High mobility group box 1 (HMGB1) and anti-HMGB1 antibodies and their relation to disease characteristics in systemic lupus erythematosus

Introduction: High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein. HMGB1, which is secreted by inflammatory cells and passively released from apoptotic and necrotic cells, may act as a pro-inflammatory mediator. As apoptotic cells accumulate in systemic lupus erythematosus (SLE), HMGB1 levels might be increased in SLE. HMGB1 may also serve as an autoantigen, leading to the production of anti-HMGB1 antibodies. In this study we determined levels of HMGB1 and anti-HMGB1 in SLE patients in comparison to healthy controls (HC) and analysed their relation with disease activity. Methods: The study population consisted of 70 SLE patients and 35 age-and sex-matched HC. Thirty-three SLE patients had quiescent disease, the other 37 patients were selected for having active disease. Nineteen of these had lupus nephritis. HMGB1 levels were measured with both Western blot and ELISA. Anti-HMGB1 levels were measured by ELISA. Clinical and serological parameters were assessed according to routine procedures. Results: HMGB1 levels in SLE patients could be measured reliably by Western blotting only, and were significantly increased compared to HC. During active disease HMGB1 levels increased, in particular in patients with renal involvement. Serum HMGB1 levels correlated with SLEDAI, proteinuria, and anti-dsDNA levels, and showed a negative correlation with complement C3. Anti-HMGB1 levels were significantly increased in SLE patients compared to HC, and positively correlated with HMGB1 levels. Conclusions: Levels of HMGB1 in the sera of SLE patients, in particular in those with active renal disease, are increased. Serum HMGB1 levels are related to SLEDAI scores and proteinuria, as well as to levels of anti-HMGB1 antibodies. These findings suggest that besides HMGB1, HMGB1-anti-HMGB1 immune complexes play a role in the pathogenesis of SLE, in particular in patients with renal involvement

Urine levels of HMGB1 in Systemic Lupus Erythematosus patients with and without renal manifestations

INTRODUCTION: Lupus nephritis (LN) is a severe and frequent manifestation of systemic lupus erythematosus (SLE). Its pathogenesis has not been fully elucidated but immune complexes are considered to contribute to the inflammatory pathology in LN. High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein which is secreted from different types of cells during activation and/or cell death and may act as a pro-inflammatory mediator, alone or as part of DNA-containing immune complexes in SLE. Urinary excretion of HMGB1 might reflect renal inflammatory injury. To assess whether urinary HMGB1 reflects renal inflammation we determined serum levels of HMGB1 simultaneously with its urinary levels in SLE patients with and without LN in comparison to healthy controls (HC). We also analyzed urinary HMGB1 levels in relation with clinical and serological disease activity. METHODS: The study population consisted of 69 SLE patients and 17 HC. Twenty-one patients had biopsy proven active LN, 15 patients had a history of LN without current activity, and 33 patients had non-renal SLE. Serum and urine levels of HMGB1 were both measured by western blotting. Clinical and serological parameters were assessed according to routine procedures. In 17 patients with active LN a parallel analysis was performed on the expression of HMGB1 in renal biopsies. RESULTS: Serum and urinary levels of HMGB1 were significantly increased in patients with active LN compared to patients without active LN and HC. Similarly, renal tissue of active LN patients showed strong expression of HMGB1 at cytoplasmic and extracellular sites suggesting active release of HMGB1. Serum and urinary levels in patients without active LN were also significantly higher compared to HC. Urinary HMGB1 levels correlated with SLEDAI, and showed a negative correlation with complement C3 and C4. CONCLUSION: Levels of HMGB1 in urine of SLE patients, in particular in those with active LN, are increased and correlate with SLEDAI scores. Renal tissue of LN patients shows increased release of nuclear HMGB1 compared to control renal tissue. HMGB1, although at lower levels, is, however, also present in the urine of patients without active LN. These data suggest that urinary HMGB1 might reflect both local renal inflammation as well as systemic inflammation

Amyloïdartropathie bij een patiënte met ATTR-amyloïdose

Bij een 66-jarige vrouw, die verwezen werd in verband met echografische verdenking op cardiale amyloïdose, werd ook een artropathie van beide schouders gevonden. Zowel in een subcutane vetpunctie als in het schouderpunctaat werd inderdaad amyloïd aangetroffen. Gezien het klinisch beeld van artropathie en cardiomyopathie werd allereerst gedacht aan een AL-amyloïdose (lichteketenamyloïdose). Echter, in serum en urine werden geen duidelijke aanwijzingen gevonden voor een verhoogde immuunglobuline vrije lichteketenproductie en evenmin was een plasmacelkloon in het beenmerg aanwezig. Vanwege de cardiomyopathie werd nader onderzoek verricht naar een DNA-mutatie in het transthyretine-gen (TTR-gen) en bleek patiënte homozygoot voor de TTR-Val122Ile-mutatie. Op basis van het vetpunctaat werd het amyloïd getypeerd als ATTR-amyloïd. Schouderartropathie als uiting van een ATTRamyloïdose is niet eerder beschreven en kan dus worden toegevoegd aan de klinische manifestaties van deze ziekte. Daarnaast toont deze casus het nut van zowel subcutane vetpunctie en gewrichtspunctaat voor de detectie van amyloïdose als het belang van een correcte typering van het aangetoonde amyloïd