Mechanism of inhibition of Na+-glucose cotransport in the chronically inflamed rabbit ileum

1997 ◽  
Vol 273 (4) ◽  
pp. G913-G919 ◽  
Author(s):  
U. Sundaram ◽  
S. Wisel ◽  
V. M. Rajendren ◽  
A. B. West
Keyword(s):  
Steady State ◽  
Brush Border Membrane ◽  
Rabbit Model ◽  
Kinetic Studies ◽  
Maximal Rate ◽  
Rabbit Ileum ◽  
Intact Cells ◽  
Protein Levels ◽  
Mechanism Of Inhibition ◽  
Villus Cell

In a rabbit model of chronic ileal inflammation, we previously demonstrated that coupled NaCl absorption was reduced because of an inhibition of Cl−/[Formula: see text]but not Na+/H+exchange on the brush-border membrane (BBM) of villus cells. In this study we determined the alterations in Na+-stimulated glucose [Na+- O-methyl-d-glucose (Na+-OMG)] absorption during chronic ileitis. Na+-OMG uptake was reduced in villus cells from the chronically inflamed ileum. Na+-K+-adenosinetriphosphatase (ATPase), which provides the favorable Na+gradient for this cotransporter in intact cells, was found to be reduced also. However, in villus cell BBM vesicles from the inflamed ileum Na+-OMG uptake was reduced as well, suggesting an effect at the level of the cotransporter itself. Kinetic studies demonstrated that Na+-OMG uptake in the inflamed ileum was inhibited by a decrease in the maximal rate of uptake for OMG without a change in the affinity. Analysis of steady-state mRNA and immunoreactive protein levels of this cotransporter demonstrates reduced expression. Thus Na+-glucose cotransport was inhibited in the chronically inflamed ileum, and the inhibition was secondary to a decrease in the number of cotransporters and not solely secondary to an inhibition of Na+-K+-ATPase or altered affinity for glucose.

Corticosteroids reverse the inhibition of Na-glucose cotransport in the chronically inflamed rabbit ileum

1999 ◽  
Vol 276 (1) ◽  
pp. G211-G218 ◽  
Author(s):  
Uma Sundaram ◽  
Steve Coon ◽  
Sheik Wisel ◽  
A. Brian West
Keyword(s):  
Atpase Activity ◽  
Brush Border Membrane ◽  
Rabbit Model ◽  
Membrane Vesicles ◽  
Kinetic Studies ◽  
Maximal Velocity ◽  
Rabbit Ileum ◽  
Protein Levels ◽  
Mechanism Of Inhibition ◽  
Villus Cell

In a rabbit model of chronic ileal inflammation, we previously demonstrated inhibition of Na-glucose cotransport (SGLT-1). The mechanism of inhibition was secondary to a decrease in the number of cotransporters and not solely secondary to an inhibition of Na-K-ATPase or altered affinity for glucose. In this study, we determined the effect of methylprednisolone (MP) on SGLT-1 inhibition during chronic ileitis. Treatment with MP almost completely reversed the reduction in SGLT-1 in villus cells from the chronically inflamed ileum. MP also reversed the decrease in Na-K-ATPase activity in villus cells during chronic ileitis. However, MP treatment reversed the SGLT-1 inhibition in villus cell brush-border membrane vesicles from the inflamed ileum, which suggested an effect of MP at the level of the cotransporter itself. Kinetic studies demonstrated that the reversal of SGLT-1 inhibition by MP was secondary to an increase in the maximal velocity for glucose without a change in the affinity. Analysis of immunoreactive protein levels of the cotransporter demonstrated a restoration of the cotransporter numbers after MP treatment in the chronically inflamed ileum. Thus MP treatment alleviates SGLT-1 inhibition in the chronically inflamed ileum by increasing the number of cotransporters and not solely secondary to enhancing the activity of Na-K-ATPase or by altering the affinity for glucose.

Mechanism of inhibition of Na+-bile acid cotransport during chronic ileal inflammation in rabbits

1998 ◽  
Vol 275 (6) ◽  
pp. G1259-G1265 ◽  
Author(s):  
U. Sundaram ◽  
S. Wisel ◽  
S. Stengelin ◽  
W. Kramer ◽  
V. Rajendran
Keyword(s):  
Bile Acid ◽  
Amino Acid ◽  
Brush Border Membrane ◽  
Rabbit Model ◽  
Membrane Vesicles ◽  
Kinetic Studies ◽  
Transport Processes ◽  
Protein Levels ◽  
Mechanism Of Inhibition ◽  
Villus Cell

In the chronically inflamed ileum, unique mechanisms of alteration of similar transport processes suggest regulation by different immune-inflammatory mediator pathways. In a rabbit model of chronic ileitis, we previously demonstrated that Na+-glucose cotransport was inhibited by a decrease in the cotransporter numbers, whereas Na+-amino acid cotransport was inhibited by a decrease in the affinity for the amino acid. In this study, we demonstrated that Na+-bile acid cotransport was reduced in villus cells from the chronically inflamed ileum. In villus cell brush-border membrane vesicles from the chronically inflamed ileum, Na+-bile acid cotransport was reduced as well, suggesting a direct effect at the cotransporter itself. Kinetic studies demonstrated that Na+-bile acid cotransport was inhibited by both a decrease in the affinity as well as a decrease in the maximal rate of uptake of the bile acid. Analysis of steady-state mRNA and immunoreactive protein levels of the Na+-bile acid cotransporter also demonstrated some reduction during chronic ileitis. Thus, in the chronically inflamed ileum, the mechanisms of inhibition of Na+-glucose, Na+-amino acid, and Na+-bile acid cotransport are different. These data suggest that different cotransporters are uniquely altered either secondary to their intrinsic differences or by different immune-inflammatory mediators during chronic ileitis.

Unique regulation of anion/HCO3- exchangers by constitutive nitric oxide in rabbit small intestine

2003 ◽  
Vol 285 (6) ◽  
pp. G1084-G1090 ◽  
Author(s):  
Steven Coon ◽  
Uma Sundaram
Keyword(s):  
Nitric Oxide ◽  
Small Intestine ◽  
Kinetic Studies ◽  
Transport Processes ◽  
Crypt Cell ◽  
Maximal Rate ◽  
Mechanism Of Inhibition ◽  
Rabbit Small Intestine ◽  
Villus Cell ◽  
Inactive Analog

In the rabbit small intestine, there are three functionally different brush-border membrane (BBM) anion/HCO3- exchangers: 1) Cl/HCO3- exchange on the BBM of villus cells responsible for coupled NaCl absorption; 2) Cl/HCO3- exchange on the BBM of crypt cells possibly involved in HCO3- secretion; and 3) short-chain fatty acid (SCFA)/HCO3- exchange on the BBM of villus cells, which facilitates SCFA absorption. Although constitutive nitric oxide (cNO) has been postulated to alter many gastrointestinal tract functions, how cNO may specifically alter these three transporters is unknown. Inhibition of cNO synthase with NG-nitro-l-arginine methyl ester (l-NAME) 1) did not affect villus cell BBM Cl/HCO3 change, 2) stimulated crypt cell BBM Cl/HCO3- exchange, and 3) inhibited villus cell BBM SCFA/HCO3- exchange. d-NAME, an inactive analog of l-NAME, and l- N6-(1-iminoethyl)lysine, a more selective inhibitor of inducible NO, did not affect these transport processes. Kinetic studies demonstrated that 1) the mechanism of inhibition of crypt cell BBM Cl/HCO3- exchange is secondary to a decrease in the maximal rate of uptake of Cl, without an alteration in the affinity of the transporter for Cl, and 2) the mechanism of stimulation of villus cell BBM SCFA/HCO3- exchange is secondary to an increase in the affinity of the transporter for SCFA without an alteration in the maximal rate of uptake of SCFA. These results indicate that cNO uniquely regulates the three BBM anion/HCO3- transporters in the rabbit small intestine.

Na-glucose and Na-neutral amino acid cotransport are uniquely regulated by constitutive nitric oxide in rabbit small intestinal villus cells

2005 ◽  
Vol 289 (6) ◽  
pp. G1030-G1035 ◽  
Author(s):  
Steven Coon ◽  
James Kim ◽  
Guohong Shao ◽  
Uma Sundaram
Keyword(s):  
Nitric Oxide ◽  
Small Intestine ◽  
Amino Acid ◽  
Basolateral Membrane ◽  
Kinetic Studies ◽  
Mrna Levels ◽  
Protein Levels ◽  
Mechanism Of Inhibition ◽  
Rabbit Small Intestine ◽  
Villus Cell

Na-nutrient cotransport processes are not only important for the assimilation of essential nutrients but also for the absorption of Na in the mammalian small intestine. The effect of constitutive nitric oxide (cNO) on Na-glucose (SGLT-1) and Na-amino acid cotransport (NAcT) in the mammalian small intestine is unknown. Inhibition of cNO synthase with NG-nitro-l-arginine methyl ester (l-NAME) resulted in the inhibition of Na-stimulated 3H- O-methyl-d-glucose uptake in villus cells. However, Na-stimulated alanine uptake was not affected in these cells. The l-NAME-induced reduction in SGLT-1 in villus cells was not secondary to an alteration in basolateral membrane Na-K-ATPase activity, which provides the favorable Na gradient for this cotransport process. In fact, SGLT-1 was inhibited in villus cell brush-border membrane (BBM) vesicles prepared from animals treated with l-NAME. Kinetic studies demonstrated that the mechanism of inhibition of SGLT-1 was secondary to a decrease in the affinity for glucose without a change in the maximal rate of uptake of glucose. Northern blot studies demonstrated no change in the mRNA levels of SGLT-1. Western blot studies demonstrated no significant change in the immunoreactive protein levels of SGLT-1 in ileal villus cell BBM from l-NAME-treated rabbits. These studies indicate that inhibition of cNO production inhibits SGLT-1 but not NAcT in the rabbit small intestine. Therefore, whereas cNO promotes Na-glucose cotransport, it does not affect NAcT in the mammalian small intestine.

Mechanism of glucocorticoid-mediated reversal of inhibition of Cl−/ HCO 3 − exchange during chronic ileitis

2000 ◽  
Vol 278 (4) ◽  
pp. G570-G577 ◽  
Author(s):  
Steve Coon ◽  
Uma Sundaram
Keyword(s):  
Direct Effect ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Inflammation ◽  
Rabbit Model ◽  
Cellular Mechanism ◽  
Maximal Rate ◽  
Nacl Absorption ◽  
Mechanism Of Inhibition ◽  
Small Intestinal

In the normal ileum, coupled NaCl absorption occurs via the dual operation of Na+/H+ and Cl−/[Formula: see text] exchange on the brush-border membrane (BBM) of villus cells. In a rabbit model of chronic small intestinal inflammation we determined the cellular mechanism of inhibition of NaCl absorption and the effect of steroids on this inhibition. Cl−/[Formula: see text] but not Na+/H+ exchange was reduced in the BBM of villus cells during chronic ileitis. Cl−/[Formula: see text] exchange was inhibited secondary to a decrease in the affinity for Cl− rather than an alteration in the maximal rate of uptake of Cl− (Vmax). Methylprednisolone (MP) stimulated Cl−/[Formula: see text] exchange in the normal ileum by increasing the Vmax of Cl− uptake rather than altering affinity for Cl−. MP reversed the inhibition of Cl−/[Formula: see text] exchange in rabbits with chronic ileitis. However, MP alleviated the Cl−/[Formula: see text] exchange inhibition by restoring the affinity for Cl− rather than altering the Vmax of Cl− uptake. These data suggest that glucocorticoids mediate the alleviation of Cl−/[Formula: see text] exchange inhibition in chronically inflamed ileum by reversing the same mechanism that was responsible for inhibition of this transporter rather than exerting a direct effect on the transporter itself, as was the case in normal ileum.

Effect of chronic inflammation on ileal short-chain fatty acid/bicarbonate exchange

2000 ◽  
Vol 278 (4) ◽  
pp. G585-G590 ◽  
Author(s):  
Tasos Manokas ◽  
John J. Fromkes ◽  
Uma Sundaram
Keyword(s):  
Chronic Inflammation ◽  
Intestinal Inflammation ◽  
Rabbit Model ◽  
Kinetic Studies ◽  
Short Chain Fatty Acids ◽  
Short Chain ◽  
Rabbit Ileum ◽  
Mechanism Of Inhibition ◽  
Chronic Intestinal Inflammation ◽  
Crypt Cells

Short-chain fatty acids (SCFA) have been demonstrated to at least partially ameliorate chronic intestinal inflammation. However, whether and how intestinal SCFA absorption may be altered during chronic intestinal inflammation is unknown. A rabbit model of chronic ileitis produced by coccidia was used to determine the effect of chronic inflammation on ileal SCFA/[Formula: see text] exchange. SCFA/[Formula: see text] exchange was present in the brush-border membrane (BBM) of villus but not crypt cells from normal rabbit ileum. An anion-exchange inhibitor, DIDS, significantly inhibited SCFA/[Formula: see text] exchange. Extravesicular Cl− did not alter the uptake of SCFA, suggesting that SCFA/[Formula: see text] exchange is a transport process distinct from Cl−/[Formula: see text] exchange. In chronically inflamed ileum, SCFA/[Formula: see text] exchange was also present only in BBM of villus cells. The exchanger was sensitive to DIDS and was unaffected by extravesicular Cl−. However, SCFA/[Formula: see text] exchange was significantly reduced in villus cell BBM vesicles (BBMV) from chronically inflamed ileum. Kinetic studies demonstrated that the maximal rate of uptake of SCFA, but not the affinity for SCFA, was reduced in chronically inflamed rabbit ileum. These data demonstrate that a distinct SCFA/[Formula: see text] exchange is present on BBMV of villus but not crypt cells in normal rabbit ileum. SCFA/[Formula: see text] exchange is inhibited in chronically inflamed rabbit ileum. The mechanism of inhibition is most likely secondary to a reduction in transporter numbers rather than altered affinity for SCFA.

Mechanism of regulation of rabbit intestinal villus cell brush border membrane Na/H exchange by nitric oxide

2007 ◽  
Vol 292 (2) ◽  
pp. G475-G481 ◽  
Author(s):  
Steven Coon ◽  
Guohong Shao ◽  
Sheik Wisel ◽  
Raju Vulaupalli ◽  
Uma Sundaram
Keyword(s):  
Nitric Oxide ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Kinetic Studies ◽  
Protein Levels ◽  
Nacl Absorption ◽  
Exchange Kinetic ◽  
Villus Cell ◽  
Inhibitory Tone ◽  
Inactive Analog

In the mammalian small intestine, coupled NaCl absorption occurs via the dual operation of Na/H and Cl/HCO3exchange on the villus cell brush border membrane (BBM). Although constitutive nitric oxide (cNO) has been demonstrated to alter gastrointestinal tract functions, how cNO may specifically alter these two transporters to regulate coupled NaCl absorption is unknown. In villus cells, inhibition of cNO synthase (cNOS) with l- NG-nitroarginine methylester (l-NAME) stimulated Na/H exchange whereas Cl/HCO3exchange was unaffected. In villus cell BBM vesicles (BBMV) prepared from rabbits treated with l-NAME, Na/H exchange was also stimulated. d-NAME, an inactive analog of l-NAME, and N6-(1-imonoethyl)-l-lysine dihydrochloride, a more selective inhibitor of inducible NO synthase, did not affect Na/H exchange. Kinetic studies demonstrated that the mechanism of stimulation is secondary to an increase in the maximal rate of uptake of Na, without an alteration in the affinity of the transporter for Na. Northern blot studies demonstrated an increase in the message for the BBM Na/H exchanger NHE3, and Western blot studies showed that the immunoreactive protein levels of NHE3 was increased when cNOS was inhibited. Thus these results indicate that cNO under nominal physiological states most likely maintains an inhibitory tone on small intestinal coupled NaCl absorption by specifically inhibiting BBM Na/H expression.

scholarly journals Unique Regulation of Intestinal Villus Epithelial Cl−/HCO3− Exchange by Cyclooxygenase Pathway Metabolites of Arachidonic Acid in a Mouse Model of Spontaneous Ileitis

2021 ◽  
Vol 22 (8) ◽  
pp. 4171
Author(s):  
M Motiur Rahman ◽  
Alip Borthakur ◽  
Sheuli Afroz ◽  
Subha Arthur ◽  
Uma Sundaram
Keyword(s):  
Arachidonic Acid ◽  
Brush Border Membrane ◽  
Kinetic Studies ◽  
Intestinal Villus ◽  
Protein Levels ◽  
Nacl Absorption ◽  
Anion Transporter ◽  
Villus Cell ◽  
Acid Metabolites ◽  
Inflammatory Bowel

Electrolytes (NaCl) and fluid malabsorption cause diarrhea in inflammatory bowel disease (IBD). Coupled NaCl absorption, mediated by Na+/H+ and Cl−/HCO3− exchanges on the intestinal villus cells brush border membrane (BBM), is inhibited in IBD. Arachidonic acid metabolites (AAMs) formed via cyclooxygenase (COX) or lipoxygenase (LOX) pathways are elevated in IBD. However, their effects on NaCl absorption are not known. We treated SAMP1/YitFc (SAMP1) mice, a model of spontaneous ileitis resembling human IBD, with Arachidonyl Trifluoro Methylketone (ATMK, AAM inhibitor), or with piroxicam or MK-886, to inhibit COX or LOX pathways, respectively. Cl−/HCO3− exchange, measured as DIDS-sensitive 36Cl uptake, was significantly inhibited in villus cells and BBM vesicles of SAMP1 mice compared to AKR/J controls, an effect reversed by ATMK. Piroxicam, but not MK-886, also reversed the inhibition. Kinetic studies showed that inhibition was secondary to altered Km with no effects on Vmax. Whole cell or BBM protein levels of Down-Regulated in Adenoma (SLC26A3) and putative anion transporter-1 (SLC26A6), the two key BBM Cl−/HCO3− exchangers, were unaltered. Thus, inhibition of villus cell Cl−/HCO3− exchange by COX pathway AAMs, such as prostaglandins, via reducing the affinity of the exchanger for Cl−, and thereby causing NaCl malabsorption, could significantly contribute to IBD-associated diarrhea.

scholarly journals Unique Regulation of Enterocyte Brush Border Membrane Na-Glutamine and Na-Alanine Co-Transport by Peroxynitrite during Chronic Intestinal Inflammation

2019 ◽  
Vol 20 (6) ◽  
pp. 1504 ◽  
Author(s):  
Subha Arthur ◽  
Palanikumar Manoharan ◽  
Shanmuga Sundaram ◽  
M Rahman ◽  
Balasubramanian Palaniappan ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Intestinal Inflammation ◽  
Intestinal Epithelial Cells ◽  
Rabbit Model ◽  
Intestinal Epithelial ◽  
Mechanism Of Inhibition ◽  
Chronic Intestinal Inflammation

Na-amino acid co-transporters (NaAAcT) are uniquely affected in rabbit intestinal villus cell brush border membrane (BBM) during chronic intestinal inflammation. Specifically, Na-alanine co-transport (ASCT1) is inhibited secondary to a reduction in the affinity of the co-transporter for alanine, whereas Na-glutamine co-transport (B0AT1) is inhibited secondary to a reduction in BBM co-transporter numbers. During chronic intestinal inflammation, there is abundant production of the potent oxidant peroxynitrite (OONO). However, whether OONO mediates the unique alteration in NaAAcT in intestinal epithelial cells during chronic intestinal inflammation is unknown. In this study, ASCT1 and B0AT1 were inhibited by OONO in vitro. The mechanism of inhibition of ASCT1 by OONO was secondary to a reduction in the affinity of the co-transporter for alanine, and secondary to a reduction in the number of co-transporters for B0AT1, which were further confirmed by Western blot analyses. In conclusion, peroxynitrite inhibited both BBM ASCT1 and B0AT1 in intestinal epithelial cells but by different mechanisms. These alterations in the villus cells are similar to those seen in the rabbit model of chronic enteritis. Therefore, this study indicates that peroxynitrite may mediate the inhibition of ASCT1 and B0AT1 during inflammation, when OONO levels are known to be elevated in the mucosa.

scholarly journals Mechanism of leukotriene D4 inhibition of Na-alanine cotransport in intestinal epithelial cells

2008 ◽  
Vol 295 (1) ◽  
pp. G1-G6 ◽  
Author(s):  
Jamilur R. Talukder ◽  
Ramesh Kekuda ◽  
Prosenjit Saha ◽  
Uma Sundaram
Keyword(s):  
Amino Acid ◽  
Intestinal Inflammation ◽  
Rabbit Model ◽  
Intestinal Epithelial ◽  
Leukotriene D4 ◽  
Real Time Quantitative Pcr ◽  
Protein Levels ◽  
Mechanism Of Inhibition ◽  
Rabbit Small Intestine ◽  
Chronic Intestinal Inflammation

In a rabbit model of chronic intestinal inflammation, we previously demonstrated inhibition of neutral Na-amino acid cotransport. The mechanism of the inhibition was secondary to a decrease in the affinity for amino acid rather than the number of cotransporters. Since leukotriene (LT)D4 is known to be elevated in enterocytes during chronic intestinal inflammation, we used rat intestinal epithelial cell (IEC-18) monolayers to determine the mechanism of regulation of Na-alanine cotransport (alanine, serine, cysteine transporter 1: ASCT1) by LTD4. Na-alanine cotransport was inhibited by LTD4 in IEC-18 cells. The mechanism of inhibition of ASCT1 (solute carrier, SLC1A4) by LTD4 is secondary to a decrease in the affinity of the cotransporter for alanine without a significant change in cotransporter numbers and is not secondary to an alteration in the Na+ extruding capacity of the cells. Real-time quantitative PCR and Western blot analysis results indicate that ASCT1 message and protein levels are also unchanged in LTD4-treated IEC-18 cells. These results indicate that LTD4 inhibits Na-dependent neutral amino acid cotransport in IEC. The mechanism of inhibition is secondary to a decrease in the affinity for alanine, which is identical to that seen in villus cells from the chronically inflamed rabbit small intestine, where LTD4 levels are significantly increased.

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