Defective Clearance Research Articles

An exhausted-like microglial population accumulates in aged and APOE4 genotype Alzheimer’s brains

The dominant risk factors for late-onset Alzheimer's disease (AD) are advanced age and the APOE4 genetic variant. To examine how these factors alter neuroimmune function, we generated an integrative, longitudinal single-cell atlas of brain immune cells in AD model mice bearing the three common human APOE alleles. Transcriptomic and chromatin accessibility analyses identified a reactive microglial population defined by the concomitant expression of inflammatory signals and cell-intrinsic stress markers whose frequency increased with age and APOE4 burden. An analogous population was detectable in the brains of human AD patients, including in the cortical tissue, using multiplexed spatial transcriptomics. This population, which we designate as terminally inflammatory microglia (TIM), exhibited defects in amyloid-β clearance and altered cell-cell communication during aducanumab treatment. TIM may represent an exhausted-like state for inflammatory microglia in the AD milieu that contributes to AD risk and pathology in APOE4 carriers and the elderly, thus presenting a potential therapeutic target for AD.

Development of Mitophagy-inducing Small Molecules as Therapeutics for Aging and Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia in those over the age of65. The underlying molecular basis for the disease remains elusive. Rather than simply viewing individual diseases in isolation, researchers have turned to studying the contribution of common age-related processes. One such process is loss in mitochondrial function, normally maintained by defective mitochondrial clearance via mitophagy. Mitophagy slows with age and with various age-related conditions including AD. An agent which has received considerable attention is urolithin A (UA) which has recently been reported to elicit neuroprotection in a variety of AD models. As part of an independent small molecule screen, we identified a second structurally-related compound we named ‘mitophagy inducing compound’ (MIC). Using C. elegans as an initial validation tool, we showed that both compounds significantly improve mitochondrial function, protect against neuronal cell loss, and extend lifespan. These effects were translatable to both in vitro and in vivo mammalian models. To identify potential drug targets, we performed Cellular Thermal Shift Assay (CETSA). Preliminary data from knockdown of identified targets suggest the involvement of a mito-hormetic mechanism which acts to restore overall mitochondrial health. These studies may have important implications for how these compounds elicit their effects.

Mitochondrial Mechanisms of Endothelial Cell Damage in Alzheimer’s Disease and Cerebral Amyloid Angiopathy

AbstractBackgroundCerebrovascular endothelial cells (EC) are crucial regulators of cerebral homeostasis and function through the maintenance of the blood‐brain barrier (BBB). ECs damage and/or dysfunction may result in defects in brain clearance and perfusion, microhemorrhages, inflammation, and neurodegeneration. Damage to the ECs may result from cardiovascular risk factors (CVRF) such as high levels of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy). In Alzheimer’s Disease (AD) and Cerebral Amyloid Angiopathy (CAA), the presence of a CVRF may further exacerbate cerebrovascular function and neurodegeneration. EC do not rely highly on mitochondrial ATP production as they are glycolytic cells. Instead, EC mitochondria serve mostly as signaling organelles, which sense cellular damage and mediate downstream pathways such as inflammation. In this study, we aim to understand the mechanistic nature of endothelial mitochondrial dysfunction and its elicited pathways in Aβ‐ and mixed (Aβ+HHcy)‐mediated vascular pathologies. Understanding the mechanisms by which the mitochondria mediate EC inflammation, may pave the way to new roads for therapeutic advancements in the field.MethodHuman brain microvascular ECs were challenged with Aβ, Hcy, or the combination. Mitochondrial metabolic function, inflammatory cascades and signals, and EC barrier function were assessed.ResultThe presence of Aβ, but not Hcy, induced deficits in mitochondrial respiration and ATP production. In addition, there is evidence of mitochondrial fragmentation and the expression of fission proteins. Preliminary results further suggest a release of mitochondrial danger associated molecular patterns (mtDAMPs) that can promote an inflammatory cascade. The mitochondrial damage and subsequent inflammatory response are associated with an increase in EC barrier permeability and cytokine release, which is exacerbated in the presence of Hcy.ConclusionThe EC dysfunction associated with Aβ is accompanied by severe deficits in mitochondrial metabolism and the release of mtDAMPS. The presence of Hcy exacerbates some of the detrimental effects of Aβ, particularly on mtDAMPS and BBB function, but Hcy does not appear to affect mitochondrial metabolic changes. Overall, our results reveal a novel role for mtDAMPs in vascular dysfunction in the presence of Aβ and/or Hcy.

Clearance of intracellular lipids by lipophagy impaired in APOE ε4 human astrocytes

AbstractBackgroundApolipoprotein E (APOE) ɛ4 is the strongest known genetic risk factor for Alzheimer’s disease. APOE ɛ4 has been found to impair lipid metabolism in human glia causing accumulation of intracellular lipid droplets. We hypothesized that this phenotype in human APOE ɛ4/ɛ4 astrocytes was due to defective clearance via lipophagy.MethodGlobal transcriptomic analyses were performed on astrocytes derived from isogenic and population model human induced pluripotent stem cells (iPSCs). Fluorescent reporters, immunocytochemistry, and western blotting were used to quantify lipid droplets and autophagic machinery in iPSC‐based models.ResultGlobal transcriptomic analyses reveal that APOE ε4 drives autophagy dysregulation in astrocytes from human iPSCs. High‐content imaging of fluorescent autophagy reporters and immunocytochemistry revealed accumulation of lipid droplets and autophagy machinery in APOE ɛ4/ɛ4 astrocytes which was ameliorated by induction of autophagy.ConclusionHuman iPSC‐derived APOE ɛ4/ɛ4 astrocytes exhibit impaired lipophagy.

Defective Clearance of Neutrophils Causes Pathogenic Microenvironmental Interactions and Offers a Candidate Immunotherapy in the Myeloproliferative Neoplasms

Neutrophils are the most abundant leukocytes and essential components of the immune microenvironment. Myeloproliferative neoplasms (MPNs) are characterized by excessive myelopoiesis and serious complications, such as thrombosis, myelofibrosis and leukemic transformation. Neutrophils and hematopoietic stem cells (HSCs) carrying the most common MPN driver mutation (JAK2 V617F) are protected from apoptosis. Moreover, mutant neutrophils aggregate with platelets and interact with activated endothelium, increasing thrombosis risk in MPN (Blood 107:3676; Thromb Res 129:263; Sci Transl Med 10:eaan8292; Leukemia 33:2544). However, possible pathogenic interactions between heterogeneous bone marrow (BM) niches in MPN (Nat Cancer doi:10.1038/s43018-023-00607-x) and neutrophils are understudied. Circulating HSCs and leukocytes home daily to the BM (Nature 452:442), where apoptotic/senescent neutrophils are cleared by macrophages (Immunology 125:281; Cell 153:1025). We found that senescent neutrophils carrying JAK2 V617F or CALR del52 mutation evade normal clearance and accumulate in the BM of MPN mice. The homeostatic recognition and efferocytosis of neutrophils by macrophages rely on the balance of “eat-me” and “don't-eat-me” signals. Supervised analyses of two independent human JAK2 V617F+ MPN granulocyte RNAseq datasets (Blood 123:e123; Blood 134:199) showed specific upregulation of CD24 - reportedly a don't-eat-me signal in solid tumors (Nature 572:392). CD24 expression was high in granulocytes from MPN transformed into AML and in the JAK inhibitors ruxolitinib and fedratinib-resistant HEL cells (Nat Cancer 4:108). Unlike CD274 or CD47, which are extensively studied in myeloid malignancies, our data showed that CD24 expression was high in JAK2 V617F+ human or mouse neutrophils. Functional blockade in co-culture with macrophages or after in vivo adoptive transfer showed that CD24 serves as a don't-eat-me signal in neutrophils. Given that oncogenic driver mutations lead to the constitutive activation of cytokine-regulated JAK-STAT signaling, we investigated the effect of cytokines activating this pathway. We found that high GM-CSF in MPN BM induces CD24 expression and prevents neutrophil clearance via JAK-STAT5 signaling. Consequently, ruxolitinib normalized GM-CSF-induced CD24 expression and decreased human and mouse neutrophils in MPN. Our study showed that accumulation of mutant senescent neutrophils in the BM triggered abnormal interactions within the BM microenvironment. Mutated neutrophils were found closer to Megakaryocytes (Mk) and ~30% of Mks showed neutrophils transiently invading their demarcation membrane system through a process termed “emperipolesis”, which increases thrombopoiesis and intercellular exchange between neutrophils and Mks (Elife 8:e44031) and frequently occurs in diseases associated with myelofibrosis, such as MPN (Blood 104:3573) and grey platelet syndrome (Blood 124:3624). To examine whether mutated neutrophils affect platelet production, we transferred wild-type or JAK2 V617F+ senescent neutrophils and found that JAK2 V617F+ mutated (but not WT) senescent neutrophils increased Mk emperipolesis and circulating platelets. Supervised RNA-seq analysis of CD24 hi JAK2 V617F+ human neutrophils highlighted their pro-inflammatory signature. Furthermore, CD24 expression positively correlated with neutrophil degranulation signatures and proteolytic enzymes that activate latent pro-fibrotic TGF-β in Mk, subsequently triggering myelofibrosis. Taken together, these findings suggest that accumulation of senescent neutrophils might lead to their pathogenic interactions with Mks or platelets, which may increase thrombocytosis and myelofibrosis risk in MPN. To test this hypothesis and the therapeutic potential of CD24 inhibition, MPN mice were chronically treated with CD24 blocking antibody. This treatment improved thrombocytosis, decreased platelet-neutrophil complexes, restored normal clearance of mutated senescent neutrophils and reduced emperipolesis levels which, in turn, decreased active TGF-β, ultimately improving myelofibrosis. This study reveals defective neutrophil clearance as a cause of pathogenic microenvironmental interactions that may increase thrombosis and myelofibrosis risk, and postulate CD24 as a candidate target for innate immune checkpoint in myeloid malignancies.

Role of neutrophils in cutaneous lupus erythematosus.

There are various types of cutaneous lupus erythematosus (CLE), either with or without the association of systemic lupus erythematosus (SLE). In some of the subtypes of cutaneous lupus, histopathology reveals neutrophil infiltration in the lesional skin; however, the significance of neutrophils in CLE is not yet fully elucidated. Recent studies have shown that neutrophil extracellular traps (NETs) formation by activated neutrophils is observed in several types of CLE, including lupus panniculitis, subacute lupus erythematosus, and acute lupus erythematosus, although the number of reports is small. Excessive NETosis, due to either increased NETs formation or defective clearance of NETs, may play a role in the induction of autoimmunity and autoantibody production in SLE, as well as endothelial damage, thrombus formation, and vascular damage in the lesional skin. CLE is an excessive interferon-driven autoimmune disease. Plasmacytoid dendritic cells are located in lupus erythematosus skin and contribute to the etiology of skin lesions as a main producing cell of type I interferon. Neutrophils, monocytes, and keratinocytes also produce type I interferon via several triggers. Neutrophils play an important role in the innate immune response in SLE. In this review, several types of CLE with neutrophil infiltration, as well as the role of neutrophils are discussed.

The Neuropharmacological Evaluation of Seaweed: A Potential Therapeutic Source.

The most common neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD) and Parkinson's disease (PD), are the seventh leading cause of mortality and morbidity in developed countries. Clinical observations of NDD patients are characterized by a progressive loss of neurons in the brain along with memory decline. The common pathological hallmarks of NDDs include oxidative stress, the dysregulation of calcium, protein aggregation, a defective protein clearance system, mitochondrial dysfunction, neuroinflammation, neuronal apoptosis, and damage to cholinergic neurons. Therefore, managing this pathology requires screening drugs with different pathological targets, and suitable drugs for slowing the progression or prevention of NDDs remain to be discovered. Among the pharmacological strategies used to manage NDDs, natural drugs represent a promising therapeutic strategy. This review discusses the neuroprotective potential of seaweed and its bioactive compounds, and safety issues, which may provide several beneficial insights that warrant further investigation.

4-Hydroxynonenal impairs miRNA maturation in heart failure via Dicer post-translational modification.

Developing novel therapies to battle the global public health burden of heart failure remains challenging. This study investigates the underlying mechanisms and potential treatment for 4-hydroxynonenal (4-HNE) deleterious effects in heart failure. Biochemical, functional, and histochemical measurements were applied to identify 4-HNE adducts in rat and human failing hearts. In vitro studies were performed to validate 4-HNE targets. 4-HNE, a reactive aldehyde by-product of mitochondrial dysfunction in heart failure, covalently inhibits Dicer, an RNase III endonuclease essential for microRNA (miRNA) biogenesis. 4-HNE inhibition of Dicer impairs miRNA processing. Mechanistically, 4-HNE binds to recombinant human Dicer through an intermolecular interaction that disrupts both activity and stability of Dicer in a concentration- and time-dependent manner. Dithiothreitol neutralization of 4-HNE or replacing 4-HNE-targeted residues in Dicer prevents 4-HNE inhibition of Dicer in vitro. Interestingly, end-stage human failing hearts from three different heart failure aetiologies display defective 4-HNE clearance, decreased Dicer activity, and miRNA biogenesis impairment. Notably, boosting 4-HNE clearance through pharmacological re-activation of mitochondrial aldehyde dehydrogenase 2 (ALDH2) using Alda-1 or its improved orally bioavailable derivative AD-9308 restores Dicer activity. ALDH2 is a major enzyme responsible for 4-HNE removal. Importantly, this response is accompanied by improved miRNA maturation and cardiac function/remodelling in a pre-clinical model of heart failure. 4-HNE inhibition of Dicer directly impairs miRNA biogenesis in heart failure. Strikingly, decreasing cardiac 4-HNE levels through pharmacological ALDH2 activation is sufficient to re-establish Dicer activity and miRNA biogenesis; thereby representing potential treatment for patients with heart failure.

Soluble LDL-receptor is induced by TNF-α and inhibits hepatocytic clearance of LDL-cholesterol

Defective LDL-C clearance and hence its elevation in the circulation is an established risk factor for cardiovascular diseases (CVDs) such as myocardial infarction (MI). A soluble LDL-receptor (sLDL-R) has been detected in human plasma which correlates strongly with circulating LDL-C and classical conditions that promote chronic inflammation. However, the mechanistic interplay between sLDL-R, inflammation, and CVDs remains to be investigated. Here, we report that stimulation of HepG2 cells with TNF-α induces the release of sLDL-R into culture supernatants. In addition, TNF-α induces gene expression of peptidases ADAM-17 and MMP-14 in HepG2 cells, and inhibiting these peptidases using TMI 1 significantly reduces the TNF-α induced sLDL-R release. We found that a soluble form of recombinant LDL-R (100 nM) can strongly bind to LDL-C and form a stable complex (KD = E-12). Moreover, incubation of HepG2 cells with this recombinant LDL-R resulted in reduced LDL-C uptake in a dose-dependent manner. In a nested case-control study, we found that baseline sLDL-R in plasma is positively correlated with plasma total cholesterol level. Furthermore, a twofold increase in plasma sLDL-R was associated with a 55% increase in the risk of future MI [AOR = 1.55 (95% CI = 1.10–2.18)]. Nevertheless, mediation analyses revealed that a significant proportion of the association is mediated by elevation in plasma cholesterol level (indirect effect β = 0.21 (95% CI = 0.07–0.38). Collectively, our study shows that sLDL-R is induced by a pro-inflammatory cytokine TNF-α via membrane shedding. Furthermore, an increase in sLDL-R could inhibit hepatic clearance of LDL-C increasing its half-life in the circulation and contributing to the pathogenesis of MI.Key messagesTNF-α causes shedding of hepatocytic LDL-R through induction of ADAM-17 and MMP-14.sLDL-R binds strongly to LDL-C and inhibits its uptake by hepatocytic cells.Plasma sLDL-R is positively correlated with TNF-α and cholesterol.Plasma sLDL-R is an independent predictor of myocardial infarction (MI).Plasma cholesterol mediates the association between sLDL-R and MI.

Neprilysin inhibitors and risk of Alzheimer's disease: A future perspective.

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disease with multifaceted neuropathological disorders. AD is characterized by intracellular accumulation of phosphorylated tau proteins and extracellular deposition of amyloid beta (Aβ). Various protease enzymes, including neprilysin (NEP), are concerned with the degradation and clearance of Aβ. Indeed, a defective neuronal clearance pathway due to the dysfunction of degradation enzymes might be a possible mechanism for the accumulation of Aβ and subsequent progression of AD neuropathology. NEP is one of the most imperative metalloproteinase enzymes involved in the clearance of Aβ. This review aimed to highlight the possible role of NEP inhibitors in AD. The combination of sacubitril and valsartan which is called angiotensin receptor blocker and NEP inhibitor (ARNI) may produce beneficial and deleterious effects on AD neuropathology. NEP inhibitors might increase the risk of AD by the inhibition of Aβ clearance, and increase brain bradykinin (BK) and natriuretic peptides (NPs), which augment the pathogenesis of AD. These verdicts come from animal model studies, though they may not be applied to humans. However, clinical studies revealed promising safety findings regarding the use of ARNI. Moreover, NEP inhibition increases various neuroprotective peptides involved in inflammation, glucose homeostasis and nerve conduction. Also, NEP inhibitors may inhibit dipeptidyl peptidase 4 (DPP4) expression, ameliorating insulin and glucagon-like peptide 1 (GLP-1) levels. These findings proposed that NEP inhibitors may have a protective effect against AD development by increasing GLP-1, neuropeptide Y (NPY) and substance P, and deleterious effects by increasing brain BK. Preclinical and clinical studies are recommended in this regard.

PIH1D3-knockout rats exhibit full ciliopathy features and dysfunctional pre-assembly and loading of dynein arms in motile cilia.

Background: Recessive mutation of the X-linked gene, PIH1 domain-containing protein 3 (PIH1D3), causes familial ciliopathy. PIH1D3 deficiency is associated with the defects of dynein arms in cilia, but how PIH1D3 specifically affects the structure and function of dynein arms is not understood yet. To gain insights into the underlying mechanisms of the disease, it is crucial to create a reliable animal model. In humans, rats, and mice, one copy of the PIH1D3 gene is located on the X chromosome. Interestingly, mice have an additional, intronless copy of the Pih1d3 gene on chromosome 1. To develop an accurate disease model, it is best to manipulate the X-linked PIH1D3 gene, which contains essential regulatory sequences within the introns for precise gene expression. This study aimed to develop a tailored rat model for PIH1D3-associated ciliopathy with the ultimate goal of uncovering the intricate molecular mechanisms responsible for ciliary defects in the disease. Methods: Novel Pih1d3-knockout (KO) rats were created by using TALEN-mediated non-homologous DNA recombination within fertilized rat eggs and, subsequently, underwent a comprehensive characterization through a battery of behavioral and pathological assays. A series of biochemical and histological analyses were conducted to elucidate the identity of protein partners that interact with PIH1D3, thus shedding light on the intricate molecular mechanisms involved in this context. Results: PIH1D3-KO rats reproduced the cardinal features of ciliopathy including situs inversus, defects in spermatocyte survival and mucociliary clearance, and perinatal hydrocephalus. We revealed the novel function of PIH1D3 in cerebrospinal fluid circulation and elucidated the mechanism by which PIH1D3 deficiency caused communicating hydrocephalus. PIH1D3 interacted with the proteins required for the pre-assembly and uploading of outer (ODA) and inner dynein arms (IDA), regulating the integrity of dynein arm structure and function in cilia. Conclusion: PIH1D3-KO rats faithfully reproduced the cardinal features of ciliopathy associated with PIH1D3 deficiency. PIH1D3 interacted with the proteins responsible for the pre-assembly and uploading of dynein arms in cilia, and its deficiency led to dysfunctional cilia and, thus, to ciliopathy by affecting the pre-assembly and uploading of dynein arms. The resultant rat model is a valuable tool for the mechanistic study of PIH1D3-caused diseases.

OR24-03 Triglyceride Clearance In Hypertriglyceridemic Pancreatitis: Time-course And Implications For Management

Abstract Disclosure: S.K. Majumdar: None. Introduction: Uncertainty exists for how to optimally manage severely elevated triglyceride (Tg) levels in patients with hypertriglyceridemic (HTg) pancreatitis. Standard recommendations include NPO (nil per os) status and intravenous (iv) insulin for most patients, yet information is lacking in regards to the natural time-course of Tg lowering, the degree of benefit insulin provides and for whom it may be indicated, and for the Tg level at which transition to feeding would be appropriate. Underlying Questions: (1) What is the natural time-course of triglyceride (Tg) lowering when nutritional intake is held and (2) does it differ according to etiology of hypertriglyceridemia? (3) What is the role of intravenous insulin in acute Tg lowering, and (4) at what threshold of Tg can nutritional intake safely resume? Methods: A retrospective study of patients hospitalized from October 2013 through December of 2018 with a diagnosis of pancreatitis associated with hypertriglyceridemia Tg ≥ 5.65 mM (500 mg/dL), in absence of other causes, was performed by medical record review. The time-course of Tg lowering was assessed for differences in relation to initial Tg values, use of iv insulin, ethanol vs. non ethanol associated causes, and time to Tg values of < 5.65 mM (500 mg/dL) vs < 11.29 (1000 mg/dL). Results: Sixty-six cases were identified and 45 had multiple measurements for time-course evaluation. Those with initial Tg values < 45.16 mM (4000 mg/dL) achieved Tg levels < 11.29 mM in < 3 days, while 18.8% with higher values took 5-9 days. Insulin therapy was associated with a longer duration, and ethanol with a shorter duration, of hypertriglyceridemia. Tg clearance in ethanol associated hypertriglyceridemia appeared independent of insulin treatment. Time to Tg < 5.65 mM vs < 11.29 mM was significantly longer when initial Tg levels were > 22.58 mM (2000 mg/dL). Conclusion: An arbitrary threshold of 45.16 mM (4000 mg/dL) for initial Tg’s in HTg pancreatitis appears to separate those likely to achieve Tg’s < 11.29 mM in < 3 vs. > 3 days, independent of cause or treatment in absence of known genetic defects in Tg clearance. Insulin therapy remains appropriate for hyperglycemic patients but appears unnecessary for isolated ethanol associated hypertriglyceridemia. A threshold Tg of <11.29 mM appears more practical than <5.65 mM for resuming nutritional intake. A randomized trial is necessary to confirm these findings. Presentation: Saturday, June 17, 2023

An unexpected role of neutrophils in clearing apoptotic hepatocytes in vivo.

Billions of apoptotic cells are removed daily in a human adult by professional phagocytes (e.g. macrophages) and neighboring nonprofessional phagocytes (e.g. stromal cells). Despite being a type of professional phagocyte, neutrophils are thought to be excluded from apoptotic sites to avoid tissue inflammation. Here, we report a fundamental and unexpected role of neutrophils as the predominant phagocyte responsible for the clearance of apoptotic hepatic cells in the steady state. In contrast to the engulfment of dead cells by macrophages, neutrophils burrowed directly into apoptotic hepatocytes, a process we term perforocytosis, and ingested the effete cells from the inside. The depletion of neutrophils caused defective removal of apoptotic bodies, induced tissue injury in the mouse liver, and led to the generation of autoantibodies. Human autoimmune liver disease showed similar defects in the neutrophil-mediated clearance of apoptotic hepatic cells. Hence, neutrophils possess a specialized immunologically silent mechanism for the clearance of apoptotic hepatocytes through perforocytosis, and defects in this key housekeeping function of neutrophils contribute to the genesis of autoimmune liver disease.

An unexpected role of neutrophils in clearing apoptotic hepatocytes in vivo

Billions of apoptotic cells are removed daily in a human adult by professional phagocytes (e.g. macrophages) and neighboring nonprofessional phagocytes (e.g. stromal cells). Despite being a type of professional phagocyte, neutrophils are thought to be excluded from apoptotic sites to avoid tissue inflammation. Here, we report a fundamental and unexpected role of neutrophils as the predominant phagocyte responsible for the clearance of apoptotic hepatic cells in the steady state. In contrast to the engulfment of dead cells by macrophages, neutrophils burrowed directly into apoptotic hepatocytes, a process we term perforocytosis, and ingested the effete cells from the inside. The depletion of neutrophils caused defective removal of apoptotic bodies, induced tissue injury in the mouse liver, and led to the generation of autoantibodies. Human autoimmune liver disease showed similar defects in the neutrophil-mediated clearance of apoptotic hepatic cells. Hence, neutrophils possess a specialized immunologically silent mechanism for the clearance of apoptotic hepatocytes through perforocytosis, and defects in this key housekeeping function of neutrophils contribute to the genesis of autoimmune liver disease.

Pathophysiological features of chronic IgE-mediated rhinosinusitis of bacterial etiology

Chronic rhinosinusitis (CRS) is a disease caused by inflammation of the paranasal sinuses and its mucous membrane lasting for more than 4 weeks continuously. The aim of our study was to examine the main pathophysiological features of chronic IgE-mediated rhinosinusitis of bacterial etiology according to publications in the Russian Federation and in the world. A search was made through English- and Russian-language literature sources using the following databases: PubMed, MedLine, Web of Science, Russian Science Citation Index, Springer, Scopus, Scientific Research, Google Scholar, Crossref, eLibrary. The epidemiological features of CRS in the Russian Federation, bacterial pathogens and pathophysiological characteristics of CRS were analyzed. A 2-fold increase in the prevalence of CRS was registered over the past 20 years. Prevalence of the disease increases at longer age ranges. Chronic rhinosinusitis ranks first among all chronic diseases in the field of otorhinolaryngology. Allergic rhinitis, asthma, bronchiectasia, immunodeficiencies, cystic fibrosis, primary ciliary dyskinesia and autoimmune diseases are associated with CRS. The most common bacterial pathogens are S. aureus, Staphylococcus epidermidis and Propionibacterium acnes, Prevotella, Streptococcus and Veillonella, and some Gram-negative bacteria, e.g., Pseudomonas aeruginosa (P. aeruginosa), Proteus mirabilis and Klebsiella pneumoniae. Staphylococcus aureus (S. aureus) is involved in pathogenesis of nasal polyps. The colonizing bacteria may contribute to pathogenesis of CRS through the formation of biofilms. Alterations in the sino-nasal microbiome may also contribute to the development of CRS. An association of the CRS and CFTR gene mutations plays a significant role in the pathogenesis of chronic rhinosinusitis. An “immune barrier hypothesis” has been proposed as potential mechanism of CRS. Reduced expression of SPINK5, impaired STAT3 signaling, and T2R38 bitter taste receptor polymorphism have been identified in the pathogenesis of CRS. The T2R38 gene stimulates epithelial cells to produce nitrous oxide with a bactericidal effect, promotes mucociliary elimination of pathogens and prevention of upper respiratory tract infections, the polymorphism of this gene predisposes patients to gram-negative infectious diseases, and therefore is a risk factor for the development of CRS. In addition, antibody deficiency is the most common primary immunodeficiency associated with CRS.Hence, the pathogenesis of chronic IgE-mediated rhinosinusitis of bacterial etiology is associated with defects in innate immunity and mucociliary clearance, influence of the sinonasal microbiome, allergies, and genetic factors. A comprehensive assessment of these factors is necessary for the development of new preventive and therapeutic options for the correction of CRS.

Whole Blood and Plasma-Based Lipid Profiling Reveals Distinctive Metabolic Changes in Systemic Lupus Erythematosus and Systemic Sclerosis.

Autoimmune diseases (AID), such as systemic lupus erythematosus (SLE) and systemic sclerosis (SS), are complex conditions involving immune system dysregulation. Diagnosis is challenging, requiring biomarkers for improved detection and prediction of relapses. Lipids have emerged as potential biomarkers due to their role in inflammation and immune response. This study uses an untargeted C18 RP-LC-MS lipidomics approach to comprehensively assess changes in lipid profiles in patients with SLE and SS. By analyzing whole blood and plasma, the study aims to simplify the lipidomic analysis, explore cellular-level lipids, and compare lipid signatures of SLE and SS with healthy controls. Our findings showed variations in the lipid profile of SLE and SS. Sphingomyelin and ceramide molecular species showed significant increases in plasma samples from SS patients, suggesting an atherosclerotic profile and potentially serving as lipid biomarkers. Phosphatidylserine species in whole blood from SLE patients exhibited elevated levels supporting previously reported dysregulated processes of cell death and defective clearance of dying cells in this AID. Moreover, decreased phospholipids bearing PUFA were observed, potentially attributed to the degradation of these species through lipid peroxidation processes. Further studies are needed to better understand the role of lipids in the pathological mechanisms underlying SLE and SS.

Astaxanthin enhances autophagy, amyloid beta clearance and exerts anti-inflammatory effects in in vitro models of Alzheimer’s disease-related blood brain barrier dysfunction and inflammation

Defective degradation and clearance of amyloid-β as well as inflammation per se are crucial players in the pathology of Alzheimer’s disease (AD). A defective transport across the blood–brain barrier is causative for amyloid-β (Aβ) accumulation in the brain, provoking amyloid plaque formation. Using primary porcine brain capillary endothelial cells and murine organotypic hippocampal slice cultures as in vitro models of AD, we investigated the effects of the antioxidant astaxanthin (ASX) on Aβ clearance and neuroinflammation. We report that ASX enhanced the clearance of misfolded proteins in primary porcine brain capillary endothelial cells by inducing autophagy and altered the Aβ processing pathway. We observed a reduction in the expression levels of intracellular and secreted amyloid precursor protein/Aβ accompanied by an increase in ABC transporters ABCA1, ABCG1 as well as low density lipoprotein receptor-related protein 1 mRNA levels. Furthermore, ASX treatment increased autophagic flux as evidenced by increased lipidation of LC3B-II as well as reduced protein expression of phosphorylated S6 ribosomal protein and mTOR. In LPS-stimulated brain slices, ASX exerted anti-inflammatory effects by reducing the secretion of inflammatory cytokines while shifting microglia polarization from M1 to M2 phenotype. Our data suggest ASX as potential therapeutic compound ameliorating AD-related blood brain barrier impairment and inflammation.

Ferroptosis of CD163+ tissue-infiltrating macrophages and CD10+ PC+ epithelial cells in lupus nephritis.

Dysregulation of cell death and defective clearance of dying cells are closely related to the pathogenesis of lupus nephritis (LN). However, the contribution of a recently discovered form of programmed cell death (PCD) called ferroptosis to LN has not been explored in detail. The purpose of this study was to investigate the role of ferroptosis and its associated metabolic pathways in the pathogenesis of LN. The composite gene expression scores were calculated by averaging the z-scored transformed log2 expressed genes within each form of PCD and pathway. Immunohistochemistry and immunofluorescence assays were used to verify the bioinformatics results. We determined that ferroptosis is prominently and specifically elevated in the glomerular compartment of LN patients compared to other forms of PCD and kidney disease. This finding was then verified by immunohistochemical staining of 4-HNE (a key indicator for ferroptosis) expression in our own cohort (P < 0.0001). Intercorrelation networks were observed between 4-HNE and blood urea nitrogen, SLE disease activity index, serum creatinine, and complement 4, and negatively correlated with glomerular filtration rate in our own LN cohort (P < 0.05). Furthermore, enhanced iron metabolism and reduced fatty acid synthesis may be the most important factors for ferroptosis within the glomerulus. Through analysis of a single cell sequencing dataset and verification of immunohistochemical and immunofluorescence staining, aberrantly activated lipid peroxidation in CD163+ macrophages and CD10+ PC+ (pyruvate carboxylase) epithelial cells indicated that they may be undergoing ferroptosis in the glomerular compartment. Two dysregulated genes, CD163 and PC, were identified and verified that were significantly associated with lipid peroxidation. Targeting ferroptosis in CD163+ macrophages and CD10+ PC+ epithelial cells may provide novel therapeutic approaches in LN.

Comparative single-cell profiling reveals distinct cardiac resident macrophages essential for zebrafish heart regeneration.

Zebrafish exhibit a robust ability to regenerate their hearts following injury, and the immune system plays a key role in this process. We previously showed that delaying macrophage recruitment by clodronate liposome (-1d_CL, macrophage-delayed model) impairs neutrophil resolution and heart regeneration, even when the infiltrating macrophage number was restored within the first week post injury (Lai et al., 2017). It is thus intriguing to learn the regenerative macrophage property by comparing these late macrophages vs. control macrophages during cardiac repair. Here, we further investigate the mechanistic insights of heart regeneration by comparing the non-regenerative macrophage-delayed model with regenerative controls. Temporal RNAseq analyses revealed that -1d_CL treatment led to disrupted inflammatory resolution, reactive oxygen species homeostasis, and energy metabolism during cardiac repair. Comparative single-cell RNAseq profiling of inflammatory cells from regenerative vs. non-regenerative hearts further identified heterogeneous macrophages and neutrophils, showing alternative activation and cellular crosstalk leading to neutrophil retention and chronic inflammation. Among macrophages, two residential subpopulations (hbaa+ Mac and timp4.3+ Mac 3) were enriched only in regenerative hearts and barely recovered after +1d_CL treatment. To deplete the resident macrophage without delaying the circulating macrophage recruitment, we established the resident macrophage-deficient model by administrating CL earlier at 8 d (-8d_CL) before cryoinjury. Strikingly, resident macrophage-deficient zebrafish still exhibited defects in revascularization, cardiomyocyte survival, debris clearance, and extracellular matrix remodeling/scar resolution without functional compensation from the circulating/monocyte-derived macrophages. Our results characterized the diverse function and interaction between inflammatory cells and identified unique resident macrophages prerequisite for zebrafish heart regeneration.

Dysfunctional mucociliary clearance in asthma and airway remodeling – New insights into an old topic

Bronchial asthma is a heterogeneous respiratory condition characterized by chronic airway inflammation, airway hyperresponsiveness and airway structural changes (known as remodeling). The clinical symptoms can be evoked by (non)specific triggers, and their intensity varies over time. In the past, treatment was mainly focusing on symptoms’ alleviation; in contrast modern treatment strategies target the underlying inflammation, even during asymptomatic periods. Components of airway remodeling include epithelial cell shedding and dysfunction, goblet cell hyperplasia, subepithelial matrix protein deposition, fibrosis, neoangiogenesis, airway smooth muscle cell hypertrophy and hyperplasia. Among the other important, and frequently forgotten aspects of airway remodeling, also loss of epithelial barrier integrity, immune defects in anti-infectious defence and mucociliary clearance (MCC) dysfunction should be pointed out. Mucociliary clearance represents one of the most important defence airway mechanisms. Several studies in asthmatics demonstrated various dysfunctions in MCC – e.g., ciliated cells displaying intracellular disorientation, abnormal cilia and cytoplasmic blebs. Moreover, excessive mucus production and persistent cough are one of the well-recognized features of severe asthma and are also associated with defects in MCC. Damaged airway epithelium and impaired function of the ciliary cells leads to MCC dysfunction resulting in higher susceptibility to infection and inflammation. Therefore, new strategies aimed on restoring the remodeling changes and MCC dysfunction could present a new therapeutic approach for the management of asthma and other chronic respiratory diseases.