Pro-inflammatory Effect of Downregulated CD73 Expression in EAE Astrocytes

Area of Science:

• Neuroimmunology
• Immunology
• Cell Biology

Background:

• CD73 (Cluster of Differentiation 73) is an ectonucleotidase crucial for regulating immune responses through adenosine production.
• Adenosine, a product of CD73 activity, generally exerts anti-inflammatory effects within the central nervous system (CNS).
• Experimental Autoimmune Uveitis (EAU) is an inflammatory disease model involving immune cell infiltration and activation within the eye and CNS.

Purpose of the Study:

• To investigate alterations in CD73 expression, localization, and activity in brain cells, particularly neuroglia, during EAU.
• To determine if changes in CD73 on brain cells influence the activation of effector T cells.
• To elucidate the role of astrocyte CD73 in the pathogenesis of EAU.

Main Methods:

• Flow cytometry was used to quantify membrane-bound CD73 on various brain cell types from naïve and EAU-induced mice.
• Wild-type and CD73-deficient (CD73-/-) astrocytes were utilized to assess CD73's impact on astrocyte function and T cell activation.
• Experiments involved manipulating extracellular adenosine levels and using CD73 inhibitors or adenosine receptor antagonists.

Main Results:

• A significant decrease in membrane-bound CD73 was observed in astrocytes from EAU-induced mice compared to controls.
• CD73 deficiency in astrocytes impaired their ability to be modulated by extracellular AMP, while adenosine could still inhibit their function.
• Interaction with CD4+ T cells led to CD73 downregulation on astrocytes in EAU models, correlating with disease progression.

Conclusions:

• Astrocytes downregulate CD73 during EAU, likely due to interactions with infiltrating CD4+ T cells.
• This CD73 loss on astrocytes reduces local adenosine generation, diminishing its anti-inflammatory effects.
• The downregulation of CD73 in astrocytes represents a pro-inflammatory mechanism that facilitates EAU pathogenesis.