TLR2 ligand engagement upregulates airway smooth muscle TNFα-induced cytokine production

Abstract

Airway inflammation and respiratory infections are important factors contributing to disease exacerbation in chronic airway diseases such as asthma and chronic obstructive pulmonary disease. Airway smooth muscle (ASM) cells express Toll-like receptors (TLRs) and may be involved in the amplification of airway inflammatory responses during infectious exacerbations. We determined whether infectious stimuli (mimicked using Pam3CSK4, a synthetic bacterial lipopeptide that binds to TLR2/TLR1) further enhance ASM cell inflammatory responses to TNFα in vitro and the signaling pathways involved. Human ASM cells were pretreated for 1 h with Pam3CSK4 (1 μg/ml) in the absence or presence of TNFα (10 ng/ml), and IL-6 and IL-8 release was measured after 24 h. As expected, stimulation with Pam3CSK4 or TNFα alone induced significant IL-6 and IL-8 release. Furthermore, Pam3CSK4 significantly increased TNFα-induced IL-6 and IL-8 mRNA expression and protein release and neutrophil chemotactic activity. The potentiating effect of Pam3CSK4 on TNFα-induced inflammatory responses was not due to enhanced TLR2 expression nor did it involve augmentation of NF-κB or MAPK signaling pathways. Rather, Pam3CSK4 induced cAMP response element (CRE) binding protein phosphorylation and induced CRE-mediated transcriptional regulation, suggesting that Pam3CSK4 and TNFα are acting in concert to enhance ASM cytokine secretion via parallel transcriptional pathways. Our findings suggest that ASM cells may be involved in the amplification of airway inflammatory responses during infectious exacerbations in chronic airway disease.

The phosphorylated form of FTY720 activates PP2A, represses inflammation and is devoid of S1P agonism in A549 lung epithelial cells

“…Given that S1P did not induce COX-2 mRNA expression in A549 cells, the possibility exists that S1P does not activate NF-κB in this cell type. To test this, we examined the degradation of IκB-α after stimulation with S1P, compared to TNF as a positive control22. IκB-α degradation is a commonly-used surrogate measure of NF-κB activation22.…”

TLR2 activation causes tachyphylaxis to β2‐agonists in vitro and ex vivo: modelling bacterial exacerbation

“…To address this, we modelled bacterial exacerbation in vitro with the synthetic bacterial lipoprotein Pam3CSK4 (a TLR2 agonist) to mimic bacterial infection and TNFa to simulate inflammation. TLR2 is a pattern-recognition receptor important for mediating the response to bacterial products, and Pam3CSK4 has been widely used to mimic bacterial infections (gram + bacteria) (18,19). TLR2 ligation robustly increased secretion of cytokines implicated as playing a role in asthmatic exacerbation (19).…”

“…TLR2 is a pattern-recognition receptor important for mediating the response to bacterial products, and Pam3CSK4 has been widely used to mimic bacterial infections (gram + bacteria) (18,19). TLR2 ligation robustly increased secretion of cytokines implicated as playing a role in asthmatic exacerbation (19). Interleukin 8, in particular, was increased by~3-fold, and IL-8-mediated neutrophil chemotaxis was greatly enhanced in the presence of the bacterial lipoprotein (19).…”

“…TLR2 ligation robustly increased secretion of cytokines implicated as playing a role in asthmatic exacerbation (19). Interleukin 8, in particular, was increased by~3-fold, and IL-8-mediated neutrophil chemotaxis was greatly enhanced in the presence of the bacterial lipoprotein (19).…”

Nitrosative Stress, Hypernitrosylation, and Autoimmune Responses to Nitrosylated Proteins: New Pathways in Neuroprogressive Disorders Including Depression and Chronic Fatigue Syndrome

“…MAPK inhibition inactivates the transcription of these cytokines in those lymphocytes but leaves the transcription of Th1 cytokines unhindered [69]. MAPK activation also mediates proinflammatory signaling pathways and, importantly in the context of the observations made above, proinflammatory cytokine production [147]. Hence, the inhibition of MAPK by S-nitrosylation [148] could have profound effects on the immune response.…”