Porphyromonas gingivalis-Induced Reactive Oxygen Species Activate JAK2 and Regulate Production of Inflammatory Cytokines through c-Jun

Abstract

Pathogen-induced reactive oxygen species (ROS) play a crucial role in host innate immune responses through regulating the quality and quantity of inflammatory mediators. However, the underlying molecular mechanisms of this effect have yet to be clarified. In this study, we examined the mechanism of action of ROS stimulated by Porphyromonas gingivalis in gingival epithelial cells. P. gingivalis induced the rapid production of ROS, which lead to the phosphorylation of JAK2 and increased levels of secreted proinflammatory cytokines interleukin-6 (IL-6) and IL-1␤. Neutralization of ROS by N-acetyl-L-cysteine (NAC) abrogated the phosphorylation of JAK2 and suppressed the production of IL-6 and IL-1␤. ROS-mediated phosphorylation of JAK2 induced the phosphoactivation of c-Jun amino-terminal protein kinase (JNK) and the downstream transcriptional regulator c-Jun. Inhibition of JAK2, either pharmacologically or by small interfering RNA (siRNA), reduced both the phosphorylation of these molecules and the production of proinflammatory cytokines in response to P. gingivalis. Furthermore, pharmacological inhibition or siRNA-mediated gene silencing of JNK or c-Jun mimicked the effect of JAK2 inhibition to suppress P. gingivalisinduced IL-6 and IL-1␤ levels. The results show that ROS-mediated activation of JAK2 is required for P. gingivalis-induced inflammatory cytokine production and that the JNK/c-Jun signaling axis is involved in the ROS-dependent regulation of IL-1␤ and IL-6 production.

FOXO responses toPorphyromonas gingivalisin epithelial cells

“…As mentioned, P. gingivalis has a number of effects on gingival epithelial cells including up‐regulation of antioxidant responses, proinflammatory cytokine production and suppression of intrinsic apoptotic pathways (Yilmaz et al ., 2004; 2008; Mao et al ., ; Yao et al ., ; Choi et al ., ; Hung et al ., ; Wang et al ., ), and all of these processes can be controlled by FOXO1. We used quantitative reverse transcription polymerase chain reaction (qRT‐PCR) to examine the expression of genes associated with these events in epithelial cells infected with P. gingivalis .…”

“…In addition to controlling antioxidant responses, FOXO transcription factors act as sensors of oxidative stress as their activity is regulated by H 2 O 2 (Essers et al ., ; Storz, ). P. gingivalis stimulates the rapid production of ROS in gingival epithelial cells (Choi et al ., ; Wang et al ., ), and hence we next sought to determine the role of ROS in the activation of FOXO1 by P. gingivalis . The antioxidant N‐acetylcysteine (NAC) was used to neutralize ROS, and FOXO responses to P. gingivalis were then examined.…”

“…The genes and pathways controlled by FOXO are manifold and by practical necessity we focused on processes that are well defined and potentially relevant to P. gingivalis infection. P. gingivalis induces ROS production in gingival epithelial cells (Choi et al ., ; Wang et al ., ), and to counteract the damaging effects of ROS, the host cell mobilizes a number of antioxidant mechanisms. These include the production of catalase, superoxide dismutase and peroxiredoxins, all of which are under the control of FOXO (Storz, ; Eijkelenboom and Burgering, ).…”

“…Conversely, P. gingivalis stimulates production and secretion of the proinflammatory cytokines IL‐1β and IL‐6. Increased IL‐1β and IL‐6 production is dependent, at least partially, on induction of reactive oxygen species (ROS), which induce the phosphorylation of Janus kinase (JAK)2 and activation of the transcriptional regulator c‐Jun (Wang et al ., ). Additionally, secretion of IL‐1β involves stimulation of ROS production by adenosine triphosphate (ATP), through a complex consisting of P2X 4 , P2X 7 and pannexin‐1 that activates the NLRP3 inflammasome (Hung et al ., ).…”

Streptococcus gordonii programs epithelial cells to resist ZEB2 induction by Porphyromonas gingivalis

“…ZEB2 can control cell migration and also production of inflammatory mediators such as IL-6 (20). As both TIGK cell migration and IL-6 secretion can be modulated by P. gingivalis (11,32), we examined the influence of ZEB2 on these processes. Fig.…”