Glutathione Transferase-M2-2 Secreted from Glioblastoma Cell Protects SH-SY5Y Cells from Aminochrome Neurotoxicity

Abstract

U373MG cells are able to take up aminochrome that induces glutathione transferase M2-2 (GSTM2) expression in a concentration-dependent manner where 100 µM aminochrome increases GSTM2 expression by 2.1-fold (P < 0.001) at 3 h. The uptake of (3)H-aminochrome into U373MG cells was significantly reduced in the presence of 2 µM nomifensine (P < 0.001) 100 µM imipramine (P < 0.001) and 50 mM dopamine (P < 0.001). Interestingly, U373MG cells excrete GSTM2 into the conditioned medium and the excretion was significantly increased (2.7-fold; P < 0.001) when the cells were pretreated with 50 µM aminochrome for 3 h. The U373MG-conditioned medium containing GSTM2 protects SH-SY5Y cells incubated with 10 µM aminochrome. The significant protection provided by U373MG-conditioned medium in SH-SY5Y cells incubated with aminochrome was dependent on GSTM2 internalization into SH-SY5Y cells as evidenced by (i) uptake of (14)C-GSTM2 released from U373MG cells into SH-SY5Y cells, a process inhibited by anti-GSTM2 antiserum; (ii) lack of protection of U373MG-conditioned medium in the presence of anti-GSTM2 antiserum on SH-SY5Y cells treated with aminochrome; and (iii) lack of protection of conditioned medium from U373MGsiGST6 that expresses an siRNA directed against GSTM2 on SH-SY5Y cells treated with aminochrome. In conclusion, our results demonstrated that U373MG cells protect SH-SY5Y cells against aminochrome neurotoxicity by releasing GSTM2 into the conditioned medium and subsequent internalization of GSTM2 into SH-SY5Y cells. These results suggest a new mechanism of protection of dopaminergic neurons mediated by astrocytes by releasing GSTM2 into the intersynaptic space and subsequent internalization into dopaminergic neuron in order to protect these cells against aminochrome neurotoxicity.

Interactions of iron, dopamine and neuromelanin pathways in brain aging and Parkinson's disease

“…Interestingly, although glutathione S-transferase M2-2 is only expressed in astrocytes, the enzyme may also protect dopaminergic neurons against aminochrome toxicity. This may be because dopaminergic neurons internalize glutathione S-transferase M2-2 secreted by astrocytes, thus acquiring this protective enzyme against aminochrome neurotoxicity, as suggested in human-derived cell cultures experiments (Cuevas et al, 2015). …”

Circadian control of BDNF-mediated Nrf2 activation in astrocytes protects dopaminergic neurons from ferroptosis

“…GSTM2 is expressed in astrocytes but not synthesized in dopaminergic neurons. As astrocytes have been shown to provide GSTM2 to neurons to help protect against neurotoxicity of aminochrome, this implicates an intercellular communication system mediating transfer of cytoplasmic proteins from astrocytes to neurons [16,48]. In addition to GSTs, GSH peroxidases (GPxs) reduce phospholipid hydroperoxides and afford protection for neurons.…”

Neuronal Activity and Its Role in Controlling Antioxidant Genes

“…As a result they rely on nearby glia for antioxidant support: in response to oxidative stress astrocytes release glutathione which is broken down and taken up by neurons for their own use [3][4][5][6][7]. Other glutathione-utilizing enzymes (specifically glutathione transferase M2-2) have also been reported to be secreted by glia for uptake by neurons with neuroprotective consequences [8].…”