Environmental chemical-induced bone marrow B cell apoptosis: death receptor-independent activation of a caspase-3 to caspase-8 pathway

An in vivo imaging approach for simultaneously assessing tumor response and cytotoxicity-induced tissue response in chemotherapy

In chemotherapeutic treatments, while cancer cells are the primary target, cytotoxic side effects are an important consideration. In the current study, we applied an in vivo imaging tool for characterizing chemotherapeutic response in a preclinical setting. The study focused on simultaneously examining the tumor and tissue response as a result of treatment with bortezomib, a mainstay proteasome inhibitor for treating multiple myeloma, in a preclinical model. OPM-2 tumor-bearing SCID-beige mice were designated as control or treated with bortezomib (1 mg/kg, i.v., every 4 days) (n = 8 per group). 99mTc-duramycin SPECT/CT whole-body scans were acquired 2 days before treatment as baseline and at days 1, 3 and 5 after treatment. Radioactivity uptake in tissues and organs was determined and quantitatively compared between control and bortezomib-treated group at each of the time points. Based on the imaging data, separate groups of tumor-bearing mice (n = 3 each) were included as control and bortezomib treated and the tissues were collected on day 5 for histopathology. In vivo imaging data identified significantly elevated 99mTc-duramycin uptake in the tumor, particularly in tumoral periphery. This was accompanied with signal changes in multiple organs and tissues including the adipose tissue, major bones, abdominal regions, spleen and testes. The imaging findings were consistent with known cytotoxic side effects of bortezomib and were supported by histopathology. The outcome of the study demonstrated potential utilities of the technology by enabling timely determination of the efficacy of anticancer treatments and the effect on collateral tissues as a result of systemic cytotoxic treatment.

Gelsemium elegans cyclic peptide induces human cervical carcinoma cells apoptosis through intrinsic and extrinsic pathways

Four novel Gelsemium elegans cyclic peptides (GEPs) were isolated in an anti-human cervical carcinoma activity tracking method, and amino acid sequence identified. GEP-1 cyclic-(Trp-Leu-His-Val)-peptide inhibited HeLa cell proliferation in a dose- and time-dependent manner. GEP-1 induced intracellular reactive oxygen species (ROS) over-production, and induced HeLa cells apoptosis in a Caspase-dependent manner. GEP-1 also induced collapse of mitochondrial membrane potential, and promoted the mitochondria releases of Cyt c, AIF and Endo G in HeLa cells. Furthermore, GEP-1 triggered extrinsic death receptor-dependent pathway, which was characterized by activating Fas and FADD. Notably, the GEP-1 is a potential anti-human cervical carcinoma peptide.

Structural characterization and anticancer potency of centipede oligopeptides in human chondrosarcoma cancer: inducing apoptosis

Anticancer oligopeptides are rarely studied because they are often present in very low concentrations in a complex matrix. In the current study, twelve oligopeptides were isolated and the amino acid sequence identified from the centipede. MTT results indicated that Trp-Gly-His-Glu (CO-10) showed excellent anti-proliferative potency against chondrosarcoma cells in vitro. Further study showed that CO-10 induced SW1353 cells apoptosis and blocked cell cycle in the G0/G1 phase. Further, results demonstrate that the apoptotic and cytotoxic effects of CO-10 are mediated by the intrinsic mitochondria-mediated apoptotic pathway, which in turn causes the release of cytochrome c and the activation of caspases. This study will be important for the development of pharmaceutical anticancer peptides from natural products as anticancer agents against chondrosarcoma.

Synthesis, crystal structure and antiproliferative mechanisms of gallium(iii) complexes with benzoylpyridine thiosemicarbazones

We have prepared six thiosemicarbazone ligands and synthesized the corresponding Ga(iii) complexes. The antitumor activity of the ligand increases with its lipophilicity, and the antitumor activity of the Ga(iii) complexes is affected by the ligands. Since C6 has the highest anticancer proliferative activity (0.14 ± 0.01 μM) against HepG-2 (Human hepatocarcinoma cell line), we characterized its structure by X-ray single crystal diffraction and explored its antiproliferation mechanism. Anti-tumor mechanism results show that Ga(iii) complex (C6) promoted HepG-2 cell cycle arrest in the G1 phase by regulating the expression of cell cycle-associated proteins (Cdk 2, cyclin A and cyclin E). Ga(iii) complex (C6) promotes apoptosis by consuming intracellular iron, enhancing intracellular reactive oxygen species (ROS), activating caspase-3/9, releasing cytochromes and apoptotic protease activating factor-1 (apaf-1).

Whole-body Imaging of Cell Death Provides a Systemic, Minimally Invasive, Dynamic, and Near-real Time Indicator for Chemotherapeutic Drug Toxicity

PURPOSE

Response to toxicity in chemotherapies varies considerably from tissue to tissue and from patient to patient. An ability to monitor the tissue damage done by chemotherapy may have a profound impact on treatment and prognosis allowing for a proactive management in understanding and mitigating such events. For the first time, we investigated the feasibility of using whole-body imaging to map chemotherapeutic drug-induced toxicity on an individual basis.

EXPERIMENTAL DESIGN

In a preclinical proof-of-concept, rats were treated with a single clinical dose of cyclophosphamide, methotrexate, or cisplatin. In vivo whole-body imaging data were acquired using ^99mTc-duramycin, which identifies dead and dying cells as an unambiguous marker for tissue injury in susceptible organs. Imaging results were cross-validated using quantitative ex vivo measurements and histopathology and compared with standard blood and serum panels for toxicology.

RESULTS

The in vivo whole-body imaging data detected widespread changes, where spatially heterogeneous toxic effects were identified across different tissues, within substructures of organs, as well as among different individuals. The signal changes were consistent with established toxicity profiles of these chemotherapeutic drugs. Apart from generating a map of susceptible tissues, this in vivo imaging approach was more sensitive compared with conventional blood and serum markers used in toxicology. Also, repeated imaging during the acute period after drug treatment captured different kinetics of tissue injury among susceptible organs in males and females.

CONCLUSIONS

This novel and highly translational imaging approach shows promise in optimizing therapeutic decisions by detecting and managing drug toxicity on a personalized basis.Toxicity to normal tissues is a significant limitation in chemotherapies. This work demonstrated an in vivo imaging-based approach for characterizing toxicity-induced tissue injury in a systemic, dynamic, and near-real time fashion. This novel approach shows promise in optimizing therapeutic decisions by monitoring drug toxicity on a personalized basis.

Ochratoxin A-Induced Apoptosis of IPEC-J2 Cells through ROS-Mediated Mitochondrial Permeability Transition Pore Opening Pathway

With the purpose to explore the mechanisms associated with the intestinal toxicity of Ochratoxin A (OTA), an intestinal porcine epithelial cell line (IPEC-J2) was applied in this study as in vitro models for intestinal epithelium. The results confirmed that OTA induced IPEC-J2 cell toxicity by MTT assay and apoptosis by Hoechst 33258 staining and flow cytometer analysis. We also observed that OTA induced the mitochondrial reactive oxygen species (ROS) production and mitochondrial permeability transition pore (mPTP) opening by confocal microscopy. Western blot showed that OTA induced cytochrome c (cyt-c) release and caspase-3 activation, which could be suppressed by inhibition of mPTP opening with cyclosporin A. Treatment with Mito-TEMPO, the mitochondria-targeted ROS scavenger, blocked OTA-induced mitochondrial ROS generation and mPTP opening and prevented cyt-c release, caspase-3 activation, and apoptosis in IPEC-J2 cells.

Enhanced therapeutic efficacy of LHRHa-targeted brucea javanica oil liposomes for ovarian cancer

Background

Although brucea javanica oil liposomes (BJOLs) have been used clinically to treat ovarian cancer, its clinical efficacy is often limited by systemic side effects due to non-specific distribution. Luteinizing hormone releasing hormone receptor (LHRHR) is overexpressed in most ovarian cancers but negligibly expressed in most of the other visceral organs. In this study, we aimed to develop a novel LHRHa targeted and BJO-loaded liposomes (LHRHa-BJOLs), and investigate its characteristics, targeting ability and anti-ovarian cancer efficiency both in vitro and in vivo.

Methods

The LHRHa-BJOLs were prepared by film-dispersion and biotin-streptavidin linkage methods, and characterized in terms of its morphology, particle size, zeta potential, ligand conjugation, encapsulation efficiency and stability. The targeting nature and antitumor effects of the liposomes were evaluated in vitro using cultured human ovarian cancer A2780/DDP cells, and in vivo using ovarian cancer-bearing nude mice.

Results

The LHRHa-BJOLs were successfully synthesized, with a uniformly spherical shape, appropriate particle size and zeta potential, as well as a high encapsulation efficiency. Compared to non-targeted liposomes and BJO emulsion, the LHRHa-BJOLs could significantly increase specific intracellular uptaking rate, enhance cell inhibitory effect and induce cell apoptosis in A2780/DDP cells in vitro. Meanwhile, LHRHa-BJOLs also had a significantly stronger activity of targeting tumor tissue, inhibiting tumor growth, inducing tumor apoptosis and prolonging survival time in ovarian cancer-bearing mice in vivo.

Conclusions

Our experiment suggests that LHRHa-BJOLs may be a useful targeted drug for the treatment of ovarian cancer.

Biological impact of environmental polycyclic aromatic hydrocarbons (ePAHs) as endocrine disruptors

Polycyclic aromatic hydrocarbons (PAHs) are often detected in the environment and are regarded as endocrine disruptors. We here designated mixtures of PAHs in the environment as environmental PAHs (ePAHs) to discuss their effects collectively, which could be different from the sum of the constituent PAHs. We first summarized the biological impact of environmental PAHs (ePAHs) found in the atmosphere, sediments, soils, and water as a result of human activities, accidents, or natural phenomena. ePAHs are characterized by their sources and forms, followed by their biological effects and social impact, and bioassays that are used to investigate their biological effects. The findings of the bioassays have demonstrated that ePAHs have the ability to affect the endocrine systems of humans and animals. The pathways that mediate cell signaling for the endocrine disruptions induced by ePAHs and PAHs have also been summarized in order to obtain a clearer understanding of the mechanisms responsible for these effects without animal tests; they include specific signaling pathways (MAPK and other signaling pathways), regulatory mechanisms (chromatin/epigenetic regulation, cell cycle/DNA damage control, and cytoskeletal/adhesion regulation), and cell functions (apoptosis, autophagy, immune responses/inflammation, neurological responses, and development/differentiation) induced by specific PAHs, such as benz[a]anthracene, benzo[a]pyrene, benz[l]aceanthrylene, cyclopenta[c,d]pyrene, 7,12-dimethylbenz[a]anthracene, fluoranthene, fluorene, 3-methylcholanthrene, perylene, phenanthrene, and pyrene as well as their derivatives. Estrogen signaling is one of the most studied pathways associated with the endocrine-disrupting activities of PAHs, and involves estrogen receptors and aryl hydrocarbon receptors. However, some of the actions of PAHs are contradictory, complex, and unexplainable. Although several possibilities have been suggested, such as direct interactions between PAHs and receptors and the suppression of their activities through other pathways, the mechanisms underlying the activities of PAHs remain unclear. Thus, standardized assay protocols for pathway-based assessments are considered to be important to overcome these issues.

The role of the aryl hydrocarbon receptor in normal and malignant B cell development

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor historically studied for its role in environmental chemical-mediated toxicity and carcinogenicity. In the last 5 years, however, it has become clear that the AhR, presumably activated by endogenous ligand(s), plays an important role in immune system development and function. Other articles in this edition summarize AhR function during T cell and antigen-presenting cell development and function, including the effects of AhR activation on dendritic cell function, T cell skewing, inflammation, and autoimmune disease. Here, we focus on AhR expression and function during B cell differentiation. Studies exploiting immunosuppressive environmental chemicals to probe the role of the AhR in humoral immunity are also reviewed to illustrate the multiple levels at which a “nominally activated” AhR could control B cell differentiation from the hematopoietic stem cell through the pro-B cell, mature B cell, and antibody-secreting plasma cell stages. Finally, a putative role for the AhR in the basic biology of B cell malignancies, many of which have been associated with exposure to environmental AhR ligands, is discussed.

Aryl hydrocarbon receptor control of adaptive immunity

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that belongs to the family of basic helix-loop-helix transcription factors. Although the AhR was initially recognized as the receptor mediating the pathologic effects of dioxins and other pollutants, the activation of AhR by endogenous and environmental factors has important physiologic effects, including the regulation of the immune response. Thus, the AhR provides a molecular pathway through which environmental factors modulate the immune response in health and disease. In this review, we discuss the role of AhR in the regulation of the immune response, the source and chemical nature of AhR ligands, factors controlling production and degradation of AhR ligands, and the potential to target the AhR for therapeutic immunomodulation.

Role and interaction of p53, BAX and the stress-activated protein kinases p38 and JNK in benzo(a)pyrene-diolepoxide induced apoptosis in human colon carcinoma cells

Polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants formed during incomplete combustion of organic material. For example benzo[a]pyrene (B[a]P) is a constituent and contaminant of cigarette smoke, automobile exhaust, industrial waste and even food products. B[a]P is carcinogenic to rodents and humans. B[a]P induces its own metabolism, which generates different metabolites such as the highly reactive electrophilic genotoxin and ultimal carcinogen B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE). BPDE can bind to nucleophilic macromolecules such as proteins and DNA and causes mutations. Multiple defence mechanisms have evolved to protect the cell from DNA damage. Specific signalling pathways operate to detect and repair different kinds of lesions. In case, the damage is poorly removed expansion of damaged cells can be counteracted, e.g., by the inhibition of proliferation or triggering apoptosis. Examples of damage sensors and transducers are stress-activated protein kinases (SAPKs) and the tumour suppressor protein p53. Here, we studied the role of p53 and the pro-apoptotic protein BAX in BPDE-induced cell death by using wild-type- or knock-out-human colon carcinoma cells. As reported previously, we could reconfirm a critical role of p53 in BPDE-induced apoptosis. Furthermore, induced levels of total p53 and its transcriptional target p21 declined at higher BPDE concentrations correlating with reduced rates of apoptosis. Interestingly, increased phosphorylation of p53 at serine 15 remained elevated at higher BPDE concentrations thus disconnecting p53 phosphorylation from downstream apoptosis. Hence, phosphorylation of p53 seems not only to be a more sensitive biomarker of BPDE exposure but might serve other functions unrelated to apoptosis. In addition, we identify BAX as a novel and essential factor to trigger the intrinsic pathway of apoptosis in response to BPDE. Furthermore, BPDE in parallel activates the SAPKs p38 and JNK, which are as well involved in apoptosis. Although several routes of mutual regulation of p53 and SAPK have been described, we present evidence that the SAPK pathway in response to genotoxic stress can unexpectedly operate independently of p53 and controls apoptosis by a novel mechanism possibly downstream of caspases.

Effects of manipulation of the caspase system on myofibrillar protein degradation in vitro

Apoptosis via the intrinsic caspase 9 pathway can be induced by oxidative stressors hydrogen peroxide (H₂O₂) and N-(4 hydroxyphenol) rentinamide (fenretinide), a synthetic retinoid. Accelerated muscle atrophy and proteolysis in muscle-wasting conditions have been linked to oxidative stress and activated protease systems. Therefore, the hypothesis of this study was that proteolysis of myofibrillar proteins could be manipulated through the induction or inhibition of the caspase system. After slaughter, LM and supraspinatus muscles from callipyge (n = 5) and normal (n = 3) lambs were excised, finely diced, and incubated with treatment buffers containing oxidative stressors fenretinide or H₂O₂, recombinant caspase 3, caspase-specific inhibitor N-acetyl-Asp-Glu-Val-Asp-CHO (DEVD), or control solution. Muscle samples were incubated for 1, 2, 7, and 21 d at 4°C. Activation of the initiator caspase, caspase 9, and myofibrillar protein degradation was determined by SDS-PAGE and Western blotting. Results showed that fenretinide, H₂O₂, and recombinant caspase 3 increased (P < 0.05) proteolysis of myofibril proteins, whereas DEVD inhibited degradation (P < 0.05). Proteolysis of myofibrillar proteins increased with incubation time (P < 0.0001), and incubation time × treatment interactions (P < 0.05) indicated that the treatment effects did not all occur at the same rate. This study has shown that manipulation of the caspase system through induction or inhibition of activity can affect degradation of myofibrillar proteins, providing further evidence that the caspase system could be involved in postmortem proteolysis and tenderization. However, these stimulated changes were not sufficient to overcome the lack of proteolysis that is characteristic of muscle from callipyge lambs.

Proximal events in 7,12-dimethylbenz[a]anthracene-induced, stromal cell-dependent bone marrow B cell apoptosis: stromal cell-B cell communication and apoptosis signaling

Intercellular communication is an essential process in stimulating lymphocyte development and in activating and shaping an immune response. B cell development requires cell-to-cell contact with and cytokine production by bone marrow stromal cells. However, this intimate relationship also may be responsible for the transfer of death-inducing molecules to the B cells. 7,12-Dimethylbenz[a]anthracene (DMBA), a prototypical polycyclic aromatic hydrocarbon, activates caspase-3 in pro/pre-B cells in a bone marrow stromal cell-dependent manner, resulting in apoptosis. These studies were designed to examine the hypothesis that an intrinsic apoptotic pathway is activated by DMBA and that the ultimate death signal is a DMBA metabolite generated by the stromal cells and transferred to the B cells. Although a loss of mitochondrial membrane potential did not occur in the DMBA/stromal cell-induced pathway, cytochrome c release was stimulated in B cells. Caspase-9 was activated, and formation of the apoptosome was required to support apoptosis, as demonstrated by the suppression of death in Apaf-1(fog) mutant pro-B cells. Investigation of signaling upstream of the mitochondria demonstrated an essential role for p53. Furthermore, DMBA-3,4-dihydrodiol-1,2-epoxide, a DNA-reactive metabolite of DMBA, was sufficient to upregulate p53, induce caspase-9 cleavage, and initiate B cell apoptosis in the absence of stromal cells, suggesting that production of this metabolite by the stromal cells and transfer to the B cells are proximal events in triggering apoptosis. Indeed, we provide evidence that metabolite transfer from bone marrow stromal cells occurs through membrane exchange, which may represent a novel communication mechanism between developing B cells and stromal cells.

The aryl hydrocarbon receptor interacts with c-Maf to promote the differentiation of type 1 regulatory T cells induced by IL-27

Type 1 regulatory T cells (Tr1 cells ) that produce interleukin 10 (IL-10) are instrumental in the prevention of tissue inflammation, autoimmunity and graft-versus-host disease. The transcription factor c-Maf is essential for the induction of IL-10 by Tr1 cells, but the molecular mechanisms that lead to the development of these cells remain unclear. Here we show that the ligand-activated transcription factor aryl hydrocarbon receptor (AhR), which was induced by IL-27, acted in synergy with c-Maf to promote the development of Tr1 cells. After T cell activation under Tr1-skewing conditions, the AhR bound to c-Maf and promoted transactivation of the Il10 and Il21 promoters, which resulted in the generation of Tr1 cells and the amelioration of experimental autoimmune encephalomyelitis. Manipulating AhR signaling could therefore be beneficial in the resolution of excessive inflammatory responses.

A previously unreported function of β(1)B integrin isoform in caspase-8-dependent integrin-mediated keratinocyte death

Integrins regulate adhesive cell-matrix interactions and mediate survival signals. On the other hand, unligated or free cytoplasmic fragments of integrins induce apoptosis in many cell types (integrin-mediated death). We have previously shown that β(1) integrin expression protects keratinocyte stem cells from anoikis, whereas the role of the β(1)B integrin isoform has not been clarified. In this study we report that suspended keratinocytes undergo apoptosis through the activation of caspase-8, independently of the Fas/Fas ligand system. Indeed, anti-β(1) integrin-neutralizing antibodies induced apoptosis in short hairpin RNA Fas-associated death domain-treated cells. Moreover, before and during suspension, caspase-8 directly associated with β(1) integrin, which in turn internalized and progressively degraded, shedding the cytoplasmic domain. β(1)B was expressed only in the cytoplasm in a perinuclear manner and remained unaltered during suspension. At 24 hours, as β(1)A was located close to the nucleus, β(1)B colocalized with β(1)A and coimmunoprecipitated with caspase-8. Caspase-8 was activated earlier in β(1)B integrin-transfected keratinocytes, and these cells underwent a higher rate of apoptosis than mock cells. In contrast, caspase-8 was not activated in small interfering RNA (siRNA) β(1)B-transfected cells. These results indicate that when β(1)A is unligated, β(1)B is responsible for "integrin-mediated death" in human keratinocytes.

Disruption of human plasma cell differentiation by an environmental polycyclic aromatic hydrocarbon: a mechanistic immunotoxicological study

BACKGROUND

The AhR is a ligand-activated transcription factor that mediates immunosuppression induced by environmental PAH and HAH. Recently, a critical role for the AhR in development of T cells involved in autoimmunity (Th17 and Treg) has been demonstrated, supporting the hypothesis that the AhR plays a key role in immune regulation both in the presence and absence of environmental ligands. Despite these results with T cells systems, little is known of the role that the AhR plays in B cell development. We have demonstrated that B cell activation with CD40 ligand, a stimulus that models adaptive immunity, induces AhR expression in primary human B cells, suggesting that activation may increase human B cell sensitivity to AhR ligands and that the AhR may play a role in B cell development.

METHODS

To test these possibilities, we developed an in vitro system in which activated human B cells expressing high AhR levels are induced to differentiate into plasma cells. Consequently, the effects of benzo [a]pyrene, a prototypic environmental AhR ligand, on plasma cell differentiation could be investigated and this chemical could be exploited essentially as drug probe to implicate the role of the AhR in plasma cell development.

RESULTS

A previously unattainable level of B cell differentiation into plasma cells (up to 45% conversion) was observed. Benzo [a]pyrene significantly suppressed that differentiation. gamma-Irradiation after an initial proliferation phase induced by CD40 ligand and immediately prior to initiation of the differentiation phase blocked cell growth but did not affect cell viability or plasma cell differentiation. B [a]P suppressed differentiation whether or not cell growth was inhibited by gamma-irradiation.

CONCLUSIONS

1) Extensive proliferation is not required during the differentiation phase per se for CD40L-activated human B cells to undergo plasma cell differentiation, and 2) an environmental PAH blocks both proliferation and differentiation of AhR expressing B cells. The results uncover a new mechanism by which environmentally ubiquitous PAHs may negatively impact human B cell-mediated immunity.

Glyphosate formulations induce apoptosis and necrosis in human umbilical, embryonic, and placental cells

We have evaluated the toxicity of four glyphosate (G)-based herbicides in Roundup formulations, from 10(5) times dilutions, on three different human cell types. This dilution level is far below agricultural recommendations and corresponds to low levels of residues in food or feed. The formulations have been compared to G alone and with its main metabolite AMPA or with one known adjuvant of R formulations, POEA. HUVEC primary neonate umbilical cord vein cells have been tested with 293 embryonic kidney and JEG3 placental cell lines. All R formulations cause total cell death within 24 h, through an inhibition of the mitochondrial succinate dehydrogenase activity, and necrosis, by release of cytosolic adenylate kinase measuring membrane damage. They also induce apoptosis via activation of enzymatic caspases 3/7 activity. This is confirmed by characteristic DNA fragmentation, nuclear shrinkage (pyknosis), and nuclear fragmentation (karyorrhexis), which is demonstrated by DAPI in apoptotic round cells. G provokes only apoptosis, and HUVEC are 100 times more sensitive overall at this level. The deleterious effects are not proportional to G concentrations but rather depend on the nature of the adjuvants. AMPA and POEA separately and synergistically damage cell membranes like R but at different concentrations. Their mixtures are generally even more harmful with G. In conclusion, the R adjuvants like POEA change human cell permeability and amplify toxicity induced already by G, through apoptosis and necrosis. The real threshold of G toxicity must take into account the presence of adjuvants but also G metabolism and time-amplified effects or bioaccumulation. This should be discussed when analyzing the in vivo toxic actions of R. This work clearly confirms that the adjuvants in Roundup formulations are not inert. Moreover, the proprietary mixtures available on the market could cause cell damage and even death around residual levels to be expected, especially in food and feed derived from R formulation-treated crops.

An endogenous prostaglandin enhances environmental phthalate-induced apoptosis in bone marrow B cells: activation of distinct but overlapping pathways

Phthalate esters are ubiquitous environmental contaminants that are produced for a variety of common industrial and commercial purposes. We have shown that mono-(2-ethylhexyl) phthalate (MEHP), the toxic metabolite of di-(2-ethylhexyl) phthalate, induces bone marrow B cell apoptosis that is enhanced in the presence of the endogenous prostaglandin 15-deoxy-Delta((12, 14))-PGJ(2) (15d-PGJ(2)). Here, studies were performed to determine whether 15d-PGJ(2)-mediated enhancement of MEHP-induced apoptosis represents activation of an overlapping or complementary apoptosis pathway. MEHP and 15d-PGJ(2) induced significant apoptosis within 8 and 5 h, respectively, in a pro/pre-B cell line and acted cooperatively to induce apoptosis in primary pro-B cells. Apoptosis induced with each chemical was accompanied by activation of a combination of initiator caspases (caspases-2, -8, and -9) and executed by caspase-3. Apoptosis induced with MEHP and 15d-PGJ(2) was reduced in APAF1 null primary pro-B cells and accompanied by alteration of mitochondrial membranes, albeit with different kinetics, indicating an intrinsically activated apoptosis pathway. Significant Bax translocation to the mitochondria supports its role in initiating release of cytochrome c. Both chemicals induced Bid cleavage, a result consistent with a truncated Bid-mediated release of cytochrome c in an apoptosis amplification feedback loop; however, significantly more Bid was cleaved following 15d-PGJ(2) treatment, potentially differentiating the two pathways. Indeed, Bid cleavage and cytochrome c release following 15d-PGJ(2) but not MEHP treatment was profoundly inhibited by Z-VAD-FMK, suggesting that 15d-PGJ(2) activates apoptosis via two pathways, Bax mobilization and protease-dependent Bid cleavage. Thus, endogenous 15d-PGJ(2)-mediated enhancement of environmental chemical-induced apoptosis represents activation of an overlapping but distinct signaling pathway.

Induction of apoptosis by 9,10-dimethyl-1,2-benzanthracene in cultured preovulatory rat follicles is preceded by a rise in reactive oxygen species and is prevented by glutathione

The polycyclic aromatic hydrocarbon (PAH) 9,10-dimethyl-1,2-benzanthracene (DMBA) destroys primordial, primary, and secondary ovarian follicles in rodents, but its effects on antral follicles have received limited attention. PAHs are metabolized to reactive species, some of which can undergo redox cycling to generate reactive oxygen species (ROS). We previously showed that ROS initiate apoptosis in preovulatory follicles cultured without gonadotropin support and that glutathione (GSH) depletion induces apoptosis in the presence of gonadotropins. In the present study, we tested the hypothesis that DMBA induces apoptosis in preovulatory follicles, which is mediated by ROS and prevented by GSH. Preovulatory follicles were isolated from ovaries of 25-day-old rats 48 h after the injection of 10 IU of eCG and were cultured with DMBA in the presence of FSH for 2 to 48 h. DMBA induced granulosa cell (GC) and theca cell (TC) apoptosis at 48 h, as judged by TUNEL and activated caspase-3 immunostaining. DMBA treatment also increased the numbers of GCs and TCs that immunostained for the proapoptotic protein BAX. Follicular ROS levels were significantly increased in DMBA-treated follicles at 12, 24, and 48 h. GSH supplementation protected against and GSH depletion enhanced the induction of apoptosis in GCs and TCs by DMBA. These findings suggest that GSH is a critical protective mechanism against DMBA-induced apoptosis in antral follicles and that ROS generation may mediate DMBA-induced GC apoptosis.

Two overrepresented B cell populations in HIV-infected individuals undergo apoptosis by different mechanisms

Perturbations of B cells in HIV-infected individuals are associated with the overrepresentation of distinct B cell populations. Here we describe high extrinsic CD95 ligand (CD95L)-mediated apoptosis in CD10-/CD21lo mature/activated B cells that likely arise from HIV-induced immune activation. In addition, high intrinsic apoptosis was observed in CD10+ immature/transitional B cells that likely arise as a result of HIV-induced lymphopenia. CD10+ B cells expressed low levels of Bcl-2 and Bcl-xL, consistent with their high susceptibility to intrinsic apoptosis. Higher levels of activated Bax and Bak were induced in CD10+ B cells compared with CD95L-treated CD10- B cells, consistent with the greater involvement of mitochondria in intrinsic vs. extrinsic apoptosis. Of interest, both extrinsic apoptosis in CD95L-treated CD10- B cells and intrinsic apoptosis in CD10+ B cells were associated with caspase-8 activation. Our data suggest that two distinct mechanisms of apoptosis are associated with B cells of HIV-infected individuals, and both may contribute to the depletion and dysfunction of B cells in these individuals.

Activation of multiple mitogen-activated protein kinases in pro/pre-B cells by GW7845, a peroxisome proliferator-activated receptor gamma agonist, and their contribution to GW7845-induced apoptosis

There is growing interest in using peroxisome proliferator-activated receptor (PPAR) gamma agonists as chemotherapeutic agents in hematologic malignancies. PPARgamma agonists of diverse chemical structure induce apoptosis in several malignant B cell lines. However, PPARgamma agonists also induce apoptosis in normal B cells. One such agonist, GW7845, rapidly induces apoptosis in early B cells. Understanding the mechanisms of PPARgamma agonist-induced death is essential to minimizing loss of normal cells during chemotherapy. PPARgamma agonists influence mitogen-activated protein kinase (MAPK) cascades in other systems, and MAPKs can be associated with apoptosis. Therefore, we investigated the activation of MAPKs in primary pro-B cells and cultured pro/pre-B cells and their role in GW7845-induced apoptosis. Treatment of a nontransformed murine pro/pre-B-cell line with GW7845 transiently induced the phosphorylation of extracellular signal-related protein kinase (ERK) 1/2, but strongly and persistently induced the activation of p38 MAPK and c-Jun NH(2)-terminal kinase (JNK). In primary pro-B-cells, p38 MAPK and JNK were activated following treatment with GW7845. Phosphorylation of activating transcription factor-2 (ATF-2) was induced strongly in both B-cell types. In pro/pre-B cells, pretreatment with the p38 MAPK/JNK inhibitor PD169316 potently suppressed multiple facets of GW7845-induced apoptosis signaling. However, when a series of p38 MAPK and JNK inhibitors were used, only SB202190, also a dual inhibitor, completely suppressed GW7845-induced apoptosis. Inhibitors specific for p38 MAPK and JNK were only partially effective, suggesting that suppression of a single MAPK is not sufficient to inhibit death. The results support the hypothesis that GW7845 initiates an apoptotic pathway in early B cells through the activation of a kinase cascade that includes at least p38 MAPK and JNK.

CYP1A1 in polycyclic aromatic hydrocarbon-induced B lymphocyte growth suppression

The AhR is a ligand-activated transcription factor that mediates immunosuppression by environmental PAH. Previous studies demonstrated that activation of mature human B cells up-regulates AhR expression, suggesting that human B cells are direct PAH targets. To test this hypothesis and to determine the metabolic requirements for PAH toxicity in a human model, the effects of a prototypic PAH, B[a]P, on B cell growth were evaluated. B[a]P and its proximal (B[a]P-7,8-dihydrodiol) and terminal (B[a]P-7,8-dihydrodiol-9,10-epoxide) metabolites inhibited growth in a dose-dependent manner. A poorly metabolized AhR ligand had no effect, suggesting that biotransformation is required for growth inhibition. Inhibition of the CYP1A1 monooxygenase completely blocked growth inhibition induced by B[a]P or B[a]P-7,8-dihydrodiol, but not by B[a]P-dihydrodiol-9,10-epoxide, indicating that CYP1A1-dependent metabolism of B[a]P into the terminal B[a]P-7,8-dihydrodiol-9,10-epoxide metabolite is required for growth inhibition. These studies show for the first time the metabolic requirements for PAH-mediated suppression of human B cell growth.

Apoptosis induced by a new member of saponin family is mediated through caspase-8-dependent cleavage of Bcl-2

OSW-1 is a new member of cholestane saponin family, which is cytotoxic against several types of malignant cells. We reported herein that OSW-1 induced apoptosis of mammalian cells in a concentration- and time-dependent manner. The drug-induced apoptosis was mediated through the mitochondrial pathway, involving the cleavage of Bcl-2. This drug-induced Bcl-2 cleavage in Chinese hamster ovary (CHO) cells could be suppressed either by dominant-negative caspase-8 or by a caspase-8 inhibitor, suggesting that the Bcl-2 cleavage is dependent on caspase-8. In contrast, the Bcl-2 cleavage was independent of caspase-3 activity. The inhibition of caspase-8 activity also resulted in the reduction of apoptotic cells, indicating that Bcl-2 cleavage induced by caspase-8 promotes the progression of apoptosis. The involvement of the caspase-8 activity in the processes of the OSW-1-induced apoptosis was further examined by using caspase-8-deficient Jurkat T cells. It was found that the caspase-8-deficient cells were resistant to OSW-1-induced Bcl-2 cleavage or apoptosis. Furthermore, the small subunit of caspase-8 was found to interact with Bcl-2 as determined by yeast two-hybrid and coimmunoprecipitation assays. Overexpression of caspase-8 small subunit reduced the cleavage of Bcl-2 and inhibited the apoptosis induced by OSW-1. Taken together, these results demonstrate that OSW-1 is capable of inducing apoptosis in mammalian cells, in which the caspase-8-dependent cleavage of Bcl-2 plays an important role.