Beneficial effect of enteral glycine in intestinal ischemia/reperfusion injury

It has been shown in vitro that glycine can protect renal tubules and hepatocytes from hypoxic injury. Glycine also attenuates ischemic injury in transplanted livers. The present study investigated the effect of enteral glycine in a murine model of ischemia/reperfusion injury of the small intestine. Mice (n = 12 in each group) were randomized to receive two gastric gavages of either a 20% glycine (Gly) or 23% balanced amino acid (AA) solution with a 6-hour interval between each gavage. One hour after the second gavage, mice underwent superior mesenteric artery clamping for 20 minutes. The clamp was then released for reperfusion. Another group of mice (n = 8) underwent a sham operation and served as additional control animals. Six hours after ischemia/reperfusion, the mice were killed in order to assess the intestinal injury (intestinal protein content, mucosal disaccharidase activity, and intestinal histologic findings) and the systemic consequences (bacterial translocation, serum interleukin-6, and lung myeloperoxidase activity). A second set of mice (n = 55) underwent identical gavages and ischemia/reperfusion and they were followed for survival. Compared to AA, enteral glycine administered prior to intestinal ischemia/reperfusion injury significantly preserved mucosal indices and intestinal histology and decreased lung myeloperoxidase activity. Survival was also significantly increased in animals receiving glycine compared to AA control mice. These data suggest that enteral glycine supplementation may be beneficial in attenuating intestinal ischemia/reperfusion injury and its related systemic effects in this murine model.

Elevation of intracellular cyclic adenosine monophosphate inhibits the epidermal growth factor signal transduction pathway and cellular growth in pancreatic adenocarcinoma cell lines

BACKGROUND

The epidermal growth factor (EGF) signal transduction pathway, frequently activated in pancreatic cancer, is an important regulator of cellular growth and transformation. This study examined whether activation of the cyclic adenosine monophosphate protein kinase A pathway may inhibit the EGF signal transduction pathway in pancreatic cancer cell lines.

METHODS

Human pancreatic cancer lines BxPC-3 and AsPC-1 were stimulated with EGF, forskolin, or both. Forskolin is a compound that increases cyclic adenosine monophosphate levels. Assays of cell lines were then obtained for cellular growth (MTT assay), anchorage-independent growth (soft agar), and EGF-induced mitogen-activated protein kinase activation as measured by an in-gel kinase assay.

RESULTS

Treatment with forskolin resulted in inhibition of EGF-induced activation of mitogen-activated protein kinase activity (BxPC-3 78% inhibition and AsPC-1 70% inhibition, p < 0.005), diminished cellular proliferation (BxPC-3 92% inhibition and AsPC-1 86% inhibition, p < 0.001), and formation of colonies in soft agar (BxPC-3 98% inhibition and AsPC-1 76% inhibition, p < 0.001). Forskolin did not inhibit EGF receptor autophosphorylation or tyrosine kinase signaling in response to EGF.

CONCLUSIONS

Forskolin-induced inhibition of mitogen-activated protein kinase is associated with diminished pancreatic cancer cell proliferation in vitro. Use of strategies to increase cyclic adenosine monophosphate levels may have therapeutic application in pancreatic cancer.

Antimicrobial effects of granulocyte-macrophage colony-stimulating factor in protein-energy malnutrition

OBJECTIVES

To evaluate, in a murine model of protein-energy malnutrition, whether granulocyte-macrophage colony-stimulating factor (GM-CSF) improves the host response to a septic challenge and to determine the potential mechanisms involved.

DESIGN

Nonblinded study of GM-CSF in mice with protein-energy malnutrition.

SETTING

A university-based surgical laboratory and animal facility.

INTERVENTION

In study 1, malnourished mice were randomized to receive either GM-CSF (120 micrograms/kg subcutaneously to receive either GM-CSF (120 micrograms/kg subcutaneously from day 4 to 7 of the protein-free diet) or saline vehicle as a control. On day 7, all mice were given Candida albicans (5 x 10(5) organisms intravenously). In study 2, malnourished mice received the same dose of GM-CSF or saline vehicle for 7 days of the protein-free diet.

MAIN OUTCOME MEASURES

In study 1 mice were followed up for survival. In study 2, after 7 days of diets, splenic macrophages were harvested and were assayed for interleukin-6, superoxide anion, and nitric oxide production. Splenocytes were stimulated with concanavalin A (5 micrograms/mL) for interleukin-4, interleukin-10, and interferon-gamma production.

RESULTS

Treatment with GM-CSF significantly enhanced survival in malnourished mice infected with C albicans. Treatment with GM-CSF was associated with increased production from splenic macrophages of interleukin-6, superoxide anion, and nitric oxide as well as decreased interleukin-4 production from splenocytes.

CONCLUSIONS

This study suggests a beneficial role for GM-CSF in the malnourished host predisposed to infection. The antimicrobial properties of GM-CSF may function through enhanced production of nitric oxide and superoxide anion.

Peritoneal and splenic macrophage functions in the tumor-bearing host

In the tumor-bearing host, depression of cell-mediated immunity has been well-demonstrated, but little is known about alterations in macrophage functions. We hypothesized that the presence of a tumor may cause functional suppression of peritoneal macrophage and splenic macrophage functions, perhaps due to prostaglandin-E2 (PGE2) and nitric oxide. C57 BL/6 mice (n = 18) were injected subcutaneously with Lewis lung carcinoma 3 tumor. Control mice (n = 18) received no tumor and were pair-fed to intake of the tumor group. On Day 21, peritoneal and splenic macrophages were harvested. Cell surface Ia expression, cytotoxicity against P815 target cells, Candida albicans killing, and production of PGE2, nitric oxide, and superoxide were measured. Mean Ia expression was decreased in tumor animals for both peritoneal and splenic macrophages. In tumor animals PGE2 production significantly increased in both peritoneal and splenic macrophages. Superoxide production significantly decreased in peritoneal macrophages but significantly increased in splenic macrophages. Nitric oxide production was also significantly depressed in tumor-bearing host peritoneal macrophages. C. albicans killing was significantly depressed in tumor animals' peritoneal macrophages but showed little change in splenic macrophages. In tumor animals cytotoxicity was significantly decreased in peritoneal macrophages but significantly increased in splenic macrophages. In the tumor-bearing host, peritoneal macrophages have significantly decreased accessory and effector functions. Splenic macrophages demonstrate decreased accessory but enhanced effector functions. PGE2, superoxide, and nitric oxide appear to be important mechanisms of altered macrophage function in the tumor-bearing host; modifying their cellular production may enhance host defense.

Raf-1 protein expression in human breast cancer cells

BACKGROUND

The Raf-1 kinase, a 72-kDa cytoplasmic serine-threonine kinase, plays a central role as a second messenger in signal transduction. After ligand binding to a variety of transmembrane tyrosine kinase growth factor receptors including epidermal growth factor (EGF) receptor, the 72-kDa kinase is activated through phosphorylation to a 74-kDa phosphoprotein. The Raf-1 kinase is constitutively activated in many transformed cells either directly, by mutations within its amino-terminus regulatory region, or indirectly, due to overstimulation by autocrine growth factors or activated proximal oncogenes. The role of Raf-1 kinase in breast cancer has not been studied.

METHODS

To investigate the role of Raf-1 kinase expression and its activation in breast cancer, we studied three human breast cancer cell lines expressing varying amounts of EGF receptor to determine the level of Raf-1 protein and the proportion expressed in the higher molecular weight form. Effects of serum starvation and stimulation with EGF on the Raf-1 protein were studied in T47D, BT474, and MDA-MB231 cells by precipitation of cell lysates with an anti-Raf-1 antibody followed by immunoblotting. [3H]Thymidine incorporation by these cells after EGF stimulation was also determined as a measure of DNA synthesis.

RESULTS

In all three breast cancer cell lines studied, the Raf-1 protein was identified in a 70- and a 74-kDa form. The level of Raf-1 was similar in all three cell lines and appeared unrelated to EGF receptor expression on the cell surface. The majority of the protein was found in the 74-kDa form even after serum starvation. A minor shift from the lower to higher molecular weight form of Raf-1 was apparent in cells treated with EGF, and increased [3H] thymidine incorporation could be demonstrated in two of the cell lines after EGF stimulation.

CONCLUSION

Baseline expression of the 74-kDa or activated form of the Raf-1 kinase appeared to be elevated in the breast cancer cells studied, indicating constitutive activation. Further investigation into the role of Raf-1 protein in the pathogenesis of breast cancer is indicated.

Inhibition of nitric oxide synthesis is detrimental during endotoxemia

BACKGROUND

Increased production of nitric oxide has been implicated as a mediator during septic shock and sepsis syndrome. Inhibition of nitric oxide production could be beneficial during endotoxemia to improve the individual's hemodynamic status and possibly outcome.

OBJECTIVE

To evaluate the effects of nitric oxide inhibition on macrophage function and survival in a murine sepsis model.

DESIGN

Sixty-eight female Swiss-Webster (ND4) mice were injected with a sublethal dose of Escherichia coli lipopolysaccharide (25 mg/kg).

INTERVENTION

The treated group (n = 34) received 10 mg/kg of NG-nitro-L-arginine methyl ester at the time of lipopolysaccharide injection.

MAIN OUTCOME MEASURES

Blood samples and peritoneal macrophages were obtained at baseline and at 2, 4, and 8 hours after injection. Nitrite levels were measured in 36 mice from plasma and supernatant samples of cultured peritoneal macrophages stimulated with interferon gamma (100 micrograms/mL) for 48 hours. Thirty-two animals were observed for survival.

RESULTS

Administration of N-nitro-L-arginine methyl ester after lipopolysaccharide injection caused significant reductions in macrophage mean nitrite production from 13 and 15 mumol/L to 7 and 11 mumol/L (P < .05) and reduced mean plasma nitrite concentrations from 100 and 118 mumol/L to 46 and 108 mumol/L (P < .05) at 2 and 4 hours, respectively. The rate of survival was significantly decreased to 0% in the group receiving N-nitro-L-arginine methyl ester after septic challenge compared with 87.5% in controls (P < .005).

CONCLUSIONS

Inhibition of nitric oxide production is detrimental in this murine model of endotoxemia.