10.2
Gastrite II: fisiopatologia
La gastrite è caratterizzata dalla rottura della barriera mucosa che solitamente protegge il tessuto gastrico dai succhi digestivi e si manifesta in f…
La gastrite è un'infiammazione del rivestimento dello stomaco che provoca l'iperemicità e l'edematosità della mucosa gastrica, con conseguente erosione superficiale.
Può derivare da varie cause, ognuna con la sua fisiopatologia unica.
Ad esempio, i farmaci antinfiammatori non steroidei o FANS inibiscono la cicloossigenasi-1, un enzima vitale nella produzione di prostaglandine.
Le prostaglandine sono essenziali per mantenere l'integrità della mucosa, la secrezione di muco e bicarbonato e il flusso sanguigno della mucosa.
La riduzione dei livelli di prostaglandine indotta dai FANS porta a una diminuzione della secrezione di muco e bicarbonato, rendendo il rivestimento dello stomaco più vulnerabile agli impatti corrosivi del succo gastrico.
Un'altra causa prevalente è l'H. pylori, un batterio implicato nella gastrite cronica, che si adatta all'ambiente acido dello stomaco producendo ureasi.
Questo enzima converte l'urea in ammoniaca, creando un ambiente meno acido che favorisce la sopravvivenza batterica.
Una volta stabilito, H. pylori innesca una risposta immunitaria e rilascia tossine, con conseguente infiammazione e danni alla mucosa.
View the full transcript and gain access to JoVE Core videos
Q1: How do NSAIDs cause gastritis?
NSAIDs inhibit cyclooxygenase-1, an enzyme essential for prostaglandin production. Prostaglandins maintain mucosal integrity, mucus and bicarbonate secretion, and mucosal blood flow. When NSAIDs reduce prostaglandin levels, the stomach lining becomes vulnerable to gastric juice damage, leading to inflammation and erosion of the gastric mucosa.
Q2: What role does urease play in H. pylori infection?
H. pylori produces urease, an enzyme that converts urea to ammonia, creating a less acidic environment favorable for bacterial survival. This adaptation allows the bacterium to penetrate the mucus layer and attach to stomach cells. Once established, H. pylori triggers an immune response and releases toxins, resulting in mucosal inflammation and damage.
Q3: What is the difference between acute and chronic gastritis?
Acute gastritis causes the gastric mucosa to become hyperemic and edematous with superficial erosion, potentially leading to bleeding. Chronic gastritis develops over an extended period from persistent or repeated insults, causing chronic inflammatory changes and eventual thinning or atrophy of gastric tissue. Chronic gastritis is often asymptomatic until later stages.
Q4: How does alcohol contribute to gastritis development?
Alcohol causes direct mucosal injury to the stomach lining and increases gastric acid secretion while decreasing prostaglandin synthesis. This dual mechanism compromises the stomach's protective mechanisms, making the mucosa more susceptible to damage from digestive juices and triggering acute gastritis.
Q5: What happens in autoimmune gastritis?
In autoimmune gastritis, the immune system produces autoantibodies that target and attack parietal cells in the stomach lining. This continuous destruction of parietal cells leads to atrophy or thinning of the gastric tissue. Autoimmune gastritis is a less common type of chronic gastritis with progressive mucosal damage.
Q6: Why is the mucosal barrier important in preventing gastritis?
The mucosal barrier protects stomach tissue from digestive juices through mucus and bicarbonate secretion, mucosal blood flow, cell turnover, and repair mechanisms. When this barrier is disrupted by NSAIDs, alcohol, H. pylori, or autoimmune attack, the gastric mucosa becomes hyperemic and edematous, leading to inflammation and erosion.
Q7: How does H. pylori's spiral shape aid its survival in the stomach?
The spiral shape of H. pylori allows it to penetrate the mucus layer, which is less acidic than the stomach's inner lining. This morphology enables the bacterium to reach and attach to cells lining the stomach's inner surface, establishing chronic infection. Understanding these mechanisms helps explain gastritis iii clinical manifestations and management in clinical practice.