Does the LTC4S rs730012 AC genotype increase cysteinyl leukotriene signaling and airway reactivity?

The LTC4S promoter variant rs730012 (−444A>C) significantly influences susceptibility to respiratory and systemic inflammatory reactivity by altering lipid mediator production.

Genetic and molecular mechanisms

• Transcription factor recruitment: The −444C allele (present in the AC genotype) creates a novel binding site for the H4TF-2 transcription factor, which is absent in wild-type AA homozygotes.
• Upregulated gene expression: This novel binding site enhances promoter activity, leading to increased LTC4S transcription, elevated mRNA expression, and heightened baseline synthesis of cysteinyl leukotrienes (LTC4, LTD4, and LTE4).

Pathophysiological effects

• Airway reactivity and remodeling: Elevated cysteinyl leukotrienes act primarily through G-protein–coupled CysLT1 receptors on airway smooth muscle and immune cells, triggering intracellular calcium mobilization, acute bronchoconstriction, and airway hyperresponsiveness.
• Structural changes: Chronic signaling drives structural airway remodeling, including airway smooth muscle hypertrophy, subepithelial collagen deposition, and goblet cell hyperplasia.
• Inflammatory amplification: This pathway promotes type 2 immune responses, recruiting and activating mast cells and eosinophils via platelet- and IL-33-dependent mechanisms.

Clinical and therapeutic implications

• Phenotypic susceptibility: The intermediate-to-high producer AC phenotype is clinically associated with conditions such as aspirin-intolerant asthma and cardiovascular inflammation.
• Pharmacogenetic responsiveness: Due to elevated baseline leukotriene output, individuals with the AC genotype show a more pronounced therapeutic benefit from CysLT1 receptor antagonists, such as montelukast.

Bottom line

• Key takeaway: The LTC4S rs730012 AC genotype directly increases susceptibility to allergic and inflammatory airway reactivity. By establishing a novel H4TF-2 binding site, this variant drives elevated cysteinyl leukotriene production, which promotes airway hyperresponsiveness, tissue remodeling, and a heightened therapeutic response to leukotriene receptor antagonists.