In the present study, MPO activity was assessed for the index of tissue oxidative load, which is considered
as one of the hallmark indicator of necrotic cell death (Erman et al. 2005). We observed that hypoxic spinal cord showed increase in MPO activity. Neutrophil and microglia activation have been shown responsible for increased MPO activity (Taoka and Okajima 1998; Erman et al. 2005; Fleming et al. 2006) during CNS injuries. In this in vitro model, since there is no blood infusion, Inhibitors,research,lifescience,medical so the probable source of MPO is microglia alone. We used two neuroimmunophilins (FK-506 and CsA) to understand their effects on spinal cord hypoxic injury induced secondary neuronal Birinapant damage in spinal cord. It was observed that both FK-506 and CsA significantly Inhibitors,research,lifescience,medical reduced the level of LPO and MPO activity in the hypoxic group. This could be due to the ability of FK-506 and CsA to inhibit microglia activation by inhibiting calcineurin, which activates transcription factor NF-AT and thereby eventually decreasing MPO and LPO level in the hypoxic spinal cord (Taoka and Okajima 1998; Erman et al. 2005). However, study by Mun and Ha (2010) has shown that CsA treatment of glioma leads to increase ROS production and neurological side effects. FK-506 has been reported to protect the spinal cord by targeting microglia cells (Guzmán–Lenis et al. 2008) after excitotoxicity. CsA and FK-506 have been used as an immunosuppressant in traumatic or ischemic Inhibitors,research,lifescience,medical CNS damage and
it was shown that these neuroprotectants inhibit microglia cells activation (Hailer 2008). FK-506 is also reported to block NF-κB, turning
off the gene of ICAM-I, thereby limiting the inflammatory damage and infarct size during ischemia/reperfusion (Squadrito et al. 2000). Nishinaka et al. (1993) reported that FK-506 Inhibitors,research,lifescience,medical exerted a protection on ischemia/reperfusion-induced damage Inhibitors,research,lifescience,medical in canine heart, which was suggested due to the ability of FK-506 to reduce superoxide radical formation. It was observed that FK-506 and CsA treatment significantly restored GSH content in the hypoxic groups. There is a correlation between the level of LPO and GSH content; both are inversely proportional to each other. The inversely proportional LPO and GSH content could help explain the mechanism by which FK-506 and CsA reduced DNA ligase peroxidative membrane damage by inhibiting microglia activation and thereby maintaining GSH content. FK-506 and CsA treatment markedly decreased mitochondrial swelling in hypoxic mitochondria. ATP content was also found to be increased with FK-506 and CsA treatment. It has been reported that ROS generation plays a central role in altering mitochondrial membrane integrity, which leads to opening of MPTP and increased ion influx, that is, calcium (Peng and Jou 2004). MPTP opening results in uncoupling respiration from ATP synthesis, organelle swelling, disruption of the outer membrane, and release of different apoptogenic factors into the cytosol (Green and Reed 1998; Kroemer et al.