Secreted adenosine triphosphate from Aggregatibacter actinomycetemcomitans triggers chemokine response

Abstract

Extracellular ATP (eATP) is an important intercellular signaling molecule secreted by activated immune cells or released by damaged cells. In mammalian cells, a rapid increase of ATP concentration in the extracellular space sends a danger signal, which alerts the immune system of an impending danger, resulting in recruitment and priming of phagocytes. Recent studies show that bacteria also release ATP into the extracellular milieu, suggesting a potential role for eATP in host-microbe interactions. It is currently unknown if any oral bacteria release eATP. As eATP triggers and amplifies innate immunity and inflammation, we hypothesized that eATP secreted from periodontal bacteria may contribute to inflammation in periodontitis. The aims of this study were to determine if periodontal bacteria secrete ATP, and to determine the function of bacterially derived eATP as an inducer of inflammation. Our results showed that Aggregatibacter actinomycetemcomitans, but not Porphyromonas gingivalis, Prevotella intermedia, or Fusobacterium nucleatum, secreted ATP into the culture supernatant. Exposure of periodontal fibroblasts to filter sterilized culture supernatant of A. actinomycetemcomitans induced chemokine expression in an eATP-dependent manner. This occurred independently of cyclic adenosine monophosphate and phospholipase C, suggesting that ionotrophic P2X receptor is involved in sensing of bacterial eATP. Silencing of P2X7 receptor in periodontal fibroblasts led to a significant reduction in bacterial eATP-induced chemokine response. Furthermore, bacterial eATP served as a potent chemoattractant for neutrophils and monocytes. Collectively, our findings provide evidence for secreted ATP of A. actinomycetemcomitans as a novel virulence factor contributing to inflammation during periodontal disease.

Extracellular ATP as an Inter-Kingdom Signaling Molecule: Release Mechanisms by Bacteria and Its Implication on the Host

“…It has also been shown that eATP promotes biofilm formation in periodontal disease as well as detachment of bacteria from Fusobacterium nucleatum biofilm into its planktonic form to build new colonies [91,92]. Extracellular ATP is also involved in maintaining inflammation and bone resorption in periodontal disease via: (1) P2X7 mediated cytokine release by immune cells and subsequent osteoclast activation [93], (2) direct P2X7 mediated fibroblast activation and chemokine production (IL-8, CXCL-1, CXCL-2, and MCP-1) on the mRNA as well as the protein level, and (3) its chemotactic properties as an attractant for leukocytes [94].…”

Elevation of the Chemokine Pair CXCL10/CXCR3 Initiates Sequential Glial Activation and Crosstalk During the Development of Bimodal Inflammatory Pain after Spinal Cord Ischemia Reperfusion

“…The sequential activation of and crosstalk between microglia and astrocytes is now known to be performed by soluble mediators, such as adenosine, growth factors, inflammatory chemokines and cytokines [3,8,9]. Among these mediators, chemokines are 8-14-kDa secreted proteins with conserved cysteine residues in their sequences.…”

Himar1 Transposon for Efficient Random Mutagenesis in Aggregatibacter actinomycetemcomitans

“…The presence of the transposon inserts was determined in 31 randomly picked transconjugants by determining their ability to grow on kanamycin resistant agar after seven passages. At the 7th passage, bacterial cells would have undergone at least 150 generations since the doubling time of A. actinomycetemcomitans is about 3 h ( Ding et al, 2016 ). This is consistent with previous reports that transposon insertions are stably inherited in A. actinomycetemcomitans ( Kolodrubetz and Kraig, 1994 ; Thomson et al, 1999 ).…”