Crystal violet staining was used to construct a mathematical model of CTCE-9908 B16 F10 (melanoma) and RAW 264.7 (non-cancerous macrophage) cell lines on cell viability to predict the half-maximal inhibitory concentration (IC50). Morphological changes were assessed using transmission electron microscopy. Flow cytometry was used to assess changes in cell cycle distribution, apoptosis via caspase-3, cell survival via extracellular signal-regulated kinase1/2 activation, CXCR4 activation and CXCL12 expression. Mathematical modelling predicted IC50 values from 0 to 100 h. At IC50, similar cytotoxicity between the two cell lines and ultrastructural morphological changes indicative of cell death were observed. At a concentration 10 times lower than IC50, CTCE-9908 induced inhibition of cell survival (p = 0.0133) in B16 F10 cells but did not affect caspase-3 or cell cycle distribution in either cell line. This study predicts CTCE-9908 IC50 values at various time points using mathematical modelling, revealing cytotoxicity in melanoma and non-cancerous cells. CTCE-9908 significantly inhibited melanoma cell survival at a concentration 10 times lower than the IC50 in B16 F10 cells but not RAW 264.7 cells. However, CTCE-9908 did not affect CXCR4 phosphorylation, apoptosis,\ or cell cycle distribution in either cell line.

L-kynurenine and quinolinic acid inhibited markers of cell survival in B16 F10 melanoma cells in vitro.

Melanoma is an aggressive malignancy and remains a major cause of skin cancer mortality, highlighting the need for new treatment strategies. Recent findings revealed that L-kynurenine and quinolinic acid induce cytotoxicity and morphological changes in B16 F10 melanoma cells in vitro. This paper highlights the effects of L-kynurenine and quinolinic acid at previously determined half-maximal inhibitory concentrations on cell cycle progression, cell death and extracellular signal-regulated protein kinase inhibition. Melanoma, B16 F10 and murine macrophages, RAW 264.7 cells were used in this study, as both cell lines express all the enzymes associated with the kynurenine pathway. Post exposure to the compounds at half-maximal inhibitory concentrations, transmission electron microscopy was used to assess intracellular morphological changes. Flow cytometry was used to analyse cell cycle progression and quantify apoptosis via the dual staining of Annexin V and propidium iodide and cell survival via extracellular signal-regulated protein kinase. L-kynurenine and quinolinic acid at half-maximal inhibitory concentrations induced intracellular morphological changes representative of cell death. Flow cytometry revealed alterations in cell cycle distribution, increased apoptosis and significantly inhibition of cell survival. L-kynurenine and quinolinic acid are exogenous kynurenine compounds which inhibited cell survival through extracellular signal-regulated protein kinase inhibition, induced cell cycle alterations and induced apoptosis in B16 F10 melanoma cells.

Gastrointestinal Effects on the Antioxidant and Immunomodulatory Properties of South African Fynbos Honey.

The Fynbos biome, Western Cape Province, South Africa, produces a unique honey from Apis mellifera capensis. The bioactivity of Fynbos (FB1-FB6) honeys and Manuka, unique manuka factor 15+ (MAN UMF15+) honey subjected to simulated in vitro digestion, was compared. The effect of each phase of digestion on the antioxidant properties and nitric oxide- (NO-) associated immunomodulatory effects was determined. The total phenolic content of MAN (UMF15+) was higher than that of FB honeys, and following digestion, the percentage bioaccessibility (BA) was 68.6% and 87.1 ± 27.0%, respectively. With the Trolox equivalent antioxidant capacity assay, the activity of FB1 and FB6 was similar to MAN (UMF15+) but reduced for FB2, FB3, FB4, and FB5 with a %BA of 77.9% for MAN (UMF15+) and 78.2 ± 13.4% for FB. The oxygen radical absorbance capacity of MAN (UMF15+) and FB honeys was similar and unaltered with digestion. In a cellular environment, using colon adenocarcinoma (Caco-2) cells, both undigested and the gastric digested honey reduced 2,2'-azobis-(2-amidinopropane) dihydrochloride- (AAPH-) mediated peroxyl radical formation. In contrast, following gastroduodenal digestion, the formation of reactive oxygen species (ROS) was increased. In murine macrophage (RAW 264.7) cells, all honeys induced different levels of NO which was significantly increased with digestion for MAN (UMF15+) and FB1. In LPS/IFN-γ stimulated RAW 264.7 macrophages, only undigested MAN (UMF15+) effectively reduced NO levels, and with digestion, NO scavenging activity of MAN (UMF15+) was reduced but increased for FB5 and FB6. In a noncellular environment, MAN (UMF15+), FB1, FB2, and FB6 scavenged NO, and with digestion, this activity was maintained. This study has identified that undigested and gastric-digested FB honey has antioxidant properties with strong potential anticancer effects following gastroduodenal digestion, related to ROS formation. MAN (UMF15+) had anti-inflammatory effects which were lost postdigestion, and in contrast, FB5 and FB6 had anti-inflammatory effects postdigestion.

An in vitro investigation of l-kynurenine, quinolinic acid, and kynurenic acid on B16 F10 melanoma cell cytotoxicity and morphology.

The metastatic behavior of melanoma has accentuated the need for specific therapy targets. Compounds, namely l-kynurenine ( l-kyn), quinolinic acid (Quin), and kynurenic acid (KA) previously displayed antiproliferative and cytotoxic effects in vitro against cancer cells. Despite the growing interest in these compounds there are limited studies examining the in vitro effects on melanoma. In B16 F10 melanoma cells, RAW 264.7 macrophage cells, and HaCat keratinocyte cells, postexposure to the compounds, crystal violet staining was used to determine the half-maximal inhibitory concentration (IC50 ), whereas polarization-optical transmitted light differential interference contrast and light microscopy after hematoxylin and eosin (H&E) staining was used to assess morphological changes.  l-kyn, Quin, and KA-induced cytotoxicity in all cell lines, with  l-kyn being the most cytotoxic compound.  l-kyn and KA at IC50 -induced morphological changes in B16 F10, RAW 264.7, and HaCat cell lines, whereas Quin had effects on B16 F10 and RAW 264.7 cells but did not affect HaCat cells.  l-kyn, Quin, and KA each display different levels of cytotoxicity, which were cell line specific.  l-kyn was shown to be the most potent compound against all cell lines and may offer future treatment strategies when combined with other viable treatments against melanoma.

The tryptophan-kynurenine pathway in immunomodulation and cancer metastasis.

INTRODUCTION: The activation of the kynurenine pathway in cancer progression and metastasis through immunomodulatory pathways has drawn attention to the potential for kynurenine pathway inhibition. The activation of the kynurenine pathway, which results in the production of kynurenine metabolites through the degradation of tryptophan, promotes the development of intrinsically malignant properties in cancer cells while facilitating tumour immune escape. In addition, kynurenine metabolites act as biologically active substances to promote cancer development and metastasis. METHODS: A literature review was conducted to investigate the role of the tryptophan-kynurenine pathway in immunomodulation and cancer metastasis. RESULTS: Evidence suggests that several enzymes and metabolites implicated in the kynurenine pathway are overexpressed in various cancers. As such, the tryptophan pathway represents a promising target for cancer treatment. However, downstream signalling pathways, including aryl hydrocarbon receptor activation, have previously induced diverse biological effects in various malignancies, which resulted in either the promotion or the inhibition of metastasis. CONCLUSION: As a result, a thorough investigation of the kynurenine pathway and its regulatory mechanisms is necessary in order to properly comprehend the effects of kynurenine pathway activation involved in cancer development and metastasis.

Chemokines as possible therapeutic targets in metastatic melanoma.

BACKGROUND: Cutaneous melanoma is a relentless form of cancer which continues to rise in incidence. Currently, cutaneous melanoma is the leading cause of skin cancer-related mortality, which can mainly be attributed to its metastatic potential. The activation of chemokine axes is a major contributor to melanoma metastasis through its involvement in promoting tumour cell migration, proliferation, survival, and adhesion. This review will focus on the role of chemokines in melanoma and possible therapeutic strategies to alter chemokine activation and subsequently inhibit the activation of signalling cascades that may promote metastasis. METHODS: A literature review was conducted to evaluate chemokines as possible therapeutic targets in metastatic melanoma. RESULTS: The crosstalk between signalling pathways and immune responses in the melanoma microenvironment resembles a complex and dynamic system. Therefore, the involvement of governing chemokine axes in the promotion of cutaneous and metastatic melanoma demands a proper understanding of the tumour microenvironment in order to identify possible targets and develop appropriate treatments against melanoma. CONCLUSION: Even though chemokine axes are regarded as promising therapeutic targets, it has become increasingly evident that chemokines can play a critical role in both tumour inhibition and promotion. The inhibition of chemokine axes to inhibit signalling cascades in target cells that regulate metastasis should, therefore, be carefully approached.

The involvement of a chemokine receptor antagonist CTCE-9908 and kynurenine metabolites in cancer development.

Cancer is the second leading cause of mortality worldwide. Skin cancer is the most common cancer in South Africa with nearly 20,000 reported cases every year and 700 deaths. If diagnosed early, the 5-year survival rate is about 90%, however, when diagnosed late, the 5-year survival rate decreases to about 20%. Melanoma is a type of skin cancer with an estimated 5-year survival rate of approximately 90%. Neuroblastoma is a paediatric cancer with a low survival rate. Sixty percent of patients with metastatic disease do not survive 5 years after diagnosis. Despite recent advances in targeted therapies, there is a crucial need to identify reliable prognostic biomarkers which will be able to contribute to the development of more precision-based chemotherapeutic strategies to prevent tumour migration and metastasis. The compound, CTCE-9908 inhibits the binding of CXC chemokine ligand 12 (CXCL12) to the CXC chemokine receptor 4 (CXCR4) receptor leading to reduced metastasis. Kynurenine metabolites are derived tryptophan, which is an essential amino acid. Kynurenine metabolites inhibit T-cell proliferation resulting in cell growth arrest. For this reason, chemokines receptors represent potential targets for the treatment of cancer growth and metastasis. In this review paper, the role of the CXCL12/CXCR4 signalling pathway in the development of cancer is highlighted together with the current available treatments involving the CTCE-9908 compound in combination with microtubule inhibitors like paclitaxel and docetaxel.

How methylglyoxal kills bacteria: An ultrastructural study.

Antibacterial activity of honey is due to the presence of methylglyoxal (MGO), H2O2, bee defensin as well as polyphenols. High MGO levels in manuka honey are the main source of antibacterial activity. Manuka honey has been reported to reduce the swarming and swimming motility of Pseudomonas aeruginosa due to de-flagellation. Due to the complexity of honey it is unknown if this effect is directly due to MGO. In this ultrastructural investigation the effects of MGO on the morphology of bacteria and specifically the structure of fimbriae and flagella were investigated. MGO effectively inhibited Gram positive (Bacillus subtilis; MIC 0.8 mM and Staphylococcus aureus; MIC 1.2 mM) and Gram negative (P. aeruginosa; MIC 1.0 mM and Escherichia coli; MIC 1.2 mM) bacteria growth. The ultrastructural effects of 0.5, 1.0 and 2 mM MGO on B. substilis and E. coli morphology was then evaluated. At 0.5 mM MGO, bacteria structure was unaltered. For both bacteria at 1 mM MGO fewer fimbriae were present and the flagella were less or absent. Identified structures appeared stunted and fragile. At 2 mM MGO fimbriae and flagella were absent while the bacteria were rounded with shrinkage and loss of membrane integrity. Antibacterial MGO causes alterations in the structure of bacterial fimbriae and flagella which would limit bacteria adherence and motility.