Prostaglandin E2 down-regulation of T cell IL-2 production is independent of IL-10 during gram-negative sepsis

Review: Immunodepression in sepsis and SIRS assessed by ex vivo cytokine production is not a generalized phenomenon: a review

Sepsis and non-infectious systemic inflammatory response syndrome (SIRS) are paradoxically associated with an exacerbated production of cytokines, as assessed by their presence in biological fluids, and a diminished ability of circulating leukocytes to produce cytokine upon in vitro activation. In this review, we depict that the observed cellular hyporeactivity is not a global phenomenon and that some signalling pathways are unaltered and allow the cells to respond normally to certain stimuli. Furthermore, we illustrate that during sepsis and SIRS, cells derived from tissues are either fully responsive to ex vivo stimuli or even primed, in contrast to cells derived from hematopoietic compartments (blood, spleen, etc.) which are hyporeactive. In addition to cytokine production, nuclear factor-κB (NF-κB) status within leukocytes can be used as a useful marker of hypo- or hyper-reactivity. We illustrate that the immune-depression reported in sepsis and SIRS patients, often revealed by a diminished capacity of leukocytes to respond to lipopolysaccharide, is not a generalized phenomenon and that SIRS is associated with a compartmentalized responsiveness which involves either anergic or primed cells.

Resting but not CpG stimulated keratinocytes suppress autologous T-helper cell proliferation--importance of PGE2 and T regulatory function

In the last decade, keratinocytes have increasingly been recognized to actively participate in the skin immune response. However, their influence on infiltrating lymphocytes - abundantly found in e.g. atopic and psoriatic inflammation - is still controversial. In this study, we aimed to investigate the influence of keratinocytes on T-cell proliferation by use of an autologous co-culture model. Because the skin has an important function with regard to detecting invading pathogens, we also investigated the influence of pathogen-associated molecular pattern on keratinocyte - T-cell interaction. We observed a clear inhibition of T-cell proliferation by co-cultured keratinocytes. This effect was found to be mediated by PGE2, as T-cell proliferation was recovered in the presence of the PGE2 inhibitor indometacin. Furthermore, presence of keratinocytes led to enhanced expression of the T regulatory cell-specific transcription factor Foxp3 in the CD4+CD25+ T-cell population which also showed regulatory function. Interestingly, the presence of the TLR9 ligand CpG was able to prevent the inhibition of T-cell proliferation. This was paralleled by a reduced PGE2 production by keratinocytes and a down-regulated T regulatory cell function. Our results indicate that the inhibitory capacity of keratinocytes in the skin is strongly influenced by the surrounding micromillieu.

Anti-inflammatory activity of the non-peptidyl low molecular weight radical scavenger IAC in carrageenan-induced oedema in rats

OBJECTIVE

In this research we investigated the anti-inflammatory activity of a non-peptidyl low molecular weight radical scavenger (IAC) in an acute and chronic animal model of inflammation.

METHODS

For this purpose the effect of IAC (10, 25, 50 mg/kg) was tested in rats on the associated behavioral responses to subsequent inflammatory and noxious challenges, such as hind paw oedema induced by intra-plantar injection of carrageenan and granuloma induced by subcutaneous implant of a cotton pellet, using indometacin (2.5 mg/kg) as reference drug. Moreover, the serum level of several cytokines was tested in the animal treated (or not) with IAC (50 mg/kg) both in the absence and presence of carrageenan-induced inflammation.

KEY FINDINGS

IAC showed a significant anti-inflammatory activity in both in acute and chronic models of inflammation. In addition IAC down regulated significantly the serum levels of interleukin (IL) 2 and IL6 whereas it increased the serum concentration of IL1α and glutathione.

CONCLUSION

Although it remains to be elucidated whether or not the antioxidant property of IAC is directly responsible for the modulation of the tested cytokines, these results suggest IAC to be a possible candidate for a novel anti-inflammatory compound.

Differential expression of toll-like receptor signaling cascades in LPS-tolerant human peripheral blood mononuclear cells

Pre-exposure to low doses of LPS induces resistance to a lethal challenge, a phenomenon known as endotoxin tolerance. In this study, tolerance was induced in human PBMC by culturing cells with 1 ng/mL LPS for 48 h. Cells were subsequently challenged with 100 ng/mL LPS for 2, 6 and 24 h, and the expression of 84 genes encoding proteins involved in the TLR signaling pathway was evaluated at each time point by PCR array. LPS pretreatment did not modulate the expression of TLR4 and CD14 on the surface of monocytes. A gene was defined as tolerized when LPS pretreatment reversed the effect of LPS challenge on the expression of the gene or as non-tolerized when LPS pretreatment did not reverse the effects of LPS challenge. We observed impaired signal transduction through the NF-κB, JNK, ERK and TRIF pathways, whereas expression of p38 pathway-related genes was preserved in LPS-tolerant cells. These results show a distinct regulation of the TLR pathway cascades during tolerance; this may account for the differential gene expression of some inflammatory mediators, such as up-regulation of IL-10 and COX2 as well as down-regulation of TNF-α and IL-12. Depending on the effect of LPS-induced gene up-regulation or down-regulation, tolerance, as a reversion of such LPS effects, may result in repression or induction of gene expression.

A role for corticosterone in impaired intestinal immunity and barrier function in a rodent model of acute alcohol intoxication and burn injury

Alcohol (EtOH) intoxication and burn injury independently activate hypothalamic-pituitary-adrenal (HPA) axis, and glucocorticoids, the end product of the HPA axis, play a role in shaping the immune response under those conditions. By utilizing a rat model of acute EtOH intoxication and burn injury, studies in our laboratory have investigated the role of corticosterone (i.e., glucocorticoids in rodents) in altered intestinal immunity and barrier function following a combined insult of EtOH and burn injury. Results from these studies suggest that EtOH intoxication prior to burn injury augments corticosterone release, which in turn suppresses intestinal T cell function by inhibiting mitogen-activated protein kinase (i.e., p38 and ERK) pathway. Furthermore, we found that corticosterone does not directly alter the intestinal barrier function; rather, it up-regulates interleukin-18, which then directly or indirectly contributes to impaired intestinal barrier function. The loss of intestinal immunity/barrier function may result in increased bacterial translocation and thereby contribute to postinjury pathogenesis, leading to sepsis and organ dysfunction in burn patients as well as in patients with a history of EtOH intoxication.

Sepsis

Sepsis is a clinical syndrome defined by a systemic response to infection. With progression to sepsis-associated organ failure (ie, severe sepsis) or hypotension (ie, septic shock) mortality increases. Sepsis is a cause of considerable mortality, morbidity, cost, and health care utilization. Abnormalities in the inflammation, immune, coagulation, oxygen delivery, and utilization pathways play a role in organ dysfunction and death. Early identification of septic patients allows for evidence-based interventions, such as prompt antibiotics, goal-directed resuscitation, and activated protein C. Appropriate care for sepsis may be more easily delivered by dividing this clinical entity into various stages and with changes in structures of delivery that extend across traditional boundaries. Better description of the molecular basis of the disease process also will allow for more targeted therapies.

Bench-to-bedside review: endotoxin tolerance as a model of leukocyte reprogramming in sepsis

Endotoxin tolerance is defined as a reduced responsiveness to a lipopolysaccharide (LPS) challenge following a first encounter with endotoxin. Endotoxin tolerance protects against a lethal challenge of LPS and prevents infection and ischemia-reperfusion damage. Endotoxin tolerance is paralleled by a dramatic reduction of tumor necrosis factor (TNF) production and some other cytokines in response to LPS. Endotoxin tolerance involves the participation of macrophages and mediators, such as glucocorticoids, prostaglandins, IL-10, and transforming growth factor-β. Endotoxin tolerance is accompanied by the up-regulation of inhibitory molecules that down-regulate the Toll-like receptor (TLR)4-dependent signaling pathway. Cross-tolerance between LPS and other TLR specific ligands, as well as IL-1 and TNF, has been regularly reported. A similar loss of LPS reactivity has been repeatedly reported in circulating leukocytes of septic patients and in patients with non-infectious systemic inflammation response syndrome (SIRS). Studies on cellular signaling within leukocytes from septic and SIRS patients reveal numerous alterations reminiscent of those observed in endotoxin tolerant cells. However, altered responsiveness to LPS of leukocytes from sepsis and SIRS patients is not synonymous with a global down-regulation of cellular reactivity. The term 'cellular reprogramming', which has been proposed to qualify the process of endotoxin tolerance, defines well the immune status of circulating leukocytes in septic and SIRS patients.

Immunologic responses to critical injury and sepsis

Almost 2 million patients are admitted to hospitals in the United States each year for treatment of traumatic injuries, and these patients are at increased risk of late infections and complications of systemic inflammation as a result of injury. Host response to injury involves a general activation of multiple systems in defending the organism from hemorrhagic or infectious death. Clinicians have the capability to support the critically injured through their traumatic insult with surgery and improved critical care, but the inflammatory response generated by such injuries creates new challenges in the management of these patients. It has long been known that local tissue injury induces systemic changes in the traumatized patient that are often maladaptive. This article reviews the effects of injury on the function of immune system cells and highlights some of the clinical sequelae of this deranged inflammatory-immune interaction.

Enhanced expression of cyclooxygenase-2 and prostaglandin E2 in response to endotoxin after trauma is dependent on MAPK and NF-kappaB mechanisms

Macrophage prostaglandin E2 (PGE2) production is important in cellular immune suppression and in affecting the potential development of sepsis after trauma. We hypothesized that macrophage PGE2 production after trauma is regulated by mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-kappaB). Mice were subjected to trauma and splenic macrophages isolated 7 days later. Macrophages from traumatized mice showed increased cyclooxygenase-2 (COX-2) mRNA, protein expression, and PGE2 production compared with controls. Increased phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38 kinase was observed in macrophages from traumatized mice. Pharmacologic inhibition of MAPK blocked trauma-induced COX-2 expression, and PGE2 production. Trauma macrophages showed increased IkappaBalpha phosphorylation and NF-kappaB binding to DNA. Inhibiting IkappaBalpha blocked trauma-induced NF-kappaB activity, COX-2 expression and PGE2 production. This suggests that trauma-induced PGE2 production is mediated through MAPK and NF-kappaB activation and offers potential for modifying the macrophages' responses following injury.

Gender affects macrophage cytokine and prostaglandin E2 production and PGE2 receptor expression after trauma1

BACKGROUND

Gender influences morbidity and mortality after injury. Hormonal differences are important; however, the role of prostaglandins as mediators in immune dysfunction relating to gender differences after trauma is unclear. We hypothesized that gender-dependent differences in PGE(2) receptor expression and signaling may be involved in immune-related differences. This study determined prostaglandin receptor subtype (EP1-EP4) expression following injury and determined whether gender differences influence EP receptor expression.

MATERIALS AND METHODS

BALB/c male and female mice (estrus and pro-estrus) (n = 6 per group) were subjected to femur fracture and 40% hemorrhage (trauma) or sham injury (anesthesia). Seven days later, the splenic macrophages were harvested and stimulated with lipopolysaccharide (Escherichia coli serotype O55:B5). After 6 h mRNA samples were collected for EP receptor mRNA expression and at 24 h supernatants were collected for PGE(2), TNF-alpha, and IL-6 production.

RESULTS

The expression of EP2-4 receptors was higher in female pro-estrus mice compared with male mice. EP1 receptor expression was higher in males than pro-estrus females. There was decreased expression of all four receptors after trauma in female estrus compared with control estrus mice. Macrophage PGE(2), TNF-alpha, and IL-6 production was significantly increased in injured female mice compared with female controls but there were no differences in injured male mice compared with male controls. PGE(2) and TNF-alpha production by traumatized male mice were significantly less than that produced by traumatized pro-estrus females.

CONCLUSIONS

These data suggest gender-related differences in response to traumatic injury and that alterations in specific EP receptor subtypes may be involved in immune dysfunction after injury. Studies to evaluate targeted modulation of these receptor subtypes may provide further insights to gender-specific differences in the immune response after injury.

Uterine response to infectious bacteria in estrous cyclic ewes

PROBLEM

Luteal-phase uteri are susceptible to infections, and PGE2 and exogenous progesterone can down-regulate, whereas PGF2alpha can up-regulate, uterine immune functions.

METHOD OF STUDY

Uteri of follicular- or luteal-phase ewes were inoculated with either saline or bacteria (Arcanobacterium pyogenes and Escherichia colt). Vena caval blood was collected for the next 3 days, and progesterone, PGE2, and PGF2alpha were measured. The effects of 10(-7) M PGE2 (Experiment 1), 10(-7) M PGF2alpha (Experiment 2), 10(-7) M indomethacin (INDO), and diluent on proliferation of lymphocytes from the vena caval blood in response to mitogens was quantified.

RESULTS

Experiment 1: Progesterone was greater (P < 0.01) in luteal than in follicular ewes (3.4 versus 0.4 ng/mL), and only luteal ewes inoculated with bacteria developed infections.Lymphocyte proliferation was least (P = 0.08) in follicular ewes (2.6 versus 4.5 pmol for follicular and luteal, respectively). Concanavalin A (Con A)-stimulated proliferation was less (P < 0.05) for ewes inoculated with bacteria and for cells cultured with diluent (5.9 versus 3.1 pmol for saline and bacteria, respectively) or with INDO (6.6 versus 2.8 pmol for saline and bacteria, respectively). Also, Con A-stimulated lymphocytes from ewes inoculated with bacteria tended to proliferate less (P < 0.1) when cultured with PGE2 (4.9 versus 3.7 pmol for saline and bacteria, respectively) or PGE2 + INDO (5.5 versus 3.8 pmol for saline and bacteria, respectively). Experiment 2: Progesterone was greater (P < 0.01) in luteal than in follicular ewes (6.5 versus 1.2 ng/mL), and only luteal ewes inoculated with bacteria developed infections. Con A-stimulated lymphocyte proliferation was greater (P < 0.001) for follicular ewes (4.1 versus 3.1 pmol for follicular and luteal, respectively). Proliferation of lymphocytes collected from follicular ewes was greater (P < 0.01) when cells were cultured with PGF2alpha (3.5 versus 2.7 pmol for follicular and luteal, respectively), but INDO did not affect unstimulated or mitogen-stimulated proliferation.

CONCLUSIONS

Prostaglandin F2alpha enhanced lymphocyte proliferation, whereas bacterial inoculation and in vitro treatment with PGE2 suppressed lymphocyte proliferation. This may signify the involvement of bacterial products and prostaglandins in regulation of uterine immunity.

Role of ovarian progesterone and potential role of prostaglandin F2alpha and prostaglandin E2 in modulating the uterine response to infectious bacteria in postpartum ewes

In sheep and cattle, the postpartum uterus is resistant to bacterial challenge until after corpora lutea develop. A 2 x 2 factorial arrangement of treatments was used to determine whether prostaglandins may mediate the effects of progesterone in transforming the postpartum uterus from resistant to susceptible. On d 14 postpartum, ewes (n = 6/group) were ovariectomized or sham ovariectomized, and the vena cava was catheterized for daily collection of uteroovarian-enriched blood. From d 15 to 20, ewes received twice daily intramuscular injections of progesterone in sesame oil or plain sesame oil. On d 20, each uterus received 75 x 10(7) cfu of Arcanobacterium pyogenes and 35 x 10(7) cfu of Escherichia coli. Uteri were collected on d 25 and examined for signs of infection. For each blood sample, unstimulated and mitogen-stimulated lymphocyte proliferation was measured as [3H]thymidine incorporation, smears were prepared for differential white blood cell (WBC) counts, and progesterone, prostaglandin F2alpha, (PGF2alpha), and prostaglandin E2 (PGE2) were quantified. All 12 progesterone-treated, but only two of the 12 oil-treated, ewes developed uterine infections (P < 0.001). Progesterone treatment increased (P < 0.001; 3.1 vs 1.5 ng/mL) and ovariectomy decreased (P < 0.001; 3.7 vs 0.9 ng/mL) vena caval progesterone. Progesterone treatment reduced (P < 0.01) PGF2alpha, (303.9 vs 801.3 pg/mL), and PGF2alpha was greater (P < 0.05) before than after inoculation (626.4 vs 478.8 pg/mL). The PGE2 concentration was greater in progesterone-treated, ovary-intact ewes than in ewes in the other groups (ovariectomy x progesterone treatment; P < 0.01). Ovariectomy increased (P < 0.005; 4.4 vs 2.9 pmol) and progesterone treatment decreased (P < 0.05; 3.2 vs 4.1 pmol) concanavalin A-stimulated lymphocyte proliferation. Ovariectomy increased lipopolysaccharides-stimulated proliferation (P < 0.05; 2.4 vs 1.9 pmol). For neutrophils per 100 WBC, the ovariectomy x progesterone and progesterone x period interactions were significant (P < 0.01). The ovariectomy x progesterone interaction was significant (P < 0.01) for lymphocytes per 100 WBC. Ovariectomy decreased monocytes (P < 0.001; 10 vs 13) and increased eosinophils (P < 0.001; 10 vs 5) per 100 WBC. Progesterone makes the postpartum uterus in ewes susceptible to infection, but ovariectomy allows ewes to remain resistant; uterine prostaglandins may mediate this change. This model creates opportunities to determine the mechanisms responsible for the shift from resistance to susceptible.

Enterococcus faecalis exacerbates burn injury-induced host responses in rats

Pathophysiology of burn injury with complications of gram-positive infections is not well characterized. We have developed an in vivo rat model to study the effects of burn injury along with intra-abdominal inoculation of Enterococcus faecalis. We hypothesized that although burn injury or E. faecalis inoculation by itself may not induce significant pathophysiological responses, the combination of the two can lead to adverse pathophysiological consequences. Sprague-Dawley rats were divided into 4 groups: group 1(C), controls; group 2(B), burn injury on 30% total body surface area; group 3(EF), intra-abdominal implantation of bacterial pellet impregnated with E. faecalis; group 4(B+EF), burn injury plus bacterial pellet implantation. The mortality was 25% and 60% on day 1 and 2 in Group 4(B+EF), respectively; no significant mortality was observed in other groups. In group 4(B+EF), metabolic acidosis, respiratory alkalosis, and a hyperdynamic state developed on day 1, and metabolic and respiratory acidosis and a hypodynamic state on day 2. There were no significant alterations in metabolic or hemodynamic measurements in other groups. Intestinal microvascular permeability to albumin on day 1 and 2 was increased in group 4(B+EF). In group 2(B), microvascular permeability was not increased significantly. Although the permeability was increased on day 1 in group 3(EF), it declined on day 2. The metabolic and hemodynamic alterations were correlated with increased intestinal microvascular permeability to albumin. E. faecalis appeared to be involved in initiating a vicious cycle of burn injury-mediated disruption of intestinal integrity along with metabolic and hemodynamic derangements.

Comparative study of the endotoxemia and endotoxin tolerance on the production of Th cytokines and macrophage interleukin-6: differential regulation of indomethacin

Endotoxin tolerance reduces the capacity of monocytes to produce proinflammatory cytokines, results in cellular immune paralysis, and down-regulates the production of helper T (Th)1 type cytokines with a shift toward a Th2 cytokine response. Prostaglandin (PG)E2 in the immune system also results in macrophage inactivation and the suppression of Th1 activation and the enhancement of Th2 activation. However, the inhibitory effects of PGE2 on the altered polarization of the Th cell and macrophage interleukin (IL)-6 production characterized in part by cellular immune paralysis in a state of endotoxin tolerance is unclear. This study was undertaken, using indomethacin, to investigate the role of endogenous PGE2 on the Th cytokines and macrophage IL-6 production in a state of endotoxin tolerance compared to those with endotoxemia mice, wherein, in this latter case, the increased production of proinflammatory cytokines and PGE2 is exhibited. Endotoxemia was induced by injection of lipopolysaccharide (LPS; 10 mg/kg in saline) ip. once in BALB/c mice, and endotoxin tolerance was induced by pretreatment with LPS (1 mg/kg in saline) injected i.p. daily for two consecutive days and then with LPS 10 mg/kg on day 4. Splenocytes or macrophages were obtained from endotoxemia and endotoxin tolerance models pretreated with indomethacin, and then cytokine production was induced by Con A-stimulated splenocytes for the Th cytokine assays and LPS-stimulated macrophages for the IL-6 assay. Our results showed that endotoxemia led to significantly reduced IL-2 and IL-4 production, to significantly increased IL-6 production, whereas interferon (IFN)-gamma production was not affected. Indomethacin in the case of endotoxemia markedly attenuated IFN-gamma and IL-6 production and didnt reverse IL-2 and IL-4 production. Endotoxin tolerance resulted in the significantly reduced production of IL-2 and IFN-gamma and the significantly increased production of IL-4 and IL-6. Indomethacin in endotoxin tolerance greatly augmented IL-2 production, significantly decreased IL-4 production, and slightly attenuated IL-6 production. These findings indicate that endogenous PGE2 may mediate the suppressed Th1 type immune response, with a shift toward a Th2 cytokine response in a state of endotoxin tolerance, whereas endotoxemia may be regulated differentially. Also, endogenous PGE2 may mediate macrophage IL-6 production in the case of endotoxemia to a greater extent than in the case of endotoxin tolerance.

Immunosuppressive properties of human amniotic membrane for mixed lymphocyte reaction

The combination of allograft limbal transplantation (ALT) and amniotic membrane transplantation (AMT) has been applied in the treatment of severe ocular surface diseases. The beneficial effect of this combination has been thought to result from possible immunosuppressive ability of amniotic membrane (AM). However, the mechanisms of any such ability remain unknown. In this study, we investigated whether human AM has the ability to suppress allo-reactive T cell responses in vitro. For mixed lymphocyte reaction (MLR), lymphocytes isolated from lymph nodes of C57BL/6 mice (Mls1b, Vbeta6+) were cultured with irradiated splenocytes from DBA/2 mice (Mls1a, Vbeta6-) with or without human AM. For carboxyfluorescein diacetate succinimidyl ester (CFSE) experiments, responder lymph node cells were labelled with a stable intracellular fluorescent dye and cultured with irradiated stimulator cells. The ratio of responder Vbeta6+ T cells was then determined by FACS analysis, and the division profiles of responder Vbeta6+ T cells were analysed by CFSE content. Furthermore, Th1 and Th2 cytokine synthesis by allo-reactive T cells in MLR culture supernatants was determined by enzyme-linked immunosorbent assay (ELISA). Addition of AM to the MLR culture resulted in the significant inhibition of thymidine incorporation compared with control culture lacking AM. The population of responder CD4+Vbeta6+ T cells was significantly reduced in the AM-treated culture in comparison to control. CFSE analysis revealed less division and lower proliferation of responder CD4+Vbeta6+ T cells in cultures with AM than without. In addition, allo-rective T cell synthesis of both Th1 (IL-2 and IFNgamma) and Th2 (IL-6 and IL-10) type cytokine was significantly decreased in the presence of AM. These results indicate that human AM has the ability to suppress allo-reactive T cells in vitro. This inhibitory effect likely contributes to the success of the ALT-AMT combination.

Role of NFAT and AP-1 in PGE2-mediated T cell suppression in burn injury

PGE2 is known to suppress T cell proliferation and IL-2 production in many inflammatory conditions. Previous studies from our laboratory have shown that such suppression of T cell proliferation in burn and sepsis could result from alteration in T cell activation signaling molecule p59fyn. In this study, we examined the role of downstream signaling molecules NFAT and AP-1 in PGE2-mediated suppression of T cell in burn injury. These studies were carried out utilizing splenic T cells from sham and burn rats 3 days after injury. The data presented in this manuscript suggest a significant suppression of IL-2 production by T cells from burn injured rats compared with the T cells from sham rats. The suppression in T cell IL-2 production was accompanied by a decrease in the activation of NFAT and AP-1 as well as a decrease in T cell p59fyn kinase activity. The treatments of burn-injured animals with PGE2 synthesis blocker indomethacin prevented both the decrease in NFAT and AP-1 binding to IL-2 sequences. In vitro incubation of control rat T cells with PGE2 suppressed the activation of NFAT and AP-1. These results suggested that the suppression of T cell IL-2 production could result from PGE2-mediated alterations in the T cell signaling molecule p59fyn and NFAT/AP-1.

Sepsis-induced immunosuppression: from bad to worse

The sepsis syndrome is characterized by the acute release of a variety of inflammatory mediators, which often result in detrimental effects to the host. The release of these mediators is regulated and counterbalanced by the coordinated expression of antiinflammatory molecules. It is the balance between the expression of pro- and antiinflammatory mediators that often determines the magnitude of early tissue injury and subsequent risk of infectious complications. As our understanding of the pathophysiology of sepsis continues to evolve, we have gained a greater appreciation for the effects that sepsis and similar states of overwhelming stress have on host antimicrobial immunity. A number of functional defects in leukocytes isolated from sepsis patients have been characterized. These defects include diminished expression of important cell surface antigens, dysregulated cytokine production, alterations in antigen-presenting ability, and accelerated apoptosis. Impaired leukocyte function has important clinical ramifications, as high mortality rates have been observed in patients displaying evidence of sepsis-induced immune deactivation. In this article, we review the current literature supporting evidence of dysregulation of host immunity occurring during sepsis syndrome, characterize the underlying pathophysiology, and describe novel therapeutic interventions directed at augmenting host immunity during sepsis.

Differential modulation of interleukin-6 and interleukin-10 by diclofenac in patients undergoing major surgery

BACKGROUND

Prostaglandins modulate cytokine release though increases in cAMP, regulating interleukin (IL) 6 and IL-10. Diclofenac inhibits cyclo-oxygenase activity and hence prostaglandin production. We hypothesized that diclofenac would affect release of IL-6 and IL-10 and modulate the immune response.

METHODS

In a randomized, double-blind, placebo-controlled study, we investigated the effect of diclofenac in patients undergoing major urological surgery. Patients were randomized to receive either diclofenac (50 mg orally every 8 h the day before surgery and 75 mg i.m. every 12 h on the day of surgery, n = 23) or placebo (n = 23). Standardized combined general anaesthesia and epidural analgesia was administered. Serum IL-6, IL-10 and cortisol were measured before surgery and 30 min and 2, 6, 12 and 24 h after skin incision. Temperature, leucocyte count and C-reactive protein concentration were measured before surgery and after 24 h.

RESULTS

IL-6 and IL-10 concentrations increased, reaching peak levels at 12 and 6 h respectively in both groups. At 12 h, the IL-6 concentration was significantly lower in patients receiving diclofenac than in those receiving placebo (P = 0.003). In contrast, IL-10 concentration at 6 h was higher in diclofenac-treated patients (P = 0.008), and this was associated with less pyrexia (P = 0.03), a lower leucocyte count (P = 0.0002) and a lower C-reactive protein concentration (P = 0.0039). Serum cortisol concentration was similar in the two groups of patients until 24 h, when the concentration was lower in patients who received diclofenac (P = 0.002). Cortisol concentration correlated with IL-6 concentration at 24 h.

CONCLUSIONS

Administration of diclofenac was associated with lower IL-6 and higher IL-10 concentrations, and lower leucocyte count, C-reactive protein concentration and temperature. Diclofenac may have an anti-inflammatory role in major surgery.

Modulation of the uterine response to infectious bacteria in postpartum ewes

PROBLEM

Exogenous progesterone and prostaglandin E2 (PGE2) can downregulate uterine immune functions and render the uterus susceptible to bacterial infection.

METHOD OF STUDY

Ewes were sham-ovariectomized (SHAM) or ovariectomized (OVEX) 9 days after parturition (day 0), and their uteri were inoculated with Arcanobacterium pyogenes and Escherichia coli on day 15. Vena caval blood was collected on day 14 and days 16-19, and uteri were collected on day 20. Ewes began receiving either canola oil (OIL) or progesterone in oil (PROG) on day 10. Lymphocytes from each blood sample were assigned to a 2 x 2 factorial array of in vitro treatments; 10(-7) M PGE2 and 10(-7) M indomethacin (INDO) were main effects. [3H]Thymidine incorporation (expressed in picomoles) was used to quantify proliferation.

RESULTS

Progesterone was greater (P = 0.001) in PROG than in OIL ewes (3.6 versus 0.7 ng/mL), and only PROG ewes developed infections. Lymphocyte proliferation was least (P = 0.02) in PROG-OVEX ewes (4.1 versus 5.4, 5.7, and 5.8 pmol for OIL-SHAM, PROG-SHAM, and OIL-OVEX, respectively). Concanavalin A (Con-A)-stimulated proliferation was less (P < 0.01) for PGE2- and PGE2 + INDO-treated lymphocytes (7.5 and 8.3 pmol, respectively) than for control or INDO-treated cells (12.9 and 14.7 pmol, respectively).

CONCLUSIONS

Progesterone treatment of postpartum ewes suppressed uterine immunity. In vitro PGE, treatment suppressed lymphocyte proliferation, regardless of PROG, and highlights a progesterone-independent level of regulation of uterine immune function.

Immunotherapy of sepsis

Sepsis is a clinical syndrome that results from a systemic host response to an infection. The outcome of sepsis is poor, and mortality rates are as high as 30-40%. Sepsis is associated with the activation of multiple inflammatory pathways, including the cytokine network and the coagulation system. Sepsis can also result in an immunodepressed state that could leave patients more susceptible to secondary nosocomial infections. Modulation of the host response to infection has been studied as an adjunctive therapeutic approach in many preclinical investigations and clinical trials in the past 20 years. As a result of these studies our knowledge of the pathogenesis of sepsis has increased considerably. This review focuses on immunomodulatory strategies that have reached the phase of clinical evaluation in patients with sepsis.

The effects of lithium on ex vivo cytokine production

BACKGROUND

Studies suggest that lithium may have profound immunomodulatory effects in animal models as well as in humans.

METHODS

In this study, whole blood cultures from normal control subjects were established for 5 days and the effects of lithium on cytokine production were investigated. Because many of lithium's actions have been postulated to be modulated through phosphoinositide (PI), protein kinase C (PKC) and cyclic adenosine monophosphate (c-AMP) signaling pathways, the effects of myo-inositol and prostaglandin E(2), alone or in combination with lithium, were also investigated.

RESULTS

We found that lithium caused an increase in interleukin-4 and interleukin-10 levels, traditionally classified as T-helper lymphocyte type-2 cytokines, and a decrease in interleukin-2 and interferon-gamma levels, traditionally classified as T-helper lymphocyte type-1 (TH-1) cytokines. This shift cannot be fully explained by lithium's actions on the PI, PKC, or c-AMP messenger systems.

CONCLUSIONS

Monocytes exposed to lithium in the presence of a mitogen for 5 days produced a shift toward the production of TH-2 cytokines and away from the production of TH-1 cytokines. The study suggests that lithium may have complex time-dependent effects on immune function.

Prostaglandin E2 receptors EP2 and EP4 are down-regulated in human mononuclear cells after injury

BACKGROUND

Recent characterization of prostaglandin receptor subtypes shows that each is critical to cellular functions and operates through separate signaling pathways that may explain differing effects of prostanoids. This study aimed to determine whether prostaglandin receptors EP2 and EP4 are modulated after injury and to evaluate the effect of prostaglandin E(2) (PGE(2)) addition and blockade on EP receptor expression.

METHODS

Peripheral blood mononuclear cells (PBMCs) isolated from 10 patients sustaining fracture or burn injury and 10 control subjects were stimulated with lipopolysaccharide +/- NS-398, an inhibitor of PGE(2) production. Samples were evaluated for production of PGE(2), tumor necrosis factor--alpha, and leukotriene B(4) as well as mRNA expression of EP receptors and COX-2. EP receptor expression was also evaluated after treating control PBMCs with PGE(2).

RESULTS

PBMCs from injured patients exhibited significant increases in PGE(2) production and COX-2 mRNA compared with control subjects, and these increases were inhibited by NS-398. In contrast, EP2 and EP4 receptors were markedly down-regulated after injury and NS-398 restored expression to control levels. Decreased EP2 and EP4 receptor expression after injury was replicated by coincubation of PBMCs with PGE(2).

CONCLUSIONS

Specific PGE(2) receptors are down-regulated after injury and NS-398 reverses this response. Furthermore, PGE(2) mediates EP2 and EP4 down-regulation. These data suggest that specific EP receptor subtypes may provide critical targets for augmenting the immune response after injury in humans.

Ethanol exacerbates T cell dysfunction after thermal injury

To understand the mechanism of suppressed immunity following alcohol consumption and thermal injury, we analyzed T cell functions in a mouse model of acute alcohol exposure and burn injury. Mice with blood alcohol levels at approximately 100 mg/dl were given a 15% scald or sham injury. Mice were sacrificed 48 h after injury. Our data demonstrated a 20-25% decrease in Con A-mediated splenic T cell proliferation (p<0.01) and 45-50% decrease in interleukin-2 (IL-2) production (p<0.01) following burn injury compared to the T cells from sham animals. A further decrease in the proliferation (25-30%) and IL-2 production (40-45%) was detected in T cells derived from burned animals receiving alcohol as compared to burn alone. No significant change in the proliferation and IL-2 production was observed in splenic T cells derived from sham-injured mice regardless of alcohol exposure. Additionally, there was no demonstrable difference in splenocyte apoptosis in any treatment group. These results suggest that alcohol consumption prior to burn injury causes a greater decrease in T cell proliferation and IL-2 production compared to either burn or alcohol injury alone that may further attenuate the cell-mediated immunity and thus enhance susceptibility to infection.

Novel experimental strategies to prevent the development of type 1 diabetes mellitus

Type 1 diabetes is an autoimmune disease leading to extensive destruction of the pancreatic beta-cells. Our research focusses on the role of beta-cells during the course of the disease, aiming at finding novel strategies to enhance beta-cell resistance against the cytotoxic damage inflicted by the immune system. Special attention has been paid to the possibility that cytokines released by the immune cells infiltrating the pancreatic islets can directly suppress and kill beta-cells. Certain cytokines (interleukin-1beta, tumor necrosis factor-alpha and interferon-gamma) either alone or in combination, are able to activate signal transduction pathways in beta-cells leading to transcription factor activation and de novo gene expression. In this context, it has been found that induction of inducible nitric oxide synthase mediates an elevated production of nitric oxide, which impairs mitochondrial function and causes DNA damage eventually leading to apoptosis and necrosis. However, other induced proteins SUCH AS heat shock protein 70 and superoxide dismutase may reflect a defense reaction elicited in the beta-cells by the cytokines. Our strategy is to further seek for proteins involved in both destruction and protection of beta-cells. Based on this knowledge, we plan to apply gene therapeutic approaches to increase expression of protective genes in beta-cells. If this is feasible we will then evaluate the function and survival of such modified beta-cells in animal models of type 1 diabetes such as the NOD mouse. The long-term goal for this research line is to find novel approaches to influence beta-cell resistance in humans at risk of developing type 1 diabetes.