Up-regulation of Protein-disulfide Isomerase in Response to Hypoxia/Brain Ischemia and Its Protective Effect against Apoptotic Cell Death

Abstract

We isolated and identified a stress protein that is upregulated in response to hypoxia in primary-cultured glial cells. Protein-disulfide isomerase (PDI) was up-regulated not only by hypoxia in glia in vitro, but also by transient forebrain ischemia in rats in vivo. To determine whether newly synthesized PDI is involved in tolerance to ischemic stress, we carried out two procedures to induce PDI gene expression in human neuroblastoma SK-N-MC cells, as well as intrahippocampal injection following electroporation of an expression vector capable of overexpressing PDI in rats. Overexpression of this gene resulted in attenuation of the loss of cell viability induced by hypoxia in neuroblastoma SK-N-MC cells and a reduction in the number of DNAfragmented cells in the CA1 area of the hippocampus in brain ischemic rats, respectively. These findings suggest that up-regulated PDI may play a critical role in resistance to ischemic damage, and that the elevation of levels of this protein in the brain may have beneficial effects against brain stroke.Two distinct phenomena are observed in the CA1 subfield of the hippocampus after transient forebrain ischemia in rodents: the death of neurons, which is referred to as "delayed neuronal death," and the proliferation of glial cells, which is termed "gliosis" (1). Neurons are thus thought to be fragile and very sensitive to such stress, and, as a consequence, apoptotic cell death occurs (2, 3). Several studies have shown that caspases are involved in this neuronal apoptosis triggered by brain ischemia. Transgenic mice expressing dominant-negative mutants of caspase-1 and caspase-1-deficient mice show a reduced neuronal cell death induced by ischemic brain injury (4 -6). Caspase inhibitors such as Z-VAD-fmk, 1 YVAD-fmk, and DEVD-fmk also significantly reduce the neuronal cell death induced by ischemia (7-9). Furthermore, overexpression of Bcl-2 in transgenic mice as well as of neuronal apoptosis inhibitory protein, a member of the inhibitor of apoptosis protein family, by injection of adenovirus expression vectors has a protective effect against the neuronal cell death induced by focal cerebral or transient forebrain ischemia (10, 11). These results suggest that caspases are involved in ischemia-induced neuronal death in an anti-apoptotic protein-dependent manner.On the other hand, glial cells show tolerance to ischemic stress, and their numbers are increased in areas originally containing neurons. Due to their abundance and ability to sustain environmental perturbations, glia play a critical role in maintaining neuronal function under both physiological and pathological conditions (12). Glial cells subjected to hypoxia express stress proteins such as a 70-kDa heat shock protein (HSP70), a 78-kDa glucose-regulated protein (GRP78), a 150-kDa oxygen-regulated protein (ORP150), a 36-kDa putative RNA-binding protein (RA301), and a 70-kDa putative vesicle transport-related protein (RA410) (13-16). Hori et al. (17) have reported that the inhibition of protein synthesis during early reoxy...

Effects of cadmium on structure and enzymatic activity of Cu,Zn‐SOD and oxidative status in neural cells

“…These two sites could lead to increased PDI expression in neurons, and result in both attenuation of the loss of cell viability in vitro and reduction of the number of DNA-fragmented cells in the rat hippocampal CA1 subregion in vivo [Lyles and Gilbert, 1991]. Recent reports demonstrate that upregulated PDI may exert a protective effect against apoptotic cell death [Tanaka et al, 2000;Ko et al, 2002]. The observed downregulated expression of PDI in our study indicates that cadmium triggers neural cells towards apoptosis.…”

S-Nitrosylation and uncompetitive/fast off-rate (UFO) drug therapy in neurodegenerative disorders of protein misfolding

“…82 Accumulation of immature and denatured proteins results in ER dysfunction in brains of AD, PD, ALS, prion disease, cerebral ischemia, and possibly other neurodegenerative disorders, but upregulation of PDI represents an adaptive response promoting protein refolding and may offer neuronal cell protection. [83][84][85][86][87][88][89][90] Recently, we reported that excessive NO can lead to S-nitrosylation of the active site thiol groups of PDI, and Figure 3 Possible mechanism of S-nitrosylated PDI (SNO-PDI) contributing to the accumulation of aberrant proteins and neuronal cell damage or death. ER stress is triggered when misfolded proteins accumulate within the ER lumen, inducing the UPR.…”

Chronic Cerebral Hypoperfusion Induced Synaptic Proteome Changes in the rat Cerebral Cortex

“…In the present study, we identified (with at least 3 peptides) 23 proteins with significantly increased (Table 1) and 23 proteins with decreased ( Table 2) (1) - (Chihara et al, 2007), (2) - (Folci et al, 2014), (3) - (Chen et al, 2002), (4) - (Tanaka et al, 2000), (5) - (Ding and Shen, 2008), (6) - (Na et al, 2012), (7) - (Lyon et al, 2007), (8) - (Sweatt et al, 2004), (9) - (Bahn et al, 2002), (10) - (Manya et al, 1998), (11) - (Kamada et al, 2003), (12) - (McKenna et al, 2000), (13) - (Christel et al, 2012), (GO) -According to Gene Ontology database. …”