Targeting Adipose Tissues with ATS9R Nanoparticles for Drug Delivery

Abstract

Nanoparticles (NPs) are a drug delivery system that can enable delivery of a drug to a targeted tissue. Previous studies have shown that the use of an adipose targeting sequence (ATS) peptide in conjunction with a drug in the form of a NP has the ability to selectively deliver the drug to mouse adipose tissues. The prohibitin protein located in adipose tissue is the target of ATS. Adipose tissue is a major source of the adipokine chemerin, a prohypertensive protein. Our laboratory has proven that liver derived chemerin, the largest source of circulating chemerin, is biologically inactive. Our goal is to understand if chemerin produced by adipose tissue contributes to hypertension. We hypothesize an ATS drug delivery system could be applied in rats to specifically reduce the levels of adipose tissue associated chemerin. We created a NP consisting of an antisense oligonucleotide (ASO) against chemerin and a FITC labeled ATS with 9 arginine sequence (ATS9R). In vitro studies showed that the ASO is functional when incorporated into NPs with ATS9R as it reduced chemerin mRNA expression in isolated epidydimal (Epi) adipocytes by 43‐fold compared to vehicle incubated cells (Veh mean 2‐ΔCT=0.039 ± 0.007; NP mean 2‐ΔCT=0.0009 ± 0.0001), and 13‐fold in isolated retroperitoneal (RP) adipocytes (Veh mean 2‐ΔCT=0.041 ± 0.007; NP mean 2‐ΔCT=0.0031 ± 0.0009) of Dahl SS rats. Ex vivo studies support the ability of the ATS9R‐ASO NP to reduce chemerin mRNA expression in tissues. In Epi fat incubated with the NP overnight at 37 oC, chemerin expression was reduced by 2.7‐fold (p<0.05) (Veh mean 2‐ΔCT=0.213 ± 0.088; NP mean 2‐ΔCT=0.079 ± 0.013). The NP also reduced chemerin expression in RP fat by 2.1‐fold (Veh mean 2‐ΔCT=0.159 ± 0.027; NP mean 2‐ΔCT=0.071 ± 0.011), although the changes did not reach statistical significance. However, this same NP was unable to deliver the ASO selectively to adipose tissue in vivo. Two days after subcutaneous injections in Dahl SS rats, the NP caused a significant (p<0.05) 2.4‐fold reduction in liver chemerin mRNA expression compared to vehicle treated animals (Veh 2‐ΔCT=0.753; NP mean 2‐ΔCT=0.311 ± 0.007), but not in Epi (1.8‐fold reduction; Veh 2‐ΔCT=0.175; NP mean 2‐ΔCT=0.095 ± 0.013) or RP fat (1.9‐fold reduction; Veh 2‐ΔCT=0.120; NP mean 2‐ΔCT=0.061 ± 0.015). Varying NP dose, administration route, and concentration of the components constituting the NP did not show any improvement in ASO delivery to fats vs liver. Further studies are needed to develop the ATS9R system to deliver ASO to adipose tissue beds in rats.