Acute Active, But Not Passive, Psychological Stress Increases Nonclassical Monocyte Proportions

Abstract

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 nonclassical (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-minute 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-minute 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 = .007) and NCM proportions increased (6.8% to 2.1%; p = .035) from baseline to immediately post-PASAT. There were no differences in monocyte subsets from baseline to post-IAPS (CM% p > .99; IM% p > .99; NCM% p > .99). NLR and SIRI did not differ from baseline in response to either the PASAT or IAPS ( p > .05).

Conclusions: 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.

Keywords: Systemic Inflammation Response Index; monocyte subsets; neutrophil lymphocyte ratio; psychological stress.