Biology subjects

Ingram, R. J.

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

5 recordsLinked to original sources

bioRxiv2023

The Achromobacter Type 3 secretion system drives pyroptosis and immunopathology via independent activation of NLRC4 and NLRP3 inflammasomes

Achromobacter species are newly recognized opportunistic, pro-inflammatory Gram-negative pathogens in immunocompromised individuals, but how they interact with the innate immune system to drive inflammation is poorly understood. We created sctV (Type 3 Secretion System baseplate) mutants in three Achromobacter clinical isolates from two species and showed that all three required the T3SS to induce cell death in human macrophages. Mutating other critical T3SS components also abolished cell death, which was restored by genetic complementation. Cell death of Achromobacter-infected macrophages was contact-dependent, enhanced by bacterial internalisation, and caused by inflammasome-dependent pyroptosis (typified by Gasdermin-D cleavage and IL-1{beta} secretion). Macrophages deficient in the inflammasome sensors NLRC4 or NLRP3 underwent pyroptosis upon bacterial internalization but those deficient in both NLRC4 and NLRP3 did not, suggesting either sensor can mediate pyroptosis induction in a T3SS-dependent manner. Detailed analysis of the intracellular trafficking of one isolate indicated that the intracellular bacteria reside in an acidic LAMP-1/dextran-positive membrane compartment. Using an intranasal mouse infection model, we observed that Achromobacter damages lung structure and causes severe illness, contingent on a functional T3SS. Together, we demonstrate that Achromobacter species can survive phagocytosis by macrophages and promote macrophage cell death and inflammation by redundant mechanisms of pyroptosis induction.

microbiology↗

bioRxiv2023

Ageing impairs the regenerative capacity of regulatory T cells in central nervous system remyelination

Myelin regeneration (remyelination) is essential to prevent neurodegeneration in demyelinating diseases such as Multiple Sclerosis, however, its efficiency declines with age. Regulatory T cells (Treg) recently emerged as critical players in tissue regeneration, including remyelination. However, the effect of ageing on Treg-mediated regenerative processes is poorly understood. Here, we show that expansion of aged Treg does not rescue age-associated remyelination impairment due to an intrinsically diminished capacity of aged Treg to promote oligodendrocyte differentiation and myelination. This decline in regenerative Treg functions can be rescued by a young environment. We identified Melanoma Cell Adhesion Molecule 1 (MCAM1) and Integrin alpha 2 (ITGA2) as novel candidates of Treg-mediated oligodendrocyte differentiation that decrease with age. Our findings demonstrate that ageing limits the neuroregenerative capacity of Treg, likely limiting their remyelinating therapeutic potential in aged patients, and describe two novel mechanisms implicated in Treg-driven remyelination that may be targetable to overcome this limitation.

neuroscience↗

bioRxiv2022

Increased GABA transmission to GnRH neurons after intrahippocampal kainic acid injection in mice is sex-specific and associated with estrous cycle disruption

Patients with epilepsy develop reproductive endocrine comorbidities at a rate higher than that of the general population. Clinical studies have identified disrupted luteinizing hormone (LH) release patterns in patients of both sexes, suggesting potential epilepsy-associated changes in hypothalamic gonadotropin-releasing hormone (GnRH) neuron function. In previous work, we found that GnRH neuron firing is increased in diestrous females and males in the intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy. Notably, GABAA receptor activation is depolarizing in adult GnRH neurons. Therefore, here we tested the hypothesis that increased GnRH neuron firing in IHKA mice is associated with increased GABAergic drive to GnRH neurons. When ionotropic glutamate receptors (iGluRs) were blocked to isolate GABAergic postsynaptic currents (PSCs), no differences in PSC frequency were seen between GnRH neurons from control and IHKA diestrous females. In the absence of iGluR blockade, however, GABA PSC frequency was increased in GnRH neurons from IHKA females with disrupted estrous cycles, but not saline-injected controls nor IHKA females without estrous cycle disruption. GABA PSC amplitude was also increased in IHKA females with disrupted estrous cycles. These findings suggest the presence of an iGluR-dependent increase in feed-forward GABAergic transmission to GnRH neurons specific to IHKA females with comorbid cycle disruption. In males, GABA PSC frequency and amplitude were unchanged but PSC duration was reduced. Together, these findings suggest that increased GABA transmission helps drive elevated firing in IHKA females on diestrus and indicate the presence of a sex-specific hypothalamic mechanism underlying reproductive endocrine dysfunction in IHKA mice. HIGHLIGHTSO_LIIncreased GABA transmission to GnRH neurons in IHKA mouse model of epilepsy C_LIO_LIIncreased GABA transmission is dependent on upstream glutamate signaling C_LIO_LIIncreased GABA transmission only seen in females with disrupted estrous cycles C_LIO_LIPotential sex-specific mechanism for reproductive endocrine dysfunction in epilepsy C_LI

neuroscience↗

bioRxiv2021

Optogenetic activation of Gq signaling in astrocytes yields stimulation-specific effects on basal hippocampal synaptic excitation and inhibition

Astrocytes play active roles at synapses and can monitor, respond, and adapt to local synaptic activity. To investigate this relationship, more tools that can selectively activate native G protein signaling pathways in astrocytes with both spatial and temporal precision are needed. Here, we tested AAV8-GFAP-Opto1AR-eYFP (Opto1AR), a viral vector to enable activation of Gq signaling in astrocytes via light-sensitive 1-adrenergic receptors. To determine if stimulating astrocytic Opto1AR modulates hippocampal synaptic transmission, recordings were made in CA1 pyramidal cells with surrounding astrocytes expressing Opto1AR, channelrhodopsin (ChR2), or GFP. Both high-frequency (20 Hz, 45-ms light pulses, 5 mW, 5 min) and low-frequency (0.5 Hz, 1-s pulses at increasing 1, 5, and 10 mW intensities, 90 s per intensity) blue light stimulation were tested. 20 Hz Opto1AR stimulation increased both inhibitory and excitatory postsynaptic current (IPSC and EPSC) frequency, and the mIPSC effect was largely reversible within 20 min. By contrast, low-frequency stimulation of Opto1AR did not modulate either IPSCs or EPSCs, whereas the same stimulation of astrocytic ChR2 was effective. These data demonstrate that Opto1AR activation in astrocytes changes synaptic excitation and inhibition in a stimulation-sensitive manner, demonstrating the efficacy and utility of GFAP-Opto1AR as a tool in studying astrocyte-neuron interactions.

neuroscience↗

bioRxiv2020

A glycoengineered antigen exploiting a conserved protein O-glycosylation pathway in the Burkholderia genus for diagnosis of glanders infections

We recently described a protein O-glycosylation pathway conserved in all species of the Burkholderia genus that results in synthesis and incorporation of a trisaccharide glycan to membrane-exported proteins. Here, we exploited this system to construct and evaluate a diagnostic tool for glanders. Burkholderia mallei, the causative agent of glanders, is a highly infectious and fatal zoonotic pathogen that mainly infects horses, mules, donkeys and occasionally humans. A highly sensitive and specific diagnostic tool is crucial for the control, elimination and eradication of B. mallei infections. We constructed plasmids carrying synthetic genes encoding a modified, previously unannotated Burkholderia glycoprotein containing three glycosylation sequons fused to the cholera toxin B-subunit. The resulting proteins were glycosylated in the B. cenocepacia K56-2 parental strain, but not in glycosylation-deficient mutants, as determined by SDS-PAGE and fluorescent lectin blots. One of these glycoproteins was used as an antigen in ELISA and western blots to screen a panel of serum samples collected from glanders-infected and healthy horses previously investigated by complement fixation test and indirect ELISA based on a semi-purified fraction of B. mallei. We show that ELISA and western blot assays based on our glycoprotein antigen provide 100 % specificity, with a sensitivity greater than 88%. The glycoprotein antigen was recognized by serum samples collected from patients infected with B. pseudomallei, B. mallei, B. multivorans and B. cenocepacia. Our results indicate that protein O-glycosylation in Burkholderia can be exploited as a biomarker for diagnosis of Burkholderia-associated infections. IMPORTANCEGlanders is a severe zoonotic disease caused by the Gram-negative bacterium Burkholderia mallei, which affects horses, mules and donkeys, as well as humans. B. mallei is also considered a category B biothreat agent. Due to insufficient pathognomonic symptoms in the early stages of glanders, diagnosis can be difficult. Complement fixation is the most accurate and reliable serological test prescribed by the World Organization for Animal Health; however, this test has a considerable number of false-positive results. We have recently described a conserved protein O-glycosylation pathway present in all species of the Burkholderia genus; we also demonstrated that Burkholderia-infected humans develop anti-glycan antibodies. Here, we exploited this system to construct and evaluate a synthetic glycoengineered protein antigen as a diagnostic tool for glanders. Our results show 100 % specificity in the detection of antibodies from infected horses, indicating that protein O-glycosylation in Burkholderia can be exploited as a biomarker for diagnosis of Burkholderia-associated infections.

microbiology↗