Wu, Long‐Jun

Abstract Increased pro‐inflammatory cytokine levels and proliferation of activated microglia have been found in Parkinson's disease (PD) patients and animal models of PD, suggesting that targeting of the microglial inflammatory response may result in neuroprotection in PD. Microglial proliferation is regulated by many factors, but colony stimulating factor‐1 receptor (CSF1R) has emerged as a primary factor. Using data mining techniques on existing microarray data, we found that mRNA expression of the CSF1R ligand, CSF‐1, is increased in the brain of PD patients compared to controls. In two different neurotoxic mouse models of PD, acute MPTP and sub‐chronic LPS treatment, mRNA and protein levels of CSF1R and CSF‐1 were significantly increased. Treatment with the CSF1R inhibitor GW2580 significantly attenuated MPTP‐induced CSF1R activation and Iba1‐positive cell proliferation, without a reduction of the basal Iba1‐positive population in the substantia nigra. GW2580 treatment also significantly decreased mRNA levels of pro‐inflammatory factors, without alteration of anti‐inflammatory mediators, and significantly attenuated the MPTP‐induced loss of dopamine neurons and motor behavioral deficits. Importantly, these effects were observed in the absence of overt microglial depletion, suggesting that targeting CSF1R signaling may be a viable neuroprotective strategy in PD that disrupts pro‐inflammatory signaling, but maintains the beneficial effects of microglia.

AbstractMicroglial activation has been recognized as a major contributor to inflammation of the epileptic brain. Seizures are commonly accompanied by remarkable microgliosis and loss of neurons. In this study, we utilize the CX3CR1GFP/+ CCR2RFP/+ genetic mouse model, in which CX3CR1+ resident microglia and CCR2+ monocytes are labeled with GFP and RFP, respectively. Using a combination of time‐lapse two‐photon imaging and whole‐cell patch clamp recording, we determined the distinct morphological, dynamic, and electrophysiological characteristics of infiltrated monocytes and resident microglia, and the evolution of their behavior at different time points following kainic acid‐induced seizures. Seizure activated microglia presented enlarged somas with less ramified processes, whereas, infiltrated monocytes were smaller, highly motile cells that lacked processes. Moreover, resident microglia, but not infiltrated monocytes, proliferate locally in the hippocampus after seizure. Microglial proliferation was dependent on the colony‐stimulating factor 1 receptor (CSF‐1R) pathway. Pharmacological inhibition of CSF‐1R reduced seizure‐induced microglial proliferation, which correlated with attenuation of neuronal death without altering acute seizure behaviors. Taken together, we demonstrated that proliferation of activated resident microglia contributes to neuronal death in the hippocampus via CSF‐1R after status epilepticus, providing potential therapeutic targets for neuroprotection in epilepsy.

ABSTRACT Microglia as immune cells of the central nervous system (CNS) play significant roles not only in pathology but also in physiology, such as shaping of the CNS during development and its proper maintenance in maturity. Emerging research is showing a close association between microglia and the neurovasculature that is critical for brain energy supply. In this review, we summarize the current literature on microglial interaction with the vascular system in the normal and diseased brain. First, we highlight data that indicate interesting potential involvement of microglia in developmental angiogenesis. Then we discuss the evidence for microglial participation with the vasculature in neuropathologies from brain tumors to acute injuries such as ischemic stroke to chronic neurodegenerative conditions. We conclude by suggesting future areas of research to advance the field in light of current technical progress and outstanding questions. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 78: 604–617, 2018