Phosphodiesterase type 4 (PDE4) modulates inflammation and epithelial integrity in which cells?

Phosphodiesterase type 4 (PDE4) is an enzyme that plays a significant role in the regulation of inflammation and cellular signaling processes. It is particularly important in immune and inflammatory responses. The correct choice highlights the involvement of PDE4 in brain cells (neurons and glial cells), where it helps to regulate the levels of cyclic adenosine monophosphate (cAMP).

In the central nervous system, PDE4 influences various physiological processes, including the modulation of neuroinflammation, which can impact conditions such as depression and neurodegenerative diseases. By degrading cAMP, PDE4 can affect signaling pathways that are crucial for maintaining neuronal health and promoting an appropriate inflammatory response.

The other options, while they may have roles in inflammation or cellular integrity to some extent, do not have the same degree of association with PDE4 as brain cells do. For instance, muscle cells are more related to physical movement and metabolic processes, liver cells primarily manage metabolism and detoxification, and skin cells are involved in barrier functions and local immune responses. However, none directly connect PDE4's modulation of inflammation and cellular integrity as directly as brain cells do.