Upregulation of cannabinoid receptor gene expression in oral tissues subjected to hyposalivation and periodontitis.

UNLABELLED: Cannabinoid receptors (CBr) 1 and 2 (CB1r and CB2r) are present in periodontal tissues and salivary glands and play a significant role in the pathogenesis of oral diseases.

AIM: To study the gene expression of CB1r and CB2r in gingival tissue and submandibular glands (SMG) of rats subjected to experimental periodontitis (EP) and/or hyposalivation (H), and discuss their possible implication in oral health.

MATERIAL AND

METHODS

Rats were divided into controls, rats with EP induced by application of lipopolysaccharide (1 mg/ml), rats with H induced by bilateral submandibulectomy, and rats with both EP and H. Alveolar bone loss was measured with a digital caliper, mRNA expression of CBr and bone parameters were determined by endpoint RT-PCR, PGE2 glandular content was assessed by radioimmunoassay, and stimulated salivary secretion was collected and weighed.

RESULTS

CB1r and CB2r mRNA in gingival tissue were upregulated in groups EP, H and EP+H as compared to controls (CB1r (AU): C 0.27±0.06A, EP 0.46±0.05B, H 0.51±0.08B, EP+H 0,49±0,1B; CB2r (AU): C 0.38±0.04A, EP 1.22±0.08B, H 0.98±0.06C, EP+H 1,041±0,1BC). Groups EP, H and EP+H showed alveolar bone loss as opposed to controls, while only groups EP and EP+H evidenced RANKL/OPG imbalance measured in the dental attachment tissue. Likewise, CB1r and CB2r mRNA in SMG showed upregulation in group EP as compared to controls (CB1r (AU): C 0.52±0.09A, EP 0.95±0.13B; CB2 (AU): C 0.23±0.12A, EP 1.48±0.22B). In group EP, salivary secretion was lower and the content of PGE2 (inhibitory mediator of said function) was higher than in controls.

CONCLUSION

The upregulation of CB2r in oral tissues under the pathophysiological conditions studied suggests that they participate actively in the response to oral diseases.