Receptors, Mediators, and Mechanisms Involved in Bacterial Sepsis and Septic Shock

Bacterial sepsis and septic shock result from the overproduction of inflammatory mediators as a consequence of the interaction of the immune system with bacteria and bacterial wall constituents in the body. Bacterial cell wall constituents such as lipopolysaccharide, peptidoglycans, and lipoteichoic acid are particularly responsible for the deleterious effects of bacteria. These constituents interact in the body with a large number of proteins and receptors, and this interaction determines the eventual inflammatory effect of the compounds. Within the circulation bacterial constituents interact with proteins such as plasma lipoproteins and lipopolysaccharide binding protein. The interaction of the bacterial constituents with receptors on the surface of mononuclear cells is mainly responsible for the induction of proinflammatory mediators by the bacterial constituents. The role of individual receptors such as the toll-like receptors and CD14 in the induction of proinflammatory cytokines and adhesion molecules is discussed in detail. In addition, the roles of a number of other receptors that bind bacterial compounds such as scavenger receptors and their modulating role in inflammation are described. Finally, the therapies for the treatment of bacterial sepsis and septic shock are discussed in relation to the action of the aforementioned receptors and proteins

Recombinant C1-Inhibitor Effects on Coagulation and Fibrinolysis in Patients with Hereditary Angioedema

Background: Recombinant human C1-inhibitor (rhC1INH; Ruconest (R)) has been developed for treatment of acute angioedema attacks in patients with hereditary angioedema (HAE) due to heterozygous deficiency of C1INH. Previous reports suggest that administration of plasma-derived C1INH products may be associated with an increased risk for thromboembolic complications. Objectives: Our aim is to evaluate the effects of rhC1INH on coagulation and fibrinolysis in symptomatic HAE patients. Methods: Levels of various coagulation and fibrinolytic parameters were determined in pre- and post-exposure plasma samples from HAE patients included in a randomized clinical trial. Patients were treated with either saline, or 50 or 100 U/kg rhC1INH for an acute angioedema attack. Results: Prior to rhC1INH treatment, the majority of patients had low to normal activated partial thromboplastin times (aPTT) and increased levels of prothrombin fragment 1+2, thrombin-antithrombin complexes, D-dimers and plasmin-antiplasmin complexes, all of which indicate activation of both coagulation and fibrinolysis. Infusion of rhC1INH at doses up to 100 U/kg did not affect these parameters except for a dose-dependent prolongation of aPTT, confirming that rhC1INH is an inhibitor of the contact system, and that F1+2 levels decreased. Conclusion: Coagulation and fibrinolytic systems are activated in HAE patients suffering from an acute angioedema attack. Treatment with rhC1INH at 50 or 100 U/kg had no effect on parameters reflecting activation of these systems except for a significant effect on aPTT, which likely reflects a pharmacodynamic effect of rhC1INH, and a reduction on plasma levels of the prothrombin activation fragment F1+2. We conclude that these results argue against a prothrombotic effect of treatment with this rhC1INH product in HAE patient

Complement inhibition attenuates acute kidney injury after ischemia-reperfusion and limits progression to renal fibrosis in mice.

The complement system is an essential component of innate immunity and plays a major role in the pathogenesis of ischemia-reperfusion injury (IRI). In this study, we investigated the impact of human C1-inhibitor (C1INH) on the early inflammatory response to IRI and the subsequent progression to fibrosis in mice. We evaluated structural damage, renal function, acute inflammatory response, progression to fibrosis and overall survival at 90-days post-injury. Animals receiving C1INH prior to reperfusion had a significant improvement in survival rate along with superior renal function when compared to vehicle (PBS) treated counterparts. Pre-treatment with C1INH also prevented acute IL-6, CXCL1 and MCP-1 up-regulation, C5a release, C3b deposition and infiltration by neutrophils and macrophages into renal tissue. This anti-inflammatory effect correlated with a significant reduction in the expression of markers of fibrosis alpha smooth muscle actin, desmin and picrosirius red at 30 and 90 days post-IRI and reduced renal levels of TGF-β1 when compared to untreated controls. Our findings indicate that intravenous delivery of C1INH prior to ischemic injury protects kidneys from inflammatory injury and subsequent progression to fibrosis. We conclude that early complement blockade in the context of IRI constitutes an effective strategy in the prevention of fibrosis after ischemic acute kidney injury

Treatment with C1INH prevented the progression to fibrosis in kidneys subjected to ischemia-reperfusion injury.

<p>(A) Immunohistochemical staining for alpha smooth muscle actin (α-SMA), desmin and picrosirius red staining in renal tissue recovered at 30 and 90-days post-ischemic injury from sham + PBS (n = 6), sham + C1INH (n = 6), IRI + PBS (n = 6) and IRI + C1INH (n = 6) mice. Representative light microscopy images (200X magnification) from each group are depicted. Semi-automated quantification of (B) α-SMA(+), (C) Desmin(+) and (D) Picrosirius Red(+) area per HPF. Stained area is calculated and shown as a percentage relative to total tissue area per field. Data are mean ± SD. Statistical comparison was performed by one-way ANOVA followed by Bonferroni’s post-hoc correction. *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001.</p

Protective renal effect of complement blockade after ischemia-reperfusion injury.

<p>Mice were assigned to four groups: 1) Sham + PBS (n = 6), 2) Sham + C1INH (n = 6), 3) IRI + PBS (n = 9), IRI + C1INH (n = 15). Ischemia was induced by clamping of the renal hilum for 60 minutes and followed by contra-lateral nephrectomy. Sterile PBS or C1INH (750 U/kg) were given intravenously via tail vein injection 1 hour prior to surgery. Serum was collected at 24 and 72 hours after injury and survival was monitored for 90 days after reperfusion. (A) Pharmacological targeting of complement activation using C1INH significantly improves animal survival after IRI (Log-rank test, <i>P</i> = 0.0015). (B) Serum creatinine level at 24 and 72 hours after IRI. Groups: 1) Sham + PBS (n = 8), 2) Sham + C1INH (n = 8), 3) IRI + PBS (n = 10), IRI + C1INH (n = 10). (C) Histopathological analysis of kidneys at 24 hours after surgery. Representative light microscopy images of hematoxylin-eosin (H&E) staining of the cortex and medulla of kidneys (200X magnification). Arrows indicate necrotic tubules, and asterisks indicate tubular casts. (D) Renal tubular injury scores (0–4, arbitrary units). All data presented are mean ± SD. Survival data was analyzed by the Kaplan–Meier survival method and the log-rank test. Statistical comparison for creatinine values and tubular injury scoring was performed by one-way ANOVA followed by Bonferroni’s post-hoc correction. *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001.</p

Renal mRNA expression and circulating level of inflammatory cytokines and chemokines at 24 and 72-hours post-injury.

<p>RT-PCR analysis was performed on renal tissue recovered at the specified time points from mice in all groups (A) mRNA expression of monocyte chemoattractant protein-1 (MCP-1, n = 6), Interleukin-6 (IL-6, n = 6) and CXCL1 (KC, n = 4). Expression was normalized to baseline expression of native controls and GAPDH was used as the endogenous control. (B) Plasma KC and CCL2 levels post-injury. Cytokine levels determined by ELISA on plasma recovered at the specified time points from mice in all groups (n = 3 for each group). Data are mean ± SD. Statistical comparison was performed by Kruskal-Wallis and Dunn’s post-hoc correction. *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001.</p

C1INH significantly decreased renal C5a cleavage and limited C3b deposition in kidneys subjected to IRI.

<p>(A) Immunoblotting analysis for C5a in renal tissue at 24 and 72 hours post-IRI. (B) Quantification of C5a band density from western blots normalized to β-tubulin. Results are expressed as mean ± SD fold changes (n = 3 for each group) compared with native controls. (C) Immunoblotting analysis of phosphorylated ERK1/2 normalized to total ERK1/2 (p44/42 MAPK) in renal tissue at 24 and 72 hours post-IRI in renal tissue. (D) Quantification of phosphorylated ERK band density from western blots normalized total ERK and β-tubulin. Results are expressed as mean ± SD fold changes (n = 3 for each group) compared with native controls. (E) Representative images of immunofluorescent microscopy performed on renal tissue at 72 hours post-injury targeting C3b deposition (200X). (F) mRNA expression of bradykinin 1 (BR1) and BR2 receptor in renal tissue. Expression was normalized to baseline expression of native controls and GAPDH was used as the endogenous control. Results are expressed as mean ± SD fold changes (n = 3 for each group).</p

Mesenchymal stem cells induce resistance to chemotherapy through the release of platinum-induced fatty acids

The development of resistance to chemotherapy is a major obstacle for lasting effective treatment of cancer. Here, we demonstrate that endogenous mesenchymal stem cells (MSCs) become activated during treatment with platinum analogs and secrete factors that protect tumor cells against a range of chemotherapeutics. Through a metabolomics approach, we identified two distinct platinum-induced polyunsaturated fatty acids (PIFAs), 12-oxo-5,8,10-heptadecatrienoic acid (KHT) and hexadeca-4,7,10,13-tetraenoic acid (16:4(n-3)), that in minute quantities induce resistance to a broad spectrum of chemotherapeutic agents. Interestingly, blocking central enzymes involved in the production of these PIFAs (cyclooxygenase-1 and thromboxane synthase) prevents MSC-induced resistance. Our findings show that MSCs are potent mediators of resistance to chemotherapy and reveal targets to enhance chemotherapy efficacy in patients