W203 - Less Precise Medicine - An Argument for Broad-kinase Inhibition in a Microglial Model of Parkinson's Disease

Abstract Text: As a kinase hub in the primary immune effector cell of the brain, leucine-rich repeat kinase 2 (LRRK2) is an attractive target for precision medicine; the selective inhibition of this malefactor should attenuate the major pathology of Parkinson’s Disease (PD). However, kinases are important regulatory nodes in signaling cascades, and complex co-regulatory networks exist between them to maintain cellular health. We posit that a less precise approach via broad, yet still targeted, inhibition of multiple kinases within a co-regulatory kinome can synergistically produce therapeutic activity at lower doses. For example, both LRRK2 and mixed-lineage kinase 3 (MLK3) are commonly implicated across various neurodegenerative diseases.
Thus, using bulk RNAseq in microglia-like BV-2 cells, we screened for differential regulation of key biological processes in response to LRRK2 inhibition (LRRK2-IN-1), MLK3 inhibition (MLK-IN-1), or dual inhibition (URMC-099). All three inhibitors attenuated inflammatory activation from pre-formed fibrils (PFFs) of α-synuclein (aSyn), the primary component of Lewy Body aggregates reported in PD. Of note, only URMC-099 returned cells to basal conditions, while inhibition of either LRRK2 or MLK3 excessively downregulated multiple cellular processes involved in homeostatic microglial function. We corroborate our transcriptomic findings with dose-response resazurin viability assays and immunocytochemical analysis. In aggregate, our data suggest that selective inhibition of only LRRK2 in microglia dysregulates transcriptional regulatory machinery and, paradoxically, excessively disrupts autophagic processing necessary for chronic attenuation of stress induced by aSyn PFFs. Targeted, broad kinase inhibition presents an alternative therapeutic mechanism for PD, with reduced dysregulation of the brain’s primary immune effector cell.