Dynamics Of The Crosstalk Between Pyroptotic And Apoptotic Signaling Pathways

Pyroptosis,is known as an inflammatory form of programmed cell death.Moderate pyroptosis is benefit for intracellular homeostasis,effectively protecting the multicellular organism and resisting infection.However,aberrant pyroptosis can lead to various diseases,including autoimmune diseases,cardiovascular,cancer,metabolic diseases,and even the infection mechanism of COVID-19,which has worldwide spreaded for the past two years,is closely related to pyroptosis.In recent years,the molecular mechanism of pyroptosis has been extensively studied,and the signaling pathway of pyroptosis has been preliminarily described.As further research,the crosstalk regulation between pyroptosis and apoptosis and other cell death modes has successively attracted attention,but the molecular mechanism for cell death decisionmaking remain to be elucidated.Due to most of the researches on pyroptosis are experimentally exploration,and theoretical researches are rare.In the first work,we constructed a five-dimensional core regulatory network model of the crosstalk between pyroptosis and apoptosis pathways in bone marrowderived macrophages(BMDMs)based on the experimental data and previous biological knowledge.Sensitivity analysis and bifurcation analysis were used to identify the two critical protein nodes,caspase-1 and Gsdmd.Moreover,the distribution of system stability in the phase plane of caspase-1 and Gsdmd expression was displayed.Nine of the 32 biochemical parameters in the model could regulate cell death modes switching,and these parameters could be divided into three categories,which regulate the activation of caspase-3 and Gsdmd and cell death modes by generating monostable,bistable and tristable dynamics.We further found that the reaction parameters of caspase-1 activation induced by stimulation can produce tristability.When the parameter is in the tristable range,cells may exhibit the concurrence of pyroptosis and apoptosis,that is the two death modes will occur simultaneously.In addition,we explored the effects of two-parameter variations in regulating cell death modes switching,which more truly revealed the possible molecular mechanism in pathological cells.In order to further study the molecular mechanism of cell death modes switching,in the second work,based on the results of above model and the three NLRP1bmediated signaling pathways proposed by biologists recently,we considered the comprehensive model for lethal toxin infection induced NLRPlb-mediated the crosstalk regulation of pyroptosis and apoptosis in ASC-reconstituted RAW 264.7 cells(RAW-asc).The model quantitatively explored the regulation of different expression levels of Gsdmd and caspase-1 on cell death modes switching.The results showed that both Gsdmd and caspase-1 expression exhibit threshold response on cell death modes switching.When the expression level of Gsdmd was 2%-20%,the concurrence of pyroptosis and apoptosis could be induced.Cells can selectively tend to pyroptosis or apoptosis,whereas pyroptosis occurs alone in the large range of 3%～100%caspase-1 expression.When the expression level of caspase-1 is exceedingly low(about 1%～3%),the concurrence of pyroptosis and apoptosis will occur.Apoptosis can be solely observed in caspl-/-cells.These results supported that Gsdmd should be considered as the optimal potential therapeutic target for NLRP lb inflammasome signaling.By further analysis,we revealed that caspase-1 employs the ASC-caspase-8dependent pathway to switch to apoptosis,while GSDMD primarily ignites the caspase-1-dependent pathway.Impairment of caspase-1 and GSDMD can severally induce the co-occurrence of pyroptosis and apoptosis.Landscape topographies of cell death uncover the co-occurrence death modes are quite different in caspase-1 and GSDMD impaired cells.Besides single pyroptosis and apoptosis state,a potential new"co-existing" state in single cells is proposed when GSDMD acts as the driving force of the landscape.The "seesaw model" is therefore proposed,which well illustrates the cell death modes that regulated by caspase-1 or GSDMD in single cells.In summary,our studies shed new light on the NLRP1b inflammasome signaling pathway and uncovers the switching mechanisms for different Gsdmd/caspase-1 expression among various death modes,providing potential clues to guide the development of more rational control strategies for diseases.