Comparative Study of Epidemiological and Anthropological Aspects of Diabetes and Hypertension in Cameroon

The traditional medicine in Africa in general and specifically in Cameroon does not manage diabetes and arterial hypertension very well. Yet, these pathologies are becoming more prevalent among the populations that need adequate knowledge to fight against them. Therefore the present study was designed to determine the knowledge, attitudes and practices of indigenous people regarding diabetes and hypertension control, and to assess the epidemiological aspects of these diseases in order to reinforce their health education and promote a better health care through traditional medicine. To achieve this objective, 1,131 households including 70 traditional healers, 114 diabetics, 167 hypertensive patients, 30 hypertensive patients-diabetics and other Cameroonians were questioned on their ethnomedical knowledge of diabetes and arterial hypertension. Fifty-eight randomly distributed tribes were taking in account. The elucidation of anthropological and epidemiological aspects of diabetes and hypertension improved the beliefs of indigenous people and facilitated the modernization of diabetes and hypertension comprehension that remained focused on the elucidation of diseases' causes and complications, as well as on the behaviors that could help translate biomedical terms into locally meaningful metaphors.

Cadmium Chloride Induces DNA Damage and Apoptosis of Human Liver Carcinoma Cells via Oxidative Stress

Cadmium is a heavy metal that has been shown to cause its toxicity in humans and animals. Many documented studies have shown that cadmium produces various genotoxic effects such as DNA damage and chromosomal aberrations. Ailments such as bone disease, renal damage, and several forms of cancer are attributed to overexposure to cadmium. Although there have been numerous studies examining the effects of cadmium in animal models and a few case studies involving communities where cadmium contamination has occurred, its molecular mechanisms of action are not fully elucidated. In this research, we hypothesized that oxidative stress plays a key role in cadmium chloride-induced toxicity, DNA damage, and apoptosis of human liver carcinoma (HepG₂) cells. To test our hypothesis, cell viability was determined by MTT assay. Lipid hydroperoxide content stress was estimated by lipid peroxidation assay. Genotoxic damage was tested by the means of alkaline single cell gel electrophoresis (Comet) assay. Cell apoptosis was measured by flow cytometry assessment (Annexin-V/PI assay). The result of MTT assay indicated that cadmium chloride induces toxicity to HepG₂ cells in a concentration-dependent manner, showing a 48 hr-LD50 of 3.6 µg/mL. Data generated from lipid peroxidation assay resulted in a significant (p < 0.05) increase of hydroperoxide production, specifically at the highest concentration tested. Data obtained from the Comet assay indicated that cadmium chloride causes DNA damage in HepG₂ cells in a concentration-dependent manner. A strong concentration-response relationship (p < 0.05) was recorded between annexin V positive cells and cadmium chloride exposure. In summary, these in vitro studies provide clear evidence that cadmium chloride induces oxidative stress, DNA damage, and programmed cell death in human liver carcinoma (HepG₂) cells.

Hepatotoxicity and Ultra Structural Changes in Wistar Rats treated with Al2O3 Nanomaterials

The present study was designed to evaluate the hepatotoxicity of aluminium oxide (Al2O3). To achieve this objective, Al2O3 of three different sizes (30nm, 40nm and bulk) was orally administered for 28 days to 9 groups of 10 Wistar rats each, at the dose of 500, 1000 and 2000 mg/Kg/rat. A tenth group of 10 rats received distilled water and served as control. After 28 days of exposure, the animals were sacrificed and the serum was collected and tested for the activity levels of aminotransferases (AST or GOT and ALT or GPT), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) enzymes following standard testing methods. Reduced glutathione (GSH) content was also measured in the liver tissue to study the oxidative stress. A histopathological evaluation was also performed to determine the extent of liver injury. Study results indicated that the activity of both the aminotransferases (AST and ALT), ALP and LDH increased significantly in Al2O3 treated rats compared to control animals. The increase was found to be more pronounced with Al2O3 - 30nm followed by Al2O3 - 40nm and Al2O3 - bulk treated rats in a dose dependent manner. However reduced glutathione content showed a decline in the activity. Ultra structural assessment showed significant morphological changes in the liver tissue in accordance with biochemical parameters. Taken together, the results of this study demonstrated that Al2O3 is hepatotoxic and the smaller size of this nanomaterial appeared to be the most toxic while the compound in the bulk form seemed to be the least toxic.

DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO₃)₂ exposure and its associated adverse health effects.

Evaluation of Arsenic Trioxide Potential for Lung Cancer Treatment: Assessment of Apoptotic Mechanisms and Oxidative Damage

Background

Lung cancer is one of the most lethal and common cancers in the world, causing up to 3 million deaths annually. The chemotherapeutic drugs that have been used in treating lung cancer include cisplatin-pemetrexed, cisplastin-gencitabinoe, carboplatin-paclitaxel and crizotinib. Arsenic trioxide (ATO) has been used in the treatment of acute promyelocytic leukemia. However, its effects on lung cancer are not known. We hypothesize that ATO may also have a bioactivity against lung cancer, and its mechanisms of action may involve apoptosis, DNA damage and changes in stress-related proteins in lung cancer cells.

Methods

To test the above stated hypothesis, lung carcinoma (A549) cells were used as the test model. The effects of ATO were examined by performing 6-diamidine-2 phenylindole (DAPI) nuclear staining for morphological characterization of apoptosis, flow cytometry analysis for early apoptosis, and western blot analysis for stress-related proteins (Hsp70 and cfos) and apoptotic protein expressions. Also, the single cell gel electrophoresis (Comet) assay was used to evaluate the genotoxic effect.

Results

ATO-induced apoptosis was evidenced by chromatin condensation and formation of apoptotic bodies as revealed by DAPI nuclear staining. Cell shrinkage and membrane blebbing were observed at 4 and 6 µg/ml of ATO. Data from the western blot analysis revealed a significant dose-dependent increase (p < 0.05) in the Hsp 70, caspase 3 and p53 protein expression, and a significant (p < 0.05) decrease in the cfos, and bcl-2 protein expression at 4 and 6 µg/ml of ATO. There was a slight decrease in cytochrome c protein expression at 4 and 6 µg/ ml of ATO. Comet assay data revealed significant dose-dependent increases in the percentages of DNA damage, Comet tail lengths, and Comet tail moment.

Conclusion

Taken together our results indicate that ATO is cytotoxic to lung cancer cells and its bioactivity is associated with oxidative damage, changes in cellular morphology, and apoptosis.

Cytotoxic, genotoxic, and neurotoxic effects of Mg, Pb, and Fe on pheochromocytoma (PC-12) cells

Metals such as lead (Pb), magnesium (Mg), and iron (Fe) are ubiquitous in the environment as a result of natural occurrence and anthropogenic activities. Although Mg, Fe, and others are considered essential elements, high level of exposure has been associated with severe adverse health effects including cardiovascular, hematological, nephrotoxic, hepatotoxic, and neurologic abnormalities in humans. In the present study we hypothesized that Mg, Pb, and Fe are cytotoxic, genotoxic and neurotoxic, and their toxicity is mediated through oxidative stress and alteration in protein expression. To test the hypothesis, we used the pheochromocytoma (PC-12) cell line as a neuro cell model and performed the LDH assay for cell viability, Comet assay for DNA damage, Western blot for oxidative stress, and HPLC-MS to assess the concentration levels of neurological biomarkers such as glutamate, dopamine (DA), and 3-methoxytyramine (3-MT). The results of this study clearly show that Mg, Pb, and Fe, respectively in the form of MgSO4 , Pb(NO3 )2 , FeCl2 , and FeCl3 induce cytotoxicity, oxidative stress, and genotoxicity in PC-12 cells. In addition, exposure to these metallic compounds caused significant changes in the concentration levels of glutamate, dopamine, and 3-MT in PC-12 cells. Taken together the findings suggest that MgSO4 , Pb(NO3 )2 , FeCl2 , and FeCl3 have the potential to induce substantial toxicity to PC-12 cells.

An innovative approach for determination of air quality health index

Fuzzy-analytical hierarchical process (F-AHP) can be extended to determine fuzzy air quality health index (FAQHI) for deducing health risk associated with local air pollution levels, and subjective parameters. The present work aims at determining FAQHI by considering five air pollutant parameters (SO2, NO2, O3, CO, and PM10) and three subjective parameters (population sensitivity, population density and location sensitivity). Each of the individual pollutants has varying impacts. Hence the combined health effects associated with the pollutants were estimated by aggregating the pollutants with different weights. Global weights for each evaluation alternatives were determined using fuzzy-AHP method. The developed model was applied to determine FAQHI in Howrah City, India from daily-observed concentrations of air pollutants over the three-year period between 2009 and 2011. The FAQHI values obtained through this method in Howrah City range from 1 to 3. Since the permissible value of FAQHI (as calculated for NAAQS) for residential areas is 1.78, higher index values are of public health concern to the exposed individuals. During the period of study, the observed FAQHI values were found to be higher than 1.78 in most of the day in the months of January to March, and October to December. However, the index values were below the recommended limit during rest of the months. In conclusion, FAQHI in Howrah city was above permissible limit in winter months and within acceptable values in summer and rainy months. Diurnal variations of FAQHI showed a similar trend during the three-year period of assessment.

Genotoxicity study of silver nanoparticles in bone marrow cells of Sprague-Dawley rats

The antimicrobial properties of silver nanoparticles (Ag-NPs) have resulted in their extensive application in consumer and health care products. Although Ag-NPs have great potential benefits, their side effects are unknown and seem inevitable due to their ability to reach the nucleus and damage genetic material. This study aimed to determine genotoxic potential of Ag-NPs using mitotic index (MI), DNA damage (comet assay), structural chromosome aberrations (SCA), micronuclei (MN) formation as genetic endpoints and induction of reactive oxygen species (ROS) as oxidative stress endpoint in bone marrow of Sprague-Dawley rats. Four groups of five male rats were orally administered Ag-NPs, once a day for five days with doses of 5, 25, 50, 100, mg/Kg. A control group was also made of five rats. Bone marrow samples were collected 24 h after the last treatment following standard protocols. Ag-NPs exposure significantly increased (p < 0.05) the induction of ROS, number of SCA, the frequency of micro-nucleated cells, damaged the DNA and decreased the mitotic index compared to negative control. The results suggest that Ag-NPs may have the potential to induce oxidative stress mediated genotoxicity in rats. Further characterization of their genotoxicity and also their potential health implications should be monitored regularly.

Preclinical Assessment of Low Doses of Cisplatin in the Management of Acute Promyelocytic Leukemia

Cis-diamminedichloroplatinum (II) (cisplatin) is the most widely used chemotherapeutic drug for various cancers, but its effectiveness is limited by tumor cell resistance and the severe side effects it causes. Since high level of cisplatin is cytotoxic to both cancer and normal cells, the goal of the present study was to explore the effectiveness of prolonged low doses of cisplatin in the management of leukemia. To achieve our goal, human leukemia (HL-60) cells were treated with different doses (1, 2, or 3 µM) of cisplatin for 24, 48, 72 and 96 hours. Cell viability was assessed by MTS assay. Both oxidative stress damage and genotoxicity were estimated by antioxidants, lipid peroxidation, and comet assays, respectively. Data obtained from the MTS assay demonstrated that cisplatin treatment decreased the number of viable tumor cells by direct cell killing or by simply decreasing the rate of cellular proliferation in a dose- and time-dependent fashion. The results of the lipid peroxidation showed a significant increase (p<0.05) of malondialdehyde levels with increasing cisplatin doses. Results obtained from super oxide dismutase and catalase assays showed a gradual increase in antioxidant enzyme activity in cisplatin-treated cells compared to control cells. Data generated from the Comet assay demonstrated a significant dose-dependent increase in genotoxicity with respect to DNA damage as a result of cisplatin treatment. Taken together, our research demonstrated that cisplatin-induced cytotoxicity in HL-60 cells is mediated at least in part via induction of oxidative stress and oxidative damage.

Trace elements and heavy metals in the Grand Bay National Estuarine Reserve in the northern Gulf of Mexico

The objectives of this study are to investigate distribution of trace elements and heavy metals in the salt marsh and wetland soil and biogeochemical processes in the Grand Bay National Estuarine Research Reserve of the northern Gulf of Mexico. The results show that Hg, Cd and to some extent, As and Pb have been significantly accumulated in soils. The strongest correlations were found between concentrations of Ni and total organic matter contents. The correlations decreased in the order: Ni>Cr>Sr>Co>Zn, Cd>Cu>Cs. Strong correlations were also observed between total P and concentrations of Ni, Co, Cr, Sr, Zn, Cu, and Cd. This may be related to the P spilling accident in 2005 in the Bangs Lake site. Lead isotopic ratios in soils matched well those of North American coals, indicating the contribution of Pb through atmospheric fallout from coal power plants.

Abstract 3811: Arsenic trioxide induces cell cycle arrest, apoptosis through interaction of DAXX and degradation of MDM2 in acute leukemia cells

Arsenic trioxide (ATO) alone or combination with all trans retinoic acid (ATRA) has been successfully used in the treatment of all age group of acute promyelocytic leukemia (APL) patients. Recent human clinical trails result of ATO and their combination with ATRA shown complete remission in both de novo and relapsed APL patients. However, the detailed molecular mechanisms of its anti-leukemic action through cell cycle arrest and apoptosis are poorly known. We have used APL cell line and transgenic mice model to elucidate the anti-cancer properties of arsenic trioxide. We hypothesized that ATO arrests cell cycle and apoptosis through activation of p53 and interaction of death domain-associated protein (DAXX), which disrupted the MDM2-DAXX-HAUSP interactions. It also promoted MDM2 self-ubiquitination and degradation. To test the hypothesis, we used western blotting, confocal imaging and other molecular techniques to identify detailed cellular and molecular mechanisms of ATO action in APL cells and transgenic mice hepatocytes as well as bone marrow cells. We found that the expression levels of p53 and p21 increased significantly, whereas MDM2, DAXX and HAUSP decreased dose dependent manner. Our immunoprecipitation (IP) studies shown that they are well associated each other in cells and ATO disrupts associations. After 21 days treatment of ATO different doses (1.25, 2.5, 5.0 and 7.5 mg/kg body wt) in transgenic mice, we have collected liver tissue and isolated hepatocytes and bone marrow. In liver tissue, we found p53 nicely activated dose dependent ATO treated mice. On the basis of these findings, we conclude that ATO induces cell cycle arrest and apoptosis in APL cell line as well as mice hepatocytes through p53 activation, MDM2 self-ubiquitination and disruption of MDM2-DAXX-HAUSP interaction. It is novel target for treatment of APL patients through designing of new anti-leukemic drugs.

Keywords: Arsenic trioxide, HL-60 cells, cell cycle arrest, apoptosis, mitochondrial pathway, Mice hepatocytes and bone marrow.

Acknowledgements: This research was financially supported by National Institutes of Health NCRR Grant No. 5G12RR013459 and MIMHD Grant No. 8G12MD007581, through the RCMI-Center for Environmental Health at Jackson State University.

Citation Format: Sanjay Kumar, Paul B. Tchounwou. Arsenic trioxide induces cell cycle arrest, apoptosis through interaction of DAXX and degradation of MDM2 in acute leukemia cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3811. doi:10.1158/1538-7445.AM2015-3811

New Approach for the Development of Improved Traditional Medicine: Case of a Preparation of an Oral Hypoglycemic Medicine from Laportea ovalifolia (Schumach. & Thonn.) Chew. (Urticaceae)

A majority of Africans rely on traditional medicine as the primary form of health care. Yet most traditional medicine products have a short shelf life, especially for water-based formulations such as macerations, infusions and decoctions. Indeed, many of these water extracts become unfit for human consumption after five to seven days of conservation either because of the degradation or toxicity of active components, and/or the growth of pathogenic organisms. The purpose of this study was to describe and apply a new approach for the development of an improved traditional medicine (ITM) that is cheap, very efficient, not toxic, and easy to produce, and that can be conserved for a longer time without a significant loss of activity. Hence, Laportea ovalifolia was selected from an ethnobotanical prospection in all regions of Cameroon, and was used to prepare an oral hypoglycemic product. This preparation required 9 steps focused on the characterization of the plant species, and the standardization of the ethnopharmacological preparation by a multidisciplinary team of scientists with expertise in botany, ecology, pharmacognosy and pharmacology. Resultantly, four galenic formulations of hypoglycemic medications were produced. A relationship between these four formulations was described as follow: One spoon of oral suspension (10 ml)=one sachet of powder=2 tablets=3 capsules. Hence, our research provides new insight into a drug discovery approach that could alleviate the major problems affecting traditional medicine and enhance its effectiveness in addressing health care in developing and undeveloped countries.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Influence of local meteorology and NO2 conditions on ground-level ozone concentrations in the eastern part of Texas, USA

The influence of local climatic factors on ground-level ozone concentrations is an area of increasing interest to air quality management in regards to future climate change. This study presents an analysis on the role of temperature, wind speed, wind direction, and NO₂ level on ground-level ozone concentrations over the region of Eastern Texas, USA. Ozone concentrations at the ground level depend on the formation and dispersion processes. Formation process mainly depends on the precursor sources, whereas, the dispersion of ozone depends on meteorological factors. Study results showed that the spatial mean of ground-level ozone concentrations was highly dependent on the spatial mean of NO₂ concentrations. However, spatial distributions of NO₂ and ozone concentrations were not uniformed throughout the study period due to uneven wind speeds and wind directions. Wind speed and wind direction also played a significant role in the dispersion of ozone. Temperature profile in the area rarely had any effects on the ozone concentrations due to low spatial variations.

Silver nanoparticle-induced oxidative stress-dependent toxicity in Sprague-Dawley rats

Due to the intensive commercial application of silver nanoparticles (Ag-NPs), their health risk assessment is of great importance. For acute toxicity evaluation of orally administered Ag-NPs, induction of reactive oxygen species (ROS), activity of liver function enzymes [(alanine (ALT/GPT), aspartate (AST/GOT), alkaline phosphatase (ALP)], concentration of lipid hydroperoxide (LHP), comet assay, and histopathology of liver in the rat model were performed. Four groups of five male rats were orally administered Ag-NPs, once a day for five days with doses of 5, 25, 50, 100 mg/kg, body weight. A control group was also made of five rats. Blood and liver were collected 24 h after the last treatment following standard protocols. Ag-NPs exposure increased the induction of ROS, activities of the liver enzymes (ALT, AST, ALP), concentration of lipid hydroperoxide (LHP), tail migration, and morphological alterations of the liver tissue in exposed groups compared to control. The highest two doses, 50 and 100 mg/kg showed statistically significant (p < 0.05) increases in ROS induction, ALT, AST, ALP activity, LHP concentration, DNA damage, and morphological alterations of liver compared to control. Based on these results, it is suggested that short-term administration of high doses of Ag-NP may cause organ toxicity and oxidative stress.

Dual effect of oxidative stress on leukemia cancer induction and treatment

Oxidative stress (OS) has been characterized by an imbalance between the production of reactive oxygen species (ROS) and a biological system's ability to repair oxidative damage or to neutralize the reactive intermediates including peroxides and free radicals. High ROS production has been associated with significant decrease in antioxidant defense mechanisms leading to protein, lipid and DNA damage and subsequent disruption of cellular functions. In humans, OS has been reported to play a role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Huntington's disease, Lou Gehrig's disease, multiple sclerosis and Parkinson's disease, as well as atherosclerosis, autism, cancer, heart failure, and myocardial infarction. Although OS has been linked to the etiology and development of chronic diseases, many chemotherapeutic drugs have been shown to exert their biologic activity through induction of OS in affected cells. This review highlights the controversial role of OS in the development and progression of leukemia cancer and the therapeutic application of increased OS and antioxidant approaches to the treatment of leukemia patients.

Rapid screening of heavy metals and trace elements in environmental samples using portable X-ray fluorescence spectrometer, A comparative study

With industrialization, great amounts of trace elements and heavy metals have been excavated and released on the surface of the earth and dissipated into the environments. Rapid screening technology for detecting major and trace elements as well as heavy metals in variety of environmental samples is most desired. The objectives of this study were to determine the detection limits, accuracy, repeatability and efficiency of a X-ray fluorescence spectrometer (Niton XRF analyzer) in comparison with the traditional analytical methods, inductively coupled plasma optical emission spectrometer (ICP-OES) and inductively coupled plasma optical emission spectrometer (ICP-MS) in screening of major and trace elements of environmental samples including estuary soils and sediments, contaminated soils, and biological samples. XRF is a fast and non-destructive method in measuring the total concentration of multi--elements simultaneously. Contrary to ICP-OES and ICP-MS, XRF analyzer is characterized by the limited preparation required for solid samples, non-destructive analysis, increased total speed and high throughout, the decreased production of hazardous waste and the low running costs as well as multi-elemental determination and portability in the fields. The current comparative study demonstrates that XRF is a good rapid non-destructive method for contaminated soils, sediments and biological samples containing higher concentrations of major and trace elements. Unfortunately, XRF does not have sensitive detection limits of most major and trace elements as ICP-OES or ICP-MS but it may serve as a rapid screening tool for locating hot spots of uncontaminated field soils and sediments.

Abstract 2291: Arsenic trioxide induces cell cycle arrest, apoptosis and MAPKinase signaling cascade in acute promyelocytic leukemia cells

Arsenic trioxide (ATO) has recently been successfully used in the treatment of all-trans retinoic acid resistant relapsing acute promyelocytic leukemia (APL) patients both alone or combination with other drugs. Its use as induction and consolidation therapy has resulted in complete remission rate of both de novo and relapsed APL patients. However, the detailed molecular mechanisms of its therapeutic action are poorly known. We have used human leukemia (HL-60) cells as a model to elucidate the anti-cancer properties of arsenic trioxide. We hypothesized that ATO arrests cell cycle progression of HL-60 cells at G1 phase and leading to cell death by intrinsic pathway of apoptotic signaling. To test the hypothesis, we used western blotting, confocal imaging and spectrofluoremetric techniques to identify detailed cellular and molecular mechanisms of ATO action in HL-60 cells. We found that the expression levels of pro-apoptotic molecules (Bax) and cytochrome C were up-regulated, while that of anti-apoptotic Bcl2 protein was down-regulated at 4 and 6mg/mL ATO doses significantly. We also found that ATO stimulates signaling molecules like P38, JNK in a dose dependent manner in HL-60 cells. Oxidative stress and related imbalance of pro- and anti-apoptotic molecules lead to change of mitochondrial membrane potential and opening of the mitochondrial membrane transition pores. Our confocal imaging data shows a clear translocation of Bax from cytosol to mitochondria and of cytochrome c from mitochondria to cytosol in ATO-treated cells. A dose-dependent decrease/drop-down in mitochondrial membrane potential was also observed in ATO-treated cells, as evidenced by JC-1 leveling and spectrofluoremetric potential recording. On the basis of these findings, we conclude that mitochondrial pathway of apoptosis plays a key role in ATO pharmacology and should be further assessed as a drug target in APL chemotherapy.

Citation Format: Sanjay Kumar, Clement Yedjou, Paul B. Tchounwou. Arsenic trioxide induces cell cycle arrest, apoptosis and MAPKinase signaling cascade in acute promyelocytic leukemia cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2291. doi:10.1158/1538-7445.AM2014-2291

Proteomics-Based Identification of Differentially Abundant Proteins from Human Keratinocytes Exposed to Arsenic Trioxide

INTRODUCTION

Arsenic is a widely distributed environmental toxicant that can cause multi-tissue pathologies. Proteomic assays allow for the identification of biological processes modulated by arsenic in diverse tissue types.

METHOD

The altered abundance of proteins from HaCaT human keratinocyte cell line exposed to arsenic was quantified using a label-free LC-MS/MS mass spectrometry workflow. Selected proteomics results were validated using western blot and RT-PCR. A functional annotation analytics strategy that included visual analytical integration of heterogeneous data sets was developed to elucidate functional categories. The annotations integrated were mainly tissue localization, biological process and gene family.

RESULT

The abundance of 173 proteins was altered in keratinocytes exposed to arsenic; in which 96 proteins had increased abundance while 77 proteins had decreased abundance. These proteins were also classified into 69 Gene Ontology biological process terms. The increased abundance of transferrin receptor protein (TFRC) was validated and also annotated to participate in response to hypoxia. A total of 33 proteins (11 increased abundance and 22 decreased abundance) were associated with 18 metabolic process terms. The Glutamate--cysteine ligase catalytic subunit (GCLC), the only protein annotated with the term sulfur amino acid metabolism process, had increased abundance while succinate dehydrogenase [ubiquinone] iron-sulfur subunit, mitochondrial precursor (SDHB), a tumor suppressor, had decreased abundance.

CONCLUSION

A list of 173 differentially abundant proteins in response to arsenic trioxide was grouped using three major functional annotations covering tissue localization, biological process and protein families. A possible explanation for hyperpigmentation pathologies observed in arsenic toxicity is that arsenic exposure leads to increased iron uptake in the normally hypoxic human skin. The proteins mapped to metabolic process terms and differentially abundant are candidates for evaluating metabolic pathways perturbed by arsenicals.

Basic apoptotic and necrotic cell death in human liver carcinoma (HepG2 ) cells induced by synthetic azamacrocycle

Treatment of diseases with synthetic materials has been an aspiration of mankind since the dawn of human development. In this research, three complex compounds of azamacrocycle (TD1, TD2, and TD3) were synthesized, and experiments were conducted to determine whether their toxicity to human liver carcinoma (HepG2 ) cells is associated with apoptotic and/or necrotic cell death. Cell survival was determined by MTT assay. Apoptosis and necrosis were measured by annexin V FITC/PI assay using the flow cytometry and by propidium iodide (PI) assay using the cellometer vision. HepG2 cells were treated with different concentrations of azamacrocycles for 48 h. Results from MTT assay indicated that all the three azamacrocycles significantly (p < 0.05) reduce cell viability in a dose-dependent manner, showing 48 h-LD50 values of about 37.97, 33.60, and 19.29 μM, for TD3, TD1 and TD2, respectively. Among the three compounds tested, TD2 showed the most pronounced cytotoxic activity against HepG2 cells, being about twofold more potent than TD3. The order of toxicity was TD2 > TD1 > TD3. Because TD2 exerted the most cytotoxic activity against HepG2 cells, it was used in the subsequent apoptosis and necrosis-related experiments. The flow cytometry assessment showed a strong dose-response relationship with regard to TD2 exposure and annexin V/PI positive cells. PI assay data indicated that TD2 exposure increased the proportion of fluorescence positive cells. Overall, our results indicate that azamacrocycle toxicity to HepG2 cells is associated with apoptotic and necrotic cell death resulting from phosphatidylserine externalization and loss of membrane integrity.

Vitamin D3 potentiates the antitumorigenic effects of arsenic trioxide in human leukemia (HL-60) cells

Background

Arsenic trioxide (ATO) is a novel form of therapy that has been found to aid acute promyelocytic leukemia (APL) patients. Our laboratory has demonstrated that ATO-induced cytotoxicity in human leukemia (HL-60) cells is mediated by oxidative stress. Pro-oxidants have been known to play a role in free radical-mediated oxidative stress. Vitamin D₃, (Vit D₃) an active metabolite of vitamin D has been reported to inhibit the growth of number neoplasms such as prostate, breast, colorectal, leukemia, and skin cancers. The goal of the present research was to use (HL-60) cells as an in vitro test model to evaluate whether low doses of Vit D₃ potentiate the toxicity of ATO and whether this toxic action is mediated via apoptotic mechanisms.

Method

HL-60 cells were treated either with a pharmacologic dose of ATO alone and with several low doses of Vit D₃. Cell survival was determined by MTT assay. Cell apoptosis was measured both by flow cytometry assessment, and DNA laddering assay.

Results

MTT assay indicated that Vit D₃ co-treatment potentiates ATO toxicity in HL-60 cells in a dose dependent manner. A statistically significant and dose-dependent increase (p <0.05) was recorded in annexin V positive cells (apoptotic cells) with increasing doses of Vit D₃ in ATO-treated cells. This finding was confirmed by the result of DNA laddering assay showing clear evidence of nucleosomal DNA fragmentation in vitamin and ATO co-treated cells.

Conclusion

The present study indicates that Vit D₃ potentiates the antitumor effects of ATO. This potentiation is mediated at least in part, through induction of phosphatidylserine externalization and nucleosomal DNA fragmentation. These findings highlight the potential impact of Vit D₃ in promoting the pharmacological effect of ATO, suggesting a possible future role of Vit D₃/ATO combination therapy in patients with acute promyelocytic leukemia (APL).

D-Glucose-Induced Cytotoxic, Genotoxic, and Apoptotic Effects on Human Breast Adenocarcinoma (MCF-7) Cells

Introduction

Glucose is a simple sugar that plays an important role in energy production in biological systems. However, it has been linked to many long-term health problems including the risk of heart disease and stroke, erectile dysfunction in men and pregnancy complications in women, and damage to the kidneys, nerves, eye and vision. Also, the underlying mechanisms of diabetic complications are poorly understood.

Methods

In the present study, D-glucose-induced cytotoxic, genotoxic, and apoptotic effects were studied using MCF-7 cells as an in vitro test model. Cell viability was determined by MTT assay. Genotoxic damage was tested by the means of alkaline single cell gel electrophoresis (Comet) assay. Cell apoptosis was measured by flow cytometry assessment (Annexin-V/PI assay).

Results

The results of MTT assay indicated that D-glucose significantly reduces the viability of MCF-7 cells in a dose and time-dependent manner. Similar trend was obtained with the trypan blue exclusion test. Data obtained from the Comet assay indicated that D-glucose causes DNA damage in MCF-7 cells in a dose-dependent manner. The flow cytometry assessment (Annexin V FITC/PI) showed a strong dose-response relationship between D-glucose exposure and annexin V positive MCF-7 cells undergoing early apoptosis.

Conclusion

Taking together, these data provide clear evidence that D-glucose induces cytotoxic, genotoxic, and apoptotic effects on MCF-7 cells. This finding represents the basis for further studies addressing the pathophysiological mechanisms of action of glucose overdose.