Caspase mechanisms in the regulation of inflammation

Caspase-1 is critical for mice in the defense against Streptococcus equi subsp. zooepidemicus infection by promoting macrophage phagocytosis

Streptococcus equi subsp. zooepidemicus (SEZ) is an important pathogen which is responsible for a wide range of diseases in various species. Macrophages are professional phagocytes that can engulf microorganisms and trigger responses leading to microbial death. Caspase-1 is considered as a proinflammatory factor that mediates antibacterial response to protect hosts from bacteria. Here, we revealed a novel role of Caspase-1 in mice against SEZ. Through both in vitro and in vivo infection assays, we demonstrated that the maturation and secretion of the cytokine IL-1β are critically dependent on Caspase-1 activation. The Caspase-1 deficient mice displayed attenuation of bactericidal activity against SEZ, mainly by decreasing the accumulation of macrophage. In addition to the recruitment of macrophages, deficiency of Caspase-1 also impaired the phagocytosis of SEZ by macrophages. Our study demonstrated that Caspase-1 is critical for mice to defense against SEZ depending on the recruitment and phagocytosis of macrophage.

Network Pharmacology Analysis and Experimental Validation of Tectoridin in the Treatment of Ischemic Stroke by Inhibiting Apoptosis and Regulating Inflammation

The flowers of Pueraria lobate (Puerariae Flos) have served as a traditional Chinese medicinal and food herbage plant for many years. Tectoridin is one of the most active metabolites extracted from flowers of Pueraria lobate and has a variety of beneficial activities, including antioxidative, hypoglycemic, and anti-inflammatory activities. Nevertheless, the functions and potential mechanisms underlying tectoridin in cerebral ischemia/reperfusion injury have not been well interpreted; thus, a network analysis strategy was performed to systematically evaluate its pharmacological mechanisms, which were further validated in rats with cerebral ischemia. Network analysis predicted that tectoridin could attenuate brain damage after stroke by modulating signaling pathways associated with redox, inflammation, and autophagy. The experimental results demonstrated an improvement in neurological function in rats treated with tectoridin, along with a significant reduction in cerebral infarction volume. The neuroprotective benefits of tectoridin stem, in part, from its antioxidant capabilities, which include the upregulation of Nrf2/HO-1 protein expression, reduction of the TLR4/MYD88/NF-κB inflammatory pathway, and inhibition of the PI3K/Akt/mTOR pathway, contributing to its anti-apoptotic effects. This investigation offers a thorough examination of the pathways and targets linked to the therapeutic effects of tectoridin on ischemic stroke, highlighting its anti-inflammatory, antioxidative, and anti-apoptotic mechanisms. These findings serve as a valuable reference for the development and exploration of effective anti-ischemic stroke medications.

ACNO hydrogel enhances diabetic wound healing by modulating the Bcl-2/Bax/Caspase-3/PARP pathway

Centella asiatica (L.) Urban, one of the authentic medicinal materials from Guizhou Province in China, has been traditionally applied for the treatment of contusions and fractures, as well as for promoting wound healing. Preliminary research suggests that asiaticoside-nitric oxide hydrogel (ACNO) exhibits the potential to enhance the healing of diabetic wounds (DWs); however, the underlying molecular mechanisms require further elucidation. Here, we aim to identify ACNO's anti-apoptotic targets and its mode of action in DWs treatment. ACNO was applied topically on db/db and db/m mice with DWs. Wound healing was evaluated through photography, histology, and molecular analyses including molecular docking, RT-qPCR, and western blotting. The impact of ACNO on cell migration and apoptosis was assessed in hyperglycosylated HFF-1 cells using CCK-8, scratch, and cloning assays, with molecular mechanisms confirmed using a Bcl-2 inhibitor. ACNO hydrogel promotes wound epithelialization and angiogenesis in diabetic mice, and also regulates abnormal apoptosis of wound cells. In vitro studies showed that ACNO promoted the proliferation and migration of hyperglycosylated HFF-1 cells and enhanced their anti-apoptotic capacity in vitro. Further experimental studies showed that ACNO hydrogel enhances the healing process of DWs by modulating the Bcl-2/Bax/Caspase-3/PARP signaling cascade, which stimulates cell growth and movement, encourages the formation of new blood vessels, and diminishes cell death. This discovery presents a pioneering approach to harnessing the potential of traditional chinese medicine for the management of persistent and challenging injuries, including DWs.

Targeting regulated cell death: Apoptosis, necroptosis, pyroptosis, ferroptosis, and cuproptosis in anticancer immunity

In the evolving landscape of cancer treatment, the strategic manipulation of regulated cell death (RCD) pathways has emerged as a crucial component of effective anti-tumor immunity. Evidence suggests that tumor cells undergoing RCD can modify the immunogenicity of the tumor microenvironment (TME), potentially enhancing its ability to suppress cancer progression and metastasis. In this review, we first explore the mechanisms of apoptosis, necroptosis, pyroptosis, ferroptosis, and cuproptosis, along with the crosstalk between these cell death modalities. We then discuss how these processes activate antigen-presenting cells, facilitate the cross-priming of CD8+ T cells, and trigger anti-tumor immune responses, highlighting the complex effects of novel forms of tumor cell death on TME and tumor biology. Furthermore, we summarize potential drugs and nanoparticles that can induce or inhibit these emerging RCD pathways and their therapeutic roles in cancer treatment. Finally, we put forward existing challenges and future prospects for targeting RCD in anti-cancer immunity. Overall, this review enhances our understanding of the molecular mechanisms and biological impacts of RCD-based therapies, providing new perspectives and strategies for cancer treatment.

Tangzu granule alleviate neuroinflammation in diabetic peripheral neuropathy by suppressing pyroptosis through P2X7R /NLRP3 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus, mainly manifested as paresthesia. Tangzu granule (TZG) is derived from famous traditional Chinese medicine decoctions and optimized by long-term temporary practice. TZG has good efficacy in improving numbness, pain and pruritus of the lower extremities of DPN patients. However, the overall regulatory mechanisms underlying its effects on DPN remain unclear.

AIM OF THE STUDY

This study aims to explore the potential mechanism of TZG for treating DPN.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were used to establish an in vivo model of DPN with streptozotocin (STZ) injection and high-fat diet (HFD) feeding. Additionally, sciatic glial RSC96 cells were induced with high glucose in vitro. SD rats in intervention group received TZG treatment for 12 weeks. After 12 weeks of treatment, sciatic nerve function was evaluated by intelligent hot plate meter and neuro electrophysiology detector. The morphological changes of sciatic nerve cells were observed by hematoxylin-eosin staining and transmission electron microscope. IL-1β, IL-18 inflammatory cytokines, pyroptosis and P2X7R/NLRP3 signaling pathway were observed by Western blotting, immunofluorescence staining and ELISA.

RESULTS

TZG improved nerve conduction velocity and sciatic neuropathy rational structural changes in DPN rats. It also inhibited RSC96 inflammatory response and cell death that induced by high glucose. This may be related to TZG inhibiting P2X7R, decreasing the activation of NLRP3 inflammasomes, down-regulating the levels of pyroptosis proteins such as caspase-1, cleaved caspase-1, gasdermin D (GSDMD), and GSDMD-N, and inhibiting the release of interleuki (IL)-18 and IL-1β inflammatory cytokines.

CONCLUSIONS

TZG inhibited pyroptosis through P2X7R/NLRP3 signaling pathway, alleviated neuroinflammation, and showed protective effect in the treatment of DPN.

Mitochondrial diseases: from molecular mechanisms to therapeutic advances

Mitochondria are essential for cellular function and viability, serving as central hubs of metabolism and signaling. They possess various metabolic and quality control mechanisms crucial for maintaining normal cellular activities. Mitochondrial genetic disorders can arise from a wide range of mutations in either mitochondrial or nuclear DNA, which encode mitochondrial proteins or other contents. These genetic defects can lead to a breakdown of mitochondrial function and metabolism, such as the collapse of oxidative phosphorylation, one of the mitochondria's most critical functions. Mitochondrial diseases, a common group of genetic disorders, are characterized by significant phenotypic and genetic heterogeneity. Clinical symptoms can manifest in various systems and organs throughout the body, with differing degrees and forms of severity. The complexity of the relationship between mitochondria and mitochondrial diseases results in an inadequate understanding of the genotype-phenotype correlation of these diseases, historically making diagnosis and treatment challenging and often leading to unsatisfactory clinical outcomes. However, recent advancements in research and technology have significantly improved our understanding and management of these conditions. Clinical translations of mitochondria-related therapies are actively progressing. This review focuses on the physiological mechanisms of mitochondria, the pathogenesis of mitochondrial diseases, and potential diagnostic and therapeutic applications. Additionally, this review discusses future perspectives on mitochondrial genetic diseases.

Expansion of the Structure-Activity Relationship Profile of Triaminopyrimidines as Inhibitors of Caspase-1

Caspase-1 is a sought-after therapeutic target for inflammatory conditions due to its role in activation and release of pro-inflammatory cytokines, but there has been little success getting drugs into the clinic. We have previously shown triaminopyrimidines such as CK-1-41 are potent, reversible small molecule inhibitors of caspase-1, likely binding in an allosteric site within the enzyme. A series of analogs of CK-1-41 were synthesized and tested against caspase-1 to develop a more robust structure-activity relationship profile. In general, alkyl and aryl groups were well tolerated via an ethylene or methylene linkage to the piperazine nitrogen, with IC50 values ranging from 13 to 200 nM. The most potent compounds were methylene linked o-tolyl (AE-2-21) and ethylene linked 4-trifluoromethylphenyl (AE-2-48) with IC50 values of 18 and 13 nM, respectively. Derivatives with electrophilic covalent warheads linked via an amide bond to the piperazine nitrogen were synthesized and characterized. CA-1-11 and EM-1-10 were semi-reversible, non-competitive inhibitors of caspase-1 with slightly reduced potencies of 134 and 144 nM, respectively. All derivatives docked well into the allosteric site, supporting our hypothesis that this family of caspase-1 inhibitors function via an allosteric non-competitive mechanism of inhibition.

"Hedgehog Ball"-Shaped Nanoprobes for Multimodal Detection and Imaging of Inflammatory Markers in Osteosarcoma Using Fluorescence and Electrochemiluminescence

Inflammation can affect the progression of cancer at tumor sites, such as in osteosarcoma, by intensifying metastasis and complicating outcomes. The current diagnostic methods lack the specificity and sensitivity required for early and accurate detection, particularly in differentiating between inflammation-induced changes and tumor activities. To address this, a novel "hedgehog ball"-shaped nanoprobe, Fe3O4@Au-pep-CQDs, was developed and designed to enhance the detection of caspase-1, a key marker of inflammation. This magnetic nanoprobe facilitates simultaneous fluorescence (FL) and electrochemiluminescence (ECL) detection. Magnetic separation minimizes the quenching of nanoparticles in solution and eliminates the need for frequent electrode replacement in ECL tests, thereby simplifying diagnostic procedures. The experimental results showed that in the detection of caspase-1, the nanoprobe had a detection limit of 0.029 U/mL (FL) and 0.033 U/mL (ECL) and had a dynamic range of 0.05 to 1.0 U/mL. Additionally, the nanoprobe achieved high recovery rates of 94.36 to 102.44% (FL) and 94.36-100.12% (ECL) in spiked biological samples. Furthermore, the nanoprobe's capabilities were extended to in vivo bioimaging to provide direct, intuitive visualization of biological processes. These novel nanoprobes were able to significantly enhance the accurate detection of inflammation at tumor sites, thereby optimizing both diagnostic and therapeutic strategies.

Dopaminergic neurons lacking Caspase-3 avoid apoptosis but undergo necrosis after MPTP treatment inducing a Galectin-3-dependent selective microglial phagocytic response

Parkinson's Disease (PD) is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons in the Substantia nigra pars compacta (SNpc). Apoptosis is thought to play a critical role in the progression of PD, and thus understanding the effects of antiapoptotic strategies is crucial for developing potential therapies. In this study, we developed a unique genetic model to selectively delete Casp3, the gene encoding the apoptotic protein caspase-3, in dopaminergic neurons (TH-C3KO) and investigated its effects in response to a subacute regime of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration, which is known to trigger apoptotic loss of SNpc dopaminergic neurons. We found that Casp3 deletion did not protect the dopaminergic system in the long term. Instead, we observed a switch in the cell death pathway from apoptosis in wild-type mice to necrosis in TH-C3KO mice. Notably, we did not find any evidence of necroptosis in our model or in in vitro experiments using primary dopaminergic cultures exposed to 1-methyl-4-phenylpyridinium in the presence of pan-caspase/caspase-8 inhibitors. Furthermore, we detected an exacerbated microglial response in the ventral mesencephalon of TH-C3KO mice in response to MPTP, which mimicked the microglia neurodegenerative phenotype (MGnD). Under these conditions, it was evident the presence of numerous microglial phagocytic cups wrapping around apparently viable dopaminergic cell bodies that were inherently associated with galectin-3 expression. We provide evidence that microglia exhibit phagocytic activity towards both dead and stressed viable dopaminergic neurons through a galectin-3-dependent mechanism. Overall, our findings suggest that inhibiting apoptosis is not a beneficial strategy for treating PD. Instead, targeting galectin-3 and modulating microglial response may be more promising approaches for slowing PD progression.

PLK1-activating IFI16-STING-TBK1 pathway induces apoptosis of intestinal epithelial cells in patients with intestinal Behçet's syndrome

Inflammatory signals from immunological cells may cause damage to intestinal epithelial cells (IECs), resulting in intestinal inflammation and tissue impairment. Interferon-γ-inducible protein 16 (IFI16) was reported to be involved in the pathogenesis of Behçet's syndrome (BS). This study aimed to investigate how inflammatory cytokines released by immunological cells and IFI16 participate in the pathogenesis of intestinal BS. RNA sequencing and real-time quantitative PCR (qPCR) showed that the positive regulation of tumor necrosis factor-α (TNF-α) production in peripheral blood mononuclear cells (PBMCs) of intestinal BS patients may be related to the upregulation of polo like kinase 1 (PLK1) in PBMCs (P = 0.012). The plasma TNF-α protein level in intestinal BS was significantly higher than in healthy controls (HCs; P = 0.009). PBMCs of intestinal BS patients and HCs were co-cultured with human normal IECs (NCM460) to explore the interaction between immunological cells and IECs. Using IFI16 knockdown, PBMC-NCM460 co-culture, TNF-α neutralizing monoclonal antibody (mAb), stimulator of interferon genes (STING) agonist 2'3'-cGAMP, and the PLK1 inhibitor SBE 13 HCL, we found that PLK1 promotes the secretion of TNF-α from PBMCs of intestinal BS patients, which causes overexpression of IFI16 and induces apoptosis of IECs via the STING-TBK1 pathway. The expressions of IFI16, TNF-α, cleaved caspase 3, phosphorylated STING (pSTING) and phosphorylated tank binding kinase 1 (pTBK1) in the intestinal ulcer tissue of BS patients were significantly higher than that of HCs (all P < 0.05). PLK1 in PBMCs of intestinal BS patients increased TNF-α secretion, inducing IEC apoptosis via activation of the IFI16-STING-TBK1 pathway. PLK1 and the IFI16-STING-TBK1 pathway may be new therapeutic targets for intestinal BS.

Inflammatory biomarkers in patients with painful knee osteoarthritis: exploring the potential link to chronic postoperative pain after total knee arthroplasty-a secondary analysis

ABSTRACT

Total knee arthroplasty (TKA) is the end-stage treatment of knee osteoarthritis (OA), and approximately 20% of patients experience chronic postoperative pain. Studies indicate that inflammatory biomarkers might be associated with pain in OA and potentially linked to the development of chronic postoperative pain after TKA. This study aimed to (1) evaluate preoperative serum levels of inflammatory biomarkers in patients with OA and healthy control subjects, (2) investigate preoperative differences of inflammatory biomarker profiles in subgroups of patients, and (3) compare subgroups of patients with and without postoperative pain 12 months after surgery. Serum samples from patients with OA scheduled for TKA (n = 127) and healthy participants (n = 39) were analyzed. Patients completed the Knee-injury-and-Osteoarthritis-Outcome-Score (KOOS) questionnaire and rated their clinical pain intensity using a visual analog scale (VAS) before and 12 months after TKA. Hierarchical cluster analysis and Orthogonal Partial Least Squares Discriminant Analysis were used to compare groups (patients vs control subjects) and to identify subgroups of patients in relation to postoperative outcomes. Difference in preoperative and postoperative VAS and KOOS scores were compared across subgroups. Twelve inflammatory markers were differentially expressed in patients when compared with control subjects. Cluster analysis identified 2 subgroups of patients with 23 proteins being significantly different ( P < 0.01). The 12-months postoperative VAS and KOOS scores were significantly different between subgroups of patients ( P < 0.05). This study identified differences in specific inflammatory biomarker profiles when comparing patients with OA and control subjects. Cluster analysis identified 2 subgroups of patients with OA, with one subgroup demonstrating comparatively worse 12-month postoperative pain intensity and function scores.

Cell organelles are retained inside pyroptotic corpses during inflammatory cell death

Many proinflammatory proteins are released via the necrotic form of cell death known as pyroptosis. Sometimes known as gasdermin D (GSDMD) dependent cell death, pyroptosis results from the formation of pores in the plasma membrane leading to eventual cell lysis. Seeking to understand the magnitude of this cell lysis we measured the size of proteins released during pyroptosis. We demonstrate that there is no restriction on the size of soluble proteins released during pyroptosis even at early timepoints. However, even though large molecules can exit the dying cell, organelles are retained within it. This observation indicates that complete cell rupture may not be a consequence of pyroptosis, and that plasma membrane architecture is retained.

Inflammasome and pyroptosis in autoimmune liver diseases

Autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and IgG4-related sclerosing cholangitis (IgG4-SC) are the four main forms of autoimmune liver diseases (AILDs), which are all defined by an aberrant immune system attack on the liver. Most previous studies have shown that apoptosis and necrosis are the two major modes of hepatocyte death in AILDs. Recent studies have reported that inflammasome-mediated pyroptosis is critical for the inflammatory response and severity of liver injury in AILDs. This review summarizes our present understanding of inflammasome activation and function, as well as the connections among inflammasomes, pyroptosis, and AILDs, thus highlighting the shared features across the four disease models and gaps in our knowledge. In addition, we summarize the correlation among NLRP3 inflammasome activation in the liver-gut axis, liver injury, and intestinal barrier disruption in PBC and PSC. We summarize the differences in microbial and metabolic characteristics between PSC and IgG4-SC, and highlight the uniqueness of IgG4-SC. We explore the different roles of NLRP3 in acute and chronic cholestatic liver injury, as well as the complex and controversial crosstalk between various types of cell death in AILDs. We also discuss the most up-to-date developments in inflammasome- and pyroptosis-targeted medicines for autoimmune liver disorders.

Hydroxysafflor yellow B induces apoptosis via mitochondrial pathway in human gastric cancer cells

OBJECTIVES

Hydroxysafflor yellow B (HSYB) is extracted from the petals of the safflower, a Chinese medicine. Relevant research results have demonstrated that HSYA can suppress the abnormal tumour cell proliferation and induce cell apoptosis. However, the properties of HSYB have rarely been reported, especially its antitumour effects on gastric cancer (GC).

METHODS

SGC-7901 and BGC-823 cells were treated with different concentrations of HSYB. Cell proliferation inhibition rate was detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and colony formation detection. The changes in morphology of cells was observed by Hoechst 33258 staining. Cell apoptosis was evaluated by Annexin V-FITC/PI (fluoresceinisothiocyanate/propidium iodide) double staining. JC-1 was used to detect the level of mitochondrial membrane potential (MMP). The protein levels of cleaved-caspase-3, cleaved-caspase-9, APAF-1, cytoplasmic cytochrome C, BAX and BCL-2 were examined by western blot.

KEY FINDINGS

HSYB significantly suppressed the proliferation of SGC-7901 and BGC-823 cells. Hoechst 33258 staining assay showed that HSYB treatment triggered apoptotic morphology and the apoptotic rates were significantly increased after being treated with HSYB and the mitochondrial membrane potential was gradually decreased in human GC cells. In addition, Western blot analysis revealed that the levels of cleaved-caspase-3 and cleaved-caspase-9 were remarkably increased in HSYB-treated BGC-823 and SGC-7901 cells. And, the levels of apoptotic protease activating factor-1 (APAF-1) and cytoplasmic cytochrome C were remarkably up-regulated in HSYB-treated cells. At the same time, HSYB could up-regulate the level of BAX and down-regulate the level of BCL-2.

CONCLUSIONS

Our data suggest that HSYB could induce GC cell apoptosis via the mitochondrial pathway.

Knowledge Mapping of Necroptosis From 2012 to 2021: A Bibliometric Analysis

Background

Necroptosis, a recently discovered programmed cell death, has been pathologically linked to various diseases and is thus a promising target for treating diseases. However, a comprehensive and objective report on the current status of entire necroptosis research is lacking. Therefore, this study aims to conduct a bibliometric analysis to quantify and identify the status quo and trending issues of necroptosis research in the last decade.

Methods

Articles were acquired from the Web of Science Core Collection database. We used two bibliometric tools (CiteSpace and VOSviewer) to quantify and identify the individual impact and cooperation information by analyzing annual publications, journals, co-cited journals, countries/regions, institutions, authors, and co-cited authors. Afterwards, we identified the trending research areas of necroptosis by analyzing the co-occurrence and burst of keywords and co-cited references.

Results

From 2012 to 2021, a total of 3,111 research articles on necroptosis were published in 786 academic journals by 19,687 authors in 885 institutions from 82 countries/regions. The majority of publications were from China and the United States, of which the United States maintained the dominant position in necroptosis research; meanwhile, the Chinese Academy of Sciences and Ghent University were the most active institutions. Peter Vandenabeele published the most papers, while Alexei Degterev had the most co-citations. Cell Death &amp; Disease published the most papers on necroptosis, while Cell was the top 1 co-cited journal, and the major area of these publications was molecular, biology, and immunology. High-frequency keywords mainly included those that are molecularly related (MLKL, TNF-alpha, NF-κB, RIPK3, RIPK1), pathological process related (cell-death, apoptosis, necroptosis, necrosis, inflammation), and disease related (cancer, ischemia/reperfusion injury, infection, carcinoma, Alzheimer’s disease).

Conclusion

Necroptosis research had a stable stepwise growth in the past decade. Current necroptosis studies focused on its cross-talk with other types of cell death, potential applications in disease treatment, and further mechanisms. Among them, the synergy with ferroptosis, further RIPK1/RIPK3/MLKL studies, its association with inflammation and oxidative stress and translational applications, and the therapeutic potential to treat cancer and neurodegenerative diseases are the trending research area. These might provide ideas for further research in the necroptosis field.

The Role of Polyphenol in Modulating Associated Genes in Diabetes-Induced Vascular Disorders

Diabetes-induced vascular disorder is considered one of the deadly risk factors among diabetic patients that are caused by persistent hyperglycemia that eventually leads to cardiovascular diseases. Elevated reactive oxygen species (ROS) due to high blood glucose levels activate signaling pathways such as AGE/RAGE, PKC, polyol, and hexosamine pathways. The activated signaling pathway triggers oxidative stress, inflammation, and apoptosis which later lead to vascular dysfunction induced by diabetes. Polyphenol is a bioactive compound that can be found abundantly in plants such as vegetables, fruits, whole grains, and nuts. This compound exerts therapeutic effects in alleviating diabetes-induced vascular disorder, mainly due to its potential as an anti-oxidative, anti-inflammatory, and anti-apoptotic agent. In this review, we sought to summarize the recent discovery of polyphenol treatments in modulating associated genes involved in the progression of diabetes-induced vascular disorder.

Resurrection of an ancient inflammatory locus reveals switch to caspase-1 specificity on a caspase-4 scaffold

Pyroptosis is a mechanism of inflammatory cell death mediated by the activation of the prolytic protein gasdermin D by caspase-1, caspase-4, and caspase-5 in human, and caspase-1 and caspase-11 in mouse. In addition, caspase-1 amplifies inflammation by proteolytic activation of cytokine interleukin-1β (IL-1β). Modern mammals of the order Carnivora lack the caspase-1 catalytic domain but express an unusual version of caspase-4 that can activate both gasdermin D and IL-1β. Seeking to understand the evolutionary origin of this caspase, we utilized the large amount of data available in public databases to perform ancestral sequence reconstruction of an inflammatory caspase of a Carnivora ancestor. We expressed the catalytic domain of this putative ancestor in Escherichia coli, purified it, and compared its substrate specificity on synthetic and protein substrates to extant caspases. We demonstrated that it activates gasdermin D but has reduced ability to activate IL-1β. Our reconstruction suggests that caspase-1 was lost in a Carnivora ancestor, perhaps upon a selective pressure for which the generation of biologically active IL-1β by caspase-1 was detrimental. We speculate that later, a Carnivora encountered selective pressures that required the production of IL-1β, and caspase-4 subsequently gained this activity. This hypothesis would explain why extant Carnivora possess an inflammatory caspase with caspase-1 catalytic function placed on a caspase-4 scaffold.