Transcriptional profiling of myeloid cells (CD11b) and astrocytes (ACSA2) from the striatum and the midbrain of control and parkinsonian animals in the MPTP mouse model
Neuroinflammation is a common hallmark of neurodegenerative diseases such as Parkinson's disease (PD). Here, we questioned about the activation state of glial cells along the degeneration process of dopaminergic terminals in the striatum and loss of neuronal cell bodies in the midbrain. We hypothesized that MPTP administration pattern would produce different inflammatory responses that could modify the course of nigrostriatal degeneration.  To reproduce the dopaminergic impairment in a PD experimental mouse model, we used two different MPTP-administration patterns: subacute (sMPTP) and chronic (cMPTP). Bulk RNA sequencing of purified midbrain microglia/myeloid cells of sMPTP mice showed an anti-inflammatory phenotype, while midbrain microglia/myeloid cells of cMPTP mice showed a pro-inflammatory and phagocytic phenotype. Midbrain astrocytes presented a phagocytic phenotype in sMPTP mice. In the striatum, microglia presented a continuous pro-inflammatory state in sMPTP and cMPTP conditions. In this region, astrocytes presented a remarkable activated and phagocytic state in sMPTP mice which was attenuated with the chronicity of MPTP administration. Overall design: Different patterns of MPTP intoxication were used. In the subacute MPTP (sMPTP) regimen, 30 mg/kg of MPTP dissolved in saline were administered intraperitoneal (i.p.) for 5 consecutive days. Control mice were injected with serum. In the chronic MPTP (cMPTP) regimen, mice received 10 i.p. injections of MPTP (20 mg/kg in saline) together with probenecid (250 mg/kg in saline) to retard the renal clearance of toxic metabolites of MPTP. Both compounds were injected twice a week along 5 weeks in two consecutive injections separated 30-60 minutes. Control mice received 10 i.p. injection of probenecid at the same concentration as parkinsonian animals. Upon sacrifice, the striatum and the ventral midbrain were dissected out to prepare a cell suspension from each region. CD11b+ myeloid cells and ACSA2+ astrocytes were subsequently separated for bulk mRNA sequencing (N = 3 animals/group).