Impaired JAK-STAT pathway signaling in leukocytes of the frail elderly

Leonard Daniël Samson; Peter Engelfriet; W M Monique Verschuren; H Susan J Picavet; José A Ferreira; Mary-Lène de Zeeuw-Brouwer; Anne-Marie Buisman; A Mieke H Boots

doi:10.1186/s12979-021-00261-w

Impaired JAK-STAT pathway signaling in leukocytes of the frail elderly

Immun Ageing. 2022 Jan 17;19(1):5. doi: 10.1186/s12979-021-00261-w.

Authors

Leonard Daniël Samson^{1

2}, Peter Engelfriet³, W M Monique Verschuren^{3

4}, H Susan J Picavet³, José A Ferreira³, Mary-Lène de Zeeuw-Brouwer³, Anne-Marie Buisman³, A Mieke H Boots⁵

Affiliations

¹ National Institute of Public Health and the Environment, Bilthoven, The Netherlands. leon.samson@rivm.nl.
² Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands. leon.samson@rivm.nl.
³ National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
⁴ Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
⁵ Department of Rheumatology and Clinical Immunology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.

Abstract

Background: Elderly often show reduced immune functioning and can develop chronic low-grade inflammation. Why some elderly are more prone to become frail is unknown. We investigated whether frailty is associated with altered cytokine signaling through the JAK-STAT pathway in leukocytes of 34 individuals aged 65-74 years. In addition, we investigated how this relation is affected by chronic low-grade inflammation during the previous 20 years. Cytokine signaling was quantified by measuring intracellular STAT1, STAT3, and STAT5 phosphorylation in monocytes, B cells, CD4⁺ T cells and CD8⁺ T cells upon stimulation with IL-2, IL-6, IL-10, IFNα and IFNγ, using phospho-flow cytometry. Presence of chronic low-grade inflammation was investigated by evaluating 18 different plasma inflammatory markers that had been measured repeatedly in the same individuals over the previous 20 years. Frailty was assessed as a score on a frailty index.

Results: We found that lower cytokine-induced pSTAT responsiveness in the various cell subsets was seen with higher frailty scores in both men and women, indicative of dysfunctional pSTAT responses in frailer individuals. Associations differed between men and women, with frailer women showing lower pSTAT1 responses in monocytes and frailer men showing lower pSTAT5 responses in CD4⁺ and CD8⁺ T cells. Notably, lower IL-10-induced pSTAT3 responses in men were related to both higher frailty scores and higher CRP levels over the past 20 years. This might indicate poor resolution of low-grade inflammation due to defective regulatory pSTAT signaling in older men.

Conclusions: Our results emphasize the importance of preserved JAK-STAT pathway signaling in healthy aging and reveal cellular pSTAT levels as a candidate biomarker of frailty.

Keywords: Chronic low-grade inflammation; Frailty; Immune function; Immunosenescence; JAK-STAT pathway; Phospho-flow cytometry.