Activation of ATF6 Signaling Confers Long-Term Beneficial Effects in Young and Aged Mice After Permanent Stroke.

Ischemic stroke disrupts protein homeostasis in brain cells, causes endoplasmic reticulum (ER) stress, and consequently activates the unfolded protein response (UPR). The primary function of UPR activation is to help cells restore ER function, thereby promoting cell survival. A major adaptive UPR branch is mediated by activating transcription factor 6 (ATF6). We previously provided experimental evidence that activation of ATF6 signaling in neurons improves short-term outcome after both transient and permanent stroke. However, the effect of ATF6 activation in astrocytes on stroke outcome remains undetermined, and critically, the long-term therapeutic potential of targeting this UPR branch in permanent stroke has not been evaluated. The current study aimed to address these two critical unknowns. First, using conditional knock-in mice in which functional short-form ATF6 (sATF6) is specifically expressed in astrocytes, we demonstrated that astrocytic ATF6 activation modestly improved outcome after permanent stroke. Then, our pharmacokinetic analysis indicated that compound AA147, an ATF6-specific activator, can cross the blood-brain barrier. Lastly, we found that post-stroke treatment with AA147 had no significant beneficial effect on short-term outcome, but improved long-term functional recovery in both young and aged mice after permanent stroke. Together with previous findings, our data support the notion that the ATF6 pathway is a promising target for stroke therapy.