SUMMARYThere is accumulating evidence that haem oxygenase (HO)-1 plays a protective role in various disorders. The beneficial efficacy of HO-1 induction therapy has been shown in renal diseases such as glomerulonephritis, interstitial nephritis and drug induced nephrotoxicity. However, involvement of HO-1 in the development of autoimmune renal diseases remains uncertain. To assess the clinical efficacy of HO-1 induction therapy for lupus glomerulonephritis, MRL/ lpr mice were intraperitoneally injected with 100 m mol/kg hemin, a potent HO-1 inducer, or PBS as controls, once a week from 6 weeks of age to 21-24 weeks-old. We found that treatment with hemin led to a significant reduction of proteinuria and remarkable amelioration of glomerular lesions accompanied by decreased immune depositions. In addition, the circulating IgG anti-double-stranded DNA antibody level was significantly decreased in hemin treated mice when compared with controls. A single intraperitoneal injection with hemin resulted in reduction of inducible nitric oxide synthase expression in the kidney and spleen, and serum interferong level. Our results suggest that HO-1 induction therapy ameliorates lupus nephritis by suppressing nitric oxide (NO) dependent inflammatory responses and attenuating production of pathogenic autoantibodies.Keywords haem oxygenase-1 (HO-1) MRL/ lpr inducible nitric oxide synthase ( i NOS) interferon-gamma (IFN-g )

Heme oxygenase-1 (HO-1), an inducible heme-degrading enzyme, is expressed by macrophages and endothelial cells in response to various stresses. Because ferritin synthesis is stimulated by Fe 2+ , which is a product of heme degradation, we examined the relation between HO-1 and ferritin levels in the serum of patients with hemophagocytic syndrome (HPS), adultonset Still's disease (ASD), and other diseases that may cause hyperferritinemia. Seven patients with HPS, 10 with ASD, 73 with other rheumatic diseases, 20 with liver diseases, 10 recipients of repeated blood transfusion because of hematological disorders, and 22 healthy volunteers were enrolled. Serum HO-1 and ferritin levels were determined by ELISA. Expression of HO-1 mRNA and protein by peripheral blood mononuclear cells (PBMCs) was determined by real-time PCR and immunocytochemical techniques, respectively. Serum levels of HO-1 were significantly higher in patients with active HPS and ASD than in the other groups (P < 0.01). HO-1 levels were not elevated in patients with other causes of hyperferritinemia but were moderately elevated in patients with dermatomyositis/polymyositis. Among patients with HPS and ASD, serum HO-1 levels correlated closely with serum ferritin levels, and the levels of both returned to normal after therapy had induced remission. Increased expression of HO-1 mRNA was confirmed in PBMCs from some patients with HPS and ASD. Hyperferritinemia correlated closely with increased serum HO-1 in patients with HPS and ASD but not other conditions, indicating that measurement of serum HO-1 and ferritin levels would be useful in the differential diagnosis of hyperferritinemia and perhaps also in monitoring disease activity in HPS and ASD.