Cannabinoid receptor 1 (CB1R) expression in rat dental pulp

Reference gene validation for the relative quantification of cannabinoid receptor expression in human odontoblasts via quantitative polymerase chain reaction

Objective

The aim of this study was to identify and validate the reference genes in cultured human odontoblasts to quantify their cannabinoid receptor transcripts.

Methods

The most stably transcribed genes in cultured human odontoblast cells were identified using the RefGenes tool and were selected for real-time polymerase chain reaction (PCR) amplification. Human odontoblast cells were differentiated from mesenchymal stem cells using a transforming growth factor-β-supplemented differentiation medium, and total RNA was purified. Reverse transcription-quantitative PCR and relative quantification analyses were performed using the Schefe's method. The relative expression dataset was analyzed to select the most stable genes.

Results

The analysis showed that the transcripts of cholinergic receptor nicotinic beta 2 subunit, LIM homeobox transcription factor 1 beta, and family with sequence similarity 223 member B presented the lowest standard deviation (SD) in expression (SD: 0.2, 0.17, and 0.16, respectively). These genes showed similar expression levels as the target genes (cannabinoid receptors). Significant differences were found in the relative expression levels of cannabinoid receptors using the selected genes compared to those calculated using beta actin transcripts as references (p < 0.05).

Conclusions

The strategy reported here for searching and verifying new reference genes will aid in the accurate and reliable expression of cannabinoid receptors in human odontoblast cells.

Immune challenges upregulate the expression of cannabinoid receptors in cultured human odontoblasts and gingival fibroblasts

Odontoblasts and gingival fibroblasts play essential roles in the physiological and pathological processes of dental tissue. Cannabinoid receptors (CB1 and CB2) are involved in analgesia by modulating the función of calcium channels that inhibit the synthesis of some neurotransmitters. A better understanding of the physiology of these receptors would provide the possibility of using them as therapeutic targets in controlling dental pain. The aim of this study was to evaluate the presence and activity of cannabinoid receptors in human odontoblast-like cells (OLC) and human gingival fibroblasts (HGF). CB1 and CB2 transcription was analyzed by real-time PCR, proteins were detected by immunofluorescence, and functional cannabinoid receptors were evaluated by measuring intracellular calcium concentration after stimulation with cannabidiol (CBD) and pre-treatment with a CB1 antagonist, a CB2 inverse agonist and a TRPV1 antagonist. Transcripts for CB1 and CB2 were found in both odontoblasts and gingival fibroblasts. Cannabidiol induced an increase in [Ca2+]i in both cells types, but surprisingly, pre-treatment with selective cannabinoid antagonists attenuated this effect, suggesting a functional communication between specific cannabinoid receptors and other CBD target receptors. In conclusion, human odontoblasts and gingival fibroblasts express functional CB1 and CB2 cannabinoid receptors, which could be modulated to improve the treatment of pain or dental sensitivity.

Expression of Cannabinoid Type 1 Receptors in Human Odontoblast Cells

INTRODUCTION

The aim of this study was to investigate the functional expression of cannabinoid type 1 (CB1) receptors in human odontoblasts (HODs) and the possible internal mechanism.

METHODS

In the present study, we examined the molecular and functional expression of the CB1 receptors in cultured HOD-like cells and native HODs obtained from healthy wisdom teeth.

RESULTS

Immunohistochemistry and immunofluorescence revealed that CB1 receptors localize to native HODs and HOD-like cells, respectively. Both reverse-transcription polymerase chain reaction and Western blot analysis confirmed gene and protein expression of CB1 receptors. The ultrastructural distribution by immunoelectron microscopy also found that CB1 receptors labeled by colloidal gold particles distribute sparsely in the cytoplasm and odontoblastic processes. In functional assays, 2-arachidonyl glycerol, as an agonist of CB receptors, elicited the increase of intracellular fluorescence intensity that could be inhibited by a CB1-specific receptor antagonist rather than a selective CB2 receptor antagonist with fluo-3AM Ca²⁺ fluorescence. The source of the increase of intracellular fluorescence intensity elicited by CB1 receptors was from extracellular Ca²⁺ but not intracellular Ca²⁺ stores. The process of 2-arachidonyl glycerol activating CB1 receptors modulated transient receptor potential vanilloid 1-mediated Ca²⁺ entry via the cyclic adenosine monophosphate signaling pathway.

CONCLUSIONS

We conclude that HODs can express functional CB1 receptors that may play an important role in mediating the physiological function in tooth pulp.