Differential expression of cytokine genes and iNOS induced by nonviable nontypeable Haemophilus influenzae or its LOS mutants during acute otitis media in the rat.
OBJECTIVE
We have previously demonstrated that the disruptions of nontypeable Haemophilus influenzae (NTHi) lipooligosaccharide (LOS) htrB and rfaD genes may play a role in the pathogenesis of otitis media (OM). The purpose of this study was to determine whether NTHi LOS gene disruptions influence the induction of gene expression for proinflammatory mediators in vivo using the rat model of acute OM.


METHODS
At 3, 6, 12, 24, 48 and 72 h after transbullar inoculation with nonviable NTHi, expression of genes for the cytokines and chemolines; tumor necrosis factor alpha (TNF-alpha), interleukin-lbeta (IL-1beta), and IL-6, IL-1alpha, IL-8, IL-10, and inducible nitric oxide synthase (iNOS) were quantitated by real-time PCR. Enzyme-linked immunosorbent assay was performed to confirm the gene expression data as determined by real-time PCR. The middle ear inflammatory responses were also evaluated.


RESULTS
The NTHi 2019 parent and its isogenic LOS htrB (B29) and rfaD (DK-1) mutant strains induced a significant up-regulation in gene expression for the cytokines examined compared to the sham-inoculated controls at 3, 6 and 12 h post-inoculation (P<0.05 in all cases). However, the NTHi 2019 cohort demonstrated a significant increase in gene expression for TNF-alpha (up to 6 h), IL-1alpha and IL-8 (up to 24 h), IL-1beta and IL-6 (up to 48 h), and IL-10 and iNOS (up to 72 h) relative to the animals inoculated with NTHi B29 (P<0.05, in all cases), Moreover, the concentrations of inflammatory cells in the middle ear lavage fluid samples from the NTHi 2019 cohort were 2.8-5.3-fold higher than those of the B29 cohort. There were no significant differences in mRNA expression of the cytokines between the NTHi 2019 and the DK-1-treated groups.


CONCLUSIONS
Data from this study indicate that the disruption of the NTHi htrB gene may impact the temporal mRNA expression of inflammatory mediators and inflammation within the middle ear.
Department of Otolaryngology, College of Medicine and Public health, The Ohio State University, Room 4024B, Cramblett Hall, 456 West 10th Avenue, Columbus, OH 43210, USA. tong.1@osu.edu
Hua Hua
HH
Tong
Yiping
Y
Chen
Xia
X
Liu
Thomas F
TF
DeMaria
D000208:Acute Disease; D000818:Animals; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics*; D004195:Disease Models, Animal; D015870:Gene Expression; D006192:Haemophilus Infections / Q000235:genetics*; D006193:Haemophilus influenzae / Q000235:genetics*; D008070:Lipopolysaccharides / Q000235:genetics*; D008297:Male; D009154:Mutation; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000235:genetics*; D010033:Otitis Media / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley
D016207:Cytokines; D008070:Lipopolysaccharides; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II