Structural Basis for Vital Function and Malfunction of Serum Amyloid A: an Acute-Phase Protein that Wears Hydrophobicity on Its Sleeve

Structural characterization of polysaccharide isolated from Inonotus hispidus and its anti-obesity effect based on regulation of the interleukin-17-mediated inflammatory response

A heteropolysaccharide (IHP3) with a molecular weight of 22.0 kDa was isolated from Inonotus hispidus (Bull.: Fr.) P. Karst using column chromatography purification from water extraction. Its backbone was predominantly composed of →6)-α-D-Galp-(1→, →2,6)-α-D-Galp-(1→,→6)-α-D-O-Me-Galp-(1→, →3)-α-D-Manp-(1→, and →3,4,6) -β-D-Galp-(1→ residues, branched at C2 of partial α-D-Galp, or C3 and C4 of β-D-Galp, and terminated by α-D-Manp, and α-L-Fucp. In high-fat diet (HFD)-fed obese mice, IHP3 effectively suppressed body weight and plasma glucose gain, decreased fat accumulation, ameliorated lipid metabolism, and protected liver function from HFD-induced damage. Combining the analysis of gut microbiota metabolomics, hepatic proteomics and biochemical detection revealed, IHP3 significantly altered cecum fecal metabolite abundances, inhibited the phosphorylation of peroxisome proliferator-activated receptor gamma, and promoted the browning of white adipose tissue and the activation of brown adipose tissue. These changes collectively contributed to alleviating obesity symptoms by suppressing the interleukin (IL)-17-mediated inflammatory response in obese mice. Therefore, these findings suggest that IHP3 could be a potential candidate for the development of anti-obesity drugs.

Research progress of biomarkers in evaluating the severity and prognostic value of severe pneumonia in children

Pneumonia is a serious and common infectious disease in children. If not treated in time, it may develop into severe pneumonia. Severe pneumonia in children is mainly characterized by hypoxia and acidosis, often accompanied by various complications such as sepsis and multiple organ dysfunction. Severe pneumonia has a rapid onset and progression, and a high mortality rate. Biomarkers assist clinicians in the early diagnosis and treatment of patients by quickly and accurately identifying their conditions and prognostic risks. In this study, common clinical and novel biomarkers of severe pneumonia in children were reviewed, and the application value of biomarkers related to the severity and prognosis of severe pneumonia in children was evaluated to provide help for early identification and precise intervention by clinicians.

Structural studies of a serum amyloid A octamer that is primed to scaffold lipid nanodiscs

Serum amyloid A (SAA) is a highly conserved acute-phase protein that plays roles in activating multiple pro-inflammatory pathways during the acute inflammatory response and is commonly used as a biomarker of inflammation. It has been linked to beneficial roles in tissue repair through improved clearance of lipids and cholesterol from sites of damage. In patients with chronic inflammatory diseases, elevated levels of SAA may contribute to increased severity of the underlying condition. The majority of circulating SAA is bound to lipoproteins, primarily high-density lipoprotein (HDL). Interaction with HDL not only stabilizes SAA but also alters its functional properties, likely through altered accessibility of protein-protein interaction sites on SAA. While high-resolution structures for lipid-free, or apo-, forms of SAA have been reported, their relationship with the HDL-bound form of the protein, and with other possible mechanisms of SAA binding to lipids, has not been established. Here, we have used multiple biophysical techniques, including SAXS, TEM, SEC-MALS, native gel electrophoresis, glutaraldehyde crosslinking, and trypsin digestion to characterize the lipid-free and lipid-bound forms of SAA. The SAXS and TEM data show the presence of soluble octamers of SAA with structural similarity to the ring-like structures reported for lipid-free ApoA-I. These SAA octamers represent a previously uncharacterized structure for lipid-free SAA and are capable of scaffolding lipid nanodiscs with similar morphology to those formed by ApoA-I. The SAA-lipid nanodiscs contain four SAA molecules and have similar exterior dimensions as the lipid-free SAA octamer, suggesting that relatively few conformational rearrangements may be required to allow SAA interactions with lipid-containing particles such as HDL. This study suggests a new model for SAA-lipid interactions and provides new insight into how SAA might stabilize protein-lipid nanodiscs or even replace ApoA-I as a scaffold for HDL particles during inflammation.

Asthmatic patients with high serum amyloid A have proinflammatory HDL: Implications for augmented systemic and airway inflammation

RATIONALE

Serum amyloid A (SAA) is bound to high-density lipoproteins (HDL) in blood. Although SAA is increased in the blood of patients with asthma, it is not known whether this modifies asthma severity.

OBJECTIVE

We sought to define the clinical characteristics of patients with asthma who have high SAA levels and assess whether HDL from SAA-high patients with asthma is proinflammatory.

METHODS

SAA levels in serum from subjects with and without asthma were quantified by ELISA. HDLs isolated from subjects with asthma and high SAA levels were used to stimulate human monocytes and were intravenously administered to BALB/c mice.

RESULTS

An SAA level greater than or equal to 108.8 μg/mL was defined as the threshold to identify 11% of an asthmatic cohort (n = 146) as being SAA-high. SAA-high patients with asthma were characterized by increased serum C-reactive protein, IL-6, and TNF-α; older age; and an increased prevalence of obesity and severe asthma. HDL isolated from SAA-high patients with asthma (SAA-high HDL) had an increased content of SAA as compared with HDL from SAA-low patients with asthma and induced the secretion of IL-6, IL-1β, and TNF-α from human monocytes via a formyl peptide receptor 2/ATP/P2X purinoceptor 7 axis. Intravenous administration to mice of SAA-high HDL, but not normal HDL, induced systemic inflammation and amplified allergen-induced neutrophilic airway inflammation and goblet cell metaplasia.

CONCLUSIONS

SAA-high patients with asthma are characterized by systemic inflammation, older age, and an increased prevalence of obesity and severe asthma. HDL from SAA-high patients with asthma is proinflammatory and, when intravenously administered to mice, induces systemic inflammation, and amplifies allergen-induced neutrophilic airway inflammation. This suggests that systemic inflammation induced by SAA-high HDL may augment disease severity in asthma.

CHRONIC CRITICAL ILLNESS-INDUCED MUSCLE ATROPHY: INSIGHTS FROM A TRAUMA MOUSE MODEL AND POTENTIAL MECHANISM MEDIATED VIA SERUM AMYLOID A

ABSTRACT

Background: Chronic critical illness (CCI), which was characterized by persistent inflammation, immunosuppression, and catabolism syndrome (PICS), often leads to muscle atrophy. Serum amyloid A (SAA), a protein upregulated in critical illness myopathy, may play a crucial role in these processes. However, the effects of SAA on muscle atrophy in PICS require further investigation. This study aims to develop a mouse model of PICS combined with bone trauma to investigate the mechanisms underlying muscle weakness, with a focus on SAA. Methods: Mice were used to examine the effects of PICS after bone trauma on immune response, muscle atrophy, and bone healing. The mice were divided into two groups: a bone trauma group and a bone trauma with cecal ligation and puncture group. Tibia fracture surgery was performed on all mice, and PICS was induced through cecal ligation and puncture surgery in the PICS group. Various assessments were conducted, including weight change analysis, cytokine analysis, hematological analysis, grip strength analysis, histochemical staining, and immunofluorescence staining for SAA. In vitro experiments using C2C12 cells (myoblasts) were also conducted to investigate the role of SAA in muscle atrophy. The effects of inhibiting receptor for advanced glycation endproducts (RAGE) or JAK2 on SAA-induced muscle atrophy were examined. Bioinformatic analysis was conducted using a dataset from the GEO database to identify differentially expressed genes and construct a coexpression network. Results: Bioinformatic analysis confirmed that SAA was significantly upregulated in muscle tissue of patients with intensive care unit-induced muscle atrophy. The PICS animal models exhibited significant weight loss, spleen enlargement, elevated levels of proinflammatory cytokines, and altered hematological profiles. Evaluation of muscle atrophy in the animal models demonstrated decreased muscle mass, grip strength loss, decreased diameter of muscle fibers, and significantly increased expression of SAA. In vitro experiment demonstrated that SAA decreased myotube formation, reduced myotube diameter, and increased the expression of muscle atrophy-related genes. Furthermore, SAA expression was associated with activation of the FOXO signaling pathway, and inhibition of RAGE or JAK2/STAT3-FOXO signaling partially reversed SAA-induced muscle atrophy. Conclusions: This study successfully develops a mouse model that mimics PICS in CCI patients with bone trauma. Serum amyloid A plays a crucial role in muscle atrophy through the JAK2/STAT3-FOXO signaling pathway, and targeting RAGE or JAK2 may hold therapeutic potential in mitigating SAA-induced muscle atrophy.

AA amyloidosis With Ig-Dominant Staining and Diagnostically Unusual Features

Introduction

Although serum amyloid A (AA) amyloid may occasionally show nonspecific staining by immunofluorescence (IF), the correct diagnosis can usually be determined by integrating pathologic features and clinical scenario, and using AA amyloid immunohistochemistry (IHC) and/or mass spectrometry. A recent mass spectrometry-based study described false-positive Ig IF staining in a subset of AA amyloid cases.

Methods

We sought to delineate clinicopathologic features of AA amyloid with Ig-dominant staining by using a retrospective review.

Results

AA amyloid with Ig-dominant staining was identified in 10 patients from 5 institutions, representing 1.2% to 4% of AA amyloid kidney biopsies. Evidence of a monoclonal protein was documented in 0% to 2.7% of patients with AA amyloid screened for inclusion, but 30% of those with Ig-dominant staining. The patient population had equal sex distribution and presented at median age of 68.5 years with nephrotic proteinuria and kidney impairment. Etiologies of AA amyloid included injection drug use (30%), autoimmune disease (20%), and chronic infection (10%); 40% had no identified clinical association. On biopsy, heavy chain (co)dominant staining by IF (in 80%), discordant distribution in Ig staining (in 20%), tubulointerstitial nephritis (in 30%), and/or crescents (in 10%) were present. Two of 3 patients with paraproteinemia had concordant heavy and/or light chain dominant staining within the AA amyloid. Two cases were initially misdiagnosed as Ig-associated amyloidosis.

Conclusion

We describe the morphologic spectrum of AA amyloidosis with Ig-dominant staining which may have clinical, laboratory, and pathologic overlap with amyloid light chain (AL), amyloid heavy chain, and heavy and light chain (AHL) amyloidosis.

Nanodot zirconium trisulfide modified conducting thread: A smart substrate for fabrication of next generation biosensor

In present work, we report an eco-friendly, flexible and highly conducting cotton thread (CT) as a smart substrate for the development of biosensing platform towards ultrasensitive detection of swine flu serum amyloid A (SAA) biomarker. The biosensor was fabricated by optimized coating of CT with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) conductive ink followed by incorporation of nanodot zirconium trisulfide (nZrS3) which helped in enhancing the electrochemical properties and improving stability of PEDOT:PSS polymeric film. The fabricated nZrS3/PEDOT:PSS/CT electrode was then used for sequential immobilization of monoclonal antibodies of SAA (anti-SAA) and bovine serum albumin (BSA). The synthesized nanomaterials and fabricated electrodes were characterized through X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy and contact angle analyser techniques. The electrochemical response of the fabricated smart thread based biosensor (BSA/anti-SAA/ZrS3/PEDOT:PSS/CT) was recorded against SAA using chronoamperometry technique which revealed superior sensitivity {30.2 μA [log (μg mL-1)]-1 cm-2}, excellent lower detection limit (0.72 ng mL-1) and prolonged shelf life up to 48 days. The response of the biosensor was also validated by analysing the electrochemical response of SAA spiked serum samples and the obtained results showed good correlation with that of standard samples.

Discovering the deep evolutionary roots of serum amyloid A protein family

Deep evolutionary origin of the conserved animal serum amyloid A (SAA) apolipoprotein family leading to yet unknown highly similar SAA-like sequences occurring in certain bacterial genomes is demonstrated in this contribution. Horizontal gene transfer event of corresponding genes between gut bacteria and non-vertebrate animals was discovered in the reconstructed phylogenetic tree obtained with maximum likelihood and neighbor-joining methods, respectively. This detailed phylogeny based on totally 128 complete sequences comprised diverse serum amyloid A isoforms from various animal vertebrate and non-vertebrate phyla and also corresponding genes coding for highly similar proteins from animal gut bacteria. Typical largely conserved sequence motifs and a peculiar structural fold consisting mainly of four α-helices in a bundle within all reconstructed clades of the SAA protein family are discussed with respect to their supposed biological functions in various organisms that contain corresponding genes.

Human lysozyme inhibits the fibrillation of serum amyloid a protein from systemic AA amyloidosis

BACKGROUND

Systemic AA amyloidosis is a world-wide occurring protein misfolding disease in humans and animals that arises from the formation of amyloid fibrils from serum amyloid A (SAA) protein and their deposition in multiple organs.

OBJECTIVE

To identify new agents that prevent fibril formation from SAA protein and to determine their mode of action.

MATERIALS AND METHODS

We used a cell model for the formation of amyloid deposits from SAA protein to screen a library of peptides and small proteins, which were purified from human hemofiltrate. To clarify the inhibitory mechanism the obtained inhibitors were characterised in cell-free fibril formation assays and other biochemical methods.

RESULTS

We identified lysozyme as an inhibitor of SAA fibril formation. Lysozyme antagonised fibril formation both in the cell model as well as in cell-free fibril formation assays. The protein binds SAA with a dissociation constant of 16.5 ± 0.6 µM, while the binding site on SAA is formed by segments of positively charged amino acids.

CONCLUSION

Our data imply that lysozyme acts in a chaperone-like fashion and prevents the aggregation of SAA protein through direct, physical interactions.

Lipid clearance and amyloid formation by serum amyloid A: exploring the links between beneficial and pathologic actions of an enigmatic protein

Serum amyloid A (SAA) is named after a life-threatening disease, yet this small evolutionarily conserved protein must have played a vital role in host defense. Most circulating SAA binds plasma lipoproteins and modulates their metabolism. However, this hardly justifies the rapid and dramatic SAA upregulation in inflammation, which is concomitant with upregulation of secretory phospholipase A2 (sPLA2). We proposed that these proteins synergistically clear cell membrane debris from the sites of injury. The present study uses biochemical and biophysical approaches to further explore the beneficial function of SAA and its potential links to amyloid formation. We show that murine and human SAA1 are powerful detergents that solubilize diverse lipids, including mammalian biomembranes, converting them into lipoprotein-size nanoparticles. These nanoparticles provide ligands for cell receptors, such as scavenger receptor CD36 or heparin/heparan sulfate, act as substrates of sPLA2, and sequester toxic products of sPLA2. Together, these functions enable SAA to rapidly clear unprotected lipids. SAA can also adsorb, without remodeling, to lipoprotein-size nanoparticles such as exosomal liposomes, which are proxies for lipoproteins. SAA in complexes with zwitterionic phospholipids stabilizes α-helices, while SAA in complexes containing anionic lipids or micelle-forming sPLA2 products forms metastable β-sheet-rich species that readily aggregate to form amyloid. Consequently, the synergy between SAA and sPLA2 extends from the beneficial lipid clearance to the pathologic amyloid formation. Furthermore, we show that lipid composition alters SAA conformation and thereby can influence the metabolic fate of SAA-lipid complexes, including their proamyloidogenic and proatherogenic binding to heparan sulfate.

Selenoprotein S: A versatile disordered protein

Selenoprotein S (selenos) is a small, intrinsically disordered membrane protein that is associated with various cellular functions, such as inflammatory processes, cellular stress response, protein quality control, and signaling pathways. It is primarily known for its contribution to the ER-associated degradation (ERAD) pathway, which governs the extraction of misfolded proteins or misassembled protein complexes from the ER to the cytosol for degradation by the proteasome. However, selenos's other cellular roles in signaling are equally vital, including the control of transcription factors and cytokine levels. Consequently, genetic polymorphisms of selenos are associated with increased risk for diabetes, dyslipidemia, and cardiovascular diseases, while high expression levels correlate with poor prognosis in several cancers. Its inhibitory role in cytokine secretion is also exploited by viruses. Since selenos binds multiple protein complexes, however, its specific contributions to various cellular pathways and diseases have been difficult to establish. Thus, the precise cellular functions of selenos and their interconnectivity have only recently begun to emerge. This review aims to summarize recent insights into the structure, interactome, and cellular roles of selenos.

Amyloid fibril structure from the vascular variant of systemic AA amyloidosis

Systemic AA amyloidosis is a debilitating protein misfolding disease in humans and animals. In humans, it occurs in two variants that are called 'vascular' and 'glomerular', depending on the main amyloid deposition site in the kidneys. Using cryo electron microscopy, we here show the amyloid fibril structure underlying the vascular disease variant. Fibrils purified from the tissue of such patients are mainly left-hand twisted and contain two non-equal stacks of fibril proteins. They contrast in these properties to the fibrils from the glomerular disease variant which are right-hand twisted and consist of two structurally equal stacks of fibril proteins. Our data demonstrate that the different disease variants in systemic AA amyloidosis are associated with different fibril morphologies.

Adaptation of Microarray Assay for Serum Amyloid a Analysis in Human Serum

Serum amyloid A is an inflammatory biomarker whose concentration changes during infectious and inflammatory diseases. SAA’s tendency for aggregation and complex formation makes it difficult to determine its concentration in samples, especially when there is an increased level of it. Immunofluorescence SAA determination on a microarray was adapted for SAA quantification in human serum. Both the procedure and the diluent for the calibrator samples were chosen to obtain a dynamic range between 1 and 100 μg/mL. Mixtures of animal (rabbit, goat, mouse) sera with recombinant antigen diluted in certain concentrations were used for the calibrator samples. The method was tested using serum samples from 15 patients with rheumatoid arthritis or ankylosing spondylitis and 9 healthy donors. The results obtained on the microarray demonstrated a good correlation with the results determined by ELISA (Pearson’s correlation coefficient is 0.93). The method developed could be a convenient tool for assessing SAA levels in a number of diseases, such as rheumatoid arthritis or infections of various etiologies, characterized by a significant increase in the level of this protein in the blood. The use of a microarray for the analysis allows the determination of the SAA concentration simultaneously with other inflammatory biomarkers.

Post-translational modification of amyloid a protein in patients with AA amyloidosis

AA amyloidosis is a disease caused by extracellular deposition of insoluble β-pleated sheet fibrils composed of amyloid A (AA) protein, an amino (N)-terminal fragment of serum amyloid A (SAA). The deposits disrupt tissue structure and compromise organ function. Although the disease is systemic, deposition in kidney glomeruli is the most common manifestation. The leading cause of AA amyloidosis is sustained or recurrent inflammation accompanied by elevated levels of SAA. Factors determining the conversion of SAA to AA amyloid fibrils have yet to be fully resolved. Herein, we present liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis of AA proteins purified from eight patients with AA amyloidosis. For the first time, post-translational modifications (PTM), including carbamylation, acetylation and oxidation, were identified on AA peptides; all eight samples showed some degree of PTM. The amyloid in 6 samples comprised peptides derived from SAA1 with few or none from SAA2, while the other two samples contained both SAA1- and SAA2-derived peptides. N-terminal AA peptides beginning with Arg1 as well as AA peptides starting with Ser2 were present in five of the eight samples, while all or nearly all of the N-terminal peptides in the other three samples lacked Arg1. These data demonstrate that multiple species of AA amyloid proteins can comprise the subunits in amyloid fibrils and raise the possibility that PTM may play a role in fibrillogenesis.

SAA fibrils involved in AA amyloidosis are similar in bulk and by single particle reconstitution: A MAS solid-state NMR study

AA amyloidosis is one of the most prevalent forms of systemic amyloidosis and affects both humans and other vertebrates. In this study, we compare MAS solid-state NMR data with a recent cryo-EM study of fibrils involving full-length murine SAA1.1. We address the question whether the specific requirements for the reconstitution of an amyloid fibril structure by cryo-EM can potentially yield a bias towards a particular fibril polymorph. We employ fibril seeds extracted from in to vivo material to imprint the fibril structure onto the biochemically produced protein. Sequential assignments yield the secondary structure elements in the fibril state. Long-range DARR and PAR experiments confirm largely the topology observed in the ex-vivo cryo-EM study. We find that the β-sheets identified in the NMR experiments are similar to the β-sheets found in the cryo-EM study, with the exception of amino acids 33–42. These residues cannot be assigned by solid-state NMR, while they adopt a stable β-sheet in the cryo-EM structure. We suggest that the differences between MAS solid-state NMR and cryo-EM data are a consequence of a second conformer involving residues 33–42. Moreover, we were able to characterize the dynamic C-terminal tail of SAA in the fibril state. The C-terminus is flexible, remains detached from the fibrils, and does not affect the SAA fibril structure as confirmed further by molecular dynamics simulations. As the C-terminus can potentially interact with other cellular components, binding to cellular targets can affect its accessibility for protease digestion.

Dynamic protein structures in normal function and pathologic misfolding in systemic amyloidosis

Dynamic and disordered regions in native proteins are often critical for their function, particularly in ligand binding and signaling. In certain proteins, however, such regions can contribute to misfolding and pathologic deposition as amyloid fibrils in vivo. For example, dynamic and disordered regions can promote amyloid formation by destabilizing the native structure, by directly triggering the aggregation, by promoting protein condensation, or by acting as sites of early proteolytic cleavage that favor a release of aggregation-prone fragments or facilitate fibril maturation. At the same time, enhanced dynamics in the native protein state accelerates proteolytic degradation that counteracts amyloid accumulation in vivo. Therefore, the functional need for dynamic protein regions must be balanced against their inherently labile nature. How exactly this balance is achieved and how is it shifted upon amyloidogenic mutations or post-translational modifications? To illustrate possible scenarios, here we review the beneficial and pathologic roles of dynamic and disordered regions in the native states of three families of human plasma proteins that form amyloid precursors in systemic amyloidoses: immunoglobulin light chain, apolipoproteins, and serum amyloid A. Analysis of structure, stability and local dynamics of these diverse proteins and their amyloidogenic variants exemplifies how disordered/dynamic regions can provide a functional advantage as well as an Achilles heel in pathologic amyloid formation.

3D-phosphorus doped mesoporous graphitic carbon nitride based immunosensor for swine flu detection

Illustrative representation of the immunosensing platform and its electrochemical response for the detection of swine flu.

Transient disorder along pathways to amyloid

High-resolution structures of amyloid fibrils formed from normally-folded proteins have revealed non-native conformations of the polypeptide chains. Attaining these conformations apparently requires transition from the native state via a highly disordered conformation, in contrast to earlier models that posited a role for assembly of partially folded proteins. Modifications or interactions that extend the lifetime or constrain the conformations of these disordered states could act to enhance or suppress amyloid formation. Understanding how the properties of both the folded and transiently disordered structural ensembles influence the process of amyloid formation is a substantial challenge, but research into the properties of intrinsically disordered proteins will deliver important insights.

The Etiology and Pathophysiology Genesis of Benign Prostatic Hyperplasia and Prostate Cancer: A New Perspective

Background: The etiology of benign prostatic hyperplasia and prostate cancer are unknown, with ageing being the greatness risk factor. Methods: This new perspective evaluates the available interdisciplinary evidence regarding prostate ageing in terms of the cell biology of regulation and homeostasis, which could explain the timeline of evolutionary cancer biology as degenerative, inflammatory and neoplasm progressions in these multifactorial and heterogeneous prostatic diseases. Results: This prostate ageing degeneration hypothesis encompasses the testosterone-vascular-inflamm-ageing triad, along with the cell biology regulation of amyloidosis and autophagy within an evolutionary tumorigenesis microenvironment. Conclusions: An understanding of these biological processes of prostate ageing can provide potential strategies for early prevention and could contribute to maintaining quality of life for the ageing individual along with substantial medical cost savings.

Downregulation of Cathepsin B Reduces Proliferation and Inflammatory Response and Facilitates Differentiation in Human HaCaT Keratinocytes, Ameliorating IL-17A and SAA-Induced Psoriasis-Like Lesion

Psoriasis is a common inflammatory dermatology disease. Strongly expressed serum amyloid A (SAA) promotes psoriasis exacerbation through inducing IL-17 secretion. What's more, SAA can stimulate the release of cathepsin B. The current work was performed to demonstrate the specific effects of cathepsin B silencing on inflammatory response, proliferation, and differentiation of IL-17A and SAA-induced keratinocytes and to report the precise role of cathepsin B in psoriasis-like lesion. HaCaT keratinocytes received treatment with IL-17A (0, 10, 50, 100 ng/ml) or SAA (0, 1, 5, 10, 20 μg/ml) for 24 h to establish psoriasis-like keratinocytes model. HaCaT keratinocytes were transfected with small interfering RNA (siRNA)-cathepsin B for the functional experiments. Cathepsin B mRNA and protein levels were separately assessed by performing RT-qPCR and Western blot analysis. Then, CCK-8 for detection of cell proliferative capacity and Western blot assay for detection of Ki67 and PCNA expression were adopted to evaluate the influence of silenced cathepsin B on proliferation of IL-17A/SAA-induced HaCaT keratinocytes. Furthermore, IL-6, IL-1β, TNF-α, and p-NF-κB p65 were detected to assess the effects of cathepsin B knockdown on inflammatory response in IL-17A/SAA-induced HaCaT keratinocytes. In addition, assessment of KRT10, FLG, and LOR levels were applied to analyze the function of cathepsin B silencing on differentiation of IL-17A/SAA-induced HaCaT keratinocytes. Cathepsin B expression is distinctly elevated in IL-17A/SAA-induced HaCaT keratinocytes. IL-17A or SAA treatment enhanced proliferation, promoted the release of inflammatory factors, and arrested differentiation in HaCaT keratinocytes. Furthermore, downregulation of cathepsin B reduced proliferation, suppressed inflammatory response, and boosted differentiation in IL-17A/SAA-induced HaCaT keratinocytes. To sum up, cathepsin B silencing rescued excessive proliferation and inflammatory response and scarce differentiation in HaCaT keratinocytes induced by IL-17A and SAA. These findings prompted that cathepsin B might be a promising therapeutic target for psoriasis-like lesion, which helps to develop an anti-psoriatic agent.

Connection between the Altered HDL Antioxidant and Anti-Inflammatory Properties and the Risk to Develop Alzheimer's Disease: A Narrative Review

The protein composition of high-density lipoprotein (HDL) is extremely fluid. The quantity and quality of protein constituents drive the multiple biological functions of these lipoproteins, which include the ability to contrast atherogenesis, sustained inflammation, and toxic effects of reactive species. Several diseases where inflammation and oxidative stress participate in the pathogenetic process are characterized by perturbation in the HDL proteome. This change inevitably affects the functionality of the lipoprotein. An enlightening example in this frame comes from the literature on Alzheimer's disease (AD). Growing lines of epidemiological evidence suggest that loss of HDL-associated proteins, such as lipoprotein phospholipase A2 (Lp-PLA2), glutathione peroxidase-3 (GPx-3), and paraoxonase-1 and paraoxonase-3 (PON1, PON3), may be a feature of AD, even at the early stage. Moreover, the decrease in these enzymes with antioxidant/defensive action appears to be accompanied by a parallel increase of prooxidant and proinflammatory mediators, in particular myeloperoxidase (MPO) and serum amyloid A (SAA). This type of derangement of balance between two opposite forces makes HDL dysfunctional, i.e., unable to exert its "natural" vasculoprotective property. In this review, we summarized and critically analyzed the most significant findings linking HDL accessory proteins and AD. We also discuss the most convincing hypothesis explaining the mechanism by which an observed systemic occurrence may have repercussions in the brain.

High-Density Lipoprotein Modifications: A Pathological Consequence or Cause of Disease Progression?

High-density lipoprotein (HDL) is well-known for its cardioprotective effects, as it possesses anti-inflammatory, anti-oxidative, anti-thrombotic, and cytoprotective properties. Traditionally, studies and therapeutic approaches have focused on raising HDL cholesterol levels. Recently, it became evident that, not HDL cholesterol, but HDL composition and functionality, is probably a more fruitful target. In disorders, such as chronic kidney disease or cardiovascular diseases, it has been observed that HDL is modified and becomes dysfunctional. There are different modification that can occur, such as serum amyloid, an enrichment and oxidation, carbamylation, and glycation of key proteins. Additionally, the composition of HDL can be affected by changes to enzymes such as cholesterol ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT), and phospholipid transfer protein (PLTP) or by modification to other important components. This review will highlight some main modifications to HDL and discuss whether these modifications are purely a consequential result of pathology or are actually involved in the pathology itself and have a causal role. Therefore, HDL composition may present a molecular target for the amelioration of certain diseases, but more information is needed to determine to what extent HDL modifications play a causal role in disease development.