Epidermal Growth Factor Receptor Transactivation by the Cannabinoid Receptor (CB1) and Transient Receptor Potential Vanilloid 1 (TRPV1) Induces Differential Responses in Corneal Epithelial Cells
ARMY AEROMEDICAL RESEARCH LAB FORT RUCKER AL
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Corneal epithelial injury induces release of endogenous metabolites that are cannabinoid receptor 1 CB1 and transient receptor potential vanilloid 1 TRPV1 agonists. We determined the functional contributions by CB1 and TRPV1 activation to eliciting responses underlying wound healing in human corneal epithelial cells HCEC. Both the selective CB1 and TRPV1 agonists i.e., WIN55,212-2 WIN and capsaicin CAP, respectively induced EGFR phosphorylation whereas either inhibition of its tyrosine kinase activity with AG1478 or functional blockage eliminated this response. Furthermore, EGFR transactivation was abolished by inhibitors of proteolytic release of heparin bound EGF HB-EGF. CB1- induced Ca2 transients were reduced during exposure to either the CB1 antagonist, AM251 or AG1478. Both CAP and WIN induced transient increases in Erk12, p38, JNK12 MAPK and AktPI-3K phosphorylation status resulting in cell proliferation and migration increases which mirrored those elicited by EGF. Neither EGF nor WIN induced any increases in IL-6 and IL-8 release. On the other hand, CAP-induced 3- and 6-fold increases, which were fully attenuated during exposure to CPZ, but AG1478 only suppressed them by 21. The mixed CB1 and TRPV1 antagonist, AM251, enhanced the CAP-induced rise in IL-8 release to a higher level than that elicited by CAP alone. In conclusion, CB1 and TRPV1 activation induces increases in HCEC proliferation and migration through EGFR transactivation leading to global MAPK and AktPI-3K pathway stimulation. On the other hand, the TRPV1-mediated increases in IL-6 and IL-8 release are elicited through both EGFR dependent and EGFR-independent signaling pathways.
- Anatomy and Physiology
- Medicine and Medical Research