The changing immune system in sepsis: is individualized immuno-modulatory therapy the answer?

Parenteral glutamine supplementation in combination with enteral nutrition improves intestinal immunity in septic rats

OBJECTIVES

The gut-associated lymphoid tissue is continuously exposed to antigens in the gut lumen and becomes the first line of defense against enteric bacteria and associated toxin. The aim of this study was to investigate the effects of parenteral glutamine (GLN) supplementation in combination with enteral nutrition (EN) on intestinal mucosal immunity in septic rats by cecal ligation and puncture (CLP).

METHODS

Male Sprague-Dawley rats were randomly assigned into four groups: A sham CLP + EN + saline group (n = 10), a sham CLP + EN + GLN group (n = 10), a CLP + EN + saline group (n = 10), and a CLP + EN + GLN group (n = 10). At 2 h after CLP or sham CLP, all rats in each of the four groups received an identical enteral nutrition solution as their base formula. Then, the rats in the sham CLP + EN + GLN group and CLP + EN + GLN group were given 0.35 g GLN/kg body weight daily for 7 d, all at the same time, via a tail vein injection; whereas those in the sham CLP + EN + saline group and CLP + EN + saline group were daily administered isovolumic sterile 0.9% saline for comparison. All rats in each of the four groups were given 290 kcal/kg body wt/d for 7 d. At the end of the seventh day after the nutritional program was finished, all rats were euthanized and the entire intestine was collected. Total Peyer's patches (PP) cell yield was counted by a hemocytometer. The percentage of PP lymphocyte subsets was analyzed by flow cytometry. The number of intestinal lamina propria IgA plasma cells was determined by the immunohistochemistry technique. The intestinal immunoglobulin A (IgA) levels were assessed by ELISA. PP apoptosis was evaluated by terminal deoxyuridine nick-end labeling.

RESULTS

The results revealed total PP cell yield, the numbers of PP lymphocyte subsets, intestinal lamina propria IgA plasma cells, and intestinal IgA levels in the CLP + EN + GLN group were significantly increased when compared with the CLP + EN + saline group (P < 0.05). On the other hand, the number of TUNEL-stained cells within PPs in the CLP + EN + GLN group was markedly decreased as compared with the CLP + EN + saline group (P < 0.05).

CONCLUSION

The results of this study show that parenteral glutamine supplementation in combination with enteral nutrition may attenuate PP apoptosis, increase PP cell yield and intestinal lamina propria IgA plasma cells, and subsequently improve intestinal mucosal immunity. Clinically, these results suggest therapeutic efforts at improving intestinal immunity may contribute to the prevention and treatment of sepsis.

Assessing the immune status of critically ill trauma patients by flow cytometry

BACKGROUND

Unintentional injury or trauma remains the leading cause of death among young adults. About one fifth of these trauma patients require care in an intensive care unit (ICU) because of severity of injuries and comorbidities. Patients hospitalized in an ICU are at increased risk for nosocomial infections, such as urinary tract infections, pneumonia, bacteremia, and wound infections. Many of these patients will develop sepsis or septic shock, and some will progress to multiple organ failure and death. The balance between the proinflammatory and counterinflammatory immune response appears to be a driving factor in this progression. At present, there is no proposed method for the timely detection of the immune status in trauma patients, making rational decisions to use immune-altering therapies difficult.

OBJECTIVE

We demonstrate that flow cytometry, with its capabilities to characterize and/or enumerate (a) leukocyte subtypes, (b) leukocyte activation markers, (c) leukocyte-derived cytokines and microvesicles, and (d) leukocyte function is well suited to monitor the immune status of critically ill trauma patients.

METHODS

Information for the review was obtained from the extant literature.

DISCUSSION

We suggest that flow cytometry is a research method that might aid nurse scientists in investigating the immune status of critically ill patients, the recovery status of conditions such as hemorrhagic shock and tissue injury and the relationship between cancer disease progression and symptoms. Therefore, flow cytometry has the potential to broaden nursing research priority areas so that a comprehensive approach to understanding the cellular response is attained.

[Adjuvant treatment of sepsis: what is known?]

BACKGROUND

Recent decades have been characterized by a large number of trials for registration of new drugs or indication approvals in the field of sepsis. Modern anti-inflammatory drugs or interventions are intended to correct the overwhelming dysregulation of inflammatory and coagulation pathways seen particularly in the early phase of sepsis. Immunostimulatory therapies are also being studied in order to correct immunoparalysis, which develops later in the course of sepsis as a compensatory mechanism.

CURRENT STUDY RESULTS

Recombinant activated protein C, drotrecogin α, was conditionally approved and later withdrawn from the market by the producer because the initially observed beneficial effect could not be confirmed. The efficacy and safety of antithrombin, which, like drotrecogin α, also modulates inflammation and coagulation as an endogenous anticoagulant could not be confirmed when used for treating sepsis. As sepsis leads to disseminated intravascular coagulation which may be counteracted by antithrombin, new guidelines recommend antithrombin as a treatment option in this subgroup of sepsis patients. Intravenous administration of immunoglobulin, enteral administration of immunomodulating substances as immunonutrition, and the substitution of selenium, all showed some effectiveness in small heterogeneous studies, but their efficacy was not confirmed in large high-quality trials. Intensive glycemic control, which was temporarily recommended for acutely ill patients, increased the risk for adverse hypoglycemia in several clinical trials so that blood glucose target levels have been redefined and guidelines now no longer ask for normalization of blood glucose values with insulin.

CONCLUSION AND OUTLOOK

None of the new drugs, however, has successfully become established as a new standard of care. In the future, studies of novel sepsis therapies may succeed better if suitable biomarkers allow for patient selection, reflecting key pathophysiologic mechanisms that are targeted by the innovative drugs.

Differences between murine and human sepsis

Sepsis can be defined as a systemic inflammatory response syndrome occurring in the presence of an infectious source. Over the past 25 years, numerous guidelines have been established to clarify definitions and improve the overall management of clinical sepsis. In light of these multiple paradigm shifts, this review attempts to summarize the innate immunologic alterations that manifest during sepsis, establish and compare mouse models of sepsis with the clinical course, and discuss the authors' views on additional elements that should be considered in modeling and predicting clinical sepsis from the standpoint of a basic research setting.

Calcium-sensing receptor in the T lymphocyte enhanced the apoptosis and cytokine secretion in sepsis

Calcium-sensing receptor (CaSR) is a member of the G protein-coupled receptor superfamily that existed in lymphocytes and promoted cytokine secretion. Lymphocytes are also involved in sepsis. However, the role of CaSR in lymphocytes in sepsis is unclear. In this study, we want to examine whether the CaSR in lymphocytes in sepsis is involved in the cytokine secretions and apoptosis and make clear the relationship between NF-κB and MAPK signal transduction pathways. We investigated the issues mentioned earlier using Western blotting, ELISA, and Flow Cytometry. The sepsis was remodeled by cecal ligation and puncture (CLP). We found that CaSR protein expression increased in the peripheral blood T lymphocytes in CLP rats. The calcimimetic R568 (NPS R568) promoted, whereas the calcilytic NPS 2143 attenuated, signaling pathways proteins P65 (subunit of NF-κB), ERK1/2, and JNK (one subgroup of MAPKs) phosphorylation. However, P-P38 and P-JAKs exhibit no significant changes. Furthermore, the production TNF-α and IL-4 was greater in CLP rats than in normal rats, and NPS R568 promoted secretion of these cytokines. Simultaneously, the apoptotic ratio of T cells in CLP increased, and NPS R 568 exacerbated the apoptosis degree. However, these effects could also be inhibited by U0126 or SP600125 (MAPKs pathway inhibitor) or Bay-11-7082 or (NF-κB pathway inhibitor). From these results, we can conclude that, in the sepsis, CaSR activation promoted T-cell apoptosis and the secretion of pro-inflammatory cytokine TNF-α and anti-inflammatory cytokines IL-4 probably through NF-κB and partial MAPK signal transduction pathways.

Role of circulating lymphocytes in patients with sepsis

Sepsis is a systemic inflammatory response syndrome due to infection. The incidence rate is estimated to be up to 19 million cases worldwide per year and the number of cases is rising. Infection triggers a complex and prolonged host response, in which both the innate and adaptive immune response are involved. The disturbance of immune system cells plays a key role in the induction of abnormal levels of immunoregulatory molecules. Furthermore, the involvement of effector immune system cells also impairs the host response to the infective agents and tissue damage. Recently, postmortem studies of patients who died of sepsis have provided important insights into why septic patients die and showed an extensive depletion of CD4 and CD8 lymphocytes and they found that circulating blood cells showed similar findings. Thus, the knowledge of the characterization of circulating lymphocyte abnormalities is relevant for the understanding of the sepsis pathophysiology. In addition, monitoring the immune response in sepsis, including circulating lymphocyte subsets count, appears to be potential biomarker for predicting the clinical outcome of the patient. This paper analyzes the lymphocyte involvement and dysfunction found in patients with sepsis and new opportunities to prevent sepsis and guide therapeutic intervention have been revealed.

Epigenetic coordination of acute systemic inflammation: potential therapeutic targets

Epigenetic reprogramming of thousands of genes directs the course of acute systemic inflammation, which is highly lethal when dysregulated during sepsis. No molecular-based treatments for sepsis are available. A new concept supports that sepsis is an immunometabolic disease and that loss of control of nuclear epigenetic regulator sirtuin 1 (SIRT-1), a NAD(+) sensor directs immune and metabolic pathways during sepsis. SIRT-1, acting as homeostasis checkpoint, controls hyper- and hypo-inflammatory responses of sepsis at the microvascular interface, which disseminates inflammatory injury to cause multiple organ failure. Modifying SIRT-1 activity, which can prevent or treat established sepsis in mice, may provide a new way to treat sepsis by epigenetically restoring immunometabolic homeostasis.

TREM-1 as a potential therapeutic target in neonatal sepsis

OBJECTIVE

Bacterial sepsis in neonates is associated with elevated morbidity and mortality. A role for the pro-inflammatory Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is suspected in the innate immune response to bacteria, but little is known about its activities in infants. To begin exploring the feasibility of treating neonatal sepsis by blocking leukocyte TREM-1, we compared TREM-1 membrane expression and mRNA in newborns without clinical or microbiological evidence of infection, to that of healthy adults. The functionality of pro-inflammatory reactions in leukocyte TREM-1 of newborns was also evaluated.

METHODS

Twenty term newborns were enrolled in this study and cord blood samples were collected at birth. For comparison, peripheral blood specimens were collected from 20 healthy adults (control adult, CA). The expression of TREM-1 protein and mRNA in leukocytes was detected with flow cytometry and real-time qPCR, respectively. Whole cord blood was also stimulated by Escherichia coli or blocked by the TREM-1-specific peptide LP17 to identify changes in the secretion of pro-inflammatory cytokines interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α, as well as soluble TREM-1 (sTREM-1) using enzyme linked immunosorbent assay (ELISA).

RESULTS

Mean fluorescence intensity (MFI) of TREM-1 on leukocytes of newborns appeared comparable to healthy adults [monocytes: 37.5 ± 6.7 vs. 37.6 ± 8.7; polymorphonuclear cells (PMNs): 32.9 ± 6.6 vs. 33.6 ± 5.8]. However, the percentage of PMNs positive for TREM-1 was lower in newborns than in healthy adults (82.3 ± 7.1 vs. 98.6 ± 4.8; P < 0.01); the percentage of TREM-1-positive CD14-positive monocytes was comparable to that of healthy adults (97.1 ± 8.3 vs. 97.5 ± 7.4). Exposure of cord blood to E. coli resulted in increased secretion of IL-6, IL-8, TNF-α, and sTREM-1. In contrast, the concentrations of IL-6, IL-8, and TNF-α decreased by a minimum of 15% when TREM-1 was blocked by LP17 then exposed to E. coli, versus E. coli alone. In addition, the concentration of sTREM-1 was positively correlated with the levels of TNF-α (r = 0.519, P < 0.05), IL-6 (r = 0.507, P < 0.05), and IL-8 (r = 0.538, P < 0.05).

CONCLUSIONS

Healthy newborns exhibit expression of TREM-1 on monocytes similar to that in healthy adults, and most PMNs express TREM-1 at the newborn stage. Detection of sTREM-1 in neonatal peripheral blood should be further investigated as a potential method for the diagnosis of neonatal infection. Finally, blocking the TREM-1 signal transduction pathway may reduce inflammatory responses of neonate leukocytes and thereby provide a new strategy for treatment of neonatal infection.

Immunomodulatory adjuvant therapy in severe community-acquired pneumonia

Severe pneumonia has a high mortality (38.2%) despite evidence-based therapy. Rising rates of antimicrobial resistance increase the urgency to develop new treatment strategies. Multiple adjuvant therapies for pneumonia have been investigated but none are currently licensed. Profound immune dysregulation occurs in patients with severe infection. An initial hyper-inflammatory response is followed by a secondary hypo-inflammatory response with 'immune-paralysis'. There is focus on the development of immunostimulatory agents to improve host ability to combat primary infection and reduce secondary infections. Successful treatments must be targeted to immune response; promising biomarkers exist but have not yet reached common bedside practice. We explore evidence for adjuvant therapies in community-acquired pneumonia. We highlight novel potential treatment strategies using a broad-based search strategy to include publications in pneumonia and severe sepsis. We explore reasons for the failure to develop effective adjuvant therapies and highlight the need for targeted therapy specific to immune activity.