Mammalian target of differentiation-inducing factor-1 is mitochondrial malate dehydrogenase for activation of AMP-activated protein kinase and induction of mitochondrial fission.

AIMS: Differentiation-inducing factor-1 (DIF-1) is a polyketide produced by Dictyostelium discoideum that inhibits growth and migration, while promoting the differentiation of Dictyostelium stalk cells through unknown mechanisms. DIF-1 localizes in stalk mitochondria. In addition to its effect on Dictyostelium, DIF-1 also inhibits growth and migration, and induces mitochondrial fission followed by mitophagy in mammalian cells, at least in part by activating AMP-activated protein kinase (AMPK). In a previous study, we found that DIF-1 binds to mitochondrial malate dehydrogenase (MDH2) and inhibits its activity in HeLa cells. In the present study, we investigated whether MDH2 serves as a pharmacological target of DIF-1 in mammalian cells. MAIN METHODS: To examine the enzymatic activity of MDH, mitochondrial morphology, and molecular mechanisms of DIF-1 action, we conducted an MDH reverse reaction assay, immunofluorescence staining, western blotting, and RNA interference using mammalian cells such as human umbilical vein endothelial cells, human cervical cancer cells, mouse endothelial cells, and mouse breast cancer cells. KEY FINDINGS: DIF-1 inhibited mitochondrial but not cytoplasmic MDH activity. Similar to DIF-1, LW6, an authentic MDH2 inhibitor, induced phosphorylation of AMPK, resulting in the phosphorylation of acetyl-CoA carboxylase (ACC) and the dephosphorylation of p70 S6 kinase with approximately the same potency. DIF-1 and LW6 induced mitochondrial fission. Furthermore, MDH2 knockdown using siRNA reproduced the DIF-1 action on the AMPK signaling and mitochondrial morphology. Conversely, an AMPK inhibitor prevented DIF-1-induced mitochondrial fission. SIGNIFICANCE: We propose that MDH2 is a mammalian target of DIF-1 for the activation of AMPK and induction of mitochondrial fission.

Differentiation-inducing factor-1 reduces lipopolysaccharide-induced vascular cell adhesion molecule-1 by suppressing mTORC1-S6K signaling in vascular endothelial cells.

AIMS: Differentiation-inducing factor-1 (DIF-1), a compound in Dictyostelium discoideum, exhibits anti-cancer effects by inhibiting cell proliferation and motility of various mammalian cancer cells in vitro and in vivo. In addition, DIF-1 suppresses lung colony formation in a mouse model, thus impeding cancer metastasis. However, the precise mechanism underlying its anti-metastatic effect remains unclear. In the present study, we aim to elucidate this mechanism by investigating the adhesion of circulating tumor cells to blood vessels using in vitro and in vivo systems. MAIN METHODS: Melanoma cells (1.0 × 105 cells) were injected into the tail vein of 8-week-old male C57BL/6 mice after administration of DIF-1 (300 mg/kg per day) and/or lipopolysaccharide (LPS: 2.5 mg/kg per day). To investigate cell adhesion and molecular mechanisms, cell adhesion assay, western blotting, immunofluorescence staining, and flow cytometry were performed. KEY FINDINGS: Intragastric administration of DIF-1 suppressed lung colony formation. DIF-1 also substantially inhibited the adhesion of cancer cells to human umbilical vein endothelial cells. Notably, DIF-1 did not affect the expression level of adhesion-related proteins in cancer cells, but it did decrease the expression of vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells by suppressing its mRNA-to-protein translation through inhibition of mTORC1-p70 S6 kinase signaling. SIGNIFICANCE: DIF-1 reduced tumor cell adhesion to blood vessels by inhibiting mTORC1-S6K signaling and decreasing the expression of adhesion molecule VCAM-1 on vascular endothelial cells. These findings highlight the potential of DIF-1 as a promising compound for the development of anti-cancer drugs with anti-metastatic properties.

DIF-1 exhibits anticancer activity in breast cancer via inhibition of CXCLs/CXCR2 axis-mediated communication between cancer-associated fibroblasts and cancer cells.

The tumor microenvironment (TME), largely composed of tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), plays a key role in cancer progression. A small molecule, differentiation-inducing factor-1 (DIF-1) secreted by Dictyostelium discoideum, is known to exhibit anticancer activity; however, its effect on the TME remains unknown. In this study, we investigated the effect of DIF-1 on the TME using mouse triple-negative breast cancer 4T1-GFP cells, mouse macrophage RAW 264.7 cells, and mouse primary dermal fibroblasts (DFBs). Polarization of 4T1 cell-conditioned medium-induced macrophage into TAMs was not affected by DIF-1. In contrast, DIF-1 decreased 4T1 cell co-culturing-induced C-X-C motif chemokine ligand 1 (CXCL1), CXCL5, and CXCL7 expression in DFBs and suppressed DFB differentiation into CAF-like cells. Additionally, DIF-1 inhibited C-X-C motif chemokine receptor 2 (CXCR2) expression in 4T1 cells. Immunohistochemical analyses of tumor tissue samples excised from breast cancer-bearing mice showed that DIF-1 did not affect the number of CD206-positive TAMs; however, it decreased the number of α-smooth muscle actin-positive CAFs and CXCR2 expression. These results indicated that the anticancer effect of DIF-1 was partially attributed to the inhibition of CXCLs/CXCR2 axis-mediated communication between breast cancer cells and CAFs.

Retraction: Transcriptome analysis reveals a role for the endothelial ANP-GC-A signaling in interfering with pre-metastatic niche formation by solid cancers.

[This retracts the article DOI: 10.18632/oncotarget.18032.].

DIF-1 inhibits growth and metastasis of triple-negative breast cancer through AMPK-mediated inhibition of the mTORC1-S6K signaling pathway.

We have previously reported that the differentiation-inducing factor-1 (DIF-1), a compound identified in Dictyostelium discoideum, suppresses the growth of MCF-7 breast cancer cells by inactivating p70 ribosomal protein S6 kinase (p70S6K). Therefore, we first examined whether the same mechanism operates in other breast cancer cells, especially triple-negative breast cancer (TNBC), the most aggressive and refractory phenotype of breast cancer. We also investigated the mechanism by which DIF-1 suppresses p70S6K by focusing on the AMPK-mTORC1 system. We found that DIF-1 induces phosphorylation of AMPK and Raptor and dephosphorylation of p70S6K in multiple TNBC cell lines. Next, we examined whether AMPK-mediated inhibition of p70S6K leads to the suppression of proliferation and migration/infiltration of TNBC cells. DIF-1 significantly reduced the expression levels of cyclin D1 by suppressing the translation of STAT3 and strongly suppressed the expression levels of Snail, which led to the suppression of growth and motility, respectively. Finally, we investigated whether DIF-1 exerts anticancer effects on TNBC in vivo. Intragastric administration of DIF-1 suppressed tumor growth and spontaneous lung metastasis of 4T1-Luc cells injected into the mammary fat pad of BALB/c mice. DIF-1 is expected to lead to the development of anticancer drugs, including anti-TNBC, by a novel mechanism.

Identification and signaling characterization of four urotensin II receptor subtypes in the western clawed frog, Xenopus tropicalis.

Urotensin II (UII) is involved, via the UII receptor (UTR), in many physiological and pathological processes, including vasoconstriction, locomotion, osmoregulation, immune response, and metabolic syndrome. In silico studies have revealed the presence of four or five distinct UTR (UTR1-UTR5) gene sequences in nonmammalian vertebrates. However, the functionality of these receptor subtypes and their associations to signaling pathways are unclear. In this study, full-length cDNAs encoding four distinct UTR subtypes (UTR1, UTR3, UTR4, and UTR5) were isolated from the western clawed frog (Xenopus tropicalis). In functional analyses, homologous Xenopus UII stimulation of cells expressing UTR1 or UTR5 induced intracellular calcoum mobilization and phosphorylation of extracellular signal-regulated kinase 1/2. Cells expressing UTR3 or UTR4 did not show this response. Furthermore, UII induced the phosphorylation of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) through the UII-UTR1/5 system. However, intracellular cAMP accumulation was not observed, suggesting that UII-induced CREB phosphorylation is caused by a signaling pathway different from that involving Gs protein. In contrast, the administration of UII to cells increased the phosphorylation of guanine nucleotide exchange factor-H1 (GEF-H1) and myosin light chain 2 (MLC2) in all UTR subtypes. These results define four distinct UTR functional subtypes and are consistent with the molecular evolution of UTR subtypes in vertebrates. Further understanding of signaling properties associated with UTR subtypes may help in clarifying the functional roles associated with UII-UTR interactions in nonmammalian vertebrates.

Differentiation-inducing factor-1 suppresses cyclin D1-induced cell proliferation of MCF-7 breast cancer cells by inhibiting S6K-mediated signal transducer and activator of transcription 3 synthesis.

Differentiation-inducing factor-1 (DIF-1) has been reported to inhibit the proliferation of various mammalian cells by unknown means, although some possible mechanisms of its action have been proposed, including the activation of glycogen synthase kinase-3 (GSK-3). Here, we report an alternative mechanism underlying the action of DIF-1 in human breast cancer cell line MCF-7, on which the effects of DIF-1 have not been examined previously. Intragastric administration of DIF-1 reduced the tumor growth from MCF-7 cells injected into a mammary fat pad of nude mice, without causing adverse effects. In cultured MCF-7, DIF-1 arrested the cell cycle in G0 /G1 phase and suppressed cyclin D1 expression, consistent with our previous results obtained in other cell species. However, DIF-1 did not inhibit the phosphorylation of GSK-3. Investigating an alternative mechanism for the reduction of cyclin D1, we found that DIF-1 reduced the protein levels of signal transducer and activator of transcription 3 (STAT3). The STAT3 inhibitor S3I-201 suppressed cyclin D1 expression and cell proliferation and the overexpression of STAT3 enhanced cyclin D1 expression and accelerated proliferation. Differentiation-inducing factor-1 did not reduce STAT3 mRNA or reduce STAT3 protein in the presence of cycloheximide, suggesting that DIF-1 inhibited STAT3 protein synthesis. Seeking its mechanism, we revealed that DIF-1 inhibited the activation of 70 kDa and/or 85 kDa ribosomal protein S6 kinase (p70S6K /p85S6K ). Inhibition of p70S6K /p85S6K by rapamycin also reduced the expressions of STAT3 and cyclin D1. Therefore, DIF-1 suppresses MCF-7 proliferation by inhibiting p70S6K /p85S6K activity and STAT3 protein synthesis followed by reduction of cyclin D1 expression.

Angiotensin II promotes pulmonary metastasis of melanoma through the activation of adhesion molecules in vascular endothelial cells.

Hypertension is considered as one of the cancer progressive factors, and often found comorbidity in cancer patients. Renin-angiotensin system (RAS) plays an important role in the regulation of blood pressure, and angiotensin II (Ang II) is well known pressor peptide associated with RAS. Ang II has been reported to accelerate progression and metastasis of cancer cells. However, its precise mechanisms have not been fully understood. In this study, we sought to elucidate the mechanisms by which Ang II exacerbates hematogenous metastasis in mouse melanoma cells, focusing the adhesion pathway in vascular endothelial cells. For this purpose, B16/F10 mouse melanoma cells, which do not express the Ang II type 1 receptor (AT1R), were intravenously injected into C57BL/6 mice. Two weeks after cell injection, the number of lung metastatic colonies was significantly higher in the Ang II-treated group (1 µg/kg/min) than in the vehicle-treated group. The AT1R blocker valsartan (40 mg/kg/day), but not the calcium channel blocker amlodipine (5 or 10 mg/kg/day), significantly suppressed the effect of Ang II. In endothelium-specific Agtr1a knockout mice, Ang II-mediated acceleration of lung metastases of melanoma cells was significantly diminished. Ang II treatment significantly increased E-selectin mRNA expression in vascular endothelial cells collected from lung tissues, and thus promoted adherence of melanoma cells to the vascular endothelium. Ang II-accelerated lung metastases of melanoma cells were also suppressed by treatment with anti-E-selectin antibody (20 mg/kg). Taken together, Ang II-treatment exacerbates hematogenous cancer metastasis by promoting E-selectin-mediated adhesion of cancer cells to vascular endothelial cells.

Transcriptome analysis reveals a role for the endothelial ANP-GC-A signaling in interfering with pre-metastatic niche formation by solid cancers.

Cancer establishes a microenvironment called the pre-metastatic niche in distant organs where disseminated cancer cells can efficiently metastasize. Pre-metastatic niche formation requires various genetic factors. Previous studies suggest that inhibiting a single niche-factor is insufficient to completely block pre-metastatic niche formation especially in human patients. Here we show that the atrial natriuretic peptide (ANP), an endogenous hormone produced by the heart, inhibits pre-metastatic niche formation and metastasis of murine solid cancer models when pharmacologically supplied in vivo. On the basis of a wealth of comprehensive RNA-seq data, we demonstrated that ANP globally suppressed expression of cancer-induced genes including known niche-factors in the lung. The lungs of mice overexpressing GC-A, a receptor for ANP in endothelial cells, were conferred resistance against pre-metastatic niche formation. Importantly, neither ANP administration nor GC-A overexpression had a detrimental effect on lung gene expression in a cancer-free condition. The current study establishes endothelial ANP-GC-A signaling as a therapeutic target to control the pre-metastatic niche.

Myeloprotective effects of C-type natriuretic peptide on cisplatin-induced bone marrow granulocytopenia in mice.

PURPOSE: Cisplatin is an effective chemotherapeutic agent used to treat a variety of malignant tumors. The major toxicity associated with cisplatin treatment is granulocytopenia. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, protects against toxicity in many organs, including the heart, blood vessels, lung, and kidney. The objective of this study was to investigate the myeloprotective effects of CNP in a mouse model of cisplatin-induced granulocytopenia. METHODS: The mice were divided into two groups: cisplatin with vehicle and cisplatin with CNP. CNP (2.5 µg/kg/min via osmotic pump, subcutaneously) or vehicle administration was started two day before cisplatin injection, and continued until the mice were killed. At 0, 2, 4, 8, and 14 days after cisplatin injection (16 mg/kg, intraperitoneally as a single dose), we counted total and living cells and granulocyte/macrophage colony-forming units (CFU-GM) in bone marrow. In addition, at 0, 1, 2, and 4 days after cisplatin injection, we measured mRNA levels of CXC chemokine receptor 4 (CXCR4) and chemokine CXC ligand 12 (CXCL12) in bone marrow. RESULTS: CNP significantly attenuated the reduction in bone marrow nucleated cell count and CFU-GM in bone marrow at 4 days after cisplatin injection. Four days after cisplatin injection, CNP significantly decreased the CXCR4 mRNA level in bone marrow, but had no effect on the level of CXCL12 mRNA. CONCLUSIONS: CNP exerts myeloprotective effects in cisplatin-induced granulocytopenia and decreases CXCR4 expression.

RETRACTED: Protective effects of ghrelin on cisplatin-induced nephrotoxicity in mice.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Authors. The Authors express that: although main outcome is correct, there are some errors in calculation, statistical analysis, description for sample numbers and data preparation including, using the common control and vehicle group already reported in the other paper. Those experiments were performed at the same time but, we lacked explanation for those condition (Cancer Chemother Pharmacol. 2015;75:123-9). Taken together, we decided to retract this article due to those errors.

Atrial natriuretic peptide protects against cisplatin-induced granulocytopenia.

PURPOSE: Granulocytopenia is the major toxicity associated with cisplatin treatment. Atrial natriuretic peptide (ANP) is a cardiac hormone used clinically for the treatment of acute heart failure in Japan. ANP exerts a wide range of protective effects on various organs, including the heart, blood vessels, lungs, and kidneys. This study's objective was to investigate the protective effects of ANP on cisplatin-induced granulocytopenia in mice. METHODS: The mice were divided into two groups: cisplatin with vehicle and cisplatin with ANP. ANP (1.5 µg/kg/min via osmotic pump, subcutaneously) or vehicle administration was started 1 day before cisplatin injection until the mice were killed. At 0, 2, 4, 8, and 14 days after cisplatin injection (16 mg/kg, intraperitoneally as a single dose), the white blood cell, red blood cell, and platelet counts were measured in the peripheral blood in both groups. The numbers of total and live cells and colony-forming unit-granulocyte-macrophage (CFU-GM) colonies in the bone marrow of the mice were also examined. In addition, at 0, 0.5, 1, and 2 days after cisplatin injection, serum granulocyte colony-stimulating factor (G-CSF) levels were measured. RESULTS: ANP significantly attenuated the white blood cell count decrease in the peripheral blood 2 and 4 days after cisplatin injection. ANP also attenuated the decrease in the number of live cells and CFU-GM colonies in bone marrow 2, 4, and 8 days after cisplatin injection. ANP significantly increased serum G-CSF levels 1 day after cisplatin injection. CONCLUSIONS: ANP has protective effects in cisplatin-induced granulocytopenia, with increased G-CSF production.

C-type natriuretic peptide ameliorates pulmonary fibrosis by acting on lung fibroblasts in mice.

BACKGROUND: Pulmonary fibrosis has high rates of mortality and morbidity; however, no effective pharmacological therapy has been established. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, selectively binds to the transmembrane guanylyl cyclase (GC)-B receptor and exerts anti-inflammatory and anti-fibrotic effects in various organs through vascular endothelial cells and fibroblasts that have a cell-surface GC-B receptor. Given the pathophysiological importance of fibroblast activation in pulmonary fibrosis, we hypothesized that the anti-fibrotic and anti-inflammatory effects of exogenous CNP against bleomycin (BLM)-induced pulmonary fibrosis were exerted in part by the effect of CNP on pulmonary fibroblasts. METHODS: C57BL/6 mice were divided into two groups, CNP-treated (2.5 µg/kg/min) and vehicle, to evaluate BLM-induced (1 mg/kg) pulmonary fibrosis and inflammation. A periostin-CNP transgenic mouse model exhibiting CNP overexpression in fibroblasts was generated and examined for the anti-inflammatory and anti-fibrotic effects of CNP via fibroblasts in vivo. Additionally, we assessed CNP attenuation of TGF-ß-induced differentiation into myofibroblasts by using immortalized human lung fibroblasts stably expressing GC-B receptors. Furthermore, to investigate whether CNP acts on human lung fibroblasts in a clinical setting, we obtained primary-cultured fibroblasts from surgically resected lungs of patients with lung cancer and analyzed levels of GC-B mRNA transcription. RESULTS: CNP reduced mRNA levels of the profibrotic cytokines interleukin (IL)-1ß and IL-6, as well as collagen deposition and the fibrotic area in lungs of mice with bleomycin-induced pulmonary fibrosis. Furthermore, similar CNP effects were observed in transgenic mice exhibiting fibroblast-specific CNP overexpression. In cultured-lung fibroblasts, CNP treatment attenuated TGF-ß-induced phosphorylation of Smad2 and increased mRNA and protein expression of α-smooth muscle actin and SM22α, indicating that CNP suppresses fibroblast differentiation into myofibroblasts. Furthermore, human lung fibroblasts from patients with or without interstitial lung disease substantially expressed GC-B receptor mRNA. CONCLUSIONS: These data suggest that CNP ameliorates bleomycin-induced pulmonary fibrosis by suppressing TGF-ß signaling and myofibroblastic differentiation in lung fibroblasts. Therefore, we propose consideration of CNP for clinical application to pulmonary fibrosis treatment.

C-type natriuretic peptide in combination with sildenafil attenuates proliferation of rhabdomyosarcoma cells.

Rhabdomyosarcoma (RMS) is a malignant mesenchymal tumor and the most common soft tissue sarcoma in children. Because of several complications associated with intensive multimodal therapies, including growth disturbance and secondary cancer, novel therapies with less toxicity are urgently needed. C-type natriuretic peptide (CNP), an endogenous peptide secreted by endothelial cells, exerts antiproliferative effects in multiple types of mesenchymal cells. Therefore, we investigated whether CNP attenuates proliferation of RMS cells. We examined RMS patient samples and RMS cell lines. All RMS clinical samples expressed higher levels of guanylyl cyclase B (GC-B), the specific receptor for CNP, than RMS cell lines. GC-B expression in RMS cells decreased with the number of passages in vitro. Therefore, GC-B stable expression lines were established to mimic clinical samples. CNP increased cyclic guanosine monophosphate (cGMP) levels in RMS cells in a dose-dependent manner, demonstrating the biological activity of CNP. However, because cGMP is quickly degraded by phosphodiesterases (PDEs), the selective PDE5 inhibitor sildenafil was added to inhibit its degradation. In vitro, CNP, and sildenafil synergistically inhibited proliferation of RMS cells stably expressing GC-B and decreased Raf-1, Mitogen-activated protein kinase kinase (MEK), and extracellular signal-regulated kinase (ERK) phosphorylation. These results suggested that CNP in combination with sildenafil exerts antiproliferative effects on RMS cells by inhibiting the Raf/MEK/ERK pathway. This regimen exerted synergistic effects on tumor growth inhibition without severe adverse effects in vivo such as body weight loss. Thus, CNP in combination with sildenafil represents a promising new therapeutic approach against RMS.

Establishment and characterization of a novel orthotopic mouse model for human uterine sarcoma with different metastatic potentials.

Uterine sarcomas are rare and aggressive gynecologic tumors with a poor prognosis because of recurrence and metastasis. However, the mechanisms of uterine sarcoma metastasis are largely unknown. To investigate this mechanism, we developed a novel uterine sarcoma tissue-derived orthotopic and metastatic model in KSN nude mice using a green fluorescent protein stably expressed uterine sarcoma cell line, MES-SA. Histological analysis showed that all orthotopic primary tumors were undifferentiated sarcoma. Primary tumors were characterized by high (18)F-fluorodeoxyglucose uptake with a positive correlation to the number of pulmonary metastases. In addition, we generated uterine sarcoma cell sublines with high or low metastatic potentials by serial in vivo selection. Microarray analysis between orthotopic tumors with high and low metastatic potentials revealed differential expression of genes related to cell proliferation and migration (TNNT1, COL1A2, and ZIC1). Our model would be useful to compensate for the limited clinical cases of uterine sarcoma and to investigate the molecular mechanisms of metastatic uterine sarcoma.

Atrial natriuretic peptide prevents cancer metastasis through vascular endothelial cells.

Most patients suffering from cancer die of metastatic disease. Surgical removal of solid tumors is performed as an initial attempt to cure patients; however, surgery is often accompanied with trauma, which can promote early recurrence by provoking detachment of tumor cells into the blood stream or inducing systemic inflammation or both. We have previously reported that administration of atrial natriuretic peptide (ANP) during the perioperative period reduces inflammatory response and has a prophylactic effect on postoperative cardiopulmonary complications in lung cancer surgery. Here we demonstrate that cancer recurrence after curative surgery was significantly lower in ANP-treated patients than in control patients (surgery alone). ANP is known to bind specifically to NPR1 [also called guanylyl cyclase-A (GC-A) receptor]. In mouse models, we found that metastasis of GC-A-nonexpressing tumor cells (i.e., B16 mouse melanoma cells) to the lung was increased in vascular endothelium-specific GC-A knockout mice and decreased in vascular endothelium-specific GC-A transgenic mice compared with control mice. We examined the effect of ANP on tumor metastasis in mice treated with lipopolysaccharide, which mimics systemic inflammation induced by surgical stress. ANP inhibited the adhesion of cancer cells to pulmonary arterial and micro-vascular endothelial cells by suppressing the E-selectin expression that is promoted by inflammation. These results suggest that ANP prevents cancer metastasis by inhibiting the adhesion of tumor cells to inflamed endothelial cells.

Atrial natriuretic peptide protects against cisplatin-induced acute kidney injury.

PURPOSE: Cisplatin is an effective chemotherapeutic agent used in the treatment of a wide variety of malignancies. Acute kidney injury (AKI) is the major toxicity associated with cisplatin and sometimes necessitates a reduction in dose or discontinuation of treatment. Atrial natriuretic peptide (ANP) is secreted by the heart and exerts a wide range of renoprotective effects, including anti-inflammatory activity. The objective of this study was to investigate the protective effects of ANP on cisplatin-induced AKI in mice. METHODS: Mice were randomly divided into three groups: control, cisplatin (20 mg/kg, intraperitoneal)/vehicle treatment, and cisplatin/ANP (1.5 µg/kg/min via osmotic-pump, subcutaneous) treatment. At 72 h after cisplatin injection, serum blood urea nitrogen and creatinine, urine albumin/creatinine, and renal expression of mRNAs encoding tumor necrosis factor-α, interleukin (IL)-1ß, IL-6, intercellular adhesion molecule-1, monocyte chemoattractant protein-1, and transforming growth factor (TGF)-ß were measured using real-time polymerase chain reaction. Histological changes were also evaluated. RESULTS: ANP treatment significantly attenuated cisplatin-induced increases in serum blood urea nitrogen and creatinine, urine albumin/creatinine, and renal expression of IL-1ß, IL-6, intercellular adhesion molecule-1, and monocyte chemoattractant protein-1 mRNAs. Cisplatin-induced renal dysfunction and renal tubular necrosis were thus attenuated by ANP treatment. CONCLUSIONS: Our results indicate that ANP exhibits a protective effect against cisplatin-induced AKI in mice. ANP may thus be of value in prophylactic strategies aimed at mitigating the adverse effects associated with chemotherapy agents, including cisplatin.

Atrial natriuretic peptide inhibits lipopolysaccharide-induced acute lung injury.

OBJECTIVES: We recently reported that administration of atrial natriuretic peptide during the perioperative period has prophylactic effects with respect to not only cardiovascular but also respiratory complications following pulmonary resection. However, its mechanisms are not well understood. The objective of the present study was to investigate the mechanism of the prophylactic effects of atrial natriuretic peptide in an acute lung injury model. METHODS: For the evaluation of the early phase of pulmonary inflammation, in vitro and in vivo studies using lipopolysaccharide were used. In the in vitro study, the effects of atrial natriuretic peptide on the induction of E-selectin by lipopolysaccharide in human pulmonary artery endothelial cells were evaluated. In the in vivo study, the effects of atrial natriuretic peptide on lipopolysaccharide-induced inflammatory cell infiltration and cytokine levels including tumor necrosis factor-alpha and interleukin-6 in the bronchoalveolar lavage fluid in the lungs of C57/B6 mice were examined. The number of myeloperoxidase-positive staining cells in the tissue sections of the lung of lipopolysaccharide-administered C57/B6 mice was also evaluated. RESULTS: Atrial natriuretic peptide significantly attenuated the up-regulation of E-selectin expression induced by lipopolysaccharide in human pulmonary artery endothelial cells. There were significantly lower cell counts and levels of tumor necrosis factor-alpha and interleukin-6 in the bronchoalveolar lavage fluid of atrial natriuretic peptide-treated mice compared to control mice after lipopolysaccharide injection. In addition, there were significantly fewer myeloperoxidase-positive cells in atrial natriuretic peptide-treated mice than in control mice after lipopolysaccharide injection. CONCLUSIONS: Atrial natriuretic peptide had a protective effect in the lipopolysaccharide-induced acute lung injury model. Atrial natriuretic peptide may be of value in therapeutic strategies aimed at the treatment of acute lung injury such as pneumonia or acute respiratory distress syndrome.

EphrinA1-EphA2 signal induces compaction and polarization of Madin-Darby canine kidney cells by inactivating Ezrin through negative regulation of RhoA.

The epithelial cells exhibit either a columnar or a flat shape dependent on extracellular stimuli or the cell-cell adhesion. Membrane-anchored ephrinA stimulates EphA receptor tyrosine kinases as a ligand in a cell-cell contact-dependent manner. The mechanism through which ephrinA1/EphA2 signal regulates the cell morphology remains elusive. We demonstrate here that ephrinA1/EphA2 signal induces compaction and enhanced polarization (columnar change) of Madin-Darby canine kidney epithelial cells by regulating Ezrin, a linker that connects plasma membrane and actin cytoskeleton. Activation of EphA2 resulted in RhoA inactivation through p190RhoGAP-A and subsequent dephosphorylation of Ezrin on Thr-567 phosphorylated by Rho kinase. Consistently, the cells expressing an active mutant of Ezrin in which Thr-567 was replaced with Asp did not change their shape in response to ephrinA1. Furthermore, depletion of Ezrin led to compaction and enhanced polarization without ephrinA1 stimulation, suggesting the role for active Ezrin in keeping the flat cell shape. Ezrin localized to apical domain irrespective of ephrinA1 stimulation, whereas phosphorylated Ezrin on the apical domain was reduced by ephrinA1 stimulation. Collectively, ephrinA1/EphA2 signal negatively regulates Ezrin and promotes the alteration of cell shape, from flat to columnar shape.