Flavonoids as regulators of TIMPs expression in cancer: Consequences, opportunities, and challenges.

Cancer is one of the leading causes of death in patients worldwide, where invasion and metastasis are directly responsible for this statement. Although cancer therapy has progressed in recent years, current therapeutic approaches are ineffective due to toxicity and chemoresistance. Therefore, it is essential to evaluate other treatment options, and natural products are a promising alternative as they show antitumor properties in different study models. This review describes the regulation of tissue inhibitors of metalloproteinases (TIMPs) expression and the role of flavonoids as molecules with the antitumor activity that targets TIMPs therapeutically. These inhibitors regulate tissue extracellular matrix (ECM) turnover; they inhibit matrix metalloproteinases (MMPs), cell migration, invasion, and angiogenesis and induce apoptosis in tumor cells. Data obtained in cell lines and in vivo models suggest that flavonoids are chemopreventive and cytotoxic against various types of cancer through several mechanisms. Flavonoids also regulate crucial signaling pathways such as focal adhesion kinase (FAK), phosphatidylinositol-3-kinase (PI3K)-Akt, signal transducer and activator of transcription 3 (STAT3), nuclear factor κB (NFκB), and mitogen-activated protein kinase (MAPK) involved in cancer cell migration, invasion, and metastasis. All these data reposition flavonoids as excellent candidates for use in cancer therapy.

Mangiferin-Loaded Polymeric Nanoparticles: Optical Characterization, Effect of Anti-topoisomerase I, and Cytotoxicity.

Mangiferin is an important xanthone compound presenting various biological activities. The objective of this study was to develop, characterize physicochemical properties, and evaluate the anti-topoisomerase activity of poly(lactic-co-glycolic acid) (PLGA) nanoparticles containing mangiferin. The nanoparticles were developed by the emulsion solvent evaporation method and the optimal formulation was obtained with a response surface methodology (RSM); this formulation showed a mean size of 176.7 ± 1.021 nm with a 0.153 polydispersibility index (PDI) value, and mangiferin encapsulation efficiency was about 55%. The optimal conditions (6000 rpm, 10 min, and 300 µg of mangiferin) obtained 77% and the highest entrapment efficiency (97%). The in vitro release profile demonstrated a gradual release of mangiferin from 15 to 180 min in acidic conditions (pH 1.5). The fingerprint showed a modification in the maximum absorption wavelength of both the polymer and the mangiferin. Results of anti-toposiomerase assay showed that the optimal formulation (MG4, 25 µg/mL) had antiproliferative activity. High concentrations (2500 µg/mL) of MG4 showed non-in vitro cytotoxic effect on BEAS 2B and HEPG2. Finally, this study showed an encapsulation process with in vitro gastric digestion resistance (1.5 h) and without interfering with the metabolism of healthy cells and their biological activity.

Structural and functional characterization of the divergent Entamoeba Src using Src inhibitor-1.

BACKGROUND: The abundant number of kinases that Entamoeba histolytica possesses allows us to assume that the regulation of cellular functions by phosphorylation-dephosphorylation processes is very important. However, the kinases responsible for the phosphorylation in Entamoeba spp. vary in the structure of their domains and, therefore, could be responsible for the unusual biological characteristics of this parasite. In higher eukaryotes, Src kinases share conserved structural domains and are very important in the regulation of the actin cytoskeleton. In both Entamoeba histolytica and Entamoeba invadens, the major Src kinase homologue of higher eukaryotes lacks SH3 and SH2 domains, but does have KELCH domains; the latter are part of actin cross-linking proteins in higher eukaryotic cells. METHODS: The function of the EhSrc protein kinase of Entamoeba spp. was evaluated using Src inhibitor-1, microscopy assays, Src kinase activity and western blot. In addition, to define the potential inhibitory mechanism of Src-inhibitor-1 for the amoebic EhSrc protein kinase, molecular dynamic simulations using NAnoscale Molecular Dynamics (NAMD2) program and docking studies were performed with MOE software. RESULTS: We demonstrate that Src inhibitor-1 is able to prevent the activity of EhSrc protein kinase, most likely by binding to the catalytic domain, which affects cell morphology via the disruption of actin cytoskeleton remodeling and the formation of phagocytic structures without an effect on cell adhesion. Furthermore, in E. invadens, Src inhibitor-1 inhibited the encystment process by blocking RhoA GTPase activity, a small GTPase protein of Rho family. CONCLUSIONS: Even though the EhSrc molecule of Entamoeba is not a typical Src, because its divergent amino acid sequence, it is a critical factor in the biology of this parasite via the regulation of actin cytoskeleton remodeling via RhoA GTPase activation. Based on this, we conclude that EhSrc could become a target molecule for the future design of drugs that can prevent the transmission of the disease.

EVALUATION OF ANTICANCER POTENTIAL OF EIGHT VEGETAL SPECIES FROM THE STATE OF OAXACA.

BACKGROUND: Eight plant species from Oaxaca, some of them used in traditional medicine, were subjected to screening of several biological activities to provide data regarding their anticancer potential, although no scientific information is available about their pharmacological effects. MATERIALS AND METHODS: Methanol extracts from stems or roots of the eight plants were tested for antioxidant activity by the DPPH- method. Antimicrobial activity was determined using the agar diffusion method and the minimal inhibitory concentration (MIC) was obtained by broth dilution method. Antitopoisomerase activity was assessed using mutant strains of Saccharomyces cerevisiae JN362a, JN394, JN394t-1, JN394t2.4 and JN394t2-5. The mutagenic activity was evaluated using the Ames test (Salmonella typhimurium TA1535). RESULTS: No extract showed significant antioxidant activity. The best antimicrobial activity was observed for Salpianthus arenarius (MIC 56.25 µg/mL) and Lantana achyranthifolia (MIC 78.12 µg/mL) against Staphylococcus aureus. Extracts of Acalypha cuspidata, Alloispermum integrifolium and L. achyranthifolia stems showed antitopoisomerase II activity with JN394t-1 growth of -30.88±0.0%, -38.11±4.95%, and -70.97±12.02% respectively. Galium mexicanum stem extract showed antitopoisomerase I activity with growth of 35.31±6.36% on the same mutant strain. All plant extracts were non-mutagenic. Fractionation of A. cuspidata extract led to identification of two subfractions with antitopoisomerase I and II activity at 154µg/mL (Positive controls 50 and 100µg/mL). CONCLUSION: Methanol extracts of A. cuspidata, A. integrifolium, G. mexicanum, and L. achyranthifolia stems showed antitopoisomerase and non-mutagenic activities, and consequently could be promising as a source of anticancer drugs.

The calmodulin antagonist W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride) inhibits DENV infection in Huh-7 cells.

Dengue virus (DENV) replicative cycle occurs in the endoplasmic reticulum where calcium ions play an important role in cell signaling. Calmodulin (CaM) is the primary sensor of intracellular Ca2+ levels in eukaryotic cells. In this paper, the effect of the calmodulin antagonist W-7 in DENV infection in Huh-7 cells was evaluated. W7 inhibited viral yield, NS1 secretion and viral RNA and protein synthesis. Moreover, luciferase activity, encoded by a DENV replicon, was also reduced. A decrease in the replicative complexes formation was clearly observed in W7 treated cells. Docking simulations suggest 2 possible mechanisms of action for W7: the direct inhibition of NS2B-NS3 activity and/or inhibition of the interaction between NS2A with Ca2+-CaM complex. This last possibility was supported by the in vitro interaction observed between recombinant NS2A and CaM. These results indicate that Ca2+-CaM plays an important role in DENV replication.

Antiamoebic Activity of Adenophyllum aurantium (L.) Strother and Its Effect on the Actin Cytoskeleton of Entamoeba histolytica.

In Mexico, the Adenophyllum aurantium (L.) Strother plant is consumed as an infusion to treat intestinal diseases such as amoebiasis, which is an endemic health problem in Mexico and other countries. However, the effect of A. aurantium on Entamoeba histolytica, the causative agent of amoebiasis, is unknown. An aerial part methanolic extract (AaMeA), a root methanolic extract (AaMeR) and a root ethyl acetate extract (AaEaR) were tested on E. histolytica trophozoites. AaMeA and AaMeR did not show antiproliferative activity; however, AaEaR exhibited an in vitro GI50 of 230 µg/ml, and it was able to inhibit the differentiation of Entamoeba invadens trophozoites into cysts. The intraperitoneal administration of AaEaR (2.5 or 5 mg) to hamsters that were infected with E. histolytica inhibited the development of amoebic liver abscesses in 48.5 or 89.0% of the animals, respectively. Adhesion to fibronectin and erythrophagocytosis were 28.7 and 37.5% inhibited by AaEaR, respectively. An ultrastructure analysis of AaEaR-treated trophozoites shows a decrease in the number of vacuoles but no apparent cell damage. Moreover, this extract affected the actin cytoskeleton structuration, and it prevented the formation of contractile rings by mechanism(s) that were independent of reactive oxygen species and RhoA activation pathways. (13)C NMR data showed that the major compounds in the AaEaR extract are thiophenes. Our results suggest that AaEaR may be effective in treatments against amoebiasis, nevertheless, detailed toxicity studies on thiophenes, contained in AaEaR, are required to avoid misuse of this vegetal species.

Entamoeba invadens: Identification of a SERCA protein and effect of SERCA inhibitors on encystation.

Calcium has an important role on signaling of different cellular processes, including growth and differentiation. Signaling by calcium also has an essential function in pathogenesis and differentiation of the protozoan parasites Entamoeba histolytica and Entamoeba invadens. However, the proteins of these parasites that regulate the cytoplasmic concentration of this ion are poorly studied. In eukaryotic cells, the calcium-ATPase of the SERCA type plays an important role in calcium homeostasis by catalyzing the active efflux of calcium from cytoplasm to endoplasmic reticulum. Here, we reported the identification of SERCA of E. invadens (EiSERCA). This protein contains a putative sequence for endoplasmic reticulum retention and all domains involved in calcium transport identified in mammalian SERCA. By immunofluorescence assays, an antibody against SERCA of E. histolytica detected EiSERCA in a vesicular network in the cytoplasm of E. invadens trophozoites, co-localizing with calreticulin. Interestingly, EiSERCA was redistributed close to plasma membrane during encystation, suggesting that this pump could participate in regulate the calcium concentration during this process. In addition, thapsigargin and cyclopiazonic acid, both specific inhibitors of SERCA, affected the number and structure of cysts, supporting the hypothesis that calcium flux mediated by SERCA has an important role in the life cycle of Entamoeba.