TLR3 Activation Augments Matrix Metalloproteinase Production through Reactive Nitrogen Species Generation in Human Lung Fibroblasts

Abstract

Viral infection often triggers asthma exacerbation and contributes to airway remodeling. Cell signaling in viral infection is mainly mediated through TLR3. Many mediators are involved in airway remodeling, but matrix metalloproteinases (MMPs) are key players in this process in asthma. However, the role of TLR3 activation in production of MMPs is unknown. In this study, we examined the effects of polyinosinic-polycytidylic acid [poly(I:C)], a ligand for TLR3, on production of MMPs in human lung fibroblasts, with a focus on nitrosative stress in TLR3 modulation of MMP production. After lung fibroblasts were treated with poly(I:C), production of MMP-1, -2, and -9 and inducible NO synthase (iNOS) was assessed. The roles of NF-κB and IFN regulatory factor-3 (IRF-3) in the poly(I:C)-mediated production of MMPs and the responsiveness to poly(I:C) of normal lung fibroblasts and asthmatic lung fibroblasts were also investigated. Poly(I:C) augmented production of MMPs and iNOS in fibroblasts, and an iNOS inhibitor diminished this production of MMPs. Poly(I:C) stimulated translocation of NF-κB and IRF-3 into the nucleus in fibroblasts and inhibition of NF-κB or IRF-3 abrogated the poly(I:C)-induced increase in both iNOS expression and release of MMPs. Poly(I:C)-induced production of iNOS and MMPs was greater in asthmatic fibroblasts than in normal fibroblasts. We conclude that viral infection may induce nitrosative stress and subsequent MMP production via NF-κB– and IRF-3–dependent pathways, thus potentiating viral-induced airway remodeling in asthmatic airways.

iNOS affects matrix production in distal lung fibroblasts from patients with mild asthma

“…Our iNOS mRNA data revealed that the fibroblasts obtained from asthmatic subjects had a tendency to increased iNOS gene activation compared to the control subjects, and specific iNOS inhibition significantly reduced NO synthesis in the distal fibroblasts from the asthmatic subjects. Higher iNOS production has been seen in another study with central lung fibroblasts from patients with asthma, although with a small number of individuals (33). Our obtained data could implicate that the ongoing inflammation and remodelling processes, as we previously seen in the distal lung (2), may cause the induction of iNOS in these asthmatic subjects.…”

“…may decrease MMP-2 and 9 protein levels and activation (33,45) by down-regulating TIMP-2 activation (14), which could partly explain the effect of iNOS inhibition on proteoglycan synthesis in our present study. However, due to limited amount of material we were not able to measure any MMPs or TIMPs which otherwise could have further strengthen this hypothesis.…”

Progression of Irreversible Airflow Limitation in Asthma: Correlation with Severe Exacerbations

“…We recently showed that TLR3 activation by dsRNA causes nitrosative stress. [18][19][20] This leads to excessive release of matrix metalloproteases in lung fibroblasts, which may contribute to airway remodeling. 18,19 Viruses can also directly modulate ASM function because ASM differentially expresses transcripts for most TLR isoforms.…”

“…[18][19][20] This leads to excessive release of matrix metalloproteases in lung fibroblasts, which may contribute to airway remodeling. 18,19 Viruses can also directly modulate ASM function because ASM differentially expresses transcripts for most TLR isoforms. 21 A recent in vivo study showed that epithelial infection with rhinovirus modulated b2-adrenoceptor activity in ASM through downregulation and desensitization of cell surface receptors.…”

Poly(I:C) induces expressions of MMP-1, -2, and -3 through various signaling pathways including IRF3 in human skin fibroblasts

“…In 7 treatment, human skin fibroblasts were first serum-starved for 24 h in DMEM containing 0.1% FBS, and then treated with poly(I:C) at 1, 10, or 20 μg/ml. The concentrations of poly(I:C) used in this study were screened and determined using the information from many published studies [6,10,[18][19]. Control samples were treated with the vehicle, PBS.…”