Overexpression Of Caspase-1 Research Articles

Loss of p53 function promotes DNA damage-induced formation of nuclear actin filaments

Tumor suppressor p53 plays a central role in response to DNA damage. DNA-damaging agents modulate nuclear actin dynamics, influencing cell behaviors; however, whether p53 affects the formation of nuclear actin filaments remains unclear. In this study, we found that p53 depletion promoted the formation of nuclear actin filaments in response to DNA-damaging agents, such as doxorubicin (DOXO) and etoposide (VP16). Even though the genetic probes used for the detection of nuclear actin filaments exerted a promotive effect on actin polymerization, the detected formation of nuclear actin filaments was highly dependent on both p53 depletion and DNA damage. Whilst active p53 is known to promote caspase-1 expression, the overexpression of caspase-1 reduced DNA damage-induced formation of nuclear actin filaments in p53-depleted cells. In contrast, co-treatment with DOXO and the pan-caspase inhibitor Q-VD-OPh or the caspase-1 inhibitor Z-YVAD-FMK induced the formation of nuclear actin filament formation even in cells bearing wild-type p53. These results suggest that the p53-caspase-1 axis suppresses DNA damage-induced formation of nuclear actin filaments. In addition, we found that the expression of nLifeact-GFP, the filamentous-actin-binding peptide Lifeact fused with the nuclear localization signal (NLS) and GFP, modulated the structure of nuclear actin filaments to be phalloidin-stainable in p53-depleted cells treated with the DNA-damaging agent, altering the chromatin structure and reducing the transcriptional activity. The level of phosphorylated H2AX (γH2AX), a marker of DNA damage, in these cells also reduced upon nLifeact-GFP expression, whilst details of the functional relationship between the formation of nLifeact-GFP-decorated nuclear actin filaments and DNA repair remained to be elucidated. Considering that the loss of p53 is associated with cancer progression, the results of this study raise a possibility that the artificial reinforcement of nuclear actin filaments by nLifeact-GFP may enhance the cytotoxic effect of DNA-damaging agents in aggressive cancer cells through a reduction in gene transcription.

Smart Mitochondria‐Specific Anchored Gold‐based Nanosystem for Integration of Tumor Imaging and Treatment

AbstractAlthough recent advances have been made in improving the efficacy of photodynamic therapy, efficient therapeutic approaches based on reactive oxygen species (ROS) are needed, particularly mitochondria‐specific targeting of nanomaterials that can alter the internal environment of organelles. Herein, we report the facile synthesis of mitochondria‐specific anchored nano‐complexes (AG‐CNP) comprised of a skeleton of gold and carbon atoms for cancer therapy. Compared to the effects of gold nanoclusters (Au NCs), AG‐CNP shows enhanced fluorescence imaging effects, which can be used for tumor monitoring. AG‐CNP targets the mitochondria and increases ROS damage in cancer cells. After treatment with AG‐CNP, the tumor inhibition rate reaches 70.94%, which is 25.98% and 36.91% higher than that of free doxorubicin (DOX) and gemcitabine (Gem), respectively. Studying the mechanism of AG‐CNP inhibiting cancer shows that AG‐CNP can promote tumor cells to produce excessive ROS by overexpressing P53 and increasing the number of apoptotic cancer cells, which is caused by overexpression of Caspase1 that was closely related to cell apoptosis. AG‐CNP is a promising anticancer drug that targets the mitochondria in vivo to trigger excessive ROS production in tumor cells and inhibit tumor growth.

Hepatocytes Are Resistant to Cell Death From Canonical and Non-Canonical Inflammasome-Activated Pyroptosis.

BackgroundPyroptosis, gasdermin-mediated programmed cell death, is readily induced in macrophages by activation of the canonical inflammasome (caspase-1) or by intracellular lipopolysaccharide (LPS)-mediated non-canonical inflammasome (caspase-11) activation. However, whether pyroptosis is induced similarly in hepatocytes is still largely controversial but highly relevant to liver pathologies such as alcoholic/nonalcoholic liver disease, drug-induced liver injury, ischemia-reperfusion and liver transplant injury, or organ damage secondary to sepsis.Methods and ResultsIn this study we found that hepatocytes activate and cleave gasdermin-D (GSDMD) at low levels after treatment with LPS. Overexpression of caspase-1 or caspase-11 p10/p20 activated domains was able to induce typical GSDMD-dependent pyroptosis in hepatocytes both in vitro and in vivo. However, morphologic features of pyroptosis in macrophages (eg, pyroptotic bodies, cell flattening, loss of cell structure) did not occur in pyroptotic hepatocytes, with cell structure remaining relatively intact despite the cell membrane being breached. Our results suggest that hepatocytes activate pyroptosis pathways and cleave GSDMD, but this does not result in cell rupture and confer the same pyroptotic morphologic changes as previously reported in macrophages. This is true even with caspase-1 or caspase-11 artificial overexpression way above levels seen endogenously even after priming or in pathologic conditions.ConclusionsOur novel findings characterize hepatocyte morphology in pyroptosis and suggest alternative use for canonical/non-canonical inflammasome activation/signaling and subsequent GSDMD cleavage because there is no rapid cell death as in macrophages. Improved understanding and recognition of the role of these pathways in hepatocytes may result in novel therapeutics for a range of liver diseases.

Subicular Caspase-1 Contributes to Pharmacoresistance in Temporal Lobe Epilepsy.

Unidentified mechanisms largely restrict the viability of effective therapies in pharmacoresistant epilepsy. Our previous study revealed that hyperactivity of the subiculum is crucial for the genesis of pharmacoresistance in temporal lobe epilepsy (TLE), but the underlying molecular mechanism is not clear. Here, we examined the role of subicular caspase-1, a key neural pro-inflammatory enzyme, in pharmacoresistant TLE. We found that the expression of activated caspase-1 in the subiculum, but not the CA1, was upregulated in pharmacoresistant amygdaloid-kindled rats. Early overexpression of caspase-1 in the subiculum was sufficient to induce pharmacoresistant TLE in rats, whereas genetic ablation of caspase-1 interfered with the genesis of pharmacoresistant TLE in both kindled rats and kainic acid-treated mice. The pro-pharmacoresistance effect of subicular caspase-1 was mediated by its downstream inflammasome-dependent interleukin-1β. Further electrophysiological results showed that inhibiting caspase-1 decreased the excitability of subicular pyramidal neurons through influencing the excitation/inhibition balance of presynaptic input. Importantly, a small molecular caspase-1 inhibitor CZL80 attenuated seizures in pharmacoresistant TLE models, and decreased the neuronal excitability in the brain slices obtained from patients with pharmacoresistant TLE. These results support the subicular caspase-1-interleukin-1β inflammatory pathway as a novel alternative mechanism hypothesis for pharmacoresistant TLE, and present caspase-1 as a potential target. ANN NEUROL 2021;90:377-390.

Necrosulfonamide reverses pyroptosis-induced inhibition of proliferation and differentiation of osteoblasts through the NLRP3/caspase-1/GSDMD pathway

The acute inflammatory stimulation occurring after a bone fracture regulates the repair and healing of local bone injury; however, under certain conditions, pyroptosis may occur in osteoblasts, which affects osteoblast proliferation and differentiation, thereby affecting the growth, development and morphological changes of bone tissue. The aim of the present study was to examine the effect of the pyroptosis inhibitor necrosulfonamide (NSA) on the proliferation and differentiation of osteoblasts and elucidate the underlying mechanism. The results revealed that NSA reversed the effects of ATP/lipopolysaccharide (LPS) on cell viability and pyroptosis, and on the mRNA and protein expression of pyroptosis-related genes. It also suppressed the secretion of IL-6, TNF-α and IL-1β and reversed the effects of ATP/LPS on the activity of ALP and the mRNA expression of differentiation-related genes in osteoblasts. The fact that overexpression of caspase-1, gasdermin D (GSDMD) and NLRP3 abolished the effects of NSA on the viability and pyroptosis of osteoblasts, as well as the mRNA expression of differentiation-related genes and the activity of ALP in osteoblasts, indicated that NSA promoted the proliferation and differentiation of osteoblasts by inhibiting the NLRP3/caspase-1/GSDMD pyroptosis pathway. The present study provides proof supporting the potential application of NSA for improving the function of osteoblasts in fracture repair and indicates the value of the NLRP3/caspase-1/GSDMD pyroptosis pathway as a pharmaceutical target.

Caspase-1 Abrogates the Salutary Effects of Hypertrophic Preconditioning in Pressure Overload Hearts via IL-1β and IL-18.

Cardiac hypertrophic preconditioning (HP) signifies cardioprotection induced by transient pressure overload to resist hypertrophic effects of subsequently sustained pressure overload. Although it is recently found that inflammation triggers the development of nonischemic cardiomyopathy, whether inflammation plays a role in the antecedent protective effects of HP remains unknown. Caspase-1 is a critical proinflammatory caspase that also induces pyroptosis; thus, we investigated the role of caspase-1 using a unique model of HP in mice subjected longitudinally to 3 days of transverse aortic constriction (TAC 3d), 4 days of de-constriction (De-TAC 4d), and 4 weeks of Re-TAC (Re-TAC 4W). Echocardiography, hemodynamics, histology, PCR, and western blot confirmed preserved cardiac function, alleviated myocardial hypertrophy and fibrosis, and less activated hypertrophic signaling effectors in Re-TAC 4W mice, compared with TAC 4W mice. Mechanistically, caspase-1 and its downstream targets IL-1β and IL-18, but not GSDMD, were less activated in Re-TAC 4W mice. Furthermore, in HP mice with AAV-9-mediated cardiac-specific caspase-1 overexpression, the salutary effects of HP were remarkably abrogated, as evidenced by exacerbated cardiac remodeling, dysfunction, and activation of IL-1β and IL-18. Collectively, this study revealed a previously unrecognized involvement of caspase-1 in cardiac HP by regulation of IL-1β and IL-18 and shed light on caspase-1 as an antecedent indicator and target for cardiac hypertrophy.

NLRP3 and NLRP1 inflammasomes are up-regulated in patients with mesial temporal lobe epilepsy and may contribute to overexpression of caspase-1 and IL-β in sclerotic hippocampi

Inflammation plays a role in the pathophysiology of mesial temporal lobe epilepsy (MTLE). Inflammasome pathways, including the NLRP1 and NLRP3-induced ones, promote neuroinflammation and pyroptosis through interleukin (IL)-1β and caspase-1 action. Evaluation of NLRP1 in sclerotic hippocampi is scarce and there are no data on NLRP3 in human TLE. The aim of this study was to evaluate the expression of these proteins alongside caspase-1 and IL-1β in the hippocampi of patients with TLE compared to control samples. We also sought to investigate peripheral levels of caspase-1 and IL-1β in an independent cohort. Sclerotic and control hippocampi were collected for both histological and immunohistochemical analyses of NLRP1, NLRP3, caspase-1 and IL-1β; plasma was sampled for the measurement of caspase-1 and IL-1β levels through enzyme-linked immunoassay (ELISA) and cytometric bead array (CBA). Sclerotic hippocampi displayed higher expression of the measured proteins than control. Both glia and neurons showed activation of these pathways. Additionally, increased expression of NLRP1 and NLRP3 was associated with elevated plasma levels of IL-1β and in TLE, and increased levels of peripheral caspase-1 were associated with bilateral hippocampal sclerosis (HS). In conclusion, NLRP1 and NLRP3 are up-regulated in sclerotic hippocampi, what may be responsible, at least in part, for the increased hippocampal expression of caspase-1 and IL-1β. Our data suggest a role for inflammasome activation in central and peripheral inflammation in TLE.

Structure‐based discovery of CZL80, a caspase‐1 inhibitor with therapeutic potential for febrile seizures and later enhanced epileptogenic susceptibility

Febrile seizures (FS), the most common seizures in childhood and often accompanied by later epileptogenesis, are not well controlled. Inflammatory processes have been implicated in the pathophysiology of epilepsy. However, whether caspase-1 is involved in FS generation and could be a target for the treatment of FS is still unclear. By using pharmacological and gene intervention methods in C57BL/6J mice, we assessed the role of caspase-1 in FS generation. We used structural virtual screening against the active site of caspase-1, to screen compounds for druggable and safe low MW inhibitors of caspase-1 in vitro. One compound was chosen to test in vivo for therapeutic potential, using FS models in neonatal mice and epileptogenesis in adult mice. In mice, levels of cleaved caspase-1 increased prior to FS onset. Caspase-1-/- mice were resistant to FS and showed lower neuronal excitability than wild-type littermates. Conversely, overexpression of caspase-1 using in utero electroporation increased neuronal excitability and enhanced susceptibility to FS. The structural virtual screening, using molecular docking approaches for the active site of caspase-1 of over 1 million compounds yielded CZL80, a brain-penetrable, low MW inhibitor of caspase-1. In neonatal mice, CZL80 markedly reduced neuronal excitability and incidence of FS generation, and, in adult mice, relieved later enhanced epileptogenic susceptibility. CZL80 was devoid of acute diazepam-like respiratory depression and chronic liver toxicity. Caspase-1 is essential for FS generation. CZL80 is a promising low MW inhibitor of FS and later enhanced epileptogenic susceptibility.

Fucoidan exerts antidepressant-like effects in mice via regulating the stability of surface AMPARs

The inflammatory hypothesis is one of the most important mechanisms of depression. Fucoidan is a bioactive sulfated polysaccharide abundant in brown seaweeds with anti-inflammatory activity. However, the antidepressant effects of fucoidan on chronic stress-induced depressive-like behaviors have not been well elucidated. Here, we used two different depressive-like mouse models, lipopolysaccharide (LPS) and chronic restraint stress (CRS) models, to explore the detailed molecular mechanism underlying its antidepressant-like effects in C57BL/6J mice by combining multiple behavioral, molecular and immunofluorescence experiments. Adenovirus-mediated overexpression of caspase-1 and pharmacological inhibitors were also used to clarify the antidepressant mechanisms of fucoidan. We found that acute administration of fucoidan did not produce antidepressant effects in the tail suspension test (TST) and forced swim test (FST). Interestingly, chronic fucoidan administration not only dose-dependently reduced stress-induced depressive-like behaviors in the TST, FST, sucrose preference test (SPT), and novelty-suppressed feeding test (NSFT), but also alleviated the downregulation of brain-derived neurotrophic factor (BDNF)-dependent synaptic plasticity via inhibiting caspase-1-mediated inflammation in the hippocampus of mice. Moreover, fucoidan significantly ameliorated behavioral and synaptic plasticity abnormalities in the overexpression of caspase-1 in the hippocampus of mice. Furthermore, blocking BDNF abolished the antidepressant-like effects of fucoidan in mice. Therefore, our findings clearly indicate that fucoidan provides a potential supplementary noninvasive treatment for depression by inhibition of hippocampal inflammation.

Sorafenib inhibits caspase-1 expression through suppressing TLR4/stat3/SUMO1 pathway in hepatocellular carcinoma

ABSTRACTSorafenib has been demonstrated to be a beneficial treatment for advanced hepatocellular carcinoma (HCC). Emerging evidence indicates that caspase-1 activation plays a crucial role in HCC progression. However, the relationship between caspase-1 and sorafenib has rarely been reported. In this study, we showed that caspase-1 was essential for lipopolysaccharide (LPS)-induced epithelial-mesenchymal transition (EMT). Moreover, sorafenib treatment could inhibit LPS-stimulated caspase-1 overexpression through restricting the nuclear transport of p65, which contributed to inactivation of NF-κB. Co-immunoprecipitation (Co-IP) experiments and immunoblot analysis indicated that sorafenib treatment decreased the SUMOylation of p65 via inhibiting TLR4/stat3/SUMO1 signaling cascades. In conclusion, the results of this study suggest that sorafenib inhibits caspase-1 expression through suppressing the nuclear translocation of p65 and provide new insights into the mechanisms of sorafenib treatment in HCC.

Expression and clinical significance of the NEK7-NLRP3 inflammasome signaling pathway in patients with systemic lupus erythematosus

BackgroundThe aim of the study was to investigate the expression of the NEK7-NLRP3 inflammasome signaling pathway in the peripheral blood mononuclear cells (PBMCs) of patients with systemic lupus erythematosus (SLE), as well as its clinical significance.MethodsA total of 38 SLE patients and 33 healthy volunteers were recruited. Real time PCR and western blotting were performed to determine mRNA and protein levels of NEK7, NLRP3 inflammasome components (NLRP3, ASC, and Caspase-1), and downstream cytokines (IL-1b and IL-18) in PBMCs from the two groups. ELISA was used to detect serum levels of IL-1b and IL-18. The same methods were used to detect changes in the above indices in the 25 SLE patients after treatment. Correlations between clinical and laboratory parameters were also analyzed.ResultsCompared to those in healthy controls, levels of NEK7, NLPR3, and ASC were lower in SLE patients; however, Caspase-1, IL-1b, and IL-18 were expressed at higher levels. mRNA levels of NEK7, NLRP3, and ASC were inversely correlated with disease activity, whereas a positive correlation was observed with IL-1b and IL-18. After treatment, mRNA levels of NEK7 and NLRP3 increased, whereas Caspase-1, IL-1b, and IL-18 decreased significantly. Compared to those in SLE patients without renal damage, patients with lupus nephritis (LN) exhibited lower mRNA levels of NEK7, NLRP3, and ASC but higher levels of Caspase-1, IL-1b, and IL-18.ConclusionsResults indicate that the expression of the NEK7-NLRP3 complex might play a protective role in the pathogenesis of SLE and is inversely correlated with disease activity. A positive effect of NEK7 on NLRP3 was observed, and the low expression of NLRP3 in SLE patients might be related to the low expression of NEK7. Overexpression of Caspase-1 in SLE patients mediates the maturation and release of IL-1b and IL-18, and contributes to the pathogenesis of SLE and LN.

The Correlation of Gene Expression of Inflammasome Indicators and Impaired Fertility in Rat Model of Spinal Cord Injury: A Time Course Study.

Expression assessment of the inflammasome genes in the acute and the chronic phases of Spinal cord injury (SCI) on adult rat testis and examination of associations between inflammasome complex expression and sperm parameters. In this study, 25 adult male rats were randomly divided into 5 groups. SCI surgery was performed at T10-T11 level of rats' spinal cord in four groups (SCI1, SCI3, SCI7, and SCI56). They were sacrificed after 1day, 3days, 7days and 56 days post SCI, respectively. One group remained intact as control (Co).CASA analysis of sperm parameters and qRT-PCR (ASC and Caspase-1) were made in all cases. Our data showed a severe reduction in sperm count and motility, especially on day 3 and 7. ASC gene expression had a non-significant increase on day 1 and 56 after surgery compared to control group. Caspase-1 expression increased significantly on day 3 post injury versus the control group (P = .009). Moreover, Caspase-1 overexpression, had significant correlations with sperm count (r = -0.555, P = .01) and sperm progressive motility (r = -0.524, P = .02). Inflammasome complex expression increase following SCI induction. This overexpression correlates to low sperm parameters in SCI rats.

Gene deficiency and pharmacological inhibition of caspase-1 confers resilience to chronic social defeat stress via regulating the stability of surface AMPARs

Both inflammatory processes and glutamatergic systems have been implicated in the pathophysiology of mood-related disorders. However, the role of caspase-1, a classic inflammatory caspase, in behavioral responses to chronic stress remains largely unknown. To address this issue, we examined the effects and underlying mechanisms of caspase-1 on preclinical murine models of depression. We found that loss of caspase-1 expression in Caspase-1−/− knockout mice alleviated chronic stress-induced depression-like behaviors, whereas overexpression of caspase-1 in the hippocampus of wild-type (WT) mice was sufficient to induce depression- and anxiety-like behaviors. Furthermore, chronic stress reduced glutamatergic neurotransmission and decreased surface expression of glutamate receptors in hippocampal pyramidal neurons of WT mice, but not Caspase-1−/− mice. Importantly, pharmacological inhibition of caspase-1-interleukin-1β (IL-1β) signaling pathway prevented the depression-like behaviors and the decrease in surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) in stressed WT mice. Finally, the effects of chronic stress on both depression- and anxiety-like behaviors can be mimicked by exogenous intracerebroventricular (i.c.v.) administration of IL-1β in both WT and Caspase-1−/− mice. Taken together, our findings demonstrate that an increase in the caspase-1/IL-1β axis facilitates AMPAR internalization in the hippocampus, which dysregulates glutamatergic synaptic transmission, eventually resulting in depression-like behaviors. These results may represent an endophenotype for chronic stress-induced depression.

Effects of hydrogen-rich water on depressive-like behavior in mice.

Emerging evidence suggests that neuroinflammation and oxidative stress may be major contributors to major depressive disorder (MDD). Patients or animal models of depression show significant increase of proinflammatory cytokine interleukin-1β (IL-1β) and oxidative stress biomarkers in the periphery or central nervous system (CNS). Recent studies show that hydrogen selectively reduces cytotoxic oxygen radicals, and hydrogen-rich saline potentially suppresses the production of several proinflammatory mediators. Since current depression medications are accompanied by a wide spectrum of side effects, novel preventative or therapeutic measures with fewer side effects might have a promising future. We investigated the effects of drinking hydrogen-rich water on the depressive-like behavior in mice and its underlying mechanisms. Our study show that hydrogen-rich water treatment prevents chronic unpredictable mild stress (CUMS) induced depressive-like behavior. CUMS induced elevation in IL-1β protein levels in the hippocampus, and the cortex was significantly attenuated after 4 weeks of feeding the mice hydrogen-rich water. Over-expression of caspase-1 (the IL-1β converting enzyme) and excessive reactive oxygen species (ROS) production in the hippocampus and prefrontal cortex (PFC) was successfully suppressed by hydrogen-rich water treatment. Our data suggest that the beneficial effects of hydrogen-rich water on depressive-like behavior may be mediated by suppression of the inflammasome activation resulting in attenuated protein IL-1β and ROS production.

Overexpression of Caspase-1 in Aorta of Patients with Coronary Atherosclerosis

Plenty of studies on animals suggest the involvement of caspase-1 in the development of atherosclerosis. The aim of this study was to investigate the changes of caspase-1 in the aorta of patients with coronary atherosclerosis and its association with atherosclerotic risk factors. We collected button-sized aortic tissues from patients (n = 48) undergoing coronary artery bypass graft (CABG) surgery. Renal arterial tissues from 18 kidney donors without atherosclerosis were taken as control. The expression of caspase-1 was determined by immunohistochemistry, and Gensini score was used to evaluate the severity of coronary atherosclerosis. Caspase-1 was strongly expressed in aortas from CABG patients. Spearman correlation revealed that the aortic caspase-1 expression was significantly correlated with coronary severity scores (r = 0.656, P < 0.05). The relative level of aortic caspase-1 expression was elevated in patients who were smokers or with hypertension or diabetes. The caspase-1 expression was positively correlated with total cholesterol, low density lipoprotein cholesterol, and lipoprotein(a) (P < 0.05); but negatively correlated with high density lipoprotein cholesterol (P < 0.05). Our findings demonstrate a highly expressed caspase-1 in aortas from patients with coronary atherosclerosis, and that modulation of caspase-1 could be a potential target for prevention and treatment of atherosclerosis.

5-Lipoxygenase Inhibitor Zileuton Inhibits Neuronal Apoptosis Following Focal Cerebral Ischemia

Previous studies from our laboratory demonstrated that zileuton, a selective 5-lipoxygenase (5-LOX) inhibitor, attenuates ischemic brain damage in rats of focal cerebral ischemia. Enormous evidences showed that inflammatory reaction and neuronal apoptosis are the two important pathophysiological events in ischemia-induced brain damage. Our previous studies demonstrate that zileuton attenuates ischemic brain damage via inhibiting inflammatory reaction. The present study was performed to explore whether 5-LOX inhibitor zileuton attenuates neuronal apoptosis following focal cerebral ischemia and further investigate the potent mechanisms underlying its neuroprotection. Adult male Sprague-Dawley rats underwent permanent middle cerebral artery occlusion (MCAO) for 72 h, then received intragastric gavage with zileuton or vehicle as a bolus after the onset of MCAO. Neurological deficit scores, cerebral infarct volume, and neuronal damage were measured 72 h after MCAO. TUNEL staining was performed to measure the extent of neuronal apoptosis. Reverse transcription-polymerase chain reaction was performed to determine the expression of caspase-1 mRNA. Western blot was performed to determine the expression of procaspase-3 and cleaved caspase-3 in rat brain. Neurological deficit scores, infarct volume, and neuronal damage were significantly attenuated by administration of zileuton. MCAO caused the elevation of neuronal apoptosis, which was significantly inhibited by the administration of zileuton. MCAO caused the over-expression of caspase-1 and cleaved caspase-3, both of which were significantly inhibited by the administration of zileuton. Expression of procaspase-3 was reduced after MCAO, which was significantly up-regulated by administration of zileuton. Our studies suggested that 5-LOX inhibitor zileuton reduces MCAO-induced brain damage and neuronal apoptosis, which might be associated with the inhibition of caspase-1 and the regulation of caspase-3.

Innate immune response and programmed cell death following carrier-mediated delivery of unmodified mRNA to respiratory cells

In this report we show that carrier-mediated delivery of mRNA may activate TLR3 signaling in respiratory cells. This activation of the innate immune system was accompanied with a massive production of type 1 interferons and other immunostimulating cytokines. The recognition of mRNA by the innate immune system was also associated with cell death, which proceeded in human respiratory cells via pyroptosis, a form of programmed cell death mediated by substantial overexpression of caspase-1. This indicated that the delivered mRNA is most likely also recognized by NOD-like receptors which regulate caspase-1 production. The viability of murine respiratory cells was less affected by mRNA transfection, which is in line with the lower transfection efficiency, lower innate immune response and the absence of a massive caspase-1 upregulation in these cells. Finally, we also demonstrated that the recognition of the delivered mRNA by the innate immune system had a negative effect on mRNA translation.

Mifepristone-Inducible Caspase-1 Expression in Mouse Embryonic Stem Cells Eliminates Tumor Formation but Spares Differentiated Cells In Vitro and In Vivo

Embryonic stem cell (ESC)-based therapy is a promising treatment for neurodegenerative diseases. But there is always a risk of tumor formation that is due to contamination of undifferentiated ESCs. To reduce the risk and improve ESC-based therapy, we have established a novel strategy by which we can selectively eliminate tumor cells derived from undifferentiated ESCs but spare differentiated cells. In this study, we generated a caspase-1-ESC line transfected with a mifepristone-regulated caspase-1 expression system. Mifepristone induced caspase-1 overexpression both in differentiated and undifferentiated caspase-1-ESCs. All the undifferentiated caspase-1-ESCs were induced to death after mifepristone treatment. Tumors derived from undifferentiated caspase-1-ESCs were eliminated following 3 weeks of mifepristone treatment in vivo. However, differentiated caspase-1-ESCs survived well under the condition of mifepristone-induced caspase-1 overexpression. To examine in vivo the impact of mifepristone-induced caspase-1 activation on grafted cells, we transplanted wild-type ESCs or caspase-1-ESCs into nude mice brains. After 8 weeks of mifepristone treatment, we could not detect any tumor cells in the caspase-1-ESC grafts in the brains of mice. However, we found that donor dopamine neurons survived in the recipient brains. These data demonstrate that mifepristone-induced caspase-1 overexpression in ESCs can eliminate the potential tumor formation meanwhile spares the differentiated cells in the host brains. These results suggest that this novel ESC-based therapy can be used in Parkinson's disease and other related disorders without the risk of tumor formation.

Active Caspase-1-Mediated Secretion of Retinoic Acid Inducible Gene-I

Caspase-1 is an inflammatory caspase that controls the activation and secretion of the inflammatory cytokines, IL-1beta and IL-18. We observed that cellular levels of retinoic acid-inducible gene-I (RIG-I) were enhanced when the pan-caspase inhibitor Z-VAD-fmk or caspase-1-specific inhibitor Z-WEHD-fmk blocked caspase activity. Overexpression of caspase-1 reduced cellular levels of RIG-I and inhibited RIG-I-mediated signaling activity. Enzymatic activity of caspase-1 was necessary to control RIG-I, although it was not a substrate of proteolytic cleavage by caspase-1. Caspase-1 physically interacted with full length RIG-I, but not with mutant forms lacking either the amino- or carboxyl-terminal domains. RIG-I was present in the supernatant of cells transfected with active caspase-1 but not with caspase-4. Stimulating cells with LPS and ATP also induced secretion of endogenous RIG-I in macrophages. Our data suggest a novel mechanism that negatively regulates RIG-I-mediated signaling activity via caspase-1-dependent secretion of RIG-I protein.

Frameshift mutation at a mononucleotide repeat in CASP1 is rare in gastric and colorectal carcinomas with microsatellite instability

Caspase-1 was initially identified as an activating enzyme for the proteolytic maturation of pro-interleukin-1β [ [1] Soung Y.H. Jeong E.G. Ahn C.H. Kim S.S. Song S.Y. Yoo N.J. et al. Mutational analysis of caspase 1, 4, and 5 genes in common human cancers. Hum Pathol. 2008; 39: 895-900 Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar ]. In addition, it is well known that caspase-1 overexpression induces apoptotic cell death. Evasion of apoptosis is one of the acquired capabilities of cancers and is considered a hallmark of cancer. Inactivation of apoptosis by somatic mutations of genes encoding proapoptotic proteins, including CASP8 and BAX, has been reported in human cancers [ 2 Kim H.S. Lee J.W. Soung Y.H. Park W.S. Kim S.Y. Nam S.W. et al. Inactivating mutations of caspase-8 gene in colorectal carcinomas. Gastroenterology. 2003; 125: 708-715 Abstract Full Text Full Text PDF PubMed Scopus (187) Google Scholar , 3 Soung Y.H. Lee J.W. Kim S.Y. Jang J. Park Y.G. Park W.S. et al. CASPASE-8 gene is inactivated by somatic mutations in gastric carcinomas. Cancer Res. 2005; 65: 815-821 PubMed Google Scholar , 4 Mori Y. Sato F. Selaru F.M. Olaru A. Perry K. Kimos M.C. et al. Instabilotyping reveals unique mutational spectra in microsatellite-unstable gastric cancers. Cancer Res. 2002; 62: 3641-3645 PubMed Google Scholar , 5 Mori Y. Yin J. Rashid A. Leggett B.A. Young J. Simms L. et al. Instabilotyping: comprehensive identification of frameshift mutations caused by coding region microsatellite instability. Cancer Res. 2001; 61: 6046-6049 PubMed Google Scholar ]. Frameshift mutations of genes containing mononucleotide repeats are features of colorectal and gastric cancers with microsatellite instability (MSI). There is a polyguanine (G8) in BAX gene that is frequently mutated in cancers with MSI [ 4 Mori Y. Sato F. Selaru F.M. Olaru A. Perry K. Kimos M.C. et al. Instabilotyping reveals unique mutational spectra in microsatellite-unstable gastric cancers. Cancer Res. 2002; 62: 3641-3645 PubMed Google Scholar , 5 Mori Y. Yin J. Rashid A. Leggett B.A. Young J. Simms L. et al. Instabilotyping: comprehensive identification of frameshift mutations caused by coding region microsatellite instability. Cancer Res. 2001; 61: 6046-6049 PubMed Google Scholar ]. The BAX mutant has a decreased apoptotic activity and is considered to contribute to cancer development.