S of the neurotrophic factor BDNF and the antioxidative gene heme oxygenase-1 (HO-1) was reduced in ATF6a 2/2 mice after MPTP/P injections (Fig. 3 B I, II). Astrocytes are ubiquitous in the brain, and upon central nervous system insult, undergo molecular and morphological changes, referred to as reactive astrogliosis or astroglial activation [18]. Activated astrocytes enhance the neuronal survival by secreting neurotrophic factors or antioxidants, as well as by reducing glutamate levels in extracellular spaces [16,17]. In our model, reduced BDNF expression was observed in ATF6a 2/2 mice and was associated with reduced GRP78 expression (Fig. 4 A, B). These results were consistent with those of our previous reports that ATF6adependent molecular chaperones, such as GRP78 and ORP150, promote the maturation of neurotrophic factors in the ER [21,22]. Expression of the PERK/ATF4-dependent anti-oxidative genes HO-1 and xCT, but not the PERK/ATF4-independent antioxidative gene MnSOD was also reduced at both the protein and mRNA level in ATF6a 2/2 mice after MPTP/P injections (Fig. 4 A). These results suggest that some of PERK/ATF4-dependent anti-oxidative genes are also transcriptionally regulated by ATF6a, similar to PERK/ATF4-dependent pro-apoptotic gene CHOP [23]. Although it is currently unknown which steps in astroglial activation are impaired in ATF6a 2/2 mice, it is possible that extracellular signals including LIF and IL-6, from damaged neurons or other cells in the brain, are too low to promote activation in ATF6a 2/2 astrocytes. Alternatively, it is also possible that enhanced levels of ER stress in ATF6a 2/2 astrocytes compromised intracellular signals which are important for the astroglial activation, as was recently reported for hepatocytes [24]. Consistent with the 
results from ATF6a 2/2 mice, administration of the IN19 to wild-type mice enhanced UPR-target gene expression, including ORP150 and GRP78, in both nigrastriatal neurons and astrocytes, and facilitated neuronal survival after 
MPTP/P injection. These results are consistent with those of previous reports demonstrating that IN19 can distribute into the brain after oral administration [25], and protect cells in both the ER stress model and acute MPTP injection model [11,25]. Although IN19 alone did not cause astrogliosis (Fig. 5 B IV), IN19 administered in the course of MPTP/P injections enhanced expression of GFAP (Fig. 6 C I, II) mildly, but GSK -3203591 significantly, suggesting that IN19 may protect dopaminergic neurons, at least in part, through the activated astrocytes after MPTP/P administration. A recent report demonstrated that Salubrinal, a compound that regulates ER stress by activating the eIF2a/ATF4 pathway, attenuated disease PS 1145 site manifestation in the A53T asynuclein-overexpressed PD model [26]. These 1527786 results emphasize the protective role of the UPR in PD. In conclusion, we found that the UPR branches were activated in a mouse model of chronic MPTP/P injection, and they contributed to nigrostriatal neuronal survival, at least in part, through activated astrocytes. Further studies to dissect the neuronglial association through the UPR should provide novel therapeutic window for PD and other neurodegenerative diseases.Supporting InformationFigure S1 Astrocyte and microglia activation in a mouse model of chronic MPTP/P injection. Total RNA (1 mg) isolated from brain samples, including the ventral midbrain, after MPTP/P injections was subjected to RT-PCR with specific primers for GFA.S of the neurotrophic factor BDNF and the antioxidative gene heme oxygenase-1 (HO-1) was reduced in ATF6a 2/2 mice after MPTP/P injections (Fig. 3 B I, II). Astrocytes are ubiquitous in the brain, and upon central nervous system insult, undergo molecular and morphological changes, referred to as reactive astrogliosis or astroglial activation [18]. Activated astrocytes enhance the neuronal survival by secreting neurotrophic factors or antioxidants, as well as by reducing glutamate levels in extracellular spaces [16,17]. In our model, reduced BDNF expression was observed in ATF6a 2/2 mice and was associated with reduced GRP78 expression (Fig. 4 A, B). These results were consistent with those of our previous reports that ATF6adependent molecular chaperones, such as GRP78 and ORP150, promote the maturation of neurotrophic factors in the ER [21,22]. Expression of the PERK/ATF4-dependent anti-oxidative genes HO-1 and xCT, but not the PERK/ATF4-independent antioxidative gene MnSOD was also reduced at both the protein and mRNA level in ATF6a 2/2 mice after MPTP/P injections (Fig. 4 A). These results suggest that some of PERK/ATF4-dependent anti-oxidative genes are also transcriptionally regulated by ATF6a, similar to PERK/ATF4-dependent pro-apoptotic gene CHOP [23]. Although it is currently unknown which steps in astroglial activation are impaired in ATF6a 2/2 mice, it is possible that extracellular signals including LIF and IL-6, from damaged neurons or other cells in the brain, are too low to promote activation in ATF6a 2/2 astrocytes. Alternatively, it is also possible that enhanced levels of ER stress in ATF6a 2/2 astrocytes compromised intracellular signals which are important for the astroglial activation, as was recently reported for hepatocytes [24]. Consistent with the results from ATF6a 2/2 mice, administration of the IN19 to wild-type mice enhanced UPR-target gene expression, including ORP150 and GRP78, in both nigrastriatal neurons and astrocytes, and facilitated neuronal survival after MPTP/P injection. These results are consistent with those of previous reports demonstrating that IN19 can distribute into the brain after oral administration [25], and protect cells in both the ER stress model and acute MPTP injection model [11,25]. Although IN19 alone did not cause astrogliosis (Fig. 5 B IV), IN19 administered in the course of MPTP/P injections enhanced expression of GFAP (Fig. 6 C I, II) mildly, but significantly, suggesting that IN19 may protect dopaminergic neurons, at least in part, through the activated astrocytes after MPTP/P administration. A recent report demonstrated that Salubrinal, a compound that regulates ER stress by activating the eIF2a/ATF4 pathway, attenuated disease manifestation in the A53T asynuclein-overexpressed PD model [26]. These 1527786 results emphasize the protective role of the UPR in PD. In conclusion, we found that the UPR branches were activated in a mouse model of chronic MPTP/P injection, and they contributed to nigrostriatal neuronal survival, at least in part, through activated astrocytes. Further studies to dissect the neuronglial association through the UPR should provide novel therapeutic window for PD and other neurodegenerative diseases.Supporting InformationFigure S1 Astrocyte and microglia activation in a mouse model of chronic MPTP/P injection. Total RNA (1 mg) isolated from brain samples, including the ventral midbrain, after MPTP/P injections was subjected to RT-PCR with specific primers for GFA.
