Biology subjects

Gharsallah, C.

Publications and source records attributed to Gharsallah, C..

4 recordsLinked to original sources

bioRxiv2024

Impact of methicillin resistance on virulence factor expression in 1 Staphylococcus aureus: Insights from gene expression profiling

Staphylococcus aureus is a major human pathogen causing various clinical infections and a leading cause of morbidity and mortality worldwide. S. aureus infections are problematic due to frequent antibiotic resistance, especially to methicillin. This study investigated 30 unduplicated S. aureus strains from clinical samples to establish a link between methicillin resistance and virulence factors.We detected and determined expression levels of the mecA gene, virulence genes (spdC, spA, atlA), and the RNAIII regulator using qRT-PCR. All virulence genes and the RNAIII regulator were detected in all strains. Phenotypic results showed only three strains (10%) were methicillin-resistant, while 12 (40%) carried the mecA gene. mecA-positive strains exhibited high expression of adhesion factors (spA) and biofilm formation factors (atlA), but low expression of the RNAIII regulator. The regulators expression was negatively correlated with mecA gene expression. Using a multilayer association network, we found a correlation between phenotypic methicillin resistance expression and mecA gene transcription in S. aureus mecA+. Understanding S. aureus virulence determinants will help develop anti-virulence strategies, especially given the lack of an anti-S. aureus vaccine and rising antibiotic resistance. HighlightsO_LIComplex interplay between methicillin resistance and virulence: Our study unveils a complex interplay between methicillin resistance and the expression of virulence genes in Staphylococcus aureus clinical isolates. C_LIO_LIPhenotypic and molecular correlation: Phenotypic resistance to methicillin was observed in only 10% of the isolates, whereas 40% carried the mecA gene. Molecular analysis revealed distinct expression patterns, notably elevated spA and atlA expression, in mecA+ strains. C_LIO_LINegative correlation with RNAIII: Our findings indicate a negative correlation between RNAIII regulator expression and the mecA gene in the same strains, shedding light on their regulatory relationship. C_LIO_LIMultilayer association network: Utilizing a multilayer association network, we established a correlation between phenotypic methicillin resistance and mecA gene transcription in S. aureus mecA+ strains. C_LI

microbiology↗

bioRxiv2024

Plant miRNAs Anti-Staphylococcus aureus: Therapeutic Perspective

Staphylococcus aureus is a pathogen that has developed resistance to each new antibiotic introduced for half a century especially through the acquisition of the mecA gene. This bacterial resistance to antibiotics represents a major public health problem. New revolutions are underway, in particular the design of drugs and vaccines targeting the system for detecting the regulatory quorum of the accessory gene (agr). It has been shown that the pathogenicity and resistance of S. aureus can be modulated through the intervention of this system. For this reason, we propose in this present work, a new therapeutic design based on an in silico study to identify plant miRNAs that could target this system as well as the mecA gene based on recent studies showing the inter-realm regulation of human transcripts by plant miRNAs. Out of a total of 20643 miRNAs from mature plants, we identified 29 miRNAs, obtained by the selection criteria MFE [≥] -25 kcal / mol, which could potentially target selected genes of S. aureus. Fifteen of them were selected on the basis of their thermodynamic stability. Interestingly, The seeds of ptc - miR171g and ptc - miR171h (Populus trichocarpa) both of which almost similar mature miRNA sequence was found to target UCCC region of RNAIII gene. miRNAs from plants targeting S. aureus have the potential to be developed as an alternative therapy of the future. To our knowledge, it is the first therapeutic alternative of the future via the in silico identification of plant miRNAs targeting pathogenic bacteria. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/598803v1_ufig1.gif" ALT="Figure 1"> View larger version (62K): org.highwire.dtl.DTLVardef@45daeaorg.highwire.dtl.DTLVardef@274b40org.highwire.dtl.DTLVardef@1bd8b25org.highwire.dtl.DTLVardef@fa3964_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2024

MAPPING CHANGES OF MIRNA-MRNA NETWORKS IN LEISHMANIA-INFECTED MACROPHAGES PREDICTS REGULATORY MIRNA-TF LOOPS AS NOVEL TARGETS OF PARASITE IMMUNE SUBVERSION

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level and play a crucial role in numerous disease processes, including infections. Although intracellular microbial pathogens are known to modulate host cell gene expression to establish permissive conditions for infection, the specific role of host-encoded miRNAs underlying such subversion remains poorly understood. In this study, we employed the protozoan parasite Leishmania amazonensis as a model system to investigate how infection of macrophages modifies the host cell miRNA profile to evade antimicrobial functions and to establish permissive conditions for intracellular proliferation. Dual RNA-seq analyses using matched mRNA and miRNA-enriched samples from uninfected and L. amazonensis-infected bone marrow-derived macrophages (BMDMs) revealed 102 differentially expressed miRNAs (padj<0.05), with 18 miRNAs showing reduced and 84 miRNAs showing increased abundance in infected BMDMs. Mapping putative networks of miRNA-mRNA interactions based on the observed expression changes, combined with Gene Ontology enrichment analyses, allowed us to identify potential miRNA target genes involved in key biological processes and metabolic pathways that permit parasite intracellular survival and proliferation. Our analyses predict the existence of a large miRNA-mRNA network affecting the expression level of numerous transcription factors that indicates inhibition of the NF-{kappa}B-dependent inflammatory response or the promotion of cholesterol biosynthesis during infection. In particular, the over 10e3-fold increase in the abundance of mmu-miR-686 in infected BMDMs was correlated with a reduced abundance of putative target transcripts implicated in miRNA biogenesis itself, in RNA binding, and in regulation of apoptosis, such as Caspase 12, the mRNA decay activator protein Zfp36l1 or Leukemia Inhibitory Factor Receptor Alpha. Likewise, the over 200-fold increase in abundance of mmu-miR-6546-3p was associated with a reduced abundance of putative target mRNAs implicated in cytokine-mediated signaling, positive regulation of apoptotic process and regulation of gene expression, affecting, for example, the MADS box transcription enhancer factor 2, the transformation related protein 53 inducible nuclear protein 1, or the G protein-coupled receptor 35. Interestingly, both miRNAs are predicted to simultaneously target 32 mRNAs that showed reduced abundance in infected BMDMs, including Maturin Neural Progenitor Differentiation Regulator (Mturn), a regulator of NF-{kappa}B transcription factor activity. In conclusion, our approach provides novel insight into molecular mechanisms that may govern macrophage subversion and intracellular Leishmania survival. Our results shed new light on the complex relationship among miRNAs, macrophage gene expression and Leishmania infection, proposing regulatory feed-forward loops (FFLs) and feedback loops (FBLs) between miRNAs and TFs as a novel target of Leishmania immune subversion. These findings open exciting new avenues for the development of intervention strategies aimed at disrupting such crucial interactions, for example using an anti-miR (antagomir) approach against mmu-miR-686 and mmu-miR-6546-3p.

microbiology↗

bioRxiv2023

Inhibition of the macrophage demethylase LSD1 reverses Leishmania amazonensis-induced transcriptomic changes and causes a decrease in parasite load

Intracellular pathogens exploit host cell functions to favor their own survival. In recent years, the subversion of epigenetic regulation has emerged as a key microbial strategy to modify host cell gene expression and evade antimicrobial immune responses. Using the protozoan parasite Leishmania as a model system, we have recently demonstrated that infection causes histone H3 hypomethylation, which is associated with the establishment of an anti-inflammatory phenotype, suggesting that host cell demethylases may play a role in the intracellular survival of these parasites. In this study, we combined pharmacological inhibition with RNA sequencing and quantitative immune-precipitation analysis to investigate the role of the macrophage lysine demethylase LSD1 (KDM1a) in Leishmania intracellular infection in vitro. Treatment of infected macrophages with validated, LSD1-specific inhibitors resulted in a significant reduction in parasite burden. We confirmed the impact of these inhibitors on LSD1 activity within macrophage nuclear extracts using an in vitro demethylase assay and established their LSD1 target engagement in situ by cellular thermal shift assay. RNA-seq analysis of infected and inhibitor-treated macrophages linked parasite killing to a partial reversion of infection-dependent expression changes, restoring the macrophage anti-microbial response and limiting cholesterol biosynthesis. While we ruled out any impact of Leishmania on LSD1 expression or localization, we uncovered significant alterations in LSD1 complex formation within infected macrophages, involving unique interactions with host cell regulatory proteins such as Rcor-1. Our study sheds important new light on the epigenetic mechanisms of macrophage immuno-metabolic subversion by intracellular Leishmania and identifies LSD1 as a potential candidate for host-directed, anti-leishmanial therapy.

cell biology↗