88 results on '"Hohman, T C"'
Search Results
2. Comparison of the effects of inhibitors of aldose reductase and sorbitol dehydrogenase on neurovascular function, nerve conduction and tissue polyol pathway metabolites in streptozotocin-diabetic rats
- Author
-
Cameron, N. E., Cotter, M. A., Basso, M., and Hohman, T. C.
- Published
- 1997
- Full Text
- View/download PDF
3. Impairment of afferent arteriolar myogenic responsiveness in the galactose-fed rat is prevented by tolrestat
- Author
-
Forster, H. G., ter Wee, P. M., Hohman, T. C., and Epstein, M.
- Published
- 1996
- Full Text
- View/download PDF
4. Interactions between essential fatty acid, prostanoid, polyol pathway and nitric oxide mechanisms in the neurovascular deficit of diabetic rats
- Author
-
Cameron, N. E., Cotter, M. A., and Hohman, T. C.
- Published
- 1996
- Full Text
- View/download PDF
5. Intervention with the aldose reductase inhibitor, tolrestat, in renal and retinal lesions of streptozotocin-diabetic rats
- Author
-
McCaleb, M. L., McKean, M. L., Hohman, T. C., Laver, N., and Robison, Jr., W. G.
- Published
- 1991
- Full Text
- View/download PDF
6. Reticular Drusen Associated with Geographic Atrophy in Age-Related Macular Degeneration
- Author
-
Alten, Florian, Schmitz-Valckenberg, S., Steinberg, J., Jaffe, G. J., Fleckenstein, M., Hohman, T. C., and Holz, F. G.
- Subjects
ddc: 610 ,610 Medical sciences ,Medicine - Abstract
Hintergrund: Im Rahmen der prospektiven, longitudinalen, multizentrischen GAP-Studie untersuchten wir retikuläre Drusen (RD) bei Patienten mit geographischer Atrophie (GA) infolge altersabhängiger Makuladegeneration (AMD). Methoden: Konfokale Scanning Laser Ophthalmoskopie (cSLO, Heidelberg[for full text, please go to the a.m. URL], 23. Jahrestagung der Retinologischen Gesellschaft
- Published
- 2010
7. ChemInform Abstract: Novel Spirosuccinimide Aldose Reductase Inhibitors Derived from Isoquinoline-1,3-diones: 2-((4-Bromo-2-fluorophenyl)methyl)-6- fluorospiro(isoquinoline-4(1H),3′-pyrrolidine)-1,2′,3,5′(2H)-tetrone and Congeners. Part 1.
- Author
-
MALAMAS, M. S., primary, HOHMAN, T. C., additional, and MILLEN, J., additional
- Published
- 2010
- Full Text
- View/download PDF
8. ChemInform Abstract: N-Substituted Spirosuccinimide, Spiropyridazine, Spiroazetidine, and Acetic Acid Aldose Reductase Inhibitors Derived from Isoquinoline-1,3- diones. Part 2.
- Author
-
MALAMAS, M. S., primary and HOHMAN, T. C., additional
- Published
- 2010
- Full Text
- View/download PDF
9. ChemInform Abstract: Novel Cycloalkenone Acetic and Oxyacetic Acids as Aldose Reductase Inhibitors.
- Author
-
MALAMAS, M. S., primary and HOHMAN, T. C., additional
- Published
- 2010
- Full Text
- View/download PDF
10. Minalrestat and leukocyte migration in diabetes mellitus
- Author
-
Cruz, J. W. C. M., primary, Soto-Suazo, M. W., additional, Hohman, T. C., additional, Akamine, E. H., additional, Zorn, T. T., additional, and Fortes, Z. B., additional
- Published
- 2003
- Full Text
- View/download PDF
11. Protein kinase C effects on nerve function, perfusion, Na + ,K + -ATPase activity and glutathione content in diabetic rats
- Author
-
Cameron, N. E., primary, Cotter, M. A., additional, Jack, A. M., additional, Basso, M. D., additional, and Hohman, T. C., additional
- Published
- 1999
- Full Text
- View/download PDF
12. The Efficacy of Tolrestat in the Treatment of Diabetic Peripheral Neuropathy: A meta-analysis of individual patient data
- Author
-
Nicolucci, A., primary, Carinci, F., additional, Graepel, J. G., additional, Hohman, T. C., additional, Ferris, F., additional, and Lachin, J. M., additional
- Published
- 1996
- Full Text
- View/download PDF
13. Impairment of Afferent Arteriolar Myogenic Responsiveness in the Galactose-Fed Rat
- Author
-
Forster, H. G., primary, ter Wee, P. M., additional, Takenaka, T., additional, Hohman, T. C., additional, and Epstein, M., additional
- Published
- 1994
- Full Text
- View/download PDF
14. Molecular mechanism(s) of insulin action on the expression of the angiotensinogen gene in kidney proximal tubular cells.
- Author
-
Wu, Xiao-Hua, Xing Chen, Zhang, Shao-Ling, Li Pang, To, Catherine, Wang, Tian-Tian, Hohman, Thomas C, Filep, Janos G, Chan, John SD, Wu, X H, Chen, X, Zhang, S L, Pang, L, To, C, Wang, T T, Hohman, T C, Filep, J G, and Chan, J S
- Abstract
To investigate the molecular mechanism(s) of insulin action on the expression of the angiotensinogen (ANG) gene in kidney proximal tubular cells, we constructed a fusion gene, pOGH (hANG N-1064/+27), containing the 5'-flanking regulatory sequence of the human ANG gene fused with the human growth hormone (hGH) gene as a reporter and stably integrated the fusion gene into the opossum kidney (OK) cell genomes. The level of expression of pOGH (hANG N-1064/+27) was quantified by the amount of immunoreactive hGH secreted into the medium. The addition of a high level of D(+)-glucose (25 mM) or phorbol 12-myristate 13-acetate (PMA, 10(-7) M) stimulated the expression of the fusion gene in OK cells. The stimulatory effect of glucose (25 mM) was blocked by insulin and tolrestat (an inhibitor of aldose reductase). Tolrestat also inhibited the increase of cellular DAG and PKC activity stimulated by 25 mM glucose. While insulin did not affect the cellular DAG and PKC activity, it did block the stimulatory effect of high glucose (25 mM) and PMA on the expression of the fusion gene. Finally, PD98059 (an inhibitor of mitogen-activated protein kinase kinase (MEK)) enhanced the stimulatory effect of high levels of glucose and blocked the inhibitory effect of insulin on the expression of the fusion gene as well as on the phosphorylation of MEK and mitogen-activated protein kinase (MAPK). In contrast, Wortmannin (an inhibitor of phosphatidylinositol-3-kinase) did not block the inhibitory effect of insulin on the ANG gene expression. These studies demonstrate that the action of insulin, blocking the stimulatory effect of a high level of D(+)-glucose (25 mM) on the ANG gene expression is mediated, at least in part, via the 5'-flanking region of the ANG gene and MAPK signal transduction pathway. [ABSTRACT FROM AUTHOR]
- Published
- 2000
- Full Text
- View/download PDF
15. Neuropathy in diabetic mice overexpressing human aldose reductase and effects of aldose reductase inhibitor.
- Author
-
Yagihashi, S, Yamagishi, S I, Wada Ri, R, Baba, M, Hohman, T C, Yabe-Nishimura, C, and Kokai, Y
- Abstract
The present study was designed to examine the effect of aldose reductase (AR) overexpression on the development of diabetic neuropathy by using mice transgenic for human AR. At 8 weeks of age, transgenic mice (Tg) and non-transgenic littermates (Lm) were made diabetic with streptozotocin. After 8 weeks of untreated diabetes, plasma glucose levels and the reduction in body weight were similar between the groups of diabetic animals. Despite the comparable levels of hyperglycaemia, levels of sorbitol and fructose were significantly greater in the peripheral nerve of diabetic Tg than in diabetic Lm (both P < 0.01). Ouabain sensitive Na(+),K(+)-ATPase activity was similarly decreased in both diabetic Tg and Lm. Protein kinase C activity in the sciatic nerve membrane fraction was unaffected by diabetes in Lm, but was reduced by nearly 40% in the diabetic Tg. Although both groups of diabetic animals exhibited a significant decrease in tibial nerve motor nerve conduction velocity (MNCV), this decrease was significantly more severe (P < 0.01) in diabetic Tg than in diabetic Lm. Consistent with these findings, nerve fibre atrophy was significantly more severe in diabetic Tg than in diabetic Lm (P < 0.01). These findings implicate increased polyol pathway activity in the pathogenesis of diabetic neuropathy. In support of this hypothesis, treating diabetic Tg with an aldose reductase inhibitor (WAY121-509, 4 mg/kg/day) for 8 weeks significantly prevented the accumulation of sorbitol, the decrease in MNCV and the increased myelinated fibre atrophy in diabetic Tg.
- Published
- 2001
- Full Text
- View/download PDF
16. Molecular Modeling of the Aldose Reductase-Inhibitor Complex Based on the X-ray Crystal Structure and Studies with Single-Site-Directed Mutants
- Author
-
Singh, S. B., Malamas, M. S., Hohman, T. C., Nilakantan, R., Carper, D. A., and Kitchen, D.
- Abstract
Aldose reductase (AR) has been implicated in the etiology of the secondary complications of diabetes. This enzyme catalyzes the reduction of glucose to sorbitol using nicotinamide adenine dinucleotide phosphate as an essential cofactor. AR has been localized at the sites of tissue damage, and inhibitors of this enzyme prevent the development of neuropathy, nephropathy, retinopathy, and cataract formation in animal models of diabetes. The crystal structure of AR complexed with zopolrestat, a potent inhibitor of AR, has been described.1
We have generated a model of the AR-inhibitor complex based on the reported Cα coordinates of the protein and results of a structure−activity relationship study using four structurally distinct classes of inhibitors, recombinant human AR, and four single-site-directed mutants of this enzyme. The effects of the site-directed mutations on residues within the active site of the enzyme were evaluated by average interaction energy calculations and by calculations of carbon atom surface area changes. These values correlated well with the IC 50 values for zopolrestat with the wild-type and mutant enzymes, validating the model. On the basis of the zopolrestat-binding model, we have proposed binding models for 10 other AR inhibitors. Our models have enabled us to gain a qualitative understanding of the binding domains of the enzyme and how different inhibitors impact the size and shape of the binding site.- Published
- 2000
17. ATP-sensitive K+ channel effects on nerve function, Na+, K+ ATPase, and glutathione in diabetic rats
- Author
-
Hohman, T. C., Cotter, M. A., and Cameron, N. E.
- Published
- 2000
- Full Text
- View/download PDF
18. Influence of tolrestat on the defective leukocyte-endothelial interaction in experimental diabetes
- Author
-
Cruz, J. W., Oliveira, M. A., Hohman, T. C., and Fortes, Z. B.
- Published
- 2000
- Full Text
- View/download PDF
19. Hydrolase secretion is a consequence of membrane recycling.
- Author
-
Hohman, T C and Bowers, B
- Abstract
Acanthamoeba releases lysosomal hydrolases continuously into the culture medium. This release is specific for lysosomal hydrolases, but not other cellular proteins, and is energy dependent. The secreted hydrolases can be separated into two groups on the basis of their secretion kinetics: one is secreted at approximately 15% of the cellular activity per hour and the other at approximately 5%. Intracellularly the lysosomal hydrolases are restricted almost exclusively to secondary lysosomes where the hydrolases demonstrate a differential pH-dependent binding to membrane. Hydrolase secretion is not the result of secondary lysosomes' fusing with the plasma membrane since soluble and particulate lysosomal contents are not released at the same rate. Together the data suggest that the secreted hydrolases are trapped in shuttle vesicles that cycle membrane from secondary lysosomes to the cell surface. The inner membrane and content of these vesicles undergo a marked pH shift when, following fragmentation from lysosomes, these vesicles fuse with plasma membrane. This rapid pH shift and the differential pH-dependent membrane binding of hydrolases appear to account for the heterogeneous hydrolase secretion kinetics.
- Published
- 1984
- Full Text
- View/download PDF
20. Relationship between proteins encoded by three human gamma-crystallin genes and distinct polypeptides in the eye lens
- Author
-
Russell, P, Meakin, S O, Hohman, T C, Tsui, L C, and Breitman, M L
- Abstract
Although individual gamma-crystallins from the human eye lens have not been successfully purified and sequenced, most of the genes coding for these lens-specific structural proteins have been cloned and characterized. To investigate the relationship between these genes and the gamma-crystallins of the human lens, we made use of mouse cell lines which contain stably integrated copies of the coding sequences for three of the human gamma-crystallin genes coupled to the human metallothionein IIA promoter. The proteins produced by these hybrid genes in cell culture were detected immunologically and compared by physical characteristics with the gamma-crystallins from the human lens. The protein encoded by the G3 gene showed properties identical to those of the 21,000-molecular-weight gamma-crystallin from 11-month-old lens. The protein isolated from the cells expressing the G4 gene was similar to a 19,000-molecular-weight lens gamma-crystallin, while gene G5 encodes a highly basic gamma-crystallin which may be synthesized in only limited amounts in the human lens. These correlations provide a basis for future investigations on the relationship between putative mutations in human gamma-crystallin genes and altered proteins in hereditary lens cataracts.
- Published
- 1987
- Full Text
- View/download PDF
21. Effect of the Aldose Reductase Inhibitor Tolrestat on Nerve Conduction Velocity, NA/K ATPase Activity, and Polyols in Red Blood Cells, Sciatic Nerve, Kidney Cortex, and Kidney Medulla of Diabetic Rats
- Author
-
Raccah, D., Coste, T., Cameron, N. E., Dufayet, D., Vague, P., and Hohman, T. C.
- Published
- 1998
- Full Text
- View/download PDF
22. Aminoguanidine Does Not Inhibit Aldose Reductase Activity in Galactose-Fed Rats
- Author
-
Dvornik, D., Hohman, T. C., and Basso, M. D.
- Published
- 1996
- Full Text
- View/download PDF
23. Reversal of Defective Peripheral Nerve Conduction Velocity, Nutritive Endoneurial Blood Flow, and Oxygenation by a Novel Aldose Reductase Inhibitor, WAY-121,509, in Streptozotocin-Induced Diabetic Rats
- Author
-
Cameron, N. E., Cotter, M. A., Dines, K. C., and Hohman, T. C.
- Published
- 1996
- Full Text
- View/download PDF
24. Phagosome-lysosome fusion inhibited by algal symbionts of Hydra viridis.
- Author
-
Hohman, T C, McNeil, P L, and Muscatine, L
- Abstract
Certain species of Chlorella live within the digestive cells of the fresh water cnidarian Hydra viridis. When introduced into the hydra gut, these symbiotic algae are phagocytized by digestive cells but avoid host digestion and persist at relatively constant numbers within host cells. In contrast, heat-killed symbionts are rapidly degraded after phagocytosis. Live symbionts appear to persist because host lysosomes fail to fuse with phagosomes containing live symbionts. Neither acid phosphatase nor ferritin was delivered via lysosomes into phagosomes containing live symbionts, whereas these lysosomal markers were found in 50% of the vacuoles containing heat-killed symbionts 1 h after phagocytosis. Treatment of symbiotic algae before phagocytosis with polycationic polypeptides abolishes algal persistence and perturbs the ability of these algae to control the release of photosynthate in vitro. Similarly, inhibition of photosynthesis and hence of the release of photosynthetic products as a result of prolonged darkness and 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU) treatment also abolishes persistence. Symbiotic algae are not only protected from host digestive attack but are also selectively transported within host cells, moving from the apical site of phagocytosis to a basal position of permanent residence. This process too is disrupted by polycationic polypeptides, DCMU and darkness. Both algal persistence and transport may, therefore, be a function of the release of products from living, photosynthesizing symbionts. Vinblastine treatment of host animals blocked the movement of algae within host cells but did not perturb algal persistence: algal persistence and the transport of algae may be initiated by the same signal, but they are not interdependent processes.
- Published
- 1982
- Full Text
- View/download PDF
25. ChemInform Abstract: Novel Cycloalkenone Acetic and Oxyacetic Acids as Aldose Reductase Inhibitors.
- Author
-
MALAMAS, M. S. and HOHMAN, T. C.
- Published
- 1995
- Full Text
- View/download PDF
26. ChemInform Abstract: N-Substituted Spirosuccinimide, Spiropyridazine, Spiroazetidine, and Acetic Acid Aldose Reductase Inhibitors Derived from Isoquinoline-1,3- diones. Part 2.
- Author
-
MALAMAS, M. S. and HOHMAN, T. C.
- Published
- 1994
- Full Text
- View/download PDF
27. ChemInform Abstract: Novel Spirosuccinimide Aldose Reductase Inhibitors Derived from Isoquinoline-1,3-diones: 2-((4-Bromo-2-fluorophenyl)methyl)-6- fluorospiro(isoquinoline-4(1H),3′-pyrrolidine)-1,2′,3,5′(2H)-tetrone and Congeners. Part 1.
- Author
-
MALAMAS, M. S., HOHMAN, T. C., and MILLEN, J.
- Published
- 1994
- Full Text
- View/download PDF
28. Galactosemia produces ARI-preventable nodal changes similar to those of diabetic neuropathy
- Author
-
Kamijo, M., Basso, M., Cherian, P. V., and Hohman, T. C.
- Published
- 1994
- Full Text
- View/download PDF
29. Neuropathy in diabetic mice overexpressing human aldose reductase and effects of aldose reductase inhibitor.
- Author
-
Yagihashi S, Yamagishi SI, Wada Ri R, Baba M, Hohman TC, Yabe-Nishimura C, and Kokai Y
- Subjects
- Animals, Diabetes Mellitus, Experimental genetics, Diabetes Mellitus, Experimental pathology, Diabetic Neuropathies genetics, Diabetic Neuropathies pathology, Enzyme-Linked Immunosorbent Assay, Female, Glucose metabolism, Humans, Hyperglycemia metabolism, Mice, Mice, Inbred C57BL, Mice, Inbred DBA, Mice, Transgenic, Motor Neurons enzymology, Neural Conduction, Protein Kinase C metabolism, Sciatic Nerve enzymology, Sciatic Nerve pathology, Sodium-Potassium-Exchanging ATPase metabolism, Aldehyde Reductase antagonists & inhibitors, Aldehyde Reductase genetics, Aldehyde Reductase pharmacology, Diabetes Mellitus, Experimental metabolism, Diabetic Neuropathies metabolism, Enzyme Inhibitors pharmacology
- Abstract
The present study was designed to examine the effect of aldose reductase (AR) overexpression on the development of diabetic neuropathy by using mice transgenic for human AR. At 8 weeks of age, transgenic mice (Tg) and non-transgenic littermates (Lm) were made diabetic with streptozotocin. After 8 weeks of untreated diabetes, plasma glucose levels and the reduction in body weight were similar between the groups of diabetic animals. Despite the comparable levels of hyperglycaemia, levels of sorbitol and fructose were significantly greater in the peripheral nerve of diabetic Tg than in diabetic Lm (both P < 0.01). Ouabain sensitive Na(+),K(+)-ATPase activity was similarly decreased in both diabetic Tg and Lm. Protein kinase C activity in the sciatic nerve membrane fraction was unaffected by diabetes in Lm, but was reduced by nearly 40% in the diabetic Tg. Although both groups of diabetic animals exhibited a significant decrease in tibial nerve motor nerve conduction velocity (MNCV), this decrease was significantly more severe (P < 0.01) in diabetic Tg than in diabetic Lm. Consistent with these findings, nerve fibre atrophy was significantly more severe in diabetic Tg than in diabetic Lm (P < 0.01). These findings implicate increased polyol pathway activity in the pathogenesis of diabetic neuropathy. In support of this hypothesis, treating diabetic Tg with an aldose reductase inhibitor (WAY121-509, 4 mg/kg/day) for 8 weeks significantly prevented the accumulation of sorbitol, the decrease in MNCV and the increased myelinated fibre atrophy in diabetic Tg.
- Published
- 2001
- Full Text
- View/download PDF
30. Streptozotocin-induced diabetes causes metabolic changes and alterations in neurotrophin content and retrograde transport in the cervical vagus nerve.
- Author
-
Lee PG, Hohman TC, Cai F, Regalia J, and Helke CJ
- Subjects
- Animals, Axonal Transport drug effects, Diabetes Mellitus, Experimental complications, Diabetes Mellitus, Experimental drug therapy, Fructose metabolism, Glucose metabolism, Hyperglycemia drug therapy, Hyperglycemia etiology, Hyperglycemia metabolism, Insulin pharmacology, Ligation, Male, Neck, Nerve Growth Factor genetics, Neurotrophin 3 genetics, RNA, Messenger metabolism, Rats, Rats, Sprague-Dawley, Sorbitol metabolism, Streptozocin, Vagus Nerve drug effects, Axonal Transport physiology, Diabetes Mellitus, Experimental metabolism, Nerve Growth Factor metabolism, Neurotrophin 3 metabolism, Vagus Nerve metabolism
- Abstract
Abnormal availability of neurotrophins, such as nerve growth factor (NGF), has been implicated in diabetic somatosensory polyneuropathy. However, the involvement of neurotrophins in diabetic neuropathy of autonomic nerves, particularly the vagus nerve which plays a critical role in visceral afferent and in autonomic motor functions, is unknown. To assess the effects of hyperglycemia on the neurotrophin content and transport in this system, cervical vagus nerves of streptozotocin (STZ)-induced diabetic rats were studied at 8, 16, and 24 weeks after the induction of diabetes. Elevations in vagus nerve hexose (glucose and fructose) and polyol levels (sorbitol), and their normalization with insulin treatment, verified that the STZ treatment resulted in hyperglycemia-induced metabolic abnormalities in the nerve. Neurotrophin (NGF and neurotrophin-3; NT-3) content and axonal transport were assessed in the cervical vagus nerves from nondiabetic control rats, STZ-induced diabetic rats, and diabetic rats treated with insulin. The NGF, but not the NT-3, content of intact vagus nerves from diabetic rats was increased at 8 and 16 weeks (but not at 24 weeks). Using a double-ligation model to assess the transport of endogenous neurotrophins, the retrograde transport of both NGF and NT-3 was found to be significantly reduced in the cervical vagus nerve at later stages of diabetes (16 and 24 weeks). Anterograde transport of NGF or NT-3 was not apparent in the vagus nerve of diabetic or control rats. These data suggest that an increase in vagus nerve NGF is an early, but transient, response to the diabetic hyperglycemia and that a subsequent reduction in neuronal access to NGF and NT-3 secondary to decreased retrograde axonal transport may play a role in diabetes-induced damage to the vagus nerve., (Copyright 2001 Academic Press.)
- Published
- 2001
- Full Text
- View/download PDF
31. Retinal capillary dilation: early diabetic-like retinopathy in the galactose-fed rat model.
- Author
-
Glover JP, Jacot JL, Basso MD, Hohman TC, and Robison WG Jr
- Subjects
- Aldehyde Reductase administration & dosage, Aldehyde Reductase antagonists & inhibitors, Animals, Basement Membrane pathology, Capillaries drug effects, Capillaries pathology, Diabetes Mellitus, Experimental chemically induced, Diabetes Mellitus, Experimental prevention & control, Diabetic Retinopathy chemically induced, Diabetic Retinopathy prevention & control, Dilatation, Pathologic, Enzyme Inhibitors administration & dosage, Female, Rats, Rats, Sprague-Dawley, Retinal Vessels drug effects, Diabetes Mellitus, Experimental pathology, Diabetic Retinopathy pathology, Galactose adverse effects, Retinal Vessels pathology
- Abstract
Unlabelled: The purpose of this study was to determine whether capillary dilation is one of the earliest structural changes in the diabetic-like retinopathy of the galactose-fed rat model and thus may represent a stage where intervention treatment might still be effective. Weanling female Sprague-Dawley rats were randomized into 3 groups and fed Purina laboratory chow plus one of the following for 4 months: 50% starch (CONTROL); 50% D-galactose (Galactose); or 50% D-galactose with ARI-509 (25 mg/kg body wt/day) (Inhibitor). One eye from each of 5 rats per treatment group was processed for retinal vasculature wholemounts using elastase digestion, stained with a standard periodic-acid-Schiff reaction and counterstained with hematoxylin. Average capillary width, overall capillary density and total capillary length were measured, using computerized image analysis, within an arc-shaped area (4.4 mm2) of each vasculature surrounding, but separated from, the optic disc margin by approximately 0.7 mm. Galactose rats exhibited significant (p < 0.001) increases in capillary width (Mean +/- SEM: 7.56 +/- 0.07 microm) and density (42.78 +/- 0.37%) compared with CONTROL rats (6.68 +/- 0.11 microm and 37.18 +/- 0.30%, respectively). These increases were prevented with inhibitor treatment (6.58 +/- 0.16 microm and 35.88 +/- 0.97%, respectively). Capillary length remained unchanged at 4 months (, Control: 246.66 +/- 2.46 mm; Galactose: 250.75 +/- 1.26 mm; Inhibitor: 242.25 +/- 8.43 mm). Retinal capillary dilation, expressed as increased width and density, is one of the earliest detectable lesions in galactose-fed rats. In these rats, the lesion occurs as early as retinal capillary basement membrane thickening (RCBMT), one of the earliest reported changes in human diabetic retinopathy. Like RCBMT, capillary dilation can be prevented in rats with aldose reductase inhibitor treatment. Unlike RCBMT, capillary dilation could be clinically detectable and may be useful for the diagnosis of early retinopathy and for determining the timing of therapeutic intervention.
- Published
- 2000
- Full Text
- View/download PDF
32. Subnormal retinal oxygenation response precedes diabetic-like retinopathy.
- Author
-
Berkowitz BA, Kowluru RA, Frank RN, Kern TS, Hohman TC, and Prakash M
- Subjects
- Animals, Blood Glucose metabolism, Carbon Dioxide administration & dosage, Diabetic Retinopathy etiology, Diabetic Retinopathy metabolism, Fructose blood, Galactitol blood, Galactose administration & dosage, Galactosemias etiology, Galactosemias metabolism, Glucose metabolism, Inositol blood, Magnetic Resonance Imaging, Oxygen administration & dosage, Partial Pressure, Rats, Retina pathology, Sorbitol blood, Diabetic Retinopathy diagnosis, Oxygen metabolism, Retina metabolism
- Abstract
Purpose: Determining which patients are at risk for the development of diabetic retinopathy is expected to greatly improve existing prevention and treatment options. In this study, using an animal model of diabetic retinopathy, the hypothesis was tested that magnetic resonance imaging (MRI) and a carbogen inhalation challenge provides important diagnostic information regarding the risk of developing diabetic retinopathy., Methods: MRI was used to measure noninvasively the change in oxygen tension along the entire inner retina (i.e., from superior ora serrata to inferior ora serrata) during a carbogen (95% O2/5% CO2) inhalation challenge (IOVS 1996;37:2089). Two animal groups were examined by this MRI method at two time points: (1) rats fed either normal rat chow (n = 20) or a 50% galactose diet (n = 20) for 3.5 months (i.e., before the appearance of extensive retinal lesions) or (2) rats fed either normal rat chow (n = 3) for 15 months or a 30% galactose diet (n = 4) for 15 to 18 months (i.e., when lesions are present). Retinal biochemical and morphometric measurements were also obtained., Results: After 3.5 months of galactosemia, before the appearance of extensive retinal morphologic lesions, a significant (P < 0.05) reduction in the panretinal oxygenation response was observed in the galactosemic group compared with its age-matched control. These galactose-fed animals also displayed a significantly (P < 0.05) larger oxygenation response in the inferior hemiretina than in the superior hemiretina. After 15 to 18 months of galactosemia, during the period when lesions are present, the panretinal oxygenation response remained significantly (P < 0.05) lower in the galactose-fed animals than in their age-matched controls. In contrast to the 3.5-month results, the oxygenation response in galactosemic animals at 15 to 18 months was significantly (P < 0.05) larger in the superior than in the inferior hemiretina. Hemiretinal oxygenation responses were not different in normal controls at either duration., Conclusions: MRI measurement of the retinal oxygenation response to a carbogen challenge appears to be a powerful new and noninvasive approach that may be useful for assessing aspects of pathophysiology underlying the development of diabetic retinopathy in galactosemic rats. These results support our working hypothesis and suggest that further research into the diagnostic potential of this MRI approach for predicting the development of diabetic retinopathy is warranted.
- Published
- 1999
33. Molecular mechanisms of glucose action on angiotensinogen gene expression in rat proximal tubular cells.
- Author
-
Zhang SL, Filep JG, Hohman TC, Tang SS, Ingelfinger JR, and Chan JS
- Subjects
- Aldehyde Reductase antagonists & inhibitors, Angiotensinogen metabolism, Animals, Cell Line, Transformed, Enzyme Inhibitors pharmacology, Glucose pharmacology, Kidney Tubules, Proximal cytology, Kidney Tubules, Proximal drug effects, Kidney Tubules, Proximal metabolism, Naphthalenes pharmacology, Protein Kinase C antagonists & inhibitors, RNA, Messenger metabolism, Rats, Stereoisomerism, Tetradecanoylphorbol Acetate pharmacology, Angiotensinogen genetics, Gene Expression Regulation physiology, Glucose physiology, Kidney Tubules, Proximal physiology
- Abstract
Background: Clinical studies have shown that the angiotensin-converting enzyme (ACE) inhibitors or angiotensin II (Ang II) receptor antagonists decrease proteinuria and slow the progression of nephropathy in diabetes, indicating that Ang II plays an important role in the development of nephropathy. We have previously reported that high levels of glucose stimulate the expression of rat angiotensinogen (ANG) gene in opossum kidney (OK) proximal tubular cells. We hypothesized that the stimulatory effect of D(+)-glucose on the expression of the ANG gene in kidney proximal tubular cells is mediated via de novo synthesis of diacylglycerol (DAG) and the protein kinase C (PKC) signal transduction pathway., Methods: Immortalized rat proximal tubular cells (IRPTCs) were cultured in monolayer. The stimulatory effect of glucose on the activation of polyol pathway and PKC signal transduction pathway in IRPTCs was determined. The immunoreactive rat ANG (IR-rANG) in the culture medium and the cellular ANG mRNA were measured with a specific radioimmunoassay and a reverse transcription-polymerase chain reaction assay, respectively., Results: D(+)-glucose (25 mM) markedly increased the intracellular levels of sorbitol, fructose, DAG, and PKC activity as well as the expression of IR-rANG and ANG mRNA in IRPTCs. These stimulatory effects of D(+)-glucose (25 mM) were blocked by an inhibitor of aldose reductase, Tolrestat. PKC inhibitors also inhibited the stimulatory effect of D(+)-glucose (25 mM) on the expression of the IR-rANG in IRPTCs. The addition of phorbol 12-myristate 13-acetate further enhanced the stimulatory effect of D(+)-glucose (25 mM) on the expression of the IR-rANG in IRPTCs and blocked the inhibitory effect of Tolrestat., Conclusion: These studies suggest that the stimulatory effect of a high level of D(+)-glucose (25 mM) on the expression of the ANG gene in IRPTCs is mediated, at least in part, via the de novo synthesis of DAG, an activator of PKC signal transduction pathway.
- Published
- 1999
- Full Text
- View/download PDF
34. Diabetic-like retinopathy: early and late intervention therapies in galactose-fed rats.
- Author
-
Robison WG Jr, Jacot JL, Glover JP, Basso MD, and Hohman TC
- Subjects
- Aldehyde Reductase therapeutic use, Animals, Basement Membrane drug effects, Basement Membrane ultrastructure, Blood Glucose analysis, Diabetic Retinopathy etiology, Diabetic Retinopathy pathology, Female, Galactose adverse effects, Galactosemias complications, Glycated Hemoglobin analysis, Random Allocation, Rats, Rats, Sprague-Dawley, Retinal Vessels ultrastructure, Aldehyde Reductase antagonists & inhibitors, Diabetic Retinopathy prevention & control, Retinal Vessels drug effects
- Abstract
Purpose: To determine whether the diabetic-like thickening of retinal capillary basement membrane (RCBM) that develops in the galactose-fed rat model of diabetic ocular complications could be halted or ameliorated after 4 or 8 months of galactosemia by treatment with ARI-509, a potent new aldose reductase inhibitor (ARI), or by withdrawal of the galactose diet., Methods: Weanling female Sprague-Dawley rats were randomized into eight groups and fed laboratory chow plus 50% starch, control group (CON); 50% D-galactose, galactose-fed group (GAL); 50% D-galactose with ARI-509 at 25 mg/kg or 10 mg/kg body wt per day, high-dose prevention group (HDP) and low-dose prevention group (LDP), respectively; 50% D-galactose for 4 or 8 months and then intervention by addition of ARI-509 (25 mg/kg body wt per day), 4-month intervention group (4IN) and 8-month intervention group (8IN), respectively; or 50% D-galactose for 4 or 8 months and then intervention by withdrawing galactose and replacing it with the 50% starch diet, 4-month galactose withdrawal group (4GW) and 8-month galactose withdrawal group (8GW), respectively. After 4, 8, 16, and 24 months of the experimental diets, the levels of carbohydrates in tissues and the extent of RCBM thickening in capillaries of the outer plexiform layer were determined in all groups., Results: Retinal polyol was reduced by 95% in all ARI-treated groups and by 100% in the 4GW and 8GW groups after withdrawal of the galactose. The mean RCBM thickness increased rapidly in GAL rats, becoming almost two times greater (189 +/- 9.4 nm) than in CON rats (103 +/- 3.4 nm) by 24 months. Treatment with ARI-509 in high and low doses (HDP, LDP) initiated with the introduction of the galactose diet significantly prevented RCBM thickening at all time points (P < 0.05). In contrast, intervention by withdrawing galactose from the diet or by adding the high dose of ARI-509 had no significant effect (P < 0.05) on RCBM thickening until the 24-month time point (4IN, 166 +/- 10.3 nm; 8IN, 161 +/- 8.2 nm; 4GW, 136 +/- 5.1 nm; 8GW, 163 +/- 9.6 nm)., Conclusions: Both early and late interventions decreased RCBM thickening compared with that in untreated GAL rats. The decreased thickening, however, was not evident until 16 to 20 months after the intervention. Because RCBM thickening is one of the earliest changes in diabetic and galactosemic retinopathy, the findings suggest that RCBM thickening and possibly subsequent retinal lesions are caused by early biochemical alterations induced by the galactose diet that are not readily reversed. The delayed response to therapy is consistent with that observed in the Diabetes Control and Complications Trial. The cumulative evidence indicates that intervention should begin as early after onset of diabetes as possible, and long follow-up periods should be used to evaluate efficacy.
- Published
- 1998
35. Probing the inhibitor-binding site of aldose reductase with site-directed mutagenesis.
- Author
-
Hohman TC, El-Kabbani O, Malamas MS, Lai K, Putilina T, McGowan MH, Wane YQ, and Carper DA
- Subjects
- Aldehyde Reductase antagonists & inhibitors, Benzothiazoles, Binding Sites genetics, Computer Simulation, Enzyme Inhibitors pharmacology, Humans, Imidazoles chemistry, Kinetics, Models, Molecular, Molecular Structure, Mutagenesis, Site-Directed genetics, NADP metabolism, Naphthalenes chemistry, Phthalazines chemistry, Recombinant Proteins chemistry, Thiazoles chemistry, Aldehyde Reductase chemistry, Enzyme Inhibitors chemistry, Imidazolidines
- Abstract
Aldose reductase (AR) has been implicated in the etiology of the secondary complications of diabetes, and enzyme inhibitors have been proposed as therapeutic agents. While effectively preventing the development of diabetic complications in animals, results from clinical studies of AR inhibitors have been disappointing, possibly due to poor potency in man. To assist in the design of more potent and specific inhibitors, crystallographic studies have attempted to identify enzyme-inhibitor interactions. Resolution of crystal complexes has suggested that the inhibitors bind to the enzyme active site and are held in place through hydrogen bonding and van der Waals interactions formed within two hydrophobic pockets. To confirm and extend these findings we quantified inhibitor activity with single, site-directed, mutant, human AR enzymes in which the apolar active-site residues tryptophan 20, -79, -111 and phenylalanine 115 were replaced with alanine or tyrosine, decreasing the potential for van der Waals interactions. Consistent with molecular models, the inhibitory activity of Tolrestat, Sorbinil and Zopolrestat decreased 800-2000-fold when tested with the mutant enzyme in which Trp20 was replaced with alanine. Further, alanine substitution for Trp111 decreased Zopolrestat's activity 400-fold, while mutations to Trp79 and Phe115 had little effect on the activity of any of the inhibitors. The alanine mutation at Trp111 had no effect on Tolrestat's activity but decreased the activity of Sorbinil by about 1000-fold. These latter effects were unanticipated based on the number of non-bonded interactions between the inhibitors, Tolrestat and Sorbinil, and Trp20 and Trp111 that have been identified in the crystal structures. In spite of these unexpected findings, our results are consistent with the hypothesis that AR inhibitors occupy the enzyme active site and that hydrophobic interactions between the enzyme and inhibitor contribute to inhibitor binding stability.
- Published
- 1998
- Full Text
- View/download PDF
36. Correction of nerve conduction and endoneurial blood flow deficits by the aldose reductase inhibitor, tolrestat, in diabetic rats.
- Author
-
Cotter MA, Cameron NE, and Hohman TC
- Subjects
- Animals, Diabetes Mellitus, Experimental physiopathology, Male, Rats, Rats, Sprague-Dawley, Regional Blood Flow drug effects, Aldehyde Reductase antagonists & inhibitors, Diabetic Nephropathies physiopathology, Enzyme Inhibitors pharmacology, Naphthalenes pharmacology, Neural Conduction drug effects, Sciatic Nerve blood supply
- Abstract
Increased activation of the first half of the polyol pathway, the conversion of glucose to sorbitol by aldose reductase, has been implicated in aldose reductase inhibitor-preventable neurochemical changes that may contribute to the aetiology of diabetic neuropathy. Tolrestat has been used as a standard aldose reductase inhibitor to dissect out polyol pathway-dependent mechanisms in many experimental studies; however, doubt has been cast upon its ability to prevent nerve conduction velocity deficits in diabetic rats. Nerve dysfunction has also been linked to abnormal endoneurial blood flow and oxygenation via increased vasa nervorum polyol pathway flux. The aim of this study was to test whether tolrestat could correct sciatic conduction velocity and perfusion defects in diabetic rats. Sciatic motor conduction velocity, 21% reduced by 1 month of streptozotocin-induced diabetes, was corrected by 23% and 84% with 1 month of tolrestat treatment at doses of 7 and 35 mg/kg/day respectively. Endoneurial blood flow, 44-52% reduced by untreated diabetes, was within the nondiabetic range with high-dose tolrestat treatment and the flow deficit was 39% corrected by the low dose. Sciatic sorbitol and fructose concentrations were approximately 13-fold and approximately 4-fold elevated by untreated diabetes. This was 32-50% attenuated by low-dose tolrestat and sorbitol and fructose content was suppressed below the nondiabetic level by high dose treatment. A 58% nerve myo-inositol deficit was partially (32%) corrected by high-dose tolrestat treatment. We conclude that tolrestat restores defective conduction and blood flow in diabetic rats and is a good pharmacological tool for studies on polyol pathway effects in peripheral nerve.
- Published
- 1998
37. An aldose reductase inhibitor and aminoguanidine prevent vascular endothelial growth factor expression in rats with long-term galactosemia.
- Author
-
Frank RN, Amin R, Kennedy A, and Hohman TC
- Subjects
- Aldehyde Reductase pharmacology, Animals, Cataract chemically induced, Cataract pathology, Diabetic Retinopathy metabolism, Diabetic Retinopathy pathology, Diabetic Retinopathy prevention & control, Factor VIII metabolism, Female, Fluorescent Antibody Technique, Indirect, Galactose, Galactosemias chemically induced, Galactosemias pathology, Glial Fibrillary Acidic Protein metabolism, Rats, Rats, Sprague-Dawley, Retina metabolism, Retina pathology, Retinal Vessels drug effects, Retinal Vessels metabolism, Retinal Vessels pathology, Vascular Endothelial Growth Factor A, Vascular Endothelial Growth Factors, Vimentin metabolism, Aldehyde Reductase antagonists & inhibitors, Endothelial Growth Factors biosynthesis, Enzyme Inhibitors pharmacology, Galactosemias metabolism, Guanidines pharmacology, Lymphokines biosynthesis, Retina drug effects
- Abstract
Objective: To study the effects of an aldose reductase inhibitor (ARI-509, Wyeth-Ayerst, Princeton, NJ) and aminoguanidine (AMG), agents that have been reported to prevent or delay diabetic retinopathy, on retinal vascular abnormalities and the immunocytochemical expression in the retina of vascular endothelial growth factor (VEGF) in rats maintained for up to 2 years on a 50% galactose diet., Methods: Albino rats were placed on a control diet, a diet containing 50% galactose, or the 50% galactose diet containing either ARI-509 or AMG. Treatment with ARI-509 or AMG was initiated at the beginning of the experiment or after 12 months of galactose feeding. After 22 to 24 months, the rats were killed and the retinal vasculature from half of one eye was isolated by trypsin-elastase digestion for semiquantitative evaluation of retinal vascular lesions. The other half of the retina was prepared for immunocytochemistry and stained for the presence of VEGF, factor VIII, vimentin, and glial fibrillary acidic protein. Red blood cells, sciatic nerves, and a portion of the retina from the second eye were assayed for glucose, galactose, fructose, sorbitol, galactitol, and myo-inositol. Red blood cells were also assayed for galactosylated hemoglobin., Results: Galactose-fed animals developed a vascular retinopathy characterized by severe cellular loss in the retinal capillaries and intensification of periodic acid-Schiff staining of the vascular basement membranes. Some animals also displayed dilation and hypercellularity of vessels in the posterior retina. These changes were substantially reduced in animals receiving ARI-509 from the beginning of the galactose diet, but were unaffected in all of the other treatment groups. None of the rats receiving ARI-509 or AMG treatment, whether initiated from the onset or after 12 months of galactosemia, demonstrated VEGF immunoreactivity. With the exception of the animals receiving ARI-509 from the beginning of the experiment, all of the galactose-fed animals developed dense cataracts within 6 weeks of the beginning of the galactose diet. Galactitol levels in animals receiving ARI-509 were 86% to 93% lower in red blood cells, retina, and sciatic nerve than those in the other galactose-fed groups., Conclusions: Although ARI-509 and AMG have different abilities to delay or prevent the diabetic-like retinopathy in galactosemic rats, even when substantial retinal microvascular acellularity occurs, both drugs prevent the immunocytochemical expression of VEGF. These results suggest that factors other than hypoxia may be responsible for VEGF expression in the retina, and that aldose reductase inhibitors and AMG have potential roles in preventing such expression and, thus, perhaps preventing retinal neovascularization.
- Published
- 1997
- Full Text
- View/download PDF
38. Diabetic-like retinopathy ameliorated with the aldose reductase inhibitor WAY-121,509.
- Author
-
Robinson WG Jr, Laver NM, Jacot JL, Glover JP, Basso MD, Blouin P, and Hohman TC
- Subjects
- Aldehyde Reductase administration & dosage, Aldehyde Reductase therapeutic use, Animals, Blood Glucose metabolism, Cataract chemically induced, Cataract physiopathology, Cataract prevention & control, Diabetic Retinopathy chemically induced, Diabetic Retinopathy pathology, Erythrocytes metabolism, Female, Galactitol metabolism, Galactose, Glycated Hemoglobin metabolism, Image Processing, Computer-Assisted, Lens, Crystalline drug effects, Lens, Crystalline physiopathology, Polymers metabolism, Random Allocation, Rats, Rats, Sprague-Dawley, Retina metabolism, Retinal Vessels drug effects, Retinal Vessels pathology, Aldehyde Reductase antagonists & inhibitors, Diabetic Retinopathy prevention & control
- Abstract
Purpose: To evaluate the efficacy of WAY-121,509, a potent new aldose reductase inhibitor (ARI), in preventing the retinopathy that develops in the galactose-fed rat model of diabetic ocular complications., Methods: Sprague-Dawley rats were randomized into treatment and duration groups and fed diets with either 50% starch of 50% galactose with or without WAY-121,509 (25 mg/kg body weight per day). Progression of cataracts was monitored by slit-lamp biomicroscopy. After duration of 4, 8, 16, and 24 months, levels of plasma glucose and glycated hemoglobin, as well as erythrocyte and retinal galactose and galactitol, were measured in rats in each group. Retinal vasculatures of the 24-month rats were isolated by elastase digestion and analyzed by computer-assisted morphometry., Results: Mature, diabetic-like cataracts developed within 5 weeks in all the galactose-fed, untreated rats, but only nonprogressive anterior cortical opacities were present in lenses of 85% of the ARI-treated galactosemic animals after 3 months. Plasma glucose remained the same in all groups. Erythrocyte and retinal galactose and glycated (galactosylated) hemoglobin were elevated with galactosemia and were unaffected by ARI treatment. Erythrocyte and retinal galactitol levels were decreased by 91% and 95%, respectively, with inhibitor treatment. At 24 months, capillary length, width, density, the number of microaneurysms, and the percent of capillary length involved in intraretinal microvascular abnormalities, expressed as hypercellular channels with diameters > 20 microns, were significantly increased by galactosemia and were attenuated in the galactose-fed, ARI-treated group., Conclusions: A dose of WAY-121,509 sufficient to reduce retinal polyol levels by 95% ameliorated the development of galactose-induced cataracts and diabetic-like retinopathy but was insufficient to prevent early lens opacifications or all the diabetic-like retinal microangiopathies.
- Published
- 1996
39. Residues affecting the catalysis and inhibition of rat lens aldose reductase.
- Author
-
Carper DA, Hohman TC, and Old SE
- Subjects
- Aldehyde Reductase chemistry, Animals, Binding Sites, Blotting, Western, Catalysis, Electrophoresis, Polyacrylamide Gel, Escherichia coli, Glutamine, Histidine, Humans, Hydrogen-Ion Concentration, Kinetics, Mutagenesis, Site-Directed, NADP metabolism, Rats, Recombinant Proteins, Structure-Activity Relationship, Substrate Specificity, Aldehyde Reductase antagonists & inhibitors, Aldehyde Reductase metabolism, Lens, Crystalline enzymology
- Abstract
Aldose reductase (AR), the first enzyme of the polyol pathway, has been implicated in diabetic complications. Results of recent clinical studies have shown that compounds that inhibit aldose reductase (ARIs) and block the flux of glucose through the polyol pathway have provided benefit to diabetic neuropathic patients. Since many ARIs show broad substrate specificity, emphasis on the structure-function properties of the AR enzyme will help in the refinement and design of future inhibitors. To this end, catalysis and inhibition of rat lens aldose reductase was examined following site-directed mutagenesis. Replacement of tyrosine 48 with phenylalanine (Y48F) resulted in an enzyme form with less than 0.25% activity with DL-glyceraldehyde and no detectable activity with p-nitrobenzaldehyde or xylose, although circular dichroism spectra and NADPH binding affinity were similar to wild-type AR. Mutation of histidine 110 to glutamine (H110Q) also resulted in a less active protein with an approximate 3-fold decrease in kcat for the reduction of DL-glyceraldehyde; slight or no activity was measured with other substrates and an increase of 195-fold over wild type was observed in the Km for glyceraldehyde. H110Q was less sensitive to inhibition by aldose reductase inhibitors. The most dramatic change was seen with imeristat, which showed an 1800-fold increase in IC50. Mutation of cysteine 298 to serine (C298S) affected enzyme function by increasing kcat 2- to 4-fold and increasing Km 15- to 48-fold, with DL-glyceraldehyde, p-nitrobenzaldehyde or xylose as substrates. As a result kcat/Km, catalytic efficiency, dropped to approx. 10% of control. Inhibition of C298S was not noticeably different from wild type. Substitution of histidine 187 or 200 with glutamine (H187Q, H200Q) had little effect on AR catalysis or inhibition. Based on structural and mutagenesis studies of human AR and the conservation of amino acids between human and rat, these data would indicate that Y48, H110, and C298 are important residues in the active site of rat AR and that Y48 is most likely the proton donor during substrate reduction by rat lens aldose reductase. In addition, these studies indicate that mutagenesis of H110 also affects aldose reductase inhibition.
- Published
- 1995
- Full Text
- View/download PDF
40. Na,K-ATPase response to osmotic stress in primary dog lens epithelial cells.
- Author
-
Old SE, Carper DA, and Hohman TC
- Subjects
- Animals, Base Sequence, Blotting, Northern, Blotting, Western, Cells, Cultured, DNA Primers, Dogs, Epithelium enzymology, Humans, Lens, Crystalline cytology, Molecular Sequence Data, Osmolar Concentration, RNA, Messenger metabolism, Sodium-Potassium-Exchanging ATPase genetics, Stress, Physiological, Hypertonic Solutions, Lens, Crystalline enzymology, Sodium-Potassium-Exchanging ATPase metabolism
- Abstract
Purpose: Na,K-ATPase activity increases in lens cells exposed to hypertonic stress. To test whether the increase in activity involves stimulation of Na,K-ATPase expression, dog lens epithelial cells were subjected to hypertonic stress, and the time course of Na,K-ATPase protein and mRNA response was measured., Methods: Primary cultures of dog lens epithelial cells were maintained in isotonic or hypertonic media over the course of several days. Rubidium-86 uptake measurements, immunoreactive protein, and northern blot analysis were performed., Results: Dog lens epithelial cells exposed to hypertonic stress from culture medium supplemented with 150 mM NaCl or 250 mM cellobiose showed a twofold increase in Na,K-ATPase activity. The increase in activity was blocked by cycloheximide and was reversible when the cells were returned to isotonic medium. This activity was unaffected by the aldose reductase inhibitor, tolrestat. Na,K-ATPase protein and mRNA levels increased in cells exposed to medium containing 150 mM NaCl. Northern blot analysis showed that the alpha-1 and beta-1 mRNA levels increased as early as 6 hours and maximally increased 1.5-fold to twofold by 12 to 24 hours., Conclusions: Elevation of Na,K-ATPase activity in dog lens epithelial cells exposed to hypertonic stress was associated with increased expression of Na,K-ATPase subunit mRNAs and was dependent on protein synthesis. These results suggest that upregulation of the enzyme activity is the result of an induction of Na,K-ATPase.
- Published
- 1995
41. Impairment of afferent arteriolar myogenic responsiveness in the galactose-fed rat.
- Author
-
Forster HG, ter Wee PM, Takenaka T, Hohman TC, and Epstein M
- Subjects
- Animals, Arterioles drug effects, Cyclooxygenase Inhibitors, Diabetes Mellitus, Experimental, Diet, Disease Models, Animal, Galactitol metabolism, Galactose administration & dosage, Galactose metabolism, Homeostasis, Hydronephrosis, Ibuprofen pharmacology, In Vitro Techniques, Kidney drug effects, Kidney physiology, Male, Perfusion, Rats, Rats, Sprague-Dawley, Vasoconstriction drug effects, Arterioles physiology, Blood Pressure, Galactose pharmacology, Kidney blood supply, Polymers metabolism
- Abstract
Previous studies from our laboratory have demonstrated impaired afferent arteriolar responsiveness to pressure in rats 4-6 weeks after the induction of diabetes mellitus. Although the responsible mechanisms mediating this renal autoregulatory defect have not been fully defined, increased polyol metabolism has been implicated as a possible factor involved in the pathogenesis of diabetic complications. We therefore investigated the possible role of this metabolic disturbance in renal autoregulation using the galactose-fed rat, a model characterized by increased polyol pathway activity independent of hyperglycemia or insulin deficiency. Hydronephrosis was induced to permit direct visualization of renal microvessels. Pressure-induced vasoconstriction of afferent arterioles was assessed by quantitating vessel diameter following stepwise increments of renal perfusion pressure (RAP; from 80 to 180 mm Hg) in the hydronephrotic kidneys from control rats and rats fed a 50% galactose diet for 2 or 4 weeks. Vessel diameters were measured from video images by computer-assisted image processing. Control rats exhibited progressive afferent arteriolar vasoconstriction when RAP was increased from 80 to 180 mm Hg (-17.3% +/- 1.0%; P < 0.001). In contrast, myogenic responses to increases in pressure were absent in the afferent arterioles of rats fed a 50% galactose diet for either 2 (-4.1% +/- 1.9%; not significant) or 4 weeks (-2.9 +/- 3.4%; not significant). Our demonstration that the impairment of afferent arteriolar responsiveness to increasing RAP in the normoglycemic galactose-fed rat was identical to that observed in the STZ-diabetic rat suggests that increased polyol accumulation may contribute to the impairment of renal autoregulation in the diabetic rat.
- Published
- 1994
- Full Text
- View/download PDF
42. N-substituted spirosuccinimide, spiropyridazine, spiroazetidine, and acetic acid aldose reductase inhibitors derived from isoquinoline-1,3-diones. 2.
- Author
-
Malamas MS and Hohman TC
- Subjects
- Acetates, Acetic Acid, Administration, Oral, Animals, Azetidines, Galactosemias drug therapy, In Vitro Techniques, Isoquinolines administration & dosage, Isoquinolines chemical synthesis, Lens, Crystalline drug effects, Lens, Crystalline enzymology, Magnetic Resonance Spectroscopy, Pyridazines, Rats, Sciatic Nerve drug effects, Sciatic Nerve enzymology, Structure-Activity Relationship, Succinimides, Aldehyde Reductase antagonists & inhibitors, Isoquinolines chemistry, Isoquinolines pharmacology
- Abstract
The isoquinoline-1,3-dione framework featured in our clinical candidate (1) and its congener was used as the template in the design of several new series of aldose reductase inhibitors (ARIs). These series included N'-substituted spirosuccinimide, spiropyridazine, spiroazetidine, and acetic acid analogues. Compounds within these series were evaluated in vitro for their ability to inhibit glyceraldehyde reduction by bovine lens aldose reductase and in vivo by their ability to inhibit galactitol accumulation in the lens and sciatic nerve of galactose-fed rats. The N'-amino- and N'-alkyl-substituted spiro[isoquinoline-4(1H),3'-pyrrolidine]-1,2',3,5'(2H)- tetrones 6 exhibited high oral potency, even though they were devoid of any intrinsic activity for the aldose reductase enzyme. Similar results were observed for the closely related spiropyridazines 8. Both of these groups are also considered to be prodrugs since they exhibited good oral potency, even though they were devoid of any intrinsic activity for the aldose reductase enzyme. In contrast, the isoquinoline-1,3-dione acetic acids 9 exhibited very high intrinsic activity for the aldose reductase enzyme, although minimal or no in vivo activity. The absence of in vivo activity for some of these compounds may be due to poor tissue penetration. In support of this suggestion, the more lipophilic acetyl alkyl carbamate derivatives of these isoquinoline-1,3-dione acetic acids, exhibited enhanced oral potency. The spiroazetidines 7 exhibited good activity for the aldoe reductase enzyme in both the in vitro and in vivo assays. The findings of this study demonstrate the utility of the isoquinoline-1,3-dione framework, as a versatile template for the design of divese series of potent ARIs.
- Published
- 1994
- Full Text
- View/download PDF
43. Novel spirosuccinimide aldose reductase inhibitors derived from isoquinoline-1,3-diones: 2-[(4-bromo-2-fluorophenyl)methyl]-6- fluorospiro[isoquinoline-4(1H),3'-pyrrolidine]-1,2',3,5'(2H)-tetrone and congeners. 1.
- Author
-
Malamas MS, Hohman TC, and Millen J
- Subjects
- Aldehyde Reductase blood, Animals, Blood Glucose metabolism, Cattle, Diabetes Mellitus, Experimental metabolism, Dogs, Drug Evaluation, Preclinical, Erythrocytes enzymology, Galactitol metabolism, Galactosemias drug therapy, Galactosemias metabolism, Glyceraldehyde metabolism, In Vitro Techniques, Isoquinolines chemical synthesis, Isoquinolines chemistry, Isoquinolines therapeutic use, Lens, Crystalline drug effects, Lens, Crystalline metabolism, Male, Oxidation-Reduction, Rats, Rats, Sprague-Dawley, Sciatic Nerve drug effects, Sciatic Nerve metabolism, Spiro Compounds chemical synthesis, Spiro Compounds chemistry, Spiro Compounds therapeutic use, Stereoisomerism, Aldehyde Reductase antagonists & inhibitors, Diabetes Mellitus, Experimental drug therapy, Isoquinolines pharmacology, Spiro Compounds pharmacology
- Abstract
The high concentrations of plasma glucose formed during diabetic hyperglycemia rapidly translate into high levels of glucose in tissues where glucose uptake is independent of insulin. In these tissues that include the lens, retina, nerve, and kidney, this excess glucose enters the sorbitol (polyol) pathway. The first enzyme in this pathway, aldose reductase, reduces glucose to sorbitol. The diabetes-induced increased flux of glucose through the polyol pathway is believed to play an important role in the development of certain chronic complications of diabetes mellitus. Compounds that inhibit aldose reductase activity and block the flux of glucose through the polyol pathway prevent the development of neuropathy and nephropathy in diabetic animals and interrupt the progression of neuropathy in diabetic patients. Here we describe the preparation and characterization of novel aldose reductase inhibitors. These spiro[isoquinoline-4(1H),3'-pyrrolidine]-1,2',3,5'-(2H)-tetrones, based on the isoquinoline-1,3-dione framework, were evaluated in vitro for their ability to inhibit glyceraldehyde reduction, using a partially purified bovine lens aldose reductase preparation, and in vivo for their ability to inhibit galactitol accumulation in the lens and sciatic nerve of galactose-fed rats. Substitution at the N-2 position of the isoquinoline-1,3-dione framework with diverse structural substituents (i.e., aralkyl, benzothiazolylmethyl, methyl) produced several excellent series of ARIs. Optimization of these new series of spirosuccinimides through structure-activity relationship (SAR) studies, including analogy from other drug series (ponalrestat, zopolrestat), led to the design of the clinical candidate 2-[(4-bromo-2-fluorophenyl)methyl]-6-fluorospiro[isoquinoline-4(1H ),3'- pyrrolidine]-1,2',3,5'(2H)-tetrone (41). Compound 41 exhibited exceptional oral potency in two animal models of diabetic complications, the 14-day galactose-fed and streptozocin-induced diabetic rats, with ED50 values for the sciatic nerve of 0.1 and 0.09 mg/kg/day, respectively. Both enantiomeric forms of 41 exhibited similar inhibitory activity in both in vitro and in vivo assays possibly due to their rapid interconversion. In an ex vivo experiment, the pharmacodynamic effect of 41 in the plasma of rats and dogs, after a single dose, appeared to be comparable to that of tolrestat.
- Published
- 1994
- Full Text
- View/download PDF
44. Hydrolase compartmentalization limits rate of digestion in Acanthamoeba.
- Author
-
Hohman TC and Bowers B
- Subjects
- Acanthamoeba enzymology, Animals, Cell Compartmentation, Muramidase metabolism, Phagosomes metabolism, Saccharomyces cerevisiae metabolism, Acanthamoeba metabolism, Hydrolases metabolism
- Abstract
The kinetics of lysosomal enzyme acquisition by newly formed phagosomes was studied by following the rate of digestion of radiolabeled yeast fed to Acanthamoeba. The distribution of hydrolases among phagosomes was assessed by electron microscopic acid phosphatase cytochemistry and by measurement of three glycosidases in isolated early and late phagosomes. The results show that compartmentalization of hydrolases limit the digestion of large phagocytic loads. The hydrolases appear to be sequestered into the early phagosomes and not to be distributed either by small vesicle transport or phagosome-phagosome fusion to those formed later. We infer from these results that newly internalized surface membrane in phagosomes is not rapidly randomized with internal pools, but is recycled to the surface as a function of the digestive process.
- Published
- 1993
- Full Text
- View/download PDF
45. Effect of hyperglycemia and the aldose reductase inhibitor tolrestat on sural nerve biochemistry and morphometry in advanced diabetic peripheral polyneuropathy. The Tolrestat Study Group.
- Author
-
Sima AA, Greene DA, Brown MB, Hohman TC, Hicks D, Graepel GJ, Bochenek WJ, Beg M, and Gonen B
- Subjects
- Axons ultrastructure, Biopsy, Blood Glucose metabolism, Diabetes Mellitus, Type 1 metabolism, Diabetes Mellitus, Type 1 physiopathology, Diabetes Mellitus, Type 2 metabolism, Diabetes Mellitus, Type 2 physiopathology, Diabetic Neuropathies metabolism, Double-Blind Method, Erythrocytes metabolism, Female, Glucose metabolism, Humans, Hyperglycemia metabolism, Male, Microscopy, Electron, Middle Aged, Neural Conduction, Neuroglia pathology, Neuroglia ultrastructure, Sorbitol blood, Sural Nerve metabolism, Sural Nerve pathology, Aldehyde Reductase antagonists & inhibitors, Diabetic Neuropathies drug therapy, Diabetic Neuropathies physiopathology, Hyperglycemia physiopathology, Naphthalenes therapeutic use, Peripheral Nerves physiopathology, Sural Nerve physiopathology
- Abstract
Tolrestat is a well tolerated nonhydantoin aldose reductase inhibitor that has been reported to improve nerve conduction in diabetic animals and humans. Its effects on nerve biochemistry and structure have not been studied in patients with diabetic neuropathy. Patients with advanced diabetic neuropathy treated with long-term open-label tolrestat were randomly assigned to continuation on drug treatment or to placebo-controlled drug withdrawal for 12 months. At the end of this period, sural nerve biopsies were obtained for measurement of glucose, sorbitol, and fructose content, and for detailed morphometric analysis. Tolrestat ameliorated the glucose-mediated increase in sorbitol and fructose in sural nerve tissue. No statistically significant differences in nerve morphometry emerged between the two groups; however, both treatment groups exhibited increased nerve-fiber regeneration and normalization of axo-glial dysfunction and segmental demyelination following long-term tolrestat treatment. These findings are similar to those previously reported in a placebo-controlled sequential nerve biopsy study with the aldose reductase inhibitor sorbinil. Thus tolrestat is a biochemically effective aldose reductase inhibitor in human diabetic nerve with potential therapeutic efficacy for diabetic neuropathy.
- Published
- 1993
- Full Text
- View/download PDF
46. Novel spirosuccinimides with incorporated isoindolone and benzisothiazole 1,1-dioxide moieties as aldose reductase inhibitors and antihyperglycemic agents.
- Author
-
Wrobel J, Dietrich A, Woolson SA, Millen J, McCaleb M, Harrison MC, Hohman TC, Sredy J, and Sullivan D
- Subjects
- Animals, Blood Glucose metabolism, Cattle, Diabetes Mellitus, Experimental blood, Diabetes Mellitus, Experimental drug therapy, Glyceraldehyde metabolism, Hypoglycemic Agents pharmacology, Hypoglycemic Agents therapeutic use, Indoles pharmacology, Male, Mice, Mice, Inbred C57BL, Molecular Structure, Rats, Structure-Activity Relationship, Succinimides pharmacology, Succinimides therapeutic use, Thiazoles pharmacology, Thiazoles therapeutic use, Aldehyde Reductase antagonists & inhibitors, Hypoglycemic Agents chemical synthesis, Indoles chemical synthesis, Succinimides chemical synthesis, Thiazoles chemical synthesis, Thiazolidinediones
- Abstract
Compounds from two novel series of spirosuccinimides were prepared. Analogs of series 2 possessed a spiro-fused isoindolone moiety while those of series 3 contained a spiro-fused benzisothiazole S,S-dioxide group. These compounds were evaluated as aldose reductase inhibitors (ARI) in vitro by their ability to inhibit glyceraldehyde reduction using a partially purified bovine lens aldose reductase preparation and in vivo as inhibitors of galactitol accumulation in the lens, sciatic nerve, and diaphragm of galactose-fed rats. Many members from the isoindolone series 2, particularly those containing an isoindolone N-methyl moiety, showed good in vitro and in vivo potency. The most potent member, the 6-chloro analog 32, was resolved, and aldose reductase activity was found to reside almost exclusively in the (+)-enantiomer. Compound 32 was approximately equipotent in the sciatic nerve of the galactose-fed rat to other cyclic imide ARI's of similar in vitro activity, namely sorbinil and ADN-138 and also to tolrestat, an acetic acid-based ARI (ED50's 4-8 mg/kg). Compounds from both series, 2 and 3, were also found to lower plasma glucose levels of genetically obese db/db and ob/ob mice with potency similar to that of ciglitazone. However, members from these series failed to lower insulin levels of the ob/ob mouse at the doses tested.
- Published
- 1992
- Full Text
- View/download PDF
47. Hypertonic stress induces alpha B-crystallin expression.
- Author
-
Dasgupta S, Hohman TC, and Carper D
- Subjects
- Animals, Blotting, Western, Cells, Cultured, Crystallins genetics, Dogs, Electrophoresis, Polyacrylamide Gel, Endothelium metabolism, Epithelium metabolism, Gene Expression Regulation, Kidney Glomerulus metabolism, Osmolar Concentration, RNA metabolism, RNA, Messenger metabolism, Stress, Physiological, Crystallins metabolism, Hypertonic Solutions, Lens, Crystalline metabolism
- Abstract
Alpha B-crystallin, a major lens protein, was induced in primary cultures of dog lens epithelial cells and glomerular endothelial cells when they were grown under conditions of hypertonic stress. With Western blot analysis using a specific alpha B-crystallin antibody, we observed a significant increase in the concentration of alpha B-crystallin protein in cells grown for 4-6 days in media supplemented with 150 mM NaCl or 250 mM cellobiose. These supplements increased the osmolarity of the medium from 300 to 550-600 mosmol kg-1. Alpha B-crystallin mRNA was also increased reaching a maximum four-fold increase in lens and 16-fold increase in kidney cells within 1-2 days. These studies demonstrate a type of regulation of alpha B-crystallin expression in cells from lenticular and non-lenticular tissues.
- Published
- 1992
- Full Text
- View/download PDF
48. Osmotic stress induces aldose reductase in glomerular endothelial cells.
- Author
-
Hohman TC, Carper D, Dasgupta S, and Kaneko M
- Subjects
- Aldehyde Reductase genetics, Aldehyde Reductase isolation & purification, Animals, Blotting, Western, Cell Division, Cell Survival, Cells, Cultured, Dogs, Electrophoresis, Polyacrylamide Gel, Endothelium cytology, Endothelium enzymology, Enzyme Induction, Kidney Glomerulus cytology, Kinetics, Naphthalenes pharmacology, Osmolar Concentration, RNA genetics, RNA isolation & purification, Sodium Chloride pharmacology, Aldehyde Reductase biosynthesis, Kidney Glomerulus enzymology
- Published
- 1991
- Full Text
- View/download PDF
49. Induction of aldose reductase expression in rat kidney mesangial cells and Chinese hamster ovary cells under hypertonic conditions.
- Author
-
Kaneko M, Carper D, Nishimura C, Millen J, Bock M, and Hohman TC
- Subjects
- Aldehyde Reductase metabolism, Animals, Cells, Cultured, Cricetinae, Cricetulus, Female, Gene Expression Regulation, Enzymologic physiology, Glomerular Mesangium drug effects, Glomerular Mesangium enzymology, Hypertonic Solutions, Male, Ovary drug effects, Ovary enzymology, RNA, Messenger genetics, RNA, Messenger metabolism, Rats, Rats, Inbred Strains, Aldehyde Reductase genetics, Gene Expression Regulation, Enzymologic drug effects, Glomerular Mesangium cytology, Oligosaccharides pharmacology, Ovary cytology, Raffinose pharmacology, Sodium Chloride pharmacology, Sorbitol pharmacology, Sugar Alcohol Dehydrogenases genetics
- Abstract
Rat kidney cortex mesangial cells (MES) and Chinese hamster ovary cells (CHO) responded to hypertonicity (600 mosmol/kg) in culture by accumulating sorbitol. The accumulation of sorbitol was due to increased aldose reductase (AR) activity, apparently brought about by increased levels of AR mRNA and protein. The levels of AR mRNA increased approximately 60-fold in MES cells and 30-fold in CHO cells by 24 h in culture media (300 mosmol/kg supplemented with 150 mM NaCl, 600 mosmol/kg total). AR activity also markedly increased (14- to 16-fold above control), but MES took 4 days and CHO 6 days to reach this maximum. Other osmolytes, raffinose and sorbitol (at concentrations of 250 to 300 mM) elicited the same response as that of 150 mM NaCl. These data show that AR expression is induced in MES and CHO cells under hypertonic conditions. Of special interest is the induction of large amounts of AR in rat kidney cortex mesangial cells, a target tissue of diabetes and a site where excessive accumulation of sorbitol is suspected to be a critical factor in diabetic nephropathy.
- Published
- 1990
- Full Text
- View/download PDF
50. Polyol and vacuole formation in cultured canine lens epithelial cells.
- Author
-
Nagata M, Hohman TC, Nishimura C, Drea CM, Oliver C, and Robison WG Jr
- Subjects
- Aldehyde Reductase antagonists & inhibitors, Animals, Cell Division drug effects, Dogs, Epithelium drug effects, Epithelium metabolism, Epithelium ultrastructure, Galactose pharmacology, Glucose pharmacology, Imidazoles pharmacology, Lens Capsule, Crystalline drug effects, Lens Capsule, Crystalline ultrastructure, Microscopy, Electron, Ampholyte Mixtures metabolism, Buffers metabolism, Imidazolidines, Lens Capsule, Crystalline metabolism, Lens, Crystalline metabolism, Polymers metabolism, Vacuoles physiology
- Abstract
Polyol accumulation and myo-inositol depletion were accompanied by extensive vacuole formation in cultured canine lens epithelial cells that were incubated for up to 96 hr in growth medium supplemented with 30 mM D-galactose or 30 mM D-glucose. These changes did not occur in cells incubated in a hypergalactosemic or hyperglycemic medium which also contained an aldose reductase inhibitor (20 microM sorbinil). In addition, these changes were not observed in lens cells incubated in growth medium supplemented with either 30 mM mannitol, which is known to enter cells only slowly, or in 30 mM L-galactose, which is not a substrate for aldose reductase. The vacuoles were visible at the ultrastructural level after 6 hr of incubation in 30 mM D-galactose and increased in both number and size with time. These vacuoles had a unique fine structure. They did not result from swelling of mitochondria or other cell organelles. As demonstrated cytochemically, they did not represent either lysosomes or Golgi saccules. The proliferation pattern of cells incubated with 30 mM D-galactose was clearly different from that of control cells, but approached normal when an aldose reductase inhibitor was added to the incubation medium. Together these findings suggest that vacuole formation and altered cell proliferation were caused by polyol accumulation and/or myo-inositol loss, both of which result from aldose reductase activity.
- Published
- 1989
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.