Gordon S. Howarth

Dipeptidyl peptidase inhibitors, an emerging drug class for inflammatory disease?

Dipeptidyl peptidase (DPP)-4 is a member of the S9b serine protease family, which also includes DPP8 and DPP9. DPP4 cleaves a number of regulatory factors, including chemokines and growth factors. DPP4 inhibitors have recently emerged as an effective treatment option for type 2 diabetes. Early in vitro studies demonstrated that DPP4 inhibitors inhibit T-cell proliferation and cytokine production, leading to their investigation in numerous pre-clinical models of inflammatory diseases, including arthritis, multiple sclerosis and inflammatory bowel disease. Recent data suggest that the early DPP4-specific inhibitors might also bind DPP8 and DPP9, thus exerting their effects through non-specific binding. This review highlights recent insights into the applicability of DPP inhibitors as novel pharmacological agents for inflammatory disease.

Probiotics, prebiotics and synbiotics: a role in chemoprevention for colorectal cancer?

Mark S. Geier, Ross N. Butler and Gordon S. Howarth Colorectal cancer (CRC) is the third most common form of cancer. Current treatments including chemotherapy, radiotherapy and surgery are all associated with a high risk of complications and are not always successful, highlighting the need to develop new treatment strategies. The ingestion of probiotics, prebiotics or combinations of both (synbiotics) represents a novel new therapeutic option. Probiotics and prebiotics act to alter the intestinal microflora by increasing concentrations of beneficial bacteria such as lactobacillus and bifidobacteria, and reducing the levels of pathogenic micro-organisms. This strategy has the potential to inhibit the development and progression of neoplasia via mechanisms including; decreased intestinal inflammation, enhanced immune function and anti-tumorigenic activity, binding to potential food carcinogens including toxins found in meat products, and a reduction in bacterial enzymes which hydrolyse pre-carcinogenic compounds, such as β-glucuronidase. There is substantial experimental evidence to suggest that probiotics and prebiotics may be beneficial in the prevention and treatment of colon cancer, however to date there have been few conclusive human trials. Probiotics and prebiotics have the potential to impact significantly on the development, progression and treatment of colorectal cancer and may have a valuable role in cancer prevention.

Insulin-like Growth Factor-I Partially Attenuates Colonic Damage in Rats with Experimental Colitis Induced by Oral Dextran Sulphate Sodium

BACKGROUND Administration of insulin-like growth factor-I (IGF-I) results in selective growth of the gastrointestinal tract. We investigated the effects of IGF-I on the colonic damage induced by oral dextran sulphate sodium (DSS) in the rat. METHODS Rats consumed 2% DSS in the drinking water for 10 days to induce colitis. Pumps were implanted on day 3 to deliver IGF-I for 7 days. Colonic histopathology and immunolocalization of transforming growth factor-beta1 (TGF-beta1) were assessed on day 10. RESULTS Compared with the colon of vehicle-treated rats consuming DSS, IGF-I increased the numbers of goblet cells by 76%, reduced the proportion of lamina propria cells expressing TGF-beta1, and reduced the thickness of submucosal and muscularis externa layers by 26% and 20%, respectively. CONCLUSIONS We conclude that the effects of IGF-I treatment on the colonic epithelium may be mediated directly, whereas the reduced inflammation in the mucosa and submucosa may be mediated by a mechanism other than up-regulation of TGF-beta1-mediated immunosuppression.

Role of endogenous microbiota, probiotics and their biological products in human health.

Although gut diseases such as inflammatory bowel disease, mucositis and the alimentary cancers share similar pathogenetic features, further investigation is required into new treatment modalities. An imbalance in the gut microbiota, breached gut integrity, bacterial invasion, increased cell apoptosis to proliferation ratio, inflammation and impaired immunity may all contribute to their pathogenesis. Probiotics are defined as live bacteria, which when administered in sufficient amounts, exert beneficial effects to the gastrointestinal tract. More recently, probiotic-derived factors including proteins and other molecules released from living probiotics, have also been shown to exert beneficial properties. In this review we address the potential for probiotics, with an emphasis on probiotic-derived factors, to reduce the severity of digestive diseases and further discuss the known mechanisms by which probiotics and probiotic-derived factors exert their physiological effects.

Increased responsiveness of rat colonic splanchnic afferents to 5-HT after inflammation and recovery

5‐Hydroxytryptamine (5‐HT) activates colonic splanchnic afferents, a mechanism by which it has been implicated in generating symptoms in postinfectious and postinflammatory states in humans. Here we compared mechanisms of colonic afferent activation by 5‐HT and mechanical stimuli in normal and inflamed rat colon, and after recovery from inflammation. Colonic inflammation was induced in rats by dextran sulphate sodium. Single‐fibre recordings of colonic lumbar splanchnic afferents revealed that 58% of endings responded to 5‐HT (10−4m) in controls, 88% in acute inflammation (P < 0.05) and 75% after 21 days recovery (P < 0.05 versus control). Maximal responses to 5‐HT were also larger, and the estimated EC50 was reduced from 3.2 × 10−6 to 8 × 10−7m in acute inflammation and recovered to 2 × 10−6m after recovery. Responsiveness to mechanical stimulation was unaffected. 5‐HT3 receptor antagonism with alosetron reduced responses to 5‐HT in controls but not during inflammation. Responses to the mast cell degranulator 48/80 mimicked those to 5‐HT in inflamed tissue but not in controls, and more 5‐HT‐containing mast cells were seen close to calcitonin gene‐related peptide‐containing fibres in inflamed serosa. We conclude that colonic serosal and mesenteric endings exhibit increased sensitivity to 5‐HT in inflammation, with both an increase in proportion of responders and an increase in sensitivity, which is maintained after healing of inflammation. This is associated with alterations in the roles of 5‐HT3 receptors and mast cells.

Oral ingestion of streptococcus thermophilus diminishes severity of small intestinal mucositis in methotrexate treated rats

Background: Currently, there are no available effective preventative or adjunctive agents to alleviate symptoms of chemotherapy-induced mucositis. This is compounded by the absence of a recognized and validated non-invasive biomarker to assess gut function. This study investigated the effects of orally ingested Streptococcus thermophilus (TH-4) on chemotherapy-induced small intestinal damage in rats using the non-invasive 13C-sucrose breath test (SBT). Methods: Gastrointestinal damage was induced in 27 female dark agouti rats (148 ± 1g) with MTX (1.5 mg/kg; i.m.). Rats received MTX or saline at 0 h; with daily treatment of: TH-4 at doses of 109 (high), 108 (low) cfu/mL, or skim milk (vehicle), 48 h pre and 96 h post-MTX. The non-invasive 13C-sucrose breath test (SBT) was conducted at -24, 24 and 96 h post-MTX to monitor gut function. At sacrifice, small intestinal tissues were collected for determinations of sucrase activity, myeloperoxidase (MPO) activity and histological assessment. Results: MTX + vehicle and MTX + low TH-4-treated rats produced significantly lower SBT and sucrase activity results compared to saline controls (p < 0.001). In contrast, MTX + high TH-4 treatment showed no significant differences in the SBT compared to saline controls, and the SBT results were significantly higher compared to MTX + vehicle and MTX + low TH-4 (p < 0.05). MPO levels were significantly elevated (p < 0.05) in MTX + vehicle and MTX + low TH-4, but not following MTX + high TH-4 treatment, compared to saline controls. This was further confirmed by histological analyses. Conclusion: Oral ingestion of TH-4 at 109 cfu/mL is capable of partially attenuating small bowel damage in rats. The non-invasive SBT is a useful technique to longitudinally assess the efficacy of treatments or interventions for small bowel disease.

Insulin-Like Growth Factor-I (IGF-I) Stimulates Regrowth of the Damaged Intestine in Rats, when Administered Following, but not Concurrent with, Methotrexate

BACKGROUND We tested the ability of insulin-like growth factor-I (IGF-I) to reduce damage to the intestinal mucosa (mucositis) in rats injected with methotrexate. IGF-I was infused concurrent with methotrexate administration and compared to IGF-I administered following the withdrawal of methotrexate. METHODS Rats were injected with methotrexate at the start of days 1, 2 and 3. IGF-I was infused for 5 days, commencing at the start of day 1 [concurrent administration] or at the start of day 4 [post-methotrexate administration]. RESULTS IGF-I administered coincident with methotrexate failed to restore mucosal integrity to the damaged small intestine. IGF-I administered post methotrexate stimulated regrowth of the damaged intestine, particularly the ileum, with 22%, 32% and 29% increases in small intestinal weight, ileal villus height and ileal crypt depth respectively. CONCLUSIONS Following intestinal damage of methotrexate, IGF-I primarily induced growth of the distal small intestine. The ineffectiveness of concurrently administered IGF-I may have represented an IGF-I induced recruitment of proliferating epithelial cells to the anti-proliferative effects of methotrexate.

Grape seed extract protects IEC-6 cells from chemotherapy-induced cytotoxicity and improves parameters of small intestinal mucositis in rats with experimentally-induced mucositis.

Mucositis is a common side-effect of high-dose chemotherapy regimens. Grape seed extract (GSE) represents a rich source of proanthocyanidins with the potential to decrease oxidative damage and inflammation within the gastrointestinal tract. We evaluated GSE for its capacity to decrease the severity of chemotherapy-induced mucositis in vitro and in vivo. In vitro: GSE was administered to IEC-6 intestinal epithelial cells prior to damage induced by 5-Fluorouracil (5-FU). Cell viability was determined by neutral red assay. In vivo: Female Dark Agouti rats (130-180g) were gavaged with 1ml GSE (400mg/kg) daily (day 3-11) and received 5-FU (150mg/kg) by intraperitoneal (i.p.) injection on day 9 to induce mucositis. Rats were sacrificed at day 12 and intestinal tissues collected for myeloperoxidase and sucrase activity assays and histological analyses. Statistical analysis was performed by one-way ANOVA. GSE prevented the decrease in IEC-6 cell viability induced by 5-FU (p

Orally administered emu oil decreases acute inflammation and alters selected small intestinal parameters in a rat model of mucositis

Mucositis resulting from cancer chemotherapy is a serious disorder of the alimentary tract. Emu oil has demonstrated anti-inflammatory properties in animal models of arthritis and wound healing; however, its effects on the intestine remain unknown. We investigated emu oil for its potential to decrease the severity of mucositis in a rat model. Female Dark Agouti rats (110-150 g) were orogastrically gavaged with emu oil (0.5 or 1 ml) or water (1 ml) for 5 d before intraperitoneal injection of 5-fluorouracil (5-FU, 150 mg/kg) or saline (control), and this was continued up to the day of sacrifice (48, 72 and 96 h post 5-FU administration). Histological (villus height, crypt depth (CD) and disease severity score) and biochemical (myeloperoxidase (MPO) activity) parameters were determined in intestinal tissues collected at sacrifice. Sucrase activity in vivo was quantified by the sucrose breath test. Activated neutrophil activity (MPO) in the ileum was significantly decreased by emu oil (0.5 ml, 451 (sem 168) U/g and 1 ml, 503 (sem 213) U/g) compared with 5-FU-treated controls (1724 (sem 431) U/g) 96 h post 5-FU administration. There were also significant increases in CD (152 (sem 8) microm) in the ileum of rats that received 1 ml emu oil at 96 h compared with 5-FU-treated controls (CD (106 (sem 12) microm)). Emu oil did not affect sucrase activity. Emu oil decreased acute ileal inflammation, and improved mucosal architecture in the intestine during recovery from chemotherapy in rats. Further studies investigating the potential benefits of emu oil as a nutritional supplement for the treatment of intestinal disorders are indicated.

Effects of insulin-like growth factor-I administration on radiation enteritis in rats.

BACKGROUND Acute radiation-induced damage to the small bowel occurs frequently during abdominal radiotherapy. Since the small intestine is selectively responsive to the growth-promoting effects of insulin-like growth factor-I (IGF-I), we investigated the effects of IGF-I administration on mucosal recovery from radiation enteritis in the rat. METHODS Rats received a single 10-Gy dose of total abdominal irradiation followed by implantation of mini-pumps infusing either IGF-I or vehicle for 4 days. After the rats had been killed, gut organs were weighed before light microscopic and biochemical examination. RESULTS Irradiated rats receiving IGF-I lost less body weight than vehicle-treated rats, whereas the wet weights of the stomach, small intestine, and colon were increased by 10%, 19%, and 21%, respectively, and crypt depth was increased in the duodenum, jejunum, and ileum. CONCLUSIONS IGF-I administration after abdominal irradiation increased small-intestinal mass and improved indicators of mucosal integrity, suggesting acceleration of small-intestinal mucosal recovery from radiation injury.