NT157 exerts antineoplastic activity by targeting JNK and AXL signaling in lung cancer cells.

Combination therapies or multi-targeted drugs have been pointed out as an option to prevent the emergence of resistant clones, which could make long-term treatment more effective and translate into better clinical outcomes for cancer patients. The NT157 compound is a synthetic tyrphostin that leads to long-term inhibition of IGF1R/IRS1-2-, STAT3- and AXL-mediated signaling pathways. Given the importance of these signaling pathways for the development and progression of lung cancer, this disease becomes an interesting model for generating preclinical evidence on the cellular and molecular mechanisms underlying the antineoplastic activity of NT157. In lung cancer cells, exposure to NT157 decreased, in a dose-dependent manner, cell viability, clonogenicity, cell cycle progression and migration, and induced apoptosis (p < 0.05). In the molecular scenario, NT157 reduced expression of IRS1 and AXL and phosphorylation of p38 MAPK, AKT, and 4EBP1. Besides, NT157 decreased expression of oncogenes BCL2, CCND1, MYB, and MYC and increased genes related to cellular stress and apoptosis, JUN, BBC3, CDKN1A, CDKN1B, FOS, and EGR1 (p < 0.05), favoring a tumor-suppressive cell signaling network in the context of lung cancer. Of note, JNK was identified as a key kinase for NT157-induced IRS1 and IRS2 phosphorylation, revealing a novel axis involved in the mechanism of action of the drug. NT157 also presented potentiating effects on EGFR inhibitors in lung cancer cells. In conclusion, our preclinical findings highlight NT157 as a putative prototype of a multitarget drug that may contribute to the antineoplastic arsenal against lung cancer.

A new synthetic antitumor naphthoquinone induces ROS-mediated apoptosis with activation of the JNK and p38 signaling pathways.

Quinones are plant-derived secondary metabolites that present diverse pharmacological properties, including antibacterial, antifungal, antiviral, anti-inflammatory, antipyretic and anticancer activities. In the present study, we evaluated the cytotoxic effect of a new naphthoquinone 6b,7-dihydro-5H-cyclopenta [b]naphtho [2,1-d]furan-5,6 (9aH)-dione) (CNFD) in different tumor cell lines. CNFD displayed cytotoxic activity against different tumor cell lines, especially in MCF-7 human breast adenocarcinoma cells, which showed IC50 values of 3.06 and 0.98 µM for 24 and 48 h incubation, respectively. In wound-healing migration assays, CNFD promoted inhibition of cell migration. We have found typical hallmarks of apoptosis, such as cell shrinkage, chromatin condensation, phosphatidylserine exposure, increase of caspases-9 and-3 activation, increase of internucleosomal DNA fragmentation without affecting the cell membrane permeabilization, increase of ROS production, and loss of mitochondrial membrane potential induced by CNFD. Moreover, gene expression experiments indicated that CNFD increased the expression of the genes CDKN1A, FOS, MAX, and RAC1 and decreased the levels of mRNA transcripts of several genes, including CCND1, CDK2, SOS1, RHOA, GRB2, EGFR and KRAS. The CNFD treatment of MCF-7 cells induced the phosphorylation of c-jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs) and inactivation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). In a study using melanoma cells in a murine model in vivo, CNFD induced a potent anti-tumor activity. Herein, we describe, for the first time, the cytotoxicity and anti-tumor activity of CNFD and sequential mechanisms of apoptosis in MCF-7 cells. CNFD seems to be a promising candidate for anti-tumor therapy.

Changes in Appetite Regulation-Related Signaling Pathways in the Brain of Mice Supplemented with Non-nutritive Sweeteners.

Non-nutritive sweeteners (NNSs) are commonly used to prevent weight gain and development of metabolic diseases associated with consumption of high-energy diets. Recent studies have demonstrated that these compounds may have unwanted detrimental effects under specific circumstances in vivo. In particular, an association between NNS consumption and changes in signaling pathways involved in the hunger-satiety system in the brain has been reported. Nonetheless, the extent of alterations in brain signaling pathways associated with consumption of these compounds has not been determined. The objective of this study was to determine the effect of frequent consumption of NNSs on the expression of proteins involved in signaling pathways related to appetite control in the brain in vivo. Eight-week-old BALB/c mice were supplemented with sucrose, sucralose, or steviol glycosides in their daily drinking water for 6 weeks. Subsequently, total brain protein extracts were used to analyze the expression of total and phosphorylated JAK2, STAT5, ERK 1/2, JNK, as well as SHP-2 and POMC, by western blot. Serum concentrations of leptin and α-MSH were quantified by ELISA. Results show that consumption of NNSs promotes significant changes in these signaling pathways, reducing the expression of pSTAT5/STAT5, pERK 1/2, SHP-2, and pJNK/JNK in male mice supplemented with steviol glycosides. Furthermore, consumption of steviol glycosides induced a decrease of α-MSH in male mice. In contrast, steviol glycosides induced overexpression of pSTAT5, pERK, and SHP-2 in females. These data suggest that chronic consumption of NNSs promotes sex-specific changes in signaling pathways related to the central hunger-satiety system in vivo.

Angiotensin-(1-7) Prevents Lipopolysaccharide-Induced Autophagy via the Mas Receptor in Skeletal Muscle.

Skeletal muscle atrophy, which occurs in lipopolysaccharide (LPS)-induced sepsis, causes a severe muscle function reduction. The increased autophagy contributes to sepsis-induced skeletal muscle atrophy in a model of LPS injection, increasing LC3II/LC3I ratio, autophagy flux, and autophagosomes. Angiotensin-(1-7) (Ang-(1-7)) has anti-atrophic effects via the Mas receptor in skeletal muscle. However, the impact of Ang-(1-7) on LPS-induced autophagy is unknown. In this study, we determined the effect of Ang-(1-7) on sepsis-induced muscle autophagy. C57BL6 wild-type (WT) mice and mice lacking the Mas receptor (KO Mas) were injected with LPS together with the systemic administration of Ang-(1-7) to determine autophagy in skeletal muscle. We also evaluated autophagy and p38 and c-Jun N-terminal kinase (JNK)activation. Our results show that Ang-(1-7) prevents LPS-induced autophagy in the diaphragm, tibialis anterior, and gastrocnemius of WT mice, which is demonstrated by a decrease in the LC3II/LC3I ratio and mRNA levels of lc3b and ctsl. This effect was lost in KO Mas mice, suggesting the role of the Mas receptor. The results in C2C12 cells show that Ang-(1-7) reduces several LPS-dependent effects, such as autophagy (LC3II/LC3I ratio, autophagic flux, and autophagosomes), activation of p38 and JNK, B-cell lymphoma-2 (BCL2) phosphorylation, and disassembly of the Beclin1/BCL2 complex. In conclusion, Ang-(1-7)/Mas receptor reduces LPS-induced autophagy in skeletal muscle. In vitro assays indicate that Ang-(1-7) prevents LPS-induced autophagy and modifies the MAPK signaling and the disassembly of a complex involved at the beginning of autophagy.

Macrophages from a type 1 diabetes mouse model present dysregulated Pl3K/AKT, ERK 1/2 and SAPK/JNK levels.

Diabetes causes dysregulation in signal transduction in immune cells leading to an impaired response to pathogens. Herein, we investigated the impact of type 1 diabetes (T1D) in bone marrow-derived macrophages (BMDM), using male non-diabetic and diabetic C57BL/6 mice (alloxan 60 mg/kg, i.v., CEUA/FCF/USP - 467). Diabetic BMDM expressed impaired phosphoinositide 3-kinase (PI3K), being lower p-PI3K p55 levels and higher levels of PI3K p110 alpha, whereas protein kinase B (PKB/Akt) (Ser-473 and Thr-308), extracellular signal-regulated kinases (ERK 1/2), and stress-activated protein kinase (SAPK/JNK) were enhanced compared to non-diabetic BMDM. Further evaluation of the responsiveness to lipopolysaccharide (LPS; 0.1 and 1 ug/mL), diabetic BMDM and peritoneal macrophage secreted dysregulated levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10 levels. In 24 h, diabetic BMDM stimulated by LPS presented lower metabolic activity, with no differences in cell surveillance. Therefore, LPS re-stimulation (0.1 ug/mL) in diabetic BMDM resulted in higher secretion of TNF-α compared to non-diabetic BMDM. However, diabetic peritoneal macrophages secreted similar IL-6 levels in the first and additional 24 h of LPS stimulation. In general, our results demonstrated that diabetes exerts an impact in both BMDM and peritoneal macrophages ability to secrete cytokine under LPS stimulation.

Activation of protein synthesis, regeneration, and MAPK signaling pathways following repeated bouts of eccentric cycling.

The aim of this study was to examine the activation of skeletal muscle signaling pathways related to protein synthesis and the gene expression of regeneration/degradation markers following repeated bouts of eccentric cycling. Nine untrained men (25.4 ± 1.9 yr) performed two 30-min eccentric cycling bouts (ECC1, ECC2) at 85% of maximal concentric workload, separated by 2 wk. Muscle biopsies were taken from the vastus lateralis before and 2 h after each bout. Indirect markers of muscle damage were assessed before and 24-48 h after exercise. Changes in the Akt/mammalian target of rapamycin (mTOR)/rbosomal protein S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) and MAPK signaling pathways were measured by Western blot and changes in mRNA expression of IL-6 and IL-1ß, and myogenic regulatory factors (MRFs) were measured by real-time PCR. ECC1 induced greater increases in indirect markers of muscle damage compared with ECC2. Phosphorylation of S6K1 and rpS6 increased after both exercise bouts (P < 0.05), whereas phosphorylation of mTOR increased after ECC2 only (P = 0.03). Atrogin-1 mRNA expression decreased after ECC1 and ECC2 (P < 0.05) without changes in muscle RING-finger protein-1 mRNA. Basal mRNA levels of myoblast determination protein-1 (MyoD), MRF4, and myogenin were higher 2 wk after ECC1 (P < 0.05). MRF4 mRNA increased after ECC1 and ECC2 (P < 0.05), whereas MyoD mRNA expression increased only after ECC1 (P = 0.03). Phosphorylation of JNK and p38 MAPK increased after both exercise bouts (P < 0.05), similar to IL-6 and IL-1ß mRNA expression. All together, these results suggest that differential regulation of the mTOR pathway and MRF expression could mediate the repeated bout effect observed between an initial and secondary bout of eccentric exercise.

Notum attenuates HBV-related liver fibrosis through inhibiting Wnt 5a mediated non-canonical pathways.

BACKGROUND: Non-canonical Wnt pathways play important roles in liver fibrosis. Notum is a newly discovered inhibitor to Wnt proteins. This study was to investigate anti-fibrotic effects of Notum. METHODS: 53 patients with hepatitis B virus (HBV) infection as well as a cell co-culture system of LX-2 and Hep AD38 cells were engaged in this study. Clinical, biological and virological data of each patient were analyzed. Cell viability was detected at different time points. mRNA and protein levels of NFATc1 (Nuclear factor of activated T-cells), Jnk, α-SMA, Col1A1 and TIMP-1 were detected both in LX-2 and liver tissue. Protein levels of NFATc1 and Jnk in liver tissue and their correlations with fibrosis score were analyzed. RESULTS: Hepatitis B virus replication up-regulated Wnt5a induced NFATc1 and Jnk activity in Hep AD38. Notum suppressed NFATc1, Jnk and fibrosis genes expression, reduced cell viability in co-cultured LX-2 cells induced by HBV. Interestingly, Patients with HBV DNA > 5log copies/ml had higher mRNA levels of NFATc1 and fibrosis genes than patients with HBV DNA < 5log copies/ml. Most importantly, protein expressions of NFATc1 and pJnk have positive correlations with liver fibrosis scores in HBV-infected patients. CONCLUSIONS: Our data showed that Notum inhibited HBV-induced liver fibrosis through down-regulating Wnt 5a mediated non-canonical pathways. This study shed light on anti-fibrotic treatment.

Notum attenuates HBV-related liver fibrosis through inhibiting Wnt 5a mediated non-canonical pathways

BACKGROUND: Non-canonical Wnt pathways play important roles in liver fibrosis. Notum is a newly discovered inhibitor to Wnt proteins. This study was to investigate anti-fibrotic effects of Notum. METHODS: 53 patients with hepatitis B virus (HBV) infection as well as a cell co-culture system of LX-2 and Hep AD38 cells were engaged in this study. Clinical, biological and virological data of each patient were analyzed. Cell viability was detected at different time points. mRNA and protein levels of NFATc1 (Nuclear factor of activated T-cells), Jnk, α-SMA, Col1A1 and TIMP-1 were detected both in LX-2 and liver tissue. Protein levels of NFATc1 and Jnk in liver tissue and their correlations with fibrosis score were analyzed. RESULTS: Hepatitis B virus replication up-regulated Wnt5a induced NFATc1 and Jnk activity in Hep AD38. Notum suppressed NFATc1, Jnk and fibrosis genes expression, reduced cell viability in co-cultured LX-2 cells induced by HBV. Interestingly, Patients with HBV DNA > 5log copies/ml had higher mRNA levels of NFATc1 and fibrosis genes than patients with HBV DNA < 5log copies/ml. Most importantly, protein expressions of NFATc1 and pJnk have positive correlations with liver fibrosis scores in HBV-infected patients. CONCLUSIONS: Our data showed that Notum inhibited HBV-induced liver fibrosis through down-regulating Wnt 5a mediated non-canonical pathways. This study shed light on anti-fibrotic treatment.

Wnt7b signalling through Frizzled-7 receptor promotes dendrite development by coactivating CaMKII and JNK.

The formation of complex dendritic arbors is crucial for the assembly of functional networks as abnormal dendrite formation underlies several neurodevelopmental and psychiatric disorders. Many extracellular factors have been postulated as regulators of dendritic growth. Wnt proteins play a critical role in neuronal development and circuit formation. We previously demonstrated that Wnt7b acts through the scaffold protein dishevelled 1 (Dvl1) to modulate dendrite arborisation by activating a non-canonical Wnt signalling pathway. Here, we identify the seven-transmembrane frizzled-7 (Fz7, also known as FZD7) as the receptor for Wnt7b-mediated dendrite growth and complexity. Importantly, Fz7 is developmentally regulated in the intact hippocampus, and is localised along neurites and at dendritic growth cones, suggesting a role in dendrite formation and maturation. Fz7 loss-of-function studies demonstrated that Wnt7b requires Fz7 to promote dendritic arborisation. Moreover, in vivo Fz7 loss of function results in dendritic defects in the intact mouse hippocampus. Furthermore, our findings reveal that Wnt7b and Fz7 induce the phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and JNK proteins, which are required for dendritic development. Here, we demonstrate that Wnt7b-Fz7 signals through two non-canonical Wnt pathways to modulate dendritic growth and complexity.

CFTR modulates RPS27 gene expression using chloride anion as signaling effector.

In Cystic Fibrosis (CF), the impairment of the CFTR channel activity leads to a variety of alterations, including differential gene expression. However, the CFTR signaling mechanisms remain unclear. Recently, culturing IB3-1 CF cells under different intracellular Cl- concentrations ([Cl-]i), we observed several Cl--dependent genes and further characterized one of them as RPS27. Thus, we hypothesized that Cl- might act as a signaling effector for CFTR signaling. Here, to test this idea, we study RPS27 expression in T84 cells modulating the CFTR activity by using CFTR inhibitors. First, we observed that incubation of T84 cells with increasing concentrations of the CFTR inhibitors CFTR(inh)-172 or GlyH-101 determined a progressive increase in the relative [Cl-]i (using the Cl- fluorescent probe SPQ). The [Cl-]i rise was concomitant with a dose-dependent down-regulation of RPS27. These results imply that CFTR inhibition produce Cl- accumulation and that RPS27 expression can be modulated by CFTR inhibition. Therefore, Cl- behaves as a signaling effector for CFTR in the modulation of RPS27 expression. In addition, the IL-1ß receptor antagonist IL1RN or the JNK inhibitor SP600125, both restored the down-regulation of RPS27 induced by CFTRinh-172, implying a role of autocrine IL-1ß and JNK signaling downstream of Cl- in RPS27 modulation.

c-Jun integrates signals from both MEK/ERK and MKK/JNK pathways upon vaccinia virus infection.

Usurpation of the host's signalling pathways is a common strategy employed by viruses to promote their successful replication. Here we show that infection with the orthopoxvirus vaccinia virus (VACV) leads to sustained stimulation of c-Jun activity during the entire infective cycle. This stimulation is temporally regulated through MEK/ERK or MKK/JNK pathways, i.e. during the early/mid phase (1 to 6 hpi) and in the late phase (9 to 24 hpi) of the infective cycle, respectively. As a transcriptional regulator, upon infection with VACV, c-Jun is translocated from the cytoplasm to the nucleus, where it binds to the AP-1 DNA sequence found at the promoter region of its target genes. To investigate the role played by c-Jun during VACV replication cycle, we generated cell lines that stably express a c-Jun-dominant negative (DNc-Jun) mutation. Our data revealed that c-Jun is required during early infection to assist with viral DNA replication, as demonstrated by the decreased amount of viral DNA found in the DNc-Jun cells. We also demonstrated that c-Jun regulates the expression of the early growth response gene (egr-1), a gene previously shown to affect VACV replication mediated by MEK/ERK signalling. VACV-induced stimulation of the MKK/JNK/JUN pathway impacts viral dissemination, as we observed a significant reduction in both viral yield, during late stages of infection, and virus plaque size. Collectively, our data suggest that, by modulating the host's signalling pathways through a common target such as c-Jun, VACV temporally regulates its infective cycle in order to successfully replicate and subsequently spread.

Epidermal growth factor prevents thallium(I)- and thallium(III)-mediated rat pheochromocytoma (PC12) cell apoptosis.

We have reported recently that the proliferation of PC12 cells exposed to micromolar concentrations of Tl(I) or Tl(III) has different outcomes, depending on the absence (EGF- cells) or the presence (EGF+ cells) of epidermal growth factor (EGF) added to the media. In the current work, we investigated whether EGF supplementation could also modulate the extent of Tl(I)- or Tl(III)-induced cell apoptosis. Tl(I) and Tl(III) (25-100 µM) decreased cell viability in EGF- but not in EGF+ cells. In EGF- cells, Tl(I) decreased mitochondrial potential, enhanced H2O2 generation, and activated mitochondrial-dependent apoptosis. In addition, Tl(III) increased nitric oxide production and caused a misbalance between the anti- and pro-apoptotic members of Bcl-2 family. Tl(I) increased ERK1/2, JNK, p38, and p53 phosphorylation in EGF- cells. In these cells, Tl(III) did not affect ERK1/2 and JNK phosphorylation but increased p53 phosphorylation that was related to the promotion of cell senescence. In addition, this cation significantly activated p38 in both EGF- and EGF+ cells. The specific inhibition of ERK1/2, JNK, p38, or p53 abolished Tl(I)-mediated EGF- cell apoptosis. Only when p38 activity was inhibited, Tl(III)-mediated apoptosis was prevented in EGF- and EGF+ cells. Together, current results indicate that EGF partially prevents the noxious effects of Tl by preventing the sustained activation of MAPKs signaling cascade that lead cells to apoptosis and point to p38 as a key mediator of Tl(III)-induced PC12 cell apoptosis.

Antioxidant Therapy Alters Brain MAPK-JNK and BDNF Signaling Path-ways in Experimental Diabetes Mellitus.

This study was designed to investigate the effects of treatment with the antioxidants N-acetylcysteine (NAC) and deferoxamine (DFX) in intracellular pathways in the brain of diabetic rats. To conduct this study we induced diabetes in Wistar rats with a single injection of alloxan, and afterwards rats were treated with NAC or DFX for 14 days. Following treatment completion, the immunocontent of c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase-38 (MAPK38), brain-derived neurotrophic factor (BDNF), and protein kinases A and C (PKA and PKC) were determined in the prefrontal cortex (PFC), hippocampus, amygdala and nucleus accumbens (NAc). DFX treatment increased JNK content in the PFC and NAc of diabetic rats. In the amygdala, JNK was increased in diabetics treated with saline or NAC. MAPK38 was decreased in the PFC of control and in diabetic rats treated with NAC or DFX; and in the NAc in all groups. PKA was decreased in the PFC with DFX treatment. In the amygdala, PKA content was increased in diabetic rats treated with either saline or NAC, compared to controls; and it was decreased in either NAC or DFX-treated groups, compared to saline-treated diabetic animals. In the NAc, PKA was increased in NAC-treated diabetic rats. PKC was increased in the amygdala of NAC-treated diabetic rats. In the PFC, the BDNF levels were decreased following treatment with DFX in diabetic rats. In the hippocampus of diabetic rats the BDNF levels were decreased. However, treatment with DFX reversed this effect. In the amygdala the BDNF increased with DFX in non-diabetic rats. In the NAc DFX treatment increased the BDNF levels in diabetic rats. In conclusion, both diabetes and treatment with antioxidants were able to alter intracellular pathways involved in the regulation of cell survival in a brain area and treatment-dependent fashion.

Leishmania mexicana promastigotes down regulate JNK and p-38 MAPK activation: Role in the inhibition of camptothecin-induced apoptosis of monocyte-derived dendritic cells.

Dendritic cells (DC) are one of the principal host cells of the obligate intracellular parasite Leishmania. Inhibition of host cell apoptosis is a strategy employed by multiple pathogens to ensure their survival in the infected cell. We have previously shown that the infection of monocyte-derived dendritic cells (moDC) with Leishmania mexicana inhibits campthotecin-induced apoptosis. Nevertheless, the mechanisms involved in the inhibition of apoptosis of dendritic cells by Leishmania have not been established. Mitogen-activated protein kinases (MAPK) are key participants in the process of apoptosis and different species of Leishmania have been shown to regulate these kinases. In the present study, we analyzed the effect of L. mexicana promastigotes in the activation of JNK and p38 MAP kinase and their participation in the inhibition of apoptosis. The infection of moDC with L. mexicana promastigotes diminished significantly the phosphorylation of the MAP kinases JNK and p38. The inhibition of both kinases diminished DNA fragmentation, but in a major extent was the reduction of DNA fragmentation when JNK was inhibited. The capacity of L. mexicana promastigotes to diminish MAP kinases activation is probably one of the strategies employed to delay apoptosis induction in the infected moDC and may have implications for Leishmania pathogenesis by favoring the invasion of its host and the persistence of the parasite in the infected cells.

Saturated fatty acids modulate autophagy's proteins in the hypothalamus.

Autophagy is an important process that regulates cellular homeostasis by degrading dysfunctional proteins, organelles and lipids. In this study, the hypothesis that obesity could lead to impairment in hypothalamic autophagy in mice was evaluated by examining the hypothalamic distribution and content of autophagic proteins in animal with obesity induced by 8 or 16 weeks high fat diet to induce obesity and in response to intracerebroventricular injections of palmitic acid. The results showed that chronic exposure to a high fat diet leads to an increased expression of inflammatory markers and downregulation of autophagic proteins. In obese mice, autophagic induction leads to the downregulation of proteins, such as JNK and Bax, which are involved in the stress pathways. In neuron cell-line, palmitate has a direct effect on autophagy even without inflammatory activity. Understanding the cellular and molecular bases of overnutrition is essential for identifying new diagnostic and therapeutic targets for obesity.

JNK and IKKß phosphorylation is reduced by glucocorticoids in adipose tissue from insulin-resistant rats.

OBJECTIVES: Peripheral insulin resistance (IR) is one of the main side effects caused by glucocorticoid (GC)-based therapies, and the molecular mechanisms of GC-induced IR are not yet fully elucidated. Thus, we aimed to investigate the effects of dexamethasone treatment on the main components of insulin and inflammatory signaling in the adipose tissue of rats. MATERIALS/METHODS: Male Wistar rats received daily injections of dexamethasone (1mg/kg body weight (b.w.), intraperitoneally (i.p.)) for 5 days (DEX), whereas control rats received saline (CTL). The metabolic status was investigated, and the epididymal fat fragments were collected for lipolysis and western blot analyses. RESULTS: The DEX rats became hyperglycemic, hyperinsulinemic, insulin resistant and glucose intolerant, compared with the CTL rats (P<0.05). The basal glycerol release in the fat fragments was 1.5-fold higher in the DEX rats (P<0.05). The phosphorylation of protein kinase B (PKB) at ser(473) decreased by 44%, whereas, the phosphorylation of insulin receptor substrate (IRS)-1 at ser(307) increased by 93% in the adipose tissue of the DEX rats after an oral bolus of glucose (P<0.05). The basal phosphorylation of c-jun-N-terminal kinase (JNK) and inhibitor of nuclear factor kappa-B (IKKß) proteins was reduced by 46% and 58%, respectively, in the adipose tissue of the DEX rats (P<0.05). This was paralleled with a significant reduction (47%) in the glucocorticoid receptor (GR) protein content in the adipose tissue of the DEX rats (P<0.05). CONCLUSION: The insulin-resistant status of rats induced by dexamethasone administration have PKB and IRS-1 activity attenuated in epididymal fat without increases in the phosphorylation of the proinflammatory signals JNK and IKKß.

Modulation of the peroxiredoxin system by cytokines in insulin-producing RINm5F cells: down-regulation of PRDX6 increases susceptibility of beta cells to oxidative stress.

Peroxiredoxins are a family of six antioxidant enzymes (PRDX1-6), and may be an alternative system for the pancreatic beta cells to cope with oxidative stress. This study investigated whether the main diabetogenic pro-inflammatory cytokines or the anti-inflammatory cytokine IL-4 modulate PRDXs levels and putative intracellular pathways important for this process in the insulin-producing RINm5F cells. RINm5F cells expressed significant amounts of PRDX1, PRDX3 and PRDX6 enzymes. Only PRDX6 was modulated by cytokines, showing both mRNA and protein down-regulation following incubation of RINm5F cells with TNF-alpha and IFN-gamma but not with IL-1beta. Separately IFN-gamma or TNF-alpha decreased PRDX6 protein but not mRNA levels. The blockage of the JNK signalling and of the calpains and proteasome proteolysis systems restored PRDX6 protein levels. IL-4 alone did not modulate PRDXs levels. However, pre/co-incubation with IL-4 substantially prevented the decrease in PRDX6 induced by pro-inflammatory cytokines. Knockdown of PRDX6 increased susceptibility of RINm5F cells to the deleterious effects of pro-inflammatory cytokines and to oxidative stress. These results show that, from the PRDXs significantly expressed in RINm5F cells, only PRDX6 is modulated by the diabetogenic cytokines IFN-gamma and TNF-alpha. This PRDX6 down-regulation depends on the calpain and proteasome systems and JNK signalling. PRDX6 is an important enzyme for protection against oxidative stress and the interaction between pro- and anti-inflammatory cytokines might be important to determine the antioxidant capacity of the cells.

Methylglyoxal-induced cytotoxicity in neonatal rat brain: a role for oxidative stress and MAP kinases.

Carbonyl compounds such as methylglyoxal (MGO) seem to play an important role in complications resulting from diabetes mellitus, in aging and neurodegenerative disorders. In this study, we are showing, that MGO is able to suppress cell viability and induce apoptosis in the cerebral cortex and hippocampus of neonatal rats ex-vivo. These effects are partially related with ROS production, evaluated by DCFH-DA assay. Coincubation of MGO and reduced glutathione (GSH) or Trolox (vitamin E) totally prevented ROS production but only partially prevented the MGO-induced decreased cell viability in the two brain structures, as evaluated by the MTT assay. Otherwise, L-NAME, a nitric oxide (NO) inhibitor, partially prevented ROS production in the two structures but partially prevented cytotoxicity in the hippocampus. Pharmacological inhibition of Erk, has totally attenuated MGO-induced ROS production and cytotoxicity, suggesting that MEK/Erk pathway could be upstream of ROS generation and cell survival. Otherwise, p38MAPK and JNK failed to prevent ROS generation but induced decreased cell survival consistent with ROS-independent mechanisms. We can propose that Erk, p38MAPK and JNK are involved in the cytotoxicity induced by MGO through different signaling pathways. While Erk could be an upstream effector of ROS generation, p38MAPK and JNK seem to be associated with ROS-independent cytotoxicity in neonatal rat brain. The cytotoxic damage progressed to apoptotic cell death at MGO concentration higher than those described for adult brain, suggesting that the neonatal brain is resistant to MGO-induced cell death. The consequences of MGO-induced brain damage early in life, remains to be clarified. However, it is feasible that high MGO levels during cortical and hippocampal development could be, at least in part, responsible for the impairment of cognitive functions in adulthood.

Pro-apoptotic effect of anti-ß1-adrenergic receptor antibodies in periodontitis patients.

An anti-ß(1)-adrenergic antibody from the sera of periodontitis patients (anti-ß(1)-AR IgG) against the second extracellular loop of the human ß(1)-adrenoceptor (ß(1)-AR) has been shown to cause rat atria apoptosis. The anti-ß(1)-AR IgG binds and activates atria ß(1)-AR, increasing the intracellular calcium concentration, which, in turn, activates caspases-3, -8, and -9. The ß(1)-AR and the post-receptor activation of calcium/calmodulin (CaM) lead to increased inducible nitric oxide synthase (iNOS) activity, with an increase in cyclic GMP (cGMP) accumulation as well as increased JNK phosphorylation and cyclic AMP (cAMP) production. We also observed an apoptotic effect of anti-ß(1)-AR IgG, with increased generation of PGE(2). Comparatively, xamoterol, an authentic ß(1)-AR agonist, mimicked the autoantibody effect on rat atria ß(1)-AR apoptosis. Our results suggest that autoantibodies from the sera of periodontitis patients bind and interact with rat atria ß(1)-AR, provoking apoptosis. This implicates a series of modulatory cardiac signaling events that could alter normal heart function and may occur with chronic stimulation of the atria ß(1)-AR, which could lead to heart failure. These results suggest an important link between periodontitis and cardiovascular disease.

Toddaculin, a natural coumarin from Toddalia asiatica, induces differentiation and apoptosis in U-937 leukemic cells.

Chemotherapeutics represent the main approach for the treatment of leukemia. However, the occurrence of adverse side effects and the complete lack of effectiveness in some cases make it necessary to develop new drugs. As part of our screening program to evaluate the potential chemotherapeutic effect of natural coumarins, we investigated the anti-leukemic activities of a series of six prenylated coumarins isolated from the stem bark of Toddalia asiatica (Rutaceae). Among these, 6-(3-methyl-2-butenyl)-5,7-dimethoxycoumarin (toddaculin) displayed the most potent cytotoxic and anti-proliferative effects in U-937 cells. To determine whether these effects resulted from induction of cell death or differentiation, we further evaluated the expression of several apoptosis and maturation markers. Interestingly, while toddaculin at 250 µM was able to induce apoptosis in U-937 cells, involving decreased phosphorylation levels of ERK and Akt, 50 µM toddaculin exerted differentiating effects, inducing both the capacity of U-937 cells to reduce NBT and the expression of differentiation markers CD88 and CD11b, but no change in p-Akt or p-ERK levels. Taken together, these findings indicate that toddaculin displays a dual effect as a cell differentiating agent and apoptosis inducer in U-937 cells, suggesting it may serve as a pharmacological prototype for the development of novel anti-leukemic agents.