Saturday, August 20, 2011

Bidirectional integrative regulation of Cav1.2 calcium channel by microRNA miR-103: role in pain

I have reported use of our i-FectTM siRNA delivery kit for gene expression analysis studies of DOR, hTERT, The β3 subunit of the Na+,K+-ATPase, rSNSR1, NTS1. NAV1.8, , TRPV1, Survivin, Flaviviruses and more.

I am pleased to add the Cav1.2 calcium channel to this growing list. Congratulations to Dr. Marc Landry for discovering the interplay between microRNA-miR-103 and this calcium channel: Alexandre Favereaux, Olivier Thoumine, Rabia Bouali-Benazzouz, Virginie Roques, Marie-Amélie Papon, Sherine Abdel Salam, Guillaume Drutel, Claire Léger, André Calas, Frédéric Nagy and Marc Landry. Bidirectional integrative regulation of Cav1.2 calcium channel by microRNA miR-103: role in pain. The EMBO Journal , (29 July 2011) | doi:10.1038/emboj.2011.249.

Abstract: Chronic pain states are characterized by long-term sensitization of spinal cord neurons that relay nociceptive information to the brain. Among the mechanisms involved, up-regulation of Cav1.2-comprising L-type calcium channel (Cav1.2-LTC) in spinal dorsal horn have a crucial role in chronic neuropathic pain. Here, we address a mechanism of translational regulation of this calcium channel. Translational regulation by microRNAs is a key factor in the expression and function of eukaryotic genomes. Because perfect matching to target sequence is not required for inhibition, theoretically, microRNAs could regulate simultaneously multiple mRNAs. We show here that a single microRNA, miR-103, simultaneously regulates the expression of the three subunits forming Cav1.2-LTC in a novel integrative regulation. This regulation is bidirectional since knocking-down or over-expressing miR-103, respectively, up- or down-regulate the level of Cav1.2-LTC translation. Functionally, we show that miR-103 knockdown in naive rats results in hypersensitivity to pain. Moreover, we demonstrate that miR-103 is down-regulated in neuropathic animals and that miR-103 intrathecal applications successfully relieve pain, identifying miR-103 as a novel possible therapeutic target in neuropathic chronic pain.

MicroRNAs as targets for pain therapies are gathering momentum. This defned miR-103 is a compelling possibilty. I will be following the story closely as it unfolds.

Wednesday, August 10, 2011

PEI transfection and Implications for a Mechanism of Cytotoxicity

This is a great article for undertanding the root causes of cytotoxicity caused by PEI-DNA Polyplexes.

Giovanna Grandinetti, Nilesh P. Ingle, and Theresa M. Reineke. Interaction of Poly(ethylenimine)–DNA Polyplexes with Mitochondria: Implications for a Mechanism of Cytotoxicity. Mol. Pharmaceutics, Article ASAP. Publication Date (Web): June 23, 2011. Copyright © 2011 American Chemical Society.

Poly(ethylenimine) (PEI) and PEI-based systems have been widely studied for use as nucleic acid delivery vehicles. However, many of these vehicles display high cytotoxicity, rendering them unfit for therapeutic use. By exploring the mechanisms that cause cytotoxicity, and through understanding structure–function relationships between polymers and intracellular interactions, nucleic acid delivery vehicles with precise intracellular properties can be tailored for specific function. Previous research has shown that PEI is able to depolarize mitochondria, but the exact mechanism as to how depolarization is induced remains elusive and therefore is the focus of the current study. Potential mechanisms for mitochondrial depolarization include direct mitochondrial membrane permeabilization by PEI or PEI polyplexes, activation of the mitochondrial permeability transition pore, and interference with mitochondrial membrane proton pumps, specifically Complex I of the electron transport chain and F0F1-ATPase. Herein, confocal microscopy and live cell imaging showed that PEI polyplexes do colocalize to some degree with mitochondria early in transfection, and the degree of colocalization increases over time. Cyclosporin a was used to prevent activation of the mitochondrial membrane permeability transition pore, and it was found that early in transfection cyclosporin a was unable to prevent the loss of mitochondrial membrane potential. Further studies done using rotenone and oligomycin to inhibit Complex I of the electron transport chain and F0F1-ATPase, respectively, indicate that both of these mitochondrial proton pumps are functioning during PEI transfection. Overall, we conclude that direct interaction between polyplexes and mitochondria may be the reason why mitochondrial function is impaired during PEI transfection.