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Inflammasome activation by cystine crystals: implications for the pathogenesis of cystinosis.

ABSTRACT: Intralysosomal cystine crystal accumulation, due to mutations in the CTNS gene, is a hallmark of nephropathic cystinosis, but the role of these crystals in disease pathogenesis remains unclear. We hypothesized that, similar to other host-derived crystalline moieties, cystine crystals can induce IL-1? production through inflammasome activation. Thus, we investigated the proinflammatory effects of cystine crystals in primary human PBMCs. LPS-primed PBMCs stimulated with cystine crystals secreted IL-1? in a dose-dependent manner. Similarly to IL-1? secretion induced by other crystalline inflammasome activators, cystine crystal-induced IL-1? secretion required activation of caspase-1. Additionally, exogenous cystine crystals were internalized by monocytes, and inhibition of phagocytosis, cathepsin B leakage, generation of reactive oxygen species, and potassium efflux reduced cystine crystal-induced IL-1? secretion. Patients with cystinosis had higher levels of circulating IL-1? and IL-18 compared with controls. Analysis of inflammasome-related gene expression in PBMCs from patients with cystinosis revealed a significant increase in IL-1? and CASP-1 transcript levels compared with controls. Moreover, knockout of cystinosin in mice led to significant increases in serum IL-18 levels and kidney expression of inflammasome-related genes (Casp-1, Pycard, Il-18, Il18r1, Il1r1, and Il1rl2). Taken together, these data demonstrate that cystine crystals are endogenous inflammasome-activating stimuli, suggesting a novel role for cystine crystals in the pathogenesis of nephropathic cystinosis.

SUBMITTER: Prencipe G

PROVIDER: S-EPMC4033370 | biostudies-other | 2014 Jun

REPOSITORIES: biostudies-other

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Inflammasome activation by cystine crystals: implications for the pathogenesis of cystinosis.

Prencipe Giusi G Caiello Ivan I Cherqui Stephanie S Whisenant Thomas T Petrini Stefania S Emma Francesco F De Benedetti Fabrizio F

Journal of the American Society of Nephrology : JASN 20140213 6

Intralysosomal cystine crystal accumulation, due to mutations in the CTNS gene, is a hallmark of nephropathic cystinosis, but the role of these crystals in disease pathogenesis remains unclear. We hypothesized that, similar to other host-derived crystalline moieties, cystine crystals can induce IL-1β production through inflammasome activation. Thus, we investigated the proinflammatory effects of cystine crystals in primary human PBMCs. LPS-primed PBMCs stimulated with cystine crystals secreted I ...[more]

PMID: 24525029

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Project description:ImportanceDevelopment of noninvasive methodology to reproducibly measure tissue cystine crystal load to assess disease status and guide clinical care in cystinosis, an inherited lysosomal storage disorder characterized by widespread cystine crystal accumulation.ObjectiveTo develop an unbiased and semi-automated imaging methodology to quantify dermal cystine crystal accumulation in patients to correlate with disease status.Design, setting and participants101 participants, 70 patients and 31 healthy controls, were enrolled at the University of California, San Diego, Cystinosis Clinics, Rady Children's Hospital, San Diego and at the annual Cystinosis Research Foundation family conference for an ongoing prospective longitudinal cohort study of cystinosis patients with potential yearly follow-up.ExposuresIntradermal reflectance confocal microscopy (RCM) imaging, blood collection via standard venipuncture, medical record collection, and occasional skin punch biopsies.Main outcomes and measuresThe primary outcome was to establish an automated measure of normalized confocal crystal volume (nCCV) for each subject. Secondary analysis examined the association of nCCV with various clinical indicators to assess nCCV's possible predictive potential.ResultsOver 2 years, 57 patients diagnosed with cystinosis (median [range] age: 15.1 yrs [0.8, 54]; 41.4% female) were intradermally assessed by RCM to produce 84 image stacks. 27 healthy individuals (38.7 yrs [10, 85]; 53.1% female) were also imaged providing 37 control image stacks. Automated 2D crystal area quantification revealed that patients had significantly elevated crystal accumulation within the superficial dermis. 3D volumetric analysis of this region was significantly higher in patients compared to healthy controls (mean [SD]: 1934.0 μm3 [1169.1] for patients vs. 363.1 μm3 [194.3] for controls, P<0.001). Medical outcome data was collected from 43 patients with infantile cystinosis (media [range] age: 11 yrs [0.8, 54]; 51% female). nCCV was positively associated with hypothyroidism (OR = 19.68, 95% CI: [1.60, 242.46], P = 0.02) and stage of chronic kidney disease (slope estimate = 0.53, 95%CI: [0.05, 1.00], P = 0.03).Conclusions and relevanceThis study used non-invasive RCM imaging to develop an intradermal cystine crystal quantification method. Results showed that cystinosis patients had increased nCCV compared to healthy controls. Level of patient nCCV correlated with several clinical outcomes suggesting nCCV may be used as a potential new biomarker for cystinosis to monitor long-term disease control and medication compliance.

Project description:BACKGROUND:Age-related macular degeneration (AMD) is a multifactorial chronic disease of the eye. Several candidate pathways have been hypothesized to play a role in AMD pathogenesis. Our work and those of others suggests inflammasome activity as a mechanism associated with retinal pigment epithelial (RPE) cell demise. X-linked inhibitor of apoptosis protein (XIAP), an anti-apoptosis factor, has recently been shown to regulate inflammasome activity in non-ocular cells. The purpose of this study is to characterize XIAP's regulatory role in RPE. METHODS:Protein lysates of eye tissues from rats (vinpocetine- or aurin tricarboxylic acid complex-treated, ATAC, vs naïve) and mice (wild type vs Caspase-4-/-) were utilized to analyze XIAP protein levels. Immunohistochemistry was used to detect NLRP3 levels in the RPE layer. In vitro inflammasome activation on RPE cells was achieved with L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) stimulation. Levels of XIAP mRNA and 18S RNA were quantified by RT-PCR. Cell culture supernatants were tested directly for secreted IL-1? by ELISA or concentrated for the detection of secreted IL-18 by western blot. Protein lysates from RPE in cell culture were collected for the measurement of cleaved caspase-1 p20, XIAP, and GAPDH. Data are presented as Mean?±?SD. p?<?0.05 is considered statistically significant. RESULTS:The XIAP protein level was significantly increased when the inflammasome was inhibited at the "activation" step by ATAC, but not the "priming" step, in vivo. Concomitantly, NLRP3 immunoreactivity was lower in the RPE layer of animals fed with ATAC. In mice where caspase-1 cleavage was impaired by the genetic deficiency in caspase-4, the XIAP protein level increased in eye tissues. In RPE cell culture, Leu-Leu-OMe stimulation led to caspase-1 cleavage, cytokine secretion, and XIAP reduction, which can be abolished by Z-YVAD-FMK. When XIAP siRNA was given as a pre-treatment to RPE in vitro, Leu-Leu-OMe induced IL-1?/IL-18 secretion was enhanced, whereas overexpressing XIAP reduced IL-1? secretion under inflammasome activation, both compared to controls cells. CONCLUSIONS:Together, these data suggest XIAP-mediated inhibition of inflammasome activity in RPE may provide insights into the biological consequences of inflammasome activation in RPE and reveals the caspase-1/XIAP/IL-1?/IL-18 axis as a target for broader applications in AMD biology and treatment design.

Dataset Information

Inflammasome activation by cystine crystals: implications for the pathogenesis of cystinosis.

Publications

Inflammasome activation by cystine crystals: implications for the pathogenesis of cystinosis.

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