Description:
The University of Texas at Dallas presents a novel class of inhibitors, specificity-derived competitive inhibitor oligonucleotides (SPOT-ONs) that bind to poly(A) binding protein (PABP), and the associated inventive strategy to treat pathological pain.
Pathological pain plasticity has been shown to take place in nociceptors, sensory neurons which sense pain and transmit signals to the spinal cord and brain, and can persist long after an injury is healed due to an alteration in gene expression of affected neurons. It has been shown that translation regulation pathways play a key role in generation of initial and pathologic pain – providing an effective and novel target for treatment of pain. The Poly(A) SPOT-ON modulates specific translation regulation signaling through the disruption of RNA-binding protein (RBP)-RNA interactions. Administration of Poly(A) SPOT-ON effectively impairs the initial phase of translation for both in vitro and in vivo models, producing significant anti-hyperalgesic effects for all pain models tested. We demonstrate that injection of the Poly(A) SPOT-ON at the site of an injury can attenuate behavioral responses to pain while additionally reducing inflammation.
Technical Summary:
We focus on the major cytoplasmic PABP isoform, PABPC1, as it is the most abundant isoform based on high-throughput sequencing of the dorsal root ganglia (DRG). Using an unbiased assessment of PABP binding specificity, the most enriched sequence was demonstrated to be an adenosine homopolymer. A chemically modified Poly(A) RNA mimic, designated as the Poly(A) SPOT-ON, binds PABP with high affinity and selectivity in vitro and impairs nascent translation in a PABP-dependent mechanism in cells. We showed SPOT-ONs have much improved stability - the half-life of unmodified RNA was approximately 18 hours, while comparable measurements of the SPOT-ON indicate half-lives of >10 days. They are efficiently taken up by U2OS cells & DRG neurons after 3-hour exposure and distributed throughout the cytoplasm. Using non-radiometric Surface Sensing of Translation (SUnSET) approach, the RNA mimic’s effects on translation are demonstrated to be specific to the initiation phase of translation and that axonal protein synthesis is impaired in nociceptor neurons. Given that the robust inhibition of protein synthesis caused by Poly(A) SPOT-ON is ameliorated by PABP overexpression – this strongly suggests that PABP is the relevant cellular target of the SPOT-ON.
We also studied the effects of RNA mimic in animals primed by Nerve Growth Factor (NGF) or interleukin 6 (IL-6) – common pro-inflammatory mediators that increase nociceptor excitability and induce plasticity. After priming, injection of prostaglandin E2 (PGE2) induces a long-lasting hypersensitivity, known as hyperalgesic priming (frequently associated with the transition from acute to chronic pain). Significantly, Poly(A) SPOT-ON markedly inhibited both NGF- and IL-6-induced mechanical hypersensitivity and blocked the development of hyperalgesic priming from PGE2. Incision-induced spontaneous pain responses, such as paw guarding and facial grimace, were also significantly reduced following local administration of Poly(A) SPOT-ON. Furthermore, administration of Poly(A) SPOT-ON decreased incision-evoked mechanical hypersensitivity, contributed to rapid resolution of mechanical pain sensitization, and blocked hyperalgesic priming produced by incisions. Also, this treatment significantly decreased paw temperature in the post-surgical assessment, a positive indication for effective control of inflammation brought by tissue injury. The compound was further validated to inhibit capsaicin-induced mechanical hypersensitivity, block the development of such hyperalgesic priming, and prevent the transient increase in paw temperature associated with intraplanar capsaicin administration. Together, these results indicate that part of the effect produced by Poly(A) SPOT-ON is mediated by blocking induction of axonal plasticity in primary afferent fibers responsive to capsaicin.
Value Proposition:
The presented RNA-based mimic, Poly(A) SPOT-ON, inhibits PABP to robustly impair pathological responses to pain - preventing mechanical hypersensitivity (from NGF, IL-6, capsaicin), blocking hyperalgesic priming, and even reducing inflammation from tissue injuries or administration of capsaicin. The Poly(A) SPOT-ON successfully demonstrates the first disruption of RNA-protein interactions through the use of chemically-stabilized mimetics.
Applications:
- Development of cell-specific SPOT-ONs for treating pain
- Investigating function of RNA-binding proteins (RBPs)
- Chemically-stabilized RNA-based mimetics for novel therapeutics
Key Benefits:
- Stable – Poly(A) SPOT-ON is an RNA-based inhibitor of PABP that is chemically modified to have a half-life over 1333% greater than unmodified RNA in vivo
- Specific – High-specificity binding to PABP demonstrated as impairing the initiation phase of translation and subsequent axonal protein synthesis
- Reduced Sensitization – Inhibits mechanical hypersensitivity (from NGF, IL-6, capsaicin), decreasing incision-invoked hypersensitivity and inflammation
- Prevents Chronic Pain – Prevents hyperalgesic priming caused by PGE2, which is associated with the transition from acute to chronic pain
- Biocompatible – SPOT-ONs are rapidly taken-up by cells and lack over signs of toxicity, may be tailored for uptake by specific cell types
Publication:
Barragán-Iglesias, Paulino, et al. “Inhibition of Poly(A)-Binding Protein with a Synthetic RNA Mimic Reduces Pain Sensitization in Mice.” Nature Communications, vol. 9, no. 1, 2 Jan. 2018, doi:10.1038/s41467-017-02449-5.
IP Status: Patent pending.
Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.
ID Number: 17057
Contact: otc@utdallas.edu