Upregulation of the TRPA1 Ion Channel in the Gastric Mucosa after Iodoacetamide-Induced Gastritis in Rats: A Potential New Therapeutic Target.

Acute gastritis is often untreatable by acid secretion-inhibiting drugs. Understanding the protective mechanisms including the role of Transient Receptor Potential Ankyrin1 (TRPA1) and Vanilloid1 (TRPV1) channels localized on capsaicin-sensitive afferents and non-neuronal structures might identify novel therapeutic approaches. Therefore, we characterized a translational gastritis model using iodoacetamide (IAA) and investigated TRPA1/V1 expressions. Wistar rats and CD1, C57Bl/6J mice were exposed to IAA-containing (0.05, 0.1, 0.2, 0.3, 0.5%) drinking water for 7 or 14 days. Body weight and water consumption were recorded daily. Macroscopic lesions were scored, qualitative histopathologic investigation was performed, TRPA1/V1 immunopositivity and mRNA expressions were measured. IAA induced a concentration-dependent weight loss and reduced water intake in both species. Hyperemia, submucosal edema, inflammatory infiltration and hemorrhagic erosions developed after 7 days, while ulcers after 14 days in rats. Trpa1 mRNA/protein expressions were upregulated at both timepoints. Meanwhile, TRPV1 immunopositivity was upregulated in the gastric corpus after 0.05% IAA ingestion, but downregulated after 0.2%, whereas Trpv1 mRNA did not change. Interestingly, no macroscopic/microscopic changes were observed in mice. These are the first data for the concentration- and duration-dependent changes in the IAA-induced gastritis in rats accompanied by TRPA1 upregulation, therefore, its therapeutic potential in gastritis should further be investigated.

PPIs Are Not Responsible for Elevating Cardiovascular Risk in Patients on Clopidogrel-A Systematic Review and Meta-Analysis.

Background: Clopidogrel and proton pump inhibitors (PPIs) are metabolized by cytochrome P450 enzymes. Contradictory results have been reported on possible complications of simultaneous PPI and clopidogrel use. Our aim was to investigate the clinical relevance of this debate with a systematic review and meta-analysis. Methods: The PubMed, Embase, and Cochrane Central Register of Controlled Trials electronic databases were searched for human studies [randomized controlled trials (RCTs) and observational studies] using the PICO format (P: patients on clopidogrel; I: patients treated with PPI; C: patients without PPI treatment; O: cardiovascular risk). We screened eligible studies from 2009 to 2016. After study exclusions, we extracted data from 27 articles for three outcomes: major adverse cardiac event (MACE), myocardial infarction (MI) and cardiovascular (CV) death. The meta-analysis was registered on PROSPERO (CRD42017054316). Results: Data were extracted on 156,823 patients from the 27 trials included (MACE: 23, CV death: 10, MI: 14). The risks of MACE (RR = 1.22, 95% CI = 1.06-1.396, p = 0.004) and MI (RR = 1.43, 95% CI = 1.24-1.66, p < 0.001) were significantly higher in the PPI plus clopidogrel group. However, subgroup analysis demonstrated that this significance disappeared in RCTs (RR = 0.99, 95% CI = 0.76-1.28, p = 0.93) in the MACE outcome group. There was no effect of combined PPI and clopidogrel therapy on CV death outcome (RR = 1.21, 95% CI = 0.97-1.50, p = 0.09). Conclusion: Concomitant use of PPIs and clopidogrel has been proved not to be associated with elevated cardiovascular risks according to RCTs. Based on our results, no restrictions should be applied whenever PPIs and clopidogrel are administered simultaneously.

Membrane-bound ATP-dependent Energy Systems, as Extra- and Intracellular Key Signals for Gastrointestinal Functions and their Regulations in the Gastrointestinal Mucosa.

AIMS: Our research group has carried out various biochemical examinations in rat gastric ulcer models and in human gastrointestinal resecates obtained from patient who underwent gastric intervention due to peptic ulcer disease. Biochemical methods gave excellent possibility to approach the biochemical events taking place in tissues, cellular and subcellular regulatory levels during of ulcer development and of its prevetions. This paper gives a brief summary of these biochemical examinations conducted during this study period started from the 1960's up till now. RESULTS AND CONCLUSIONS: 1. The decreased action of gastric acid secretory responses is not needed for duodenal and gastric ulcer healing in patients with peptic ulcer; 2. The surgical and chemical vagotomy resulted in various biochemical changes in the rat stomach; 3. The presence of Na+-K+-dependent ATPase and adenylate cyclase can be demostrated both in the rat and human gastric fundic mucosa; 4. The mitocondrial ATP is a common substrate for these membrane-bound ATP-dependent enzymes, and a multiple feedback mechanism existing between these two membrane-bound enzymes altered by mediators, hormones and drugs; 5. This feedback mechanism exists in the GI mucosa under different pathological conditions and during certain drug actions; 6. The development of mucosal damage and prevention depends on the actual regulatory state of above mentioned feedback mechanism between the membrane-bound ATP-dependent energy systems; 7.The drug actions depend on the actual functional state of target organ; 8. Biochemical gradients exist between the biochemical structure of the fundic, antral, duodenal and jejunal mucosa in patients with gastric hyperacidity, which is gradually downregulated by the decrease of gastric acid secretory responses, and totally disappears in patients with hypacidity; 9. No biochemically proven tissue hypoxia - around the chronic ulcer, duodenal and jejunal ulcers - exists in patients with chronic peptic ulcer; 10. The cellular and tissue protection differ from each other in the gastrointestinal tract; 11. Helicobacter pylori does not produce damage at the level of cell membrane, mitochondrion and DNA - given alone or in combination with indomethacin - on freshly isolated rat gastric mucosal cells. 12. A biochemical explanation is given to ulcer development in humans and in different animal models.

Role of nitric oxide in the central interferon-alpha-induced inhibition of gastric acid secretion in rats.

Cytokines are known to play a key role in regulation of gastric functions. Interferon-alpha (IFN-α) has been published to impair gastric motility. Aims of this study were to clarify effect of IFN-α on gastric acid secretion (GAS) and determine role of nitric oxide (NO) in the process. Both subcutaneous (1000, 10000, 100 000 IU, s.c.) and intracisternal (10, 100, 1000 IU, i.c.) injections of IFN-α dose-dependently inhibited GAS induced by pylorus ligation in male SD rats in 2 hrs (370±40, 233±39, 208±50 micromol vs control 415±59 micromol and 481±50, 249±75, 141±25 micromol vs control 485±65 micromol, respectively). Central doses inducing same level inhibition were 100 times lower. NOS inhibitor L-NAME (3 mg/kg, i.v.) blocked the inhibitory effect of i.c. ED(50) dose 100 IU IFN-α (507±75 micromol/2 hrs), while L-arginine, the substrate of nitric oxide synthase (NOS) prevented L-NAME action (266±82 micromol/2 hrs). D-arginine failed to prevent L-NAME action on IFN-α-induced inhibition of GAS. Aminoguanidine, a selective inhibitor of inducible NOS (iNOS) failed to block IFN-α induced inhibition of GAS. Results suggest that IFN-α inhibits GAS centrally through nitric oxide pathways probably mediated by continuous isoform of NOS that can be important in regulation of GAS in healthy or pathological conditions.

Molecular pharmacological approaches to effects of capsaicinoids and of classical antisecretory drugs on gastric basal acid secretion and on indomethacin-induced gastric mucosal damage in human healthy subjects (mini review).

BACKGROUND: Actions of various drugs have been tested on the gastric acid basal secretion and on the drug (Indomethacin)- induced gastric mucosal damage; however their physiological and pharmacological mechanisms have not been compared. AIMS: The effects of capsaicinoids, atropine, cimetidine, omeprazole, famotidine and ranitidine were studied on gastric basal acid output, whereas the gastric mucosal preventive effects of capsaicinoids (capsaicin), atropine and cimetidine were tested on the indomethacin-induced gastric mucosal microbleedings in human healthy subjects. Results were presented by molecular pharmacological method; affinity (pD) and intrinsic activity (α-values) were calculated. Intrinsic activity curves are based on comparison to atropine effect (α(atropine)= 1.00). For evaluation of physiological and pharmacological effects of compounds molar doses of pD(2) (necessary doses to produce 50% inhibition) and pA(2) (50% inhibion on intrinsic activity) were calculated from affinity and intrinsic activity curves. RESULTS: The pD(2) values for compounds were as follows: 5.88 for capsaicinoids, 5.40 for atropine , 2.23 for cimetidine, 3.33 for ranitidine, 3.77 for famotidine and 3.97 for omeprazole. α - value results for compounds were: 0.76 for capsaicinoids, and 1.00 for atropine, cimetidine, ranitidine, famotidine and omeprazole all equal to 1.00 on gastric acid basal secretion. The pD(2) values on indomethacin-induced gastric mucosal microbleeding were found as follows: 6.00 for capsaicinoids, 5.50 for atropine, and 3.50 for cimetidine, meanwhile α-values resulted 0.76 for capsaicinoids, 1.00 for atropine and cimetidine. CONCLUSIONS: Comparison classical antisecretory drugs acting on different pathways but in much more higher molar concentrations. The atropine and capsaicinoids act in about the same molar concentration which suggests a significant physiological role for capsaicin sensitive afferent nerves in the regulation of gastric basal acid secretion and in the prevention of chemically- induced gastric mucosal protection in human healthy subjects, suggesting a novel physiological pathway in regulation. These results clearly indicate the molecular pharmacological backgrounds of actions of classical antisecretory drugs and physiological role of capsaicin- sensitive afferent nerves in human healty subjects on the gastric basal secretion and on the prevention of drug-induced gastric mucosal damage.