Acute Active, but not Passive, Psychological Stress Increases non-classical Monocyte Proportions.

Objective: Psychological stress exposure is a modifiable risk factor for cardiovascular disease (CVD), possibly through promoting a heightened inflammatory milieu. Under psychological stress, changes in monocyte subsets from classical (CM) to intermediate (IM) and non-classical (NCM) could indicate a more pro-inflammatory environment. We investigated the impact of acute psychological stress (active and passive) on monocyte subsets and leukocyte count ratios.

Methods: Twenty-four participants completed a 20-min baseline period, followed by a passive (International Affective Picture System: IAPS) and active stress task (socially evaluative Paced Auditory Serial Addition Test: PASAT) with 90-min recovery after each task. Blood samples were collected to determine changes in: CM, IM and NCM count/proportions, systemic inflammation response index (SIRI) and neutrophil:lymphocyte ratio (NLR).

Results: CM proportions decreased (89.4% to 87.0%; P=0.007) and NCM proportions increased (6.8% to 2.1%; P=0.035) from baseline to immediately post-PASAT. There were no differences in monocyte subsets from baseline to post-IAPS (CM% P>0.99; IM% P=>0.99; NCM% P>0.99). NLR and SIRI did not differ from baseline in response to either the PASAT or IAPS (P>0.05).

Conclusion: Acute active, but not passive, psychological stress promoted a transition in monocyte subsets towards a more pro-inflammatory environment, which may be an important advancement in markers used to assess the inflammatory response to acute psychological stress.