Question

Inhibition of 5-lipoxygenase is useful in:

• A. Cardiac failure
• B. Bronchial asthma
• C. Hepatic failure
• D. Arthritis

Hint:

5-lipoxygenase makes leukotrienes, which cause bronchoconstriction. Blocking this enzyme (for example zileuton) helps in asthma.

Answer 1

The Correct Option is B

Arachidonic acid released from cell membranes can be turned into two different families of chemical messengers. The cyclooxygenase route makes prostaglandins and thromboxane, while the lipoxygenase route, driven by the enzyme 5-lipoxygenase, makes leukotrienes. Knowing what leukotrienes do tells us where blocking this enzyme helps.

1. Cardiac failure: treated with diuretics, ACE inhibitors, beta blockers and similar drugs that manage fluid overload and heart workload. Leukotrienes are not a target in this disease.
2. Bronchial asthma: the cysteinyl leukotrienes made by 5-lipoxygenase (LTC4, LTD4, LTE4) cause strong, lasting narrowing of the airways and extra mucus. Blocking the enzyme with a drug like zileuton cuts off this whole leukotriene supply, easing bronchospasm, which is why 5-LOX inhibition is used as add-on asthma therapy.
3. Hepatic failure: managed by removing the cause and supporting liver function; the leukotriene pathway has no established treatment role here.
4. Arthritis: mainly controlled with NSAIDs (which block cyclooxygenase, not lipoxygenase) and disease-modifying drugs. 5-LOX inhibitors are not standard therapy for arthritis.

Only bronchial asthma directly connects to the leukotrienes that 5-lipoxygenase produces, so blocking this enzyme is clinically useful there.

Let's summarize:

• 5-lipoxygenase makes leukotrienes from arachidonic acid.
• Leukotrienes cause bronchoconstriction and airway inflammation.
• Blocking this pathway (zileuton) or its receptors (montelukast) helps control asthma.

The correct answer is bronchial asthma.