Biology subjects

Ahmad, R.

Publications and source records attributed to Ahmad, R..

At least 37 records · Page 2Linked to original sources

bioRxiv2024

Chronic exposure to glucocorticoids amplifies inhibitory neuron cell fate during human neurodevelopment in organoids

Disruptions in the tightly regulated process of human brain development have been linked to increased risk for brain and mental illnesses. While the genetic contribution to these diseases is well established, important environmental factors have been less studied at molecular and cellular levels. In this study, we used single-cell and cell-type-specific techniques to investigate the effect of glucocorticoid (GC) exposure, a mediator of antenatal environmental risk, on gene regulation and lineage specification in unguided human neural organoids. We characterized the transcriptional response to chronic GC exposure during neural differentiation and studied the underlying gene regulatory networks by integrating single-cell transcriptomics-with chromatin accessibility data. We found lasting cell type-specific changes that included autism risk genes and several transcription factors associated with neurodevelopment. Chronic GCs influenced lineage specification primarily by priming the inhibitory neuron lineage through key transcription factors like PBX3. We provide evidence for convergence of genetic and environmental risk factors through a common mechanism of altering lineage specification.

neuroscience↗

bioRxiv2024

Polygenic risk for schizophrenia converges on alternative polyadenylation as molecular mechanism underlying synaptic impairment

Schizophrenia (SCZ) is a genetically heterogenous psychiatric disorder of highly polygenic nature. Correlative evidence from genetic studies indicate that the aggregated effects of distinct genetic risk factor combinations found in each patient converge onto common molecular mechanisms. To prove this on a functional level, we employed a reductionistic cellular model system for polygenic risk by differentiating induced pluripotent stem cells (iPSCs) from 104 individuals with high polygenic risk load and controls into cortical glutamatergic neurons (iNs). Multi-omics profiling identified widespread differences in alternative polyadenylation (APA) in the 3 untranslated region of many synaptic transcripts between iNs from SCZ patients and healthy donors. On the cellular level, 3APA was associated with a reduction in synaptic density of iNs. Importantly, differential APA was largely conserved between postmortem human prefrontal cortex from SCZ patients and healthy donors, and strongly enriched for transcripts related to synapse biology. 3APA was highly correlated with SCZ polygenic risk and affected genes were significantly enriched for SCZ associated common genetic variation. Integrative functional genomic analysis identified the RNA binding protein and SCZ GWAS risk gene PTBP2 as a critical trans-acting factor mediating 3APA of synaptic genes in SCZ subjects. Functional characterization of PTBP2 in iNs confirmed its key role in 3APA of synaptic transcripts and regulation of synapse density. Jointly, our findings show that the aggregated effects of polygenic risk converge on 3APA as one common molecular mechanism that underlies synaptic impairments in SCZ.

neuroscience↗

bioRxiv2023

Long-term hematopoietic stem cells trigger quiescence in Leishmania parasites

Quiescence and posttreatment relapse constitute an important therapeutic constraint across the microbiological spectrum. This study unveils that Leishmania infantum and L. donovani parasites rapidly enter quiescence after an estimated 4-6 divisions in both mouse and human stem cells of the bone marrow but not in macrophages as primary host cells. Quiescent amastigotes display a reduced size and evidence for a rapid evolutionary adaptation response with genetic alterations. We formally demonstrate that acquisition of a quiescent phenotype endows parasites with a capacity to survive antileishmanial treatment. Transition through quiescence also results in an increased cellular infectivity and high transmission capacity through the sand fly vector. Transcriptional profiling of quiescent and non-quiescent metabolic states identified a limited set of 26 upregulated genes that are of particular interest given their predicted involvement as regulators of cell cycle progression and of gene expression at various levels. The differential gene set constitutes a reliable source for the identification of novel markers and potential drivers of quiescence, a metabolic state bestowing parasites the capacity to escape drug treatment.

microbiology↗

bioRxiv2023

Glucose intolerance induces anxiety-like behaviors independent of obesity and insulin resistance in a novel model of nutritional metabolic stress

Type 2 diabetes (T2D) and its comorbidities are a major public health concern. In addition to peripheral tissues, T2D also impacts the central nervous system leading to neurocognitive impairments, including memory deficits, anxiety, and depression. The metabolic determinants of these neurocognitive impairments remain unidentified. Here, we used a novel proprietary high-fat diet, in which glucose intolerance precedes weight gain, to decipher the metabolic determinants of neurocognitive affects. We show that this model exhibits anxiety-like behaviors, without eliciting depression nor recognition memory deficits. Long-term feeding leads to weight gain, brain glucose hypometabolism and impaired recognition memory alongside the early onset anxiety-like behavior. Using an established genetic model of T2D (db/db) and of diet-induced obesity we show that additional insulin resistance and obesity are associated with depressive-like behaviors and recognition memory deficits. Our findings indicate that glucose intolerance alone can elicit anxiety-like behaviors. Through this study we also provide a novel nutritional model to characterize the discrete effects of glucose intolerance on cognition, behavior, and the physiology of metabolic disease.

animal behavior and cognition↗

bioRxiv2023

Inflammation causes insulin resistance via interferon regulatory factor 3 (IRF3)-mediated reduction in FAHFA levels

Obesity-induced inflammation causes metabolic dysfunction, but the mechanisms remain elusive. Here we show that the innate immune transcription factor interferon regulatory factor (IRF3) adversely affects glucose homeostasis through induction of the endogenous FAHFA hydrolase androgen induced gene 1 (AIG1) in adipocytes. Adipocyte-specific knockout of IRF3 protects mice against high-fat diet-induced insulin resistance, whereas overexpression of IRF3 or AIG1 in adipocytes promotes insulin resistance on a high-fat diet. Furthermore, pharmacological inhibition of AIG1 reversed obesity-induced insulin resistance and restored glucose homeostasis in the setting of adipocyte IRF3 overexpression. We, therefore, identify the adipocyte IRF3/AIG1 axis as a crucial link between obesity-induced inflammation and insulin resistance and suggest an approach for limiting the metabolic dysfunction accompanying obesity.

physiology↗

bioRxiv2023

ANGPTL8 R59W variant influences inflammation through modulating NF-κB pathway under TNFα stimulation

BackgroundANGPTL8 is known to regulate lipid metabolism and inflammation. It interacts with ANGPTL3 and ANGPTL4 to regulate LPL activity, and with IKK/{beta} to modulate NF-{kappa}B activity. Further, a SNP leading to ANGPTL8 R59W variant associates with reduced LDL/HDL and increased FBG in Hispanic and Arab individuals, respectively. In this study, we investigate the impact of R59W variant on the inflammatory activity of ANGPTL8. MethodsANGPTL8 R59W variant was genotyped in a discovery cohort of 867 Arab individuals from Kuwait. Plasma levels of ANGPTL8 and inflammatory markers were measured and tested for associations with the genotype; the associations were tested for replication in an independent cohort of 278 Arab individuals. Impact of the ANGPTL8 R59W variant on NF-{kappa}B activity was examined using approaches including overexpression, luciferase assay, and structural modeling of binding dynamics. ResultsThe ANGPTL8 R59W variant was associated with increased circulatory levels of TNF and IL7. NF-{kappa}B activity, as assessed by the increased in the phosphorylation of IKK-/{beta} protein, I{kappa}B, and NF-{kappa}B p-65 in R59W variant compared to wild type, and TNF stimulation further elevated it. This finding was substantiated by increased luciferase activity of NF-{kappa}B p65 with the R59W variant. Modeled structural and binding variation due to R59W change in ANGPTL8 agreed with the observed increase in NF-{kappa}B activity. ConclusionANGPTL8 R59W is associated with increased circulatory TNF, IL7 and NF-{kappa}B p65 activity. Weak transient binding of ANGPTL8 R59W variant explains its regulatory role on the NF-{kappa}B pathway and inflammation.

biochemistry↗

bioRxiv2023

Cell type and condition specific functional annotation of schizophrenia associated non-coding genetic variants

Schizophrenia (SCZ) is a highly polygenic disease and genome wide association studies have identified thousands of genetic variants that are statistically associated with this psychiatric disorder. However, our ability to translate these associations into insights on the disease mechanisms has been challenging since the causal genetic variants, their molecular function and their target genes remain largely unknown. In order to address these questions, we established a functional genomics pipeline in combination with induced pluripotent stem cell technology to functionally characterize ~35,000 non-coding genetic variants associated with schizophrenia along with their target genes. This analysis identified a set of 620 (1.7%) single nucleotide polymorphisms as functional on a molecular level in a highly cell type and condition specific fashion. These results provide a high-resolution map of functional variant-gene combinations and offer comprehensive biological insights into the developmental context and stimulation dependent molecular processes modulated by SCZ associated genetic variation.

genomics↗

bioRxiv2023

A novel, precise and high-throughput technology for viroid detection in cannabis (MFDetectTM)

Hop latent viroid (HLVd) is a severe disease of cannabis, causing substantial economic losses in plant yield and crop value for growers worldwide. The best way to control the disease is early detection to limit the spread of the viroid in grow facilities. This study describes MFDetect as a rapid, highly sensitive, and high-throughput tool for detecting HLVd in the early stages of plant development. Furthermore, we compared MFDetect with RT-PCR in a time course experiment using different plant tissue, leaf, petiole, and roots at different plant development stages to demonstrate both technologies are comparable. Our study found leaf tissue is a suitable plant material for HLVd detection, with the viroid titer increasing in the infected leaf tissue with the age of plants. The study showed that other tissue types, including petiole and roots, were equally sensitive to detection via MFDetect. The assay developed in this research allows the screening of thousands of plants in a week. The assay can be scaled easily to provide the growers with a quick turnaround and cost-effective diagnostic tool for screening many plants and tissue types at different stages of development.

plant biology↗

bioRxiv2023

SERS nanowire chip and machine learning enabled instant identification and classification of clinically relevant wild-type and antibiotic resistant bacteria at species and strain level

The world health organization considers antimicrobial resistance (AMR) to be a critical global public health problem. Conventional culture-based methods that are used to detect and identify bacterial infection are slow. Thus, there is a growing need for the development of robust, cost-effective, and fast diagnostic solutions for the identification of pathogens. Surface-enhanced Raman spectroscopy (SERS) can be used to identify target analytes with sensitivity down to the single-molecule level. Here, we developed a SERS chip by optimizing the entire fabrication pipeline of the metal-assisted chemical etching (MACE) method. The MACE approach offers a large-scale, densely packed silver (Ag) nanostructure on top of silicon nanowires (Si-NWs) with a large aspect ratio that significantly enhances the Raman signal due to localised surface plasmonic enhancement. The optimised SERS chips exhibited sensitivity down to 10-12 M concentration of R6G molecule and detected reproducible Raman spectra of bacteria down to a concentration of 100 colony forming units (CFU)/ml, which is a thousand times lower than the clinical threshold of bacterial infections like UTI (105 CFU/ml). A Siamese neural network model was used to classify SERS Raman spectra from bacteria specimens. The trained model identified 12 different bacterial species, including those which are causative agents for tuberculosis and urinary tract infection (UTI). Next, the SERS chips and another Siamese neural network model were used to differentiate antibiotic-resistant strains from susceptible strains of E. coli. The enhancement offered by SERS chip enabled acquisitions of Raman spectra of bacteria directly in the synthetic urine by spiking the sample with only 103 CFU/ml E. coli. Thus, the present study lays the ground for the identification and quantification of bacteria on SERS chips, thereby offering a potential future use for rapid, reproducible, label-free, and low limit detection of clinical pathogens.

biophysics↗

bioRxiv2022

Gut Microbiome Prediction: From Current Human Evidence to Future Possibilities

The gut microbiome is an indispensable component of the human body. Alteration in the gut microbiota composition leads to various diseases such as obesity, Type 2 Diabetes, Inflammatory Bowel Syndrome, and depression. Microbiome-based precision tests offer a futuristic strategy for wellness and longevity. However, this approach is limited by the lack of definition of a healthy microbiome in different populations and accurate disease prediction. In this study, we aimed to capture the healthy gut microbiome for different populations using the xNARA Gut Profile Test kit and in-house built proprietary algorithm and reference databases. We found that gut microbiome of different populations from India, UAE, and Singapore varied significantly, indicating a distinct geographic gut microbiome signature and Gut Health Index. The gut microbial diversity as measured by the Shannon index revealed UAE had significantly greater alpha diversity than India and Singapore. Prevotella copri (19.27%), Faecalibacterium prausnitzii (4.08%) and Levilactobacillus brevis (4.0%) were the predominant species in the Indian gut. Faecalibacterium prausnitzii (8.54%), Blautia obeum (8.10%), and Phocaeicola vulgatus (4.6%) were primarily present in Singapore participants whereas Prevotella copri (14.92%), Blautia obeum (6.09%) and Roseburia intestinalis (5.81%) were present in UAE participants. Beta diversity indicated the gut microbiota of Indian-origin participants in Singapore and UAE clustered with the indigenous inhabitants of Singapore and UAE. This highlights that geographic location has a profound effect on shaping the gut microbiome architecture than ethnicity. Regional diet and lifestyle could be crucial factors responsible for shaping the gut microbiome. The prediction accuracy of the xNARA Gut algorithm ranged from 66.66-100% when matched with the blood reports. Participants agreed with the xNARA disease risk outcomes for metabolic conditions (60%-100%), gastrofitness (62.5%-100%), mental health (50%-100%), skin conditions (50%-100%) and physical fitness (50%-100%). These observations imply the promising role of gut-based personalized diet and probiotic recommendations for lifestyle and wellness management.

microbiology↗

bioRxiv2022

Highly sensitive quantitative phase microscopy and deep learning complement whole genome sequencing for rapid detection of infection and antimicrobial resistance

The current state-of-the-art infection and antimicrobial resistance diagnostics (AMR) is based mainly on culture-based methods with a detection time of 48-96 hours. Slow diagnoses lead to adverse patient outcomes that directly correlate with the time taken to administer optimal antimicrobials. Mortality risk doubles with a 24-hour delay in providing appropriate antibiotics in cases of bacteremia. Therefore, it is essential to develop novel methods that can promptly and accurately diagnose microbial infections at both species and strain levels in clinical settings. Here, we demonstrate that the complimentary use of label-free optical assay with whole-genome sequencing (WGS) can enable high-speed culture-free diagnosis of infection and AMR. Our assay is based on microscopy methods exploiting label-free, highly sensitive quantitative phase microscopy (QPM) followed by deep convolutional neural networks (DCNNs) based classification. We benchmarked our proposed workflow on 21 clinical isolates from four WHO priority pathogens (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Acinetobacter baumannii) that were antibiotic susceptibility testing (AST) phenotyped, and their antimicrobial resistance (AMR) profile was determined by WGS. The proposed optical assay was in good agreement with the WGS characterization. Highly accurate classification based on the gram staining (100% for gram-negative and 83.4% for gram-positive), species (98.6%), and resistant/susceptible type (96.4%), as well as at the individual strain level (100% accurate in predicting 19 out of the 21 strains). These results demonstrate the potential of the QPM assay as a rapid and first-stage tool for species, presence, and absence of AMR, and strain-level classification, which WGS can follow up for confirmation of the pathogen ID and the characterization of the AMR profile and susceptibility antibiotic. Taken together, all this information is of high clinical importance. Such a workflow could potentially facilitate efficient antimicrobial stewardship and prevent the spread of AMR.

microbiology↗

bioRxiv2022

Multi-excitation Raman Spectroscopy Complements Whole Genome Sequencing for Rapid Detection of Bacterial Infection and Resistance in WHO Priority Pathogens

Current methods for diagnosing acute and complex infections mostly rely on culture-based methods and, for biofilms, fluorescence in-situ hybridization. These techniques are labor-intensive and can take 2-4 days to return a test result, especially considering an extra culturing step required for the antibiotic susceptibility testing (AST). This places a significant burden on healthcare providers, delaying treatment and leading to adverse patient outcomes. Here, we report the complementary use of our newly developed multi-excitation Raman spectroscopy (ME-RS) method with whole-genome sequencing (WGS). Four WHO priority pathogens are AST phenotyped and their antimicrobial resistance (AMR) profile determined by WGS. On application of ME-RS method we find high correlation with the WGS characterization. Highly accurate classification based on the species (98.93%), wild-type/non-wild type (99.45%), and presence or absence of thick peptidoglycan layers in cell walls (100%), as well as at the individual strain level (99.29%). These results clearly demonstrate the potential of ME-RS as a rapid and first-stage tool for species, resistance and strain-level classification which can be followed up by WGS for confirmation. Such a workflow can facilitate efficient antimicrobial stewardship to handle and prevent the spread of AMR.

microbiology↗

bioRxiv2021

A glycerol shunt functions as a glucose excess security valve in pancreatic β-cells

The recently identified glycerol-3-phosphate (Gro3P) phosphatase (G3PP) in mammalian cells, encoded by the PGP gene, was shown to regulate intermediary metabolism by hydrolyzing Gro3P and to control glucose-stimulated insulin secretion (GSIS) in {beta}-cells, in vitro. We now examined in inducible {beta}-cell specific G3PP-KO (BKO) mice, the role of G3PP in the control of insulin secretion in vivo, {beta}-cell function and glucotoxicity. BKO mice, compared to MCre controls, showed increased body weight, adiposity, fed insulinemia, GSIS, reduced plasma triglycerides and mildly altered glucose tolerance. Isolated BKO mouse islets at high (16.7 mM) but not low or intermediate glucose (3-8 mM) showed elevated GSIS, Gro3P, metabolites reflecting {beta}-cell activation, O2 consumption, ATP production and reduced glycerol release. BKO islets chronically exposed to elevated glucose showed increased apoptosis, reduced insulin content and expression of Pdx-1, MafA and Ins-2 genes. As G3PP channels glucose carbons towards glycerol formation and release, the results demonstrate that {beta}-cell are endowed with a "glycerol shunt" acting as a glucose excess security valve. We propose that the glycerol shunt plays a role in glucodetoxification, the prevention of insulin hypersecretion, acts as a defense against excess body weight gain and contributes to {beta}-cell mass preservation in the face of hyperglycemia.

biochemistry↗

bioRxiv2021

Anomalous propulsion regime in axonemal-propelled cargoes

Bio-hybrid micro-swimmers, composed of biological entities integrated with synthetic constructs, actively transport cargo by converting chemical energy into mechanical work in a fluid at low Reynolds number, where viscous drag dominates over inertia. Here, using isolated and demembranated flagella from green algae Chlamydomonas reinhardtii (C. reinhardtii), we build efficient axonemally-driven micro-swimmers that consume ATP to propel micron-sized beads. Depending on the calcium concentration, we observed two main classes of motion: Whereas beads move along curved trajectories at calcium concentrations below 0.03 mM, they are propelled along straight paths when the calcium concentration increases. In this regime, they reached velocities of approximately 20 m/sec, comparable to human sperm velocity in vivo. We relate this transition to the properties of beating axonemes, in particular the reduced static curvature with increasing calcium concentration. To quantify the motion, we used mode decomposition of the flagellar waveform, and we studied both analytically and numerically the propulsion of the bead as a function of the axonemal waveform and bead-axoneme attachment geometry. While our analysis semi-quantitatively describes the experimental results, it also reveals the existence of a counter-intuitive propulsion regime where the speed of the axonemally-driven bead increases with the size of the bead. Moreover, we demonstrated that asymmetric, sideways attachment of the axoneme to the bead can also contribute to the rotational velocity of the micro-swimmer. The uncovered mechanism has potential applications in the fabrication of synthetic micro-swimmers, and in particular, bio-actuated medical micro-robots for targeted drug delivery.

biophysics↗

bioRxiv2021

Time-reversal symmetric component of the flagellar beat enhances the translational and rotational velocities of isolated Chlamydomonas flagella

The beating of cilia and flagella is essential to perform many important biological functions, including generating fluid flows on the cell surface or propulsion of micro-organisms. In this work, we analyze the motion of isolated and demembranated flagella from green algae Chlamydomonas reinhardtii, which act as ATP-driven micro-swimmers. The waveform of the Chlamydomonas beating flagella has an asymmetric waveform that is known to involve the superposition of a static component, corresponding to a fixed, intrinsic curvature, and a dynamic wave component traveling in the base-to-tip direction at the fundamental beat frequency, plus higher harmonics. Here, we demonstrate that these modes are not sufficient to reproduce the observed flagella waveforms. We find that two extra modes play an essential role to describe the motion: first, a time-symmetric mode, which corresponds to a global oscillation of the axonemal curvature, and second, a secondary tip-to-base wave component at the fundamental frequency that propagates opposite to the dominant base-to-tip wave, albeit with a smaller amplitude. Although the time-symmetric mode cannot, by itself, contribute to propulsion (scallop theorem), it does enhance the translational and rotational velocities of the flagellum by approximately a factor of 2. This mode highlights a long-range coupled on/off activity of force-generating dynein motors and can provide further insight into the underling biology of the ciliary beat.

biophysics↗

bioRxiv2020

Light-powered reactivation of flagella: towards self-sustained movement of artificial cells

Artificial systems capable of self-sustained movement with self-sufficient energy are of high interest with respect to the development of many challenging applications including medical treatments but also technical applications. The bottom-up assembly of such systems in the context of synthetic biology is still a challenging task. In this work, we demonstrate the biocompatibility and efficiency of an artificial light-driven energy module and a motility functional unit by integrating light-switchable photosynthetic vesicles with demembranated flagella that provide ATP for dynein molecular motors upon illumination. The flagellar propulsion is coupled to the beating frequency and dynamic ATP synthesis in response to illumination allows us to control beating frequency of flagella in a light-dependent manner. In addition, we verified the functionality of light-powered synthetic vesicles in in vitro motility assays by encapsulating microtubules assembled with force-generating kinesin-1 motors and the energy module to investigate the dynamics of a contractile filamentous network in cell-like compartments by optical stimulation. Integration of this photosynthetic system with various biological building blocks such as cytoskeletal filaments and molecular motors may contribute to the bottom-up synthesis of artificial cells that are able to undergo motor-driven morphological deformations and exhibit directional motion in a light-controllable fashion. Graphical TOC Entry O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/212191v3_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@79347aorg.highwire.dtl.DTLVardef@164463dorg.highwire.dtl.DTLVardef@3f8b01org.highwire.dtl.DTLVardef@1bef3e8_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

A comprehensive germline variant and expression analyses of ACE2, TMPRSS2 and SARS-CoV-2 activator FURIN genes from the Middle East: Combating SARS-CoV-2 with precision medicine

The severity of the new COVID-19 pandemic caused by the SARS-CoV-2 virus is strikingly variable in different global populations. SARS-CoV-2 uses ACE2 as a cell receptor, TMPRSS2 protease, and FURIN peptidase to invade human cells. Here, we investigated 1,378 whole-exome sequences of individuals from the Middle Eastern populations (Kuwait, Qatar, and Iran) to explore natural variations in the ACE2, TMPRSS2, and FURIN genes. We identified two activating variants (K26R and N720D) in the ACE2 gene that are more common in Europeans than in the Middle Eastern, East Asian, and African populations. We postulate that K26R can activate ACE2 and facilitate binding to S-protein RBD while N720D enhances TMPRSS2 cutting and, ultimately, viral entry. We also detected deleterious variants in FURIN that are frequent in the Middle Eastern but not in the European populations. This study highlights specific genetic variations in the ACE2 and FURIN genes that may explain SARS-CoV-2 clinical disparity. We showed structural evidence of the functionality of these activating variants that increase the SARS-CoV-2 aggressiveness. Finally, our data illustrate a significant correlation between ACE2 variants identified in people from Middle Eastern origins that can be further explored to explain the variation in COVID-19 infection and mortality rates globally.

genetics↗

bioRxiv2020

Neutral sphingomyelinase 2 regulates inflammatory responses in monocytes/macrophages induced by TNF-α

Obesity is associated with elevated levels of TNF- and proinflammatory CD11c monocytes /macrophages. TNF- mediated dysregulation in the plasticity of monocytes/macrophages is concomitant with pathogenesis of several inflammatory diseases, including metabolic syndrome, but the underlying mechanisms are incompletely understood. Since neutral sphingomyelinase 2 (nSMase2; product of the sphingomyelin phosphodiesterase 3 gene, SMPD3) is a key enzyme for ceramide production involved in inflammation, we investigated whether nSMase2 contributed to the inflammatory changes in the monocytes/macrophages induced by TNF-. In this study, we demonstrate that the disruption of nSMase activity in monocytes/macrophages either by chemical inhibitor GW4869 or small interfering RNA (siRNA) against SMPD3 results in defects in the TNF- mediated expression of CD11c. Furthermore, blockage of nSMase in monocytes/macrophages inhibited the secretion of inflammatory mediators IL-1b and MCP-1. In contrast, inhibition of acid SMase (aSMase) activity did not attenuate CD11c expression or secretion of IL-1b and MCP-1. TNF--induced phosphorylation of JNK, p38 and NF-{kappa}B was also attenuated by the inhibition of nSMase2. Moreover, NF-kB/AP-1 activity was blocked by the inhibition of nSMase2. SMPD3 was elevated in PBMCs from obese individuals and positively corelated with TNF- gene expression. These findings indicate that nSMase2 acts, at least in part, as a master switch in the TNF- mediated inflammatory responses in monocytes/macrophages.

immunology↗