Mechanism of reduced colonic contractility in experimental colitis: role of sarcoplasmic reticulum pump isoform-2

Protection by pure and genistein fortified extra virgin olive oil, canola oil, and rice bran oil against acetic acid-induced ulcerative colitis in rats

Conjugation of genistein and dietary oils improves the anti-inflammatory and antioxidant effects of genistein on colitis in rats.

Activation of LANCL2 by BT-11 Ameliorates IBD by Supporting Regulatory T Cell Stability Through Immunometabolic Mechanisms

BACKGROUND

Inflammatory bowel disease (IBD) afflicts 5 million people and is increasing in prevalence. There is an unmet clinical need for safer and effective treatments for IBD. The BT-11 is a small molecule oral therapeutic that ameliorates IBD by targeting lanthionine synthetase C-like 2 (LANCL2) and has a benign safety profile in rats.

METHODS

Mdr1a-/-, dextran sodium sulphate , and adoptive transfer mouse models of colitis were employed to validate therapeutic efficacy and characterize the mechanisms of therapeutic efficacy of BT-11. In vitro cultures of CD4+ T cell differentiation and human peripheral blood mononuclear cells from Crohn's disease patients were used to determine its potential for human translation.

RESULTS

BT-11 reduces inflammation in multiple mouse models of IBD. Oral treatment with BT-11 increases the numbers of lamina propria regulatory T cells (Tregs) in a LANCL2-dependent manner. In vitro, BT-11 increases the differentiation in Treg phenotypes, the upregulation of genes implicated in Treg cell stability, and conditions Treg cells to elicit greater suppressive actions. These immunoregulatory effects are intertwined with the ability of BT-11 to regulate late stage glycolysis and tricarboxylic acid cycle. Immunometabolic mechanistic findings translate into human peripheral blood mononuclear cells from healthy individuals and Crohn's disease patients.

CONCLUSIONS

BT-11 is a safe, efficacious oral therapeutic for IBD with a human translatable mechanism of action that involves activation of LANCL2, immunometabolic modulation of CD4+ T cell subsets leading to stable regulatory phenotypes in the colonic LP.

The effect of sphingosine-1-phosphate on colonic smooth muscle contractility: Modulation by TNBS-induced colitis

Aim

Increased levels of circulating sphingosine-1-phosphate (S1P) have been reported in ulcerative colitis. The objective of this study was to examine the effect of S1P on colonic smooth muscle contractility and how is it affected by colitis.

Methods

Colonic inflammation was induced by intrarectal administration of trinitrobenzene sulfonic acid. Five days later colon segments were isolated and used for contractility experiments and immunoblotting.

Results

S1P contracted control and inflamed colon segments and the contraction was significantly greater in inflamed colon segments. S1P-induced contraction was mediated by S1PR1 and S1PR2 in control and S1PR2 in inflamed colon segments. S1PR3 did not play a significant role in S1P-induced contractions in control or inflamed colon. S1PR1, S1PR2 and S1PR3 proteins were expressed in colon segments from both groups. The expression of S1PR1 and S1PR2 was significantly enhanced in control and inflamed colon segments, respectively. S1PR3 levels however were not significantly different between the two groups. Nifedipine significantly reduced S1P-induced contraction in control but not inflamed colon segments. Thapsigargin significantly reduced S1P-induced contraction of the inflamed colon. GF 109203X and Y-27632, alone abolished S1P-induced contraction of the control but not inflamed colon segments. Combination of GF 109203X, Y-27632 and thapsigargin abolished S1P-induced contraction of inflamed colon segments.

Conclusion

S1P contracted control colon via S1PR1 and S1PR2 and inflamed colon exclusively via S1PR2. Calcium influx (control) or release (inflamed) and calcium sensitization are involved in S1P-induced contraction. Exacerbated response to S1P in colitic colon segments may explain altered colonic motility reported in patients and experimental models of inflammatory bowel disease.

The Involvement of Ca(2+) Signal Pathways in Distal Colonic Myocytes in a Rat Model of Dextran Sulfate Sodium-induced Colitis

Background:

Disrupted Ca²⁺ homeostasis contributes to the development of colonic dysmotility in ulcerative colitis (UC), but the underlying mechanisms are unknown. This study aimed to examine the alteration of colonic smooth muscle (SM) Ca²⁺ signaling and Ca²⁺ handling proteins in a rat model of dextran sulfate sodium (DSS)-induced UC.

Methods:

Male Sprague-Dawley rats were randomly divided into control (n = 18) and DSS (n = 17) groups. Acute colitis was induced by 5% DSS in the drinking water for 7 days. Contractility of colonic SM strips (controls, n = 8 and DSS, n = 7) was measured in an organ bath. Cytosolic resting Ca²⁺ levels (n = 3 in each group) and Ca²⁺ transients (n = 3 in each group) were measured in single colonic SM cells. Ca²⁺ handling protein expression was determined by Western blotting (n = 4 in each group). Differences between control and DSS groups were analyzed by a two-sample independent t-test.

Results:

Average tension and amplitude of spontaneous contractions of colonic muscle strips were significantly enhanced in DSS-treated rats compared with controls (1.25 ± 0.08 g vs. 0.96 ± 0.05 g, P = 0.007; and 2.67 ± 0.62 g vs. 0.52 ± 0.10 g, P = 0.013). Average tensions of carbachol-evoked contractions were much weaker in the DSS group (1.08 ± 0.10 g vs. 1.80 ± 0.19 g, P = 0.006). Spontaneous Ca²⁺ transients were observed in more SM cells from DSS-treated rats (15/30 cells) than from controls (5/36 cells). Peak caffeine-induced intracellular Ca²⁺ release was lower in SM cells of DSS-treated rats than controls (0.413 ± 0.046 vs. 0.548 ± 0.041, P = 0.033). Finally, several Ca²⁺ handling proteins in colonic SM were altered by DSS treatment, including sarcoplasmic reticulum calcium-transporting ATPase 2a downregulation and phospholamban and inositol 1,4,5-trisphosphate receptor 1 upregulation.

Conclusions:

Impaired intracellular Ca²⁺ signaling of colonic SM, caused by alteration of Ca²⁺ handing proteins, contribute to colonic dysmotility in DSS-induced UC.

Tumor necrosis factor-neuropeptide Y cross talk regulates inflammation, epithelial barrier functions, and colonic motility

BACKGROUND

Neuro-immune interactions play a significant role in regulating the severity of inflammation. Our previous work demonstrated that neuropeptide Y (NPY) is upregulated in the enteric nervous system during murine colitis and that NPY knockout mice exhibit reduced inflammation. Here, we investigated if NPY expression during inflammation is induced by tumor necrosis factor (TNF), the main proinflammatory cytokine.

METHODS

Using primary enteric neurons and colon explant cultures from wild type and NPY knockout (NPY(-/-)) mice, we determined if NPY knockdown modulates TNF release and epithelial permeability. Further, we assessed if NPY expression is inducible by TNF in enteric neuronal cells and mouse model of experimental colitis, using the TNF inhibitors-etanercept (blocks transmembrane and soluble TNF) and XPro1595 (blocks soluble TNF only).

RESULTS

We found that enteric neurons express TNF receptors (TNFR1 and R2). Primary enteric neurons from NPY(-/-) mice produced less TNF compared with wild type. Further, TNF activated NPY promoter in enteric neurons through phospho-c-Jun. NPY(-/-) mice had decreased intestinal permeability. In vitro, NPY increased epithelial permeability through phosphatidyl inositol-3-kinase (PI3-K)-induced pore-forming claudin-2. TNF inhibitors attenuated NPY expression in vitro and in vivo. TNF inhibitor-treated colitic mice exhibited reduced NPY expression and inflammation, reduced oxidative stress, enhanced neuronal survival, and improved colonic motility. XPro1595 had more protective effects on neuronal survival and motility compared with etanercept.

CONCLUSIONS

We demonstrate a novel TNF-NPY cross talk that modulates inflammation, barrier functions, and colonic motility during inflammation. It is also suggested that selective blocking of soluble TNF may be a better therapeutic option than using anti-TNF antibodies.

STW 5 is effective in dextran sulfate sodium-induced colitis in rats

PURPOSE

An herbal preparation, STW 5, used clinically in functional dyspepsia and irritable bowel syndrome, has been shown to possess properties that may render it useful in inflammatory bowel disease (IBD). The present work was conducted to study its effectiveness in a rat model of IBD.

METHODS

An experimental model reflecting ulcerative colitis in man was adopted, whereby colitis was induced in Wistar rats by feeding them 5 % dextran sulfate sodium (DSS) in drinking water for one week. STW 5 and sulfasalazine (as a reference standard) were administered orally daily for 1 week before colitis induction and continued during DSS feeding. The animals were then sacrificed, and the severity of colitis was evaluated macroscopically and microscopically. Colon samples were homogenized for determination of reduced glutathione, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-3 as well as myeloperoxidase, glutathione peroxidase, and superoxide dismutase. In addition, colon segments were suspended in an organ bath to test their reactivity towards carbachol, KCl, and trypsin.

RESULTS

STW 5 and sulfasalazine were both effective in preventing the shortening of colon length and the increase in both colon mass index and total histology score as well as the changes in biochemical parameters measured except changes in dismutase activity. DSS-induced colitis led to marked depression in colonic responsiveness to the agents tested ex vivo, an effect which was normalized by both drugs.

CONCLUSIONS

The findings point to a potential usefulness of STW 5 in the clinical setting of ulcerative colitis.

Regulation of gastrointestinal motility by Ca2+/calmodulin-stimulated protein kinase II

Gastrointestinal (GI) motility ultimately depends upon the contractile activity of the smooth muscle cells of the tunica muscularis. Integrated functioning of multiple tissues and cell types, including enteric neurons and interstitial cells of Cajal (ICC) is necessary to generate coordinated patterns of motor activity that control the movement of material through the digestive tract. The neurogenic mechanisms that govern GI motility patterns are superimposed upon intrinsic myogenic mechanisms regulating smooth muscle cell excitability. Several mechanisms regulate smooth muscle cell responses to neurogenic inputs, including the multifunctional Ca(2+)/calmodulin-stimulated protein kinase II (CaMKII). CaMKII can be activated by Ca(2+) transients from both extracellular and intracellular sources. Prolonging the activities of Ca(2+)-sensitive K(+) channels in the plasma membrane of GI smooth muscle cells is an important regulatory mechanism carried out by CaMKII. Phospholamban (PLN) phosphorylation by CaMKII activates the sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA), increasing both the rate of Ca(2+) clearance from the myoplasm and the frequency of localized Ca(2+) release events from intracellular stores. Overall, CaMKII appears to moderate GI smooth muscle cell excitability. Finally, transcription factor activities may be facilitated by the neutralization of HDAC4 by CaMKII phosphorylation, which may contribute to the phenotypic plasticity of GI smooth muscle cells.

Mechanism of regulation of Na-H exchanger in inflammatory bowel disease: role of TLR-4 signaling mechanism

OBJECTIVE

We investigated the role of toll-like receptor-4 (TLR-4) signal transduction in the regulation of Na-H exchanger-1 isoform (NHE-1) in ulcerative colitis (UC).

METHODS

Colonic biopsies from control and UC patients were selected from four groups: controls (group 1), untreated UC patients (group 2), UC patients treated with 5'-aminosalicylic acid (5'-ASA) plus steroid (group 3), and UC patients treated with 5'-ASA plus azathioprine (AZA) (group 4). Patients presenting with abdominal pain (n = 13) and a normal colon on endoscopy served as controls. NHE-1, TLR-4, MyD88, NFkB and actin protein levels were estimated using Western blot analysis and sodium pump activity (PNPase) by a spectrophotometeric method. Myeloperoxidase (MPO) activity and histologic evaluation confirmed inflammation.

RESULTS

PNPase activity decreased significantly (P < 0.05) in the untreated UC patients as compared to the controls or treated UC groups 3 and 4. There was a significant decrease of NHE-1 and a significant increase (P < 0.05) of TLR-4, MyD88 and NFkB protein levels in the untreated UC or 5'-ASA plus steroid treated UC patients as compared to the controls. NHE-1, TLR-4, MyD88 and NFkB protein levels were not significantly different in 5'-ASA plus AZA treated biopsies as compared to controls. The level of actin remained unaltered. Inflammatory cells' infiltration and MPO activity increased significantly in the untreated UC, but was significantly lower in the treated UC groups 3 and 4 (P < 0.05).

CONCLUSIONS

These findings suggest that NHE-1 in UC is regulated by NFkB induced through TLR-4 and MyD88 signaling mechanism. These findings identify TLR-4 as a putative therapeutic target for IBD.

Expression of Na-H exchanger-8 isoform is suppressed in experimental colitis in adult rat: lack of reversibility by dexamethasone

OBJECTIVES

Mechanism of the apical transporter Na-H exchanger-8 (NHE-8) regulation was investigated by examining the effects of anti-inflammatory dexamethasone in experimental colitis. In addition, its localization was investigated in the lipid rich membrane domain called membrane rafts.

MATERIAL AND METHODS

Colitis was induced by trinitrobenzene sulfonic acid (TNBS) and colon segments were removed from 5 day post-TNBS and used to estimate the levels of NHE-8 protein and mRNA using ECL western blot analysis and a competitive RT-PCR method. Myeloperoxidase activity, malondialdehyde levels and histologic changes were evaluated.

RESULTS

NHE-8 protein level was decreased in inflamed colon and was not reversed by dexamethasone. However, mRNA levels remained unchanged in inflamed colon. The levels of NHE-8 protein and mRNA were not significantly different in non-colitic control as compared to dexamethasone treated non-colitis. Elevation of myeloperoxidase activity, malondialdehyde and infiltration of inflammatory cells in inflamed colon were suppressed by dexamethasone treatment of colitis significantly. Furthermore, NHE-8 protein was not detected in the detergent resistant membrane (DRM) or lipid rafts, but was present in the detergent sensitive membrane (DRS) fractions. Actin showed its partition similar to NHE-8. On the contrary, NHE-3 was present in both DRM and DRS fractions. Flotillin-1 and caveolin were enriched in the fractions designated as lipid rafts.

CONCLUSIONS

These findings demonstrate the suppression of NHE-8 protein in inflamed adult rat colon, which seems to be regulated post-transcriptionally. Furthermore, the absence of NHE-8 in lipid rafts suggests its regulation independent of cAMP or recycling through endocytosis unlike NHE-3 isoform.

CaM kinase II in colonic smooth muscle contributes to dysmotility in murine DSS-colitis

BACKGROUND

Altered calcium mobilization has been implicated in the development of colonic dysmotility in inflammatory bowel disease. The aim of this study was to investigate the mechanisms by which disrupted intracellular Ca(2+) signalling contributes to the impaired contractility of colon circular smooth muscles.

METHODS

Acute colitis was induced in C57Bl/6 mice with dextran sulphate sodium (DSS) in the drinking water for 5 days.

KEY RESULTS

Spontaneous and acetylcholine-evoked contractions, caffeine-evoked hyperpolarization, and SERCA2 and phospholamban expression were reduced compared with controls. Tetrodotoxin did not restore control levels of contractile activity. The amplitudes, but not the frequency, of intracellular Ca(2+) waves were increased compared with controls. Caffeine abolished intracellular Ca(2+) waves in control smooth muscle cells, but not in smooth muscle cells from DSS-treated mice. CaM kinase II activity and cytosolic levels of HDAC4 were increased, and I kappaB alpha levels were decreased in distal colon smooth muscles from DSS-treated mice.

CONCLUSIONS & INFERENCES

These results suggest that disruptions in intracellular Ca(2+) mobilization due to down-regulation of SERCA2 and phospholamban expression lead to increased CaM kinase II activity and cytosolic HDAC4 that may contribute to the dysmotility of colonic smooth muscles in colitis by enhancing NF-kappaB activity.