ATP is an important signaling molecule in the immune system, and it is able to bind the P2X7 purinergic receptor. Recently, our group showed that ATP-treated macrophages eliminate Leishmania amazonensis. It has been reported that leukotriene B4 (LTB4) reduces the parasitic load of infected macrophages. Additionally, it has been demonstrated that the P2X7 receptor can induce PLA2 activation and arachidonic acid mobilization. Based on these findings, we investigated whether LTB4 is produced upon P2X7 receptor activation and examined whether LTB4 modulates parasite elimination. Using macrophages lacking the P2X7 receptor, we observed that ATP was not able to reduce L. amazonensis load. This result suggests a role of the P2X7 purinergic receptor in parasite elimination. In addition, ATP was sufficient to induce LTB4 release from infected control macrophages but not from macrophages lacking the P2X7 receptor. Moreover, we found that ATP failed to decrease the parasitic load in 5-lipoxygenase (LO)–deficient macrophages. Treatment with the 5-LO inhibitor AA861 also impairs the ATP effect on parasitic loads. Furthermore, macrophages from 5-LO knockout mice eliminated L. amazonensis in the presence of exogenous LTB4, and macrophages obtained from P2X7 receptor knockout mice eliminated L. amazonensis when incubated with ionomycin. Finally, we demonstrated that in the presence of CP105696, an antagonist for LTB4 high-affinity receptor, ATP was not able to reduce parasitic load. These results indicate that P2X7 receptor activation leads to LTB4 formation, which is required for L. amazonensis elimination.

High concentrations of free heme found during hemolytic events or cell damage leads to inflammation, characterized by neutrophil recruitment and production of reactive oxygen species, through mechanisms not yet elucidated. In this study, we provide evidence that heme-induced neutrophilic inflammation depends on endogenous activity of the macrophage-derived lipid mediator leukotriene B4 (LTB4). In vivo, heme-induced neutrophil recruitment into the peritoneal cavity of mice was attenuated by pretreatment with 5-lipoxygenase (5-LO) inhibitors and leukotriene B4 receptor 1 (BLT1) receptor antagonists as well as in 5-LO knockout (5-LO−/−) mice. Heme administration in vivo increased peritoneal levels of LTB4 prior to and during neutrophil recruitment. Evidence that LTB4 was synthesized by resident macrophages, but not mast cells, included the following: 1) immuno-localization of heme-induced LTB4 was compartmentalized exclusively within lipid bodies of resident macrophages; 2) an increase in the macrophage population enhanced heme-induced neutrophil migration; 3) depletion of resident mast cells did not affect heme-induced LTB4 production or neutrophil influx; 4) increased levels of LTB4 were found in heme-stimulated peritoneal cavities displaying increased macrophage numbers; and 5) in vitro, heme was able to activate directly macrophages to synthesize LTB4. Our findings uncover a crucial role of LTB4 in neutrophil migration induced by heme and suggest that beneficial therapeutic outcomes could be achieved by targeting the 5-LO pathway in the treatment of inflammation associated with hemolytic processes.

Brazil, which is hyperendemic for dengue virus (DENV), has had recent Zika (ZIKV) and (CHIKV) Chikungunya virus outbreaks. Since March 2016, CHIKV is the arbovirus infection most frequently diagnosed in Rio de Janeiro. In the analysis of 1835 syndromic patients, screened by real time RT-PCR, 56.4% of the cases were attributed to CHIKV, 29.6% to ZIKV, and 14.1% to DENV-4. Sequence analyses of CHIKV from sixteen samples revealed that the East-Central-South-African ( ECSA) genotype of CHIKV has been circulating in Brazil since 2013 [95% bayesian credible interval (BCI): 03/2012-10/2013], almost a year before it was detected by arbovirus surveillance program. Brazilian cases are related to Central African Republic sequences from 1980’s. To the best of our knowledge, given the available sequence published here and elsewhere, the ECSA genotype was likely introduced to Rio de Janeiro early on 2014 (02/2014; BCI: 07/2013-08/2014) through a single event, after primary circulation in the Bahia state at the Northestern Brazil in the previous year. The observation that the ECSA genotype of CHIKV was circulating undetected underscores the need for improvements in molecular methods for viral surveillance.

Platelets are crucial effector cells in hemostasis. In addition, platelets are increasingly recognized as major inflammatory cells with key roles in innate and adaptive immune responses. Activated platelets have key thromboinflammatory activities linking coagulation to inflammatory response in a variety of coagulation disorders and vasculopathies. Recently identified inflammatory activities of platelets include the synthesis of IL-1β from spliced pre-RNA, as well as the presence and assembly of inflammasome which intermediate IL-1β secretion. Here we review the mechanisms by which platelets activate translation machinery and inflammasome assembly to synthesize and release IL-1β. The contributions of these processes to protective and pathogenic responses during infectious and inflammatory diseases are discussed.

Postsepsis lung injury is a common clinical problem associated with significant morbidity and mortality. Leukotrienes (LTs) are important lipid mediators of infection and inflammation derived from the 5-lipoxygenase (5-LO) metabolism of arachidonate with the potential to contribute to lung damage after sepsis. To test the hypothesis that LTs are mediators of lung injury after sepsis, we assessed lung structure, inflammatory mediators, and mechanical changes after cecal ligation and puncture surgery in wild-type (WT) and 5-LO knockout (5-LO 2/2 ) mice and in WT mice treated with a pharmacologic LT synthesis inhibitor (MK886) and LT receptor antagonists (CP105,696 and montelukast). Sixteen hours after surgery, WT animals exhibited severe lung injury (by histological analysis), substantial mechanical impairment (i.e., an increase in static lung elastance), an increase in neutrophil infiltration, and high levels of LTB 4 , cysteinyl-LTs (cys-LTs), prostaglandin E 2 , IL-1b, IL-6, IL-10, IL-17, KC (CXCL1), and monocyte chemotactic protein-1 (CCL2) in lung tissue and plasma. 5-LO 2/2 mice and WT mice treated with a pharmacologic 5-LO inhibitor were significantly protected from lung inflammation and injury. Selective antagonists for BLT1 or cys-LT1, the high-affinity receptors for LTB 4 and cysLTs, respectively, were insufficient to provide protection when used alone. These results point to an important role for 5-LO products in sepsis-induced lung injury and suggest that the use of 5-LO inhibitors may be of therapeutic benefit clinically.

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Oxidative stress is considered one of the early underlying contributors of acute lung injury (ALI) and ventilator-induced lung injury (VILI). DJ-1, also known as PARK7, has a well-established role as an antioxidant. We have previously shown maintaining oxidative balance via the ATF3-Nrf2 axis was important in protection from ALI. Here, we exclusively characterize the role of DJ-1 in sterile LPS-induced ALI and VILI. DJ-1 protein expression was increased after LPS treatment in human epithelial and endothelial cell lines and lungs of wild-type mice. DJ-1 deficient mice exhibited greater susceptibility to LPS-induced acute lung injury as demonstrated by increased cellular infiltration, augmented levels of pulmonary cytokines, enhanced ROS levels and oxidized by-products, increased pulmonary edema and cell death. In a two-hit model of LPS and mechanical ventilation (MV), DJ-1 deficient mice displayed enhanced susceptibility to inflammation and lung injury. Collectively, these results identify DJ-1 as a negative regulator of ROS and inflammation, and suggest its expression protects from sterile lung injury driven by high oxidative stress.

The mechanism of immunosuppression induced by severe sepsis is not fully understood. The production of prostaglandin E2 (PGE2) during sepsis is well known, but its role in long-term consequences of sepsis has not been explored. The current study evaluates the role of PGE2 in the development of immunosuppression secondary to sepsis and its potential as therapeutic target. Cecal ligation and puncture was used as an experimental model for sepsis induction in Balb/c and C57BL/6 mice. Immunosuppression was evaluated by the response to secondary infection with Aspergillus fumigatus in sepsis survivors. The role of prostanoids was evaluated in vivo and in vitro by treatment with the cyclooxygenase inhibitor ketoprofen. Balb/c mice were more susceptible than C57BL/6 to severe sepsis and to secondary infection, with a greater mortality rate. Prostaglandin E2 concentrations found in bronchoalveolar lavage in sham and cecal ligation and puncture group after fungal challenge were much higher in Balb/c than in C57BL/6 mice. Ketoprofen treatment improved survival of septic Balb/c mice subjected to secondary infection, while also enhancing macrophage phagocytosis and neutrophil recruitment to the lungs. We identified a pivotal role for PGE2 acting on EP4 receptors in modulating cytokine production differentially by sham and septic macrophages. Furthermore, sepsis also altered key enzymes in PGE2 synthesis and degradation. Our results indicate the involvement of PGE2 in severe sepsis-induced immunosuppression. Inhibition of PGE2 production represents an attractive target to improve innate immune response against secondary infection in the immunocompromised host.