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Sustained enzymatic correction by rAAV-mediated liver gene therapy protects against induced motor neuropathy in acute porphyria mice.

ABSTRACT: Acute intermittent porphyria (AIP) is characterized by a hereditary deficiency of hepatic porphobilinogen deaminase (PBGD) activity. Clinical features are acute neurovisceral attacks accompanied by overproduction of porphyrin precursors in the liver. Recurrent life-threatening attacks can be cured only by liver transplantation. We developed recombinant adeno-associated virus (rAAV) vectors expressing human PBGD protein driven by a liver-specific promoter to provide sustained protection against induced attacks in a predictive model for AIP. Phenobarbital injections in AIP mice induced porphyrin precursor accumulation, functional block of nerve conduction, and progressive loss of large-caliber axons in the sciatic nerve. Hepatocyte transduction showed no gender variation after rAAV2/8 injection, while rAAV2/5 showed lower transduction efficiency in females than males. Full protection against induced phenobarbital-attacks was achieved in animals showing over 10% of hepatocytes expressing high amounts of PBGD. More importantly, sustained hepatic expression of hPBGD protected against loss of large-caliber axons in the sciatic nerve and disturbances in nerve conduction velocity as induced by recurrent phenobarbital administrations. These data show for the first time that porphyrin precursors generated in the liver interfere with motor function. rAAV2/5-hPBGD vector can be produced in sufficient quantity for an intended gene therapy trial in patients with recurrent life-threatening porphyria attacks.

SUBMITTER: Unzu C

PROVIDER: S-EPMC3034840 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Sustained enzymatic correction by rAAV-mediated liver gene therapy protects against induced motor neuropathy in acute porphyria mice.

Unzu Carmen C Sampedro Ana A Mauleón Itsaso I Alegre Manuel M Beattie Stuart G SG de Salamanca Rafael Enríquez RE Snapper Jolanda J Twisk Jaap J Petry Harald H González-Aseguinolaza Gloria G Artieda Julio J Rodríguez-Pena María Sol MS Prieto Jesús J Fontanellas Antonio A

Molecular therapy : the journal of the American Society of Gene Therapy 20100928 2

Acute intermittent porphyria (AIP) is characterized by a hereditary deficiency of hepatic porphobilinogen deaminase (PBGD) activity. Clinical features are acute neurovisceral attacks accompanied by overproduction of porphyrin precursors in the liver. Recurrent life-threatening attacks can be cured only by liver transplantation. We developed recombinant adeno-associated virus (rAAV) vectors expressing human PBGD protein driven by a liver-specific promoter to provide sustained protection against i ...[more]

PMID: 20877347

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Project description:Background & aimsPorphyrias result from anomalies of heme biosynthetic enzymes and can lead to cirrhosis and hepatocellular cancer. In mice, these diseases can be modeled by administration of a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC), which causes accumulation of porphyrin intermediates, resulting in hepatobiliary injury. Wnt/β-catenin signaling has been shown to be a modulatable target in models of biliary injury; thus, we investigated its role in DDC-driven injury.Methodsβ-Catenin (Ctnnb1) knockout (KO) mice, Wnt co-receptor KO mice, and littermate controls were fed a DDC diet for 2 weeks. β-Catenin was exogenously inhibited in hepatocytes by administering β-catenin dicer-substrate RNA (DsiRNA), conjugated to a lipid nanoparticle, to mice after DDC diet and then weekly for 4 weeks. In all experiments, serum and livers were collected; livers were analyzed by histology, western blotting, and real-time PCR. Porphyrin was measured by fluorescence, quantification of polarized light images, and liquid chromatography-mass spectrometry.ResultsDDC-fed mice lacking β-catenin or Wnt signaling had decreased liver injury compared to controls. Exogenous mice that underwent β-catenin suppression by DsiRNA during DDC feeding also showed less injury compared to control mice receiving lipid nanoparticles. Control livers contained extensive porphyrin deposits which were largely absent in mice lacking β-catenin signaling. Notably, we identified a network of key heme biosynthesis enzymes that are suppressed in the absence of β-catenin, preventing accumulation of toxic protoporphyrins. Additionally, mice lacking β-catenin exhibited fewer protein aggregates, improved proteasomal activity, and reduced induction of autophagy, all contributing to protection from injury.Conclusionsβ-Catenin inhibition, through its pleiotropic effects on metabolism, cell stress, and autophagy, represents a novel therapeutic approach for patients with porphyria.Lay summaryPorphyrias are disorders resulting from abnormalities in the steps that lead to heme production, which cause build-up of toxic by-products called porphyrins. Liver is commonly either a source or a target of excess porphyrins, and complications can range from minor abnormalities to liver failure. In this report, we inhibited Wnt/β-catenin signaling in an experimental model of porphyria, which resulted in decreased liver injury. Targeting β-catenin affected multiple components of the heme biosynthesis pathway, thus preventing build-up of porphyrin intermediates. Our study suggests that drugs inhibiting β-catenin activity could reduce the amount of porphyrin accumulation and help alleviate symptoms in patients with porphyria.

Dataset Information

Sustained enzymatic correction by rAAV-mediated liver gene therapy protects against induced motor neuropathy in acute porphyria mice.

Publications

Sustained enzymatic correction by rAAV-mediated liver gene therapy protects against induced motor neuropathy in acute porphyria mice.

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