Differential expression of Toll-like receptor 2 and 4 on peritoneal leukocyte populations from long-lived and non-selected old female mice

Intracellular cytokines in peritoneal leukocytes relate to lifespan in aging and long-lived female mice

Peritoneal immune cell function is a reliable indicator of aging and longevity in mice and inflammaging is associated with a shorter lifespan. Nevertheless, it is unknown if the content of cytokines in these immune cells is linked to individual differences in lifespan. Therefore, this work aimed to investigate different peritoneal leukocyte populations and their content in intracellular pro-inflammatory (TNF and IL-6) and anti-inflammatory (IL-10) cytokines by flow cytometry in adult (10 months-old, n = 8) and old (18 months-old, n = 20) female Swiss/ICR mice. In addition, old mice were monitored longitudinally throughout their aging process, and the same markers were analyzed at the very old (24 months-old, n = 8) and long-lived (30 months-old, n = 4) ages. The longitudinal follow-up allowed us to relate the investigated parameters to individual lifespans. The results show that long-lived female mice exhibit an adult-like profile in most parameters investigated but also display specific immune adaptations, such as increased CD4+ and CD8+ T cells containing the pro-inflammatory TNF cytokine and CD4+ T cells and macrophages containing the anti-inflammatory cytokine IL-10. These adaptations may underlie their exceptional longevity. In addition, a negative correlation was obtained between the percentage of cytotoxic T cells, KLRG-1/CD4, large peritoneal macrophages, and the percentage of CD4+ T cells containing IL-6 and macrophages containing IL-10 in old age and lifespan, whereas a positive correlation was found between the CD4/CD8 ratio and the longevity of the animals at the same age. These results highlight the crucial role of peritoneal leukocytes in inflammaging and longevity.

Senescent endothelial cells: Potential modulators of immunosenescence and ageing

Recent studies have demonstrated that the accumulation of senescent endothelial cells may be the primary cause of cardiovascular diseases. Because of their multifunctional properties, endothelial cells actively take part in stimulating the immune system and inflammation. In addition, ageing is characterized by the progressive deterioration of immune cells and a decline in the activation of the immune response. This results in a loss of the primary function of the immune system, which is eliminating damaged/senescent cells and neutralizing potential sources of harmful inflammatory reactions. In this review, we discuss cellular senescence and the senescence-associated secretory phenotype (SASP) of endothelial cells and summarize the link between endothelial cells and immunosenescence. We describe the possibility that age-related changes in Toll-like receptors (TLRs) and microRNAs can affect the phenotypes of senescent endothelial cells and immune cells via a negative feedback loop aimed at restraining the excessive pro-inflammatory response. This review also addresses the following questions: how do senescent endothelial cells influence ageing or age-related changes in the inflammatory burden; what is the connection between ECs and immunosenescence, and what are the crucial hypothetical pathways linking endothelial cells and the immune system during ageing.

Higher mortality and impaired elimination of bacteria in aged mice after intracerebral infection with E. coli are associated with an age-related decline of microglia and macrophage functions

Incidence and mortality of bacterial meningitis are strongly increased in aged compared to younger adults demanding new strategies to improve prevention and therapy of bacterial central nervous system (CNS) infections the elderly.

Here, we established a geriatric mouse model for an intracerebral E. coli infection which reflects the clinical situation in aged patients: After intracerebral challenge with E. coli K1, aged mice showed a higher mortality, a faster development of clinical symptoms, and a more pronounced weight loss. Elimination of bacteria and systemic inflammatory response were impaired in aged mice, however, the number of infiltrating leukocytes and microglial cells in the CNS of aged and young mice did not differ substantially.

In vitro, primary microglial cells and peritoneal macrophages from aged mice phagocytosed less E. coli and released less NO and cyto-/chemokines compared to cells from young mice both without activation and after stimulation by agonists of TLR 2, 4, and 9.

Our results suggest that the age-related decline of microglia and macrophage functions plays an essential role for the higher susceptibility of aged mice to intracerebral infections. Strategies to improve the phagocytic potential of aged microglial cells and macrophages appear promising for prevention and treatment of CNS infections in elderly patients.

Age and low levels of circulating vitamin D are associated with impaired innate immune function

This study investigated in vivo the influence of age and vitamin D status on innate immune function in HC. Serum 25OHD was measured in 71 HC. TLR expression on various subpopulations of PBMCs, as well as TLR function by stimulating PBMCs with specific ligands, was assessed by flow cytometry. Circulating cathelicidin levels were determined by ELISA. Serum 25OHD levels decreased with age, and there was a significant inverse correlation between 25OHD levels and age. There was a negative correlation between serum 25OHD levels and MFI expression of TLR7 on B cells, T cells, and monocytes. TLR7 function, addressed by in vitro stimulation with a specific agonist, was significantly correlated with serum 25OHD levels, and this was especially a result of the results in HC older than 60 years. MFI expression of TLR5 on T cells and TLR2 on monocytes was also negatively correlated with serum 25OHD levels. TLR1 (monocytes) and TLR2 (monocytes) expression was positively correlated with age. Furthermore, TLR4 and TLR8 function was negatively correlated with age. Circulating cathelicidin levels decreased with age and were positively correlated with 25OHD levels. Aging is accompanied by changes in expression and function of several TLRs. Serum 25OHD levels decrease with age and are also associated with a change in expression and defective function of certain TLRs, especially those involved in viral response.