Ronald Mathison

Effects of cannabinoid receptor-2 activation on accelerated gastrointestinal transit in lipopolysaccharide-treated rats.

The biological effects of cannabinoids (CB) are mediated by CB1 and CB2 receptors. The role of CB2 receptors in the gastrointestinal tract is uncertain. In this study, we examined whether CB2 receptor activation is involved in the regulation of gastrointestinal transit in rats. Basal and lipopolysaccharide (LPS)‐stimulated gastrointestinal transit was measured after instillation of an Evans blue‐gum Arabic suspension into the stomach, in the presence of specific CB1 and CB2 agonists and antagonists, or after treatment with inhibitors of mediators implicated in the transit process. In control rats a CB1 (ACEA; 1 mg kg−1), but not a CB2 (JWH‐133; 1 mg kg−1), receptor agonist inhibited basal gastrointestinal transit. The effects of the CB1 agonist were reversed by the CB1 antagonist AM‐251, which alone increased basal transit. LPS treatment increased gastrointestinal transit. This increased transit was reduced to control values by the CB2, but not the CB1, agonist. This inhibition by the CB2 agonist was dose dependent and prevented by a selective CB2 antagonist (AM‐630; 1 mg kg−1). By evaluating the inhibition of LPS‐enhanced gastrointestinal transit by different antagonists, the effects of the CB2 agonist (JWH‐133; 1 mg kg−1) were found to act via cyclooxygenase, and to act independently of inducible nitric oxide synthase (NOS) and platelet‐activating factor. Interleukin‐1β and constitutive NOS isoforms may be involved in the accelerated LPS transit. The activation of CB2 receptors in response to LPS is a mechanism for the re‐establishment of normal gastrointestinal transit after an inflammatory stimulus.

Neuroendocrine regulation of inflammation and tissue repair by submandibular gland factors

Interactions between the immune, nervous and endocrine systems are important in inflammation and tissue repair. One neuroendocrine pathway involves polypeptide factors derived from the submandibular glands, whose synthesis and release are controlled by cervical sympathetic nerves. This novel pathway of immune-neuroendocrine communication is the cervical sympathetic trunk-submandibular gland (CST-SMG) axis. Here, Ronald Mathison, Joseph Davison and Dean Befus discuss the contributions of this axis to the neuroendocrine regulation of inflammation and tissue repair.

Effects of repeated fluoxetine and citalopram administration on cytokine release in C57BL/6 mice

This study examines the effects of repeated administration of the selective serotonin reuptake inhibitors (SSRIs), fluoxetine and citalopram (10 mg/kg, i.p.), on immunoreactivity in C57BL/6 mice. Immune functions were evaluated by the ability of splenocytes to reduce a tetrazolium salt to formazan (MTT test), to proliferate, and to produce cytokines, including interleukin (IL)-1, IL-2, IL-4, IL-6, IL-10 and interferon gamma (IFN gamma). Citalopram administered for 1, 2 and 4 weeks stimulates the proliferative activity of splenocytes and suppresses their ability to secrete the anti-inflammatory cytokine IL-4. Fluoxetine administration for 1 and 2 weeks, but not 4 weeks, stimulates the proliferative activity of splenocytes, whereas a 4-week administration of fluoxetine suppresses the secretion of IL-4. Four weeks of prolonged administration of citalopram and fluoxetine induces a significant increase in the production of IL-6 and IL-10, a cytokine with immunosuppressive and anti-inflammatory activities. The results show that, in C57BL/6 mice, the immunomodulatory effects of SSRIs depend on the SSRI used and the duration of administration.

The effect of repeated amitriptyline and desipramine administration on cytokine release in C57BL/6 mice

This study examines the effects of repeated amitriptyline and desipramine administration (10 mg/kg, IP) on the immunoreactivity of saline-injected C57BL/6 mice, as evaluated by the ability of splenocytes to reduce a tetrazolium salt to formazan (MTT test), to proliferate, and to produce cytokines, such as interleukin (IL)-1, IL-2, IL-4, IL-6, IL-10 and interferon gamma (IFN-gamma). Desipramine and amitriptyline administered for one or two weeks enhance the biochemical (estimated by MTT test) and proliferative activities of splenocytes. One and two weeks administration of desipramine significantly reduces the secretion of IL-4, an anti-inflammatory cytokine. Amitriptyline administration for four weeks stimulates the proliferative activity of splenocytes and enhances IL-2 bioactivity, whereas four weeks desipramine aministration does not change these parameters in comparison to saline treated control mice. Prolonged desipramine administration (seven and 28 days) significantly increased the bioactivity of IL-1. Four weeks of prolonged administration of amitriptyline and desipramine induces a significant increase in the secretion of IL-10, a cytokine with immunosuppressive and anti-inflammatory activities. The results show that the immunoregulatory effects of tricyclic antidepressants in C57BL/6 mice depend on the drugs used and on the duration of administration.

Frontline: Inhibition of allergen-induced pulmonary inflammation by the tripeptide feG: a mimetic of a neuro-endocrine pathway.

Interactions between the neuro‐endocrine system and immune system help maintain health. One interaction involves the superior cervical ganglia (SCG), which regulate the prohormone submandibular rat 1 (SMR1) produced by the submandibular gland (SMG). A peptide derived from SMR1, feG, has anti‐inflammatory activity, and modification to D‐isomer feG enhances bioactivity. We tested feG as a therapeutic agent for airways inflammation, using rats sensitized by OVA or Nippostrongylus brasiliensis (Nb). Treatment with feG but not fdG down‐regulated OVA‐challenge‐induced increases in bronchoalveolar lavage (BAL)‐derived macrophages, eosinophils and PMN (neutrophils) by 44%, 69% and 67%, respectively, at 24 h. We found that feG also reduced ICAM‐1 on BAL‐derived macrophages and eosinophils by 27% and 65%, and L‐selectin on PMN by 55% following OVA challenge. Furthermore, feG but not fdG reduced the OVA‐induced TNF increase in BAL fluid. We showed that feG also down‐regulated both hyper‐responsiveness to methacholine (by 27%) and microgranulomata formation in the lung parenchyma. In Nb‐challenged rats, feG treatment inhibited ex vivo allergen‐induced contraction of tracheal smooth muscle by up to 73%. In conclusion, feG, which is a mimetic of a peptide derived from a rat salivary gland prohormone, has anti‐inflammatory properties in allergic airways inflammation in Brown‐Norway rats. The role of the SCG‐SMG neuro‐endocrine pathway in allergic asthma and other inflammatory diseases requires additional study.

ATTENUATION OF INTESTINAL AND CARDIOVASCULAR ANAPHYLAXIS BY THE SALIVARY GLAND TRIPEPTIDE FEG AND ITS D-ISOMERIC ANALOG FEG

The effects of the submandibular gland peptide-T (SGP-T; Thr-Asp-Ile-Phe-Gly-Gly; TDIFEGG), its carboxy-terminal fragment (the tripeptide FEG; Phe-Glu-Gly), and the D-isomeric analog (feG) on intestinal and cardiovascular anaphylactic reactions were studied. The tripeptides, FEG and feG, when administered intravenously or orally to egg albumin-sensitized Hooded Lister or Sprague-Dawley rats 30 min prior to challenge with the antigen, totally prevented the disruption of intestinal motility and the development of anaphylaxis provoked diarrhea and inhibited anaphylactic hypotension by 66%. Submandibular gland peptides participate in the regulation of systemic inflammatory reactions, and the D-amino acid tripeptide, feG, is a potent, orally active anti-anaphylactic agent.

Modulation of neutrophil function by the tripeptide feG

BackgroundNeutrophils are critical in the defense against potentially harmful microorganisms, but their excessive and inappropriate activation can contribute significantly to tissue damage and a worsening pathology. Through the release of endocrine factors submandibular glands contribute to achieving a balance in neutrophil function by modulating the state of activation and migratory potential of circulating neutrophils. A putative hormonal candidate for these effects on neutrophils was identified as a heptapeptide named submandibular gland peptide T (SGP-T; sequence = TDIFEGG). Since the tripeptide FEG, derived from SGP-T, and its D-amino acid analogue feG had similar inhibitory effects on inflammatory reactions, we investigated the effects of feG on human and rat neutrophil function.ResultsWith human neutrophils feG had no discernible effect on oxidative burst or phagocytosis, but in picomolar amounts it reduced PAF-induced neutrophil movement and adhesion, and the binding of CD11b by 34% and that of CD16b close to control values. In the rat feG (10-11M) reduced the binding of CD11b and CD16 antibodies to PAF-stimulated circulating neutrophils by 35% and 43%, respectively, and at 100 micrograms/kilograms intraperitoneally feG reduced neutrophil in vivo migration by 40%. With ovalbumin-sensitized rats that were challenged with antigen, feG inhibited binding of antibodies against CD16b but not CD11b, on peritoneal leukocytes.ConclusionsThe inhibitory effect of feG on neutrophil movement may be mediated by alterations in the co-stimulatory molecules CD11b and CD16.

Role for the submandibular gland in modulating pulmonary inflammation following induction of systemic anaphylaxis

Previous studies have shown that bilateral decentralization of the superior cervical ganglia (SCG; decentralization) attenuates allergen-induced pulmonary inflammatory responses in male rats sensitized to the nematode Nippostrongylus brasiliensis. The present report examines the neuronal and glandular mechanisms mediating the protection against pulmonary inflammation afforded by decentralization. Tissues and organs innervated by the SCG are responsible for this protection since, in a manner similar to decentralization, bilateral removal of the SCG (ganglionectomy) reduced anaphylaxis-induced accumulation of inflammatory cells in bronchoalveolar lavage fluid. Removal of the submandibular gland (sialadenectomy) did not modify the severity of the pulmonary inflammation, but concurrent sialadenectomy and decentralization abolished the protective effect of decentralization. Thus, we postulate that cervical sympathetic nerves tonically inhibit release of anti-inflammatory factors from submandibular glands. No relationship was found between noradrenaline and serotonin content of submandibular glands and the degree of protection against pulmonary inflammation offered by decentralization and ganglionectomy. Both decentralization and ganglionectomy appeared to increase the level of transcripts that encode immunomodulatory growth factors (nerve growth factor and epidermal growth factor) in submandibular glands, but these denervations evidently did not modify the transcripts for TGF beta 2. Systemic inflammatory events are regulated by the central nervous system at a level superior to the SCG probably through modulation of immunoregulatory factors in submandibular glands.

The tripeptide analog feG ameliorates severity of acute pancreatitis in a caerulein mouse model

Acute pancreatitis (AP) is associated with significant morbidity and mortality; however, there is no specific treatment for this disease. A novel salivary tripeptide analog, feG, reduces inflammation in several different animal models of inflammation. The aims of this study were to determine whether feG reduced the severity of AP and modifies the expression of pancreatic ICAM-1 mRNA during AP in a mouse model. AP was induced in mice by hourly (x12) intraperitoneal injections of caerulein. A single dose of feG (100 microg/kg) was coadministered with caerulein either at time 0 h (prophylactic) or 3 h after AP induction (therapeutic). Plasma amylase and pancreatic MPO activities and pancreatic ICAM-1 mRNA expression (by RT-PCR) were measured. Pancreatic sections were histologically assessed for abnormal acinar cells and interstitial space. AP induction produced a sevenfold increase in plasma amylase, a tenfold increase in pancreatic MPO activity, and a threefold increase in interstitial space, and 90% of the acinar cells were abnormal. Prophylactic treatment with feG reduced the AP-induced plasma amylase activity by 45%, pancreatic MPO by 80%, the proportion of abnormal acinar cells by 30%, and interstitial space by 40%. Therapeutic treatment with feG significantly reduced the AP-induced abnormal acinar cells by 10% and the interstitial space by 20%. Pancreatic ICAM-1 mRNA expression was upregulated in AP and was reduced by 50% with prophylactic and therapeutic treatment with feG. We conclude that feG ameliorates experimental AP acting at least in part by modulating ICAM-1 expression in the pancreas.

Submandibular Gland Peptide-T (SGP-T) Inhibits Intestinal Anaphylaxis

A novel peptide, submandibular gland peptide-T(SGP-T), which reduces allergen-induced hypotension, wasexamined for effects on intestinal anaphylaxis.Hooded-Lister rats were sensitized to egg albumin and prepared for the measurement of in vivomyoelectric activity of the jejunum. The disruption ofmigrating myoelectric complexes (MMCs) that occurs uponintraluminal, duodenal challenge with antigen of sensitized rats was inhibited by 75% uponintravenous treatment with 100 μg/kg of SGP-T. Inaddition, SGP-T reduced the number of rats experiencinganaphylactic diarrhea and disrupted MMCs, but thepeptide did not alter antigen-provoked release of ratmast cell protease II. The mechanism of action of SGP-Tremains to be determined, but it apparently does not actdirectly on mast cells to exert its antianaphylactic action. These results emphasize that modulationof immediate hypersensitivity reactions is only one ofseveral gastrointestinal activities that are affected bygrowth factors and peptides released from salivary glands.