Flashcards in lecture 4- gastric ulcers Deck (21):
What are three diseases that a person infected with helicobacter pylori bacteria may have as a consequence?
They may experience no symptoms, have a peptic ulcer, gastric adenocarcinoma/ lymphoma or chronic gastritis.
Describe chronic gastritis and its symptoms.
Chronis gastritis is the inflammation of the gastric mucosa, which leads to atrophy of the mucosal cells and metaplasia of the epithelial cells. The symptoms are nausea, vomiting and upper abdominal discomfort.
Describe peptic ulcer and its symptoms.
Basically a fancy way of saying a hole through the gastric mucosa caused by the digestion from stomach acid. The hole extends through the muscularis and submuscularis layers. The symptoms include gnawing, aching or burning pain.
Describe gastric carcinoma and its symptoms.
It is a malignant tumour that grows in the gastric mucosa and is very fatal.
Describe gastric lymphoma and its symptoms.
it is the cancer of the gastric lymphoid tissue. Symptoms include gastric inflammation.
What was the initial dogma behind peptic ulcers and how was it treated?
No acid, no ulcer- thus acid secretion was stopped in patients and the ulcer began to heal itself.
What are the three factors that affect whether or not helicobacter pylori will give them a disease?
The first is virulence meaning the pathogenic nature of that particular strain of H.pylori. Type and extent of the immune response from the individual, genetics and the environment.
What features does the Helicobacter pylori bacterium possess that enable it to survive in the harsh stomach environment?
high motility- curved body and multiple flagella for swimming around.
acid resistant- produces urease which buffers the acid around it and chemotaxis enable the bacterium to detect high pH areas of the stomach.
How do the helicobacter pylori interact with the gastric mucosa?
The bacteria attaches to but doesn't invade the mucosa. It 's also able to adhere to epithelial cell membranes. This is rare though and most float around in the acid though.
what are the three virulence genes that helicobacter pylori genes can have that cause disease?
The VacA gene enables production of a vacuolating cytotoxin that damages the epithelial cells of the gastric mucosa.
The BabA gene enables adhesion to the epithelial cells.
The CagA gene enables production of a carcinogenic protein, responsible for duodenal and gastric cancers.
Describe how the VacA gene in a helicobacter pylori bacterium can induce disease.
The VacA gene encodes for production of hexameric spores that are endocytosed into the epithelial cells of the mucosa. The spores then attack organelles with empty spaces in them (e.g the mitochondria), which induces apoptosis of the cell through cytochrome c pathway.
Describe how the BabA gene in a helicobacter pylori bacerium can induce disease.
it enables epithelial cell adhesion, and then enables the bacterium to proliferate and cause inflammation of the gastric mucosa.
Describe how the CagA gene in a helicobacter pylori bacterium can induce disease.
The bacterium with the CagA gene are able to bind to the gastric epithelial cell and inject the gene into the cell. The CagA gene then changes the cellular function, and alters the epithelial cell barrier and proliferation (hence why it is carcinogenic).
Does the helicobacter pylori bacterium induce an immune response in its host?
Yes, but in most cases the immune response is unable to clear the infection. The bacteria have found a way to evade the immune response. The inflammation is an important part of the pathogenesis.
How are the helicobacter pylori bacteria able to evade the immune response?
They can alter their PAMP expressed so that the innate immune system doesn't recognise them. They are also able to inhibit the NO secreted by macrophages and they produce anti-bacteriacidal enzymes to protect themselves.
Describe how helicobacter pylori are able to induce chronic gastritis.
The helicobacter bind to the gastric epithelial cells and induce changes to them that prevent them from secreting their mucous, which makes the cells prone to acid degradation and can lead to gastric ulcer later on.
Describe how helicobacter pylori are able to induce peptic ulcer from gastritis.
Untreated gastritis means that the epithelial layer will die and the necrotic tissue will be eroded away creating a hole. The stomach acid can then digest and breakdown the muscularis and submuscularis layers of the stomach lumen, resulting in an ulcer.
Describe how helicobacter pylori are able to induce duodenal ulcers.
Inflammation of the antrum of the stomach results in increased acid secretion into the duodenum. The acid then breaksdown the delicate duodenal epithelial cells, leading to an ulcer.
Describe how helicobacter pylori are able to induce gastric adenocarcinoma/lymphoma.
Mitochondrial damage within the gastric epithelial cells can lead to increased ROS, which cause DNA mutations and promote cancerous growth. Acid exposure and inflammation increases epithelial cell metaplasia, which encourages mutations of DNA. The CagA gene itself is able to induce a carcinogenic state in the epithelial cell directly.
what are other potential causes of gastric acid aside from helicobacter pylori infection?
Use of NSAIDs, corticosteroids, smoking, alcohol consumption and super acidic acid.