Inflammation

Pathophysiology of Inflammation

  1. Inflammation is the response of any living tissue to injury.
  2. Acute inflammation comprises of all the reactions that occur in the injured tissue within first few minutes to an hour of encountering an injury.
  3. This is caused by many immune and hormonal responses that result in the release of various mediators of inflammation.
  4. The release of mediators of inflammation will result in migration of many inflammatory cells to the site of injury.
  5. Acute inflammatory response will offer protection and initiates the process of repair and restitution of the injured tissue to the normal state.

Signs and Symptoms of Inflammation

  1. Pain
  • Pain at the site of injury is secondary to chemical mediators of pain, such as, histamine, bradykinin, and prostaglandins.
  1. Heat
  • Heat is secondary to increased blood flow to the site of injury, providing more oxygen and cells needed for protection and healing of the site.
  1. Redness
  • Redness is secondary to increased blood flow to the site of injury, providing more oxygen and cells needed for protection and healing of the site.
  1. Swelling
  • Increased accumulation of fluid at the site of injury results in swelling.

Mechanism of Inflammation

  1. Every tissue in the body has some cells that play an important role in inflammation. These cells are native to that tissue and initiate the inflammatory process.
  2. Mast cells and macrophages available locally in the tissues are the major groups of cells that initiate the inflammatory response.
  3. Injury to the tissue results in activation of these mast cells and macrophages, which lead to production of enzymes called cyclooxygenases.
  4. Injured tissues, through the mediation of these cyclooxygenase enzymes, produce chemical mediators of inflammation called prostaglandins.
  5. Prostaglandins result in swelling of the injured tissues and amplify the sensitivity to pain.
  6. Mast cells upon activation release other chemical inflammatory mediators, histamine and bradykinin.
  7. Prostaglandins, histamine, and bradykinin increase the pain sensitivity and the individual experiences increased pain in the tissue involved, which is one of the most important symptom of inflammation.
  8. Also, bradykinin and histamine cause vascular smooth muscle relaxation and contribute to local vasodilation in the tissue injured. Vasodilation results in increased blood flow to the tissue, resulting in local redness and warmth in the tissue involved.
  9. Local vasodilation also results in increased permeability of the blood vessels, which results in leaking of plasma proteins, such as, immunoglobulins or antibodies into the tissue injured. These immunoglobulins are protective in nature.
  10. Proteins such as, fibrin, also leak through the blood vessels into the tissues. Fibrin helps with healing of the injured tissue.
  11. Water always follows movement of plasma proteins and consequently, leaks and accumulates in the tissue, contributing to the swelling.
  12. Chemical mediators also induce chemotaxis, whereby neutrophils are attracted to the site of injury, along the chemotactic gradient.
  13. Neutrophils help in the further release of chemical mediators called cytokines, which amplify the inflammatory response further.
  14. Also, neutrophils along with macrophages in the tissues help by engulfing the attacking agent at the site of injury.

 

Types of Cyclooxygenase Enzymes

Patient was educated on types of cyclooxygenase enzymes as follows:

  1. Cyclooxygenase enzymes are produced in the inflammatory cells of the tissues, secondary to an injury.
  2. Injured tissues, through the mediation of these cyclooxygenase enzymes, produce chemical mediators of inflammation called prostaglandins.
  3. Prostaglandins result in swelling of the injured tissues and amplification of the sensitivity to pain.
  4. There are two main types of cyclooxygenase enzymes (COX enzymes)
  5. Cyclooxygenase-1
  • COX-1 is a type of cyclooxygenase enzyme produced in various tissues of the body, including stomach and gastrointestinal tract.
  • Production of COX-1 in these tissues result in production of prostaglandins.
  • Apart from amplification of pain sensitivity and inducing inflammatory signs, prostaglandins also perform important function of protection of the lining of stomach and gastrointestinal tract from the action of the acid contents of the stomach and thus, prevent development of gastric ulcers.
  1. Cyclooxygenase-2
  • COX-2 is a type of cyclooxygenase enzyme produced mainly in the inflammatory cells during an inflammatory response.
  • Production of COX-2 by the inflammatory cells in the injured tissues result in production of prostaglandins, which bring about amplification of pain sensitivity and induce other inflammatory signs of swelling and redness.
  1. In general, inhibition of COX-2 in the injured sites by NSAIDs contributes to the anti-inflammatory effect of NSAIDs. Inhibition of COX-1 in various tissues by NSAIDs contributes to the side-effects of NSAIDs, such as, elevated blood pressure, gastric ulcers and bleeding, sodium retention, renal failure, and increased risk for bleeding.

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