Biology subjects

Timblin, G. A.

Publications and source records attributed to Timblin, G. A..

5 recordsLinked to original sources

bioRxiv2023

The microenvironment dictates glycocalyx construction and immune surveillance

Efforts to identify anti-cancer therapeutics and understand tumor-immune interactions are built with in vitro models that do not match the microenvironmental characteristics of human tissues. Using in vitro models which mimic the physical properties of healthy or cancerous tissues and a physiologically relevant culture medium, we demonstrate that the chemical and physical properties of the microenvironment regulate the composition and topology of the glycocalyx. Remarkably, we find that cancer and age-related changes in the physical properties of the microenvironment are sufficient to adjust immune surveillance via the topology of the glycocalyx, a previously unknown phenomenon observable only with a physiologically relevant culture medium. Key PointsO_LICulture medium dictates cellular mechanoresponse signatures in vitro C_LIO_LIEpithelial glycocalyx construction is mediated by Heat Shock Factor 1 (HSF1) C_LIO_LISialic acid topology dictates Natural Killer cell cytotoxicity C_LIO_LIPhysiological microenvironments reveal distinct glycobiology C_LI

cell biology↗

bioRxiv2022

Coenzyme A governs proinflammatory macrophage metabolism

Toll-like receptor (TLR)-dependent macrophage responses rely on acute increases in oxidative mitochondrial glucose metabolism that epigenetically support rapid proinflammatory transcriptional programming via histone acetylation. Subsequent suppression of oxidative metabolism restrains this metabolic-epigenetic support of proinflammatory gene transcription to enforce tolerance, an immunosuppressed state of innate immune memory. Identifying biology that promotes or counters these metabolic-epigenetic changes will inform therapeutic approaches to influence proinflammatory, antimicrobial, and immunosuppressed myeloid cellular states. Here, we demonstrate that Coenzyme A (CoA) is a "metabolic adjuvant", as supplying exogenous CoA to macrophages both enhances the magnitude of TLR-driven proinflammatory and antimicrobial responses, and reverse tolerance, via promotion of oxidative metabolism. Extracellular CoA, which we isotopically trace to show its direct uptake by macrophages, works synergistically with tonic TLR signaling, which we demonstrate is a critical regulator of nutrient uptake, metabolism, histone acetylation, and gene expression in macrophages. Together, TLR signaling and exogenous CoA promote mitochondrial glucose oxidation, acetyl-CoA production, and TLR target gene-specific histone acetylation, enhancing metabolic-epigenetic support of proinflammatory transcriptional programming. Exogenous CoA unlocks tumor-associated macrophage (TAM)-dependent TLR agonist anti-tumor activity in an in vivo breast cancer model, and promotes macrophage restriction of the intracellular bacterial pathogen Legionella pneumophila in vitro via an Irg1-dependent antimicrobial state of CoA-augmented itaconate biosynthesis. Our findings demonstrate direct acquisition of intact extracellular CoA, and the ability of this exogenously supplemented metabolic cofactor to augment a key oxidative metabolic-epigenetic pathway supporting proinflammatory and antimicrobial macrophage phenotypes. This may inform host-targeted metabolic adjuvant therapies to reverse myeloid immunosuppression.

immunology↗

bioRxiv2022

Coenzyme Q regulates UCP1 expression and thermogenesis through the integrated stress responses

Coenzyme Q (CoQ) is an essential component of mitochondrial respiration1 and required for thermogenic activity in brown adipose tissues2 (BAT). CoQ deficiency leads to a wide range of pathological manifestations3 but mechanistic consequences of CoQ deficiency in specific tissues such as BAT remain poorly understood. Here we show that pharmacological or genetic CoQ deficiency (50-75% reduction) in BAT leads to accumulation of cytosolic mitochondrial RNAs (mtRNAs) and activation of the eIF2 kinase PKR resulting in the induction of the integrated stress response (ISR) and suppression of UCP1 expression in an ATF4-dependent fashion. Surprisingly, despite diminished UCP1 levels, BAT CoQ deficiency increases whole-body metabolic rates at room temperature and thermoneutrality resulting in decreased weight gain on high fat diets (HFD). This mitohormesis like effect of BAT CoQ insufficiency is dependent on the ATF4-FGF21 axis in BAT revealing an unexpected role for CoQ in the modulation of whole-body energy expenditure with wide-ranging implications for primary and secondary CoQ deficiencies.

cell biology↗

bioRxiv2020

Mitohormesis reprograms macrophage metabolism to enforce tolerance

Macrophages generate mitochondrial reactive oxygen and electrophilic species (mtROS, mtRES) as antimicrobials during Toll-like receptor (TLR)-dependent inflammatory responses. Whether mitochondrial stress caused by these molecules impacts macrophage function is unknown. Here we demonstrate that both pharmacologically- and lipopolysaccharide (LPS)-driven mitochondrial stress in macrophages triggers a stress response called mitohormesis. LPS-driven mitohormetic stress adaptations occur as macrophages transition from an LPS-responsive to LPS-tolerant state where stimulus-induced proinflammatory gene transcription is impaired, suggesting tolerance is a product of mitohormesis. Indeed, like LPS, pharmacologically-triggered mitohormesis suppresses mitochondrial oxidative metabolism and acetyl-CoA production needed for histone acetylation and proinflammatory gene transcription, and is sufficient to enforce an LPS-tolerant state. Thus, mtROS and mtRES are TLR-dependent signaling molecules that trigger mitohormesis as a negative feedback mechanism to restrain inflammation via tolerance. Moreover, bypassing TLR signaling and pharmacologically triggering mitohormesis represents a novel anti-inflammatory strategy that co-opts this stress response to impair epigenetic support of proinflammatory gene transcription by mitochondria. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/347443v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@c5c03org.highwire.dtl.DTLVardef@16cd130org.highwire.dtl.DTLVardef@119b461org.highwire.dtl.DTLVardef@914ee4_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2019

Phf15, a novel transcriptional repressor regulating inflammation in mouse microglia

AimExcessive microglial inflammation has emerged as a key player in mediating the effects of aging and neurodegeneration on brain dysfunction. Thus, there is great interest in discovering transcriptional repressors that can control this process. We aimed to examine whether Phf15--one of the top differentially expressed genes in microglia during aging in humans--could regulate transcription of pro-inflammatory mediators in microglia. MethodsRT-qPCR was used to assess Phf15 mRNA expression in mouse brain during aging. Loss-of-function (shRNA-mediated knockdown (KD) and CRISPR/Cas9-mediated knockout (KO) of Phf15) and gain-of-function (retroviral overexpression (OE) of murine Phf15 cDNA) studies in a murine microglial cell line (SIM-A9) followed by immune activation with lipopolysaccharide (LPS) were used to determine the effect of Phf15 on pro-inflammatory factor (Tnf, Il-1{beta}, Nos2) mRNA expression. RNA-sequencing was used to determine global transcriptional changes after Phf15 knockout under basal conditions and after LPS stimulation. ResultsPhf15 expression increases in mouse brain during aging, similar to humans. KD, KO and OE studies determined that Phf15 represses mRNA expression levels of pro-inflammatory mediators such as Tnf, Il-1{beta} and Nos2. Global transcriptional changes after Phf15 KO showed that Phf15 specifically represses genes related to the antiviral (type I interferon) response and cytokine production in microglia. ConclusionWe provide the first evidence that Phf15 is an important transcriptional repressor of microglial inflammation, regulating the antiviral response and pro-inflammatory cytokine production. Importantly, Phf15 regulates both basal and signal-dependent activation and controls the magnitude and duration of the microglial inflammatory response.

neuroscience↗