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

Background: The proteolytic enzyme elastase released by granulocytes (polymorphonuclear leukocytes [PMN]) in high concentrations during sepsis causes degradation of essential plasma proteins, endothelial damage, and tissue edema. This may result in organ dysfunction and organ failure during sepsis, since increased elastase plasma levels correlate with the mortality rate of patients with sepsis. In vitro studies demonstrated a regulatory role of inflammatory cytokines (tumor necrosis factor-α [TNF-α], interleukin 1β [IL-1β], IL-8]) upregulatingprotease release by PMN. In this light, the interactions between cytokine release by macrophages and altered elastase secretion during sepsis remain to be determined. Methods: An ex vivo model consisting of lipopolysaccharide stimulation of human whole blood as a relevant physiological milieu was used. Heparinized blood was obtained from 20 patients with sepsis syndrome (APACHE II [Acute Physiology and Chronic Health Evaluation II] score 28.5±1.2 points [mean±SD]) on days 0 through 3, 5, 7, and 10 after sepsis diagnosis and from 20 control patients without infection. Blood was incubated with lipopolysaccharide (1 mg/L) for 8 hours. Plasma levels of elastase, TNF-α, IL-1β, and IL-8 were determined using enzyme-linked immunosorbent assay or bioassay (TNF-α), respectively. Results: Elastase plasma levels in whole blood from patients with sepsis were increased up to 188% (P Conclusions: These data indicate an increased release of elastase by PMN despite a reduced secretion of PMNactivating cytokines. Although priming effects of TNF-α, IL-1β, and IL-8 on protease secretion in vivo cannot be excluded completely, other mediators or mechanisms may be involved in the upregulation of detrimental protease release during sepsis. (Arch Surg. 1994;129:90-98)

/pdf/enhanced-release-of-elastase-is-not-concomitant-with-32belphdq1.pdf

Enhanced Release of Elastase Is Not Concomitant With Increased Secretion of Granulocyte-Activating Cytokines in Whole Blood From Patients With Sepsis

Objectives: To determine the potential of interleukin-13 (IL-13) to modify in vitro lipopolysaccharide-induced monocyte-macrophage (MO) activity in human cells from individuals who had sustained either major mechanical or burn injury and to investigate whether the effect of IL-13 is different on MOs that have been preactivated under traumatic stress than on monocytic cells from healthy volunteers. Design: Peripheral MOs from 20 controls and 16 patients after major burn or mechanical trauma were separated on days 1, 3, 5, and 7 after injury and incubated with lipopolysaccharide (1 μg/mL) in the presence or absence of IL-13 (10 ng/mL) for 4 hours and for 20 hours. Thereafter, the following measures were determined from the culture supernatants: neopterin, nitric oxide, tumor necrosis factor α, IL-1β, IL-6, and IL-8. Results: Ex vivo lipopolysaccharide-activated MOs, compared with control cells, displayed considerably enhanced inflammatory activity during the immediate posttraumatic course, with a substantial and consistent elevation of levels of tumor necrosis factor α and IL-6. The addition of human recombinant IL-13 to the MO cultures resulted in an effective down-regulation of the synthesis of tumor necrosis factor α, IL-1β, and IL-6 as well as IL-8, showing an average reduction of mediator production to two thirds of the value found in corresponding sole lipopolysaccharide-stimulated cultures. The impact of human recombinant IL-13 on control MOs was almost identical for IL-6 and IL-1β, slightly lower for IL-8, and nonexistent for tumor necrosis factor α, Conclusion: From this study and preexisting findings, we conclude that, based on its biologic properties, IL-13 should be tested as a biologic response modifier for acute states of trauma-induced host defense deficiency. (Arch Surg. 1995;130:1330-1336)

Interleukin-13 effectively down-regulates the monocyte inflammatory potential during traumatic stress.

Background: Recent data suggest that ubiquitin (Ub) is systemically released after trauma, has pleiotropic effects on host defense mechanisms, and that Ub administration reduces fluid shifts into tissues during inflammation. Ub release after burns (B) has not been studied and its association with injury severity and outcome after blunt trauma (T) is unknown. Thus, we evaluated Ubs association with injury severity and outcomes after B and T. Methods: Injury severity was assessed with the Injury Severity Score (ISS) in T and burn size (% total body surface area, %TBSA) in B. A total of 129 T (ISS: 26 13) and 55 B (46% 18% TBSA) were observed for sepsis/multiple organ failure (MOF) and survival. In B, sequential organ failure assessment scores were documented daily. Fifty volunteers served as controls (C) Ub serum levels were measured on day 0 (admission), 1, 3, 5, and 7 by enzyme-linked immunosorbent assay. Data were analyzed using bivariate or partial correlation analyses, t test, and analysis of variance with Tukey post-hoc test for multiple comparisons (two-tailed p < 0.05). Results: Ub was significantly elevated in patients. Peak levels (ng/mL) were detectable on day 0 (C: 118 76; T: 359 205; B: 573 331) and increased with increased ISS, %TBSA, and presence of inhalation injury. In T, Ub normalized by day 3, but remained elevated in B. In B, Ub correlated significantly negative with sequential organ failure assessment scores (r: 0.143; p 0.0147), sepsis/MOF development (r: 0.363; p 0.001), and survival (r: 0.231; p 0.009). Compared with B who recovered uneventfully, Ub levels were significantly lower on days 1 to 7 and on days 5/7 in B who developed sepsis/MOF or died, respectively. Conclusion: Ub concentrations reflect the extent of tissue damage. Along with Ubs previously described antiinflammatory properties, this study suggests that its systemic release is protective, that burn patients who develop sepsis/MOF have a relative Ub deficiency and that Ub could play an important role during the physiologic response to burn injury.

Eugen Faist

Papers

Enhanced Release of Elastase Is Not Concomitant With Increased Secretion of Granulocyte-Activating Cytokines in Whole Blood From Patients With Sepsis

Interleukin-13 effectively down-regulates the monocyte inflammatory potential during traumatic stress.

Systemic ubiquitin release after blunt trauma and burns: association with injury severity, posttraumatic complications, and survival.

Multiple Organ Failure

Depression of Cellular Immunity After Major Injury