Sustained exposure to high glucose induces differential expression of cellular senescence markers in murine macrophages but impairs immunosurveillance response to senescent cells secretome.

Abstract

The influence of chronic diseases on various facets of macrophage cellular senescence is poorly understood. This study evaluated the impact of chronic hyperglycemia on the induction of cellular senescence and subsequent immunosurveillance functions in RAW264.7 macrophages. Macrophages were cultured under normal glucose (NG; 5mM), high glucose (HG; 20mM), and very high glucose (VHG; 40mM) conditions and assessed for markers of cellular senescence. Hyperglycemia induced strong upregulation of SA-β-gal activity, and loss ofPCNAandLamin B1gene expression while markers of cell cycle arrest generally decreased. Non-significant changes in SASP-related proteinswere observed while ROS levels slightly decreased and mitochondrial membrane potential increased. Protein concentration on the exosome membrane surface and their stability appeared to increase under hyperglycemic conditions. However, when macrophages were exposed to the secretory media (SM) of senescent preadipocytes, a dramaticincrease in the levels of all inflammatory proteins was recorded especially in the VHG group that was also accompanied by upregulation of NF-κB and NLRP3 gene expression. SM treatment to hyperglycemic macrophages activated theTLR-2/Myd88pathway but decreased the expression of scavenger receptorsRAGE, CD36, andOlr-1whileCD44andCXCL16expression increased. On exposure to LPS, a strong upregulation in NO, ROS, and inflammatory cytokines was observed. Together, these results suggest that primary markers of cellular senescence are aberrantly expressed under chronic hyperglycemic conditions in macrophages with no significant SASP activation. Nonetheless, hyperglycemia strongly deregulates macrophage functions leading to impaired immunosurveillance of senescent cells and aggravation of inflamm-aging. This work provides novel insights into howhyperglycemia-induced dysfunctions can impact the potency of macrophages to manage senescent cell burden in aging tissues.