Intestinal mucosal alterations in rats with carbon tetrachloride-induced cirrhosis: changes in glycosylation and luminal bacteria

Spontaneous bacterial peritonitis is a major cause of mortality after liver cirrhosis. Altered permeability of the mucosa and deficiencies in host immune defenses through bacterial translocation from the intestine due to intestinal bacterial overgrowth have been implicated in the development of this complication. Molecular mechanisms underlying the process are not well known. In order to understand mechanisms involved in translocation of bacteria, this study explored the role of oxidative stress in mediating changes in intestinal mucosal glycosylation and luminal bacterial content during cirrhosis. CCl4-induced cirrhosis in rats led to prolonged oxidative stress in the intestine, accompanied by increased sugar content of both intestinal brush border and surfactant layers. This was accompanied by changes in bacterial flora in the gut, which showed increased hydrophobicity and adherence to the mucosa. Inhibition of xanthine oxidase using sodium tungstate or antioxidant supplementation using vitamin E reversed the oxidative stress, changes in brush border membrane sugar content, and bacterial adherence. In conclusion, oxidative stress in the intestine during cirrhosis alters mucosal glycosylation, accompanied by an increased hydrophobicity of luminal bacteria, enabling increased bacterial adherence onto epithelial cells. This might facilitate translocation across the mucosa, resulting in complications such as spontaneous bacterial peritonitis

Intestinal Mucosal Alterations in Rats With Carbon Tetrachloride-Induced Cirrhosis: Changes in Glycosylation and Luminal Bacteria

Spontaneous bacterial peritonitis is a major cause of mortality after liver cirrhosis. Altered permeability of the mucosa and deficiencies in host immune defenses through bacterial translocation from the intestine due to intestinal bacterial overgrowth have been implicated in the development of this complication. Molecular mechanisms underlying the process are not well known. In order to understand mechanisms involved in translocation of bacteria, this study explored the role of oxidative stress in mediating changes in intestinal mucosal glycosylation and luminal bacterial content during cirrhosis. CCl4-induced cirrhosis in rats led to prolonged oxidative stress in the intestine, accompanied by increased sugar content of both intestinal brush border and surfactant layers. This was accompanied by changes in bacterial flora in the gut, which showed increased hydrophobicity and adherence to the mucosa. Inhibition of xanthine oxidase using sodium tungstate or antioxidant supplementation using vitamin E reversed the oxidative stress, changes in brush border membrane sugar content, and bacterial adherence. In conclusion, oxidative stress in the intestine during cirrhosis alters mucosal glycosylation, accompanied by an increased hydrophobicity of luminal bacteria, enabling increased bacterial adherence onto epithelial cells. This might facilitate translocation across the mucosa, resulting in complications such as spontaneous bacterial peritonitis

A simple method of rat renal brush border membrane preparation using polyethylene glycol precipitation

A simple method for preparation of brush border membranes (BBM) from rat kidney using polyethylene glycol (PEG) precipitation has been described. This method avoids the use of cations for the preparation, which might alter membrane lipid composition. These preparations were assessed for enrichment of marker enzymes, contamination by subcellular structures, lipid composition and transport function. An enrichment of 11.8910-fold of alkaline phosphatase, 13.9500-fold of amino peptidase and 13.6500-fold of γ-glutamyl transpeptidase and an approximate yield of 60% were seen in the final membrane preparation as compared to the homogenate. There was very little contamination of basolateral membranes, peroxisomes, microsomes or lysosomes in the final membrane preparation. Analysis of sugars indicated high content of fucose and sailic acid as compared to hexoses. Isolated membranes appeared as vesicles as seen by electron microscopy. Lipid analysis indicated the presence of various neutral and phospholipids with a high content of sphingomyelin along with a cholesterol/phospholipid ratio of 0.4850. The isolated membrane vesicles were able to transport glucose. This study has shown a simple method of renal brush border membrane preparation, which is comparatively pure and functionally active

Indomethacin-induced renal damage: role of oxygen free radicals

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

Somatostatin preserved blood brain barrier against cytokine induced alterations: possible role in multiple sclerosis.

Multiple sclerosis (MS) is an inflammatory neurological disorder associated with demyelination, impaired blood brain barrier (BBB), axonal damage and neuronal loss. In the present study, we measured somatostatin (SST) and tumor necrosis factor-α (TNF-α) like immunoreactivity in CSF samples from MS and non-MS patients. We also examined the role of SST in cytokines and lipopolysaccharide (LPS)-induced damage to the BBB using human brain endothelial cells in culture. Most of the cerebrospinal fluid (CSF) samples studied from definite MS patients exhibited lower somatostatin (SST)-like immunoreactivity and higher expression of TNF-α in comparison to non-MS patients. Treatment of cells with cytokines and LPS blocked SST secretion and decreased SST expression. Human brain endothelial cells expressed all five somatostatin receptors (SSTRs) with increased expression of SSTR2 and 4 upon treatment with cytokines and LPS. Cytokines and LPS-induced disruption of the tight junction proteins Zonula occludens (ZO-1) organization was restored in presence of SST, SSTR2 or SSTR4 selective agonists. Furthermore, inflammation induced changes in extracellular signal-regulated kinases (ERK1/2 and ERK5) signaling and altered expression of endothelial and inducible nitric oxide synthase are modulated in presence of SST. These data indicate that decreased levels of SST contribute to failure of the BBB in MS

Indomethacin-induced free radical-mediated changes in the intestinal brush border membranes

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 85 kDa isoform of phospholipase A<SUB>2</SUB>. 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

Renal Damage in Experimentally-Induced Cirrhosis in Rats: Role of Oxygen Free Radicals

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