The innate immune system provides the first line of defense against cellular perturbations. Innate immune activation elicits inflammatory programmed cell death in response to microbial infections or alterations in cellular homeostasis. Among the most well-characterized programmed cell death pathways are pyroptosis, apoptosis, and necroptosis. While these pathways have historically been defined as segregated and independent processes, mounting evidence shows significant crosstalk among them. These molecular interactions have been described as ‘crosstalk’, ‘plasticity’, ‘redundancies’, ‘molecular switches’, and more. Here, we discuss the key components of cell death pathways and note several examples of crosstalk. We then explain how the diverse descriptions of crosstalk throughout the literature can be interpreted through the lens of an integrated inflammatory cell death concept, PANoptosis. The totality of biological effects in PANoptosis cannot be individually accounted for by pyroptosis, apoptosis, or necroptosis alone. We also discuss PANoptosomes, which are multifaceted macromolecular complexes that regulate PANoptosis. We consider the evidence for PANoptosis, which has been mechanistically characterized during influenza A virus, herpes simplex virus 1, Francisella novicida, and Yersinia infections, as well as in response to altered cellular homeostasis, in inflammatory diseases, and in cancers. We further discuss the role of IRF1 as an upstream regulator of PANoptosis and conclude by reexamining historical studies which lend credence to the PANoptosis concept. Cell death has been shown to play a critical role in infections, inflammatory diseases, neurodegenerative diseases, cancers, and more; therefore, having a holistic understanding of cell death is important for identifying new therapeutic strategies.

Innate immunity provides the critical first line of defense against infection and sterile triggers. Inflammatory cell death is a key component of the innate immune response to clear pathogens, but excessive or aberrant cell death can induce inflammation, cytokine storm, and pathology, making it a central molecular mechanism in inflammatory diseases. Alcohol-associated liver disease (ALD) is one such inflammatory disease, and the specific innate immune mechanisms driving pathology in this context remain unclear. Here, by leveraging RNA-seq and protein expression analyses in tissues from clinical samples, we identified increased expression of the innate immune sensor ZBP1 in patients with ALD. ZBP1 expression correlated with ALD progression in patients and that ethanol induced ZBP1-dependent lytic cell death, PANoptosis, in immune (macrophages, monocytes, and Kupffer cells) and nonimmune cells (hepatocytes). Mechanistically, the interferon regulatory factors (IRFs) IRF9 and IRF1 upregulated basal ZBP1 expression. Activation of ZBP1 led to PANoptosis via caspase-8 and cell membrane rupture through NINJ1, independent of gasdermin D, gasdermin E, and MLKL. In mouse models of ALD, ZBP1-deficient mice were significantly protected from disease pathology and liver damage. Furthermore, the expressions of ZBP1 and NINJ1 were upregulated in both liver and serum samples from patients with ALD, implicating these molecules as potential biomarkers. Overall, our findings establish the critical role of the IRF–ZBP1–caspase-8–NINJ1 axis in driving inflammatory cell death, PANoptosis, suggesting that targeting these molecules will have therapeutic potential in ALD and other inflammatory conditions.

The liver stage of the Plasmodium life cycle features sporozoite traversal of the liver sinusoidal barrier through Kupffer cells (KCs) followed by invasion of hepatocytes. Little is known about the interaction of Plasmodium sporozoites with KCs, the liver-resident macrophages. Previous reports suggest KCs do not mount a pro-inflammatory response and undergo cell death following this interaction. Our work explores this interaction using primary rat KCs (PRKCs) and Plasmodium berghei sporozoites. We analyzed PRKC culture supernatants for markers of an immunological response through cytokine arrays. Additionally, cell wounding and death were assessed by monitoring lactate dehydrogenase (LDH) levels in these supernatants and by live/dead cell imaging. We found that PRKCs mount an immunological response to P. berghei sporozoites by releasing a diverse set of both pro- and anti-inflammatory cytokines, including IFNγ, IL-12p70, Mip-3α, IL-2, RANTES, IL-1α, IL-4, IL-5, IL-13, EPO, VEGF, IL-7, and IL-17α. We also observed no difference in LDH level or live/dead staining upon sporozoite exposure, suggesting that the KCs are not deeply wounded or dying. Overall, our data suggest that sporozoites may be actively modulating the KC’s reaction to their presence and altering the way the innate immune system is triggered by KCs.

Innate immunity provides the critical first line of defense against infection and sterile triggers. Cell death is a key component of the innate immune response to clear pathogens, but excessive or aberrant cell death can induce inflammation, cytokine storm, and pathology, making it a central molecular mechanism in inflammatory diseases. Alcohol-associated liver disease (ALD) is one such inflammatory disease, but the specific innate immune mechanisms driving pathology in this context remain unclear. Here, by leveraging RNAseq and tissue expression in clinical samples, we identified increased expression of the innate immune sensor Z-DNA binding protein (ZBP1) in patients with ALD. We discovered that ZBP1 expression correlated with ALD progression in patients, and that ethanol induced ZBP1-dependent lytic cell death, PANoptosis, in immune (macrophages, monocytes, Kupffer cells) and non-immune cells (hepatocytes). Mechanistically, the interferon regulatory factors (IRFs) IRF9 and IRF1 upregulated ZBP1 expression, allowing ZBP1 to sense Z-NAs through its Zα2 domain and drive PANoptosis signaling, cell membrane rupture through NINJ1, and DAMP release. Furthermore, the expressions of ZBP1 and NINJ1 were upregulated in both liver and serum samples from patients with ALD. In mouse models of chronic and acute ALD, ZBP1-deficient mice were significantly protected from disease pathology and liver damage. Overall, our findings establish the critical role of the ZBP1-NINJ1 axis regulated by IRFs in driving inflammatory cell death, PANoptosis, in liver cells, suggesting that targeting these molecules will have therapeutic potential in ALD and other inflammatory conditions.