Biology subjects

Lockwood, C.

Publications and source records attributed to Lockwood, C..

5 recordsLinked to original sources

bioRxiv2025

Dexamethasone inhibits the LPS-induced activation of hypoxia-inducible factor 1 alpha (HIF-1α) in macrophages independently of the DUSP1-p38-TTP-HIF-1α regulatory axis.

The oxygen-sensitive transcription factor HIF-1 (hypoxia-inducible factor 1) is a master regulator of cellular and organism-level adaptations to decreasing oxygen availability. Under conditions of oxygen sufficiency HIF-1 is constitutively produced and degraded. In response to hypoxia, the degradation pathway is inhibited and HIF-1 protein accumulates via mechanisms that are now well understood. Additional signals combine with the oxygen-sensitive protein degradation pathway to modulate the expression and/or activity of HIF-1. In the context of the immune system, HIF-1 can be activated under normoxic conditions by a variety of stimuli, including the pro-inflammatory agonist lipopolysaccharide. Here we use a variety of genetic and pharmacological approaches to reveal that lipopolysaccharide-induced HIF-1 accumulation in primary macrophages is dependent on mitogen-activated protein kinase p38. This response is not dependent on modulation of HIF-1 protein stability: instead, it involves the phosphorylation and inactivation of tristetraprolin, an mRNA destabilizing protein that targets Hif1a mRNA for degradation. We previously reported that the glucocorticoid dexamethasone inhibits lipopolysaccharide-induced HIF-1 accumulation and metabolic reprograming in primary macrophages. Here we tested and disproved the hypothesis that dexamethasone prevents HIF-1 accumulation by inducing expression of dual specificity phosphatase 1 and thereby inhibiting p38 function. Hence two novel mechanisms critically regulate HIF-1 activation in lipopolysaccharide-treated macrophages: a p38-dependent mechanism that operates at the post-transcriptional level to control Hif1a mRNA expression, and a glucocorticoid-sensitive mechanism that operates at the post-translational level to control HIF-1 protein stability. Combined targeting of these two mechanisms may exert therapeutic effects in contexts where HIF-1 contributes to immune-mediated inflammatory pathology.

immunology↗

bioRxiv2023

The glucocorticoid dexamethasone inhibits HIF-1alpha stabilisation and metabolic reprogramming in lipopolysaccharide-stimulated primary macrophages.

Synthetic glucocorticoids are used to treat many chronic and acute inflammatory conditions. Frequent adverse effects of prolonged exposure to glucocorticoids include disturbances of glucose homeostasis, caused by changes of glucose traffic and metabolism in muscle, liver and adipose tissues. Macrophages are important targets for the anti-inflammatory actions of glucocorticoids. These cells rely on aerobic glycolysis to support various pro-inflammatory and antimicrobial functions. Employing a potent pro-inflammatory stimulus in two commonly-used model systems (mouse bone marrow-derived and human monocyte-derived macrophages), we showed that the synthetic glucocorticoid dexamethasone inhibited lipopolysaccharide-mediated activation of the hypoxia- inducible transcription factor HIF-1, a critical driver of glycolysis. In both cell types, dexamethasone-mediated inhibition of HIF-1 reduced the expression of the glucose transporter GLUT1, which imports glucose to fuel aerobic glycolysis. Aside from this conserved response, other metabolic effects of lipopolysaccharide and dexamethasone differed between human and mouse macrophages. These findings suggest that glucocorticoids exert anti-inflammatory effects by impairing HIF-1-dependent glucose uptake in activated macrophages. Furthermore, harmful and beneficial (anti-inflammatory) effects of glucocorticoids may have a shared mechanistic basis, depending on alteration of glucose utilisation. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=128 SRC="FIGDIR/small/558626v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@4edbb5org.highwire.dtl.DTLVardef@13a5ab2org.highwire.dtl.DTLVardef@18776borg.highwire.dtl.DTLVardef@4816fa_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2022

The establishment and transmission of novel foraging techniques indicates a capacity for culture in bumblebees (Bombus terrestris).

The astonishing behavioural repertoires of social insects have been thought largely innate, but these insects have repeatedly demonstrated remarkable capacities for both individual and social learning. Using the bumblebee Bombus terrestris as a model, we developed a two-option puzzle box task and used open diffusion paradigms to observe the transmission of novel, non-natural foraging behaviours through populations. Box-opening behaviour spread through colonies seeded with a demonstrator trained to perform one of the two possible behavioural variants, and the observers acquired the demonstrated variant. This preference persisted among observers even when the alternative technique was discovered. In control diffusion experiments that lacked a demonstrator, some bees spontaneously opened the puzzle boxes but were significantly less proficient than those that learned in the presence of a demonstrator. This suggested that social learning was crucial to proper acquisition of box-opening. Additional open diffusion experiments where two behavioural variants were initially present in similar proportions ended with a single variant becoming dominant, due to stochastic processes. This could lead to the emergence and maintenance of local cultural variation. These results suggest that bumblebees, like mammals and birds, may have the capacity for culture and to sustain cultural variation.

animal behavior and cognition↗

bioRxiv2019

Sensitive detection of highly fragmented cytomegalovirus nucleic acid in human cfDNA

Congenital human cytomegalovirus (CMV) infections are the leading cause of newborn hearing and central nervous system impairments worldwide. Currently, routine prenatal screening for congenital CMV is not performed in the United States and confirmation in suspected perinatal cases requires invasive sampling by amniocentesis. We hypothesized that detection of CMV from maternal cell-free DNA (cfDNA) plasma could provide a non-invasive indicator of congenital CMV infection. We analyzed sequence data from 2,208 individuals undergoing routine non-invasive prenatal aneuploidy screening at the University of Washington. CMV reads were identified in 117 (5.3%) samples. Positive samples were stratified based on CMV reads per million sample reads (RPM), resulting in ten samples being classified as strong positive (RPM > 0.3) and 107 as intermediate positive (0.01<RPM<0.3). Subsequent qPCR testing identified CMV in 9/10 strong positive samples and 2/32 intermediate positive samples. Median cfDNA insert size derived from CMV was significantly shorter than cfDNA derived from human chromosomes (103 vs 172 bp, p<0.0001), corresponding to the 3rd percentile of human cfDNA insert size. In addition, CMV cfDNA fragment lengths were distributed over a wider range than human cfDNA reads. These studies reveal the highly fragmented nature of CMV cfDNA and offer precise measurements of its length: these features likely explain discrepancies in serum CMV viral loads measurements determined by different qPCR assays, despite widespread efforts to standardize results. More work is required to determine how detection of CMV from maternal cfDNA can be best used as tool for congenital CMV screening or diagnosis.

microbiology↗

bioRxiv2018

Evaluation of a guideline developed to reduce HIV-related stigma and discrimination in healthcare settings and establishing consensus

BackgroundDeveloping guidelines and policies is critical to address HIV-related stigma and discrimination (SAD) in healthcare settings. To this end, a multidisciplinary panel developed a guideline to reduce SAD. This project evaluated the appropriateness of implementing the guideline in the Ethiopian context.\n\nMethodsA consensus of the expert panel was established through a Delphi technique which was followed by a panel meeting. Initial tentative recommendations were distributed to experts through e-mails to be evaluated using the modified guideline implementability appraisal (GLIA) v.2.0 checklist.\n\nResultsIn the first round of the Delphi survey, all (13) panel members evaluated the guideline. The overall score for the general domain of the modified GLIA checklist was 96.56%. The scores for individual recommendations ranged from 68.33% to 92.76%. Maximum and minimum scores were attained for measurability (97.71%) and flexibility (59.77%) domains respectively. Percentages mean score lower than 75% was obtained for flexibility and validity domains. Participants suggested that additional tools and training should be added to the guideline. In the second round of the survey, all the recommendations received endorsement with scores above 75%. Maximum and minimum scores were attained for measurability (100%) and flexibility (86.88%) domains respectively. During the panel meeting, issues of responsibility for implementing the guideline were discussed.\n\nConclusionThe project evaluated implementability of a guideline developed to reduce HIV-related SAD in healthcare settings. The Delphi survey was followed by a half-day meeting that helped in further clarification of points.

scientific communication and education↗