Heme Oxygenase-1 Induction Attenuates Inducible Nitric Oxide Synthase Expression and Proteinuria in Glomerulonephritis

Abstract

Abstract. In glomerulonephritis, there is intraglomerular activation of inducible nitric oxide synthase (iNOS) leading to high output production of nitric oxide (NO). This can result in supraphysiologic amounts of NO and cause oxidative injury. It is unknown whether mechanisms of cellular defense against NO-mediated injury exist. Induction of the heme catabolizing enzyme heme oxygenase-1 (HO-1), which generates biliverdin, carbon monoxide (CO), and iron (Fe), may provide such a mechanism, as CO and Fe are two negative modulators of iNOS activity and expression. This study assessed whether upregulation of HO-1 by a specific inducer, hemin, negatively modulates iNOS expression and activity in anti-glomerular basement membrane antibody-mediated glomerulonephritis. Glomerular HO-1 expression in nephritic animals was upregulated by treatment with hemin (30 μmol/kg body wt). iNOS and HO-1 mRNA expression were assessed by reverse transcription-PCR of glomerular total RNA from nephritic animals or nephritic animals pretreated with hemin. iNOS activity in glomeruli was measured by assessing conversion of [14C] L-arginine to [14C] L-citrulline. HO-1 protein levels in glomeruli were assessed by Western blot analysis. The effect of hemin treatment on monocyte/macrophage infiltration was assessed by enumeration of ED-1-positive cells in nephritic glomeruli. iNOS and HO-1 were coinduced in nephritic glomeruli. Hemin treatment of nephritic animals resulted in upregulation of glomerular HO-1 levels and a two- to threefold reduction in glomerular iNOS mRNA levels. iNOS activity in glomeruli was significantly reduced in hemin-treated nephritic animals in which proteinuria was also attenuated without a change in monocyte/macrophage infiltration. Hemin (100 to 200 μM) also reduced iNOS protein levels and enzyme activity in cultured mesangial cells stimulated with cytokines. These studies demonstrate that in glomerular immune injury, hemin treatment upregulates glomerular HO-1 with an attendant downregulation of iNOS expression, and thus points to regulatory interaction between the two systems. The beneficial effect of hemin treatment on proteinuria could be linked to downregulation of iNOS.

Genetic BACH1 deficiency alters mitochondrial function and increases NLRP3 inflammasome activation in mouse macrophages

“…It is important to point out that iNOS and COX-2 are heme-containing proteins the synthesis of which is dependent on the availability of intracellular labile heme. Because the BACH1/HO-1 axis has been shown to regulate intracellular heme levels in LPS-stimulated macrophages [ 49 ], genetic BACH1 deficiency with consequent increase in HO-1 may indirectly impact iNOS and COX-2 expression, as previously reported [ 50 , 51 ].…”

Flacourtia indica fruit extract modulated antioxidant gene expression, prevented oxidative stress and ameliorated kidney dysfunction in isoprenaline administered rats

“…Nrf-2 translocation also regulates the induction of HO-1 [ 46 ]. Previous report also suggests that increased HO-1 expression showed cytoprotective role in cisplatin, rapamycin induced nephrotoxicity, and in ischemia and glycerol induced nephritis [ 47 , 48 ]. This study also showed that HO-1 and HO-2 expression were also down regulated in kidney of ISO administered rats.…”

Metalloporphyrins as Tools for Deciphering the Role of Heme Oxygenase in Renal Immune Injury

“…Administration of subcutaneous FePP treatment prior to the induction of GN increased glomerular infiltration by HO-1 overexpressing macrophages at early stages (24 h following induction) and reduced proteinuria as well as iNOS expression and activity. It was suggested that HO-1 negatively regulates iNOS in infiltrating macrophages, indicating a switch from a pro- to an anti-inflammatory phenotype [ 82 ]. Interestingly, iNOS-derived NO was a negative regulator of iNOS and also suppressed cyclooxygenase (COX)-2 levels but maintained HO-1 levels [ 76 ].…”