Age-dependent messenger RNA expression of toll-like receptor 4 and intercellular adhesion molecule-1 in peripheral blood mononuclear cells

Background: Inflammation plays an important role in the ageing process in which monocytes/macrophages are important players. Intercellular adhesion molecule-1 (ICAM-1), tumour necrosis factor-α (TNF-α) and Toll-like receptor 4 (TLR4) are well-known inflammatory markers. This study aimed to investigate the relationship between age and the expression and correlation of ICAM-1, TNF-α and TLR4 mRNA in peripheral blood mononuclear cells (PBMCs).

Methods: A total of 239 participants were recruited in a medical centre in Taiwan. The mRNA isolated from the PBMCs was used to determine the levels of ICAM-1, TNF-α and TLR4 mRNAs with real-time polymerase chain reaction (PCR). The propensity-matched analysis was also applied for subgroup analysis.

Results: When compared 189 older adults (≧65 years) to 50 younger adults (<65 years), the ICAM-1, TNF-α and TLR4 mRNA levels in PBMCs were significantly higher in older adults (2.00 ± 0.72 vs 0.87 ± 0.34 for ICAM-1, 2.32 ± 0.69 vs 1.15 ± 0.44 for TNF-α and 1.56 ± 0.47 vs 1.05 ± 0.51 for TLR4, and all P < .0001). Also, both age and TLR4 were independent factors affecting mononuclear cell ICAM-1 in the multiple linear regression analysis (P < .0001).

Conclusion: The mRNA levels of ICAM-1 and TLR4 in PBMCs are higher in older adults than those in younger adults. TLR4 is an independent factor affecting ICAM-1 expression in PBMCs, especially in older adults. This may suggest that ICAM-1 and TLR4 in PBMCs are potential biomarkers and their relationship may shed some light on the ageing process.