Topical Naltrexone Accelerates Full Thickness Wound Healing in Normal and Type 1 Diabetic Rats
Open Access
- Author:
- Pothering, Christian A.
- Graduate Program:
- Anatomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 03, 2009
- Committee Members:
- Dr Patricia Mc Laughlin, Thesis Advisor/Co-Advisor
Patricia Mclaughlin, Thesis Advisor/Co-Advisor - Keywords:
- Type 1 Diabetes
Full thickness wounds
Naltrexone - Abstract:
- Abstract Diabetes Mellitus affects almost 20 million people in the United States and 6% of the total world’s population. It results in a reduced life expectancy and an overall poor quality of life, requiring patients to be dependent on regular medication, supplements and altered diets. Full thickness wound healing presents a number of complications to diabetic patients. Often, due to neuropathy, a wound can go unnoticed increasing its severity and risk of infection. Moreover, even when wounds are found and treated, a slow rate of wound closure is observed further increasing the risk of higher severity and infection level. Treatments are typical for epithelial defects such as bandaging and antibiotic ointments but they leave out a key element to the wounding process in diabetes, increased levels of plasma [Met5]-enkephalin, or OGF. OGF interacts specifically with its receptor OGFr, which is a nuclear receptor, and together they act directly on DNA to tonically inhibit DNA synthesis and thus cell proliferation. To counteract this effect, naltrexone (NTX) serves as a long acting opioid antagonist and through high affinity binding with the OGFr it blocks the effect of OGF, increasing DNA synthesis and cell proliferation. NTX has been shown to be an effective treatment in re-epithelialization of the rat and rabbit cornea in vivo and human cornea in tissue culture. In the current study 10-5M NTX is shown to increase both DNA synthesis in the epithelium of normal and diabetic rats, and to increase wound closure rates in normal and diabetic rats. Initially a topical dose and a proper vehicle were selected. In order to test the doses and vehicles, Sprague-Dawley rats were rendered diabetic by Streptozotocin injections and maintained hyperglycemic for 5 weeks. Topical applications of 10-4M, 10-5M, and 10-6M NTX in Sorenson’s phosphate buffer, DMSO, Neutrogena moisturizing cream, and KY jelly were administered to unwounded skin of both normal and diabetic (glucose  350mg/dL) rats. Animals received BrdU injections and DNA synthesis was calculated in the basal layers of epithelium. In comparison to DNA labeling indexes in untreated rats, as well as though receiving only vehicles, dosages and vehicles were selected that significantly increased labeling indexes. Although all of the vehicles significantly increased cell proliferation at the basal layer of epithelium with at least one of the doses mentioned, moisturizing cream and KY jelly vehicles were shown to be the most effective at a concentration of 10-5M NTX in both normal and diabetic rats. In the second study, 6 mm full thickness wounds were surgically created on the dorsum of normal and diabetic rats. The wound were treated 3 times daily with topical applications of moisturizing cream, moisturizing cream + 10-5M NTX, KY jelly or KY jelly + 10-5M NTX beginning immediately after surgery and lasting until complete wound closure (no more than 13 days in any treatment group). Wounds were photographed and areal analyses conducted. Data revealed that in comparison to animals receiving only vehicle, wound closure of NTX treated animals was increased on day 3 in normal rats and significantly increased on days 3, 5, 7 and 9 in diabetic rats. On day 7 in diabetic rats wound closure was accelerated by more than 2 fold in topical moisturizing cream + 10-5M NTX when compared to topical moisturizing cream alone. By day 9, wound closure in diabetic rats was accelerated by more than 2.8 fold in topical KY jelly + 10-5M NTX when compared to topical KY jelly control. Additional studies demonstrated that the type of moisturizing cream had no significant effect on wound closure rate. No differences in wound closure rates were noted between Oil of Olay moisturizing cream and Neutrogena moisturizing cream on days 3, 5, 7 and 9 in normal animals and days 5, 7 and 9 in diabetic animals. The number of applications of moisturizing cream plus NTX was studied. There were no significant differences in rates of wound closure between diabetic animals receiving 1x daily or 2x daily application and 3x daily application at day 3, 5, 7 or 9. In normal animals there were no significant differences in rates of wound closure between diabetic animals receiving 1, 2, or 3 applications daily of NTX + moisturizing cream at days 3, 5 or 9. Along with being an effective treatment for increasing wound closure rates, NTX was also shown to be non-toxic. Gross observation of unwounded skin showed no redness or irritation. Animals display unusual behavior after receiving topical treatment. Topical applications of cream and NTX did not result in qualitative increases in redness, infection, discharge, or swelling of the wounded or surrounding areas. Histopathological studies supported that the processes of wound healing were similar between untreated rats and those receiving topical applications. Furthermore, apoptosis was not observed in the epidermis or dermis of skin sections from any treatment group. In conclusion, these studies demonstrate a new and novel treatment for wound healing that involves the disruption of biological processes invoked by the OGF-OGFr pathway.