The systematic search of the literature on caspase-1 inhibitors was performed by searching the relevant papers using the major scientific sources, such as PubMed, ScienceDirect and Google Scholar (June, 2025). The keywords used included the caspase-1 inhibitors, inhibition of inflammasome, NLRP3 and caspase-1 and IL-1β or IL-18 inhibition. The criteria for inclusion in this review were based on studies that provided direct evidences regarding inhibition of caspase-1 or modulations of NLRP3 inflammasome pathway as evident from effects on caspase-1 activity or on IL-1β and IL-18 generation via experimental and computational methods. Studies that were not mechanistically supportive, non-peer reviewed articles and duplicate references were not included in this review.

Further literature sources were used to validate the data about enzymes such as the BRENDA enzyme database (Hauenstein et al. 2026) and to find the compounds that affect caspase-1. For example, Google and ResearchGate were only used for additional searches and getting full texts. This strategy aimed at providing transparency of the process of literature selection. (Hauenstein et al. 2026)

Caspases: classifications and biology

Caspases are cysteine-aspartate proteases that have diverse functions in living organisms. For example, caspases like caspase-1, have functions related to inflammation and innate immunity, while other caspases like caspase-3 and caspase-7, contributes in apoptosis (Sahoo et al. 2023). Caspase-10 takes part in the apoptotic signaling in humans while caspase-12 plays a role in ER stress response. The caspase-14 enzyme plays a role in skin differentiation (Eckhart et al. 2008). Through these distinct roles, caspases contribute in maintaining cellular homeostasis and coordinating appropriate responses to cellular stress and other pathogenic challenges (Kumar 2007). All caspases have a similar basic structure and function in the same general way, but activated differently and targeting different proteins for cleavage Although the fold and catalytic activity of caspases are highly conserved, their activation mechanism and substrate specificity are different (Stegh and Peter 2001). In the human body, caspases perform a unique role in apoptosis and other biological processes related to programmed cell death (Eckhart et al. 2008). Caspases are classified based on their structure, domain organization and biological function, including their roles in apoptosis and inflammatory signaling (Fig. 1).

Inflammatory caspases

Inflammatory caspases include caspase-1, -4, and -5 in humans, and caspase-1 and caspase-11 in mice, where caspase-11 is the functional ortholog of human caspase-4 and -5. (Martinon and Tschopp 2007). Caspase-12 is also expressed in mice, although its function is more limited than in humans. The caspases are primarily expressed in vertebrates and they have an involvement in the innate immunity (Sakamaki and Satou 2009). Caspases become activated through protein multiprotein complexes called inflammasome which facilitates activation of particular inflammatory caspases (Shinkai et al. 2005) In the caspase family, caspase-1 is the one that is highly important since its role involves the cleavage of inactive cytokines IL-1β and IL-18. Upon activation, caspase-1 results to an apoptotic process called pyroptosis. (Sun and Scott 2016).

Apoptotic caspasesInitiator caspases

This class of cysteine proteases encompasses caspases-2, 8, 9, and -10. Among them, Caspase-2, 8 and 9 are thoroughly present both in human as well as mice, while caspase-10 unique to human only (Sahoo et al. 2023). Initiator caspases are produced as inactive precursors and possess elongated pro-domains such as the death effector domain (DED) or the caspase recruitment domain (CARD) that enable their interaction with certain signaling complexes (Salvesen and Dixit 1999). The pro-domains of initiator caspases undergo auto-processing following dimerization via the involvement of oligomeric signaling complexes (Salvesen 2002; Bao and Shi 2007). Additionally, they commence the execution phase of apoptosis upon receiving particular death signals. All these caspases are responsible for the initiation of apoptosis, thereby acting as the top precursor of caspase cascade signaling pathway (Chen and Wang 2002).

Executioner caspases

This class of caspases encompasses caspases-3, -6 and -7 and are entirely activated by initiator caspases (Slee et al. 2001). Executioner caspases are also called effector caspases. Upon activation, the role of executioner caspases is synchronized to diminish essential structural proteins and stimulate other enzymes. resulting in their morphological, structural, and biochemical alteration associated with apoptosis (Nano et al. 2023). Both intrinsic and extrinsic apoptotic TNF-associated apoptosis-induced ligand (TRAIL) signaling pathways are triggered by initiator caspases, which in turn enhance the activation of other caspases, such as executioner caspases, leading to the cleavage of cellular components and ultimately causing apoptosis. More interestingly, initiator caspases have been thoroughly identified in humans as well as mice (Horuz et al. 2013; Hojo-Souza et al. 2015).

Other caspases

The origin and role of certain caspases, such as caspase-13, -14 and -16, are still under debate. However, among them, caspase-14 is a unique member of the caspase-1 family due to its highly tissue-specific expression pattern, being predominantly restricted to mammalian confining epithelia (Lippens et al. 2004). It is mainly expressed in the differentiating epidermal layers and hair follicles, where its distribution appears highly conserved among other species (Alibardi et al. 2004, 2005). In contrast, the existence and functional relevance of caspase-16 remain controversial, although it was initially identified as a caspase-14-like protease in several mammals (Eckhart et al. 2025). However, the structure and function of its human ortholog are still under consideration, and some studies, for example, Eskhart et al. (2008) and Sakamaki and Satou (2009) propose that it is a pseudogene.

Despite its inclusion in recent reviews of the human caspase repertoire, there is no definitive evidence confirming the expression of an appropriate and effective caspase-16 protease in humans. Furthermore, caspase-13 represents another controversial member of the caspase family. Although it was first investigated in 1998 by Humke et al. (1998), the subsequent finding failed to detect its expression in human tissues, contradicting earlier findings based on Northern blot analysis. However, later studies further demonstrated that caspase-13 does not constitute a genuine member of the human caspase-1 family, but exists in bovines (Taylor et al. 2000; Koenig et al. 2001).

Fig. 1

The figure illustrates the structural architecture and classification of mammalian caspases based on their biological role and domain composition. For example, inflammatory caspases, involving caspase-1, -4, -5, -11 and -12, are actively characterized by the presence of an N-terminal caspase recruitment domain (CARD), which mediates inflammatory responses. Similarly, apoptotic caspases encompass initiator caspases (caspase-2, -8, -9 and -10) that contain either a CARD or a death effector domain (DED), enabling them to recruit to activation complexes such as the apoptosome or the death-inducing signalling complex (DISC). In contrast, executioner caspases, including caspase-3, -6 and -7 possess short prodomains and play a key role in the downstream of initiator caspases to mediate proteolytic cleavage of cellular substrates during the process of apoptosis. In a similar manner, the catalytic region of caspases is mainly composed of a large (L) and small (S) subunit, which together form the active heterotetrameric enzyme following proteolytic maturation. The figure is assembled and modified in PowerPoint and derived from (Shalini et al. 2015; Fang and Peng 2022)

Structural and functional insights of caspase-1

Caspase-1 also known as interleukin-1 converting enzyme (ICE) is one of the key enzyme belong to a group of enzymes called aspartate-specific cysteine proteases (Vande Walle and Lamkanfi 2011)This was thought to be a unique proteolytic characteristic, holding an evolutionarily conserved enzyme that cleaves precursor proteins into their active forms i.e. the maturation of interleukin-1β and interleukin-18 followed by the pyroptosis inducer gasdermin D (GSDMD) into active mature peptides (Sollberger et al. 2014; McNair et al. 2018). Upon caspase-1 activation via inflammasomes and/or apoptosis, it progressively increasing the inflammation response in the cells (Kumaresan et al. 2016). Although some studies have claimed that proIL-1β and proIL-18 can also be activated in the absence of caspase-1 by some other proteases, especially in neutrophil cells (Guma et al. 2009; Joosten et al. 2009)Therefore, before discussing the maturation, caspase-1 is present in the inactive form known as ‘zymogen’ and can be activated by recruiting to a proper and well-known molecular platform termed the inflammasome (Elliott et al. 2009).

Inflammasomes that lead to the activation of caspase-1 are primarily made up of pattern-recognition receptors (PRRs) that are part of the NOD-like receptor (NLR) family. This includes NLRP1, NLRP3, NLRP6, NLRP7 and NLRC4. Apart from NLRs, there are also other types of sensors such as AIM2 that detect DNA and RIG-I that detect viral RNA (Hauenstein et al. 2015). These inflammasomes are primarily composed of several key domains, including a leucine-rich repeat domain, essential for sensing pathogen-associated molecular patterns (PAMPs) and/or damage-associated molecular patterns (DAMPs), a nucleotide-binding domain (required for oligomerization) and a caspase-1 activation and recruitment (CARD) domain, as well as a PYD domain for recruitment to caspase-1 (Chopra et al. 2024). However, among all above listed inflammasomes, NLRP3 is noted to be the most important inflammasome, especially in the inflammatory pathway, and can be activated by different stimuli like PAMPs and DAMPs (Jin and Flavell 2010; Carriere et al. 2021).

A single pro-caspase-1 (p45) is responsible for the creating of two sub-units i.e. p20 and p10, respectively (Romanowski et al. 2004). The activation of pro-caspase-1 can be achieved, thereby cleaving it to produce 20 kDa (p20) and 10 kDa (p10) subunits, respectively (Thornberry 1997; Mariathasan et al. 2004). Active caspase-1 consist of a catalytic domain as well as an active site, which forming catalytic dyad consisting of C285 and H237, respectively (Clark 2016). Similarly, during the cleavage of pro-caspase-1 a 119-residue pro-peptide and an 18-residue sequences are removed seperates the mature enzyme’s large (p20; residues 120–298) and small (p10; residues 317–404) subunits (Wilson et al. 1994). On the same way, auto-proteolytic cleavage at three aspartic acid residues are the main sites of this (D119, D297 and D316), resulting in the release of the pro-domains, i.e., caspase recruitment domain (CARD), caspase docking loop (CDL) and interdomain linker (IDL) and serving as a crucial step in the activation of caspase-1 (Lu et al. 2016).

Additionally, the active/mature caspase-1 consists of two heterodimers of p20 and p10. The catalytic domain has an active site that goes across both subunits (Huang et al. 2009); Boucher et al. 2018). Active caspase-1 actively interact with other protein such as apoptosis-associated speck-like protein containing a (ASC) and Nod-Like Receptor (NLR) proteins, which are caspase activation recruitment domain (CARD) proteins forming inflammasomes (Huang et al. 2009). Similarly, Caspase Activation and Recruitment Domain (CARD) that interacts with other proteins, such as Apoptosis-Associated Speck-like Protein Containing a CARD (ASC) and Nod-Like Receptor (NLR) Family CARD Domain-Containing Protein 4 (NLRC4) (Newton and Dixit 2003; Jorgensen and Miao 2015).

NLRP3: occurrence, activation, and role in inflammation

Inflammasome are the class of cytosolic protein complexes that are formed in order to mediate host immunological responses to microbial infection and cellular stresses, infections and/or injuries (Yi 2020). Inflammasome like NLRP3 The NLRP3 inflammasome is a multi-protein complex comprising the apoptosis-associated speck-like protein (ASC), which contains a caspase recruitment domain (CARD) and a pro-caspase-1 domain. NLRP3 inflammasome is present in immune cells like neutrophils, macrophages, epithelial cells and also in non-immune cells (Jin and Flavell 2010). Inflammasome activation is initiated by pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), which are recognized through pattern-recognition receptors and trigger the assembly of inflammasome complexes, including ‌NLRP3 (Shi et al. 2016). Upon activation, the NLRP3 inflammasome recruits the adoptor protein apoptosis-associated speck-like protein containing a CARD (ASC), facilitating the recruitment and autocatalytic activation of caspase-1 (Fig. 2). Interestingly, similar mechanisms have also been described in parasitic pathogens, such as Schistosoma mansoni, which activate ASC-NLRP3 inflammasome axis, resulting caspase-1 activation and subsequent maturation of cytokines i.e. IL-1β and IL-18, thereby promoting inflammatory and innate immune responses (Sanches et al. 2020). In addition, emerging evidences indicates that caspase-4 contributes to the expression and functional activation of the NLRP3 inflammasome in THP-1 cells and human keratinocytes, highlighting the complex interplay between inflammatory caspases and regulating inflammasome signalling (Garrido et al. 2019).

Fig. 2

Structural organization, assembly, oligomerization and activation. Here the NLRP3 inflammasome is a multiprotein complex composed of three main components: the sensor protein NLRP, the adaptor ASC (apoptosis-associated speck-like protein containing caspase recruitment domain and pro-caspse-1. Similarly, NLRP3 in its inactive form consisted of different components characterized by the presence of leucine-rich repeat (LLR), followed by NACHT and pyrin (PYD) domains. Upon sensing cellular stress signals in the form of PAMS and DPAMS, NLRP3 undergoes ATP-dependent conformational changes and oligomerization. The activated NLRP3 recruits ASC through PYD-mediated interactions and ASC subsequently recruits pro-caspase-1 through caspase recruitment domain (CARD)-mediated interactions. This multiprotein assembly promotes proximity-induced activation of caspase-1, which further catalyzes the maturation of proinflammatory cytokines pro-IL-1β and pro-IL-18 into their active forms IL-1β and IL-18, respectively. The release of these cytokines triggers downstream inflammatory signaling and contributes to innate immune defense response. The figure was designed in the Microsoft PowerPoint 2019

The activation of the NLRP3 inflammasome is widely recognized as a two-step mechanism comprising a priming signal followed by an activation signal (Sutterwala et al. 2014). In the very first stage (known as priming), the transcriptional upregulation of NLRP3 and the inactive cytokine precursors, including pro-IL-1β and IL-18 (Swanson et al. 2019). This process is typically initiated by the activation of pattern-recognition receptors (PRRs), particularly, toll-like receptors (TLRs), following the recognition of pathogen-which detect damage-associated molecular pattern (DAMPs) and/or pathogens-associated molecular pattern (PAMPs), which activate the NF-κB signalling pathway (Sutterwala et al. 2014). Similarly, a well-characterized example of a priming stimulus lipopolysaccharide (LPS), a major structural component of the outer membrane of gram-negative bacteria and is recognized by TLR4. In contrast, endogenous danger signals such as uric acid crystal act as DAMPs and contribute to inflammasome activation in response to cellular stress and/or tissues injuries (Martinon et al. 2006).

The‍‌‍‍‌‍‌‍‍‌ second tier of NLRP3 inflammasome activation is triggered by a wide range of cellular stress signals, including the efflux of potassium (K+) and chloride (Cl−) ions, the influx of calcium (Ca2+), accumulations of cytosolic nucleic acids, metabolic perturbations, lysosomal disruption, mitochondrial dysfunctions and the generation of reactive oxygen species (ROS) (Li et al. 2020). Although, these are the stimuli/signals are different in origin and structure, however, they converge on common cellular events that promote NLRP3 activation. Similarly, among the key regulatory proteins Never in Mitosis Gene A-related Kinase 7 (NEK7) and thioredoxin-interacting protein (TXNIP) actively facilitate NLRP3 activation by promoting conformational changes and oligomerization of the receptor‍‌‍‌‍‍‌ (Shen and Abe 2019). The activated NLRP3 subsequently undergoing oligomerization and recruits the adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) through and PYD-PYD) interactions. ASC then polymerizes into filamentous structures that assemble into a well-defined characteristic ASC speck, which serves a molecular platform for the recruitment of procaspase-1 via caspase recruitment domain CARD-CARD interactions, ultimately leading to the caspase-1 activation (Isazadeh et al. 2022).

Following activation, NLRP3 under oligomerization, exposing its N-terminal pyrin domains (PYDs), which recruit the adaptor protein apoptosis-associated speck-like protein containing CARD (ASC) through homotypic PYD-PYD interactions (Oroz et al. 2016). ASC subsequently polymerizes into filamentous structures that assemble into large perinuclear ASC speck, providing a molecular platform for the recruitment of procaspase-1 via caspase-1 recruitment of domain (CARD-CARD) interactions (Hauenstein et al. 2015). Similarly, the close proximity of procaspase-1 molecules with the inflammasome promotes their autocatalytic cleavage, generating enzymatically active caspase-1. thus, it is the main enzyme that brings about the whole inflammatory response (Kesavardhana and Kanneganti 2017). The activated caspase-1 then proteolytically processes the inactive cytokines pro-inflammatory cytokines (pro-IL-1β and pro-IL-18) into their mature, biologically active forms and cleave gasdermin D (GSDMD). The released N-terminal fragment of GSDMD oligomerizes and inserts into the plasma membrane to form transmembrane pores, actively facilitating the release and secretion of IL-1β and IL-18 and ultimately triggering pyroptosis, a highly inflammatory form of programmed cell death characterized by membrane rupture and release of intracellular inflammatory mediators (IL-1β and IL-18) (Hu 2025) (Fig. 3).

Fig. 3

Schematic representation of the canonical and non-canonical signaling pathway involved in NLRP3 inflammasome activation that leads to the activation of caspase-1 and ultimately pyroptosis. The figure actively illustrates the priming, assembly, and activation mechanisms of the NLRP3 inflammasome triggered by diverse inflammatory stimuli, including TNF, followed by IL-1β, PAMPs, viral RNA, ATP, ions influxes (K+, Cl− and Ca2+). Similarly, cellular contents comprise lysosomal damage, mitochondrial damage, and radicals in the form of ROS and particulate crystals. These signals activate NF-κβ/IRF3-mediated transcription of NLRP3, pro-IL-1β, and pro-IL-18 and caspase-11, while mitochondrial ROS, oxidized mtDNA, MAVS, cardiolipin, cathepsin release, and NEK3 promote NLRP3 oligomerization. The assembled inflammasome recruits ASC and pro-caspase-1, leading to caspase-1 activation and, therefore, the maturation of IL-1β and IL-18 takes place, and cleavage of GSDMD into N-GSDMD and induction of pyroptosis cell death, accompanied by inflammatory cytokine release. The figure was adopted from (Molla et al. 2020) using BioRender (https://www.biorender.com/) and Microsoft PowerPoint 2019

Role of caspase-1 inhibitors in inflammation

Caspase-1 inhibitors play a crucial role in regulating excessive inflammatory reactions, thereby preventing the activation of pro-inflammatory cytokines, including IL-1β and IL-18 (Molla et al. 2020). These inhibitors are important in the treatment of chronic inflammatory illnesses like gout, rheumatoid arthritis, and inflammatory bowel problems, where persistent inflammation causes substantial morbidity and tissue damage (Lamkanfi et al. 2007; Sun and Scott 2016). Similarly, these caspase-1 inhibitors can decrease the inflammation, thereby enhancing the quality of life and relieving symptoms in autoimmune disorders like multiple sclerosis and systemic erythematosus, where aberrant immune system activation causes substantial harm and destruction in the body (Denes et al. 2012).

Likewise, caspase-1 inhibitors could prove useful as therapeutic agents, particularly in neuroinflammatory conditions such as Parkinson’s and Alzheimer’s, where inflammation plays a significant role in disease progression (Flores et al. 2022). Interestingly, by decreasing caspase-1 expression and lowering neuroinflammation, these inhibitors may be able to prevent the worsening of these debilitating disorders (Gao et al. 2020). Additionally, caspase-1 inhibitors provide a novel way to lower these inflammatory processes and enhance cardiovascular health in cardiovascular disorders, when inflammation leads to atherosclerosis and ultimately heart failure (Dh