RESUMEN
In diabetes there is a long latency between the onset of hyperglycemia and the appearance of structural microangiopathy. Because Ly6Clow patrolling monocytes (PMo) behave as housekeepers of the vasculature, we tested whether PMo protect microvessels against diabetes. We found that in wild-type mice, diabetes reduced PMo in the general circulation but increased by fourfold the absolute number of PMo adherent to retinal vessels (leukostasis). Conversely, in diabetic NR4A1-/- mice, a model of absence of PMo, there was no increase in leukostasis, and at 6 months of diabetes, the number of retinal acellular capillaries almost doubled compared with diabetic wild-type mice. Circulating PMo showed gene expression changes indicative of enhanced migratory, vasculoprotective, and housekeeping activities, as well as profound suppression of genes related to inflammation and apoptosis. Promigratory CXCR4 was no longer upregulated at longer duration when retinal acellular capillaries begin to increase. Thus, after a short diabetes duration, PMo are the cells preferentially recruited to the retinal vessels and protect vessels from diabetic damage. These observations support the need for reinterpretation of the functional meaning of leukostasis in diabetes and document within the natural history of diabetic retinopathy processes of protection and repair that can provide novel paradigms for prevention.
Asunto(s)
Diabetes Mellitus Experimental/complicaciones , Retinopatía Diabética/metabolismo , Monocitos/fisiología , Vasos Retinianos/patología , Animales , Regulación de la Expresión Génica/fisiología , Ratones , Ratones Noqueados , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares/genética , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares/metabolismoRESUMEN
The roles of transforming growth factor (TGF)-ß in extracellular matrix production and vascular remodeling, coupled with increased TGF-ß expression and signaling in diabetes, suggest TGF-ß as an important contributor to the microangiopathy of diabetic retinopathy and nephropathy. To investigate whether increased TGF-ß signaling could be a therapeutic target for preventing retinopathy, we used a pharmacologic approach (SM16, a selective inhibitor of the type 1 TGF-ß receptor activin receptor-like kinase 5, orally active) to inhibit the increased, but not the basal, Tgf-ß signaling in retinal vessels of diabetic rats. At the level of vascular gene expression, 3.5 months' diabetes induced minimal changes. Diabetes + SM16 for 3 weeks caused widespread changes in gene expression poised to enhance vascular inflammation, thrombosis, leakage, and wall instability; these changes were not observed in control rats given SM16. The synergy of diabetes and SM16 in altering gene expression was not observed in the lung. At the level of vascular network morphology, 7 months' diabetes induced no detectable changes. Diabetes + SM16 for 3 weeks caused instead distorted morphology and decreased density. Thus, in diabetes, retinal vessels become dependent on a small increase in TGF-ß signaling via activin receptor-like kinase 5 to maintain early integrity. The increased TGF-ß signaling may protect against rapid retinopathy progression and should not be a target of inhibitory interventions.
Asunto(s)
Diabetes Mellitus Experimental/metabolismo , Vasos Retinianos/metabolismo , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Receptores de Activinas/metabolismo , Animales , Apoptosis/efectos de los fármacos , Compuestos de Azabiciclo/farmacología , Glucemia/metabolismo , Peso Corporal/efectos de los fármacos , Capilares/efectos de los fármacos , Capilares/patología , Quimiocina CCL2/metabolismo , Diabetes Mellitus Experimental/sangre , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/patología , Células Endoteliales/efectos de los fármacos , Células Endoteliales/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Hemoglobina Glucada/metabolismo , Masculino , Proteína Quinasa 14 Activada por Mitógenos/metabolismo , Ratas Sprague-Dawley , Reproducibilidad de los Resultados , Vasos Retinianos/efectos de los fármacos , Vasos Retinianos/patología , Transducción de Señal/efectos de los fármacos , Factores de TiempoRESUMEN
PURPOSE: We seek to identify pathogenic mechanisms for diabetic retinopathy that can become therapeutic targets beyond hyperglycemia and hypertension. We investigated if a defective myogenic response of retinal arteries to increased perfusion pressure, which exposes capillaries to increased pressure and flow, is associated with the onset of clinical retinopathy. METHODS: We examined prospectively the incidence of retinopathy in type 1 diabetic individuals tested 4 years earlier for the retinal arterial myogenic response, and in a cross-sectional study the prevalence of defective myogenic response in type 1 patients who had diabetic retinopathy. Among these, we contrasted early-onset (after 15 ± 2 years of diabetes, E-DR; n = 5) to late-onset (after 26 ± 3 years of diabetes, L-DR; n = 7) retinopathy. We measured the myogenic response using a laser Doppler blood flowmeter after a change in posture from sitting to reclining, which increases retinal perfusion pressure. RESULTS: Five of seven participants who 4 years prior had a defective myogenic response had now developed clinical retinopathy; as compared with only one of six participants who 4 years prior had a normal response (P = 0.10). In the cross-sectional study, all participants had normal retinal hemodynamics at steady state. In response to the postural change, only the E-DR group showed defective myogenic response (P = 0.005 versus controls, P = 0.02 versus L-DR) and abnormally high retinal blood flow (P = 0.016 versus controls). CONCLUSIONS: In type 1 diabetic patients, a defective myogenic response of retinal arteries to pressure is not required for the development of clinical retinopathy, but is prominently associated with an accelerated onset of retinopathy.
Asunto(s)
Diabetes Mellitus Tipo 1/fisiopatología , Retinopatía Diabética/fisiopatología , Músculo Liso Vascular/fisiopatología , Arteria Retiniana/fisiopatología , Adulto , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Estudios Transversales , Femenino , Hemoglobina Glucada/metabolismo , Humanos , Flujometría por Láser-Doppler , Masculino , Persona de Mediana Edad , Perfusión , Estudios Prospectivos , Flujo Sanguíneo Regional , Adulto JovenRESUMEN
BACKGROUND: Choroidal neovascularization (CNV) is the main cause of vision loss in age-related macular degeneration (AMD). In experimental CNV, endothelial progenitor cells (EPCs) contribute to the formation of new vessels. The aim of this study was to investigate whether the behavior of EPCs in patients with AMD supports a role for EPCs in human CNV. METHODS: The number of circulating EPCs that are considered pure endothelial precursors and EPCs with monocytic characteristics, and the plasma levels of regulatory cytokines were evaluated in 23 patients with AMD with active CNV and 20 matched controls. In the patients, this profile was re-evaluated after ranibizumab. RESULTS: When compared with controls, the patients with AMD showed a lower number of both EPC types (P = 0.03) and higher plasma levels (P = 0.03) of stromal cell-derived factor 1. Three monthly injections of ranibizumab returned to control levels the number of circulating EPCs considered pure endothelial precursors and of stromal cell-derived factor 1, but not of monocytic EPCs. CONCLUSION: The observations indicate responsiveness of circulating EPCs to the CNV process in AMD. They suggest the hypothesis that increased stromal cell-derived factor 1 production at the CNV site (reflected in higher plasma levels) recruits EPCs from the circulation, and that antivascular endothelial growth factor therapy selectively decreases the recruitment of cells to be incorporated into new vessels.
Asunto(s)
Inhibidores de la Angiogénesis/uso terapéutico , Anticuerpos Monoclonales Humanizados/uso terapéutico , Neovascularización Coroidal/tratamiento farmacológico , Células Progenitoras Endoteliales/fisiología , Degeneración Macular/tratamiento farmacológico , Anciano , Antígenos CD34/sangre , Quimiocina CXCL12/sangre , Neovascularización Coroidal/fisiopatología , Citocinas/sangre , Ensayo de Inmunoadsorción Enzimática , Femenino , Citometría de Flujo , Humanos , Inyecciones Intravítreas , Antígenos Comunes de Leucocito/sangre , Receptores de Lipopolisacáridos/sangre , Degeneración Macular/fisiopatología , Masculino , Ranibizumab , Factor A de Crecimiento Endotelial Vascular/antagonistas & inhibidores , Receptor 2 de Factores de Crecimiento Endotelial Vascular/sangreRESUMEN
Endothelial progenitor cells (EPCs) enter the systemic circulation in response to cues related to vascular damage and need for neovascularization. Thus, EPCs could become readily accessible informers of vascular status and enable the survey of vascular pathologies during preclinical stages. To identify EPC changes with biomarker potential, we investigated whether discrete EPC abnormalities were associated with early nonproliferative diabetic retinopathy (NPDR). Two EPC subtypes with different functions have been characterized to date-one solely committed to the endothelial lineage and the other carrying both endothelial and monocytic markers. We found that only the latter, colony-forming units (CFU)-Hill cells, manifested abnormalities in type 1 diabetic patients with NPDR compared with control subjects. The abnormalities consisted in an increased number of colonies formed in vitro and downregulation of the molecules that facilitate homing at sites of vascular injury. The abnormalities were absent in type 1 diabetic patients free of retinopathy and other complications, despite long diabetes duration, but were detected in some of the patients without clinical retinopathy after short diabetes duration. CFU-Hill cells are potential informers of diabetic microangiopathy but may be preempted from carrying out reparative functions if the molecular abnormalities compromise interactions with the damaged vascular wall.
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Biomarcadores , Diabetes Mellitus Tipo 1/metabolismo , Retinopatía Diabética/metabolismo , Células Endoteliales/citología , Monocitos/citología , Células Madre/metabolismo , Adulto , Estudios de Casos y Controles , Células Cultivadas , Células Endoteliales/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Monocitos/metabolismo , Adulto JovenRESUMEN
PURPOSE: To identify by noninvasive means early retinal abnormalities that may predict diabetic macular edema. METHODS: The authors analyzed retrospectively data from consecutive patients with Type 1 (n = 16) or Type 2 (n = 23) diabetes who presented for routine follow-up of early retinopathy, had no clinical signs or symptoms of diabetic macular edema, and were evaluated with spectral-domain optical coherence tomography. Age- and gender-matched nondiabetic subjects provided normative data. RESULTS: Spectral-domain optical coherence tomography revealed in the macular region of diabetic patients small hyporeflective areas (median diameter, 55 µm) contained within discrete retinal layers that we named micropseudocysts (MPCs). Micropseudocysts are associated with vascular leakage. The patients showing MPCs had more frequently systemic hypertension and increased central foveal thickness than those without MPCs. The association with increased central foveal thickness was only in the patients with Type 2 diabetes. CONCLUSION: Macular MPCs in patients with mild diabetic retinopathy appear to reflect leakage and can precede macular thickening. The association of MPCs with increased central foveal thickness in patients with Type 2 diabetes, but not in patients with Type 1 diabetes, points to a greater tendency to retinal fluid accumulation in patients with Type 2 diabetes. Studies in larger cohorts will determine the usefulness of MPCs in strategies to abort diabetic macular edema.
Asunto(s)
Quistes/diagnóstico , Retinopatía Diabética/diagnóstico , Enfermedades de la Retina/diagnóstico , Adulto , Anciano , Quistes/complicaciones , Diabetes Mellitus Tipo 1/complicaciones , Diabetes Mellitus Tipo 2/complicaciones , Retinopatía Diabética/clasificación , Retinopatía Diabética/complicaciones , Femenino , Humanos , Masculino , Persona de Mediana Edad , Enfermedades de la Retina/complicaciones , Estudios Retrospectivos , Tomografía de Coherencia ÓpticaRESUMEN
PURPOSE: The current approach to the prevention of diabetic retinopathy relies on intensive anti-diabetes treatment and is only partially successful. A marker of retinopathy risk would enable strategies of surveillance, screening of adjunct drugs, and targeted drug interventions. The authors sought to identify early abnormalities of retinal vessels that are not prevented by the current therapeutic approach. METHODS: Retinal thickness (an informer of vascular permeability) and hemodynamic parameters at baseline and longitudinally were measured in 27 subjects (age, 32 ± 9 years [mean ± SD]) with well-controlled type 1 diabetes of 12.4 ± 6.4 years' duration and no retinopathy, and in 27 control subjects. In a subset of 17 patients and 11 controls, the hemodynamic response to reclining, a postural change that increases retinal perfusion pressure, was measured. RESULTS: Baseline foveal thickness and hemodynamic parameters were similar in the diabetic and control subjects. Foveal thickness increased over 12 months in the diabetic subjects, from 217 ± 22 µm to 222 ± 20 µm (P = 0.0036), remaining however within the normal range. Reclining uncovered in 47% of diabetic subjects (P = 0.016 compared with controls) an absent myogenic response (i.e., unchanged or increased arterial diameter instead of the normal decrease). The patterns were repeatable. Only the diabetic group with defective vasoconstriction showed widening arterial diameter over 12 months, a change presaging vascular dilatation in diabetic retinopathy. CONCLUSIONS: Defective myogenic response to pressure was the first detectable abnormality of retinal vessels in subjects with well-controlled type 1 diabetes. Because of its selective occurrence, interpretability in individual patients, and pathogenic potential, the abnormality deserves evaluation as a risk marker for retinopathy.
Asunto(s)
Diabetes Mellitus Tipo 1/fisiopatología , Músculo Liso Vascular/fisiopatología , Postura/fisiología , Arteria Retiniana/fisiopatología , Retinopatía de la Prematuridad/fisiopatología , Adolescente , Adulto , Arteriolas/fisiopatología , Biomarcadores , Velocidad del Flujo Sanguíneo , Presión Sanguínea , Femenino , Hemoglobina Glucada/metabolismo , Frecuencia Cardíaca , Humanos , Recién Nacido , Flujometría por Láser-Doppler , Masculino , Persona de Mediana Edad , Flujo Sanguíneo Regional , Tomografía de Coherencia Óptica , Vasoconstricción/fisiología , Adulto JovenRESUMEN
OBJECTIVE: Prevention of diabetic retinopathy would benefit from availability of drugs that preempt the effects of hyperglycemia on retinal vessels. We aimed to identify candidate drug targets by investigating the molecular effects of drugs that prevent retinal capillary demise in the diabetic rat. RESEARCH DESIGN AND METHODS: We examined the gene expression profile of retinal vessels isolated from rats with 6 months of streptozotocin-induced diabetes and compared it with that of control rats. We then tested whether the aldose reductase inhibitor sorbinil and aspirin, which have different mechanisms of action, prevented common molecular abnormalities induced by diabetes. The Affymetrix GeneChip Rat Genome 230 2.0 array was complemented by real-time RT-PCR, immunoblotting, and immunohistochemistry. RESULTS: The retinal vessels of diabetic rats showed differential expression of 20 genes of the transforming growth factor (TGF)-beta pathway, in addition to genes involved in oxidative stress, inflammation, vascular remodeling, and apoptosis. The complete loop of TGF-beta signaling, including Smad2 phosphorylation, was enhanced in the retinal vessels, but not in the neural retina. Sorbinil normalized the expression of 71% of the genes related to oxidative stress and 62% of those related to inflammation. Aspirin had minimal or no effect on these two categories. The two drugs were instead concordant in reducing the upregulation of genes of the TGF-beta pathway (55% for sorbinil and 40% for aspirin) and apoptosis (74 and 42%, respectively). CONCLUSIONS: Oxidative and inflammatory stress is the distinct signature that the polyol pathway leaves on retinal vessels. TGF-beta and apoptosis are, however, the ultimate targets to prevent the capillary demise in diabetic retinopathy.
Asunto(s)
Retinopatía Diabética/prevención & control , Factor de Crecimiento Transformador beta/fisiología , Animales , Aspirina/farmacología , Diabetes Mellitus Experimental/fisiopatología , Retinopatía Diabética/genética , Retinopatía Diabética/fisiopatología , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Imidazolidinas/farmacología , Inflamación/genética , Inflamación/fisiopatología , Análisis de Secuencia por Matrices de Oligonucleótidos , Estrés Oxidativo/genética , ARN/genética , ARN/aislamiento & purificación , Ratas , Receptores de Factores de Crecimiento Transformadores beta/fisiología , Retina/fisiopatología , Vasos Retinianos/fisiopatología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factor de Crecimiento Transformador beta/efectos de los fármacos , Factor de Crecimiento Transformador beta/genéticaAsunto(s)
Células Endoteliales/química , Neoplasias/irrigación sanguínea , Neovascularización Patológica , Antígeno AC133 , Antígenos CD , Células Endoteliales/inmunología , Glicoproteínas , Humanos , Antígenos Comunes de Leucocito , Péptidos , Células Madre/química , Células Madre/inmunología , Receptor 2 de Factores de Crecimiento Endotelial VascularRESUMEN
The polyol pathway is a two-step metabolic pathway in which glucose is reduced to sorbitol, which is then converted to fructose. It is one of the most attractive candidate mechanisms to explain, at least in part, the cellular toxicity of diabetic hyperglycemia because (i) it becomes active when intracellular glucose concentrations are elevated, (ii) the two enzymes are present in human tissues and organs that are sites of diabetic complications, and (iii) the products of the pathway and the altered balance of cofactors generate the types of cellular stress that occur at the sites of diabetic complications. Inhibition (or ablation) of aldose reductase, the first and rate-limiting enzyme in the pathway, reproducibly prevents diabetic retinopathy in diabetic rodent models, but the results of a major clinical trial have been disappointing. Since then, it has become evident that truly informative indicators of polyol pathway activity and/or inhibition are elusive, but are likely to be other than sorbitol levels if meant to predict accurately tissue consequences. The spectrum of abnormalities known to occur in human diabetic retinopathy has enlarged to include glial and neuronal abnormalities, which in experimental animals are mediated by the polyol pathway. The endothelial cells of human retinal vessels have been noted to have aldose reductase. Specific polymorphisms in the promoter region of the aldose reductase gene have been found associated with susceptibility or progression of diabetic retinopathy. This new knowledge has rekindled interest in a possible role of the polyol pathway in diabetic retinopathy and in methodological investigation that may prepare new clinical trials. Only new drugs that inhibit aldose reductase with higher efficacy and safety than older drugs will make possible to learn if the resilience of the polyol pathway means that it has a role in human diabetic retinopathy that should not have gone undiscovered.
Asunto(s)
Retinopatía Diabética/metabolismo , Fructosa/biosíntesis , Glucosa/metabolismo , Sorbitol/metabolismo , Aldehído Reductasa/antagonistas & inhibidores , Animales , Retinopatía Diabética/prevención & control , Humanos , Oxidación-ReducciónRESUMEN
Previously studied inhibitors of aldose reductase were largely from two chemical classes, spirosuccinamide/hydantoins and carboxylic acids. Each class has its own drawbacks regarding selectivity, in vivo potency, and human safety; as a result, the pathogenic role of aldose reductase in diabetic retinopathy remains controversial. ARI-809 is a recently discovered aldose reductase inhibitor (ARI) of a new structural class, pyridazinones, and has high selectivity for aldose versus aldehyde reductase. To further test the possible pathogenic role of aldose reductase in the development of diabetic retinopathy, we examined the retinal effects of this structurally novel and highly selective ARI in insulinized streptozotocin-induced diabetic rats. ARI-809 treatment was initiated 1 month after diabetes induction and continued for 3 months at a dose that inhibited the polyol pathway in the retina of diabetic rats to a similar extent as sorbinil, a poorly selective hydantoin ARI previously shown to prevent retinopathy in this model. ARI-809 improved survival, inhibited cataract development, normalized retinal sorbitol and fructose, and protected the retina from abnormalities that also occur in human diabetes: neuronal apoptosis, glial reactivity, and complement deposition. Because ARI-809 is a novel chemotype highly selective for aldose reductase, these results support the notion that aldose reductase is the key relay that converts hyperglycemia into glucose toxicity in neural and glial cell types in the retina.
Asunto(s)
Aldehído Reductasa/antagonistas & inhibidores , Retinopatía Diabética/prevención & control , Inhibidores Enzimáticos/uso terapéutico , Piridazinas/uso terapéutico , Retina/metabolismo , Animales , Diabetes Mellitus Experimental/tratamiento farmacológico , Diabetes Mellitus Experimental/patología , Retinopatía Diabética/tratamiento farmacológico , Molécula 1 de Adhesión Intercelular/biosíntesis , Masculino , Polímeros/metabolismo , Ratas , Ratas Sprague-Dawley , Retina/efectos de los fármacos , Retina/patología , Regulación hacia ArribaRESUMEN
Evidence converges from multiple directions to indicate that prevention or very early intervention is the correct approach to diabetic retinopathy. Preclinical studies are identifying promising drugs or classes of drugs to be added to antidiabetic treatment. Recent clinical trials were still initiated at such late stages of retinopathy that the results are not readily interpretable. The challenge for the next few years is to find ways faster than clinical trials to ascertain the relevance to human diabetic retinopathy of adjunct drugs successful in animal studies.
Asunto(s)
Diabetes Mellitus/tratamiento farmacológico , Retinopatía Diabética/tratamiento farmacológico , Retinopatía Diabética/prevención & control , Animales , Ensayos Clínicos como Asunto , Evaluación Preclínica de Medicamentos , HumanosRESUMEN
The prevention of diabetic retinopathy requires drugs that leverage the benefits of glycemic control without adding the burden of side effects. Aspirin at dosages of 1-1.5 g/day has prevented manifestations of diabetic retinal microangiopathy in a clinical trial as well as in studies with dogs. Because lower and safer doses of aspirin could be used if its beneficial effects on retinopathy were due to antithrombotic effects, we compared the effects of a selective antiplatelet drug (clopidogrel) to those of aspirin in streptozotocin-induced diabetic rats. Clopidogrel did not prevent neuronal apoptosis, glial reactivity, capillary cell apoptosis, or acellular capillaries in the retina of diabetic rats. Aspirin, at doses yielding serum levels (<0.6 mmol/l) well below the anti-inflammatory range for humans, prevented apoptosis of capillary cells and the development of acellular capillaries but did not prevent neuroglial abnormalities. The aldose reductase inhibitor sorbinil, used as the benchmark for the effect of the other drugs, prevented all abnormalities. The diabetic rat retina showed increased expression of the transcription factor CCAAT/enhancer-binding protein-beta, one of the known targets of low-intermediate concentrations of aspirin. Thus we found a spectrum of drug efficacy on the prevention of experimental diabetic retinopathy, ranging from the absent effect of a selective antiplatelet drug to the prevention of all abnormalities by an aldose reductase inhibitor. Aspirin at low-intermediate concentrations selectively prevented microangiopathy. The minimal effective dose of aspirin should now be sought.
Asunto(s)
Aspirina/uso terapéutico , Diabetes Mellitus Experimental/fisiopatología , Retinopatía Diabética/tratamiento farmacológico , Vasos Retinianos/fisiopatología , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Apoptosis/efectos de los fármacos , Plaquetas/fisiología , Clopidogrel , Dinoprostona/metabolismo , Humanos , Neuronas/efectos de los fármacos , Neuronas/patología , Neuronas/fisiología , Inhibidores de Agregación Plaquetaria/uso terapéutico , Ratas , Retina/metabolismo , Vasos Retinianos/efectos de los fármacos , Ticlopidina/análogos & derivados , Ticlopidina/uso terapéuticoRESUMEN
The polyol (sorbitol) pathway of glucose metabolism is activated in many cell types when intracellular glucose concentrations are high, and it can generate cellular stress through several mechanisms. The role of the polyol pathway in the pathogenesis of diabetic retinopathy has remained uncertain, in part because it has been examined preferentially in galactose-induced retinopathy and in part because inhibition studies may not have achieved full blockade of the pathway. Having observed that the streptozotocin-induced diabetic rat accurately models many cellular processes characteristic of human diabetic retinopathy, we tested in the diabetic rat if documented inhibition of the polyol pathway prevents a sequence of retinal vascular abnormalities also present in human diabetes. An inhibitor of aldose reductase, the rate-limiting enzyme in the pathway, prevented the early activation of complement in the wall of retinal vessels and the decreased levels of complement inhibitors in diabetic rats, as well as the later apoptosis of vascular pericytes and endothelial cells and the development of acellular capillaries. Both rat and human retinal endothelial cells showed aldose reductase immunoreactivity, and human retinas exposed to high glucose in organ culture increased the production of sorbitol by a degree similar to that observed in the rat. Excess aldose reductase activity can be a mechanism for human diabetic retinopathy.
Asunto(s)
Retinopatía Diabética/metabolismo , Retinopatía Diabética/patología , Imidazolidinas , Sorbitol/metabolismo , Anciano , Aldehído Reductasa/metabolismo , Animales , Apoptosis , Capilares/efectos de los fármacos , Capilares/fisiología , Inhibidores Enzimáticos/farmacología , Femenino , Glucosa/farmacología , Humanos , Imidazoles/farmacología , Masculino , Persona de Mediana Edad , Pericitos/efectos de los fármacos , Pericitos/fisiología , Polímeros , Ratas , Ratas Sprague-Dawley , Vasos Retinianos/efectos de los fármacos , Vasos Retinianos/patologíaRESUMEN
We tested the hypothesis that the apoptosis of inner retina neurons and increased expression of glial fibrillary acidic protein (GFAP) observed in the rat after a short duration of diabetes are mediated by polyol pathway activity. Rats with 10 weeks of streptozotocin-induced diabetes and GHb levels of 16 +/- 2% (mean +/- SD) showed increased retinal levels of sorbitol and fructose, attenuation of GFAP immunostaining in astrocytes, appearance of prominent GFAP expression in Müller glial cells, and a fourfold increase in the number of apoptotic neurons when compared with nondiabetic rats. The cells undergoing apoptosis were immunoreactive for aldose reductase. Sorbinil, an inhibitor of aldose reductase, prevented all abnormalities. Intensive insulin treatment also prevented most abnormalities, despite reducing GHb only to 12 +/- 1%. Diabetic mice, known to have much lower aldose reductase activity in other tissues when compared with rats, did not accumulate sorbitol and fructose in the retina and were protected from neuronal apoptosis and GFAP changes in the presence of GHb levels of 14 +/- 2%. This work documents discrete cellular consequences of polyol pathway activity in the retina, and it suggests that activation of the pathway and "retinal neuropathy" require severe hyperglycemia and/or high activity of aldose reductase. These findings have implications for how to evaluate the role of the polyol pathway in diabetic retinopathy.
Asunto(s)
Apoptosis , Diabetes Mellitus Experimental/patología , Retinopatía Diabética/patología , Imidazolidinas , Neuroglía/patología , Polímeros/metabolismo , Retina/patología , Animales , Apoptosis/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Proteína Ácida Fibrilar de la Glía/metabolismo , Imidazoles/farmacología , Masculino , Ratones , Ratas , Ratas Sprague-Dawley , Retina/efectos de los fármacos , Retina/metabolismoRESUMEN
Diabetic retinal microangiopathy is characterized by increased permeability, leukostasis, microthrombosis, and apoptosis of capillary cells, all of which could be caused or compounded by activation of complement. In this study, we observed deposition of C5b-9, the terminal product of complement activation, in the wall of retinal vessels of human eye donors with 9 +/- 3 years of type 2 diabetes, but not in the vessels of age-matched nondiabetic donors. C5b-9 often colocalized with von Willebrand factor in luminal endothelium. C1q and C4, the complement components unique to the classical pathway, were not detected in the diabetic retinas, suggesting that C5b-9 was generated via the alternative pathway, the spontaneous activation of which is regulated by complement inhibitors. The diabetic donors showed a prominent reduction in the retinal levels of CD55 and CD59, the two complement inhibitors linked to the plasma membrane by glycosylphosphatidylinositol anchors, but not in the levels of transmembrane CD46. Similar complement activation in retinal vessels and selective reduction in the levels of retinal CD55 and CD59 were observed in rats with a 10-week duration of streptozotocin-induced diabetes. Thus, diabetes causes defective regulation of complement inhibitors and complement activation that precede most other manifestations of diabetic retinal microangiopathy. These are novel clues for probing how diabetes affects and damages vascular cells.
Asunto(s)
Activación de Complemento , Proteínas Inactivadoras de Complemento/metabolismo , Retinopatía Diabética/sangre , Glicosilfosfatidilinositoles/metabolismo , Anciano , Animales , Complemento C3/metabolismo , Complejo de Ataque a Membrana del Sistema Complemento/metabolismo , Vía Clásica del Complemento/fisiología , Retinopatía Diabética/metabolismo , Femenino , Glicosilfosfatidilinositoles/antagonistas & inhibidores , Humanos , Masculino , Ratas , Ratas Sprague-Dawley , Vasos Retinianos/metabolismo , Factores de Tiempo , Distribución TisularRESUMEN
To reconstruct the events that may contribute to the accelerated death of retinal vascular cells in diabetes, we investigated in situ and in vitro the activation of nuclear factor-kappaB (NF-kappaB), which is triggered by cellular stress and controls several programs of gene expression. The retinal capillaries of diabetic eye donors showed an increased number of pericyte nuclei positive for NF-kappaB, when compared with nondiabetic donors, whereas endothelial cells were negative. Microvascular cell apoptosis and acellular capillaries were increased only in the diabetic donors with numerous NF-kappaB-positive pericytes. Likewise, high glucose in vitro activated NF-kappaB in retinal pericytes but not in endothelial cells, and increased apoptosis only in pericytes. Studies with NF-kappaB inhibitors suggested that in pericytes, basal NF-kappaB has prosurvival functions, whereas NF-kappaB activation induced by high glucose is proapoptotic. Pericytes exposed to high glucose showed increased expression of Bax and of tumor necrosis factor-alpha, which were prevented by the NF-kappaB inhibitors and mimicked by transfection with the p65 subunit of NF-kappaB, and failed to increase the levels of the NF-kappaB-dependent inhibitors of apoptosis. Colocalization of activated NF-kappaB and Bax overexpression was observed in the retinal pericytes of diabetic donors. A proapoptotic program triggered by NF-kappaB selectively in retinal pericytes in response to hyperglycemia is a possible mechanism for the early demise of pericytes in diabetic retinopathy.