SP2 The impact of metabolic stress on inflammasome activation in endothelial cells

Project Leader: Regine Heller

Background and previous work
Cellular metabolic stress arises in conditions of either nutrient excess (increased glucose, cholesterol or long chain saturated fatty acids) or nutrient depletion. Nutrient excess is often associated with increased generation of reactive oxygen species (ROS) and an inflammatory response via activation of the inflammasome while nutrient depletion activates several energy-sensing pathways including induction of autophagy. Autophagy is also involved in stress responses leading to cell protection under mild stress and to cell damage under severe stress. Data from our current RTG project show that autophagy is essentially involved in the maintenance of endothelial function under basal and growth factor-stimulated conditions and is dose-dependently induced by oxidants.

Specific aims and working programme
The aim of this follow-up RTG project is to investigate the effect of metabolic stressors on the activation of the inflammasome in endothelial cells and to clarify the role of autophagy as an antiinflammatory mechanism contributing to resistance and persistence. Our hypothesis is that metabolic stressors stimulate an inflammatory response, which can be counteracted by simultaneously induced autophagy. We propose that balancing the inflammatory response by autophagy depends on the extent of metabolic stress and that either increasing stress or inhibiting autophagy may lead to cellular damage and cell death.
To address these questions we will investigate the dose- and time-dependent effects of metabolic stressors such as high glucose or palmitate on parameters of the NLRP3 inflammasome activation (expression of NLRPS, ASC and procaspase-1; caspase 1 activation, IL1b cleavage, ROS) and on autophagy induction (expression of autophagy proteins, LC3B conjugation, mitophagy markers). In addition, we will characterise how inhibition of autophagy (downregulation of autophagy proteins, PI3K inhibitors) affects the inflammatory response and explore the underlying mechanisms. Finally, we will apply activators of AMPK, which have been shown to stimulate autophagy in our previous studies, in vitro and in vivo and test their effects on inflammasome activation.