Optimisation of a screening platform for determining IL-6 inflammatory signalling in the senescence-associated secretory phenotype (SASP)

Cellular senescence has been shown to be sufficient for the development of multiple age-related pathologies. Senescent cells adopt a secretory phenotype (the SASP) which comprises a large number of pro-inflammatory cytokines, chemokines and proteases. The SASP itself is thought to be causative in many pathologies of age-related diseases, and there is growing interest in developing seno-modifying agents that can suppress the SASP. However, in order to identify new agents, it is necessary to conduct moderate to high throughput screening with robust assays for the required outcome. Here, we describe optimisation and validation of a cell-based biosensor HEK cell line for measurement of IL-6 concentrations within the range secreted into conditioned medium by primary senescent fibroblasts, adapted for a 384 well plate format suitable for library screening applications. We further show that the assay can measure changes in IL-6 secretion dependent on cell population age, and that the assay is responsive to mTOR inhibition in the senescent cells, which reduces the SASP, including IL-6. Hence, we propose that this optimised biosensor, which we term HEK-SASP, may prove of value in studies requiring robust, renewable and relatively inexpensive assays for measuring SASP factors.