A high-fat diet increases the efficacy by which DSS induces colitis in mice.

<p>(A) Body weight changes in C57BL/6 mice on regular chow or a high-fat diet, drinking either a 3% (w/v) dextran or a 3% (w/v) DSS solution, for 6 days. Body weight changes are shown as means±SEMs. * P<0.05, ** P<0.01. (B) Determination of colon length (an index of colonic inflammation). <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032084#s3" target="_blank">Results</a> are expressed in mm and represent means±SEMs of three independent determinations. * P<0.05. (C) Consumption of DSS and a high-fat diet significantly increases production of pro-inflammatory cytokines and chemokine mRNAs compared to what is seen in animals consuming DSS but (otherwise) regular chow. * P<0.05, ** P<0.01, *** P<0.001.</p

Dextran-loaded nanoparticles but not free dextran induce colitis.

<p>Mouse body weight changes during treatment with DSS supplemented with dextran-loaded NPs (“dextran-loaded NPs”) or empty NPs (“DSS 3%”) compared to those of control mice gavaged with empty NPs suspended in water. C57BL/6 mice drank a 3% (w/v) DSS solution, or water, for the indicated numbers of days. (A) Body weight changes are shown as means±SEMs. * P<0.05. (B) Colon length (mm) of DSS-treated mice given dextran-loaded or empty NPs, compared to that of control animals (drinking water only). * P<0.05. (C) Determination of MPO enzymatic activity as an index of neutrophil infiltration into injured tissue. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032084#s3" target="_blank">Results</a> are expressed as units of MPO per µg of protein, are compared to the values in control mice, and are means±SEMs of three independent determinations. ** P<0.01, *** P<0.001. (D) Dextran-loaded NPs can significantly increase production of IL-1β and IL-6, compared to use of empty NPs, in animals drinking DSS (3% w/v). mRNA expression was measured in test and control animals. * P<0.05. (E) Hematoxylin-stained colon sections of mice receiving daily gavage with dextran-loaded or empty NPs (“DSS”) in the interval during which the drinking water contained DSS (3% w/v); thus on day 7. (F) Histological scores. (G) Macroscopic inflammation was assessed using a mouse colonoscope. Photographs were obtained on the day of sacrifice and, (H), endoscopic scores were calculated.</p

DSS induces colitis.

<p>(A) Mouse body weight changes during DSS treatment compared to that of control animals (drinking water). C57BL/6 mice were exposed to 3% (w/v) DSS in the drinking water for the indicated numbers of days. Body weight changes are shown as means±SEMs. * P<0.05, ** P<0.01. (B) Hematoxylin-stained colonic sections of mice treated with DSS; the mice were sacrificed on day 8. (C) Associated histological scores. *** P<0.001. (D) Macroscopic inflammation was assessed using a mouse colonoscope. Photographs were obtained on the day of sacrifice and (E) an endoscopic score was calculated. *** P<0.001. (F) KC mRNA expression was measured in test and control animals. *** P<0.001. (G) Determination of MPO enzymatic activity as an index of neutrophil infiltration into injured tissue. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032084#s3" target="_blank">Results</a> are expressed as MPO –fold increases compared to those of control mice and represent means±SEMs of three independent determinations. *** P<0.01.</p

DSS but not DSS-associated molecules induce colitis.

<p>(A) Mouse body weight changes during consumption of water, DSS (3% w/v), dextran (1.49% w/v) in sulfate solution (2.6% w/v), dextran (1.49% w/v), sulfate solution (2.6% w/v), glucose (1.73% w/v), and glucose (1.73% w/v) in sulfate solution (2.6% w/v). C57BL/6 mice were given the various solutions as drinking water for the indicated numbers of days. Body weight changes are depicted as means±SEMs for each group. * P<0.05. (B) DSS significantly increased production of chemokine KC mRNA compared to the rises seen when DSS-associated molecules were given. KC mRNA expression was measured via qRT-PCR of extracts of colonic cells. *** P<0.001. (C) Determination of MPO enzymatic activity as an index of neutrophil infiltration into injured tissue. (D) Macroscopic observations of colons of mice treated with DSS-associated molecules [DSS = dextran sodium sulfate, D+S = dextran (1.49% w/v) in sulfate solution (2.6% w/v), D = dextran (1.49% w/v), S = sulfate solution (2.6% w/v), and Glc+S = glucose (1.73% w/v) in sulfate solution (2.6% w/v)] were made using a mouse colonoscope. Photographs were obtained from all treatment groups on the day of sacrifice. * P<0.05, ** P<0.01.</p

DSS and DSS-associated molecules affect luminal intestinal osmolarity.

<p>(A) Macroscopic observations of the effects of DSS-associated molecules [DSS = dextran sodium sulfate, D+S = dextran (1.49% w/v) in sulfate solution (2.6% w/v), D = dextran (1.49% w/v), S = sulfate solution (2.6% w/v), and Glc+S = glucose (1.73% w/v) in sulfate solution (2.6% w/v)] on colonic epithelium were assessed using a mouse colonoscope. Photographs were obtained from all treatment groups on the day of sacrifice. (B) Fecal relative osmolarity values (means±SEM, ANOVA statistical test, * P<0.05).</p

DSS-associated molecules do not affect the resistance of Caco2-BBE monolayers.

<p>Confluent cultures of Caco2-BBE cells were obtained after 48 h (dark lines) and epithelial resistance was assessed by conduct of continuous resistance measurements at pH 7.4 (cellular pH) and pH 6.2 (colonic pH). Resistance (Ohm) of Caco2-BBE cells was measured at Ω = 500 Hz and V = 1 V by electrical impedance sensing method (ECIS) on ECIS 8W1E electrodes. After confluence (colored lines), DMEM-based solutions containing glucose 17.33 g/L (Glc), dextran 14.9 g/L (D), dextran 14.9 g/L and sodium sulfate 25.99 g/L (D+S) and glucose 17.33 g/L and sulfate 25.99 g/L (Glc+S) were added at both pH. Data represent means of n = 3/condition.</p

DSS and fatty acids form nano-lipocomplexes that disrupt Caco2-BBE monolayer resistance.

<p>(A) Confluent cultures were obtained after 48 h of growth and epithelial resistance was assessed by continuous resistance measurement at pH 7.4 (cellular pH) or pH 6.2 (colonic pH). The epithelial resistances of cultures treated with dodecanoate alone (10 mM) or with 3% (w/v) DSS (1 or 10 mM dodecanoate), at pH 6.2 or pH 7.4, were assessed by ECIS. (B) Light scattering measurement of the diameters (nm) of particles formed by DSS (3% w/v) alone; DSS (3% w/v) with Ca⁺⁺ (1 mM); and DSS (3% w/v) with Ca⁺⁺ (1 mM) and butyrate (1 or 10 mM) or dodecanoate (1 or 10 mM).</p