The effect of hypoxia/reoxygenation on the cellular function of intestinal epithelial cells

BACKGROUND

Previously, using in vivo models, we have demonstrated that ischemia/reperfusion can increase intestinal mucosal permeability, promote bacterial translocation, and induce gut cytokine production. Because of the cellular heterogeneity of the gut, however, studies investigating the direct effects of hypoxia/reoxygenation on intestinal epithelial cells are confounded in in vivo model systems. Consequently, this study examines oxidant-mediated enterocyte injury using an in vitro intestinal enterocyte hypoxia/reoxygenation model system.

METHODS

Two intestinal epithelial cell lines, IEC-6 and Caco-2, were seeded onto 3-microm filters in a Transwell bicameral system and grown until tight junction integrity was established. Cells were subjected to hypoxia in a sealed chamber with 95% nitrogen and 5% carbon dioxide and incubated at 37 degrees C for 60 or 90 minutes. Reoxygenation was initiated by replacing the media and putting the cells in an environment of room air plus 5% carbon dioxide. Permeability and bacterial translocation were assayed by measuring the phenol red concentration and culturing the bacteria that crossed the cell monolayer and reached the basal chamber of the bicameral system. Monolayer tight junction integrity was monitored by serial measurements of transepithelial electrical resistance (TEER), and cell viability was assessed by trypan blue dye.

RESULTS

IEC-6 cell monolayers subjected to 60 or 90 minutes of hypoxia showed significantly higher permeability to phenol red, with 54+/-5% and 57+/-5% of the dye crossing the monolayers, respectively, compared with normoxic control (38+/-2%; p < 0.01). Caco-2 cell monolayers also had increased permeability to phenol red, with 24+/-6% and 20+/-4% of the phenol red crossing the monolayer after 60 or 90 minutes of hypoxia, respectively, compared with 8+/-3% in the normoxic controls (p < 0.01). At 3 hours after challenge with Escherichia coli, the monolayers subjected to 60 or 90 minutes of hypoxia had significantly increased bacterial translocation (IEC-6 cells, p < 0.05; Caco-2 cells, p < 0.01) compared with controls. The increased permeability of the hypoxic Caco-2 and IEC-6 monolayers was associated with a decrease in TEER beginning as early as 1 hour after reoxygenation (p < 0.01). Cell viability, however, was not decreased.

CONCLUSION

These results indicate that hypoxia/reoxygenation can directly impair cellular function as manifested by increased monolayer permeability to phenol red, increased E. coli bacterial translocation, and a decrease in TEER values.

Expression of a fusion protein of scFv-biotin mimetic peptide for immunoassay

We constructed two fusion proteins of scFv linked to biotin mimetic sequence (BMS) via different linkers, and expressed them in the Pichia pastoris expression/secretion system. We found that both bi-functional scFv proteins exhibited their intrinsic binding activities to antigen CA125 determined in competitive radioimmunoassay experiments, but the fusion protein with a spacer between the scFv and BMS (scFv-spacer-BMS) showed higher binding activity of streptavidin than the one with c-Myc peptide as a linker.

Gut-derived mesenteric lymph but not portal blood increases endothelial cell permeability and promotes lung injury after hemorrhagic shock

OBJECTIVE

To determine whether gut-derived factors leading to organ injury and increased endothelial cell permeability would be present in the mesenteric lymph at higher levels than in the portal blood of rats subjected to hemorrhagic shock. This hypothesis was tested by examining the effect of portal blood plasma and mesenteric lymph on endothelial cell monolayers and the interruption of mesenteric lymph flow on shock-induced lung injury.

SUMMARY BACKGROUND DATA

The absence of detectable bacteremia or endotoxemia in the portal blood of trauma victims casts doubt on the role of the gut in the generation of multiple organ failure. Nevertheless, previous experimental work has clearly documented the connection between shock and gut injury as well as the concept of gut-induced sepsis and distant organ failure. One explanation for this apparent paradox would be that gut-derived inflammatory factors are reaching the lung and systemic circulation via the gut lymphatics rather than the portal circulation.

METHODS

Human umbilical vein endothelial cell monolayers, grown in two-compartment systems, were exposed to media, sham-shock, or postshock portal blood plasma or lymph, and permeability to rhodamine (10K) was measured. Sprague-Dawley rats were subjected to 90 minutes of sham or actual shock and shock plus lymphatic division (before and after shock). Lung permeability, pulmonary myeloperoxidase levels, alveolar apoptosis, and bronchoalveolar fluid protein content were used to quantitate lung injury.

RESULTS

Postshock lymph increased endothelial cell monolayer permeability but not postshock plasma, sham-shock lymph/plasma, or medium. Lymphatic division before hemorrhagic shock prevented shock-induced increases in lung permeability to Evans blue dye and alveolar apoptosis and reduced pulmonary MPO levels. In contrast, division of the mesenteric lymphatics at the end of the shock period but before reperfusion ameliorated but failed to prevent increased lung permeability, alveolar apoptosis, and MPO accumulation.

CONCLUSIONS

Gut barrier failure after hemorrhagic shock may be involved in the pathogenesis of shock-induced distant organ injury via gut-derived factors carried in the mesenteric lymph rather than the portal circulation.

Effect of acute-phase and heat-shock stress on apoptosis in intestinal epithelial cells (Caco-2)

OBJECTIVES

a) To determine if the sequence of exposure of intestinal epithelial cells to heat-shock or acute-phase stimuli would affect whether cellular protection or injury would occur; and b) to determine if the effects of a thermally induced heat-shock response can be mimicked by sodium arsenite, a nonthermal inducer of the heat-shock response.

DESIGN

In vitro controlled study.

SETTING

Institutional laboratories.

SUBJECTS

Caco-2 human intestinal cell line.

INTERVENTIONS

Human intestinal epithelial cells (Caco-2) were grown on 35-mm culture dishes, chamber slides, or in a bicameral culture system to confluence or until tight-junction integrity was established. The cells were examined for viability, apoptosis, and bacterial translocation after exposure to a series of insults.

MEASUREMENTS AND MAIN RESULTS

Control Caco-2 cells (medium only) and cells exposed to arsenite or to LPS alone had an apoptotic cell rate of 5.7%, 7.9%, and 8.6%, respectively. However, Caco-2 cells exposed to the cytokines IL-1beta and IL-6 had a significantly higher rate of apoptosis (22.1%, p < .01 vs. other groups). Caco-2 cells exposed to arsenite followed by LPS had 6.7% apoptotic cells, while cells exposed to LPS followed by arsenite had a significantly greater number of apoptotic cells (19.7%, p < .05). In addition, cells exposed to cytokines followed by arsenite had a higher apoptotic rate than cells exposed to arsenite followed by cytokines (28.4% vs. 10.6%, p < .01). Similar results were seen when cell viability was quantitated. At 3 hrs after challenge with Escherichia coli, the cytokine-exposed Caco-2 monolayers had a significantly increased rate of bacterial passage across the Caco-2 monolayer than control monolayers (p < .05), while the Caco-2 monolayers exposed to arsenite followed by cytokines or arsenite alone had a decreased rate of bacterial passage (p < .05). Conversely, cells exposed to cytokines or LPS before arsenite had the highest number of bacteria crossing the monolayer (p < .05).

CONCLUSIONS

These results indicate that preinduction of a heat-shock response (arsenite) can protect against cytokine or LPS-induced apoptosis and enterocyte dysfunction, as manifested by the passage of E. coli across an intact enterocyte monolayer. In contrast, the induction of a heat-shock response after exposure to acute-phase response inducers (cytokines and LPS) may result in decreased enterocyte viability, increased apoptosis, and cellular dysfunction.

A new method to generate quadromas by electrofusion and FACS sorting

Bispecific monoclonal antibodies (bsMAbs) are unique molecules incorporating two different paratopes in a single antibody molecule. BsMAbs can be useful in different areas of research as well in clinical applications. Traditionally, bsMAbs are produced by hybrid-hybridomas that are generated by the fusion of two pre-established hybridomas. The development of such hybrid-hybridomas can be difficult and time-consuming. Here, we introduce a new technique to generate such hybrids, electro-FACS-fusion. In this procedure, before the electrofusion, one of the hybridomas is labeled with fluorescein isothiocyanate (FITC) and the other with tetramethylrhodamine isothiocyanate (TRITC). The mixture of cells is then electrofused, and cells exhibiting dual fluorescence are selected by fluorescence activated cell sorting (FACS). The fused cells are directly plated in microplates for clonal growth. Using this technique, we produced three new hybrid-hybridomas secreting bsMAb that could be used for the next generation of immunoassays.

Effect of heat shock and endotoxin stress on enterocyte viability apoptosis and function varies based on whether the cells are exposed to heat shock or endotoxin first

BACKGROUND

Stress-gene responses, including the heat shock (HS) response and the acute phase response, are protective mechanisms for cells after exposure to stress. Both responses cannot occur simultaneously, and, in endothelial cells, the sequence of stress-gene expression seems to be a critical factor in whether cellular protection or injury occurs.

OBJECTIVE

To determine if the sequence of stress-gene expression affects cellular protection or injury in epithelial cells.

DESIGN

Randomized controlled in vitro study.

SETTING

University research laboratory.

SUBJECTS

Rat intestinal epithelial cell-6 (IEC-6) cells were grown on 35-mm culture dishes, chamber slides, or in a bicameral system to confluence or until tight junction integrity was established.

INTERVENTIONS

Rat IEC-6 cells were examined for viability, apoptosis, and bacterial translocation (BT) after exposure to 25-micrograms/mL lipopolysaccharide (LPS) for 18 hours to HS (43 degrees C) for 90 minutes, to LPS followed by HS, or to HS followed by LPS.

MAIN OUTCOME MEASURES

The IEC-6 cells were stained for viability and apoptosis using trypan blue and a direct immunoperoxidase detection of digoxigenin-labeled genomic DNA (Apop Tag Plus In Situ Apoptosis Detection Kit, Oncor, Gaithersburg, Md), respectively. Bacterial translocation was measured by culturing the bacteria (ie, Escherichia coli) that crossed the IEC-6 cell monolayer in the bicameral system.

RESULTS

Control cells (medium only) and cells exposed to LPS alone, HS alone, or HS followed by LPS had a viability from 92% to 98%, and the percentage of apoptotic cells ranged from 2.2% to 5.7%. In contrast, IEC-6 cells exposed to LPS followed by HS had a significantly lower viability (83%, P < .05 vs all other groups) and a higher percentage of apoptotic cells (12.2%, P < .01). At 3 hours after challenge with E coli, the LPS-exposed IEC-6 cell monolayers had significantly increased BT vs control monolayers (P < .05), while the IEC-6 cell monolayers exposed to HS followed by LPS had decreased BT (P < .05). Conversely, cells exposed to LPS followed by HS had the highest magnitude of BT (P < .01 vs all other groups).

CONCLUSIONS

These results indicate that preinduction of HS response can diminish LPS-induced cell injury, while induction of HS response after the LPS challenge (ie, the acute phase response) may lead to decreased enterocyte viability, increased apoptosis, and cellular dysfunction as manifested by BT.

Effects of nimodipine, felodipine, and verapamil on isolated human arteries

AIM

To evaluate whether there might be some difference in the action modes of nimodipine (Nim) and felodipine (Fel).

METHODS

Compare the inhibitory effects of Nim and Fel with that of verapamil (Ver) as a representative of phenylalklamine on norepinephrine (NE)- and CaCl2-evoked contractions of human arteries.

RESULTS

In Ca(2+)-free and high K+ depolarized solution, inhibitory effects of Nim, Fel, and Ver were more potent on CaCl2-induced contractions on isolated human arteries than those on NE-induced contractions. In CaCl2-induced contraction, the pD2 values for Nim, Fel, and Ver were 7.5, 7.42, 6.35 on uterine arteries; 7.38, 7.65, 7.20 on mesenteric arteries and 7.87, 9.10, 7.32 on renal arteries, respectively. Ver inhibited 2 components of NE-evoked contraction, while Nim and Fel only inhibited extracellular Ca(2+)-dependent contractions.

CONCLUSION

The result indicates that Fel has a selective action on human renal arteries.

Protein malnutrition alone and in combination with endotoxin impairs systemic and gut-associated immunity

Because protein-malnourished or endotoxemic patients are at an increased risk of developing nosocomial infections, this study was performed to investigate the effects of protein malnutrition and endotoxemia, alone and in combination, on systemic and intestinal immunity. Protein malnutrition was created by feeding the animals a solid diet containing 0.03% protein. Subgroups of these protein-malnourished mice were killed after being challenged with saline or endotoxin on days 0, 7, 14, or 21. At death, the animals were weighed, tissues were harvested for histologic analysis (ileum, mesenteric lymph node [MLN], liver, and spleen), mitogen responsiveness (MLN, Peyer's patches, and spleen), and xanthine oxidase measurements (ileum and cecum). Separate groups were evaluated for survival. Both the saline and endotoxin-challenged mice had lost about 30% of their body weight after 21 days on the low-protein diet. The protein-malnourished mice were more susceptible to endotoxin-induced mortality (70% at 21 days) than the normally nourished mice (0%) (p less than .001). The mitogen responsiveness of the protein-malnourished mice to the T-cell mitogens (PHA and Con-A) progressively decreased the longer the mice were protein malnourished, and this decreased in blastogenic responsiveness was associated with histologic evidence of lymphoid atrophy. In contrast, the blastogenic response to the primarily B-cell mitogen, PWM, was largely preserved. The endotoxin challenge further depressed the immune state of mice tested after 0, 7, or 14 (but not 21) days of protein malnutrition. Thus, both protein malnutrition and endotoxin impaired systemic and gut-associated immune responsiveness to mitogens. However, in the protein-malnourished mice, the degree of immune suppression did not correlate with endotoxin-induced mortality.

Oral-TPN-induced bacterial translocation and impaired immune defenses are reversed by refeeding

Although certain defined diets have been shown to promote bacterial translocation (BT), the ability to reverse diet-induced BT has not previously been investigated. Furthermore, little is known about the effects of defined diets on host immune defenses. To address these questions, we measured BT and immune reactivity in rats fed a normal diet or enteral elemental (ORAL-TPN) diet. After 7 days on the elemental or normal diet, the rats were killed, and BT and mitogen responsiveness to concanavalin A and phytohemagglutinin were measured. In separate experiments, the effects of these diets on in vivo host defenses was measured with a Staphylococcus aureus abscess model. Additional experiments were performed to determine the time required to reverse ORAL-TPN-induced BT and impairment of host immune defenses by reinstituting normal feedings. Administration of the ORAL-TPN diet for 7 days was associated with BT to the mesenteric lymph node complex of all animals, decreased blastogenic response of blood and splenic lymphocytes to mitogens, and decreased ability to control an in vivo infectious challenge with S. aureus. Each of the derangements was reversed by the reinstitution of normal feedings. In summary, the enteral administration of an elemental diet for 7 days is associated with disruption of the gut microflora, BT, and the development of an immunocompromised state, all of which can be reversed by refeeding the animals a normal diet.

Bacterial translocation from the gut impairs systemic immunity

The goal of this study was to determine the influence of bacterial translocation on systemic immunity, since bacteria and their products play a major role in the development and maintenance of the host's immune system. To test this hypothesis, we measured the blastogenic response of mononuclear cells harvested from the blood, spleen, Peyer's patches, and mesenteric lymph nodes of control and Escherichia coli C25 monoassociated mice to a battery of mitogens. The E. coli C25 monoassociation model was used because this bacterial translocation model is not associated with experimental manipulations that are likely to affect the systemic immune system. The mitogenic response of lymphocytes isolated from the E. coli C25 monoassociated mice was significantly depressed compared to the control groups (p less than 0.01). Since the biologic significance of depressed in vitro mitogen responsiveness is difficult to determine, we assessed the ability of the mice to control a bacterial challenge using an in vivo Staphylococcus aureus abscess model. It appears that the observed changes in mitogen responsiveness may be of biologic significance, since the ability of the E. coli C25 monoassociated mice to control the injected S. aureus was impaired (p less than 0.01). These results suggest that an association exists between bacterial translocation and decreased systemic immune responsiveness.

Randomized trial of the effect of drugs on cervical dilatation for termination of first trimester pregnancy

A randomized triple-blind and placebo-controlled clinical trial on the effect of lidocaine and Anodyne-lubricant jelly (ALJ) containing dicaine on cervical dilatation is reported. Three-hundred-seventy-two consecutive cases were randomly allocated to 4 groups. The four groups were given: ALJ and placebo (placebo 1); and lidocaine and placebo (placebo 2). ALJ and placebo 1 treatment was by topical application, and lidocaine and placebo 2 by injection. In parous women, a significant difference was found for satisfactory dilatation (SD) rate (p less than 0.01) among four groups. It was unexpected that there were no significant differences between drug and placebo groups, neither between ALJ treatment group and placebo 1 group (p greater than 0.5), nor between lidocaine and placebo 2 (p greater than 0.75). However, the combined SD rate was 60.9% for the topical groups compared with 39.0% for the injection groups (p less than 0.005). The findings suggested that the effect of ALJ on cervical dilatation was not mainly due to dicaine, but associated with the lubricant and the topical treatment.

Effect of local and systemic burn microenvironment on neutrophil activation as assessed by complement receptor expression and morphology

Previously, we documented that humoral factors, especially complement products, contained in burn wound blister fluid (BF) modulate normal neutrophil (PMN) function and metabolism. The goal of the current study was to examine the effects of the local (BF) and systemic (burn serum or plasma) burn microenvironment on PMN activation as assessed by complement receptor expression and morphology. Induction of CR1 (C3b) and CR3 (iC3b) receptor expression of normal PMNs after incubation in medium, BF, or plasma (serum) from healthy volunteers or burned patients was measured using monoclonal antibodies and flow cytometry. BF (10% v/v, 37 degrees C) induced 25% more CR1 receptor expression than control or burn plasma (p less than 0.05), while the levels of CR3 expression of PMNs incubated in BF (10% or 80% v/v at 37 degrees C) was more than 300% that found when the PMNs were incubated in medium, burn, or patient plasma (p less than 0.05). The electron microscopic appearance of PMNs incubated in these fluids documented that degranulation was greater when cells were incubated in BF than medium, control, or patient plasma. These results indicate that PMN activation (CR1 and CR3 expression) is greater in cells exposed to the local (BF) than the systemic (plasma) humoral microenvironment shortly after thermal injury.

Different lymphocyte compartments respond differently to mitogenic stimulation after thermal injury

Because of the association between the development of an immunocompromised state and an increased risk of infection, increasing attention has been focused on describing and characterizing the immune consequences of thermal injury. Results of human studies are largely based on the in vitro responsiveness of peripheral blood leukocytes, while splenocytes are generally used in the animal studies. Because the response of lymphocytes from different lymphocyte compartments may vary, we compared the responses of murine peripheral blood, splenic, Peyer's patch, and mesenteric lymph node lymphocytes to a battery of mitogens after thermal injury. Burn-induced immunosuppression was maximal in the splenic lymphocyte compartment, where the responses to all three test mitogens were depressed throughout the 28-day postburn study period. Although the PHA-induced mitogen response of lymphocytes from the other three lymphoid compartments remained suppressed throughout the study period, the response to the mitogens Con-A and PWM generally returned to normal or supranormal levels by the seventh postburn day, Therefore it appears that the effect of a thermal injury on lymphocyte function varies according to the lymphocyte compartment examined and the mitogen tested. These results raise the question of whether animal studies using splenic lymphocytes can be correlated with human studies performed on circulating blood lymphocytes.

[A modified procedure for estimating pA2--equi-concentration effect method]

This new procedure was proposed under the necessity of a fixed concentration of an agonist in the absence/presence of an antagonist. As the odds ratio (OR) of the effects in the absence/presence of the antagonist under a fixed concentration is equal to the equi-effective dose ratio (DR) under a fixed effect, it is possible to substitute OR for DR in A - S equation. Since the experiment is less expensive and more convenient than that of Arunlakshana and Schild, and the procedure for obtaining OR is much more time-saving and economic than that for obtaining DR, it is worthy for analyzing a competitive antagonist.

Etiological types and clinical and epidemiological features of acute viral hepatitis in Xi'an in China

The etiological types and some features of 163 in-patients with acute viral hepatitis in Xi'an in China are reported. Hepatitis A (HA) accounted for 89.2% in the age group 0-15 years, whereas hepatitis B (HB) mainly occurred at the age of 16 to 30 and non-A, non-B hepatitis 31 to 50. This is different from the age distribution in western countries. The cause of the difference is discussed. The transmission factors of NANB hepatitis might be different from those of HA and HB. Fever was more often seen in HA than in HB and NANB, while the maximal bilirubin was higher in HB than in NANB. Hepatic dysfunction of all three types of hepatitis seemed to be closely associated with the age of the patients. Of ten cases with fulminant hepatitis, none was due to hepatitis A; nine were adults.