Caspase-11-Mediated Cell Death Contributes to the Pathogenesis of Imiquimod-Induced Psoriasis

Gasdermin D (GSDMD) Is Upregulated in Psoriatic Skin-A New Potential Link in the Pathogenesis of Psoriasis

Psoriasis is an important issue in daily dermatological practice. Not only is it an aesthetic defect but it is also a matter of decreased life quality and economic burden. However frequent, the pathogenesis of psoriasis remains uncertain despite numerous investigations. Gasdermins are a family of six proteins. Gasdermin D (GSDMD) is the best-studied from this group and is involved in the processes of inflammation, proliferation, and death of cells, especially pyroptosis. GSDMD has never been studied in psoriatic sera or urine before. Our study involved 60 patients with psoriasis and 30 volunteers without dermatoses as controls. Serum and urinary GSDMD concentrations were examined by ELISA. The tissue expression of GSDMD was assessed by immunohistochemistry. The serum-GSDMD concentration was insignificantly higher in the patients than controls. There were no differences in the urinary-GSDMD concentrations between the patients and controls. Strong tissue expression of GSDMD was significantly more prevalent in psoriatic plaque than in the non-lesional skin and healthy skin of the controls. There was no correlation between the serum-GSDMD concentrations and the psoriasis severity in PASI, age, or disease duration. Taking into consideration the documented role of gasdermins in cell proliferation and death, the increased expression of GSDMD in psoriatic skin may demonstrate the potential involvement of this protein in psoriasis pathogenesis. Neither serum, nor urinary GSDMD can be currently considered a psoriasis biomarker; however, future studies may change this perspective.

Classification and biomarker gene selection of pyroptosis-related gene expression in psoriasis using a random forest algorithm

Background: Psoriasis is a chronic and immune-mediated skin disorder that currently has no cure. Pyroptosis has been proved to be involved in the pathogenesis and progression of psoriasis. However, the role pyroptosis plays in psoriasis remains elusive.

Methods: RNA-sequencing data of psoriasis patients were obtained from the Gene Expression Omnibus (GEO) database, and differentially expressed pyroptosis-related genes (PRGs) between psoriasis patients and normal individuals were obtained. A principal component analysis (PCA) was conducted to determine whether PRGs could be used to distinguish the samples. PRG and immune cell correlation was also investigated. Subsequently, a novel diagnostic model comprising PRGs for psoriasis was constructed using a random forest algorithm (ntree = 400). A receiver operating characteristic (ROC) analysis was used to evaluate the classification performance through both internal and external validation. Consensus clustering analysis was used to investigate whether there was a difference in biological functions within PRG-based subtypes. Finally, the expression of the kernel PRGs were validated in vivo by qRT-PCR.

Results: We identified a total of 39 PRGs, which could distinguish psoriasis samples from normal samples. The process of T cell CD4 memory activated and mast cells resting were correlated with PRGs. Ten PRGs, IL-1β, AIM2, CASP5, DHX9, CASP4, CYCS, CASP1, GZMB, CHMP2B, and CASP8, were subsequently screened using a random forest diagnostic model. ROC analysis revealed that our model has good diagnostic performance in both internal validation (area under the curve [AUC] = 0.930 [95% CI 0.877–0.984]) and external validation (mean AUC = 0.852). PRG subtypes indicated differences in metabolic processes and the MAPK signaling pathway. Finally, the qRT-PCR results demonstrated the apparent dysregulation of PRGs in psoriasis, especially AIM2 and GZMB.

Conclusion: Pyroptosis may play a crucial role in psoriasis and could provide new insights into the diagnosis and underlying mechanisms of psoriasis.

Modulation of Autoimmune and Autoinflammatory Diseases by Gasdermins

Autoimmune diseases and autoinflammatory diseases are two types of the immune system disorders. Pyroptosis, a highly inflammatory cell death, plays an important role in diseases of immune system. The gasdermins belong to a pore-forming protein gene family which are mainly expressed in immune cells, gastrointestinal tract, and skin. Gasdermins are regarded as an executor of pyroptosis and have been shown to possess various cellular functions and pathological effects such as pro-inflammatory, immune activation, mediation of tumor, etc. Except for infectious diseases, the vital role of gasdermins in autoimmune diseases, autoinflammatory diseases, and immune-related neoplastic diseases has been proved recently. Therefore, gasdermins have been served as a potential therapeutic target for immune disordered diseases. The review summarizes the basic molecular structure and biological function of gasdermins, mainly discusses their role in autoimmune and autoinflammatory diseases, and highlights the recent research on gasdermin family inhibitors so as to provide potential therapeutic prospects.

Caspase-4 and -5 Biology in the Pathogenesis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic relapsing inflammatory disease of the gastrointestinal tract, associated with high levels of inflammatory cytokine production. Human caspases-4 and -5, and their murine ortholog caspase-11, are essential components of the innate immune pathway, capable of sensing and responding to intracellular lipopolysaccharide (LPS), a component of Gram-negative bacteria. Following their activation by LPS, these caspases initiate potent inflammation by causing pyroptosis, a lytic form of cell death. While this pathway is essential for host defence against bacterial infection, it is also negatively associated with inflammatory pathologies. Caspases-4/-5/-11 display increased intestinal expression during IBD and have been implicated in chronic IBD inflammation. This review discusses the current literature in this area, identifying links between inflammatory caspase activity and IBD in both human and murine models. Differences in the expression and functions of caspases-4, -5 and -11 are discussed, in addition to mechanisms of their activation, function and regulation, and how these mechanisms may contribute to the pathogenesis of IBD.

Regulation, Activation and Function of Caspase-11 during Health and Disease

Caspase-11 is a pro-inflammatory enzyme that is stringently regulated during its expression and activation. As caspase-11 is not constitutively expressed in cells, it requires a priming step for its upregulation, which occurs following the stimulation of pathogen and cytokine receptors. Once expressed, caspase-11 activation is triggered by its interaction with lipopolysaccharide (LPS) from Gram-negative bacteria. Being an initiator caspase, activated caspase-11 functions primarily through its cleavage of key substrates. Gasdermin D (GSDMD) is the primary substrate of caspase-11, and the GSDMD cleavage fragment generated is responsible for the inflammatory form of cell death, pyroptosis, via its formation of pores in the plasma membrane. Thus, caspase-11 functions as an intracellular sensor for LPS and an immune effector. This review provides an overview of caspase-11—describing its structure and the transcriptional mechanisms that govern its expression, in addition to its activation, which is reported to be regulated by factors such as guanylate-binding proteins (GBPs), high mobility group box 1 (HMGB1) protein, and oxidized phospholipids. We also discuss the functional outcomes of caspase-11 activation, which include the non-canonical inflammasome, modulation of actin dynamics, and the initiation of blood coagulation, highlighting the importance of inflammatory caspase-11 during infection and disease.

Pyroptosis by caspase-11 inflammasome-Gasdermin D pathway in autoimmune diseases

Inflammasomes are a group of supramolecular complexes primarily comprise a sensor, adaptor protein and an effector. Among them, canonical inflammasomes are assembled by one specific pattern recognition receptor, the adaptor protein apoptosis-associated speck-like protein containing a CARD and procaspase-1. Murine caspase-11 and its human ortholog caspase-4/5 are identified as cytosolic sensors which directly responds to LPS. Once gaining access to cytosol, LPS further trigger inflammasome activation in noncanonical way. Downstream pore-forming Gasdermin D is a pyroptosis executioner. Emerging evidence announced in recent years demonstrate the vital role played by caspase-11 non-canonical inflammasome in a range of autoimmune diseases. Pharmacological ablation of caspase-11 and its related effector results in potent therapeutic effects. Though recent advances have highlighted the potential of caspase-11 as a drug target, the understanding of caspase-11 molecular activation and regulation mechanism remains to be limited and thus hampered the discovery and progression of novel inhibitors. Here in this timeline review, we explored how caspase-11 get involved in the pathogenesis of autoimmune diseases, we also collected the reported small-molecular caspase-11 inhibitors. Moreover, the clinical implications and therapeutic potential of caspase-11 inhibitors are discussed. Targeting non-canonical inflammasomes is a promising strategy for autoimmune diseases treatment, while information about the toxicity and physiological disposition of the promising caspase-11 inhibitors need to be supplemented before they can be translated from bench to bedside.

Caspase-4: A Therapeutic Target for Peptic Ulcer Disease

Peptic ulcers are caused by the interaction between bacterial and host factors. This study demonstrates enhanced expression of caspase-4 in peptic ulcer patient biopsies, indicating that pyroptosis and noncanonical inflammasome activity may be processes involved in peptic ulcer disease. We show that primary murine macrophages infected with Helicobacter pylori upregulate caspase-11 (the ortholog of human caspase-4), activate caspase-1, and secrete IL-1β. We demonstrate that misoprostol (a stable PGE1 analogue) decreased IL-1β secretion and delayed lethality in vivo in a murine peritonitis model. PGE2 was shown to inhibit caspase-11-driven pyroptosis and IL-1β secretion in macrophages. Overall, we provide evidence for a pathological role of caspase-4/11 in peptic ulcer disease and propose that targeting caspase-4 or inhibiting pyroptosis may have therapeutic potential in the management of peptic ulcers.