Staphylococcus aureus functional amyloids catalyze degradation of β-lactam antibiotics

Antibiotic resistance of bacteria is considered one of the most alarming developments in modern medicine. While varied pathways for bacteria acquiring antibiotic resistance have been identified, there still are open questions concerning the mechanisms underlying resistance. Here, we show that alpha phenol-soluble modulins (PSMαs), functional bacterial amyloids secreted by Staphylococcus aureus, catalyze hydrolysis of β-lactams, a prominent class of antibiotic compounds. Specifically, we show that PSMα2 and, particularly, PSMα3 catalyze hydrolysis of the amide-like bond of the four membered β-lactam ring of nitrocefin, an antibiotic β-lactam surrogate. Examination of the catalytic activities of several PSMα3 variants allowed mapping of the active sites on the amyloid fibrils' surface, specifically underscoring the key roles of the cross-α fibril organization, and the combined electrostatic and nucleophilic functions of the lysine arrays. Molecular dynamics simulations further illuminate the structural features of β-lactam association upon the fibril surface. Complementary experimental data underscore the generality of the functional amyloid-mediated catalytic phenomenon, demonstrating hydrolysis of clinically employed β-lactams by PSMα3 fibrils, and illustrating antibiotic degradation in actual S. aureus biofilms and live bacteria environments. Overall, this study unveils functional amyloids as catalytic agents inducing degradation of β-lactam antibiotics, underlying possible antibiotic resistance mechanisms associated with bacterial biofilms.

Native Glucagon Amyloids Catalyze Key Metabolic Reactions

Glucagon is a prominent peptide hormone, playing central roles in the regulation of glucose blood-level and lipid metabolism. Formation of glucagon amyloid fibrils has been previously reported, although no biological functions of such fibrils are known. Here, we demonstrate that glucagon amyloid fibrils catalyze biologically important reactions, including esterolysis, lipid hydrolysis, and dephosphorylation. In particular, we found that glucagon fibrils catalyze dephosphorylation of adenosine triphosphate (ATP), a core metabolic reaction in cell biology. Comparative analysis of several glucagon variants allowed mapping the catalytic activity to an enzymatic pocket-like triad formed at the glucagon fibril surface, comprising the histidyl-serine domain at the N-terminus of the peptide. This study may point to previously unknown physiological roles and pathological consequences of glucagon fibrillation and supports the hypothesis that catalytic activities of native amyloid fibrils play functional roles in human physiology and disease.

Amyloid fishing: β-Amyloid adsorption using tailor-made coated titania nanoparticles

Amyloidoses are a family of diseases characterized by abnormal protein folding that leads to fibril aggregates, amyloids. Extensive research efforts are devoted to developing inhibitors to amyloid aggregates. Here we set to explore functionalized titania (TiO₂) nanoparticles (NPs) as potential amyloid inhibiting agents. TiO₂ NPs were coated by a catechol derivative, dihydroxy-phenylalanine propanoic acid (DPA), and further conjugated to the amyloids' specific dye Congo-Red (CR). TiO₂-DPA-CR NPs were found to target mature fibrils of β-amyloid (Aβ). Moreover, coated NPs incubated with Aβ proteins suppressed amyloid fibrillation. TiO₂-DPA-CR were found to target amyloids in solution and induce their sedimentation upon centrifugation. This work demonstrates the potential utilization of TiO₂-DPA NPs for labeling and facilely separating from solution mature amyloid fibrils.

Dual concentration-dependent effect of ascorbic acid on PAP(248-286) amyloid formation and SEVI-mediated HIV infection

Human semen contains various amyloidogenic peptides derived from Prostatic Acid Phosphatase (PAP) and Semenogelin proteins that are capable of enhancing HIV-1 infection when assembled into fibrils. The best characterized among them is a 39 amino acid peptide PAP(248–286), which forms amyloid fibrils termed SEVI (semen-derived enhancer of viral infection) that increase the infectivity of HIV-1 by orders of magnitude. Inhibiting amyloid formation by PAP(248–286) may mitigate the sexual transmission of HIV-1. Several vitamins have been shown to reduce the aggregation of amyloids such as Aβ, α-Synuclein, and Tau, which are associated with neurodegenerative diseases. Since ascorbic acid (AA, vitamin C) is the most abundant vitamin in semen with average concentrations of 0.4 mM, we here examined how AA affects PAP(248–286) aggregation in vitro. Using ThT binding assays, transmission electron microscopy, and circular dichroism spectroscopy, a dual and concentration-dependent behavior of AA in modulating PAP(248–286) fibril formation was observed. We found that low molar ratios of AA:PAP(248–286) promoted whereas high molar ratios inhibited PAP(248–286) fibril formation. Accordingly, PAP(248–286) aggregated in the presence of low amounts of AA enhanced HIV-1 infection, whereas excess amounts of AA during aggregation reduced the infectivity enhancing effect in cell culture. Collectively, this work provides a biophysical insight into the effect of AA, an important seminal component, on SEVI fibrillation which might impact amyloid formation kinetics, thereby modulating the biological activity of semen amyloids.

Human semen contains various amyloidogenic peptides derived from Prostatic Acid Phosphatase (PAP) and Semenogelin proteins that are capable of enhancing HIV-1 infection when assembled into fibrils.

Inhibition of tau amyloid formation and disruption of its preformed fibrils by Naphthoquinone-Dopamine hybrid

Misfolding and aggregation of tau protein, into pathological amyloids, are hallmarks of a group of neurodegenerative diseases collectively termed tauopathies and their modulation may be therapeutically valuable. Herein, we describe the synthesis and characterization of a dopamine-based hybrid molecule, naphthoquinone-dopamine (NQDA). Using thioflavin S assay, CD, transmission electron microscopy, dynamic light scattering, Congo Red birefringence, and large unilamellar vesicle leakage assays, we demonstrated its efficacy in inhibiting the in vitro aggregation of key tau-derived amyloidogenic fragments, PHF6 (VQIVYK) and PHF6* (VQIINK), prime drivers of aggregation of full-length tau in disease pathology. Isothermal titration calorimetry analysis revealed that the interaction between NQDA and PHF6 is spontaneous and has significant binding efficiency driven by both entropic and enthalpic processes. Furthermore, NQDA efficiently disassembled preformed fibrils of PHF6 and PHF6* into nontoxic species. Molecular dynamic simulations supported the in vitro results and provided a plausible mode of binding of NQDA with PHF6 fibril. NQDA was also capable of inhibiting the aggregation of full-length tau protein and disrupting its preformed fibrils in vitro in a dose-dependent manner. In a comparative study, the IC₅₀ value (50% inhibition of fibril formation) of NQDA in inhibiting the aggregation of PHF6 (25 µm) was ~ 17 µm, which is lower than for other bona fide amyloid inhibitors, naphthoquinone-tryptophan, rosmarinic acid, epigallocatechin gallate, ~ 21, ~ 77, or ~ 19 µm, respectively. Comparable superiority of NQDA was observed for inhibition of PHF6*. These findings suggest that NQDA can be a useful scaffold for designing new therapeutics for Alzheimer's disease and other tauopathies.

Purpurin modulates Tau-derived VQIVYK fibrillization and ameliorates Alzheimer's disease-like symptoms in animal model

Neurofibrillary tangles of the Tau protein and plaques of the amyloid β peptide are hallmarks of Alzheimer's disease (AD), which is characterized by the conversion of monomeric proteins/peptides into misfolded β-sheet rich fibrils. Halting the fibrillation process and disrupting the existing aggregates are key challenges for AD drug development. Previously, we performed in vitro high-throughput screening for the identification of potent inhibitors of Tau aggregation using a proxy model, a highly aggregation-prone hexapeptide fragment 306VQIVYK311 (termed PHF6) derived from Tau. Here we have characterized a hit molecule from that screen as a modulator of Tau aggregation using in vitro, in silico, and in vivo techniques. This molecule, an anthraquinone derivative named Purpurin, inhibited ~ 50% of PHF6 fibrillization in vitro at equimolar concentration and disassembled pre-formed PHF6 fibrils. In silico studies showed that Purpurin interacted with key residues of PHF6, which are responsible for maintaining its β-sheets conformation. Isothermal titration calorimetry and surface plasmon resonance experiments with PHF6 and full-length Tau (FL-Tau), respectively, indicated that Purpurin interacted with PHF6 predominantly via hydrophobic contacts and displayed a dose-dependent complexation with FL-Tau. Purpurin was non-toxic when fed to Drosophila and it significantly ameliorated the AD-related neurotoxic symptoms of transgenic flies expressing WT-FL human Tau (hTau) plausibly by inhibiting Tau accumulation and reducing Tau phosphorylation. Purpurin also reduced hTau accumulation in cell culture overexpressing hTau. Importantly, Purpurin efficiently crossed an in vitro human blood-brain barrier model. Our findings suggest that Purpurin could be a potential lead molecule for AD therapeutics.

Revisiting thioflavin T (ThT) fluorescence as a marker of protein fibrillation - The prominent role of electrostatic interactions

Thioflavin T (ThT), a benzothiazole-based fluorophore, is a prominent dye widely employed for monitoring amyloid fibril assembly. Despite the near-universal presumption that ThT binds to β-sheet domains upon fibrillar surface via hydrophobic forces, the contribution of the positive charge of ThT to fibril binding and concomitant fluorescence enhancement have not been thoroughly assessed. Here we demonstrate a considerable interdependence between ThT fluorescence and electrostatic charges of peptide fibrils. Specifically, by analyzing both fibril-forming synthetic peptides and prominent natural fibrillar peptides, we demonstrate pronounced modulations of ThT fluorescence signal that were solely dependent upon electrostatic interactions between ThT and peptide surface. The results further attest to the fact that fibril ζ-potential rather than pH-dependent assembly of the fibrils constitute the primary factor affecting ThT binding and fluorescence. This study provides the first quantitative assessment of electrostatically driven ThT fluorescence upon adsorption to amyloid fibrils.

Deciphering the Rules for Amino Acid Co-Assembly Based on Interlayer Distances

Metabolite materials are extremely useful to obtain functional bioinspired assemblies with unique physical properties for various applications in the fields of material science, engineering, and medicine by self-assembly of the simplest biological building blocks. Supramolecular co-assembly has recently emerged as a promising extended approach to further expand the conformational space of metabolite assemblies in terms of structural and functional complexity. Yet, the design of synergistically co-assembled amino acids to produce tailor-made functional architectures is still challenging. Herein, we propose a design rule to predict the supramolecular co-assembly of naturally occurring amino acids based on their interlayer separation distances observed in single crystals. Using diverse experimental techniques, we demonstrate that amino acids with comparable interlayer separation strongly interact and co-assemble to produce structural composites distinctly different from their individual properties. However, such an interaction is hampered in a mixture of differentially layer-separated amino acids, which self-sort to generate individual characteristic structures. This study provides a different paradigm for the modular design of supramolecular assemblies based on amino acids with predictable properties.

Tryptophan–glucosamine conjugates modulate tau-derived PHF6 aggregation at low concentrations

Tryptophan–glucosamine conjugates efficiently inhibit tau-derived PHF6-peptide fibrillization and disrupt its preformed fibrils at very low concentrations.

Unravelling the role of amino acid sequence order in the assembly and function of the amyloid-β core

Here we report the influence of amino acid sequence order on the self-assembly and biological functions of the core recognition motif of Amyloid β.

Chiral modulation of amyloid beta fibrillation and cytotoxicity by enantiomeric carbon dots

Enantiomeric carbon dots (C-dots) synthesized from l-lysine or d-lysine, modulate aggregation and cytotoxicity of amyloid beta-42 (Aβ42), the primary constituent of the amyloid plaques associated with Alzheimer's disease. In particular, l-Lys-C-dots dramatically remodeled Aβ42 secondary structure and fibril morphologies, as well as inhibited Aβ42 cytotoxicity and membrane interactions.

Self-implanted artificial nodules: a computed tomography mimic of penile pathology

Self-introduction of foreign bodies along the penile shaft has been reported in several ethnic and social groups, mainly in Asia, and recently has been described in Europe. We present the case of a 34-year-old homeless Russian immigrant who had an abdominal CT performed during an emergency department visit. On the CT scan, several hyperdense, well-demarcated subcutaneous nodules along the penile shaft were noted. Following a focused history and physical examination, the nodules were found to represent artificial foreign bodies made of glass, which were self-introduced by the patient in order to allegedly increase the pleasure of sexual partners. Penile nodules may be a manifestation of diverse pathological entities including infectious, inflammatory, and neoplastic processes. It is important for the radiologist to be familiar with this social phenomenon and its radiological appearance in order to avoid erroneous diagnosis.

Cutaneous larva migrans, sacroileitis, and optic neuritis caused by an unidentified organism acquired in Thailand

We report the case of a 32-year-old pregnant woman with an unidentified intraocular parasite. The parasite, which had been acquired in Thailand, caused cutaneous larva migrans, sacroileitis, and 2 years later optic neuritis and panuveitis. The patient was successfully treated with ivermectin and albendazole. The diagnostic possibilities of this peculiar presentation are discussed. Parasitic infections are a leading cause of medical problems in travelers to tropical countries.1 While most parasites cause gastrointestinal problems, some may migrate throughout the body and lodge in critical organs. Ocular parasitic infections may occur by direct inoculation onto the eye,2 or incidentally during systemic migration. Subconjunctival parasites are easily diagnosed by removal and careful microscopic examination.3 Parasites, which lodge within the eye, are more difficult to diagnose, especially if not removed. In this report we describe a patient who presented with an intraocular parasite causing optic neuritis and panuveitis, 2 years after travel to Thailand.

Is there a role for low doses of mitotane (o,p'-DDD) as adjuvant therapy in adrenocortical carcinoma?

Four patients suffering from adrenocortical carcinoma were treated with low doses (1.5-2.0 g) of mitotane (o,p'-DDD) for the complete follow-up time following surgery (21-68 months). Treatment with mitotane was started shortly after surgical removal of the tumor (three patients) or the tumor and multiple lung metastasis (one patient). No significant side effects or complications from the medication were noted. Two patients remain disease free after 57 and 21 months on treatment. A third patient died of an unrelated reason (varicose vein bleeding) after 68 months on mitotane without evidence of tumor recurrence or metastasis. In the fourth patient, two lung metastasis were successfully removed after 48 months of follow-up. The patient is doing well and is disease free 6 months later. Though our series is too small to draw final conclusions, we suggest that low doses of mitotane, which are well tolerated, might offer prolonged disease-free survival in adrenocortical carcinoma. To be beneficial treatment has to be started early after surgical removal of the tumor and metastasis, and be continued for long periods of time.

Pituitary mass and inflammatory pseudotumours of lung and peritoneum

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Late complications in remission from Cushing disease. Recurrence of tumor with reinfarction or transformation into a silent adenoma

Two of 4 patients who underwent spontaneous remission from Cushing disease (CD) demonstrated regrowth of the pituitary adenoma 2 and 5 years later. In the first patient, the recurrent tumor also secreted corticotropin, with subsequent relapse of fulminant cushingoid features. However, after 14 more months, it again became infarcted, and the patient underwent complete clinical remission, which has persisted for about 3 years. In the second patient, the regrowth of the tumor occurred silently, as no clinical cushingoid features or rise in cortisol levels were noticed. Because of its size, the tumor was resected and found to have immunoreactivity for corticotropin (silent corticotroph adenoma). About 4 years after the first operation, a second surgical procedure was performed because of massive regrowth of the tumor. Again, there was no concomitant elevation of cortisol levels or endocrinologic symptoms. This time, the tumor did not even stain for corticotropin. While spontaneous remission in CD is rare, recurrence is even rarer. Reremission of CD and the change from a corticotropin-secreting adenoma to a silent one are described herein for the first time (to our knowledge). These cases demonstrate that patients with CD have to receive careful follow-up, even if they undergo remission, and that the long-term outcome of such remission is unpredictable.

One microgram is the lowest ACTH dose to cause a maximal cortisol response. There is no diurnal variation of cortisol response to submaximal ACTH stimulation

There are many suggestions in the literature that the adrenal gland is more sensitive to ACTH in the evening than in the morning. However, all these studies in humans were conducted when the basal cortisol level was not suppressed, and were based on the observation that, after stimulation, the increases in cortisol differed, though the peak values were the same. To examine this, we established the lowest ACTH dose that caused a maximal cortisol stimulation even when the basal cortisol was suppressed, and used a smaller dose of ACTH for morning and evening stimulation. The lowest ACTH dose to achieve maximal stimulation was found to be 1.0 microgram, with which dose cortisol concentration increased to 607.2 +/- 182 nmol/l, compared with 612.7 +/- 140.8 nmol/l with the 250 micrograms test (P > 0.3). The use of smaller doses of ACTH (0.8 and 0.6 microgram) achieved significantly lower cortisol responses (312 +/- 179.4 and 323 +/- 157.3 nmol/l respectively; both P < 0.01 compared with the 1 microgram test). When a submaximal ACTH dose (0.6 microgram) was used to stimulate the adrenal at 0800 and 1600 h, after pretreatment with dexamethasone, no difference in response was noted at either 15 min (372.6 +/- 116 compared with 394.7 +/- 129.7 nmol/l) or 30 min (397.4 +/- 176.6 compared with 403 +/- 226.3 nmol/l; P > 0.3 for both times). These results show that 1.0 microgram ACTH, used latterly as a low-dose test, is very potent in stimulating the adrenal, even when baseline cortisol is suppressed; smaller doses cause reduction of this potency. Our data show that there is probably no diurnal variation in the response of the adrenal to ACTH, if one eliminates the influence of the basal cortisol level and uses physiologic rather than superphysiologic stimuli.

[Hemorrhagic cystitis as a presenting symptom of acute infection with Salmonella typhi]

Salmonellae are frequently isolated from urine during the course of typhoid fever, although cystitis in typhoid is rare. In a young man who had returned from India with severe hemorrhagic cystitis, urine and bone marrow cultures confirmed the diagnosis of typhoid. Full recovery followed treatment with chloramphenicol. This case illustrates an unusual presentation of typhoid fever and the illustrates an unusual presentation of typhoid fever and the diagnostic difficulties occasionally encountered in patients returning from developing countries.

Ablation of remaining functioning thyroid lobe with radioiodine after hemithyroidectomy for carcinoma

Nineteen patients who had hemithyroidectomy as a surgical procedure for thyroid cancer were given radioiodine to ablate the residual hemithyroid. Two different protocols were used, with either a larger single dose or multiple smaller doses. Ablation was achieved in 28% with the single large dose approach and in 33% of patients given split doses of similar total amount. This response to the initial attempt at eradication of the residual normal hemithyroid is considerably lower than the accepted ablation rate with comparable doses administered to patients with small thyroid residues after total thyroidectomy. It is suggested that the effect of radioiodine treatment may relate inversely to the size of the thyroid remnant. Our findings also are in support of the surgical approach advocating total thyroidectomy for patients contemplating ablation of thyroid residues after surgery for thyroid carcinoma.

Fractionated doses of radioiodine for ablation of postsurgical thyroid tissue remnants

Patients who have differentiated thyroid carcinoma and have undergone total thyroidectomy are treated with radioiodine for ablation of functional thyroid remnants. Administration of a single therapeutic dose in excess of 30 mCi of l-131 requires hospitalization. In an attempt to obviate the necessity for hospitalization, the prospective ablative dose was divided into two or three fractions given at weekly intervals on an ambulatory basis. To assess the effectiveness of this approach, this group of patients was compared to a cohort of hospitalized patients treated with a single dose. Ablation was achieved in 9 out of 12 patients treated in a fractionated manner (a 75% success rate), whereas in 16 out of 20 patients given a single dose the thyroid remnants were completely eradicated (an 80% success rate). That the use of split, smaller doses administered at weekly intervals on an ambulatory basis presents a reasonable alternative for ablation of postsurgical, residual-functioning thyroid tissue.

Massive hepatic steatosis complicating adult celiac disease: report of a case and review of the literature

Hepatomegaly, chronic diarrhea, and weight loss in a middle-aged woman were found to be due to massive hepatic steatosis and adult celiac disease. After she was on a gluten-free diet for 1 yr, improvement in clinical, laboratory, and pathological parameters was witnessed. Massive hepatic steatosis complicating adult celiac disease is an uncommon occurrence, differing from other, more frequently encountered hepatopathies in this disease, insofar as pathogenetic and prognostic aspects are concerned.