Dexamethasone Promotes The Regeneration Of Inferior Alveolar Nerve Crush Through Inhibiting The Activation Of NF-?B(P65) In Adult Rats

Objective:The aim of this study is to investigate the effects of dexamethasone(Dex),an inhibitor of NF-?B(P65),on inferior alveolar nerve injury in adult rats.Methods:The crushed inferior alveolar model is established in Wistar rats and they are randomly divided into three groups according to treatment:PDTC(pyrrolidinedithiocarbamate),Dex(dexamethasone),and saline(physiological saline).After treatment,the rats are respectively sacrificed at 3,7,and 14 d,and inferior alveolar nerves are extracted for histochemical and western blot analysis.Results:HE staining shows that the saline group exhibited the most serious vacuole degeneration and broken fibers;Schwann cells were distinguished by their oval or rounded nuclei,and axons were disrupted in some of the nerve fibers.The PDTC and Dex groups had less vacuole,more arranged fibers,and more complete axons at 7d post-crush.Compared with 7d,nerve tissues obtained better regeneration at 14 d in all groups.Results shows a decreased number of tissue vacuoles,with more regularly arranged nerve fibers,in the Dex group compared with other groups at 14 d.Tissues in the Dex group were most similar to naive(non-crush)tissues.Immunohistochemical results showed that nerve cells in all groups exhibited larger nuclei,and NF-?B(P65)expression was visible at 7d.At 7 and 14 d post-crush,nuclear expression of NF-?B(P65)decreased in the Dex group compared with the PDTC and saline group.Compared with 14 d post-injury IANs,p65 expression was greater in the 7 d post-injury LANs in all three groups.Results shows representative western blots of NF-?B(P65)and GAP-43 expression in crushed nerves samples after 3,7,and 14 d.In the saline group,NF-?B(P65)expression gradually increased at 3,7,and 14 d post-injury,although expression significantly decreased following treatment with PDTC and Dex.In the Dex group,NF-?B(P65)was less expressed and GAP-43 was significantly higher expressedthan other groups at 3,7,and 14 d post-crush.In particular,GAP-43 expression in the Dex group was present at 3 d;meanwhile there was no GAP-43 expression at 3 d in the other groups.Conclusion:Results from this study show that dexamethasone and PDTC can efficiently promote IAN regeneration after crush injury.Similar to PDTC,dexamethasone can inhibit NF-?B(P65)expression and promote IAN restoration;however,these results suggest that dexamethasone provides a more effective and stable inhibition against NF?B(P65).Dexamethasone can be a promising treatment of IAN regeneration by inhibiting NF-?B(P65)expression.