Biology subjects

Pence, B. D.

Publications and source records attributed to Pence, B. D..

6 recordsLinked to original sources

bioRxiv2026

Mycoplasma gallisepticum uses itaconate-associated mitochondrial inhibition to suppress host immunometabolism

Many pathogens actively suppress early host immune responses to enhance their fitness. Mitochondria function as key regulators of immune activation, yet whether pathogens suppress host immunity by manipulating mitochondrial metabolism in vivo remains largely unknown. During an innate immune response, the metabolite itaconate increases in abundance and acts as an immunomodulator, due to its inhibition of succinate dehydrogenase (SDH), a key mitochondrial regulator of cellular immunity. We hypothesized that Mycoplasma gallisepticum (MG), a recently emerged pathogen of wild songbirds, most notably house finches (Haemorhous mexicanus), suppresses early host immune responses by limiting SDH-dependent immune activation via itaconate. We tested these hypotheses using experimental 3-day infection of finches with heat-killed MG, live MG or pharmacological elevation of the SDH inhibitor itaconate. Following inoculation, we quantified intracellular itaconate and mitochondrial respiratory function in peripheral blood mononuclear cells (PBMCs) and pro-inflammatory cytokine gene expression in erythrocytes, in addition to infected tissues (trachea and conjunctiva). Heat-killed MG increased SDH-dependent mitochondrial respiration in PBMCs and cytokine gene expression in erythrocytes, but live MG did not show these increases, but revealed increased itaconate accumulation in PBMCs. Dimethyl itaconate administration reproduced the suppressed metabolic and immune phenotype in blood cells observed with live MG, suggesting an itaconate-associated mechanism. In contrast, live MG increased mitochondrial respiration and gene expression levels of cytokines in eyelid conjunctiva, whereas other treatments did not. These findings indicate that MG suppresses host metabolic and cytokine signaling in systemically circulating immune cells through a mechanism consistent with itaconate-mediated inhibition of SDH-dependent mitochondrial respiration, while still inducing an inflammatory response at the site of infection. Our data suggest that MG, like other pathogens, can commandeer host immunometabolic pathways during infection to their benefit and that mitochondria are a key site of competition between host and pathogen.

immunology↗

bioRxiv2025

Immunoregulatory effect of metformin in monocytes exposed to SARS-CoV-2 spike protein subunit 1

BackgroundSevere COVID-19 is characterized by a hyperinflammatory state associated with an exacerbated inflammatory activation of monocytes and macrophages in the respiratory tract. Metformin has been identified as a potent monocyte inflammatory suppressor, and it has been demonstrated to attenuate inflammation in COVID-19. The mechanisms underlying metformin anti-inflammatory effects are, however, unclear. We thus sought to investigate metformins main interactions and their respective isolated effects in modulating monocyte inflammatory response to SARS-CoV-2 stimulation. MethodsClassical human monocytes were isolated from healthy 18-40-year-old individuals and stimulated in vitro with recombinant spike protein subunit 1 (rS1) to assess glycolytic and oxidative metabolic responses by Seahorse extracellular flux analysis, and inflammatory gene expression by qPCR. Stimulated monocytes were either pre-treated with metformin, rotenone, S1QEL, or A769662. ResultsMonocytes stimulated in vitro with rS1 showed an increased glycolytic response associated with production of pro-inflammatory cytokines. Metformin pre-treatment reduced glycolytic activation while partially suppressing inflammation. Rotenone-dependent mitochondrial complex I inhibition was not able to replicate the same effect, and neither complex I specific ROS scavenging. Conversely, A769662 induced AMPK activation led to suppressed glycolytic inflammatory response and cytokine expression pattern similar to metformin, thus suggesting AMPK modulation as a possible central component for metformins mode of action upon S1 stimulation. ConclusionsIn summary, further investigation into the interactions underlying AMPK activity on monocytes in the context of SARS-CoV-2 may provide a better elucidation of metformins anti-inflammatory effect.

immunology↗

bioRxiv2024

Modulatory Effects of Mdivi-1 on OxLDL-Induced Metabolic Alterations, Inflammatory Responses, and Foam Cell Formation in Human Monocytes

Atherosclerosis, a major contributor to cardiovascular disease, involves lipid accumulation and inflammatory processes in arterial walls, with oxidized low-density lipoprotein (OxLDL) playing a central role. OxLDL is increased during aging and stimulates monocyte transformation into foam cells and induces metabolic reprogramming and pro-inflammatory responses, accelerating atherosclerosis progression and contributing to other age-related diseases. This study investigated the effects of Mdivi-1, a mitochondrial fission inhibitor, and S1QEL, a selective complex I-associated reactive oxygen species (ROS) inhibitor, on OxLDL-induced responses in monocytes. Healthy monocytes isolated from participants were treated with OxLDL, with or without Mdivi-1 or S1QEL, and assessed for metabolic shifts, inflammatory cytokine expression, foam cell formation, and ROS production. OxLDL treatment elevated glycolytic activity (ECAR) and expression of pro-inflammatory cytokines IL1B and CXCL8, promoting foam cell formation and mitochondrial ROS (mtROS) production. Mdivi-1 and S1QEL effectively reduced OxLDL-induced glycolytic reprogramming, inflammatory cytokine levels, and foam cell formation while limiting mtROS. These findings suggest that both Mdivi-1 and S1QEL modulate key monocyte responses to OxLDL, providing insights into potential therapeutic approaches for age-related diseases.

immunology↗

bioRxiv2021

Metformin Suppresses Monocyte Immunometabolic Activation by SARS-CoV-2 and Spike Protein Subunit 1

A hallmark of COVID-19 is a hyperinflammatory state that is associated with severity. Various anti-inflammatory therapeutics have shown mixed efficacy in treating COVID-19, and the mechanisms by which hyperinflammation occurs are not well understood. Previous research indicated that monocytes, a key innate immune cell, undergo metabolic reprogramming and produce inflammatory cytokines when stimulated with SARS-CoV-2. We hypothesized that binding by the viral spike protein mediates this effect, and that drugs which regulate immunometabolism could inhibit the inflammatory response in monocytes. Monocytes stimulated with recombinant SARS-CoV-2 spike protein subunit 1 showed a dose-dependent increase in glycolytic metabolism that was associated with production of pro-inflammatory cytokines including interleukin-6 and tumor necrosis factor-. This response was dependent on hypoxia-inducible factor-1, as chetomin inhibited glycolysis and cytokine production. Inhibition of glycolytic metabolism by 2-deoxyglucose (2-DG) or glucose deprivation also inhibited the glycolytic response, and 2-DG strongly suppressed cytokine production. Glucose-deprived monocytes rescued cytokine production by upregulating oxidative phosphorylation, an effect which was not present in 2-DG-treated monocytes due to the known effect of 2-DG on suppressing mitochondrial metabolism. Finally, pre-treatment of monocytes with metformin strongly suppressed spike protein-mediated cytokine production in monocytes, and abrogated glycolytic and mitochondrial metabolism. Likewise, metformin pre-treatment blocked cytokine induction by SARS-CoV-2 strain WA1/2020 in direct infection experiments in monocytes. In summary, the SARS-CoV-2 spike protein induces a pro-inflammatory immunometabolic response in monocytes that can be suppressed by metformin, and metformin likewise suppresses inflammatory responses to live SARS-CoV-2. This has potential implications for the treatment of hyperinflammation during COVID-19.

immunology↗

bioRxiv2020

Growth differentiation factor-15 is associated with age-related monocyte immunosenescence

BackgroundImmunosenescence is an age-associated decrease in function of immune cells precipitated by a variety of mechanisms and affecting nearly every immune cell subset. In myeloid cell subsets, aging reduces numbers of phagocytes and impairs their functional abilities, including antigen presentation, phagocytosis, and bacterial clearance. Recently, we have described an aging effect on several functions indicating immunosenescence in monocytes, including impaired mitochondrial function and reduced inflammatory cytokine gene expression during stimulation with lipopolysaccharide (LPS). We hypothesized that circulating factors altered by the aging process underly these changes. Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor-beta superfamily that has known anti-inflammatory effects in macrophages and has recently been shown to be highly differentially expressed during aging. We used biobanked serum and plasma samples to assay circulating GDF-15 levels in subjects from our previous studies and examined correlations between GDF-15 levels and monocyte mitochondrial function and inflammatory responses. ResultsMonocyte interleukin-6 production due to lipopolysaccharide stimulation was negatively correlated to plasma GDF-15 levels. Additionally, serum GDF-15 was positively correlated to circulating CD16+ monocyte proportions and negatively correlated to monocyte mitochondrial respiratory capacity. ConclusionsThe results of these analyses suggest that GDF-15 is a potential circulating factor affecting a variety of monocyte functions and promoting monocyte immunosenescence, and thus may be an attractive candidate for therapeutic intervention to ameliorate this.

immunology↗

bioRxiv2019

Monocytes from Older Adults Maintain Capacity for Metabolic Compensation during Glucose Deprivation and Lipopolysaccharide Stimulation

Inflammaging is the chronic low-grade inflammation that occurs with age that contributes to the pathology of age-related diseases. Monocytes are innate immune cells that become dysregulated with age and which can contribute to inflammaging. Metabolism plays a key role in determining immune cell functions, with anti-inflammatory cells primarily relying on fatty acid oxidation and pro-inflammatory cells primarily relying on glycolysis. It was recently shown that lipopolysaccharide (LPS)-stimulated monocytes can compensate for a lack of glucose by utilizing fatty acid oxidation. Given that mitochondrial function decreases with age, we hypothesized that monocytes taken from aged individuals would have an impaired ability to upregulate oxidative metabolism along with impaired effector functions. Aging did not impair LPS-induced oxygen consumption rate during glucose deprivation as measured on a Seahorse XFp system. Additionally, aged monocytes maintained inflammatory gene expression responses and phagocytic capacity during LPS stimulation in the absence of glucose. In conclusion, aged monocytes maintain effector and metabolic functions during glucose deprivation, at least in an ex vivo context.

immunology↗