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ABSTRACT: Retinoids are important mediators of cellular differentiation and proliferation in various epithelia of the body including the small intestine. Though alterations in intestinal epithelial cell proliferation have been noted in liver cirrhosis, mechanisms involved in the process are not well understood. This study examined the levels of various retinoids and retinoid-metabolizing enzymes in the small intestine during development of liver cirrhosis.
Four groups of animals were used (control, phenobarbitone control, thioacetamide and carbon tetrachloride treatment). Twice-weekly intragastric or i.p. administration of carbon tetrachloride or thioacetamide, respectively, produced liver cirrhosis after 3 months, which was confirmed through histology and serum markers. Retinoid levels were measured by high-performance liquid chromatography.
A decrease in the levels of retinal, retinoic acid and retinol was evident in the intestine by 3 months, when cirrhosis was evident histologically, and these remained low until 6 months. A decrease in the activities of retinaldehyde oxidase, retinaldehyde reductase and retinol dehydrogenase was also seen in intestine from cirrhotic rats.
These results suggest that altered retinoid metabolism in the intestine of cirrhotic rats might have an influence on changes in intestinal epithelial cell differentiation, seen in liver cirrhosis.
Journal of Gastroenterology and Hepatology 03/2009; 24(5):821-9. · 2.87 Impact Factor
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ABSTRACT: Oxidative stress and mitochondrial dysfunction have been implicated in the pathogenesis of indomethacin-induced enteropathy. We evaluated the potential of curcumin, a known cytoprotectant, as an agent to protect against such effects. Rats were pretreated with curcumin (40 mg/kg by intra-peritoneal injection) before administration of indomethacin (20 mg/kg by gavage). One hour later, the small intestine was isolated and used for assessment of parameters of oxidative stress. Mitochondria, brush border membranes (BBM) and surfactant-like particles (SLP) were also isolated from the tissue. Mitochondria were used for assessment of functional integrity, estimation of products of lipid peroxidation and lipid content. BBM were used for estimation of products of lipid peroxidation and lipid content, while the SLP were used for measurement of lipid content. The results showed that oxidative stress and mitochondrial dysfunction occurred in the small intestine of indomethacin-treated rats. Pre-treatment with curcumin was found to ameliorate these drug-induced changes. Significant changes were seen in some of the lipids in the mitochondria, BBM and SLP in response to indomethacin. However, curcumin did not have any significant effect on these drug-induced changes. We conclude that curcumin, by attenuating oxidative stress and mitochondrial dysfunction, holds promise as an agent that can potentially reduce NSAID-induced adverse effects in the small intestine.
Archive für Toxikologie 08/2008; 82(7):471-81. · 4.67 Impact Factor
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ABSTRACT: Spontaneous bacterial peritonitis (SBP) is a major complication of liver cirrhosis and accounts for significant mortality. Although oxygen free radicals and nitric oxide been implicated in the pathophysiology of liver cirrhosis, information on their role during the development of SBP is scarce. This study examined these active species in ascitic fluid from patients with SBP, and in response to treatment.
Forty-nine consecutive patients with cirrhosis and ascitic fluid neutrophil counts less than 250/cumm were studied as controls. Another 21 patients whose ascitic neutrophil count exceeded 250/cumm were treated as cases. Ascitic fluid was collected from these patients at entry and 48 h after treatment with antibiotics. Nitrate and markers of oxidative stress such as malondialdehyde, protein carbonyl content and total and protein thiols were measured.
A significant increase in malondialdehyde and protein carbonyl levels was seen in ascites from patients with SBP when compared to controls. This was accompanied by a decrease in total thiols and protein thiols. In addition, there was a significant increase in ascitic fluid nitrate in patients with SBP when compared to control patients. After antibiotic treatment, malondialdehyde, protein carbonyl and nitrate levels dropped back towards control values, and total thiols also recovered.
This study demonstrated the presence of oxidative stress in ascitic fluid from patients with SBP, and showed that ascitic fluid nitrate may be a marker for diagnosing SBP and a useful index in determining therapeutic response to antibiotic treatment.
Journal of Gastroenterology and Hepatology 03/2007; 22(2):177-81. · 2.87 Impact Factor
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ABSTRACT: Hepatic microvesicular steatosis is a clinical manifestation seen in a number of liver diseases. Although the role of mitochondrial beta-oxidation in the development of the disease has been well studied, information on lipid peroxidative damage in liver subcellular organelles is scarce. The present study looked at oxidative stress in hepatic peroxisomes and microsomes in microvesicular steatosis, using an animal model of the disease.
Rats were given i.p. injections of sodium valproate (700 mg/kg bodyweight) to induce microvesicular steatosis, which was confirmed by histology.
Oxidative stress was evident in liver in steatosis, accompanied by structural and functional alterations in hepatic mitochondria. Alterations in lipid composition, with decreased phosphatidyl choline and ethanolamine and increased lysophosphatidyl choline and ethanolamine, were seen. An increase in triglyceride content was also seen. In addition, increased lipid peroxidation was also evident in peroxisomes and microsomes from steatotic rats. Pretreatment with clofibrate results in partial reversal of changes produced by valproate.
These results suggest that in addition to impaired mitochondrial beta-oxidation, oxidative stress is also seen in the hepatic peroxisomes and microsomes during microvesicular steatosis.
Journal of Gastroenterology and Hepatology 09/2006; 21(8):1240-9. · 2.87 Impact Factor
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ABSTRACT: Cirrhosis with ascites is associated with impaired renal function accompanied by sodium and water retention. Although it has been suggested that mediators such as nitric oxide play a role in the development of renal failure in this situation, other mechanisms underlying the process are not well understood. This study examined the role of oxidative stress in mediating renal damage during the development of cirrhosis in order to understand mechanisms involved in the process. It was shown that carbon tetrachloride- or thioacetamide-induced cirrhosis in rats results in oxidative stress in the kidney as seen by increased lipid peroxidation and protein oxidation, accompanied by altered antioxidant status. Cirrhosis was also found to affect renal mitochondrial function, as assessed by measurement of the respiratory control ratio, the swelling of mitochondria, and calcium flux across mitochondrial membranes. Increased lipid peroxidation and changes in lipid composition were evident in the renal brush border membranes, with compromised transport of 14C glucose across these membranes. In conclusion, renal alterations produced as a result of cirrhosis in the rat are possibly mediated by oxidative stress.
Hepatology 07/2006; 43(6):1248-56. · 11.66 Impact Factor
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ABSTRACT: Oxidative stress has been implicated in liver cirrhosis. Carbon tetrachloride and thioacetamide are the most widely used models to develop cirrhosis in rats and the present study compares oxidative stress in the liver induced by these compounds at different stages of cirrhosis development.
Twice-weekly intragastric or intraperitoneal administration of carbon tetrachloride or thioacetamide, respectively, produced liver cirrhosis after 3 months. Histology, serum markers and hepatic hydroxy proline content confirmed the cirrhosis.
An increase in oxidative stress parameters was seen in mitochondria, peroxisomes and microsomes from the liver after carbon tetrachloride or thioacetamide treatment. Oxidative stress was more severe in carbon tetrachloride treated animals than thioacetamide. Mild oxidative stress was evident at 1 and 2 months of treatment and a significant increase was seen by 3 months of treatment with either compound. By this time, frank liver cirrhosis was also observed.
These results suggest that evidence of oxygen free radicals is also found early in the development of fibrosis and cirrhosis in both models.
Journal of Gastroenterology and Hepatology 07/2006; 21(6):947-57. · 2.87 Impact Factor
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ABSTRACT: Mild heat treatment can modulate metabolism and prevent stress-induced alterations in cells and tissues. Retinoids are known to influence cellular metabolism and are essential for growth and differentiation, particularly of epithelial tissue. This study examines the effect of mild heat treatment on retinoid alterations in enterocytes in the rat small intestine. Heat treatment changed the differentiation pattern of enterocytes along the villus-crypt axis, accompanied by increases in retinol, retinaldehyde, and retinoic acid in proliferating crypt cells. Activities of retinoid metabolizing enzymes such as retinaldehyde oxidase and retinaldehyde reductase were also increased. These results suggest that mild heat treatment can alter retinoid metabolism in the small intestine, which might influence epithelial cell proliferation and differentiation.
Digestive Diseases and Sciences 04/2006; 51(3):466-70. · 2.12 Impact Factor
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ABSTRACT: Nonsteroidal anti-inflammatory drugs (NSAIDs), used extensively in clinical medicine, tend to cause adverse effects in the gastrointestinal tract. Earlier work has shown that oral administration of indomethacin produced oxidative damage in the small intestine and attenuation of the glycocalyx layer of the mucosa. The present study assessed, in greater detail, the alterations produced in the glycocalyx of rat small intestinal mucosa in response to indomethacin, with specific reference to surfactant-like particles (SLP) and brush border membranes (BBM). Changes in gut flora in response to the drug were also studied, as it has been shown that luminal bacteria play a role in the pathogenesis of NSAID-induced intestinal damage. The levels of sugars such as sialic acid, fucose, hexose and hexosamine were increased in SLP and decreased in the BBM following indomethacin treatment, with the effects being maximal 24h after the administration of the drug. The composition of lipids in the SLP was also found to be altered. There was a significant increase in the number of bacteria in the luminal contents of the small intestine and caecum in these animals, as compared with controls. The number of bacteria adherent to the intestinal mucosa was also significantly higher in the drug-treated group. In vitro studies revealed that there was an increased tendency for bacteria to adhere to SLP isolated from indomethacin-treated rats. These results suggest that alterations in glycosylation of SLP and BBM in response to indomethacin, along with qualitative and quantitative changes in the luminal bacterial flora, may facilitate translocation of bacteria into the mucosa. These changes may contribute to the enteropathy observed as a result of NSAID treatment.
The International Journal of Biochemistry & Cell Biology 12/2005; 37(11):2321-32. · 4.63 Impact Factor
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ABSTRACT: Vitamin A (retinol) is essential for epithelial cell growth, differentiation and proliferation. The absorption of retinol occurs in the small intestine, and the metabolism of this vitamin is not well studied in this organ. The intestinal epithelium has a high rate of cell proliferation and differentiation, and the present study looked at the level of retinoids and metabolizing enzymes involved in their interconversion along the villus-crypt axis under normal conditions. Intestine was removed from control rats, and enterocytes at various stages of maturation and differentiation were quantified by the metal chelation method. Using HPLC, various retinoid concentrations in the cell homogenate and the metabolizing enzymes in the cytosol were quantified. The proliferating crypt cells were found to have a higher level of retinoic acid as well as of the enzymes involved in its formation, such as retinaldehyde oxidase and retinol dehydrogenase, compared with the villus cells, suggesting a possible role for this compound in intestinal epithelial cell proliferation and differentiation. The high level of retinol and high retinaldehyde reductase activity in the villus cells suggest the important role played by this enzyme in the conversion of dietary beta-carotene to retinol via retinaldehyde. In summary, this study has given for the first time a detailed analysis of the retinoid levels and metabolizing enzymes in different cell populations in the rat small intestinal epithelium.
British Journal Of Nutrition 02/2005; 93(1):59-63. · 3.01 Impact Factor
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ABSTRACT: The use of NSAIDs (non-steroidal anti-inflammatory drugs), although of great therapeutic value clinically, is limited by their tendency to cause mucosal damage in the gastrointestinal tract. In the small intestine, the effects these drugs have been shown to produce include inhibition of cyclo-oxygenase, mitochondrial dysfunction and free radical-induced oxidative changes, all of which contribute to the mucosal damage seen. Glutamine is a fuel preferentially used by enterocytes and is known to contribute to maintaining the integrity of these cells. In the present study, we investigated the effect of glutamine on indomethacin-induced changes in the small intestinal mucosa. Rats were given 2% glutamine or glutamic acid or isonitrogenous amino acids, glycine or alanine, in the diet for 7 days. Indomethacin was then administered orally at a dose of 40 mg/kg of body weight. After 1 h, the small intestine was removed and used for the measurement of parameters of oxidative stress and mitochondrial and BBM (brush border membrane) function. Evidence of oxidative stress was found in the mucosa of the small intestine of drug-treated rats, as indicated by significantly increased activity of xanthine oxidase (P < 0.001) and myeloperoxidase (P < 0.001), with corresponding decreases in the levels of several free radical scavenging enzymes and alpha-tocopherol (P < 0.001 in all cases). Levels of products of peroxidation were also significantly elevated (P < 0.001 for all the parameters measured). In addition, oxidative stress was evident in isolated intestinal mitochondria and BBMs (P < 0.001 for all the parameters measured), with associated alterations in function of these organelles (P < 0.001 for all the parameters measured). Supplementation of the diet with glutamine or glutamic acid prior to treatment with indomethacin produced significant amelioration in all the effects produced by the drug in the small intestine (P < 0.001 for all the parameters measured). Glycine and alanine were found to be much less effective in these respects.
Clinical Science 10/2004; 107(3):281-9. · 4.61 Impact Factor
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ABSTRACT: To look at the qualitative and quantitative changes in the luminal bacterial flora in response to surgical manipulation of the small intestine.
The barrier function of the intestine is compromised in pathologic conditions, such as shock, trauma, or surgical stress. Our earlier work has shown that surgical manipulation results in oxidative stress in the intestinal mucosa leading to permeability alterations.
Studies were done on rats, which were randomly divided into four groups (n = 8): group I, control, group II, III, IV different time periods, such as 8, 12, and 24 hours after surgical manipulation, which was simulated by opening the abdominal wall and handling the intestine. The cecal wall and cecal luminal contents were harvested under sterile conditions and processed for quantitation for aerobes and anaerobes. Adherence assays using Hep-2 cells were carried out on Escherichia coli isolated under different experimental conditions. In addition, control E. coli were exposed to superoxide or hydrogen peroxide, followed by subculture and adherence studies.
Surgical manipulation of the intestine resulted in qualitative and quantitative alterations in the aerobic bacteria. There was an increase in the number and relative proportion of E. coli in the cecal flora, and there was also an increase in adherence of E. coli to cecal mucosa, which was confirmed by in vitro bacterial adherence studies with HEp-2 cells. These changes were maximum at 12 hours following surgical manipulation and by 24 hours, this came back to control pattern. Control E. coli after in vitro exposure to oxidants also showed increased adherence.
These studies suggest that oxidative stress in the mucosa following surgical manipulation results in alterations in the luminal bacteria leading to increased bacterial adherence onto mucosal epithelium, which may contribute to postsurgical complications.
Annals of Surgery 09/2004; 240(2):248-54. · 7.49 Impact Factor
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ABSTRACT: Surgery at any location in the body leads to surgical stress response and alterations in normal body homeostasis. The intestine is extremely sensitive to surgical stress even at remote locations and the gastrointestinal tract plays an important role in the development of postsurgical complications such as sepsis, the systemic immune response syndrome (SIRS), and multiple organ failure syndrome (MOFS). The generation of free radicals and subsequent biochemical alterations at the cellular and subcellular level in the intestine has been suggested to play an important role in this process. These oxidative stress-induced events in the mucosa might act as an initiator of distant organ damage and also facilitate bacterial adherence onto the epithelium and translocation into the systemic circulation. This review attempts to highlight the important role of intestine and oxygen free radicals in initiating post-surgical complications.
Free Radical Biology and Medicine 04/2004; 36(6):745-56. · 5.42 Impact Factor
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ABSTRACT: Nonsteroidal anti-inflammatory drugs are used extensively in clinical medicine. In spite of their therapeutic utility, however, they are known to cause significant gastrointestinal and renal toxicities, circumstances that limit their use. The side effects produced in these organs have been attributed mainly to the inhibitory effect of these drugs on the activity of cyclooxygenase, a key enzyme in prostaglandin synthesis. In addition to this, in the small intestine it is known that reactive oxygen species also contribute to the enteropathy seen in response to these drugs. In the kidney, however, there is little information whether other mechanisms contribute to the renal toxicity. This study was designed to look at the possible biochemical mechanisms involved in indomethacin-induced renal damage. Rats fasted overnight were dosed with indomethacin (20 mg/kg) by gavage and sacrificed 24 hr later. Histology of the kidney showed abnormalities in the mitochondria in the proximal tubules. Evidence of oxidative stress was found in the kidney associated with mitochondrial dysfunction and neutrophil infiltration. The lipid composition in the mitochondria was also altered. Such effects were abolished by the prior administration of arginine, a donor of nitric oxide. This study, thus, suggests that one of the mechanisms by which nonsteroidal anti-inflammatory drugs induce renal damage is through oxygen free radicals possibly generated by activated neutrophils and mitochondrial dysfunction.
Biochemical Pharmacology 03/2004; 67(3):587-99. · 4.70 Impact Factor
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ABSTRACT: Nonsteroidal anti-inflammatory drugs (NSAIDs) cause small intestinal damage but the pathogenesis of this toxicity is not well established. Our earlier work has shown that villus enterocytes are most susceptible to the effects of indomethacin, a commonly used NSAID. This study looked at the acute effect of indomethacin on brush border membranes (BBM), which are present mainly in the villus cells and are in immediate contact with the contents of the small intestinal lumen. Evidence of oxidative stress was found in the mucosa of the small intestine of rats dosed with indomethacin, as indicated by increased activity of xanthine oxidase with corresponding decrease in the levels of several free radical scavenging enzymes. These changes were associated with an increase in peroxidation parameters in the BBM and a fall in the level of alpha-tocopherol. These BBM also exhibited impairment in glucose transport. Significant changes were seen in the lipid composition of these membranes, with upregulation of an 85kDa isoform of phospholipase A(2). Pretreatment of animals with allopurinol, arginine or zinc protected against these effects of indomethacin. Thus this study suggests that in an acute model of indomethacin dosing there is impairment in structure and function of the BBM in enterocytes, with the effects possibly mediated by free radicals and phospholipases.
Biochemical Pharmacology 03/2003; 65(4):683-95. · 4.70 Impact Factor
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ABSTRACT: Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to cause small intestinal damage but the pathogenesis of this toxicity is not well established. Intestinal epithelial cells are thought to be affected by these drugs in the course of their absorption. These cells are of different types, viz. villus, middle and crypt cells. There is little information on which of these cells, if any, are particularly vulnerable to the effects of NSAIDs. This paper aimed to study the effects of indomethacin, an NSAID commonly used in toxicity studies, on different populations of enterocytes. Effects of the drug were assessed in terms of oxidative damage, mitotic activity, mitochondrial function and lipid composition in enterocytes isolated from the small intestine of rats that had been orally administered indomethacin. In addition, the effects of arginine and zinc in protecting against such changes were assessed. Cell viability, tetrazolium dye (MTT) reduction and oxygen uptake were significantly reduced in villus tip cells from rats dosed with the drug. Thymidine uptake was higher in the crypt cell fraction from these rats. Similarly, products of lipid peroxidation were elevated in the villus tip cells with a corresponding decrease in the level of the anti-oxidant, alpha-tocopherol. In isolated mitochondrial preparations from various enterocyte fractions, significant functional impairment and altered lipid composition were seen mainly in mitochondria from villus cells. Arginine and zinc pre-treatment were found to protect against these effects. These results suggest for the first time that the villus tip cells are more vulnerable to the damaging effects of indomethacin and that oxidative stress is possibly involved in this damage.
Biochemical Pharmacology 08/2002; 64(2):339-49. · 4.70 Impact Factor
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ABSTRACT: Cirrhosis is associated with altered gastrointestinal function, and bacterial translocation from the gut plays an important role in the etiology of spontaneous bacterial peritonitis (SBP) seen in this condition. Although alterations in gut motility and intestinal permeability are recognized in cirrhosis, the intestinal damage at the cellular and subcellular levels is not well understood. This study looked at the mucosal alterations in experimental cirrhosis and the role of oxygen free radicals in this process. It was shown that cirrhosis results in oxidative stress in the intestine, as seen by increased xanthine oxidase (XO) activity and altered antioxidant status. Cirrhosis also affects enterocyte mitochondrial function, as assessed by respiratory control ratio, swelling, and calcium flux. Increased lipid peroxidation of the brush border membranes (BBMs) was seen along with altered intestinal transport. In conclusion, this study shows that intestinal mucosal alterations are seen in experimental cirrhosis and are possibly mediated by oxidative stress.
Hepatology 04/2002; 35(3):622-9. · 11.66 Impact Factor
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ABSTRACT: Apoptosis is now recognized as an important process responsible for maintenance of the cellular balance between proliferation and death. Apoptosis is distinct from necrosis in that it is a programmed form of cell death and occurs without any accompanying inflammation. This form of cell death can be induced by a wide range of cellular signals, which leads to activation of cell death machinery within the cell and is characterized by distinct morphological changes. Apoptosis is especially relevant in the gastrointestinal tract, as the mammalian intestinal mucosa undergoes a process of continual cell turnover that is essential for maintenance of normal function. Cell proliferation is confined to the crypts, while differentiation occurs during a rapid, orderly migration up to the villus. The differentiated enterocytes, which make up the majority of the cells, then undergo a process of programmed cell death (apoptosis). Although apoptosis is essential for the maintenance of normal gut epithelial function, dysregulated apoptosis is seen in a number of pathological conditions in the gastrointestinal tract. The cellular mechanisms regulating this tightly regimented process have not been clearly defined and this topic represents an area of active investigation as delineation of this process will lead to a better understanding of normal gut mucosal growth.
Journal of Gastroenterology and Hepatology 01/2000; 15(2):109 - 120. · 2.87 Impact Factor
