Colitis ImmunoPET: Defining Target Cell Populations and Optimizing Pharmacokinetics.

BACKGROUND: Positron emission tomography combined with a specific probe presents the ability to noninvasively assess inflammatory bowel disease. We previously reported increased intestinal uptake of a Cu-labeled anti-ß7 integrin antibody (clone FIB504.64) in colitic mice. Here, we evaluated an anti-α4ß7 integrin antibody (clone DATK32), and the F(ab')2 and Fab fragments of the anti-ß7 antibody, which should have faster blood clearance than the intact antibody, as imaging probes for the detection of colitis in a mouse model. METHODS: The immunoproteins were labeled with Cu, injected into mice with dextran sodium sulphate-induced colitis. Positron emission tomography data were collected between 1 and 48 hours postinjection. RESULTS: Focal uptake of the anti-ß7 fragments was observed in the gut as early as 1 hour postinjection, and they cleared more rapidly from normal tissues than the whole antibody. For example, the blood concentrations at 24 hours postinjection were 23.3 ± 3.0% ID/g for Cu-labeled DATK32, 12.9 ± 2.1% ID/g for FIB504.64, 4.1 ± 0.4% ID/g for FIB504.64-F(ab')2, and 0.62 ± 0.2% ID/g for FIB504.64-Fab (P < 0.0001, analysis of variance). The ratio of uptake of DATK32 between the colitis and control groups in the large intestine (1.38) was lower than for the FIB504.64 fragments (3.15 for F(ab')2, 1.84 for Fab) or intact FIB504.64 (1.78). CONCLUSIONS: The lower intestinal uptake ratio of the Cu-labeled anti-α4ß7 antibody (DATK32) compared with the anti-ß7 immunoproteins suggests that targeting all ß7-expressing lymphocytes, not just those expressing α4ß7, is a more promising route to the development of an inflammatory bowel disease imaging agent. The FIB504.64-F(ab')2 fragment demonstrated the greatest differential between colitis and control groups, and is therefore the most promising lead molecule for the development of an inflammatory bowel disease-specific imaging agent.

RNAi-based nanomedicines for targeted personalized therapy.

RNA interference (RNAi) has just made it through the pipeline to clinical trials. However, in order for RNAi to serve as an ideal personalized therapeutics and be clinically approved-safe, specific, and potent strategies must be devised for efficient delivery of RNAi payloads to specific cell types, which despite the immense potential, remains a challenge. Through evaluating the recent reported studies in this field, we introduce the progress in designing targeted nano-scaled strategies that are anticipated to overcome the delivery drawbacks and along with the exciting "omics" discipline to personalize RNAi-based therapeutics.

A ceramide analog inhibits cPLA(2) activity and consequent PGE(2) formation in LPS-stimulated macrophages.

Prostaglandin E(2) (PGE(2)) is an important mediator of the inflammatory response. Phospho-ceramide analogue-1 (PCERA-1), a synthetic phospholipid-like molecule, was previously reported to modulate pro- and anti-inflammatory cytokine production. We show here that PCERA-1 inhibited LPS-stimulated PGE(2) production in RAW264.7 macrophages, without affecting COX-2 expression. Furthermore, PCERA-1 efficiently suppressed arachidonic acid (AA) release in response to LPS. The dephosphorylated derivative of PCERA-1, ceramide analogue-1 (CERA-1), mimicked the inhibitory effect of PCERA-1 on AA release and PGE(2) production in macrophages. Inhibition of PGE(2) production by CERA-1 was completely rescued by addition of exogenous AA. Importantly, PCERA-1 and ceramide-1-phosphate (C1P) stimulated the enzymatic activity of cPLA(2)α in an in vitro assay, whereas CERA-1 and ceramide inhibited both basal and C1P-stimulated cPLA(2)α activity. Collectively, these results indicate that CERA-1 suppresses AA release and subsequent PGE(2) production in LPS-stimulated macrophages by direct interaction with cPLA(2), and suggest that ceramide may similarly counteract C1P effect on cPLA(2) activity in cells. The suppression of PGE(2) production is suggested to contribute to the anti-inflammatory action of PCERA-1.