FLCN regulates transferrin receptor 1 transport and iron homeostasis.

Birt-Hogg-Dubé (BHD) syndrome is a multiorgan disorder caused by inactivation of the folliculin (FLCN) protein. Previously, we identified FLCN as a binding protein of Rab11A, a key regulator of the endocytic recycling pathway. This finding implies that the abnormal localization of specific proteins whose transport requires the FLCN-Rab11A complex may contribute to BHD. Here, we used human kidney-derived HEK293 cells as a model, and we report that FLCN promotes the binding of Rab11A with transferrin receptor 1 (TfR1), which is required for iron uptake through continuous trafficking between the cell surface and the cytoplasm. Loss of FLCN attenuated the Rab11A-TfR1 interaction, resulting in delayed recycling transport of TfR1. This delay caused an iron deficiency condition that induced hypoxia-inducible factor (HIF) activity, which was reversed by iron supplementation. In a Drosophila model of BHD syndrome, we further demonstrated that the phenotype of BHD mutant larvae was substantially rescued by an iron-rich diet. These findings reveal a conserved function of FLCN in iron metabolism and may help to elucidate the mechanisms driving BHD syndrome.

Mas receptor mediates cardioprotection of angiotensin-(1-7) against Angiotensin II-induced cardiomyocyte autophagy and cardiac remodelling through inhibition of oxidative stress.

Angiotensin II (Ang II) plays an important role in the onset and development of cardiac remodelling associated with changes of autophagy. Angiotensin1-7 [Ang-(1-7)] is a newly established bioactive peptide of renin-angiotensin system, which has been shown to counteract the deleterious effects of Ang II. However, the precise impact of Ang-(1-7) on Ang II-induced cardiomyocyte autophagy remained essentially elusive. The aim of the present study was to examine if Ang-(1-7) inhibits Ang II-induced autophagy and the underlying mechanism involved. Cultured neonatal rat cardiomyocytes were exposed to Ang II for 48 hrs while mice were infused with Ang II for 4 weeks to induce models of cardiac hypertrophy in vitro and in vivo. LC3b-II and p62, markers of autophagy, expression were significantly elevated in cardiomyocytes, suggesting the presence of autophagy accompanying cardiac hypertrophy in response to Ang II treatment. Besides, Ang II induced oxidative stress, manifesting as an increase in malondialdehyde production and a decrease in superoxide dismutase activity. Ang-(1-7) significantly retarded hypertrophy, autophagy and oxidative stress in the heart. Furthermore, a role of Mas receptor in Ang-(1-7)-mediated action was assessed using A779 peptide, a selective Mas receptor antagonist. The beneficial responses of Ang-(1-7) on cardiac remodelling, autophagy and oxidative stress were mitigated by A779. Taken together, these result indicated that Mas receptor mediates cardioprotection of angiotensin-(1-7) against Ang II-induced cardiomyocyte autophagy and cardiac remodelling through inhibition of oxidative stress.

AXL is a key regulator of inherent and chemotherapy-induced invasion and predicts a poor clinical outcome in early-stage colon cancer.

PURPOSE: Despite the use of 5-fluorouracil (5-FU)-based adjuvant treatments, a large proportion of patients with high-risk stage II/III colorectal cancer will relapse. Thus, novel therapeutic strategies are needed for early-stage colorectal cancer. Residual micrometastatic disease from the primary tumor is a major cause of patient relapse. EXPERIMENTAL DESIGN: To model colorectal cancer tumor cell invasion/metastasis, we have generated invasive (KRASMT/KRASWT/+chr3/p53-null) colorectal cancer cell subpopulations. Receptor tyrosine kinase (RTK) screens were used to identify novel proteins that underpin the migratory/invasive phenotype. Migration/invasion was assessed using the XCELLigence system. Tumors from patients with early-stage colorectal cancer (N = 336) were examined for AXL expression. RESULTS: Invasive colorectal cancer cell subpopulations showed a transition from an epithelial-to-mesenchymal like phenotype with significant increases in migration, invasion, colony-forming ability, and an attenuation of EGF receptor (EGFR)/HER2 autocrine signaling. RTK arrays showed significant increases in AXL levels in all invasive sublines. Importantly, 5-FU treatment resulted in significantly increased migration and invasion, and targeting AXL using pharmacologic inhibition or RNA interference (RNAi) approaches suppressed basal and 5-FU-induced migration and invasion. Significantly, high AXL mRNA and protein expression were found to be associated with poor overall survival in early-stage colorectal cancer tissues. CONCLUSIONS: We have identified AXL as a poor prognostic marker and important mediator of cell migration/invasiveness in colorectal cancer. These findings provide support for the further investigation of AXL as a novel prognostic biomarker and therapeutic target in colorectal cancer, in particular in the adjuvant disease in which EGFR/VEGF-targeted therapies have failed.

Epigenetics, vitamin supplements and cellular reprogramming.

The simple addition of vitamin C to cell culture medium can induce extensive remodeling of the cellular epigenome and facilitates reprogramming of somatic cells to pluripotency. A new study shows that the activity of the enzyme TET1 can inhibit or enhance reprogramming efficiency, dependent on the presence or absence of vitamin C.

Intense nanosecond pulsed electric fields promote cancer cell apoptosis through centrosome-dependent pathway involving reduced level of PLK1.

BACKGROUND: Intense nanosecond pulsed electric fields (nsPEFs) have been known to promote apoptosis without physically changing membrane structure or damaging morphology of tumor cells. To determine the contribution of centrosome to the progression of apoptosis by nsPEFs, HeLa cells were exposed to high intensity (6 kV/cm) nsPEFs (8-32 ns) in normal culture condition and cell biology and molecular parameters of cells were investigated. MATERIALS AND METHODS: Apoptotic cell death was identified by TUNEL assay after being exposed to the nsPEFs with various pulse durations, while immunofluorescent staining was performed to detect the number and distribution of centrosomes. To clarify whether nsPEFs-induced centrosome over-duplication is the consequence of DNA damage, we used comet assay to detect simultaneous DNA damage. And additionally Western Blot was used to detect PLK1 protein level to explore the correlation between apoptotic cell death and nsPEFs-induced centrosome over-duplication. Correlation between nsPEFs and molecular parameters was statistically analyzed. RESULTS: NsPEFs induced a clear apoptosis reaching a maximum at 24ns, 24h after exposure (p < 0.05), where DNA fragmentation and over-duplicated centrosomes were observed. This apoptosis may be promoted in a time- and pulse duration-dependent manner. Polo-like kinase (PLK1) protein levels were significantly decreased by such nsPEFs (p < 0.05). Control treatment without the nsPEFs did not cause any damage to the cultured HeLa cells. CONCLUSIONS: Intense nsPEFs promote cell apoptosis through a centrosome-mediated pathway involving a reduction in the level of PLK1, which may provide new therapeutic targets for human cancer treatment.

Mer receptor tyrosine kinase promotes invasion and survival in glioblastoma multiforme.

The infiltration of glioma cells into adjacent tissue is one of the major obstacles in the therapeutic management of malignant brain tumours, in most cases precluding complete surgical resection. Consequently, malignant glioma patients almost invariably experience tumour recurrences. Within the brain, glioma cells migrate rapidly either amoeboidly or mesenchymally to invade surrounding structures, in dependence on the extracellular environment. In addition, radiotherapy, frequently applied as adjuvant therapeutic modality, may enhance tumour cell mobility. Here, we show that the receptor tyrosine kinase Mer (MerTK) is overexpressed in glioblastoma multiforme (GBM) and that this is accompanied with increased invasive potential. MerTK expression is maintained in primary GBM-derived tumour spheres under stem cell culture conditions but diminishes significantly in serum-containing cultures with concomitant downregulation of Nestin and Sox2. Depletion of MerTK disrupts the rounded morphology of glioma cells and decreases their invasive capacity. Furthermore, the expression and phosphorylation of myosin light chain 2 are strongly associated with MerTK activity, indicating that the effect of MerTK on glioma cell invasion is mediated by actomyosin contractility. Finally, DNA damage robustly triggers the upregulation and phosphorylation of MerTK, which protects cells from apoptosis. This effect is strongly impaired upon MerTK depletion or overexpression of an inactive MerTK mutant. Collectively, our data suggests that MerTK is a novel therapeutic target in the treatment of the malignant gliomas.

Inhibition of Bcl-2 antiapoptotic members by obatoclax potently enhances sorafenib-induced apoptosis in human myeloid leukemia cells through a Bim-dependent process.

Interactions between the multikinase inhibitor sorafenib and the BH3-mimetic obatoclax (GX15-070) were examined in human acute myeloid leukemia (AML) cells. Treatment with sorafenib/obatoclax induced pronounced apoptosis in and reduced the clonogenic growth of multiple AML lines and primary AML cells but not normal CD34(+) cells. Sorafenib triggered rapid and pronounced Mcl-1 down-regulation accompanied by enhanced binding of Bim to Bcl-2 and Bcl-xL, effects that were abolished by obatoclax coadministration. Notably, shRNA knockdown of Bim, Bak, or Bax, but not Noxa, significantly attenuated obatoclax/sorafenib lethality, whereas ectopic expression of Mcl-1 exerted a protective effect. Furthermore, exposure of leukemia cells to sorafenib and obatoclax markedly induced autophagy, reflected by rapid and pronounced LC3 processing and LC3-green fluorescent protein (GFP) punctate formation. Multiple autophagy inhibitors or VPS34 knockdown, significantly potentiated sorafenib/obatoclax lethality, indicating a cytoprotective role for autophagy in this setting. Finally, studies in a xenograft mouse model revealed that combined sorafenib/obatoclax treatment markedly reduced tumor growth and significantly prolonged survival in association with Mcl-1 down-regulation and apoptosis induction, whereas agents administered individually had only modest effects. These findings suggest that combining sorafenib with agents that inhibit Mcl-1 and Bcl-2/Bcl-xL such as obatoclax may represent a novel and potentially effective strategy in AML.

A small-molecule p53 activator induces apoptosis through inhibiting MDMX expression in breast cancer cells.

The tumor suppressor p53 is often inactivated in breast cancer cells because the overexpression of its repressors (e.g., MDM2 and MDMX). Restoration of p53 activity by small molecules through counteracting p53 repressors can lead to in vivo tumor regression and is therefore considered a promising strategy for treatments of cancer. Recent efforts in high-throughput drug screening and rational drug design have identified several structurally diverse small-molecule p53 activators, including a pseudourea derivative XI-011 (NSC146109). This small molecule strongly activates p53 while selectively inhibiting growth of transformed cells without inducing genotoxicity, indicating its potential as a drug lead for p53-targeted therapy. However, the mechanism(s) by which XI-011 activates p53 and the effects of XI-011 on growth of breast cancer cells are currently unknown. Here, we report that XI-011 promoted breast cancer cells to undergo apoptosis through activating p53 and inducing expression of proapoptotic genes. Importantly, we found that activation of p53 by this small molecule was achieved through a novel mechanism, that is, inhibition of MDMX expression. XI-011 repressed the MDMX promoter, resulting in down-regulation of MDMX messenger RNA level in MCF-7 cells. In line with these results, XI-011 decreased the viability of breast cancer cells expressing low levels of MDMX in a less-efficient manner. Interestingly, XI-011 acted additively with the MDM2 antagonist Nutlin-3a to inhibit growth of breast cancer cells. We conclude that XI-011 belongs to a novel class of small-molecule p53 activators that target MDMX and could be of value in treating breast cancer.

Low-dose endotoxin induces inflammation by selectively removing nuclear receptors and activating CCAAT/enhancer-binding protein δ.

Subclinical levels of circulating endotoxin are associated with the pathogenesis of diverse human inflammatory diseases, by mildly inducing the expression of proinflammatory mediators. In this study, we examined the molecular mechanism responsible for the effect of low-dose LPS in macrophages. In contrast to high-dose LPS, which activates NF-κB and induces the robust expression of proinflammatory mediators, we observed that low-dose LPS failed to activate NF-κB. Instead, it selectively activated C/EBPδ and removed nuclear repressors, including peroxisome proliferator-activated receptor α and retinoic acid receptor α, enabling a mild and leaky expression of proinflammatory mediators. The effect of low-dose LPS required IRAK-1, which interacts with and acts upstream of IκB kinase ε to contribute to LPS-mediated induction of C/EBPδ and proinflammatory mediators. Additionally, mice fed a high-fat diet acquired elevated levels of endotoxin and proinflammatory mediators in an IRAK-1-dependent fashion. Taken together, these data reveal a distinct pathway preferentially used by low-dose endotoxin in initiating low-grade inflammation.

Wnt5a promotes differentiation of human dental papilla cells.

AIM: To investigate the role of Wnt5a in the process of differentiation of human dental papilla cells (HDPCs). METHODOLOGY: Recombinant adenovirus encoding full-length Wnt5a cDNA was constructed to investigate the biological role of Wnt5a on the differentiation of HDPCs. The effect of Wnt5a on HDPCs differentiation was determined by ALP activity assay, ALP staining and mineral induction assay. Mineralization-related gene expressions were assessed by RT-PCR. RESULTS: Immunostaining revealed Wnt5a expression in the odontoblast layer and dental papilla tissue. Over-expression of Wnt5a by transfecting HDPCs with an Wnt5a-carrying construct increased ALPase activity and the formation of mineralized nodules of HDPCs. RT-PCR analysis showed that the expressions of mineralization-related genes, such as bone sialoprotein, collagen type I, osteonectin, osteopontin (OCN), dentine matrix protein-1 were up-regulated by Wnt5a. CONCLUSIONS: Wnt5a promoted differentiation of HDPCs.

Ski acts as therapeutic target of qingyihuaji formula in the treatment of SW1990 pancreatic cancer.

BACKGROUND: Qingyihuaji formula (QYHJ) is a widely used herbal formula that has shown promising antitumor effect in the treatment of pancreatic cancer in the Cancer Hospital, Fudan University, Shanghai, China. OBJECTIVE: This research was conducted to study whether Ski acts as a therapeutic target of QYHJ formula in the treatment of SW1990 pancreatic cancer. METHODS: The expression changes of Ski mRNA and protein in SW1990 pancreatic cancer subcutaneously transplanted tumor treated with QYHJ were detected by real-time polymerase chain reaction and Western blot. Then, we established a stable transfection SW1990 cell with low expression of Ski through lentivirus-mediated RNA interference (RNAi) technique. The responses to QYHJ treatment on a subcutaneously transplanted tumor with different Ski expression statuses were evaluated. Finally, the effect of Ski downregulation on SW1990 cell biological behavior was also evaluated. RESULTS: Expression of Ski mRNA and protein in SW1990 subcutaneously transplanted tumor decreased dramatically after the treatment with QYHJ. Stable transfection cells with low expression of Ski (SW1990/Ski RNAi) were created, and negative vector-transfected cells (SW1990/con RNAi) were used as controls. The tumor weight inhibitory rates of QYHJ on subcutaneously transplanted tumors formed by SW1990 or SW1990/con RNAi were 29.6% and 32.2%, respectively, whereas they were 16.0% to 17.8% when the tumors were formed by SW1990/Ski RNAi. Ski downregulation sensitized the response of SW1990 cells to TGF-beta1-induced growth inhibition in vitro. Flow cytometric analyses revealed that the percentage of cells in the G1 phase increased from 40.4% to 62.9% when Ski was downregulated. The subcutaneously transplanted tumors formed by SW1990/Ski RNAi grew much more slowly than those formed by parental and control vector-transfected cells. CONCLUSION: Ski acts as therapeutic target of QYHJ in the treatment of SW1990 pancreatic cancer cells, and its expression status mediates different responses to QYHJ treatment.

Polo-like kinase 1 (Plk1) as a novel drug target in chronic myeloid leukemia: overriding imatinib resistance with the Plk1 inhibitor BI 2536.

In most patients with chronic myeloid leukemia (CML), the disease can be kept under control using the BCR/ABL kinase inhibitor imatinib. Nevertheless, resistance or intolerance to imatinib and other BCR/ABL inhibitors may occur during therapy. Therefore, CML research is focusing on novel targets and targeted drugs. Polo-like kinase 1 (Plk1) is a serine/threonine kinase that plays an essential role in mitosis. In this study, we examined the expression of Plk1 in CML cells and its potential role as a therapeutic target. Plk1 was found to be expressed in phosphorylated form in the CML cell line K562 as well as in primary CML cells in all patients tested. Inhibition of BCR/ABL by imatinib or nilotinib (AMN107) led to decreased expression of the Plk1 protein in CML cells, suggesting that BCR/ABL promotes Plk1 generation. Silencing of Plk1 in CML cells by a small interfering RNA approach was followed by cell cycle arrest and apoptosis. Furthermore, the Plk1-targeting drug BI 2536 was found to inhibit proliferation of imatinib-sensitive and imatinib-resistant CML cells, including leukemic cells, carrying the T315 mutation of BCR/ABL with reasonable IC(50) values (1-50 nmol/L). The growth-inhibitory effects of BI 2536 on CML cells were found to be associated with cell cycle arrest and apoptosis. Moreover, BI 2536 was found to synergize with imatinib and nilotinib in producing growth inhibition in CML cells. In conclusion, Plk1 is expressed in CML cells and may represent a novel, interesting target in imatinib-sensitive and imatinib-resistant CML.

Oncoprotein Bmi-1 renders apoptotic resistance to glioma cells through activation of the IKK-nuclear factor-kappaB Pathway.

One of the features of malignant gliomas is their deviant resistance to cellular apoptosis induced by cytotoxic reagents. Bmi-1, an oncoprotein, has been linked to oncogenesis and cancer progression in various types of human cancers including gliomas. However, the mechanisms underlying Bmi-1 antiapoptotic function remain largely unknown. In this study, we report that Bmi-1 renders apoptotic resistance to glioma cells through nuclear factor-kappaB (NF-kappaB). In glioma cells, ectopic expression of Bmi-1 significantly inhibits doxorubicin-, BCNU-, or UV irradiation- induced apoptosis through reduction of activated caspase-3 and PARP, and induction of Bcl-X(L). Cellular depletion of Bmi-1 enhances the sensitivity of glioma cells to apoptosis induced by doxorubicin, BCNU, or UV irradiation. Bmi-1 activates NF-kappaB through stimulation of IkappaB phosphorylation, nuclear translocation, and transcriptional activity of NF-kappaB and expression of downstream genes of NF-kappaB including caspase-3, PARP, Bcl-X(L), and c-Myc. Inhibition of the IKK-NF-kappaB pathway abrogates the antiapoptotic effect of Bmi-1 on glioma cells. In high-grade gliomas, Bmi-1 and NF-kappaB are co-expressed in the cell nucleus. Up-regulation of Bmi-1 also correlates with tumor progression and poor survival of patients with gliomas. Together, our data demonstrate that Bmi-1 bestows apoptotic resistance to glioma cells through the IKK-NF-kappaB pathway and suggest Bmi-1 as a useful indicator for glioma prognosis.

KSHV manipulates Notch signaling by DLL4 and JAG1 to alter cell cycle genes in lymphatic endothelia.

Increased expression of Notch signaling pathway components is observed in Kaposi sarcoma (KS) but the mechanism underlying the manipulation of the canonical Notch pathway by the causative agent of KS, Kaposi sarcoma herpesvirus (KSHV), has not been fully elucidated. Here, we describe the mechanism through which KSHV directly modulates the expression of the Notch ligands JAG1 and DLL4 in lymphatic endothelial cells. Expression of KSHV-encoded vFLIP induces JAG1 through an NFkappaB-dependent mechanism, while vGPCR upregulates DLL4 through a mechanism dependent on ERK. Both vFLIP and vGPCR instigate functional Notch signalling through NOTCH4. Gene expression profiling showed that JAG1- or DLL4-stimulated signaling results in the suppression of genes associated with the cell cycle in adjacent lymphatic endothelial cells, indicating a role for Notch signaling in inducing cellular quiescence in these cells. Upregulation of JAG1 and DLL4 by KSHV could therefore alter the expression of cell cycle components in neighbouring uninfected cells during latent and lytic phases of viral infection, influencing cellular quiescence and plasticity. In addition, differences in signaling potency between these ligands suggest a possible complementary role for JAG1 and DLL4 in the context of KS.

Polo-like kinase (PLK) inhibitors in preclinical and early clinical development in oncology.

Polo-like kinases (PLKs) are a group of highly conserved serine/threonine protein kinases that play a key role in processes such as cell division and checkpoint regulation of mitosis. About 80% of human tumors, of various origins, express high levels of PLK transcripts. However, PLK mRNA is mostly absent in surrounding healthy tissues. Overexpression of PLK is associated with a poor prognosis in several tumor types and a lower overall survival rate. The overexpression of PLKs in human tumors, but not in healthy nondividing cells, makes them an attractive, selective target for cancer drug development. PLK inhibitors interfere with different stages of mitosis, such as centrosome maturation, spindle formation, chromosome separation, and cytokinesis. They induce mitotic chaos and severely perturb cell cycle progression, eventually leading to cancer cell death. Several PLK inhibitors are in development and are undergoing evaluations as potential cancer treatments. This review includes an overview of PLK inhibitors in early clinical development (i.e., BI 2536, BI 6727, GSK461364, ON 019190.Na, and HMN-214) and in advanced preclinical development (i.e., ZK-thiazolidinone, NMS-1, CYC-800, DAP-81, and LC-445). If proof of principle is confirmed in large studies, PLK inhibitors will offer a new targeted antitumor therapy for cancer patients.

In vivo molecular mediators of cancer growth suppression and apoptosis by selenium in mammary and prostate models: lack of involvement of gadd genes.

We used acute selenium (Se) treatments (i.e., daily single oral gavage of 2 mg Se per kilogram of body weight for 3 days) of female Sprague-Dawley rats bearing 1-methyl-1-nitrosourea-induced mammary carcinomas to increase the probability of detecting in vivo apoptosis and the associated gene/protein changes in the cancerous epithelial cells. The results show that whereas control carcinomas doubled in volume in 3 days, Se-methylselenocysteine and selenite treatments regressed approximately half of the carcinomas, accompanied by a 3- to 4-fold increase of morphologically observable apoptosis and approximately 40% inhibition of 5-bromo-2'-deoxyuridine index of the cancerous epithelial cells. The mRNA levels of growth arrest-DNA damage inducible 34 (gadd34), gadd45, and gadd153 genes were, contrary to expectation, not higher in the Se-treated carcinomas than in the gavage or diet restriction control groups. The gadd34 and gadd153 proteins were localized in the nonepithelial cells and not induced in the cancer epithelial cells of the Se-treated carcinomas. On the other hand, both Se forms decreased the expression of cyclin D1 and increased levels of P27Kip1 and c-Jun NH2-terminal kinase activation in a majority of the mammary carcinomas. Furthermore, the lack of induction of gadd genes in vivo by methylseleninic acid was confirmed in a human prostate xenograft model in athymic nude mice. In summary, these experiments showed the induction of cancer epithelial cell apoptosis and inhibition of cell proliferation by Se in vivo through the potential involvement of cyclin D1, P27Kip1, and c-Jun NH2-terminal kinase pathways. They cast doubt on the three gadd genes as mediators of Se action in vivo.

Expression and physiological role of CCN4/Wnt-induced secreted protein 1 mRNA splicing variants in chondrocytes.

CCN4/Wnt-induced secreted protein 1 (WISP1) is one of the CCN (CTGF/Cyr61/Nov) family proteins. CCN members have typical structures composed of four conserved cysteine-rich modules and their variants lacking certain modules, generated by alternative splicing or gene mutations, have been described in various pathological conditions. Several previous reports described a CCN4/WISP1 variant (WISP1v) lacking the second module in a few malignancies, but no information concerning the production of WISP1 variants in normal tissue is currently available. The expression of CCN4/WISP1 mRNA and its variants were analyzed in a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8, and primary rabbit growth cartilage (RGC) chondrocytes. First, we found WISP1v and a novel variant of WISP1 (WISP1vx) to be expressed in HCS-2/8, as well as full-length WISP1 mRNA. This new variant was lacking the coding regions for the second and third modules and a small part of the first module. To monitor the expression of CCN4/WISP1 mRNA along chondrocyte differentiation, RGC cells were cultured and sampled until they were mineralized. As a result, we identified a WISP1v ortholog in normal RGC cells. Interestingly, the WISP1v mRNA level increased dramatically along with terminal differentiation. Furthermore, overexpression of WISP1v provoked expression of an alkaline phosphatase gene that is a marker of terminal differentiation in HCS-2/8 cells. These findings indicate that WISP1v thus plays a critical role in chondrocyte differentiation toward endochondral ossification, whereas HCS-2/8-specific WISP1vx may be associated with the transformed phenotypes of chondrosarcomas.

Exercise improves insulin and leptin sensitivity in hypothalamus of Wistar rats.

Prolonged exercise of medium to high intensity is known to promote a substantial effect on the energy balance of rats. In male rats, moderately to severely intense programs lead to a reduction in food intake. However, the exact causes for the appetite-suppressive effects of exercise are not known. Here, we show that intracerebroventricular insulin or leptin infusion reduced food intake in exercised rats to a greater extent than that observed in control animals. Exercise was associated with a markedly increased phosphorylation/activity of several proteins involved in leptin and insulin signal transduction in the hypothalamus. The regulatory role of interleukin (IL)-6 in mediating the increase in leptin and insulin sensitivity in hypothalamus was also investigated. Treatment with insulin or leptin markedly reduced food intake in exercised rats that were pretreated with vehicle, although no increase in sensitivity to leptin- and insulin-induced anorexia after pretreatment with anti-IL-6 antibody was detected. The current study provides direct measurements of leptin and insulin signaling in the hypothalamus and documents increased sensitivity to these hormones in the hypothalamus of exercised rats in an IL-6-dependent manner. These findings provide support for the hypothesis that the appetite-suppressive actions of exercise may be mediated by the hypothalamus.

Impairment of conditioned freezing to tone, but not to context, in Fyn-transgenic mice: relationship to NMDA receptor subunit 2B function.

We previously demonstrated that transgenic mice overexpressing Fyn tyrosine kinase exhibit higher seizure susceptibility and enhanced tyrosine phosphorylation of several proteins, including the N-methyl-D-aspartate (NMDA) receptor subunit 2B (NR2B). In the present study, we analysed behavioural phenotypes, especially conditioned fear responses, of Fyn-transgenic (TG) mice to better understand the role of Fyn in learned emotional behaviour. Tone-dependent conditioned freezing was significantly attenuated in Fyn-TG mice, whereas context-dependent freezing was unaffected. Neither massed nor spaced conditioning ameliorated the attenuation of tone-dependent freezing. However, the selective NR2B antagonist ifenprodil, when administered before conditioning, restored tone-dependent freezing in Fyn-TG mice at a dose that did not affect freezing in wild-type (WT) mice. These results suggest that impairment of tone-dependent conditioned freezing in Fyn-TG mice is caused by disruption of the NR2B-containing NMDA receptor function. Tyrosine phosphorylation of brain proteins, including NR2B, was enhanced in Fyn-TG mice compared with that in WT mice. We also found that ifenprodil significantly suppressed the enhanced tyrosine phosphorylation. Thus, our data support the notion that NMDA receptor activity is tightly correlated with protein tyrosine phosphorylation, and Fyn might be one key molecule that controls tone-dependent conditioned freezing through the regulation of NMDA receptor function.