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Strategies to rescue the consequences of inducible arginase-1 deficiency in mice.

Ballantyne LL, Sin YY, St Amand T, Si J, Goossens S, Haenebalcke L, Haigh JJ, Kyriakopoulou L, Schulze A, Funk CD - PLoS ONE (2015)

Bottom Line: Arginase-1 catalyzes the conversion of arginine to ornithine and urea, which is the final step of the urea cycle used to remove excess ammonia from the body.Standard clinical care regimens for arginase-1 deficiency (low-protein diet, the nitrogen-scavenging drug sodium phenylbutyrate, ornithine supplementation) either failed to extend lifespan (ornithine) or only minimally prolonged lifespan (maximum 8 days with low-protein diet and drug).Delivery of an arginase-1/enhanced green fluorescent fusion construct by adeno-associated viral delivery (rh10 serotype with a strong cytomegalovirus-chicken β-actin hybrid promoter) rescued about 30% of male mice with lifespan prolongation to at least 6 months, extensive hepatic expression and restoration of significant enzyme activity in liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.

ABSTRACT
Arginase-1 catalyzes the conversion of arginine to ornithine and urea, which is the final step of the urea cycle used to remove excess ammonia from the body. Arginase-1 deficiency leads to hyperargininemia in mice and man with severe lethal consequences in the former and progressive neurological impairment to varying degrees in the latter. In a tamoxifen-induced arginase-1 deficient mouse model, mice succumb to the enzyme deficiency within 2 weeks after inducing the knockout and retain <2 % enzyme in the liver. Standard clinical care regimens for arginase-1 deficiency (low-protein diet, the nitrogen-scavenging drug sodium phenylbutyrate, ornithine supplementation) either failed to extend lifespan (ornithine) or only minimally prolonged lifespan (maximum 8 days with low-protein diet and drug). A conditional, tamoxifen-inducible arginase-1 transgenic mouse strain expressing the enzyme from the Rosa26 locus modestly extended lifespan of neonatal mice, but not that of 4-week old mice, when crossed to the inducible arginase-1 knockout mouse strain. Delivery of an arginase-1/enhanced green fluorescent fusion construct by adeno-associated viral delivery (rh10 serotype with a strong cytomegalovirus-chicken β-actin hybrid promoter) rescued about 30% of male mice with lifespan prolongation to at least 6 months, extensive hepatic expression and restoration of significant enzyme activity in liver. In contrast, a vector of the AAV8 serotype driven by the thyroxine-binding globulin promoter led to weaker liver expression and did not rescue arginase-1 deficient mice to any great extent. Since the induced arginase-1 deficient mouse model displays a much more severe phenotype when compared to human arginase-1 deficiency, these studies reveal that it may be feasible with gene therapy strategies to correct the various manifestations of the disorder and they provide optimism for future clinical studies.

No MeSH data available.


Related in: MedlinePlus

Real time quantitative PCR expression of Arg1.Brain (A), kidney (B), and liver (C) of control C57BL/6 (n = 3), R26-Arg1 transgenic (TG; n = 3–5), and Arg1Δ knockout (KO; n = 3–5) mice.
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pone.0125967.g005: Real time quantitative PCR expression of Arg1.Brain (A), kidney (B), and liver (C) of control C57BL/6 (n = 3), R26-Arg1 transgenic (TG; n = 3–5), and Arg1Δ knockout (KO; n = 3–5) mice.

Mentions: Since neonatal mice only showed signs of limited rescue, we next focused on 4 week old mice (control C57BL/6, R26-Arg1 TG (Group 2), and Arg1Δ KO (Group 1) mice and sought to examine the relative change in Arg1 expression due to the induced Arg1 transgene in three tissues by real-time quantitative PCR. Arg1 expression was significantly greater in liver, brain, and kidney of tamoxifen-treated R26-Arg1 TG mice compared to Arg1Δ KO mice and was also greater than in control, non-tamoxifen treated C57BL/6 mouse brain and kidney (Fig 5). However, expression of Arg1 in liver was substantially greater in control mice compared to the TG mice and this may explain why the R26-Arg1 TG mice still continued to show signs of demise and were not rescued to any great extent at this age with hyperargininemia and modestly elevated guanidino acetic acid (Fig 6A and 6B). Plasma ornithine levels were elevated in the tamoxifen-treated TG mice compared to KO mice (Fig 6C).


Strategies to rescue the consequences of inducible arginase-1 deficiency in mice.

Ballantyne LL, Sin YY, St Amand T, Si J, Goossens S, Haenebalcke L, Haigh JJ, Kyriakopoulou L, Schulze A, Funk CD - PLoS ONE (2015)

Real time quantitative PCR expression of Arg1.Brain (A), kidney (B), and liver (C) of control C57BL/6 (n = 3), R26-Arg1 transgenic (TG; n = 3–5), and Arg1Δ knockout (KO; n = 3–5) mice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4418594&req=5

pone.0125967.g005: Real time quantitative PCR expression of Arg1.Brain (A), kidney (B), and liver (C) of control C57BL/6 (n = 3), R26-Arg1 transgenic (TG; n = 3–5), and Arg1Δ knockout (KO; n = 3–5) mice.
Mentions: Since neonatal mice only showed signs of limited rescue, we next focused on 4 week old mice (control C57BL/6, R26-Arg1 TG (Group 2), and Arg1Δ KO (Group 1) mice and sought to examine the relative change in Arg1 expression due to the induced Arg1 transgene in three tissues by real-time quantitative PCR. Arg1 expression was significantly greater in liver, brain, and kidney of tamoxifen-treated R26-Arg1 TG mice compared to Arg1Δ KO mice and was also greater than in control, non-tamoxifen treated C57BL/6 mouse brain and kidney (Fig 5). However, expression of Arg1 in liver was substantially greater in control mice compared to the TG mice and this may explain why the R26-Arg1 TG mice still continued to show signs of demise and were not rescued to any great extent at this age with hyperargininemia and modestly elevated guanidino acetic acid (Fig 6A and 6B). Plasma ornithine levels were elevated in the tamoxifen-treated TG mice compared to KO mice (Fig 6C).

Bottom Line: Arginase-1 catalyzes the conversion of arginine to ornithine and urea, which is the final step of the urea cycle used to remove excess ammonia from the body.Standard clinical care regimens for arginase-1 deficiency (low-protein diet, the nitrogen-scavenging drug sodium phenylbutyrate, ornithine supplementation) either failed to extend lifespan (ornithine) or only minimally prolonged lifespan (maximum 8 days with low-protein diet and drug).Delivery of an arginase-1/enhanced green fluorescent fusion construct by adeno-associated viral delivery (rh10 serotype with a strong cytomegalovirus-chicken β-actin hybrid promoter) rescued about 30% of male mice with lifespan prolongation to at least 6 months, extensive hepatic expression and restoration of significant enzyme activity in liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada.

ABSTRACT
Arginase-1 catalyzes the conversion of arginine to ornithine and urea, which is the final step of the urea cycle used to remove excess ammonia from the body. Arginase-1 deficiency leads to hyperargininemia in mice and man with severe lethal consequences in the former and progressive neurological impairment to varying degrees in the latter. In a tamoxifen-induced arginase-1 deficient mouse model, mice succumb to the enzyme deficiency within 2 weeks after inducing the knockout and retain <2 % enzyme in the liver. Standard clinical care regimens for arginase-1 deficiency (low-protein diet, the nitrogen-scavenging drug sodium phenylbutyrate, ornithine supplementation) either failed to extend lifespan (ornithine) or only minimally prolonged lifespan (maximum 8 days with low-protein diet and drug). A conditional, tamoxifen-inducible arginase-1 transgenic mouse strain expressing the enzyme from the Rosa26 locus modestly extended lifespan of neonatal mice, but not that of 4-week old mice, when crossed to the inducible arginase-1 knockout mouse strain. Delivery of an arginase-1/enhanced green fluorescent fusion construct by adeno-associated viral delivery (rh10 serotype with a strong cytomegalovirus-chicken β-actin hybrid promoter) rescued about 30% of male mice with lifespan prolongation to at least 6 months, extensive hepatic expression and restoration of significant enzyme activity in liver. In contrast, a vector of the AAV8 serotype driven by the thyroxine-binding globulin promoter led to weaker liver expression and did not rescue arginase-1 deficient mice to any great extent. Since the induced arginase-1 deficient mouse model displays a much more severe phenotype when compared to human arginase-1 deficiency, these studies reveal that it may be feasible with gene therapy strategies to correct the various manifestations of the disorder and they provide optimism for future clinical studies.

No MeSH data available.


Related in: MedlinePlus