Crystallization of L-cystine is a critical process in the pathogenesis of kidney stone formation in cystinuria, a disorder affecting at least 20,000 U.S. citizens. Current therapeutic treatments for this disease are somewhat effective but often lead to adverse side effects. Real-time in situ atomic force microscopy (AFM) reveals that L-cystine dimethylester (L-CDME) and L-cystine methylester (L-CME) – structural mimics of L-cystine – dramatically reduce the growth velocity of the six symmetry-equivalent {100} steps, emanating from well-defined hexagonal spiral dislocations, due to specific binding at the crystal surface that frustrates the attachment of L-cystine solute molecules. Surprisingly, L-CDME and L-CME produce L-cystine crystals with different habits that reveal different binding modes of the two inhibitors at the crystal surfaces. The AFM observations at the nanoscale are mirrored by reduced crystal yield and crystal size in the presence of L-CDME and L-CME, collectively suggesting a new pathway to the prevention of L-cystine stones through the design of crystal growth inhibitors.

Bacterial biofilms are associated with numerous human infections. The predominant protein expressed in enteric biofilms is the amyloid curli, which forms highly immunogenic complexes with DNA. Infection with curli-expressing bacteria or systemic exposure to purified curli-DNA complexes triggers autoimmunity via the generation of type I interferons (IFNs) and anti-double-stranded DNA antibodies. Here, we show that DNA complexed with amyloid curli powerfully stimulates Toll-like receptor 9 (TLR9) through a two-step mechanism. First, the cross beta-sheet structure of curli is bound by cell-surface Toll-like receptor 2 (TLR2), enabling internalization of the complex into endosomes. After internalization, the curli-DNA immune complex binds strongly to endosomal TLR9, inducing production of type I IFNs. Analysis of wild-type and TLR2-deficient macrophages showed that TLR2 is the major receptor that drives the internalization of curli-DNA complexes. Suppression of TLR2 internalization via endocytosis inhibitors led to a significant decrease in Ifnβ expression. Confocal microscopy analysis confirmed that the TLR2-bound curli was required for shuttling of DNA to endosomal TLR9. Structural analysis using small-angle X-ray scattering revealed that incorporation of DNA into curli fibrils resulted in the formation of ordered curli-DNA immune complexes. Curli organizes parallel, double-stranded DNA rods at an inter-DNA spacing that matches up well with the steric size of TLR9. We also found that production of anti-double-stranded DNA autoantibodies in response to curli-DNA was attenuated in TLR2- and TLR9-deficient mice and in mice deficient in both TLR2 and TLR9 compared to wild-type mice, suggesting that both innate immune receptors are critical for shaping the autoimmune adaptive immune response. We also detected significantly lower levels of interferon-stimulated gene expression in response to purified curli-DNA in TLR2 and TLR9 deficient mice compared to wild-type mice, confirming that TLR2 and TLR9 are required for the induction of type I IFNs. Finally, we showed that curli-DNA complexes, but not cellulose, were responsible elicitation of the immune responses to bacterial biofilms. This study defines the series of events that lead to the severe pro-autoimmune effects of amyloid-expressing bacteria and suggest a mechanism by which amyloid curli acts as a carrier to break immune tolerance to DNA, leading to the activation of TLR9, production of type I IFNs, and subsequent production of autoantibodies.

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The direct interrogation of fleeting intermediates by rapid-mixing kinetic methods has significantly advanced our understanding of enzymes that utilize dioxygen. The gas’s modest aqueous solubility (< 2 mM at 1 atm) presents a technical challenge to this approach, because it limits the rate of formation and extent of accumulation of intermediates. This challenge can be overcome by use of the heme enzyme chlorite dismutase (Cld1) for the rapid, in situ generation of O2 at concentrations far exceeding 2 mM. This method was used to define the [O2] dependence of the reaction of the class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis, in which the enzyme’s MnIV/FeIII cofactor forms from a MnII/FeII complex and O2 via a MnIV/FeIV intermediate, at effective O2 concentrations as high as ~10 mM. With a more soluble receptor, myoglobin, an O2 adduct was accumulated to > 6 mM in < 15 ms. Finally, the C–H-bond-cleaving FeIV-oxo complex, J, in taurine:α-ketoglutarate dioxygenase and superoxo-Fe2III/III complex, G, in myo-inositol oxygenase, and the tyrosyl-radical-generating Fe2III/IV intermediate, X, in Escherichia coli RNR were all accumulated to yields more than twice those previously attained. This means of in situ O2 evolution permits a > 5 mM “pulse” of O2 to be generated in < 1 ms at the easily accessible [Cld] of 50 μM. It should therefore significantly extend the range of kinetic and spectroscopic experiments that can routinely be undertaken in the study of these enzymes and could also facilitate resolution of mechanistic pathways in cases of either sluggish or thermodynamically unfavorable O2-addition steps.

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Pulmonary arterial hypertension (PAH) is a disease of the lung blood vessels that results in right heart failure. PAH is thought to occur in about 5% to 10% of patients with hepatosplenic schistosomiasis, particularly due to S. mansoni. The lung blood vessel injury may result from a combination of embolization of eggs through portocaval shunts into the lungs causing localized Type 2 inflammatory response and vessel remodeling, triggering of autonomous pathology that becomes independent of the antigen, and high cardiac output as seen in portopulmonary hypertension. The condition is likely underdiagnosed as there is little systematic screening, and risk factors for developing PAH are not known. Screening is done by echocardiography, and formal diagnosis requires invasive right heart catheterization. Patients with Schistosoma-associated PAH show reduced functional capacity and can be treated with pulmonary vasodilators, which improves symptoms and may improve survival. There are animal models of this disease that might help in understanding disease pathogenesis and identify novel targets to screen and treatment. Pathogenic mechanisms include Type 2 immunity and activation and signaling in the TGF-β pathway. There are still major uncertainties regarding Schistosoma-associated PAH development, course and treatment.

Altered metabolism in pulmonary artery smooth muscle cells (pASMcs) and endothelial cells (pAecs) contributes to the pathology of pulmonary hypertension (pH), but changes in substrate uptake and how substrates are utilized have not been fully characterized. We hypothesized stable isotope metabolomics would identify increased glucose, glutamine and fatty acid uptake and utilization in human pASMcs and pAecs from pH versus control specimens, and that tGf-β treatment would phenocopy these metabolic changes. We used 13 c-labeled glucose, glutamine or a long-chain fatty acid mixture added to cell culture media, and mass spectrometry-based metabolomics to detect and quantify 13 c-labeled metabolites. We found pH pASMcs had increased glucose uptake and utilization by glycolysis and the pentose shunt, but no changes in glutamine or fatty acid uptake or utilization. Diseased pAecs had increased proximate glycolysis pathway intermediates, less pentose shunt flux, increased anaplerosis from glutamine, and decreased fatty acid β-oxidation. tGf-β treatment increased glycolysis in pASMcs, but did not recapitulate the pAec disease phenotype. in tGf-β-treated pASMcs, glucose, glutamine and fatty acids all contributed carbons to the tcA cycle. in conclusion, pASMcs and pAecs collected from pH subjects have significant changes in metabolite uptake and utilization, partially recapitulated by TGF-β treatment. Changes in cellular metabolism are increasingly recognized as a hallmark of pulmonary hypertension (PH) pathobiology 1-4. Shifts in the uptake of metabolic substrates and how they are utilized downstream enables the disease phenotype of vascular cells in PH, including increased proliferation, apoptosis resistance, hypertrophy and vasoconstriction 3. One critical metabolic shift observed in PH is an increase in glycolysis, which is thought to occur in resident vascular wall cells including pulmonary artery smooth muscle cells (PASMCs), endothelial cells (PAECs) and fibroblasts 5-7. Increased glucose uptake can be demonstrated in vivo by increased uptake of the glucose analog 18 F-fluorodeoxyglucose in the lung parenchyma of PH subjects 6,8. The concept that glycolysis in PH is detrimental has led to investigation of the potential utility of dichloroacetate (DCA), which by blocking pyruvate dehydrogenase kinase causes increased glucose flux into the TCA cycle, and less glycolysis 9. Glutamine uptake and metabolism by PAECs has also been shown to contribute to their disease phenotype 10. However, comprehensive assessment of substrate uptake and how the substrates are utilized by pulmonary vascular cells in PH is lacking. A potential driver of altered cellular metabolism is transforming growth factor β (TGF-β) signaling, which underlies many forms of heritable (through mutations in BMPR2 and other members of the TGF-β signaling superfamily) and idiopathic PAH, and PAH etiologies associated with other conditions such as autoimmune

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