Markers of the cytokine profile in determining the aging phenotype

BACKGROUND . Age-related changes occurring in the immune system during aging include dysregulation at the level of innate immunity and are described as inflammatory aging or “inflammaging.” Inflammatory aging presupposes lowlevel systemic inflammation, which is present even in clinically healthy people of older age groups and characterized by elevated blood levels of inflammatory mediators, including proinflammatory cytokines. Inflammatory reactions play a dual role: on the one hand, providing a protective reaction; on the other hand, mediating tissue damage with excess inflammation and its chronization. It is assumed that the nature of the aging process and the development of age-associated pathology are related to the balance of pro- and anti-inflammatory cytokines. AIM. To assess the levels of pro- and anti-inflammatory cytokines in long-living and elderly patients with various aging phenotypes.

MATERIALS AND METHODS. The study included 80 elderly participants (mean age: 81.8 years), 100 long-living participants (mean age: 92.2 years) and 50 young participants (mean age: 22.4 years) as a comparison group. The groups of elderly and long-living participants were divided into subgroups of the physiological and pathological phenotype of aging based on clinical data: the Charlson Comorbidity Index, the Short Physical Performance Battery and the MiniMental State Examination. The cytokine levels of patients in the study groups were assessed by enzyme immunoassay (ELISA) in blood serum, as well as in mononuclear cell culture (MNC) supernatants after 24 h of cultivation. The concentrations of the following cytokines were determined: IL-1β, IL-4, IL-6, IL-10, IL-18, TNFa, TGFß (Vector-Best kits, Russia and CloudClone Corp.,USA). The obtained data were assessed using the Statistica 14 software package (StatSoft, Europe) and GraphPad Prizm (Prizm, USA).

RESULTS. Assessment of serum cytokine levels showed that the concentration of both pro-inflammatory cytokines IL-6, TNFa, IL-1β, IL-18 and anti-inflammatory cytokines IL-10, TGFß was increased in the group of long-living participants. At the same time, an imbalance of cytokines was revealed in the elderly group, manifested by an increase in the concentration of IL-6 and a decrease in the level of IL-10 and TGFß. This imbalance of pro- and anti-inflammatory cytokines assumedly determines the transition from the phenotype of normal aging to a pathological variant characterized by the development of age-associated pathology. In addition, we revealed an increase in the level of IL-4 with a normal aging phenotype, which can be considered as a marker of this phenotype, and an increase in the levels of IL-6, TNFα as markers of the pathological phenotype of aging in elderly and long-living participants. The concentrations of cytokines IL-1, IL-4, IL-6, IL-10 and TNFα detected in blood serum are quite low. This leads to the need to make a diagnostic decision based on values at the lower detection limits of modern test systems, and, consequently, to low sensitivity of such markers. In this regard, we evaluated the levels of these cytokines in MNC cultures isolated from the peripheral blood of patients in the study groups. The obtained data showed that the concentrations of cytokines IL-1, IL-6, IL-10 and TNFα in cell culture are ten-fold higher than their concentration in peripheral blood, while they are significantly increased in elderly and long-living participants compared with young participants. Increased production of IL-6 and TNFα was also detected in the group of elderly and longliving participants with a pathological aging phenotype. At the same time, the concentration of the anti-inflammatory cytokine IL-10 also increased with age, but did not depend on the aging phenotype, which characterizes the revealed imbalance of pro- and anti-inflammatory cytokines in the pathological aging phenotype.

CONCLUSIONS. The identified markers of the pathological and normal aging phenotypes help predict the development of age-associated pathology or longevity. Our proposed study of cytokines in MNC culture may be more informative than the assessment of cytokines in peripheral blood serum.