Acetalated dextran encapsulated AR-12 as a host-directed therapy to control Salmonella infection

Abstract

AR-12 has been evaluated in clinical trials as an anti-cancer agent but also has demonstrated host-directed, broad-spectrum clearance of bacteria. We have previously shown that AR-12 has activity in vitro against Salmonella enterica serovar Typhimurium and Francisella species by inducing autophagy and other host immune pathways. AR-12 treatment of S. Typhimurium-infected mice resulted in a 10-fold reduction in bacterial load in the liver and spleen and an increased survival time. However, AR-12 treatment did not protect mice from death, likely due poor formulation. In the current study, AR-12 was encapsulated in a microparticulate carrier formulated from the novel degradable biopolymer acetalated dextran (Ace-DEX) and subsequently evaluated for its activity in human monocyte-derived macrophages (hMDMs). Our results show that hMDMs efficiently internalized Ace-DEX microparticles (MPs), and that encapsulation significantly reduced host cell cytotoxicity compared to unencapsulated AR-12. Efficient macrophage internalization of AR-12 loaded MPs (AR-12/MPs) was further demonstrated by autophagosome formation that was comparable to free AR-12 and resulted in enhanced clearance of intracellular Salmonella. Taken together, these studies provide support that Ace-DEX encapsulated AR-12 may be a promising new therapeutic agent to control intracellular bacterial pathogens of macrophages by targeting delivery and reducing drug toxicity.

Needle-Free Delivery of Acetalated Dextran-Encapsulated AR-12 Protects Mice from Francisella tularensis Lethal Challenge

“…The spherical morphology of AR-12/ MPs was conserved relative to that in our previous work (Fig. 1), and the size of the MPs aligned with our submicrometer particle sizer measurements (29).…”

“…Free base AR-12 was kindly provided by Arno Therapeutics, Inc. Encapsulation of AR-12-encapsulated Ace-DEX microparticles (AR-12/MPs) was performed as described in our previous publication (29). In brief, 1 day prior to particle formation, all glassware was soaked in 1 M sodium hydroxide overnight.…”

“…Endotoxinfree AR-12/MPs were prepared as previously described (29). Particle size was determined using a model 370 Nicomp submicrometer particle sizer (Santa Barbara, CA).…”

“…It has been investigated as an anticancer agent that suppresses tumor cell viability through multiple mechanisms, including the induction of autophagy (24)(25)(26). We have shown that AR-12 enhances the clearance of the intracellular bacterial pathogens Salmonella and Francisella from infected macrophages specifically via induction of autophagy (27)(28)(29). The effect of AR-12 on control of Francisella was fully reversed in the presence of the autophagy inhibitor 3-ME or the lysosomal inhibitor chloroquine (27).…”

“…We recently showed that encapsulation of AR-12 in acetalated dextran (Ace-DEX) microparticles (AR-12/MPs) dramatically reduces cytotoxicity while retaining the ability to enhance Salmonella clearance via autophagy in human monocyte-derived macrophages (hMDMs) (29). Ace-DEX is derived from Food and Drug Administration (FDA)-approved dextran and is an acidsensitive polymer that is stable at neutral pH but will degrade rapidly upon introduction to an acidic environment, such as that in the phagolysosome (33).…”