Enzyme replacement with PEGylated cystathionine β-synthase ameliorates homocystinuria in murine model
Erez M. Bublil, … , Viktor Kožich, Jan P. Kraus
Erez M. Bublil, … , Viktor Kožich, Jan P. Kraus
Published May 16, 2016
Citation Information: J Clin Invest. 2016;126(6):2372-2384. https://doi.org/10.1172/JCI85396.
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Research Article Genetics Metabolism

Enzyme replacement with PEGylated cystathionine β-synthase ameliorates homocystinuria in murine model

Abstract

Homocystinuria, which typically results from cystathionine β-synthase (CBS) deficiency, is the most common defect of sulfur amino acid metabolism. CBS condenses homocysteine and serine to cystathionine that is then converted to cysteine. Individuals with homocystinuria have markedly elevated plasma levels of homocysteine and methionine and reduced concentrations of cystathionine and cysteine. Clinical disease manifestations include thromboembolism and neuropsychiatric, ocular, and skeletal complications. Here, we have shown that administration of PEGylated CBS into the circulation of homocystinuria model mice alters the extra- and intracellular equilibrium of sulfur amino acids, resulting in a decrease of approximately 75% in plasma total homocysteine (tHcy) and normalization of cysteine concentrations. Moreover, the decrease in homocysteine and the normalization of cysteine in PEGylated CBS–treated model mice were accompanied by improvement of histopathological liver symptoms and increased survival. Together, these data suggest that CBS enzyme replacement therapy (ERT) is a promising approach for the treatment of homocystinuria and that ERT for metabolic diseases may not necessitate introduction of the deficient enzyme into its natural intracellular compartment.

Authors

Erez M. Bublil, Tomas Majtan, Insun Park, Richard S. Carrillo, Helena Hůlková, Jakub Krijt, Viktor Kožich, Jan P. Kraus

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Figure 7

PEGC15S administration rescues complete CBS-KO mice from early lethality.

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PEGC15S administration rescues complete CBS-KO mice from early lethality...
(A) Kaplan-Meier survival curve of KO mice that were injected twice weekly with PEGC15S (n = 30) versus mice injected with PBS (n = 16). Mice were maintained on betaine water until day 21. A log-rank test was used for comparison of the 2 survival curves, and significance was calculated using the χ2 test. (B) Liver histology results for 2 PEGC15S-injected KO mice that were sacrificed on day 35 versus liver histology results for 2 PBS-injected KO animals that died on days 17 and 24 (H&E staining). Low-magnification views of the liver parenchyma (left panels) show moderate changes, with slightly irregular liver cell plates and mild-to-moderate steatosis, in PEGC15S-injected KO-1 and KO-2 mice, contrasting with massive zonal necroses of hepatocytes (KO-3 mouse, marked by arrowheads) and diffuse steatosis, with multiple dispersed hepatocellular necroses (KO-4 mouse, necroses marked by arrowheads) in the PBS-injected KO mice. A specific stain for apolar lipids in the cytoplasm of hepatocytes is shown in the insets. Higher-magnification views (right panels) demonstrate the presence of frequent mitoses (marked by arrows and shown in detail in the insets) and enlarged pleiomorphic nuclei, with prominent nucleoli in hepatocytes, in the PEGC15S-injected KO mice. Higher-magnification views of the liver parenchyma in PBS-injected KO mice demonstrate confluent hepatocellular necroses, with a sparse inflammatory infiltration (KO-3 mouse, marked by arrowheads) or multiple dispersed necroses, accompanied by a prominent resorptive inflammatory reaction (KO-4 mouse, marked by arrowheads). The remaining liver parenchyma show micro- and macrovesicular steatosis in PBS-injected KO mice. CV, central vein; PT, portal tract. Scale bars: 200 μm (low-magnification images); 100 μm (high-magnification images); and 50 μm (insets).