Mitochondrial aldehyde dehydrogenase (ALDH2) rescues cardiac contractile dysfunction in an APP/PS1 murine model of Alzheimer's disease via inhibition of ACSL4-dependent ferroptosis.

Alzheimer's disease (AD) is associated with high incidence of cardiovascular events but the mechanism remains elusive. Our previous study reveals a tight correlation between cardiac dysfunction and low mitochondrial aldehyde dehydrogenase (ALDH2) activity in elderly AD patients. In the present study we investigated the effect of ALDH2 overexpression on cardiac function in APP/PS1 mouse model of AD. Global ALDH2 transgenic mice were crossed with APP/PS1 mutant mice to generate the ALDH2-APP/PS1 mutant mice. Cognitive function, cardiac contractile, and morphological properties were assessed. We showed that APP/PS1 mice displayed significant cognitive deficit in Morris water maze test, myocardial ultrastructural, geometric (cardiac atrophy, interstitial fibrosis) and functional (reduced fractional shortening and cardiomyocyte contraction) anomalies along with oxidative stress, apoptosis, and inflammation in myocardium. ALDH2 transgene significantly attenuated or mitigated these anomalies. We also noted the markedly elevated levels of lipid peroxidation, the essential lipid peroxidation enzyme acyl-CoA synthetase long-chain family member 4 (ACSL4), the transcriptional regulator for ACLS4 special protein 1 (SP1) and ferroptosis, evidenced by elevated NCOA4, decreased GPx4, and SLC7A11 in myocardium of APP/PS1 mutant mice; these effects were nullified by ALDH2 transgene. In cardiomyocytes isolated from WT mice and in H9C2 myoblasts in vitro, application of Aß (20 µM) decreased cell survival, compromised cardiomyocyte contractile function, and induced lipid peroxidation; ALDH2 transgene or activator Alda-1 rescued Aß-induced deteriorating effects. ALDH2-induced protection against Aß-induced lipid peroxidation was mimicked by the SP1 inhibitor tolfenamic acid (TA) or the ACSL4 inhibitor triacsin C (TC), and mitigated by the lipid peroxidation inducer 5-hydroxyeicosatetraenoic acid (5-HETE) or the ferroptosis inducer erastin. These results demonstrate an essential role for ALDH2 in AD-induced cardiac anomalies through regulation of lipid peroxidation and ferroptosis.

Very Low Density Lipoprotein Receptor Sequesters Lipopolysaccharide Into Adipose Tissue During Sepsis.

OBJECTIVES: Obese patients have lower sepsis mortality termed the "obesity paradox." We hypothesized that lipopolysaccharide, known to be carried within lipoproteins such as very low density lipoprotein, could be sequestered in adipose tissue during sepsis; potentially contributing a survival benefit. DESIGN: Retrospective analysis. SETTING: University research laboratory. SUBJECTS AND PATIENTS: Vldlr knockout mice to decrease very low density lipoprotein receptors, Pcsk9 knockout mice to increase very low density lipoprotein receptor, and Ldlr knockout mice to decrease low density lipoprotein receptors. Differentiated 3T3-L1 adipocytes. Caucasian septic shock patients. INTERVENTIONS: We measured lipopolysaccharide uptake into adipose tissue 6 hours after injection of fluorescent lipopolysaccharide into mice. Lipopolysaccharide uptake and very low density lipoprotein receptor protein expression were measured in adipocytes. To determine relevance to humans, we genotyped the VLDLR rs7852409 G/C single-nucleotide polymorphism in 519 patients and examined the association of 28-day survival with genotype. MEASUREMENTS AND MAIN RESULTS: Lipopolysaccharide injected into mice was found in adipose tissue within 6 hours and was dependent on very low density lipoprotein receptor but not low density lipoprotein receptors. In an adipocyte cell line decreased very low density lipoprotein receptor expression resulted in decreased lipopolysaccharide uptake. In septic shock patients, the minor C allele of VLDLR rs7852409 was associated with increased survival (p = 0.010). Previously published data indicate that the C allele is a gain-of-function variant of VLDLR which may increase sequestration of very low density lipoprotein (and lipopolysaccharide within very low density lipoprotein) into adipose tissue. When body mass index less than 25 this survival effect was accentuated and when body mass index greater than or equal to 25 this effect was diminished suggesting that the effect of variation in very low density lipoprotein receptor function is overwhelmed when copious adipose tissue is present. CONCLUSIONS: Lipopolysaccharide may be sequestered in adipose tissue via the very low density lipoprotein receptor and this sequestration may contribute to improved sepsis survival.

Reduced Proprotein convertase subtilisin/kexin 9 (PCSK9) function increases lipoteichoic acid clearance and improves outcomes in Gram positive septic shock patients.

Previous studies have shown lipopolysaccharide from Gram-negative bacteria is cleared from the circulation via LDL receptors on hepatocytes, which are downregulated by PCSK9. Whether clearance of Gram positive bacterial lipoteichoic acid (LTA) shows similar dependence on PCSK9, and whether this is clinically relevant in Gram positive human sepsis, is unknown. We examined survival data from three cohorts of patients who had Gram positive septic shock (n = 170, n = 130, and n = 59) and found that patients who carried a PCSK9 loss-of-function (LOF) allele had significantly higher 28-day survival (73.8%) than those with no LOF alleles (52.8%) (p = 0.000038). Plasma clearance of LTA was also found to be increased in PCSK9 knockout mice compared to wildtype control mice (p = 0.002). In addition, hepatocytes pre-treated with recombinant wildtype PCSK9 showed a dose-dependent decrease in uptake of fluorescently-labeled LTA (p < 0.01). In comparison to wildtype PCSK9, hepatocytes pre-treated with 3 different LOF variants of recombinant PCSK9 showed an increase in LTA uptake. This study shows the clearance of LTA follows a similar route as lipopolysaccharide, which is dependent on hepatic LDL receptors. This has important implications in health as strategies aimed at inhibiting PCSK9 function may be an effective treatment option for both Gram-positive and negative sepsis.

Correction: Lipopolysaccharide Is Cleared from the Circulation by Hepatocytes via the Low Density Lipoprotein Receptor.

[This corrects the article DOI: 10.1371/journal.pone.0155030.].

Lipopolysaccharide Is Cleared from the Circulation by Hepatocytes via the Low Density Lipoprotein Receptor.

Sepsis is the leading cause of death in critically ill patients. While decreased Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) function improves clinical outcomes in murine and human sepsis, the mechanisms involved have not been fully elucidated. We tested the hypothesis that lipopolysaccharide (LPS), the major Gram-negative bacteria endotoxin, is cleared from the circulation by hepatocyte Low Density Lipoprotein Receptors (LDLR)-receptors downregulated by PCSK9. We directly visualized LPS uptake and found that LPS is rapidly taken up by hepatocytes into the cell periphery. Over the course of 4 hours LPS is transported towards the cell center. We next found that clearance of injected LPS from the blood was reduced substantially in Ldlr knockout (Ldlr-/-) mice compared to wild type controls and, simultaneously, hepatic uptake of LPS was also reduced in Ldlr-/- mice. Specifically examining the role of hepatocytes, we further found that primary hepatocytes isolated from Ldlr-/- mice had greatly decreased LPS uptake. In the HepG2 immortalized human hepatocyte cell line, LDLR silencing similarly resulted in decreased LPS uptake. PCSK9 treatment reduces LDLR density on hepatocytes and, therefore, was another independent strategy to test our hypothesis. Incubation with PCSK9 reduced LPS uptake by hepatocytes. Taken together, these findings demonstrate that hepatocytes clear LPS from the circulation via the LDLR and PCSK9 regulates LPS clearance from the circulation during sepsis by downregulation of hepatic LDLR.

TNFAIP2 Inhibits Early TNFα-Induced NF-x03BA;B Signaling and Decreases Survival in Septic Shock Patients.

During septic shock, tumor necrosis factor alpha (TNFα) is an early response gene and induces a plethora of genes and signaling pathways. To identify robust signals in genes reliably upregulated by TNFα, we first measured microarray gene expression in vitro and searched methodologically comparable, publicly available data sets to identify concordant signals. Using tag single-nucleotide polymorphisms in the genes common to all data sets, we identified a genetic variant of the TNFAIP2 gene, rs8126, associated with decreased 28-day survival and increased organ dysfunction in an adult cohort in the Vasopressin and Septic Shock Trial. Similar to this cohort, we found that an association with rs8126 and increased organ dysfunction is replicated in a second cohort of septic shock patients in the St. Paul's Hospital Intensive Care Unit. We found that TNFAIP2 inhibits NF-x03BA;B activity, impacting the downstream cytokine interleukin (IL)-8. The minor G allele of TNFAIP2 rs8126 resulted in greater TNFAIP2 expression, decreased IL-8 production and was associated with decreased survival in patients experiencing septic shock. These data suggest that TNFAIP2 is a novel inhibitor of NF-x03BA;B that acts as an autoinhibitor of the TNFα response during septic shock.

Characterization of the dehydration products due to thermal decomposition of peptides by liquid chromatography-tandem mass spectrometry.

Thermal decomposition (TD) of proteins is being investigated as a rapid digestion step for bottom-up proteomics. Mass spectrometry (MS) analyses of the TD products of simple peptides and intact proteins have revealed several nonvolatile products at masses lower than the precursor biomolecule (M). In addition to products stemming from site-specific cleavages, many signals are also observed at a corresponding M-18, most likely because of dehydration (M-H2O) during the heating process. Understanding the structural nature of the water loss product is important in establishing the utility of their tandem mass spectra (collision-induced dissociation) in determining the precursor ion amino acid sequence in a bottom-up proteomic workflow. Dehydration of a peptide can take place from a variety of sources including side chain groups, C-terminus, and/or intramolecular cyclization (C to N-terminus cyclization). In this work, liquid chromatography-tandem MS (LC-MS/MS) and a series of standard peptides (angiotensin II, DRVYIHPF and its cyclic analog) are implemented to decipher the structure of the TD dehydration product. In addition, a derivatization strategy incorporating N-terminus acetylation was developed that allowed the direct comparison of tandem mass spectra of standard cyclic peptides with those resulting from the TD process, thus eliminating any ambiguity from the direct comparison of their mass spectra (due to gas-phase cyclization of b-ions, which can result in sequence scrambling of the precursor ion). Results from these investigations indicated that peptide dehydrated TD products were mostly linear in nature, and water loss was favored from the C-terminus carboxyl group or, when present, the aspartic acid side chain. Given the predictable nature of the formation of TD dehydration products, their MS/MS analysis can be of utility in providing complementary and confirmatory sequence information of the precursor peptide.

Listeria monocytogenes exopolysaccharide: origin, structure, biosynthetic machinery and c-di-GMP-dependent regulation.

Elevated levels of the second messenger c-di-GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food-borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis and identified diguanylate cyclases activating its synthesis. Phylogenetic analysis of EPS biosynthesis proteins suggests that they have evolved within monoderms. Scanning electron microscopy revealed that L. monocytogenes EPS is cell surface-bound. Secreted carbohydrates represent exclusively cell-wall debris. Based on carbohydrate composition, linkage and NMR analysis, the structure of the purified EPS is identified as a ß-1,4-linked N-acetylmannosamine chain decorated with terminal α-1,6-linked galactose. All genes of the pssA-E operon are required for EPS production and so is a separately located pssZ gene. We show that PssZ has an EPS-specific glycosylhydrolase activity. Exogenously added PssZ prevents EPS-mediated cell aggregation and disperses preformed aggregates, whereas an E72Q mutant in the presumed catalytic residue is much less active. The diguanylate cyclases DgcA and DgcB, whose genes are located next to pssZ, are primarily responsible for c-di-GMP-dependent EPS production.

Chelation of Ca²âº ions by a peptide from the repeat region of the Plasmodium falciparum circumsporozoite protein.

BACKGROUND: Elegant efforts towards the determination of the structural tendencies of peptides derived from the Plasmodium falciparum circumsporozoite protein allowed the proposal of a left-handed helical conformation for this protein. The use of circular dichroism and Fourier-transformed infrared spectroscopy applied to various peptides derived from this protein, indicated that they bind Ca²âº ions in helical environments. The essential role of calcium in cell function and biological mechanisms is well known. It influences the development of several stages of the P. falciparum parasite. However, there is very little knowledge regarding calcium coordination to circumsporozoite proteins. In the present investigation the chelation of Ca²âº by the (NANPNVDP)3NANP peptide, which contains the first seven 4-amino-acid blocks of the repeat region of the P. falciparum circumsporozoite protein, is tested with the use of circular dichroism and nuclear magnetic resonance spectroscopies. Spectroscopy-based solution conformations of the Ca-bound peptide are also determined. METHODS: NMR spectroscopy and circular dichroism were used to test Ca²âº coordination by the peptide (NANPNVDP)3NANP. Solution conformations for the Ca-bound peptide were determined through molecular dynamics calculations. RESULTS: The NMR spectra collected for (NANPNVDP)3NANP indicate that the signals generated by some of the amino acids located at its C-terminal end are shifted from their original positions upon Ca²âº addition. The solution conformations determined for the Ca-bound peptide indicate that the metal ion can be either six- or seven-coordinate. CONCLUSIONS: The investigation described herein strongly supports the coordination of Ca²âº ions to some of the amino acids located at the C-terminus of the peptide (NANPNVDP)3NANP. The solution conformations determined for the Ca-bound congener of this peptide display many structural features associated to Ca-binding proteins.

Novel curcumin derivative CNB-001 mitigates obesity-associated insulin resistance.

Type 2 diabetes is growing at epidemic proportions, and pharmacological interventions are being actively sought. This study examined the effect of a novel neuroprotective curcuminoid, CNB-001 [4-((1E)-2-(5-(4-hydroxy-3-methoxystyryl-)-1-phenyl-1H-pyrazoyl-3-yl)vinyl)-2-methoxy-phenol], on glucose intolerance and insulin signaling in high-fat diet (HFD)-fed mice. C57BL6 mice (5-6 weeks old) were randomly assigned to receive either a HFD (45% fat) or a low-fat diet (LFD, 10% fat) for 24 weeks, together with CNB-001 (40 mg/kg i.p. per day). Glucose tolerance test revealed that the area under the curve of postchallenge glucose concentration was elevated on HF-feeding, which was attenuated by CNB-001. CNB-001 attenuated body weight gain, serum triglycerides, and IL-6, and augmented insulin signaling [elevated phosphoprotein kinase B (p-Akt), and phosphoinsulin receptor (p-IR)ß, lowered endoplasmic reticulum (ER) stress, protein-tyrosine phosphatase 1B (PTP1B)] and glucose uptake in gastrocnemius muscle of HFD-fed mice. Respiratory quotient, measured using a metabolic chamber, was elevated in HFD-fed mice, which was unaltered by CNB-001, although CNB-001 treatment resulted in higher energy expenditure. In cultured myotubes, CNB-001 reversed palmitate-induced impairment of insulin signaling and glucose uptake. Docking studies suggest a potential interaction between CNB-001 and PTP1B. Taken together, CNB-001 alleviates obesity-induced glucose intolerance and represents a potential candidate for further development as an antidiabetic agent.

Contributions of NMR to the understanding of the coordination chemistry and DNA interactions of metallo-bleomycins.

Bleomycins are a family of glycopeptide antibiotics that have the ability to bind and degrade DNA when bound to key metal ions, which is believed to be responsible for their antitumor activity. Knowledge of the structures of metallo-bleomycins is vital to further characterize their mechanism of action. To this end, numerous structural studies on metallo-bleomycins have been conducted. NMR spectroscopy has had a key role in most of these studies, and has led to very important findings involving the coordination chemistry of metallo-bleomycins, and the details of many metallo-bleomycin-DNA spatial correlations for this important drug. This paper reviews the most important contributions of NMR to the bleomycin field.

Effects of enzymatically inactive recombinant botulinum neurotoxin type A at the mouse neuromuscular junctions.

Botulinum neurotoxin A (BoNT/A) is used clinically to treat several neurological and metabolic diseases. However, the mechanisms that underlie the clinical use of the toxin remain still to be elusive. BoNT/A inhibits acetylcholine (ACh) release at the motor nerve terminals (MNT) and causes neuroparalysis. The toxic effects of BoNT/A at the MNT occur in sub-pico molar range, and it is invaluable to determine the half-life and the persistence of catalytic activity of the toxin to develop therapeutics against BoNT/A intoxication. However, the use of extremely low concentrations of BoNT/A in cellular, or animal models due to high toxicity makes it difficult to determine new cellular mechanisms and binding or interacting partners of BoNT/A. In order to address this, a catalytically deactivated, non-toxic version of BoNT/A, designated as DrBoNT/A, was characterized. DrBoNT/A lacks endoprotease activity (SNAP-25 cleavage) at concentrations as high as 46,875-fold, compared to wild-type BoNT/A. Unlike BoNT/A injection (3.2 pg), injection of the recombinant product (150 ng or 3.2 pg) into mouse hind limbs failed to cause neuroparalysis as exhibited by the lack of inhibition of toe spread reflex (ability of the mouse to spread its hindlimb toes), and inhibit ACh release at the MNT. The in vitro experiments also demonstrate that DrBoNT/A uptake (at concentrations equivalent to BoNT/A), internalization and localization at the MNT remained unaltered. In addition, modeling studies support that DrBoNT/A lacked the zinc binding ability, and the ability to directly participate in the hydrolysis of SNAP-25 substrate. Collectively, we demonstrate that DrBoNT/A is non-toxic to the MNT and can be used as a surrogate tool to understand the mechanism by which BoNT/A modulates signal transduction mechanisms.

Nox4-generated superoxide drives angiotensin II-induced neural stem cell proliferation.

Reactive oxygen species (ROS) have been reported to affect neural stem cell self-renewal and therefore may be important for normal development and may influence neurodegenerative processes when ROS activity is elevated. To determine if increasing production of superoxide, via activation of NADPH oxidase (Nox), increases neural stem cell proliferation, 100 nM angiotensin II (Ang II) - a strong stimulator of Nox - was applied to cultures of a murine neural stem cell line, C17.2. Twelve hours following a single treatment with Ang II, there was a doubling of the number of neural stem cells. This increase in neural stem cell numbers was preceded by a gradual elevation of superoxide levels (detected by dihydroethidium fluorescence) from the steady state at 0, 5, and 30 min and gradually increasing from 1 h to the maximum at 12 h, and returning to baseline at 24 h. Ang II-dependent proliferation was blocked by the antioxidant N-acetyl-L-cysteine. Confocal microscopy revealed the presence of two sources of intracellular ROS in C17.2 cells: (i) mitochondrial and (ii) extramitochondrial; the latter indicative of the involvement of one or more specific isoforms of Nox. Of the Nox family, mRNA expression for one member, Nox4, is abundant in neural stem cell cultures, and Ang II treatment resulted in elevation of the relative levels of Nox4 protein. SiRNA targeting of Nox4 mRNA reduced both the constitutive and Ang II-induced Nox4 protein levels and attenuated Ang II-driven increases in superoxide levels and stem cell proliferation. Our findings are consistent with our hypothesis that Ang II-induced proliferation of neural stem cells occurs via Nox4-generated superoxide, suggesting that an Ang II/Nox4 axis is an important regulator of neural stem cell self-renewal and as such may fine-tune normal, stress- or disease-modifying neurogenesis.

T1BT* structural study of an anti-plasmodial peptide through NMR and molecular dynamics.

BACKGROUND: T1BT* is a peptide construct containing the T1 and B epitopes located in the 5' minor repeat and the 3' major repeat of the central repeat region of the Plasmodium falciparum circumsporozoite protein (CSP), respectively, and the universal T* epitope located in the C-terminus of the same protein. This peptide construct, with B = (NANP)3, has been found to elicit antisporozoite antibodies and gamma-interferon-screening T-cell responses in inbred strains of mice and in outbred nonhuman primates. On the other hand, NMR and CD spectroscopies have identified the peptide B' = (NPNA)3 as the structural unit of the major repeat in the CSP, rather than the more commonly quoted NANP. With the goal of assessing the structural impact of the NPNA cadence on a proven anti-plasmodial peptide, the solution structures of T1BT* and T1B'T* were determined in this work. METHODS: NMR spectroscopy and molecular dynamics calculations were used to determine the solution structures of T1BT* and T1B'T*. These structures were compared to determine the main differences and similarities between them. RESULTS: Both peptides exhibit radically different structures, with the T1B'T* showing strong helical tendencies. NMR and CD data, in conjunction with molecular modelling, provide additional information about the topologies of T1BT* and T1B'T*. Knowing the peptide structures required to elicit the proper immunogenic response can help in the design of more effective, conformationally defined malaria vaccine candidates. If peptides derived from the CSP are required to have helical structures to interact efficiently with their corresponding antibodies, a vaccine based on the T1B'T* construct should show higher efficiency as a pre-erythrocyte vaccine that would prevent infection of hepatocytes by sporozoites.