Purine derivatives such as caffeine and uric acid have neuroprotective activities and reduce the risk of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. We have reported that caffeine, uric acid and paraxanthine, a major metabolite of caffeine, promote cysteine uptake in hippocampal slices. We have also reported that paraxanthine promotes the cysteine uptake and the synthesis of intracellular antioxidant molecule, glutathione (GSH), in HEK293 cells.
Glutathione (GSH) is an important antioxidants that plays a critical role in neuroprotection. GSH depletion in neurons induces oxidative stress and thereby promotes neuronal damage, which in turn is regarded as a hallmark of the early stage of neurodegenerative diseases. The neuronal GSH level is mainly regulated by excitatory amino acid carrier 1 (EAAC1) and its inhibitor, glutamate transporter-associated protein 3-18 (GTRAP3-18). In this study, we found that GTRAP3-18 level was increased by the up-regulation of the microRNA miR-96-5p, which has been reported to decrease EAAC1 level in our previous study. Since the 3'-UTR region of GTRAP3-18 lacks the consensus sequence for miR-96-5p, an unidentified protein should intermediately regulate GTRAP3-18 expression by miR-96-5p. Here we discovered that neuro-oncological ventral antigen 1 (NOVA1) is an intermediate protein for GTRAP3-18 expression via miR-96-5p. Moreover, we show that the administration of a miR-96-5p-inhibiting nucleic acid to living mice by a drug delivery system decreased the level of GTRAP3-18 via NOVA1 and increased the levels of EAAC1 and GSH in mouse brain. These findings suggest that the delivery of a miR-96-5p inhibitor to the brain would efficiently increase the neuroprotective activity by increasing GSH levels via EAAC1, GTRAP3-18 and NOVA1.
Abstract Glutathione (GSH) is an important antioxidant that plays a critical role in neuroprotection. GSH depletion in neurons induces oxidative stress and thereby promotes neuronal damage, which in turn is regarded as a hallmark of the early stage of neurodegenerative diseases. The neuronal GSH level is mainly regulated by cysteine transporter EAAC1 and its inhibitor, GTRAP3-18. In this study, we found that the GTRAP3-18 level was increased by up-regulation of the microRNA miR-96-5p, which was found to decrease EAAC1 levels in our previous study. Since the 3’-UTR region of GTRAP3-18 lacks the consensus sequence for miR-96-5p, an unidentified protein should be responsible for the intermediate regulation of GTRAP3-18 expression by miR-96-5p. Here, we discovered that RNA-binding protein NOVA1 functions as an intermediate protein for GTRAP3-18 expression via miR-96-5p. Moreover, we show that intra-arterial injection of a miR-96-5p-inhibiting nucleic acid to living mice by a drug delivery system using microbubbles and ultrasound decreased the level of GTRAP3-18 via NOVA1 and increased the levels of EAAC1 and GSH in the dentate gyrus of the hippocampus. These findings suggest that the delivery of a miR-96-5p inhibitor to the brain would efficiently increase the neuroprotective activity by increasing GSH levels via EAAC1, GTRAP3-18 and NOVA1.
Glutathione (GSH) is an important antioxidant that plays a critical role in neuroprotection. GSH depletion in neuron induces oxidative stress promoting neuronal damage, which is regarded as a hallmark of the early stage in some neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. The neuronal GSH levels are mainly regulated by excitatory amino acid carrier 1 (EAAC1) and its inhibitory protein, glutamate transporter-associated protein 3-18 (GTRAP3-18). In this study, we found that GTRAP3-18 levels were increased by the up-regulation of the microRNA miR-96-5p, which has been reported to decrease EAAC1 levels in our previous study. We also discovered that neuro-oncological ventral antigen 1 (NOVA1) is an intermediate protein for GTRAP3-18 expression via miR-96-5p. Moreover, we show that the intra arterial administration of a miR-96-5p-inhibiting nucleic acid to living mice by a drug delivery system using microbubbles and ultrasound decreased the levels of GTRAP3-18 via NOVA1, while increased the levels of both EAAC1 and GSH in the mouse brain. Moreover, we found that the administration of a miR-96-5p inhibitor increased autophagy activation in the mouse hippocampus. These findings suggest that the delivery of a miR-96-5p inhibitor to the brain would efficiently increase the neuroprotective activity by increasing GSH levels via EAAC1, GTRAP3-18 and NOVA1.
7-Nitroindazole (NI) is a widely used inhibitor of neuronal nitricoxide synthase (nNOS) used to study the role of the neuronal NO pathway in the nervous system. 7-NI prevents convulsions, including 2-amino-4-methylphosphinobutyric acid (glufosinate)-induced convulsions, in experimental models. Herein, we examined nNOS involvement in glufosinate-induced convulsions and the specificity of 7-NI for nNOS. Another nNOS inhibitor, 1-[2-(trifluoromethyl)phenyl]imidazole (TRIM), inhibited NOS activity in vivo, and it prevented glufosinate-induced convulsions. In contrast, an endothelial NOS inhibitor, N5-(1-iminoethyl)-l-ornithine, inhibited NOS activity in vivo, but it did not prevent the convulsions. These results suggest the involvement of nNOS in glufosinate-induced convulsions. However, a nonspecific NOS inhibitor, Nω-nitro-l-arginine methyl ester, inhibited NOS activity in vivo, but it failed to prevent glufosinate-induced convulsions. 6-NI and indazole, which did not inhibit NOS activity in vivo, suppressed glufosinate-induced convulsions. Moreover, glufosinate elicited convulsions in nNOS-deficient mice. These results suggest the anticonvulsant effects of 7-NI and TRIM on glufosinate-induced convulsions do not involve nNOS inhibition, instead possibly being related to an undefined property of nitrogen-containing chemical structures.
Pro-opiomelanocortin (POMC)-expressing neurons provide alpha-melanocyte-stimulating hormone (α-MSH), which stimulates melanocortin-4 receptor (MC4R) to induce hypophagia by AMP-activated protein kinase (AMPK) inhibition in the hypothalamus. The POMC precursor protein is synthesized in the endoplasmic reticulum (ER) and subsequently translocates to the Golgi complex to secrete POMC-derived peptides, including α-MSH, from the secretory granules. However, no evidence has been reported in the post-transcriptional regulation of POMC in the ER.
