Inhibition of inflammation signaling by DNA “Decoy” treatment improves sensory and motor recovery after spinal cord injury in rats by neuroprotection and microglial inhibition

Abstract

Spinal cord injury (SCI) results in a number of deficits, triggering primary and secondary injury signaling cascades characterized by early and prolonged inflammatory responses. Early after SCI, IL-1B increases trigger increased activation of the transcription factor Nuclear Factor-kB (NF-kB) that mediates secondary injuries via synthesis of proteins that maintain inflammation. There are different NF-kB subunits. Subunit-specific inhibition can be accomplished with synthetic double stranded “decoy” deoxyoligonucleotides containing selective NF-kB protein dimer binding consensus sequences. Spinal cord contusion injury (IH Impactor, 150 kdynes, 1 sec dwell) was given to male Sprague-Dawely (235 to 245 gm) rats and divided randomly into two groups: 1) decoy treated (N = 10) or 2) vehicle treated (N = 9). Treatment was delivered stereotaxically with a Hamilton syringe (28 gage needle) into the spinal lesion site in an injection regimen of four treatments of 2ul/10min at 15 minutes, 7, 14 and 21 days after injury. Locomotor scores were recorded daily for 21 days and then weekly using the BBB rank score system. At presurgical times and 42 days or longer following SCI, cutaneous mechanical thresholds, deep pressure thresholds (Randall and Selitto, 1957) and thermal thresholds were measured for paw withdrawal accompanied by supraspinal measures in forepaws and separately for hindpaws (Hulsebosch et al., 2000). Levels of COX-2 and iNOS were measured in both groups. In this study, DNA ”decoys” that target the COX-2 gene promoter NF-kB binding site, attenuated the SCI-induced increases in COX-2 and iNOS protein levels, improved locomotor function, improved sensory, decreased neuronal death and attenuated microglial activation. The approach is innovative because of the use of a new technology (DNA promoter decoys) to selectively block injury response mechanisms. Supported by Mission Connect/TIRR Foundation, The M.D. Anderson Foundation, The Liddell and The Dunn Foundations and NS11255.