The role of Bradykinin in process of inflammation is –
## **Core Concept**
Bradykinin is a peptide that plays a significant role in the inflammatory process. It is a key mediator involved in the pathogenesis of inflammation, particularly in the context of pain, vascular permeability, and smooth muscle contraction. Bradykinin is part of the kinin-kallikrein system, which is activated during tissue injury.
## **Why the Correct Answer is Right**
The correct answer highlights the role of bradykinin in increasing vascular permeability. Bradykinin causes blood vessels to dilate and increases vascular permeability, leading to edema (swelling) and the characteristic signs of inflammation: redness, heat, swelling, and pain. This action is primarily mediated through the stimulation of **B2 receptors** on endothelial cells, leading to the release of nitric oxide and prostacyclin, which in turn cause vasodilation and increased permeability.
## **Why Each Wrong Option is Incorrect**
- **Option A:** While bradykinin does cause pain, saying it only causes pain overlooks its broader role in inflammation, including vascular effects.
- **Option B:** This option might be considered partially correct as bradykinin does cause smooth muscle contraction. However, its role in increasing vascular permeability is more directly related to the inflammatory process.
- **Option C:** This option might seem plausible because bradykinin does have effects that could indirectly relate to all listed effects. However, the question seems to seek the most directly related and comprehensive answer regarding inflammation.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **ACE inhibitors**, commonly used to treat hypertension and heart failure, work by inhibiting the conversion of angiotensin I to angiotensin II. As a side effect, they also inhibit the breakdown of bradykinin, which can lead to increased levels of bradykinin. This increase in bradykinin levels is thought to contribute to the side effect of **cough**, experienced by some patients on ACE inhibitors.
## **Correct Answer:** . increase vascular permeability.