Effects of multifunctional antioxidants on mitochondrial dysfunction and amyloid-ß metal dyshomeostasis.

BACKGROUND: Redox-active metal dyshomeostasis and oxidative stress are associated with mitochondrial dysfunction and amyloid-ß (Aß) neurotoxicity that are linked to both the development of age-related macular degeneration (AMD) and Alzheimer's disease (AD). As potential therapeutic agents, orally active multifunctional antioxidants (MFAOs) possessing two independent functional groups capable of binding redox-active metals and scavenging free radicals have been synthesized. OBJECTIVE: To determine whether MFAOs affect mitochondrial function and reduce the presence of Aß plaque formation. METHODS: The MFAOs were evaluated in cultured SH-SY5Y cells and ARPE-19 cells. MFAO effects on mitochondrial function were investigated using rhodamine 123 staining after 2 hour exposure to MnCl2. MFAO effects on Aß:Zn complex formation were evaluated with Zinquin staining and the ability of the Aß:Zn complex to be degraded by matrix metalloproteinase-2 (MMP-2). The ability of MFAOs to reduce Aß plaque in the brain was determined by orally feeding MFAO for one year to B6;129-Psen1tm1Mpm Tg(AßPPSwe,tauP301L) 1Lfa/Mmjax transgenic mice. Aß levels were determined by ELISA. RESULTS: MFAOs neither adversely affected mitochondrial signaling nor labile cytoplasmic zinc levels. MFAOs protected cells against Mn2+-induced mitochondrial dysfunction. MFAOs also removed zinc from the Aß:Zn complex so that Aß plaque could be degraded by MMP-2. Zinquin staining indicated that the removed zinc was present in the cytoplasm as labile zinc. Orally administered MFAOs reduced the brain levels of both Aß40 and Aß42 isoforms of Aß. CONCLUSION: These studies demonstrate that these MFAOs have metal attenuating properties with therapeutic potential in the treatment of both AMD and AD.

Diagnosing nephrogenic systemic fibrosis in the post-FDA restriction era.

The emergence of an association between gadolinium-based contrast agents (GBCA) and the rare condition nephrogenic systemic fibrosis (NSF) led to a warning in 2006 from the Food and Drug Administration (FDA) restricting the use of the GBCAs to patients with an estimated glomerular filtration rate of >30 mL/min/1.73m(2) . We discuss our experience with a post-FDA restriction presentation of NSF and subsequent patient death in which the prolonged lead-time of ∼5.5 years led to challenges in ensuring a secure diagnosis of NSF and establishing risk exposures. Accurate contemporary records of contrast administration and clinical factors alongside clinical and pathological expertise ensured that we were able to confidently diagnose NSF, despite the length of lead time and confounding factors.

Topical nutraceutical Optixcare EH ameliorates experimental ocular oxidative stress in rats.

PURPOSE: Based on the hypothesis that oral nutraceuticals do not adequately reach all ocular tissues in the anterior segment, we evaluated the ability of a 3% concentration of the ingredients in a topical nutraceutical antioxidant formulation called Optixcare Eye Health (Optixcare EH) to ameliorate oxidative stress in rat models of age-related ocular diseases. METHODS: Diabetes was induced by tail-vein injection of streptozotocin, and the development of cataracts was monitored by slit lamp. Young rats were exposed to ultraviolet (UV) light, and the reduction in lens glutathione (GSH) levels and increase in 4-hydroxynonenol (4-HNE) were measured. Oxidative stress in the neural retina was generated by exposure of dark-adapted rats to 1,000 lx of light, and oxidative stress markers were measured. Dry eye was induced in rats by twice daily (b.i.d.) subcutaneous scopolamine injections. Topical Optixcare EH was administered b.i.d. and compared in select experiments to the multifunctional antioxidant JHX-4, the topical aldose reductase inhibitor (ARI) Kinostat™, oral Ocu-GLO™, and the topical ocular comfort agents Optixcare Eye Lube, Optixcare Eye Lube + Hyaluron, and Idrop Vet Plus hyaluronic acid. RESULTS: In diabetic rats, topical ARI treatment prevented cataract formation while the nutraceuticals delayed their development with Optixcare EH>Ocu-GLO. In UV-exposed rats, the reduction of GSH and increase in 4-HNE in the lens were normalized in order JHX-4>Optixcare EH>Ocu-GLO. In the retina, oxidative stress markers were reduced better by oral JHX-4 compared with topical Optixcare EH. In the scopolamine-induced dry-eye rats, tear flow was maintained by Optixcare EH treatment, while none of the comfort agents examined altered tear flow. CONCLUSIONS: Topical administration of a 3% concentration of the ingredients in Optixcare EH reduces experimentally induced reactive oxygen species in rats exposed to several sources of ocular oxidative stress. In addition, Optixcare EH maintains tear volume in scopolamine-induced dry eye. This suggests that in the anterior segment, the ingredients in Optixcare EH may have clinical potential against ocular oxidative stress.

Novel transgenic mouse models develop retinal changes associated with early diabetic retinopathy similar to those observed in rats with diabetes mellitus.

Retinal capillary pericyte degeneration has been linked to aldose reductase (AR) activity in diabetic retinopathy (DR). Since the development of DR in mice and rats has been reported to differ and that this may be linked to differences in retinal sorbitol levels, we have established new murine models of early onset diabetes mellitus as tools for investigating the role of AR in DR. Transgenic diabetic mouse models were developed by crossbreeding diabetic C57BL/6-Ins2(Akita)/J (AK) with transgenic C57BL mice expressing green fluorescent protein (GFP), human aldose reductase (hAR) or both in vascular tissues containing smooth muscle actin-α (SMAA). Changes in retinal sorbitol levels were determined by HPLC while changes of growth factors and signaling were investigated by Western Blots. Retinal vascular changes were quantitatively analyzed on elastase-digestion flat mounts. Results show that sorbitol levels were higher in neural retinas of diabetic AK-SMAA-GFP-hAR compared to AK-SMAA-GFP mice. AK-SMAA-GFP-hAR mice showed induction of the retinal growth factors VEGF, IGF-1, bFGF and TGFß, as well as signaling changes in P-Akt, P-SAPK/JNK, and P-44/42 MAPK. Increased loss of nuclei per capillary length and a significant increase in the percentage of acellular capillaries presented in 18 week old AK-SMAA-GFP-hAR mice. These changes are similar to those observed in streptozotocin-induced diabetic rats. Retinal changes in both mice and rats were prevented by inhibition of AR. These studies confirm that the increased expression of AR in mice results in the development of retinal changes associated with the early stages of DR that are similar to those observed in rats.

Novel diabetic mouse models as tools for investigating diabetic retinopathy.

OBJECTIVE: Mouse models possessing green fluorescent protein (GFP) and/or human aldose reductase (hAR) in vascular tissues have been established and crossed with naturally diabetic Akita mice to produce new diabetic mouse models. RESEARCH DESIGN AND METHODS: Colonies of transgenic C57BL mice expressing GFP (SMAA-GFP), hAR (SMAA-hAR) or both (SMAA-GFP-hAR) in vascular tissues expressing smooth muscle actin were established and crossbred with C57BL/6-Ins2(Akita)/J (AK) mice to produce naturally diabetic offspring AK-SMAA-GFP and AK-SMAA-GFP-hAR. Aldose reductase inhibitor AL1576 (ARI) was administered in chow. Retinal and lenticular sorbitol levels were determined by HPLC. Retinal functions were evaluated by electroretinography (ERGs). Growth factor and signaling changes were determined by Western Blots using commercially available antibodies. Retinal vasculatures were isolated from the neural retina by enzymatic digestion. Flat mounts were stained with PAS-hematoxylin and analyzed. RESULTS: Akita transgenics developed DM by 8 weeks of age with blood glucose levels higher in males than females. Sorbitol levels were higher in neural retinas of AK-SMAA-GFP-hAR compared to AK-SMAA-GFP mice. AK-SMAA-GFP-hAR mice also had higher VEGF levels and reduced ERG scotopic b-wave function, both of which were normalized by AL1576. AK-SMAA-GFP-hAR mice showed induction of the retinal growth factors bFGF, IGF-1, and TGFß, as well as signaling changes in P-Akt, P-SAPK/JNK and P-44/42 MAPK that were also reduced by ARI treatment. Quantitative analysis of flat mounts in 18 week AK-SMAA-GFP-hAR mice revealed increased loss of nuclei/capillary length and a significant increase in the percentage of acellular capillaries present which was not seen in AK-SMAA-GFP-hAR treated with ARI. CONCLUSIONS/SIGNIFICANCE: These new mouse models of early onset diabetes may be valuable tools for assessing both the role of hyperglycemia and AR in the development of retinal lesions associated with diabetic retinopathy.

Osmotic stress, not aldose reductase activity, directly induces growth factors and MAPK signaling changes during sugar cataract formation.

In sugar cataract formation in rats, aldose reductase (AR) activity is not only linked to lenticular sorbitol (diabetic) or galactitol (galactosemic) formation but also to signal transduction changes, cytotoxic signals and activation of apoptosis. Using both in vitro and in vivo techniques, the interrelationship between AR activity, polyol (sorbitol and galactitol) formation, osmotic stress, growth factor induction, and cell signaling changes have been investigated. For in vitro studies, lenses from Sprague Dawley rats were cultured for up to 48 h in TC-199-bicarbonate media containing either 30 mM fructose (control), or 30 mM glucose or galactose with/without the aldose reductase inhibitors AL1576 or tolrestat, the sorbitol dehydrogenase inhibitor (SDI) CP-470,711, or 15 mM mannitol (osmotic-compensated media). For in vivo studies, lenses were obtained from streptozotocin-induced diabetic Sprague Dawley rats fed diet with/without the ARIs AL1576 or tolrestat for 10 weeks. As expected, lenses cultured in high glucose/galactose media or from untreated diabetic rats all showed a decrease in the GSH pool that was lessened by ARI treatment. Lenses either from diabetic rats or from glucose/galactose culture conditions showed increased expression of basic-FGF, TGF-ß, and increased signaling through P-Akt, P-ERK1/2 and P-SAPK/JNK which were also normalized by ARIs to the expression levels observed in non-diabetic controls. Culturing rat lenses in osmotically compensated media containing 30 mM glucose or galactose did not lead to increased growth factor expression or altered signaling. These studies indicate that it is the biophysical response of the lens to osmotic stress that results in an increased intralenticular production of basic-FGF and TGF-ß and the altered cytotoxic signaling that is observed during sugar cataract formation.

Orally active multi-functional antioxidants delay cataract formation in streptozotocin (type 1) diabetic and gamma-irradiated rats.

BACKGROUND: Age-related cataract is a worldwide health care problem whose progression has been linked to oxidative stress and the accumulation of redox-active metals. Since there is no specific animal model for human age-related cataract, multiple animal models must be used to evaluate potential therapies that may delay and/or prevent cataract formation. METHODS/PRINCIPAL FINDINGS: Proof of concept studies were conducted to evaluate 4-(5-hydroxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 4) and 4-(5-hydroxy-4,6-dimethoxypyrimidin-2-yl)-N,N-dimethyl-3,5-dioxopiperazine-1-sulfonamide (compound 8), multi-functional antioxidants that can independently chelate redox metals and quench free radicals, on their ability to delay the progression of diabetic "sugar" cataracts and gamma radiation-induced cataracts. Prior to 15 Gy of whole head irradiation, select groups of Long Evans rats received either diet containing compound 4 or 8, or a single i.p. injection of panthethine, a radioprotective agent. Compared to untreated, irradiated rats, treatment with pantethine, 4 and 8 delayed initial lens changes by 4, 47, and 38 days, respectively, and the average formation of posterior subcapsular opacities by 23, 53 and 58 days, respectively. In the second study, select groups of diabetic Sprague Dawley rats were administered chow containing compounds 4, 8 or the aldose reductase inhibitor AL1576. As anticipated, treatment with AL1576 prevented cataract by inhibiting sorbitol formation in the lens. However, compared to untreated rats, compounds 4 and 8 delayed vacuole formation by 20 days and 12 days, respectively, and cortical cataract formation by 8 and 3 days, respectively, without reducing lenticular sorbitol. Using in vitro lens culture in 30 mM xylose to model diabetic "sugar" cataract formation, western blots confirmed that multi-functional antioxidants reduced endoplasmic reticulum stress. CONCLUSIONS/SIGNIFICANCE: Multi-functional antioxidants delayed cataract formation in two diverse rat models. These studies provide a proof of concept that a general cataract treatment focused on reducing oxidative stress instead of a specific mechanism of cataractogenesis can be developed.

Efficacy of structurally diverse aldose reductase inhibitors on experimental periodontitis in rats.

BACKGROUND: To study aldose reductase and the sorbitol pathway in periodontitis and diabetes, rats with experimental periodontitis with or without diabetes were treated with three structurally diverse aldose reductase inhibitors (ARIs). METHODS: Periodontitis was induced with three consecutive palatal injections of Porphyromonas gingivalis lipopolysaccharide (LPS) at 48-hour intervals between the first and second molars on the right side in young, age-matched, streptozotocin-induced rats with and without diabetes 44 days after initiation of diets with and without the ARIs tolrestat, imirestat, and quercetin. As an internal control, phosphate-buffered saline (PBS) was similarly injected on the left side. Twenty-four days after the final injection, all rats were euthanized. Defleshed samples were stained with 5% toluidine blue and palatal digital images were traced to include the enamel crown and exposed root. The root/enamel ratios (to estimate alveolar bone loss) were analyzed with repeated measures analysis of variance. RESULTS: LPS injections resulted in significantly more bone loss versus PBS injections in both the rats with and without diabetes on normal diets (P <0.0001). All three ARIs significantly reduced LPS-induced periodontitis in the animals with and without diabetes (P ≤0.003) to the level where they were not different from PBS-injected sites in normal diet controls. CONCLUSION: All ARIs demonstrated efficacy in preventing alveolar bone loss because of periodontitis in both animals with and without diabetes, suggesting a role for the sorbitol pathway and the potential for ARIs to reduce inflammatory responses downstream from aldose reductase.

Effect of an aldose reductase inhibitor on alveolar bone loss associated with periodontitis in diabetic rats.

Periodontitis is a lesser known but frequent complication of diabetes mellitus and is the major cause of tooth loss in patients with diabetes. Dental therapy for this complication is primarily focused on the control of oral infections. No current therapy directly addresses the potential effects of diabetes itself on this complication. In studies conducted in young normal control and streptozotocin diabetic rats (100 g) treated with and without the aldose reductase inhibitor (ARI) imirestat, experimental periodontitis was induced in one side of the mouth by 3 injections of lipopolysaccharide (LPS) from Escherichia coli 055:B5 9 into the palatal gingiva between the first and second maxillary molars at 48-hour intervals. The other control side was injected with phosphate buffered saline (PBS). Fourteen days after the final injection, all rats were euthanized and the heads were defleshed. The maxillary area was separated from the remaining skull. The cleaned maxillary alveoli were stained in 5% aqueous toluidine blue to identify the cemento-enamel junction (CEJ) on the molars. Alveolar bone loss was measured according to standard methods by determining both the distance between the CEJ and the alveolar bone on the 2 molars between which the injections were made, and by measuring the ratio of root area/enamel area in the same region. These measurements showed that LPS injections resulted in significant bone loss compared with PBS injections in both control and diabetic rats, and that this bone loss was not present in the ARI-treated diabetic rats (P < 0.05). These results suggest that the sorbitol pathway plays a critical role in the pathophysiological mechanism(s) of diabetic periodontitis and that AR may be a direct pharmacological target for the treatment for this disease.

Polyol formation in cell lines of rat retinal capillary pericytes and endothelial cells (TR-rPCT and TR-iBRB).

PURPOSE: The two most widely investigated animal models for diabetic retinopathy (DR) are the rat and dog. In dogs, aldose reductase (AR) is present only in retinal capillary pericytes and their destruction has been linked to polyol accumulation and resulting apoptosis. Since both rat capillary pericytes and endothelial cells have been reported to contain AR, the role of polyol pathway activity in capillary cell destruction has been investigated in rat retinal capillary pericyte (TR-rPCT) and endothelial (TR-iBRB) cells. METHODS: TR-rPCT and TR-iBRB cell lines were recloned and their identities were reconfirmed by characteristic immunostaining. Cells were cultured up to 72 h in media containing 50 mM glucose or galactose with/without the AR inhibitors or a sorbitol dehydrogenase inhibitor (SDI) or with 30 mM 3-fluoro-3-deoxyglucose. Polyol levels were determined by HPLC or (19)F-NMR. Apoptosis was detected with TUNEL/DAPI staining. RESULTS: Smooth muscle actin is present only in pericytes while only endothelial cells stain for von Willebrand factor and accumulate acetylated low-density lipoprotein. AR is present in both cells but AR levels are lower in endothelial cells. Aldehyde reductase is also present in both cells. Cells cultured in 50 mM glucose or galactose show significant polyol accumulation in pericytes but endothelial cells show little accumulation of galactitol and no accumulation of sorbitol. Sorbitol accumulation in pericytes resulted in increased cellular permeability and increased TUNEL staining, which was reduced by AR inhibition. CONCLUSIONS: Although both rat retinal pericytes and endothelial cells contain AR, sorbitol accumulation and TUNEL staining primarily occur in pericytes and are inhibited by AR inhibitors.

Topical aldose reductase inhibitor formulations for effective lens drug delivery in a rat model for sugar cataracts.

PURPOSE: In the topical delivery of drugs to the lens, drug retention on the eye surface is considered to be important because increased retention on the ocular surface should lead to increased ocular absorption of a drug through the cornea into the aqueous humor and subsequently the lens. The aim of this study was to investigate whether increasing the viscosity of a topical aldose reductase inhibitor suspension increases the lenticular bioavailability of the inhibitor and whether such a formulation can arrest sugar cataract formation. METHODS: Five topical suspensions of 3% 2-methylsorbinil (2-MS) were prepared using (1) hydroxypropyl methylcellulose (HPMC, 0.5% w/v), (2) xanthan gum (0.5% w/v), (3) gellan gum (0.5% w/v), (4) carbopol (0.25% w/v), and (5) carbopol (0.25% w/v)--hydroxypropyl methylcellulose (HPMC) (0.25% w/v). Viscosity measurements were conducted with a viscometer. Lenticular levels of 2-MS were determined in the lenses from young Sprague Dawley rats receiving 1 drop of selected topical suspension twice-daily for 7 days. The efficacy of the suspensions to arrest sugar cataract formation was evaluated by administering the suspensions for 21 days to similar rats fed a diet containing 50% galactose. Lens changes were examined by portable slit lamp following mydriasis. RESULTS: Lenticular levels of 2-MS was highest in rats administered suspensions containing 0.25% carbopol + 0.25% HPMC as vehicles followed by 0.5% gellan gum, 0.5% HPMC, 0.25% carbopol, and 0.5% xanthan gum. All untreated rats fed a 50% galactose diet developed hypermature cataracts within 15 days; however, none of the topical treated rats demonstrated cortical vacuole formation after 21 days of galactose feeding. CONCLUSIONS: In the suspensions examined, no direct relationship between the lenticular drug levels of 2-MS and either viscosity or pH of the vehicles were observed. The observed arrest of sugar cataract formation indicated that therapeutically adequate lenticular levels of 2-MS were provided by all topical suspensions.

Evaluation of the vascular targeting agent combretastatin a-4 prodrug on retinal neovascularization in the galactose-fed dog.

PURPOSE: Combretastatin A-4 (CA-4) is a vascular targeting agent known to rapidly shut off blood flow in new vessels and, as a result, regress neovascularization. In this pilot study, the ability of CA-4 to modify retinal neovascularization, which results in altered retinal vessel blood flow and retinal permeability, was evaluated in aphakic long-term galactose-fed beagles, an animal model that develops diabetes-like retinal neovascularization. METHODS: Two (2) groups of aphakic dogs, each group comprised of 4 galactose-fed dogs and 2 age-matched controls dogs, were utilized. Each group initially received the combretastatin A-4-phosphate prodrug (CA-4P) as either sub-Tenon's injections, administered at the corneoscleral junction, or intravitreal injections. Six (6) weeks after this treatment, all dogs also received systemic (intravenous) injections of CA-4P. Retinal vascular changes were monitored at 2-week intervals by fluorescein angiography. RESULTS: All galactose-fed dogs demonstrated the presence of retinal neovascular lesions by fluorescein angiograms. Fluorescein leakage or perfusion through neovascular vessels was not altered by either sub-Tenon's, intravitreal, or systemic CA-4P administration. Whereas CA-4P was well tolerated by the healthy eyes of the control animals, its administration to some galactose-fed dogs was associated with corneal edema and increases in intraocular pressure following sub-Tenon's and intraocular injections. CONCLUSIONS: Neovascularization in the galactose-fed dog progresses over a period of years, similar to that observed with clinical diabetic retinopathy. The failure of CA-4P to ameliorate neovascularization suggests that chronic, long-term administration may be required to destroy the slowly growing retinal endothelial cells.

Age-dependent retinal capillary pericyte degeneration in galactose-fed dogs.

The galactose-fed beagle develops diabetes-like microvascular changes that are histologically and clinically similar in appearance to all stages of human diabetic retinopathy. This animal model is extremely useful for evaluating drugs for the treatment of diabetic retinopathy; however, the time required to develop the various retinal lesions (24-72 months for background to the proliferative stage) may be considered prohibitive. Retinal vascular changes begin with an initial degeneration of capillary pericytes, which has been linked to the aldose reductase catalyzed formation of galactitol. Because aldose reductase-linked sugar cataract formation is known to be age dependent, with the onset and severity of cataract higher in younger diabetic and galactose-fed animals, retinal capillary changes in the eyes of initially 2- versus 9-month-old beagles fed a diet containing 30% galactose were compared. Eyes were enucleated after 36 months of galactose feeding, the intact retinal capillaries were isolated by trypsin digestion, and defined retinal regions were evaluated by computer image analysis. Nicotinamide adenine dinucleotide phosphate-dependent reductase activity, using DL-glyceraldehyde and D-xylose as substrates, was also compared in the lenses and whole retinas of eyes from the 2- and 9-month-old beagles. Significantly (P

Effects of topical administration of an aldose reductase inhibitor on cataract formation in dogs fed a diet high in galactose.

OBJECTIVE: To determine effects of a topical formulation of an aldose reductase inhibitor (ARI) on the development of sugar cataracts in dogs fed a diet high in galactose. Animals-Ten 6-month old Beagles. PROCEDURES: Dogs were fed a diet containing 30% galactose, and after 16 weeks, 6 dogs were treated topically with a proprietary ARI formulation and 4 dogs were treated with a placebo. Cataract formation was monitored by means of slit-lamp biomicroscopy and fundus photography. Dogs were euthanized after 10 weeks of treatment, and lenses were evaluated for degree of opacity, myo-inositol and galactitol concentrations, and concentration of the ARI. RESULTS: All dogs developed bilateral cortical opacities dense enough to result in a decrease in the tapetal reflex after being fed the galactose-containing diet for 16 weeks. Administration of the ARI arrested further development of cataract formation. In contrast, cataracts in the vehicle-treated dogs progressed over the 10-week period to the mature stage. Evaluation of the isolated lenses after 26 weeks of galactose feeding indicated that lenses from treated dogs were significantly less optically dense than lenses from control dogs. Lenticular myo-inositol concentration was significantly higher in the treated than in the control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that topical application of a proprietary ARI formulation may arrest or reverse the development of sugar cataracts in dogs fed a diet high in galactose. This suggests that this ARI formulation may be beneficial in maintaining or improving functional vision in diabetic dogs with early lens opacities.

Aqueous flow in galactose-fed dogs.

Dogs fed galactose develop diabetes-like ocular complications that include keratopathy, cataracts, and retinopathy. The purpose of this study was to investigate whether galactosemic dogs display reduced aqueous flow similar to that observed in patients with insulin-dependent diabetes mellitus. Twelve male beagles at 9 months of age were divided into three groups of four. The Galactose group was fed diet containing 30% galactose for 97 months and the Reversal group was fed the galactose diet for an initial 38 months then standard dog diet for the remaining period. The Control group was fed standard dog diet for 97 months. Aqueous flow was determined by fluorophotometry in one eye per dog at 96 and 97 months after the initiation of galactose feeding. Intraocular pressure (IOP) was measured once in the morning by pneumatonometry. Anterior chamber depth was measured by A-scan. At the end of the experiment, eyes were enucleated and processed for histological examination. Dogs fed galactose diet for 97 months had significantly (p<0.05) increased body weights but similar IOP and anterior chamber depth compared to the other groups, and significantly (p=0.05) reduced aqueous flow compared to the control group (4.4+/-2.2 vs. 6.8+/-2.4 microl/min, mean+/-standard deviation, respectively). Additionally, aqueous flow decreased in the Reversal group to 3.1+/-1.3 microl/min (p=0.002). This decrease correlated with morphological changes of the ciliary processes. Like patients with insulin-dependent diabetes mellitus, galactose-fed dogs demonstrate reduced aqueous flow. This reduction was irreversible and independent of the retinopathy present. This animal model may be useful for the study of aqueous humor dynamics in diabetes.

Anticataract activity of analogs of a sorbitol dehydrogenase inhibitor.

The initiation of sugar cataract formation by the aldose reductase catalyzed accumulation of sorbitol in diabetic rats, and its prevention by the administration of aldose reductase inhibitors at the onset or early stages of diabetes, has been well established. In contrast, the inhibition of sorbitol dehydrogenase by 4-[4-(N,N-dimethylsulfamoyl)piperazino]-2-hydroxymethylpyrimidine (SDI-1) has been observed to increase the onset in severity of sugar cataract formation in diabetic rats. Two analogs of SDI-1 have been synthesized, where the 4-(2-hydroxymethyl)pyrimidine ring has been replaced with either a 4-(2,6-dimethoxy)-pyrimidine ring or a 2-pyrimidine ring. Neither compound, 2-[4-(N,N-dimethylsulfamoyl)piperazino]-pyrimidine (SRA-1) or 4-[4-(N,N-dimethylsulfamoyl) piperazino]-2,6-dimethoxypyrimidine (SRA-2), demonstrated significant sorbitol dehydrogenase or aldose reductase inhibition. Oral administration of these compounds to streptozotocin diabetic rats, however, delayed cataract formation without reducing the levels of hyperglycemia or lens polyol.

Effect of galactose diet removal on the progression of retinal vessel changes in galactose-fed dogs.

PURPOSE: Feeding dogs a diet containing 30% galactose induces experimental galactosemia and results in the formation of diabetes-like microvascular lesions of the retina. The appearance and progression of these retinal lesions can be arrested in a dose-dependent manner by treating these dogs with aldose reductase inhibitors from the onset of galactosemia. To determine whether the elimination of galactosemia can also reduce the progression of retinal lesions, the galactose diet was removed from the galactosemic dogs after either the appearance of pericyte ghosts or formation of microaneurysms. METHODS: Ten control dogs were fed a normal diet, and 50 dogs were fed a diet containing 30% galactose. The galactose diet was removed from 15 dogs after 24 months, the time at which pericyte ghosts had previously been observed to develop, and from another 15 dogs after 31 months, when microaneurysms had previously been observed to develop. Eighteen dogs were continued on a galactose diet. Beginning at 24 months, eyes from each group were enucleated at approximately 6-month intervals. Changes in retinal lesions were quantified by computer image analyses. RESULTS: Significant (P < 0.05-0.01) increases in the endothelium-pericyte (E-P) ratio and decreases in pericyte density were observed with increased duration of galactose feeding. Although no reversal of retinal lesions occurred, differences in the progression of retinal lesions between the galactose-fed and galactose-deprived groups became evident after 12 to 24 months. CONCLUSIONS: Discontinuation of galactose in the diet at the initial stages of background retinopathy beneficially delays the progression of retinal lesions.