Zinc enhancement of nonviral salivary gland transfection

Abstract

Gene transfer to exocrine glands, including the major salivary glands, presents an attractive method to deliver proteins for therapeutic applications. Previous efforts using nonviral gene delivery to these glands have resulted in limited success. In this report, zinc and other divalent transitions were coadministered with plasmid DNA in an effort to improve nonviral salivary gland transfection efficiency. The inclusion of zinc into plasmid DNA solutions resulted in a 20-fold enhancement in transgene expression without noticeable inflammation compared to a solution of plasmid DNA only. This observed enhancement in transgene expression was dependent upon the DNA dose and correlated with the accumulation of plasmid DNA by salivary gland tissues.

Enhanced systemic transgene expression after nonviral salivary gland transfection using a novel endonuclease inhibitor/DNA formulation

“…The zinc concentrations (1.8 or 3.6 mM) used in this and subsequent studies were those that were previously found to be optimal for SG transfection. 6 Administration of plasmid DNA without added zinc or ATA did not result in plasma SEAP concentrations above the SEAP assay background (50 pg/ml). For all the formulations screened, transgene expression in either plasma or tissue samples was transient, with a maximum observed at 48 h post-DNA administration (data not shown).…”

“…6 It was hypothesized that this increased transfection activity may be attributed to zinc-mediated inhibition of DNase activity. ATA, another known DNase inhibitor, was evaluated in this context.…”

“…[2][3][4][5] More recently, we have demonstrated that systemic protein expression can also be obtained with nonviral DNA formulations. 6 Although administration of viral-based vectors to the SGs of experimental animals results in therapeutic concentrations of protein in blood, the recent complications that have occurred in clinical studies have increased concerns about the general safety of viral technologies. 7,8 In the light of these developments, nonviral formulations are a more appealing alternative to viral-based vectors.…”

“…The concentration of deoxyribonucleases (DNases) found in the salivary gland is generally substantially higher than the concentration found in other tissues. 6,10 Recently, we have discovered that zinc and other divalent metals enhance local and systemic gene expression following retroductal administration of metal/plasmid DNA formulations to the submandibular gland. 6 Although the mechanism for the observed transfection enhancement is likely to be multifaceted, our results indicated that endonuclease inhibition may be responsible, at least in part.…”

“…6,10 Recently, we have discovered that zinc and other divalent metals enhance local and systemic gene expression following retroductal administration of metal/plasmid DNA formulations to the submandibular gland. 6 Although the mechanism for the observed transfection enhancement is likely to be multifaceted, our results indicated that endonuclease inhibition may be responsible, at least in part. Preliminary studies in our laboratories have shown that aurintricarboxylic acid (ATA), a known nuclease inhibitor, also enhances SG transfection.…”