High mobility group 1 (HMGB1) protein is both a nuclear factor and a secreted protein. In the cell nucleus it acts as an architectural chromatin-binding factor that bends DNA and promotes protein assembly on specific DNA targets. Outside the cell, it binds with high affinity to RAGE (the receptor for advanced glycation end products) and is a potent mediator of inflammation. HMGB1 is secreted by activated monocytes and macrophages, and is passively released by necrotic or damaged cells. Here we report that Hmgb1(-/-) necrotic cells have a greatly reduced ability to promote inflammation, which proves that the release of HMGB1 can signal the demise of a cell to its neighbours. Apoptotic cells do not release HMGB1 even after undergoing secondary necrosis and partial autolysis, and thus fail to promote inflammation even if not cleared promptly by phagocytic cells. In apoptotic cells, HMGB1 is bound firmly to chromatin because of generalized underacetylation of histone and is released in the extracellular medium (promoting inflammation) if chromatin deacetylation is prevented. Thus, cells undergoing apoptosis are programmed to withhold the signal that is broadcast by cells that have been damaged or killed by trauma.

Release of chromatin protein HMGB1 by necrotic cells triggers inflammation

Sepsis is the leading cause of death in critically ill patients in the United States. Yet the individual host response to septicemia is variable, depending on the patient's immune response, age, nutritional status, and coexisting conditions, as well as on the virulence of the organism and the size of the inoculum. This review examines evolving concepts of sepsis and discusses new and potential therapies. Recent clinical advances include therapy with activated protein C, stringent control of blood glucose, and early goal-directed therapy to treat cellular oxygen deficit. Future therapies may be focused on modulating the immune response in the light of the characteristics of the specific pathogen, the genetic profile of the patient, and the duration of the disease.

https://www.nejm.org/doi/pdf/10.1056/NEJMra021333

The pathophysiology and treatment of sepsis.

Vertebrates achieve internal homeostasis during infection or injury by balancing the activities of proinflammatory and anti-inflammatory pathways. Endotoxin (lipopolysaccharide), produced by all gram-negative bacteria, activates macrophages to release cytokines that are potentially lethal. The central nervous system regulates systemic inflammatory responses to endotoxin through humoral mechanisms. Activation of afferent vagus nerve fibres by endotoxin or cytokines stimulates hypothalamic-pituitary-adrenal anti-inflammatory responses. However, comparatively little is known about the role of efferent vagus nerve signalling in modulating inflammation. Here, we describe a previously unrecognized, parasympathetic anti-inflammatory pathway by which the brain modulates systemic inflammatory responses to endotoxin. Acetylcholine, the principle vagal neurotransmitter, significantly attenuated the release of cytokines (tumour necrosis factor (TNF), interleukin (IL)-1beta, IL-6 and IL-18), but not the anti-inflammatory cytokine IL-10, in lipopolysaccharide-stimulated human macrophage cultures. Direct electrical stimulation of the peripheral vagus nerve in vivo during lethal endotoxaemia in rats inhibited TNF synthesis in liver, attenuated peak serum TNF amounts, and prevented the development of shock.

Vagus nerve stimulation attenuates the systemic inflammatory response to endotoxin

Inflammation is a local, protective response to microbial invasion or injury. It must be fine-tuned and regulated precisely, because deficiencies or excesses of the inflammatory response cause morbidity and shorten lifespan. The discovery that cholinergic neurons inhibit acute inflammation has qualitatively expanded our understanding of how the nervous system modulates immune responses. The nervous system reflexively regulates the inflammatory response in real time, just as it controls heart rate and other vital functions. The opportunity now exists to apply this insight to the treatment of inflammation through selective and reversible 'hard-wired' neural systems.

The inflammatory reflex

High quality protocols facilitate proper conduct, reporting, and external review
 of clinical trials. However, the completeness of trial protocols is often
 inadequate. To help improve the content and quality of protocols, an
 international group of stakeholders developed the SPIRIT 2013 Statement
 (Standard Protocol Items: Recommendations for Interventional Trials). The SPIRIT
 Statement provides guidance in the form of a checklist of recommended items to
 include in a clinical trial protocol. This SPIRIT 2013 Explanation and Elaboration paper provides important
 information to promote full understanding of the checklist recommendations. For
 each checklist item, we provide a rationale and detailed description; a model
 example from an actual protocol; and relevant references supporting its
 importance. We strongly recommend that this explanatory paper be used in
 conjunction with the SPIRIT Statement. A website of resources is also available
 (www.spirit-statement.org). The SPIRIT 2013 Explanation and Elaboration paper, together with the Statement,
 should help with the drafting of trial protocols. Complete documentation of key
 trial elements can facilitate transparency and protocol review for the benefit
 of all stakeholders.

https://www.bmj.com/content/bmj/346/bmj.e7586.full.pdf

SPIRIT 2013 explanation and elaboration: guidance for protocols of clinical trials

• This study examined a group of surgical patients with respect to the ability of their peripheral blood mononuclear cells to respond to phytohemagglutinin (PHA). Depression of the PHA response of more than 30% below baseline five to seven days after injury was found in 11 of 19 patients, and eight of them developed infectious complications. The addition of indomethacin to in vitro cultures resulted in an average enhancement of the PHA response of 37% baseline. Improvement at five to seven days with in vitro indomethacin was from 34% to 74% in infected patients. These data suggest that major injury can lead to depression of the PHA response, which correlates with the subsequent development of infectious complications. Indomethacin in vitro seems to be able to reverse or decrease this immunologic defect and deserves further study. ( Arch Surg 1986;121:1000-1005)

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=SURG&articleId=591961&pdfFileName=archsurg_121_9_004.pdf

Depression of Cellular Immunity After Major Injury: Its Association With Posttraumatic Complications and Its Reversal With Immunomodulation

• The macrophage exerts its stimulatory and regulatory functions within the specific immune response via the interleukin 1 (IL-1) and prostaglandin E 2 (PGE 2 ), respectively. In a screening study of macrophage-related variables following injury, a total of 58 patients (mean age, 32 years; mean Injury Severity Score, 38), macrophagic phenotyping with the monoclonal antibody Leu M3 and serial measuring of the antagonistic monokines IL-1 and PGE 2 and of the macrophage-activating lymphokine interferon gamma were carried out on posttrauma days 0,1,3,5,7,10,14, and 21. The posttraumatic course was characterized by significant monocytosis, showing a peak value of 32% of Leu M3—positive cells compared with 15% of these cells in normal control subjects. During the posttrauma course, the macrophagic PGE 2 output was significantly elevated up to eightfold on days 5 and 7 compared with that of control subjects (0.441 ±0.14 ng/mL vs 0.052 ± 0.01 ng/mL). Conversely, macrophagic IL-1 synthesis was significantly suppressed until day 10. Levels of interferon gamma were suppressed to a significant degree during the two-day observation period, with a trend to slow recovery at the end of week 3. These data suggest that a negative regulatory macrophagic function may be the event initiating posttraumatic immunosuppression. To restore impaired macrophagic T-helper cell interaction, cyclo-oxygenase inhibition and substitution of interferon gamma may be useful to potentiate facilitatory macrophagic function and to block inhibitory macrophagic activity. ( Arch Surg 1988;123:287-292)

https://jamanetwork.com/HttpHandlers/ArticlePdfHandler.ashx?journal=surg&articleId=593014&pdfFileName=archsurg_123_3_002.pdf

Alteration of Monocyte Function Following Major Injury

Several studies indicate that organ failure is the leading cause of death in surgical patients. An excessive inflammatory response followed by a dramatic paralysis of cell-mediated immunity following major surgery appears to be responsible for the increased susceptibility to subsequent sepsis. In view of this, most of the scientific and medical research has been directed towards measuring the progression and inter-relationship of mediators following major surgery. Furthermore, the effect of those mediators on cell-mediated immune responses has been studied. This article will focus on the effect of blood loss and surgical injury on cell-mediated immune responses in experimental studies utilizing models of trauma and hemorrhagic shock, which have defined effects on the immunoinflammatory response. Subsequently these findings will be correlated with data generated from surgical patients. The results of these studies may generate new approaches for the treatment of immunodepression following major surgery, thus reducing the susceptibility to infection and increasing the survival rate of the critical ill surgical patient.

/pdf/clinical-review-immunodepression-in-the-surgical-patient-and-55szp9dl6x.pdf

Clinical review: Immunodepression in the surgical patient and increased susceptibility to infection

Objectives Complex regional pain syndrome type 1 (CRPS 1) is a disorder that can affect an extremity after minor trauma or surgery. The pathogenesis of this syndrome is unclear. It has clinical signs of severe local inflammation as a result of an exaggerated inflammatory response, but neurogenic dysregulation also may contribute to it. Methods For further insights into the pathogenesis of CRPS 1, the authors investigated inflammatory and neurogenic mediators-C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-8 (IL-8), soluble tumor necrosis factor receptor I/II (sTNFR I/II), sE-selectin, sL-selectin, sP-selectin, substance P, neuropeptide Y, and calcitonin gene-related peptide-in venous blood from both the healthy arm and the arm with acute CRPS I from 25 patients and from 30 healthy volunteers. Results Levels of IL-8 and sTNFR I/II were significantly elevated in patients, whereas all soluble forms of selectins were significantly suppressed. There was no significant difference in white blood cell count (WBC), CRP, and IL-6. Substance P was significantly elevated in patients. The other two neuropeptides were unchanged. None of the parameters studied showed any differences between the CRPS I-affected arm and the normal arm. Conclusions Elevated IL-8 and sTNFR I/II levels indicate an association between CRPS I and an inflammatory process. Normal WBC, CRP, and IL-6 give evidence for localized inflammation. The hypothesis of neurogenic-induced inflammation mediated by neuropeptides is supported by elevated substance P levels.

Inflammatory mediators are altered in the acute phase of posttraumatic complex regional pain syndrome.

The depression of interleukin-2 synthesis represents a major dysfunction within the cascade of immunologic defects induced by mechanical and thermal trauma. This study was undertaken to elucidate the negative control mechanisms that were responsible for the deficiency of IL-2 production in polytraumatized patients. Peripheral blood mononuclear cells (PBMC's) from 29 patients (average age, 35.8 years; average ISS, 35) were separated on post-trauma days 1, 3, 5, 7, 10, 14, and 21 and cultured as untreated cells (C), cells treated with indomethacin (C + INDO), and cells depleted of adherent cells (C-AC). Cell cultures were assayed for proliferative responses to PHA, IL-2 synthesis, PGE2 production, gamma-interferon levels, and phenotyping studies. On all days post-trauma there was found a marked reduction of IL-2 production compared to controls with a highly significant nadir from day 5 to day 10 with an almost 80% inhibition of IL-2 (p less than 0.005). C + INDO cells showed increases of IL-2 synthesis over untreated cells ranging from 48% (Day 1) to 220% (Day 7). Removal of adherent cells (C-AC) did not reverse the suppression of IL-2 production. gamma-interferon levels were depressed in parallel with IL-2 levels but did not increase with C + INDO. The phenotyping of the PBMC's showed highly significant suppression of OKT3+, OKT4+, and IL-2R+ lymphocytes as well as a highly significant elevation of the monocyte (p less than 0.005) count. There was a highly significant increase of PGE2 synthesis from monocytes, due to the monocytosis and to a higher capacity of synthesis of the individual cells following trauma. PGE2 levels peaked on Day 5 and 7 post-trauma at 400% of control (p less than 0.005). These data suggest that the suppression of IL-2 synthesis post trauma is caused mainly by two factors: the excessive PGE2 output of inhibitory monocytes and inadequate function in immature and/or blocked lymphocytes. The partial restoration of IL-2 synthesis by indomethacin suggests that blockade of the cyclo-oxygenase pathway as an immunomodulating therapy may reverse some of the immunologic abnormalities in multiple trauma patients.

Eugen Faist

Papers

Depression of Cellular Immunity After Major Injury: Its Association With Posttraumatic Complications and Its Reversal With Immunomodulation

Alteration of Monocyte Function Following Major Injury

Clinical review: Immunodepression in the surgical patient and increased susceptibility to infection

Inflammatory mediators are altered in the acute phase of posttraumatic complex regional pain syndrome.

Prostaglandin E2 (PGE2)-dependent suppression of interleukin alpha (IL-2) production in patients with major trauma.