Interferon-gamma attenuates hemorrhage-induced suppression of macrophage and splenocyte functions and decreases susceptibility to sepsis.

Although it is known that interferon-gamma synthesis and macrophage functions are depressed after hemorrhage, it remains to be determined whether systemic administration of interferon-gamma has any effect on hemorrhage-induced depression of macrophage and splenocyte functions. To study this, C3H/HEN mice were bled to a mean blood pressure of 35 mm Hg, maintained for 60 minutes, and followed by adequate fluid resuscitation. The mice then received either 1000 units interferon-gamma or saline solution (vehicle). Peritoneal (pM phi) and splenic (sM phi) macrophages and splenocytes were isolated 24 hours later. PM phi antigen presentation was measured by coculturing pM phi with the D10.G4.1 cell clone. Major histocompatibility complex class II (Ia) antigen expression was determined by direct immunofluorescence. Cytokine release by pM phi, sM phi, and splenocytes was assessed with specific bioassays. For survival studies, mice were subjected to sepsis 3 days after hemorrhage. Treatment with interferon-gamma restored (p less than or equal to 0.05) hemorrhage-induced suppression of pM phi antigen presentation capacity and Ia antigen expression and increased (p less than or equal to 0.05) interleukin-1 and tumor necrosis factor release by pM phi and sM phi, as well as splenocyte proliferation (p less than or equal to 0.05). Interferon-gamma also decreased (p less than or equal to 0.007) the susceptibility to sepsis after hemorrhage. Thus interferon-gamma represents a potent agent for treating hemorrhagic shock-induced immunosuppression and for increasing the ability of the host defense system to combat bacterial infections after hemorrhage.     

Ibuprofen restores cellular immunity and decreases susceptibility to sepsis following hemorrhage.

Although hemorrhage depresses splenocyte (SPL) functions and increases susceptibility to sepsis, it is not known whether increased tumor necrosis factor (TNF) or prostaglandin (PG) production are responsible for it. To study this, mice (C3H/HeN) were bled to a mean blood pressure of 35 mm Hg, maintained at that pressure for 60 min, resuscitated, and treated with ibuprofen (1.0 mg/kg body weight) or vehicle (saline). Hemorrhage reduced (P less than 0.05) SPL proliferation by 60%, SPL release of interleukin-2 (IL-2) by 47%, interferon-gamma (IFN-gamma) by 67%, TNF by 54%, and interleukin-6 (IL-6) by 46% compared to sham. In addition, splenic macrophage (sM phi) release of interleukin-1 (IL-1) and TNF was decreased by 58 and 67% (P less than 0.05), respectively. However, ibuprofen treatment increased (P less than 0.05) SPL proliferation, lymphokine (IL-2, IFN-gamma, and IL-6) synthesis, and IL-1 release by sM phi compared to hemorrhage alone. Furthermore, ibuprofen enhanced the release of TNF by SPL (+175%, P less than 0.05) and sM phi (+68%) compared to the vehicle group. Ibuprofen also decreased (P = 0.011) the susceptibility to sepsis following hemorrhage. These results indicate that PGs are involved in hemorrhage-induced suppression of cellular immunity and in the increased mortality of such animals following a septic challenge.     

Inhibition of cyclooxygenase-2 by NS-398 following hemorrhage and subsequent sepsis: no beneficial effects in either gender

BACKGROUND: Inhibition of cyclooxygenase-2 with a reduction of prostaglandin E(2)production by the specific antagonist NS-398 has been shown to have beneficial effects on immune function and survival in a trauma model. Immune function after experimental hemorrhagic shock and subsequent sepsis may be gender-related, with enhanced immunity and better survival in females. However, it remains unclear if the observed effect of NS-398 treatment is gender-related following hemorrhagic shock and subsequent sepsis. METHODS: Male and female CBA/J mice (age: 2-3 months) were subjected to hemorrhagic shock (35 +/- 5 mm Hg for 90 min and fluid resuscitation) or sham operation. At resuscitation and after 20 and 40 h each received either NS-398 10 mg/kg or placebo i.p. At 48 h after resuscitation, either splenocytes and peritoneal macrophages (pM phi) were harvested (n = 8 per group), or polymicrobial sepsis was induced by cecal ligation and puncture (CLP). Following CLP, either 10-day survival (n = 15 per group) was determined or pM phi and splenocytes were harvested 4 h after CLP (n = 8 per group). Cytokine release of pM phi, and splenocyte proliferation and responsiveness in vitro were assessed. RESULTS: Treatment with NS-398 led to lower PGE(2) levels as compared to placebo-treated animals, reaching significance (p < 0.05) in males. Placebo-treated males had significantly depressed proinflammatory immune response (IL-1, IL-6, IL-2, IFN-gamma) after hemorrhagic shock and experienced further suppression by CLP (all, p < 0.05). In contrast, young females displayed unchanged cytokine release after hemorrhagic shock, but a comparable suppression following CLP. Treatment with NS-398 did not influence cytokine release nor survival. CONCLUSIONS: Despite a significant reduction of PGE(2) concentration, NS-398 treatment has no beneficial effects on cytokine release and survival in this model of hemorrhage and subsequent sepsis.     

L-arginine: a unique amino acid for improving depressed wound immune function following hemorrhage

OBJECTIVE: To determine whether L-arginine has any salutary effects on wound immune cell function following trauma-hemorrhage. BACKGROUND: Depressed wound immune function contributes to an increased incidence of wound infections following hemorrhage. Although administration of L-arginine has been shown to restore depressed cell-mediated immune responses following hemorrhage potentially by maintaining organ blood flow, it remains unknown whether L-arginine has any salutary effects on the depressed local immune response at the wound site. METHODS: Male mice were subjected to a midline laparotomy and polyvinyl sponges were implanted subcutaneously in the abdominal wound prior to hemorrhage (35 +/- 5 mm Hg for 90 min and resuscitation) or sham operation. During resuscitation mice received 300 mg/kg body weight L-arginine or saline (vehicle). Sponges were harvested 24 h thereafter, wound fluid collected and wound immune cells cultured for 24 h in the presence of LPS. Pro- (IL-1 beta, IL-6) and anti-inflammatory (IL-10) cytokines were determined in the supernatants and the wound fluid. In addition, wounds were stained for IL-6 immunohistochemically. In a separate set of animals, skin and muscle blood flow was determined by microspheres. RESULTS: The capacity of wound immune cells to release IL-1 beta and IL-6 in vitro was significantly depressed in hemorrhaged mice receiving vehicle. Administration of L-arginine, however, improved wound immune cell function. In contrast, in vivo the increased IL-6 release at the wound site was decreased in L-arginine-treated mice following hemorrhage. Moreover, IL-10 levels were significantly increased in the wound fluid in hemorrhaged animals receiving L-arginine compared to vehicle-treated mice. In addition, the depressed skin and muscle blood flow after hemorrhage was restored by L-arginine. CONCLUSIONS: Thus, L-arginine might improve local wound cell function by decreasing the inflammatory response at the wound site. Since L-arginine protected wound immune cell function this amino acid might represent a novel and useful adjunct to fluid resuscitation for decreasing wound complications following hemorrhage.     

Inhibition of macrophage-activating cytokines is beneficial in the acute septic response.

Interferon-gamma and other cytokines enhance macrophage (M phi) antimicrobial function and have been considered for therapeutic use in sepsis. Systemic sequelae of macrophage activation, however, are unclear. This study examined the effects of M phi activating cytokines (interferon-gamma [IFN-gamma] and interleukin-4 [IL-4]) and monoclonal antibodies directed against these cytokines in modulating the acute septic response. CFW/Swiss Webster mice (n = 345) received endotoxin (lipopolysaccharide [LPS]: 60 mg/kg body weight intraperitoneally) and were randomized to five treatment groups: IFN-gamma (10(4) units), IL-4 (10(4) units), IgG1 isotype antibody (TRFK5: 200 micrograms), anti-IFN-gamma (200 micrograms), or anti-IL-4 (200 micrograms) monoclonal antibodies (MAbs) given simultaneously or 2 hours after LPS. Animals were divided into two groups and studied for mortality or measurement of peritoneal M phi superoxide anion release (O2-), tumor necrosis factor (TNF), and IL-6 production 6 hours after administration of LPS +/- experimental regimens. Serum TNF and IL-6 also were assessed at 2 and 4 hours after LPS, respectively. Administration of LPS resulted in a 27% survival compared with 10% in the IFN-gamma and 13% in the IL-4 groups. Treatment with anti-IFN-gamma offered protection against LPS lethality (93%-100% survival, p less than 0.001 vs. other groups) when given either simultaneously or 2 hours after LPS. Anti-IFN-gamma also significantly decreased PM phi O-2 and TNF release. Thus anti-IFN-gamma may have an important role in the modulation of the acute septic response.     

The complex pattern of cytokines in sepsis. Association between prostaglandins, cachectin, and interleukins.

Although the cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1), and interleukin-6 (IL-6) are important mediators of hemodynamic, metabolic, and immunologic alterations in the host during sepsis, it is not known whether there is any association between the release of these cytokines and prostanoids during sepsis. Sepsis induced by cecal ligation and puncture in rats led to a persistent elevation (p less than 0.05) of plasma TNF until 10 hours, steadily increasing (p less than 0.05) IL-1 plasma levels, and enhanced (p less than 0.05) IL-6 plasma levels at all time points compared to the sham group. Prostaglandin E2 plasma levels were elevated (p less than 0.05) at 5 hours (153 +/- 29 pg/mL; control: 47 +/- 11 pg/mL) and 10 hours (96 +/- 16 pg/mL; control: 21 +/- 5 pg/mL). Prostaglandin E2 production by splenic macrophages (sM phi) from septic animals was increased (p less than 0.05) at 5 hours (9.1 +/- 2.2 ng/mL) and 10 hours (5.6 +/- 1.5 ng/mL) compared to controls (3.3 +/- 0.3 ng/mL at 5 hours; 1.3 +/- 1.3 ng/mL at 10 hours). Incubation of sM phi from septic animals with ibuprofen enhanced (p less than 0.05) IL-1 and TNF synthesis, while IL-6 production was reduced (p less than 0.05). These results indicate that the alterations in prostanoid release and elevated plasma prostanoids may regulate the release and consequently the circulating levels of cytokines during sepsis.     

Sepsis induces an early increased spontaneous release of hepatocellular stimulatory factor (interleukin-6) by Kupffer cells in both endotoxin tolerant and intolerant mice.

Previous studies have shown that hepatocellular function is significantly depressed early during sepsis and that this is associated with a marked increase in the circulating levels of the hepatocellular stimulatory factor (IL-6). It remains unknown, however, whether or not Kupffer cells (KC) are activated during sepsis and whether these cells are the major contributors to the increased circulating levels of this cytokine. The objectives of this study were, therefore, to determine whether or not during sepsis: (1) KC are stimulated in vivo to release IL-6, as compared to other cytokines; (2) KC differ from splenic macrophages (SM phi) in their ability to release cytokines; and (3) there is a difference in macrophage (M phi) cytokine release between endotoxin (ET)-tolerant (C3H/HeJ) and ET-intolerant (C3H/HeN) mice. To assess this, KC and SM phi were harvested at 1 or 24 hr from mice which had been subjected to polymicrobial sepsis by cecal ligation and puncture (CLP) or sham-operation. Following depletion of the nonadherent cells, KC and SM phi cultures were incubated for 24 hr in the presence or absence of 10 micrograms of ET/ml, and the levels of interleukin (IL)-1, IL-6, and TNF release were determined by bioassays. Sepsis induced an early (at 1 hr) in vivo stimulation of KC but not SM phi IL-6 release, irrespective of ET-tolerance/intolerance. However, the release of IL-1 or TNF was not markedly different for either CLP or sham KC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blockade of prostaglandin production increases cachectin synthesis and prevents depression of macrophage functions after hemorrhagic shock.

Although hemorrhage severely depresses macrophage functions, it is not known whether the increased TNF-alpha or PGE2 production is responsible for it. To study this C3H/HeN mice were bled to mean blood pressure of 35 mmHg for 60 minutes, resuscitated, and treated with either ibuprofen (1.0 mg/kg body weight) or vehicle (saline). Hemorrhage increased plasma prostaglandin E2 (PGE2) levels by 151.7% +/- 40.0% (p less than 0.05) and significantly decreased peritoneal macrophage (pM phi) antigen presentation (AP) by 60.5% +/- 7.3%, Ia expression by 52.3% +/- 7.6%, and interleukin-1 (IL-1) synthesis by 60.5% +/- 12.3% compared to shams. However ibuprofen treatment reduced PGE2 plasma levels by 61.3% +/- 12.1% and significantly increased AP (+237.0% +/- 95.3%), Ia expression (+72.8% +/- 27.5%), IL-1 synthesis (+235.7% +/- 134.7%), and cachectin synthesis (+485.8% +/- 209.0%) compared to vehicle-treated animals. These results indicate that prostaglandins but not cachectin are involved in the suppression of pM phi functions following hemorrhage because blockade of prostaglandin synthesis improved depressed macrophage functions despite enhanced cachectin synthesis.     

Endotoxin tolerance from lipopolysaccharide pretreatment induces nuclear factor-kappaB alterations not present in C3H/HeJ mice

BACKGROUND: Lipopolysaccharide (LPS) activation of macrophage (MO) cytokine secretion requires activation and translocation of nuclear factor-kappaB (NF-kappaB). Endotoxin tolerance induced in LPS-responsive C3H/HeN MOs by LPS pretreatment results in decreased tumor necrosis factor (TNF) secretion and altered NF-kappaB activation. C3H/HeJ MOs have a genetic defect that renders them tolerant to LPS activation. We hypothesized that the alterations of NF-kappaB activation seen with LPS tolerance in HeN MOs would be present in HeJ mice. METHODS: MOs from C3H/HeJ and C3H/HeN mice were cultured with +/- 10 ng/mL LPS pretreatment for 24 hours and then stimulated with 1 to 1,000 ng/mL LPS. Activation of NF-kappaB was assayed by gel shift using a 32P-labeled specific oligonucleotide 30 minutes after LPS activation. TNF secretion 6 hours after LPS stimulation was measured by bioassay. RESULTS: LPS stimulation activated NF-kappaB in both HeN and HeJ MOs. We observed decreased NF-kappaB activation and a characteristic mobility shift in endotoxin-tolerant MOs from HeN mice that were not present in HeJ MOs. In contrast with the results in HeN mice, LPS pretreatment did not induce any alterations in NF-kappaB activation in HeJ MOs. LPS-stimulated TNF secretion was decreased in HeN MOs after LPS pretreatment. There was no change in TNF secretion in HeJ MOs, but, overall, TNF secretion by these cells was much less than that seen in HeN cells. CONCLUSION: MOs from C3H/HeN mice rendered LPS-tolerant by low-dose LPS pretreatment have alterations in activation of NF-kappaB not present in LPS-hyporesponsive C3H/HeJ mice.     

Differential modulation of TLR2 and TLR4-induced TNF production by murin haemorrhagic shock

OBJECTIVE: To investigate the influence of haemorrhagic shock in mice on ex vivo TNF production by whole blood cells (WBC) stimulated through Toll-like receptors (TLR) 4 and 2. STUDY DESIGN AND ANIMALS: Experimental study using BALB/c male mice. METHODS: Haemorrhage (0,026+/-0,003 ml/g) by transparietal cardiac puncture under general anaesthesia. Measurement of left intraventricular pressure through a direct subcostal cardiac puncture. Possible restitution of shed blood volume (SBV) in retroorbital venous plexus, 60 minutes following haemorrhage. Lethal exsanguination 120 minutes following general anaesthesia (Control group), cardiac puncture (Sham group), blood sample (Haemorrhage group), or 60 minutes following SBV retransfusion (SBV group). Cultures (24 hours) of whole blood from the exsanguination, alone or with Escherichia coli endotoxin (LPS, TLR 4) or with heat-killed Staphylococcus aureus Cowan (SAC, TLR 2). Assessment of TNF levels in the cultures supernatant (Elisa). RESULTS: Hemorrhage (approximately 30% of calculated blood volume) resulted in arterial hypotension (-50%) which was reversed by SBV retransfusion. TNF production by LPS-stimulated WBC was reduced by haemorrhage (approximately -50%) with or without SBV retransfusion. TNF production by SAC-stimulated WBC remained unchanged. CONCLUSION: The reduction of proinflammatory cytokines production by WBC stimulated with pathogen-associated molecular patterns is not a generalized phenomenon following murin haemorrhagic shock. It depends on the used stimulus and studied signalling pathways.     

Antitumor effects of bacterial lipopolysaccharide and tumor necrosis factor in mice

The effects of lipopolysaccharide (LPS) against tumor growth and on cellular immunity were studied in comparison with those of tumor necrosis factor (TNF). LPS and TNF, which were administered into mice with tumors, induced hemorrhagic necrosis within 48 hours after the initiation of the treatment. LPS and TNF significantly inhibited the tumor growth, as compared with findings in the controls. There was no significant difference in inhibitory effect on tumor growth between mice treated with LPS or TNF once or twice. Both LPS and TNF prevented the decrease of delayed type hypersensitivity in the tumor bearing mice.     

Antitumor effects of bacterial lipopolysaccharide and tumor necrosis factor in mice

The effects of lipopolysaccharide (LPS) against tumor growth and on cellular immunity were studied in comparison with those of tumor necrosis factor (TNF). LPS and TNF, which were administered into mice with tumors, induced hemorrhagic necrosis within 48 hours after the initiation of the treatment. LPS and TNF significantly inhibited the tumor growth, as compared with findings in the controls. There was no significant difference in inhibitory effect on tumor growth between mice treated with LPS or TNF once or twice. Both LPS and TNF prevented the decrease of delayed type hypersensitivity in the tumor bearing mice.     

Effects of nicardipine on the ex vivo release of eicosanoids after experimental subarachnoid hemorrhage

The activation of lipid peroxidation and the enhancement of arachidonic acid metabolism have been demonstrated as indicators of brain damage after subarachnoid hemorrhage (SAH). Meanwhile, the final common pathway of neuronal damage seems to be related to the impaired homeostasis of Ca++. The present study evaluated the effect of the calcium-antagonist nicardipine on arachidonate metabolism after experimental induction of SAH. The ex vivo release of four eicosanoids (prostaglandin (PG)D2, PGE2, 6-keto-PGF1 alpha, and leukotriene (LT)C4) was measured at different intervals after SAH induction. Rats were separated into the following three groups: a sham-operated group, an SAH group (rats were injected with 0.3 ml autologous arterial blood), and an SAH-treated group (after SAH induction, rats were treated with nicardipine 1.2 mg/kg intraperitoneally). Nicardipine significantly decreased the ex vivo release of PGD2 at 48 hours after SAH (p less than 0.01). The release of PGE2 was significantly enhanced at 6 hours after SAH, while in the nicardipine-treated group PGE2 release is significantly reduced. Nicardipine also affects the lipoxygenase pathway, reducing the release of LTC4 at 1, 6, and 48 hours after SAH induction. The results of the present study show that nicardipine treatment exerts an inhibitory effect on both biochemical pathways of arachidonic acid metabolism; aside from vascular effects, nicardipine could exert a protective role against the release of arachidonate metabolites, which could play a significant role in the pathogenesis of brain damage after SAH.     

Chloroquine attenuates hemorrhagic shock-induced immunosuppression and decreases susceptibility to sepsis.

Hemorrhagic shock causes a severe suppression of cellular immunity and an increased susceptibility to sepsis that may be due to increased release of prostaglandin E2 by macrophages. Since chloroquine inhibits the secretion of prostaglandin E2 by macrophages in vitro, the effects of chloroquine administration in vivo following hemorrhagic shock on macrophage prostaglandin E2 secretion and on depressed cellular immunity were examined. Inbred C3H/HeN male mice, aged 6 to 8 weeks, were bled to a mean blood pressure of 35 mm Hg, which was maintained for 60 minutes, and adequately, resuscitated. Mice then received intramuscular injections of either saline (vehicle) or chloroquine (10 mg/kg of body weight). Prostaglandin E2 in macrophage supernatants (radioimmunoassay) concanavalin A-dependent splenocyte proliferation, and interleukin 2 in splenocyte supernatants (CTLL 20 interleukin 2-dependent proliferation) were determined 2 or 24 hours later. Hemorrhage caused a significant decrease of splenocyte proliferation (47%) and interleukin 2 release (49%) at 24 hours, while prostaglandin E2 secretion from macrophages was elevated at 2 hours. Chloroquine treatment attenuated depression of splenocyte functions and reduced prostaglandin E2 release. Furthermore, chloroquine treatment decreased the mortality of septic mice after hemorrhage to levels comparable with those of sham-operated mice. Thus, chloroquine may be a useful adjunct in the clinical setting for the treatment of shock-induced immunodepression and increased susceptibility to sepsis following hemorrhage.     

Production of tumor necrosis factor by rat mesangial cells in response to bacterial lipopolysaccharide

Tumor necrosis factor (TNF) is a cytokine which is produced by mononuclear phagocytes upon activation by bacterial lipopolysaccharide (LPS) and various other stimuli. In immune-mediated glomerulonephritis, infiltration of glomeruli by monocytes-macrophages is associated with production of TNF. The purpose of the present experiments was to determine whether mesangial cells could also contribute to glomerular TNF synthesis. TNF activity has been determined in the culture medium of rat mesangial cells using a L-929 fibroblast lytic assay. This activity was detectable only when the cells were exposed to LPS (0.1 to 10 micrograms/ml) and for periods longer than one hour. The cytotoxic factor was identified as TNF since: (1) the lytic activity was completely inhibited by an anti-mouse TNF polyclonal antibody and was associated with suppression of lipoprotein lipase activity in adipocytes; (2) its molecular weight (110,000 daltons) corresponded to that observed for murine TNF under non-denaturing conditions; and (3) mRNA encoding TNF was expressed by mesangial cells two hours after addition of LPS. To assess the mechanisms whereby TNF production was regulated, the role of prostaglandin E2 (PGE2) was determined. LPS caused a dose-dependent increase of PGE2 synthesis by mesangial cells. Treatment by indomethacin promoted a suppression of PGE2 production together with an increase of TNF synthesis, indicating that PGE2 acted in a negative feedback manner to regulate the production of TNF. Addition of PGE2 (0.1 to 300 nM) or 8-bromo cyclic AMP (0.1 to 100 microM) induced similar dose-dependent reductions of TNF synthesis. Thus the inhibitory effect of PGE2 probably required in part cyclic AMP accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tumor necrosis factor production by Kupffer cells requires protein kinase C activation

Tumor necrosis factor (TNF) has been proposed as a primary inflammatory mediator of septic shock. In vitro and in vivo studies indicate that endotoxin- or lipopolysaccharide (LPS)-activated macrophages are a principle source of TNF; however, membrane signal transduction and intracellular pathways by which LPS triggers TNF production in macrophages are unclear. Recent evidence indicates that specific protein phosphorylation via activation of protein kinase C (PKC) is an early, critical step in the signaling of macrophage TNF production by phorbol esters. We hypothesize that PKC activation is also required in LPS-signaled Kupffer cell (KC) TNF production. Murine KCs were obtained by liver perfusion and digestion and then stimulated with LPS (Escherichia coli O111:B4) or LPS in the presence of H-7, a selective PKC inhibitor. Conditioned media was collected at 3 hr for assay of TNF utilizing the L929 cytolysis bioassay standardized to murine-rTNF-alpha. We found that H-7 inhibited significantly LPS signaled TNF release at a concentration of 10 microM, while H-8 (a cyclic nucleotide specific inhibitor) had no effect. The effect of H-7 was dose dependent and present at varying concentrations of LPS. Down regulation of PKC activity by preincubation of KCs with phorbol myristate acetate (PMA, a direct activator of PKC) also resulted in significantly reduced TNF release after LPS stimulation. The inhibitor H-7 (10 microM) also significantly inhibited LPS signaled prostaglandin E2 release in Kupffer cells. Total and specific intracellular protein phosphorylation was determined by trichloroacetic acid precipitation and SDS-polyacrylamide gel electrophoresis after labeling stimulated Kupffer cells with 32Pi. Total protein phosphorylation was not significantly altered by LPS stimulation; however, autoradiograms from PMA- and LPS-stimulated KCs demonstrate enhanced phosphorylation of a 40-kDa protein (2.7 +/- 0.9-fold) and a 33-kDa protein (3.1 +/- 1.0-fold) which were inhibited by H-7. We conclude that activation of PKC and protein phosphorylation are required steps in the signal transduction pathway of LPS-stimulated TNF production in Kupffer cells.     

Regulation of tumor necrosis factor-alpha production in the isolated rat heart stimulated by bacterial lipopolysaccharide or reactive oxygen

Reperfusion after cardiopulmonary bypass causes induction of reactive oxygen species (ROS), elevated plasma levels of bacterial lipopolysaccharide (LPS), and production of tumor necrosis factor-alpha (TNF) by the heart. Nuclear factor-kappaB (NF-kappaB) regulates the expression of TNF. Because NF-kappaB is activated by both LPS and ROS, we hypothesized that an inhibitor of NF-kappaB, pyrrolidine dithiocarbamate (PDTC), would block release of TNF from the heart stimulated by these two agents. With Institutional animal care and use committee (IACUC) approval, rat hearts were perfused Langendorf style. LPS was infused and ROS were generated with a hypoxanthine/xanthine oxidase system. PDTC was added to the perfusion buffer. Other hearts were treated with forskolin in order to elevate cyclic AMP. Timed collections of coronary effluent were made for the determination of coronary flow and measurement of TNF. LPS stimulated TNF release to a maximum of 2247 +/- 133 pg/min at 150 minutes. PDTC inhibited LPS-stimulated TNF release. For instance, at 150 minutes, LPS-stimulated TNF release was 449 +/- 49 pg/min with 100 microM PDTC and was 70 +/- 65 pg/mL with 250 microM PDTC (P < 0.05 vs LPS alone). ROS stimulated TNF release was 1494 +/- 130 pg/min at 150 minutes and was not affected by PDTC. Forskolin almost completely blocked TNF release stimulated by LPS or ROS. These data are consistent with the notion that inhibitors of NF-kappaB block cytokine production stimulated by some agents but not others.     

Involvement of p38 mitogen-activated protein kinase in the induction of tolerance to hemorrhagic and endotoxic shock

BACKGROUND: Exposure to sublethal hemorrhage (SLH) makes rats tolerant to subsequent hemorrhagic or septic shock and is associated with altered NF-kappaB activity. The purpose of this study was to explore whether changes in p38 mitogen-activated protein (MAP) kinase activity also occur in the induction of tolerance by SLH. METHODS: Rats were made tolerant by SLH or sham operation. Twenty-four hours later rats were exposed to lipopolysaccharide (LPS) or had peritoneal macrophages (Mphi) isolated. CNI-1493, a p38 MAP kinase inhibitor, or saline was given prior to SLH. Lungs were harvested 1 h after SLH or LPS and total protein was extracted. Peritoneal Mphi were stimulated with LPS (10 microg/ml) and total protein was isolated 1 h later. Active, dually phosphorylated p38 MAP kinase was determined by Western blot. Tumor necrosis factor (TNF) was measured in Mphi supernatants by enzyme-linked immunosorbent assay (ELISA) 18 h after LPS. RESULTS: SLH activated p38 MAP kinase in the lung and this was inhibited by CNI-1493. Twenty-four hours later, lung p38 MAP kinase activity increased to the same degree in tolerant and sham rats following LPS, but much more prominently in the CNI-1493 treated rats. There was no p38 activity in peritoneal Mphi at baseline, and similar to lung p38, LPS led to increased p38 activity which was most significant in Mphi from rats that received CNI-1493 prior to SLH. TNF production by tolerant Mphi in response to LPS was significantly (P < 0.05, t test) decreased and p38 inhibition with CNI-1493 at the time of SLH reversed the inhibitory effects of tolerance on TNF production. CONCLUSIONS: TNF production by tolerant Mphi following a second insult (LPS) is attenuated despite preservation of normal p38 MAP kinase activity. However, activation of this intracellular second messenger is a necessary step in the "cellular reprogramming" that occurs during the induction of tolerance by SLH.