Induction of long-term cardiac allograft survival by heme oxygenase-1 gene transfer

Abstract

Elevated expression of heme oxygenase-1 (HO-1), an intracellular enzyme that degrades heme into carbon monoxide (CO), biliverdine and free iron, has anti-inflammatory and antiapoptotic effects in diverse models. Here, we analyzed the effects of specific overexpression of HO-1 following adenovirus-mediated (AdHO-1) gene transfer in an acute cardiac allograft rejection model. The intragraft (i.g.) injection of AdHO-1 into cardiac allografts, as well as intramuscular (i.m.) or intravenous (i.v.) administration, prolonged allograft survival with, respectively, 13.3, 62.5 and 80% of the grafts surviving long term (4100 days), whereas control grafts were rejected with acute kinetics. HO-1 overexpression was associated with inhibited allogeneic responses in MLRs using graft-infiltrating leukocytes and splenocytes, but not with lymph node cells. The inhibition of splenocyte proliferation was mediated by soluble factors and was dependent on the presence of APCs, since purified T cells proliferated normally. i.v. but not i.g. AdHO-1 administration decreased the number of graft-infiltrating leukocytes, cytokine mRNA accumulation and apoptosis in transplanted hearts, whereas i.v. and i.g. AdHO-1 did not modify normal immune responses against cognate antigens, indicating that there was no general immunosuppression. These results indicate that HO-1 overexpression prolongs the survival of vascularized allografts by promoting tolerogenic mechanisms acting on allogeneic cellular immune responses.

CD40Ig treatment results in allograft acceptance mediated by CD8+CD45RClow T cells, IFN-γ, and indoleamine 2,3-dioxygenase

“…The adenovirus AdCD40Ig coding for the extracellular portion of mouse CD40 fused to the coding sequences of the constant domains of human IgG1 and the noncoding vector Addl324 have been described previously (19). An adenovirus coding for IDO was constructed as previously described (46) and was confirmed to express enzymatically active IDO (data not shown). A total of 2 × 10 10 adenovirus infectious particles (IP) was slowly injected at 3 points into the graft ventricular walls.…”

“…The sequences of primer pairs for HPRT, TGF-β1, IFN-γ, IL-10 (48), and HO-1 (46) have been described previously, and the other primer sequences used are listed in Supplemental Table 1. The PCR and quantification methods, which have been previously described (46), were used after normalization of sequences to HPRT values.…”

An Integral Role for Heme Oxygenase-1 and Carbon Monoxide in Maintaining Peripheral Tolerance by CD4+CD25+ Regulatory T Cells

“…Although HO-1 clearly demonstrates nonspecific cytoprotective functions against oxidative damage and inflammation, evidence is now mounting that HO-1 acts more prominently to inhibit allogeneic immune responses following transplantation. Indeed, viral gene transfer of HO-1 promoted long-term allograft survival in an acute cardiac allograft rejection model (32). Another recent study suggests HO-1 action specifically modulates T cell responses by promoting activation-induced cell death of alloreactive T cells (33).…”

Heme Oxygenase-1 Expression in Macrophages Plays a Beneficial Role in Atherosclerosis

“…6 One such protective gene is heme oxygenase-1 (HO-1), the stress-inducible isoform of HO which is the rate limiting enzyme in the catabolism of heme. 7 Several lines of evidence support the antioxidant, 8 antiinflammatory, 9 and possibly immunomodulatory 10 properties of HO-1 responsible for its antiatherogenic actions. 5,6 Lack of HO-1 has been shown to promote atherosclerosis in apoEnull mice, 11 whereas its overexpression by either pharmacological manipulation 12,13 or genetic means 14 results in decreased atherosclerotic lesions.…”