The colony-stimulating factor 1 receptor (CSF1R) is a key tyrosine kinase transmembrane receptor modulating microglial homeostasis, neurogenesis, and neuronal survival in the central nervous system (CNS). CSF1R, which can be proteolytically cleaved into a soluble ectodomain and an intracellular protein fragment, supports the survival of myeloid cells upon activation by two ligands, colony stimulating factor 1 and interleukin 34. CSF1R loss-of-function mutations are the major cause of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) and its dysfunction has also been implicated in other neurodegenerative disorders including Alzheimer’s disease (AD). Here, we review the physiological functions of CSF1R in the CNS and its pathological effects in neurological disorders including ALSP, AD, frontotemporal dementia and multiple sclerosis. Understanding the pathophysiology of CSF1R is critical for developing targeted therapies for related neurological diseases.

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Background Mutations in colony-stimulating factor 1 receptor (CSF1R) are known to cause adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), which has been recently demonstrated as a primary microgliopathy characterized by cognitive impairment. Although the molecular mechanism underlying CSF1R-mediated microgliopathy remains unclear, therapeutic strategies have generally targeted modulation of microglial function. In particular, the microglial inhibitor, minocycline, has been shown to attenuate learning and memory deficits in several neurodegenerative diseases. The objectives of this study were to investigate the pathogenic mechanisms underlying ALSP and to explore the therapeutic effects of minocycline in an in vivo model of ALSP. We hypothesized that inhibiting microglial activation via minocycline could reverse the behavior and pathological defects in ALSP model mice. Methods We generated a Csf1r haploinsufficiency mouse model of ALSP using CRISPR/Cas9 genome editing and conducted electrophysiological recordings of long-term potentiation (LTP) and behavioral tests to validate the recapitulation of clinical ALSP characteristics in 8- to 11-month-old mice. RNA-sequencing was used to explore enriched gene expression in the molecular pathogenesis of ALSP. Microglial activation was assessed by immunofluorescent detection of Iba1 and CD68 in brain sections of male ALSP mice and pro-inflammatory activation and phagocytosis were assessed in Csf1r+/− microglia. Therapeutic effects were assessed by behavioral tests, histological analysis, and morphological examination after four weeks of intraperitoneal injection with minocycline or vehicle control in Csf1r+/− mice and wild-type control littermates. Results We found that synaptic function was reduced in LTP recordings of neurons in the hippocampal CA1 region, while behavioral tests showed impaired spatial and cognitive memory specifically in male Csf1r+/− mice. Increased activation, pro-inflammatory cytokine production, and enhanced phagocytic capacity were also observed in Csf1r+/− microglia. Treatment with minocycline could suppress the activation of Csf1r+/− microglia both in vitro and in vivo. Notably, the behavioral and pathological deficits in Csf1r+/− mice were partially rescued by minocycline administration, potentially due to inhibition of microglial inflammation and phagocytosis in Csf1r+/− mice. Conclusions Our study shows that CSF1R deficiency results in aberrant microglial activation, characterized by a pro-inflammatory phenotype and enhanced phagocytosis of myelin. Our results also indicate that microglial inhibition by minocycline can ameliorate behavioral impairment and ALSP pathogenesis in CSF1R-deficient male mice, suggesting a potential therapeutic target for CSF1R-related leukoencephalopathy. Collectively, these data support that minocycline confers protective effects against CSF1R-related microgliopathy in male ALSP model mice.

Background: Imatinib, sunitinib, and gefitinib are the three most common tyrosine kinase inhibitors (TKIs). However, their quantitative drug-drug interaction potentials In vivo and the relationship between their structure and inhibitory activity remain unknown. Objective: This study aimed to investigate the potential drug-drug interaction risk of three TKIs based on CYP3A. Methods: 6β-Hydroxylated testosterone formation was selected to probe the CYP3A activity in human liver microsomes. Molecular docking simulation was performed to explore the potential structural alerts. Results: Imatinib exhibited the strongest inhibitory effect towards CYP3A, while the inhibitory potential of gefitinib and sunitinib were comparable to each other but weaker than imatinib. IC50 shift assays demonstrated that the inhibitory potential of all three TKIs was significantly increased after a 30-min preincubation with NADPH. The KI and Kinact values of imatinib, sunitinib, and gefitinib were 3.75 μM and 0.055 min–1, 1.96 μM and 0.037 min–1, and 9.94 μM and 0.031 min–1, respectively. IVIVE results showed that there was a 1.3- to 43.1-fold increase in the AUC of CYP3A-metabolizing drugs in the presence of the TKIs. Conclusion: All three TKIs exhibited a typical irreversible inhibitory effect towards CYP3A. The presence of more N-heterocycles and the resulting better binding confirmation of imatinib may have been responsible for its stronger inhibitory effect than sunitinib and gefitinib. Therefore, caution should be taken when CYP3A-metabolizing drugs are co-administrated with imatinib, sunitinib, or gefitinib.