Cytokine expression in response to root canal infection in gnotobiotic mice.
OBJECTIVE
To examine cytokine expression profiles during periapical lesion development in response to synergetic human pathogens in a gnotobiotic mouse model.


METHODS
Human strains of Fusobacterium nucleatum and Peptostreptococcus prevotii were inoculated into the root canals of germ-free mice in either mono- or bi-association. Animals were killed 7 and 14 days after infection, and periapical tissues were collected. mRNA expression of the cytokines IFN-γ, TNF-α, Receptor activator of nuclear factor kappa-B ligand (RANKL), IL-10, IL-4 and transforming growth factor β (TGF-β) was assessed using real-time PCR. Levene's test was used to assess the equality of variance of the data, whereas a t-test for independent samples was used to evaluate the significance of the differences between groups (P < 0.05).


RESULTS
The mRNA expression of IFN-γ and TNF-α was up-regulated by F. nucleatum during the acute (day 7) and chronic phase (day 14) of periapical lesion development. However, in bi-infection the expression of IFN-γ and TNF-α were effectively absent at both time-points. RANKL mRNA expression was down-regulated during dual infection at the chronic phase. As IL-4 expression was similar at both time-points, IL-4 does not appear to be involved in the periapical response to these bacterial strains. IL-10 was up-regulated during the chronic phase by mono-infection with either F. nucleatum or P. prevotii. Dual infection increased TGF-β mRNA expression on day 7, which paralleled the decrease in IFN-γ and TNF-α mRNA levels at the same time-point. F. nucleatum increased TGF-β mRNA expression during the chronic phase.


CONCLUSIONS
Cytokine profiles depend on the nature of the bacterial challenge. Both TGF-β and IL-10 appeared to be regulating the proinflammatory cytokine responses at both time-points of the periapical immune response.
Departamento de Odontologia Restauradora, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
K F
KF
Maciel
L C
LC
Neves de Brito
W L F
WL
Tavares
G
G
Moreira
J R
JR
Nicoli
L Q
LQ
Vieira
A P
AP
Ribeiro Sobrinho
D000818:Animals; D060085:Coinfection / Q000276:immunology; D016207:Cytokines / Q000032:analysis*; D003788:Dental Pulp Diseases / Q000276:immunology / Q000382:microbiology*; D005674:Fusobacterium Infections / Q000276:immunology*; D016967:Fusobacterium nucleatum / Q000276:immunology*; D005856:Germ-Free Life; D016908:Gram-Positive Bacterial Infections / Q000276:immunology*; D006801:Humans; D018836:Inflammation Mediators / Q000032:analysis; D007371:Interferon-gamma / Q000032:analysis; D016753:Interleukin-10 / Q000032:analysis; D015847:Interleukin-4 / Q000032:analysis; D051379:Mice; D010462:Peptostreptococcus / Q000276:immunology*; D010483:Periapical Diseases / Q000276:immunology / Q000382:microbiology*; D053245:RANK Ligand / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000032:analysis; D015854:Up-Regulation / Q000276:immunology
D016207:Cytokines; D018836:Inflammation Mediators; D053245:RANK Ligand; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma