Relevant genetic polymorphisms and kidney expression of Toll‐like receptor (TLR)‐5 and TLR‐9 in lupus nephritis

Summary

Toll‐like receptor (TLR) genetic polymorphisms may modify their expression causing inflammatory disorders and influencing both susceptibility and severity of lupus erythematosus. We aim to determine whether TLR‐5 and TLR‐9 gene polymorphisms are implicated in the susceptibility to systemic lupus erythematosus (SLE) and lupus nephritis (LN) and to evaluate their expressions and distributions in renal LN patients' biopsies. The frequencies of two SNP in the TLR‐9 gene and one in the TLR‐5 gene was examined in 106 SLE patients (among them 37 LN patients) and in 200 matched controls by polymerase chain reaction–restriction fragment‐length polymorphisms (PCR–RFLP) analysis. TLR‐9 and TLR‐5 expressions were assessed by reverse transcription (RT)–PCR and immunohistochemistry carried on LN renal biopsies compared to healthy renal tissue. A significant genotypic and allelic association was revealed between TLR‐9‐rs352140 and both SLE and LN ( P < 0·05). The TLR‐9 transcript level was significantly higher in LN biopsies compared to control ( P < 0·05). This increase was observed histochemically in the tubulointerstitial compartment. TLR‐9 was detectable in LN glomeruli patients but not in normal control glomeruli. No allelic nor genotype association was found with TLR‐5‐rs5744168 in SLE. but the T allele and the TT genotype were raised significantly in the LN group ( P < 0·05). A significant increase in TLR‐5 gene expression in LN biopsies, which contrasted with normal kidneys ( P < 0·05), was confirmed by an intense and diffuse staining for TLR‐5 only in LN tubules ( P < 0·05). Our data show that TLR‐5 and TLR‐9 are susceptible genes to LN and that their expression is dysregulated in LN patients' kidneys, supporting a role of these mediators in the pathogenesis of LN.