Background Inflammatory bowel disease (IBD) is a family of debilitating disorders that affects more than 1 million people in the United States. Many animal studies of IBD use a dextran sulfate sodium (DSS) mouse model of colitis that induces rapid and severe colitis symptoms. Although the typical seven-day DSS model is appropriate for many studies, it destroys intestinal barrier function and results in intestinal permeability that is substantially higher than what is typically observed in patients. As such, therapies that enhance or restore barrier integrity are difficult or impossible to evaluate. Methods We identify administration conditions that result in more physiologically relevant intestinal damage by systematically varying the duration of DSS administration. We administered 3.0% DSS for four to seven days and assessed disease metrics including weight, fecal consistency, intestinal permeability, spleen weight, and colon length. Histology was performed to assess the structural integrity of the intestinal epithelium. Results Extended exposure (seven days) to DSS resulted in substantial, unrecoverable loss of intestinal structure and intestinal permeability increases of greater than 600-fold. Attenuated DSS administration durations (four days) produced less severe symptoms by all metrics. Intestinal permeability increased only 8-fold compared to healthy mice, better recapitulating the 2–18 fold increases in permeability observed in patients. The attenuated model retains the hallmark properties of colitis against which to compare therapeutic candidates. Our results demonstrate that an attenuated DSS colitis model obtains clinically relevant increases in intestinal permeability, enabling the effective evaluation of therapeutic candidates that promote barrier function.

Although patients generally prefer oral drug delivery to injections, low permeability of the gastrointestinal tract makes this method impossible for most biomacromolecules. One potential solution is codelivery of macromolecules, including therapeutic proteins or nucleic acids, with intestinal permeation enhancers; however, enhancer use has been limited clinically by modest efficacy and toxicity concerns surrounding long-term administration. Here, we hypothesized that plant-based foods, which are well tolerated by the gastrointestinal tract, may contain compounds that enable oral macromolecular absorption without causing adverse effects. Upon testing more than 100 fruits, vegetables, and herbs, we identified strawberry and its red pigment, pelargonidin, as potent, well-tolerated enhancers of intestinal permeability. In mice, an oral capsule formulation comprising pelargonidin and a 1 U/kg dose of insulin reduced blood glucose levels for over 4 h, with bioactivity exceeding 100% relative to subcutaneous injection. Effects were reversible within 2 h and associated with actin and tight junction rearrangement. Furthermore, daily dosing of mice with pelargonidin for 1 mo resulted in no detectable side effects, including weight loss, tissue damage, or inflammatory responses. These data suggest that pelargonidin is an exceptionally effective enhancer of oral protein uptake that may be safe for routine pharmaceutical use.

Although oral drug delivery is preferred by patients, it is not possible for proteins because the gastrointestinal tract is not sufficiently permeable. To enable the non-toxic oral uptake of protein drugs, we investigated plant-based foods as intestinal permeation enhancers, hypothesizing that compounds found in food would be well-tolerated by the gastrointestinal tract. Following a screen of over 100 fruits, vegetables, herbs, and fungi, we identified strawberry as a potent enhancer of macromolecular permeability in vitro and in mice. Natural product chemistry techniques identified pelargonidin, an anthocyanidin, as the active compound. In mice, insulin was orally administered with pelargonidin to induce sustained pharmacodynamic effects with doses as low as 1 U/kg and bioactivity of over 100% relative to the current gold standard of subcutaneous injection.Pelargonidin-induced permeability was reversible within two hours of treatment, and one month of daily dosing did not adversely affect mice as determined by weight tracking,

Although protein drugs are powerful biologic therapeutics, they cannot be delivered orally because their large size and hydrophilicity limit their absorption across the intestinal epithelium. One potential solution is the incorporation of permeation enhancers into oral protein formulations; however, few have advanced clinically due to toxicity concerns surrounding chronic use. To better understand these concerns, we conducted a 30‐day longitudinal study of daily oral permeation enhancer use in mice and resultant effects on intestinal health. Specifically, we investigated three permeation enhancers: sodium caprate (C 10 ), an industry standard, as well as 1‐phenylpiperazine (PPZ) and sodium deoxycholate (SDC). Over 30 days of treatment, all mice gained weight, and none required removal from the study due to poor health. Furthermore, intestinal permeability did not increase following chronic use. We also quantified the gene expression of four tight junction proteins (claudin 2, claudin 3, ZO‐1, and JAM‐A). Significant differences in gene expression between untreated and permeation enhancer‐treated mice were found, but these varied between treatment groups, with most differences resolving after a 1‐week washout period. Immunofluorescence microscopy revealed no observable differences in protein localization or villus architecture between treated and untreated mice. Overall, PPZ and SDC performed comparably to C 10 , one of the most clinically advanced enhancers, and results suggest that the chronic use of some permeation enhancers may be therapeutically viable from a safety standpoint.

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