Safety study of topical naltrexone therapy for diabetic skin wounds is confirmed in Göttingen mini-pigs.

This study was conducted to determine the safety of topical naltrexone treatment in Göttingen swine. Efficacy of topical naltrexone was performed previously in Sprague-Dawley rats. In this study, 25 male and female mini-pigs received topical naltrexone once daily for 30 days. The gel at doses of 1%, 2%, and 10% naltrexone was applied at a dose volume of 0.01 ml/cm2 to an area of unbroken skin encompassing 10% of the animal's surface. Body and food consumption, skin and organ morphology, and clinical signs, including blood analyses were taken periodically. Naltrexone levels in serum were measured at the time of death. No adverse observations were made in the cutaneous skin, autopsied organs, or biochemical parameters. The no-observed adverse effect level (NOAEL) was considered to be 2% topical application daily. The conclusions from the veterinarians and researchers are that topical naltrexone at 1% or 2% can be used safely in clinical efficacy studies.

Efficacy and safety of a novel naltrexone treatment for dry eye in type 1 diabetes.

BACKGROUND: Dry eye disease (DED) is a prevalent complication of diabetes and presents as reduced tear production and/or increased corneal surface sensitivity often with secondary ocular surface changes. This study examined the safety and efficacy of a proprietary new eye drop formulation for topical treatment of DED. METHODS: Type 1 diabetes (T1D) was established in male Sprague-Dawley rats to study the efficacy and safety of the investigational compound that contained 20 µg/ml of naltrexone (NTX). Tear production was measured by the Schirmer's 1 test, and ocular surface sensitivity was measured using an aesthesiometer. Diabetic rats received twice daily applications of a single drop (~ 0.02 ml) of the proprietary formulation (NTX-001) or vehicle onto one eye. For comparison, some diabetic rats received eye drops containing NTX in sterile Vigamox®. Safety was monitored by assessment of ocular histopathology in naïve male rats and naïve male rabbits receiving twice daily treatment of two drops for 30 days. RESULTS: Dry eye in T1D rats was reversed within hours of a single treatment of NTX-001, and over a period of 10 days NTX-001 restored corneal sensitivity and reversed dry eye relative to values measured in diabetic rats receiving vehicle. In comparison to NTX dissolved in Vigamox®, the proprietary NTX-001 was more effective at reversing dry eye. Safety studies in naïve rats and rabbits revealed no visible ocular pathology after 30 days of treatment. CONCLUSIONS: An investigational new eye drop containing 20 µg/ml NTX effectively reversed tear film deficits and restored corneal surface sensitivity in diabetic animals without causing toxic side effects.

Ocular surface abnormalities related to type 2 diabetes are reversed by the opioid antagonist naltrexone.

BACKGROUND: Ocular surface complications of type 2 diabetes are associated with reductions in tear production, increased corneal surface sensitivity, and delayed corneal re-epithelialization. This study examined the efficacy of topical application of the opioid antagonist naltrexone (NTX) in reversing these diabetic-related ocular surface complications in mice. METHODS: The genetic db/db mouse model of type 2 diabetes, along with C57Bl/6 wild-type mice were investigated. Tear production was assessed by phenol red impregnated threads, and ocular surface sensitivity was measured using Von Frey filaments. Centrally located, circular corneal abrasions were created in mice and residual epithelial defects measured by fluorescein photography. Animals in each group received topical applications of drops of 10(-5) M NTX in sterile Vigamox (Vigamox, Alcon Laboratories, Fort Worth, Texas, USA) or sterile Vigamox alone, and tear production, corneal sensitivity, and reepithelialization were monitored. RESULTS: In comparison to diabetic mice receiving vehicle only, db/db mice treated with one drop of NTX demonstrated a marked reversal in dry eye and ocular surface hypersensitivity within 1 h of one drop of NTX. Reversal of the complications in db/db mice usually lasted for 48-90 h. Corneal epithelial repair in db/db mice was enhanced following a regimen of three drops of NTX daily such that by 72 h, residual wounds were one third the size in db/db mice receiving NTX relative to diabetic mice receiving vehicle. Application of Vigamox alone had no effect. No adverse effects of NTX administration were noted in the cornea. CONCLUSIONS: This is the first report of the efficacy of topical NTX in reversing corneal surface complications in type 2 diabetic mice.

Elevated Opioid Growth Factor Alters the Limbus in Type 1 Diabetic Rats.

Ocular surface complications occur in more than 50% of individuals diagnosed with diabetes. The financial and health-related burden of diabetes is increasing annually. Several major ocular complications associated with diabetes involve the limbus. The vascular limbus, adjacent to the avascular cornea, is the source of circulating growth factors, elevated glucose, and cytokines for the cornea. The Opioid Growth Factor (OGF) - Opioid OGF Receptor (OGFr) axis is comprised of its effector peptide, OGF, [Met5]-enkephalin and the nuclear-associated receptor, OGFr, and has been demonstrated to be dysfunctional in diabetes with elevated serum and tissue levels of the inhibitory growth factor OGF recorded in corneal tissue. Little is known regarding the impact of OGF-OGFr axis dysregulation in diabetes on the functioning of the limbus constituents in support of corneal homeostasis. Adult male and female Sprague-Dawley rats were rendered hyperglycemic through intraperitoneal injections of streptozotocin (T1D); a subset of T1D rats received topical naltrexone (NTX) applied to the cornea and limbus daily for 8 weeks. At 4 and/or 8 weeks of hyperglycemia, different cohorts of animals were euthanized, eyes removed and processed for assessment of limbal morphology, expression of OGF, OGFr, cytokeratin 15, a marker for limbal cells, and Ki-67, a marker of proliferation. Limbal epithelial morphology (cell diameter, packing density) was altered in T1D male and female rats. OGF and OGFr were overexpressed in the limbus and CK15 expression was decreased, relative to normal control rats of the same sex. Blockade of the OGF- OGFr axis with NTX reversed limbal epithelial cell defects, and reduced OGF limbal tissue levels to those recorded in non-diabetic rats. In summary, OGF-OGFr axis dysregulation was observed in the limbus of T1D rats, contributing to the altered limbal morphology and delayed corneal surface healing observed in diabetic animals.

Sex Differences in Diabetic Ocular Surface Complications and Dysregulation of the OGF-OGFr Pathway.

Background: Diabetes is a chronic disorder that affects more than 500 million individuals worldwide. It is a life-long disease with complications that attack nearly all other systems within the body. Although there is a slight increase in the prevalence of diabetes in males, ocular surface complications are equally present in males and females. Aim: This review provides a discussion on preclinical studies related to the dysregulation of a biological pathway that appears to be causally related to diabetic ocular surface complications including dry eye, delayed corneal epithelial healing, and decreased corneal sensitivity. Most basic science and clinical studies focus on male sex in animal models in order to avoid confounders related to hormonal cycling. However, with approximately 10.2% of all women in the US aged 18-44 being diagnosed with diabetes and nearly 4% additional women having undiagnosed disease, it is prudent to examine the onset of these dysregulations also in females and to note any sex-related differences in the timing of onset or severity of ocular surface complications. Summary: Data from several well-controlled investigations have documented that female rats with type 1 diabetes develop ocular surface complications before male rats. In part, this finding may be due to the increase in the inhibitory peptide Opioid Growth Factor (OGF) that occurs within 2 weeks of the induction of hyperglycemia in female animals in comparison to the changes in OGF levels in male rats which occur at 4 weeks. It was noted that estrogen levels drop within weeks of induction of hyperglycemia and could serve as another marker for the onset of disease activity and/or its complications. Finally, insulin does not appear to protect against early changes in OGF levels or estrogen secretion in diabetic female rats, setting the stage for a distinction in the disease profile of diabetes between males and females. These data encourage further studies on both sexes in order to establish a complete understanding of the underlying pathologies associated with complications associated with diabetes.

Dysregulation of the OGF-OGFr pathway and associated diabetic complications.

BACKGROUND: Diabetes is a worldwide epidemic with more than 550 million individuals expected to be diagnosed with the disease by 2030. Complications associated with diabetes affect nearly all systems, but more than 54% of diabetic individuals have ocular surface disorders including keratopathy, dry eye or altered corneal surface sensitivity, and nearly 70% experience slow healing foot ulcers which if left untreated, can lead to amputation. There is new information regarding the underlying pathophysiology associated with these complications, as well as potential treatment. AIM: This commentary assembles data on preclinical studies showing that corneal surface complications such as dry eye and sensitivity, as well as delayed epithelial wound healing in the cornea and skin in diabetic rats and mice, correlate with a dysregulation of the opioid growth factor (OGF)-opioid growth factor receptor (OGFr) regulatory axis. The peptide in this pathway, OGF, chemically termed [Met5]-enkephalin, is elevated in the serum of humans and animals with either type 1 or type 2 diabetes. The cause for this finding is unknown. However, there are studies that demonstrate that blockade of the interactions between OGF (or elevated levels of OGF) and its receptor can reverse and, in some cases, prevent the onset of diabetic corneal complications. Clinicians and healthcare workers need to recognize this fundamental pathophysiology leading to diabetic complications. SUMMARY: Dysfunction of the OGF-OGFr growth regulatory system plays a role in the development of ocular surface complications and delayed cutaneous wound healing complications in multiple animal models of both Type 1 and Type 2 diabetes. Modulation of this system may hold promise for reversing or even preventing these diabetic complications in humans. Moreover, monitoring serum levels of OGF should be investigated as an indicator of the development of these and other diabetic complications.

Blockade of OGFr delays the onset and reduces the severity of diabetic ocular surface complications.

The opioid growth factor (OGF)-OGF receptor (OGFr) pathway is present in the ocular surface and functions to maintain homeostasis of the epithelium. The OGF-OGFr pathway has been reported to be dysregulated in diabetic individuals and animal models, and is reflected in elevations of the inhibitory growth factor, OGF, chemically termed [Met5]-enkephalin. Recently, our laboratory reported elevated levels of OGF and OGFr in the serum and corneal epithelium of type 1 diabetic rats, suggesting that dysregulation of the OGF-OGFr axis may lead to dry eye, abnormal corneal surface sensitivity, and delayed re-epithelialization. Blockade of OGF-OGFr pathway using naltrexone, a potent opioid receptor antagonist, reverses dry eye symptoms and restores corneal surface sensitivity in diabetic rats when used as a therapy. Based on the evidence that both OGF and OGFr are elevated in type 1 diabetic rats, this study examined whether systemic or topical naltrexone treatment initiated at the time of induction of hyperglycemia could protect against the development of diabetic ocular surface complications. Diabetic male Sprague-Dawley rats treated systemically or topically with naltrexone had a delayed onset of dry eye and altered corneal surface sensitivity, and an improved healing rate for corneal wounds, that were comparable to non-diabetic rats. Serum levels of OGF were normal for rats receiving systemic naltrexone, and OGF tissue levels were normal for type 1 diabetic rats receiving twice daily naltrexone drops. OGFr levels remained elevated. These data support the role of the OGF-OGFr axis in regulation of ocular surface complications, and suggest that naltrexone therapy may be beneficial for pre-diabetic and early diabetic individuals.

Ocular surface complications in diabetes: The interrelationship between insulin and enkephalin.

Diabetes is a multi-faceted disorder with increasing prevalence and rising healthcare costs. The burden of diabetes is increased because of associated complications affecting nearly all organs including the eye. The underlying pathophysiology for the onset of these ocular surface disorders is not well known. Enkephalins are endogenous opioids that originate in the brain and have numerous actions in the human body. Opioid growth factor (OGF), chemically termed [Met5]-enkephalin, binds to a novel, nuclear-associated receptor and mediates cellular homeostasis. Serum OGF levels are elevated in diabetic individuals and rodent models of diabetes. Sustained blockade of the OGF receptor (OGFr) with opioid receptor antagonists, such as naltrexone (NTX), reverses many complications of diabetes in the animal model, including delayed cutaneous wound healing, dry eye, altered corneal surface sensitivity, and keratopathy. The increased enkephalin levels observed in diabetes suggest a relationship between endogenous opioid peptides and the pathophysiology of diabetes. It is common for diabetic patients to undergo insulin therapy to restore normal blood glucose levels. However, this restoration does not alter OGF serum levels nor ameliorate ocular surface complications in the animal model of diabetes. Moreover, sex differences in the prevalence of diabetes, response to insulin therapy, and abnormalities in the OGF-OGFr axis have been reported. This review highlights current knowledge on the dysregulation of the OGF-OGFr pathway and possible relationships of insulin and enkephalins to the development of ocular surface defects in diabetes. It proposes that this dysregulation is a fundamental mechanism for the pathobiology of diabetic complications.

Ocular surface complications result from dysregulation of the OGF-OGFr signaling pathway in female diabetic rats.

Approximately 4.5 million women in the United States exhibit diabetes-associated ocular complications. The time course and magnitude of these complications, and their association with the dysregulation of the opioid growth factor (OGF)-OGF receptor (OGFr) signaling pathway are unknown. The present study investigated the onset and magnitude of ocular surface complications and the association with a dysregulated OGF-OGFr signaling pathway in diabetic female rats. Adult female Sprague-Dawley rats were injected with streptozotocin in order to establish a model of type 1 diabetes (T1D), and a subset received insulin (T1D-INS). Blood glucose, body weight, tear production and corneal sensitivity, as well as serum and tissue expression levels of OGF and OGFr, were assessed. Corneal epithelial wound healing was also evaluated. In a second study, female T1D rats were treated with topical naltrexone (NTX) to determine whether blockade of the OGF-OGFr signaling pathway by NTX altered development of corneal surface complications. Female T1D rats had elevated glucose levels and reduced body weight compared with control and T1D-INS rats. In both diabetic groups, tear production was decreased within 2 weeks and corneal sensitivity was decreased 2.5-fold within 5 weeks, while corneal epithelial wound healing was delayed only in T1D rats. Serum and tissue levels of OGF and OGFr were elevated in diabetes. Twice daily NTX treatment reversed most ocular surface complications in the diabetic female rats. The present data demonstrated a seminal discovery in female T1D rats, in which the onset and magnitude of diabetes-associated ocular surface complications were associated with dysregulation of the OGF-OGFr regulatory pathway. Blockade of the OGF-OGFr pathway with the opioid receptor antagonist NTX prevented the onset and/or decreased the magnitude of these deficits. The current data support the need for translational research on this therapeutic approach for diabetic human subjects.

Sex differences in the magnitude of diabetic ocular surface complications: Role of serum OGF.

Diabetes is associated with dysregulation of the Opioid Growth Factor (OGF) - OGF receptor (OGFr) regulatory pathway leading to elevated OGF levels in serum and tissues. This study was designed to investigate the role of sex on the magnitude of ocular surface complications by direct comparison of male and female type 1 diabetic (T1D) rats. Male and female adult Sprague-Dawley rats were rendered T1D; a cohort of T1D male and female rats received insulin (=T1D-INS). Tear production, corneal surface sensitivity, as well as serum levels of estrogen, testosterone, OGF and OGFr were measured. Multivariate analyses were performed for correlations between sex, condition and magnitude of ocular surface alterations. Significant differences were noted in all parameters tested between male and female Normal, T1D, and T1D-INS animals over the 8-week observation period. Multivariate analyses revealed that the magnitude of complications is greater in female T1D rats and has a strong negative correlation with serum estrogen and OGF. Ocular surface complications associated with T1D have an earlier onset and greater magnitude in female T1D rats than male diabetic animals, and are related to elevated levels of OGF.

Failure of radiation therapy in orbital xanthogranuloma.

PURPOSE: The efficacy of radiation therapy in orbital xanthogranuloma in patients who fail medical therapy is unclear. The purpose of this study was to ascertain its effectiveness. METHODS: The records of 11 cases were reviewed retrospectively for histopathologic findings, age, gender, site of involvement, clinical manifestations, and outcomes of treatment. The case histories of the 4 patients treated with radiation, all of whom had failed medical treatment, were described. RESULTS: Of 11 patients, 5 were female, and all were white. The age range at the time of presentation was 25 to 85 years. Nine patients had bilateral involvement. Five patients, all of whom had bilateral disease, had systemic manifestations or autoimmune disease thought to be related to their orbital disease. In general, patients treated with systemic corticosteroids had at least a partial response of their lesion. However, none of the 4 patients treated with orbital radiation (3 of whom had not responded to steroid treatment and 1 of whom had responded only to high-dose steroids) experienced improvement, and at least 3 experienced exacerbation of their disease. The histologic features before treatment in all cases were similar and consistent with xanthogranuloma. CONCLUSION: Orbital xanthogranuloma may be a unilateral or bilateral condition. Particularly when bilateral, it may be associated with similar lesions elsewhere or with systemic autoimmune disorders. The results of this study suggest that fractionated radiotherapy not only may be ineffective but also may exacerbate the progression of the orbital lesions in patients who do not respond to medical therapy or who are steroid dependent on intolerable doses of medication.

Naltrexone as a Novel Therapeutic for Diabetic Corneal Complications.

Diabetes is a widespread autoimmune disorder that affects nearly 10% of the adult population in the United States. In addition to the primary disease, there are numerous complications associated with inflammation including abnormalities of the heart, visual system, and peripheral nervous system. More than half of the individuals with diabetes will have one or more ocular related complications such as dry eye disease (DED), keratopathy, or retinopathy. Research over the last 3 decades has focused on the role of the opioid growth factor - opioid growth factor receptor (OGF-OGFr) axis as a regulatory system that maintains homeostasis in corneal epithelialization and tear secretion. In diabetes, OGF appears to be dysregulated resulting in decreased cell replication and increased corneal surface sensitivity. Utilization of naltrexone as a topical therapeutic to block the OGF-OGFr axis results in reversal of dry eye and restoration of corneal sensitivity and rates of corneal re-epithelialization. Naltrexone treatment at dosages that are substantially lower than systemically approved doses appear to be safe and effective therapy for corneal surface abnormalities associated with diabetes.

Dysregulation of the OGF-OGFr pathway correlates with elevated serum OGF and ocular surface complications in the diabetic rat.

IMPACT STATEMENT: This research extends our knowledge about the presence and role of the OGF-OGFr regulatory axis in type 1 diabetes (T1D) and demonstrates specific targets within the pathway that are dysregulated. Serum levels of OGF, an inhibitory growth factor, are significantly elevated in male T1D rats, and OGFr serum values are increased in T1D. The onset of elevated OGF corresponds to the onset of ocular surface complications including dry eye, delayed corneal epithelial repair, and abnormal corneal surface sensitivity in T1D. Systemic insulin does not protect against elevated OGF levels or the onset of dry eye and sensitivity. These data are the first to associate some ocular surface defects in T1D with alterations in the OGF-OGFr pathway.

Naltrexone and insulin are independently effective but not additive in accelerating corneal epithelial healing in type I diabetic rats.

Patients with diabetes are at increased risk for developing corneal disorders, termed diabetic keratopathy. Treatments for diabetic keratopathy are limited. Preclinical studies have demonstrated that topical administration of either naltrexone (NTX) or insulin (INS) accelerates corneal re-epithelialization in type I diabetic rats. This study determined whether the combination of NTX and INS would have additive effect(s) on the re-epithelialization of corneal abrasions in diabetic male Sprague-Dawley rats beyond either agent alone. Type 1 diabetes (DB) (glucose levels>400mg/dl) was induced with streptozotocin; glycemic levels were not controlled with INS. Eight weeks after induction of diabetes, a 5mm diameter circular abrasion was created in the center of the cornea in one eye of each rat. Eye drops (0.05ml) of INS [1U ( approximately 6nM)] and NTX (10(-5)M) in Vigamox were administered separately 4 times daily for 7 days (NTX/INS); DB control rats received drops of sterile vehicle (DB SV) 4 times daily. Two other groups of rats were given only NTX (DB NTX) or only INS (DB INS). Re-epithelialization was monitored by fluorescein staining, and images were recorded with a CCD camera. Areal measurements were made using Optimas software, and the percentage of epithelial defect over a 40h period was calculated. Twenty-four hour after formation of an abrasion ( approximately 21.7+/-0.4mm(2)area), corneal wounds in DB rats treated with NTX, INS, or NTX/INS were significantly smaller (p<0.001) than those in DB SV rats, with reductions in the size of the defect ranging from 24 to 84%. DB rats treated with NTX or INS alone also were observed to have reductions in wound size of 22 and 29%, respectively, from subjects in the DB SV group at 16h. At 16h both the DB NTX and DB INS groups had defects that were 13 and 27%, respectively, smaller than those for the DB NTX/INS group, and at 40h the DB INS animals had 78% smaller corneal wounds than in the DB NTX/INS group. Therefore, the DB NTX/INS group exhibited some slight delays in wound repair compared to the DB NTX and DB INS groups. Topical application of NTX and/or INS to the cornea had no effect on non-invasive measures that included ocular morphology, intraocular pressure, or corneal thickness. These data demonstrate that although NTX or INS accelerates wound healing, concomitant application of NTX and INS to corneal abrasions in diabetic animals does not have an additive effect on re-epithelialization.

Insulin treatment ameliorates impaired corneal reepithelialization in diabetic rats.

Patients with diabetes are at an increased risk for developing corneal disorders, often as a result of surgical and nonsurgical trauma. This study investigated whether intensive treatment of diabetes with the goal of maintaining blood glucose concentrations close to the normal range could ameliorate the delayed corneal wound healing found in animals with uncontrolled diabetes. Diabetes was induced with streptozotocin, and rats were divided into groups based on the degree of blood glucose control: 1) not treated with insulin implants (DB group), 2) receiving insulin implants and determined to be normoglycemic (DB-IN group), and 3) normal, nondiabetic animals serving as controls. Immediately before wounding at 9 or 11 weeks after the induction of the diabetic state, corneal thickness and corneal sensitivity of the DB and DB-IN groups were comparable with controls. DB, but not DB-IN, rats exhibited subnormal intraocular pressure. At 9 and 11 weeks after the onset of diabetes, the corneas of the right and left eyes, respectively, were abraded by mechanical scraping. The DB rats had residual corneal epithelial defects that ranged from 23% to 5.6-fold larger compared with the control group and a rate of healing that was 19% slower than control animals. The DB-IN group had healing characteristics similar to the control group. DNA synthesis in the peripheral cornea and conjunctiva, but not the limbus, of DB animals was reduced 50 and 91%, respectively, from control levels. Cell proliferation in the DB-IN group was comparable with the control group, with the exception of a 72% increase in the peripheral cornea in the DB-IN group. These results indicate that intensive therapy with insulin, which establishes normoglycemia in rats with diabetes, prevents the delay in wound healing of ocular surface epithelium observed in poorly controlled diabetic animals.

Use of topical insulin to normalize corneal epithelial healing in diabetes mellitus.

OBJECTIVE: To determine whether topical application of insulin normalizes delayed corneal wound healing in rats with diabetes mellitus (DB). METHODS: Diabetes mellitus was induced with streptozocin. A 5-mm corneal abrasion at 9 or 11 weeks was treated topically for 7 days (4 times daily) with 1, 2, or 5 U of insulin or with sterile vehicle (SV). RESULTS: Residual corneal epithelial defects of rats with DB receiving SV (hereafter called DB SV rats or animals) were approximately 35% larger than in healthy animals receiving SV (hereafter called healthy SV rats or animals). Rats with DB receiving topical insulin had wounds ranging from 19% to 60% smaller than DB SV rats, corresponding to wound sizes in healthy SV rats. Topical insulin had no effect on reepithelialization of corneal wounds in healthy SV rats. Insulin did not affect corneal thickness, ocular pressure, or serum glucose level. The corneal sensitivity of DB SV rats was markedly reduced from healthy SV rats, but rats with DB given insulin had corneal sensitivity values comparable to the healthy SV group. DNA synthesis was decreased in DB SV corneal epithelium but was comparable to that in healthy SV rats after they received insulin; apoptosis and necrosis levels were similar in all groups. CONCLUSION: Topical insulin normalizes corneal reepithelialization in diabetic rats. CLINICAL RELEVANCE: Direct application of insulin may serve as an important strategy for treating diabetic keratopathy.

Naltrexone accelerates healing without compromise of adhesion complexes in normal and diabetic corneal epithelium.

Naltrexone (NTX) is an opioid antagonist that accelerates wound healing of corneal epithelium in normal and diabetic animals. Junctional complexes (hemidesmosomes) are important in establishing adhesion of the corneal epithelium to the stroma. This study was designed to examine whether NTX, at a concentration that enhances corneal re-epithelialization, influences the appearance and number of hemidesmosomes in Normal, diabetic (DB) (hyperglycemic), and DB animals receiving insulin (DB-IN) (normoglycemic), and treated topically with NTX (10(-4) M) or sterile vehicle (SV) for 7 days following abrasion. Electron microscopic analysis of the peripheral cornea 2 weeks after removal of the epithelium indicated hemidesmosomes that could be classified into four sectional profiles. No differences were detected in either the structure or the number of junctional complexes in the cornea between Normal, DB, or DB-IN groups receiving vehicle or treated with NTX. Moreover, the fine structure of the basal and suprabasal layers of the corneal epithelium in all groups--including those treated with NTX--were comparable. These results indicate that topical application of NTX accelerates diabetic corneal epithelial healing without causing morphologic abnormalities in the reassembly of adhesion structures. Furthermore, controlled and uncontrolled diabetes for up to 3 months does not affect corneal adhesion complexes when compared to normal corneas. Thus, recurrent erosion following abrasion of the diabetic cornea, with preservation of the basal lamina, cannot be explained by structural abnormalities in the reformation of the epithelial adhesion complex.

Topically applied naltrexone restores corneal reepithelialization in diabetic rats.

PURPOSE: Complications of diabetes include an increased risk of delayed corneal epithelial wound healing. This study examined the efficacy of naltrexone (NTX), an opioid antagonist, by topical application in facilitating the repair of such lesions. METHODS: NTX, in concentrations of 10(-4), 10(-5), or 10(-6) M, was administered topically 4 times per day for 7 days to the abraded eye of type 1 diabetic rats (DB), DB animals receiving insulin and normoglycemic (DB-IN), and nondiabetic (Normal) rats, beginning 8 weeks following the onset of diabetes. RESULTS: In comparison to DB animals receiving sterile vehicle (SV), DB-NTX rats had 25%-83% smaller defects, a reduction of 24 h (approximately 33%) in closure time, and 20%-42% faster healing rates. DB rats receiving 10(-4) and 10(-5) M NTX were equal to, or surpassed, Normal animals in all parameters of wound closure. NTX also enhanced wound repair in DB-IN and Normal animals relative to their respective SV group. No adverse effects of NTX administration on a variety of noninvasive or invasive measures were discerned. CONCLUSIONS: Topically applied NTX is not only feasible, but also effective over a one hundredfold dosage for accelerating corneal wound healing in diabetic subjects.

Topical Naltrexone Is a Safe and Effective Alternative to Standard Treatment of Diabetic Wounds.

Objective: Diabetes affects more than 29 million individuals in the United States, resulting in healthcare costs approaching $245 billion. Approximately 15% of these individuals will develop a chronic, non-healing foot ulcer (diabetic foot ulcer [DFU]) that, if untreated, may lead to amputation. The current treatments for DFU are expensive, have significant side-effects, and often result in non-compliance. A new topical treatment is described that accelerates cutaneous wound repair and is disease modifying by targeting underlying aberrant diabetic pathways. Approach: The efficacy of naltrexone (NTX), an opioid receptor antagonist, and Regranex® was compared in preclinical studies using type 1 diabetic rats. Dorsal cutaneous wounds were treated topically with 0.03% NTX, Regranex, or moisturizing cream alone. Wound closure, DNA synthesis, and cytokine production were monitored. Results: Wound closure rates with topical NTX in type 1 diabetic rats were comparable to Regranex. Topical NTX accelerated DNA synthesis, as measured by BrdU incorporation, increased mast cells, and enhanced expression of platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), a marker for angiogenesis. Regranex had little effect on DNA synthesis, mast cells, and VEGF expression relative to vehicle-treated wounds, and it only temporarily increased PDGF expression. Fibroblast growth factor expression was not altered by either treatment. Innovation: Topical application of 0.03% NTX cream accelerates diabetic wound closure. Conclusion: Blockade of the opioid growth factor (OGF)-OGF receptor (OGFr) axis utilizing 0.03% NTX cream is comparable to standard care in preclinical studies, and it provides a safe, inexpensive, and effective alternative for treatment of diabetic wounds.

Regulation of corneal repair by particle-mediated gene transfer of opioid growth factor receptor complementary DNA.

OBJECTIVE: To determine whether molecular manipulation of the opioid growth factor receptor (OGFr) alters corneal reepithelialization following central corneal abrasion in rats. METHODS: The plasmid pcDNA3.1 + OGFr, carrying the rat OGFr complementary DNA in both the sense and antisense orientations, and empty vector (EV), were delivered by gene gun to the rat cornea. After 24 hours, corneas were abraded and reepithelialization was documented by fluorescein photography. Twenty-four hours after wounding, DNA synthesis (with bromodeoxyuridine) was examined. RESULTS: Eyes transfected with sense constructs of OGFr had corneal defects that were 24%, 52%, and 50% larger than the EV group at 16, 24, and 28 hours, respectively. Conversely, corneas transfected with antisense constructs of OGFr had corneal defects that were 56% and 48% smaller than the EV group at 16 and 24 hours, respectively. Bromodeoxyuridine labeling in the basal and suprabasal layers of the antisense group were increased 3.3- and 3.7-fold, respectively, in DNA synthesis from corresponding EV layers; DNA synthesis was comparable in the sense and EV groups. CONCLUSIONS: Excess OGFr delays reepithelialization, whereas attenuation of OGFr accelerates repair of the corneal surface. Clinical Relevance Inhibition of opioid growth factor action using gene therapy could be important in the treatment of corneal diseases such as nonhealing and recurrent erosions, diabetic keratopathy, and neurotrophic keratitis.