Role of nitric oxide in the impairment of circular muscle contractility of distended, uninflamed mid-colon in TNBS-induced acute distal colitis in rats

2,4,6-trinitrobenzenesulfonic acid-induced colitis in Rattus norgevicus: a categorization proposal

Reproducibility in animal research is crucial for its reliance and translational relevance. The 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced model of inflammatory bowel disease (IBD) is widely used but inconsistently and incompletely characterized throughout the literature. This hinders comparisons between studies and influences the low rate of translation of effective preclinical molecules. The purpose of this study was to categorize TNBS-induced colitis, based on macroscopic and microscopic scoring systems, and to identify basic routine parameters that could anticipate those categories. We retrospectively analysed male Wistar Rattus norvegicus (n=28 for the control group and n=87 for the TNBS group) and categorized TNBS-induced colitis in three phenotypes: Mild, Moderate and Severe colitis, as for human IBD. Also, we showed that the time course of food intake and fecal excretion (but not body weight, fluid intake or welfare scores) could foresee those categories. So, routine evaluation of food intake and fecal excretion may guide researchers in planning their experiments, selecting the animals with the severity of colitis that better matches their aims, or applying early humane endpoints to animals that will not be used in the experiments. In conclusion, categorizing TNBS-induced colitis enhances the reproducibility of data gathered with this experimental model and strengths its translational relevance.

Neurochemistry of Enteric Neurons Following Prolonged Indomethacin Administration in the Porcine Duodenum

Gastrointestinal inflammation resulting from prolonged NSAID drugs treatment constitutes a worldwide medical problem. The role of enteric neuroactive substances involved in this process has recently gained attention and neuropeptides produced by the enteric nervous system may play an important role in the modulation of gastrointestinal inflammation. Therefore, the aim of this study was to determine the effect of inflammation caused by indomethacin supplementation on vasoactive intestinal polypeptide (VIP), substance P (SP), neuronal nitric oxide synthase (nNOS), galanin (GAL), pituitary adenylate cyclase-activating polypeptide (PACAP), and cocaine- and amphetamine-regulated transcript peptide (CART) expression in enteric duodenal neurons in domestic pigs. Eight immature pigs of the Pietrain × Duroc race (20 kg of body weight) were used. Control animals (n=4) received empty gelatine capsules. Experimental pigs (n=4) were given indomethacin for 4 weeks, orally 10 mg/kg daily, approximately 1 h before feeding. The animals from both groups were then euthanized. Frozen sections were prepared from the collected duodenum and subjected to double immunofluorescence staining. Primary antibodies against neuronal marker PGP 9.5 and VIP, nNOS, SP, GAL, CART, and PACAP were visualized with Alexa Fluor 488 and 546. Sections were analyzed under an Olympus BX51 fluorescence microscope. Microscopic analysis showed significant increases in the number of nNOS-, VIP-, SP-, GAL-, PACAP-, and CART-immunoreactive ganglionic neurons, in both the myenteric and submucous plexuses of the porcine duodenum. The obtained results show the participation of enteric neurotransmitters in the neuronal duodenal response to indomethacin-induced inflammation.

Mechanical effects of load speed on the human colon

The aim of this study was to examine the mechanical behavior of the colon using tensile tests under different loading speeds. Specimens were taken from different locations of the colonic frame from refrigerated cadavers. The specimens were submitted to uniaxial tensile tests after preconditioning using a dynamic load (1 m/s), intermediate load (10 cm/s), and quasi-static load (1 cm/s). A total of 336 specimens taken from 28 colons were tested. The stress-strain analysis for longitudinal specimens indicated a Young's modulus of 3.17 ± 2.05 MPa under dynamic loading (1 m/s), 1.74 ± 1.15 MPa under intermediate loading (10 cm/s), and 1.76 ± 1.21 MPa under quasi-static loading (1 cm/s) with p < 0.001. For the circumferential specimen, the stress-strain curves indicated a Young's modulus of 3.15 ± 1.73 MPa under dynamic loading (1 m/s), 2.14 ± 1.3 MPa under intermediate loading (10 cm/s), and 0.63 ± 1.25 MPa under quasi-static loading (1 cm/s) with p < 0.001. The curves reveal two types of behaviors of the colon: fast break behavior at high speed traction (1 m/s) and a lower break behavior for lower speeds (10 cm/s and 1 cm/s). The circumferential orientation required greater levels of stress and strain to obtain lesions than the longitudinal orientation. The presence of taeniae coli changed the mechanical response during low-speed loading. Colonic mechanical behavior varies with loading speeds with two different types of mechanical behavior: more fragile behavior under dynamic load and more elastic behavior for quasi-static load.

Identification of Specific Oral and Gut Pathogens in Full Thickness Colon of Colitis Patients: Implications for Colon Motility

Impaired colon motility is one of the leading problems associated with inflammatory bowel disease (IBD). An expanding body of evidence supports the role of microbiome in normal gut function and in progression of IBD. The objective of this work is to determine whether diseased full thickness colon specimens, including the neuromuscular region (critical for colon motility function), contain specific oral and gut pathogens. In addition, we compared the differences in colon microbiome between Caucasians (CA) and African Americans (AA). Thirty-nine human full thickness colon (diseased colon and adjacent healthy colon) specimens were collected from Crohn's Colitis (CC) or Ulcerative Colitis (UC) patients while they underwent elective colon surgeries. We isolated and analyzed bacterial ribosomal RNA (rRNA) from colon specimens by amplicon sequencing of the 16S rRNA gene region. The microbiome proportions were quantified into Operational Taxonomic Units (OTUs) by analysis with Quantitative Insights Into Microbial ecology (QIIME) platform. Two hundred twenty-eight different bacterial species were identified by QIIME analysis. However, we could only decipher the species name of fifty-three bacteria. Our results show that proportion of non-detrimental bacteria in CC or UC colon samples were altered compared to adjacent healthy colon specimens. We further show, for the first time in full thickness colon specimens, that microbiome of CC and UC diseased specimens is dominated by putative oral pathogens belonging to the Phyla Firmicutes (Streptococcus, Staphylococcus, Peptostreptococcus), and Fusobacteria (Fusobacterium). In addition, we have identified patterns of differences in microbiome levels between CA and AA specimens with potential implications for health disparities research. Overall, our results suggest a significant association between oral and gut microbes in the modulation of colon motility in colitis patients.

The Indices of Nitric Oxide System in Rats with Carrageenan-Induced Enterocolitis Combined with Diabetes Mellitus

Background and aims: Diabetes mellitus (DM) represents a considerable public health issue, being one of the major causes of morbidity and mortality in the modern societies. Chronic hyperglycemia is accompanied by significant physiological, biochemical, and histological changes, e.g. development of oxidative stress that affects the motor activity of the intestine. This study aimed to evaluate the indices of nitric oxide (NO) system in blood serum and colon tissue supernatant of rats with carrageenan-induced enterocolitis combined with streptozotocin-induced diabetes.

Material and methods: The total NOS activity was determined by monitoring the rate of conversion of L-arginine into citrulline. The total quantity of NO metabolites was assessed by evaluating their amount, which included nitrite ions that were initially present in the sample (NO2 −) and nitrate ions reducted to nitrites (NO3 −).

Results: We found a significant increase in total NOS activity in colon tissue of all experimental groups vs. control animals (54.8, 30.6 and 79.2 % respectively). The total content of NO metabolites in colon tissue of all experimental groups also significantly increased (2.8, 1.9 and 3.4 times respectively) compared to the control animals.

Conclusions: We observed activation of nitroxydergic process in blood serum and colon tissue of rats with carrageenan-induced enterocolitis. Nitroxydergic processes markedly intensified in rats with carrageenan-induced enterocolitis combined with diabetes mellitus.

Acute colonic pseudo-obstruction: A systematic review of aetiology and mechanisms

AIM

To critically review the literature addressing the definition, epidemiology, aetiology and pathophysiology of acute colonic pseudo-obstruction (ACPO).

METHODS

A systematic search was performed to identify articles investigating the aetiology and pathophysiology of ACPO. A narrative synthesis of the evidence was undertaken.

RESULTS

No consistent approach to the definition or reporting of ACPO has been developed, which has led to overlapping investigation with other conditions. A vast array of risk factors has been identified, supporting a multifactorial aetiology. The pathophysiological mechanisms remain unclear, but are likely related to altered autonomic regulation of colonic motility, in the setting of other predisposing factors.

CONCLUSION

Future research should aim to establish a clear and consistent definition of ACPO, and elucidate the pathophysiological mechanisms leading to altered colonic function. An improved understanding of the aetiology of ACPO may facilitate the development of targeted strategies for its prevention and treatment.

Acute colonic pseudoobstruction

Acute colonic pseudoobstruction (ACPO), often referred to as Ogilvie syndrome, is a clinical entity characterized by severe colonic distension (adult acute megacolon) in the absence of mechanical obstruction. It can result in abdominal ischemia and perforation if left untreated. This article discusses the epidemiology and current pathophysiologic theories of ACPO as well as the clinical presentation and diagnostic modalities utilized to identify the disease. In addition, this article describes the current treatment options for ACPO, which range from conservative medical therapy, therapeutic endoscopy, to subtotal colectomy.

Decrease of guanylyl cyclase β1 subunit and nitric oxide (NO)-induced relaxation in mouse rectum with colitis and its reproduction on long-term NO treatment

Nitric oxide (NO) influences motility in the colon in patients with ulcerative colitis, but the exact mechanism involved remains unknown. Colitis was induced in mice by the oral administration of 2.5% dextran sodium sulfate (DSS), and the motility in longitudinal preparations from rectum and distal colon and expression of β1 subunit of soluble guanylyl cyclase (sGCβ1) were analyzed. Electrical stimulation (ES) caused a transient relaxation via the NO pathway in both rectum and colon from control mice. Stimulation with sodium nitroprusside (SNP) caused relaxation in the two regions, and the half-time (T (1/2)) of the maximal relaxation induced by 100 μM SNP was 8.1 ± 1.0 s in rectum. DSS treatment (1) abolished the ES-induced relaxation, but not dibutyryl cyclic GMP-induced response, in both regions, (2) decreased the maximal response to SNP accompanied by a loss of immunoreactive sGCβ1 protein in rectum, but did not affect the amplitude of the relaxant response or the protein in distal colon, and (3) caused an increase in the T (1/2) value in response to SNP in both regions. Pretreatment of both preparations from control mice with 600 μM SNP for 30 min decreased both ES- and SNP-induced relaxation, SNP-induced cyclic GMP formation, and immunoreactive sGCβ1 levels. NO-mediated relaxation was impaired by a dysfunctional sGC with and without a loss of immunoreactivity to sGCβ1 in rectum and colon from DSS-treated mice, respectively. Long-term exposure of the tissues with an excess amount of NO changes the sGC-mediated relaxation.

Historical evolution of the management of severe ulcerative colitis

Ulcerative colitis was first described in 1859, but it was not until the early 20th century that it became a well recognized clinical entity. The patients of the old series showed high mortality rate ranging from 30% in the severe forms to 60% in the fulminating forms. The introduction of corticosteroids in the 1950s dramatically improved the prognosis of patients with severe ulcerative colitis. The strategy based on intensive medical treatment, early detection of risk factors and early surgery progressively reduced the mortality rate to less than 1%. Tachycardia, fever, reduced number of intestinal sounds, hypoalbuminaemia, hypokalaemia metabolic alkalosis and elevated C-reactive protein were recognized to be the most useful risk factors. Plain abdominal X-ray remains the very reliable suitable tool to detect early complications of severe colitis. Once reduced the mortality near to zero, treatment has been addressed to avoid colectomy. Cyclosporine and Infliximab are currently used as rescue therapy, however, despite the high remission rates achieved with both drugs, about 50% of the treated patients ultimately will come to colectomy over the next few years.

Severe ulcerative colitis: present medical treatment strategies

A total of 15-19% of ulcerative colitis patients have a severe attack at some time during their illness. As a consequence of its high associated mortality and morbidity rates, a close collaboration between gastroenterologists and surgeons in their management is mandatory, in order to define, as best as possible, the timing of surgery (i.e., colectomy) when patients fail to respond to medical treatment or worsen despite optimal medical treatment. The first step in medical treatment consists of using intravenous corticosteroids as they have been demonstrated to reduce drastically the mortality rates. However, at 1 year approximately 25% of patients become corticosteroid dependent and 30% require colectomy, which can consistently affect their quality of life. Therefore, intravenous ciclosporin has been proposed as a rescue therapy, with a further improvement of short-term efficacy and reduction of surgery requirement. Nevertheless, its use is associated with a risk of toxicity and intravenous ciclosporin is not easy to use in non-specialised centres. In addition, long-term studies suggest that colectomy is often only delayed and relapse frequent. Consequently, some authors evaluate the potential use of infliximab. Available data are encouraging, reporting a significant short-term reduction in colectomy rate. Nevertheless, additional trials are required to better define the more effective and safe treatment option(s), for both the short- and long-term, in this patient setting; a question addressed in ongoing trials.

Current management of severe ulcerative colitis

Approximately 15% of patients with ulcerative colitis develop an acute attack of severe colitis, and 30% of these patients require colectomy. Severe ulcerative colitis is therefore considered a medical emergency, the management of which requires close collaboration between gastroenterologists and surgeons. The mortality rate for patients with severe ulcerative colitis is now <1% in specialist centers, but it was high before intravenous steroid therapy and early surgery were introduced; indeed, mortality is still high in nonspecialized centers. As colectomy severely affects quality of life, therapy with intravenous ciclosporin and, more recently, infliximab has been introduced to try to avoid the need for surgery. Ciclosporin induces short-term remission, but the long-term benefit remains unsatisfactory as colectomy is often only delayed. A significant short-term reduction in the colectomy rate has, however, been observed after infliximab treatment. The use of infliximab versus ciclosporin in patients with severe ulcerative colitis remains to be defined. The timing of surgery remains a cardinal decision in the management of severe ulcerative colitis; increased morbidity resulting from prolonged ineffective medical treatment and, therefore, a delay in surgical treatment should be avoided.