Ahad Noor Khan Yusufi

Protective effect of green tea extract on gentamicin-induced nephrotoxicity and oxidative damage in rat kidney

Gentamicin (GM) is an effective aminoglycoside antibiotic against severe infections but nephrotoxicity and oxidative damage limits its long term clinical use. Various strategies were attempted to ameliorate GM nephropathy but were not found suitable for clinical practice. Green tea (GT) polyphenols have shown strong chemopreventive and chemotherapeutic effects against various pathologies. We hypothesized that GT prevents GM nephrotoxicity by virtue of its antioxidative properties. A nephrotoxic dose of GM was co-administered to control and GT-fed male Wistar rats. Serum parameters and enzymes of oxidative stress, brush border membrane (BBM), and carbohydrate metabolism were analyzed. GM increased serum creatinine, cholesterol, blood urea nitrogen (BUN), lipid peroxidation (LPO) and suppressed superoxide dismutase (SOD) and catalase activities in renal tissues. Activity of hexokinase, lactate dehydrogenase increased whereas malate dehydrogenase decreased. Gluconeogenic enzymes and glucose-6-phosphate dehydrogenase were differentially altered in the cortex and medulla. However, GT given to GM rats reduced nephrotoxicity parameters, enhanced antioxidant defense and energy metabolism. The activity of BBM enzymes and transport of Pi declined by GM whereas GT enhanced BBM enzymes and Pi transport. In conclusion, green tea ameliorates GM elicited nephrotoxicity and oxidative damage by improving antioxidant defense, tissue integrity and energy metabolism.

Time dependent effects of gentamicin on the enzymes of carbohydrate metabolism, brush border membrane and oxidative stress in rat kidney tissues

Gentamicin (GM), an antibiotic against life threatening bacterial infection, induces remarkable toxicity in the kidney. Histological studies have indicated that mitochondria, microsomes, lysosomes and plasma membranes of renal proximal convoluted tubules in particular are major GM targets. Despite numerous investigations, the biochemical/cellular basis of GM nephrotoxicity is not well understood. Recently reactive oxygen species (ROS) are considered to be important mediators of GM-induced nephrotoxicity. We hypothesize that GM causes damage to intracellular organelles and affects their structural integrity and alters metabolic and other functional capabilities. To address above hypothesis a long-term, time-dependent effect of GM has been studied on blood/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM) and basolateral (BLM), lysosomes and oxidative stress in renal tissues. A nephrotoxic dose of GM (80 mg/kg body weight) was administered to rats daily for 15 days. The long-term treatment with GM induced a significant increase in serum creatinine, blood urea nitrogen followed by massive proteinuria, glucosuria, enzymuria along with loss of electrolytes in the urine. The activities of the enzymes of carbohydrate metabolism, plasma membranes, lysosomes significantly declined. The activities of antioxidant enzymes e.g. superoxide dismutase, catalase and glutathione peroxidase were severely depressed and lipid peroxidation was significantly increased in the renal cortex and medulla. We conclude that GM administration induced oxidative damage to renal tissues that resulted in impaired carbohydrate metabolism and decreased activities of BBM, BLM and lysosomes associated with increased lipid peroxides.

Studies on the protective effect of green tea against cisplatin induced nephrotoxicity

Cisplatin (CP) an anticancer drug is known to induce nephrotoxicity, which limits its long-term clinical use. Green tea (GT), consumed since ancient times is known for its numerous health benefits. It has been shown to improve kidney functions in animal models of acute renal failure. The present study was undertaken to see whether GT can prevent CP-induced nephrotoxic and other deleterious effects. A nephrotoxic dose of CP was co-administered to control and GT-fed male Wistar rats every fifth day for 25 days. The effect of GT was determined on CP-induced alterations in various serum parameters and on enzymes of carbohydrate metabolism, brush border membrane, and antioxidant defense system in renal cortex and medulla. CP nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. CP increased the activities of lactate dehydrogenase and acid phosphatase whereas, the activities of malate dehydrogenase, glucose-6-phosphatase, superoxide dismutase, catalase, and (32)Pi transport significantly decreased. GT consumption increased the activities of the enzymes of carbohydrate metabolism, brush border membrane, oxidative stress, and (32)Pi transport. GT ameliorated CP-induced nephrotoxic and other deleterious effects due to its intrinsic biochemical/antioxidant properties.

Effect of uranyl nitrate on enzymes of carbohydrate metabolism and brush border membrane in different kidney tissues

Uranium, the heaviest of the naturally occurring elements is widely present as environmental contaminant from natural deposits, industrial emissions and most importantly from modern weapons. Histopathological examinations revealed that uranyl nitrate (UN) exposure caused severe damage to pars recta of renal proximal tubule. However, biochemical events involved in cellular response to renal injury are not completely elucidated. We hypothesized that UN exposure would severely damage kidney tissues and alter their metabolic functions. Rats were treated with a single nephrotoxic dose of UN (0.5mg/kg body weight) i.p. After 5d, effect of UN was studied on the activities of various enzymes of carbohydrate metabolism, brush border membrane (BBM) and oxidative stress in different kidney tissues. Activity of lactate dehydrogenase increased whereas activities of isocitrate, succinate and malate dehydrogenases, glucose-6-phosphatase and fructose-1,6-bisphosphatase significantly decreased by UN exposure. Activity of glucose-6-phosphate dehydrogenase decreased whereas that of NADP-malic enzyme increased. The activities of BBM enzymes were significantly lowered and after dissociation from BBM excreted in urine. Lipid peroxidation and the activities of superoxide dismutase and glutathione peroxidase increased whereas catalase activity decreased by UN. UN treatment caused specific alterations in the activities of metabolic and membrane enzymes and perturbed antioxidant defenses.

Effect of cisplatin on renal brush border membrane enzymes and phosphate transport

Cisplatin (CDDP) is widely used in the treatment of various cancers but its clinical use is associated with dose limiting nephrotoxicity. The present work was carried out to study the effect of administration of CDDP on rat renal brush border membrane (BBM) marker enzymes and inorganic phosphate (Pi) transport across BBM vesicles (BBMV). Animals were administered a single intraperitoneal dose of CDDP (6 mg/kg body weight) or normal saline and then sacrificed 2, 4, 8 and 16 days after this treatment. The administration of CDDP resulted in increased serum creatinine and blood urea nitrogen levels and decreased activity of BBM marker enzymes in the BBM as well as in the homogenates of cortex and medulla. Kinetic studies showed that the Vmax of the enzymes was decreased in BBM from CDDP treated rats while the Km remained unchanged. The Na+-gradient dependent transport of Pi across BBMV was also significantly reduced after CDDP treatment. These results strongly suggest that the administration of a single nephrotoxic dose of CDDP results in impairment of the functions of renal BBM.

Effect of reversible and irreversible ischemia on marker enzymes of BBM from renal cortical PT subpopulations

The effect of the reversible and relatively irreversible ischemia induced acute renal failure (ARF) in the activities of alkaline phosphatase (AlkPase) and γ-glutamyltransferase (GGTase) after early (15-30 min) and prolonged (45-60 min) ischemia in the homogenates, and the brush-border membranes (BBM) from rat renal whole, superficial (SC), and juxtamedullary (JMC) cortices were studied. The enzyme activities declined progressively in proportion to the duration of ischemia. Early blood reflow of 15 min to the ischemic rats caused a further decrease in the enzyme activities. However, prolonged reflow (up to 120 min) resulted in partial reversal of the ischemic effect in the early but not in the prolonged ischemic rats. The decrease in the enzyme activities was due to the loss of membrane-bound enzyme components from the damaged BBM into the supernatant fraction as membrane-free enzymes. The activities of AlkPase and GGTase were significantly more decreased by the ischemia in the brush-border membrane vesicles (BBMV)-JMC than in BBMV-SC. The rate of recovery due to reflow for AlkPase was greater in BBMV-SC than apparently for GGTase in BBMV-JMC in early ischemic (15-30 min) rats.

Influence of ramadan-type fasting on enzymes of carbohydrate metabolism and brush border membrane in small intestine and liver of rat used as a model

During Ramadan, Muslims the world over abstain from food and water from dawn to sunset for a month. We hypothesised that this unique model of prolonged intermittent fasting would result in specific intestinal and liver metabolic adaptations and hence alter metabolic activities. The effect of Ramadan-type fasting was studied on enzymes of carbohydrate metabolism and the brush border membrane of intestine and liver from rat used as a model. Rats were fasted (12 h) and then refed (12 h) daily for 30 d, as practised by Muslims during Ramadan. Ramadan-type fasting caused a significant decline in serum glucose, cholesterol and lactate dehydrogenase activity, whereas inorganic phosphate increased but blood urea N was not changed. Fasting resulted in increased activities of intestinal lactate (+34%), isocitrate (+63%), succinate (+83%) and malate (+106%) dehydrogenases, fructose 1,6-bisphosphatase (+17%) and glucose-6-phosphatase (+22%). Liver lactate dehydrogenase, malate dehydrogenase, glucose-6-phosphatase and fructose 1,6-bisphosphatase activities were also enhanced. However, the activities of glucose-6-phosphate dehydrogenase and malic enzyme fell significantly in the intestine but increased in liver. Although the activities of alkaline phosphatase, gamma-glutamyl transpeptidase and sucrase decreased in mucosal homogenates and brush border membrane, those of liver alkaline phosphatase, gamma-glutamyl transpeptidase and leucine aminopeptidase significantly increased. These changes were due to a respective decrease and increase of the maximal velocities of the enzyme reactions. Ramadan-type fasting caused similar effects whether the rats fasted with a daytime or night-time feeding schedule. The present results show a tremendous adaptation capacity of both liver and intestinal metabolic activities with Ramadan-type fasting in rats used as a model for Ramadan fasting in people.

Studies on the effect of sodium arsenate on the enzymes of carbohydrate metabolism, brush border membrane, and oxidative stress in the rat kidney.

Arsenic is an environmental pollutant and its contamination in drinking water poses serious world wide environmental health threats. It produces multiple adverse effects in various tissues, including the kidney. However, biochemical mechanism and renal response to its toxic insult are not completely elucidated. We hypothesized that sodium arsenate (ARS) induces oxidative stress and alters the structure and metabolic functions of kidney. Male Wistar rats were administered ARS (10 mg/kg body weight/day), intraperitoneally daily for 10 days. ARS administration increased blood urea nitrogen, serum creatinine, cholesterol, glucose, and phospholipids but decreased inorganic phosphate, indicating kidney toxicity. The activity of brush border membrane (BBM) enzymes significantly lowered in both cortex and medulla. Activity of hexokinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenases, and NADP-malic enzyme significantly increased whereas malate dehydrogenase, glucose-6-phosphatase, and fructose 1,6 bis phosphatase decreased by ARS exposure. The activity of superoxide dismutase, GSH-peroxidase, and catalase were selectively altered in renal tissues along with an increase in lipid peroxidation. The present results indicated that ARS induced oxidative stress caused severe renal damage that resulted in altered levels of carbohydrate metabolism and BBM enzymes.

Influence of Ramadan-type fasting on carbohydrate metabolism, brush border membrane enzymes and phosphate transport in rat kidney used as a model.

Ramadan fasting is a unique model of fasting in which Muslims the world over abstain from food and water from dawn to sunset for 1 month. We hypothesized that this model of prolonged intermittent fasting would result in specific adaptive alterations in rat kidney to keep a positive balance of metabolites and inorganic phosphate (Pi). The effect of Ramadan-type fasting was studied on enzymes of carbohydrate metabolism and brush border membrane (BBM) and BBM uptake of 32Pi in different renal tissue zones in the rat model. Rats were fasted (12 h) and then re-fed (12 h) daily for 30 d similar to human Ramadan fasting. Ramadan-type fasting resulted in increased serum Pi and phospholipids, whereas Pi clearance decreased. Serum creatinine and its clearance were not affected. Fasting caused a significant decrease in the activities of lactate and malate dehydrogenases, glucose-6-phosphatase and fructose-1,6-bisphosphatase, both in the renal cortex and medulla. However, the activity of glucose-6-phosphate dehydrogenase profoundly increased but that of malic enzyme decreased. The activities of alkaline phosphatase and gamma-glutamyl transpeptidase in BBM decreased, whereas transport of 32Pi significantly increased. The decrease in enzyme activities and increase in 32Pi transport were due to alterations of both maximal velocities and relative affinities. The results indicate that Ramadan-type fasting caused specific metabolic alterations with enhanced Pi conservation in different kidney tissues in a rat model used for Ramadan fasting in man.

Effect of Fasting on Enzymes of Carbohydrate Metabolism, Brush Border Membrane and on Transport Functions in Superficial and Juxta-Medullary Cortex of Rat Kidney

The effect of 1, 3 and 5-day fasting was studied on serum parameters; enzymes of brush border membrane and carbohydrate metabolism; transport of Pi and proline in different parts of the rat kidney. Fasting decreased the activities of lactate dehydrogenase, malate dehydrogenase but increased the activities of glucose-6-phosphatase and fructose 1,6-bisphosphatase; glucose-6-phosphate dehydrogenase and malic enzyme. These observations suggest that the degradation of glucose is decreased but its production by gluconeogenesis is enhanced upon fasting. Fasting led to significant decrease in the specific activities of Brush Border Membrane (BBM) enzymes, alkaline phosphatase and γ-glutamyl transferase in BBM vesicles prepared from superficial and juxta-medullary cortex. The transport of Pi was also decreased albeit differentially in these BBM preparations. Kinetic studies revealed that the activity of BBM enzymes and Pi transport decreased due to changes in Vmax and Km values. The results show that fasting caused significant decrease in metabolic enzymes involved in energy generation that led to decreased transport functions of the kidney.