Involvement of ADAM10 in acrolein-induced astrocytic inflammation

Neuroprotection by acrolein sequestration through exogenously applied scavengers and endogenous enzymatic enabling strategies in mouse EAE model

We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in MS pathology. In this study, we found that the acrolein scavenger hydralazine (HZ), when applied from the day of induction, can suppress acrolein and alleviate motor and sensory deficits in a mouse experimental autoimmune encephalomyelitis (EAE) model. Furthermore, we also demonstrated that HZ can alleviate motor deficits when applied after the emergence of MS symptoms, making potential anti-acrolein treatment a more clinically relevant strategy. In addition, HZ can reduce both acrolein and MPO, suggesting a connection between acrolein and inflammation. We also found that in addition to HZ, phenelzine (PZ), a structurally distinct acrolein scavenger, can mitigate motor deficits in EAE when applied from the day of induction. This suggests that the likely chief factor of neuroprotection offered by these two structurally distinct acrolein scavengers in EAE is their common feature of acrolein neutralization. Finally, up-and-down regulation of the function of aldehyde dehydrogenase 2 (ALDH2) in EAE mice using either a pharmacological or genetic strategy led to correspondent motor and sensory changes. This data indicates a potential key role of ALDH2 in influencing acrolein levels, oxidative stress, inflammation, and behavior in EAE. These findings further consolidate the critical role of aldehydes in the pathology of EAE and its mechanisms of regulation. This is expected to reinforce and expand the possible therapeutic targets of anti-aldehyde treatment to achieve neuroprotection through both endogenous and exogenous manners.

ADAM metallopeptidase domain 10 knockdown enables podocytes to resist high glucose stimulation by inhibiting pyroptosis via MAPK pathway

Diabetic nephropathy (DN) is a common severe microvascular complication of diabetes mellitus, and podocyte damage occurs in the early stages of DN. The urine of patients with various types of glomerular disease presents increased levels of ADAM metallopeptidase domain 10 (ADAM10). The present study aimed to explore the role of ADAM10 in podocyte damage. Therefore, the expression of ADAM10 in high glucose (HG)-stimulated podocytes was measured by reverse transcription-qPCR and western blot. Moreover, the effects of ADAM10 knockdown on podocyte inflammation and apoptosis were determined by ELISA, western blot and TUNEL assay after confirming the efficacy of cell transfection. Subsequently, the effects of ADAM10 knockdown on the MAPK pathway and pyroptosis were assessed by western blot. Through performing the aforementioned experiments, the role of the MAPK pathway in the regulatory effects of ADAM10 was then investigated by pretreating podocytes with pathway agonists. ADAM10 expression was upregulated in HG-stimulated podocytes, while ADAM10 knockdown suppressed inflammation, apoptosis and pyroptosis of HG-stimulated podocytes and inhibited the activation of the MAPK signaling pathway. However, when podocytes were pretreated with pathway agonists (LM22B-10 or p79350), the aforementioned effects of ADAM10 knockdown were suppressed. The present study demonstrated that ADAM10 knockdown suppressed the inflammation, apoptosis and pyroptosis of HG-stimulated podocytes by blocking the MAPK signaling pathway.

Abacavir causes leukocyte/platelet crosstalk by activating neutrophil P2X7 receptors thus releasing soluble lectin-like oxidized low-density lipoprotein receptor-1

BACKGROUND AND PURPOSE

Abacavir, an antiretroviral drug used in HIV therapy associated with myocardial infarction, promotes thrombosis through P2X7 receptors. The role of platelets as pro-thrombotic cells is acknowledged whereas that of neutrophils-due to their secretory capacity-is gaining recognition. This study analyses the role of neutrophils-specifically the secretome of abacavir-treated neutrophils (SN_ABC )-in platelet activation that precedes thrombosis.

EXPERIMENTAL APPROACH

Effects of abacavir or SN_ABC on platelet activation and platelet-leukocyte interactions and expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) were analysed by flow cytometry. The secretome was analysed by proteomics. The role of leukocytes in the actions of abacavir was evaluated in a mouse model of thrombosis.

KEY RESULTS

Abacavir induced platelet-leukocyte interactions, not directly via effects of abacavir on platelets, but via activation of neutrophils, which triggered interactions between platelet P-selectin and neutrophil P-selectin glycoprotein ligand-1 (PSGL-1). SN_ABC stimulated platelet activation and platelet-leukocyte interactions through a process that was dependent on LOX-1, neutrophil P2X7 and platelet P2Y1, P2Y12 and P2X1 receptors. Abacavir induced the expression of LOX-1 on neutrophils and of the soluble form of LOX-1 (sLOX-1) in SN_ABC . Neutrophils, LOX-1, P2X7, P2Y1, P2Y12 and P2X1 receptors were required for the pro-thrombotic actions of abacavir in vivo.

CONCLUSION AND IMPLICATIONS

Neutrophils are target cells in abacavir-induced thrombosis. Abacavir released sLOX-1 from neutrophils via activation of their P2X7 receptors, which in turn activated platelets. Hence, sLOX-1 could be the missing link in the cardiovascular risk associated with abacavir.

The role of ADAM10 in astrocytes: Implications for Alzheimer’s disease

Much of the early research into AD relies on a neuron-centric view of the brain, however, evidence of multiple altered cellular interactions between glial cells and the vasculature early in AD has been demonstrated. As such, alterations in astrocyte function are widely recognized a contributing factor in the pathogenesis of AD. The processes by which astrocytes may be involved in AD make them an interesting target for therapeutic intervention, but in order for this to be most effective, there is a need for the specific mechanisms involving astrocyte dysfunction to be investigated. “α disintegrin and metalloproteinase” 10 (ADAM10) is capable of proteolytic cleavage of the amyloid precursor protein which prevents amyloid-β generation. As such ADAM10 has been identified as an interesting enzyme in AD pathology. ADAM10 is also known to play a role in a significant number of cellular processes, most notable in notch signaling and in inflammatory processes. There is a growing research base for the involvement of ADAM10 in regulating astrocytic function, primarily from an immune perspective. This review aims to bring together available evidence for ADAM10 activity in astrocytes, and how this relates to AD pathology.

The Role of Acrolein in Neurodegenerative Diseases and Its Protective Strategy

Neurodegenerative diseases are characterized by a massive loss of specific neurons, which can be fatal. Acrolein, an omnipresent environmental pollutant, is classified as a priority control contaminant by the EPA. Evidence suggests that acrolein is a highly active unsaturated aldehyde related to many nervous system diseases. Therefore, numerous studies have been conducted to identify the function of acrolein in neurodegenerative diseases, such as ischemic stroke, AD, PD, and MS, and its exact regulatory mechanism. Acrolein is involved in neurodegenerative diseases mainly by elevating oxidative stress, polyamine metabolism, neuronal damage, and plasma ACR-PC levels, and decreasing urinary 3-HPMA and plasma GSH levels. At present, the protective mechanism of acrolein mainly focused on the use of antioxidant compounds. This review aimed to clarify the role of acrolein in the pathogenesis of four neurodegenerative diseases (ischemic stroke, AD, PD and MS), as well as protection strategies, and to propose future trends in the inhibition of acrolein toxicity through optimization of food thermal processing and exploration of natural products.

Apigenin and apigenin-7, 4'-O-dioctanoate protect against acrolein-aggravated inflammation via inhibiting the activation of NLRP3 inflammasome and HMGB1/MYD88/NF-κB signaling pathway in Human umbilical vein endothelial cells (HUVEC)

Exposure to acrolein, one environmental and dietary pollutant, has been shown to cause inflammation. Here, we reported for the first time that acrolein aggravated lipopolysaccharide (LPS)-induced inflammation in Human umbilical vein endothelial cells (HUVEC) as evidenced by the further increased mRNA expression of three pro-inflammatory cytokines, including interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor-alpha (TNF-α). Acrolein also further increased the generation of reactive oxygen species (ROS) and decreased the activity of glutathione peroxidase (GSH-Px) in LPS-pretreated HUVEC. Moreover, acrolein treatment further increased the nucleotide oligomerization domain-like receptor protein 3 (NLRP3) and apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC) expression, caspase-1 cleavage, and downstream matures interleukin 18 (IL-18) and IL-1β level in LPS-pretreated HUVEC. Acrolein treatment also further increased the expressions of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88), and phospho-NF-κB P65 (P-P65) in the LPS pre-treated HUVEC. Thus, acrolein aggravated LPS-induced HUVEC inflammation through induction of oxidative stress, and activation of NLRP3 inflammasome and HMGB1/MYD88/NF-κB signaling pathway. In addition, apigenin and apigenin-7, 4'-O-dioctanoate attenuated acrolein-aggravated inflammation by targeting the above signaling pathways. Our findings could help to develop potential therapeutic strategies against acrolein-enhanced inflammation.

Glial Cells and Brain Diseases: Inflammasomes as Relevant Pathological Entities

Inflammation mediated by the innate immune system is a physiopathological response to diverse detrimental circumstances such as microbe infections or tissular damage. The molecular events that underlie this response involve the assembly of multiprotein complexes known as inflammasomes. These assemblages are essentially formed by a stressor-sensing protein, an adapter protein and a non-apoptotic caspase (1 or 11). The coordinated aggregation of these components mediates the processing and release of pro-inflammatory interleukins (IL-β and IL-18) and cellular death by pyroptosis induction. The inflammatory response is essential for the defense of the organism; for example, it triggers tissue repair and the destruction of pathogen microbe infections. However, when inflammation is activated chronically, it promotes diverse pathologies in the lung, liver, brain and other organs. The nervous system is one of the main tissues where the inflammatory process has been characterized, and its implications in health and disease are starting to be understood. Thus, the regulation of inflammasomes in specific cellular types of the central nervous system needs to be thoroughly understood to innovate treatments for diverse pathologies. In this review, the presence and participation of inflammasomes in pathological conditions in different types of glial cells will be discussed.

Amino Acid Solute Carrier Transporters in Inflammation and Autoimmunity

The past decade exposed the importance of many homeostasis and metabolism related proteins in autoimmunity disease and inflammation. Solute carriers (SLCs) are a group of membrane channels that can transport amino acids, the building blocks of proteins, nutrients, and neurotransmitters. This review summarizes the role of SLCs amino acid transporters in inflammation and autoimmunity disease. In detail, the importance of Glutamate transporters SLC1A1, SLC1A2, and SLC1A3, mainly expressed in the brain where they help prevent glutamate excitotoxicity, is discussed in the context of central nervous system disorders such as multiple sclerosis. Similarly, the cationic amino acid transporter SLC7A1 (CAT1), which is an important arginine transporter for T cells, and SLC7A2 (CAT2), essential for innate immunity. SLC3 family proteins, which bind with light chains from the SLC7 family (SLC7A5, SLC7A7 and SLC7A11) to form heteromeric amino acid transporters, are also explored to describe their roles in T cells, NK cells, macrophages and tumor immunotherapies. Altogether, the link between SLC amino acid transporters with inflammation and autoimmunity may contribute to a better understanding of underlying mechanism of disease and provide novel potential therapeutic avenues. Significance Statement SIGNIFICANCE STATEMENT In this review, we summarize the link between SLC amino acid transporters and inflammation and immune responses, specially SLC1 family members and SLC7 members. Studying the link may contribute to a better understanding of related diseases and provide potential therapeutic targets and useful to the researchers who have interest in the involvement of amino acids in immunity.

Urinary acrolein metabolites, systemic inflammation, and blood lipids: Results from the National Health and Nutrition Examination Survey

Exposure to acrolein was reported to be related with adverse health effects. However, the associations between acrolein exposure and blood lipids remain largely unknown. We assessed the associations of urinary acrolein metabolites with blood lipids using data from the National Health and Nutrition Examination Survey (NHANES) and further investigated the existence of mediation by systemic inflammation in the associations. Urinary acrolein metabolites, N-acetyl-S-(carboxyethyl)-l-cysteine (CEMA) and N-acetyl-S-(3-hydroxypropyl)-l-cysteine (3-HPMA), blood lipids, and serum high sensitivity C-reactive protein (hs-CRP) were measured in the NHANES. The associations of urinary acrolein metabolites with blood lipids and dyslipidemia and hs-CRP were estimated by multiple linear and logistic regression models. Mediation analysis was conducted to evaluate the mediating effects of hs-CRP on the associations between urinary acrolein metabolites and blood lipids. We found urinary CEMA+3-HPMA (∑acrolein) was significantly associated with higher levels of serum triglycerides (TG), hs-CRP, and lower levels of high-density lipoprotein cholesterol (HDL-C). Each 1-unit increment in ln-transformed level of ∑acrolein was associated with a 0.06 mmol/L increment in TG and 0.02 mmol/L decrement in HDL-C (all P <0.05). A positive dose-response relationship was observed between urinary ∑acrolein and dyslipidemia risk. In addition, hs-CRP significantly mediated the associations of urinary ∑acrolein with serum TG and HDL-C, with mediated proportions of 22.12% and 41.41%, respectively. In conclusion, acrolein exposure is associated with the levels of serum TG, HDL-C, and hs-CRP. Hs-CRP may mediate acrolein-associated alterations of blood lipids. Our results indicated that decreased exposure to acrolein may reduce systemic inflammation and dyslipidemia risk.

Inhibition of ADAM10 ameliorates doxorubicin-induced cardiac remodeling by suppressing N-cadherin cleavage

The present research was designed to examine the effects of disintegrin metalloproteinases 10 (ADAM10) on the doxorubicin (DOX)-induced dilated cardiomyopathy (DCM) and the mechanisms involved, with a focus on ADAM10-dependent cleavage of N-cadherin. The present study constructed recombinant lentiviral vectors expressing short hairpin RNA (shRNA) targeting the ADAM10 gene. H9C2 cells were treated with the recombinant lentivirus or GI254023 (an ADAM10 inhibitor). The expression level of N-cadherin and its C-terminal fragment1 (CTF1) was tested by western blotting and flow cytometry. The adhesion ability was analyzed using a plate adhesion model. Cardiac function and morphology were assessed in control and lentivirus-transfected rats with or without DOX treatment. The inhibition of ADAM10 activity significantly increased the expression of full-length N-cadherin on the cellular surface and reduced CTF1 generation in vivo and in vitro. The adhesion ability was also increased in ADAM10-knockdown H9C2 cells. Furthermore, DOX-induced myocardial dysfunction was ameliorated in rats transfected with ADAM10-shRNA lentivirus. These findings demonstrated that ADAM10 specifically cleaves N-cadherin in cardiomyocytes. ADAM10-induced N-cadherin cleavage results in changes in the adhesive behavior of cells. Therefore, ADAM10 may serve as a therapeutic target to reverse cardiac remodeling in DCM.

Neuroprotective effect of selumetinib on acrolein-induced neurotoxicity

Abnormal accumulation of acrolein, an α, β unsaturated aldehyde has been reported as one pathological cause of the CNS neurodegenerative diseases. In the present study, the neuroprotective effect of selumetinib (a MEK-ERK inhibitor) on acrolein-induced neurotoxicity was investigated in vitro using primary cultured cortical neurons. Incubation of acrolein consistently increased phosphorylated ERK levels. Co-treatment of selumetinib blocked acrolein-induced ERK phosphorylation. Furthermore, selumetinib reduced acrolein-induced increases in heme oxygenase-1 (a redox-regulated chaperone protein) and its transcriptional factor, Nrf-2 as well as FDP-lysine (acrolein-lysine adducts) and α-synuclein aggregation (a pathological biomarker of neurodegeneration). Morphologically, selumetinib attenuated acrolein-induced damage in neurite outgrowth, including neuritic beading and neurite discontinuation. Moreover, selumetinib prevented acrolein-induced programmed cell death via decreasing active caspase 3 (a hallmark of apoptosis) as well as RIP (receptor-interacting protein) 1 and RIP3 (biomarkers for necroptosis). In conclusion, our study showed that selumetinib inhibited acrolein-activated Nrf-2-HO-1 pathway, acrolein-induced protein conjugation and aggregation as well as damage in neurite outgrowth and cell death, suggesting that selumetinib, a MEK-ERK inhibitor, may be a potential neuroprotective agent against acrolein-induced neurotoxicity in the CNS neurodegenerative diseases.

Protective effect of lutein against acrolein-induced ototoxicity in rats

BACKGROUND

Acrolein is a reactive aldehyde that forms during burning of wood and other fuels. It is also a product of lipid peroxidation (LPO) reactions and is present in cigarette smoke. Acrolein is known to cause oxidative stress and inflammatory nerve tissue damage. Lutein is a tetraterpenoid molecule with antioxidant and anti-inflammatory properties. There appear to be no studies on the effect of lutein on vestibulocochlear nerve damage induced by acrolein. The aim of this study was to investigate the effect of lutein on vestibulocochlear nerve damage induced by acrolein in rats using biochemical and histopathological methods.

METHODS

The rats were divided into three groups (n = 6, for each group) a healthy control group (HG), an acrolein (ACR) group and a lutein and acrolein (LACR) group. In the LACR group, lutein was administered (1 mg/kg) via oral gavage. The ACR and HG groups received saline via oral gavage. Then, 1 h after the administration of lutein and saline, the LACR and ACR groups were treated with 3 mg/kg of acrolein via oral gavage. This procedure was repeated once a day for 30 days.

RESULTS

The results of biochemical experiments showed that in the vestibulocochlear nerve tissues of the animals treated with acrolein, the levels of malondialdehyde, total oxidants, nuclear factor kappa b, tumor necrosis factor alpha and interleukin 1 beta significantly increased, whereas the levels of total glutathione and total antioxidants decreased as compared to those in the HG and LACR groups. In addition, severe histopathological damage was observed in vestibulocochlear nerve tissue of the acrolein group, whereas this damage was alleviated in the lutein group.

CONCLUSION

Lutein protected vestibulocochlear nerve tissue from acrolein-associated oxidative and proinflammatory damage. This suggests that lutein might be useful in preventing or treating acrolein-induced ototoxicity.

Elevated Cerebrospinal Fluid and Plasma N-Cadherin in Alzheimer Disease

N-cadherin is a synaptic adhesion molecule stabilizing synaptic cell structure and function. Cleavage of N-cadherin by γ-secretase produces a C-terminal fragment, which is increased in the brains of Alzheimer disease (AD) patients. Here, we investigated the relationship between fluid N-cadherin levels and AD pathology. We first showed that the cleaved levels of N-cadherin were increased in homogenates of postmortem brain from AD patients compared with that in non-AD patients. We found that cleaved N-cadherin levels in the cerebrospinal fluid were increased in AD dementia compared with that in healthy control. ELISA results revealed that plasma levels of N-cadherin in 76 patients with AD were higher than those in 133 healthy control subjects. The N-cadherin levels in the brains of an AD mouse model, APP Swedish/PS1delE9 Tg (APP Tg) were reduced compared with that in control. The N-terminal fragment of N-cadherin produced by cleavage at a plasma membrane was detected extravascularly, accumulated in senile plaques in the cortex of an APP Tg mouse. In addition, N-cadherin plasma levels were increased in APP Tg mice. Collectively, our study suggests that alteration of N-cadherin levels might be associated with AD pathology.

Role of Inflammasomes in HIV-1 and Drug Abuse Mediated Neuroinflammaging

Despite the effectiveness of combined antiretroviral therapy (cART) in suppressing virus replication, chronic inflammation remains one of the cardinal features intersecting HIV-1, cART, drug abuse, and likely contributes to the accelerated neurocognitive decline and aging in people living with HIV-1 (PLWH) that abuse drugs. It is also estimated that ~30–60% of PLWH on cART develop cognitive deficits associated with HIV-1-associated neurocognitive disorders (HAND), with symptomatology ranging from asymptomatic to mild, neurocognitive impairments. Adding further complexity to HAND is the comorbidity of drug abuse in PLWH involving activated immune responses and the release of neurotoxins, which, in turn, mediate neuroinflammation. Premature or accelerated aging is another feature of drug abusing PLWH on cART regimes. Emerging studies implicate the role of HIV-1/HIV-1 proteins, cART, and abused drugs in altering the inflammasome signaling in the central nervous system (CNS) cells. It is thus likely that exposure of these cells to HIV-1/HIV-1 proteins, cART, and/or abused drugs could have synergistic/additive effects on the activation of inflammasomes, in turn, leading to exacerbated neuroinflammation, ultimately resulting in premature aging referred to as “inflammaging” In this review, we summarize the current knowledge of inflammasome activation, neuroinflammation, and aging in central nervous system (CNS) cells such as microglia, astrocytes, and neurons in the context of HIV-1 and drug abuse.

The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.