Genetic suppression of IKK2/NF-κB in astrocytes inhibits neuroinflammation and reduces neuronal loss in the MPTP-Probenecid model of Parkinson's disease

Neuroinflammatory activation of glia is considered a pathological hallmark of Parkinson's disease (PD) and is seen in both human PD patients and in animal models of PD; however, the relative contributions of these cell types, especially astrocytes, to the progression of disease is not fully understood. The transcription factor, nuclear factor kappa B (NF kappa B), is an important regulator of inflammatory gene expression in glia and is activated by multiple cellular stress signals through the kinase complex, IKK2. We sought to determine the role of NF kappa B in modulating inflammatory activation of astrocytes in a model of PD by generating a conditional knockout mouse (hGfapere/Ikbk2(F/F)) in which IKK2 is specifically deleted in astrocytes. Measurements of IKK2 revealed a 70% deletion rate of IKK2 within astrocytes, as compared to littermate controls (Ikbk2(F/F)). Use of this mouse in a subacute, progressive model of PD through exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTPp) revealed significant protection in exposed mice to direct and progressive loss of dopaminergic neurons in the substantia nigra (SN). hGfapcre/Ikbk2(F/F) mice were also protected against MPTPp-induced loss in motor activity, loss of striatal proteins, and genomic alterations in nigral NF kappa B gene expression, but were not protected from loss of striatal catecholamines. Neuroprotection in hGfapere/Ikbk2(F/F) mice was associated with inhibition of MPTPp-induced astrocytic expression of inflammatory genes and protection against nitrosative stress and apoptosis in neurons. These data indicate that deletion of IKK2 within astrocytes is neuroprotective in the MPTPp model of PD and suggests that reactive astrocytes directly contribute the potentiation of dopaminergic pathology.