Dysfunction of Nrf2-regulated cellular defence system and JNK activation induced by high dose of fly Ash particles are associated with pulmonary injury in mouse lungs

The mechanisms of the exposure to fine particulate matter (PM) as a risk factor for pulmonary injury are not fully understood. The transcription factor, NF-E2-related factor 2 (Nrf2), plays a key role in protection lung against PM insult and cancer chemoprevention. In this study, F3-S fly ash particles from a municipal waste incinerator were evaluated as a PM model. We found that F3-S triggered hierarchical oxidative stress responses involving the prolonged activation of the cytoprotective Nrf2 transcriptional program via Keap1 Cys151 modification, and c-Jun NH2-terminal kinase (JNK) phosphorylation at higher doses. In mouse lungs exposed to fly ash particles at a low dose (10-20 mg/kg), Nrf2 signalling was upregulated, while in those exposed to a high fly ash particle dose (40 mg/kg), there was significant activation of JNK, and this correlated with Nrf2 phosphorylation and the downregulation of antioxidant response element (ARE)-driven genes. The JNK inhibitor, SP600125, reversed Nrf2 phosphorylation, and downregulation of detoxifying enzymes. Silencing JNK expression in mouse lungs using adenoviral shRNA inhibited JNK activation and Nrf2 phosphorylation, promoted ARE-driven gene expression, and reduced pulmonary injury. Furthermore, we found that the 452-515 amino acid region within the Neh1 domain of Nrf2 was required for its interaction with P-JNK. We demonstrated that Nrf2 was an important P-JNK target in fly ash-induced pulmonary toxicity. JNK phosphorylated Nrf2, leading to a dysfunction of the Nrf2-mediated defence system.

A novel JNK induces innate immune response by activating the expression of antimicrobial peptides in Chinese mitten crab Eriocheir sinensis

c-Jun NH₂-terminal kinase (JNK) is a member of mitogen-activated protein kinases (MAPKs) that participates in the regulation of various physiological and pathological processes. In this study, we identified a novel JNK (EsJNK) and determined the cDNA sequence of its isoform (EsJNK-a) from the Chinese mitten crab Eriocheir sinensis. The open reading frame (ORF) of EsJNK was predicted to encode 421 peptides with a serine/threonine protein kinase, a catalytic (S_TKc) domain, and a low complexity region. The ORF of EsJNK-a was 1380 bp encoding a protein with 459 amino acids, which was 38 amino acids more than that of EsJNK. The predicted tertiary structure of EsJNK was conserved and contained 15 α-helices and 10 β-sheets. Phylogenetic tree analysis revealed that EsJNK was clustered with the JNK homologs of other crustaceans. Quantitative real-time PCR assays showed that EsJNK was expressed in all the tissues examined, but it was relatively higher in hemocytes, muscles, and intestines. The expression of EsJNK mRNA in the hemocytes was upregulated by lipopolysaccharides and peptidoglycans, as well as by Staphylococcus aureus or Vibrio parahaemolyticus challenge. Functionally, after silencing EsJNK by siRNA in crabs, the expression levels of two antimicrobial peptides (AMPs), namely, anti-lipopolysaccharide factor and crustin, were significantly inhibited. The purified recombinant EsJNK protein with His-tag accelerated the elimination of the aforementioned bacteria in vivo. However, knockdown of EsJNK had an opposite effect. These findings suggested that EsJNK might be involved in the antibacterial immune defense of crabs by regulating the transcription of AMPs.

Mutual interaction of kisspeptin, estrogen and bone morphogenetic protein-4 activity in GnRH regulation by GT1-7 cells

Reproduction is integrated by interaction of neural and hormonal signals converging on hypothalamic neurons for controlling gonadotropin-releasing hormone (GnRH). Kisspeptin, the peptide product of the kiss1 gene and the endogenous agonist for the GRP54 receptor, plays a key role in the regulation of GnRH secretion. In the present study, we investigated the interaction between kisspeptin, estrogen and BMPs in the regulation of GnRH production by using mouse hypothalamic GT1-7 cells. Treatment with kisspeptin increased GnRH mRNA expression and GnRH protein production in a concentration-dependent manner. The expression levels of kiss1 and GPR54 were not changed by kisspeptin stimulation. Kisspeptin induction of GnRH was suppressed by co-treatment with BMPs, with BMP-4 action being the most potent for suppressing the kisspeptin effect. The expression of kisspeptin receptor, GPR54, was suppressed by BMPs, and this effect was reversed in the presence of kisspeptin. It was also revealed that BMP-induced Smad1/5/8 phosphorylation and Id-1 expression were suppressed and inhibitory Smad6/7 was induced by kisspeptin. In addition, estrogen induced GPR54 expression, while kisspeptin increased the expression levels of ERα and ERβ, suggesting that the actions of estrogen and kisspeptin are mutually enhanced in GT1-7 cells. Moreover, kisspeptin stimulated MAPKs and AKT signaling, and ERK signaling was functionally involved in the kisspeptin-induced GnRH expression. BMP-4 was found to suppress kisspeptin-induced GnRH expression by reducing ERK signaling activity. Collectively, the results indicate that the axis of kisspeptin-induced GnRH production is bi-directionally controlled, being augmented by an interaction between ERα/β and GPR54 signaling and suppressed by BMP-4 action in GT1-7 neuron cells.

Modulation of mitochondrial functions by the indirect antioxidant sulforaphane: a seemingly contradictory dual role and an integrative hypothesis

The chemotherapeutic isothiocyanate sulforaphane (SFN) was early linked to anticarcinogenic and antiproliferative activities. Soon after, this compound, derived from cruciferous vegetables, became an excellent and useful trial for anti-cancer research in experimental models including growth tumor, metastasis, and angiogenesis. Many subsequent reports showed modifications in mitochondrial signaling, functionality, and integrity induced by SFN. When cytoprotective effects were found in toxic and ischemic insult models, seemingly contradictory behaviors of SFN were discovered: SFN was inducing deleterious changes in cancer cell mitochondria that eventually would carry the cell to death via apoptosis and also was protecting noncancer cell mitochondria against oxidative challenge, which prevented cell death. In both cases, SFN exhibited effects on mitochondrial redox balance and phase II enzyme expression, mitochondrial membrane potential, expression of the family of B cell lymphoma 2 homologs, regulation of proapoptotic proteins released from mitochondria, activation/inactivation of caspases, mitochondrial respiratory complex activities, oxygen consumption and bioenergetics, mitochondrial permeability transition pore opening, and modulation of some kinase pathways. With the ultimate findings related to the induction of mitochondrial biogenesis by SFN, it could be considered that SFN has effects on mitochondrial dynamics that explain some divergent points. In this review, we list the reports involving effects on mitochondrial modulation by SFN in anti-cancer models as well as in cytoprotective models against oxidative damage. We also attempt to integrate the data into a mechanism explaining the various effects of SFN on mitochondrial function in only one concept, taking into account mitochondrial biogenesis and dynamics and making a comparison with the theory of reactive oxygen species threshold of cell death. Our interest is to achieve a complete view of cancer and protective therapies based on SFN that can be extended to other chemotherapeutic compounds with similar characteristics. The work needed to test this hypothesis is quite extensive.

Signaling pathways involved in isoprostane-mediated fibrogenic effects in rat hepatic stellate cells

Despite evidence supporting a potential role for F2-isoprostanes (F2-IsoP's) in liver fibrosis, their signaling mechanisms are poorly understood. We have previously provided evidence that F2-IsoP's stimulate hepatic stellate cell (HSC) proliferation and collagen hyperproduction by activation of a modified form of isoprostane receptor homologous to the classic thromboxane receptor (TP). In this paper, we examined which signal transduction pathways are set into motion by F2-IsoP's to exert their fibrogenic effects. HSCs were isolated from rat liver, cultured to their activated myofibroblast-like phenotype, and then treated with the isoprostane 15-F2t-isoprostane (15-F2t-IsoP). Inositol trisphosphate (IP3) and adenosine 3',5'-cyclic monophosphate (cAMP) levels were determined using commercial kits. Mitogen-activated protein kinase (MAPK) and cyclin D1 expression was assessed by Western blotting. Cell proliferation and collagen synthesis were determined by measuring [(3)H]thymidine and [(3)H]proline incorporation, respectively. 15-F2t-IsoP elicited an activation of extracellular-signal-regulated kinase (ERK), p38 MAPK, and c-Jun NH2-terminal kinase (JNK), which are known to be also regulated by G-protein-coupled receptors. Preincubation with specific ERK (PD98059), p38 (SB203580), or JNK (SP600125) inhibitors prevented 15-F2t-IsoP-induced cell proliferation and collagen synthesis. 15-F2t-IsoP decreased cAMP levels within 30 min, suggesting binding to the TPβ isoform and activation of Giα protein. Also, 15-F2t-IsoP increased IP3 levels within a few minutes, suggesting that the Gq protein pathway is also involved. In conclusion, the fibrogenic effects of F2-IsoP's in HSCs are mediated by downstream activation of MAPKs, through TP binding that couples via both Gqα and Giα proteins. Targeting TP receptor, or its downstream pathways, may contribute to preventing oxidative damage in liver fibrosis.

Monascin and ankaflavin act as natural AMPK activators with PPARα agonist activity to down-regulate nonalcoholic steatohepatitis in high-fat diet-fed C57BL/6 mice

Yellow pigments monascin (MS) and ankaflavin (AK) are secondary metabolites derived from Monascus-fermented products. The hypolipidemic and anti-inflammatory effects of MS and AK indicate that they have potential on preventing or curing nonalcoholic fatty liver disease (NAFLD). Oleic acid (OA) and high-fat diet were used to induce steatosis in FL83B hepatocytes and NAFLD in mice, respectively. We found that both MS and AK prevented fatty acid accumulation in hepatocytes by inhibiting fatty acid uptake, lipogenesis, and promoting fatty acid beta-oxidation mediated by activating peroxisome proliferator-activated receptor (PPAR)-α and AMP-activated kinase (AMPK). Furthermore, MS and AK significantly attenuated high-fat diet-induced elevation of total cholesterol (TC), triaceylglycerol (TG), free fatty acid (FFA), and low density lipoprotein-cholesterol (LDL-C) in plasma. MS and AK promoted AMPK phosphorylation, suppressed the steatosis-related mRNA expression and inflammatory cytokines secretion, as well as upregulated farnesoid X receptor (FXR), peroxisome proliferator-activated receptor gamma co-activator (PGC)-1α, and PPARα expression to induce fatty acid oxidation in the liver of mice. We provided evidence that MS and AK act as PPARα agonists to upregulate AMPK activity and attenuate NAFLD. MS and AK may be supplied in food supplements or developed as functional foods to reduce the risk of diabetes and obesity.

Estrogen attenuates lipopolysaccharide-induced nitric oxide production in macrophages partially via the nongenomic pathway

Steroid hormones exert genotropic effects through members of the nuclear hormone receptor family. In the present study, we examined the effects of 17β-estradiol (E2) on nitric oxide (NO) production following lipopolysaccharide (LPS) stimulation and investigated the mechanisms in mouse bone marrow-derived macrophages (BMMs). E2 alone did not affect NO production. In contrast, E2 inhibited LPS-induced production of NO in BMMs. Using a cell-impermeable E2 conjugated to BSA (E2-BSA), which has been used to investigate the nongenomic effects of estrogen, we found that the increase in NO production induced by LPS was also attenuated. In addition, the intracellular estrogen receptor blocker, ICI 182780, only partially antagonized the total effects of E2 on LPS-stimulated NO production capacity. E2 also attenuated the LPS activation of p38 mitogen-activated protein kinase (MAPK) but not that of extracellular-regulated protein kinase 1/2 (ERK1/2) and c-Jun NH2-terminal kinase (JNK). This attenuation was not abrogated by ICI 182780. Moreover, the p38 inhibitor, SB 203580, greatly reduced the LPS-induced NO production, and the remaining NO levels were no longer regulated by E2. Additionally, E2-BSA inhibited LPS-mediated changes in p38 MAPK activation to the same extent as E2. Moreover, E2 and E2-BSA inhibited LPS-induced activation of nuclear factor-kappa B (NF-κB) and activator protein 1 (AP-1). This inhibitory effect of E2 was only partially antagonized by ICI 182780. Taken together, these results suggest that E2 has an inhibitory effect on LPS-induced NO production in BMMs through inhibition of p38 MAPK phosphorylation, and blockade of NF-κB and AP-1 activation. These effects are mediated at least in part via a nongenomic pathway.

Sphingosine-1-phosphate stimulated connective tissue growth factor expression in human buccal fibroblasts: Inhibition by epigallocatechin-3-gallate

BACKGROUND/PURPOSE

Connective tissue growth factor (CCN2) has been associated with the pathogenesis of various fibrotic diseases, including oral submucous fibrosis (OSF). The chemical constituents of areca nut along with the mechanical trauma cause OSF. The coarse fibers of areca nut injure the mucosa and hence sphingosine-1-phosphate (S1P) is released at the wounded sites. Recent studies have shown that S1P is involved in wound healing and the development of fibrosis. The aims of this study were to investigate the effects of S1P on CCN2 expression in human buccal fibroblasts (HBFs) and identify the potential targets for drug intervention or chemoprevention of OSF.

METHODS

Western blot analyses were used to study the effects of S1P on CCN2 expression and its signaling pathways in HBFs and whether epigallocatechin-3-gallate (EGCG), the main and most significant polyphenol in green tea, could inhibit this pathway.

RESULTS

S1P significantly enhanced CCN2 synthesis in HBFs. This effect can be inhibited by c-Jun NH2-terminal kinase (JNK) inhibitor and extracellular signal-regulated kinase inhibitor but not by P38 mitogen-activated protein kinase inhibitor. Interestingly, EGCG completely blocked S1P-induced CCN2 expression via suppressing S1P-induced JNK phosphorylation.

CONCLUSION

S1P released by repetitive mechanical trauma during AN chewing may contribute to the pathogenesis of OSF through upregulating CCN2 expression in HBFs. EGCG could be an adjuvant to the current offered therapy options or the prevention of OSF through suppression of JNK activation.

Somatostatin receptors: from signaling to clinical practice

Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.