What is gastric mucosal injury?

Gastric mucosal injury refers to damage or disruption of the mucous membrane lining the stomach, known as the gastric mucosa. The gastric mucosa serves as a protective barrier that helps to prevent damage to the underlying stomach tissue from stomach acid, digestive enzymes, and other harmful substances. When this protective barrier is compromised, gastric mucosal injury can occur, leading to various symptoms and complications.


Causes of gastric mucosal injury can include:


  • Nonsteroidal Anti-Inflammatory Drugs (NSAIDs): NSAIDs such as aspirin, ibuprofen, and naproxen are commonly associated with gastric mucosal injury. These medications can disrupt the gastric mucosal barrier, increase stomach acid production, and impair blood flow to the stomach lining, leading to irritation, inflammation, and ulcer formation.


  • Helicobacter pylori Infection: Infection with the bacterium Helicobacter pylori (H. pylori) is a major cause of gastric mucosal injury and peptic ulcer disease. H. pylori can colonize the stomach lining, leading to inflammation, damage to the gastric mucosa, and the development of gastric ulcers or gastritis.


  • Excessive Alcohol Consumption: Chronic alcohol consumption can irritate and damage the gastric mucosa, leading to gastritis, erosions, and ulcers. Alcohol can increase stomach acid production, disrupt the gastric mucosal barrier, and impair the repair mechanisms of the stomach lining.


  • Stress: Severe physical or emotional stress can lead to gastric mucosal injury through mechanisms such as increased production of stomach acid, decreased blood flow to the stomach, and disruption of the protective mucosal barrier. Stress-related mucosal injury can occur in critically ill patients, those undergoing major surgery, or individuals experiencing significant psychological stress.


  • Smoking: Smoking cigarettes can contribute to gastric mucosal injury by increasing stomach acid production, impairing blood flow to the stomach lining, and weakening the gastric mucosal barrier. Smoking is a risk factor for gastritis, peptic ulcers, and other gastrointestinal disorders.


  • Acid Reflux: Gastroesophageal reflux disease (GERD) can cause gastric mucosal injury when stomach acid refluxes back into the esophagus and irritates the stomach lining. Chronic acid reflux can lead to inflammation, erosion, and ulceration of the gastric mucosa, known as reflux esophagitis or peptic ulcer disease.


What is the relationship between gastric mucosal injury and oxidative stress?

The relationship between gastric mucosal injury and oxidative stress involves complex interactions between various factors that contribute to tissue damage and inflammation in the stomach lining. Here’s how oxidative stress may be related to gastric mucosal injury:


  • Reactive Oxygen Species (ROS) Production: Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense mechanisms in the gastric mucosa. ROS, such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals, can be generated during normal cellular metabolism or in response to external factors such as inflammation, infection, or exposure to toxins. Excessive production of ROS in the gastric mucosa can overwhelm antioxidant defenses and lead to oxidative damage to lipids, proteins, and DNA in gastric epithelial cells.


  • Inflammation and Immune Response: Oxidative stress can activate inflammatory pathways and stimulate the release of pro-inflammatory cytokines, chemokines, and inflammatory mediators in the gastric mucosa. Chronic inflammation in the stomach lining can contribute to mucosal injury, disrupt the integrity of the gastric mucosal barrier, and impair tissue repair mechanisms. Inflammatory cells such as neutrophils and macrophages can also produce ROS as part of their antimicrobial defense mechanisms, further exacerbating oxidative stress and tissue damage.


  • NSAID-Induced Gastric Mucosal Injury: Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to cause gastric mucosal injury and increase the risk of gastric ulcers through multiple mechanisms, including oxidative stress. NSAIDs can inhibit the activity of cyclooxygenase (COX) enzymes, leading to a decrease in the production of prostaglandins, which play a protective role in maintaining gastric mucosal integrity and promoting mucosal blood flow. Additionally, NSAIDs can directly induce oxidative stress in gastric epithelial cells by promoting the generation of ROS and impairing antioxidant defenses.


  • Helicobacter pylori Infection: Infection with the bacterium Helicobacter pylori (H. pylori) is a major risk factor for gastric mucosal injury, gastritis, and peptic ulcer disease. H. pylori colonization of the stomach lining can induce oxidative stress through multiple mechanisms, including the production of ROS and reactive nitrogen species (RNS) by inflammatory cells, activation of inflammatory pathways, and disruption of mitochondrial function in gastric epithelial cells. Oxidative stress induced by H. pylori infection can lead to DNA damage, lipid peroxidation, and inflammation, contributing to mucosal injury and the development of gastric ulcers.


  • Ischemia-Reperfusion Injury: Ischemia-reperfusion injury occurs when blood flow to the gastric mucosa is temporarily interrupted (ischemia) and then restored (reperfusion), leading to oxidative stress and tissue damage. Ischemia-reperfusion injury can occur during conditions such as gastric volvulus, gastric torsion, or gastric bypass surgery. Reperfusion of ischemic tissues can result in the generation of ROS, activation of inflammatory pathways, and disruption of cellular homeostasis, leading to mucosal injury, ulcer formation, and impaired tissue repair.


Overall, oxidative stress plays a critical role in the pathogenesis of gastric mucosal injury by promoting inflammation, disrupting mucosal integrity, impairing tissue repair mechanisms, and increasing susceptibility to injury from external insults such as NSAIDs or H. pylori infection.