scholarly journals Effect of chronic alcohol feeding on physiological and molecular parameters of renal thiamin transport

2010 ◽  
Vol 299 (1) ◽  
pp. F28-F34 ◽  
Author(s):  
Veedamali S. Subramanian ◽  
Sandeep B. Subramanya ◽  
Hidekazu Tsukamoto ◽  
Hamid M. Said
Keyword(s):  
Alcohol Use ◽  
Epithelial Cells ◽  
Basolateral Membrane ◽  
Significant Inhibition ◽  
Transcriptional Level ◽  
Chronic Alcohol ◽  
Molecular Parameters ◽  
Renal Epithelial Cells ◽  
Renal Brush Border Membrane ◽  
Thiamin Transport

The renal thiamin reabsorption process plays an important role in regulating thiamin body homeostasis and involves both thiamin transporters-1 and -2 (THTR1 and THTR2). Chronic alcohol use is associated with thiamin deficiency. Although a variety of factors contribute to the development of this deficiency, effects of chronic alcohol use on renal thiamin transport have not been thoroughly examined. We addressed this issue by examining the effect of chronic alcohol feeding of rats with liquid diet on physiological and molecular parameters of renal thiamin transport. Chronic alcohol feeding caused a significant inhibition in carrier-mediated thiamin transport across the renal brush-border membrane and was evident as early as 2 wk after initiation of alcohol feeding. Similarly, thiamin transport across the renal basolateral membrane was significantly inhibited by chronic alcohol feeding. The inhibition in renal thiamin transport was associated with a marked decrease in the level of expression of THTR1 and -2 proteins, mRNAs, and heterogeneous nuclear RNAs. Chronic alcohol feeding also caused a significant reduction in the level of expression of thiamin pyrophosphokinase but not that of the mitochondrial thiamin pyrophosphate transporter. These studies show that chronic alcohol feeding inhibits the entry and exit of thiamin in the polarized renal epithelial cells and that the effect is, at least in part, mediated at the transcriptional level. These findings also suggest that chronic alcohol feeding interferes with the normal homeostasis of thiamin in renal epithelial cells.

scholarly journals Inhibition of intestinal biotin absorption by chronic alcohol feeding: cellular and molecular mechanisms

2011 ◽  
Vol 300 (3) ◽  
pp. G494-G501 ◽  
Author(s):  
Sandeep B. Subramanya ◽  
Veedamali S. Subramanian ◽  
Jeyan S. Kumar ◽  
Robert Hoiness ◽  
Hamid M. Said
Keyword(s):  
Alcohol Use ◽  
Transgenic Mice ◽  
Animal Studies ◽  
Molecular Mechanisms ◽  
Basolateral Membrane ◽  
Regulatory Region ◽  
Significant Inhibition ◽  
Water Soluble ◽  
Rat Colon ◽  
Chronic Alcohol

The water-soluble vitamin biotin is essential for normal cellular functions and its deficiency leads to a variety of clinical abnormalities. Mammals obtain biotin from exogenous sources via intestinal absorption, a process mediated by the sodium-dependent multivitamin transporter (SMVT). Chronic alcohol use in humans is associated with a significant reduction in plasma biotin levels, and animal studies have shown inhibition in intestinal biotin absorption by chronic alcohol feeding. Little, however, is known about the cellular and molecular mechanisms involved in the inhibition in intestinal biotin transport by chronic alcohol use. These mechanisms were investigated in this study by using rats and transgenic mice carrying the human full-length SLC5A6 5′-regulatory region chronically fed alcohol liquid diets; human intestinal epithelial Caco-2 cells chronically exposed to alcohol were also used as models. The results showed chronic alcohol feeding of rats to lead to a significant inhibition in carrier-mediated biotin transport events across jejunal brush border and basolateral membrane domains. This inhibition was associated with a significant reduction in level of expression of the SMVT protein, mRNA, and heterogenous nuclear RNA. Chronic alcohol feeding also inhibited carrier-mediated biotin uptake in rat colon. Studies with transgenic mice confirmed the above findings and further showed chronic alcohol feeding significantly inhibited the activity of SLC5A6 5′-regulatory region. Finally, chronic exposure of Caco-2 cells to alcohol led to a significant decrease in the activity of both promoters P1 and P2 of the human SLC5A6 gene. These studies identify for the first time the cellular and molecular parameters of the intestinal biotin absorptive processes that are affected by chronic alcohol feeding.

scholarly journals Chronic alcohol feeding inhibits physiological and molecular parameters of intestinal and renal riboflavin transport

2013 ◽  
Vol 305 (5) ◽  
pp. C539-C546 ◽  
Author(s):  
Veedamali S. Subramanian ◽  
Sandeep B. Subramanya ◽  
Abhisek Ghosal ◽  
Hamid M. Said
Keyword(s):  
Intestinal Absorption ◽  
Brush Border ◽  
Basolateral Membrane ◽  
Alcohol Exposure ◽  
Significant Inhibition ◽  
Membrane Domains ◽  
Chronic Alcohol ◽  
Molecular Parameters ◽  
High Prevalence ◽  
Chronic Alcohol Exposure

Vitamin B2 (riboflavin, RF) is essential for normal human health. Mammals obtain RF from exogenous sources via intestinal absorption and prevent its urinary loss by reabsorption in the kidneys. Both of these absorptive events are carrier-mediated and involve specific RF transporters (RFVTs). Chronic alcohol consumption in humans is associated with a high prevalence of RF deficiency and suboptimal levels, but little is known about the effect of chronic alcohol exposure on physiological and molecular parameters of the intestinal and renal RF transport events. We addressed these issues using rats chronically fed an alcohol liquid diet and pair-fed controls as a model. The results showed that chronic alcohol feeding significantly inhibits carrier-mediated RF transport across the intestinal brush-border and basolateral membrane domains of the polarized enterocytes. This inhibition was associated with a parallel reduction in the expression of the rat RFVT-1 and -3 at the protein, mRNA, and heterogeneous nuclear RNA (hnRNA) levels. Chronic alcohol feeding also caused a significant inhibition in RF uptake in the colon. Similarly, a significant inhibition in carrier-mediated RF transport across the renal brush-border and basolateral membrane domains was observed, which again was associated with a significant reduction in the level of expression of RFVT-1 and -3 at the protein, mRNA, and hnRNA levels. These findings demonstrate that chronic alcohol exposure impairs both intestinal absorption and renal reabsorption processes of RF and that these effects are, at least in part, mediated via transcriptional mechanism(s) involving the slc52a1 and slc52a3 genes.

scholarly journals The carboxyl-terminally truncated kidney anion exchanger 1 R901X dRTA mutant is unstable at the plasma membrane

2016 ◽  
Vol 310 (9) ◽  
pp. C764-C772 ◽  
Author(s):  
Ensaf Almomani ◽  
Rawad Lashhab ◽  
R. Todd Alexander ◽  
Emmanuelle Cordat
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Anion Exchanger ◽  
Basolateral Membrane ◽  
Recycling Rate ◽  
Wild Type ◽  
Anion Exchanger 1 ◽  
Renal Epithelial Cells ◽  
Gene Coding ◽  
Renal Tubular

Mutations in the SLC4A1 gene coding for kidney anion exchanger 1 (kAE1) cause distal renal tubular acidosis (dRTA). We investigated the fate of the most common truncated dominant dRTA mutant kAE1 R901X. In renal epithelial cells, we found that kAE1 R901X is less abundant than kAE1 wild-type (WT) at the plasma membrane. Although kAE1 WT and kAE1 R901X have similar half-lives, the decreased abundance of kAE1 R901X at the surface is due to an increased endocytosis rate and a decreased recycling rate of endocytosed proteins. We propose that, in polarized renal epithelial cells, the apically mistargeted kAE1 R901X mutant is endocytosed faster than kAE1 WT and its recycling to the basolateral membrane is delayed. This resets the equilibrium, such that kAE1 R901X resides predominantly in an endomembrane compartment, thereby likely participating in development of dRTA disease.

scholarly journals Chronic alcohol consumption and intestinal thiamin absorption: effects on physiological and molecular parameters of the uptake process

2010 ◽  
Vol 299 (1) ◽  
pp. G23-G31 ◽  
Author(s):  
Sandeep B. Subramanya ◽  
Veedamali S. Subramanian ◽  
Hamid M. Said
Keyword(s):  
Alcohol Consumption ◽  
Basolateral Membrane ◽  
Significant Inhibition ◽  
Model Systems ◽  
Rat Colon ◽  
Activity Levels ◽  
Mrna Levels ◽  
Chronic Alcohol ◽  
Chronic Alcohol Consumption ◽  
Uptake Process

Thiamin is essential for normal cellular functions, and its deficiency leads to a variety of clinical abnormalities. Humans and other mammals obtain the vitamin via intestinal absorption. The intestine is exposed to two sources of thiamin, a dietary and a bacterial (i.e., normal microflora of the large intestine) source. Chronic alcohol consumption is associated with thiamin deficiency, which is caused (in part) by inhibition in intestinal thiamin absorption. However, little is known about the physiological and molecular aspects of the intestinal thiamin uptake process that are affected by chronic alcohol use. To address these issues, we used rats fed an alcohol-liquid diet and human intestinal epithelial HuTu-80 cells chronically exposed to ethanol as model systems. The results showed that chronic alcohol feeding to rats led to a significant inhibition in carrier-mediated thiamin transport across both the jejunal brush-border membrane and basolateral membrane domains. This was associated with a significant reduction in level of expression of thiamin transporter-1 (THTR-1), but not THTR-2, at the protein and mRNA levels. Level of expression of the heterogenous nuclear RNA of THTR-1 in the intestine of alcohol-fed rats was also decreased compared with their pair-fed controls. Chronic alcohol feeding also caused a significant inhibition in carrier-mediated thiamin uptake in rat colon. Studies with HuTu-80 cells chronically exposed to ethanol also showed a significant inhibition in carrier-mediated thiamin uptake. This inhibition was associated with a reduction in level of expression of human THTR-1 and THTR-2 at the protein, mRNA, and transcriptional (promoter activity) levels. These studies demonstrate that chronic alcohol feeding inhibits intestinal thiamin absorption via inhibition of the individual membrane transport event across the polarized absorptive epithelial cells. Furthermore, the inhibition is, at least in part, mediated via transcriptional mechanism(s).

scholarly journals Effect of chronic alcohol exposure on folate uptake by liver mitochondria

2012 ◽  
Vol 302 (1) ◽  
pp. C203-C209 ◽  
Author(s):  
Arundhati Biswas ◽  
Sundar Rajan Senthilkumar ◽  
Hamid M. Said
Keyword(s):  
Hepg2 Cells ◽  
Mammalian Cells ◽  
Regulatory Region ◽  
Alcohol Exposure ◽  
Significant Inhibition ◽  
Water Soluble ◽  
Transcriptional Level ◽  
Chronic Alcohol ◽  
Mitochondrial Carrier ◽  
Chronic Alcohol Exposure

Mammalian cells obtain folate, a water-soluble vitamin, from their surroundings via transport across cell membrane. Intracellular folate is compartmentalized between the cytoplasm and the mitochondria. Transport of folate from the cytoplasm into the mitochondria is via a specific carrier-mediated process involving the mitochondrial folate transporter (MFT). Chronic alcohol use negatively impacts folate homeostasis, but its effect on mitochondrial folate uptake is not clear. We addressed this issue using mitochondrial preparations isolated from the liver of rats chronically fed an alcohol liquid diet and from human liver HepG2 cells chronically exposed to alcohol. The results showed that chronic alcohol feeding of rats leads to a significant inhibition in mitochondrial carrier-mediated folate uptake. This inhibition was associated with a significant reduction in the level of expression of the MFT protein, mRNA, and heterogenous nuclear RNA (hnRNA). Similarly, chronic alcohol exposure (96 h) of HepG2 cells led to significant inhibition in mitochondrial carrier-mediated folate uptake, which was associated with a marked reduction in the level of expression of the human MFT (hMFT). To determine whether the latter effect is, in part, being exerted at the transcriptional level, we cloned the 5′-regulatory region of the human SLC25A32 gene (which encodes the hMFT) and showed that chronic alcohol exposure of HepG2 cells leads to a significant inhibition in its promoter activity. These studies show for the first time that chronic alcohol feeding/exposure leads to a significant inhibition in mitochondrial carrier-mediated folate uptake and that the inhibition is, in part, being exerted at the level of transcription of the SLC25A32 gene.

Both Sp1 and Smad participate in mediating TGF-β1-induced HGF receptor expression in renal epithelial cells

2005 ◽  
Vol 288 (1) ◽  
pp. F16-F26 ◽  
Author(s):  
Xianghong Zhang ◽  
Junwei Yang ◽  
Yingjian Li ◽  
Youhua Liu
Keyword(s):  
Growth Factor ◽  
Epithelial Cells ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β1 ◽  
Receptor Expression ◽  
Transcriptional Level ◽  
Renal Epithelial Cells ◽  
Tgf Β1

Hepatocyte growth factor (HGF) receptor is a transmembrane receptor tyrosine kinase encoded by the c-met protooncogene. In this study, we demonstrated that c-met expression was upregulated in the kidney after obstructive injury in mice. Because the pattern of c-met induction was closely correlated with transforming growth factor-β1 (TGF-β1) expression in vivo, we further investigated the regulation of c-met expression in renal tubular epithelial (HKC) cells by TGF-β1 in vitro. Real-time RT-PCR and Northern and Western blot analyses revealed that TGF-β1 significantly induced c-met expression in HKC cells, which primarily took place at the gene transcriptional level. Overexpression of inhibitory Smad7 completely abolished c-met induction, indicating its dependence on Smad signaling. Interestingly, TGF-β1-induced c-met expression was also contingent on a functional Sp1, as ablation of Sp1 binding with mithramycin A abrogated c-met induction in HKC cells. Transfection and sequence analysis identified a cis-acting TGF-β1-responsive region in the c-met promoter, in which resided a putative Smad-binding element (SBE) and an adjacent Sp1 site. TGF-β1 not only induced Smad binding to the SBE/Sp1 sites in the c-met promoter, but also enhanced the binding of Sp proteins. Furthermore, Sp1 could form a complex with Smads in a TGF-β1-dependent fashion. These results suggest a novel regulatory mechanism controlling c-met expression by TGF-β1 in renal epithelial cells, in which both Smad and Sp proteins participate and cooperate in activating c-met gene transcription.

Metalloprotease-mediated cleavage secretion of pulmonary ACE by vascular endothelial and kidney epithelial cells

1996 ◽  
Vol 271 (2) ◽  
pp. H744-H751 ◽  
Author(s):  
R. Ramchandran ◽  
S. Kasturi ◽  
J. G. Douglas ◽  
I. Sen
Keyword(s):  
Epithelial Cells ◽  
Cysteine Proteases ◽  
Significant Inhibition ◽  
The Body ◽  
Rabbit Serum ◽  
Vascular Endothelial ◽  
Renal Epithelial Cells ◽  
Proximal Tubular Epithelial Cells

The pulmonary isozyme of angiotensin-converting enzyme (ACEP) is present in the body both as a cell-associated protein in endothelial, epithelial, and monocytic cells and as a soluble protein in various body fluids including serum. The mechanism by which soluble ACEP is produced in vivo is unknown. Using in vitro transfected cell culture systems, we previously demonstrated that the rabbit testicular isozyme of ACE (ACET), which shares extensive homology with ACEP, is first synthesized as a plasma membrane-anchored ectoprotein and then secreted to the culture medium by cleavage removal of its COOH-terminal membrane-anchored tail. Here, using in vitro cultures of arterial endothelial cells and acutely isolated renal epithelial cells, we demonstrate that ACEP is also cleavage secreted from their natural producer cells. Biochemical and immunological characterization of the in vitro secreted ACEP protein revealed that it is missing the COOH-terminal membrane-anchored region of the cell-associated ACEP. Similar analysis of ACEP proteins present in rabbit serum, lung, and kidney established that ACEP secretion in vivo is also caused by the cleavage removal of the COOH-terminal region of the cell-associated protein. To characterize the proteolytic enzyme responsible for ACEP secretion, we employed rabbit renal proximal tubular epithelial cells and demonstrated significant inhibition of secretion by compound 3, a hydroxamic acid-based inhibitor of specific metalloproteases. In contrast, the inhibitors of chymotrypsin, trypsin, serine, aspartate, and cysteine proteases were ineffective. These results indicate that soluble ACEP production by vascular endothelial and renal epithelial cells, both in vitro and in vivo, is achieved by cleavage removal of its membrane-anchoring COOH-terminal tail by a metalloprotease.

Regulation of renal ion transport and cell growth by sodium

1989 ◽  
Vol 257 (1) ◽  
pp. F1-F10 ◽  
Author(s):  
B. A. Stanton ◽  
B. Kaissling
Keyword(s):  
Cell Growth ◽  
Epithelial Cells ◽  
Basolateral Membrane ◽  
Extracellular Fluid ◽  
Sodium Concentration ◽  
Intracellular Sodium ◽  
Sodium Efflux ◽  
Renal Epithelial Cells ◽  
Sodium Uptake ◽  
Cell Growth And Proliferation

Intracellular sodium has been implicated in a variety of cellular processes including regulation of Na+-K+-ATPase activity, mitogen-induced cell growth, and proliferation and stimulation of Na+-K+-ATPase by aldosterone. In renal epithelial cells a rise in sodium uptake across the apical membrane increases intracellular sodium concentration, which in turn stimulates the turnover rate of Na+-K+-ATPase and thereby enhances sodium efflux across the basolateral membrane. A prolonged increase in sodium uptake causes dramatic hypertrophy and hyperplasia and a rise in the quantity of Na+-K+-ATPase in the basolateral membrane. These structural and functional changes occur in the kidney in the absence of alterations in plasma aldosterone and vasopressin levels. Several mitogens induce growth and proliferation by initiating a cascade of events, which include a rise in intracellular sodium. Accordingly, an increase in the sodium concentration within renal epithelial cells may elicit a “mitogen-like” effect by initiating the cascade at the sodium step, even in the absence of a mitogen. A rise in cell sodium may also stimulate the production of autocrine growth factors that directly or indirectly regulate cell growth and proliferation, by modifying the response to mitogens or to changes in the ionic composition of the extracellular fluid. In this review we will examine the evidence that supports a role for intracellular sodium in regulating these cellular events in renal epithelial cells.

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