The transient and constitutive inflammatory signaling in tumorigenesis

Comment on: Rokavec M, et al. Mol Cell 2012; 45:777-89.     

Plant action: Multiple levels of regulation

This lecture is devoted to the relative contribution of various levels of regulation of the actin cytoskeleton functioning in the cell. Regulation at the levels of gene expression, mRNA and protein synthesis and stability, processes of actin polymerization/depolymerization and actin structures reorganization is briefly considered. Novel information about the pathways of signal transduction to the actin cytoskeleton with the involvement of Arp2/3 complex and RIC proteins is highlighted.     

NP7 protects from cell death induced by oxidative stress in neuronal and glial midbrain cultures from parkin null mice

Parkin mutations produce Parkinson’s disease (PD) in humans and nigrostriatal dopamine lesions related to increased free radicals in mice. We examined the effects of NP7, a synthetic, marine derived, free radical scavenger which enters the brain, on H₂O₂ toxicity in cultured neurons and glia from wild-type (WT) and parkin null mice (PK-KO).NP7, 5-10 μM, prevented the H₂O₂ induced apoptosis and necrosis of midbrain neuronal and glial cultures from WT and PK-KO mice. NP7 suppressed microglial activation and the H₂O₂ induced drop-out of dopamine neurons_. Furthermore, NP7 prevented the increased phosphorylation of ERK and AKT induced by H₂O₂. NP7 may be a promising neuroprotector against oxidative stress in PD.     

Calcium-loaded 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid blocks cell-to-cell diffusion of carboxyfluorescein in staminal hairs of Setcreasea purpurea

The effect of microinjected calcium-loaded 1,2-bis(2-aminophenoxy) ethane-N,N,N,N-tetraacetic acid (CaBAPTA) on cell-to-cell diffusion of carboxyfluorescein (CF) was examined in staminal hairs of S. purpurea Boom. The CaBAPTA was microinjected into the cytoplasm of the staminal hairs either with CF or prior to a subsequent microinjection of CF. The cell-to-cell diffusion of CF along the hair was monitored using enhanced-fluorescence video microscopy. Cytoplasmic streaming stopped in cells treated with CaBAPTA, indicating that intracellular Ca²⁺ had increased. Cell-to-cell diffusion of CF was blocked in cells treated with Ca-BAPTA. An inhibition of cytoplasmic streaming and cell-to-cell diffusion was observed in the cells adjoining the CaBAPTA-microinjected cell, indicating that the Ca-BAPTA appeared to pass through plasmodesmata. While cytoplasmic streaming resumed 5–10 min after CaBAPTA treatment, cell-to-cell diffusion did not resume until 30–120 min later. These data support an involvement of calcium in the regulation of cell-to-cell communication in plants.Abbreviations BAPTA 1,2-bis(2-aminophenoxy)ethane-N,N,N, N-tetraacetic acid - CF carboxyfluorescein This work was supported by Professional Staff Congress-City University (PSC-CUNY) of New York grant No. 667180 and U.S. Department of Agriculture grant No. 87-CRCR-1-244.     

The C-Terminal Domain of the mGluR1 Metabotropic Glutamate Receptor Affects Sensitivity to Agonists

Abstract: The metabotropic glutamate receptor (mGluR) subtype 1 exists as at least three variants (−1a, −1b, and −1c) generated by alternative splicing at the C-terminal domain. Fluorometric Ca²⁺ measurements were used to compare the concentration dependency of agonist-induced rises in intracellular free Ca²⁺ concentration ([Ca²⁺]_i) in human embryonic HEK 293 cells transiently expressing rat mGluR1a, mGluR1b, or mGluR1c. The rank order of agonist potencies was quisqualate ≫ (2 S, 1' S, 2' S )-2-(carboxycyclopropyl)glycine (L-CCG-I) > (1 S, 3 R )-1-aminocyclopentane-1,3-dicarboxylic acid [(1 S, 3 R )-ACPD] and did not differ among the splice variants. However, agonists were consistently more potent at mGluR1a than at mGluR1c and mGluR1b. In the same system, we characterized the agonist pharmacology of two chimeric rat mGluR3/1 receptors where the first and/or the second intracellular loop(s) and the C-terminal domain were exchanged with the corresponding mGluR1a or mGluR1c sequences and that were previously shown to mediate elevations in [Ca²⁺]_i in response to agonists. The potency of agonists was higher at the chimera having the C-terminus of mGluR1a as compared with those having the mGluR1c C-terminus. Both chimeric mGluR3/1 receptors had the same rank order of agonist potencies: L-CCG-I ≫ (1 S, 3 R )-ACPD ∼ quisqualate. These data support the hypothesis that the C-terminal domain of mGluRs plays a role in determining the potency of agonists for inducing mGluR-mediated functional responses.     

Inhibition of gap junctional intercellular communication in heptachlor- and heptachlor epoxide-treated normal human breast epithelial cells

Based on the concern of organochlorides in the environment and in human tissue, this study was designed to determine whether various noncytotoxic levels of heptachlor and heptachlor epoxide could inhibit, reversibly, gap junctional intercellular communication in human breast epithelial cells (HBEC). Cytotoxicity and gap junctional intercellular communication (GJIC) were evaluated by lactate dehydrogenase assay and fluorescence redistribution after photobleaching analysis, respectively. Both heptachlor and heptachlor epoxide were noncytotoxic up to 10 μg/ml. At this concentration, heptachlor and heptachlor epoxide inhibited GJIC of normal human breast epithelial cells after 1 h treatment. Within a 24 h treatment with heptachlor and heptachlor epoxide at 10 μg/ml, recovery of GJIC had not returned. GJIC completely recovered after a 12 h treatment of 1 μg/ml heptachlor epoxide, but it did not recover after a 24 h treatment of 1 μg/ml heptachlor. RT-PCR and Western blots were analyzed to determine whether the heptachlor or heptachlor epoxide might have altered the steady-state levels of gap junction mRNA and/or connexin protein levels or phosphorylation state. No significant difference in the level of connexin 43 (Cx43) message between control and heptachlor-treated cells was observed. Western blot analyses showed hypophosphorylation patterns in cells treated with 10 μg/ml heptachlor and heptachlor epoxide for 1 h with no recovery within 24 h. Immunostaining of Cx43 protein in normal HBEC indicated that heptachlor and heptachlor epoxide caused a loss of Cx43 from the cell membranes at noncytotoxic dose levels. Taken together, these results suggest that heptachlor and heptachlor epoxide can alter GJIC at the post-translational level, and that, under the conditions of exceeding a threshold concentration in the breast tissue containing ‘initiated’ cells for a long time and not being counteracted by anti-tumor-promoting chemicals, they could act as breast tumor promoters.     

The gap junctional intercellular communication is no prerequisite for the stabilization of xenobiotic metabolizing enzyme activities in primary rat liver parenchymal cells in vitro

Summary In primary monocultures of adult rat liver parenchymal cells (PC), the activities of the xenobiotic metabolizing enzymes microsomal epoxide hydrolase (mEH_b), soluble epoxide hydrolase (sEH), glutathione S-transferases (GST), and phenolsulfotransferase (ST) were reduced after 7 d to values below 33% of the initial activities. Furthermore, the gap junctional intercellular communication (GJIC), measured after microinjection by dye transfer, decreased from 90% on Day 1 to undetectable values after 5 d in monoculture. Co-culture of PC with nonparenchymal rat liver epithelial cells (NEC) increased (98% on Day 1) and stabilized (82% on Day 7) the homotypic GJIC of PC. Additionally, most of the measured xenobiotic metabolizing enzyme activities were well stabilized over 1 wk in co-culture. Because GJIC is one of several mechanisms playing an important role in cell differentiation, the importance of GJIC for the stabilization of xenobiotic metabolizing enzymes in PC was investigated. PC in monoculture were, therefore, treated with 2% dimethyl sulfoxide (DMSO), a differentiation promoting factor, and 1,1,1-trichloro-2,2,-bis (p-chlorophenyl) ethane (DDT) (10 μg/ml), a liver tumor promotor and inhibitor of GJIC, was given to co-cultures of PC with NEC. DMSO significantly stabilized (68% on Day 7), while DDT significantly inhibited (8% on Day 7) homotypic GJIC of PC in the respective culture systems. In contrast, the activities of mEH_b, sEH, GST, and ST were not affected in the presence of DMSO or DDT. These results lead to the assumption that the differentiation parameters measured in this study (i.e., homotypic GJIC and the activities of xenobiotic metabolizing enzymes) are independently regulated in adult rat liver PC.