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6 figures.-- Supplemenatry material available.--This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions., [Aims]: Recent in vitro findings suggest that the serine protease Granzyme K (GzmK) may act as a proinflammatory mediator. However, its role in sepsis is unknown. Here we aim to understand the role of GzmK in a mouse model of bacterial sepsis and compare it to the biological relevance of Granzyme A (GzmA)., [Methods]: Sepsis was induced in WT, GzmA-/- and GzmK-/- mice by an intraperitoneal injection of 2x108 CFU from E. coli. Mouse survival was monitored during 5 days. Levels of IL-1α, IL-1β, TNFα and IL-6 in plasma were measured and bacterial load in blood, liver and spleen was analyzed. Finally, profile of cellular expression of GzmA and GzmK was analyzed by FACS., [Results]: GzmA and GzmK are not involved in the control of bacterial infection. However, GzmA and GzmK deficient mice showed a lower sepsis score in comparison with WT mice, although only GzmA deficient mice exhibited increased survival. GzmA deficient mice also showed reduced expression of some proinflammatory cytokines like IL1-α, IL-β and IL-6. A similar result was found when extracellular GzmA was therapeutically inhibited in WT mice using serpinb6b, which improved survival and reduced IL-6 expression. Mechanistically, active extracellular GzmA induces the production of IL-6 in macrophages by a mechanism dependent on TLR4 and MyD88., [Conclusions]: These results suggest that although both proteases contribute to the clinical signs of E. coli-induced sepsis, inhibition of GzmA is sufficient to reduce inflammation and improve survival irrespectively of the presence of other inflammatory granzymes, like GzmK., This work was supported by grant SAF2017-83120-C2-1-R and PID2020-113963RBI00 from the Ministry of Science, Innovation and Universities and FEDER (Group B29_17R, Aragon Government). IU-M , MG-T and CP were supported by a PhD fellowships from Aragon Government, Ministry of Science, Innovation and Universities (FPI) and Asociacion Española contra el Cancer (AECC). MA and LS were supported by a post-doctoral fellowship “Juan de la Cierva-formación” (MA, LS) and "Juan de la Cierva-incorporacion" (MA) from the Ministry of Science, Innovation and Universities. JP was supported by ARAID Foundation.

7 figures, 1 table., [Aims]: Peritonitis is one of the most common causes of sepsis, a serious syndrome characterized by a dysregulated systemic inflammatory response. Recent evidence suggests that Granzyme A (GzmA), a serine protease mainly expressed by NK and T cells, could act as a proinflammatory mediator and could play an important role in the pathogenesis of sepsis. This work aims to analyze the role and the therapeutic potential of GzmA in the pathogenesis of peritoneal sepsis., [Methods]: The level of extracellular GzmA as well as GzmA activity were analyzed in serum from healthy volunteers and patients with confirmed peritonitis and were correlated with the Sequential Organ Failure Assessment (SOFA) score. Peritonitis was induced in C57Bl/6 (WT) and GzmA-/- mice by cecal ligation and puncture (CLP). Mice were treated intraperitoneally with antibiotics alone or in combination serpinb6b, a specific GzmA inhibitor, for 5 days. Mouse survival was monitored during 14 days, levels of some proinflammatory cytokines were measured in serum and bacterial load and diversity was analyzed in blood and spleen at different times., [Results]: Clinically, elevated GzmA was observed in serum from patients with abdominal sepsis suggesting that GzmA plays an important role in this pathology. In the CLP model GzmA deficient mice, or WT mice treated with an extracellular GzmA inhibitor, showed increased survival, which correlated with a reduction in proinflammatory markers in both serum and peritoneal lavage fluid. GzmA deficiency did not influence bacterial load in blood and spleen and GzmA did not affect bacterial replication in macrophages in vitro, indicating that GzmA has no role in bacterial control. Analysis of GzmA in lymphoid cells following CLP showed that it was mainly expressed by NK cells. Mechanistically, we found that extracellular active GzmA acts as a proinflammatory mediator in macrophages by inducing the TLR4-dependent expression of IL-6 and TNFα., [Conclusions]: Our findings implicate GzmA as a key regulator of the inflammatory response during abdominal sepsis and provide solid evidences about its therapeutic potential for the treatment of this severe pathology., This work was supported by grant SAF2017-83120-C2-1-R and SAF2014-54763-C2-2-R from the Ministry of Science, Innovation and Universities and FEDER (Group B29_17R, Aragon Government). MG and LS were supported by a PhD fellowship (FPI) from the Ministry of Science, Innovation and Universities. IUM was supported by a PhD fellowship from Aragon Government, MA was supported by a post-doctoral fellowship “Juan de la Cierva-formación” from the Ministry of Science, Innovation and Universities. JP was supported by ARAID Foundation.

3 figuras.-- Póster presentado en el 42º Congreso SEI, Congreso de la Sociedad Española de Inmunología, formato virtual, 24-26 marzo de 2021, Madrid., Peritonitis is one of the most common causes of sepsis. Evidence suggests that Granzyme A (GzmA), a serine protease mainly expressed by NK and T cells, could act as proinflammatory mediator and could play an important role in the pathogenesis of sepsis. Here, we aim to analyze the role and therapeutic potential of GzmA in the pathogenesis of peritoneal sepsis.

of the work presented at the 30th ECCMID 2020, European Congress of Clinical Microbiology and Infectious Diseases, organized by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID).-- www.eccmid.org .-- www.escmid.org.-- Accepted abstract 1508., [Background] Peritonitis is one of the most common leading cause of sepsis. Recent evidence suggests that Granzyme A (GzmA), a serine protease mainly expressed in NK cells and T cells, could act as a proinflammatory mediator and could play an important role in the pathogenesis of sepsis. This work aims to analyze the role of serum GzmA as a biomarker and therapeutic target in peritoneal sepsis., [Materials/methods] Concentration and enzyme activity of soluble GzmA were sequentially analyzed in serum from healthy donors and patients with peritonitis and were correlated with the Sequential Organ Failure Assessment (SOFA) score. Peritonitis was induced in C57Bl/6 (Wt) and GzmA-KO mice by cecal ligation and puncture (CLP). Mice were treated intraperitoneally with antibiotics and with serpinb6b, a specific GzmA inhibitor, for 5 days. Mouse survival was monitored during 14 days and the levels of serum proinflammatory cytokines and bacterial load in blood and spleen were analyzed at 6 and 24h from CLP., [Results] We have found high levels of GzmA in serum of patient with peritonitis. Most importantly, we observed that GzmA activity in serum correlates with SOFA score, suggesting that active GzmA could play an important role in sepsis development in peritonitis patients and could be a new biomarker of sepsis severity. In order to analyze the therapeutical potential of soluble GzmA in peritoneal sepsis, we used the CLP mouse model. After peritonitis induction, GzmA-KO mice exhibit increased survival compared with Wt mice, which correlated with reduced levels of proinflammatory cytokines in serum. The analysis of bacterial load in blood and spleen showed no differences between Wt and GzmA-KO mice suggesting that GzmA does not play an important role in bacterial control. Treatment with serpinb6b reduced mortality, which correlated with reduced cytokine serum levels in serum, confirming the therapeutical potential of gzmA to treat peritoneal sepsis., [Conclusions] Our findings confirm that soluble GzmA plays an important role in the pathogenesis of sepsis and could be a new therapeutic target and a biomarker for the treatment of peritoneal sepsis.

1 figure, 1 table Sepsis is a serious global health problem. In addition to a high incidence, this syndrome has a high mortality and is responsible for huge health expenditure. The pathophysiology of sepsis is very complex and it is not well-understood yet. However, it is widely accepted that the initial phase of sepsis is characterized by a hyperinflammatory response while the late phase is characterized by immunosuppression and immune anergy, increasing the risk of secondary infections. Granzymes (Gzms) are a family of serine proteases classified according to their cleavage specificity. Traditionally, it was assumed that all Gzms acted as cytotoxic proteases. However, recent evidence suggests that GzmB is the one with the greatest cytotoxic capacity, while the cytotoxicity of others such as GzmA and GzmK is not clear. Recent studies have found that GzmA, GzmB, GzmK, and GzmM act as pro-inflammatory mediators. Specially, solid evidences show that GzmA and GzmK function as extracellular proteases that regulate the inflammatory response irrespectively of its ability to induce cell death. Indeed, studies in animal models indicate that GzmA is involved in the cytokine release syndrome characteristic of sepsis. Moreover, the GZM family also could regulate other biological processes involved in sepsis pathophysiology like the coagulation cascade, platelet function, endothelial barrier permeability, and, in addition, could be involved in the immunosuppressive stage of sepsis. In this review, we provide a comprehensive overview on the contribution of these novel functions of Gzms to sepsis and the new therapeutic opportunities emerging from targeting these proteases for the treatment of this serious health problem. This work was supported in part by FEDER/Gobierno de Aragón (group B29), Ministerio de Economia y Competitividad [SAF2014-54763-C2-1 and SAF2017-83120-C2-1-R (JP-P), SAF2014-54763-C2-2-R (EG)] and Instituto de Salud Carlos III (PI16-00526, LM-L; PI18/00527, JP-P). Predoctoral grants/contracts from Fundacion Santander/Universidad de Zaragoza (LS and MA), Ministerio de Ciencia, Innovación y Universidades (MG-T). MA has a Juan de la Cierva Contract (Ministerio de Ciencia, Innovación y Universidades) and JS-M a Rio Hortega Contract (Instituto de Salud Carlos III). JP was supported by Fundación Aragon I+D (ARAID).