+Model
ARTICLE IN PRESS
CLINRE-569; No. of Pages 3
Clinics and Research in Hepatology and Gastroenterology (2014) xxx, xxx—xxx
Available online at
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COMMENTARY
Bile acids in cholestasis: Bad for the liver, not so good for the kidney Serge Erlinger ∗ University of Paris 7, 75013 Paris, France
Summary The elegant paper by Fickert et al. on bile duct ligated mice provides convincing evidence for the hypothesis that bile acids retained in the serum during cholestasis and excreted through the kidneys are toxic to collecting duct cells. The authors propose that bile acids initiate a chain of reactions leading to tubulointerstitial nephritis and fibrosis. Mice with cholestasis were protected by prefeeding with the hydrophilic bile acid norursodeoxycholic acid, an observation which suggests a potential therapeutic option for cholemic nephropathy. © 2014 Published by Elsevier Masson SAS.
Bile acids are thought to trigger hepatocyte and cholangiocyte damage in patients with cholestasis [1,2]. Bile acid-induced damage in cholestasis is probably due to several mechanisms, in particular oxidative stress, apoptosis, necrosis, inflammation, and membrane alterations. A recent paper by Fickert et al. suggests that bile acids excreted in urine during cholestasis may also play a major initiating role in renal tubular epithelial injury in cholestatic patients [3]. We know that cholestatic liver diseases may be associated with tubulointerstitial kidney lesions [4,5]. Patients with obstructive jaundice frequently have acute kidney injury and renal failure in the perioperative period and acute tubular injury on renal biopsy [6], a condition sometimes referred to as cholemic nephropathy [7]. Bile acid concentration is elevated in the liver and serum of cholestatic patients, and cholestatic hepatocytes try to limit intracellular accumulation of bile acids by inducing basolateral bile acid export
∗
1422, route des Mauvares, 13840 Rognes, France. E-mail address: [email protected]
pumps [8,9]. Likewise, adaptive changes in the renal tubule facilitate their renal excretion, but increase the bile acid burden to the tubular cells [8,9]. Fickert et al. have tested the hypothesis that this increased bile acid load to the tubules could be a mechanism to trigger tubular cell damage during cholestasis. To this end, they established and characterized a mouse model of combined cholestatic liver and kidney disease. They used common bile duct ligated (CBDL) mice studied sequentially at 3 and 7 days, and 3, 6 and 8 weeks. They performed conventional liver biochemical tests (alanine aminotransferases[ALT], alkaline phosphatase[ALP], total serum bile acids), and measured urea levels. They examined the livers and kidneys by light microscopy and used immunohistochemistry and immunofluorescence (IF) microscopy to localize markers of kidney tubular cells. As controls, they used unilateral ureter ligation as a model of tubulointerstitial kidney injury. They also examined the possibility that norursodeoxycholic acid (norUDCA), a hydrophilic bile acid much less toxic than physiological bile acids [10], could protect the kidneys from bile acid-induced injury.
http://dx.doi.org/10.1016/j.clinre.2014.03.003 2210-7401/© 2014 Published by Elsevier Masson SAS.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
+Model CLINRE-569; No. of Pages 3
ARTICLE IN PRESS
2
S. Erlinger
The main results of the study may be summarized as follows: • as expected, CBDL mice progressively developed biliary fibrosis demonstrating chronic cholestatic liver disease, with marked elevations of serum ALT, ALP and bile acid concentration. At 8 weeks, the kidney surface appeared irregular and greenish, and the kidneys size and weight were significantly reduced. (The kidney weight/body weight ratio remained unchanged, due to a decrease of body weight). There was an increase in serum urea levels and urinary volume, indicating polyuric renal failure; • at the same time (8 weeks), light microscopy revealed markedly dilated tubuli, with tubulointerstitial nephritis and pronounced fibrosis, confirmed biochemically by induction of collagen ␣1(I) and tgf-1; • sequential analysis showed that tubular injury was seen as early as 3 days after CBDL, and predominated on collecting ducts, as demonstrated by IF staining of aquaporin 2, which is specifically expressed in the apical membrane of collecting duct cells [11,12]. In addition, there was frequently a loss of basement membrane continuity, which resulted in urinary leakage of fluorescent UDCA injected into the portal vein of the animals, thus confirming profound functional alteration of collecting tubules; • farnesoid X receptor knock-out (FXR-/- ) mice, which have a more hydrophilic bile acid pool and much less elevated serum bile acid concentration than wild-type mice [13], were completely protected from CBDL-induced renal injury at 8 weeks, although they had tubular epithelial injury at 3 days. In these FXR-/- mice, unilateral ureter ligation induced tubulointerstitial nephritis and fibrosis, showing that the animals were not protected from renal injury. Prefeeding the mice with norUDCA during 7 days before CBDL prevented tubular epithelial injury at 3 days, as demonstrated by PAS- and aquaporin 2 stained kidney sections; • finally, screening of pathology archives for cholestatic patients with kidney impairment allowed to demonstrate, at histology, tubular casts, interstitial nephritis, renal fibrosis and collecting duct lesions. This elegant and well-designed experimental study convincingly suggests that kidney lesions in CBDL mice are due to, or at least initiated by the toxicity of bile acids on collecting tubules. Interestingly, the authors point out that studies in dogs with cholestasis, from the 1940s and 1950s, showed renal alterations close to those observed in the present study [14]. In subsequent years, many laboratories switched to rats: the renal alterations in CBDL rats are much less impressive than those in mice [15,16]. These species differences may be due to differences in the metabolism and transport of bile acids. CBDL mice have the far highest serum bile acid levels among the various experimental animals: it is then tempting to speculate that bile acids are an important agent for the observed renal lesions in these mice. Two major arguments support this speculation. First, the observations on FXR-/- mice: at 3 days, they have tubular cells injury at histological examination, and, at this time, a high urinary bile acid concentration; later, at 8 weeks, they excrete mainly polyhydroxylated non-toxic bile acids [13] and they are protected completely from renal injury. The
second argument supporting the renal toxicity of bile acids is the complete protective effect on kidney lesions of pretreatment with the hydrophilic norUDCA, which is extensively excreted in the urine. The authors propose a three-step model for the development of kidney injury in cholestasis: • tubular epithelial injury with basement membrane alterations, and leakage of urine into the renal parenchyma; • induction of a reactive phenotype of renal tubular cells with overexpression of pro-inflammatory and profibrogenetic cytokines and; • tubulointerstitial renal fibrosis. The model can be further tested experimentally and it offers potential targets to prevent potentially severe kidney damage in cholestatic patients.
Disclosure of interest The author declares that he has no conflicts of interest concerning this article.
References [1] Hirschfield GM, Heathcote EJ, Gershwin ME. Pathogenesis of cholestatic liver disease and therapeutic approaches. Gastroenterology 2010;139:1481—96. [2] Woolbright BL, Jaeschke H. Novel insight into mechanisms of cholestatic liver injury. World J Gastroenterol 2012;18:4985—93. [3] Fickert P, Krones E, Pollheimer MJ, Thueringer A, Moustafa T, Silbert D, et al. Bile acids trigger cholemic nephropathy in common bile-duct-ligated mice. Hepatology 2013;58:2056—69. [4] Montini G, Carasi C, Zancan L, Dall’Amico R, Murer L, Zacchello G, et al. Chronic cholestatic liver disease with associated tubulointerstitial nephropathy in early childhood. Pediatrics 1997;100:E10. [5] Popovic-Rolovic M, Kostic M, Sindjic M, Jovanovic O, Peco-Antic A, Kruscic D. Progressive tubulointerstitial nephritis and chronic cholestatic liver disease. Pediatr Nephrol 1993;7:396—400. [6] Uslu A, Tasli FA, Nart A, Postaci H, Aykas A, Bati H, et al. Human kidney histopathology in acute obstructive jaundice: a prospective study. Eur J Gastroenterol Hepatol 2010;22:1458—65. [7] Betjes MG, Bajema I. The pathology of jaundice-related renal insufficiency: cholemic nephrosis revisited. J Nephrol 2006;19:229—33. [8] Boyer JL, Trauner M, Mennone A, Soroka CJ, Cai SY, Moustafa T, et al. Upregulation of a basolateral FXR-dependent bile acid efflux transporter OSTalpha-OSTbeta in cholestasis in humans and rodents. Am J Physiol Gastrointest Liver Physiol 2006;290:G1124—30. [9] Zollner G, Wagner M, Moustafa T, Fickert P, Silbert D, Gumhold J, et al. Coordinated induction of bile acid detoxification and alternative elimination in mice: role of FXR-regulated organic solute transporter-alpha/beta in the adaptive response to bile acids. Am J Physiol Gastrointest Liver Physiol 2006;290:G923—32. [10] Hofmann AF, Zakko SF, Lira M, Clerici C, Hagey LR, Lambert KK, et al. Novel biotransformation and physiological properties of norursodeoxycholic acid in humans. Hepatology 2005;42:1391—8.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
+Model CLINRE-569; No. of Pages 3
ARTICLE IN PRESS
Bile acids and the kidney [11] Brown D, Breton S, Ausiello DA, Marshansky V. Sensing, signaling and sorting events in kidney epithelial cell physiology. Traffic 2009;10:275—84. [12] Nielsen S, DiGiovanni SR, Christensen EI, Knepper MA, Harris HW. Cellular and subcellular immunolocalization of vasopressin-regulated water channel in rat kidney. Proc Natl Acad Sci U S A 1993;90:11663—7. [13] Marschall HU, Wagner M, Bodin K, Zollner G, Fickert P, Gumhold J, et al. FXR(-/- ) mice adapt to biliary obstruction by enhanced phase I detoxification and renal elimination of bile acids. J Lipid Res 2006;47:582—92.
3 [14] Masumoto T, Masuoka S. Kidney function in the severely jaundiced dog. Am J Surg 1980;140:426—30. [15] Kaler B, Karram T, Morgan WA, Bach PH, Yousef IM, Bomzon A. Are bile acids involved in the renal dysfunction of obstructive jaundice?An experimental study in bile duct ligated rats. Ren Fail 2004;26:507—16. [16] Schlattjan JH, Winter C, Greven J. Regulation of renal tubular bile acid transport in the early phase of an obstructive cholestasis in the rat. Nephron Physiol 2003;95: 49—56.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
ARTICLE IN PRESS
CLINRE-569; No. of Pages 3
Clinics and Research in Hepatology and Gastroenterology (2014) xxx, xxx—xxx
Available online at
ScienceDirect www.sciencedirect.com
COMMENTARY
Bile acids in cholestasis: Bad for the liver, not so good for the kidney Serge Erlinger ∗ University of Paris 7, 75013 Paris, France
Summary The elegant paper by Fickert et al. on bile duct ligated mice provides convincing evidence for the hypothesis that bile acids retained in the serum during cholestasis and excreted through the kidneys are toxic to collecting duct cells. The authors propose that bile acids initiate a chain of reactions leading to tubulointerstitial nephritis and fibrosis. Mice with cholestasis were protected by prefeeding with the hydrophilic bile acid norursodeoxycholic acid, an observation which suggests a potential therapeutic option for cholemic nephropathy. © 2014 Published by Elsevier Masson SAS.
Bile acids are thought to trigger hepatocyte and cholangiocyte damage in patients with cholestasis [1,2]. Bile acid-induced damage in cholestasis is probably due to several mechanisms, in particular oxidative stress, apoptosis, necrosis, inflammation, and membrane alterations. A recent paper by Fickert et al. suggests that bile acids excreted in urine during cholestasis may also play a major initiating role in renal tubular epithelial injury in cholestatic patients [3]. We know that cholestatic liver diseases may be associated with tubulointerstitial kidney lesions [4,5]. Patients with obstructive jaundice frequently have acute kidney injury and renal failure in the perioperative period and acute tubular injury on renal biopsy [6], a condition sometimes referred to as cholemic nephropathy [7]. Bile acid concentration is elevated in the liver and serum of cholestatic patients, and cholestatic hepatocytes try to limit intracellular accumulation of bile acids by inducing basolateral bile acid export
∗
1422, route des Mauvares, 13840 Rognes, France. E-mail address: [email protected]
pumps [8,9]. Likewise, adaptive changes in the renal tubule facilitate their renal excretion, but increase the bile acid burden to the tubular cells [8,9]. Fickert et al. have tested the hypothesis that this increased bile acid load to the tubules could be a mechanism to trigger tubular cell damage during cholestasis. To this end, they established and characterized a mouse model of combined cholestatic liver and kidney disease. They used common bile duct ligated (CBDL) mice studied sequentially at 3 and 7 days, and 3, 6 and 8 weeks. They performed conventional liver biochemical tests (alanine aminotransferases[ALT], alkaline phosphatase[ALP], total serum bile acids), and measured urea levels. They examined the livers and kidneys by light microscopy and used immunohistochemistry and immunofluorescence (IF) microscopy to localize markers of kidney tubular cells. As controls, they used unilateral ureter ligation as a model of tubulointerstitial kidney injury. They also examined the possibility that norursodeoxycholic acid (norUDCA), a hydrophilic bile acid much less toxic than physiological bile acids [10], could protect the kidneys from bile acid-induced injury.
http://dx.doi.org/10.1016/j.clinre.2014.03.003 2210-7401/© 2014 Published by Elsevier Masson SAS.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
+Model CLINRE-569; No. of Pages 3
ARTICLE IN PRESS
2
S. Erlinger
The main results of the study may be summarized as follows: • as expected, CBDL mice progressively developed biliary fibrosis demonstrating chronic cholestatic liver disease, with marked elevations of serum ALT, ALP and bile acid concentration. At 8 weeks, the kidney surface appeared irregular and greenish, and the kidneys size and weight were significantly reduced. (The kidney weight/body weight ratio remained unchanged, due to a decrease of body weight). There was an increase in serum urea levels and urinary volume, indicating polyuric renal failure; • at the same time (8 weeks), light microscopy revealed markedly dilated tubuli, with tubulointerstitial nephritis and pronounced fibrosis, confirmed biochemically by induction of collagen ␣1(I) and tgf-1; • sequential analysis showed that tubular injury was seen as early as 3 days after CBDL, and predominated on collecting ducts, as demonstrated by IF staining of aquaporin 2, which is specifically expressed in the apical membrane of collecting duct cells [11,12]. In addition, there was frequently a loss of basement membrane continuity, which resulted in urinary leakage of fluorescent UDCA injected into the portal vein of the animals, thus confirming profound functional alteration of collecting tubules; • farnesoid X receptor knock-out (FXR-/- ) mice, which have a more hydrophilic bile acid pool and much less elevated serum bile acid concentration than wild-type mice [13], were completely protected from CBDL-induced renal injury at 8 weeks, although they had tubular epithelial injury at 3 days. In these FXR-/- mice, unilateral ureter ligation induced tubulointerstitial nephritis and fibrosis, showing that the animals were not protected from renal injury. Prefeeding the mice with norUDCA during 7 days before CBDL prevented tubular epithelial injury at 3 days, as demonstrated by PAS- and aquaporin 2 stained kidney sections; • finally, screening of pathology archives for cholestatic patients with kidney impairment allowed to demonstrate, at histology, tubular casts, interstitial nephritis, renal fibrosis and collecting duct lesions. This elegant and well-designed experimental study convincingly suggests that kidney lesions in CBDL mice are due to, or at least initiated by the toxicity of bile acids on collecting tubules. Interestingly, the authors point out that studies in dogs with cholestasis, from the 1940s and 1950s, showed renal alterations close to those observed in the present study [14]. In subsequent years, many laboratories switched to rats: the renal alterations in CBDL rats are much less impressive than those in mice [15,16]. These species differences may be due to differences in the metabolism and transport of bile acids. CBDL mice have the far highest serum bile acid levels among the various experimental animals: it is then tempting to speculate that bile acids are an important agent for the observed renal lesions in these mice. Two major arguments support this speculation. First, the observations on FXR-/- mice: at 3 days, they have tubular cells injury at histological examination, and, at this time, a high urinary bile acid concentration; later, at 8 weeks, they excrete mainly polyhydroxylated non-toxic bile acids [13] and they are protected completely from renal injury. The
second argument supporting the renal toxicity of bile acids is the complete protective effect on kidney lesions of pretreatment with the hydrophilic norUDCA, which is extensively excreted in the urine. The authors propose a three-step model for the development of kidney injury in cholestasis: • tubular epithelial injury with basement membrane alterations, and leakage of urine into the renal parenchyma; • induction of a reactive phenotype of renal tubular cells with overexpression of pro-inflammatory and profibrogenetic cytokines and; • tubulointerstitial renal fibrosis. The model can be further tested experimentally and it offers potential targets to prevent potentially severe kidney damage in cholestatic patients.
Disclosure of interest The author declares that he has no conflicts of interest concerning this article.
References [1] Hirschfield GM, Heathcote EJ, Gershwin ME. Pathogenesis of cholestatic liver disease and therapeutic approaches. Gastroenterology 2010;139:1481—96. [2] Woolbright BL, Jaeschke H. Novel insight into mechanisms of cholestatic liver injury. World J Gastroenterol 2012;18:4985—93. [3] Fickert P, Krones E, Pollheimer MJ, Thueringer A, Moustafa T, Silbert D, et al. Bile acids trigger cholemic nephropathy in common bile-duct-ligated mice. Hepatology 2013;58:2056—69. [4] Montini G, Carasi C, Zancan L, Dall’Amico R, Murer L, Zacchello G, et al. Chronic cholestatic liver disease with associated tubulointerstitial nephropathy in early childhood. Pediatrics 1997;100:E10. [5] Popovic-Rolovic M, Kostic M, Sindjic M, Jovanovic O, Peco-Antic A, Kruscic D. Progressive tubulointerstitial nephritis and chronic cholestatic liver disease. Pediatr Nephrol 1993;7:396—400. [6] Uslu A, Tasli FA, Nart A, Postaci H, Aykas A, Bati H, et al. Human kidney histopathology in acute obstructive jaundice: a prospective study. Eur J Gastroenterol Hepatol 2010;22:1458—65. [7] Betjes MG, Bajema I. The pathology of jaundice-related renal insufficiency: cholemic nephrosis revisited. J Nephrol 2006;19:229—33. [8] Boyer JL, Trauner M, Mennone A, Soroka CJ, Cai SY, Moustafa T, et al. Upregulation of a basolateral FXR-dependent bile acid efflux transporter OSTalpha-OSTbeta in cholestasis in humans and rodents. Am J Physiol Gastrointest Liver Physiol 2006;290:G1124—30. [9] Zollner G, Wagner M, Moustafa T, Fickert P, Silbert D, Gumhold J, et al. Coordinated induction of bile acid detoxification and alternative elimination in mice: role of FXR-regulated organic solute transporter-alpha/beta in the adaptive response to bile acids. Am J Physiol Gastrointest Liver Physiol 2006;290:G923—32. [10] Hofmann AF, Zakko SF, Lira M, Clerici C, Hagey LR, Lambert KK, et al. Novel biotransformation and physiological properties of norursodeoxycholic acid in humans. Hepatology 2005;42:1391—8.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
+Model CLINRE-569; No. of Pages 3
ARTICLE IN PRESS
Bile acids and the kidney [11] Brown D, Breton S, Ausiello DA, Marshansky V. Sensing, signaling and sorting events in kidney epithelial cell physiology. Traffic 2009;10:275—84. [12] Nielsen S, DiGiovanni SR, Christensen EI, Knepper MA, Harris HW. Cellular and subcellular immunolocalization of vasopressin-regulated water channel in rat kidney. Proc Natl Acad Sci U S A 1993;90:11663—7. [13] Marschall HU, Wagner M, Bodin K, Zollner G, Fickert P, Gumhold J, et al. FXR(-/- ) mice adapt to biliary obstruction by enhanced phase I detoxification and renal elimination of bile acids. J Lipid Res 2006;47:582—92.
3 [14] Masumoto T, Masuoka S. Kidney function in the severely jaundiced dog. Am J Surg 1980;140:426—30. [15] Kaler B, Karram T, Morgan WA, Bach PH, Yousef IM, Bomzon A. Are bile acids involved in the renal dysfunction of obstructive jaundice?An experimental study in bile duct ligated rats. Ren Fail 2004;26:507—16. [16] Schlattjan JH, Winter C, Greven J. Regulation of renal tubular bile acid transport in the early phase of an obstructive cholestasis in the rat. Nephron Physiol 2003;95: 49—56.
Please cite this article in press as: Erlinger S. Bile acids in cholestasis: Bad for the liver, not so good for the kidney. Clin Res Hepatol Gastroenterol (2014), http://dx.doi.org/10.1016/j.clinre.2014.03.003
