Novel Blood Purification System for Regulating Excessive Immune Reactions in Severe Sepsis and Septic Shock: An Ex Vivo Pilot Study

Targeting Cytokines, Pathogen-Associated Molecular Patterns, and Damage-Associated Molecular Patterns in Sepsis via Blood Purification

Sepsis is characterized by a dysregulated immune response to infections that causes life-threatening organ dysfunction and even death. When infections occur, bacterial cell wall components (endotoxin or lipopolysaccharide), known as pathogen-associated molecular patterns, bind to pattern recognition receptors, such as toll-like receptors, to initiate an inflammatory response for pathogen elimination. However, strong activation of the immune system leads to cellular dysfunction and ultimately organ failure. Damage-associated molecular patterns (DAMPs), which are released by injured host cells, are well-recognized triggers that result in the elevation of inflammatory cytokine levels. A cytokine storm is thus amplified and sustained in this vicious cycle. Interestingly, during sepsis, neutrophils transition from powerful antimicrobial protectors into dangerous mediators of tissue injury and organ dysfunction. Thus, the concept of blood purification has evolved to include inflammatory cells and mediators. In this review, we summarize recent advances in knowledge regarding the role of lipopolysaccharides, cytokines, DAMPs, and neutrophils in the pathogenesis of sepsis. Additionally, we discuss the potential of blood purification, especially the adsorption technology, for removing immune cells and molecular mediators, thereby serving as a therapeutic strategy against sepsis. Finally, we describe the concept of our immune-modulating blood purification system.

Physiological heating augments the anti-inflammatory reactions during granulocyte/monocyte apheresis: A in vitro study

Granulocyte and monocyte adsorptive apheresis (GMA), an effective therapy for inflammatory disorders, exerts an anti-inflammatory influence by utilizing the biological reaction between blood and cellulose acetate (CA) beads, which are the carriers of the GMA column. Although the biological reaction has an optimum temperature, blood contacts the CA beads below body temperature as GMA is performed in an extracorporeal circulation system. We investigated various soluble factors in blood treated with CA beads at 25°C and 37°C. Here, the optimal temperature for IL-1 receptor antagonist (IL-1ra) release induced by CA beads was 37°C, and IL-6 production from monocytic cells was inhibited by the addition of plasma prepared from the CA bead-treated blood at 37°C, rather than at 25°C. These results indicated that physiological heating of the apheresis carrier augmented the anti-inflammatory reaction in vitro. Thus, heating during GMA may be a new approach for augmenting clinical efficacy.

Adsorption kinetics of high mobility group box 1 protein in a polyacrylonitrile hemofiltration membrane

The high mobility group box 1 protein (HMGB1) is recognized as a prototypical endogenous danger cytokine in sepsis. We previously reported that a polyacrylonitrile (AN69ST) membrane rapidly adsorbed HMGB1. Herein, an in vitro hemofiltration system was designed to assess the HMGB1 adsorption capacity, adsorption sites, and adsorption mechanism of the AN69ST membrane. HMGB1 was repeatedly added seven times during hemofiltration. A rapid decrease in circulating HMGB1 was observed after every addition with no sign of saturation. Presence of HMGB1 on the filter membrane was observed on both membrane surfaces and within the bulk layer using a high concentration of HMGB1 by immunoelectron microscopy. We hypothesized that the addition of heparin to the membrane surface or filtration rate would contribute to the adsorption mechanism. We could not measure the influence of heparin and filtration. Although the membrane was too large to saturate under the μg/mL HMGB1 conditions, our results show that the AN69ST membrane has a robust absorption capacity that could be used to treat sepsis.

Role of TXNIP/NLRP3 in sepsis-induced myocardial dysfunction

Myocardial injury is one of the main symptoms of sepsis. However, the mechanisms underlying sepsis-induced myocardial dysfunction remain unclear. In the present study, the concentration of cardiac troponin T (CTnT) in serum was measured using an enzyme-linked immunosorbent assay kit. The levels of interleukin (IL)-1β and IL-18 were assessed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis and the level of malondialdehyde (MDA) was determined using a corresponding kit. Myocardial pathology was analyzed via hematoxylin and eosin staining. RT-qPCR analysis and western blotting and/or immunohistochemistry were used to quantify the expression levels of thioredoxin-interacting protein (TNXIP), NOD-like receptor pyrin domain containing 3 (NLRP3), cleaved caspase-1, caspase-1, catalase and manganese-superoxide dismutase (MnSOD). The viability of cells was determined using a cell counting kit-8. Apoptosis and reactive oxygen species (ROS) were examined using flow cytometry. Models of sepsis-induced myocardial injury were successfully established; evidence included increases in the levels of CTnT, IL-1β, IL-18 and MDA and myocardial tissue damage in vivo, and decreased cell viability and improvements in IL-1β and IL-18 in vitro. The levels of TXNIP, NLRP3 and cleaved caspase-1 were upregulated in the sepsis models. Small interfering RNA targeting TNXNIP (siTXNIP) increased cell viability, reduced the apoptotic rate and attenuated the release of IL-1β and IL-18. The levels of TXNIP, NLRP3 and cleaved caspase-1 and production of ROS were suppressed by siTXNIP, accompanied by increases in catalase and MnSOD. TXNIP/NLRP3 serves an important role in the development of sepsis-induced myocardial damage.

Immune therapy in sepsis: Are we ready to try again?

Immune therapy to ease the burden of sepsis has thus far failed to consistently improve patient outcomes. Advances in cancer immune therapy and awareness that prolonged immune-suppression in sepsis can leave patients vulnerable to secondary infection and death have driven resurgence in the field of sepsis immune-therapy investigation. As we develop and evaluate these novel therapies, we must learn from past experiences where single-mediator targeted immune therapies were blindly delivered to heterogeneous patient cohorts with complex and evolving immune responses. Advances in genomics, proteomics, metabolomics, and point-of-care technology, coupled with a better understanding of sepsis pathogenesis, have meant that personalised immune-therapy is on the horizon. Here, we review the complex immune pathogenesis in sepsis and the contemporary immune therapies that are being investigated to manipulate this response. An outline of the immune biomarkers that may be used to support this approach is also provided.

A new sight for paraquat poisoning from immunology

Paraquat (methyl viologen, PQ) is highly toxic to humans. Pulmonary fibrosis is the most common cause of death after PQ poisoning. However, no effective therapy is available. The current treatment dilemma and pathology suggest that we should reconsider how to treat the poisoning using other methods, such as immunization. Some clues indicate that immune mechanisms may play important roles in the pathology of PQ poisoning. We implemented a simple experiment to test the hypothesis that activated innate immunity was involved in acute lung injury induced by PQ. Six rats were randomly distributed to two groups: PQ poisoning group and Immunosuppression group (cyclophosphamide pretreatment). Forty-eight hours after PQ administration, rats were anesthetized. The right lungs were excised for histopathology. The experimental results confirmed that in the set of immune deficiency, the inflammatory response in Immunosuppression group could not be effectively triggered so the lung pathology was much better than PQ poisoning group. The immunopathogenic mechanism of PQ poisoning may be essentially a sterile inflammation triggered and amplified by damage-associated molecular patterns (DAMPs). If the hypothesis is established, it may change the therapeutic regimen of PQ poisoning and the prognosis of patients.

Granulocyte and monocyte adsorptive apheresis ameliorates sepsis in rats

Background

Overwhelming activation of granulocytes and monocytes is central to inflammatory responses during sepsis. Granulocyte and monocyte adsorptive apheresis (GMA) is an extracorporeal leukocyte apheresis device filled with cellulose acetate beads and selectively adsorbs granulocytes and monocytes from the peripheral blood.

Methods

In this study, septic rats received the GMA treatment for 2 h at 18 h after cecal ligation and puncture.

Results

GMA selectively adsorbed activated neutrophils and monocytes from the peripheral blood, reduced serum inflammatory cytokine expression, and seemed to improve organ injuries and animal survival. GMA potentially reduced lung injury by alleviating the infiltration of inflammatory cells and the secretion of cytokines.

Conclusions

This study showed that selective granulocyte and monocyte adsorption with cellulose acetate beads might ameliorate cecal ligation and puncture (CLP)-induced sepsis and improve survival and organ function.

Sepsis and Immunosenescence in the Elderly Patient: A Review

Sepsis is a prevalent, serious medical condition with substantial mortality and a significant consumption of health-care resources. Its incidence has increased around 9% annually in general population over the last years and specially in aged patients group. Several risk factors such as comorbidities, preadmission status, malnutrition, frailty, and an impared function in the immune system called immunosenescence are involved in the higher predisposition to sepsis in the elderly patients. Immunosenescence status consists in a functional impairment in both cell-mediated immunity and humoral immune responses and increases not only the risk for develop sepsis but also lead to more severe presentation of infection and may be is also related with a higher mortality. There is a also a concern about to admit patients in the intensive care units taking into account that the outcome of elderly patients is poorer compared to younger people. Nevertheless, the management of septic elderly patients does not differ substantially from younger people. In addition, the quality of life in septic elderly survivors is also lower than in younger people. But age, as alone factor, should not be used to determine treatment options because the poorer outcomes is thought to be due to the increased comorbidities and frailty in this group of patients.

Adjunctive treatment in septic shock: What's next?

Sepsis is a leading cause of death and long-term sequels worldwide. For more than a decade, the scientific community is providing physicians, patients and policy makers with regularly updated guidelines. There is some evidence that implementation of the Surviving Sepsis Campaign guidelines is associated with improved patients outcomes. Though there were major advances in the understanding of sepsis, the management of sepsis mainly relies on anti-infective treatments and restoration of cardiovascular and respiratory function according to quantitative protocolized care. Except some hormonal interventions such as insulin to maintain blood glucose levels of less than 180mg/dL and low doses of corticosteroids and vasopressin in highly selected patients, there is no adjunct therapy for the routine management of sepsis. Recent years have shown some interest in revolutionary concepts such as selective beta-1 receptor antagonists or interventions to boost the immune system. These provocative approaches yielded promising results in various experimental models of sepsis and in preliminary data in humans. The current narrative review summarized some of the numerous adjunct therapies that are currently being investigated in sepsis.