Tumor necrosis factor-induced mortality is reversed with cyclooxygenase inhibition

Department of Surgery/College of Medicine University of South Alabama: Historical and Contemporaneous Perspectives

Many members of the medical profession in Mobile, Alabama, have exemplified a strong commitment to the education of their colleagues and successors, a tradition (L., traditio, “to hand over”) that dates from the early 18th century. The Mobile General (city/county) Hospital (1830 to 1970) and its successor, the Medical Center, University of South Alabama (1971 to the present), were the institutional foci of those endeavors. Because it is individuals who create, design, and vitalize institutions, this monograph is an acknowledgment of the accomplishments of those who gave that endeavor purpose, direction, and meaning, particularly with reference to the evolution of surgical education. Numerous clinical and societal forces—cultural, economic, political, and social—influenced that evolution. This compilation gives attribution to a legacy of commitment to health and medical/surgical care, education, and research within southern Alabama.

Cyclooxygenase-2 deficiency leads to intestinal barrier dysfunction and increased mortality during polymicrobial sepsis

Sepsis remains the leading cause of death in critically ill patients, despite modern advances in critical care. Intestinal barrier dysfunction may lead to secondary bacterial translocation and the development of the multiple organ dysfunction syndrome during sepsis. Cyclooxygenase (COX)-2 is highly upregulated in the intestine during sepsis, and we hypothesized that it may be critical in the maintenance of intestinal epithelial barrier function during peritonitis-induced polymicrobial sepsis. COX-2(-/-) and COX-2(+/+) BALB/c mice underwent cecal ligation and puncture (CLP) or sham surgery. Mice chimeric for COX-2 were derived by bone marrow transplantation and underwent CLP. C2BBe1 cells, an intestinal epithelial cell line, were treated with the COX-2 inhibitor NS-398, PGD(2), or vehicle and stimulated with cytokines. COX-2(-/-) mice developed exaggerated bacteremia and increased mortality compared with COX-2(+/+) mice following CLP. Mice chimeric for COX-2 exhibited the recipient phenotype, suggesting that epithelial COX-2 expression in the ileum attenuates bacteremia following CLP. Absence of COX-2 significantly increased epithelial permeability of the ileum and reduced expression of the tight junction proteins zonula occludens-1, occludin, and claudin-1 in the ileum following CLP. Furthermore, PGD(2) attenuated cytokine-induced hyperpermeability and zonula occludens-1 downregulation in NS-398-treated C2BBe1 cells. Our findings reveal that absence of COX-2 is associated with enhanced intestinal epithelial permeability and leads to exaggerated bacterial translocation and increased mortality during peritonitis-induced sepsis. Taken together, our results suggest that epithelial expression of COX-2 in the ileum is a critical modulator of tight junction protein expression and intestinal barrier function during sepsis.

Synergistic Therapeutic Potential of Dexamethasone and l-arginine in Lipopolysaccharide-Induced Septic Shock

BACKGROUND

Dexamethasone (DEX) is demonstrated to have anti-inflammatory properties and known to induce hemodynamic improvement in sepsis and septic shock. L-arginine (L-arg), a semi-essential amino acid, depending on its metabolic pathway, becomes very essential in stress situations such as heatstroke, burns, sepsis, trauma, and wound healing. The aim of this study was to evaluate the synergistic therapeutic effect of DEX and L-arg in rescuing the mice from experimental septic shock induced by bacterial lipopolysaccharide (LPS). The experiments were designed to delineate the molecular mechanisms responsible for the increased therapeutic benefit of the combination therapy (CT) in LPS-induced septic shock.

METHODS

Acute endotoxemia was induced in Swiss male mice by i.p. injection of LPS (18 mg kg(-1)) at 0 h. LPS-treated mice were divided into four groups. The first group (DEX group) received DEX (2 mg kg(-1)) i.p. at +2 h of LPS. The second group (L-arg group) received L-arg i.p. at a dose of 120 mg/kg at +6 h of LPS injection. The third group (CT group) received DEX (2 mg kg(-1)) at +2 h LPS followed by L-arg at +6 h of LPS injection. The fourth group received saline in place of L-arg or DEX (LPS group). A sham group was also included, where normal mice received saline in place of LPS or L-arg or DEX. At +6 h, mice from sham group, LPS group, and DEX group were sacrificed at +24 h. Mice from sham group, DEX group, L-arg group, and CT group were sacrificed to examine various parameters associated with LPS endotoxemia.

RESULTS

The CT with DEX followed by L-arg significantly increased the survival of mice injected with a lethal dose of LPS. Monotherapy with either DEX or L-arg given at the same dose and time did not increase the survival of the mice injected with LPS. DEX administration could significantly reduce the levels of serum TNF-alpha, IL-1beta, IFN-gamma, aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), and nitrite. DEX also down-regulated the expression of liver-inducible nitric oxide synthase (iNOS), and up-regulated the levels of serum anti-inflammatory cytokines like TGF-beta1 and IL-4, hepatic and splenic arginase, in LPS-injected mice. The enhanced therapeutic effect of CT correlated with reduced pathological symptoms, decreased Th1 cytokines, increased TGF-beta1 and arginase levels compared to the mice administered with either of the monotherapies. The CT group had significantly increased expression of hepatic Hsp 70 and reduced septic shock associated histopathology, in lung and liver, compared to the mice treated with either DEX or L-arg.

CONCLUSIONS

The therapeutic combination therapy with DEX and L-arg, at the appropriate dose, time, and sequence of administration, changed the cytokine profile, in favor of reducing the inflammatory response. The significantly enhanced survival observed in the CT group was accompanied by an increased hepatic Hsp 70, hepatic arginase, splenic arginase, and decreased organ injury. This novel concept of combined therapy could form the basis of an effective therapeutic approach in the treatment of sepsis and septic shock.

Effects of lornoxicam on the physiology of severe sepsis

Introduction

The purpose of the present study was to evaluate the effects of intravenous lornoxicam on haemodynamic and biochemical parameters, serum cytokine levels and patient outcomes in severe sepsis.

Methods

A total of 40 patients with severe sepsis were included, and were randomly assigned (20 per group) to receive either lornoxicam (8 mg administered intravenously every 12 hours for six doses) or placebo. For both groups the following were recorded: haemodynamic parameters (heart rate, mean arterial pressure), nasopharyngeal body temperature, arterial blood gas changes (pH, partial oxygen tension, partial carbon dioxide tension), plasma cytokine levels (IL-1β, IL-2 receptor, IL-6, IL-8, tumour necrosis factor-α), biochemical parameters (lactate, leucocytes, trombocytes, creatinine, total bilirubin, serum glutamate oxalate transaminase), length of stay in the intensive care unit, duration of mechanical ventilation and mortality. All measurements were obtained at baseline (before the start of the study) and at 24, 48 and 72 hours from the start of lornoxicam/placebo administration.

Results

No significant differences were found between the intravenous lornoxicam and placebo groups in major cytokines, duration of ventilation and length of intensive care unit stay, and inspired fractional oxygen/arterial oxygen tension ratio (P > 0.05).

Conclusion

In these patients with severe sepsis, we found intravenous lornoxicam to exert no effect on haemodynamic and biochemical parameters, cytokine levels, or patient outcomes. Because of the small number of patients included in the study and the short period of observation, these findings require confirmation by larger clinical trials of intravenous lornoxicam, administered in a dose titrated manner.

Alteration in heme oxygenase-1 and nitric oxide synthase-2 gene expression during endotoxemia in cyclooxygenase-2-deficient mice

Sepsis is a systemic inflammatory response to a blood-borne infection that is associated with an extremely high rate of morbidity and mortality. The present article reviews our recent studies involving the role of cyclooxygenase (COX)-2 in host responses to bacterial endotoxemia and its role in the regulation of nitric oxide synthase (NOS)2 and heme oxygenase (HO)-1. COX-2-deficient (-/-) mice display a blunted and delayed induction of the cytokine-inducible genes NOS2 and HO-1 after administration of Escherichia coli lipopolysaccharide (LPS or endotoxin). Translocation and activation of transcription factors important for signaling events during an inflammatory response, such as nuclear factor-kappaB and activating protein-1, are also reduced. In addition, COX-2(-/-) mice have reduced leukocyte infiltration into critical organs (kidneys and lungs) after LPS administration. Interestingly, the absence of COX-2 does not alter the LPS induction of several proinflammatory cytokines in tissue macrophages, but induction of the antiinflammatory cytokine interleukin-10 is exaggerated. After LPS administration, 50% of wild-type (+/+) mice die; however, COX-2(-/-) mice display a dramatic improvement in survival during endotoxemia. Taken together, our findings suggest that COX-2(-/-) mice are resistant to many of the detrimental consequences of endotoxemia.

Protection against lipopolysaccharide-induced sepsis and inhibition of interleukin-1β and prostaglandin E2 synthesis by silymarin

Silymarin is known to have hepatoprotective and anticarcinogenic effects. Recently, anti-inflammatory effect of silymarin is attracting an increasing attention, but the mechanism of this effect is not fully understood. Here, we report that silymarin protected mice against lipopolysaccharide (LPS)-induced sepsis. In this model of sepsis, silymarin improved the rate of survival of LPS-treated mice from 6 to 38%. To further investigate the mechanism responsible for anti-septic effect of silymarin, we examined the inhibitory effect of silymarin on interleukin-1beta (IL-1beta) and prostaglandin E2 (PGE2) production in macrophages. Silymarin dose-dependently suppressed the LPS-induced production of IL-1beta and PGE2 in isolated mouse peritoneal macrophages and RAW 264.7 cells. Consistent with these results, the mRNA expression of IL-1beta and cyclooxygenase-2 was also completely blocked by silymarin in LPS-stimulated RAW 264.7 cells. Moreover, the LPS-induced DNA binding activity of nuclear factor-kappaB/Rel was also inhibited by silymarin in RAW 264.7 cells. Taken together, these results demonstrate that silymarin has a protective effect against endotoxin-induced sepsis, and suggest that this is mediated, at least in part, by the inhibitory effect of silymarin on the production of IL-1beta and PGE2.

Cyclooxygenase-2-deficient mice are resistant to endotoxin-induced inflammation and death

Sepsis is a systemic inflammatory response to a blood-borne infection that is associated with an extremely high rate of morbidity and mortality. The present study investigates the role of cyclooxygenase (COX)-2 in host responses to bacterial endotoxemia. After administration of Escherichia coli lipopolysaccharide, 50% of wild-type mice die within 96 h. COX-2 deficient mice displayed a dramatic improvement in survival with reduced leukocyte infiltration into critical organs (kidneys and lungs) and a blunted and delayed induction of the cytokine inducible genes nitric oxide synthase 2 and heme oxygenase-1. Translocation and activation of transcription factors important for signaling events during an inflammatory response, such as nuclear factor (NF)-kappaB, were also markedly reduced. While the absence of COX-2 did not alter the induction of several pro-inflammatory cytokines in tissue macrophages, induction of the anti-inflammatory cytokine IL-10 was exaggerated. Administration of IL-10 to wild-type mice reduced NF-kappaB activation. Taken together, our data suggest that COX-2 deficient mice are resistant to many of the detrimental consequences of endotoxemia. These beneficial effects occur, in part, by a compensatory increase in IL-10 that counterbalances the pro-inflammatory host response to endotoxemia.

Effects of ibuprofen on the physiology and outcome of rabbit endotoxic shock

BACKGROUND

Despite major developments in the management of septic shock, the mortality rate had progressively increased. Ibuprofen has been shown to have beneficial physiological effects when used as a treatment. However, there are conflicting results with respect to survival. This study aims to investigate the effect of ibuprofen on vital functions, various physiological parameters and survival during endotoxic shock in rabbits.

METHODS

Twenty-eight New Zealand rabbits were randomly separated into four groups. The first group received only saline, the second was given 2 mg/kg intravenous endotoxin at t0, the third received 30 mg/kg ibuprofen 30 minutes after endotoxin administration, whilst the fourth group received ibuprofen 30 minutes before the endotoxin. Respiratory and heart rate, mean arterial blood pressure and rectal temperature were recorded. Complete blood counts were performed and thromboxane B2 was measured every 30 minutes for the first two hours, and then hourly over the course of the experiment. Urine samples were collected at the same time points for the measurement of prostaglandin E2.

RESULTS

Ibuprofen was found to improve respiratory rate, heart rate, and arterial pressure. However, it did not improve the negative effects of endotoxin on body temperature, haematocrit values, white blood cell count, and thrombocyte number. Thromboxane B2 levels in group IV were significantly lower than in the other groups, and the increase started at a later timepoint. In ibuprofen-treated animals, Prostaglandin E2 levels stayed low for at least 90 minutes, but started to rise thereafter. While the average survival in Group II animals was 192.9 +/- 46.9 minutes, those of groups III and IV were 339.1 +/- 33.5 minutes (p < 0.05) and 383.0 +/- 39.6 minutes (p = 0.01), respectively.

CONCLUSIONS

Ibuprofen appears to increase survival in endotoxic shock-induced animals. Therefore, it may be helpful for the prophylaxis and treatment of patients with, or who are likely to develop, septic shock.

The expression of cyclooxygenase and the production of prostaglandin E2 in neutrophils after burn injury and infection

Recent studies have demonstrated that neutrophils have the capacity to produce a variety of cytokines after stimulation. The synthesis and release of prostaglandin E2 (PGE2) via the cyclooxygenase (COX) pathway has been reported to occur in activated neutrophils. In the present study, we sought to determine the status of COX protein synthesis and PGE2 production in murine neutrophils after burn injury. The effect of burn injury on neutrophil COX and PGE2 response to infection or lipopolysaccharide (LPS) was also examined. Peritoneal neutrophils were obtained from BDF1 mice at 4, 18, 24, and 36 hours after a 15% TBSA full-thickness scald burn or sham burn. We found that neutrophils from healthy mice express a low level of COX-2 protein. Neutrophil COX-2 protein expression in burn animals was significantly increased at 4 hours and dramatically decreased at 36 hours after burn injury. Animals 36 hours after burn and topically infected with Pseudomonas Aeruginosa had neutrophil COX-2 expression almost identical to burn injury only. Neutrophils harvested from healthy mice cocultured with LPS (1 microg/ml) had a marked induction of COX-2 protein. Neutrophils 24 hours after burn were unresponsive to LPS-stimulated COX-2 enhancement. COX-1 protein was strongly expressed constitutively and not affected further by burn injury or LPS. The production of PGE2 corresponded with the changes in COX-2 expression for all groups of mice. Our data suggested that neutrophils express both COX-1 and COX-2 and produce PGE2. The effects of burn injury on neutrophil COX-2 protein synthesis and PGE2 production suggest that after burn there is a time-dependent response. Insights into not only the global cellular response to injury and infection but also temporal nature of the response are important in the development of the therapeutic treatment strategies for burn patients.

Gadolinium chloride inhibits lipopolysaccharide-induced mortality and in vivo prostaglandin E2 release By splenic macrophages

The monocytic phagocytic system, consisting primarily of tissue macrophages of the liver and spleen, produces prostaglandin E(2) (PGE(2)), a modulator of the septic response. Macrophages are known to internalize gadolinium chloride (GD), a lanthanide metal, which inhibits phagocytic function. Thus we studied the effect of in vivo GD on lipopolysacchride (LPS)-induced mortality and on LPS-stimulated PGE(2) release by cultured splenic macrophages. GD (7 mg/kg intravenously) given on the two days prior to LPS challenge (30 mg/kg intravenously) completely prevented the uniform mortality in rats. This protective effect was transient since rechallenge with LPS 10 days later was uniformly lethal. Previous work in this laboratory has established a critical role of arginine concentration on macrophage behavior in vitro. Therefore, to establish culture conditions reflective of the milieu within the portal venous system, alanine and arginine levels were measured in the portal and hepatic veins of normal and endotoxemic (LPS, 10 mg/kg intraperitoneally) rats. In contrast to alanine levels, which were not altered by endotoxemia, there was a reduction of arginine concentrations from a range of 50 to 250 micromol/L in normal rats to a range of 10 to 50 micromol/L after LPS challenge. Consequently subsequent in vitro assays of splenic macrophage secretory behavior were performed in concentrations of 1200 micromol/L arginine (in standard RPMI-1640), as well as in concentrations reflective of physiologic arginine levels (10 and 100 micromol/L in modified RPMI-1640). Rat splenic macrophages harvested after two consecutive days of either in vivo saline or GD injection (7 mg/kg intravenously) were stimulated with LPS (0.025 to 2.5 microg/ml). At 72 hours of culture, the release of PGE(2) by splenic macrophages from GD-treated rats was significantly (P <0.0001) reduced at all LPS concentrations. Increased PGE(2) production was not present when the splenic macrophages were cultured in the supraphysiologic arginine (1200 micromol/L) concentration. The results demonstrate the relevance of physiologic arginine concentrations in cell culture studies and suggest that the protection conferred by GD against septic mortality may be related to downregulation of the release of immunosuppressive PGE(2) by the monocytic phagocytic system.

Arachidonic acid is preferentially metabolized by cyclooxygenase-2 to prostacyclin and prostaglandin E2

The two cyclooxygenase isoforms, cyclooxygenase-1 and cyclooxygenase-2, both metabolize arachidonic acid to prostaglandin H2, which is subsequently processed by downstream enzymes to the various prostanoids. In the present study, we asked if the two isoforms differ in the profile of prostanoids that ultimately arise from their action on arachidonic acid. Resident peritoneal macrophages contained only cyclooxygenase-1 and synthesized (from either endogenous or exogenous arachidonic acid) a balance of four major prostanoids: prostacyclin, thromboxane A2, prostaglandin D2, and 12-hydroxyheptadecatrienoic acid. Prostaglandin E2 was a minor fifth product, although these cells efficiently converted exogenous prostaglandin H2 to prostaglandin E2. By contrast, induction of cyclooxygenase-2 with lipopol- ysaccharide resulted in the preferential production of prostacyclin and prostaglandin E2. This shift in product profile was accentuated if cyclooxygenase-1 was permanently inactivated with aspirin before cyclooxygenase-2 induction. The conversion of exogenous prostaglandin H2 to prostaglandin E2 was only modestly increased by lipopolysaccharide treatment. Thus, cyclooxygenase-2 induction leads to a shift in arachidonic acid metabolism from the production of several prostanoids with diverse effects as mediated by cyclooxygenase-1 to the preferential synthesis of two prostanoids, prostacyclin and prostaglandin E2, which evoke common effects at the cellular level.

Effects of ibuprofen on the physiology and survival of hypothermic sepsis. Ibuprofen in Sepsis Study Group

OBJECTIVES

The objective was to compare the clinical and physiologic characteristics of febrile septic patients with hypothermic septic patients; and to examine plasma levels of cytokines tumor necrosis factor alpha (TNF-alpha and interleukin 6 (IL-6) and the lipid mediators thromboxane B2 (TxB2) and prostacyclin in hypothermic septic patients in comparison with febrile patients. Most importantly, we wanted to report the effect of ibuprofen treatment on vital signs, organ failure, and mortality in hypothermic sepsis.

SETTING

The study was performed in the intensive care units (ICUs) of seven clinical centers in the United States and Canada.

PATIENTS

Four hundred fifty-five patients admitted to the ICU who met defined criteria for severe sepsis and were suspected of having a serious infection.

INTERVENTION

Ibuprofen at a dose of 10 mg/kg (maximum 800 mg) was administered intravenously over 30 to 60 mins every 6 hrs for eight doses vs. placebo (glycine buffer vehicle).

MEASUREMENTS AND MAIN RESULTS

Forty-four (10%) septic patients met criteria for hypothermia and 409 were febrile. The mortality rate was significantly higher in hypothermic patients, 70% vs. 35% for febrile patients. At study entry, urinary metabolites of TxB2, prostacyclin, and serum levels of TNF-alpha and IL-6 were significantly elevated in hypothermic patients compared with febrile patients. In hypothermic patients treated with ibuprofen, there was a trend toward an increased number of days free of major organ system failures and a significant reduction in the 30-day mortality rate from 90% (18/20 placebo-treated patients) to 54% (13/24 ibuprofen-treated patients).

CONCLUSIONS

Hypothermic sepsis has an incidence of approximately 10% and an untreated mortality twice that of severe sepsis presenting with fever. When compared with febrile patients, the hypothermic group has an amplified response with respect to cytokines TNF-alpha and IL-6 and lipid mediators TxB2 and prostacyclin. Treatment with ibuprofen may decrease mortality in this select group of septic patients.

Gadolinium blocks rat Kupffer cell calcium channels: relevance to calcium-dependent prostaglandin E2 synthesis and septic mortality

Hepatic Kupffer cells (KC), the major tissue macrophage population, produce the septic response mediators, tumor necrosis factor alpha (TNF-alpha) and prostaglandin E2 (PGE2), and have been shown to internalize gadolinium chloride (GD), a rare earth metal of the lanthanide series. Because GD pretreatment of rats has been shown to inhibit the mortality of sepsis, we studied the secretory response to lipopolysaccharide (LPS) by KC isolated from rats injected with either saline or GD (7 mg/kg, intravenously) on the 2 days before KC isolation. Using culture conditions modified to reflect the intrasinusoidal milieu of arginine (RPMI-1640 media with 10 or 100 micromol/L arginine), KC from GD-treated rats responded to LPS (0. 0025 microg/mL) with significantly (P <.01) reduced PGE2 release. In contrast, TNF-alpha release by treated KC was significantly (P <.05) enhanced, consistent with the loss of PGE2 autocoid inhibition of TNF-alpha. Calcium flux is an early signaling event in eicosanoid synthesis, and GD is known to block calcium channels. Therefore, KC were loaded with fura-2-AM to study the effect of GD on KC calcium flux. GD prevented ionomycin and platelet-activating factor (PAF)-mediated [Ca++]i increase and calcium-dependent PGE2 synthesis, while GD did not affect PGE2 synthesis when protein kinase C (PKC) was directly activated with tetradecanoylphorbolacetate (TPA). The inhibition of calcium flux and calcium-dependent PGE2 synthesis in the major cell of the monocytic phagocytic system by GD may explain the previously reported ability of this lanthanide to prevent the mortality of endotoxemia.

Regulation of macrophage eicosanoid generation is dependent on nuclear factor kappaB

BACKGROUND

Prostaglandin E2 (PGE2) is a major contributor to the production and maintenance of immunosuppression after overwhelming injury, leading to increased infectious morbidity and mortality in trauma patients. Elucidation of the cellular pathways involved in PGE2 production could lead to potential therapeutic interventions. The purpose of this study was to determine the role of cyclooxygenase II (COX-2) in PGE2 production by Mphi and to investigate the cellular mechanism of COX-2 gene activation.

METHODS

Mouse macrophages (Mphi), RAW 264.7, were exposed to Escherichia coli lipopolysaccharide (LPS) in the presence of cyclooxygenase inhibitors (ibuprofen or NS398). COX-1 and COX-2 mRNA expression and PGE2 production were measured by Northern blot assay and enzyme-linked immunosorbent assay, respectively. Nuclear factor kappaB (NFkappaB) activity was measured by electrophoretic mobility shift assay. To elucidate the role of NFkappaB in LPS-induced COX-2 gene activation, Mphi were exposed to LPS in the presence of an NFkappaB inhibitor, TPCK.

RESULTS

LPS increased Mphi COX-2 mRNA expression but had no effect on COX-1 mRNA expression. Both ibuprofen and NS398 inhibited COX-2 mRNA as well as PGE2 production by LPS-stimulated Mphi. In addition, LPS-induced NFkappaB activity was attenuated by these agents. Inhibition of NFkappaB with TPCK reduced COX-2 but not COX-1 gene expression and decreased PGE2 production by LPS-stimulated Mphi.

CONCLUSION

Our data indicate that COX-2 gene expression by LPS-stimulated Mphi is dependent on NFkappaB. Cyclooxygenase inhibitors reduced PGE2 production by inhibiting both COX-2 mRNA expression and preventing NFkappaB activation.

Burn wound infection-induced myeloid suppression: the role of prostaglandin E2, elevated adenylate cyclase, and cyclic adenosine monophosphate

Suppressed granulocyte and macrophage growth after burn infection or endotoxicosis appears to be mediated by macrophage-derived products. In this study, we found that after burn, burn plus infection, or endotoxicosis, peritoneal-elicited macrophages or bone marrow cells released increased amounts of prostaglandin E2 (PGE2) and inhibited growth of granulocyte-macrophage progenitor cells (GM-CFC). PGE2, when added in culture, inhibited in vitro GM-CFC growth in a dose-dependent manner. Pretreatment of bone marrow cells with either dibutyryl cyclic adenosine monophosphate or Forskolin in vitro mimicked the PGE2 inhibition, further aggravated the inhibition induced by burn, burn plus infection, or endotoxicosis, and was not blocked by co-culture with indomethacin. Pretreatment of bone marrow cells with SQ22536, an adenylate cyclase inhibitor, significantly restored the suppressed GM-CFC growth found after burn, burn plus infection, or endotoxicosis. Alterations in myeloid production after burn infection appear to be related in part to the level of intracellular cyclic adenosine monophosphate for the GM-CFC and are responsive to PGE2.

Human lymphotoxin mutein lacks hypotensive activity but has higher in vivo antitumor activity than lymphotoxin or tumor necrosis factor

A serious drawback of tumor necrosis factor alpha (TNF) as a clinical antitumor agent is that it also has hypotensive activity. To overcome this problem, derivatives of its sister cytokine lymphotoxin (TNF-beta or LT) were prepared. One of them, mutein 2 (Mut2) has a deletion of amino acids 1-7 but contains substituted amino acids, Met-Phe-Pro at positions 8-10 of the mature human LT. This mutein has no hypotensive activity at the maximum dose (10 mg/kg) tested on rats. In contrast, a much lower dose (1 mg/kg) of TNF and LT caused a significant blood pressure drop. In vivo studies revealed that Mut2 was more effective than TNF or LT against MethA (a mouse tumor line) as judged by the therapeutic ratio [calculated as LD50 (dose that kills 50% of the animals)/ED50 (dose that reduces the tumor size by 50%)]. With five other different mouse tumors and two different human tumors, Mut2 was also effective and the effectiveness was comparable or superior to that of TNF or LT. These results suggest the possibility that this derivative may be usable as a clinical antitumor agent without the serious side effects associated with TNF.

Effects of Prostacyclin on Hemodynamics after Intestinal Ischemia-Reperfusion

Ten rabbits underwent 30 minutes of superior mesenteric artery occlusion to assess the release of tumor necrosis factor, subcellular damage, and hemodynamic changes after intestinal ischemia-reperfusion injury. Five were treated with prostacyclin 5 ng/kg/min 5 minutes before the arterial occlusion. It was increased to 25 ng/kg/min during occlusion, decreased to 5 ng/kg/min for the first 5 minutes of reperfusion, and then discontinued. A control group of 5 rabbits did not receive any pharmacological agent. Specimens were obtained from the small intestine for electron microscopy after 10 minutes and after 60 minutes of reperfusion, while simultaneous blood samples were collected for measurement of tumor necrosis factor. Minimal changes were seen in tissue from the prostacyclin group but severe mitochondrial damage and vacuolation occurred in the control group. The tumor necrosis factor level was 11.97 ± 3.17 U/mL in the control group and 5.06 ± 2.19 U/mL in the prostacyclin group, one hour after the end of mesenteric occlusion ( p < 0.05). Hemodynamic status, assessed by central venous and arterial pressures, was much more affected in the control group than in the prostacyclin group. Mean arterial pressure was 71 ± 5 mm Hg in the control group, and 91 ± 6 mm Hg in the prostacyclin group ( p < 0.05). Central venous pressure was 5.3 ± 0.9 mm Hg in the control group and 2.3 ± 0.7 mm Hg in the prostacyclin group ( p < 0.05). We conclude that intravenous prostacyclin reduced the severity of reperfusion injury occurring during the early period of reperfusion by inhibiting the release of the toxic mediator tumor necrosis factor, thus decreasing distant organ injury.

Prostaglandin E2 production by endotoxin-stimulated alveolar macrophages is regulated by phospholipase C pathways

BACKGROUND

Eicosanoids play an important role in many aspects of systemic inflammatory responses and host defense. Although the synthesis of eicosanoids by different enzymes has been elucidated, the regulatory mechanism of eicosanoid production is not clear. We designed this study to investigate the hypothesis that PGE2 production by endotoxin (lipopolysaccharide; LPS)-stimulated macrophages (MO) is dependent on phospholipase C (PLC) signaling pathways.

METHODS

Rabbit alveolar macrophages (MO) were obtained by bronchoalveolar lavage. MO were suspended in RPMI-1640 medium at 1 x 10(6)/mL and were exposed to Escherichia coli LPS (10 ng/mL) +/- various agonists and antagonists of PLC and its secondary messengers. After 24 hours of incubation, prostaglandin E2 (PGE2) production was measured by ELISA.

RESULTS

LPS-activated MO produced four times as much PGE2 as did control unstimulated MO. The increase in PGE2 production was inhibited by PLC inhibitors (U73122 or D609) and a low-molecular-weight PLA2 inhibitor, manoalide. An increase in intracellular calcium and activation of both the calmodulin and protein kinase C kinase pathways increase PGE2 production.

CONCLUSIONS

PGE2 production is intimately dependent on several phospholipases. Production is not only dependent on low-molecular-weight PLA2 cleavage of arachidonic acid from membrane phospholipids, but also by-products of PLC activation. PLC-dependent intracellular Ca-calmodulin signaling and protein kinase C activation provide significant modulation of PGE2 production.

Immunomodulatory spectrum of lipids associated with Mycobacterium avium serovar 8

Lipid fractions obtained from Mycobacterium avium serovar 8 were assessed for the ability to affect various immune functions of human peripheral blood mononuclear cells (PBM). Lipids included a total lipid fraction and fractions eluted from silicic acid column separation of that total lipid fraction, using chloroform and chloroform-methanol combinations. Lipid fractions were assayed for total carbohydrate and total 6-deoxyhexose content and were assessed for the ability to influence human macrophage function and the capacity to induce secretion of prostaglandin E2 (PGE2) and tumor necrosis factor alpha in PBM. The total lipid and serovar-specific glycopeptidolipid (GPL) fractions both induced significant levels of tumor necrosis factor alpha, as well as PGE2, in PBM exposed to a sublethal concentration of 100 micrograms lipid per 2 x 10(6) cells. In addition, the same concentrations of the 5 to 7% and GPL fractions induced significant levels of leukotriene B4 in PBM. Comparison of carbohydrate and 6-deoxyhexose contents of each fraction suggested a relationship to carbohydrate content and ability of fractions to induce immune modulator secretion. Analysis of GPL fractions from M. avium serovars 4 and 20 revealed that those GPL lacked the ability to induce PGE2. These results are explained by considering the difference in the carbohydrate residues of the oligosaccharide moieties.

Postsurgical complications in older patients. The role of pharmacological intervention

The number of elderly patients undergoing surgery has been rapidly increasing during the last few years. Following surgical interventions, high rates of mortality and morbidity have been reported in the most advanced age groups. Nevertheless, perioperative evaluation and postoperative care are the major determinants of the overall outcome. Postsurgical complications are common in advanced age, since multiple pathology is often present in geriatric patients. Furthermore, the decreased efficiency of homeostatic mechanisms may facilitate the development of multiple organ failure (MOF), even as a consequence of apparently slight alterations in immune, cardiac or respiratory systems. Thus, prompt recognition and treatment of any complication often prevents the development of irreversible conditions. While cardiac and pulmonary complications account for 50% of early postoperative adverse events, infections, thromboembolism, renal failure, stress ulcers and coagulation disorders may occur well after surgical procedures. An important part of postoperative geriatric care is the diagnosis and correction of fluid, electrolyte and acid-base disturbances. These disturbances may manifest as mild, atypical signs, such as slight neuromuscular depression or delirium. Yet, they often constitute life-threatening conditions that should be rapidly and properly corrected. Finally, it should be remembered that, due to the frequent use of multiple drugs, elderly patients are at high risk of developing adverse drug reactions. Thus, the treatment of postoperative complications requires a strong rational effort to disentangle the combined effects of aging, drugs and pathology.