<i>in vitro</i> activation of complement and contact system by lactic acidosis

Sonntag, Josef; Emeis, Michael; Strauss, Evelyn; Obladen, Michael

doi:10.1080/09629359891388

Cited by 18 publications

(11 citation statements)

References 15 publications

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“…Interestingly, previous studies have also shown that acidosis activates the alternative pathway of complement (23)(24)(25), supporting the hypothesis that two of the most important pathways of innate immunity are activated by protons.…”

supporting

confidence: 50%

Extracellular Acidosis Induces Neutrophil Activation by a Mechanism Dependent on Activation of Phosphatidylinositol 3-Kinase/Akt and ERK Pathways

Martínez

Vermeulen

Trevani

et al. 2006

The Journal of Immunology

128

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Inflammation in peripheral tissues is usually associated with the development of local acidosis; however, there are few studies aimed at analyzing the influence of acidosis on immune cells. We have shown previously that extracellular acidosis triggers human neutrophil activation, inducing a transient increase in intracellular Ca2+ concentration, a shape change response, the up-regulation of CD18 expression, and a delay of apoptosis. In this study, we analyzed the signaling pathways responsible for neutrophil activation. We found that acidosis triggers the phosphorylation of Akt (the main downstream target of PI3K) and ERK MAPK, but not that of p38 and JNK MAPK. No degradation of IκB was observed, supporting the hypothesis that NF-κB is not activated under acidosis. Inhibition of PI3K by wortmannin or LY294002 markedly decreased the shape change response and the induction of Ca2+ transients triggered by acidosis, whereas the inhibition of MEK by PD98059 or U0126 significantly inhibited the shape change response without affecting the induction of Ca2+ transients. We also found that acidosis not only induces a shape change response and the induction of Ca2+ transients in human neutrophils but also stimulates the endocytosis of FITC-OVA and FITC-dextran. Stimulation of endocytosis was partially prevented by inhibitors of PI3K and MEK. Together, our results support the notion that the stimulation of human neutrophils by extracellular acidosis is dependent on the activation of PI3K/Akt and ERK pathways. Of note, using mouse peritoneal neutrophils we observed that the enhancement of endocytosis induced by acidosis was associated with an improved ability to present extracellular Ags through a MHC class I-restricted pathway.

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supporting

confidence: 50%

Extracellular Acidosis Induces Neutrophil Activation by a Mechanism Dependent on Activation of Phosphatidylinositol 3-Kinase/Akt and ERK Pathways

Martínez

Vermeulen

Trevani

et al. 2006

The Journal of Immunology

128

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“…Accordingly, it is possible that a pH decrease was evoked at the site of infection in our mouse experiments, because of the reduced effect of SpeB on neutrophils. Several studies have found that low pH activates the complement system (42)(43)(44). Our results showed that PepO is involved in the pathological mechanism (Fig.…”

Section: Discussionmentioning

confidence: 49%

Streptococcus pyogenes Endopeptidase O Contributes to Evasion from Complement-mediated Bacteriolysis via Binding to Human Complement Factor C1q

Honda-Ogawa

Sumitomo

Mori

et al. 2017

Journal of Biological Chemistry

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Edited by Luke O'NeillStreptococcus pyogenes secretes various virulence factors for evasion from complement-mediated bacteriolysis. However, full understanding of the molecules possessed by this organism that interact with complement C1q, an initiator of the classical complement pathway, remains elusive. In this study, we identified an endopeptidase of S. pyogenes, PepO, as an interacting molecule, and investigated its effects on complement immunity and pathogenesis. Enzyme-linked immunosorbent assay and surface plasmon resonance analysis findings revealed that S. pyogenes recombinant PepO bound to human C1q in a concentration-dependent manner under physiological conditions. Sites of inflammation are known to have decreased pH levels, thus the effects of PepO on bacterial evasion from complement immunity was analyzed in a low pH condition. Notably, under low pH conditions, PepO exhibited a higher affinity for C1q as compared with IgG, and PepO inhibited the binding of IgG to C1q. In addition, pepO deletion rendered S. pyogenes more susceptible to the bacteriocidal activity of human serum. Also, observations of the morphological features of the pepO mutant strain (⌬pepO) showed damaged irregular surfaces as compared with the wild-type strain (WT). WT-infected tissues exhibited greater severity and lower complement activity as compared with those infected by ⌬pepO in a mouse skin infection model. Furthermore, WT infection resulted in a larger accumulation of C1q than that with ⌬pepO. Our results suggest that interaction of S. pyogenes PepO with C1q interferes with the complement pathway, which enables S. pyogenes to evade complement-mediated bacteriolysis under acidic conditions, such as seen in inflammatory sites.The human pathogen Streptococcus pyogenes is a ␤-hemolytic Gram-positive bacterium that causes a wide variety of diseases in various anatomical sites. Superficial infection of S. pyogenes generally leads to local suppurative lesions, such as seen in pharyngitis and impetigo cases. Such mucosal and skin infections are occasionally followed by onset of immune sequelae, including acute rheumatic fever and acute glomerulonephritis. Furthermore, S. pyogenes infection can also cause invasive diseases, such as necrotizing fasciitis, cellulitis, bacteremia, and streptococcal toxic shock syndrome (STSS), 2 with a high mortality rate, which has been a serious problem throughout the world (1-3).Host possesses various immune systems such as the complement system, one of the most important components of innate immunity, that contributes to host defense against pathogens, especially in the early stage of infection (4). Recognition of an invading pathogen is the trigger for complement pathway activation, and then each complement factor is activated in a sequential manner with precise control (5). Together with opsonization, complement-mediated direct killing of pathogens is attributable to formation of the membrane attack complex (MAC), which consists of late complement factors and induces bacteriolysis by pore formati...

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“…Indeed, Lopez and colleagues (37) showed that acidic pH increases the activity of human immunoglobulin G (IgG) binding to human neutrophils, monocytes, and NK cells. Furthermore, as shown by a number of studies (38)(39)(40)(41)(42)(43), increased activity of the complement system is also observed at lower pH. Trevani and colleagues (44) showed delayed apoptosis of neutrophils in low pH, as well as increased binding of neutrophils to endothelial cells during inflammation via upregulated expression of surface molecules, such as CD18.…”

Section: Humoral and Nonadaptive Immune Effectsmentioning

confidence: 93%

The Emerging “Hallmarks” of Metabolic Reprogramming and Immune Evasion: Distinct or Linked?

2013

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The role of the immune system in tumor elimination has been shown to be increasingly ambiguous, as many tumors not only escape recognition by the adaptive immune response but also even prime the immune cells to promote tumor growth. This effect is achieved through a number of mechanisms, which include both direct interference with the cells of the adaptive immune response and indirect immunosuppression achieved through modification of the tumor microenvironment. We propose that through upregulation of glycolysis and the consequent lowering of pH in the tumor microenvironment, tumors can take advantage of a pH control system, already exploited by specific immune cell subpopulations, to gain control of the immune system and suppress both cytotoxic and antigen-presenting cells. This is accomplished through the direct competition of tumor cells with actively proliferating glycolytic immune cells for glucose and indirectly through the creation by the tumor of a microenvironment that interferes with maturation and activation of antigen-presenting cells and na€ ve cytotoxic T cells. Immunosuppressive properties of an acidic microenvironment in the vicinity of the tumor can thus provide additional benefits for upregulation of glycolysis by tumor cells, suggesting that the two emerging "hallmarks of cancer," altered glucose metabolism and immune suppression, are in fact fundamentally linked. Cancer Res; 73(9); 2737-42. Ó2013 AACR.

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in vitro activation of complement and contact system by lactic acidosis

Cited by 18 publications

References 15 publications

Extracellular Acidosis Induces Neutrophil Activation by a Mechanism Dependent on Activation of Phosphatidylinositol 3-Kinase/Akt and ERK Pathways

Extracellular Acidosis Induces Neutrophil Activation by a Mechanism Dependent on Activation of Phosphatidylinositol 3-Kinase/Akt and ERK Pathways

Streptococcus pyogenes Endopeptidase O Contributes to Evasion from Complement-mediated Bacteriolysis via Binding to Human Complement Factor C1q

The Emerging “Hallmarks” of Metabolic Reprogramming and Immune Evasion: Distinct or Linked?

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