The gene expression of NGAL and TLR9 in glomerulus and tubulo-interstitium of patients with lupus nephritis

Background The role of neutrophil gelatinase associated lipocalin (NGAL) and Toll-like receptor 9 (TLR9) in the pathogenesis of lupus nephritis remain elusive. Methods We quantified the glomerular and tubulointerstitial mRNA expression of NGAL and TLR9 in 42 patients with lupus nephritis (LN group) and 10 controls. Results As compared to controls, LN group had higher glomerular expression of TLR9, and higher tubulointerstitial expression of NGAL and TLR9. Tubulointerstitial NGAL expression significantly correlated with proteinuria (r = 0.492; p = 0.003), renal function (r = -0.386; p = 0.022) and histological chronicity index (r = 0.540; p = 0.004). Proteinuria had significant correlation with glomerular (r = 0.554; p = 0.001) and tubulointerstitial (r = 0.379; p = 0.043) TLR9 expression. Furthermore, there was a significant difference in tubulointerstitial expression of NGAL between treatment response groups. Conclusion There is an increase in intra-renal mRNA expression of NGAL and TLR9 in LN. Although tubulointerstitial expression of NGAL does not correlate with systemic disease activity, it correlates with proteinuria, renal function, and therapeutic response. The role of NGAL in the pathogensis in LN, as well as its application as biomarker for lupus nephritis, requires further study.