PDE4B deficiency aids macrophage differentiation and contributes to Cryptococcus neoformans brain infection

Area of Science:

• * Neuroimmunology
• * Infectious Diseases
• * Cellular and Molecular Biology

Background:

• * Cryptococcal meningitis is a life-threatening complication of Cryptococcus neoformans (C. neoformans) infection.
• * Macrophages are implicated as

Purpose of the Study:

• * To elucidate the mechanisms of macrophage-mediated C. neoformans brain invasion.
• * To identify regulators of macrophage function in cryptococcal meningitis.
• * To explore phosphodiesterase 4B (PDE4B) as a potential therapeutic target.

Main Methods:

• * Single-cell RNA sequencing (scRNA-Seq) of immune cells from a murine model of cryptococcal meningitis.
• * Bioinformatics analysis to identify key regulatory molecules.
• * In vitro and in vivo experiments assessing the role of PDE4B in macrophage function and fungal dissemination.

Main Results:

• * PDE4B expression in macrophages is associated with C. neoformans infection, with a paradoxical decrease by virulent strains.
• * PDE4B inhibition enhances macrophage markers (Arg1, CXCR4, CCR7) and promotes C. neoformans-infected macrophage transmigration across the blood-brain barrier (BBB) in vitro.
• * PDE4B inhibition or knockout increases fungal burden in the brain, while PDE4B activation reduces it, even after infection onset.

Conclusions:

• * PDE4B is a critical regulator of macrophage programming during C. neoformans infection.
• * The study reveals a macrophage-mediated dissemination mechanism contributing to cryptococcal meningitis.
• * PDE4B represents a promising therapeutic target for cryptococcal meningitis.