Urinary high-mobility group box-1 associates specifically with lupus nephritis class V

Area of Science:

• Nephrology
• Immunology
• Biochemistry

Background:

• High-mobility group box 1 protein (HMGB-1) is implicated in lupus nephritis (LN) pathogenesis.
• Elevated HMGB-1 expression is observed in LN kidneys, serum, and urine.
• This study investigated if urinary HMGB-1 elevation specifically indicates active lupus or is a consequence of renal damage.

Purpose of the Study:

• To determine if increased urinary HMGB-1 is specific to active lupus nephritis.
• To investigate the association between urinary HMGB-1 levels and different classes of lupus nephritis.
• To explore the correlation between urinary HMGB-1 and proteinuria in lupus patients.

Main Methods:

• Analyzed urine samples from 61 lupus patients (32 with active LN, 29 with SLE without LN) and 14 proteinuric controls.
• Detected HMGB-1 using Western blot.
• Normalized urine HMGB-1 to urine creatinine and assessed urine protein to creatinine ratio (P/C).

Main Results:

• Median urinary HMGB-1 levels were significantly higher in active LN patients compared to lupus patients without kidney disease (p < 0.001).
• Significant differences in median urinary HMGB-1 levels were observed between LN classes, notably higher in membranous LN (Class V) than proliferative LN.
• Urinary HMGB-1 correlated with the urine P/C ratio overall and specifically in membranous LN (r = 0.71, p = 0.022).

Conclusions:

• Urinary HMGB-1 is elevated in patients with active lupus nephritis.
• HMGB-1 levels correlate with LN class, with higher levels in membranous LN (Class V).
• Urinary HMGB-1 may serve as a potential biomarker for membranous lupus nephritis, requiring further validation.