C-reactive protein expression is up-regulated in apical lesions of endodontic origin in association with interleukin-6.
BACKGROUND
C-reactive protein (CRP) is the prototype component of acute-phase proteins induced ultimately by interleukin (IL)-6 in the liver, but it is unknown whether periradicular tissues locally express CRP. The present study aimed to identify whether CRP messenger RNA synthesis occurs in situ within apical lesions of endodontic origin (ALEOs) and healthy periodontal ligament and its association with IL-6 and to determine their protein levels and tissue localization.


METHODS
Patients with asymptomatic apical periodontitis and healthy volunteers presenting at the School of Dentistry, University of Chile, Santiago, Chile, were enrolled. ALEOs and healthy teeth were obtained and processed for either immunohistochemistry and double immunofluorescence to assess IL-6 and CRP tissue localization, whereas healthy periodontal ligaments were processed as controls for real-time reverse-transcription polymerase chain reaction for their RNA expression levels and multiplex assay to determine their protein levels. Statistic analysis was performed using the unpaired t test or Mann-Whitney test according to data distribution and Pearson correlation.


RESULTS
IL-6 and CRP were synthesized in ALEOs, whereas their RNA expression and protein levels were significantly higher when compared with healthy periodontal ligament. IL-6 and CRP immunolocalized to the inflammatory cells, vascular endothelial cells, and mesenchymal cells. Both, IL-6 and CRP colocalized in ALEOs, and a positive correlation was found between their expression levels (P < .05).


CONCLUSIONS
IL-6 and CRP messenger RNA are constitutively expressed in periodontal ligament and up-regulated in ALEOs along with higher protein levels. Given their pleiotropic effects, IL-6 and CRP protein levels in apical tissues might partially explain the development and progression of ALEOs as well as potentially asymptomatic apical periodontitis-associated systemic low-grade inflammation.
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Mauricio
M
Garrido
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Andrea
A
Dezerega
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
María José
MJ
Bordagaray
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Montserrat
M
Reyes
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Rolando
R
Vernal
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Samantha
S
Melgar-Rodríguez
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Pía
P
Ciuchi
Escuela de Medicina Veterinaria, Facultad de Ecología y Recursos Naturales, Universidad Andrés Bello, Santiago, Chile.
Rodolfo
R
Paredes
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Jocelyn
J
García-Sesnich
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile.
Pablo
P
Ahumada-Montalva
Laboratorio de Biología Periodontal, Facultad de Odontología, Universidad de Chile, Santiago, Chile; Departmento de Patología, Facultad de Odontología, Universidad de Chile, Santiago, Chile. Electronic address: mhernandezrios@gmail.com.
Marcela
M
Hernández
D000293:Adolescent; D002097:C-Reactive Protein / Q000096:biosynthesis* / Q000235:genetics; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D008875:Middle Aged; D010518:Periodontitis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D015854:Up-Regulation
D015850:Interleukin-6; D012333:RNA, Messenger; D002097:C-Reactive Protein
Apical periodontitis; C-reactive protein; interleukin-6