Suppression of systemic autoimmunity by the innate immune adaptor STING.

Cytosolic DNA-sensing pathways that signal via Stimulator of interferon genes (STING) mediate immunity to pathogens and also promote autoimmune pathology in DNaseII- and DNaseIII-deficient mice. In contrast, we report here that STING potently suppresses inflammation in a model of systemic lupus erythematosus (SLE). Lymphoid hypertrophy, autoantibody production, serum cytokine levels, and other indicators of immune activation were markedly increased in STING-deficient autoimmune-prone mice compared with STING-sufficient littermates. As a result, STING-deficient autoimmune-prone mice had significantly shorter lifespans than controls. Importantly, Toll-like receptor (TLR)-dependent systemic inflammation during 2,6,10,14-tetramethylpentadecane (TMPD)-mediated peritonitis was similarly aggravated in STING-deficient mice. Mechanistically, STING-deficient macrophages failed to express negative regulators of immune activation and thus were hyperresponsive to TLR ligands, producing abnormally high levels of proinflammatory cytokines. This hyperreactivity corresponds to dramatically elevated numbers of inflammatory macrophages and granulocytes in vivo. Collectively these findings reveal an unexpected negative regulatory role for STING, having important implications for STING-directed therapies.

Multiple Cathepsins Promote Pro-IL-1ß Synthesis and NLRP3-Mediated IL-1ß Activation.

Sterile particles induce robust inflammatory responses that underlie the pathogenesis of diseases like silicosis, gout, and atherosclerosis. A key cytokine mediating this response is IL-1ß. The generation of bioactive IL-1ß by sterile particles is mediated by the NOD-like receptor containing a pyrin domain 3 (NLRP3) inflammasome, although exactly how this occurs is incompletely resolved. Prior studies have found that the cathepsin B inhibitor, Ca074Me, suppresses this response, supporting a model whereby ingested particles disrupt lysosomes and release cathepsin B into the cytosol, somehow activating NLRP3. However, reports that cathepsin B-deficient macrophages have no defect in particle-induced IL-1ß generation have questioned cathepsin B's involvement. In this study, we examine the hypothesis that multiple redundant cathepsins (not just cathepsin B) mediate this process by evaluating IL-1ß generation in murine macrophages, singly or multiply deficient in cathepsins B, L, C, S and X. Using an activity-based probe, we measure specific cathepsin activity in living cells, documenting compensatory changes in cathepsin-deficient cells, and Ca074Me's dose-dependent cathepsin inhibition profile is analyzed in parallel with its suppression of particle-induced IL-1ß secretion. Also, we evaluate endogenous cathepsin inhibitors cystatins C and B. Surprisingly, we find that multiple redundant cathepsins, inhibited by Ca074Me and cystatins, promote pro-IL-1ß synthesis, and to our knowledge, we provide the first evidence that cathepsin X plays a nonredundant role in nonparticulate NLRP3 activation. Finally, we find cathepsin inhibitors selectively block particle-induced NLRP3 activation, independently of suppressing pro-IL-1ß synthesis. Altogether, we demonstrate that both small molecule and endogenous cathepsin inhibitors suppress particle-induced IL-1ß secretion, implicating roles for multiple cathepsins in both pro-IL-1ß synthesis and NLRP3 activation.

Inducing cells to disperse nickel nanowires via integrin-mediated responses.

We present non-cytotoxic, magnetic, Arg-Gly-Asp (RGD)-functionalized nickel nanowires (RGD-nanowires) that trigger specific cellular responses via integrin transmembrane receptors, resulting in dispersal of the nanowires. Time-lapse fluorescence and phase contrast microscopy showed that dispersal of 3 µm long nanowire increased by a factor of 1.54 with functionalization by RGD, compared to polyethylene glycol (PEG), through integrin-specific binding, internalization and proliferation in osteosarcoma cells. Further, a 35.5% increase in cell density was observed in the presence of RGD-nanowires, compared to an increase of only 15.6% with PEG-nanowires. These results promise to advance applications of magnetic nanoparticles in drug delivery, hyperthermia, and cell separation where uniformity and high efficiency in cell targeting is desirable.

The IL-1-dependent sterile inflammatory response has a substantial caspase-1-independent component that requires cathepsin C.

The sterile inflammatory response to cell death and irritant crystals is medically important because it causes disease. Although these stimuli are structurally distinct, they cause inflammation through a common pathway that requires the cytokine IL-1. In vitro, the inflammasome, and in particular its generation of active caspase-1, is absolutely required to produce bioactive IL-1ß. However, in this study, we report that caspase-1 is not required in vivo for much of the IL-1ß-dependent sterile inflammatory response. Furthermore, we find that cathepsin C, which controls the activity of a number of leukocyte serine proteases capable of processing IL-1ß, plays a major role in this caspase-1-independent pathway. Mice that are deficient in cathepsin C have reduced inflammatory responses to dying cells and silica crystals. In the absence of cathepsin C, caspase-1 becomes rate limiting such that mice doubly deficient in both of these proteases make little IL-1ß in vivo and have markedly attenuated inflammatory responses to the sterile stimuli. In contrast, these mutant mice generate normal inflammation in response to exogenous IL-1ß, indicating that cathepsin C and caspase-1 function upstream of IL-1ß, and, in their absence, all components of the pathway downstream of mature IL-1ß are intact.

Hidradenitis suppurativa: a new, principle-centered paradigm for managing a dynamic disease.

Hidradenitis suppurativa (HS) is a chronic, debilitating skin condition that disproportionately affects socioeconomically underserved patients. Currently, treatment outcomes for patients with HS remain poor, largely because of a deficiency in current guidelines on exactly how and when to employ the myriad treatment tools, resulting in heterogeneous care models and confusion. Aggressive medical therapy is often started too late, pursued for too long whilst delaying procedural intervention, or skipped over altogether for procedures. Here, we propose a new, principle-centered management paradigm for HS that emphasizes the need for prompt intervention to minimize suffering and an understanding of how sinus tract development dictates the timing of medical and procedural interventions.

Multiple atypical vascular lesions following breast-conserving surgery and radiation.

Atypical vascular lesions (AVLs) of the breast are purple papules or nodules that have been reported in breast cancer patients following radiation treatment, typically presenting with fewer than 5 lesions at diagnosis. We report a patient with 29 lesions within previously irradiated breast tissue. Due to the large number of lesions and concern for development of angiosarcoma, the patient's case was brought before a multidisciplinary tumor board that decided she should undergo a radical mastectomy with flap reconstruction. We discuss the dermatologist's role in managing this complex and increasingly common disorder.

Treatment With Ataluren for Wound Healing and Health Complications in a Patient With Junctional Epidermolysis Bullosa.

This case report describes an 11-year-old boy with widespread chronic wounds, frequent corneal erosions, dental caries, a tracheostomy, and failure to thrive.

Frontline Science: Multiple cathepsins promote inflammasome-independent, particle-induced cell death during NLRP3-dependent IL-1ß activation.

Sterile particles cause several chronic, inflammatory diseases, characterized by repeating cycles of particle phagocytosis and inflammatory cell death. Recent studies have proposed that these processes are driven by the NLRP3 inflammasome, a platform activated by phagocytosed particles, which controls both caspase-1-dependent cell death (pyroptosis) and mature IL-1ß secretion. After phagocytosis, particles can disrupt lysosomes, and inhibitor studies have suggested that the resulting release of a lysosomal protease-cathepsin B-into the cytosol somehow activates NLRP3. However, using primary murine macrophages, we found that particle-induced cell death occurs independent of NLRP3/caspase-1 and depends instead on multiple, redundant cathepsins. In contrast, nigericin, a soluble activator of NLRP3 inflammasomes, induced cell death that was dependent on the NLRP3. Interestingly, nigericin-induced cell death depended partly on a single cathepsin, cathepsin X. By inhibiting or silencing multiple cathepsins in macrophages, several key proinflammatory events induced by sterile particles are blocked, including cell death, pro-IL-1ß production, and IL-1ß secretion. These data suggest that cathepsins might be potential therapeutic targets in particulate-mediated inflammatory disease. In support of this concept, we find that a broad-spectrum cathepsin inhibitor can suppress particle-induced IL-1-dependent peritonitis.

Exploiting the mitochondrial unfolded protein response for cancer therapy in mice and human cells.

Fine tuning of the protein folding environment in subcellular organelles, such as mitochondria, is important for adaptive homeostasis and may participate in human diseases, but the regulators of this process are still largely elusive. Here, we have shown that selective targeting of heat shock protein-90 (Hsp90) chaperones in mitochondria of human tumor cells triggered compensatory autophagy and an organelle unfolded protein response (UPR) centered on upregulation of CCAAT enhancer binding protein (C/EBP) transcription factors. In turn, this transcriptional UPR repressed NF-κB-dependent gene expression, enhanced tumor cell apoptosis initiated by death receptor ligation, and inhibited intracranial glioblastoma growth in mice without detectable toxicity. These data reveal what we believe to be a novel role of Hsp90 chaperones in the regulation of the protein-folding environment in mitochondria of tumor cells. Disabling this general adaptive pathway could potentially be used in treatment of genetically heterogeneous human tumors.