Genetic overexpressing of GPx-1 attenuates cocaine-induced renal toxicity via induction of anti-apoptotic factors.

The present study investigates the role of the glutathione peroxidase (GPx)-1 gene in cocaine-induced renal damage in mice. Multiple doses of cocaine increased lipid peroxidation, protein oxidation, and glutathione oxidation in the kidney of the non-transgenic mice (non-TG mice). The enzymatic activities of GPx and glutathione reductase were significantly decreased in non-TG mice, whereas superoxide dismutase was increased in the early phase of cocaine exposure. Treatment with cocaine resulted in significant decreases in expression of Bcl-2 and Bcl-xl in the kidney of non-TG mice, which resulted in significant increases in Bax and cleaved-caspase 3. Consistently, cocaine-induced tubular epithelial vacuolization and focal tubular necrosis were mainly observed in the proximal tubules in the kidneys of non-TG mice. These renal pathologic changes were much less pronounced in GPx-1 TG than in non-TG mice. These results suggest that the GPx-1 gene is a protective factor against nephrotoxicity induced by cocaine via interactive modulations between antioxidant and cell survival signaling processes.

Astrocytic mobilization of glutathione peroxidase-1 contributes to the protective potential against cocaine kindling behaviors in mice via activation of JAK2/STAT3 signaling.

Compelling evidence indicates that oxidative stress contributes to cocaine neurotoxicity. The present study was performed to elucidate the role of the glutathione peroxidase-1 (GPx-1) in cocaine-induced kindling (convulsive) behaviors in mice. Cocaine-induced convulsive behaviors significantly increased GPx-1, p-IkB, and p-JAK2/STAT3 expression, and oxidative burdens in the hippocampus of mice. There was no significant difference in cocaine-induced p-IkB expression between non-transgenic (non-TG) and GPx-1 overexpressing transgenic (GPx-1 TG) mice, but significant differences were observed in cocaine-induced p-JAK2/STAT3 expression and oxidative stress between non-TG and GPx-1 TG mice. Cocaine-induced glial fibrillary acidic protein (GFAP)-labeled astrocytic level was significantly higher in the hippocampus of GPx-1 TG mice. Triple-labeling immunocytochemistry indicated that GPx-1-, p-STAT3-, and GFAP-immunoreactivities were co-localized in the same cells. AG490, a JAK2/STAT3 inhibitor, but not pyrrolidone dithiocarbamate, an NFκB inhibitor, significantly counteracted GPx-1-mediated protective potentials (i.e., anticonvulsant-, antioxidant-, antiapoptotic-effects). Genetic overexpression of GPx-1 significantly attenuated proliferation of Iba-1-labeled microglia induced by cocaine in mice. However, AG490 or astrocytic inhibition (by GFAP antisense oligonucleotide and α-aminoadipate) significantly increased Iba-1-labeled microglial activity and M1 phenotype microglial mRNA levels, reflecting that proinflammatory potentials were mediated by AG490 or astrocytic inhibition. This microglial activation was less pronounced in GPx-1 TG than in non-TG mice. Furthermore, either AG490 or astrocytic inhibition significantly counteracted GPx-1-mediated protective potentials. Therefore, our results suggest that astrocytic modulation between GPx-1 and JAK2/STAT3 might be one of the underlying mechanisms for protecting against convulsive neurotoxicity induced by cocaine.

Protein Kinase Cδ Gene Depletion Protects Against Methamphetamine-Induced Impairments in Recognition Memory and ERK1/2 Signaling via Upregulation of Glutathione Peroxidase-1 Gene.

Accumulating evidence has suggested that repeated treatment with methamphetamine (MA) resulted in cognitive impairments. Importantly, we show that selective upregulation of protein kinase Cδ (PKCδ) in the prefrontal cortex (PFC) of wild-type mice persisted for 28 days post withdrawal of MA. On day 28, the MA-induced increase in phospho-PKCδ expression and decrease in phospho-ERK1/2 expression were significantly attenuated by both the Src inhibitor PP2 and the dopamine D1 receptor antagonist SCH 23390. However, neither protein kinase A inhibitor H89 nor calmodulin-dependent protein kinase II inhibitor KN93 attenuated MA-induced alterations in phospho-PKCδ expression and phospho-ERK1/2 expression. Since PKCδ knockout (KO) significantly increased the expression of glutathione peroxidase (GPx)-1, we also utilized GPx-1 KO and GPx-1-overexpressing transgenic (GPx-1 TG) mice. Repeated MA treatment induced cognitive impairment, as assessed by the novel object recognition test. Moreover, the extent of cognitive impairment correlated with the extent of increased phospho-PKCδ expression and decreased GPx1 expression. In the absence of MA, exposure to novel objects increased phospho-ERK1/2 and GPx-1 expression in the PFC; however, these expression levels were decreased in the presence of MA. PKCδ KO and GPx-1 TG mice each exhibited significantly attenuated MA-induced decreases in phospho-ERK1/2 and GPx-1 expression. Consistently, PKCδ inhibition induces GPx/GSH-dependent antioxidant systems. More importantly, the antipsychotic drug clozapine significantly protected against cognitive impairment and was associated with alterations in phospho-ERK1/2 and phospho-PKCδ expression. However, GPx-1 KO potentiated MA-induced cognitive deficits and alterations in phospho-ERK1/2 and phospho-PKCδ expression. These results suggest that MA induces cognitive impairment by inhibiting ERK1/2 signaling, activating PKCδ, and inactivating GPx-1 by upregulating Src kinase or the D1 receptor. They also suggest that clozapine requires activation of ERK1/2 signaling via positive modulation between the phospho-PKCδ and GPx-1 genes to restore cognitive function.