Mechanisms of gastric damage by non-steroidal anti-inflammatory drugs

Indomethacin impairs mitochondrial dynamics by activating the PKCζ-p38-DRP1 pathway and inducing apoptosis in gastric cancer and normal mucosal cells

The subcellular mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in gastric cancer and normal mucosal cells is elusive because of the diverse cyclooxygenase-independent effects of these drugs. Using human gastric carcinoma cells (AGSs) and a rat gastric injury model, here we report that the NSAID indomethacin activates the protein kinase Cζ (PKCζ)-p38 MAPK (p38)-dynamin-related protein 1 (DRP1) pathway and thereby disrupts the physiological balance of mitochondrial dynamics by promoting mitochondrial hyper-fission and dysfunction leading to apoptosis. Notably, DRP1 knockdown or SB203580-induced p38 inhibition reduced indomethacin-induced damage to AGSs. Indomethacin impaired mitochondrial dynamics by promoting fissogenic activation and mitochondrial recruitment of DRP1 and down-regulating fusogenic optic atrophy 1 (OPA1) and mitofusins in rat gastric mucosa. Consistent with OPA1 maintaining cristae architecture, its down-regulation resulted in EM-detectable cristae deformity. Deregulated mitochondrial dynamics resulting in defective mitochondria were evident from enhanced Parkin expression and mitochondrial proteome ubiquitination. Indomethacin ultimately induced mitochondrial metabolic and bioenergetic crises in the rat stomach, indicated by compromised fatty acid oxidation, reduced complex I- associated electron transport chain activity, and ATP depletion. Interestingly, Mdivi-1, a fission-preventing mito-protective drug, reversed indomethacin-induced DRP1 phosphorylation on Ser-616, mitochondrial proteome ubiquitination, and mitochondrial metabolic crisis. Mdivi-1 also prevented indomethacin-induced mitochondrial macromolecular damage, caspase activation, mucosal inflammation, and gastric mucosal injury. Our results identify mitochondrial hyper-fission as a critical and common subcellular event triggered by indomethacin that promotes apoptosis in both gastric cancer and normal mucosal cells, thereby contributing to mucosal injury.

Effect of Bifidobacterium bifidum BF-1 on gastric protection and mucin production in an acute gastric injury rat model

Homeostasis in the stomach environment is maintained by the balance of protective factors such as gastric mucus and aggressive factors such as gastric acid, stress, alcohol, and drugs. An overload of aggressive factors that upsets this balance can induce gastric injury. Fermented milk that contains Bifidobacterium bifidum BF-1 (BF-1), a probiotic strain, and Streptococcus thermophilus YIT 2021 (ST) is known to improve Helicobacter pylori-associated gastritis in humans. Here, we investigated the gastroprotective potential of BF-1 in a rat model of acid-ethanol-induced acute gastric injury to fully elucidate its potential compared with ST. Living BF-1, ST, or vehicle was orally administrated to rats, and acid-ethanol gastric injury was induced 2h later. The gastric injury rate was determined and shown to be significantly lower in the BF-1 group than in the vehicle group, which showed a similar level to the ST group. The production of gastric mucin and the expression of several target genes associated with protection and inflammation were examined before and after induction of gastric injury. Interestingly, mucin 5ac (muc5ac) gene expression in gastric corpus samples and gastric mucin production in stomach samples from the BF-1 group, but not the ST group, were significantly higher than those in the respective samples from the vehicle group. These findings indicate that BF-1 has the potential to provide gastroprotection, alleviating acute gastric injury by enhancing the production of gastric mucin in a rat model.

Gastric antiulcer, antisecretory and cytoprotective properties of celery (Apium graveolens) in rats

In the present investigation, an ethanol extract of celery [Apium graveolens L. (Apiaceae/Umbelliferae)], at doses of 250 and 500 mg/kg body weight, was evaluated for antigastric ulcer activity using various experimental gastric ulcer models in rats. Ulcers were induced by indomethacin, cytodestructive agents (80% ethanol, 0.2 M NaOH and 25% NaCl) and cold restraint stress. Gastric secretory studies were undertaken by using pylorus ligation (Shay rat model). In addition to gastric wall mucus (GWM), non-protein sulfhydryl (NP-SH) and malondialdehyde (MDA) were also estimated in gastric tissues after 80% ethanol treatment. Pretreatment of celery extract produced dose-dependent reduction in all experimentally induced gastric lesions. Ethanol (80%) decreased the levels of GWM, NP-SH and increase in MDA concentration in gastric tissue. Celery extract showed the ability to significantly replenish the ethanol-induced depleted levels of GWM and gastric mucosal NP-SH. The gastric mucosal MDA level was also significantly lowered in extract pretreated rats. The celery extract showed stomach protection against the models used for ulcerogenesis. Results were further confirmed by using histopathological assessment. The phytochemical screening showed the presence of various chemical constituents such as flavonoids, tannins, volatile oils, alkaloids, sterols and/or triterpenes. Acute toxicity test revealed no deleterious or toxic symptoms or mortality over a period of 14 days. However, the LD(50) was found to be 7.55 g/kg, and showed a large margin of safety. The results suggest that Apium graveolens extract significantly protects the gastric mucosa and suppresses the basal gastric secretion in rats, possibly through its antioxidant potential.

Mucosal acid causes gastric mucosal microcirculatory disturbance in nonsteroidal anti-inflammatory drug-treated rats

The mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) suppress gastric mucosal blood flow is not fully understood, although the depletion of mucosal prostaglandin E2 has been proposed as one possible explanation. We investigated the role of gastric acid on gastric mucosal blood flow in NSAID-treated rats. A rat stomach was mounted in an ex vivo chamber, and gastric mucosal blood flow was measured sequentially in a 5-mm2 area of the gastric corpus using a scanning laser Doppler perfusion image system. Results showed that diclofenac (5 mg/kg s.c.) and indomethacin (10 mg/kg s.c.) did not affect gastric mucosal blood flow, although both strongly decreased mucosal prostaglandin E2 when saline was instilled into the gastric chamber. On replacement of the saline in the chamber with 100 mM hydrochloric acid, these drugs caused a decrease in gastric mucosal blood flow levels within 30 min. The specific cyclooxygenase (COX)-2 inhibitors celecoxib (50 mg/kg s.c.) and rofecoxib (25 mg/kg s.c.) did not affect mucosal prostaglandin E2 level, nor did they decrease gastric mucosal blood flow, even when hydrochloric acid was added to the chamber. Furthermore, measurement of vasoconstrictive factors present in the mucosa showed that endothelin-1 levels increased after administration of diclofenac s.c. in the presence of intragastric hydrochloric acid. This indicates that the presence of mucosal hydrochloric acid plays an important role in the NSAID-induced decrease in gastric mucosal blood flow, while the COX-1-derived basal prostaglandin E2, which is unlikely to control gastric mucosal blood flow itself, protects microcirculatory systems from mucosal hydrochloric acid.

Canine gastritis

Gastritis--inflammation of the stomach--is a frequently cited differential yet rarely characterized diagnosis in cases of canine anorexia and vomiting. Although the list of rule-outs for acute or chronic gastritis is extensive, a review of the veterinary literature reveals fewer than 15 articles that have focused on clinical cases of canine gastritis over the last 25 years. The dog frequently appears in the human literature as an experimentally manipulated model for the study of endoscopic techniques or the effect of medications on gastric mucosa. In the veterinary patient, cases of acute gastritis are rarely pursued with the complete diagnostic armamentarium, and cases of chronic gastritis are rarely found to occur as an entity isolated from the rest of the gastrointestinal tract. This article focuses on those findings most clinically relevant to cases of canine gastritis in veterinary medicine.

Comparative effects of nabumetone, naproxen, piroxicam, and diclofenac on rat gastric irritancy following acute exposure to OTC non-steroidal anti-inflammatory agents and other gastric irritants

This study examined the relative effects of equally-effective anti-inflammatory doses of nabumetone, naproxen, piroxicam and diclofenac on gastric irritancy induced by over-the-counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs) aspirin and ibuprofen and a variety of necrotizing agents (0.6 N HCl, 0.2 N NaOH and 25% NaCl). Within one hour, aspirin 100 and 200 mg/kg and ibuprofen up to 15 mg/kg produced significant gastric mucosal injury. Aspirin 50 mg/kg produced only minimal damage that was enhanced by 5 x ID25 piroxicam and naproxen, but not by nabumetone or diclofenac. 5 x ID25 naproxen, piroxicam, and diclofenac significantly enhanced mucosal damage produced by ibuprofen 2.5 mg/kg. An equivalent anti-inflammatory dose of nabumetone failed to enhance the gastric irritancy produced by ibuprofen 2.5 mg/kg. Similarly, naproxen, piroxicam, and diclofenac enhanced the susceptibility of the gastric mucosa to the necrotizing actions of 0.6 N HCl, 0.2 N NaOH or 25% NaCl. Naproxen, piroxicam, or diclofenac are more likely than nabumetone to enhance gastric mucosal injury produced by OTC NSAIDs (aspirin and ibuprofen) or other gastric irritants.

Gastroprotective capability of exogenous phosphatidylcholine in experimentally induced chronic gastric ulcers in rats

Phosphatidylcholine (PC) is a main component of the hydrophobic gastric mucosal barrier. Exogenously administered, it prevents acute lesions. We evaluated the gastroprotective capacity of exogenous PC in both acute (ethanol- and indomethacin-induced) and chronic (indomethacin-induced) lesions in rats. Polyunsaturated (PPC) or hydrogenated PC in different concentrations were given intragastrically, before or after the injury factor, in single or repeated doses. Mucosal lesions were significantly reduced by a single dose of PPC, given before or after the injury factor, in both acute models. In the chronic model a single dose of PPC or hydrogenated PC significantly reduced lesions evaluated 6 h after ulcer induction, whereas after 72 h no protective effect was noticed. Repeated doses of PC were ineffective. In conclusion, in acute models exogenous PC reduces lesions in a dose-dependent manner and contributes to the mucosal defense. In chronic models an incomplete and temporary protection might be due to complex pathogenesis that requires activation of all levels in the mucosal defense. Strengthening of only one level was insufficient to restrict injury.