Prokineticin-2 promotes chemotaxis and alternative A2 reactivity of astrocytes.

Astrocyte reactivity is disease- and stimulus-dependent, adopting either a proinflammatory A1 phenotype or a protective, anti-inflammatory A2 phenotype. Recently, we demonstrated, using cell culture, animal models and human brain samples, that dopaminergic neurons produce and secrete higher levels of the chemokine-like signaling protein Prokineticin-2 (PK2) as a compensatory protective response against neurotoxic stress. As astrocytes express a high level of PK2 receptors, herein, we systematically characterize the role of PK2 in astrocyte structural and functional properties. PK2 treatment greatly induced astrocyte migration, which was accompanied by a shift in mitochondrial energy metabolism, a reduction in proinflammatory factors, and an increase in the antioxidant genes Arginase-1 and Nrf2. Overexpression of PK2 in primary astrocytes or in the in vivo mouse brain induced the A2 astrocytic phenotype with upregulation of key protective genes and A2 reactivity markers including Arginase-1 and Nrf2, PTX3, SPHK1, and TM4SF1. A small-molecule PK2 agonist, IS20, not only mimicked the protective effect of PK2 in primary cultures, but also increased glutamate uptake by upregulating GLAST. Notably, IS20 blocked not only MPTP-induced reductions in the A2 phenotypic markers SPHK1 and SCL10a6 but also elevation of the of A1 marker GBP2. Collectively, our results reveal that PK2 regulates a novel neuron-astrocyte signaling mechanism by promoting an alternative A2 protective phenotype in astrocytes, which could be exploited for development of novel therapeutic strategies for PD and other related chronic neurodegenerative diseases. PK2 signals through its receptors on astrocytes and promotes directed chemotaxis. PK2-induced astrocyte reactivity leads to an increase in antioxidant and anti-inflammatory proteins while increasing glutamate uptake, along with decreased inflammatory factors.