Hyaluronic acid prevents oxygen free-radical damage to granulation tissue: a study in rats

Oxygen free-radicals are known to impair wound healing after ischaemia-reperfusion or polymorphonuclear cell stimulation. Furthermore, they reduce the breaking strength of all recent wounds and might be a cause of wound leakage. This study was performed to evaluate whether or not hyaluronic acid can reduce the risk of wound impairment caused by free-radicals, in rats with abdominal sepsis, polymorphonuclear cell stimulation or cytochrome C function derangement produced by xenobiotics. Male Sprague-Dawley rats with open wounds received phenazine methosulfate or zimosan, or had abdominal sepsis to induce oxygen free-radical generation. There were three groups of treatment: hyaluronic acid cream, hyaluronic acid ethyl ester gel, and placebo. The reduction in wound size was measured from the 1st to the 11th postoperative day; biopsies were taken for histological evaluation. Every other day, a gentle debridement was performed in all the groups of animals. We found that hyaluronic acid and its ethyl ester derivative significantly improved the wound healing of rats subjected to an increased generation of oxygen free-radicals. It remains to be established whether or not hyaluronic acid acts as a scavenger of free-radicals.     

Low molecular weight hyaluronic acid prevents oxygen free radical damage to granulation tissue during wound healing

Hyaluronic acid protects granulation tissue from oxygen free radical damage and stimulates wound healing, but its molecular weight prevents it from permeating the epidermal barrier A low molecular weight hyaluronic acid preparation is able to permeate the skin, but it is unknown whether or not it retains the scavenging effects of oxygen free radicals in granulation tissue. Our experiments were conducted in rats with excisional or incisional wounds. Wound contraction over 11 days and breaking strength on the fifth day were measured. Oxygen free radical production was induced by intraperitoneal administration of two different xenobiotics: phenazine methosulfate and zymosan. The wounds were treated topically with low molecular weight hyaluronic acid (0.2%) cream or placebo. In the incisional wound group, the effects of superoxide dismutase were also determined. Absolute controls received wounds and placebo but no xenobiotics. Wound healing was significantly slower in the xenobiotic group than in the control groups. These effects were strongly reduced by topical administration of low molecular weight hyaluronic acid (0.2%) cream and in incisional wounds by topically injected superoxide dismutase. Low molecular weight hyaluronic acid is effective as the native compound against oxygen free radicals. Its pharmacological effects through transdermal administration should be tested in appropriate models.     

TGF-beta 1 accelerates wound healing: reversal of steroid-impaired healing in rats and rabbits.

TGF-beta modulates events of normal wound healing through multiple pathways that influence cell infiltration, proliferation, angiogenesis, extracellular matrix synthesis and remodeling. The effects of topically applied TGF-beta 1 on wound healing in two models of healing were evaluated when the healing response was impaired by the administration of methylprednisolone to rats or rabbits. TGF-beta 1 increased the healing of linear incision wounds on rats, as measured by breaking strength, to that of normal rats. Full thickness open wounds were also created on the inner ears of rabbits to simulate a non-contracting wound with limited blood supply. Healing was further impaired by the administration of methylprednisolone. The single application of TGF-beta 1 improved the healing of open wounds. TGF-beta 1 stimulated increased granulation tissue formation, as well as reepithelialization. The amount of granulation tissue and epithelialization were similar to wounds from normal-healing control rabbits. The delayed healing caused by methylprednisolone permitted the evaluation of multiple applications of TGF-beta 1 to wounds. Two applications of TGF-beta 1 spaced 7 days apart further improved the healing response when compared to a single application. Thus, single or multiple topical applications of TGF-beta 1 reversed impaired healing conditions secondary to methylprednisolone when used on incisional or open wounds. These observations support the hypothesis that growth factors, such as TGF-beta 1, may be useful as accelerators of wound repair in patients with impaired healing conditions.     

Effect of cimetidine on wound healing in rats

Cimetidine, an H-2 antagonist, is one of the most commonly prescribed drugs and is used in the management of peptic ulcer disease and prevention of stress ulcerations following major trauma or operations. It has been shown that histamine has a stimulatory effect on wound healing which is believed to be mediated through H-2 receptors. We hypothesized that cimetidine would have an inhibitory effect on wound healing. Fifty-two adult rats were divided into two groups: Group A was placed on a standard chow and Group B was given chow supplemented with cimetidine (300 mg/Kg diet), a dose equivalent to that clinically used in man and effective in inhibiting gastric hypersecretion in the rat. Ten days later, all rats underwent a dorsal skin incision under pentobarbital anesthesia and implantation of a polyvinyl alcohol sponge subcutaneously. Animals were maintained on their respective diets. Rats were killed with ether five and ten days postoperatively, the wounds were excised and breaking strength measured. Sponge hydroxyproline content was measured. No significant difference in breaking strength or sponge hydroxyproline content was found between the two groups. We thus conclude that cimetidine has no effect on wound healing in rats when used in doses equivalent to the clinical dose in man.Supported in part by Army Medical Research and Development Command Contract DADA-17-82-C-2091 to the Albert Einstein College of Medicine, and the Department of Surgery Research Fund.     

The role of mast cells in wound healing

Mast cells are known to participate in three phases of wound healing: the inflammatory reaction, angiogenesis and extracellular-matrix reabsorption. The inflammatory reaction is mediated by released histamine and arachidonic acid metabolites. Compound 48/80 and disodium-cromoglycate are both able to increase skin breaking strength shortly after wounding. Under light and electron microscopy we found that small, granule-poor, irregular mast cells (MLMC) accumulate in the wound. This suggests that the small MLMC (mucosal-like mast cells) migrate into the skin during wound healing, and that both CTMC (connective-tissue mast cells) and MLMC are involved in tissue repair. Moreover, there is some evidence that mast cells participate in angiogenesis, since heparin is able to stimulate endothelial-cell migration and proliferation in vitro, and protamine to inhibit these processes and also angiogenesis in vivo. When the effect of protamine on wound breaking strength was examined, we encountered a decrease which was not prevented by heparin administration. Further studies are needed to demonstrate that protamine is specifically involved in inhibiting heparin-mediated angiogenesis in wounded tissue. Finally, mast cells may play a role in the extracellular matrix remodelling, on the basis of in-vitro experiments (but there are still no in-vivo data).     

Glucose oxidase incorporated collagen matrices for dermal wound repair in diabetic rat models: a biochemical study

Impaired wound healing in diabetes is a well-documented phenomenon. Emerging data favor the involvement of free radicals in the pathogenesis of diabetic wound healing. We investigated the beneficial role of the sustained release of reactive oxygen species (ROS) in diabetic dermal wound healing. In order to achieve the sustained delivery of ROS in the wound bed, we have incorporated glucose oxidase in the collagen matrix (GOIC), which is applied to the healing diabetic wound. Our in vitro proteolysis studies on incorporated GOIC show increased stability against the proteases in the collagen matrix. In this study, GOIC film and collagen film (CF) are used as dressing material on the wound of streptozotocin-induced diabetic rats. A significant increase in ROS (p?相似文献   

Free radical-induced contractile protein dysfunction in endotoxin-induced sepsis

Recent studies have indicated that sepsis is associated with enhanced generation of several free-radical species (nitric oxide [NO], superoxide, hydrogen peroxide) in skeletal muscle. It is also known that this enhanced free-radical generation results in reductions in skeletal muscle force-generating capacity, but the precise mechanism(s) by which free radicals exert this effect in sepsis has not been determined. We postulated that free radicals might react directly with the contractile proteins in this condition, altering contractile protein force-generating capacity. To test this theory, we compared the force generation of single Triton-skinned diaphragmatic fibers (Triton skinning exposes the contractile apparatus, permitting direct assessment of contractile protein function) from the following groups of rats: (1) control animals; (2) endotoxin-treated animal; (3) animals given endotoxin plus polyethylene glycol- superoxide dismutase (PEG-SOD), a superoxide scavenger; (4) animals given endotoxin plus N(omega)-nitro-L-arginine methylester (L-NAME), a NO synthase inhibitor; (5 ) animals given only PEG-SOD or L-NAME; and (6 ) animals given endotoxin plus denatured PEG-SOD. We found that endotoxin administration produced both a reduction in the maximum force-generating capacity (Fmax) (i.e., a decrease in Fmax) of muscle fibers and a reduction in fiber calcium sensitivity (i.e., an increase in the Ca2+ concentration required to produce half-maximal activation [Ca50]). L-NAME and PEG-SOD administration preserved Fmax and Ca50 in endotoxin-treated animals; neither drug affected these parameters in non-endotoxin treated animals. Denatured PEG-SOD failed to inhibit endotoxin-related alterations in contractile protein function. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of skinned fibers from endotoxin-treated animals revealed a selective depletion of several proteins; administration of L-NAME or PEG-SOD to endotoxin-treated animals prevented this protein depletion, paralleling the effect of these two agents to prevent a reduction in contractile protein force-generating capacity. These data indicate that free radicals (superoxide, NO, or daughter species of these radicals) play a central role in altering skeletal muscle contractile protein force-generating capacity in endotoxin-induced sepsis.     

Reduction in endotoxin-induced organ dysfunction and cytokine secretion by a cyclic nitrone antioxidant

Multiple organ dysfunction (MOD) is the leading cause of mortality in septic patients with circulatory shock. Recent evidence suggests that the overproduction of the cytokine, tumor necrosis factor-α (TNF), and oxygen free radical molecules may mediate the progression of sepsis to MOD and death. In this study, we have examined the ability of MDL 101,002, a free radical scavenger, to reduce organ dysfunction and cytokine secretion induced by lipopolysaccharide (LPS) administration in rats. Treatment with MDL 101,002 (10–60 mg/kg, i.p.) 30 min prior to an LPS challenge resulted in a dose-dependent reduction in several markers indicative of organ dysfunction and mortality. MDL 101,002 markedly decreased LPS-induced liver and kidney damage as indicated by serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) or urea and creatinine, respectively. MDL 101,002 also prevented LPS-induced pulmonary edema, but did not prevent leukopenia and only partially reduced thrombocytopenia. Associated with these improvements in organ dysfunction and survival was a modest decrease in LPS-stimulated interleukin-1α (IL-1α) and interleukin-1β (IL-1β) secretion and a marked (>90%) inhibition of TNF secretion by MDL 101,002. The data are consistent with a role for oxygen free radicals in the development of endotoxin-induced organ dysfunction and shock and suggest that free radical scavengers could reduce the mortality consequent to sepsis by decreasing organ dysfunction, at least in part, through a reduction in free radical stimulated cytokine secretion.     

Effect of allopurinol on damage caused by free radicals to cryptorchid testes

Cryptorchidism causes apoptosis of germ cells. It has been suggested that the redox regulatory system is involved in this process. The free radicals produced are thought to be generated during the production of uric acid, a reaction catalyzed by xanthine oxidase. This enzyme is inhibited by allopurinol; however, the role of allopurinol in neonate rats with inguinal cryptorchidism has not been assessed yet. Sixty male Wistar rats were used and five groups were formed: a control, a sham, a sham group with allopurinol administration and two groups with surgical unilateral cryptorchidism, which either did not receive, or received, allopurinol. The rats were assessed at 40 days post-partum. Reactive oxygen species concentration and epithelial area were measured and the histopathological, apoptotic and cellular proliferation indexes were determined. We found a decrease in reactive oxygen species, histopathological and apoptotic indexes and an increase in proliferation index and epithelial area in rats with cryptorchidism treated with allopurinol in comparison with rats with untreated cryptorchidism. We suggest that the over-production of reactive oxygen species plays an important role in the damage of the cryptorchid testes. Allopurinol administration decreases reactive oxygen species concentrations as well as the damage to the germ epithelium.     

Dermal wound healing processes with curcumin incorporated collagen films

The wound healing process involves extensive oxidative stress to the system, which generally inhibits tissue remodeling. In the present study, an improvement in the quality of wound healing was attempted by slow delivery of antioxidants like curcumin from collagen, which also acts as a supportive matrix for the regenerative tissue. Curcumin incorporated collagen matrix (CICM) treated groups were compared with control and collagen treated rats. Biochemical parameters and histological analysis revealed that increased wound reduction, enhanced cell proliferation and efficient free radical scavenging in CICM group. The higher shrinkage temperature of CICM films suggests increased hydrothermal stability when compared to normal collagen films. Spectroscopic studies revealed that curcumin was bound to the collagen without affecting its triple helicity. Further we adopted the antioxidant assay using 2,2'-azobisisobutyronitrile to assess in vitro antioxidant activity of CICM. The antioxidant studies indicated that CICM quenches free radicals more efficiently. This study provides a rationale for the topical application of CICM as a feasible and productive approach to support dermal wound healing.     

Wound healing in tenascin-X deficient mice suggests that tenascin-X is involved in matrix maturation rather than matrix deposition

Tenascin-X (TNX) is an extracellular matrix glycoprotein whose absence in humans leads to a recessive form of Ehlers-Danlos Syndrome (EDS). TNX deficient patients have hypermobile joints and fragile skin, but unlike the classical type of EDS, no atrophic scars were observed. Anecdotal evidence suggested that wound healing in TNX deficient patients is abnormal, but no detailed study has been performed so far. To address the role of TNX in wound healing, we analyzed skin wound morphology and mechanical properties of scars in TNX knockout (KO) mice. Breaking strength of unwounded skin of KO mice is significantly lower (<50%) than that of wild-type (WT) mice. In the early stage of wound healing when TNX is hardly expressed in WT wounds (day 7), WT and KO skin are of similar strength. After 14 days, when TNX starts to be expressed at moderate levels in wounds of WT mice, the WT scars gain a further increase in breaking strength, whereas KO scars do not progress beyond the mechanical strength of uninjured KO skin. No obvious differences between KO and WT mice were noted in the rate of wound closure, or in expression of fibrillar collagens during wound healing. We conclude that TNX is unlikely to be involved in matrix deposition in the early phase of wound healing, but it is required in the later phase when remodeling and maturation of the matrix establishes and improves its biomechanical properties.     

A novel role for erythropoietin during fibrin-induced wound-healing response

In this study, we investigated the role of the hematopoietic cytokine erythropoietin (EPO) during wound healing, the physiological response to tissue injury. We used an in vivo wound-healing assay (fibrin Z-chambers) consisting of fibrin-filled chambers implanted subcutaneously in rats. The fibrin inside the chambers is replaced by granulation tissue consisting of new blood vessels, macrophages and fibroblasts as part of the wound-healing response. Local, exogenous recombinant EPO administration into the fibrin matrix significantly increased granulation tissue formation in a dose-dependent manner. To investigate the physiological role of endogenous EPO during wound healing, we used soluble EPO receptor or anti-EPO monoclonal antibodies to neutralize EPO and observed dose-dependent inhibition of granulation tissue formation, consistent with an important role for EPO in the wound-healing cascade. The ability of recombinant EPO to promote wound healing was associated with a proangiogenic effect during granulation tissue formation. We also found abundant expression of EPO receptor protein in macrophages, cells that play a pivotal role during wound healing. Modulation of wound healing because of administration of recombinant EPO or inhibition of endogenous EPO-EPO receptor correlated with changes in levels of inducible nitric oxide synthase protein in granulation tissue. These data demonstrate a novel function for EPO by providing in vivo evidence for a physiological role during fibrin-induced wound healing.     

Healing of skin incision wounds treated with topically applied BAPN free base in the rat

β-Aminopropionitrile as free base (BAPN) was applied onto the incised or intact skin of rats at the dose of 5, 20, 100, and 200 μl for 9 days, twice daily. Breaking strength of the skin wound or intact skin was significantly reduced at doses of 20 μl and higher; body weight growth was significantly retarded at the two highest dosages. It is concluded that at a given dose (20 μl) collagen polymerization (evaluated by reduced breaking strength and increased extractability of collagen) was specifically inhibited by BAPN. Furthermore, no evidence of topical or general toxic effects were observed, as reflected in histology, body weight growth, and behavior of the rats. Acute LD₅₀ of BAPN base and fumarate, administered either ip or topically, was determined in mice. While BAPN base in ip administration shows LD₅₀ of 1.15 g/kg, in cutaneous application it is more than 12.8 g/kg. It is suggested that topically applied BAPN base is percutaneously absorbed and affects collagen polymerization in the skin and adjacent tissues.     

Effect of prostaglandins and superoxide dismutase administration on oxygen free radical production in experimental acute pancreatitis

Oxygen free radicals and prostaglandins are implicated in the pathophysiology of acute pancreatitis, although their mechanisms of action remain unclear. We have studied the effect of administration of exogenous 16, 16-dimethyl prostaglandin E₂ and superoxide dismutase on oxygen free radical production in acute pancreatitis. For this purpose, five experimental rat groups were studied: group I, control; group II, sodium taurocholate-induced acute pancreatitis; group III, same as group II but with previous administration of 16, 16-dimethyl prostaglandin E₂; group IV, same as group II but with previous administration of indomethacin; and group V, same as group II but with previous administration of superoxide dismutase. In sodium taurocholate-treated rats, xanthine dehydrogenase is completely converted to xanthine oxidase within the first 5 min with subsequent oxygen free radical production while in 16,16-dimethyl prostaglandin E₂-treated rats this enzyme transformation does not occur. In the superoxide dismutase-treated group xanthine oxidase activation is partially prevented. These data suggest that xanthine oxidase is the main source of oxygen free radicals, which contribute to extending the cellular damage in sodium taurocholate-induced acute pancreatitis.     

Reactive oxygen metabolites and anti-oxidative defenses in aspirin-induced gastric damage in rats: Gastroprotection by Vitamin E

OBJECTIVE: It has been proposed that neutrophil infiltration and oxygen radicals may be the important prime events that lead to mucosal injury induced by aspirin. Vitamin E acts as a potent antioxidant, and is capable of scavenging free radicals. The aim of this study was to evaluate the oxygen metabolites and anti-oxidative defenses in acute gastric damage induced by aspirin and to find the effects of Vitamin E. METHODS: Ninety-six Wistar rats were divided into four groups of 24 rats each as follows: (1) the control group; (2) the ASA group that received 300mg/kg of ASA; (3) the Vitamin E plus ASA group and (4) the Vitamin E group that received Vitamin E (75 units) alone. At 3, 6, 9 and 24h after the drug administration, six rats were randomly selected from each group and gastric mucosal injury, prostaglandin E2, and the activities of myeloperoxidase, xanthine-oxidase, superoxide dismutase, glutathione peroxidase as well as glutathione level were measured and compared between the groups. RESULTS: Oral administration of ASA caused acute gastric erosions and an increase in myeloperoxidase activity. It also decreased prostaglandin E2, superoxide dismutase activity, glutathione peroxidase activity and glutathione level. Concomitant administration of Vitamin E and ASA restored all the changes toward the control levels. CONCLUSION: Free radicals and suppression of anti-oxidizing enzymes play important roles in gastric damage induced by aspirin. Increased myeloperoxidase activity suggests that activated neutrophils may be a major source of free radicals. Vitamin E protects against ASA-induced damage due to its anti-oxidizing activity.     

Effects of meloxicam on oxygen radical generation in rat gastric mucosa

AIM AND DESIGN: In addition to a deficiency of endogenous prostaglandins due to inhibition of cyclo-oxygenase and a host of prostaglandin-mediated effects on mucosal protection, it has recently been proposed that neutrophil- and oxygen radical - dependent microvascular injuries may be important prime events that lead to mucosal injury induced by non-steroidal anti-inflammatory drugs. Therefore, we evaluated the role of oxygen free radicals in the pathogenesis of acute gastric ulceration induced by meloxicam, a preferential COX-2 inhibitor. MATERIAL: Studies were performed in Wistar rats. Treatment: Meloxicam was given by oral administration (3.75-30 mg/kg body weight). METHODS: Determinations were made of gastric mucosal injury, xanthine-oxidase, myeloperoxidase and superoxide dismutase activities, as well as the effect of meloxicam on gastric prostaglandin synthesis (PGE2 levels) and glutathione homeostasis. RESULTS: Oral administration of meloxicam dose-dependently (3.75-30 mg/kg) caused acute gastric haemorrhage erosions. The total area of gastric lesions increased with time until 24 hours after dosing. Xanthine-oxidase activity increased significantly after administration of the drug. Myeloperoxidase activity, as an index of neutrophil infiltration, as well as glutathione peroxidase, an important enzyme that scavenges lipid peroxides, were unaffected by meloxicam administration. In addition, superoxide dismutase activity, PGE2 and glutathione levels were significantly reduced. CONCLUSION: These results support the hypothesis that in addition to suppression of prostaglandin synthesis, oxygen free radicals, probably derived via the action of xanthine oxidase, the decrease in superoxide dismutase activity, and the depletion of mucosal glutathione contribute to the pathogenesis of meloxicam-induced ulceration.     

Effect of vitamin E administration on response to ischaemia-reperfusion of hearts from cold-exposed rats

In both 3,5,3-triiodothyronine (T(3))-induced hyperthyroidism and cold-induced functional hyperthyroidism, the heart displays an increased susceptibility to oxidative challenge in vitro. Hearts from T(3)-treated rats also exhibit an increased susceptibility to ischaemia-reperfusion, a condition that raises free radical production. The present study was designed to establish whether cold-exposed rats exhibit an increased cardiac susceptibility to ischaemia-reperfusion which can be attenuated by vitamin E. The following four groups of animals were used: C, control rats (n = 8, temperature 24°C); C+VE, vitamin E-treated rats (n = 8, temperature 24°C); CE, cold-exposed rats (n = 8, temperature 4°C); and CE+VE, cold-exposed vitamin E-treated rats (n = 8, temperature 4°C). Langendorff preparations from these animals were submitted to 20 min ischaemia followed by 25 min reperfusion. At the end of the ischaemia-reperfusion protocol, homogenates and mitochondria were prepared and used for analytical procedures. With respect to control hearts, cold hearts showed a lower inotropic recovery and a higher oxidative stress, as inferred by higher levels of oxidized proteins and lipids and lower reduced glutathione levels. These changes were prevented when cold rats were treated with vitamin E. Evidence was also obtained that mitochondria are involved in the tissue derangement of cold hearts. Indeed, they display a faster production of reactive oxygen species, which causes mitochondrial oxidative damage and functional decline that parallel the tissue dysfunction. Moreover, vitamin E-linked improvement of tissue function was associated with a lower oxidative damage and a restored function of mitochondria. Finally, the mitochondrial population composition and Ca(2+)-induced swelling data indicate that the decline in mitochondrial function is in part due to a decrease in the amount of the highly functional heavy mitochondria linked to their higher susceptibility to oxidative damage and swelling. In conclusion, our work shows that vitamin E treatment attenuates harmful side-effects of the cardiac response to cold, such as oxidative damage and susceptibility to oxidants, thus preserving mitochondrial function and tissue recovery from ischaemia-reperfusion.     

Increased chemiluminescence of polymorphonuclear leucocytes in dogs with volume overload heart failure

Polymorphonuclear leucocyte (PMN) stimulation is known to generate oxygen free radicals. Exogenous oxygen free radicals, generated by xanthine and xanthine oxidase, have been implicated in the decrease of cardiac contractility. It is possible that PMN have increased capacity to release oxygen free radicals in failing heart. It was, therefore, decided to investigate PMN chemiluminescence (oxygen free radicals) from blood in dogs with heart failure due to chronic volume overload. The dogs were divided into two groups: (A) normal, six dogs; (B) dogs with mitral insufficiency (MI) of 6-9 months' duration, six dogs. Haemodynamic parameters were recorded to assess cardiac failure. Mixed venous blood was collected to measure PMN chemiluminescence. Stimulation of PMN was initiated by addition of opsonized zymosan and chemiluminescence was monitored using a luminometer. The haemodynamic parameters in dogs with MI showed that these dogs had left ventricular failure. The peak chemiluminescent activity of PMN in blood of dogs with left ventricular failure was approximately four times that in the blood from normal dogs. This increase in chemiluminescence reflects an increase in the generation of oxygen free radicals from PMN in dogs with chronic heart failure. The decrease in the myocardial contractility in cardiac failure might be due to an increase in the oxygen free radicals produced by the PMN.     

Phenytoin inhibition: failure to inhibit periosteal responses to lathyrogen

beta-Aminopropionitrile (BAPN) administered to rats has caused exostosis formation at sites of muscle attachment and also caused delay in the healing of soft tissue wounds and of bone fractures. Since phenytoin sodium has an opposite effect on wound healing, bone fractures, and the tensile strength of connective tissues, an experiment was performed to determine whether or not BAPN could produce periosteal exostoses in the presence of phenytoin. Rats that were given both BAPN and phenytoin produced similar exostoses as rats that were given BAPN alone. This indicates that phenytoin does not prevent inhibition of lysyl oxidase by BAPN, does not promote increased tensile strength of connective tissues in the presence of BAPN, and does not facilitate the detoxification of BAPN. Further, no evidence for an increased cellular response with phenytoin was observed. The mechanism by which phenytoin promotes wound healing is still unknown.