Paracrine CCL20 loop induces epithelial-mesenchymal transition in breast epithelial cells.

We previously found that CCL20 induced primarily cultured healthy breast cell proliferation and migration. The objective of this study was to investigate the hypothesis that CCL20 modulated the epithelial-mesenchymal transition (EMT) of primarily cultured healthy breast epithelial cells and the angiogenesis in areas adjacent to the tumor. Key results showed that CCL20 (a) down-regulated E-cadherin and ZO-1; (b) up-regulated N-cadherin, vimentin, and Snail expressions; (c) increased mRNA and secretion of VEGF and (d) increased angiogenic micro vessel sprouting. Thus, the signal transduction pathways evoked by CCL20 were investigated. We showed that NF-kB p65 down-regulation (by small interfering RNA, siRNA) reversed CCL20-induced Snail and blocked the up-regulation of vimentin and N-cadherin mRNAs. Furthermore, PI3K/AKT inhibition (by LY294002) completely blocked CCL20-induced Snail and NF-kB activation. Inhibition of JNK1/2 (by SP60125) or PKC-α (by siRNA) or src (by PP1) blocked NF-kB activation and Snail expression suggesting that these kinases are all upstream of NF-kB/Snail. Inhibition of mTOR (by rapamycin) abolished the effects of CCL20 on N-cadherin and vimentin protein synthesis. Furthermore, siRNA of PKC-δ inhibited the phosphorylation of CCL20-induced mTOR and S6, increased vimentin and N-cadherin expressions and, finally, blocked the CCL20 induced-EMT. CCL20 increased mRNA and secretion of VEGF by healthy breast cells by using PKC-α, src, Akt, NF-kB, and Snail signalling. In summary, tumor cells signal to the surrounding healthy cells through CCL20 inducing the modulation of the expression of molecules involved in EMT and promoting angiogenesis directly and indirectly through the secretion of VEGF, a major contributor to angiogenesis. © 2015 Wiley Periodicals, Inc.

Effect of two incremental intensity field tests on wellness indices, recovery state, and physical enjoyment in soccer players.

OBJECTIVE: Competitive athletes must undergo fitness testing to monitor athlete progress and to create appropriate, progressive training programs. However, fitness testing adds to training stress; therefore, impacts of testing on wellness and recovery must be considered in test selection. This study investigated the effects of two incremental field tests [VAMEVAL test (T-VAM) and 20-m maximum shuttle test (20-m MST)] on wellness, total quality of recovery (TQR) and physical enjoyment (PE) in competitive soccer players. SUBJECTS AND METHODS: Twenty-two soccer players (20.9±1.5 years) completed two T-VAM and two 20-m MST in a randomized order on separate days with a 1-week interval between tests. TQR and wellness indices (sleep, fatigue, stress and muscle soreness) measures were collected before and 24 hours after each test. Heart rate (HR) was continuously monitored during each test. Rating of perceived exertion (RPE) and PE were assessed after each test. RESULTS: T-VAM resulted in higher PE, TQR and wellness scores than 20-m MST (p<0.05). T-VAM and 20-m MST resulted in similar HR and maximal aerobic speed. For T-VAM, TQR was correlated (p<0.01) with RPE and wellness indices. For 20-m MST, TQR was correlated (p<0.01) with wellness indices. HRmax and RPE were not correlated with wellness indices, TQR or PE. CONCLUSIONS: Overall, T-VAM and 20-m MST produced similar aerobic fitness testing results, but athletes responded more favorably to T-VAM. Coaches can use T-VAM for evaluating aerobic fitness while maximizing well-being and physical enjoyment among soccer players.

Role of epidermal growth factor receptor signaling in a Pt(II)-resistant human breast cancer cell line.

Platinum complexes are currently used for breast cancer therapy, but, as with other drug classes, a series of intrinsic and acquired resistance mechanisms hinder their efficacy. To better understand the mechanisms underlying platinum complexes resistance in breast cancer, we generated a [Pt(O,O'-acac)(γ-acac)(DMS)]-resistant MCF-7, denoted as [Pt(acac)2]R. [Pt(O,O'-acac)(γ-acac)(DMS)] was chosen as previous works showed that it has distinct mechanisms of action from cisplatin, especially with regard to cellular targets. [Pt(acac)2]R cells are characterized by increased proliferation rates and aggressiveness with higher PKC-δ, BCL-2, MMP-9 and EGFR protein expressions and also by increased expression of various genes covering cell cycle regulation, invasion, survival, and hormone receptors. These [Pt(acac)2]R cells also displayed high levels of activated signaling kinases Src, AKT and ERK/2. [Pt(acac)2]R cells incubated with [Pt(O,O'-acac)(γ-acac)(DMS)], showed a relevant EGFR activation due to PKC-δ and Src phosphorylation that provoked proliferation and survival through MERK1/2/ERK1/2 and PI3K/Akt pathways. In addition, EGFR shuttled from the plasma membrane to the nucleus maybe acting as co-transcriptional factor. The data suggest that growth and survival of resistant cells rely upon a remarkable increase in EGFR level which, in collaboration with an enhanced role of PKC-δ and Src kinases support [Pt(acac)2]R cell. It could therefore be assumed that combination treatments targeting both EGFR and PKC-δ/Src can improve therapy for breast cancer patients.

PKC-epsilon-dependent cytosol-to-membrane translocation of pendrin in rat thyroid PC Cl3 cells.

We studied the expression and the hormonal regulation of the PDS gene product, pendrin, which is, in thyrocytes, responsible for the iodide transport out of the cell. We show that PC Cl3 cells, a fully differentiated thyroid cell line, grown without TSH and insulin, express very low level of PDS mRNA; such expression is greatly increased after stimulation with insulin or TSH. (125)I pre-loaded cells showed an (125)I efflux accelerated in chloride-containing buffer with respect to chloride-free buffer, suggesting that this efflux is chloride dependent. By immunoblotting, pendrin was found in agonists-stimulated cells, whereas it was barely detectable in un-stimulated cells. An increase in both PDS mRNA and protein was also obtained using phorbol ester PMA, or using 8-Br-cAMP and forskolin. Stimulation with insulin (1 microg/ml; 0-40 min) provoked the cytosol-to-membrane translocation of pendrin and a decrease of intracellular I(-) content in (125)I pre-loaded cells. Insulin- or PMA-treated cells also showed a cytosol-to-membrane translocation of PKC-delta and -epsilon. Inhibition of both PKC-delta and -epsilon activities by GF109203X blocked pendrin translocation, whilst the inhibition of PKA did not. The selective inhibition of PKC-delta by rottlerin did not affect the insulin-provoked translocation of pendrin whilst it was inhibited by a PKC-epsilon translocation inhibitor peptide and also by PKC-epsilon downregulation using the small interfering RNA, thus indicating that such translocation was due to PKC-epsilon activity. In conclusion, our study demonstrates that, in PC Cl3 cells, pendrin expression and localisation are regulated by insulin and influenced by a PKC-epsilon-dependent intracellular pathway.

[Pt(O,O'-acac)(gamma-acac)(DMS)], a new Pt compound exerting fast cytotoxicity in MCF-7 breast cancer cells via the mitochondrial apoptotic pathway.

BACKGROUND AND PURPOSE: We showed previously that a new Pt complex containing an O,O'-chelated acetylacetonate ligand (acac) and a dimethylsulphide in the Pt coordination sphere, [Pt(O,O'-acac)(gamma-acac)(DMS)], induces apoptosis in HeLa cells. The objective of this study was to investigate the hypothesis that [Pt(O,O'-acac)(gamma-acac)(DMS)] is also cytotoxic in a MCF-7 breast cancer cell line relatively insensitive to cisplatin, and to gain a more detailed analysis of the cell death pathways. EXPERIMENTAL APPROACH: Cells were treated with Pt compounds and cytotoxicity tests were performed, together with Western blotting of various proteins involved in apoptosis. The mitochondrial membrane potential was assessed by fluorescence microscopy and spectrofluorometry and the Pt bound to cell fractions was measured by atomic absorption spectrometry. KEY RESULTS: In contrast to cisplatin, the cytotoxicity of [Pt(O,O'-acac)(gamma-acac)(DMS)] correlated with cellular accumulation but not with DNA binding. Also, the Pt content in DNA bases was considerably higher for cisplatin than for [Pt(O,O'-acac)(gamma-acac)(DMS)], thus excluding DNA as a target of [Pt(O,O'-acac)(gamma-acac)(DMS)]. [Pt(O,O'-acac)(gamma-acac)(DMS)] exerted high and fast apoptotic processes in MCF-7 cells since it provoked: (a) mitochondria depolarization; (b) cytochrome c accumulation in the cytosol; (c) translocation of Bax and truncated-Bid from cytosol to mitochondria and decreased expression of Bcl-2; (d) cleavage of caspases -7 and -9, and PARP degradation; (e) chromatin condensation and DNA fragmentation. CONCLUSIONS AND IMPLICATIONS: [Pt(O,O'-acac)(gamma-acac)(DMS)] is highly cytotoxic for MCF-7 cells, cells relatively resistant to many chemotherapeutic agents, as it activates the mitochondrial apoptotic pathway. Hence, [Pt(O,O'-acac)(gamma-acac)(DMS)] has the potential to provide us with new opportunities for therapeutic intervention.

Antitumour and antiangiogenic activities of [Pt(O,O'-acac)(γ-acac)(DMS)] in a xenograft model of human renal cell carcinoma.

BACKGROUND AND PURPOSE: It is thought that the mechanism of action of anticancer chemotherapeutic agents is mainly due to a direct inhibition of tumour cell proliferation. In tumour specimens, the endothelial cell proliferation rate increases, suggesting that the therapeutic effects of anticancer agents could also be attributed to inhibition of tumour angiogenesis. Hence, we investigated the potential effects of [Pt(O,O'-acac)(γ-acac)(DMS)] ([Pt(DMS)]), a new platinum drug for non-genomic targets, on human renal carcinoma and compared them with those of the well-established anticancer drug, cisplatin. EXPERIMENTAL APPROACH: Tumour growth, tumour cell proliferation and microvessel density were investigated in a xenograft model of renal cell carcinoma, developed by injecting Caki-1 cells into BALB/c nude mice. The antiangiogenic potential of compounds was also investigated using HUVECs. KEY RESULTS: Treatment of the Caki-1 cells with cisplatin or [Pt(DMS)] resulted in a dose-dependent inhibition of cell survival, but the cytotoxicity of [Pt(DMS)] was approximately fivefold greater than that of cisplatin. [Pt(DMS)] was much more effective than cisplatin at inhibiting tumour growth, proliferation and angiogenesis in vivo, as well as migration, tube formation and MMP1, MMP2 and MMP9 secretion of endothelial cells in vitro. Whereas, cisplatin exerted a greater cytotoxic effect on HUVECs, but did not affect tube formation or the migration of endothelial cells. In addition, treatment of the xenograft mice with [Pt(DMS)] decreased VEGF, MMP1 and MMP2 expressions in tumours. CONCLUSIONS AND IMPLICATIONS: The antiangiogenic and antitumour activities of [Pt(DMS)] provide a solid starting point for its validation as a suitable candidate for further pharmacological testing.

Bradykinin stimulates cell proliferation through an extracellular-regulated kinase 1 and 2-dependent mechanism in breast cancer cells in primary culture.

We have previously reported that bradykinin (BK) represents an influential mitogenic agent in normal breast glandular tissue. We here investigated the mitogenic effects and the signalling pathways of BK in primary cultured human epithelial breast cells obtained from a tumour and from the histologically proven non-malignant tissue adjacent to the tumour. BK provoked cell proliferation, increase in cytosolic calcium, activation of protein kinase C (PKC)-alpha, -beta, -delta, -epsilon and -eta and phosphorylation of the extracellular-regulated kinases 1 and 2 (ERK1/2). The following compounds blocked the proliferative effects of BK: Hyp3-BK, a B2 receptor subtype inhibitor; U73122, a phospholipase C-beta inhibitor; GF109203X, a protein kinase C (PKC) inhibitor; and PD98059, a mitogen-activated protein kinase kinase inhibitor. Gö6976, a Ca(2+)-dependent PKC inhibitor, did not have any effect. In conclusion, the mitogenic effects of BK are retained in peritumour and tumour cells; hence, it is likely that BK has an important role in cancer endorsement and progression.

AT1 angiotensin II receptor mediates intracellular calcium mobilization in normal and cancerous breast cells in primary culture.

Angiotensin II (Ang II) increases intracellular calcium concentration ([Ca2+]i) in both normal and cancerous human breast cells in primary culture. Maximal [Ca2+]i increase is obtained using 100nM Ang II in both cell types; in cancerous breast cells, [Ca2+]i increase (delta[Ca2+]i) is 135+/-10nM, while in normal breast cells it reaches 65+/-5 nM (P<0.0001). In both cell types, Ang II evokes a Ca2+ transient peak mediated by thapsigargin (TG) sensitive stores; neither Ca2+ entry through L-type membrane channels or capacitative Ca2+ entry are involved. Type I Ang II receptor subtype (AT1) mediates Ang II-dependent [Ca2+]i increase, since losartan, an AT1 inhibitor, blunted [Ca2+]i increase induced by Ang II in a dose-dependent manner, while CGP 4221A, an AT2 inhibitor, does not. Phospholipase C (PLC) is involved in this signaling mechanism, as U73122, a PLC inhibitor, decreases Ang II-dependent [Ca2+]i transient peak in a dose-dependent mode.Thus, the present study provides new information about Ca2+ signaling pathways mediated through AT1 in breast cells in which no data were yet available.

Angiotensin II receptors in the gill of sea water- and freshwater-adapted eel.

Immunocytochemistry of paraffin-embedded and cryostat sections of eel (Anguilla anguilla) gill showed that angiotensin II receptors (Ang II-R) were present in chloride cells, uniformly distributed in the cytoplasm and on surface membranes. Computerised image analysis of these preparations showed that gills from sea water (SW)-adapted animals had a significantly (3-fold) higher Ang II-R concentration compared with freshwater (FW)-adapted eel gills. Isoelectric focusing gel electrophoresis revealed two Ang II-R isoforms with pI 6.5 and 6.6 that were differentially modulated by environmental salinity: they were equally abundant in SW while in FW the pI 6.6/pI 6.5 ratio was 1.66. Using catalytic cytochemistry with image analysis, gill chloride cell membrane Na+/K+ATPase activity was shown to increase 4-fold in response to SW adaptation. Additionally, perfusion of gills for 30 min with 0.1, 10 or with 100 nM Ang II provoked a dose-dependent increment in Na+/K+ATPase activity in FW, and a biphasic response in SW gills in which activity was significantly increased at low Ang II concentrations but was reduced to basal values at 100 nM. The data suggest that adaptation to sea water significantly increases Ang II-R concentration in the chloride cell and, together with the effects of Ang II on Na+/K+ATPase activity, suggest a role for this hormone in gill NaCl retention. The different responses of Na+/K+ATPase to Ang II stimulation in FW and SW may be attributed to the presence of two receptor subtypes that are differently modulated by salinity and that have opposing effects on Na+/K+ATPase.

Multiple isoforms of the oestrogen receptor in endometrial cancer.

We evaluated the presence and variability of oestrogen receptor (ER) isoforms in endometrial cancer by using [3H]oestradiol-labelled ERs and the H222 monoclonal antibody obtained from the Abbott enzyme immunoassay kit. Using isoelectric focusing (IEF), endometrial ER was shown to be composed of four different species, with pI values of 6.1, 6.3, 6.6 and 6.8, indistinguishable from the isoforms found in normal rat uterus, and human breast and larynx carcinomas. The isoforms at pI 6.3, 6.6 and 6.8, all sedimenting at 4S by sucrose gradient fractionation, showed, on two-dimensional SDS electrophoresis, relative masses of 50, 70 and 65 kDa respectively, equal to the masses previously found in breast cancer. These isoforms did not alter their pI values during IEF fractionation performed in a linear gradient of urea, while the pI 6.1, sedimenting at 8S, generated a new isoform at about 9 mol/l urea with pI 7.2 and a relative mass of 65 kDa. The urea-dissociated isoform (pI 7.2) was able approximately to double the antibody binding with respect to the nondissociated oligomer, which suggested that some epitopes are 'masked', i.e. not accessible to the antibodies when ER is present in its complexed form. The evidence thus suggested that the oligomer at pI 6.1 contained a single 65 kDa ER form which, as a monomer, focused at pI 7.2. The variability in the ER isoform profile found in endometrial cancer was similar to the variability previously reported in breast and larynx carcinomas. The balance between these isoforms could be a dynamic parameter involved in the functionality of this receptor and consequently in cell transformation.

A monoclonal antibody to mammalian angiotensin II AT1 receptor recognizes one of the angiotensin II receptor isoforms expressed by the eel (Anguilla anguilla).

Using labelled ligand-binding methods, previous studies have identified specific angiotensin II receptors (Ang II-Rs) in eel liver, kidney and intestine membranes. Isoelectric focusing on polyacrylamide gels also showed that there are two Ang II-R isoforms in eel liver, focusing at isoelectric points (pI) 6.5 and 6.7. These may have different functions. In contrast, eel enterocyte plasma membrane and renal brush border membranes contain only the pI 6.5 form. To characterize the eel receptors more fully, a newly developed monoclonal antibody (6313/G2) which selectively recognizes the AT1 subtype of mammalian Ang II-R was used. In ligand-binding experiments, the preincubation of eel liver membranes with 6313/G2 antibody eliminated the specific [3,5-3H]Tyr4-Ile5-Ang II binding. Moreover, Ang II-receptor complexes from solubilized liver membranes, which were immunoprecipitated by 6313/G2-coated beads, had a pI of 6.5. In immunoblotting experiments, the antibody recognized the isoform focusing at pI 6.5 in eel intestine and liver preparations, but not the liver pI 6.7 isoform. Immunoblotting of SDS gels showed that the antibody bound to a single protein of molecular mass of 75 kDa in eel liver, gill and kidney and to a doublet of molecular mass of about 74 and 75 kDa in intestinal membrane preparations. Immunocytochemistry of paraffin-embedded and cryostat sections of eel liver, kidney, intestine and gill showed that antibody 6313/G2 bound to uniformly distributed intracellular sites and cell surface membranes in proximal tubular cells, absorptive intestinal cells, hepatocytes and chloride cells. It also stained endothelium and both the longitudinal and circular layers of smooth muscle cells in the intestine. The data suggest that the previously described Ang II-R from eel liver, kidney and intestine may be similar to the mammalian AT1 subtype.

Angiotensin II stimulation of the basolateral located Na+/H+ antiporter in eel (Anguilla anguilla) enterocytes.

The pH-sensitive fluorescent dye, 2',7'-bis-carboxyethyl-5, 6-carboxyfluorescein acetoxymethyl ester, was used to examine the effects of fish or human angiotensin II (Ang II) on the activity of the basolateral located Na+/H+ antiporter in eel intestinal cell suspensions. Exposure of eel enterocytes to either hormone led to an increased activity of the antiporter. This time- and dose-dependent stimulatory effect was inhibited by the specific antiporter inhibitor dimethylamiloride (DMA). Preincubation with a monoclonal antibody (6313/ G2), directed against the N-terminal extracellular domain of the mammalian AT1 Ang II receptor, prevented the stimulatory effect of the hormone and inhibited the binding of [3,5-3H] Tyr4-Ile5-Ang II to intestinal cell suspensions, suggesting specific binding of the antibody to the eel Ang II receptor. The results indicate that both fish and human Ang II stimulate the DMA-sensitive Na+/H+ antiporter present in eel intestinal cells by means of a mammalian AT1-like receptor.

Human larynx expresses isoforms of the oestrogen receptor.

Commercially available enzyme immunoassays (EIAs) were used for oestrogen (ER) and progesterone (PR) receptor determination in the cytosol fraction of 118 human larynx cancer specimens and in the corresponding histologically proven non-malignant tissues. Fifty-one ER positive cancerous samples had corresponding non-cancerous tissues also expressing the receptor. A high resolution isoelectric focusing (IEF) technique followed by immunoblotting with the H222 anti-ER monoclonal antibody was used to evaluate the presence of ER isoforms in the 51 ER positive human larynx cancer specimens and in their corresponding non-malignant tissues. In both tissues, four ER isoforms were detected, with isoelectric points (pI) similar to those obtained in breast and endometrium carcinomas (6.1, 6.3, 6.6 and 6.8). A significant difference in the expression of ER isoforms between cancerous and non-cancerous tissue was found; precisely, the 94.1% of the ER positive non-malignant specimens co-expressed the four isoforms while they were detected in only the 35.5% of the malignant specimens (P < 0.0001 by Fisher's exact test). In larynx cancer, the concentration values of ER and PR did not correlate, nevertheless tumours co-expressing the four ER isoforms had PR levels significantly higher than those which did not (P = 0.02 by Mann-Whitney Wilcoxon sum rank test). To investigate the possibility that the isoforms of the monomeric 4S form of the ER (those with pI 6.3, 6.6, and 6.8) could dimerise, a cold agarose gel electrophoresis technique was used on IEF-separated ER isoforms. In summary, the evidence shows that all the isoforms are able to form homodimers and that the isoforms at pI 6.3 and 6.8 are able to dimerise with that at pI 6.6 but, under the same experimental conditions, they do not form the 6.3/6.8 heterodimer. It was concluded that: (1) the four isoforms of the ER are co-expressed by the non-malignant human larynx and the cancer loses the capacity to express some of them; (2) the complete complement of ER isoforms (all four) is needed for PR expression; (3) the monomeric 4S isoform with pI 6.6 has the capacity to form homo- and heterodimers, while the remaining two are only able to homodimerise.

AT1 angiotensin II receptor subtype in the human larynx and squamous laryngeal carcinoma.

The presence of the angiotensin type 1 receptor (AT1 Ang II-R) was investigated in normal and diseased human larynx using a specific monoclonal antibody (6313/G2). When tissue AT1 content was studied by SDS electrophoresis with immunoblotting, the receptor was detected in 10/10 laryngeal tumours, and in 7/10 samples of normal tissue from the same patients. Two immunostaining bands, approximately 75 kDa, were present in all cases. Immunocytochemistry performed on sections of 45 formalin-fixed, paraffin-embedded laryngeal tissue samples showed that the receptor was expressed in normal respiratory epithelium only in a perinuclear pattern, above the nucleus toward the cell apex. In addition, the antigen was invariably present in skeletal muscle cells and in the columnar duct epithelium of minor salivary glands. The secretory cells were negative, but the antibody stained the adjacent myoepithelial cell layer. As expected, smooth muscle cells of the vessel walls also expressed Ang II-R. In metaplastic epithelium deriving from respiratory epithelium, the receptors were distributed diffusely throughout the cytoplasm of basal and parabasal cells. In dysplastic epithelium, cells of all layers were strongly positive. Finally, squamous cell tumours showed varying numbers of immunoreactive cells, which stained in a diffuse cytoplasmic and membranous pattern. Computer-assisted image analysis of the stained sections showed that the positivity for Ang II-R dramatically increased in dysplastic and well-differentiated cancer cells (3- and 5.5-fold higher than in normal epithelium, respectively), but there was less in poorly and very poorly differentiated cancer. Receptor abundance was not correlated with tumour size nor lymph node involvement. These results suggest a possible role of Ang II in the growth or function of normal and neoplastic larynx tissue, which is especially significant in early neoplastic change.

Enzyme-linked immunosorbent assay of HER-2/neu gene product (p185) in breast cancer: its correlation with sex steroid receptors, cathepsin D and histologic grades.

One hundred and nine primary breast cancers were analyzed to assess the presence of the HER-2/neu gene product (p185), the oestrogen (ER) and the progesterone (PR) receptors, and the total cathepsin D status. An enzyme-linked immunosorbent assay (ELISA kit, Oncogene Science Inc.) was used for the evaluation of p185 in pellets obtained after a 100,000 x g centrifugation, ER and PR were measured by enzyme immunoassay (EIA kit, Abbott Laboratories), and the total cathepsin D content was evaluated by immunoradiometric assay (IRMA kit, CIS Biointernational). We showed that the ELISA kit is feasible to quantify the p185 present in breast cancer cell membranes, and that the detector antibody recognises a protein of apprroximatly M(r) 185,000. The detected antigen was inversely related to both ER and PR, but it did not correlate to total cathepsin D. No significant differences were found in the expression of p185, ER, PR, cathepsin D between infiltrating ductal carcinomas without special features (NOS) and non-ductal (non-NOS) carcinomas. Nevertheless, in NOS carcinomas, a trend was observed in the p185 levels expressed by the tumours with different histological grades, in that p185 concentration was higher in the poorly differentiated grade 3 with respect to grade 2 and grade 1.

Angiotensin II modulates the activity of the Na+/K+ATPase in eel kidney.

We have previously shown that angiotensin II (Ang II) has a role at the level of the eel gill chloride cell regulating sodium balance, and therefore osmoregulation; the purpose of the present study was to extend these findings to another important osmoregulatory organ, the kidney. By catalytic histochemistry Na(+)/K(+)ATPase activity was found in both sea water (SW)- and freshwater (FW)-adapted eel kidney, particularly at the level of both proximal and distal tubules. Quantitation of tubular cell Na(+)/K(+)ATPase activity, by imaging, gave values in SW-adapted eels which were double those found in FW-adapted eels (Student's t-test: P<0.0001). This was due to a reduced number of positive tubules present in FW-adapted eels compared with SW-adapted eels. By conventional enzymatic assay, the Na(+)/K(+)ATPase activity in isolated tubular cells from SW-adapted eels showed values 1.85-fold higher those found in FW-adapted eels (Student's ttest: P<0.0001). Perfusion of kidney for 20 min with 100 nM Ang II provoked a significant increase (1.8-fold) in Na(+)/K(+)ATPase activity in FW, due to up-regulation of Na(+)/K(+)ATPase activity in a significantly larger number of tubules (Student's t-test: P<0.0001). The effect of 100 nM Ang II in SW-adapted kidneys was not significant. Stimulation with increasing Ang II concentrations was performed on isolated kidney tubule cells: Ang II provoked a dose-dependent stimulation of the Na(+)/K(+)ATPase activity in FW-adapted eels, reaching a maximum at 100 nM (1.82-fold stimulation), but no significant effect was found in SW-adapted eels (ANOVA: P<0.001 and P>0.05 respectively). Isolated tubule cells stimulated with 100 nM Ang II showed a significant generation of inositol trisphosphate (InsP(3)) and an increment in calcium release from intracellular stores. In conclusion, our results suggest that tubular Na(+)/K(+)ATPase is modulated by environmental salinity, and that Ang II has a role in regulating its activity in FW-adapted eels, probably through an InsP(3)-dependent mechanism.

Angiotensin II stimulation of Na+/K+ATPase activity and cell growth by calcium-independent pathway in MCF-7 breast cancer cells.

Here we demonstrated, by RT-PCR analysis, the expression of both angiotensin II (Ang II) receptor subtypes, AT1 and AT2, in a breast cancer epithelial cell line, MCF-7. Ang II was not able to affect the intracellular Ca2+ concentration in Fura-2 loaded cells suggesting that AT1-mediated phospholipid hydrolysis is not involved in its intracellular transduction pathway. Ang II modulated the activity of the Na+/K+ATPase in a dose- and time-dependent manner and was mitogenic, with a dose-dependent (1-1000 nM) proliferative effect and a maximal response at 100 nM. Both Na+/K+ATPase activation and stimulation of proliferation were mediated by binding of Ang II to AT1, as the effects were completely blocked by DuP 753, a specific AT1 antagonist. CGP 42112, an AT2 antagonist, did not affect Ang II actions. The main conclusion of this study is that Ang II exerts its effects on cell proliferation and Na+/K+ATPase in breast cancer epithelial cells, MCF-7, via AT1 activation independently of the Ca(2+) signalling mechanism.

Na+/K+ATPase activity inhibition and isoform-specific translocation of protein kinase C following angiotensin II administration in isolated eel enterocytes.

In the eel, angiotensin II (Ang II) has a role at the level of both gill chloride and kidney tubular cells, regulating sodium balance and therefore osmoregulation. The present study extends these findings to another important osmoregulatory organ - the intestine. Enterocytes were obtained from sea-water (SW)-acclimated eels to investigate the role of Ang II on the intestinal Na+/K+ATPase activity, because in SW-acclimated animals the intestine represents an important site of water and NaCl transport from the mucosal to the serosal side. This paper demonstrates that isolated enterocytes stimulated with increasing Ang II concentrations (0.01-100 nM) showed a dose-dependent inhibition of the Na+/K+ATPase activity. The threshold decrease was at 0.01 nM Ang II; it reached a maximum at 10 nM (81.5% inhibition) and did not decrease further with the use of higher hormone doses. These hormonal effects were blocked by a specific competitive antagonist of the AT1 receptor subtype, DuP-753 (100% inhibition at 10 microM), indicating that these effects are mediated by an AT1-like receptor. Isolated enterocytes stimulated with 10 nM Ang II showed a transient increase in intracellular calcium ([Ca2+]i), followed by a lower sustained phase. Removal of extracellular Ca2+ did not reduce the initial transient response and completely abolished the plateau phase. The inhibition of the Na+/K+ATPase activity was dependent on protein kinase C (PKC) activation since PKC antagonists (calphostin C and staurosporine) abolished the inhibitory effect of Ang II, and the PKC activator phorbol 12-myristate 13-acetate reduced transporter activity. Western blot analysis with antibodies to PKC alpha, beta I, beta II, gamma, delta, epsilon, iota, eta and zeta isoforms showed that eel enterocytes expressed the conventional isoforms (alpha and beta I), the novel isoforms (delta and eta) and the atypical isoforms (zeta and iota). Ang II stimulated the translocation from the cytosol to the plasma membrane of PKC alpha, PKC delta and PKC eta isoforms. In conclusion, our results suggest that Ang II modulates intestinal Na+/K+ATPase in SW-acclimated eels via calcium mobilization and PKC activation.

Muscarinic acetylcholine receptor activation induces Ca2+ mobilization and Na+/K+-ATPase activity inhibition in eel enterocytes.

The effect of carbachol (Cch) on intracellular calcium concentration ([Ca2+]i) in eel enterocytes was examined using the fluorescent Ca2+ indicator fura-2. Cch caused a biphasic increase in [Ca2+]i, with an initial spike followed by a progressively decreasing level (over 6 min) to the initial, pre-stimulated, level. The effect of Cch was dose-dependent with a 7.5-fold increase in [Ca2+]i over basal level induced by the maximal dose of Cch (100 microM). In Ca2+-free/EGTA buffer the effect of Cch was less pronounced and the [Ca2+]i returned rapidly to basal levels. The increment of [Ca2+]i was dose-dependently attenuated in cells pre-treated with U73122, a specific inhibitor of phospholipase C, suggesting that the Cch-stimulated increment of [Ca2+]i required inositol triphosphate formation. In the presence of extracellular Ca2+, thapsigargin (TG), a specific microsomal Ca2+-ATPase inhibitor, caused a sustained rise in [Ca2+]i whereas in Ca2+-free medium the increase in [Ca2+]i was transient; in both cases, subsequent addition of Cch was without effect. When 2 mM CaCl2 were added to the cells stimulated with TG or with Cch in Ca2+-free medium, a rapid increase in [Ca2+]i was detected, corresponding to the capacitative Ca2+ entry. Thus, both TG and Cch depleted intracellular Ca2+ stores and stimulated influx of extracellular Ca2+ consistent with capacitative Ca2+ entry. K+ depolarization obtained with increasing concentrations of KCl in the extracellular medium induced a dose-related increase in [Ca2+]i which was blocked by 2 microM nifedipine, a non-specific L-type Ca2+ channel blocker. Nifedipine also changed significantly the height of the Ca2+ transient, and the rate of decrement to the pre-stimulated [Ca2+]i level, indicating that Ca2+ entry into enterocytes also occurs through an L-type voltage-dependent calcium channel pathway. We also show that isolated enterocytes stimulated with increasing Cch concentrations (0.1-1000 microM) showed a dose-dependent inhibition of the Na+/K+-ATPase activity. The threshold decrease was at 1 microM Cch; it reached a maximum at 100 microM (50.5% inhibition) and did not decrease further with the use of higher dose. The effect of Cch on Na+/K+-ATPase activity was dependent on both protein kinase C (PKC) and protein phosphatase calcineurin activation since the PKC inhibitor calphostin C abolished Cch effects, while the calcineurin inhibitor FK506 augmented Cch effect. Collectively, these data establish a functional pathway by which Cch can modulate the activity of the Na+/K+-ATPase through a PKC-dependent (calphostin C-sensitive) pathway and a calcineurin-dependent (FK506-sensitive) pathway.

Activation of angiotensin II type I receptor promotes protein kinase C translocation and cell proliferation in human cultured breast epithelial cells.

The effect of angiotensin II (Ang II) on Ca(2+) signalling in human primary cultured breast epithelial cells was investigated by using fura-2 as the Ca(2+) probe. Ang II (0.1-1000 nM) induced an intracellular free calcium ([Ca(2+)](i)) transient peak which was unchanged by external Ca(2+ )removal. In Ca(2+)-free medium pretreatment with thapsigargin abolished Ang II-induced Ca(2+ )release. Suppression of 1,4,5-inositol trisphosphate formation by U73122, a phospholipase C inhibitor, blocked the Ang II-induced Ca(2+) response. Losartan (DuP753), an inhibitor of Ang II type I receptor (AT1), decreased the [Ca(2+)](i) increase evoked by Ang II, while CGP4221A, an inhibitor of Ang II type II receptor (AT2) did not. AT1 desensitisation was demonstrated with respect to the Ca(2+) response after subsequent exposure of cells to Ang II and also after pretreatment for 25 min with 1000 nM phorbol 12-myristate 13-acetate. Staurosporine, an inhibitor of protein kinases C (PKC), inhibited the AT1 desensitisation. Epithelial breast cells expressed PKC-alpha, -beta1, -delta and -zeta isozymes, and Ang II provoked translocation from the cytosol to the membranes of PKC-alpha, -beta1, and -delta (but not -zeta). Ang II was also able to stimulate cell proliferation in a dose-dependent manner; this effect was blocked by Gö 6976, a specific inhibitor of PKC-alpha and -beta1, the Ca(2+)-dependent isozymes. The main conclusion of this study is that the the Ang II signalling mechanism in breast epithelial cells is based on the elevation of [Ca(2+)](i )released from intracellular stores through AT1 activation. In addition, Ang II stimulates cell proliferation by the activation of PKC isozymes.