Streptococcal M1 Protein-Induced Lung Injury is Independent of Platelets in Mice

Abstract

Streptococcus pyogenes of the M1 serotype is frequently associated with severe streptococcal infections. M1 protein challenge can cause widespread microthrombosis, suggesting a role of platelets in streptococcal sepsis. Herein, we hypothesized that platelets may play a role in M1 protein-induced lung inflammation and injury. M1 protein was injected intravenously in C57Bl/6 mice. For platelet and neutrophil depletion, an anti-GP1bα antibody and an anti-Gr-1 antibody, respectively, were administered before M1 protein challenge. Bronchoalveolar fluid and lung tissue were harvested for analysis of neutrophil infiltration, edema, and macrophage inflammatory protein 2 (MIP-2) formation. Blood was collected for analysis of membrane-activated complex 1 (Mac-1) and CD40 ligand (CD40L) expression on neutrophils and platelets as well as soluble CD40L in plasma. M1 protein caused significant pulmonary damage characterized by neutrophil infiltration, increased formation of edema and MIP-2 in the lung, and enhanced Mac-1 expression on neutrophils. However, M1 protein challenge had no effect on platelet surface expression of CD40L or soluble CD40L levels in plasma. Interestingly, platelet depletion had no influence on M1 protein-induced neutrophil recruitment, MIP-2 production, and tissue damage in the lung or Mac-1 expression on neutrophils. Moreover, we observed that M1 protein could bind to neutrophils but not to platelets. On the other hand, neutrophil depletion abolished M1 protein-induced edema formation and tissue damage in the lung. Our data suggest that neutrophils but not platelets are involved in the pathophysiology of M1 protein-provoked pulmonary damage. Thus, neutrophils may constitute a key target in infections caused by S. pyogenes of the M1 serotype.

Streptococcal M1 Protein Triggers Farnesyltransferase-Dependent Formation of CXC Chemokines in Alveolar Macrophages and Neutrophil Infiltration of the Lungs

“…Moreover, several reports indicate that statin treatment inhibits pulmonary damage (39) and increases survival in murine sepsis (21,22). Indeed, we have recently shown that simvastatin is a potent inhibitor of M1 protein-triggered neutrophil recruitment and lung damage (40). Convincing data in the literature demonstrate that statins, such as simvastatin, exert pleiotropic anti-inflammatory effects, including attenuated expression of cytokines, chemokines, and adhesion molecules, as well as decreased formation of nitric oxide (10,34,36).…”

Targeting CD162 protects against streptococcal M1 protein-evoked neutrophil recruitment and lung injury

“…A functional role of CXC chemokines has been proposed in streptococcal infections (44), and we have demonstrated that M1 protein is a potent stimulator of CXCL1 and CXCL2 production in the lung (41). Herein, we found that inhibition of CD162 reduced M1 protein-induced formation of CXCL1 and CXCL2 in the lung.…”

“…Although M1 protein challenge is not identical to an infection with whole bacteria, M1 protein is a dominant virulence factor on S. pyogenes, and the M1 serotype of these bacteria is most frequently associated with STSS (7). Acute lung damage is a key feature in STSS, and accumulating data suggest that activation of neutrophils is a critical component in the onset of the M1 protein-provoked lung injury (7,35,37,41). Herein, we show for the first time that targeting CD162 decreases edema formation and tissue injury in the lungs of mice exposed to M1 protein, suggesting that CD162 plays a key role in regulating acute lung damage in streptococcal infections.…”

“…Excessive accumulation infiltration of neutrophils is a ratelimiting step in septic lung damage (11,17). For example, it has been shown that depletion of neutrophils abolishes M1 protein-induced lung damage (35,41).Extravascular localization of neutrophils is coordinated by secreted CXC chemokines, including KC (CXCL1) and MIP-2 (CXCL2) (45). A recent study demonstrated that M1 proteinprovoked pulmonary accumulation of neutrophils is critically dependent on the synthesis and action of CXC chemokines (44).…”

“…Excessive accumulation infiltration of neutrophils is a ratelimiting step in septic lung damage (11,17). For example, it has been shown that depletion of neutrophils abolishes M1 protein-induced lung damage (35,41).…”