Markus A. Weigand

TREM-1 amplifies inflammation and is a crucial mediator of septic shock

Host innate responses to bacterial infections are primarily mediated by neutrophils and monocytes/macrophages. These cells express pattern recognition receptors (PRRs) that bind conserved molecular structures shared by groups of microorganisms. Stimulation of PRR signalling pathways initiates secretion of proinflammatory mediators, which promote the elimination of infectious agents and the induction of tissue repair. Excessive inflammation owing to bacterial infections can lead to tissue damage and septic shock. Here we show that inflammatory responses to microbial products are amplified by a pathway mediated by triggering receptor expressed on myeloid cells (TREM)-1. TREM-1 is an activating receptor expressed at high levels on neutrophils and monocytes that infiltrate human tissues infected with bacteria. Furthermore, it is upregulated on peritoneal neutrophils of patients with microbial sepsis and mice with experimental lipopolysaccaride (LPS)-induced shock. Notably, blockade of TREM-1 protects mice against LPS-induced shock, as well as microbial sepsis caused by live Escherichia coli or caecal ligation and puncture. These results demonstrate a critical function of TREM-1 in acute inflammatory responses to bacteria and implicate TREM-1 as a potential therapeutic target for septic shock.

FADD/MORT1 and Caspase-8 Are Recruited to TRAIL Receptors 1 and 2 and Are Essential for Apoptosis Mediated by TRAIL Receptor 2

Apoptosis induced by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL/APO-2L) has been shown to exert important functions during various immunological processes. The involvement of the death adaptor proteins FADD/MORT1, TRADD, and RIP and the apoptosis-initiating caspases-8 and -10 in death signaling by the two death-inducing TRAIL receptors 1 and 2 (TRAIL-R1 and TRAIL-R2) are controversial. Analysis of the native TRAIL death-inducing signaling complex (DISC) revealed ligand-dependent recruitment of FADD/MORT1 and caspase-8. Differential precipitation of ligand-stimulated TRAIL receptors demonstrated that FADD/MORT1 and caspase-8 were recruited to TRAIL-R1 and TRAIL-R2 independently of each other. FADD/MORT1- and caspase-8-deficient Jurkat cells expressing only TRAIL-R2 were resistant to TRAIL-induced apoptosis. Thus, FADD/MORT1 and caspase-8 are essential for apoptosis induction via TRAIL-R2.

Receptor for advanced glycation end products (RAGE) regulates sepsis but not the adaptive immune response

While the initiation of the adaptive and innate immune response is well understood, less is known about cellular mechanisms propagating inflammation. The receptor for advanced glycation end products (RAGE), a transmembrane receptor of the immunoglobulin superfamily, leads to perpetuated cell activation. Using novel animal models with defective or tissue-specific RAGE expression, we show that in these animal models RAGE does not play a role in the adaptive immune response. However, deletion of RAGE provides protection from the lethal effects of septic shock caused by cecal ligation and puncture. Such protection is reversed by reconstitution of RAGE in endothelial and hematopoietic cells. These results indicate that the innate immune response is controlled by pattern-recognition receptors not only at the initiating steps but also at the phase of perpetuation.

Caspase‐10 is recruited to and activated at the native TRAIL and CD95 death‐inducing signalling complexes in a FADD‐dependent manner but can not functionally substitute caspase‐8

The involvement of the death adaptor protein FADD and the apoptosis‐initiating caspase‐8 in CD95 and TRAIL death signalling has recently been demonstrated by the analysis of the native death‐inducing signalling complex (DISC) that forms upon ligand‐induced receptor cross‐linking. However, the role of caspase‐10, the other death‐effector‐domain‐containing caspase besides caspase‐8, in death receptor signalling has been controversial. Here we show that caspase‐10 is recruited not only to the native TRAIL DISC but also to the native CD95 DISC, and that FADD is necessary for its recruitment to and activation at these two protein complexes. With respect to the function of caspase‐10, we show that it is not required for apoptosis induction. In addition, caspase‐10 can not substitute for caspase‐8, as the defect in apoptosis induction observed in caspase‐8‐deficient cells could not be rescued by overexpression of caspase‐10. Finally, we demonstrate that caspase‐10 is cleaved during CD95‐induced apoptosis of activated T cells. These results show that caspase‐10 activation occurs in primary cells, but that its function differs from that of caspase‐8.

Meta‐analysis of standard, restrictive and supplemental fluid administration in colorectal surgery

Optimal fluid therapy for colorectal surgery remains uncertain.

Pharmacologic cholinesterase inhibition improves survival in experimental sepsis

Objective: Lethal sepsis occurs when an excessive inflammatory response evolves that cannot be controlled by physiologic anti-inflammatory mechanisms, such as the recently described cholinergic anti-inflammatory pathway. Here we studied whether the cholinergic anti-inflammatory pathway can be activated by pharmacologic cholinesterase inhibition in vivo. Design: Prospective, randomized laboratory investigation that used an established murine sepsis model. Setting: Research laboratory in a university hospital. Subjects: Female C57BL/6 mice. Interventions: Sepsis in mice was induced by cecal ligation and puncture. Animals were treated immediately with intraperitoneal injections of nicotine (400 &mgr;g/kg), physostigmine (80 &mgr;g/kg), neostigmine (80 &mgr;g/kg), or solvent three times daily for 3 days. Measurements and Main Results: Treatment with physostigmine significantly reduced lethality (p ≤ .01) as efficiently as direct stimulation of the cholinergic anti-inflammatory pathway with nicotine (p ≤ .05). Administration of cholinesterase inhibitors significantly down-regulated the binding activity of nuclear factor-&kgr;B (p ≤ .05) and significantly reduced the concentration of circulating proinflammatory cytokines tumor necrosis factor-&agr;, interleukin-1&bgr;, and interleukin-6 (p ≤ .001), and pulmonary neutrophil invasion (p ≤ .05). Animals treated with the peripheral cholinesterase inhibitor neostigmine showed no difference compared with physostigmine-treated animals. Conclusions: Our results demonstrate that cholinesterase inhibitors can be used successfully in the treatment of sepsis in a murine model and may be of interest for clinical use.

Bench-to-bedside review: The inflammation-perpetuating pattern-recognition receptor RAGE as a therapeutic target in sepsis

Sepsis still represents an important clinical and economic challenge for intensive care units. Severe complications like multi-organ failure with high mortality and the lack of specific diagnostic tools continue to hamper the development of improved therapies for sepsis. Fundamental questions regarding the cellular pathogenesis of experimental and clinical sepsis remain unresolved. According to experimental data, inhibiting macrophage migration inhibitory factor, high-mobility group box protein 1 (HMGB1), and complement factor C5a and inhibiting the TREM-1 (triggering receptor expressed on myeloid cells 1) signaling pathway and apoptosis represent promising new therapeutic options. In addition, we have demonstrated that blocking the signal transduction pathway of receptor of advanced glycation endproducts (RAGE), a new inflammation-perpetuating receptor and a member of the immunglobulin superfamily, increases survival in experimental sepsis. The activation of RAGE by advanced glycation end-products, S100, and HMGB1 initiates nuclear factor kappa B and mitogen-activated protein kinase pathways. Importantly, the survival rate of RAGE knockout mice was more than fourfold that of wild-type mice in a septic shock model of cecal ligation and puncture (CLP). Additionally, the application of soluble RAGE, an extracellular decoy for RAGE ligands, improves survival in mice after CLP, suggesting that RAGE is a central player in perpetuating the innate immune response. Understanding the basic signal transduction events triggered by this multi-ligand receptor may offer new diagnostic and therapeutic options in patients with sepsis.

TNF-Related Apoptosis-Inducing Ligand Mediates Tumoricidal Activity of Human Monocytes Stimulated by Newcastle Disease Virus

The Newcastle disease virus (NDV) has antineoplastic and immunostimulatory properties, and it is currently clinically tested in anticancer therapy. However, the tumoricidal mechanisms of NDV tumor therapy are not fully understood. The results presented here demonstrate that NDV-stimulated human monocytes (Mφ) kill various human tumor cell lines and that this tumoricidal activity is mediated by TRAIL. In contrast to soluble TRAIL-R2-Fc, soluble CD95-Fc and TNF-R2-Fc showed only minimal blocking of the antitumor effect. TRAIL expression is induced on human Mφ after stimulation with NDV and UV-inactivated NDV. These results show that TRAIL induction on human Mφ after NDV stimulation is independent from viral replication and that TRAIL mediates the tumoricidal activity of NDV-stimulated human Mφ.

The use of high‐dose melatonin in liver resection is safe: first clinical experience

Abstract:  Experimental data suggest that melatonin decreases inflammatory changes after major liver resection, thus positively influencing the postoperative course. To assess the safety of a preoperative single dose of melatonin in patients undergoing major liver resection, a randomized controlled double‐blind pilot clinical trial with two parallel study arms was designed at the Department of General and Transplantation Surgery, Ruprecht‐Karls‐University, Heidelberg. A total of 307 patients, who were referred for liver surgery, were screened. One hundred and thirteen patients, for whom a major liver resection (≥3 segments) was scheduled, were eligible. Sixty‐three eligible patients refused to participate, and therefore, 50 patients were randomized. A preoperative single dose of melatonin (50 mg/kg BW) dissolved in 250 mL of milk was administered through the gastric tube after the intubation for general anesthesia. Controls were given the same amount of microcrystalline cellulose. Primary endpoint was safety. Secondary endpoints were postoperative complications. Melatonin was effectively absorbed with serum concentrations of 1142.8 ± 7.2 ng/mL (mean ± S.E.M.) versus 0.3 ± 7.8 ng/mL in controls (P < 0.0001). Melatonin treatment resulted in lower postoperative transaminases over the study period (P = 0.6). There was no serious adverse event in patients after melatonin treatment. A total of three infectious complications occurred in either group. A total of eight noninfectious complications occurred in five control patients, whereas three noninfectious complications occurred in three patients receiving preoperative melatonin (P = 0.3). There was a trend toward shorter ICU stay and total hospital stay after melatonin treatment. Therefore, a single preoperative enteral dose of melatonin is effectively absorbed and is safe and well tolerated in patients undergoing major liver surgery.

Vitamin E inhibits CD95 ligand expression and protects T cells from activation-induced cell death

Apoptosis is a morphologically distinct form of cell death involved in many physiological and pathological processes. Expression of the CD95 (APO-1/Fas) ligand (CD95L) is critically involved in activation-induced cell death (AICD) of activated T cells. Here we show that the natural free radical scavenger vitamin E suppresses the activity of the transcription factors NF-kappa B and AP-1, thus blocking expression of CD95L and preventing T cell AICD. Since AICD is a major cause of T cell depletion in AIDS, we examined 35 HIV-1-positive individuals and found that their T cells are more susceptible to AICD than are T cells isolated from healthy controls. Administration of vitamin E suppresses CD95L mRNA expression and protects T cells of HIV-1-infected individuals from CD95-mediated apoptosis. This evidence that vitamin E can affect T cell survival may merit further clinical investigation.