Mast cell chymase decreases the severity of group B Streptococcus infections.

Group B Streptococcus (GBS) or Streptococcus agalactiae are β-hemolytic gram-positive bacteria that colonize the lower genital tracts of women and are frequently associated with infections during pregnancy. Innate immune defenses are critical for controlling GBS dissemination and systemic infection. Mast cells are resident sentinel cells that come into contact with pathogens early during colonization and infection. We aimed to investigate the contribution of chymase to systemic GBS infection and rates of preterm birth. Pharmacologic and genetic approaches using mice deficient in mast cell protease (MCPT) 4, the mouse functional homologue of human chymase, were used. Our studies show that mast cells release a protease with chymotrypsin-like cleavage specificity in response to GBS. Additionally, increased GBS systemic infection and preterm births were observed in MCPT4-deficient mice versus MCPT4-sufficient mice. Furthermore, we observed that proteolytic cleavage of the host extracellular matrix protein fibronectin by peritoneal cell-derived mast cell lysates diminished GBS adherence. Consistent with this observation, the increase in GBS dissemination and preterm births observed in MCPT4-deficient mice was abolished when GBS was deficient in expression of the fibronectin-binding protein SfbA. Taken together, our results suggest that the protective effect of MCPT4 against GBS dissemination and preterm labor can be attributed in part to MCPT4-mediated proteolysis of fibronectin. Our studies reveal a novel role of mast cells in defense against bacterial infections.

Gendrin C ，Shubin NJ ，Boldenow E ，Merillat S ，Clauson M ，Power D ，Doran KS ，Abrink M ，Pejler G ，Rajagopal L ，Piliponsky AM ... -  《-》

Critical role of mast cell chymase in mouse abdominal aortic aneurysm formation.

Sun J ，Zhang J ，Lindholt JS ，Sukhova GK ，Liu J ，He A ，Abrink M ，Pejler G ，Stevens RL ，Thompson RW ，Ennis TL ，Gurish MF ，Libby P ，Shi GP ... -  《-》

Mast Cell Chymase/Mcpt4 Suppresses the Host Immune Response to Plasmodium yoelii, Limits Malaria-Associated Disruption of Intestinal Barrier Integrity and Reduces Parasite Transmission to Anopheles stephensi.

An increase in mast cells (MCs) and MCs mediators has been observed in malaria-associated bacteremia, however, the role of these granulocytes in malarial immunity is poorly understood. Herein, we studied the role of mouse MC protease (Mcpt) 4, an ortholog of human MC chymase, in malaria-induced bacteremia using Mcpt4 knockout (Mcpt4-/-) mice and Mcpt4+/+ C57BL/6J controls, and the non-lethal mouse parasite Plasmodium yoelii yoelii 17XNL. Significantly lower parasitemia was observed in Mcpt4-/- mice compared with Mcpt4+/+ controls by day 10 post infection (PI). Although bacterial 16S DNA levels in blood were not different between groups, increased intestinal permeability to FITC-dextran and altered ileal adherens junction E-cadherin were observed in Mcpt4-/- mice. Relative to infected Mcpt4+/+ mice, ileal MC accumulation in Mcpt4-/- mice occurred two days earlier and IgE levels were higher by days 8-10 PI. Increased levels of circulating myeloperoxidase were observed at 6 and 10 days PI in Mcpt4+/+ but not Mcpt4-/- mice, affirming a role for neutrophil activation that was not predictive of parasitemia or bacterial 16S copies in blood. In contrast, early increased plasma levels of TNF-α, IL-12p40 and IL-3 were observed in Mcpt4-/- mice, while levels of IL-2, IL-10 and MIP1β (CCL4) were increased over the same period in Mcpt4+/+ mice, suggesting that the host response to infection was skewed toward a type-1 immune response in Mcpt4-/- mice and type-2 response in Mcpt4+/+ mice. Spearman analysis revealed an early (day 4 PI) correlation of Mcpt4-/- parasitemia with TNF-α and IFN-γ, inflammatory cytokines known for their roles in pathogen clearance, a pattern that was observed in Mcpt4+/+ mice much later (day 10 PI). Transmission success of P. y. yoelii 17XNL to Anopheles stephensi was significantly higher from infected Mcpt4-/- mice compared with infected Mcpt4+/+ mice, suggesting that Mcpt4 also impacts transmissibility of sexual stage parasites. Together, these results suggest that early MCs activation and release of Mcpt4 suppresses the host immune response to P. y. yoelii 17XNL, perhaps via degradation of TNF-α and promotion of a type-2 immune response that concordantly protects epithelial barrier integrity, while limiting the systemic response to bacteremia and parasite transmissibility.

Céspedes N ，Donnelly EL ，Lowder C ，Hansten G ，Wagers D ，Briggs AM ，Schauer J ，Haapanen L ，Åbrink M ，Van de Water J ，Luckhart S ... -  《Frontiers in Immunology》

The combined action of mast cell chymase, tryptase and carboxypeptidase A3 protects against melanoma colonization of the lung.

Grujic M ，Paivandy A ，Gustafson AM ，Thomsen AR ，Öhrvik H ，Pejler G ... -  《Oncotarget》

Mast cell chymase degrades the alarmins heat shock protein 70, biglycan, HMGB1, and interleukin-33 (IL-33) and limits danger-induced inflammation.

Roy A ，Ganesh G ，Sippola H ，Bolin S ，Sawesi O ，Dagälv A ，Schlenner SM ，Feyerabend T ，Rodewald HR ，Kjellén L ，Hellman L ，Åbrink M ... -  《-》