Everolimus and plicamycin specifically target chemoresistant colorectal cancer cells of the CMS4 subtype

Colorectal cancers (CRC) can be classified into four consensus molecular subtypes (CMS), among which CMS1 has the best prognosis, contrasting with CMS4 that has the worst outcome. CMS4 CRC is notoriously resistant against therapeutic interventions, as demonstrated by preclinical studies and retrospective clinical observations. Here, we report the finding that two clinically employed agents, everolimus (EVE) and plicamycin (PLI), efficiently target the prototypic CMS4 cell line MDST8. As compared to the prototypic CMS1 cell line LoVo, MDST8 cells treated with EVE or PLI demonstrated stronger cytostatic and cytotoxic effects, increased signs of apoptosis and autophagy, as well as a more pronounced inhibition of DNA-to-RNA transcription and RNA-to-protein translation. Moreover, nontoxic doses of EVE and PLI induced the shrinkage of MDST8 tumors in mice, yet had only minor tumor growth-reducing effects on LoVo tumors. Altogether, these results suggest that EVE and PLI should be evaluated for their clinical activity against CMS4 CRC.

Co-Treatments of Edible Curcumin from Turmeric Rhizomes and Chemotherapeutic Drugs on Cytotoxicity and FLT3 Protein Expression in Leukemic Stem Cells

This study aims to enhance efficacy and reduce toxicity of the combination treatment of a drug and curcumin (Cur) on leukemic stem cell and leukemic cell lines, including KG-1a and KG-1 (FLT3+ LSCs), EoL-1 (FLT3+ LCs), and U937 (FLT3- LCs). The cytotoxicity of co-treatments of doxorubicin (Dox) or idarubicin (Ida) at concentrations of the IC10-IC80 values and each concentration of Cur at the IC20, IC30, IC40, and IC50 values (conditions 1, 2, 3, and 4) was determined by MTT assays. Dox-Cur increased cytotoxicity in leukemic cells. Dox-Cur co-treatment showed additive and synergistic effects in several conditions. The effect of this co-treatment on FLT3 expression in KG-1a, KG-1, and EoL-1 cells was examined by Western blotting. Dox-Cur decreased FLT3 protein levels and total cell numbers in all the cell lines in a dose-dependent manner. In summary, this study exhibits a novel report of Dox-Cur co-treatment in both enhancing cytotoxicity of Dox and inhibiting cell proliferation via FLT3 protein expression in leukemia stem cells and leukemic cells. This is the option of leukemia treatment with reducing side effects of chemotherapeutic drugs to leukemia patients.

Circ-SPECC1 modulates TGFβ2 and autophagy under oxidative stress by sponging miR-33a to promote hepatocellular carcinoma tumorigenesis

Circular RNAs (circRNAs) play vital roles in the pathogenesis and development of multiple cancers, including hepatocellular carcinoma (HCC). Nevertheless, the regulatory mechanisms of circ-SPECC1 in HCC remain poorly understood. In our study, we found that circ-SPECC1 was apparently downregulated in H2 O2 -treated HCC cells. Additionally, knockdown of circ-SPECC1 inhibited cell proliferation and promoted cell apoptosis of HCC cells under H2 O2 treatment. Moreover, circ-SPECC1 inhibited miR-33a expression by direct interaction, and miR-33a inhibitor partially reversed the effect of circ-SPECC1 knockdown on proliferation and apoptosis of H2 O2 -treated HCC cells. Furthermore, TGFβ2 was demonstrated to be a target gene of miR-33a and TGFβ2 overexpression rescued the phenotypes of HCC cells attenuated by miR-33a mimics. Meanwhile, autophagy inhibition by 3-methyladenine (3-MA) abrogated the effect of miR-33a mimics on proliferation and apoptosis of H2 O2 -treated HCC cells. Finally, knockdown of circ-SPECC1 hindered tumor growth in vivo. In conclusion, our study demonstrated that circ-SPECC1 regulated TGFβ2 and autophagy to promote HCC tumorigenesis under oxidative stress via miR-33a. These findings might provide potential treatment strategies for patients with HCC.

Effects of arsenic trioxide on the expression of ezrin in hepatocellular carcinoma

The aim of the study was to investigate the effects of arsenic trioxide (As2O3) treatment on the expression of ezrin and serum alpha-fetoprotein (AFP) levels in hepatocellular carcinoma (HCC).A total of 24 patients (20 males and 4 females) with resectable HCC were treated with venous injection of As2O3 for 14 days (10 mg/d) before surgery. The ezrin expression and serum AFP levels were assessed before and after treatment, respectively.The serum AFP levels were 325.5 ng/L before treatment and 278.6 ng/L after treatment, with statistical significant difference (Z = -2.360, P < .05). The expression of ezrin was negative, weak positive, and strong positive in 11, 7, and 6 cases, respectively, before As2O3 treatment, and 17, 5, 2 cases respectively after the treatment. The difference between the 2 groups was statistically significant (χ = 5.619, P < .05). Also, the results showed that there was a significant correlation between the high serum AFP level (AFP ≥ 500 ng/L) and high expression of ezrin (χ = 8.080, P < .05).As2O3 treatment can significantly downregulate the expression of ezrin in HCC.

Chronic intermittent alcohol disrupts the GluN2B-associated proteome and specifically regulates group I mGlu receptor-dependent long-term depression

N-Methyl-d-aspartate receptors (NMDARs) are major targets of both acute and chronic alcohol, as well as regulators of plasticity in a number of brain regions. Aberrant plasticity may contribute to the treatment resistance and high relapse rates observed in alcoholics. Recent work suggests that chronic alcohol treatment preferentially modulates both the expression and subcellular localization of NMDARs containing the GluN2B subunit. Signaling through synaptic and extrasynaptic GluN2B-NMDARs has already been implicated in the pathophysiology of various other neurological disorders. NMDARs interact with a large number of proteins at the glutamate synapse, and a better understanding of how alcohol modulates this proteome is needed. We employed a discovery-based proteomic approach in subcellular fractions of hippocampal tissue from chronic intermittent alcohol (CIE)-exposed C57Bl/6J mice to gain insight into alcohol-induced changes in GluN2B signaling complexes. Protein enrichment analyses revealed changes in the association of post-synaptic proteins, including scaffolding, glutamate receptor and PDZ-domain binding proteins with GluN2B. In particular, GluN2B interaction with metabotropic glutamate (mGlu)1/5 receptor-dependent long-term depression (LTD)-associated proteins such as Arc and Homer 1 was increased, while GluA2 was decreased. Accordingly, we found a lack of mGlu1/5 -induced LTD while α1 -adrenergic receptor-induced LTD remained intact in hippocampal CA1 following CIE. These data suggest that CIE specifically disrupts mGlu1/5 -LTD, representing a possible connection between NMDAR and mGlu receptor signaling. These studies not only demonstrate a new way in which alcohol can modulate plasticity in the hippocampus but also emphasize the utility of this discovery-based proteomic approach to generate new hypotheses regarding alcohol-related mechanisms.

Effect of propofol on microRNA expression in rat primary embryonic neural stem cells

BACKGROUND

Propofol is a widely used intravenous anesthetic that is well-known for its protective effect in various human and animal disease models. However, the effects of propofol on neurogenesis, especially on the development of neural stem cells (NSCs), remains unknown. Related microRNAs may act as important regulators in this process.

METHODS

Published Gene Expression Omnibus (GEO) DataSets related to propofol were selected and re-analyzed to screen neural development-related genes and predict microRNA (miRNA) expression using bioinformatic methods. Screening of the genes and miRNAs was then validated by qRT-PCR analysis of propofol-treated primary embryonic NSCs.

RESULTS

Four differentially expressed mRNAs were identified in the screen and 19 miRNAs were predicted based on a published GEO DataSet. Two of four mRNAs and four of 19 predicted miRNAs were validated by qRT-PCR analysis of propofol-treated NSCs. Rno-miR-19a (Rno, Rattus Norvegicus) and rno-miR-137, and their target gene EGR2, as well as rno-miR-19b-2 and rno-miR-214 and their target gene ARC were found to be closely related to neural developmental processes, including proliferation, differentiation, and maturation of NSCs.

CONCLUSION

Propofol influences miRNA expression; however, further studies are required to elucidate the mechanism underlying the effects of propofol on the four miRNAs and their target genes identified in this study. In particular, the influence of propofol on the entire development process of NSCs remains to be clarified.

Design and Synthesis of Irreversible Analogues of Bardoxolone Methyl for the Identification of Pharmacologically Relevant Targets and Interaction Sites

Semisynthetic triterpenoids such as bardoxolone methyl (methyl-2-cyano 3,12-dioxooleano-1,9-dien-28-oate; CDDO-Me) (4) are potent inducers of antioxidant and anti-inflammatory signaling pathways, including those regulated by the transcription factor Nrf2. However, the reversible nature of the interaction between triterpenoids and thiols has hindered attempts to identify pharmacologically relevant targets and characterize the sites of interaction. Here, we report a shortened synthesis and SAR profiling of 4, enabling the design of analogues that react irreversibly with model thiols, as well as the model protein glutathione S-transferase P1, in vitro. We show that one of these analogues, CDDO-epoxide (13), is comparable to 4 in terms of cytotoxicity and potency toward Nrf2 in rat hepatoma cells and stably modifies specific cysteine residues (namely, Cys-257, -273, -288, -434, -489, and -613) within Keap1, the major repressor of Nrf2, both in vitro and in living cells. Supported by molecular modeling, these data demonstrate the value of 13 for identifying site(s) of interaction with pharmacologically relevant targets and informing the continuing development of triterpenoids as novel drug candidates.

Mild Thyroid Hormone Insufficiency During Development Compromises Activity-Dependent Neuroplasticity in the Hippocampus of Adult Male Rats

Severe thyroid hormone (TH) deficiency during critical phases of brain development results in irreversible neurological and cognitive impairments. The mechanisms accounting for this are likely multifactorial, and are not fully understood. Here we pursue the possibility that one important element is that TH affects basal and activity-dependent neurotrophin expression in brain regions important for neural processing. Graded exposure to propylthiouracil (PTU) during development produced dose-dependent reductions in mRNA expression of nerve growth factor (Ngf) in whole hippocampus of neonates. These changes in basal expression persisted to adulthood despite the return to euthyroid conditions in blood. In contrast to small PTU-induced reductions in basal expression of several genes, developmental PTU treatment dramatically reduced the activity-dependent expression of neurotrophins and related genes (Bdnft, Bdnfiv, Arc, and Klf9) in adulthood and was accompanied by deficits in hippocampal-based learning. These data demonstrate that mild TH insufficiency during development not only reduces expression of important neurotrophins that persists into adulthood but also severely restricts the activity-dependent induction of these genes. Considering the importance of these neurotrophins for sculpting the structural and functional synaptic architecture in the developing and the mature brain, it is likely that TH-mediated deficits in these plasticity mechanisms contribute to the cognitive deficiencies that accompany developmental TH compromise.

Corticosterone-induced enhancement of memory and synaptic Arc protein in the medial prefrontal cortex

Acute administration of the stress hormone corticosterone enhances memory consolidation in a manner that is dependent upon the modulatory effects of the basolateral complex of the amygdala (BLA). Posttraining administration of corticosterone increases expression of the activity-regulated cytoskeletal-associated protein (Arc) in hippocampal synaptic-enriched fractions. Interference with hippocampal Arc expression impairs memory, suggesting that the corticosterone-induced increase in hippocampal Arc plays a role in the memory enhancing effect of the hormone. Blockade of β-adrenoceptors in the BLA attenuates the corticosterone-induced increase in hippocampal Arc expression and blocks corticosterone-induced memory enhancement. To determine whether posttraining corticosterone treatment affects Arc protein expression in synapses of other areas of the brain that are involved in memory processing, a memory-enhancing dose of corticosterone was administered to rats immediately after inhibitory avoidance training. As seen in the hippocampus, Arc protein expression was increased in synaptic fractions taken from the prelimbic region of the medial prefrontal cortex (mPFC). Blockade of Arc protein expression significantly impaired memory, indicating that the protein is necessary in the mPFC for long-term memory formation. To test the hypothesis that blockade of β-adrenoceptors in the BLA would block the effect of systemic corticosterone on memory and attenuate mPFC Arc expression, as it does in the hippocampus, posttraining intra-BLA microinfusions of the β-adrenoceptor antagonist propranolol were given concurrently with the systemic corticosterone injection. Although this treatment blocked corticosterone-induced memory enhancement, it increased corticosterone-induced Arc protein expression in mPFC synaptic fractions. These findings suggest that the BLA mediates stress hormone effects on memory by participating in the negative or positive regulation of corticosterone-induced synaptic plasticity in efferent brain regions.

New player on an old field; the keap1/Nrf2 pathway as a target for treatment of type 2 diabetes and metabolic syndrome

Nuclear erythroid factor 2 like 2 (Nrf2) has been described as a transcription factor that serves as a master regulator of the adaptive response to exogenous and endogenous oxidative and electrophilic stresses. Evidence of Nrf2 crosstalk with other molecular pathways is increasing; recent publications have proposed a role of Nrf2 in the development of obesity and in the highly regulated process of adipocyte differentiation through its interaction with other transcription factors and receptors implicated in metabolic regulation. In the present review, we discuss the available data on the possible role of Nrf2 in obesity and metabolic syndrome and the feasibility of using Nrf2 as a therapeutic target in the clinical setting.

On the path to a Duchenne muscular dystrophy therapy

Duchenne Muscular Dystrophy (DMD) is a devastating inherited disease of children with no effective therapies. Here I discuss the landscape for new treatments and the history, current status and prospects for our work developing recombinant biglycan as DMD therapy.

RNAi-mediated serotonin transporter suppression rapidly increases serotonergic neurotransmission and hippocampal neurogenesis

Current antidepressants, which inhibit the serotonin transporter (SERT), display limited efficacy and slow onset of action. Here, we show that partial reduction of SERT expression by small interference RNA (SERT-siRNA) decreased immobility in the tail suspension test, displaying an antidepressant potential. Moreover, short-term SERT-siRNA treatment modified mouse brain variables considered to be key markers of antidepressant action: reduced expression and function of 5-HT(1A)-autoreceptors, elevated extracellular serotonin in forebrain and increased neurogenesis and expression of plasticity-related genes (BDNF, VEGF, Arc) in hippocampus. Remarkably, these effects occurred much earlier and were of greater magnitude than those evoked by long-term fluoxetine treatment. These findings highlight the critical role of SERT in serotonergic function and show that the reduction of SERT expression regulates serotonergic neurotransmission more potently than pharmacological blockade of SERT. The use of siRNA-targeting genes in serotonin neurons (SERT, 5-HT(1A)-autoreceptor) may be a novel therapeutic strategy to develop fast-acting antidepressants.

Exercise partly reverses the effect of maternal separation on hippocampal proteins in 6-hydroxydopamine-lesioned rat brain

Animals subjected to maternal separation stress during the early stages of development display behavioural, endocrine and growth factor abnormalities that mirror the clinical findings in anxiety/depression. In addition, maternal separation has been shown to exacerbate the behavioural deficits induced by 6-hydroxydopamine (6-OHDA) in a rat model of Parkinson's disease. In contrast, voluntary exercise reduced the detrimental effects of 6-OHDA in the rat model. The beneficial effects of exercise appeared to be largely due to compensation in the non-lesioned hemisphere. The aim of the present study was to investigate whether voluntary exercise for 3 weeks could reverse the effects of maternal separation in rats challenged with the neurotoxin 6-OHDA infused into the medial forebrain bundle after 1 week of exercise, at postnatal day 60. The rats were killed 2 weeks later, at postnatal day 74. Their brains were dissected and the hippocampus rapidly removed for proteomic analysis by isobaric tagging (iTRAQ) and quantification of peptides by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS). Maternal separation upregulated hippocampal proteins functionally involved in energy metabolism (nucleoside diphosphate kinase B, enolase and triosephosphate isomerase) and synaptic plasticity (α-synuclein, tenascin-R, Ba1-667, brevican and neurocan core protein) in the non-lesioned hemisphere. Exercise reversed many of these changes by downregulating the levels of hippocampal proteins functionally associated with energy metabolism (nucleoside diphosphate kinase B, enolase and triosephosphate isomerase) and synaptic plasticity (α-synuclein, tenascin-R, Ba1-667, brevican and neurocan core protein) in the non-lesioned hemisphere of rats subjected to maternal separation. Exercise and maternal separation therefore appeared to have opposing effects on the hippocampus in the non-lesioned hemisphere of the rat brain. Exercise seemed partly to reverse the effects of maternal separation stress on these proteins in the non-lesioned hemisphere. The partial reversal of maternal separation-induced proteins by exercise in the non-lesioned side sheds some insight into the mechanism by which exercise alters the molecular role players involved in determining the consequences of early life stress.

The influence of hyaluronic acid on vascular endothelial cell proliferation and the relationship with ezrin/merlin expression

It has been established that hyaluronic acid (HA) glycans (nHA) and oligosaccharide (oHA) exert different effects on the biological function of the vascular endothelial cell (EC), resulting in altered regulation of angiogenesis. However, the specific mechanism is still unclear. Our study focused on the effects of nHA and oHA on the ezrin and merlin proteins in EC. The expression of ezrin and merlin was silenced by siRNA, and the regulation on EC growth as well as the mRNA expression and activation (phosphorylation) of ezrin and merlin stimulated by oHA and nHA was investigated. The results revealed that when treated with nHA, there was no significant change in ezrin expression or activation. After being treated with oHA, the expression and activation of ezrin were definitively increased whereas there were no obvious changes in merlin expression (including its phosphorylation). With ezrin expression silenced, the expression of merlin as well as its phosphorylation levels in nHA-stimulated human umbilical vein endothelial cells were notably elevated, while there was no significant change induced by oHA. With merlin expression silenced, no obvious change was found in the expression of ezrin (including its phosphorylation) induced by nHA. Conversely, the expression of ezrin and its activation was significantly improved after being treated with oHA. The results suggest that the mechanism for the promotion of EC proliferation by oHA is likely related to the expression and activation of ezrin, and the inhibition of EC proliferation by nHA is likely related to the expression and activation of merlin.

Post-training disruption of Arc protein expression in the anterior cingulate cortex impairs long-term memory for inhibitory avoidance training

The activity-regulated-cytoskeletal-associated protein (Arc) has a well established role in memory consolidation and synaptic plasticity in the hippocampus and amygdala. However the role of Arc within the anterior cingulate cortex (ACC), an area of the brain involved in processing memory for pain, has yet to be examined. Here we sought to determine if Arc protein within neurons of the rat ACC is necessary for the consolidation of a single-trial, contextual inhibitory avoidance (IA) task. Immunohistochemistry and western blotting revealed an increase in Arc protein within the ACC following IA training in a shock-specific manner, suggesting that ACC Arc expression may play a critical role in the consolidation of the aversive task. To directly test this hypothesis, male Sprague-Dawley rats were trained on the IA task and given post-training intra-ACC infusions of Arc antisense oligodeoxynucleotides (ODNs), designed to suppress Arc translation, or control scrambled ODNs that do not suppress Arc translation. Memory retention was tested 48h after training. Arc antisense-induced disruption of Arc protein expression in the ACC impaired long-term memory for the IA task as compared to rats given intra-ACC infusions of the scrambled control ODNS, suggesting that Arc expression in the ACC is important for the consolidation of emotional memory. Results further indicate that knock down of Arc 6h after training impairs IA memory. This is consistent with time course findings indicating elevated Arc expression at 3 and 6h after IA training but not 12 or 48h. Taken together, these findings support the hypothesis that Arc expression in the ACC participates in synaptic plasticity that underlies long-term memory.

Memory-enhancing corticosterone treatment increases amygdala norepinephrine and Arc protein expression in hippocampal synaptic fractions

Considerable evidence indicates that glucocorticoid hormones enhance the consolidation of memory for emotionally arousing events through interactions with the noradrenergic system of the basolateral complex of the amygdala (BLA). We previously reported that intra-BLA administration of a beta-adrenoceptor agonist immediately after inhibitory avoidance training enhanced memory consolidation and increased hippocampal expression of the protein product of the immediate early gene activity-regulated cytoskeletal-associated protein (Arc). In the present experiments corticosterone (3 mg/kg, i.p.) was administered to male Sprague-Dawley rats immediately after inhibitory avoidance training to examine effects on long-term memory, amygdala norepinephrine levels, and hippocampal Arc expression. Corticosterone increased amygdala norepinephrine levels 15 min after inhibitory avoidance training, as assessed by in vivo microdialysis, and enhanced memory tested at 48 h. Corticosterone treatment also increased expression of Arc protein in hippocampal synaptic tissue. The elevation in BLA norepinephrine appears to participate in corticosterone-influenced modulation of hippocampal Arc expression as intra-BLA blockade of beta-adrenoceptors with propranolol (0.5 microg/0.2 microL) attenuated the corticosterone-induced synaptic Arc expression in the hippocampus. These findings indicate that noradrenergic activity at BLA beta-adrenoceptors is involved in corticosterone-induced enhancement of memory consolidation and expression of the synaptic-plasticity-related protein Arc in the hippocampus.

Cytoskeletal modulation and tyrosine phosphorylation of tight junction proteins are associated with mainstream cigarette smoke-induced permeability of airway epithelium

Cigarette smoke increases the permeability of the lung epithelium. Consequences of increased permeability include increased access of toxins and pathogens from the air spaces to the interstitium and even the blood stream, and leakage of fluids into the air spaces. The mechanisms for permeability alterations have not been elucidated for airway epithelia. By analogy with other types of epithelia, we hypothesized that changes in the phosphorylation status and function of tight junction (TJ) or cytoskeletal proteins might mediate the smoke-induced permeability changes. We investigated the effects of exposure to mainstream cigarette smoke (MS) on cultures of Calu-3 cells, an airway epithelial cell line. Specifically, MS exposure caused increases in phosphorylation of the myosin-binding subunit (MBS) of myosin phosphatase and myosin light chain (MLC), proteins involved in the regulation of actin polymerization. These results implicate activation of Rho kinase (ROCK), consistent with previously reported data indicating that inhibition of ROCK activation suppressed MS-induced increases in permeability. MS exposure also increased polymerized (filamentous) actin (f-actin) content and caused redistribution of the TJ proteins from the normal apical circumferential band to a more basal location. The translocation of the TJ proteins was spatially associated with local increases in both f-actin and macromolecular permeability. Finally, MS exposure increased tyrosine phosphorylation of occludin but not ZO-1 and decreased association between the two TJ proteins. These results indicate that MS exposure causes alterations in cytoskeletal and TJ structure and function, resulting in increased macromolecular permeability that may contribute to the adverse health effects of MS.

Estrogen stimulates activity-regulated cytoskeleton associated protein (Arc) expression via the MAPK- and PI-3K-dependent pathways in SH-SY5Y cells

Activity-regulated cytoskeleton associated protein (Arc) is known to be induced by synaptic plasticity following memory consolidation. Since estrogen has been shown to play an important role in synaptogenesis, a key aspect of the synaptic plasticity, we aimed to study the effects of estrogen on Arc expression in SH-SY5Y human neuroblastoma cells. Using quantitative real-time PCR, Western blot, and confocal immunocytochemistry techniques we found that estrogen markedly increased Arc mRNA and protein expression in SH-SY5Y cells. Estrogen-activated Arc expression was mediated via mitogen-activated protein kinase (MAPK) and phosphoinositide-3 kinase (PI-3K), but not protein kinase C (PKC) and Rho-associated kinase (ROCK), and in the estrogen receptor (ER)-dependent manner. Estrogen also significantly upregulated the dendritic spine scaffolding protein, postsynaptic density-95 (PSD-95), as well as expression of the presynaptic vesicle protein, synaptophysin. Our findings demonstrate the possible mechanisms of estrogen-induced synaptic plasticity, as well as memory consolidation.

Colchicine update: 2008

OBJECTIVES

To review recent advances in the understanding of molecular mechanisms of drug disposition and cellular mechanisms of action and targets of colchicine, and disease applications and guidelines for oral colchicine use.

METHODS

Summarized and interpreted here is the pertinent English and non-English language literature on MEDLINE since the last update of colchicine in this journal in 1998 and published up to July 2008 regarding colchicine pharmacology, toxicology, mechanisms of action, and clinical applications in gout and other medical conditions.

RESULTS

Assessment, after review of 1512 publications, is that oral colchicine therapy is being refined by attention to novel targets such as NALP3 and pyrin. The drug has a narrow therapeutic-toxicity window, and potentially serious drug-drug interactions (eg, with clarithromycin and cyclosporine) are better recognized and therefore preventable. Reviewed here are recent advances in colchicine pharmacogenomics, and recognition of drug-drug interactions and predictors of potential toxicities, including alterations in the P-glycoprotein multidrug transporter ABCB1, cytochrome P450 3A4 isoenzyme, and hepatobiliary and renal function. Current understanding of optimization of colchicine dosing is reviewed, as are recent findings on colchicine therapy of nonrheumatic cardiovascular, hepatic, and renal diseases (eg, lowering of C-reactive protein, and treatment of acute and recurrent pericarditis). Finally, the article reviews the recent U.S. Food and Drug Administration-mandated cessation of marketing of injectable colchicine.

CONCLUSIONS

Oral colchicine has unique anti-inflammatory and antiproliferative effects with broad ramifications for rheumatic and nonrheumatic disease applications. Significant advances in the last decade have increased understanding of predictors of both colchicine efficacy and toxicity.

TUDCA prevents cholestasis and canalicular damage induced by ischemia-reperfusion injury in the rat, modulating PKCalpha-ezrin pathway

Cholestasis, induced by liver ischemia-reperfusion injury (IRI), is characterized by dilatation of bile canaliculi and loss of microvilli. Tauroursodeoxycholic acid (TUDCA) is an anti-cholestatic agent, modulating protein kinase C (PKC) alpha pathway. PKC reduces ischemic damage in several organs, its isoform alpha modulates ezrin, a key protein in the maintenance of cell lamellipoidal extensions. We evaluated the effects of TUDCA on cholestasis, canalicular changes and PKCalpha-ezrin expression in a rat model of liver IRI. Livers flushed and stored with Belzer solution or Belzer + 10 mm TUDCA (4 degrees C for 6 h) were reperfused (37 degrees C with O(2)) with Krebs-Ringer bicarbonate + 2.5 micromol/min of Taurocholate or TUDCA. Bile was harvested for bile flow assessment. Liver tissue was employed for Electron Microscopy (EM) and for PKCalpha and ezrin immunoblot and immunofluorescence. The same experiments were conducted with the PKCalpha inhibitor Go-6976. TUDCA-treated livers showed increased bile flow (0.25+/-0.17 vs. 0.042+/-0.02 microl/min/g liver, P<0.05) and better preservation of microvilli and bile canalicular area at EM. These effects were associated with increased PKCalpha and ezrin expression (P=0.03 and P=0.04 vs. control respectively), as also confirmed by immunofluorescence data. PKCalpha inhibition abolished these TUDCA effects. TUDCA administration during IRI reduces cholestasis and canalicular damage in the liver modulating PKCalpha-ezrin pathway.

Acid-induced loss of functional properties of bacterial cell division protein FtsZ: evidence for an alternative conformation at acidic pH

Several types of bacteria live in highly acidic environments. Since the assembly of FtsZ is important for bacterial cytokinesis, the effects of pH on the assembly and structural properties of FtsZ were examined. FtsZ retained GTP binding ability but lost GTPase activity at pH 2.5. In the presence of GTP, FtsZ formed protofilaments at pH 7 while it formed aggregates instead of protofilaments at pH 2.5, indicating that GTP hydrolysis is important for the assembly of FtsZ into protofilaments. Further, the acid-inactivated state of FtsZ recovered its structural and functional properties upon refolding at pH 7, indicating that the cellular functions of FtsZ may be restored after removal of the external stress. In addition, the affinity of 1-anilinonaphthalene-8-sulfonic acid (ANS) binding to FtsZ was found to be higher at pH 2.5 than at pH 7. FtsZ-ANS complex had a higher quantum yield and lifetime at pH 2.5 than at pH 7. However, the secondary structures of FtsZ were similar at pH 7 and 2.5, indicating that FtsZ attained an alternatively folded state (A) at pH 2.5, which has some characteristics of a molten-globule-like state. The A state was more stable than the native state (N) against urea-induced unfolding. The transition from N to A state involves the formation of aggregates of FtsZ (I). The association of FtsZ monomers occurred in the narrow pH range (3.2-2.8) and it was found to be a fully reversible process. The results suggest that a productive intermediate (I) forms in the acid-induced unfolding pathway of FtsZ and that the unfolding pathway may be minimally described as N <==> I <==> A.

FtsZ: A Novel Target for Tuberculosis Drug Discovery

The emergence of multi-drug resistant Mycobacterium tuberculosis (Mtb) strains has made many of the currently available anti-TB drugs ineffective. Accordingly there is a pressing need to identify new drug targets. FtsZ, a bacterial tubulin homologue, is an essential cell division protein that polymerizes in a GTP-dependent manner, forming a highly dynamic cytokinetic ring, designated as the Z ring, at the septum site. Following recruitment of other cell division proteins, the Z ring contracts, resulting in closure of the septum and then formation of two daughter cells. Since inactivation of FtsZ or alteration of FtsZ assembly results in the inhibition of Z ring and septum formation, FtsZ is a very promising target for new antimicrobial drug development. This review describes the function and dynamic behaviors of FtsZ, its homology to tubulin, and recent development of FtsZ inhibitors as potential anti-TB agents.

Regulation of neurite growth in immortalized mouse hypothalamic neurons and rat hippocampal primary cultures by teneurin C-terminal-associated peptide-1

Teneurins are a highly conserved family of four type II transmembrane proteins that are expressed in the CNS. The protein possesses several functional domains including a unique bioactive 40-41 amino acid sequence at the extracellular terminus. Synthetic versions of this teneurin C-terminal-associated peptide (TCAP) can modulate cyclic AMP accumulation, cell proliferation and teneurin mRNA levels in vitro. Furthermore, i.c.v. injections of TCAP-1 into rat brain induce major changes in acoustic startle response behavior 3 weeks after administration, suggesting that the peptide may act to alter interneuron communication via changes in neurite and axon outgrowth. Synthetic mouse/rat TCAP-1 was used to treat cultured immortalized mouse hypothalamic cells, to determine if TCAP-1 could directly regulate neurite and axon growth. TCAP-1-treated cells showed a significant increase in the length of neurites accompanied by a marked increase in beta-tubulin transcription and translation as determined by real-time PCR and Western blot analysis, respectively. Changes in alpha-actinin-4 transcription and beta-actin protein expression were also noted. Immunofluorescence confocal microscopy using beta-tubulin antiserum showed enhanced resolution of beta-tubulin cytoskeletal elements throughout the cell. In order to determine if the effects of TCAP-1 could be reproduced in primary neuronal cultures, primary cultures of E18 rat hippocampal cells were treated with 100 nM TCAP-1. The TCAP-1-treated hippocampal cultures showed a significant increase in both the number of cells, dendritic branching and the presence of large and fasciculated beta-tubulin immunoreactive axons. These data suggest that TCAP acts, in part, as a functional region of the teneurins to regulate neurite and axonal growth of neurons.

Axonal retraction and regeneration induced byN,N-diethyldithiocarbamate (DEDTC) in the central nervous system

Dithiocarbamates (DTCs), such as disulfiram, have been used in aversion therapy for alcoholism even though an inherent toxicity is induced, which is related mainly to peripheral neuropathy and is associated with behavioural and neurological complications. At anatomical and histopathological levels, DTCs affect structural elements in nervous tissue, such as axonal degeneration and alterations in the cytoskeletal proteins of astrocytes. Therefore, given the axonal effects of DTCs and to gain further insight into axonal growth and axonal pathfinding in the central nervous system (CNS), here we established an in vivo experimental model of mouse development. Daily intraperitoneal injections of N,N-diethyldithiocarbamate (DEDTC), the first metabolite of disulfiram, were given from postnatal day 2 (P2) until P15. From P16 until P30, animals were not treated. Treatment induced considerable physiological alterations, such as growth delay, throughout postnatal development. Moreover, by immunohistochemistry techniques, we observed important alterations in the cytoskeletal glial protein at early stages of postnatal development. At later stages (P15), the immunoreactivity pattern detected by an antibody against axonal neurofilaments (anti-NF-H) showed alteration in the axonal distribution pattern followed by drastic axonal loss at P22, data that were corroborated using an anti-MBP (myelin basic protein) antibody. Using an antibody against the beta amyloid precursor protein (APP), we detected axonal injury. Furthermore, given that we observed axonal re-growth in adulthood in the in vivo model presented, we propose that this model would be a good system in which to identify new strategies for inducing regenerative growth in neural diseases in which axonal regeneration is blocked.

Memantine protects against LPS-induced neuroinflammation, restores behaviorally-induced gene expression and spatial learning in the rat

Neuroinflammation is reliably associated with the pathogenesis of a number of neurodegenerative diseases, and can be detected by the presence of activated microglia. Neuroinflammation can be induced by chronic lipopolysaccharide (LPS) infusion into the 4th ventricle of the rat resulting in region-selective microglia activation and impaired hippocampal-dependent memory. Furthermore, this treatment results in altered behaviorally-induced expression of the immediate early gene Arc, indicating altered network activity. LPS is known to activate microglia directly, leading to increased glutamate release, and in enhanced N-methyl-d-aspartate (NMDA) -dependent signaling. Taken together, the foregoing suggests that decreasing NMDA receptor activation during early stages of chronic neuroinflammation should reduce a) microglia activation, b) overexpression of Arc, and c) spatial memory deficits. Memantine, a low to moderate affinity open channel uncompetitive NMDA receptor antagonist, at low doses was used here to test these hypotheses. Rats were chronically infused into the 4th ventricle for 28 days with LPS alone, vehicle alone (via osmotic minipump) or LPS and memantine (10 mg/kg/day memantine s.c.). The results reported here demonstrate that memantine reduces OX6-immunolabeling for activated microglia, spares resident microglia, returns Arc (activity-regulated cytoskeletal associated protein, protein) -expressing neuronal populations to control levels (as revealed by Arc immunolabeling and fluorescence in situ hybridization), and ameliorates the spatial memory impairments produced by LPS alone. These data indicate that memantine therapy at low doses, recreating plasma levels similar to those of therapeutic doses in human, acts in part through its ability to reduce the effects of neuroinflammation, resulting in normal gene expression patterns and spatial learning. Combined, these findings suggest that low, therapeutically relevant doses of memantine delivered early in the development of neuroinflammation-influenced diseases may confer neural and cognitive protection.

Synthesis of antimicrobial natural products targeting FtsZ: (+/-)-dichamanetin and (+/-)-2' ''-hydroxy-5' '-benzylisouvarinol-B

[chemical structure: see text]. Two natural products have been synthesized using a ZnCl2-mediated benzylic coupling reaction. Both are potent inhibitors of the GTPase activity of FtsZ, a highly conserved protein that is essential for bacterial cytokinesis.

Signal transduction induced by apoptotic cells inhibits HIV transcription in monocytes/macrophages

The primary targets of HIV are CD4(+) T cells and macrophages. HIV infection is associated with an increase in apoptosis of infected and uninfected CD4(+) T cells, and these infected cells undergo apoptosis and produce HIV virions with phosphatidylserine (PS) on their surface. During phagocytosis of apoptotic cells, macrophages, using an array of receptors, are able to perceive various surface changes on apoptotic cells. The engagement of phagocytic receptors by ligands on the apoptotic cell surface results in the activation of signaling cascades, which facilitate engulfment. In this study, we examined how PS associated with virions and apoptotic cells influences HIV replication. We demonstrate that virus-associated PS is required for HIV infection of macrophages at a step prior to integration but following strong-stop, indicating that PS-initiated signals alter the establishment of HIV provirus. Conversely, apoptotic cells inhibited HIV transcription in infected macrophages, although this ability to suppress transcription was independent of PS. Furthermore, we show that ELMO, a key signaling molecule that participates in the phagocytosis of apoptotic cells, inhibited HIV transcription; however, knocking down endogenous ELMO expression in infected U937 cells rescued HIV transcription when these cells were coincubated with apoptotic targets. Taken together, these data show that apoptotic cells and the signals, which they initiate upon recognition by macrophages, influence the successful establishment of HIV infection and provirus transcription.

A MORN-repeat protein is a dynamic component of the Toxoplasma gondii cell division apparatus

Apicomplexan parasites divide and replicate through a complex process of internal budding. Daughter cells are preformed within the mother on a cytoskeletal scaffold, endowed with a set of organelles whereby in the final stages the mother disintegrates and is recycled in the emerging daughters. How the cytoskeleton and the various endomembrane systems interact in this dynamic process remains poorly understood at the molecular level. Through a random YFP fusion screen we have identified two Toxoplasma gondii proteins carrying multiple membrane occupation and recognition nexus (MORN) motifs. MORN1 is highly conserved among apicomplexans. MORN1 specifically localizes to ring structures at the apical and posterior end of the inner membrane complex and to the centrocone, a specialized nuclear structure that organizes the mitotic spindle. Time-lapse imaging of tagged MORN1 revealed that these structures are highly dynamic and appear to play a role in nuclear division and daughter cell budding. Overexpression of MORN1 resulted in severe but specific defects in nuclear segregation and daughter cell formation. We hypothesize that MORN1 functions as a linker protein between certain membrane regions and the parasite's cytoskeleton. Our initial biochemical analysis is consistent with this model. Whereas recombinant MORN1 produced in bacteria is soluble, in the parasite MORN1 was associated with the cytoskeleton after detergent extraction.

Positional cloning, association analysis and expression studies provide convergent evidence that the cadherin gene FAT contains a bipolar disorder susceptibility allele

A susceptibility locus for bipolar disorder was previously localized to chromosome 4q35 by genetic linkage analysis. We have applied a positional cloning strategy, combined with association analysis and provide evidence that a cadherin gene, FAT, confers susceptibility to bipolar disorder in four independent cohorts (allelic P-values range from 0.003 to 0.024). In two case-control cohorts, association was identified among bipolar cases with a family history of psychiatric illness, whereas in two cohorts of parent-proband trios, association was identified among bipolar cases who had exhibited psychosis. Pooled analysis of the case-control cohort data further supported association (P=0.0002, summary odds ratio=2.31, 95% CI: 1.49-3.59). We localized the bipolar-associated region of the FAT gene to an interval that encodes an intracellular EVH1 domain, a domain that interacts with Ena/VASP proteins, as well as putative beta-catenin binding sites. Expression of Fat, Catnb (beta-catenin), and the three genes (Enah, Evl and Vasp) encoding the Ena/VASP proteins, were investigated in mice following administration of the mood-stabilizing drugs, lithium and valproate. Fat was shown to be significantly downregulated (P=0.027), and Catnb and Enah were significantly upregulated (P=0.0003 and 0.005, respectively), in response to therapeutic doses of lithium. Using a protein interaction map, the expression of genes encoding murine homologs of the FAT (ft)-interacting proteins was investigated. Of 14 interacting molecules that showed expression following microarray analysis (including several members of the Wnt signaling pathway), eight showed significantly altered expression in response to therapeutic doses of lithium (binomial P=0.004). Together, these data provide convergent evidence that FAT and its protein partners may be components of a molecular pathway involved in susceptibility to bipolar disorder.

Viscum album agglutinin-I (VAA-I) induces apoptosis and degradation of cytoskeletal proteins in human leukemia PLB-985 and X-CGD cells via caspases: Lamin B1 is a novel target of VAA-I

Viscum album agglutinin-I (VAA-I) is a potent inducer of cell apoptosis and possesses anti-tumoral activity. Using PLB-985 and chronic granulomatous disease (X-CGD) cells, which lack expression of gp91(phox), VAA-I was found to induce apoptosis in both cell lines as assessed by cytology, DNA laddering and degradation of the cytoskeletal protein gelsolin. Both cell lines expressed caspase-3 and -8 and VAA-I activated these caspases. We demonstrated that lamin B(1) is a novel target to VAA-I and its degradation was reversed by a pan-caspase inhibitor and by a caspase-6, but not a caspase-8, inhibitor.

1alpha,25-Dihydroxyvitamin D3 regulates the expression of Id1 and Id2 genes and the angiogenic phenotype of human colon carcinoma cells

1alpha,25-Dihydroxyvitamin D3 (1alpha,25(OH)2D3) has antitumor activity in addition to its classical action on calcium metabolism and bone tissue biology. It is thought to regulate the expression of multiple target genes and thus modulate processes critical for tumor growth and metastases. Here we show that 1alpha,25(OH)2D3 differentially regulates the expression of Id1 and Id2 genes, members of a family of transcriptional regulators of cell proliferation and differentiation. 1alpha,25(OH)2D3 induced epithelial differentiation in SW480-ADH human colon carcinoma cell line by promoting expression of the proteins implicated in adherent junction formation, including E-cadherin, and by inhibiting beta-catenin transcriptional activity. 1alpha,25(OH)2D3 activated the human Id1 gene promoter and rapidly induced Id1 RNA and protein. Ectopic overexpression of Id1 was not sufficient to induce E-cadherin, which was critical for the morphological changes induced by 1alpha,25(OH)2D3 in SW480-ADH cells. Conversely, Id2 transcription rate, RNA and protein levels were decreased by 1alpha,25(OH)2D3. Id2 downregulation by 1alpha,25(OH)2D3 mediated the antiproliferative effect of 1alpha,25(OH)2D3 on SW480-ADH cells. In addition, we showed that 1alpha,25(OH)2D3 changed the levels of the inducer of angiogenesis, vascular endothelial growth factor and the potent antiangiogenic factor thrombospondin-1, leading to a balanced change in the angiogenic potential of SW480-ADH human colon carcinoma cells.

Indirect immunofluorescence study on the cytoskeleton of normal (FG) and neoplastic (SGS/3A) cadmium treated fibroblasts

Cadmium is a heavy metal dangerous for the environment and for the human health, with well shown carcinogenic potentiality. Many studies have related the professional exposure of the Cadmium with human pulmonary, prostatic and renal tumors, and it would be a role also in the tumors of the liver, of the hemopoietic system, of the bladder and of the stomach. The aim of the current study is to examine in normal and neoplastic fibroblasts culture cells the modifications induced by the Cadmium at cellular level, in particular on the cytoskeleton, responsible not only of the intracellular transport of vesicles and cell organules, but also of their positioning and of the cellular integrity. Two fibroblastic cellular strains, normal (FG) and neoplastic (SGS/3A), have been incubated in a 5 microM Cadmium acetate added medium for 1, 8, 24 hours and studied by indirect immunofluorescence methods, particularly for the following proteins: Actin, Tubulin and Vimentin. The observations show in normal and neoplastic fibroblasts comparables modifications and anomalies of cytoskeletal shape. In both the cases the cellular morphology suffers drastic modifications, gradually evolving through intermediary shapes: from triangular and spindle-shaped in the normal fibroblasts to irregular, star-shaped, and globular in the neoplastic ones. The Cadmium action on the morphology of the normal and tumoral cells changes according to the time of incubation, producing structural alterations of the cytoskeletal. The modifications that start to be observable at the first hour of incubation are more evident after the eighth hour of exposure, reaching the maximum expression at the twenty-fourth hour, often with reduction of the total volume of the cells and loss of their ability to adhere to the substratum. Such modifications can be related to great alterations of the cellular membrane, producing the change of shape and the progressive partial separation from the substratum. The intermediary filaments seem to be less sensitive, from a morphological but not functional point of view, to the action of the Cadmium in comparison to the Actin and the microtubules that, on the contrary, seem to lose their proper morphological characteristics.

Viscum album agglutinin-I induces apoptosis and degradation of cytoskeletal proteins via caspases in human leukaemia eosinophil AML14.3D10 cells: differences with purified human eosinophils

Although there are several agents that induce neutrophil apoptosis, few are known as inducers of eosinophil apoptosis. As eosinophils are potent effector cells contributing to allergic inflammation and asthma, we investigated whether the pro-apoptotic agent Viscum album agglutinin-I (VAA-I) could induce eosinophil apoptosis. VAA-I was found to induce apoptosis in eosinophilic AML14.3D10 (3D10) cells and that these cells expressed caspases-1, -2, -3, -4, -7, -8, -9 and -10. VAA-I-induced gelsolin degradation was reversed by the pan-caspase inhibitor N-benzyloxycarbonyl-V-A-D-O-methylfluoromethyl ketone (z-VAD). Also, paxillin, vimentin and lamin B1 were cleaved by caspases in VAA-I-induced 3D10 cells. VAA-I activated caspase-3 and -8 in 3D10 cells but, unlike z-VAD, treatment with a caspase-8 inhibitor slightly reversed apoptosis. Treatment of purified human eosinophils with VAA-I was found to induce apoptosis, degradation of gelsolin and lamin B1, but unlike 3D10 cells, cleavage of lamin B1 and cell apoptosis was not reversed by z-VAD. We conclude that VAA-I is a potent inducer of eosinophil apoptosis and that proteases other than those inhibited by z-VAD in 3D10 cells are involved in VAA-I-induced peripheral blood eosinophil apoptosis and lamin B1 cleavage. Thus, VAA-I represents a potential candidate for the reduction of the number of eosinophils in diseases where they play important roles.

Layilin, a cell surface hyaluronan receptor, interacts with merlin and radixin

Layilin is a widely expressed integral membrane hyaluronan receptor, originally identified as a binding partner of talin located in membrane ruffles. We have identified merlin, the neurofibromatosis type 2 tumor suppressor protein and radixin, as other interactors with the carboxy-terminal domain of layilin. We show that the carboxy-terminal domain of layilin is capable of binding to the amino-terminal domain of radixin. An interdomain interaction between the amino- and the carboxy-terminal domains of radixin inhibits its ability to bind to layilin. In the presence of acidic phospholipids, the interdomain interaction of radixin is inhibited and layilin can bind to full-length radixin. In contrast, layilin binds both full-length and amino-terminal merlin-GST fusion proteins without a requirement for phospholipids. Furthermore, layilin antibody can immunoprecipitate merlin, confirming association in vivo between these two proteins, which also display similar subcellular localizations in ruffling membranes. No interaction was observed between layilin and ezrin or layilin and moesin. These findings expand the known binding partners of layilin to include other members of the talin/band 4.1/ERM (ezrin, radixin, and moesin) family of cytoskeletal-membrane linker molecules. This in turn suggests that layilin may mediate signals from extracellular matrix to the cell cytoskeleton via interaction with different intracellular binding partners and thereby be involved in the modulation of cortical structures in the cell.

Hyperosmotic mannitol induces Src kinase-dependent phosphorylation of beta-catenin in cerebral endothelial cells

Mannitol, which is a cell-impermeable and nontoxic polyalcohol, has been shown to be a useful tool for reversible opening of the blood-brain barrier (BBB). Despite successful clinical trials, the molecular mechanism of the mannitol-induced changes in cerebral endothelial cells (CECs) are poorly understood. For our experiments, we used CECs in culture, which were treated with different, clinically relevant concentrations of mannitol. We found that mannitol induced a rapid, concentration-dependent, and reversible tyrosine phosphorylation of a broad range of proteins between 50 and 190 kDa. One of the targets of tyrosine phosphorylation turned out to be the adherens junction protein beta-catenin. Phosphorylation of beta-catenin on tyrosine residues caused its subcellular redistribution and its dissociation from cadherin and alpha-catenin as shown by coimmunoprecipitation studies. All these effects could be inhibited by the Src kinase inhibitor PP-1 but not by the Erk inhibitor U0126, the Rho kinase inhibitor Y27632, or the calcium channel blocker verapamil. Because beta-catenin is a key component of the junctional complex, its Src-mediated phpsphorylation may play an important role in the mannitol induced reversible opening of the BBB.

Gastrin stabilises beta-catenin protein in mouse colorectal cancer cells

As gastrin may play a role in the pathophysiology of gastrointestinal (GI) malignancies, the elucidation of the mechanisms governing gastrin-induced proliferation has recently gained considerable interest. Several studies have reported that a large percentage of colorectal tumours overexpress or stabilise the β-catenin oncoprotein. We thus sought to determine whether gastrin might regulate β-catenin expression in colorectal tumour cells. Amidated gastrin-17 (G-17), one of the major circulating forms of gastrin, not only enhanced β-catenin protein expression, but also one of its target genes, cyclin D1. Furthermore, activation of β-catenin-dependent transcription by gastrin was confirmed by an increase in LEF-1 reporter activity, as well as enhanced cyclin D1 promoter activity. Finally, G-17 prolonged the τ_1/2 of β-catenin protein, demonstrating that gastrin appears to exert its mitogenic effects on colorectal tumour cells, at least in part, by stabilising β-catenin.

Cell relaxation after electrodeformation: effect of latrunculin A on cytoskeletal actin

Precise measurement of the mechanical properties of a cell provides useful information about its structural organization and physiological state. It is interesting to understand the effect of individual components on the mechanical properties of the entire cell. In this study, we investigate the influence of the cytoskeletal actin on the viscoelastic properties of a cell. Actin-specific agents, including latrunculin A and jasplakinolide, are used to alter the organization of the cytoskeletal actin. Brassica oleracea protoplasts are treated with the drugs and deformed under an external electric potential. The relaxation processes of single protoplasts after electrodeformation are measured. The data are analyzed by a model-independent spectrum recovery algorithm. Two distinct characteristic time constants are obtained from the relaxation spectra. Treatment with latrunculin A increases both of the relaxation time constants. The longest relaxation times for control, latrunculin A treated, and jasplakinolide treated cells are determined to be 0.28, 1.0, and 0.21 s, respectively.

Significance and role of early-lesions in experimental colorectal carcinogenesis

Preneoplastic or precancerous lesions in the large bowel have attracted much attention, and aberrant crypt foci (ACF) topographically identified in the colonic mucosa have found application as effective endpoint lesions for detection of chemopreventive agents as well as carcinogenic risk assessment of environmental agents. While many ACF are regarded as hyperplastic in nature, lacking the potential lesion to give rise to neoplasia, a subset termed dysplastic ACF, or newly identified "mucin depleted foci (MDF)", and "beta-catenin accumulated crypts (BCAC)" are suggested to be more reliably related to colorectal tumorigenesis in rodents. ACF and MDF can be visualized on the surface of colonic mucosa and BCAC were recently identified by our laboratory in rodents en face in cross sections. In particular, BCAC having a similar pattern of beta-catenin gene mutation to that observed in colonic carcinomas appear to be direct precursors. This review provides a review and discussion of the relevant literature relative to early lesions in colorectal carcinogenesis.

Attenuation of okadaic acid-induced hyperphosphorylation of cytoskeletal proteins by heat preconditioning and its possible underlying mechanisms

An imbalanced phosphorylation system is recognized to be one of the main reasons for Alzheimer-like hyperphosphorylation of cytoskeletal proteins. However, little is known about the strategies rectifying the lesions caused by this disrupted phosphorylation. To search for the means to arrest Alzheimer-like damages and explore the underlying mechanisms, in this study we treated N2a/peuht40 cells with okadaic acid (OA), a specific inhibitor of protein phosphatase-2A (PP-2A) and PP-1, to mimic an Alzheimer-like phosphatase-deficient system and then used heat preconditioning (42 degrees C for 1 hour) to induce the expression of inducible heat shock protein 70 (Hsp70) in the cells. We observed that heat preconditioning arrested OA-induced hyperphosphorylation of neurofilament (NF) protein at SMI34 and SMI33 epitopes as well as hyperphosphorylation of tau at Tau-1 and PHF-1 epitopes. It counteracted OA-induced decrease in PP-2A activity with a concurrent inhibition in constitutive activity of mitogen-activated protein kinases (MAPKs) and cyclic adenosine 5'-monophosphate-dependent protein kinase A (PKA). Conversely, quercetin, a recognized blocker of stress-responsive Hsp70 expression, diminished the effects caused by heat preconditioning. These results suggested that Hsp70 antagonized OA-induced Alzheimer-like NF and tau hyperphosphorylation, and the restoration of PP-2A and inhibition of MAPKs-PKA activity might be part of the underlying mechanisms for the rectification of OA-induced hyperphosphorylation.

The nonsteroidal anti-inflammatory drug, nabumetone, differentially inhibits beta-catenin signaling in the MIN mouse and azoxymethane-treated rat models of colon carcinogenesis

The mechanisms through which beta-catenin signaling is inhibited during colorectal cancer chemoprevention by nonsteroidal anti-inflammatory agents is incompletely understood. We report that nabumetone decreased uninvolved intestinal mucosal beta-catenin levels in the MIN mouse with a concomitant increase in glycogen synthase kinase (GSK)-3beta levels, an enzyme that targets beta-catenin for destruction. However, in the azoxymethane-treated rat, where beta-catenin is frequently rendered GSK-3beta-insensitive, nabumetone failed to alter beta-catenin levels but did decrease beta-catenin nuclear localization and transcriptional activity as gauged by cyclin D1. In conclusion, we demonstrate that the differential mechanisms for beta-catenin suppression may be determined, at least partly, by GSK-3beta.

Morphological and oxidative alterations on Sertoli cells cytoskeleton due to retinol-induced reactive oxygen species

Retinol (vitamin A) is involved in several cellular processes, like cell division, differentiation, transformation and apoptosis. Although it has been shown that retinol is a limitant factor for all these processes, the precise mechanisms by which retinol acts are still unknown. In the present study we hypothesised that alterations in the cytoskeleton of Sertoli cells induced by retinol supplementation could indicate an adaptive maintenance of its functions, since it plays an important role in the transformation process that we observed. Previous results demonstrated that Sertoli cells treated with retinol showed an oxidative imbalance, that leads the cell to two phenotypes: apoptosis or transformation. Our group has identified characteristics of Sertoli cells transformed by retinol which results in normal cell functions modification. In the present study the actin filament fluorescence assay and the deformation coefficient showed a modification in the morphology induced by retinol. We also observed an oxidative alteration in isolated cytoskeleton proteins and did not show alterations when these proteins are analyzed by electrophoreses. Our results showed an increase in mitochondria superoxide production and a decrease in nitric oxide levels. All results were partially or completely reverted by co-treatment of the antioxidant Trolox. These findings suggest that the cytoskeleton components suffer individual alterations in different levels and that these alterations generate a global phenotype modification and that these processes are probably ROS dependent. We believe that the results from this study indicate an adaptation of the cytoskeleton to oxidative imbalance since there was not a loss of its function.

Geranylgeranylacetone inhibits lysophosphatidic acid-induced invasion of human ovarian carcinoma cells in vitro

BACKGROUND

Lysophosphatidic acid (LPA) induced a dose-dependent increase of cancer cell invasion by promoting Rho/Rho-associated kinase signaling. Prenylation of Rho is essential for regulating cell growth, motility, and invasion. Geranylgeranylacetone (GGA), an isoprenoid compound, is used clinically as an antiulcer drug. Recent findings suggested that GGA might inhibit the small GTPase activation by suppressing prenylation. The authors hypothesized that the anticancer effects of GGA result from the inhibition of Rho activation.

METHODS

The authors examined the effect of GGA using an in vitro invasion assay in human ovarian carcinoma cells, and analyzed the mechanism of the GGA effect on Rho activation, stress fiber formation and focal adhesion assembly, which are essential processes for cell invasion.

RESULTS

The induction of ovarian carcinoma cell invasion by LPA was inhibited by the addition of GGA in a dose-dependent manner. Treatment of cancer cells with GGA resulted in inactivation of Rho, changes in cell morphology, loss of stress fiber formation and focal adhesion assembly, and the suppression of tyrosine phosphorylation of focal adhesion proteins. The effect of GGA on cancer cells was partially prevented by the addition of geranylgeraniol, which is an intermediate of geranylgeranyl pyrophosphate and compensates geranylgeranylation of Rho.

CONCLUSIONS

The inhibition of LPA-induced invasion by GGA was, at least in part, derived from suppressed Rho activation by preventing geranylgeranylation.

LPA2 receptor mediates mitogenic signals in human colon cancer cells

Lysophosphatidic acid (LPA) is a mediator of multiple cellular responses. LPA mediates its effects predominantly through the G protein-coupled receptors LPA1, LPA2, and LPA3. In the present work, we studied LPA2-mediated signaling using human colon cancer cell lines, which predominantly express LPA2. LPA2 activated Akt and Erk1/2 in response to LPA. LPA mediated Akt activation was inhibited by pertussis toxin (PTX), whereas Erk1/2 activation was completely inhibited by a blocker of phospholipase Cbeta, U-73122. LPA also induced interleukin-8 (IL-8) synthesis in the colon cancer cells by primarily activating LPA2 receptor. We also found that LPA2 interacts with Na+/H+ exchanger regulatory factor 2 (NHERF2). Activation of Akt and Erk1/2 was significantly attenuated by silencing of NHERF2 expression by RNA interference, suggesting a pivotal role of NHERF2 in LPA2-mediated signaling. We found that expression of LPA2 was elevated, whereas expression of LPA1 downregulated in several types of cancers, including ovarian and colon cancer. We conclude that LPA2 is the major LPA receptor in colon cancer cells and cellular signals by LPA2 are largely mediated through its ability to interact with NHERF2.

The anti-inflammatory and cholinesterase inhibitor bifunctional compound IBU-PO protects from β-amyloid neurotoxicity by acting on Wnt signaling components

Changes in signal transduction are implicated in neuronal responses to the Alzheimer's amyloid-beta-peptide (Abeta), which include neurotransmitter systems and pathways involved in the maintenance of the nervous system. We report here that a new bifunctional compound IBU-PO, which combines a non-steroidal anti-inflammatory drug (NSAID) (Ibuprofen) and a cholinesterase (ChE) inhibitor (Octyl-Pyridostigmine), is neuroprotective against Abeta-neurotoxicity, and its activity is associated to Wnt signaling components in rat hippocampal and mouse cortical neurons. IBU-PO (0.01-1 microM) inhibits glycogen-synthase-kinase-3beta (GSK-3beta) and stabilizes cytoplasmic beta-catenin reverting the silencing of the Wnt pathway caused by Abeta-toxicity and GSK-3beta overexpression. In addition, IBU-PO enhances, dose-dependently, the non-amyloidogenic amyloid precursor protein (APP) cleavage by increasing secreted APP and decreasing endogenous Abeta1-40 in rat hippocampal neurons.

Influence of retinoic acid on adhesion complexes in human hepatoma cells: a clue to its antiproliferative effects

Retinoic acid exerts antiproliferative and differentiative effects in normal and transformed in vitro hepatocytes. In order to verify whether these effects are related to a modulation of adhesion molecules, we used Western blot analysis and immunofluorescence microscopy to investigate the E-cadherinl/beta-catenin complex, the main system of adherens junctions, and the occludin/ZO-1 complex present in the tight junctions in HepG2 cells cultured in the presence or absence of retinoic acid. Results showed that retinoic acid treatment increases the amount of beta-catenin bound to E-cadherin by decreasing its tyrosine-phosphorylation level. Similar results were obtained with the tight junction system, in which the amount of occludin/ZO-1 complex is increased by a similar mechanism that reduced the level of ZO-1 phosphorylation on tyrosine. Immunofluorescence images also confirm these results, showing the localization on the cell surface of both adhesion complexes. Their insertion into the plasma membrane could be suggestive of an optimal reassembly and function of adherens and tight junctions in hepatoma cells, indicating that retinoic acid, besides inhibiting cell proliferation, improves cell-cell adhesion, sustaining or inducing the expression of a more differentiated phenotype.

Both ERK and Wnt/beta-catenin pathways are involved in Wnt3a-induced proliferation

The Wnt family of proteins regulates development and cell growth. We identified Wnt3a-based regulatory mechanisms for cell proliferation in NIH3T3 fibroblast cells. The degree of Wnt3a-induced proliferation was reduced by beta-catenin small interfering RNA (siRNA) and extracellular signal-regulated kinase (ERK) siRNA, indicating that both the ERK and Wnt/beta-catenin pathways are involved in Wnt3a-induced proliferation. Wnt3a immediately and transiently activated the Raf-1-MEK-ERK cascade in a manner distinct from that of the beta-catenin increase seen in cells treated with Wnt3a. Wnt3a-induced ERK activation was maintained even though basal ERK activities were reduced by beta-catenin siRNA, indicating that Wnt3a may activate the ERK pathway independently of beta-catenin. The ERK pathway was however, activated by beta-catenin transfection, which was abolished by co-transfection with dominant-negative Tcf-4. Therefore, ERK pathway activation by Wnt signaling could occur at multiple levels, including beta-catenin-independent direct signaling resulting from a Wnt3a and beta-catenin/Tcf-4-dependent post gene transcriptional event. Wnt3a stimulated the G1 to S phase cell cycle progression. This stimulation was reduced by the ERK pathway inhibitor, indicating that Wnt3a promotes proliferation by stimulating the ERK pathway. Wnt3a therefore stimulates the proliferation of fibroblast cells, at least in part, via activation of the ERK and Wnt/beta-catenin pathways.

Mechanisms involved in prostaglandin E2-mediated neuroprotection against TNF-α: possible involvement of multiple signal transduction and β-catenin/T-cell factor

Cerebrospinal fluid prostaglandin E2 (PGE2) and tumor necrosis factor-alpha (TNF-alpha) levels are elevated in patients with Alzheimer's disease (AD), which suggests that they are involved in neurodegeneration. We previously reported that TNF-alpha derived from human macrophages, in response to beta-amyloid or amyloidogenic C-terminal peptide, is a main mediator of inflammatory neurotoxicity. In a continuation of this work, the present study investigated the direct effect of PGE2, one of the major prostaglandins produced in the brain, on cell viability in SH-SY5Y neuronal cells treated with TNF-alpha. PGE2 did not promote neurotoxicity, but rather had a strong protective effect against TNF-alpha by ameliorating TNF-alpha-induced apoptosis and also by rescuing the intracellular level of beta-catenin, a key transducer of the Wnt signaling pathway. PGE2-mediated stabilization of beta-catenin was accompanied by T-cell factor/lymphoid enhancer factor (Tcf/Lef)-mediated transcriptional activation, which was followed by an increase in the cyclinD1 level. Pharmacological studies provided further evidence supporting the notion that PGE2-mediated neuroprotection against TNF-alpha involves the stimulation of Tcf/Lef signaling through EP1-, EP2-, and EP4-mediated increases of beta-catenin in SH-SY5Y cells. In addition, this PGE2 effect appears to be dependent on the activation of protein kinase A, phosphatidylinositol 3-kinase, phospholipase C, and to a lesser extent protein kinase C. Thus, the molecular mechanism governing the inhibitory effect of PGE2 against TNF-alpha may involve the activation and cross talk of multiple signal transduction and play an important role in regulating the survival of neurons during the neurotoxic inflammatory response associated with neurodegenerative diseases including AD.

Colonic adenocarcinomas rapidly induced by the combined treatment with 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and dextran sodium sulfate in male ICR mice possess beta-catenin gene mutations and increases immunoreactivity for beta-catenin, cyclooxygenase-2 and inducible nitric oxide synthase

Heterocyclic amines are known to be important environmental carcinogens in several organs including the colon. The aim of this study was to induce colonic epithelial malignancies within a short-term period and analyze the expression of cycooxygenase (COX)-2, inducible nitric oxide synthase (iNOS) and beta-catenin, and mutations of beta-catenin gene in induced tumors. Male Crj: CD-1 mice were given a single i.g. administration (200 mg/kg body wt) of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) followed by 2% dextran sodium sulfate (DSS) in the drinking water for a week. The expression of beta-catenin, COX-2 and iNOS was immunohistochemically assessed in colonic epithelial lesions and the beta-catenin gene mutations in colonic adenocarcinomas induced were analyzed by the single strand conformation polymorphism method, restriction enzyme fragment length polymorphism and direct sequencing. At week 16, a high incidence of colonic neoplasms with dysplastic lesions developed in mice that received PhIP and DSS, but only a few developed in those given MeIQx and DSS. Immunohistochemically, the adenocarcinomas induced were all positive for three proteins. All seven adenocarcinomas induced by PhIP and DSS have mutations. The findings suggest that DSS exerts powerful tumor-promoting effects on PhIP-initiated colon carcinogenesis in mice and this mouse model is useful for investigating environment-related colon carcinogenesis within a short-term period.

γ-Diketone neuropathy: axon atrophy and the role of cytoskeletal protein adduction

Multifocal giant neurofilamentous axonal swellings and secondary distal degeneration have been historically considered the hallmark features of gamma-diketone neuropathy. Accordingly, research conducted over the past 25 years has been directed toward discerning mechanisms of axonal swelling. However, this neuropathological convention has been challenged by recent observations that swollen axons were an exclusive product of long-term 2.5-hexanedione (HD) intoxication at lower daily dose-rates (e.g., 175 mg/kg/day); that is, higher HD dose-rates (e.g., 400 mg/kg/day) produced neurological deficits in the absence of axonal swellings. The observation that neurological toxicity can be expressed without axonal swelling suggests that this lesion is not an important pathophysiological event. Instead, several research groups have now shown that axon atrophy is prevalent in nervous tissues of laboratory animals intoxicated over a wide range of HD dose-rates. The well-documented nerve conduction defects associated with axon atrophy, in conjunction with the temporal correspondence between this lesion and the onset of neurological deficits, strongly suggest that atrophy has pathophysiological significance. In this commentary, we present evidence that supports a pathognomonic role for axon atrophy in gamma-diketone neuropathy and suggests that the functional consequences of this lesion mediate the corresponding neurological toxicity. Previous research has demonstrated that HD interacts with proteins via formation of pyrrole adducts. We therefore discuss the possibility that this chemical process is essential to the mechanism of atrophy. Evidence presented in this review suggests that "distal axonopathy" is an inaccurate classification and future nosological schemes should be based on the apparent primacy of axon atrophy.

Wnt-3a overcomes β-amyloid toxicity in rat hippocampal neurons

The aim of this study was to evaluate whether the direct activation of the Wnt signaling pathway by its endogenous Wnt-3a ligand prevents the toxic effects induced by amyloid-beta-peptide (Abeta) in rat hippocampal neurons. We report herein that the Wnt-3a ligand was indeed able to overcome toxic effects induced by Abeta in hippocampal neurons, including a neuronal impairment on cell survival, an increase in glycogen synthase kinase-3beta (GSK-3beta) and tau phosphorylation, a decrease in cytoplasmic beta-catenin and a decrease in the expression of the Wnt target gene engrailed-1. We further demonstrate that Wnt-3a protects hippocampal neurons from apoptosis induced by Abeta. Our results support the hypothesis that a loss of function of Wnt signaling may play a role in the progression of neurodegenerative diseases such as Alzheimer's disease.