The Antioxidant Effects of Ribonuclease Inhibitor

Abstract

Ribonuclease inhibitor (RI) is an acidic cytosolic glycoprotein with molecular weight of about 50 kDa, which contains 32 cysteine residues. It is possibly that RI may have antioxidant effect by thiol-disulfide exchange reaction. We studied the effects of RI over-expression on the rat glial cell line C6 injured with H2O2. The transfected C6 cells with RI cDNA (C6') had higher viability, less LDH leakage and MDA contents, but more GSH contents compare that in the control C6 cells. In transfected C6 cells, the activities of CAT and GST were higher than that in the control C6 cells. Without H202 stress, the activities of CAT and GST in the C6' cells were 1.73 and 3.62 times that in the control C6 cells, respectively; With 1.00 mmol/L H2O2 stress, the activities of CATand GSTin the C6' cells were 3.38 and 2.11 times that in the C6 cells, respectively. These results suggest that the over-expression RI has antioxidant activity and it is able to protect cells from per-oxidative injuries. Moreover, we investigated whether RI has a protective role against mouse hepatic damage in vivo. The mice pretreated with different doses of human RI were injected by CC14. The results show that the SOD activities of therapy groups were significantly higher than that of the control group (p < 0.01), while the contents of MOD and activities of ALT and AST in blood were remarkably lower than that of the control group (p < 0.01). Pathological examination shows that the degree of damage was alleviated with RI therapy. These results suggest that RI has the protective role against mouse hepatic damage induced by CC14. The anti-oxidative effects of RI may play an important role in cell protection from per-oxidative injuries.

The ribonuclease/angiogenin inhibitor is also present in mitochondria and nuclei

“…HeLa cells on the other hand show increased resistance to H 2 O 2 induced mortality when RI is overexpressed [14]. The evidence reported here provides a new direct basis, through experimental methodologies distinct from the others so far proposed on the role of RI as a ROS scavenger.…”

“…Hofsteenge and co-workers have early reported that in cultured cells an oxidative insult with H 2 O 2 , a general oxidant, or with diamide, a thiol specific oxidant, engenders a severe cellular loss of RI as a protein [13]. More recently, it has been reported that cells over-expressing RI become more resistant to H 2 O 2 stress [14], and that RI has a strong scavenging activity on reactive oxygen species (ROS) [15]. These data, and those from a parallel investigation of the effects of oxidants and antioxidants on normal and RI deprived cells, has led to the proposal that RI plays the physiological role of a defensive system against oxidative stress [16] Abbreviations: RI, RNase inhibitor; RNase, ribonuclease; ROS, reactive oxygen species; PBS, Phosphate Buffered Saline; PBS GS, PBS containing 0.2% Gelatin and 0.075% Saponin; MPTP, mitochondrial permeability transition pore; ANT, ADP/ATP Translocase; SDS-PAGE, polyacrylamide gel electrophoresis in sodium dodecylsulfate; TRITC, tetramethylrhodamine isothiocyanate as an oxidant RI inhibits the action of angiogenin, leading to inactivation of tRNAs and translational arrest [17,18].…”

Ribonuclease Inhibitor: Structure and Function

“…One hypothesis suggests that RI is an oxidation sensor in the cell. Overexpression of RI in rat glial cells conferred protection against hydrogen peroxideinduced stress, as indicated by the increased viability of cells, decreased leakage of lactate dehydrogenase, and increased content of reduced glutathione (125). Injection of RI into mice also conferred protection from per-oxidative injuries of the liver induced by exposure to carbon tetrachloride (125).…”

Ribonuclease/angiogenin inhibitor 1 regulates stress-induced subcellular localization of angiogenin and controls its growth and survival activities

“…Thus, a major role of RNH1 is to regulate cellular localization of ANG, thereby controlling cell growth and survival. The reported antioxidant (Cui et al, 2003) and redox homeostatic (Monti et al, 2007) effects might also contribute to the regulatory function of RNH1 in cell survival. RNH1 has also been shown to mediate pri-miR-21 processing, thereby contributing to cancer progression (Kim et al, 2011).…”