Gene expressions in Jurkat cells poisoned by a sulphur mustard vesicant and the induction of apoptosis

Dichloroacetate protects against sulfur mustard-induced neurotoxicity via the PDK/PDH axis and Akt/Nrf2 pathway

Sulfur mustard (SM) is a major toxic chemical threat to public health. Mitochondrial dysfunction is considered a critical contributing factor to mustard agent-induced damage. The brain is vulnerable to SM, which can lead to various types of acute and long-term psychiatric distress after exposure, but the neurotoxic mechanisms of SM, let alone drug candidates for antidotes, are seldom studied. In this study, we employed a library of mitochondrion-targeted compounds to screen for antidotes for SM-induced neurotoxicity. Our data revealed that dichloroacetate (DCA) noticeably reduced neuronal death and helped maintain the normal morphology and function of mitochondria both in vitro and in vivo. Further experiments revealed that DCA protected neurons by inhibiting pyruvate dehydrogenase kinase (PDK), thus upregulating pyruvate dehydrogenase (PDH) and activating the protein kinase B (Akt)/Nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway. Overall, our results indicated that DCA could protect against SM-induced neurotoxicity through the PDK/PDH axis and the Akt/Nrf2 pathway, suggesting that DCA is a potentially novel antidote for SM poisoning.

Evaluation of TNF Family Gene Expression under the Influence of Single-Walled and Multi-Walled Carboxylated Carbon Nanotubes in Jurkat Cell Line and Rat

Background:

Nanomaterials, e.g.carbon nanotubes (CNTs), have broad usage in medicine for diagnosis, treatment, and drug delivery. Prior to the widespread use of CNTs, any potential toxicity issues must be considered. Apoptosis is an important issue in toxicological studies, and tumor necrosis factor (TNF) family members execute crucial roles in apoptosis and inflammation. We examined the survival of Jurkat cells under the influence of single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) as well as their impacts on the mRNA levels of TNF family transcripts in Jurkat cells and rats.

Objective:

To evaluate the toxicity or safety of a specific concentration and form of CNT on the expression of one of the gene families of the apoptotic pathway.

Materials and Methods:

Jurkat cells were exposed to SWCNTs and MWCNTs in carboxylated form (SWCNTS-COOH and MWCNTs-COOH). MTT assay assessed the cell survival, and using qRT-PCR, the expression levels of TNF, CD40LG, TNFSF10, TNFSF8, CD40, TNFRSF10A, TNFRSF10B, TNFRSF11B, TNFRSF1A, TNFRSF21, TNFRSF25, and TNFRSF9 were examined. The housekeeping genes β-actin and glyceraldehyde 3-phosphate dehydrogenase was utilized for normalization. We also evaluated the expression levels of TNF and TNFRSF10A in rats in vivo 30 and 60 days after being injected with CNTs.

Results:

After 72 h of carboxylated CNTs at 100 µg. mL^-1, no significant change was observed in the survival rate of treated Jurkat cells. The expression of two genes (TNF and TNFRSF10A) changed significantly. Examining the expression profiles of these two genes in rats demonstrated an insignificant change in the expression of any of these genes after 30 and 60 days. The qRT-PCR analysis exhibited the elevated levels of TNF and TNFRSF10A mRNA in the CNT-treated cells, while expression of other TNF family members did not significantly differ from control (untreated) Jurkat cells. There was also no significant change in the gene expression levels of TNF and TNFRSF10A in CNT-treated rats after 30 and 60 days.

Conclusions:

Administration of SWCNTs-COOH and MWCNTs-COOH could result in the up-regulation of TNF and TNFRSF10A but did not initiate apoptosis in Jurkat cells. Carboxylated SWCNTs showed more potent activity than MWCNTs in activating TNF gene expression and probably trigger cell death through external apoptotic pathways.

Synthesis and Investigation of Therapeutic Potential of Isoform-Specific HDAC8 Inhibitors for the Treatment of Cutaneous T Cell Lymphoma

BACKGROUND

The available treatment option for any type of cancer including CTCL is chemotherapy and radiation therapy which indiscriminately persuade on the normal cells. One way out for selective destruction of CTCL cells without damaging normal cells is the use of histone deacetylase inhibitors (HDACi). Despite promising results in the treatment of CTCL, these HDACi have shown a broadband inhibition profile, moderately selective for one HDAC class but not for a particular isotype. The prevalence of drug-induced side effects leaves open a narrow window of speculation that the decreased therapeutic efficacy and observed side effects may be most likely due to non specific HDAC isoform inhibition. The aim of this paper is to synthesis and evaluates HDAC8 isoform specific inhibitors.

METHODS

Based on the preliminary report on the design and in silico studies of 52 hydroxamic acid derivatives bearing multi-substituent heteroaromatic rings with chiral amine linker, five compounds were shortlisted and synthesized by microwave assisted approach and high yielding synthetic protocol. A series of in vitro assays in addition to HDAC8 inhibitory activity was used to evaluate the synthesised compounds.

RESULTS

Inhibitors 1e, 2e, 3e, 4e and 5e exerted the anti-proliferative activities against CTCL cell lines at 20- 100 µM concentrations. Both the pyrimidine- and pyridine-based probes exhibited μM inhibitory activity against HDAC8. The pyrimidine-based probe 1e displayed remarkable HDAC8 selectivity superior to that of the standard drug, SAHA with an IC50 at 0.1µM.

CONCLUSION

Our study demonstrated that simple modifications at different portions of pharmacophore in the hydroxamic acid analogues are effective for improving both HDAC8 inhibitory activity and isoform selectivity. Potent and highly isoform-selective HDAC8 inhibitors were identified. These findings would be expedient for further development of HDAC8-selective inhibitors.

Effects of CEES and LPS synergistically stimulate oxidative stress inactivates OGG1 signaling in macrophage cells

2-chloroethyl ethyl sulphide (CEES), a monofunctional analogue of sulfur mustard, is a strong vesicant and an alkylating chemical warfare agent. We studied the molecular mechanism of oxidative stress triggered signaling cascades in murine macrophages exposed to CEES with lipopolysaccharide (LPS). Exposure of CEES with specific dose of LPS stimulates oxidative stress caused increasing level of intracellular ROS and RNS, decreased antioxidant enzymes, increasing bimolecular damage, reduced cell viability, and cell cycle arrest. Synergistic exposure of CEES and LPS provoked significant increase in phosphorylation of MAPKs, Akt, tuberin, that down regulate OGG1 expression and 8-OHdG accumulations. Treatment with Akt and ERK1/2 inhibitors, the cells with constitutively active inhibiting activity of Akt and ERK1/2MAPK significant reduce CEES and LPS challenge tuberin but not the OGG1. In addition, the N-acetylcysteine inhibited ROS/RNS generation, elevation of antioxidants level, expression of ERK1/2, Akt, tuberin phosphorylation, resulted in deceased 8-OHdG accumulation and upregulation of OGG1 protein expression suggesting no involvement of Akt and ERK1/2MAPK pathways after CEES and LPS challenge. Collectively, our results indicate that exposure of CEES and LPS induces oxidative stress and the activation of tuberin, and 8-OHdG accumulation via upstream signaling pathways including Akt and ERK1/2MAPK pathway in macrophages but not the down regulation of OGG1.

Biological and molecular mechanisms of sulfur mustard analogue-induced toxicity in JB6 and HaCaT cells: possible role of ataxia telangiectasia-mutated/ataxia telangiectasia-Rad3-related cell cycle checkpoint pathway

Effective medical treatment and preventive measures for chemical warfare agent sulfur mustard (HD)-caused incapacitating skin toxicity are lacking, because of limited knowledge of its mechanism of action. The proliferating basal epidermal cells are primary major sites of attack during HD-caused skin injury. Therefore, employing mouse JB6 and human HaCaT epidermal cells, here, we investigated the molecular mechanism of HD analogue 2-chloroethyl ethyl sulfide (CEES)-induced skin cytotoxicity. As compared to the control, up to 1 mM CEES treatment of these cells for 2, 4, and 24 h caused dose-dependent decreases in cell viability and proliferation as measured by DNA synthesis, together with S and G2-M phase arrest in cell cycle progression. Mechanistic studies showed phosphorylation of DNA damage sensors and checkpoint kinases, ataxia telangiectasia-mutated (ATM) at ser1981 and ataxia telangiectasia-Rad3-related (ATR) at ser428 within 30 min of CEES exposure, and modulation of S and G2-M phase-associated cell cycle regulatory proteins, which are downstream targets of ATM and ATR kinases. Hoechst-propidium iodide staining demonstrated that CEES-induced cell death was both necrotic and apoptotic in nature, and the latter was induced at 4 and 24 h of CEES treatment in HaCaT and JB6 cells, respectively. An increase in caspase-3 activity and both caspase-3 and poly(ADP-ribose)polymerase (PARP) cleavage coinciding with CEES-caused apoptosis in both cell lines suggested the involvement of the caspase pathway. Together, our findings suggest a DNA-damaging effect of CEES that activates ATM/ATR cell cycle checkpoint signaling as well as caspase-PARP pathways, leading to cell cycle arrest and apoptosis/necrosis in both JB6 and HaCaT cells. The identified molecular targets, quantitative biomarkers, and epidermal cell models in this study have the potential and usefulness in rapid development of effective prophylactic and therapeutic interventions against HD-induced skin toxicity.

Sulfur mustard analog induces oxidative stress and activates signaling cascades in the skin of SKH-1 hairless mice

A monofunctional analog of the chemical warfare agent sulfur mustard (HD), 2-chloroethyl ethyl sulfide (CEES), induces tissue damage similar to HD. Herein we studied the molecular mechanisms associated with CEES-induced skin inflammation and toxicity in SKH-1 hairless mice. Topical CEES exposure caused an increase in oxidative stress as observed by enhanced 4-hydroxynonenal and 5,5-dimethyl-2-(8-octanoic acid)-1-pyrroline N-oxide protein adduct formation and an increase in protein oxidation. The CEES-induced increase in the formation of 8-oxo-2-deoxyguanosine indicated DNA oxidation. CEES exposure instigated an increase in the phosphorylation of mitogen-activated protein kinases (MAPKs; ERK1/2, JNK, and p38). After CEES exposure, a significant increase in the phosphorylation of Akt at Ser473 and Thr308 was observed as well as upregulation of its upstream effector, PDK1, in mouse skin tissue. Subsequently, CEES exposure caused activation of AP-1 family proteins and the NF-kappaB pathway, including phosphorylation and degradation of IkappaBalpha in addition to phosphorylation of the NF-kappaB essential modulator. Collectively, our results indicate that CEES induces oxidative stress and the activation of the transcription factors AP-1 and NF-kappaB via upstream signaling pathways including MAPKs and Akt in SKH-1 hairless mouse skin. These novel molecular targets could be supportive in the development of prophylactic and therapeutic interventions against HD-related skin injury.

A clinically relevant in vitro model for evaluating the effects of aerosolized vesicants

The chemical warfare vesicant sulfur mustard (HD) is a known toxic agent to the human respiratory tract and the major airways are considered to be a primary target of HD-induced injury. However, there is no consensus regarding which model systems are most appropriate for studying the effects of aerosolized vesicants on human airway epithelium. In this study, we evaluated the consequences of exposure of differentiated human respiratory epithelial cells in air-liquid interface to mechlorethamine (HN2), an HD functional analog. HN2 challenge was administered via the apical (air) interface over a wide dose range (20-400 microM) to differentiated HBE1 cells. Cultures were observed over 1-48 h for evidence of HN2-induced morphologic abnormalities as well as for possible cellular cytotoxicity, apoptotic changes, and induction of cytokine secretion. HN2 at concentrations of > or =200 microM caused disruption and denudation of the airway epithelial architecture within 24h of exposure. Moreover, HN2-induced cytotoxic and apoptotic changes in HBE1 cells in a dose- and time-dependent fashion. HN2 challenge also induced secretion of chemokines and proinflammatory cytokines including TNF-alpha, IL-1 alpha, IL-1 beta, IL-6, IL-8, RANTES, MCP-1, IP-10, G-CSF, GM-CSF and IL-15. These observations parallel those described in the lungs of HD-exposed victims and underscore the utility and potential applicability of this model to future mechanistic studies of vesicant-induced pulmonary injury.

Microarray Analysis of Mouse Ear Tissue Exposed to Bis-(2-chloroethyl) Sulfide: Gene Expression Profiles Correlate with Treatment Efficacy and An Established Clinical Endpoint

Bis-(2-chloroethyl) sulfide (sulfur mustard; SM) is a potent alkylating agent. Three treatment compounds have been shown to limit SM damage in the mouse ear vesicant model: dimercaprol, octyl homovanillamide, and indomethacin. Microarrays were used to determine gene expression profiles of biopsies taken from mouse ears after exposure to SM in the presence or absence of treatment compounds. Mouse ears were topically exposed to SM alone or were pretreated for 15 min with a treatment compound and then exposed to SM. Ear tissue was harvested 24 h after exposure for ear weight determination, the endpoint used to evaluate treatment compound efficacy. RNA extracted from the tissues was used to generate microarray probes for gene expression profiling of therapeutic responses. Principal component analysis of the gene expression data revealed partitioning of the samples based on treatment compound and SM exposure. Patterns of gene responses to the treatment compounds were indicative of exposure condition and were phenotypically anchored to ear weight. Pretreatment with indomethacin, the least effective treatment compound, produced ear weights close to those treated with SM alone. Ear weights from animals pretreated with dimercaprol or octyl homovanillamide were more closely associated with exposure to vehicle alone. Correlation coefficients between gene expression level and ear weight revealed genes involved in mediating responses to both SM exposure and treatment compounds. These data provide a basis for elucidating the mechanisms of response to SM and drug treatment and also provide a basis for developing strategies to accelerate development of effective SM medical countermeasures.

Protection by antioxidants against toxicity and apoptosis induced by the sulphur mustard analog 2-chloroethylethyl sulphide (CEES) in Jurkat T cells and normal human lymphocytes

1. The mechanism of toxicity of sulphur mustard was investigated by examining the biochemical effects of the analog 2-chloroethylethyl sulphide (CEES) in both human Jurkat cells as well as normal human lymphocytes. 2. Exposure of both types of cells to CEES resulted in a marked decrease in the intracellular concentration of the reduced form of glutathione (GSH), and CEES-induced cell death was potentiated by l-buthionine sulphoximine, an inhibitor of GSH synthesis. 3. CEES increased the endogenous production of reactive oxygen species (ROS) in Jurkat cells, and CEES-induced cell death was potentiated by hydrogen peroxide. 4. CEES induced various hallmarks of apoptosis, including collapse of the mitochondrial membrane potential, proteolytic processing and activation of procaspase-3, and cleavage of poly (ADP-ribose) polymerase. 5. The effects of CEES on the accumulation of ROS, the intracellular concentration of GSH, the mitochondrial membrane potential, and caspase-3 activity were all inhibited by pretreatment of cells with the GSH precursor N-acetyl cysteine or with GSH-ethyl ester. Furthermore, CEES-induced cell death was also prevented by these antioxidants. 6. CEES toxicity appears to be mediated, at least in part, by the generation of ROS and consequent depletion of GSH. Given that sulphur mustard is still a potential biohazard, the protective effects of antioxidants against CEES toxicity demonstrated in Jurkat cells and normal human lymphocytes may provide the basis for the development of a therapeutic strategy to counteract exposure to this chemical weapon.

Lipopolysaccharide enhances the cytotoxicity of 2-chloroethyl ethyl sulfide

BACKGROUND

The bacterial endotoxin, lipopolysaccharide (LPS), is a well-characterized inflammatory factor found in the cell wall of Gram-negative bacteria. In this investigation, we studied the cytotoxic interaction between 2-chloroethyl ethyl sulfide (CEES or ClCH2CH2SCH2CH3) and LPS using murine RAW264.7 macrophages. CEES is a sulfur vesicating agent and is an analog of 2,2'-dichlorodiethyl sulfide (sulfur mustard). LPS is a ubiquitous natural agent found in the environment. The ability of LPS and other inflammatory agents (such as TNF-alpha and IL-1beta) to modulate the toxicity of CEES is likely to be an important factor in the design of effective treatments.

RESULTS

RAW 264.7 macrophages stimulated with LPS were found to be more susceptible to the cytotoxic effect of CEES than unstimulated macrophages. Very low levels of LPS (20 ng/ml) dramatically enhanced the toxicity of CEES at concentrations greater than 400 microM. The cytotoxic interaction between LPS and CEES reached a maximum 12 hours after exposure. In addition, we found that tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1-beta) as well as phorbol myristate acetate (PMA) also enhanced the cytotoxic effects of CEES but to a lesser extent than LPS.

CONCLUSION

Our in vitro results suggest the possibility that LPS and inflammatory cytokines could enhance the toxicity of sulfur mustard. Since LPS is a ubiquitous agent in the natural environment, its presence is likely to be an important variable influencing the cytotoxicity of sulfur mustard toxicity. We have initiated further experiments to determine the molecular mechanism whereby the inflammatory process influences sulfur mustard cytotoxicity.