Biology subjects

Pareek, V.

Publications and source records attributed to Pareek, V..

8 recordsLinked to original sources

bioRxiv2025

Structural Validation of the Intermediate Leptomeningeal Layer in the Human Central Nervous System

Traditionally, the human central nervous system (CNS) is described as having three meningeal layers, from outer to inner: dura mater, arachnoid mater, and pia mater. The arachnoid and pia mater are called the leptomeninges, and the space between them is filled with cerebrospinal fluid (CSF). Using gross dissection, light microscopy, and ultrastructural analysis of fresh postmortem and cadaveric CNS specimens spanning fetal to adult ages (N=61), we demonstrate a fibrocellular intermediate leptomeningeal layer (ILL) from the cortex to the caudal end of the spinal cord. The ILL divides the subarachnoid space (SAS) into two distinct structural compartments, through which vessels and nerves pass. The ILL shows unique structural features, such as dips into the brains sulci and fissures, as a double-fold membrane that bears intra-layer trabeculae, carries vessels, and forms the perivascular sheath. Moreover, throughout the CNS, it appears to be a non-sieved barrier, characterized by the presence of tight and adherens junctions. ILL, predominantly in the spinal cord, contains macrophage-like cells, indicating its layer-specific immune properties. The ILL warrants recognition as a distinct human meningeal layer with potential barrier and immune functions. SignificanceO_ST_ABSAn Intermediate Leptomeningeal Layer encloses the Central Nervous System in HumansC_ST_ABSThe integrated analysis of our macroscopic, microscopic, and ultrastructural study provides robust support for an intermediate leptomeningeal layer (ILL) in the subarachnoid space (SAS) of the human central nervous system (CNS) along the entire neural axis. The ILL is a fibrocellular macroscopic structure, with restricted permeability, that divides the cerebrospinal fluid (CSF)-filled SAS into two distinct structural compartments. Uniquely, ILL revealed the presence of cells with macrophage-like properties, suggesting a possible role in immune surveillance. The ILL may redefine the established concept of protective coverings of CNS, CSF circulation dynamics, and the role of leptomeninges in health and disease, including drug delivery.

neuroscience↗

bioRxiv2024

N-acetyl-transferases required for iron uptake and aminoglycoside resistance promote virulence lipid production in M. marinum

Phagosomal lysis is a key aspect of mycobacterial infection of host macrophages. Acetylation is a protein modification mediated enzymatically by N-acetyltransferases (NATs) that impacts bacterial pathogenesis and physiology. To identify NATs required for lytic activity, we leveraged Mycobacterium marinum, a nontubercular pathogen and an established model for M. tuberculosis. M. marinum hemolysis is a proxy for phagolytic activity. We generated M. marinum strains with deletions in conserved NAT genes and screened for hemolytic activity. Several conserved lysine acetyltransferases (KATs) contributed to hemolysis. Hemolysis is mediated by the ESX-1 secretion system and by phthiocerol dimycocerosate (PDIM), a virulence lipid. For several strains, the hemolytic activity was restored by the addition of second copy of the ESX-1 locus. Using thin-layer chromatography (TLC), we found a single NAT required for PDIM and phenolic glycolipid (PGL) production. MbtK is a conserved KAT required for mycobactin siderophore synthesis and virulence. Mycobactin J exogenously complemented PDIM/PGL production in the {Delta}mbtK strain. The {Delta}mbtK M. marinum strain was attenuated in macrophage and Galleria mellonella infection models. Constitutive expression of either eis or papA5, which encode a KAT required for aminoglycoside resistance and a PDIM/PGL biosynthetic enzyme, rescued PDIM/PGL production and virulence of the {Delta}mbtK strain. Eis N-terminally acetylated PapA5 in vitro, supporting a mechanism for restored lipid production. Overall, our study establishes connections between the MbtK and Eis NATs, and between iron uptake and PDIM and PGL synthesis in M. marinum. Our findings underscore the multifunctional nature of mycobacterial NATs and their connection to key virulence pathways. Significance StatementAcetylation is a modification of protein N-termini, lysine residues, antibiotics and lipids. Many of the enzymes that promote acetylation belong to the GNAT family of proteins. M. marinum is a well-established as a model to understand how M. tuberculosis causes tuberculosis. In this study we sought to identify conserved GNAT proteins required for early stages of mycobacterial infection. Using M. marinum, we determined that several GNAT proteins are required for the lytic activity of M. marinum. We uncovered previously unknown connections between acetyl-transferases required for iron uptake and antimicrobial resistance, and the production of the unique mycobacterial lipids, PDIM and PGLOur data support that acetyl-transferases from the GNAT family are interconnected, and have activities beyond those previously reported.

microbiology↗

bioRxiv2024

Aligning with the predecessors and counterarguments: A systematic review of the anatomical correlates for the newly discovered meningeal layer in the existing literature

A recent study reported the existence of a subarachnoid lymphatic-like membrane (SLYM) -an intermediate leptomeningeal layer between the arachnoid and pia mater in mice and human brains - dividing the subarachnoid space (SAS) into two functional compartments. Despite being a macroscopic structure, how it missed detection in previous studies is surprising. We systematically reviewed the published reports in animals and humans to explore whether prior descriptions of this meningeal layer have existed. An electronic search was conducted in PubMed/Medline, EMBASE, Google Scholar, Science Direct, and Web of Science databases using combinations of MeSH terms and keywords with Boolean operators from inception until 31st Dec 2023. We found at least eight studies that provided structural evidence of an intermediate leptomeningeal layer in the brain or spinal cord. However, unequivocal descriptions for this layer all along the central nervous system were scarce. Obscured names were used to describe it, i.e., the epipial layer, intermediate meningeal layer, intermediate lamella, and outer pial layer. Its microscopic/ultrastructural details closely resembled the SLYM. Further, we examined the counterarguments in current literature that are skeptical of this layers existence. Considering the significant physiological/clinical implications, exploring further structural and functional details of the new meningeal layer is a need of the hour.

neuroscience↗

bioRxiv2022

NRP1 and furin as putative mediators of SARS-CoV-2 entry into human brain cells

COVID-19 has prominent neurological manifestations including psychiatric symptoms, indicating significant synaptic pathology. Surprisingly, existing evidence suggests negligible expression of the key SARS-CoV-2 host cell entry mediators ACE2 and TMPRSS2 in human brain, which complicates understanding of the pathomechanisms of the neuropsychiatric manifestations in COVID-19. Recent studies suggested that an alternative host-cell entry receptor, NRP1, can mediate entry of furin cleaved SARS-CoV-2 spike proteins into the host cells. However, the role of NRP1 and furin in mediating SARS-CoV-2 entry in human brain cells has been least explored and remains a lacuna in the literature. We performed an in silico analysis of the transcriptomic and proteomic expressions of SARS-CoV-2 host-cell entry receptors and associated tissue proteases in human brain tissue, using the publically available databases. Based on the expression analysis, SARS-CoV-2 entry in human brain cells is likely to be mediated through NRP1 and furin. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=198 HEIGHT=200 SRC="FIGDIR/small/476893v1_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@1c818baorg.highwire.dtl.DTLVardef@1cf7c0corg.highwire.dtl.DTLVardef@d92e19org.highwire.dtl.DTLVardef@61866a_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Silver nanoparticles induce a triclosan like antibacterial action mechanism in multi-drug resistant Klebsiella pneumoniae

Infections associated with antimicrobial-resistant bacteria now represent a significant threat to human health using conventional therapy, necessitating the development of alternate and more effective antibacterial compounds. Silver nanoparticles (Ag NPs) have been proposed as potential antimicrobial agents to combat infections. A complete understanding of their antimicrobial activity is required before these molecules can be used in therapy. Lysozyme coated Ag NPs were synthesized and characterized by TEM-EDS, XRD, UV-vis, FTIR spectroscopy, zeta potential and oxidative potential assay. Biochemical assays and deep level transcriptional analysis using RNA sequencing were used to decipher how Ag NPs exert their antibacterial action against multi-drug resistant Klebsiella pneumoniae MGH78578. RNAseq data revealed that Ag NPs induced a triclosan-like bactericidal mechanism responsible for the inhibition of the type II fatty acid biosynthesis. Additionally, released Ag+ generated oxidative stress both extra- and intracellularly in K. pneumoniae. The data showed that triclosan-like activity and oxidative stress cumulatively underpinned the antibacterial activity of Ag NPs. This result was confirmed by the analysis of the bactericidal effect of Ag NPs against the isogenic K. pneumoniae MGH78578{Delta} soxS mutant, which exhibits a compromised oxidative stress response compared to the wild type. Silver nanoparticles induce a triclosan-like antibacterial action mechanism in multi-drug resistant K. pneumoniae. This study extends our understanding of anti-Klebsiella mechanisms associated with exposure to Ag NPs. This allowed us to model how bacteria might develop resistance against silver nanoparticles, should the latter be used in therapy.

microbiology↗

bioRxiv2020

Relevance of enriched expression of SARS-CoV-2 binding receptor ACE2 in gastrointestinal tissue with pathogenesis of digestive symptoms, diabetes-associated mortality, and disease recurrence in COVID-19 patients

IntroductionCOVID-19 is caused by a new strain of coronavirus called SARS-coronavirus-2 (SARS-CoV-2), which is a positive sense single strand RNA virus. In humans, it binds to angiotensin converting enzyme 2 (ACE2) with the help a structural protein on its surface called the S-spike. Further, cleavage of the viral spike protein (S) by the proteases like transmembrane serine protease 2 (TMPRSS2) or Cathepsin L (CTSL) is essential to effectuate host cell membrane fusion and virus infectivity. COVID-19 poses intriguing issues with imperative relevance to clinicians. The pathogenesis of GI symptoms, diabetes-associated mortality, and disease recurrence in COVID-19 are of particular relevance because they cannot be sufficiently explained from the existing knowledge of the viral diseases. Tissue specific variations of SARS-CoV-2 cell entry related receptors expression in healthy individuals can help in understanding the pathophysiological basis the aforementioned collection of symptoms. Materials and MethodsThe data were downloaded from the Human Protein Atlas available at (https://www.proteinatlas.org/humanproteome/sars-cov-2) and the tissue specific expressions (both mRNA and protein) of ACE2 and TMPRSS2 as yielded from the studies with RNA sequencing and immunohistochemistry (IHC) were analyzed as a function of the various components of the digestive tract. A digestive system specific functional enrichment map of ACE2 gene was created using g:profiler (https://biit.cs.ut.ee/gprofiler/gost) utility and the data were visualized using Cytoscape software, version 3.7.2 (https://cytoscape.org/). ResultsThe correlated expression (transcriptomic and proteomic) of ACE2 (to which SARS-CoV-2 binds through the S-spike) was found to be enriched in the lower gastrointestinal tract (GIT) (highest in small intestine, followed by colon and rectum), and was undetectable in the upper GIT components: mouth cavity (tongue, oral mucosa, and salivary glands), esophagus, and stomach. High expression of ACE2 was noted in the glandular cells as well as in the enterocytes in the lining epithelium (including brush border epithelium). Among other digestive system organs, Gall bladder (GB) showed high expression of ACE2 in glandular cells, while any protein expression was undetectable in liver and pancreas. TMPRSS2 was found enhanced in GIT and exocrine glands of pancreas, and co-localized with ACE2 in enterocytes. ConclusionsBased on the findings of this study and supportive evidence from the literature we propose that a SARS-CoV-2 binding with ACE2 mediates dysregulation of the sodium dependent nutrient transporters and hence may be a plausible basis for the digestive symptoms in COVID-19 patients. ACE2 mediated dysregulation of sodium dependent glucose transporter (SGLT1 or SLC5A1) in the intestinal epithelium also links it to the pathogenesis of diabetes mellitus which can be a possible reason for the associated mortality in COVID-19 patients with diabetes. High expression of ACE2 in mucosal cells of the intestine and GB make these organs potential sites for the virus entry and replication. Continued replication of the virus at these ACE2 enriched sites may be a basis for the disease recurrence reported in some, thought to be cured, patients. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

pathology↗

bioRxiv2019

Transcriptomic Analysis of the Neurogenesis Signature suggests Continued but Minimal Neurogenesis in the Adult Human Hippocampus

PurposeSince immunohistological investigations have given rise to divergent perspectives about continued hippocampal neurogenesis in adult humans, a comprehensive transcriptomic analysis of the neurogenesis signature markers supplemented with insights from gliogenesis and apoptotic markers (in context to the developmental stages across age) may discern important aspects and may well be the appropriate methodology for resolving this conflict.\n\nMaterials and MethodsRNA expression data for the salient neurogenesis, gliogenesis, and apoptotic marker genes in post-mortem human hippocampal tissue of the Prenatal (n=15), Infant/Early childhood (n= 5), Adolescence (n=4), and Adulthood (n=6) ages were downloaded from Allen Brain Atlas database (http://www.brainspan.org/rnaseq). Gene expression data was categorized, median values were computed, and age group specific differential expression was statistically analyzed (the confidence level of 95%, p value [≤] 0.05 is used).\n\nResultsA sharp fall in prenatal to infant/early childhood expression was observed for all studied neurogenesis markers, except that for the post-mitotic late maturation (CALB1, CALB2, MAP2, NEUN, STMN2) which showed no significant differences in expression profiles. A continued post childhood decrease across advancing age was observed in the neural stem cells and progenitor markers with insignificant differences across close age groups. Uniquely, the postnatal sharp fall of KI67 and TBR2 continued across advancing age groups, reached near baseline until adolescent age. The immature granule cell, post mitotic early maturation, and late maturation markers showed a maintained or slightly increased (albeit insignificant) post childhood expression. The gliogenesis markers mostly showed a significant downregulation between prenatal and infant /early childhood age groups; this decline was persistent thereafter with insignificant differences between close age groups. A continued postnatal decrease occurred in apoptotic markers with observable, but insignificant, differences between adolescent and adult age.\n\nConclusionsOur findings indicate a possibility of continued but minimal neurogenesis in the adult human hippocampus. A significant part of the newborn cells in the neurogenic niche may be glial cells.\n\n(Findings of this study were first presented at the Annual Meeting of Society for Neuroscience (SFN), 3rd-7th November, 2018, San Diego, USA. https://abstractsonline.com/pp8/#!/4649/presentation/37213)\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=153 SRC=\"FIGDIR/small/664995v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (43K):\norg.highwire.dtl.DTLVardef@3268f3org.highwire.dtl.DTLVardef@18855bborg.highwire.dtl.DTLVardef@1b46bdaorg.highwire.dtl.DTLVardef@14b929_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract\n\nC_FIG HighlightsO_LIA varying but continued fall in expression was observed for all studied neurogenesis markers across advancing age groups, except that for the immature granule cells, early and post-mitotic late neuronal maturation markers.\nC_LIO_LIA continued postnatal sharp fall of progenitor markers KI67 and TBR2 reached near baseline until adolescent age.\nC_LIO_LIGliogenesis markers showed continued but insignificant fall in expression post infant/early childhood.\nC_LIO_LIApoptotic markers showed continued post infant/early childhood downfall but changes were negligible between adolescent and adult age.\nC_LI

neuroscience↗

bioRxiv2017

Altered Expression Of A Unique Set Of Genes Reveals Complex Etiology Of Schizophrenia

PurposeThe etiology of schizophrenia is extensively debated, and multiple factors have been contended to be involved. A panoramic view of the contributing factors in a genome-wide study can be an effective strategy to provide a comprehensive understanding of its causality.\n\nMaterials and MethodsGSE53987 dataset downloaded from GEO-database, which comprised mRNA expression data of post-mortem brain tissue across three regions from control and age-matched subjects of schizophrenia (N= Hippocampus (HIP): C-15, T-18, Prefrontal cortex (PFC): C-15, T-19, Associative striatum (STR): C-18, T-18). Bio-conductor-affy-package used to compute mRNA expression, and further t-test applied to investigate differential gene expression. The analysis of the derived genes performed using PANTHER Classification System and NCBI database.\n\nResultsA set of 40 genes showed significantly altered (p<0.01) expression across all three brain regions. The analyses unraveled genes implicated in biological processes and events, and molecular pathways relating basic neuronal functions.\n\nConclusionsThe deviant expression of genes maintaining basic cell machinery explains compromised neuronal processing in SCZ.\n\nAbbreviationsSchizophrenia (SCZ), Hippocampus (HIP), Associative striatum (STR), Prefrontal cortex (PFC)

neuroscience↗