MAP kinases differentially regulate the expression of macrophage hyperactivity after thermal injury

ASMq protects against early burn wound progression in rats by alleviating oxidative stress and secondary mitochondria‑associated apoptosis via the Erk/p90RSK/Bad pathway

Burn wounds present an evolutionary progression, in which the initial wound tissue deepens and expands following thermal injury. Progressive tissue damage in the zone of stasis may worsen burn injury, which is associated with oxidative stress and secondary apoptosis, and worsen the prognosis of patients with burn wounds. The mitochondrial apoptotic pathway is involved in receiving oxidative signals and regulating tissue apoptosis. Previously, Abnormal Savda Munziq (ASMq), a natural compound of traditional Uyghur Medicine, which includes ten types of herb, has been reported to exhibit a number of effects, including anti-inflammatory, antioxidative and anti-apoptotic activities. The present study demonstrated that ASMq protected against early burn wound progression following thermal injury in rats; this effect may be mediated by its ability to attenuate oxidative stress-induced mitochondria-associated apoptosis. The present study may provide a novel therapeutic method to prevent early burn wound progression following burn injury.

Drug-specific differences in the ability of opioids to manage burn pain

Burn injury pain is a significant public health problem. Burn injury treatment has improved tremendously in recent decades. However, an unintended consequence is that a larger number of patients now survive more severe injuries, and face intense pain that is very hard to treat. Although many efforts have been made to find alternative treatments, opioids remain the most effective medication available. Burn patients are frequently prescribed opioids in doses and durations that are significantly higher and longer than standard analgesic dosing guidelines. Despite this, many continue to experience unrelieved pain. They are also placed at a higher risk for developing dependence and opioid use disorder. Burn injury profoundly alters the functional state of the immune system. It also alters the expression levels of receptor, effector, and signaling molecules within the spinal cord's dorsal horn. These alterations could explain the reduced potency of opioids. However, recent studies demonstrate that different opioids signal preferentially via differential signaling pathways. This ligand-specific signaling by different opioids implies that burn injury may reduce the antinociceptive potency of opioids to different degrees, in a drug-specific manner. Indeed, recent findings hint at drug-specific differences in the ability of opioids to manage burn pain early after injury, as well as differences in their ability to prevent or treat the development of chronic and neuropathic pain. Here we review the current state of opioid treatment, as well as new findings that could potentially lead to opioid-based pain management strategies that may be significantly more effective than the current solutions.

Hck is a key regulator of gene expression in alternatively activated human monocytes

IL-13 is a Th2 cytokine that promotes alternative activation (M2 polarization) in primary human monocytes. Our studies have characterized the functional IL-13 receptor complex and the downstream signaling events in response to IL-13 stimulation in alternatively activated monocytes/macrophages. In this report, we present evidence that IL-13 induces the activation of a Src family tyrosine kinase, which is required for IL-13 induction of M2 gene expression, including 15-lipoxygenase (15-LO). Our data show that Src kinase activity regulates IL-13-induced p38 MAPK tyrosine phosphorylation via the upstream kinases MKK3 or MKK6. Our findings also reveal that the IL-13 receptor-associated tyrosine kinase Jak2 is required for the activation of both Src kinase as well as p38 MAPK. Further, we found that Src tyrosine kinase-mediated activation of p38 MAPK is required for Stat1 and Stat3 serine 727 phosphorylation in alternatively activated monocytes/macrophages. Additional studies identify Hck as the specific Src family member, stimulated by IL-13 and involved in regulating both p38 MAPK activation and p38 MAPK-mediated 15-LO expression. Finally we show that the Hck regulates the expression of other alternative state (M2)-specific genes (Mannose receptor, MAO-A, and CD36) and therefore conclude that Hck acts as a key regulator controlling gene expression in alternatively activated monocytes/macrophages.

Ondansetron attenuates hepatic injury via p38 MAPK-dependent pathway in a rat haemorrhagic shock model

BACKGROUND

Ondansetron is a 5-HT3 receptor antagonist with potent antiemetic, analgesic, and antiphlogistic effects. Recent evidence suggests that the co-existence of 5-HT3 receptors in various cell types is involved in inflammation. However, the effects that 5-HT3 antagonists produce in haemorrhagic shock and resuscitation remain unknown. In this study, we hypothesized that ondansetron administration in male rats, after haemorrhagic shock, decreases cytokine production and protects against hepatic injury through a p38 mitogen-activated protein kinase (MAPK) pathway.

METHODS

Male Sprague-Dawley rats underwent haemorrhagic shock (mean arterial blood pressure 40 mm Hg for 90 min), followed by resuscitation. Various doses of ondansetron (0.1, 0.3, 1, 3 mg kg(-1)) or a single dose of ondansetron (1 mg kg(-1)) with or without a p38 MAPK inhibitor (SB-203580, 2 mg kg(-1)) or vehicle were administered intravenously during resuscitation. Plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) concentrations and various liver proinflammatory parameters were measured at 24h after resuscitation.

RESULTS

Results show that haemorrhagic shock increases plasma AST and ALT concentrations, hepatic myeloperoxidase activity, cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-3, intercellular adhesion molecule-1 (ICAM-1), interleukin-6 (IL-6) and tumor necrosis factor α (TNF-α) levels. These parameters were significantly improved in the ondansetron-treated rats subjected to haemorrhagic shock. Ondansetron treatment restored phos-p38 MAPK expression as compared with vehicle-treated haemorrhaged rats. Coadministration of SB-203580 prevented the beneficial effects of ondansetron on postresuscitation proinflammatory responses and hepatic injury.

CONCLUSION

Ondansetron attenuates hepatic injury following haemorrhagic shock, which is, at least in part, to be due to its anti-inflammatory effect via p38 MAPK signal pathway.

Selective effect of burn injury on splenic CD11c(+) dendritic cells and CD8alpha(+)CD4(-)CD11c(+) dendritic cell subsets

Burn injury causes an immunosuppression associated with suppressed adaptive immune function. Dendritic cells (DCs) are APCs for which signaling via their Toll-like receptors (TLRs) induces their maturation and activation, which is essential for the adaptive immune response. In this study, we examined if burn injury alters the TLR activity of splenic DCs. After injury, we noticed that DC functions were impaired, characterized by a suppressed capacity to prime naive T cells when triggering the TLR4 signaling cascade using specific ligands (LPS or rHSP60). The observed perturbations on LPS-primed DCs isolated from burned mice exhibited significantly diminished IL-12p40 production and enhanced IL-10 secretion-associated impairment in mitogen-activated protein kinase activation. Interestingly, we observed a decrease of TLR4/MD-2 expression on the CD8alpha(+) DC subset that persisted following LPS stimulation. The altered TLR4 expression on LPS-stimulated CD8alpha(+) DCs was associated with reduced capacity to produce IL-12 after stimulation. Our results suggested that TLR4 reactivity on DCs, especially CD8alpha(+) DCs, is disturbed after burn injury.

Local wound p38 MAPK inhibition attenuates burn-induced cardiac dysfunction

BACKGROUND

Topical inhibition of activated p38 MAPK within burn wounds attenuates the local and systemic inflammatory response. In this study, we investigated the effects of local activated p38 MAPK inhibition on burn-induced cardiac dysfunction.

METHODS

Using a standardized rat model of scald burn injury, rats were given a 30% total body surface area partial thickness burn or sham injury, and the wounds were treated with an activated p38 MAPK inhibitor (SB) or vehicle. Systemic blood pressure measurements were recorded in vivo followed by in vitro assessment of sarcomere contraction in single-cell suspensions of isolated cardiomyocytes.

RESULTS

Systolic blood pressure or maximum left ventricular pressures in vivo and peak cardiomyocyte sarcomere contractility in vitro were significantly reduced after burn injury. These functional deficits were abolished 24 h after burn injury following local p38 MAPK inhibition. In vitro incubation of normal cardiomyocytes with homogenate from burned skin or burn serum resulted in a similar pattern of impaired cardiomyocyte contractility. These effects were reversed in normal cardiomyocytes exposed to burn skin homogenates treated topically with a p38 MAPK inhibitor. A Western blot analysis showed that cardiac p38 MAPK activation was not affected by dermal blockade of activated p38 MAPK, arguing against systemic absorption of the inhibitor and indicating the involvement of systemic cytokine signaling.

CONCLUSION

Topical activated p38 MAPK inhibition within burned skin attenuates the release of proinflammatory mediators and prevents burn-induced cardiac dysfunction after thermal injury. These results support the inhibition of burn-wound inflammatory signaling as a new therapeutic approach to prevent potential postthermal injury multiorgan dysfunction syndrome.

Toll-like receptor 4 regulates heme oxygenase-1 expression after hemorrhagic shock induced acute lung injury in mice: requirement of p38 mitogen-activated protein kinase activation

Acute lung injury (ALI) leading to respiratory distress is a common sequela of shock or trauma. The toll-like receptors (TLRs) stand at the interface of innate immune activation in the settings of both infection and sterile injury by responding to a variety of microbial and endogenous ligands alike. This work explored the effects of TLR-4 on hemorrhage-induced ALI and characterizes the signaling pathways and the mechanisms involved in noninfectious ALI. Mice underwent hemorrhagic shock and resuscitation (HSR). Arterial blood gases; expressions of TLR-4, heme oxygenase 1 (HO-1), and p38 mitogen-activated protein kinase (p38MAPK); myeloperoxidase activity; lung wet/dry ratios; and IL-10 levels in lung tissues were obtained at 6, 24, and 48 h after HSR. Hemorrhagic shock and resuscitation induced significant expressions of TLR-4, HO-1, and p38MAPK in C3H/HeN mice. IL-10 and myeloperoxidase were markedly increased at 24 h after HSR, and C3H/HeN mice had ALI with PaO2/fraction of inspired oxygen less than 300 mmHg. The induced amount of each cytokine level and the expressions of TLR-4, HO-1, and p38MAPK of C3H/HeN mice were significantly higher compared with C3H/HeJ mice. This study demonstrated that lung p38MAPK is activated after HSR, and p38MAPK inhibitor FR167653 suppresses HO-1 induction after ALI. We concluded that TLR-4 might induce HO-1 messenger RNA expression, which is probably involved in p38MAPK activation in the development of the lung dysfunction after HSR.

Up-regulation of cell surface Toll-like receptors on circulating gammadelta T-cells following burn injury

Burn injury is associated with profound inflammation and activation of the innate immune system involving gammadelta T-cells. Similarly, Toll-like receptors (TLR) are associated with activation of the innate immune response; however, it is unclear whether TLR expression is altered in gammadelta T-cells after major burn injury. To study this, male C57BL/6 mice were subjected to burn injury (25% TBSA) and 1 or 7 days thereafter, blood and spleen cells were isolated and subjected to FACs analysis for TLRs and other phenotypic markers (gammadelta TCR, alphabeta TCR, CD69, CD120b). A marked increase in the number of circulating gammadelta T-cells was observed at 24h post-burn (14% vs. 4%) and a higher percentage of these cells expressed TLR-2. TLR-4 expression was also increased post-burn, but to a lesser degree. These changes in TLR expression were not associated with altered CD69 or CD120b expression in gammadelta T-cells. The mobilization of, and increased TLR expression in, gammadelta T-cells was transient, as phenotypic changes were not evident at 7 days post-burn or in gammadelta T-cells from the circulation or spleen. The increases in TLR expression were not observed in alphabeta T-cells after burn injury. In conclusion, 24h after burn injury mobilization of gammadelta T-cells with increased TLR expression was observed. This finding suggests that this unique T-cell population is critical in the innate immune response to injury, possibly through the recognition of danger signals by TLRs.

Estradiol's salutary effects on keratinocytes following trauma-hemorrhage are mediated by estrogen receptor (ER)-alpha and ER-beta

Although administration of 17beta-estradiol (estrogen) following trauma-hemorrhage attenuates the elevation of cytokine production and mitogen-activated protein kinase (MAPK) activation in epidermal keratinocytes, whether the salutary effects of estrogen are mediated by estrogen receptor (ER)-alpha or ER-beta is not known. To determine which estrogen receptor is the mediator, we subjected C3H/HeN male mice to trauma-hemorrhage (2-cm midline laparotomy and bleeding of the animals to a mean blood pressure of 35 mmHg and maintaining that pressure for 90 min) followed by resuscitation with Ringer's lactate (four times the shed blood volume). At the middle of resuscitation we subcutaneously injected ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), estrogen (50 microg/kg), or ER antagonist ICI 182,780 (150 microg/kg). Two hours after resuscitation, we isolated keratinocytes, stimulated them with lipopolysaccharide for 24 h (5 microg/mL for maximum cytokine production), and measured the production of interleukin (IL)-6, IL-10, IL-12, and TNF-alpha and the activation of MAPK. Keratinocyte cytokine production markedly increased and MAPK activation occurred following trauma-hemorrhage but were normalized by administration of estrogen, PPT, and DPN. PPT and DPN administration were equally effective in normalizing the inflammatory response of keratinocytes, indicating that both ER-alpha and ER-beta mediate the salutary effects of estrogen on keratinocytes after trauma-hemorrhage.

Trauma-hemorrhage inhibits splenic dendritic cell proinflammatory cytokine production via a mitogen-activated protein kinase process

Although splenic dendritic cell (DC) functions are markedly altered following trauma-hemorrhage, the mechanism(s) responsible for the altered DC functions remains unknown. We hypothesized that trauma-hemorrhage inhibits DC function via suppressing toll-like receptor 4 (TLR4) expression and mitogen-activated protein kinases (MAPKs). To examine this, male C3H/HeN (6–8 wk) mice were randomly assigned to sham operation or trauma-hemorrhage. Trauma-hemorrhage was induced by midline laparotomy and ∼90 min of hypotension [blood pressure (BP) 35 mmHg], followed by fluid resuscitation (4× the shed blood volume in the form of Ringer lactate). Two hours later, mice were euthanized, splenic DCs were isolated, and the changes in their MAPK activation, TLR4-MD-2 expression, and ability to produce cytokines were measured. The results indicate that trauma-hemorrhage downregulated the lipopolysaccharide (LPS)-induced MAPK activation in splenic DCs. In addition to the decrease in MAPK activation, surface expression of TLR4-MD-2 was suppressed following trauma-hemorrhage. Furthermore, LPS-induced cytokine production from splenic DCs was also suppressed following trauma-hemorrhage. These findings thus suggest that the decrease in TLR4-MD-2 and MAPK activation may contribute to the LPS hyporesponsiveness of splenic DCs following trauma-hemorrhage. Hyporesponsiveness of splenic DCs was also found after stimulation with the TLR2 agonist zymosan. Our results may thus explain the profound immunosuppression that is known to occur under those conditions.

Vitamin E inhibits endotoxin-mediated transport of phosphatases to lipid rafts

The production and release of inflammatory mediators is regulated by the coordinated activity of kinases and phosphatases. These proteins are known to regulate one another through an unknown mechanism. Previously, we have demonstrated that autocrine release of oxidants regulates macrophage activation in a similar fashion. The purpose of this study is to determine if attenuated oxidant activity by antioxidant exposure can regulate endotoxin-mediated kinase and phosphatase activity. Human promonocytic THP-1 cells were stimulated with lipopolysaccharide. Selected cells were pretreated with alpha-tocopherol succinate, LY294002, or an AKT inhibitor (1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate). Lipid raft and cellular protein were analyzed for lipid raft toll-like receptor 4 (TLR4) receptor formation and mitogen-activated protein kinase (MAPK) activation. Harvested supernatants were analyzed for tumor necrosis factor (TNF)-alpha production. Lipopolysaccharide stimulation led to the lipid raft mobilization of TLR4 and heat shock protein 70. This was followed by lipid raft mobilization of SH related complex homology 2 domain-containing inositol-5-phosphate (SHIP), activation of the MAPK, and production of TNF-alpha. Pretreatment with alpha-tocopherol succinate did not affect mobilization of TLR4 or heat shock protein 70, but did result in attenuated mobilization of SHIP, activation of the MAPK, and production of TNF-alpha. In addition, alpha-tocopherol succinate was associated with increased activation of the counter-regulatory kinase protein kinase B. Pretreatment with LY294002 or 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate reversed the effects of alpha-tocopherol succinate. Thus, it seems that endotoxin-mediated activation requires the coordinated activity of kinases and phosphatases. Antioxidant exposure in the form of vitamin E seems to attenuate endotoxin-mediated SHIP activation resulting in increased AKT activity, and attenuated MAPK activation and TNF-alpha production.

Postburn monocytes are the major producers of TNF-alpha in the heterogeneous splenic macrophage population

Increased tumor necrosis factor (TNF)-alpha production by postburn splenic macrophages is well documented. Splenic macrophages are a heterogeneous population, and the effect of thermal injury on these subpopulations has not been documented. We examined the effects of scald injury on myeloid cells with the phenotype of red pulp, white pulp, and marginal zone monocyte/macrophages. We found that thermal injury greatly increased the number of splenocytes with the phenotype of white pulp monocytes. These cells were the major producers of TNF-alpha in the postburn spleen. Cells with the red pulp macrophage phenotype had an increased ability to make TNF-alpha after burn injury, but had only half the capacity to make TNF-alpha as did postburn monocytes. The postburn changes in TNF-alpha production correlated with an increased in vivo susceptibility to endotoxin. The increase in monocytes in the spleen from postburn days 1 to 10 correlated with an increasing ability of splenocytes to produce granulocyte colony-stimulating factor, monocyte chemoattractant protein 1, macrophage inflammatory protein 2, and macrophage inflammatory protein 1-alpha. These data suggest that the monocyte is a major source of inflammatory cytokines in the postburn spleen.

Estrogen receptor-alpha predominantly mediates the salutary effects of 17beta-estradiol on splenic macrophages following trauma-hemorrhage

Although 17beta-estradiol administration following trauma-hemorrhage prevents the suppression in splenic macrophage cytokine production, it remains unknown whether the salutary effects are mediated via estrogen receptor (ER)-alpha or ER-beta and which signaling pathways are involved in such 17beta-estradiol effects. Utilizing ER-alpha- or ER-beta-specific agonists, this study examined the role of ER-alpha and ER-beta in 17beta-estradiol-mediated restoration of macrophage cytokine production following trauma-hemorrhage. In addition, since MAPK and NF-kappaB are known to regulate macrophage cytokine production, we also examined the activation of those signaling molecules. Male rats underwent trauma-hemorrhage (mean arterial pressure of 40 mmHg for 90 min) and fluid resuscitation. The ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), the ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), 17beta-estradiol (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, splenic macrophages were isolated, and their IL-6 and TNF-alpha production and activation of MAPK and NF-kappaB were measured. Macrophage IL-6 and TNF-alpha production and MAPK activation were decreased, whereas NF-kappaB activity was increased, following trauma-hemorrhage. PPT or 17beta-estradiol administration after trauma-hemorrhage normalized those parameters. DPN administration, on the other hand, did not normalize the above parameters. Since PPT but not DPN administration following trauma-hemorrhage was as effective as 17beta-estradiol in preventing the suppression in macrophage cytokine production, it appears that ER-alpha plays the predominant role in mediating the salutary effects of 17beta-estradiol on macrophage cytokine production following trauma-hemorrhage and that such effects are likely mediated via normalization of MAPK but not NF-kappaB signaling pathways.

The role of MAPK in Kupffer cell toll-like receptor (TLR) 2-, TLR4-, and TLR9-mediated signaling following trauma-hemorrhage

Severe injury deranges immune function and increases the risk of sepsis and multiple organ failure. Kupffer cells play a major role in mediating posttraumatic immune responses, in part via different Toll-like receptors (TLR). Although mitogen-activated protein kinases (MAPK) are key elements in the TLR signaling pathway, it remains unclear whether the activation of different MAPK are TLR specific. Male C3H/HeN mice underwent midline laparotomy (i.e., soft tissue injury), hemorrhagic shock (MAP approximately 35 mm Hg for 90 min), and resuscitation. Kupffer cells were isolated 2 h thereafter, lysed and immunoblotted with antibodies to p38, ERK1/2, or JNK proteins. In addition, cells were preincubated with specific inhibitors of p38, ERK1/2, or JNK MAPK followed by stimulation with the TLR2 agonist, zymosan; the TLR4 agonist, LPS; or the TLR9 agonist, CpG DNA. Cytokine (TNF-alpha, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and KC) production was determined by cytometric bead array after 24 h in culture. MAPK activity as well as TNF-alpha, MCP-1, and KC production by Kupffer cells were significantly increased following trauma-hemorrhage. TLR4 activation by LPS stimulation increased the levels of all measured cytokines. CpG-stimulated TLR9 signaling increased TNF-alpha and IL-6 levels; however, it had no effect on chemokine production. Selective MAPK inhibition demonstrated that chemokine production was mediated via p38 and JNK MAPK activation in TLR2, -4, and -9 signaling. In contrast, TNF-alpha and IL-6 production was differentially regulated by MAPK depending on the TLR pathway stimulated. Thus, Kupffer cell TLR signaling employs different MAPK pathways in eliciting cytokine and chemokine responses following trauma-hemorrhage.

Estrogen-mediated activation of non-genomic pathway improves macrophages cytokine production following trauma-hemorrhage

Although 17beta-estradiol (E2) attenuates the alterations in Kupffer cells and splenic macrophages (MPhi) cytokine production following trauma-hemorrhage, the mechanism by which this occurs remains unknown. Utilizing a cell-impermeable E2 conjugated with BSA (E2-BSA), we examined the non-genomic effects of E2 on the above two cell population cytokine production, MAPK and transcription factors activation following trauma-hemorrhage. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean BP 40 mmHg for 90 min, then resuscitation). E2, E2-BSA (1 mg/kg E2) with or without an estrogen receptor antagonist (ICI 182,780), or vehicle was administrated during resuscitation. Two hrs thereafter, Kupffer cells and SMPhi production of IL-6, TNF-alpha, and IL-10, activation of MAPK (p38, ERK-1/2, and JNK), and transcription factors (NF-kappaB and AP-1) were determined. IL-6, TNF-alpha, and IL-10 productive capacity, MAPK, and transcription factors activation increased in Kupffer cells while they decreased in SMPhi following trauma-hemorrhage. However, E2 administration normalized all of these alterations. Although E2-BSA also attenuated the alterations in cytokine production/transcription factors, the values were higher in Kupffer cells and lower in SMPhi compared to shams. In contrast, E2-BSA prevented trauma-hemorrhage-mediated changes in MAPK activation to the same extent as E2. Co-administration of ICI 182,780 abolished E2-BSA effects. Although some MAPK inhibitors suppressed cytokine production, the inhibitor effectiveness was dependent on cytokine, cell type and animal condition (trauma-hemorrhage or sham). Thus, E2 effects on Kupffer cells and SMPhi cytokine production and transcription factors activation following trauma-hemorrhage are mediated at least in part via non-genomic pathway and these non-genomic effects are likely mediated via MAPK pathways.

17β-estradiol administration following trauma-hemorrhage prevents the increase in Kupffer cell cytokine production and MAPK activation predominately via estrogen receptor-α

BACKGROUND

17 beta-estradiol (E2) administration following trauma-hemorrhage (T-H) attenuates the elevation in plasma cytokines and Kupffer cell (KC) cytokine production; however, it remains unknown whether the salutary effects are mediated via estrogen receptor (ER)-alpha or ER-beta. We hypothesized that E2 mediates its salutary effects via ER-alpha and normalization of MAPK under those conditions.

METHODS

Male rats underwent T-H (mean blood pressure [BP] 40 mmHg for 90 min) and fluid resuscitation. ER-alpha agonist propyl pyrazole triol (PPT; 5 microg/kg), ER-beta agonist diarylpropionitrile (DPN; 5 microg/kg), E2 (50 microg/kg), or vehicle (10% DMSO) was injected subcutaneously during resuscitation. Twenty-four hours thereafter, KCs were isolated and their cytokine production (IL-6, TNF-alpha, IL-10) and MAPK activation were measured.

RESULTS

Cytokine production increased after T-H, however, PPT or E2 administration after T-H normalized KC cytokine production. Although DPN attenuated increased production of these cytokines, KC capacity to produce the cytokines remained significantly higher than sham. PPT or E2 also prevented T-H-mediated activation of MAPK in KC. However, DPN did not prevent MAPK activation.

CONCLUSIONS

Since PPT administration after T-H was more effective in decreasing KC cytokine production and MAPK activation than DPN, the salutary effects of E2 on KC functions are mediated predominantly via ER-alpha and normalization of MAPK following T-H.

Src family kinases regulate p38 MAPK-mediated IL-6 production in Kupffer cells following hypoxia

Tissue hypoxia is a common sequel of trauma-hemorrhage but can occur even without blood loss under hypoxic conditions. Although hypoxia is known to upregulate Kupffer cells (KC) to release cytokines, the precise mechanism of release remains unknown. We hypothesized that Src family kinases play a role in mediating KC mitogen-activated protein kinase (MAPK) signaling and their cytokine production after hypoxia. Male C3H/HeN mice received either Src inhibitor PP1 (1.5 mg/kg body wt) or vehicle 1 h before hypoxia. KCs were isolated 1 h after hypoxia, lysed, and immunoblotted with antibodies to Src, p38, ERK1/2, or JNK proteins. In addition, KCs were cultured to measure interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) production. Hypoxia produced a significant increase in KC Src and MAPK (p38, ERK, JNK) activity compared with normoxic controls. This was associated with an increase in IL-6 and MCP-1 production. Treatment with PP1 abolished the increase in KC Src activation as well as p38 activity. However, PP1 did not prevent the increase in KC ERK1/2 or JNK phosphorylation. Furthermore, administration of PP1 prevented the hypoxia-induced increase in IL-6 but not MCP-1 release by KC. Additional in vitro results suggest that p38 but not ERK1/2 or JNK are critical for KC IL-6 production. In contrast, the production of MCP-1 by KC was found to be independent of MAPK. Thus hypoxia increases KC IL-6 production by p38 MAPK activation via Src-dependent pathway. Src kinases may therefore be a novel therapeutic target for preventing immune dysfunction following low-flow conditions in trauma patients.

Nitric oxide contributes to the development of a post-injury Th2 T-cell phenotype and immune dysfunction

Severe injury induces immune dysfunction resulting in increased susceptibility to opportunistic infections. Previous studies from our laboratory have demonstrated that post-burn immunosuppression is mediated by nitric oxide (NO) due to the increased expression of macrophage inducible nitric oxide synthase (iNOS). In contrast, others suggest that injury causes a phenotypic imbalance in the regulation of Th1- and Th2 immune responses. It is unclear whether or not these apparently divergent mediators of immunosuppression are interrelated. To study this, C57BL/6 mice were subjected to major burn injury and splenocytes were isolated 7 days later and stimulated with antiCD3. Burn injury induced NO-mediated suppression of proliferative responses that was reversed in the presence of the NOS inhibitor L-monomethyl-L-arginine and subsequently mimicked by the addition of the NO donor, S-nitroso-N-acetyl-penicillamine (SNAP). SNAP also dose-dependently suppressed IFN-gamma and IL-2 (Th1), but not IL-4 and IL-10 (Th2) production. Delaying the addition of SNAP to the cultures by 24 h prevented the suppression of IFN-gamma production. The Th2 shift in immune phenotype was independent of cGMP and apoptosis. The addition of SNAP to cell cultures also induced apoptosis, attenuated mitochondrial oxidative metabolism and induced mitochondrial membrane depolarization. However, these detrimental cellular effects of NO were observed only at supra-physiologic concentrations (>250 microM). In conclusion, these findings support the concept that NO induces suppression of cell-mediated immune responses by selective action on Th1 T cells, thereby promoting a Th2 response.

Comparison of Inhibitory Effects of Polyanions on Nitric Oxide Production by Macrophages Stimulated with LPS

In this paper, we investigated the inhibitory mechanism of the production of nitric oxide (NO) by polyanions and liposomes composed of phosphatidylserine (PS-liposomes) focusing on cytokine production and mitogen activated protein kinase (MAP kinase) activation. NO production by macrophages was inhibited by treatment with oxidized lipoprotein (OxLDL), maleylated bovine serum albumin (mBSA), and heparin. No inhibitory effect was exhibited by poly-cytidilic acid (PolyC). To clarify the mechanism of the inhibitory effect of polyanions on NO production, we evaluated the productions of transforming growth factor-beta (TGF-beta) and interleukin (IL)-10 which are known to be anti-inflammatory cytokines. TGF-beta was produced when macrophages were treated with OxLDL as was the case with PS-liposomes. No increase in TGF-beta production was observed for mBSA, heparin, and PolyC. On the other hand, significant production of IL-10 was observed using mBSA. Extracellular signal-regulated kinase (ERK), a member of the MAP kinase superfamily, was activated when macrophages were treated with OxLDL as well as PS-liposomes. In the case of mBSA, the activation of ERK and c-Jun N-terminal kinase (JNK) was observed. No activation of p38 MAP kinase was observed using any of the polyanions. Although heparin had an inhibitory effect on NO production by macrophages, no activation of MAP kinase or production of TGF-beta and IL-10 was observed. The inhibitory effect of these ligands on NO production may be regulated via different signaling pathways.

Enhanced TLR4 reactivity following injury is mediated by increased p38 activation

Severe injury primes the innate-immune system for increased Toll-like receptor 4 (TLR4)-induced proinflammatory cytokine production by macrophages. In this study, we examined changes in TLR4 signaling pathways in splenic macrophages from burn-injured or sham mice to determine the molecular mechanism(s) responsible for the increased TLR4 responsiveness. Using flow cytometry and specific antibodies, we first looked for injury-induced changes in the expression levels of several TLR-associated signaling molecules. We found similar levels of myeloid differentiation primary-response protein 88 (MyD88) and interleukin-1 receptor-associated kinase-M (IRAK-M) and somewhat lower levels of total p38, extracellular signal-regulated kinase (ERK), and stress-activated protein kinase (SAPK)/c-jun N-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) in burn compared with sham macrophages. However, with the use of antibodies specific for the phosphorylated (activated) forms of the three MAPKs, we found that macrophages from burn mice showed a twofold increase in purified lipopolysaccharide (LPS)-stimulated p38 activation as compared with cells from sham mice on days 1 and 7 post-injury, whereas ERK and SAPK/JNK activation was increased by burn injury only on day 1. Using the specific p38 inhibitor (SB203580), we confirmed that the increase in tumor necrosis factor alpha production by LPS-stimulated burn macrophages requires p38 activation. Although we demonstrated that injury increases macrophage TLR4 mRNA expression and intracellular expression of TLR4-myeloid differentiation protein-2 (MD-2) protein, macrophage cell-surface expression of TLR4-MD-2 was not changed by burn injury. Our results suggest that the injury-induced increase in TLR4 reactivity is mediated, at least in part, by enhanced activation of the p38 signaling pathway.

Involvement of ERK, a MAP kinase, in the production of TGF-β by macrophages treated with liposomes composed of phosphatidylserine

We have already reported that TGF-beta could be involved in the inhibitory effects of negatively charged liposomes composed of phosphatidylserine (PS-liposome) on the production of nitric oxide (NO) by mouse peritoneal macrophages stimulated with LPS [Biochem. Biophys. Res. Commun. 281 (2001) 614]. In this paper, we explored the mechanism by which PS-liposomes promote the production of TGF-beta and the involvement of MAP kinases. When macrophages were treated with PS-liposomes, extracellular signal-regulated kinase (ERK), a member of MAP kinase superfamily, was activated quickly and potently. However, no activation was observed with p38 MAP kinase. TGF-beta production was completely inhibited by U0126, a specific inhibitor for ERK. Furthermore, TGF-beta neutralizing antibody and U0126 decreased the inhibitory effect of PS-liposomes on NO production by macrophages. These findings suggested that TGF-beta is the factor produced by PS-liposomes that suppresses production of NO, and the ERK signaling pathway is intimately involved in TGF-beta production by macrophages following treatment with PS-liposomes.