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Inducible and reversible breaching of the blood brain barrier by RNAi.

Rossi JJ - EMBO Mol Med (2011)

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Beckman Research Institute of the City of Hope, Duarte, CA, USA. jrossi@coh.org

ABSTRACT

Sequence-specific knockdown of gene expression is a goal that has been long sought by both basic and clinical investigators. In this regard, the discovery of RNA interference (RNAi) in Caenorhabditis elegans was immediately recognized as a potential breakthrough for studying gene function (Fire et al, 1998). These findings demonstrated that double-stranded (ds)RNAs are triggers for sequence-specific, post-transcriptional gene silencing via targeted degradation of messenger RNAs harbouring a complementary sequence to one of the two strands. Initially, it was thought that such post-transcriptional regulation of gene expression could not be achieved in mammalian systems due to the strong induction of interferon by dsRNAs. This potential restriction was short lived with the demonstration that endonuclease processed dsRNAs of 21–25 nucleotides in length, designated small interfering RNAs (siRNAs), were able to elicit sequence-specific degradation of mRNAs in mammalian cells without triggering interferon responses (Elbashir et al, 2001). These findings provided a huge impetus to develop RNAi as a therapeutic modality. The dream to selectively block the expression of deleterious proteins and treat formerly non-drugable diseases led to the rapid establishment of new biotech companies and branches of major pharmaceutical companies devoted to RNAi therapeutics.

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BBB or iBRB tight junctions prevent diffusion of small molecular weight drugsVascular endothelial cells are transduced with AAV 2/9 harbouring doxycycline-inducible anti-claudin-5 shRNA. Following induction, shRNAs are transcribed and processed by Dicer and the processed guide strand is incorporated into the RNAi-induced silencing complex where it guides targeted destruction of claudin-5 mRNA and subsequent reduction of the protein. This results in perturbation of tight junctions allowing the small drugs to penetrate across the blood vessel and into the brain or retinal neurons.
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fig01: BBB or iBRB tight junctions prevent diffusion of small molecular weight drugsVascular endothelial cells are transduced with AAV 2/9 harbouring doxycycline-inducible anti-claudin-5 shRNA. Following induction, shRNAs are transcribed and processed by Dicer and the processed guide strand is incorporated into the RNAi-induced silencing complex where it guides targeted destruction of claudin-5 mRNA and subsequent reduction of the protein. This results in perturbation of tight junctions allowing the small drugs to penetrate across the blood vessel and into the brain or retinal neurons.

Mentions: To date, the major emphases for the applications of RNAi have been functional genomics and therapeutics. For the latter, the ability to knock down deleterious target gene expression has been the primary goal. A conceptually different and novel application of RNAi is described in this issue of EMBO Molecular Medicine (Campbell et al, 2011). These investigators explored the use of doxycycline-inducible shRNA expression for transient knockdown of an mRNA encoding the tight junction protein claudin-5, a component of the microneurovasculature that regulates the entry of small molecules through the blood brain barrier (BBB) and inner blood retinal barrier (iBRB) (Fig 1). The objective of these studies was to selectively modulate the levels of tight junction proteins to render these barriers transiently permeable to low molecular weight compounds that are used to treat neural or retinal disorders. Thus, the rationale was not to develop an RNAi therapeutic agent per se, but to use RNAi to allow the application of conventional drugs for treating diseases of the brain, CNS or eye.


Inducible and reversible breaching of the blood brain barrier by RNAi.

Rossi JJ - EMBO Mol Med (2011)

BBB or iBRB tight junctions prevent diffusion of small molecular weight drugsVascular endothelial cells are transduced with AAV 2/9 harbouring doxycycline-inducible anti-claudin-5 shRNA. Following induction, shRNAs are transcribed and processed by Dicer and the processed guide strand is incorporated into the RNAi-induced silencing complex where it guides targeted destruction of claudin-5 mRNA and subsequent reduction of the protein. This results in perturbation of tight junctions allowing the small drugs to penetrate across the blood vessel and into the brain or retinal neurons.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3377071&req=5

fig01: BBB or iBRB tight junctions prevent diffusion of small molecular weight drugsVascular endothelial cells are transduced with AAV 2/9 harbouring doxycycline-inducible anti-claudin-5 shRNA. Following induction, shRNAs are transcribed and processed by Dicer and the processed guide strand is incorporated into the RNAi-induced silencing complex where it guides targeted destruction of claudin-5 mRNA and subsequent reduction of the protein. This results in perturbation of tight junctions allowing the small drugs to penetrate across the blood vessel and into the brain or retinal neurons.
Mentions: To date, the major emphases for the applications of RNAi have been functional genomics and therapeutics. For the latter, the ability to knock down deleterious target gene expression has been the primary goal. A conceptually different and novel application of RNAi is described in this issue of EMBO Molecular Medicine (Campbell et al, 2011). These investigators explored the use of doxycycline-inducible shRNA expression for transient knockdown of an mRNA encoding the tight junction protein claudin-5, a component of the microneurovasculature that regulates the entry of small molecules through the blood brain barrier (BBB) and inner blood retinal barrier (iBRB) (Fig 1). The objective of these studies was to selectively modulate the levels of tight junction proteins to render these barriers transiently permeable to low molecular weight compounds that are used to treat neural or retinal disorders. Thus, the rationale was not to develop an RNAi therapeutic agent per se, but to use RNAi to allow the application of conventional drugs for treating diseases of the brain, CNS or eye.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Beckman Research Institute of the City of Hope, Duarte, CA, USA. jrossi@coh.org

ABSTRACT

Sequence-specific knockdown of gene expression is a goal that has been long sought by both basic and clinical investigators. In this regard, the discovery of RNA interference (RNAi) in Caenorhabditis elegans was immediately recognized as a potential breakthrough for studying gene function (Fire et al, 1998). These findings demonstrated that double-stranded (ds)RNAs are triggers for sequence-specific, post-transcriptional gene silencing via targeted degradation of messenger RNAs harbouring a complementary sequence to one of the two strands. Initially, it was thought that such post-transcriptional regulation of gene expression could not be achieved in mammalian systems due to the strong induction of interferon by dsRNAs. This potential restriction was short lived with the demonstration that endonuclease processed dsRNAs of 21–25 nucleotides in length, designated small interfering RNAs (siRNAs), were able to elicit sequence-specific degradation of mRNAs in mammalian cells without triggering interferon responses (Elbashir et al, 2001). These findings provided a huge impetus to develop RNAi as a therapeutic modality. The dream to selectively block the expression of deleterious proteins and treat formerly non-drugable diseases led to the rapid establishment of new biotech companies and branches of major pharmaceutical companies devoted to RNAi therapeutics.

Show MeSH