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The role of arginine and arginine-metabolizing enzymes during Giardia - host cell interactions in vitro.

Stadelmann B, Hanevik K, Andersson MK, Bruserud O, Svärd SG - BMC Microbiol. (2013)

Bottom Line: In addition, the secreted, arginine-consuming giardial enzyme arginine deiminase (GiADI) actively reduces T-cell proliferation in vitro.Interestingly, the effects on NO production and T cell proliferation could be reversed by addition of external arginine or citrulline.Many of the effects can be reversed by addition of arginine or citrulline, which could be a beneficial supplement in oral rehydration therapy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cell- and Molecular Biology, Uppsala University, BMC, Box 596, Uppsala SE-751 24, Sweden. staffan.svard@icm.uu.se.

ABSTRACT

Background: Arginine is a conditionally essential amino acid important in growing individuals and under non-homeostatic conditions/disease. Many pathogens interfere with arginine-utilization in host cells, especially nitric oxide (NO) production, by changing the expression of host enzymes involved in arginine metabolism. Here we used human intestinal epithelial cells (IEC) and three different isolates of the protozoan parasite Giardia intestinalis to investigate the role of arginine and arginine-metabolizing enzymes during intestinal protozoan infections.

Results: RNA expression analyses of major arginine-metabolizing enzymes revealed the arginine-utilizing pathways in human IECs (differentiated Caco-2 cells) grown in vitro. Most genes were constant or down-regulated (e.g. arginase 1 and 2) upon interaction with Giardia, whereas inducible NO synthase (iNOS) and ornithine decarboxylase (ODC) were up-regulated within 6 h of infection. Giardia was shown to suppress cytokine-induced iNOS expression, thus the parasite has both iNOS inducing and suppressive activities. Giardial arginine consumption suppresses NO production and the NO-degrading parasite protein flavohemoglobin is up-regulated in response to host NO. In addition, the secreted, arginine-consuming giardial enzyme arginine deiminase (GiADI) actively reduces T-cell proliferation in vitro. Interestingly, the effects on NO production and T cell proliferation could be reversed by addition of external arginine or citrulline.

Conclusions: Giardia affects the host's arginine metabolism on many different levels. Many of the effects can be reversed by addition of arginine or citrulline, which could be a beneficial supplement in oral rehydration therapy.

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Expression of arginine-metabolizing enzymes in IECs upon Giardia infection. Differentiated Caco-2 IECs were in vitro infected with Giardia trophozoites of three different assemblages (isolates WB (squares), GS (circles) and P15 (triangles)) and expression of arginine-consuming enzymes in host cells was assessed after 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. The data is presented as fold change gene expression in arbitrary units on a logarithmic scale as compared to 0 h expression. GAPDH was used as reference gene. In total 12 different arginine-consuming genes and the control gene ccl20 were assessed for their expression. Note the changed scale for ccl20. adc, arginine decarboxylase; agat, arginine-glycine amidinotransferase; arg, arginase; asl, argininosuccinate lyase; ass, argininosuccinate synthetase; cat, cationic amino acid transporter; ccl20, chemokine (C-C motif) ligand 20; nos, nitric oxide synthase; oat, ornithine aminotransferase; oct, ornithine carbamoyl transferase; odc, ornithine decarboxylase.
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Figure 2: Expression of arginine-metabolizing enzymes in IECs upon Giardia infection. Differentiated Caco-2 IECs were in vitro infected with Giardia trophozoites of three different assemblages (isolates WB (squares), GS (circles) and P15 (triangles)) and expression of arginine-consuming enzymes in host cells was assessed after 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. The data is presented as fold change gene expression in arbitrary units on a logarithmic scale as compared to 0 h expression. GAPDH was used as reference gene. In total 12 different arginine-consuming genes and the control gene ccl20 were assessed for their expression. Note the changed scale for ccl20. adc, arginine decarboxylase; agat, arginine-glycine amidinotransferase; arg, arginase; asl, argininosuccinate lyase; ass, argininosuccinate synthetase; cat, cationic amino acid transporter; ccl20, chemokine (C-C motif) ligand 20; nos, nitric oxide synthase; oat, ornithine aminotransferase; oct, ornithine carbamoyl transferase; odc, ornithine decarboxylase.

Mentions: Our earlier data showed that arginine is depleted in the growth medium already after 1-2 h of in vitro interaction between Giardia trophozoites and human IECs [7]. A number of enzymes and transporters are directly and indirectly involved in the arginine-metabolism of human cells (Figure 1). Pathogenic microbes are known to affect the expression of these enzymes, especially arginase 1 and 2 [18]. However, arginine-metabolism in human IECs is poorly characterized and it is not known how it is affected by Giardia infection. In order to study this, the expression of arginine-consuming enzymes was assessed in differentiated TC7 Caco-2 cells, that exhibit small intestinal epithelial characteristics, by qPCR at time points 0, 1.5, 3, 6 and 24 h post in vitro Giardia infection. To study if different Giardia assemblages have different effects on the arginine metabolism we used trophozoites from three different isolates: WB (assemblage A), GS (assemblage B) and P15 (assemblage E) [2]. The assessed genes were the chemokine ccl20 as positive infection control [20] and several arginine-consuming enzymes (see Figure 1 and 2, Additional file 1: Table S1). Except for cat2 and nos1, all tested genes were expressed in IECs, however, adc, argI and nos3 only at very low levels (Additional file 1: Tables S2-S4). Most of the genes showed only slight changes in expression on RNA level over the 24 h experiment (Figure 2). The strong induction of ccl20 already after 1.5 h of infection with Giardia trophozoites is in line with our earlier results [20]. None of the tested arginine-consuming enzymes were up-regulated more than 2 times after 1.5 h of WB interaction. After 3 and 6 h, odc and nos2 were up-regulated more than 2 times in the WB interaction, but expression dropped at 24 h. The same observations were made in interactions with parasites of the isolates GS and P15. However, the effects on induction of ccl20, nos2 and odc were much more pronounced upon infection with the isolate GS than with WB and P15 (Figure 2). arg1, arg2 and agat were down-regulated at all time points with a 4- (arg1), 3- (arg2) and 6.5-fold (agat) reduction at 6 h of WB interaction, followed by recovery to near basal expression levels after 24 h. This profile was also seen in interactions with the two other isolates. Several other genes (adc, oat, oct) showed the same expression profiles with an initial decrease followed by an increase at 24 h. Thus, upon depletion of arginine by Giardia trophozoites (after 1-2 h), expression levels of most host arginine-metabolizing enzymes are reduced, independent of the parasite isolate. The results are summarized in Figure 1, which shows the complex gene expression changes occurring when Giardia trophozoites interact with host IECs.


The role of arginine and arginine-metabolizing enzymes during Giardia - host cell interactions in vitro.

Stadelmann B, Hanevik K, Andersson MK, Bruserud O, Svärd SG - BMC Microbiol. (2013)

Expression of arginine-metabolizing enzymes in IECs upon Giardia infection. Differentiated Caco-2 IECs were in vitro infected with Giardia trophozoites of three different assemblages (isolates WB (squares), GS (circles) and P15 (triangles)) and expression of arginine-consuming enzymes in host cells was assessed after 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. The data is presented as fold change gene expression in arbitrary units on a logarithmic scale as compared to 0 h expression. GAPDH was used as reference gene. In total 12 different arginine-consuming genes and the control gene ccl20 were assessed for their expression. Note the changed scale for ccl20. adc, arginine decarboxylase; agat, arginine-glycine amidinotransferase; arg, arginase; asl, argininosuccinate lyase; ass, argininosuccinate synthetase; cat, cationic amino acid transporter; ccl20, chemokine (C-C motif) ligand 20; nos, nitric oxide synthase; oat, ornithine aminotransferase; oct, ornithine carbamoyl transferase; odc, ornithine decarboxylase.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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Figure 2: Expression of arginine-metabolizing enzymes in IECs upon Giardia infection. Differentiated Caco-2 IECs were in vitro infected with Giardia trophozoites of three different assemblages (isolates WB (squares), GS (circles) and P15 (triangles)) and expression of arginine-consuming enzymes in host cells was assessed after 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. The data is presented as fold change gene expression in arbitrary units on a logarithmic scale as compared to 0 h expression. GAPDH was used as reference gene. In total 12 different arginine-consuming genes and the control gene ccl20 were assessed for their expression. Note the changed scale for ccl20. adc, arginine decarboxylase; agat, arginine-glycine amidinotransferase; arg, arginase; asl, argininosuccinate lyase; ass, argininosuccinate synthetase; cat, cationic amino acid transporter; ccl20, chemokine (C-C motif) ligand 20; nos, nitric oxide synthase; oat, ornithine aminotransferase; oct, ornithine carbamoyl transferase; odc, ornithine decarboxylase.
Mentions: Our earlier data showed that arginine is depleted in the growth medium already after 1-2 h of in vitro interaction between Giardia trophozoites and human IECs [7]. A number of enzymes and transporters are directly and indirectly involved in the arginine-metabolism of human cells (Figure 1). Pathogenic microbes are known to affect the expression of these enzymes, especially arginase 1 and 2 [18]. However, arginine-metabolism in human IECs is poorly characterized and it is not known how it is affected by Giardia infection. In order to study this, the expression of arginine-consuming enzymes was assessed in differentiated TC7 Caco-2 cells, that exhibit small intestinal epithelial characteristics, by qPCR at time points 0, 1.5, 3, 6 and 24 h post in vitro Giardia infection. To study if different Giardia assemblages have different effects on the arginine metabolism we used trophozoites from three different isolates: WB (assemblage A), GS (assemblage B) and P15 (assemblage E) [2]. The assessed genes were the chemokine ccl20 as positive infection control [20] and several arginine-consuming enzymes (see Figure 1 and 2, Additional file 1: Table S1). Except for cat2 and nos1, all tested genes were expressed in IECs, however, adc, argI and nos3 only at very low levels (Additional file 1: Tables S2-S4). Most of the genes showed only slight changes in expression on RNA level over the 24 h experiment (Figure 2). The strong induction of ccl20 already after 1.5 h of infection with Giardia trophozoites is in line with our earlier results [20]. None of the tested arginine-consuming enzymes were up-regulated more than 2 times after 1.5 h of WB interaction. After 3 and 6 h, odc and nos2 were up-regulated more than 2 times in the WB interaction, but expression dropped at 24 h. The same observations were made in interactions with parasites of the isolates GS and P15. However, the effects on induction of ccl20, nos2 and odc were much more pronounced upon infection with the isolate GS than with WB and P15 (Figure 2). arg1, arg2 and agat were down-regulated at all time points with a 4- (arg1), 3- (arg2) and 6.5-fold (agat) reduction at 6 h of WB interaction, followed by recovery to near basal expression levels after 24 h. This profile was also seen in interactions with the two other isolates. Several other genes (adc, oat, oct) showed the same expression profiles with an initial decrease followed by an increase at 24 h. Thus, upon depletion of arginine by Giardia trophozoites (after 1-2 h), expression levels of most host arginine-metabolizing enzymes are reduced, independent of the parasite isolate. The results are summarized in Figure 1, which shows the complex gene expression changes occurring when Giardia trophozoites interact with host IECs.

Bottom Line: In addition, the secreted, arginine-consuming giardial enzyme arginine deiminase (GiADI) actively reduces T-cell proliferation in vitro.Interestingly, the effects on NO production and T cell proliferation could be reversed by addition of external arginine or citrulline.Many of the effects can be reversed by addition of arginine or citrulline, which could be a beneficial supplement in oral rehydration therapy.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Cell- and Molecular Biology, Uppsala University, BMC, Box 596, Uppsala SE-751 24, Sweden. staffan.svard@icm.uu.se.

ABSTRACT

Background: Arginine is a conditionally essential amino acid important in growing individuals and under non-homeostatic conditions/disease. Many pathogens interfere with arginine-utilization in host cells, especially nitric oxide (NO) production, by changing the expression of host enzymes involved in arginine metabolism. Here we used human intestinal epithelial cells (IEC) and three different isolates of the protozoan parasite Giardia intestinalis to investigate the role of arginine and arginine-metabolizing enzymes during intestinal protozoan infections.

Results: RNA expression analyses of major arginine-metabolizing enzymes revealed the arginine-utilizing pathways in human IECs (differentiated Caco-2 cells) grown in vitro. Most genes were constant or down-regulated (e.g. arginase 1 and 2) upon interaction with Giardia, whereas inducible NO synthase (iNOS) and ornithine decarboxylase (ODC) were up-regulated within 6 h of infection. Giardia was shown to suppress cytokine-induced iNOS expression, thus the parasite has both iNOS inducing and suppressive activities. Giardial arginine consumption suppresses NO production and the NO-degrading parasite protein flavohemoglobin is up-regulated in response to host NO. In addition, the secreted, arginine-consuming giardial enzyme arginine deiminase (GiADI) actively reduces T-cell proliferation in vitro. Interestingly, the effects on NO production and T cell proliferation could be reversed by addition of external arginine or citrulline.

Conclusions: Giardia affects the host's arginine metabolism on many different levels. Many of the effects can be reversed by addition of arginine or citrulline, which could be a beneficial supplement in oral rehydration therapy.

Show MeSH
Related in: MedlinePlus