Dopamine Activates the D1R-Zn²⁺ Signaling Pathway to Trigger Inflammatory Response in Primary-Cultured Rat Embryonic...

Neuroinflammation is an early event during the pathogenesis of neurodegenerative disorders. Most studies focus on how the factors derived from pathogens or tissue damage activate the inflammation-pyroptosis cell death pathway. It is unclear whether endogenous neurotransmitters could induce inflammatory responses in neurons. Our previous reports have shown that dopamine-induced elevation of intracellular Zn²⁺ concentration via the D1-like receptor (D1R) is a prerequisite for autophagy and cell death in primary cultured rat embryonic neurons. Here we further examined that this D1R-Zn²⁺ signaling initiates the transient inflammatory response leading to cell death in cultured cortical neurons. Pretreating the cultured neurons with Zn²⁺ chelator and inhibitors against inflammation could enhance the cell viability in neurons treated with dopamine and dihydrexidine, an agonist of D1R. Both dopamine and dihydrexidine greatly enhanced inflammasome formation; a Zn²⁺ chelator, N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine, suppressed this increment. Dopamine and dihydrexidine increased the expression levels of NOD-like receptor pyrin domain-containing protein 3 and enhanced the maturation of caspase-1, gasdermin D, and IL-1β; these changes were all Zn²⁺-dependent. Dopamine treatment did not recruit the N-terminal of the gasdermin D to the plasma membrane but enhanced its localization to the autophagosomes. Pretreating the neurons with IL-1β could increase the viability of neurons challenged with dopamine. These results demonstrate a novel D1R-Zn²⁺ signaling cascade activating neuroinflammation and cell death. Therefore, maintaining a balance between dopamine homeostasis and inflammatory responses is an important therapeutic target for neurodegeneration. Dopamine elicits transient inflammatory responses in cultured cortical neurons via the D1R-Zn²⁺ signaling pathway. Dopamine elevates [Zn²⁺]_i to induce the formation of inflammasomes, which activates caspase-1, resulting in the maturation of IL-1β and gasdermin D (GSDMD). Therefore, the homeostasis of dopamine and Zn²⁺ are critical therapeutic targets for inflammation-derived neurodegeneration.