Surgical management of gastrointestinal stromal tumors of the stomach.

BACKGROUND: Laparoscopy has emerged as the "gold standard" procedure for many diseases that require surgical treatment. Our goal was to assess the outcomes of laparoscopic vs open partial gastrectomies for the management of gastrointestinal stromal tumors of the stomach (gGIST) using a national database. METHODS: Using the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database (2006-2009), we identified patients who underwent laparoscopic and open partial gastrectomy gGIST. Overall morbidity and mortality were assessed. The relationships between anesthesia time, operative duration, surgical site infection (SSI), and hospital stay were also examined. Two-sample t tests were used. RESULTS: Of 486 patients, 146 (30%) underwent laparoscopic resection (LR) and 340 (70%) underwent open resection (OR). Patients who underwent LP were older (mean: 65 vs 62 years; P = .062). Patients treated with LR experienced shorter anesthesia time (mean: 183 vs 212 minutes; P < .05) and shorter operative time (mean: 119 vs 149 minutes; P < .05) compared with those who underwent OR. All patients treated with LR had fewer SSIs compared with those who underwent OR (0.68% vs 6.7%; P < .001). Patients treated with LR were less likely to experience an overall morbidity (mean: 3.9% vs 11.7%; P < .001) or mortality (mean: 0.23% vs 0.72%; P < .001) and shorter total hospital stay (mean: 3.17 vs 7.50 days; P < .001) compared with those who underwent OR. CONCLUSIONS: In ACS NSQIP hospitals, laparoscopic resection of gGIST appears to be preferable to open surgery. However, prospective studies with large sample sizes comparing both surgical approaches with size-matched tumors are strongly suggested.

An unusual case of pleural chordoma.

Chordoma is a rare slow-growing neoplasm arising from notochordal remnants. In the United States, the annual incidence of chordoma is 0.08 per 100,000 and is more common in men than in women. The most common locations of chordoma are the cranial (32%), spinal (32.8%), and sacral (29.2%) regions [1]. We report an unusual case of pleural chordoma in a 45-year-old man.

Gpr125 modulates Dishevelled distribution and planar cell polarity signaling.

During vertebrate gastrulation, Wnt/planar cell polarity (PCP) signaling orchestrates polarized cell behaviors underlying convergence and extension (C&E) movements to narrow embryonic tissues mediolaterally and lengthen them anteroposteriorly. Here, we have identified Gpr125, an adhesion G protein-coupled receptor, as a novel modulator of the Wnt/PCP signaling system. Excess Gpr125 impaired C&E movements and the underlying cell and molecular polarities. Reduced Gpr125 function exacerbated the C&E and facial branchiomotor neuron (FBMN) migration defects of embryos with reduced Wnt/PCP signaling. At the molecular level, Gpr125 recruited Dishevelled to the cell membrane, a prerequisite for Wnt/PCP activation. Moreover, Gpr125 and Dvl mutually clustered one another to form discrete membrane subdomains, and the Gpr125 intracellular domain directly interacted with Dvl in pull-down assays. Intriguingly, Dvl and Gpr125 were able to recruit a subset of PCP components into membrane subdomains, suggesting that Gpr125 may modulate the composition of Wnt/PCP membrane complexes. Our study reveals a role for Gpr125 in PCP-mediated processes and provides mechanistic insight into Wnt/PCP signaling.

Glia and methylmercury neurotoxicity.

Methylmercury (MeHg) is a global environmental pollutant with significant adverse effects on human health. As the major target of MeHg, the central nervous system (CNS) exhibits the most recognizable poisoning symptoms. The role of the two major nonneuronal cell types, astrocytes and microglia, in response to MeHg exposure was recently compared. These two cell types share several common features in MeHg toxicity, but interestingly, these cells types also exhibit distinct response kinetics, indicating a cell-specific role in mediating MeHg-induced neurotoxicity. The aim of this study was to review the most recent literature and summarize key features of glial responses to this organometal.

Methylmercury-induced alterations in astrocyte functions are attenuated by ebselen.

Methylmercury (MeHg) preferentially accumulates in glia of the central nervous system (CNS), but its toxic mechanisms have yet to be fully recognized. In the present study, we tested the hypothesis that MeHg induces neurotoxicity via oxidative stress mechanisms, and that these effects are attenuated by the antioxidant, ebselen. Rat neonatal primary cortical astrocytes were pretreated with or without 10 µM ebselen for 2h followed by MeHg (0, 1, 5, and 10 µM) treatments. MeHg-induced changes in astrocytic [(3)H]-glutamine uptake were assessed along with changes in mitochondrial membrane potential (ΔΨ(m)), using the potentiometric dye tetramethylrhodamine ethyl ester (TMRE). Western blot analysis was used to detect MeHg-induced ERK (extracellular-signal related kinase) phosphorylation and caspase-3 activation. MeHg treatment significantly decreased (p<0.05) astrocytic [(3)H]-glutamine uptake at all time points and concentrations. Ebselen fully reversed MeHg's (1 µM) effect on [(3)H]-glutamine uptake at 1 min. At higher MeHg concentrations, ebselen partially reversed the MeHg-induced astrocytic inhibition of [(3)H]-glutamine uptake [at 1 min (5 and 10 µM) (p<0.05); 5 min (1, 5 and 10 µM) (p<0.05)]. MeHg treatment (1h) significantly (p<0.05) dissipated the ΔΨ(m) in astrocytes as evidenced by a decrease in mitochondrial TMRE fluorescence. Ebselen fully reversed the effect of 1 µM MeHg treatment for 1h on astrocytic ΔΨ(m) and partially reversed the effect of 5 and 10 µM MeHg treatments for 1h on ΔΨ(m). In addition, ebselen inhibited MeHg-induced phosphorylation of ERK (p<0.05) and blocked MeHg-induced activation of caspase-3 (p<0.05-0.01). These results are consistent with the hypothesis that MeHg exerts its toxic effects via oxidative stress and that the phosphorylation of ERK and the dissipation of the astrocytic mitochondrial membrane potential are involved in MeHg toxicity. In addition, the protective effects elicited by ebselen reinforce the idea that organic selenocompounds represent promising strategies to counteract MeHg-induced neurotoxicity.

Comparative study on the response of rat primary astrocytes and microglia to methylmercury toxicity.

As the two major glial cell types in the brain, astrocytes and microglia play pivotal but different roles in maintaining optimal brain function. Although both cell types have been implicated as major targets of methylmercury (MeHg), their sensitivities and adaptive responses to this metal can vary given their distinctive properties and physiological functions. This study was carried out to compare the responses of astrocytes and microglia following MeHg treatment, specifically addressing the effects of MeHg on cell viability, reactive oxygen species (ROS) generation and glutathione (GSH) levels, as well as mercury (Hg) uptake and the expression of NF-E2-related factor 2 (Nrf2). Results showed that microglia are more sensitive to MeHg than astrocytes, a finding that is consistent with their higher Hg uptake and lower basal GSH levels. Microglia also demonstrated higher ROS generation compared with astrocytes. Nrf2 and its downstream genes were upregulated in both cell types, but with different kinetics (much faster in microglia). In summary, microglia and astrocytes each exhibit a distinct sensitivity to MeHg, resulting in their differential temporal adaptive responses. These unique sensitivities appear to be dependent on the cellular thiol status of the particular cell type.

Neonatal rat primary microglia: isolation, culturing, and selected applications.

Microglial cells elaborate trophic factors and cytokines and remove toxins and debris from the extracellular space in the central nervous system, acting analogously to peripheral macrophages. Over the past two decades, increased attention has been directed at the role of microglia, not only in normal physiology, but also in mediating neurotoxicity. Activation of microglia is inherent to multiple neurodegenerative disorders and exposure to toxic compounds. In large measure, these revelations have come about as a result of technologies that enable researchers to obtain high yield and purity primary cultures of rodent microglia. The mechanical isolation protocol discussed in this unit offers an economical method to isolate large amounts of microglia in a short and not too labor-intensive manner. Most importantly, it ensures a high yield of cells with great reproducibility. Given the ever-increasing importance of microglia to the field of neurotoxicology research, the ability to isolate large quantities of primary microglia makes it possible to investigate the role and mechanisms associated with microglial modulation of neurotoxicity. We provide a detailed description on the methods that are routinely used in our laboratory for the isolation and culture of microglia, with emphasis on the steps that are deemed most critical for obtaining pure and healthy cultures.

Manganese-induced downregulation of astroglial glutamine transporter SNAT3 involves ubiquitin-mediated proteolytic system.

SNAT3 is a major facilitator of glutamine (Gln) efflux from astrocytes, supplying Gln to neurons for neurotransmitter synthesis. Our previous investigations have shown that, in primary cortical astrocyte cultures, SNAT3 protein is degraded after exposure to manganese (Mn(2+)). The present studies were performed to identify the processes responsible for this effect. One of the well-established mechanisms for protein-level regulation is posttranslational modification via ubiquitination, which leads to the rapid degradation of proteins by the 26S proteasome pathway. Here, we show that astrocytic SNAT3 directly interacts with the ubiquitin ligase, Nedd4-2 (neural precursor cells expressed developmentally downregulated 4-2), and that Mn(2+) increases both Nedd4-2 mRNA and protein levels. Additionally, we have found that Mn(2+) exposure elevates astrocytic ubiquitin B mRNA expression, free ubiquitin protein levels, and total protein ubiquitination. Furthermore, Mn(2+) effectively decreases astrocytic mRNA expression and the phosphorylation of serum and glucocorticoid-inducible kinase, a regulatory protein, which, in the active phosphorylated form, is responsible for the phosphorylation and subsequent inactivation of Nedd4-2. Additional findings establish that Mn(2+) increases astrocytic caspase-like proteolytic proteasome activity and that the Mn(2+)-dependent degradation of SNAT3 protein is blocked by the proteasome inhibitors, N-acetyl-leu-leu-norleucinal and lactacystin. Combined, these results demonstrate that Mn(2+)-induced SNAT3 protein degradation and the dysregulation of Gln homeostasis in primary astrocyte cultures proceeds through the ubiquitin-mediated proteolytic system.

Methylmercury induces acute oxidative stress, altering Nrf2 protein level in primary microglial cells.

The neurotoxicity of methylmercury (MeHg) is well documented in both humans and animals. MeHg causes acute and chronic damage to multiple organs, most profoundly the central nervous system (CNS). Microglial cells are derived from macrophage cell lineage, making up approximately 12% of cells in the CNS, yet their role in MeHg-induced neurotoxicity is not well defined. The purpose of the present study was to characterize microglial vulnerability to MeHg and their potential adaptive response to acute MeHg exposure. We examined the effects of MeHg on microglial viability, reactive oxygen species (ROS) generation, glutathione (GSH) level, redox homeostasis, and Nrf2 protein expression. Our data showed that MeHg (1-5 microM) treatment caused a rapid (within 1 min) concentration- and time-dependent increase in ROS generation, accompanied by a statistically significant decrease in the ratio of GSH and its oxidized form glutathione disulfide (GSSG) (GSH:GSSG ratio). MeHg increased the cytosolic Nrf2 protein level within 1 min of exposure, followed by its nuclear translocation after 10 min of treatment. Consistent with the nuclear translocation of Nrf2, quantitative real-time PCR revealed a concentration-dependent increase in the messenger RNA level of Ho-1, Nqo1, and xCT 30 min post MeHg exposure, whereas Nrf2 knockdown greatly reduced the upregulation of these genes. Furthermore, we observed increased microglial death upon Nrf2 knockdown by the small hairpin RNA approach. Taken together, our study has demonstrated that microglial cells are exquisitely sensitive to MeHg and respond rapidly to MeHg by upregulating the Nrf2-mediated antioxidant response.

Ferroportin is a manganese-responsive protein that decreases manganese cytotoxicity and accumulation.

Although manganese (Mn) is an essential trace element for human development and growth, chronic exposure to excessive Mn levels can result in psychiatric and motor disturbances, referred to as manganism. However, there are no known mechanism(s) for efflux of excess Mn from mammalian cells. Here, we test the hypothesis that the cytoplasmic iron (Fe) exporter ferroportin (Fpn) may also function as a Mn exporter to attenuate Mn toxicity. Using an inducible human embryonic kidney (HEK293T) cell model, we examined the influence of Fpn expression on Mn-induced cytotoxicity and intracellular Mn concentrations. We found that induction of an Fpn-green fluorescent protein fusion protein in HEK293T cells was cytoprotective against several measures of Mn toxicity, including Mn-induced cell membrane leakage and Mn-induced reductions in glutamate uptake. Fpn-green fluorescent protein mediated cytoprotection correlated with decreased Mn accumulation following Mn exposure. Thus, Fpn expression reduces Mn toxicity concomitant with reduced Mn accumulation. To determine if mammalian cells may utilize Fpn in response to increased intracellular Mn concentrations and toxicity, we assessed endogenous Fpn levels in Mn-exposed HEK293T cells and in mouse brain in vivo. We find that 6 h of Mn exposure in HEK293T cells is associated with a significant increase in Fpn levels. Furthermore, mice exposed to Mn showed an increase in Fpn levels in both the cerebellum and cortex. Collectively, these results indicate that (i) Mn exposure promotes Fpn protein expression, (ii) Fpn expression reduces net Mn accumulation, and (iii) reduces cytotoxicity associated with exposure to this metal.