An inflammatory response is an innate immune response that protects the body from pathogen infection and cellular danger signals and consists of two steps: priming and triggering [1,2]. The priming step prepares inflammatory responses by the transcriptional activation of multiple inflammatory mediators, such as pro-inflammatory cytokines, inflammatory effectors, and enzymes, while the triggering step activates inflammatory responses by activating inflammasomes, cytosolic multiprotein complexes comprising pattern recognition receptor (PRR) and inflammatory molecules, such as ASC and caspases [2-6]. Inflammasomes are classified into two types: Canonical and non-canonical inflammasomes. Canonical inflammasomes were previously discovered, and several types of canonical inflammasomes were identified, including the NLR family inflammasomes, such as NLRP1, NLRP3, NLRC4, NLRP6, NLEP9, and NLRP12 inflammasomes and non-NLR family inflammasomes, such as AIM2, IFI-16, and pyrin inflammasomes [2-6]. In-depth studies have demonstrated that each canonical inflammasome is differentially activated by different pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) [6-9]. Under some conditions, the activation of inflammatory responses bypasses the canonical inflammasome pathways; instead non-canonical inflammasomes. Non-canonical inflammasomes were recently discovered in the mice lacking the functional caspase-11 and showed characteristics distinct from those of canonical inflammasomes. These observations provided strong evidence that caspase-11 is not a component of canonical inflammasomes, and the molecular mechanisms of caspase-11 inflammasome-mediated inflammatory responses are distinct from those of canonical inflammasomes. Therefore, caspase-11 inflammasome was named as a non-canonical inflammasome [10-13]. A series of follow-up studies identified that caspase-4 and caspase-5 are human homologues of mouse caspase-11, therefore, non-canonical inflammasomes include mouse caspase-11, human caspase-4, and caspase-5 inflammasomes [10-13]. Despite the wide range of PAMPs and DAMPs specific to each PRR of canonical and non-canonical inflammasomes, canonical and non-canonical inflammasomes share downstream inflammatory signaling pathways. Upon activation, inflammasomes promote the proteolytic processing of gasdermin D (GSDMD), leading to the formation of GSDMD pores in the cell membrane and GSDMD pore-mediated pyroptosis, a form of inflammatory cell death [14-17]. Inflammasome activation simultaneously induces proteolytic maturation and secretion of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 through GSDMD pores in an NLRP3 inflammasome-dependent manner [14-17]. Several studies have demonstrated that canonical inflammasomes, particularly the NLRP3 inflammasome, play pivotal roles in many human diseases [18-22]. Recently, substantial literature has emphasized that non-canonical inflammasomes are key players in various human diseases [23-34].

Autophagy, also known as autophagocytosis, is a cellular self-degradative and recycling process to remove unnecessary or dysfunctional subcellular elements through a lysosome-dependent regulated mechanism [35,36]. Autophagy serves as a self-protective system that is crucial for maintaining cellular homeostasis [37]. Therefore, unregulated or dysfunctional autophagy cannot maintain normal cellular protective functions, resulting in cell damage and the pathogenesis of various diseases [38-40]. As a cellular protective mechanism, autophagy protects the body from exogenous threats such as pathogen infection and endogenous mediators of inflammation such as DAMPs, damaged organelles, and molecular aggregates [41], indicating that autophagy may play a critical role in inflammatory responses and diseases. Substantial literature exists emphasizing the role of autophagy in immunity, inflammation, and inflammatory diseases [42-44]. Recent studies have demonstrated that autophagy plays a pivotal role in inflammasome-mediated inflammatory responses and diseases [45-47]. This review discusses research investigating the functional interplay between non-canonical inflammasomes and autophagy in inflammatory responses and diseases and further highlights insights into the regulation of autophagy as a potential strategy to prevent and treat various human inflammatory diseases associated with inflammasomes, particularly non-canonical inflammasomes.

Classification and structures of non-canonical inflammasomes

As described above, there are two classes of inflammasomes, and the molecular structures of canonical and non-canonical inflammasomes are quite different. In response to their PAMPs and DAMPs, all PRRs of canonical inflammasomes interact with caspase-1 via a bipartite adaptor, ASC [6]. However, PRRs of non-canonical inflammasomes, such as mouse caspase-11 and human caspase-4/5, sense PAMPs and do not interact with caspase-1 and ASC [14-17]. Mouse caspase-11 and human caspase-4/5 are structurally similar. They all have the same domains: an amino-terminal caspase recruitment domain (CARD), followed by a large catalytic domain (p20) and a small catalytic domain (p10) at the carboxyl terminus (Fig. 1A). Although they have the same structural domains, the amino acid lengths of mouse caspase-11 and human caspase-4/5 are 373, 377, and 434 amino acids, respectively (Fig. 1A). Lipopolysaccharide (LPS), an endotoxin present in the gram-negative bacterial cell wall, is the only PAMP that can directly bind to caspase-4/5/11 and consequently activate caspase-4/5/11 non-canonical inflammasomes [14-17]. Caspase-4/5/11 directly interacted with cytosolic LPS by binding to the caspase CARD and LPS lipid A (Fig. 1B). LPS-caspase-4/5/11 complexes are then oligomerized by CARD-CARD interaction to generate caspase-4/5/11 non-canonical inflammasomes, and the caspase-4/5/11 non-canonical inflammasomes are subsequently activated by autoproteolysis, leading to the initiation of non-canonical inflammasome-mediated inflammatory signaling pathways (Fig. 1C).

Figure 1. Non-canonical inflammasomes and non-canonical inflammasome-activated inflammatory signaling pathways. (A) Domain structure of mouse caspase-11 and human caspase-4 and caspase-5. Caspase-11, caspase-4, and caspase-5 have same domain structure composed of amino-terminal CARDs, followed by large (p20) and small (p10) catalytic domains, but different amino acid lengths; 373, 377, and 434 amino acids, respectively. (B) Sensing of LPS by caspase-4/5/11. Caspase-4/5/11 senses cytosolic LPS by direct interaction between CARDs of caspase-4/5/11 and lipid A of LPS, which leads to the formation of LPS-caspase-4/5/11 complexes. (C) Non-canonical inflammasome-activated inflammatory signaling pathways. LPS derived from gram-negative bacteria is internalized into the host cells, and caspase-4/5/11 directly senses the cytosolic LPS, leading to the formation of LPS-caspase-4/5/11 complexes and caspase-4/5/11 non-canonical inflammasomes by oligomerization through CARD-CARD interaction. Caspase-4/5/11 non-canonical inflammasomes activated by autoproteolytic cleavage induce the proteolytic cleavage of GSDMD and the generation of GSDMD pores, resulting in pyroptosis of the cells. Caspase-4/5/11 non-canonical inflammasome activation induces NLRP3 inflammasome-mediated proteolytic activation of caspase-1, leading to the proteolytic maturation and secretion of IL-1β and IL-18 through GSDMD pores. CARD, caspase recruitment domain; LPS, lipopolysaccharide; GSDMD, gasdermin D; IL, interleukin.

Non-canonical inflammasome-activated inflammatory signaling pathways

Internalization and cytosolic access of LPS: Non-canonical inflammasome-activated inflammatory signaling pathways are initiated by sensing cytosolic LPS, and extracellular LPS can be internalized into cells via several mechanisms. Extracellular LPS binds to Toll-like receptor (TLR) 4 or receptor for advanced glycation end‐product (RAGE) with the help of MD2 and hepatocyte‐related high‐mobility group box 1 (HMGB1), respectively, and TLR4-MD2-LPS or RAGE-HMGB1-LPS complexes enter the cells via receptor-mediated endocytosis [2]. Gram-negative bacteria produce outer membrane vesicles (OMVs) containing LPS, and the OMVs can be internalized by cells via receptor-mediated endocytosis [2]. Receptor-mediated endocytosed LPS in endosomes and the LPS of intracellular vacuole‐living gram‐negative bacteria are required to be released from the endosomes and vacuoles into the cytosol to be detected by mouse caspase-11 and human caspase-4/5, the PRRs of non-canonical inflammasomes. Guanylate‐binding proteins (GBPs), family members of interferon (IFN)‐inducible GTPases expressed by IFN signaling, bind to the endosomes and vacuoles and then disrupt membrane integrity, leading to the cytosolic access of LPS to the PRRs of non-canonical inflammasomes [2].

Direct sensing of LPS by caspase-4/5/11 and non-canonical inflammasome activation: The activation of non-canonical inflammasomes is initiated by sensing cytosolic LPS via PRRs, mouse caspase-11, and human caspase-4/5 [14-17]. Caspase-4/5/11 senses cytosolic LPS through a direct interaction between caspase-4/5/11 CARDs and LPS lipid A, which forms LPS-caspase-4/5/11 complexes [14-17]. The LPS-caspase-4/5/11 complexes are then oligomerized through direct CARD-CARD interactions to generate mouse caspase-11 and human caspase-4/5 non-canonical inflammasomes, which are activated by the autoproteolytic processing of caspase-4/5/11 [48,49]. Mouse caspase-11 is autoproteolytically processed at 285 aspartic acid, and a 254 cysteine of mouse caspase-11 is the active catalytic residue for caspase-11 autoproteolytic processing [48]. However, the autoproteolytic processing of human caspase-4/5 and its underlying molecular mechanisms have not been fully elucidated.

Non-canonical inflammasome-activated inflammatory signaling pathways: The activated non-canonical inflammasomes induce two main inflammatory signaling pathways: 1) GSDMD pore-mediated pyroptosis and 2) maturation and secretion of pro-inflammatory cytokines through the GSDMD pores. The activation of non-canonical inflammasomes catalyzes the proteolytic processing of GSDMD at 276 aspartic acid residues, which generates amino- and carboxy-terminal fragments of GSDMD (N-GSDMD and C-GSDMD, respectively) [14-17]. N-GSDMD moves to the cell membrane and is oligomerized to generate GSDMD pores, resulting in GSDMD pore-mediated pyroptosis [14-17]. Non-canonical inflammasome activation simultaneously promotes activation of the NLRP3 canonical inflammasome. Mechanistic studies have revealed that non-canonical inflammasome activation facilitates potassium ion (K⁺) efflux, a key determinant of NLRP3 canonical inflammasome activation, through GSDMD pores, membrane damage, P2X7, and bacterial pore-forming toxins [2]. The activation of the NLRP3 canonical inflammasome then promotes the proteolytic activation of caspase-1 and the caspase-1-induced proteolytic maturation of inactive pro-forms of IL-1β and pro-IL-18, subsequently leading to the secretion of mature and active IL-1β and IL-18 through the GSDMD pores and the further boosting of inflammatory responses by stimulating other types of immune cells with the secreted IL-1β and IL-18 [14-17]. The non-canonical inflammasome-activated inflammatory signaling pathway is summarized in Fig. 1C.

Mouse caspase-11 non-canonical inflammasome and autophagy

Autophagy is a biological process that removes unnecessary or dysfunctional subcellular elements, including DAMPs, to maintain cellular homeostasis. Inflammasome-mediated inflammatory responses are a host defensive innate immunity triggered in response to DAMPs and PAMPs, suggesting that inflammasomes and autophagy may be functionally associated with inflammatory responses. Studies have investigated the functional relationship between the caspase-11 non-canonical inflammasome and autophagy and have reported that autophagy inhibits the caspase-11 non-canonical inflammasome in inflammatory responses and diseases.

Meunier et al. [50] investigated the role of autophagy during infection with vacuolar gram-negative bacteria. GBPs directly bind to cytosolic vacuoles containing gram-negative bacteria and then lyse the vacuoles, leading to the cytosolic access of LPS to caspase-11 and activation of the caspase-11 non-canonical inflammasome [16]. This study demonstrated that GBP-mediated lysed vacuoles were detected by the DAMP sensor, galectin-8, which initiated the uptake of gram-negative bacteria into autophagosomes, leading to the inhibition of caspase-11 non-canonical inflammasome activation and caspase-11 non-canonical inflammasome-activated inflammatory responses, such as pyroptosis and secretion of IL-1β in bone marrow-derived macrophages (BMDMs) [50]. These results suggest that host cell-induced lysis of pathogen-containing vacuoles and autophagosomes is a critical immune response and that autophagy negatively regulates inflammatory responses by reducing the activation of the caspase-11 non-canonical inflammasome in macrophages (Fig. 2A).

Figure 2. Summary of functional interplay between mouse caspase-11 non-canonical inflammasome and autophagy. (A) Inhibitory role of autophagy in caspase-11 non-canonical inflammasome during infection with vacuolar gram-negative bacteria in mouse macrophages. (B) Inhibitory role of autophagy in NRF2-mediated caspase-11 non-canonical inflammasome activation and HMGB1 release during inflammatory responses in hepatocytes. (C) Inhibitory role of autophagy-related proteins in caspase-11 non-canonical inflammasome in macrophages and LPS-induced acute lethal septic mice. (D) Induction of autophagy by caspase-11 non-canonical inflammasome in response to bacterial infection in the macrophages. HMGB1, high‐mobility group box 1; LPS, lipopolysaccharide; GBP, guanylate‐binding protein.

Khambu et al. [51] investigated the functional relationship between autophagy caspase-11 non-canonical inflammasome and inflammatory responses in hepatocytes. NRF2 transcriptionally increases caspase-11 expression, resulting in the activation of the caspase-11 non-canonical inflammasome and the release of HMGB1, a hepatocyte DAMP participating in macrophage-mediated inflammatory responses, in autophagy-deficient hepatocytes [51]. A previous study by the same research group reported that HMGB1 is actively released from autophagy-deficient hepatocytes and is dependent on caspase-11 non-canonical inflammasome activation [52]. These two studies revealed that autophagy is negatively correlated with NRF2-mediated caspase-11 non-canonical inflammasome activation and HMGB1 release during inflammatory responses in hepatocytes (Fig. 2B).

The complex molecular machinery consisting of autophagy-related proteins plays a crucial role in the regulation of autophagy. Recent studies have demonstrated the functional involvement of autophagy-related proteins in the activation of the caspase-11 non-canonical inflammasome in inflammatory responses and diseases. Autophagy-related proteins, such as Atg3/Atg5/Atg7 and Atg16L1, are required for the modification of Atg8 family proteins and GABARAP during autophagy [53], and Sakaguchi et al. [54] investigated the role of GABARAP autophagy-related proteins in caspase-11 non-canonical inflammasome-mediated inflammatory responses and lethal endotoxic shock. Deficiency of GABARAP autophagy-related proteins, Gate-16 (Gabarapl2) and Gabarap, induces GBP2-mediated activation of the caspase-11 non-canonical inflammasome but not canonical inflammasomes, leading to caspase-11 non-canonical inflammasome-mediated inflammatory responses such as pyroptosis and IL-1β secretion in BMDMs [54]. In addition, higher mortality has been observed in GABARAP autophagy-related protein-deficient mice during LPS-induced lethal sepsis [54]. These results suggest an inhibitory role of GABARAP autophagy-related proteins in caspase-11 non-canonical inflammasome-activated inflammatory responses and lethal septic shock (Fig. 2C).

Human immunity-related GTPase M clade proteins and their mouse isoforms Irgm1, Irgm2, and Irgm3 are autophagy- and dynamin-related membrane remodeling proteins, and a few Irgm isoforms regulate autophagic flux [55-57]. Finethy et al. [58] investigated the role of the autophagy-related protein, Irgm, in caspase-11 non-canonical inflammasome-mediated inflammatory responses and lethal septic shock. Irgm2 deficiency aberrantly activates the caspase-11 non-canonical inflammasome and caspase-11 non-canonical inflammasome-induced inflammatory responses in BMDMs [58]. Additionally, Irgm2-dieificnet mice were more susceptible to caspase-11 non-canonical inflammasome-activated lethal septic shock [58]. These results indicated that the autophagy-related protein Irgm2 negatively modulates caspase-11 non-canonical inflammasome activation and alleviates LPS-induced lethal septic shock in mice (Fig. 2C).

Finethy et al. [58] demonstrated the role of two autophagy-related proteins, Irgm2 and Gate-16, in caspase-11 non-canonical inflammasome activation and lethal septic shock. The Irgm2/Gate-16 axis cooperatively inhibits caspase-11 non-canonical inflammasome activation by gram-negative bacteria, which suppresses caspase-11 non-canonical inflammasome-activated pyroptosis and cytokine secretion in BMDMs [59]. In addition, the deficiency of either Irgm2 or Gate-16 induces GBP-induced activation of the caspase-11 non-canonical inflammasome in response to gram-negative bacteria [59]. Moreover, Irgm2-dieificnet mice are more susceptible to LPS-induced lethal septic shock [59]. These results suggest that the autophagy-related proteins Irgm2 and Gate-16 inhibit caspase-11 non-canonical inflammasome-activated inflammatory responses in macrophages and lethal septic shock in mice (Fig. 2C).

Previous studies have demonstrated the inhibitory role of autophagy or autophagy-related proteins in mouse caspase-11 or human caspase-4 non-canonical inflammasome-activated inflammatory responses and diseases such as lethal sepsis and myocardial ischemia/reperfusion in mice. However, a recent study reported a regulatory role for the caspase-11 non-canonical inflammasome in autophagy induced by bacterial infection. Krause et al. [60] demonstrated that macrophages with caspase-11 deficiency failed to form autophagosomes in response to infection by the gram-negative bacterium Burkholderia cenocepacia. Caspase-11 non-canonical inflammasome promotes the formation of autophagosomes containing B. cenocepacia and the fusion of autophagosomes with lysosomes in BMDMs [60]. The caspase-11-deficient BMDMs exhibited defects in the delivery of B. cenocepacia to lysosomes and the formation of autophagosomes in response to infection with B. cenocepacia [60]. In addition, the caspase-11 non-canonical inflammasome enhances the elimination of intracellular B. cenocepacia by promoting autophagy in BMDMs [60]. These results suggest that activation of caspase-11 non-canonical inflammasome in response to bacterial infection induces autophagosome formation in macrophages and bacterial elimination (Fig. 2D).

Despite the evidence from these studies demonstrating the inhibitory role of autophagy and autophagy-related proteins in caspase-11 non-canonical inflammasome-activated inflammatory responses and lethal sepsis, the underlying molecular mechanisms by which autophagy inhibits caspase-11 non-canonical inflammasome activation and consequent inflammatory responses are still unclear, which remains to be identified.

Human caspase-4 non-canonical inflammasome and autophagy

Caspase-4 is a human homologue of mouse caspase-11 [16]. Functional crosstalk between the caspase-4 non-canonical inflammasome and autophagy in inflammatory diseases and infection-induced inflammatory responses has been reported. Sun et al. [61] investigated the role of beclin1-driven autophagy in controlling the caspase-4 non-canonical inflammasome in myocardial ischemia/reperfusion injury. Beclin1 is an essential protein for autophagy [62], and beclin1 overexpression ameliorated myocardial ischemia/reperfusion injury in mice by enhancing autophagic flux in human cardiac microvascular endothelial cells (CMECs) [61]. Myocardial ischemia/reperfusion induces the activation of the caspase-4 non-canonical inflammasome and caspase-4 non-canonical inflammasome-mediated inflammatory responses, such as pyroptosis and IL-1β secretion in human CMECs and the heart of myocardial ischemia/reperfusion mice [61]. Beclin1 overexpression inhibited the activation of the caspase-4 non-canonical inflammasome and caspase-4 non-canonical inflammasome-mediated inflammatory responses by promoting autophagic flux in myocardial ischemia/reperfusion mice. Impaired autophagic flux activates the caspase-4 non-canonical inflammasome in human CMECs [61]. Beclin1 overexpression-driven autophagic flux dampens the activation of the caspase-4 non-canonical inflammasome and caspase-4 non-canonical inflammasome-mediated inflammatory responses in human CMECs [61]. These results suggest that autophagy promoted by beclin1 inhibits human caspase-4 non-canonical inflammasome activation and inflammatory responses in myocardial ischemia/reperfusion injury. However, despite clear evidence, the molecular mechanisms by which beclin1 regulates autophagic flux and autophagy inhibits caspase-4 non-canonical inflammasome activation need to be further elucidated. The roles of autophagy in human caspase-4 non-canonical inflammasome-activated inflammatory responses and diseases are summarized in Fig. 3.

Figure 3. Summary of functional interplay between human caspase-4 non-canonical inflammasome and autophagy. CMECs, cardiac microvascular endothelial cells.

Inflammasomes are cytosolic protein complexes that act as molecular platforms for inflammatory signaling pathways in response to various PAMPs and DAMPs [14,15,63]. Canonical inflammasomes were discovered earlier, and many studies have demonstrated the functional interplay between canonical inflammasomes, particularly the NLRP3 inflammasome, and autophagy in the inflammatory response and various immunopathological conditions [46,47,64,65]. Non-canonical inflammasomes were discovered later than canonical inflammasomes, and recent studies have demonstrated that, similar to canonical inflammasomes, non-canonical inflammasomes have a functional interplay with autophagy in inflammatory responses and diseases. This review comprehensively discusses studies investigating the functional interplay between non-canonical inflammasomes and autophagy during non-canonical inflammasome-activated inflammatory responses and diseases, as summarized in Table 1. Most studies discussed in this review suggest that autophagy and autophagy-related proteins, such as Gate-16, Gabarap, Irgm2, and Beclin1, inhibit mouse caspase-11 and human caspase-4 non-canonical inflammasomes, leading to the suppression of non-canonical inflammasome-mediated inflammatory responses and diseases such as infection-induced lethal sepsis and myocardial ischemia/reperfusion injury. The mechanisms by which autophagy inhibits the activation of non-canonical inflammasomes still remain largely unknown. However, some previous studies might provide the clues about the inhibitory role of autophagy in the activation of non-canonical inflammasomes. Autophagy inhibits NLRP3 inflammasome by decreasing the expression of inflammasome components and the activity of NLRP3 through NLRP3 phosphorylation [46]. Autophagy also inhibits NLRP3 inflammasome by degrading components of the NLRP3 inflammasomes [41]. These studies suggest that autophagy might inhibit non-canonical inflammasomes by decreasing the expression of caspase-4/5/11, regulating the post-translational modification of caspase-4/5/11, and degrading caspase-4/5/11. Indeed, a recent study demonstrated that the function of caspase-11 is regulated by its arginine ADP-riboxanation [66]. Autophagy is a biological process to remove damaged organelles and results in the reduced release of DAMPs, which suggests that autophagy might remove the vacuoles containing Gram-negative bacteria or LPS, leading to the inhibition of non-canonical inflammasome activation by clearing cytosolic LPS.

Table 1 . Functional interplay between non-canonical inflammasomes and autophagy.

Inflammasomes	Functional interplay with autophagy	Models	Ref.
Mouse caspase-11 non-canonical inflammasome	• Detection of GBP-mediated lysed vacuoles by galectin-8 initiated the uptake of gram-negative bacteria into autophagosomes. • Uptake of autophagosome inhibited caspase-11 non-canonical inflammasome activation, which suppressed pyroptosis and secretion of IL-1β in BMDMs.	Mouse BMDMs	[50]
	• Caspase-11 deletion prevented HMGB1 release, and caspase-11 activation induced HMGB1 release from autophagy-deficient hepatocytes. • NRF2 is directly bound to the caspase-11 promoter and transcriptionally increases the expression of caspase-11 in hepatocytes. • Autophagy-deficiency-induced NRF2-mediated transcriptional activation of caspase-11 and HMGB1 release from hepatocytes.	Mouse hepatocytes	[51]
	• Deficiency of GABARAP autophagy-related proteins, Gate-16 and Gabarap, induced GBP2-mediated activation of caspase-11 non-canonical inflammasomes, but not canonical inflammasomes, leading to pyroptosis and IL-1β secretion in BMDMs. • Higher mortality was observed in GABARAP autophagy-related protein-deficient mice during LPS-induced lethal sepsis.	Mouse BMDMs LPS-induced lethal septic mice	[54]
	• Deficiency of Irgm2 aberrantly activated caspase-11 non-canonical inflammasome and caspase-11 non-canonical inflammasome-induced inflammatory responses in BMDMs. • Irgm2-dieificnet mice were more susceptible to caspase-11 non-canonical inflammasome-activated lethal septic shock.	Mouse BMDMs LPS-induced lethal septic mice	[58]
	• Irgm2/Gate-16 axis cooperatively inhibited caspase-11 non-canonical inflammasome activation and suppressed caspase-11 non-canonical inflammasome-activated pyroptosis and cytokine secretion in BMDMs. • Deficiency of Irgm2 or Gate-16-induced GBP-mediated activation of caspase-11 non-canonical inflammasome. • Irgm2-dieificnet mice were more susceptible to LPS-induced lethal septic shock.	Mouse BMDMs LPS-induced lethal septic mice	[59]
	• Caspase-11 non-canonical inflammasome promoted Burkholderia cenocepacia-containing autophagosome formation in BMDMs. • Caspase-11 non-canonical inflammasome promoted fusion of autophagosomes with lysosomes in BMDMs. • Caspase-11-deficient BMDMs exhibited a defect in B. cenocepacia delivery to lysosomes and autophagosome formation in response to infection with B. cenocepacia in BMDMs. • Caspase-11 non-canonical inflammasome enhanced the elimination of intracellular B. cenocepacia by promoting autophagy in BMDMs.	Mouse BMDMs B. cenocepacia-infected mice	[60]
Human caspase-4 non-canonical inflammasome	• Beclin1 overexpression ameliorated myocardial reperfusion injury in mice by enhancing autophagic flux in human CMECs. • Myocardial ischemia/reperfusion-induced caspase-4 non-canonical inflammasome activation, pyroptosis, and IL-1β secretion in human CMECs and heart of myocardial ischemia/reperfusion mice. • Beclin1 overexpression inhibited caspase-4 non-canonical inflammasome activation, pyroptosis, and IL-1β secretion by promoting autophagic flux in myocardial ischemia/reperfusion mice. • Impaired autophagic flux activated caspase-4 non-canonical inflammasome in human CMECs. • Beclin1 overexpression-driven autophagic flux dampened caspase-4 non-canonical inflammasome activation, pyroptosis, and IL-1β secretion in human CMECs.	Human CMECs Myocardial ischemia/reperfusion mice	[62]

GBP, guanylate‐binding protein; IL, interleukin; BMDMs, bone marrow-derived macrophages; HMGB1, high‐mobility group box 1; LPS, lipopolysaccharide; CMECs, cardiac microvascular endothelial cells.

Unlike the studies discussed above, a study suggests that the human caspase-4 non-canonical inflammasome induces autophagy in response to bacterial infection, which suggests a different role for non-canonical inflammasomes and autophagy in inflammatory responses. Despite evidence from these studies, the functional correlation between non-canonical inflammasomes and autophagy and the underlying molecular mechanisms are still largely unknown. Therefore, studies demonstrating the functional correlation between non-canonical inflammasomes and autophagy in inflammatory conditions and diseases are in high demand. Additionally, the identification of novel molecules that play critical roles in the functional interplay between non-canonical inflammasomes and autophagy, such as non-canonical inflammasome-associated molecules and autophagy-related proteins, and the validation of the underlying molecular mechanisms need to be further investigated. Moreover, non-canonical inflammasomes and autophagy may be potential targets for alleviating inflammatory responses and treating inflammatory diseases. The non-canonical inflammasomes play critical roles in a variety of human inflammatory diseases [67], which indicates that modulating the functions of non-canonical inflammasomes could be a promising strategy to treat the diseases. Also, targeting autophagy is considered as a therapeutic strategy for numerous human diseases, and the molecules activating or inhibiting the autophagic pathways are currently under development [68]. Therefore, the development of novel therapeutics that can modulate non-canonical inflammasomes and/or autophagy as well as the functional interplay between non-canonical inflammasomes and autophagy needs to be investigated. Moreover, validating the proof of concept of these therapeutics by conducting translational research in patients suffering from various diseases is highly demanded.

In conclusion, recent accumulating evidence reveals that the functional interplay between non-canonical inflammasomes and autophagy is an essential cellular mechanism to protect the body from dangerous pathogens and signals and to maintain cellular homeostasis. Therefore, understanding the functional correlation between non-canonical inflammasomes and autophagy increases scientific knowledge on how they work together in inflammatory responses and diseases and provides clues to develop novel anti-inflammatory therapeutics for the treatment of various human inflammatory diseases.

None.

The author declares no conflict of interest.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (MSIT) (RS-2023-00239222).