A P2RY12 deficiency results in sex-specific cellular perturbations and sexually dimorphic behavioral anomalies.

Microglia are sexually dimorphic, yet, this critical aspect is often overlooked in neuroscientific studies. Decades of research have revealed the dynamic nature of microglial-neuronal interactions, but seldom consider how this dynamism varies with microglial sex differences, leaving a significant gap in our knowledge. This study focuses on P2RY12, a highly expressed microglial signature gene that mediates microglial-neuronal interactions, we show that adult females have a significantly higher expression of the receptor than adult male microglia. We further demonstrate that a genetic deletion of P2RY12 induces sex-specific cellular perturbations with microglia and neurons in females more significantly affected. Correspondingly, female mice lacking P2RY12 exhibit unique behavioral anomalies not observed in male counterparts. These findings underscore the critical, sex-specific roles of P2RY12 in microglial-neuronal interactions, offering new insights into basal interactions and potential implications for CNS disease mechanisms.

Distinguishing the effects of systemic CSF1R inhibition by PLX3397 on microglia and peripheral immune cells.

Microglia, the primary immune cells of the central nervous system (CNS), are derived from the yolk sac and populate the brain during development. Once microglia migrate to the CNS, they are self-renewing and require CSF1R signaling for their maintenance. Pexidartinib (PLX3397, PLX), a small molecule inhibitor of the CSF1R, has been shown to effectively deplete microglia since microglial maintenance is CSF1R-dependent. There have, however, been several conflicting reports that have shown the potential off-target effects of PLX on peripheral immune cells particularly those of lymphoid origin. Given this controversy in the use of the PLX family of drugs, it has become important to ascertain to what extent PLX affects the peripheral immune profile in lymphoid (spleen, and bone marrow) and non-lymphoid (kidney, lungs, and heart) organs. PLX3397 chow treatment at 660 mg/kg for 7 days significantly reduced CD45+ macrophages, CX3CR1-GFP cells, CD11b+CD45intermediate cells, and P2RY12 expression in the brain. However, there were minimal effects on peripheral immune cells from both lymphoid and non-lymphoid organs except in the heart where there was a significant decrease in CD3+ cells, inflammatory and patrolling monocytes, and CD11b+Ly6G+ neutrophils. We then stimulated the immune system with 1 mg/kg of LPS which resulted in a significant reduction in the number of innate immune cells. In this context, PLX did not alter the cytokine profile in the serum and the brain of naïve mice but did so in the LPS-stimulated group resulting in a significant reduction in TNFα, IL-1α, IFN-γ and IL-1ß. Furthermore, PLX did not alter locomotor activity in the open field test suggesting that microglia do not contribute to LPS-induced sickness behavior. Our results provide an assessment of immune cell populations with PLX3397 treatment on brain, lymphoid and non-lymphoid organs without and during LPS treatment that can serve as a resource for understanding consequences of such approaches.

Potential link between Complement 5a Receptor and mood disorders in mouse exposed to experimental malaria in utero.

In Africa, a large number of pregnancies are exposed to Plasmodium falciparum infection. The in-utero environment extremely influences childhood neurodevelopment and behaviour. The complement 5a receptor (C5aR) is linked to several disease conditions. However, the influence of Plasmodium berghei during pregnancy on maternal complement 5a receptor and subsequently on fetal behaviour is unknown. Pregnant mice were intra-peritoneally inoculated on gestational day 13 with 1.02x105 infected red blood cells (iRBCs). iRBCs used in this experiment were gotten by in vivo passage of P. berghei in mice when the level of iRBCs have gotten to about 10-20%. A section of pregnant mice (both test and control groups) were earmarked to give birth and their offspring monitored up to postnatal day 42 when depression-like behaviour was evaluated using tail suspension test model. The other pregnant mice were subjected to cardiac puncture on gestational day 19 for C5a receptor estimation using Elisa assay. Results showed that pregnant mice infected with P. berghei had elevated C5a receptor compared with uninfected pregnant females. It was also shown that P. berghei-exposed offspring presented a depressive-like behaviour compared to unexposed controls. It may be concluded from this study, that complement 5a receptor demonstrates a pathogenic role in signaling and its possible role in mediating depression linked to Plasmodium berghei exposure in utero.