Interaction between galectin-3 and cystinosin uncovers a pathogenic role of inflammation in kidney involvement of cystinosis.

Inflammation is involved in the pathogenesis of many disorders. However, the underlying mechanisms are often unknown. Here, we test whether cystinosin, the protein involved in cystinosis, is a critical regulator of galectin-3, a member of the ß-galactosidase binding protein family, during inflammation. Cystinosis is a lysosomal storage disorder and, despite ubiquitous expression of cystinosin, the kidney is the primary organ impacted by the disease. Cystinosin was found to enhance lysosomal localization and degradation of galectin-3. In Ctns-/- mice, a mouse model of cystinosis, galectin-3 is overexpressed in the kidney. The absence of galectin-3 in cystinotic mice ameliorates pathologic renal function and structure and decreases macrophage/monocyte infiltration in the kidney of the Ctns-/-Gal3-/- mice compared to Ctns-/- mice. These data strongly suggest that galectin-3 mediates inflammation involved in kidney disease progression in cystinosis. Furthermore, galectin-3 was found to interact with the pro-inflammatory cytokine Monocyte Chemoattractant Protein-1, which stimulates the recruitment of monocytes/macrophages, and proved to be significantly increased in the serum of Ctns-/- mice and also patients with cystinosis. Thus, our findings highlight a new role for cystinosin and galectin-3 interaction in inflammation and provide an additional mechanistic explanation for the kidney disease of cystinosis. This may lead to the identification of new drug targets to delay cystinosis progression.

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

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-1ß 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-1ß in a dose-dependent manner. Similarly to IL-1ß secretion induced by other crystalline inflammasome activators, cystine crystal-induced IL-1ß 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-1ß secretion. Patients with cystinosis had higher levels of circulating IL-1ß and IL-18 compared with controls. Analysis of inflammasome-related gene expression in PBMCs from patients with cystinosis revealed a significant increase in IL-1ß 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.

New-onset lupus nephritis in a kidney transplant recipient with cystinosis-differential diagnosis with cysteamine-induced lupus: case report.

A case of lupus nephritis in an adult female kidney transplant recipient with cystinosis under cysteamine therapy is reported. Previous reports of new-onset lupus in cystinotic patients have focused in a possible relationship of lupus with cysteamine therapy, but no obvious pathophysiological association has been disclosed. The authors present a case of a 19-year-old female kidney transplant recipient with cystinosis admitted for acute allograft dysfunction, with clinical and immunologic manifestations of lupus nephritis. Cysteamine was considered as a potential cause of drug-induced lupus, and we temporarily interrupted this drug. The clinical picture, the negativity of antihistone antibodies, the nondisappearance of antinuclear antibodies after discontinuation of the drug, and the clinical stability after resuming cysteamine therapy suggested that the underlying mechanism of lupus was unrelated to the drug. This may be the first report of new-onset lupus in a kidney transplant recipient with cystinosis. Clinicians should be aware of the association of autoimmune abnormalities in patients with cystinosis.

Increased monocyte-dependent suppression of polyclonal activation of B lymphocytes from cystinotic children.

In infantile cystinosis the amino acid cystine preferentially accumulates in phagocytic cells, polymorphonuclear leucocytes (PMN) and monocytes, rather than in lymphocytes. We previously described functional abnormalities in the oxidative metabolism and locomotion of cystinotic PMN and monocytes. The present study shows an abnormal lymphocyte polyclonal activation as evidenced by a decreased immunoglobulin (Ig) production and generation of Ig-containing cells (ICC) in cultures of peripheral blood mononuclear cells (PBMC) from cystinotic children upon stimulation with pokeweed mitogen and Staphylococcus aureus Cowan I. However, monocyte depletion from cystinotic PBMC fully reconstituted Ig production and ICC generation, indicating: (1) the presence of an increased monocyte-dependent suppression on lymphocyte polyclonal activation, and (2) that the intrinsic ability of cystinotic lymphocytes to respond to polyclonal stimulation was preserved. The increased cystinotic monocyte-dependent suppressive effect was not mediated by prostaglandin E2 (PGE2) since its production by cystinotic PBMC upon polyclonal activation was not different from that of controls. In addition, the sensitivity of cystinotic lymphocytes to the immunosuppressive effect of varying concentrations of exogenous PGE2 was similar to that of controls. Finally, indomethacin and 2-mercaptoethanol, two agents able to scavenge hydroxyl (.OH) radicals, restored Ig production by cystinotic PBMC, suggesting a role for reactive oxygen species in the increased cystinotic monocyte-dependent suppression.

Altered oxidative metabolism, motility, and adherence in phagocytic cells from cystinotic children.

The present study investigates whether the metabolic abnormalities in cystinotic cells could affect nonspecific immune responses. Lymphocytes showed normal antibody-dependent cellular cytotoxicity and natural killer activity. However, cystinotic polymorphonuclear and mononuclear phagocytes exhibited altered oxidative responses as monitored by a luminol dependent chemiluminescence (CL) assay. Both isolated polymorphonuclear and mononuclear phagocytes in the absence of stimuli showed significantly increased CL production which was not found when cells were tested directly within whole blood. CL responses to a panel of stimuli differed markedly according to the type of cells and agents tested. Indeed, isolated polymorphonuclear demonstrated increased CL responses to soluble but not particulate agents, whereas isolated mononuclear phagocytes and overall cell CL responses in whole blood were found to be within the normal range regardless of the type of stimulus used. We also studied some membrane related properties of phagocytic cells. Fc and C3b receptors were normally expressed as tested by erythrocyte-antibody and erythrocyte-antibody-complement rosette-forming cells. Nevertheless, cystinotic polymorphonuclear and mononuclear phagocytes presented decreased random and directed migrations in an under-agarose chemotaxis assay. Finally, cystinotic granulocytes showed an impaired adhesiveness in a nylon fiber assay.

Association of certain human leukocyte antigens with nephropathic cystinosis in the absence of linkage between these loci.

The HLA phenotypes of 41 patients (22 males and 19 females) with classical nephropathic cystinosis were analyzed and compared with those reported from a control group of 1,465 Americans of Caucasian origin. There was a significantly increased association of cystinosis with HLA B7, and a reduced association with A9. The calculated A3B7 and A1B7 haplotypes were also significantly increased in cystinosis. Lod score analysis of five families indicated that linkage between the gene(s) for cystinosis and the HLA loci is unlikely. While associations of other genetic diseases with specific HLA types should be sought, such relationships, as documented here, do not imply true genetic linkage.