In vitro macrophage endotoxin tolerance: defective in vitro macrophage map kinase signal transduction after LPS pretreatment is not present in macrophages from C3H/HeJ endotoxin resistant mice

Altered endotoxin (LPS) signal transduction in macrophages (Mphi) may mediate development of organ dysfunction in sepsis. C3H/HeJ Mphi have a specific genetic defect that renders them "tolerant" to in vitro LPS activation. LPS tolerance can be induced in normal C3H/HeN Mphi following in vitro LPS pretreatment. In these experiments, in vitro LPS-stimulated activation of Mphi mitogen-activated protein (MAP) kinases were compared in C3H/HeJ and C3H/HeN mice. C3H/HeJ and C3H/HeN Mphi were cultured+/-10 ng/mL LPS pretreatment for 24 h, then stimulated with 0-1,000 ng/mL LPS for 6 h. Western blots were performed on lysates with monoclonal antibody to active ERK1,2 (p42/44), stress-activated protein kinase (SAPK, p54/46), and p38 kinase. Supernatant TNF or IL-1 was determined by bioassay. High dose LPS stimulation activated ERK, SAPK, and p38 kinases in both C3H/HeN and C3H/HeJ Mphi. ERK activation, p46 SAPK, and p38 activation were inhibited in C3H/HeN Mphi after LPS pretreatment, whereas they were unchanged or increased in HeJ Mphi. TNF secretion was significantly decreased in C3H/HeN Mphi following LPS pretreatment, but absent in C3H/HeJ Mphi at all times. Mphi from normal C3H/HeN mice rendered endotoxin tolerant by in vitro, low dose LPS pretreatment have specific signal transduction defects that are not present in genetically LPS hyporesponsive C3H/HeJ mice.

Acetazolamide treatment prevents in vitro endotoxin-stimulated tumor necrosis factor release in mouse macrophages

We previously showed that incubation in carbon dioxide (CO2), but not air or helium (He), markedly decreased macrophage intracellular pH (pHi) and resulted in reversible inhibition of lipopolysaccharide- (LPS) stimulated tumor necrosis factor (TNF) and interleukin-1 release. We sought to determine whether carbonic anhydrase inhibition with acetazolamide would prevent CO2-mediated inhibition of LPS-stimulated TNF release. Murine peritoneal macrophages were treated with acetazolamide for 1 h under control atmosphere (95% air/5% CO2) and then switched to incubator modules containing: 1) 80% CO2/20% O2, 2) 80% He/20% O2, or 3) 100% air. Before transfer to experimental atmospheric conditions the macrophages were stimulated with 0 or 1 microg/mL of LPS (Escherichia coli 0111 B4). Supernatant TNF was measured 4 h later by bioassay. In parallel experiments LPS-stimulated cytokine mRNA was estimated using reverse transcriptase polymerase chain reaction (RT-PCR) 2 h after LPS stimulation. Viability was determined using dye uptake. Incubation in CO2 or helium had no effect on TNF production in the absence of LPS. In the absence of acetazolamide CO2 produced marked inhibition of LPS-stimulated TNF release, but this was not blocked by the presence of acetazolamide. This CO2-mediated inhibition of TNF was associated with normal levels of TNF mRNA. In acetazolamide-treated macrophages, LPS resulted in a dose-dependent inhibition of TNF release when the cells were incubated in air or helium. Maintenance of normal intracellular pH is required for TNF release, but not TNF mRNA induction by LPS. Factors that alter intracellular pH regulation may modulate LPS-stimulated cytokine production.

Assessment of the relationship between timing of fixation of the fracture and secondary brain injury in patients with multiple trauma

BACKGROUND

It has been suggested that early fixation of a fracture is deleterious to eventual neurologic outcome. We undertook this study to determine whether the timing of fracture fixation is correlated to neurologic outcome.

METHODS

We retrospectively reviewed patients with severe head and orthopedic injuries requiring fracture fixation. Patients were divided into two groups: early fracture fixation (< 24 hours after injury) and late fracture fixation (> 24 hours after injury).

RESULTS

One hundred twenty-three patients met entry criteria. During fracture fixation, the early group had a significant 2-, 3-, and 2-fold increase in crystalloid, blood infusion, and blood loss, respectively. There was no difference in oxygen saturation and systolic blood pressure or episodes of cranial hypertension or hypoperfusion. There was no difference in outcomes as measured by in-hospital complications, stay in the intensive care unit or hospital, mortality rates, hospital discharge or follow-up Glasgow Coma Scores, or long-term orthopedic or neurologic results.

CONCLUSIONS

Patients undergoing fracture fixation with severe head injury mandate monitoring of intracranial pressure and perfusion and tailored fluid resuscitation to meet specific organ end points. Integrating end organ perfusion and pressure with meticulous fluid status during the definitive repair phase may reduce the exposure to secondary brain injury in patients undergoing early fracture fixation.

Lipopolysaccharide pretreatment produces macrophage endotoxin tolerance via a serum-independent pathway

BACKGROUND

Lipopolysaccharide activation (LPSa) of macrophages is thought to occur via a CD14-dependent mechanism with a requirement for the serum factor, lipopolysaccharide binding protein. LPS-stimulated, CD14-dependent signal transduction is associated with phosphorylation of mitogen-activated protein kinase (MAPK), nuclear factor-kappaB (NF-kappaB) translocation, and secretion of tumor necrosis factor (TNF) and interleukin-1 (IL-1). Macrophage endotoxin tolerance after low-dose LPS pretreatment (LPSp) is characterized by inhibition of LPSa-stimulated TNF and augmentation of IL-1 secretion. We sought to determine the role of CD14-dependent pathways in the induction of endotoxin tolerance by comparing the effects of LPSp in the presence or absence of serum.

METHODS

Murine peritoneal macrophages were exposed to a range of LPSp concentrations in the presence or absence of serum. MAPK activation and NF-kappaB were assayed 30 minutes after LPSp stimulation. TNF production and IL-1 were measured 6 hours after stimulation with 100 ng/mL LPSa, with or without 24-hour 10 ng/mL LPSp.

RESULTS

In the presence of serum, 100 ng/mL LPSp activated MAPK and NF-kappaB, whereas no activation of MAPK or NF-kappaB was seen at this LPSp concentration in the absence of serum. The absence of serum during 10 ng/mL LPSp did not prevent LPSp-mediated inhibition of TNF secretion, and it significantly augmented IL-1 secretion after stimulation with 100 ng/mL LPSa in the presence of serum.

CONCLUSION

Induction of the alterations in subsequent LPSa-stimulated cytokine secretion characteristic of endotoxin tolerance by LPSp occurs via a serum-independent signal transduction pathway.

Arabidopsis LEAFY COTYLEDON1 is sufficient to induce embryo development in vegetative cells

The Arabidopsis LEAFY COTYLEDON1 (LEC1) gene is required for the specification of cotyledon identity and the completion of embryo maturation. We isolated the LEC1 gene and showed that it functions at an early developmental stage to maintain embryonic cell fate. The LEC1 gene encodes a transcription factor homolog, the CCAAT box-binding factor HAP3 subunit. LEC1 RNA accumulates only during seed development in embryo cell types and in endosperm tissue. Ectopic postembryonic expression of the LEC1 gene in vegetative cells induces the expression of embryo-specific genes and initiates formation of embryo-like structures. Our results suggest that LEC1 is an important regulator of embryo development that activates the transcription of genes required for both embryo morphogenesis and cellular differentiation.

Arabidopsis LEAFY COTYLEDON1 is sufficient to induce embryo development in vegetative cells

The Arabidopsis LEAFY COTYLEDON1 (LEC1) gene is required for the specification of cotyledon identity and the completion of embryo maturation. We isolated the LEC1 gene and showed that it functions at an early developmental stage to maintain embryonic cell fate. The LEC1 gene encodes a transcription factor homolog, the CCAAT box-binding factor HAP3 subunit. LEC1 RNA accumulates only during seed development in embryo cell types and in endosperm tissue. Ectopic postembryonic expression of the LEC1 gene in vegetative cells induces the expression of embryo-specific genes and initiates formation of embryo-like structures. Our results suggest that LEC1 is an important regulator of embryo development that activates the transcription of genes required for both embryo morphogenesis and cellular differentiation.

Minor psychiatric disorder in NHS trust staff: occupational and gender differences

BACKGROUND

It is widely suggested that many National Health Service (NHS) workers experience high levels of minor psychiatric disorder. However, inadequacies of sampling and measurement in studies to date have not allowed this suggestion to be properly evaluated.

METHOD

The present study was designed to overcome these methodological weaknesses by using a sample of over 11,000 employees from 19 NHS trusts and a well-established measure of minor psychiatric disorder for which there are comparative data.

RESULTS

The findings show that 26.8% of the health service workers reported significant levels of minor psychiatric disorder, compared with 17.8% of people in the general population. Psychiatric morbidity was highest among managers, doctors, nurses and professions allied to medicine, with each of these groups recording higher rates than their professional counterparts outside the health service. It was lower among those in support occupations, such as administrative and ancillary staff. A feature of the findings was that female doctors and managers showed a much higher prevalence of minor psychiatric disorder than their male colleagues.

CONCLUSION

Studies are required to establish the organisational, occupational and individual determinants of minor psychiatric disorder among NHS employees.

Isolation and ultrastructural study of the flagellar basal body complex from Rhodobacter sphaeroides WS8 (wild type) and a polyhook mutant PG

Filament-Hook-Basal Body (FHBB) complexes were isolated from the purple non-sulphur facultative anaerobic bacterium Rhodobacter sphaeroides (WS8) by lysozyme digestion of the cells followed by an alkaline treatment and ultracentrifugation, and they were analysed by electron microscopy. The structure is composed of a filament linked through an enlarged junction to the hook and a basal body composed of L and P rings, a rod, and a less well-defined cytoplasmic ring that has evidence of additional attached structures. Hook-basal body complexes isolated from a mutant (PG) which produces an extended hook but no filament shows basal body structures identical to those of wild-type FHBBs.

The role of ADP-ribosylation factor and phospholipase D in adaptor recruitment

AP-1 and AP-2 adaptors are recruited onto the TGN and plasma membrane, respectively. GTPgammaS stimulates the recruitment of AP-1 onto the TGN but causes AP-2 to bind to an endosomal compartment (Seaman, M.N.J., C.L. Ball, and M.S. Robinson. 1993. J. Cell Biol. 123:1093-1105). We have used subcellular fractionation followed by Western blotting, as well as immunofluorescence and immunogold electron microscopy, to investigate both the recruitment of AP-2 adaptors onto the plasma membrane and their targeting to endosomes, and we have also examined the recruitment of AP-1 under the same conditions. Two lines of evidence indicate that the GTPgammaS-induced targeting of AP-2 to endosomes is mediated by ADP-ribosylation factor-1 (ARF1). First, GTPgammaS loses its effect when added to ARF-depleted cytosol, but this effect is restored by the addition of recombinant myristoylated ARF1. Second, adding constitutively active Q71L ARF1 to the cytosol has the same effect as adding GTPgammaS. The endosomal membranes that recruit AP-2 adaptors have little ARF1 or any of the other ARFs associated with them, suggesting that ARF may be acting catalytically. The ARFs have been shown to activate phospholipase D (PLD), and we find that addition of exogenous PLD has the same effect as GTPgammaS or Q71L ARF1. Neomycin, which inhibits endogenous PLD by binding to its cofactor phosphatidylinositol 4,5-bisphosphate, prevents the recruitment of AP-2 not only onto endosomes but also onto the plasma membrane, suggesting that both events are mediated by PLD. Surprisingly, however, neither PLD nor neomycin has any effect on the recruitment of AP-1 adaptors onto the TGN, even though AP-1 recruitment is ARF mediated. These results indicate that different mechanisms are used for the recruitment of AP-1 and AP-2.

Mechanism of decreased in vitro murine macrophage cytokine release after exposure to carbon dioxide: relevance to laparoscopic surgery

OBJECTIVE

The objective of this study was to determine the effect of carbon dioxide (CO2) on the function of peritoneal macrophages.

SUMMARY BACKGROUND DATA

Laparoscopic surgery is associated with minimal pain, fever, and low levels of inflammatory cytokines. To understand the mechanisms involved, the authors investigated the effect of different gases on murine peritoneal macrophage intracellular pH and correlated these alterations with alterations in LPS-stimulated inflammatory cytokine release.

METHODS

Peritoneal macrophages were incubated for 2 hours in air, helium, or CO2, and the effect of the test gas on immediate or next day lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) and interleukin-1 release compared. Cytosolic pH of macrophages exposed to test gases was measured using single-cell fluorescent imaging. The in vivo effects of test gases were determined in anesthetized rats during abdominal insufflation.

RESULTS

Macrophages incubated in CO2 produced significantly less TNF and interleukin-1 in response to LPS compared to incubation in air or helium. Cytokine production returned to normal 24 hours later. Exposure to CO2, but not air or helium, caused a marked cytosolic acidification. Pharmacologic induction of intracellular acidification to similar levels reproduced the inhibitory effect. In vitro studies showed that CO2 insufflation lowered tissue pH and peritoneal macrophage LPS-stimulated TNF production.

CONCLUSIONS

The authors propose that cellular acidification induced by peritoneal CO2 insufflation contributes to blunting of the local inflammatory response during laparoscopic surgery.

Protein kinase C regulates macrophage tumor necrosis factor secretion: direct protein kinase C activation restores tumor necrosis factor production in endotoxin tolerance

BACKGROUND

Macrophages pretreated in vitro with endotoxin (LPSp) secrete less tumor necrosis factor (TNF) in response to a second LPS activating (LPSa) stimulus. Protein kinase C (PKC) is required for TNF secretion in a macrophage stimulated with LPSa. In these experiments we examined the role of PKC in TNF signal transduction in naive and tolerant macrophages.

METHODS

Murine macrophages were cultured +/- LPSp for 24 hours. Cultures were washed and treated for 1 hour with PKC inhibitors or phorbol myristate acetate (PMA), a direct PKC activator. Cells were then stimulated with a range of LPSa for 6 hours, and TNF was determined by bioassay.

RESULTS

LPSa-stimulated TNF secretion by nontolerant macrophages was inhibited by LPSp in the absence of PMA. PKC inhibitors decreased TNF by naive macrophages and exaggerated inhibition in tolerant cells. Depletion of PKC by 24 hours of PMA decreased TNF production by both naive and tolerant macrophages. PKC activation with PMA 1 hour before LPSa augmented TNF secretion in naive cells and reversed TNF inhibition of tolerant cells.

CONCLUSIONS

Direct PKC activation with PMA restored TNF secretion in LPS-tolerant macrophages. Endotoxin tolerance may alter the LPSa signal transduction pathway between the LPS receptor and PKC activation.

Opposite effects on two different measures of retention following unilateral inactivation of the amygdala

We previously reported finding differential effects of unilateral infusion of lidocaine into the right and left amygdalae prior to a retention test 24 h after one-trial inhibitory avoidance training. The present study was undertaken to determine whether the degree of training in an escape task influences the effects of unilateral inactivation of the amygdala with lidocaine prior to the retention test. Male Sprague-Dawley rats, implanted with bilateral cannulae aimed at the amygdaloid complex received 0 (no shock), 2, or 10 training trials in a footshock-motivated escape task (0.4 mA). Forty-eight h later, the rats received bilateral microinfusions into the amygdalae of either buffer, or lidocaine into one amygdala and buffer in the other, 5 min before they were tested for retention of the escape training using a continuous multiple trial inhibitory avoidance (CMIA) procedure (0.4 mA). Forty-eight h after CMIA training the animals were retested, this time without influence of drugs. As indicated by initial response latencies on the first retention test, unilateral inactivation of either the right or the left amygdala severely impaired retention performance for the escape training regardless of the number of prior escape training trials received. However, unilateral inactivation of either amygdala had no effect on acquisition of CMIA. Furthermore, unilateral inactivation of either amygdala during CMIA training did not affect retention tested 48 h later. These results suggest that the differential involvement of the right and left amygdalae may be limited to certain training conditions. Furthermore, these findings demonstrate opposite effects on 2 different measures of retention indicating that the method of testing retention affects the interpretation of the memory impairment induced by infusion of lidocaine into the amygdala.

In vivo endotoxin tolerance: impaired LPS-stimulated TNF release of monocytes from patients with sepsis, but not SIRS

In vitro pretreatment of human monocytes (MO) with low-dose lipopolysaccharide (LPSp) inhibits TNF release in response to subsequent LPSa activation. Septic patients are often indistinguishable from patients with systemic inflammatory response syndrome (SIRS). We hypothesized that in vivo exposure to "septic" stimuli impairs subsequent LPSa-stimulated MO TNF production in vitro. Human peripheral MO were obtained after informed consent from controls or patients with sepsis, SIRS, or posttrauma [ACCP/SCCM definitions]. Cells were plated in vitro, incubated 24 hr, and then stimulated with 0-1000 ng/ml LPSa for 4 hr. Parallel control MO were incubated in vitro with 100 ng/ml LPSp for 24 hr and then stimulated with 1000 ng/ml LPSa for 4 hr. Supernatant TNF (mean U/ml +/- SEM) was measured by bioassay. ANOVA was used to determine statistical significance. In vitro LPSp pretreatment markedly inhibited subsequent LPSa-stimulated TNF release. In vitro LPSa-stimulated TNF release was likewise significantly inhibited with MO from septic patients compared to controls. Inhibition was more profound in septic patients with shock (not shown). No impaired TNF release was seen with MO from SIRS or trauma patients. In conclusion, in vivo preexposure to inflammatory stimuli in septic patients alters monocyte regulation in a manner similar to in vitro endotoxin tolerance. Provocative in vitro monocyte LPS stimulation may distinguish patients with sepsis and SIRS.

LPS pretreatment reprograms macrophage LPS-stimulated TNF and IL-1 release without protein tyrosine kinase activation

Pretreatment of macrophages with low-dose endotoxin (LPSp) profoundly alters cytokine release in response to subsequent LPSa activation. These qualitative and quantitative alterations in cytokine release have been termed macrophage reprogramming. Macrophage activation by LPS is thought to occur via a mechanism involving an early protein tyrosine kinase (PTK) phosphorylation step. PTK inhibition with genistein or herbimycin A blocks LPSa-stimulated secretion of tumor necrosis factor (TNF) and interleukin-1 (IL-1). In this study we investigated whether a PTK pathway participates in LPSp pretreatment reprogramming. We show that LPSp pretreatment inhibited TNF and augmented IL-1 release in response to subsequent LPSa stimulation. Blockade of PTK activation pathways during the interval when macrophages were exposed to LPSp prevented mitogen-activated protein kinase phosphorylation, as well as LPSp-stimulated release of TNF and IL-1, but did not block LPSp reprogramming effects. We conclude that LPSp pretreatment reprogramming of macrophage cytokine production does not require PTK activation.

Role of calcium in lipopolysaccharide-stimulated tumor necrosis factor and interleukin-1 signal transduction in naive and endotoxin-tolerant murine macrophages

OBJECTIVE

Dysregulated macrophage cytokine production may predispose to organ failure during sepsis. Macrophages pretreated in vitro with low-dose endotoxin (LPSp) become "tolerant" to subsequent lipopolysaccharide (LPS) activation (LPSa), characterized by inhibition of tumor necrosis factor (TNF) and augmentation of interleukin-1 (IL-1). To understand cytokine dysregulation we examined the Ca2+ dependence of TNF and IL-1 signal transduction to LPSa and whether it was altered by LPSp.

METHODS

Murine peritoneal exudate macrophages received +/- 100 ng/mL of LPSp for 24 hours. Cultures were pretreated for 2 hours with specific signal transduction inhibitors (verapamil, a Ca2+ channel inhibitor; TMB-8, an inhibitor of intracellular Ca2+ release; U73122, an inhibitor of phospholipase C; or W7, a calmodulin inhibitor) before 24 hours LPSa-stimulation. TNF and IL-1 mRNA were estimated 6 hours after LPSa by using reverse transcriptase polymerase chain reaction. Supernatant TNF and IL-1 were measured by bioassay.

RESULTS

Treatment with verapamil, TMB-8, U73122, or W7 markedly inhibited TNF release by LPSa, but had little effect on IL-1 release. Reprogramming by LPSp did not alter the Ca2+ signal transduction pathways for either cytokine. U73122 and verapamil did prevent the augmentation of IL-1 release seen after LPSp. TNF message was present after LPSa despite reprogrammed inhibition of TNF protein by LPSp. Signal transduction inhibitors that blocked Ca2+ altered TNF and IL-1 message in reprogrammed macrophages in a pattern similar to their effects on naive cells.

CONCLUSIONS

Intracellular Ca2+ is required for TNF protein release by naive macrophages and TNF mRNA transcription of both naive and LPSp reprogrammed cells, however LPSa-stimulated IL-1 release in peritoneal macrophages does not require Ca2+ dependent signaling pathways.

Kinetics of decreased LPS-stimulated cytokine release by macrophages exposed to CO2

The mechanisms responsible for the lack of inflammation after laparoscopic surgery remain unknown. Peritoneal macrophages (M phi) incubated in carbon dioxide (CO2) but not air or helium (He), had significant, reversible inhibition of lipopolysaccharide (LPS)-stimulated tumor necrosis factor (TNF) and interleukin-1 (IL-1) release. In these experiments the kinetics of these C02-induced alterations in cytokine secretion were examined. Murine peritoneal Mphi were stimulated with LPS for 4 hr and incubated in different test gases (95% air/5% CO2,80%CO2/20%O2,80% He/20% O2) for intervals between 0.25 and 4 hr. Time between gas incubation and LPS stimulation was varied to determine the persistence of CO2 inhibition. Parallel M phi groups received LPS stimulation 24 hr later. Supernatant TNF and IL-1 were measured by bioassay and polymerase chain reaction was used to examine cytokine mRNA. Significant reversible inhibition of TNF and IL-1 was seen with CO2, but not He or air. Inhibition of IL-1 occurred 15 min after CO2 exposure, was associated with decreased IL-1 mRNA, and was rapidly lost following incubation in the control atmosphere. TNF inhibition was seen despite normal levels of TNF message, required more than 30 min of CO2 exposure, and persisted after CO2 removal. CO2 produced profound, reversible, inhibition of LPS-stimulated cytokine release by peritoneal Mphi. The transient inability to secrete inflammatory cytokines after CO2 exposure may explain the lack of systemic inflammation after laparoscopic surgery with CO2.

Discordant reprogramming of LPS-stimulated cytokine gene transcription and secretion by macrophages after LPS pretreatment

Dysregulated macrophage (Mphi) cytokine release occurs during systemic inflammation and may predispose to organ failure. We showed that Mphis pretreated (PreRx) in vitro with low-dose LPSp are "reprogrammed" to release less TNF and more IL-1 in response to subsequent LPS activation (LPSa). The effects of this LPSp "reprogramming" on Mphi cytokine gene transcription were investigated in the present study. Murine peritoneal exudate Mphis were cultured in vitro 48 hr, then PreRx 24 hr +/- 100 ng/ml of LPSp. Cultures were stimulated with 0-1000 ng/ml LPSa and 6-hr supernatant TNF and IL-1 were measured using specific bioassays. Cytokine gene transcription was estimated 6 hr after LPSa using RT-PCR. PreRx with LPSp inhibited TNF and augmented IL-1 release by LPSa. PreRx with LPSp significantly inhibited cytokine gene transcription; however, messages for both TNF and IL-1 were detectable after high-dose LPSa. Despite LPSp inhibition of IL-1 transcription by most LPSa concentrations, IL-1 protein was augmented by PreRx. High-dose LPSa can override LPSp reprogrammed inhibition of cytokine gene transcription, but altered TNF and IL-1 protein release after LPSp may be regulated posttranscriptionally.

A novel adaptor-related protein complex

Coat proteins are required for the budding of the transport vesicles that mediate membrane traffic pathways, but for many pathways such proteins pathways, but for many pathways such proteins have not yet been identified. We have raised antibodies against p47, a homologue of the medium chains of the adaptor complexes of clathrin-coated vesicles (Pevsner, J., W. Volknandt, B.R. Wong, and R.H. Scheller. 1994. Gene (Amst.). 146:279-283), to determine whether this protein might be a component of a new type of coat. p47 coimmunoprecipitates with three other proteins: two unknown proteins of 160 and 25 kD, and beta-NAP, a homologue of the beta/beta'-adaptins, indicating that it is a subunit of an adaptor-like heterotetrameric complex. However, p47 is not enriched in preparations of clathrin-coated vesicles. Recruitment of the p47-containing complex onto cell membranes is stimulated by GTP gamma S and blocked by brefeldin A, indicating that, like other coat proteins, its membrane association is regulated by an ARF. The newly recruited complex is localized to non-clathrin-coated buds and vesicles associated with the TGN. Endogenous complex in primary cultures of neuronal cells is also localized to the TGN, and in addition, some complex is associated with the plasma membrane. These results indicate that the complex is a component of a novel type of coat that facilitates the budding of vesicles from the TGN, possibly for transporting newly synthesized proteins to the plasma membrane.

Hypoxic alterations in cellular signal transduction in shock and sepsis

Many different cellular processes are altered by microenvironmental changes in the oxygen level, particularly hypoxia. In most cases, these hypoxic effects are mediated via alterations in cellular signal transduction pathways. Low oxygen states are generally viewed as deleterious; however, recent studies show that alterations in oxygen levels are physiologically important, influencing cells in a variety of ways. Low oxygen levels can stimulate cellular processes, such as the production of tumor necrosis factor, interleukin (IL)-1, IL-8, and nuclear factor kappa B. Kupffer cell-mediated alterations in cocultured hepatocyte function are altered by pre-exposure to hypoxic culture conditions, whereas superoxide production, intracellular pH, and adenosine triphosphate levels are decreased by hypoxia. Hypoxia followed by reoxygenation stimulates tyrosine kinase enzymes and increases intracellular calcium in a variety of cells. This review highlights recent findings concerning the manner and mechanisms by which low oxygen levels influence cell functions and cellular signaling systems. Detailed information is still lacking about the location and mechanism of most hypoxic-mediated alterations in cell signaling pathways. However, information about how factors altered by trauma and sepsis, such as Po2, acidosis, and endotoxin, effect cellular signaling pathways is rapidly emerging. Understanding the mechanism by which oxygen availability alters cell function will be important to the development of optimal therapies for post-traumatic shock and organ dysfunction.

Malignancy, mortality, and medicosurgical management of Clostridium septicum infection

BACKGROUND

Necrotizing Clostridium septicum infections (CSI) have a strong association with malignancy or immunosuppression. To clarify this relationship and determine how it impacted mortality, the experience with CSI at a single institution was reviewed.

METHODS

Records of all patients admitted to our hospital with culture proven clostridial infection from 1966 through 1993 were reviewed.

RESULTS

Among patients presenting with clinical gas gangrene, 281 had culture proven clostridial infection and 32 (11.4%) had CSI. The mortality among CSI patients was 56%, whereas 26% of all patients with clostridial infections died (p = 0.001). An associated malignancy was found in 50% of patients with CSI, whereas this was seen in only 11% of patients with other clostridial infections (p = 0.0001 for CSI versus clostridial infection overall). The remaining patients with spontaneous CSI all had evidence of immunosuppression.

CONCLUSIONS

The high mortality and likelihood of associated malignancy or hematologic disease underscore the importance of a high index of suspicion and the need to search for and treat associated conditions in all patients with CSI.

Reprogrammed macrophage tumor necrosis factor and interleukin-1 release with inflammatory pretreatment: differential regulation by endotoxin and zymosan

OBJECTIVE

To determine whether different reprogrammed alterations in endotoxin (lipopolysaccharide, LPS)-stimulated tumor necrosis factor (TNF) and interleukin-1 (IL-1) release are seen following pretreatment with endotoxin (LPSp) or pretreatment with the particulate inflammatory stimulus zymosan.

METHODS

Murine peritoneal macrophages (M phi) pretreated for 24 hours in vitro with medium, LPSp, zymosan, latex beads, or killed Escherichia coli. After 24 hours M phi were restimulated with medium, LPSa, zymosan, latex beads, or E. coli, M phi supernatant TNF and IL-1 were measured after 24 hours and mRNA levels determined after 6 hours with reverse-transcriptase polymerase chain reaction.

RESULTS

Pretreatment with low dose LPSp markedly inhibited TNF release by both LPSa or zymosan, while pretreatment with zymosan increased LPSa-stimulated TNF release. Pretreatment with both LPSp and zymosan augmented LPSa and zymosan-stimulated IL-1. Zymosan pretreatment augmentation of TNF and IL-1 was accompanied by lower than basal levels of cytokine message.

CONCLUSION

Reprogrammed macrophage TNF and IL-1 release was differentially regulated by distinct inflammatory stimuli. Understanding reprogrammed macrophage cytokine regulation may enable specific therapy to modify dysregulated cytokine release during sepsis and trauma.

Mechanisms of reprogrammed macrophage endotoxin signal transduction after lipopolysaccharide pretreatment

BACKGROUND

Dysregulation of macrophage tumor necrosis factor (TNF) and interleukin-(IL-1) release results from repetitive lipopolysacharride (LPS) stimulation. In this study we investigated the mechanisms of LPS pretreatment (LPSp) signal transduction producing altered LPS-activated (LPSa) cytokine release.

METHODS

Murine macrophages were treated with medium alone, actinomycin D, cycloheximide, a protein kinase C inhibitor (H7), or the nitric oxide synthase inhibitor L-NMA. Macrophages were then pretreated with 100 ng/ml LPSp and cultured in medium alone, a nitric oxide donor (sodium nitroprusside), or a cyclic adenosine monophosphate donor (8 bromoadenosine) for 20 hours. Cultures were then washed, and fresh medium containing 1 microgram/ml LPSa was added. TNF and IL-1 release in 24-hour supernatant was measured by bioassays.

RESULTS

LPSp inhibited TNF and enhanced IL-1 release. The results with actinomycin D and cycloheximide suggested that LPSp effects did not require transcription, but IL-1 enhancement required protein synthesis. Addition of 8-bromo-cyclic adenosine monophosphate, H7, or nitroprusside prevented LPSp-induced augmentation of IL-1 but had no effect on inhibition of TNF release. Inhibition of LPSp-induced nitric oxide production with L-NMA had no effect on TNF or IL-1.

CONCLUSIONS

Complex, independent, but incompletely understood signal transduction pathways for LPSp-induced alterations in LPSa-stimulated macrophage TNF and IL-1 release were shown. Understanding altered signal transduction from prior LPS stimulation may suggest new therapies to control dysregulated macrophage cytokine release in sepsis.

Efficacy of radioprotective agents in preventing small and large bowel radiation injury

PURPOSE

A variety of adjuvant treatments and cytoprotective agents have been proposed to lessen the toxicity of radiation therapy. The following study was designed to evaluate the benefit of six agents or combinations using anastomotic bursting strength as a measure of transmural radiation injury.

METHODS

The 40-Gy study consisted of the following. Seventy-two male Sprague-Dawley rats were divided into eight equal groups: nonradiated control, radiated untreated control, and six radiated treated groups. The radioprotective treatments included ribose-cysteine (Rib-Cys), WR-2721, glutamine, vitamin E, MgCl2/adenosine triphosphate, and RibCys/glutamine in combination. Radiated animals received 40 Gy to the abdomen. Two weeks after radiation, all animals underwent small bowel and colonic resection with primary anastomosis. Animals were sacrificed one week postoperatively, at which time anastomoses were evaluated and bursting strengths determined. The 70-Gy study consisted of the following. The same protocol was repeated for five groups of nine rats divided into nonradiated, radiated untreated, and three radiated treated groups receiving RibCys (8 mmol/kg), RibCys (20 mmol/kg), and WR-2721. All radiated animals received 70-Gy doses.

RESULTS

In the 40-Gy group, there were 10 radiation-related deaths and 6 anastomotic leaks among 70 rats studied. None of the differences between groups were significant. Nonradiated control group small bowel and large bowel anastomotic bursting pressures were significantly elevated compared with all radiated groups. Compared with radiated controls, there were significant improvements in small bowel bursting strength in the RibCys, WR-2721, RibCys-glutamine, and vitamin E groups and significant improvement in colonic bursting strength in MgCl2/adenosine triphosphate, WR-2721, and RibCys groups. In the 70-Gy group, all nine nonradiated control rats survived. All eight untreated radiated control rats died, four of eight WR-2721 animals died (P = 0.03), all RibCys (8 mmol/kg) animals died (P = 0.03), and three of nine treated with RibCys (20 mmol/kg) survived (P = 0.08).

CONCLUSIONS

WR-2721 and RibCys gave consistent protection against large and small bowel radiation injury. The lower incidence of treatment-related toxicity and potentially equal or greater radioprotective effects may make RibCys more clinically useful than WR-2721.