Researchers have discovered the skin's natural protection from nighttime bacterial invasion in mice, which may provide a basis for eventually developing a drug treatment.

The team focused on Staphylococcus aureus, a common skin-resident pathogen, which grows actively during the daytime in the skin of mice deficient in chemokine CXCL14. Healthy mice usually showed low bacterial growth during the day when the expression of this signaling protein was higher.

"Our results revealed the very strong rhythmic presence of CXCL14 -- high in the daytime and low in nighttime -- in mouse epidermis," says the senior author. 

"Among the chemokine family members, only CXCL14 is produced in epidermal cells in a circadian rhythm-dependent manner," notes the author. 

“The circadian-dependent role of CXCL14 is crucial as it transports important DNA into immune cells,” adds another author. This is akin to the timely delivery of strategic battle plans to an infantry platoon carrying out a defensive maneuver on invaders. 

The results of this study may also suggest that disrupting the circadian rhythm might be linked to poor skin health.

"It may be possible to enhance the antimicrobial function at the initial stage of infection by increasing the expression of CXCL14," adds the author.

https://www.pnas.org/doi/full/10.1073/pnas.2116027119