Mitochondrial dysfunction has been described in inflammatory bowel disease. Systemic delivery of P110, a drug designed to prevent fragmentation of the mitochondrial network, significantly reduced the severity of disease (eg, clinical signs, histopathology, and pain) in murine models of colitis.Systemic delivery of P110 in prophylactic or treatment regimens reduced the severity of DSS-or DNBS-colitis and the subsequent hyperalgesia in DNBS-mice. Application of DSS to epithelial cells or macrophages caused mitochondrial fragmentation. DSS-evoked perturbation of epithelial cell energetics and mitochondrial fragmentation, but not cell death, were ameliorated by in vitro co-treatment with P110. CONCLUSIONS:We speculate that the anti-colitic effect of systemic delivery of the anti-fission drug, P110, works at least partially by maintaining enterocyte and macrophage mitochondrial networks. Perturbed mitochondrial dynamics can be a feature of intestinal inflammation, the suppression of which is a potential novel therapeutic direction in inflammatory bowel disease.

Intestinal homeostasis is highly dependent on optimal epithelial barrier function and permeability. Intestinal epithelial cells (IEC) regulate these properties acting as cellular gatekeepers by selectively absorbing nutrients and controlling the passage of luminal bacteria. These functions are energy demanding processes that are presumably met through mitochondrial-based processes. Routine methods for examining IEC mitochondrial function remain sparse, hence, our objective is to present standardized methods for quantifying mitochondrial energetics in an immortalized IEC line. Employing the murine IEC4.1 cell line, we present adapted methods and protocols to examine mitochondrial function using two well-known platforms: the Seahorse Extracellular Flux Analyzer and Oxygraph-2 k. To demonstrate the applicability of these protocols and instruments, IEC were treated with and without the murine colitogenic agent, dextran sulfate sodium (DSS, 2% w/v). Profound impairments with DSS treatment were found with both platforms, however, the Oxygraph-2 k allowed greater resolution of affected pathways including short-chain fatty acid metabolism. Mitochondrial functional analysis is a novel tool to explore the relationship between IEC energetics and functional consequences within the contexts of health and disease. The outlined methods offer an introductory starting point for such assessment and provide the investigator with insights into platform-specific capabilities.

SignificanceInflammatory bowel disease (IBD) encompasses a group of disorders that involve an exaggerated immune response to intestinal microbes. Maintenance of intestinal epithelial barrier function is highly dependent on normal mitochondrial networks. When the barrier is compromised, excessive pathological fission ensues via the enzyme dynamin related protein‐1 (DRP1) and its interaction with the receptor fission protein‐1 (Fis1), creating fragmented networks of mitochondria. Fragmented mitochondrial networks have impaired respiratory capacity, generate elevated reactive oxygen species and exacerbate inflammationObjectiveTo determine whether a novel peptide, P110, can mitigate dextran sodium sulfate (DSS) and dinitrobenzene sulfonic acid (DNBS) induced colitis by inhibiting DRP1 and Fis1 mediated fission in murine models.DesignHypothesising that elevated mitochondrial fission occurs in DSS and DNBS colitis, male Balb/c mice were split into control (n=15), P110 (3 mg/kg/d, intraperitoneally)(n=8), DSS (5% (w/v), 5 days + 3 days water)(n=16) and DSS+P110 (n=16). For the DNBS protocol, male Balb/c mice were divided into control (n=8), DNBS (3 mg/kg/d, intraperitoneally)(n=11) and DNBS+P110 (3 mg/kg/d, intraperitoneally)(n=8). Experimental measures included: body mass, colon length, macroscopic disease score, cross‐sectional histopathology and colonic motility.ResultsUpon necropsy DSS and DNBS treated mice displayed the characteristic signs of colitis associated with these models. Disease was substantially less in both DSS+P110 and DNBS+P110 treated mice as gauged by: (i) percent weight loss (ii) macroscopic disease score and (iii) colon shortening (p<0.05). Functional improvements in colonic motility were seen in P110 treated mice when compared to DSS alone (p<0.05). Analysis of histopathology on H&E stained sections of mid‐colon revealed significant improvement in DNBS mice with P110 (p<0.05). P110 was also found to improve survival rate of mice, compared to DNBS alone.ConclusionsSystemic administration of a selective inhibitor of mitochondrial fission (P110) reduced the severity of disease in two different, commonly used murine models of colitis. Future studies are required to define the mechanism of P110's action in terms of the target cell in IBD (e.g. epithelium, nerve, macrophage). We conclude that inhibition of DRP1 and Fis1 interaction provides a novel approach to mitigating gut barrier deterioration in IBDSupport or Funding InformationCrohn's and Colitis Canada. The authors wish to thank Daria Mochly‐Rosen for donating P110.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

SignificanceRecent evidence has shown that mitochondrial dynamics and more specifically, mitochondrial fission, play an important role in numerous disease of energy intensive tissues. In particular, mitochondrial fission mediated by the enzyme dynamin related protein‐1 (DRP1) and the receptor fission protein‐1 (Fis1) is associated with reduced ATP production, ROS generation and inflammation. Examination of this interaction and corresponding pathological mitochondrial fission has yet to be examined in the colon in the context of inflammatory bowel disease.ObjectiveTo identify if a common murine colitis agent, dextran sodium sulfate (DSS), induces mitochondrial respiration dysfunction and if the novel peptide (P110), can restore these deficiencies by inhibiting DRP1 and Fis1 mediated fission.DesignThe murine intestinal epithelial cell line, IEC4.1, was separated into control, P110, DSS and DSS + P110. Cell were seeded and allowed to incubate for 24 hrs before receiving their respective treatments and further incubation for another 24hrs.MethodsOptimization of both DSS (1–2w./v.%) and P110 (0.5–1.5 uM) dosage and exposure time was performed with the AlamarBlue cell proliferation assay. Basal, mitochondrial complex and maximal respiratory activity were assessed using the Oxygraph‐2k (OROBOROS Instruments, Austria). Respiratory function of cells under various substrate pathways was also examined.ResultsDSS (2%) significantly reduced cell proliferation compared to control and P110 groups (p<0.05). Administration of P110 in 2% DSS cells dose dependently increased cell proliferation, with 1.5 uM P110 exhibiting cell proliferation similar to control. Analysis of mitochondrial complexes revealed that DSS reduced basal, complex I, II, IV and maximal activity (p<0.05). P110 was found to restore DSS associated respiratory deficiencies in complex I, II and IV (p<0.05).ConclusionThis study highlights novel findings regarding the role of mitochondrial fission in a model system of epithelial dysfunction. Importantly, we show i) evidence that DRP1 and Fis1 mediated fission hold potential; pathological consequences in energetically demanding tissues like the colon and ii) P110 treatment reduces DSS induced damage and its associated respiratory deficiencies. These results suggest mitochondrial dysfunction could be intricately involved in gut barrier deterioration seen in inflammatory bowel disease.Support or Funding InformationCrohn's and Colitis Canada. The authors wish to thank Daria Mochly‐Rosen for donating P110.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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