CXCR2 is a negative regulator of p21 in p53-dependent and independent manner via Akt-mediated Mdm2 in ovarian cancer

Ovarian cancer (OC) has the highest rate of mortality among gynecological malignancy. Chemokine receptor CXCR2 in OC is associated with poor outcomes. However, the mechanisms by which CXCR2 regulates OC proliferation remain poorly understood. We generated CXCR2-positive cells from parental p53 wild-type (WT), mutant and null OC cells, and assessed the roles of CXCR2 on proliferation of OC cells in p53-dependent and independent manner. CXCR2 promoted cell growth rate: p53WT > mutant = null cells. Nutlin-3, a p53 stabilizer, inhibited cell proliferation in p53WT cells, but had little effect in p53-mutant or null cells, indicating p53-dependence of CXCR2-mediated proliferation. CXCR2 decreased p53 protein, a regulator of p21, and downregulated p21 promoter activity only in p53WT cells. The p53 responsive element (RE) of p21 promoter played a critical role in this CXCR2-mediated p21 downregulation. Moreover, CXCR2-positive cells activated more Akt than CXCR2-negative cells followed by enhanced murine double minute (Mdm2). Silencing Mdm2 or Akt1 upregulated p21 expression, whereas Akt1 overexpression downregulated p21 at the promoter and protein levels in p53WT cells. Cell cycle analysis revealed that CXCR2 decreased p21 gene in p53-null cells. Interestingly, romidepsin (histone deacetylase inhibitor)-induced p21 upregulation did not involve the p53 RE in the p21 promoter in p53-null cells. Romidepsin decreased the protein levels of Akt1 and Mdm2, leading to induction of p21 in p53-null cells. CXCR2 reduced romidepsin-induced p21 upregulation by activating Akt-induced Mdm2. Taken together, CXCR2 enhances cell proliferation by suppressing p21 through Akt-Mdm2 signaling in p53-dependent and independent manner.

NF-κB-Mediated CCL20 Reigns Dominantly in CXCR2-Driven Ovarian Cancer Progression

Ovarian cancer is an inflammation-associated malignancy with a high mortality rate. CXCR2 expressing ovarian cancers are aggressive with poorer outcomes. We previously demonstrated that CXCR2-driven ovarian cancer progression potentiated NF-κB activation through EGFR-transactivated Akt. Here, we identified the chemokine signature involved in CXCR2-driven ovarian cancer progression using a mouse peritoneal xenograft model for ovarian cancer spreading with CXCR2-negative (SKA) and positive (SKCXCR2) cells generated previously from parental SKOV-3 cells. Compared to SKA bearing mice, SKCXCR2 bearing mice had the following characteristics: 1) shorter survival time, 2) greater tumor spreading in the peritoneal cavity and 3) higher tumor weight in the omentum and pelvic site. Particularly, SKCXCR2-derived tumor tissues induced higher activation of the NF-κB signaling pathway, while having no change in EGFR-activated signaling such as Raf, MEK, Akt, mTOR and Erk compared to SKA-derived tumors. Chemokine PCR array revealed that CCL20 mRNA levels were significantly increased in SKCXCR2-derived tumor tissues. The CCL20 promoter activity was regulated by NF-κB dependent pathways. Interestingly, all three κB-like sites in the CCL20 promoter were involved in regulating CCL20 and the proximal region between -92 and -83 was the most critical κB-like site. In addition, SKCXCR2-derived tumor tissues maintained high CCL20 mRNA expression and induced greater CCL24 and CXCR4 compared to SKCXCR2 cells, indicating the shift of chemokine network during the peritoneal spreading of tumor cells via interaction with other cell types in tumor microenvironment. Furthermore, we compared expression profiling array between human ovarian cancer cell lines and tumor tissues based on GEO datasets. The expression profiles in comparison with cell lines revealed that dominant chemokines expressed in ovarian tumor tissues are likely shifted from CXCL1-3 and 8 to CCL20. Taken together, the progression of ovarian cancer in the peritoneal cavity involves NF-κB-mediated CCL20 as a main chemokine network, which is potentiated by CXCR2 expression.

Preferential effect of akt2-dependent signaling on the cellular viability of ovarian cancer cells in response to EGF

OBJECTIVE

Overexpression of the epidermal growth factor receptor (EGFR) is associated with the malignant phenotype in many cancers including ovarian cancer, which leads to increased cell proliferation and survival. In spite of emerging EGFR inhibitors as a potentially useful agent, they are largely ineffective in patients with advanced or recurrent ovarian cancers. Since Akt as a key downstream factor of EGFR is highly activated in some high grade serous ovarian tumors, the augmented Akt activation may attribute to irregular EGFR-mediated signaling observed in ovarian cancer. Here we investigated the differential effect of Akt on the EGF-induced cell viability in a panel of ovarian cancer cell lines.

METHODS

Cellular viability assay and western blot analysis were used to measure cell viability and expression levels of proteins, respectively. Knockdown of Akt was achieved with siRNA and stable transfection of expression vectors was performed.

RESULTS

Cellular viability increased in OVCAR-3 ovarian cancer cells exposed to EGF, but little to no difference was observed in the 5 other ovarian cancer cells including SKOV-3 cells despite of the expression of EGFR. In OVCAR-3 cells, EGF activated Erk and Akt, but an Erk inhibitor had no impact on cellular viability. On the other hand, the EGFR and PI3K inhibitors decreased EGF-induced cellular viability, indicating the involvement of Akt signaling. Although EGF activated Erk in SKOV-3 cells, the Akt activation was very weak as compared to OVCAR-3 cells. Furthermore, we observed a different expression of Akt isoforms: Akt1 was constitutively expressed in all tested ovarian cancer cells, while Akt3 was little expressed. Interestingly, Akt2 was highly expressed in OVCAR-3 cells. Knockdown of Akt2 blocked EGF-induced OVCAR-3 cell viability whereas knockdown for Akt1 and Erk1/2 had no significant effect. Stable transfection of Akt2 into SKOV-3 cells phosphorylated more Akt and enhanced cell viability in response to EGF.

CONCLUSIONS

Akt2-dependent signaling appears to play an important role in EGFR-mediated cellular viability in ovarian cancer and targeting specific Akt isoform may provide a potential therapeutic approach for EGFR-expressing ovarian cancers.

Chemokine network during adipogenesis in 3T3-L1 cells: Differential response between growth and proinflammatory factor in preadipocytes vs. adipocytes

Obesity is recognized as a low-grade chronic inflammatory state which involves a chemokine network contributing to a variety of diseases. As a first step toward understanding the roles of the obesity-driven chemokine network, we used a 3T3-L1 cell differentiation model to identify the chemokine profiles elicited during adipogenesis and how this profile is modified by epidermal growth factor (EGF) and tumor necrosis factor-α (TNF) as a growth and proinflammatory factor, respectively. The chemokine network was monitored using PCR arrays and qRT-PCR while main signaling pathways of EGF and TNF were measured using immunoblotting. The dominant chemokines in preadipocytes were CCL5, CCL8, CXCL1, and CXCL16, and in adipocytes CCL6 and CXCL13. The following chemokines were found in both preadipocytes and adipocytes: CCL2, CCL7, CCL25, CCL27, CXCL5, CXCL12, and CX3CL1. Among chemokine receptors, CXCR7 was specific for preadipocytes and CXCR2 for adipocytes. These findings indicate the development of a CXCL12–CXCR7 axis in preadipocytes and a CXCL5–CXCR2 axis in adipocytes. In addition to induction of CCL2 and CCL7 in both preadipocytes and adipocytes, EGF enhanced specifically CXCL1 and CXCL5 in adipocytes, indicating the potentiation of CXCR2-mediated pathway in adipocytes. TNF induced CCL2, CCL7, and CXCL1 in preadipocytes but had no response in adipocytes. EGFR downstream activation was dominant in adipocytes whereas NFκB activation was dominant in preadipocytes. Taken together, the adipocyte-driven chemokine network in the 3T3-L1 cell differentiation model involves CXCR2-mediated signaling which appears more potentiated to growth factors like EGF than proinflammatory factors like TNF.

Aspirin Blocks EGF-stimulated Cell Viability in a COX-1 Dependent Manner in Ovarian Cancer Cells

Objective: Although aspirin has been associated with a reduction of the risk of cancer when used as a nonsteroidal anti-inflammatory drug, its use to reduce the risk of ovarian cancer is controversial. Ovarian cancer cells usually express high levels of cyclooxygenase-1 (COX)-1. Because aspirin is a rather selective inhibitor of COX-1, the ability of aspirin to reduce the risk of ovarian cancer may be dependent on the level of COX-1 expression in those cells. Furthermore, epidermal growth factor receptor (EGFR) is frequently overexpressed in the malignant phenotype of ovarian cancer leading to increased cell proliferation and survival. Here we investigated if aspirin attenuates EGFR-activated ovarian cancer cell growth in a COX-1 dependent manner.

Methods: Cell viability assays and Western blot analyses were used to determine the effect of aspirin on EGF-stimulated cell proliferation. Gene silencing and gene expression techniques were employed to knockdown or to express COX-1, respectively.

Results: Aspirin inhibited cell viability induced by EGF in a dose dependent manner in COX-1 positive ovarian cancer cells. On the other hand, aspirin had no effect on cell viability in COX-1 negative ovarian cancer cells. In particular, aspirin decreased phosphorylated Akt and Erk activated by EGF. COX-1 silencing in COX-1 positive cells attenuated the inhibitory effect of aspirin on EGF-stimulated cell viability. Furthermore, we developed a COX-1 expressing cell line (SKCOX-1) by stably transfecting COX-1 expression vector into COX-1 negative SKOV-3 cells. SKCOX-1 cells were more responsive to aspirin when compared to cells transfected with empty vector, and decreased EGF-activated Akt and Erk as well as cell viability.

Conclusions: Taken together, aspirin inhibits viability of ovarian cancer cells by blocking phosphorylation of Akt and Erk activated by EGF. Thus it may potentiate the therapeutic efficacy of drugs used to treat COX-1 positive ovarian cancer subsets.

Characteristics of chemokine signatures elicited by EGF and TNF in ovarian cancer cells

Background

Ovarian cancer, an inflammation-associated cancer, is the fifth leading cause of cancer deaths in women. The malignancy produces a large amount of tumor necrosis factor (TNF) which promotes a proinflammatory tumor microenvironment. In addition, the epidermal growth factor receptor (EGFR) is frequently overexpressed in high-grade ovarian cancer, which likely aggravates cancer progression. Since ovarian cancer progression is closely associated with chemokine networks driven by inflammation or EGFR activation, we investigated the chemokine signatures elicited by EGF and TNF in ovarian cancer cells to determine their individual profiles and if there was in fact some kind of synergy between their actions on the chemokine network.

Methods

We used a PCR array for the chemokine network to examine the signature of chemokines and their receptors elicited by EGF and TNF in four ovarian cancer cell lines (OVCAR-3, SKOV-3, CaOV-3 and TOV-21G).

Results

The chemokine network revealed that ovarian cancer cells commonly expressed high levels of proinflammatory chemokines such as CCL20, CXCL1-3 and CXCL8 in response to EGF or TNF. However, the responsiveness to EGF or TNF displayed a cell line specific pattern. Although OVCAR-3 and SKOV-3 cells were responsive to either EGF or TNF, their TNF responsiveness was dominant. On the other hand, CaOV-3 and TOV-21G cells were responsive to EGF but less to TNF, probably due to the high levels of non-canonical nuclear factor (NF)-κB components such as IKKα and p52 in these cell lines compared to OVCAR-3 and SKOV-3 cells. Among chemokine receptors, only CXCR5 was responsive to EGF or TNF in CaOV-3 cells. Finally, CCL20 and CXCL8 responded synergistically in response to EGF and TNF in OVCAR-3 and SKOV-3 cells.

Conclusion

Our results indicate that CCL20, CXCL1-3 and CXCL8 are the primary chemokines induced by EGF or TNF and are elicited in these ovarian cancer cells via NF-κB, Akt and Erk signaling pathways. Of interest, there was a syngergistic response in terms of CCL20 and CXCL8 levels, when OVCAR-3 and SKOV-3 cells were exposed to EGF plus TNF. Targeting these proinflammatory chemokines may be a promising therapeutic strategy for ovarian cancer with abundant TNF and EGFR activation patterns.

Abstract 527: Proinflammatory chemokine receptor CXCR2 promotes cellular proliferation through suppression of cell cycle inhibitor p21 protein in ovarian cancer

Introduction: Ovarian cancer is responsible for the highest rate of mortality in gynecological malignancy. Increased expression for proinflammatory chemokine receptor CXCR2 and its ligand CXCL1 in ovarian cancer have been shown to be associated with poor patient outcomes. However, the mechanisms regulating the interplay between CXCR2 and ovarian cancer remain poorly understood. This study was designed to assess the role and molecular mechanisms of CXCR2 in ovarian cancer cell progression.

Methods: The influence of CXCR2 on cell proliferation was examined in CXCR2 null ovarian cancer cells A2780, OVCAR3 and SKOV3, and its stable transfected cells as a molecular tool. The signaling pathways and related genes and protein expressions were determined by Western blot, PCR array and promoter activity assay.

Results: CXCR2 promoted cell proliferation in all ovarian cancer cell lines examined. CXCL1, a CXCR2 ligand, further enhanced the potentiation of CXCR2 in cell proliferation. PCR array for cell cycle-related genes displayed inhibited expression for cell cycle inhibitor p21 gene in CXCR2 expressing cells. Western blotting showed that CXCR2 decreased tumor suppressor p53 protein, a tightly regulator for p21, particularly in p53 wild-type A2780 cells. Interestingly, CXCR2 down-regulated histone deacetylase inhibitor (romidepsin)-induced p21 protein expression, even in p53 mutant OVCAR-3 and p53 null SKOV-3 cells, implying the interaction between CXCR2 and p21 protein in a p53-indepentent manner. Nutlin-3, a p53 stabilizer, inhibited ovarian cancer cell proliferation in p53 wild-type cells, and CXCR2 expressing cells were more responsive to nutlin-3 in cell proliferation, indicating the substantial impact of nutlin-3 on p53 stabilization. On the other hand, nutlin-3 had no or little effect on cell proliferation in p53 mutant or null cells. Furthermore, a CXCR2 antagonist, SB225002, recovered the CXCR2-induced down-regulation of p21 protein, and the expression for murine double minute (Mdm2), an important negative regulator of p53, was enhanced in CXCR2 expressing cells. As an evidence to regulate Mdm2, CXCR2 activated epidermal growth factor receptor (EGFR) followed by PI3k/Akt phosphorylation, suggesting the involvement of Akt signaling in the induction of Mdm2 protein.

Conclusions: CXCL2-induced cell proliferation is specifically mediated by suppressing cell cycle inhibitor p21 protein, probably resulting from EGFR-Akt-Mdm2 signaling. Therefore, targeting this signaling pathway may represent a potential therapeutic and prophylactic approach for CXCR2 expressing cancer cells.

Citation Format: Yuanlin Dong, Syeda M. Kabir, Eunsook Lee, Deok-Soo Son. Proinflammatory chemokine receptor CXCR2 promotes cellular proliferation through suppression of cell cycle inhibitor p21 protein in ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 527. doi:10.1158/1538-7445.AM2013-527

Abstract 1090: Impact of CXCL1/CXCR2 signaling in ovarian cancer proliferation

Introduction: Chemokine network plays a critical role in the development and progression of cancer. Human ovarian tumors express chemokine CXCL1 and its receptor CXCR2, but its role in ovarian cancer development and progression remains unclear. In this study, we investigate whether CXCL1/CXCR2 have functional significance in ovarian cancer cell proliferation. Methods: CXCR2 was overexpressed by stable transfection into the human ovarian surface epithelial cancer cell lines A2780, OVCAR3, and SKOV3. The influence of CXCL1 and CXCR2 on cell proliferation, cell cycle progression, and changes in related proteins and gene expression were determined by using confocal image analysis, MTT assay, Western blotting, flow cytometry, and PCR array. Results: CXCR2 was mainly expressed on the cell surface and intracellular localization, and these expressions were profoundly enhanced in CXCR2 overexpressed cell lines when compared to controls. CXCR2 significantly increased the proliferation of A2780, OVCAR3 and SKOV3 cells in a time-dependent manner, and these increases were abolished by the CXCR2 inhibitor, SD 225002. Furtermore, CXCR2-induced cancer cell proliferation was suppressed by Gefitinib, an inhibitor of epidermal growth factor receptor (EGFR), indicating crosstalk between CXCR2 and EGFR in ovarian cancer cell proliferation. CXCR2 induced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and NF-kappa B, probably contributing to ovarian tumor growth and metastatic progression. CXCL1 significantly stimulates the cell proliferation in CXCR2 overexpressed cell lines, and the stimulations were substantially blocked by the ERK1/2 inhibitor, PD 98059, further confirming the involvement of MAPK signaling. CXCR2 reduced cell cycle arrest in the G0-G1 phase and increased the cell population in the S and G2-M phase, and these changes were associated with enhanced expression for CDK6, a G1-S cell cycle transition regulatory gene. Chemokine specific PCR array revealed that CXCR2 enhances proinflammatory chemokines CCL2, CXCL1, CXCL2, CXCL3, and CXCL6, suggesting that CXCR2 accelerates proinflammatory tumor microenvironment to provide the suitable condition for ovarian cancer progression. Conclusions: Taken together, this study demonstrated that CXCL1/CXCR2 signaling plays critical roles in ovarian cancer growth and progression through the activation of ERK1/2 and NF-kappa B. Thus, CXCL1/CXCR2 signaling may be important in the pathogenesis of ovarian cancer, providing a basis for the therapeutic targets in ovarian cancer patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1090. doi:1538-7445.AM2012-1090

Desensitization of beta-adrenergic receptors in lung injury induced by 2-chloroethyl ethyl sulfide, a mustard analog

2-Choloroethyl Ethyl Sulfide (CEES) exposure causes inflammatory lung diseases, including acute respiratory distress syndrome (ARDS) and pulmonary fibrosis. This may be associated with oxidative stress, which has been implicated in the desensitization of beta-adrenergic receptors (beta-ARs). The objective of this study was to investigate whether lung injury induced by intratracheal CEES exposure (2 mg/kg body weight) causes desensitization of beta-ARs. The animals were sacrificed after 7 days and lungs were removed. Lung injury was established by measuring the leakage of iodinated-bovine serum albumin ([(125)I]-BSA) into lung tissue. Receptor-binding characteristics were determined by measuring the binding of [(3)H] dihydroalprenolol ([(3)H] DHA) (0.5-24 nM) to membrane fraction in the presence and absence of DLDL-propranolol (10 micro M). Both high- and low-affinity beta-ARs were identified in the lung. Binding capacity was significantly higher in low-affinity site in both control and experimental groups. Although CEES exposure did not change K(D) and B(max) at the high-affinity site, it significantly decreased both K(D) and B(max) at low affinity sites. A 20% decrease in beta(2)-AR mRNA level and a 60% decrease in membrane protein levels were observed in the experimental group. Furthermore, there was significantly less stimulation of adenylate cyclase activity by both cholera toxin and isoproterenol in the experimental group in comparison to the control group. Treatment of lungs with 3-isobutyl-1-methylxanthine (IBMX), an inhibitor of phosphodiesterase (PDE) could not abolish the difference between the control group and the experimental group on the stimulation of the adenylate cyclase activity. Thus, our study indicates that CEES-induced lung injury is associated with desensitization of beta(2)-AR.

Beneficial effects of soy protein in the initiation and progression against dimethylbenz [a] anthracene-induced breast tumors in female rats

This study was to demonstrate by histological grading whether soy protein protects against dimethylbenz[a]anthracene (DMBA) -induced breast tumors in female rats. At 25 days of age, rats were fed diets containing either casein or soy protein. After 25 days on diets, a single dose of DMBA in sesame oil (80 mg/kg) was administered by gavage. All tumors were detected by palpation. The number of tumors per rat was less in soy group than that in casein group at any time point up to 122 days after DMBA administration. Incidence of tumors was less in soy protein group than that in casein group. Casein group had 20% grade I, 60% grade II, and 20% grade III adenocarcinoma. However, the soy group had 100% grade I adenocarcinoma and no aggressive grade II or grade III tumor. There was a delay in the development of tumor in the soy protein group in comparison to the casein group. Again, unlike casein, the soy group had cessation of angiogenesis at several sites of tumor, and reduced levels of angiogenic markers, VEGF and bFGF. Immunohistochemical analysis of the breast tissues did not show any CD-31 positive stain in soy protein group, whereas some CD-31 positive stain was revealed in casein group, which further suggests that soy protein controls angiogenesis. Furthermore, proliferative index as assessed by Ki-67 staining was less in soy protein group than that in casein group. These findings suggest that the soy protein may protect against the development of a more aggressive breast carcinoma.

Lysophosphatidylcholine inhibits insulin-induced Akt activation through protein kinase C-alpha in vascular smooth muscle cells

To better understand the intracellular signaling mechanism that causes the association of insulin resistance and hyperlipidemia with cardiovascular diseases, we specifically looked at the ability of lysophosphatidylcholine (lysoPC) to inhibit the Akt activation induced by insulin in cultured rat aortic vascular smooth muscle cells. LysoPC inhibited the insulin-induced phosphorylation of Akt at Ser473, and the inhibition was concentration dependent. Phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, inhibited the insulin-induced phosphorylation of Akt. LysoPC stimulated PKC phosphorylation at Ser660, which was inhibited by the PKC inhibitor GF109203X. The PKC-alpha/beta-selective inhibitor Go6976 also blocked the PMA- and lysoPC-induced inhibition of Akt phosphorylation by insulin. PKC-alpha, but not PKC-beta, is expressed in vascular smooth muscle cells, and overexpression of PKC-alpha, but not PKC-beta or PKC-delta, inhibited insulin-induced Akt activation. LysoPC rapidly stimulated PKC-alpha translocation to the membrane. In contrast, pretreatment with the p42/44 mitogen-activated protein kinase kinase inhibitor PD98059 or the p38 mitogen-activated protein kinase inhibitor SB203580 did not block the lysoPC-induced inhibition of Akt phosphorylation by insulin. In addition, lysoPC inhibited the insulin-induced tyrosine phosphorylation of insulin receptor substrate (IRS)-1 but not that of the insulin receptor beta subunit or insulin binding. PMA treatment or PKC-alpha overexpression also inhibited the tyrosine phosphorylation of IRS-1. From these data, we conclude that lysoPC negatively regulates the insulin signal at the point of IRS-1 through PKC-alpha in the vasculature, which may explain the association of hyperlipidemia with hyperinsulinemia in cardiovascular diseases.

Protein kinase C inhibits insulin-induced Akt activation in vascular smooth muscle cells

Protein kinase C (PKC) activation, enhanced by hyperglycemia, is associated with many tissue abnormalities observed in diabetes. Akt is a serine/threonine kinase that mediates various biological responses induced by insulin. We hypothesized that the negative regulation of Akt in the vasculature by PKC could contribute to insulin resistant states and, may therefore play a role in the pathogenesis of cardiovascular disease. In this study, we specifically looked at the ability of PKC to inhibit Akt activation induced by insulin in cultured rat aortic vascular smooth muscle cells (VSMCs). Activation of Akt was determined by immunoblotting with a phospho-Akt antibody that selectively recognizes Ser473 phosphorylated Akt. A PKC activator, phorbol 12-myristate 13-acetate (PMA), inhibited insulin-dependent Akt phosphorylation. However, PMA did not inhibit platelet-derived growth factor (PDGF)-induced activation of Akt. We further showed that the PKC inhibitor, G06983, blocked the PMA-induced inhibition of Akt phosphorylation by insulin. In addition, we demonstrated that PMA inhibited the insulin-induced tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1). From these data, we conclude that PKC is a potent negative regulator of the insulin signal in the vasculature, which indicate an important role of PKC in the development of insulin resistance in cardiovascular disease.

Indapamide blocks the rapid component of the delayed rectifier current in atrial tumor cells (AT-1 cells)

We studied the effects of a well known blocker (indapamide) of the slow component (I(ks)) of the delayed rectifier (I(k)) on K(+) currents in atrial tumor myocytes derived from transgenic mice (AT-1 cells) using one electrode voltage clamp method. These cells have been shown to express mRNAs encoding cardiac K(+) channels and display a cardiac electrophysiological phenotype. The major K(+) current is the rapid component (I(kr)) of the delayed rectifier current (I(k)). The purpose of this study was to show that a diuretic agent, indapamide, which was shown to be a selective blocker of the slow component (I(ks)) of delayed rectifier, also blocks I(kr) in a dose dependent manner. The steady state current at the end of a 1s pulse (I(1s), step to +40 mV from a holding potential of -40 mV) was 1070.4+/-202.2 pA (n=5) and the tail current (I(tail)) was 416.3+/-112.9 pA. Indapamide (750 microM) reduced I(1s) and I(tail) to 254.5+/-62.3 pA and 42.2+/-37.7 pA respectively. Indapamide induced block was partially reversible for higher concentrations (> or =750 microM).

Role of action potential shortening in the prevention of arrhythmias in canine cardiac tissue

1. The effects of the K+ channel opener diazoxide and the oxime-containing Ca2+ and K+ channel blocker salicylaldoxime were tested in canine cardiac Purkinje tissue. 2. Both drugs shortened action potential duration (APD). For salicylaldoxime (0.1-1.0 mmol/L), the reductions in APD were statistically significant at the 25% level of repolarization (APD25) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6), at the 50% level of repolarization (APD50) for 0.1 mmol/L (P < 0.05, n = 14) and 0.5 and 1.0 mmol/L (P < 0.01, n = 6) and at the 90% level of repolarization (APD90) for 0.5 and 1.0 mmol/L (P < 0.01, n = 6). In contrast, diazoxide (0.05-0.1 mmol/L) significantly shortened APD at all levels of repolarizations, with the APD50 and APD90 reduced most significantly (P < 0.01, n = 6) for higher concentrations of the drug (0.07-0.1 mmol/L). Both drugs significantly reduced the force of contraction. 3. Diazoxide (10 experiments) was more potent in suppressing strophanthidin-induced arrhythmias than salicylaldoxime (three of seven experiments). Salicylaldoxime reduced APD even further in the presence of diazoxide. 4. Although salicylaldoxime and diazoxide modulate different ion channels, it appears APD shortening may be a necessary, but insufficient, factor for the suppression of strophanthidin-induced arrhythmias.

Causes and consequences of unwanted pregnancy from Asian women's perspectives

Shortcomings of contraceptives and of family planning delivery systems are major reasons for unwanted pregnancy and unsafe abortion in Third World countries. Family planning and health programs should provide empathetic counseling for contraceptive choices and pregnancy termination, adjust management systems and procedures to facilitate women's access to services and information, and offer comprehensive services to meet their multiple reproductive health needs.

A study of costs and behavioral outcomes of menstrual regulation services in Bangladesh

This paper reports the results of a program evaluation of menstrual regulation (MR) services provided by the Bangladesh Women's Health Coalition, a nongovernmental organization formed in response to a concern about the availability of quality MR services to Bangladeshi women. The program emphasizes individual counseling which stresses informed choice in reproductive health care. The evaluation examines the cost of this process as a function of behavioral outcomes which include the percentage of clients who are post-MR contraceptive acceptors and the percentage which return for follow-up care and consultation 2 weeks after the procedure. The average cost per post MR contracepting client is $3.75; the average cost per returning client is $5.68, figures which appear to be well within the range of costs reported by family planning programs in developing countries.