Cannabinoid receptors in conjunctival epithelium: identification and functional properties.
OBJECTIVE
Preservation of the ocular surface barrier requires complex control of epithelial cell proliferation and inflammation mechanisms. The endocannabinoid system may be regulating these processes. Therefore, the authors explored the presence and properties of cannabinoid receptors (CB1 and CB2) in conjunctival epithelial cells.


METHODS
The authors used immunohistochemistry to detect CB1 and CB2 in normal mouse conjunctiva, human conjunctival cryosections and impression samples, and IOBA-NHC cells, a human conjunctiva-derived cell line. The presence of CB1 and CB2 proteins and transcripts was studied in IOBA-NHC cells by Western blot and RT-PCR, respectively. The authors also used this cell line to assay cannabinoid ligand-induced changes in cAMP levels, cell growth, and tumor necrosis factor-alpha (TNF-alpha)-induced activation of c-jun N-terminal kinase (JNK) and nuclear factor-kappaB (NF-kappaB).


RESULTS
Mouse and human conjunctival epithelial cells displayed CB1 and CB2 proteins and transcripts. Cannabinoid receptor activation decreased cAMP levels in IOBA-NHC cells, and specific CB1 and CB2 antagonists canceled this effect. Cannabinoid ligands also increased cell growth and blocked stress pathways activated by TNF-alpha in vitro.


CONCLUSIONS
Cannabinoid receptors are present in mouse and human conjunctival cells. Functional responses, such as decreased cAMP levels, proliferation, and modulation of stress signaling pathways, were mediated by CB1 and CB2 stimulation. Thus, these receptors might be involved in the regulation of epithelial renewal and inflammatory processes at the ocular surface.
Iribarne
María
M
Facultad de Ciencias Biomédicas, Universidad Austral, Pilar, Buenos Aires, Argentina.
Torbidoni
Vanesa
V
Julián
Karina
K
Prestifilippo
Juan P
JP
Sinha
Debasish
D
Rettori
Valeria
V
Berra
Alejandro
A
Suburo
Angela M
AM
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D003228:Conjunctiva / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007124:Immunoenzyme Techniques; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000235:genetics / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016328:NF-kappa B; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D014409:Tumor Necrosis Factor-alpha; D000242:Cyclic AMP; D048031:JNK Mitogen-Activated Protein Kinases