Study on cytotoxicity and structure-activity relationship of HL-7702 cell exposed to naphthoquinones

Biogenic nanoporous silicon carrier improves the efficacy of buparvaquone against resistant visceral leishmaniasis

Visceral leishmaniasis is a vector-borne protozoan infection that is fatal if untreated. There is no vaccination against the disease, and the current chemotherapeutic agents are ineffective due to increased resistance and severe side effects. Buparvaquone is a potential drug against the leishmaniases, but it is highly hydrophobic resulting in poor bioavailability and low therapeutic efficacy. Herein, we loaded the drug into silicon nanoparticles produced from barley husk, which is an agricultural residue and widely available. The buparvaquone-loaded nanoparticles were several times more selective to kill the intracellular parasites being non-toxic to macrophages compared to the pure buparvaquone and other conventionally used anti-leishmanial agents. Furthermore, the in vivo results revealed that the intraperitoneally injected buparvaquone-loaded nanoparticles suppressed the parasite burden close to 100%. By contrast, pure buparvaquone suppressed the burden only by 50% with corresponding doses. As the conclusion, the biogenic silicon nanoparticles are promising carriers to significantly improve the therapeutic efficacy and selectivity of buparvaquone against resistant visceral leishmaniasis opening a new avenue for low-cost treatment against this neglected tropical disease threatening especially the poor people in developing nations.

Hepatocellular Toxicity of Paris Saponins I, II, VI and VII on Two Kinds of Hepatocytes-HL-7702 and HepaRG Cells, and the Underlying Mechanisms

Rhizoma paridis is a popularly-used Chinese medicine in clinics, based on the pharmacodynamic properties of its saponin components. The four main saponins in Rhizoma paridis are designated saponins I, II, VI, and VII. At present, much attention is focused on the anticancer effect of Rhizoma paridis which is manifested in its cytotoxicity to various cancer cells. The purpose of this study was to investigate the hepatocellular toxicities of the four saponins in Rhizoma paridis and the relative intensities of their cytotoxic effects. It was found that the four saponins were cytotoxic to two types of hepatocytes-HL-7702 and HepaRG cells. The cytotoxicities of the four saponins to the two cell models were compared. One of the most cytotoxic saponins was Rhizoma paridis saponin I (PSI). This was used to determine the mechanism of hepatocellular toxicity. Results from MTT assays demonstrated that the four saponins induced apoptosis of the two hepatocyte models in a dose-dependent and time-dependent manner. In addition, fluorescent 4′,6-diamidino-2-phenylindole (DAPI) staining was used to observe the morphological changes of HepaRG cells after saponin administration. Further, as the concentration increased, PSI-induced lactate dehydrogenase (LDH) release from HepaRG cells increased gradually. In addition, PSI enhanced the levels of reactive oxygen species (ROS) and blocked the S and G2 phases of the cell cycle in HepaRG cells. A western blot indicated that PSI upregulated the protein expression levels of p53, p21, and Fas. Furthermore, the PSI-induced changes in the p53 protein increased the Bax/bcl-2 ratio, resulting in enhancement of the release of mitochondrial cytochrome c, activation of caspases-3, -8, and -9, poly-ADP ribose polymerase (PARP), and ultimately apoptosis. Increased Fas protein activated caspase-8, which led to the activation of caspase-3 and its downstream PARP protein, resulting in cell apoptosis. These results indicate that PSI induced apoptosis in HepaRG cells through activation of ROS and death receptor pathways. The results obtained in this study suggest that the hepatocellular toxicity of saponins in Rhizoma paridis should be considered during the clinical application of this drug. In addition, they provide a reference for future anti-cancer studies on Rhizoma paridis.

Cytotoxicity, hemolysis and in vivo acute toxicity of 2-hydroxy-3-anilino-1,4-naphthoquinone derivatives

The 1,4-naphthoquinones, important members of the family of quinones are used as both crude extracts and as compound manipulated by the pharmaceutical industry. They have gained great emphasis by presenting different pharmacological properties as antibacterial, antiviral, antiprotozoal and anthelmintic, and has antitumor activity. Our aim was to evaluate the cytotoxicity, hemolytic activity and in vivo acute toxicity of three derivatives of 2-hydroxy-1,4-naphthoquinones. The cell viability in vitro against RAW Cell Line displayed IC₅₀ ranging of 483.5–2044.8 μM, whereas in primary culture tests using murine macrophages, IC₅₀ were 315.8–1408.0 μM for naphthoquinones derivatives 4a and 4c respectively, besides no hemolysis was observed at the dose tested. The in vivo acute toxicity assays exhibited a significant safety margin indicated by a lack of systemic and behavioral toxicity up to 300 mg/kg, and at a dose of 1000 mg/kg the derivatives not triggering signs of toxicity although the compound 4a have promoted hepatic steatosis and hyperemia in kidney tissue. Thereby, these modifications decrease the toxicity of the tested derivatives naphthoquinones, providing a high potential for the development of news drugs.

Amphipathic silica nanoparticles induce cytotoxicity through oxidative stress mediated and p53 dependent apoptosis pathway in human liver cell line HL-7702 and rat liver cell line BRL-3A

The aim of this study was to evaluate the potential cytotoxicity and the underlying mechanism of amphipathic silica nanoparticles (SiO2 NPs) exposure to human normal liver HL-7702 cells and rat normal liver BRL-3A cells. Prior to the cellular studies, transmission electron microscopy (TEM), dynamic light scattering (DLS), and X ray diffraction (XRD) were used to characterize SiO2 NPs, which proved the amorphous nature of SiO2 NPs with TEM diameter of 19.8±2.7nm. Further studies proved that exposure to SiO2 NPs dose-dependently induced cytotoxicity as revealed by cell counting kit (CCK-8) and lactate dehydrogenase (LDH) assays, with more severe cytotoxicity in HL-7702 cells than BRL-3A cells. Reactive oxygen species (ROS) and glutathione (GSH) assays showed elevated oxidative stress in both cells. Morphological studies by microscopic observation, Hochest 33258 and AO/EB staining indicated significant apoptotic changes after the cells being exposed to SiO2 NPs. Further studies by western blot indicated that SiO2 NPs exposure to both cells up-regulated p53, Bax and cleaved caspase-3 expression and down-regulated Bcl-2 and caspase-3 levels. Activated caspase-3 activity detected by colorimetric assay kit and caspase-3/7 activity detected by fluorescent real-time detection kit were significantly increased by SiO2 NPs exposure. In addition, antioxidant vitamin C significantly attenuated SiO2 NPs-induced caspase-3 activation, which indicated that SiO2 NPs-induced oxidative stress was involved in the process of HL-7702 and BRL-3A cell apoptosis. Taken together, these results suggested that SiO2 NPs-induced cytotoxicity in HL-7702 and BRL-3A cells was through oxidative stress mediated and p53, caspase-3 and Bax/Bcl-2 dependent pathway and HL-7702 cells were more sensitive to SiO2 NPs-induced cytotoxicity than BRL-3A cells.

Targeting of Helicobacter pylori thymidylate synthase ThyX by non-mitotoxic hydroxy-naphthoquinones

ThyX is an essential thymidylate synthase that is mechanistically and structurally unrelated to the functionally analogous human enzyme, thus providing means for selective inhibition of bacterial growth. To identify novel compounds with anti-bacterial activity against the human pathogenic bacterium Helicobacter pylori, based on our earlier biochemical and structural analyses, we designed a series of eighteen 2-hydroxy-1,4-naphthoquinones (2-OH-1,4-NQs) that target HpThyX. Our lead-like molecules markedly inhibited the NADPH oxidation and 2′-deoxythymidine-5′-monophosphate-forming activities of HpThyX enzyme in vitro, with inhibitory constants in the low nanomolar range. The identification of non-cytotoxic and non-mitotoxic 2-OH-1,4-NQ inhibitors permitted testing their in vivo efficacy in a mouse model for H. pylori infections. Despite the widely assumed toxicity of naphthoquinones (NQs), we identified tight-binding ThyX inhibitors that were tolerated in mice and can be associated with a modest effect in reducing the number of colonizing bacteria. Our results thus provide proof-of-concept that targeting ThyX enzymes is a highly feasible strategy for the development of therapies against H. pylori and a high number of other ThyX-dependent pathogenic bacteria. We also demonstrate that chemical reactivity of NQs does not prevent their exploitation as anti-microbial compounds, particularly when mitotoxicity screening is used to prioritize these compounds for further experimentation.

In-vitro sensitivity of Pakistani Leishmania tropica field isolate against buparvaquone in comparison to standard anti-leishmanial drugs

In this study, in vitro anti-leishmanial activity of buparvaquone was evaluated against promastigotes and intracellular amastigotes of Pakistani Leishmania tropica isolate KWH23 in relation to the current standard chemotherapy for leishmaniasis (sodium stibogluconate, sodium stibogluconate, amphotericin B and miltefosine). For buparvaquone, mean % inhibition in intracellular amastigotes at four different concentrations (1.35 µM, 0.51 µM, 0.17 µM and 0.057 µM) was 78%, 44%, 20% and 14% respectively, whereas, against promastigotes it was 89%, 77%, 45% and 35% respectively. IC50 values calculated to estimate the anti-leishmanial activity of buparvaquone against intra-cellular amastigotes and promastigotes was 0.53 µM (95% C.I. = 0.32-0.89) and 0.15 µM (95% C.I. = 0.01-1.84) respectively. Amphotericin B was the most potent in-vitro drug tested, with an IC50 of 0.075 µM (95% C.I. = 0.006-0.907) against promastigotes, and 0.065 µM (95% C.I. = 0.048-0.089) against intra-cellular amastigotes. Amphotericin B was more cytotoxic against THP1 cells, with an IC50 of 0.15 µM (95% C.I. = 0.01-0.95) and an apparent in-vitro therapeutic index of 2.0, than was buparvaquone, with an IC50 of 12.03 µM (95% C.I. = 5.36-26.96) against THP1 cells and a therapeutic index of 80.2. The study proposes that buparvaquone may be further investigated as a candidate drug for treatment of cutaneous leishmaniasis.

Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators.

Antifungal activity of naphthoquinoidal compounds in vitro against fluconazole-resistant strains of different Candida species: a special emphasis on mechanisms of action on Candida tropicalis

In recent decades, the incidence of candidemia in tertiary hospitals worldwide has substantially increased. These infections are a major cause of morbidity and mortality; in addition, they prolong hospital stays and raise the costs associated with treatment. Studies have reported a significant increase in infections by non-albicans Candida species, especially C. tropicalis. The number of antifungal drugs on the market is small in comparison to the number of antibacterial agents available. The limited number of treatment options, coupled with the increasing frequency of cross-resistance, makes it necessary to develop new therapeutic strategies. The objective of this study was to evaluate and compare the antifungal activities of three semisynthetic naphthofuranquinone molecules against fluconazole-resistant Candida spp. strains. These results allowed to us to evaluate the antifungal effects of three naphthofuranquinones on fluconazole-resistant C. tropicalis. The toxicity of these compounds was manifested as increased intracellular ROS, which resulted in membrane damage and changes in cell size/granularity, mitochondrial membrane depolarization, and DNA damage (including oxidation and strand breakage). In conclusion, the tested naphthofuranquinones (compounds 1-3) exhibited in vitro cytotoxicity against fluconazole-resistant Candida spp. strains.