Toll-like receptor 4 (TLR-4), a bacterial lipopolysaccharide sensor, is an innate immunity essential modulator. It is expressed on both immune and non-immune cells and may contribute to the cutaneous and renal manifestations during lupus erythematosus (LE). Our purpose is to evaluate TLR-4 expression and analyzing its role in lupus nephritis (LN) and chronic cutaneous lupus erythematosus (CLE) pathogenesis. TLR-4 immunohistochemical staining was performed on 30 LN renal biopsies compared with 11 healthy renal tissues and 30 skin biopsies from CLE patients compared with 15 normal individuals. CLE patients' biopsies showed a strong and diffuse TLR-4 expression throughout the epidermis and labeled inflammatory infiltrate and glands in the dermis whereas controls' skin expressed weakly TLR-4 only in the epidermis basal layer. LN glomeruli and tubules showed an increased and more intense TLR-4 expression compared with normal controls where TLR-4 expression was weak and rarely detected in glomeruli, diffuse and weak in tubules. A significant difference in TLR-4 expression between LN classes, both in glomeruli and tubules, was observed. These data confirm an up-regulation of TLR-4 expression in the affected tissues of CLE and LN patients and highlight the critical role of TLR-4 in the pathogenesis of cutaneous and renal disorders in LE.
Keywords: Toll-like receptor 4; chronic lupus erythematosus; cutaneous expression; lupus nephritis; renal expression.