Moderate Toxicity of Potential Boron-containing Therapeutic, Dipotassium-trioxohydroxytetrafl uorotriborate - K2 (B3 O3 F4 OH) in Rats and Mice

Abstract Biological activity of boron-containing compounds (BCCs) has been well-known. Growing interest and numerous applications for BCCs have been reported. Boron and boron-containing acids show low acute toxicity in mammals but data on halogenated boroxine (HB) - dipotassium-trioxohydroxytetrafluorotriborate, K2(B3O3F4OH) acute toxicity have not been reported before. This compound, characterized as a potential therapeutic for skin changes, exhibits no observable genotoxicity in doses lower that 0.1 mg/ml in vitro and 55 mg/kg in vivo. It has also been confirmed as an antitumour agent both in vitro and in vivo as well as an inhibitor of enzymes involved in antioxidant mechanisms. The aim of this study was to assess the acute toxicity of HB and to determine the maximum tolerated dose as well as a dose free of any signs of toxicity in different test organisms. Acute toxicity of HB was tested in Sprague-Dawley and Wistar rats and BALB/c mice after single parenteral application of different doses. We determined doses free of any sign of toxicity and LD50 after single dose administration. LD50 of HB ranges from 63 to 75 mg/kg in different test models, meaning that HB shows moderate toxicity

Novel boron-containing compound, halogenated boroxine, induces selective cytotoxicity through apoptosis triggering in UT-7 leukemia.

Apoptosis induction is a promising approach in targeting tumor cells. As halogenated boroxine (HB) shows antitumor activity, but its mechanism of action in hematological tumors remains unclear, in this study, we aimed to analyze apoptosis triggering in normal and UT-7 leukemia cells by HB. Methods for assessing cell viability and cytotoxicity, apoptosis detection, relative expression of 84 apoptosis-associated genes and BCL-2, and functional analysis were applied. Pronounced HB activities in inhibition of cell viability, cytotoxicity, and apoptosis induction with measurable differences between tumor and normal cells were found. HB modulated the expression of 21 genes, predominantly downregulated the antiapoptotic genes in leukemia. The functional association revealed HB's impact on inhibition of NF-κB signaling pathway. BCL-2 expression decreasing was found only in UT-7 leukemia. This study identified HB as an apoptosis inducer affecting leukemia but not normal cells considering mechanisms of selective activity that may be a great advantage of HB applications.

Biochemical and histomorphological findings in Swiss Wistar rats treated with potential boron-containing therapeutic - K2[B3O3F4OH].

BACKGROUND: Boron and boron containing compounds are known for their biological and protective roles being non-toxic and non-mutagenic in low concentrations. Male rats were exposed to halogenated boroxine (HB), dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH], a potential new boron-containing therapeutic, aiming to determine concentrations with no adverse effects on selected serum biochemical parameters and histomorphological features. METHODS: HB was prepared by reacting potassium hydrofluoride (KHF2) with boric acid in molar ratios 2:3 at room temperature and its primary structure contains 4 fluorine atoms substituted in 6-membered ring. In concentrations of 10, 25, 35 and 45 mg/kg, HB was administered intraperitoneally as a single dose. Biochemical parameters were observed 24 and 96 h following the treatment. Effects of HB on biochemical blood parameters were also observed 24 h following continuous nine days application in concentrations of 10 mg/kg intraperitoneally and 50 mg/kg per os. Histomorphological observation of kidneys, liver, spleen, lungs and heart was performed for all treated animals. RESULTS: Administration of single high dose of HB (35 mg/kg-45 mg/kg) effected high levels of urea and creatinine, which indicated renal injury that appeared to be temporary. Possible cause of concern is pancreatic injury indicated by elevated levels of serum amylase in the groups of animals that received the highest dosages of the substance. Histopathological examination of selected tissues revealed mild to moderate lesions in the kidneys and livers associated with administration of HB. CONCLUSION: Observation of biochemical serum parameters or histopathology of examined tissues revealed no adverse effects of HB either after the administration of single dose lower than 35 mg/kg or following repeated administration at 10 mg/kg. These dosages should be further considered for potential therapeutic applications.

Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate K2[B3O3F4OH] inhibits emerging multidrug-resistant and ß-lactamase-producing opportunistic pathogens.

Halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate, K2[B3O3F4OH] (boroxine) was previously shown to be very effective in inhibition of several carcinoma cell lines, including the skin cancer. Here, we investigated its antimicrobial potential by targeting the multidrug-resistant opportunistic pathogens associated with skin and wound infections. The antimicrobial testing against eleven bacterial and four fungal species revealed good activity of boroxine against pathogenic filamentous fungi Penicillium funiculosum and Aspergillus niger (MIC50 64 and 128 µg/ml), and a moderate bioactivity against the yeast Candida albicans (MIC50 512 µg/ml). Among the tested multidrug-resistant bacteria, the best antibacterial effect, stable over a 24-h period, was observed against the methicillin-resistant Staphylococcus aureus strain (MRSA) at MIC of 1024 µg/ml. The atomic force microscopy (AFM) used to investigate the morphology of S. aureus cells revealed indentations on its cell envelope after the boroxine exposure. These results show that in addition to the antitumor effect, boroxine exerts wide spectrum antimicrobial activity, thus may help preventing the development of skin and wound-related opportunistic infections.

In vitro and in vivo antitumour effects of phenylboronic acid against mouse mammary adenocarcinoma 4T1 and squamous carcinoma SCCVII cells.

The cytotoxic activity of phenylboroxine acid was evaluated in vitro on mouse mammary adenocarcinoma 4T1, mouse squamous cell carcinoma SCCVII, hamster lung fibroblast V79 and mouse dermal fibroblasts L929 cell lines. The cytotoxic effects were dose dependent for all tested tumour and non-tumour cell lines. Under in vivo conditions, three application routes of phenylboronic acid were studied: intra-peritoneal (i.p.), intra-tumour (i.t.) and per-oral. After tumour transplantation in syngeneic mice, phenylboronic acid was shown to slow the growth of both tumour cell lines (4T1 and SCCVII) compared with the control. The inhibitory effects were pronounced during the application of phenylboronic acid. For both tested tumour cell lines, the most prominent antitumour effect was obtained by intraperitoneal administration, followed significantly by oral administration.

Advantages of an Electrochemical Method Compared to the Spectrophotometric Kinetic Study of Peroxidase Inhibition by Boroxine Derivative.

In this study, boroxine derivative (K2[B3O3F4OH]) was tested as an inhibitor of horseradish peroxidase (HRP) by spectrophotometric and electrochemical methods. The activity of horseradish peroxidase was first studied under steady-state kinetic conditions by a spectrophotometric method which required the use of guaiacol as a second substrate to measure guaiacol peroxidation. The results of this method have shown that, by changing the concentration of guaiacol as the literature suggests, a different type of inhibition is observed than when changing the concentration of hydrogen peroxide as the substrate. This suggests that guaiacol interferes with the reaction in some way. The electrochemical method involves direct electron transfer of HRP immobilized in Nafion nanocomposite films on a glassy carbon (GC) electrode, creating a sensor with an electro-catalytic response to the reduction of hydrogen peroxide. The electrochemical method simplifies kinetic assays by removing the requirement of reducing substrates.

Impact of calcium ion on cytotoxic effect of the boroxine derivative, K2[B3O3F4OH].

The effect of Ca2+ ions on the cytotoxic ability of boron heterocyclic compound dipotassium-trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]), on in vitro tumor cells (mammary adenocarcinoma 4T1, melanoma B16F10 and squamous cell carcinoma SCCVII) and non-tumoral fibroblast cells (mouse dermal L929 and hamster lung V79) was examined. At small concentrations of Ca2+ ions (0.42 mM), K2[B3O3F4OH] (3.85 mM) has a very strong cytotoxic effect on all cancer cells tested (89.1, 85.6 and 84.6%) and significantly less effect on normal cells (19.5 and 24.2%), respectively. Applying larger concentrations of Ca2+ ions (9.42-72.42 mM), at the same concentration of K2[B3O3F4OH], no significant cytotoxic effect was detected on cancer cells and normal cells investigated. The selective ability of K2[B3O3F4OH], in the medium with a low concentration of Ca2+ ions has a strong cytotoxic effect on cancer cells and very weak effect in normal cells, opens up the possibility of its application in antitumor therapy.

Effects of dipotassium-trioxohydroxytetrafluorotriborate, K2[B3O3F4OH], on cell viability and gene expression of common human cancer drug targets in a melanoma cell line.

Recently it was found that dipotassium-trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), is a potent and highly specific inhibitor of precancerous cell processes. We conducted gene expression profiling of human melanoma cells before and after treatment with two concentrations (0.1 and 1 mM) of this boron inorganic derivative in order to assess its effects on deregulation of genes associated with tumor pathways. Parallel trypan blue exclusion assay was performed to assess the cytotoxicity effects of this chemical. Treatment with K2(B3O3F4OH) induced a significant decrease of cell viability in melanoma cellline at both tested concentrations. Furthermore, these treatments caused deregulation of more than 30 genes known as common anti-tumor drug targets. IGF-1 and hTERT were found to be significantly downregulated and this result may imply potential use of K2(B3O3F4OH) as an inhibitor or human telomerase and insulin-like growth factor 1, both of which are associated with various tumor pathways.

Genotoxicity Evaluation of Dipotassium -Trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), in Human Lymphocyte Cultures and Mice Reticulocytes

ABSTRACT Genotoxic effects of inorganic molecule dipotassium-trioxohydroxytetrafluorotriborate, K2(B3O3F4OH), a promising new therapeutic for the epidermal changes treatment, have been evaluated. In vitro analysis included evaluation of genotoxic and cytotoxic potential of K2(B3O3F4OH) in concentrations of 0.01, 0.02, 0.05 and 0.06 mg/mL applying cytokinesis-block micronucleus cytome assay in human lymphocyte culture. With the increase of concentration the frequency of micronuclei elevated but the differences were not significant. Also, there were no significant differences among the frequencies of nuclear buds and nucleoplasmic bridges between controls and treated cultures. Nuclear division index and nuclear division cytotoxycity index values did not reveal significant cytotoxic effect of K2(B3O3F4OH). In vivo genotoxic effects were analyzed on BALB/c mice applying reticulocytes micronucleus assay. K2(B3O3F4OH) was administrated intraperitoneally in final concentrations of 10, 20, 50 and 55 mg/kg. Significant decrease of reticulocytes ratio and increase of micronuclei frequencies against pre-treatments were found for both sampling periods of 48 and 72 hours of the highest applied concentration. This study confirmed that K2(B3O3F4OH) is not genotoxic in tested concentrations in vitro as well as in concentrations lower than 55 mg/kg in vivo. This study presents a reliable basis for further pre-clinical and potential clinical investigations.

Dipotassium-trioxohydroxytetrafluorotriborate, K2[B3O3F4OH], is a potent inhibitor of human carbonic anhydrases.

The boron heterocyclic compound dipotassium-trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]) was investigated as inhibitor of the zinc enzyme, carbonic anhydrase (CA, EC 4.2.1.1). Eleven human (h) CA isoforms, hCA I-IV, VA, VI, VII, IX and XII-XIV, were included in the investigations. The anion, similar to tetraborate or phenylboronic acid, inhibited most of them. hCA III was not inhibited by K2[B3O3F4OH], whereas hCA VA, hCA VI, hCA IX and hCA XIII were inhibited in the submillimolar range, with KIs of 0.31-0.63 mM. hCA I and II (cytosolic, widespread isoforms), hCA IV (membrane-bound isoform), hCA XII (tumor-associated, transmembrane) and hCA XIV (transmembrane) were much more effectively inhibited by this anion, with inhibition constants ranging from 25 to 93 µM. hCA VII, a cytosolic enzyme present in the brain and associated to oxidative stress, was very effectively inhibited by K2[B3O3F4OH], with a KI of 8.0 µM. We propose that K2[B3O3F4OH] binds to the metal ion from the enzyme active site, coordinating to the Zn(II) ion monodentately through its B-OH functionality. We hypothesize that some of the beneficial antitumor effects reported for K2[B3O3F4OH] may be due to the inhibition of CAs present in skin tumors.

In vitro and in vivo antitumor activity of the halogenated boroxine dipotassium-trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]).

Dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was listed as a promising new therapeutic for cancer diseases. For in vitro and in vivo investigation of its antitumor effects 4T1 mammary adenocarcinoma, B16F10 melanoma and squamous cell carcinoma SCCVII were used. The detailed in vitro investigation undoubtedly showed that K2[B3O3F4OH] affects the growth of cancer cells. The proliferation of cells depends on the concentration so that aqueous solution of K2[B3O3F4OH], the concentrations of 10(-4) M and less, does not affect cell growth, but the concentrations of 10(-3) M or more, significantly slows cells growth. B16F10 and SCCVII cells show higher sensitivity to the cytotoxic effects of K2[B3O3F4OH] compared to 4T1 cells. Under in vivo conditions, K2[B3O3F4OH] slows the growth of all three tumors tested compared to the control, and the inhibitory effect was most pronounced during the application of the substance. There is almost no difference if K2[B3O3F4OH] was applied intraperitoneally, intratumor, peroral or as ointment. Addition of 5-FU did not further increase the antitumor efficacy of K2[B3O3F4OH].

A study of the inhibition of catalase by dipotassium trioxohydroxytetrafluorotriborate K2[B3O3F4OH].

In the development of boronic acid-based enzyme inhibitors as potential pharmaceutical drugs, dipotassium trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was listed as a promising new therapeutic for treatment of these diseases. The catalase-mediated conversion of hydrogen peroxide, in the presence and absence of K2[B3O3F4OH] was studied. The kinetics conformed to the Michaelis-Menten model. Lineweaver-Burk plots were linear and plotted the family of straight lines intersected on the abscissa indicating non-competitive inhibition of the catalase. It appears that in the absence of inhibitor, catalase operates the best at conditions around pH 7.1 and in the presence of K2[B3O3F4OH] the optimum is around pH 6.2. The uncatalyzed reaction of hydrogen peroxide decomposition generally has a value of activation energy of 75 kJ mole(-1), whereas catalase, in the absence of inhibitor, lowers the value to 11.2 kJ mole(-1), while in the presence 69 mmoles L(-1) of K2[B3O3F4OH] it was 37.8 kJ mole(-1).

Effects of dipotassium trioxohydroxytetrafluorotriborate (K2[BO3F4OH]) on genetic material and inhibition of cell division in human cell cultures.

We have examined antiproliferative, cytotoxic, and genotoxic potential of a halogenated boroxine dipotassium trioxohydroxytetrafluorotriborate (K2[B3O3F4OH]). The impact on cell growth was evaluated by alamarBlue assay in basal cell carcinoma culture. Cytostatic, cytotoxic, and genotoxic potential were evaluated in lymphocytes culture, applying cytokinesis-block micronucleus cytome assay and chromosome aberrations analysis. Tested concentrations (0.05, 0.1, 0.2, and 0.4 mg/mL) were correlated with inhibition of cell growth in basal cell carcinoma culture and with the lymphocytes proliferation. Clastogenic activity has been confirmed, without evidences of aneugenic activity, in human lymphocytes.