Suppression of fibrin(ogen)-driven pathologies through controlled knockdown by lipid nanoparticle delivery of siRNA

Fibrinogen plays a pathologic role in multiple diseases. It contributes to thrombosis and modifies inflammatory and immune responses, supported by studies in mice expressing fibrinogen variants with altered function or with a germline fibrinogen deficiency. However, therapeutic strategies to safely and effectively tailor plasma fibrinogen concentration are lacking. Here, we developed a strategy to tune fibrinogen expression by administering lipid nanoparticle (LNP)-encapsulated siRNA targeting the fibrinogen α chain (siFga). Three distinct LNP-siFga reagents reduced both hepatic Fga mRNA and fibrinogen levels in platelets and plasma, with plasma levels decreased to 42%, 16% and 4% of normal within one-week of administration. Using the most potent siFga, circulating fibrinogen was controllably decreased to 32%, 14%, and 5% of baseline with a 0.5, 1, and 2 mg/kg dose, respectively. Whole blood from mice treated with siFga formed clots with significantly decreased clot strength ex vivo, but siFga treatment did not compromise hemostasis following saphenous vein puncture or tail transection. In an endotoxemia model, siFga suppressed the acute phase response and decreased plasma fibrinogen, D-dimer, and proinflammatory cytokine levels. In a sterile peritonitis model, siFga restored normal macrophage migration in plasminogen-deficient mice. Finally, treatment of mice with siFga decreased the metastatic potential of tumour cells in a manner comparable to that observed in fibrinogen-deficient mice. The results indicate that siFga causes robust and controllable depletion of fibrinogen and provide the proof-of-concept that this strategy can modulate the pleiotropic effects of fibrinogen in relevant disease models.

Translation rescue by targeting Ppp1r15a upstream open reading frame in vivo

The eIF2 initiation complex is central to maintaining a functional translation machinery. Extreme stress such as life-threatening sepsis exposes vulnerabilities in this tightly regulated system, resulting in an imbalance between the opposing actions of kinases and phosphatases on the main regulatory subunit eIF2α. Here, we report that translation shutdown is a hallmark of established sepsis-induced kidney injury brought about by excessive eIF2α phosphorylation and sustained by blunted expression of the counterregulatory phosphatase subunit Ppp1r15a. We determined that the blunted Ppp1r15a expression persists because of the presence of an upstream open reading frame (uORF). Overcoming this barrier with genetic approaches enabled the derepression of Ppp1r15a, salvaged translation and improved kidney function in an endotoxemia model. We also found that the loss of this uORF has broad effects on the composition and phosphorylation status of the immunopeptidome that extended beyond the eIF2α axis. Collectively, our findings define the breath and potency of the highly conserved Ppp1r15a uORF and provide a paradigm for the design of uORF-based translation rheostat strategies. The ability to accurately control the dynamics of translation during sepsis will open new paths for the development of therapies at codon level precision.

Analysis of Lipid-Associated Gene Expression in Mouse Endotoxin Model

Background/Objective: Sepsis-induced kidney injury is a major clinical problem and is an independent risk factor for mortality. We and others have reported that renal tissue metabolism is profoundly altered in the septic milieu. However, whether such metabolic shift is an adaptive response or pathologic process remains unclear. For instance, decreased lipid metabolism in the renal peroxisomes could limit the genesis of deleterious reactive oxygens species whereas the lack of lipid usage in peroxisomes could contribute to energy depletion. Accordingly, here we examined gene expression changes involved in lipid metabolism using mouse models of endotoxemia. Specifically, we compared gene expression changes between injurious high-dose endotoxemia and protective low-dose endotoxin preconditioning models with the goal of identifying favorable reprogramming in lipid metabolism. Methods: To induce protective preconditioning, mice were subjected to low-dose endotoxin followed 24 hours later by high-dose endotoxin. Non-preconditioned mice were subjected to a single high-dose endotoxin. Renal tissues were processed and single-cell RNA-sequencing was performed. Tissue metabolomic data was also obtained. Results: We found that renal lipid metabolism is deranged in the non-preconditioned endotoxemia model. Plin2, a marker for lipid accumulation, was significantly upregulated in the proximal tubules of non-preconditioned animals. In contrast, Plin2 expression was preserved in the preconditioned animals, suggesting that altered Plin2 expression is a maladaptive response. Similarly, Pdzk1 and Lrp2, genes involved in HDL/LDL receptor expression, were concurrently downregulated in the injurious model, whereas their expression levels were preserved in the protective model. The stable expression of these two genes may be important for maintaining metabolic capacity and anti-inflammatory effects observed in the preconditioned state. These findings were further supported by our tissue metabolomics analysis. Conclusion/Impact: Our data indicate that aberrant lipid metabolism is a prominent feature of endotoxin-induced kidney injury. The use of protective preconditioning served as a platform to identify several candidate genes that could be studied further for the development of biomarkers and precise intervention.

Intravenous administration of LPS activates the kynurenine pathway in healthy male human subjects: a prospective placebo-controlled cross-over trial

Background Administration of lipopolysaccharide (LPS) from Gram-negative bacteria, also known as the human endotoxemia model, is a standardized and safe model of human inflammation. Experimental studies have revealed that peripheral administration of LPS leads to induction of the kynurenine pathway followed by depressive-like behavior and cognitive dysfunction in animals. The aim of the present study is to investigate how acute intravenous LPS administration affects the kynurenine pathway in healthy male human subjects. Methods The present study is a prospective, single-blinded, randomized, placebo-controlled cross-over study to investigate the effects of intravenously administered LPS (Escherichia coli O113, 2 ng/kg) on tryptophan and kynurenine metabolites over 48 h and their association with interleukin-6 (IL-6) and C-reactive protein (CRP). The study included 10 healthy, non-smoking men (18–40 years) free from medication. Statistical differences in tryptophan and kynurenine metabolites as well as associations with IL-6 and CRP in LPS and placebo treated subjects were assessed with linear mixed-effects models. Results Systemic injection of LPS was associated with significantly lower concentrations of plasma tryptophan and kynurenine after 4 h, as well as higher concentrations of quinolinic acid (QUIN) after 48 h compared to the placebo injection. No differences were found in kynurenic acid (KYNA) or picolinic acid plasma concentrations between LPS or placebo treatment. The KYNA/kynurenine ratio peaked at 6 h post LPS injection while QUIN/kynurenine maintained significantly higher from 3 h post LPS injection until 24 h. The kynurenine/tryptophan ratio was higher at 24 h and 48 h post LPS treatment. Finally, we report an association between the kynurenine/tryptophan ratio and CRP. Conclusions Our findings strongly support the concept that an inflammatory challenge with LPS induces the kynurenine pathway in humans, activating both the neurotoxic (QUIN) and neuroprotective (KYNA) branch of the kynurenine pathway. Trial registration This study is based on a study registered at ClinicalTrials.gov, NCT03392701. Registered 21 December 2017.

THE STATE OF THE CELLS OF THE IMMUNE SYSTEM IN EXPERIMENTAL IMMUNE-MEDIATED INFLAMMATION OF VARIOUS GENESIS

Relevance. Immune-mediated inflammation of various genesis plays a significant pathogenetic role in autoimmune, allergic, inflammatory and infectious diseases. The objective of the work was a comparative study of the functional status and pathways of cell death of natural and adaptive immunity in mice under the conditions of experimental hyperimmunocomplexemia and endotoxemia to identify the features and common cellular mechanisms of these pathologies. Materials and methods. Hyperimmunocomplexemia was simulated by six-fold immunization of female mice with increasing doses of the antigen, bovine serum albumin (BSA), once a week; the endotoxemia model was induced by the administration of lipopolysaccharide (LPS). Results. The use of both BSA and LPS led to a systemic inflammatory process with significant neutrophilia with a shift of the leukogram to the left. There was a significant increase in the functional and metabolic activity of nonspecific resistance cells. Genotoxic stress was observed in thymus cells and lymph nodes with significant DNA damage, decreased viability, and a significant increase in necrotic death. Violation of the plasma membrane integrity of primary alteration and the release of the cellular content outside has a strong pro-inflammatory and immunogenic effect, which can lead to further intensification of the disease and an increase in its duration with a tendency to chronicity of the pathological process. Conclusions. Thus, both models are characterized by the development of immune-inflammatory processes that lead to significant DNA damage and cell death, which can cause a new round of intensification of necrotic, inflammatory and autoimmune reactions in the body.

Effects of remote ischemic preconditioning on the deformability and aggregation of red blood cells in a rat endotoxemia model

BACKGROUND: The prevention of rheologic alterations in erythrocytes may be important for reducing sepsis-associated morbidity and mortality. Remote ischemic preconditioning (RIPC) has been shown to prevent tissue damage caused by severe ischemia and mortality resulting from sepsis. However, the effect of RIPC on erythrocytes in sepsis is yet to be determined. OBJECTIVE: To investigate the effect of RIPC on rheologic alterations in erythrocytes in sepsis. METHODS: Thirty male Sprague-Dawley rats were used in this study. An endotoxin-induced sepsis model was established by intraperitoneally injecting 20 mg/kg LPS (LPS group). RIPC was induced in the right hind limb using a tourniquet, with three 10-minute of ischemia and 10 min of reperfusion cycles immediately before the injection of LPS (RIPC/LPS group) or phosphate-buffered saline (RIPC group). The aggregation index (AI), time to half-maximal aggregation (T1/2), and maximal elongation index (EImax) of the erythrocytes were measured 8 h after injection. RESULTS: The AI, T1/2, and EImax values in the LPS and RIPC/LPS groups differed significantly from those in the RIPC group, but there were no differences between the values in the LPS and RIPC/LPS groups. CONCLUSIONS: RIPC did not prevent rheologic alterations in erythrocytes in the rat model of LPS-induced endotoxemia.

γδ T/Interleukin-17A Contributes to the Effect of Maresin Conjugates in Tissue Regeneration 1 on Lipopolysaccharide-Induced Cardiac Injury

The mechanisms underlying sepsis-induced cardiomyopathy (SIC) remain poorly understood, and there are no specific therapeutics for SIC. We investigated the effects of maresin conjugates in tissue regeneration 1 (MCTR1) on SIC and explored its potential mechanisms. The experiments were conducted using an endotoxemia model induced by lipopolysaccharide (LPS). Mice were given MCTR1 intravenously 6 h after LPS stimulation. Echocardiography was performed to assess cardiac function 12 h after LPS administration. Treatment with MCTR1 significantly enhanced cardiac function and reduced LPS-induced increase of mRNA expression levels of inflammation cytokines. Transcriptomic analysis indicated that MCTR1 inhibited neutrophil chemotaxis via the IL-17 signaling pathway. We confirmed that MCTR1 reduced the expressions of neutrophil chemoattractants and neutrophil infiltration in the LPS-stimulated hearts. MCTR1 also resulted in a considerable reduction in IL-17A production mainly derived from γδ T cells. Moreover, our results provided the first evidence that neutralizing IL-17A or depletion of γδ T cells markedly decreased neutrophil recruitment and enhanced cardiac function in LPS-induced cardiac injury. These results suggest that MCTR1 alleviates neutrophil infiltration thereby improves cardiac function in LPS-induced cardiac injury via the IL-17 signaling pathway. Thus, MCTR1 represented a novel therapeutic strategy for patients with SIC.