Abstract P1-01-22: TGFβ-Smad3-TMEPAI axis drives the tumor progression of triple negative breast cancer

Background: In the absence of mutations and/or deletions in the TGF-β signaling molecules, how triple negative breast cancer (TNBC) cells become resistant to growth inhibitory signaling of TGF-β was addressed by screening of several TNBC cell lines for Smad proteins involved in TGF-β signaling. Unexpectedly, altered Smad2 and Smad3 protein levels were detected in breast cancer cells relative to normal mammary epithelial cells, suggesting a novel mechanism to escape from TGF-β mediated growth inhibition. In order to reflect the true functional status of the endogenous molecules, Smad2 or Smad3 were individually knocked down and tested its effect on pro-oncogenic behavior of TGF-β.

Materials and Methods: All cell lines were cultured according to the recommended standard procedures. TMEPAI knockdown was achieved by using lentiviral vectors and knockdown of Smad2 and Smad3 was achieved by using retroviral vectors. DNA transfections and luciferase assays were performed according to vendor instructions. Cell proliferation was measured by quantitation of total cellular DNA. Immunoblotting, invasion and immunohistochemical assays were performed using standard methods. Bioinformatics: Triple negative breast cancer patient dataset (GSE58812) was used to compare Smad2, Smad3, Smad4 and TMEPAI/PMEPA1 expressions correlated with overall survival using the PROGgene tool by using median gene expression value as a dividing point.

Results: While Smad2 deficiency has no effect on breast cancer cell behavior, Smad3 deficiency reduced growth and invasion capacity of breast cancer cells. Interestingly, Smad3 deficiency was associated with reduced gene expressions of transmembrane prostate androgen induced (TMEPAI or PMEPA1) gene and EMT inducing transcription factors and increased expression of cell cycle inhibitors. In contrast, Smad2 deficiency had opposite effect on these regulators. Importantly, the decreased growth and invasion and their associated gene expressions in Smad3 knockdown cells were largely reversed by overexpression of TMEPAI. Meta-analysis of Jezequel dataset of triple negative breast cancer patients suggested higher TMEPAI/PMEPA1 and lower Smad2 expressions are significantly associated with decreased survival. Our results support the idea that development of several triple negative breast cancers may involve expansion of cell populations with altered Smad2 and Smad3 levels resulting in Smad3 dependent expression of TMEPAI, which provides a competitive advantage for cancer cells to grow and metastasize in presence of TGF-β. Moreover, following meta-analysis of published microarray datasets in lung and gastric cancers also revealed that increased TMEPAI and Smad3 expression and decreased Smad2 expressions were significantly associated with poorer patient prognosis in non-small cell lung adenocarcinomas and gastric cancers suggesting universality of this phenomenon.

Conclusion: We identified TGF-β-Smad3-TMEPAI signaling axis as a driver of tumor progression in triple negative breast cancer. Our results suggest that novel therapeutics targeting TMEPAI will selectively inhibit oncogenic activity of TGF-β and promote its tumor suppressive activity in treating TNBC.

Citation Format: Saikumar P, Singha PK, Pandeswara S, Manjeri VA. TGFβ-Smad3-TMEPAI axis drives the tumor progression of triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-01-22.

Civil construction work: The unseen contributor to the occupational and global disease burden

Background:

Construction industry is the second largest employment giving industry in India with many semi-skilled or unskilled workers taking up the occupation for livelihood without any training and proper guidance.

Aim:

To evaluate the pathogenic association of cement exposure to occupational contact dermatoses as evidenced by immune markers and to correlate their pulmonary functions with years of exposure to cement.

Setting and Design:

This was a cross-sectional study conducted among randomly selected cement workers. Methods and material: Evaluation of socioeconomic status (SES) and years of exposure of cement workers was done using a questionnaire. Clinical examination of skin lesions and strip patch test with application of potassium dichromate on unexposed skin was performed. Results were interpreted after 48 hours. Absolute eosinophil count (AEC) and IgE levels measured, and spirometric evaluation was performed.

Statistical Analysis:

Analysis of variance and Pearson's correlation test were used for data analysis. P < 0.05 was considered to be statistically significant.

Results:

Clinically, skin lesions were noticed in 51%, elevated AEC in 47%, and raised Anti IgE in 73%. Two participants developed positive reactions to the skin strip patch test. Duration of exposure to cement and SES were compared with clinical skin lesions. Spirometry result was normal in 81%, obstruction in 8%, restriction in 10%, and mixed pattern in 1%. Forced expiratory volume at 1.0 second, forced expiratory flow (25–75%), and  (PEFR) Peak Expiratory Flow Rate were markedly reduced with years of exposure. Workers who had greater skin lesions and with increase in exposure had increased AEC and IgE levels, although statistically not significant.

Conclusions:

Exposure to cement and poor SES is strongly correlated to increased prevalence of skin lesions and reduced pulmonary functions.

Abstract P3-14-09: Targeting TMEPAI/ PMEPA1 inhibited triple negative breast cancer cell growth and metastasis through growth suppressive TGF-β signaling

Background: Triple negative breast cancers (TNBC) that lack estrogen receptor (ER), progesterone receptor (PR) and hormone epidermal growth factor receptor 2 (HER-2/neu) are aggressive and cause high mortality among breast cancer patients. Transforming growth factor beta (TGF-β) dependency for their aggressive behavior (growth and metastasis) has been well established in many of these tumors. Although targeting TGF-β signaling has major potential to treat TNBCs, however it carries the risk of disturbing the tumor suppressive effects of TGF-β in early tumors and its homeostatic control of normal tissues. Hence there is a need to identify novel targets to impede tumor progression without compromising the beneficial effects of TGF-β signaling. To satisfy this unmet need, earlier we identified that transmembrane prostate androgen induced (TMEPAI/PMEPA1), a direct target gene of TGF-β could act as a "molecular switch" that converts TGF-β from a tumor suppressor to promoter in TNBC. Thus, we undertook the present study that identified a novel compound that blocked TMEPAI expression.

Materials and Methods: All cell lines were cultured according to the ATCC recommendations. Cell proliferation was measured by quantitation of total cellular DNA. Immunoblotting, migration, invasion, tumor xenografts and lung metastasis were performed using standard methods.

Results: We identified a terpenoid derivative (TD) which inhibited the expression of TMEPAI, enhanced TGF-β signaling and blocked proliferation, migration and invasion of several triple negative breast cancer cells in vitro. Our results showed that TD increased phosphorylation of Smad2/3 and increased PTEN, p21 and p27 proteins that cause growth suppression. Concomitantly, TD decreased Akt phosphorylation and reduced Snail and Slug that are required for cell growth and metastasis. Interestingly, TD did not affect the growth of normal human mammary epithelial cells and failed to cause associated molecular changes that can result in growth suppression. Notably, using mice models (nude mice and syngeneic BALB/c mice), we showed that TD reduced tumor burden significantly with little or no toxicity. Consistent with its ability to inhibit Akt phosphorylation and induction of Snail and Slug proteins, TD suppressed lung metastasis of TNBC in mice model. Importantly, reduced tumors derived from TD treated mice exhibited increased expression of pSmad2/3, PTEN, p21, p27 and reduced expression of pAkt compared to tumors obtained from vehicle treated mice.

Conclusions: Our results have two important dimensions: On one hand, TD inhibited TMEPAI induction to promote growth suppressive TGF-β dependent Smad signaling in TNBC but not in normal cells. On the other hand, TD also inhibited non-Smad signaling that promotes growth and metastasis of TNBC both in vitro and in vivo. Hence our findings suggest that drugs that target TMEPAI will not only inhibit growth and metastasis of TNBC but will also restore homeostatic functions of TGF-β to prevent new tumor development.

Citation Format: Singha PK, Pandeswara S, Venkatachalam MA, Saikumar P. Targeting TMEPAI/ PMEPA1 inhibited triple negative breast cancer cell growth and metastasis through growth suppressive TGF-β signaling. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-14-09.

Anti mullerian hormone: a potential marker for recruited non growing follicle of ovarian pool in women with polycystic ovarian syndrome

BACKGROUND

Polycystic ovarian disease is one of the most common causes of infertility in women of reproductive age. Anti- mullerian hormone (AMH), a member of transforming growth factor (TGF) family which is secreted by granulosa cells of growing follicle, is found to be increased to three to four fold in Poly Cystic Ovarian Syndrome (PCOS) patients as evidenced by previous studies. But the level of AMH in relation to the infertile status of PCOS was not studied yet. The present study was focused to determine the discriminative power of AMH in infertility subjects with regular cycles and infertility subjects associated with PCOS.

METHODS

The subjects under study were one hundred and twenty infertile women of age group ranging from 27-35 years. Subjects, were further divided into sixty infertile with regular cycles as controls (Group1) and sixty infertile subjects with PCOS as cases (Group 2). Hormones like FSH, E2 and AMH were assayed for all the subjects. Mean and student t- test for all hormones were compared between controls and cases. The diagnostic power of AMH pertaining to sensitivity and specificity was evaluated by Receiver operating characteristic (ROC) curve.

RESULTS

Serum AMH level were two fold higher in PCOS patients than in controls. The mean value of AMH also shows a test of significance between the two groups. The area under the receiver operating characteristic curve for the AMH assay was 0.95 in infertile group when 3.34ng/ml was used as cut off point indicating its better discriminative power and good diagnostic potency. Setting the AMH value at 3.34ng/ml sensitivity, specificity,Positive Predictive Value(PPV) and Negative Predictive Value(NPV) were observed 98% ,93%, 93% and 98% respectively.

CONCLUSION

The diagnostic potency of Area Under Curve (AUC) for AMH in infertile subjects reflects that AMH is a potential marker for recruited non growing follicles rather than a simple marker for ovarian reserve as it is predominantly produced by small follicles rather than a simple marker for ovarian reserve.

Effect of Hb% on Cognitive Skills in UG Medical Students

INTRODUCTION

The cognitive functions in adults can be altered by a number of diseases, nutritional deficiencies, hormonal changes, ageing and drugs. Anaemia, through various possible mechanisms, has been suggested to result in a cognitive deterioration.

AIM AND OBJECTIVE

To study the effect of Hb% on cognitive skills of 100 UG medical students of Sree Balaji Medical College and Hospital, Chromepet, Chennai, India.

METHODOLOGY

One hundred UG medical students who were in the age group of 17 to 19 years were selected and their Hb% estimations were done by using Drabkin's method. Their cognitive skills were assessed by using the Mini Mental State Examination (MMSE). Correlation between Hb% and their cognitive skills was done.

RESULTS

This study showed that there was a significant correlation between the Hb concentration and the cognitive skills in the students.

The effect of counselling on the academic performance of college students

INTRODUCTION

The adjustment difficulties of college students have been an emerging issue. Many studies have proved that the adjustment difficulties like appetite disturbance, concentration problems and depression are most evident in freshmen. To help college students in resolving their adjustment issues, we made efforts in the form of establishing a counselling system to provide intervention to the students, so that their social and emotional problems did not interfere with their academic performances, for the current study. We chose to examine the relationship between the college counselling experience and the academic performance in a sample of freshmen.

AIM

To explore the relationship and the effect of counselling on the academic performance of college students.

OBJECTIVE

1. To find the relationship between the academic performance and counselling. 2. To find the relationship between the number of sessions and the academic performance.

MATERIAL AND METHODS

Fifty Four First MBBS college students of the SBMCH 2007-2008 batch, who underwent face to face individual intake interviews with college faculty members, were given questionnaires and the analysis was based on their response to the questions and their academic performance.

RESULT

This study showed that there was an increase in the average marks by about 15%-25% among 43% of the students and by about 10% -15% of marks among 13% of the students. There was no marked improvement among 31% of them and there was no change in 4% of the students .The second part of the study showed that the number of sessions correlated positively with the academic performance.

CONCLUSION

This study showed that the counselling services in colleges had been effective in easing out the students' personal difficulties. The constructive support which was received from individual counselling seemed to have a positive influence on the academic performance and the number of sessions correlated positively with the academic performance.

P2-11-04: TMEPAI Is a Feedback Regulator of TGF-b Signaling during Breast Cancer Progression

Background: Despite lack of hormone receptors (ER/PR) and HER2, many triple negative breast cancers (TNBC) depend on transforming growth factor beta (TGF-β) signaling activity for late growth and metastasis. Thus TGF-β signaling is a major potential target to treat TNBC patients. However, inhibition of TGF-β signaling pathway carries the risk of disturbing the tumor suppressive activity of TGF-β in normal tissues and early cancers. Hence, present study was undertaken with a goal to identify suitable markers which will enable to develop drugs that retard only the “oncogenic activity” of TGF-β while preserving its growth suppressive activities.

Materials and Methods: All cell lines were cultured according to the recommended standard procedures. Lentiviral mediated expression vector was used to stably knockdown endogenous TMEPAI expression. DNA transfections and luciferase assays were performed according to vendor instructions. Cell proliferation was measured by quantitation of total cellular DNA. Immunoblotting and immunohistochemical analysis were performed using standard methods.

Results: Previously we have shown that Transmembrane prostate androgen-induced protein (TMEPAI), a TGF-β inducible gene has the potential to convert tumor suppressive TGF-β into a tumor promoter. In the present study, we show that Smad binding elements driven luciferase reporter activity, a measure of TGF-β signaling, was dramatically increased in TMEPAI knockdown cells. While wild type cancer cells showed transient raise in phosphorylation of Smad2 and Smad3 with TGF-β treatment, TMEPAI knockdown resulted in increased and sustained levels of phosphorylated Smad2 and Smad3. In normal mammary epithelial cells, continuous presence of TGF-β blocked their growth. In contrast, breast cancer cells showed a biphasic growth response (moderate inhibition up to 72h followed by strong growth stimulation) to TGF-β, while TMEPAI-deficiency blocked this response to TGF-β. Furthermore, exogenous expression of TMEPAI in normal mammary epithelial cells and TMEPAI-knockdown cells resulted in reduced TGF-β-dependent Smad activity. Additionally, we found that TMEPAI subverts tumor suppressive TGF-β dependent Smad signaling into tumor promotive non-Smad signaling through stimulation of stress activated protein kinases. Inhibition of stress kinases also reduced the growth of cancer cells similar to TMEPAI deficiency. To evaluate the translational importance of TMEPAI as predictive marker, immunohistochemical analysis on human breast cancer specimens revealed the gain of TMEPAI expressions in aggressive human breast tumor samples but not in normal human breast tissue specimens.

Conclusions: Our results show that TMEPAI, which subverts tumor suppressive Smad signaling, may serve as a novel prognostic and predictive marker for aggressive and TGF-β dependent of metastatic breast cancers. These studies will further provide new clues to develop an effective and decisive anti-TGF-β therapy against aggressive breast cancers without disturbing the growth suppression by TGF-β in normal tissues and early tumors.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-11-04.

Abstract P4-06-03: TMEPAI a Novel Prognostic Marker for TGF-β Dependency of Metastatic Breast Cancers: Converts Tumor Suppressive TGF-β into a Tumor Promoter

Background: The dependency of many aggressive and treatment resistant breast cancers on transforming growth factor-beta (TGF-β) for their growth and invasiveness is paradoxical because TGF-β is a classical tumor suppressor that inhibits the growth of normal and early neoplastic breast epithelium. Therefore, we addressed the question how does TGF-β signaling transform from its expected role as a tumor suppressor in early cancer to that of a tumor promoter that facilitates growth and invasion in the late stages?

Materials and methods: TMEPAI RNA was quantitated by for qPCR with SYBR green in an Applied Biosystems 7500 Real Time PCR System. pLKO. 1 based lentiviral vector was used to knockdown TMEPAI. Immunoblotting, invasion assays and tumor xenografts were performed using standard methods.

Results: TMEPAI expression is observed in ER/PR-negative and HER2-negative breast tumors compared to their matched normal/benign tissues. TMEPAI protein was found to be highly expressed in aggressive and invasive breast cancer cells compared to non-invasive ER-positive and HER2-negative breast cancer cells. Importantly, TGF-β induced late growth spurt in MDA-MB-231 cells and inhibited cell growth in normal mammary epithelial cells (HME). While TGF-β stimulated TMEPAI RNA by ∼40 fold and protein by ∼8-10 fold in MDA-MB-231 cells, it had minimal effect on HME. Both basal expression and TGF-β induction of TMEPAI were completely abolished by SB431542, a pharmacological inhibitor of TGF-β signaling as well as by overexpression of Smad7 or dominant negative TGF-β RI (DN Alk-5). We confirmed TMEPAI as a direct target gene of TGF-β signaling when breast cancer cells MDA-MB-468 and MCF-7 that do not express TMEPAI and are defective in either Smad4 or TGF-β receptor I respectively, by exogenously expressing Smad4 in MDA-MB-468 and Alk-5 in MCF-7 to restore TMEPAI induction by TGF-β. Notably, knockdown of TMEPAI has profound corrective effects on cancer cell growth in vitro and in vivo. These important biological effects were accompanied by increase of cellular levels of the tumor suppressor PTEN and p27kip1, decreased activation of the PI3K signaling mediator Akt, and diminished expression of the oncogenic proteins Hif-1a, and VEGF.

Discussion: Our results indicate that increase of TMEPAI protein — further exacerbated by TGF-β — may play a crucial role in TGF-β mediated tumor promotion. We believe that increased expression of TMEPAI by genomic amplification and/or epigenetic events contributes to the cancer phenotype and oncogenic progression through regulation of critical proteins involved in growth, epithelial mesenchymal transition (EMT), and angiogenesis, thereby increasing the aggressiveness of breast carcinomas. Thus, increase of TMEPAI and its induction by TGF-β to pathological levels may be the key lynchpin that explains the conversion of tumor suppressive TGF-β into a tumor promoter and TGF-β dependent cancer cell aggressiveness. Moreover, the data suggest that TMEPAI might serve as a novel prognostic marker for aggressiveness, invasiveness and TGF-β dependency of metastatic breast cancers.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-06-03.

Up-regulation of apoptosis inhibitory protein IAP-2 by hypoxia. Hif-1-independent mechanisms

Hypoxia is a key determinant of tissue pathology during tumor development and organ ischemia. However, little is known regarding hypoxic regulation of genes that are directly involved in cell death or death resistance. Here we report the striking induction by severe hypoxia of the anti-apoptotic protein IAP-2. Hypoxic cells with IAP-2 up-regulation became resistant to apoptosis. IAP-2 was induced by hypoxia per se rather than by the secondary effects of hypoxia, including ATP depletion and cell injury. The inductive response did not relate to alterations of cellular redox status or arrest of mitochondrial respiration. On the other hand, IAP-2 induction was attenuated by actinomycin D, suggesting a role for gene transcription. In vitro nuclear run-on assays demonstrated specific increases in IAP-2 transcriptional activity after hypoxia exposure. HIF-1, the primary transcription factor that is responsible for multiple gene activation under hypoxia, does not have a role in IAP-2 expression. HIF-1 and IAP-2 were induced by different degrees of hypoxia; severe hypoxia or anoxia was required for IAP-2 induction. Moreover, cobalt chloride and desferrioxamine activated HIF-1 but not IAP-2. Finally, IAP-2 was induced by severe hypoxia in mouse embryonic stem cells that were deficient of HIF-1. Thus, this study not only provides the first demonstration of hypoxic regulation of an anti-apoptotic gene but also suggests the participation of novel hypoxia-responsive transcription mechanisms.

Bcl-2 prevents Bax oligomerization in the mitochondrial outer membrane

ATP depletion results in Bax translocation from cytosol to mitochondria and release of cytochrome c from mitochondria into cytosol in cultured kidney cells. Overexpression of Bcl-2 prevents cytochrome c release, without ameliorating ATP depletion or Bax translocation, with little or no association between Bcl-2 and Bax as demonstrated by immunoprecipitation (Saikumar, P., Dong, Z., Patel, Y., Hall, K., Hopfer, U., Weinberg, J. M., and Venkatachalam, M. A. (1998) Oncogene 17, 3401-3415). Now we show that translocated Bax forms homo-oligomeric structures, stabilized as chemical adducts by bifunctional cross-linkers in ATP-depleted wild type cells, but remains monomeric in Bcl-2-overexpressing cells. The protective effects of Bcl-2 did not require Bcl-2/Bax association, at least to a degree of proximity or affinity that was stable to conditions of immunoprecipitation or adduct formation by eight cross-linkers of diverse spacer lengths and chemical reactivities. On the other hand, nonionic detergents readily induced homodimers and heterodimers of Bax and Bcl-2. Moreover, associations between translocated Bax and the voltage-dependent anion channel protein or the adenine nucleotide translocator protein could not be demonstrated by immunoprecipitation of Bax, or by using bifunctional cross-linkers. Our data suggest that the in vivo actions of Bax are at least in part dependent on the formation of homo-oligomers without requiring associations with other molecules and that Bcl-2 cytoprotection involves mechanisms that prevent Bax oligomerization.

Protection of ATP-depleted cells by impermeant strychnine derivatives: implications for glycine cytoprotection

Glycine and structurally related amino acids with activities at chloride channel receptors in the central nervous system also have robust protective effects against cell injury by ATP depletion. The glycine receptor antagonist strychnine shares this protective activity. An essential step toward identification of the molecular targets for these compounds is to determine whether they protect cells through interactions with intracellular targets or with molecules on the outer surface of plasma membranes. Here we report cytoprotection by a cell-impermeant derivative of strychnine. A strychnine-fluorescein conjugate (SF) was synthesized, and impermeability of plasma membranes to this compound was verified by fluorescence confocal microscopy. In an injury model of Madin-Darby canine kidney cells, ATP depletion led to lactate dehydrogenase release. SF prevented lactate dehydrogenase leakage without ameliorating ATP depletion. This was accompanied by preservation of cellular ultrastructure and exclusion of vital dyes. SF protection was also shown for ATP-depleted rat hepatocytes. On the other hand, when a key structural motif in the active site of strychnine was chemically blocked, the SF lost its protective effect, establishing strychnine-related specificity for SF protection. Cytoprotective effects of the cell-impermeant strychnine derivative provide compelling evidence suggesting that molecular targets on the outer surface of plasma membranes may mediate cytoprotection by strychnine and glycine.

Anaerobic and aerobic pathways for salvage of proximal tubules from hypoxia-induced mitochondrial injury

We have further examined the mechanisms for a severe mitochondrial energetic deficit, deenergization, and impaired respiration in complex I that develop in kidney proximal tubules during hypoxia-reoxygenation, and their prevention and reversal by supplementation with alpha-ketoglutarate (alpha-KG) + aspartate. The abnormalities preceded the mitochondrial permeability transition and cytochrome c loss. Anaerobic metabolism of alpha-KG + aspartate generated ATP and maintained mitochondrial membrane potential. Other citric-acid cycle intermediates that can promote anaerobic metabolism (malate and fumarate) were also effective singly or in combination with alpha-KG. Succinate, the end product of these anaerobic pathways that can bypass complex I, was not protective when provided only during hypoxia. However, during reoxygenation, succinate also rescued the tubules, and its benefit, like that of alpha-KG + malate, persisted after the extra substrate was withdrawn. Thus proximal tubules can be salvaged from hypoxia-reoxygenation mitochondrial injury by both anaerobic metabolism of citric-acid cycle intermediates and aerobic metabolism of succinate. These results bear on the understanding of a fundamental mode of mitochondrial dysfunction during tubule injury and on strategies to prevent and reverse it.

Serine protease inhibitors suppress cytochrome c-mediatedcaspase-9 activation and apoptosis during hypoxia-reoxygenation

We have shown that reoxygenation of hypoxic rat kidney proximaltubule cells leads to apoptosis. This is mediated by translocation ofBax from the cytosol to mitochondria, accompanied by release ofmitochondrial cytochrome c (cyt.c). The present studyhas examined the proteolytic mechanisms responsible for apoptosisduring hypoxia-reoxygenation. Caspases were activated duringhypoxia, as shown by cleavage of fluorogenic peptide substrates. By5 h caspase-3-like activity to cleave carbobenzoxy-Asp-Glu-Val-Asp-7-amino-4-trifluoromethyl coumarin was increased approx. 30-fold. Thiswas accompanied by specific processing of pro-caspase-3, -8 and -9 intoactive forms. Caspase activation during hypoxia was blocked bycarbobenzoxy-Val-Ala-Asp-fluoromethyl ketone and overexpression of Bcl-2. Of particular interest, caspase activation was also suppressed bythe chymotryptic inhibitors N-tosyl-L-phenylalaninechloromethyl ketone (TPCK) and Ala-Pro-Phe chloromethyl ketone (APF),and the general serine protease inhibitor 4-(2-aminoethyl)benzenesulphonyl fluoride. Inhibition of caspase activationby these compounds resulted in arrest of apoptosis. On the other hand,the serine protease inhibitors did not prevent release of mitochondrialcyt.c during hypoxia, suggesting that these compounds blockeda critical step in post-mitochondrial caspase activation. Furtherstudies using an in vitro reconstitution model showedthat cyt. c/dATP stimulated caspase-9 processing and downstreamcaspase activation were significantly suppressed in the presence ofTPCK and APF. Based on these results, we speculate that serineproteases may be involved in post-mitochondrial apoptotic events thatlead to activation of the initiator, caspase-9.

Role of hypoxia-induced Bax translocation and cytochrome c release in reoxygenation injury

We investigated mechanisms of cell death during hypoxia/reoxygenation of cultured kidney cells. During glucose-free hypoxia, cell ATP levels declined steeply resulting in the translocation of Bax from cytosol to mitochondria. Concurrently, there was cytochrome c release and caspase activation. Cells that leaked cytochrome c underwent apoptosis after reoxygenation. ATP depletion induced by a mitochondrial uncoupler resulted in similar alterations even in the presence of oxygen. Moreover, inclusion of glucose during hypoxia prevented protein translocations and reoxygenation injury by maintaining intracellular ATP. Thus, ATP depletion, rather than hypoxia per se, was the cause of protein translocations. Overexpression of Bcl-2 prevented cytochrome c release and reoxygenation injury without ameliorating ATP depletion or Bax translocation. On the other hand, caspase inhibitors did not prevent protein translocations, but inhibited apoptosis during reoxygenation. Nevertheless, they could not confer long-term viability, since mitochondria had been damaged. Omission of glucose during reoxygenation resulted in continued failure of ATP production, and cell death with necrotic morphology. In contrast, cells expressing Bcl-2 had functional mitochondria and remained viable during reoxygenation even without glucose. Therefore, Bax translocation during hypoxia is a molecular trigger for cell death during reoxygenation. If ATP is available during reoxygenation, apoptosis develops; otherwise, death occurs by necrosis. By preserving mitochondrial integrity, BCL-2 prevents both forms of cell death and ensures cell viability.

Mechanisms of cell death in hypoxia/reoxygenation injury

Investigation of death pathways during cell injury in vivo caused by ischemia and reperfusion is of clinical importance, but technically difficult. Heterogeneity of cell types, differences between organ systems, diversity of death paradigms and exacerbation of tissue damage caused by inflammation are only some of the variables that need to be taken into account. With respect to the identification of necrosis and apoptosis in affected organs, technical issues related to preparation artifacts, occurrence of internucleosomal DNA cleavage in necrotic as well as apoptotic cells and other overlaps in death pathways bear consideration. In that caspase independent as well as caspase dependent processes cause cell death and that caspase inhibitors can act as anti-inflammatory agents, evaluation of ischemic death mechanisms in parenchymal cells needs to be performed with caution. When the effects of inflammation are removed by appropriate in vitro studies using purified or cultured cells, several mitochondrial factors that lead to cell death can be studied. Substantial evidence exists for the participation of electron transport defects, mitochondrial permeability transitions (MPT) and release of cytochrome c from mitochondria, effected by pro-apoptotic proteins such as Bax. The anti-apoptotic protein Bcl-2 exerts an overriding protective role in this type of injury by preserving mitochondrial structure and function. In contrast, caspase inhibitors cannot offer long-term protection to ischemically injured parenchymal cells regardless of how effectively they can inhibit apoptotic events, if the cells have suffered permanent mitochondrial damage impairing respiration.

Development of porous defects in plasma membranes of adenosine triphosphate-depleted Madin-Darby canine kidney cells and its inhibition by glycine

Studies during the past decade have led to the recognition of a fundamental, widely expressed mechanism of structural damage in energy-deprived cells, which is suppressed by physiologic levels of glycine and is independent of Ca2+ availability or alterations of cytosolic free Ca2+. To gain insight into this process, Madin-Darby canine kidney (MDCK) cells were depleted of adenosine triphosphate (ATP) by a mitochondrial uncoupler in glucose-free medium, and intracellular free Ca2+ was clamped at 100 nM to avoid calcium cytotoxicity. Although the ATP-depleted cells swelled and blebbed and their plasma membranes appeared to be under tension, they nevertheless became permeable to macromolecules. The plasma membranes of these cells retained structural continuity, as determined by morphologic observations, and confocal microscopy of a plasma membrane protein label (Biotin: Ultra Avidin-Texas Red) and a lipid label (NBD-sphingomyelin). Using fluoresceinated dextrans of graded molecular size, membrane permselectivity was examined noninvasively by confocal microscopy. Measured as inside/outside ratios of fluorescence intensity, the permeability indices showed progressively greater restriction to diffusion of increasingly larger dextran molecules across plasma membranes, with sharp break-points between 70,000 and 145,000 daltons (d). The results indicated that the membranes behaved as if they were perforated by water-filled channels or "pores," with size-exclusion limits of molecular dimensions. The membrane defects evolved from small pores permeable only to propidium iodide (668 d) and the smallest dextran (4,000 d), before enlarging with time to become permeable to larger dextrans. Inclusion of glycine during ATP depletion did not affect cell swelling or blebbing but completely prevented the development of permeability defects. Treatment of cells before ATP depletion with a membrane-impermeant homobifunctional "nearest neighbor" cross-linking agent, 3,3' dithiobis(sulfosuccinimidylpropionate), suppressed the development of permeability defects, even in the absence of glycine. These observations suggest that the cellular abnormality that is suppressed by glycine involves rearrangement of plasma membrane proteins to form water-filled pores large enough to leak macromolecules.

Intracellular Ca2+ thresholds that determine survival or death of energy-deprived cells

Increase of intracellular ionized or free Ca2+ is thought to play a central role in cell death due to ATP depletion. However, concurrently operative mechanisms of injury that do not require intracellular Ca2+ increases have made it difficult to test this hypothesis or to determine the concentrations at which intracellular Ca2+ becomes lethal. The predominant Ca2+-independent mechanism of injury during ATP depletion involves the loss of cellular glycine. This type of damage can be fully inhibited by adding the amino acid exogenously. Using glycine to suppress Ca2+-independent plasma membrane damage, we have examined the effect of intracellular Ca2+ elevations on cell viability during ATP depletion. Madin-Darby canine kidney (MDCK) cells were depleted of ATP by incubation with a mitochondrial uncoupler in glucose-free medium. Free Ca2+ concentration in the medium was varied between 26 nmol/L and 1.25 mmol/L in the presence of a Ca2+ ionophore. Measurements with the Ca2+ probes fura-2, furaptra, and fura-2FF showed that intracellular Ca2+ was clamped at extracellular levels under these conditions. Cell survival during ATP depletion was indicated by viable cells recovered 24 hours later. The results show that ATP-depleted cells can sustain high levels of intracellular Ca2+ (100 micromol/L) for prolonged periods and remain viable if plasma membrane damage is prevented by glycine. Cell death was observed only when intracellular free Ca2+ was allowed to increase beyond 100 micromol/L, and this was associated with dramatic nuclear alterations: chromatin condensation, loss of nuclear lamins, and breakdown of DNA into large 50- to 150-kb fragments. Our studies demonstrate unexpectedly high resistance of cells to calcium cytotoxicity if glycine that is lost during ATP depletion is restored. In addition, they provide insights into novel mechanisms of nuclear disintegration and DNA damage that are triggered when the high thresholds of intracellular Ca2+ required for cell death are exceeded.

Internucleosomal DNA cleavage triggered by plasma membrane damage during necrotic cell death. Involvement of serine but not cysteine proteases

Autolytic DNA breakdown, detected as smears in electrophoretic gels, is a late event in necrosis. On the other hand, internucleosomal DNA cleavage, visualized as ladders, is thought to be a hallmark of apoptosis. We now report that this specific form of DNA fragmentation also occurs during necrosis and is an early event but appears to be triggered by proteolytic mechanisms significantly different from those documented in apoptosis. Treatment of MDCK cells with a mitochondrial uncoupler and a Ca2+ ionophore led to ATP depletion, necrotic morphology, and progressive fragmentation of DNA in an internucleosomal or ladder pattern. DNA breakdown was immediately preceded by increased permeability of the plasma membrane to macromolecules. Provision of glycine along with the noxious agents did not modify the extent of ATP depletion, but prevented plasma membrane damage. This was accompanied by complete inhibition of DNA fragmentation. Internucleosomal DNA cleavage was observed also during necrosis after rapid permeabilization of plasma membranes by detergents or streptolysin-O in hepatocytes, thymocytes, and P19, Jurkat, and MDCK cells. DNA fragmentation associated with necrosis was Ca2+/Mg2+ dependent, was suppressed by endonuclease inhibitors, and was abolished by serine protease inhibitors but not by inhibitors of interleukin-1 beta converting enzyme (ICE)-related proteases or caspases. Moreover, unlike apoptosis, it was not accompanied by caspase-mediated proteolysis. On the other hand, the cleavage-site-directed chymotryptic inhibitor N-tosyl-L-phenylalanyl-chloromethyl ketone (TPCK) suppressed DNA fragmentation not only in necrotic cells but also during Fas-mediated apoptosis, without inhibiting caspase-related proteolysis. The results suggest a novel pathway of endonuclease activation during necrosis not involving the participation of caspases. In addition, they indicate that techniques based on double-strand DNA breaks may not reliably differentiate between apoptosis and necrosis.

Cytoprotection of kidney epithelial cells by compounds that target amino acid gated chloride channels

Glycine, strychnine and certain chloride channel blockers were reported to protect cells against lethal cell injury. These effects have been attributed to interactions with membrane proteins related to CNS glycine gated chloride channel receptors. We have investigated the pharmacology of these actions. Madin-Darby canine kidney (MDCK) epithelial cells were depleted of adenosine triphosphate (ATP) by incubation in glucose free medium containing a mitochondrial uncoupler. Medium Ca2+ was adjusted to 100 nM in the presence of an ionophore such that intracellular Ca2+ did not increase, and Ca(2+)-related injury mechanisms were inhibited. This permitted more sensitive quantitation of protection against cell injury attributable to glycine or other agents whose actions might be related to those of the amino acid. Two classes of compounds showed cytoprotective activity in this system: (1) ligands at chloride channel receptors, such as glycine, strychnine and avermectin B1a; (2) chloride channel blockers, including cyanotriphenylboron and niflumic acid, both of which are known to bind to channel domains of CNS glycine receptors. Morphological and functional studies showed that the compounds preserved plasma membrane integrity, but permitted cell swelling. Substitution of medium chloride by gluconate, or chloride salts by sucrose, did not substantially modify lethal damage or its prevention by glycine or other drugs. The compounds did not modify ATP declines. At least for some compounds, cytoprotection appeared to be specific to structural features on the molecules. These observations are consistent with the hypothesis that a plasma membrane protein related to glycine-gated chloride channel receptors plays a significant role in cell injury, but indicate that the mechanisms of injury and protection by compounds active in this system are not related to chloride fluxes.

High glucose elevates c-fos and c-jun transcripts and proteins in mesangial cell cultures

It has been previously shown that rat glomerular mesangial cells synthesized increased amounts of fibronectin, laminin, and type IV collagen when grown in medium containing 30 mM glucose. High glucose exerted its effect at the mRNA level since transcripts for all three extracellular matrix (ECM) proteins were similarly elevated. High glucose appeared to exert its effect on ECM mRNA levels through protein kinase C activation. Using quantitative reverse transcription (RT) PCR, we now report that mRNA levels for c-fos and c-jun were increased approximately twofold after treatment with high glucose. The fos levels were elevated 15 minutes after addition of high glucose and were maintained elevated through 30 minutes; by one hour mRNA levels for fos returned to control levels. c-jun, on the other hand, was increased at two hours and remained elevated at 24 and 48 hours. Fibronectin mRNA levels were increased three- to fourfold at 24 and 48 hours. Immunofluorescence studies with polyclonal antibodies to c-fos and c-jun revealed that high glucose treatment for four hours increased nuclear staining intensity two- to threefold for both proteins. Nuclear staining for fos returned to control levels by 24 hours while staining for jun remained elevated. These determinations were made on images obtained on a confocal laser scanning microscope. Thus, high glucose may effect gene expression of ECM proteins by elevating the transcription factors c-fos and c-jun which complex with one another to form activator protein 1 (AP-1).

The Myb oncogene product induces DNA-bending

The nuclear oncogene v-myb and its cellular counterpart c-myb code for proteins that bind to DNA in a sequence specific manner and act as regulators of transcription. The Myb protein contains DNA binding and trans-regulatory domains which are important for its function. The DNA binding domain of Myb protein has been shown to contain three imperfectly conserved repeats of 50-52 amino acids that constitute the amino terminal end. In this communication, we show that Myb protein induces conformational change in DNA after protein-DNA complex formation. Circular permutation assays indicate that Myb protein induces DNA bending at the site of binding. Phasing analysis confirm the DNA bending and allowed the detection of relative orientation of bend. Myb proteins which comprise only DNA-binding domains either with three repeats or two repeats also bend DNA in the same orientation as the larger proteins with both DNA-binding and transactivating domains. However, the transactivating region seems to influence the magnitude of bend angle. We used molecular modeling to analyse the structure of Myb-DNA complex formation resulting in the bending of DNA. Data presented here show that Myb protein, like other transcriptional regulators, bends DNA upon binding allowing the interaction of regulatory elements.

Competing peroxidase and oxidase reactions in scopoletin-dependent H2O2-initiated oxidation of NADH by horseradish peroxidase

Addition of NADH inhibited the peroxidative loss of scopoletin in presence of horseradish peroxidase and H2O2 and decreased the ratio of scopoletin (consumed):H2O2 (added). Concomitantly NADH was oxidized and oxygen was consumed with a stoichiometry of NADH:O2 of 2:1. On step-wise addition of a small concentration of H2O2 a high rate of NADH oxidation was obtained for a progressively decreasing time period followed by termination of the reaction with NADH:H2O2 ratio decreasing from about 40 to 10. The rate of NADH oxidation increased linearly with increase in scopoletin concentration. Other phenolic compounds including p-coumarate also supported this reaction to a variable degree. A 418-nm absorbing compound accumulated during oxidation of NADH. The effectiveness of a small concentration of H2O2 in supporting NADH oxidation increased in presence of SOD and decreased in presence of cytochrome c, but the reaction terminated even in their presence. The results indicate that the peroxidase is not continuously generating H2O2 during scopoletin-mediated NADH oxidation and that both peroxidase and oxidase reactions occur simultaneously competing for an active form of the enzyme.

Oral vaccination of racoons (Procyon lotor) with baculovirus-expressed rabies virus glycoprotein

Successful field oral vaccination and protection against viral diseases have so far been achieved only with live-attenuated or live-recombinant virus vaccines. In this communication, we present data that demonstrate that a glycoprotein derived from recombinant baculovirus-infected insect cells is efficacious as an oral vaccine. The glycoprotein (G) of rabies virus (Evelyn Rokitnicki Abelseth strain) was abundantly expressed in a baculovirus expression system and oral vaccination of racoons with the baculovirus-expressed G protein resulted in the production of rabies virus-neutralizing antibodies and protection against a lethal challenge with a street rabies virus. The potential for using the baculovirus-expressed G protein for oral immunization of wildlife is discussed.

Mutational analysis of Max: role of basic, helix-loop-helix/leucine zipper domains in DNA binding, dimerization and regulation of Myc-mediated transcriptional activation

The Max protein forms a heterodimeric complex with the Myc family of proteins and binds to DNA in a sequence-specific manner. We investigated the role of the helix-loop-helix (HLH), leucine zipper (LZ) and basic domains of Max in protein complex formation, DNA-binding activity and transcriptional regulation. We mutagenized the basic, HLH and LZ domains of Max and studied the ability of the normal and mutant proteins to bind to DNA as both homo- and heterodimers and their ability to heterodimerize with Myc. Helix-1 and helix-2 regions of Max were found to be critical for homodimer formation and subsequent DNA binding, while the LZ was essential for heterodimer formation. In transient transfection assays the Myc protein functioned as a transcriptional activator while Max protein repressed the trans-activation observed with Myc.

The cellular proto-oncogene product Myb acts as transcriptional activator of the long terminal repeat of human T-lymphotropic virus type I

The proto-oncogene c-myb encodes a nuclear transcription factor that binds to DNA in a sequence-specific manner and activates transcription of several viral and cellular genes. Expression of the c-myb gene is induced in mitogen- and/or antigen-stimulated T lymphocytes, which are also the preferential target cells of human T-lymphotropic virus type I (HTLV-I) in vivo and in vitro. We report here that Myb binds to the HTLV-I long terminal repeat (LTR) in four different regions in a sequence-specific manner. Electrophoretic mobility shift assay using labeled LTR fragments as well as labeled double-stranded oligonucleotides show that there are two high-affinity and two low-affinity Myb-binding sites present in the HTLV-I LTR. DNase I footprinting analysis and oligonucleotide competition experiments indicate that this binding is sequence specific. Cotransfection experiments in HeLa cells, using a Myb expression vector and chloramphenicol acetyltransferase reporter gene linked to the HTLV-I LTR, show that Myb activates HTLV-I LTR-mediated transcription by a factor of four-to sixfold. Thus, in HTLV-I-infected T cells, Myb protein binding to the HTLV-I LTR may constitute one of the signal that regulate HTLV-I transcription in vivo.

Expression of human Alzheimer amyloid precursor protein in insect cells

The amyloid beta-peptide is a major constituent of amyloid deposited in the brains of patients with Alzheimer's disease and is derived from a larger precursor protein/s (APP-695, 751, 770). A human cDNA encoding full-length APP-751 was inserted into the genome of Autographa californica nuclear polyhedrosis virus under transcriptional regulation of the viral polyhedrin gene promoter. The recombinant virus was used to infect insect cells, which resulted in the abundant expression of APP-751. Analysis of infected cell proteins indicate that APP-751 is localized in the membrane fraction; however, a significant amount of the protein was cleaved and released into the medium. The NH2-terminal sequence of recombinant APP-751 from the membrane fraction was identical to that of mammalian APP. Immunoblot analysis suggests that the secreted form results from cleavage within the beta-peptide.

Role of tryptophan repeats and flanking amino acids in Myb-DNA interactions

The c-myb protooncogene codes for a sequence-specific DNA-binding protein that appears to act as a transcriptional regulator and is highly conserved through evolution. The DNA-binding domain of Myb has been shown to contain three imperfectly conserved repeats of 52 amino acids that constitute the amino-terminal end. Within each repeat, there are three tryptophans that are separated by 18 or 19 amino acids and are flanked by basic amino acids. To determine the role of tryptophans and the flanking basic amino acids in the DNA-binding activity of Myb proteins, we have selectively mutagenized individual tryptophans as well as some of the amino acid residues that flank these tryptophans. Replacement of these tryptophans with glycine, proline, or arginine abolished the DNA-binding activity whereas replacement with other aromatic amino acids or leucine or alanine did not appreciably affect this activity. On the other hand the replacement of two amino acids, asparagine and lysine, that flank the last tryptophan with acidic amino acids completely abolished their DNA-binding activity. These results are consistent with a model we present in which the tryptophans form a hydrophobic scaffold that plays a crucial role in maintaining the helix-turn-helix structure of the DNA binding domain. Basic and polar amino acids adjacent to these tryptophans seem to participate directly in DNA binding.

Myb protein binds to human immunodeficiency virus 1 long terminal repeat (LTR) sequences and transactivates LTR-mediated transcription

The protooncogene c-myb encodes a nuclear transcription factor that binds to DNA in a sequence-specific manner and transactivates transcription of several viral and cellular genes. The expression of c-myb is induced in mitogen-stimulated peripheral blood lymphocytes and is constitutively expressed in several CD4+ T-cell and myeloid cell lines, all of which constitute excellent targets for human immunodeficiency virus (HIV) infection and replication. We looked for the presence of Myb-binding motifs in human retroviral long terminal repeats (LTRs) and tested for Myb binding to HIV-1 LTR sequences by using a highly purified recombinant Myb protein. Our results show that HIV-1 LTR contains one high-affinity Myb-binding site along with two or more low-affinity binding sites. DNase I protection analysis as well as oligonucleotide competition experiments indicate that this binding is sequence specific. Introduction of purified Myb protein directly into HeLa cells harboring HIV-1 LTR chloramphenicol acetyltransferase vectors indicates that Myb protein transactivates HIV-1 LTR-mediated transcription. Thus, Myb protein binding to HIV LTR sequences may constitute one of the signals that regulates HIV-1 transcription.

Effect of administration of 2-methyl-4-dimethylaminoazobenzene on the half-lives of rat liver mitochondria and cytochrome oxidase

The turnover of total mitochondrial proteins and cytochrome oxidase in the livers of rats administered with 2-methyl-4-dimethylaminoazobenzene (2-Me-DAB) has been determined. The incorporation of [14C]bicarbonate revealed a half-life of 3.1 days in control and 6 to 9 days in azodye administered animals for whole mitochondrial proteins. The incorporation of [35S]methionine yielded t1/2 values of 8.5 days and 15.4 days, respectively. The t1/2 of cytochrome oxidase, 10.8 days for control and 19.3 days for 2-Me-DAB-treated animals, indicated that the delay in the decay of the enzyme was of the same order as that of whole mitochondria. Short term incorporation revealed that the administration of the azodye stimulated the synthesis of the enzyme. Mitochondria isolated from azodye-administered animals appeared less susceptible to lysosomal proteolysis. Also, azodye administration seemed to impair the ability of lysosomes to degrade mitochondria.

Functional changes in rat liver mitochondria on administration of 2-methyl-4-dimethylaminoazobenzene

Administration of 2-methyl-4-dimethylaminobenzene in the diet (0.1%, w/w) for 85-90 days doubled the content of mitochondria in the livers of rats. The azodye was covalently bound to liver proteins, and about 15% of the amount found in liver was associated with the mitochondrial fraction. Mitochondria isolated from the livers of azodye-fed animals showed drastically lowered ability to oxidize NAD+-linked substrates. The inhibited electron-transfer step was the reduction of ubiquinone. The organelles showed a large increase in succinate oxidase activity. The activity of cytochrome oxidase and the content of cytochrome aa3 were substantially higher in these organelles. Azodye-fed animals showed depressed serum cholesterol concentrations. The content of ubiquinone in liver also registered a small increase.