RO 23-6457 prolongs survival of vascularized allografts in rodents and primates

Chemopreventive anti-cancer agent acyclic retinoid suppresses allogeneic immune responses in rats

Acyclic retinoid NIK-333 (ACR) is a chemopreventive agent that acts by suppressing the recurrence of hepatocellular carcinoma (HCC) following initial treatment and is now being employed in clinical trials. The chemopreventive effects of ACR have been analyzed from various aspects, and it is well known that some retinoic acid (RA) derivatives affect host immunity. The objective of this study is to investigate the effects of ACR on host immunity. The results demonstrated that ACR prolonged heart and liver graft and recipient survival in rat allogeneic organ transplantation. The immunosuppressive effect of ACR administered at 100mg/kg/day was almost equivalent to that of CsA administered at 1mg/kg/day in vivo. In the mixed lymphocyte reaction (MLR), ACR suppressed lymphocyte proliferation non-specifically. Gene expression analysis of splenic lymphocytes from ACR-treated recipient rats revealed no distinct change in Interleukin (IL)-2 and increases in Interferon (IFN)-gamma. In conclusion, ACR possesses immunosuppressive potential in vivo and is a promising chemopreventive drug for long term use against HCC.

13-cis retinoic acid inhibits development and progression of chronic allograft nephropathy

Chronic allograft nephropathy is characterized by chronic inflammation and fibrosis. Because retinoids exhibit anti-proliferative, anti-inflammatory, and anti-fibrotic functions, the effects of low and high doses of 13-cis-retinoic acid (13cRA) were studied in a chronic Fisher344-->Lewis transplantation model. In 13cRA animals, independent of dose (2 or 20 mg/kg body weight/day) and start (0 or 14 days after transplantation) of 13cRA administration, serum creatinine was significantly lower and chronic rejection damage was dramatically reduced, including subendothelial fibrosis of preglomerular vessels and chronic tubulointerstitial damage. The number of infiltrating mononuclear cells and their proliferative activity were significantly diminished. The mRNA expression of chemokines (MCP-1/CCL2, MIP-1alpha/CCL3, IP-10/CXCL10, RANTES/CCL5) and proteins associated with fibrosis (plasminogen activator inhibitor-1, transforming growth factor-beta1, and collagens I and III) were strikingly lower in treated allografts. In vitro, activated peritoneal macrophages of 13cRA-treated rats showed a pronounced decrease in protein secretion of inflammatory cytokines (eg, tumor necrosis factor-alpha, interleukin-6). The suppression of the proinflammatory chemokine RANTES/CCL5 x 13cRA in fibroblasts could be mapped to a promoter module comprising IRF-1 and nuclear factor-kappaB binding elements, but direct binding of retinoid receptors to promoter elements could be excluded. In summary, 13cRA acted as a potent immunosuppressive and anti-fibrotic agent able to prevent and inhibit progression of chronic allograft nephropathy.

Isotretinoin ameliorates renal damage in experimental acute renal allograft rejection

BACKGROUND

Retinoic acids, derivatives of vitamin A, act through retinoid receptors that are expressed in renal and immunocompetent cells (B and T cells; monocytes and macrophages). In experimental models of glomerulonephritis and renal interstitial disease, retinoids were shown to reduce both glomerular and tubular damage and inflammation. We therefore examined whether retinoids reduce cellular rejection and renal damage in a model of acute renal allograft rejection.

METHODS

Kidneys of Fisher rats (F344, RT11v1) were orthotopically grafted to Lewis rats (RT11). Animals were killed 7 or 14 days after transplantation. Rats undergoing transplantation were treated with isotretinoin (13 cis-retinoic acid) at a low dose of 2 mg/kg body weight per day (LD isotretinoin) or at a high dose of 20 mg/kg body weight per day (HD isotretinoin) or with vehicle.

RESULTS

At day 14, albuminuria was reduced by approximately 70% (vehicle: 1.1+/-0.2 mg/24 hr vs. LD isotretinoin: 0.32+/-0.1 mg/24 hr; P<0.001). At days 7 and 14 serum creatinine levels were significantly higher in the vehicle-treated group than in the LD and HD isotretinoin-treated rats (P<0.05). Both LD and HD isotretinoin significantly reduced acute vascular injury compared with vehicle-treated rats (score at day 14: LD isotretinoin 20.1+/-5.1 vs. vehicle 57.8+/-9.9, P<0.01), acute glomerular injury (score: LD isotretinoin 6.8+/-1.0 vs. vehicle 10.6+/-0.9 P<0.05), and the number of glomerular monocytes and macrophages and cytotoxic T cells. Isotretinoin also significantly lessened tubulointerstitial damage, tubulointerstitial cell proliferation, and the number of cells infiltrating the tubulointerstitium.

CONCLUSIONS

Isotretinoin significantly ameliorated functional, vascular, glomerular, and tubulointerstitial lesions in acute graft rejection. Although the current study did not definitely eliminate the possibility that isotretinoin only delayed the rejection process, retinoic acid derivatives may provide a new approach in the treatment of acute rejection injury.