Antiinflammatory action of steroid is due to inhibition of
**Core Concept**
The anti-inflammatory action of steroids is a crucial aspect of their pharmacological profile. Steroids exert their effects by influencing key cellular pathways involved in inflammation. The primary mechanism of action underlying the anti-inflammatory effects of steroids involves the modulation of gene expression.
**Why the Correct Answer is Right**
The anti-inflammatory action of steroids is primarily attributed to their ability to inhibit the synthesis of pro-inflammatory cytokines, such as IL-1β and TNF-α, through the suppression of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). This is achieved by inducing the expression of the protein IκBα, which inhibits the activity of NF-κB. Furthermore, steroids also reduce the expression of the enzyme phospholipase A2 (PLA2), which is involved in the production of prostaglandins, key mediators of inflammation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the inhibition of the enzyme cyclooxygenase (COX) is associated with the anti-inflammatory action of non-steroidal anti-inflammatory drugs (NSAIDs), not steroids.
* **Option B:** This option is incorrect because the inhibition of the enzyme lipoxygenase (LOX) is also associated with the anti-inflammatory action of NSAIDs, not steroids.
* **Option C:** This option is incorrect because the inhibition of the enzyme inducible nitric oxide synthase (iNOS) is associated with the anti-inflammatory action of certain compounds, but it is not the primary mechanism of action of steroids.
**Clinical Pearl / High-Yield Fact**
Steroids are effective anti-inflammatory agents because they modulate the expression of key genes involved in the inflammatory response, making them a crucial component of the treatment regimen for various inflammatory conditions.
**Correct Answer: D. Inhibition of the transcription factor NF-κB.**