Nontypeable Haemophilus influenzae-Induced MyD88 Short Expression Is Regulated by Positive IKKβ and CREB Pathways and Negative ERK1/2 Pathway

Abstract

Airway diseases such as asthma and chronic obstructive pulmonary disease (COPD) are characterized by excessive inflammation and are exacerbated by nontypeable Haemophilus influenzae (NTHi). Airway epithelial cells mount the initial innate immune responses to invading pathogens and thus modulate inflammation. While inflammation is necessary to eliminate a pathogen, excessive inflammation can cause damage to the host tissue. Therefore, the inflammatory response must be tightly regulated and deciphering the signaling pathways involved in this response will enhance our understanding of the regulation of the host inflammatory response. NTHi binds to TLR2 and signal propagation requires the adaptor molecule myeloid differentiation factor 88 (MyD88). An alternative spliced form of MyD88 is called MyD88 short (MyD88s) and has been identified in macrophages and embryonic cell lines as a negative regulator of inflammation. However, the role of MyD88s in NTHi-induced inflammation in airway epithelial cells remains unknown. Here we show that NTHi induces MyD88s expression and MyD88s is a negative regulator of inflammation in airway epithelial cells. We further demonstrate that MyD88s is positively regulated by IKKβ and CREB and negatively regulated by ERK1/2 signaling pathways. Taken together these data indicate that airway inflammation is controlled in a negative feedback manner involving MyD88s and suggest that airway epithelial cells are essential to maintain immune homeostasis.

Receptor Interacting Protein-2 acts as negative regulator for nontypeable Haemophilus influenzae-induced mucin MUC5AC expression

“…NTHi were grown as previously described [12][13][14][15][16]. For in vitro experiments, NTHi was resuspended in PBS and used at a multiplicity of infection (MOI) of 50.…”

“…Total RNA extraction and RT-qPCR were performed as previously described [2][3][4][12][13][14][15][16][17]. The relative quantities of mRNAs were determined by using the comparative Ct method and were normalized by using human cyclophilin for in vitro or mouse glyceraldehyde-3-phosphate dehydrogenase (GAPDH) for in vivo as endogenous controls.…”

“…Western blot procedures were previously described [2][3][4][12][13][14][15][16][17]. Western blots were performed using whole-cell extracts, separated on 8-10 % SDS-PAGE gels, and transferred to polyvinylidene difluoride we hypothesized that RIP-2 may play a critical role in regulating mucin production [22].…”

NF-κB mediates lipopolysaccharide-induced alternative pre-mRNA splicing of MyD88 in mouse macrophages

“…MyD88-S has been identified in multiple species including humans and mice and in multiple cell types including macrophages, monocytes, T-cells, B-cells, dendritic cells, and epithelial cells (17,(25)(26)(27)(28)(29)(30). Thus, production of this negatively acting isoform is likely a universal mechanism for terminating TLR signaling.…”

“…Thus, production of this negatively acting isoform is likely a universal mechanism for terminating TLR signaling. Production of MyD88-S is induced by LPS and other immune challenges, indicating that production of MyD88-S likely represents a key negative feedback loop to terminate inflammation (12,17,26).…”