Biology subjects

Lamont, R. J.

Publications and source records attributed to Lamont, R. J..

6 recordsLinked to original sources

bioRxiv2025

The Nox2 NADPH oxidase regulates neutrophilic inflammation in the oral cavity

The leukocyte NADPH oxidase 2 (NOX2) is an important regulator of inflammatory responses, independent of its antimicrobial activity. Inactivating mutations in NOX2 cause chronic granulomatous disease (CGD), a severe immunodeficiency associated with recurrent infections and dysregulated neutrophilic inflammation. Recurrent oral ulcers, stomatitis, gingivitis, and other inflammatory issues affecting the oral mucosa have been observed in patients with CGD; however, the underlying mechanisms are not known. Here, we present evidence that the extensive inflammatory destruction of oral mucosal tissues observed in Nox2-deficient or CybbKOmice was not caused by impaired antimicrobial surveillance against oral pathobionts but instead resulted from a cell-intrinsic dysregulation of neutrophil inflammatory responses. Transcriptional and cellular profiling of oral tissues isolated from wild-type and CybbKO mice showed a dominant neutrophil signature, which was accompanied by a significant upregulation of several bone-resorbing, tissue-degrading inflammatory cytokines and a reduced expression of nuclear factor erythroid 2-related factor 2 (Nrf2) regulated genes. Mechanistically, hyperinflammatory responses were mitigated by restoring Nrf2 transcriptional activity using a synthetic agonist. Thus, our studies show that Nox2 oxidase and its derived reactive oxygen species are crucial for balanced recruitment and cell-intrinsic regulation of neutrophil inflammatory responses within oral tissues in an Nrf2-dependent manner.

immunology↗

bioRxiv2025

Episymbiotic Saccharibacteria suppresses epithelial immunoactivation through Type IV pili and TLR2 dependent endocytosis

Saccharibacteria are episymbionts that require host-bacteria to grow. They are positively associated with inflammatory diseases within the human microbiome, yet their mechanisms for interacting with the human host and contributing to diseases remain unknown. This study investigated interactions between a Saccharibacterium (Nanosynbacter lyticus), its host-bacteria (Schaalia odontolytica), and oral epithelial cells. The host-bacteria induced proinflammatory cytokines in epithelial cells, while Saccharibacteria were immune silent. Remarkably, Saccharibacteria dampened cytokine responses to host-bacteria during coinfection. This effect was driven by Saccharibacteria-induced clustering of TLR2 receptors, a process likely facilitated by type IV, ultimately leading to reduced TLR2-mediated cytokine signalling. High resolution imaging showed that Saccharibacteria were endocytosed by oral epithelial cells, and colocalized with endosome markers, eventually trafficking to lysosomes. Moreover, a subset of the Saccharibacteria survive endocytosis long-term, and retains their capability to reinfect host-bacteria, highlighting a mechanism for persistence in the oral microbiome and a vital role in mammalian immune system modulation.

immunology↗

bioRxiv2025

Virion stripping: A new role for bacterial proteases

We demonstrate that proteases produced by the oro-pharyngeal bacterial colonizer Porphyromonas gingivalis (Pg) reduce viral burden and modulate host interferon responses during respiratory syncytial virus (RSV) infection. Several oral bacteria, including Pg, have been shown to translocate to the upper airways through sub-clinical micro-aspiration. Our findings reveal that Pg, upon translocating to this new niche, significantly attenuated lung damage by reducing viral loads during respiratory viral infections in the lungs of wild-type mice. This protective effect was attributed to the activity of gingipains, cysteine endopeptidases produced by Pg, which cleaved envelope glycoproteins on RSV as well as on related murine-specific Sendai virus (SeV), thereby impairing their infectious capacity. Notably, the reduction in viral loads was independent of interferon lambda (IFN-{lambda}) signaling, which is actively suppressed by Pg in airway epithelial cells. However, the complete absence of IFN-{lambda} signaling resulted in a stronger inflammatory response despite a low viral load. Thus, we show a previously undescribed role for the oro-respiratory bacterial colonizer Pg in creating bottlenecks to viral infection by the activity of its proteases. SIGNIFICANCE STATEMENTReciprocal interactions between microbial colonizers and host epithelial cells are critical for providing initial defense against viral infections. However, our understanding of this phenomenon has been limited to microbiota-derived ligands that activate host pattern recognition receptors (PRRs), inducing basal interferon expression and downstream antiviral genes. Here, we present a novel mechanism that relies on microbial proteases to directly reduce viral load. Specifically, we discovered that the infectious capacity of the Respiratory Syncytial Virus (RSV) was significantly inhibited upon contact with the proteases (gingipains) produced by the oropharyngeal colonizer Porphyromonas gingivalis. Gingipains caused proteolytic degradation of the RSV envelope and attachment proteins, rendering them inactive. This preemptive reduction in viral infectious capacity consequently diminished the severity of respiratory viral infections in an IFN-independent manner.

microbiology↗

bioRxiv2025

Tyrosine phosphorylation coupling of one carbon metabolism and virulence in an endogenous pathogen

Endogenous pathogens can constrain virulence to ensure survival in the host. Pathogenic state can be controlled by metabolic responses to the prevailing microenvironment; however, the coupling and effector mechanisms are not well understood. Flux through the One Carbon Metabolism (OCM) pathway can modulate virulence of the oral pathobiont Porphyromonas gingivalis, and here we show that this is controlled by tyrosine phosphorylation-dependent differential partitioning of gingipain proteases. The OCM essential precursor pABA inhibits the low molecular weight tyrosine phosphatase Ltp1, and consequently relieves inhibition of its cognate kinase, Ptk1. We found that in the absence of pABA, reduced Ptk1 kinase activity blocks extracellular release of gingipains. Surface retention of gingipains confers resistance to neutrophil mobilization and killing, and virulence in animal models of disease is elevated. Reciprocally, Ptk1 and gingipains are required for maximal flux through OCM, and Ptk1 can phosphorylate the OCM pathway enzymes GlyA and GcvT. Further, ALP, an alkaline phosphatase involved in synthesis of DHPPP, which combines with pABA to make DHP, is phosphorylated and activated by Ptk1. We propose, therefore, that although the primary function of Ptk1 is to maintain OCM balance, it mechanistically couples metabolism with tunable pathogenic potential through directing the location of proteolytic virulence factors.

microbiology↗

bioRxiv2021

Fusobacterium nucleatum metabolically integrates commensals and pathogens in oral biofilms

Fusobacterium nucleatum is a common constituent of the oral microbiota in both periodontal health and disease. Previously, we discovered ornithine cross-feeding between F. nucleatum and Streptococcus gordonii, where S. gordonii secretes ornithine via an arginine-ornithine antiporter (ArcD), which in turn supports the growth and biofilm development of F. nucleatum; however, broader metabolic aspects of F. nucleatum within polymicrobial communities and their impact on periodontal pathogenesis have not been addressed. Here, we show that when co-cultured with S. gordonii, F. nucleatum increased amino acid availability to enhance the production of butyrate and putrescine, a polyamine produced by ornithine decarboxylation. Co-culture with Veillonella parvula, another common inhabitant of the oral microbiota, also increased lysine availability, promoting cadaverine production by F. nucleatum. We confirmed that ArcD-dependent ornithine excretion by S. gordonii results in synergistic putrescine production, and mass spectrometry imaging revealed this metabolic capability creates a putrescine-rich microenvironment inside F. nucleatum biofilms. We further demonstrated that polyamines caused significant changes in the biofilm phenotype of a periodontal pathogen, Porphyromonas gingivalis, with putrescine being a potent stimulator of biofilm development and dispersal, and confirmed that F. nucleatum-mediated conversion of ornithine to putrescine enhances biofilm formation by P. gingivalis. Lastly, analysis of plaque samples revealed cooccurrence of P. gingivalis with genetic modules for putrescine production by S. gordonii and F. nucleatum. Overall, our results highlight the ability of F. nucleatum to induce synergistic polyamine production within multi-species consortia, and provide insight into how the trophic web in oral biofilm ecosystems can eventually shape disease-associated communities. Significance StatementPeriodontitis is caused by the pathogenic transition of subgingival microbiota ecosystems, which is accompanied by alterations to microbiome functions including metabolic systems and the establishment of metabolic cross-feeding. While Fusobacterium nucleatum is a major constituent of the periodontal microbiota, its metabolic integration within polymicrobial communities and the impact on periodontal pathogenesis are poorly understood. Here, we report that amino acids supplied by other commensal bacteria induce polyamine production by F. nucleatum, creating polyamine-rich microenvironments. We further show that this trophic web results in enhancement of biofilm formation and dispersal of a periodontal pathogen, Porphyromonas gingivalis. This work provides mechanistic insight into how cooperative metabolism within oral biofilms can tip the balance toward periodontitis.

microbiology↗

bioRxiv2019

Pneumococcal carriage requires KDM6B, a histone demethylase, for its unique inflammatory signature

Streptococcus pneumoniae is a natural colonizer of the human upper respiratory tract and an opportunistic pathogen. After colonization, bacteria either remain in the human upper respiratory tract, or may progress to cause pneumococcal disease. Although epithelial cells are among the first to encounter pneumococci, the cellular processes and contribution of epithelial cells to the host response are poorly understood. Here, we show a S. pneumoniae serotype 6B ST90 strain, which does not cause disease in a murine infection model, induces a unique NF-{kappa}B signature response distinct from an invasive disease causing isolate of serotype 4 (TIGR4). This signature is characterized by activation of p65 (RelA) and requires a histone demethylase, KDM6B. At the molecular level, we show that interaction of the 6B strain with epithelial cells leads to chromatin remodeling within the IL-11 promoter in a KDM6B dependent manner, where KDM6B specifically demethylates histone H3 lysine 27 di-methyl. Chromatin remodeling of the IL-11 locus facilitates p65 access to three NF-{kappa}B sites, which are otherwise inaccessible when stimulated by IL-1{beta} or TIGR4. Finally, we demonstrate through chemical inhibition of KDM6B, with GSK-J4 inhibitor, and through exogenous addition of IL-11 that the host responses to 6B ST90 and TIGR4 strains can be interchanged both in vitro and in a murine model of infection in vivo. Our studies hereby reveal how a chromatin modifier governs cellular responses during infection.

microbiology↗