Anti-inflammatory activity of an IL-6 missense variant against crystal-induced inflammatory response

Interleukin-6 (IL-6) has an important modulator effect on inflammation and immunity and is involved in the progression of nephrolithiasis (kidney stone). However, whether IL-6 genetic variants affect the pathogenesis of kidney stones remains unclear. The present study conducted a combined investigation of candidate gene-driven screening and systematic screening on whole exome sequencing data from 28 patients of calcium oxalate stones, identifying a non-synonymous single nucleotide polymorphism (SNP) rs13306435 in IL-6 as a candidate research locus, which was further validated using HRM genotyping in an expanded cohort comprising 241 cases and 229 healthy subjects. Western blotting and qRT-PCR were used to assess the effects of this variant on crystal-induced inflammation, while molecular dynamics simulation was employed to analyze structural alterations in the receptor binding complex. In individuals aged ≤40 years, the A allele of rs13306435 was nominally associated with a reduced risk of stone formation, but no association was observed for the whole population. This missense variant causes an aspartate-to-glutamate substitution (D/E), inhibiting calcium oxalate monohydrate (COM)-triggered JAK2/STAT3 activation and inflammatory responses. However, it decreased the binding energy of IL-6/IL-6R/gp130 complex by increasing hydrogen bonds and salt brigdge at remote interfaces, suggesting that enhanced receptor binding does not necessarily translate to increased downstream signaling. Although this variant is not associated with general stone susceptibility, it exhibits notable anti-inflammatory activity by attenuating COM-induced JAK2/STAT3 activation and may influence the progression of stones through this pathway. These findings provide new insights into the role of anti-inflammatory mechanisms in nephrolithiasis.