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1.
Invest New Drugs ; 39(3): 785-795, 2021 06.
Artículo en Inglés | MEDLINE | ID: mdl-33389388

RESUMEN

Background Ulixertinib is the first-in-class ERK1/2 kinase inhibitor with encouraging clinical activity in BRAF- and NRAS-mutant cancers. Dermatologic adverse events (dAEs) are common with ulixertinib, so management guidelines like those established for epidermal growth factor receptor inhibitor (EGFRi)-associated dAEs are needed. Patients and Methods This was an open-label, multicenter, phase I dose escalation and expansion trial of ulixertinib evaluating data from 135 patients with advanced malignancies enrolled between March 2013 and July 2017. Histopathological features, management, and dAEs in 34 patients are also reported. Twice daily oral ulixertinib was administered at 10 to 900 mg in the dose escalation cohort (n = 27) and at 600 mg in 21-day cycles in the expansion cohort (n = 108). Results The incidence of ulixertinib-induced dAEs and combined rash were 79% (107/135) and 76% (102/135). The most common dAEs included acneiform rash (45/135, 33%), maculopapular rash (36/135, 27%), and pruritus (34/135, 25%). Grade 3 dAEs were observed in 19% (25/135) of patients; no grade 4 or 5 dAEs were seen. The presence of at least 1 dAE was associated with stable disease (SD) or partial response (PR) (OR = 3.64, 95% CI 1.52-8.72; P = .003). Acneiform rash was associated with a PR (OR = 10.19, 95% CI 2.67-38.91; P < .001). Conclusion The clinical spectrum of ulixertinib-induced dAEs was similar to EGFR and MEK inhibitors; dAEs may serve as a surrogate marker of tumor response. We propose treatment algorithms for common ERK inhibitor-induced dAEs to maintain patients' quality of life and dose intensity for maximal clinical benefit. Clinical Trial Registration: NCT01781429.


Asunto(s)
Aminopiridinas/efectos adversos , Analgésicos/uso terapéutico , Antibacterianos/uso terapéutico , Antineoplásicos/efectos adversos , Erupciones por Medicamentos/tratamiento farmacológico , Quinasas MAP Reguladas por Señal Extracelular/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/efectos adversos , Pirroles/efectos adversos , Esteroides/uso terapéutico , Adulto , Anciano , Anciano de 80 o más Años , Erupciones por Medicamentos/patología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neoplasias/tratamiento farmacológico , Neoplasias/patología , Piel/efectos de los fármacos , Piel/patología , Adulto Joven
2.
Ann Oncol ; 31(9): 1207-1215, 2020 09.
Artículo en Inglés | MEDLINE | ID: mdl-32422171

RESUMEN

BACKGROUND: The tropomyosin receptor kinase (TRK) pathway controls appetite, balance, and pain sensitivity. While these functions are reflected in the on-target adverse events (AEs) observed with TRK inhibition, these AEs remain under-recognized, and pain upon drug withdrawal has not previously been reported. As TRK inhibitors are approved by multiple regulatory agencies for TRK or ROS1 fusion-positive cancers, characterizing these AEs and corresponding management strategies is crucial. PATIENTS AND METHODS: Patients with advanced or unresectable solid tumors treated with a TRK inhibitor were retrospectively identified in a search of clinical databases. Among these patients, the frequency, severity, duration, and management outcomes of AEs including weight gain, dizziness or ataxia, and withdrawal pain were characterized. RESULTS: Ninety-six patients with 15 unique cancer histologies treated with a TRK inhibitor were identified. Weight gain was observed in 53% [95% confidence interval (CI), 43%-62%] of patients and increased with time on TRK inhibition. Pharmacologic intervention, most commonly with glucagon-like peptide 1 analogs or metformin, appeared to result in stabilization or loss of weight. Dizziness, with or without ataxia, was observed in 41% (95% CI, 31%-51%) of patients with a median time to onset of 2 weeks (range, 3 days to 16 months). TRK inhibitor dose reduction was the most effective intervention for dizziness. Pain upon temporary or permanent TRK inhibitor discontinuation was observed in 35% (95% CI, 24%-46%) of patients; this was more common with longer TRK inhibitor use. TRK inhibitor reinitiation was the most effective intervention for withdrawal pain. CONCLUSIONS: TRK inhibition-related AEs including weight gain, dizziness, and withdrawal pain occur in a substantial proportion of patients receiving TRK inhibitors. This safety profile is unique relative to other anticancer therapies and warrants careful monitoring. These on-target toxicities are manageable with pharmacologic intervention and dose modification.


Asunto(s)
Proteínas Tirosina Quinasas , Receptor trkA , Humanos , Proteínas Proto-Oncogénicas , Pirazoles , Pirimidinas , Estudios Retrospectivos
3.
Ann Oncol ; 29(6): 1402-1408, 2018 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-29659672

RESUMEN

Background: Arginine depletion is a putative target in hepatocellular carcinoma (HCC). HCC often lacks argininosuccinate synthetase, a citrulline to arginine-repleting enzyme. ADI-PEG 20 is a cloned arginine degrading enzyme-arginine deiminase-conjugated with polyethylene glycol. The goal of this study was to evaluate this agent as a potential novel therapeutic for HCC after first line systemic therapy. Methods and patients: Patients with histologically proven advanced HCC and Child-Pugh up to B7 with prior systemic therapy, were randomized 2 : 1 to ADI-PEG 20 18 mg/m2 versus placebo intramuscular injection weekly. The primary end point was overall survival (OS), with 93% power to detect a 4-5.6 months increase in median OS (one-sided α = 0.025). Secondary end points included progression-free survival, safety, and arginine correlatives. Results: A total of 635 patients were enrolled: median age 61, 82% male, 60% Asian, 52% hepatitis B, 26% hepatitis C, 76% stage IV, 91% Child-Pugh A, 70% progressed on sorafenib and 16% were intolerant. Median OS was 7.8 months for ADI-PEG 20 versus 7.4 for placebo (P = 0.88, HR = 1.02) and median progression-free survival 2.6 months versus 2.6 (P = 0.07, HR = 1.17). Grade 3 fatigue and decreased appetite occurred in <5% of patients. Two patients on ADI-PEG 20 had ≥grade 3 anaphylactic reaction. Death rate within 30 days of end of treatment was 15.2% on ADI-PEG 20 versus 10.4% on placebo, none related to therapy. Post hoc analyses of arginine assessment at 4, 8, 12 and 16 weeks, demonstrated a trend of improved OS for those with more prolonged arginine depletion. Conclusion: ADI-PEG 20 monotherapy did not demonstrate an OS benefit in second line setting for HCC. It was well tolerated. Strategies to enhance prolonged arginine depletion and synergize the effect of ADI-PEG 20 are underway. Clinical Trial number: www.clinicaltrials.gov (NCT 01287585).


Asunto(s)
Carcinoma Hepatocelular/terapia , Hidrolasas/uso terapéutico , Neoplasias Hepáticas/terapia , Cuidados Paliativos , Polietilenglicoles/uso terapéutico , Carcinoma Hepatocelular/patología , Terapia Combinada , Femenino , Estudios de Seguimiento , Humanos , Neoplasias Hepáticas/patología , Masculino , Persona de Mediana Edad , Pronóstico , Tasa de Supervivencia
4.
Biochim Biophys Acta ; 1800(3): 392-7, 2010 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-20004233

RESUMEN

alpha-Crystallin, one of the main constituent proteins in the crystalline lens, is an important molecular chaperone both within and outside the lens. Presently, the structural relationship between alpha-crystallin and its target proteins during chaperone action is poorly understood. It has been hypothesised that target proteins bind within a central cavity. Small-angle neutron-scattering (SANS) experiments in conjunction with isotopic substitution were undertaken to investigate the interaction of a target lens protein (gammaE-crystallin) with alpha-crystallin (alpha(H)) and to measure the radius of gyration (Rg) of the proteins and their binary complexes in solution under thermal stress. The size of the alpha(H) in D(2)O incubated at 65 degrees C increased from 69+/-3 to 81+/-5 A over 40 min, in good agreement with previously published small-angle X-ray scattering (SAXS) and SANS measurements. Deuterated gammaE-crystallin in H(2)O buffer (gammaE(D)/H(2)O) and hydrogenous gammaE-crystallin in D(2)O buffer (gammaE(H)/D(2)O) free in solution were of insufficient size and/or too dilute to provide any measurable scattering over the angular range used, which was selected primarily to investigate gammaE:alpha(H) complexes. The evolution of the aggregation size/shape as an indicator of alpha(H) chaperone action was monitored by recording the neutron scattering in different H:D solvent contrasts under thermally stressed conditions (65 degrees C) for binary mixtures of alpha(H), gammaE(H), and gammaE(D). It was found that Rg(alpha(H):gammaE(D)/D(2)O)>Rg(alpha(H):gammaE(H)/D(2)O)>Rg(alpha(H)/D(2)O) and that Rg(alpha(H):gammaE(H)/D(2)O) approximately Rg(alpha(H)/D(2)O). The relative sizes observed for the complexes weighted by the respective scattering powers of the various components imply that gammaE-crystallin binds in a central cavity of the alpha-crystallin oligomer, during chaperone action.


Asunto(s)
Cristalino/metabolismo , alfa-Cristalinas/metabolismo , gamma-Cristalinas/metabolismo , Animales , Bovinos , Peso Molecular , Neutrones , Dispersión de Radiación , Programas Informáticos , Solventes , Termodinámica , alfa-Cristalinas/química , gamma-Cristalinas/química , gamma-Cristalinas/aislamiento & purificación
5.
Mol Vis ; 14: 2282-91, 2008.
Artículo en Inglés | MEDLINE | ID: mdl-19081783

RESUMEN

PURPOSE: To investigate the effect of carnosine (CA), aminoguanidine (AG), and aspirin (ASA) drops, all inhibitors of glycation, on the development of diabetic cataract in rat. METHODS: Rats were made diabetic with streptozotocin, and based on the level of plasma glucose, they were assigned as non-diabetic rats (<14 mmol/l plasma glucose) and diabetic rats (>14 mmol/l plasma glucose). Animals in the treated groups received CA, AG, and ASA as drops to the left eyes starting from the day of streptozotocin injection. Progression of lens opacification was recorded using the slit lamp at regular time intervals. All the rats were killed after the week 13, and the levels of advanced glycation end products (AGE), glutathione reductase (GR), catalase (CAT), and glutathione (GSH) were determined. RESULTS: Lens opacification progressed in a biphasic manner in the diabetic rats, an initial slow increase during the first eight weeks of diabetes followed by a steep increase in the next five weeks. Carnosine treatment delayed the progression of cataracts in diabetic rats, and the delay was statistically significant on the fourth week of diabetes (p<0.05, when compared with untreated moderately diabetic rats). A decrease in the antioxidant enzymes of CAT and the level of GSH was found in the lens of the untreated diabetic rats at 13 weeks after injection. Some protection was provided in the treated eyes. The level of glycation in the untreated diabetic rats was significantly higher than that in the normal rats (p<0.001). After treatment with CA, AG, and ASA, those diabetic rats had a lower level of glycated lens protein compared to the untreated diabetic rats (p<0.001). CONCLUSIONS: These results thus suggest that the effect of CA, AG, and ASA is indeed inhibition of the formation of AGEs. However, the effect of CA, AG, and ASA is overwhelmed by the excessive accumulation of AGEs in the severely diabetic rats. CA compared with AG and ASA treatment can delay the progression of lens opacification in the diabetic rats only during the earlier stages. It also protects against the inactivation of enzymes.


Asunto(s)
Aspirina/uso terapéutico , Carnosina/uso terapéutico , Catarata/complicaciones , Catarata/prevención & control , Diabetes Mellitus Experimental/complicaciones , Guanidinas/uso terapéutico , Animales , Aspirina/farmacología , Glucemia/efectos de los fármacos , Glucemia/metabolismo , Peso Corporal/efectos de los fármacos , Carnosina/farmacología , Catarata/patología , Córnea/efectos de los fármacos , Córnea/patología , Diabetes Mellitus Experimental/patología , Progresión de la Enfermedad , Proteínas del Ojo/metabolismo , Glicosilación/efectos de los fármacos , Guanidinas/farmacología , Cristalino/efectos de los fármacos , Cristalino/enzimología , Cristalino/patología , Masculino , Soluciones Oftálmicas , Ratas , Ratas Sprague-Dawley , Coloración y Etiquetado , Estreptozocina
6.
Mol Vis ; 14: 862-70, 2008 May 12.
Artículo en Inglés | MEDLINE | ID: mdl-18490958

RESUMEN

PURPOSE: To evaluate the effect of N-acetylcysteine (NAC) and glutathione ethyl ester (GSH-EE) eye drops on the progression of diabetic cataract formation induced by streptozotocin (STZ). METHODS: One hundred and thirty Sprague-Dawley (SD) rats were selected, and diabetes was induced by streptozotocin (65 mg/kg bodyweight) in a single intraperitoneal injection. The control group (group I) received only vehicle. Then, 78 rats with random blood glucose above 14 mmol/l were divided into four groups (group II-V). The drug-treated rats received NAC and GSH-EE eye drops five days before STZ injection. Group I and V animals received sodium phosphate buffer drops (pH 7.4), and those in groups II, III, and IV received 0.01% NAC, 0.05% NAC, and 0.1% GSH-EE drops, respectively. Lens transparency was monitored with a slit lamp biomicroscope and classified into six stages. At the end of four weeks, eight weeks, and 13 weeks, animals were killed and components involved in the pathogenesis of diabetic cataract including thiols (from glutathione and protein), glutathione reductase (GR), catalase (CAT), and glycated proteins were investigated in the lens extracts. Blood glucose, urine glucose, and bodyweight were also determined. RESULTS: The progression in lens opacity induced by diabetes showed a biphasic pattern in which an initial slow increase in the first seven weeks after STZ injection was followed by a rapid increase in the next six weeks. The progression of lens opacity in the treated groups (group II-IV) was slower than that of the untreated group (group V) in the earlier period and especially in the fourth week. There were statistically significant differences between the treated groups and the untreated group (p<0.05). However, these differences became insignificant after the sixth week, and the progression of lens opacification in all diabetic groups became aggravated. The content of thiol (from glutathione and protein), glutathione reductase (GR), and catalase (CAT) were lower in the lens extracts of the diabetic rats four weeks, eight weeks, and 13 weeks after the STZ injection while the levels of thiol and CAT activity were both higher in the treated groups (group II-IV) than in the untreated group (group V) at every stage. However, there was no statistically significant difference (p>0.05). Moreover, the diabetes resulted in an increased level of glycated proteins in both the treated groups and the untreated group, but there was no statistically significant difference between all the diabetic groups (p>0.05). CONCLUSIONS: NAC and GSH-EE can slightly inhibit the progression of the diabetic cataract at the earlier stage. They may maintain lens transparency and function by serving as a precursor for glutathione biosynthesis and by protecting sulfhydryl groups from oxidation.


Asunto(s)
Acetilcisteína/farmacología , Catarata/complicaciones , Diabetes Mellitus Experimental/complicaciones , Glutatión/análogos & derivados , Soluciones Oftálmicas/farmacología , Animales , Glucemia/metabolismo , Peso Corporal/efectos de los fármacos , Catalasa/metabolismo , Catarata/enzimología , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/enzimología , Proteínas del Ojo/metabolismo , Glutatión/farmacología , Glutatión Reductasa/metabolismo , Glicosilación/efectos de los fármacos , Inyecciones , Cristalino/efectos de los fármacos , Cristalino/enzimología , Ratas , Ratas Sprague-Dawley , Solubilidad/efectos de los fármacos , Estreptozocina , Compuestos de Sulfhidrilo/metabolismo , Agua/metabolismo
7.
Eye (Lond) ; 17(5): 637-45, 2003 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-12855974

RESUMEN

PURPOSE: To investigate the role of chaperone activity of alpha-crystallin in selenite-induced cataract formation. METHODS: Selenite cataract was induced in Sprague-Dawley rats by five subcutaneous injections of sodium selenite over a 20-day period starting at 8-10 days postpartum. alpha-Crystallin was separated from the rat lenses by size-exclusion chromatography. Bovine alpha(L)-crystallin and beta(L)-crystallin were isolated for studies in vitro, and for the chaperone assays. The protective effects of both alpha(H)- and alpha(L)-crystallin were measured spectrophotometrically in four different assay procedures including the thermally induced aggregation of catalase and beta(L)-crystallin, and the fructation- and heat-induced inactivation of catalase. The bovine alpha(L)-crystallin was incubated with different concentrations of sodium selenite for 72 h and then its chaperone activity against heat-induced beta(L)-crystallin aggregation was assayed. The aggregation of selenite-treated alpha(L)-crystallin was analysed by molecular sieve high-performance liquid chromatography (HPLC). RESULTS: The protection of alpha(H)-crystallin was less than that of alpha(L)-crystallin in both normal and cataractous lenses. The chaperone activities of both alpha(H)- and alpha(L)-crystallin in selenite cataract were decreased compared with normal lenses. The protection provided by both alpha(H)-crystallin and alpha(L)-crystallin against the thermal aggregation of catalase was much greater than their protection against thermally and chemically induced inactivation. HPLC analysis demonstrated aggregation of alpha-crystallin by sodium selenite after 24 h incubation in a dose-dependent fashion. CONCLUSION: The chaperone activity of alpha-crystallin presented parallel patterns of activity with different methods, further supporting the view that the different assays measure essentially the same property. The decreased chaperone activity of alpha-crystallin in selenite cataract may result from selenite-induced aggregation.


Asunto(s)
Catarata/metabolismo , Chaperonas Moleculares/metabolismo , alfa-Cristalinas/metabolismo , Animales , Catarata/inducido químicamente , Cromatografía Líquida de Alta Presión , Electroforesis en Gel de Poliacrilamida , Cristalino/metabolismo , Chaperonas Moleculares/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Selenito de Sodio
8.
Drugs Aging ; 18(7): 473-86, 2001.
Artículo en Inglés | MEDLINE | ID: mdl-11482741

RESUMEN

Cataract is the major cause of blindness and of visual impairment worldwide, so its prevention is of the greatest importance. At present no drug therapy is licensed for use in the UK or the US, so the only treatment for cataract is by surgery, which is expensive and has adverse effects. This article reviews research on prevention of cataract by a variety of agents, including micronutrients as well as drugs. Benefits have been claimed for many compounds or mixtures and this review concentrates on those most extensively studied. Information on possible benefits of putative anticataract agents comes from a variety of approaches, from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients. Sorbitol-lowering drugs were the first to be examined systematically and progressed to clinical trials which were disappointing, and now the entire rationale for their use in prevention of cataract is questionable. Micronutrients showed little promise in animals but came to clinical trial in patients with cataract without the publication of any major benefit. Pantethine showed more promise in animal studies but the only clinical trial was abandoned early. A variety of laboratory and epidemiological evidence supports the benefits of aspirin-like drugs but there has been no trial specifically in patients with cataract. Add-on studies to trials of aspirin for other indications have not been encouraging. Research into other compounds is interesting but less advanced.


Asunto(s)
Catarata/prevención & control , Panteteína/análogos & derivados , Aldehído Reductasa/antagonistas & inhibidores , Aspirina/uso terapéutico , Ensayos Clínicos como Asunto , Diseño de Fármacos , Estrógenos/uso terapéutico , Glutatión/uso terapéutico , Humanos , Panteteína/uso terapéutico
9.
Eur J Biochem ; 268(3): 713-21, 2001 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-11168410

RESUMEN

A major stress protein, alpha-crystallin, functions as a chaperone. Site-directed mutagenesis has been used to identify regions of the protein necessary for chaperone function. In this work we have taken some of the previously described mutants produced and assessed their chaperone function by both a traditional heat-induced aggregation method at elevated temperature and using enzyme methods at 37 degrees C. In general the different assays gave parallel results indicating that the same property is being measured. Discrepancies were explicable by the heat lability of some mutants. Most mutants had full chaperone function showing the robust nature of alpha-crystallin. A mutant corresponding to a minor component of rodent alpha A-crystallin, alpha Ains-crystallin, had decreased chaperone function. Decreased chaperone function was also found for human Ser139--> Arg, Thr144-->Arg, Ser59-->Ala mutants of alpha B-crystallin and double mutants Ser45-->Ala/Ser59-->Ala, Lys103--> Leu/His104-->Ile, and Glu110-->His/His111-->Glu. A mutant Phe27-->Arg that was the subject of previous controversy was shown to be fully active at physiological temperatures.


Asunto(s)
Cristalinas/química , Cristalinas/genética , Chaperonas Moleculares , Mutación , Secuencia de Aminoácidos , Animales , Sitios de Unión , Bovinos , Electroforesis en Gel de Poliacrilamida , Gliceraldehído-3-Fosfato Deshidrogenasas/metabolismo , Calor , Humanos , Malato Deshidrogenasa/química , Malato Deshidrogenasa/metabolismo , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Miocardio/enzimología , Ratas , Porcinos , Temperatura
10.
Br J Ophthalmol ; 84(7): 697-700, 2000 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-10873976

RESUMEN

BACKGROUND/AIM: Hereditary hyperferritinaemia cataract syndrome (HHCS) is an autosomal dominant disorder characterised by elevated serum L-ferritin and bilateral cataracts. The ocular manifestations of this disorder are poorly studied. This study therefore sought to determine the origin of cataracts in HHCS. METHODS: L-ferritin ELISA, immunohistochemical and ultrastructural analysis of a lens nucleus from an HHCS individual. RESULTS: The HHCS lens L-ferritin content was 147 microg/g dry weight of lens compared with <16 microg/g for a non-HHCS control cataract lens. The cataract comprised discrete crystalline inclusions with positive staining with anti-L-ferritin but not anti-H-ferritin. CONCLUSIONS: This unusual finding of crystalline opacities in the lens may be unique to HHCS and is likely to result from disturbed metabolism of L-ferritin within the lens or an abnormal interaction between L-ferritin and lens proteins.


Asunto(s)
Catarata/genética , Ferritinas/genética , Cristalino/química , Animales , Estudios de Casos y Controles , Catarata/sangre , Catarata/patología , Perros , Ensayo de Inmunoadsorción Enzimática , Femenino , Ferritinas/biosíntesis , Ferritinas/sangre , Humanos , Lactante , Microscopía Electrónica , Persona de Mediana Edad , Mutación Puntual/genética , ARN Mensajero/genética , Síndrome
12.
Ophthalmologica ; 214(1): 86-104, 2000.
Artículo en Inglés | MEDLINE | ID: mdl-10657747

RESUMEN

The human lens grows by a process of epithelial cell division at its equator and the formation of generations of differentiated fibre cells. Despite the process of continuous remodelling necessary to achieve growth within a closed system, the lens can retain a high level of light transmission throughout the lifetime of the individual, with the ability to form sharp images on the retina. Continuous growth of the lens solves the problem imposed by terminal differentiation within a closed, avascular system, from which cells cannot be shed. The lens fibre tips arch over the equator to meet anteriorly and posteriorly and form branching sutures of increasing complexity. The stages of branching may create the optical zones of discontinuity seen on biomicroscopy. The lens is exposed to the cumulative effects of radiation, oxidation and postranslational modification. These later proteins and other lens molecules in such a way as to impair membrane functions and perturb protein (particularly crystallin) organisation, so that light transmission and image formation may be compromised. Damage is minimised by the presence of powerful scavenger and chaperone molecules. Progressive insolublisation of the crystallins of the lens nucleus in the first five decades of life, and the formation of higher molecular weight aggregates, may account for the decreased deformability of the lens nucleus which characterises presbyopia. Additional factors include: the progressive increase in lens mass with age, changes in the point of insertion of the lens zonules, and a shortening of the radius of curvature of the anterior surface of the lens. Also with age, there is a fall in light transmission by the lens, associated with increased light scatter, increased spectral absorption, particularly at the blue end of the spectrum, and increased lens fluorescence. A major factor responsible for the increased yellowing of the lens is the accumulation of a novel fluorogen, glutathione-3-hydroxy kynurenine glycoside, which makes a major contribution to the increasing fluorescence of the lens nucleus which occurs with age. Since this compound may also cross-link with the lens crystallins, it may contribute to the formation of high-molecular-weight aggregates and the increases in light scattering which occur with age. Focal changes of microscopic size are observed in apparently transparent, aged lenses and may be regarded as precursors of cortical cataract formation.


Asunto(s)
Envejecimiento , Cristalino/citología , Animales , Catarata/etiología , Catarata/metabolismo , Catarata/patología , Cristalinas/metabolismo , Humanos , Cristalino/crecimiento & desarrollo
13.
Biochem J ; 345 Pt 3: 467-72, 2000 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-10642503

RESUMEN

alpha-Crystallin, a major lens protein, has many of the properties of a molecular chaperone, but its ability to assist refolding of proteins has been less certain. In the present work it was shown that alpha-crystallin specifically increased the reactivation of guanidine-denatured glyceraldehyde-3-phosphate dehydrogenase with most of the activity being recovered. In the incubation mixture the recovered enzyme activity was partly free but mostly it appeared in a protective complex with alpha-crystallin. The aggregation of the denatured enzyme on dilution from the guanidine solution was prevented. Thus alpha-crystallin not only protects against aggregation and inactivation of enzymes during denaturation, but can also prevent aggregation and assist recovery of the native structure during renaturation.


Asunto(s)
Cristalinas/metabolismo , Gliceraldehído-3-Fosfato Deshidrogenasas/metabolismo , Renaturación de Proteína , Animales , Bovinos , Cromatografía de Afinidad , Cromatografía en Gel , Cristalinas/química , Cristalinas/farmacología , Activación Enzimática , Gliceraldehído-3-Fosfato Deshidrogenasas/química , Gliceraldehído-3-Fosfato Deshidrogenasas/efectos de los fármacos , Guanidina/química , Guanidina/farmacología
14.
Biochim Biophys Acta ; 1500(1): 49-58, 2000 Jan 03.
Artículo en Inglés | MEDLINE | ID: mdl-10564717

RESUMEN

The present work investigates the effect of malondialdehyde (MDA) binding on the enzymic activity and on some structural properties of glucose 6-phosphate dehydrogenase (G6PD). We studied whether alpha-crystallin could protect the enzyme against MDA damage, and if so, by what mechanism. We also studied whether alpha-crystallin could renature G6PD denatured by MDA. alpha-Crystallin was prepared from bovine lenses by gel chromatography. MDA was freshly prepared and incubated with G6PD with or without alpha-crystallin. The results show that MDA reacted with G6PD non-enzymically causing inactivation at concentrations lower than those used previously on structural proteins. The modified enzyme became fluorescent. alpha-Crystallin, acting as a molecular chaperone, specifically protected the enzyme against inactivation by MDA. The enzyme was not reactivated by alpha-crystallin, but it was stabilised and protected against further denaturation. Complex formation between alpha-crystallin and the modified enzyme was demonstrated by immunoprecipitation. G6PD was very susceptible to MDA and we have shown for the first time that alpha-crystallin is able to protect the enzyme against this damage.


Asunto(s)
Cristalinas/metabolismo , Cristalinas/farmacología , Glucosafosfato Deshidrogenasa/antagonistas & inhibidores , Glucosafosfato Deshidrogenasa/metabolismo , Malondialdehído/farmacología , Animales , Bovinos , Cristalinas/química , Cristalinas/aislamiento & purificación , Relación Dosis-Respuesta a Droga , Electroforesis en Gel de Poliacrilamida , Activación Enzimática/efectos de los fármacos , Cristalino/química , Malondialdehído/metabolismo , Chaperonas Moleculares/metabolismo , Pruebas de Precipitina , Desnaturalización Proteica/efectos de los fármacos , Pliegue de Proteína , Espectrometría de Fluorescencia
16.
Curr Eye Res ; 19(2): 131-6, 1999 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10420182

RESUMEN

PURPOSE: Sugars in the aqueous humour of the eye serve both as a source of nutrients to the lens and other anterior ocular tissues, and potentially as an indicator of waste products from these tissues. In this work we intended to measure the levels of sugars in human blood and aqueous humour from cataract patients with and without diabetes. After initial results we decided to identify an unknown sugar component. METHODS: Sugars were measured by hplc. The unknown sugar peak was identified by gas chromatography/mass spectrometry RESULTS: Very little fructose and sorbitol were found. Glucose levels were higher in both blood and aqueous from diabetic patients. During these analyses we found a major component that did not correspond to any sugar reported previously in aqueous humour. This was identified as a mixture of threonic and erythronic acids. CONCLUSIONS: Glucose levels increase in human aqueous humour in diabetes without markedly raised levels of sorbitol or fructose. Erythronic and threonic acids are normal components of aqueous humour and blood. They may be derived from glycated proteins or from degradation of ascorbic acid.


Asunto(s)
Humor Acuoso/metabolismo , Butiratos/metabolismo , Metabolismo de los Hidratos de Carbono , Anciano , Anciano de 80 o más Años , Cromatografía Líquida de Alta Presión , Diabetes Mellitus/metabolismo , Femenino , Cromatografía de Gases y Espectrometría de Masas , Humanos , Masculino , Valores de Referencia
17.
Biochim Biophys Acta ; 1454(2): 183-90, 1999 Jul 07.
Artículo en Inglés | MEDLINE | ID: mdl-10381563

RESUMEN

Glycation, the non-enzymic reaction of sugars with proteins, has an important role in the complications of diabetes. It has been studied mostly in structural proteins but more recently has been shown to inactivate enzymes. Previous evidence from our laboratory indicated that glycation-induced inactivation and loss of antigenicity of catalase and superoxide dismutase are simultaneous. Esterase, which decreases activity in the lens in senile cataract and diabetes, was measured by a spectrophotometric assay using p-nitrophenyl acetate as the substrate. Here we investigated the inactivation of carboxylesterase (EC 3.1.1.1) by sugars of different glycating power and prednisolone-21-hemisuccinate while simultaneously monitoring the loss of antigenicity. Antigenicity was assessed by immunoprecipitation and by dot-blotting the glycated and non-glycated fractions of enzymes separated by affinity chromatography. Ribose and fructose inactivated more rapidly than glucose and glucose 6-phosphate. The esterase was progressively inactivated by prednisolone-21-hemisuccinate at a lower concentration. Activity and antigenicity were lost simultaneously. The glycated enzyme had entirely lost its antigenicity. These results further support the idea that inactivation of enzyme and loss of antigenicity are simultaneous.


Asunto(s)
Hidrolasas de Éster Carboxílico/inmunología , Activación Enzimática/efectos de los fármacos , Envejecimiento/metabolismo , Carboxilesterasa , Hidrolasas de Éster Carboxílico/aislamiento & purificación , Hidrolasas de Éster Carboxílico/metabolismo , Cromatografía de Afinidad , Diabetes Mellitus/metabolismo , Fructosa/farmacología , Glucosa/farmacología , Glucosa-6-Fosfato/farmacología , Glicosilación , Humanos , Pruebas de Precipitina , Prednisolona/análogos & derivados , Prednisolona/farmacología , Ribosa/farmacología
18.
Prog Retin Eye Res ; 18(4): 463-509, 1999 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-10217480

RESUMEN

The role of alpha-crystallin as a molecular chaperone may explain how the lens stays transparent for so long. Alpha-crystallin prevents the aggregation of other lens crystallins and proteins that have become unfolded by "trapping" the protein in a high molecular weight complex. It also protects enzyme activities. The substrate protein may interact while in a molten globule state. Alpha-crystallin predominantly binds to proteins very early in the denaturation pathways. The amphiphilic nature of alpha-crystallin, a polar C-terminal-region and a hydrophobic N-terminal-region are all essential for chaperone function. The flexible C-terminal extension maintains solubility and can bind to opposing charged residues of unfolding proteins. Hydrophobic regions in the N-terminal region then hold the unfolded protein. Specific areas important for chaperone binding and function have been identified throughout the N-terminal-region, connecting peptide and C-terminal extension. After a substantial amount of chemical data and models, cryo-EM images of alpha-crystallin have confirmed a variable 3D surface with a hollow interior. Alpha-crystallin taken from the lens nucleus shows an age-dependent decrease in chaperone function. High molecular weight aggregates and alpha-crystallin found within the nucleus from clear and cataract lenses have reduced chaperone function. Post-translational modifications, known to occur during ageing, such as glycation, carbamylation, oxidation, phosphorylation and truncation cause a decrease in chaperone function. Alpha-crystallin is expressed outside the lens. AlphaB-crystallin can be induced by heat shock in many tissues where it is translocated from cytoplasm to nucleus. Increased expression of alphaB-crystallin has been seen in many pathological states. Conformational disorders, including cataract may have a common aetiology and potentially a common therapy.


Asunto(s)
Cristalinas/química , Cristalinas/metabolismo , Chaperonas Moleculares/química , Chaperonas Moleculares/metabolismo , Conformación Proteica , Secuencia de Aminoácidos , Animales , Bovinos , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Alineación de Secuencia , Homología de Secuencia de Aminoácido
19.
Eye (Lond) ; 13 ( Pt 3b): 454-6, 1999 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-10627824

RESUMEN

The feasibility of preventing cataract by elimination of risk factors or by anti-cataract therapy is reviewed. Elimination of the major risk factors in Western countries would be difficult, although it has potential in the developing world. Various approaches to drug therapy have been made but ran into problems. The development of aldose reductase inhibitors received by far the greatest financial support but problems with toxicity were rapidly followed by the collapse of the original hypothesis. The case of aspirin, paracetamol and ibuprofen built up more slowly with no encouragement from the pharmaceutical industry. Positive results have been achieved in vitro, and in the prevention of diabetic cataract in rats, as well as the identification of an association with a protective effect against cataract in human patients. A clinical trial of these compounds is required. Other anti-cataract agents are also being investigated.


Asunto(s)
Catarata/prevención & control , Aldehído Reductasa/antagonistas & inhibidores , Animales , Antiinflamatorios no Esteroideos/uso terapéutico , Catarata/etiología , Humanos , Factores de Riesgo
20.
Br J Ophthalmol ; 82(5): 526-7, 1998 May.
Artículo en Inglés | MEDLINE | ID: mdl-9713060

RESUMEN

BACKGROUND: It has been suggested that season of birth might influence the susceptibility to cataract in later life. METHODS: This hypothesis was investigated using data pooled from two case-control studies carried out in Oxfordshire. RESULTS/CONCLUSION: The results showed no relation between month or season of birth and cataract in later life in an English population.


Asunto(s)
Catarata/etiología , Efectos Tardíos de la Exposición Prenatal , Estaciones del Año , Factores de Edad , Anciano , Estudios de Casos y Controles , Catarata/embriología , Inglaterra , Femenino , Humanos , Recién Nacido , Persona de Mediana Edad , Embarazo , Factores de Riesgo , Factores Sexuales
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