Polynitroxyl Albumin Inhibits Sickle RBC Retention Initiated by TNF Alpha

Abstract

Abstract: : Purpose: Clinical trials to alleviate sickle cell painful crisis and acute lung syndrome by breathing nitric oxide (NO) are in progress. Both events in sickle cell disease are caused by sickle RBC (sRBC)-mediated occlusions. Reactive oxygen species (ROS) are formed in both events and destroy NO. This study evaluates, in a rat model of sickle RBC-mediated occlusion in retina and choroid, the therapeutic potential of polynitroxyl albumin (PNA), a multifunctional antioxidant vascular protectant. Methods:At time zero two groups of anesthetized male Sprague Dawley (SD) rats were given 20 mg tumor necrosis factor alpha (TNF)/kg IP and one group was given phosphate buffered saline (PBS) as control. For each group, the first dose of PNA or control human serum albumin (HSA) (1 ml) was administered via the penile vein at 1hr post TNF. The second dose of PNA or HSA (2 ml) was given via a femoral catheter at 4.75 hrs post TNF. Finally, fluorescent labeled reticulocyte-rich sickle RBCs were administer via a femoral catheter at 5 hrs and permitted to circulate for 5 minutes. The number of sRBCs/retina and number per mm2 of choroids were counted. Results:Administration of PNA or HSA did not affect blood pressure nor PaO2. TNF significantly increased retina retention of sRBCs receiving HSA compared to rats receiving PBS/HSA (p=0.0014). Rats receiving PNA/TNF had significantly less retained cells than those receiving HSA/TNF (p <2.3 E-5). The number of sRBCs retained in the PNA/TNF treatment group was indistinguishable to that of PBS/HSA control group. Likewise, TNF increased retention of sRBCs per mm2 of choroid (p=0.005) and PNA inhibited the TNF-mediated retention of sRBCs in choroid with the same efficacy (p=0.0025). Conclusions: Sickle RBC vaso-occlusion induced by TNF in retina and choroid in a rat model was completely inhibited by PNA. This positive outcome may be due to PNA’s ability to scavenge ROS, which destroy NO. Based on our ocular observations, we hypothesize that PNA may be also an efficacious treatment for painful crisis and acute chest syndrome, which are triggered by sRBC-mediated occlusions and inflammatory cascade

Keywords: vascular occlusion/vascular occlusive disease • antioxidants • hypoxia