cAMP-dependent protein kinase A acts as a negative regulator for nontypeable Haemophilus influenzae-induced GM-CSF expression via inhibition of MEK-ERK signaling pathway

Abstract

Otitis media (OM) is the most common bacterial infection in children, and often leads to conductive hearing loss. The Gram-negative bacterial pathogen, nontypeable Haemophilus influenzae (NTHi) is one of the primary causative agents. A classic hallmark of NTHi-induced OM is inflammation in middle ear. While appropriate inflammation is critical for host defense, an overactive response can often be detrimental to the host. Thus, inflammation must be tightly controlled. Here, we show that NTHi up-regulates the expression of granulocyte macrophage-colony stimulating factor (GM-CSF), one of the major proinflammatory mediator, via MEK-ERK signaling pathway in human middle ear epithelial cells. Moreover, cAMP-dependent protein kinase A (PKA) negatively regulates NTHi-induced GM-CSF expression through inhibition of MEK-ERK signaling pathway. Collectively, our studies unveil a new mechanism underlying the tight regulation of GM-CSF expression via a negative cross-talk between cAMP-PKA and MEK-ERK pathways and may shed light on developing new anti-inflammatory strategies.In the present study, we investigated the role and underlying

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].…”