Naltrexone accelerated oral traumatic ulcer healing and downregulated TLR-4/NF-kB pathway in Wistar rats

Objective

To assess the effect of naltrexone on oral mucosal healing using a traumatic ulcer model

Design

Wistar rats (n = 112) received distilled water (control) or naltrexone (0.5, 10, or 50 mg/kg/day). Ulcers were induced on the buccal mucosa using a round skin biopsy punch (diameter 6 mm). Euthanasia was performed on days 1, 3, 7, and 14. Healing was assessed by ulcer area, histological scores, histomorphometric analysis (number of polymorphonuclears, mononuclears, and fibroblasts), and collagen percentage. Immunohistochemistry for TLR-2, TLR-4, NF-kB, and CD31 was evaluated. Nociceptive threshold was measured daily.

Results

The 50 mg/kg group showed reduced ulcer area on days 1 (p < 0.001), 3 (p < 0.05), and 14 (p < 0.01). In this group, there was, on day 14, an increase in the percentage of reepithelization (p = 0.043) and collagen (p < 0.05), an increase in connective tissue maturation (p = 0.016), and on day 7 an increase in fibroblasts (p < 0.001). The 10 mg/kg dose reduced the ulcer area on day 1 (p < 0.001). The 50 mg/kg group showed lower expression of TLR-4 (p < 0.001) on day 1, NF-kB on days 1 (p < 0.05) and 14 (p < 0.05), and CD31 on day 14 (p < 0.05). The 0.5 and 10 mg/kg doses reduced TLR-4 expression on day 1 (p < 0.05; p < 0.01, respectively). Nociceptive threshold increased in the 50 mg/kg group (p < 0.01).

Conclusion

Naltrexone enhanced traumatic oral ulcer healing by reducing TLR-4/NF-kB signaling and promoting fibroblast proliferation and collagen deposition. Additionally, naltrexone reduced pain in rats.