Role of neurokinin 1 receptors in dextran sulfate-induced colitis: studies with gene-deleted mice and the selective receptor antagonist netupitant

Effect of antiemetics on zolbetuximab-induced gastric injury and emesis in ferrets

Claudin-18 splice variant 2 (CLDN18.2), a tight junction protein, is a highly cell type-specific antigen that is expressed by differentiated gastric mucosa cells. The expression of CLDN18.2 in gastric mucosa cells may be retained upon malignant transformation and is displayed on the surface of several tumors, including gastric/gastroesophageal junction adenocarcinoma. Zolbetuximab is a genetically engineered, highly purified chimeric (mouse/human IgG1) antibody directed against CLDN18.2. Nausea and vomiting were observed as adverse events of zolbetuximab. To investigate the mechanism of nausea and vomiting in humans, we evaluated emesis (retching and vomiting) and conducted histopathologic assessment in ferrets after the administration of zolbetuximab. Emesis was frequently observed in all ferrets treated with zolbetuximab in the first hour after administration. Histopathologic assessment revealed the surface of the gastric mucosa was the primary site of emesis-associated tissue damage. The effect of antiemetics (dexamethasone, ondansetron, fosaprepitant, and olanzapine) on emesis induced by zolbetuximab was investigated. Fosaprepitant showed suppressive effects on emesis, and use of dexamethasone or concomitant use of fosaprepitant with other antiemetics tended to alleviate gastric tissue damage. The onset of emesis in humans receiving zolbetuximab may be associated with damage in the gastric mucosa, and antiemetics may mitigate gastrointestinal adverse events.

Roles of TRP and PIEZO receptors in autoimmune diseases

Autoimmune diseases are pathological autoimmune reactions in the body caused by various factors, which can lead to tissue damage and organ dysfunction. They can be divided into organ-specific and systemic autoimmune diseases. These diseases usually involve various body systems, including the blood, muscles, bones, joints and soft tissues. The transient receptor potential (TRP) and PIEZO receptors, which resulted in David Julius and Ardem Patapoutian winning the Nobel Prize in Physiology or Medicine in 2021, attracted people's attention. Most current studies on TRP and PIEZO receptors in autoimmune diseases have been carried out on animal model, only few clinical studies have been conducted. Therefore, this study aimed to review existing studies on TRP and PIEZO to understand the roles of these receptors in autoimmune diseases, which may help elucidate novel treatment strategies.

Oral commensal bacterial flora is responsible for peripheral differentiation of neutrophils in the oral mucosa in the steady state

OBJECTIVES

Commensal bacteria in the host body play a fundamental role in the differentiation and maintenance of the immune system. Studies on intestinal immunity have revealed that, under steady-state conditions, microflora have an important role in the maintenance of health. However, the role of oral commensal bacteria on the oral immune system is still unclear. Here, we clarify the interactions between commensal bacteria and the oral mucosal immune system under steady-state conditions.

METHODS

We used germ-free mice that had never been exposed to bacteria and conventional mice grown with normal bacterial flora. Oral cells were isolated from the oral mucosa, stained with specific antibodies, and analyzed by flow cytometry. For the detection of myeloperoxidase and intracellular cytokines, oral cells were stimulated with N-formyl-methionine-leucyl-phenylalanine and phorbol 12-myristate 13-acetate/ionomycin, respectively.

RESULTS

We found that the oral mucosa harbored more neutrophils in germ-free mice than in conventional mice. However, the majority of neutrophils in the germ-free oral mucosa exhibited an immature phenotype. Other immune cells, including macrophages, T cells, and B cells, in the oral mucosa of germ-free mice showed similar differentiation to those in conventional mice. These results indicate that in the steady-state oral mucosa, the normal commensal flora promote the peripheral differentiation of neutrophils.

CONCLUSIONS

The presence of commensal flora is critical for the development of adequate immune system in the oral mucosa.

Role of TRPV1 and TRPA1 Ion Channels in Inflammatory Bowel Diseases: Potential Therapeutic Targets?

Inflammatory bowel diseases (IBD) have long been recognized to be accompanied by pain resulting in high morbidity. Transient receptor potential vanilloid 1 (TRPV1) and ankyrin 1 (TRPA1) ion channels located predominantly on the capsaicin-sensitive sensory neurons play a complex role in hyperalgesia and neurogenic inflammation. This review provides an overview of their expression and role in intestinal inflammation, in particular colitis, that appears to be virtually inconsistent based on the thorough investigations of the last twenty years. However, preclinical results with pharmacological interventions, as well as scarcely available human studies, more convincingly point out the potential therapeutic value of TRPV1 and TRPA1 antagonists in colitis and visceral hypersensitivity providing future therapeutical perspectives through a complex, unique mechanism of action for drug development in IBD.

TNF-α inhibits SCF, ghrelin, and substance P expressions through the NF-κB pathway activation in interstitial cells of Cajal

Ulcerative colitis is a chronic inflammatory disease of the colon where intestinal motility is disturbed. Interstitial cells of Cajal (ICC) are required to maintain normal intestinal motility. In the present study, we assessed the effect of tumor necrosis factor-alpha (TNF-α) on viability and apoptosis of ICC, as well as on the expression of stem cell factor (SCF), ghrelin, and substance P. ICC were derived from the small intestines of Swiss albino mice. Cell viability and apoptosis were measured using CCK-8 assay and flow cytometry, respectively. ELISA was used to measure the concentrations of IL-1β, IL-6, ghrelin, substance P, and endothelin-1. Quantitative RT-PCR was used to measure the expression of SCF. Western blotting was used to measure the expression of apoptosis-related proteins, interleukins, SCF, and NF-κB signaling pathway proteins. TNF-α induced inflammatory injury in ICC by decreasing cell viability and increasing apoptosis and levels of IL-1β and IL-6. TNF-α decreased the levels of SCF, ghrelin, and substance P, but had no effect on endothelin-1. TNF-α down-regulated expressions of SCF, ghrelin, and substance P by activating the NF-κB pathway in ICC. In conclusion, TNF-α down-regulated the expressions of SCF, ghrelin, and substance P via the activation of the NF-κB pathway in ICC.

Integrative characterization of chronic cigarette smoke-induced cardiopulmonary comorbidities in a mouse model

Cigarette smoke-triggered inflammatory cascades and consequent tissue damage are the main causes of chronic obstructive pulmonary disease (COPD). There is no effective therapy and the key mediators of COPD are not identified due to the lack of translational animal models with complex characterization. This integrative chronic study investigated cardiopulmonary pathophysiological alterations and mechanisms with functional, morphological and biochemical techniques in a 6-month-long cigarette smoke exposure mouse model. Some respiratory alterations characteristic of emphysema (decreased airway resistance: Rl; end-expiratory work and pause: EEW, EEP; expiration time: Te; increased tidal mid-expiratory flow: EF50) were detected in anaesthetized C57BL/6 mice, unrestrained plethysmography did not show changes. Typical histopathological signs were peribronchial/perivascular (PB/PV) edema at month 1, neutrophil/macrophage infiltration at month 2, interstitial leukocyte accumulation at months 3-4, and emphysema/atelectasis at months 5-6 quantified by mean linear intercept measurement. Emphysema was proven by micro-CT quantification. Leukocyte number in the bronchoalveolar lavage at month 2 and lung matrix metalloproteinases-2 and 9 (MMP-2/MMP-9) activities in months 5-6 significantly increased. Smoking triggered complex cytokine profile change in the lung with one characteristic inflammatory peak of C5a, interleukin-1α and its receptor antagonist (IL-1α, IL-1ra), monokine induced by gamma interferon (MIG), macrophage colony-stimulating factor (M-CSF), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) at months 2-3, and another peak of interferon-γ (IFN-γ), IL-4, 7, 13, 17, 27 related to tissue destruction. Transient systolic and diastolic ventricular dysfunction developed after 1-2 months shown by significantly decreased ejection fraction (EF%) and deceleration time, respectively. These parameters together with the tricuspid annular plane systolic excursion (TAPSE) decreased again after 5-6 months. Soluble intercellular adhesion molecule-1 (sICAM-1) significantly increased in the heart homogenates at month 6, while other inflammatory cytokines were undetectable. This is the first study demonstrating smoking duration-dependent, complex cardiopulmonary alterations characteristic to COPD, in which inflammatory cytokine cascades and MMP-2/9 might be responsible for pulmonary destruction and sICAM-1 for heart dysfunction.

Anti-inflammatory action of angiotensin 1-7 in experimental colitis may be mediated through modulation of serum cytokines/chemokines and immune cell functions

We recently demonstrated Ang 1-7 reduced inflammation in the dextran sulfate sodium (DSS) colitis model. In this study we examined the effect of Ang 1-7 on modulation of plasma levels of selected cytokines and chemokines and immune cell effector functions (apoptosis, chemotaxis and superoxide release) in vitro. The degree of neutrophil recruitment to the colon was assessed by immunofluorescence and myeloperoxidase activity. Daily Ang 1-7 treatment at 0.01 mg/kg dose which previously ameliorated colitis severity, showed a significant reduction in circulating levels of several cytokines and chemokines, and neutrophil recruitment to the colonic tissue. It also significantly enhanced immune cell apoptosis, and reduced neutrophil chemotaxis and superoxide release in vitro. In contrast, daily administration of the Ang 1-7R antagonist A779 which previously worsened colitis severity showed significant up-regulation of specific mediators. Our results demonstrate a novel anti-inflammatory action of Ang 1-7 through modulation of plasma levels of cytokines/chemokines and immune cell activity.

Sensory neuron regulation of gastrointestinal inflammation and bacterial host defence

Sensory neurons in the gastrointestinal tract have multifaceted roles in maintaining homeostasis, detecting danger and initiating protective responses. The gastrointestinal tract is innervated by three types of sensory neurons: dorsal root ganglia, nodose/jugular ganglia and intrinsic primary afferent neurons. Here, we examine how these distinct sensory neurons and their signal transducers participate in regulating gastrointestinal inflammation and host defence. Sensory neurons are equipped with molecular sensors that enable neuronal detection of diverse environmental signals including thermal and mechanical stimuli, inflammatory mediators and tissue damage. Emerging evidence shows that sensory neurons participate in host-microbe interactions. Sensory neurons are able to detect pathogenic and commensal bacteria through specific metabolites, cell-wall components, and toxins. Here, we review recent work on the mechanisms of bacterial detection by distinct subtypes of gut-innervating sensory neurons. Upon activation, sensory neurons communicate to the immune system to modulate tissue inflammation through antidromic signalling and efferent neural circuits. We discuss how this neuro-immune regulation is orchestrated through transient receptor potential ion channels and sensory neuropeptides including substance P, calcitonin gene-related peptide, vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide. Recent studies also highlight a role for sensory neurons in regulating host defence against enteric bacterial pathogens including Salmonella typhimurium, Citrobacter rodentium and enterotoxigenic Escherichia coli. Understanding how sensory neurons respond to gastrointestinal flora and communicate with immune cells to regulate host defence enhances our knowledge of host physiology and may form the basis for new approaches to treat gastrointestinal diseases.

Inhibition of α2A-Adrenoceptors Ameliorates Dextran Sulfate Sodium-Induced Acute Intestinal Inflammation in Mice

It has been hypothesized that α2-adrenoceptors (α2-ARs) may be involved in the pathomechanism of colitis; however, the results are conflicting because both aggravation and amelioration of colonic inflammation have been described in response to α2-AR agonists. Therefore, we aimed to analyze the role of α2-ARs in acute murine colitis. The experiments were carried out in wild-type, α2A-, α2B-, and α2C-AR knockout (KO) C57BL/6 mice. Colitis was induced by dextran sulfate sodium (DSS, 2%); alpha2-AR ligands were injected i.p. The severity of colitis was determined both macroscopically and histologically. Colonic myeloperoxidase (MPO) and cytokine levels were measured by enzyme-linked immunosorbent assay and proteome profiler array, respectively. The nonselective α2-AR agonist clonidine induced a modest aggravation of DSS-induced colitis. It accelerated the disease development and markedly enhanced the weight loss of animals, but did not influence the colon shortening, tissue MPO levels, or histologic score. Clonidine induced similar changes in α2B- and α2C-AR KO mice, whereas it failed to affect the disease activity index scores and caused only minor weight loss in α2A-AR KO animals. In contrast, selective inhibition of α2A-ARs by BRL 44408 significantly delayed the development of colitis; reduced the colonic levels of MPO and chemokine (C-C motif) ligand 3, chemokine (C-X-C motif) ligand 2 (CXCL2), CXCL13, and granulocyte-colony stimulating factor; and elevated that of tissue inhibitor of metalloproteinases-1. In this work, we report that activation of α2-ARs aggravates murine colitis, an effect mediated by the α2A-AR subtype, and selective inhibition of these receptors reduces the severity of gut inflammation.

In vitro and in vivo pharmacological characterization of Pronetupitant, a prodrug of the neurokinin 1 receptor antagonist Netupitant

The aim of the present study was to investigate the pharmacological activity of Pronetupitant, a novel compound designed to act as prodrug of the NK1 antagonist Netupitant. In receptor binding experiments Pronetupitant displayed high selectivity for the NK1 receptor. In a calcium mobilization assay performed on CHONK1 cells Pronetupitant (100 nM, 15 min preincubation) behaved as an NK1 antagonist more potent than Netupitant (pK(B) 8.72 and 7.54, respectively). In the guinea pig ileum bioassay Pronetupitant antagonized the contractile effect of SP showing a similar potency as Netupitant (pK(B)≈9). Similar results were obtained with 5 min preincubation time while at 2 min only Pronetupitant produced significant effects. In vivo in mice the intrathecal injection of 0.1 nmol SP elicited the typical scratching, biting and licking (SBL) nociceptive response. This effect of SP was dose dependently (0.1-10 mg/kg) antagonized by Pronetupitant given intravenously 2 h before the peptide. Superimposable results were obtained using Netupitant. Pharmacokinetic studies performed in rats demonstrate that Pronetupitant, after i.v. administration, is quickly (few minutes) and completely converted to Netupitant. Collectively the present results indicated that Pronetupitant acts in vitro as selective NK1 antagonist more potent than Netupitant. However based on the short half-life measured for Pronetupitant in rats, the in vivo action of Pronetupitant can be entirely interpreted as due to its conversion to Netupitant.

Upregulation of the transient receptor potential ankyrin 1 ion channel in the inflamed human and mouse colon and its protective roles

Transient Receptor Potential Ankyrin 1 (TRPA1) channels are localized on sensory nerves and several non-neural cells, but data on their functional significance are contradictory. We analysed the presence and alterations of TRPA1 in comparison with TRP Vanilloid 1 (TRPV1) at mRNA and protein levels in human and mouse intact and inflamed colons. The role of TRPA1 in a colitis model was investigated using gene-deficient mice. TRPA1 and TRPV1 expressions were investigated in human colon biopsies of healthy subjects and patients with inflammatory bowel diseases (IBD: ulcerative colitis, Crohn's disease) with quantitative PCR and immunohistochemistry. Mouse colitis was induced by oral 2% dextran-sulphate (DSS) for 10 days. For investigating the functions of TRPA1, Disease Activity Index (weight loss, stool consistency, blood content) was determined in C57BL/6-based Trpa1-deficient (knockout: KO) and wildtype (WT) mice. Sensory neuropeptides, their receptors, and inflammatory cytokines/chemokines were determined with qPCR or Luminex. In human and mouse colons TRPA1 and TRPV1 are located on epithelial cells, macrophages, enteric ganglia. Significant upregulation of TRPA1 mRNA was detected in inflamed samples. In Trpa1 KO mice, Disease Activity Index was significantly higher compared to WTs. It could be explained by the greater levels of substance P, neurokinins A and B, neurokinin 1 receptor, pituitary adenylate-cyclase activating polypeptide, vasoactive intestinal polypeptide, and also interleukin-1beta, macrophage chemoattractant protein-1, monokine induced by gamma interferon-1, tumor necrosis factor-alpha and B-lymphocyte chemoattractant in the distal colon. TRPA1 is upregulated in colitis and its activation exerts protective roles by decreasing the expressions of several proinflammatory neuropeptides, cytokines and chemokines.