Transcriptomic profiling reveals a pronociceptive role for angiotensin II in inflammatory bowel disease.

ABSTRACT: Visceral pain is a leading cause of morbidity in inflammatory bowel disease (IBD), contributing significantly to reduced quality of life. Currently available analgesics often lack efficacy or have intolerable side effects, driving the need for a more complete understanding of the mechanisms causing pain. Whole transcriptome gene expression analysis was performed by bulk RNA sequencing of colonic biopsies from patients with ulcerative colitis (UC) and Crohn's disease (CD) reporting abdominal pain and compared with noninflamed control biopsies. Potential pronociceptive mediators were identified based on gene upregulation in IBD biopsy tissue and cognate receptor expression in murine colonic sensory neurons. Pronociceptive activity of identified mediators was assessed in assays of sensory neuron and colonic afferent activity. RNA sequencing analysis highlighted a 7.6-fold increase in the expression of angiotensinogen transcripts, Agt , which encode the precursor to angiotensin II (Ang II), in samples from UC patients ( P = 3.2 × 10 -8 ). Consistent with the marked expression of the angiotensin AT 1 receptor in colonic sensory neurons, Ang II elicited an increase in intracellular Ca 2+ in capsaicin-sensitive, voltage-gated sodium channel subtype Na V 1.8-positive sensory neurons. Ang II also evoked action potential discharge in high-threshold colonic nociceptors. These effects were inhibited by the AT 1 receptor antagonist valsartan. Findings from our study identify AT 1 receptor-mediated colonic nociceptor activation as a novel pathway of visceral nociception in patients with UC. This work highlights the potential utility of angiotensin receptor blockers, such as valsartan, as treatments for pain in IBD.

KV7 but not dual small and intermediate KCa channel openers inhibit the activation of colonic afferents by noxious stimuli.

In numerous subtypes of central and peripheral neurons, small and intermediate conductance Ca2+-activated K+ (SK and IK, respectively) channels are important regulators of neuronal excitability. Transcripts encoding SK channel subunits, as well as the closely related IK subunit, are coexpressed in the soma of colonic afferent neurons with receptors for the algogenic mediators ATP and bradykinin, P2X3 and B2, highlighting the potential utility of these channels as drug targets for the treatment of abdominal pain in gastrointestinal diseases such as irritable bowel syndrome. Despite this, pretreatment with the dual SK/IK channel opener SKA-31 had no effect on the colonic afferent response to ATP, bradykinin, or noxious ramp distention of the colon. Inhibition of SK or IK channels with apamin or TRAM-34, respectively, yielded no change in spontaneous baseline afferent activity, indicating these channels are not tonically active. In contrast to its lack of effect in electrophysiological experiments, comparable concentrations of SKA-31 abolished ongoing peristaltic activity in the colon ex vivo. Treatment with the KV7 channel opener retigabine blunted the colonic afferent response to all applied stimuli. Our data therefore highlight the potential utility of KV7, but not SK/IK, channel openers as analgesic agents for the treatment of abdominal pain.NEW & NOTEWORTHY Despite marked coexpression of small (Kcnn1, Kcnn2) and intermediate (Kcnn4) conductance calcium-activated potassium channel transcripts with P2X3 (P2rx3) or bradykinin B2 (Bdkrb2) receptors in colonic sensory neurons, pharmacological activation of these channels had no effect on the colonic afferent response to ATP, bradykinin or luminal distension of the colon. This is in contrast to the robust inhibitory effect of the KV7 channel opener, retigabine.

Protective effect of Sesbania grandiflora on acetic acid induced ulcerative colitis in mice by inhibition of TNF-α and IL-6.

ETHNOPHARMACOLOGICAL RELEVANCE: The plant Sesbania grandiflora (Linn) belonging to the family Fabaceae is commonly known as sesbania, agathi, and katurai. The plant is accredited for alleviating a spectrum of ailments including inflammation, colitis, diarrhea, dysentery, leprosy, gout, rheumatism, jaundice, bronchitis, convulsion and anxiety. It is also used as antitumour, anthelmintic, and laxatives in Ayurveda and Siddha system of Indian traditional medicine. AIM: To reveal protective effect of Sesbania grandiflora in acetic acid induced ulcerative colitis in mice. MATERIALS AND METHOD: Polyphenol, flavonoid and flavanone contents of different extracts of S. grandiflora leaves were quantified and correlated with their antioxidant capacity in-vitro (DPPH assay) for identification of potential fraction. In further studies hydroalocholic extract (HASG, 100 and 200 mg/kg) was evaluated for protective effect towards acetic acid induced ulcerative colitis (UC) animals administered with 150 µl of 5% acetic acid once, intrarectally. The colonic mucosal injury was assessed by estimating disease activity index (DAI), which took into account weight loss, stool consistency and occult/gross bleeding. Macroscopic changes like colon length, spleen weights, ulcer area and ulcer index were determined. Haematological parameters like WBC count, RBC count, Hb (g/dL), HCT (%), PLT count and FFA level were determined. Biochemical analysis was carried out for asserting the levels of tissue myeloperoxidase (MPO) accumulation, SOD concentrations, reduced GSH and lipid peroxidation in UC induced and treated animals. The cardinal inflammatory biomarkers like nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin (IL-6) were determined. Histopathological investigation was carried out and scores were calculated. RESULTS: HASG showed presence of highly polymerized polyphenols and flavonoids amongst other extracts of S. grandiflora, which is correlated to its rich antioxidant potential (IC50 =19.21). HPLC fingerprinting quantifies the presence of quercetin in concentration of 81.7 µg/mg of HASG. HASG (200 mg/kg) and Prednisolone (2 mg/kg) significantly reduced DAI and macroscopic scores. The haematological changes in experimental animals were restored upon treatment with HASG and Prednisolone. HASG showed potent antioxidant activity (In-vivo) by restoring the levels of SOD, GSH, MPO, MDA and NO. HASG was found to inhibit FFA levels, which may indicate inhibition of TLR4 receptor mediated inflammation. The levels of serological biomarkers like TNF-α and IL-6 were found to be suppressed. Histopathological investigation reveals decrease signs of ulceration, necrosis, cellular infiltration, hyperaemia in HASG treated animals. The results of HASG (200 mg/kg) were found to be comparable with Prednisolone (2 mg/kg) significantly. CONCLUSION: The protective action of HASG against acetic acid induced UC is attributed to the antioxidant like action (In-vitro and In-vivo) of highly polymerized polyphenols and flavonoids especially quercetin. Also HASG was found to reduce the levels of TNF-α and IL-6, thereby suppressing their inflammatory response in UC.

Effect of piperine on inhibition of FFA induced TLR4 mediated inflammation and amelioration of acetic acid induced ulcerative colitis in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Piperine, a main component of Piper longum Linn. and Piper nigrum Linn., is a plant alkaloid with a long history of medicinal use. Piperine exhibits antidepressant, hepatoprotective, anti-metastatic, anti-thyroid, immunomodulatory, antitumor and anti-inflammatory activities, However its therapeutic potential in amelioration of ulcerative colitis and the underlying mechanism for anti-inflammatory activity remains unknown.The objective of the present investigation was to unravel the therapeutic potential of piperine on amelioration of IBD using acetic acid induced experimental animal model for ulcerative colitis and to determine the role of TLR4 receptor in signalling pathway of inflammatory gene expression in ulcerative colitis. MATERIALS AND METHODS: We induced colitis using acetic acid (150µl of 5% once, intrarectally) in mice and estimated disease activity index (DAI), which took into account weight loss, stool consistency, and occult/gross bleeding. Colon length, spleen weights, ulcer area and ulcer index were measured; histological changes were observed by H&E staining. Effect of piperine on various antioxidant parameter of mice colon such as tissue myeloperoxidase (MPO) accumulation, SOD concentrations, reduced GSH and lipid peroxidation were determined. Pro-inflammatory mediators, namely, nitric oxide (NO), tumour necrosis factor-α (TNF-α) were determined by a TNF-α ELISA kit obtained from Thermo fisher scientific India Pvt. Ltd. Effect of piperine on haematological parameters of mice in acetic acid induced IBD was also determined which involves the estimation of FFA using a commercial free fatty acid fluorometric assay kit. RESULT: Piperine significantly attenuated acetic acid induced DAI score which implies that it suppresses weight loss, diarrhoea, gross bleeding and infiltration of immune cells. Piperine administration also effectively and dose dependently prevented shortening of colon length and enlargement of spleen size. Histological examination indicated that piperine reduces oedema in sub-mucosa, cellular infiltration, reduced haemorrhages and ulceration as compare to acetic acid induced colitis in mice. Furthermore piperine inhibited abnormal secretion of pro-inflammatory mediators namely NO, cytokines TNF-α and reduces FFA induced TLR4 mediated inflammation. CONCLUSION: These results suggest that piperine has an anti-inflammatory effect at colorectal sites that is due to down- regulations of the productions and expression of inflammatory mediators and it also reduces FFA induced TLR4 mediated inflammation. Thus it may have therapeutic potential on amelioration of IBD.