Small Interfering RNA Targeting Heme Oxygenase-1 Enhances Ischemia-Reperfusion-induced Lung Apoptosis

Abstract

Heme oxygenase-1 (HO-1) is emerging as an important cytoprotective enzyme system in a variety of injury models. To optimize future therapeutic applications of HO-1, it is necessary to delineate the precise functions and mechanisms as well as modes of externally regulating HO-1 expression. Investigations have been limited by difficulties with the generation of HO-1 null mice and the lack of specific HO-1 inhibitors. Lung ischemiareperfusion (I-R) injury is the inciting event in acute lung failure following transplantation, surgery, and shock. To study the function of HO-1 in I-R-induced lung injury, we designed small interfering RNA (siRNA) sequences that effectively suppress HO-1 expression both in vitro and in vivo in an organ-specific manner. In this study we show that there is enhanced apoptosis, via increased Fas expression and caspase 3 activity, in the presence of HO-1 siRNA in endothelial cells and mouse lung during I-R injury, whereas HO-1 overexpression attenuates apoptosis. To the best of our knowledge, we are the first to demonstrate that lung-specific siRNA delivery can be achieved by intranasal administration without the need for viral vectors or transfection agents in vivo, thereby obviating potential concerns for toxicity if siRNA technology is to have clinical application in the future.

The silent treatment: siRNAs as small molecule drugs

“…Remarkably, pulmonary epithelial cells have even been transduced in vivo by siRNAs given without transfection reagents or other delivery molecules. 42,73 This suggests that the lung (and possibly other tissues) may have a means for siRNA uptake, not generally present in most mammalian cells. The transformed cell lines and primary hematopoietic cells commonly used for in vitro RNAi experiments require a transfection reagent or other mechanism for siRNA uptake.…”

“…In the lung and vagina, siRNA uptake is extremely efficient and occurs even in the absence of transfection reagents. 42 For clinical indications where siRNAs only need to be delivered to a localized region, such as the eye, 71,72 pulmonary 73 or vaginal mucosa, 74 or superficial tumors, [75][76][77][78] efficient siRNA delivery and silencing can be achieved by mixing siRNAs with cationic lipid transfection reagents used for in vitro transfection and directly injecting the siRNAlipid complexes into the relevant tissue or instilling it into the body cavity. A similar approach is certain to apply to the skin.…”

siRNA therapeutics: big potential from small RNAs

“…In addition, siRNAs have been successfully delivered via intranasal delivery to the lungs. 52 One recent report examined direct application of siRNAs in the rat brain. 53 Although siRNAs against the dopamine D1 receptor effectively degraded D1 transcipts in vitro, delivery with a miniosmotic pump via a cannula into the caudate-putamen failed to induce RNAi in vivo, suggesting that the development of effective delivery systems may be the key barrier to siRNA therapeutics.…”

A Multi-Targeted Antisense Oligonucleotide-Based Therapy Directed at Phosphodiesterases 4 and 7 for COPD

“…Firstly, as PXS TPI1100 is administered via inhalation, it is delivered directly to the intended site of action of the lung (Ali et al 2001;Duan et al 2005;Gauvreau et al 2008;Guimond et al 2008) where the drug can enter target cells directly (Zhang et al 2004;Griesenbach et al 2006) thus potentially reducing total dose as compared to orally-available treatments. A further advantage of pulmonary administration of AON is that they are principally www.intechopen.com A Multi-Targeted Antisense Oligonucleoitde-Based Therapy Directed at Phosphodiesterases 4 and 7 for COPD 449 metabolized in the lung with very limited systemic delivery after inhalation (Templin et al 2000;Ali et al 2001;Guimond et al 2008) which leads to reduced systemic bioavailability of the drug.…”