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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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Related in: MedlinePlus

Expression of arginine-metabolizing enzymes in Giardia trophozoites upon host-cell interaction. Differentiated Caco-2 IECs were infected with Giardia trophozoites (isolate WB) and expression of arginine-consuming enzymes (adi, arginine deiminase; oct, ornithine carbamoyltransferase; ck, carbamate kinase) was assessed at 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. GL50803_17364 was used as reference gene. Fold change gene expression is shown with substracted medium effects.
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Figure 4: Expression of arginine-metabolizing enzymes in Giardia trophozoites upon host-cell interaction. Differentiated Caco-2 IECs were infected with Giardia trophozoites (isolate WB) and expression of arginine-consuming enzymes (adi, arginine deiminase; oct, ornithine carbamoyltransferase; ck, carbamate kinase) was assessed at 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. GL50803_17364 was used as reference gene. Fold change gene expression is shown with substracted medium effects.

Mentions: RNA expression changes of arginine-consuming enzymes upon Giardia-host cell interaction. Based on an interpretation of results from this and previous studies, the encircled numbers point out various ways by which Giardia interferes with the host immune response: (1) consumption of arginine via arginine-ornithine antiporter, (2) release of arginine-consuming ADI and OCT, (3) blocking of arginine-uptake into host cells by ornithine, (4) down-regulation of host iNOS, (5) up-regulation of host ODC, (6) up-regulation of parasite FlHb upon NO-stress. Human intestinal epithelial cells (Caco-2) were in vitro interacted with Giardia trophozoites and the expression changes of arginine-consuming enzymes were assessed by qPCR. Various enzymes involved in the arginine-metabolism of host cells and of Giardia are shown (adapted from Stadelmann et al 2012 [7]). Changes in expression after 1.5, 3, 6 and 24 h as compared to 0 h are indicated for interactions with the parasite isolate WB according to Figures 2 and 4 (square for no change, triangle pointing up for up-regulation, triangle pointing down for down-regulation; cut-off value 2). Expression of inos and flhb in host cells that were stimulated with cytokines (TNF-α (200 ng/mL), IL-1α (200 ng/mL), IFN-γ (500 ng/mL) to produce nitric oxide is also shown (non-filled triangles for up- and down-regulation, non-filled square for no change). ADC, arginine decarboxylase; ADI, arginine deiminase; AGAT, arginine-glycine amidinotransferase; ARG, arginase; ASL, argininosuccinate lyase; ASS, argininosuccinate synthetase; CAT, cationic amino acid transporter; CK, carbamate kinase; FlHb, flavohemoglobin; NO, nitric oxide; NOS, nitric oxide synthase; OAT, ornithine aminotransferase; OCT, ornithine carbamoyl transferase; ODC, ornithine decarboxylase; p6C, Δ1-pyrroline-5-carboxylate.


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 Giardia trophozoites upon host-cell interaction. Differentiated Caco-2 IECs were infected with Giardia trophozoites (isolate WB) and expression of arginine-consuming enzymes (adi, arginine deiminase; oct, ornithine carbamoyltransferase; ck, carbamate kinase) was assessed at 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. GL50803_17364 was used as reference gene. Fold change gene expression is shown with substracted medium effects.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4225669&req=5

Figure 4: Expression of arginine-metabolizing enzymes in Giardia trophozoites upon host-cell interaction. Differentiated Caco-2 IECs were infected with Giardia trophozoites (isolate WB) and expression of arginine-consuming enzymes (adi, arginine deiminase; oct, ornithine carbamoyltransferase; ck, carbamate kinase) was assessed at 0, 1.5, 3, 6 and 24 h on the RNA level by qPCR in technical quadruplicates. GL50803_17364 was used as reference gene. Fold change gene expression is shown with substracted medium effects.
Mentions: RNA expression changes of arginine-consuming enzymes upon Giardia-host cell interaction. Based on an interpretation of results from this and previous studies, the encircled numbers point out various ways by which Giardia interferes with the host immune response: (1) consumption of arginine via arginine-ornithine antiporter, (2) release of arginine-consuming ADI and OCT, (3) blocking of arginine-uptake into host cells by ornithine, (4) down-regulation of host iNOS, (5) up-regulation of host ODC, (6) up-regulation of parasite FlHb upon NO-stress. Human intestinal epithelial cells (Caco-2) were in vitro interacted with Giardia trophozoites and the expression changes of arginine-consuming enzymes were assessed by qPCR. Various enzymes involved in the arginine-metabolism of host cells and of Giardia are shown (adapted from Stadelmann et al 2012 [7]). Changes in expression after 1.5, 3, 6 and 24 h as compared to 0 h are indicated for interactions with the parasite isolate WB according to Figures 2 and 4 (square for no change, triangle pointing up for up-regulation, triangle pointing down for down-regulation; cut-off value 2). Expression of inos and flhb in host cells that were stimulated with cytokines (TNF-α (200 ng/mL), IL-1α (200 ng/mL), IFN-γ (500 ng/mL) to produce nitric oxide is also shown (non-filled triangles for up- and down-regulation, non-filled square for no change). ADC, arginine decarboxylase; ADI, arginine deiminase; AGAT, arginine-glycine amidinotransferase; ARG, arginase; ASL, argininosuccinate lyase; ASS, argininosuccinate synthetase; CAT, cationic amino acid transporter; CK, carbamate kinase; FlHb, flavohemoglobin; NO, nitric oxide; NOS, nitric oxide synthase; OAT, ornithine aminotransferase; OCT, ornithine carbamoyl transferase; ODC, ornithine decarboxylase; p6C, Δ1-pyrroline-5-carboxylate.

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